JPS61248553A - Solid-state image pickup device - Google Patents

Abstract

PURPOSE:To obtain a high density solid-state image pickup device, by providing a first light sensitive part in a signal-charge reading part, and laminating a second light sensitive part having a different sensing wavelength region so that a common area is provided at neighboring picture elements of the first light sensitive part. CONSTITUTION:A line of Shottky diodes 3 is formed on a p-type Si substrate 1. A transfer gate electrode 5 of a vertical CCD 11 is formed through an insulating film 4. A transparent picture element electrode 7 is provided through an insulating layer 6. The surface is covered by an a-Si layer 8, which is sensitive to visible light. An ITO transparent electrode 9 is laminated. The a-Si 8 absorbs the visible light and generates a signal charge. Electrons are made to run to the electrode 7 by the electric field between the electrodes 9 and 7. The electrons are stored in an N<+> diode layer 10-2. Infrared light is inputted through the electrode 9 and reaches the Schottky diode 3 at the first light sensitive part. The generated holes are diffused in the substrate 1. The electrons are stored in a neighboring n<+> layer. The signal charge accumulated in the diodes 10-1 and 10-2 is transferred to an n<+> vertical CCD channel layer 2 by applying a positive pulse voltage to an electrode 5-1 or 5-2. The signal is read out. Four-phase negative CPphi1-phi4 are applied to the transfer electrodes.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a solid-state imaging device [C] in which photosensitive parts having different sensing wavelength ranges are stacked on the same semiconductor substrate.

[Technical background of the invention and its problems]

Nowadays, there is a growing demand for solid-state imaging devices to have more pixels, that is, higher pixel density, and to have more functions. As one way of increasing the functionality of solid-state imaging devices, we have proposed a solid-state imaging device having the function of capturing optical images in a plurality of wavelength regions (Japanese Patent Application No. 166563/1982). However, the solid-state imaging device described above has photosensitive parts for a plurality of wavelength bands on the same substrate and in the same plane, and is not suitable for increasing the density of pixels. Therefore, we proposed a solid-state imaging device in which photosensitive parts for a plurality of wavelength bands are formed not on the same plane but in a layered manner (Japanese Patent Application No. 58-239382).

According to the above-described stacked solid-state imaging device, it is possible to obtain a solid-state imaging device that is capable of capturing images in a plurality of wavelength ranges and is fully compatible with increasing pixel density.

By the way, as an example of the above-mentioned stacked structure solid-state imaging device,
An infrared light image is captured by a photosensitive part (first photosensitive part) on the semiconductor substrate.
A method is conceivable in which a visible light image is captured using the photosensitive section (the second photosensitive section).

At this time, the size of the second photosensitive section that captures the visible light image is limited only by the patterning accuracy of the pixel electrode, whereas the first photosensitive section that captures the infrared light image is The size of the photosensitive area is limited by the vertical COD, element isolation area, storage diode section for visible imaging, polysilicon wiring for the gate, etc., and is defined as the double ratio of the photosensitive area and pixel separation area. Is the fill factor around 10%? It becomes ni. As a result, the sensitivity to infrared light is significantly lower than the sensitivity to visible light.

[Purpose of the invention]

The present invention combines photosensitive areas with different sensing wavelength ranges in a high density (:
An object of the present invention is to provide a solid-state imaging device.

[Summary of the invention]

The present invention involves laminating first and second photosensitive sections having different sensing wavelength regions on a semiconductor substrate, and providing a signal charge readout section for reading out signal charges accumulated in each photosensitive section. In the solid-state imaging device configured with C2, the number of pixels and the pixel pitch of the photosensitive portion of jll and the second photosensitive portion are changed to form a stacked solid-state imaging device.

〔Effect of the invention〕

According to the present invention, it is possible to provide a high-density solid-state imaging device in which photosensitive portions having different sensing wavelength ranges are provided at a high density.

[Embodiments of the invention]

Embodiments of the present invention will be described using the drawings. FIG. 1 shows an embodiment of the present invention, in which an interline transfer CCD (interline transfer CCD) is used in the signal charge readout section.
1 is a structural explanatory diagram of a solid-state image sensor using a ferCCD (hereinafter referred to as IT-CCD); FIG.

(a) is a plan view of a total of 4 pixel parts, 2 pixel parts in the direction orthogonal to the transfer direction of vertical COD and 2 pixel parts along the transfer direction C2, (b) and (C) are A-A of (,), respectively. '
, is a BB' cross-sectional view. To explain this along the manufacturing process, a vertical COD channel n+ layer (2) for reading out signal charges on a P-type semiconductor substrate (1) and a first photosensitive portion sensitive to infrared light are made of, for example, PtSi. An array of Schottky barrier diodes (3) is formed by metal silinide such as and a silicon substrate C2. A vertical CC is then formed on this semiconductor substrate via a gate insulating layer (4).
Form the transfer gate electrode (5) of D (11). Next, a second insulating layer (6) is provided on top of this, and then this insulating layer (
6) A transparent electrode (two pixel electrodes (7) is provided on the pixel electrode (7).
An ITO (IndizmT) layer (8) is formed on the entire surface, and finally, an ITO (IndizmT) layer (8) is formed on the photoconductive film (8).
A transparent electrode (9) is formed on the entire surface (: inOxlda ), etc. (:).

In this way, the pixel electrode (7), the a-81 layer (8), and the transparent electrode (9) are laminated on the second photosensitive part that is more sensitive to visible light. ) is connected to the Schottky barrier diode (3) (n”li (tO− z
) +=Connected.

The a-8l layer (8), which is a photoconductive film, absorbs visible wavelength light (λ=0
．． 4 to 0.7 μm) and generate signal charges. This signal charge (electrons in this case) is generated by an electric field (two-pixel electrode (7) formed between the transparent electrode (9) and the pixel electrode (7)).
7), and the storage diode (10-2) (': accumulates.

In addition, the infrared wavelength light (λ>0.7 μm) component passes through the transparent electrode (9), the A-8L layer (8), the pixel electrode (7), and the insulating layer (6), and passes through the first photosensitive area. Schottky
The electrons reach the barrier diode (3) and generate electron-hole pairs in the metal silinide, and the holes diffuse into the substrate (1). =N middle layer (10-1)c which becomes an adjacent storage diode accumulates.

Two storage diodes (10-1) (10-2) (=The accumulated signal charges are transferred to the vertical COD transfer electrode (5-
A positive pulse voltage is applied to 1) or (5-2) and the data is transferred to the vertical C(α)Df- layer (2) and read out. In this case, vertical C+G11)ff of signal charge
Transfer within the fya channel n"1ii (2) is performed using a 4-phase negative clock on the transfer electrodes (5-1) (5-2) and the transfer electrodes formed adjacently and continuously. Pulse φ1~φ
Perform this by applying 4.

The above description is completely the same as the conventional structure shown in FIG. 5, but the arrangement of each part within the pixel is different. Fifth
Figures (a) (b) (c) are similar to Figure 1 1: (a)
is a plan view of a 2 pixel part along the vertical COD transfer direction (- and a 2 pixel part perpendicular to the transfer direction, a total of 4 pixel parts, (
b) (C) are AA' and BB' cross-sectional views, respectively.

There are two differences between the embodiment of the present invention shown in FIG. 1C and the conventional structure shown in FIG.

1. In the conventional structure shown in FIG. Portion key barrier diode (3)
The left-right relationship is constant. (FIG. 6) On the other hand, in the embodiment of the present invention shown in FIG.
Channel n (middle layer) and storage diode n”m (10
-1) The left-right relationship between (10-2) and Schottky barrier diode-F (3) is not constant, but is reversed every other pixel in the direction perpendicular to the vertical COD transfer direction.

(FIG. 2) 2. In the conventional structure shown in FIG. 5, an independent Schottky barrier diode (3) is provided for each pixel and ζ. On the other hand, in the embodiment of the present invention shown in FIG.
Transfer direction C of D: Two pixels adjacent in the orthogonal direction (two common Schottky barrier 6 diodes (3) are provided.
Barrier diode (3) C, two storage diodes (
10-1) is set up to capture the signal charge generated by infrared light (;
It is divided.

The sensitivity of a solid-state imaging device is as follows, if the characteristics of the light receiving part are the same:
It is proportional to the area of the light-receiving area, and therefore, if the pixel sizes are equal, the ratio of the area of the light-receiving area to the pixel area is proportional. It is considered one of the important parameters that determines the characteristics of the device.

The infrared aperture ratio, that is, the ratio of the Schottky barrier diode (3) area to the pixel area in FIG. 1 and FIG. 5 will be compared. In Figure 1, the Schottky barrier diode (3) is shared between two pixels and the signal charge is divided into two, so the actual aperture ratio is equal to the area of one Schottky barrier diode. , is the ratio of the areas of two pixels. By sharing the Schottky barrier diode (3) with 2 elements as shown in Figure 1, the area occupied by the element isolation region 0 is converted into a Schottky barrier diode. The external aperture ratio improves.

Furthermore, in the structure shown in FIG. 5, the visible light signal charge storage diode (10-2) and the vertical COD channel n+ layer of the adjacent pixel (
2) is narrow, and due to constraints on the minimum processing width in the semiconductor device manufacturing process, element isolation regions (L and Schottky barrier diodes (3)) are placed in the region between the two.
However, by adopting the structure shown in Fig. 1, a Yotsky barrier diode (3 ), and further supervision:
The infrared aperture ratio is improved.

As a result, it becomes possible to obtain a solid-state imaging device with high infrared sensitivity.

By the way, in the case of the structure shown in Figure 1, the same Schottky
Since exactly the same infrared light signal charge is read out in the two pixels l2 that share the barrier diode (3), the infrared resolution in the horizontal direction is reduced to 1/2. However, when an infrared light image and a visible light image of the same subject are simultaneously captured and displayed, the visible light image is essentially dominant, and the decrease in resolution of the infrared light image is a practical problem for C2. No.

Furthermore, according to the structure shown in FIG. 1, the pitch in the horizontal direction of the visible light signal charge storage diode (10-2) is not constant; Since the area is defined by the pixel electrode (7), the imaging characteristics of visible light images are the same as those of the conventional structure shown in FIG.

In the above explanation, It is also possible to share a Schottky barrier diode between two pixels.

In the structure shown in FIG. 3, since it is necessary to drive the vertical COD in at least three phases, a three-layer gate electrode structure using vertical CCD gates φ1 to φ3 is adopted. In this case, the infrared resolution in the vertical direction is 1/2 that of the conventional structure, but the infrared resolution in the horizontal direction is the same as that of the conventional structure.

Furthermore, it is also possible to obtain the structure shown in FIG. 4 by combining the structures shown in FIGS. 1 and 3. In the structure shown in FIG. 4, four pixels adjacent in the vertical and horizontal directions share a Schottky barrier diode (3), making it possible to significantly improve the aperture ratio.

In addition, in the above explanation, the signal charge readout section is
-COD was used, but for example, X-Y address type MOS
, line-address type CPD (Charge Pri
mimgDevice), charge sweeping element C8D
(Charge 8weepDevice), the present invention can be applied to any device that can read out signal charges.

Furthermore (2. In the above embodiments, a-8 is used as the visible light sensitive part.
A Pt8l-8i V Yotsky barrier diode was used as the first layer and the infrared light sensitive part, but instead of the a-8l layer (a photoconductive film typified by two 5e-A8-Ta, Zn5e-ZrCd're, etc.) can be used -Pt&5
mtx&aP4. βl.

14 [iiP, t 2g, li; Ji5 l J, tT
Metal silicides such as FB % 14 T i S i 1 can be used.

The above explanation is based on the case where the first photosensitive section detects infrared light and the second photosensitive section detects visible light. The region combination ζ2 is also applied.

[Brief explanation of the drawing]

1, 2, 3, and 4 are diagrams for explaining the structure of a photosensitive cell according to an embodiment of the present invention (Fig. 5).
This figure and FIG. 6 are diagrams for explaining the conventional structure. 1.-φ type silicon substrate 2...Vertical COD channel n+ layer 3...Schottky barrier diode 4.6--
・Insulating layers 5-1, 5-2...Transfer gate electrode 7...Pixel electrode 9.-a-81 layer 9...Transparent electrode 10-1.10-2-...Storage diode n+ layer 11・
- Vertical CCD 12 - Element isolation region 13...
・Horizontal CCD 14・-Storage unit 15...Preamplifier representative Nori Chika Kensuke (1 idiot) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] In a stacked solid-state imaging device in which a signal charge readout section and a first photosensitive section are provided adjacent to each other on a substrate, and a second photosensitive section having a different sensing wavelength region is layered thereon, the first
A solid-state imaging device characterized in that a photosensitive portion is shared between adjacent pixels.