JPH05226265A - Epitaxial growth method - Google Patents

Abstract

PURPOSE:To obtain an epitaxial growth layer which is on the same face orientation with a silicon substrate and excellent in crystallivity and isolated from the silicon substrate by an insulating film. CONSTITUTION:A mask M is left over at its face orientation (100) on a silicon substrate 10 of a face orientation (100) and a seed window 13 is laid out in the shape of lattice. Then, the silicon substrate 10 is etched under the condition that the mask M is left over from the seed window, thereby forming seed crystal 14 under the mask M. A field oxide film 16 is formed by oxidation and the seed crystal 14 is separated from the silicon substrate 10. After the separation, the seed crystal 14 is arranged to make an epitaxial growth laterally, thereby forming a series of epitaxial growth layers 17, which are intercommunicated with each other, in the upper part of a field oxide film 16. This construction enables this epitaxial growth process to make an epitaxial growth under the condition that all the orientation of the seed crystal are all right.

Description

Detailed Description of the Invention

[0001]

BACKGROUND 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 that of a silicon substrate on an appropriate 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 this epitaxial growth layer. By the way, in the above-mentioned structure, the silicon substrate and the epitaxial growth layer form a PN junction and have a capacitance. This P
The capacitance of the N-junction reduces the operating speed of the device. Therefore, the structure is not suitable for forming an element that requires high-speed operation.

In order to address the above problem, in recent years, an insulating layer is formed on a silicon substrate, and a silicon single crystal layer is further formed thereon (SOI (Semicond).
ector On Insulator technology) is desired. That is, the SOI technology aims to eliminate the PN junction between the semiconductor element formed in 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)
A conventional SOI technique using the lateral overgrowth method is shown (Lateral Epitaxia).
lOvergrowth of Silicon on
SiO ₂ : D.I. D. Rathmanet. at. : J
OURRNAL OF ELECTRO-CHEMIC
AL SOCIETY SOLID-STATE SC
IENCE AND TECHNOLOGYY, 1982
October issue, page 2303).

In the ELO method of FIG. 4, first, as shown in FIG. 4A, a silicon oxide film 2 is grown on a silicon substrate 1 by a vapor phase epitaxy method, and a photoresist is used to grow the silicon oxide film 2. An opening (hereinafter, referred to as a seed crystal) growth (hereinafter referred to as a seed crystal) is selectively etched
(Seed window) 3 is formed. Next, as shown in FIG. 2B, selective epitaxial growth of seed crystals is performed in the vertical direction from the seed window 3, and subsequently, selective epitaxial growth of seed crystals is performed in the horizontal direction to form a seed crystal on the silicon oxide film 2. The 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 to speed up the device operation.

[0006]

However, in the ELO method of FIG. 4, although the silicon substrate, the epitaxial growth layer and the PN junction are small,
In the seed window portion, the PN junction portion is not completely removed, and the silicon substrate and the epitaxial growth layer cannot be completely separated. Therefore, it is difficult to obtain a large-area SOI structure on a silicon substrate, and further speeding up of the device is 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 is different from the plane orientation of the silicon substrate. In view of the above, the present invention makes it possible to completely separate a silicon substrate and a seed crystal growth layer by an insulating film, and to obtain a seed crystal growth layer having the same plane orientation as that of the silicon substrate and good crystallinity. The purpose is to provide a method.

[0008]

In the epitaxial growth method according to the present invention, a mask made of a silicon oxide film and a silicon nitride film is formed on a silicon substrate, and then the mask is formed into a lattice so that it has the same plane orientation as that of the silicon substrate. The step of removing by etching and forming the silicon seed crystal growth openings by arranging them in a grid pattern, the silicon substrate is etched with the mask left from the seed crystal growth openings formed in the previous step. The step of forming the seed crystal below, after depositing the silicon nitride film on the entire surface of the mask and the seed crystal,
With the deposited nitride film left on all sides of the mask and seed crystal, a step of etching away the nitride film deposited on the surface of the silicon substrate, oxygen injection from the surface of the silicon substrate exposed in the previous step A step of forming an insulating film for separating the seed crystal and the silicon substrate on the silicon substrate,
And the nitride film on the side surface of the seed crystal is removed by etching while leaving the oxide film on the surface of the seed crystal, and then the seed crystal is laterally epitaxially grown to form a series of seed crystals in the same plane orientation as the silicon substrate. The method is characterized by including a step of forming a growth layer on the insulating film.

[0009]

In the epitaxial growth method of the present invention, after the mask is formed on the silicon substrate, the mask is etched and removed in a lattice shape so as to have the same plane orientation as the silicon substrate, and the openings for growing the silicon seed crystal are arranged in a lattice shape. In the next step, the silicon substrate is etched with the mask left from the seed crystal growth opening to form the seed crystal under the mask. In the step of separating the seed crystal and the silicon substrate by oxidation, the seed crystal is not tilted or twisted, and the orientation of the whole seed crystal is maintained. Therefore, in the epitaxial growth process, since it is possible to perform epitaxial growth with all the orientations of the seed crystal aligned, a series of mutually connected epitaxial growth layers having the same plane orientation as the silicon substrate are completely separated from the silicon substrate by an insulating film. Can be obtained in the

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. Further, the thickness of the seed crystal growth layer can be controlled by the etching depth.

[0011]

EXAMPLE An epitaxial growth method according to an example 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 an 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. 1A, the plane orientation (10
A silicon oxide film 11 and a silicon nitride film 12 are sequentially formed on the silicon substrate 10 of 0) by a vapor phase epitaxy method. Particularly, the film 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, exposed to ultraviolet rays, and then developed to form openings arranged in a lattice pattern in the photoresist. In this state, using the photoresist as a mask, the oxide film 11 and the nitride film 12 are etched so that the oxide film 11 and the nitride film 12 remain in the same plane orientation as the silicon substrate 10. After that, 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 description, the silicon oxide film 11 will be described.
And the silicon nitride film 12 is generically called a mask M.

Next, as shown in FIG. 1B, anisotropic etching is performed from the seed window 13 to the silicon substrate 10 while leaving the mask M left in the step of FIG. 1A.
Of the 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 vapor phase epitaxy.

Then, as shown in FIG. 1D, FIG.
The nitride film 15 deposited on the surface of the silicon substrate 10 is removed by etching by anisotropic etching such as RIE while leaving the nitride film 15 deposited in the step of (1) on all sides of the mask M and the seed crystal 14. Further, as shown in FIG. 1E, the silicon substrate 1 exposed in the step of FIG.
A silicon oxide insulating film (hereinafter referred to as a field oxide film) 1 for injecting oxygen from the surface of 0 and separating the seed crystal 14 and the silicon substrate 10 on the silicon substrate 10 1
6 is formed.

Next, as shown in FIG. 1F, the nitride film 15 and the nitride film 12 left on all side surfaces of the seed crystal 14 in the state where the oxide film 11 on the surface of the seed crystal is left, are treated with phosphoric acid or the like. Then, the side wall of the seed crystal 14 is exposed, and the side wall of the seed crystal 14 is cleaned by wet etching or the like. By this cleaning, a good growth surface of the seed crystal 14 can be obtained in the epitaxial growth in the next step.

Thereafter, as shown in FIG. 1G, a seed crystal 14 is laterally epitaxially grown by a vapor phase epitaxy method, and a series of seed crystal growth layers (hereinafter referred to as a seed crystal growth layer) interconnected with each other are formed on the field oxide film 16. , Epitaxial growth layer) 17 is formed. Then, the silicon substrate 1
0 and the epitaxial growth layer 17 are connected to the field oxide film 1
Can be completely separated by 6.

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. In addition, the epitaxial growth 17
The thickness of can also be controlled. Further, during epitaxial growth, a stacking fault may occur at the interface with the oxide film 11. However, if the oxide film 11 is thinly formed in the step of FIG. Defects can be prevented. Further, the epitaxial growth is, for example, 9
It is preferable to carry out 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.

Further, in the process of FIG.
0) The seed window 13 is formed in a lattice pattern on the silicon substrate 10 of (0) with the plane orientation (100), and the silicon substrate 10 is formed into a rectangular pattern from the seed window 13 in the process of FIG. 1 to form the seed crystal 14 under the mask M, the seed crystals 14 are arranged in a lattice and remain (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 sandwiched, and the seed crystal 14 tilts, It is not twisted 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 the state where all the orientations of the seed crystal 14 are aligned, it is possible to obtain a series of mutually connected epitaxial growth layers 17 having the same plane orientation as the silicon substrate 10.

The present invention is not limited to the above 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 step of FIG. 1D, as shown in FIG. 3A, the nitride film 1 at the base end portion A of the seed crystal 14 is subjected to isotropic wet etching.
If the silicon contacting the lower end of 5 is removed, in the step of separating the seed crystal 14 and the silicon substrate 10, oxygen easily enters from the base end A as shown in FIG. The field oxide film 16 can be formed in a good state below 14 as well.

[0020]

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

[Brief description of drawings]

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

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

FIG. 3 is a cross-sectional view showing a modification of part of FIG.

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

[Explanation of symbols]

 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)

[Claims] 1. An opening for growing a silicon seed crystal is formed by forming a mask made of a silicon oxide film and a silicon nitride film on a silicon substrate and then etching the mask in a lattice pattern so as to have the same plane orientation as the silicon substrate. To form a seed crystal under the mask by etching the silicon substrate while leaving the mask through the seed crystal growth opening formed in the previous step. A step of depositing a silicon nitride film on the entire surface of the seed crystal, and then etching away the nitride film deposited on the surface of the silicon substrate with the deposited nitride film left on all sides of the mask and the seed crystal. , A step of injecting oxygen from the surface of the silicon substrate exposed in the previous step to form an insulating film for separating the seed crystal and the silicon substrate on the silicon substrate, and the seed crystal surface After removing the nitride film on the side surface of the seed crystal by etching while leaving the oxide film of, the step of epitaxially growing the seed crystal in the lateral direction and forming a series of interconnected seed crystal growth layers on the insulating film is performed. An epitaxial growth method comprising: