JP2000091549A - Manufacture of on-chip microlenses and of solid-state image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve durability through prevention of aluminum wiring corrosion and of cracking in on-chip microlenses by having a transparent resin layer irradiated with ultraviolet light for forming on-chip microlenses, while heating a substrate in the process of forming on-chip microlenses on the substrate. SOLUTION: A photosensitive resin layer is patterned causing it to be exposed to ultraviolet light on regions other than the upper parts of light receiving regions and is developed to form a specified pattern for making on-chip microlenses. Then, by masking with the patterned photosensitive resin layer, a transparent resin layer 109 is dry etched with a fluorine-based mixed gas to transfer the pattern formed on the photosensitive resin layer to the transparent resin layer 109. Subsequently, after peeling off the photosensitive resin layer, the transparent resin layer 109 is deformed thermally by applying heat processing lower than 160 deg.C from the side, on which on-chip microlenses are to be formed. With this procedure, the transparent resin layer 109 forms microlenses 111 of semispherical or barrel shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing an on-chip microlens and a method for manufacturing a solid-state imaging device having the on-chip lens.

[0002]

2. Description of the Related Art Conventionally, as a method of forming an on-chip microlens on a solid-state imaging device such as a CCD, a lens-shaped pattern in which a positive resist is thermally deformed on a transparent resin formed on the solid-state imaging device. There is known a method of forming a film, etching it back and transferring it to the transparent resin layer.

For example, Japanese Patent Application Laid-Open No. 3-152977 discloses a method of manufacturing a solid-state imaging device in which a microlens is formed for each pixel and external light is condensed on a light receiving portion. A negative resist layer for ultraviolet light or far ultraviolet light is used, and the resist layer formed opposite to each light receiving portion is heat-treated to form a microlens, and then the microlens is exposed to ultraviolet light or far ultraviolet light. Is described.

Japanese Patent Application Laid-Open No. 3-192204 discloses a color solid having an on-chip color filter configuration in which a microlens is formed for each light receiving unit or each light receiving unit group so that external light is condensed on the light receiving unit. In the imaging device, when forming the microlens facing the upper surface of the light receiving portion or the light receiving portion group, heat treatment is performed on the microlens resist layer as long as the color filter is not deteriorated, and far ultraviolet light is applied. Alternatively, there is described a method for manufacturing a color solid-state imaging device in which the resist layer is cured by irradiating the resist layer with ultraviolet rays.

Japanese Patent Application Laid-Open No. 286566/1996 discloses a method for manufacturing a solid-state imaging device in which a charge transfer path layer and a photosensitive layer are provided on a semiconductor substrate, and a light-shielding layer is formed on an upper surface of the charge transfer path layer. Covering the photosensitive layer and the light-shielding layer with a light-shielding layer in common; and heating the heat-deformable resin layer to a position on the upper surface of the light-shielding layer opposite to the photosensitive layer to apply heat to the light collector having a lens-shaped cross-sectional shape. A method of manufacturing a solid-state imaging device, which includes a step of deforming and a step of performing ultraviolet hardening on a light-condensing body thermally deformed to the lens-shaped cross-sectional shape, is described.

Further, Japanese Patent Application Laid-Open No. Hei 4-12568 discloses a process of forming a transparent material layer on a semiconductor substrate on which a solid-state imaging device having a plurality of light receiving portions and charge transfer portions is formed, Forming a photosensitive resin layer, exposing the photosensitive resin layer to form a pattern corresponding to the light receiving portion on the photosensitive resin layer, and forming the photosensitive resin layer on which the pattern is formed. Manufacturing a solid-state imaging device comprising: a step of decolorizing by ultraviolet irradiation to increase the transparency; and a step of heating and thermally deforming the photosensitive resin layer having increased transparency by the ultraviolet irradiation to form a microlens. A method is described.

[0007]

In the above-mentioned conventional method for manufacturing a solid-state imaging device or a solid-state imaging device, generally, as a transparent resin forming the microlens,
A polystyrene-based negative photosensitive resin is used, and a resist for forming a lens pattern by causing thermal deformation is formed of a novolak-based positive resist. The polystyrene-based negative resin not only forms an on-chip microlens but also plays a role as a color filter and a protective film for aluminum wiring on the solid-state imaging device.

The on-chip microlens formed by etching back in this manner is usually viewed as completed as it is, but this negative photosensitive resin is etched back to form an on-chip microlens. Therefore, the film thickness must be as thick as about 2 μm to 5 μm as compared with a normal positive resist. Further, since only the resin on the bonding pad is removed by exposure and development, a resin having a low resist resolution is often used.

Incidentally, some of such negative photosensitive resin materials contain chlorine in the monomer composition. Therefore, if the above-mentioned conventional method is applied as it is using a negative photosensitive resin, the free chlorine contained in the photosensitive resin (resist resin) cannot be completely removed by the exposure and remains in the resist resin as it is. When a device was assembled and packaged and subjected to a durability test under conditions of high temperature and high humidity, corrosion of wiring aluminum and the like were sometimes caused by the influence of chlorine. In addition, during the durability test, the resist resin is not sufficiently polymerized on the on-chip microlens, which may cause a problem such as cracking.

Accordingly, the present invention has excellent durability without causing corrosion of the wiring aluminum and preventing the on-chip microlens from cracking even under severe conditions such as high temperature and high humidity. An object is to provide a method for manufacturing an on-chip microlens and a solid-state imaging device having the on-chip microlens.

[0011]

In order to achieve the above object, the present invention provides a step of forming a transparent resin layer made of a negative photosensitive resin on a solid-state imaging device formed on a substrate;
Forming a photosensitive resin layer made of a positive photosensitive resin on the transparent resin layer, and exposing the photosensitive resin layer to form a pattern corresponding to a microlens on the photosensitive resin layer; A method for manufacturing an on-chip microlens, comprising: a step of transferring the pattern to the transparent resin layer; and a step of irradiating the transparent resin layer with ultraviolet rays while heating the substrate.

In the method of manufacturing an on-chip microlens according to the present invention, the step of irradiating the transparent resin layer with ultraviolet rays while heating the substrate may include removing the transparent resin layer by 10 mj while heating the substrate. / Cm ² -500m
It is preferably a step of irradiating an ultraviolet ray having an energy of j / cm ² .

The step of irradiating the transparent resin layer with ultraviolet rays while heating the substrate may include irradiating the transparent resin layer with ultraviolet rays containing light having a wavelength of 320 nm or less while heating the substrate. The step is preferably performed.

[0014] The step of irradiating the transparent resin layer with ultraviolet light while heating the substrate may include:
More preferably, the step is a step of irradiating the transparent resin layer with an ultraviolet ray while heating to a temperature of ° C.

[0015] The step of irradiating the transparent resin layer with ultraviolet light while heating the substrate may include:
While heating ℃ in, the transparent resin layer, 10 mj / cm ²
It is more preferable that the process is a process of irradiating an ultraviolet ray having an energy of about 500 mj / cm ² .

Further, according to the present invention, there is provided a process for forming a transparent resin layer made of a negative photosensitive resin on a semiconductor substrate having a light receiving section and a charge transfer section, and forming a positive photosensitive layer on the transparent resin layer. Forming a pattern corresponding to the light receiving section on the photosensitive resin layer by exposing the photosensitive resin layer, and forming the pattern on the transparent resin layer. And a method of manufacturing a solid-state imaging device including a step of irradiating the transparent resin layer with an ultraviolet ray while heating the semiconductor substrate.

[0017] The step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate is performed by heating the semiconductor substrate while heating the transparent resin layer at 10 mj / cm ² to 50 mJ / cm ^2.
It is preferably a step of irradiating an ultraviolet ray having an energy of 0 mj / cm ² .

Further, the step of irradiating the transparent resin layer with ultraviolet rays while heating the semiconductor substrate may include: irradiating the transparent resin layer with ultraviolet rays containing light having a wavelength of 320 nm or less while heating the semiconductor substrate. Preferably, the step is an irradiation treatment.

The step of irradiating the transparent resin layer with ultraviolet rays while heating the semiconductor substrate includes the steps of:
More preferably, the step is a step of irradiating the transparent resin layer with ultraviolet light while heating to 00 to 200 ° C.

[0020] The step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate comprises:
While heating to 200 ° C., the transparent resin layer was heated to 10 mj /
More preferably, the step is a step of irradiating an ultraviolet ray having an energy of cm ^{2 to} 500 mj / cm ² .

In the present invention, a negative photosensitive resin is used as a material for forming the on-chip microlens. As described above, this negative photosensitive resin contains chlorine which causes various troubles.

According to the present invention, when forming the on-chip microlenses on the substrate, the transparent resin layer is irradiated with ultraviolet rays to form the on-chip microlenses while heating the substrate. It is characterized by having a step of completely removing chlorine.

According to the present invention, even under severe conditions such as high temperature and high humidity, the on-chip has excellent durability without causing corrosion or the like of the wiring aluminum and without causing cracks in the microlenses. A microlens and a solid-state imaging device having the on-chip microlens can be obtained.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings according to embodiments of the present invention. FIG. 5 shows a device having a color solid-state imaging device, which is an example of the solid-state imaging device of the present invention. In this imaging device, the semiconductor substrate 101 is p-type, and the light receiving unit 102 is n-type. As shown in the figure, on the semiconductor substrate 101 of the transfer section sandwiched between the plurality of light receiving sections 102, two transfer electrodes 103 and 104 are formed on the insulating layer 205 made of silicon oxide or the like.
Is formed through.

A light-shielding metal layer 106 is formed on the transfer electrode 104 so that external light does not enter the transfer portion.

The upper surface of the light shielding metal layer 106 and the light receiving section 10
A flattening layer 107 using an acrylic resin or the like is formed on the upper surface of each of the two, and the surface thereof is flattened.
Then, for colorization, color filters 108a and 108 as shown in FIG.
b, 108c and 108d (hereinafter, collectively,
Also referred to as “color filter 108”. ) Is formed. These color filters 108a, 108b, 108c
And 108d are formed so as to face the light receiving unit 102, respectively, and monochromatic light of red, green, and blue is incident on each light receiving unit 102.

The color filters 108a, 108b, 10
An on-chip micro lens 111 made of a negative photosensitive resin is formed on 8c and 108d.

The negative photosensitive resin is transparent and not only forms the on-chip micro lens 111 but also plays a role of a color filter 108 on the solid-state image sensor and a protective film of an aluminum wiring (not shown).

The on-chip micro lens 111 plays a role of condensing external light on the light receiving section 102.

Next, a method of manufacturing the solid-state imaging device shown in FIG. 5 will be described in detail. First, as shown in FIG. 1A, a light-receiving portion 102 is formed at a predetermined position of a semiconductor substrate 101 such as a p-type silicon semiconductor substrate by doping a conductive type impurity opposite to that of the semiconductor substrate 101. In this embodiment,
A p-type silicon semiconductor substrate is used as the semiconductor substrate 101, and the light receiving section 102 is formed by doping an n-type impurity.

Next, as shown in FIG. 1B, transfer electrodes 103 and 104 are formed on the upper surface of the transfer portion of the semiconductor substrate 101 sandwiched between the light receiving portions 102, and an insulating layer 105 such as silicon oxide is formed on the entire surface. Cover with. Transfer electrodes 103, 104
Can be formed, for example, by depositing a conductive material such as aluminum, polysilicon, and tungsten by, for example, a CVD method and then performing a predetermined process. The insulating layer 105 is formed of, for example, TEOS (Tet
can be formed by a CVD method using raethylorthosilicate) -O _2, and the like. These can all use a well-known technique.

Next, as shown in FIG. 1C, a light-shielding metal layer 106 is formed on the upper surface of the transfer electrode 104 via an insulating layer 105. The light-shielding metal layer 106 is provided to prevent incident light from entering the transfer unit. For example, after depositing a metal such as aluminum by a sputtering method or the like, a predetermined After patterning, it can be formed by etching.

Further, the surface is flattened by forming a flattening layer 107 on the entire surface. The flattening layer 107 can be formed of, for example, an acrylic resin, a polyimide resin, an isocyanate resin, a urethane resin, or the like with a thickness of, for example, 3 μm to 10 μm by a spin coating method.

Next, as shown in FIG. 2D, the color filters 108a, 108b,
108c and 108d are formed. Color filter 10
8 can be formed by dyeing gelatin, casein, or the like with a dye.

Thereafter, as shown in FIG. 2E, the first negative photosensitive resin is applied onto the color filter 108 by, for example, a spin coating method and dried to form a transparent resin layer 109. For example, a film thickness of 1 μm to 7 μm
Formed.

Here, the negative photosensitive resin is a resin in which only the exposed portion remains after exposure and development. In the present invention, as the negative photosensitive resin to be used as the material of the transparent resin layer, if it is a transparent and photosensitive negative resin, it can be used for ultraviolet light, far ultraviolet light, etc. without any particular limitation. Can be. As such a negative photosensitive resin, for example, a polystyrene negative photosensitive resin can be used.

Next, as shown in FIG. 3F, a photosensitive resin layer 110 made of a positive photosensitive resin is applied on the transparent resin layer 109 by, for example, a spin coating method and dried. Thus, for example, a film having a thickness of 1 μm to 7 μm is formed.

Here, the positive photosensitive resin refers to a photosensitive resin in which only the unexposed photosensitive resin remains after exposure and development. In the present invention, as the positive photosensitive resin used as the material of the photosensitive resin layer, a photosensitive resin for ultraviolet rays or far ultraviolet rays can be used without any particular limitation. As such a positive photosensitive resin, for example, a novolak-based positive photosensitive resin can be used.

Thereafter, as shown in FIG. 3 (g), the photosensitive resin layer 110 is provided with a portion other than the upper portion of the light receiving portion 102 so as to have a predetermined pattern for forming on-chip microlenses, for example, Exposure and development with ultraviolet light are performed for patterning.

Next, as shown in FIG. 4 (h), using the patterned photosensitive resin layer 110 as a mask, the transparent resin layer 109 is made of, for example, a mixed gas of oxygen gas and a fluorine-based gas such as CF _4. The pattern applied to the photosensitive resin layer 110 is transferred to the transparent resin layer 109 by dry etching.

Thereafter, after the photosensitive resin 110 is peeled off, a temperature of 160 ° C. or less, preferably 130 to 150 ° C.
Then, heat treatment is performed from the side where the on-chip microlens is formed, and the transparent resin layer 109 is thermally deformed. As a result, as shown in the figure, the transparent lens layer 109 can form a hemispherical or lumpy microlens 111.

Here, the reason why the heating temperature is set to 160 ° C. or less is to consider the heat resistance of the color filter 108.
This is to prevent the color filter 108 from being thermally deformed.

Finally, as shown in FIG. 4 (i), ultraviolet rays are irradiated from above (that is, on the on-chip microlens side) by using, for example, an ultraviolet ray irradiation apparatus capable of simultaneously heating the silicon substrate. A heat treatment is performed on the back surface of the semiconductor substrate.

This is because the transparent resin layer 10
This is because chlorine atoms remain inside 9 and this chlorine content is completely removed.

As the ultraviolet light, 10 mj / cm ^2-
Preferably, it has an energy of 500 mj / cm ² . Ultraviolet light having an energy of less than 10 mj / cm ² has a poor effect of ultraviolet irradiation. On the other hand, 500mj
When an ultraviolet ray having an energy exceeding / cm ² is used, the dye may be photolyzed, discolored and discolored depending on the type of the dye in the color filter.

Preferably, the ultraviolet light contains light having a wavelength of 320 nm or less. Ultraviolet light having a wavelength of 320 nm or less has sufficient energy to photodecompose a photosensitive agent contained in the photosensitive resin to promote bleaching.

The temperature for heating the substrate is 100 to 20
Preferably it is 0 ° C. If the temperature is lower than 100 ° C., the effect of heating is poor. On the other hand, if the temperature exceeds 200 ° C., the color filter 208 and the like may be discolored or thermally deformed.

The heating is preferably performed from the semiconductor substrate side. By heating from the semiconductor substrate side, it becomes possible to completely remove the chlorine remaining inside the transparent resin layer (below the microlens side).

FIG. 6 shows an example in which the heating temperature of the substrate and the conditions of the ultraviolet irradiation are set. FIG. 6 shows a method in which the irradiation energy of ultraviolet rays is set to 30 mj / cm ² for 100 seconds, and the plate temperature when the substrate is heated is continuously raised to 100 to 150 ° C.

As described above, the hardening of the on-chip microlenses and the removal of chlorine can be performed without causing the color filter 108 of the solid-state image sensor to undergo fading or thermal deformation.

If the color filter 108 is made of a material having excellent light resistance, the ultraviolet light intensity may be increased to about 300 mj / cm ² and the processing time may be reduced to about 10 seconds for the purpose of shortening the processing time. It is possible. In this case, the operation is performed without changing the processing temperature.

By forming the on-chip microlens 211 as described above, a desired solid-state imaging device can be obtained.

In the on-chip microlens obtained in this embodiment and the solid-state imaging device having the microlens, the chlorine content is completely removed from the transparent resin constituting the on-chip microlens, so that the aluminum wiring is not corroded. It is excellent in durability without occurrence of cracks due to incomplete polymerization caused by residual chlorine.

The above embodiment is merely an embodiment of a method for manufacturing an on-chip microlens and a solid-state imaging device according to the present invention. For example, a solid-state imaging device may be used without departing from the gist of the present invention. , The type of photosensitive resin, the conditions of ultraviolet irradiation and substrate heating, etc. can be freely changed.

[0055]

As described above, according to the on-chip lens and the method for manufacturing a solid-state imaging device having the on-chip lens of the present invention, chlorine is completely removed from the transparent resin constituting the on-chip micro lens. A durable on-chip lens which does not cause cracks or the like due to incomplete polymerization caused by corrosion of aluminum wiring or residual chlorine content, and a solid-state imaging device having the on-chip lens A device can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main manufacturing process for manufacturing a solid-state imaging device of the present invention.

FIG. 2 is a sectional view of a main manufacturing process for manufacturing the solid-state imaging device of the present invention.

FIG. 3 is a sectional view of a main manufacturing process for manufacturing the solid-state imaging device of the present invention.

FIG. 4 is a cross-sectional view of a main manufacturing process for manufacturing the solid-state imaging device of the present invention.

FIG. 5 is a sectional view of a main manufacturing process for manufacturing the solid-state imaging device of the present invention.

FIG. 6 is a diagram illustrating an example in which a heating temperature of a substrate and a condition of ultraviolet irradiation are set in a process of manufacturing the solid-state imaging device of the present invention.

[Explanation of symbols]

101: semiconductor substrate, 102: light receiving unit, 103, 104
... transfer electrode, 105 ... insulating layer, 106 ... light shielding metal layer,
107: flattening layer, 108, 108a, 108b, 10
8c, 108d: color filter, 109: transparent resin layer, 110: photosensitive resin layer, 111: on-chip micro lens

Claims (10)

[Claims] A step of forming a transparent resin layer made of a negative photosensitive resin on a solid-state imaging device formed on a substrate; and forming a photosensitive resin made of a positive photosensitive resin on the transparent resin layer. Forming a conductive resin layer, exposing the photosensitive resin layer to form a pattern corresponding to a microlens on the photosensitive resin layer, and transferring the pattern to the transparent resin layer. A method for producing an on-chip microlens, comprising a step of irradiating the transparent resin layer with ultraviolet light while heating the substrate. 2. The step of irradiating the transparent resin layer with ultraviolet light while heating the substrate, wherein the transparent resin layer is heated at 10 mj /
The method for producing an on-chip microlens according to claim 1, wherein the method is a step of irradiating an ultraviolet ray having an energy of cm ^{2 to} 500 mj / cm ² . 3. The step of irradiating the transparent resin layer with ultraviolet light while heating the substrate, wherein the transparent resin layer is heated to 320 nm while heating the substrate.
The method for producing an on-chip microlens according to claim 1, wherein the method is a step of irradiating an ultraviolet ray containing light having the following wavelength. 4. The step of irradiating the transparent resin layer with ultraviolet light while heating the substrate is a step of irradiating the transparent resin layer with ultraviolet light while heating the substrate to 100 to 200 ° C. Item 2. The method for producing an on-chip microlens according to Item 1. 5. A while heating the substrate, the step of the transparent resin layer to the ultraviolet irradiation treatment, while heating the substrate to 100 to 200 ° C., the transparent resin layer, 10mj / cm ² ~500mj / cm ^The method for producing an on-chip microlens according to claim 1, wherein the method is a step of irradiating an ultraviolet ray having energy of ² . 6. A step of forming a transparent resin layer made of a negative photosensitive resin on a semiconductor substrate having a light receiving section and a charge transfer section, and comprising a step of forming a positive photosensitive resin on the transparent resin layer. A step of forming a photosensitive resin layer; a step of exposing the photosensitive resin layer to form a pattern corresponding to the light receiving portion on the photosensitive resin layer; and a step of transferring the pattern to the transparent resin layer. And a step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate. 7. The step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate, wherein the transparent resin layer is heated while heating the semiconductor substrate.
is mj / cm ² ~500mj / cm ² of irradiating process ultraviolet energy, a method for manufacturing a solid-state imaging device according to claim 6, wherein. 8. The step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate, wherein the transparent resin layer is heated to 32% while heating the semiconductor substrate.
The method for manufacturing a solid-state imaging device according to claim 6, wherein the method is a step of irradiating an ultraviolet ray containing light having a wavelength of 0 nm or less. 9. The step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate is a step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate to 100 to 200 ° C. The method for manufacturing a solid-state imaging device according to claim 6. 10. A step of irradiating the transparent resin layer with ultraviolet light while heating the semiconductor substrate, wherein the transparent resin layer is heated to 100 to 200 ° C. while the transparent resin layer is heated to ^{10 to} 500 mj. / Cm ²
The method of manufacturing a solid-state imaging device according to claim 6, wherein the step of irradiating the solid-state imaging device with ultraviolet light having energy of: