Method and apparatus for measuring surface properties of polishing pad

An apparatus configured to measure surface properties of a polishing pad, comprising:

• an optical system configured to apply a laser beam to a polishing pad at at least two different incident angles;
• and
• a processing device configured to determine surface properties of the polishing pad by performing a Fourier transform on light reflected by the polishing pad and received by the optical system;
• wherein the optical system comprises:
• a light source configured to emit the laser beam;
• a first mirror configured to apply the laser beam emitted from the light source to the polishing pad at a first incident angle;
• a second mirror disposed at a second position lower than a first position of the first mirror and configured to apply the laser beam emitted from the light source to the polishing pad at a second incident angle;
• at least two light receivers configured to receive the light reflected by the surface of the polishing pad at a first reflection angle corresponding to the first incident angle and at a second reflection angle corresponding to the second incident angle;
• and
• wherein the laser beam emitted from the light source passes through the first mirror and is refracted by the first mirror, and the refracted light is applied to the second mirror;
• wherein the Fourier transform is performed on the received light reflected at the first and second reflection angles to determine the surface properties of the polishing pad by the processing device.

A method of measuring surface properties of a polishing pad, comprising:

• moving a mirror configured to reflect a laser beam emitted from a light source and apply the reflected laser beam to a surface of a polishing pad at a plurality of incident angles, wherein the plurality of incident angles are different from each other;
• receiving light reflected by the surface of the polishing pad at a plurality of reflection angles;
• and
• performing a Fourier transform is performed on the received light reflected at the plurality of reflection angles to determine surface properties of the polishing pad.

An apparatus configured to measure surface properties of a polishing pad, comprising:

• an optical system configured to apply at least two laser beams to a polishing pad at at least two different incident angles;
• and
• a processing device configured to determine surface properties of the polishing pad by performing a Fourier transform on light reflected by the polishing pad and received by the optical system;
• wherein the optical system comprises:
• a first light source configured to emit a first laser beam;
• a second light source provided at a second position different from a first position of the first light source and configured to emit a second laser beam;
• a mirror configured to reflect the first laser beam emitted from the first light source and to apply the first laser beam to the polishing pad at a first incident angle, and configured to reflect the second laser beam emitted from the second light source and to apply the second laser beam to the polishing pad at a second incident angle;
• and
• at least two light receivers configured to receive the light reflected by the surface of the polishing pad at a first reflection angle corresponding to the first incident angle and at a second reflection angle corresponding to the second incident angle;
• wherein the Fourier transform is performed on the received light reflected at the first and second reflection angles to determine the surface properties of the polishing pad by the processing device.

An apparatus configured to measure surface properties of a polishing pad, comprising:

• an optical system configured to apply a laser beam to a polishing pad at at least two different incident angles;
• and
• a processing device configured to determine surface properties of the polishing pad by performing a Fourier transform on light reflected by the polishing pad and received by the optical system;
• wherein the optical system comprises:
• a light source configured to emit the laser beam;
• a first optical fiber coupled to the light source and configured to apply the laser beam emitted from the light source to the polishing pad at a first incident angle;
• and
• a second optical fiber coupled to the light source and configured to apply the laser beam emitted from the light source to the polishing pad at a second incident angle;
• and
• at least two light receivers configured to receive the light reflected by the surface of the polishing pad at a first reflection angle corresponding to the first incident angle and at a second reflection angle corresponding to the second incident angle;
• wherein the Fourier transform is performed on the received light reflected at the first and second reflection angles to determine the surface properties of the polishing pad by the processing device.