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Semiconductor Diffusion & Ion Implantation

This document provides a preview and preparation for lectures on diffusion and ion implantation. Students are instructed to read sections of Plummer Chapter 7 on diffusion and Chapter 8 on ion implantation. The document outlines key points about solving differential equations that will be relevant to understanding diffusion, including the need for boundary conditions. It also notes that mobile charges introduced by dopants can cause an internal electric field affecting diffusion profiles. The preview for the lecture on ion implantation lists two topics that will be covered: factors determining ion penetration depth and how diffusion following implantation influences dopant spatial distribution.

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48 views1 page

Semiconductor Diffusion & Ion Implantation

This document provides a preview and preparation for lectures on diffusion and ion implantation. Students are instructed to read sections of Plummer Chapter 7 on diffusion and Chapter 8 on ion implantation. The document outlines key points about solving differential equations that will be relevant to understanding diffusion, including the need for boundary conditions. It also notes that mobile charges introduced by dopants can cause an internal electric field affecting diffusion profiles. The preview for the lecture on ion implantation lists two topics that will be covered: factors determining ion penetration depth and how diffusion following implantation influences dopant spatial distribution.

Uploaded by

stansilaw
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as PDF, TXT or read online on Scribd
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3.155J/6.

152J Spring Term, 2005

Preview and preparation for Lecture 6, Feb.22: Diffusion.


Read Plummer Chap. 7, sections 7.1-7.4, 7.5.2, 7.5.3, 7.5.8

In this lecture we will study the diffusion process, especially for dopants in Si. You
should come to these lectures with a reasonable background in solving differential
equations. You should recall for example the following points.
∂c
1. Solving a first-order differential equation, such as J x = -D b simple
∂x
integration will give a constant of integration that must be determined from a
foreknown boundary condition.

2. Solving a second-order differential equation having a term d2c/dx2, similarly


will require knowledge of TWO different spatial boundary conditions.

3. Solving a time-dependent second-order differential equation, such as that for


∂2 f ∂f
heat flow or Schrödinger’s equation, 2 = A , demands that you have
∂x ∂t
TWO boundary conditions and ONE initial condition.

4. Different boundary conditions on the same equation can result in different


solutions having very different forms.

You should also be aware that if we are diffusing in dopants into Si, those dopants bring
with them mobile charges. So, just as in the case of the dipole layers we saw in Si
oxidation, there may be a separation of the mobile charge from the donor or acceptor
species being diffused in. This charge separation causes an internal electric field that can
alter the diffusion profile.

Preview and preparation for Lecture 7, Feb.23: Ion implantation.


Read Plummer Chap. 8, sections 8.1-8.4, and 8.5.1-8.5.6, or Campbell 5.1-5.6

1. We will look at the factors that determine how far an ion, accelerated to a
given energy, penetrates a target wafer. Ionic mass and charge, as well as the
crystal structure and composition of the target are important. What are the
physical processes that stop incoming ions?

2. We will also look at how a diffusion process following ion-implantation


influences the spatial distribution of dopants.

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