Browse Prior Art Database

Electrically Conducting Anti-reflection Coating for Silicon Chips

IP.com Disclosure Number: IPCOM000122359D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 1 page(s) / 45K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

This article describes a method, procedure, and construction of semiconductor chips which facilitates the replacement of such chips joined to ceramic or other substrate by solder contacts or other heat-sensitive means. Such chips can be heated and pulled from a ceramic substrate for replacement. Lasers or incoherent infrared or visible light sources can be used for this heating. However, the semiconductors, like silicon or gallium arsenide, are 30-40% reflecting for visible and near infrared light wavelengths. We disclose that a quarter wavelength coating of polycrystalline diamond will reduce the reflectivity to nearly zero at the wavelength chosen for the chip heating. For example, a typical industrial laser using a Nd-YAG crystal emits at 1.06 micron wavelength, and the quarter wavelength diamond film will be .

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Electrically Conducting Anti-reflection Coating for Silicon Chips

      This article describes a method, procedure, and
construction of semiconductor chips which facilitates the replacement
of such chips joined to ceramic or other substrate by solder contacts
or other heat-sensitive means.  Such chips can be heated and pulled
from a ceramic substrate for replacement. Lasers or incoherent
infrared or visible light sources can be used for this heating.
However, the semiconductors, like silicon or gallium arsenide, are
30-40% reflecting for visible and near infrared light wavelengths.
We disclose that a quarter wavelength coating of polycrystalline
diamond will reduce the reflectivity to nearly zero at the wavelength
chosen for the chip heating.  For example, a typical industrial laser
using a Nd-YAG crystal emits at 1.06 micron wavelength, and the
quarter wavelength diamond film will be .1205 microns thick using a
refractive index of 2.2 for diamond.

      The cooling piston is grounded, and the film must be conducting
at a level of about 10 ohms over a square cm of the chip in
order to avoid problems with floating ground. In order to make the
diamond film conducting, we propose to dope the diamond with boron.
The silicon itself is p+, so the boron doped diamond (which will also
be P type) will cause no electrical junction problems.

      The index of refraction of diamond at 1.0 microns is 2.2, while
the index of the silicon is about 4.  A perfect antireflec...