JPS61174197A - Production of epitaxial wafer - Google Patents

Abstract

PURPOSE:To control easily the concn. of impurities and to prevent the contamination of the device forming region by forming the diffusion layer of the same impurities as the impurities contained in an Si substrate, forming an oxide- coated film after specified treatment, polishing the one surface, and then forming an epitaxial layer having the same electric conductivity as the Si substrate. CONSTITUTION:Intrinsic gettering is applied to an Si substrate 1 of usual impurity content produced by the CZ method to form an oxide depositing neucleus 2 at the inside of the substrate 1. After the same impurities as the contained impurities are diffused at the surface and in the vicinity of the surface of the substrate 1 to form a diffusion layer 3, an oxide coated film (SiO2) 4 is formed on the surface of the substrate 1 by oxidation or the rear surface CVD method. The one surface is subsequently mirror-polished to remove the oxide film 4. An epitaxial layer 5 having the same electric conductivity as the substrate 1 having high resistivity is formed on the polished surface by the reduction with hydrogen or thermal decomposition, and the desired epitaxial wafer is produced.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for manufacturing epitaxial wafers used in the manufacture of high-density devices such as dynamic RAN and OMO8.

[Prior Art] Conventionally, epitaxial wafers have been manufactured using a CZ method (Czochralski method) to reduce the impurity concentration by doping boron, phosphorus, antimony, etc. in order to reduce the series resistance of devices. cd') Sin
After mirror polishing one side of this Si substrate using a plate,
An oxide film for autodoping prevention is formed on the surface of the substrate by an oxidation method or a CVD method, and the oxide film on the mirror surface side is peeled off. After that, the mirror surface is made into the same -S electric type as the Si substrate and has a high specific resistance. It is manufactured by a method of forming an epitaxial layer.

[Problems to be Solved by the Invention] However, according to the above-mentioned conventional manufacturing method, the impurity concentration must be controlled from the stage of crystal pulling, and the concentration of impurities with the substrate is too large to cause problems at the interface of the epitaxial layer. The problem of lattice misalignment arises, and also by such a method! When the LJ fabricated epitaxial wafer is introduced into the device manufacturing process, it does not have a getter effect, so
There are problems such as contamination with heavy metals during the manufacturing process.

[Means for Solving the Problems] In order to solve the above problems, the present invention diffuses the same impurities as the impurities contained in the Si substrate with the usual impurity concentration (1014 to 1016 pieces/i) by the CZ method. Before or after forming the diffusion layer, an intrinsic gettering process is performed to form an oxide film on the surface of the Si substrate, and after removing the oxide film on one side by mirror polishing, the polished surface is Then, an epitaxial layer of the same conductivity type as the 81 substrate is formed.

[Function] By forming a diffusion layer of the same impurity as the impurity contained in the Si substrate with a normal impurity concentration, a layer with sufficiently low resistivity is formed near the surface of the Si substrate. In addition, due to the intrinsic gettering process, oxygen precipitate nuclei are formed between the diffusion layers on the front and back surfaces of the Si substrate, and by introducing this epitaxial wafer into the device manufacturing process, the internal oxygen precipitate nuclei are removed. It grows into microscopic defects that getter contaminant impurities.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

Figures 1a, b, c, d, e, and f are process diagrams showing the first embodiment of the present invention. Concentration (10”~1016 pieces/CI!>(F)Si
Using the substrate 1 (see FIG. 1C), the Si substrate 1 is subjected to an intrinsic gettering process to form oxygen precipitation nuclei 2 inside the Si substrate 1 (see FIG. 1C). At this time, in order to obtain a suitable intrinsic gettering effect, the Si substrate 1 has an oxygen concentration of 1.0×101
8 pieces/i (If the infrared spectrometer absorption coefficient is α, αx
3. Ox 1017 exchange concentration) or higher.

Next, this Si is deposited on and near the surface of the Si substrate 1.
A diffusion layer 3 is formed by diffusing the same impurity as that contained in the substrate 1 (see FIG. 1C). Due to the formation of this diffusion layer 3, the surface of the Si substrate 1 and its vicinity have a conductivity comparable to that of a Si substrate with a high impurity concentration (1018 to 1019 impurities/ci).

After forming the diffusion layer 3, when forming an epitaxial layer, which will be described later,
In order to suppress the autodoping phenomenon from the back side (lower side in the figure), an oxidizing solution 1! is applied to the surface of the Si substrate 1! (Si0
2) 4 is formed by an oxidation method or a backside CVD method (see FIG. 1C). Thereafter, the oxide film on one side (the upper side in the figure) or the protrusions and residues 4 surrounding the surface during CVD on the back side are removed by mirror polishing (see FIG. 1C).

Then, on the polished surface of the Si substrate 1, an epitaxial layer 5 having the same conductivity type as the 81 substrate 1 and having a high resistivity is formed.
is formed by a hydrogen reduction method, a thermal decomposition method, etc. (Fig. 1C)
), the desired epitaxial wafer is completed.

Figures 2a, b, c, d, and e are process diagrams showing a second embodiment of the present invention. /L/. In order to manufacture a wafer, as in the case of the first embodiment described above, Si with a normal impurity concentration manufactured by the CZ method is used.
Using a substrate 1 (see FIG. 2C), a diffusion layer 3 is formed by diffusing the same impurity as that contained in the Si substrate 1 on and near the surface of the Si substrate 1 (see FIG. 2C). reference).

Due to the formation of this diffusion WJ3, the surface of the 81 substrate 1 and its vicinity have a conductivity comparable to that of a conventional Si substrate with high impurity levels of 5ttxt.

Next, the Si substrate 1 is subjected to an intrinsic gettering process to form oxygen precipitation nuclei 2 inside the Si substrate 1, and an oxygen film (Si02) 4 is formed on the surface of the Si substrate 1 to suppress the autodoping phenomenon. form (see Figure 2C).

Then, the oxide film on one side of the Si substrate 1 or the CV on the back side
After mirror-polishing and removing the protrusions and residue 4 that went around the surface in D (see Figure 2C), the Si substrate 1 was placed on this polished surface.
Epitaxial H5 having the same conductivity type and high resistivity is formed by hydrogen reduction method etc. (see Figure 2C).
The desired epitaxial wafer is then completed.

Note that the intrinsic gettering treatment in each example includes low-temperature heat treatment (heating in nitrogen gas at a temperature of 500 to 900°C for 4 to 32 hours) depending on the type of device manufactured using the epitaxial wafer. )
or after forming oxygen precipitate nuclei 2 by low-temperature heat treatment (500 to 900°C), high-temperature heat treatment (heating at a temperature of 1000 to 1100°C in nitrogen gas for several hours) Either of the following methods can be used to grow 2 to some extent into minute defects.

It has been found that the out-diffusion treatment of oxygen at a high temperature in the intrinsic gettering treatment, which is an important point in the present invention, can be replaced by a process of forming the diffusion layer 3 on a normal concentration substrate. That is, in the diffusion layer forming step of the present invention (boron, phosphorus, antimony, etc.
The process of diffusing at a temperature of 0 to 1250°C to form a diffusion layer of 10 to 20 μm is a sufficient condition to outwardly diffuse oxygen near the substrate surface. We have confirmed that no defects occur.

In addition, the oxygen precipitation nuclei 2 formed by the intrinsic gettering process grow into micro defects during the device manufacturing process, and also getter contaminants such as heavy metals mixed in during the manufacturing process. A defect-free layer is formed around the outer periphery of the layer.

[Effects of the Invention] As described above, according to the present invention, various effects described below can be obtained compared to the conventional technology.

(1) A Si substrate with a normal impurity concentration can be used, and the impurity concentration can be easily controlled during single crystal growth.

(2) Contamination caused by heavy metals and the like during the device manufacturing process can be gettered on the epitaxial wafer itself, and contamination of the device formation region can be prevented.

(3) Device latch-up can be prevented, and
Device malfunctions caused by unnecessary diffusion of carriers can be improved.

[Brief explanation of drawings]

Figure 1 a, b, c, d, e, f and Figure 2 a, b, c
, d and e are process diagrams showing a first embodiment and a second embodiment of the present invention, respectively. 1...Si substrate 2...Oxygen precipitation nucleus 3...
・Diffusion layer 4...Acidic coating 5...Epitaxial layer Inventor: Norihiro Takai Inventor: Takashi M. -
-Inventor: Kuni Fushii Producer: Toshiba Ceramics Corporation Figure 1
Figure 2

Claims (1)

[Claims] Intrinsic gettering treatment is performed before or after forming a diffusion layer by diffusing the same impurity as the impurity contained in the Si substrate with a normal impurity concentration by the CZ method,
An epitaxial method characterized by forming an oxide film on the surface of the Si substrate, removing the oxide film on one side by mirror polishing, and then forming an epitaxial layer having the same conductivity type as the Si substrate on the polished surface. Wafer manufacturing method.