JPS58209270A - Solid-state image pickup element - Google Patents

Abstract

PURPOSE:To uniformize the dark current generated at each light receiving part and to degrade its level, by coating whole surace of the light receiving part with a silicon nitride film. CONSTITUTION:A P-N junction of an N type diffused layer 4 and a P type base board 1 forms a light receiving part, and a built-in channel area 5 and storage gate 6, etc., constitute a CCD element. The 7 is a gate for transferring a carrier generated by the light receiving part to the channel area 5. In a soild image pickup element so constituted as mentioned aobve, a silicon nitride film 8 is provided to cover whole surface of a cell part. The silicon nitide film 8 generates hydrogen when growing. The hydrogen stays in a silicon oxide film 2 to fill always an interface between the silicon oxide film 2 and the N type area 4. Since the trap of the interface is filled with the hydrogen, dark current is reduced as the result. Also, dark current between large number of light receiving parts is uniformized.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a solid-state imaging single quadrant, which has particularly low dark current.
Furthermore, the present invention relates to a solid-state sensor that can be made uniform in size by adjusting the current in each light receiving section.

Traditionally, solid-state photography [in the electronic device, Angiryu? Efforts were made to make it smaller. There are two types of dark current: large spike-like ones caused by crystal defects in semiconductors, and small ones caused by thermal excitation. In the former case, gettering is gradually being improved through treatment, but in the latter case, it is far from being improved due to its generation mechanism. Especially if the dark current generated in each light receiving part is not uniform, the dark area kkJ
When there is a shadow, does the black on the screen have shading? It grows and becomes very unsightly and ugly.

The purpose of the present invention is the latter dark current? It is an object of the present invention to provide a solid-state image sensing device that can be made uniform and small among the light receiving parts.

The present invention is a single-area solid-state imaging device characterized in that at least the entire light-receiving portion is coated with a t-silico/chamber film.

By the way, the cause of the dark current mentioned above is due to thermally excited carriers, but most of the excitation process is caused by 8
This is due to traps at the i-8iOz interface. Therefore, in order to reduce the dark current, the traps at the 3i-8iOz interface may be filled with some kind of atoms, such as hydrogen. However, even at a low temperature of 550°C, hydrogen atoms have 5
Since it diffuses as much as 3 μm per second, even if the trap is temporarily buried, it will leave the trap with a slight heat treatment.

This phenomenon occurs non-uniformly throughout the light-receiving section, so the VC dark current is not uniform, and there are always empty traps, so the dark current is not uniform. It makes it bigger.

In the present invention, by covering the 8i0z on the light receiving part with a silicon nitride film, a sufficient amount of hydrogen is confined in the 5in2, and the traps at the 5i-8iUz interface are always filled with hydrogen, thereby reducing the dark current. reduction and uniformity can be achieved.

Next, drawing the invention? Refer to and explain. The figure is for explaining the present invention, and is a cross-sectional view of one cell consisting of a light receiving part and a CCI of a solid-state sensor for use in a CCDCD device. In the figure, 1 is a P-type semiconductor substrate.

2 is a tail silicon oxide film that is thick around the cell and thinner elsewhere, 3 is P, channel stopper%4 is N
A light receiving section is formed by joining the diffusion layer to P- with the P type substrate 1. 5 is the N-buried channel region of the CCI) device;
6 is an accumulation gate of the CCD element, 7 is a transfer gate for transferring carriers generated in the light receiving part to the rational channel region, 8 is a silicon nitride covering the entire surface of the cell part, and 9 is a gate other than the light receiving part. Does it allow light to enter?It is made of aluminum that prevents light from entering.

In the figure, a trap that causes a dark current exists at the interface between the arsenic silicon oxide film 2 and the N 2 region 4 .

Here, when growing the silicon nitride film 8, silane 8iH
4 and ammonia NH3 using the CVD method.

As can be seen from the reaction equation 3SiH4+4^NHa→Si3N4+12H2, a large amount of hydrogen is generated and remains in the silicon oxide film 2, and since the silicon nitride film 8 hardly allows hydrogen to pass through, the silicon oxide ratio is hydrogen becomes immobile,
The rice is constantly supplied to fill the traps at the interface between the silicon oxide ratio film 2 and the N+ region 4. As a result, the dark current is reduced, and the uniformity of the dark current among the large number of light receiving sections is also improved.

or.

In addition to using hydrogen generated by CVD, a silicon nitride film of 8T--for example, 700A after being grown at 200A@degrees.
The above effect can be achieved even by performing hydrogen treatment at a temperature of about 40 minutes. At this time, when the aluminum 9 on the silicon nitride film 8 is heat-treated at, for example, about 500° C. when sintering, the silicon nitride film 8 does not allow hydrogen to pass through at all. 5 more
For the iOzZ monkey.

Since it originally contains a large amount of hydrogen, is it actively hydrogen?
It is not necessary to confine it in a silicon oxide film, and it is sufficient to simply form the entire silicon nitride film 8 on the silicon oxide film 2.

Although the solid-state sensor for use with CCDCD devices has been described above, it is of course applicable to similar devices of MOS type. Also, in this text, we have described the case where the entire cell is covered with a silicon nitride film, but at least only the light receiving part is covered with a silicon nitride film.
That is, even if only the N+ region 4 is coated, the effects of the present invention will not be compromised in any way.

[Brief explanation of drawings]

The figure is a cross-sectional view of a solid-state image sensor for explaining the present invention. In the figure, 1...P-type semiconductor substrate, 2...
...Silicon plate ratio membrane, 3...Channel stopper, 4...N IJ[, 5...Dan, CC
D N-buried channel, 6... CCD storage gate, 7... Transfer gate, 8... Silicon nitride [arsenic film, 9... River/shading aluminum, It is. Agent: Susumu Uchihara, patent attorney [Fig.

Claims (1)

[Claims] At least the entire top of the light receiving part? Did you coat it with silicon nitrate? Solid-state imaging element with 1 symbol.