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Measurement of Ion Implantation Dosage

IP.com Disclosure Number: IPCOM000038847D
Original Publication Date: 1987-Mar-01
Included in the Prior Art Database: 2005-Feb-01
Document File: 2 page(s) / 39K

Publishing Venue

IBM

Related People

Guidotti, D: AUTHOR [+2]

Abstract

Non-intrusive measurement of ion implantation dosage in semiconductors is made by determining changes in the real and imaginary part of the index of refraction as a function of the implantation dose. In Fig. 1, light from helium-neon laser 1 is formed into two beams by beam splitter 2 and mirror 3. One beam passes through variable alternator 4 and chopper 5 and is reflected from the surface of a reference, non-implanted silicon wafer 6 to photo-diode 7. The second beam from mirror 3 also passes through chopper 5 and is reflected from sample silicon wafer 8 onto photo-diode 7. The photo-diode output signal is amplified at 9 and fed to a commercial lock-in amplifier 10. The resulting DC output is proportional to the difference in reflectance between the reference and sample wafers. An example of a chopper is shown in Fig.

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Measurement of Ion Implantation Dosage

Non-intrusive measurement of ion implantation dosage in semiconductors is made by determining changes in the real and imaginary part of the index of refraction as a function of the implantation dose. In Fig. 1, light from helium-neon laser 1 is formed into two beams by beam splitter 2 and mirror 3. One beam passes through variable alternator 4 and chopper 5 and is reflected from the surface of a reference, non-implanted silicon wafer 6 to photo-diode 7. The second beam from mirror 3 also passes through chopper 5 and is reflected from sample silicon wafer 8 onto photo-diode 7. The photo-diode output signal is amplified at 9 and fed to a commercial lock-in amplifier 10. The resulting DC output is proportional to the difference in reflectance between the reference and sample wafers. An example of a chopper is shown in Fig. 2A and has an equal number of alternate openings A and B so that the activating radiation is sensed alternatively from the two wafers. If more reflectance occurs from one than the other, the output signal will be similar to that shown in Fig. 2B. When this signal is observed with a lock-in amplifier tuned to the scanning frequency of one band of slots, the in-phase output is proportional to the difference in power between the two beams. Relative reflectivity, or transmissivity, can be determined by nulling the difference.

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