ME310

Manufacturing Processes

Rahul Panat

School of Mechanical and Materials Engineering

Washington State University

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HW-1 REVIEW OF SELECT QUESTIONS

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HW-1 REVIEW OF SELECT QUESTIONS

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Manufacturing of Microelectronics

and MEMS Devices

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Ack: Prof. McCloy for some material

Why study this topic?• Electronic devices have revolutionized our world!

BACKGROUND

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Google Contact Lens Apple Watch Intel-FossilBracelet

Conceptual

Core Material

(woven glass

composite)

Cu Layers

(Patterned)

Dielectric Film

Solder Resist

PTH

Filling material

Highly Complicated Layered Structure

Patterned Cu Dielectric

Thick Core

Bump(lead free)

Vias connecting Cu layers

Vias

Plated through holes in core Solder resist and bumping

LENGTH SCALES IN ELECTRONIC

DEVICES

Length scales drive specialized manufacturing methods

Flexible Boards with components* (100um~10mm)

*Source: Teardown.com

Google Glass

Processor**

(10s nm ~ 100um)

**Intel public information

Intel’s 32nm Si **

(10s nm ~ 10um)PCB (10um ~ 100um)

LENGTH SCALE DRIVEN MANUFACTURING

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Intel lithography now at 14um in HVMAnd 11 nm and below in research

Needs cleanrooms!

• Transistor discovered in Bell labs enabling modern

computing revolution

• Vacuum tubes used in computers – limiting the number of

circuits in the computer; highly bulky

• Solution: Jack Kilby patented first IC design and showed

first prototype; Bob Noyce (Intel founder) patented Al

metallization connect the ICs

• Microelectronic manufacturing as a separate area emerged

from the miniaturization started by Kilby/Noyce

BRIEF HISTORY

Jack Kilby, Texas Instruments, “Miniaturized electronic circuits”, U.S. Patent US3138743 A Robert Noyce, Intel Corporation, “Semiconductor device”, U.S. Patent 2,981,877

Bob Noyce

Jack Kilby

• Miniaturization of circuits continues per the prediction by Intel’s Moore

(Moore’s Law) – “With unit cost falling as the number of components per

circuit rises, by 1975 economics may dictate squeezing as many as 65 000

components on a single silicon chip.”…………………….well….a chip with

3.1 billion components* was released in 2012 by Intel……..

IC MINIATURIZATION

Major area of manufacturing research in electronics due to the massive (exponential)

pace of miniaturization!

SILICON

• Why Si

– Cheap

– SiO2, used for isolation and passivation and can be reliably and easily formed to

form the basis for metal oxide semiconductor (MOS) devices

• Doping required for to make Si a semiconductor

– N-type dopant – Phosphorous (group IV)

– P-type dopant – Boron (group III)

SILICON WAFER

Video Link

SiO2 + C95-98% pure polycrystalline Si

Trichlorisilane ECG

• Making electronic grade silicon

• Crystal growth by Czochralski (CZ) method

High TH2 atm

Heat

WAFER PROCESSING

CLEANING

CLEANING

Wafers in a Chemical Bath

Total Time: >1 hour

Cross-contamination due to close spacing between wafers

● >1 hour process: long chemical

exposure causes undesired loss

of silicon and oxide

● Long cycle time and high work-

in-process

● Large footprint

● 30 year old technology

PHOTOLITHOGRAPHY

● Masking● Projection

system● Photoresist

● Considerations● Feature size● Wavelength

TYPICAL RESIST PROCESSES

HMDS: hexamethyldisilzane

OXIDATION

OXIDATION

DIFFUSION AND ION IMPLANTATION

DIFFUSION AND ION IMPLANTATION

Other types of PVD used in research• Molecular beam epitaxy (MBE)• Pulsed laser deposition (PLD)• Atomic layer deposition (ALD)

Types of CVD• Atmospheric pressure CVD (APCVD)• Low pressure CVD (LPCVD)• Plasma enhanced CVD (PECVD)• Hybrid physical-chemical VD (HPCVD)

DIFFERENCE BETWEEN PVD AND CVD METHODS: chemical decomposition of precursor gas (CVD) versus vaporization of solid source (PVD)

CVD

PVD

PVD: Sputtering

DEPOSITION

ETCHING

ETCHING PROCESSES

ETCHING PROCESSES

WET vs PLASMA ETCHING

CHEMICAL vs PHYSICAL ETCHING

ETCHING ISSUES

BACKEND: DIELECTRICS AND

INTERCONNECTS

PACKAGE TYPES

LeadframeStacked Chip Scale Package

FC-CSPFlip Chip

www.emeraldinsight.com computing-dictionary.thefreedictionary.com

CSP: Chip Scale Package

FLIP CHIP PACKAGE: MICROPROCESSOR

First Level InterconnectPassives

Substrate (fiber reinforced polymer with metal traces connecting die to second level interconnect)

die

Motherboard (containing chipsets, power supply, Signal I/O connectivity and other peripherals)

die

substrate

substrate

PCB board

solder

solder

Underfill (polymer)

Second Level

Interconnect

Die Bump

Si: ~3ppm/K

Package: ~17ppm/K

Schematic Ack Dr. Hill

LAYERED COMPOSITE

Core Material

(woven glass

composite)

Cu Layers(Patterned)

Dielectric Film

Solder Resist

PTH Filling material

Highly Complicated Layered Structure Patterned Cu Dielectric Thick Core

Bump(lead free)

Vias connecting Cu layers

Vias Plated through holes in core Solder resist and bumping

STACKED CSP* PACKAGE: MEMORY

5 die stacked memory package(Molding compound removed – isometric view)

Multiple dies stacked one above the other Chip scale package (Intel makes NAND memory) Thinning of the wafer is required

Stacked Dies

Molding Compound

Gold Wires(~20um Ø)

Substrate

*CSP: Chip Scale Package

FLIP CHIP ASSEMBLY

Substrate

C4 bumps LSCs

Application of flux

Substrate

Die

Die Placement

Substrate

FLI joint

formation

Capacitors

(land side)

Die

Flux evaporation, reflow

and joint formation

Application of solder paste

Capacitor

Soldered

joint

STACKED CSP ASSEMBLY

Backgrinding/cutting wafer into individual dies

EPOXY DISPENSE

(or FILM)

EPOXY (or FILM)

DIE BONDING

SUBSTRATE

DIE

GOLD

WIRE

+

Overmolding

Repeat the process for multiple

dies if necessary

Ball attach and reflow

DFM: Cu-MIGRATION

Per JEDEC standards, all packages must meet certain accelerated test requirements such as high temperature and moisture under biased condition, temperature cycling

After several hours at high Temp and moisture

Polymeric matrix of the substrateor dielectric of the silicon

Copper line

Dendrite

Example of dendrite formation: Cu in acidic solution at 0.6V (Gabrielli et al, J Electrochem

Soc, 154, H393 (2007)

H2O H+ + OH-

Anode: Cu Cu+ + e-

2Cu++ 2OH---> Cu2O + H2O

Movement of Cu+ ion to cathode under electric fieldCathode: Cu+ + e-

Cu2H+ + 2e-

H2

+ -

Cu Migration Video

SUMMARY

W-CMPCopper Deposition

PVD + ECP

Dielectric

DepositionDielectric

Etch

Copper

CMP

Metal

Deposition

PVD + WCVD

Dielectric

EtchDielectric

Deposition

• 6 Dielectric

Deposition Steps

• 12 Dielectric

Etch Steps

• 6 Ta/Cu PVD Steps

• 6 Cu Plating Steps

• 6 Cu CMP Steps

• 12 Wet Clean Steps

Interconnect

Shallow Trench

Isolation Etch

Shallow Trench

Isolation CMP

Gate Oxide

Growth

Poly Silicon

DepositionPoly Silicon

Gate EtchShallow Trench

Isolation Dielectric

Deposition

Intel’s Microprocessor

Courtesy of Intel Silicon Wafer

Ion Implantation

• 16 Thermal Steps

• 11 Implant Steps

• 5 Etch Steps

• 2 CMP Steps

• 38 Wet Clean Steps

Transistor

Both interconnect and transistor are important