JPH05235005A - Semiconductor substrate and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] [Purpose] To realize a semiconductor substrate having a gettering ability with high durability. [Structure] Carbon, which is an impurity serving as an oxygen precipitation nucleus, is ion-implanted into the back surface side of the silicon wafer 10. Furthermore, a phosphorus-diffused dislocation region (extrinsic gettering layer) is formed thereon (outer side). A surface protection film 11 is formed on the wafer mirror surface side. By using such a semiconductor substrate, minute defects due to oxygen precipitation are formed inside, which enhances the gettering effect and enhances the sustainability of the ability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor substrate and a method of manufacturing the same, and more particularly to an extrinsic gettering technique.

[0002]

2. Description of the Related Art In gettering, a silicon wafer is subjected to a certain treatment during a device manufacturing process or in a state of a starting material to remove a defect in an element formation region or inactivate harmful impurities. It is a technology that gives people the ability. The current semiconductor device manufacturing process is performed in an ultra-clean room of class 100 or less.
Impurity contamination from gas, water, equipment, etc. is unavoidable to some extent, and sometimes reaches 10 ¹² atms / cm ² on the wafer surface. If these impurities and defects are present in the element active region where the field effect transistor (FET) and the charge-coupled image pickup element (CCD) are formed, the electrical characteristics of the element are significantly deteriorated. Therefore, in order to manufacture a high quality semiconductor device with high yield, it is necessary to control or remove the impurities and defects and clean the element active region. The gettering technique is performed for this purpose, and is roughly classified into extrinsic gettering (ED) and intrinsic gettering (IG).

Intrinsic gettering uses a silicon wafer having a relatively high oxygen concentration in the crystal, and a specific heat treatment is performed to precipitate oxygen in the crystal, which causes microdefects (SiO _2). Precipitates, stacking faults, etc.) are formed to form a gettering layer, which captures heavy metal impurities mixed during the process (getter), and at the same time,
This is a method of forming a defect-free layer in the vicinity of the surface on which an element is formed. This intrinsic gettering (IG) is generally more durable than extrinsic gettering (EG). In FIG. 5, this intrinsic gettering is applied to form a gettering layer 1A, which is a high-density defect region, inside the silicon wafer 1 (intermediate part between the front and back surfaces), and an epitaxial layer 2 is formed on the surface of the silicon wafer 1. An example is shown.

Another method is extrinsic gettering (EG). This method intentionally forms a processing flaw or a CVD polycrystal layer on the back surface of the wafer to form a gettering layer, and has the same effect as the above-mentioned intrinsic gettering. FIG. 6 shows an example in which this extrinsic gettering is applied. The polycrystalline silicon film 3 and the SiO ₂ film 4 are intentionally formed on the back surface of the silicon wafer 1 by the CVD method to form a gettering layer. None, an example in which the epitaxial layer 2 is grown on the surface of the silicon wafer 1 is shown.

[0005]

However, the above-mentioned intrinsic gettering cannot form fine defects inside the crystal when the oxygen concentration is low (<25 ppma) like the MCZ-Si crystal. , Phosphorus (P) diffusion on the back surface of the wafer (dislocations are formed by high-concentration phosphorus diffusion to form getter sites), and polycrystalline silicon formation (dislocations are formed by stress between the polycrystalline silicon and the substrate single crystal silicon). Getter site and) extrinsic gettering is commonly used. However, such extrinsic gettering has a problem in the sustainability of the getter ability because the strain is relaxed during the device forming process.

The present invention was devised by focusing on the problem of the conventional extrinsic gettering as described above, and an object of the invention is to obtain a semiconductor substrate having a highly durable gettering ability and a manufacturing method thereof. Is.

[0007]

Therefore, according to the present invention, an extrinsic gettering layer is formed on the back surface of a semiconductor wafer, and an element which becomes an oxygen precipitation nucleus is formed between the extrinsic gettering layer and the element formation region. The formation of the implantation region is the solution.

[0008]

[Function] The implanted region of the element which becomes the oxygen precipitation nuclei formed on the semiconductor wafer is accompanied by the SiO ₂ precipitate,
Small defects such as stacking faults are formed in the wafer.
The minute defects have an action of gettering heavy metal impurities and the like mixed during the process of applying to the semiconductor substrate, and have an action of enhancing the gettering ability of the semiconductor substrate in addition to the gettering action of the extrinsic gettering layer.

[0009]

The details of a semiconductor substrate and a method of manufacturing the same according to the present invention will be described below with reference to the embodiments shown in the drawings.

FIG. 1 is a sectional view showing an embodiment of a semiconductor substrate according to the present invention. In the figure, 10 is a silicon wafer made of MCZ-Si crystal. A carbon implantation region 10A formed by ion-implanting carbon is formed on the back surface of the silicon wafer 10, and phosphorus (P) is further provided outside the carbon implantation region 10A.
Diffusion dislocation regions 10B are formed. The carbon in the carbon-implanted region 10A has a function of accelerating the oxygen precipitation, and minute defects are formed in the wafer due to the oxygen precipitation, and the minute defects are mixed in the process in the same manner as the intrinsic gettering. It has an effect of gettering impurities and the like.

FIG. 2 is a sectional view showing each step of the embodiment of the method for manufacturing a semiconductor substrate according to the present invention.

First, MCZ-S having an oxygen density of 20 ppma
A surface protection film 11 such as a CVD-SiO ₂ film or a silicon nitride (Si ₃ N ₄ ) film is deposited on the element formation surface of the i-crystal silicon wafer 10, that is, the mirror surface side.
Next, as shown in FIG. 2 (A), carbon is implanted into the back surface of the silicon wafer 10 at 10 ¹³ cm ^-2 at 3 MeV to form a carbon-implanted region 10A. The distribution of carbon at this time is approximately R
p-4 μm, peak concentration-10 ¹⁷ atms / cm ³ , which is sufficient for precipitating 20 ppma of carbon by the heat treatment of the subsequent device forming process.

Next, as shown in FIG. 2B, POCl
Dislocation region (extrinsic gettering layer) 1 is formed by phosphorus (P) diffusion at 1100 ° C. using ₃ , O ₂ and N ₂ gases.
0B is formed.

Further, FIG. 2C shows that, on the dislocation region 10B, phosphorus (P) is prevented from outdiffusing during the process step.
The figure shows a state in which a Si ₃ N ₄ film 12 and a polycrystalline silicon film 13 are sequentially formed by, for example, a CVD method, and the surface protection film 11 on the mirror surface side of the silicon wafer 10 is etched off.

In this way, the carbon implantation region 10A is formed between the extrinsing gettering layer on the back surface side of the silicon wafer 10 and the element forming region on the mirror surface side. Figure 4
FIG. 4 is a graph showing the carbon concentration dependence of the amount of oxygen precipitation in a silicon wafer, showing that carbon is an impurity that accelerates oxygen precipitation. As a result, minute defects (SiO ₂ precipitates, stacking faults, etc.) resulting from the precipitation of internal oxygen can be formed in the dislocation regions formed by extrinsic gettering, and the semiconductor substrate should have a highly sustainable getter ability. Is possible.

3A and 3B are sectional views showing another embodiment of the method for manufacturing a semiconductor substrate according to the present invention. In this embodiment, first, as shown in FIG.
Carbon is injected into the back surface side of the silicon substrate 10 in the same manner as in the above-mentioned embodiment to form the carbon injection region 10A.

Subsequently, as shown in FIG. 3B, a polycrystalline silicon film 13 is deposited by the CVD method. Generally, this step is performed more efficiently in the wafer processing step as described below.

First, after slicing the silicon wafer 10, a lapping process is performed, and after the normal processing step of etching is completed, carbon is injected or diffused into the side which is the back surface of the wafer. Next, a polycrystalline silicon film 13 is formed on the same back surface by CVD by 1-2.
It is formed to a thickness of μm. Then, the surface side is primary-polished and secondary-polished in the same manner as in a normal processing step to complete.

Although the embodiments have been described above, the present invention is not limited to these, and various design changes associated with the gist of the configuration can be made.

For example, although the carbon implantation region is formed by ion implantation in the above embodiment, it may be formed by diffusion. For example, carbon can be diffused by about 4 μm by heat treatment at 1200 ° C. for 1 hour.

Further, although carbon is used as an impurity which becomes an oxygen precipitation nucleus in the above-mentioned embodiment, if it is an impurity that substantially accelerates the precipitation of oxygen and does not directly affect the device characteristics, it may be added to this. The material is not limited, and germanium (Ge) or the like may be used.

Further, the silicon crystal used is not limited to MCZ, but a CZ crystal having a high oxygen concentration can improve the getter ability as compared with the intrinsic gettering method. It should be noted that the getter effect increases as the crystal having a lower oxygen concentration.

Further, in the above embodiment, the P diffusion region and polycrystalline silicon are applied as the extrinsic gettering layer, but the getter ability can be improved by using Si ₃ N ₄ or the like.

[0024]

As is apparent from the above description, according to the present invention, the effect of being able to impart a highly durable gettering ability to the semiconductor substrate is achieved, and the yield of devices is greatly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a semiconductor substrate according to the present invention.

2A, 2B, and 2C are cross-sectional views showing respective steps of an embodiment of a method for manufacturing a semiconductor substrate according to the present invention.

FIGS. 3A and 3B are cross-sectional views showing steps of another embodiment of the present invention.

FIG. 4 is a graph showing the carbon concentration dependence of the oxygen precipitation amount in a silicon wafer.

FIG. 5 is a sectional view of a conventional example using an intrinsic gettering method.

FIG. 6 is a sectional view of a conventional example using an extrinsic gettering method.

[Explanation of symbols]

10 ... Silicon wafer, 10A ... Carbon implantation region, 10B
... dislocation regions, 11 ... surface protective film, 12 ... Si ₃ N ₄ film, 1
3 ... Polycrystalline silicon film.

Claims (2)

[Claims] 1. An extrinsic gettering layer is formed on the back surface of a semiconductor wafer, and an implantation region of an element serving as an oxygen precipitation nucleus is formed between the extrinsic gettering layer and an element formation region. Semiconductor substrate. 2. A step of forming an extrinsic gettering layer on the back surface of a semiconductor wafer, and a step of implanting an element which becomes an oxygen precipitation nucleus between the extrinsic gettering layer and an element formation region of the semiconductor wafer. A method of manufacturing a semiconductor substrate, comprising: