JPS60236246A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To form an insulating film for separating elements with necessary thickness only on a necessary region by forming the insulating film for separating by a selective oxidizing method, and removing by etching an unnecessary portion of bird beak. CONSTITUTION:An oxide film 12 for separating is formed by a selective oxidizing method, and a polysilicon film 16, a nitride film 17 and an organic polymer film 18 are laminated. The layer 18 is etched, the layer 17 is exposed at the portion of the separating region X, and the portion of an element region Y remains masked with the layer 18. The exposed portion of the layer 17 is etched, and the layer 16 is exposed. The layer 18 is removed, and a mask oxide film 19 is grown on the exposed portion of the layer 16. The portions of the layers 17, 18 are removed by etching. The film 19 and the bird beak 15' of the film 12 are removed by etching. Separating oxide film 15 remains only at the portion of the separating region X, and the bird beak does not exist on the element region Y.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of manufacturing an insulating film for element isolation.

[Technical background of the invention]

Each element that is a component of a semiconductor device is generally insulated and isolated by a thick oxide film. One method for manufacturing this thick oxide film is to form a thick oxide film over the entire surface of the semiconductor substrate and then remove the oxide film in the element region.

However, this method has the disadvantage that it is difficult to form a so-called channel cut region in the isolation region, so recently, a selective oxidation method is generally used.

A method of manufacturing an insulating film using a conventional selective oxidation method will be briefly explained using FIG. First, as shown in Figure 3(a),
A buffer oxide film 12 is formed on a semiconductor substrate 11, and a nitride film 13 is further formed thereon. Subsequently, an opening 14 is provided in the nitriding region and the barrel portion (FIG. 3(b)), and the opening 14 is oxidized to form a thick isolation oxide film 1.
5 (Figure 3(0)).

In FIGS. 3(i) and 3(C), the region indicated by This is the point where a thin oxide film 1- called J-1 enters.

[Problems with background technology]

LSI devices are becoming more and more highly integrated year by year, and for example, the integration of dynamic RAM, which is a typical type of MO memory, has been doubled in just two years. Under these circumstances, in order to achieve high integration of LSIs, it is necessary not only to reduce the size of the elements themselves but also to reduce the isolation regions between the elements.

However, in the selective oxidation method described above, the bird's beak IFI'
penetrates into the element region, substantially expanding the isolation region.

Generally, there are various etching processes in each LSI manufacturing process after the isolation region is formed, and the number of etching processes usually increases as the degree of integration increases. Therefore, in anticipation of the insulating film formed in the isolation region being eroded by these etching processes, the higher the degree of integration, the thicker the insulating film initially formed becomes.

However, when the insulating film is made thicker, the portion of the bird's beak that penetrates also increases, which goes against the reduction in the isolation region required for higher integration.

A method of making the openings 14 smaller in advance to anticipate the occurrence of bird's beaks may be considered, but if the openings 14 become smaller, the oxidation process required to form the insulating film will not take place sufficiently.
It becomes difficult to form a thick oxide film.

As described above, the conventional selective oxidation method has the disadvantage that it is difficult to achieve high integration on the row 9.

[Purpose of the invention]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for manufacturing a semiconductor device that can form an element isolation insulating film having a necessary thickness only in a necessary region.

[A chest of inventions]

A feature of the present invention is that in a method for manufacturing a semiconductor device having an isolation insulating film, after forming an isolation insulating film by a conventional selective oxidation method, only necessary portions of the isolation insulating film are masked, and bird's beaks are formed. The semiconductor device is highly integrated by removing unexploded parts such as etching by etching and forming an insulating film only in necessary areas.

[Embodiments of the invention]

A detailed description will be given below based on an example illustrating a xylophone. First, a conventional selective oxidation method is used to form an isolation oxide film as shown in FIGS. FIG. 1(a) is the same diagram as FIG. For example, 4000
λ is laminated, and a new nitride film 17 is formed as the first layer, for example, by one layer.
000λ is laminated to form a second layer, and an organic polymer film 18 is further laminated from above to form a third layer. The steps up to this point are shown in FIG. 1(b). Note that the surface of the third layer is made to be flat. This means, for example, that a solution of an organic polymer is
This can be achieved by pouring the solvent onto the semiconductor substrate and evaporating the solvent while rotating the semiconductor substrate. Although a polysilicon film is used as the first layer 16 in this embodiment, other materials may be used as long as they have etching characteristics different from those of the isolation oxide film 12. Although a nitride film is used as the second layer 17, other materials may be used as long as they are oxidation resistant and have etching characteristics different from those of the first layer 16. In addition, the third layer 18
For example, an organic polymer film is used, which has different etching characteristics from the second layer 17 and can be layered so that the upper surface is flat (for example, an inorganic material such as spin-on glass). Other materials may be used as long as the materials are suitable.

Next, layer 18 of candy 3 with R (Reactive I)
Etching is performed using anisotropic etching such as onEtching) to expose the second protrusion 17 to the same extent as the opening 14 (tJ=', Figure 1(c)). That is, the second W 117 is exposed in the isolation region X, and the process for forming the third layer 18 and above can be easily performed in the element region Y.

Next, using the remaining third layer 18 as a mask, the second layer 18 is
The exposed portions of 117 are etched to expose first layer 16. Subsequently, all remaining third layer 18 is removed. Furthermore, a masking oxide film 19 is grown to a thickness of, for example, 2000λ on the exposed portion of the first layer 16 (FIG. 1(d)).
.

Subsequently, the remaining portion of the second layer 17 is removed by etching, and the first 1#1 is etched using the mask oxide film 19 as a mask.
The unmasked portions of No. 6 are removed by etching. Finally, the bird's beak 15° portion of the mask oxide film 19 and isolation oxide film is removed by etching.

The state after the completion of the above steps is shown in FIG. 1(e). The isolation oxide film 15 remains only in the isolation region X together with the first layer 16, leaving only the element region! Bird's beak no longer exists and can be effectively used for element arrangement. Furthermore, since the first layer 16 remains on the isolation oxide film, it is possible to prevent the isolation oxide film from becoming fragile due to etching or the like in the subsequent element formation process.

For example, due to the second factor, a cell capacitor portion 10 with an area of 10 μm8
If 0 is designed as the element region and the isolation oxide film is formed with a thickness of 0.8 μm using the conventional method, the actual device region 110 will be reduced in area to 5.6 μm due to the invasion of bird's beaks. . In the method according to the present invention, the actual device area has the same area as the device area 100 at the beginning of the design, and it is possible to secure a device area that is 1.79 times larger than the conventional method.

Conventionally, masks with so-called conversion differences were used in anticipation of the reduction in device area due to bird's beak invasion during design, but with the present invention, this is no longer necessary and the degree of integration is improved. Not only can it be done easily, but it can also be designed very easily.

As an additional effect of the present invention, the area of the final separation region can be increased or decreased by controlling the amount of etching of the third layer and increasing or decreasing the exposed area of the second layer. This is useful when using the same mask to form isolation regions with different areas.

〔Effect of the invention〕

As described above, according to the present invention, since the bird's beak, which is an unnecessary part of the insulating film for element isolation in a semiconductor device, is removed, an insulating film having the necessary thickness can be formed only in the necessary area. , the degree of integration can be further increased.

[Brief explanation of drawings]

FIG. 1 is a process explanatory diagram of the method for manufacturing a semiconductor device according to the present invention, FIG. 2 is a comparative diagram of semiconductor devices manufactured by the method according to the present invention and a conventional method, and FIG. 3 is a diagram explaining the process of manufacturing a semiconductor device according to the present invention. It is a process explanatory diagram of the manufacturing method of a device. 11... Semiconductor substrate, 12... Buffer oxide film, 13.
...Nitride film, 14...Opening portion, 15...Isolation oxide film, 16...First layer (polysilicon film), 17...
・Second layer (sealed), 18... Third layer (organic polymer film), 19... Oxide film for mask, 100... Element area at the time of design, 101... Bird's beak The element area after the agile reception. Applicant's agent Kiyoshi Inomata 61 Kuchi 62 Figure 3 Closed

Claims (1)

[Claims] 1. A step of forming a buffer oxide film on a semiconductor substrate and an oxidation-resistant film thereon, a step of providing an opening in the oxidation-resistant film, and a step of forming the buffer oxide film on the semiconductor substrate. a step of oxidizing a portion corresponding to the opening to increase the film thickness of the portion of the buffer oxide film corresponding to the opening to form an isolation oxide film; and a step of removing the oxidation-resistant film. forming a mask layer made of a material having etching characteristics different from those of the isolation oxide film only on the isolation oxide film; and removing the buffer oxide film by etching using the mask layer. A method for manufacturing a semiconductor device, comprising the steps of: 2. A step of forming a buffer oxide film on a semiconductor substrate and an oxidation-resistant film thereon; and a step of providing an opening in the oxidation-resistant film. oxidizing a portion of the semiconductor substrate corresponding to the opening;
a step of increasing the thickness of a portion of the buffer oxide film corresponding to the opening to form an isolation oxide film; a step of removing the oxidation-resistant film; and a step of removing the buffer oxide film and the isolation film. forming a first layer on the oxide film made of a material that has etching properties different from those of the oxide films; forming a third layer made of a material having etching properties different from those of the second layer on the second layer so that the upper surface thereof is flat; etching a portion of the third layer to expose a portion of the second layer; etching and removing the exposed portion of the second layer; exposing a portion of the first layer; removing the remaining portion of the third layer; forming a masking oxide film on the exposed portion of the first layer; a step of removing by etching the remaining portion of the second layer; a step of removing by etching a portion of the first layer where the mask oxide film is not formed; and the buffer oxide film. and a step of removing by etching a portion of the isolation oxide film where the mask oxide film is not formed. 3. The semiconductor device according to claim 2, wherein the first layer is formed to have a sufficient thickness so that the first layer remains even after the entire manufacturing process of the semiconductor device is completed. Production method. 4. The method of manufacturing a semiconductor device according to claim 2 or 3, wherein the first layer is made of polysilicon. 5. The method for manufacturing a semiconductor device according to any one of claims 2 to 4, wherein the second layer is made of silicon nitride. 6. The method for manufacturing a semiconductor device according to any one of claims 2 to 5, wherein the third layer is made of an organic polymer.