Browse Prior Art Database

Silicon Deposition Mask

IP.com Disclosure Number: IPCOM000119808D
Original Publication Date: 1991-Mar-01
Included in the Prior Art Database: 2005-Apr-02
Document File: 1 page(s) / 47K

Publishing Venue

IBM

Related People

Brady, MJ: AUTHOR [+4]

Abstract

Disclosed is a mask made of single-crystal silicon possessing enhanced rigidity and durability and the process that describes its construction. Prior art teaches a way of metal evaporation through metal masks at elevated temperatures which requires a good match of the coefficient of thermal expansion (CTE) between that of the mask materials and that of the silicon semiconductor substrates upon which the metal is deposited. The use of silicon as the mask material provides a precise matching of the CTE of the mask to that of the silicon substrate. However, silicon is not used because it is generally thought to be fragile and holes etched in crystalline silicon are limited to square shapes.

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Silicon Deposition Mask

      Disclosed is a mask made of single-crystal silicon
possessing enhanced rigidity and durability and the process that
describes its construction.  Prior art teaches a way of metal
evaporation through metal masks at elevated temperatures which
requires a good match of the coefficient of thermal expansion (CTE)
between that of the mask materials and that of the silicon
semiconductor substrates upon which the metal is deposited.  The use
of silicon as the mask material provides a precise matching of the
CTE of the mask to that of the silicon substrate.  However, silicon
is not used because it is generally thought to be fragile and holes
etched in crystalline silicon are limited to square shapes.  The
technique disclosed represents an advance over the state of the art
in that it solves these concerns, and also eliminates the thermal
mismatch since the mask is made of silicon.

      Crystalline silicon can be etched anisotropically (1,2).
Anisotropic etching of (100) silicon results in the formation of a
square pyramidal pit, whose walls slope inward at an angle of 54.74
degrees.  The fragility problem and the problem of square holes is
solved by a structure which uses two etched silicon substrates.  The
first substrate is etched in the normal manner.  The second substrate
is etched using a mirror image mask.  However, before etching, the
(110) crystal axis of the second substrate is rotated through a 45
degree angle, with respect to...