JPH03190272A - Solid-state camera device - Google Patents

Abstract

PURPOSE:To make it possible to inhibit the generation of smear induced by light by way of a layer insulation film and prevent the generation of crystal defect induced by a diffused heavy metal, and embody a solid camera device without optical blank by installing a silicon nitriding film to the lower part of a polycide film which serves as a light screen film. CONSTITUTION:The lower part of a polycide light screen film 13 on both the ends is formed on a silicon nitriding film 9. More precisely, the silicon nitriding film exists on the lower part of the polycide film 13 on both ends. An oxide film will not make growth on the silicon nitriding film 9 even when a polysilicon film is increased in thickness for the withstand voltage between a polysilicon electrode 10 and the polycide film 13, but only the thickness of the silicon nitriding film 9 is increased on the lower part of the polycide film 13 on the both ends, which is effective to light by way of an interlayer film, such as smear. Furthermore, since the silicon nitriding film 9 exists on the lower part of the polycide film on the both ends, the heavy metal contained in the polycide is prohibited to be diffused into a photodiode by the silicon nitriding film 9. It is, therefore, possible to inhibit the generation of crystal defect and embody a solid camera device without optical blank as a result.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a solid-state imaging device that can be used in video cameras and the like.

2. Description of the Related Art In recent years, solid-state imaging devices have been widely put into practical use in video cameras and the like. The solid-state imaging device has improved performance.

As image quality becomes higher, characteristics such as smears and white scratches, which are a type of noise signal, have become a problem.

A conventional solid-state imaging device will be described below with reference to the drawings.

Figure 2 shows the photoelectric conversion section (
1 is a cross-sectional view of a vertical shift register (hereinafter referred to as a photodiode) and a vertical shift register (hereinafter referred to as a vertical COD), and 1 is an n-
type silicon substrate, 2 is a p-type well, 3 is an n-type region, 4
is a p-type region, 5 is an n-type region, 6 is a p+-type region 7 is a p+
The mold region 8 is a gate oxide film, 9 is a silicon nitride film, and 10 is a gate oxide film.
11 is a polysilicon electrode, 12 is a polysilicon oxide film, and 12 is a polysilicon electrode.
1 is a p++ type region, 13 is a polycide film, 14 is an interlayer insulating film, and 15 is an aluminum light shielding film.

The solid-state imaging device configured as above will be described below.

First, on an n-type silicon substrate 1, a p-type well 2, an n-type region 3 that will become a photodiode, a p-type region 4 that prevents the diffusion of noise charges in the substrate, and an n-type region 5 that will become a vertical CCD section are formed. Form. A p+ type region 6 is formed by ion implantation to prevent signal charges from entering from an adjacent photodiode. do. Next, a gate oxide film 8 and a silicon nitride film 9 are grown to improve breakdown voltage, a polysilicon film that will become an electrode is deposited, and etching is performed.
At the same time as buttering the polysilicon electrode 10, the silicon nitride film on the underlying photodiode is removed. A p++ type region 12 is formed to form a polysilicon oxide film 11 and a buried photodiode structure, a polycide film 13 is applied as a light shielding film to prevent smear, and an interlayer insulating film 14. After forming the aluminum light-shielding film 15, the solid-state imaging device is completed.

Problems to be Solved by the Invention However, in the conventional method described above, by providing a polycide light-shielding film close to the polysilicon electrode, light that directly enters the polysilicon electrode and light that enters the polysilicon electrode through the interlayer insulating film under the aluminum light-shielding film are removed. Although it improves the light shielding properties and reduces smear caused by light entering, it does not protect against light that is reflected on the photodiode substrate surface and enters the polysilicon electrode through the polysilicon oxide film. Because there is a polysilicon oxide film under the polycide light-shielding film,
shows almost no shading effect. It is possible to reduce the incidence of light by reducing the thickness of the polysilicon oxide film, but on the other hand, the electrical withstand voltage of the polysilicon electrode and polycide film decreases, making it impossible to operate as an imaging device. It becomes. In other words, even if a polycide light-shielding film is applied, its smear characteristics are determined by the thickness of the polysilicon oxide film that satisfies the electrical breakdown voltage between the polysilicon electrode and the polycide light-shielding film, and it is necessary to further reduce the smear value. was difficult.

Additionally, when a polycide film is formed near the photodiode, heavy metals such as tungsten in the film diffuse through the oxide film and reach the photodiode, causing crystal defects in the photodiode due to contamination from the heavy metals. Occur. When operated as a solid-state imaging device, the crystal defects are detected as white scratches, which poses major problems including reliability.

The present invention is intended to solve the above conventional problems,
An object of the present invention is to provide a solid-state imaging device that is free from smear, satisfies electrical breakdown voltage, and suppresses the occurrence of white scratches.

Means for Solving the Problems In order to solve this problem, the solid-state imaging device of the present invention has the following features:
After forming the gate oxide film and silicon nitride film, only the silicon nitride film is removed by etching to match the finished shape of the polysilicon electrode. Then, a polysilicon film is grown and patterned by etching to form electrodes. It is constructed by growing a polysilicon oxide film and forming the lower portions of both ends of the polycide light-shielding film on the silicon nitride film.

Function According to this configuration, a silicon nitride film exists under both ends of the polycide film. No oxide film grows on top, and the bottom of both ends of the polycide film has a thickness of only silicon nitride film.
It is very effective against light passing through interlayer films such as smears.

In addition, since there is a silicon nitride film at the bottom of both ends of the polycide film, the heavy metals in the polycide are prevented from diffusing into the photodiode by the silicon nitride film, suppressing the occurrence of crystal defects, and resulting in no white scratches. It becomes possible to realize a solid-state imaging device.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sectional view of a solid-state imaging device according to an embodiment of the present invention. In FIG. 1, 1 is an n-type silicon substrate, 2 is a p-type well, 3 is an n-type region, 4 is an n-type region, 5 is an n-type region, 6 is a p+ type region, 7 is a p+ type region 8 is a gate oxide film, 9 is a silicon nitride film, 10 is a polysilicon electrode, 11 is a polysilicon oxide film, 12 is a p+
+ type region, 13 is a polycide film, 14 is an interlayer insulating film, 1
5 is an aluminum light-shielding film, which has the same structure as the conventional example.

First, as in the conventional example, after forming each well and implantation region in an n-type silicon substrate, a gate oxide film 8.
A silicon nitride film 9 is grown.

Next, the silicon nitride film is etched into the same shape as the polysilicon electrode (including the first layer polysilicon electrode and the second layer polysilicon electrode). Here, the etching dimension of the silicon nitride film is approximately 0.0 mm on one side with respect to the polysilicon electrode.
Make it thicker by 6 μm. Next, polysilicon is grown to a thickness of about 0.5 μm, and a polysilicon electrode 10 is formed by etching.

The polysilicon electrode is oxidized to grow a polysilicon oxide film 11 of about 0.2 μm. Thereafter, the vertical CCD section is shielded from light with a polycide film 13 of about 0.4 μm. Here, the silicon nitride film is about 0.0 mm on one side with respect to the polysilicon electrode.
Since the silicon nitride film is 6 μm wide, the silicon nitride film exists as a base completely to the bottom of the polycide light-shielding film, making it possible to shorten the distance between the bottom of the polycide film and the silicon substrate. Furthermore, the presence of the silicon nitride film can also reduce the diffusion of heavy metals.

Effects of the Invention The present invention provides a silicon nitride film under a polycide film, which is a light-shielding film, so that even if the thickness of the polysilicon oxide film is increased, the thickness of the silicon nitride film underlying the polycide film remains the same. Since this does not change, the thickness of the insulating film under the polycide light-shielding film is equal to the thickness of the gate oxide film and the silicon nitride film, making it possible to make the film thinner. Therefore, it is possible to suppress the occurrence of smear caused by light through the interlayer insulating film, suppress the occurrence of crystal defects due to the diffusion of heavy metals, and realize a solid-state imaging device without white scratches.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a conventional solid-state imaging device. 1...n-type silicon substrate, 2...p
type well, 3... n-type region, 4...
n-type region, 5...n-type region, 6...p
+ type region 7...p+ type region 8...
Gate oxide film, 9...Silicon nitride film, 10.
...Polysilicon electrode, 11...Polysilicon oxide film, 12...P++ type region, 13.
... Polycide film, 14 ... Interlayer insulating film, 15 ... Aluminum light shielding film.

Claims (1)

[Claims] In a solid-state imaging device consisting of a photoelectric conversion section and a vertical shift register arranged in a matrix on a silicon substrate, an oxide film and a silicon nitride film are grown on the vertical shift register section, and a part of the silicon nitride film is removed by etching. Then, a polysilicon electrode is formed only in the region of the silicon nitride film, a polysilicon oxide film and a polycide light-shielding film are formed to cover the polysilicon electrode, and the lower portions of both ends of the polycide light-shielding film are formed in the region of the silicon nitride film. A solid-state imaging device characterized by being located above.