Automatic alignment system

Claim 2

An alignment system for positioning at a required position an object to be worked which has on its surface straight-line areas whose image density changes relatively abruptly at both side edges, said system comprising holding means for holding the object to be worked, moving means for moving the holding means, camera means for taking at least a part of the image of the surface of the object held on the holding means and outputting analog signals representative of the densities of x-y matrix arrayed pixels, A/D converter means for converting the analog signals outputted by the camera means into multi-value digital signals, operation means for performing a mathematical operation on the multi-value digital signals to produce binary digital signals, detecting means for detecting the position of at least one side edge of a straight-line area, and thus the position of the straight-line area, on the basis of the binary digital signals, and movement control means for actuating the moving means according to the detected position of the straight-line area and thus positioning the object held on the holding means at the required position.

Claim 3

A system as clamed in claim 1 wherein the object to be worked is a semiconductor wafer having on its surface a plurality of straight-line areas of predetermined widths arranged in a lattice pattern at predetermined intervals.

Claim 4

A system as claimed in claim 1 or 2 wherein the moving means includes an x-direction moving source for moving the holding means in the x-direction, a y-direction moving source for moving the holding means in the y-direction and a direction moving source for moving the holding means in the H-direction.

Claim 8

A system as claimed in claim 6 wherein the two parts are spaced from each other either in the x-direction or the y-direction.

Claim 10

A system as claimed in claim 8 wherein the differentiation emphasizes a change in the density of the image either in the x-direction or the y-direction.

Claim 11

A system as claimed in claim 9 wherein the differentiation is performed by using the following differentiation mask: -1 -1 -1 0 0 0 1 1 1 rs ~

Claim 14

1 3. A system as claimed in claim 12 wherein the parity check produces processed values which distinguish the case where the intermediate binary digital signals are the same at three addresses, i.e. (x = m, y = n), (x - m + 1, y = m), and (x = m, y = n + 1), from the case where they are not.

Claim 16

A system as claimed in claim 14 wherein whether a predetermined number or more of digital signals "1" '' exist or not is detected in either the x-direction or the y-direction and in a plurality of directions inclined thereto within a predetermined angular range.

Claim 17

A system as claimed in claim 14 or 15 wherein the detecting means detects whether the other side edge of the straight-line area is disposed at a position spaced a predetermined distance from one detected side edge of the straight-line area, and thus determines whether the detected one side edge is actually the one side edge of the straight-line area.

Claim 18

An automatic alignment system for positioning at a required position a semiconductor wafer having a plurality of straight-line areas arranged in a lattice pattern on its surface and a circuit pattern applied to each of a plurality of rectangular areas defined by the straight-line areas, said system comprising holding means for holding the semiconductor wafer, moving means for moving the holding means, camera means for taking at least a part of the image of the surface of the semiconductor wafer held on the holding means and outputting analog signals showing the densities of x-y matrix arrayed pixels, an image frame memory for memorizing signals corresponding to the analog signals outputted by the camera means, a key pattern memory for memorizing a signal showing a key pattern corresponding to a specified area on said surface of the semiconductor wafer located at a predetermined position and a signal showing the position of the key pattern, pattern matching-type position detecting means for detecting the position of a straight-line area by detecting the same pattern as the key pattern in the image taken by the camera means on the basis of the signals stored in the image frame memory and the key pattern signals stored in the key pattern memory, non-pattern matching type position detecting means for detecting the position of a straightline area by methods other than pattern metching, and movement control means for primarily positioning the semiconductor wafer held on the. holding means by actuating the moving means according to the detection of the position of the straight-line area by the non-pattern matching type position detecting means and thereafter secondarily positioning the semiconductor wafer held on the holding means by actuating the moving means according to the detection of the position of the straight-line area by the pattern matching-type position detecting means.

Claim 19

An automatic alignment system for positioning at a required position a semiconductor wafer having a plurality of straight-line areas arranged in a lattice pattern on its surface and a circuit pattern applied to each of a plurality of rectangular areas defined by the straight-line areas, said system comprising holding means for holding the semiconductor wafer, moving means for moving the holding means, camera means for taking at least a part of the image of the surface of the semiconductor wafer held on the holding means and outputting analog signals showing the densities of x-y matrix arrayed pixels, an image frame memory for memorizing signals corresponding to the analog signals outputted by the camera means, a key pattern memory for memorizing a signal showing a key pattern corresponding to a specified area on said surface of the semiconductor wafer located at a predetermined position and a signal showing the position of the key pattern, pattern matching-type position detecting means for detecting the position of a straight-line area by detecting the same pattern as the key pattern in the image taken by the camera means on the basis of the signals stored in the image frame memory and the key pattern signals stored in the key pattern memory, non-pattern matching type position detecting means for detecting the position of a straightline area by methods other than pattern metching, and movement control means for primarily positioning the semiconductor wafer held on the. holding means by actuating the moving means according to the detection of the position of the straight-line area by the non-pattern matching type position detecting means and thereafter secondarily positioning the semiconductor wafer held on the holding means by actuating the moving means according to the detection of the position of the straight-line area by the pattern matching-type position detecting means.

Claim 20

A system as claimed in claim 17 wherein the key pattern memory memorizes at least one key pattern corresponding to at least one specified area on said surface of the semiconductor wafer when the semiconductor wafer is at a first predetermined position and at least one key pattern corresponding to at least one specified area on said surface of the semiconductor wafer when the semiconductor wafer is at a second predetermined position by being rotated through 90 degrees with respect to the first predetermined position; and in the secondary positioning, the movement control means. performs positioning with regard to the first predetermined position, then rotates the holding means through 90 degrees, and thereafter performs positioning with regard to the second predetermined position.

Claim 21

A system as claimed in claim 17 or 18 wherein-said camera means includes an-A/D converter means for converting said analog signals to multi-value digital signals, and the image frame memory memorizes the multi-value digital signals generated by the A/D converter means.

Claim 22

A system as claimed in claim 19 wherein the non-pattern matching type position detecting means includes a mathematical operation means for performing mathematical operations on the multi-value digital signals memorized in the image frame memory to generate binary digital signals, and a straight-line area detecting means for detecting the position of at least one side edge of the straight-line area on the basis of the binary digital signals and thus de#tecting the relative position of the straight-line area.

Claim 23

A system as claimed in claim 19 or 20 wherein the signal showing the key pattern and stored in the key pattern memory is a multi-value digital signal corresponding to the densities of a plurality of pixels in the key pattern.

Claim 24

A system as claimed in claim 21 wherein the pattern matching-type position detecting means calculates the degree of matching, P, on the basis of the following equation P = z z [ f(i,j)-# ] - [ g(i,j)-g ] j , ,, wherein f is a value corresponding to the density of each of a plurality of pixels in a collation area on the surface of the semiconductor wafer held on the holding means, T is an average of f values, g is a value corresponding to the density of each of a plurality of pixels in the key pattern, and g is an average of g values.

Claim 25

A system as claimed in claim 21 wherein the pattern matching-type position detecting means calculates the degree of matching, p, on the basis of the following equation wherein f is a value corresponding to the density of each of a plurality of pixels in a collation area on the surface of the semiconductor wafer held on the holding means, f is an average of f value, g is a value corresponding to the density of each of a plurality of pixels in the key pattern, g is an average of g values, and U means binarization.

Claim 26

A system as claimed in claim 21 wherein the pattern matching-type position detecting means calculates the degree of matching, P, on the basis of the following equation wherein f is a value corresponding to the density of each of a plurality of pixels in a collation area on the surface of the semiconductor wafer held on the holding means, f is an average of f values, g is a value corresponding to the density of each of a plurality of pixels in the key pattern, and g ia an average of g values.

Claim 30

A system as claimed in claim 27 wherein the two parts are spaced from each other either in the x-direction or the y-direction.

Claim 31

A system as claimed in claim 28 wherein the movement control means performs the primary positioning such that at least the straight-line areas exist in both of the two portions taken by the camera means.

Claim 32

An alignment system substantially as hereinbefore described with reference to the accompanying drawings.

Claim 33

An alignment system substantially as hereinbefore described with reference to the accompanying drawings.