JPH1174276A - Epitaxial silicon semiconductor substrate and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epitaxial silicon semiconductor substrate that performs improved gettering for all heavy metal impurities, irrespective of diffusion coefficients in silicon. SOLUTION: After mirror polishing a silicon semiconductor substrate 1, ions are implanted from the surface of the substrate, so as to form a dislocation/ distortion layer 2 near the surface of the substrate, and a silicon epitaxial layer 3 is formed on the surface of the substrate through an epitaxial growth. Thus, there is no adverse effects in a region approximately several μm from the surface to be used for the device process, and gettering can be performed for heavy metal elements, irrespective of high or low diffusion coefficients in silicon.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an epitaxial silicon semiconductor substrate. In a semiconductor substrate manufacturing process, a semiconductor substrate is mirror-polished to a step before forming an epitaxial layer from a surface of a silicon semiconductor substrate. The present invention relates to an epitaxial silicon semiconductor substrate having improved gettering ability of heavy metal impurities by performing ion implantation, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the miniaturization of semiconductor devices,
High energy ion implantation has been used to form the WELL diffusion layer, and the device process has been performed at a low temperature of 1000 ° C. or less in order to make the junction depth shallower. For this reason, since oxygen outward diffusion does not sufficiently occur and it is difficult to form a DZ layer near the surface, the oxygen concentration of the substrate has been reduced. It was difficult to completely suppress the occurrence.

[0003] Under such circumstances, a so-called silicon epitaxial wafer in which a high-quality epitaxial layer substantially free of crystal defects is grown on a silicon wafer has come to be widely used in today's highly integrated devices.

Conventionally, a wafer used as an epitaxial silicon semiconductor substrate is roughly sliced from an ingot → lapping → etching → mirror polishing.
It is manufactured in the following process.

As a gettering source of this epitaxial silicon semiconductor substrate, a BSD which damages the back surface of the substrate is used.
After the etching or mirror polishing, there is a PBS type in which a polycrystalline silicon film is formed on the back side surface by a low pressure CVD method or the like, and a substrate doped with boron at a high concentration is used. There is an oxygen precipitate (IG) and the like.

[0006]

SUMMARY OF THE INVENTION In the epitaxial silicon semiconductor substrate, when heavy metal contamination occurs from the surface, a heavy metal element (iron, iron, etc.) having a large diffusion coefficient in silicon.
Copper and the like can be sufficiently diffused to the gettering source on the back surface of the substrate and the gettering source inside the substrate by heat treatment in a normal device process.

However, heavy metal elements (such as molybdenum) having a small diffusion coefficient in silicon cannot sufficiently diffuse to the gettering source on the back surface of the silicon semiconductor substrate and the gettering source inside the silicon semiconductor substrate, and remain in the epitaxial layer. The present inventors have confirmed this.

Further, the present inventors have confirmed that in such a state, the life time of the epitaxial silicon semiconductor substrate is deteriorated, and have reported (Miyazaki et al .;
It was 30p-ZP-12 in the spring of 1993.

According to the present invention, an element having a large diffusion coefficient in silicon and an element having a small diffusion coefficient can be sufficiently gettered.
That is, it is an object of the present invention to provide an epitaxial silicon semiconductor substrate having improved gettering ability of all heavy metal impurities and a method of manufacturing the same.

[0010]

Means for Solving the Problems The inventors of the present invention have conducted various studies for a gettering source for improving the gettering ability of heavy metal impurities, and have focused on the introduction of dislocation / strain layers by ion implantation. That is, high energy ion implantation is used in a semiconductor device process, but in a conventional epitaxial silicon semiconductor substrate manufacturing process, ion implantation is not performed in a step before an epitaxial layer is formed on a silicon semiconductor substrate. This is because the presence of dislocations, strains, and the like near the surface caused by ion implantation adversely affects the device.

As a result of various studies aimed at introducing a dislocation / strain layer by ion implantation, the inventors of the present invention have conducted a mirror polishing of a silicon semiconductor substrate and then implanted ions from the substrate surface to form a dislocation / strain layer near the substrate surface. Then, the inventors have found that there is no adverse effect in a region about several μm from the surface used in the device process by epitaxially growing and forming a silicon layer on the substrate surface, and completed the present invention.

According to the present invention, an epitaxial silicon semiconductor substrate having a dislocation / strain layer formed by ion implantation near the substrate surface and having an epitaxial silicon layer formed on the substrate surface has a gettering source near the epitaxial layer. Thus, gettering is possible regardless of a heavy metal element having a large diffusion coefficient in silicon and a heavy metal element having a small diffusion coefficient, and a region provided for a device process is an epitaxial silicon semiconductor substrate having no adverse effect on a device.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Mo on a silicon semiconductor substrate
In order to investigate the influence of the impurities on the electric characteristics, 6 inches by PZ method, P (100), N (100), oxygen concentration 12
× 10 ¹⁷ atoms / cc (ASTM F-121, 1
979), using a silicon semiconductor substrate with a specific resistance of 11 Ωcm, spin coating with Mo aqueous solution,
Heat treatment was performed at 00 ° C. for 10 minutes.

The concentration of Mo on the surface after the contamination and the concentration of Mo in the oxide film after the heat treatment are determined by ICP after recovery by a gas phase decomposition method.
-Analyzed by MS (nebulizer method). For evaluation, the measurement of recombination lifetime (τr) is μ-wav.
e Photoconductive Decay (μ
-PCD) method. As a result, FIG. 2 shows the relationship between the surface contamination amount of molybdenum (Mo) and the recombination lifetime of silicon. It can be seen that Mo deteriorates the recombination lifetime of silicon.

Table 1 shows a comparison of diffusion distances of Mo, iron (Fe) and copper (Cu) in silicon. From this table, it can be seen that Mo is an element whose diffusion rate is much lower than that of Fe or Cu. For example, when Mo contamination occurs from the front side of the epitaxial silicon semiconductor substrate, it takes 1000 hours or more at 1000 ° C. to reach the back side of the epitaxial silicon semiconductor substrate having a thickness of 600 μm. It is easy to imagine that gettering is not possible during the heat treatment of the device process that is normally performed at the source.

Therefore, to getter an element having a low diffusion rate in silicon, it is necessary to form a gettering source near the surface of the silicon semiconductor substrate used for the epitaxial silicon semiconductor substrate.

[0017]

[Table 1]

Referring to FIG. 1, a method for manufacturing an epitaxial silicon semiconductor substrate according to the present invention will be described. FIG. 1A
As shown in the figure, ions are implanted from the surface of the silicon semiconductor substrate 1. By this ion implantation, as shown in FIG.
A dislocation / strain layer 2 is formed near the surface of the substrate 1, and this portion serves as a gettering source. The gettering source formed near the surface enables gettering even for an element having a small diffusion coefficient.

However, the dislocation / strain layer 2, which is a gettering source formed by ion implantation, is present in the device formation region when the substrate is used as it is, so that the dislocation / strain caused by the ion implantation adversely affects the device. As shown in FIG. 1C, a substrate 1 on which a dislocation / strain layer 2 of a gettering source is formed by performing ion implantation.
By forming the epitaxial layer 3 on the substrate, the region used in the device process, that is, the epitaxial layer 3 is about several μm from the surface, and it can be used for a device because there is no dislocation or distortion.

Furthermore, the gettering source is present near the epitaxial layer 3 in the epitaxial silicon semiconductor substrate according to the present invention, so that the gettering ability is superior to the conventional epitaxial silicon semiconductor substrate.

In the present invention, the conditions of the ion implantation for forming the dislocation / strain layer as the gettering source depend on the required intensity of the gettering source, the depth from the surface, and the like. It can be controlled by appropriately selecting the implantation energy and the like. Preferably, the ionic species is a light element such as hydrogen or helium which does not affect the device. The injection amount is 1 × 10 ¹⁵ atoms / cm ²
As described above, the density is preferably 1 × 10 ¹⁸ atoms / cm ² or less. The implantation energy is preferably 30 keV to 300 keV.

[0022]

[Example] Specific resistance 10Ωcm, oxygen concentration 12-15 × 1
0 ¹⁷ atoms / cc (ASTMF-121, 197
9) A silicon semiconductor substrate (1) having a specific resistance of 10 Ωcm and an oxygen concentration of 12 to 15
An epitaxial silicon semiconductor substrate (2) provided with an epitaxial layer of × 10 ¹⁷ / atoms / cc, and an epitaxial silicon semiconductor substrate (3) according to the manufacturing method of the present invention having specifications equivalent to those of the epitaxial silicon semiconductor substrate (2). Produced. The conditions of the ion implantation are as follows: the ion species is helium (He);
× 10 ¹⁶ atoms / cm ² , implantation energy 40 ke
V.

Using the above silicon semiconductor substrate, Mo
After the contamination, the Mo concentration was measured. The surface contamination of Mo is performed by a spin coating method, and the contamination amount is 1 × 10 ¹² atoms.
s / cm ² . Mo diffusion heat treatment is 1000
C. for 1 hour in a nitrogen atmosphere. Mo concentration is DLT
S (Deep Level Transient Sp)
(Ectroscopy) method.

FIG. 3 shows a comparison of Mo concentration using three types of silicon semiconductor substrates. The sample level of each of (1) to (3) is (1) silicon semiconductor substrate: specific resistance 10Ω
・ Cm, oxygen concentration 12-15 × 10 ¹⁷ atoms / c
c, (2) Epitaxial silicon semiconductor substrate: The specific resistance of the silicon semiconductor substrate is 15 Ω · cm, the specific resistance of the epitaxial layer is 10 Ω · cm, and the oxygen concentration is the same as that of (1). (3) Epitaxial silicon semiconductor substrate in which an epitaxial layer is formed on a silicon semiconductor substrate on which He ion implantation has been performed: The specific resistance and oxygen concentration of the silicon semiconductor substrate and the epitaxial layer are the same as in (2).

FIG. 3 shows that the concentration of Mo decreased only in the epitaxial silicon semiconductor substrate obtained by implanting ions into the silicon semiconductor substrate. This indicates that the gettering source was formed near the surface by the ion implantation, and Mo was gettered. Here, only the result of Mo is shown, but the concentration of Fe and Cu also decreased most in the epitaxial silicon semiconductor substrate into which the ion implantation was performed.

[0026]

According to the present invention, after a silicon semiconductor substrate is mirror-polished, ions are implanted from the substrate surface to form dislocation / strain layers near the substrate surface, and then a silicon layer is epitaxially grown and formed on the substrate surface. There is no adverse effect in the region about several μm from the surface used in the device process, and gettering is possible regardless of the heavy metal element having a large diffusion coefficient in silicon and the heavy metal element having a small diffusion coefficient.

[Brief description of the drawings]

FIGS. 1A, 1B, and 1C are cross-sectional views of a substrate showing a method for manufacturing an epitaxial silicon semiconductor substrate according to the present invention.

FIG. 2 is a graph showing the relationship between surface Mo contamination concentration and recombination lifetime.

FIG. 3 is a graph showing the relationship between the difference in silicon semiconductor substrate and the concentration of surface Mo contamination in Examples.

[Explanation of symbols]

 Reference Signs List 1 silicon semiconductor substrate 2 dislocation / strain layer 3 epitaxial layer

Claims (2)

[Claims] Claims: 1. Dislocation by ion implantation near the surface of a substrate
An epitaxial silicon semiconductor substrate having a strained layer and having an epitaxial silicon layer formed on a substrate surface. 2. Manufacturing an epitaxial silicon semiconductor substrate in which a silicon semiconductor substrate is mirror-polished, ion implantation is performed from the substrate surface to form a dislocation / strain layer near the substrate surface, and then a silicon layer is epitaxially grown and formed on the substrate surface. Method.