JP2007025305A - Method for manufacturing resist pattern, method for manufacturing substrate surface pattern, method for manufacturing mold, and method for manufacturing molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a resist pattern with a large level difference. <P>SOLUTION: First, (a) a positive resist 2 is applied on a substrate (optical substrate) 1 made of quartz or glass; (b) the resist 2 is exposed by using a gray scale mask 2, wherein the dose of exposure light is controlled to a range not to induce foaming in the resist 2; (c) the resist 2 is developed; then (d) the same gray scale mask 4 as the above mask is prepared to again expose the resist 2, wherein the dose of exposure light is also controlled to a range not to induce foaming in the resist 2; and (e) the resist 2 is again developed. Thus, a microlens comprising the resist 2 having a large SAG amount as a target is formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a resist pattern, a method for producing a substrate surface pattern, a method for producing a mold, and a method for producing a molding.

  As one of the microlens manufacturing methods, a method of exposing a photoresist and manufacturing a microlens corresponding to the exposure pattern has been generally used. As one of such methods, there is a method in which a photoresist is exposed and developed with a binarized pattern to form a resist shape having a cylindrical convex portion, and the surface shape of the resist is made spherical by thermal reflow. is there. However, with this method, it is easy to make a spherical shape, but it is difficult to make an aspheric shape.

  In order to manufacture an aspherical lens, a photoresist is exposed and developed using a grayscale mask, and an aspherical lens having an uneven shape corresponding to the gray degree (light transmittance) of the grayscale mask is manufactured. The method is used. However, the gray level of the gray scale mask is limited to a certain range. When the gray level is less than the lower limit, there is a problem that the aperture ratio of the gray scale mask is reduced and the manufacturing error is increased. Further, when the gray level exceeds the upper limit value, there is a problem in that the gray level becomes inaccurate due to an overlap with the light passing through the adjacent opening.

  In recent years, there has been an increasing demand for microlenses with high SAG content and high shape accuracy. Therefore, a positive resist is used because the shape can be formed with high accuracy corresponding to the light quantity distribution of the gray scale mask. However, when a gray scale mask is used, the range of the gray degree is limited as described above, so that there is a problem that the ratio of contrast applied at the time of exposure is limited. In order to increase the SAG amount with a gray scale mask having the same contrast ratio, the exposure amount may be increased or the exposure may be performed in multiple steps.

However, when the exposure amount is increased, there is a problem that N ₂ contained in the positive resist photoresist is vaporized and foamed. FIG. 5 is a diagram showing this example. FIG. 5 shows the amount of SAG and top film when a positive type photoresist is applied to a thickness of 88 μm, the gray level of the gray scale mask is set within a certain range, exposed, and developed to produce a microlens. The relationship between the amount of sliding and the exposure amount (exposure time) is shown. The amount of film slip at the position corresponding to the top of the lens indicates the amount lost by developing the portion corresponding to the portion of the gray scale mask having the lowest gray degree.

  Referring to FIG. 5, when the exposure amount (exposure time) exceeds 14000 ms, a foaming phenomenon occurs. Therefore, when this gray scale mask and photoresist are used, the maximum SAG amount of the microlens that can be manufactured is limited to about 60 μm.

  Such a foaming phenomenon occurs when the total exposure amount exceeds a predetermined value even when the exposure is performed in a plurality of times. This is presumably because the foaming phenomenon is determined by the energy accumulated in the photoresist.

  The above describes an example of manufacturing a microlens using a gray scale mask, but the same can be said when a photoresist is exposed using a mask having a binarized pattern. That is, in order to increase the level difference of the concavo-convex pattern to be formed, it is necessary to increase the exposure amount. However, because of the foaming phenomenon as described above, the exposure amount is limited, and therefore can be formed in a photoresist. There is a limit to the size of the step of the concavo-convex pattern.

  The present invention has been made in view of such circumstances, and a method of manufacturing a resist pattern having a large step, a method of manufacturing a substrate surface pattern using the resist pattern, a method of manufacturing a mold, and a molded object It is an object to provide a manufacturing method.

  A first means for solving the above problems is a resist pattern forming method in which a positive photoresist applied on a substrate is exposed to an exposure pattern and developed to form an uneven shape corresponding to the exposure pattern. In the resist pattern manufacturing method, exposure and development of the exposure pattern are repeatedly performed a plurality of times.

  The inventor has found that exposure of the exposure pattern and development are repeated a plurality of times, so that even if the exposure is performed with a large exposure amount as a total exposure amount, the foaming phenomenon of the photoresist does not occur. The reason for this is not clear, but in the case of a positive type photoresist, a portion that has received a large exposure amount is removed by development, so even when performing multiple exposures, when performing multiple exposures without performing development. In comparison, it is estimated that the energy actually stored in the photoresist is reduced. Thereby, it is possible to obtain a resist uneven shape having a large level difference while avoiding the foaming phenomenon. Needless to say, the exposure pattern (for example, the gray degree pattern of the gray scale mask) does not have to be the same in each exposure.

  The second means for solving the problem is the first means, wherein the exposure pattern is formed using a gray scale mask, and the uneven shape is a microlens shape. It is characterized by.

  According to this means, a microlens having a large SAG amount can be manufactured with high accuracy, and is particularly effective as a method for manufacturing an aspheric lens.

  The third means for solving the problem is to form a resist pattern by the resist pattern manufacturing method as the first means or the second means, and then simultaneously etch the photoresist and the substrate, A method for producing a substrate surface pattern comprising the step of transferring the resist pattern to a substrate.

  According to this means, a substrate surface pattern having a large uneven shape with a large step can be manufactured.

  A fourth means for solving the above-mentioned problem is characterized in that a transfer surface of a mold is constituted by the resist pattern manufactured by the resist pattern manufacturing method of the first means or the second means. This is a mold manufacturing method.

  According to this means, it is possible to manufacture a mold having a transfer surface having a large unevenness with a large step.

  According to a fifth means for solving the above problem, after forming a resist pattern by the method for producing a resist pattern of the first means or the second means, the photoresist and the substrate are simultaneously etched, A mold manufacturing method comprising a step of transferring a resist pattern to a substrate.

  According to this means, it is possible to manufacture a mold having a transfer surface having a large unevenness with a large step.

  A sixth means for solving the above-described problems includes a step of transferring a transfer surface of a mold manufactured by the mold manufacturing method of the fourth means or the fifth means to a molding object. It is a manufacturing method of the to-be-molded object made into.

  According to the present invention, it is possible to produce a concavo-convex shaped article having a large step on the surface.

  According to the present invention, there are provided a method for producing a resist pattern having good shape accuracy and a large level difference, a method for producing a substrate surface pattern using this resist pattern, a method for producing a mold, and a method for producing a molding. can do.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 illustrates an outline of a manufacturing method of a microlens (resist pattern having a large step, a substrate surface pattern using this resist pattern), a microlens mold, and a mold base material, which is an example of an embodiment of the present invention. It is a figure for doing.

First, a positive resist 2 is applied on a substrate (optical base material) 1 made of quartz or glass (a). The reason for using a positive resist as the resist is that, as described above, the correspondence between the distribution of the amount of light at the time of exposure and the resist shape after development is better for the positive resist than for the negative resist. It is. Then, the resist 2 is exposed using the gray scale mask 3. The exposure amount at this time is an exposure amount in a range where the resist 2 does not foam (b). Then, the resist 2 is developed (c). Next, the same gray scale mask 4 is prepared, and using this, the resist 2 is exposed again. The exposure amount at this time is also an exposure amount within a range where the resist 2 does not foam (d). Then, the resist 2 is developed again (e). In this manner, a microlens made of the resist 2 having a desired large SAG amount is formed. In the above description, the exposure and development of the resist 2 are performed in two steps, but can be performed in three or more steps.
In this state, the resist 2 can be used as a microlens, or a microlens mold or a matrix.

  When the resist 2 having the target shape is obtained in the state (e), the resist 2 and the substrate 1 are simultaneously dry etched to remove the resist 2, and the pattern of the resist 2 is transferred to the substrate 1. The substrate 1 having the shape of a microlens array on the surface can be obtained (f). At this time, due to the difference in etching rate between the substrate 1 and the resist 2, the pattern shape of the resist 2 and the pattern shape of the surface of the substrate 1 are not equal, but the resist pattern is obtained so that the desired pattern shape can be obtained on the surface of the substrate 1. The pattern shape of 2 is determined in advance. Through the above steps, a microlens array in which a lens shape is formed on the surface of the substrate 1 is completed. The substrate 1 may not be used as a microlens but may be used as a microlens mold or a mother mold. When used as a mold or a mother mold, the substrate 1 does not need to be manufactured with an optical member.

  An example of a process in which the above-obtained shape (e) or (f) shape is not used as a microlens but is used as a microlens mold or a matrix material. Is shown in FIG. In the example shown in FIG. 2, the substrate 1 having a microlens shape formed on the surface shown in FIG. 1 (f) is used as a mold or a matrix material.

  In FIG. 2, an ultraviolet curable resin 6 is placed on such a mold 5 by a dispenser or the like, and is molded by applying pressure from above with a surface plate 7 made of a quartz substrate or the like. Then, ultraviolet rays are irradiated through the surface plate 7 to cure the ultraviolet curable resin 6 (a). Then, when the ultraviolet curable resin 6 is peeled from the mold 5 and the surface plate 7, the microlens 8 is completed (b). In this way, a large number of resin microlenses can be manufactured from one mold 5.

  When the mold 5 is used as a matrix material, the cured ultraviolet curable resin 6 becomes the mold. An ultraviolet curable resin 10 is placed on a surface plate 11 made of quartz or the like by a dispenser or the like, and is molded by applying pressure from above with a mold 9 made of a cured ultraviolet curable resin 6. Then, ultraviolet rays are irradiated through the surface plate 11 to cure the ultraviolet curable resin 10 (c). Then, when the ultraviolet curable resin 10 is peeled from the mold 9 and the surface plate 11, the microlens 12 is completed (d).

A microlens using a resist was manufactured by a process as shown in FIG.
(1) After baking a positive resist on a glass substrate using a spinner, soft baking was performed. This process was repeated twice to make the resist thickness 87.5 μm.
(2) The exposure was performed using a gray scale mask. The exposure amount was set to a half of the total exposure amount for obtaining the target SAG amount, but within a range where foaming did not occur in the resist. Thereafter, the exposed substrate was placed in a developing solution after exposure, and development was performed. The developed resist was stored so as not to be exposed to ultraviolet rays.
(3) Exposure was again performed using a gray scale mask. The exposure amount was set to a half of the total exposure amount for obtaining the target SAG amount, but within a range where foaming did not occur in the resist. Thereafter, the exposed substrate was placed in a developing solution after exposure, and development was performed.

  FIG. 3 shows the relationship between the amount of exposure (per one time) and the amount of SAG for samples taken out after the first exposure and development and those subjected to the exposure and development up to the second time. Both exposures are performed with an exposure time of 14000 ms or less in which the resist foaming phenomenon does not occur. According to this, when exposure and development are performed twice, a SAG amount close to 80 μm is obtained. As shown in FIG. 5, in one exposure, the maximum value of the SAG amount is limited to 60 μm due to the foaming phenomenon, whereas a large SAG amount can be obtained.

  The changes in the γ characteristics of the resists that were exposed and developed only once and the two resists that were exposed and developed separately were investigated. The result is shown in FIG. In FIG. 4, the γ characteristic in exposure / development in which the thin line is only one time, and the γ characteristic in the case where the exposure / development is performed in two divided lines are shown. As can be seen from the figure, the amount of film slippage is larger and the slope of the γ characteristic is larger when the process is divided into two times than when it is performed only once. This is because, in the second exposure, the thickness of the resist is reduced particularly in the portion where the film was severed in the first exposure / development, so that the ultraviolet ray passing distance is shortened and attenuated in the middle. It is presumed that if the exposure / development is performed in two steps, the overall γ characteristics will be increased. If this property is utilized, a large film slip can be generated with a small change in gray level, which is effective in increasing the SAG amount.

  In the above description of the embodiment, the microlens and the method for manufacturing the mold have been described as examples. However, the present invention is not limited to such an application range, and for example, a binarized uneven pattern is formed. It is effective to make the level difference (difference between the maximum value and the minimum value) larger than the range that can be formed by one exposure / development when forming any uneven pattern such as formation. Note that the grayscale mask used for the second and subsequent times may be different from the first one.

The figure for demonstrating the outline | summary of the manufacturing method of the microlens (resist pattern with a big level | step difference, the substrate surface pattern using this resist pattern) which is an example of embodiment of this invention, a microlens type | mold, and a mold base material It is. It is a figure which shows the example of the process of using what has the shape of (e) of FIG. 1, or what has the shape of (f) as a microlens type | mold or a matrix material, without using it as a microlens. . It is a figure which shows the relationship between exposure amount (per time) and SAG amount of what was taken out as a sample after the first exposure and development, and what was exposed and developed up to the second time. It is a figure which shows the change of the (gamma) characteristic of a resist when the exposure and development are performed only once, and when exposure and development are performed in two steps. The amount of SAG when a positive type photoresist is applied to a thickness of 88 μm, exposure is performed with the minimum and maximum gray levels of the gray scale mask set to optimum values, and development is performed to produce microlenses. FIG. 6 is a graph showing the relationship between the amount of film slip and the top film slip.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Resist, 3 ... Gray scale mask, 4 ... Gray scale mask, 5 ... Mold, 6 ... UV curable resin, 7 ... Surface plate, 8 ... Micro lens, 9 ... Mold, 10 ... UV curable type Resin, 11 ... Surface plate, 12 ... Microlens

Claims (6)

A positive photoresist applied on a substrate is exposed to an exposure pattern and developed to form a concavo-convex shape corresponding to the exposure pattern, wherein the exposure pattern is exposed and developed. A method for producing a resist pattern, which is repeated a plurality of times. 2. The method for producing a resist pattern according to claim 1, wherein the exposure pattern is formed using a gray scale mask, and the uneven shape is a microlens shape. A method of forming a resist pattern by the method for producing a resist pattern according to claim 1 or 2, and simultaneously etching the photoresist and the substrate to transfer the resist pattern to the substrate. A method for manufacturing a substrate surface pattern. A mold manufacturing method, wherein a transfer surface of a mold is formed by the resist pattern manufactured by the resist pattern manufacturing method according to claim 1. A method of forming a resist pattern by the method for producing a resist pattern according to claim 1 or 2, and simultaneously etching the photoresist and the substrate to transfer the resist pattern to the substrate. Mold manufacturing method. 6. A method for manufacturing a molding, comprising a step of transferring a transfer surface of a mold manufactured by the method for manufacturing a mold according to claim 4 or 5 to the molding.

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