Debris determination method

A debris determination method of determining, using an image obtained by an appearance inspection device, debris that occurs around a hard laser mark on a backside of a wafer after the hard laser mark is formed on the backside or after the backside is polished after formation of the hard laser mark, comprising:

• a step A of replacing luminance data of a grayscale image obtained by the appearance inspection device with matrix data;
• a step B of extracting a hard laser mark-printed region including the hard laser mark from the matrix data;
• a step C of obtaining a least-squares plane of luminance with reference to a portion without the hard laser mark within the extracted hard laser mark-printed region;
• a step D of obtaining normalized matrix data by subtracting the least-squares plane of the luminance from the hard laser mark-printed region and removing a gradient of the luminance of the hard laser mark-printed region;
• a step E of obtaining protrusion-side matrix data by substituting 0 for a matrix value less than 0 from the normalized matrix data;
• a step F of obtaining recess-side matrix data by inverting a sign of the normalized matrix data and substituting 0 for a matrix value representing dots that constitute the hard laser mark and for a matrix value representing noise;
• a step G of adding the protrusion-side matrix data and the recess-side matrix data to obtain composite matrix data;
• a step H of obtaining low-pass matrix data by applying a two-dimensional moving average process to the composite matrix data;
• and
• a step I of determining, as the debris, data that indicate a matrix value exceeding a predetermined threshold from the low-pass matrix data, and obtaining an area ratio of the debris by counting a number of pieces of data of the debris and dividing the number by a number of pieces of data of the hard laser mark-printed region to determine presence or absence of the debris in the hard laser mark-printed region based on the area ratio of the debris.