JPH01220862A - Solid-state image sensing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention provides a driving field effect transistor having a channel portion made of a single crystal silicon layer and a photodiode made of an amorphous silicon layer on a transparent insulating substrate. The present invention relates to a solid-state image sensor.

[Conventional technology]

A conventional solid-state image sensor having a driving field-effect transistor having a channel portion made of a single-crystal silicon layer is
It is described in Japanese Patent Application Laid-Open No. 62-58549. FIG. 3 shows a cross-sectional view of a conventional solid-state image sensor. In the same figure,
A p-type impurity diffusion layer 16 is provided on the entire surface of the n-type substrate 15, and an n-swelled diffusion layer constituting the source electrode part 4 and train electrode part 5 of the MOS transistor, and a gate insulating film 6 are provided on the p-type impurity diffusion layer 16. Then, the gate electrode 7 is arranged. The n-swelled diffusion layer 4 constitutes a photodiode together with the P-type impurity diffusion layer 16, and a buried layer 17 is provided on the substrate side of the junction surface of this photodiode. Each photoelectric conversion element is insulated and isolated by an interlayer insulating film 19 and an interelement isolation oxide film 18, but the buried layer 17 has a configuration in which each photodiode arranged in one direction is electrically connected. Further, the n-swelled diffusion layer 5 as each train of each field effect transistor of each photoelectric conversion element arranged in a matrix is connected to a common signal wiring ll.

(Problem to be solved by the invention) However, in the above conventional example, since the driving field effect transistor is provided in the silicon substrate, the photoexcited charges in the silicon substrate are transferred to the source electrode portion 4 of the field effect transistor and the train electrode. It easily gets mixed into the n-swelled diffusion layer constituting the portion 5, causing a so-called smear phenomenon and causing false signals. Furthermore, when light with energy exceeding the acceptance limit is incident on the photodiode section, the excess charge photoelectrically converted in the photodiode section flows out of the photodiode section and mixes into the photodiode section of the adjacent pixel. This has the problem of causing a so-called blooming phenomenon, making precise photoelectric conversion impossible. Therefore,
By configuring a P-type impurity diffusion layer 16 on an n-type substrate 15 and configuring a buried layer 17 for increasing junction capacitance in the middle thereof, the saturated charge storage capacity of the photodiode portion is increased.
Although measures have been taken to suppress the blooming phenomenon, the number of steps involved in configuring the diffusion layer is large, and variations in photodiode characteristics are likely to occur due to variations in impurity diffusion within the substrate. In addition, even if a photodiode is configured with such a complex structure, there is still charge transfer between photodiodes that occurs through the substrate, and α that has entered the substrate.
It has not been possible to eliminate the incorporation of charges within the substrate caused by radiation such as wires into the photodiode portion or field effect transistor. Furthermore, since the silicon substrate is opaque, the direction of incidence of the incident light beam onto the photodiode portion is limited to only one surface of the substrate. Furthermore, since the phototiode section and the field effect transistor are formed on the same substrate surface, light easily enters the field effect transistor. The generation of current may lead to deterioration of the switching characteristics of the field effect transistor.

Therefore, the solid-state imaging device of the present invention eliminates the blooming phenomenon and the smear phenomenon without configuring multiple impurity layers within the substrate, and allows light to enter from the ambiguous surface of the substrate.
The aim is to suppress the generation of photo-excited current in field-effect transistors without forming a light-shielding layer, and to realize a high-performance solid-state imaging device that is less susceptible to the effects of radiation.

[Means to solve the problem]

In order to achieve such an object, the solid-state image sensor of the present invention is a solid-state image sensor in which a group of photoelectric elements consisting of a photodiode and a field-effect transistor for driving is arranged. A field-effect transistor for driving is provided having a crystalline silicon layer and a channel portion made of a single-crystalline silicon layer configured with the polycrystalline silicon layer as a seed crystal on the polycrystalline silicon layer, and on the field-effect transistor. an insulating layer, a photodiode made of an amorphous silicon layer on the insulating layer, and one of the electrode parts connected to the channel part of the field effect transistor communicates with the photodiode via a wiring layer. It is characterized by

〔Example〕

Hereinafter, the solid-state imaging device according to the present invention will be described in detail using Examples. FIG. 1 is a sectional view of a main part showing an embodiment of a solid-state image sensor according to the present invention.

In the figure, a polycrystalline silicon layer 2 is provided on a transparent insulating substrate 1 (for example, a quartz glass substrate). When the light incident surface of the polycrystalline silicon layer 2 is set to the opposite surface of the transparent insulating substrate l to the surface on which the polycrystalline silicon layer 2 is provided,
It functions as a light shielding layer to prevent light from entering the field effect transistor, and also functions as a seed crystal during the formation of the single crystal silicon layer 3 that constitutes the main body of the field effect transistor. have. On the polycrystalline silicon layer 2, a source electrode section 4 and a train electrode section 5 are formed by a semiconductor layer consisting of a single crystal silicon layer 3 and impurity diffusion. Furthermore, a gate insulating film 6 made of silicon dioxide and a gate electrode 7 are provided to constitute a field effect transistor. This field effect transistor is of a completely isolated type, with its sides and upper part surrounded by an insulating layer 8 (for example, silicon dioxide or silicon nitride), and its lower part surrounded by a transparent insulating substrate l with a polycrystalline silicon layer 2. Therefore, a phenomenon in which charges within the substrate invade into the field effect transistor due to radiation or optical excitation, which occurs in a field effect transistor fabricated within a conductive silicon substrate, does not occur. Therefore, in particular, the amount of photoexcitation current generated is small, and the field effect transistor of the present invention can suppress the photoexcitation current to a level lower than that of a field effect transistor formed in a silicon substrate. A photodiode 10 made of an amorphous silicon layer is provided on the field effect transistor with an insulating layer 8 in between. The photodiode 10 made of amorphous silicon is of the so-called pin-planted layer type, so the order of the layers differs depending on which main surface of the transparent insulating substrate l is set as the light incident surface. Therefore, the pine layer and the nlpu layer can be used as partners. Furthermore, the photodiode 10 made of an amorphous silicon layer plays the role of photoelectric conversion, and when the light incident surface is set on the layered surface of the photodiode 10 and the field effect transistor made of a transparent insulating substrate, It also has the role of blocking light that enters the field effect transistor. As mentioned above, when the light is on the incident surface or the surface opposite to the stacked surface of the solid-state image sensor, the polycrystalline silicon layer 2 serving as a seed crystal becomes a light shielding layer, and the light incident surface is set on the stacked surface side. When this happens, the photodiode 10 made of an amorphous silicon layer, which becomes a photoelectric conversion section, becomes a light shielding layer. Therefore, even if the light incident surface is set on either main surface of the transparent insulating substrate l, it can be realized using a light shielding layer or basic components, and a field effect transistor based on light incidence can be realized even without creating a light shielding layer. It is possible to suppress the deterioration of the characteristics. moreover,
Photodiode 10 is located on insulating layer 8 and is located apart from adjacent photodiodes. Therefore, blooming due to the mixing of excess charges between the photodiodes provided in the conductive silicon substrate does not occur, and abnormal inflow of charges from outside the photodiode IO does not occur. In addition, as shown in Figure 2, the photodiode lO
The optical wavelength dependence of the sensitivity 13 of the amorphous silicon photodiode constituting the photodiode is close to the human visibility 12, and there is no deviation from the human visibility compared to the visibility 14 of the single-crystal silicon photodiode. . For this reason,
In order to match the sensitivity of a photodiode constructed in a silicon substrate to the human visual sensitivity of 12, it is necessary to cut long wavelength light before it enters the photodiode, which requires an infrared cut filter. . However, since the photodiode IO of the present invention is formed from an amorphous silicon layer, it is possible to easily perform photoelectric conversion that matches the human visual sensitivity of 12 without adding an infrared cut filter. Furthermore, since it has a structure in which a single crystal silicon layer 3 is formed using a polycrystalline silicon layer 2 as a seed crystal, unlike a solid-state image sensor that uses a 5-inch or 6-inch silicon substrate, a large-area, inexpensive transparent insulator is used. It is possible to use a solid-state substrate, and a large number of solid-state imaging device groups can be obtained from the substrate at low cost. Moreover, unlike the case of using a silicon substrate, there is no need for a well structure using impurity diffusion. Therefore, variations in device characteristics due to variations in diffusion length can also be suppressed.

(Effects of the Invention) As explained above, the solid-state imaging device according to the present invention has the following effects.

l... Due to the presence of a polycrystalline silicon layer that serves as a seed crystal, it is possible to create a large number of solid-state image sensors on a silicon substrate, which is an inexpensive and large-area transparent insulating substrate, resulting in a low-cost solid-state image sensor. can.

2. By using a transparent insulating substrate, it is possible to set the light incident surface on either of the two main surfaces, thereby increasing the flexibility of the photodiode structure.

3. Since the polycrystalline silicon layer and the photodiode shield light incident on the field effect transistor, there is no need to create a light shielding layer, and characteristic deterioration of the field effect transistor due to photocurrent can be suppressed.

4. A photodiode made of an amorphous silicon layer is separated from adjacent photodiodes, so charges generated in excess of the saturated accumulated charge of the photodiode flow through the conductive layer and are transferred between adjacent photodiodes. No flowing trooming phenomenon occurs. For this reason,
Precise photoelectric conversion is possible.

5. Since the field effect transistor has an element isolation shape surrounded by an insulator, no abnormal charge flows into the field effect transistor from the surroundings. Therefore, accurate operation of the driving field effect transistor is possible.

6. Unlike when using a silicon substrate, there is no need to construct a well by diffusion of impurities, there is no need for precise control of diffusion, there is no need for a diffusion process, and it is possible to suppress variations in device characteristics due to variations in diffusion length. be.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part showing an embodiment of the solid-state image sensor of the present invention, and FIG. 2 shows the relative sensitivity of photodiodes made of amorphous silicon and single crystal silicon and the wavelength dependence of human visual sensitivity. 3 are cross-sectional views showing a conventional solid-state image sensor. l... Transparent insulating substrate 2... Polycrystalline silicon layer 3... Single crystal silicon layer 4... Source electrode portion 5... Train electrode portion 6... Gate insulating film 7... Gate Electrode 8...Insulating layer 9...Arrangement! 1 layer 10...Photodiode 11...Signal wiring 12...Human visibility 13...Sensitivity of amorphous silicon photodiode 14...Sensitivity of single crystal silicon photodiode 15... N-type substrate 16...P-type impurity diffusion layer 17...Buried layer 18...Element isolation oxide film 19...Interlayer insulating film or above 1 Mother ¥ 21 Genka 3 1i

Claims (1)

[Claims] In a solid-state image sensor in which a photoelectric conversion element group consisting of a photodiode and a driving field-effect transistor is arranged,
A driving device having a polycrystalline silicon layer on a part of the surface of a transparent insulating substrate, and having a channel portion made of a single crystal silicon layer formed on the polycrystalline silicon layer using the polycrystalline silicon layer as a seed crystal. A field effect transistor is provided, an insulating layer is provided on the field effect transistor, a photodiode made of an amorphous silicon layer is provided on the insulating layer, and an electrode portion is connected to the photodiode and a channel portion of the field effect transistor. One is a solid-state image sensor that is characterized by being connected via a wiring layer.