Method for checking wafers having a lacquer layer for faults
First Claim
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1. A method for automatically checking wafers having a lacquer layer, which comprises:
- a) directly illuminating a wafer having a lacquer layer reflecting light;
b) ascertaining a reflectance value of the reflected light by pixels simultaneously for a plurality of points on a surface of the wafer with a picture-taking device disposed at a given angle above the wafer for detecting pictures to be taken by pixels, and buffer-storing the reflectance value with an evaluation device connected to the picture-taking device;
c) comparing the ascertained and buffer-stored reflectance values with reflectance comparison values of a comparison wafer;
d) ascertaining whether the wafer is OK or defective from a result of the comparison between the ascertained and buffer-stored reflectance values and the comparison values, in accordance with at least two predetermined judgment criteria, including;
determining a first judgment criterion as a predetermined minimum amount of agreement between particular ascertained, buffer-stored reflectance values and the comparison values associated with them; and
determining a second judgment criterion as follows;
ascertaining a location of points on the wafer having pixels exceeding the first judgment criterion, in the event that the first judgment criterion shows that the wafer is defective;
ascertaining which of the points form coherent regions on the wafer from the location of the points; and
determining that the wafer is OK in the event that the number of the coherent regions is below a predetermined maximum amount; and
e) separating the wafer having been found defective from wafers having been found defect-free, if a plurality of wafers are being checked.
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Abstract
A wafer with a lacquer layer applied to it is checked automatically by lighting the wafer directly, so that the lacquer layer reflects the light. Resultant reflectance values of the reflected light are ascertained and buffer-stored and compared with corresponding values for a comparison wafer. It is ascertained whether the wafer is OK or defective from the result of the comparison in accordance with at least one predetermined judgment criterion.
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Citations
10 Claims
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1. A method for automatically checking wafers having a lacquer layer, which comprises:
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a) directly illuminating a wafer having a lacquer layer reflecting light; b) ascertaining a reflectance value of the reflected light by pixels simultaneously for a plurality of points on a surface of the wafer with a picture-taking device disposed at a given angle above the wafer for detecting pictures to be taken by pixels, and buffer-storing the reflectance value with an evaluation device connected to the picture-taking device; c) comparing the ascertained and buffer-stored reflectance values with reflectance comparison values of a comparison wafer; d) ascertaining whether the wafer is OK or defective from a result of the comparison between the ascertained and buffer-stored reflectance values and the comparison values, in accordance with at least two predetermined judgment criteria, including; determining a first judgment criterion as a predetermined minimum amount of agreement between particular ascertained, buffer-stored reflectance values and the comparison values associated with them; and determining a second judgment criterion as follows; ascertaining a location of points on the wafer having pixels exceeding the first judgment criterion, in the event that the first judgment criterion shows that the wafer is defective; ascertaining which of the points form coherent regions on the wafer from the location of the points; and determining that the wafer is OK in the event that the number of the coherent regions is below a predetermined maximum amount; and e) separating the wafer having been found defective from wafers having been found defect-free, if a plurality of wafers are being checked. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification