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INTEGRATED CIRCUITS. Dr. Esam Yosry. Lec . #4. 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

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Integrated circuits

INTEGRATED CIRCUITS

Dr. EsamYosry

Lec. #4


Ion implantation

  • 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

Ion Implantation


Introduction chip fabrication cycle
Introduction(Chip Fabrication Cycle)


Introduction processes
Introduction(Processes)

  • Oxidation

  • Diffusion

  • Ion Implantation

  • Deposition

  • Etching

  • Lithography

  • Deposition

  • Removal

  • Patterning

  • Modification of electrical properties


Ion implantation process
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 process1
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 profile

    Amount of dose and profile (position and area) are accurately obtainable.

  • Broad range of doping levels 1011– 1018cm-3

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

  • Arbitrary doping profile

    Placing the peak anywhere under the wafer surface.


Advantages compared to Diffusion

  • Low contamination

  • Shallow depths with uniform profiles

  • Low temperature processing

    The 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 diffusion

    Dopant ions have no momentum in the horizontal direction.


Disadvantages compared to diffusion
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
Implantation Doping Profiles Compared to Diffusion

Projected range (mean penetration depth)

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

Standard deviation


Implantation doping profiles compared to diffusion1
Implantation Doping Profiles Compared to Diffusion


Implantation doping profiles compared to diffusion2
Implantation Doping Profiles Compared to Diffusion


Implantation doping profiles parameters
Implantation Doping Profiles Parameters


Implantation doping profiles parameters1
Implantation Doping Profiles Parameters


Example
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 = 5.7x1017cm-3


Multiple implant process
Multiple Implant Process

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



Thanks

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


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