JPH0613387A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To provide a solid-state image sensing device having excellent gettering efficiency, short annealing time, and less gettering dispersion. CONSTITUTION:Polysilicon 15 is grown on isolation parts of a photoelectric transfer element to form a getting means on the surface of an n-type silicon substrate 11. Since the gettering of heavy metals captured in defects 14 existing on the surface of the n-type silicon substrate 11 and in the vicinity of the surface, is performed on the surface of the n-type silicon substrate 11, it becomes possible to perform the gettering surely and increase the gettering efficiency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid-state image pickup device.

[0002]

2. Description of the Related Art FIG. 2 is a sectional view showing a conventional solid-state image pickup device.

In FIG. 2, 1 is an n-type silicon substrate, 2
Is a p-type well, and 3 is an n-type region serving as a photoelectric conversion element. Defects 4 are formed on the surface of the n-type silicon substrate 1 and in the vicinity of the surface during ion implantation and growth of a thermal oxide film. Then, when heavy metals (Cu, Fe, Ni, etc.) are introduced during the process, these heavy metals collect at the defects 4 and are electrically activated. As a result, a dark current is locally increased, and when this solid-state imaging device is used for display, white spots or white scratches are generated in the image.

According to the conventional technique, defects of a silicon crystal on the surface or near the surface are formed by diffusing phosphorus on the back surface of the n-type silicon substrate 1 to form an n ⁺ region 6 serving as a gettering means of defects and annealing. The heavy metal trapped in the substrate was moved to the back surface gettering means to electrically inactivate the defect in the device active portion.

[0005]

However, in the above conventional structure, in order to move the defect 4 from the front surface or the vicinity of the front surface to the back surface, the n-type silicon substrate 1 having a thickness of 65 is used.
Since 0 to 700 μm has to be moved, the annealing time becomes long. Therefore, there is a drawback that the gettering tends to vary. Further, heavy metals such as Fe have a defect that the gettering efficiency is poor and cannot be removed sufficiently by the above method.

In view of the above-mentioned drawbacks, it is an object of the present invention to provide a solid-state image pickup device having a good gettering efficiency, a short annealing time, and a small gettering variation.

[0007]

In order to achieve the above object, a solid-state image pickup device of the present invention comprises a semiconductor substrate, a plurality of photodiodes formed on the semiconductor substrate, and the semiconductor between the photodiodes. And a gettering means formed on the substrate.

[0008]

According to this structure, by forming the gettering means on the surface of the semiconductor substrate, the heavy metal trapped by the defects existing on the surface of the semiconductor substrate and in the vicinity of the surface can be surely gettered. You can increase efficiency.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a photoelectric conversion region of a solid-state imaging device according to an embodiment of the present invention. In FIG. 1, 11 is an n-type silicon substrate which is a semiconductor substrate, 12 is a p-type well formed on the surface of the n-type silicon substrate 11, and 13
Is a photodiode that is a photoelectric conversion element unit.
A shaped region, 14 is a defect, 15 and 17 are polysilicon as a gettering means, and 16 is an oxide film.

The oxide film 16 on the surface of the n-type silicon substrate 11 is selectively removed by etching only a part of the isolation region. The oxide film 16 is removed, and the polysilicon 15 is grown at a low temperature on the exposed portion of the surface of the n-type silicon substrate 11. At this time, the oxide film is prevented from entering between the surface of the n-type silicon substrate 11 and the polysilicon 15. Further, at the same time, polysilicon 17 as a gettering means is also formed on the back surface of the n-type silicon substrate 11. n-type silicon substrate 1
(1) Defects near the back surface are taken in by the gettering means on the back surface and do not move in the front surface direction, so that gettering can be performed more reliably.

The operation of the solid-state image pickup device configured as described above will be described below. n-type silicon substrate 1
On the surface 1 and in the vicinity of the surface, defects 14 are generated in the silicon crystal when the photodiode is formed by ion implantation or when the oxide film 16 is grown. Heavy metal ions (Cu, Fe, Ni, etc.) taken in during the solid-state imaging device manufacturing process are concentrated in the defects 14 and become electrically active. By annealing these heavy metal ions, polysilicon 15,
17 and n-type silicon substrate 11 and polysilicon 15,
Focus on the interface with 17.

At this time, the polysilicon 15 on the front surface of the n-type silicon substrate 11 and the polysilicon 1 on the back surface of the silicon substrate 11
Gettering is simultaneously performed at 7. In particular, heavy metals such as Fe are intensively taken into the interface between the polysilicon 15 and the n-type silicon substrate 11. Since the defects of the intermediate layer between the back surface and the back surface of the n-type silicon substrate 11 can be gettered, the gettering effect is more reliable than the conventional one.

Polysilicon layers 15 and 17 are formed on the rear surface of the n-type silicon substrate 11 where the photodiodes are separated. Therefore, the operation of the solid-state imaging device is not adversely affected. As described above, white spots and white spots do not occur even when the display is performed using the solid-state imaging device according to this embodiment.

In the above embodiment, the semiconductor substrate is the n-type silicon substrate, but it is clear that the same effect can be obtained by using the p-type silicon substrate.

[0015]

As described above, according to the present invention, the heavy metal ions on the surface of the semiconductor substrate and in the vicinity of the surface can be caught on the surface by the gettering means formed on the semiconductor substrate. The gettering efficiency can be improved and the annealing time can be shortened as compared with the case of moving.

[Brief description of drawings]

FIG. 1 is a sectional view of a photoelectric conversion region of a solid-state imaging device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a photoelectric conversion region of a conventional solid-state imaging device.

[Explanation of symbols]

 11 n-type silicon substrate 12 p-type well 13 n-type region 14 defect 15 polysilicon 16 oxide film 17 polysilicon

Claims (2)

[Claims] 1. A solid-state imaging device comprising a semiconductor substrate, a plurality of photoelectric conversion element portions formed on the semiconductor substrate, and gettering means formed on the semiconductor substrate between the photoelectric conversion element portions. . 2. The solid-state image pickup device according to claim 1, wherein the gettering means is polysilicon.