JP2006337956A - Manufacturing method of microlens array - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a microlens array by which gaps between microlenses are made minute. <P>SOLUTION: A film consisting of a thermally deformable photosensitive material is formed with a uniform film thickness on a flat transparent film and then the film consisting of the photosensitive material is subjected to patterning to form a shape separating every forming region of the microlens. The photosensitive material subjected to patterning is heated to form a convex microlens and dry etching is applied to an arranging surface of the microlens to remove a flat part of a gap part between the microlenses. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a method for manufacturing a microlens array.

  In recent years, with the miniaturization of electronic devices and the increase in operating frequency, there is an increasing need for micro optical components.

  A microlens is a microlens having a diameter of several millimeters or less, and a microlens array in which a large number of microlenses having a diameter of about 10 μm are arranged to improve light utilization efficiency in an image sensor such as a solid-state imaging device incorporated in a portable terminal or the like. Is used (see, for example, Patent Document 1).

  Since the microlens has a minute shape, various manufacturing methods different from polishing and mold used for normal lens manufacturing have been developed and used. For example, in the reflow method, a polymer layer is placed on a lower side of a substrate, a photoresist layer is overlaid thereon, spin coated, a cylindrical photoresist pattern is produced by photolithography, and the substrate is heated to form a resist. The shape and refractive index distribution that naturally occur due to surface tension are used as a lens.

  This reflow method is often used to manufacture a microlens array for portable terminals and the like.

The microlens is required to be miniaturized due to a demand for increasing the amount of light taken from the outside. However, at present, the gap between the microlenses is limited to, for example, 0.4 to 0.3 μm in view of the performance of the photolithography apparatus, and further miniaturization is necessary.
Japanese Unexamined Patent Publication No. 2000-206310

  An object of the present invention is to provide a method of manufacturing a microlens array in which a gap between microlenses is miniaturized.

  According to one aspect of the present invention, a step of forming a film made of a heat-deformable photosensitive material on a flat transparent film with a uniform film thickness, and forming the film made of the photosensitive material into a microlens formation region Patterning into separate and independent shapes for each step, heating the patterned photosensitive material to form convex microlenses, and subjecting the microlens array surface to dry etching, There is provided a method of manufacturing a microlens array, comprising a step of narrowing a gap between lenses of a microlens.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the microlens array which refined | miniaturized the gap between microlenses is provided.

  Hereinafter, a method for manufacturing a microlens array according to an embodiment of the present invention will be described with reference to the drawings.

  A microlens array in which a plurality of microlenses are arranged in the vertical and horizontal directions is incorporated in, for example, a solid-state imaging device. As shown in FIG. 2, the solid-state imaging device includes, for example, a light receiving portion 21, a polysilicon electrode 22, a metal light shielding film 23, an element surface protective film 24, a planarization film 25, a filter 26, and an acrylic planarization on a semiconductor substrate 20. A film 27 and a microlens 28 are formed.

  First, the design specification of the microlens is determined in response to the user specification of a portable terminal or the like on which the microlens array is mounted. As design specifications of the microlens, for example, the height, inclination angle, gap interval, and the like of the microlens are determined.

  Next, the design data, which is the design specification of the determined microlens, is converted into a photoresist pattern shape. At the time of conversion to the photoresist pattern, the photoresist shape is set by correcting the design specifications of the microlens in consideration of the shape change at the time of etching which is a subsequent process. Here, the shape change during etching depends on, for example, the type of etching apparatus, the etching gas, the material of the substrate, and the like.

Next, a photomask is created based on the resist pattern design data. As this photomask, for example, an area gradation type mask in which a large number of minute opening patterns are arranged and the transmittance is adjusted according to the area ratio between the opening portion and the light shielding portion can be used.

  Next, a photoresist pattern is formed using the produced photomask. As a pretreatment for this resist forming step, the substrate substrate, which is the base, is cleaned and removed and dehydrated and baked at 0 to 150 ° C.

  Thereafter, for example, the chemically adsorbed water molecule layer is hydrophobized using a silane coupling agent such as hexamethyldisilazane (HMDS) to improve the adhesion to the resist.

The underlying substrate is formed of a flat transparent film made of, for example, an acrylic or phenolic resin.

  FIG. 1 is an explanatory diagram for explaining a method of manufacturing a microlens array according to an embodiment of the present invention.

  As shown in FIG. 1A, the resist pattern is formed by dropping a heat-deformable phenol-based photosensitive material on a flat transparent film 10 made of, for example, an acrylic resin, for example, at a high speed of 3000 to 6000 rpm. By rotating, a resist film 11 made of a photosensitive material 11 is formed on the transparent film 10 with a desired film thickness. The coating film thickness depends on the atmosphere such as the resist viscosity, molecular weight, concentration, solvent boiling point, rotation speed, and humidity.

  Next, the coating solvent remaining in the resist film 11 after coating is volatilized by heating, for example, at 80 to 100 ° C. for about 60 seconds to improve the film quality and adhesion.

  Next, the resist film 11 made of the photosensitive material is irradiated with light, a chemical reaction is caused in the resist by exposure energy, the solubility of the resist in the developer is changed, and the latent pattern corresponding to the exposure pattern is changed. Create an image. Light irradiation may be g-line or KrF.

  After the exposure, for example, heating is performed at 90 to 120 ° C. for about 90 seconds. By heating, the photosensitive agent diffuses and the fidelity of the pattern dimension and the resist dimension is improved.

  Next, development is performed. As the developer, an alkaline aqueous solution such as tetramethylammonium hydroxide (TMAH) is used. By developing, as shown in FIG. 1B, the photosensitive material 11 is patterned into a shape in which the photosensitive material 11 is separated and independent for each microlens formation region. After development, rinse and spin dry.

  Next, the patterned resist film 11 is heated on a hot plate at, for example, 170 to 220 ° C. for 10 minutes. Such temperature is equal to or higher than the thermal deformation temperature of the photosensitive material, and softens as shown in FIG. As the heating proceeds, the corners are rounded to form a smooth convex microlens 12 as shown in FIG. 1 (d) due to the effects of thermal deformation and surface tension of the photosensitive material.

  The heat-deformable photosensitive material may be styrene.

  Next, dry etching is performed on the surface on which the convex surfaces are arrayed. The action of etching acts on the convex shape and substrate of the photosensitive material.

  As the dry etching agent, for example, a mixed gas of oxygen and fluorocarbon (CF4, CHF3, etc.) is used. When such a mixed gas is used and dry etching is performed under a predetermined pressure (low vacuum) and temperature (low temperature), HF molecules are formed, and molecules other than HF molecules are etched while being deposited on the side wall of the transparent film 10. Therefore, the gap part between microlenses can be narrowed more reliably. Since the pressure and temperature are also related to the ion energy during etching and the deposition amount during etching, it is preferable to control the pressure and temperature to predetermined values.

  The convex microlens 12 and the transparent film 10 are dry-etched, so that the inter-lens gap portion 13 of the convex microlens 12 that is curved and close is narrowed as shown in FIG. The convex microlens 12 thus formed can be formed. Of course, the gap between the lenses may be substantially free of flat portions.

Depending on the dry etching conditions, convex microlenses having different curvatures in the horizontal, vertical and diagonal directions, or microlenses having the same curvature in the horizontal, vertical and diagonal directions can be formed. For example, in the case of O ₂ / N ₂ conditions (gas ratio 1: 2) or O ₂ single gas, a film made of a C material is processed, so that the selection ratio cannot be obtained, and the shape of the lens itself is changed, and can be changed in the horizontal and vertical directions. it can.

(Example)
An example of dry etching will be described. Here, a parallel plate type reactive ion etching apparatus manufactured by Tokyo Ohka Kogyo Co., Ltd. was used. The conditions at this time were RF power: 650 W, process time: 5 seconds, internal pressure: 33 Pa, EPD Copy: none, O ₂ flow rate: 400 ml / min, stage temperature: 80 ° C.

  By performing the etching process, the gap length between the microlenses of the conventional 0.4 to 0.3 μm can be changed to a gap length of 0.1 μm or less, and miniaturization is possible. The gap length between the microlenses can be managed, for example, by observing a surface SEM image with a scanning electron microscope.

  According to the embodiment of the present invention, a flat transparent film 10 and a film 11 made of a heat-deformable photosensitive material are formed on the transparent film 10 with a uniform thickness, and a resist film 11 made of a photosensitive material is formed. Are formed into patterns that are separated and separated for each microlens formation region, and further, the patterned photosensitive material is heated to form convex microlenses 12, and the convex microlenses 12 are arranged on the array surface. On the other hand, by performing the dry etching, the convex microlens 12 is transferred, and the gap between the lenses is controlled to be narrow according to the dry etching conditions, so that a highly condensed microlens array can be formed.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention described in the claims, and these are also included in the scope of the present invention. Needless to say.

It is explanatory drawing explaining the manufacturing method of the microlens array which concerns on embodiment of this invention. It is sectional drawing explaining the structure of the solid-state image sensor incorporating a micro lens.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Transparent film, 11 ... Resist film, 12 ... Micro lens, 13 ... Gap between lenses.

Claims (4)

A step of forming a film made of a heat-deformable photosensitive material on a flat transparent film with a uniform thickness, and patterning the film made of the photosensitive material into a shape that is separated and independent for each microlens formation region Forming a convex microlens by heating the patterned photosensitive material, and performing dry etching on the arrangement surface of the microlens to narrow the gap between the lenses of the microlens The process of
A method for manufacturing a microlens array, comprising:   2. The method of manufacturing a microlens array according to claim 1, wherein the dry etching is performed by processing the gap between the microlenses into a forward tapered shape by a parallel plate RIE apparatus.   2. The method of manufacturing a microlens array according to claim 1, wherein the microlens array is processed so that a gap length between the lenses is 0.1 [mu] m or less.   2. The method of manufacturing a microlens array according to claim 1, wherein the gap between the lenses of the microlens is processed so that a substantially flat portion does not exist.

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