JP3412724B2 - Mold making method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a mold having a fine structure capable of mass-producing various microstructures such as waveguides for optical integrated circuits and micromachines.

[0002]

2. Description of the Related Art In order to manufacture an optical component having a fine structure such as a waveguide for an optical integrated circuit or a grating used for an optical pickup head at a low cost, a mold having a fine structure is used. Manufacturing methods suitable for mass production such as injection molding and cast molding are effective. Several methods have been proposed so far as a method for producing a mold having such a fine structure.

The first is known as the LIGA process, in which a thick film resist is exposed using an X-ray mask and X-rays to form a resist pattern, and then electroforming is performed to perform metal casting. Is what makes (for example,
A. Rogner et al., Proc. Of SPIE, 1506, 1991, p. 80). Since this method uses X-ray lithography technology,
Although there is an advantage that a pattern with a high aspect ratio can be manufactured, there is a problem that the cost is too high because it is necessary to use a special mask for X-rays as a mask and a light source.

The second method is to expose a resist using a photomask and ultraviolet light to form a resist pattern, and then to form a metal mold by plating (for example, A.N.
eyer la, ELECTRONICS LETTERS, Volume 29, Issue 4, 1993 399
See page). According to this method, a pattern having a depth of several microns can be formed by adjusting the resist thickness. However, when the resist thickness is increased to about 7 to 10 microns, which corresponds to the core diameter of the single mode waveguide that is most suitable for the commonly used single mode optical fiber, sagging occurs on the wall surface of the resist pattern after exposure. There is a problem that it becomes cheaper and it is difficult to manufacture a rectangular pattern excellent in terms of loss and coupling characteristics.

Further, since the above two methods use a mask, an expensive mask has to be manufactured every time when the structural parameters of the pattern to be manufactured are changed, and therefore the flexibility of the pattern that can be manufactured. There is a problem that is low.

The third method is to expose a resist with an electron beam to form a resist pattern, and then form a metal mold by plating (eg, Hosokawa et al., Proc. Of).
See SPIE, 1559, 1991, p. 229). This method is suitable for the production of submicron fine patterns because it uses electron beam exposure, but it is difficult to produce patterns with a depth of several microns or more due to the limited resist thickness. is there.

[0007]

As described above,
In the conventional method for producing a mold having a fine structure, the core diameter of a single mode waveguide that is most suitable for a commonly used single mode optical fiber is 7-1.
In order to accurately form a deep rectangular pattern of about 0 micron or more, it is necessary to use the X-ray lithography technique described as the first method, which requires a large-scale device and a special mask. This technique has a problem that it is too expensive.

Further, in the exposure process using a mask, an expensive mask must be produced every time when the structural parameters of the pattern to be produced are changed, so that the flexibility of the produced pattern is low. there were.

The present invention has been made in view of the above circumstances, and an object thereof is to mass-produce various microstructures such as a waveguide for an optical integrated circuit and a micromachine.
It is to provide a method for manufacturing a mold having a fine structure.

[0010]

In order to solve the above problems, the present invention applies a resist on a polymer, forms a desired resist pattern by lithography, and then etches a lower layer polymer using the resist pattern as a mask to form a master. In a method for producing a die having a fine structure in which a pattern is produced and a metal die is produced by plating, a silicon-containing resist is used as a resist.

The silicon-containing resist may be a photoresist or an electron beam resist.

The invention according to claim 2 is characterized in that the lithography is electron beam lithography and the silicon-containing resist is an electron beam resist.

Further, the invention according to claim 3 is characterized in that the lithography is laser beam direct writing lithography.

The silicon content in the silicon-containing resist is preferably 10% by weight or more.
It is more preferably 3% by weight or more. When it is 13% by weight or more, a sufficient etching ratio can be obtained.

The silicon-containing resist is roughly classified into the following two types.

Those containing silicon in the main chain or side chain of the resist polymer. After coating and exposing a resist containing no silicon, H
A method in which a substance containing silicon such as MDS (hexamethyldisilazane) is brought into contact with the exposed portion of the resist layer surface to selectively silylate.

In the case of 1, the entire film contains about 10% by weight or more of silicon, but in the case of 1, the selectively silylated surface (depth of about 0.1 to 1 micron) in the resist film. Only contains about 10% by weight or more of silicon.

[0018]

FIG. 1 is a diagram showing the structure of the present invention.

A silicon-containing resist 3 is applied on the polymer 2 applied on the substrate 1 (FIG. 1A). After that, the resist 3 is exposed and developed (FIG. 1B) and patterned (FIG. 1C). Using this resist pattern as a mask, the polymer 2 is etched by reactive ion etching with oxygen gas (FIG. 1D), the resist 3 is peeled off, and a master pattern 7 is produced (FIG. 1E). Then, a metal such as nickel is vacuum-deposited on the master pattern, and a metal such as nickel is plated with the deposited film as a nucleus to form a plating layer 6 (FIG. 1 (f)). The plating layer 6 is peeled off from the master pattern 7 to produce a mold 8 (FIG. 1 (g)).

Here, the polymer 2 may be any polymer such as acrylic resin, epoxy resin, polyimide, etc., which has excellent coatability and can be etched by reactive ion etching of oxygen gas. Further, instead of the polymer 2 coated on the substrate 1, a polymer substrate having an appropriate thickness such as an acrylic plate may be used. In addition, the exposure process of the resist of FIG. 1B may be performed by a batch exposure using a photomask and an aligner, an electron beam writing apparatus, or a laser beam direct writing apparatus. You can go.

Since the silicon-containing resist has extremely high etching resistance to oxygen gas, even if a thin resist film of about 1 micron is used, a pattern having a depth of several tens of microns can be etched. Therefore, as compared with a case where a thick film resist is exposed and developed, a rectangular pattern with a small wall surface sag and a deep depth can be manufactured. When performing the exposure process using a beam (not parallel light) as in laser beam direct writing lithography,
Since the exposure beam is focused on the resist surface by the lens, the upper and lower surfaces of the resist have different beam diameters. When a thin resist film of about 1 micron is used, this difference in beam diameter does not pose a problem, but when exposing a thick film resist of several microns or more, this difference in beam diameter causes sagging on the wall surface. . Therefore, the effect of not using a thick film resist becomes particularly important when the exposure process is performed using a beam as in laser beam direct writing lithography.

Since laser beam direct writing lithography can expose a master pattern of a die to be produced by inputting data on a computer, it is necessary to order an expensive mask each time when producing a master pattern having a different pattern. It is a flexible and economical method. Further, compared with electron beam exposure, there are advantages that the exposure apparatus is inexpensive, exposure can be performed in the atmosphere (no need to make a vacuum), and no antistatic layer is required.

[0023]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited to these examples.

(Example 1) Polymethylmethacrylate (PMMA) was dissolved in methyl isobutyl ketone to prepare a solution, which was applied on a silicon substrate and baked to give a thickness of 8
A μm PMMA film was prepared. A silicon-containing photoresist (trade name FH-SP: manufactured by Fuji Hunt Co., Ltd.) was applied on top of this to form a resist layer having a thickness of 0.7 μm. Furthermore, after exposing using a photomask and an aligner, it developed and patterned the resist. Using this resist pattern as a mask, etching is performed until the silicon substrate surface appears by reactive ion etching with oxygen gas, a rectangular groove having a width of 8 μm and a depth of 8 μm is formed in the PMMA layer, and then the resist layer is peeled off. A master pattern was prepared. Thereafter, nickel was vacuum-deposited on the surface of the master pattern in a thickness of 500 angstrom, and then a nickel plating layer was formed by using the deposited film as a nucleus. Finally, this nickel layer was peeled off from the master pattern to prepare a mold for optical waveguide circuit injection molding. The produced pattern includes not only straight lines but also circular arcs, directional couplers, Y-branches, and the like, and all of them were molds having good shape, dimensional accuracy, and smoothness.

Example 2 A solution of PMMA in methyl isobutyl ketone was applied onto a silicon substrate and baked to form a PMMA film having a thickness of 8 μm. A silicon-containing electron beam resist (trade name: SNR: manufactured by Tosoh Corp.) was applied on top of this to form a resist layer having a thickness of 0.7 μm. Further, after exposure using an electron beam exposure device, development and Further, using this resist pattern as a mask, etching was performed by reactive ion etching with oxygen gas until the surface of the silicon substrate was exposed to form a rectangular pattern with a width of 8 μm and a depth of 8 μm on the PMMA layer, and then the resist layer was peeled off. Then, a master pattern was prepared.
Then, nickel is applied to the surface of the master pattern by 500
Angstrom vacuum deposition was performed, and then a nickel plating layer was formed using this deposited film as a nucleus. Finally, this nickel layer was peeled off from the master pattern to prepare a mold for optical waveguide circuit injection molding. The produced pattern includes not only straight lines but also circular arcs, directional couplers, Y-branches, and the like, and all of them were molds having good shape, dimensional accuracy, and smoothness.

Example 3 A PMMA methyl isobutyl ketone solution was applied onto a silicon substrate and baked to form a PMMA film having a thickness of 8 μm. A silicon-containing photoresist was applied thereon to form a resist layer having a thickness of 0.7 μm. Further, after exposure using a laser beam direct writing apparatus, development was performed and the resist was patterned. Further, using this resist pattern as a mask, etching is performed by reactive ion etching with oxygen gas until the surface of the silicon substrate appears, and the PMMA layer is 8 μm wide and 8 μm deep.
After digging the rectangular groove, the resist layer was peeled off to prepare a master pattern. Thereafter, nickel was vacuum-deposited on the surface of the master pattern in a thickness of 500 angstrom, and then a nickel plating layer was formed by using the deposited film as a nucleus. Finally, this nickel layer was peeled off from the master pattern to prepare a mold for optical waveguide circuit injection molding. The produced pattern includes not only straight lines but also circular arcs, directional couplers, Y-branches, and the like, and all of them were molds having good shape, dimensional accuracy, and smoothness.

Example 4 A methylisobutylketone solution of PMMA was applied onto a silicon substrate and baked to form a PMMA film having a thickness of 5 μm. A silicon-containing photoresist was applied thereon to form a resist layer having a thickness of 0.7 μm. Further, after exposure using a laser beam direct writing apparatus, development was performed and the resist was patterned. Further, using this resist pattern as a mask, etching is carried out by reactive ion etching with oxygen gas until the surface of the silicon substrate appears, and the PMMA layer is 5 μm wide and 5 μm deep.
After digging the rectangular groove, the resist layer was peeled off to prepare a master pattern. Thereafter, nickel was vacuum-deposited on the surface of the master pattern in a thickness of 500 angstrom, and then a nickel plating layer was formed by using the deposited film as a nucleus. Finally, the nickel layer was peeled off from the master pattern to prepare a diffraction grating mold. As for the produced pattern, a mold having good shape, dimensional accuracy, and smoothness was obtained.

(Embodiment 5) Instead of PMMA, epoxy UV resin, acrylic UV resin, and polyimide resin are applied on a silicon substrate to form a film, and otherwise the mold is manufactured by the method described in Embodiments 1 to 4. Was produced. The created pattern is the shape,
A mold with good dimensional accuracy and smoothness was obtained.

Example 6 A silicon-containing photoresist was applied on an acrylic substrate to form a resist layer having a thickness of 1 μm. Further, after exposure using a laser beam direct writing apparatus, development was performed and the resist was patterned. Further, using this resist pattern as a mask, the acrylic substrate was etched by 50 μm by reactive ion etching with oxygen gas to form a rectangular groove having a width of 50 μm and a depth of 50 μm, and then the resist layer was peeled off to prepare a master pattern. . Then, nickel is added to the surface of the master pattern.
A vacuum deposition of 00 angstrom was carried out, and then a nickel plating layer was formed by using this deposited film as a nucleus. Finally, the nickel layer was peeled off from the master pattern to prepare a mold for injection molding of a multimode optical waveguide circuit. A mold with excellent wall surface smoothness and verticality was obtained.

[0030]

As described above, by using the method of manufacturing a mold according to the present invention, a grating having a width / depth of submicron to several microns or a single mode optical waveguide circuit having a width / depth of about 8 microns is used. , Molds with a fine structure required for mass production of microstructures such as multimode optical waveguide circuits with width and depth of tens to hundreds of microns can be manufactured with high precision and low cost. it can. If optical parts are manufactured using these molds, it becomes possible to supply high-performance and low-priced optical parts.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a method of manufacturing a mold according to the present invention.

[Explanation of symbols]

1 substrate, 2 polymer layer, 3 silicon-containing resist, 4 exposure light (mercury lamp light, laser beam, electron beam), 5 oxygen plasma, 6 metal plating layer, 7 mask pattern, 8 mold.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hiroshi Nakagome 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation (56) Reference JP-A-5-12722 (JP, A) JP JP-A-63-302439 (JP, A) JP-A-62-161533 (JP, A) JP-A-5-4232 (JP, A) JP-A-4-310642 (JP, A) JP-A-4-157403 (JP , A) JP-A-8-252830 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) B29C 33/38 B81B 1/00 G02B 6/13

Claims (3)

(57) [Claims] 1. A series of steps in which a resist is applied on a polymer, a desired resist pattern is formed by lithography, a lower layer polymer is etched by using the resist pattern as a mask to form a master pattern, and a metal mold is further formed by plating. A method of manufacturing a mold, wherein a silicon-containing resist is used as a resist in the step of. 2. The method for producing a mold according to claim 1, wherein the lithography is electron beam lithography and the silicon-containing resist is an electron beam resist. 3. The method for producing a mold according to claim 1, wherein the lithography is laser beam direct writing lithography, and the silicon-containing resist is a photoresist.