Process Engineering in Microelectronic Fabrication Siddhartha Panda - - PowerPoint PPT Presentation

Process Engineering in Microelectronic Fabrication

Siddhartha Panda Department of Chemical Engineering IIT Kanpur

Miniturization Enhanced capabilities Electronic chips Logic Memory Drivers Trends Trends

BS, CHE, 1960 PhD, CHE, 1963 Andy Grove Sequence of unit processes Enabled by process engineers

Evolution

Developments of the semiconductor industry Structure developments Process developments Process Engineering Chip/Circuit/System design * Process development * Equipment design/fab. * Integration

Unit Processes and role of chemical technology

• Layering

film growth vapor depositions (plasma enhanced, chemical, physical etc.) epitaxy

• Patterning

( wet and dry) etching – dielectrics, semiconductors (silicon), metals resist development

• Doping

chemical, ion implantation

• Heating

Hot plates, IR

• Planarization

chemical and mechanical polishing (slurry)

Mass, momentum, energy, species balance Electromagnetic field (Poisson’s eqn)

• xidation kinetics

2 phase flow

polymer processing diffusion heat transfer

Not just processes but also equipment designs

Some unit processes

* Crystal Growth and Wafer Fabrication * Oxidation (thermal) * Dopant Diffusion * Ion Implantation * Rapid Thermal Processing * Chemical Mechanical Planarization * Physical Vapor Deposition * Chemical Vapor Deposition * Lithography * Wet Etching * Plasma Deposition and Plasma Etching

16 Mbit (~1991) 64 Mbit (~1996)

An example DRAM chips

(Courtesy – Siemens)

Non-planar Advent of CMP (early 1990s) enabled *denser packing * more metallization layers

Quartz Tube Rotating Chuck Seed Crystal Growing Crystal (boule) RF or Resistance Heating Coils Molten Silicon (Melt) Crucible * How to control the diameter of the boule? * What is the maximum velocity of pulling the crystal from the melt?

Crystal Growth

Analysis at the melt interface Heat transfer Mass transfer Dopants - segregation Cz

Need to formulate a model describing incorporation of dopants into growing crystals

L S

• C

C k =

Concentration profiles Moving molten zones (boundaries)

bulk gas flow stagnant gas layer

• xide

silicon Cg Cs Co Ci F1 F2 F3

Oxidation

Mass transport Reactions

x C v x C D t C ∂ ∂ − ∂ ∂ = ∂ ∂

2 2

      ∂ ∂ ∂ ∂ = ∂ ∂ x C D x t C

eff

        + =

* * * V V V I I I eff

C C f C C f D D

∫ ∫ ∫ ∫

+ = + = = =

2 1

) ( ) ( /

E E e n R E P

E f E f dE S S dE dx dE dE dx R

P

Dopant diffusion

Drift diffusion Concentration dependence of D Defect dependence

RTP

Ion stopping distance Material properties Transport phenomena

substrate source material heat heat substrate

Surface chemistry  surface reaction direct reaction between incoming species and surface site  Eley-Rideal mechanism reaction between surface species  Langmuir-Hinselwood mechanism

ζ ν ν δ δ

i RT E E r d i r d i r

J e J k k J R

s d r

=             + = + =

− − / ) (

1 / 1

Ed – Er

Physical Vapor Deposition

RT E E c s

s c

e a

/ ) ( −

= Λ ν ν

2RT Thermodynamics (statistical mech) Transport Reactions Parameters – Transport, Kinetic, …. Macroscale Atomic phenomena Surface diffusion

Chemical Vapor Deposition

Equipment design

Wet etching

PLASMA

RF heating  electron generation Electron impact with atoms  more electrons + ions + fragments Cascading reactions  species generation

2 / 1 2

        = e n kT

e e D

ε λ

Plasma processing – deposition and etching

time

etch stop

(Panda et al., Microelectronic Engineering, 2004)

Knudsen diffusion Surface reactions * Transport Momentum, Mass, Energy, Charge * Reactions

Tunable gas distribution Dual zone chuck Specialized gases Multiple frequency configuration AMAT – Mariana Etch - Sub 70 nm Si trenches

Advances in equipment design

AMAT RTP Heat transfer Filamant design/configuration  Uniform heat flux

Thoughts

• Process engineering
• PE in Microelectronic fabrication
• - India perspective

* Demand for electronic goods * Domestic manufacturing * Need for trained manpower