Surface inspection system

• US 4,402,613 A
• Filed: 03/29/1979
• Issued: 09/06/1983
• Est. Priority Date: 03/29/1979
• Status: Expired due to Term

• Current Assignee: ASM America Incorporated (ASM International NV)
• Original Assignee: ASM International NV
• Inventors: Daly, John K., Terry, Malvin D.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Bovernick, Rodney B.
• Application Number:
  US06/024,944
• Time in Patent Office: 1,622 Days
• Field of Search: 356/445, 356/446, 356/430, 356/431, 356/426, 356/244, 250/562, 250/563, 250/548, 414/416
• US Class Current: 356/446
• CPC Class Codes: G01N 21/88 Investigating the presence of flaws or contamination
• CPC Class Codes: Y10S 414/137 including means for charging or discharging wafer cassette

Abstract

A surface inspection system utilizes a laser light source, and a vacuum chuck to support the material whose surface is to be inspected. The vacuum chuck is rotatable. The laser beam may be translated across the work surface while the chuck is rotated, all the while maintaining mutual perpendicularity of the vacuum chuck work surface and the laser beam. An airtrack transports the material whose surface is to be inspected. Sensors are utilized to detect the position of such material along the track and to guide the system in its operation.

Claims

1. A scattered light surface measuring system for the detection of surface anomalies on reflective surfaces of flat articles to be tested, comprising:

a support having a horizontal upper surface to support a flat test article with its upper reflective surface in a horizontal position;

a collimated light light source mounted above the support and positioned and arranged to transmit a collimated light beam directly perpendicularly upon the horizontal reflective surface in the absence of interception by reflectors, prisms, lenses, or other optical path bending devices;

a scattered light detector surrounding the collimated light beam above the support to intercept the light rays scattered by the surface anomalies of the test article;

the support for the test article is controllably powered to rotate continuously about a vertical axis as required;

the light source is mounted to travel transversely over the support and test article while maintaining the perpendicularity of the collimated light beam to the surface of the test articles;

controllable power means is provided to produce the transverse travel of the light source;

and the control means are operable to cause simultaneous rotation of the test sample and transverse travel of the light source between the center and the perimeter of the test article and produce impingement of the light beam upon the entire area of the test sample in the form of an Archimedean spiral; and

the support for the test article has a perforated upper surface and a controllable vacuum pump is connected thereto through the interior of the support to constitute a vacuum chuck for holding the test article securely in place while the chuck is stationary or rotating.

2. A scattered light surface measuring system for the detector of surface anomalies on reflective surfaces of flat articles to be tested, comprising:

a support having a horizontal upper surface to support a flat test article with its upper reflective surface in a horizontal position;

a collimated light light source mounted above the support and positioned and arranged to transmit a collimated light beam directly perpendicularly upon the horizontal reflective surface in the absence of interception by reflectors, prisms, lenses, or other optical path bending devices;

and a scattered light detector surrounding the collimated light beam above the support to intercept the light rays scattered by the surface anomalies of the test article;

the support for the test article is controllably powered to rotate continuously about a vertical axis as required;

the light source is mounted to travel transversely over the support and test article while maintaining the perpendicularity of the collimate light beam to the surface of the test articles;

controllable power means is provided to produce the transverse travel of the light source;

the control means are operable to cause simultaneous rotation of the test sample and transverse travel of the light source between the center and the perimeter of the test article and produce impingement of the light beam upon the entire area of the test sample in the form of an Archimedean spiral;

loading means are provided for moving successive test articles from a storage location to the vicinity of the rotatable support for test;

unloading means are provided for moving the articles from the test location to a second storage location;

the loading and unloading means include an air track provided with jet means for conveying the articles along the track;

an intermediate section of the track is formed with an aperture located above the rotary support at the test location;

stop means is mounted on the track to intercept each article above the aperture;

the intermediate section of the track is vertically movable with respect to the other sections; and

means are provided to lower the track and deposit a test article on the rotary support for the test operation free of interference by other parts of the apparatus.

3. The measuring system of claim 2 said loading means further comprising:

input cassette means having at least an input cassette for housing an uninspected plurality of said test articles; and

input indexing means for selectively shifting a selected one of said uninspected plurality of said test articles onto said track.

4. The measuring system of claim 2 said unloading means comprising:

lifting means for raising said portion of said track so that said test articles is thereby lifted from said rotary work surface; and

release means for removing the impediment of said stop means so that said jet means can further propel said test article along said track.

5. A scattered light surface measuring system for the detection of surface anomalies on reflective surfaces of flat articles to be tested, comprising:

a support having a horizontal upper surface to support a flat test article with its upper reflective surface in a horizontal position;

a collimated light light source mounted above the support and positioned and arranged to transmit a collimated light beam directly perpendicularly upon the horizontal reflective surface in the absence of interception by reflectors, prisms, lenses, or other optical path bending devices;

and a scattered light detector surrounding the collimated light beam above the support to intercept the light rays scattered by the surface anomalies of the test article;

said scattered light detector has an annular shape and further has a disposition about said beam of collimated light so that said beam of collimated light passes undetected through the center of the annulus while reflected light scattered by a surface anomaly is detected.