ch.3 overview of standard cell design

Ch.3 Overview of Standard Cell Design

TAIST ICTES ProgramVLSI Design Methodology

Hiroaki Kunieda

Tokyo Institute of Technology

4.1 Design Style

Design Method

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.

Gate Array FPGA Design

Standard Cell Design

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. 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 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

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 DesignLogic gates, latches, flip-flops, or larger logic

Routingchannels

Layout

Place & Rout

Standard Cell Library

Circuit description at RTL level Layout description in GDSII format TLF Format Data

Logical information Transistor and interconnect parastics Spice netlist Power information Process, temperature and supply

voltage

4.2 Cell

Library Design Flow I

Layout DesignMask Data

GDSII

Abstract Generator

Extraction

Analog Environment

Library DataLEF

Circuit DataNetlist

Circuit DataTLF

I/O delay pathsTiming check valuesInterconnect delays

Cell InformationTechnology information

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 theinternal netlist of the cells

1.Technology: layer, design rules, via definitions, metal capacitancea. type: Layer type can be routing, cut (contact), masterslice (poly,

active), overlap.b. width/pitch/spacing rulesc. directiond. resistance and capacitance per unit squaree. antenna Factor

2. Site: Site extension３． 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 ofconditions 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

Synopsys Design Compiler

Cadence Design Planner

Cadence Silicon Ensemble

Cadence ICFB

Modelsim

VHDL Model

Verilog Model

DEF File

DEF File

Verilog Model

VHDL -> VerilogConversion

Standard Cell Placement

Standard Cell Routing

Export to Other Formats,SPICE Verification

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)

7/31/2001 WLT

DC Characteristic

slope -1

slope -1

VOHMIN

VOLMAX

VIHMINVILMAX

Low

VOHMIN

High

VOLMAX

Propagation Delay with loads

4.2 LSI Design Procedure

Logic Design

Functional Verification

Logic Synthesis

Scan Path Design

RTL SimulationRTL

Synthesis Netlist

Scan Netlist Timing Analysis

Functional Verification

Layout Design

Gate Level Simulatior

Layout Design

Netlist

Mask Data

Layout Netlist

DRC/LVS

Functional Verification

ATPG

TestPattern