Laser interferometer system and method for monitoring and controlling IC processing
First Claim
1. A process for monitoring the change in thickness of a layer of material being fabricated on a substrate as by one of etching, growth or deposition, based upon the change in thickness of the layer on a substrate scribe line or other selected feature, comprising focusing a laser beam to a beam spot on the substrate, the focused beam spot being of a small size selected based upon the size of the selected feature, for providing an enhanced signal-to-noise ratio;
- repetitively scanning the beam spot across the selected feature to generate an optical interference signal characteristic of the repetitive scanning and the thickness of the selected substrate feature; and
converting the optical signal into a corresponding electrical signal adapted for monitoring the fabrication process.
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Abstract
A laser interferometer system and associated method for etching endpoint detection, and for monitoring etching or growth to a selected depth. The process implemented by the system involves scanning the laser beam across scribe lines on a wafer which is undergoing fabrication (growth or etching) and monitoring the resulting interference pattern. Alternatively, the process implemented by this system involves moving the laser beam across the scribe line to detect the position of the scribe line; locking the laser beam on the scribe line; and monitoring the resulting interference pattern.
195 Citations
25 Claims
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1. A process for monitoring the change in thickness of a layer of material being fabricated on a substrate as by one of etching, growth or deposition, based upon the change in thickness of the layer on a substrate scribe line or other selected feature, comprising focusing a laser beam to a beam spot on the substrate, the focused beam spot being of a small size selected based upon the size of the selected feature, for providing an enhanced signal-to-noise ratio;
- repetitively scanning the beam spot across the selected feature to generate an optical interference signal characteristic of the repetitive scanning and the thickness of the selected substrate feature; and
converting the optical signal into a corresponding electrical signal adapted for monitoring the fabrication process. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
- repetitively scanning the beam spot across the selected feature to generate an optical interference signal characteristic of the repetitive scanning and the thickness of the selected substrate feature; and
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13. A process for monitoring the change in thickness of a layer of material being fabricated on a substrate as by one of etching, growth or deposition, based upon the change in thickness of the layer over a substrate scribe line or other selected feature, comprising focusing a laser beam to a beam spot on the substrate, the focused beam spot being of a small size selected based upon the size of the selected feature, for providing a high signal-to-noise ratio;
- controllably moving the beam spot across the substrate to intersect the selected substrate feature while monitoring the resulting first optical interference signal;
stopping the movement of the beam spot upon reaching a predetermined value of the optical signal characteristic of the selected substrate feature to thereby focus the beam on the selected substrate feature;
fabricating the layer and thereby generating a second optical signal characteristic of the changing thickness of the layer; and
converting the second optical interference signal into a corresponding electrical signal for monitoring the fabrication process. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
- controllably moving the beam spot across the substrate to intersect the selected substrate feature while monitoring the resulting first optical interference signal;
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24. A process for monitoring the varying thickness of a layer of material being fabricated on a semiconductor substrate, comprising scanning a focused beam of collimated light in a reciprocal path between scribe lines on the substrate while monitoring the resulting optical interference pattern of peak values;
- the scanning path length being longer than the distance thereon between adjacent scribe lines and the cross-sectional width of the focused beam being substantially the same dimension as the width of the scribe line; and
stopping the fabrication process upon reaching a selected one of said peak values corresponding to a selected thickness change.
- the scanning path length being longer than the distance thereon between adjacent scribe lines and the cross-sectional width of the focused beam being substantially the same dimension as the width of the scribe line; and
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25. A process for monitoring the varying thickness of a layer of material being fabricated on a semiconductor substrate comprising moving a focused beam of collimated light along a path between scribe lines on the substrate while monitoring the resulting optical interference signal comprising at least a selected peak value;
- the path length being longer than the distance thereon between adjacent scribe lines and the cross-sectional width of the focused beam being based upon the width of the scribe line;
stopping the scanning at the selected peak value to position the beam at a scribe line;
monitoring the resulting optical signal; and
stopping the fabrication process upon reaching a selected point corresponding to a selected thickness change.
- the path length being longer than the distance thereon between adjacent scribe lines and the cross-sectional width of the focused beam being based upon the width of the scribe line;
Specification