JPS5974619A - Zone melting method and equipment therefor - Google Patents

Abstract

PURPOSE:To obtain a zone melting method and an equipment therefor with good controllability and high productivity by operating zone melting utilizing a radiation from a body heated by radiation of energy beam. CONSTITUTION:A susceptor 1 is made of graphite coated by SiC and heated by high frequency power applied to a water-cooled coil 13 made of copper pipe. A rod shape radiation body 2 is also made of graphite coated by SiC and heated by radiation of CO2 laser 4. The susceptor 1 and a substrate 3 put on the susceptor 1 and the radiation body 2 are placed in a quartz tube 14 whose inside is filled by argon gas introduced from a gas inlet 15. The laser 4 is scanned reciprocally to the horizontal direction through a window 17. The susceptor 1 is transferred together with the substrate 3 and the substrate 3 and the radiation body 2 are transferred relatively to each other. A single-crystal domain of a large area can be formed with good reproducibility.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a band melting method performed for single crystallization of a semiconductor (amorphous or polycrystalline) thin film deposited on the surface of an insulating substrate. The present invention relates to a method and apparatus suitable for productivity and mass production.

[Prior art]

Zone melting is a well-known method for producing single crystal materials. There are several variations of this method depending on the target material and other factors.
The zone (FIoating Zone) method is also one of them.

Recently, it has become possible to melt and recrystallize amorphous or polycrystalline silicon deposited on a silicon single crystal substrate covered with an insulating film such as silicon dioxide by irradiating it with an energy beam such as a laser beam. However, in a structure where a part of the silicon dioxide film is opened, a part of the deposited amorphous or polycrystalline silicon film is in direct contact with the base single crystal at the opening. , it has been shown that it is possible to single-crystallize at least a part of the deposited film epitaxially from the substrate by using the substrate single crystal as a seed crystal (for example, J.
C.C.Fan et al., Appl, PhysLett
, 38.365.1981).

One of the main difficulties with Jin's method is the high degree of control required for the applied energy beam, the shape of the irradiated area,
It is necessary to precisely control the distribution and absolute value of energy density, and it is currently difficult to perform single crystallization over a large area with good reproducibility.

Another method for single crystallization of a film with a similar structure is the band melting method, which is similar in principle, but the substrate is placed on a graphite plate heater, and a linear graphite heater is placed directly above it. is provided, and both heaters are energized and heated, and the linear heater is moved relative to the base (for example, 1.M, W).

Qeis et ol, Appl, Phys, L
ett, 40 (1982) 158).

This method has a major problem in terms of the structure of the production equipment, as the energized graphite heater must be moved with precision along with the conductor, and there is also a large time loss associated with heating and cooling the substrate. , the disadvantage is that it is difficult to increase production throughput.

Among the above-mentioned known technologies, the first one is energy/
When we examined the factors that govern the controllability required for beam strength in forming a molten zone using a beam, we found that one of the main factors is the volume of the area to be heated to a high temperature by beam irradiation, Therefore, it was found that the heat capacity is very small, and the necessary precision of temperature setting is high (within a few degrees Celsius in a range of 10-100 degrees Celsius). For this reason,
Extremely tight control had to be exercised regarding the temporal and spatial distribution of the beam intensity.

In the second technique shown in the known example, a major problem other than the above-mentioned drawbacks is the difficulty in temperature distribution control. That is, a wire (or rod) shaped heater is held by cooled terminals at both ends, and the temperature becomes low on the end side. However, when the temperature distribution of the region to be single crystallized is convex in the center, crystallization starts at multiple locations in the periphery, and the mutual orientations are different, causing dislocations at the part where the crystallized regions meet. In some cases, small-angle grain boundaries consisting of a network are formed.It is extremely difficult to control such locations, so elements may be formed in such locations during the element formation process, which may have an unfavorable effect on device characteristics. may be given.

[Purpose of the invention]

An object of the present invention is to provide a zone melting method and apparatus for forming a single crystal coating, which is free from the above-mentioned shortcomings and drawbacks, has good controllability, and has high productivity.

[Summary of the invention]

The structure of the present invention to achieve the above object is to carry out band melting using re-radiation from an object heated by irradiation with an energy beam.

A conceptual diagram of the present invention is shown in FIG. Reference numeral 1 denotes a susceptor, which is heated by conventional methods such as resistance heating, high frequency heating, lamp heating, etc. A rod-shaped radiator 2 is provided slightly away from the surface of the susceptor 1. At this time, susceptor 1
The distance between the rod-shaped radiator and the rod-shaped radiator must be such that the substrate 3 to be subjected to band melting can sufficiently pass therethrough. The rod-shaped radiator is heated by the energy beam 4. This energy beam applies equally well whether it comes from a single source or from multiple sources or types. Further, when a particle beam such as an electron beam or an ion beam is used as the energy beam, usually at least the rod-shaped radiator 2 and the beam path 4 are used.
Although it is common to make the space containing a vacuum vacuum, it is important to irradiate the beam from the opening of the vacuum container toward a rod-shaped radiator placed in a gas atmosphere close to the opening.

The energy beam may be formed into a band shape and irradiated, or may be irradiated by scanning along the longitudinal direction of the rod-shaped radiator. However, when using the latter method, the heat capacity of the rod-shaped radiator,
It is appropriate to determine the scanning frequency or speed in relation to the energy beam irradiation position and the like.

2A to 2C show examples of the energy beam irradiation intensity distribution and the temperature distribution on the upper surface of the rod-shaped radiator in order to clearly explain the present invention. Figure (C
) is a longitudinal cross-section of the rod-shaped radiator in Figure (a). The average intensity distribution of the energy beam in the longitudinal direction of the bar-shaped radiator was as shown by curve 7.

The irradiation position of the beam was centered at the position of the broken line 9, which was somewhat close to the top surface of the rod-shaped radiator, and its vertical intensity distribution was as shown by the curve 12 in Figure (C). In addition, at this time, a curve 8 shown in FIG. 8(b) could be obtained as the temperature distribution on the lower surface of the rod-shaped radiator. In other words, it is possible to realize a temperature distribution that allows the peripheral portion of the substrate to have a slightly higher temperature.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 3 and 4. FIG. 3 is a schematic diagram of the main parts of the apparatus used in this example, and is similar in principle to FIG. 1 described above.

The susceptor 1v'1 is made of graphite coated with SiCk and is heated by high frequency power applied to a water cooling coil 13 made of a copper pipe. This method is commonly used in ordinary epitaxial growth equipment, and the equipment used in this example was able to stably heat the susceptor 1 to 13,000 ℃. The rod-shaped radiator 2 is also the same <SiC coated graphite, its heating is 0
This is done by irradiating the 02 laser 4. A susceptor, a base 3 placed on it, and a rod-shaped radiator 2
is installed in a quartz tube 14, and the inside has a gas inlet 15.
Filled with argon gas, which was then introduced. Gas is continuously introduced at a flow rate of about 2 t/m in a so-called open pipe manner, and then exits from the outlet 16.

C02 laser beam passes through the optical system at 200cm/s
It is possible to reciprocate in the horizontal direction at the following speed and irradiate through the window 17. Using a C02 laser with a maximum output of 100W, the center part 13111771 of the above rod-shaped radiator with a cross-sectional area of about 11cm2 and a length of 20Cr was heated to about 2000C.
The temperature can be raised to .

Although it is necessary to move the molten material on the substrate through relative motion between the substrate 3 and the rod-shaped radiator 2, this apparatus adopts a method in which the susceptor 1 is moved together with the substrate 3. It goes without saying that it is necessary to select various forms of movement depending on the purpose.

The above is an example of an apparatus based on the principle of the present invention.Next, description will be given of the single crystallization of polycrystalline Si deposited on a 5iOz film deposited on the surface of a Si single crystal substrate using this apparatus. The detailed structure of the base is as shown in FIG. Diameter 75
8. The thickness of the thermal oxide film 20 formed on the S+ single crystal substrate 19 with a thickness of 400 μm and a surface orientation of <1'00> is 5QQ.
The thickness of the polycrystalline Si film 21 deposited on the film 20 by the low pressure CVD method is 550 nm. The substrate surface is further covered with a 1.5 μm thick SiO2 film 22 deposited by low pressure CVD. The polycrystal 5i21 and the base single crystal 5i19 have a thermal oxide film 20 in the peripheral part of the base.
The removed parts are in contact with each other.

The formation of single polycrystalline Si into J,i is carried out as follows.

The base is placed on a susceptor, and the susceptor is positioned so that the rod-shaped radiator is slightly removed from the periphery of the base.

Next, the high frequency power source is turned on, and the power is heated to adjust the substrate surface temperature to 1210±2C.

The time required for this heating was approximately 2 minutes. After confirming that the temperature of the substrate surface is stable, the laser is turned on, and the temperature of the rod-shaped radiator is adjusted so that the minimum value at the center of the distribution in Fig. 2 is 1780 ± 2C1, and the extreme value at the periphery is 40 degrees higher than the central minimum value. Set. During this time, the surrounding air was replaced with argon gas prior to raising the temperature of the susceptor. The gas flow rate is approximately 2t/ni,r. Further, the distance between the rod-shaped radiator and the base surface is set to 2.5 mm.

Under the above conditions, 2. When the substrate was moved at a constant speed of Orrvn/s and passed under the rod-shaped radiator, polycrystalline Si formed on the surface of the substrate could be stably turned into a single crystal.

Another example involves polycrystalline Si deposited on fused silica.

The surface of a fused silica plate with a diameter of 75mm and a thickness of 500μm was carefully polished to a mirror finish while avoiding residual polishing scratches, and then subjected to low-pressure CVD.
Polycrystalline Si with a thickness of 500 nm (average grain size approximately 0)
．． A 5f02 film having a thickness of 2 μm was further deposited using the same low-pressure CVD method to form a substrate.

After setting the substrate on the susceptor as in the previous example, the temperature was set as follows. Susceptor temperature 1130±2C, rod-shaped radiator temperature 1850±3tT0
The atmosphere and the distance between the rod-shaped radiator and the substrate surface were the same as in the previous example.

When the base body was passed under a bar-shaped radiator at a moving speed of 2.4 tan/S, a 50 x 30 w beam was observed in the center of the base body.
A compact single crystal region of about m2 in size could be formed.

These results show an improvement of about 100 times as much as in the case of conventional example 1 and about 10 times as much as that in conventional example 2 in terms of grain size, which shows the effectiveness of the present invention. .

In the above embodiments, the relative movement between the base and the rod-shaped radiator was carried out by moving the base together with the susceptor, but as mentioned above, the rod-shaped radiator is small and lightweight, and can be made independent from other parts. Therefore, in a system in which an energy beam is emitted from a bar-shaped radiator in parallel to the surface of the substrate, as in the apparatus in the above embodiment, it is easy to construct a mechanism that does this by moving the radiator. Almost the same results as in the above example could be obtained. In addition, in a device that uses a fixed rod-shaped radiator, the energy that irradiates it
It will be clear that the direction of incidence of the beam is not limited to being parallel to the substrate surface as shown in the above embodiments.

It should be noted that the apparatus based on the principles of the present invention is not only capable of belt melting;
It is also obvious that the present invention can be applied to other heat treatment steps in the semiconductor device manufacturing process.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to perform band melting of the semiconductor thin film deposited on the substrate surface while providing a desired distribution and stably controlling the temperature distribution, thereby forming a large-area single crystal region with good reproducibility. In addition to greatly improving the economics of the process, the construction of the device mechanically facilitates relative movement between each part, so accuracy can be improved with respect to the movement of the necessary parts. This has the effect that a good mechanism can be constructed at low cost.

[Brief explanation of the drawing]

FIG. 1(a) is a cross-sectional view of the main part of a device as an embodiment of the present invention, FIG. 1(b) is a bird's eye view, and FIG. A glass showing the energy beam intensity and temperature distribution in the same direction, and a graph showing the energy beam intensity in a direction perpendicular to the same direction, FIG. 3 is a cross-sectional view of the device used in another embodiment of the present invention, FIG. 4 is an enlarged sectional view of the base used in FIG. 3. 1°°° Susceptor, 2... Rod-shaped radiator, 3... Substrate, 4... Energy beam incident direction, End... Axis indicating energy beam intensity and temperature, 6... Position (
Longitudinal direction) axis, 7...Energy beam intensity, 8.
... Temperature, 9... Position of base body periphery, 10... Axis indicating energy beam intensity, 11... Axis indicating vertical position, 12... Energy beam intensity in vertical direction, 13... Water-cooled high frequency coil, 14... Quartz tube, 15... Gas inlet, 16... Gas outlet,
17... Laser window, 18... Substrate moving device, 19
... Single crystal sj substrate, 20... Thermal oxidation 5102 film,
21... Polycrystalline Si film, 22... CvD SiO2
film. Summary 3 Figure ■ 4 Figure

Claims (1)

[Scope of Claims] 1. A method for band melting a semiconductor thin film formed by radiation from a heated object on an amorphous insulating substrate or a semiconductor substrate at least partially covered with an insulating film, which comprises: A band melting method characterized by irradiating an energy beam with. 2. In a band melting device having a quartz tube, heating means provided outside the tube, and a base support provided within the tube, radiators are spaced apart at predetermined intervals on the base support. A belt melting device characterized by being provided with.