JPH01260811A - Formation of soi crystal - Google Patents

Abstract

PURPOSE:To obtain an SOI film processing a satisfactory crystalline property, by controlling a temperature gradient in the vicinity of a solid-liquid interface after irradiating an energy beam in such a way that its strength distribution has a plurality of peaks with the respect to the scanning direction of the energy beam. CONSTITUTION:On the occasion of forming an SOI film which is singly crystallized by melting-and-solidifying a poly or amorphous silicon film, an energy beam whose strength distribution has a plurality of peaks is irradiated with respect to the scanning direction of the energy beam. It is possible that the process of irradiating the energy beam is performed either as the whole of a melting process of the amorphous silicon film for solidification or else as the part of the above process as well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for forming an SOI crystal, and more specifically to a method for forming an SOI crystal by melting and solidifying a polysilicon film or an amorphous silicon film.

[Prior Art] Usually, the intensity distribution of an energy beam is close to a Gaussian distribution, and therefore, such a Gaussian distribution is often used as an energy beam for melting a polysilicon film or an amorphous silicon film. In addition, special processing is used to create a -like intensity distribution or a bimodal intensity distribution in the direction perpendicular to the beam scanning direction, but it is possible to obtain a broad temperature distribution in the scanning direction. There is no example of using a beam with an intensity distribution similar to that of the previous method, and the number of beam irradiation was only one time.

[Problems to be Solved by the Invention] However, in the single crystallization of an SOI film, it is important to appropriately control the temperature gradient near the solid-liquid interface in order to obtain an SOI film with good crystallinity. It has been difficult to accurately control the temperature gradient near the solid-liquid interface with conventionally used energy beams that have a Gaussian intensity distribution in the scanning direction of the beam.

Further, since the number of times of beam irradiation is only one, it is not possible to change the substrate temperature during beam irradiation, and therefore, the only way to change the temperature gradient is to change the scanning speed of the beam. However, the range that can be changed by the above method is limited to a narrow range due to the power density of the beam, so it has been difficult to accurately control the temperature gradient near the solid-liquid interface within an arbitrary range.

An object of the present invention is to provide a method for forming an SOI crystal that can accurately control the temperature gradient near the solid-liquid interface to obtain an SO2 film with good crystallinity.

[Means for Solving the Problems] The present invention provides a method for forming a single-crystal SOI film by melting and assimilating a polysilicon film or an amorphous silicon film. This method of forming an SOI crystal is characterized by comprising a step of irradiating an energy beam whose distribution has a plurality of peaks.

In the present invention, the step of irradiating an energy beam whose intensity distribution has multiple peaks may be performed as the entire process of melting and solidifying the poly- or amorphous silicon film, or may be performed as a part thereof. .

If it is carried out as a part, for example, a step of irradiating the entire sample with a beam having a different intensity may be included prior to irradiating the predetermined energy beam.

[Function] Figure 2 shows the beam intensity distribution (a) when the energy beam has a Gaussian intensity distribution in the scanning direction;
It shows the heat generation distribution (b) obtained on the sample.

In this case, the temperature gradient near the solid-liquid interface depends mainly on the scanning speed of the beam.

On the other hand, Figure 1 shows the energy beam intensity distribution (a) when the energy beam has an intensity distribution with multiple peaks in the scanning direction according to the method of the present invention, and the heat generation distribution obtained on the sample (b). This is what is shown. In this case, the temperature gradient near the solid-liquid interface is determined by the number of peak series and the peak height (
intensity).

In addition, before scanning the beam with the above-mentioned multiple intensity peaks, the entire sample is heated with a beam of -like intensity, and then a beam with an intensity distribution as shown in Figure 1 (a) is heated. By melting and solidifying the sample, the temperature gradient near the solid-liquid interface can be changed over a wider range.

[Example] Hereinafter, one embodiment of the present invention will be described in detail.

The beam diameter is 50Ij as an energy beam! Using an electron beam with a Gaussian intensity distribution, the beam was first scanned at high speed over the entire polysilicon film of the sample to heat the entire sample. The irradiation conditions are, for example, acceleration voltage 1
0kV, beam current 5mA, scanning speed 10Cm/SeC
The test was carried out for 10 seconds. Next, the polysilicon film was melted and recrystallized using an electron beam whose intensity distribution in the -scanning direction had three different peaks as shown in FIG. The height of the peak, that is, the intensity, is the highest value of 10
0% was set as 30%, then 10%. The distance between the three peaks in the rough scanning direction was 0.05 mm. The melting and recrystallization conditions were an accelerating voltage of 10 kV and a beam current of 3.
mA and a scanning speed of 2 cm/sec. Note that an electron beam having an intensity distribution as shown in FIG. 3 can be obtained by applying pulses having different amplitudes and pulse lengths to a deflector of an electron beam device.

As a result of melting and recrystallizing the polysilicon film under the above conditions, an optimal temperature gradient was obtained, and S with good crystallinity was obtained.
An OI film could be obtained.

In this example, the polysilicon film was recrystallized, but similar results can be obtained by using an amorphous silicon film instead. In addition, although we used a beam intensity distribution in the scanning direction in which multiple peaks were placed only on one side of the largest intensity peak, they may be placed on both sides, and a laser beam may be used instead of an electron beam. good.

[Effects of the Invention] As explained above, according to the method for forming SOI crystals of the present invention, the temperature gradient near the solid-liquid interface can be appropriately controlled, and as a result, SOI crystals with good crystallinity can be produced.
membrane can be obtained. Therefore, by using this SOI crystal as a substrate for forming a device, it is possible to create a device with better characteristics than conventional SOI devices.

[Brief explanation of the drawing]

Fig. 1 shows the beam intensity distribution in the scanning direction of an example of the energy beam used in the present invention and the temperature distribution on the sample surface, and Fig. 2 shows the beam intensity distribution of the energy beam used in the conventional SOI crystal formation method. FIG. 3 is a diagram showing the temperature distribution on the sample surface, and FIG. 3 is a diagram showing the beam intensity distribution in the scanning direction of the electron beam used in one embodiment of the present invention.

Claims (1)

[Claims] (1) In a method of forming a single crystal SOI film by melting and solidifying a polysilicon film or an amorphous silicon film, with respect to the scanning direction of the energy beam,
A method for forming an SOI crystal, comprising the step of irradiating an energy beam whose intensity distribution has a plurality of peaks.