JPS63254764A - Solid-state image sensing device - Google Patents

Abstract

PURPOSE:To decrease dark current, to decrease defects in images and to suppress the occurrence of cross talk and smear, by forming a crystal defect layer in a region other than a photodiode part from the surface of a wafer at a depth, where optical carriers are formed from the surface. CONSTITUTION:One cell of this device comprises the following parts: a photodiode part 2, which is formed by implanting, e.g., n<+> type impurities in the surface of a p-type semiconductor 1; a charge transfer part 3, which is formed by implanting n<-> type impurities; and a transfer gate 4, which is formed between the photodiode part 2 and the charge transfer part 3 and performs the field shift of charge. The element is isolated from neighboring cells with channel stopper regions 5, which are formed by implanting p<+> impurities. Crystal defects are formed in a part of each p<+> type channel stopper region 5 in each element isolating region other than the photodiode part in the device, which is formed in this way before or after the formation of said region. Therefore, optical carriers, which are generated in the deep part of the photodiode part and cause cross talk and smear, are trapped and decreased by said defect layer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a solid-state imaging device that simultaneously reduces dark current and reduces crosstalk and smear.

(Prior Art) Intrinsic gettering method (IG method), extrinsic gettering method (EC method), shrimp wafer use, etc. have been used as methods for reducing dark current found in solid-state imaging devices.

In the IG method, micro defects are formed on the negative side in the bulk of the Si substrate, and the contaminants are absorbed and removed by the micro defects, and in the EC method, micro defects are formed on the back surface of the Si substrate (highly concentrated crystals). Contaminants are removed from the outside of the substrate by forming defects, distortions, etc.

(Problems to be Solved by the Invention) However, in any of the conventional gettering methods described above, it is difficult to reduce the dark current that occurs due to the contamination of contaminants or crystal defects that occur during the manufacturing process. However, it was not possible to reduce crosstalk and smear at the same time. Therefore, in conventional methods, it is necessary to take other measures to reduce crosstalk and smear, such as structurally suppressing the diffusion of carriers generated deep in the photodiode, or reducing smear components during the horizontal blanking period. An external circuit for discharging was required.

An object of the present invention is to provide a solid-state imaging device in which image defects are reduced by reducing dark current by applying the EG method, and crosstalk and smear are also reduced.

(Means for Solving the Problems) That is, the above-mentioned object of the present invention is to provide a solid-state imaging device in which a plurality of photodiode sections are formed on a semiconductor substrate, in which an extrinsic gate is formed in an area other than the photodiode section. A region that absorbs contaminants is formed by the ring method at a depth where photocarriers are generated from the substrate surface, and a strain is provided at the interface of the defective region to trap photocarriers. This is achieved using a solid-state imaging device.

In the present invention, a groove is formed in a part of the silicon region that forms the channel stopper region from the surface to a depth where photocarriers are generated, and a material that directly contacts the silicon and causes distortion, such as polysilicon, is placed in the groove. By embedding, the strain at the silicon-polysilicon interface becomes a defective region and gettered in a subsequent thermal process. Furthermore, the strain caused by the thin defect layer generated around the groove acts as a carrier trap that causes crosstalk and smear.

(Example) Hereinafter, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a horizontal cross-sectional view of one cell of a CCD type device according to an embodiment of the present invention.

The device has substantially the same structure as the conventional one. That is, one cell of the device includes, for example, a photodiode section 2 formed by implanting n° type impurities into the surface of a p-type semiconductor substrate 1, and a charge transfer section 3 formed by implanting n-type impurities. , a transfer gate section 4 formed between the photodiode section 2 and the charge transfer section 3 to field shift charges, and the adjacent cell is a channel stopper formed by implanting p-type impurities. The elements are isolated by region 5.

In the present invention, in the device isolation region excluding the photodiode portion of the device formed as described above,
It has a structure in which crystal defects are formed in a part of the channel stopper region before or after the formation of this N region.

The manufacturing process will be explained below.

A groove in the depth direction of the wafer is formed in a portion of the channel stopper region 5 by reactive ion etching (RIE). The depth of the groove is set to correspond to the depth at which optical carriers are generated from the wafer surface. After forming the trench, polysilicon is deposited and buried in the trench by CVD.

The interface between silicon and polysilicon thus formed acts as a defect region 6 during a subsequent heat treatment process, for example, an oxidation process, and absorbs contaminants mixed in from the outside. Moreover, this strain at the interface between silicon and polysilicon leaves a defective layer 7 around the interface even after the manufacturing process is completed. Therefore, optical carriers that cause crosstalk and smear generated deep in the photodiode portion are trapped and reduced by the defect layer.

Although the above embodiments have been described with respect to CCD type devices, it is clear that the present invention can also be applied to MO3 type devices. Furthermore, as shown in FIG. 2, the device can be similarly applied to a device in which element isolation is formed by a field oxide film 8 provided by a thick oxide film and a p9 ion implantation region 5 under this oxide film. . Furthermore, the present invention configures the photodiode section 2 in a p-type diffusion region (p-well) formed on the surface of an n-type substrate, as shown in FIG. The present invention can also be applied to a device having a vertical overflow drain structure in which the p-well is completely depleted to absorb excess charge by using a reverse bias voltage of , and a defect region 6 can be provided in the pixel isolation region. Particularly in such a device, blooming can be suppressed, making it a desirable device.

(Effects of the Invention) As described above, according to the solid-state imaging device of the present invention,
By forming a crystal defect layer from the wafer surface to a depth where photocarriers are generated from the surface in areas other than the photodiode area, dark current can be reduced and image defects can also be reduced.
Moreover, the occurrence of crosstalk and smear can be suppressed at the same time.

[Brief explanation of drawings]

FIG. 1 is a horizontal sectional view of a solid-state imaging device according to one embodiment of the present invention, and FIGS. 2 and 3 are horizontal sectional views of solid-state imaging devices according to other embodiments. 1... Semiconductor substrate, 2... Photodiode section,
3...Charge transfer part, 4...Transfer gate, end...Channel stopper, 6...Defect region, 7...Defect layer, 8...Field oxide film box 1
Figure 2

Claims (1)

[Claims] In a solid-state imaging device in which multiple photodiode sections are formed on a semiconductor substrate, a region other than the photodiode section that absorbs contaminants using the extrinsic gettering method has a depth at which photocarriers are generated from the substrate surface. What is claimed is: 1. A solid-state imaging device characterized in that the interface of the defective region is provided with a strain that traps optical carriers.