JPS62293634A - Mask alignment - Google Patents

Abstract

PURPOSE:To enable an azimuth of a single-crystal mask substrate to be exactly and easily detected, by using a Bragg's reflection phenomenon of X-rays on the mask substrate. CONSTITUTION:X-rays of only desirable wavelengths from a X-ray generating device 1 are made to pass through a monochrome meter 2. The Xrays of desirable wavelength obtained from the meter 2 are reflected on a single-crystal mask substrate 3. A detector d detects the X-rays reflected on the substrate 3. Because a reflection factor of X-rays on the single crystal is extremely sensitive to the angular change of the substrate, even a small crystal shift of 0.1 second or so can be detected. Hence, the azimuth of the substrate 3 can be exactly and easily detected.

Description

Detailed Description of the Invention 3. Detailed Description of the Invention A) Field of Industrial Application The present invention relates to phosphorography technology for manufacturing semiconductor devices, and is particularly directed to improving mask alignment technology.

(2) Conventional technology In the semiconductor field, a problem in microfabrication on the order of um is mask alignment. Conventionally, the "High Precision Alignment Method for rX-ray Lithography" was published in 1986 (Showa 6).
1st year) Align the laser beam with appropriate marks on the mask, zone plates, and diffraction gratings, as described in the 33rd Spring Applied Physics Association Lecture Preliminary Lecture Collection p. 326. is being carried out, but 0.01. It is not easy to perform positioning with a precision as high as um.

C) Problems to be solved by the invention In order to perform submicron microfabrication, it is necessary to transfer several types of patterns in layers, and the 0 position requires a high mask alignment accuracy of about 0.01 μm. There are a total of three degrees of freedom: rotation, or orientation, of the inner surface of the mask, and translation in two directions parallel to the surface, and all three need to be precisely controlled, but in order to put X-ray lithography into practical use, Therefore, the emergence of positioning technology with higher precision than the current one is awaited.

2) Means for solving the problem The present invention focuses on the fact that a high-quality single crystal can be used as a mask substrate, and considers the orientation and translational degrees of freedom separately among the problems to be avoided. We are proposing a method to accurately determine only the direction of the mask using this phenomenon.

(e) Operation By using the Bragg reflection phenomenon of X-rays by the single crystal mask substrate, the orientation of the mask can be detected accurately and easily.

f) Example Figure 2 shows an example of an X-ray Bragg reflection curve (rocking curve) due to a perfect crystal surface with absorption. The horizontal axis is the angle and the vertical axis is the reflectance. The angular width at which total reflection occurs varies depending on the crystal plane used, but is usually several seconds. Using a silicon single crystal as a mask substrate, as shown in Fig. 3,
The side surface is cut so that a specific crystal plane (for example, 110 plane) is exposed. Since Bragg reflection by a crystal lattice is used, the smoothness of the surface and slight deviation from the 110 plane are not a problem, but the surface must be chemically polished to prevent lattice distortion.

The configuration of an apparatus for implementing the present invention is shown in the first IsA. In the figure, (1) is an X-ray generator, (2) is a monochromator that allows only X-rays of a desired wavelength to pass through, and (3) is a monochromator that allows only X-rays of a desired wavelength to pass through.
is the substrate crystal of the mask, and (4) is the X-ray detector. Cut plane and incident X made in advance on the side of the mask substrate
The relative position of i is arranged so that Bragg reflection occurs, and the intensity of the reflected X-ray is detected in (4). The reflectance of X-rays by a single crystal is 0 because it responds very sensitively to the angle change in (3).
．． It is possible to detect a crystal shift of about 1 second.

Accurate orientation adjustment is possible by feeding back the output of the detector to the orientation adjustment mechanism of the mask aligner.

Next, specific examples of the present invention will be described by citing numerical values. X
Enclosed type X using a copper target as a line generator, for example
Place the Il tube (microfocus is better) as shown in Figure 1. The wavelength of the Cu-Ka line is λ■1.5405, and the monochromator is silicon single crystal (lattice constant 5, 4301).
A three-crystal asymmetric arrangement is used. 100 as a mask substrate
Let us take the case of using a silicon wafer as an example. Since there is a 110 lattice plane perpendicular to the substrate surface, 220 reflection of that plane is used. The Bragg angle is θa = 23, 65 degrees. The angular spread of monochromatic X-rays is set to about 0.11 seconds. The intensity of the reflected xm is detected with a scintillation counter. By measuring the reflectance curve, the orientation of the crystal is controlled with an accuracy on the order of 0.1 seconds. If one end of a 10ffi square mask is aligned, a 1 second azimuth disturbance will cause a positional shift of about 0.5 μm at the other end, so in the case of a mask with a line width of μm, the azimuth will be on the order of 0.1 seconds. It is sufficient if the detection accuracy is as follows. If the mask size is smaller than this, the orientation detection accuracy may be even lower.

g) Effects of the Invention As is clear from the above description, the present invention uses a single crystal as the mask substrate and detects the intensity of X-rays reflected from the crystal lattice plane, so the orientation of the mask can be detected extremely accurately and the position Can be used together. If used in current aligners and steppers, the problem of adjusting the orientation of aligners for microfabrication of 0.01 A1m or less can be solved. If the orientation is determined accurately using this method, the mark used for translational alignment is 1
This eliminates the trouble of using multiple marks (for example, at the four corners) and processing signals from them as in conventional aligners.

It is clear that the method of the present invention can be applied both to the formation of a mask pattern on a mask substrate and to the X-ray exposure using a mask.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing the configuration of an apparatus for implementing the present invention, Fig. 2 is a reflectance curve of X-rays from a single crystal surface, and Fig. 3 is a mask substrate and a lattice surface that reflects X-rays. FIG. (1)...X-ray generator, (2)...monochromator, (3)...mask substrate, (4)...X-ray detector.

Claims (1)

[Claims] (1) An X-ray generator, a monochromator that allows only X-rays of a desired wavelength to pass through, a single-crystal mask substrate that reflects X-rays of a desired wavelength obtained from the monochromator, and a single-crystal mask substrate that reflects X-rays from this mask substrate. A method for aligning a mask, comprising: a detector for detecting the X-ray intensity, and accurately controlling the orientation of the mask by detecting the X-ray intensity.