JPH0362967A - Solid image-pickup device - Google Patents

Abstract

PURPOSE:To obtain an improved picture image by forming so that the lower surface of a photoelectric conversion film is flat and by restricting generation of picture image defect such as white stripe or picture image spot. CONSTITUTION:A picture electrode is formed by being embedded into a surface flattening film 8, thus flattening the ground where a photoconductive film 10 is subjected to lamination-formation as well as the bottom surface of the photoconductive film 10. Namely, when the photoconductive film 10 is subjected to lamination-formation, the bottom surface of the photoconductive film 10 is flattened, thus enabling the film quality of the photoconductive film 10 to be uniform over the entire surface and achieving a desired withstand voltage. As a result, it is possible to prevent white stripe due to faulty withstand voltage from being generated. Further, since the upper surface of the photoconductive film 10 is flattened, a transparent electrode film 11 which is lamination-formed on the photoconductive film 10 is subjected to lamination-forming flatly, thus preventing the transparent electrode film 11 from being cut off. As a result, electric field is uniformly applied to the photoconductive film 10, thus preventing picture image spot due to nonuniformity in electric field from occurring.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Field of Application) The present invention relates to a solid-state imaging device in which a photoelectric conversion section is stacked on a signal charge transfer section formed on a semiconductor substrate, and particularly relates to a solid-state imaging device in which a photoelectric conversion section is stacked on a signal charge transfer section formed on a semiconductor substrate. This invention relates to a solid-state VRI imager with an improved electrode structure.

(Prior art) A photoconductor comprising a signal charge transfer section consisting of an accumulation section for accumulating signal charges and a readout section for reading out the accumulated signal charges, and a photoconductive film laminated on the signal charge transfer section. As a conductive film stack type solid-state imaging device, there is one having a structure as shown in FIG. 4, for example.

Figure 4 shows Photoconductivity II! 4m is a diagram showing a cross-sectional structure of a pixel portion in a skin-shaped solid-state imaging device.

In FIG. 4, an n" type storage diode 2 that stores signal charges generated in response to incident light is formed on a P type silicon substrate 1, and an M product diode is formed adjacent to this storage diode 2. A vertical CCD 3 consisting of an n-type buried channel COD is formed for reading out the signal charges which are divided into two.

On this vertical CG[) 3, a transfer gate electrode 4 that controls the transfer of signal charges accumulated in the storage diode 2 to the vertical CCD 3 is insulated from the surroundings by an insulating film 5 made of an oxide film or the like. Made of polysilicon. Also,
A P+ type channel stop region 6 is formed in the silicon substrate 1 to isolate pixels to be separated.

An extraction electrode 7 made of, for example, AI or MoSi is formed on the storage diode 2 from its upper part to the upper part of the gate electrode 4 . In order to flatten the surface of such a structure, a surface flattening film 8 made of an insulating film such as a BPSG (boron phosphorus silicate glass) film is formed on the silicon substrate 1. A pixel electrode 9 made of /l, Ti, etc. is formed on this surface flattened IUI film 8 and is electrically connected to the extraction electrode 7 through a contact hole formed in the surface flattened film 8. .

As described above, the photoconductive film 10 made of amorphous material 31 or the like is formed on the signal charge storage section formed on the silicon substrate 1 by glow discharge or photo-CVD. On this photoconductive film 10, a transparent Ti electrode film 11 for applying a voltage to the photoconductive film 10 is laminated with ITO (indium tin oxide film) or the like.

In such a structure, the pixel electrode 9 is connected to the extraction electrode 7.
A photoconductive film 10 is formed on the surface planarizing film 8 with a predetermined width through a contact hole formed in the surface planarizing film 8, and a photoconductive film 10 is laminated thereon. Therefore, there is a step 12 at the peripheral end of the pixel electrode 9 and a step 12 at the photoconductive film 10.
occurs. Further, since the pixel electrode 9 is buried in the contact ball formed in the surface flattening film 8, unevenness 13 is generated on the surface of the pixel electrode above the contact hole.

As a result, when the photoconductive film 10 is laminated on the pixel electrode 9 and the surface flattening film 8, the film quality of the photoconductive film 10 becomes non-uniform in areas where the steps 12 or unevenness occur. For this reason, in areas where the film quality is non-uniform, the withstand voltage deteriorates and erroneous current flows, resulting in the occurrence of white scratches on reproduced images.

In addition, the photoconductive film 1 in the areas where the steps 12 and the unevenness 13 are formed
Even in the transparent electrode film 11 formed in a layered manner as shown in FIG. When a break occurs in the transparent electrode film 11, the m-field applied from the transparent electrode film 11 to the photoconductive film 10 becomes non-uniform, resulting in mottling in the reproduced image.

(Problems to be Solved by the Invention) As described above, in the structure of the conventional light guiding KG stacked solid-state imaging device, the bottom surface of the photoconductive film 10, that is, the photoconductive film 10, the pixel electrode 9 and the surface flattening. Due to the presence of steps and irregularities on the bonding surface with the film 8, the photoconductive film 10 had poor sweat resistance, resulting in image defects such as self-shipping.

Furthermore, the transparent electrode film 11 is prone to breakage, causing image unevenness, which is an obstacle to obtaining good images.

Therefore, the present invention has been made in view of the above, and its purpose is to provide a solid-state imaging device that can obtain good image quality by suppressing the occurrence of image defects such as white scratches and image spots. The goal is to capture and provide information.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, an accumulation part for accumulating (q) signal charges according to the required light, and an accumulation part 811<
In a solid-state imaging device, a photoelectric conversion film electrically connected to the signal charge storage section via an electrode section is laminated on a signal charge storage section including a readout section for reading out signal charges that have been detected. The gist of the present invention is that the photoelectric conversion film is formed so that the lower surface thereof is flat.

(Function) In the above configuration, the present invention provides a photoelectric conversion film and a photoelectric conversion film by flattening the lower surface of the photoelectric conversion 11Q.
Second, the transparent electrode film laminated thereon is prevented from having any steps or irregularities.

(Example> Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a diagram showing a cross-sectional structure of a pixel portion in a solid-state imaging device according to an embodiment of the present invention.

The solid-state imaging device H shown in the same figure is a solid-state 11i1 image device with a photoconductive film hM type in which an interline transfer type COD is used as a charge transfer section and a photoconductive film is laminated on the charge transfer section. The feature of the embodiment shown in FIG. 1 is that, in contrast to the conventional structure shown in FIG. The reason is that the underlying layer to be coated is flattened, and the bottom surface of the photoconductive film 10 is flattened. In FIG. 1, the same reference numerals as in FIG. 4 are the same, and their explanation will be omitted.

Next, an example of a manufacturing method for the structure shown in FIG. ff11 will be described with reference to the process cross section shown in FIG.

First, diffusion layers which will become the storage diode 2 and the vertical CCD 3 are formed in a silicon substrate 1 by a conventional method, and a channel stop region 6 is formed. Further, on the top of the silicon oxide film 1 on which the vertical CCD 3 is formed, an insulator II! made of a silicon oxide film is placed. 5
Then, a gate electrode 4 made of a polycrystalline silicon film insulated from the surroundings is formed.

Furthermore, after forming an extraction electrode 7 on the top of the gate electrode 4 from the surface of the storage diode 2 along the insulating film 5, a surface flattening film 8 is formed to flatten the surface (see FIG. 2(a)). 〉.

Next, a resist material 16 is applied to the entire surface, and the resist material 16 is applied using a ring graphing technique to open the area where the pixel electrode 15 is to be formed and expose the surface flattening film 8. Buttering. Thereafter, using the patterned resist material 16 as a mask, the exposed portion of the surface planarized film 8 is etched and removed to the extent that the lead-out electrode 1Li7 is exposed (FIG. 2(b)).

Next, a conductive material 17 such as AU is applied to the surface flattening film 8.
It is formed in the opening portion which has been removed by etching by vapor deposition or sputtering so as to have approximately the same height as the surface of the surface leveling film 8. At this time, the conductive material 17 is also deposited on the resist material 16 (second
Figure (C)).

Next, the remaining resist material 16 that has become a mask pattern is
By the lift-off method, the conductive material 17 deposited on the top of the resist material 16 is removed by removing the resist material 16.
Remove unnecessary conductive material 17. As a result, the conductive material 5117 is buried only in the etched-removed portion of the surface flattening film 8 so that the surface becomes flat, and the pixel electrode 15 electrically connected to the extraction electrode is formed. Figure 2 (d〉〉).

For example, amorphous S is applied to the entire flattened surface of Qm.
A photoconductive film 10 consisting of photoconductive film 1 is laminated.
A transparent electrode film 11 made of, for example, an ITO sample is laminated on top of the pixel 0, thereby completing the structure of the pixel portion in the solid-state decoy image device as shown in FIG.

In the structure shown in FIG. 1 formed by such a manufacturing method, since the base upon which the photoconductive film 10 is formed is flat, when the photoconductive film 10 is laminated, the structure is The bottom surface of the conductive film 10 becomes flat. As a result, the film quality of the photoconductive pA10 becomes uniform over the entire surface, and a desired breakdown voltage can be obtained.

As a result, it is possible to prevent the occurrence of white scratches that may lead to poor withstand voltage.

Furthermore, since the upper surface of the photoconductive film 10 is also flattened, the transparent electrode film 11 laminated on the photoconductive film 10 is laminated flatly. Thereby, breakage of the transparent electrode film 11 can be prevented. As a result, the electric field is uniformly applied to the photoconductive film 10, and image unevenness caused by non-uniformity of the electric field can be prevented.

For these reasons, reliability can be improved and good image quality can be obtained.

Next, an embodiment of another %Ij manufacturing method for the structure shown in FIG. 1 will be described with reference to the process cross-sectional diagram shown in FIG. 3.

First, as described above, after passing through a method similar to that shown in FIGS. 2(a) and 2(b), the In shown in FIG. The resist material 16 that has been etched is then removed by etching.Then, the surface flattening film 8 is removed by etching, and a film, for example A11, which will become the pixel electrode 15 is deposited on the ft1 opening formed by vapor deposition or sputtering.
A conductive material 17 such as the like is formed over the entire surface so that the opening is sufficiently filled (FIG. 3(a)).

Next, a resist material 18 having approximately the same T-setting ratio as the conductive material 17 formed in the # layer is applied to the entire surface so as to be embedded in the opening (FIG. 3(b)).

Next, the resist material 18 and the conductive material 17 are etched away by RIE until the surface of the surface flattening film 8 that is not opened is exposed. That is, the surface flattening film 8
The resist material 18 is etched by an etch-back method so that the opening formed in the conductive material 17 is completely filled with the conductive material 17 and the surfaces of the conductive material 17 and the surface flattening film 8 are approximately at the same height. The conductive material 17 is removed by etching.

As a result, a structure similar to that shown in FIG. 2(d) is obtained, and the subsequent steps are the same as described above.

Even with such a manufacturing method, it is possible to form a structure of a pixel portion in a solid silver image device that achieves the effects described above.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and the signal charge transfer section may be configured such that, for example, a storage diode is used.
Even if it is formed of an OS type or CP D g', it can be applied.

Further, the insulating film may be a S'13N4 film or a composite film thereof in addition to the silicon oxide film.

In general, the photoconductive film is made of 5b2s3 in addition to amorphous Si.
, Se-As-Te, CdSe, CdZnT
It may be InSb or PbSnTc.

An infrared photoelectric material such as Cd)-IUTe may also be used.

Moreover, it is not limited to a photoconductive conversion film, but may be a photovoltaic film.

Furthermore, the pixel electrode is made of 7i and Mo in addition to Al.

It may be a 1ffi material such as P[, 8u, MO silicide, MoSi, polysilicon film, or a multilayer film thereof.

[Effect of explanation] As explained above, according to the present invention, the lower surface of the charge conversion film is formed to be flat so that there are no steps or unevenness in the photoelectric conversion film, so that the photoelectric conversion It is possible to form a film with uniform film quality and reduce breakdown voltage defects. This makes it possible to suppress the occurrence of image defects such as white spots.

Further, even in the transparent electrode film laminated on the photoelectric conversion film, there are no steps or irregularities, and breakage is prevented. As a result, an electric field is uniformly applied to the photoelectric conversion film, making it possible to prevent image unevenness.

As a result, it is possible to provide a solid silver image device with improved reliability and good image quality.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the main structure of a solid-state imaging device according to an embodiment of the present invention, FIG. 2 is a process cross-sectional view showing a method of manufacturing the device shown in FIG. 1, and FIG. Other than the equipment shown in Figure 1! FIG. 4 is a cross-sectional view showing the construction of a main part of a conventional solid-state imaging circuit. 1...Silicon substrate, 2...Storage diode, 3...Vertical COD. 4... Gate electrode, 5... Insulating film, 6... Channel stop region, 7... Extracting electrode, 8... Surface flattening film, 9... Pixel electrode, 0... Photoconductive film, 1... Transparent electrode film, 2... Step, 3... Irregularities, 5... Pixel electrode, 6.18... Resist material, 7... Conductive material.

Claims (1)

[Claims] An accumulation section that accumulates signal charges obtained in response to incident light;
A solid state in which a photoelectric conversion film electrically connected to the storage section through an electrode section is laminated on a signal charge transfer section that includes a readout section that reads out the signal charges accumulated in the storage section. A solid-state imaging device, characterized in that the photoelectric conversion film is formed so that a lower surface thereof is flat.