JPH06103272B2 - Method for inspecting foreign matter on mask of X-ray exposure mask - Google Patents

Description

The present invention relates to a method for inspecting foreign matter on a mask of an X-ray exposure mask (photomask), and in particular, extremely minute foreign matter on an X-ray exposure mask used for exposure of semiconductors and the like. The present invention relates to a method for inspecting foreign matter on a mask used for detecting the.

[Conventional technology]

In a semiconductor, the pattern on the mask is repeatedly exposed on the wafer, so if there is a foreign substance on the mask, all the exposed patterns become defective.

As one method of solving this problem, the conventional technology is disclosed in Koizumi et al., Evaluation System “Latest Semiconductor Factory Automation System Comprehensive Technology Compilation”, Reprint, 342p, published by Science Forum (issued July 25, 1984). As described above, a transparent thin film called a pellicle is provided on the mask to prevent foreign matters from directly adhering to the pattern on the mask.

In addition, as another method, in order to detect a foreign substance, the method disclosed in
As disclosed in Japanese Patent Laid-Open No. 59-186324, a light beam is emitted from one of the light-transmissive plate-shaped substrates, and scattered light generated from the particles adhered to the plate-shaped object is detected to inspect for the presence of the particles. There is a method of doing so, which makes it possible to inspect only foreign matters without being affected by the pattern on the mask.

[Problems to be Solved by the Invention]

Although the method using the pellicle described above can reduce the adherence of foreign matter, it cannot completely eliminate the adherence of foreign matter. Therefore, it is necessary to inspect the foreign matter on the pellicle. If they are provided close to each other, the pattern below interferes with the detection of foreign matter on the pellicle.

Further, the minimum detectable foreign matter in the method disclosed in Japanese Patent Laid-Open No. 59-186324 is 2 μm, and a foreign matter smaller than this cannot be detected.

However, in the case of an X-ray mask used for the exposure of ultra-ultra LSI in the future, the pellicle is difficult to use because the distance between the mask and the wafer must be 30 μm or less.
Further, since the size of the foreign matter that causes defects during exposure is about 0.15 μm, the method disclosed in JP-A-59-186324 cannot be applied.

An object of the present invention is to enable detection of extremely small foreign matter on an X-ray exposure mask for which it is difficult to use a pellicle as described above, and particularly to detect foreign matter when there is unevenness on the film deposited on the surface. To provide a way to do.

[Means for Solving the Problems]

One of the main configurations of the invention taken to solve the above-mentioned problems is to provide a method for inspecting foreign matter on a mask of an X-ray exposure mask for exposing a pattern on a semiconductor or the like by using X-rays, wherein An organic film having a minimum film thickness that almost absorbs light in a specific wavelength region other than the X-ray wavelength region used for the exposure of the pattern is applied onto the pattern of the line exposure mask, P of the wavelength of the specific region is added to the organic film.
It is characterized in that polarized light is radiated at an incident angle of Brewster's angle to detect the presence or absence of scattered light to detect foreign matter. In another configuration, the base material of the pattern of the X-ray exposure mask is The first organic film having a minimum film thickness that almost absorbs light in a specific wavelength region other than the X-ray wavelength region used for exposing the pattern is used as a main constituent material, and the first organic film is formed on the pattern. A second organic film similar to the organic film is applied, the base material side is irradiated with light of the wavelength of the specific region with the incident angle being vertical, and the pattern side of the wavelength of the specific region is irradiated. It is characterized by irradiating P-polarized light at an incident angle of Brewster's angle and detecting the presence or absence of scattered light to detect a foreign substance.

[Action]

In the present invention, an organic film that absorbs light having a wavelength in a specific region is applied onto a patterned mask, and light scattered at a specific wavelength is detected to detect scattered light from the surface of the organic film. Light of a wavelength is absorbed by the organic film and does not reach the pattern on the mask. Therefore, scattered light due to the pattern on the mask is not generated.

On the other hand, if there is a foreign substance on the organic film, the irradiation light is strongly scattered by the foreign substance. Therefore, if the scattered light from the surface of the organic film is constantly detected, the foreign substance can be detected.

However, when the surface of the organic film has irregularities, specularly reflected light on the irregularities is detected together with the foreign substance scattered light. FIG. 3 is an explanatory view of an exposure state in such a case, where 1 is an X-ray mask, 2 is a condenser, 3 is a detector, and 4 is illumination light, and the X-ray mask 1 is a support 1a. , Substrate 1b (first layer), 1c (second layer) pattern 1d, organic film 1e, 5 is a foreign matter, 6 and 7
Indicates scattered light from the foreign matter 5 and the organic film 1e, respectively. Then, when the illumination light 4 enters, the foreign matter 5 and the organic film
Since the scattered lights 6 and 7 are generated from 1e, it is not possible to discriminate between the foreign matter and the unevenness, resulting in erroneous detection.

Therefore, in the present invention, when the organic film surface has irregularities, P
A method of irradiating with a polarized Brewster angle is used.
Therefore, the specular reflection light component on the surface of the organic film can be made zero, and only the foreign substance scattered light can be detected. Since there is no unevenness on the surface of the organic film on the side of the base material, it is possible to detect foreign matter by vertical epi-illumination.

〔Example〕

 Examples will be described below.

FIG. 1 is an explanatory view of an implementation state of one embodiment, and FIG. 2 is an illustration of an on-mask foreign matter inspection device for an X-ray exposure mask used in the implementation of one embodiment. And the case of performing epi-illumination at the same time. In these figures, the same parts as those in FIG. 3 are designated by the same reference numerals. Reference numeral 8 indicates a Brewster's angle illumination unit, and 9 indicates an epi-illumination unit.

The X-ray mask 1 includes a base material 1b (first layer) made of BN and a PIQ (P
Base material 1c consisting of olyimide isoindroquinazolinedione)
It is formed on a composite with (second layer). For example, the pattern 1d made of Au is covered with the organic film 1e made of PIQ, for example, and is fixed on the holder portion 11 on the uniaxial stage 10.

The PIQ used as the organic film has a film thickness of 5 μm or less,
The one having a thickness of 0.5 μm or more is used.

The Brewster illumination unit 8 includes a laser oscillator 12, a beam expander 13, and a condenser lens that generate light with a wavelength of 380 nm or less.
In order to make the light 17 (Brewster angle illuminating light) 17 that has a scanning direction 14 and is deflected and scanned by the galva mirror 15 in the direction perpendicular to the moving direction 16 of the uniaxial stage 10 at the Brewster angle. Concentrator 20 for condensing the light 19 scattered by the foreign substance 5 on the organic film 1e of the X-ray mask 1, and the detection for detecting the light condensed by the concentrator 20 It has a container 3.

Although not shown in FIG. 2, the epi-illumination unit 9 emits light (illumination light) that is generated in the same manner as the Brewster angle illumination unit 8 and is deflected and scanned in a direction perpendicular to the moving direction 16 of the uniaxial stage 10. ) 21 is made to enter the X-ray mask 1 from a right angle direction, and a light collector 24 that collects the light 23 scattered by the foreign matter 22 on the X-ray mask 1 and a light collector 24 It has a detector 25 for detecting light.

In order to inspect an X-ray exposure mask using this on-mask foreign matter inspection method, the PIQ-coated X-ray mask 1 is placed on the holder portion 11 on the uniaxial stage 10 with the pattern 1d side facing up. When the pattern 1d side is scanned in the Brewster's angle illumination section 8 and the substrate side is scanned in the epi-illumination section 9 in conjunction with the movement of the uniaxial stage 10, on the organic film 1e on the pattern side,
When the foreign substances 5 and 22 are present on the substrate 1b (first layer), the lights 19 and 23 scattered by the foreign substances 5 and 22 are collected by the light collectors 20 and 24, respectively, and detected. It can be detected with instruments 3 and 25.

At this time, light having a wavelength of 380 nm or less is used as the Brewster angle illumination light 17 and the illumination light 21.

The spectral transmittance of PIQ is the wavelength (n
As is clear from FIG. 4 showing m) and transmittance (%), the transmittance is extremely small for light of 380 nm or less. On the other hand, even shorter wavelengths (1-
For 20 nm), the PIQ transmittance has a value close to 100%.

Therefore, as shown in FIG. 1, an organic film is formed on the X-ray mask 1.
If PIQ is applied as 1e, the foreign matter 5 in the air adheres to the PIQ film. Then, in the foreign matter inspection, when light with a wavelength of 380 nm or less is irradiated, the light hitting the PIQ film is absorbed by the PIQ film and does not generate scattered light, but the light hitting the foreign material 22 on the PIQ film is scattered. Since the light 23 is generated, the foreign matter can be detected only by detecting the scattered light 23 with the scattered light detector 25.

That is, on the side of the base material 1b (first layer), since the base material 1b + 1c is sufficiently thick, the surface of the base material 1b + 1c has no unevenness. Therefore, the foreign material may be detected using the epi-illumination unit 9 on the substrate side.

On the other hand, the organic film 1e is formed on the pattern 1d side due to the step of the pattern 1d.
As the surface has irregularities, as described above (see FIG. 3),
Since both the foreign matter scattered light 6 and the surface unevenness scattered light 7 reach the detector 3, it is impossible to distinguish between the unevenness and the foreign matter. In this embodiment, however, the illumination is detected at the P-polarized Brewster angle. Therefore, the specularly reflected light due to the surface irregularities can be made almost zero, and only the scattered light of the foreign matter can be detected. That is, the PIQ surface illuminated with the Brewster's angle illumination light 17 has zero surface reflection, and only the scattered light 19 generated from the foreign matter 5 is detected by the detector 3 via the condenser 20. .

Next, the principle will be described with reference to FIGS. 5 and 6. 26 and 27 are mediums having refractive indices n and n ', 28, 29 and 3 respectively.
0 is P-polarized incident light of intensity Ep, reflected light of intensity Rp,
Refracted light, i ₁ and i ₂ respectively indicate the incident angle and the refraction angle, and in FIG. 6, the horizontal axis and the vertical axis respectively show the incident angle i ₁ (degree) and There is

When polarized light is incident on a substance having a different refractive index, the intensity Rp of the reflected light 30 depends on the incident angle i ₁ , and the ratio of Ep and Rp is given by Fresnel's equation. However, n <n '.

Therefore, when PQ polarized illumination is performed and PIQ is used as the organic film, the refractive index of PIQ is 1.8 and the refractive index of air is 1. Therefore, n = 1, n ′ = 1.8 is used and equation (1) is used. Ep and Rp
When the ratio of is calculated, FIG. 6 is obtained. From this figure i ₁ = 61
When °, the ratio of Ep and Rp becomes zero. Further, within the range of 61 ° ± 5 °, the ratio of Ep and Rp can be suppressed to 0.5% or less.

Therefore, when an organic film having a refractive index of n '= 1.8 is used, if the irradiation angle of P-polarized illumination is set to 61 °, the foreign substance scattered light is detected without being affected by the unevenness of the organic film. be able to.

By using the method of this embodiment, without being affected by the pattern on the mask and the unevenness of the surface organic film,
It is possible to detect minute foreign particles of 0.15 μm or less, and it is possible to significantly reduce defects during exposure, which is very effective in improving the yield of LSI products.

〔The invention's effect〕

The method for inspecting foreign matter on a mask for X-ray exposure according to the present invention detects extremely small foreign matter on a mask for X-ray exposure, which makes it difficult to use a pellicle, and particularly when unevenness is present on a film deposited on the surface. It provides a method that enables detection of foreign matter, and has a great industrial effect.

[Brief description of drawings]

FIG. 1 is an explanatory view of an implementation state of an embodiment of the method for inspecting foreign matter on a mask for X-ray exposure of the present invention, FIG. 2 is an illustration of an apparatus used for implementing the embodiment of FIG. 1, and FIG. The figure is an explanatory view of the exposure state when the organic film surface has irregularities, FIG. 4 is a diagram showing the spectral transmittance of PIQ used in the X-ray exposure mask of FIG. 1, and FIG. 5 is the X of the present invention. FIG. 6 is a diagram for explaining the principle of the method for inspecting foreign matter on a mask for line exposure, and FIG. DESCRIPTION OF SYMBOLS 1 ... X-ray mask, 1a ... Support material, 1b, 1c ... Base material, 1d ... Pattern, 1e ... Organic film, 3,25 ... Detector, 5,22 ... Foreign matter, 8 ... Brewster angle illumination part, 9 … Epi-illumination unit, 17… Brewster angle illumination light, 21… Illumination light.

Claims (4)

[Claims] 1. A method for inspecting foreign matter on a mask of an X-ray exposure mask for exposing a pattern on a semiconductor or the like using X-rays, wherein X used for exposing the pattern on the pattern of the X-ray exposure mass. An organic film having a minimum film thickness that almost absorbs light in a specific wavelength region other than the line wavelength region is applied, and the P-polarized light having a wavelength in the specific region is incident on the organic film at an incident angle. A method for inspecting foreign matter on a mask for an X-ray exposure mask, which comprises irradiating as a Brewster angle and detecting the presence or absence of scattered light to detect foreign matter. 2. The organic film has a film thickness of 5 μm or less, 0.5 μm
With the above PIQ, the wavelength of light in the specific range is 380 nm
The method for inspecting foreign matter on a mask for an X-ray exposure mask according to claim 1, which has the following wavelengths. 3. A method for inspecting foreign matter on a mask of an X-ray exposure mask for exposing a pattern to a semiconductor or the like using X-rays, wherein a base material of the pattern of the X-ray exposure mask is used for the exposure of the pattern. A first organic film having a minimum film thickness that almost absorbs light in a specific wavelength region other than the wavelength region of the X-ray used is used as a main constituent material, and the first organic film is formed on the pattern. A similar second organic film is applied, and light having a wavelength of the specific region is irradiated on the base material side with a vertical incident angle, and P of the wavelength of the specific region is applied to the pattern side.
A mask foreign matter inspection method for an X-ray exposure mask, which comprises irradiating polarized light with an incident angle of Brewster's angle and detecting the presence or absence of scattered light to detect foreign matter. 4. The organic film, wherein the film thickness is 5 μm or less, 0.5 μm
With the above PIQ, the wavelength of light in the specific range is 380 nm
The method for inspecting foreign matter on a mask of an X-ray exposure mask according to claim 3, which has the following wavelengths.