Browse Prior Art Database

Monitor Wafer for Etch End Point Detection

IP.com Disclosure Number: IPCOM000051401D
Original Publication Date: 1981-Jan-01
Included in the Prior Art Database: 2005-Feb-10
Document File: 2 page(s) / 30K

Publishing Venue

IBM

Related People

Gallus, G: AUTHOR [+3]

Abstract

Precise control of etching processes (using sputtering or liquid etchants) requires an in situ determination of the etch end-points; some applications also require an in situ measurement of the film growth on previously etched surfaces.

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Monitor Wafer for Etch End Point Detection

Precise control of etching processes (using sputtering or liquid etchants) requires an in situ determination of the etch end-points; some applications also require an in situ measurement of the film growth on previously etched surfaces.

An optical end-point detection system meeting both these requirements is shown in the figure for an example of a sputter process. The detection system consists of a laser 1, a sandwich-structured monitor wafer 2 and a light detector 3 recording the intensity of the laser beam reflected at monitor wafer 2. Monitor wafer 2 together with objects 4 to be sputtered is contained in sputter hood 5 with appropriately arranged optical windows 11.

Monitor wafer 2 has a topmost layer 6, whose thickness and etch rate are correlated with those of layers 7 on objects 4 to be etched. Under layer 6 of monitor wafer 2 a second layer 8 is provided, which is followed by a third layer 9 on substrate 10. The second layer 8 is very thin and preferably has a reflectivity index which substantially differs from that of layer 6. Layer 9 should consist of the same material as layer 6 and be relatively thick.

After removal of layer 6 by etching, the laser beam is reflected at layer 8, changing its intensity because of the different reflectivity of this layer. As layer 8 is very thin and easily etched, it is removed quickly, thus leading to a pronounced and clearly distinguishable change in the recorded intensity.

Th...