JPS6276715A - Forming method for single crystal silicon thin film - Google Patents

Abstract

PURPOSE:To form a single crystal Si thin film having crystallinity of large crystal grains by disposing at random Si crystal grains on an insulating substrate, and single crystallizing a polycrystalline Si film or an amorphous Si film with the grains as seed crystal. CONSTITUTION:An SiO2 film 2 is formed on an Si substrate 1, and an alloy deposited layer 6 made of Al and Si is formed on the film 2. Then, a heat treatment is executed at a predetermined temperature, and Si crystal grains 7 of solid solution limit or more are segregated on the film 2 at the temperature of the heat treatment. Thereafter, an alloy layer 8 of the remaining Al and Si segregated from the grains 7 is removed. Subsequently, a polycrystalline Si film 3 is formed on the film 2 to cover the grains 7, Si ions are implanted to the film 3 to form an amorphous Si film 4. Then, the grains 7 are heat treated to convert the film 4 to single crystal Si film 5 as seed crystal of recrystallization. Thus, preferable crystal growth can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method of forming a single crystal silicon thin film suitable for use, for example, in forming three-dimensional integrated circuit devices.

[Summary of the invention]

The present invention provides a method for forming a single crystal silicon thin film suitable for use in forming a three-dimensional integrated circuit element, for example, after forming a layer of silicon and a metal that forms an alloy with the silicon on an insulating substrate. , heat treatment is performed at a predetermined temperature to precipitate silicon above the solid solubility limit V at the temperature of this heat treatment, then the alloy of silicon and metal is removed, and a polycrystalline silicon layer is formed on the insulating substrate and the precipitated crystal grains of silicon. After forming an amorphous silicon layer, heat treatment is performed to convert the polycrystalline silicon layer or the amorphous silicon layer into a single crystal, thereby eliminating all pattern constraints when laying out tertiary elements. This makes it possible to form a monocrystalline silicon thin film with large crystal grains and good crystallinity that is free from damage.

[Conventional technology]

In recent years, research has been actively conducted on three-dimensional semiconductor integrated circuit elements, which are three-dimensional integrated circuit elements that can transmit and process signals three-dimensionally. There is. It is expected that such three-dimensional elements will realize many new functions that cannot be achieved with two-dimensional integration, such as faster signal processing and advanced sequence signal processing. The basic button for such a 3D element is to form the entire semiconductor element region two-dimensionally on a silicon substrate, then form a silicon thin film on top of it with an insulating film such as a SIO It is constructed by forming a semiconductor element region in the semiconductor element region. Therefore, when forming tertiary elements, an important issue is how to form a single crystal silicon thin film with large crystal grains and good crystallinity on an insulating substrate.

Here, as a method of forming a crystalline silicon thin film via an insulating film on an already formed semiconductor element region, an amorphous silicon thin film is formed on an insulating film by fully utilizing an energy beam such as a laser beam or an electron beam. This amorphous silicon 7JEJ[
A method for single crystallizing lil has been proposed. However, this method has the disadvantage that large crystal grains cannot be grown because there is no seed crystal that serves as a nucleus for recrystallization, and polycrystalization occurs due to random nucleation.

A method has also been proposed in which a polycrystalline silicon film is entirely formed on the absolute R film, silicon ions are implanted into the polycrystalline silicon film to make it amorphous, and then the film is made into a single crystal by so-called solid-phase epitaxial growth. In this case, there was also the disadvantage that large crystal grains could not be grown because there was no seed crystal to serve as a nucleus for recrystallization.

Therefore, recently, a method as shown in FIG. 2 has been proposed as a method of forming a single crystal silicon film on an insulating film.

According to this method, first, a single crystal silicon substrate (1) is prepared as shown in FIG.
) A KS10□ film (2 residues) is formed on the 5i02 film (2), and then an opening (2&) is formed at a predetermined position in the 5i02 film (2) to partially expose the surface of the single crystal silicon substrate (1).

Next, as shown in FIG. 2B, a polycrystalline silicon film (3) is formed on the entire surface by laser plasma CVD, and then silicon ions are implanted into the polycrystalline silicon film (3) as shown in FIG. 2C. The crystalline silicon film (3) is made amorphous to form an amorphous silicon film (4).

Next, the amorphous silicon film (4) is subjected to heat treatment, and the exposed part (la) of the single crystal silicon substrate (1) is used as a seed crystal to form a single crystal of this amorphous silicon film (4), as shown in Figure 2. Thus, a single crystal silicon film (5) can be obtained.

In such a conventional method for forming a single crystal silicon film, since the exposed portion (1a) of the single crystal silicon substrate (1) is used as a seed crystal for recrystallization, the process is faster than in the case without the seed crystal described above. A good single crystal silicon film (5) can be obtained.

[Problem that the invention seeks to solve]

However, in the conventional method of forming a single crystal silicon film, a part of the single crystal silicon substrate (1) is used as a seed crystal for recrystallization, so there are restrictions on the pattern when laying out tertiary elements. There was the inconvenience of receiving

There is also the disadvantage that good crystal growth becomes difficult to obtain as the distance from the exposed portion (1a) of the single-crystal silicon substrate (1) increases.

In view of this, the present invention provides a crystal structure that does not use a part of a single crystal silicon substrate as a seed crystal for recrystallization and is free from tree/top constraints when all tertiary elements are laid out on an insulating substrate. An object of the present invention is to provide a method for forming a single crystal silicon thin film with large grains and good crystallinity.

[Means to solve all problems]

As shown in FIG. 1, the method for forming a single crystal silicon thin film according to the present invention involves forming a layer (6) of silicon and a metal forming an alloy with silicon on an insulating substrate (2), and then The silicon (7) is completely precipitated on the solid solubility limit at the temperature of this heat treatment, and then the silicon-metal alloy (8) is completely removed, and the insulating substrate (2) and the precipitated silicon crystals are removed. A polycrystalline silicon film (3) is formed on the grain (7).
) or after forming an amorphous silicon film, heat treatment is performed to convert the polycrystalline silicon film (3) or the amorphous silicon film into a single crystal.

[Effect]

According to the present invention, after the layer (6) consisting of silicon and a metal forming an alloy with silicon is completely formed on the insulating substrate (2), heat treatment is performed at a predetermined temperature, so that the insulating substrate (2) Silicon crystal grains (7) are scattered on the top, and the polycrystalline silicon film (3) or amorphous silicon film is single-crystallized using the silicon crystal grains (7) as seed crystals for recrystallization. As a result, the number of seed crystals is larger than when a part of the single crystal silicon substrate (1) is used as a seed crystal for recrystallization, and good crystal growth is achieved. A monocrystalline silicon thin film (5) with large crystal grains and good crystallinity is formed without being subject to any restrictions on the A' turn.

〔Example〕

Hereinafter, an embodiment of the method for forming a single-crystal silicon thin film according to the present invention will be described with reference to FIG.

In FIG. 1, parts corresponding to those in FIG. 2 are given the same reference numerals, and detailed explanation thereof will be omitted.

First, as shown in FIG. 1A, a silicon substrate (1) is prepared,
This silicon substrate (1) is completely thermally oxidized to form a SiO□ film (2)
Then, as shown in FIG. 1B, this S10□ film (
2) Form a skin (6) on which an alloy consisting of 99% At and 1% St is deposited.

Next, heat treatment was performed at 400°C for 30 to 60 minutes, and i1
As shown in Figure C, silicon (
7) on the insulating film (2), and then, as shown in Figure 1, the At and Sl alloy layer (8) remaining after the silicon crystal grains (7) have been segregated is etched with, for example, phosphoric acid. and remove it.

Next, as shown in FIG. 1E, a polycrystalline silicon film (3) is formed on the insulating film (2) by, for example, Lede plasma CVD so as to cover the silicon crystal grains (7), and then this polycrystalline silicon film is Silicon ions are implanted into (3) to make it amorphous, forming amorphous silicon &(4)'. In this case, the silicon ion implantation amount, implantation energy, and conditions for making only the entire polycrystalline silicon film (3) amorphous can be selected, and by doing this, the silicon crystal grains (7
) can be avoided in any way.

Next, by performing heat treatment, the amorphous silicon film (4) is made into a single crystal by using the silicon ions (7) as seed crystals for recrystallization. In this case, when heat treatment begins, the insulating film (
2) The silicon crystal grains (7) scattered on the top are shown in Figure 1G.
As shown in Figure 1H, the grain size was increased so that the grains bonded with each other, and the amorphous silicon film (4
) It becomes like a complete single crystal.

Next, as shown in Fig. 1, a photoresist (9 layers) is formed on the entire surface, and then reactive ion etching (RIE) is performed to obtain a single crystal silicon thin film (5) as shown in Fig. 1J.

The silicon crystal grains (7) exceeding the solid solubility limit at 400 °C are completely precipitated, and the remaining alloy (8) is completely removed. The amorphous silicon film (4) is used as a seed crystal for recrystallization, so that the entire amorphous silicon film (4) is made into a single crystal.
) is used as a seed crystal for recrystallization, the seed crystal is cut more often and good crystal growth can be achieved.

Further, according to this embodiment, since a part of the base silicon substrate (1) is not exposed, large crystal grains are not subject to pattern restrictions when laying out tertiary elements. There is an advantage that the entire single crystal silicon thin film (5) with good properties can be formed.

In this example, 993i was applied on the StO□ film (2).
We have described the case where an alloy of i percent of A7 and IFtJtz''-cent of Sl is deposited and heat-treated at 400°C to completely precipitate silicon crystal grains (7).
The conditions such as the mixing ratio of t and Sl and the heat treatment temperature are not limited to these cases.
) Various other conditions for t-precipitation can be obtained, and it goes without saying that the same effects as described above can also be obtained in this case.

Furthermore, in this example, a case has been described in which all aluminum is used as the metal to form an alloy with silicon, but various other metals can be used instead, and the same effects and effects as described above can be obtained in this case as well. Of course, this can be done.

Furthermore, in this embodiment, the case was described in which SlO□cross (2) was formed as the insulating film, but it is also possible to use an insulating film of other types of glaze in place of this. can be obtained.

In addition, in this example, a polycrystalline silicon film (3) is entirely formed on the 5lO2 layer (2) and silicon crystal grains (7), and silicon ions are implanted into this polycrystalline silicon group (3) to form an amorphous silicon film. (4), the amorphous silicon film (4) is formed with the SiO□ film (2) and silicon crystal grains (7) without forming polycrystalline silicon U(3)e.
), and it goes without saying that the same effects as described above can be obtained in this case as well.

Furthermore, it goes without saying that the present invention is not limited to the above-described embodiments, and can take various other configurations without departing from the gist of the present invention.

〔Effect of the invention〕

According to the present invention, all silicon crystal grains are scattered on an insulating substrate, and the silicon crystal grains are used as seed crystals for recrystallization to monocrystallize a polycrystalline silicon film or an amorphous silicon film. Therefore, the number of seed crystals is larger than when using a single crystal silicon substrate as a seed crystal for partial total recrystallization, and good crystal growth can be achieved. It is possible to form a single-crystal silicon thin film with large grains and good crystallinity without being subject to pattern restrictions.

[Brief explanation of drawings]

The if diagram is a diagram showing an example of the method for forming a single crystal silicon thin film of the present invention, and FIG. 2 is a diagram showing an example of the conventional method for forming a single crystal silicon thin film. (1) is a single crystal silicon substrate, (2) is an insulating film, (3)
is a polycrystalline silicon film, (4) is an amorphous silicon film, (5
) is a single crystal silicon film, (6) is an alloy layer consisting of 99 weight percent At and 1 weight percent Si, (7
) are silicon crystal grains.

Claims (1)

[Claims] After forming a layer consisting of silicon and a metal forming an alloy with the silicon on an insulating substrate, heat treatment is performed at a predetermined temperature to precipitate the silicon in an amount equal to or higher than the solid solubility limit at the temperature of the heat treatment. After removing the alloy of and the above-mentioned metal and forming a polycrystalline silicon layer or an amorphous silicon layer on the above-mentioned insulating substrate and the precipitated crystal grains of silicon, heat treatment is performed to form the above-mentioned polycrystalline silicon layer or amorphous silicon layer. A method for forming a single-crystal silicon thin film, characterized by monocrystalizing a silicon layer.