JP2001267235A - Exposure system and method of aligning photomask in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a pattern very accurately and easily on a wafer along its crystal orientation. SOLUTION: An exposure system is equipped with a stage 11 set in a rotatable manner, an X-ray source 13 which irradiates a wafer 12 mounted on the stage 11 with an X-ray, and an X-ray detector 14 which detects the intensity of the diffracted ray of the X-ray beam. For instance, when a first pattern is formed on a wafer 12 where no target is provided, the crystal orientation of the wafer 12 is detected with the X-ray source 13 and X-ray detector 14 through an X-ray diffraction method, the wafer 12 can be positioned resting on the crystal orientation, so that a deviation (angular deviation) of the crystal orientation from a pattern can be reduced to an irreducible minimum. Moreover, as the intensity of a diffracted ray is detected, the detecting operation can be easily carried out or easily automated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus suitable for use in forming a pattern when an optical waveguide or the like is formed on a semiconductor crystal wafer, for example, and a method of aligning a photomask in the exposure apparatus.

[0002]

2. Description of the Related Art When an optical waveguide is formed using a semiconductor crystal wafer or an optical waveguide is formed using the semiconductor crystal, a pattern is formed along the crystal orientation (direction of atomic arrangement) of the wafer. By doing so, it is possible to suppress the waveguide loss that occurs when light passes through the waveguide. When exposing a semiconductor crystal wafer with a conventional exposure apparatus, a cutout portion (referred to as an orientation flat; hereinafter, abbreviated as an orientation flat) which indicates a specific crystal orientation provided on the wafer in advance is air-probe or the like. Detect and position the wafer, determine the position to transfer the pattern using a specific target (target) provided on the wafer and a specific pattern on the photomask,
Exposure is performed.

However, when no target is provided on the wafer, for example, when a first pattern is formed, the above method cannot be used, and only the alignment using the orientation flat is performed. In this case, the deviation between the pattern and the crystal orientation in the formation of the optical waveguide pattern depends on the orientation accuracy of the orientation flat and the detection accuracy of the orientation flat. For example, the orientation accuracy of the orientation flat is ± 0.2 degrees with respect to a specific crystal orientation, and the orientation accuracy of the orientation flat is ±
Assuming that the angle is about 0.2 degrees, the angle deviation of the pattern with respect to a specific crystal orientation occurs at a maximum of about 0.4 degrees.

[0004] As a result of calculation of a waveguide loss in an InGaAsP waveguide provided on an InP (indium phosphide) wafer,
When guided by 100 μm, the angle deviation between the crystal orientation and the waveguide pattern is 0.3 dB at 0.1 degree, 1.1 dB at 0.2 degree,
At 0.5 degrees, a result of 6.0 dB is obtained. From this result, if it is attempted to suppress the waveguide loss to, for example, 1 dB or less,
The angle shift must be kept within 0.2 degrees. However, at present, such high accuracy cannot be satisfied from the viewpoint of the production accuracy and the detection accuracy of the orientation flat. Therefore, for example, it is necessary to inspect each wafer one by one and the production accuracy of the orientation flat is excellent. In other words, those having a small orientation deviation of the orientation flat with respect to the crystal orientation are selectively used.

[0005]

As described above, conventionally, for example, in forming a pattern of an optical waveguide or the like on a semiconductor crystal wafer, when forming a first pattern on a wafer on which no target is provided. In order to obtain an optical waveguide with small waveguide loss by suppressing the angle shift between the pattern and the crystal orientation, it is necessary to select a wafer and use only the one with a small angle deviation of the orientation flat with respect to the crystal orientation. As a result, such wafer sorting is inefficient and unsuitable for mass production.

On the other hand, in order to be able to form a pattern along the crystal orientation of a wafer without depending on the production accuracy and detection accuracy of such an orientation flat, the crystal orientation of the wafer is measured and detected. Can be considered. As a method for determining the crystal orientation of a wafer, for example, Japanese Patent Laid-Open No.
Japanese Patent No. 36214 describes that the crystal orientation of a wafer is determined using X-rays. However, since the method described in Japanese Patent Application Laid-Open No. 3-236214 determines the crystal orientation using a Laue image, it is necessary to decode the pattern to determine the crystal orientation. It is not a simple method, and for example, when automation of positioning is considered, the configuration becomes considerably complicated, and in that respect it is not suitable for automation.

An object of the present invention is to provide an exposure apparatus capable of easily and highly accurately forming a pattern along a crystal orientation of a semiconductor crystal wafer in view of the above-mentioned problems, and further provide the exposure apparatus. The object of the present invention is to provide a simple and highly accurate alignment method of a photomask in the above.

[0008]

According to the first aspect of the present invention, there is provided an exposure apparatus comprising: a rotatable stage; an X-ray source for irradiating a wafer mounted on the stage with X-rays; And an X-ray detector for detecting the intensity of the diffracted light. According to the second aspect of the present invention, the rotatable stage and the wafer mounted on the stage have X
The alignment of a photomask in an exposure apparatus including an X-ray source for irradiating a beam and an X-ray detector for detecting the intensity of diffracted light of the X-ray is performed by rotating the stage on a semiconductor crystal wafer mounted on the stage. X-rays are irradiated using the X-ray source and the X-ray detector while detecting the intensity of the diffracted light to detect the crystal orientation of the semiconductor crystal wafer, and the X-ray path is formed by the crystal orientation. Position the semiconductor crystal wafer so that the plane is parallel, insert a photomask with a pair of slits on the axis to be aligned with the crystal orientation into the X-ray optical path, pass through one of the slits This is performed by adjusting the position of the photomask so that the intensity of the diffracted light of the X-ray radiated on the semiconductor crystal wafer and passing through the other and incident on the X-ray detector is maximized.

[0009]

Embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a schematic configuration of an exposure apparatus according to the present invention. In this example, an X-ray source 13 for irradiating a wafer 12 mounted on a stage 11 with X-rays and an X-ray detector 14 for detecting the intensity of diffracted light of the X-rays are provided. Above the stage 11, a light source used for exposure, an optical system such as a lens and a mirror, and a position adjustment mechanism for a photomask are arranged, and an automatic wafer transfer mechanism and the like are arranged laterally (horizontally) of the stage 11. However, these illustrations are omitted in this example. In addition,
In the figure, reference numeral 15 denotes a photomask, and 16 denotes an X-ray optical path.

The stage 11 can vacuum chuck the wafer 12, is rotatable, and is movable in the XYZ three-axis directions. In this example, the wafer 12 is a semiconductor crystal wafer, which is taken out of the cassette one by one by a transfer mechanism and transferred onto the stage 11, and transferred from the stage 11 to the cassette when exposure is completed. For example, an X-ray tube is used for the X-ray source 13.
For the X-ray detector 14, for example, a scintillation counter is used. These X-ray source 13 and X-ray detector 14
Is fixed so that the optical path of the incident light of the X-ray (for example, CuKα ray) to the wafer 12 and the diffracted light of the X-ray from the wafer 12 to be detected have a predetermined angle with respect to the surface of the wafer 12. Note that this angle is uniquely determined by the material of the semiconductor crystal wafer to be used and the crystal plane to be detected.

As described above, in this exposure apparatus, the X-ray source 13
And the X-ray detector 14, the stage 11
Is rotated so that the wafer 1 can be
The second specific crystal orientation can be detected, and the wafer 12 can be positioned with high accuracy based on the detected crystal orientation. Next, the details of a method for aligning a photomask in this exposure apparatus will be described. Note that the following method is applied when no target is present on the wafer 12 as in the case where the first pattern is formed on the wafer 12. Is provided, a specific pattern on the photomask and its target are aligned to perform exposure and pattern formation as before.

First, the crystal orientation of the wafer 12 is detected using the X-ray source 13 and the X-ray detector 14. This detection is carried out by mounting the wafer 12 on the stage 11 and rotating the stage 11 as shown in FIG.
Is displaced in the Z direction, the intensity of the diffracted light is detected by the X-ray detector 14, and the crystal orientation is detected by determining the position (angle) at which the intensity of the diffracted light becomes maximum. In FIG. 2, 17 indicates X-ray incident light, and 18 indicates diffracted light.

The wafer 12 is positioned based on the detected crystal orientation. Positioning is performed by aligning the wafer 12 such that the plane formed by the X-ray optical path and the crystal orientation are parallel. Next, the photomask 15 is aligned. This alignment is performed by detecting the crystal orientation of the wafer 12 and then inserting a photomask 15 into the X-ray optical path as shown in FIG.

As shown in FIG. 4, for example, an axis 19 to be matched with the crystal orientation of the wafer 12 is provided on the photomask 15.
A pair of slits 21 are provided along. FIG.
Reference numeral 22 denotes a region where a pattern for exposure is formed. The X-ray incident light 17 passes through one slit 21 and irradiates the wafer 12, and the diffracted light 18 passes through the other slit 21 and enters the X-ray detector 14. The position of the photomask 15 is adjusted so that the intensity of the diffracted light of the transmitted X-ray becomes maximum.

By this adjustment, the crystal orientation of the wafer 12 and
The pattern to be matched with the crystal orientation matches, that is, a pattern strictly aligned with the crystal orientation can be formed. At the time of exposure, if necessary, for example, the wafer 12
Is moved in the X, Y, and Z directions to expose. As described above, according to the above-described photomask alignment method, the position of the wafer 12 and the position of the photomask 15 can be strictly determined in the θ direction with respect to the optical path of the X-ray. A pattern can be accurately provided on the upper surface along the crystal orientation.

[0016]

As described above, according to the exposure apparatus of the present invention, since the crystal orientation of the wafer can be detected, the wafer can be positioned based on the detected crystal orientation. The angle deviation between the crystal orientation and the pattern does not depend on the orientation flat fabrication accuracy at all, and the angle deviation can be made very small, so that the wafer sorting that has been performed conventionally is not required, and the crystal orientation is not required. Can be easily and accurately realized.

Further, according to the photomask positioning method of the present invention, the position (angle) of the wafer and the position (angle) of the photomask can be determined strictly with respect to the optical path of the X-ray. Even when forming a pattern on a wafer that is not provided, it is possible to minimize the angle deviation between the crystal orientation of the wafer and the pattern, and thus, for example, when forming an optical waveguide on a semiconductor crystal wafer, the waveguide loss is small. In addition, it is possible to produce a simple optical waveguide, and in processing (such as etching and crystal growth) that depends on the crystal orientation, it is possible to suppress a variation in processing accuracy to an unprecedented level.

Since the detection of the crystal orientation of the wafer and the alignment of the photomask are performed by detecting the intensity of the diffracted light of the X-ray, it is suitable for automation and can be easily automated.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining an embodiment of an exposure apparatus according to the present invention.

FIG. 2 is a view for explaining a method for detecting a crystal orientation of a wafer.

FIG. 3 is a diagram for explaining a method of aligning a photomask.

FIG. 4 is a plan view showing a schematic configuration of a photomask in FIG. 3;

Claims (2)

[Claims] 1. An apparatus comprising: a rotatable stage; an X-ray source for irradiating a wafer mounted on the stage with X-rays; and an X-ray detector for detecting the intensity of diffracted light of the X-rays. Exposure apparatus characterized by the above-mentioned. 2. An exposure apparatus comprising: a rotatable stage; an X-ray source for irradiating a wafer mounted on the stage with X-rays; and an X-ray detector for detecting the intensity of diffracted light of the X-rays. A method of aligning a photomask in an apparatus, comprising irradiating a semiconductor crystal wafer mounted on the stage with X-rays using the X-ray source and the X-ray detector while rotating the stage, and diffracting the semiconductor crystal wafer. By detecting the light intensity, the crystal orientation of the semiconductor crystal wafer is detected, and the semiconductor crystal wafer is positioned so that the crystal orientation and the plane formed by the X-ray optical path are parallel to each other. A photomask having a pair of slits on an axis to be inserted is inserted into the X-ray optical path, the semiconductor crystal wafer is irradiated through one of the slits, and the X-ray is transmitted through the other. The position of the photomask is adjusted with respect to the crystal orientation of the semiconductor crystal wafer by adjusting the position of the photomask so that the intensity of the diffracted light of the X-ray incident on the detector is maximized. Photomask alignment method.