JPH09175835A - Surface-working method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a surface-working method capable of forming the surface of a working object to a desired uneven pattern by forming a surface of a mold to an uneven state by lithography and transferring the pattern as it is to the surface of the working object. SOLUTION: This surface-working method comprises a preparatory step to form a surface of a mold 4 consisting of a silicon wafer, etc., to an uneven pattern by lithography and a main step to contact a working object 2 heated to a deformable temperature with the uneven surface of the mold 4 interposing a bond-preventing layer 8 between the working object 2 and the mold 4 to prevent the bonding of the object and the mold. The uneven pattern on the surface of the mold 4 is transferred to the surface of the working object 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of processing the surface of a work material into a concavo-convex shape, and more specifically, by using a mold to transfer the surface shape formed on the mold to the work material. , A technique for processing the surface of a material to be processed into an uneven shape.

[0002]

2. Description of the Related Art Conventionally, a work material other than a semiconductor substrate such as a soda glass substrate has been used as a component of various micromachines and sensors by forming fine irregularities on the surface thereof. As a method of processing the surface of a material to be processed other than such a semiconductor substrate, for example, in the case of a glass substrate, there are a wet etching method and a sandblast method.
However, the wet etching method cannot be processed into a desired uneven shape because the side etching amount is large. Further, in the sandblasting method, needle-like protrusions remain on the blasted surface of the substrate, and thus the desired uneven shape cannot be obtained.

On the other hand, as described in JP-A-5-57867, reactive ion etching used in a semiconductor process can be applied to the surface processing of a glass substrate. However, since components other than SiO ₂ in the glass substrate hinder the etching, it is difficult to perform deep (1 μm or more) etching on an ordinary glass substrate. To perform etching efficiently, the composition of SiO ₂ is 80 wt.
% Or more of the glass substrates must be used, which limits the usable substrates. As described above, although there are various methods for processing the surface of the material to be processed other than the semiconductor substrate, in reality, it is difficult to process the surface of the material to be processed into a desired uneven shape.

[0004]

Therefore, in view of the above-mentioned conventional problems, the present invention transfers the surface shape of a mold, which has been processed into an uneven shape using lithography, to the surface of a work piece as it is. An object is to provide a surface processing method capable of processing the surface of a processed material into a desired uneven shape.

[0005]

Means for Solving the Problems In order to solve the above problems, the present inventors have completed the following invention. That is, according to the present invention, a preliminary step of processing the surface of the mold into an uneven shape using lithography and a bonding prevention layer for preventing bonding between the material to be processed and the mold, and heating to a deformable temperature is performed. A surface processing method, comprising: a main step of superposing a processed material and an uneven shape forming side of the mold. According to the present invention, the surface of the mold is processed into a desired uneven shape by using lithography. The deformably heated work piece can be along the contacting surface. When the deformable work material and the uneven surface of the mold are superposed, the surface of the work material is deformed following the uneven surface of the mold, while the bonding prevention layer interposed between the two. This prevents the work piece and the die from being joined. As a result, the uneven shape of the mold is transferred to the surface of the material to be processed, and the uneven shape complementary to the uneven shape is formed.

In the present invention, lithography means
Light, ultraviolet, electron beam, ion beam, laser beam,
A method of forming a concave-convex pattern on a processed surface of a mold including a step of irradiating a specific region on the processed surface of the mold with energy by X-rays or the like, or including this energy irradiation step and an etching step. Say.

In the present invention, it is particularly preferable that the mold is mainly composed of silicon (Si). For silicon as a semiconductor material, various energy irradiation methods and etching methods can be widely applied, and an appropriate method can be selected as necessary, and these steps can be performed accurately and in a desired shape. You can do it. Here, as the material mainly containing silicon, Si single crystal, polycrystalline Si,
Substrates or thin films made of amorphous Si, SiO ₂ , PSG, BSG, etc. can be mentioned.

In the present invention, a glass substrate is particularly preferable as the material to be processed. The glass substrate is difficult to be finely processed by direct etching or the like, and by processing the glass substrate into a desired uneven shape, the performance of a micromachine, a sensor, or the like using the glass substrate can be improved.

In the present invention, in this step,
It is particularly preferable to generate an electrostatic attractive force between the workpiece and the mold facing each other. In order to generate electrostatic attraction, a DC electric field is applied in a direction in which the mold side has a positive potential when the workpiece and the mold are superposed. Due to the generation of electrostatic attraction due to the application of this electric field, the deformable work material is attracted to the concave-convex shape side of the mold through the bonding prevention layer. Therefore, the material to be processed can easily approach the uneven shape side and is further deformed following the uneven shape.

According to the present invention, when the die and the work material are superposed on each other with electrostatic attraction, the bonding prevention layer is
Particularly preferably, it is made of any one of silicon dioxide, silicon nitride, platinum, gold, silver and chromium. These bonding prevention layers are thin films formed by sputtering or the like.
It can be integrally formed on the surface of the mold. When the mold is made of silicon, a silicon dioxide film can be formed on the mold surface by thermal oxidation.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. As the mold in the present invention, it is preferable to use a mold made of a material to be etched in the semiconductor integrated circuit manufacturing process. Examples of such a mold include various semiconductor substrates and various thin films formed on these semiconductor substrates. Specifically, in the process of silicon semiconductor, Si single crystal, polycrystalline Si, amorphous Si, SiO ₂ , PSG, BSG,
Examples include Si ₃ N ₄ , Si compounds such as various silicides, substrates and thin films made of metals such as aluminum (Al), molybdenum (Mo), tungsten (W), nickel (Ni), and chromium (Cr). it can. further,
Other semiconductor processes include substrates and thin films made of titanium, tantalum, germanium, or the like.
In the compound semiconductor process, a substrate or a thin film made of a tantalum compound, a titanium compound, gallium arsenide or the like can be used. These molds are selected in consideration of the required form of the uneven shape, the processing accuracy, the type of the material to be processed, the pressurizing and heating conditions at the time of superposition, and the like.

The surfaces of these molds are processed into an uneven shape by lithography. Lithography is mainly performed by a method including an energy irradiation step and an etching step. By using the mold made of the material to be etched in the semiconductor integrated circuit manufacturing process, the surface of the mold is processed with good accuracy. In lithography, specifically, energy is applied to a specific region of a mold having a resist formed on the surface to form a resist pattern, and then the exposed mold surface is etched to form fine irregularities on the processed surface of the mold. This is performed by forming a pattern of shape. It is also possible to directly process the surface of the mold into a concavo-convex shape by performing energy irradiation with an ion beam, a laser beam, or the like, without going through an etching process.

The surface of the mold is etched into an uneven shape by wet etching or dry etching which is usually used in the semiconductor integrated circuit manufacturing process, that is, 3
It is processed into a three-dimensional shape. As the dry etching, gas etching, plasma etching (chemical dry etching, reactive ion etching, microwave etching, etc.), ion etching (sputter etching, ion beam etching, etc.) can be used. The etching method is selected in consideration of the type of mold, the form and accuracy of the uneven shape, and the like. However, in order to efficiently obtain a desired uneven shape, it is preferable to mainly use anisotropic etching.

By the preliminary process as described above, an uneven shape is formed on the mold surface. The uneven shape of this mold is complementary to the shape to be formed on the surface of the workpiece. By carrying out this step using this mold, a desired uneven shape is transferred to the surface of the workpiece.

The material to be processed is not particularly limited. It is useful for work materials made of materials other than semiconductor materials, which makes it difficult to process uneven shapes. As the material to be processed, various glass substrates made of, for example, soda lime glass, lead potassium soda glass, aluminosilicate glass, borosilicate glass, or the like can be used. It is preferable that the materials to be processed and the molds have similar thermal expansion coefficients.

The workpiece is heated to such an extent that the workpiece can be deformed. The heating method is not particularly limited, but the workpiece may be directly heated by a heat source, the mold may be heated to indirectly heat the surface of the workpiece to be abutted, and Alternatively, the processed material may be placed alone or together with the mold in an atmosphere of a constant temperature.

The work piece and the uneven surface of the mold are superposed on each other by applying pressure as required. Further, when generating an electrostatic attractive force between the workpiece and the mold which face each other,
A DC electric field is applied in the direction in which the mold side has a positive potential. Generating an electrostatic attractive force to attract the workpiece to the mold is
This is an application of anodic bonding technology, which is one of the bonding technologies for glass substrates and silicon substrates. Therefore, in a combination capable of anodic bonding, a material that can be used in place of the glass substrate can be used as a workpiece, and a material that can be used in place of the silicon substrate can be used as a mold. Specifically, as the material to be processed, one type is selected from the glass substrates made of any one of Pyrex # 7740, # 0120, # 1720, and # 7070 (manufactured by Dow Corning), As
1 from a substrate made of silicon, tantalum, titanium, gallium arsenide, or germanium, or a thin film made of nickel, chromium, aluminum, molybdenum, tungsten, silicon nitride, or silicon dioxide.
A combination of a material to be processed and a mold, which are selected as seeds, is preferable. Further, among these combinations, a combination in which the coefficient of thermal expansion of the mold is close to the coefficient of thermal expansion of the glass substrate is more preferable.

When surface processing is performed by generating electrostatic attraction between the work material and the die, it is possible to join the die and the work material in the portion where the joining prevention layer is not interposed. Therefore, for example, in a state in which the bonding site on the silicon semiconductor substrate is exposed, a thin film having an uneven shape on the surface and a bonding prevention layer are formed at a position other than the bonding site, and the silicon semiconductor substrate and the glass substrate are anodically bonded. When superposed under the conditions, the glass substrate is bonded to the silicon semiconductor substrate at the bonding site, and the surface is formed in an uneven shape at the thin film site. The structure of the silicon semiconductor substrate and the glass substrate, in which the surface of the glass substrate facing the silicon semiconductor substrate is provided with irregularities by selectively removing the thin film and the bonding prevention layer that have become molds by etching or the like. You can get the body.

In the present invention, the surface of the material to be processed can be deformed by heating it, but it is necessary to prevent the material from being joined to the mold during superposition. The bonding prevention layer is interposed between the uneven surface of the mold and the surface of the material to be processed, and is capable of following the uneven shape of the mold and does not bond to the material to be processed. For example, silicon dioxide, silicon nitride, platinum,
Gold, silver, chrome, etc. can be mentioned. The bonding prevention layer can be integrally formed on the surface of the mold. For example,
The silicon dioxide film formed on the surface of the substrate made of silicon functions as a bonding prevention layer. The bonding prevention layer that can be formed on the mold surface by thermal oxidation, sputtering, or the like is convenient because it can be formed following the uneven shape of the mold. Further, the bonding prevention layer can be interposed as a single thin film in a state separated from the mold.

After the work material is deformed following the uneven shape of the mold, the work material is separated from the mold. The work piece is easily separated from the mold due to the bonding prevention layer. An uneven shape is formed on the surface of the separated work material so as to be substantially complementary to the uneven shape formed on the mold. Furthermore, since the surface of the mold formed in the semiconductor integrated circuit manufacturing process is flat, minute roughness of the work material is reduced. Therefore, it is not necessary to remove fine surface roughness before and after surface processing.

As described above, according to the present invention, by interposing the joining prevention layer between the work piece and the die, the joining is prevented, and the surface deformation of the work piece is utilized to obtain the work piece. The uneven shape of the mold can be transferred to the surface of the. As a result, the surface of the material to be processed can be processed into an uneven shape without etching or blasting. Moreover, when an electrostatic attractive force is generated between the opposing mold and the work material, the work material approaches the mold positively,
The uneven shape is easily and faithfully transferred.

Next, the present invention will be specifically described based on FIGS. 1 and 2 by way of examples. (Embodiment) This embodiment relates to processing of a glass substrate 2 which is a work material used in a capacitive acceleration sensor. FIG. 2 shows steps for processing the glass substrate 2. The glass substrate 2 of the present embodiment is made of borosilicate glass (Pyrex # 7740 (manufactured by Dow Corning)) and has a thermal expansion coefficient of 32.5 × 10 ⁻⁷ / ° C. (0
~ 300 ° C), and 37 × 10 ^-7 / ° C (25 to 535)
° C).

In this embodiment, a silicon wafer 4 is used as a mold. First, after forming a resist film on the surface of the silicon wafer 4, patterning is performed by photolithography to form openings. Then, the exposed surface of the silicon wafer 4 is etched by reactive ion etching, and then the resist film is removed to form a recess 6 having a predetermined shape. The shape of the concave portion 6 substantially corresponds to the convex shape to be formed on the surface of the glass substrate 2.

Next, on the surface of the silicon wafer 4,
A SiO ₂ film 8 having a thickness of 500 nm is formed as a bonding prevention layer by a thermal oxidation method. The SiO ₂ film 8 has a film thickness of about 20.
If it is 0 nm or more, it functions as a bonding prevention layer, but if it is thin, it may be bonded to the glass substrate without preventing bonding. The silicon wafer 2 having the SiO ₂ film 8 thus formed is placed on the plate 10 having a heat source, with the SiO ₂ film 8 on the upper surface side, and the processed surface of the glass substrate 2 is placed thereon. Put the sides together. On this plate 10, an electrode 12 is provided on the upper surface of the glass substrate 2, and a DC electric field can be applied through the plate 10 in a direction in which the silicon wafer 4 side has a positive potential. .

In this state, the heat source is switched on and the plate 10 is heated, so that the silicon wafer 4 is heated, and as a result, the glass substrate 2 which is superposed thereon is also heated. Then, when the glass substrate 2 is heated to about 450 ° C., a voltage of 1 kV is applied between the glass substrate 2 and the silicon wafer 4.

By applying a voltage, an electrostatic attractive force is generated between the silicon wafer 4 and the glass substrate 2. at the same time,
Due to this electrostatic attraction, the surface portion of the glass substrate 2 becomes Si.
It deforms so as to be close to the surface of the silicon wafer 4 via the O ₂ film 8 (see FIG. 1). As a result, the glass substrate 2
Is deformed according to the uneven shape of the silicon wafer 4,
The uneven shape formed on the silicon wafer 4 is transferred to the surface of the glass substrate 2. After confirming the deformation, the electrode 12 is removed and the glass substrate 2 is separated from the silicon wafer 4. Since the SiO ₂ film 8 is formed on the silicon wafer 4, the deformed glass substrate 2 can be easily separated.

The concavo-convex shape formed on the silicon wafer 4 is transferred to the separated glass substrate 2. In this embodiment, the concave portion 6 formed on the silicon wafer 4 is transferred.
Corresponding to, the convex portion 14 was formed. Further, the surface of the glass substrate 2 is not roughened due to processing.

[0028]

According to the present invention, the surface of the material to be processed can be processed into the uneven shape by using the mold having the uneven shape obtained by lithography and transferring the uneven shape to the surface of the material to be processed. Therefore, the surface of the material to be processed can be processed into a desired shape regardless of the difficulty of etching the material itself.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state in which a convex portion is formed on the surface of a glass substrate according to an embodiment of the present invention.

FIG. 2 is a diagram showing a process when the present invention is applied to the surface processing of a glass substrate.

[Explanation of symbols]

2 glass substrate 4 silicon wafer 6 concave part on silicon wafer 8 SiO ₂ film 10 plate 12 electrode 14 convex part on glass substrate

Claims (5)

[Claims] 1. A method of processing a surface of a work material, comprising a preliminary step of working the surface of a mold into an uneven shape by using lithography, and a bonding prevention layer for preventing bonding between the work material and the mold. And a main step of superposing a work piece heated to a deformable temperature and a side of the mold on which the concavo-convex shape is formed with the intervening step. 2. The surface processing method according to claim 1, wherein the mold is mainly composed of silicon. 3. The surface processing method according to claim 1, wherein the material to be processed is a glass substrate. 4. The surface processing method according to claim 1, 2 or 3, wherein in this step, an electrostatic attractive force is further generated between the workpiece and the die which face each other. Processing method. 5. The surface processing method according to claim 4, wherein the bonding prevention layer is made of any one of silicon dioxide, silicon nitride, platinum, gold, silver and chromium. .