Wafer shape accuracy using symmetric and asymmetric...

Optics: measuring and testing – Plural test

Reexamination Certificate

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

C356S485000, C356S496000, C356S504000, C702S034000, C702S035000, C702S036000

Reexamination Certificate

active

06594002

ABSTRACT:

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
N/A
BACKGROUND OF THE INVENTION
The present invention relates generally to apparatus and methods of measuring the shape and thickness of wafers, and more specifically to wafer shape and thickness measuring apparatus and methods that employ symmetric and asymmetric instrument error signatures.
Semiconductor circuits are grown on semiconductor wafers that are being manufactured in increasingly larger diameters. The fineness of the circuit lines making up the semiconductor circuits requires a precise focus on an extremely flat wafer. Test equipment has been developed to measure the shape and thickness of wafers, but the quality of the measurement is limited by the error that is induced by the equipment. In test equipment that grips the wafers by the edge and measures the wafer without touching either surface, the measurement precision and consistency have been good when wafers are placed on the test equipment at the same angular orientation. The shape accuracy has not been as good when the wafers are measured at various angular orientations. The measurements from this equipment may be degraded by two types of errors; symmetrical error that is independent of the orientation of the wafer to the grippers and asymmetric error which is correlated with the angular orientation of the wafer on the instrument.
BRIEF SUMMARY OF THE INVENTION
Wafer shape can to be determined with a relatively low spatial frequency resolution. When a wafer is measured while the load angle between measurements is varied, a strong signature that also rotates with the load angle is observed. This instrument signature is independent of the wafer shape and is fairly stationary. A technique that strongly rejects wafer shape can be used to obtain most of this signature, which is called the symmetric signature. The remainder that is not removed by this first step is called the asymmetric signature. The asymmetric instrument signature is evaluated statistically by considering the residual errors in the data. The total corrector is defined by adding both the symmetric and the asymmetric instrument signature. Other aspects, features, and advantages of the present invention are disclosed in the detailed description that follows.


REFERENCES:
patent: 3748602 (1973-07-01), Delfrate et al.
patent: 5048023 (1991-09-01), Buehler et al.
patent: 5155633 (1992-10-01), Grove et al.
patent: 5909282 (1999-06-01), Kulawiec
patent: 6275297 (2001-08-01), Zalicki
patent: 6353473 (2002-03-01), Ishimori et al.

LandOfFree

Say what you really think

Search LandOfFree.com for the USA inventors and patents. Rate them and share your experience with other people.

Rating

Wafer shape accuracy using symmetric and asymmetric... does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Wafer shape accuracy using symmetric and asymmetric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wafer shape accuracy using symmetric and asymmetric... will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFUS-PAI-O-3092054

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.