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End-Point Detection Method for Mask Etching

IP.com Disclosure Number: IPCOM000043816D
Original Publication Date: 1984-Sep-01
Included in the Prior Art Database: 2005-Feb-05
Document File: 2 page(s) / 37K

Publishing Venue

IBM

Related People

Bergendahl, AS: AUTHOR [+4]

Abstract

Short and long term periodic adjustments to the chrome end-point detection system can be eliminated by taking advantage of polarized light in conjunction with the properties of Brewster's angle of incidence. A polarizer 11 is inserted between the light bundles 12 and the quartz mask 13. Due to the organic nature of polarizers, they are used with a plate 14 for protection from physical and chemical damage. For simplicity, plate 14 can be made from the same material as the mask substrate 13. Angle O and spacings A and B are then adjusted to make sure that the light 15 approaches the quartz "air" interface at Brewster's angle. The polarizer 11 is positioned so that the light 15 is filtered twice so that no light from the internal reflection is allowed to reach the detector 16.

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End-Point Detection Method for Mask Etching

Short and long term periodic adjustments to the chrome end-point detection system can be eliminated by taking advantage of polarized light in conjunction with the properties of Brewster's angle of incidence. A polarizer 11 is inserted between the light bundles 12 and the quartz mask 13. Due to the organic nature of polarizers, they are used with a plate 14 for protection from physical and chemical damage. For simplicity, plate 14 can be made from the same material as the mask substrate 13. Angle O and spacings A and B are then adjusted to make sure that the light 15 approaches the quartz "air" interface at Brewster's angle. The polarizer 11 is positioned so that the light 15 is filtered twice so that no light from the internal reflection is allowed to reach the detector 16. This implies that the only signal measured at the detector 16 would be the signal from the etching plasma (in the case of dry etching) and the detector's 16 "dark" signal. The plasma light can be eliminated or minimized through the use of filters (optical) and gain adjustments. This leaves only the dark signal from the detector. The dark signal is usually very small. Usually, it is only a function of temperature which can be easily corrected and does not drift significantly with time. This leads to practically no parameters which should be adjusted over time to reach reproducible end points.

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