Browse Prior Art Database

Micromanipulator Wafer Aligner

IP.com Disclosure Number: IPCOM000107339D
Original Publication Date: 1992-Feb-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 4 page(s) / 172K

Publishing Venue

IBM

Related People

Khoury, HA: AUTHOR [+2]

Abstract

Disclosed is a tool for high accuracy wafer alignment on chucks without wafer edge contact or need for intermediate alignment stations. This tool makes possible the: (1) elimination of contamination due to edge contact/damage of wafer, and (2) subsequent wafer misalignment inaccuracy due to the edge damage encountered with edge contact aligners. Additional unique advantages of this tool over known solutions are: (1) it can operate in a vacuum environment, and (2) design simplification due to elimination of dual-stage alignment (rotation with final translational pre-align) station.

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Micromanipulator Wafer Aligner

       Disclosed is a tool for high accuracy wafer alignment on
chucks without wafer edge contact or need for intermediate alignment
stations.  This tool makes possible the:  (1) elimination of
contamination due to edge contact/damage of wafer, and (2) subsequent
wafer misalignment inaccuracy due to the edge damage encountered with
edge contact aligners. Additional unique advantages of this tool over
known solutions are:  (1) it can operate in a vacuum environment, and
(2) design simplification due to elimination of dual-stage alignment
(rotation with final translational pre-align) station.

      In conventional lithography, metrology and inspection systems
wafers are retrieved from a cassette on an individual basis and
placed on an orientor where they are oriented and pre-aligned in
automatic mode until the V-notch, at the edge of the wafer, is at a
given rotational (theta) orientation and coarsely aligned to no less
than .5 degree in theta and 1000 microns in X and Y.  In order to
achieve significantly more accurate alignment necessary for meeting
initial pattern centrality specifications at the first
photolithographic process step and additionally for subsequent
masking level to masking level final overlay alignment (accomplished
via the "pull-in-range" of the automatic optical or scanning electron
microscope alignment system within each of the foregoing process
tools), each wafer is transferred by means of a robotic system to a
separate mechanical aligner unit where the wafer undergoes an
intermediate alignment process to an accuracy of .1 degree in theta
and 75 microns in X and Y to locate the wafer within the pull-in
range of the final auto-align system in the optical and/or E-beam
systems. Unfortunately, this intermediate aligner unit is comprised
of a fixed-pin arrangement into which the V-notch of the wafer is
forcefully detented.  The detenting process is accomplished when the
wafer is pushed by two other movable pins which, by design, move
towards the fixed pin, impacting the wafer edge at two diametrically
opposite locations. These two movable pins drag the wafer in the
direction of the fixed pin until the wafer comes to a hard stop at
the fixed pin.  At this point the wafer is tightly "locked in" and
"held" by the three pins, and the V-notch is fully detented in the
fixed pin.  The three pins are typically placed around the
circumference of the wafer at an angular orientation of 120 degrees
apart from each other.  This process of edge impact alignment causes
wafer edge damage and, consequently, by current chip design
groundrules, a high level of contamination.

      This article describes a novel technique where the intermediate
wafer alignment accuracy is obtained without wafer edge contact and
without the need for separate pre-align and intermediate align
stations.  The mechanism, as shown in Fig. 1, not only eliminates the
contamination due to wafer edge damage but yields...