Appeal No. 1999-1871 Page 2
Application No. 08/688,337
BACKGROUND
Appellant’s invention relates to micromachining, and more particularly, to a method for
constructing suspending structures such as diaphragms and membranes (specification at 1, ll. 5-
6). Claims 1 and 8 are illustrative:
1. A method for fabricating a suspended structure comprising a layer of membrane
material over a substrate, said suspended structure overlying a cavity in said substrate, said
method comprising steps of:
generating a sacrificial layer comprising a first material that will remain bonded to said
substrate at a temperature greater than 450BC.
depositing said layer of membrane material over said sacrificial layer, said membrane
material comprising a second material different from said first material;
opening at least one via in said layer of membrane material thereby exposing said
sacrificial layer;
applying a first etchant to said sacrificial layer through said via until said sacrificial layer
is removed leaving a portion of said cavity, said first etchant being chosen such that said first
etchant removes said first material more rapidly than said second material; and
introducing a second etchant into said cavity, said second etchant being chosen such that
said second etchant removes said substrate more rapidly than said second material.
8. The method of claim 1, wherein:
said step of generating a sacrificial layer includes a step of depositing a layer of said first
material on said substrate;
said step of opening at least one via in said layer of membrane material defines a location
of said cavity in said substrate; and
said step of applying said first etchant to said sacrificial layer through said at least one via
is performed for a predetermined time to remove a portion of said first material overlying said
location of said cavity in said substrate.
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