JPS59186322A - Photomask testing apparatus - Google Patents

Abstract

PURPOSE:To measure the relative dimensional error between a reference photomask and a tested photomask accurately by a method wherein the coordinates of the reference mask and the coordinates of the tested mask are measured and compared. CONSTITUTION:The coordinates of a reference photomask are measured by a coordinates measuring part 32 and the coordinates data are memorized by a memory part 33. In the same way, the coordinates data of a tested photomask are also measured by the coordinates measuring part 32 and memorized by the memory part 33. Then the dimensional difference of whole arrangement, the square rate difference of the arrangement, the difference of each pitch of the arrangement, the dimensional difference of each chip and the difference of the chip rotation against the direction of the arrangement between the reference photomask and the tested photomask are calculated by a comparison processing part 34 according to the both coordinates data memorized by the memory part 33 and indicated to an output part 35. With this constitution, the relative dimensional error of the tested photomask to the reference photomask can be measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photomask inspection apparatus, and more particularly to a photomask inspection apparatus used in the manufacture of integrated circuits.

In the production of semiconductor integrated circuits, it takes approximately 5 to 2 to produce one type of semiconductor integrated circuit.
0 types of photomasks are used. The pattern deviation between each photomask must be minimized as it directly affects the manufacturing yield characteristics and reliability of the integrated circuit. However, absolute positional accuracy is not so strictly required for masks for manufacturing integrated circuits as long as the relative positional deviation of patterns between photomasks used for manufacturing one type of mask is small. For this reason, comparative errors between photomasks have traditionally been focused on as one of the quality standards for photomasks.

In other words, one photomask appropriately determined as a photomask for the fruit pattern circuit of the variety is used as a comparison reference photomask, and all pattern positions on other photomasks are relative position errors with respect to the pattern positions of this reference photomask. Quality control is carried out using

Here, types of errors in the relative positions of the photomask patterns are shown in FIG. In the figure, identical chip patterns 2 are regularly arranged vertically and horizontally on a photomask 1. In this photomask, the following types of misalignment of patterns of other masks with respect to the reference mask are included due to the characteristics of the mask manufacturing apparatus. i.e. the size of the entire array 3
, the squareness of the array 4, the individual pitch of the array 5, the chip dimension 6, and the rotation of the chip with respect to the array direction 7.

Conventionally, as a means for measuring this relative error, a method has been used in which photomasks are optically overlapped and the amount of deviation is measured. However, this method relies heavily on the sensibilities of the operator and has the disadvantage that precise measurements cannot be made. The present invention has been made to solve the above-mentioned drawbacks of the prior art, and includes the coordinates of a reference pattern placed on a first photomask serving as a reference and the reference of the first photomask serving as a reference. means for measuring the coordinates of a reference pattern placed on a second photomask for inspection corresponding to the pattern; means for storing measured values of both coordinates; and a reference pattern placed on the first photomask. and a means for measuring a relative dimensional error of the second photomask with respect to the first photomask by comparing the coordinates of the reference pattern on the second photomask with the coordinates of the reference pattern on the second photomask. The present invention provides an inspection device. Embodiments of the invention will be described in detail below with reference to the drawings.

FIG. 2 shows how the dimensions of the entire array of photomasks are measured. The center coordinates of the reference pattern 11 placed on the chip 9 on the mask 8 and the center coordinates of the reference pattern 12 on the chip 10 are respectively measured. Similarly, the center coordinates of the reference pattern 16 placed on the chip 14 and the reference pattern 17 placed on the chip 15 on the photomask 13 to be tested are measured. Here, the reference photomask 8
The dimensional difference of the entire array of photomasks 16 to be tested is ("2
,z,)2+(y,,yI)2(r4 Z3)2+
It is expressed as (Y4 ys)2. Here, xl...X coordinate of the reference pattern 11, yl...X coordinate of the reference pattern 11, x2...X coordinate of the reference pattern 12, y2.
...X coordinate of reference pattern 12 1.21-3...X coordinate of reference pattern 16, ys...X of reference pattern 16
Coordinates 1.2:4...X coordinate of reference pattern 17, y4
. . . is the X coordinate of the reference pattern 17.

FIG. 6 shows the case of measuring the orthogonality of arrays. A reference pattern 22 placed on the chip 19 on the reference photomask 18, a reference pattern 26 placed on the chip 20, and a reference pattern 2 placed on the chip 21.
Measure the center coordinates of 4.

Similarly, the reference pattern 29 placed on the chip 26 on the photomask 25 to be tested, the reference pattern 60 placed on the chip 27, and the reference pattern 31 placed on the chip 28 are measured. Here, the error in orthogonality between the photomasks 18 and 25 is (jan ” yI
3'2)/ (,2++ xz)+tan'(3'2
ys)/(,ra-,r2))-(jan'
(y4 ys)/ (,;5-,z6) 十tan'
(3'5 y6)/ (, expressed as r6x6 months.

Here, X,...X coordinate of the reference pattern 22, yI...
・X coordinate of the reference pattern 22, x2...X coordinate of the reference pattern 23, y2...X coordinate of the reference pattern 23,
x3...X coordinate of the reference pattern 24, ys...X coordinate of the reference pattern 24, x4...X coordinate of the reference pattern 29, y4...X coordinate of the reference pattern 29, x5.
...X coordinate of the reference pattern 30, y5--X coordinate of the reference pattern 30, x6--X coordinate of the reference pattern 31, y6--X coordinate of the reference pattern 61.

Similarly, differences in the pitches of the individual arrays, differences in chip dimensions, and differences in rotation of the chips with respect to the array direction can also be measured by the same means. FIG. 4 is a block diagram showing an outline of the present invention. The coordinate measuring section 62 measures the coordinates of the reference photomask, and the coordinate data is stored in the storage section 33.

Similarly, the coordinate data of the photomask to be tested is also stored in the coordinate measurement unit 52.
After being measured, it is stored in the storage unit 63. Here, the coordinate data of the reference photomask and the test photomask are transferred to the comparison processing section 64 as necessary.

The comparison processing unit 34 calculates, from the coordinate data of the reference photomask and the test photomask, the difference in dimensions of the entire array of the reference photomask and the test photomask, the difference in orthogonality of the arrays, the individual pitch difference in the array, and the chip. The dimensional difference and the difference in rotation of the chips with respect to the arrangement direction are calculated and displayed by the output unit 65.

As described above, the apparatus for measuring comparison errors between masks according to the present invention has the effect of being able to perform highly accurate measurements without relying on the sensibility of the operator.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the types of errors in the relative position of photomask patterns, Fig. 2 is a diagram showing the dimensions of the entire photomask array in the present invention, and Fig. 3 is a diagram showing the photomask arrangement in the present invention. FIG. 3 is a diagram showing how the degree of orthogonality is measured. FIG. 4 is a block diagram of the apparatus of the present invention. 1...Photomask, 2...Chip pattern, ro・
... Dimensions of the entire array, 4... Orthogonality of the array, 5...
Individual pitch of the array, 6... Chip dimension, 7... Rotation of the chip with respect to the array direction, 8... Reference photomask, 9... Chip, 10... Chip, 11... Reference pattern , 12... Reference pattern, 13... Test photomask, 14... Chip, 15... Chip, 16
...Reference pattern, 17...Reference pattern, 18.
...Reference photomask, 19...Chip, 20...
Chip, 21...Chip, 22...Reference pattern, 2
6... Reference pattern, 24... Reference pattern, 25
...Test photomask, 26...Chip, 27...
・Chip, 28...Chip ', 29...Reference pattern, 60...Reference number turn, 51...Store pattern based on, 32...Coordinate measurement unit, 63...Word memory b, 64
. . . Comparison processing section, 35 . . . Output section. Patent applicant NEC Corporation Representative Patent attorney Naka Kanno Figure 1/Figure 4

Claims (1)

[Claims] Coordinates of a reference pattern placed on a first photomask serving as a reference and a reference pattern placed on a second photomask to be inspected corresponding to the reference pattern on the first photomask serving as a reference a means for measuring the coordinates of the first photomask; a means for storing the measured values of both coordinates; A photomask inspection apparatus comprising means for measuring a relative dimensional error of a second photomask with respect to the second photomask.