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LAYOUT IMPLEMENTATION OF

DIGITAL TO ANALOG

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LAYOUT IMPLEMENTATION OF DIGITAL TO ANALOG


CHAPTER 1

INTRODUCTION

INTRODUCTION TO INTEGRATED CIRCUIT LAYOUT(IC LAYOUT):

Integrated circuit layout, also known IC layout, IC mask layout, or mask design, is the

representation of an integrated circuit in terms of planar geometric shapes which correspond to the

patterns of metal, oxide, or semiconductor layers that make up the components of the integrated

circuit. It‘s nothing but Top View of the Cross-sectional Device.

When using a standard process - where the interaction of the many chemical, thermal, and

photographic variables are known and carefully controlled - the behavior of the final integrated

circuit depends largely on the positions and interconnections of the geometric shapes. A layout

engineer's job is to place and connect all the components that make up a chip so that they meet all

criteria. Typical goals are performance, size, and manufacturability.

The layout must pass a series of checks in a process known as verification; the two most

common checks in the verification process are Design Rule Checking (DRC), and Layout Versus

Schematic (LVS). When all verification is complete the data is translated into an industry standard

format, typically GDSII, and sent to a semiconductor foundry. The process of sending this data to the

foundry is called tape out, due to the fact the data used to be shipped out on a magnetic tape. The

foundry converts the data into another format and uses it to generate the photo masks used in a

photolithographic process of semiconductor device fabrication.

In the earlier, simpler, days of IC design, layout was done by hand using opaque tapes and

films, much like the early days of PCB design. Modern IC Layout is done with the aid of IC layout

editor software, or even automatically using EDA tools, including place and route tools or schematic

driven layout tools. The manual operation of choosing and positioning the geometric shapes is

informally known as "polygon pushing".



CHAPTER 2

SEMICONDUCTOR AND TECHNOLOGY

2.1 RELIABILITY OF SEMICONDUCTOR DEVICES

Semiconductor devices are very sensitive to impurities and particles. Therefore, to

manufacture these devices it is necessary to manage many processes while accurately controlling the

level of impurities and particles. The finished product quality depends upon the many layered

relationship of each interacting substance in the semiconductor, including metallization, chip

material (list of semiconductor materials) and package.

The problems of micro-processes, and thin films and must be fully understood as they apply

to metallization and bonding wire bonding. It is also necessary to analyze surface phenomena from

the aspect of thin films.

Due to the rapid advances in technology, many new devices are developed using new

materials and processes, and design calendar time is limited due to non-recurring engineering

constraints, plus time to market concerns. Consequently, it is not possible to base new designs on the

reliability of existing devices.

To achieve economy of scale, semiconductor products are manufactured in high volume.

Furthermore repair of finished semiconductor products is impractical. Therefore incorporation of

reliability at the design stage and reduction of variation in the production stage have become

essential.

Reliability of semiconductor devices may depend on assembly, use, and environmental

conditions. Stress factors effecting device reliability include gas, dust, contamination, voltage,

current density, temperature, humidity, mechanical stress, vibration, shock, radiation, pressure, and

intensity of magnetic and electrical fields.

Design factors affecting semiconductor reliability include: voltage derating, power derating,

current derating, metastability, logic timing margins (logic simulation), timing analysis, temperature

derating, and process control.



CHAPTER 3

DIGITAL VS ANALOG SYSTEMS

3.1 DIGITAL VS ANALOG SYSTEMS

Connecting digital circuitry to sensor devices is simple if the sensor devices are inherently

digital themselves. Switches, relays, and encoders are easily interfaced with gate circuits due to the

on/off nature of their signals. However, when analog devices are involved, interfacing becomes

much more complex. What is needed is a way to electronically translate analog signals into digital

(binary) quantities, and vice versa. An analog-to-digital converter, or ADC, performs the former task

while a digital-to-analog converter, or DAC, performs the latter.

An ADC inputs an analog electrical signal such as voltage or current and outputs a binary

number. In block diagram form, it can be represented as shown in fig1. A DAC, on the other hand,

inputs a binary number and outputs an analog voltage or current signal. In block diagram form, it is

shown in Fig 3.1.

Fig.3.1.a Fig.3.1.b

Together, they are often used in digital systems to provide complete interface with analog

sensors and output devices for control systems such as those used in automotive engine controls:



Fig.3.2

It is much easier to convert a digital signal into an analog signal than it is to do the reverse.

Therefore, we will begin with DAC circuitry and then move to ADC circuitry.

3.2 DIFFERENCE BETWEEN DAC AND ADC

There is a philosophical difference, as well, that plays into how these converters are used and

sometimes taken for granted. In simplest terms, it's this: an ADC is attempting to capture and convert

a largely unknown signal into a known representation. In contrast, a DAC is taking a fully known,

well-understood representation and "simply" generating an equivalent analog value.

The challenge for an ADC is much greater than it is for a DAC. To get the most out of an

ADC, especially a higher-performance one (speed or precision) takes a well-designed analog signal-

conditioning input channel, often with an ADC driver carefully matched to the ADC itself.

The DAC's life is much easier. But that relative ease shouldn't encourage complacency on the

designer's part. It's too easy not to give the analog output of the DAC the attention it needs, regarding

parameters such as slew rate, output drive (voltage, current, range) and protection against faults at its

load. And that can lead to nasty circuit and system-level headaches, at both the prototype evaluation

and in the field.



CHAPTER 4

ASIC & FULL CUSTOM VS SEMI CUSTOM

4.1 WHAT IS ASIC?

Any IC other than a general purpose IC which contains the functionality of thousands of gates is

usually called an ASIC (Application Specific Integrated Circuit). ASICs are designed to fit a certain

application. or A chip designed to perform a particular operation as opposed to General Purpose

integrated circuits

An ASIC is a digital or mixed-signal circuit designed to meet specifications set by a Specific project.

And it is NOT software programmable to perform different tasks.

4.1.1 General Purpose Integrated Circuits:

• Programmable microprocessors (e.g. Intel Pentium Series, Motorola HC-11)

Used in PCs to washing machines

• Programmable Digital Signal Processors (e.g. TI TMS 320 Series)

Used in many multimedia, sensor processing and communications applications

• Memory (DRAM, SRAM, etc.)

4.1.2 Examples of ASICs:

• Video processor to decode MPEG-2 digital TV signals

• Audio processor to perform Dolby AC3 encoding

• Low power DSP/controller for cell phone

4.2 ASIC DESIGN STYLES

Several design styles can be considered for chip implementation of specified algorithms or logic

functions. Each design style has its own merits and shortcomings, and thus a proper choice has to be

made by designers in order to provide the functionality at low cost.

They belong to two general cases

1 Full-custom layout approaches

2 Semi-custom layout approaches



4.2.1. Full-Custom Layout

Full-custom layout refers to manual layout design.

Full-custom design is a time-consuming and difficult task.

Gives full control to the artwork designer in placing/interconnecting.

A high degree of optimization in both the area and performance is possible.

Takes several man-months to layout a chip.

Therefore is used only for circuits that are mass produced (microprocessors).

For circuits which will be reproduced in millions, it is important to optimize on the area as

well as performance.

Designer‘s productivity is increased with the help of a good layout editor.

4.2.2. Standard Cell Layout or Semi-Custom Layout

Standard Cells are custom designed and then inserted into a library

A standard cell, known also as a poly cell, is a logic that performs a standard function.

Examples of standard-cells are two-input NAND gates, two-input XOR gate, D flip-flop,

two-input multiplexer.

A cell library is a collection of information pertaining to standard-cells.

These cells are then used in the design by being placed in rows and wired together using

‗place and route‘ tools

Some standard cells, such as RAM and ROM cells, and some data path cells (e.g. a

multiplier) are tiled together to create macro cells



CHAPTER 5

ASIC FABRICATION & PROCESSING STEPS

5.1 THE ANALOG IC DESIGN PROCESS

Fig 5.1



5.2 Electrical Design

Electrical design is the process of going from the specifications to a circuit solution. The

inputs and outputs of electrical design are:

Fig 5.2

The electrical design requires active and passive device electrical models for

- Creating the design

- Verifying the design

- Determining the robustness of the design

5.2.1 Steps in Electrical Design

1.) Selection of a solution- Examine previous designs

Literature

Patents

Textbook

Web

Your previous experience (if you are new in the field this is a challenge)

Experienced colleagues

2.) Investigation of a solution

Analyze, analyze, analyze

Determine the ability of the solution to satisfy most or all of the specifications

Observe the weaknesses and strengths of the solution

―Get a feeling‖ for the circuit operation



Fig 5.3

3.) Modification of a solution

- The previous step should identify the weaknesses or inability to satisfy the

specifications

- Look for modifications in the design to improve its performance (the key principles,

concepts and techniques in this study will be a great help in this step)

- Evaluate the modifications through analysis

- Most of the analysis up to this point in the design has not used a computer or a model that

is precise

Fig 5.4

4.) Verification of a solution

- Use a simulator with precise models and verify the solution

- Large disagreements with hand analysis and computer verification should be carefully

examined

- Use models that capture the technology variations to make sure the design will work

for the given technology (if this information is not available, run the circuit over a wide

temperature range to get similar results)



5.3 PHYSICAL DESIGN

Physical design is the process of representing the electrical design in a layout consisting of

many distinct geometrical rectangles at various levels. The layout is then used to create the actual,

three-dimensional integrated circuit through a process called fabrication.

Fig 5.5

5.3.1 What is the Purpose of the Layout?

The layout is used to create the masks that enable the fabrication of the chip.

Metal level mask example:

Fig 5.6

5.3.2 Layout Process

1.) The inputs are the W/L values and the schematic (generally from schematic entry used for

simulation).

2.) A tool is used to enter the various geometries. The designer must enter the location, shape, and

level of the particular geometry.

3.) During the layout, the designer must obey a set of rules called design rules. These rules are for the

purpose of ensuring the robustness and reliability of the technology.



4.) Once the layout is complete, then a process called layout versus schematic (LVS) is applied to

determine if the physical layout represents the electrical schematic.

5.) The next step is now that the physical dimensions of the design are known, the parasitics can be

extracted. These parasitics primarily include:

a.) Capacitance from a conductor to ground

b.) Capacitance between conductors

c.) Bulk resistance

6.) The extracted parasitics are entered into the simulated database and the design resimulated to

insure that the parasitics will not cause the design to fail.

5.4.1 Fabrication Process Flow

This topic briefly describes a simplified version of the fabrication of a transistor on the

silicon wafer. The ability to visualize the cross-section of a layout is a basic skill that all layout

designers should master.

Note that each processing step requires that certain areas are defined on chip by appropriate

masks. Consequently, the integrated circuit may be viewed as a set of patterned layers of doped

silicon, polysilicon, metal and insulating silicon dioxide. In general, a layer must be patterned before

the next layer of material is applied on chip. The process used to transfer a pattern to a layer on the

chip is called lithography. Since each layer has its own distinct patterning requirements, the

lithographic sequence must be repeated for every layer, using a different mask.

To illustrate the fabrication steps involved in patterning silicon dioxide through optical

lithography, let us first examine the process flow shown below

Step 1: Well formation stage. Implants n-type impurities into the wafer followed by diffusing the

impurities deep into the substrate to form the N-Wells. For CMOS process, the silicon substrate is

usually p-type.

Fig 5.7

Step 2: Active & isolation stage. Thick oxide is grown outside the active areas. Active areas are

defined as areas where the CMOS transistors are fabricated. Thick oxide is also known as field

oxide. Field oxides isolate the transistors from one another.



Fig 5.8

The first two steps describe a formation of a conventional well. The depth and doping profile of a

conventional well are controlled by the diffusion drive-in at high temperature. A better way to form

the well, known as retrograde well, is usually used in 0.25um 1 and smaller process technologies.

Retrograde well is formed by very high energy implantation. The depth and doping profile of a

retrograde well are controlled by implantation energy and impurity dose. Retrograde well is formed

AFTER the field oxide. Since retrograde well does not require diffusion drive-in, it has smaller

lateral diffusion and a more ideal doping profile.

Step 3: Gate oxide formation stage. A thin gate oxide is grown across the wafer. Gate oxide of only

tens of silicon oxide atoms thick is created during the fabrication process with the current

technology. Gate oxide is the insulator between the transistor‘s gate and its channel. Gate oxide

refers to the ―O‖ in ―MOS‖ which stands for Metal-Oxide-Semiconductor.

Fig 5.9

Step 4: Gate formation stage. Poly (i.e. poly-silicon) is deposited on the wafer. The poly that are

deposited on the gate oxides are the gates of the transistors which are usually known as gate poly.

The gate poly will incline upward when it extends over the field oxide. The gate oxide in the active

area that are not covered by the gate poly will be etched away to form the source and the drain of the

transistor.

Fig 5.10



Step 5: Source and drain formation stage. P-type and n-type impurities are implanted into the active

areas. The impurities are diffused into the silicon to form the source terminals and the drain

terminals. As the impurities diffuse both vertically and laterally, the gate poly will slightly overlap

the sources and the drains which will result in gate overlap capacitances. The diffusions for the

sources and the drains of NMOS and PMOS are N-diffusion (N-diff) and P-diffusion (P-diff)

respectively.

Fig 5.11

P-diff in p-substrate is known as p-tap, while n-diff in N-well is known as n-tap. Connections from

the metal routings to the substrate and the Nwells are made through the p-tap and the n-tap. This is

necessary to ensure the wells are properly tied down and the transistors are isolated. The p-substrate

should be biased to the lowest voltage potential while the N-well should be biased to the highest

voltage potential. In this way, all the P-N junctions are reverse biased and hence the transistors are

electrically isolated from one another as shown in the diagram below.

Fig 5.12

Isolating the transistors with the thick field oxide is commonly found in 0.35um and larger process

technologies. For 0.25um and smaller process technologies, shallow trench isolation (STI) shown in

the diagram below is more commonly used to isolate the transistors. In STI fabrication, trenches are

etched into the wafer and filled with silicon oxide to isolate the islands of transistor active area.

Fig 5.13



5.5 PACKAGING

Packaging of the integrated circuit is an important part of the physical design process.

The function of packaging is:

1.) Protect the integrated circuit

2.) Power the integrated circuit

3.) Cool the integrated circuit

4.) Provide the electrical and mechanical connection between the integrated circuit and the

outside world.

Packaging steps:

Fig 5.14



CHAPTER 6

RELIABILITY ISSUES AND YIELD

1. Latch up

2. Electro migration

3. ESD

6.1 LATCH UP:

The structure of a bulk CMOS process introduces a problem known as latch-up in which the

circuits fail to operate and the chip draws excessive power supply current.

A problem which is inherent in the p-well and n-well process is due to the relevantly large

number of junctions which are formed in these structures and, the consequent presence of parasitic

transistor and diodes, Latchup is a condition in which the parasitic components give rise to the

establishment of low resistance conducting paths between VDD and VSS with disastrous results.

Careful control during fabrication is necessary to avoid this problem.

Consider the n-well structure of Fig 6.1. The n-p-n-p structure is formed by the source of the

NMOS, the p-substrate, the n-well and the sources of the PMOS. An equivalent circuit is shown in

Fig 6.2. when one of the two bipolar transistors gets forward-biased (e.g., due to current flowing

through the well or substrate), it feeds the base of the other transistor. This positive feedback

increases the current until the circuit fails or burns out.

Fig 6.1



Fig 6.2

The remedies for the latchup problem include:

i. An increase in substrate doping levels with a consequent drop in the value of Rpsub.

ii. Reducing Rnwell by control of fabrication parameters and ensuring a low contact resistance to

VDD

iii. By introducing guard rings.

6.2.1 Electro Migration (EM):

Electro migration is the diffusion of metal atoms along the conductor in the direction of electron flow.

This directional diffusion process occurs because the momentum transfer between the electrons and

the metal atoms increases the probability that an aluminum atom will move in the direction of the

electron flow. Since the mass of the electron is very much smaller than aluminum atoms the transfer

of momentum is only enough to have a statistical effect upon the diffusion of aluminum. This

diffusion process will preferentially fill metal ion vacancies found in crystal defects, leaving a

vacancy in the location from which the metal atom came.

The flow of metal ions in the direction of electron flow in itself does not cause damage to the

aluminum wires. Damage only occurs when there is a metal ion flux divergence that causes metal

ions to be taken from one part of a wire and deposit them in some other location without replenishing

the metal ions from a reservoir. The flux divergence causes vacancies to coalesce in one location to

produce a void. This void volume grows until there is no aluminum in a short length of the wire;

causing current flow is interrupted leading to circuit failure.

6.2.2 Electro Migration – Failure Modes:

Electro migration occurs when some of the momentum of a moving electron is transferred to

a nearby activated ion. This causes the ion to move from its original position.

a) Over time this force knocks a significant number of atoms far from their original positions. A

break or gap can develop in the conducting material, preventing the flow of electricity. In narrow

interconnect conductors, such as those linking transistors and other components in integrated circuits,

this is known as a void or internal failure open circuit. (Fig 6.3.a)



b) Electro migration can also cause the atoms of a conductor to pile up and drift toward other nearby

conductors, creating an unintended electrical connection known as a hillock failure or whisker

failure (short circuit). (Fig 6.3.b)

Both of these situations can lead to a malfunction of the circuit.

Fig 6.3, a, b

6.3 ELECTRO STATIC DISCHARGES (ESD):

Electrostatic discharge is defined as the transfer of charge between bodies at different electric

potentials. The amount of charge created by contact charging is affected by the area of contact, the

speed of separation, relative humidity, and other factors.

6.3.1 Damage from ESD’s can

Cause complete device failure by parametric shifts, or

Device weakness by locally heating, melting or otherwise damaging oxides, junctions

or device components

6.3.2 Remedies

Special circuitry with ESD protection diodes, guard rings etc.

6.4 YIELD CONSIDERATIONS:

6.4.1 Yield:

High-density chip designs consist of a few tens of millions of MOSFETs. This has become so

common place that the technical achievement of silicon processing is generally overlooked. Consider

the implications of having a ―good die‖. This means that, so far as the testing process has shown,

every circuit in the die operates as it should. In other words, every important feature of every

transistor and the interconnect wiring has the correct behavior and, therefore, the correct structure. In

the real world of semiconductor manufacturing, we are continually faced with the fact that only a

percentage of the die is functional. This is expressed by the yield Y of a process such that

Obviously, a high yield is required to have a profitable design.



CHAPTER 7

INSTRUCTION TO 0.13UM DESIGN & IMPORTANCE OF THE

RULES

7.1 DESIGN RULES & SIGNIFICANCE:

Design Rules are a series of parameters provided by semiconductor manufacturers that enable

the designer to verify the correctness of a mask set. Design rules are specific to a particular

semiconductor manufacturing process. A design rule set specifies certain geometric and connectivity

restrictions to ensure sufficient margins to account for variability in semiconductor manufacturing

processes, so as to ensure that most of the parts work correctly.

7.1.1 In General Design Rules:

Design rules govern the layout of individual components: transistors, wires, contacts, vias

How small can the gates be, and how small can the wires be made

Conflicting Demands:

Component packing: more functionality, higher speed

Chip yield: smaller sizes can reduce yield (fraction of good chips)

Conservative vs aggressive design rule

7.1.2 Foundry Interface:

Fig 7.1

http://en.wikipedia.org/wiki/Semiconductor_fabrication

http://en.wikipedia.org/wiki/Mask_set



7.2 DESIGN RULE VIOLATION:

Violating a design rule might result in a non-functional circuit or low yield.

Fig 7.2

7.3 TYPES OF DESIGN RULES:

Scalable Design Rules: Lambda parameter

Based on scalable ―coarse grid‖ - L (lambda).

Idea: reduce L value for each new process, but keep rules the same.

Key advantage: portable layout.

Key disadvantage: not everything scales the same.

Not used in ―real life‖.

Absolute Dimensions (micron rules)

Based on absolute distances (e.g. 0.75µm).

Layouts not portable.

7.4:0.13u Design rules for TSMC (Taiwan Semiconductor Manufacturing Company) Fab

House:

DESIGN RULES OF .13µM TSMC

Cell Height 3.690

Rail Height 0.50

POLY

1 Width 0.13

2 Minimum Width(Interconnect) 0.13

3 Minimum Space 0.18

4 Minimum Space On OD 0.18

5 Minimum Field Poly Space To OD 0.07

6 Minimum OD Extension On Poly 0.23

7 Minimum PO Extension On OD 0.18

metal1 metal1

After Fabrication

Spacing violation

After Fabrication

Width violation



8 Minimum Poly Area 0.09

9 Minimum Enclosed Area 0.15

METAL 1

1 Minimum Width 0.16


3 Minimum Enclosure Of Contact 0.00

4 Minimum Area 0.122

5 Minimum Enclosure Of Contact (End Of Line) 0.05

6 Minimum Enclosed Area 0.2

CONTACT

1 Size 0.16X0.16


3 Minimum Enclosed By Active 0.07

4 Minimum Enclosed By Poly 0.07

5 Minimum Gate Spacing ( Inside OD) 0.11

6 Contact Inside Poly, Minimum Space To OD 0.14

OD



3 Minimum N+ Active Space To Nwell 0.31

4 Minimum P+ Active Enclose By Nwell 0.31

5 Minimum Area 0.122

PP



3 Minimum Space To N+ Active 0.18

4 Minimum Area 0.25

5 Minimum Extension On Pactive 0.18

NP



3 Minimum Space To P+ Active 0.18

4 Minimum Area 0.25

5 Minimum Extension On Nactive 0.18



CHAPTER 8

STICK DIAGRAMS & FOLDING CONCEPT

8.1 STICK DIAGRAMS:

Stick diagrams provide an easy approach to performing simple CMOS circuit layouts.

Planning a physical design using stick diagrams before going to CAD tool can save a lot of time and

energy.

They are useful for planning the layout and routing of integrated circuits. In a stick diagram,

every line of a conducting material layer is represented by a line of a distinct color. For below given

examples we will use basic color coding:

Fig 8.1

Other layers will be introduced later.

The width of a line is not important, as stick diagrams give only wiring and routing

information.

A stick diagram is thus a schematic representation of a circuit at physical design level. With a

practice we will be able to read a stick diagram and translate it into a conventional circuit schematic.

Fig 8.2

In terms of stick diagrams, we say that an nFET is formed whenever Red (Poly) crosses over Green

(Active).

Fig 8.3



This is consistent with top view of a transistor.

A pFET is described by the same ―red over green ―coding, but the crossing point is contained within

an nWell boundary

Fig 8.4

8.2 BASIC RULES

The rules for constructing stick diagrams are based on the characteristics of the conducting layers.

Only the routing is important, not the line widths

Red over green a FET

Blue may cross over green or red without a connection

Fig 8.5

Connections between layers are specified by X. this represents an oxide etch

Fig 8.6



Metal lines on different layers can cross one another. Contacting two metal lines require a via

Fig 8.7

8.3 EXAMPLES

Fig 8.8

Stick diagrams are often used to solve routing problems.



Fig 8.9



CHAPTER 9

LAYOUTS OF STD CELLS (DIGITAL) WITH NET LIST

9.1 STANDARD CELL DESCRIPTIONS

9.1.1 Inverter:

Cell Description: The INV cell provides the logical inversion of a single input (A). The output (Y)

is represented by the logic equation. Y = A!.

A CMOS inverter contains a PMOS and a NMOS transistor connected at the drain and gate

terminals, a supply voltage VDD at the PMOS source terminal, and a ground connected at the

NMOS source terminal, were VIN is connected to the gate terminals and VOUT is connected to the

drain terminals.(See diagram). It is important to notice that the CMOS does not contain any resistors,

which makes it more power efficient that a regular resistor-MOSFET inverter. As the voltage at the

input of the CMOS device varies between 0 and 5 volts, the state of the NMOS and PMOS varies

accordingly. If we model each transistor as a simple switch activated by VIN, the inverter‘s

operations can be seen very easily:

Logic Symbol: Function Table:

Schematic:

Spice Net list : .subckt INVX1 Y A

M0 VDD A Y VDD P l=0.13u w=0.64u

M1 Y A VSS VSS N l=0.13u w=0.42u

.ends INVX1

*.SCALE meter

.GLOBAL VSS VDD



Cross Sectional View:

Stick Diagram:

Fig 9.1

Layout:



Fig 9.2

9.1.2 NAND:

The NAND2 cell provides the logical NAND of two inputs (A, B). The output (Y) is represented by

the logic equation:

Description: The NAND gate is a digital logic gate that behaves in a manner that corresponds to the

truth table to the left. A LOW output results only if both the inputs to the gate are HIGH. If one or

both inputs are LOW, a HIGH output results. The NAND gate is a universal gate in the sense that

any Boolean function can be implemented by NAND gates.



Schematic :

Symbol:

Functional Table:

Spice Net list : .subckt NAND2X1 Y A B

M0 hnet11 B VSS VSS N l=0.13uw=0.58u

M1 Y A hnet11 VSS N l=0.13u w=0.58u

M2 VDD B Y VDD P l=0.13u w=0.64u

M3 VDD A Y VDD P l=0.13u w=0.64u

.ends NAND2X1

*.SCALE meter

.GLOBAL VSS VDD



Stick diagram:

Fig 9.3

Layout:

Fig 9.4



9.1.3 NOR:

The NOR2 cell provides a logical NOR of two inputs (A,B). The output (Y) is represented by the

logic equation. .

Description: The NOR gate is a digital logic gate that implements logical NOR - it behaves

according to the truth table to the right. A HIGH output (1) results if both the inputs to the gate are

LOW (0). If one or both input is HIGH (1), a LOW output (0) results. NOR is the result of the

negation of the OR operator. NOR is a functionally complete operation—combinations of NOR gates

can be combined to generate any other logical function. By contrast, the OR operator is monotonic as

it can only change LOW to HIGH but not vice versa.

Symbol: Functional Table: Schematic:

Spice Net list: .subckt NOR2X1 Y A B

M0 Y B VSS VSS N l=0.13u w=0.42u

M1 Y A VSS VSS N l=0.13u w=0.42u

M2 VDD B hnet7 VDD P l=0.13u w=0.84u

M3 hnet7 A Y VDD P l=0.13u w=0.84u

.ends NOR2X1

*.SCALE meter

.GLOBAL VSS VDD



Stick Diagram:

Fig 9.5

Layout:

Fig 9.6



9.1.4 OAI21X1:

The AOI21cell provides the logical inverted OR of one AND group and an additional input. The

output (Y) is represented by the logic equation:

Logic Symbol:

A0

A1

Y

B0

Functional Table:

Schematic:

Spice Net list:

.subckt OAI21X1 Y A0 A1 B0

M0 VDD A1 hnet11 VDD P l=0.13u w=0.84u

M1 hnet11 A0 Y VDD P l=0.13u w=0.84u

M2 Y B0 net25 VSS N l=0.13u w=0.58u

M3 net25 A1 VSS VSS N l=0.13u w=0.58u

M4 net25 A0 VSS VSS N l=0.13u w=0.58u

M5 Y B0 VDD VDD P l=0.13u w=0.64u

.ends OAI21X1

*.SCALE meter

.GLOBAL VSS VDD

A0, A1 & B0 are inputs & Y is output



Stick diagram:

Fig 9.7

Layout:

Fig

9.8



CHAPTER 10

LAYOUT TECHNIQUE IN ANALOG

10.1 ANALOG LAYOUT:

Device Matching

- Why do I care?

- Matching ‗theory‘

- Basic approach for transistors, capacitors, resistors

Noise and Decoupling

- Capacitive coupling

- Substrate noise

- Thermal noise

- Shielding

10.2 ANALOG DESIGNERS THINK A LOT ABOUT MATCHING:

• Basic operation of some circuits depends directly on matchingeg. pipelined A/D converters

• Common-mode rejection limited by matching

Common-mode to differential-mode conversion is proportional to mismatch

• Supply noise rejection limited by mismatch in fully-differential circuits

In fully-differential circuits supply noise appears like a common-mode signal applied to the supply

• Amplifier offsets greatly degrade the performance of band gap references

Digital designers also care about matching of transistors and routing because of skew and in

memories.

If you follow some simple rules, you can avoid gross matching problems. If you‘re trying to ratio

two transistors

• Use the same W and L and vary M (takes out ΔW and ΔL effects)

• Use M‘s that are even, preferably factors of 4 (transistors are not truly symmetrical!)

• Use common-centroid, or nearly common-centroid, layout (takes out oxide and doping gradients)



• Use dummy transistors at the ends of the row (takes out poly etch loading and mask misalignment

effects)

• Make clean and well balanced routing

• Use a suitable area and overdrive

• Use plenty of substrate and well taps

• Route currents a long way, not voltages - IR drops can cause big Mismatches

10.3 SYSTEMATIC MISMATCH

Systematic mismatch refers to a spatial gradient in component values. It is very undesirable: it can be

very large and swamp out random mismatch, it can cause various circuit problems such as harmonic

distortion in A/D converters, while random mismatch is usually somewhat more benign in its impact

on higher level specs.

Systematic mismatch can be caused by processing gradients and inadequate layout. Follow the rules

of matching.

Imbalanced loads can look like a systematic mismatch: eg. The strobe signal in an edge triggered

regenerative latch can easily imbalance the circuit by 100mV! This is hard to distinguish from a

static offset in the test lab although it is a dynamic effect.

A good test of the symmetry of routing is a power supply rejection simulation on the back annotated

net list.

10.4 MATCHING CAPACITORS AND RESISTORS

To match caps and resistors, use unit cells and dummy edge devices

Fig 11.1



10.5 MATCHING TECHNIQUES

Goals of Good Analog Layout

Minimum parasitics

Low crosstalk

Less Area

Minimum substrate Noise

Good Device matching

10.6 SYMMETRY:

Fig 11.3

Consider matching two transistors: A and B (DASBD)

- Orientation mismatch develops due to diagonal shift in S/D implantation

- Tilted implant cause S/D to differ

- If devices are arranged in (DASBD), drain of left differs from drain of right

- A Small difference in Tran conductance

- mismatch worse at high voltage, as titled implant has string impact on hot carrier effect

- This problem is cancelled if they have equal chirality



CHAPTER 11

PHYSICAL VERIFICATION (DRC & LVS FLOW) &SAMPLE RUN

SETS FOR DRC & LVS

11.1 PHYSICAL VERIFICATION (DRC/LVS):

Physical verification is a process whereby an IC layout design is checked via EDA software

tools to see if it meets certain criteria. Verification involves DRC (Design rule check), LVS (Layout

versus schematic), ERC (Electrical Rule Check), and Antenna Checks.

Physical Verification Flow:

Fig 12.1

11.2 DESIGN RULE CHECK (DRC)

11.2.1 Design Rule Checking Software

The main objective of design rule checking (DRC) is to achieve a high overall yield and reliability

for the design. If design rules are violated the design may not be functional. To meet this goal of

improving die yields, DRC has evolved from simple measurement and Boolean checks, to more

involved rules that modify existing features, insert new features, and check the entire design for

process limitations such as layer density. A completed layout consists not only of the geometric

representation of the design, but also data that provides support for the manufacture of the design.

While design rule checks do not validate that the design will operate correctly, they are constructed

to verify that the structure meets the process constraints for a given design type and process

technology.

DRC software usually takes as input a layout in the GDSII standard format and a list of rules

specific to the semiconductor process chosen for fabrication. From these it produces a report of

design rule violations that the designer may or may not choose to correct. Carefully "stretching" or



waiving certain design rules is often used to increase performance and component density at the

expense of yield.

Some example of DRC‘s in IC design includes:

Active to active spacing

Well to well spacing

Minimum channel length of the transistor

Minimum metal width

Metal to metal spacing

Metal fill density (for processes using CMP)

ESD and I/O rules

11.2.2 Design Rule Sets

It is not usually necessary to create design rules sets from scratch. If you have a previous

design file that uses a set of rules similar to those you want to employ in your current design, you can

modify the rule set from the previous design.

In general, you must perform the following three steps to create or edit a design rule set:

1. Determine which rules must be specified. Fabrication services or foundries are typically able to

provide design rule sets.

2. Determine which generated layers, if any, will be needed to implement each rule in the set.

3. Enter the rules in the Setup Design Rules.

11.2.3 Specifying DRC Standard Design Rules

Select Tools > DRC Setup from the menu, highlight DRC Standard Rule Set in the rule set list,

then press the Edit button ( ) to open the Setup DRC Standard Rule Set dialog, which allows you to

modify the DRC standard design rules.



Fig 12.2

11.3 LAYOUT VERSUS SCHEMATIC (LVS)

The Layout Versus Schematic (LVS) is the class of electronic design automation (EDA) verification

software that determines whether a particular integrated circuit layout corresponds to the original

schematic or circuit diagram of the design.

Background

A successful Design rule check (DRC) ensures that the layout conforms to the rules

designed/required for faultless fabrication. However, it does not guarantee if it really represents the

circuit you desire to fabricate. This is where an LVS check is used.

11.3.1 LVS Check

LVS checking software recognizes the drawn shapes of the layout that represent the electrical

components of the circuit, as well as the connections between them. The software then compares

them with the schematic or circuit diagram.

11.3.2 LVS Checking involves following three steps:

1. Extraction: The software program takes a database file containing all the layers drawn to

represent the circuit during layout. It then runs the database through many logic operations to

determine the semiconductor components represented in the drawing by their layers of construction.

It then examines the various drawn metal layers and finds how each of these components connects to

others.



2. Reduction: During reduction the software combines the extracted components into series and

parallel combinations if possible and generates a netlist representation of the layout database.

3. Comparison: The extracted layout netlist is then compared to the netlist taken from the circuit

schematic. If the two netlists match, then the circuit passes the LVS check. At this point it is said to

be "LVS clean."

Fig 12.3

11.4 EXAMPLES OF LVS ERRORS

In most cases the layout will not pass LVS the first time requiring the layout engineer to examine the

LVS software's reports and make changes to the layout. Typical errors encountered during LVS

include:

1. Shorts: Two or more wires that should not be connected together have been and must be separated.

2. Opens: Wires or components that should be connected are left dangling or only partially

connected. These must be connected properly to fix this.

3. Component Mismatches: Components of an incorrect type have been used (e.g. a low Vt MOS

device instead of a standard Vt MOS device)

4. Missing Components: An expected component has been left out of the layout.

5. Property Errors: A component is the wrong size compared to the schematic.

In some cases of property errors, where it is not critical to performance, the designer may modify the

schematic to match the layout.



11.4.1 LVS: Extract Errors – Short

Same net named with different pin names

Example:

Fig 12.4

LVS: Extract Errors – Short (Contd.)

Two different nets shorting together.

Example - A and B are shorted being on the same net ―net1‖.

Fixing:

Two nets: n1 connected to Pin: A, n2 connected to Pin: B Accidentally got shorted, during routing.

Left is a problem, right is the fix.

Fig 12.5

A

A

B

A



11.4.2 LVS: Extract Errors – Open

Same net is routed in two different metal layers but not connected.

Example

Fig 12.6

This slide explains a text open error which occurs when there is no connectivity exists between a

single net routed in two different metal layers.

11.4.3 LVS: Compare Errors – Parameter Mismatch

Device parameters on schematic and layout are compared.

Example: Let us consider a transistor here, LVS checks are necessary parameters like width,

length, multiplication factor etc…

Fig 12.7

A



11.4.4 LVS: Compare Errors – Device/Net Mismatch

Fig 12.8

Here we are discussing about a Device mismatch and net mismatch error. In the schematic net 1 is

connected to pin A of nand2 and net 2 is connected to pin B of nand2, in the incorrect layout net 2 is

connected to pin A and net 1 is connected to pin B. which is fixed in on the right hand side layout.

This leads to device mismatch and net mismatch errors.

11.4.5 LVS: Compare Errors – Pin Errors

Fig 12.9

This slide explains an LVS pin error which occurs when pins on schematic and layout are not

matching. In the figure nand2 schematic has two pins namely a and b but layout of nand2 has only

pin a and pin b is missing which leads to a pin error.

LVS: Compare Errors – Malformed Devices



Fig 12.10

Here we are explaining malformed devices which are created accidentally when a poly crosses

diffusion. These devices are unintentional and should be removed from the design.

11.5 EXTRACT DEFINITION FILE FORMAT

The extract definition file contains a list of comments, connection statements, and device statements.

L-Edit is shipped with a directory containing a set of extract definition files that correspond to

various technology processes. You can modify these files as necessary to define additional

connections and devices for extraction.

11.5.1 Extract definition files must conform to the following restrictions:

Layer names are case-sensitive, and must match the case of layer names defined in the TDB

file.

The rest of the definition file is case-insensitive; upper and lower cases can be used

interchangeably.

Layer names cannot contain commas or semicolons and they cannot be longer than 40

characters.

Layer names cannot have leading or trailing spaces.

Pin names cannot contain commas, semicolons, or spaces, and they cannot be named

MODEL.

Model names cannot contain commas, semicolons, spaces, or closing parentheses.

for compatibility with existing extract definition files, the WIDTH keyword is ignored for all

devises except a GAASFET/MESFET.

IGNORE_SHORTS indicates that if the device has all of its pins connected to the same

node then it will be considered shorted and the device will be written to the extract net list file

as a comment.



CHAPTER 12

DAC

12.1 BASIC BLOCK DIAGRAM DIGITAL-TO-ANALOG CONVERTER:

Digital-to-analog converter chips transform information from digital to analog form. They convert

signals that have two defined states, on and off, into signals that have a theoretically infinite number

of states

Fig 13.1

8-bit R-2R Ladder Digital To Analog Converter (DAC) with Equal Currents Design and Layout

The project is an 8-bit digital-to-analog converter that utilizes a resister ladder network to

divide current with equal current sources, and an operational amplifier to sum these currents and

convert them into an output voltage. The use of an R-2R ladder architecture is very useful for binary-

weighted currents. However, the R-2R based converter is easy to implement and the resistance ratio

is independent of the number of bits the precision of the resistor is significant. Because the resistance

of the R-2R architecture must be so closely matched (as close as 0.01% for the LSB on an 8-bit

DAC) and the current ratio through the switches is still large the implementation of current sources is

needed. With equal current flow through all the switches the architecture will be slower but more

stable.

12.2 DAC APPLICATIONS

i) Modems convert digital computer data that consists of ones and zeroes into audio

frequency (AF) tones that can be transmitted over telephone lines.

ii) Most modern audio signals are stored in digital form (for example MP3s and CDs) and

in order to be heard through speakers they must be converted into an analog signal. DACs are

therefore found in CD Players, Digital Music Players, and PC Sound Cards.



iii) Specialist stand-alone DACs can also be found in high-end hi-fi systems. These normally

take the digital output of a CD Player (or dedicated transport) and convert the signal into a line-

level output that can then be fed into a pre- Amplifier stage.

iv) Similar digital-to-analog converters can be found in Digital speakers such as USB

speakers, and in Sound Cards.

v) Video signals from a digital source, such as a computer, must be converted to analog

form if they are to be displayed on an analog monitor.

vi) A video DAC is, however, incorporated in any Digital Video Player with analog outputs.

The DAC is usually integrated with some memory(RAM), which contains conversion tables for

gamma correction, contrast and brightness, to make a device called a RAMDAC.

12.3 R-2R LADDER DAC CIRCUIT DIAGRAM:

Objective

The objective of this project is to design an 8-bit R-2R digital-to-analog converter with current

sources in 130nm technology, TSMC and Checking for design rules check (DRC), and Layout vs.

Schematic (LVS).

Design

The basic principle of this type of R-2R DAC is to split the reference currents equally through the

switches. The current sources that were used were N-type transistors with a size of W/L = 5/1.5. The

current sources used a bias generator that produced 1.68V to allow ~80uA of current. The current

sources were necessary for the R-2R DAC to work properly due to the switches and the matching of

the resistors. The high poly 2 resistance (R) was equal to 4kW. The switches used a pass transistor

configuration and had a resistance value of approximately 500W with the size of W/Ln = 25/0.6 and

W/Lp = 50/0.6.



12.3.1 DAC Modules:

1. Inverter – to get compliment binary output

2. Pass Transistor Switch – it is for Bit selection based on its binary weight

3. Current Sources - to produce equal current flow through all the switches

4. Current Source Bias Generator - for current sources (without a resistor)

5. Opamp without Bias Generator - The operational amplifier used in the DAC has 3

stages (Differential – input stage, Common – source stage and an Output buffer).

6. Bias Generator - for the operational amplifier

7. R-2R D/A Convert - R/2R ladder networks provide a simple means to convert digital

information to an analog output



12.3.2 Schematic Diagram of DAC

Fig 13.3



12.4 INVERTER

Schematic diagram:

Fig 13.4

Inverter layout:

Fig 13.5



DRC Report:

Fig 13.6

12.5 PASS TRANSISTOR SWITCH

Schematic:

Fig 13.7



Layout:

Fig 13.8

DRC report:

Fig 13.9



12.6 CURRENT SOURCE BIAS GENERATOR

Schematic:

Fig 13.10

Layout:

Fig 13.11

DRC report:



Fig 13.12

12.7 OPAMP WITHOUT BIAS GENERATOR

Schematic:

Fig 13.13

Layout:

Block1



Fig 13.14

Block2

Fig 13.15



12.8 BIAS GENERATOR - FOR THE OPERATIONAL AMPLIFIER

Schematic:

Fig 13.16

Layout:

Fig 13.17



12.9 BASIC RESISTANCE:

Fig 13.18

12.10 CAPACITANCE BLOCK:

Fig 13.19



12.11 COMPLETE DAC MODULE:

Fig 13.20



12.12 DRC REPORT FOR COMPLETE MODULE:

With density errors:

Fig 13.21

Density errors cleared:

Fig 13.21



LVS report:

Fig 13.22

SUMMARY

The complete schematic diagram of R-2R ladder DAC is divided into sub modules and

layout is drawn for each and every module DRC and LVS are cleared for each module using

TANNER EDA Tool and TSMC 0.13um technology, then every module is clubbed together to get

final module, and now DRC and LVS is cleared for final DAC layout the given specifications.



APPENDIX-A

HANDS ON TANNER EDA TOOL

1.1 GATE LAYOUT:

Layout can be very time consuming

Design gates to fit together nicely

Build a library of standard cells

Standard cell design methodology

VDD and GND should abut (standard height)

Adjacent gates should satisfy design rules

nMOS at bottom and pMOS at top

All gates include well and substrate contacts

1.2 GUIDELINES FOR STANDARD CELL LAYOUTS

1) All The Standard cells should be of the same height.

2) Routing within the cell should be done either with POLY or metal1.

3) Cell Width should be multiples of via to line pitch

4) The power and ground straps should be designed so that they can be shared with cells placed

above/below.

5) The cell boundary should also be multiples of via to line pitch

6) The I/P and O/P pins should be placed evenly throughout the cell and can be placed at half of

the via to line pitch

1.3 IC LAYOUT EDITOR:

An Integrated circuit layout editor or IC layout editor is an electronic design automation

software tool that allows a user to digitize the shapes and patterns that form an integrated circuit.

Typically the view will include the components (usually as pcells), metal routing tracks,

Via(electronics) and electrical pins. Software of this type is similar to computer aided drafting

software, but is specialized for the task of integrated circuit layout.

1.4 THE TYPICAL FLOW FOR THE LAYOUT OF ANALOG CIRCUITS

MIGHT BE:

1. The layout engineer receives the schematic from the designer in electrical form

2. Either the tool or the layout engineer creates a physical view of the circuit including all of the

required components and electrical pins

3. The layout engineer positions the components to minimize both the area required and the

negative effects of layout parasitics upon the circuit performance and also to allow good

routing to neighboring cells



4. The layout engineer uses metal routing to connect all of the components, again taking care to

avoid unwanted layout parasitic on critical nodes

5. The layout engineer uses DRC and LVS checks to ensure that the circuit is both

manufacturable and functional

In some cases the layout engineer will request minor changes to the schematic to simplify the layout.

1.5 INTRODUCTION TO LAYOUT EDITING (TANNER L-EDIT)

Launching L-Edit:

To launch L-Edit, click the Start button on the Windows taskbar and navigate to the L-Edit

directory in the Tanner EDA directory. You can also double-click the L-Edit icon on your desktop,

which looks like this:

Setup Files:

Every L-Edit design file contains basic information such as a layer list, technology settings,

and module-specific options for SPR, DRC, and Extract. Collectively, this information is known as

the ―setup.‖ You can transfer this information between design files using File > Replace Setup and

File > Export Setup. See ―Application and Design Setup‖ on page 75 for further information. When

you launch L-Edit, the program attempts to locate the file ledit.tdb and read it for setup information.

If it does not find this file in the current directory, L-Edit searches the directory where the executable

is located. If L-Edit does not locate ledit.tdb, it displays a warning. With or without setup

information from ledit.tdb, when L-Edit launches it creates a new file (Layout1) with one cell, Cell0.

To start L-Edit with a specific TDB file, double-click the TDB file in Windows Explorer.

Command-Line Arguments:

L-Edit may be launched with or without command-line arguments. If a command-line TDB

File is not specified in the command line, L-Edit starts with a new empty layout file modeled after

ledit.tdb. To launch L-Edit with a command-line argument, click the Start button on the Windows

taskbar and select Run. Use the Browse button and navigate to the directory that contains ledit.exe.

Command line options can also be

put into a program shortcut by

editing the shortcut properties.

Elements of the User Interface:

The application interface is

displayed on the next page. Each

of the components is described in

the Following sections.

Title Bar and Menu Bar

The title bar indicates the active

file and cell. The menu bar, the

horizontal space at the top of the



screen, contains the titles of the L-Edit command menus.

File: Commands for creating, opening, saving, and printing files

Edit: Commands for copying, deleting, selecting, finding, and textual editing

View: Commands for expanding, contracting, and shifting the view

Draw: Commands for transforming design elements

Cell: Commands for creating, manipulating, and instancing cells

Setup: Commands for customizing setup parameters for the application, design, layers,

color palette, and tools

Tools: Commands for examining XrefCells, creating and clearing generated layers,

DRC, placing and routing the design, extracting a netlist, viewing a cross-section, and running L-

Edit macros

Window: Commands for displaying document windows

Help: Commands for accessing online user guides and general information about L-Edit

and Tanner EDA

Layer Palettes: L-Edit supports an unlimited number of technology layers. They can be

displayed using either of two layer ―palettes.‖ The Compact Layer Palette, a grid of icons that

replicate each layer‘s color and pattern, provides a quick way to select layers. The Layer Palette is

also used for layer selection, but provides additional features for layer display and manipulation.

Either or both palettes can be open at once, and can float or be docked. You can resize the palettes or

use the scroll bars to view layers not visible in the current display. Both can be filtered using a pull-

down category list to display just those layers that are just those Drawn, In Use, Generated or Special.

You can also select Filter then enter text in the entry field to limit display to layers that include the

exactly the characters entered, anywhere in the layer name.

Working with Files:

Files

A complete L-Edit design is composed of cells contained in a design file. You can open as many

design files simultaneously as your hardware allows. The name of the active file appears in the L-

Edit title bar.

Creating Files

Create new files by choosing File > New, which opens the New File dialog:



L-Edit will open a layout window or the Tanner text editor, depending upon the file type you have

selected. You can also drag and drop a text file into the layout window to open it. If you use the right

mouse button to drag and drop the file, you can open a text file as a specific type. L-Edit will prompt

you to indicate the document type and also show the expected type in a bold font.

Options include:

Setup Files

The list of predefined setup files will contain:

<empty>—this is a standard empty setup (this is the default setup with white background, single

layer and no DRC rules).

The list of currently loaded TDB files (displayed in bold face).

The list of TDB setup files found in the predefined setup directories. You can specify the TDB setup

path in the Setup Application dialog. When you create a new file, L-Edit will assign it a default name

(ex. Text or Spice), followed by a number, e.g., Text2 or Spice5, depending on the history of the

current session. When you first save the new file, you will be prompted to change the filename, if

needed.

TDB File Format

Tanner Database (TDB) is a proprietary, machine-readable format optimized for the Tanner

Tools environment. TDB files are saved with the .tdb filename extension. By default, the scrollable

list displays TDB files.Along with the design itself, a TDB file contains setup information including

layer rendering information, CIF and GDSII setup information, design rules, and L-Edit

configuration settings. Setup information can be read into L-Edit with File > Replace Setup.When a

file is saved, L-Edit automatically backs up previously-saved versions of the file with a .tdo

extension.



Application and Design Setup

Replacing the Setup

Every L-Edit design file contains basic information such as a layer list, technology settings, and

module-specific options for SPR, DRC, and Extract. Collectively, this information is known as the

―setup.‖

File > Replace Setup transfers setup information from a file (the source file) to the current file (the

destination file).Options include:

From file: Name of the TDB file whose setup is to be imported. Click Browse to navigate to an

existing file.

Layers: Imports layer setup from the specified file.

Replace deletes the layers in the destination file and replaces them with the layers from the

source file.

Merge adds the layers from the source file to the list of available layers in the destination file.

Source file layers not present in the destination file are appended to the layer list in the

destination file. If a layer in the source file has the same name as a layer in the destination file,

the position it has in the destination file is maintained.

Additional layer-specific setup options include:

CIF names

GDS II numbers

Wire settings



Technology Options include:

Maintain physical size—With this option, L-Edit checks all objects in all cells and unit-

specific parameters entered in other dialogs to determine if the layout will be truncated when

it is rescaled. L-Edit presents one warning for each cell and set of parameters if a truncation

will occur. If you answer yes to all the warnings, or if no truncation will occur, L-Edit

rescales the design. If you answer No to any of the warnings, L-Edit cancels the rescaling

operation.

Rescale—L-Edit rescales the design by applying technology scaling parameters in the source

file to objects in the destination file.

Draw Transfers the parameters entered in Setup Design—Drawing.

Palette Transfers the color parameters entered in Setup Colors.

Show/Hides Transfers the view settings for grid, origin, ports, and other objects.

Properties If checked, replaces the System and other parameters set in File > Info>Properties.

Selection Transfers the parameters entered in Setup Design—Selection.

Grid Transfers the parameters for the display grid and mouse snap grid.

Xref files If checked, replaces the TDB files that will be used as cross-reference

of library files, as set in Setup > Design—Xref files.

Modules Check the corresponding box to replace setup information for:

DRC rules

Extract

Cross-Section

SPR: Check the corresponding box to replace setup information for

Core setup (see SPR Core Setup on page 354)

Pad frame setup (see SPR Pad frame Setup on page 365)

Pad route setup (see SPR Pad Route Setup on page 369)

Place and Route configuration (see SPR Setup on page 351)

Uncheck All Deselects all options

Importing a Setup from Virtuoso

This import feature simplifies transitions of designs from the Cadence Virtuoso to the Tanner L-Edit

design environment. Importing a Virtuoso setup always creates a new L-Edit file. The display and

tech files are concatenated and read as one.

The Setup > Import Virtuoso® Setup command creates an L-Edit technology setup by reading a

Virtuoso technology file. Imported elements include palette colors, background color, grid colors,

layers (including rendering information, GDS layer number and GDS datatype) and manufacturing

grid. L-Edit elements that are missing from Virtuoso (such as user-defined rendering) are

automatically generated.



Display file Specifies rendering information (palette colors and stipple patterns.)

Tech file: Specifies technology information (layers, purposes, and bindings

between these and display data).

Display name: In Virtuoso, ―displays‖ are used to identify particular drawing styles, often optimized

for specific display devices (e.g., screen, plotter, printer). One of these displays must be selected to

import into L-Edit.

Create L-Edit layers from: L-Edit layers can be created from any of three sources:

Virtuoso tech Layers/tech Purposes—An L-Edit layer can be created or each pair of Virtuoso layer

/ purpose. A Virtuoso ―purpose‖ identifies an application of a given layer; for example, layer ―metal‖

can have two purposes: ―contact‖ and ―wire‖. Each layer-purpose pair has its own rendering

information, GDS number, etc.

Virtuoso Tech Layers (in Tech Display order): An L-Edit layer can be created for

Each Virtuoso layer. The renderin information is taken from the first packet bound to that layer,

for the particular display specified.

Virtuoso packets—Rendering information in Virtuoso (line styles, colors and weights, fill colors

and stipples) is grouped into ―packets‖. An L-Edit layer can be created for each Virtuoso packet.

Merging Layer Setups

When you merge layer setups, L-Edit adds source-file layers to the layer list in the destination file. If

the source file has layers not present in the destination file, L-Edit appends them to the destination-

file layer list. If the source file and destination file have a layer with the same name, the layer

maintains its position in the destination file‘s layer list.

For example, a source file contains layers A, B, and C (in that order), and a destination file contains

layers B, D, and E (in that order). After replacing, the destination file will contain layers A, B, and C.



After merging, the destination file will contain layers B, D, E, A, and C. (The destination file‘s

information on layer B is replaced with the source file‘s information on layer B.)

________________________________________________________________________

Note: Importing a layer setup also transfers a layer‘s lock status from the source file to the target file.

For example, if you lock Metal1 in the source file, it will be locked in the target file. Conversely, if

you lock Metal1 in the target file but unlock it in the source file, it will then be unlocked in the target

file after you replace the layer setup.

Color Parameters

You can display an L-Edit design file using 16, 32, 64, 128, or 256 colors in your palette. You use

the

Setup > Colors command to set the number of and RGB definition of your design colors.

Each color has two attributes, a unique identifying binary code and an RGB color definition. The

Setup

Colors dialog provides the following options:

Number of colors: Select the number of colors that will be available for defining layer colors.

Options are 16, 32, 64, 128, or 256 (True Color mode) colors.

Sort colors by: Select how colors will be sorted. This setting applies to both this dialog and the

Setup Layers dialog.

Options are:

Index: sorts by index number, which is the binary value of a color.

Number of bits: sorts by the number of bits used to define a color and then by index number if the

number of bits set are equal.

Hue: sorts by hue, then saturation, then luminosity, then index number.

Brightness: sorts by luminosity in descending order, then hue, then saturation, then index number.

(Left pane) Shows a sample of each defined color and the associated 4- to 8- bit binary code used to



assign a unique color index number to that color. The number of bits used in each color depends on

the number of colors available in the file (for example, 4 bits are used in a 16 color file).

Color (RGB): Displays the composition of each color as a function of its Red, Green, and Blue

values, which can range from 0 to 255. You can use the slider controls or type a number in the red,

green and blue colored boxes to modify a color.

Color Picker: Opens the standard Windows Color dialog that allows you to select and

define colors.

Application Parameters: To modify application-level settings in L-Edit, choose Setup >

Application. Application-level settings are divided into nine categories, which appear on separate

tabs. General, Keyboard, Mouse, Warnings, UPI, Rendering, Selection, Text Editor and Text Style.

Configuration Files: Application settings are saved in application configuration (.ini)

files. You specify configuration file options in the top portion of the

Setup Application dialog. Configuration files are ASCII files containing

application-wide setup information that can be edited and shared among multiple users. To load

settings from an existing file, enter the name of the file in the Workgroup or User field, or choose

from available files using the Browse

button next to the desired field. Click

Load to load the settings into L-Edit.

Workgroup and User Configuration

Files

L-Edit can load configuration

information from either a Workgroup or a User file. Workgroup files are intended to be shared by

multiple users; for example, they may contain key remapping sequences that will be used by many

users. User files are intended to contain preferences specific to a particular individual. Changes in the

Setup Application dialog can only be saved to User configuration files. Therefore, an INI file loaded

as a Workgroup file is protected from accidentally being changed. When both workgroup and user

files are specified in Setup Application, settings from the user file override settings in the workgroup

file. To create a workgroup configuration file, first save the desired settings in a user configuration

file. You can then copy the user configuration file to a new name to create a workgroup file.



BIBLIOGRAPHY

1. CMOS IC Layout Concepts, methodologies and tools-Dan Clein

Technical Contributor: Gregg Shimokura

2. Stick diagram fundamentals-John P.Uyemura.

3. The art of analog layouts-Allen Hastings

4. Principles of CMOS VLSI design- Neil weste.

5. T. E. Dillinger, VLSI Engineering, Englewood Cliffs, NJ: Prentice-Hall, Inc., 1988.

6. S.M. Sze, VLSI Technology, New York, NY: McGraw-Hill, 1983.

7. Dr. Paul D. Franzon, www.ece.ncsu.edu/erl/faculty/paulf.html

8. Sung Kang and Yusuf Leblebici, CMOS Digital Integrated Circuits, 3rd edition, McGraw-Hill,

2004

9.R. Jacob Baker, CMOS Circuit Design, Layout, and Simulation, 2nd edition, IEEE Press, 2005

10. Dan Clein, CMOS IC Layout: Concept, Methodologies and Tools, Newnes, 1999

11. Alan Hastings, Art of Analog Layout, 2nd edition, Prentice Hall, 2005

12. Alan Hastings, Art of Analog Layout, 2nd edition, Prentice Hall, 2005

13 http://www.end.utah.edu/browen/

14 http://ami.ac.uk/

15 http://www.epfl.eh/lsi2001/

d22 Layout Implementation of Digital to Analog

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