Circuit for machine-vision system

• US 6,603,103 B1
• Filed: 07/08/1999
• Issued: 08/05/2003
• Est. Priority Date: 07/08/1998
• Status: Expired due to Fees

• Current Assignee: Ismeca Semiconductor Holding S.A (COHU Incorporated)
• Original Assignee: PPT Vision, Inc. (Datalogic S.p.A.)
• Inventors: Ulrich, Franz W., Tonkin, Steven W., Bourn, Charles T.
• Primary Examiner(s): Le, Que T.
• Assistant Examiner(s): Luu, Thanh X
• Application Number:
  US09/350,051
• Time in Patent Office: 1,489 Days
• Field of Search: 250/205, 250/204, 250/201.1, 250/559.2, 250/559.3, 250/559.31, 250/234, 250/559.22, 250/559.23, 250/559.24, 250/559.38, 250/559.48, 315/150-159, 356/511, 356/23, 356/601-608, 382/274, 362/247
• US Class Current: 250/205
• CPC Class Codes: G01B 11/2513 with several lines being projected in more than one direction, e.g. grids, patterns
• CPC Class Codes: G01B 11/2518 Projection by scanning of the object
• CPC Class Codes: G03F 7/70483 Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06V 10/243 by compensating for image skew or non-uniform image deformations
• CPC Class Codes: G06V 2201/06 Recognition of objects for industrial automation
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
• CPC Class Codes: H01L 21/67288 Monitoring of warpage, curvature, damage, defects or the like

Abstract

Manufacturing lines include inspection systems for monitoring the quality of parts produced. Manufacturing lines for making semiconductor devices generally inspect each fabricated part. The information obtained is used to fix manufacturing problems in the semiconductor fab plant. A machine-vision system for inspecting devices includes a light source for propagating light to the device and an image detector that receives light from the device. Also included is a light sensor assembly for receiving a portion of the light from the light source. The light sensor assembly produces an output signal responsive to the intensity of the light received at the light sensor assembly. A controller controls the amount of light received by the image detector to a desired intensity range in response to the output from the light sensor. The image detector may include an array of imaging pixels. The imaging system may also include a memory device which stores correction values for at least one of the pixels in the array of imaging pixels. To minimize or control thermal drift of signals output from an array of imaging pixels, the machine-vision system may also include a cooling element attached to the imaging device. The light source for propagating light to the device may be strobed. The image detector that receives light from the device remains in a fixed position with respect to the strobed light source. A translation element moves the strobed light source and image detector with respect to the device. The strobed light may be alternated between a first and second level.

Claims

1. A machine-vision system for inspecting a device, said machine-vision system comprising:

a light source for propagating light to the device;

an image detector that receives light from the device, wherein the image detector and the propagated light from the light source are maintained in a fixed relationship to one another and the image detector is moved relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point, when combined with one another, being useful to obtain a three-dimensional geometric measurement of said each point of the device;

a computational device that derives the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point;

a light sensor assembly receiving a portion of the light from the light source, said light sensor assembly producing an output responsive to the intensity of the light received at the light sensor assembly; and

a controller for controlling an amount of the propagated light received by the image detector, said controller controlling the amount of light received in each of the plurality of images within a desired range in response to the output from the light sensor assembly.

2. The system of claim 1 wherein the light sensor assembly further comprises:

a beam splitter positioned between the light source and the device; and

a light sensor positioned to receive light from the beam splitter.

3. The system of claim 2 wherein the beam splitter filters infrared light from the light source.

4. The system of claim 1 wherein said controller controls the amount of light received by the image detector by controlling the amount of time the image detector receives light to acquire an image.

5. The system of claim 1 wherein the image detector further comprises an array of imaging pixels, wherein said controller controls the amount of light received by the image detector by controlling the amount of time the array of imaging pixels receives light to acquire an image.

6. The system of claim 5 further comprising a memory device which stores correction values for at least one of the pixels in said array of imaging pixels, wherein a received-light value, representing an amount of received light, is generated for each of a plurality of pixels of the array of imaging pixels and the received-light value associated with said at least one of the pixels is corrected with a correction value stored in said memory.

7. The system of claim 5 further comprising a memory device which stores correction values for at least one of the pixels-in said array of imaging pixels, wherein the controller can control :

a correction value stored in said memory.

8. The system of claim 1 wherein said light sensor assembly further comprises a photo diode.

9. A machine-vision system for inspecting a device, said machine-vision system comprising:

a light source for propagating light to the device;

an image detector that receives light from the device, wherein the image detector and the propagated light from the light source are maintained in a fixed relationship to one another and the image detector is moved relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point, when combined with one another, being useful to obtain a three-dimensional geometric measurement of said each point of the device;

a computational device that derives the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point;

a light sensor assembly receiving a portion of the light from the light source, said light sensor assembly producing an output responsive to the intensity of the light received at the light sensor assembly;

a controller for controlling an amount of light output from the light source, said controller controlling the amount of light across the plurality of images within a desired range in response to the output from the light sensor assembly; and

a power supply which supplies power to the light source, said controller controlling the amount of light received by the image detector by controlling the amount of power output from the power supply.

10. A method for acquiring physical three-dimensional geometric information associated with a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of:

projecting light from the light source to the device;

receiving light reflected from the device into the image detector;

maintaining the image detector and the projected light in a fixed relationship to one another;

moving the image detector relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point when combined with one another being useful to obtain a three-dimensional geometric measurement of said each point of the device;

sensing an intensity of light;

deriving the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point; and

controlling the amount of light received for each of the plurality of images at the image detector to a value within a desired range based on the sensed intensity of light.

11. A method for acquiring physical three-dimensional geometric information associated with a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of:

projecting light from the light source to the device;

receiving light reflected from the device into the image detector;

maintaining the image detector and the projected light in a fixed relationship to one another;

moving the image detector-relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images useful to obtain a three-dimensional geometric measurement of the device; and

controlling the amount of light projected for each of the plurality of images to a value within a desired range, wherein the step of controlling the amount of light received at the image detector further comprises the steps of;

sensing the light projected from the light source and producing a value based on the sensed light; and

controlling an amount of power input to the light source in response to the value produced by said sensing step.

12. A method for acquiring physical three-dimensional geometric information associated with a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of:

projecting light form the light source to the device;

receiving light reflected from the device into the image detector;

maintaining the image detector and the projected light in a fixed relationship to one another;

moving the image detector relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point when combined with one another being useful to obtain a three-dimensional geometric measurement of said each point of the device;

deriving the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point; and

controlling the amount of light received for each of the plurality of images at the image detector to a value within a desired range,

wherein the image detector further comprises an array of pixels which produce a signal dependent on the length of time the pixel is exposed to the reflected light, wherein the step of controlling the amount of light received at the image detector further comprises the steps of;

sensing the light projected from the light source and producing a value based on the sensed light; and

controlling the length of time the image detector is exposed to reflected light in response to the value produced by said sensing step.

13. A method for acquiring physical three-dimensional geometric information associated with a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of:

projecting light from the light source to the device;

receiving light reflected from the device into the image detector;

maintaining the image detector and the projected light in a fixed relationship to one another;

moving the image detector relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point when combined with one another being useful to obtain a three-dimensional geometric measurement of said each point of the device;

deriving the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point; and

controlling the amount of light received for each of the plurality of images at the image detector to a value within a desired range,

wherein the image detector further comprises an array of pixels which produce a signal dependent on the length of time the pixel is exposed to the reflected light, wherein the step of controlling the amount of light received at the image detector further comprises the steps of;

producing a value based on the light that was reflected from the device; and

controlling the length of time the image detector is exposed to reflected light in response to the value produced by said producing step.

14. A manufacturing system, comprising:

a semiconductor part fabrication unit that fabricates a part for a semiconductor device; and

an inspection station, the inspection station further comprising;

(a) a first light source projecting light onto the device;

(b) an image detector which receives light reflected from the device, the image detector including a plurality of lines of semiconductor imaging pixels, wherein the image detector and the propagated light from the first light source are maintained in a fixed relationship to one another and the image detector is moved relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images useful to, obtain a three-dimensional geometric measurement,of the device;

(c) a light sensor assembly receiving a portion of the light from the first light source, said light sensor assembly producing an output responsive to the intensity of the light received at the light sensor assembly; and

(d) a controller for controlling an amount of the propagated light received by the image detector, said controller controlling the amount of light within a desired range in response to the output from the light sensor assembly.

15. The manufacturing system of claim 14 wherein the inspection station further comprises memory for storing correction values associated with at least one of the pixels in the image detector.

16. The manufacturing system of claim 14 wherein the inspection station further comprises a light source controller for producing strobed light of a first level and strobed light of a second level.

17. The manufacturing system of claim 16 wherein the inspection station further comprises a ring light.

18. The manufacturing system of claim 14 wherein the inspection station further comprises:

a ring light; and

a ring light controller for strobing the ring light, wherein said ring light controller strobes the ring light interleaved with strobes to the first light source.

19. The manufacturing system of claim 14 wherein the inspection station further comprises:

a ring light; and

a ring light controller operatively coupled to the ring light, wherein the ring light controller strobes the ring light at a first intensity and at a different second intensity for each image acquired by the plurality of lines of pixels in said image detector.

20. A method for acquiring physical three-dimensional geometric information associated with a device using a machine-vision station having a light source and having an image detector, said method comprising the steps of:

projecting light from the light source to the device;

receiving light reflected from the device into the image detector;

maintaining the image detector and the projected light in a fixed relationship to one another;

moving the image detector relative to the device to obtain a plurality of images of each point being measured on the device, the plurality of images of said each point when combined with one another being useful to obtain a three-dimensional geometric measurement of said each point of the device;

deriving the three-dimensional geometric measurement of said each point of the device from the plurality of images of said each point; and

controlling the amount of light received for each of the plurality of images at the image detector to a value within a desired range,

wherein the plurality of images of said each point include an image value from a first predetermined pixel of the image detector, an image value from a second predetermined pixel of the image detector, and an image value from a third predetermined pixel of the image detector.