JPH06163556A - Semiconductor device - Google Patents

Abstract

PURPOSE:To provide a semiconductor device having an epitaxial layer on a semiconductor substrate in which gettering effect and latch-up free effect can be achieved. CONSTITUTION:A P<+>-type impurity layer 2 is formed at the border of a lightly doped P-type silicon substrate 1 and a P-type epitaxial layer 3. Consequently, latch-up free effect and gettering effect are achieved and since a lightly doped P-type silicon substrate is employed, outward diffusion of impurities from the rear surface can be restrained completely. The semiconductor device thus fabricated can withstand wet etching process and high temperature long time diffusion process.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor device, and more particularly to a semiconductor device having an epitaxial layer.

[0002]

2. Description of the Related Art In order to obtain a gettering effect and a latch-up free effect, a conventional semiconductor device has a high impurity concentration in a semiconductor substrate. This will be described below with reference to FIG.

For example, a P type epitaxial layer 3 having boron as an impurity is formed on the surface of a P ⁺ type silicon substrate 1A made of a silicon single crystal having a high concentration of boron as an impurity. The P ⁺ type silicon substrate 1A in this structure is manufactured to have a concentration of about 8.0 × 10 ¹⁸ pieces / cm ³ , and the P type epitaxial layer 3 has a concentration of 7 × 10 ¹⁴ pieces / cm ^3.
It is about cm ³ . High-performance gettering effect by the P ⁺ type silicon substrate 1A having the above structure
Latch-up free effect can be expected.

However, the P ⁺ -type silicon substrate to a high concentration of boron of about 10 ¹⁸ / cm ³ and an impurity, since the outward diffusion of impurities generated from the back surface, the back surface thereof,
For example, the silicon oxide film 4 formed by LPCVD is grown to 500
It is formed to a thickness of about nm. This silicon oxide film 4
Although it is initially possible to suppress the out-diffusion of boron by this method, in this diffusion process, in the diffusion process that requires thinning of the backside oxide film by wet etching and the use of heat history at high temperature for a long time. , It is difficult to prevent outward diffusion of boron from the back surface of the substrate.

[0005]

As described above, in the conventional semiconductor substrate, in order to obtain the gettering effect and the latch-up free effect, high concentration boron (10 ¹⁸ /
A P ⁺ type silicon substrate having an impurity of the order of cm ³ ) is used. For this reason, a silicon oxide film for preventing the outward diffusion of boron is formed on its back surface, but this silicon oxide film cannot withstand the wet etching in the semiconductor element forming process and the thermal history of high temperature for a long time. It becomes impossible to suppress the outward diffusion of. Therefore, there is a problem that the gettering effect and the latch-up free effect are reduced during the manufacturing process, and the characteristics and yield of the semiconductor device are reduced.

[0006]

The semiconductor device of the present invention comprises:
In a semiconductor device having an epitaxial layer on a semiconductor substrate, a layer having a higher impurity concentration than the epitaxial layer and the semiconductor substrate is provided at a boundary portion between the epitaxial layer and the semiconductor substrate.

[0007]

The present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention.

A silicon single crystal containing boron as an impurity, for example, 8.0 × boron is also formed on the surface of a P-type silicon substrate 1 having a low concentration of about 1.0 × 10 ¹² pieces / cm ^3.
A P ⁺ -type impurity layer 2 containing about 10 ¹⁸ / cm ³ and having a depth of about 5 μm is formed. The P ⁺ -type impurity layer 2 can be formed by epitaxial growth of silicon or gas diffusion. Then, on the surface of the P ⁺ -type impurity layer 2, boron is used as an impurity and the concentration is 7 × 10 ¹⁴ pieces / cm ³
A P-type epitaxial layer 3 having a certain degree is formed.

According to this embodiment thus formed, P
^The gettering effect and the latch-up free effect are obtained by the ⁺ type impurity layer 3. Furthermore, P-type silicon substrate 1
Since boron in the inside has a low concentration, outward diffusion of boron from its back surface is suppressed. Further, it is not necessary to form a silicon oxide film on the back surface of the silicon substrate, which has been conventionally required.

In the above embodiment, the case of using the P-type impurity has been described, but the same effect can be obtained even in the case of the N-type impurity.

[0012]

As described above, according to the present invention, in the semiconductor device having the epitaxial layer on the semiconductor substrate, the high-concentration impurity layer is formed in the boundary region between the semiconductor substrate and the epitaxial layer. The latch-up free effect can be maintained even in the latter half of the manufacturing process.
Further, it becomes possible to reduce the concentration of impurities in the semiconductor substrate, and it is possible to completely suppress the outward diffusion of impurities such as boron from the back surface thereof.

For this reason, it is possible to carry out a high temperature and long time element formation diffusion process without using a silicon oxide film on the back surface, which is required for a high concentration impurity substrate which has been used conventionally. Since the influence of diffusion on the semiconductor substrate can be minimized, the reliability and yield of the semiconductor device can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of the present invention.

FIG. 2 is a sectional view of an example of a conventional semiconductor device.

[Explanation of symbols]

1 P-type silicon substrate 1A P ⁺ type silicon substrate 2 P ⁺ type impurity layer 3 P type epitaxial layer 4 Silicon oxide film

Claims (1)

[Claims] 1. A semiconductor device having an epitaxial layer on a semiconductor substrate, wherein a layer having a higher impurity concentration than the epitaxial layer and the semiconductor substrate is provided at a boundary portion between the epitaxial layer and the semiconductor substrate. Semiconductor device.