Alignment correction prior to image sampling in inspection systems
First Claim
1. A method for providing a coarse alignment between a first image signal and a second image signal for a substrate on an x/y stage of an inspection machine defining x and y directions, said inspection machine having a fixed pixel size and pixel grid that is correlated to positions of said x/y stage, for each selected x position in the x direction during scanning of said substrate, said substrate in the y direction, said coarse alignment method comprising the steps of:
- a. storing a first swath signal of said first image signal in a first memory;
b. determining x and y position coordinates in the x and y directions, respectively, of a first pixel of said first swath signal of said first image signal of step a. relative to boundaries of a pixel of said pixel grid;
c. scanning across a first pattern on said substrate to determine a first swath signal of said second image signal;
d. determining x and y position coordinates of a first pixel of said first swath signal of said second image signal detected in step c. relative to the boundaries of a pixel of said pixel grid in which said first pixel of said first swath of said second image signal is detected;
e. calculating the positional offset of said x and y coordinates of said first pixel of said first swath of said second image signal within said pixel of said pixel grid of step d. from said x and y coordinates of said first pixel of said first image signal within said pixel of said pixel grid from step b.; and
f. performing a running alignment of said first pixel of each swath signal of said second image signal within said pixel grid in relation to said first pixel of said first image signal using said positional offset calculated in step e. by advancing or retarding said x path to correct for said x positional offset, and advancing or retarding the scan in the y direction to correct for said y positional offset to realign each swath signal of said second image signal with each swath signal of said first image signal.
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Abstract
A method and apparatus, and variations of each, for inspecting a wafer defining at least one die thereon is disclosed. The present invention first obtains the electronic image equivalent of two die, and then determines the x and y offset between those electronic images. Prior to inspection for defects, those two electronic images are aligned by adjusting the x and y positions of one electronic image of one die with respect to the electronic image of the other die. Once that is accomplished, those electronic images are compared to detect any defects that may exist on one of the die.
76 Citations
28 Claims
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1. A method for providing a coarse alignment between a first image signal and a second image signal for a substrate on an x/y stage of an inspection machine defining x and y directions, said inspection machine having a fixed pixel size and pixel grid that is correlated to positions of said x/y stage, for each selected x position in the x direction during scanning of said substrate, said substrate in the y direction, said coarse alignment method comprising the steps of:
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a. storing a first swath signal of said first image signal in a first memory; b. determining x and y position coordinates in the x and y directions, respectively, of a first pixel of said first swath signal of said first image signal of step a. relative to boundaries of a pixel of said pixel grid; c. scanning across a first pattern on said substrate to determine a first swath signal of said second image signal; d. determining x and y position coordinates of a first pixel of said first swath signal of said second image signal detected in step c. relative to the boundaries of a pixel of said pixel grid in which said first pixel of said first swath of said second image signal is detected; e. calculating the positional offset of said x and y coordinates of said first pixel of said first swath of said second image signal within said pixel of said pixel grid of step d. from said x and y coordinates of said first pixel of said first image signal within said pixel of said pixel grid from step b.; and f. performing a running alignment of said first pixel of each swath signal of said second image signal within said pixel grid in relation to said first pixel of said first image signal using said positional offset calculated in step e. by advancing or retarding said x path to correct for said x positional offset, and advancing or retarding the scan in the y direction to correct for said y positional offset to realign each swath signal of said second image signal with each swath signal of said first image signal. - View Dependent Claims (2, 3, 4, 5, 6)
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7. An apparatus to provide coarse alignment between a first image signal with a second image signal of a pattern on a substrate, to generate an image pattern said apparatus comprising:
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an x-y stage defining x and y directions to transport said substrate with a fixed pixel size and pixel grid that is correlated to positions of said x/y stage; a scanner to image said pattern on said substrate in sequential swaths, and to generate electronic sequential swath signals of said second image signal as said substrate is scanned in said y direction at successive x locations of said pattern; a FIFO memory coupled to said scanner to sequentially receive said swath signals of said second image signal; a pixel memory to receive, and store therein, sequential swath signals of said first image signal; an alignment computer; coupled to said pixel memory to receive a first swath signal of said first image signal therefrom for performing a first process step of determining x and y position coordinates of a first pixel of said first swath signal of said first image signal relative to boundaries of a pixel of said pixel grid; coupled to said scanner to sequentially receive swath signals of said second image signal therefrom and to perform a second process step of determining x and y position coordinates of a first pixel of said first swath signal of said second image signal relative to the boundaries of a pixel of said pixel grid in which said first pixel of said first swath of said second image signal is detected; performing a third process step of calculating the positional offset of said x and y coordinates of said first pixel of said first swath signal of said second image signal within said pixel of said pixel grid in which said first pixel of said first swath signal of said second image signal is detected from said x and y coordinates of said first pixel of said first image signal within said pixel of said pixel grid in which said first pixel of said first swath signal of said first image signal is detected; and an alignment corrector coupled to said alignment computer to receive said positional offset and coupled to said pixel memory; performing a fourth process step of a running alignment of said first pixel of each swath signal of said second image signal within said pixel grid in relation to said first pixel of said first image signal using said positional offset of said third process step by advancing or retarding the scan in said x direction to correct for said x positional offset, and advancing or retarding the scan in the y direction to correct for said y positional offset, to realign each swath signal of said second image signal with each swath signal of said first image signal. - View Dependent Claims (8, 9, 10, 11, 12, 13, 14)
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15. An apparatus to inspect a substrate utilizing a first image signal and a second image signal of a pattern on said substrate, to generate an image pattern said apparatus comprising:
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an x-y stage defining x and y directions to transport said substrate with a fixed pixel size and pixel grid that is correlated to positions of said x-y stage; a scanner to image said pattern on said substrate in sequential swaths, and to generate electronic sequential swath signals of said second image signal as said substrate is scanned in said y direction at successive x locations of said pattern; a FIFO memory coupled to said scanner to sequentially receive said swath signals of said second image signal; a pixel memory to receive, and store therein, sequential swath signals of said first image signal; an alignment computer; coupled to said pixel memory to receive a first swath signal of said first image signal therefrom for performing a first process step of determining x and y position coordinates of a first pixel of said first swath signal of said first image signal relative to boundaries of a pixel of said pixel grid; coupled to said scanner to sequentially receive swath signals of said second image signal therefrom and to perform a second process step of determining x and y position coordinates of a first pixel of said first swath signal of said second image signal relative to the boundaries of a pixel of said pixel grid in which said first pixel of said first swath of said second image signal is detected; performing a third process step of calculating the positional offset of said x and y coordinates of said first pixel of said first swath signal of said second image signal within said pixel of said pixel grid in which said first pixel of said first swath signal of said second image signal is detected from said x and y coordinates of said first pixel of said first image signal within said pixel of said pixel grid in which said first pixel of said first swath signal of said first image signal is detected; an alignment corrector coupled to said alignment computer to receive said positional offset and coupled to said pixel memory; performing a fourth process step of a running alignment of said first pixel of each swath signal of said second image signal within said pixel grid in relation to said first pixel of said first image signal using said positional offset of said third process step by advancing or retarding the scan in said x direction to correct for said x positional offset, and advancing or retarding the scan in the y direction to correct for said y positional offset, to realign each swath signal of said second image signal with each swath signal of said first image signal; and a defect detector coupled to said alignment corrector and said FIFO memory to detect and identify defects in said second image signal as aligned by comparison with said first image signal. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23)
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24. A method for inspecting a substrate utilizing a first image signal and a second image signal of a pattern on said substrate with said substrate on an x/y stage of an inspection machine, said inspection machine having a fixed pixel size and pixel grid that is correlated to positions of said x/y stage defining x and y directions, for each selected x position in the x direction during scanning of said substrate, a swath is scanned across said substrate in the y direction, said inspection method comprising the steps of:
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a. storing a first swath signal of said first image signal in a first memory; b. determining x and y position coordinates in the x and y directions, respectively, of a first pixel of said first swath signal of said first image signal of step a. relative to boundaries of a pixel of said pixel grid; c. scanning a first swath across said pattern on said substrate to determine a first swath signal of said second image signal; d. determining x and y position coordinates of a first pixel of said first swath signal of said second image signal detected in step c. relative to the boundaries of a pixel of said pixel grid in which said first pixel of said first swath of said second image signal is detected; e. calculating the positional offset of said x and y coordinates of said first pixel of said first swath of said second image signal within said pixel of said pixel grid of step d. from said x and y coordinates of said first pixel of said first image signal within said pixel of said pixel grid from step b.; f. performing a running alignment of said first pixel of each swath signal of said second image signal within said pixel grid in relation to said first pixel of said first image signal using said positional offset calculated in step e. by advancing or retarding said x path to correct for said x positional offset, and advancing or retarding the scan in the y direction to correct for said y positional offset to realign each swath signal of said second image signal with each swath signal of said first image signal; g. sequentially storing each swath signal of said first image signal in said first memory; h. sequentially scanning said substrate and storing each realigned swath signal of said second image signal in a second memory; and i. sequentially comparing each swath signal of said first image signal with a corresponding realigned swath signal of said second image signal to determine if defects are present in said pattern on said substrate that corresponds to said second image signal. - View Dependent Claims (25, 26, 27, 28)
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Specification