JPH05121401A - Manufacture of semiconductor device - Google Patents

Abstract

(57) [Abstract] [Purpose] Manufacturing a semiconductor device that inherits a simple element isolation method by selective oxidation and that can easily produce an element isolation region with a small bird's beak and a small conversion difference suitable for microfabrication. Providing a way. A process of forming an oxide thin film layer 4 on the surface of a semiconductor substrate 2 and an oxidation prevention layer 6 on the surface of the oxide thin film layer 4.
Forming a predetermined pattern, and the oxidation prevention layer 6
A step of forming a damage layer 14 on the surface of the semiconductor substrate 2 not covered with the oxide, the oxidation rate of which is faster than that of the other portion, and a step of thermally oxidizing the surface of the semiconductor substrate not covered with the oxidation prevention layer 6. And a step of forming an element isolation region 10 made of an oxide film layer thicker than the oxide thin film layer 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a semiconductor device, and more particularly to a method of manufacturing an element isolation region suitable for microfabrication with few bird's beaks.

[0002]

2. Description of the Related Art In a semiconductor device, a large number of fine semiconductor element regions are formed on the surface of a semiconductor substrate made of silicon or the like. It is necessary to provide an element isolation region between each semiconductor element region and to isolate each semiconductor element region from each other. If the element isolation is not perfect, a short circuit may occur between the semiconductor element regions, and the semiconductor device may not operate well. Therefore, in the process of manufacturing the semiconductor device, the process of forming the element isolation region is indispensable, and the miniaturization of the element isolation region is required along with the miniaturization of the semiconductor device.

In the manufacturing process of a semiconductor device, element isolation regions are provided on the surface of a semiconductor substrate in the conventional manner as follows. First, a relatively thin silicon oxide thin film layer is formed on the surface of a silicon semiconductor substrate by means of thermal oxidation or the like, and a silicon nitride film layer is formed thereon.
Next, a resist mask matching the element isolation pattern is formed on the surface of the silicon nitride film layer by a resist process, and the silicon nitride film layer is selectively removed by means of reactive ion etching (RIE) or the like. Then, after removing the resist mask, when the surface of the silicon semiconductor substrate is oxidized, only the semiconductor surface of the removed portion of the silicon nitride film layer is selectively oxidized to form a thick oxide film layer, and that portion is removed. It becomes an element isolation region.

After that, when the silicon nitride film is removed, the element isolation process in the manufacturing process of the semiconductor device is completed. After the element isolation process, ion implantation for forming a semiconductor element or a process of forming various functional thin films is started in each semiconductor element region.

[0005]

FIG. 5 shows a cross section of a main part of an element isolation region obtained by an element isolation process in a conventional semiconductor device manufacturing process. As shown in the figure, the end of the element isolation region 3 formed of a relatively thick silicon oxide film formed on the surface of the silicon semiconductor substrate 2 has an end of the silicon nitride film layer 6 used during the selective oxidation. It spreads so as to go under the department. The edge-shaped portion of the element isolation region that extends so as to sneak under the silicon nitride film layer 6 in this manner is referred to as a bird's beak 5.

The bird's beak 5 is generated because the thermal oxidation proceeds to the lower end portion of the silicon nitride film layer 6 when the surface of the semiconductor substrate is selectively thermally oxidized. The narrower the area width of the bird's beak 5, the better. This is because if the region width of the bird's beak 5 is wide, the area of each semiconductor element region formed on both sides of the element isolation region 3 is narrowed, which hinders high integration. Further, if the area width of the bird's beak 5 is large, the difference between the design dimension value of the mask and the area actually formed (conversion difference S1) becomes large, and the desired element characteristics obtained in the semiconductor circuit design can be obtained. There is a possibility that there is no.

Particularly, in the recent very fine design rule, for example, a design rule of 0.5 μm or less (defined by the minimum line width formed by photolithography or the minimum gate length), the conventional method is used. In the formed element isolation region, the conversion difference S1 is very large as compared with the design rule length, which is not practical. For example, when the film thickness of the element isolation region 3 is about 3000 angstrom, the conversion difference S1 by the bird's beak 5 is about 0.05 μm in the conventional method.
The design rule of 0.35 μm has a problem in that the conversion difference of 2 × 0.05 μm on both sides of the element isolation region 3 has a great influence and desired element performance cannot be obtained.

The present invention has been made in view of such circumstances, and while inheriting a simple element isolation method by selective oxidation,
An object of the present invention is to provide a method of manufacturing a semiconductor device, which has a small bird's beak and can easily manufacture an element isolation region having a small conversion difference and suitable for microfabrication.

[0009]

In order to achieve the above object, a method of manufacturing a semiconductor device according to the present invention comprises a step of forming an oxide thin film layer on the surface of a semiconductor substrate, and a step of forming an oxide thin film layer on the surface of the oxide thin film layer. A step of forming an oxidation prevention layer in a predetermined pattern, a step of forming a damaged layer on the surface of the semiconductor substrate not covered with the oxidation prevention layer, the oxidation layer having a higher oxidation rate than other portions, and the oxidation prevention layer A step of thermally oxidizing the surface of the semiconductor substrate which is not covered by the step of forming an element isolation region made of an oxide film layer thicker than the oxide thin film layer.

[0010]

The cause of generation of bird's beaks by selective thermal oxidation is that the diffusion coefficient of oxidants that promote oxidation, such as oxygen and water molecules, is very large near the interface between the surface of the semiconductor substrate and the oxide film. .. In the present invention, the damage layer is formed in advance on the surface of the semiconductor substrate on which the element isolation region is formed, so that the oxidation rate is higher than that of other portions. As a result, it becomes possible to form an element isolation region made of an oxide film having a desired film thickness in an extremely short time as compared with the related art, and it is possible to significantly suppress the growth of bird's beaks. Therefore, the conversion difference with respect to the design dimension value by bird's beak can be made extremely small,
It becomes possible to form an element isolation region corresponding to a recent ultra-fine design rule.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A semiconductor device manufacturing method according to an embodiment of the present invention will be described in detail below with reference to the drawings.
1 to 4 are cross-sectional views of essential parts showing a manufacturing process of a semiconductor device according to an embodiment of the present invention.

As shown in FIG. 1, in a method of manufacturing a semiconductor device according to an embodiment of the present invention, first, a semiconductor substrate 2 is prepared. The semiconductor substrate 2 is not particularly limited, but a semiconductor substrate made of silicon, for example, is used. An oxide thin film layer 4 is formed on the surface of the semiconductor substrate 2. The oxide thin film layer 4 is, for example, a silicon oxide thin film layer obtained by thermally oxidizing the surface of the silicon semiconductor substrate 2. The film thickness of the oxide thin film layer 4 is not particularly limited and is, for example, a film thickness sufficiently thin to form a gate insulating film formed in a semiconductor element region.

On the surface of the oxide thin film layer 4, an oxidation prevention layer 6 composed of a silicon nitride film layer or the like is formed. The oxidation prevention layer 6 is formed by, for example, a CVD method. Next, as shown in FIG. 2, a resist film 8 is formed on the surface of the oxidation prevention layer 6 in a predetermined pattern according to the element isolation pattern, and the oxidation prevention layer 6 not covered with the resist film 8 is formed.
Are selectively removed using RIE or the like. At this time, the oxide thin film layer 4 formed on the surface of the semiconductor substrate 2 is not removed.

Next, impurity ions, preferably silicon or oxygen ions, are implanted into the surface of the semiconductor substrate 2 not covered with the resist film 8 by means such as an ion implantation method to damage the surface of the semiconductor substrate 2. Form the layer 14.
The implantation energy and dose during ion implantation are
Although not particularly limited, in order to obtain the element isolation region 10 having a thickness of about 3000 Å, it is determined to be implanted from the surface of the semiconductor substrate 2 to a depth of about 1500 to 2000 Å. In particular,
Assuming that silicon is ion-implanted, the implantation energy is
It is about 70 keV or less and the dose amount is 1 × 10 ¹⁵ /
It is preferably about cm ² or more.

By performing such ion implantation, an amorphized damage layer 14 is formed on the surface of the semiconductor substrate 2 which is not covered with the resist film 8. When the semiconductor substrate 2 is a silicon single crystal, the amorphized damage layer 14 is made of the single crystal silicon.
On the other hand, the oxidation rate is approximately doubled.

Next, as shown in FIG. 3, the resist film 8 is removed, and the surface of the semiconductor substrate 2 is thermally oxidized in an oxidizing atmosphere, so that the semiconductor not covered with the oxidation blocking layer 6 made of a silicon nitride film layer. The surface of the substrate 2 is selectively thermally oxidized to form the element isolation region 10 made of a silicon oxide film layer. Element isolation region 1 made of this silicon oxide film layer
The film thickness of 0 is not particularly limited, but is about 3000 angstroms. Element isolation region 1 having such a film thickness
In the present embodiment, the thermal oxidation time for obtaining 0 is theoretically about 1/4 of the time in comparison with the conventional case because the damaged layer 14 is formed in this portion in advance. This is because the oxidation rate of the damage layer 14 is about twice as high as that of the semiconductor substrate 2 in other portions, as described above.

Therefore, the growth of the bird's beak 12 is suppressed, and the conversion difference S2 from the design value by the bird's beak 12 is reduced.
(Illustrated in FIG. 4) can be significantly reduced. Therefore, the semiconductor element regions formed on the surface of the semiconductor substrate 2 located on both sides of the element isolation region 10 are not narrowed,
High integration of a semiconductor device becomes possible. Moreover, in this embodiment, since the element isolation region is basically formed by the thermal oxidation method, the manufacturing process is not complicated. Moreover, since the bird's beak 12 can be reduced by simply forming the damaged layer 14 by the ion implantation method or the like before the thermal oxidation, the number of manufacturing steps is also small.

After thermal oxidation, as shown in FIG.
The oxidation prevention layer 6 is removed, and the element isolation process is completed. After the element isolation process, ion implantation for forming a semiconductor element or a process of forming various functional thin films is started in each semiconductor element region.

The present invention is not limited to the above embodiments, but can be variously modified within the scope of the present invention. For example, the means for forming the damaged layer is not limited to ion implantation, and means such as dry etching can be used. In addition, the semiconductor substrate 2
The semiconductor substrate is not limited to a silicon semiconductor substrate, and other semiconductor substrates can be used. Further, the oxidation prevention layer 6 is not limited to the silicon nitride film layer, and other thin films can be used.

[0020]

As described above, according to the present invention, a damaged layer is formed in advance on the surface of a semiconductor substrate where an element isolation region is formed so that the oxidation rate is higher than that of other portions. There is. As a result, it becomes possible to form the element isolation region made of an oxide film having a desired film thickness by a simple thermal oxidation means in an extremely short time compared with the conventional case.
Moreover, in the present invention, unlike the conventional method, it is possible to significantly suppress the growth of bird's beaks. Therefore, the conversion difference with respect to the design dimension value due to the bird's beak can be made extremely small, and the element isolation region corresponding to the recent ultrafine design rule can be extremely easily formed by a simple method.

[Brief description of drawings]

FIG. 1 is a main-portion cross-sectional view showing the manufacturing process of a semiconductor device according to an embodiment of the invention.

FIG. 2 is a sectional view of a key portion showing the manufacturing process of the semiconductor device according to the embodiment of the present invention.

FIG. 3 is a sectional view of a key portion showing the manufacturing process of the semiconductor device according to the embodiment of the present invention.

FIG. 4 is a sectional view of a key portion showing the manufacturing process of the semiconductor device according to the embodiment of the present invention.

FIG. 5 is a fragmentary cross-sectional view of an element isolation region obtained by a method for manufacturing a semiconductor device according to a conventional example.

[Explanation of symbols]

 2 ... Semiconductor substrate 4 ... Oxide thin film layer 6 ... Oxidation prevention layer 10 ... Element isolation region 12 ... Bird's beak 14 ... Damage layer

Claims (2)

[Claims] 1. A step of forming an oxide thin film layer on the surface of a semiconductor substrate, a step of forming an oxidation inhibiting layer in a predetermined pattern on the surface of this oxide thin film layer, and a step of not being covered with this oxidation inhibiting layer. On the surface of the semiconductor substrate,
A step of forming a damaged layer having an oxidation rate higher than that of other portions, and an element isolation region formed of an oxide film layer thicker than the oxide thin film layer by thermally oxidizing the surface of the semiconductor substrate not covered with the oxidation prevention layer And a step of forming a semiconductor device. 2. The method for manufacturing a semiconductor device according to claim 1, wherein the damaged layer is formed by an ion implantation method.