JPH0712055B2 - Method for manufacturing semiconductor device - Google Patents

Description

The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a semiconductor device in which an active element is formed in an epitaxial region formed using a selective epitaxial growth technique.

[Conventional technology]

Conventionally, in this type of semiconductor device, when a high-concentration buried region is required for an epitaxial region to be grown, an opening portion is formed so as to surround the buried region, and then the selected inside of the opening is selected. The method of growing an epitaxial layer is taken.

For example, FIGS. 4A to 4C are sectional views showing an example thereof in the order of steps.

That is, FIG. 4A shows a state in which the buried layer 2 of arsenic is formed on the silicon substrate 1 and the oxide film 3 is formed by high-pressure oxidation at 950 ° C. Here, the arsenic buried layer 2 has a concentration of 10 cm.
^{-3 The} depth is 1.5 μm, but the oxide film is 1.5 where there is no buried layer.
When oxidation is performed so that the thickness becomes μm, the oxide film thickness on the buried layer becomes 1.75 μm. At this time, the oxide film on the buried layer rises from the surroundings by about 1350Å, and in the buried layer, about 11
50 Å It bites and a step is generated.

Next, as shown in FIG. 4B, the oxide film 3 is selectively etched using the reactive ion etching (RIE) technique to open a region for forming a selective epitaxial layer so as to surround the buried region 2. Make a hole.

Then, after the exposed surface of the silicon substrate is cleaned by an appropriate method, the selective epitaxial layer 4 is grown as shown in FIG. 4 (c). In this selective epitaxial growth, when an epitaxial layer is formed on a substrate having regions of silicon and silicon oxide, a silicon layer is not grown on the surface of silicon oxide by appropriately selecting the flow rate ratio of SiH ₄ system gas and HCl. This is a technology for growing an epitaxial layer of silicon only on the silicon surface. Typical growth conditions are: temperature 950 ° C, pressure 50 Torr, SiHCl ₂ flow rate 300SCC.
The flow rate of M HCl is 1100 SCCM and the flow rate of H ₂ is 170 SCM. Since the growth rate is about 0.1 μm / min, the surface of the selective epitaxial layer and the surface of the oxide film can be made to coincide with each other by growing for 15 minutes.

[Problems to be solved by the invention]

However, in the conventional structure described above, there is a step of 1150Å generated at the time of forming the oxide film 3 at the boundary portion of the arsenic burying layer 2 existing in the silicon epitaxial growth region. As shown in (c), a defect X occurs on the epitaxial surface on the buried step. This defect causes a characteristic defect of the element formed in the epitaxial layer, which causes a problem that the manufacturing yield of the semiconductor device is reduced. FIG. 6 is a surface microscope observation view showing the appearance of the defects.

It is an object of the present invention to provide a method for manufacturing a semiconductor device that can grow an epitaxial layer without causing defects.

[Means for solving problems]

According to the method of manufacturing a semiconductor device of the present invention, an oxide film is formed by thermally oxidizing the surface of a semiconductor substrate having a buried layer, and the oxide film is formed in the buried layer region and by the oxide film. The step of opening a hole within the range of the step to expose the surface of the buried layer, and further growing an epitaxial layer on the exposed surface of the buried layer in the hole by a selective epitaxial growth method.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an embodiment of the present invention, and its manufacturing method is shown in FIGS. 2 (a) and 2 (b).

As shown in FIG. 1, this semiconductor device has a silicon substrate 1
An arsenic burying layer 2 is formed on the substrate, an N type epitaxial layer 4 is grown on the arsenic burying layer 2, and the periphery thereof is surrounded by an oxide film 3. An element (not shown) is formed in the epitaxial layer 4. Further, here, the epitaxial layer 4 has a plane dimension smaller than that of the buried layer 2 and is configured to grow only in the region of the buried layer 2.

First, FIG. 2 (a) shows a state in which an arsenic burying layer 2 is formed on the surface of a silicon substrate 1 and an oxide film 3 of 1.75 μm is formed on this burying layer. A step of 1150 Å due to the oxide film biting is seen on the silicon surface around the buried layer 2.

Then, selective etching is performed on this oxide film 3 by the RIE method to open an opening for epitaxial growth. At this time, the opening is formed as shown in FIG. 2 (b).
It is made smaller than the buried layer 2. In other words, the selective etching is performed so that the openings are formed in the region of the buried layer 2.

Then, selective epitaxial growth is carried out in this opening to form the epitaxial layer 4, so that the first
The structure of the figure is completed.

According to this structure, the step formed in the buried layer 2 when the oxide film 3 is formed by forming the buried layer 2 does not enter the region of the epitaxial layer 4. Therefore, no defects are generated during the epitaxial growth, the characteristic defects of the elements formed in the epitaxial layer 4 can be prevented, and the yield of the semiconductor device can be improved.

FIG. 3 is a vertical sectional view of an example to which the present invention is applied. Here, an example is shown in which a plurality of N-type silicon selective epitaxial regions 4a, 4b, to 4n are provided on the same arsenic buried layer 2, and all the selective epitaxial regions 4a, 4b, to 4n are arranged in the arsenic buried layer 2.
Of the selective epitaxial layers 4a, 4
No defects occur in b, ~ 4n. FIG. 5 is a surface microscopic observation view of this example, and it can be seen that no defect has occurred.

The present invention can be similarly applied to the structure in which the P-type selective epitaxial layer is formed on the high-concentration boron burying layer.

〔The invention's effect〕

As described above, the present invention includes a step of forming an epitaxial layer by opening an oxide film formed on a semiconductor substrate in a region of a buried layer, so that the oxide film can be formed by a thermal oxidation method. Even if there is a step in the buried layer due to, the step of the buried layer does not exist in the selective epitaxial region, a defect-free epitaxial layer can be formed, and defective characteristics of the element can be prevented, and There is an effect that the manufacturing yield of semiconductor devices can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view of an embodiment of a semiconductor device according to the present invention, FIGS. 2 (a) and 2 (b) are sectional views showing the manufacturing method in the order of steps, and FIG. 3 is another embodiment of the present invention. 4A to 4C are sectional views showing a conventional structure in the order of manufacturing steps, FIG. 5 is a microscope observation view of a semiconductor device of the present invention, and FIG. 6 is a microscope observation of a conventional semiconductor device. It is a figure. 1 ... Silicon substrate, 2 ... Buried layer, 3 ... Oxide film, 4,
4a, 4b, ~ 4n ... Epitaxial layers.

Claims (1)

[Claims] 1. A semiconductor substrate having a buried layer has an oxide film on a surface thereof, and the oxide film has an opening on the buried layer, and an epitaxial layer is formed in the opening. In the method of manufacturing a semiconductor device, the step of forming the oxide film by thermally oxidizing the surface of the semiconductor substrate, and the step of the oxide film in the region of the buried layer and on the surface of the buried layer caused by the oxide film. And exposing the surface of the buried layer within the range, and growing an epitaxial layer on the exposed surface of the buried layer in the opening by a selective epitaxial growth method. And a method for manufacturing a semiconductor device.