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Secondary Electron Detector for Scanning Electron Microscope Investigation of Semiconductor Lasers Under Operation

IP.com Disclosure Number: IPCOM000104931D
Original Publication Date: 1993-Jun-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Jakubowicz, A: AUTHOR [+2]

Abstract

Scanning Electron Microscope (SEM) investigation of laser diodes under operation can be beneficial for understanding many reliability problems of these devices. However, when using commercial SEMs, it is either very difficult or not possible at all to investigate devices that emit light of high intensity. The reason is as follows:

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Secondary Electron Detector for Scanning Electron Microscope Investigation of Semiconductor Lasers Under Operation

      Scanning Electron Microscope (SEM) investigation of laser
diodes under operation can be beneficial for understanding many
reliability problems of these devices.  However, when using
commercial SEMs, it is either very difficult or not possible at all
to investigate devices that emit light of high intensity.  The reason
is as follows:

      Any commercial scanning electron microscope SEM is equipped
with an Everhart Thornley detector[1] that is constructed as an
integral unit.  This detector is used to obtain secondary electron
images representing the SEM's standard operation mode.  Fig. 1 shows
the standard construction.  Secondary electrons to be detected are
accelerated and then impinge upon a scintilator 4.  The generated
photons are transmitted via a waveguide 3 to a photomultiplier 1.
Thus, an amplified electric signal is obtained which carries the
information needed to produce a SEM image.  From the above it is
clear that an additional light source present in the SEM chamber
disturbs the operation of the SEM, if the light spectrum overlaps
that of the detector.  Furthermore, if the intensity of the secondary
electrons, the detector becomes saturated and no image can be
obtained.  Even at lower intensitier of the disturbing light it is
difficult or impossible to obtain an image when the additional light
source introduces noise.

      Our modified construction of the detector permits overcoming
the the described dif...