JPS58202673A - Solid-state image pickup element - Google Patents

Abstract

PURPOSE:To prevent the breakdown of a photoelectric converting film, by contacting a metallic electrode provided to an image pickup element which extracts a transparent electrode to the outside with a junction type diode of a different type from an element substrate and them utilizing the breakdown of said junction to shunt the high voltage applied to the electrode toward the substrate. CONSTITUTION:An oxide film 9 for insulation is formed on a semiconductor substrate 1 of the 1st conduction type, and a diffusion layer 16 is formed in the stages to form a source 3 and a drain 4 of an MOS switch 2. Electrodes 17, 6 and 14 are formed on the film 9, and at the same time a photoelectric converting film 7 is vapor deposited at the region of the switch 2 by a sputtering or glow discharge method. In addition, a transparent electrode 8 for application of target voltage is formed to the electrode 14 formed on the film 7 and the layer 16 to drive the film 7 by a sputtering or glow discharge method. In this case, the high voltage generated within a sputtering device is shunted toward the substrate 1 via the electrode 14 and the layer 16 by means of the junction different from the substrate 1 and formed to the lower layer of the electrode 14. Thus the breakdown is avoided for the film 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Application of the Invention The present invention relates to a solid-state image sensor in which a scanning circuit and a photoelectric conversion film are integrated on a semiconductor substrate.

(2) Prior art CCD (Ch
Two types have been considered: a MOS type (a device that uses the source junction of a MOS switch as a photodiode) and a MOS type (a device that uses the source junction of a MOS switch as a photodiode).

All of these devices have the advantage that they can be manufactured using highly integrated MOS process technology. However, since the photosensitive section is located below the electrode (in the case of COD) or on the same plane as the scanning switch and signal output line (in the case of MOS type), there is an area where the incidence of light is blocked by the electrode or switch section. The disadvantage is that there is a large amount of light loss, that is, there is a large optical loss. Furthermore, since the photosensitive section and the scanning section are on the same plane as mentioned above, the area occupied by the picture elements becomes large.In other words, there is a problem in that the density of the picture elements cannot be increased and the resolution cannot be increased. are doing.

As a structure to solve these problems (photosensitivity, resolution), the inventors applied for a two-story solid-state image sensor in which a photosensitive photoelectric conversion film is provided above the scanning section (Japanese Patent Application No. 49-7
6372. (Patent application filed July 5, 1972). Taking as an example the case where this two-story solid-state image sensor is constructed with MO8 type elements, the outline of the element structure is shown in Figure 1.
(You can replace it with OD). 1 is a semiconductor substrate of a first conductivity type; 2 is an MO8 field effect transistor constituting a scanning circuit (not shown) or a switch that is opened and closed by the output of the scanning circuit; Reference numeral 6 consisting of the gate 5 is an electrode that determines the dimensions of one picture element, and is connected to the source here.

7 is a photoelectric conversion film serving as a photosensitive material, and 8 is a transparent electrode for applying a target voltage to drive the photoelectric conversion film. Further, 9 is an oxide film for insulation. As you can see from this figure,
A semiconductor substrate 1, a scanning IC substrate on which a scanning circuit and a switch 2 are integrated, and a photoelectric conversion section 7 and 8 have a two-story structure. Therefore, the area utilization η is high and the dimension 10 per picture element is small, that is, the resolution is high.

Since the photoelectric conversion section is located above the incident light 11, there is no light loss and the light sensitivity is high. Furthermore, by selecting a photoelectric conversion film, a desired spectral sensitivity can be obtained, and extremely superior performance can be expected compared to conventional solid-state imaging devices.

However, in the process of developing this device, when forming transparent electrodes (e.g., metal thin film, 5NO2 film, ■TO film), it was necessary to
'e film, CdTe film, PbO,, CdS.

It has been found that the camera has an extremely troublesome problem in that the film (such as SeBAS 2) is destroyed and point-like defects (which appear as white spots on the monitor and degrade the image quality) occur. It has been found that the cause of this destruction is that high voltage is generated within a device such as a sputtering device, and the photoelectric conversion film is exposed to a voltage higher than the withstand voltage.

(3) Purpose of the Present Invention The purpose of the present invention is to provide a solid-state imaging device that prevents the underlying photoelectric conversion film from being destroyed when transparent electrodes are laminated.

(4) Detailed Description of the Invention In order to achieve the above object, the present invention specifically provides an impurity layer of a type different from that of the element substrate (a bonding type The high voltage applied to the transparent electrode is released to the element substrate side by using the breakdown of this junction.

(5) Examples Hereinafter, the present invention will be explained in detail with reference to Examples. Second
The figure is a diagram showing the overall structure of the solid-state imaging device of the present invention. 7 is a photoconductive film (for example, S e -A s -T
e, Cd'pe, hydrogenated amorphous silicon, etc.),
8 is a transparent electrode (SnOl, I'L"0 film, etc.)
6 is as explained in FIG. Reference numeral 12 indicates a photoelectric conversion area in which picture element electrodes are arranged in a two-dimensional manner, and reference numeral 13 indicates an area in which scanning circuits are integrated.

14 is an electrode (for example, At, Mo, etc.) provided around the element chip for applying a target voltage;
It is in ohmic contact with the transparent electrode 8 at the portion 5.

16 is a substrate 1 (for example, P) that is in ohmic contact with the electrode 14.
diffusion layer 16 made of impurity atoms different from the type (for example, N
type). In addition, 17 indicates one of the plurality of bonding pad electrodes (which may be made of the same material as the electrode 14) provided around the chip, and 18 connects the pad electrode to the pin terminal of the package that houses the chip. Bonding wires are shown.

First, the scanning IC board of this device is a normal MOS/LSI.
The electrodes 17, 6° 14 are formed using the same technique. Here, the diffusion layer 16 is formed in the same process as the source and drain of the MO8 switch 2. Subsequently, a photoconductive film is deposited by sputtering or glow discharge (the processing of the heavy film is carried out by conventional photoetching techniques or by mask evaporation). Finally, a transparent electrode 8 is deposited by sputtering or glow discharge. During the deposition of this electrode film, the photoconductive film produced in the previous step is exposed to a high voltage generated within the sputtering apparatus during the deposition period. The generated voltage ranges from 50 V to several hundred volts, depending on the sputter bias conditions for producing the electrode film. The strength of the photoconductive film is 50 to 10 per 1 μm of film thickness, although it depends on the material.
In most cases, the film thickness is set to several μm, and the current photoelectric conversion film is destroyed in almost the entire photoelectric conversion region.

Furthermore, as the sensitivity of photoelectric conversion films increases, the film thickness will become thinner in the future, and the degree of destruction will increase and increase. However, in the structure of the present invention, since the np junction (-!take pn junction) is provided by the diffusion layer 16 in the lower layer of the electrode 14, the high voltage is applied to the electrode 14 through the laminated transparent electrode film. , the diffusion layer 16, and the substrate 1. Here, a junction (that is, a diode) that breaks down due to high voltage is responsible for discharging the energy to the substrate.

The breakdown voltage of the junction depends on the impurity concentration of the substrate 1, but it is 5×10′4 to 1×10 used as a general IC substrate.
``At the concentration of 8 pieces per piece, it is 20 to 40 V, and as a result,
The voltage applied to the photoelectric conversion film can be suppressed to 20 to 40V at most. In addition, the breakdown of the junction is instantaneous because the current that flows through the junction diode when a breakdown occurs is so small that it can be ignored, and once the voltage is removed, there is no problem and the junction is normal. It can fully withstand the target voltage (generally 5 to 10 μm) applied during the imaging operation.

FIG. 3 is a diagram showing the planar configuration of the solid-state imaging device according to the invention. The same figure (a) shows MO on the scanning IC board shown in Figure 2.
It is a figure which shows the structure when an 8-type board|substrate is used. 19 is an image sensor chip, 20 is a horizontal scanning circuit, 13' is a vertical scanning circuit, 7' is a region where a photoelectric conversion film is formed, 8' is a region where a transparent electrode is formed, and 17'-1 is, for example, a scanning circuit. Bonding pads 18'-1 and 18'-2 are bonding wires for applying power to drive the components and the like. Here, a portion of the transparent electrode 8' (in this example, a portion below the chip) is in contact with a target electrode 14' provided with a diffusion layer 16'. In addition, 17'-2 is the electrode 14
This is a bonding pad for applying a target voltage provided in a part of .

FIG. 1 (1) is a diagram showing the configuration when a KCCD type substrate is used for scanning or the like. 21 is a horizontal CCD shift register, and 7' is a photoelectric conversion film area.
An array of OD shift registers is arranged. Reference numeral 8' denotes a transparent electrode region, which is in contact with an electrode 14' provided with a diffusion layer 16' at a portion (in this example, a portion above the chip).

Further, 17'-1 is a bonding pad for applying power for driving a vertical COD shift register, and 17'-2 is a bonding pad for applying a target voltage provided on a part of the electrode 14'. be. On the other hand, the same figure (
C) is an example using the same <CCD type substrate as in FIG. A case is shown in which the diffusion layer 16 connected to the lower layer is divided into a plurality of blocks. When the diffusion junction 16'' breaks down due to the high electric field generated in the sputtering equipment, the current flowing through the main diffusion layer is extremely small as described above, so the main diffusion layer is It is not necessary to take a large value in terms of area as in this example, and the area may be reduced to a necessary value according to the current capacity by dividing it as in this example.

(9) The voltage applied to the photoelectric conversion film during the formation of the transparent electrode can be further reduced by making the structure of the electrode 14 as shown in FIG. 16 is an impurity layer of a different type from the substrate 1 provided under the electrode 14 shown in FIG. 2, and 22 is an impurity layer 1-1.
This is an impurity layer of the same type as the substrate provided further below the layer 6 and of a higher concentration than the substrate. In this structure, the breakdown voltage of the junction formed by the impurity layers 16 and 22 is low, and the value of this breakdown voltage can be set to a desired value in the range of 1 V to several tens of volts by setting the impurity concentration of the impurity layer 22. I can do it. However, this breakdown voltage needs to be set higher than the target voltage applied during imaging. In this way, by lowering the breakdown voltage of the impurity layer 16 than in the case of FIG. 2, the effect of preventing destruction of the photoelectric conversion film can be further enhanced.

The inventors have confirmed that the device structure of the present invention can prevent almost 100% destruction of the photoelectric conversion film. It was confirmed that the occurrence of white spots (10) was also reduced and the image quality and reliability were significantly improved. Therefore, the present invention has extremely high practical value.

In the above embodiment, a MOS (MOS) transistor was used as a component of the scanning IC board, but as mentioned above, a CC
It is obvious that the structure of the present invention can be applied in exactly the same manner to the case of D and also to CID.

[Brief explanation of drawings]

Figure 1 is a diagram showing the pixel structure of a conventional solid-state image sensor;
The figure shows the overall structure of the solid-state image sensing device of the present invention.
The figure shows the planar configuration of the solid-state image sensing device of the present invention, and FIG. 4 is a diagram showing a device structure different from that shown in FIG. 2 of the solid-state image sensing device of the present invention. Patent attorney Toshiyuki Usuda (11) 3rd Bud 3 Diagram (C) VJ4 diagram

Claims (1)

[Claims] 1. The upper part of a scanning semiconductor integrated circuit board that integrates a plurality of picture element electrodes arranged in a two-dimensional manner, switches connected to the picture electrodes, and scanning elements that transfer photocharges sequentially taken out via these switches. In a solid-state imaging device having a photoconductive film and a transparent electrode film that are laminated to generate the photocharge, the area around the transparent electrode is used to apply a predetermined target voltage to the transparent electrode as a driving electric field for the photoconductive film. 1. A solid-state imaging device, wherein the target voltage input metal layer that makes ohmic contact in a part of the region is connected to a different type of impurity layer formed on the scanning semiconductor substrate.