Optical method and apparatus for inspecting large area planar objects

• US 6,809,809 B2
• Filed: 03/04/2003
• Issued: 10/26/2004
• Est. Priority Date: 11/15/2000
• Status: Active Grant

• Current Assignee: Onto Innovation Inc.
• Original Assignee: Real Time Metrology Inc.
• Inventors: Kinney, Patrick D., Gupta, Anand, Rao, Nagaraja P.
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): Nguyen, Sang H.
• Application Number:
  US10/379,016
• Publication Number:
  US 20040012775A1
• Time in Patent Office: 602 Days
• Field of Search: 356/237--23, 356/600-601, 356/609, 356/614, 250/201.1, 250/201.2, 250/201.3, 250/201.4, 250/250, 250/559.28, 250/559.31
• US Class Current: 356/237.5
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10

Abstract

An optical inspection module is provided for detecting defects on a substrate having first and second opposite planar surfaces. The module includes a substrate holding position and first and second measurement instruments. The first instrument includes a first illumination path extending to the substrate holding position and having a grazing angle of incidence with the first surface, which illuminates substantially the entire first surface. A first optical element is oriented to collect non-specularly reflected light scattered by the first surface. A first photodetector has a plurality of pixels positioned within a focal plane of the first lens, which together form a field of view that covers substantially the entire first surface. The second instrument includes a sensor oriented for sensing a physical characteristic of the second surface when the substrate is held in the substrate holding position and the first surface is being illuminated.

Claims

1. An optical inspection module for inspecting a substrate having first and second opposite planar surfaces, the module comprising:

a substrate holding position;

a first measurement instrument comprising;

a first illumination path extending to the substrate holding position and having a grazing angle of incidence with respect to the first surface of the substrate when the substrate is held in the substrate holding position, wherein the first illumination path illuminates substantially the entire first surface;

a first optical element, which is oriented to collect non-specularly reflected light that is scattered from the first illumination path by the first surface, the first optical element having a focal plane; and

a first photodetector having a plurality of pixels which are positioned within the focal plane of the first optical element, wherein each pixel corresponds to an area on the first surface and the plurality of pixels together form a field of view that covers substantially the entire first surface; and

a second measurement instrument comprising a sensor oriented for sensing a physical characteristic of the second surface when the substrate is held in the substrate holding position and the first surface is being illuminated.

2. The optical inspection module of claim 1 wherein the first surface comprises a back surface of the substrate, and the second surface comprises an active surface of the substrate.

3. The optical inspection module of claim 1 wherein the second measurement instrument comprises:

a second illumination path extending to the substrate holding position and illuminating at least a portion of the second surface when the substrate is held in the substrate holding position;

an optical element, which is oriented to collect light reflected from the second illumination path by the second surface and has a focal plane; and

a second photodetector positioned within the focal plane of the optical element.

4. The optical inspection module of claim 3 wherein:

the second illumination path has a grazing angle of incidence with respect to the second surface of the substrate and illuminates substantially the entire second surface;

the optical element comprises a second lens, which is oriented to collect non-specularly reflected light that is scattered from the second illumination path by the second surface; and

the second photodetector comprises a plurality of pixels, wherein each pixel of the second photodetector corresponds to an area on the second surface and the plurality of pixels together form a field of view that covers substantially the entire second surface.

5. The optical inspection module of claim 3 wherein the second measurement instrument has a defect sensitivity that is greater than that of the first measurement instrument and is capable of detecting smaller defects on the second surface than the first measurement instrument is capable of detecting on the first surface.

6. The optical inspection module of claim 3 wherein:

the second illumination path has a non-grazing angle of incidence with respect to the second surface of the substrate; and

the optical element is oriented to collect specularly light that reflected from the second illumination path by the second surface.

7. The optical inspection module of claim 3 and further comprising:

a first light source having a first light beam port, which is optically coupled to the first illumination path; and

a second light source having a second light beam port, which is optically coupled to the second illumination path.

8. The optical inspection module of claim 3 and further comprising:

a single light source having a light beam port, which is optically coupled to the first and second illumination paths.

9. The optical inspection module of claim 1 wherein the second measurement instrument comprises:

a second illumination path extending to the substrate holding position and having a grazing angle of incidence with respect to the second surface of the substrate when the substrate is held in the substrate holding position, wherein the second illumination path illuminates substantially the entire second surface;

a second optical element which is oriented to collect non-specularly reflected light that is scattered from the second illumination path by the second surface; and

an optical path extending from the second optical element to the first optical element for passing the non-specularly reflected light from the second surface to the first optical element, wherein each pixel of the first photodetector further corresponds to an area on the second surface and the plurality of pixels together form a field of view that covers substantially the entire second surface.

10. The optical inspection module of claim 1 wherein:

the first surface of the substrate defines an object plane at the substrate holding position;

the first optical element comprises a first lens having a lens plane; and

the plurality of pixels of the first photodetector define an image plane within the focal plane of the first lens, wherein the lens plane and the image plane are non-parallel to the object plane and intersect with the object plane along a line.

11. The optical inspection module of claim 10 wherein the first lens has an optical axis that is oriented at an oblique angle to the object plane.

12. An optical inspection module for inspecting a substrate having first and second opposite planar surfaces, the module comprising:

a substrate holding position;

a first illumination path extending to the substrate holding position and having a grazing angle of incidence with respect to the first surface of the substrate when the substrate is held in the substrate holding position, wherein the first illumination path illuminates substantially the entire first surface;

a first optical element, which is oriented to collect non-specularly reflected light that is scattered from the first illumination path by the first surface, the first optical element having a focal plane;

a first photodetector having a plurality of pixels which are positioned within the focal plane of the first optical element, wherein each pixel corresponds to an area on the first surface and the plurality of pixels together form a field of view that covers substantially the entire first surface;

a second illumination path extending to the substrate holding position and having a grazing angle of incidence with respect to the second surface of the substrate when the substrate is held in the substrate holding position, wherein the second illumination path illuminates substantially the entire second surface;

a second optical element, which is oriented to collect non-specularly reflected light that is scattered from the second illumination path by the second surface, the second optical element having a focal plane; and

a second photodetector having a plurality of pixels which are positioned within the focal plane of the second optical element, wherein each pixel corresponds to an area on the second surface and the plurality of pixels together form a field of view that covers substantially the entire second surface.

13. The optical inspection module of claim 12 and further comprising:

a first light source having a first light beam port, which is optically coupled to the first illumination path; and

a second light source having a second light beam port, which is optically coupled to the second illumination path.

14. The optical inspection module of claim 12 and further comprising:

a single light source having a light beam port, which is optically coupled to the first and second illumination paths.

15. An optical inspection module for inspecting a substrate having an active surface and an opposite, back surface, the module comprising:

a substrate holding position;

a first measurement instrument comprising;

a first illumination path extending to the substrate holding position and having a grazing angle of incidence with the back surface when the substrate is held in the substrate holding position, wherein the first illumination path illuminates substantially the entire back surface;

a first optical element, which is oriented to collect non-specularly reflected light that is scattered from the first illumination path by the back surface, the first optical element having a focal plane; and

a first photodetector having a plurality of pixels which are positioned within the focal plane of the first optical element, wherein each pixel corresponds to an area on the back surface and the plurality of pixels together form a field of view that covers substantially the entire back surface; and

a second measurement instrument comprising;

a second illumination path extending to the substrate holding position and illuminating at least a portion of the active surface when the substrate is held in the substrate holding position;

a second optical element, which is oriented to collect light reflected from the second illumination path by defects on the active surface and has a focal plane; and

a second photodetector having at least one pixel, which is positioned within the focal plane of the second optical element, wherein the second measurement instrument has a defect sensitivity that is greater than that of the first measurement instrument and is capable of detecting smaller defects on the active surface than the first measurement instrument is capable of detecting on the back surface.