JPS5895687A - Growth of crystal granule of thin film - Google Patents

Abstract

PURPOSE:To grow the crystal granule of the first thin film efficiently, by laminating the second and the third thin films to the first thin film, irradiating the 1 a minate with light ( or electron) beam so that the third thin film is heated, heating the first thin film by the heat conduction produced by the irradiation. CONSTITUTION:The silicon base plate 11 is provided with the silicon oxide film 12 by thermal oxidation, the polycrystalline silicon film 13 (the first thin film) having a thickness of about 5,000Angstrom is deposited on the base plate by chemical deposition, the film is converted into the oxidized film 14 in such a way the polycrystalline silicon region 13' lie island is left and surrounded by the oxide film, and the thin thermally oxidized film 15 (the second thin film) having a thickness of about 500Angstrom is formed on the region 13'. The titanium oxide film 16[the third thin film (surface absorption layer)]having a thickness of about 500Angstrom is deposited on the thin thermally oxidized film, irradiated with carbon dioxide gas laser light (wavelength of 10.6mu) 17, the light is absorbed in the titanium oxide film 16 so that it is heated, and the polycrystalline silicon film 13' is heated by the heat conduction from the film 16 to increase the particle diameter of the crystal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for growing crystal grains or single crystallizing a thin film.

Growth of crystal grains in thin films such as silicon by irradiating and heating them with laser beams or electron beams, or using the so-called beam annealing method to achieve single crystallization. Single crystallization technology is 80 I (
It has attracted the attention of many people for its 109 points and the realization of a structure in which a silicon thin film with a single crystal or a large crystal diameter is formed on an amorphous insulating substrate.

In the conventional crystal growth technology for round thin films using the beam annealing method, a method was adopted in which the thin film itself was heated by directly absorbing most of the laser beam or electron beam energy. When using such a direct heating method, once the material and structure of the heated object is determined,
The appropriate beam type and irradiation condition range are automatically determined accordingly, which has the disadvantage that there is less freedom in beam m* and irradiation conditions. For example, when trying to single-crystallize a silicon thin film using laser annealing technology, carbon dioxide laser with a small coefficient (wavelength 10.4i7)
1 m) is not only undesirable from the point of view of energy utilization efficiency, but also avoids directly heating the substrate and substrate through the thin film. In addition, even when using an electron beam, when the thickness of the thin film to be heated becomes less than several thousand amps, the heat generated by the electron beam is mainly absorbed by the thin film. In order to confine the electron beam, K reduces the acceleration energy of the electron beam to several ke.
It becomes necessary to limit the value to a low value of V or less. In such a low acceleration region, the extraction electrode voltage must also be lowered, which causes the problem that it is difficult to obtain a sufficient electron beam current density.

The present invention significantly improves the problems of the conventional methods described above and relates to a novel method for growing crystal grains or forming single crystals in thin films.

The method according to the present invention allows direct application of the first film onto the first thin film. I or irises 2
The structure in which the third thin film is deposited is irradiated with one light or electron beam through the thin film of K. The first thin film is heated by the heat conduction of the thin film of 9II3, which is heated mainly by line light or electron beam irradiation. I'm happy to do it 1
The growth of crystal grains in a thin film is characterized by single crystallization. Therefore, in the method according to the present invention, for example, when using a laser annealing method, the growth of crystal grains in a thin film is Decide the type of laser regardless of the optical properties such as absorption coefficient and reflection coefficient of the first thin film to be grown or single crystallized, and select the material and thickness of the third thin film as the surface absorption layer accordingly. In addition, when using the electron beam annealing method, the acceleration energy of the electron beam is determined regardless of the thickness of the lNl0 thin film whose crystal grain size is to be grown, and the I ! All you have to do is choose the material and thickness of the thin film in step 3. In the method according to the present invention, the first thin film is heated mainly by heat conduction from the third thin film as a surface absorption layer, so that microscopic intensity fluctuations within the beam gyF of the laser or electron beam are caused by heat. It has been found that a new advantage arises in that it is averaged by diffusion and the influence of #11 thin film on hot coal distribution is alleviated.

Next, embodiments of the method according to the present invention will be described in detail with reference to the drawings. The first example uses carbon dioxide laser irradiation)
This is a case in which the crystal grains of a polycrystalline silicon film are grown.
(As shown in @. First, as shown in Figure I! Next, by a combination of well-known photoetching methods and selective oxidation methods, the polycrystalline silicon region is left in an island shape 13' as shown in FIG. A thin thermally oxidized film 15 of approximately 500 μm is formed on the island-shaped polycrystalline silicon region 13' by thermal oxidation (see Figure C1).

Next, by performing so-called reactive sputtering using titanium (Ti) as a target in a mixed atmosphere of argon (Ar) and oxygen (0. The titanium film 16 was deposited to a thickness of about 5 mm.Next, heat treatment was performed in an oxygen atmosphere at 1000°C to make the titanium oxide film 16 denser and to improve the adhesion strength with the underlying silicon oxide film. As shown in FIG. 1(e), the carbon dioxide laser beam 17 (wavelength IQ,
6 Jlm). At this time, the titanium oxide film 16
Since the absorption coefficient for carbon dioxide laser light is significantly larger than that for the polycrystalline silicon film 1fK, it acts as a good absorption layer for carbon dioxide laser light. Therefore,
The polycrystalline silicon film 13' is heated by thermal conduction through the titanium oxide film 166 and the like, and its crystal grain size ranges from several sm to several am.
This increased by one to two orders of magnitude compared to the case without carbon dioxide laser irradiation.

The jllD example has a structure in which a polycrystalline silicon film is in direct contact with a single crystal silicon substrate in a part, so-called 1ate
This corresponds to what is called the Rsil seeding method. In the case of the first embodiment, a structure as shown in the schematic cross-sectional view of FIG. 2 is formed using the well-known photoetching method, selective oxidation method, chemical vapor deposition method, reactive sputtering method, etc., as in the case of the first embodiment.

Here, 21 is a silicon single crystal substrate, 22 is a silicon oxide film, 23 is a polycrystalline silicon film, 24 is a silicon oxide film,
25 is a titanium oxide film. Next, when the carbon dioxide laser beam is scanned and irradiated in the direction from left to right in FIG. The V-licozo film 23 could be made into a single crystal.

In the third embodiment, an electron beam with acceleration energy of 15 ke VO was used for the carbon dioxide laser beam irradiation in the second embodiment, and a surface absorption layer 25 was formed by sputtering on titanium oxide with a thickness of 9. A 6000A titanium film was used. Further, the film thickness of the polycrystalline silicon film 23 is 30 GOA, and the film thickness of the silicon oxide JII 22 is 5 GOA.
Use 00mu-9. When a 15 ke V electron beam was irradiated onto the silicon KWA, the heat generation peak position of Kuba-kai was approximately 63 mm from the surface.
Since it is at a depth of 0.00 m, it is necessary to
When an eVO electron beam is directly irradiated onto a silicon film with a thickness of 1.5 keV, the peak position of heat generation exceeds the silicon film and becomes inside the base.However, when the method of the present invention is used, the 15 keV electron Since the heat generation peak position of the beam in titanium is about 3300 μm, most of the heat generated by electron beam irradiation occurs in the titanium film. Therefore, the polycrystalline silicon film 23 is effectively heated by heat conduction from the titanium film 25, and the silicon film 23 of the underlying oxide film 22 is heated.
In addition, in the nine embodiments described so far, the silicon film and the titanium oxide film or the silicon film and the titanium film were laminated with the silicon oxide film interposed in between.
In the case of a silicon film and a titanium oxide film, they do not interact with each other even when heated, so it is possible to directly stack them without using a silicon oxide film. As mentioned above, suppressing unnecessary heating of the 'F' ground means not thermally changing the device characteristics of the lower layer that has already been formed in a structure where devices are integrated in multiple layers, such as a three-dimensional integrated circuit. , is extremely important.

[Brief explanation of the drawing]

1 and 2 are schematic cross-sectional views of elements at main steps in an embodiment of the method according to the present invention. 11.21 --- Silicon substrate, 12.14
．． 15.22.24--Silicon monoxide% 13. la; 23·······Polycrystalline silicon, 16········Titanium oxide, 17········
Carbon dioxide laser beam 25-------Titanium oxide or titanium, 2t/A fan crystal silicon, micro-insulator difference plate and tilting. Figure 1 (le)

Claims (1)

[Claims] Directly on the thin film of III or! 3rd through 12 thin films
By irradiating a structure with a thin film deposited with a single light or electron beam, I
A method for growing crystal grains in a thin film, characterized in that when the thin film of 11 is heated, the crystal grains of the first thin film grow or become single crystallized.