JPS5944867A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To enable the ion implantation at a low acceleration voltage by a method wherein impurity atoms are ion-implanted after a part of the Si dioxide film on a region scheduled for forming a semiconductor element is made thinner than the other part, and heat treatment is performed in non-oxidizing atmosphere and oxidizing atmosphere. CONSTITUTION:An N type low resistant buried layer 12 is formed on a P type Si substrate 11. Successively, an N type Si epitaxial layer 13 is formed. Next, a P type element isolation region 14 is formed, and then an SiO2 film 15 is formed on the layer 13. Here, the SiO2 film 16 on the region for the base of a transistor is thinned. Thereafter, B<+> atom is ion-implanted onto the substrate 13, resulting in the formation of an ion implanted region 17. It is heat-treated in non-oxidizing N2 gas atmosphere and oxidizing wet O2 gas atmosphere. As the result, a B diffused layer 19 of a fixed thickness and an SiO2 film 20 on the layer 19 are formed.

Description

[Detailed description of the invention] (a) Technical field of the invention The present invention relates to an improvement in a method for manufacturing a semiconductor device.

■) Background of the technology A method of forming a semiconductor element by ion-implanting predetermined impurity atoms into a region where the element is to be formed in a semiconductor substrate such as a silicon (Si) substrate is a method in which the impurity diffusion region formed after implantation is formed shallowly. It is well known that it is widely used in the manufacture of semiconductor devices that operate at high speed.

(0) Prior Art and Problems A conventional method for manufacturing bipolar resin C using such an ion implantation method will be described with reference to FIG.

First, a buried layer 2 is formed by diffusing or ion-implanting N and ip impurity atoms, such as antimony (Sb), in a P-type Sj-substrate pattern.

Thereafter, two N-type silicon epitaxial layers 3 are formed on the substrate 1.
After that, P-type impurity atoms such as poron (B) are diffused in a predetermined pattern to form element isolation regions 4.

Next, silicon dioxide (si, o
2) Forming a film 5 with a thickness of 8000 to 4000 nm by thermal oxidation of the substrate.

After that, a photoresist film is applied on the substrate to a thickness of l-1,5μt.
A predetermined pattern is formed on the region where the base is to be formed by exposure to light and development. In the figure, 6 is a photoresist film formed in this manner. Next, boron (B+) atoms are ion-implanted from above the substrate as shown by arrow A, and then the substrate is introduced into a reaction tube, and oxygen (02) gas that has passed through water is introduced into the reaction tube. So-called Wet0
The reaction tube was heat-treated under a 2i atmosphere, and the SQL substrate into which 10 B atoms were ion-implanted was heat-treated to diffuse the implanted 10 B atoms.

However, in this conventional method, due to the ten B atoms ion-implanted on the Si substrate surface, the S1 atoms of the Si crystal after implantation are not regularly arranged in the Sl crystal lattice, and therefore The atomic arrangement is disordered,
Therefore, the introduced 02 gas and the S protruding from the crystal lattice
Due to the reaction of i atoms, the surface of the Si substrate becomes rough, resulting in drawbacks such as a decrease in breakdown voltage as an element characteristic.

In addition, the parasitic MO of the transistor formed in the later process described above
3 S:lO2 film 5 to reduce the effect is 3000 ~
It is quite thick with 4,000 people, so part 5
In order to ion-implant (B+) atoms through the in2 film, it is necessary to raise the acceleration voltage to about 180 eV, which requires a large-scale ion implantation device or a large acceleration voltage. Therefore, the crystal plane of the Si substrate is disturbed or roughened.

OBJECT OF THE INVENTION The present invention aims to provide a novel method for manufacturing a semiconductor device that eliminates the above-mentioned drawbacks, does not require a large-scale ion implantation device, and prevents the crystal plane of a Si substrate from becoming rough after ion implantation. This is the purpose.

(θ) Structure of the Invention In order to achieve the above object, the method for manufacturing a semiconductor device of the present invention provides a semiconductor device manufacturing method in which a silicon dioxide film is formed on the surface and a semiconductor element formation area of a silicon substrate is defined by an element isolation area. When manufacturing a semiconductor device having a step of forming a semiconductor element region by ion-implanting impurity atoms for element formation into the substrate, a part of the silicon dioxide film on the area where the semiconductor element is to be formed of the substrate is made thinner than other areas. The method is characterized by including the steps of ion-implanting impurity atoms from the substrate, heat-treating the substrate in a non-oxidizing atmosphere, and then heat-treating the substrate in an oxidizing atmosphere.

(f) Embodiment of the Invention An embodiment of the invention will be described in detail below with reference to the drawings. FIG. 2 to FIG. 7 are main part sectional views showing the steps of the method for manufacturing a semiconductor device of the present invention.

First, as shown in FIG. 2, N-type impurity atoms, such as sb, are diffused in a predetermined pattern onto a P-type 81 substrate
After forming the type low resistance buried layer 121r, an N type 81 pitaxial layer 13 is formed on the substrate.

Next, P type impurity atoms, for example B, are diffused onto the substrate in a predetermined pattern to form a P type element isolation region 141. Next, an 8102 film 15 having a thickness of approximately 8000 angstroms is formed on the epitaxial layer 18 by thermal oxidation of the substrate. This Si,02 film prevents the substrate surface from converting from N type to JP type, or prevents phenomena such as parasitic MOS effects that occur in transistors when semiconductor elements such as transistors are formed on the substrate in a later process. It is intended to remove.

Next, using a photoresist film (not shown) with a predetermined pattern formed on the substrate as a mask, a plasma etching method or the like is performed to remove SiO2 on the region where the base x of the transistor is to be formed.
The film is formed by etching into a predetermined pattern as shown in FIG.

Next, as shown in FIG. 4, the substrate is thermally oxidized at a low temperature of about 800 DEG C., and the surface of the substrate exposed by the patterning is oxidized again to form a thin Si.sub.2 film 16 of approximately 500 layers.

The 5102 film 16 can also be formed by etching after forming a thick oxide film 16.

Next, as shown in FIG. 5, ten B atoms are ion-implanted onto the substrate 18 from the direction of arrow B under the conditions of an acceleration voltage of 50 KeV and a dose of 8XIO14/ad.

In this way, the SiO2 film 16 on the part where the pace region is to be formed by ion implantation is formed as thin as 500, so the accelerating voltage is lower than in the conventional method, and therefore large-scale ion implantation is possible. There is no need for an implantation device, and the crystal plane on the surface of the S1 substrate after ion implantation is less damaged than before, and a P-type B+ ion implantation region 17 is formed.

Next, the substrate is introduced into a reaction tube in a non-oxidizing nitrogen (N2) gas atmosphere and heat-treated at a temperature of 1170° C. for 40 minutes. Then, the crystal on the surface of the S1 substrate after ion implantation is S1
The atoms are displaced from their normal interstitial positions, but when heat treated with non-oxidizing gas, these displaced Si atoms do not react much with the non-oxidizing N2 gas. Therefore, the Si substrate is heat-treated without causing much roughness of the crystal plane on the substrate surface. By this heat treatment, the displaced Si atoms return to their normal Si interstitial positions, and B atoms are diffused to a predetermined thickness to form a B diffusion layer 18, as shown in FIG. .

Thereafter, the substrate is inserted into a reaction tube in an atmosphere of O2 gas passed through water (H20), so-called WetOa gas, and the substrate is heat-treated at a temperature of 1000° C. for 60 minutes. In this way, as shown in FIG. 7, a B diffusion layer 19 of a predetermined thickness and a 5i02 film 20 on the diffusion layer are formed. Furthermore, the method of the present invention is also applicable to the case where a semiconductor device is formed using impurity atoms other than B.

(2) Effects of the Invention As described above, according to the method of the present invention, the accelerating voltage during ion implantation of B+ atoms can be low, and therefore a large-scale ion implantation device is not required, and the S1 Since the surface of the substrate becomes less rough, there is an advantage that the characteristics of the formed semiconductor element are improved.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing a conventional semiconductor device manufacturing method, and FIGS. 2 to 7 are cross-sectional views showing an embodiment of the semiconductor device manufacturing method of the present invention. In the figure, 1.11 is the Si substrate, 2, 2 is the buried layer, 8
．． 13 is the Sj-epitaxial layer, 4.14 is the element isolation region, 5.15.16.20 is the S:LO2 film, 17 is the ion implantation layer, 18.19 is the diffusion layer, A and B are the directions of ion implantation. This is an arrow indicating. 1st meat Δ Figure 2 Figure 3

Claims (1)

[Claims] A semiconductor device having a step of forming a semiconductor element region by ion-implanting impurity atoms for element formation into a region of a silicon substrate where a silicon dioxide film is formed on the surface and where a semiconductor element is to be formed, which is defined by an inter-element isolation region. During manufacturing,
A part of the silicon dioxide film on the area where the semiconductor element is to be formed on the substrate is made thinner than other areas, and impurity atoms are ion-implanted, and then the substrate is heat-treated in a non-oxidizing atmosphere, and then in an oxidizing atmosphere. A method for manufacturing a semiconductor device, the method comprising the step of heat treatment.