8/14/2019 L1 Intro Fabrication
1/31
Lecture-1
GENERAL INTRODUCTION
and
FABRICATION OF MOSFET
Dr. Arti Noor,M. Tech Division, CDAC Noida.Email : [email protected]
14-9-2009
8/14/2019 L1 Intro Fabrication
2/31
Lecture-1
Course Outline:
Basic MOS Theory : Introduction, Basic MOS Model,MOS inverter, MOS Circuit Layout & Simulation.
Combinational MOS Logic Design : Static and DynamicMOS Design.
Sequential MOS Logic Design. Interconnect & Clock Distribution . BiCMOS Logic Circuits.
Details are given in Handout.LAB TOOLS Tanner Tools.Mentor Graphics Tools.
8/14/2019 L1 Intro Fabrication
3/31
Lecture-1
TEXT BOOKS:
1. Kang & Leblebigi CMOS Digital IC Circuit Analysis &Design- McGraw Hill, 2003.
2. Rabey, Digital Integrated Circuits Design, PearsonEducation, Second Edition, 2003.
References:
Weste and Eshraghian, Principles of CMOS VLSI design Addison-Wesley, 2002.
Additional reading from selected journals / papers.
8/14/2019 L1 Intro Fabrication
4/31
Lecture-1
Course Objectives:Students should be able to :
Derive basic analytical MOS circuit equations.Locate information not presented in class, in the library.Analyze circuits using both analytical and CAD tools.
Use a design flow to design a CMOS integrated circuit in a teamenvironment.Interpret a design specification.Design test benches that can prove that a design meet a
specification.Identify regions where circuit models are valid.
8/14/2019 L1 Intro Fabrication
5/31
Lecture-1
Course Objectives
For students to learn IC design usingstate-of-art design flows and CAD tools.
8/14/2019 L1 Intro Fabrication
6/31
Lecture-1
Lets get started
We will review (learn for first time?) MOSphysics (in detail).
Why MOSFETs? CMOS circuits dissipate power only when switching
(they do use power when not switching, but is muchless than other circuits).
This allows for more circuits to be placed on one die.
8/14/2019 L1 Intro Fabrication
7/31
Lecture-1
SIMPLIFIED VLSI DESIGN FLOW VIEW IN
THREE DOMAINS
8/14/2019 L1 Intro Fabrication
8/31
Lecture-1
Introduction
IC technologies :
NMOS PMOS CMOS SOI BiCMOS GaAs
8/14/2019 L1 Intro Fabrication
9/31
Lecture-1
Basic Fabrication Steps:
Wafer Processing. Mask making. Photolithography.
Oxidation. Diffusion. Etching. Poly-gate formation.
Metallization.
8/14/2019 L1 Intro Fabrication
10/31
Lecture-1
Basic Fabrication Steps: Wafer Processing : single crystal wafer, diameter
70 mm to 200 mm, thickness less than 1mm, front facepolished, scratch free mirror finish.
8/14/2019 L1 Intro Fabrication
11/31
Lecture-1
Basic Fabrication Steps:
Mask making : After complete design the drawing is broken into
subsequent IC processing steps. These steps are called mask levels.
Electron beam machine known as patterngenerator is used for mask making. The interface is CIF between layout and mask
machine.
Mask machine transfers design features directly onphotosensitive glass plate using CIF.
8/14/2019 L1 Intro Fabrication
12/31
Lecture-1
Basic Fabrication Steps:
Photolithography : The process used to transfer apattern on wafer is called lithography. The processhas 6 steps.
1. Photoresist Coating.2. Pre baking.
8/14/2019 L1 Intro Fabrication
13/31
Lecture-1
Basic Fabrication Steps:
3. Alignment and exposing.
8/14/2019 L1 Intro Fabrication
14/31
Lecture-1
Basic Fabrication Steps:
4. Development.5. Post baking.
8/14/2019 L1 Intro Fabrication
15/31
8/14/2019 L1 Intro Fabrication
16/31
Lecture-1
Basic Fabrication Steps:
Wafer after Removal of photoresist.
8/14/2019 L1 Intro Fabrication
17/31
Lecture-1
Basic Fabrication Steps:
Oxidation : The purpose of SiO 2 layer is
1. acts as component in MOS.2. acts as mask against diffusion.
3. used to isolate the devices4. provides electrical isolation in multilevelmetallization.
Several techniques : thermal oxidation, wetoxidation, CVD, Plasma oxidation.
LOCOS Oxidation for isolation.
8/14/2019 L1 Intro Fabrication
18/31
Lecture-1
Basic Fabrication Steps:
Diffusion : The purpose is to alter the type of conductivityby diffusing impurities.
Goal :
1. Control of impurity concentration.2. Uniformity.3. Reproducibility.
Two techniques : Furnace diffusion and IonImplantation.
8/14/2019 L1 Intro Fabrication
19/31
Lecture-1
Basic Fabrication Steps:
Metallization :
Is done to provide low resistance interconnects.
Common method is evaporation and sputtering. In high vacuum chamber the metal is deposited by
evaporation with subsequent condensation on
substrate target.
8/14/2019 L1 Intro Fabrication
20/31
Lecture-1
Basic NMOS Fabrication Steps:
Formation of SiO 2 and then photoresist coating
8/14/2019 L1 Intro Fabrication
21/31
Lecture-1
Basic NMOS Fabrication Steps:
Photo-mask and then etching of selected area.
8/14/2019 L1 Intro Fabrication
22/31
Lecture-1
Basic NMOS Fabrication Steps:
The wafer is then placed into an oxidation furnace andthin oxide (the gate oxide) is grown to cover the etchedregion
8/14/2019 L1 Intro Fabrication
23/31
Lecture-1
Basic NMOS Fabrication Steps:A layer of poly-crystalline silicon is deposited all over the
wafer.This layer is then patterned and etched to form the gate
of transistor .
8/14/2019 L1 Intro Fabrication
24/31
Lecture-1
Basic NMOS Fabrication Steps:
An n-type dopant is introduced into the opened regionsand diffused into the wafers.
8/14/2019 L1 Intro Fabrication
25/31
Lecture-1
Basic NMOS Fabrication Steps:
Oxide is deposited using Low Pressure Chemical Vapor Deposition (LPCVD) and is used for top coat protection.
8/14/2019 L1 Intro Fabrication
26/31
Lecture-1
Basic NMOS Fabrication Steps:A layer of aluminum is deposited all over the wafer and
patterned and etched to form the interconnecting layersand the connections to channel Metal OxideSemiconductor.
8/14/2019 L1 Intro Fabrication
27/31
Lecture-1
N-Well CMOS Fabrication Steps
8/14/2019 L1 Intro Fabrication
28/31
Lecture-1
N-Well CMOS Fabrication Steps (contd.)
8/14/2019 L1 Intro Fabrication
29/31
Lecture-1
N-Well CMOS Fabrication Steps (contd.)
8/14/2019 L1 Intro Fabrication
30/31
Lecture-1
N-Well CMOS Fabrication Steps (contd.)
8/14/2019 L1 Intro Fabrication
31/31
Lecture-1
Next Class Topic
Design Rules and MOS Transistor