JPH05110053A - Solid-state imaging device and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a method of manufacturing a solid-state imaging device where white spots or white damage is prevented from being generated and a annealing time cart be lessened by enhancing gettering. CONSTITUTION:A photoelectric conversion element composed of an n-type impurity region 3 and a transfer section are formed on a P-type well 2 formed on an N-type silicon substrate 1, and a high concentration P-type impurity region 5 serving as a trapping center which traps heavy metal is formed on an isolating region which isolates the photoelectric conversion elements 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 image pickup device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A conventional solid-state image pickup device will be described below. FIG. 2 is a sectional view of a main part of a conventional solid-state imaging device.
In FIG. 2, reference numeral 21 is an n-type silicon substrate, 22 is a p-type well, 23 is an n-type impurity region constituting a photoelectric conversion element portion, 24 is a crystal defect, and 25 is a capture center (hereinafter referred to as a gettering site) for capturing a heavy metal. This is an n-type impurity region.

In the conventional solid-state imaging device configured as described above, crystal defects 24 are generated on the surface of the n-type silicon substrate 21 and in the vicinity of the surface during the ion implantation step and the thermal oxide film forming step. Heavy metals (Cu, Fe, Ni, etc.) that are mixed in during the process are gathered in the crystal defects 24 and become electrically active, resulting in a local increase in dark current, resulting in white spots or white scratches on the screen. Cause. To prevent this, n
Phosphorus is diffused on the back surface of the n-type silicon substrate 1 to form the n-type impurity region 25, and then annealing is performed to remove the heavy metal trapped by the crystal defects 24 on the surface of the n-type silicon substrate 1 and near the surface from the gettering site. To the n-type impurity region 25, which electrically inactivates crystal defects in the device region formed on the surface of the n-type silicon substrate 1.

[0004]

However, in the above conventional structure, since the heavy metal has to be moved from the front surface of the silicon substrate to the gettering site on the back surface (about 650 to 700 μm), the annealing time becomes long and
There is a problem that variations in gettering occur.

The present invention solves the above-mentioned conventional problems, and provides a solid-state imaging device that does not cause white spots or white scratches on the screen, and a method of manufacturing a solid-state imaging device that enhances gettering and reduces the annealing time. The purpose is to provide.

[0006]

In order to achieve this object, a solid-state image pickup device according to the present invention has a photoelectric conversion element portion in which an isolation region is ion-implanted with the same impurity as the isolation region at a high concentration or silicon. It has a structure in which a heavy metal trap center is formed by ion implantation.

[0007]

With this structure, the heavy metal captured by the crystal defects existing on the surface of the silicon substrate and in the vicinity of the surface can be gettered on the surface of the silicon substrate.

[0008]

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 main part of a solid-state imaging device according to an embodiment of the present invention. In FIG. 1, 1 is n
Silicon substrate, 2 is a p-type well, 3 is an n-type impurity region that constitutes a photoelectric conversion element portion, 4 is a crystal defect, and 5 is a high-concentration p-type impurity region that serves as a trap center.

The high-concentration p-type impurity region 5 is formed in a separation region for separating the photoelectric conversion element portion, that is, a region which is not related to the operation of the solid-state image pickup device. The high-concentration p-type impurity region 5 captures and inactivates the heavy metal mixed in during the manufacturing process to reduce white spots and white scratches on the screen.

In such a solid-state image pickup device, a p-type well 2 is formed on an n-type silicon substrate 1, and an n-type impurity region 3 forming a photoelectric conversion element portion and a transfer for transferring a signal charge are formed in the p-type well 2. After forming a portion (not shown) and the like, for example, boron is implanted as impurity ions to form a high-concentration p-type impurity region 5, and is annealed. The same effect can be obtained by forming a trap center by implanting electrically inactive ions such as silicon into the silicon substrate instead of boron.

In this embodiment, the n-type silicon substrate is used as an example. However, even if a p-type silicon substrate is used, impurities of the same conductivity type as the isolation region are ion-implanted or silicon is ion-implanted. The same effect can be obtained.

[0012]

As described above, according to the present invention, an impurity of the same conductivity type is ion-implanted into the isolation region at a high concentration or silicon is ion-implanted to form a heavy metal trap center on the surface of the semiconductor substrate. To enhance gettering,
It is possible to realize an excellent solid-state imaging device that can reduce the annealing time and reduce white spots and white scratches on the screen, and a manufacturing method thereof.

[Brief description of drawings]

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

FIG. 2 is a sectional view of a main part of a conventional solid-state imaging device.

[Explanation of symbols]

 2 P-type well (semiconductor substrate) 5 High-concentration p-type impurity region (trap center)

Claims (7)

[Claims] 1. A photoelectric conversion element section on a surface of a semiconductor substrate, and a transfer section for transferring signal charges converted by the photoelectric conversion element section, wherein a heavy metal is captured in a separation region for separating the photoelectric conversion element section. A solid-state imaging device provided with a capture center. 2. The solid-state imaging device according to claim 1, wherein the trap center is formed of an impurity region of the same conductivity type which is formed on the surface of the isolation region and has an impurity concentration higher than that of the isolation region. 3. The solid-state imaging device according to claim 1, wherein the trap center is formed by ion implantation with a high dose amount. 4. The solid-state imaging device according to claim 1, wherein the trap center is formed by ion-implanting silicon. 5. A step of forming an isolation region, a photoelectric conversion element portion, a transfer portion for transferring signal charges converted by the photoelectric conversion element portion on a surface of a semiconductor substrate, and a step of implanting impurities into the isolation region. A method of manufacturing a solid-state imaging device, comprising: 6. The impurity ion-implanted into the isolation region is
6. The method for manufacturing a solid-state imaging device according to claim 5, wherein the impurity has the same conductivity type as that of the isolation region and has a high dose. 7. The method for manufacturing a solid-state imaging device according to claim 5, wherein the impurity ion-implanted into the isolation region is silicon.