JPH0198246A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To scale down a bird beak generated by thermal oxidation by forming a semiconductor layer difficult to be oxidized more than an insulating film between the insulating film and an anti-oxidizing film on a semiconductor substrate. CONSTITUTION:An SiO2 film 12 is shaped first by thermally oxidizing the surface of an Si substrate 11. A polycrystalline Si film 13, an Si3N4 film 14 and an SiO2 film 19 are formed successively onto the film 12. The SiO2 film 19, the Si3N4 film 14 and the polycrystalline Si film 13 are removed selectively to specified patterns. The ions of an impurity 15 for shaping a channel stopper are implanted under the state. Only the SiO2 film 19 is gotten rid of, heat treatment for, activating the impurity 15 is conducted, and thermal oxidation is performed, using the Si3N4 film 14 as an anti-oxidizing film. Consequently, an SiO2 film 16 as an element isolation region and a channel stopper 17 under the SiO2 film 16 are formed. The Si3N4 film 14 and the polycrystalline Si film 13 are taken off.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of forming an isolation region of a semiconductor device.

[Summary of the invention]

The present invention provides a method for manufacturing a semiconductor device as described above.
An insulating film, a semiconductor layer that is less oxidized than the insulating film, an oxidation prevention film, and an ion implantation blocking film are sequentially formed on the semiconductor substrate, and the ion implantation blocking film is used for ion implantation of impurities for channel stoppers. By performing thermal oxidation with the ion implantation blocking film removed, it is possible to manufacture a semiconductor device with a high six-inch through voltage despite its high degree of integration. .

[Conventional technology]

In semiconductor devices, higher integration is always being pursued. Therefore, the present applicant has already proposed a method for manufacturing a semiconductor device in which the bird's beak is reduced when forming an element isolation region by the LOCO3 method in Japanese Patent Application No. 59-196308.

In this method, as shown in FIG. 3A, for example, a SiO
A polycrystalline Si film 13 with a thickness of about 1,000 layers and an i3N4 film 14 with a thickness of about 1,000 layers are sequentially formed, and the 5iJ4 film 14 and the polycrystalline Si film 13 with a thickness of about 300 layers are selectively removed. In this state, an impurity 15 such as B for forming a channel stopper is ion-implanted, and then thermal oxidation is performed.

In this method, since the diffusion coefficient of 0□ in the polycrystalline Si film 13 is smaller than the diffusion coefficient of 02 in the SiO2 film 12, the progress of oxidation in the direction parallel to the surface of the Si substrate 11 is suppressed. Ru.

For this reason, the case of FIG. 3B by this method and the case of polycrystalline S
As is clear from the comparison with the case shown in FIG. 4, which was obtained by the previous method in which the i-film 13 was not formed, the Sing of the element isolation region
The size X of the bird's beak 16a in the film 16 is smaller in this method.

[Problem that the invention seeks to solve]

However, in the method of the prior application described above, the portion of the polycrystalline Si film 13 that is not covered with the Si3N4 film 14 is also oxidized to become the Si film 16. For this reason, the relationship between the thickness y of the portion below the surface of the Si substrate 11 and the thickness 2 of the portion above the SiO□ film 16 thickness 6 is y#z in the previous method, whereas Therefore, in the method of the prior application, y<z.

Therefore, if the thickness 6 of the SiO□ film 16 is the same,
The depth of the channel stopper 17 from the surface of the Si substrate 11 is shallower in the method of the prior application. As a result, the depletion layer from the conductive region 18 tends to extend under the channel stopper 17, resulting in a low punch-through breakdown voltage.

In this case, 5iJ4
In order to prevent the impurity 15 from being ion-implanted into the Si substrate 11 under the film 14, the Si3N film 14 is formed thickly in advance, and by ion-implanting the impurity 15 with high energy, the impurity 15 is ion-implanted into the Si substrate 11 at a deep position. It is conceivable to form the channel stopper 17 up to the length.

However, thermal oxidation is performed using the Si, N, film 14 as a mask, so if the Si3N film 14 is made too thick, the stress generated during thermal oxidation will increase, crystal defects will occur in the Si substrate 11, and leakage current will increase. I do things.

[Means for solving problems]

In the method for manufacturing a semiconductor device according to the present invention, a semiconductor substrate 11
There is an insulating film 12 on top, a semiconductor layer 13 that is less oxidized than the insulating film 12, an oxidation prevention film 14, and an ion implantation prevention film 19.
a step of sequentially forming and removing the ion implantation blocking region to form an ion implantation blocking region; a step of ion implanting impurity 15 for the channel stopper 17 using the ion implantation blocking region as a mask; and after this ion implantation, The method includes a step of removing the ion implantation blocking film 19, and a step of performing thermal oxidation using the oxidation preventing film 14 as a mask after this removal.

[Effect]

In the method for manufacturing a semiconductor device according to the present invention, a semiconductor substrate 1
Since the semiconductor layer 13, which is less oxidized than the insulating film 12, is formed between the insulating film 12 and the oxidation prevention film 14 on the semiconductor substrate 1, the progress of oxidation in the direction parallel to the surface of the semiconductor substrate 11 is suppressed. As a result, the bird's beak 16a produced by thermal oxidation can be made smaller than before.

Furthermore, since the impurity 15 for the channel stopper 17 is ion-implanted after forming the ion-implantation blocking region including the ion-implantation blocking film 19, even if ion implantation is performed at high energy, the semiconductor under the ion-implantation blocking region The impurity 15 is not implanted into the substrate 11.

On the other hand, the semiconductor substrate l under the region other than the ion implantation blocking region
The impurity 15 can be ion-implanted deep into the semiconductor substrate 11, and the channel stopper 17 can be formed deep into the semiconductor substrate 11.

Moreover, since thermal oxidation is performed after removing the ion implantation blocking film 19, even if the ion implantation blocking film 19 is formed before ion implantation, the stress generated during thermal oxidation does not increase and is generated in the semiconductor substrate 11. There is no increase in crystal defects.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In this embodiment, as shown in FIG. 1A, for example, p-type Si
By thermally oxidizing the surface of the substrate 11, a thickness of 40~
First, about 50 NG films 12 are formed.

Next, a layer of 700 to 800 mm thick is deposited on this Sin film 12.
I membrane 13 with a multicondensation level of about the same size as a person, i3N with a thickness of about 1000 people, membrane 14 with a thickness of about 3000 to 4000 people, and 5 with a thickness of about 3000 to 4000 people.
in2 and about 9 are sequentially formed by the CVD method.

Next, as shown in FIG. 1B, for the SiO□ film 19 film 9: +
A portion of the N4 film 14 and the polycrystalline Si film 13 with a thickness of approximately 300 mm is selectively removed in a predetermined pattern.

In this state, impurity 1 for forming a channel stopper is added.
5 is ion-implanted. B is used as the impurity 15,
Acceleration energy is approximately 60 keV (BFg acceleration energy is approximately 300 keV), dose amount is approximately 7 x 10”
/n (closed.

Even if high acceleration energy as mentioned above is used, SiJ.

There is also a Sing film 19 on the film 14, so 5
The impurity 15 is not implanted into the Si substrate 11 under the iJn film 14.

On the other hand, in the Si substrate 11, Si3N and the film 14
In regions other than the bottom, as shown in FIG. 2, impurities are added so that the concentration is highest at a deep position near the interface between the SiO□ film 16 (FIG. 1D) and the Si substrate 11 due to subsequent thermal oxidation. 15 is injected.

Next, as shown in FIG. 1C, only the 5iO1 film 19 is removed, heat treatment is performed to activate the impurity 15, and the S
i 3N, thermal oxidation is performed using the film 14 as an oxidation prevention film.

Then, as shown in FIG. 1D, 5i becomes an element isolation region.
02 film 16 and a channel stopper 17 under this Sing film 16 are formed. Thereafter, the Si, N, film 14 and polycrystalline Si film 13 are removed.

In the semiconductor device manufactured according to this example as described above,
As is clear from the comparison between FIG. 1D and FIG. 3B, the channel stopper 17 is formed at a deeper position in the Si substrate 11 than in the semiconductor device according to the method of the prior application, so the batch-through breakdown voltage is higher.

Also, since the ion implantation is performed so that the concentration of the impurity 15 is distributed as shown in FIG. 2, the channel stopper 1
The oxidation-enhanced diffusion of 7 is suppressed, and the narrow channel effect in which the channel stopper 17 extends in the direction of the element region is also reduced (suppressed).

In order to enhance the mask effect for ion implantation, in this embodiment, the SiO□ film 19 was used, but SOG, resist, etc. may be used instead of SiO□.

[Effects of the Invention] In the method for manufacturing a semiconductor device according to the present invention, bird's beaks caused by thermal oxidation can be made smaller than in the conventional method, so a semiconductor device with a high degree of integration can be manufactured.

Furthermore, since the channel stopper can be formed deep within the semiconductor substrate without increasing crystal defects occurring in the semiconductor substrate, a semiconductor device with high punch-through breakdown voltage can be manufactured.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view sequentially showing one embodiment of the present invention;
The figure is a graph showing the concentration distribution of impurities ion-implanted in one example. FIG. 3 is a side sectional view sequentially showing the method of the prior application by the present applicant, and FIG. 4 is a side sectional view of a semiconductor device manufactured by another conventional method. In addition, in the symbols used in the drawings, 11---1-----------Si substrate 12--------------- 5i O
□ Film 13・-・−・・−・Polycrystalline St film 14・−
・・−−１−−−−・−・−5i3N, film 15−・・・・
−・−・−・・−・・Impurity 16a・・・・・−・
・−・Birds Beak 17−・・＝・−・−・−・・
・−・・Channel Strike, Part 19・−1−−−・・−・・
−・−・−5iO□ film.

Claims (1)

[Scope of Claims] A step of sequentially forming an insulating film, a semiconductor layer that is less oxidizable than the insulating film, an oxidation prevention film, and an ion implantation prevention film on a semiconductor substrate, the ion implantation prevention film and the oxidation prevention film. forming an ion implantation blocking region by selectively removing the film and at least a portion of the semiconductor layer in the heat direction; and using the ion implantation blocking region as a mask, ion-implanting an impurity for a channel stopper. A method for manufacturing a semiconductor device, comprising the steps of: removing the ion implantation blocking film after the ion implantation; and performing thermal oxidation using the antioxidation film as a mask after the removal.