JPH03192204A - Production of color solid state image pickup element - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a color solid-state imaging device such as a CCD in which a light-condensing microlens is formed on the upper surface of a light-receiving portion.

[Prior Art] With the miniaturization of chip size and increase in the number of pixels in color solid-state image sensors such as CCDs, the area of light-receiving sections as pixels formed therein has also become smaller. As a result, the amount of light received by each light-receiving section decreases, resulting in a problem of decreased sensitivity (output/amount of incident light).

To solve this problem, a color solid-state image sensor has been proposed in which a microlens is formed using a positive resist on the top surface of each light-receiving portion that becomes a pixel. Since the amount of incident light is condensed by the microlens, the effective light-receiving area of the light-receiving section increases, making it possible to compensate for the decrease in sensitivity.

FIG. 3 is a sectional view of a main part of an example of a color solid-state image sensor 60 whose sensitivity is improved by using such a microlens, in which the semiconductor substrate 12 is of P type and the light receiving section 14 is of N type.

16 is a charge transfer section, 18 and 20 are transfer electrodes, and 22 is an insulating layer. 24 is a light shielding metal.

26 is a flattening layer, and 40 (40R, 40G, 40B) is an on-chip color filter.

30 is a protective layer of the color filter 40.

A microlens 28 is completely formed on the upper surface of this protective layer 30 at a position facing the light receiving section 14.

The microlens 28 is formed by etching the positive resist layer that is the base of the microlens, and then utilizing the sagging of the positive resist layer due to heat treatment.

The microlenses 28 may be formed for each individual light receiving section 14, or may be formed for each column or row of light receiving sections.

[Problem to be solved by the invention] By the way, color filters 40R, 4 in on-chip format
When forming 0G and 40B, gelatin, casein, or the like is usually used as the material, and color filters are formed by dyeing.

On the other hand, microlenses are thermally deformed into a semicircular or spherical shape due to thermal sag during heat treatment of the resist layer that is the base of the microlens and surface tension.

In that case, in order to thermally stabilize the resist layer after thermal deformation, it is necessary to set the temperature during the heat treatment to 160° C. or higher.

However, if heat treatment is performed at such high temperatures, there is a risk that the rumored color filters 40R, 40G, and 40B will change in quality. Color filter 40R, 40G.

408Ltifl It's because I don't have a fever.

Therefore, the present invention solves these conventional problems with a simple structure, and does not cause any deterioration of the color filter.
This paper proposes a color solid-state image sensor in which the microlens is thermally stable.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, a microlens is formed for each light receiving section or for each group of light receiving sections, and external light is focused on the light receiving section. In a color solid-state image sensor having an on-chip color filter configuration, when forming the microlens facing the top surface of the light receiving section or the group of light receiving sections, the resist layer for the microlens is coated within a range that does not alter the quality of the color filter. The method is characterized in that the resist layer is subjected to a heat treatment, and the resist layer is hardened by irradiating the resist layer with deep ultraviolet rays or ultraviolet rays.

[Function 1 As a manufacturing method when forming the microlens 28, the first to
The third method will be illustrated.

The microlens resist layer 52 can be heated completely at a constant temperature (160° C. or less) within a range where the upper plate color filters 40R, 40G, and 40B are not thermally altered.

At the same time, resist layer of far ultraviolet rays or ultraviolet rays!
52.

Then, the resist layer 52 undergoes thermal deformation due to the heat treatment, and one resist layer 52 undergoes thermal deformation due to thermal sagging and surface tension.
is deformed into a cylindrical or spherical shape.

Further, the resist layer 52 that has been thermally deformed by irradiation with deep ultraviolet rays or ultraviolet rays is hardened. This improves heat resistance to about 150°C.

In contrast to the first method, the heating temperature is repeatedly raised and lowered within the range of 35°C to 150°C. The same effect as the first method can be obtained.

After heating at a constant temperature with standing air, deep ultraviolet or ultraviolet treatment is applied. The same effect as the first method can be obtained.

[Example] Next, an example of the method for manufacturing a color solid-state image sensor according to the present invention will be described in detail with reference to FIG. I #I. A COD is exemplified as a solid-state image sensor. The image sensor can be applied either in one-dimensional configuration or in two-dimensional configuration.

FIG. 1 shows an example of a color solid-state image sensor manufactured according to the present invention.

In this color solid-state image sensor 60, the semiconductor substrate 12
is of the P type as described above, and the light receiving section 14 is of the N type. On the semiconductor substrate 12 of the charge transfer section 160 sandwiched between the light receiving sections 14 and 14, two layers of transfer electrodes 18 and 20 are completely formed with an insulating layer 22 such as 5i02 interposed therebetween as shown in the figure.

A light-shielding metal 24 is formed on the upper surface of the transfer electrode 20 to prevent external light from entering the charge transfer section 16.

A flattening layer 26 made of acrylic resin or the like is applied to the upper surface of the light-shielding metal 24 and the upper surface of the light-receiving section 14, respectively, to flatten the surfaces. And to colorize it,
A color filter 40 (40R, 400° 40B) as shown in the figure is completely formed on the upper surface of this flattening layer 26.

Color filters 40R, 40G, and 40B are each light receiving section 1
4, and therefore monochromatic light of R, 0, 8 (red, green, helmet) is incident on each light receiving section 14.

The color filters 40R, 40G, and 403Lt can be formed by dyeing gelatin, casein, or the like with a dye, as described above.

Generally speaking, a protective layer 3 is provided to protect the color filters 401, 40G and 40B and to fix the microlens layer.
0 can be formed. On the upper surface of this protective layer 3°, the light receiving part 14
A microlens 28 is formed at a position facing the.

The protective layer 30 is subjected to a curing treatment before the microlens 28 is formed. That is, when using an ultraviolet ray or far ultraviolet resist as the protective layer 30, it is irradiated with ultraviolet 1 or far ultraviolet rays, and when a thermosetting resin is used, it is heated and hardened.

Due to this hardening treatment, the protective layer 30 is not thermally deformed even if heat treatment is applied in the process of forming the microlens 28, so that the microlens 28 having a good shape can be formed.

The microlens 28 may be formed for each light receiving section 14, or may be formed for each column or row of light receiving sections.

Each of the microlenses 28 is formed so that the respective peripheral edges 28a are continuous with each other.

Since the respective peripheral portions 28a are continuous with each other, external light incident on the peripheral flals 28a is also guided to the light receiver 1114 as shown in the figure, so that the amount of incident light is increased compared to the case of the configuration shown in FIG. Therefore, the sensitivity is improved accordingly.

For the microlens 28, a photosensitive resin for ultraviolet rays or far ultraviolet rays is used. This photosensitive resin is applied to the resist layer 5.
2 (described later).

This resist layer 52 is thermally deformed by heat treatment before being irradiated with ultraviolet rays or deep ultraviolet rays, so even if its initial shape is layered, it is naturally deformed into a spherical or semicircular shape due to sag or surface tension. At the same time as this heat treatment, ultraviolet rays (t) are applied to far ultraviolet rays (its wavelength is 200 to 300 nm).
00 nm) to harden the microlens 28.

As the resist layer 52, acrylic resin, polystyrene resin, polyimide resin, polyetheramide resin, epoxy resin, novolak resin, etc. can be used.

Next, FIG. 2 shows an example of a method for manufacturing a color solid-state image sensor according to the present invention. Microlens 28 receives light 1114
The following is an example of a case in which it is formed separately.

First, the light-receiving portion 14 is formed by doping N-type impurities from a predetermined position on a P-type semiconductor 1 plate 12 such as silicon. Then, on the upper surface of the semiconductor substrate 12, the transfer electrodes 18 and 20, the light-shielding metal 24, the planarization layer 26, etc. shown in FIG.
They are sequentially formed using a well-known method.

For the flattening layer 26, other than acrylic resin, polyimide resin, isocyanate resin, urethane resin, etc. can be used. In this example, acrylic resin 'FVR-10'
(manufactured by Fuji Pharmaceutical Co., Ltd.)! I am using it. This planarizing layer 26 is applied by a spin code method or the like so that the thickness thereof is, for example, 5.0 um. On its top,
After forming color filters 4OR, 40G, 40B,
A protective layer 30 is applied and hardened. These layers are collectively shown as a fixed layer 50 (second nationals).

On the upper surface of this fixed layer 50, a resist layer for ultraviolet rays or far ultraviolet rays (FI optical 111?), a negative resist layer 52 in this example, is formed by a spin code method or the like, and the thickness thereof is approximately 2.0 μm, for example. It is applied so that (
Same 1! ! IA).

As the negative resist layer 52, a photosensitive resin known as 'MES-u' (manufactured by Japan Synthetic Rubber Co., Ltd.) was used.

After coating the negative resist layer 52 and drying it, the part facing the light receiving part 14 is exposed to deep ultraviolet rays at a predetermined amount of exposure so as to form a predetermined pattern, and the patterning is completed (see the figure). 8).

Its temperature below 1.160℃, preferably 130~15℃
Heat treated under the concentration condition of 0℃, and at the same time 200~300℃
The negative type resist 162 for deep ultraviolet rays is thermally deformed by irradiation with deep ultraviolet rays (C).

By thermally deforming the negative resist layer 52 for deep ultraviolet rays, microlenses 28 having a semi-cylindrical shape in the figure and whose peripheral edges 28a are fully connected to each other are obtained.

The color filters 40R and 40G inserted into the fixed layer 50 made the heating temperature 160° C. or lower.

This is done in consideration of the heat resistance of the color filters 40B and to prevent the color filters 40R, 40G, and 40B from being deteriorated by heat.

By thermally deforming the negative resist layer 52 for far ultraviolet rays and at the same time irradiating this resist layer 52 with far ultraviolet rays of 200 to 300 nm to perform an exposure treatment, the resin layer constituting the microlens 28 is hardened and thermally deformed. becomes stable.

In this way, the negative resist layer 52 for far ultraviolet rays was thermally deformed and simultaneously hardened because the negative resist layer 52 easily softens at 120 to 160° C. before being exposed to far ultraviolet rays, but - This method takes advantage of the property of being extremely thermally stable after exposure to ultraviolet rays.

1/ Don't perform heat treatment and deep ultraviolet ray treatment on the cyst layer 52 at the same time (even if deep ultraviolet ray treatment is performed after heat treatment, similar microlenses 28 will be formed).

Also in this case, color filters 40R and 40G. 40B is not subject to thermal deterioration, and the heat resistance of the microlens 28 is improved.

In addition, the temperature during the heat treatment mentioned above is not a constant temperature,
The temperature may be raised and lowered repeatedly within a predetermined range, for example, from 35°C to 150°C. When this temperature control is appropriate, the thermal sagging state of the resist layer 52 can be effectively controlled, so the shape of the microlens 28 can be determined appropriately.

Note that the manufacturing method of the color solid-state image sensor in the present invention is CC
It can be applied not only to D but also to color solid-state image sensors of other types.

[Effects of the Invention] As explained above, in the present invention, a microlens resist layer is subjected to heat treatment and deep ultraviolet rays or ultraviolet rays treatment to form a microlens of a predetermined shape.

According to this, the heat resistance of the microlens can be improved without causing thermal deterioration of the on-chip color filter.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a color solid-state image sensor manufactured by the manufacturing method of the present invention, FIG. 2 is a cross-sectional view showing an example of the manufacturing method of the color solid-state image sensor according to the present invention, and FIG. 3 is a cross-sectional view of a conventional color solid-state image sensor. FIG. 12 ・ 4- 6- 26 ・ 28 ・ ・Semiconductor substrate・Light receiving section・Transfer section・Flattening layer e Microlens 28a...Peripheral part 40R to 40B Fist・e Color filter 50...Fixed layer 52... Far ultraviolet resist layer 60...color solid-state image sensor

Claims (1)

[Claims] (1) In a color solid-state image sensor having an on-chip color filter configuration in which a microlens is formed for each light receiving section or for each group of light receiving sections to focus external light on the light receiving section, the light receiving section or the light receiving section When forming the microlenses facing the top surface of the group, heat treatment is applied to the microlens resist layer within a range that does not alter the quality of the color filter, and the resist layer is irradiated with deep ultraviolet rays or ultraviolet rays. A method for manufacturing a color solid-state image sensor, characterized in that the resist layer is hardened.