JPH0675186B2 - Defect inspection board - Google Patents

Description

The present invention relates to a defect inspection substrate, and inspects for defects of various masks used in a lithography method widely used in the semiconductor industry and other technical fields, for example. Which is used when carrying out one method, wherein the thin film formed on the substrate surface of the defect inspection substrate uses the mask to be inspected, and a fine pattern of the mask such as a reticle to be inspected. Forming a fine pattern corresponding to
The present invention relates to the one used when inspecting the presence or absence of defects in the mask to be inspected by examining the fine pattern obtained by this.

[Prior Art] For example, various masks on which a fine pattern is formed are used to perform a lithography method, and this mask is used as one of the methods for inspecting the fine pattern formed on the various masks. To form a fine pattern corresponding to the fine pattern of the mask on the test piece, and then, by checking the presence or absence of defects in the fine pattern formed on the test piece, the defects of the fine pattern of the mask to be inspected There is a method of indirect inspection.

Conventionally, as a test piece used in this inspection method, there is known a defect inspection substrate in which a thin film of aluminum (Al) is formed on the surface of a transparent substrate such as quartz glass by a sputtering method or the like.

That is, this defect inspection substrate uses the mask to be inspected on the Al thin film formed on the photomask substrate surface, and forms a fine pattern corresponding to the fine pattern of the mask to be inspected on the Al thin film, After that, inspect the obtained fine pattern with a transmission type defect inspection device,
By checking the presence or absence of a defect in this pattern, the defect of the fine pattern of the mask to be inspected is indirectly inspected.

[Problems to be Solved by the Invention] By the way, the test piece used for the inspection by the above-mentioned method needs to be capable of transferring a fine pattern faithfully corresponding to the fine pattern of the mask to be inspected. Next, it is required that the etching be easy and the inspection of defects in the formed pattern be accurate and easy.

The defect inspection substrate of the conventional example described above has excellent etching properties because the thin film is made of Al, and has a sufficiently high optical density (reciprocal logarithm of transmittance). Inspection of defects in a fine pattern by inspection can be performed relatively easily and accurately.

However, the Al thin film has a surface reflectance of 90% or more with respect to ultraviolet light (wavelength 400 to 450 nm) used as light for exposure when transferring the fine pattern of the mask to be inspected to the defect inspection substrate. Since it shows a high value,
When the thin film is exposed to light by the mask to be inspected using this ultraviolet light, the ultraviolet light easily causes interference with incident light on the surface of the thin film, which is why the fine pattern of the mask to be inspected is generated. Could not be accurately transferred to the thin film.

An object of the present invention is to provide a substrate for defect inspection which eliminates the above-mentioned defects.

[Means for Solving the Problems] In view of the above-mentioned circumstances, the inventors of the present invention have met the respective conditions required for the test piece such that the interference is unlikely to occur and etching property and pattern inspection are easy. The thin film to be formed on the surface of the defect inspection substrate in order to obtain the defect inspection substrate is composed of various materials, as a result of various experimental investigation,
It has been clarified that all the above conditions can be satisfied by forming the thin film from a material of which at least the surface portion is made of aluminum containing nitrogen.

The present invention has been made based on this fact and has the following configurations.

A thin film that is capable of being etched is formed on the surface of a transparent substrate, and the thin film is used in a lithography method that is an inspection target, and a mask on which a fine pattern is formed is used. In a defect inspection substrate for forming a corresponding fine pattern, and then inspecting for defects of the fine pattern of the mask to be inspected by examining the defects of the fine pattern, the transparent substrate surface A substrate for defect inspection, characterized in that the surface portion of the thin film formed on the substrate is composed of aluminum (Al) containing at least nitrogen.

[Operation] According to the above configuration, the surface reflectance of the thin film formed on the surface of the translucent substrate is the ultraviolet light (wavelength 40%) that is the light for exposure.
It becomes 50% or less with respect to 0 to 450 nm), and the possibility of causing the above-mentioned interference during the exposure processing is significantly reduced.

Moreover, the etching property is almost the same as that of the Al thin film and is extremely good, and the optical density is 3.0, which is sufficient, and the inspection by a transmission type defect inspection device or the like can be easily and accurately performed.

Therefore, by using this defect inspection substrate as a test piece, it is possible to accurately inspect for defects in the fine pattern of the mask to be inspected.

[Embodiment] FIG. 1 is a partial vertical sectional view showing a defect inspection substrate according to an embodiment of the present invention.

In the figure, reference numeral 1 is a transparent substrate made of quartz glass having the same shape as a silicon wafer having a diameter of 125 mm, an orientation flat dimension of 42.5 mm and a thickness of 0.625 mm. Has a thin film (thickness 850 Å) 2 made of Al containing oxygen and nitrogen.

This thin film 2 is formed as follows.

That is, first, the surface of the translucent substrate 1 is precisely polished, and then the surface of the translucent substrate 1 is mixed gas atmosphere of 80% by volume of argon, 3% by volume of oxygen, and 17% by volume of nitrogen (pressure 1.5%). It is formed by applying a sputtering method using Al as a target in ( ^10-3 Torr).

The ultraviolet light of the thin film 2 thus obtained (wavelength 400 to 450
(nm) was 38 to 45%, and the optical density was 3.0.

Next, using the defect inspection substrate according to the above-described embodiment as a test piece, a master mask to be inspected is used for the thin film 2 of the defect inspection substrate which is the test piece, and a fine pattern corresponding to the fine pattern of the master mask is formed. An example in which the presence or absence of defects in the fine pattern of the master mask is inspected by forming and then inspecting the presence or absence of defects in the fine pattern formed on the defect inspection substrate as the test piece will be given.

First, a positive photoresist (for example, AZ1350 manufactured by Hoechst; trade name) is dropped on the surface of the thin film 2 of the defect inspection substrate, and the dropped photoresist is evenly rotated by rotating the defect inspection substrate. By applying a so-called spin coating method, the film thickness of about 5000 is applied to the surface of the thin film 2.
Form angstrom photoresist.

Next, as an inspection target, ultraviolet light (wavelength 400 to 450 nm) is applied to the defect inspection substrate on which the photoresist is formed using a master mask on which a fine pattern having a line width of 2 μm is formed.
Exposure process.

Next, the substrate for defect inspection after this exposure processing is subjected to development processing with a developer for AZ (for example, AZ 312MIF aqueous solution manufactured by Hoechst).

Thereafter, the thin film of the substrate for defect inspection after development is subjected to etching treatment with the above-mentioned developing solution for about 160 seconds.

After that, the remaining photoresist is removed.

This makes it possible to obtain a test piece in which the fine pattern 3 corresponding to the fine pattern of the master mask to be inspected is formed on the thin film 2.

FIG. 2 is a partial cross-sectional view of the test piece thus obtained, in which the fine pattern 3 corresponding to the fine pattern of the master mask to be inspected is formed on the surface of the transparent substrate 1.

When this test piece and the fine pattern of the master mask to be inspected are precisely compared and observed with an operation electron microscope or the like, the fine pattern formed on the test piece is always the fine pattern formed on the master mask. It was confirmed that the image was reproduced extremely faithfully including the details thereof (that is, even the minute defect occurring in the master mask was faithfully reproduced).

In addition, when this test piece was actually inspected by a transmission type defect inspection device and tested for inspectability and the like, it was found that the defects generated in the master mask to be inspected could be completely detected with almost no leakage. It has been confirmed.

Note that the present inventors have used a quartz glass substrate for comparison.
Using the conventional defect inspection substrate on which an Al thin film is formed, an experiment is performed to form a fine pattern corresponding to the fine pattern of the master mask on the Al thin film by the same master mask as the master mask used in the example. The following is an example of the results.

First, an Al thin film having a film thickness of 500 angstrom was formed on a quartz glass substrate similar to that of the above-described example by a sputtering method in an argon gas atmosphere (pressure 3 × 10 ⁻³ Torr) using Al as a sputtering target.

The thin film thus obtained had an optical density of 3.0 and a surface reflectance of 90% with respect to ultraviolet light (wavelength 400 to 450 nm).

On this thin film, a fine pattern corresponding to the fine pattern of the master mask to be inspected was formed in the same manner as in the example, and comparative observation was performed using a scanning electron microscope or the like as in the example, In the fine pattern formed on the test piece of this comparative example, the taper of the line width of the pattern which is not found in the master mask to be inspected is seen,
In addition, as compared with the case of the above-mentioned embodiment, a degree of faithfully reproducing the fine pattern of the master mask to be inspected, such as when some of the minute defects that were present in the master mask are missing. It was confirmed that it was significantly inferior.

As described above, the defect inspection substrate of the embodiment is a thin film formed on the transparent substrate surface of the defect inspection substrate, a fine pattern of the master mask to be inspected, including the details thereof. It is possible to faithfully reproduce (i.e., faithfully reproduce even minute defects occurring in the master mask). Therefore, by inspecting the test piece thus formed with a transmission type defect inspection device or the like, It is possible to completely detect the defects that have occurred in the master mask to be inspected, with almost no omission.

In the embodiment, the thin film formed on the surface of the light-transmitting substrate is an example in which Al containing nitrogen and oxygen is almost evenly formed in the entire part of the thin film, but this is not always the case. It is not necessary that the whole portion of the thin film contains oxygen and nitrogen, and at least the surface portion may contain oxygen and nitrogen.

Further, although Al and nitrogen and oxygen are included, it is not necessary to include oxygen and it is sufficient that at least nitrogen is included.

Further, in the above-described embodiment, the shape of the translucent substrate is a shape like a silicon wafer, but it may be another shape, for example, a rectangle.

Furthermore, in the above-mentioned embodiment, an example of using quartz gas as a translucent substrate is given, but the present invention is not limited to this, and for example, soda lime glass, aluminosilicate glass, aluminopolysilicate glass, etc. You may use the transparent glass material of.

Further, as a method for forming a thin film on the surface of the transparent substrate, other well-known thin film forming techniques such as a vacuum vapor deposition method and an ion plating method may be applied instead of the sputtering method of the above embodiment. You can also

[Effects of the Invention] As described above in detail, the defect inspection substrate according to the present invention has a thin film formed on the substrate surface of the defect inspection substrate.
A transparent pattern is formed by forming a fine pattern corresponding to a fine pattern of a mask to be inspected and indirectly checking the presence or absence of a defect in the fine pattern to check the presence or absence of a defect in the mask to be inspected. At least the surface portion of the thin film formed on the surface is composed of aluminum (Al) containing nitrogen and oxygen, thereby faithfully reproducing the fine pattern of the mask to be inspected on the thin film of the defect inspection substrate. It is possible to form it and facilitate an accurate inspection.

[Brief description of drawings]

FIG. 1 is a partial vertical sectional view showing a defect inspection substrate according to an embodiment of the present invention, and FIG. 2 is a partial vertical sectional view showing a state in which a fine pattern is formed on the defect inspection substrate shown in FIG. Is. 1 ... Translucent substrate, 2 ... Thin film, 3 ... Fine pattern.

Claims (1)

[Claims] 1. A thin film that can be etched is formed on the surface of a light-transmissive substrate, and a mask having a fine pattern used in a lithography method that is an inspection target is used for the thin film. A fine pattern corresponding to the fine pattern of the mask is formed, and then, in the defect inspection substrate adapted to inspect the presence or absence of the defect of the fine pattern of the mask to be inspected by examining the defect of the fine pattern, A substrate for defect inspection, wherein a surface portion of a thin film formed on the surface of the transparent substrate is made of aluminum (Al) containing at least nitrogen.