JPH11219891A - Mask inspection method and apparatus - Google Patents

Abstract

(57) [Summary] To accurately detect a defect of an X-ray reduction exposure mask. Kind Code: A1 Abstract: The same NA, σ as when performing X-ray reduction exposure
The mask is inspected by illuminating the mask with the values and wavelengths and forming an image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of inspecting a mask for X-ray reduction exposure, and an inspection method using the inspection method.
The present invention relates to an exposure method using a corrected mask and a device manufactured using the exposure method.

[0002]

2. Description of the Related Art In projection exposure for transferring a pattern of a semiconductor integrated circuit or the like drawn on a mask onto a wafer, resolution and depth of focus are important. Generally, assuming that the numerical aperture of the imaging optical system is NA and the exposure wavelength is λ, the resolution R and the depth of focus DOF are given by Equations 1 and 2, respectively.

[0003]

R = k ₁ λ / NA (1)

[0004]

## EQU2 ## DOF = k ₂ λ / NA ₂ (2) where k ₁ and k ₂ are constants.

At present, using a KrF excimer laser having a wavelength of 248 nm, a lens optical system having a NA of about 0.6, a phase shift mask, and a multilayer resist, a resolution of 0.13 μm,
A depth of focus of 1 μm has been realized.

In order to increase the density of a semiconductor integrated circuit, a projection exposure method with higher resolution is required. Equation 1 above
As can be seen from the graph, the larger the NA or the shorter the exposure wavelength, the higher the resolution. However, when the NA is increased, the depth of focus decreases according to the above equation (2).
There is a limit to increasing the resolution by this method.

On the other hand, the exposure wavelength is set to several tens nm or several nm.
When the wavelength is shortened to the soft X-ray region, it is possible to achieve a resolution of 0.1 μm or less while securing a depth of focus of 1 μm. However, since the refractive index of a substance is very close to 1 with soft X-rays, it is difficult to apply a lens type optical system, and it is necessary to use a mirror (reflection type) optical system.

In recent years, a multilayer mirror in which a large number of thin films of two kinds of substances having different refractive indexes are alternately laminated has been put to practical use.
Lines can be reflected with high efficiency at any angle of incidence. Therefore, an X-ray projection exposure method using an imaging optical system using a multilayer mirror has been actively studied. The period length of the multilayer film is Λ, the reflection wavelength is λ, and the incident angle is θ (θ = 0 °
), Reflection occurs when the condition of Equation 3 is satisfied.

[0009]

2Λcos θ = nλ (n = 1, 2, 3, 4,...) (3) The reflection of the multilayer film has selectivity. It can be seen that it changes.
The mask for X-ray reduction exposure forms this soft X-ray reflection multilayer film on a smooth substrate to form a soft X-ray reflection portion, and forms a soft X-ray absorbing substance on the reflection portion ( It has a reflective structure in which a non-reflective portion (light-shielding portion) is formed by patterning the absorber by means such as an absorber and etching.

[0010]

A mask for X-ray reduction exposure having such a structure is not suitable for soft X-rays as exposure light.
The reflective part and non-reflective part are designed to have sufficient contrast, so the contrast is not always high with respect to visible light and electron beams such as lasers. Inspection of the defect, foreign matter, and pattern dimensions with sufficient detection sensitivity could not be performed with the inspection device.

On the other hand, an inspection method and an inspection apparatus for an X-ray reduction exposure mask are disclosed in Japanese Patent Application Laid-Open No. 6-349715. Here, soft X-rays having exactly the same wavelength as soft X-rays used as exposure light in X-ray reduction exposure are used as probes of an inspection apparatus.

FIG. 3 is a block diagram showing the conventional inspection apparatus. In the figure, laser plasma X is used as the light source.
Using a radiation source 37, the generated soft X-rays were condensed and monochromatized by a spheroid mirror 31 coated with a multilayer film, and a filter 32 was used to remove long-wavelength components from the ultraviolet to visible light regions.
The obtained soft X-ray 33 is reflected by a reflective mask 34 to be inspected.
Irradiation. The soft X-rays reflected by the mask 34 are enlarged and imaged on the X-ray CCD 36 by the zone plate 35 (structure in which the zone plate pattern is formed of Au on the SiN membrane), and the image is captured by the X-ray CCD 36. After the numerical processing, the image is compared with data designed as a mask pattern, and a mask inspection is performed. The resolution is 50 μm in the area where a pattern having a size of 0.2 μm can be recognized.
Since the angle is about m square, the mask stage 38 is moved to inspect the entire area of the mask.

This inspection method is much more advantageous than the above-described probe inspection method in that visible light and an electron beam can detect a defect of a multilayer film as a reflecting portion in principle. As a result, the detection sensitivity and accuracy of the X-ray reduction exposure mask for defects and foreign substances are greatly improved.

However, regarding the optical system of the mask inspection apparatus,
Since the NA or σ value on the mask side is not variable, the NA of the X-ray reduction exposure
When the σ value is changed, the contrast of the pattern obtained on the CCD of the inspection device and the detection sensitivity and accuracy of defects / contaminants are changed by the contrast of the light intensity and the defects / defects actually obtained on the wafer by the exposure using the X-ray reduction exposure. The detection sensitivity / accuracy of foreign matter may be different.

As described above, the conventional mask inspection apparatus does not disclose a sufficient inspection method for a mask for X-ray reduction exposure.

[0016]

According to the present invention, there is provided a mask inspection apparatus for X-ray reduction exposure, wherein the mask is illuminated with a probe having the same wavelength and the same NA and σ value as those used in X-ray reduction exposure. The above problem was solved by forming an image of the scattered light from the light source.

[0017]

(Embodiment 1) FIG. 1 shows a first embodiment of the present invention.
The following shows an example. A laser plasma X-ray source 10 is used as a source of a probe of a mask inspection apparatus. After the soft X-rays 11 generated from the light source are condensed by the oblique incidence mirror 12, soft X-rays having a wavelength of 13 nm are extracted using the diffraction grating 13 and illuminated on the X-ray reduction exposure mask 14 to be inspected. This wavelength is the soft X-ray used for pattern transfer in the X-ray reduction exposure apparatus.
It is almost the same as the wavelength of the line. The light scattered by the mask is enlarged and imaged on the X-ray CCD 16 by the transmission type zone plate 15 (structure in which the zone plate pattern is formed of Au on the SiN membrane), and the image is sensitive to the exposure wavelength. Captured by CCD 16 with Then, the image data is subjected to software calculation or numerical processing by a dedicated electronic circuit or the like, and is converted into image data corresponding to an image obtained on a wafer of the X-ray reduction exposure apparatus.

Here, the magnification of the X-ray reduction exposure apparatus is 1 /
5. The NA of the exposure apparatus when transferring the 0.08 μm L & S pattern onto the wafer is 0.1 (the NA on the mask side is 0.0
Since the σ value is 0.5 in 2), the apertures 18a and 18b installed before and after the mask are adjusted in the mask inspection apparatus of the present embodiment, and the NA · σ value of the illumination light of the mask is adjusted in the mask inspection apparatus. Are 0.02 and 0.5, respectively.

In the inspection apparatus having the above configuration, 0.08
μm L & S pattern transfer mask (0.4 μm L & S
S pattern was formed), and the mask was inspected. At the time of mask inspection, the mask stage 17 is
It is possible to move in the Y direction and read the image of the mask pattern of the entire area requiring inspection by the CCD 16. In a conventional X-ray reduction exposure mask inspection apparatus, the NA and σ value of the mask illumination light are fixed at 0.024 and 0.5, respectively (corresponding to １ ／ of the pattern dimension on the mask). ), The detection sensitivity for foreign matter and defects of 0.1 μm is 50
%, But 0.0% using the mask inspection apparatus of this embodiment.
N of illumination light optimized for 8 μm pattern transfer mask
Since the A · σ value can be set, the mask defect detection sensitivity has been improved to 95%.

(Embodiment 2) Next, a second embodiment of the present invention will be described. The configuration of the inspection device is the same as that of the first embodiment,
The pattern of the mask to be inspected is 0.3 μm (0.3 μm on the wafer).
And the NA of the X-ray reduction exposure apparatus used for transfer is 0.08 (the NA on the mask side is 0.01).
Since the σ value is 0.5 in 6), the inspection apparatus of this embodiment adjusts the aperture 18 to change the NA on the mask side from 0.024 to 0.016, and changes the σ value to 0.5. And

As in the first embodiment, a mask (0.3 μm
(L & S pattern is formed), the detection sensitivity of the conventional X-ray reduction exposure mask inspection apparatus for foreign matter and defects of 0.075 μm (corresponding to の of the pattern size on the mask) is 30. %, But the detection sensitivity of the inspection apparatus of this example was improved to 85%. Further, since the image contrast obtained by the CCD is also doubled, the time for numerical processing such as image processing is shortened, and the inspection time of the mask is reduced to 70% of the conventional method.

(Embodiment 3) Next, as a third embodiment of the present invention, an example in which a semiconductor device is manufactured will be described. N-substrate 2
0 was formed by a usual method to form a P well layer 21, a P layer 22, a field oxide film 23, a poly-Si / SiO ₂ gate 24, a P high concentration diffusion layer 25, an N high concentration diffusion layer 26 (FIG. 2 ( a)). Next, an insulating film 27 such as BPSG was formed by a normal method (FIG. 2B). Resist 30 on top
After the application, was inspected using the method described in the first embodiment of the present invention, and a hole pattern was formed using a mask modified by an FIB apparatus (FIG. 2C). Next, using this resist as a mask, the insulating film 27 was dry-etched to form a contact hole. Then, after forming the W / Ti electrode wiring 28 by a normal method, an interlayer insulating film 29 was formed by CVD (FIG. 2D).

The subsequent steps were formed in the same manner as usual. Although only the main manufacturing steps have been described in this embodiment,
The same process as the conventional process was used except that the mask used in the lithography process for forming the contact hole was inspected using the first embodiment of the present invention. Since the detection sensitivity of the mask defect is improved as compared with the conventional method, the CMOS-L
The SI could be manufactured with a high yield.

In the above embodiment, the zone plate is used as the image forming optical system of the inspection apparatus. However, even if the image forming optical system is a combination of one or a plurality of total reflection mirrors, a Schwarz mirror using a multilayer mirror is used. Even if it is a silt optical system, if it has an imaging function at a wavelength almost the same as the exposure wavelength,
It goes without saying that the present invention is applicable. Also,
Although aperture mechanisms for controlling NA and σ values are arranged one by one before and after the mask, the configuration of the present invention is not limited to the location and number of such apertures. It is needless to say that the present invention is not limited to a mask inspection apparatus for X-ray reduction exposure at an exposure wavelength of 13 nm, but can be applied to an exposure apparatus having an arbitrary wavelength in the X-ray region, vacuum ultraviolet, or extreme vacuum ultraviolet region.

[0025]

As described in detail above, the mask inspection apparatus for X-ray reduction exposure has the same NA,
By illuminating and forming an image on the mask at the σ value and the wavelength, the detection sensitivity of detectable defects is improved, and the inspection time can be shortened. In addition, by using the mask, which has been inspected for defects by the inspection apparatus of the present invention and corrected, for transferring a fine pattern, the yield at the time of manufacturing the device has been improved.

[Brief description of the drawings]

FIG. 1 is a block diagram of an X-ray reduction exposure mask inspection apparatus according to a first embodiment of the present invention.

FIG. 2 is a sectional view showing a device manufacturing process using a third embodiment of the present invention.

FIG. 3 is a block diagram of a conventional X-ray reduction exposure mask inspection apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Laser plasma X-ray source, 11 ... Spheroid mirror, 12 ... Filter, 13 ... Soft X-ray, 14 ... Reflection mask, 15 ... Zone plate, 16 ... X-ray CCD, 1
7: Mask stage, 18: Stop, 19: Optical path turning mirror, 20: N-substrate, 21: P-well layer, 22:
P layer, 23: field oxide film, 24: poly-Si
/ SiO ₂ gate, 25: P high concentration diffusion layer, 26: N high concentration diffusion layer, 27: insulating film, 28: W / Ti electrode wiring,
29: interlayer insulating film, 30: resist, 31: spheroid mirror, 32: filter, 33: soft X-ray, 34: reflective mask, 35: zone plate, 36: CC for X-ray
D, 37: laser plasma X-ray source, 38: mask stage.

Claims (10)

[Claims] In a mask inspection method for inspecting an X-ray reduction exposure mask, the same NA, NA as when performing X-ray reduction exposure is used.
A mask inspection method, wherein the mask is illuminated and imaged at a σ value and a wavelength. 2. A mask inspection apparatus for inspecting an X-ray reduction exposure mask, which has the same NA and NA as when performing X-ray reduction exposure.
A mask inspection apparatus, wherein the mask is illuminated and imaged at a σ value and a wavelength. 3. The mask inspection apparatus according to claim 2, wherein at least one of NA, σ value, and wavelength of illumination light of an optical system for illuminating and forming an image on the mask is variable. . 4. The mask inspection apparatus according to claim 2, wherein the imaging optical system includes a zone plate. 5. The mask inspection apparatus according to claim 2, wherein the imaging optical system includes at least one multilayer mirror or oblique incidence mirror. 6. A mask inspection apparatus according to claim 2, wherein the light source of the inspection probe light is a synchrotron radiation light, a laser plasma X-ray source, an X-ray laser, an electron beam excitation type X-ray source. A mask inspection apparatus, which is at least one of an excimer laser and a semiconductor laser. 7. An X-ray and a beam in a vacuum ultraviolet or extreme ultraviolet region are illuminated on a mask through an illumination optical system, and a fine pattern drawn on the mask is irradiated on a substrate through an imaging optical system. 7. A fine pattern transfer method, wherein a defect / foreign matter inspection of the mask is performed by the inspection method or the inspection apparatus according to claim 1. 8. An X-ray and a beam in a vacuum ultraviolet or extreme ultraviolet region are illuminated on a mask through an illumination optical system, and a fine pattern drawn on the mask is irradiated on a substrate through an imaging optical system. An inspection apparatus according to any one of claims 1 to 6, wherein the mask is inspected in an exposure apparatus that reduces and transfers the mask.
Alternatively, an exposure apparatus comprising the mask performed by an inspection apparatus. 9. An X-ray and a beam in a vacuum ultraviolet or extreme ultraviolet region are illuminated on a mask via an illumination optical system, and a fine pattern drawn on the mask is irradiated on a substrate via an imaging optical system. Means for monitoring the light intensity distribution obtained by the wafer at the time of pattern transfer, by replacing the position of a detector having sensitivity to light of an exposure wavelength with the position of the wafer or a member holding the wafer. An exposure apparatus comprising: 10. An electronic device manufactured using at least one of a fine pattern transfer method and an exposure apparatus according to claim 7.