Browse Prior Art Database

Illuminator for Integrated Circuits Having Raised Features

IP.com Disclosure Number: IPCOM000100503D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 119K

Publishing Venue

IBM

Related People

Cipolla, TM: AUTHOR [+3]

Abstract

Disclosed is a device for illuminating integrated circuit chips for critical machine vision applications. The particular property of the object exploited in this device is the relief of features on the surface generally used for interconnections. Locating the position of these features accurately and unambiguously is essential when attempting to derive information that may be used to align another object to these features. Since these features are raised substantially above the underlying surface and their edges scatter light readily, the edges of the features appear bright when observed under conditions of dark field illumination. The underlying surface may also have edges that scatter light.

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Illuminator for Integrated Circuits Having Raised Features

       Disclosed is a device for illuminating integrated circuit
chips for critical machine vision applications.  The particular
property of the object exploited in this device is the relief of
features on the surface generally used for interconnections.
Locating the position of these features accurately and unambiguously
is essential when attempting to derive information that may be used
to align another object to these features.  Since these features are
raised substantially above the underlying surface and their edges
scatter light readily, the edges of the features appear bright when
observed under conditions of dark field illumination.  The underlying
surface may also have edges that scatter light.  The light scattered
from these features must be suppressed, if possible, to avoid the
difficulties of distinguishing between features of the background
that appear (when viewed from a direction normal to the surface)
similar to the features of interest.  In the case of computer chips,
the "Manhattan street" aspect of the circuitry may be exploited by
orienting the incident light with respect to the chip's circuitry at
such an angle that light scattered from the circuitry fails,
substantially, to enter the imaging lens.

      The illuminator consists of the following two major components:
1) A one-to-four optical splitter designed to accept, as input, light
delivered to the splitter through a large diameter fiber-optic bundle
and to illuminate the input faces of four output fiber-optic bundles
such that the light emerging from the four optic bundles has been
randomized, filtered and the relative intensity of the four outputs
equalized, and  2) A four-point illuminator head assembly with four
degrees of freedom that directs the output of the four fiber-optic
bundles towards the object, nearly at grazing incidence, in such a
manner that the features of interest are highlighted and those which
may appear to "confuse" the observed object are significantly
suppressed.

      The properties of these two components are discussed below.
They are illustrated in the figure.

      The optical splitter is a metal housing incorporating a means
for supporting the input and output fiber-optic bundles and into
which the appropriate optical components may be mounted.  Light power
is delivered to the splitter by a large diameter fiber-optic bundle,
the input face being illuminated by a standard fiber-optic light
source.  The light emerging from the input fiber-optic bundle
i...