JPH04280677A - Laminated type solid-state image pickup device - Google Patents

Abstract

PURPOSE:To prevent false signals from occurring in a laminated type solid-state image pickup device due to the capacitive coupling between pixels by a method wherein a parasitic capacitance between the pixels is eliminated. CONSTITUTION:In a laminated type solid-state image pickup device of structure composed of the pasted substrates 1 and 2, photosensors 3 arranged on the substrate 1 as unit pixels are separately surrounded with conductive materials, and the conductive materials are kept at a certain potential so as to shield the pixels from each other.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state imaging device, and more particularly to a so-called stacked solid-state imaging device having a structure in which substrates are bonded together.

0002

2. Description of the Related Art A solid-state imaging device for HDTV (high-definition television) is required to have a large number of pixels, about 2 million pixels. As a structure to solve the problems associated with this increase in the number of pixels, a semiconductor substrate is formed by two-dimensionally arranging a plurality of photosensor sections in pixel units, and a structure for transferring signal charges generated in the photosensor sections. The present applicant has proposed a stacked solid-state imaging device in Japanese Patent Application No. 2-219985, which has a structure in which a semiconductor substrate having a charge transfer section formed thereon is bonded to the semiconductor substrate.

0003

[Problem to be Solved by the Invention] This stacked solid-state imaging device made by bonding substrates together has a structure in which photocarriers generated by light incident on the photosensor section of a unit pixel are confined within the photosensor section. Therefore, it is necessary to isolate pixels using trenches or PN junctions. When this isolation is performed using an insulating film or a floating PN junction, charge coupling occurs between pixels due to parasitic capacitance. There is a problem in that capacitive coupling due to parasitic capacitance causes charges to be induced even in the photosensor portion of the pixel to which no light is incident, resulting in generation of false signals.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a stacked solid-state imaging device that eliminates the parasitic capacitance between pixels and prevents the generation of false signals due to capacitive coupling due to the parasitic capacitance.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides that a plurality of photosensor sections in each pixel are
A laminated type having a structure in which a first semiconductor substrate formed in a dimensional arrangement and a second semiconductor substrate formed with a charge transfer section for transferring signal charges generated in a photosensor section are bonded together. A solid-state imaging device employs a configuration in which each of a plurality of photosensor sections is surrounded by a conductive material and the conductive material is maintained at a constant potential.

[0006]

[Operation] In the stacked solid-state imaging device according to the present invention, each of the plurality of photosensor sections arranged in pixel units is surrounded by a conductive material, and by keeping this conductive material at a constant potential, each pixel You can shield between. Thereby, parasitic capacitance between pixels can be eliminated. As a result, since there is no capacitive coupling due to parasitic capacitance between pixels, generation of false signals (color mixing) due to capacitive coupling between pixels can be prevented.

[0007]

Embodiments Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The stacked solid-state imaging device according to the present invention is shown in FIG.
As shown in the cross-sectional structure diagram, two silicon substrates 1 and 2
The photo sensor section 3 is arranged on one silicon substrate 1, and the charge transfer section 4 is arranged on the other silicon substrate 2. The silicon substrate 1 is a single-crystal semiconductor substrate, and a plurality of photosensor sections 3 in pixel units are arranged horizontally and vertically on this silicon substrate 1.
It is formed by dimensional arrangement. The photosensor section 3 is
It has a photodiode configuration consisting of a P+ type region 5 on the front side and an N type region 6 disposed below it, and generates and accumulates signal charges according to incident light. A silicon oxide film 7 is formed between the photosensor parts 3 so as to surround each photosensor part 3 to separate each pixel, and a shielding material 8 made of a conductive material such as aluminum is embedded. The pixels are shielded by being held at a constant potential V. The shield material 8 is
A light shielding film 10 made of aluminum that blocks light between each pixel
is formed integrally with. As shown in FIG. 2, the light shielding film 1
The plane pattern of 0 is in the form of a lattice, and each photosensor section 3 is located at the mesh portion of the lattice. A protective film 9 is formed on the surface side of the light shielding film 10 and the photosensor section 3.

The silicon substrate 2 is also a single-crystal semiconductor substrate like the silicon substrate 1, and this silicon substrate 2 contains carbon.
CD (Charge Coupled Device)
A charge transfer section 4 of the structure is formed. That is, a P-type well region 12 is formed on an N-type substrate 11, an N- type region 13 that functions as a buried channel is formed on the surface of this well region 12, and each vertical column is formed on the main surface of the substrate. A channel stop 14 is formed to separate the . On the N- type region 13, 2
Layer transfer electrodes 15a, 15b are formed. By applying, for example, four-phase drive pulses to the transfer electrodes 15a and 15b, signal charges are transferred in a direction perpendicular to the cross section in FIG. Transfer electrodes 15a and 15b are covered with an insulating film 16. A contact hole 17 is formed so as to penetrate this insulating film 16, and an N+ type region 18 for charge supply is formed at the bottom of this contact hole 17. This N+ type region 18 is provided at a position separated from the N- type region 13. And areas 18 and 13
Due to the potential of the transfer electrode 15a extending over the region between
Both regions 18 and 13 are electrically connected. Contact hole 17 is filled with polysilicon containing N-type impurities, and polysilicon layer 19 extends to above insulating film 16 . The silicon substrate 1 on which the photosensor parts 3 are arranged in a matrix is attached to the surface 19a of the polysilicon layer 19, and the two silicon substrates 1 and 2 are eventually bonded together by this polysilicon layer 19. There is.

In such a CCD solid-state imaging device, when the light receiving surface (imaging surface) is irradiated with light, first, signal charges are generated in each photosensor section 3 of the silicon substrate 1 in accordance with the incident light. The generated signal charges are sent to the N+ type region 18 of the silicon substrate 2 via the polysilicon layer 19. For example, when driving the transfer electrodes 15a and 15b at three levels, when the potential of the transfer electrode 15a is highest, N
By forming a channel between + type region 18 and N- type region 13, signal charges in N+ type region 18 can be transferred to N- type region 13, which is a buried channel layer. Then, by applying, for example, four-phase drive pulses to the transfer electrodes 15a and 15b, the signal charges in the N- type region 13 are transferred in the vertical direction (direction perpendicular to the cross section in FIG. 1), and then in the horizontal direction. It will be transferred and finally read.

Further, in the CCD solid-state imaging device having the above structure, each of the plurality of photosensor sections 3 arranged in a matrix on a pixel basis is surrounded by a shield material 8,
By keeping this shielding material 8 at a constant potential V, for example, at the ground level, each pixel can be shielded, so that parasitic capacitance between pixels can be eliminated. Thereby, since there is no capacitive coupling between pixels due to parasitic capacitance, generation of false signals (color mixture) due to capacitive coupling between pixels can be prevented.

In the above embodiment, aluminum is used as the material of the shield material 8, and the shield material 8 is formed integrally with the light shielding film 10 that blocks light between each pixel. In addition to aluminum, doped-Polysilicon is also used as a material.
It is also possible to use conductive materials such as
Further, as shown in FIG. 3, a shield material 8 made of polysilicon, for example, may be formed separately from the light shielding film 10.

0012

[Effects of the Invention] As explained above, according to the present invention,
In a stacked solid-state imaging device with a structure in which substrates are bonded together, each of the multiple photosensor parts is surrounded by a conductive material (shielding material), and this conductive material is kept at a constant potential. Since the parasitic capacitance is eliminated, it is possible to prevent the generation of false signals due to capacitive coupling due to parasitic capacitance between pixels.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional structural diagram showing an embodiment of a stacked solid-state imaging device according to the present invention.

FIG. 2 is a plan view of the structure of FIG. 1;

FIG. 3 is a cross-sectional structural diagram of main parts showing another embodiment of the present invention.

[Explanation of symbols]

1, 2 Silicon substrate 3 Photo sensor section 4 Charge transfer section 8 Shield material 10 Light shielding film 14 Channel stop 15a, 15b Transfer electrode 17 Contact hole

Claims (1)

[Claims] 1. A first semiconductor substrate formed by two-dimensionally arranging a plurality of photo sensor sections in pixel units;
In a stacked solid-state imaging device having a structure in which a second semiconductor substrate is bonded to a second semiconductor substrate on which a charge transfer section for transferring signal charges generated in the photosensor section is formed, each of the plurality of photosensor sections is bonded together. A stacked solid-state imaging device characterized by being surrounded by a conductive material and maintaining the conductive material at a constant potential.