JP2000100741A - Manufacturing method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily eliminate impurities after diffusing wafers by using a filmy- shape diffusing source. SOLUTION: Impurities are diffused into wafers from a filmy diffusing source by piling and heating the low concentration wafers and the high concentration film-like source (step 1). After the diffusion film residue is eliminated from the filmy diffusing source (2) and the wafers are separated one by one (3). After this, oxygenation is performed in a low temperature and oxide films are formed on the wafer surfaces. The oxide films and impurity layers, including organic matter on the wafer surfaces, are eliminated by oxygen fluoride (5). After eliminating the oxide films, a semiconductor layer of which wafer surfaces are diffused in a high concentration is eliminated through etching (6), and a semiconductor device having stable wafers is obtained by further drive diffusion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a semiconductor device in which a semiconductor layer is formed by diffusing impurities into a wafer using a film-like diffusion source.

[0002]

2. Description of the Related Art In a method of manufacturing a semiconductor device in which a semiconductor layer is formed by diffusing impurities into a wafer using a film-like diffusion source (hereinafter referred to as a film diffusion method), a P-type impurity and an N-type impurity are simultaneously diffused. Although it has the advantage that it can be obtained, after diffusion, a residue remains on the wafer and it is necessary to remove this residue.

When a diode is formed by the film diffusion method, for example, as shown in FIG. 2, a P-type high-concentration film-type diffusion source 42 is mounted on an N-type low-concentration wafer 41, and this film-type diffusion source is mounted. An N-type low-concentration wafer 43 is mounted on the diffusion source 42. Further, the wafer 43
An N-type high-concentration film-like diffusion source 44 is mounted thereon. An N-type low-concentration wafer 45 is mounted on the film-like diffusion source 44. Further, the wafer 45
A P-type high-concentration film-type diffusion source 46 is mounted on the substrate, and an N-type low-concentration wafer 47 is mounted on the film-type diffusion source 46. Further, an N-type high-concentration film-type diffusion source 48 is mounted on the wafer 47, and an N-type low-concentration N-type wafer 49 is mounted on the film-type diffusion source 48.

[0004] The block in which the wafer and the film-like diffusion source are overlapped in this manner is placed in a diffusion furnace and diffused at a high temperature, for example, 1250 ° C for 90 minutes. For example, in the third wafer 45 from the bottom, as shown in FIG. 3, a high-concentration N-type semiconductor layer 45b is formed below a low-concentration N-type semiconductor substrate 45a, and a high-concentration P-type semiconductor layer 45b is formed on the upper side. The semiconductor layer 45c is formed. Further, a very high-concentration N ++ semiconductor layer 45d is formed below the N + semiconductor layer 45b, and a very high-concentration P ++ semiconductor layer 45e is formed about several μm above the P + semiconductor layer 45c.
It is formed with.

After diffusion of the film-form diffusion source, the film-form diffusion source remains between the wafers as a film residue. Therefore, as shown in FIG.
When the block of the wafer is immersed in hydrofluoric acid, for example, for about 24 hours, the film residue is removed. At this time, the hydrofluoric acid remains between the wafers, and the adjacent wafers are stuck. Therefore, as shown in FIG. 4B, cleaning is performed while radiating ultrasonic waves in water, and adjacent wafers are manually separated as shown in FIG.

[0006] The wafer thus formed is shown in FIG.
As shown in the figure, the lower part of the N ++ semiconductor layer 45d and P ++
Above the semiconductor layer 45e, impurity layers 45f and 45g each containing a film organic substance and not providing semiconductor characteristics are provided.
Are formed. For this reason, as shown by 4 in FIG. 4, a thin impurity layer 45f which does not provide semiconductor characteristics by using a weak acid is used.
The semiconductor layers 45d and 45e are etched by silicon, including 45g. As a result, the impurity layer 45f and the very high-concentration N ++ semiconductor layer 45d form a coating that is raised from the high-concentration N-type semiconductor layer 45b. Further, the impurity layer 45g and the very high concentration P ++ semiconductor layer 4
5e is a film in a state of being lifted from the high concentration P-type semiconductor layer 45c. After this silicon etching, cleaning is performed as shown by 5 in FIG.

[0007] Thin films are formed on the lower portion of the N + semiconductor layer 45b and on the upper portion of the P + semiconductor layer 45c of the silicon-etched and cleaned wafer.
Then, it is scrubbed away as shown in FIG. 4 and further washed as shown in FIG. Thereafter, the wafer is drive-diffused as shown at 8 in FIG. 4 to obtain a predetermined wafer.

[0008]

However, since scrubbing is performed one by one, it requires a lot of man-hours. The removal accuracy of the impurity layers 45f and 45g is as follows.
Since the amount of etching at the time of silicon etching of 4 in FIG. 4 is greatly affected, it is necessary to control the amount of etching.
It was very difficult to control the amount of etching, and it was difficult to stabilize the process.

[0009]

According to the present invention, there is provided a method of manufacturing a semiconductor device, comprising: a diffusion step in which a low-concentration wafer and a high-concentration film-like diffusion source are stacked and heated; A step of separating the wafer except for the source film residue, a step of separating the wafer and then oxidizing at a low temperature to form an oxide film on the surface of the wafer, and forming the oxide film with dilute hydrofluoric acid after forming the oxide film. It comprises a removing step, an etching step of etching silicon after removing the oxide film, and a step of drive diffusion after etching.

A low-concentration wafer and a high-concentration film-form diffusion source are stacked and heated to diffuse impurities from the film-form diffusion source to the wafer. After the diffusion, the film residue of the film-form diffusion source is removed, and the wafers are separated one by one. After the separation, each wafer is oxidized at a low temperature to form an oxide film on the surface of the wafer. After the oxide film is formed, the impurity layer on the wafer surface is removed together with the oxide film using diluted hydrofluoric acid. After removing the oxide film, the semiconductor layer diffused to a very high concentration on the wafer surface is removed by etching. Further, after etching, drive diffusion is performed to obtain a stable wafer semiconductor device.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to FIG. 1 showing an embodiment thereof. In FIG. 1, the point different from FIG. 4 is that the conventional thin film shown in FIG. 4 is formed by scrubbing a thin film formed under the N + semiconductor layer 45b and a thin film formed over the P + semiconductor layer 45c after silicon etching. On the other hand, in the case of FIG. 1, after separating each wafer, the lower part of the N + semiconductor layer 45b and the P
+ An oxide film is formed up to the upper portion of the semiconductor layer 45c, and impurities are removed together with the oxide film by dilute hydrofluoric acid.

That is, as shown in FIG. 2, a block in which a wafer and a high-concentration N-type film-like diffusion source and a wafer and a high-concentration P-type film-like diffusion source are alternately stacked is shown in FIG. As shown, 9 ° C at high temperature, eg 1250 ° C
Spread for 0 minutes. After diffusion, the block is immersed in hydrofluoric acid, for example, for 24 hours as shown in FIG. Further, as shown in FIG. 1C, cleaning is performed while irradiating ultrasonic waves in pure water, and adjacent wafers are manually separated one by one. At this time, for example, as shown in FIG. 3, a low-concentration N-type semiconductor layer 45a at the center and a high-concentration N +
Is formed, and a high-concentration P + is formed above the N-type semiconductor layer 45a.
A type semiconductor layer 45c is formed. Further, N + semiconductor layer 4
5b and an upper part of the P + semiconductor layer 45c, each having a thickness of several μm and a very high concentration of the N ++ semiconductor layer 45d.
And a very high concentration P ++ semiconductor layer 45e is formed,
Further, impurity layers 45f and 45 which are not used for semiconductor characteristics including an organic substance of a film-form diffusion source are provided below the N ++ semiconductor layer 45d and above the P ++ semiconductor layer 45e, respectively.
g is formed.

The wafer is oxidized at a low concentration, for example, at 800 ° C. for about 1 hour at a low temperature, as shown in FIG. At this time, the surface of the N ++ semiconductor layer 45d and the P ++
An oxide film is formed on the surface of 5e. Thereafter, as shown by 5 in FIG. 1, when the substrate is immersed in dilute hydrofluoric acid for about 5 minutes, the impurity layers 45f and 45g are removed together with the oxide film.

The wafer from which the impurities 45f and 45g have been removed is subjected to silicon etching as shown at 6 in FIG. 1, so that the N ++ semiconductor layer 45d and the P ++ semiconductor layer 45e are removed and the wafer is cleaned as shown at 7 in FIG. Is done. Thereafter, as shown at 8 in FIG. 1, the wafer is drive-diffused to obtain a predetermined stable semiconductor wafer.

The wafer thus obtained can remove many impurity layers and N ++ semiconductor layers and P ++ semiconductor layers which do not provide semiconductor characteristics at a very high concentration, so that a large number of wafers can be processed at once by batch.

In the above embodiment, the film-type diffusion source is an N-type semiconductor diffusion source and a P-type diffusion source alternately. However, the present invention is not limited to this. A diffusion source can be used, or both sides of the wafer can be P-type diffusion sources. Also,
In the above embodiment, the diode has been described.
The present invention can be applied to other semiconductor devices.

[0017]

According to the semiconductor manufacturing method of the present invention, a large number of removals of impurity layers and very high-concentration semiconductor layers which do not contribute to semiconductor characteristics can be performed at once, and the manufacturing process is simplified and inexpensive. A semiconductor device can be provided.

[Brief description of the drawings]

FIG. 1 is a flowchart of the steps of a method for manufacturing a semiconductor device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a block in the process of FIG. 1;

FIG. 3 is a schematic sectional view of the semiconductor device manufactured according to FIG. 1;

FIG. 4 is a process flowchart of a conventional semiconductor device manufacturing method.

[Explanation of symbols]

 41, 43, 45, 47, 49 Wafers 42, 46 (high-concentration P-type) film-type diffusion source 44, 48 (high-concentration N-type) film-type diffusion source 45a (low-concentration) N-type semiconductor layer 45b (high concentration) N + type semiconductor layer 45c (high concentration) P + type semiconductor layer 45d (very high concentration) N ++ type semiconductor layer 45e (very high concentration) P ++ type semiconductor layer 45f, 45g impurity layer

Claims (1)

[Claims] A diffusion step of stacking and heating a low-concentration wafer and a high-concentration film diffusion source; and separating the wafer by removing the film residue of the film diffusion source with hydrofluoric acid after the diffusion. Forming the oxide film on the surface of the wafer by oxidizing the wafer at a low temperature after separation, removing the oxide film with dilute hydrofluoric acid after the formation of the oxide film, and etching the silicon after removing the oxide film. A method of manufacturing a semiconductor device, comprising: a step of performing drive diffusion after etching.