JPS6011453B2 - Manufacturing method of semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a semiconductor device, and in particular to a method for manufacturing a semiconductor device, in particular an SO semiconductor device comprising a single crystal silicon layer and a sapphire substrate on which an element is formed.
The present invention relates to a method of manufacturing a semiconductor device using an improved S substrate.

In order to manufacture semiconductor devices using a so-called SOS substrate in which a single crystal silicon layer is deposited on a sapphire substrate, it is necessary to grow a single crystal silicon layer with good crystallinity in order to obtain good transistor characteristics. It is important to use a substrate.

For this reason, conventionally, as a method for depositing a single-crystal silicon layer on a sapphire substrate, a low-pressure vapor phase epitaxial method has been adopted in which the epitaxial growth reaction of silicon is carried out at a pressure lower than 1 atmosphere. According to this method, aluminum in the sapphire substrate penetrates into the single crystal silicon layer. The amount of so-called autodoping can be reduced. However, in the above conventional method, (11) defects occurring near the interface between the sapphire substrate and the single-crystal silicon layer, [21] dislocations in the single-crystal silicon layer occurring near the interface, and '3' stacking in the single-crystal silicon layer near the interface. Defects, lattice defects, etc. are not reduced, and the crystallinity of the single crystal silicon layer is not sufficiently improved.As a result, when MOS transistors are manufactured using this SOS substrate, compared to when manufactured using silicon wafers, This results in drawbacks such as deterioration of electrical characteristics such as a decrease in carrier mobility in the single crystal silicon layer.
For these reasons, the inventors of the present invention have conducted various studies to overcome the above-mentioned drawbacks, and have attempted to irradiate the single crystal silicon layer side of the SOS substrate with laser light.

When the single crystal silicon layer is irradiated with laser light in this way,
The temperature near the surface of the single-crystal silicon layer irradiated with laser light is highest, and although defects and dislocations decrease in that area, the number of defects and dislocations in the single-crystal silicon layer is far greater than that in the single-crystal silicon layer. There is a disadvantage that defects and dislocations near the interface between the silicon layer and the sapphire substrate cannot be effectively reduced.
However, as a result of further intensive research based on the above findings, the inventors of the present invention focused on the fact that the optical absorption coefficient of sapphire is much smaller than that of single crystal silicon. Regarding irradiation, a large amount of laser light is absorbed by the single crystal silicon layer near the interface between the sapphire substrate and the single crystal silicon layer, and that part becomes high temperature, causing a process of melting and recrystallization, and the single crystal silicon layer is removed from the sapphire substrate. Effectively eliminates defects and dislocations at the interface between the sapphire substrate and single-crystal silicon layer, which are far more numerous than the number of defects and dislocations in the single-crystal silicon layer, without creating new doping of aluminum into the crystalline silicon layer. In addition to reducing defects and dislocations in the single crystal silicon layer, SOS has significantly improved crystallinity of the single crystal silicon layer.
I investigated the board.

Therefore, we discovered and developed a method for manufacturing a semiconductor device with high electron mobility and good electrical characteristics by forming elements on this SOS substrate. That is, the present invention is an SO film formed by depositing a single crystal silicon layer on a sapphire substrate.
In manufacturing a semiconductor device by forming an element on an S substrate, the method is characterized in that a laser beam is irradiated onto the SOS substrate from the sapphire substrate side.The laser beam used in the present invention converts energy from light into heat. From the viewpoint of heating a single crystal silicon layer epitaxially grown by conversion with high efficiency, it is necessary to oscillate at a wavelength having a large optical absorption coefficient relative to single crystal silicon.

For example, such a laser light source has an oscillation wavelength of 0.69.
A 4-meter ruby laser with an oscillation wavelength of 0.442
．． 325 mountain helium cadmium laser, an argon ion laser with an oscillation wavelength in the near-ultraviolet and visible light regions, an excimer laser with an oscillation wavelength in the ultraviolet region, or an Nd-YAG laser or Nd-YAG laser with a fundamental oscillation wavelength of 1.06 Am.
Examples include harmonic light such as glass laser.
When using an argon ion laser or an oxymer laser as a laser light source, heating efficiency can be improved by selecting the most suitable wavelength for heating based on the relationship between the laser light output for the oscillation wavelength and the light absorption coefficient of single crystal silicon. It is necessary to increase the In the present invention, the amount of heat input into the single crystal silicon layer by laser irradiation can be controlled by changing the spot size of laser light at the interface between the sapphire substrate and the single crystal silicon layer.

When continuous wave laser light or high-speed repetitive pulse laser light is used, the amount of heat input to the single crystal silicon layer can be controlled by changing the scanning speed of the laser light with respect to the sapphire substrate. However, the L output power is 4.
However, when using a laser beam, the surface of the sapphire substrate into which the laser beam is incident is mirror-polished in advance to reduce scattering of the laser beam on the sapphire substrate surface while polishing the surface of the sapphire substrate on the interface between the sapphire substrate and the single crystal silicon layer. It is necessary to focus the laser beam to prevent the amount of heat input per unit area into the single crystal silicon layer from decreasing. On the other hand, when using a laser beam with a large output power, it is not necessary to focus the laser beam on the interface between the sapphire substrate and the single crystal silicon layer, and as a result, the laser beam is scattered on the sapphire substrate surface. Since a decrease in the amount of heat input per unit area to the crystalline silicon layer is of little concern, mirror polishing of the surface side of the sapphire substrate is not necessary. In the present invention, the atmosphere of the SOS substrate during laser beam irradiation is low-pressure air, low-pressure air, Vacuum: Low-pressure helium or low-pressure nitrogen is preferable.

However, laser light irradiation can be performed in air depending on the heat input conditions for laser light irradiation. Note that ``regardless of the atmosphere at the time of laser beam irradiation, it is desirable to perform laser beam irradiation for heat input at high speed and in a short time in order to avoid contamination of the SOS board from the outside. An example will be explained.

EXAMPLE As shown in FIG. 1, vapor phase epitaxial growth was carried out on a sapphire substrate 1 with a thickness of 0.4 ribs, mirror-polished on both sides, by supplying silane gas at a reaction temperature of 1100 OO and a pressure of 1 Pa. Then, a single crystal silicon layer 2 having a thickness of 1.3 cm was grown to produce an SOS substrate.

At this time, the crystal plane on the surface of the sapphire substrate 1 is (1102
), and the crystal plane of the single crystal silicon layer 2 was (100). After that, the sapphire substrate 1 side of the SOS substrate was irradiated with a ruby laser beam 3 with an oscillation wavelength of 0.694 French and an output IKW nopulse in a vacuum. When protons were introduced into the layer at an accelerating voltage of 720 keV and the backscattered energy and number of protons were measured using a backscattering method to examine the crystallinity of the single crystal silicon layer, a characteristic diagram as shown in FIG. 2 was obtained. In addition, the dashed-dotted line in the figure is a random orientation curve when the incident direction of protons is different from the 100> direction of the single crystal silicon layer, and the broken line is the random orientation curve when the incident direction of protons is different from the 100> direction of the single crystal silicon layer, and the broken line is the random orientation curve when the incident direction of protons is different from the 100> direction of the single crystal silicon layer. 10
0> direction. Crystallinity characteristic curve when ton is incident,
The solid line is a crystallinity characteristic curve when protons are incident in the 100> direction of the single crystal silicon layer of the SOS substrate irradiated with laser light. As is clear from this figure 2,
The SOS substrate that was irradiated with laser light from the sapphire substrate side had a change in the count number of the single crystal silicon layer near the interface between the sapphire substrate and single crystal silicon and other silicon layer parts compared to the SOS substrate that was not irradiated with laser light. This results in a single crystal silicon layer with improved crystallinity due to fewer defects and dislocations near the interface between the sapphire substrate and the single crystal silicon layer, and fewer defects and dislocations in the single crystal silicon layer. It has been found that an SOS substrate having the following characteristics can be obtained. Next, using the SOS substrates that were irradiated with laser light and the SOS substrates that were not irradiated with laser light, MOS transistors with channels in which boron ions were implanted at concentrations of 1 and 7 were made. Electron mobility was measured.

As a result, the electron mobility was 30% in a MOS transistor made from an SOS substrate that was not irradiated with laser light.
0 'Vsec, whereas a MOS transistor made from an SOS substrate irradiated with laser light had a voltage of 380 Vsec.
'Vsec. In this way, "SOS with a single crystal silicon layer whose crystallinity has been improved by laser beam irradiation"
It can be seen that the external mobility of the MOS transistor made from the substrate is large and the electrical characteristics etc. are improved. As detailed above, according to the present invention, by irradiating a SOS substrate made of a single crystal silicon layer epitaxially grown on a sapphire substrate with laser light from the sapphire substrate side,
SO with a single crystal silicon layer with good crystallinity
The present invention can provide a method for manufacturing a semiconductor device with high electron mobility and excellent electrical characteristics by forming an SOS substrate and forming elements on this SOS substrate.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing the laser beam irradiation process during the manufacturing of a semiconductor device in an embodiment of the present invention, and FIG. 2 is a schematic diagram showing an SOS substrate subjected to laser beam irradiation and an SOS substrate not subjected to laser beam irradiation. FIG. 3 is a characteristic diagram showing the crystallinity of a single-crystal silicon layer. 1...Sapphire substrate, 2...Single crystal silicon layer, 3...Laser light. Figure 1 Figure 2

Claims (1)

[Claims] 1. A semiconductor device characterized in that when manufacturing a semiconductor device by forming an element on an SOS substrate formed by depositing a single crystal silicon layer on a sapphire substrate, a laser beam is irradiated onto the SOS substrate from the sapphire substrate side. manufacturing method.