JP2000022117A - Manufacture of solid-state image-pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the sensitivity of a solid-state image-pickup device by eliminating the clearance between microlenses. SOLUTION: A method of manufacturing a solid-stage image-pickup device includes a step of forming a transparent resin layer on a semiconductor substrate on which a plurality of light receiving sections is formed, a step of forming a first microlens 15 in an area on the surface of the transparent resin layer above a light receiving section, and a step of again forming a lens material layer 16 on the surface of the transparent resin layer. The method also includes a step of forming a lens material pattern 17 above the other light receiving section adjacent to the light receiving section by patterning the lens material layer 16 and another step of forming a second microlens 18, in such a way that the microlens 18 is brought into contact with the first microlens 15 by melting the lens material pattern through heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a solid-state image pickup device, and more particularly, to a solid-state image pickup device provided with an on-chip microlens for condensing incident light to a light-receiving portion at each pixel. And a method for producing the same.

[0002]

2. Description of the Related Art In recent years, in a solid-state imaging device, a microlens has to be provided for each pixel in order to improve the sensitivity of the solid-state imaging device by selectively condensing incident light on a light receiving portion to increase the light utilization rate. The mainstream is equipped with. A method of manufacturing a solid-state imaging device having the microlens will be described with reference to FIG.

First, a transparent resin layer including a flattening layer is formed on the surface of a solid-state image sensor 30 in which a plurality of unit pixels including a light receiving section 31 and a charge transfer section are arranged two-dimensionally on a semiconductor substrate. After forming the transparent resin layer 32,
A photosensitive thermoplastic resin is applied thereon to form a lens material layer 33 (FIG. 5A). Next, after exposing the lens material layer 33 through the mask 301 (FIG. 5).
(B)) Patterning is performed by removing a portion solubilized by exposure. Through this step, a lens material pattern 34 is formed above the light receiving section 31 of each pixel (FIG. 5C). Subsequently, the lens material pattern 34 is heated and melted and fluidized (hereinafter, this heat treatment is referred to as “flow treatment”). By this flow processing, the surface of the fluidized lens material pattern 34 becomes convex due to surface tension, and the microlens 35a is formed.
(D)). Thus, in the conventional manufacturing method, all the microlenses are formed simultaneously.

[0004]

In a solid-state imaging device having microlenses, the gap between the microlenses is reduced or preferably eliminated, so that the light collection rate can be further increased and the sensitivity can be improved.

In order to reduce the gap between the microlenses in the above-described manufacturing method, the gap between the lens material patterns 34 formed at the time of patterning the lens material layer may be reduced. However, in the above-described manufacturing method, since all the microlenses are formed at the same time, there are the following problems. First, the resolution of the photolithography technique is limited, and it is very difficult to reliably form a pattern of a desired size by patterning at a resolution lower than the resolution. Therefore, there is a limit in reducing the gap between the lens material patterns 34. In addition, when the gap between the lens material patterns 34 is reduced or eliminated, the lens material patterns fluidized by the flow processing come into contact with each other. Therefore, the cross section of the region where the adjacent microlenses contact is formed by one continuous curve. There is a high possibility that a microlens with a defective shape (35b in FIG. 5D) will be formed. Therefore, it has been difficult to reduce or eliminate the gap between the microlenses while maintaining the convex lens shape of the microlenses.

As a method for solving the above problem, Japanese Patent Laid-Open No.
In Japanese Patent Application Laid-Open No. 145813, a microlens is first formed by the above-described method, and then a gap between the microlenses is eliminated by depositing and forming a transparent film on the surface of the microlens by spin coating using a CVD method or spin-on-glass. A method has been proposed. However, as shown in FIG. 6, a transparent film 46 formed by such a method tends to thickness L ₂ of the micro lens edge is larger than the thickness L ₁ of the micro lens central portion. Further, the transparent film 46 is deposited not only on the microlens surface but also in the gap between the lenses. Therefore, it is difficult to set the film forming conditions to completely eliminate the gap between the lenses, and there is a problem that the effect of improving the light collection rate is small. Also, the above publication discloses a method in which a microlens is first formed by the above-described method, and then the transparent resin layer exposed between the lenses and the lens is etched by reactive ion etching to eliminate the gap between the lenses. Has also been proposed. However, in this method, since the gap portion needs to be etched at a high etching rate, there is a problem that the surface is roughened and the image quality is deteriorated. Also, it has been difficult to control the etching so that the gap between the lenses is completely eliminated.

An object of the present invention is to provide a method of manufacturing a solid-state imaging device having improved sensitivity by eliminating a gap between microlenses.

[0008]

In order to achieve the above object, a first method of manufacturing a solid-state imaging device according to the present invention is directed to a method of manufacturing a solid-state image pickup device, wherein a plurality of light receiving sections are arranged in a matrix on a semiconductor substrate surface, and each of the light receiving sections is provided. Forming a transparent resin layer above the semiconductor substrate, wherein the surface of the transparent resin layer corresponds to a part of the light receiving portion. Forming a first microlens, forming a lens material pattern in a region of the transparent resin layer surface adjacent to the first microlens, and deforming the lens material pattern surface into a convex shape by heating. Forming a second microlens, and forming the second microlens,
The first microlens and the second microlens are implemented so as to be in contact with each other.

[0009] With such a configuration, the adjacent microlenses are formed so as to be in contact with each other.
By improving the light collection rate, a high-sensitivity solid-state imaging device can be obtained. Further, since the adjacent microlenses are formed in different steps, the shape of the microlenses can be easily controlled. In addition, the gap formed between the lens material patterns can be set to a size that allows for the resolution of the photolithography method, and it is easy to uniformly form the size of each lens material pattern. The occurrence of image defects due to variations in the dimensions can be reduced.

In the first manufacturing method, the second manufacturing method
It is preferable that the step of forming the microlens is performed in a state where the first microlens is not deformed. This is because control of the shape of the microlens becomes easier.

[0011] In the first manufacturing method, the step of forming the second microlens may include the step of forming the curved surface of the first microlens and the curved surface of the second microlens into the transparent resin layer. It is preferable to carry out the process so as to be in contact with the surface of. This is because the distance from the curved surface of the microlens to the light receiving portion can be reduced, so that the light collection rate can be further improved.

In order to achieve the above object, a second method of manufacturing a solid-state imaging device according to the present invention is directed to a method of manufacturing a solid-state imaging device, wherein pixels including a light receiving section and a charge transfer section are arranged in a matrix on a semiconductor substrate surface, and each of the light receiving sections is provided. Forming a transparent resin layer above the semiconductor substrate, wherein the surface of the transparent resin layer corresponds to a part of the light receiving portion. Forming a first microlens, forming a lens material pattern in a region of the transparent resin layer surface adjacent to the first microlens, and deforming the lens material pattern surface into a convex shape by heating. Forming a second microlens, and forming the first microlens,
The width of the first microlens is equal to or larger than the width of the pixel.

[0013] With this configuration, adjacent microlenses are formed in different steps, respectively.
Since the adjacent microlenses can be formed so as to be in contact with each other, the same effects as those of the first manufacturing method of the present invention can be obtained. Note that the width of the microlens refers to the length of the bottom surface of the first microlens (for example,
The length of one side when the bottom surface is rectangular, and the diameter when the bottom surface is circular), and the width of the pixel is equal to the distance between the light receiving portion corresponding to the first microlens and the light receiving portion adjacent thereto. It is the length of the section divided by the plane to be set.

In the second manufacturing method, the second manufacturing method
It is preferable that the step of forming the microlens is performed in a state where the first microlens is not deformed. This is because control of the shape of the microlens becomes easier.

[0015] In the second manufacturing method, the step of forming the first microlens may include the step of forming a difference between the width of the first microlens and the width of the pixel of 2.0 μm.
It is preferred to be implemented as follows. Furthermore,
It is preferable that the width of the bottom surface of the first microlens is equal to the width of the pixel. This is because the distance from the curved surface of the microlens to the light receiving portion can be reduced, so that the light collection rate can be further improved.

In the first and second manufacturing methods,
The step of forming the first microlens includes the step of forming the first microlens.
It is preferable that the light receiving unit in which the microlenses are formed and the light receiving unit in which the microlenses are not formed are alternately arranged in the row direction and the column direction. That is,
It is preferable that the arrangement of the light receiving unit where the first microlens is formed and the light receiving unit where the first microlens is not formed be arranged in a checkered pattern on the surface of the semiconductor substrate. According to this preferred example, with a smaller number of steps,
Microlenses can be formed in all pixels.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for manufacturing a solid-state imaging device according to the present invention will be described below with reference to the drawings. 1 and 2
FIG. 3 is a process sectional view showing the first embodiment of the manufacturing method of the present invention.

First, pixels including a light receiving portion and a charge transfer portion are formed so as to be two-dimensionally arranged on a main surface of a semiconductor substrate. The light receiving portions 11a and 11b are formed by introducing an n-type impurity into a p-type well formed in a surface layer portion of the semiconductor substrate. The charge transfer portion is formed by introducing an n-type impurity into a p-type well in a surface layer portion of the semiconductor substrate, and a transfer electrode is formed above the charge transfer portion via a gate insulating film. Further, a light-shielding film is formed on the transfer electrode via an interlayer insulating film, and the solid-state imaging device 10 is formed. On the surface of the solid-state image sensor,
An insulating film and a surface protection layer are formed.

Subsequently, a transparent resin layer 12 is formed on the solid-state imaging device 10. The transparent resin layer 12 includes a flattening layer,
This is a layer including a color filter layer and an intermediate layer as necessary. The planarization layer and the intermediate layer include, for example, PMMA
Acrylic resins such as (polymethyl methacrylate),
Phenolic resins and styrene resins can be used.
For the color filter layer, for example, an acrylic resin dyed in a predetermined color can be used.

For the steps up to the formation of the transparent resin layer, the conventional method for manufacturing a solid-state imaging device can be applied, and the structure in the solid-state imaging device and the structure of the transparent resin layer are not particularly limited.

A first lens material layer 13 is formed on the transparent resin layer 12 (FIG. 1A). First lens material layer 1
3 is a lens material to which a solvent or the like is added if necessary.
It is formed by applying by a spin coating method or the like.
The thickness of the first lens material layer 13 is set so that the focal point of the microlens to be formed is formed on the corresponding light receiving portion, and depends on the layer thickness of the transparent resin layer 12;
About μm is appropriate.

As the lens material, for example, a material conventionally used as a material of a microlens, such as a synthetic resin such as a phenol resin, a styrene resin, and an acrylic resin, can be used. The lens material shows fluidity once by heating, but when heating is further continued, the resin becomes hardened by the action of a hardener or heat and becomes infusible (hereinafter, referred to as a resin).
It is simply called “thermosetting resin”. ) Is used. Furthermore,
A photosensitive resin is used for the lens material. Specifically, it is preferable to use a photosensitive resin obtained by adding naphthoquinonediazide to a polyparavinylphenol-based resin as such a lens material. In addition, as the photosensitive resin, any of a positive type and a negative type can be used,
1 and 2 illustrate a case where a positive photosensitive resin is used.

Next, the first lens material layer 13 is patterned (FIGS. 1B to 1C). In the patterning of the first lens material layer 13, the first lens material pattern 14 is formed only above a part of the pixels, and at least the pixel on which the first lens material pattern 14 is formed (for example, the light receiving portion 11a). This is performed so that the first lens material pattern is not formed in a pixel (for example, a pixel including the light receiving portion 11b) adjacent to the pixel including the light-receiving portion 11b. For example, in a semiconductor substrate in which a plurality of pixels are arranged in a matrix, the pixels on which the first microlenses are formed and the pixels on which the first microlenses are not formed are alternately arranged in both the row direction and the column direction, as if drawing a checkered pattern. Is implemented as shown in

A photolithography method is employed for patterning. After the first lens material layer 13 is exposed through a mask 101 (FIG. 1B), a portion solubilized by the exposure is removed by a developer. A first lens material pattern 14 is formed (FIG. 1C). For exposure, g-line (436 nm) or i-line (365 nm) is used depending on the photosensitive material used. As the developer, for example, a non-metal organic ammonium developer can be used.

The formed first lens material pattern 14
The light 1 that the lens material is exposed to for bleaching
02 is irradiated (FIG. 1D). As a result, the remaining photosensitive component is discolored, the photosensitivity of the first lens material pattern is lost, and the visible light transmittance of the lens material pattern can be improved.

Next, the first lens material pattern 14 is fluidized by heating, and is deformed from a shape having a rectangular cross section to a shape of a convex lens, thereby forming a first micro lens 15. Also, the formed first micro lens is
It is further cured by heating (FIG. 1 (e)). The heating temperature is set according to the lens material used. For example, when a polyparavinylphenol-based resin is used, it is preferable to first heat to 120 to 160 ° C. to form a convex lens shape, and then heat to 180 to 200 ° C. to cure the resin.

In the present embodiment, as shown in FIG. 1 (e), the width W _L of the first microlens 15 in the horizontal direction is adjusted to be larger than the width W _C of the pixel. The width W _L of the first microlenses 15, first
The width of the microlens pattern is controlled by adjusting the width 14 of the lens material pattern. At this time, it is considered that the microlens width is slightly larger than the lens material pattern width.

Subsequently, a second lens material layer 16 is formed on the surface of the transparent resin layer 12 on which the first microlenses 15 are formed.
Is formed (FIG. 2F). In this step, the first
The same lens material and forming method as the step (FIG. 1A) of forming the lens material layer can be used.

Next, the second lens material layer 16 is patterned (FIGS. 2G to 2H). The patterning of the second lens material layer 16 is performed by the first micro lens 15.
(For example, a pixel including the light receiving portion 11a) in which is formed
The second lens material pattern 17 is formed above a pixel (for example, a pixel including the light receiving portion 11b) adjacent to the second lens material pattern. The distance between the second lens material pattern 17 and the adjacent first microlens 15 is such that the second lens material pattern 17 that has been fluidized in the subsequent heating step (the step in FIG. The distance is not particularly limited as long as it can contact the micro lens 15 of
It is about 0.8 μm.

Photolithography is employed for patterning. After exposing the second lens material layer 16 through the mask 103 (FIG. 2 (g)), the portion solubilized by the exposure is removed by a developer. A second lens material pattern 17 is formed (FIG. 2 (h)). As the stepper and the developer used for the exposure, the same as those used in the patterning of the first lens material layer (FIGS. 1B to 1C) can be used. In the exposure and development of the second lens material layer, the first microlens has already lost its photosensitivity due to the bleaching in the step of FIG.

The formed second lens material pattern 17
The light 1 that the lens material is exposed to for bleaching
02 is irradiated (FIG. 2 (i)).

Next, the second lens material pattern 17 is fluidized by heating and deformed into a convex lens shape to form a second micro lens 18 (FIG. 2 (j)). This step is performed so that the formed second microlens 18 contacts the adjacent first microlens 15.
In the first embodiment, the first micro lens 15
Since the width W _L is greater than the width W _C of the pixel of the second microlenses 18 are formed in such a way rides on the first microlens 15. In other words, the curved surface of the first microlens 15 and the curved surface of the second microlens 18 are formed so as to contact above the surface of the transparent resin layer 12.

Further, since the first microlens 15 is already hardened by the heating at the time of formation (heating in the step of FIG. 1E), the first microlens 15 is not fluidized by the heating at the time of forming the second microlens, and the shape thereof changes. Do not wake up. Therefore, even when the fluidized second lens material pattern comes into contact, the convex lens shape of the first microlens 15 is maintained. Therefore, the cross section of the region where the first microlens and the second microlens come into contact can be formed into a shape constituted by two upwardly convex curves. The first
The bottom surface of the second microlens is not particularly limited as long as it has a shape capable of condensing light, and may be a polygon, a circle, an ellipse, or the like.

[0034] In the first embodiment described above, the first micro lens 15 and the width W _L is formed to be larger than the width W _C of the pixel, in the manufacturing method of the present invention, it is preferred that the first microlens width W _L is formed to be equal to the width W _C of the pixel. This is referred to as a second embodiment of the present invention, and sectional views of the steps are shown in FIGS.

In the second embodiment, the steps of FIGS. 3B to 3C are performed by changing the dimensions of the first lens material pattern 24 to be formed in the first embodiment (FIGS. 1B to 1C). 3), and the width W _L of the first microlens 25 formed in the step of FIG. _3D is made equal to the width W _C of the pixel. Other steps are substantially the same as those of the first embodiment.

In this embodiment, the second microlens 28 is formed such that its curved surface is in contact with the curved surface of the first microlens 25 on the surface of the transparent resin layer 22 (FIG. 4 (j)). ). As a result, it is possible to reduce the distance from the surface of the microlens to the light receiving unit, thereby providing a solid-state imaging device with higher sensitivity.

In the manufacturing method of the present invention, a series of microlens forming steps (steps from a lens material layer forming step to a flow processing step) are repeatedly performed in order to form adjacent microlenses in another step. The number of repetitions is not particularly limited. For example, as described above, if the first microlens is formed so that the pixel on which the first microlens is formed and the pixel on which the first microlens is not formed draw a checkerboard pattern on the semiconductor substrate, two microlens formations are performed. In the process, it is possible to form microlenses on all pixels.

Further, in the manufacturing method of the present invention, after forming the first microlenses and the second microlenses on the surface of the transparent resin layer by the above-described method, the surface layers of the respective microlenses and the transparent resin layer are dry-etched. Alternatively, a step of performing etch back by wet etching can be performed. This etching is performed under the condition that the etching rates of the lens material and the surface layer of the transparent resin layer become substantially equal. According to this method, since the distance from the surface of the microlens to the light receiving unit can be reduced by performing the etch back, a solid-state imaging device with higher sensitivity can be provided.

As described above, in the method of manufacturing a solid-state imaging device according to the present invention, the first micro lens and the second micro lens adjacent to each other are formed in different steps, respectively, and the second micro lens is formed. The formation is performed to contact the already formed first microlens. Accordingly, the area where the microlens is formed can be increased, so that the light-collecting efficiency can be improved and a high-sensitivity solid-state imaging device can be obtained.

Further, according to the manufacturing method of the present invention, when the second microlens is formed, the first microlens is already infused and does not change its shape. Even if the lens material pattern contacts, the convex lens shape of the first microlens is maintained, so that the shape control of the microlens is easy.

In the step of patterning the lens material layer, the gap formed between the lens material patterns is at least one lens material pattern, and has a size that allows for the resolution of photolithography.
Therefore, since it is easy to uniformly form the dimensions of each lens material pattern, it is possible to reduce the occurrence of image defects due to variations in microlens dimensions.

The manufacturing method of the present invention is not limited to the CCD solid-state imaging device exemplified in the above embodiment, but can be applied to various solid-state imaging devices such as a MOS (CMOS) solid-state imaging device.

[0043]

As described above, according to the method of manufacturing a solid-state imaging device of the present invention, a solid-state imaging device in which a plurality of light receiving portions are formed on a semiconductor substrate and a microlens is formed above each of the light receiving portions. Forming a transparent resin layer above the semiconductor substrate, and forming a first microlens on the surface of the transparent resin layer to correspond to a part of the light receiving portion, Forming a lens material pattern in a region of the surface of the transparent resin layer adjacent to the first microlens; and forming a second microlens by deforming the surface of the lens material pattern into a convex shape by heating. And the step of forming the second microlens is performed so that the first microlens and the second microlens are in contact with each other. The solid-state imaging device of high sensitivity with improved light collection efficiency by the lens can be easily manufactured.

[Brief description of the drawings]

FIG. 1 is a process cross-sectional view for explaining a method for manufacturing a solid-state imaging device according to a first embodiment of the present invention.

FIG. 2 is a process sectional view for describing the method for manufacturing the solid-state imaging device according to the first embodiment of the present invention.

FIG. 3 is a process cross-sectional view for describing a method for manufacturing a solid-state imaging device according to a second embodiment of the present invention.

FIG. 4 is a process cross-sectional view for explaining the method for manufacturing the solid-state imaging device according to the second embodiment of the present invention.

FIG. 5 is a process cross-sectional view for explaining an example of a conventional method for manufacturing a solid-state imaging device.

FIG. 6 is a cross-sectional view illustrating an example of a structure of a solid-state imaging device obtained by a conventional manufacturing method.

[Explanation of symbols]

 10, 20, 30, 40 Solid-state imaging device 11a, 11b, 21, 31, 41 Light receiving portion 12, 22, 32, 42 Transparent resin layer 13, 23 First lens material layer 14, 24 First lens material pattern 15 , 25 First microlens 16, 26 Second lens material layer 17, 27 Second lens material pattern 18, 28 Second microlens 33 Lens material layer 34 Lens material pattern 35a, 35b, 45 Microlens 46 Transparent film

Claims (8)

[Claims] 1. A method for manufacturing a solid-state imaging device, wherein a plurality of light receiving units are arranged in a matrix on a surface of a semiconductor substrate, and a microlens is formed above each of the light receiving units. A step of forming a transparent resin layer, and a first step on the surface of the transparent resin layer so as to correspond to a part of the light receiving portions.
Forming a micro lens, forming a lens material pattern in a region adjacent to the first micro lens on the surface of the transparent resin layer, and deforming the lens material pattern surface into a convex shape by heating. Forming the second microlens, wherein the step of forming the second microlens is performed such that the first microlens and the second microlens contact each other. Manufacturing method of a solid-state imaging device. 2. The method according to claim 1, wherein the step of forming the second micro lens is performed in a state where the first micro lens is not deformed. 3. The step of forming the second microlens is performed such that the curved surface of the first microlens and the curved surface of the second microlens are in contact with the surface of the transparent resin layer. A method for manufacturing the solid-state imaging device according to claim 1. 4. A method for manufacturing a solid-state imaging device in which pixels including a light receiving unit and a charge transfer unit are arranged in a matrix on a surface of a semiconductor substrate, and a micro lens is formed above each of the light receiving units. A step of forming a transparent resin layer above the semiconductor substrate, a step of forming a first microlens on the surface of the transparent resin layer so as to correspond to a part of the light receiving sections, and Forming a lens material pattern in a region adjacent to the first microlens;
Forming a second microlens by deforming the surface of the lens material pattern into a convex shape by heating, wherein the step of forming the first microlens includes the step of: A method for manufacturing a solid-state imaging device, which is performed so as to have a width equal to or larger than the width of the solid-state imaging device. 5. The method according to claim 4, wherein the step of forming the second microlens is performed in a state where the first microlens is not deformed. 6. The method according to claim 4, wherein the step of forming the first microlens is performed such that the difference between the width of the first microlens and the width of the pixel is 2.0 μm or less.
Or the method for manufacturing a solid-state imaging device according to 5. 7. The method according to claim 4, wherein the step of forming the first microlens is performed such that a width of the first microlens is equal to a width of the pixel. A method for manufacturing a solid-state imaging device. 8. In the step of forming the first microlens, the light receiving portion on which the first microlens is formed and the light receiving portion not formed are alternately arranged in a row direction and a column direction. Claims 1 to 3 implemented as follows:
8. The method for manufacturing a solid-state imaging device according to any one of 7.