JPH06138306A - Production of microlens array - Google Patents

Abstract

PURPOSE:To provide the process for production of the microlens array which easily forms a microlens array having excellent performance, such as heat resistance and solvent resistance, with high accuracy on a solid-state image pickup element. CONSTITUTION:This process for production of the microlens array consists in forming positive photoresist patterns on the solid-state image pickup element, then making the patterns transparent by full-surface exposing and forming microlenses 3 by heat flow. These lenses are molded by the heat flow and are treated with a silane coupling agent; thereafter, the lenses are cured.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microlens array formed on a solid-state image pickup device [charge coupled device (CCD) or liquid crystal display device (LCD), and color filter formed on these]. It relates to a manufacturing method.

[0002]

2. Description of the Related Art With regard to solid-state image pickup devices such as CCDs, as a result of technological innovation, resolution and sensitivity have been improved, which has greatly contributed to miniaturization of television cameras. Conventionally, in order to improve the resolution, a means for increasing the number of pixels of the light receiving section integrated on the solid-state imaging device has been adopted. However, if the number of pixels per unit area is increased, the total light receiving area becomes smaller, and the utilization factor of the light incident through the lens is lowered, so that there is a problem that the sensitivity of the television camera is lowered. In order to solve this, a method has been adopted in which a microlens is attached to each pixel of the solid-state image pickup element to improve the light collection rate (Japanese Patent Laid-Open No. 1-257901, Japanese Patent Laid-Open No. 1-257901).
257902 and JP-A-1-263601). As a method of forming a microlens, for example, a photosensitive resin is patterned into a planar shape of the lens by a photolithography technique, and then heated to a temperature equal to or higher than the softening point of the resin so as to have fluidity (hereinafter, referred to as a heat There is a method of producing a convex lens by causing sagging of the pattern edge. In this case, the conditions for the lens-forming material are that the refractive index is large and that the transparency in the visible light region is high.
In addition to excellent heat resistance and solvent resistance after lens formation, it also has excellent lens forming ability and high sensitivity,
It has a high-resolution resist function. However, when a positive photoresist using a photosensitive resin for semiconductor integrated circuits is diverted as a microlens forming material, it is unsatisfactory from the viewpoint of heat resistance and solvent resistance after forming the positive photoresist pattern. In particular,
If the heat resistance is not excellent, there is a problem that the microlens pattern is reflowed by heating when it is cured after forming the microlens.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and easily and highly accurately forms a microlens excellent in heat resistance and solvent resistance on a solid-state image pickup device. , And a method for producing a microlens array.

[0004]

The present invention is a method for producing a microlens array in which a positive type photoresist pattern is formed on a solid-state image pickup device, the whole surface is exposed to make it transparent, and then a lens is formed by heat flow. Then, the lens is molded by a heat flow, and then the lens is cured after being treated with a silane coupling agent.

The present invention will be described in detail below. First, a positive type photosensitive resin is applied on a solid-state image sensor, and patterning is performed at a predetermined position with a predetermined size by photolithography to obtain a positive photoresist pattern. As the positive type photosensitive resin, those for semiconductor integrated circuits, which are composed of a quinonediazide compound (photosensitizer) and an alkali-soluble resin, are used.

Examples of the quinonediazide compound include 1,2-benzoquinonediazide-4-sulfonic acid ester, 1,2-naphthoquinonediazide-4-sulfonic acid ester, and 1,2-naphthoquinonediazide-5-sulfonic acid ester. To be These esters can be obtained by a known method, for example, by subjecting a quinonediazidesulfonic acid halide such as 1,2-naphthoquinonediazidesulfonic acid chloride or benzoquinonediazidosulfonic acid chloride to a condensation reaction with a compound having a hydroxyl group in the presence of a weak base. Can be manufactured by.

As the compound having a hydroxyl group,
Hydroquinone, resorcin, phloroglucin, 2,4
-Dihydroxybenzophenone, 2,3,4-trihydroxybenzophenone, 2,2 ', 3-trihydroxybenzophenone, 2,2', 4-trihydroxybenzophenone, 2,2 ', 5-trihydroxybenzophenone, 2,3 , 3'-trihydroxybenzophenone,
2,3,4'-trihydroxybenzophenone, 2,
3 ', 4-trihydroxybenzophenone, 2,3',
5-trihydroxybenzophenone, 2,4,4'-trihydroxybenzophenone, 2,4 ', 5-trihydroxybenzophenone, 2', 3,4-trihydroxybenzophenone, 3,3 ', 4-trihydroxybenzophenone or Trihydroxybenzophenones such as 3,4,4′-trihydroxybenzophenone, 2,
3,3 ', 4-tetrahydroxybenzophenone, 2,
3,4,4'-tetrahydroxybenzophenone, 2,
2 ', 4,4'-tetrahydroxybenzophenone,
2,2 ', 3,4-tetrahydroxybenzophenone,
2,2 ', 3,4'-tetrahydroxybenzophenone, 2,2', 5,5'-tetrahydroxybenzophenone, 2,3 ', 4', 5-tetrahydroxybenzophenone or 2,3 ', 5,5 Tetrahydroxybenzophenones such as'-tetrahydroxybenzophenone, 2,2 ', 3,4,4'-pentahydroxybenzophenone, 2,2', 3,4,5'-pentahydroxybenzophenone, 2,2 ', 3 , 3 ', 4-pentahydroxybenzophenone or 2,3,3', 4,5 '
-Pentahydroxybenzophenones such as pentahydroxybenzophenone, 2,3,3 ', 4,4', 5'-
Hexahydroxybenzophenone or 2,2 ',
Hexahydroxybenzophenones such as 3,3 ', 4,5'-hexahydroxybenzophenone, alkyl esters of gallic acid, oxyflavans described by the general formula (I) in JP-A-2-84650, JP-A-2 Examples include phenols described by the general formula (I) in JP-A-269351 and phenols described by the general formula (I) in JP-A-3-185447. The amount of the quinonediazide compound used is usually 5 to 50% by weight, preferably 10 to 40% by weight, based on the total solid content of the positive photosensitive resin.

Examples of the alkali-soluble resin include polyvinylphenol and novolac resin. Examples of the novolac resin include phenol and o-
Cresol, m-cresol, p-cresol, 2,5
-Xylenol, 3,5-xylenol, 3,4-xylenol, 2,3,5-trimethylphenol, 4-t
-Butylphenol, 2-t-butylphenol, 3-
t-butylphenol, 3-ethylphenol, 2-ethylphenol, 4-ethylphenol, 3-methyl-
6-t-butylphenol, 4-methyl-2-t-butylphenol, 2-naphthol, 1,3-dihydroxynaphthalene, 1,7-dihydroxynaphthalene or 1,5-dihydroxynaphthalene, or the following formula

[0009]

[Chemical 1]

[In the formula, R _{2 to} R ₄ each independently represent a hydrogen atom or an alkyl or alkoxy group having 1 to 4 carbon atoms, and k represents 1 or 2. ] One or more phenols represented by

[0011]

[Chemical 2]

[In the formula, R _{5 to} R ₁₀ each independently represent a hydrogen atom or an alkyl or alkoxy group having 1 to 4 carbon atoms, and R ₁₁ is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms or an aryl group. Represents a to c each represent 0, 1 or 2, and a + b + c> 2. ] Resins obtained by condensing one or a mixture of two or more of the compounds represented by the above, alone or in combination of two or more with a carbonyl compound by a conventional method can be mentioned.

Examples of the carbonyl compound include formaldehyde, paraformaldehyde, acetaldehyde, propylaldehyde, benzaldehyde, phenylacetaldehyde, α-phenylpropylaldehyde,
β-phenylpropyl aldehyde, o-hydroxybenzaldehyde, m-hydroxybenzaldehyde, p-
Examples thereof include hydroxybenzaldehyde, o-methylbenzaldehyde, p-methylbenzaldehyde, glutaraldehyde and glyoxal.

From the viewpoint of resolution, heat resistance and scum, the novolak resin obtained by condensation is subjected to, for example, a fractionation operation, and the pattern area by GPC of a component having a polystyrene reduced molecular weight of 900 or less (using a 254 nm uv detector) Is preferably 20% or less with respect to the total pattern area excluding the pattern area of unreacted phenols. More preferably 15
%, Particularly preferably 10% or less. Fractionation is performed by using a novolak resin obtained by condensation as a good solvent such as alcohol (methanol or ethanol), ketone (acetone, methyl ethyl ketone or methyl isobutyl ketone), ethylene glycol and its ethers, ether esters (ethyl cellosolve acetate etc.) or It is carried out by dissolving in tetrahydrofuran or the like and then pouring the obtained solution into water for precipitation, or by pouring into a solvent such as pentane, hexane, heptane or cyclohexane for liquid separation. The polystyrene-reduced weight average molecular weight of the novolac resin after fractionation measured by GPC is preferably 3000 to 20000. The addition amount of the alkali-soluble resin (for example, polyvinylphenol) other than the novolac resin is not particularly limited as long as the effect of the present invention is not impaired. The preferable amount of alkali-soluble resin used is 50 to 90% by weight based on the total solid content of the positive photosensitive resin.
Is.

After patterning to obtain a positive photoresist pattern, the entire surface is exposed to light (for example, irradiation with ultraviolet rays) to decompose the photosensitizer, thereby making it transparent in the visible light region. Then, a desired microlens shape (for example, spherical surface) is prepared by heat flow. Further, a silane coupling agent treatment is performed. The silane coupling agent treatment is performed, for example, by immersing a microlens molded into a desired shape in a silane coupling agent solution. Examples of the silane coupling agent include vinyltriethoxysilane, γ-aminopropyltriethoxysilane, γ-
Aminopropyltrimethoxysilane, mercaptopropyltrimethoxysilane, chloropropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-β (aminoethyl) γ-aminopropylmethyldimethoxysilane, N- Phenyl-γ-aminopropyltrimethoxysilane and the like can be mentioned. Preferred are those having an amino group in the molecule. The silane coupling agent having an amino group in the molecule, for example, the general formula (I) or _{(II) (R 1 O)} 3 Si CH 2 CH (NH 2) - [CH _{2] n} NH ₂ (I) ( R ₁ O) ₃ Si - [CH _{2] n} NH ₂ (II) (wherein, the R ₁ is an alkyl group, n represents an integer of 1 to 4, at least one each represents) a compound represented by. Some include. The compound represented by the general formula (I) or (II) is preferably, for example, (CH ₃ O) ₃ Si
CH ₂ CH (NH ₂ ) CH ₂ CH ₂ NH ₂ , (CH
₃ O) ₃ Si CH ₂ CH ₂ CH ₂ NH _{2 and the} like.

[0016]

According to the present invention, a microlens array having excellent heat resistance, solvent resistance and the like can be manufactured easily and highly accurately.

[0017]

EXAMPLES The present invention will now be specifically described with reference to examples, but the present invention is not limited thereto.

Reference Example 1 Polystyrene-equivalent weight average obtained by reacting in the presence of an oxalic acid catalyst under the conditions of m-cresol / p-cresol = 55/45 and cresol / formalin = 1 / 0.7 (both are molar ratios). 13.5 g of novolak resin with a molecular weight of 11,000 and 2,
1,4 of 3,4,4'-tetrahydroxybenzophenone
After dissolving 4.0 g of 2-naphthoquinonediazide-5-sulfonic acid ester (reaction molar ratio 1: 2.7, photosensitizer) in 47.0 g of ethyl cellosolve acetate, it was filtered with a Teflon filter having a pore size of 0.2 μm and a positive photosensitive resin Was prepared.

Example 1 A positive type photosensitive resin obtained in Reference Example 1 was applied to a silicon wafer having an on-chip type color filter formed on a CCD by spin coating so as to have a film thickness of 2.0 μm, and then air dried in a clean room. did. Then, this silicon wafer was exposed using a reduction projection exposure machine (NSR1505G3C NA = 0.42 manufactured by Nikon Corporation) having an exposure wavelength of 436 nm, and then developed with a developer SOPD manufactured by Sumitomo Chemical Co., Ltd. A mold photoresist pattern was obtained. Next, the entire surface of the silicon wafer was exposed (436 nm) to make the positive photoresist pattern transparent. An exposure dose of 1.5 J / cm ² is required for transparency, which gives a transmittance of 95% at 400-700 nm.
That's it. Next, the transparentized silicon wafer was heated by a hot plate (150 ° C. for 180 seconds) and heat flow was performed to form a lens. Then, in a 1% aqueous solution of 3- (2-aminoethyl) aminopropyltrimethoxysilane [LS-2480 manufactured by Shin-Etsu Chemical Co., Ltd.] at 23 ° C./3.
After soaking for 1 minute and rinsing with ultrapure water, the lens was cured by heating for 1 minute on a hot plate at 140 ° C. The solvent resistance of the obtained lens was tested by immersing it in water, isopropyl alcohol and ethyl cellosolve acetate for 10 minutes each. Pattern collapse and surface roughness do not occur,
It was confirmed to maintain transparency. In addition, heat resistance was tested by heating for 60 minutes on a hot plate at 150 ° C. It was confirmed that the microlens shape was maintained without causing heat flow. Although a spherical microlens array is manufactured in this embodiment, a cylindrical microlens (cylindrical lens, lenticular lens, etc.) array can be manufactured in the same manner.

[0020]

[Brief description of drawings]

FIG. 1 is a positive photoresist pattern formed after development.

FIG. 2 shows a state in which the photosensitizer disappears and is made transparent by the whole surface exposure.

FIG. 3 shows a lens cured by a silane coupling agent treatment after heat flow.

[Explanation of symbols]

 1 Positive photoresist pattern 2 Photosensitizer 3 Microlens 4 Solid-state image sensor

Claims (3)

[Claims] 1. A method of manufacturing a microlens array, comprising forming a positive photoresist pattern on a solid-state image sensor, exposing the entire surface to make it transparent, and then forming a lens by heat flow, wherein the lens is formed by heat flow. And then curing the lens after treatment with a silane coupling agent. 2. The method for producing a microlens array according to claim 1, wherein the silane coupling agent has an amino group in the molecule. 3. A silane coupling agent having an amino group in the molecule is a compound represented by formula (I) or (II) (R ₁ O) ₃ Si CH ₂ CH (NH ₂ )-[CH ₂ ] _n NH ₂ (I ) (R ₁ O) ₃ Si - [CH _{2] n} NH ₂ (II) (wherein, at least one of the R ₁ is an alkyl group, n represents an integer of 1 to 4, each represents) a compound represented by. The method for producing a microlens array according to claim 2, wherein the microlens array contains a seed.