JPS63136531A - Semiconductor device - Google Patents

Abstract

PURPOSE:To conduct gettering positively by forming a gettering region to the surface of a semiconductor substrate. CONSTITUTION:Gettering regions 2 are shaped so as to be positioned at the predetermined positions of the surface of a semiconductor substrate 1, and a metallic impurity existing in the semiconductor substrate 1 is absorbed in the surface of the substrate 1 in the gettering regions 2, but the metallic impurity diffused and moved 1 in the cross direction in the surface of the substrate 1 is particularly absorbed positively. Such gettering regions 2 are formed in regions except regions functioning as semiconductor devices, active regions 3 and a channel stop region, and the metallic impurity electrically activating crystal defects can be removed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to a semiconductor device used in a solid-state image sensor, etc., and in particular, a getter region for removing metal impurities that cause crystal defects. The present invention relates to a formed semiconductor device.

(Prior Art) Metal impurities such as heavy metals and alkali metals contained in a semiconductor substrate cause crystal defects and become a factor that activates the crystal defects. Therefore, in the manufacture of semiconductor devices, various gettering treatments are performed to remove metal impurities. FIGS. 5, 6, and 7 show cross-sectional views of semiconductor devices on which this gettering process is performed.

The semiconductor device shown in FIG. 5 is one that is subjected to ring gettering, in which an active region 53 is formed in an insulating layer 52 formed on a semiconductor substrate 51, and phosphorus 54 is formed in the insulating layer 52 around this active region 53. is being spread. diffused phosphorus 5
4 changes into phosphorus glass within the insulating layer 52 and absorbs and removes metal impurities such as heavy metals present within the insulating layer 52. Furthermore, semiconductors! ! In order to remove the metal impurities in the temporary 1, phosphorus is similarly diffused from the back surface of the substrate 1 to be absorbed and removed. However, in this semiconductor device, since the phosphorus diffusion process is incorporated into the process of forming the semiconductor element, there is a problem that phosphorus is diffused into the active region 53 and the withstand voltage of the insulating layer 52 is deteriorated due to the phosphorus diffusion. .

The semiconductor device shown in FIG. 6 is subjected to intrinsic gettering, in which a crystal defect layer 56 is formed inside a semiconductor substrate 51, and metal impurities 55 are absorbed by this crystal defect layer 56. There is. However, in this semiconductor device, since crystal defects 56 are formed inside the semiconductor substrate 51, the getter ability for metal impurities that diffuse laterally on the surface of the semiconductor substrate 51 is small.
There was a problem that reliable gettering was not possible.

Moreover, resistance to thermal stress is also deteriorated.

The semiconductor device in FIG. 7 has been subjected to backside gettering. Backside gettering involves generating mechanical strain on the backside of the semiconductor substrate 51 or by implanting ions into the backside to form a damaged layer 57. This allows the damaged layer 57 to absorb the metal impurity 55. However, even in this semiconductor device, the getter ability for metal impurities that diffuses laterally on the surface of the semiconductor substrate 51 is small, and in particular, the damaged layer 57 is formed on the back surface, so that the semiconductor device shown in FIGS. The problem was that the getter ability was small compared to .

(Problems to be Solved by the Invention) As described above, in the conventional semiconductor device, it is difficult to form a getter region, and in particular, the gettering ability of metal impurities that diffuses laterally into the substrate surface is low.

The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a semiconductor device that can perform reliable gettering.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, a semiconductor device according to the present invention is characterized in that a getter region is formed on the surface of a semiconductor substrate.

(Function) Since the present invention is configured as described above, the getter region of the semiconductor device according to the present invention absorbs metal impurities in the semiconductor substrate. In particular, it has a high getter ability for metal impurities that diffuse laterally on the substrate surface. Further, the getter region relieves thermal stress at the surface portion of the substrate during the numerous heating steps performed during the semiconductor device manufacturing process.

(Examples) The present invention will be specifically described below with reference to illustrative examples.

FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention. Active regions 3 are formed at predetermined locations on the surface of a semiconductor substrate 1 constituting a semiconductor wafer or the like. This active region 3 is formed by a well-known semiconductor manufacturing process. Furthermore, channel stop regions (not shown) are formed at appropriate locations.

In this embodiment, a getter region 2 that absorbs metal impurities is formed on the surface of such a semiconductor substrate 1.

The getter region 2 is formed to be located at a predetermined location on the surface of the semiconductor substrate 1, and thereby absorbs metal impurities present in the semiconductor substrate 1 on the surface of the substrate 1.
It is designed to reliably absorb metal impurities that diffuse and move laterally on the surface.

The getter region 2 is formed in a region that functions as a semiconductor device, that is, in a region other than the active region 3 and the channel stop region, and can remove metal impurities that electrically activate crystal defects. Further, the getter region 2 is formed by a method described later, but this region 2
Since the region includes defects in its crystal structure, the crystal lattice is likely to change, and thermal stress generated in the semiconductor substrate 1 is selectively concentrated in the getter region 2 . Moreover, since the getter region 2 is formed on the surface of the semiconductor substrate 1 where the active 11'i region 3 is formed, the thermal stress applied to the active region 3 etc. is relaxed in the getter region 2, and the thermal stress causes the active region will no longer be destroyed. In this case, the getter region 2 can be formed for each semiconductor chip, thereby making it possible to alleviate local thermal stress within the semiconductor substrate 1.

Next, a method for manufacturing the above semiconductor device will be explained.

2 to 4 are cross-sectional views showing the manufacturing method, respectively. The method shown in FIG.
)). Next, the semiconductor substrate 1 is etched by a photo-etching process to expose the semiconductor substrate 1 other than the portion where the active region is to be formed (FIG. 2(b)). As a result, the active region portion is masked by the oxide film layer 4, and in this state, phosphorus can be diffused to selectively form a getter region 4 with a high phosphorus concentration on the exposed surface of the semiconductor substrate 1.

The method shown in FIG. 3 is similar to the method shown in FIG.
On the top surface of the oxide film layer 4 with a thickness of about A, an additional layer with a thickness of 4000 A
A getter region 2 is formed by forming polysilicon layers, patterning and etching these layers, and further performing phosphorus diffusion.

The method shown in FIG. 4 utilizes the semiconductor substrate 1 obtained by the method shown in FIG. 3 before phosphorus diffusion.

In this method, a resist film 6 is formed on a polysilicon layer 5 (FIG. 2(a)), then a portion where a getter region is to be formed is patterned and photoetched, and then a polysilicon layer 5 is etched by chemical etching, reactive ion etching, etc. The silicon film 5 and the oxide film layer 4 are etched to expose a portion of the semiconductor substrate where the getter region is to be formed (FIG. 4(b)). After this exposure, etching is continued to expose the exposed portion to etching, and if necessary, ions are implanted into the exposed portion. This changes the crystalline state of the exposed portion, but in the subsequent oxidation step, the exposed portion is selectively distorted and the OSF
(Oxidizatlon 1nduced Sta.
ckingFault) occurs, and a damaged region 7 is formed.

This OSF is generated by excess silicon during oxidation. This damaged region 7 can absorb metal impurities and functions as a getter region.

〔Effect of the invention〕

As described above, according to the present invention, since a getter region that absorbs metal impurities is formed on the surface of the semiconductor substrate, the gettering ability of the metal impurities that diffuses laterally on the semiconductor substrate surface is increased, and crystal defects can be suppressed. can. Furthermore, thermal stress generated in the semiconductor device manufacturing process is alleviated in the semiconductor substrate, and crystal defects can be prevented from occurring.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a semiconductor device according to an embodiment of the present invention;
FIG. 2 is a cross-sectional view of the manufacturing process of the same semiconductor device, FIG. 3 is a cross-sectional view of another manufacturing process of the same semiconductor device, FIG. 4 is a cross-sectional view of yet another manufacturing process of the same semiconductor device, and FIG. , FIG. 6, and FIG. 7 are sectional views of each side of a conventional semiconductor device, respectively. 1... Semiconductor substrate, 2... Getter region, 3...
active area. Applicant's agent Mr. Sato Figure 1 (!D) (C) Figure 2 Figure 3 (a) (b) (C) Figure 4 Figure 5 Figure 6 Figure 7

Claims (1)

[Scope of Claims] 1. A semiconductor device characterized in that a getter region for gettering metal impurities is formed in a predetermined region on the surface of a semiconductor substrate. 2. A semiconductor device according to claim 1, wherein the getter region is one in which phosphorus is diffused. 3. The semiconductor device according to claim 1, wherein the gator region is a damaged region having defects.