JPH06132515A - Solid-state imaging device - Google Patents

Abstract

PURPOSE:To make lens effect, that refracts incident light from a passivation step into a transfer side, smaller by farming a two-layer-structure passivation film, consisting of the first film containing hydrogen and the second film whose refractivity is lower than the first film, to reduce boundary level. CONSTITUTION:An Al film 22 is covered with a P-SiO film 25, or a light-shield film, and a P-SiN film 24 is formed on the film 25, so that these P-SiN film 24 and P-SiO film 25 form a two-layer-structure passivation film. The hydrogen in the P-SiN film 24 reaches the boundary between an Si substrate 11 and an SiO film 16 when thermal treatment is made after the film 24 is formed. The hydrogen terminates the unsaturated bond between Si and O at the boundary, to reduce boundary level. Incident light 27 an a step part 26 is made to refract into a vertical transfer register 14 side by the film 24, with the amount of light path deviation negligible. It refracts again, at the boundary between the films 24 and 25, in the direction opposite to the vertical transfer register 14, so the refraction of the light 27 is slight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device having a passivation film.

[0002]

2. Description of the Related Art FIG. 2 shows a first conventional example of a CCD solid-state image pickup device. In the first conventional example, the impurity layer 13 forming the photosensor 12 and the impurity layer 15 forming the vertical transfer register 14 are formed in the Si substrate 11, and the SiO ₂ film 16 on the surface of the Si substrate 11 is formed. The electrode of the vertical transfer register 14 is formed by the polycrystalline Si film 17 in FIG.

The polycrystalline Si film 17 and the like are covered with the SiO ₂ film 21, and the Al film 22 as a light-shielding film or the like is patterned on the SiO ₂ film 21 so that A on the photosensor 12 is formed.
The l film 22 is provided with an opening 23 for receiving light. A P-SiN film 24 as a passivation film covers the Al film 22 and the like in order to prevent moisture and Na from the outside from entering the device and deteriorating the device characteristics.
Further, although not shown, a flattening film is formed on the P-SiN film 24, and microlenses are formed on the flattening film.

The passivation film is A as a light-shielding film.
Since it is provided as an upper layer of the I film 22 and an Al film (not shown) as wiring, it is necessary to form it at a low temperature of about 400 ° C. or less. Therefore, generally, the P-SiN film 24, which is a silicon nitride film deposited by the plasma CVD method, or the P-SiO film 25 (FIG. 4), which is a silicon oxide film deposited by the plasma CVD method, is passivated. It is used as a film.

[0005]

The P-SiN film 24 is composed of
Since it contains a large amount of hydrogen, Si substrate 11 and SiO ₂
S, which is one of the causes of the interface state at the interface with the film 16.
Hydrogen in the P-SiN film 24 terminates the unsaturated bond between i and O, and has the effect of reducing the interface state and reducing the dark current.

By the way, in the step portion at the inner peripheral edge of the opening 23 of the Al film 22, as shown in FIGS.
The step portion 26 is also formed in the passivation film such as the film 24. On the other hand, the refractive index of the flattening film made of an organic material is about 1.6, whereas the refractive index of the P-SiN film 24 is as high as 1.95 to 2.00. For this reason, the P-SiN film 24, as shown in FIG.
Has a large lens effect of refracting the light toward the vertical transfer register 14 side. The light 27 refracted in this way is multiply reflected between the Al film 22 and the surface of the Si substrate 11 to generate a smear.

On the other hand, since the P-SiO film 25 has a low refractive index of 1.45 to 1.50, as shown in FIG. 4, the light 27 incident on the step portion 26 is directed to the vertical transfer register 14 side. The lens action to refract is small, and there is little smear. However, since the P-SiO film 25 does not contain hydrogen like the P-SiN film 24, it does not have the effect of reducing the interface state and dark current. Therefore, the first shown in FIGS.
In both the conventional example and the second conventional example shown in FIG. 4, it was not possible to reduce both dark current and smear at the same time to obtain a high-quality image.

[0008]

A solid-state image sensor according to the present invention has a two-layer structure of passivation of a first film 24 containing hydrogen and a second film 25 having a refractive index lower than that of the first film 24. Has a membrane.

[0009]

In the solid-state imaging device according to the present invention, since the first film 24 forming the passivation film contains hydrogen, the unsaturated bond which is one of the causes of the interface state is formed in the first film 24. There are few interface states due to the termination of hydrogen inside. On the other hand, since the second film 25, which forms the passivation film together with the first film 24, has a lower refractive index than the first film 24, the second film 25 is incident from the step portion 26 of the passivation film in the peripheral portion of the light receiving unit 12. The lens action for refracting the generated light 27 toward the transfer unit 14 side is small.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention applied to a CCD solid state image pickup device will be described below with reference to FIG. The components corresponding to those of the first and second conventional examples shown in FIGS. 2 to 4 are designated by the same reference numerals.

In this embodiment, as shown in FIG. 1, an Al film 22 as a light shielding film is covered with a P-SiO film 25, and a P-SiN film 24 is laminated on this P-SiO film 25. However, except that the P-SiN film 24 and the P-SiO film 25 form a passivation film having a two-layer structure, it is substantially the same as the first and second conventional examples shown in FIGS. Have a similar configuration. However, the P-SiN film 24
Is so thin that the optical path shift due to the refraction of the light 27 in the step portion 26 can be ignored.

In this embodiment as described above, the P-SiN film 24 is used.
The light 27 incident on the stepped portion 26 of the P-SiO film 25 is refracted toward the vertical transfer register 14 due to the P-SiN film 24, but the optical path shift due to this refraction is negligible as described above. Moreover, the light 27 emits light to the P-SiN film 24 and P-
At the interface with the SiO film 25, the light is refracted again to the side opposite to the vertical transfer register 14. Therefore, as compared with the first conventional example shown in FIGS. 2 and 3, refraction of the light 27 in the step portion 26 is small and smear is small.

Moreover, hydrogen in the P-SiN film 24 is converted into Si by the heat treatment after the P-SiN film 24 is formed.
It reaches the interface between the substrate 11 and the SiO ₂ film 16. This hydrogen terminates the unsaturated bond between Si and O at this interface and reduces the interface state, so that the dark current is also small.
In other words, in this embodiment, since the dark current and smear are small, a high quality image can be obtained.

In the above embodiment, the P-SiO film 25 is used.
The passivation film is formed in a two-layer structure in which the P-SiN film 24 is laminated on the stepped portion 26 as described above.
If the film thickness of the P-SiN film 24 is so small that the optical path shift due to the refraction of the light 27 in FIG. 2 can be ignored, the P-SiON film 25 is laminated on the P-SiN film 24, contrary to the present embodiment. It may have a two-layer structure.

[0015]

In the solid-state image sensor according to the present invention, since the interface state is small, the dark current is small, and further, the lens function of refracting the light incident from the step portion of the passivation film at the peripheral portion of the light receiving portion to the transfer portion side is provided. Since it is small and has few smears, high quality images can be obtained.

[Brief description of drawings]

FIG. 1 is an enlarged side sectional view of a main part of an embodiment of the present invention.

FIG. 2 is a side sectional view of a first conventional example of the present invention.

FIG. 3 is an enlarged side sectional view of a main part of a first conventional example.

FIG. 4 is an enlarged side sectional view of a main part of a second conventional example.

[Explanation of symbols]

 12 Photosensor 14 Vertical transfer register 24 P-SiN film 25 P-SiO film 26 Stepped portion 27 Light

Claims (2)

[Claims] 1. A solid-state imaging device having a passivation film having a two-layer structure of a first film containing hydrogen and a second film having a refractive index lower than that of the first film. 2. The first film containing hydrogen is plasma CV.
The solid-state imaging device according to claim 1, which is a silicon nitride film formed by the D method.