JPH01119038A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent generation of defects in an epitaxial layer due to steps created by a buried layer by causing the epitaxial layer to grow while opening an oxide film within a region of the buried layer. CONSTITUTION:An arsenic buried layer 2 is formed on the surface of a silicon substrate 1. When forming an oxide film 3 on such buried layer, steps created due to biting in of the oxide film are observed around the buried layer 2 on the silicon surface. When selectively etching the oxide film 3, an aperture must be constructed so that the aperture is smaller than the buried layer 2. Then an epitaxial layer 4 is formed within such aperture. According to the constitution, the presence of the buried layer 2 prevents the steps created on the buried layer 2 when forming the oxide film 3 from protruding into the region of the epitaxial layer 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a semiconductor device, and particularly to a semiconductor device in which active elements are formed in an epitaxial region formed using selective epitaxial growth technology.

[Conventional technology]

Conventionally, in this type of semiconductor device, when a high-concentration buried region is required in the epitaxial region to be grown, an opening is formed to surround the buried region, and then a hole is formed inside the opening. A method has been adopted in which selective epitaxial layers are grown.

For example, FIGS. 4(a) to 4(C) are cross-sectional views showing an example of the method in the order of steps.

That is, FIG. 4(a) shows a state in which an arsenic buried layer 2 is formed on a silicon substrate 1, and an oxide film 3 is formed by high-pressure oxidation at 950''C. 2 has a concentration of 10 cm and a depth of 1.5 μm, but if oxidation is performed so that the oxide film becomes 1.5 μm in a place where there is no buried layer, the oxide film thickness on the buried layer will be 1.75 μm. At this time, the oxide film on the buried layer rises by about 1,350 layers from the surroundings, and the oxide film digs into the buried layer by about 1,150 layers from the surroundings, creating a step.

Next, as shown in Figure 4(b), reactive ion etching (
The oxide film 3 is selectively etched using the RIE technique to form a region surrounding the buried region 2 for forming a selective epitaxial layer.

Next, after cleaning the exposed surface of the silicon substrate by an appropriate method, a selective epitaxial layer 4 is grown as shown in FIG. 4(c). This selective epitaxial growth prevents the growth of a silicon layer on the silicon oxide surface by appropriately selecting the flow rate ratio of 5iHn gas and H(l) when forming an epitaxial layer on a substrate having regions of silicon and silicon oxide. This is a technology that attempts to grow an epitaxial layer of silicon only on the silicon surface, and its typical growth conditions are at a temperature of 950°C and a pressure of 50 Torr.

S i HCl z flow rate 300SCCM T(Cf
fi flow rate 1l100SCC, H, flow rate 170SCM
It is. The growth rate is approximately 0.1 μm/win, so 15
By growing the selective epitaxial layer, the surface of the selective epitaxial layer and the surface of the oxide film can be made to coincide with each other.

[Problem that the invention seeks to solve]

However, in the conventional structure described above, there is a 1,150-layer step created during the formation of the oxide film 3 at the boundary of the arsenic buried layer 2 existing in the silicon epitaxial growth region. Figure (C
) A defect X occurs on the epitaxial surface on the buried layer. These defects cause defects in the characteristics of elements formed in the epitaxial layer, resulting in a problem in that the manufacturing yield of semiconductor devices is reduced. FIG. 6 is a surface microscopic observation diagram showing how this defect occurs.

An object of the present invention is to provide a semiconductor device in which an epitaxial layer can be grown without causing defects.

[Means for solving problems]

The semiconductor device of the present invention is a semiconductor device in which an oxide film is formed on the surface of a semiconductor substrate on which a buried layer is formed, a hole is formed in the oxide film on the buried layer, and an epitaxial layer is formed in the hole. The epitaxial layer is grown by forming the opening in the region of the buried layer, thereby preventing defects in the epitaxial layer due to steps in the buried layer.

〔Example〕

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

FIG. 1 is a cross-sectional view of one embodiment of the present invention, and the manufacturing method thereof is shown in FIGS. 2(a) and 2(b).

As shown in FIG. 1, this semiconductor device consists of a silicon substrate l
An arsenic buried layer 2 is formed thereon, an N-type epitaxial layer 4 is grown thereon, and an oxide film 3 surrounds it. Elements (not shown) are formed within this epitaxial layer 4. Further, here, the epitaxial layer 4 has a smaller planar dimension than the buried layer 2, and is configured to grow only within the region of the buried layer 2.

First, in FIG. 2(a), an arsenic buried 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 buried layer.
The figure shows the state in which it has been formed. Around the buried layer 2, 1150 steps are seen on the silicon surface due to the encroachment of the oxide film.

Then, this oxide film 3 is selectively etched by the RIE method to open an opening for epitaxial growth. Make it smaller than 2. In other words, selective etching is performed so that openings are created in the region of the buried layer 2.

Then, selective epitaxial growth is performed in this opening to form an epitaxial layer 4, thereby forming the first layer.
The composition of the diagram is completed.

According to this configuration, by forming the buried layer N2, a step formed in the buried layer 2 when the oxide film 3 is formed does not enter into the region of the epitaxial layer 4. Therefore, defects do not occur during epitaxial growth (epitaxial N
It is possible to prevent the occurrence of characteristic defects in elements formed in the semiconductor device 4 and improve the yield of semiconductor devices.

FIG. 3 is a longitudinal 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 eIM4a, 4b, ~4n are provided on the same arsenic-embedded N2, and all the selective epitaxial regions 4a
, 4b, .about.4n are located within the region of the arsenic buried layer 2, so that no defects occur in each selective epitaxial layer 4a, 4b, .about.4n.

FIG. 5 is a surface microscopic observation of this example, and it can be seen that no defects have occurred.

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

[Effects of the Invention] As explained above, the present invention has a structure in which the epitaxial layer is formed by opening holes in the oxide film formed on the semiconductor substrate in the region of the buried layer. There is no layer step difference, and a defect-free epitaxial layer can be formed to prevent defective device characteristics, and the manufacturing yield of semiconductor devices can be improved.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of one embodiment of the semiconductor device of the present invention, and FIG.
Figures (a) and (b) are cross-sectional views showing the manufacturing method in order of steps, Figure 3 is a cross-sectional view of another embodiment of the present invention, and Figure 4 (a).
) to (C) are cross-sectional views showing the conventional structure in the order of manufacturing steps, FIG. 5 is a microscopic view of the semiconductor device of the present invention, and FIG. 6 is a microscopic view of the conventional semiconductor device. DESCRIPTION OF SYMBOLS 1... Silicon substrate, 2... Buried layer, 3... Oxide film, 4°4a, 4b, -4n... Epitaxial layer.

Claims (1)

[Claims] (1) In a semiconductor device in which an oxide film is formed on the surface of a semiconductor substrate on which a buried layer is formed, a hole is formed in the oxide film on the buried layer, and an epitaxial layer is formed in the hole, the hole is 1. A semiconductor device, wherein the epitaxial layer is grown by forming a hole in a region of the buried layer.