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Method to Detect the Presence or Absence of Laminated Thin Film in Silicon Wafer Fabrication

IP.com Disclosure Number: IPCOM000112854D
Original Publication Date: 1994-Jun-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 106K

Publishing Venue

IBM

Related People

Nahata, P: AUTHOR [+3]

Abstract

Described is a hardware implementation used in the fabrication of silicon wafers to provide a means of detecting the presence, or absence, of any film attached to another surface. The design incorporates an adjustable sensitive sensor switch which enables various film thickness to be detected.

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This is the abbreviated version, containing approximately 52% of the total text.

Method to Detect the Presence or Absence of Laminated Thin Film in
Silicon Wafer Fabrication

      Described is a hardware implementation used in the fabrication
of silicon wafers to provide a means of detecting the presence, or
absence, of any film attached to another surface.  The design
incorporates an adjustable sensitive sensor switch which enables
various film thickness to be detected.

      Generally, during the fabrication of silicon wafers a process
step is used involving the separation of laminated wafer material
from the transport tape.  In prior art, difficulty was experienced in
determining whether the top thin film of the layered blank, usually
mylar, remained on the wafer after tape separation, or remained stuck
to the transfer tape.  Due to the geometry of the fabrication tool
and the clear nature of the mylar, it was difficult to detect where
the thin film was actually deposited.  The concept described herein
involves a mechanism designed to detect the presence or absence of
the laminated thin film during the process.

      Typically, within the fabrication of silicon wafers, a product
known as Riston is applied to the wafers by means of a Riston Apply
Tool.  The Riston is supplied in a roll consisting of layered
lamination of mylar, Riston, and polyolefin.  During the apply
process, a disk of the lamination is blanked from the roll and
transferred to the transport tape with the mylar side up attached to
the tape and the polyolefin side down in the exposed position.  The
tape is indexed to a position where the polyolefin is removed so as
to expose the Riston.  A wafer is then joined and bonded to the
Riston thereby becoming joined to the tape.  The wafer, with the
Riston and mylar, is then separated from the transport tape and
placed in a cassette.  This separation is successful if the wafer,
Riston and mylar are removed intact.  However, occasionally during
the tape separation step, instead of the mylar separating from the
transport tape, it separates from the Riston and stays bonded to the
tape.  This causes rejection of the wafer.

      In order to reduce wafer rejections, a Mylar Film Presence
Detector (MFPD) was developed to sense the presence of the mylar film
on the transport tape, thereby denoting a rejected wafer.  The MFPD
incorporates a mechanical sensor that has a small detection
threshold, typically 0.0004".  The switch is mounted in the center of
a rigid mechanical beam that is mounted perpendicular to, and
centered on, the center-line of the transport tape.  Mounted on the
ends of this beam are two semi-spherical toolin...