JP2002097030A - Die and method of producing the same - Google Patents

Abstract

(57) [Problem] An object of the present invention is to reduce defects such as missing of an engraved pattern and an excessive pattern in a mold used for injection molding of a lens or a diffraction grating made of glass or plastic. Another object of the present invention is to provide a mold capable of producing a shape and dimensions such as a line width and an engraving depth of an engraving pattern with high precision, and having a long life and a strong mold. SOLUTION: In the mold according to the present invention, a pattern layer on a surface layer of the mold is SiC (silicon carbide);
The main feature is that an intermediate film other than SiC such as SiN is provided below the SiC. Also, S on the surface of the mold
Silicon dioxide (SiO 2) in which an iC film is coated on a SiC film
₂ ) Since the pattern size of the SiC metal film can be manufactured with high precision by using a method in which the film or Cr is processed into a predetermined pattern and the pattern is marked on the SiC film using a mask as a mask. A highly accurate mold can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a camera lens,
Microlens used for signal reading unit (optical pickup) such as compact disk (CD) and DVD,
The present invention relates to a mold used in injection molding of glass or plastic for manufacturing optical components such as a diffraction grating or a mirror, or optical communication components such as an optical waveguide or an optical demultiplexer.

[0002]

2. Description of the Related Art Conventionally, high-hardness molds include WC, TaC, a compound of a metal such as tungsten (W), titanium (Ti) or tantalum (Ta) and carbon (C).
A pattern is imprinted on a surface of a cemented carbide metal or the like produced by mixing and sintering TiC or the like with a binder metal such as Cr, Ni, or Co using an electric discharge machine, a lathe, or a grinding machine to form a mold. . The dies thus machined are assembled into glass or plastic injection molding machines to produce glass lenses and plastic optical components in large quantities.

[0003]

In a mold manufactured by such machining, the pattern dimensional accuracy depends on the accuracy of the machine to be machined. For example, a diffraction grating used for an optical pickup or a part of optical communication is used. It is difficult to imprint a pattern with an accuracy of about 10 nm required for the pattern. Furthermore, in EDM machines, lathes, and grinding machines, lathe marks, which are linear marks, are always formed on the surface layer on which the pattern is imprinted. For this reason, lenses made by injection molding using the mold, etc. A linear trace generated by machining is transferred to the surface layer, and the optical characteristics of a part formed by injection molding are not improved. For example, optical parts having high light transmittance cannot be manufactured by injection molding. Furthermore, in the case of a glass filled in an injection molding apparatus at a high temperature of 600 ° C. or more, if a conventional mold having a cemented carbide in the surface layer is used for a long time, the surface of the mold reacts with the activated glass. There has been a problem that the surface layer is deformed and deformed, and the life of the mold for injection molding is short.

An object of the present invention is to provide a mold used for injection molding of a lens or a diffraction grating made of glass or plastic, which is free from defects such as missing or excessive patterns in the engraved pattern, An object of the present invention is to provide a mold that can be manufactured with high precision in dimensions such as a line width and an engraved depth and has a long life and a strong mold.

Heretofore, there has been no strong and long-lasting mold for injection molding of glass or plastic capable of forming a high-precision pattern on the order of microns on the surface of glass or the like.

[0006]

According to the present invention, there is provided a mold comprising:
In order to achieve such an object, a pedestal and a pattern layer for engraving a predetermined pattern on the surface of an object are provided on a surface layer of the pedestal, and the pattern layer is made of SiC (silicon carbide). Main features.

[0007] The present invention relates to a mold used for manufacturing optical components such as lenses and diffraction gratings by injection molding.
The pattern layer on which the pattern on the surface of the mold is formed is made of SiC
It consists of. SiC is a stable compound having a high melting point of 2300 ° C. and excellent heat resistance, a large Young's modulus of 460 Gpa and excellent wear resistance, and excellent chemical resistance to acids and alkalis. . For this reason, even if glass or plastic that has been melted and activated at a high temperature during molding and adheres to the mold surface layer having a pattern, the mold surface layer can be stably obtained without deterioration in quality and obtained many times of molding. Has the effect of being able to

[0008] The invention is characterized in that the pattern layer is made of polycrystalline SiC. In the single crystal state, when the load is locally concentrated and a minute crack is generated in the crystal, a large crack is generated in the SiC film due to the dislocation. On the other hand, in a polycrystalline structure having small crystal grains, cracks converge within a range of crystal grains of several tens of nanometers, so that there is an effect that mechanical strength is increased and stability is increased.

The pedestal is characterized in that it is made of an alloy containing carbon such as WC, TaC, TiC or the like. The use of these mold materials for the pedestal has the effect of facilitating workability.

In addition, SiN is provided between the pattern layer and the pedestal surface layer.
(Silicon nitride), SiO ₂ (silicon dioxide), or an intermediate film of TiN. S on the mold surface
By providing an intermediate film such as a SiN film at the interface between the iC film and a mold base made of a cemented carbide such as WC,
At the interface between the pedestal of the cemented carbide such as WC and the SiC, the C atoms in the SiC and the WC do not diffuse and move freely, and the metal atoms of the binder such as Co in the cemented carbide are SiC. The mold can be used stably without diffusing and moving inside.

In order to achieve the above object, a method of manufacturing a mold according to the present invention includes a step of coating a surface layer of a pedestal with a SiC film, a step of coating a Cr film on the SiC film, A step of coating a resist film on the Cr film, a step of processing the resist film into a predetermined pattern, a step of etching the Cr film using the patterned resist film as a mask, and a step of etching the patterned Cr film. A step of removing the resist film on the film, a step of patterning the SiC film by etching using the patterned Cr film as a mask, and a step of removing the Cr film on the patterned SiC film. It is characterized by having. The SiC film on the surface of the mold is
Silicon dioxide (SiO ₂ ) film or Cr coated on iC film
By using a method in which the pattern is processed into a predetermined pattern and the pattern is imprinted on the SiC film using the mask as a mask, the pattern size of the SiC metal film can be manufactured with high accuracy. Is obtained.

Further, SiN (silicon nitride) is provided on the surface of the base,
A step of coating one of an intermediate film of SiO ₂ (silicon dioxide) and TiN, a step of coating a SiC film on the intermediate film, a step of coating a Cr film on the SiC film,
a step of coating a resist film on the r film, a step of processing the resist film into a predetermined pattern, a step of etching the Cr film using the patterned resist film as a mask, and a step of etching the Cr film Removing the upper resist film; and using the patterned Cr film as a mask to remove the SiC.
The method includes a step of patterning the film and the intermediate film by etching, and a step of removing the Cr film on the patterned SiC film. A SiC film on the mold surface,
By providing an intermediate film such as a SiN film at an interface with a mold base made of a cemented carbide such as WC, it is possible to provide a stable mold in which C atoms and metal atoms do not move beyond the intermediate film. .

[0013]

FIG. 1 shows the structure of a mold according to a first embodiment of the present invention. 1 is thickness from 1mm to several tens
The pedestal is made of metal or ceramics of about mm. The surface of the pedestal 1 is covered with a pattern layer SiC film 2. A pattern 3 is imprinted on the SiC film 2. In order to use this for injection molding, the melted glass or plastic is pressed against the SiC film 2 while applying pressure, and the glass or plastic is cooled and solidified.
Separate from C film 2 and apply Si on the surface of glass or plastic.
The pattern 3 of the C film is transferred. SiC film 2 on the surface of base 1
In order to form the pattern 3 on the SiC film 2 with high precision, a fine pattern forming technique used in integrated circuit manufacturing, such as photolithography or dry etching, can be applied. An accurate shape can be formed as a mold pattern. Furthermore, S
The melting point of the iC film 2 is as high as 2300 ° C. and 1000 ° C.
However, the crystal state does not change, and the film stress does not change. Further, the Young's modulus is 400 Gpa or more, which is high in rigidity and excellent in abrasion resistance, and is excellent in chemical resistance without changing even in an alkali or acidic solution, and is extremely excellent in stability. For this reason, if it is used for a mold, it does not change even after molding many times, and can be used for a long period of time.

FIG. 2 shows the structure of a mold according to a second embodiment of the present invention. A SiC film 2 of a pattern layer is formed by CVD to form a polycrystalline SiC film containing tetragonal SiC (β-SiC), and the pedestal 1 is made of WC, TaC, TiC.
A metal mold was formed by using a cemented carbide metal containing carbon (C), and further laying a SiN film 4 under the SiC film. The conditions for forming the SiC film 2 by the CVD method include a hydrogen gas, a mixed gas of dichlorosilane (SiH ₂ Cl ₂ ) and an acetylene (C ₂ H ₂ ) gas at a gas pressure of about 1 Torr, at about 1000 ° C. to about 1200 ° C. When reacted at a temperature, polycrystalline SiC is formed. As described above, by forming a polycrystalline crystal structure, a single-crystal Si
Strength is higher than C. That is, in the case of a single crystal, when the load is locally concentrated and a minute crack occurs in the crystal,
The dislocation causes large cracks in the SiC film. On the other hand, in a polycrystalline structure having small crystal grains, cracks converge within a range of crystal grains of several tens of nanometers, so that there is an effect that mechanical strength is increased and stability is increased. In addition, pedestal 1
WC, TaC, TiC that can be subjected to electrical discharge machining and grinding
Use of a mold material containing carbon such as that described above has an effect of facilitating workability. Here, in order to use a cemented carbide metal as the base 1, SiN (silicon nitride), SiN
An intermediate film such as O ₂ (silicon dioxide), TiN, etc.
And the SiC film 2. That is, a metal having a relatively low melting point, such as Co or Ni, is used as a binder and directly sintered onto a superhard metal surface layer such as WC, which is manufactured by sintering.
When a SiC film is formed at a high temperature of 0 ° C. or more by CVD or the like,
Non-high melting point metals such as Co and Ni in the WC diffuse and move to the surface layer and react with the SiC film to obtain high quality S.
iC film cannot be formed. In contrast, an SiN film that can be formed by a plasma CVD method at a substrate temperature of about 300 ° C. or a CVD method at a film forming temperature of 900 ° C. or less is formed on the surface of the pedestal 1 before forming the SiC film. When the film is formed to a thickness of about 0.05 μm to 0.2 μm,
Even if the film is formed at a high temperature of 000 ° C. or higher, the SiN film 4 does not block the metal of the binder such as Ni on the surface layer of the pedestal 1 and precipitates. There is an effect that the film 2 can be formed. Furthermore, SiC
When the SiN film 4 is provided at the interface between the film 2 and the pedestal 1 of a hard metal such as WC, even if the temperature is high when used as a mold, the easily diffused carbon (SiC or WC) in the WC is used. C) It is Si that atoms diffuse and move between the two layers.
It is prevented by the N film 4 and has an effect that the composition can be stably used even at a high temperature of 500 ° C. or more without changing the composition of the SiC film 2 and the pedestal 1.

FIG. 3 shows a method of making the mold shown in the second embodiment. FIG. 3A shows that the surface layer of the pedestal 1 made of a hard metal such as WC has a thickness of 0.05 μm to 2 μm.
Covered with a SiN film of about the thickness, and further on the SiN film,
At a temperature of about 1000 ° C., in a hydrogen gas, for example, Si
Mixing H ₂ Cl ₂ and C ₂ H ₂ , or mixing a SiCl ₂ (CH ₃ ) gas in a hydrogen gas and using a CVD apparatus capable of growing a polycrystalline SiC film to a thickness of 1 μm
The SiC film 2 is formed to a thickness of about 10 μm. FIG. 3B shows an example of a film structure for forming the SiC film pattern 3. In order to imprint a predetermined pattern 3 on the SiC film 2, lithography used in the manufacture of semiconductor circuits is used. That is, S
A Cr film as an intermediate film 6 is provided on the iC film 2, and an organic film (resist) 5 sensitive to ultraviolet rays and electron beams is further provided thereon. FIG. 3C depicts a pattern to be imprinted on the mold with ultraviolet light or an electron beam on the resist 5, a portion exposed to ultraviolet light or the like is immersed in a chemical solution, and the resist pattern 7 is removed on the intermediate film 6. Has formed. FIG.
(D), the Cr film of the lower intermediate film 6 is etched by high-frequency plasma or microwave plasma of a gas containing an element such as chlorine, oxygen or argon using the resist pattern 7 as an etching mask, and the Cr film of the intermediate film is etched. Is formed. 3E, the resist 5 on the Cr film 8 has been removed. FIG. 3F shows an intermediate film 6.
Using the Cr pattern 8 formed of Cr as an etching mask, the lower SiC film 2 is engraved on the SiC film 2 by high-frequency plasma or microwave plasma of a gas containing an element such as fluorine, oxygen, or argon. Finally, as shown in FIG. 3G, the intermediate film 6 on the SiC film 2 is removed, and the pattern 3 of the SiC film 2 is engraved.

When the surface of a resist which is an organic substance is exposed to plasma during etching, the surface is etched and thinned, and disappears during the etching of the SiC film to a predetermined depth. As shown in FIG. 3B, a structure in which a Cr film 6 as an intermediate film is provided between an organic film (resist) 5 and an SiC film 2 which are sensitive to ultraviolet rays or electron beams, and first, a resist pattern is used. Etching the Cr film to imprint a pattern on the Cr film, removing the resist, and then etching the pattern on the SiC film using the pattern of the Cr film as an etching mask. Since it is hardly etched, there is an effect that the pattern of the SiC film can be formed with high accuracy. Further, since Cr does not deteriorate even when exposed to plasma, the remaining Cr film thickness is accurately measured, and as a result, there is an effect that the etching depth of the SiC film can be measured accurately.

In this embodiment, the Cr film 6 is used for etching the SiC film 2, but instead of the Cr film, Ni, Ti, and the like whose etching rate is much smaller than that of the SiC film are used.
A metal film such as Ta can be used. Further, the intermediate film 6 is
For example, assuming a two-layer structure in which an SiO ₂ film is provided on a Cr film, the SiO ₂ film is etched with a resist pattern to form a S layer.
It is also possible to form a pattern with higher accuracy by adding an iO ₂ pattern and adding a step of forming a pattern by etching the Cr intermediate film 6 using the SiO ₂ pattern as a mask.

In this embodiment, the pattern 3 is a diffraction grating pattern, but the pattern of the micro lens is
Any pattern such as a step-like pattern and a saw-tooth-like pattern can be formed.

Further, in this embodiment, the pedestal 1
Although the embodiment is shown as an example of a flat plate shape, even if the pedestal 1 has a curved shape, if the surface is coated with the SiC film 2 by CVD or the like, it can be used as a mold for molding containers and mechanical parts. Can be used.

[0020]

As described above, according to the present invention, in a mold used for manufacturing a diffraction grating or a lens of glass or plastic by injection molding, the pattern of the mold is constituted by an SiC film. Because of its structure, it has a high melting point, is extremely stable at high temperatures and has excellent abrasion resistance. Also, it uses SiC that is not corroded by chemicals such as acids and alkalis, so it was dissolved at high temperatures during molding. Even if glass or plastic comes into contact with the pattern of the mold, the surface of the mold is not deteriorated and the molding can be stably performed many times.

In addition, since the pattern layer is made of polycrystalline SiC having small crystal grains, cracks converge within a range of crystal grains of several tens of nm, so that mechanical strength is increased. Has the effect of increasing stability.

Further, since the pedestal is made of an alloy containing carbon such as WC, TaC, or TiC, there is an effect that workability is facilitated.

Also, by providing an intermediate film such as a SiN film at the interface between the SiC film of the mold surface layer and the mold pedestal made of a cemented carbide such as WC, the cemented carbide pedestal such as WC is provided. At the interface between SiC and SiC, the C atoms in SiC and WC do not diffuse and move freely, and the metal atoms of the binder such as Co in the cemented carbide diffuse and move into SiC. And the mold can be used stably.

The method of manufacturing a mold according to the present invention uses a method in which a SiC film serving as a pattern layer is manufactured by a dry etching process using plasma using an inorganic substance such as a Cr film as a mask. Has the effect that it can be manufactured with high accuracy. Due to such effects, molded products can be stably mass-produced with high pattern shape accuracy.

[Brief description of the drawings]

FIG. 1 is a view showing a structure of a mold having a SiC film pattern on a surface of a pedestal 1 according to a first embodiment of the present invention.

FIG. 2 is a view showing a structure of a mold in which a SiN film is provided at an interface between a SiC film as a pattern layer and a pedestal 1 according to a second embodiment of the present invention.

FIG. 3 is a diagram illustrating a manufacturing method for manufacturing a SiC mold according to a second embodiment. FIG. 3A shows SiC by CVD.
A step in which the film is coated on a pedestal covered with a SiN film, (b)
(A) is a step in which a Cr film and a resist are coated on the SiC film in (a), (c) is a step in which the resist is patterned, (d)
Is a step in which the underlying Cr film is patterned using the resist as a mask, (e) is a step in which the resist on the Cr film is stripped, and (f) is an underlying SiC pattern using the patterned Cr film as a mask. Is a patterned process, (g)
FIG. 4 is a view showing a process in which the Cr film on the SiC film is peeled off and the SiC film is formed into a mold.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mold base 2 SiC film 3 SiC film pattern 4 SiN film 5 resist film 6 Cr film 7 resist pattern 8 Cr film pattern

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Akira Motoyoshi 2-1-1, Nishi-Shinjuku, Shinjuku-ku, Tokyo NTT Advanced Technology Corporation (72) Inventor Hideo Yoshihara Shinjuku-ku, Tokyo 2-1-1, Nishi-Shinjuku F-term in NTT Advanced Technology Corporation (reference) 4F202 AJ02 AJ07 CA11 CB01 CD07 CD22 CD24 CD30

Claims (6)

[Claims] 1. A mold comprising: a pedestal; and a pattern layer for engraving a predetermined pattern on the surface of the object on a surface layer of the pedestal, wherein the pattern layer is made of SiC (silicon carbide). . 2. The pattern layer according to claim 1, wherein the pattern layer has a polycrystalline structure.
A mold comprising iC. 3. The pedestal according to claim 1, wherein the base is WC, TaC, TiC.
A mold made of an alloy containing carbon such as 4. The method according to claim 1, wherein:
SiN (silicon nitride), SiO ₂ (silicon dioxide), TiN
A mold comprising any one of the above intermediate films. 5. A step of coating a surface layer of a pedestal with a SiC film, a step of coating a Cr film on the SiC film,
A step of coating a resist film on the film, a step of processing the resist film into a predetermined pattern, and a step of etching the Cr film using the patterned resist film as a mask,
Removing the resist film on the patterned Cr film, etching the SiC film using the patterned Cr film as a mask, and removing the Cr film on the patterned SiC film. And a step of removing the mold. 6. SiN (silicon nitride), Si
A step of coating any one of an intermediate film of O ₂ (silicon dioxide) and TiN, a step of coating a SiC film on the intermediate film, a step of coating a Cr film on the SiC film,
A step of coating a resist film on the film, a step of processing the resist film into a predetermined pattern, and a step of etching the Cr film using the patterned resist film as a mask,
Removing the resist film on the patterned Cr film; and patterning the SiC film and the intermediate film by etching using the patterned Cr film as a mask;
Removing the Cr film on the patterned SiC film.