JPS58110041A - Inspection of pattern - Google Patents

Abstract

PURPOSE:To effect a pattern inspection through the detection of a transmitted light when a polarized light is scattered by a foreign matter or a pattern edge, by interposing polarizers between a transparent substrate and an illuminating light source and between the substrate and a light-detecting means, respectively. CONSTITUTION:If a foreign matter 4 exists on the surface of a substrate 2, the S-polarized component of light transmitted by the substrate 2 is scattered by the foreign matter 4 and depolarized. Since the other components of light than the S-polarized component are transmitted by a P-polarizer 9, they are incident on a light-receiver 6 and detected. If there are a cut 11 and a projection 12 on an edge of a pattern 3a or 3b, the polarization is canceled by these parts, and the depolarized light is detected by the light-receiver 6 or 7. When there is no abnormality on the object to be inspected, the quantity of light incident on the light receivers is 0. By this constitution, the quality can easily be judged, and a defective mode can be automatically discriminated by setting a proper slice level.

Description

Detailed Description of the Invention] (al Technical Field of the Invention The present invention relates to an improvement in a photomask pattern inspection method using transmitted light ↓ (bl Prior art and problems) As a method for inspecting defective modes such as size, foreign matter adhesion, and abnormal shape of pattern edges, a method is used that detects transmitted light by utilizing the fact that the photomask substrate is a transparent substrate made of glass or quartz. It is being

For example, a light receiver is placed on the same part of two adjacent pattern areas on a photomask, and the two light receivers receive the light projected from the illumination light source provided on the back of the photomask and transmitted through the photomask substrate. However, there is a method of detecting foreign matter adhesion by comparing the light intensity of the two, or a method of scanning the back side of the photomask with a laser beam, detecting the transmitted light density according to the position, and detecting the pattern edge by detecting the density change. A method is used in which the position of the pattern is detected and the dimensions of the pattern are measured accordingly.

The conventional inspection method described above is a method of detecting subtle changes in the amount of transmitted light, so it is difficult to obtain contrast, and furthermore, disturbances such as the influence of stray light are added, so the inspection accuracy is not necessarily satisfactory.

10) Object of the Invention An object of the present invention is to eliminate the above-mentioned problems and provide a pattern inspection method that can clearly detect changes in the amount of transmitted light.

+dl Structure of the Invention The feature of the present invention is that polarizers are interposed between the transparent substrate and the illumination light source and between the transparent substrate and the light detection means, respectively,
The purpose is to detect transmitted light only when the polarization is disturbed by attached foreign matter or pattern edges.

le) Examples of the invention Preferred embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a main part of an inspection apparatus used in a failure mode inspection method as an embodiment of the present invention. In the figure, ■ is a photomask of the sample to be inspected, 2 is a transparent photomask substrate (hereinafter simply referred to as the substrate), 3a,
3b is a pattern, 4 is a foreign substance to be attached to the substrate surface, 5 is an illumination light source, 6°7 is a light receiver, 8 is a polarizer interposed between the illumination light fs5 and the back surface of the substrate 2, and 9 is a Photoreceiver6.
This is a polarizer interposed between 7 and 7. Said polarizers 8 and 9
assumes that one side (for example, polarizer 8) is an S polarizer and the other side (for example, polarizer 9) is a P polarizer. In the inspection apparatus shown in the same figure, the other configurations except for the polarizers 8 and 9 are the same as those of the conventional apparatus.

The inspection apparatus is configured as described above, and the substrate 2 is irradiated with the illumination light source 5 provided on the back surface of the substrate 2 through the polarizer 8. The irradiation light 10 is made into only the S-polarized component by passing through the polarizer 8 , and only the component passing through the portion of the surface of the substrate 2 where no pattern exists is incident on the P-polarizer 9 . This P polarizer 9 does not transmit the S polarized light component. Therefore, patterns 3a, 3b
If there is no abnormality at all and no foreign matter is attached, the amount of light incident on the light receivers 6 and 7 is zero.

If there is any abnormality, for example, as shown in the same figure, the board 2
When foreign matter 4 such as minute dust is attached to the surface, the S-polarized light component transmitted through the substrate 2 hits the foreign matter 4 and is scattered, and the polarization is canceled. Since light components other than the S-polarized component are transmitted through the P-polarizer 9, the light component depolarized by the foreign object 4 passes through the P-polarizer 9, enters the light receiver 6, and is detected.

Further, as shown in FIG. 2, there is a chip 11. at the pattern edge of pattern 3a or pattern 3b. Even if there is a protrusion 12 or the like, the polarization is canceled at that part, and the light is detected by the light receiver 6 or 7 in the same way as when the foreign object 4 is present.

As described above, in this embodiment, when there is no abnormality in the part to be inspected, the amount of light incident on the light receiver is O, and light is detected only when some abnormality exists. Therefore, it is extremely easy to determine whether the defective mode is good or not. Moreover, since the amount of light incident on the receiver differs depending on the defective mode, such as disordered pattern edges or adhesion of foreign matter, defective modes can be automatically identified by setting an appropriate slice level. It is also possible to determine.

FIG. 3 is a sectional view of essential parts of a dimension measuring device used in a pattern dimension measuring method as a modified example of the present invention.

In this modification, a laser 21 is used as the irradiation light source, and S
The back surface of the substrate 2 is scanned by a minute spot laser beam 22 through a polarizer 8, and the amount of light passing through the P polarizer 9 and entering the light receiver 6 is detected in correspondence with the position on the substrate 2. .

FIG. 4 shows the amount of transmitted light incident on the light receiver 6 when the pattern edge portion is scanned by the laser beam 22 in this modification. In the same figure (al, 23 is a pattern, 2
4 is a pattern edge. When the pattern edge 24 portion is irradiated, the irradiated light is scattered by the Taber portion of the pattern edge 24, depolarized, passes through the P polarizer 9, and enters the light receiver 6.

In other parts except the pattern edge 24, the amount of light incident on the geophone 6 is 0 regardless of the presence or absence of a pattern.

That is, in the pattern 23 part, the irradiated light is blocked by the pattern 23, and in the part where no pattern exists, the transmitted light is blocked by the P polarizer because it is only an S polarized component, and in both cases, it reaches the light receiver 6. I can't. Therefore, according to this modification, as shown in FIG. fb), transmitted light is detected only at the pattern edge 24 portion.

In the conventional method, as shown in the same figure (C), a change in the intensity of transmitted light is detected at the pattern edge 24, but this change is gradual, and the influence of stray light cannot be completely removed. Ta. Comparing this to the case where it was difficult to improve the detection accuracy, the effect of this modification can be understood.

(fl) DETAILED DESCRIPTION OF THE INVENTION As described above, the present invention provides a pattern inspection method that can clearly detect changes in the amount of transmitted light.

[Brief explanation of the drawing]

1 and 2 are a cross-sectional view and a top view of a main part showing one embodiment of the present invention, and FIGS. 3 and 4 are a cross-sectional view and a curve diagram of a main part showing a modification of the present invention. be. In the figure, ■ is a photomask, 2 is a transparent substrate, 3.3a
, 3b, 23 are patterns, 4 is a foreign object, 5゜21 is an illumination light source, 6.7 is a light detection means, 8.9 is a polarizer, 10.22
11.12 indicates the irradiation light, 11.12 indicates the pattern abnormality, and 24 indicates the pattern edge.

Claims (1)

[Claims] Transmitted light projected from an illumination light source disposed opposite the other main surface of a transparent substrate having a pattern formed on its surface and transmitted through the transparent substrate is directed to face the surface of the transparent substrate. In the pattern inspection method of inspecting the pattern on the entire surface of the transparent substrate by detecting the pattern with the light detection means arranged at the A pattern inspection method characterized in that a polarizer is interposed between each.