JPS61280670A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain diffused regions which have different depths in a same diffusion process by employing doped oxide which is doped with a high concentration impurity of the same conductive type. CONSTITUTION:After an opposite conductive type epitaxial layer 2 is deposited on a semiconductor substrate 1, a silicon oxide film 3 is formed and the first gate diffusion aperture 4 and the second gate diffusion aperture 5 are drilled. Then the first semiconductor films 6 are formed. After that, the second semiconductor film 7 which is doped with a high concentration impurity of the same conductive type is formed above the region for a deep diffused layer to be formed in the epitaxial layer 2. As a diffusion process is carried out after the doped oxide 7 which is doped with a high concentration impurity of the same conductive type is further formed on the polycrystalline silicon film 6 corresponding to a deep diffused layer 8, the quantity of the impurity is larger on this polycrystalline silicon film 6 than on the other polycrystalline silicon film 6 by the quantity of the impurity in the doped oxide 7 so that the diffused regions which have different depths can be obtained in the same diffusion process. Finally, after the diffusion process is carried out, the doped oxide film 7 is removed and the polycrystalline silicon films 6 to be used as electrodes 6 are etched to have the predetermined shapes.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Field of Industrial Application The present invention relates to a method of manufacturing a semiconductor device, and particularly relates to a method of manufacturing a semiconductor device having regions of different diffusion depths within the same substrate.

(B) Prior Art As mentioned above, the present invention relates to a method of manufacturing a semiconductor device having regions with different diffusion depths within the same substrate, and in particular, the explanation will be given here using a dual-gate junction FET. .

Figure 4 shows the dual gate junction FET.
A cross-sectional view is shown. The feature of this FET is that it has two gate regions, and the diffusion depths of the first gate (8) and the second gate (9) are different, and this difference in diffusion depth must be precisely controlled. be. In addition, since the structure has a fine pattern and shallow diffusion, the two gate regions (8) (
9) Formation requires some ingenuity.

Generally, as shown in Figure 2 (a), after laminating an epitaxial layer (2) of the opposite conductivity type on a semiconductor substrate (1) of one conductivity type, a first gate diffusion layer is formed in the oxide film (3) using an etching method. Hole (
4) and a second gate diffusion hole (5) are formed.

Next, as shown in FIG. 2(B), the second gate diffusion hole (5) is covered with an impurity permeation prevention film (T) (eg, photoresist), and P-type impurities (eg, boron) are ion-implanted.

Therefore, the P-type impurity ions are implanted only into the first gate region (8).

Subsequently, as shown in FIG. 2(c), after removing the photoresist (a), the P-type impurity is ion-implanted into the first gate region (8) and the second gate region (9) again.

Therefore, the first gate region (8) and the second gate region (9)
) there is a difference in the amount of ions implanted.

Finally, heat diffusion treatment is performed as shown in Figure 2), and the electrode (
b) to form. Therefore, the first gate region (8) can be diffused deeper than the second gate region (9). Further, this difference in diffusion depth can be controlled by changing the amount of ion implantation.

Another method is Japanese Patent Publication No. 60-8623 (No. 3
As shown in FIG. ) and the second
A gate diffusion hole (5) is formed.

Next, as shown in FIG. 3(b), polysilicon (6) containing no impurities is laminated on the semiconductor substrate (2), and then the polysilicon film (6) corresponding to the second gate region (9) is laminated on the semiconductor substrate (2).
) An impurity permeation prevention film (g) (for example, silicon oxide film or photoresist) is formed on the film. After that, P-type impurity ions are implanted. Here, the amount of ions implanted into the polysilicon (6) under the impurity permeation prevention film (6) becomes relatively small.

Finally, as shown in FIG. 3(C), thermal diffusion treatment is performed, and the poly-silicon film (6) is etched and used as it is as an electrode (6).

(c) Problems to be solved by the invention In the method explained in FIGS. 2(a) to 2(b) or FIGS. 3(a) to 3(c), the first gate region (
8) and the diffusion depth of the second gate region (9) can be controlled, but it has the following drawbacks.

First, in the method shown in Figures 2 and 2), (1) ions are directly implanted into the silicon substrate (2), which induces crystal defects and increases leakage current;
) (9) is shallow, so aluminum spikes are likely to occur; and (3) costly ion implantation is used twice.

Furthermore, in the methods shown in Figures 3 (a) to 3 (c), (1
) The impurity permeation prevention film (g) requires precision in controlling the film thickness because the amount of impurities entering the semiconductor substrate (2) changes rapidly due to a slight difference in film thickness. (2) Figure 3 Although the polysilicon film (6) is used as an electrode as in (c), it has drawbacks such as the need for extremely large amounts of costly ion implantation in order to reduce the resistance.

B.) Means for Solving the Problems The present invention has been made in view of the above drawbacks, and includes an impurity of one conductivity type corresponding to the deep diffusion region (8) formed on the semiconductor substrate (2). The first semiconductor film (6
), a second semiconductor film (7) doped with impurities of the same conductivity type at a high concentration is deposited, and then heat treatment is performed to diffuse the semiconductor film (7) into the semiconductor substrate (2). This will solve the problem.

(e) A first semiconductor film (6) doped with conductive impurities at an appropriate concentration, for example a polysilicon film, corresponding to the deep diffusion region (8) formed in the semiconductor substrate (2). When a second semiconductor film (7) doped with impurities of the same conductivity type at a high concentration, for example, doped oxide, is deposited on the polysilicon film (6) and then subjected to a diffusion process, the deep diffusion region (8) is formed. Since the diffusion source to be formed has a larger amount of impurities corresponding to the doped oxide, diffusion regions with different depths can be formed by the same diffusion.

On the other hand, the second semiconductor film (7) formed on the polysilicon film (6) serves as an out-diffusion prevention film from the first semiconductor film (6), and the second semiconductor film (7)
) is diffused into the first half, the conductor film (6), so that the sheet resistance of the first semiconductor film (6), which becomes the electrode (6), can be reduced.

Furthermore, since ion implantation is not performed, no crystal defects occur, and leakage current and aluminum spikes are prevented.

(F) Embodiment An embodiment of the method for manufacturing a semiconductor device according to the present invention will be described below with reference to FIGS. 1(A) to 1(C). Here, dual gate junction FE
Although the description will be made using T, the same applies to other semiconductor devices.

As shown in FIG. 1(a), first, a semiconductor substrate of one conductivity type (1
) after laminating an epitaxial layer (2) of opposite conductivity type,
A silicon oxide film (3) is formed on the semiconductor substrate (2) using a thermal oxidation method or the like, and a first gate diffusion hole (4) and a second gate diffusion hole (4) are formed in the silicon oxide film (3) using a photolithography method. A gate diffusion hole (5) is opened.

Next, as shown in FIG. 1(B), a first semiconductor film (6), such as a polysilicon film, doped with an impurity of one conductivity type, such as boron, is formed on the semiconductor substrate (2).

After that, boron, which is an impurity made of the same conductivity, is further added to a high concentration on the deep diffusion region (in this case, the polyimide film (6) corresponding to the first gate region (8)) formed in the semiconductor substrate (2). A second doped semiconductor film (7) is formed, for example a doped oxide film.

This step is a feature of the present invention, in which a doped oxide (7) doped with an impurity of the same conductivity type is deposited on the polysilicon film (6) corresponding to the deep diffusion region (8). Since the diffusion process is performed after this, the amount of impurities in the doped oxide increases, making it possible to perform diffusion to different depths with the same diffusion.

Furthermore, since ion implantation is not performed, no crystal defects occur and leakage current can be prevented. Furthermore, by using polysilicon, it is possible to prevent aluminum spikes from occurring due to electrode formation.

Finally, after performing a diffusion process as shown in FIG. 1(C), the doped oxide (7) is removed and the polysilicon (6) used as the electrode (6) is etched into a predetermined shape.

This step is a feature of the present invention, in which the doped oxide (
7) is when impurities in the first semiconductor film (6) go out to the outside.
It becomes a so-called out-diffusion prevention film. Also, some of the impurities in the doped oxide (7) are absorbed by the electrode (
6) because it is diffused into the polysilicon film (6),
The sheet resistance of this polysilicon film (6) can be further reduced.

(G) Effects of the Invention As is clear from the above description, the present invention has the following advantages: (1) By using doped oxide (7) doped with highly concentrated impurities of the same conductivity type, the depth can be increased by the same diffusion. Different diffusions are possible. (2) Since ion implantation is not performed, no crystal defects occur and leakage current can be prevented. It is also possible to prevent aluminum spikes from occurring due to electrode formation. Furthermore, since no ion implantation is required, costs can be reduced.

(3) Furthermore, since the doped oxide (7) serves as an out-diffusion prevention film for the polysilicon film (6), the impurities in the polysilicon film (6) can be effectively utilized.

(4) Since the impurity of the doped oxide (7) diffuses into the polysilicon film (6), the sheet resistance can be further reduced. (5) Also, impurity permeation prevention film←O
Although thick film precision was required in the present invention, precision is not required in the present invention and the manufacturing process can be simplified.

[Brief explanation of drawings]

1(A) to 1(C) are cross-sectional views showing a method for manufacturing a semiconductor device having regions with different diffusion depths, which is an embodiment of the present invention, and FIGS. 2(A) to 2(C) ) and FIGS. 3(a) to 3(c) are cross-sectional views showing a conventional method for manufacturing a semiconductor device having regions with different diffusion depths, and FIG. be. Explanation of the main drawing numbers (1) is - conductivity type semiconductor substrate, (2) is opposite conductivity type epitaxial layer, (3) is silicon oxide film, (4)
is the first gate diffusion hole, (5) is the second gate diffusion hole, and (6) is the second gate diffusion hole.
) is the first semiconductor film, (7) is the second semiconductor film, (8)
is the first gate region, and (9) is the second gate region. Applicant Sanyo Electric Co., Ltd. and 1 other representative Patent attorney Shizuo Sano 6 Figure 3 C δ 9 Hayabusa Figure 4

Claims (1)

[Claims] (1) In a method for manufacturing a semiconductor device, in which at least two diffusion regions having different diffusion depths are formed in a semiconductor substrate using a semiconductor film doped with a predetermined impurity, the semiconductor device is formed on the semiconductor substrate. A second semiconductor film doped with impurities of the same conductivity type at a high concentration is deposited on the first semiconductor film doped with impurities of one conductivity type corresponding to the deep diffusion region, and then heat-treated to make the semiconductor film thinner than the semiconductor film. A method for manufacturing a semiconductor device characterized by performing a diffusion process on a semiconductor substrate.