JP2002096333A - Mold and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a long-lived and strong mold which is almost free from such defects as the omission of a stamped pattern and an excess pattern and is capable of producing the highly precise dimensions of a configuration such as the lineal width of the stamped pattern and the depth of the stamping, in the mold used for injection-molding glass or plastic lens or diffraction grating or the like. SOLUTION: This mold is characterized in that above all, a pattern layer formed on the surface layer of the mold is made up of silicon nitride(SiN). In addition, the pattern dimensions of the SiN metallic film can be manufactured with high precision by employing a method for stamping a pattern on the SiN film formed on the surface layer of the mold with the help of a mask, of a Cr film applied on the SiN film, which is obtained by working the Cr film into a specified pattern. Thus the mold with a high pattern dimensional precision is 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. Further, in the case of a glass filled in an injection molding apparatus at a high temperature of 600 ° C. or more, if a cemented carbide mold is used for a long time, the surface of the mold reacts with the activated glass to change the surface layer. There is a problem that the mold is 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 the surface of the pedestal, and the pattern layer is made of SiN (silicon nitride). 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 layer of the mold is formed is SiN.
It consists of. SiN is a stable compound having a melting point of 1900 ° C. and having excellent heat resistance, a large Young's modulus of 160 Gpa and being excellent in abrasion resistance, and also having excellent chemical resistance to acids and alkalis. . For this reason, even if the glass or plastic melted and activated at a high temperature at the time of molding and adheres to the mold surface layer having a pattern, the mold surface layer is not deteriorated, and the molding is stably performed many times. It has the effect that can be. A SiN film on the surface of the mold and W
C atoms in C do not diffuse and move freely,
Further, there is an effect that the metal mold of the binder such as Co in the cemented carbide does not diffuse and move into SiN and the mold can be used stably.

[0008] The invention is characterized in that the pattern layer is made of SiN having an amorphous structure. 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 order to achieve the above object, a method of manufacturing a mold according to the present invention includes a step of coating a SiN film on a surface layer of a pedestal, a step of coating a Cr film on the SiN film, Coating a Cr film on the SiN film;
A step of coating a resist film on the 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; Removing the resist film;
A step of patterning the SiN film by etching using the patterned Cr film as a mask;
removing the Cr film on the iN film. The pattern size of the SiN metal film is manufactured with high accuracy by using a method of processing a Cr film or the like coated on the SiN film on the surface layer of the mold into a predetermined pattern and using the mask as a mask to mark the pattern on the SiN film. Therefore, there is an effect that a mold having high pattern dimension accuracy can be obtained.

[0011]

FIG. 1 shows the structure of a mold according to the present invention. Reference numeral 1 denotes a pedestal made of metal or ceramic having a thickness of about 1 mm to several tens mm. The surface layer of the pedestal 1 is covered with a SiN film 2 as a pattern layer. A pattern 3 is imprinted on the SiN film 2. In order to use this for injection molding, melted glass or plastic is pressed against the SiN film 2 while applying pressure, and after the glass or plastic is cooled and solidified, the glass or plastic is separated from the SiN film 2. SiN on glass or plastic surface
Transfer the pattern 3 of the membrane. A CVD method or a sputtering method is used to form the SiN film 2 on the surface layer of the base 1,
In order to form the pattern 3 with high precision, a fine pattern forming technique used in the manufacture of integrated circuits, such as photolithography or dry etching, can be applied, so that a highly accurate mold pattern can be formed. Furthermore, Si
The N film 2 has a high melting point of 1900 ° C. and does not change its crystalline state even at 1000 ° C., and is stable even at extremely high temperatures. Further, it has high Young's modulus of 100 Gpa or more and high rigidity and excellent abrasion resistance. Further, it does not change even in an alkali or acidic solution, has excellent chemical resistance, and is extremely excellent in chemical 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.

In this embodiment, the SiN film 2 of the pattern layer is used.
Is formed by CVD to form a non-crystalline SiN film.
Is composed of a hard metal containing carbon (C) such as WC, TaC, TiC, and the like. further. CVD of SiN film 2
The conditions for forming a film by the dichlorosilane (SiH ₂ C
l ₂ ) and ammonia (NH ₃ ) gas mixed gas of several To
When the reaction is performed at a gas pressure of about rr and a temperature of about 700 ° C. to about 1000 ° C., an amorphous SiN film is formed.
As described above, the strength is increased by making the crystal structure non-crystalline. That is, in the case of a single crystal, when a load is locally concentrated and a minute crack is generated in the crystal, the crack spreads in the film due to the dislocation. On the other hand, in the non-crystalline structure, since the cracks converge in the range of several tens of nm, there is an effect that mechanical strength is increased and stability is increased. Also, on pedestal 1,
Use of a mold material containing carbon such as WC, TaC, or TiC, which can be subjected to electric discharge machining or grinding, has an effect of facilitating workability. At the interface between the SiN film 2 and the pedestal 1 of a hard metal such as WC, even if the temperature becomes high when used as a mold, the W
Carbon (C) atoms that are easily diffused in C do not freely diffuse and move between the two layers. That is, Si
Even if the composition of the N film 2 and the pedestal 1 does not change, there is an effect that the mold can be stably used even at a high temperature of 500 ° C. or more.

FIG. 2 shows a method of manufacturing a mold according to the present invention. FIG. 2A shows an example in which, for example, SiH ₂ Cl ₂ and NH ₃ are mixed on a surface layer of the pedestal 1 made of a hard metal such as WC at a temperature of about 1000 ° C. to form amorphous SiN.
Using a CVD apparatus capable of growing a film, 1 μm to 10 μm
The SiN film 2 is formed to a thickness of about μm. FIG. 2B shows an example of a film structure for forming the SiN film pattern 3. In order to imprint a predetermined pattern 3 on the SiN film 2, lithography used in the manufacture of semiconductor circuits is used. That is, SiN
On the film 2, a Cr film as an intermediate film 5 is provided, and further thereon, an organic film (resist) 4 sensitive to ultraviolet rays and electron beams is provided. FIG. 2C depicts a pattern to be imprinted on the mold of the resist 4 with ultraviolet light or an electron beam, and a portion exposed to ultraviolet light or the like is immersed in a chemical solution to be removed, and a resist pattern 6 is formed on the intermediate film 5. Has formed. FIG.
(D) shows that the resist pattern 6 is used as an etching mask to etch the lower Cr film of the intermediate film 5 by high-frequency plasma or microwave plasma of a gas containing an element such as chlorine, oxygen, or argon, and the Cr film of the intermediate film is etched. Is formed. 2E, the resist 4 on the intermediate film pattern 7 is removed. FIG. 2F shows that the lower SiN film 2 is formed by high-frequency plasma or microwave plasma of a gas containing an element such as fluorine, oxygen, or argon using the Cr pattern 7 formed of Cr of the intermediate film 5 as an etching mask. The SiN film 2 is stamped. Finally, the intermediate film 5 on the SiN film 2 is removed as shown in FIG.
The pattern 3 of the iN film 2 is stamped.

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 SiN film to a predetermined depth. As shown in FIG. 2B, a structure is provided in which a Cr film 5 as an intermediate film is provided between an organic film (resist) 4 and an SiN film 2 which are sensitive to ultraviolet rays and electron beams. Etching the Cr film to imprint a pattern on the Cr film, removing the resist, and then etching the pattern on the SiN 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 SiN 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 SiN film can be measured accurately.

In the present embodiment, the Cr film 5 is used for etching the SiN film 2, but instead of the Cr film, Ni, Ti, and the like whose etching rate is much smaller than that of the SiN film are used.
Metal films such as Ta and W can be used. Further, the intermediate film 6
For example, silicon dioxide (SiO ₂ )
As a two-layer structure provided with a film, the SiO ₂ film is etched with a resist pattern to produce a SiO ₂ pattern, and the Si 2
It is also possible to form a pattern with higher accuracy by adding a step of forming a pattern by etching the Cr intermediate film 6 using the O ₂ pattern as a mask.

In this embodiment, the pattern 3 is a diffraction grating pattern, but any pattern such as a lens pattern, a step pattern, and a sawtooth pattern can be formed.

Further, in the present embodiment, the pedestal 1
Has shown an example of a flat plate shape. However, even if the pedestal 1 has a curved shape, if the SiN film 2 is coated on the surface by CVD or the like, it can be used as a mold for molding an aspherical lens or the like.

[0018]

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 SiN film. Because of its structure, it has a high melting point, is extremely stable at high temperatures and has excellent abrasion resistance.Since it uses SiN that is not corroded by chemicals such as acids and alkalis, it melts 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. Also, the CN atoms in the SiN film on the mold surface and the WC do not freely diffuse and move, and the metal atoms of the binder such as Co in the cemented carbide diffuse and move into the SiN. Without this, there is an effect that the mold can be used stably.

Further, since the pattern layer is made of polycrystalline SiN 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, TiC, etc., there is an effect that workability is facilitated.

The method of manufacturing a mold according to the present invention uses a method in which a SiN film 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. This has the effect that the shape 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 shows an embodiment of the present invention, in which a surface of a base 1 is S
It is a figure which shows the structure of the metal mold | die which has the pattern of an iN film.

FIG. 2 is a diagram showing a manufacturing method for manufacturing a SiN mold in the embodiment according to the present invention. FIG.
(B) is a process in which a Cr film and a resist are coated on the SiN film of (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,
(F) is a step in which the underlying SiN pattern is patterned using the patterned Cr film pattern as a mask;
It is a figure which shows the process in which the Cr film on the iN film was peeled off and the SiN film was made into a mold.

[Explanation of symbols]

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

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 4F202 AH73 AJ02 AJ09 CA11 CB01 CD24 CK11 4K030 AA03 AA06 AA13 BA40 CA03 LA23

Claims (4)

[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 SiN (silicon nitride). . 2. The pattern layer according to claim 1, wherein said pattern layer has an amorphous structure.
A mold comprising iN. 3. The pedestal according to claim 1, wherein the base is WC, TaC, Ti.
A mold comprising a carbon-containing alloy such as C. 4. A step of coating an SiN film on a surface layer of a pedestal, a step of coating a Cr film on the SiN film,
A step of coating a Cr film on the N film, a step of coating a resist film on the Cr film, a step of processing the resist film into a predetermined pattern, and a step of processing the Cr film using the patterned resist film as a mask. A step of etching the film, a step of removing a resist film on the patterned Cr film, a step of patterning the SiN film by etching using the patterned Cr film as a mask, and a step of etching the SiN film. Removing the Cr film on the SiN film.