JP2005053198A - Method for molding minute uneven shape - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To materialize easy resin demolding without needing galvanization, electrocasting, etc., in order to transfer a minute uneven shape of a high aspect ratio or a smooth surface and the transfer molding of the minute uneven shape. <P>SOLUTION: The surface of a silicon substrate having the minute uneven shape of the high aspect ratio is made hydrophilic and used as a transfer mold. After a resin is applied on the surface of the transfer mold and hardened, a resin part is peeled off from the transfer mold, for example, by immersing the resin part in a hot water, so that the resin of the minute uneven shape of the high aspect ratio or the smooth processing surface can be transfer-molded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a manufacturing technique for realizing mass productivity improvement and cost reduction of microfabricated parts used for sensors, electric circuits, optical parts and the like.

  In recent years, with the miniaturization of sensors, the reduction in line width of electric circuits, and the multi-functionalization of optical components, various devices are required to be miniaturized and highly functional. Due to such demands, development of technology for microfabrication of various parts on the micrometer order is underway. For example, development of small sensors using MEMS (Micro Electro Mechanical System) technology, AWG (Arrayed Wave-Guide) used in D-WDM (Dense Wavelength Division Multiplexing) systems that enable high-capacity high-speed optical communication The microfabrication technology of micrometer order is used.

  In order to expand these high-performance and fine devices for consumer use, cost reduction is being promoted by developing mass production technology. For example, a microlens array used for a liquid crystal display can be mass-produced and reduced by transferring a structure on the order of several tens to several hundreds of micrometers to a resin using a stamper as disclosed in JP-A-05-134103. Cost reduction is realized. In recent years, it has begun to attract attention to realize mass production and cost reduction of various devices and parts by transfer molding such a micro structure on the order of micrometers or less.

  Examples of the resin transfer molding technique using a mold such as a stamper generally include an injection molding method and a hot embossing method. A typical example of the injection molding method is transfer molding of an optical disk substrate such as a CD or DVD as described in Patent Document 1 (Japanese Patent Laid-Open No. 05-342642) and Patent Document 2 (Japanese Patent Laid-Open No. 07-210901). Transfer of fine structure is realized. Even in the hot embossing method, as described in Patent Document 3 (Japanese Patent Laid-Open No. 2001-146017), transfer molding of an inkjet head or the like having a fine structure is possible.

However, when transferring a submicron-order fine structure by injection molding, the aspect ratio is limited to about 2 because the resin is not only difficult to enter the fine part of the mold but also difficult to peel off from the transfer mold. However, there is a problem that transfer molding of a structure having a higher aspect ratio cannot be performed. In addition, when a high-aspect-ratio submicron-order structure is transferred and molded by the hot embossing method, it is necessary to apply a high pressure to the workpiece, which causes a problem that the apparatus becomes large. Further, both the injection molding method and the hot embossing method are basically formed of a thermoplastic resin, and are not suitable for forming a thermosetting resin or an ultraviolet curable resin.
Furthermore, when producing stampers by injection molding or hot embossing, it is generally necessary to perform operations such as transfer plating and electroforming, which increases the roughness of the stamper surface, making it difficult to form a smooth surface. There is a problem of becoming. In addition, when a silicon substrate is used as a transfer mold, there is a problem that release from the resin does not work because the adhesion between the silicon surface and the resin is generally good.
Japanese Patent Laid-Open No. 05-342642 JP 07-210901 A JP 2001-146017

  The object of the present invention is to transfer a fine uneven shape with a high aspect ratio without requiring a work such as plating or electroforming to transfer a fine uneven shape with a high aspect ratio or a smooth surface. It is to realize molding. Further, the object is to realize transfer molding of a fine concavo-convex shape having a high aspect ratio with respect to various resins and transfer molding of a smooth surface, which cannot be achieved by the conventional technology, by a simple process.

  In the present invention, a silicon substrate having a fine concavo-convex shape and having a hydrophilic surface is used as a transfer mold, a resin is applied to the surface of the transfer mold and solidified, and then the resin portion is peeled off from the transfer mold. It is a forming method characterized by transferring an uneven shape.

  According to the present invention, easy release from the molding resin is possible. Because the silicon surface that is hydrophobic is not in direct contact with the molding resin, but because the hydrophilic silicon oxide layer is in contact with the molding resin, the bonding force with the hydrophobic molding resin can be weakened. Conceivable. Moreover, since silicon processing technology can be utilized, it is possible to easily produce a transfer mold having a fine uneven shape having a high aspect ratio. Further, by adjusting the viscosity (concentration) of the liquid resin applied to the surface of the transfer mold, it is possible to easily transfer a fine uneven shape having a high aspect ratio. In addition, since any resin can be molded as long as the resin to be molded becomes liquid in this method, thermosetting resins and ultraviolet curable resins, which were relatively difficult by the injection molding method and hot embossing method, can be used. Can be easily formed. In addition, since this method does not require work such as plating or electroforming to produce the transfer mold, it is possible to maintain a smooth surface of the transfer mold itself, thereby smoothing the surface of the workpiece. Can be formed.

  Furthermore, in the present invention, the surface hydrophilization treatment is preferably performed by forming a silicon oxide layer on the silicon substrate surface.

By forming the silicon oxide layer in this manner, it is not necessary to make the surface hydrophilic when the transfer mold is used again, and it is possible to use the transfer mold as many times as is convenient. At this time, the baking treatment for forming the silicon oxide layer is preferably performed in an oxygen atmosphere. More preferably, the firing time can be shortened by performing the firing treatment in an O ₃ (ozone) atmosphere.

  Furthermore, in the present invention, the surface hydrophilization treatment is preferably performed by immersing a silicon substrate in hydrogen peroxide water.

  Thus, by making it hydrophilic by immersion in hydrogen peroxide water, the fine uneven shape formed on the surface of the silicon substrate is not deformed, and it becomes possible to mold the size and shape as designed on the transfer mold.

  Furthermore, in the present invention, in order to release the transfer mold from the resin portion, it is preferable to peel the resin portion by immersing the transfer mold together with warm water.

  By using warm water for releasing the mold in this way, it becomes possible to use the transfer mold as many times as possible without destroying the fine irregularities formed on the surface of the silicon transfer mold by resin peeling. Furthermore, with this transfer method, it is possible to mold the resin through a simple process such as application of resin and peeling with hot water, so there is no need to mold using a large apparatus like the injection molding method or hot embossing method. It is possible to realize molding by a simple process using an apparatus.

  Further, in the present invention, in order to release the transfer mold from the resin portion, it is preferable to peel the resin portion by immersing the transfer mold in a liquid under ultrasonic vibration.

  By using ultrasonic vibration to release the mold as described above, it is possible to shorten the time for removing the resin.

  Furthermore, in the present invention, in order to release the transfer mold from the resin portion, it is preferable to peel the resin portion by exposing the transfer mold to warm air with high humidity.

  By using warm air to release the mold in this way, it becomes possible to transfer even a resin that is easily deteriorated by immersion in the liquid, and the degree of freedom in selecting a resin material is increased.

Here, the fine uneven shape preferably has a depth in the range of 0.1 μm to 100 μm, a lower limit of the minimum width on the surface of the recess of 0.01 μm, and an upper limit of 100 μm. Further, the upper limit of the minimum width is more preferably 50 μm.
The aspect ratio calculated as depth / minimum width is preferably 1 or more, more preferably 2 or more. The thickness of the silicon oxide film formed on the silicon substrate is preferably 0.1 μm to 1 μm. The resin molded product obtained by the present invention is used for sensors, electric circuits, optical parts, and the like.

  As described above, if the transfer molding method of the present invention is used, the silicon substrate can be used as it is as a transfer mold, so that the high-aspect-ratio fine irregularities formed on the silicon transfer mold surface can be easily transferred to the resin. The smooth surface of the silicon transfer mold surface can be transferred to the resin as it is. Further, since transfer molding can be performed by a technique such as resin application and peeling with warm water, transfer molding can be performed by a simple process without using a large apparatus.

The inventors of the present invention have made the surface of a silicon substrate hydrophilized as a transfer mold, and after applying and hardening a resin on the transfer mold surface, the transfer mold is immersed in warm water or a liquid under ultrasonic vibration. The present inventors have found that the resin part can be easily peeled off from the transfer mold and molded.
Furthermore, it has been found that the transfer molding method can transfer a fine uneven shape with a high aspect ratio and a smooth surface. That is, a resist is applied to the surface of the silicon substrate, and the resist is exposed and developed so that the resist remains as an etching mask at a portion where the projections and depressions are fine by ordinary lithography. Then, the surface of the silicon substrate is exposed to an etching atmosphere. Etching may be wet etching or dry etching. Thereafter, by removing the etching mask, fine irregularities are formed on the surface of the silicon substrate. The etching mask may be used by patterning a SiO ₂ film or a SiN film in addition to the resist. At this time, by reducing the interval between the patterned etching masks and increasing the etching time for deep etching, a high-aspect uneven shape can be obtained.

As one of hydrophilic treatment methods for the silicon substrate surface, a silicon oxide layer may be formed on the surface of the silicon substrate on which fine irregularities are formed. The silicon oxide layer may be a thermally oxidized silicon film obtained by heat-treating a silicon substrate at 500 ° C. or higher in the presence of oxygen.
The transfer substrate is obtained by hydrophilizing the surface of the silicon substrate having the fine irregularities thus obtained. After the resin is applied to the surface of the transfer mold and hardened, the resin is immersed together with the transfer mold in warm water or a liquid under ultrasonic vibration, or exposed to the transfer mold on which the resin adheres to humidified warm air. Peel from the transfer mold. By such a simple process, it is possible to realize transfer molding of a fine concavo-convex shape having a high aspect ratio. In addition, what is necessary is just to adjust the viscosity (concentration) of the liquid fluorinated polyimide apply | coated according to the aspect-ratio of fine uneven | corrugated shape.
As the resin of the molding material, a thermosetting resin is preferable, and among them, a fluorinated polyimide resin is preferable because of excellent transferability of a fine uneven shape.
As the hydrophilic treatment, the silicon oxide thin film layer forming method can be formed by implanting oxygen ions into the surface of the fine irregular shape in addition to the high-temperature baking treatment. In addition to forming a silicon oxide thin film layer, it can be hydrophilized by immersing a silicon substrate in hydrogen peroxide water.

In order to peel the molded product from the silicon transfer mold, the temperature of the hot water is preferably 50 ° C. or higher. More preferably, the peeling time can be shortened by immersion under ultrasonic vibration. Further, instead of using warm water, the resin portion can be peeled by exposure to hot air with high humidity. Here, the humidity of the hot air is preferably 50% RH to 90% RH.
By such a simple process, the fine uneven shape 6 having a high aspect ratio can be transferred to a fluorinated polyimide resin.

  Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings.

An embodiment of the present invention will be described with reference to FIGS. In the process of this embodiment, first, a fine uneven shape 2 having an aspect ratio (b / a) = 2 or more is formed on the surface of the silicon substrate 1 (FIG. 1). Here, the width a of the recess on the surface of the silicon substrate was 0.3 μm, and the depth b of the recess was 0.6 μm. Here, the aspect ratio is b / a in FIG. This silicon substrate surface processing was performed by etching with a KOH solution using the patterned SiO ₂ film as a mask. A concave portion having a triangular cross section was obtained by using the <100> plane as the main surface of the silicon substrate. Next, the silicon substrate 1 whose surface was processed into a fine concavo-convex shape was baked at a high temperature of 1000 ° C. for 10 hours to form a silicon oxide thin film layer 3 on the surface of the fine concavo-convex shape to make it hydrophilic (FIG. 2). ).
The raw material polyamic acid solution was applied to the surface of the silicon transfer mold obtained by the above process by spin coating, and further dried at 380 ° C. to solidify the resin 4 (FIG. 3). As a result, a fluorinated polyimide resin copolymer represented by the chemical formula (1) was obtained.

At this time, the viscosity (concentration) of the solution to be applied was adjusted according to the aspect ratio of the fine uneven shape. Finally, the silicon transfer mold was immersed in warm water 5 at 70 ° C. to peel the fluorinated polyimide portion from the transfer mold in about 30 minutes (FIG. 4), and a polyimide film having fine irregularities on the surface was obtained ( FIG. 5).

A second embodiment of the present invention will be described with reference to FIGS. In the process of this example, a fine rectangular shape 8 having an aspect ratio (b / a) = 2 or more was first formed on the surface of the silicon substrate 7 (FIG. 6). The difference from Example 1 is that a vertical etching surface is formed by anisotropically etching the <111> surface of the silicon substrate as a main surface. Here, a is 1 μm and b is 2 μm. The process of forming a rectangular shape on the surface of the silicon substrate was performed by wet etching using the patterned SiO ₂ as a mask. Next, the silicon substrate 7 whose surface was processed into a fine rectangular shape was baked at a high temperature of 1000 ° C. for 10 hours, thereby forming a silicon oxide thin film layer 9 on the surface of the fine rectangular shape to make it hydrophilic (FIG. 7).

The same liquid as in Example 1 was applied to the surface of the silicon transfer mold obtained by the above process, and the resin 10 was hardened by drying at 380 ° C. (FIG. 8). At this time, the viscosity (concentration) of the solution to be applied was adjusted according to the aspect ratio of the fine rectangular shape. Finally, the silicon transfer mold was immersed in warm water 11 at 70 ° C., and the fluorinated polyimide portion could be peeled from the transfer mold in about 30 minutes (FIG. 9). As a result, a polyimide film having fine rectangular 12 irregularities with a high aspect ratio on the surface was obtained (FIG. 10).
In the above embodiment, fluorinated polyimide is used as a molding material, but it is of course possible to use a resin other than fluorinated polyimide.

This method of forming a fine uneven shape can be used for manufacturing because it is an optical component such as an optical waveguide.

It is a figure explaining the silicon substrate which has the fine uneven | corrugated shape of Example 1. FIG. FIG. 3 is a diagram illustrating a silicon transfer mold of Example 1. It is a figure explaining the process of apply | coating and drying resin to the transfer mold of Example 1. FIG. It is a figure explaining the process which peels the to-be-molded resin of Example 1 with warm water. It is a figure explaining the resin by which the fine uneven | corrugated shape of the high aspect ratio of Example 1 was transfer-molded. It is a figure explaining the silicon substrate which has the fine rectangular shape of Example 2. FIG. It is a figure explaining the silicon | silicone transfer mold of Example 2. FIG. It is a figure explaining the process of apply | coating and drying resin to the transfer mold of Example 2. FIG. It is a figure explaining the process which peels the to-be-molded resin of Example 2 with warm water. It is a figure explaining resin by which the fine rectangular shape of the high aspect ratio of Example 2 was transfer-molded.

Explanation of symbols

1: Silicon substrate, 2: Fine uneven shape 3: Silicon oxide thin film layer, 4: Resin 5: Hot water, 6: Fine uneven shape, 7: Silicon substrate, 8: Fine rectangular shape, 9: Silicon oxide thin film layer, 10: Resin 11: Hot water, 12: Fine rectangular shape

Claims (6)

  A silicon substrate having a fine concavo-convex shape and a hydrophilized surface is used as a transfer mold, a resin is applied to the surface of the transfer mold and solidified, and then the resin is peeled from the transfer mold to transfer the fine concavo-convex shape. A forming method characterized by:   The molding method according to claim 1, wherein the hydrophilization treatment of the surface is performed by forming a silicon oxide layer on a silicon substrate surface.   The molding method according to claim 1, wherein the surface hydrophilization treatment is performed by immersing a silicon substrate in hydrogen peroxide water.   The molding method according to any one of claims 1 to 3, wherein the resin is peeled from the transfer mold by immersing the transfer mold to which the resin is attached in warm water.   The molding method according to any one of claims 1 to 3, wherein the resin is peeled from the transfer mold by immersing the transfer mold to which the resin is attached in a liquid under ultrasonic vibration.   The molding method according to any one of claims 1 to 3, wherein the resin is peeled from the transfer mold by exposing the transfer mold to which the resin is adhered to humid air.

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