Defect inspection apparatus and defect inspection method

摘要

Method for realizing an inspection with short wavelength, high power light source and large numerical aperture, high performance optics to improve defect inspection sensitivity is disclosed. Short wavelength high power laser is realized by using a pulse oscillation type laser suitable for generation of high output power in a short-wavelength region. In addition, a spectral bandwidth of the laser is narrowed down so that amount of chromatic aberration of detection optics with single glass material (i.e. without compensation of chromatic aberration) is lowered to permissible level. Using highly workable glass material to construct the detection optics enables necessary surface accuracy or profile irregularity conditions to be met, even if the number of lenses is increased for large NA or the lens doesn't have a rotationally symmetrical aperture.

主权项

1. A defect inspection apparatus comprising:
a pulsed laser light source for emitting ultraviolet light; illumination optics for irradiating with the light a surface of a sample; first detection optics for forming a first enlarged image of the surface of the sample; an image sensor for detecting light scattered on the sample to acquire the first enlarged image of the sample; and an image processing unit for processing the first enlarged image of the sample; wherein: the pulsed laser light source comprises: a semiconductor laser as an oscillator; a signal source for generating pulse signals for driving the semiconductor laser; an amplifier disposed posterior to the semiconductor laser; and a wavelength converter configured to convert light amplified by the amplifier into the ultraviolet light, a spectral bandwidth of the semiconductor laser is controlled by changing a pulse length of each of the pulse signals, and a spectral bandwidth of the ultraviolet light emitted from the pulsed laser light source falls within a light-spectral bandwidth range permissible according to a particular chromatic aberration level of the illumination optics and a particular chromatic aberration level of the first detection optics.