JPH03273679A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To enable influence due to unneeded charge which is generated at an interface between an insulating film such as a silicon oxide on a trench side wall and an N<-> type diffusion layer by allowing an electrode to be buried in the trench which is used for isolation between photoelectric conversion parts through the insulating film. CONSTITUTION:A photoelectric conversion part consists of an N-type silicon substrate 1, a P-type diffusion layer 2 which is formed by ion implantation, an N<-> type diffusion layer 3 which is formed by ion implantation, and an NPN junction consisting of a P<+> type diffusion layer 4 formed by ion implantation, and it is so designed as to enable a junction surface between the P-type diffusion layer 2 and the N<-> type diffusion layer 3 to be for example 1mum from the surface of the silicon substrate 1. Further, the photoelectric conversion part is isolated by forming a trench 5 which is deeper than the N<-> type diffusion layer 3 (for example, 1.5mum). A silicon oxide film 10 which is for example 70nm is formed on an N<-> type diffusion layer surface 12 and an inner wall 11 and a first polysilicon electrode 13 is buried in the trench 5.

Description

[Detailed description of the invention] Industrial applications The present invention relates to a solid-state imaging device.

BACKGROUND OF THE INVENTION In recent years, demand for solid-state imaging devices has been increasing with the spread of camera-integrated VTRs. Along with this, demands for higher sensitivity and higher resolution of solid-state imaging devices are increasing.

A conventional solid-state imaging device will be described below.

FIG. 2 is a sectional view of a photoelectric conversion section of a conventional solid-state imaging device. In FIG. 2, 1 is an N-type silicon substrate, 2 is a P-type diffusion layer formed on the N-type silicon substrate 1, 3 is an N-type diffusion layer formed on the P-type diffusion layer 2, and 4 is a A P-type diffusion layer formed on the N-type diffusion layer 3, 5 a trench deeper than the N-type diffusion layer 3 (hereinafter referred to as a trench), and 6 a P-type diffusion layer formed at the bottom of the trench 5. In the diffusion layer, 7 and 8 are polysilicon electrodes, 9 is an aluminum light-shielding film, 10 is an insulating film such as silicon oxide, 11 is a side wall of trench 4, and 12 is a surface of an N- type diffusion layer.

The operation of the solid-state imaging device configured as described above using a trench to separate the photoelectric conversion sections will be described below.

The photoelectrically converted optical signal charges are accumulated in the N-type diffusion layer 3. Since the adjacent N-type diffusion layer is completely separated by the trench 5 which is deeper than the N-type diffusion layer and the insulation 1110 made of silicon oxide or the like, punch-through through the P-type diffusion layers 2 and 6 is prevented. Unless this occurs, the optical signal charges accumulated in each N-type diffusion layer 3 will not be mixed in.

Problems to be Solved by the Invention However, in the conventional configuration described above, the N-type diffusion layer 3 that accumulates optical signal charges is exposed on the trench sidewall 11 and the N-type diffusion layer surface 12. When the solid-state imaging device is operating, the N-type diffusion layer 3 is depleted, so unnecessary charges (so-called dark current) generated on the trench sidewall 4 wall 11 and the N-type diffusion layer surface 12 become N-type. There was a problem in that the particles entered the diffusion layer 3 and mixed into the optical signal charges.

In particular, when the amount of optical signal charge is small or when used at high temperatures, unnecessary charges generated on the trench sidewall 11 and the N-type diffusion layer surface 12 become dominant, resulting in image defects such as dark current unevenness. It had

The present invention solves the above-mentioned conventional problems, and aims to provide a solid-state imaging device that reduces the influence of unnecessary charges generated at the interface between an insulating film such as silicon oxide on the side wall of a trench and an N-type diffusion layer. purpose.

Means for Solving the Problems To achieve this object, the solid-state imaging device of the present invention includes a first diffusion layer of one conductivity type formed on a semiconductor substrate of one conductivity type, and a first diffusion layer of the other conductivity type. A photoelectric conversion section consisting of a second diffusion layer of one conductivity type formed on the second diffusion layer and a third diffusion layer of the other conductivity type formed on the second diffusion layer is formed on the second diffusion layer. It is separated from an adjacent photoelectric conversion section by a deep trench, and has an electrode embedded in the trench and on the surface of the second diffusion layer with an insulating film interposed therebetween.

Effect: With this configuration, a predetermined voltage is supplied to the electrode embedded inside the trench to prevent pinning and depletion of the second diffusion layer near the trench sidewall, and to prevent the second diffusion layer from being depleted by the insulating film on the trench sidewall. It is possible to prevent unnecessary charges (dark current) generated at the interface with the diffusion layer from being mixed into the optical signal charges.

EXAMPLE An example of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of a photoelectric conversion section of a solid-state imaging device according to an embodiment of the present invention. Note that the same reference numerals are attached to the same whistle stations as in the conventional example shown in FIG. 2, and detailed explanations are omitted. However, 13 is a polysilicon electrode buried inside the trench.

In FIG. 1, it consists of an N-type silicon substrate 1, a P-type diffusion layer 2 formed by ion implantation, an N- type diffusion layer 3 formed by ion implantation, and a P+ type diffusion layer 4 formed by ion implantation. A photoelectric conversion section is constituted by an NPN junction, and the P-type diffusion layer 2 and the N-type diffusion layer 3
The bonding surface with the silicon substrate 1 is designed to be, for example, 1 μm from the surface of the silicon substrate 1. Furthermore, the N-type diffusion layer 3
A deeper trench 5 (for example, depth 1.5 μm) is formed to separate the photoelectric conversion parts. A silicon oxide film 10 of, for example, 70 nm is formed on the surface 12 of the N- type diffusion layer and the trench sidewall 11, and a first polysilicon electrode 13 is buried inside the trench 5. 8 is a second polysilicon electrode, and 9 is an aluminum light-shielding film.

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

Polysilicon electrode 13 embedded inside trench 5
By applying a predetermined negative voltage to the trench sidewall 11, the N'''' type diffusion diffusion layer 3 is reduced, and the depletion layer is prevented from expanding. Therefore, silicon oxide film 10
The influence of unnecessary charges generated at the interface between the N-type diffusion layer 3 and the N- type diffusion layer 3 can be significantly reduced. Furthermore, as is well known in the art, a P+ type diffusion layer 4 is formed on the surface of the light receiving portion, thereby suppressing the spread of the depletion layer.

Effects of the Invention As described above, the present invention provides an electric potential to the side walls of the trench by embedding an electrode through an insulating film inside the trench used for separating photoelectric conversion parts, thereby increasing the second diffusion near the four walls of the trench side wall. By pinning the layer, unnecessary charges generated at the interface with the silicon oxide insulating film can be prevented from being mixed into the video signal, making it possible to create an excellent solid-state imaging device that can transmit clear images. be.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a photoelectric conversion section of a solid-state imaging device according to an embodiment of the present invention, and FIG. 2 is a sectional view of a photoelectric conversion section of a conventional solid-state imaging device. 1... N-type silicon substrate (semiconductor substrate), 2.
...P-type diffusion layer (first diffusion layer), 3...
・N-type diffusion layer (second diffusion layer), 4...P medium-sized diffusion layer (third diffusion layer), 5...trench
groove), 10... silicon oxide film (insulating film), 1
DESCRIPTION OF SYMBOLS 1... Side wall, 12... N-type diffusion layer surface (surface of second diffusion layer), 13... First polysilicon electrode (electrode).

Claims (1)

[Claims] a first diffusion layer of one conductivity type formed on a semiconductor substrate of one conductivity type; a second diffusion layer of one conductivity type formed on the first diffusion layer; and a second diffusion layer of one conductivity type. a third diffusion layer of the other conductivity type formed above, and a photoelectric conversion section is separated from an adjacent photoelectric conversion section by a groove deeper than the second diffusion layer; A solid-state imaging device with electrodes embedded on its surface via an insulating film.