1. VLSI Overview

Hiroaki Kunieda

Dept. of Communications and Computer Engineering

Tokyo Institute of Technology

2

Outline

1. What is VLSI ?2. Classification3. Current Industry4. Design Hierarchy

1.1 VLSI

1. What is VLSI ?

Circuit System implemented on the surface of semiconductor, consisting of

Transistors (MOS or bipolar tr.) connecting wires

One chip consists of 10 Million Gates or 40 Million Transistors in one circuit.

Performance is decided not only by Circuit configuration Placement of transistors and connection schemes of connecting wires

SoC (System_on_Chip) Example

SoC layout

process 0.18um CMOS/6M1P

package 360 TFBGA

Power supply

3.3V (I/O), 1.8V(core)

RISC speed

200MHz

SRAM 32KB

ROM 64KB

SoC die size

5mm x 5mm

Soc gate count

1400K

Manufacturing on Wafer

A series of identical chips are patterned onto the Wafer.

Some space is reserved fortest circuit structures.

Wafer

1) Put tubs into wafer.2) Form an oxide

covering on wafer and the polysilicon wires.

3) Diffusion (wires) (polysilicon masks the formation of diffusion wires.=self-aligned)

4) Metal connections are made with filling cuts (via) to make connections after another oxide layer is deposited.

Example of Process

Wiring Processes

Example of Complex Layout

1.2 Classification

Manufacture

1.Monolithic LSI Made of one semiconductor

　 1.1 Silicon LSI Silicon is used as substrate.

　　　 1.1.1 MOS LSI MOS technology such as MOS transistors are employed.l

　　　　 1.1.1.1 　　CMOS LSI

nMOS and pMOS are used to reduce power consumption.

　　　　 1.1.1.2 NMOS LSI

nMOS (Enhancement and Depletion Types) are used for smaller area.

　　　 1.1.2 Bipolar LSI　

High speed is achieved, but complicated fabrication process, suitable for Analog LSI.

1.2 GaAs LSI2. Hybrid LSI

Semiconductor is used for high frequency use.Semiconductor chip and other components on thin film substrate.

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

Structure of LSI

Sorce DrainSource Drain

Wire

Silicon Substrate (n)

gate gate

Wire Wire Wire

P-Well pMOS ｎ MOS

1.3 Semiconductor Industry

Size of Industry (2006)

Semiconductor28 B$

MicroprocessorDRAM, flashROM

SoCAnalog, Discrete

Automobile　　 700 B$

Digital Consumer Electronics　　 350 B$　　　 PC　　 3 ２ 0 B$

Cellular Phone

140 B$

Growth Forecast

0 10 20 30 40 50 B$ Market

20

15

10

5

0

Growth Rate (%)

■specific logic

■MPU

■Analog

■DRAM■MCU■DSP

■NAND FlashROM■sensor

Moore’s Law and Intel microprocessors

microprocessor Date of introduction

#transistors Feature size (microns)

80286 1982.02 134,000 1.5

80386 1985.10 275,000 1.5

80486 1989.04 1,200,000 1.0

Pentium 1993.03 3,100,000 0.8

Pentium pro 1995.11 5,500,000 0.6

Pentium II 1997 9,500,000 0.25

Pentium III 2001 42,000,000 0.18

Dual Core 2008 0.065

The transistor counts would double every 18 months.

1.4 Design Hierarchy

Design Partitioning

• Architecture: User.s perspective, what does it do?• Instruction set, registers• MIPS, x86, Alpha, PIC, ARM, .

• Micro architecture• Single cycle, multcycle, pipelined, superscalar?

• Logic: how are functional blocks constructed• Ripple carry, carry lookahead, carry select adders

• Circuit: how are transistors used•Complementary CMOS, pass transistors, domino

• Physical: chip layout•Datapaths, memories, random logic

Microprocessor

DRAM (Main Memory)

ＣＰＵ

ExecutionUnit

registersControl Unit

① fetch instruction from main memory and send it to control unit

② control unit gets instruction and control execution units and registers to execute command of instructions.

③ Data are manipulated according to commands① send data from registers (source) to execution

units② execution has been performed by execution

units③ results is sent to register (destination)

Micro operations• Micro operations are performed by one clock corresponding to register transfer logic.• Processor works according to instructions (machine codes), which are a sequence of micro operations.•As an example, ADD instruction is performed as 1. ADD instruction is transferred from memory to inside. 2. the data is sent to Instruction Register. 3. the instruction is decoded and its information is sent to control execution. 4. the required data for addition is transferred from specified register to execution units such as ALU. 5. ALU executes addition. 6. the result is sent to the destination register.

ＲＴＬ

A B

S

Register B

Register A

Register Cclock

Load_A Load_B

Load_C

ALU (Arithmetic and Logic Units)

A B

S

A 　００１１　　　３B 　１０１０　　１０Ｓ　１１０１　　１３

＋）

ALU performs arithmetic and logic operationsfor 2 input data as A and B and to producethe result S.Operations are specified by control signals.

1 bit Adder

D

D

D

ab

0

head

carry_out

sum

head_out

1

0

Master-Slave Flip Flop

rst

clk

~clk

clk

~clkclk

~clk

clk

~clkD Q

Clocked Inverter

clk

~clk

clk

~clk

IN IN OUT

Operation of Transister

High Voltage Input Low Voltage Input

Switch ON Switch OFF

Layout Pattern of LSI

Silicon Substrate

Gate

wiringwiring

Gate

Ｄｅｓｉｇｎ　Ｍｅｔｒｉｃｓ

Cost (chip area) Reliability (design margin Scalability (expansion to larger system) Speed (delay, operating frequency) Power dissipation (Heat problem, battery Drive) Energy to perform a function