Optical scanning system for surface inspection

An optical scanning method for detection of anomalies, such as particles and pattern defects, on a surface, comprising;

• directing a focused beam of light onto a sample surface to produce an illuminated spot thereon, said spot illuminating a common area on the surface;
• scanning the spot across the surface along a first scan line in a first scan and then subsequently along at least one second scan line in the at least one second scan, so that said spot illuminates a line of pixels during the at least two scans;
• positioning a detector adjacent to said surface to collect scattered light from the spot, wherein the detector includes a group of sensors including at least a first and a second line of sensors, said sensors providing output signals in response to the collected scattered light from an array of surface portions defining a line of pixels in the common area, so that during the at least two scans, scattered light from one of the pixels is collected by a corresponding sensor in the first line of sensors and by a corresponding sensor in the second line of sensors, said detector located away from a specular reflection direction of the beam;
• and
• focusing scattered light from the illuminated spot at each of the pixels in the line of pixels during the first scan to a corresponding sensor in the first line of sensors, and scattered light from the illuminated spot at each of the pixels in the line of pixels during the at least one second scan to a corresponding sensor in the second line of sensors without forming an image of the spot at the detector;
• transferring output signals from said first line of sensors to the at least one second line of sensors, thereby performing time delayed integration of the output signals corresponding to light scattered by the line of pixels during the at least two scans;
• and
• analyzing the time integrated output signals of the sensors to detect anomalies on the surface.

An optical system for detection of anomalies, such as particles or pattern defects, on a surface comprising:

• an optical source providing a beam of radiation illuminating the surface;
• two or more sensors;
• an optical element collecting light scattered from the surface and directing the collected and scattered radiation to the two or more sensors, causing the sensors to provide output signals in response thereto, each of the two or more sensors located to sense radiation scattered from the surface in directions different from those of radiation sensed by the other sensor(s);
• a device causing relative motion between the beam and the surface so that the beam is caused to scan the surface and so that the two or more sensors provide output signals in response to radiation from different parts of the surface scanned by the beam;
• a storage storing said sensor output signals;
• and
• a processor providing a plurality of maps by providing a map from said stored sensor output signals from each of the two or more sensors during the scan and comparing at least two of the maps for identifying anomalies.

An optical method for detection of anomalies, such as particles or pattern defects, on a surface comprising:

• illuminating the surface using a beam of radiation;
• collecting light scattered from the surface and directing the collected and scattered light to two or more sensors, causing the sensors to provide output signals in response thereto, each of the two or more sensors located to sense radiation scattered from the surface in directions different from those of radiation sensed by the other sensor(s);
• scanning the beam across the surface so that the two or more sensors provide output signals in response to radiation from different parts of the surface scanned by the beam;
• storing said sensor output signals;
• and
• providing a plurality of maps by providing a map from said stored sensor output signals from each of the two or more sensors during the scan and comparing at least two of the maps for identifying anomalies.

An optical scanning system for detection of anomalies, such as particles or pattern defects, on a surface comprising:

• a source providing a focused beam of radiation to produce an illuminated spot on a sample surface;
• a device causing relative motion between the beam and the surface so that the spot is scanned across the surface along a first scan line in a first scan and then subsequently along at least a second scan line in at least a second scan, so that said spot illuminates a common area on the surface during the at least two scans;
• a detector positioned adjacent to said surface to collect scattered light from the spot, wherein the detector includes a group of sensors including a first and at least one second line of sensors, said sensors providing output signals in response to the collected scattered light from an array of surface portions defining a line of pixels in the common area, so that during the at least two scans, scattered light from one of the pixels is collected by a corresponding sensor in the first line of sensors and by a corresponding sensor in the second line of sensors, said detector located away from a specular reflection direction of the beam;
• an optical element focusing scattered light from each of the pixels in the line of pixels during the first scan to the corresponding sensor in the first line of sensors, and scattered light from each of the pixels in the line of pixels during the at least one second scan to the corresponding sensor in the at least one second line of sensors;
• a circuit that synchronizes a transfer of signals from said first line of sensors to the at least one second line of sensors, thereby performing time delayed integration of signals at scattered by the line of pixels;
• and
• an instrument that analyzes the outputs of the sensors to detect anomalies on the surface.