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Exposure Monitor for Microlithography

IP.com Disclosure Number: IPCOM000099397D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-14
Document File: 4 page(s) / 104K

Publishing Venue

IBM

Related People

Starikov, A: AUTHOR

Abstract

This article describes an auxiliary reticle structure whose purpose is to provide measurements of the exposure dose coupled into the photoresist film used in microlithographic printing.

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

Exposure Monitor for Microlithography

       This article describes an auxiliary reticle structure
whose purpose is to provide measurements of the exposure dose coupled
into the photoresist film used in microlithographic printing.

      Two alternative methods can be used.  One uses partially
transmitting windows in a reticle formed by deposition of various
thicknesses of absorber material.  The other relies on linewidth
measurements, typically measurements of conventional lines.

      Some advantages of this structure over a set of windows of
varying transmittance are as follows:

      1.  structure made by the same process as device images,
    2.  structure is compact,
    3.  structure may be printed in device-like lay-outs,
    4.  measurable by conventional optical linewidth metrology tools,

      5.  method does not cause local resist developer depletion.

      On the other hand, unlike the approach using measurements of
conventional lines, it is more sensitive to dose variations and is
not susceptible to defocus.

      This structure combines high sensitivity to the dose and
insensitivity to defocus in a compact package built by conventional
mask making.  Use of this structure helps to monitor exposure dose
accurately in both the set-up of an optical projection tool for an
optimal exposure process window and for in-line monitoring of a dose
for job disposition.  (Sensitive set-up and monitoring of focus is
desirably done independently of dose; several methods are available.)

      One possible embodiment of the proposed dose Exposure Monitor
Structure (EMS) is presented in Fig. 1 for an optical projection tool
with a wavelength of 435 nm and numerical aperture of 0.35.  Fig. 1
represents a particular design of EMS next to a conventional 1-micro-
meter line. For example, the fine pitch is 0.5 micrometer and the
smallest size increment is 0.1 micrometer (at 1X).  It consists of a
wide transparent core area surrounded by several s...