JPH0653475A - Fabrication of solid state image sensor - Google Patents

Abstract

PURPOSE:To provide a solid state image sensor, and fabrication thereof, in which potential at a read out part is stabilized even upon progress of micromachining and thereby saturation signal voltage is stabilized to leave no after-image. CONSTITUTION:A charge transfer electrode is formed of double structure of silicide 14 and poly-Si 9 and an n-type diffusion layer (photodiode part) 15 is formed through ion implantation with the charge transfer electrode as a mask thus preventing positional error from occurring between the charge transfer electrode (silicide 14 and poly-Si 9) and the n-type diffusion layer (photodiode part) 15.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photosensitive pixel portion for generating a signal charge according to incident light and a C for sequentially transferring the signal charge.
The present invention relates to a method of manufacturing a solid-state imaging device having a CD (Charge Coupled Device), and more particularly to a method of manufacturing a gate for reading out signal charges from a photosensitive pixel portion and an impurity diffusion layer thereunder.

[0002]

2. Description of the Related Art A solid-state image pickup device mounted on a camera-integrated VTR has been miniaturized year by year, and the cell size of a pixel portion has been reduced. Therefore, a fine processing technique is required for manufacturing the solid-state imaging device. Nevertheless, the characteristics of the solid-state imaging device are required to be equal to or better than those of the conventional one.

FIG. 3 is a sectional view of a conventional solid-state image pickup device. 1 is an n-type semiconductor substrate, 2 is a p-well, 3
Is an n-type diffusion layer (photodiode section), 4 is an n-type diffusion layer (vertical charge transfer section), 5 is a signal charge reading section, and 6 is p
⁺ Type diffusion layer (separation part), 7 is a surface p ⁺ type diffusion layer, 8 is a silicon oxide film, 9 is a polycrystalline silicon charge transfer electrode, 10 is light-shielding aluminum, and 11 is a surface protective film.

Here, x in FIG. 3 indicates the distance between the boundary between the n-type diffusion layer (photodiode section) 3 and the signal reading section 5 and the end of the polycrystalline silicon charge transfer electrode 9. . Further, y represents the width of the signal reading unit.

FIGS. 4A to 4C show a part of a conventional method for manufacturing a solid-state image pickup device. First, as shown in FIG. 4A, the p well 2 is formed on the n-type semiconductor substrate 1.
Is formed, the photoresist 12 is patterned thereon, and phosphorus ions 13 are further implanted. Next, as shown in FIG. 4B, the resist 12 is removed to form the n-type diffusion layer 3 in the p-well 2. Then, as shown in FIG. 4C, the n-type diffusion layer (vertical charge transfer portion) 4
And the p ⁺ type diffusion layer (separation part) 6 are formed, and the silicon oxide film 8 and the polycrystalline silicon charge transfer electrode 9 are patterned.

[0006]

However, when the solid-state imaging device is manufactured by the manufacturing method shown in FIG. 4, the boundary between the n-type diffusion layer (photodiode part) 3 and the signal reading part 5 in FIG. , Polycrystalline silicon charge transfer electrode 9
The maximum distance x from the edge of the pattern is 0.
An error of 4 μm occurs. That is, the width y of the signal readout portion in FIG. 3 is 0.8 μm due to the reduction in cell size.
Although it is necessary to reduce the pixel size to the following, the error of the distance x causes the readout portion potential to fluctuate in reducing the cell size of the pixel portion, and the imaging characteristics, especially the saturation signal voltage and the afterimage It had a great impact and was a major obstacle in promoting miniaturization.

The present invention solves the above problems, and an object of the present invention is to provide a method for manufacturing a solid-state imaging device in which the read-out portion potential is stable, the saturation signal voltage is stable, and there is no afterimage even when microfabrication is advanced. It is what

[0008]

In order to solve the above problems, a method of manufacturing a solid-state image pickup device according to the present invention comprises forming a charge transfer electrode with a two-layer structure of silicide and polycrystalline silicon, and forming the charge transfer electrode The photodiode portion is formed using the mask.

[0009]

With the above structure, the read-out side of the photodiode section is formed by using the charge transfer electrode having the two-layer structure of silicide and polycrystalline silicon as a mask, so that an error occurs in the position between the charge transfer electrode and the photodiode section. It is possible to provide a solid-state imaging device in which the saturation signal voltage is stable and there is no afterimage.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view of a solid-state image pickup device showing an embodiment of the present invention. The same functions as those of the conventional example are designated by the same reference numerals, and the description thereof will be omitted.

As shown in FIG. 2, the charge transfer electrode has a two-layer structure in which silicide 14 is formed on polycrystalline silicon 9. The n-type diffusion layer (photodiode portion) 15 is formed in self-alignment by using the charge transfer electrode having a two-layer structure as a mask.

FIGS. 1A to 1C are schematic sectional views showing the manufacturing process of the solid-state image pickup device. First, as shown in FIG. 1A, a p-well 2 is formed on an n-type semiconductor substrate 1, and an n-type diffusion layer (vertical charge transfer portion) 4 and a p ⁺ -type diffusion layer (separation portion) 6 are formed. , A silicon oxide film 8 is formed.

Next, as shown in FIG. 1 (b), polycrystalline silicon 9 as a charge transfer electrode and silicide 14 are formed, and phosphorus ions 13 are implanted after patterning. Here, the film thickness of the polycrystalline silicon 9 was 100 nm, WSi ₂ was used as the silicide 14, and the film thickness was 2000 nm.

Then, as shown in FIG. 1C, the ion implantation is blocked by the mask of the silicide 14, and the n-type diffusion layer (photodiode portion) 15 is formed by self-alignment. Therefore, the distance x between the boundary between the n-type diffusion layer (photodiode portion) 15 and the signal reading portion 5 and the end portions of the polycrystalline silicon 9 and the silicide 14 is 0 μm.
Therefore, the error as in the past does not occur.

[0015]

As described above, according to the present invention,
By forming one end of the impurity diffusion layer forming the photoelectric conversion element by ion implantation using the charge transfer electrode having a two-layer structure of silicide and polycrystalline silicon as a mask, an error occurs in the position between the charge transfer electrode and the impurity diffusion layer. And the saturation signal voltage becomes stable when the cell size of the pixel portion of the solid-state imaging device is reduced, and there is a great effect in eliminating the afterimage.

[Brief description of drawings]

1A to 1C are cross-sectional views showing a manufacturing process of a solid-state imaging device showing an embodiment of the present invention.

FIG. 2 is a sectional view of the solid-state imaging device.

FIG. 3 is a sectional view of a conventional solid-state imaging device.

4A to 4C are cross-sectional views showing manufacturing steps of a conventional solid-state imaging device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 n-type semiconductor substrate 2 p-well 4 n-type diffusion layer (vertical charge transfer section) 5 signal charge reading section 6 p ⁺ type diffusion layer (separation section) 7 surface p ⁺ type diffusion layer 8 silicon oxide film 9 polycrystalline silicon 14 Silicide 15 n-type diffusion layer (photodiode part)

Claims (1)

[Claims] 1. A plurality of photoelectric conversion elements for generating signal charges according to the amount of incident light, a vertical charge transfer element for transferring the signal charges generated by the photoelectric conversion elements, and the photoelectric conversion element on one conductive semiconductor substrate. A method for manufacturing a solid-state imaging device having a read gate for reading signal charges generated from a conversion element to the vertical charge transfer element, the read gate having a two-layer structure of silicide and polycrystalline silicon, A method for manufacturing a solid-state imaging device, wherein one end of an impurity diffusion layer forming the photoelectric conversion element is formed by ion implantation using the read gate as a mask.