JPH01256168A - Semiconductor device and manufacture thereof - Google Patents

Abstract

PURPOSE:To decrease production of noise charge, by burying charged particles in an insulating film on a semiconductor region used in the non-equilibrium state. CONSTITUTION:Charged particles 6 having the same polarity as the conductivity type of a photoelectric converting section 1 are buried in an insulating film 5 formed on a photoelectric converting section 2. The presence of the charged particles 6 creates an inversion layer on the surface of the photoelectric converting section 2 to prevent the interfacial level from being as the center of production and to inhibit excitation of electrons. In order to bury the charged particles 6 in the insulating layer 5, the insulating layer 5 may be treated with mixture of hydrofluoric acid and nitric acid solutions in the case of positively charged particles, or with mixture of ammonia and hydrogen peroxide solutions in the case of negatively charged particles. In this manner, generation of dark current can be reduced substantially.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a semiconductor device, particularly a photoelectric conversion device and a method for manufacturing the same.

2. Description of the Related Art In recent years, solid-state imaging devices incorporating photoelectric conversion devices have been widely used in video cameras.

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

FIG. 2(a) shows a conventional cross-sectional structure of a unit pixel portion of a solid-state imaging device called an interline transfer type CCD. l
is a P substrate, 2 is a photoelectric conversion element in an N-type region, 3 is a transfer electrode of a vertical transfer CCD, 4 is a channel stopper, and 5 is a 5i
It is 02. In the same figure, the potential distribution along the line B-B' is
Shown in Figure (b).

Problems to be Solved by the Invention As shown in the figure, the surface of the charge conversion section 2 is depleted. Therefore, electrons in the valence band are likely to be excited into the conduction band via the interface state 20. The electrons at this time are so-called dark current, and are noise charges generated even when the photoelectric conversion section is not irradiated with light. This significantly degrades image quality in solid-state imaging devices, particularly when capturing images of objects at high temperatures or with low illumination.

In view of the above drawbacks, the present invention provides a solid-state imaging device that reduces dark current and improves image quality.

Means for Solving the Problems In order to solve the above problems, the solid-state imaging device of the present invention includes charged particles having the same polarity as the conductivity type of the photoelectric conversion section in an insulating film formed on the photoelectric conversion section. Embed.

Effect The above configuration lowers the potential on the surface of the charging converter,
By forming an inversion layer on the surface, depletion of the surface can be prevented. Therefore, the interface state contributes to significantly reducing the generation of dark current.

EXAMPLES Hereinafter, examples of the present invention will be described with reference to the drawings.

FIG. 1 shows an embodiment of the invention. FIG. 2A is a sectional view of a unit pixel portion of a solid-state imaging device. In the figure, 1 to 5 are the same as the conventional example. It is the negatively charged particles 6 that are relevant to the present invention. Due to the presence of the charged particles 6, a hole layer 7, that is, an inversion layer, is formed on the surface of the photoelectric conversion section 2, as shown in FIG. 1B, which shows the potential distribution along the line A' in FIG. Therefore, the interface level does not act as a generation center, so electrons become less excited, and the generation of dark current is significantly reduced.

At this time, it is clear that in order to actually form a surface inversion layer, an amount of charged particles having a surface density of a predetermined amount or more is required. At this time, if it is not possible to embed more than a certain volume density, the insulating film may be made thicker as necessary.

To embed charged particles in the insulating layer, if the particles are positively charged, they can be treated with a mixture of hydrofluoric acid and nitric acid, and if they are negatively charged, they can be treated with a mixture of ammonia and hydrogen peroxide. .

Up to this point, the explanation has been given using a solid-state imaging device as an example, but dark current in a solid-state imaging device is the generation of charge in an unbalanced state, and causes pause time failure in other semiconductor devices, such as DRAM. In this way, the effects of this invention are not limited to solid-state imaging devices;
It can be widely applied to semiconductor devices operated in non-equilibrium conditions.

Effects of the Invention As described above, by embedding charged particles in an insulating film on a semiconductor region used in a non-equilibrium state, surface depletion can be prevented and the generation of noise charges can be significantly reduced. The practical effects are significant.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of a semiconductor device according to an embodiment of the present invention, FIG. 1(b) is a potential distribution diagram along line A-A' in FIG. 1(a), and FIG. 2 is for explaining a conventional structure. This is a diagram. ■... P-type semiconductor substrate, 2... N-type photoelectric conversion element, 3... Transfer electrode of vertical transfer CCD, 5... SiO2, 6... ...Charged particles,
7...Hole layer, 20...Interface level.

Claims (3)

[Claims] (1) A semiconductor device characterized in that charged particles having the same polarity as the opposite conductivity type are embedded in an insulating layer formed on a semiconductor region of an opposite conductivity type formed in a semiconductor region of one conductivity type. . (2) The semiconductor device according to claim 1, wherein the areal density of the charged particles is a predetermined amount or more. (3) When forming an insulating layer on a semiconductor region of an opposite conductivity type formed in a semiconductor region of one conductivity type, if the opposite conductivity type is N type, a mixture of ammonia and hydrogen peroxide solution is used. 1. A method for manufacturing a semiconductor device, characterized in that when the opposite conductivity type is P type, the process is performed with a mixed solution of hydrofluoric acid and nitric acid.