JPH0927608A - Solid-state image pick-up device and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state image pick-up device and its manufacturing method having microlens structure capable of adopting mold package structure without adopting hollow package structure. SOLUTION: A solid-state image pick-up device 11 is provided with a photodetecting parts 3 for photoelectric conversion and flare stopping films 8 without covering the photodetecting surface 3a of the photodetecting part 3. A transparent lens 12 made of the first transparent material having concave lenses 12a to be concave on the opposite side covering the photodetecting surface 3a is provided. On the other hand, a transparent flattened layer 13 having at least flattened top surface thereof made of the second transparent material in higher refractive index than that of the first transparent material is provided on the transparent lens layer 12 in contact with said layer 13.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a charge-coupled device (C
The present invention relates to a solid-state imaging device using a CD and the like and a manufacturing method thereof.

[0002]

2. Description of the Related Art Conventionally, in this type of solid-state image pickup device, since an area such as a transfer register that does not contribute to photoelectric conversion exists in each pixel, the aperture ratio of the light receiving surface of the light receiving portion in the entire pixel surface is usually 50. % Or less, and there is a complaint that the utilization rate of incident light is not sufficient. In order to eliminate such dissatisfaction and improve the sensitivity, for example, it is possible to increase the ratio of the light receiving surface to the entire pixel surface.
Since there is a structural limit to increasing the proportion of the light-receiving surface, in recent years, a convex microlens is provided on the light-receiving surface to concentrate incident light on the light-receiving surface for efficient light collection. None, there is provided a solid-state image pickup device having a so-called on-chip microlens for increasing the effective aperture ratio.

FIG. 6 is a side sectional view of an essential part showing an example of a conventional solid-state image pickup device using such a convex microlens. In FIG. 6, reference numeral 1 is a solid-state imaging device, and 2 is a semiconductor substrate made of a silicon wafer or the like. On the semiconductor substrate 2, a light receiving portion 3 for performing photoelectric conversion, a transfer register 4 and a channel stop 5 are formed on its surface layer portion,
Further, a thin insulating film 6 is formed on the surface thereof. Further, a transfer electrode 7 for driving the transfer register 4 is formed on the insulating film 6, and further, in order to prevent light from entering the transfer electrode 7 and the transfer register 4, the transfer electrode 7 is covered and a light shielding film 8 is formed. Are formed. Here, the light shielding film 8 formed on the insulating film 6 is formed without covering the light receiving surface 3 a of the light receiving section 3.

A convex microlens 9 made of a transparent resin or the like is formed on the unit pixel composed of these constituent elements so as to be convex upward. The microlens 9 is formed and arranged so that the light receiving surface 3a of the light receiving unit 3 serves as its focal point. With such a configuration, the solid-state imaging device 1 emits light as indicated by an arrow in FIG. When incident, the incident light is collected on the light receiving surface 3a due to the condensing effect of the microlens 9, thereby increasing its effective aperture ratio.

[0005]

However, in the solid-state image pickup device 1, the microlens 9 has a condensing effect. Therefore, air or a substance having a sufficiently lower refractive index than the material of the lens 9 is provided above the lens 9. Low refractive index layer 10 made of
It is necessary to cover with. Therefore, the ideal package structure is a so-called hollow package structure in which air is sandwiched between the chip and the sealing material. However, this hollow package structure requires a higher assembly cost than a mold package structure that is generally used as a semiconductor device, and therefore cost reduction is strongly desired.

On the other hand, in the case of adopting the mold package structure, the condition of low refractive index is added to the performance required for the molding material such as transparency, humidity resistance, strength, etc.
The selection of the molding resin material is subject to very strong restrictions, and in reality, it is impossible to find an appropriate material as the material. The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a solid-state imaging device having a microlens structure capable of adopting a mold package structure without adopting a hollow package structure, and manufacturing thereof. To provide a method.

[0007]

In the solid-state image pickup device of the present invention, it is made of a first transparent material having a concave lens which covers the light receiving surface of the light receiving portion and becomes concave toward the side opposite to the light receiving surface. A transparent lens layer is provided, and a transparent flattening layer made of a second transparent material having a refractive index higher than that of the first transparent material and having at least the uppermost surface thereof flattened is formed on the transparent lens layer. The provision of the lens layer in contact with the lens layer was a means for solving the above-mentioned problems.

According to this solid-state image pickup device, there is provided a transparent lens layer having a concave lens which is concave toward the side opposite to the light receiving surface, and further, on the transparent lens layer, in contact therewith. Since it has a transparent flattening layer made of a transparent material having a higher refractive index than the material of the transparent lens layer, the focus of the concave lens formed by the difference in refractive index between the transparent flattening layer and the transparent lens layer, If a transparent lens layer is formed in advance so as to match the light receiving surface, the effective aperture ratio will be high as in the conventional case. Further, since the transparent flattening layer serving as the outermost layer is formed of a material having a high refractive index, it is possible to use a conventionally known transparent resin or the like as this material, and the degree of freedom in selecting the material is increased. At the same time, since it is not necessary to adopt the hollow package structure, the assembly cost can be reduced. Further, it becomes possible to use the mold resin as it is as the material for forming the transparent flattening layer, and in that case, it is possible to further reduce the assembly cost.

Further, in the method of manufacturing a solid-state image pickup device of the present invention, a step of forming a first transparent material layer made of a first transparent material so as to cover the light receiving surface of the light receiving portion and the light shielding film, and the first transparent material layer. Forming a resist layer on the transparent material layer, forming a groove in the resist layer in the vicinity of a position immediately above the peripheral edge of the light-receiving surface, heating the resist layer to soften / melt it, and Forming a first planarization layer on the melted resist layer, and etching using an etchant having a larger etching rate for the resist layer than for the first planarization layer, Removing the first planarization layer and the resist layer to expose the first transparent material layer, and on the exposed first transparent material layer, in contact therewith and higher than the first transparent material. A second transparent material with a refractive index Forming a second planarizing layer of material, further comprising a set to solutions of the problems.

Further, according to the method for manufacturing the solid-state image pickup device, the first transparent material layer is formed on the light receiving surface, the resist layer is formed on the first transparent material layer, and the peripheral edge of the light receiving surface of the resist layer is formed. Since a groove is formed near the position directly above and then the resist layer is heated to be softened and melted, the surface tension of the resist layer causes the resist layer to be low at the groove side and high at a position distant from the groove. It has a convex curved shape. Then, a first flattening layer is formed on this resist, and etching is performed using an etching agent having a larger etching rate for the resist layer than for the first flattening layer. At the provided position, the etching rate increases after the first planarizing layer is etched.

Therefore, when the etching of the first planarization layer is completed at the portion where the resist layer is not provided,
The etching of the resist layer has already been completed at the place where the resist layer is provided, and the etching of the first transparent material layer thereunder is advanced. At this time, the etching in the first transparent material layer corresponds to the thickness of the resist layer, that is, progresses faster at a thick resist layer portion and slower at a thin resist layer portion. When the etching is completed, the first transparent material layer has a shape opposite to that of the resist layer after the softening / melting, that is, a curved shape having an upward concave shape. Then, after forming a concave curved shape on the first transparent material layer in this way, on the first transparent material layer, in contact with this, having a refractive index higher than that of the first transparent material. Since the second flattening layer made of the second transparent material is formed, the concave curved shape portion is used as a concave lens, and the transparent flattening layer made of the transparent material is provided on the concave lens, thereby obtaining the solid-state imaging device. .

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to embodiments. FIG. 1 is a diagram showing an example of a first embodiment of a solid-state imaging device according to the present invention, in which reference numeral 11 is a solid-state imaging device. The solid-state imaging device 11 differs from the solid-state imaging device 1 shown in FIG. 6 in the structure of the microlenses formed on the insulating film 6 and the light-shielding film 8. That is, in the solid-state imaging device 11 shown in FIG. 1, the transparent lens layer 12 is formed on the insulating film 6 so as to cover the light receiving surface 3 a of the light receiving unit 3, and the transparent flattening layer is formed on the transparent lens layer 12. Thirteen
Are formed.

The transparent lens layer 12 is made of a material (first transparent material) such as a fluorinated transparent resin such as CYTOP (trade name; manufactured by Asahi Glass Co., Ltd.) or an acrylic transparent resin whose refractive index is adjusted to be low. And its refractive index is 1.2 to 1.4
Of the degree. In addition, the transparent lens layer 12 includes
A concave lens 12a, which is concave on the upper surface thereof, that is, the surface opposite to the light receiving surface 3a, is concave toward the side opposite to the light receiving surface 3a.
Are formed in large numbers. These concave lenses 12a are formed one by one for each unit pixel of the solid-state image pickup device 1, and as will be described later, their focal points are aligned on the light receiving surface 3a of the light receiving unit 3 in the same unit pixel. Has become.

The transparent flattening layer 13 is made of a material (second transparent material) such as an epoxy transparent resin or an acrylic transparent resin whose refractive index is adjusted to be relatively high, and a transparent silicone resin. Its refractive index is 1.5 ~
It was adjusted to about 1.7. Further, the transparent flattening layer 13 is formed so as to be in direct contact with the upper surface of the transparent lens layer 12, and therefore the concave lens 12a has its upper side (light incident side) and its lower side (light emission side). side)
Due to the difference in refractive index between the transparent flattening layer 13 on the light incident side and the lower refractive index on the transparent lens layer 12 on the light emitting side. Light incident from above 13 is collected in one place without being dispersed as shown by an arrow in FIG.

Next, the solid-state image pickup device 11 having such a configuration.
Based on the manufacturing method of 1., one embodiment example of the manufacturing method of the present invention will be described. First, as shown in FIG. 2A, the light receiving portion 3, the transfer register 4, and the channel stop 5 are formed on the semiconductor substrate 2.
Each of the constituent elements such as is formed by a technique such as photoresist and ion implantation in the same manner as in the conventional case, and an insulating film 6, a transfer electrode 7, and a light shielding film 8 are further formed thereon by photoresist, ion implantation, thermal oxidation, and deoxidization. It is also formed in the same manner as in the past by the technique of position. Next, the first transparent material layer 14 made of the first transparent material is formed so as to cover the insulating film 6 and the light shielding film 8. As the first transparent material, a fluorine-based transparent resin or an acrylic transparent resin having a refractive index of about 1.2 to 1.4 is used as described above. In addition,
When forming the first transparent material layer 14, the upper surface thereof is flattened by a conventionally known method.

Next, a resist layer is formed on the first transparent material layer 14. The resist for forming the resist layer is not particularly limited, and conventionally known ones such as polymethylmethacrylate (PMMA) can be used. Then, the formed resist layer is patterned by a known exposure / development technique, as shown in FIG.
As shown in (c), a groove 16 is formed in the vicinity of a position directly above the peripheral edge of the light receiving surface 3a. Then, the resist patterns 15 formed of the obtained resist layer are heated to soften and melt the resist patterns 15. As heat treatment,
Although it depends on the resist used, when the polymethyl methacrylate is used, the process is performed at about 150 ° C. for about several minutes. When the heat treatment is performed in this manner, the resist pattern becomes low on the groove 16 side and becomes high at a position apart from the groove 16 due to the surface tension, and as a result, the resist pattern is convex upward as shown in FIG. The resist 15a has a curved shape.

Next, the resist 1 formed by softening and melting
A layer made of, for example, a resist material such as novolac resin is formed on 5a, and the surface of this layer is flattened by a known flattening technique to form a first flattening layer 17 as shown in FIG. 2 (e). Form. Then, this first planarization layer 1
7, that is, the material for forming the first planarization layer 17 is etched with an etchant having a higher etching rate with respect to the resist layer (resist 15a), for example, oxygen plasma. 2F, the first flattening layer 17 and the resist 15a are removed, and the first transparent material layer 14 is removed.
To expose.

When such etching is performed, the difference in etching rate between the first flattening layer 17 and the resist 15a of the used etching agent causes a difference in the resist 15a.
At the position where is formed, the etching rate is increased after the first planarization layer 17 is etched. The difference in etching rate between the portion where the resist 15a is formed and the portion where the resist 15a is not formed causes the etching of the first planarization layer 17 at the portion where the resist 15a is not formed. When finished, the resist 15a has already been formed in the area where the resist 15a is formed.
After the etching of a is completed, the first transparent material layer 1 thereunder
We are proceeding to the etching of 4. At this time, the etching in the first transparent material layer 14 progresses almost in proportion to the thickness of the resist 15a, that is, the etching progresses faster where the resist 15a is thick and slower where the resist 15a is thin. Therefore, the first transparent material layer 14 has
When the etching is finished, the surface of the concave lens 12a having a shape opposite to that of the softened / melted resist 15a, that is, a concave curved shape is formed. Regarding the formation of the surface of the concave lens 12a, the transparent material, the resist, the type of the etching agent, the resist heating conditions, etc. are appropriately determined in advance by experiments or the like.
The focal point of 2a is positioned on the light receiving surface 3a.

Then, on the exposed surface of the first transparent material layer 14, that is, on the surface on which the surface of the concave lens 12a is formed, a layer of the second transparent material is formed in contact with it.
Further, the obtained layer is flattened by a conventionally known flattening technique to form the transparent flattening layer (second flattening layer) 13 shown in FIG. 1 to obtain the solid-state imaging device 1. As the second transparent material, a material having a refractive index sufficiently higher than that of the first transparent material, specifically, a refractive index of 1.5 to 1.7 or higher is used, and as described above, for example, Epoxy transparent resin, acrylic transparent resin, and transparent silicone resin are used.

In the solid-state image pickup device 1 thus obtained, the transparent lens layer 12 having the concave lens 12a is formed.
And a transparent flattening layer 13 in contact therewith, and the focal point of the concave lens 12a formed by the difference in refractive index between the transparent flattening layer 13 and the transparent lens layer 12 is received as indicated by an arrow in FIG. Since it is formed so as to match the surface 3a, it has a high effective aperture ratio like the conventional one.

Further, in the method of manufacturing such a solid-state image pickup device 1, since the transparent flattening layer 13 which is the outermost layer is formed of a material having a high refractive index (second transparent material), this material is used. A conventionally known transparent resin or the like can be used as the material, and the degree of freedom in selecting the material can be increased.

FIG. 3 is a diagram showing a modification of the solid-state image pickup device of the present invention. In FIG. 3, reference numeral 20 is a solid-state image pickup device. The solid-state imaging device 20 is different from the solid-state imaging device 11 shown in FIG. 1 in that the solid-state imaging device 11 shown in FIG.
In addition to the above, the transparent mold resin layer 21 is added. That is, in the solid-state imaging device 20 shown in FIG. 3, the transparent mold resin layer 21 is provided on the transparent flattening layer 13 to form a mold package structure.
In order to obtain such a solid-state imaging device 20, FIG.
In addition to the step shown in (f), the solid-state imaging device 11 shown in FIG. 1 is sealed with a transparent mold resin by a known mold sealing technique, thereby obtaining a mold package structure.

In the solid-state image pickup device 20 having such a structure, since the outermost transparent flattening layer 13 is made of a material having a high refractive index (second transparent material), for example, an epoxy-based transparent material is used. Even if a transparent mold resin such as a resin having the same refractive index as that of the transparent flattening layer 13 is formed on the transparent flattening layer 13, the lens function of the concave lens 12a is not impaired, and therefore the effective aperture ratio can be increased. At the same time, a mold package structure that is generally used as a package structure and has a low assembly cost can be adopted.

In the above embodiment, the transparent mold resin layer 21 is formed on the transparent flattening layer 13 to form a mold package structure.
Instead of, a transparent mold resin layer is formed directly on the transparent lens layer 12 by potting sealing of a transparent resin,
The upper surface of the transparent mold resin layer (the surface on the light receiving surface 3a side) is flattened to form the transparent mold resin layer as the transparent flattening layer 13.
You may make it function similarly to. In this case, the transparent flattening layer 1
Since the molding resin encapsulation can be performed directly by omitting the forming step of 3, the assembling cost can be further reduced.

FIG. 4 is a diagram showing a specific example in which a transparent mold resin layer is directly formed on the transparent lens layer 12 instead of the transparent flattening layer 13. Reference numeral 40 in FIG. Is a CCD chip obtained by removing the transparent flattening layer 13 from the solid-state imaging device 11 shown in FIG. On the CCD chip 41, a transparent mold resin layer 42 is formed by directly covering the transparent lens layer 12 formed on the surface of the CCD chip 41. Further, the transparent mold resin layer 42 is covered by a transparent glass or A transparent flat plate 43 made of a transparent plastic lid is provided. The TAB lead 46 is connected to the electrode 44 formed on the surface of the CCD chip 41 via the gold bump 45. The connecting portions of the electrodes 44, the gold bumps 45, and the TAB leads 46 are sealed with the transparent mold resin 42 and covered with the transparent flat plate 43 in this state.

In the solid-state image pickup device 40 having such a structure, when manufacturing the solid-state image pickup device 40, the step of forming the transparent flattening layer 13 can be omitted and the molding resin can be directly sealed as described above. The cost can be reduced and the surface of the transparent mold resin layer 42 can be flattened.
Since the transparent flat plate 43 can be easily provided on the transparent flat plate 43, the assembling cost can be further reduced.

FIG. 5 is a diagram showing a second embodiment of the solid-state image pickup device of the present invention. In FIG. 5, reference numeral 30 is a solid-state image pickup device. The solid-state imaging device 30 is different from the solid-state imaging device 11 shown in FIG. 1 in that the passivation film 3 is provided between the insulating film 6 and the light-shielding film 8 and the transparent lens layer 12.
1 is that the color filter film 32 is provided.
That is, in the solid-state imaging device 30 shown in FIG. 4, the passivation film 31 is formed so as to cover the insulating film 6 and the light shielding film 8, the color filter film 32 is provided on the passivation film 31, and the transparent film is further provided thereon. Lens layer 1
2 has a structure formed. Therefore, in the solid-state imaging device 30 having such a configuration, it is possible to selectively receive only a certain wavelength range of the incident light and photoelectrically convert it, so that, for example, the color filter film 3 is used.
It is possible to perform color display by using three kinds of materials corresponding to the wavelength ranges of red, blue, and green as 2.

[0028]

As described above, the solid-state image pickup device of the present invention has the transparent lens layer having the concave lens which is concave toward the opposite side to the light receiving surface, and further the transparent lens layer Since the transparent flattening layer made of a transparent material having a higher refractive index than the material of the transparent lens layer is provided in contact therewith, it is formed by the difference in refractive index between the transparent flattening layer and the transparent lens layer. If a transparent lens layer is formed in advance so that the focal point of the concave lens is aligned with the light-receiving surface, it will have a high effective aperture ratio like the conventional one.
Further, since the transparent flattening layer serving as the outermost layer is formed of a material having a high refractive index, a conventionally known transparent resin or the like can be used as this material, and the degree of freedom in selecting the material can be increased. it can. In addition, since the condensing effect of the lens does not depend on the sealing method, and because the mold package structure can be adopted without adopting the hollow package structure, the assembly cost can be reduced as compared with the conventional case.

Further, since the transparent mold resin can be used as it is as the material for forming the transparent flattening layer, the assembly cost can be further reduced in that case. Further, since the surface of the transparent flattening layer is flattened by the provision of the transparent flattening layer, it is easy to remove dust generated in the dicing or assembling process, which facilitates the production thereof. Further, the method for manufacturing a solid-state imaging device according to the present invention can manufacture the solid-state imaging device having the above-mentioned excellent effects, and thus is extremely effective industrially.

[Brief description of drawings]

FIG. 1 is a side sectional view showing a schematic configuration of a first embodiment of a solid-state imaging device of the present invention.

2A to 2F are side cross-sectional views of main parts for explaining the method of manufacturing the solid-state imaging device of the present invention in the order of steps.

FIG. 3 is a side sectional view showing a schematic configuration of a modification of the solid-state imaging device shown in FIG.

4 is a side sectional view showing a schematic configuration of another modification of the solid-state imaging device shown in FIG.

FIG. 5 is a side sectional view showing a schematic configuration of a second embodiment of the solid-state imaging device of the present invention.

FIG. 6 is a side sectional view showing a schematic configuration of a conventional solid-state imaging device.

[Explanation of symbols]

3 light receiving part 3a light receiving surface 8 light shielding film 11, 20, 30, 40 solid-state imaging device 12 transparent lens layer 12a concave lens 13 transparent flattening layer (second flattening layer) 14 first transparent material layer 15 resist pattern
15a Resist 16 Groove 17 First Flattening Layer 41 CCD Chip 42 Transparent Mold Resin Layer 43 Transparent Flat Plate

Claims (2)

[Claims] 1. A solid-state imaging device comprising a light-receiving portion for performing photoelectric conversion and a light-shielding film provided without covering the light-receiving surface of the light-receiving portion, the light-receiving surface of the light-receiving portion being covered with the light-receiving surface. A transparent lens layer made of a first transparent material having a concave lens that is concave toward the opposite side, and a second transparent layer having a higher refractive index than the first transparent material is provided on the transparent lens layer. A solid-state imaging device comprising a transparent flattening layer made of a material, at least the uppermost surface of which is flattened, in contact with the transparent lens layer. 2. A method of manufacturing a solid-state imaging device, comprising: a light-receiving portion that performs photoelectric conversion; and a light-shielding film that is provided without covering the light-receiving surface of the light-receiving portion. Forming a first transparent material layer made of a first transparent material covering the film; forming a resist layer on the first transparent material layer; and forming a resist layer on the periphery of the light receiving surface of the resist layer. A step of forming a groove in the vicinity of a position immediately above, a step of heating and softening / melting the resist layer, a step of forming a first planarizing layer on the softened / melted resist layer, Etching is performed using an etchant having a higher etching rate than the flattening layer with respect to the resist layer, and the first flattening layer and the resist layer are removed to expose the first transparent material layer. And the exposed first Forming a second planarizing layer on the transparent material layer, which is in contact with the transparent material layer and is made of a second transparent material having a higher refractive index than the first transparent material. Manufacturing method of solid-state imaging device.