Ch.3 Overview of
Standard Cell Design
TAIST ICTES Program
VLSI Design Methodology
Hiroaki Kunieda
Tokyo Institute of Technology
4.1 Design Style
Design Method
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Standard Design --------- Design by maker’s spec.
Full Custom Design ------ Design of all masks by customer’s spec.
 Manual Design
 Cell-Based Design
 Custom Cell/ Full Custom Design
 Standard Cell Design
Semi Custom Design ----- Design of routing wire & logic functions
by customer’s spec.
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Gate Array
FPGA Design
Standard Cell Design
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Design Using Standard Cell, pre-design by professionals.
Cells includes Verilog, Circuit, Layout Information for
NAND, NOR, D-FF
Logic Design and Layout Design done by CAD.
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Logic Design --- by use of Cells with specified delays
Layout Design – by use of Cells
Generated Data is mainly interconnection wires.
List of Standard Cells
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Inverter
Inverting Buffer
Non-inverting Buffer
Tri-state Non-inverting Buffer
AND 2, 3, 4 inputs
NAND 2,3,4 inputs
OR 2, 3, 4 inputs
NOR 2,3,4 inputs
XNOR 2,3 inputs
AND-OR
AND-OR-Inverter
OR-AND
OR-AND-Inverter
Multiplexer 2 to 1
Multiplexer 4 to 1
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Decoder 2 to 4
Half Adder 1bit
Full Adder 1bit
Pos Edge DFF
Neg Edge DFF
Scan Pos Edge DFF
Scan Neg Edge DFF
RS NAND Latch
High-Active
Clock Gating Latch
Non-inverting Delay line
Pass Gate
Bidirectional Switch
Hold 0/1 Isolation Cell
Standard Cell Design
Logic gates, latches,
flip-flops, or larger logic
Routing
channels
Layout
Place & Rout
Standard Cell Library
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Circuit description at RTL level
Layout description in GDSII format
TLF Format Data
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Logical information
Transistor and interconnect parastics
Spice netlist
Power information
Process, temperature and supply voltage
4.2 Cell
Library Design Flow I
Cell Information
Technology information
I/O delay paths
Timing check values
Interconnect delays
Layout Design
Mask Data
GDSII
Abstract Generator
Library Data
LEF
Extraction
Circuit Data
Netlist
Analog Environment
Circuit Data
TLF
Library Design Flow II
Physical Layout (gdsII, Virtuoso Layout Editor)
Should follow specific design standards eg. constant height, offsets etc.
Logical View (verilog description or TLF)
Verilog is required for dynamic simulation. Place and route tools usually can
use TLF. Verilog description should preferably support back annotation of
timing information.
Abstract View (Cadence Abstract Generator, LEF)
LEF: Contains information about each cell as well as technology information
Timing, power and parasitics (TLF)
Transistor and interconnect parasitics are extracted using Cadence or other
extraction tools (SPACE). Spice or Spectre netlist is generated and detailed
timing simulations are performed. Power information can also be generated
during these simulations. Data is formatted into a TLF file including process,
temperature and supply voltage variations.
Library Exchange Format (LEF)
An ASCII data format, used to describe a standard cell library includes
the design rules for routing and the Abstract of the cells, no information
about the
internal netlist of the cells
1. Technology: layer, design rules, via definitions, metal capacitance
a. type: Layer type can be routing, cut (contact), masterslice (poly,
active), overlap.
b. width/pitch/spacing rules
c. direction
d. resistance and capacitance per unit square
e. antenna Factor
2. Site: Site extension
３．Macros: cell descriptions, cell dimensions, layout of pins and
blockages, capacitances.
Timing Library Format (TLF)
TLF is an ASCII representation of the timing and power parameters associated
with any cell in a particular semiconductor technology. The timing and power
parameters are obtained by simulating the cells under a variety of
conditions and the data is represented in the TLF format、
The TLF file contains timing models and data to calculate
1. I/O delay paths
2. Timing check values
3. Interconnect delays
Standard Cell I
Standard Cell II
Layout
Cell Design Flow
VHDL Model
Synopsys Design Compiler
VHDL -> Verilog
Conversion
Verilog Model
Cadence Design Planner
Standard Cell Placement
DEF File
Cadence Silicon Ensemble Standard Cell Routing
DEF File
Cadence ICFB
Export to Other Formats,
SPICE Verification
Verilog Model
Modelsim
Verilog Verification
Layout Condition
parameter
Symbol
value
figure
Cell height
H
36λ
900 nm
Power rail width
W1
2λ
50 nm
Vertical grid
W2
4λ
100 nm
Horizontal gird
W3
4λ
100 nm
Nwell height
W4
20λ+α
525 nm
45 nm Process (λ=25nm, Minimum wire width=2λ)
DC Characteristic
Low
slope -1
VOHMIN
VOHMIN
High
slope -1
VOLMAX
VOLMAX
VILMAX VIHMIN
7/31/2001
WLT
Propagation Delay with loads
4.2 LSI Design Procedure
Logic Design
RTL
RTL Simulation
Logic Synthesis
Synthesis
Netlist
Functional Verification
Scan Path Design
Functional Verification
Scan
Netlist
Timing Analysis
Layout Design
Netlist
Layout Design
Functional Verification
ATPG
Test
Pattern
Layout
Netlist
Gate Level Simulatior
Mask Data
DRC/LVS