JPS62117367A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To reduce smears due to a leakage light from an isolation region without reduction of a sensitivity by applying self-alignment etching using a picture element electrode as a mask to provide a step between the picture element electrode and the picture element isolation region, and thereafter stacking a photoconductive film and forming a recessed portion in the film. CONSTITUTION:A P-type Si substrate 1 is isolated with a P<+> layer 2 by means of a known process, and a CCD channel N<+> layer 3 and a storage diode N<++> layer 4 are formed. Through a gate insulating film, transfer gate electrodes 5-1, 5-2 are formed. An insulating film 6 is stacked, and a picture element electrode wiring 7 is provided. This is covered with an insulat ing layer 8, an Al picture element electrode 9 is provided to a planar surface, with the elec trode 9 as a mask etching is performed, and a step is formed between the electrode 9 and an isolation region 12 by self alignment. Subsequently, when an a-Si 10 is formed, a recessed portion is formed, and a transparent electrode 11 is provided, completing the device. Since the light incident upon the isolation region 12 is directed to the picture element electrode 9 by the lens effect of the recessed portion, the infrared light which is not absorbed by the photoconductive film 10 does not enter the substrate 1, which results in the reduction of smears due to a leakage light as well as the improvement of the sensitivity and also reduces the leakage light on the picture element isolation region 12.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention provides a signal charge transfer section formed on a semiconductor substrate;
The present invention relates to a stacked solid-state imaging device including a photoelectric conversion section using a photoconductive film.

[Technical background of the invention and its problems]

As an example of a stacked solid-state imaging device, there is a CCI in the signal charge transfer section of the semiconductor substrate.
lod 1) ov, ioe: charge coupled device) on the photoconductive film a-5i (amorphousSi, 1icon
:Amorphous silicon) will be described below. (Fig. 3) In the stacked solid-state imaging device as shown in Fig. 3,
When light enters from the surface, the light with energy greater than the band gap of the a-8i layer (10) generates electron-hole pairs in the a-8i layer, and the generated electrons and holes are transferred to the pixel electrode. Electrons move due to the electric field formed between the electrode (1) and the transparent electrode (11), and in the case of an N-channel CCN, for example, electrons are accumulated in the storage die feed (2) as signal charges.

In particular, when forming the metal grid (15) for a light shield after forming the pixel electrode (2) as shown in FIG. Since it partially obstructs the area, the effective photosensitive area decreases, that is, the photosensitivity decreases.

[Purpose of the invention]

An object of the present invention is to provide a stacked solid-state imaging device in which smear caused by light leaking from a pixel separation region is significantly reduced.

[Summary of the invention]

The present invention provides self-aligned etching using a pixel electrode as an etching mask on an insulating layer in a pixel isolation region in a stacked solid-state imaging device consisting of a signal charge transfer section formed on a semiconductor substrate and a photoelectric conversion section using a photoconductive film. and search tl! By forming a photoconductive film after providing a step between the pole and the pixel separation region, a stacked solid-state imaging device in which the photoconductive film in the pixel separation region 1- has a gate shape can be fabricated by 1%.
6 [Effects of the Invention] According to the present invention, it is possible to obtain a stacked solid-state imaging device in which smear caused by light leaking from the pixel separation region is significantly reduced without lowering the sensitivity.

At this time, the effective photosensitive area, which is an important parameter that determines the sensitivity of the solid-state image sensor, is defined by the area of pixel electrode 0, so the area between the pixel electrodes, that is, the pixel separation area (1
2) is required to be as narrow as possible. However, the pixel isolation region (12) is essential for electrical isolation between the pixel electrodes.

On the other hand, light with energy below the bandgap of the a-5i layer (10), that is, infrared light, is transmitted through the a-Si layer (10).
0) is transmitted. Generally, since a metal such as AQ is used as the material of the pixel electrode 0, most of the infrared light transmitted through the a-8i layer (10) is reflected by the pixel electrode (1) and does not enter the semiconductor substrate (O). However, in the pixel isolation region (12) where the pixel electrode (b) does not exist, the light that has passed through the a-5i layer (10) leaks and enters the semiconductor substrate (1) as light, generating electron-hole pairs. , the carriers generated in this semiconductor substrate (1) form a CCD channel for charge transfer.
Smear occurs due to injection into the solid state imaging device, which deteriorates the imaging characteristics of the solid-state imaging device.

In a stacked solid-state imaging device, in order to prevent the smear described in L, a metal grid (13) for a light shield is placed on either the upper side of the pixel electrode 0 as shown in FIGS. 4, 5, and 6.
There is a method of suppressing light leaking into the semiconductor substrate 0) by forming (1, 4) (15), but the manufacturing process becomes complicated in order to form a metal grid.

[Embodiments of the invention]

Embodiments of the present invention will be described using the drawings. Figures 1-3 to 1-3 show an embodiment of the present invention, in which interline transfer CG11 (1, nLorljnoTra
FIG. 2 is a structural explanatory diagram of a stacked solid-state imaging device using a nsjr CCD (IT-CCD).

To explain this along the manufacturing process, on a P-type semiconductor substrate ω, an element isolation region 1]10 layers (3), a vertical CCD channel n10 layers (3), and a storage diode n10 layers 0) are formed.

Then, vertical CCD transfer gate insulating layers (5-1) (5-2) are formed on this semiconductor substrate via a gate insulating layer. Next, an insulating layer 0 is provided on this, and furthermore, a pixel electrode wiring dQ is placed on this. Thereafter, a pixel electrode υ consisting of AQ after providing an insulating layer Q9 is formed to flatten the surface shape (FIG. 2 (8)).

In the case of a conventional stacked solid-state imaging device (Fig. 3), the photoconductive film (10) and the transparent electrode (11) are formed immediately after the pixel electrode 0 is formed.
However, in the present invention, after the pixel electrode 0 is formed, this pixel electrode is used as an etching mask to perform self-line etching of the insulating layer (marked) of the pixel isolation region (12), and then etching is performed as a photoconductive film (10), for example. An a-5L film is formed on the entire surface, and further, as a transparent electrode (11), for example, ITO (Indium Tiri Oxide) is formed on the entire surface.

According to the process used in the present invention, a step is formed between the pixel electrode 0 and the pixel isolation region (12). (Fig. 2(b)) Plasma C, for example, is placed on a substrate with such a step structure.
When the a-8i layer (10) is formed by VD, a rounded gate-shaped a-Si layer (10) is formed at one step. (FIG. 2(C)) In this way, a stacked solid-state imaging device is obtained in which the photoconductive film (10) on the pixel isolation region (12) has a concave shape.

Next, the effects of the stacked solid-state imaging device obtained by the present invention will be explained. The light incident on the pixel separation region (12) J- passes through the concave transparent electrode (IJ) and the photoconductive film (1
0) is refracted by the lens effect, and the pixel separation area (12)
Instead of heading towards the pixel electrode ■. As a result, the infrared light of the incident light that is not absorbed by the photoconductive film (10) does not pass through the pixel separation region (12) and is reflected to the pixel electrode 0.
). Therefore, since no electron-hole pairs are generated in the semiconductor substrate O), smear caused by leaked light is significantly reduced.

In addition, the light absorbed by the a-3i layer (jO) is also absorbed by the pixel electrode ■
Since the direction of incidence is changed in this direction, the effective photosensitive area increases, that is, the sensitivity increases, and crosstalk in the pixel separation region (12) J- is also reduced.

In the above explanation, an IT-CCD was used for the signal charge transfer unit, but for example, an X, -Y address type MO5, a line address type CPD (Charge Printin
gDevice), charge sweeping element C5D (Char
ge Sweep Device) The present invention can be applied to any other devices that can read signals.

In addition, in the explanation below-1, the a-5i layer was used as the light guide mis, but for example, 5o-As-To, Zn5s-
A photoconductive film typified by ZnCdTo or the like can be used.

Furthermore, in the above description, the COD was explained as an N-channel COD, but the present invention can also be applied to a) channel COD.

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[Brief explanation of drawings]

FIG. 1 is a diagram for explaining the structure of a photosensitive cell in an embodiment of the present invention, FIG. 2 is a diagram for explaining a method for forming a photoconductive film having a gate shape on a pixel isolation region, and FIG. 3, 4, 5, and 6 are diagrams for explaining conventional structures. In the figure, 1... Semiconductor substrate 2... Element isolation region 3
...Vertical COD channel 4...Storage diode 5-1.5-2...Vertical CCD transfer gate electrode 6.
8... Insulating layer 7... Pixel electrode wiring 9...
Pixel electrode work 0... Photoconductive film 11... Transparent electrode 12... Pixel separation region 13.14
．． 15...Metal grid agent for light shield Patent attorney Nori Chika Ken Yudo Kikuo Takehana Yoshitate Shima

Claims (1)

[Claims] A signal charge transfer section formed on a semiconductor substrate, an insulating layer covering the entirety, a pixel electrode electrically connected to the signal charge transfer section through an opening made in the insulating layer, and a pixel electrode covering the entirety. What is claimed is: 1. A solid-state imaging device having a photoelectric conversion layer deposited on the photoelectric conversion layer, wherein the insulating layer between the pixel electrodes is etched using the pixel electrode as a mask to create a recess on the surface of the photoelectric conversion layer.