Method for detecting wafer backside defect

A method for detecting a wafer backside defect, comprising the following steps:

• Step 1, providing a signal database, the signal database comprising signal data corresponding to various different defects, the defects comprising convex defects of various different heights or widths and concave defects of various different depths or widths, the signal data being data formed by transforming reflected and scattered light signals collected after an oblique incident light source is irradiated to the defects, each type of the defects corresponding to one type of the signal data, the signal data reflecting 3D information of corresponding defects, and the 3D information of the defects comprising height or depth information, and
• establishing the signal database, the establishing the signal database comprising the following sub-steps:
• Step 11, providing a plurality of different test patterns each corresponding to a convex defect of one height or width or a concave defect of one depth or width;
• Step 12, using the oblique incident light source to irradiate each of the different test patterns separately, and collecting reflected and scattered light signals corresponding to the each of the different test patterns;
• and
• Step 13, converting the collected reflected and scattered light signals into signal data corresponding to a defect and forming the signal database;
• Step 2, performing backside scanning on a tested wafer by using oblique incident light, and collecting corresponding reflected and scattered light data;
• and
• Step 3, comparing the reflected and scattered light data collected in Step 2 with the signal data in the signal database, and fitting a defect 3D distribution map of the backside of the tested wafer, the defect 3D distribution map comprising height or depth information corresponding to the wafer backside defect.