Method and apparatus for detection, analysis and identification of particles

A method of analyzing particles in a material, the method comprising:

• generating a polarized laser beam;
• modulating the intensity of the polarized laser beam at a first frequency;
• splitting the polarized laser beam into two orthogonally polarized beams;
• phase shifting the two polarized laser beams with respect to each other at a second frequency;
• directing the two orthogonally polarized, phase shifted laser beams onto the material;
• and
• detecting light scattered by particles in the material at an angle to the two beams, at the first and second frequencies.

A method of analyzing particles on the surface of a semiconductor, the method comprising:

• generating a polarized laser beam;
• modulating the intensity of the polarized laser beam at a first frequency;
• splitting the polarized laser beam into two orthogonally polarized beams;
• phase shifting the two polarized laser beams with respect to each other at a second frequency;
• directing the two orthogonally polarized, phase shifted laser beams onto the surface of the semiconductor;
• detecting light scattered by particles on the surface of the semiconductor at an angle to the two beams;
• and
• synchronously demodulating the detected scattered light.

An apparatus for analyzing particles in a material, the apparatus comprising:

• means for generating a polarized laser beam;
• means for applying current modulation to the means for generating;
• means for splitting the polarized laser beam into two orthogonal polarized laser beams;
• means for phase shifting the two orthogonally polarized laser beams with respect to each other;
• means for directing the phase shifted, orthogonally polarized laser beams onto the material;
• means for detecting scattered light produced by the particles;
• and
• means for synchronously demodulating the detected scattered light.

An apparatus for the analysis of particles in a material, the apparatus comprising:

• a laser source producing an intensity modulated, polarized laser beam;
• a phase modulator comprising a polarized beam splitter cube comprising a center, first and second adjacent sides, a first quarter-wave plate located adjacent the first side and a second quarter-wave plate adjacent the second side, a first mirror adjacent the first quarter-wave plate and a second mirror adjacent the second quarter-wave plate, the first and second mirrors being spaced from the center of the polarized beam splitter cube by different distances, wherein the phase modulator splits the laser beam into two orthogonally polarized laser beams, phase shifted with respect to each other;
• a sampling cell comprising the material to be analyzed, wherein the two orthogonally polarized laser beams are incident upon the sampling cell;
• a photoreceiver for detecting light scattered by particles in the material;
• and
• a synchronous demodulator operatively connected to the photoreceiver.

An apparatus for the analysis of particles on the surface of a semiconductor, the apparatus comprising:

• a laser source producing an intensity modulated, polarized laser beam;
• a phase modulator comprising a polarized beam splitter cube comprising a center, first and second adjacent sides, a first quarter-wave plate located adjacent the first side and a second quarter-wave plate adjacent the second side, a first mirror adjacent the first quarter-wave plate and a second mirror adjacent the second quarter-wave plate, the first and second mirrors being spaced from the center of the polarized beam splitter cube by different distances, wherein the phase modulator splits the laser beam into two orthogonally polarized laser beams, phase shifted with respect to each other;
• a sampling cell containing the semiconductor to be analyzed, wherein the two orthogonally polarized laser beams are incident upon the surface of the semiconductor;
• a photoreceiver for detecting light scattered by particles on the surface of the semiconductor;
• and
• a synchronous demodulator operatively connected to the photoreceiver.