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Introduction
System-on-Chip
Pietro AndreaniDept. of Electrical and Information Technology
Lund University, Sweden
Overview
• Modern MOS processes• High-k + metal gate 45nm CMOS process from Intel
• Moore’s law
• Interconnects
P. Andreani – System-on-Chip Introduction 2
• International Technology Semiconductor Roadmap (ITRS)• more Moore and more than Moore
• Packaging
The march of materials
(potential)
P. Andreani – System-on-Chip Introduction 3
• CMOS is not simple any more• CMOS is not cheap any more (but, maybe/hopefully, cheaper?)
MOS with polysilicon gate
P. Andreani – System-on-Chip Introduction 4
• Depleted region in polysilicon gate decreased “on” current, increased “off” current
• SiO2 dielectric cannot be too thin, otherwise tunneling current through the gate becomes unacceptably large
This and most following slides from Intel documents
MOS with polysilicon gate - problems
P. Andreani – System-on-Chip Introduction 5
• SiON scaling running out of atoms!• Dielectric cannot be too thin, otherwise tunneling current through the gate
becomes unacceptably large
• Polysilicon depletion limits inversion
New HK+MG MOS device
P. Andreani – System-on-Chip Introduction 6
Advantages of HK+MG
P. Andreani – System-on-Chip Introduction 7
Polysilicon removed after annealing
P. Andreani – System-on-Chip Introduction 8
• A problem with metal gates is that they would melt during annealing (however, there is intense research to avoid the so-called “gate last” process)
Some process details
P. Andreani – System-on-Chip Introduction 9
• Hafnium-based high-k dielectric, dual-metal gate, strained silicon• High-k first, metal-gate last (metal gate deposition after high-T anneals)• Strained silicon process; transistor mask count same as 65nm• Gate leakage reduce 1000x for PMOS, 25x for NMOS
Strained silicon
P. Andreani – System-on-Chip Introduction 10
• Photos from 65nm CMOS • Strained silicon improves mobility of charge carriers
Device photo (45nm CMOS)
P. Andreani – System-on-Chip Introduction 11
• 35nm minimum gate length• 160nm contacted gate pitch• 20% Ge in SiGe
Comparison
P. Andreani – System-on-Chip Introduction 12
At an earlier stage (HK dielectric)
P. Andreani – System-on-Chip Introduction 13
From G. Moore, ISSCC ‘02
Device scaling – keeping Moore’s law alive and well
P. Andreani – System-on-Chip Introduction 14
• Contacted gate pitch of 160nm 0.7x scaling continues
Moore’s law – transistors per die
P. Andreani – System-on-Chip Introduction 15
From G. Moore, ISSCC ‘02
Minimum insulator thickness
P. Andreani – System-on-Chip Introduction 16
From G. Moore, ISSCC ‘02
Transistors shipped per year
P. Andreani – System-on-Chip Introduction 17
From G. Moore, ISSCC ‘02
Average transistor price by year
P. Andreani – System-on-Chip Introduction 18
From G. Moore, ISSCC ‘02
MIPS by computer generation
P. Andreani – System-on-Chip Introduction 19
From G. Moore, ISSCC ‘02
SRAM
P. Andreani – System-on-Chip Introduction 20
• SRAM density doubles every two years
Next Intel generations
P. Andreani – System-on-Chip Introduction 21
Interconnects
• Low-k ILD (organic inter-level dielectrics)
• CDO = carbon doped oxide
• Reduces capacitance
P. Andreani – System-on-Chip Introduction 22
• Reduces capacitance reduces delay increases speed
• M1-M3 pitches match MOS pitch
Metal 9 + PAD (no lead any more)
P. Andreani – System-on-Chip Introduction 23
• M9: ReDistribution layer (RDL) 7μm!!• Polymer ILD• Improved on-chip power distribution
Signal delay / integrity
• 10km of wiring crammed into a space smaller than a postage stamp• Signal lag not caused by transistors (they are very fast
nowadays) but to RC time constant in wirings, where C is the inter-wire capacitances
• This capacitance causes extra lag and possibly signal corruption• Better insulation between wires carbon-doped silicon dioxide
good, but nothing can beat vacuum!
P. Andreani – System-on-Chip Introduction 24
• Natural glass: k=4.2; fluorinated SiO2: k≈3.5; highly carbonated SiO2: k≈2.7; vacuum: k=1(minimum possible)
• Problem with vacuum: does not provide structural support; hardly compatible with standard chip production steps
• IMB makes use of a self-assembling two-dimensional copolymer, forming a mesh of 20nm cylindrical holes
• IBM: k≈1.9 10-15% improvement of RC time constant• Structural integrity is still an important issue
The ultimate inter-wire dielectric – nothing
P. Andreani – System-on-Chip Introduction 25
• IBM’s air-gap technology nanoscale holes into the insulation between copper wires in production in 2009
Functions per chip – Moore’s law
P. Andreani – System-on-Chip Introduction 26
International Technology Roadmap for Semiconductors, ITRS
Moore’s law (from 1970)
P. Andreani – System-on-Chip Introduction 27
Size reduction
P. Andreani – System-on-Chip Introduction 28
More Moore and more than Moore
P. Andreani – System-on-Chip Introduction 29
More Moore and more than Moore – II
• Scaling (more Moore)1. Geometrical scaling continued shrinking of horizontal/vertical
feature size2. Equivalent scaling new devices and/or new materials
P. Andreani – System-on-Chip Introduction 30
• Functional diversification (more than Moore)1. New devices/functionalities not necessarily scaling with Moore
provide added value to end customer2. Typically, non-digital functions such as RF communications, power
control, passive components, sensors, actuators, etc3. Migrate from board level to SiP or even SoC level
Future: tri-gate FET / FinFET?
P. Andreani – System-on-Chip Introduction 31
Packaging
P. Andreani – System-on-Chip Introduction 32
From ITRS
PoPs and PiPs
P. Andreani – System-on-Chip Introduction 33
Examples of stacked-die packages
P. Andreani – System-on-Chip Introduction 34
Wafer-level SiP with inter-chip vias
P. Andreani – System-on-Chip Introduction 35