JPH01262621A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To control an impurity density without ion implantation, by outdiffusing an impurity of a first semiconductor film on a substrate via a second semiconductor film which is formed on the first film and has a large impurity diffusion coefficient. CONSTITUTION:On a semiconductor substrate 1, a first semiconductor film 2 such as a polysilicon film which contains an unnecessary impurity such as boron is formed. A second semiconductor film 3 such as a silicon dioxide film which has a large diffusion coefficient of boron is formed on the film 2 by a thermal oxidation method or another method. When this is exposed to a reducing atmosphere containing H2 to be heat-treated, boron in the film 1 is outdiffused via the film 2, resulting in the reduction of boron density in the film 1. By this method, a semiconductor device having such a semiconductor film as has good characteristics can be manufactured with an impurity density controlled easily, accurately and rapidly by the use of a heat treatment furnace without ion implantation.

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-diffusing impurities in a semiconductor film to the outside.

(b) Conventional Technology In recent years, research has been conducted into techniques for forming a semiconductor film, such as a polysilicon layer, on a semiconductor substrate and controlling the impurity concentration of this polysilicon to form transistors, diodes, resistors, and the like.

For example, JP-A-60-3161, JP-A-60-4
5050, JP-A-61-129859, etc. These can form semiconductor elements three-dimensionally,
This is a very effective method because it can improve the packaging density.

The figures shown in Figures 3A to 3 are Japanese Patent Application Laid-Open No. 61-129.
The technology of Publication No. 859 will be explained. First, as shown in FIG. 3A, an insulating film (31) is formed on a semiconductor substrate (31).
32) is formed, and polysilicon (33) is formed on this insulating film (32) by a CVD method or the like, and then etched into the shape of the intended resistor.

Next, as shown in FIG. 3B, a mask for ion implantation (34
) (e.g. photoresist) on the polysilicon (33).
There is a step of opening a region (35) which becomes a high-resistance material.

Furthermore, as shown in FIG. 3C, there is a step of performing ion implantation. Here, when ions are implanted into the high resistance region (35) and polysilicon with a high concentration of boron is used, for example,
Phosphorus, arsenic, antimony, etc., which are of the conductivity type opposite to boron, are ion-implanted to form a high-resistance region 35).

Finally, as shown in the third diagram, an insulating film (37) is formed on the semiconductor substrate (31) and the resistor layer, the high concentration region (38) where ions were not implanted is opened, and an aluminum electrode (39) is formed. There is a step of vapor depositing to form electrodes.

In addition, Fig. 4A to Fig. 4 are published in Japanese Unexamined Patent Publication No. 60-45050.
This describes the technology of the publication, as shown in Figure 4A, a thermal oxide film (42) is formed on a semiconductor substrate (41), and polysilicon is deposited on this thermal oxide film (42) by CVD. A film (43) is formed, and a thinner silicon oxide film (4) is formed.
4), there is a step of forming a silicon nitride film (45). Here, this silicon nitride film (45) is
All parts except those that will become future resistance elements have been removed.

Next, as shown in FIG. 4B, this silicon nitride film (45)
There is a step of converting polysilicon (43) other than under the silicon nitride film (45) into a silicon oxide film (46) by utilizing it as an oxidation-resistant film.

Furthermore, as shown in FIG. 4C, there is a step of implanting boron ions using the photoresist film (47) as an ion implantation mask.

Finally, as shown in the fourth diagram, the region (48) into which boron was implanted at a high concentration was opened to form an aluminum electrode (49).

Furthermore, the technique disclosed in Japanese Patent Application Laid-Open No. 60-3161 uses polysilicon, which will not be explained here, and forms polysilicon containing boron across the PN junction. The surface of the substrate is made of P to facilitate the expansion of the depletion layer.

As described above, polysilicon is formed on a semiconductor substrate, and this polysilicon is used to form semiconductor elements such as transistors, diodes, and resistors.

(c) Problems to be Solved by the Invention As explained above, after introducing impurities into the semiconductor films (33) and (43), in order to control the concentration of some impurities again, it is necessary to introduce impurities of the same conductivity type as this impurity. Alternatively, it is necessary to ion-implant impurities of the opposite conductivity type.

On the other hand, ion implantation requires expensive equipment and does not have a processing capacity per wafer, so the above-mentioned method has the problem of increasing costs.

(d) Means for Solving the Problems The present invention has been made in view of the above-mentioned problems, and includes a step of forming a first semiconductor film (2) containing an impurity on a semiconductor substrate (1), and a diffusion coefficient of the impurity. A second semiconductor film with a large
3) is solved by a step of forming the semiconductor layer on the first semiconductor film (2) and a step of out-difusing the impurity through the second semiconductor film (3).

(*) Effect The present invention is a technique for actively removing impurities rather than allowing them to remain in the semiconductor film (2).

For example, on polysilicon containing boron as an impurity,
When a silicon oxide film is formed using a thermal oxidation method and then heat treated in a reducing atmosphere, the diffusion coefficient of boron within the silicon oxide film increases, and boron is released to the outside through this silicon oxide film. Diffuse.

Therefore, the impurity concentration in polysilicon, which is the semiconductor film (2), decreases.

(f) Example Embodiments of the present invention will be described in detail below with reference to the drawings.

First, a method for manufacturing a semiconductor device according to the present invention, particularly a method for out-diffusion of impurities to the outside, will be described in detail with reference to FIGS. 1A to 1C.

As shown in FIG. 1A, there is a step of forming a first semiconductor film (2) containing impurities on a semiconductor substrate (1).

Here, a silicon semiconductor substrate is used as the semiconductor substrate (1), and a polysilicon film is used as the first semiconductor film (2). This polysilicon film (2) contains boron as an impurity.

Next, as shown in FIG. 1B, there is a step of forming a second semiconductor film (3) having a large diffusion coefficient of impurities on the first semiconductor film (2).

Here, impurities should be out-diffused to the outside in the polysilicon film (2) [In (4), a silicon oxide film (3) is formed by a thermal oxidation method, etc., and the area other than that is Forms a film (5) having a very small boron diffusion coefficient, such as a silicon nitride film. This film (5) only needs to have a small diffusion coefficient, and may be coated with other metals or the like.

Furthermore, as shown in FIG. 1C, there is a step of out-difusing the impurity through the second semiconductor film (3).

Here, this semiconductor substrate (1) is placed in a heat treatment furnace, and N
Heat treatment is performed at about 1000°C in a reducing atmosphere by flowing gas and hydrogen gas (several percent). Then, boron, which is an impurity in the polysilicon film (2), out-diffuses to the outside via the silicon oxide film (3).

This step is a simultaneous feature of the present invention, and by increasing the diffusion coefficient of the second semiconductor film (3), impurities in the first semiconductor film (2) can be out-diffused to the outside. .

“ This focuses on the following points.
RNAL OF APPLIED PHYSIC5VO
L, 35, No, 9SEPrEMBER1964P,
2695-P, 27Q1 states the following.

It is stated that the diffusion coefficient of boron in silicon oxide is approximately three orders of magnitude larger in an atmosphere containing H8 than in a N atmosphere.

The present invention applies this fact to form a silicon oxide film (3) on a polysilicon film (2), greatly increases the diffusion coefficient of boron in this silicon oxide (3) using the above-mentioned technique, and (2) This silicon oxide film (3)
out-diffusion through. Therefore, it is possible to reduce impurities in polysilicon (2).

Here, if a semiconductor element is formed within the semiconductor substrate (1) and a semiconductor element is further formed using this polysilicon to form a circuit, the impurity concentration in this polysilicon can be controlled, so that the circuit characteristics can be controlled.

Further, in this example, the formation of the second semiconductor film (3) and the out-diffusion were performed in separate steps, but they may be performed in the same step.

For example, here, the heat treatment may be performed in an atmosphere in which an oxidizing atmosphere and a reducing atmosphere are mixed. To explain in more detail,
This can be achieved by flowing steam into a reducing atmosphere containing nitrogen gas and hydrogen gas. This is because steam forms a silicon oxide film and out-diffusion occurs in a reducing atmosphere.

Next, another embodiment will be described in detail using FIGS. 2A to 2D. This will be explained using the method of forming a resistor described in the section of the prior art.

First, as shown in FIG. 2A, there is a step of forming a first semiconductor film (23) containing impurities via an insulating film (22) formed on a semiconductor substrate (21).

Before this step, although not shown in the drawing, there is a step of forming semiconductor elements in the semiconductor substrate (21).Transistors, diodes, etc. are formed in a well-known step, and then oxidized by thermal oxidation method etc. An insulating film (22) such as a silicon film is formed. Subsequently, a polysilicon film (23) containing boron as an impurity is formed on this insulating film (22).

Further, this polysilicon film (23) is etched into a predetermined shape,
The desired resistance value can be obtained by controlling the thickness, width, length, and impurity concentration of the polysilicon film.

Next, as shown in FIG. 2B, the second semiconductor film (24) having a large diffusion coefficient of impurities is transferred to the first semiconductor film (23).
) There is a process of forming on top.

Here, first, a film having a small boron diffusion coefficient (2.degree. 5), a silicon nitride film, a metal, etc., which serves as a so-called diffusion prevention film, is formed in a region where boron is not out-diffused. After that, a silicon oxide film that will become the second semiconductor film (24) is formed by, for example, a thermal oxidation method, a CVD method, or the like in order to cause out-diffusion of boron.

Furthermore, as shown in FIG. 2C, the second semiconductor film (24)
There is a step of out-difusing the impurities through the second semiconductor film (24) and forming a semiconductor element in this second semiconductor film (24).

Here, first, the semiconductor substrate (21) is placed in a heat treatment furnace, and N gas and hydrogen gas (several percent) are flowed to create a reducing atmosphere, and heat treatment is performed at about 1000°C. Then, boron in the polysilicon film (23), which is the first semiconductor film, out-diffuses through the silicon oxide film (24), which is the second semiconductor film.

This step is performed simultaneously in the present invention, and by increasing the diffusion coefficient of boron in the second semiconductor film (24), impurities in the first semiconductor film (23) are out-diffused to the outside. can do.

Therefore, since both ends of the resistor can be made highly doped and the central resistance region can be made low doped, it is possible to obtain the intended resistor, which is a semiconductor element.

Of course, by changing conditions such as hydrogen gas concentration and temperature,
It goes without saying that the out-diffusion efficiency can be controlled.

Semiconductor elements that can be considered here include transistors, diodes, capacitors, fuses, etc., and can be built into the first semiconductor film (23) or by stacking semiconductor films.

Finally, as shown in the second diagram, the second semiconductor film (24)
There is a step of forming an electrode (27) on a semiconductor element formed from the semiconductor element in the semiconductor substrate (21) and the second semiconductor film (23) to form a semiconductor circuit.

Since a resistor is formed here, the insulating film (29) corresponds to the high concentration region (28) of the resistor
) and insert the aluminum electrode (
27). Therefore, the semiconductor element within the semiconductor substrate (21) and the semiconductor element formed by the first semiconductor film (23) can be connected in a circuit manner, and a semiconductor device having a predetermined function can be manufactured.

Furthermore, as explained in the previous example, the second semiconductor film (
24) and the out-diffusion process may be performed in the same process.

(g) As described in detail of the invention, the impurity concentration of the semiconductor film formed on the semiconductor substrate can be out-diffused to the outside, and this can be done in a heat treatment furnace, so the processing capacity can be greatly increased.

In addition, since the impurity concentration of the semiconductor film can be selectively controlled,
It is possible to form a semiconductor element configured with this semiconductor film with good characteristics.

[Brief explanation of the drawing]

1A to 1C1, 2A to 2D are cross-sectional views showing the manufacturing method of the semiconductor device of the present invention, 3A to 3D, and 4A to 4D. 1 is a cross-sectional view showing a conventional method of manufacturing a semiconductor device. (1)...Semiconductor substrate, (2)...First semiconductor film, (3>...Second semiconductor film, (21)...Semiconductor substrate, (23)...First semiconductor film, (24)
...Second semiconductor film.

Claims (14)

[Claims] (1) A step of forming a first semiconductor film having an impurity on a semiconductor substrate; a step of forming a second semiconductor film having a large diffusion coefficient of the impurity on the first semiconductor film; A method for manufacturing a semiconductor device, comprising at least a step of out-diffusing the impurity through the semiconductor film. (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 impurity, the first semiconductor film, and the second semiconductor film are boron, a polysilicon film, and a silicon oxide film, respectively. (4) The method for manufacturing a semiconductor device according to claim 1, 2, or 3, wherein a semiconductor element is formed on the semiconductor substrate and the first semiconductor film, respectively. (5) forming a first semiconductor film having an impurity on a semiconductor substrate; and forming a second semiconductor film having a large diffusion coefficient of the impurity on the first semiconductor film; A method for manufacturing a semiconductor device, comprising at least a step of out-diffusing the second impurity through a semiconductor film. (6) The method for manufacturing a semiconductor device according to claim 5, wherein the out-diffusion is performed in a state in which a reducing atmosphere and an oxidizing atmosphere coexist. (7) The method for manufacturing a semiconductor device according to claim 5 or 6, wherein the impurity, the first semiconductor film, and the second semiconductor film are boron, a polysilicon film, and a silicon oxide film, respectively. (8) The method for manufacturing a semiconductor device according to claim 5, 6, or 7, wherein a semiconductor element is formed on the semiconductor substrate and the first semiconductor film, respectively. (9) forming a semiconductor element in a semiconductor substrate; forming a first semiconductor film containing an impurity on an insulating film formed on the semiconductor substrate; and a second semiconductor film having a large diffusion coefficient of the impurity. a step of forming a semiconductor film on the first semiconductor film; a step of out-diffusing the impurity through the second semiconductor film and forming a semiconductor element on the first semiconductor film; A method for manufacturing a semiconductor device, comprising at least the step of forming an electrode on a semiconductor element in a semiconductor substrate and a semiconductor element formed by the first semiconductor film to form a semiconductor circuit. (10) The method for manufacturing a semiconductor device according to claim 9, wherein the out-diffusion is performed in a reducing atmosphere. (11) The method for manufacturing a semiconductor device according to claim 9 or 10, wherein the impurity, the first semiconductor film, and the second semiconductor film are boron, a polysilicon film, and a silicon oxide film, respectively. (12) The method of manufacturing a semiconductor device according to claim 9, wherein the formation of the second semiconductor film and the out-diffusion are performed simultaneously. (13) The method for manufacturing a semiconductor device according to claim 2, wherein the out-diffusion is performed in a state in which a reducing atmosphere and an oxidizing atmosphere coexist. (14) The method for manufacturing a semiconductor device according to claim 12 or 13, wherein the impurity, the first semiconductor film, and the second semiconductor film are boron, a polysilicon film, and a silicon oxide film, respectively.