JPS60233851A - Solid-state image sensor - Google Patents

Abstract

PURPOSE:To obtain the titled device of high resolution and high sensitivity by a method wherein a groove narrow and deep is provided by surrounding a photoelectric conversion element, and an isolating region is formed by covering the groove wall with an insulation film and filling with a transparent dielectric, so as to prevent the leakage of light charges. CONSTITUTION:Photoelectric conversion elements 23 and 24 are constructed by superposing P<+> epitaxial layers on an N type Si substrate 21, and then surrounded by the groove 25 narrow and deep. The groove wall is coated with an SiO2 film 26, and the groove is filled with transparent alumina 27 or the like by the CVD method. Then, the whole surface is covered with an SiO2 28. This construction enables the increase in effective photo receiving area of the elements 24 and 25 because of the small width of the groove 25. Besides, a light 29 incident to the isolated region passed through and reaches the substrate 21, thus causing light charges 30 and yielding high sensitivities. The light charges 30 are completely interrupted from lateral migration by an insulation film 26, and do not flow into the adjacent elements. Therefore, crosstalks are well reduced, and image signals of high resolution can be obtained.

Description

[Detailed Description of the Invention] Technical Field The present invention arranges a plurality of photoelectric conversion elements such as photodiodes and phototransistors two-dimensionally on the same chip, and generates photocharge signals corresponding to incident light from these photoelectric conversion elements. The present invention relates to a solid-state image sensor that sequentially extracts image signals to obtain image signals.

Prior Art In the solid-state image sensor having the above-mentioned configuration, photoelectric charges flow from the photoelectric conversion element that receives light into the photoelectric conversion element that does not receive light, and the photoelectric conversion element that does not receive light receives light as well. When such a phenomenon, ie, four-stalk occurs, the resolution decreases, and in severe cases, blooming or smear appears in the reproduced image. Therefore, in solid-state image sensors, in order to reduce such losstalk, isolation regions are usually provided between adjacent photoelectric conversion elements to achieve isolation. Figure 1 shows the structure of a conventional solid-state image sensor. The isolation is performed by forming a high impurity concentration region between the photoelectric conversion elements.

That is, an r-type surface layer 2 is formed on the surface of an N-type substrate l,
By diffusing and forming an N+ type isolation region 8 from the surface of this P+ type layer, PN photodiodes 4 and 5 are formed which are separated from each other by the isolation region. Note that an insulating film 6 is formed on the surface of the surface layer 2 and the isolation region 8. Further, the type 1 diffusion isolation region 8 is formed so as to completely surround the photodiodes 4 and 5 in a plan view.

In a solid-state image sensor having such a configuration, the photocharge 8 generated in the photodiode 5 by the incident light 7 is
The potential barrier created by the isolation region 8 doped with N-type impurities at a high concentration prevents it from flowing into the adjacent photodiode 4.

However, in the conventional solid-state image sensor shown in No. 1, when forming the separation region 8, impurities are thermally diffused from a predetermined position on the surface of the P+ type surface layer 2, not only in the depth direction. It will also spread laterally and in the direction.

Therefore, if it is attempted to form the separation region 8 deeply, the separation region occupies a large proportion of the entire surface of the chip, resulting in a disadvantage that the resolution decreases. Furthermore, since the light incident on the separation region hardly contributes to the photoelectric conversion effect, there is also the drawback that sufficiently high sensitivity cannot be obtained. On the other hand, if an attempt is made to reduce the ratio of the isolation region to the entire surface of the chip, the isolation region will become shallower, resulting in a drawback that the isolation effect will not be sufficiently exhibited. Furthermore, when using a diffusion separation region with a high impurity concentration, the flow of photocharges is blocked only by a potential barrier, so when strong light is incident and a large amount of photocharge is generated, some of the photocharges are adjacent to each other. Problems such as leakage to photoelectric conversion elements have also arisen. If the separation area is further narrowed, the light incident obliquely on the solid-state image sensor will pass through the separation area from the photoelectric conversion element to the adjacent photoelectric conversion element.
will also be incident, resulting in a decrease in resolution.

Such drawbacks cause color mixture, particularly in color solid-state image sensors, resulting in a decrease in color reproducibility.

OBJECTS OF THE INVENTION An object of the present invention is to prevent leakage of photocharges between adjacent photoelectric conversion elements by providing a deep and narrow separation region, thereby reducing crosstalk and improving resolution and sensitivity. The aim is to provide a high quality solid-state image sensor.

Another object of the present invention is to reduce crosstalk between adjacent photoelectric conversion elements by providing a deep, narrow, and light-shielding isolation region, thereby increasing resolution and preventing diagonally incident light from adjacent The object of the present invention is to provide a solid-state image sensor that can particularly prevent color mixture by preventing the light from entering the photoelectric conversion element simultaneously.

Summary of the Invention The solid-state image sensor of the present invention is a solid-state image sensor in which a plurality of photoelectric conversion elements are two-dimensionally arranged on the same chip. It is characterized by having a deep and narrow groove, the walls of the groove being covered with an insulating film, and an isolation region formed by burying a transparent dielectric material inside the groove.

Furthermore, the solid-state image sensor of the present invention is a solid-state image sensor in which a plurality of photoelectric conversion elements are two-dimensionally arranged on the same chip, and a deep and deep groove is dug inward from the surface to surround each photoelectric conversion element. It has a narrow groove, and the walls of this groove are covered with an insulating film, and a light-shielding film is coated on top of this insulating film, and a dielectric material is buried inside the groove, or light-shielding properties can be achieved without covering with a light-shielding film. The device is characterized by providing an isolation region formed by embedding a dielectric material.

The solid-state image sensor of the present invention is a MOS type or COD type image sensor in which the photoconversion element is a photodiode, or a 'JF type image sensor in which the photoelectric conversion element is a phototransistor.
It can be configured as an ET or SIT image sensor.

Embodiment FIG. 2 is a sectional view showing the structure of an embodiment of the solid-state image sensor of the present invention. In this example, photoelectric conversion, the element is P+N
It is constructed using silicon photodiodes. A P+ type silicon surface layer 2 is formed on an N type silicon substrate 21.
2 is epitaxially grown to form P''N silicon photodiodes 28 and 24.A groove 25 having a figure 7 cross section is formed around each photodiode so as to surround it. An insulating film 26 made of silicon oxide or nitride is deposited on the walls of the trench 25, and a dielectric material 27 is filled inside the trench by the GVD method or sputter deposition method. It's crowded.

As the dielectric material 27, transparent dielectric materials such as oxides such as Sin, Ta, O, etc., nitrides such as 5i8N, alumina, and magnesia are used. An insulating film 28 is deposited on the surfaces of the P+ type surface layer 22 and the dielectric 27.

In the embodiment shown in FIG. 2, the isolation region is formed by the groove 25, the insulating film 26 attached to the wall of the groove, and the dielectric material 27 embedded in the groove, but the width of the groove 25 is Because of its narrow size, the effective light-receiving area of each phototransistor 24, 25 becomes large, and the light 29 incident on the separation region also passes through this and reaches the substrate 21, generating a photocharge 80, making it an extremely sensitive solid state. An image sensor is obtained. That is, in this embodiment, the separation region also serves as the light receiving region, so that the photoelectric conversion efficiency is improved and high sensitivity is obtained. On the other hand, photodiode 24.25
The photocharges 80 generated in the groove 25 are prevented from moving in the lateral direction by the insulating film 26 deposited on the walls of the groove 25.
Since the photoelectric charges 80 are formed deeply, it is possible to almost completely prevent the photocharges 80 from flowing into adjacent photodiodes.

Therefore, crosstalk between adjacent photodiodes can be sufficiently reduced, and a high-resolution image signal can be obtained.

In this way, a deep and narrow groove 25 is formed around each photoelectric conversion element so as to surround it, and the walls of this groove are covered with an insulating film z6.
By covering the groove with a transparent dielectric material 27 and forming a separation region, a solid-state image sensor with no crosstalk and high light-receiving sensitivity can be obtained. Such a configuration of the separation region is particularly suitable for application to a high-sensitivity black-and-white solid-state image sensor in which sensitivity is more important than resolution.

FIG. 8 is a sectional view showing another embodiment of the solid-state image sensor of the present invention. In this example as well, a type 1 silicon surface layer 82 is epitaxially grown on the surface of an N type silicon substrate 81 to form a P''N silicon photodiode 88,84. A groove 85 with a 7-shaped cross section is deep and narrow in the opposite direction.
are formed to surround each photodiode 88, 84.

A silicon oxide insulating film 86 is coated on the wall of this groove 85, and a light shielding film 87 is deposited thereon.

This light-shielding film can be formed by depositing a high melting point metal such as NolOr or W or a silicide thereof using a thin film manufacturing method such as an OVD method or a sputter deposition method. Furthermore, a dielectric material 88 having good adhesion to a high melting point metal, such as polysilicon, is buried inside the trench 85 to form an isolation region. An insulating film 89 made of silicon oxide is deposited on the surface of the type 1 surface layer 82 and the isolation region. Although polysilicon is opaque, the transparent dielectrics mentioned above can also be used.

In the solid-state image sensor of this example, since the light shielding film 87 is provided in the separation region, the light 40 incident obliquely on the photodiode 84 is reflected at the interface between the insulating film 86 and the light shielding film 87 and enters the adjacent photodiode 88. Never. If this light shielding film 87 were not present, the light 40 would also be incident on the adjacent photodiode 88 as shown by the broken line, resulting in a decrease in resolution.

Red on the front in a color solid-state image sensor.

In devices with green and blue filters, unless the signal separation between adjacent photoelectric conversion elements is performed more strictly than in black-and-white solid-state image sensors, red will appear.

Color mixture between green and blue will occur. Such color mixture significantly deteriorates image color reproducibility and is a fatal drawback for color solid-state image sensors. In the embodiment shown in FIG. 8, it is possible to effectively prevent the circulation of photocharges between adjacent photoelectric conversion elements by the deep layer separation region, and the provision of the light-shielding film prevents obliquely incident light from occurring. Since the light does not enter adjacent photoelectric conversion elements at the same time, the above-mentioned color mixture can be suppressed and a clear color image can be obtained.

In the embodiment shown in FIG. 8, the dielectric 88 may be transparent or opaque.

The present invention is not limited to the embodiments described above, but can be modified in many ways. For example, in the embodiments described above, a silicon semiconductor chip is used as the chip, but a chip made of a compound semiconductor or an amorphous material may also be used. Further, although the photoelectric conversion element is constructed using a photodiode, it can also be constructed using a phototransistor. Furthermore, in the embodiment of FIG. 8, if an opaque dielectric material is embedded in the groove, it is not necessary to separately provide a light shielding film. Further, in the above-mentioned embodiment, the cross-sectional shape of the groove is V-shaped, but if the groove is deep and narrow, it may be formed into another shape such as U-shape. In this method, deep and narrow grooves were formed to surround adjacent photoelectric conversion elements, the walls of these grooves were covered with an insulating film, and a transparent dielectric material was buried inside the grooves to form an isolation region. Leakage of photocharges between adjacent photoelectric conversion elements is eliminated, crosstalk can be suppressed, and clear images with no pluming or smearing can be obtained, and the narrow width of the separation region makes it possible to reduce pixel dimensions. A high-density, high-resolution solid-state image sensor can be obtained. Furthermore, by making the dielectric transparent, the separation region can also be used as a light-receiving region, which increases the aperture ratio and provides a highly sensitive solid-state image sensor.

Furthermore, if the separation area has a light-shielding property, it can also prevent light from leaking between pixels, so when applied to a color solid-state image sensor, it is useful for red and green.

A clear color image with less color mixing between blue colors can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the configuration of a conventional solid-state image sensor, FIG. 2 is a sectional view showing the configuration of an embodiment of the solid-state image sensor of the present invention, and FIG. 8 is a sectional view of another solid-state image sensor of the present invention. FIG. 2 is a cross-sectional view showing the configuration of an example. 21, 81...Substrate 22.82...Surface layer 28,
24.88.84...Photodiode 25, 85.
...Groove 26.36...Insulating film 27, 88...Dielectric material 87...Light shielding film 28, 89...Insulating film 29.
40...Incoming light 80...Photocharge. Figure 1 Figure 2 Procedures Amendment Document June 10, 1985 Manabu Shiga, Director General of the Patent Office1, Indication of the incident, Patent Application No. 75782 of 1982, Title of the invention, Solid-state image sensor 3, Amendment. Relationship with the case involving the person who filed the patent application (037) Olympus Optical Industry Co., Ltd. 4, Agent 1. “Phototransistor 2” on page 7, line 20 of the specification
4. Correct 254 to "Photodiode 28, 24J." 2. "Photodiode 24°2" on page 8, lines 7-8.
5" is corrected to "Photodiode 28.g4J. Figure 8 of the 8 drawings is corrected as shown in the attached sheet. Figure 3.

Claims (1)

[Claims] L In a solid-state image sensor in which a plurality of photoelectric conversion elements are two-dimensionally arranged on the same chip, a deep and wide trench is dug from the surface to the inside so as to surround each photoelectric conversion element. 1. A solid-state image sensor comprising a narrow groove, the walls of the groove being covered with an insulating film, and an isolation region formed by burying a transparent dielectric material inside the groove. A solid-state image sensor in which a plurality of photoelectric conversion elements are two-dimensionally arranged on the same chip, having a deep and narrow groove dug inward from the surface so as to surround each photoelectric conversion element, The walls of this groove are coated with an insulating film, and then a light-shielding film is coated on top of this insulating film, and a dielectric is buried inside the groove, or a light-shielding dielectric is buried without covering the light-shielding film. A solid-state image sensor characterized by having a separated region.