Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTR week2-1 Lecture 4 Transistor as...
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Transcript of Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTR week2-1 Lecture 4 Transistor as...
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-1
Lecture 4
Transistor as Switch
Jan. 13 2003
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-2
Topics
Transistor structures. Transistor as a switch
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-3
Transistor structure
n-type transistor:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-4
The Nobel Prize in Physics 1956
William Bradford Shockley – Semiconductor Laboratory of Beckman
Instruments, Inc. Mountain View, CA, USA
John Bardeen – University of Illinois Urbana, IL, USA
Walter Houser Brattain – Bell Telephone Laboratories Murray Hill, NJ,
USA
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-7
Transistor
Digital: switch Analog: many characteristics
Example: inverter– P transistor + N transistor == one inverter
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-9
Inverter layout
(tubs notshown)a out
+
transistors
GND
VDD
a out
tub ties
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-10
Example 1
+
ba
out
Write the truth Table of this circuit?
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-11
NAND layout
+
ba
out
b
a
out
VDD
GND
tubties
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-12
Example 2
+
b
a
out
Write the truth Table of this circuit?
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-14
NOR layout
b
a
out
a
b
out
VDD
GND
tub ties
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-15
Difference of digital and analog
Digital: switch– High level
Analog: characteristics of transistor – Low level
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-16
Example 3
Transmission gate:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-17
Lecture 5
Transistor Fabrication Process
Jan. 15 2003
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-18
Topics
Transistor structure (switch) Basic fabrication steps.
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-19
Transistor structure
n-type transistor:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-20
Fabrication services
Educational services:– U.S.: MOSIS– EC: EuroPractice– Taiwan: CIC– Japan: VDEC
Fab companies: mainly South Asia
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-21
Fabrication processes
IC built on silicon substrate:– some structures diffused into substrate;– other structures built on top of substrate.
Substrate regions are doped with n-type and p-type impurities. (n+ = heavily doped)
Wires made of polycrystalline silicon (poly), multiple layers of aluminum (metal).
Silicon dioxide (SiO2) is insulator.
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-22
Simple cross section
substraten+ n+p+
substrate
metal1
poly
SiO2
metal2
metal3
transistor via
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-23
What is
N and P
Substrate Poly Well (tub) Metal Via
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-24
Photolithography
Mask patterns are put on wafer using photo-sensitive material:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-25
Process steps
First place tubs to provide properly-doped substrate for n-type, p-type transistors:
p-tub p-tub
substrate
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-26
Process steps, cont’d.
Pattern polysilicon before diffusion regions:
p-tub p-tub
poly polygate oxide
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-27
Process steps, cont’d
Add diffusions, performing self-masking:
p-tub p-tub
poly poly
n+n+ p+ p+
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-28
Process steps, cont’d
Start adding metal layers:
p-tub p-tub
poly poly
n+n+ p+ p+
metal 1 metal 1
vias
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-29
Transistor structure
n-type transistor:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-30
Question
How many layers? Aluminum or copper? Technology is P-MOS or N-MOS? What is the purpose of silicon?
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-31
A complete fabrication process
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-32
Transistor structure (cont’d)
n-type transistor:
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-33
Questions (cont’d)
Order of Poly !!!– Self-aligned
What is the carrier for N-transistor and P-transistor?
Complete inverter ? – Need metals and vias
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-34
0.25 micron transistor (Bell Labs)
poly
silicide
source/drain
gate oxide
Modern VLSI Design 3e: Chapter 2 Partly from 2002 Prentice Hall PTRweek2-35
Review
N transistor P transistor