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Controlled Laser Annealing By Raman Frequency Feedback

IP.com Disclosure Number: IPCOM000048241D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Jain, K: AUTHOR

Abstract

A system is described which utilizes the feedback of a characteristic Raman frequency to control the power and/or dwell of an annealing laser beam.

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Controlled Laser Annealing By Raman Frequency Feedback

A system is described which utilizes the feedback of a characteristic Raman frequency to control the power and/or dwell of an annealing laser beam.

Feedback of the Raman frequency, which is a precise indicator of the extent of crystallization, is useful for fine and automatic control of annealing in semiconductor processing. In a perfect single crystal of silicon, the frequency of the Raman-active zone-center optic phonon 520.4 per cm. As the material becomes polycrystalline or amorphous, the Raman phonon frequency shifts to lower values due to size effects associated with microcrystallites. This shift can be as large as 10 per cm Laser annealing of semiconductors is normally employed to recrystallize material which is originally polycrystalline or amorphous. This shift in the Raman frequency can be utilized not only to monitor the progress of the recrystallization, but it can also be fed back to servo-control the annealing laser 10. Since the power in the annealing laser (approx. 5 watts) is large enough to generate a strong Raman signal, no separate probe laser is needed. The feedback signal can be generated by the apparatus shown in the drawing. Suitable collection optics 14 are employed to direct the light scattered from substrate 12 to apparatus 16 for monitoring the Raman line. For example, apparatus 16 may comprise means to locate the peak of the Raman line and take its difference from 520.4 per cm. Si...