Evaluation of etching processes in semiconductors
First Claim
1. A method of evaluating a semiconductor wafer including a substrate and at least one layer formed there, said wafer having been subjected to an etching process, said method comprising the steps of:
- measuring the wafer by obtaining optical measurements at a plurality of wavelengths, said measurements including reflectivity measurements;
comparing the average reflectivity across one wavelength range with the average reflectivity across another wavelength range to determine if the wafer has been over or under etched; and
evaluating the characteristics of wafer based on the measurements, said characteristics including at least one of layer thickness, index of refraction and extinction coefficient, with the evaluation being premised upon the determination of whether the wafer has been over or under etched.
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Abstract
The subject invention relates to an approach for analyzing etched semiconductor samples using optical measurements. In use, one or more optical measurements are taken on an etched semiconductor wafer. At least one of the measurements includes a range of reflectivity measurements in the visible light region. The average reflectivities in the blue and red visible regions are compared to provide information as to whether the sample has been over or under etched. Once this determination is made, a more accurate analysis can be made of the exact structure of the sample. This approach overcomes the difficulties associated with attempting to analyze a sample where the data must be analyzed without knowledge of whether the sample has been over or under etched. The subject approach can also be utilized in other situations which require the treatment of an upper layer of a sample.
20 Citations
18 Claims
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1. A method of evaluating a semiconductor wafer including a substrate and at least one layer formed there, said wafer having been subjected to an etching process, said method comprising the steps of:
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measuring the wafer by obtaining optical measurements at a plurality of wavelengths, said measurements including reflectivity measurements;
comparing the average reflectivity across one wavelength range with the average reflectivity across another wavelength range to determine if the wafer has been over or under etched; and
evaluating the characteristics of wafer based on the measurements, said characteristics including at least one of layer thickness, index of refraction and extinction coefficient, with the evaluation being premised upon the determination of whether the wafer has been over or under etched. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of evaluating a semiconductor wafer including a substrate and at least one layer formed there, said wafer having been subjected to an etching process, said method comprising the steps of:
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measuring the wafer by obtaining optical measurements at a plurality of wavelengths, said measurements including reflectivity measurements;
comparing the average reflectivity across one wavelength range with the average reflectivity across another wavelength range to determine if the wafer has been over or under etched;
selecting an analytical model for evaluating the wafer based on whether the wafer has been over or under etched; and
evaluating the characteristics of the wafer based on the measurements using a fitting algorithm applied to the selected analytical model. - View Dependent Claims (9, 10, 11, 12, 13)
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14. A method of evaluating a sample including a substrate and at least one layer formed thereon, said sample having been subjected to a treatment process intended to modify the upper layer, said method comprising the steps of:
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measuring the sample by obtaining optical measurements at a plurality of wavelengths, said measurements including reflectivity measurements;
comparing the average reflectivity across one wavelength range with the average reflectivity across another wavelength range to determine the extent to which the upper layer has been modified;
selecting an analytical model for evaluating the wafer based on the extent to which the upper layer has been modified; and
evaluating the sample based on the measurements using a fitting algorithm applied to the selected analytical model. - View Dependent Claims (15, 16, 17, 18)
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Specification