Holographic scatterometer for detection and analysis of wafer surface deposits
AssigneeSentec Ltd
InventorsAlex Klooster, James M. Marks, Takeo Sawatari
Life of this patent
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Abstract
A holographic scatterometer with continuous readout can rapidly identify the presence of deposits (particles or other defects) on an unpatterned wafer surface and determine the volume density (size) and location. The scatterometer can also determine chemical composition of the detected deposits. The range of the deposit (particle) size to be measured is below 80 nm, which currently existing scatterometer type instruments cannot readily detect. The inspection can be achieved as an in-line stage during the processing of wafers or in situ in combination with another processing tool or as a separate off-line analysis device.
Claims29
An apparatus for inspecting a surface of an object comprising:
- a light source configured to generate an illumination light beam, said illumination beam when incident upon a particle on the surface being scattered to define a scattered beam;
- a photodetector;
- an optical assembly configured to direct said scattered beam and a reference beam derived from said illumination beam to said photodetector;
- a positioning assembly configured to provide a movement of said object such that said surface moves relative to said illumination beam;
- a controller coupled to said photodetector configured to detect the presence of said particle in accordance with a spatial interference pattern from a superposition of said reference beam and said scattered beam.
A method of inspecting a wafer surface comprising the steps of:
- (A) directing an illumination beam to the wafer surface;
- (B) moving the wafer surface relative to the illumination beam;
- (C) generating a reference beam when the illumination beam impinges on the surface;
- (D) generating a scattered beam when the illumination light beam impinges on a particle on the wafer surface;
- (E) detecting the presence of the particle in accordance with an interference pattern formed by a superposition of the reference beam and the scattered beam by moving an image of the scattered beam within a detection device synchronously with the step of moving the wafer.
An apparatus for inspecting a surface of an object comprising:
- a light source configured to generate an illumination light beam over a field of view area of the surface, said illumination beam when incident upon a particle on the surface being scattered to define a scattered beam;
- a photodetector having a plurality of elements;
- an optical assembly configured to direct said scattered beam and a reference beam derived from said illumination beam to said photodetector, said optical assembly providing a defocused beam to said photodetector;
- a positioning assembly configured to move said object such that said surface moves relative to said illumination beam;
- a controller coupled to said photodetector and said positioning assembly configured to detect the presence of said particle in accordance with a spatial interference pattern from a superposition of said reference beam and said scattered beam.
A method of inspecting a wafer surface comprising the steps of:
- directing an illumination beam to the wafer surface;
- generating a reference beam when the illumination beam impinges on the surface;
- generating a scattered beam when the illumination light beam impinges on a particle on the wafer surface;
- defocusing the scatted beam at the surface of a detector;
- forming an interference pattern image formed by a superposition of the reference beam and the scattered beam within the detector;
- synchronously moving the wafer surface relative to the illumination beam and the image within the detector;
- and
- detecting the presence of the particle in accordance with the interference pattern image.
Dependencies are inferred from the claim text.