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Interferometer for in Situ Measuring Etch and Deposition Rates

IP.com Disclosure Number: IPCOM000045480D
Original Publication Date: 1983-Mar-01
Included in the Prior Art Database: 2005-Feb-07
Document File: 3 page(s) / 61K

Publishing Venue

IBM

Related People

Stein, H: AUTHOR

Abstract

The interferometer, which is suitable for in situ measurements, consists of a laser unit, several beam splitters, a detector unit, and means to compensate for the roughness of the surface to be treated. At each measuring position, a reference plane is provided which is substantially unaffected by etching and deposition, respectively.

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Interferometer for in Situ Measuring Etch and Deposition Rates

The interferometer, which is suitable for in situ measurements, consists of a laser unit, several beam splitters, a detector unit, and means to compensate for the roughness of the surface to be treated. At each measuring position, a reference plane is provided which is substantially unaffected by etching and deposition, respectively.

The interferometer is described below in greater detail by means of etch rate measurements. It is used for in situ measurements of the etch rates on substrates located at different points, for example, on the rotary cathode 10 (Fig.
1) of a planar plasma etching reactor. The interferometer comprises a laser 1, a semitransparent mirror 2, several beam splitters 3, and a detector unit 4. The distances of beam splitters 3 from mirror 2 differ, so that measurements can be made at points spaced differently from the rotary axis of the cathode. The substrates 8 to be etched are located on substrate carriers 5, each of which is equipped with a slit 6, whose depth-to-width ratio is so large that its depth is changed only insignificantly when substrate 8 is etched. Therefore, plane 7 at the bottom of slit 6 can be used as the reference plane for interferometric measurements.

The etching of substrates positioned, for example, on rotary cathode 10, is monitored by the interferometer. Cathode 10 rotates in steps, and each substrate is tested once per rotation. The interferometer is arranged outside the reactor chamber. Windows 11 and 12 (Fig. 1) in top plate 13 of the plasma reactor and in anode 14, respectively, permit the laser beam to pass between the substrate holders and interferometer. For each measurement, a two-beam interference signal, generated by interference of the beam reflected from the reference plane and the beam reflected from the surface to be etched, is detected by detector unit 4. The signal value obtained from an individual substrate to be etched is discretely stored in an associated channel. T...