Method and apparatus for detecting defects

Abstract

An inspection apparatus projects a laser beam on the surface of a SOI wafer and detects foreign matter on and defects in the surface of the SOI wafer by receiving scattered light reflected from the surface of the SOI wafer. The wavelength of the laser beam used by the inspection apparatus is determined so that a penetration depth of the laser beam in a Si thin film may be 10 nm or below to detect only foreign matter on and defects in the outermost surface and not to detect foreign matter and defects in a BOX layer. Only the foreign matter on and defects in the outermost surface layer can be detected without being influenced by thin-film interference by projecting the laser beam on the surface of the SOI wafer and receiving scattered light rays.

1 . A defect detecting method comprising the steps of:
 projecting a laser beam having a wavelength in the range of 210 to 390 nm on a surface, coated with an optically transparent thin film, of a test sample in a direction inclined at an angle of 30° or below to the surface of the test sample;   detecting scattered light rays reflected from the surface of the test sample; and   detecting defects of sizes below 0.1 μm formed on the surface of the test sample by processing detection signals provided upon the detection of the defects.   
   
   
       2 . The defect detecting method according to  claim 1 , wherein scattered light rays reflected from the surface of the test sample are detected by a plurality of detectors set respectively at different detecting angles relative to the surface. 
   
   
       3 . The defect detecting method according to  claim 1 , wherein the test sample is a bare Si wafer. 
   
   
       4 . The defect detecting method according to  claim 1 , wherein the test sample is a SOI wafer. 
   
   
       5 . The defect detecting method according to  claim 1 , wherein a depth of penetration of the laser beam into the thin film formed on the surface of the test sample is 10 nm or below. 
   
   
       6 . A defect detecting method comprising the steps of:
 projecting a laser beam having a wavelength obliquely on a surface, coated with an optically transparent thin film, of a test sample, intensity of reflected light rays produced by reflecting the laser beam by the optically transparent thin film varying in a narrow range of variation relative to a range of variation of thickness of the optically transparent thin film;   receiving scattered light rays reflected from the surface of the test sample from a plurality of directions for detection; and   detecting defects formed on the surface of the test sample by processing detection signals provided upon the reception of scattered light rays reflected from the surface of the test sample.   
   
   
       7 . The defect detecting method according to  claim 6 , wherein the test sample is a bare Si wafer. 
   
   
       8 . The defect detecting method according to  claim 6 , wherein the test sample is a SOI wafer. 
   
   
       9 . The defect detecting method according to  claim 6 , wherein a depth of penetration of the laser beam into the thin film formed on the surface of the test sample is 10 nm or below. 
   
   
       10 . A defect detecting apparatus comprising:
 a laser beam projecting means for projecting a laser beam having a wavelength in the range of 210 to 390 nm on a surface, coated with an optically transparent thin film, of a test sample in a direction inclined at an angle of 30° or below to the surface of the test sample;   a scattered light detecting means for detecting scattered light rays reflected from the surface of the test sample; and   a defect detecting means for detecting defects of sizes below 0.1 μm formed on the surface of the test sample by processing detection signals provided upon the detection of the defects.   
   
   
       11 . The defect detecting apparatus according to  claim 10 , wherein the scattered light detecting means includes a plurality of detectors that receive scattered light rays reflected from the surface of the test sample from a plurality of directions at different angles to the surface of the test sample for detection. 
   
   
       12 . The defect detecting apparatus according to  claim 10 , wherein the test sample is a bare Si wafer. 
   
   
       13 . The defect detecting apparatus according to  claim 1 , wherein the test sample is a SOI wafer. 
   
   
       14 . The defect detecting apparatus according to  claim 10 , wherein a depth of penetration of the laser beam in the thin film formed on the surface of the test sample is 10 nm or below.