Lab 1: To generate layout for CMOS
Inverter circuit and simulate it for
verification.
VLSI Lab
VLSI
LABORATORY
FRONT END
DESIGN
(CAD)
BACK END
DESIGN
(CAD)
TECHNOLOGY
(TCAD)
A complete VLSI lab set up should contain
Proper hardware
 Proper software
 Foundry or link up with some fab lab
 Test facility
 Purpose

DESIGN STEPS
•
•
•
•
•
•
SCHEMATIC
LAYOUT DESIGN
DRC
LAYOUT Vs SCHEMATIC
PARASITIC EXTRACTION
POST LAYOUT SIMULTION
List of Experiments
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
To generate layout for CMOS Inverter circuit and simulate it for verification.
To prepare layout for given logic function and verify it with simulations.
Introduction to programmable devices (FPGA, CPLD), Hardware Description
Language (VHDL), and the use programming tool.
Implementation of basic logic gates and its testing.
Implementation of adder circuits and its testing.
Implementation of J-K and D Flip Flops and its testing.
Implementation 4 to 1 multiplexer and its testing.
Implementation of 3 to 8 decoder and its testing.
Implementation of sequential adder and its testing.
Implementation of BCD counter and its testing.
Simulation of CMOS Inverter using SPICE for transfer characteristic.
Simulation and verification of two input CMOS NOR gate using SPICE.
Introduction to Block Diagram Mathod
Design of digital Logic using block diagram.
Project
• Mini Project: VHDL/Verilog based mini project
with emphasis on design and implementation
into the group of maximum 3 students.
Design Abstraction Levels
SYSTEM
MODULE
+
GATE
CIRCUIT
DEVICE
G
S
n+
D
n+
Microwind
• Microwind is a tool for designing and
simulating circuits at layout level. The tool
features full editing facilities (copy, cut, past,
duplicate, move), various views (MOS
characteristics, 2D cross section, 3D process
viewer), and an analog simulator
Tools from Microwind
•
•
•
•
•
•
•
•
Microwind
DSCH
Microwind3 Editor
Microwind 2D viewer
Microwind 3D viewer
Microwind analog simulator
Microwind tutorial on MOS devices
View of Silicon Atoms
Getting Microwind
• Go to the website
http://www.microwind.net/document
• Download the freeware version of the
microwind
• Unzip the files in a Folder
Microwind Downloads
INTRODUCTION THE TOOL
User-friendly and intuitive
design tool for educational
use.
Editing icons
The student draws the masks
of the circuit layout and
performs analog simulation
One dot on the
grid is 5
lambda, or
0.175 µm
The tool displays the layout in
2D, static 3D and animated 3D
Layout
library
2D, 3D views
Access to
simulation
Simulation
properties
Editing window
Palette of layers
Active technology
Ion current
List of model
parameters
for BSIM4
Threshold voltage effect
Voltage
cursors
Memory effect due to
source capacitance
Our Approach
MOS DEVICE
Traditional teaching : in-depth
explanation of the potentials,
fields, threshold voltage, and
eventually the expression of
the current Ids
Our approach : step-by-step
illustration of the most
important relationships
between layout and
1.
2.
3.
4.
1.
2.
performance.
Design of the MOS
I/V Simulation
2D view
Time domain analysis
3.
4.
Feature Size
• Chips are specified with set of masks
• Minimum dimensions of masks determine transistor
size (and hence speed, cost, and power)
• Feature size f = distance between source and drain
• Set by minimum width of polysilicon
• Feature size improves 30% every 3 years or so
• Normalize for feature size when describing design
Rules
• E.g. λ = 0.090 μm in 0.180 μm process
Layout design rules:
For
complex processes, it becomes difficult to
understand the intricacies of the fabrication process
and interpret different photo masks.
They act as interface between the circuit designer
and the process engineer.
Microwind Environment
Menu Command
One dot on the grid is
5 lambda or 0.30 µm
Editing Icons
Access to
Simulation
Layout Library
2D 3D Views
Simulation Properties
Palette of Layers
Work Area
Active Layers
Current Technology
Design Rules
N- Well
r101
r102
r110
Minimum width
Between wells
Minimum well Area
r 101
N - Well
r 102
12λ
12 λ
144 λ2
r201
Minimum N+ and P+ diffusion width 4λ
r 201
P+ Diff
r 201
N+ Diff
N - Well
r202
Between two P+ and N+ diffusions
r 202
P+ Diff
N - Well
r 202
N+ Diff
4λ
r203
Extra N-well after P+ diffusion
r 203
P+ Diff
r 203
N - Well
N+ Diff
6λ
r204
Between N+ diffusion and n-well
P+ Diff
N - Well
r 204
N+ Diff
6λ
r210
Minimum diffusion area
r 210
P+ Diff
r 210
N+ Diff
N - Well
16λ2
r301
Polysilicon Width
2λ
Polysilicon
r 301
P+ Diff
N - Well
Polysilicon
r 301
N+ Diff
r302
Polysilicon gate on Diffusion
Polysilicon
r 302
P+ Diff
N - Well
Polysilicon
r 302
N+ Diff
2λ
r307
Extra Polysilicon surrounding Diffusion 3λ
Polysilicon
r 307
P+ Diff
r 307
N - Well
Polysilicon
r 307
N+ Diff
r 307
r304
Between two Polysilicon boxes
Polysilicon
r 304
P+ Diff
N - Well
Polysilicon
r 304
N+ Diff
3λ
r307
Diffusion after Polysilicon
Polysilicon
r 307
r 307
P+ Diff
N - Well
Polysilicon
r 307
r 307
N+ Diff
4λ
r401
Contact width 2λ
Contact
r 401
Polysilicon Contact
Metal/Polysilicon Contact
r404
Extra Poly surrounding contact
Contact
r 404
Polysilicon Contact
Metal/Polysilicon Contact
r 404
1λ
r405
Extra metal surrounding contact
Contact
Polysilicon Contact
Metal/Polysilicon Contact
r 405
r 405
1λ
r403
Extra diffusion surrounding contact 1λ
r 403
Polysilicon
P+ Diff
N - Well
r 403
Polysilicon
N+ Diff
r501
Between two Metals 4λ
Metal 1
Metal 4
r 501
Metal 2
Metal 5
r 501
Metal 3
Metal 6
r510
Metal 1
Metal 2
Minimum Metal area 16λ2
r 510
r 510
r 510
r 510
Metal 3
Metal 4
Metal 5
Metal 6
r 510
r 510
Step 1: Select Foundary
Step 2: Select Foundary
Step 3: n+ Diffussion
Step 4: Polysilicon
Step 5: n+diff and Metal Contact
• This Completes nMOS design
• Now go for pMOS Design, and the first need is
to construct N Well
Step 6: Create N Well
Step 6: p+ Diffusion
Step 7: Polysilicon
Step 8: Contacts
Final Connections
• pMOS Completed
• Now Interconnection of pMOS and nMOS to
complete inverter
• Connect Source of pMOS to VDD and Source of
nMOS to VSS.
• Short the Drain of both pMOS and nMOS.
INVERTER: Complete Design
Check DRC
Assign Source
• Assign Signal (Clock) to Gate Terminal
• Add Visible node at Output
Inverter with Source
Run Simulation
VTC Characteristics
Thanks
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