JPH0412567A - Manufacture of microlens for solid-state image pickup device - Google Patents

Abstract

PURPOSE:To simply manufacture a microlens excellent in light converging efficiency, with a small number of processes, by forming a microlens by fusing 3 photo resist layer and a substratum resin layer, and making the edge parts formed of the substratum resin layer mutually link. CONSTITUTION:A substratum resin layer 2 and a patterned photo resist layer 3 linking via the layer 2 are fused in a unified body at the time of heating. By the effect of surface tension the surface is turned into a convex lens type, and microlenses are formed. At this time, the edge parts of the respective microlenses 4 formed of the substratum resin layer 2 link with each other, and flat parts are not generated between the respective microlenses 4. Thereby microlenses excellent in light converging efficiency are manufactured, and the number of processes is reduced.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a method for manufacturing a microlens for a solid-state image sensor.

[Conventional technology]

In a CCD imaging device such as an area sensor or a line sensor, as shown in FIG. There is something that was formed from The microlens can increase the amount of light incident on the photodiode 101 due to its light condensing effect, thereby realizing an improvement in the effective sensitivity of the imaging device. Also, CC
As the number of pixels of the D image sensor increases, the area of a single photodiode becomes smaller, so increasing the light focusing effect of the microlens will become increasingly important in the future. Conventionally, as a microlens manufacturing method, there is a method as shown in FIG. Figure 5 shows the steps (A)-(B)-(C)-(D)-(E)-(
It is sectional drawing shown in order of F). (A) First, a microlens transparent resin layer 52 is formed on a COD wafer 51. (B) U on the transparent resin layer 52 for microlenses.
A photoresist 53 made of V-resist, DUV-renost, or the like is formed. (C) The photoresist 53 is exposed and developed to form a resist pattern corresponding to the microlens. (D) Using the resist pattern as a mask, the microlens transparent resin layer 52 is etched. (E) Remove the resist pattern. (F) The transparent resin layer 52 is heated at 120°C to 160°C.
The microlens 54 is formed by heating and softening the surface and making the surface spherical due to surface tension. In this manufacturing method, after step (F), if necessary, the microlens 54 is further irradiated with ultraviolet rays, far ultraviolet rays, or electron beams to harden the microlens 54, thereby improving the heat resistance of the imaging device. Improve reliability. By the way, in the method for manufacturing a microlens for a solid-state image sensor shown in FIG. 5, as shown in FIG. Therefore, there was a problem that the light collection efficiency was not good. Therefore, by eliminating the flat part between the microlenses,
There is a method for manufacturing a microlens for a solid-state imaging device that can increase light collection efficiency, as shown in FIG. Figure 6 shows the microlens manufacturing process (A)-(B).
)-(C)-(D)-(E)-(P). (A) First, a microlens transparent resin layer 62 is formed on a COD wafer 61. (B) U on the microlens transparent resin layer 62
A photoresist 63 made of V resist, DUV resist, or the like is formed. (C) The photoresist 63 is exposed and developed to form a resist pattern corresponding to the microlens. (D) Using the above resist pattern as a mask, CO
The microlens transparent resin layer 62 is etched until just before the D wafer 61 is exposed. (E) Remove the resist pattern. (F) The transparent resin layer 62 is heated at 120°C-160°
The microlens 64 is formed by heating and softening the microlens 64 by heating and making the surface into a convex lens shape due to surface tension. In this microlens manufacturing method, the microlens transparent resin layer 62 before heating in step (F) is heated in step (D).
) during etching, since the microlenses are not separated but connected, flat parts between the microlenses can be eliminated, and microlenses with high light collection efficiency can be formed.

[Invention or problem to be solved]

By the way, in the conventional microlens manufacturing method for a solid-state image sensor shown in FIG. 5, the flat area between each microlens becomes large, resulting in poor light collection efficiency of the microlens and the number of microlens manufacturing steps. The problem is that there are too many. In addition, the conventional method for manufacturing a microlens for a solid-state image sensor shown in FIG.
2 must be etched until just before the COD wafer 61 is exposed, requiring highly accurate etching.
The problem is that it is difficult to manufacture. SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing microlenses for solid-state imaging devices, which eliminates flat parts between each microlens and allows microlenses with high light collection efficiency to be easily manufactured with a small number of steps. .

[Means to solve the problem]

In order to achieve the above object, a microlens manufacturing method for a solid-state imaging device according to the first invention includes manufacturing a microlens for a solid-state imaging device by sequentially forming a base resin layer and a photoresist layer on a COD wafer. The method includes forming the photoresist layer using a resin that melts with the photoresist layer by heating as the base resin layer, exposing the photoresist layer to form a pattern, and then forming the photoresist layer and the base resin layer. The resin layer is heated to fuse the photoresist layer and the base resin layer to form microlenses, and the edges formed by the base resin layer of each microlens are connected to each other. It is said that Mako, the second invention of the microlens manufacturing method for a solid-state imaging device is a solid-state imaging device in which a microlens is manufactured by sequentially forming a base resin layer, a microlens transparent resin layer, and a photoresist layer on a COD wafer. The method for manufacturing a microlens comprises using a resin that melts with the transparent resin layer for microlens by heating as the base resin layer,
After forming the photoresist layer, exposing the photoresist layer to form a pattern, etching the transparent resin layer using the photoresist pattern, removing the photoresist layer, and then The transparent resin layer for microlens and the base resin layer are heat-treated to fuse the transparent resin layer for microlens and the base resin layer to form a microlens, and each microlens is formed of the base resin layer for each microlens. The feature is that the edges are connected to each other.

[Effect]

In the first invention, the base resin layer and the pattern-formed niphotrect layer that is continuous through the base resin layer are fused and integrated when heated, and due to surface tension, the surface becomes a convex lens shape, and the micro A lens is formed. At this time, the edges of each microlens formed from the base resin layer are connected to each other, and no flat portions are formed between the microlenses, so that a microlens with high light collection efficiency is manufactured. In this manufacturing method, since the photoresist itself is used as the material for the microlens, a transparent resin for the microlens is not required, and the etching step of the transparent resin for the microlens and the step of removing the photoresist are eliminated, thereby reducing the number of steps. In addition, in the second invention, the transparent resin layer for a microlens, which is etched using a patterned photoresist layer as a mask, is continuous through the base resin layer, fuses into one body when heated, and due to surface tension, the surface becomes a convex lens. microlenses are formed. At this time,
The edges of each microlens formed from the base resin layer are connected to each other, and there are no flat parts between the microlenses, producing a microlens with high light collection efficiency. In this manufacturing method, since the edges of the microlenses that are connected to each other are formed in the base resin layer, there is no need for highly accurate etching as in the conventional example shown in FIG.

【Example】

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments. FIG. 1 shows (A) the process of manufacturing a microlens by the method for manufacturing a microlens for a solid-state image sensor according to the first invention.
It is sectional drawing shown in order of -(B)-(C)-(D)-(E). (A) First, an acrylic resin as a base resin is applied onto a COD wafer to form a base resin layer 2. (B) The base resin layer 2 is irradiated with ultraviolet rays to incompletely cure the base resin layer 2. (C) A positive resist for microlenses (for example, noholac resin) is applied on the incompletely cured base resin layer 2 to form a photoresist layer 3. (D) The photoresist layer 3 is pattern-exposed and developed to form a pattern corresponding to the microlens. (E) The base resin layer 2 and the photoresist layer 3 are heated to fuse the base resin layer 2 and the photoresist layer 3 together. Then, the surface of the fused base resin layer 2 and photoresist layer 3 becomes convex lens-shaped due to surface tension, and a microlens 4 is formed. In step (E) of this microlens manufacturing method, the base resin layer 2 and the intermediate resist layer 3 are fused, so that each microlens has a flat portion where the edges made of the base resin layer 2 are connected to each other. Therefore, the light collection efficiency is improved. Moreover, since the photoresist layer 3 itself is used as the material for the microlens 4, the conventional transparent resin for the microlens is not required, and the step of etching the transparent resin for the microlens and the step of removing the photoresist are eliminated, reducing the number of steps. In this example, acrylic resin was used as the base resin, but novolak resin, which is the same material as the transparent layer, may also be used. Further, in order to incompletely cure the base resin, ultraviolet rays may be irradiated, or electron beams or far ultraviolet rays may be irradiated. Furthermore, heating may be performed simultaneously with the above-mentioned irradiation, or heating may be performed alone. Next, an embodiment of the second invention is shown in FIG. FIG. 2 shows the steps (A)-(B)-(C)-(D)-(E)-(F) for manufacturing a microlens according to the above embodiment.
)-(G). (A) First, a base resin is applied onto the COD wafer 21 to form the base resin layer 22. (B) A microlens transparent resin layer 23 is formed on the base resin layer 22. Note that the base resin and the microlens transparent resin are selected in advance from materials that melt together when heated. (C) On the microlens transparent resin layer 23,
A photoresist layer 24 is formed by applying a photoresist such as UV lenost or DUV lenost. (D) exposing and developing the photoresist layer 24;
A resist pattern corresponding to the microlens is formed. (E) Using the resist pattern as a mask, the microlens transparent resin layer 23 is etched. (F) Remove the resist pattern. (G) The base resin layer 22 and the patterned transparent resin layer 23 are heated at 120° C. to 160° C. to fuse them together. Then, the surface of the fused base resin layer 22 and transparent resin layer 23 becomes convex lens-shaped due to surface tension, and a microlens 25 is formed. In step (G) of this microlens manufacturing method, the base resin layer 22 and the photoresist layer 23 are fused, and the base resin layer 22 is continuous throughout, so that each microlens 23 is made of the base resin layer 22. In this manufacturing method, the transparent resin layer 2 for microlens is
3 until it reaches the base resin layer 22, and can be easily manufactured without requiring highly accurate etching as in the conventional example shown in FIG. In addition, in the embodiments of the first invention and the embodiments of the second invention, the microlenses were formed by heat treatment in the final step, or by irradiation with ultraviolet rays, deep ultraviolet rays, electron beams, etc. at the same time as heating. good. [Effects of the Invention] As is clear from the above description, the method for manufacturing a microlens for a solid-state image sensor according to the first invention forms a photoresist layer on a base resin layer that fuses with the photoresist layer during heating, and then, The photoresist layer is exposed to light to form a pattern, and the base resin layer and photoresist layer are heated and fused together to form a convex lens surface due to surface tension, thereby forming a microlens. The edges made of the base resin layer of each microlens are connected to each other, and there are no flat parts between each microlens.
A microlens with high light collection efficiency can be formed. Furthermore, since the photoresist itself is used as the microlens material, there is no need to use a transparent resin for microlenses as in the past, and the etching process and photoresist removal process are no longer necessary, so the number of process steps can be reduced. Further, in the method for manufacturing a microlens for a solid-state image sensor according to the second invention, a transparent resin layer for a microlens is formed on a base resin layer that fuses with a transparent resin layer for a microlens during heating, and a photoresist is applied thereon. Next, the photoresist layer is exposed to light to form a pattern corresponding to the microlens, and the transparent resin layer is etched using the pattern to form the base resin layer and the microlens transparent resin layer. The microlenses are formed by heating and fusing them into one piece, and the surfaces of the microlenses are made into a convex lens shape due to surface tension. There is no flat part between the two, and therefore a microlens with good light collection efficiency can be manufactured relatively easily.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a method of manufacturing a microlens for a solid-state image sensor according to an embodiment of the first invention, FIG. 2 is a sectional view showing an embodiment of the second invention, and FIG. 4 is an enlarged sectional view of a conventional microlens, FIG. 5 is a sectional view showing a method of manufacturing a conventional microlens for a solid-state image sensor, and FIG. 6 is a sectional view of another conventional example. A sectional view shown. 1.21 51.61...COD wafer 2.22.
・Base resin layer, 3.24, 53.63... Photoresist layer, 4.25
, 54.64...Micro lens, 23.52.62...
...Transparent resin layer for microlenses.

Claims (2)

[Claims] (1) A microlens manufacturing method for a solid-state imaging device, in which a microlens is manufactured by sequentially forming a base resin layer and a photoresist layer on a CCD wafer, the base resin layer being a resin that melts with the photoresist layer by heating. After forming the photoresist layer using a method, the photoresist layer is exposed to light to form a pattern, and then the photoresist layer and the base resin layer are heat-treated to fuse the photoresist layer and the base resin layer. 1. A method of manufacturing a microlens for a solid-state image sensor, characterized in that microlenses are formed, and edges formed of a base resin layer of each of the microlenses are connected to each other. (2) A method for manufacturing a microlens for a solid-state image sensor, in which a microlens is manufactured by sequentially forming a base resin layer, a transparent resin layer for microlens, and a photoresist layer on a CCD wafer, the base resin layer being formed by heating. After forming the photoresist layer using a resin that melts with the transparent resin layer for microlenses, the photoresist layer is exposed to form a pattern, and then the transparent resin layer is formed using the pattern of the photoresist layer. Next, the photoresist layer is removed. Next, the transparent resin layer for microlens and the base resin layer are heat-treated to fuse the transparent resin layer for microlens and the base resin layer to form a microlens. A method for manufacturing a microlens for a solid-state image sensor, characterized in that the edges formed of the base resin layer of each of the microlenses are continuous with each other.