JPH0421333B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an X-ray exposure alignment method, and particularly to a method for aligning an X-ray mask and a semiconductor substrate.

[Conventional technology]

Conventionally, in X-ray exposure, a method using a Fresnel zone plate has been known as a method for aligning an X-ray mask and a semiconductor substrate.
Science and Technology) Volume 19, No. 4, p.
1224 (1981), M.Feldman et al. This method involves forming circular Fresnel zone plate marks on the mask and wafer, and irradiating these marks with laser light to align the reflection spots from the mask and wafer.
This is a method of performing alignment between wafers.

[Problem that the invention seeks to solve]

In the conventional X-ray exposure alignment method described above,
A concentric pattern of Fresnel zone plate marks must be formed on the X-ray mask and semiconductor substrate. For the production of X-ray masks, electron beam direct writing or focused ion beams are used due to high precision requirements. However, in direct writing with an electron beam or writing using a focused ion beam, the beam can only be scanned in two orthogonal directions, X and Y. Therefore, in order to draw a circular pattern, the circle must be drawn as an approximate pattern by a collection of small rectangles. Approximating a circle to a set of small rectangles has the drawback that the amount of data required for drawing becomes enormous, which not only complicates data handling but also requires an enormous amount of time to draw. Furthermore, since the Fresnel zone plate mark becomes an approximate pattern, there is a drawback that alignment accuracy between the mask and the wafer deteriorates.

An object of the present invention is to provide an X-ray exposure alignment method that can easily form alignment marks and has excellent alignment accuracy.

[Means for solving problems]

In the X-ray exposure alignment method of the present invention, a first single crystal with a diameter of several mm or less formed in an X-ray mask is irradiated with a single wavelength that is thin and narrowed to a size that allows the first single crystal to completely bathe. irradiate parallel X-rays so that the first single crystal is completely bathed, detect the position of diffracted X-rays corresponding to a certain index (hkl) from the first single crystal using a scintillator, and further, A second single crystal with a diameter of several mm or less formed in a semiconductor substrate is irradiated with the X-rays, and the diffraction X corresponding to a specific index (h′k′l′) from the second single crystal is detected. It is constructed by detecting the position of the line using the scintillator, and adjusting the position and spacing between the X-ray mask and the semiconductor substrate.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a principle diagram for explaining one embodiment of the present invention.

As shown in FIG. 1, the X-ray mask includes a silicon nitride film 1, which is a film that transmits X-rays in the exposure wavelength region;
X that absorbs X-rays corresponding to the pattern to be exposed
It is composed of a gold pattern 2 which is a line absorber and a support part 3 for supporting these. X-ray masks are usually manufactured by processing a Si substrate. That is, after the silicon nitride film 1 and the gold pattern 2 are formed on the Si substrate, the Si substrate is etched away leaving the supporting portion 3. When removing this Si substrate by etching, the Si
A portion of the substrate is left by an appropriate method to form alignment marks 4. Alignment mark 4
The size is selected depending on the X-ray intensity used for alignment, but is usually about 100 to 1000 μm.
In addition, the alignment mark 4 is placed on the gold pattern 2 with respect to the silicon nitride film 1 so as not to become an obstacle during exposure.
Place it on the back side. It is desirable that one X-ray mask has alignment marks 4 at three or more locations. Si single crystal alignment marks 6 are formed on the semiconductor substrate 5 by etching. For alignment, first, the alignment mark 4 is irradiated with a single wavelength X-ray 9 that is collimated to a size that completely covers the alignment mark 4. When a single crystal is irradiated with X-rays of a single wavelength, reflection occurs in a direction that satisfies Bragg's condition. In this embodiment, since a semiconductor substrate is used, the crystal orientation of the alignment mark 4 is the same as that of the semiconductor substrate and is known, and the direction in which reflection occurs is already known by calculation. Therefore, a suitable reflection 11 is selected and measured using a scintillator 13. By measuring the reflections of the three alignment marks on the X-ray mask, the three-dimensional positions can be determined. Next, for the wafer as well, the alignment mark 6 is irradiated with X-rays 10, and the appropriate reflection 12 is measured using the scintillator 13. This is performed for three points on the wafer to determine three-dimensional positions. As described above, the positional relationship between the X-ray mask and the wafer is measured, and alignment is performed to obtain the optimum position and spacing.

Note that the alignment mark may be made of any material as long as it is a single crystal.Furthermore, in this embodiment, the alignment mark was formed on the back surface of the wafer, but the same effect can be obtained even if it is formed on the front surface. In addition, the film that transmits X-rays may be not only a silicon nitride film but also a boron nitride film, etc., while the X-ray absorber may be made of other materials (X
Needless to say, other heavy metals that have a radiation absorption effect are also good.

〔Effect of the invention〕

As explained above, according to the present invention, there is no need to handle complicated and enormous amounts of data and a huge amount of time when forming alignment marks, and there is no deterioration in alignment accuracy due to approximate alignment marks, and the process is simple. By forming accurate alignment marks, highly accurate alignment is achieved. Therefore, the workability of the manufacturing process is improved and high quality semiconductors can be provided at low cost.

[Brief explanation of drawings]

FIG. 1 is a principle diagram for explaining the X-ray exposure alignment method of the present invention. 1... X-ray transparent film (silicon nitride film), 2...
X-ray absorber (gold pattern), 3... Support part, 4...
...Mask side alignment mark, 5...Semiconductor substrate, 6...Semiconductor substrate side alignment mark, 7
...X-ray transparent film, 8...X-ray sensitive film, 9...X
Ray, 10... X-ray, 11... Diffraction X-ray, 12...
Diffraction X-ray, 13...Scintillator.

Claims (1)

[Claims] 1 The first layer with a diameter of several mm or less formed inside the X-ray mask
The single crystal is irradiated with parallel X-rays of a single wavelength narrowed to a size that allows the first single crystal to take a complete bath, so that the first single crystal is completely bathed. A scintillator detects the position of diffracted X-rays corresponding to a certain index (hkl) from the semiconductor substrate, and further irradiates the second single crystal with a diameter of several mm or less formed in the semiconductor substrate with the X-rays. detecting the position of diffracted X-rays corresponding to a specific index (h′k′l′) from the second single crystal using the scintillator, and aligning the X-ray mask and the semiconductor substrate;
An X-ray exposure alignment method characterized by adjusting intervals.