JPS5821824B2 - Manufacturing method of semiconductor device - Google Patents

Description

[Detailed Description of the Invention] This invention is based on SOS (Silicon On S
The present invention relates to a method of manufacturing a semiconductor device such as an APPPHIRE device.

Integrated circuits (SOS) using semiconductor films on insulating substrates are
Due to its structure, it is more advantageous than those using semiconductor substrates in terms of high density and high speed.

On the other hand, since a single crystal film of a different type from the substrate is grown on the substrate, it has the disadvantage of a high density of lattice defects.

The problem is that the lattice defects present at a high density deteriorate the electrical characteristics of the device.

For example, a MOS using a silicon film on a sapphire substrate
When a device is manufactured, leakage current increases among the device characteristics (H.

Tango:Proc. 6th Conf. Soli
dStateDevices! Tokyo, 1
974, Suppl, J., Jap.

Soc. Appl, Phys. 44, 1975
P225) or reduce mobility (M.D.
ruminski; Proc7th Conf. So
lid. State Devices, Tokyo.

1 975, Suppl. Jap. J. Appl. P
hys. 15, 1976.

P217) have been reported.

Therefore, it is required to reduce the lattice defect density in a semiconductor film from the viewpoint of improving device characteristics.

The reason why lattice defects are introduced into the film is that misorien-tation occurs between particles during the initial growth process because the film is epitaxially grown on a substrate different from that of the growth material.

(M.S, Abrahama-ms; J.A.P. 47, 1
976, P5139) Therefore, it is necessary to reduce misorientation between particles as much as possible in the early stage of growth in order to produce a high-quality film.

Therefore, many factors that affect the growth process have been investigated.

For example, growth equipment, growth method, type and orientation of substrate,
These include substrate surface treatment, growth conditions, etc.

In addition, a general method for reducing lattice defects existing in materials is recrystallization by annealing, which is called normal thermal annealing.

Laser annealing, which has recently begun to be used for semiconductor materials, is being considered.

An object of the present invention is to obtain a semiconductor device with good characteristics by reducing the lattice defect density of a semiconductor film on an insulating substrate.

The present invention aims to manufacture a semiconductor device that can reduce the lattice defect density in the film by irradiating a semiconductor film deposited on an insulating substrate with laser light from the insulating substrate side, thereby improving device characteristics. The present invention provides a method.

Hereinafter, one embodiment of the present invention will be explained in detail with reference to the drawings.

1) Semiconductor film growth conditions A sapphire single crystal substrate 1 having a (1012) plane was used as an insulating substrate.

On this substrate 1, a silicon (Si) film 2 was grown to a thickness of 0.7 μm as a semiconductor film.

The growth method is the commonly used CVD (Chemical
al vapor depth) method,
The growth conditions were a growth temperature of 950°C and a growth rate of 2 μrr.
l/7nJIL (Fig. 1a).

2) Laser irradiation conditions Next, laser light E was irradiated from the back side of the substrate 1 (Fig. 1b
).

The laser beam used was Q-switched Nd-YAG (wavelength: 1.064 μm), the pulse width was 20 Hsec, and the irradiation energy was 5 J/cd.

3) Experimental results Using selective etching as a method for evaluating lattice defect density,
The linear defect density on the silicon surface was determined.

In order to obtain the effects of the present invention, (A)...No laser irradiation was performed, and (B)...Laser light was irradiated from the silicon 2 side under the same conditions as in the above example. (C)... Laser light irradiated from the sapphire 1 side, (D)... (B), (C
1200°C60 in N2 instead of laser light irradiation in 1.
Heat treated for 30 minutes.

I followed the four types. The results (defect density) were as shown below.

(A) 10-15 x 103/cIrL (B) 8.2-11.5 X 103/me (C)
1.0~1.3X10"/crfL(D) 10~1
5×10 3 /CrrL A method of irradiating amorphous silicon deposited on a crystalline silicon substrate with a pulsed laser beam from the silicon side is known (Japanese Patent Publication No. 49-47630).

Comparing the results of (A) and (B) using this known method, it appears to be somewhat effective.

However, the method of the present invention has shown greater effects.

The reason for this is not clear, but one reason seems to be that by irradiating the laser beam from the substrate side, heat propagates from the substrate toward the silicon side, and the temperature becomes higher at the interface with the substrate.

In addition, heating efficiency is high by using an insulating substrate having optical transparency.

That is, since the substrate absorbs only a small amount of energy, the semiconductor film is efficiently heated by the laser beam.

Comparing the experimental results (B) and (C), it can be seen that the lattice defect density is significantly reduced when the laser beam is irradiated from the substrate side.

Moreover, when compared with (3), the lattice defect density of (C) was reduced to a sufficiently low level.

As described above, the present invention significantly reduces the lattice defect density of the semiconductor film on the insulating substrate, and the performance of integrated circuits manufactured using this material includes faster operation speed and reduced power consumption. The effect of this can be obtained.

The substrate may be an insulating single crystal substrate having optical transparency.

In addition to sapphire (α-A1203), spinel (M
go41203), beryllium oxide (Beo), silica (α5t02), thorium dioxide (Tho2), and the like.

In addition to silicon, germanium (Ge) is used as a semiconductor film.
), gallium arsenide (GaAs), gallium phosphide (G
It was confirmed that binary compounds such as aP) and boron phosphorus (BP), as well as ternary to multi-element compounds, have similar effects.

Laser irradiation conditions can be selected appropriately depending on wavelength, pulse width, and irradiation energy.

However, the wavelength is preferably in a wavelength range that is absorbed by the semiconductor and transmitted through the insulating substrate.

In addition, in the case of silicon, the wavelength is 1.1 μm or less, the pulse width is 10 nSeC to 3 m5 eC, the irradiation energy is 2 to 10
A similar effect can be obtained under conditions such as J/d.

Furthermore, although the silicon film thickness was 0.7 .mu.m in the example, sufficient effects were found when experiments were actually conducted with a thickness of 0.02 .mu.m to 10 .mu.m.

Further, it is preferable that both sides of the sapphire substrate be mirror-polished, but even if the back surface is roughly polished, it is of course sufficient to irradiate the substrate with laser light to compensate for energy loss due to scattering.

In the examples, laser irradiation was performed immediately after silicon growth.

However, when manufacturing a semiconductor device, the process is not limited to this, and may be performed during or after forming elements on the semiconductor film.

For example, a silicon gate MOS device is taken as an example of a semiconductor device having an SO8 structure (FIG. 2).

Laser light irradiation was performed after the element shown in FIG. 2 was formed in a semiconductor film.

When using polysilicon 3 for gate electrode as wiring 4, after depositing polysilicon 3 and 4, a laser beam F is applied.
By irradiating the polycrystalline silicon 3 and 4, it is possible to reduce the resistance of the polycrystalline silicon 3 and 4 for gate electrodes and interconnections in addition to improving the crystallinity described above.

5 is a sapphire substrate, 6 is an island region formed by etching a semiconductor film, and 7 is a gate oxide film.

Further, 8 is a source, and 9 is a drain. The polycrystalline silicon film was actually doped with phosphorus.

A film with a thickness of 0.3 μm and a surface resistance of 20 Ω/b is
After annealing, the surface resistance became 10Ω/b.

In this case, the process may be performed at any time after the deposition of polycrystalline silicon.

Similar effects were also obtained with polysilicon films doped not only with phosphorus but also with boron and arsenic.

In this way, laser annealing of the epitaxial Si film may be performed during or at the end of the device manufacturing process.

Note that the effect can be expected even if the semiconductor film is not only single crystal but also amorphous or polycrystalline.

[Brief explanation of the drawing]

FIG. 1 a = b is a process cross-sectional view for explaining one embodiment of the present invention, and FIG. 2 is a cross-sectional view for explaining another embodiment of the present invention. In the figure, 1, 5... sapphire substrate, 2...
...Silicon film, 3...Polysilicon for gate electrode. 4...Polysilicon for wiring, 6...Semiconductor island region. 7... Kate oxide film, 8... Source,
9...Drain.

Claims (1)

[Claims] 1. A semiconductor film is deposited on an insulating substrate having optical transparency,
A method for manufacturing a semiconductor device, comprising the step of irradiating a semiconductor film with laser light from the insulating substrate side. 2. The method of manufacturing a semiconductor device according to claim 1, wherein the laser light irradiation is performed during or after forming the element on the semiconductor film.