JPH0158659B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of manufacturing a semiconductor device, and in particular to an element isolation technique.

[Prior art]

As an effective element isolation technology for conventional semiconductor devices,
After forming an insulating film such as a silicon oxide film in a predetermined area on a silicon substrate, a semiconductor layer is formed on the exposed substrate using a selective epitaxial growth method to form an active region. Since lattice defects occur near the interface with the oxide, a method using selective oxidation may be considered in order to avoid using this region as an active region.

FIG. 2 shows an example of such an element isolation method.
In the figure, after first forming an insulating film 2 made of silicon oxide (SiO ₂ ), silicon nitride (Si ₃ N ₄ ), etc. on the main surface of a silicon substrate 1,
This is selectively removed by photolithography or the like to form an opening 3 and expose that portion of the silicon substrate 1 (FIG. 2a). Next, a semiconductor layer 4 is epitaxially grown in the opening 3 using the remaining insulating film 2 as a mask. At this time, the semiconductor layer 4 is formed to be thicker than the insulating film 2 so as to cover the insulating film 2 (FIG. 2b). Next, a silicon nitride film 5 is formed on the semiconductor layer 4, and the silicon nitride film 5 is left on the portion corresponding to the active region of the semiconductor device by photolithography or the like (FIG. 2c).
Next, using this as a mask, selective oxidation is performed on the semiconductor layer 4 to form a field oxide film 6 in contact with the insulating film 2, and then the silicon nitride film 5 is removed (FIG. 2d).

As a result, an active region consisting of the epitaxial semiconductor layer 4 that is physically separated by the insulating film 2 and the field oxide film 6 is formed, and the region where defects occur near the interface with the insulating film 2 is formed by the field oxide film 6. Due to the presence of the film 6, it is excluded from the active region, so that good element isolation of the semiconductor device is possible.

[Problem that the invention seeks to solve]

However, in this method, when the epitaxial semiconductor layer 4 is grown to cover the insulating film 2 as described above, the shape of the underlying insulating film 2 becomes difficult to see in the next step of photo-etching the silicon nitride film 5. Therefore, there was a problem that it was difficult to match the masks.

This invention was made to solve these problems, and its purpose is to
When performing element isolation using epitaxial growth and selective oxidation after forming an insulating film,
It is an object of the present invention to provide a method for manufacturing a semiconductor device in which mask alignment for selective oxidation can be easily performed even when an epitaxial layer is formed thicker than a first insulating film.

[Means for solving problems]

In order to achieve such an object, in the present invention, when forming the first insulating film, the width of the insulating film in the alignment pattern portion is made wider than that for element isolation.

[Effect]

By forming the first insulating film in the alignment pattern part to be wide, even when the first insulating film for element isolation is completely covered with the epitaxial semiconductor layer, it remains in the alignment pattern part. Therefore, mask matching can be performed using this as a reference.

〔Example〕

FIG. 1 is a process sectional view showing an embodiment of the present invention. In the figure, the left side of the broken line is a region where a semiconductor element is formed, and the right side is a region where an alignment pattern is formed. Further, a, b, and c in the figure correspond to the same stages as a, b, and d in FIG. 2, respectively.

In FIG. 1, an insulating film made of silicon oxide, silicon nitride, etc. is first formed on the main surface of a silicon substrate 1, and an opening 3 is formed by photolithography or the like.
, the width D2 of the insulating film 2A in the alignment pattern section is made wider than the width D1 of the insulating film 2 for element isolation on the left side in the figure (first
Diagram a).

As a result, when the semiconductor layer 4 is next formed by the epitaxial growth method, even if the insulating film 2 for element isolation is completely covered with the semiconductor layer 4, the insulating film 2A in the alignment pattern part will be It can be uncovered so that its surface is exposed (FIG. 1b). This is because the semiconductor layer 4 on the insulating film 2 or 2A is formed by the lateral growth of the semiconductor layer 4, which grows thicker than the insulating film in the opening 3. This is because even when the insulating film 2 is completely covered with the semiconductor layer 4, the insulating film 2A in the wide alignment pattern portion is not completely covered.

Therefore, the width of the insulating film 2 for element isolation is formed sufficiently wide, for example, about 2 μm or less, and the width of the insulating film 2A of the alignment pattern part is formed sufficiently wide, for example, about 10 μm or more. If the epitaxial growth is stopped when the film 2 is covered with the epitaxial semiconductor layer 4, the insulating film 2A is still exposed, which facilitates mask alignment in the next step, such as photolithography.

Therefore, although not shown in the figure, the silicon nitride film 5 shown in FIG. 2 was formed by photolithography using a mask aligned in the same manner as described above, using the exposed insulating film 4A as a reference. A field oxide film 6 is formed by performing selective oxidation as a mask,
Then, by removing the silicon nitride film 5, an active region consisting of the epitaxial semiconductor layer 4 separated by the insulating film 2 and the field oxide film 6 can be formed as described above (FIG. 1c).

It is desirable that the width of the insulating film 2A is sufficiently wide for the above-mentioned purpose of using it as an alignment pattern, but according to experiments by the inventors, when the width of the insulating film 2A is set to 500 μm or more, the width of the insulating film 2A is Silicon may grow abnormally on the surface, and to prevent this, the thickness is preferably 500 μm or less.

Such a method according to the present invention can be commonly used as a prerequisite element isolation technique when forming various semiconductor devices using a silicon substrate. Note that the conductivity types of the substrate and the epitaxial semiconductor layer have not been specifically mentioned because the present invention can be applied regardless of these conductivity types, and the conductivity types of both may be P type or N type.
They may be the same or different in shape.

〔Effect of the invention〕

As explained above, according to the present invention, the first
When forming the insulating film of
When forming a semiconductor layer in the opening using an epitaxial growth method, the first insulating film in the alignment pattern portion is not buried by the epitaxial semiconductor layer, and the exposed first insulating film is Mask alignment can be easily carried out based on the reference, and a field insulating film can be formed with high precision on the first insulating film by selective oxidation.

[Brief explanation of drawings]

FIG. 1 is a process sectional view showing an embodiment of the present invention;
FIG. 2 is a process sectional view showing a conventional element isolation method using selective epitaxial method and selective oxidation method. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2, 2A... Insulating film (first insulating film), 3... Opening, 4... Epitaxial semiconductor layer, 5... Silicon nitride film as a mask for selective oxidation, 6 ...Field oxide film (second insulating film).

Claims (1)

[Claims] 1. A step of forming a first insulating film on the main surface of a semiconductor substrate, a step of selectively etching this first insulating film to form an opening through which the semiconductor substrate is exposed, and etching an epitaxial layer in the opening. The method includes a step of forming a semiconductor layer by a growth method, and a step of forming a second insulating film on the first insulating film by applying a selective oxidation method to the formed epitaxial semiconductor layer, and forming the second insulating film on the first insulating film. Of the first insulating film left between the openings during formation, the first insulating film for semiconductor element isolation is
The width of the first insulating film in the alignment pattern part is made wider than the insulating film in the alignment pattern part, and when forming a semiconductor layer by an epitaxial growth method, the first insulating film in the alignment pattern part is made wider than the width of the first insulating film in the alignment pattern part. A method for manufacturing a semiconductor device, characterized in that it is prevented from being buried by layers.