Method for automated testing of the modulation transfer function in image sensors

• US 7,646,016 B2
• Filed: 06/22/2006
• Issued: 01/12/2010
• Est. Priority Date: 09/17/2003
• Status: Active Grant

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Reuven, Moshe, Robinson, Donald E., Duesman, Kevin, Jenkins, Ed, Shah, Joey, Altice, Peter P. Jr., Bruce, Jeffrey
• Primary Examiner(s): Pham; Long
• Application Number:
  US11/472,435
• Publication Number:
  US 20060237755A1
• Time in Patent Office: 1,300 Days
• Field of Search: 257/48, 257/91, 438/14
• US Class Current: 257/48
• CPC Class Codes: G01R 31/2829 Testing of circuits in sensor or actuator systems testing of apparatus for measuring electric or magnetic variables G01R35/00; testing of indicating or recording apparatus G01D; in airbag systems B60R21/0173; checking gas analysers G01N33/007; monitoring or fail-safe circuits for electromagnets H01F7/1844
• CPC Class Codes: H01L 21/76805 the opening being a via or contact hole penetrating the underlying conductor
• CPC Class Codes: H01L 23/53238 Additional layers associated with copper layers, e.g. adhesion, barrier, cladding layers
• CPC Class Codes: H01L 27/14603 Special geometry or disposition of pixel-elements, address-lines or gate-electrodes
• CPC Class Codes: H01L 27/14623 Optical shielding
• CPC Class Codes: H01L 27/14627 Microlenses
• CPC Class Codes: H01L 27/14636 Interconnect structures
• CPC Class Codes: H01L 27/14687 Wafer level processing
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 31/022408 for devices characterised by at least one potential jump barrier or surface barrier
• CPC Class Codes: H04N 17/002 for television cameras

Abstract

A method for automatically measuring the modulation transfer function of an imager is disclosed. A opaque mask is placed over selected columns and rows of the imager during fabrication. In the course of an automated process, photons are uniformly shone over the image sensor. The amount of the input signal that flows from the unmasked pixel cells to the masked pixel cells can then be measured and the modulation transfer function can be determined.

Claims

1. An apparatus for testing a modulation transfer function of an imager comprising photosensitive cells, the apparatus comprising:

an opaque material permanently blocking a plurality of rows and columns of photosensitive cells; and

an opening in the opaque material, wherein an edge of said opening is aligned between a row or column of image-acquisition photosensitive cells of the imager and a respective adjacent row or column of the photosensitive cells permanently blocked by the opaque material.

2. The apparatus of claim 1, wherein the apparatus is configured to measure an output from said adjacent row or column of photosensitive cells for calculation of the modulation transfer function.

3. The apparatus of claim 2, wherein said measurement occurs during an automated testing process.

4. The apparatus of claim 1, wherein a plurality of photosensitive cells blocked by said opaque material are configured to be measured and a plurality of image-acquisition photosensitive cells, adjacent to said blocked photosensitive cells, are configured to be measured.

5. The apparatus of claim 4, wherein said measurements taken from said plurality of photosensitive cells blocked by said opaque material are averaged and said plurality of image-acquisition photosensitive cells, adjacent to said blocked photosensitive cells, are averaged.

6. An imager comprising:

an array of pixel cells arranged in a plurality of rows and columns;

an opaque material permanently formed over a plurality of rows and columns, the opaque material having an opening, wherein an edge of said opening is aligned between a row or column of image-acquisition pixel cells and a respective adjacent row or column of pixel cells residing below the opaque material; and

a circuit configured to calculate a modulation transfer function for the imager.

7. The imager of claim 6, wherein the opaque material is formed over a predetermined number of columns of pixel cells on the left and right edges of the array of pixel cells.

8. The imager of claim 6, wherein the opaque material is formed over a predetermined number of rows of pixel cells on the top and bottom edges of the array of pixel cells.

9. The imager of claim 6, wherein said plurality of pixel cells blocked by said opaque material are configured to be measured and averaged and said plurality of image-acquisition pixel cells, adjacent to said blocked pixel cells, are configured to be measured and averaged to calculate the modulation transfer function.

10. An imager comprising:

an array of pixel cells arranged in a plurality of rows and columns, the array of pixel cells comprising a first and second array section;

an opaque material permanently formed on at least a portion of the second array section, the opaque material having a window where an edge of said window is aligned between a row or column of first-section pixel cells and a respective adjacent row or column of second-section pixel cells under the opaque material; and

a circuit configured to calculate a modulation transfer function of the imager.

11. The image of claim 10, wherein the second array section is not used to collect data representing an image.

12. The image of claim 10, wherein measurements are taken in the second array section, the measurements from said second-section plurality of pixel cells blocked by said opaque material are averaged and said plurality of first-section pixel cells not blocked by said opaque material, adjacent to said blocked pixel cells, are averaged to calculate the modulation transfer function.