JPH01244304A - Appearance defect inspection method - Google Patents

Abstract

PURPOSE:To check defects in an outer appearance of a single reticle in a short time, by preliminarily forming a sacrifice pattern on a mask corresponding to a regular pattern and detecting outside defects of said mask through the identity of these patterns. CONSTITUTION:Regular patterns 5-8 are formed in a single reticle (photomask) 1 and at the same time, sacrifice patterns 5'-8' are also formed. For detecting outside defects, only the patterns 1A-1C of the patterns formed on the reticle 1 are transferred onto a dummy wafer 9 by an exposing device. Then, the identity between the sacrifice patterns 5'-8' and regular patterns 5-8 on the dummy wafer 9 are compared by an outside defect checking device of a two- chip comparison type, and a non-identical part is detected as a defective one. Accordingly, even a single reticle or the like having single patterns formed thereon, its defects can be examined through the two-chip comparison.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to visual defect inspection technology, in particular visual defect inspection technology for photomasks, for example, photomasks used in lithography processing in the manufacturing process of semiconductor devices. This invention relates to an effective technique that can be used to inspect appearance defects in patterns.

[Conventional technology]

With the recent trend towards large pellets due to the high integration of semiconductor devices, reticles used as enlarged photomasks used in lithography processing in the semiconductor device manufacturing process have only - unit pellet patterns formed on them. (hereinafter referred to as a single reticle) is occurring.

On the other hand, in the manufacturing process of semiconductor devices, as an external defect inspection method for inspecting defects in a reticle pattern, the reticle is illuminated, the light reflected by the reticle pattern is detected by a light receiver, and two or more defects on the reticle are detected based on the signal from the light receiver. Some are configured to inspect for defects by comparing identical locations of two pellet patterns and detecting mismatched portions.

Another visual defect inspection method is to detect defects by optically detecting the pattern on the reticle, comparing the same parts of this pattern with the design data for this pattern, and detecting mismatched parts. There are some things that are configured to test.

An example of a mask inspection technique is "Electronic Materials November 1986 Special Issue" published by Kogyo Research Association Co., Ltd., November 18, 1986, pages 221 to 229.

[Problem to be solved by the invention]

However, in the former method, in which defect inspection is performed by comparing the same locations of two pellet patterns on a reticle, it is not possible to perform defect inspection on peripheral circuit patterns other than repetitive memory cell portions on a single reticle. In addition, in the latter method, where defect inspection is performed by comparing the pattern and design data, it is possible to inspect even a single reticle, but there is a problem that the inspection time is extremely long.
revealed by the inventor.

SUMMARY OF THE INVENTION An object of the present invention is to provide a visual defect inspection method that can perform defect inspection using a two-chip comparison method even on a single reticle.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings. An overview of what is going on is as follows.

That is, by forming a discarded pattern that corresponds to a regular pattern in a photomask separately from the regular pattern, and comparing the identity of this discarded pattern with its corresponding regular pattern, the regular pattern of the photomask can be determined. It is designed to inspect appearance defects.

[Effect]

According to the above-mentioned means, since the discarded pattern is formed identically to the regular pattern, defects can be inspected by comparing the same parts of the discarded pattern and the regular pattern and detecting mismatched parts. . Since this discarded pattern is placed on one photomask, even if a single pattern is formed, such as on a single reticle, defect inspection can be performed by comparing two chips. .

〔Example〕

Fig. 1 is a plan view showing a single reticle used in the external defect inspection method which is an embodiment of the present invention, Fig. 2 is a plan view showing its transfer state, and Fig. 3 is a plan view showing the single reticle used in the external defect inspection method. FIG. 4 is a schematic diagram showing a two-chip comparative visual defect inspection device, and FIG. 4 is an enlarged partial plan view for explaining its operation.

In this embodiment, the visual defect inspection method according to the present invention is such that a single reticle is inspected for visual defects using a single-lens, two-chip comparison type visual defect inspection apparatus as shown in FIG. A single reticle l as shown in FIG. 1 is created in advance.

The single reticle 1 has one pattern 3 for a relatively large chip arranged approximately at the center of the exposure area 2 in an exposure device (not shown), and this chip pattern 3 has a memory cell section. 4, and a first peripheral circuit section 5, a second peripheral circuit section 6, and a third peripheral circuit section as each regular pattern.
A peripheral circuit section 7 and a fourth peripheral circuit section 8 are formed.

The memory cell section 4 is composed of a repeating pattern, but each of the peripheral circuit sections 5, 6, 7 and 8 is different from each other and is composed of a non-repetitive pattern. Further, in the exposure area 2, a first sacrificial pattern 5', a second sacrificial pattern 6', a third sacrificial pattern 7', and a fourth sacrificial pattern 8' are formed on the outside of the four sides of the chip pattern 3, respectively. Each discard pattern 5', 6', 7'
and 8' are the first, second, and third regular patterns.
and fourth peripheral circuit sections 5.6.7 and 8, respectively.

When a visual defect inspection is performed on the single reticle 1 configured in this way, the pattern formed on the single reticle 1 is exposed to a dummy wafer 9 by an exposure device (not disclosed) as shown in FIG. Multiple transcriptions are made. That is, in FIG. 2, the dummy wafer 9 has a first transfer pattern IA and a second transfer pattern IB formed by reducing projection exposure of a single reticle degree 1 pattern.
and a third transfer pattern IC are formed respectively, and each transfer pattern IA, IB, IC includes chip patterns 3A, 3B, 3G, and each transfer discard pattern 5'A.
, 5' B, 5'C...8' A, 8' B, 8' C
are formed respectively.

Next, using the dummy wafer 9 onto which the pattern of the single reticle 1 has been transferred in this manner, a defect inspection of the single reticle 1 is relatively performed by the external defect inspection apparatus shown in FIG.

The external defect inspection apparatus 10 shown in FIG. It is configured to be able to move in the XY force directions. Xe is placed outward on the XY child table 1.
A light 'tA23 consisting of a lamp or the like is provided, and this light source 23 is configured to illuminate the pattern on the dummy wafer 9 via the first microscopic mirror 13 and the objective lens 12. A second glaucroic mirror 13' is arranged on the optical axis of the lens 12,
This second mirror 13' is configured to split the incident light into two optical paths. An autofocus circuit section 19 is disposed on the optical axis on the reflection side of the second mirror 13', and is connected to the central processing unit 21 so as to be able to automatically adjust the focus.

Further, a TV camera 14 as a pattern detection device is installed directly above the XY child table 1, and this TV camera 14 is configured to be able to image the pattern of the dummy wafer 9.

One input terminal of the defect determination section 1 is connected to the output terminal of the TV camera 14, and the storage section 15 is connected to the other input terminal of the defect determination section 18.

The output end of the defect determination section 18 is connected to the central processing unit 21.
The central processing unit 21 is connected to a result display section 22 and a table control section 20, and is configured to detect defects by the operation described below.

Next, the effect will be explained.

When the dummy wafer 9 is illuminated by the light source 23 through the first optical mirror 13 and the objective lens 12,
First, as a first step, as shown in FIG. 14, the objective lens 12, the first
The image is captured via the second mechanical mirror 13, 13', and this image is stored in the storage section 15.

Next, the XY child table 1 is moved, and an image of the small area 6A-1 of the second peripheral circuit section 6A corresponding to the transfer discarded pattern 6'A is captured by the TV camera 14, and this image is The signal is input as an inspection image signal 16 to one input terminal of the defect determination section 18 .

When this inspection image signal 16 is input, the image of the small area 6A-1 of the transferred discarded pattern 6'A previously stored in the storage section 15 is input to the other input end of the defect determination section 18. It is input as a reference image signal 17. Then, in the defect determination section 18, the inspection image signal 16
The grayscale image and the reference image signal 17 are compared, and if there is a difference between the two, it is determined that there is a defect.

Such a method is executed over the entire area between the discarded pattern 6'A and the peripheral circuit section 6A, and is further performed on other discarded patterns and the peripheral circuit section, 5'A and 5A, 7'A and 7A.
, 8'A and 8A, respectively, and defect inspection is performed in the same manner. The inside of the memory shell is also inspected using a similar method.

Then, as a second step, a defect common to all pellets is extracted from the defects detected in the first step. That is, since the defects detected in the first step include random defects, foreign object defects, defects common to all pellets, etc., it is necessary to extract the defects common to all pellets.

The extraction is performed by moving the XY child table 1 and changing the inspection target from the first transfer pattern IA on the wafer 9 to the second and third transfer patterns IB and IC. That is, the defects found in the first transfer pattern IA are applied to the second and third transfer patterns IB and IC.
If the defect is found at the same location, it is determined that the defect is common to all pellets. Then, the result is outputted by the display section 22.

According to the embodiment described above, the following effects can be obtained.

(1) A discarded pattern corresponding to the regular pattern is formed in advance in a photomask separately from the regular pattern, and the identity of this discarded pattern and the corresponding regular pattern is compared to determine the regular pattern of the photomask. By inspecting the appearance defects of a single reticle, it is possible to perform an appearance defect inspection on a regular non-repetitive pattern using a two-chip comparison method, making it possible to perform an appearance defect inspection on a single reticle in a short time. can.

(2) By increasing the workability of visual defect inspection for a single reticle, it is possible to promote the adoption of a single reticle, thereby promoting larger size and higher integration of semiconductor chips.

Although the invention made by the present inventor has been specifically explained based on the examples above, the present invention is not limited to the examples described above, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say.

For example, the target, number, and arrangement of the discarded patterns are set under optimal conditions, not only in response to the peripheral circuitry, but also in accordance with the circuit configuration of the chip pattern and the specifications of the external defect inspection equipment to be used. It is desirable to do so.

The material for transferring the reticle pattern is not limited to a dummy wafer, but may also be a glass, quartz substrate, or the like.

In the above explanation, the invention made by the present inventor was mainly applied to the field of application, which is the field of application, which is the field of application, which is the field of application of the invention, which is the field of application, which is the visual defect inspection method technology for a single reticle. or,
It can be applied to all external defect inspection methods for photomasks and the like.

(Effects of the Invention) The effects obtained by typical inventions disclosed in this application will be briefly described as follows.

A discarded pattern corresponding to the regular pattern is formed in advance in a photomask separately from the regular pattern, and the identity of this discarded pattern and the corresponding regular pattern is compared to determine the appearance defects of the regular pattern on the photomask. By inspecting the regular patterns of non-repeating patterns, the visual defect inspection can be performed using the two-chip comparison method, so that the visual defect inspection of a single reticle can be performed in a short time.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a single reticle used in the external defect inspection method which is an embodiment of the present invention, Fig. 2 is a plan view showing its transfer state, and Fig. 3 is a plan view showing the single reticle used in the external defect inspection method. FIG. 4 is a schematic diagram showing a two-chip comparative visual defect inspection device, and FIG. 4 is an enlarged partial plan view for explaining its operation. 1... Single reticle (photomask), 2 river exposure areas, 3... Chip pattern, 4... Memory cell section, 5.6.7.8... Peripheral circuit section (regular pattern)
, 5', 6', 7', 8'...Discard pattern, 9.
...Dummy wafer, IA, IB, IC...transfer pattern, 10...1-eye, 2-chip comparative visual defect inspection device,
11...XY child table 12...Objective lens, 13
．． 13'...Dichroic ink mirror, 14-TV camera, 15...Storage unit, 16...Inspection image signal, 17
. . . Reference image signal, 18 . . Defect determination unit, 19 .
・Auto focus circuit section, 20...table system? Part 11, 2
1...Central processing unit, 22...Result display section, 2
3...Light source.

Claims (1)

[Claims] 1. By forming a discarded pattern corresponding to the regular pattern in a photomask separately from the regular pattern, and comparing the identity of this discarded pattern with the corresponding regular pattern, 1. A method for inspecting appearance defects, which comprises inspecting regular patterns on a photomask for defects in appearance. 2. A pattern formed on a photomask is transferred onto an object to be transferred, and a comparative inspection is performed on the discarded pattern and the regular pattern transferred to the object. Appearance defect inspection method. 3. The visual defect inspection method according to claim 1, wherein the visual defect inspection is performed using a two-chip comparison type visual defect inspection apparatus.