Method and apparatus for detecting defects on a wafer

An apparatus for detecting a defect on a substrate, the apparatus comprising:

• a support for supporting a substrate, wherein the substrate has a plurality of device units formed thereon, each device unit including a plurality of pixels;
• a light source for irradiating a light on the substrate;
• an image detector for sensing a reflecting light reflected by a surface of the substrate from the light source;
• a data processing unit for calculating a raw datum of a target pixel by subtracting digital image information of a corresponding pixel from digital image information of the target pixel, wherein the corresponding pixel is located in a first device unit that is adjacent to a second device unit that includes the target pixel, the corresponding pixel corresponding to the target pixel;
• a setting unit for presetting a threshold region, wherein the threshold region includes at least one pair of upper and lower limits;
• and
• a judging unit for judging whether or not the target pixel is a defective pixel by comparing the raw datum of the target pixel with the threshold region and marking the pixel as defective if within the threshold range.

A method of detecting a defect on a substrate, the method comprising:

• irradiating a light on a substrate, wherein the substrate has a plurality of device units on a surface thereof, each device unit including a plurality of pixels;
• measuring image information for the plurality of pixels by sensing the light reflected by a surface of the substrate from the irradiating light;
• calculating a raw datum of a target pixel by subtracting the image information of a corresponding pixel from the image information of the target pixel, wherein the target pixel is a subject pixel for detecting a defect, wherein the corresponding pixel is a pixel located in a first device unit and corresponds to the target pixel, and wherein the first device unit is located adjacent to a second device unit that includes the target pixel;
• presetting a threshold region including at least one pair of upper and lower limits not including a zero value within the region;
• and
• comparing the raw datum with the threshold region.