JPH02199817A - High-frequency annealing - Google Patents

Abstract

PURPOSE:To improve the quality of a semiconductor layer by a method wherein the semiconductor layer is formed on an insulating substrate, this whole assembly is heated at a heat-resisting temperature or lower of the insulating substrate and the semiconductor layer is heated selectively while high-frequency radio waves are radiated. CONSTITUTION:An insulating substrate 1 on which a semiconductor layer 2 has been deposited is heated at a heat-resisting temperature or lower of the insulating substrate by means of a heating part 3; a state that sufficient carriers exist in the semiconductor layer 2 is set by utilizing a property that a carrier concentration of a semiconductor is increased in terms of an exponential function with reference to a temperature. When high-frequency radio waves 4 are radiated in this state, a large difference in an absorption coefficient of the high-frequency radio waves is caused between the insulating substrate 1 and the semiconductor layer 2; accordingly, the radio waves are absorbed mostly in the semiconductor layer 2 and only the semiconductor layer 2 is heated selectively. Since the carrier concentration of the semiconductor is increased in terms of the exponential function with reference to the temperature, a positive feedback is applied and the absorption coefficient of the radio waves is increased furthermore; the layer is heated. Thereby, a quality of the semiconductor layer 2 can be improved; this layer can be recrystallized.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a substrate in which a high-quality semiconductor layer is formed on an insulating substrate, which can be used as a substrate for manufacturing thin film transistors, etc. In particular, the present invention relates to a method of manufacturing a substrate in which a high-quality semiconductor layer is formed on a low heat-resistant insulating substrate.

[Conventional technology]

For the purpose of application to thin film transistors, attempts are being made to improve the film quality by annealing and recrystallizing semiconductor layers, such as silicon layers, deposited on insulating substrates using various methods. . These are methods of annealing using laser light, electron beams, or linear heat sources. Considering the case of laser light annealing, the optical constants such as the light absorption coefficient of the silicon layer change significantly before and after the silicon layer is melted. Therefore, the energy absorbed by the silicon layer changes greatly, and the distribution of the silicon layer's thickness etc. directly affects the temperature distribution.

Therefore, in order to improve reproducibility and controllability, the substrate is heated to a temperature ranging from several hundred degrees to about 1000 degrees before being irradiated with laser light. In addition, in the case of electron beam annealing, when using an insulating substrate or when annealing a silicon layer formed in an island shape on an insulating layer, a charging phenomenon due to electrons occurs, reducing reproducibility. etc. are being moved. Furthermore, when a linear heat source is used, the physical size of the heating source is large compared to the thickness of the silicon layer, making it difficult to selectively heat the silicon layer. The material is annealed at temperatures ranging from several hundred degrees to about 1,000 degrees. As described above, with conventional annealing methods, it is difficult to anneal a semiconductor layer deposited on an insulating substrate with good reproducibility and controllability while keeping the substrate temperature below several hundred degrees. In order to solve the above problems, he invented the "high frequency annealing method" by patent application No. 160690/1983, which selectively heats the semiconductor layer deposited on an insulating substrate to improve its quality. made possible.

FIG. 2 is a schematic diagram showing an example of implementing the above invention.

There, 5i0 was applied to a low heat-resistant glass substrate 5 by CVD.
Two layers 6 are deposited and a silicon layer 7 is deposited thereon. Furthermore, a thin high-quality contamination prevention 5i02 layer 6 is formed,
After depositing the high melting point metal 8 such as tungsten, it was necessary to irradiate the metal with pulsed electromagnetic waves 9 to anneal it. However, there are problems such as the deposited high melting point metal 8 must be removed after annealing and is highly likely to become a source of contamination during annealing.

[Problems to be Solved by the Invention] The present invention solves the problems of the conventional annealing method described above as well as the problems of the patent application No. 160690/1982 "High frequency annealing method", and It is an object of the present invention to provide a high-frequency annealing method that can selectively heat a semiconductor layer deposited on an insulating substrate to improve its quality without fear of contamination and with a simpler process.

[Means to solve the problem]

In order to solve the above-mentioned problems, the present invention provides a semiconductor layer on an insulating substrate, heats the entire structure to a temperature below the heat-resistant temperature of the insulating substrate, and then irradiates the semiconductor layer with high-frequency radio waves. The layers are selectively heated and annealed.

[Effect]

FIG. 1 is a schematic diagram explaining the principle of the main components of the present invention, in which 1 is an insulating substrate, 2 is a semiconductor layer, 3 is a heating section, and 4 is a schematic diagram explaining the principle of the main components of the present invention.
is a high frequency radio wave. The present invention utilizes the property that the carrier concentration of a semiconductor increases exponentially with temperature, and the property that high frequency radio waves are selectively absorbed into a low resistance layer. First, the insulating substrate 1 on which the semiconductor layer 2 has been deposited is heated by the heating section 3 below the heat-resistant temperature of the insulating substrate, taking advantage of the property that the carrier and a concentration of the semiconductor increases exponentially with temperature. Thus, a state is created in which sufficient carriers exist in the semiconductor layer 2. In this case, if a sufficient amount of carriers exist in the semiconductor layer at room temperature, there is no need for heating.If the high-frequency radio waves 4 are irradiated in this state, the insulating substrate 1 and the semiconductor layer 2 will be separated. Since there is a large difference in the absorption coefficient of high-frequency radio waves, most of the radio waves are absorbed in the semiconductor M2, and only the semiconductor layer 2 is selectively heated. Since the carrier concentration of a semiconductor increases exponentially with temperature, positive feedback occurs, which further increases the radio wave absorption coefficient and heats the semiconductor. As a result, the quality of the semiconductor layer 2 can be improved and recrystallized.

〔Example〕

FIG. 3 is a sectional view showing a specific embodiment of the present invention, in which a high frequency coil 10 is provided inside the heating section 3, a high frequency power source 11 is connected to the high frequency coil 10, and a low heat resistant glass substrate 5 is connected to the high frequency coil 10. A substrate is placed on top of which a CVD Si02 layer 6, a silicon layer 7, and a CVD 5i02 layer 6 are deposited. The heating unit 3 heats the substrate up to the allowable temperature limit of the low heat resistant glass substrate 5. In this state, high frequency radio waves are generated inside the high frequency coil 10 by the high frequency power supply 11. Furthermore, all silicon layers on the substrate have been improved in quality.
The substrate is scanned as it is recrystallized.

FIG. 4 is a sectional view showing another embodiment of the present invention.

In the cavity resonator 13 having the impedance matching device 14,
The cavity resonator 1 is connected to the waveguide 12 and the high frequency power source 11, and the base explained in FIG.
A heating unit 3 that can be scanned inside is installed.

CVD 5i02 layer 6 on low heat resistant glass substrate 5,
A substrate on which a silicon layer 7 and a CVD 5in2 layer 6 are deposited is placed on the heating section 3 . Thereafter, the heating unit 3 similarly heats the substrate to the allowable temperature of the low heat resistant glass substrate. In this state, high frequency radio waves are generated inside the cavity resonator 13 by the high frequency power supply 11. Furthermore, the heating unit 3 and the substrate are scanned so that the entire silicon layer on the substrate is improved in quality and recrystallized.

〔Effect of the invention〕

According to the present invention, it is possible to improve the quality and recrystallize a semiconductor layer using a low-cost, high-output, high-frequency power source. Furthermore, since such a power source has better controllability than a linear heat source such as a laser beam or a strip heater, it is possible to perform annealing with good reproducibility. In addition, even if a low heat-resistant glass substrate that is available at a low price is used, it is possible to form a high-quality semiconductor layer on it.
It becomes possible to manufacture torns at low cost.

Ru.

1... Insulating substrate, 2. ... Semiconductor layer, 3... Heating part, 4... High frequency radio wave, 5... Low heat resistant glass substrate, 6... CVD S i02 layer, 7... Silicon layer, 8... Tungsten layer, 9... Pulsed electromagnetic waves, 10... High frequency coil, 11... High frequency power supply,
12... Waveguide, 13... Cavity resonator, 14...
Impedance matching box.

Claims (1)

[Claims] It is characterized by providing a semiconductor layer on an insulating substrate, heating the whole to a temperature below the heat resistance temperature of the insulating substrate, and further selectively heating the semiconductor layer by irradiating high-frequency radio waves. High frequency annealing method.