JPH11251423A - Method for isolating semiconductor element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for isolating a semiconductor element, which improves an isolating characteristic by forming uniform insulating films inside each trench in the cell region of the memory element and in the peripheral circuit region, and by making the insulating film finer. SOLUTION: On the upper plane of a semiconductor substrate 10, a buffer film 12 and an antioxidant film 14 are formed successively, the buffer film 12 and the antioxidant film 14 in an element isolating region are etched, and a semiconductor substrate 10 is etched to form a trench 16 by using the antioxidant film 14 as mask. Then, an oxidizable film 18 is formed on the inner surface of the trench, the oxidizable film 18 is oxidized to form an insulating film 20 with which the trench 16 is filled, the buffer film 12 and the antioxidant film 14 are removed, and a semiconductor element is isolated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for isolating a semiconductor device, and more particularly, to a method for isolating a shallow trench by simply filling an insulating layer in the shallow trench.
(Rench isolution).

[0002]

2. Description of the Related Art A conventional method for isolating a semiconductor device is described below.
This will be described with reference to FIGS. First, FIG.
2), an oxide film as a first insulating film 2 is formed on the semiconductor substrate 1 by a thermal oxidation process to a thickness of 500 to 100 °, and a second insulating film is formed on the first insulating film 2. A nitride film 3 is formed to a thickness of 2000 ° and the second insulating film 3 is formed.
A photosensitive film 4 is formed thereon.

Next, as shown in FIG. 4B, a portion of the photosensitive film 4 is exposed and removed so that the surface of the second insulating film 3 is exposed, thereby forming a photosensitive film pattern 4a. And
Using the photosensitive film pattern 4a as a mask, the first insulating film 2
And the second insulating film 3 are sequentially patterned to form a first insulating film pattern 2a and a second insulating film pattern 3a,
The photoresist pattern 4a is removed by wet etching.

Next, as shown in FIG. 4C, the first insulating film 2 and the first insulating film 3 are removed by using the first insulating film pattern 2a and the second insulating film pattern 3a as a mask. The lower semiconductor substrate 1 is etched to form a trench 5, an oxide film as a thin third insulating film 6 is formed in the trench 5 by a thermal oxidation process, and the trench 5 is formed so as to include the trench 5. The fourth insulating film 7 is formed on the second insulating film pattern 3a. As a result, the trench 5 is filled with the fourth insulating film 7.

At this time, the fourth insulating film 7 is formed by high-density plasma enhanced chemical vapor deposition (HDP CVD).
The fourth insulating film 7 is an oxide film formed by a chemical vapor deposition (CVD) method, and is heat-treated to form a high-quality device isolation film, thereby densifying the fourth insulating film 7 (densifactio).
n) Next, as shown in FIG. 4D, the fourth insulating film 7 is subjected to chemical mechanical polishing until the surface of the second insulating film pattern 3a is exposed.
shing, hereinafter referred to as CMP. ) To remove. At this time, the second insulating layer pattern 3a is formed by an etch stop layer (etch).
Acts as a stopper film).

Next, as shown in FIG. 4E, the first insulating film pattern 2a and the second insulating film pattern 3a are removed from the semiconductor substrate 1, and the conventional method of isolating a semiconductor device is completed. I was Here, the second insulating film pattern 3a is removed by wet etching using an H ₃ PO ₄ solution.

[0007]

However, in such a conventional method for isolating a semiconductor device, a process of forming an oxide film for filling a trench and a polishing process for etching the oxide film are expensive. Semiconductor devices are used, and the slurry used as a polishing agent and pure water used in performing the CMP process are excessively consumed, thereby increasing the manufacturing cost.

In addition, if a heat treatment is performed at a high temperature after an oxide film is deposited by performing HDP CVD as a fourth insulating film, defects are induced on the surface of the semiconductor substrate due to thermal stress of the thick silicon nitride film. was there. Further, when the oxide film formed by performing HDP CVD as the fourth insulating film is subjected to chemical mechanical polishing, there is an inconvenience that it becomes difficult to adjust the uniformity of the oxide film surface.

When the fourth insulating film is etched using a CMP process, the third insulating film and the fourth insulating film at the edge of the trench are etched to a level below the surface of the semiconductor substrate.
Although not shown in FIG. 3, when polysilicon is deposited and etched to form a gate electrode as a subsequent process,
Polysilicon deposited on the edge of the trench is not etched away, resulting in a short circuit.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem, and has been made to increase the density of an insulating film filled in a trench, thereby improving the isolation characteristics of an element and reducing the cost. It is an object of the present invention to provide a method for isolating a semiconductor device obtained. It is another object of the present invention to provide a method of isolating a semiconductor device by forming a uniform insulating film in trenches having different sizes formed in a cell region and a peripheral region of a memory device, thereby improving the isolation characteristics of the device. The purpose is to provide.

[0011]

The invention according to claim 1 is
Forming a buffer film and an antioxidant film sequentially on the upper surface of the semiconductor substrate, etching an element isolation region of the buffer film and the antioxidant film, and using the antioxidant film as a mask, the removed buffer film Forming a trench by etching a semiconductor substrate below the anti-oxidation film, forming an oxidizable film on an inner surface of the trench, and filling the trench by oxidizing the oxidizable film. Forming an insulating film, and removing the buffer film and the antioxidant film;
Are sequentially performed.

The invention according to claim 2 is a step of sequentially forming a buffer film and an antioxidant film on the upper surface of the semiconductor substrate, a first trench of the buffer film and the antioxidant film, and a second trench wider than the first trench. Removing each of the formation regions with the trench, and etching the semiconductor substrate below the removed buffer film and the antioxidant film using the antioxidant film as a mask to form a first trench and a second trench The process of
A first oxidizable film is formed in the first trench, and a second oxidizable film is formed in the second trench, the second oxidizable film being thicker than the first oxidizable film.
Forming an oxidizable film, and oxidizing each of the first oxidizable film and the second oxidizable film to form a first insulating film and a second insulating film filling the first trench and the second trench, respectively; And forming are sequentially performed.

According to a third aspect of the present invention, the step of forming the first oxidizable film and the second oxidizable film includes forming a first insulating film on lower surfaces and side surfaces of the first trench and the second trench. Removing the first insulating film in the first trench; forming a first oxidizable film in the first trench; and removing the first oxidizable film and the second trench in the first trench. Forming a second insulating film on the first insulating film of the trench, removing the first insulating film and the second insulating film of the second trench, and forming a second oxidizable film in the second trench And removing the second insulating film of the first trench.

The invention according to claim 4 is characterized in that one of germanium ions and silicon ions is selected and implanted into the first oxidizable film and the second oxidizable film. The invention according to claim 5 is characterized in that the oxidation step of the oxidizable film is performed at 800 to 900 ° C. in an oxygen atmosphere.
The heat treatment is performed within the temperature range.

[0015]

As described above, according to the first aspect of the present invention, a method for filling a trench with an insulating film by CVD is used.
Without using expensive semiconductor equipment such as equipment and CMP equipment,
Since an oxidizable film may be formed and oxidized in the trench, the manufacturing cost may be reduced, and the density of the insulating film filling the trench may be increased, thereby improving the isolation characteristics of the device. This has the effect.

According to the second aspect of the present invention, an oxidizable film is formed in the trench without using expensive semiconductor equipment such as CVD equipment and CMP equipment for filling the trench with the insulating film. In this case, the manufacturing cost is reduced, and a uniform insulating film is formed in the trenches having different sizes formed in the cell region and the peripheral circuit region of the memory device. There is an effect that it can be improved.

According to the third aspect of the present invention, there is provided an oxidizable film capable of forming a uniform insulating film in trenches having different sizes respectively formed in a cell region and a peripheral circuit region of a memory device. This has the effect of improving the isolation characteristics of the device. According to the fourth and fifth aspects of the present invention, since the crystal structure of the oxidizable film in the trench is made amorphous by performing ion implantation, the oxidation step is performed at a relatively low temperature, thereby preventing oxidation. The thickness of the film (nitride film) is made thin (less than 500 mm or less) and defects (defec
There is an effect that occurrence of t) can be suppressed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. First Embodiment of a method for isolating a semiconductor device according to the present invention will be described with reference to FIGS.
Explanation will be made based on (e). First, as shown in FIG. 1A, a buffer film 12 as an oxide film is formed on the upper surface of a semiconductor substrate 10 to a thickness of 50 to 100 ° by performing a thermal oxidation process. Antioxidant film 1 as nitride film
4 is formed to a thickness of 500 to 2000 °, and a photosensitive film 15 is formed on the antioxidant film 14.

Next, as shown in FIG. 1B, a part of the photosensitive film 15 is exposed and removed in order to determine an element isolation region in a cell region and a peripheral circuit region, and the photosensitive film pattern 15a is removed. The buffer film 12 and the antioxidant film 14 are sequentially patterned using the photosensitive film pattern 15a as a mask to form the buffer film pattern 12a and the antioxidant film pattern 14a. Then, the photosensitive film pattern 15a is wet-etched. Remove.

Next, as shown in FIG. 1C, using the buffer film pattern 12a and the antioxidant film pattern 14a as a mask, the semiconductor substrate 10 below the removed buffer film 12 and the antioxidant film 14 is removed. And trench 1
6 and an oxidizable film 18 is
It is formed to a thickness of 00 °. Here, the oxidizable film 18
Is to form a polysilicon film doped with P-type or N-type impurities by chemical vapor deposition (CVD),
Alternatively, it is formed of an epitaxial silicon film. When forming the epitaxial silicon film, SiH ₂ Cl ₂ (DCS: Dichlorosilane) as a silicon source and B ₂ H ₆ (Diborane) as a P-type impurity are injected into the reaction chamber. Further, when forming the epitaxial silicon film, HCl gas may be added to the reaction chamber in order to delay generation of nuclei of silicon atoms.

Next, as shown in FIG. 1D, germanium (Ge) ions or silicon (Si) ions are implanted into the oxidizable film 18 of the trench 16 from an inclined direction, and the trench 16 is formed. The oxidizable film 18 and the semiconductor substrate 10 are oxidized to fill the insulating film 2.
0 is formed. Here, germanium ions and silicon ions are implanted because the crystal structure of the oxidizable film 18 is changed to an amorphous state to increase the oxidation rate, thereby relatively reducing the oxidation of the semiconductor substrate 10. To do that. Such an oxidation process is performed in a furnace having a temperature range of 800 to 900 ° C. in an oxygen atmosphere.
).

Next, as shown in FIG. 1 (e), the buffer film pattern 12a and the antioxidant film pattern 14a are removed by performing wet etching, thereby isolating the semiconductor device according to the first embodiment of the present invention. End the method. Next, a second embodiment of the method for isolating a semiconductor device according to the present invention will be described with reference to FIGS. 2 (a) to 2 (d) and 3 (a) to 3 (c).

First, as shown in FIG. 2A, a thermal oxidation process is performed on the upper surface of the semiconductor substrate 30 in which the cell region and the peripheral circuit region have been determined, so that the oxide buffer film 32 is formed in a thickness of 50-10.
Then, a nitride anti-oxidation film 34 is formed on the buffer film 32 to a thickness of 500 to 2000 厚, and a first photosensitive film 35 is formed on the anti-oxidation film 34. Next, as shown in FIG. 2 (b), in order to determine an element isolation region in each of the cell region and the peripheral circuit region, the first region is formed.
The photosensitive film 35 is exposed and removed to form a first photosensitive film pattern 35.
After forming the buffer film pattern 32a and the antioxidant film pattern 34a by removing the buffer film 32 and the antioxidant film 34 using the first photosensitive film pattern 35a as a mask, the first photosensitive film pattern 35a is formed. Is removed.

Next, the semiconductor substrate 30 below the removed buffer film 32 and antioxidant film 34 is etched using the buffer film pattern 32a and the antioxidant film pattern 34a as a mask. One trench 36 is formed, and a second trench 38 is formed in the peripheral circuit region. At this time, the surface area of the second trench 38 in the peripheral circuit region is formed larger than that of the first trench 36 in the cell region.

Then, an oxidation process is performed on the lower surface and side surfaces of the first trench 36 and the second trench 38 to form a thin first insulating film 39 of an oxide film. Next, as shown in FIG. 2C, the second trench 38 in the peripheral circuit region is masked using a second photoresist pattern 50, and the first insulating film 39 in the cell region is HF solution. Then, the second photoresist pattern 50 is removed.
Then, the first oxidizable film 5 is selectively epitaxially grown on the inner surface of the first trench 36 in the cell region.
One silicon layer is formed to a thickness of 1000 °.

Next, as shown in FIG. 2D, the first oxidizable film 51 in the first trench 36 and the second
An oxidation process is performed on the upper surface of the first insulating film 39 in the trench 38 to form an oxide second insulating film 52. Next, as shown in FIG. 3A, the first trench 36 is masked using a third photoresist pattern 53, and the second trench 36 is removed.
The first insulating film 39 and the second insulating film 52 in the trench 38 are
After the removal using the HF solution, the third photoresist pattern 53 is removed. Next, a second oxidizable film 55 of a silicon layer is formed on the second trench 38 to a thickness of 2000 .ANG. By selective epitaxial growth.

At this time, the first oxidizable film 51 is formed thinner than the second oxidizable film 55 because the surface area of the first trench 36 is smaller than that of the second trench 38. This is because the speed at which the first trench 36 is filled with an oxide film in the oxidation process is faster than that of the second trench.
According to the surface area of the trench 38, the first oxidizable film 51 may be formed.
In addition, the thickness of the second oxidizable film 55 can be adjusted.

Next, as shown in FIG.
After removing the second insulating film 52 of the trench 36, the first oxidizable film 51 of the first trench 36 and the second
Germanium (Ge) ions or silicon (Si) ions are implanted into the oxidizable film 55 from an inclined direction. here,
The reason for implanting these germanium (Ge) ions and silicon (Si) ions is to change the crystal structure of the first oxidizable film 51 and the second oxidizable film 55 to an amorphous state to increase the oxidation rate, This is because the oxidation of the semiconductor substrate 30 is relatively reduced. In order to fill the first trench 36 and the second trench 38, the semiconductor substrate 30 and the first oxidizable film 51 and the second oxidizable film 55 adjacent to the first trench 36 and the second trench 38 are formed. Is oxidized to form a third insulating film 57 and a fourth insulating film 59.

Next, as shown in FIG. 3C, the buffer film pattern 32a and the antioxidant film pattern 34a are removed by performing wet etching, and the semiconductor device according to the second embodiment of the present invention is removed. End the isolation method for.

[Brief description of the drawings]

1 (a) to 1 (e) are longitudinal sectional views showing a first embodiment of a method for isolating a semiconductor device according to the present invention.

FIGS. 2A to 2D are longitudinal sectional views (first stage) showing a second embodiment of the method for isolating a semiconductor device according to the present invention;

FIGS. 3A to 3C are longitudinal sectional views of a process showing a second embodiment of a method for isolating a semiconductor device according to the present invention (second stage).

4 (a) to 4 (e) are longitudinal sectional views showing steps of a conventional method for isolating a semiconductor device.

[Explanation of symbols]

10, 30: semiconductor substrate 12,
32: buffer film 14, 34: antioxidant film 16,
36, 38: Trench 18, 51, 55: Oxidizable film 15,
35: photosensitive film 20, 39, 52, 57, 59: insulating film 32a
: Buffer film pattern 15a, 35a, 50, 53: Photosensitive film pattern 34a
: Oxidation prevention film pattern

Claims (5)

[Claims] A step of sequentially forming a buffer film and an antioxidant film on an upper surface of a semiconductor substrate; a step of etching an element isolation region of the buffer film and the antioxidant film; Etching the semiconductor substrate below the removed buffer film and antioxidant film to form a trench; forming an oxidizable film on the inner surface of the trench; and oxidizing the oxidizable film. A method for isolating a semiconductor device, comprising: sequentially forming an insulating film filling the trench; and removing the buffer film and the antioxidant film. 2. A step of sequentially forming a buffer film and an antioxidant film on an upper surface of a semiconductor substrate, and forming a region for forming a first trench of the buffer film and the antioxidant film and a second trench wider than the first trench. Removing each of the steps, and using the antioxidant film as a mask, etching the semiconductor substrate below the removed buffer film and the antioxidant film to form a first
Forming a trench and a second trench; forming a first oxidizable film in the first trench; and forming a second oxidizable film in the second trench that is thicker than the first oxidizable film.
Forming an oxidizable film, and oxidizing each of the first oxidizable film and the second oxidizable film;
Forming a first insulating film and a second insulating film filling the first trench and the second trench, respectively. 3. The step of forming the first oxidizable film and the second oxidizable film, comprising: forming a first insulating film on lower surfaces and side surfaces of the first trench and the second trench; Removing the first insulating film, forming a first oxidizable film in the first trench, and forming the first insulating film in the first trench and the first insulating film in the second trench. Forming a second insulating film on the film; removing the first insulating film and the second insulating film of the second trench; forming a second oxidizable film in the second trench; 3. The method as claimed in claim 2, further comprising: removing a second insulating film of the first trench. 4. The semiconductor according to claim 2, wherein one of germanium ions and silicon ions is selected and implanted into the first oxidizable film and the second oxidizable film. Element isolation method. 5. The method according to claim 2, wherein the oxidizing film is oxidized by heat treatment in an oxygen atmosphere at a temperature in a range of 800 to 900 ° C.