JPH0587141B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a three-dimensional semiconductor device having a grooved region in a semiconductor substrate, and particularly to a method for manufacturing an isolation film thereof.

[Conventional technology]

FIGS. 8 to 15 show the formation of an element isolation oxide film on the surface of a conventional semiconductor substrate other than the grooved area and on the sidewalls and bottom surfaces of the groove in a three-dimensional semiconductor device having a grooved area on the semiconductor substrate. FIG. 2 is a fragmentary cross-sectional view of a main part showing each step sequence of the method.

(Components) In FIG. 8, 1 is a semiconductor substrate such as single crystal silicon, 2 is an oxidation mask material such as a silicon nitride film, 3 is an underlay material such as a silicon oxide film for the silicon nitride film 2, and the following: 4 in Figure 9 of the process is
An element isolation oxide film such as a silicon oxide film, 5 in FIGS. 10 to 14 is an etching mask material such as a silicon oxide film used when trenching and etching the silicon substrate 1, and 6 in FIG.
1 is an etching mask material such as a resist used when patterning the oxide mask material 2, and 7 in the next step in FIG. Etching mask material such as silicon oxide film used in

(Conventional Manufacturing Method) Next, a conventional manufacturing method will be described. 7th
The figure is a sectional view of a main part in the final step according to the method of the present invention, which will be described later. The purpose is to form an isolation oxide film 4. First, as shown in FIG. 8, an oxide mask material 2 is deposited on the entire surface of the semiconductor substrate 1, and then the isolation regions other than the grooved regions on the semiconductor substrate 1 are formed through a photolithography process. FIG. 9 shows the state in which the oxidation mask 2 is patterned and separated and oxidized as shown in 4. Next, the oxide mask 2 was removed, a new oxide mask of the same type was formed on the entire surface, and then an etching mask material 5 used for trench etching of the semiconductor substrate 1 was formed and patterned through a photolithography process. After that, the grooved and etched state is shown in Figure 10, followed by the semiconductor substrate 1.
Figure 11 shows the state in which a silicon nitride film, which will become oxidation mask 2, is formed on the entire surface after thermally oxidizing the single crystal silicon. Figure 12 shows the patterned state after the photolithography process.
This figure shows a state in which the first layer of resist 6 has not yet been removed. That is, here, the oxidation mask 2 is removed only in the region where the sidewalls of the trench dug in the surface of the semiconductor substrate 1 are separated.

Next, the resist 6 is removed and a silicon oxide film 7 is formed on the entire surface as shown in FIG. 13, and the silicon oxide film 7 is subsequently etched by anisotropic etching such as reactive ion etching. In FIG. 14, the silicon oxide film 7 only on the side wall surface of the trench is thick from the top surface direction, so it remains as a frame without being etched. continue,
The state after the entire surface etching of the oxide mask 2 and the entire surface etching of the silicon oxide films 3, 5, and 7 is the 15th etching state.
In this figure, only the oxide mask 2 at the bottom of the groove is removed. That is, the surface of the semiconductor substrate 1 other than the trenching region is covered with a silicon oxide film 5, which is a mask material for trenching and etching, and the sidewall surface of the trench is
It is masked by a frame of silicon oxide film 7 formed by anisotropic etching, and only the oxide mask 2 at the bottom of the groove is removed. In the steps up to this point, the oxide mask 2 on the sidewalls of the trench was patterned, and then the oxide mask 2 on the bottom of the trench was removed. Figure 7 shows the separated and oxidized state.
This completes the process of isolation between elements.

To briefly summarize the above steps, initially, the isolation oxide film 4 on the surface of the semiconductor substrate 1 other than the grooved region is
, and then after digging a trench, the entire surface is covered with an oxide mask 2, the oxide mask on the side wall of the trench is patterned, the oxide mask 2 on the bottom of the trench is removed, and finally the side wall of the trench is removed. This process sequence can be summarized as a process sequence in which the isolation region between the bottom surface and the bottom surface is simultaneously oxidized.

[Problem that the invention seeks to solve]

However, in the conventional manufacturing method as described above, the isolation oxidation of the surface other than the grooved region on the semiconductor substrate 1 and the isolation oxidation of the side wall surface of the trench are performed in independent steps, so that the patterning of each A mask is required, and self-alignment between the two cannot be achieved. In addition, a margin for mask alignment must be taken in terms of pattern layout, and furthermore, mask misalignment is likely to occur during the trenching process, and the isolation oxide film region on the surface other than the trenching region on the substrate 1 and the trenching region are If they overlap, diagonal etching of the semiconductor 1 will occur, and the oxide mask 2 on the side wall of the trench may be removed without leaving the frame of the silicon oxide film 7 shown in FIG. There was a problem.

This invention was made in order to solve the problems of the conventional manufacturing method as described above. self-alignment, and prevents defective patterning of the oxide mask during isolation oxidation on the side wall surface of the trench due to overlap between the isolation oxide film region on the surface other than the trench region on the semiconductor substrate and the trench region. The purpose is to provide a semiconductor manufacturing method that can be used.

[Means for solving problems]

Therefore, in the semiconductor manufacturing method according to the present invention, after a trench is dug on a semiconductor substrate, the isolation oxide film on the surface other than the trench region on the semiconductor substrate and the isolation oxide film on the side wall surface of the trench are oxidized. The above object is achieved by adopting a process method in which a single patterning mask is used to pattern the semiconductor substrate at the same time, and simultaneously perform isolation oxidation on the surface of the semiconductor substrate other than the grooved area, as well as on the sidewalls and bottom surfaces of the groove. It is something to do.

[Effect]

By using the manufacturing method described above, the oxide mask on the surface of the semiconductor substrate other than the grooved area and the sidewall surface of the groove is patterned at the same time, so there is no need to take a margin for mask alignment in the pattern layout, and the semiconductor device Miniaturization/miniaturization becomes easy.

In addition, since an isolation oxide film is formed on the surface of the substrate after trenches are dug in the semiconductor substrate, diagonal etching of the substrate due to overlap between the trench region and the isolation region on the substrate surface is eliminated, and the side of the trench is Defective patterning of the oxidation mask on the wall surface is prevented.

Further, patterning is performed using a single patterning mask for isolation oxidation of the surface of the semiconductor substrate other than the trenched region and isolation oxidation of the sidewall surface of the trench, and that the surface of the semiconductor substrate other than the trenched region and the groove By simultaneously oxidizing the sidewall and bottom isolation regions, the manufacturing process is shortened compared to conventional methods.

〔Example〕

The method of this invention will be explained below based on examples.

1 to 7 are fragmentary cross-sectional views of essential parts showing one embodiment of each process sequence of the semiconductor manufacturing method using the present invention, and 1 to 7 are explanatory diagrams 8 to 7 of the conventional semiconductor manufacturing method. These components are exactly the same (equivalent) to the components shown in FIG.

(Manufacturing method) Next, the manufacturing method according to the present invention will be explained. As in the conventional example, the final purpose is to form an element isolation oxide film 4 on the surface of the semiconductor substrate 1, as shown in FIG. First, as shown in Figure 1,
After forming an oxide mask material 2 on the entire surface of the semiconductor substrate 1, a silicon oxide film 5 used as an etching mask material for trench etching is formed, and then the silicon oxide film 5 of 5 is subjected to a photolithography process. FIG. 2 shows a state in which the semiconductor substrate 1 has been patterned and grooved and etched. The process up to this point is
In addition to the formation of a grooved region on the semiconductor substrate 1, an oxide mask 2 covers the surface other than the grooved region, and a silicon oxide film 5, which is an etching mask material for trenching etching, is covered thereon. It is.

Next, the single crystal silicon of the semiconductor substrate 1 is thermally oxidized to form a silicon nitride film 2 on the entire surface, and then a silicon oxide film 7 is further formed on the entire surface.
Figure 4 shows the silicon oxide film 7 etched by anisotropic etching such as reactive ion etching. Because it is so thick, it is not etched and remains as a frame. FIG. 5 shows a state in which the entire surface of the oxide mask 2 and the silicon oxide films 3, 5, and 7 are etched, and here only the oxide mask 2 at the bottom of the groove is removed. That is, the surface of the semiconductor substrate 1 other than the grooved region is covered with a silicon oxide film 5, which is used as a mask material for trenching and etching.
The side wall surfaces of the trench are masked by a frame of silicon oxide film 7 formed by anisotropic etching, and only the oxide mask 2 at the bottom of the trench is removed. As described above, this process is exactly the same as that of the conventional example.

Subsequently, the silicon nitride film 2, which serves as an oxidation mask for the isolation oxidation of the surface other than the grooved region on the semiconductor substrate 1 and the isolation oxidation of the sidewall surface of the trench, is simultaneously patterned through a photolithography process using a multilayer resist. FIG. 6 shows a state in which the first resist layer 6 of the multilayer resist has not yet been removed. Next, this resist 6 is removed and the separated and oxidized state is shown in FIG. 7, which completes the process of isolation between elements.

By the way, in the description of the above embodiment, the seventh
Although the method for manufacturing the element isolation oxide film shown in the figure has been described, this invention is applicable not only to the structure shown in FIG.
It goes without saying that it can be applied to other general manufacturing methods for isolation between elements when a selective oxide film is used on the surface other than the grooved area and on the side wall surface of the groove in a three-dimensional semiconductor device equipped with a grooved area. .

〔Effect of the invention〕

As described above, according to the manufacturing method of the present invention, after a trench is dug on a semiconductor substrate, an oxide mask of a selective oxide film used for separating the surface other than the trench region and the side wall surface of the trench is simultaneously applied. By patterning and separating and oxidizing all areas on the substrate at the same time, the number of photolithography steps and separation oxidation steps is reduced compared to conventional manufacturing methods, and patterning accuracy is improved, resulting in miniaturization and miniaturization of semiconductor devices. can contribute to

[Brief explanation of the drawing]

1 to 7 are fragmentary cross-sectional views of main parts showing each process sequence of a semiconductor manufacturing method according to an embodiment of the present invention, and FIGS. 8 to 15 are each process sequence of an example of a conventional manufacturing method. FIG. 1... Semiconductor substrate, 2... Oxidation mask, 3...
Oxide mask underlay, 4... Separation oxide film, 5, 6, 7
...Etching masks.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a semiconductor device having a groove on the main surface of a semiconductor substrate, comprising: preparing a semiconductor substrate, and applying a first oxide mask made of a thin silicon oxide film to the main surface of the semiconductor substrate. forming a first oxide mask made of a thin silicon nitride film on the upper surface of the first oxide mask underlay; and a step of forming a first oxide mask made of a thick silicon oxide film on the upper surface of the first oxide mask. forming a first etching mask; patterning the first etching mask into a predetermined pattern; and performing an etching process using the first etching mask as a mask to form a groove in the main surface of the semiconductor substrate. forming a second oxide mask made of a thin silicon oxide film on the bottom and side surfaces of the trench; and a second oxide mask made of a thin silicon nitride film on the entire exposed surface including the top surface of the second oxide mask. forming a second etching mask made of a thick silicon oxide film on the top surface of the second oxide mask; and performing anisotropic etching from the top surface of the second etching mask. a step of removing the second etching mask; and a step of removing the second oxide mask on the side surface of the trench and the first oxide mask on the main surface of the semiconductor substrate other than the region of the trench using a multilayer resist. a step of removing only a predetermined region; and a step of performing thermal oxidation to form an element isolation oxide film made of a thick silicon oxide film on the bottom and side surfaces of the trench and on the main surface of the semiconductor substrate other than the region of the trench. Semiconductor manufacturing method.