JPH0529311A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To easily form a fine element isolation wherein its isolation width is not reduced by the growth of a bird's beak and its film thickness is thick, regarding the fine element isolation techinque of a semiconductor device. CONSTITUTION:A silicon nitride film 12, a silicon oxide film 13 and a second silicon nitride film 14 are formed on the surface of a semiconductor silicon substrate 11; after that, the first silicon nitride film 12 is exposed selectively. Then, tin ions are implanted into the exposed silicon nitride film 12; in addition, boron ions are impinged. After that, the first silicon nitride film 12 is etched and removed. Thereby, a phosphorus-ion implanted region 16 on the semiconductor silicon substrate 11 is exposed. The substrate is heat-treated in an oxygen atmosphere, at a temperature which is lower than that in conventional cases and for a definite time. Thereby, the region of the semiconductor silicon substrate into which phosphorus ions have been implanted is changed to a thick oxide film 17. After that, the silicon oxide film 13 and the silicon nitride film 12 are removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine element isolation technique for semiconductor devices, and more particularly to an improvement in a method of manufacturing a semiconductor device by a selective oxidation method.

[0002]

2. Description of the Related Art An integrated circuit includes a plurality of active elements which are separated from each other by insulating layers on a common semiconductor silicon substrate. Conventional LOCOS (LocalOxidation of Silicon)
In the method for manufacturing a semiconductor device by the method, a semiconductor substrate is separated into an active region and a field region via a buried insulator, and an element is formed in the active region.
The separation was performed by the selective oxidation method according to the process shown in FIG.

First, a silicon oxide film layer 51 is formed on the surface of the semiconductor silicon substrate 11, and a silicon nitride film layer 52 is further formed on the silicon oxide film layer (FIG. 5).
(A)). Next, the silicon nitride film layer and the silicon oxide film layer are selectively removed by the lithography technique and the dry etching technique to selectively expose the semiconductor silicon substrate, and an oxidation-resistant mask layer is formed on the planned active region. Are formed (FIG. 5 (b)). Next, a thick field oxide film 53 deeply buried in the semiconductor silicon substrate is formed by performing heat treatment in an oxygen atmosphere at a constant temperature for a predetermined time to oxidize it (FIG. 5C). Next, the silicon nitride film layer and the silicon oxide film layer on the active region are removed to expose the surface of the semiconductor silicon substrate to perform element isolation (FIG. 5D).

By the method described above, element isolation can be performed by the insulating film of the semiconductor device. But,
In the oxidation step in this method, oxygen laterally moves through the thin silicon oxide film layer, and as a result, oxide growth occurs on the outer peripheral portion of the surface of the active region. The lateral oxide protrusions formed in this manner are called bird's beaks. The formation of this bird's beak changes the dimensions of the pre-specified active area by moving the edges of the peripheral oxide, while also curving the outer peripheral portion of the active area, thereby reducing the available area of the active area. Will be reduced.

[0005]

As described above, in this conventional manufacturing method, as shown in FIG. 5 (c), the field oxide film greatly penetrates into the active region during the growth of the field oxide film. , (FIG. 5 (d)), the active area becomes narrow. Therefore, in order to obtain a desired size of the active region, it is necessary to consider the amount of the field oxide film penetrating in the lateral direction, which requires a large area. In addition, when the active area becomes fine, the finished active area becomes very narrow or cannot be formed due to the lateral penetration of the field oxide film. FIG. 4A shows the relationship between the design 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, and the size of the active region is reduced by 0.3 μm. That is, in the process of forming a thick oxide film, a bird's beak of 0.3 μm grew laterally. Furthermore, 0.3 μm
With the design separation width of, there arises a problem that the separation cannot be completely performed in the actual process.

Therefore, in order to suppress the growth of bird's beaks, various methods improved from the LOCOS method have been proposed. However, these methods make the process more complicated, the surface step becomes tight, and crystal defects also occur. It also has the drawback of increasing the leakage current because it increases. These have a drawback that they become a major obstacle to high integration of the semiconductor integrated circuit device. In order to solve these problems, the present inventors have completed a method of manufacturing a semiconductor device by a selective oxidation method in a fine element isolation technique for semiconductor devices.

[0007]

According to a method of manufacturing a semiconductor device of the present invention, a silicon nitride film layer is formed on a surface of a semiconductor silicon substrate, and a silicon oxide film layer and a second silicon oxide film layer are formed on the silicon nitride film layer. A step of forming a silicon nitride film layer, forming a resist pattern on the second silicon nitride film layer, and etching the second silicon nitride film and the silicon oxide film layer using the resist pattern as a mask to form a pattern. Transferring and selectively exposing the first silicon nitride film, irradiating the exposed silicon nitride film with a certain amount of ions having sufficient energy, and the first silicon Remove the nitride film,
Exposing the semiconductor silicon substrate, and heat-treating the substrate in an oxygen atmosphere at a constant temperature for a predetermined time to change the semiconductor silicon substrate region irradiated with the ions into a thick oxide film. And a step of removing the silicon nitride film and the silicon oxide film layer to expose the surface of the semiconductor silicon substrate. And, desirably, the irradiation amount of ions to be irradiated on the silicon nitride film layer is 5 × 10 ¹³ / cm ² or more, the acceleration voltage is 50 kV or less, and the irradiation amount is 1 × 10 ¹⁴ / cm ² or less, acceleration Voltage is 5
A method that is 0 kV or higher is provided.

Still further, according to the present invention, a step of forming a silicon oxide film layer on a surface of a semiconductor silicon substrate and forming a silicon nitride film and a silicon oxide film layer on the silicon oxide film layer; A resist pattern is formed on the second silicon oxide film layer, the second silicon oxide film and the silicon nitride film layer are etched using the resist pattern as a mask to transfer the pattern, and the first silicon oxide film is selected. Exposing the exposed silicon oxide film layer with a certain amount of ions having sufficient energy, removing the first silicon oxide film, and removing the semiconductor silicon substrate. By exposing the substrate and heat-treating the substrate in an oxygen atmosphere at a constant temperature for a predetermined time, the substrate is not irradiated with the ions. Wherein the step of changing the thick oxide film of the semiconductor silicon substrate area, in which by removing the silicon nitride film and a silicon oxide film layer to provide a method comprising a step of exposing the semiconductor silicon substrate surface. And, desirably, the irradiation amount of ions for irradiating the silicon oxide film layer is 5 × 10 ¹³ / cm ² or more, the acceleration voltage is 50 kV or less, and the irradiation amount is 1 × 10 ¹⁴ / cm ² or less, acceleration. A method is provided wherein the voltage is 50 kV or higher.

That is, by irradiating the silicon semiconductor material with ions, damage is induced in the silicon substrate, and silicon is more easily oxidized. Also,
As the irradiation dose of ions to irradiate the semiconductor silicon substrate,
Sufficiently high enough to substantially increase the oxidation rate of the ion-irradiated silicon semiconductor material relative to the union-irradiated silicon semiconductor material. (Figure 3)
Shows the relationship between the oxidation temperature and the oxidation rate in comparison between the conventional method and the present method. It can be seen that a higher oxidation rate can be obtained at a lower oxidation temperature by performing the oxidation by this method than by the conventional method. As a result, the region that has been subjected to ion irradiation can be easily oxidized at a temperature lower than the conventional oxidation temperature, the intrusion of the oxide film in the lateral direction can be suppressed, and the size of the bird's beak can be reduced. be able to. In addition, since the ion irradiation is performed on the silicon substrate through the silicon oxide film or the silicon nitride film, it is possible to suppress the diffusion and spread of the ions in the silicon substrate and suppress the occurrence of bird's peak. The relationship between the design separation width and the actual separation width obtained by this method is shown in FIG. 4 (b). It can be seen that there is almost no bird's beak penetration, and the actually obtained separation width is almost the same as the designed separation width. Further, phosphorus, tin, antimony, or the like is most suitable as the ions for irradiating the semiconductor silicon substrate, and when ion implantation into the silicon substrate is necessary, it can be performed simultaneously after the ion irradiation.

[0010]

According to the present invention, by the above-described method of manufacturing a semiconductor device, it is possible to easily form a fine element isolation having a large film thickness and without reducing the isolation width due to the growth of bird's beaks. In particular, by using phosphorus, tin, antimony, or the like as ions for irradiating the silicon semiconductor material, the oxidation rate of silicon in the irradiated region is rapidly increased, and these ions are easy in the silicon semiconductor process. And can be performed simultaneously with ion implantation. In addition, since the ion irradiation is performed on the silicon substrate through the silicon oxide film or the silicon nitride film, it is possible to suppress the diffusion and spread of the ions in the silicon substrate and suppress the occurrence of bird's peak.
That is, by irradiating the silicon semiconductor material with these ions and oxidizing them at a low temperature, it is possible to suppress the oxidation of the non-irradiated region, and it is possible to form separations according to the designed separation width. Therefore, by using the present invention, it works effectively at low temperature easily, accurately and with few defects to form fine element isolation of a semiconductor device.

[0011]

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

FIG. 1 is a process sectional view showing a method of manufacturing a semiconductor device according to an embodiment of the present invention. A silicon nitride film layer 12 as an oxidation resistant film having a thickness of 100 to 300 nm is formed on the surface of the semiconductor silicon substrate 11 by a chemical vapor reaction method.
The silicon oxide film layer 13 is formed to a thickness of 10 to 30 nm by the chemical vapor deposition method, and the second silicon nitride film layer 14 is formed to a thickness of 100 to 300 nm thereon. A resist pattern is formed on the silicon nitride film layer by using a lithography technique, the silicon nitride film and the silicon oxide film layer are etched using the resist pattern as a mask, and the pattern is transferred to form the first silicon nitride film layer. Selectively exposed. Next, phosphorus ions 15 are applied on the exposed silicon nitride film layer at an accelerating voltage of 5
Irradiation was performed at 0 kV and an irradiation dose of 1 × 10 ¹⁴ / cm ² , and phosphorous ions were further irradiated at an acceleration voltage of 200 kV and an irradiation dose of 5 × ^{10 10} / cm ² (FIG. 1 (a)). Then, the first silicon nitride film 12 was removed by etching to expose the ion irradiation region 16 formed on the semiconductor silicon substrate (FIG. 1).
(B)). At this time, the thickness of the ion irradiation region is about 0.5.
The silicon substrate below the remaining portion of the silicon oxide film is not irradiated with phosphorus ions by using the silicon nitride film and the silicon oxide film as a mask. By subjecting this substrate to heat treatment in an oxygen atmosphere at a temperature lower than a conventional temperature for a certain period of time, the semiconductor silicon substrate region irradiated with phosphorus ions is exposed to 300 to 100.
It was possible to change to a thick oxide film 17 of 0 nm (Fig. 1
(C)). At this time, the oxidation rate of the silicon semiconductor material irradiated with phosphorus ions is higher than that of the silicon semiconductor material not conventionally irradiated with ions as shown in (FIG. 3), Longitudinal oxidation occurs at a substantially faster rate than lateral oxidation. Further, since the ion irradiation is performed on the silicon substrate through the silicon nitride film, it is possible to suppress the diffusion and spread of the ions in the silicon substrate. As a result, bird's beak penetration due to lateral oxidation could be substantially reduced, and a separation width close to the design dimension could be obtained, as shown in the figure. Then, by removing the silicon oxide film and the silicon nitride film layer to expose the surface of the semiconductor silicon substrate,
It was possible to form fine device isolation (FIG. 1D).

In the present invention, the irradiation amount of the first phosphorus ion may be such that the oxidation rate of the silicon semiconductor material can be substantially increased, and the irradiation amount is 5 × 10 5.
¹³ / cm ² or more is sufficient, and the irradiation depth on the silicon substrate may be about the thickness of oxidation, and the acceleration voltage at this time is 50 kV or less.

A second embodiment of the present invention will be described below with reference to the drawings. (FIG. 2) is a process sectional view of a method for manufacturing a semiconductor device, showing a second embodiment of the present invention. A silicon oxide film layer 21 of 100 to 200 nm is formed on the surface of the semiconductor silicon substrate 11 by thermal oxidation at 900 to 1100 ° C.
A silicon nitride film layer 22 as an oxidation resistant film is formed thereon to a thickness of 100 to 300 nm by a chemical vapor reaction method, and a second silicon oxide film layer 23 is further formed thereon.
It was formed to a thickness of 00 to 200 nm. A resist pattern is formed on the silicon oxide film layer by using a lithography technique, the silicon oxide film and the silicon nitride film layer are etched using the resist pattern as a mask, and the pattern is transferred to form the first silicon oxide film layer. Exposed. Then, tin ions 24 are formed on the exposed silicon oxide film layer.
At an accelerating voltage of 50 kV and a dose of 1 × 10 ¹⁴ / cm ² ,
Furthermore, boron ions are used at an acceleration voltage of 100 kV and an irradiation dose of 1
Irradiation was performed at x10 ¹³ / cm ² (Fig. 2 (a)). Then, the first silicon oxide film 21 was removed by etching to expose the ion irradiation region 25 formed on the semiconductor silicon substrate (FIG. 2B). At this time, the thickness of the tin ion irradiation region is about 0.2 μm, and the silicon substrate below the remaining portion of the silicon nitride film does not receive the ion irradiation because the silicon nitride film and the silicon oxide film serve as a mask. .
By subjecting this substrate to heat treatment in an oxygen atmosphere at a temperature lower than a conventional temperature for a certain period of time, the semiconductor silicon substrate region irradiated with tin ions is exposed to 30
It was possible to change to a thick oxide film 26 of 0 to 1000 nm (FIG. 2C). At this time, the oxidation rate of the silicon semiconductor material irradiated with tin ions is higher than that of the silicon semiconductor material not conventionally irradiated with ions, as shown in (FIG. 3). Longitudinal oxidation occurs at a substantially faster rate than lateral oxidation.
Further, since the ion irradiation is performed on the silicon substrate via the silicon oxide film, it is possible to suppress the diffusion and spread of the ions in the silicon substrate. As a result, bird's beak penetration due to lateral oxidation could be substantially reduced, and a separation width close to the design dimension could be obtained, as shown in the figure. After that, the silicon nitride film and the silicon oxide film layers were removed to expose the surface of the semiconductor silicon substrate, whereby fine element isolation could be formed (FIG. 2D).

In the present invention, the dose of tin ions may be such that the oxidation rate of the silicon semiconductor material can be substantially increased, and the dose is 5 × 10 ¹³ / cm ^2.
The above is sufficient, the irradiation depth to the silicon substrate may be about the thickness of oxidation, and the acceleration voltage at this time is 50 kV or less.

[0016]

As described above, according to the present invention,
By irradiating ions into the silicon semiconductor material before forming the field oxide film, the oxidation rate of the irradiated silicon region is essentially improved, and a sufficiently high oxidation rate can be obtained even at a low temperature. Since it is possible to reduce the penetration of the field oxide film into the active region in the selective oxidation, which has been a drawback of, the ion irradiation is performed through the silicon oxide film or the silicon nitride film on the silicon substrate. It is possible to suppress the diffusion and spread of ions in the silicon substrate and suppress the occurrence of bird's peaks. As a result, a margin area considering the penetration of the field oxide film is almost unnecessary. Also, it has good compatibility with the semiconductor process, and the irradiated ions can be used easily in the silicon semiconductor process and can be performed simultaneously with the ion implantation, so that a minute active area can be easily reproducibly and easily formed. Since it can be formed and effectively acts as an element isolation which is accurate and has few defects, it can greatly contribute to the manufacture of an ultra high density integrated circuit.

[Brief description of drawings]

FIG. 1 is a process sectional view of a method for manufacturing a semiconductor device according to a first embodiment of the present invention.

FIG. 2 is a process 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 a relationship between a design separation width and an actual separation width.

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

[Explanation of symbols]

11 Semiconductor silicon substrate 12 Silicon nitride film 13 Silicon oxide film 14 Silicon nitride film 15 ion 16 Ion irradiation area 17 Oxide film

Claims (4)

[Claims] 1. A step of forming a first silicon nitride film layer on a surface of a semiconductor silicon substrate, forming a silicon oxide film layer on the silicon nitride film layer, and further forming a second silicon nitride film layer. And forming a resist pattern on the second silicon nitride film layer, using the resist pattern as a mask to etch the second silicon nitride film and the silicon oxide film layer to transfer the pattern, Selectively exposing the nitride film layer, irradiating the exposed silicon nitride film layer with a certain amount of ions having sufficient energy, and removing the first silicon nitride film layer. The step of exposing the semiconductor silicon substrate and the heat treatment of the substrate in an oxygen atmosphere at a constant temperature for a predetermined period of time receive the ion irradiation. A semiconductor device comprising: a step of changing the semiconductor silicon substrate region into a thick oxide film; and a step of removing the silicon nitride film and the silicon oxide film layer to expose the surface of the semiconductor silicon substrate. Manufacturing method. 2. The dose of the ions is 5 × 10 ¹³ / cm ² or more, the acceleration voltage is 50 kV or less, and the dose is 1 ×.
^{2. The} method of manufacturing a semiconductor device according to claim 1, wherein the acceleration voltage is 10 ¹⁴ / cm ² or less and the acceleration voltage is 50 kV or more. 3. A step of forming a first silicon oxide film layer on a surface of a semiconductor silicon substrate, and forming a silicon nitride film layer and a second silicon oxide film layer on the silicon oxide film layer, A resist pattern is formed on the second silicon oxide film layer, the silicon oxide film and the silicon nitride film layer are etched using the resist pattern as a mask to transfer the pattern, and the first silicon oxide film layer is selectively removed. Exposing the exposed silicon oxide film layer to the exposed silicon oxide film layer with a certain amount of ions having sufficient energy, removing the first silicon oxide film layer, and removing the semiconductor silicon substrate. The step of exposing
Heating the substrate in an oxygen atmosphere at a constant temperature for a predetermined time to change the semiconductor silicon substrate region irradiated with the ions into a thick oxide film; and the silicon nitride film and the silicon oxide film. Removing the layer to expose the surface of the semiconductor silicon substrate. 4. The dose of the ions is 5 × 10 ¹³ / cm ² or more, the acceleration voltage is 50 kV or less, and the dose is 1 ×.
4. The method of manufacturing a semiconductor device according to claim 3, wherein the acceleration voltage is 10 ¹⁴ / cm ² or less and the acceleration voltage is 50 kV or more.