Method and apparatus for CMP end point detection using confocal optics
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorsChun-Hung Lu, Mei-Yen Li
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Abstract
End point detection during a CMP process on a semiconductor wafer employs confocal optics to increase signal-to-noise ratio near the end point. The use of confocal optics for sensing reflected light from the wafer surface exhibits greater selectivity where intermediate layers of metal are present in the wafer. A laser diode is used as a light source to examine the wafer surface. Light reflected back to the laser diode reduces its power state, and this power state is sensed by a current detector which outputs a signal representative of reflected light intensity.
Claims19
A method of detecting an end point of a chemical mechanical polishing (CMP) process used in processing a semiconductor wafer, comprising the steps of:
- (A) generating light from a light source of laser diode and passing through a focusing lens such that the light is focused onto the said wafer at a distance from the lens corresponding to the end point of the CMP process;
- (B) passing light reflected from said wafer back through said focusing lens and onto said laser diode;
- and
- (C) detecting the intensity of light as a power state received by said laser diode, the detected light intensity being related to said end point.
A method of detecting an end point of a chemical mechanical polishing (CMP) process used in processing a semiconductor wafer having at least two layers of a metallic compound comprising the steps of:
- (A) directing light beam from a light source through a focusing lens;
- (B) focusing the light passing through said lens in step (A) onto the wafer during the CMP process at a distance corresponding to said end point;
- (C) directing light reflected from said wafer surface back through said lens, wherein the intensity of said reflected light is related to the distance from said lens to said wafer surface, said distance being related to said end point;
- and,
- (D) detecting the intensity of the light directed back through said lens in step (C).
A method of detecting an end point of a chemical mechanical polishing (CMP) process, wherein the surface of a semiconductor wafer is pressed into contact with a deformable polishing head, comprising the steps of:
- (A) focusing light from a first light source onto said wafer surface;
- (B) at the commencement of said CMP process, detecting the intensity of light reflected from said wafer surface and originating from said first light source, the detected light from said first source representing the start point of said CMP process;
- (C) directing light from a second light source onto said wafer surface;
- (D) focusing the light directed in step (C) at a focal point corresponding to a depth into said wafer representing said end point.
Apparatus for detecting an end point of a chemical mechanical polishing (CMP) process used in processing a semiconductor wafer, comprising;
- at least a first light source;
- at least a first detector for detecting the intensity of light originating from said source and reflected from the surface of said wafer;
- and,
- at least a first optical lens for focusing light from said source onto said wafer surface, and
- for focusing light reflected from said wafer surface onto said wafer,
- wherein the intensity of the light detected by said detector is related to the distance of said lens from said wafer surface, said distance being related to said end point.
Dependencies are inferred from the claim text.