JPH04188612A - Crystal growth method and crystallized substance obtained by said method - Google Patents

Abstract

PURPOSE:To contrive improvement of growth distance in transverse direction by a method wherein, after accelerated ions have been implanted into an amorphous thin film using the energy with which the projection range almost equal to the film thickness of the amorphous thin film can be obtained. CONSTITUTION:When ions 5 are implanted on the whole surface of an amorphous thin film 4, the accelerating energy of the implanted ions is set in such a manner that their projection range becomes equal to the film thickness of the amorphous thin film. Then, when a heat treatment is conducted thereon at the temperature lower than the melting point of the amorphous thin film 4, a single crystal region 7 is grown by solid phase epitaxial growth on the interface between the single crystal substrate surface 6, which is exposed to an aperture part 3, and the amorphous thin film 4. Moreover, when the heat treatment is conducted continuously, the single crystal region 7 is grown in lateral direction as far as to the point above an insulating film 2. As a result, a wide single crystal region 7 can be obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a crystal growth method and a crystalline article obtained by the method, and particularly relates to a thin-film crystal S obtained by forming a thin-film crystal by lateral epitaxial growth. OI (S
The present invention relates to an ilicon (on indulator) structure and a method for forming the same.

The present invention is applied, for example, to thin film crystals used in electronic devices such as semiconductor integrated circuits, optical devices, and the like.

[Prior Art and Problems to be Solved by the Invention] Lateral solid phase epitaxial growth has been proposed as one method in the field of crystal formation technology for growing a single crystal thin film on an amorphous insulating film.

As shown in FIG. 3, an amorphous thin film 4 is formed on an insulating film 2 having a partial opening 3 provided on a single crystal substrate 1, and this is heat-treated to form an opening. In this method, an amorphous thin film 4 is epitaxially grown in the same phase using the single crystal substrate surface exposed at 3 as a seed, and then a single crystal region 7 is laterally grown from the opening onto the insulating film.

However, although many studies have been conducted regarding this method, there is a limit to the distance over which the single crystal region 7 can be grown laterally on the insulating film 2, and the maximum distance is only about 3 to 5 μm. This is because crystal nuclei 10 randomly generated in the amorphous thin film 4 on the insulating film 2 prevent the elongation of the single crystal region 7 that has grown laterally. If the film thickness of the amorphous thin film 4 is relatively thin, it takes a long time for the single crystal region to reach from the interface 8 between the single crystal substrate surface and the amorphous thin film 4 in the opening 3 to the surface of the amorphous thin film 4. Although this does not require much time, it takes time to grow horizontally for a long time on the insulating film 2. On the other hand, when an amorphous thin film is heat-treated,
Spontaneous nucleation of crystal nuclei occurs stochastically after a certain period of time, so when the growth end face 9 of the single crystal region 7 that has continued to grow laterally during that time comes into contact with the crystal nucleus 10, the single crystal Lateral growth of the area is forced to stop.

In order to solve these problems in lateral solid-phase epitaxial growth and to ensure a sufficient lateral growth distance, it is necessary to Either the incubation time until formation occurs can be extended, or even if random nucleation occurs, it can be made amorphous again. An invention based on the former idea was proposed in Japanese Patent Application Laid-Open No. 101017/1982, and the latter was proposed in Japanese Patent Application Laid-open No. 166212/1983, so these will be explained as examples.

JP-A-62-101017 proposes the idea of performing heat treatment after implanting neutral ions into an amorphous thin film. This is mainly due to the fact that ions are implanted almost uniformly throughout the thickness of the amorphous thin film, which prolongs the time required for structural relaxation prior to crystallization of the amorphous thin film. This is an attempt to increase the latency time for nucleation. Therefore, if the amorphous thin film is thin, ions will be implanted so that the projected range is located approximately in the middle of the film thickness, and if the film is thick, multi-step implantation with different energy levels will be required. becomes. However, as will be explained in detail later, in addition to the complexity of multi-stage implantation, implanting ions into a region shallower than the middle layer of the film thickness is not necessarily the best method for suppressing random nucleation.

In JP-A No. 63-166212, a non-single-crystallized region near the growth end face of a single-crystal region growing laterally is sequentially made amorphous by local ion implantation while continuing heat treatment. A method has been proposed.If this method can be realized, even if there are randomly generated crystal nuclei, they will be amorphized by ion implantation immediately before the single crystalline region comes into contact with them, so the principle is In terms of the lateral growth distance, the culm can be lengthened without βH.However, since the lateral solid phase growth rate is generally slow at several thousand people/hour, it is possible to stabilize the lateral growth distance over the necessary time to achieve a sufficient lateral growth distance. It goes without saying that ion implantation cannot be continued, but it is not common to continue heat treatment inside an ion implantation device for a long time, and it is difficult to synchronize local ion implantation with the lateral growth of a single crystal region. For these reasons, this method cannot necessarily be said to be the best method.

Therefore, an object of the present invention is to provide a crystal growth method in which the lateral growth distance is significantly improved in lateral solid-phase epitaxial growth, and a crystalline article obtained by the method.

[Means and effects for solving the problem] That is, the present invention includes a single-crystal substrate and an opening provided on the single-crystal substrate and exposing a part of the surface of the single-crystal substrate. In the crystal growth method, an amorphous thin film is formed on a substrate consisting of an insulating film, and then the amorphous thin film is grown by lateral solid phase epitaxial growth onto the insulating film using the opening as a seed. A crystal growth method, characterized in that ions accelerated to an energy that provides a projected range approximately equal to the film thickness of the thin film are implanted into the amorphous thin film, and then crystallized by heat treatment, and by the method. This is the obtained crystal article.

Furthermore, a polycrystalline thin film is formed on a base consisting of an insulating film coated on the single crystal substrate and provided with an opening such that a part of the surface of the single crystal substrate is exposed; In a crystal growth method in which the polycrystalline thin film is laterally grown solid-phase epitaxially on the insulating film using a polycrystalline thin film as a seed, ions are A crystal growth method characterized in that the polycrystal thin film is injected and then crystallized by heat treatment, and a crystal article obtained by the method.

In the present invention, prior to the heat treatment, the projected range of ion implantation is made such that the thickness of the amorphous thin film on the insulating film and the range are almost the same, that is, By implanting ions accelerated to energies near the interface, the formation of random crystal nuclei in the amorphous thin film on the insulating film is most effectively suppressed, resulting in the formation of single crystals. This makes it possible to further extend the lateral growth distance of the region.

[Embodiments] Below, the crystal growth method according to the present invention will be explained in detail from its principle.

Nucleation of crystal nuclei in an amorphous thin film formed on the surface of an insulating film occurs depending on the location: (1) on the surface of the amorphous thin film, (2) in the film, and (3) at the interface with the underlying insulating film. Among these, it is generally known that (3) is the most likely to occur. Therefore, if the thickness of the amorphous thin film is sufficiently thin relative to the growth rate of crystal grains after nucleation and the frequency of nucleation in the film, the crystal grains nucleated at the interface will immediately reach the film surface by their own growth. After that, the crystallization process is rate-determined by nucleation at the interface. Furthermore, in order to suppress random nucleation in the amorphous thin film, it is first of all necessary to suppress the nucleation of crystal nuclei generated at the interface with the underlying insulating film.

Therefore, we investigated the formation process of crystal nuclei in amorphous thin films of several materials by implanting ions prior to the heat treatment process and then performing the heat treatment, and found that the first nucleus formation occurred after the heat treatment started. incubation time
On time) was found to depend on the projected range of the implanted ions. FIG. 2 is an example showing the tendency of the latency time dependence on the projected range of ions in an amorphous thin film as varied by implantation energy. The incubation time for nucleation is maximum near the interface of the underlying insulating film of the amorphous thin film, where the projected range of the implanted ions is equal to the film thickness (T
)showed that. This result is attributable to the fact that the nucleation of the crystal nuclei that would initially be formed near the interface was suppressed by the ion implantation near the interface.

Furthermore, such dependence of the nucleation latency time on the ion implantation energy is not only due to ion implantation into a thin film deposited in an amorphous state from the beginning, but also due to ion implantation into a crystalline thin film. A similar tendency was observed even when this was made amorphous.

However, in this case, ion implantation not only controls the interface state with the underlying insulating film (but also plays the role of making the crystal amorphous), so to obtain the same effect, it is necessary to implant an amorphous thin film. In general, a higher dose was required than in the case of ion implantation.

The method for forming a thin film crystal according to the present invention utilizes the above findings. The formation process will be explained using FIG.

First, an insulating film 2 is formed on a single-crystal substrate 1, an opening 3 is provided in the insulating film 2 so that a portion of the surface of the single-crystal substrate 1 is exposed, and an amorphous thin film 4 is formed on top of the insulating film 2 to be grown in a solid phase. Then, a substrate for crystal formation is created [FIG. 1(a) 1°] Next, ions 5 are implanted into the entire surface of this amorphous thin film 4 [
Figure 1(b)]. At this time, the acceleration energy of the implanted ions must be set so that its projected range is exactly equal to the thickness of the amorphous thin film 4.

Therefore, when this is heat-treated at a temperature lower than the melting point of the amorphous thin film 4, a single crystal region 7 grows by solid phase epitaxial growth from the interface between the single crystal substrate surface 6 exposed in the opening 3 and the amorphous thin film 4. [FIG. 1(c) 1°] When the heat treatment is further continued, the single crystal region 7 grows laterally even on the insulating film 2, and a wide single crystal region is obtained. [FIG. 1(d) 1°] Here, in the step shown in FIG. 1(a), a polycrystalline thin film may be formed instead of the amorphous thin film 4. This is because, if a sufficient dose is given, the polycrystalline thin film will be made amorphous in the next ion implantation process. However, as mentioned above (to make a polycrystalline thin film amorphous and further suppress nucleation at the interface between it and the underlying insulating film, the cost is higher than when an amorphous film is formed from the beginning). A dose is required.

[Example] Below, an example will be described in which the method for forming a thin film crystal according to the present invention is applied to the formation of a thin film crystal of Si by the steps shown in the embodiment.

<Example 1> Using a (100) Si wafer as a single-crystal substrate, it was first oxidized by a thermal oxidation method to form 5iO
A z insulating film was formed.

Then, this oxide film is patterned using a normal photolithography process, and the surface of the single crystal substrate (11
0) Installed along the direction.

Next, amorphous Si was deposited on this substrate by low-pressure CVD.
Thin films were deposited to a thickness of 1000.

Then, Si"" ions accelerated to an energy of 70 keV were implanted from this surface at a dose of I x 101101s. In this case, the implanted Si ions
The projected range in the film is 997 people, and it is located at the interface with the underlying 5in2 insulating film.

The substrate prepared in this way was heated to 550°C in a N2 atmosphere.
When heat treated for 50 hours at a temperature of
It had expanded to the width of On the other hand, only a small amount of random nucleation was still observed in the region on 5i02 that was not covered by the single crystal region. This means that the method according to the present invention allows the lateral solid phase epitaxial growth distance to reach 10 μm or more.

<Example 2> A (100) Si wafer was used as a single crystal substrate, and a 5isN<5 film was formed on this surface by low pressure CVD.
Approximately 10,000 people were deposited and this was used as an insulating film.

Then, this nitride film is buttered by a normal photolithography process, and an opening groove with a width of 2 μm is formed at +11 in the wafer plane so that the surface of the underlying single crystal substrate is exposed.
'0) Installed along the direction.

Next, a polycrystalline Si thin film was deposited on this substrate to a thickness of 1000 nm by low pressure CVD.

Then, Si" ions accelerated to an energy of 70 keV were implanted from this surface at a dose of 5 x 10"c+n-". In this case, the projected range of the implanted Si ions in the Si film was 997 people. Habojitaru 5
It is located at the interface with the i-N4 insulating film. Also,
The polycrystalline Si thin film was completely amorphized by this ion implantation.

The substrate prepared in this way was heated to 550°C in a N2 atmosphere.
When the sample was heat-treated for 50 hours at a temperature of 1, the same results as in Example 1 were obtained.

[Effects of the Invention] The present invention utilizes the fact that the random crystal nucleation process in an amorphous thin film on an insulating film depends on the projected range of ion implantation into the thin film. As a seed, when an amorphous thin film is laterally grown solid-phase epitaxially on an insulating film, it is possible to extend the distance over which the amorphous thin film can be laterally grown.

In order to suppress nucleation at the interface between the amorphous thin films on the insulating film, which is the main cause of random nucleation in the amorphous thin film on the insulating film, the present invention aims to By injecting ions from the surface that are accelerated to an energy that is approximately equal to, that is, located near the interface with the underlying insulating film, random nucleation that prevents the growth of a single crystal region that grows laterally can be prevented. This is to minimize the Furthermore, since random nucleation by ion implantation can be suppressed most effectively, it is also possible to keep the dose of ion implantation to the necessary minimum.

As a result, the crystal growth method according to the present invention provides an SOI-structured crystal thin film having a sufficiently large single crystal region to form various devices at low cost.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the steps of the crystal growth method according to the present invention. Figure 2 shows the nucleation latency as a function of the film thickness of the amorphous thin film and the projected range of the implanted ions in the solid phase recrystallization process of the amorphous thin film, which is the basis of the thin film crystal forming method according to the present invention. This is an example showing the tendency of time dependence. FIG. 3 is a cross-sectional view showing one prior art process in a crystal growth method. 1... Single crystal substrate, 2... Insulating film, 3...
・Opening portion, 4...Amorphous thin film, 5...
ions, 6...Substrate surface, 7...Single crystal region, 8...Interface, 9...Growth end surface,
lO...Crystal nucleus. Agent Patent Attorney Johei Yamashita

Claims (4)

[Claims] (1) An amorphous thin film is formed on a substrate consisting of a single crystal substrate and an insulating film coated on the single crystal substrate and provided with an opening that exposes a part of the surface of the single crystal substrate. In a crystal growth method in which the amorphous thin film is laterally grown on the insulating film by lateral solid-phase epitaxial growth using the opening as a seed, a projected range approximately equal to the film thickness of the amorphous thin film can be obtained. 1. A crystal growth method, which comprises implanting ions accelerated to a specific energy into the amorphous thin film, and then crystallizing the film by heat treatment. (2) An amorphous thin film is formed on a substrate consisting of a single crystal substrate and an insulating film coated on the single crystal substrate and provided with an opening that exposes a part of the surface of the single crystal substrate. and then laterally growing the amorphous thin film onto the insulating film using the opening as a seed, the crystalline article has a projected range approximately equal to the thickness of the amorphous thin film. A crystalline article characterized in that it is obtained by implanting ions accelerated to such energy into the amorphous thin film and then crystallizing it by heat treatment. (3) A polycrystalline thin film is formed on a base consisting of a single-crystal substrate and an insulating film coated on the single-crystal substrate and provided with an opening that exposes a part of the surface of the single-crystal substrate. In a crystal growth method in which the polycrystalline thin film is laterally grown on the insulating film by lateral solid-phase epitaxial growth using the opening as a seed, an energy such that a projected range approximately equal to the film thickness of the polycrystalline thin film is obtained. 1. A method for growing a crystal, comprising implanting ions accelerated into the polycrystalline thin film into the polycrystalline thin film, and then crystallizing the film by heat treatment. (4) A polycrystalline thin film is formed on a base consisting of a single-crystal substrate and an insulating film coated on the single-crystal substrate and provided with an opening that exposes a part of the surface of the single-crystal substrate. In a crystalline article obtained by forming a polycrystalline thin film and then laterally growing the polycrystalline thin film onto an insulating film using the opening as a seed, a projected range approximately equal to the film thickness of the polycrystalline thin film can be obtained. 1. A crystalline article, characterized in that it is obtained by implanting ions accelerated to such energy into the polycrystalline thin film and then crystallizing it by heat treatment.