JPH0269385A - Production of thin single crystal film - Google Patents

Abstract

PURPOSE:To form a thin single crystal film of a material useful for industry such as electronics on a substrate on which the direct growth of a single crystal is not possible by effective solid phase epitaxial growth in a vertical direction by using a specific method. CONSTITUTION:The following method is adopted in order to form the thin single crystal film of a desired material on the substrate on which the growth of the single crystal of this material is not possible: The thin amorphous film 3 of the above-mentioned material (e.g.: Si) is first formed on the surface of the above-mentioned substrate (e.g., a silicon single crystal 1 is used as a base and has the structure coated with a thermally oxidized SiO2 film 2 over the entire surface thereof), then a seed crystal face (e.g.; silicon single crystal) 4 is brought into tight contact with the surface of the thin amorphous film 3 and the substrate is heated 5 to about the temp. at which the two materials do not fuse to each other to epitaxially grow the above-mentioned material 3 which is amorphous to the single crystal. The single crystal film is thus obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for forming a single crystal thin film of a substance useful in industries such as electronics on a substrate on which single crystal growth cannot be directly performed. It is something to leap into.

[Prior Art] Such technology has been developed particularly in recent years by the S01 (Semiconductor on In
It has become essential for manufacturing sulator (semiconductor on insulator) structures, and there is a strong demand for the development of an industrially effective method. Below, silicon (Si) is used as a semiconductor.
A case in which a single crystal thin film is formed on amorphous silicon dioxide (SiO2), which is an insulator, will be explained below as an example.

Partly because 5i02 is amorphous, even if Si is deposited thereon by a gas phase reaction, the Si will only become amorphous or polycrystalline.

One of the methods that have been tried in the past to make this Sl film into a single crystal is the beam melting recrystallization method. As shown in FIG. 6, this is achieved by applying a laser or electron beam 7 to the polycrystalline deposited Sl film 6, melting it locally, and sweeping the beam. When the Si resolidifies, the crystal grains become larger. This is a method of hoping that it will happen. In particular, as shown in the same figure, siU# crystal 1 is used as a base, and 5i02 on top of it is
If a window is opened in a part of the film 2 and a structure is created in which the polycrystalline Si film 6 is in contact with the base Si single crystal 1 at this part 1a, the polycrystalline 5i is epitaxially grown using this part as a seed crystal.
lii is recrystallized to obtain a single crystal region 6b. However, even in that case, defects such as a gradual shift in crystal orientation appear as the sweep is made farther from the seed crystal portion 1a, so the dimension of the single crystal region 6b is 100 μm in the sweep direction.
It will only be about m. In addition, it is necessary to control the beam output and sweep speed so as to melt only the deposited Si film 6 in order to prevent thermal damage to the underlying layer.
Not only the thickness of i6 (the thickness of 5i02 film 2 and the structure of the underlying layer also have an influence, so extremely complicated control is required.
There are also restrictions on the throughput.

Another method is lateral solid phase epitaxial growth. As shown in FIG.
Deposit the i film 3, heat it to about 600°C, and
This is a method in which in-phase epitaxial growth is started from the window portion without melting i, and the resulting Si single crystal region 3a is further extended laterally to the Si film portion on the SiO□ film 2. However, the progress of lateral solid phase growth is e.g.
At 0.degree. C., it takes 8 hours to reach a thickness of about 25 .mu.m, which is slow, and furthermore, if heated beyond this point, polycrystalline nuclei will be generated, so the single crystal region cannot be stretched.

Furthermore, a method using seed crystals was announced in Japanese Patent Publication No. 37-9875 and at the 10th Union of Applied Physics Lectures held in the spring of 1960 (Proceedings p. 238). As shown in Fig. 8, the micro seed crystal 8 is brought into contact with only a part of the semiconductor layer (thin film or powder molded) 10 on the jig 9, and a beam 7 such as an electron beam is used. This method involves sweeping the beam 7 in the lateral direction while melting and resolidifying the semiconductor layer 10, and should be classified as the beam melting recrystallization method described above. Therefore, it is impossible to avoid the drawbacks of this law mentioned earlier.

First, an amorphous thin film of the substance is formed, and then the seed crystal plane is brought into close contact with the surface of the amorphous thin film, and heated at a temperature that does not allow the two to fuse together.The amorphous substance is then epitaxially made into a single crystal. It is characterized by being a membrane.

[Problems to be Solved by the Invention] The crystal plane orientation of the single crystal region 3a or 6b obtained by the conventional method is determined by the orientation of the base crystal 1, and a selection different from this cannot be made. Portion 1a and minute seed crystal 9 cannot be used as an SOI structure.

The present invention proposes a new method that eliminates the drawbacks of the conventional method by using a technique that is fundamentally different from the conventional method described above.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a method for forming a single crystal thin film of a substance on a substrate on which a desired substance cannot be grown as a single crystal. [Function] In order to avoid the drawbacks of the above-mentioned conventional method, the present invention introduces a seed crystal not from the base side but from the surface side of the amorphous thin film.
In addition, measures are taken to simultaneously supply it over the entire required area, rather than locally.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

Specifically, as illustrated in FIG.
From the top of the thin film 3, it is brought into close contact with the surface so as to cover the entire required area, and using this crystal plane as a seed, the amorphous Si thin film is heated to an extent that does not reach its melting point from the surface to the bottom. This is to advance vertical solid-phase epitaxial growth. Thermal energy 5 for heating may be applied from the side of the seed crystal 4 as shown in FIG. 1(b), or on the contrary, may be applied from the side of the base Si single crystal 1. Further, this may be done by radiation or by contacting with a heater.

As an example, as shown in Fig. 1(a), Sii crystal 1
A structure in which the entire surface was covered with a thermally oxidized 5in2 film 2 with a thickness of 1 μm was used as a substrate, and an amorphous Si film 3 with a thickness of 1 μm was deposited on the entire surface of the Si by thermal decomposition of monosilane SiH4 at 500°C. Ta. Next figure (
As shown in b), another Si single crystal 4 (1
00) When the surfaces were brought into close contact and heated at 600°C, a solid phase growth portion 3 was formed at the interface between the amorphous Si film 3 and the single crystal 4.
a was grown, and in 55 minutes the amorphous Si film could be completely single-crystalized from the surface to the bottom in the [1003 direction. Therefore, the rate of vertical solid-phase epitaxial growth is 60
It is estimated to be 3 x 10-'cm/sec at 0°C, which is the previously reported value for the [100] direction of Si (edited by Seiji Furuyo, "S01 Structure Formation Technology", Sangyo Tosho 1987.p.
, 107).

It is also possible to provide a 5in2 film on the surface of the single crystal film grown in this manner and repeat the above steps to laminate a plurality of insulating films and single crystal films.

In this method, it is necessary that the seed crystal surface be in close contact with the sample surface, but this point can be solved by pressing the seed crystal surface onto the sample using a jig equipped with a spring mechanism, etc. This can be easily achieved thanks in part to the fact that the elastic constant is small. Further, if the sample surface has a step difference due to a device manufacturing process, etc., the surface of the amorphous Si film may be processed to form a single plane by a planarization process commonly used in integrated circuit process technology.

If the seed crystal surface and the sample are left in close contact with each other during long-term heating or during the cooling period after heating, if there is a risk that the seed crystal surface and the sample will stick together, please refer to Figure 2. As shown in FIG.
When the solid phase growth has progressed to some extent from the surface of the film, the seed crystal surface 4 is removed and heating is continued only for the sample 4 (
There is no problem in crystallizing the entire amorphous S1 film 3 even if the method shown in FIG. 3(b) is used.

Another important point for implementing this method is that both the surface of the amorphous Si film of the sample and the seed crystal surface are clean. There is a method of cleaning the surface by sputtering or the like using argon ions. Or Figure 3 (
As shown in a), not only the sample but also the Si single-crystal plate 4, which will serve as a seed crystal substrate, is attached to the apparatus for depositing Si together with a heater, and both are placed in a line and exposed to the Si reaction gas 11 at the same time. Then, amorphous Si 3 is formed on the sample whose base is amorphous 5i02, and an epitaxially grown single-crystal Si layer 4' is formed on the surface of the heated single-crystal plate 4, and at the same time as the deposition is completed, the atmosphere is raised to an extremely high temperature. It is also possible to switch to vacuum, immediately bring the two into close contact with each other, and heat them as shown in Figure (b). A method that combines both is also effective.

One of the features of this method is that it is possible to arbitrarily select the plane orientation of the seed crystal plane and create a Sol structure with a Si single crystal film with the same plane orientation. Si on 5i02 is not constrained by the crystal plane orientation of
When crystallizing the layer, by using the (100) plane as the seed crystal plane, this 54 layer 3a can be made to have the (100) plane orientation passed through the N-channel MO5 transistor, or vice versa. , it is possible to arrange devices suitable for each layer. Alternatively, as shown in FIG. 4(b), the base Si single crystal 1 has a (110) plane suitable for a P-channel MO5 transistor, and the upper layer 3a has a (110) plane suitable for an N-channel MO5 transistor.
100) planes or vice versa, it is also possible to construct a 0M05 circuit using upper and lower layers. These problems cannot be achieved by the beam melting recrystallization method or the lateral solid phase epitaxial growth method using the base 5i41i crystal as a seed crystal.

Next, let's compare this method with the conventional method in terms of time required.

For example, the time required for one sweep of 1 μm thick in an area of locm x 10 cm is 2 seconds, but since the width of the beam is limited to about 20 μm, it would be necessary to scan the entire area as shown in Figure 5 (
As shown in a), 5000 sweeps are required divided into stripes, and the total time is 170 minutes.

In the lateral solid-phase epitaxial method, if the seed crystal portion 1a were to have the same width across its area as shown in Figure 5(b), lateral growth would be required only once, but the growth rate would be as low as the above-mentioned rate. Although it does not depend much on the Si film thickness, as mentioned above, the speed is at most 3 μm/hour, so it takes 30,000 hours to cover a distance of 10 cm. Although the time can be shortened by providing seed crystal portions at multiple locations on the sample surface, grain boundaries occur more or less where crystal layers grown from different seed crystal portions collide. Furthermore, in both of the above methods, the area of the seed crystal portion 1a is wasted as a Sol structure.

On the other hand, in this method, as shown in FIG. 5(C), the IQ
By heating the seed crystal planes 4 of cm x 10 cm in close contact with each other, the entire 1 μm thick Si film can be made into a single crystal in 55 minutes as described above. Moreover, even if the area increases, the required time will not change as long as the seed crystal surface 4 λ corresponding to the increase in area can be obtained. Moreover, unlike the conventional method, the entire surface can be formed into a 501 structure, and there is no waste in providing a seed crystal region.

[Effects of the Invention] As described above, the present invention provides the Sol
When applied to the fabrication of structures, it enables the formation of structures with a high degree of freedom that is not possible using conventional methods, and allows the formation of single-crystal layers with different crystal orientations from the underlying semiconductor. . Furthermore, it is not limited to the case of the exemplified Sin and the above Si, but also a combination of arbitrary semiconductors, a Sol stacked structure with a plurality of layers, a heterojunction structure between semiconductors, and furthermore, metals, semiconductors, It can be widely used to form laminated structures made of arbitrary combinations of insulators, and has important industrial value.

[Brief explanation of the drawing]

FIG. 1 is a conceptual process diagram showing the method of the present invention, FIGS. 2 and 3 are conceptual diagrams showing other implementation methods of the present invention, and FIG. 4 is a diagram showing an example of a SOR structure produced by the final method. , Figure 5 is a diagram comparing the final method and the conventional method focusing on throughput, Figure 6 is a conceptual diagram of the conventional beam melting recrystallization method, and Figure 7 is a conceptual diagram of the conventional lateral solid phase epitaxial growth method. , FIG. 8 is a diagram showing a conventional proposal using seed crystal contact. l...Silicon single crystal forming the base, 2...Silicon oxide film, 3...Amorphous silicon film, 3a...In-phase epitaxially grown part, 4...
Large-area seed crystal, 5... Thermal energy for heating 6... Polycrystalline silicon film, 6a, 6b... Melted portion and recrystallized portion thereof, 7...
Laser or electron beam, 8... Microscopic seed crystal, 9... Jig, lO... Polycrystalline semiconductor layer, 11... Reactive gas for depositing a silicon film. Figure 1 Figure 3 Figure 4

Claims (1)

[Claims] 1) In order to form a single crystal thin film of a desired substance on a substrate on which the substance cannot be grown as a single crystal, an amorphous thin film of the substance is first formed on the surface of the substrate, and then an amorphous thin film of the substance is formed on the surface of the substrate. A single crystal characterized in that the seed crystal plane is brought into close contact with the surface of the amorphous thin film and heated at a temperature that does not allow the two to fuse, thereby epitaxially crystallizing the amorphous substance into a single crystal film. Method for manufacturing thin films. 2) The seed crystal surface is made of the same material as the desired material, and is obtained by depositing an amorphous film of the material and epitaxially growing it on a separate single crystal substrate in the same device. 2. The method for producing a single crystal thin film according to claim 1, wherein the method uses: 3) The seed crystal plane is brought into close contact with the surface of the amorphous thin film for only a part of the time during heating, and the heating of the amorphous thin film is continued with the seed crystal plane separated. The method for producing a single crystal thin film described in . 4) The substrate uses a semiconductor single crystal as the base of the lowermost layer, and the surface thereof is covered with an insulating film, and a single crystal film of a semiconductor of a type different from the semiconductor of the base is formed on the surface of the insulating film. A claim characterized in that a desired number of layers of two or more types of semiconductor single crystal thin films are stacked with the insulating film in between by repeating the steps of forming the single crystal film and forming the insulating film on the single crystal film. 1. The method for producing a single crystal thin film according to 1. 5) The substrate has a surface of a semiconductor single crystal forming a base covered with an insulating film, and a semiconductor single crystal film having a crystal orientation different from that of the base semiconductor single crystal on the surface of the insulating film. 2. The method of manufacturing a single crystal thin film according to claim 1, further comprising: forming a single crystal thin film.