JP3143188B2 - Epitaxial growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed device and a three-dimensional IC.
The present invention relates to an epitaxial growth method for forming a silicon seed crystal growth layer in the same crystal direction as a silicon substrate on a silicon substrate via an insulating film.

[0002]

2. Description of the Related Art Generally, in a semiconductor integrated circuit, a silicon seed crystal growth layer (hereinafter, referred to as an epitaxial growth layer) is formed on a silicon substrate, and a circuit is formed on the epitaxial growth layer. By the way, in the above structure, the silicon substrate and the epitaxial growth layer form a PN junction and have a capacity. This P
The capacitance at the N junction reduces the operating speed of the device. Therefore, the structure is not suitable for forming an element requiring high-speed operation.

In order to address the above problem, in recent years, an insulating layer has been formed on a silicon substrate and a silicon single crystal layer has been further formed thereon (SOI (Semicond.
actor on insulator technology). That is, the SOI technique aims to eliminate the PN junction between the semiconductor element formed on the silicon seed crystal layer and the silicon substrate by insulating the silicon single crystal layer from the silicon substrate.

FIG. 4 shows an ELO (Epitaxial L).
2 shows a conventional SOI technique by a lateral overgrowth method (Lateral Epitaxia).
10 Overgrowth of Silicon on
SiO ₂ : D. D. Ratmanet. at. : J
OURNAL OF ELECTRORO-CHEMIC
AL SOCIETY SOLID-STATE SC
IENCE ANDTECHNOLOGYY, 1982
October, 2303).

In the ELO method of FIG. 4, first, as shown in FIG. 1A, a silicon oxide film 2 is grown on a silicon substrate 1 by a vapor phase growth method, and the silicon oxide film 2 is formed by using a photoresist. Selective etching, and an opening (hereinafter, referred to as a seed crystal) for growing a silicon seed crystal (hereinafter, referred to as a seed crystal).
A seed window 3 is formed. Next, as shown in FIG. 3B, selective epitaxial growth of the seed crystal is performed in the vertical direction from the seed window 3 and subsequently, selective epitaxial growth of the seed crystal is performed in the horizontal direction. An epitaxial growth layer 4 is formed. By doing so, the PN junction surface between the epitaxial growth layer 4 and the silicon substrate 1 can be reduced to the size of the seed window 3. Therefore, the area of the PN junction capacitance can be reduced, and the operation speed of the device can be increased.

[0006]

However, in the ELO method of FIG. 4, although the silicon substrate, the epitaxially grown layer and the PN junction are small,
In the seed window portion, the PN junction is not completely removed, and the silicon substrate and the epitaxial growth layer cannot be completely separated. Therefore, it has been difficult to obtain a large-area SOI structure on a silicon substrate, and furthermore, speeding up of the device has been hindered.

Further, since the crystallinity of the epitaxial growth layer on the side surface of the silicon oxide film is poor and the vertical growth of the epitaxial growth layer cannot be suppressed, the plane orientation of the epitaxial growth layer differs from the plane orientation of the silicon substrate. In view of the above, the present invention provides an epitaxial growth method that can completely separate a silicon substrate and a seed crystal growth layer by an insulating film and can obtain a seed crystal growth layer having good crystallinity in the same plane orientation as the silicon substrate. The purpose is to provide a method.

[0008]

In the epitaxial growth method according to the present invention, after a mask made of a silicon oxide film and a silicon nitride film is formed on a silicon substrate, the mask is formed in a lattice so as to have the same plane orientation as the silicon substrate. A step of forming the openings for silicon seed crystal growth by arranging them in a lattice pattern, and etching the silicon substrate while leaving the mask from the seed crystal growth openings formed in the previous step. Step of forming a seed crystal below, after depositing a silicon nitride film on the entire surface of the mask and the seed crystal,
With the deposited silicon nitride film remaining on all sides of the mask and the seed crystal, the silicon nitride film deposited on the surface of the silicon substrate is removed.
A step of etching away the con nitride film, the side surface of the sheet forming an insulating film for separating the upper portion of the silicon substrate and the seed crystal and the silicon substrate, as well as species while leaving the silicon oxide film of the upper surface of the seed crystal crystal After removing the nitride film by etching, the silicon oxide film is left on the upper surface of the seed crystal.
In, and comprising the step of forming a series of seed crystal growth layer interconnected by epitaxially growing a seed crystal in the transverse direction on top of the insulating film.

[0009]

According to the epitaxial growth method of the present invention, after forming a mask on a silicon substrate, the mask is etched and removed in a lattice so as to have the same plane orientation as the silicon substrate, and openings for growing a silicon seed crystal are arranged in a lattice. In the next step, the silicon substrate is etched with the mask left from the opening for seed crystal growth to form a seed crystal under the mask, so that the seed crystals are arranged in a lattice and remain. in the process you separate the seed crystal and the silicon substrate by oxidation, tilting the seed crystal, without twisting, it maintained the orientation of the entire seed crystal. Therefore, in the epitaxial growth step, since epitaxial growth can be performed in a state where all the orientations of the seed crystal are aligned, a series of interconnected epitaxial growth layers having the same plane orientation as the silicon substrate is formed.
It can be obtained in a state of being completely separated from the silicon substrate by the insulating film.

At this time, since the epitaxial growth of the seed crystal in the vertical direction is suppressed by the silicon oxide film, the epitaxial growth in the horizontal direction is promoted. Also, the thickness of the seed crystal growth layer can be controlled by the etching depth.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An epitaxial growth method according to an embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a sectional view showing an epitaxial growth method according to one embodiment of the present invention in the order of steps, and FIG. 2 is a perspective view at the time when the step of FIG.

First, as shown in FIG.
A silicon oxide film 11 and a silicon nitride film 12 are sequentially formed on the silicon substrate 10 of FIG. In particular, the thickness of the silicon oxide film 11 is, for example, 30 to
It is preferable to form it as thin as about 300 nm. This is to reduce stacking faults described later. Then, a photoresist is applied on the nitride film 12, a mask is placed on the photoresist, and ultraviolet light exposure is performed, followed by development to form openings arranged in a lattice in the photoresist. In this state, the oxide film 11 and the nitride film 12 are etched using the photoresist as a mask so that the oxide film 11 and the nitride film 12 remain in the same plane orientation as the silicon substrate 10. Thereafter, the photoresist is removed with a mixed solution of sulfuric acid and hydrogen peroxide. As a result, openings (hereinafter, referred to as seed windows) 13 for growing silicon seed crystals (hereinafter, referred to as seed crystals) arranged in a lattice are formed on the silicon substrate 10. In the following description, for convenience of explanation, the silicon oxide film 11 will be described.
And the silicon nitride film 12 is generally referred to as a mask M.

Next, as shown in FIG. 1B, while the mask M left in the step of FIG. 1A is left, the silicon substrate 10 is removed from the seed window 13 by anisotropic etching.
Is etched in a rectangular pattern to form a mask M (oxide film 1).
A seed crystal 14 is formed below 1). The state at this time is shown in FIG. Thereafter, as shown in FIG. 1C, a silicon nitride film 15 is deposited on the entire surface of the mask M and the seed crystal 14 by a vapor growth method.

Then, as shown in FIG. 1D, FIG.
The nitride film 15 deposited on the surface of the silicon substrate 10 is etched and removed by anisotropic etching such as RIE, while the nitride film 15 deposited in the step is left on the mask M and all side surfaces of the seed crystal 14. Further, as shown in FIG. 1E, the silicon substrate 1 exposed in the process of FIG.
A silicon oxide insulating film (hereinafter referred to as a field oxide film) 1 for separating the seed crystal 14 and the silicon substrate 10 from the surface of the silicon substrate 10 by injecting oxygen from the surface of the silicon substrate 10
6 is formed.

[0015] Next, as shown in FIG. 1 (f), the nitride film 15 is left on all sides of the seed crystal 14 while leaving the oxide film 11 above plane of the seed crystal, and phosphoric acid or the like and a nitride film 12 Then, the side wall of the seed crystal 14 is exposed, and the side wall of the seed crystal 14 is washed by wet etching or the like. By this washing, a good growth surface of the seed crystal 14 can be obtained in the next step of epitaxial growth.

[0016] Then, as shown in FIG. 1 (g), the seed crystal
While the oxide film 11 is left on the upper surface of the field oxide film 14, the seed crystal 14 is laterally epitaxially grown by vapor phase epitaxy to form a series of interconnected seed crystal growth layers (hereinafter, referred to as “top”) on the field oxide film 16. 17 (referred to as an epitaxial growth layer). Then, the silicon substrate 10
And epitaxial growth layer 17 with field oxide film 16
Can be completely separated.

At this time, since the epitaxial growth of the seed crystal 14 in the vertical direction is suppressed by the oxide film 11, the epitaxial growth in the horizontal direction is promoted. Therefore, the growth in the vertical direction is controlled to 1 μm or less by the oxide film 11. Also, the epitaxial growth 17
Can also be controlled. In addition, during epitaxial growth, stacking faults may occur at the interface with the oxide film 11, but if the oxide film 11 is formed thin in the step of FIG. Defects can be prevented. The epitaxial growth is performed, for example, in 9
It is preferable to perform the treatment at a temperature as low as possible within the range of 00 to 1100 ° C. This is because stacking faults can be suppressed by performing epitaxial growth at a low temperature in this manner.

Further, in the step of FIG.
1) The seed windows 13 are arranged in a lattice pattern on the silicon substrate 10 of FIG. 1B with the plane orientation (100) being left, and the silicon substrate 10 is cut from the seed window 13 into a rectangular pattern in the process of FIG. Since the seed crystal 14 is formed under the mask M by etching in FIG. 1, the seed crystal 14 remains arranged in a lattice pattern (see FIG. 2).
When the seed crystal 14 and the silicon substrate 10 are separated by the oxidation in the step (e), the oxidation of the portion below the seed crystal 14 proceeds symmetrically with the seed crystal 14 interposed therebetween, and the seed crystal 14 tilts, No twisting occurs, and the orientation of the entire seed crystal 14 is maintained. Thus, FIG.
In the step (g), since the epitaxial growth can be performed in a state where all the orientations of the seed crystal 14 are aligned, a series of interconnected epitaxial growth layers 17 having the same plane orientation as the silicon substrate 10 can be obtained.

It should be noted that the present invention is not limited to the above-described embodiment, and it goes without saying that many modifications and changes can be made within the scope of the present invention. For example, in the process of FIG. 1D, as shown in FIG. 3A, the nitride film 1 at the base end A of the seed crystal 14 is formed by using isotropic wet etching.
When the silicon in contact with the lower end of the seed crystal 5 is removed, in the step of separating the seed crystal 14 and the silicon substrate 10, as shown in FIG. Field oxide film 16 can be formed in a good condition below 14 as well.

[0020]

As is apparent from the above description, according to the present invention, in the step of separating the seed crystal from the silicon substrate by oxidation, the seed crystal does not tilt or twist,
Since the orientation of the entire seed crystal is maintained, in the epitaxial growth step, epitaxial growth can be performed with all the orientations of the seed crystal aligned. Therefore, a series of interconnected epitaxial growth layers having the same plane orientation as the silicon substrate can be obtained while being completely separated from the silicon substrate by the insulating film.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an epitaxial growth method according to an embodiment of the present invention in the order of steps.

FIG. 2 is a perspective view at the time when the step of FIG. 1B is completed.

FIG. 3 is a sectional view showing a modification of a part of FIG. 1;

FIG. 4 is a cross-sectional view showing a conventional epitaxial growth method.

[Explanation of symbols]

 Reference Signs List 10 silicon substrate 11 silicon oxide film 12 silicon nitride film 13 seed window 14 seed crystal 15 nitride film 16 field oxide film 17 epitaxial growth layer M mask

Claims (1)

(57) [Claims] A mask comprising a silicon oxide film and a silicon nitride film is formed on a silicon substrate, and the mask is etched and removed in a lattice pattern so as to have the same plane orientation as the silicon substrate. Forming a seed crystal under the mask by etching the silicon substrate while leaving the mask from the seed crystal growth opening formed in the previous step; and after depositing a silicon nitride film on the entire surface of the seed crystal, while leaving the deposited silicon nitride film to all aspects of the mask and the seed crystal, etched silicon nitride film deposited on the surface of the silicon substrate to step, forming an insulating film on top of the silicon substrate to separate the seed crystal and the silicon substrate, and the upper surface of the seed crystal silicon
After the nitride film on the side surface of the seed crystal is removed by etching while the con oxide film is left, the silicon oxide film is
While leaving the epitaxial growth method characterized in that a series of seed crystal growth layer interconnected by epitaxially growing a seed crystal in the transverse direction with a step of forming an upper portion of the insulating film.