JPH0570928B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a method for manufacturing a semiconductor crystal thin film on an insulating substrate such as SOS.

[Prior art and its problems]

Integrated circuits using a silicon film on an insulating substrate, particularly an insulating single crystal substrate, are structurally more advantageous than those using a semiconductor substrate in terms of higher density and higher speed. On the other hand, since a single crystal film of a different type is grown on a substrate, the silicon film has the disadvantage of having a high density of lattice defects.

For example, when we fabricated a MOS device using SOS (silicon film on a sapphire single crystal substrate) and investigated its basic characteristics, we found an increase in drain leakage current and a decrease in inversion layer mobility compared to bulk silicon MOS devices. It will be done. The former is caused by a recombination current generated near the drain side, and the latter is caused by scattering of carrier carriers because there are many scattering centers in the silicon film. Since these are both caused by lattice defects, it is required to significantly reduce them and to electrically inactivate deep levels created by lattice defects.

[Purpose of the invention]

An object of the present invention is to reduce lattice defects existing in semiconductor thin films and to electrically inactivate deep levels caused by lattice defects, thereby providing insulation for semiconductor devices with excellent characteristics. The objective is to obtain a semiconductor crystal thin film on a substrate.

[Summary of the invention]

In the present invention, a halogen compound of the semiconductor is ion-implanted into a semiconductor crystal thin film formed on an insulating substrate to make a part of the semiconductor film amorphous, and then the amorphous layer is recrystallized by heat treatment to form a semiconductor film. The electrical properties of the semiconductor thin film are improved by removing the lattice defects contained therein and inactivating the unpaired electrons in the lattice defects by the ion-implanted halogen atoms.

〔Effect of the invention〕

According to the present invention, the lattice defect density in the semiconductor film is greatly reduced by making it amorphous by ion implantation and the subsequent heat treatment, and the unpaired electrons formed by the still existing lattice defects are removed from the halogen. The electrical properties of the semiconductor thin film are approximately the same as those of the bulk semiconductor.

[Embodiments of the invention]

Embodiments of the present invention will be described in detail with reference to the drawings. In FIG. 1, the insulating substrate 11 (11
A sapphire single crystal substrate having a 0, 2) plane was used. A silicon (Si) film 12 with a thickness of 0.3 μm was deposited thereon. The growth method is chemical vapor deposition (CVD), and the conditions are a growth temperature of 950℃ and a growth rate of 2μ.
m/min, a (001) silicon single crystal film is formed (FIG. 1a). Next, a silicon fluorine compound (SiF ⁺ ) was selected as the ion species, and the acceleration voltage was set to 170 kV so that the projected range (Rp) was approximately at the center of the silicon film, and the dose was 2 × 10 ¹⁵
Ions are implanted into the silicon film 12 under cm ^-2 conditions to make the silicon surface side amorphous 13 . (1st
Figure b). Next, at 1000℃, in a _N2 gas atmosphere,
Heat treatment is performed for a minute to recrystallize the amorphous silicon layer 13 in a solid-phase epitaxial manner (FIG. 1c).

Using the sample thus obtained, next
We fabricated a MOS device and evaluated its characteristics. The prototype was manufactured using a commonly used polycrystalline silicon gate process. As a result of evaluating N-channel and P-channel MOS transistors, the carrier mobility of N-channel transistors is 800 cm ² /V.
sec, 220cm ² /V for P channel transistor.
sec, which was found to be significantly higher than the carrier mobility of 450 cm ² /V·sec (N channel) and 180 cm ² /V·sec (P channel) in conventional SOSMOS transistors. In addition, the drain leakage current is also 1
Much improved from ×10 ^-10 A/μm to 1×
It became 10 ^-12 A/μm. The reason for this significant improvement in carrier mobility and drain leakage current is that the lattice defect density in the recrystallized silicon layer decreases and that fluorine electrically inactivates unpaired electrons due to lattice defects. It is possible to do so.

[Other embodiments of the invention]

In order to further improve the crystallinity on the silicon interface side of the SOS film obtained through the steps described above, the steps shown in FIG. 2 can be performed. That is,
Acceleration energy of SiF 350KeV, dose 1×
Ions are implanted into the silicon film 22 under conditions of 10 ¹⁵ cm ^-2 (FIG. 2a). As a result, the silicon interface side becomes amorphous 23 (FIG. 2b). Next, heat treatment is performed for 20 minutes in a N ₂ gas atmosphere at 1000° C. to recrystallize the amorphous layer 23 from the silicon surface side. After going through this process, the characteristics of the MOS device produced had the effect of further reducing drain leakage current by one order of magnitude.

In this example, ion implantation was performed once each on the interface side and the surface side, but crystallinity can be further improved by repeating the ion implantation and heat treatment steps alternately under the same conditions. .

Furthermore, a silicon single crystal film having a desired thickness can be obtained by further epitaxially growing a silicon film on the silicon single crystal film after implementing the present invention.

The substrate may be an insulating single crystal substrate;
Other than saphire (a-Al ₂ Os), spinunel (MgO.Al ₂ Os), beryllium oxide (BeO), silica (α-SiO ₂ ), thorium dioxide (ThO ₂ ), etc. can be mentioned.

Examples of the semiconductor thin film include zirmanium, tin, and the like in addition to silicon. The ion implantation conditions may be any conditions that allow the formation of the desired amorphous layer, and the ion species may be Si-F systems such as SiF ₂ and SiF ₃ , SiCl, SiCl, etc. in addition to SiF.
Of course, Si--Cl and Si--I compounds such as SiCl ₂ may also be used. Further, the halogen compound may be used for other semiconductors as well.
The heat treatment temperature may be the temperature at which recrystallization occurs.
Furnace treatment at 500° C. or higher, or energy beam irradiation such as laser or electron beam may be used. Furthermore, similar effects were observed in the heat treatment atmosphere using inert gases such as N ₂ gas, O ₂ gas, and Ar gas. The silicon film forming method is not limited to the CVD method, but also includes vacuum evaporation method, molecular beam epitaxial method, etc.

[Brief explanation of the drawing]

1A to 1C are process sectional views for explaining one embodiment of the present invention, and FIGS. 2A to 2C are process sectional views for explaining another embodiment of the present invention. In the figure, 11, 21... sapphire substrate,
12, 22... Silicon single crystal film, 13, 23...
...Amorphous silicon layer, 14, 24... Recrystallized silicon layer.

Claims (1)

[Claims] 1. It includes the steps of making a semiconductor thin film on an insulating substrate amorphous by ion implantation, and then recrystallizing the amorphous region by heat treatment, and using the semiconductor as the ion species in the ion implantation. A method for producing a semiconductor crystal thin film, characterized by using a halogen compound as a constituent element.