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Browse Prior Art Database

Improved Process for Through Hole Fabrication in Silicon

IP.com Disclosure Number: IPCOM000104582D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 2 page(s) / 57K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+4]

Abstract

This article describes a process for fabricating through holes in thin silicon substrates.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 65% of the total text.

Improved Process for Through Hole Fabrication in Silicon

      This article describes a process for fabricating through holes
in thin silicon substrates.

      For about 2 decades, structures have been etched into silicon
by direction-dependent wet etching [*].  For a 100-wafer, the
boundary planes of the fabricated structures are the 111-planes
inclined at an angle of 54.7º  to the 100-surface.  In this
way, pyramidal holes (as well as through holes) may be fabricated in
a silicon wafer.  However, the angle of 54.7º  limits the hole
depth obtainable to about 0.7 times the hole width.

      A favourable aspect ratio is obtained by etching from both
sides at a given wafer thickness, although in practice difficulties
have been encountered.  Whenever the two etch fronts (100-planes)
meet in the center of the wafer, convex edges (with angles >
180º) of colliding 111-planes occur (Fig. 1).  For some holes
the ideal etch end point may be determined by approximation.
However, when several thousand holes are etched simultaneously, their
definition is relatively poor (Fig. 2) and their shape differs as a
result of fast etching crystal planes.

      The novel fabrication process is shown in Figs. 3A - 3I.  The
wafer is initially (thermally) oxidized on both sides (Fig. 3A).
Then the front mask is lithographically treated and etched (Fig. 3B).
The mask dimensions are such that the subsequent anisotropic wet etch
step (with KOH) continues until the "natura...