Method of detecting an end point of surface treatment

Details Method of detecting an end point of surface treatment Method of detecting an end point of surface treatment

1989-11-17

1991-03-05

Nelms, David C.

Radiant energy

Photocells; circuits and apparatus

Optical or pre-photocell system

356357, 156626, G01N 2186, G01B 1102, H01L 21306

Patent

active

049980211

ABSTRACT:
A method of detecting an end point of surface treatment of a wafer includes the steps of: projecting coherent light onto an upper surface of the wafer provided with a layer to be treated; receiving superposed light caused by interference of light reflected on a surface of the layer to be treated and on the other surface thereof and converting it to a photoelectric signal; sampling the photoelectric signal; detecting a first point where a variation range caused by the interference in the sampled data becomes smaller than a predetermined value; detecting a second point where an extreme value of the variation of the photoelectric signal caused by the interference occurs prior to the first point; and determining the end point of treatment by prescribed calculation using the second point as a reference point. The detection of the first point may be incorrect depending on the detection conditions. However, the second point prior to the first point is detected in a relatively stable manner irrespective of the detecting conditions. Thus, since the end point of treatment is determined by the prescribed calculation using the second point as a reference point, the end point of treatment is detected correctly and with good repeatability.

REFERENCES:
patent: 3612692 (1971-10-01), Kruppa et al.
patent: 4462860 (1984-07-01), Szmanda
patent: 4611919 (1986-09-01), Brooks, Jr. et al.
patent: 4618262 (1986-10-01), Maydan et al.
patent: 4838694 (1989-06-01), Betz et al.

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