JPH03112125A - Aligner - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to semiconductor manufacturing equipment.

[Conventional technology]

In recent exposure equipment for manufacturing semiconductor devices such as ICs and LSIs, as semiconductor devices become more highly integrated, it is possible to perform higher-resolution printing, for example, using X-rays with a wavelength of 1 to 150. Exposure apparatuses that utilize .

Since such an X-ray exposure apparatus performs proximity exposure, a high level of flatness and parallelism between the mask and the wafer has been required.

Furthermore, in order to perform high-resolution printing, X-ray exposure apparatuses require highly accurate positioning, and alignment means such as US Pat. No. 4,326,005 using a zone plate using light (including visible light and infrared light) have been proposed. However, no matter how precisely the mask and wafer are positioned with respect to the alignment means by this alignment means, it is meaningless unless the alignment optical system and the exposure optical system used for transfer are configured stably with a predetermined precision. do not have. Therefore, in order to align the optical axes of the alignment optical system and the exposure optical system, a method has been proposed that uses a reference plane fixed to the apparatus, and the applicant proposed a method of using a mask stage as the reference plane. Proposed.

[Problem that the invention is trying to solve]

However, even if the exposure light and alignment light are adjusted with high precision by aligning the optical axes of the exposure optical system and the alignment optical system with the mask stage as a reference, conventional mask processing accuracy does not allow the mask support to have a mask pattern or alignment mark. The film and mask stage are well oriented.
Because the alignment was not done properly, it was not possible to obtain sufficient alignment accuracy.

[Means to solve the problem]

In view of the above problems, the present invention is an apparatus that transfers and exposes a pattern on a mask held on a mask stage onto a wafer held on a wafer stage using X-rays as exposure light. and an exposure apparatus comprising an alignment optical system for aligning the wafer, and aligning the optical axis of the alignment optical system and the optical axis of the exposure light with reference to the holding surface of the mask stage. The mask holding surface of the mask stage, the suction surface of the mask to the mask stage holding surface, and the back surface of the suction surface each have a flatness of 1.0 μm or less, and each surface has a flatness of 1.0 μm or less. Accuracy is 0.1 ltm (=
Ra) or less, or the holding surface has a surface accuracy of 0.1 μm (=Ra)
This is an apparatus that transfers and exposes a pattern on a mask held on a mask stage, which is processed as follows, onto a wafer held on a wafer stage using X-rays as exposure light. an exposure apparatus that includes an alignment optical system for aligning the wafer, and aligns an optical axis of the alignment optical system and an optical axis of the exposure light with reference to a holding surface of the mask stage; In the X-ray mask used in
In addition, the above problem is solved by processing each surface with a precision of 0.1 am (=Ra) or less.

〔Example〕

Embodiments of the box 1 of the present invention will be described below using the drawings.

FIG. 1 is a sectional view of an X-ray mask structure and a mask stage in the present invention.

First, in FIG. 1, 1 is an X-ray absorber, and in this example, A
Although n is used, Ta, W, etc. may also be used. 2 is a support film supporting the absorber 1, which is made of polyimide (Kapton film), but 5iNSS is an inorganic film.
iCSBN, AIN, or a composite film of an organic film and an inorganic film may be used. 3 is a holding frame that holds the support membrane 2, and is made of machined full ceramics. Low expansion glass or the like may also be used. Reference numeral 14 denotes an X-ray mask, which is composed of an absorber 11, a support film 2, and a holding frame 3. Reference numeral 4 denotes a mask support film that holds the mask by suction when printing the pattern on the mask onto the resist on the wafer in an X-ray exposure device.

302 is a surface of the holding frame 3 that is in contact with the mask stage, and 301 is a surface that is located substantially parallel to 302 and supports the support film 2.

401 is a reference surface in contact with the holding frame 3 on the mask stage 4.

FIG. 2 is a simplified diagram of the X-ray exposure apparatus in the present invention,
10 is an exposure chamber. 21 is a part of X-rays used for exposure such as synchrotron radiation, and has a divergence angle θ with respect to the optical axis. 11 is the Be window port, 2
0 is an exhaust boat, and the exposure chamber 10 is blocked from the X-ray light source side by Be, and exposure can be performed in any state such as an atmospheric vacuum He atmosphere inside the chamber. 12 is a mask stage, 13 is an alignment detection section, 14 is a mask, 1
Reference numeral 5 indicates a wafer 16, a wafer chuck, 17 a wafer stage, 18 an X stage drive motor, and 19 a Y guide.

When the mask 14 is attracted to the mask stage 12, it is mechanically set in a windowed direction to some extent using positioning pins or orientation flats. The wafer 15 is similarly set on the wafer chuck 16.

Thereafter, the X-ray drive motor 18 and Y guide 19 are moved to determine the relative positional relationship between the mask 14 and the wafer 15 based on instructions from the alignment detection section 13, and the wafer 15 is exposed to X-rays.

FIG. 3 is a diagram illustrating an embodiment of the present invention in detail.

14- is an X-ray mask, the support film 2 of which has a flatness of Δ. Align the support film 2 of the mask 14'' at the 3 position, and align the pattern on the wafer 15 with the pattern b at the position a and the flatness △. When printing a pattern at the same position, let σ be the amount of positional deviation on the wafer from when the mask is attached.

Note that a2 indicates the position of al on the mask when the flatness is 0.

Here, if the optical axes of the alignment light and the X-ray 21 are adjusted accurately, the maximum angle between the alignment light passing through the position b and the X-ray 21 passing through the position al is the divergence angle of the X-ray 21. This corresponds to θ. Therefore, the maximum value of the positional deviation amount σ is determined by ΔXθ.

In Figure 1, each surface accuracy of 301, 302, and 401 is 1
When the flatness is .mu.m, the flatness .DELTA. of the support film 2 has a maximum value of 3 .mu.m with respect to the plane that is the reference for the optical axis of X-rays and alignment light, although it depends on the hardness of the holding frame 3.

On the other hand, in exposure equipment using synchrotron radiation, SO
The irradiation surface of the X-rays emitted from R is expanded on the wafer using an oblique incidence mirror, but the divergence angle depends on the exposure area of the mask and the length of the boat. Exposure area is 30mm,
If the length of the boat is 5 m or less, the divergence angle will be 3 mrad or more.The length of the boat is limited to 5 m because it determines the exclusive area of each exposure device.

Therefore, the maximum value of the positional deviation amount σ is 0.009 μm.

In addition, there are many factors contributing to the amount of positional deviation, such as errors in alignment light and X-ray adjustment due to the flatness of the wafer, but it depends on the flatness of the mask support film due to the allocation of tolerance to each error factor. Positional deviation amount σ is 0.01μm
Only less than this is acceptable.

Therefore, at a divergence angle of 3 m r a d, the flatness of the mask support film with respect to the plane that is the reference of the optical axis is limited to 3 μm. Therefore, the flatness of the reference surface of the mask stage and both surfaces of the mask holding frame, which determine the flatness △ of the support film 2, is 1μ.
It must be less than m.

In addition, to obtain a flatness of 1 μm, the surface roughness of each surface is Ra001 μm.
m processing is required. Note that the allowable ranges of flatness and surface roughness vary depending on the allowable range of error that is included in the amount of positional deviation σ. In other words, any relationship that satisfies the following equation is sufficient.

The flatness between each surface may be set so that the sum of the flatness on each surface is equal to or less than Δ. The aspect here is
These are the holding surface of the mask stage, the suction surface of the mask, and its back surface.

Further, as shown in FIG. 4, this is often used when the support film 2 is made of an inorganic material, but the same applies when the holding frame 3 is made of a back-etched silicon wafer combined with a reinforcing body.

〔Effect of the invention〕

As described above, by making the flatness between both sides of the mass holding frame and the reference plane of the mask stage 1 μm or less, and by making the processing accuracy of each surface 0.1 μm (=Ra) or less, The flatness of the support film 2 of the mask is 3 μm with respect to the plane that serves as the reference for the optical axis of alignment light and X-rays.
The amount of positional deviation when printing with sink convex tron radiation with a divergence angle of 3 m r a d is 0.01 μ.
It can be less than m. This enables highly accurate transfer exposure.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an X-ray mask and a mask stage in the present invention. FIG. 2 is a simplified diagram of an X-ray exposure apparatus using an X-ray mask and a mask stage according to the present invention, and FIG. 3 is an enlarged view of a portion thereof. FIG. 4 is a sectional view of the X-ray mask and mask stage in the present invention. l...Absorber, 2...Support membrane 3・
・・Holding frame 4 ・・Mask stage 14
・・・ X-ray mask 5-dimensional diagram

Claims (2)

[Claims] (1) It is an apparatus that transfers and exposes a pattern on a mask held on a mask stage onto a wafer held on a wafer stage using X-rays as exposure light, and at the time of the transfer exposure, the pattern on the mask and the wafer are transferred. The exposure apparatus includes an alignment optical system for aligning the alignment optical system, and aligns the optical axis of the alignment optical system and the optical axis of the exposure light with reference to the holding surface of the mask stage. The mask holding surface of the mask stage, the suction surface of the mask to the mask stage holding surface, and the back surface of the suction surface each have a flatness of 1.0 μm or less, and each surface accuracy is 0. An exposure device characterized by being processed to a thickness of .1 μm (=Ra) or less. (2) Transfer exposure of a pattern on a mask held on a mask stage whose holding surface is processed to a surface precision of 0.1 μm (=Ra) or less onto a wafer held on a wafer stage using X-rays as exposure light and an alignment optical system for aligning the mask and the wafer during the transfer exposure, the optical axis of the alignment optical system and the optical axis of the exposure light, In an X-ray mask used in an exposure apparatus that performs optical axis alignment using the holding surface of the mask stage as a reference, the suction surface of the mask to the mask stage holding surface and the back surface of the suction surface have a mutual flatness of 1.0 μm. An X-ray mask characterized by having the following relationship and each surface precision being processed to be 0.1 μm (=Ra) or less.