JPS62190716A - Manufacture of semiconductor thin film crystal layer - Google Patents

Abstract

PURPOSE:To uniformly anneal a region by guiding a beam to a region except the region to be annealed for a predetermined time that the voltage value of the envelope of a high frequency electric signal waveform approaches zero to prevent the center of the region to be annealed from becoming stronger than the periphery. CONSTITUTION:A high frequency electric signal amplitude-modulated as predetermined is applied to a high speed deflector 17, an electron beam is deflected in one direction at a high speed to form a quasi-linear electron beam. Simultaneously, a predetermined deflection signal is applied to a scanning coil 16, and the quasi-linear beam is scanned in a direction perpendicular to the high speed deflecting direction on a sample. Thus, a polycrystalline Si film 24 is melted and recrystallized in a striplike manner by scanning the beam 26 to become a single crystal Si layer 27. When forming the quasi-linear beam, it can prevent the center of the region to be annealed from being annealed at higher temperature than the periphery by blanking the beam at the portion near zero at the voltage level of an envelope to anneal it with more uniform beam.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a method for manufacturing a semiconductor thin film crystal layer on an insulating film by beam annealing, and in particular to a method for manufacturing a semiconductor thin film crystal layer using a quasi-linear electron beam. Regarding the method.

[Technical background of the invention and its problems]

In recent years, in the field of semiconductor industry, formation of Sol (silicon on insulating film) films using beam annealing technology has been actively performed. In this technology, an insulating film such as a silicon oxide film or a silicon nitride film is formed on a silicon substrate, a semiconductor i1111 such as a polycrystalline silicon film or an amorphous silicon film is formed on top of this, and this semiconductor thin film is exposed to an electron beam. Alternatively, the semiconductor thin film is melted and recrystallized by annealing with a laser beam.

Among these methods, the annealing method using a pseudo-linear electron beam is significantly superior to other methods in terms of controllability. This is a method in which a linear beam is formed by deflecting an electron beam at high speed with a high-frequency sine wave, and by scanning this beam in a direction perpendicular to the direction of deflection, a fixed area is made into a single crystal. be.

Of course, when a sine wave is used as the high-speed deflection waveform as described above, the residence probability time of electrons is not uniform at each position in the annealing region. For example, when the beam is deflected with a waveform of X=a-sinωt, the residence time of electrons at each position is as follows. This shows that when X=a, that is, at both ends of the pseudo-linear electron beam, the residence time of the electrons becomes very long. Therefore, when annealing is performed using this method, only the ends of the annealed region are likely to melt. This becomes a serious problem because it is difficult to make the annealed region sufficiently uniform when the beam deflection width (width of the quasi-linear electron beam) is increased.

Therefore, the present inventors devised a method of using a waveform obtained by amplitude modulating a high frequency wave as a deflection waveform when forming a pseudo-linear electron beam. In this method, the probability of the beam staying at the end is high and the temperature tends to rise, so by reducing the high-speed deflection waveform with the amplitude up to the maximum value and deflecting with several waveforms with different amplitudes, The apparent electron retention probabilities above can be averaged. One example of this is shown in FIG. In the figure, A is a modulated wave, and B is a waveform after modulation. The frequency commonly used is that the fundamental wave is 10 to 50[
MH2], and the modulated wave is 10 to 100 [K I-jZ]. Note that amplitude modulation means finding the product of a fundamental wave and a modulated wave. There are several modulated waves used for this purpose, but what they have in common is that they almost perpendicularly cross the horizontal axis (time axis).

However, this type of method has the following problems. That is, when calculating the product of the two waves described above using an electronic circuit, the electronic circuit becomes unable to follow such rapid changes. For this reason, even though the probability of electron residence is theoretically equalized, a large portion of the probability of electron residence occurs in the center of the quasi-linear electron beam, and this becomes an obstacle to uniform annealing. It becomes.

[Purpose of the invention]

The present invention has been made in consideration of the above-mentioned circumstances, and the purpose of the present invention is to prevent the central part of the annealing region from occurring due to the fact that a large portion of electron residence probability occurs in the central part of the quasi-linear electron beam. It is an object of the present invention to provide a method for manufacturing a semiconductor thin film crystal layer, which can prevent the semiconductor thin film crystal layer from being annealed more strongly than the peripheral part, and can perform uniform annealing.

[Summary of the invention]

The gist of the present invention is that even though a proper modulated wave is used, the waveform after modulation does not have a predetermined shape due to the limitations of the device, and as a result, the central part is annealed more strongly than the peripheral part. In order to prevent this, the beam is moved to areas other than the annealing region where the waveform is blunt.

That is, the present invention deflects an electron beam in one direction at high speed with an amplitude-modulated high-frequency electric signal to a polycrystalline or amorphous semiconductor thin film formed on an insulating substrate, and
In the method for manufacturing a semiconductor thin film crystal layer in which the thin film is annealed by scanning an electron beam on the semiconductor thin film in a direction substantially perpendicular to the deflection direction, the voltage value of the envelope of the high frequency electric signal waveform becomes close to zero. In this method, the beam is guided outside the annealing region for a certain period of time.

〔Effect of the invention〕

According to the present invention, when performing beam annealing with a quasi-linear electron beam that is deflected at high speed by an amplitude-modulated high-frequency electric signal, the beam is guided outside the annealing region at the center where a large portion of the electron residence probability occurs. Therefore, it is possible to prevent the central part of the annealing region from being annealed to a higher temperature than the peripheral part. In addition, by guiding the beam outside the annealing region at the center, the amount of beam irradiation to the periphery of the annealing region will increase compared to the center of the annealing region, but generally the amount of heat dissipated by heat conduction at the periphery of the annealing region is smaller than that of the center. Therefore, the annealing temperature can be made substantially uniform even if the beam irradiation amount in the central portion is reduced. In other words,
Uniform annealing can be performed, and even large-area semiconductor thin films can be sufficiently made into single crystals.

(Example of the invention) Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

FIG. 1 is a schematic diagram showing an electron beam annealing apparatus used in an embodiment of the present invention. In the figure, 11 is an electron gun, 12 is a blanking electrode, 13 is an aperture mask,
14 is a focusing lens, 15 is an objective lens, 16 is a scanning coil, 17 is a high-speed deflection plate, and 18 is a sample. electron gun 11
The electron beam emitted from the sample 18 is focused by a lens 14.15 and irradiated onto the sample 18. Blanking electrode 12
is for blanking (OFF) the beam,
The beam is blanked by applying a predetermined voltage to this electrode. The scanning coil 16 is for scanning the beam over the sample in one direction. The high-speed deflection plate 17 is for high-speed deflection of the beam in a direction perpendicular to the beam deflection direction by the scanning coil 16, and a deflection 1iPi (high frequency electric signal) as described later is applied to this deflection plate 17. It has become something that

Next, a method of manufacturing a semiconductor thin film crystal layer using the above-mentioned apparatus will be explained with reference to FIG.

First, as shown in FIG. 2(a), an Si02 film 22 is deposited on a single crystal Si substrate 21, and an opening 23 is formed in a part of this 8i02 film 22 to serve as a seed for single crystal growth.

Next, as shown in FIG. 2(b), a polycrystalline S1 film (
A semiconductor thin film) 24 is formed, and an Si02 film 25 as a protective film is further formed thereon.

Next, using the electron beam annealing apparatus shown in FIG. 1, the sample is electron beam annealed to form the polycrystalline S1 film 2.
4 is made into a single crystal. That is, a predetermined amplitude-modulated high-frequency electrical signal is applied to the high-speed deflection plate 17 to deflect the electron beam in one direction at high speed to form a pseudo-linear electron beam. At the same time, a predetermined deflection signal is applied to the scanning coil 16 to scan the pseudo-linear electron beam over the sample in a direction perpendicular to the high-speed deflection direction.

As a result, as shown in FIG. 2(C), the polycrystalline S1
The film 24 is melted and recrystallized in a band shape as the pseudo-linear electron beam 26 scans, and becomes a single crystal 3i layer 27. By sequentially overlapping the belt-shaped melted regions, a large area of polycrystalline 5
il124 will also be made into a single crystal.

Here, the signal waveform (envelope waveform) applied to the high-speed deflection plate 17 is ideally a waveform as shown by the solid line A in FIG. Due to problems such as response characteristics of electronic circuits, the waveform actually becomes dull at low voltage levels as shown by the broken line B in the figure. In this case, as shown in FIG. 3(b), the electron residence probability has a peak at a point near the center, and the residence probability in this portion is 30 to 40% higher than the average level. As a result, the degree of 7-niel dryness in the central part of the annealing region is higher than in the peripheral part.

Therefore, in the method of this embodiment, the area where the voltage level is low (the third
In area C shown in figure (a), the blanking electrode 1
A blanking voltage is applied to 2 to blank the electron beam. By performing this operation, the annealing temperature deviates from the ideal planarization, but according to calculations, it is about 10%. Also, considering that the thermal radiation at the periphery of the annealing region is larger than that at the center, the electron residence probability at the center may be smaller than that at the periphery, so the above 10[%] The difference becomes even smaller.

Thus, according to the method of this embodiment, when an electron beam is deflected at high speed using an amplitude-modulated high-frequency electric signal to form a pseudo-linear beam, the beam is planked at a portion where the voltage level of the envelope is close to zero. By doing so, it is possible to prevent the central part of the annealing region from being annealed to a higher temperature than the peripheral part, and more uniform beam annealing can be performed. Therefore, the characteristics of the single crystal layer to be created can be improved, and even a large-area polycrystalline Si film can be sufficiently made into a single crystal.

FIG. 4 is a schematic diagram for explaining another embodiment method of the present invention. The difference between this embodiment method and the embodiment method explained earlier is that instead of blanking the beam in the part where the voltage level of the envelope of the fast deflection waveform approaches zero, the voltage level of the fast deflection waveform in this part is The goal is to make it extremely large.

That is, in the method of this embodiment, a high-speed deflection waveform R is formed by superimposing a rectangular wave Q having a peak value sufficiently higher than the peak value of the waveform on the amplitude-modulated high-frequency electric signal waveform P. The voltage at the neck portion at P is made extremely large. In this case, since the electron beam is guided to a region other than the annealing region at the center of the annealing region, the beam is substantially blanked at the center.

Therefore, the probability of beam residence in the central part of the annealing region can be reduced, and the same effect as the method of the previous embodiment can be obtained.

Note that the present invention is not limited to the methods of each embodiment described above. For example, the beam is guided outside the annealing region at a portion where the voltage level of the envelope of the high-speed deflection waveform approaches zero, and the time for this portion may be adjusted as appropriate depending on the thermal conductivity characteristics of the annealing region and other conditions. That's fine. Generally, it is about 1/10 or less of one period of the high-speed deflection waveform. Furthermore, as the semiconductor thin film, it is possible to use amorphous silicon or other semiconductors instead of polycrystalline silicon. Further, the scanning direction of the beam does not necessarily have to be exactly orthogonal to the high-speed deflection direction of the beam, but may be slightly inclined. Furthermore, the apparatus used for annealing is not limited to the configuration shown in FIG. It is sufficient as long as it has the following. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic configuration diagram showing an electron beam annealing apparatus used in an embodiment of the present invention, FIG. 2 is a sectional view showing the manufacturing process of a semiconductor thin film crystal layer according to the embodiment method, and FIG. A characteristic diagram showing a high-speed deflection waveform and an electron residence probability distribution, FIG. 4 is a schematic diagram for explaining another embodiment method of the present invention, and FIG. 5 is a signal waveform diagram for explaining conventional problems. be. 11...Electron gun, 12...Blanking electrode, 14
゜15...Lens, 16...Scanning coil, 17...
・High-speed deflection plate, 18...sample, 21...single crystal Si
Substrate, 22...5102 film (insulating film), 23... opening, 24... polycrystalline S1 film (semiconductor thin film).

Claims (4)

[Claims] (1) A polycrystalline or amorphous semiconductor thin film formed on an insulating substrate is deflected at high speed in one direction by an amplitude-modulated high-frequency electric signal, and the electron beam is deflected onto the semiconductor thin film. In the method for manufacturing a semiconductor thin film crystal layer in which the thin film is annealed by scanning in a direction substantially perpendicular to the direction of deflection, the beam is applied to the annealing region for a certain period of time during which the voltage value of the envelope of the high frequency electric signal waveform approaches zero. A method for manufacturing a semiconductor thin film crystal layer, characterized by guiding the semiconductor thin film crystal layer to the outside. (2) As a means for guiding the beam outside the annealing region,
2. The method of manufacturing a semiconductor thin film crystal layer according to claim 1, wherein the beam is blanked by a blanking electrode. (3) The method for manufacturing a semiconductor thin film crystal layer according to claim 1, wherein the certain period of time is 1/10 or less of one period of the high-frequency electric signal waveform. (4) The method for manufacturing a semiconductor thin film crystal layer according to claim 1, wherein the insulating substrate is a single crystal semiconductor substrate on which an insulating film is formed.