JPH01262620A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To remove unnecessary impurities before a diffusion process by adding an impurity outdiffusion process. CONSTITUTION:On a P-type semiconductor substrate 2 on which a silicon oxide film 3 is formed in a specified thickness and patterned, a silicon film 5 containing antimony, an N-type impurity, and boron, a P-type impurity, is laminated. Then, putting this in a reducing atmosphere containing H2, a diffusion coefficient of impurity boron which is unnecessary for forming a buried layer in the film 5 becomes big and boron is diffused from the layer 5 and is removed. Next, when this is treated at high temperature, antimony in the film 5 is diffused into the substrate 2 and a good N-type buried layer diffusion region 1 is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for out-diffusion of impurities in a silicon film.

(b) Conventional technology For example, in the manufacturing method of IC, LSI, etc., which is detailed in Japanese Unexamined Patent Publication No. 60-74613, when an impurity diffusion layer is formed on a semiconductor substrate, a spin film is used as a diffusion source film. There is a method using an on-glass membrane.

As a method using such a method, for example, there is a method for forming a buried layer. First, as shown in FIG. A silicon oxide film (32) of a predetermined thickness is formed on a type semiconductor substrate (31>) and patterned using a well-known photolithography technique to obtain a predetermined opening (33).

Next, as shown in FIG. 2(B), for example, in the case of antimony diffusion, a coating solution in which a silicon compound and 5bC1 are dissolved in an organic solvent is applied by spin coating, and baked to form an sb-doped silicate. A glass film (34) is formed, and an N'' type impurity diffusion layer (35) is formed by high temperature treatment using this as a diffusion source.

Furthermore, as shown in FIG. 2(C), the silicon oxide film (3
2) and the silicate glass film (34), an N-type epitaxial layer (34) is grown by a well-known vapor phase growth method.
6) and finally heat-treated to form the diffusion layer (35).
An N0 type buried layer (37) was formed by diffusing impurities.

However, in this method, the N+ type buried layer (37
), it is known that an extremely low concentration P-type diffusion layer <38) is sometimes present in the periphery. For example, Japanese Patent Publication No. 5B-11743, IEEE1'RANS
ACrIONS ON ELECTRON DEVIC
ES, VOL, ED-14, Arashi 7, JUL
Y 1967 P, 381~ etc. are detailed.

In the former publication, donor impurities such as antimony and arsenic, which have a slow diffusion rate, and donor impurities, such as phosphorus, which have a fast diffusion rate, are added by ion implantation, etc., to reduce the adverse effects of P-type impurities. be.

On the other hand, the following may be considered as the reason why the P- type diffusion layer (38) is formed.

First of all, it is not possible to obtain a pure 5bC1 solution, and a very small amount of boron is mixed in from the beginning of the coating solution.

Second, boron, which is trapped in quartz glass or the like that is the material of the diffusion treatment jig, and exists in large quantities, enters the coating liquid during the spin coating process and becomes mixed therein.

During thermal diffusion, boron mixed in the silicate glass film formed by spin coating under these conditions is mixed with sb into the diffusion layer (<35), and is absorbed during and after vapor phase growth. diffused during heat treatment. As a result, since the diffusion coefficient of boron is larger than that of antimony,
Embedding! (37) is surrounded by a low concentration P-type diffusion layer (38
).

(c) Problems to be Solved by the Invention The above-mentioned problems become more pronounced as the impurity concentration of the N-type epitaxial layer (36) is lower, and can occur even if a very small amount of boron infiltrates.

Furthermore, in the technology disclosed in the above-mentioned publication, even if impurities such as phosphorus are added, a P-type diffusion layer (38) is still formed due to processing conditions and external factors. Ta.

(d) Means for Solving the Problems The present application has been made in view of the above-mentioned problems, and involves processing the silicon film (5) having the unnecessary impurities to actively out-diffuse the unnecessary impurities to the outside. Specifically, the diffusion coefficient of the unnecessary impurities is increased in a reducing atmosphere, and the unnecessary impurities are removed before forming the diffusion region.

(*) Effect As described above, the present application is a technology that actively removes boron, which is an unnecessary impurity, before the diffusion process, instead of leaving it remaining in the silicon film (5).

For example, suppose that the silicon film (5) contains antimony, which is an impurity for forming the buried layer (6), and boron, which is an unnecessary impurity.

Since boron in the silicon oxide film has a large diffusion coefficient in a reducing atmosphere, this unnecessary boron is out-diffused to the outside, and the boron concentration in the silicon oxide film decreases.

Therefore, formation of the P- type diffusion layer (38) can be suppressed.

(F) EXAMPLE Hereinafter, an example of the present invention, particularly a method for forming the diffusion layer (1), will be described in detail using FIGS. 1A to 1D.

First, as shown in FIG.
A silicon oxide film (3) of a predetermined thickness is formed on a P-type semiconductor substrate (2) with a plane orientation (1,0,0), and is patterned using a well-known photolithography technique to form a predetermined opening (4).
).

Next, as shown in FIG. 1B, for example, a silicon compound and 5bC
A solution prepared by dissolving 1 in an organic solvent is applied to at least the opening (4) on the semiconductor substrate (2) by spin coating.
to form a silicon film (5).

Here, this silicon film (5) is made of silanol (Si(O
R) a) It is composed of the main components of 5bC1n and a solvent such as methanol and ethyl acetate. Also, in order to allow the solvent to volatilize and form a film, the temperature is about 200°C.
Heat treatment is performed for several minutes.

Furthermore, as stated in the conventional section, it is considered that boron has permeated into the 5bC1 solution in this embodiment.

Further, the silicon film referred to here refers to a glass film formed by this spin coating method, but other examples include a silicon oxide film and a polycrystalline silicon film.

Furthermore, as shown in FIG. 1C, there is a step of out-difusing boron in the silicon film 5.

To describe this step in more detail, the silicon film (5) has become a glass film, which is mostly a silicon oxide film, by the heat treatment in the previous step.

By exposing the silicon film (5) whose main component is a glass film to a reducing atmosphere, the diffusion coefficient of boron in the silicon film (5) can be increased. Therefore, boron in the silicon film (5) rapidly outdiffuses to the outside.

This step is a feature of the present invention, and focuses on the following points. In other words, JOURNAL 0FAPP
LIED PHYSIC5VOL, 35, No.
9 SEPTEMBER1964P, 2695-27
01 states the following:

In other words, it is stated that the diffusion coefficient of boron in silicon oxide is approximately three orders of magnitude larger in an atmosphere where Hl is present than in an N atmosphere.

In the present application, by applying this fact, a glass film (5) whose main composition is silicon oxide is formed on a semiconductor substrate (2) made of silicon. Therefore, the boron present in the glass film (5) is
Outdiffusion to the outside.

However, the atmosphere at this time is N, gas, and hydrogen gas (several percent).
The process is carried out at a temperature of about 1000°C in a reducing atmosphere.

Therefore, antimony for diffusion formation is applied to the silicon substrate (2).
Boron, which is an unnecessary impurity, is out-diffused from the glass film (5) to the outside without being diffused into the silicon substrate (2).

Thereafter, as shown in the first diagram, high temperature treatment is performed to diffuse antimony into the silicon substrate (2).

Therefore, since boron has been out-diffused in the previous process, even when driven in, boron can be further reduced and a good diffusion region (1) can be formed.

As mentioned above, in this example, the unnecessary impurities were boron, and the silicon film (5) was a glass film mainly composed of silicon oxide, but basically, unnecessary impurities and silicon films are made of a glass film mainly composed of silicon oxide. Even if there is, if the diffusion coefficient of the silicon film (5) containing these unnecessary impurities is large, the unnecessary impurities will be out-diffused to the outside.

Next, referring to FIGS. 3A to 3, the buried layer (
The formation method of 6) will be explained.

Since FIGS. 3A to 3D are almost the same as the previous embodiment, the explanation will be simplified.

First, as shown in FIG. 3A, an insulating film (3) is formed on a P-type semiconductor substrate (2), and an opening (4) is formed in this insulating film (3) using a well-known etching method. . Here, the insulating film (3
) is a silicon oxide film formed by a thermal oxidation method, a CVD method, or the like.

Next, as shown in FIG. 3B, a glass film (3) is formed on this semiconductor substrate (2). In this glass membrane (3),
It contains antimony as the first impurity, and although it is preferable that it contains no other impurities, there is a risk that it may contain a very small amount of boron.

Therefore, as shown in FIG. 3C, there is a step of out-difusing the second impurity, boron.

In this step, a heat treatment is performed at approximately 1000° C. in a reducing atmosphere (for example, an atmosphere in which N gas and several percent hydrogen gas are flowing) to out-diffuse boron.

Finally, high temperature treatment is performed to drive in the first impurity, antimony, and then, as shown in the third diagram, after removing the oxide film (3) on the surface of the semiconductor substrate, an N-type epitaxial layer (7) is formed. The upper and lower layers (7
) and (2) to form a buried layer (6).

In this method of forming the buried layer (6), since boron is out-diffused in the step shown in FIG. 3C, boron is formed between the buried layer (6) and the epitaxial layer (7). The occurrence of P-type diffusion (38) can be suppressed.

Next, a method for manufacturing a semiconductor integrated circuit will be described with reference to FIGS. 4A to 4G.

First, as shown in FIG. 4A, a silicon oxide film (3) is formed on a P-type semiconductor substrate (2), and the silicon oxide film (3) is etched to form an opening (4).

Next, as shown in FIG. 4B, a first
A glass film (5) which becomes a silicon film containing antimony as an impurity is coated.

This glass film (5) contains antimony as the first impurity, and although it is preferable that it contains nothing other than antimony, there is a risk that it may contain a very small amount of boron.

Therefore, as shown in FIG. 4C, there is a step in which boron, which is a second impurity, is out-diffused from the glass film (5).

In this step, a heat treatment is performed at approximately 1,000° C. in a reducing atmosphere (for example, an atmosphere in which N gas and several percent hydrogen gas are flowing) to out-diffuse boron.

Next, as shown in the fourth diagram, after further high temperature treatment is performed to drive in the first impurity, antimony, the substrate (
2) Remove the upper oxide film (3), apply VtJi to the N-type epitaxial layer (7), and heat the upper and lower layers (7) at a predetermined temperature.
(2) to form a buried layer (6).

Next, as shown in FIG. 4E, there is a step of forming an isolation region (8) within the epitaxial layer (7).

The epitaxial H (7) is of N type conductivity type,
Further, the isolation region (8) surrounds the buried layer (6) and reaches the semiconductor substrate (2). Therefore, this separation area (8
) to form an island region (9).

Finally, as shown in FIGS. 4F and 4G, the island area (9
) includes a process of forming semiconductor elements.

Here, a transistor is formed within the island region (9), but other materials such as a diode are also conceivable. In the above steps, a P-type diffusion layer (38) is formed around the buried layer (6).
Since the occurrence of can be suppressed, the collector resistance can be set to the designed value.

FIG. 6 shows the relationship between the boron concentration in the glass film (5) and the boron concentration in the P- layer (38) in the epitaxial layer (7). Here, boron was intentionally added to the glass membrane,
The measurements were taken after the buried layer was formed. As can be seen from the figure, compared to the conventional method, the method of the present application has a
- The boron concentration of the layer can be lowered by about one order of magnitude, and even if the impurity concentration of the epitaxial layer (7) is low, the generation of the P''' type diffusion layer (38) can be suppressed.

Further, FIGS. 5A to 5G show a method of manufacturing a semiconductor integrated circuit using upper and lower separation.

Basically, it is the same as FIGS. 4A to 4G, but since the upper and lower separated diffusion regions (11) are used, FIGS.
As shown in Figure E, it is necessary to deposit diffused sources of opposite conductivity type on the semiconductor substrate (2).

Therefore, the glass film containing antimony as the first impurity (
5), out-diffusion of the second impurity boron, and subsequent initial diffusion, the silicon corresponding to the lower diffusion region (12) of the upper and lower isolation region (11) is formed as shown in the fifth diagram. A glass film (14) containing boron is formed by opening the oxide film region (13), and this lower diffusion region (
12) initial diffusion to form.

Here, since boron is used in the separation region (11),
By performing the initial diffusion of antimony first, the buried and separated regions (6) and (12) of a predetermined shape can be formed.

Subsequently, as shown in FIG. 5E, after laminating an epitaxial layer (7), high-temperature treatment is performed to drive in antimony for embedding and boron for separation, and further, as shown in FIG. 5F,
forming an upper diffusion region (15) and forming an upper diffusion region (15);
12), and a semiconductor element is formed in the island region (9) surrounded by this isolation region (Dan) as shown in FIG. 5G.

(G) Effects of the Invention As is clear from the above description, unnecessary impurities in the silicon film can be out-diffused to the outside, so that semiconductor elements that can be formed in a semiconductor substrate can be formed satisfactorily.

In particular, a P′″ type diffusion layer (38
), and the characteristics (for example, collector resistance) of the semiconductor element can be formed favorably.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIGS. 1A to 1D1, FIGS. 3A to 3D1, FIGS. 4A to 4G, and FIGS. 5A to 5G are semiconductors of the present invention. FIGS. 2A to 2C are cross-sectional views of a semiconductor device for explaining a method for manufacturing the device, and FIG. 6 is a cross-sectional view of a semiconductor device for explaining a conventional method for manufacturing a semiconductor device. FIG. 3 is a diagram showing the boron concentration with respect to a P-type diffusion layer in an epitaxial layer. (2)...Semiconductor substrate, (5)...Silicon film,
(6)...Embedded layer.

Claims (10)

[Claims] (1) A step of forming a silicon film having a first impurity and a second impurity of a conductivity type opposite to that of the first impurity on a semiconductor substrate; and a step of out-difusing the second impurity. A method for manufacturing a semiconductor device, comprising at least the steps of: diffusing the first impurity into a semiconductor substrate. (2) The method for manufacturing a semiconductor device according to claim 1, wherein the out-diffusion is performed in a reducing atmosphere. (3) The method for manufacturing a semiconductor device according to claim 1 or 2, wherein the second impurity is boron and the silicon film is silicon oxide. (4) forming a silicon film having a first impurity and a second impurity of a conductivity type opposite to the first impurity on a semiconductor substrate of one conductivity type; a step of fusion, a step of diffusing the first impurity into the semiconductor substrate, a step of forming an epitaxial layer of an opposite conductivity type after removing the silicon film on the semiconductor substrate, and a step of diffusing the first impurity into the epitaxial layer. 1. A method for manufacturing a semiconductor device, comprising at least the step of diffusing an impurity. (5) The method for manufacturing a semiconductor device according to claim 4, wherein the out-diffusion is performed in a reducing atmosphere. (6) The method for manufacturing a semiconductor device according to claim 4 or 5, wherein the second impurity is boron and the silicon film is silicon oxide. (7) forming a diffusion opening in an insulating film formed on a semiconductor substrate of one conductivity type; a step of out-difusing the second impurity; a step of diffusing the first impurity into the semiconductor substrate through the diffusion opening; a step of removing an upper insulating film and forming an epitaxial layer of opposite conductivity type; a step of diffusing the first impurity into the epitaxial layer; a step of forming an isolation region in the epitaxial layer; 1. A method of manufacturing a semiconductor device, comprising at least the step of forming a semiconductor element in an island region surrounded by regions. (8) The method for manufacturing a semiconductor device according to claim 7, wherein the out-diffusion is performed in a reducing atmosphere. (9) The method for manufacturing a semiconductor device according to claim 7 or 8, wherein the second impurity is boron and the silicon film is silicon oxide. (10) The method of manufacturing a semiconductor device according to claim 7, 8, or 9, wherein the lower diffusion region of the upper and lower isolation regions is formed after the step of out-difusing the second impurity.