JPH06105696B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device having a buried diffusion layer.

(Prior Art) In a method of manufacturing a semiconductor device, a step of adding impurities into a semiconductor crystal is a basic step. The impurity diffusion technique used in such a process is one of the most important process techniques. With the diversification of the structures and functions of semiconductor devices, the impurity diffusion technology has become more sophisticated and more diverse.

A typical example of applying the impurity diffusion technique is to form a buried diffusion layer in which a high concentration of impurities is added between a semiconductor substrate and an epitaxial growth layer formed thereon. Examples of the buried diffusion layer formed in a semiconductor device include a buried diffusion layer of a bipolar integrated circuit provided to reduce collector series resistance and a vertical diffusion layer.
There is a buried diffusion layer in the gate region in the FET structure. Conventionally, such a buried diffusion layer has been formed as follows, for example. First, on a P-type semiconductor substrate,
After forming an oxide film serving as a mask for impurity diffusion, a hole is opened in the oxide film in the region where the impurities are to be diffused. Then N
A solution of silicate glass containing antimony chloride (SbCl ₃ ) as a type impurity dissolved in an organic solvent is applied to the surface. Then, it is heated to a temperature of about 200 ° C. in a nitrogen atmosphere to evaporate the organic solvent, and then in a nitrogen atmosphere.
It is heated to a temperature of 600 to 800 ° C., and the glass material is converted into a glass layer. Then, by heating at a high temperature of 1150 to 1250 ° C. in a nitrogen atmosphere, antimony in the glass layer is diffused into the semiconductor substrate to form a diffusion layer. After removing the glass layer and the oxide film, an N-type semiconductor layer is epitaxially grown on the substrate on which the diffusion layer is formed. After this growth, by heating, antimony is diffused from the diffusion layer into the semiconductor layer to form an N ⁺ -type buried diffusion layer.

(Problems to be Solved by the Invention) However, in such a method, boron, which is a P-type impurity existing in the atmosphere or in the glass material, is incorporated into the glass layer before the glass layer is formed on the semiconductor substrate. .

In this case, the boron taken into the glass layer diffuses into the P-type semiconductor substrate in the impurity diffusion step at high temperature,
In the subsequent epitaxial growth process, it diffuses into the N-type semiconductor layer. As a result, an N-type high resistance layer or a P-type inversion layer is formed between the N-type semiconductor layer and the N ⁺ -type buried diffusion layer depending on the boron diffusion concentration. Such an N-type high resistance layer increases collector resistance, and a P-type inversion layer causes a parasitic transistor.

The present invention is to solve the above-mentioned conventional problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device having a buried diffusion layer capable of preventing contamination by boron.

(Means and Actions for Solving the Problem) A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device having a buried diffusion layer at a junction between a semiconductor substrate and a semiconductor layer formed on the semiconductor substrate. A method comprising the steps of forming a mask for impurity diffusion on a semiconductor substrate, applying a solution of a glass material containing impurities dissolved in a solvent to the surface, and heating in an inert atmosphere. By removing the solvent and humidifying in a high-humidity atmosphere, a low-volatile boron compound existing in the atmosphere or in the glass material is reacted with water to change into a highly-volatile boron compound. And a step of volatilizing and removing a highly volatile boron compound by heating in an inert atmosphere, and changing the glass material into a glass layer, and a step in an inert atmosphere. A step of forming a diffusion layer by heating and diffusing impurities in the glass layer into the semiconductor substrate; a step of removing the glass layer and the mask; and a step of forming the diffusion layer on the semiconductor substrate. And then heating the semiconductor layer to diffuse impurities in the diffusion layer into the semiconductor layer to form an embedded diffusion layer. To be achieved.

In the production method of the present invention, a low-volatility boron compound existing in the atmosphere or in the glass material reacts with water during the step 4) to be changed to a highly-volatile boron compound. In this case, the following reactions are considered to occur.

B ₂ O ₃ + 3H ₂ O → 2H ₃ BO ₃ ↑ B ₂ O ₃ + H ₂ O → 2HBO ₂ ↑ The generated highly volatile boron compound is volatilized by heating during the above step 5). Thus, since boron is not incorporated in the buried diffusion layer, it does not diffuse from the buried diffusion layer to the epitaxial growth layer during the subsequent epitaxial growth and heat treatment steps. Therefore, formation of the N-type high resistance layer and the P-type inversion layer between the buried diffusion layer and the epitaxial growth layer is prevented.

(Embodiment) As an embodiment of the present invention, as shown in FIG. 1, a P-type semiconductor substrate 1 and an N-type semiconductor layer 2 formed on the P-type semiconductor substrate 1 are described below.
A case where the N ⁺ type buried diffusion layer 3 is formed at the junction with and will be described.

First, an oxide film 4 serving as a mask for impurity diffusion is formed on the P-type semiconductor substrate 1, and then, as shown in FIG. 2A, the oxide film in the region where the impurities are to be diffused is removed by photoetching. . Then, a solution of silicate glass 5 containing an N-type impurity antimony chloride (SbCl ₃ ) dissolved in an organic solvent was applied to the surface by spin coating (second step).
Figure (b)). Then, the organic solvent in the glass material is volatilized by heating to about 200 ° C. in a nitrogen atmosphere, and then the substrate 12 thus formed is used with a humidifier 8 as shown in FIG. Humidify over 10 minutes. The humidifier 8 comprises a container 9 containing purified water 11 and a humidification chamber 10 connected to the container 9. The carrier gas 13 was introduced into the humidifying chamber 10 after being sufficiently moistened by being blown into the water 11 in the container 9. At this time, the humidity inside the humidifying chamber 10 was maintained as high as possible without dew condensation. As a carrier gas,
Nitrogen gas or clean air can be used. By this humidifying step, the low volatile boron compound contained in the atmosphere or in the glass material is changed to the highly volatile boron compound.

Next, the substrate 12 was heated to 400 to 800 ° C. in a nitrogen atmosphere to remove the highly volatile boron compound and change the glass material to the glass layer 5. The glass layer 5 thus obtained was stable and did not adsorb impurities in the subsequent steps. Then, by heating this substrate 12 to 1150 to 1250 ° C. in a nitrogen atmosphere, the antimony in the glass layer 5 is diffused into the semiconductor substrate 1 and the diffusion layer 6 as shown in FIG. Was formed.

After removing the glass layer 5 and the oxide film 4, the N-type semiconductor layer 2 was epitaxially grown on the semiconductor substrate 1 on which the diffusion layer 6 was formed. After this growth, by heating,
Diffusing antimony from the diffusion layer 6 into the semiconductor layer 2;
An N ⁺ type buried diffusion layer 3 as shown in FIG. 1 was formed. It was found that the N ⁺ type buried diffusion layer 3 thus obtained did not contain boron and was not contaminated.

(Effect of the Invention) According to the manufacturing method of the present invention, a buried diffusion layer which is not contaminated with boron can be obtained. N-type high resistance layers and P-type inversion layers are not formed around such buried diffusion layers. Therefore, the manufacturing method of the present invention makes it possible to manufacture a semiconductor device having improved element characteristics with high yield.

[Brief description of drawings]

FIG. 1 is a sectional view of a buried diffusion layer formed by the manufacturing method of the present invention, and FIGS. 2A to 2C show specific steps in the process of forming the buried diffusion layer by the manufacturing method of the present invention. A sectional view, FIG. 3 is a sectional view for explaining that a P-type inversion layer is generated around a buried diffusion layer formed by a conventional manufacturing method, and FIG. 4 is used for the manufacturing method of the present invention. It is sectional drawing which shows an example of a humidifier. 1 ... P-type semiconductor substrate, 2 ... N-type semiconductor layer, 3 ... N ⁺ type buried diffusion layer, 4 ... Oxide film, 5 ... Impurity-containing glass layer (or silicate glass), 6 ... Diffusion layer, 7 ... P Type inversion layer, 8 ... Humidifier.

Claims (1)

[Claims] 1. A method of manufacturing a semiconductor device having a buried diffusion layer at a junction between a semiconductor substrate and a semiconductor layer formed on the semiconductor substrate, wherein a mask for impurity diffusion is formed on the semiconductor substrate. And a solution of a glass material containing impurities dissolved in a solvent,
A low volatility boron present in the atmosphere or the glass material by applying to the surface, heating in an inert atmosphere to remove the solvent, and humidifying in an atmosphere of high humidity. The step of reacting the compound with water to convert it into a highly volatile boron compound, and heating in an inert atmosphere to volatilize and remove the highly volatile boron compound, and to transform the glass material into a glass layer. A step of changing, a step of forming a diffusion layer by heating in an inert atmosphere to diffuse impurities in the glass layer into the semiconductor substrate, a step of removing the glass layer and the mask, A step of forming a buried diffusion layer by growing a semiconductor layer on the semiconductor substrate on which the diffusion layer is formed, and then heating the semiconductor layer to diffuse the impurities in the diffusion layer into the semiconductor layer. The method of manufacturing a semiconductor device including.