Wafer edge inspection and metrology

• US 20080013822A1
• Filed: 09/22/2006
• Published: 01/17/2008
• Est. Priority Date: 07/11/2006
• Status: Active Grant

• Current Assignee: Onto Innovation Inc.
• Original Assignee: Rudolph Technologies Incorporated (Onto Innovation Inc.)
• Inventors: Le, Tuan D., Pai, Ajay
• Granted Patent: US 7,616,804 B2
• Time in Patent Office: Days
• US Class Current: 382/145
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G01N 21/9503 Wafer edge inspection

Abstract

Some aspects of the present invention relate to a wafer inspection method. A plurality of images is acquired about an edge portion of a wafer. Each of the images comprises a pixel array having a first dimension and a second dimension. A composite image of compressed pixel arrays is generated by compressing each of the pixel arrays in the first dimension and concatenating the pixel arrays. The composite image is analyzed to identify a wafer feature, for example using a sinusoidal line fit.

Claims

1. A wafer edge inspection method comprising:

acquiring a plurality of images about an edge portion of a wafer, each of the images comprising an array of pixels having a first dimension and a second dimension;

generating a composite image of compressed pixel arrays by compressing each of the pixel arrays in the first dimension and concatenating the pixel arrays; and

analyzing the composite image to evaluate a wafer feature.

2. The method of claim 1, wherein the wafer feature is evaluated to identify at least one of:

a location of the wafer edge, a location of an edge of a layer disposed on the wafer, a location of a center of the wafer, a geometry of an edge bevel, a location of an origin of an edge bevel, a geometry of an exposed top region of the wafer, a location of one or more EBR lines, a number of crossing points of one or more EBR lines, an edge of an insulating layer, an edge of a silicon layer, a thickness of a silicon layer, and a thickness of an insulating layer.

3. The method of claim 1, wherein the wafer feature is a film edge of a layer of film disposed on the wafer and analyzing the composite image to evaluate the wafer feature includes locating the film edge, the method further comprising:

locating the wafer edge; and

evaluating a relative position of the located film edge to the located wafer edge.

4. The method of claim 1, wherein the wafer edge has a bevel defining an origin, the wafer feature is the bevel origin, and analyzing the composite image to evaluate the wafer feature includes locating the bevel origin, the method further comprising:

identifying the wafer edge; and

evaluating a width of the edge bevel corresponding to a distance between the bevel origin and the wafer edge.

5. The method of claim 1, wherein the first dimension of each of the pixel arrays is substantially tangential to the wafer edge.

6. The method of claim 1, wherein each of the pixel arrays is only compressed in the first dimension.

7. The method of claim 1, wherein each pixel of the array of pixels has a characteristic pixel value, and further wherein compressing each pixel array in the first dimension comprises:

averaging the characteristic pixel values of the pixels across the first dimension.

8. The method of claim 1, wherein acquiring the plurality of images about the edge portion of the wafer includes imaging an edge normal of the wafer.

9. The method of claim 1, further comprising:

displaying the composite image.

10. The method of claim 9, further comprising:

providing a user interface adapted to allow a user to select a portion of the displayed composite image, wherein a non-compressed image corresponding to the selected portion of the composite image is displayed upon selection of the corresponding portion of the displayed composite image.

11. The method of claim 1, further comprising:

analyzing the composite image to identify the wafer edge;

normalizing the composite image to the identified wafer edge; and

displaying the normalized composite image.

12. The method of claim 1, wherein analyzing the composite image to identify the wafer feature comprises:

analyzing the composite image to generate a plurality of edge segments; and

performing a sinusoidal line fitting operation on the plurality of edge segments to select one or more edge segments corresponding to the wafer feature to be identified.

13. A method of inspecting a wafer comprising:

acquiring a plurality of images about an edge portion of the wafer, each of the images comprising a pixel array having a first dimension and a second dimension;

compressing each pixel array across the first dimension to generate a plurality of compressed pixel arrays;

analyzing the plurality of compressed pixel arrays to generate a plurality of edge segments; and

evaluating a wafer feature by identifying edge segments of the plurality of edge segments that correspond to the wafer feature using a sinusoidal line fitting operation.

14. The method of claim 13, wherein the edge portion of the wafer is an annular region extending circumferentially about the wafer, the annular region defined by an inner diameter inside of an exposed region of the wafer characterized as being substantially free of resist and an outer diameter outside of the edge of the wafer.

15. The method of claim 13, wherein analyzing the plurality of compressed pixel arrays to identify the plurality of edge segments comprises:

applying an edge detector to the plurality of compressed pixel arrays to generate edge gradient data; and

performing edge analysis on the edge gradient data to generate edge segment data corresponding to the plurality of edge segments.

16. The method of claim 14, wherein analyzing the plurality of compressed pixel arrays to identify the plurality of edge segments further comprises:

filtering the edge segment data according to at least one of edge segment edge strength and edge segment length.

17. The method of claim 13, wherein the wafer feature is a first edge bead removal (EBR) line and evaluating the wafer feature includes locating the edge bead removal (EBR) line, the method further comprising:

locating a second edge bead removal (EBR) line using the composite image; and

identifying one or more potential crossing points between the located first edge bead removal (EBR) line and the located second edge bead removal (EBR) line.

18. The method of claim 13, wherein the wafer feature is a film edge of a layer of film deposited on the wafer, the method further comprising:

providing one or more tolerances for the film edge; and

evaluating whether the film edge is at a desired distance from the wafer edge.

19. The method of claim 13, further comprising:

selecting a regular wafer feature to be removed from analysis; and

disregarding image data corresponding to the regular wafer feature.

20. An edge inspection system comprising:

an edge sensor having an inspection area for acquiring a plurality of images about an edge portion of a wafer;

an image acquisition module for receiving the acquired images, each of the images having a first dimension and a second dimension;

a composite image module for generating a composite image of compressed images, the composite image module comprising;

an image concatenating module for stitching the images; and

an image compression module for compressing the images in the first dimension; and

an image analysis module for analyzing the composite image to evaluate a wafer feature.

21. The system of claim 20, wherein the image analysis module is adapted to perform a sinusoidal line fitting operation on data related to the composite image to evaluate the wafer feature.

22. The system of claim 20, further comprising:

a user interface module adapted for displaying the composite image and allowing a user to select a portion of the composite image, wherein upon selection of the portion of the composite image a non-compressed image corresponding to the selected portion of the composite image is displayed to the user.

23. The system of claim 22, wherein the wafer feature is an edge bead removal line (EBR) line, wherein the image analysis module is adapted to locate the edge bead removal (EBR) line, and further wherein the user interface module is adapted to display a representation of the located edge bead removal (EBR) line at a corresponding location on the non-compressed image.