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Optical In-Situ Determination of Multilayer Film Characteristics

IP.com Disclosure Number: IPCOM000049732D
Original Publication Date: 1982-Jul-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 43K

Publishing Venue

IBM

Related People

Hinkel, H: AUTHOR [+4]

Abstract

A phase-sensitive optical detection method is proposed for measuring refractive indices and layer boundaries in multilayer film structures that is particularly useful during layer growth or etching.

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Optical In-Situ Determination of Multilayer Film Characteristics

A phase-sensitive optical detection method is proposed for measuring refractive indices and layer boundaries in multilayer film structures that is particularly useful during layer growth or etching.

In Fig. 1 the output beam 2 of laser 1 is directed (by beam splitter 3) to birefringent crystal 4, where it is split up in an ordinary beam, reference beam 5, and an extraordinary beam, measurement beam 6. Reference beam 5 is reflected at a constant reference plane, e.g., a mirror 7 attached to crystal 4. Measurement beam 6 is directed to a multilayer system 8 at a location that is subject to etching (or growth). In the example of Fig. 1, the layer system consists of an SiO(2) layer sandwiched between a top poly-Si layer and a Si substrate; in crater 9, the poly-Si layer is continually removed by an impinging ion beam 10 used for a reactive ion etching (RIE) or secondary ion mass spectroscopy (SIMS). Measurement beam 6 is reflected partly at the interfaces air-poly-Si, poly-Si-SiO(2) and SiO(2)Si. The reflected parts of measurement beam 6 are recombined with reference beam 5 when again passing birefringent crystal 4. The relative phase difference of the recombined measurement and reference beams due to their different optical paths is measured in electro-optic phase detector 11 whose operation is described in detail in German Patent Application 28,51,75O.

The output signal (phi)(m)of phase detector 11 over the sputter time is shown in Fig. 2. By comparison with the SIMS-signal (dashed curve) it is apparent...