JPH04245633A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To facilitate fine element isolation wherein reduction of isolation width is not caused by growth of bird's beak and film thickness is large. CONSTITUTION:A silicon oxide film layer 12 and a silicon nitride film layer 13 are formed on the surface of a silicon substrate 11; a resit pattern 13 is formed on the silicon nitride film layer 13; by using said pattern as a mask, the film layers 13 and 12 are etched; thus the pattern is transferred, and the semiconductor silicon substrate 11 is selectively exposed; said substrate 11 is irradiated with hydrogen ion 14, and a hydrogen ion irradiation region 15 is formed; said substrate is heat-treated in an oxidizing atmosphere for a specified period, at a temperature lower than or equal to the conventional temperature, and a semiconductor silicon substrate region irradiated with hydrogen ions is transformed into a thick oxide film 16. After that, the silicon nitride film and the silicon oxide film layer are eliminated, and the semiconductor silicon substrate surface is exposed.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to fine element isolation technology for semiconductor devices, and in particular to improvements in a method for manufacturing semiconductor devices using a selective oxidation method.

0002

2. Description of the Related Art An integrated circuit includes a plurality of active elements separated from each other by an insulating layer on a common semiconductor silicon substrate. Conventional LOCOS (Local Oxida)
In a method of manufacturing a semiconductor device using the ion of silicon method, a semiconductor substrate is separated into an active region and a field region via a buried insulator, and elements are formed in the active region. Conventionally, the separation is performed using selective oxidation. The process was carried out by the process shown in FIG. 5.

First, a silicon oxide film layer 51 is formed on the surface of a semiconductor silicon substrate 11, and a silicon nitride film layer 52 is further formed on the silicon oxide film layer (FIG. 5(a)).
. Next, using lithography technology and dry etching technology, the silicon nitride film layer and silicon oxide film layer are selectively removed, the semiconductor silicon substrate is selectively exposed, and an oxidation-resistant mask layer is formed on the planned active area. (Fig. 5(b)). Next, oxidation is performed by heat treatment at a constant temperature for a constant time in an oxidizing atmosphere to form a thick field oxide film 53 deeply buried in the semiconductor silicon substrate (FIG. 5(c)). Next, the silicon nitride film layer and silicon oxide film layer on the active region are removed to expose the semiconductor silicon substrate surface and perform element isolation (FIG. 5(d)).

[0004] By the method described above, it is possible to perform element isolation using an insulating film of a semiconductor device. but,
The oxidation step in this method results in oxide growth at the outer periphery of the surface of the active region as a result of the lateral movement of oxygen through the thin silicon oxide layer. The lateral oxide projections formed in this way are called bird's beaks. This bird's beak formation changes the pre-specified dimensions of the active area by moving the edges of the peripheral oxide, and also reduces the usable portion of the active area by curving the outer periphery of the active area. This will result in a decrease.

[0005]

[Problems to be Solved by the Invention] As described above, in this conventional manufacturing method, as shown in FIG. , (FIG. 5(d)), the active region becomes narrow. Therefore, in order to obtain a desired active region size, consideration must be given to the lateral penetration of the field oxide film, which requires a large area. Furthermore, when the size of the active region becomes fine, the finished active region becomes very narrow or cannot be formed due to the lateral invasion of the field oxide film. (FIG. 4) shows the relationship between the designed separation width and the separation width actually obtained through the process. From this figure, when the designed separation width is 0.5 μm, the actual separation width is about 0.2 μm, which shows a reduction in the size of the active region by 0.3 μm. That is, in the process of forming a thick oxide film, a bird's beak of 0.3 μm was grown in the lateral direction. Furthermore, with the designed separation width of 0.3 μm, there arises a problem that complete separation cannot be achieved in an actual process.

[0006] In order to suppress the growth of bird's beak, various improved methods of the LOCOS method have been proposed, but these methods require more complicated processes, tighter surface steps, and crystal defects. This also has the disadvantage of increasing leakage current. These have the drawback of being a major obstacle to increasing the degree of integration of semiconductor integrated circuit devices. In order to solve these problems, the present inventors have completed a method for manufacturing a semiconductor device using a selective oxidation method in fine element isolation technology for semiconductor devices.

[0007]

Means for Solving the Problems A method for manufacturing a semiconductor device of the present invention includes the steps of forming a silicon oxide film layer on the surface of a semiconductor silicon substrate, and forming a silicon nitride film layer on the silicon oxide film layer; forming a resist pattern on the silicon nitride film layer, using the resist pattern as a mask, etching the silicon nitride film and silicon oxide film layer to transfer the pattern and selectively exposing the semiconductor silicon substrate; irradiating the semiconductor silicon substrate with a certain amount of ions with sufficient energy selected from the group consisting of hydrogen ions; and heating the substrate in an oxidizing atmosphere at a certain temperature for a certain period of time. changing the semiconductor silicon substrate region irradiated with the ions into a thick oxide film, and removing the silicon nitride film and silicon oxide film layer to expose the semiconductor silicon substrate surface. It provides a method to achieve this goal. and,
Desirably, a method is provided in which the amount of ion irradiation onto the semiconductor silicon substrate is 5×10 14 /cm 2 or more, and the acceleration voltage is 40 kV or less.

Furthermore, the present invention also provides a step of forming a silicon oxide film layer on the surface of a semiconductor silicon substrate, forming a silicon nitride film layer on the silicon oxide film layer, and forming a resist on the silicon nitride film layer. forming a pattern, using the resist pattern as a mask, etching the silicon nitride film and silicon oxide film layer to transfer the pattern and selectively exposing the semiconductor silicon substrate; irradiation with a certain amount of ions with sufficient energy, selected from the group consisting of and a step of removing the silicon nitride film and the silicon oxide film layer to expose the surface of the semiconductor silicon substrate. . Preferably, the amount of ion irradiation onto the semiconductor silicon substrate is 5×1014/c.
m2 or more and the acceleration voltage is 200 kV or less.

That is, by irradiating a silicon semiconductor material with ions, damage is induced to the silicon substrate, making the silicon more susceptible to oxidation. Also,
As the ion irradiation amount to the semiconductor silicon substrate,
Sufficient to substantially increase the oxidation rate of silicon semiconductor material that has been irradiated with ions compared to silicon semiconductor material that has not been irradiated with ions. (Figure 3)
shows a comparison of the relationship between oxidation temperature and oxidation rate between the conventional method and the present method. It can be seen that a faster oxidation rate is obtained at a lower oxidation temperature when oxidation is performed using the present method than when using the conventional method. As a result, the area irradiated with ions can be easily oxidized at a lower temperature than the conventional oxidation temperature, suppressing the lateral penetration of the oxide film, and reducing the size of the bird's beak. can do. The relationship between the designed separation width and the actual separation width obtained by this method is shown in FIG. 4. It can be seen that there is almost no intrusion of the bird's beak, and the actually obtained separation width is almost the same as the designed separation width. Further, in consideration of defects to the semiconductor silicon substrate, hydrogen or nitrogen is optimal as the ion to be irradiated to the silicon semiconductor material, and can be easily used in the silicon semiconductor process.

0010

According to the present invention, by the method of manufacturing a semiconductor device described above, it is possible to easily form a fine element isolation which is thick and does not reduce the isolation width due to the growth of bird's beaks. In particular, as ions for irradiating silicon semiconductor materials,
By using hydrogen or nitrogen, the oxidation rate of silicon in the irradiated area is rapidly increased, and these ions can also be easily used in silicon semiconductor processes. That is, by irradiating a silicon semiconductor material with these ions and oxidizing it at a low temperature, oxidation of the non-irradiated region can be suppressed, and an isolation can be formed as per the designed isolation width. Therefore,
By using the present invention, it is possible to effectively form fine element isolations of semiconductor devices easily, accurately, and with fewer defects at low temperatures.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of manufacturing a semiconductor device according to an embodiment of the present invention will be described below with reference to the drawings.

(FIG. 1) shows a process cross-sectional view of a method for manufacturing a semiconductor device in an embodiment of the present invention. A silicon oxide film layer 12 with a thickness of 10 to 50 nm is formed on the surface of the semiconductor silicon substrate 11 by thermal oxidation at 900 to 1100°C, and a silicon nitride film layer 13 is further formed thereon as an oxidation-resistant film by a chemical vapor phase reaction method. 100-300nm
It was formed thickly (Fig. 1(a)). A resist pattern is formed on this silicon nitride film layer using lithography technology, and using this resist pattern as a mask, the silicon nitride film and silicon oxide film layer are etched to transfer the pattern and selectively expose the semiconductor silicon substrate. I let it happen. Next, 1 hydrogen ion is placed on the exposed semiconductor silicon substrate.
4, acceleration voltage 30kV, irradiation amount 1x1015/cm2
A hydrogen ion irradiation region 15 was formed on the semiconductor silicon substrate by irradiation with hydrogen ions (FIG. 1(b)). At this time, the thickness of the hydrogen ion irradiation area was approximately 0.5 μm,
The silicon substrate below the remaining portion of the silicon nitride film is not irradiated with hydrogen ions because the silicon nitride film serves as a mask. By heat-treating this substrate in an oxidizing atmosphere at a temperature lower than the conventional temperature for a certain period of time, the area of the semiconductor silicon substrate irradiated with hydrogen ions can be changed into a thick oxide film 16 of 300 to 1000 nm. (Figure 1(c)). At this time, the oxidation rate of the silicon semiconductor material that has been irradiated with hydrogen ions is faster than that of the silicon semiconductor material that has not been irradiated with ions, as shown in Figure 3. ,
Longitudinal oxidation occurs at a substantially faster rate than transverse oxidation. As a result, the invasion of bird's beaks due to lateral oxidation could be substantially reduced, and as shown in the figure, a separation width close to the design dimension could be obtained. Thereafter, by removing the silicon nitride film and the silicon oxide film layer to expose the surface of the semiconductor silicon substrate, fine element isolation could be formed (FIG. 1(d)).

In the present invention, the amount of hydrogen ion irradiation may be such that the oxidation rate of the silicon semiconductor material can be substantially increased, and the amount is 5×10 14 /
cm2 or more is sufficient. Further, the depth of irradiation of the silicon substrate with hydrogen ions may be approximately the same as the oxidized thickness, and an acceleration voltage of 40 kV or less is sufficient at this time.

A second embodiment of the present invention will be described below with reference to the drawings. (FIG. 2) is a process cross-sectional view of a method for manufacturing a semiconductor device showing a second embodiment of the present invention. A silicon oxide film layer 21 with a thickness of 10 to 50 nm is formed on the surface of the semiconductor silicon substrate 11 by thermal oxidation at 900 to 1100° C., and a silicon nitride film layer 22 is further formed thereon as an oxidation-resistant film by a chemical vapor phase reaction method. 100-300nm
It was formed thickly (FIG. 2(a)). A resist pattern is formed on this silicon nitride film layer using lithography technology, and using this resist pattern as a mask, the silicon nitride film and silicon oxide film layer are etched to transfer the pattern and selectively expose the semiconductor silicon substrate. I let it happen. Next, 2 nitrogen ions are placed on the exposed semiconductor silicon substrate.
3, acceleration voltage is 150kV, irradiation amount is 1x1015/c
A nitrogen ion irradiation region 24 was formed on the semiconductor silicon substrate by irradiating with m2 (FIG. 2(b)). At this time, the thickness of the nitrogen ion irradiation region is about 0.4 μm, and the silicon substrate below the remaining portion of the silicon nitride film is not irradiated with nitrogen ions because the silicon nitride film serves as a mask. By heat-treating this substrate in an oxidizing atmosphere at a temperature lower than the conventional temperature for a certain period of time, the area of the semiconductor silicon substrate irradiated with nitrogen ions can be changed into a thick oxide film 25 of 300 to 1000 nm. (Figure 2(c)). At this time, the oxidation rate of the silicon semiconductor material irradiated with nitrogen ions is (Fig. 3
), the vertical oxidation occurs at a substantially faster rate than the lateral oxidation, as it is faster than that of silicon semiconductor materials that have not been conventionally irradiated with ions. As a result, the invasion of bird's beaks due to lateral oxidation could be substantially reduced, and as shown in the figure, a separation width close to the design dimension could be obtained. after that,
By removing the silicon nitride film and the silicon oxide film layer to expose the surface of the semiconductor silicon substrate, fine element isolation could be formed (FIG. 2(d)).

In the present invention, the amount of nitrogen ion irradiation may be such that the oxidation rate of the silicon semiconductor material can be substantially increased, and the amount is 5×10 14 /
cm2 or more is sufficient. Further, the depth of irradiation of the silicon substrate with nitrogen ions may be approximately the same as the oxidized thickness, and an acceleration voltage of 200 kV or less is sufficient at this time.

Although the silicon oxide film layer is formed on the semiconductor silicon substrate, it is not necessary to form this silicon oxide film layer. In addition, ion irradiation was performed after etching the silicon nitride film and silicon oxide film layer, but
Ion irradiation may be performed after etching the silicon nitride film layer.

[0017]

[Effects of the Invention] As explained above, according to the present invention,
By irradiating hydrogen ions or nitrogen ions into the silicon semiconductor material before forming the field oxide film, the oxidation rate of the irradiated silicon area is essentially improved, and a sufficiently high oxidation rate can be obtained even at low temperatures. , it is possible to reduce the intrusion of the field oxide film into the active region due to selective oxidation, which was a drawback of conventional manufacturing methods, and as a result, there is almost no need for extra area to take into account the intrusion of the field oxide film. I'm done. It also has good compatibility with semiconductor processes, making it possible to easily form fine active regions with good reproducibility, and working effectively as an accurate element isolation with few defects, making it ideal for manufacturing ultra-high density integrated circuits. It can make a big contribution.

[Brief explanation of the drawing]

FIG. 1 is a process cross-sectional view of a method for manufacturing a semiconductor device in a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view of a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the growth rate of an oxide film and the oxidation temperature.

FIG. 4 is a diagram showing the relationship between the designed separation width and the actual separation width.

FIG. 5 is a process cross-sectional view of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

11 Semiconductor silicon substrate 12 Silicon oxide film 13 Silicon nitride film 14 Hydrogen ion 15 Hydrogen ion irradiation area 16 Oxide film

Claims (4)

[Claims] 1. A step of forming a silicon nitride film layer on the surface of a semiconductor silicon substrate, forming a resist pattern on the silicon nitride film layer, etching the silicon nitride film using the resist pattern as a mask, and patterning the silicon nitride film. a step of transferring and selectively exposing the semiconductor silicon substrate; a step of irradiating the semiconductor silicon substrate with a certain amount of ions with sufficient energy including hydrogen ions; and a step of placing the substrate in an oxidizing atmosphere. A step of changing the semiconductor silicon substrate region irradiated with the ions into a thick oxide film by heat treatment at a constant temperature for a certain period of time, and removing the silicon nitride film to expose the surface of the semiconductor silicon substrate. A method for manufacturing a semiconductor device, comprising the steps of: [Claim 2] Ion irradiation dose is 5×1014/cm
2 or more, and the acceleration voltage is 40 kV or less. 3. A step of forming a silicon nitride film layer on the surface of a semiconductor silicon substrate, forming a resist pattern on the silicon nitride film layer, and etching the silicon nitride film using the resist pattern as a mask to form a pattern. a step of transferring and selectively exposing the semiconductor silicon substrate; a step of irradiating the semiconductor silicon substrate with a certain amount of ions with sufficient energy including nitrogen ions; and a step of placing the substrate in an oxidizing atmosphere. A step of changing the semiconductor silicon substrate region irradiated with the ions into a thick oxide film by heat treatment at a constant temperature for a certain period of time, and removing the silicon nitride film to expose the surface of the semiconductor silicon substrate. A method for manufacturing a semiconductor device, comprising the steps of: [Claim 4] Ion irradiation dose is 5×1014/cm
4. The method of manufacturing a semiconductor device according to claim 3, wherein the acceleration voltage is 2 or more and the acceleration voltage is 200 kV or less.