JP4747893B2 - Microlens manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a macro lens with good sphericity suitable for use in combination with an optical fiber or the like by anisotropic dry etching.

Conventionally, a method of manufacturing a microlens array by transferring a plurality of convex spherical resist (photosensitive resin) patterns on the surface of a transparent substrate by anisotropic dry etching is known. Further, as a method of manufacturing this type of microlens array, there is known a method of controlling the flow rate ratio of two or more kinds of fluorocarbon gases for the purpose of improving the sphericity of the lens during dry etching ( For example, see Patent Document 1).
JP 2002-321951 A

  According to the above-described conventional technology, there is a problem in that expensive control is required to perform precise control, resulting in high cost.

  An object of the present invention is to provide a novel method for producing a microlens that can improve the sphericity by a simple method.

The manufacturing method of the microlens according to the present invention is as follows:
Forming a circular resist layer on one main surface of a transparent substrate made of a transparent oxide by photolithography,
Applying a heat reflow treatment to the resist layer to give a convex spherical pattern to the resist layer;
Forming a convex spherical lens by transferring a convex spherical pattern of the resist layer to one main surface of the transparent substrate by anisotropic dry etching,
In the anisotropic dry etching process, the etching is performed in a state where the ratio of carbon and oxygen generated during the etching is set so as to obtain a desired sphericity for the lens.

  According to the inventor's research, carbon generated during etching when a convex spherical pattern of a resist layer is transferred to one main surface of a transparent substrate by anisotropic dry etching to form a convex spherical lens. It was found that the sphericity of the lens can be controlled by controlling the ratio of oxygen to oxygen. Therefore, in the manufacturing method of the present invention, the etching is performed with the ratio of carbon and oxygen generated during etching set to obtain a desired sphericity for the lens. Is obtained.

  In the manufacturing method of the present invention, in the anisotropic dry etching treatment, the etching is performed in a state where the transparent substrate is placed on the graphite electrode plate in an etching chamber, and the exposed area of the graphite electrode plate is set to S1, When the projected area of the convex spherical pattern of the resist layer on the transparent substrate is S2, and the exposed area of the oxygen generation part including the transparent substrate is S3, the area ratio (S1 + S2) / S3 is a desired sphericity for the lens. The etching may be performed in a state set to obtain the above. In this way, the ratio of carbon and oxygen can be easily controlled by placing a quartz plate or the like on the graphite electrode plate in addition to the transparent substrate as the oxygen generating part, and a lens with good sphericity can be reduced. It can be formed at a cost.

  According to the present invention, in the anisotropic dry etching process for forming a lens, the ratio of carbon and oxygen generated during etching is controlled, so that a lens having a good sphericity can be obtained. . When the area ratio (S1 + S2) / S3 is set, a lens with good sphericity can be formed easily and at low cost. Further, in the microlens, when the sphericity of the lens is improved, the aberration is improved and the light beam is focused almost at one point. For this reason, when a light beam is introduced into the optical fiber through the lens, the light beam can be incident on the core portion of the optical fiber from the lens with low loss.

  FIGS. 1-3 show the manufacturing method of the micro lens array based on one Embodiment of this invention, and process (1)-(3) corresponding to each figure is demonstrated sequentially.

(1) On one main surface of the quartz substrate 10 as a transparent substrate, circular resist layers S _{1 to} S ₄ are formed by photolithography. In the photolithography process, a photoresist is applied to the substrate surface by a spin coating method, and then the applied resist is exposed and developed to obtain resist layers S _{1 to} S ₄ having a thickness t = 50 to 60 μm.

(2) By applying a heat reflow process to the resist layers S _{1 to} S ₄ , a convex spherical pattern is imparted to each resist layer such as S ₁ . The heat treatment temperature at this time can be about 170 to 200 ° C., and the resist height h after reflow can be about 80 to 100 μm.

(3) Convex spherical lenses L _{11 to} L ₁₄ made of quartz are formed by transferring the convex spherical pattern of each resist layer such as S ₁ to the quartz substrate 10 by anisotropic dry etching. As the anisotropic dry etching process, a reactive ion etching process using a fluorocarbon-based gas (for example, CF ₄ gas) as an etching gas can be used.

  In the dry etching process, for example, as shown in FIG. 4, rectangular quartz plates (quartz strips) 14a are formed on the graphite electrode (cathode electrode) plate 12 along the four sides of the square quartz substrate 10 in the etching chamber. ˜14d are arranged without gaps, and between the quartz plates 14a and 14b, between the quartz plates 14b and 14c, between the quartz plates 14c and 14d, and between the quartz plates 14d and 14a, square quartz plates 16a and 16b, Etching is performed in a state where 16c and 16d are arranged without a gap. The reason why the quartz plates 14a to 14d and 16a to 16d are arranged around the quartz substrate 10 in this way is to control the sphericity of the lens by controlling the ratio of carbon and oxygen generated during etching. . That is, the quartz substrate 10 and the quartz plates 14a to 14d and 16a to 16d act as an oxygen generating material during etching, and oxygen acts to increase the etching rate of the resist. Therefore, by controlling the ratio of carbon to oxygen, The sphericity of the lens can be controlled.

  When the area ratio of the carbon generation part to the oxygen generation part in the etching chamber is a carbon area ratio C / Q, the area ratio C / Q is expressed by the following equation (1).

C / Q = (S1 + S2) / S3 (1)
Here, S1 is the exposed area of the graphite electrode plate 12,
S2 is the projected area of the resist pattern on the quartz substrate 10,
S3 is an exposed area of the oxygen generation part including the quartz substrate 10 and the quartz plates 14a to 14d and 16a to 16d. Since the resist pattern is a carbon supply source, the area of the carbon generating portion was set to (S1 + S2). By arranging the quartz plates 14a to 14d and 16a to 16d as shown in FIG. 4, the exposed area S1 of the graphite electrode plate 12 is reduced, and the oxygen generating parts (10, 14a to 14d, 16a to 16d) are reduced. The exposed area increases, and the area ratio can be set within an appropriate range of 7 to 45 (preferably 10 to 32).

The quartz plates 14a to 14d and 16a to 16d are arranged without a gap, but may be arranged with a gap of 1 mm or more. Further, quartz as the oxygen generating material is not limited to a quadrilateral shape or a plate shape, but may be a circular shape, a polygonal shape, a cylindrical shape, a polygonal columnar shape, or the like. Further, the oxygen generating material is not limited to quartz, and may be an optical glass, an oxide such as TiO ₂ or the like.

  FIG. 5 shows a first modification of the resist pattern arrangement on the quartz substrate 10 in the etching chamber. In this example, the number of resist layers S arranged on the quartz substrate 10 is reduced as compared with the case of FIG. 4 and the resist layers S are concentrated on the central portion of the quartz substrate 10 to concentrate the resist on the quartz substrate 10. The frame-like region 10F is exposed around the group of layers S. In this way, at the area ratio (S1 + S2) / S3, the projected area S2 of the resist pattern onto the quartz substrate 10 decreases and the exposed area S3 of the quartz substrate 10 serving as the oxygen generating portion increases.

  FIG. 6 shows a second modification of the resist pattern arrangement on the quartz substrate 10 in the etching chamber. In this example, the number of resist layers S arranged on the quartz substrate 10 is reduced as compared with the case of FIG. 4, and a set of five resist rows is arranged with a wider interval than in the case of FIG. In the substrate 10, the surface region 10G surrounding the 14 resist rows is exposed. In this way, at the area ratio (S1 + S2) / S3, the projected area S2 of the resist pattern onto the quartz substrate 10 decreases, and the exposed area of the quartz substrate 10 as the oxygen generating portion increases.

  FIG. 7 shows a conventional example of the quartz substrate arrangement in the etching chamber, which corresponds to the quartz substrate arrangement of FIG. 4 with the quartz plates 14a to 14d and 16a to 16d removed.

  Next, referring to FIG. 8, a method for measuring the true spherical deviation will be described. In FIG. 8, a resist layer S is formed on the surface 10 a of the quartz substrate 10, and a true sphere (ideal spherical surface) IS is indicated by a broken line in relation to the resist layer S. The horizontal axis indicates the distance from the lens center, and the vertical axis indicates the height. The lens center corresponds to the center of the true sphere. As a measuring device, a non-contact type three-dimensional measuring device was used, and the shape of the resist layer S and the lens was measured in a range of −550 μm to 550 μm at 3 μm / step. Each measurement data was compared with true sphere (ideal sphere) data to determine true sphere deviation (deviation amount from true sphere [ideal sphere]).

  In FIG. 9, the evaluation result of a spherical displacement is shown about Comparative Examples 1-3 and Examples 1-7. Comparative Example 1 corresponds to the conventional example shown in FIG. 7, and the control method of the area ratio C / Q is a case without a quartz plate, and C / Q = 60. Comparative Example 2 is a case where the quartz plate arrangement shown in FIG. 4 is adopted, and C / Q = 3.3. Comparative Example 3 was a case where the quartz plate arrangement shown in FIG. 4 was adopted, and C / Q = 50.2.

  Example 1 was a case where the quartz plate arrangement shown in FIG. 4 was adopted, and C / Q = 10.2. In Example 2, the quartz plate arrangement shown in FIG. 4 was employed, and C / Q = 17.5. In Example 3, the quartz plate arrangement shown in FIG. 4 was employed, and C / Q = 31.3. Example 4 is a case where the quartz plate arrangement shown in FIG. 4 was adopted, and C / Q = 6.9. In Example 5, the quartz plate arrangement shown in FIG. 4 was employed, and C / Q = 45.6. In Example 6, as shown in FIG. 5, the exposed frame-like region 10F having no resist pattern was provided on the outer periphery of the quartz substrate 10, and C / Q = 20.1. In Example 7, as shown in FIG. 6, the exposed surface region 10G was enlarged by arranging the resist patterns sparsely, and C / Q = 20.1.

  In any of Comparative Examples 1 to 3 and Examples 1 to 7, the lens diameter was 1050 μm, the effective diameter was 850 μm, the etching method was RIE (reactive ion etching), and the RF (high frequency) power was 220 W. The evaluation standard for the vacuum deviation was a good (◯ mark) if the sum of the absolute values of the positive and negative sphere deviations after RIE was 1 μm or less, and a bad (× mark) if greater than 1 μm. . FIG. 9 shows the values of plus and minus true sphere deviation before RIE and plus and minus true sphere deviation after RIE for each of Comparative Examples 1 to 3 and Examples 1 to 7. The direction value and the evaluation result of true spherical deviation are shown. As can be seen from FIG. 9, in Examples 1 to 7, C / Q = 6.9 to 45.6, and a lens satisfying the evaluation criteria can be obtained.

  10 to 13 each show the relationship between the distance from the lens center and the amount of deviation from the ideal spherical surface (true sphere). FIG. 10 shows the measurement result of true sphere deviation before RIE for Example 2, and FIG. 11 shows the measurement result of true sphere deviation after RIE for Example 2. 12 shows the measurement result of true sphere deviation after RIE for Comparative Example 1, and FIG. 13 shows the measurement result of true sphere deviation after RIE for Comparative Example 2. When FIG. 11 is compared with FIG. 12 or FIG. 13, the effect of improving the sphericity according to the present invention is apparent.

It is sectional drawing which shows the resist layer formation process in the manufacturing method of the micro lens array which concerns on one Embodiment of this invention. It is sectional drawing which shows the heating reflow process following the process of FIG. FIG. 3 is a cross-sectional view showing a dry etching process following the process of FIG. 2. It is a perspective view which shows the example of arrangement | positioning of the quartz substrate and quartz plate in an etching chamber. It is a perspective view which shows the 1st modification of the resist pattern arrangement | positioning on the quartz substrate in an etching chamber. It is a perspective view which shows the 2nd modification of the resist pattern arrangement | positioning on the quartz substrate in an etching chamber. It is a perspective view which shows the prior art example of quartz substrate arrangement | positioning in an etching chamber. It is a sectional view of a true sphere and a resist layer for explaining a true sphere deviation measuring method. It is a figure which shows the evaluation result of a spherical displacement about Comparative Examples 1-3 and Examples 1-7. It is a graph which shows the measurement result of the true spherical deviation before RIE about Example 2. FIG. It is a graph which shows the measurement result of the true spherical deviation after RIE about Example 2. FIG. It is a graph which shows the measurement result of the true spherical deviation after RIE about the comparative example 1. It is a graph which shows the measurement result of the true spherical deviation after RIE about the comparative example 2.

Explanation of symbols

10: quartz substrate, 12: Graphite electrode plate, 14a to 14d, 16 a to 16 d: a quartz _plate, S 1 _{to S} 4, S: resist _layer, L 11 _{~L 14:} lens.

Claims (1)

Forming a circular resist layer on one main surface of a transparent substrate made of a transparent oxide by photolithography,
Applying a heat reflow treatment to the resist layer to give a convex spherical pattern to the resist layer;
Forming a convex spherical lens by transferring a convex spherical pattern of the resist layer to one main surface of the transparent substrate by anisotropic dry etching,
In the anisotropic dry etching process, the ratio of carbon and oxygen generated during etching is controlled by placing an oxygen generating material together with the transparent substrate on a graphite electrode plate in an etching chamber. The manufacturing method of the micro lens array.

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