JP2006289684A - Microprocessing mold - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a microprocessing mold constituted so as to be easily supported on a press machine in forming a microstructure on a substrate by a nano-imprinting method, a hot embossing method or the like, preventing the deformation or distortion caused by pressure and heating at the time of pressing and capable of performing microprocessing with high precision at a low cost. <P>SOLUTION: The microprocessing mold is constituted by joining a thin piece mold 2 having a microstructure formed thereto and a pedestal 3, which is composed of a material of which the coefficient of thermal expansion is same to or almost equal to that of the material of the thin piece mold 2 and thicker than the thin piece mold 2, through a thin film 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

    The present invention relates to a microfabrication mold for performing microfabrication by transferring a fine concavo-convex pattern onto the surface of a substrate such as a semiconductor.

  In recent years, a so-called nanoimprint technique has attracted attention as a new technique for forming a fine concavo-convex pattern at a low cost in order to produce a high-density optical recording medium or an optical element. In this technology, a predetermined pattern is transferred by embossing a stamper (mold) having the same pattern as the pattern to be formed on the substrate against a material such as a resin formed on the surface of the substrate to be transferred. (See Patent Documents 1 and 2, Non-Patent Document 1, etc.).

  In particular, according to the nanoimprint technology described in Patent Document 2 and Non-Patent Document 1, a silicon wafer is used as a stamper (mold), and a fine structure (fine pattern) of 25 nm or less can be formed by transfer.

  Similarly, in order to manufacture high-density optical recording media and optical elements, a mold with the same fine structure is used in the so-called hot embossing technology area in which a fine uneven pattern is formed on the surface of a glass or resin structure. The technology for press forming is drawing attention.

With these technologies called nanoimprinting and hot embossing, it is possible to produce a microstructured mold (hereinafter also referred to as “microfabrication mold”) at a low cost, transfer it to a substrate with high accuracy, and use it repeatedly. It is an important point that determines the quality and cost of the final product. Precise control is necessary to press-form a fine structure of several tens to several hundreds of nanometers in size, but heat is applied together with pressure during pressing, so there are problems such as mold deformation, distortion, and misalignment during heating. Become. Further, it is important to apply pressure uniformly during pressing and to cleanly remove the mold from the molded product. For example, Patent Document 3 has also been proposed.
US Pat. No. 5,259,926 US Pat. No. 5,772,905 JP 2004-288845 A S. Y. Chou et al. , J .; Vac. Sci. Technol. B, vol. 14, no. 6, p. 4129 (1996)

  The molds used in these technologies are mainly formed by a method such as semiconductor microfabrication technology, photolithography, electron beam drawing, dry etching, etc. From the compatibility with these technologies, about several hundred μm A silicon wafer, quartz, or a plated metal material is used.

  These are generally thin, and it is difficult not only to apply pressure evenly but also to support the mold.

  In Patent Document 3, it is proposed to support a mold made of a metal material such as Ni via an elastic body. However, no consideration is given to deformation of the mold due to pressure or heat during pressing.

  For example, even when a resin is processed (transferred to a resin), a pressure of 10 MPa or more is required, but for a silicon mold having a thickness of about 500 μm and a length of about 10 mm, this pressure is supported by supporting both ends of the mold. It can be determined by a simple calculation that a deflection of about several hundreds of μm will occur when a voltage is applied.

  Further, when a thin mold of 1 mm or less is used, it is difficult to fix it to the press apparatus, and a problem arises when peeling from the molded product. Even if an adhesive or the like is used to fix the mold and the press device, it is difficult to avoid uneven pressure and deterioration of mounting accuracy during pressurization.

  Further, since the mold itself is thin, the mold is warped due to the difference in thermal expansion coefficient from the adhesive layer and the fixing portion of the press apparatus, and the press accuracy is deteriorated.

  The present invention has been made in order to avoid the above problems, and in forming a fine structure on a substrate (molded material) by a method such as nanoimprinting or hot embossing, it is easy to support the pressing device, It is another object of the present invention to provide a fine processing mold that can prevent deformation and distortion due to pressurization and heating during pressing and can be processed with high accuracy and low cost.

  The invention according to claim 1 includes a thin piece mold in which a fine structure is formed, and a pedestal made of a material having the same or substantially the same thermal expansion coefficient as that of the thin piece mold and having a thickness larger than that of the thin piece mold, The thin processing mold and the pedestal are joined to form a microfabrication mold.

  The invention according to claim 2 is the microfabrication mold according to claim 1, wherein the thin piece mold and the pedestal are both made of an inorganic material, or one of them is made of an inorganic material.

  According to a third aspect of the present invention, in the first aspect, the flake mold is made of one material selected from the group consisting of silicon, quartz, glassy carbon, diamond, diamond-like carbon, and glassy carbon. It is a mold for fine processing.

  According to a fourth aspect of the invention, the pedestal is made of one material selected from the group consisting of silicon, quartz, borosilicate glass, glassy carbon, diamond, diamond-like carbon, glassy carbon, and boron nitride. It is a type | mold for microfabrication of Claim 1 or 3.

According to a fifth aspect of the present invention, in the microfabrication mold according to any one of the first to fourth aspects, the thin piece mold and the pedestal are joined via a thin film containing SiO ₂ as a main component. It is.

  The invention according to claim 6 is the mold for fine processing according to any one of claims 1 to 5, wherein the thin piece mold and the pedestal are joined by hydrofluoric acid joining.

  The invention according to claim 7 is the mold for microfabrication according to claim 1, wherein the flake mold is made of diamond and formed on the pedestal by vapor phase synthesis.

In the invention according to claim 8, the pedestal has a shape in which the cross-sectional shape in at least one direction in the thickness direction is widened toward the surface opposite to the joint surface with the thin piece mold. It is a type | mold for microfabrication of any one of 1-7.
Here, the “azimuth” means a direction on a plane perpendicular to the thickness direction of the pedestal.

  According to the present invention, by adopting a structure in which a thin piece mold and a pedestal having a thickness larger than this are joined directly or via a thin film, it becomes easier to support the press apparatus, and the thermal expansion coefficient is the same or substantially the same. By creating a thin piece mold and a pedestal using materials, it has become possible to effectively prevent deformation and distortion due to heating during pressing. As a result, it has become possible to provide a fine processing mold capable of processing a substrate with high accuracy and low cost.

Embodiment
Embodiments of a micromachining die according to the present invention will be described below with reference to the drawings.

(1) Configuration of Micromachining Mold According to the Present Invention FIG. 1 is a longitudinal sectional view showing a configuration of an embodiment of a micromachining mold according to the present invention. A pedestal 3 is joined and formed via a thin film 4.

  For example, the thin mold 2 is formed by forming a fine pattern (fine structure) on a silicon wafer by using a photolithography method, processing the dry pattern by a dry etching method, and then cutting it into a predetermined size. It is possible to reduce the manufacturing cost of the flake mold 2 by forming a large number of flake molds 2 on a large-diameter silicon wafer at a time like a semiconductor production line and cutting it later (see Example 1 described later). ).

  In addition, this invention is especially suitable when the thickness of the thin piece type | mold 2 is 1 mm or less.

  The pedestal 3 is formed by cutting a single crystal silicon ingot, which is the same material as the thin piece mold 2 (that is, a material having the same thermal expansion coefficient), for example, so as to be thicker than the thin piece mold 2. The pedestal 3 can be easily created by machining if it satisfies the requirement of sufficient flatness.

  By adopting a structure in which the flake mold 2 and a thicker base 3 are bonded together, it is possible to maintain the mechanical strength that can withstand the pressure during pressing, and to support the pressing device and peel it from the molding material. It becomes possible to give the pedestal 3 a function that makes it easy.

  For example, it is preferable to form the pedestal 3 by machining so that the cross-sectional shape in a certain direction in the thickness direction is a flared shape, for example, a trapezoidal shape, as shown in FIG. Thereby, as will be described later, it can be easily and reliably supported by the pressing device.

The thin film 4 is formed by, for example, forming an SiO ₂ layer by the CVD method on the upper surface (horizontal surface on the side having a smaller area) of the pedestal 3. And the mold 1 for microfabrication is obtained by joining the surface of the thin piece mold 3 on the anti-concave / convex pattern side and the surface of the thin film 4 by, for example, a hydrofluoric acid joining method.

As described above, the thin film 4 made of SiO ₂ (quartz) is formed at the interface between the thin piece mold 2 and the pedestal 3 and the hydrofluoric acid bonding is performed, so that the bonding can be easily performed only by pressing at about room temperature to 80 ° C.

  In this case, the surface on which the fine pattern is formed is protected with a resin such as a photoresist, and the bonding can be performed while protecting the pattern surface by removing with an organic solvent after the bonding. Even if the thin film 4 is formed at the interface between the flake mold 2 and the pedestal 3, if it is very thin, problems such as warping do not occur, and the mechanical accuracy does not deteriorate.

(2) Pattern Forming Method Using Micromachining Mold According to the Present Invention FIG. 2 is a longitudinal sectional view for explaining a method for forming a pattern on a molding material using the micromachining mold according to the present invention. is there.

  First, the micromachining die 1 obtained as described above is mounted on the head 5a of the pressing device 5 in which a heater (not shown) is embedded, while the fixed base 5b of the pressing device 5 is to be processed. The material 6 to be molded is fixed (see FIG. 5A). Then, the heater 5 is turned on, the head 5a heated to a predetermined temperature is lowered, the thin piece mold 2 is pressed against the material 6 to be molded, and pressure and temperature are applied (see FIG. 5B). Next, the heater 2 is turned off and cooled to room temperature while pressing the thin piece mold 2 against the molding material 6, and then the head 5 a is lifted and extracted to transfer a fine pattern to the molding material 6 (the same figure). (See (c)).

  The pedestal 3 has a trapezoidal shape in which the cross-sectional shape in a certain direction in the thickness direction spreads toward the surface (bottom surface) 3b opposite to the joint surface (upper surface) 3a with the thin mold 2. For this reason, as shown in FIG. 2A, for example, the trapezoidal section of the pedestal 3 is formed on both sides by the supporting means 7 including a fixing portion 7a fixed to the head 5a with a screw and a pressing portion 7b connected to a spring. It is possible to easily and reliably support the pedestal 3 on the head 5a of the pressing device 5, and to peel off after pressing can be performed with high accuracy in combination with the following deformation preventing effect.

  In addition, since the same material (silicon in this example) is used for the thin piece mold 2 and the pedestal 3, both have the same coefficient of thermal expansion, so that the thin piece mold 2 and / or the pedestal 3 are warped by heating during pressing. Is also unlikely to occur, and peeling between the flake mold and the pedestal is unlikely to occur.

  Furthermore, since silicon has a low coefficient of thermal expansion of 2 to 4 ppm / ° C. and high thermal conductivity, it is not easily deformed or distorted by heat and is known as a material having excellent characteristics as a mold material for nanoimprint technology. .

  Therefore, by using the microfabrication mold according to this embodiment, deformation and distortion due to heat during pressing can be effectively prevented, and a substrate having a fine structure can be processed with high accuracy and low cost.

[Modification]
In the above embodiment, the thin piece mold and the pedestal are examples using the same thermal expansion coefficient (that is, the same material). However, as long as the thin flake mold and / or the pedestal are not substantially deformed or distorted. Alternatively, a material having substantially the same thermal expansion coefficient may be used. Here, the material having substantially the same thermal expansion coefficient means a material in which the thermal expansion coefficient of the pedestal material is within ± 2 ppm / ° C. with respect to the thermal expansion coefficient of the thin piece type material. In addition, as a measuring method of a thermal expansion coefficient, JIS R1618 "The measuring method of the thermal expansion by the thermomechanical analysis of fine ceramics" is mentioned.

  In addition, although the thermal expansion coefficient varies depending on the temperature, it is desirable to select a material with a small difference in thermal expansion coefficient in the operating temperature range (from the heating temperature during pressing to the room temperature after cooling). It is preferable that the difference in thermal expansion coefficient is 1 ppm / ° C. or less. The heating temperature at the time of pressing is, for example, about 100 to 150 ° C. when the material to be microprocessed is a resin, and about 400 to 600 ° C. when the material to be microprocessed is a glass-based material.

  In the above embodiment, an example in which an inorganic material (silicon in this example) is used for both the thin piece mold and the pedestal has been described. However, both may be a noble metal material, or one may be an inorganic material and the other may be a noble metal material.

  In addition to silicon, quartz, glassy carbon, diamond, diamond-like carbon, or glassy carbon can be used as the inorganic material used for the flake mold.

  As an inorganic material used for the pedestal, quartz, borosilicate glass, glassy carbon, diamond, diamond-like carbon, glassy carbon, or boron nitride can be used in addition to silicon.

  Of the inorganic materials used for both the flake mold and the pedestal, silicon, borosilicate glass, and glassy carbon have substantially the same thermal expansion coefficient, and therefore, it is particularly preferable to use them in combination as appropriate. For example, as shown in FIG. 4, silicon and Pyrex glass (a kind of borosilicate glass; “Pyrex” is a registered trademark of Corning, USA) has a thermal expansion coefficient of about 400 ° C. or less. Match. SD1 glass and SD2 glass (both trade names of HOYA) have values very close to the thermal expansion coefficient of silicon. For example, in the case of SD2 glass, 3.20 ppm / ° C. (30 to 300 ° C.) and 3 A value of .41 ppm / ° C. (30-450 ° C.) is shown.

  As materials used for the flake mold and the pedestal, in addition to the above, tungsten carbide (WC), titanium carbide (TiC), aluminum oxide, alumina ceramic, zirconium carbide and other metal carbides, metal oxides, metal nitrides, A metal boron compound or the like, or a refractory metal having a small thermal expansion coefficient such as tungsten, tantalum, or molybdenum can also be used.

  When quartz is used for the thin piece mold, the base 3 is also made of quartz so that it can be directly joined by hydrofluoric acid joining without using a thin film.

  Further, when diamond is used as the thin piece material, for example, diamond may be formed on the pedestal by vapor phase synthesis.

  Moreover, although the example which joins a thin piece type | mold and a base via a thin film was shown in the said embodiment, you may join directly without a thin film. As described above, for example, when quartz is used for the thin piece mold, the base 3 can be made of quartz so that it can be directly joined by hydrofluoric acid joining. In addition, by using a method such as anodic bonding or plasma activation bonding, direct bonding can be performed without a thin film at a low temperature of 400 ° C. or lower.

  Furthermore, it is also possible to join using a low melting point metal such as solder. In addition, low melting point metal tends to have low strength, and there is a concern about deformation during pressurization and heating. It can be avoided. Specifically, the thickness of the bonding layer (thin film) is preferably about submicron or less.

In the above embodiment has illustrated a SiO ₂ as the material of the thin film may be one composed mainly of SiO _2, may be used such as water glass.

  Moreover, although the example which makes the cross-sectional shape of the thickness direction of a base into a trapezoid was shown in the said embodiment, it should just be a shape of hem-spreading, for example, the hypotenuse of a trapezoid may be curvilinear.

  In the above-described embodiment, an example in which only the cross-sectional shape of one azimuth in the thickness direction of the pedestal is a flared shape is shown. For example, the cross-sectional shape of two perpendicular directions (two directions) is trapezoidal and is supported from two perpendicular directions, so that it can be fixed more reliably without rattling.

  In this example, the micromachining mold described in the above embodiment was created. First, a pattern was formed on a silicon wafer (silicon substrate) using a photolithography method, and processing was performed by dry etching. The silicon substrate used in this example was a 200 mm diameter, 0.7 mm thick material that can be processed on a normal semiconductor production line. Using. The pedestal was formed by machining a 3 mm thick flat plate cut out from a single crystal silicon ingot into a trapezoidal cross section in the thickness direction by machining.

The thin piece mold and the pedestal were joined by the procedure shown in FIG. First, the surface of the silicon wafer on which the fine pattern is formed is covered with a photoresist resin to protect it (see FIG. 1A), cut into a size of 10 mm square by dicing, and this is made into a thin piece type (FIG. 2B). )reference). On the other hand, a SiO ₂ film having a thickness of 0.1 μm is formed on the pedestal by CVD, and after washing both the thin piece mold and the pedestal, dilute hydrofluoric acid is applied and both are pressurized and bonded at room temperature. (Hydrofluoric acid bonding method) (see FIG. 3C). Finally, the resin covering the surface of the silicon wafer was removed with an organic solvent and washed to obtain a microfabrication mold (see FIG. 4D).

  The microfabrication mold thus obtained is mounted on the head of a press device in which a heater is embedded, and pressed into a PMMA resin or thermoplastic resin formed on a silicon substrate as a molding material. The pattern was transferred (see FIG. 2 described above). Since the cross-sectional shape of the pedestal is trapezoidal, it can be easily supported by the support means as shown in FIG. 2 (a), and can be easily peeled off from the molding material after pressing. did it. It was also confirmed that the fine pattern was transferred with high accuracy.

  In this embodiment, a case where diamond is used as a thin piece type will be described. Carbon-based materials such as diamond, diamond-like carbon, and glassy carbon not only have high hardness and excellent durability, but also have a low thermal expansion coefficient (small misalignment during heating) and high thermal conductivity ( It is an excellent material for forming a flake mold because it has the property that heat is transmitted well. In general, it is difficult to react with other materials, and since it has a large surface energy, it is difficult to adhere to the material to be processed, and it has excellent releasability.

  A diamond flake mold was prepared as follows. That is, after forming a fine pattern on a silicon substrate, polycrystalline diamond was deposited by CVD. Then, the surface of the diamond was polished and flattened, and silicon was dissolved to obtain a diamond flake mold.

In the case of a diamond flake type, the base material is preferably diamond. However, since the base material is very expensive, it is practical to use other materials for the base as a structural material. Diamond has a low coefficient of thermal expansion of about 1 ppm / ° C. Therefore, by using a material with a low coefficient of thermal expansion such as SiO ₂ (thermal expansion coefficient of about 0.5 ppm / ° C) or some sintered materials, High accuracy can be maintained. Since the pedestal portion is also required to have heat transfer performance as described above, a BN sintered body (boron nitride; thermal expansion coefficient 1.8 ppm / ° C., thermal conductivity 8.2 W / (m · K)) is used here. Using.

The thin piece mold and the pedestal can be joined by the same hydrofluoric acid joining method as in the first embodiment by forming a thin SiO ₂ thin film on each of the thin piece mold and the pedestal. In addition, by forming a metal film such as aluminum as thin as about several hundreds nm and using this as a bonding layer (thin film), it is possible to form a mold for microfabrication by other bonding methods such as plasma bonding.

It is a longitudinal cross-sectional view which shows the structure of one Embodiment of the type | mold for microfabrication which concerns on this invention. It is a longitudinal cross-sectional view for demonstrating the method of forming a pattern in a to-be-molded material using the type | mold for microfabrication which concerns on this invention. In Example 1, it is a longitudinal cross-sectional view for demonstrating the procedure which joins a thin piece type | mold and a base. It is a graph which shows the relationship between temperature in a silicon | silicone and pyrex glass, and a thermal expansion coefficient.

Explanation of symbols

1: Micro processing mold 2: Thin mold 3: Pedestal 3a: Bonding surface (upper surface)
3b: Surface (bottom surface) opposite to the bonding surface 3a
4: Thin film 5: Press device 5a: Head 5b: Fixing base 6: Molding material 7: Support means 7a: Fixing part 7b: Pressing part

Claims (8)

  A thin piece mold in which a fine structure is formed, and a pedestal made of a material having the same or substantially the same thermal expansion coefficient as that of the thin piece mold and having a larger thickness than the thin piece mold, and the thin piece mold and the pedestal are joined to each other A mold for microfabrication characterized by being made.   The mold for microfabrication according to claim 1, wherein the thin piece mold and the pedestal are both made of an inorganic material, or one of them is made of an inorganic material.   2. The mold for microfabrication according to claim 1, wherein the flake mold is made of one material selected from the group consisting of silicon, quartz, glassy carbon, diamond, diamond-like carbon, and glassy carbon.   The fine structure according to claim 1 or 3, wherein the pedestal is made of one material selected from the group consisting of silicon, quartz, borosilicate glass, glassy carbon, diamond, diamond-like carbon, glassy carbon, and boron nitride. Mold for processing. The mold for microfabrication according to any one of claims 1 to 4, wherein the thin piece mold and the pedestal are joined via a thin film containing SiO ₂ as a main component.   The mold for microfabrication according to any one of claims 1 to 5, wherein the thin piece mold and the pedestal are joined by hydrofluoric acid joining.   The fine processing mold according to claim 1, wherein the flake mold is made of diamond and formed on the pedestal by vapor phase synthesis. 8. The pedestal according to claim 1, wherein a cross-sectional shape of at least one direction in a thickness direction of the pedestal is a shape that spreads toward the surface opposite to the joint surface with the thin piece mold. The mold for microfabrication described.

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