INTEGRATED CIRCUITSDr. Esam Yosry

Lec. #4

Ion

Im

pla

nta

tion

Introduction

Ion Implantation Process

Advantages Compared to Diffusion

Disadvantages Compared to Diffusion

Implantation Doping Profiles Compared to Diffusion

Implantation Doping Profiles Parameters

Multiple Implant Process

Ion Implantation Technology

Intr

od

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ion

(Chip

Fabri

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on C

ycl

e)

Intr

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uct

ion

(Pro

cess

es)

Oxidation

Diffusion

Ion Implantation

Deposition

Etching

Lithography

Deposition Removal Patterning Modification of

electrical properties

Ion Implantation Process

Ion Implantation: is a method of introducing impurities in a controlled manner into wafer.

Dopant ions are accelerated by a high electric field and directed at the substrate.

They enter the crystal at high kinetic energy, collide with host atoms, gradually lost energy and finally come to rest at some depth.

Ion Implantation Process

Room Temp process.

High energy ion bombardment (10 - 500 KeV)

The penetration depth and dopant profile are be controlled by the accelerating electric field.

Advantages compared to Diffusion

Better control on profileAmount of dose and profile (position and area) are accurately obtainable.

Broad range of doping levels 1011 – 1018 cm-3

By low doping we can make fine tune the values of some electrical parameters.

Arbitrary doping profilePlacing the peak anywhere under the wafer surface.

Advantages compared to Diffusion

Low contamination

Shallow depths with uniform profiles

Low temperature processingThe growth of masking oxide layer is no longer needed. Also low temperature processing allows us to maintain the shape of any previously introduced profiles.

Less lateral dopant diffusionDopant ions have no momentum in the horizontal direction.

Disadvantages compared to Diffusion

• Only for shallow junctions

• Incident ions damage the semiconductor lattice

• Silicon damage (anneal at 500 - 1000oC)

• Very expensive and complex equipment

• Profiles can have tails (channeling)

• 1 wafer at a time vs. up to 200 for diffusion

• Long processing time

Implantation Doping Profiles Compared to

Diffusion

21

2( )

p

p

x R

R

peakN x N e

Projected range (mean penetration depth)

Standard deviation

Higher implantation energy Ξ deeper penetration Rp and wider distribution ∆ Rp 0.4peak

p

QN

R

Implantation Doping Profiles Compared to

Diffusion

Implantation Doping Profiles Compared to

Diffusion

Imp

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D

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Pro

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s

Para

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rs

Imp

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Example

A boron dose of 1x1013 cm-3 is implanted into 5x1015 cm-3 n-type Si at 100 kev. Find the junction depth.

Solution From charts for B into Si at 100 kev, one gets

Rp=0.3µ

and ∆Rp=0.07µ

Npeak=0.4x 1013/0.07x10-4 = 5.7x1017 cm-3

2 ln peakj p p

B

NX R R

N

17

15

5.7 100.3 2 0.07 ln 0.52

5 10jX

Multiple Implant Process

Fairly flat, deep dopant profiles can be made by multiple implants of different energies.

Ion Implantation Technology

Many thanks to Prof. Hany Fikry and Prof Wael Fikry for their useful materials that help me to prepare this presentation.

Thanks