JPS61236678A - Process for preparing semiconductor single crystal layer and electron beam annealing device - Google Patents

Abstract

PURPOSE:To minimize thermal strain to be generated in a specimen and to prepare a single crystal layer having good quality by controlling temperature distribution in the longitudinal direction of false linear beam to make the temp. distribution flat and making the gradient of temp. distribution in the external periphery of the part exposed to the electron beam mild. CONSTITUTION:Electron beam emitted from an electron gun 31 is converged by a condenser lens 32 and an objective lens 33. A specimen 34 is exposed to the converged electron beam and the surface of the specimen is scanned with a scanning coil 35. A polarizing plate 38 is provided between the lens 32 and the scanning coil 35, and the beam is polarized at high speed in the Y direction. A high frequency voltage is impressed on the polarizing plate 38 from a high frequency source 40. If the working space is large enough, a polarizing plate 39 is provided below the polarizing coil 35 instead of the polarizing plate 38.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a technique for forming a semiconductor single crystal layer on an insulator, and in particular to a method for manufacturing a semiconductor single crystal layer using a pseudo-linear electron beam and a method for manufacturing a semiconductor single crystal layer using a pseudo-linear electron beam. The present invention relates to an electron beam annealing device used in the method.

(Technical background of the invention and its problems) In recent years, in the field of semiconductor industry, 801 (Silicon OnI) using electronic double annealing technology has been developed.
Research and development on technology for forming n5Ulator films is active. In this technology, an insulating film such as a silicon oxide film or a silicon nitride film is formed on a silicon single crystal substrate, and a polycrystalline silicon film or an amorphous silicon film is deposited on top of it.
By beam irradiation such as electron beam or laser beam,
To grow a silicon single crystal layer by melting and recrystallizing the silicon film, a finely focused electron beam (Gaussian distribution) is scanned in the X and Y directions to uniformly anneal the sample l+1 plane. In this case, the diameter of the electron beam used is approximately 10 to 500 [μm], and the width of the silicon film that can be melted in one beam scan is approximately - [beam diameter], so a large area It was unsuitable for the purpose of obtaining a single crystal layer. This is because it is difficult to suppress the occurrence of grain boundaries in areas where scanning lines overlap.

Recently, as shown in Figure 13, a promising technology has been developed to create a pseudo-linear electron beam and form a wide molten region by deflecting a narrowly focused electron beam at high speed in a direction perpendicular to its scanning direction. ing. In this case, the length of the linearized beam is determined by the amplitude of the high-speed deflection, and in principle there is no limit to its length. However, when a spot beam with a constant beam current is deflected at high speed, as the amplitude increases, the temperature of the sample surface irradiated with the electron beam decreases as shown in FIG. 14. In order to manufacture a semiconductor crystal layer, it is necessary to sufficiently melt the semiconductor film. Therefore, to increase the fast deflection amplitude, the beam current must be increased. Under these circumstances, the length of the linearized beam is actually determined by the limit of the beam current (ie, the brightness characteristics of the electron gun).

On the other hand, in the production of a single crystal layer using the above-mentioned pseudo-linear electron beam, there is a problem of controlling the temperature distribution in the length direction of the linearized beam on the surface of the sample irradiated with the beam. Originally, a linear electron beam emitter was used to project a linear beam onto the sample surface. FIG. 15 is a diagram showing the silicon surface temperature distribution in the linearization direction when high-speed deflection is performed using a sine wave. As a characteristic of a sine wave, there is a value of 2 near both ends of the amplitude.
There are two temperature peaks, with the central region being cooler than these regions. Therefore, if the vicinity of both ends of the quasi-linear beam is appropriately melted when the sample is irradiated with an electron beam, the vicinity of the center will not be melted. Therefore, it is difficult to uniformly anneal the sample surface.

In order to solve this problem, it is possible to use a waveform such as a triangular wave, in which the existence probability of the electron beam is constant regardless of the position within the amplitude, instead of using a sine wave, but as the high-speed deflection frequency increases, the waveform distortion increases and approaches the characteristics of a sine wave, making it difficult to solve the above problem. High speed deflection signals require frequencies on the order of MHz. It is the 16th
As shown in the figure, 4.: As described above, the conventional pseudo-linear beam technology has ten points. In addition to making it possible to make the temperature distribution at the outer periphery of the electron beam irradiation area gentle, thermal distortion generated within the sample can be minimized, and a high-quality single crystal layer can be manufactured. An object of the present invention is to provide a method for manufacturing a single crystal layer.

Another object of the present invention is to provide an electron beam annealing apparatus for implementing the above method.

[Summary of the invention]

The gist of the present invention is to perform amplitude modulation (A
M), by controlling the intensity distribution of the linearized beam by controlling the modulation signal, and by controlling the magnitude of the amplitude A of the JA main wave!・Can be executed. The waveform in FIG. 1 is Y-(A-5in oos
t+B) −5in ω2 t.

ω1 and ω2 are the frequencies of the modulated wave and the fundamental wave, respectively. A/B represents the modulation degree m. FIG. 2 shows the electron beam existence probability density distribution when the modulation degree m is used as a parameter. Here, B=1. When there is no amplitude modulation of m=Q, there is a huge peak of the existence probability density at the beam position Y=1, and the distribution becomes gentler as it approaches the center. The temperature distribution on the sample surface when irradiated with an electron beam having such an intensity distribution is as shown in FIG. 15 above. Note that the reason why the temperature peak is small in FIG. 15 is that heat diffusion occurs on the sample to be annealed.

Also, from FIG. 2, m=0.2. As m-0,5 and m increase, the peak of the electron beam existence probability density described above becomes smaller, and the difference from the value at the center becomes smaller. When the peak becomes smaller and the difference from the value at the center becomes smaller, the above-mentioned thermal diffusion is added, and the temperature gradient with respect to the periphery of the region becomes smaller.

Therefore, the non-uniformity of the temperature distribution as shown in FIG.
By optimizing the value of , it can be significantly reduced and uniform melting of the semiconductor layer can be achieved. The value of 1m is approximately 0.2
A value between approximately 0.8 and 0.8 provides appropriate conditions, but the optimum value varies depending on the structure of the annealed sample, temperature conditions, etc.

By the way, when using a simple sine wave whose waveform is symmetrical in the positive and negative directions with respect to the reference potential as described above as a modulating wave, it is difficult to independently control the temperature of the inside and outside of the semiconductor molten layer, and It is also difficult to strictly equalize the temperature distribution within the layer.

Therefore, in the present invention, as shown in FIG. 3, an electron beam is used which is deflected at high speed by a signal whose amplitude is modulated by a modulated wave whose amplitude in the positive and negative directions is asymmetric with respect to a reference potential. In this case, the waveform inside the reference potential can control the temperature in the center of the melting region, and the waveform outside the reference potential can control the temperature in the periphery of the melting region, making the central and peripheral parts independent. This makes it possible to control the temperature accordingly.

91 The present invention focuses on these points, and provides a method for manufacturing a semiconductor single crystal layer in which a polycrystalline or amorphous semiconductor film formed on an insulating substrate is annealed by scanning with an electron beam.
The beam is deflected in one direction by an amplitude-modulated electric signal, and the beam is scanned in a direction crossing this direction, and a waveform having different amplitudes in positive and negative directions is used as a modulated wave of the electric signal. This is the method.

a second deflector that deflects the beam at high speed in a direction intersecting the scanning direction; and a high-frequency power source that applies an amplitude-modulated electric signal to the second deflector; 9 uses a waveform having different amplitudes in positive and negative directions with respect to a reference potential as a modulation wave of an electric signal in a high frequency power source.

〔Effect of the invention〕

temperature distribution can be controlled independently. For this reason,
A high quality semiconductor single crystal layer with low residual thermal distortion can be manufactured over a large area.

[Embodiments of the invention]

Reference numeral 31 denotes an electron gun, and the electron beam emitted from the electron gun 31 is focused by a focusing lens 32 and an objective lens 33 and irradiated onto a sample 434, and a scanning coil (first deflector) 35 is scanned on the sample 34 by. The scanning coil 35 is actually composed of an X-direction deflection coil that deflects the beam in the X direction (left and right directions in the paper) and a Y-direction deflection coil that deflects the beam in the Y direction (front and back directions in the paper). Further, an aperture mask 36 is arranged on the main surface of the focusing lens 32, and the electron gun 31 and the nozzle 3
A blanking north pole 37 for turning the beam ON and OFF is arranged between the two.

The configuration up to this point is the same as a normal electron beam annealing device, and the difference in this embodiment device is that there is a deflection plate (second The reason is that a deflector) 38 is provided.

That is, the deflection plates 38 are arranged to face each other in the Y direction as shown in FIG. 13, and deflect the beam in the Y direction at high speed.

In addition, the deflection plate 38 has a drive system (highly placed, i,'!7-Kingedance is large enough,
FIG. 2 is a block diagram showing a circuit configuration of a high frequency power source 40 of a deflection cell. This power supply 40 includes two oscillators 41a and 41b that generate sine waves, and a diode 42a.

42b, phase controllers 43a, 43b, and waveform synthesizer 1.

214, an oscillator 45 that generates a fundamental wave, a modulator 46,
It is composed of an i-power amplifier 47 and the like.

- The oscillation output of the oscillator 41a is supplied to the phase controller 43a via the diode 42a. Similarly, the oscillation output of the oscillator 41b is transmitted to the phase controller 43b via the diode 42b.
supplied to Each output signal of the phase controllers 43a and 43b is then supplied to a waveform synthesizer 44. Waveform synthesizer 4
The signal (modulated signal) synthesized in step 4 is supplied to the modulator 46 together with the output signal (fundamental wave) of the oscillator 45. The signal modulated by the modulator 46 is amplified via the amplifier 47. The output voltage of the amplifier 47 causes the amplitude of the force signal to be P as shown in FIG. 6(a), and the amplitude of the output signal of the oscillator 41b to be Q as shown in FIG. 6(b). Then, the diodes 42a and 42b are present. Then, the symmetry, amplitude, etc. of this signal with respect to the modulated wave are determined. The value of P is mainly effective in controlling the heating outside the melting region of the sample during annealing, and may be selected so that the temperature gradient there is appropriate. Further, the value of Q is mainly effective for controlling the temperature distribution in the melting region of the sample, and may be selected so as to make the temperature distribution uniform.

Next, a method for manufacturing a silicon single crystal layer using the above apparatus will be described.

First, the signal applied to the deflection plate 38 is 50 [
A waveform obtained by amplitude-modulating a sine wave of [MHz] with a signal as shown in FIG. 6(c) was used. That is, the oscillator 4.1a,
The oscillation frequency of 41b is 15 [KHzl, the value of amplitude P is 8
[V], and the value of the amplitude Q was set to 14 [V]. In addition, the frequency of the fundamental wave, which is the output of the generator 45, is set to 50 [Ml-12
1. The amplitude was set to 60 [V].

Under this high-speed deflection condition, 1″ of 150 [μTrL] diameter
″-12 [mA, scanning speed 100 [m/sec]
]T: Conducted an electron beam annealing experiment.

n) A polycrystalline S film (
A semiconductor film) 53 is deposited, and a W film 54 with a thickness of 0.5 [I1m] and 0.5 [μm] is deposited on top of it as a cap layer.
A two-layered thick SiN film 55 was used.

In the sample after annealing, a silicon recrystallized layer with a width of 3.5 ml was obtained, and its surface condition was extremely flat. Moreover, the Si under the polycrystalline silicon film 53
In a sample with a structure in which the O2 film 52 is partially opened, the above S
During the recrystallization of the polycrystalline silicon film 53 that is in direct contact with the substrate silicon at the opening of the iO2 film 52, it grows vertically epitaxially from the substrate, and then the silicon layer on the 5i02 film 52 also grows epitaxially laterally, resulting in this width of 3.5%. [
#] In the region included in the melting zone, a large area of (100
) orientation was obtained.

Next, a second embodiment of the present invention will be described.

In this example, a sine wave of 100 KHz is amplitude-modulated with a waveform having different amplitudes in the direction of the right angle with respect to the reference potential described in the first embodiment, and this modulated waveform is used to generate a sine wave of 50 KHz.
The oscillation frequency of the oscillator 181 is 100 [kHz], and the output signal of the oscillator 81 is amplitude-modulated by the output signal of the waveform synthesis circuit 80 by the modulator 82 . Then, the output signal of this modulator 82 is
The signal is supplied to the modulator 46 as a modulation signal.

FIG. 9 shows the high speed deflection waveform used in this example. When annealing was performed using this waveform under the same conditions as in the first example, a silicon recrystallized layer with a width of 4.5 [#I11] was obtained, and its surface had even better uniformity and flatness. It was something like that. Moreover, the crystallinity was also extremely good.

Note that, in this embodiment as well, two sine waves were used to form the modulated wave in the waveform synthesis circuit 80.

Similar effects were obtained even when one or both of these waves were made into a triangular wave, a polygonal wave, or a sawtooth wave.

Next, a third embodiment of the present invention will be described.

In this device, first, an arbitrary waveform was converted into m-digits, and the data obtained by converting the intensity into binary numbers was stored in the semiconductor memory 91. Next, this data is read out and sent to the DA converter 92.
was passed through to obtain an analog quantity, which was input to the modulator 46 to amplitude-modulate the fundamental wave. As a result, it has become possible to perform high-speed deflection using modulated waves of arbitrary waveforms, which was difficult with the analog modulation method described above. Therefore, it was possible to completely freely control the electron beam existence probability distribution, and it was possible to completely flatten the temperature distribution in the length direction of the linearized beam.

Next, a fourth embodiment of the present invention will be described.

In this embodiment, a computer (C
P tJ ) to create an arbitrary waveform, and the waveform (
When the output (binary number) is input to a DA converter, optimal annealing conditions are always created during the formation of the semiconductor crystal layer (during electron beam annealing), and the waveform is changed online so that the The temperature is constantly monitored by the non-contact temperature sensor 49, etc., and the CPU 93
The optimum solution for the electron beam existence probability density distribution may be calculated using the following steps, and a modulation waveform corresponding to the result may be output.

The advantage of this method is that it can compensate for temperature drops due to heat diffusion to the surroundings, especially at the edges of the annealing region, and can compensate for excessive heating in areas where the scans overlap when the linearized beam is raster scanned. However, it is effective in achieving uniform crystal growth. However, the present invention is not limited to the embodiments described above. For example, the frequency of the fundamental wave is 50
The present invention is not limited to [Mtlz], and any material that can reduce the variation in sample surface temperature as shown in FIG. 15 may be used. In order to reduce temperature fluctuation, 50 [
Of course, electromagnetic deflection may be performed at frequencies above [KHz] if desired.

Furthermore, the substrate material is GaAs, G instead of Sl.
Other semiconductor materials such as E, I np, etc. may also be used. In addition, the thickness of the 5i02 film as an insulating film can be changed as appropriate, and in addition, a 5i-N film, a 5i-N film,
It is also possible to use other insulating films such as an A° C. 20B film. Furthermore, as the semiconductor film formed on the insulating film, amorphous silicon can be used instead of polycrystalline silicon.
Furthermore, it is also possible to use other semiconductor materials such as Ge, GaAs, etc. In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawings] Figures 1 to 3 are for explaining the present invention in detail, and Figure 1 shows an electric signal amplitude modulated by a sine wave as an electric signal for deflecting an electron beam at high speed. FIG. 2 is a signal waveform diagram showing a high-speed deflection waveform, and FIG. Fig. 4 is a schematic configuration diagram showing the electron beam annealing device, Fig. 5 is a block diagram showing the two-circuit configuration of the drive system, and Fig. 6 is a diagram showing the configuration of the 5 reference potentials. Fig. 7 is a cross-sectional view showing the schematic structure of the sample to be annealed, and Figs. 8 and 9 are the second Fig. 8 is a block diagram showing the circuit configuration of the drive system, Fig. 9 is a signal waveform diagram showing a high-speed deflection signal, and Fig. 10 is used to explain the third embodiment. Block diagram showing the circuit configuration of the drive system, No. 11
11 and 12 are for explaining the fourth embodiment, respectively. FIG. 11 is a block diagram showing the circuit configuration of the drive system, FIG. 12 is a schematic configuration diagram showing an example of monitoring the sample surface, and FIG. Figures 13 to 16 are for explaining the problems of the conventional method, respectively. Figure 13 is a schematic diagram showing the principle of forming a quasi-linear beam, and Figure 14 is a diagram showing the relationship between the length of the quasi-linear beam and the sample surface temperature. Figure 15 is a characteristic diagram showing the relationship between the distance from the center of beam high-speed deflection = 22- and the sample surface temperature, and Figure 16 is a characteristic diagram showing the relationship between the beam high-speed deflection when the fundamental wave frequency is used as a parameter. Distance from center and sample surface (first deflector)
, 36... Aperture mask, 37... Blanking electrode, 38.39... Deflection plate (second deflector), 4
0... Drive system (high frequency type m>,), 1°・41b・4
5・81-°゛oscillator・42a, 42b・'l ion, 43a, 43b...phase controller, 44...waveform synthesizer, 46.82...modulator, 47...amplifier, 49
... Temperature sensor, 51 ... Single crystal Si substrate, 52.
...SiO2 film (insulating film), 53...polycrystalline S1 film (
semiconductor film), 54, . 55... Cap layer, 91...
・PROM, 92...DA converter, 93...cpu
.

Claims (7)

[Claims] (1) In a method for manufacturing a semiconductor single crystal layer in which a polycrystalline or amorphous semiconductor film formed on an insulating surface of a substrate is annealed by scanning an electron beam, the beam is energized by an amplitude-modulated electric signal. A semiconductor single crystal characterized in that the beam is deflected in a direction and scanned in a direction crossing the same, and a waveform having different amplitudes in positive and negative directions with respect to a reference potential is used as a modulation wave of the electric signal. Method of manufacturing layers. (2) The semiconductor unit according to claim 1, characterized in that, as the modulated wave of the electric signal, a waveform having different amplitudes in positive and negative directions with respect to a reference potential and subjected to amplitude modulation is used. Method of manufacturing a crystal layer. (3) The temperature of the semiconductor film during annealing is detected by a non-contact temperature sensor, and the modulation waveform of the electrical signal is changed based on the detected humidity.
A method for manufacturing a semiconductor single crystal layer as described in 1. (4) Claim 1, characterized in that the base body is one in which an insulating film is formed on a single crystal semiconductor substrate.
A method for manufacturing a semiconductor single crystal layer as described in 1. (5) The method for manufacturing a semiconductor single crystal layer according to claim 4, wherein the insulating film has an opening formed in a portion thereof. (6) a lens system that controls the focusing of the electron beam emitted from the electron gun; a first deflector that scans the beam on the sample to be annealed; and a first deflector that deflects the beam at high speed in a direction intersecting the scanning direction. It comprises a second deflector and a high frequency power source that applies an amplitude modulated electric signal to the second deflector, and the high frequency power source modulates a waveform having different amplitudes in positive and negative directions with respect to a reference potential. An electron beam annealing device characterized in that it is used as a. (7) The electron beam according to claim 6, wherein the high-frequency power source has different amplitudes in positive and negative directions with respect to a reference potential, and uses a waveform subjected to amplitude modulation as a modulating wave. Annealing equipment.