JPH04225563A - Solid state image sensor - Google Patents

Abstract

PURPOSE:To enhance reliability without reducing sensitivity in a solid state image sensor. CONSTITUTION:In a solid state image sensor having at least a photosensitive pixel 3 formed on a semiconductor substrate 1, a silicon oxide film 7 is formed as a surface protective film on the pixel 3 except the vicinity of the periphery of the pixel 3, and a silicon nitride film 11 is formed at least as a surface protective film on the substrate 1 except the pixel 3 formed only with the film 7.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device that suppresses attenuation of incident light reaching a light-receiving region and provides high reliability.

0002

2. Description of the Related Art A sectional view of a typical structure of a conventional solid-state imaging device is shown in FIG. 1 is an n-type semiconductor substrate, 2 is a P well, 3 is a photosensitive pixel, 4 is a CCD, 5 is a transfer channel section, 6
1 is a channel stop portion, 7 is a silicon oxide film, 8 is a charge transfer electrode, 9 is a light-shielding aluminum, and 10 is a surface protection film.

As for the material of the surface protection film 10, there are cases where a silicon oxide film is used and cases where a silicon nitride film is used.

[0004] The surface protective film 10 is formed on the photosensitive pixel 3 and on the C
It had a structure that completely covered CD4.

[0005]

[Problems to be Solved by the Invention] In such conventional solid-state imaging devices, when silicon oxide is used as the material for the surface protective film 10, moisture and ions can enter the film due to the low density of the film. It's easy to do. Therefore, moisture and ions that have entered from directly above the CCD 4 reach below the charge transfer electrode 8, and the CCD
There was a reliability problem in that the characteristics of CD4 were deteriorated.

Furthermore, when a nitride film is used as the material for the surface protection film 10, the film is highly dense and there is no problem of moisture or ion infiltration, but the light transmittance is lower than that of silicon oxide. , the sensitivity of solid-state imaging devices is about 4% lower than that of silicon oxide.
There was a problem that the ratio also decreased.

The present invention is intended to solve the above-mentioned conventional problems, and aims to provide a solid-state imaging device that does not have a decrease in sensitivity and is highly reliable.

[0008]

[Means for Solving the Problems] In order to achieve this object, the solid-state imaging device of the present invention has a structure in which the photosensitive pixels are covered only with a silicon oxide film, and the surfaces other than the photosensitive pixels are covered with a silicon nitride film. did.

[0009]

[Operation] With this configuration, the photosensitive pixels are covered with a silicon oxide film with high light transmittance, so there is no decrease in sensitivity.
On the other hand, since the CCD is covered with a silicon nitride film, there is no penetration of moisture or ions and high reliability can be obtained.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a solid-state imaging device in one embodiment of the present invention. In the figure, 1 to 9 have the same configuration as the conventional example, so the explanation will be omitted. In the present invention,
The silicon nitride film 1 is directly above the photosensitive pixel 3 except for the peripheral part.
Since the silicon oxide film 7 is removed, it is covered only with the silicon oxide film 7. Further, the silicon nitride film 11 serves as a surface protection film directly above the CCD 4.

In the fixed imaging device constructed as described above, the surface of the photosensitive pixel 3 is almost entirely made of the silicon oxide film 7, so there is no reduction in sensitivity due to the surface protective film.

Furthermore, since the surface directly above the CCD 4 is covered with a silicon nitride film 11, there is no intrusion of moisture or ions, resulting in high reliability.

[0013]

As is clear from the above embodiments, according to the present invention, a silicon oxide film is formed as a surface protective film on the photosensitive pixel except for the vicinity of the periphery of the photosensitive pixel, and only the silicon oxide film is Since the structure is such that a silicon nitride film is formed at least as a surface protective film on the semiconductor substrate other than the formed photosensitive pixels, an excellent solid-state imaging device that does not reduce sensitivity and has high reliability can be provided.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a solid-state imaging device according to an embodiment of the present invention.

[Figure 2] Cross-sectional view of a conventional solid-state imaging device

[Explanation of symbols]

1 N-type semiconductor substrate (semiconductor substrate) 3 Photosensitive pixel 7 Silicon oxide film 11 Silicon nitride film

Claims (1)

[Claims] 1. A solid-state imaging device having at least a photosensitive pixel formed on a semiconductor substrate, wherein a silicon oxide film is formed as a surface protective film on the photosensitive pixel except for the vicinity of the periphery of the photosensitive pixel, and the silicon oxide film is A solid-state imaging device characterized in that a silicon nitride film is formed at least as a surface protection film on the semiconductor substrate other than the photosensitive pixels on which only the film is formed.