Browse Prior Art Database

Method and Apparatus for Testing Time Delay Integration-Charge Coupled Device Imaging Devices

IP.com Disclosure Number: IPCOM000113079D
Original Publication Date: 1994-Jul-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 107K

Publishing Venue

IBM

Related People

Schlig, ES: AUTHOR

Abstract

The TDI imager is operated either in a test bed (if packaged) or in a wafer prober, with a normal clocking sequence applied, with the device protected from room or prober lighting. At appropriate intervals the parallel and parallel-serial interface clocks are interrupted (with the serial and output stage clocks preferably continuing) and a pulse of uniform illumination is applied to the device. After each illumination pulse terminates, the parallel and interface clocks resume for at least a few more parallel clock cycles than there are stages in the parallel register. The output of the device in response to this stimulus may be observed with an oscilloscope and/or processed by an automatic data acquisition system to determine the quality of the device.

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Method and Apparatus for Testing Time Delay Integration-Charge Coupled
Device Imaging Devices

      The TDI imager is operated either in a test bed (if
packaged) or in a wafer prober, with a normal clocking sequence
applied, with the device protected from room or prober lighting.  At
appropriate intervals the parallel and parallel-serial interface
clocks are interrupted (with the serial and output stage clocks
preferably continuing) and a pulse of uniform illumination is applied
to the device.  After each illumination pulse terminates, the
parallel and interface clocks resume for at least a few more parallel
clock cycles than there are stages in the parallel register.  The
output of the device in response to this stimulus may be observed
with an oscilloscope and/or processed by an automatic data
acquisition system to determine the quality of the device.
Optionally, the output signal may be enhanced by electronic
filtration and correlated double sampling as known in the art before
observation or processing.

      The output is in the form of a first sequence of occurrences of
second sequences of individual output voltage values.  The second
sequences each represents the photocharge accumulated by a row of
stages of the parallel array, as transferred in parallel to the
serial register and then serially to the output stage.  The overall
quality of the output signal gives information about the quality of
the output stage.  The leading and trailing edges of the second
sequences give information about the charge transfer efficiency of
the serial registers.  The leading and trailing edges of the first
sequence give information about the charge transfer efficiency of the
parallel registers and parallel-serial interface.  Each individual
voltage value represents the photocharge and dark charge accumulated
in an individual imaging site of the array during the illumination
pulse.  The uniformity of the signal within the sequences gives
information about the existence and precise location of light
occlusions, defective stages, dark charge "spike" generation centers
etc.  These interpretations are known in the art.

      Information about the magnitude and distribution of dark
current is obtained by disabling the pulsed illuminator and
lengthening the clock interruption period during which the
illumination pulse would normally occur.  The output when the clocks
resume then represents the dark charge accumulated in each site
during the clock interruption period.

      The illumination source should be suitable for fast pulsing,
uniform area coverage, and have a color content near the middle of
the visible spectrum.  This is because TDI devices are excessively
transparent to long wavelengths, causing photocharge sp...