JPH086232A - Method and apparatus for inspecting mask pattern - Google Patents

Abstract

PURPOSE:To make it possible to progress.a mask to the ensuing processing regardless of the varying speeds of development of design patterns by storing one of optical pattern information in one auxiliary storage device, reducing out this information and comparing with design pattern information. CONSTITUTION:The optical image of the mask 2 is formed by an optical system consisting of a photoirradiating section 1 and a lens system 3, is processed by a photoelectric conversion section 4 and is outputted as optical patterns 5a and 5b which are electrical information. The optical pattern information 5a obtd. in order to compare and inspect the patterns in the mask 2 with each other is previously stored in an auxiliary storage device 10, such as hard disk, and the comparison with the design pattern information 9 obtd. by developing design data 8 is executed by reading out the stored information and, therefore, the need for keeping the mask 2 which is the examinee in the inspection apparatus is eliminated. Then, the mask is progressed to the ensuing stage right after reading of the optical information for the purpose of comparison and inspection within the mask, by which the delay occurring in the mask inspection is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mask pattern inspection method and inspection apparatus for photolithography, and in particular, data in a pattern inspection effective when applied to a pattern inspection of a mask including a plurality of identical patterns. It is related to processing.

The lithographic process in the recent IC manufacturing process mainly uses a reticle mask (hereinafter simply referred to as a mask). In this method, a transfer pattern of about 1 to 2 chips is often stored in one mask and used, and a pattern with a defect is created, or a defect occurs in the pattern due to dust that is accidentally attached after creation. If so, all or half of the chips are defective.
Therefore, it is necessary to perform a thorough pattern inspection, but the pattern is becoming finer and more complicated with the high integration of ICs, and the pattern inspection time is also long. In order to reduce the throughput of IC manufacturing, it is also necessary to shorten the mask inspection time, and a measure for that is required.

[0003]

2. Description of the Related Art Conceptually, a mask pattern inspection uses an optical device and a photoelectric conversion device to obtain optical pattern information which is electronic shape information of a mask pattern, and develops this and IC design data. The presence or absence of a defect in the mask is determined by comparing the obtained design pattern information. In reality, in order to cope with the miniaturization and complexity of patterns, inspection is performed in a form in which this basic configuration is modified.

For example, when patterns for a plurality of chips are arranged on one mask, patterns in the chips are first compared with each other, and good / defective is judged according to the difference.
Next, for non-defective products, if it is confirmed that there is no common defect in both patterns, the total required time can be shortened. FIG. 3 and FIG. 4 schematically show the processing of this system, and FIG. 3 shows the processing procedure for comparing and inspecting the mask patterns, which is the first step of the above system, in the fourth processing. In the figure, the processing procedure for comparing and inspecting the mask pattern and the design pattern, which is the second stage, is shown respectively. A conventional pattern inspection method will be described below with reference to these drawings. In this specification, the shape information of the actual pattern obtained by using the optical means is referred to as optical pattern information.
(Or optical pattern), and pattern information obtained by expanding design data is called design pattern information (or design pattern).

In FIG. 3, the reading light is irradiated from the light irradiation unit 1 to the mask 2 to be inspected, and the optical image generated by the two lens systems 3 is processed by the photoelectric conversion unit 4 to obtain optical pattern information. Converted to (5a, 5b). The distance between the optical axes of the two sets of lens systems is adjusted so as to match the distance on the mask on which the same pattern is arranged. Both optical patterns are arithmetically processed by the comparison unit 6a, and when a difference is detected, the defect detection unit 7a determines whether or not the difference is a defect within an allowable range.

In FIG. 4 as well, in the same manner as in FIG. 3, the optical pattern is obtained and the process proceeds. 1 is a light irradiation part, 2 is a mask to be inspected, and 3 is a lens system. The optical pattern 5 which is the output of the photoelectric conversion unit 4, and the design pattern 9 obtained by expanding the design data 8 are processed by the comparison unit 6b,
If there is a difference between the two patterns, the defect detection unit 7b determines whether or not it is within the allowable range.

If the inspection is divided into two stages in this way, the one determined to be defective only by the previous stage inspection can be eliminated without performing the subsequent stage inspection, so that the throughput is improved.

[0008]

Considering a case where the above-mentioned two types of comparative inspections are executed as a series of operations, the optical device and the photoelectric conversion device to be prepared may be the same, and the comparison and the pass / fail judgment may be performed. Since it is natural that the work is processed by a single computer, the continuous processing avoids duplication of the devices and shortens the work time.

However, for that purpose, the work must be started after preparing a design pattern which is a reference value in advance, and a process for obtaining pattern information from the design information, such as when successively inspecting different kinds of masks, is required. If it is delayed, the mask will be stopped on the spot and wait, and there is a problem that it cannot be sent to the next step.

Further, when either one of the optical patterns is determined to be defective, the comparison with the design pattern is not necessary, so that only the necessary design pattern information that may be unnecessary is developed. Is desirable.

An object of the present invention is to solve the above problems and to provide a two-step pattern inspection method capable of advancing a mask to the next processing regardless of the slowness of development of a design pattern.

[0012]

In order to achieve the above object, the present invention stores optical pattern information obtained by using an optical device and a photoelectric conversion device in an auxiliary storage device such as a hard disk, and stores it as necessary. It is configured so that it can be read out.

That is, the mask pattern inspection method of the present invention compares optical pattern information obtained from a plurality of real patterns on the same mask, stores one of the pattern information in an auxiliary storage device, and stores the auxiliary information in the auxiliary storage device. The mask pattern inspection apparatus according to the present invention includes a process of comparing the pattern information read from the storage device with design pattern information obtained from the design information of the mask. A device for obtaining optical pattern information from the shape of an actual pattern, an auxiliary storage device for storing the optical pattern information, and a design pattern obtained by expanding the optical pattern information read from the auxiliary storage device and the design data of the mask. It is characterized by comprising a device for comparing information.

[0014]

According to the present invention, the optical pattern information obtained for the comparative inspection of the patterns in the mask is stored in the auxiliary storage device such as a hard disk and the design pattern information obtained by expanding the design data is compared. Since the stored information is read out and stored, it is not necessary to keep the mask, which is the subject, in the inspection apparatus. Therefore, by reading the optical pattern information for the comparative inspection of the patterns in the mask, immediately moving the mask to the next step,
The delay caused by mask inspection is eliminated.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 schematically shows the processing procedure of the first embodiment of the present invention. Hereinafter, description will be given with reference to FIG.

An optical system of the light irradiation unit 1 and the lens system 3 forms an optical image of the mask 2, which is processed by the photoelectric conversion unit 4 and output as optical patterns 5a and 5b which are electronic information. It These pieces of information are compared and calculated by the comparison unit 6a to obtain the difference. The existence of the difference here means that
It means that there are different parts in both patterns that should be originally the same.

Whether or not this difference is within the allowable range is determined by analyzing the difference information in the defect detecting section 7a.
Basically, is the area of the difference part not exceeding the standard value?
However, since the allowable amount varies depending on in which area the difference occurs, it is desirable to make the determination in consideration of it. If this difference exceeds the allowable value, it is determined that one pattern has a defect exceeding the allowable range, and the mask is determined to be defective.

As a result of this comparison process, if the difference is small, it is highly possible that both patterns are non-defective products. However, since there may be a common defect in both patterns, one of the information, for example, 5a. Then, the process proceeds to the stage of comparing the design pattern information 9 obtained by expanding the design data. The design data is information relating to the pattern shape, but since it is vector data, it is not possible to immediately obtain the difference from the optical pattern, and it is necessary to develop this to be image data, that is, design pattern information. .

In the present embodiment, the optical pattern 5a is also sent to and stored in the auxiliary storage device 10, and the optical pattern information 5a and the design pattern information 9 read from this are stored in the comparison section 6b.
Is compared and calculated. Based on the difference data, the defect detection unit 7b determines the quality of the mask. This work content is similar to the processing of comparing optical patterns, but since the content of the difference indicates all defects in the optical pattern, the acceptance criterion is set in consideration of that point.

If the design pattern information 9 is prepared at the time of starting the comparison process of the second stage, the comparison process is performed by directly importing the optical pattern information from the photoelectric conversion unit 4 without inputting it to the auxiliary storage device. May be. In any case, after obtaining the optical pattern information, it is not necessary to hold the mask, which is the subject, in the inspection apparatus, and it is possible to send the mask to the apparatus that uses it and prepare for the preparation.

The comparison units 6a and 6b and the defect detection units 7a and 7b are essentially the one computer equipped with the necessary programs. Further, the auxiliary storage device is required to be accessed at high speed and has a large storage capacity, and for example, a hard disk is suitable. Generally speaking, the size of the graphic information is larger than that of the character information and may reach several hundred KB, but the hard disk having a storage capacity exceeding 1 GB is also provided and the capacity is sufficient. Further, if necessary, the optical capacity can be increased by compressing and writing the optical pattern information.

FIG. 2 shows the processing procedure of the second embodiment of the present invention. This embodiment differs from the first embodiment in that the optical pattern information 5c stored in the auxiliary storage device is used.
Is the point output from the comparison unit 6a. This information is obtained by adding difference information to one of the optical pattern information to be subjected to the comparison processing, and performing the second-stage comparison processing by using such information is substantially two optical patterns and a design pattern. Is equivalent to making a comparison with.

If the comparison process is performed in this manner, even if the mask is highly likely to be defective due to the size of the difference in the first-stage comparison, both patterns are acceptable in the allowable range in comparison with the design pattern. In some cases, it may become clear that the logical operation may be slightly complicated, but it is possible to more appropriately determine the pass / fail.

[0024]

As described above, according to the present invention, in the pattern inspection in which the optical pattern information is compared with each other and the optical pattern information and the design pattern information are compared with each other, when both the inspections are continuously processed, It is not necessary to wait for the preparation of the design pattern information, and once the optical pattern information is acquired, the mask can be advanced to the next step, and the throughput of the inspection step is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first embodiment.

FIG. 2 is a diagram showing a configuration of a second embodiment.

FIG. 3 is a diagram showing a first stage of the prior art.

FIG. 4 shows a second stage of the prior art.

[Explanation of symbols]

 1 Light irradiation part 2 Mask 3 Lens system 4 Photoelectric conversion part 5,5a, 5b Optical pattern 6a, 6b Comparison part 7a, 7b Defect detection part 8 Design data 9 Design pattern 10 Auxiliary storage device

Claims (3)

[Claims] 1. Optical pattern information obtained from a plurality of real patterns on the same mask are compared with each other, the optical pattern information is stored in an auxiliary storage device, and the optical pattern information read from the auxiliary storage device is stored in the auxiliary storage device. A mask pattern inspection method comprising a process of comparing with design pattern information obtained from design data of the mask. 2. A device for converting the shapes of a plurality of real patterns on the same mask (2) into respective optical pattern information (5a, 5b).
(1, 3, 4) and an auxiliary storage device (10) for storing the optical pattern information (5a)
And the optical pattern information read from the auxiliary storage device (10)
A mask pattern inspection apparatus comprising: (5a) and an apparatus (6b) for comparing design pattern information (9) obtained by developing the design data (8) of the mask. 3. In addition to the configuration of claim 2, the optical pattern information (5a, 5b) is compared with each other, and the optical pattern information (5a, 5b) is supplemented with the difference between the two optical pattern information. A mask pattern inspection apparatus comprising a device (6a) for outputting 5c), wherein the auxiliary storage device is configured to store the differential complementary optical pattern information.