JPS63185015A - Forming method for semiconductor thin film - Google Patents

Abstract

PURPOSE:To form a semiconductor thin film having large crystal grain size and preferable crystallinity by introducing phosphorus or phosphorus ions to the front surface of an amorphous semiconductor thin film and then heat-treating it. CONSTITUTION:After an amorphous semiconductor thin film 2 is formed on an insulator 1, phosphorus P or phosphorus ions P<+> are introduced to the surface region of the film 2, then heat-treated, and a phosphorus P or phosphorus ions P<+>-containing layer 3 is removed. Nuclei of the phosphorus P or phosphorus ions P<+> as center are previously generated, and crystal grains 4... 4 are grown at the nuclei as centers. In this case, lateral growth occurs earlier but also in depthwise direction. Accordingly, the grains 4...4 having large grain size are resultantly grown to obtain a semiconductor thin film 5 having preferable crystallinity.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for forming a semiconductor thin film by a so-called recrystallization method.

[Summary of the invention]

The present invention is a method for forming a semiconductor thin film by a so-called recrystallization method, in which an amorphous semiconductor i-film is formed on an insulator, and then phosphorus or phosphorus ions are introduced into the surface region of this amorphous semiconductor thin film. , followed by heat treatment, and then phosphorus or phosphorus.
By removing the ion-containing layer, it is possible to form a semiconductor thin film with good crystallinity on the insulator, which has crystal grains that are large, large, and have uniform grain size. be.

[Conventional technology]

Conventionally, when forming a silicon thin film on an insulator, one method is to form a polycrystalline silicon thin film on the insulator and then inject silicon ions and Si+ into this polycrystalline silicon thin film.
A method has been adopted in which ions are implanted, the polycrystalline silicon thin film is made into an amorphous silicon M film, and then heat treatment is performed.

[Problem that the invention seeks to solve]

However, in such conventional methods of forming silicon thin films, it is not possible to make the grain size of silicon crystal grains uniform, and moreover, it is not possible to make the grain size of silicon crystal grains uniform! There was a disadvantage that it could only be grown to a size of about 11 to 5 μm, and a silicon thin film with good crystallinity could not be obtained.

Incidentally, in such a silicon thin film, since the crystal grains are small, it is not possible to form a MOS FET with high mobility, and the grain size of the crystal grains varies, so it is difficult to integrate the MOS FET. In each case? There is a problem in that the number of grain boundaries in the channel region of the IO5FET varies, which causes variations in the characteristics of the integrated MOS FfET.

In view of the above, an object of the present invention is to provide a method for forming a semiconductor thin film that is capable of forming a semiconductor thin film with good crystallinity and having crystal grains having large grain sizes and uniform grain sizes. shall be.

[Means for solving problems]

The method for forming a semiconductor i-film according to the present invention is illustrated in, for example, FIGS.
As shown in Figure 6, an amorphous semiconductor 'a' is formed on the insulator (1).
After forming the film (2), phosphorus P or phosphorus ions P+ is introduced into the surface region of this amorphous semiconductor thin film (2), followed by heat treatment, and then phosphorus P or phosphorus ions P+ is introduced into the surface region of the amorphous semiconductor thin film (2).
The content layer (3) is removed.

[Effect]

In the present invention, a nucleus centered on phosphorus P or phosphorus ion P+ is generated in advance, and crystal grains (4) (4) grow around this nucleus. In this case, growth occurs quickly in the lateral direction, but it also grows in the depth direction, so
As a result, crystal grains (4)...(4) with large grain sizes grow, and a semiconductor thin film (5) with good crystallinity is obtained.

〔Example〕

Hereinafter, with reference to FIGS. 1 to 6, one embodiment of the method for forming a semiconductor thin film of the present invention will be described, taking as an example the case of forming a silicon thin film.

In this example, as shown in FIG. 1, first, a quartz glass substrate (1) which is an insulator is prepared,
1) Polycrystalline silicon thin film with a film thickness of 800 nm (6
) is formed, for example, by CVD.

Next, as shown in FIG.
(For example, add silicon ion St" to 61, 5 x 10
The polycrystalline silicon thin HfA (6) is formed into an amorphous silicon thin film (2) by implantation under the conditions of 151 solids/cd and 4QKeV.

Next, as shown in FIG. 3, phosphorus ions P+ are added to the amorphous silicon thin film (2) at a rate of, for example, 5 x 10"/cni, 4
It was implanted under 0 KeV conditions to form an amorphous silicon thin film (
Region (3) containing phosphorus ions P+ on the surface side of 2)
form.

Next, heat treatment is performed at 600° C. in an N2 atmosphere. In this way, a nucleus centered on phosphorus ions P+ is generated within 4 hours after the start of heat treatment, and as shown in Fig. 4,
Silicon crystal grains (4)...(4) center around this core.
begins to grow. In this case, this nucleus grows at a rate as shown by the solid line X in FIG.

Also, in this case, growth occurs quickly in the lateral direction, but also in the depth direction.

Then, when the heat treatment is further progressed, the heat treatment starts at t&10.
As time passes, nuclei centered around silicon ions, Si+, begin to form, but at this time, phosphorus ions, P+
The silicon crystal grains (4)...(4) centered on the ions are quite large, and the silicon crystal grains (4)...(4) centered on the ions P+ are quite large. ) is faster than the growth rate of silicon crystal grains centered on silicon ions (Si+) (indicated by the broken line Y in FIG. 7). As shown in the figure, crystal grains centered on phosphorus ions P+ (4)
...The layer (3) containing (4) having a particle size of about 15 μm is removed by etching.

As described above, according to this embodiment, the crystal grain size is larger than that of the conventional example, for example, about 15 μm (4
)...(4) Silicon i 1 with good crystallinity
1Q +5> can be formed. Therefore, when forming, for example, a MOS FET on such a silicon thin film (5), this MOS FIT can be made to have high mobility, and the silicon thin film (5) of this example has few irregularities. When such a silicon thin film (5) is used as a gate electrode, there is an advantage that the gate oxide film can be made thinner than when the gate electrode is formed of polycrystalline silicon.

Furthermore, according to this embodiment, it is possible to generate nuclei centered on phosphorus ions P+, which grow rapidly, within 4 hours after the start of the heat treatment, so there is an advantage that the heat treatment time can be shortened.

In the above embodiment, a case was described in which a silicon thin film was formed on a quartz glass substrate (1), but the present invention is not limited to this embodiment. It can also be used to form silicon thin films.
In this case as well, the same effects as described above can be obtained.

Furthermore, in the above embodiment, the case where phosphorus ions P+ were implanted into the amorphous silicon thin layer III (21) was described, but instead of this, phosphorus P may be diffused, and in this case, the same applies as above. It is possible to obtain the following effects.

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, phosphorus or phosphorus ions are introduced into the surface side of an amorphous semiconductor thin film, and then heat treatment is performed. It has the advantage of being able to form thin films.

Further, according to the present invention, since a nucleus mainly composed of phosphorus ions is generated and grown, there is an advantage that the heat treatment time can be shortened compared to the conventional example.

[Brief explanation of the drawing]

1, 2, 3, 4, 5, and 6 are process diagrams showing one embodiment of the method for forming a semiconductor thin film of the present invention, and FIG. 7 is a growth diagram of silicon crystal grains. It is a diagram showing speed. (1) is a quartz glass substrate, (2) is an amorphous silicon thin film, (3) is a phosphorus ion-containing layer, (4) is a silicon crystal grain, (5) is a silicon thin film, and (6) is polycrystalline silicon. It is a thin film. Fig. 3 Fig. 4 Ichiji) Color A JIJ Meko JLtJ Fig. 5 - Prize J4 Eup I J1's Work JLr5ri Fig. B

Claims (1)

[Claims] After forming an amorphous semiconductor thin film on an insulator, introducing phosphorus or phosphorus ions into the surface region of the amorphous semiconductor thin film,
A method for forming a semiconductor thin film, characterized in that a heat treatment is then performed, and then the phosphorus or phosphorus ion-containing layer is removed.