JPH01251753A - Solid-state image sensing device and manufacture thereof - Google Patents

Abstract

PURPOSE:To let a microlens display its function effectively on a photosensitive picture element part which has been made fine by use of multiple picture elements by a method wherein a flat layer whose surface has been made flat is laminated on the top surface of a solid-state image sensor and a microlens layer along the photosensitive picture element part is formed on the flat layer. CONSTITUTION:A flat layer 10 whose surface 10a has been flattened and which is composed of a water-soluble transparent photosensitive resin is formed on the top surface of a smooth layer 7; an intermediate layer 11 composed of an acryl-based transparent resin is formed on the top surface of the flat layer 10; a microlens layer 8 composed of a water-soluble casein resin is formed on the top surface of the intermediate layer 11 in the Y direction along the upper part of a photodiode 2. Since this microlens layer 8 is formed on the surface 10a of the flat layer 10 whose surface 10a has been flattened, its rear surface is flat and the layer can be used easily as a convex lens. By this setup, a function as a microlens can be displayed sufficiently.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention aims to improve sensitivity by providing a microlens layer on each photosensitive pixel portion, and is particularly suitable for use in black and white. The present invention relates to a solid-state imaging device and a manufacturing method thereof.

(Prior art) In addition to the advantages of solid-state imaging devices as semiconductor devices, such as small size, light weight, high reliability, and long lifespan, solid-state imaging devices do not suffer from the drawbacks of image pickup tubes, such as burn-in and pattern distortion, and in addition, have low afterimages. It has characteristics. For this reason, they are widely used not only in color compact video cameras and still cameras, but also in measuring instruments, production machines, image information processing devices, and the like.

An example of the above-mentioned conventional image processing apparatus will be explained based on FIG. 3, taking a CCD (charge coupled device) as an example.

In the photosensitive pixel area 101 (FIG. 5) on the surface of the semiconductor substrate 1, photodiodes 2 that function as photoelectric conversion elements are formed at a predetermined pitch, and charge transfer in the insulating layer between the photodiodes 2 is performed. In the portion 103, a transfer electrode that controls this is formed of polysilicon or the like (not shown), and furthermore, an insulating film 3 made of an oxide film is formed on the upper surface of the transfer electrode.
is formed. Then, on this insulating film 3, P
An SG (phosphosilicate glass) film 4 is formed, and furthermore, an aluminum light-shielding film 5 and a silicon nitride film 6 functioning as a substrate film are provided thereon, respectively.

The portion on the semiconductor substrate 1 where the photodiode 2 is formed is a portion that becomes a photosensitive pixel portion, and the aluminum light shielding film 5 has an opening 5 in a region corresponding to this photosensitive pixel portion.
a is provided, and the inside of this opening 5a becomes a photosensitive pixel section 102 shown in FIG.

In the so-called interline transfer type CCD created in this way, as shown in FIG.
As shown in FIG. 6, this photosensitive pixel region 101 includes the above-mentioned photosensitive pixel section 102 that generates and accumulates signal charges by incident light on the surface of the semiconductor substrate 1, and the photosensitive pixel section 102 that generates and accumulates signal charges on the surface of the semiconductor substrate 1, and the signal charges accumulated in this photosensitive pixel section 102. It mainly consists of a charge transfer section 103 that transfers charges.

In the fixed imaging device mentioned above, in order to increase the resolution,
Although it is necessary to increase the number of pixels, this reduces the area of the photosensitive pixel portion relative to the effective pixel area, resulting in a decrease in sensitivity. Sensitivity is an important element of solid-state imaging devices, and this decrease in sensitivity becomes a fatal drawback and leads to a decrease in performance.

Therefore, as shown in FIG. 4, a smooth layer 7 is formed on the upper surface of the semiconductor device shown in FIG.
A microlens layer 8 is provided along the upper position (Y direction in FIG. 6), and this upper surface is further covered with a protective layer 9, and the microlens layer 8 allows more light to be transmitted to the photosensitive pixel portion 102.
It has been proposed that the data be collected in

(Problem to be Solved by the Invention) However, although the microlens layer 8 is formed on the upper surface of the smooth layer 7, the surface of this smooth layer 7 is not necessarily flat, and especially the shape of this lower layer There is usually a waveform undulation along the photosensitive pixel portion 102.
Since the upper part of the photodiode 2 is located in the four parts of this undulation, even if the microlens layer 8 is formed here, a lens that follows the shape of this concave part, that is, a concave lens is formed instead of a convex lens. As a result, the light is instead diffused, which not only prevents the sensitivity from increasing, but also makes it extremely difficult to form a convex lens.

In view of the above, the present invention provides a solid-state imaging device and a method for manufacturing the same, in which a microlens for preventing a decrease in sensitivity can effectively perform its function on a photosensitive pixel section whose definition has been increased by increasing the number of pixels. The purpose is to

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the solid-state imaging device of the present invention includes a photosensitive pixel section that generates and accumulates signal charges by incident light on the surface of a semiconductor substrate, and a photosensitive pixel section that generates and accumulates signal charges on the surface of a semiconductor substrate, and A flat layer with a flattened surface is laminated on the top surface of a solid-state image sensor equipped with a charge transfer section that transfers the signal charge, and a microlens layer is formed along the photosensitive pixel section on top of this flat layer. The manufacturing method includes a photosensitive pixel section that generates and accumulates signal charges by incident light on the surface of a semiconductor substrate;
A step of forming a charge transfer section to transfer signal charges accumulated in the photosensitive pixel section to form a solid-state image sensor, and a step of laminating a transparent resin on the top surface of the solid-state image sensor to flatten the surface. and a step of forming a microlens layer along the photosensitive pixel portion on this flat layer.

(Function) In the solid-state imaging device configured as described above, since the microlens layer is formed on the flat layer whose surface is flattened, the microlens formed by this microlens layer can be easily formed. It can be made into a convex lens, and thereby the function of the microlens for preventing a decrease in sensitivity can be effectively exhibited.

(Example) Embodiments will be described below with reference to FIGS. 1 and 2.

FIG. 1 shows a cross-sectional view of a solid-state imaging device. On the surface of a semiconductor substrate 1, photodiodes 2 that function as photoelectric conversion elements are formed at a predetermined pitch. In the charge transfer section 103, a transfer electrode that controls the transfer electrode is formed of polysilicon or the like, and an insulating film 3 made of an oxide film is further formed on the upper surface of the transfer electrode.

On this insulating film 3, PSG (phosphosilicate glass)
A film 4 is formed, and an aluminum light shielding film 5 and a silicon nitride film 6 functioning as a passivation film are provided on this film, respectively.

On the upper surface of this silicon nitride film 6, a smooth layer 7 with a thickness of about 2 μm is laminated, for example, from acrylic transparent resin.

On the upper surface of this smooth layer 7, a flat layer 10 made of a water-soluble transparent photosensitive resin and having a flat surface 10a is formed, for example, with a thickness of 1.5 μm.
It is formed with a film thickness of approximately In order to make the surface 10a flat as described above, this flat layer 10 is preferably made of a water-soluble transparent photosensitive resin, such as casein, to which about 1% of ammonium dichromate as a photosensitizer is added. It can also be constructed using a transparent oil-based resin such as an acrylic transparent resin, a transparent oil-based photosensitive resin, a transparent oil-based curable resin, or the like.

On the upper surface of the flat layer 10, an intermediate layer 11 made of transparent acrylic resin is formed with a thickness of, for example, about 0.5 μm. This intermediate layer 11 is not necessarily required when the water-soluble resin is laminated thereon after the water-soluble resin is formed. Further, if the flat layer 10 is made of acrylic transparent resin, it is not necessary.

On the upper surface of this intermediate layer 11, a microlens layer 8 made of water-soluble casein resin is formed along the upper side of the photodiode 2, that is, in the Y direction in FIG.

Since the microlens layer 8 is formed on the surface 10a of the flat layer 10, which is obtained by flattening the surface 10a, the lower surface thereof becomes flat and can easily become a convex lens. This allows the microlens to fully function as a microlens.

The surface of this microlens layer 8 is covered with a protective layer 9 made of acrylic resin, thereby constructing a solid-state imaging device with a photosensitive pixel region 101 having the above-mentioned structure in the center as shown in FIG.

Next, an example of manufacturing the solid-state imaging device will be described with reference to FIG. 2.

First, as shown in FIG. 2A, a photodiode 2 and a transfer electrode in a charge transfer section 103 between the photodiode 2 and the transfer electrode are formed on the upper surface of the semiconductor substrate 1, and then an insulating film 3 made of an oxide film is formed thereon. A PSG film 4 is provided thereon, and an aluminum light-shielding film 5 is formed with an opening corresponding to the photodiode 2, and on top of this is formed a silicon oxide film 6 and a transparent acrylic resin with a film thickness of approximately 2 μm. Smooth layers 7 are sequentially formed.

Next, as shown in FIG. 7(b), a water-soluble transparent photosensitive resin, for example, made by adding about 1% ammonium dichromate as a photosensitizer to casein, is applied to the entire surface of the smooth layer 7, for example, in 1. After applying the film to a thickness of about 5 μm and subsequently prebaking, it is exposed to light using a high-pressure mercury lamp through a predetermined mask to flatten the surface 10a over the entire surface of the photosensitive pixel area 101 shown in FIG. A flat layer 10 is formed.

Note that, as described above, this flat layer 10 may be formed using a transparent acrylic resin like the smooth layer 7 described above.

Next, as shown in FIG. 3(C), an acrylic transparent resin is applied onto the flat layer 10 to form an intermediate layer 11, for example, in a film thickness of about 0.5 μm, and then a water-soluble Using casein resin, this is applied to a film thickness of, for example, about 1.0 μm, exposed to light through a predetermined mask, and then immersed together with the substrate in pure water, and then post-baked to form the structure shown in Fig. 6. As shown, a striped microlens layer 8 is formed along the photodiode 2 in the Y direction.

As mentioned above, the intermediate layer 11 can be omitted when the smooth layer 7 is made of acrylic resin.

Then, an acrylic resin is applied to a thickness of about 1.0 μm, for example, on the substrate on which the microlens layer 8 is formed, exposed to light through a predetermined mask, and all at once with a special developer, and the protective layer 9 and image area 1 shown in FIG.
A pattern that remains only in 01 is formed, and the butt portion is exposed to complete the solid-state imaging device.

〔Effect of the invention〕

Since the present invention has the above-described configuration, the microlens layer is formed on a flat layer with a flattened surface, and therefore the microlens formed by this microlens layer can be easily made into a convex lens.

Therefore, by collecting a lot of light with this microlens and increasing the amount of light focused on the photosensitive pixel area, the sensitivity can be reliably improved and the microlens can effectively perform its function to prevent a decrease in sensitivity. It has the effect of

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a sectional view sequentially showing the manufacturing process, FIG. 3 is a sectional view of a conventional solid-state imaging device, and FIG. 4 is a sectional view of another solid-state imaging device. FIG. 5 is a cross-sectional view showing a conventional solid-state imaging device in the order of manufacturing steps, FIG. 5 is an overall plan view of the solid-state imaging device, and FIG. 6 is an enlarged view of the main parts thereof. 1... Semiconductor substrate, 2... Photodiode, 4...
... PSG film, 5... Aluminum light-shielding film, 6...
Silicon nitride film, 7... Smooth layer, 8... Microlens layer, 10... Flat layer, 10a... Same surface, 11
...Intermediate layer, 101...Photosensitive pixel area, 102...
- Photosensitive pixel section, 103...charge transfer section. Applicant's agent Sato - Rotori 1 Figure (A) (C) Figure 2 Figure Figure 3. (B) (B) Figure 4 Horse Figure 5 Trap Figure 6

Claims (1)

[Claims] 1. A solid-state imaging device comprising a photosensitive pixel section that generates and accumulates signal charges from incident light on the surface of a semiconductor substrate, and a charge transfer section that transfers the signal charges accumulated in the photosensitive pixel section. 1. A solid-state imaging device characterized in that a flat layer with a flattened surface is laminated on the upper surface of the element, and a microlens layer is formed along the photosensitive pixel portion on the flat layer. 2. A step of forming a solid-state image sensor by forming a photosensitive pixel section that generates and accumulates signal charges caused by incident light on the surface of the semiconductor substrate, and a charge transfer section that transfers the signal charges accumulated in the photosensitive pixel section. , a step of laminating a transparent resin on the top surface of this solid-state image sensor to form a flat layer with a flattened surface, and a step of forming a microlens layer along the photosensitive pixel portion on this flat layer. A method for manufacturing a solid-state imaging device, characterized by: