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Interferometric Etch End-Point Detection for Two-Component Materials

IP.com Disclosure Number: IPCOM000046432D
Original Publication Date: 1983-Jul-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 2 page(s) / 31K

Publishing Venue

IBM

Related People

Bayer, T: AUTHOR [+4]

Abstract

During etching, materials consisting of two components with a statistical microscopic grain distribution and different etch rates develop a surface roughness which is measured from the phase difference in a coherent light beam reflected at the different grain types.

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Interferometric Etch End-Point Detection for Two-Component Materials

During etching, materials consisting of two components with a statistical microscopic grain distribution and different etch rates develop a surface roughness which is measured from the phase difference in a coherent light beam reflected at the different grain types.

In-situ measurements of ceramic materials with two components (hatched and white grains, Fig. 1, during reactive ion etching (RIE) can be made for step heights d up to some 1OO nanometers by interferometric methods until the strong scattering of the light beams destroys the interference pattern. If very small step heights d (of the order of 20 - 40 nm) are to be analyzed, a two-step procedure is proposed, the first step of which provides for a monitor sample to be etched to a step height dl corresponding to g 1/4 of a first wavelength g 1 (e.g., an argon laser with g 1 = 514 nm). In the second step, the monitor wafer is etched together with the samples to be processed and subjected to a laser beam with a longer wavelength g 2 (e.g., an HeNe laser with g 2 = 633 nm). When the first minimum d2 is reached in the interferometric signal g 2, the additional etch step of d2 - d1 =

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corresponds to the desired surface roughness of the sample. In Fig. 2, the interference patterns for wavelengths g 1, g 2 are shown with their first minima at depths d1 and d2, respectively; the influence of scattering dampens the interferometric s...