Browse Prior Art Database

Rotational Oblique Viewing Microscope for Pad Analysis Systems

IP.com Disclosure Number: IPCOM000119236D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 4 page(s) / 129K

Publishing Venue

IBM

Related People

Kolber, JC: AUTHOR [+3]

Abstract

This article describes a rotational oblique viewing microscope (OVM) which allows the analysis of C4 pads on logic chips regardless of the pad orientation.

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

Rotational Oblique Viewing Microscope for Pad Analysis Systems

      This article describes a rotational oblique viewing
microscope (OVM) which allows the analysis of C4 pads on logic chips
regardless of the pad orientation.

      A pad analysis system (PAS) is shown in Fig. 1 in perspective
with the cover broken away to illustrate the position of the
rotational OVM of this disclosure.  It is used to measure the size of
the C4 pads on logic/array chips.  A shadow technique is used for
measuring the relative volumes of the C4 pads.  This shadow technique
employs illumination of each chip at an angle sufficient to cast a
shadow of each pad.  The optics must detect the entire dark area
created by each individual pad and shadow. For this reason the
shadows cannot overlap each other.  An illuminator and detection
optics are part of the OVM assembly.  This assembly is orientated at
a static 45-degree offset to the X-Y axes of the wafer handler which
places the chip arrays under the center line of the OVM optics.  This
arrangement generates C4 pad shadows at a constant 45-degree angle to
the vertical and horizontal X-Y axes of travel of the wafer chuck.
Wafer chuck theta rotation is limited to a +5 degrees for the initial
wafer alignment only.  Wafer rotation is also undesirable since this
would require reprogramming of the wafer map.  The rotational OVM
disclosed herein allows a change to the illumination angle suitable
to the C4 pad orientation of individu al products.  The rotational
range is 45 degrees from the present position to parallel
(horizontal) with the Y-axis of the tool, as shown in Fig. 2.

      The rotat...