JPH0136688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field of the Invention The present invention relates to a lateral epitaxial growth method, and particularly to a method for controlling the amount of electron beam irradiation to a non-single crystal silicon layer.

(b) Background of the Technology In recent years, lateral epitaxial growth has attracted attention as a technology for realizing multilayer integrated circuits or three-dimensional integrated circuits.

For example, an amorphous silicon layer is deposited on a silicon dioxide layer, and recrystallization starts from one point and then affects the entire area.Since single crystallization progresses in the horizontal direction, it is called lateral epitaxial. It's called growth.

Lateral epitaxial growth may also be performed on single crystal silicon substrates with selectively deposited insulators. In this case, the newly formed single crystal layer inherits the crystal orientation of the substrate crystal on the single crystal silicon, and inherits the crystal orientation of the single crystal layer grown up to that point on the insulator.

As a heating means for single crystallizing a non-single crystal silicon layer, scanning irradiation with laser light, electron beam, etc. is generally used, but a rod-shaped infrared heater is sometimes used. This rod-shaped heater is also used in a sweeping manner. The area that can be heated at one time is a minute area in the form of a dot with a laser beam or an electron beam, and a band-shaped area with a rod-shaped heater.

Since laser beams and electron beams have point-shaped heating regions, in actual heating, a belt-shaped heating region is created by scanning at high speed in the X direction, and the belt-shaped heating region is swept at a relatively low speed in the Y direction. As a result, the surface area is heated.

Since the electron beam is electrostatically or electromagnetically deflected, it can be scanned at a much higher speed (on the order of tens of MHz) than laser light, and can perform strip heating more effectively.

(c) Prior art and problems When electron beam scanning is performed using electrostatic deflection, a high-frequency triangular voltage is applied to the deflection electrode in the
This is usually done by applying a sawtooth wave to the direction deflection electrode. These voltage waveforms are shown in FIG. 1, where a shows the deflection voltage waveform in the X direction and b shows the deflection voltage waveform in the Y direction.

When the deflection in the X direction is performed using such a voltage, a uniform amount of heat is injected from one turning point to the other turning point of the electron beam, as shown in FIG. 2b. When the irradiation area is further swept in the Y direction, the heat radiation is maximum at the turning position, so
As shown in FIG. 2a, the silicon molten region becomes narrow near the folding point, and solidification starts from the region adjacent to the polycrystalline silicon. In such crystallization, crystal growth progresses using the crystal grains in the polycrystalline region as nuclei, so that the recrystallized region becomes polycrystalline. In the figure, 1 is a polycrystalline silicon region, 2
3 is a melting region, 3 is a recrystallization region, and crystal growth progresses in the direction shown by arrow 4.

(d) Purpose of the Invention The purpose of the present invention is to prevent preferential cooling of the vicinity of the folding point during single crystallization of non-single crystal silicon by electron beam irradiation, and to ensure that single crystallization progresses completely. An object of the present invention is to provide an electron beam irradiation method that

(e) Structure of the Invention The solution to the above object is to irradiate a vibrating electron beam onto a non-single crystal semiconductor layer formed on a substrate, and sweep the electron beam in a direction perpendicular to the vibration direction. Single crystallization of the non-single crystal semiconductor layer is achieved by a lateral epitaxial growth method characterized by using a periodic waveform whose peak is clamped as a deflection voltage for vibrating the electron beam.

(f) Embodiment of the Invention In a first embodiment of the present invention, a triangular wave (or sine wave) with a peak clamped waveform as shown in FIG. 3a is used as the X-direction deflection voltage.
If the sweep in the Y direction is ignored, an electron beam scanned by a deflection voltage having such a waveform will remain stationary for a time t ₀ at the turning point of the scan, and the beam will be emitted as shown in Figure 4b. As shown, more energy is injected near the turning point.

Therefore, the temperature of this region becomes higher than that of other irradiated regions, and as a result, as shown in Figure 4a, the silicon melting region expands near the turning point, and single crystallization occurs from the center of the swept region. , progresses toward the surrounding polycrystalline region, so the recrystallized region does not become polycrystalline.

The above explanation was made assuming that the scanning speed in the X direction is sufficiently large compared to the sweeping speed in the Y direction. However, if the amount of movement in the Y direction during turning cannot be ignored, the third A Y-direction deflection voltage having a waveform with a pause time of t ₀ in the middle as shown in FIG. b is used. The two types of voltages shown in FIG. 3 can be easily generated by known methods.

In the second embodiment of the present invention, the X-direction deflection voltage is an unclamped triangular wave (or sine wave) with a peak as in the normal case, but the current value of the electron beam is increased near the turning point. will be carried out. This method also makes it possible to achieve an implantation energy distribution similar to that shown in FIG. 4b. The resulting effect is the same as in the first embodiment. According to this method, scanning in the X direction can be performed faster than in the first embodiment.

Increasing the current value near the turning point can be achieved, for example, by comparing the X-direction deflection voltage with a slice level set near its peak value, and inputting a control signal containing the comparison circuit output to the current control electrode. This can be accomplished in a number of ways.

It is also possible to use the first and second embodiments together.

(g) Effects of the Invention As explained above, according to the present invention, single crystallization of a non-single crystal layer by scanning electron beam irradiation progresses from the center to the peripheral portion of the sweep region, so that re-crystallization is possible. The crystalline region does not become polycrystalline,
Lateral epitaxial growth can be carried out without any problems.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the electron beam deflection waveform of the prior art, FIG. 2 is a diagram showing the progress of single crystallization according to the prior art, FIG. 3 is a diagram showing the electron beam deflection waveform of the present invention, and FIG. 4 is a diagram showing the electron beam deflection waveform of the present invention. 1 is a diagram showing the progress of single crystallization according to the present invention, in which 1 is a polycrystalline silicon region, 2 is a silicon melting region, and 3 is a recrystallization finished region.

Claims (1)

[Claims] 1. Irradiating a vibrating electron beam onto a non-single-crystal semiconductor layer formed on a substrate, and sweeping the electron beam in a direction perpendicular to the vibration direction to remove the non-single-crystal semiconductor layer. A lateral epitaxial growth method characterized in that a periodic waveform whose peak is clamped is used as a deflection voltage for vibrating the electron beam when crystallizing the electron beam.