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Doppler Monitor for Additive/Subtractive Process

IP.com Disclosure Number: IPCOM000049551D
Original Publication Date: 1982-Jun-01
Included in the Prior Art Database: 2005-Feb-09
Document File: 2 page(s) / 27K

Publishing Venue

IBM

Related People

Magill, PJ: AUTHOR

Abstract

Optical monitor system 10 uses the Doppler effect to monitor and/or control the deposition (additive process) or removal (subtractive process) of a layer to or from, as the case might be, a workpiece, such as a printed circuit (PC) board or the like.

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Doppler Monitor for Additive/Subtractive Process

Optical monitor system 10 uses the Doppler effect to monitor and/or control the deposition (additive process) or removal (subtractive process) of a layer to or from, as the case might be, a workpiece, such as a printed circuit (PC) board or the like.

Consider, for example, the etching of a thin metal film F on a substrate S, such as ceramic or epoxy-glass, into PC conductor lines.

Light beam B of system 10 is provided from a suitable light source, e.g., He-Ne laser 11. The component of beam B, which passes through beam splitter 12, intercepts the film F as it is being etched at a substantially uniform rate, and is reflected back to splitter 12.

Beam splitter 12 also transmits another component of beam B to stationary mirror 13 from where it is reflected back as a reference beam. The reflected beams from mirror 13 and film F are combined by beam splitter 12 and reflected by it to photodetector 14. As the film F is being etched, there results a Doppler frequency shift in the combined reflected beams in response to the changing thickness of film F. The detector 14 converts the optical Doppler frequency shift to an output signal which is thus correlated with the measurement of the thickness of film F as it is being removed by the etching process and/or which can be used to control the etching process.

It can be shown that the monitoring of the deposition of a layer is effected in a similar manner with system 10.

Inform...