JPH05218193A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form fine, flat element isolation featuring only a few crystal defects by highly integrating a semiconductor IC. CONSTITUTION:(b): With a silicon nitride film 12 formed optionally as a mask, etching is performed by using mixed liquid composed of fluorine and nitric acid, and a moderate inclined groove is formed on a semiconductor silicon substrate 11. (c): A field oxide 13 is formed by applying optionally thermal oxidation on the semiconductor silicon substrate 11. (d): To coat thickly resist 15 on a silicon nitride film 12, and to apply anisotropic dry etching under the conditions of the same etching rate as that for the resist 15, the silicon nitride film 12, the field oxide 13, and the semiconductor silicon substrate 11. (e): To form flat and fine element isolation featuring only a few crystal defects, by etching the field oxide 13 and the silicon substrate 11 up to an etching backspace line 14, as shown in (d).

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, which is an improved technique for fine element isolation of a semiconductor device.

[0002]

2. Description of the Related Art An integrated circuit includes a plurality of active devices which are separated from each other by insulating layers on a common semiconductor silicon substrate. Conventional LOCOS (Local Oxidation of Silico
In the method of manufacturing a semiconductor device by the method n), the semiconductor substrate is separated into an active region and a field region through a buried insulator, and an element is formed in the active region. (FIG. 3).

First, a silicon nitride film layer 12 is formed on the surface of a semiconductor silicon substrate 11 (FIG. 3 (a)). Next, the silicon nitride film is selectively removed by lithography and dry etching to expose the semiconductor silicon substrate selectively, and an oxidation resistant mask layer is formed on the planned active region (FIG. 3). (B)). Next, oxidation is performed by performing heat treatment at a constant temperature for a predetermined time in an oxidizing atmosphere to form a thick field oxide film 13 deeply buried in the semiconductor silicon substrate (FIG. 3C). Next, the silicon nitride film on the active region is removed to expose the surface of the semiconductor silicon substrate to perform element isolation (FIG. 3 (d)).

By the method as described above, element isolation can be performed by the insulating film of the semiconductor device. But,
In the oxidation step of this method, lateral movement of oxygen through the thin silicon oxide film layer results in oxide growth 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. With the entry of this bird's beak,
The size of the active area becomes smaller than the design size. Therefore, the usable portion of the active area is reduced. Moreover, stress is generated in the silicon crystal due to the expansion of the selective oxide film, and many crystal defects are generated in the silicon crystal near the bird's beak.

[0005]

As described above, in this conventional manufacturing method, as shown in FIG. 3 (c), the field oxide film greatly penetrates into the active region during the growth of the field oxide film. , (FIG. 3 (d)), the active area becomes narrow. Therefore, as the device becomes finer, the finished active area becomes very narrow due to the lateral penetration of the field oxide film.
Alternatively, the active area cannot be formed. If the film thickness of the field oxide film is reduced, bird's beak penetration is reduced, but sufficient element isolation characteristics cannot be obtained. Moreover, the crystal defect generated in the silicon crystal near the bird's beak increases the leak current between the elements and deteriorates the characteristics of the transistor formed in the active region. Therefore, the conventional LOCOS method has a limit to miniaturization of the element,
It is difficult to obtain good element characteristics, which is a major obstacle to high integration of the semiconductor integrated circuit device. Moreover, in the conventional LOCOS method, a step is generated, which makes it difficult to perform a process such as a bit wiring in a post process.

The present invention solves the above problems, and an object of the present invention is to provide a method of manufacturing a semiconductor device in which fine element isolation is realized.

[0007]

According to the present invention, there is provided a step of selectively etching the exposed semiconductor substrate using a silicon nitride film selectively formed on the semiconductor substrate as a mask, and the exposed semiconductor substrate. Forming a thermal oxide film on the semiconductor substrate, applying a resin on the semiconductor substrate, etching the resin, the silicon nitride film and the semiconductor substrate, and removing a part of the upper layer portion of the thermal oxide film. The present invention provides a method for manufacturing a semiconductor device, which comprises: And, preferably, in the step of selectively etching the exposed semiconductor substrate using the silicon nitride film selectively formed on the semiconductor substrate as a mask, etching is performed using a mixed solution of hydrofluoric acid and nitric acid. A method for manufacturing the above semiconductor device is provided. Further preferably, the step of etching the resin, the silicon nitride film and the semiconductor substrate to remove a part of an upper layer portion of the thermal oxide film is performed by the resin, the silicon nitride film, the semiconductor substrate and the thermal oxidation film. There is provided a method for manufacturing a semiconductor device as described above, characterized in that anisotropic dry etching is performed under the condition that the film has an equal etching rate.

Further, according to the present invention, a step of forming a thermal oxide film on the exposed semiconductor substrate using the silicon nitride film selectively formed on the semiconductor substrate as a mask, and the thermal oxide film is removed. The step of forming a thermal oxide film on the exposed semiconductor substrate, the step of applying a resin on the semiconductor substrate, the resin, the silicon nitride film and the semiconductor substrate are etched, and the thermal oxidation is performed. And a step of removing a part of an upper layer portion of the film, to provide a method for manufacturing a semiconductor device. And
It is desirable that the step of removing the thermal oxide film be etching using hydrofluoric acid. Also preferably, the resin, the silicon nitride film and the semiconductor substrate are etched,
The step of removing a part of the upper layer portion of the thermal oxide film is performed by anisotropic dry etching under the condition that the resin, the silicon nitride film, the semiconductor substrate and the thermal oxide film have the same etching rate. A method for manufacturing the above semiconductor device is provided.

[0009]

According to the present invention, by the method of manufacturing a semiconductor device described above, it is possible to reduce the penetration of bird's beaks in the selective oxide film, and it is possible to form fine element isolation with few crystal defects. In particular, a groove is formed in the semiconductor substrate, the inside of the groove is selectively oxidized, and a part of the upper layer portion of the selective oxide film is removed by etchback, so that the bird's beak intrusion of the selective oxide film can be reduced. At the same time, since a part of the silicon crystal near the edge of the oxide film is etched at the same time, crystal defects can be reduced as compared with the normal LOCOS method. Further, as a method of forming a groove in a semiconductor substrate, isotropic wet etching using a mixed solution of hydrofluoric acid and nitric acid can be performed to form a groove having a gentle slope. The stress on the substrate at can be relaxed. As another method of forming a groove on a semiconductor substrate, a selective oxide film is formed by using a normal LOCOS method, and the selective oxide film is removed by using hydrofluoric acid to form a groove having a gentle slope. It can be formed, and the stress on the substrate at the time of forming the thermal oxide film can be relaxed. By forming the selective oxide film in the gently sloping groove in this manner, element isolation with fewer crystal defects can be formed. Further, since the step-back which is seen in the normal LOCOS method does not occur due to the etch-back, the post-process is simplified. Therefore, the use of the present invention effectively acts on the fine element isolation formation of a semiconductor device with few crystal defects.

[0010]

DETAILED 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 of a method for manufacturing a semiconductor device according to an embodiment of the present invention. After depositing the silicon nitride film 12 having a thickness of 160 nm on the semiconductor silicon substrate 11, the silicon nitride film 12 was selectively removed by the photolithography technique and the dry etching technique (FIG. 1A). By using the silicon nitride film 12 as a mask and performing isotropic wet etching using a mixed solution of hydrofluoric acid and nitric acid, the semiconductor silicon substrate 11
It was possible to form a groove having a gentle slope with a depth of 300 nm (FIG. 1 (b)). By performing heat treatment in an oxidizing atmosphere at a constant temperature for a constant time, the groove on the semiconductor silicon substrate 11 is selectively oxidized to form a field oxide film 13 deeply buried in the semiconductor silicon substrate to a thickness of 500 nm. (FIG. 1 (c)). Then, a resist 15 having a thickness of 1. is formed on the silicon nitride film 12.
5 μm was applied (FIG. 1 (d)). By performing anisotropic dry etching on the resist 15, the silicon nitride film 12, the field oxide film 13, and the semiconductor silicon substrate 11 under the condition of having the same etching rate,
The field oxide film 13 and the silicon substrate 11 were etched to a depth of 200 nm up to the etching receding line 14 shown in FIG. 1 (d) (FIG. 1 (e)). In this way, thickness 3
It was possible to form a fine element separation of 00 nm.

As described above, according to this embodiment, the field oxide film is etched back by etching under the condition that the resist, the silicon nitride film, the field oxide film, and the silicon substrate have the same etching rate. By removing a part of the upper layer portion, it was possible to reduce the penetration of bird's beaks, and it was possible to form fine element isolation. Further, since the silicon crystal near the edge of the field oxide film is partly etched, the crystal defects generated in the silicon crystal near the edge of the field oxide film could be reduced. Moreover, by etching back, it was possible to form a flat element isolation having no step. Further, in this embodiment, since the groove having a gentle slope is formed on the semiconductor silicon substrate and the selective oxide film is formed in the groove, the stress on the semiconductor silicon substrate can be reduced and the crystal defects can be further suppressed. I was able to do it.

In this embodiment, a mixed solution of hydrofluoric acid and nitric acid is used for forming the groove on the semiconductor silicon substrate, but wet etching using another etching solution or dry etching may be used.

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 according to an embodiment of the present invention. After depositing the silicon nitride film 12 having a thickness of 160 nm on the semiconductor silicon substrate 11, the silicon nitride film 12 was selectively removed by the photolithography technique and the dry etching technique (FIG. 2A). By performing heat treatment at a constant temperature for a predetermined time in an oxidizing atmosphere, the semiconductor silicon substrate 11 was selectively oxidized to form a field oxide film 13 having a thickness of 600 nm (FIG. 2B). By performing wet etching with hydrofluoric acid, the field oxide film 13 was removed, and a groove having a gentle slope with a depth of 300 nm could be formed on the semiconductor silicon substrate 11 (FIG. 2C). By performing heat treatment at a constant temperature for a predetermined time in an oxidizing atmosphere, the groove on the semiconductor silicon substrate 11 is selectively oxidized to form a field oxide film 13 deeply buried in the semiconductor silicon substrate to a thickness of 500 nm. (Fig. 2
(D)). Then, a resist 15 having a thickness of 1.5 μm was applied on the silicon nitride film 12 (FIG. 2E). Anisotropic dry etching is performed on the resist 15, the silicon nitride film 12, the field oxide film 13, and the semiconductor silicon substrate 11 under the condition of having the same etching rate, so that the etching recession shown in FIG. Line 1
The field oxide film 13 and the silicon substrate 11 were etched to a depth of 200 nm up to 4 (FIG. 2 (f)). In this way, fine element isolation having a thickness of 300 nm could be formed.

As described above, according to this embodiment, the field oxide film is etched back by etching back under the condition that the resist, the silicon nitride film, the field oxide film, and the silicon substrate have the same etching rate. By removing a part of the upper layer portion, it was possible to reduce the penetration of bird's beaks, and it was possible to form fine element isolation. Further, since the silicon crystal near the edge of the field oxide film is partly etched, the crystal defects generated in the silicon crystal near the edge of the field oxide film could be reduced. Moreover, by etching back, it was possible to form a flat element isolation having no step. Further, in this embodiment, since the groove having a gentle slope is formed on the semiconductor silicon substrate and the selective oxide film is formed in the groove, the stress on the semiconductor silicon substrate can be reduced and the crystal defects can be further suppressed. I was able to do it.

In this embodiment, a method of forming a selective oxide film and removing the selective oxide film with hydrofluoric acid was used for forming the trench on the semiconductor silicon substrate. Wet etching using another etching solution or dry etching may be used.

[0017]

As described above, according to the method of manufacturing a semiconductor device of the present invention, a groove having a gentle slope is formed in the semiconductor substrate, the inside of the groove is selectively oxidized, and the selected by etching back. To remove a part of the upper layer of the oxide film,
Intrusion of bird's beaks in the selective oxide film can be reduced, and at the same time, a part of the silicon crystal near the edge of the oxide film is etched, so that crystal defects can be reduced as compared with the normal LOCOS method. Therefore, the area of the active region does not decrease due to the entry of bird's beaks in the selective oxide film, and it is possible to form a finer element isolation with a higher density than that of the usual LOCOS method, and it is possible to form an element gap caused by crystal defects A leak current can be suppressed, and a semiconductor device having excellent element characteristics can be formed in the active region. Further, since the etching back is performed, the level difference seen in the normal LOCOS method does not occur, a flat element isolation can be formed, and a process such as a bit wiring in a post process becomes easy. Therefore, the use of the present invention effectively acts on the formation of fine element isolation of a semiconductor device which has few crystal defects and is flat, and can greatly contribute to 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 process sectional view of a conventional method for manufacturing a semiconductor device.

[Explanation of symbols]

 11 semiconductor silicon substrate 12 silicon nitride film 13 field oxide film 14 etching receding line 15 resist

Claims (6)

[Claims] 1. A step of selectively etching the exposed semiconductor substrate using a silicon nitride film selectively formed on the semiconductor substrate as a mask, and a step of forming a thermal oxide film on the exposed semiconductor substrate. And a step of applying a resin on the semiconductor substrate, and a step of etching the resin, the silicon nitride film and the semiconductor substrate to remove a part of an upper layer portion of the thermal oxide film. A method of manufacturing a semiconductor device, which is characterized. 2. The step of selectively etching the exposed semiconductor substrate using the silicon nitride film selectively formed on the semiconductor substrate as a mask is performed by using a mixed solution of hydrofluoric acid and nitric acid. Claim 1 characterized by the above.
A method of manufacturing a semiconductor device according to claim 1. 3. The step of etching the resin, the silicon nitride film, and the semiconductor substrate to remove a part of an upper layer portion of the thermal oxide film includes the resin, the silicon nitride film, the semiconductor substrate, and the heat treatment. 2. The method for manufacturing a semiconductor device according to claim 1, wherein anisotropic dry etching is performed under the condition that the oxide film has an equal etching rate. 4. A step of forming a thermal oxide film on the exposed semiconductor substrate using the silicon nitride film selectively formed on the semiconductor substrate as a mask, a step of removing the thermal oxide film, and an exposing step. Forming a thermal oxide film on the semiconductor substrate; applying a resin on the semiconductor substrate; etching the resin, the silicon nitride film, and the semiconductor substrate to form an upper layer portion of the thermal oxide film. And a step of removing the portion. 5. The method of manufacturing a semiconductor device according to claim 4, wherein in the step of removing the thermal oxide film, etching is performed using hydrofluoric acid. 6. The step of etching the resin, the silicon nitride film, and the semiconductor substrate to remove a part of an upper layer portion of the thermal oxide film includes the resin, the silicon nitride film, the semiconductor substrate, and the heat treatment. 5. The method for manufacturing a semiconductor device according to claim 4, wherein anisotropic dry etching is performed under the condition that the oxide film has an equal etching rate.