Browse Prior Art Database

High Precision Silicon Masks for Deposition Monitors

IP.com Disclosure Number: IPCOM000123318D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2005-Apr-04
Document File: 7 page(s) / 178K

Publishing Venue

IBM

Related People

Speidell, JL: AUTHOR [+2]

Abstract

This invention relates to thin film depositions and a device for high precision measurements.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

High Precision Silicon Masks for Deposition Monitors

   FIELD OF INVENTION

   This invention relates to thin film depositions and a
device for high precision measurements.

   BACKGROUND

   Thin layers of materials such as metals and insulators,
typically used in manufacturing of integrated circuits are applied
using a variety of deposition techniques, such as electron beam
evaporation and sputtering.  Controlling the thickness of these
materials is critical in controlling the function of these circuits.
Many techniques are available for measuring the thickness of thin
films which range in cost and complexity.  A simple process for
measuring thin films involves masking a section of a monitor wafer in
a deposition run in such a way as to leave a distinct area which does
not receive deposition leaving an interface which can be measured
with a surface profilometer.  The problem with this method is that
this mask typically has a shadowing effect on the monitor and does
not give an accurate profile when measured with the profilometer (see
figure 1).  This disclosure describes a device which provides much
more reliable measurements.

   SUMMARY

   This disclosure describes a device which is used to
provide inexpensive, reliable thickness measurements for thin film
deposition.

   DESCRIPTION OF DRAWINGS

   Figure 1 is a cross section of a standard masking
configuration for a deposition process.  Figure 2 shows a
magnification of an area of Figure 1 which displays the problem with
the current masking technique.  Figure 3 is a cross section of the
knife edge mask which is being disclosed.  Figure 4 shows a
magnification of an area of Figure 3 which displays the improved
deposition profile when using this invention.  Figure 5 shows a
pictorial of the fabrication process as described in the Fabrication
Process section of the Detailed Description of Invention.  Figure 6
shows actual profiles of samples deposited without and with the
disclosed device.

   DETAILED DESCRIPTION OF INVENTION

   It is typical to use a physical mask on a monitor wafer
in a deposition process to provide a region for the measurement of
thickness of the material deposited.  This mask is in contact with
the substrate such that it blocks the deposition from landing on the
substrate and provides a boundary which can be measured to determine
the thickness deposited.  These masks are typically made by sawing a
silicon wafer to make small chips.  The problem with this type of
mask is that the vertical walls of the mask cause the deposit to be
partially blocked at the very edge of the boundary and the thickness
of the mask interferes with the trajectory of the arriving atoms for
a significant distance relative to the measurement region (see
Figures 1 and 2).  Figure 2 shows that an overhang forms on the edge
of the mask due to buildup of...