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End-Point Detection Technique Utilizing Changes in Birefringence

IP.com Disclosure Number: IPCOM000119343D
Original Publication Date: 1991-Jan-01
Included in the Prior Art Database: 2005-Apr-01
Document File: 2 page(s) / 61K

Publishing Venue

IBM

Related People

Maldonado, JR: AUTHOR [+2]

Abstract

This article describes an end-point detection technique for resist development in submicron lithographic applications. The technique involves the monitoring of the light reflected by a suitable resist pattern on the wafer while it is being processed. The method differs from previous monitoring schemes in the use of cross-polarizers to detect the small birefringence changes that take place as the resist reaches the end of its development. Using polarized light and a crossed analyzer, a distinct change of the reflected intensity can be observed during the final stages of the development. Fig. 1 shows a zone plate pattern with 70 nm features in cross-polarized light at two different development stages: (a) shortly before and (b) after the completion of development.

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End-Point Detection Technique Utilizing Changes in Birefringence

      This article describes an end-point detection technique
for resist development in submicron lithographic applications. The
technique involves the monitoring of the light reflected by a
suitable resist pattern on the wafer while it is being processed.
The method differs from previous monitoring schemes in the use of
cross-polarizers to detect the small birefringence changes that take
place as the resist reaches the end of its development.  Using
polarized light and a crossed analyzer, a distinct change of the
reflected intensity can be observed during the final stages of the
development.  Fig. 1 shows a zone plate pattern with 70 nm features
in cross-polarized light at two different development stages:  (a)
shortly before and (b) after the completion of development.  This
phenomenon of form birefringence is caused by the arrangements of the
submicron discontinuities on the surface which perform as an
anisotropic media and rotate the vector of polarization. Thus, an
increase in the light intensity after the analyzer will indicate near
completion of development in the bright areas.  When the detected
intensity saturates, as shown in Fig. 1B, close to full development
of the test pattern has been accomplished.  A reflective substrate
increases the effect.  Experimental results indicate that the method
can be used for features around 30 nm and possibly down to a few
tenths of a nm.

      An em...