JPH0379023A - Method of improving silicon monocrystal film - Google Patents

Abstract

PURPOSE:To reduce crystal defect and improve element characteristics by a method wherein silicon is ion-implanted along a low index crystal axis of a silicon monocrystalline film and annealing is done with respect to the silicon monocrystalline film formed on an insulation film. CONSTITUTION:After silicon ions are implanted along a low index crystal axis of a silicon monocrystalline film on a silicon dioxide film obtained conventionally, annealing is performed. For example, silicon ions 4 are implanted into a silicon substrate 1 under the conditions of implantation energy of 70keV and dosage of 5X10<14>cm<-2> in a perpendicular direction, that is, <001> direction into a silicon substrate 1 and annealing at 1000 deg.C for 1 hour is performed in N2 atmosphere. Thus crystal defects remaining in the silicon monocrystalline film 3 formed on the silicon dioxide film 2 can be largely reduced thereby improving obtained element characteristics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for improving a silicon film, and more particularly to a method for reducing defects present in a silicon film formed on a silicon dioxide film.

[Conventional technology]

A silicon single crystal film on an insulator, so-called 5OI (Sil
This structure has advantages such as reduced stray capacitance and improved latch-up resistance. This SOI structure can be achieved, for example, by forming a silicon polycrystalline film on a silicon dioxide film and melting it with laser light or a heater, or by implanting high concentration oxygen ions into the silicon substrate and annealing it. The so-called S IMOX (f
ieparation by LplantedQx
ygen) method is known.

[Problem to be solved by the invention]

A disadvantage is that lattice defects such as dislocations and stacking faults often remain in the silicon single crystal film on the silicon dioxide film formed by the method described above, which adversely affects the characteristics of devices formed there.

[Means to solve the problem]

The improved method of the present invention is characterized by implanting silicon ions along the low index crystal axis into a silicon single crystal film on a silicon dioxide film obtained by a conventional method, and then annealing.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a longitudinal sectional view of one embodiment of the present invention.

The substrate was formed by SIMOX method, (OO1)
Oxygen ions are implanted into the silicon substrate 1 at an energy of 180K.
eV and a dose of 2 x 10 "cm-" and annealed at 1200° C. for 6 hours in a N2 atmosphere. By this annealing, a silicon dioxide layer 2 of about 500 nm is formed in the silicon substrate, and a single crystal silicon layer 3 of about 150 nm is formed on the surface.

When the SIMOX substrate formed under these conditions was observed using a cross-sectional electron microscope, about one lattice defect was observed every 100 to 150 nm. In this way, silicon ions 4 are implanted into the substrate at an energy of 70 KeV and a dose of 5
Injected into the substrate from the vertical direction, that is, <000 direction, under the condition of IQ 14 am-'', annealed at 1000° C. for 1 hour in N2, and observed with a cross-sectional electron microscope.
No defects were observed. This silicon film has a MOS (
Metal-oxide-semiconductor
r)) When a transistor was formed and investigated, the leakage current was improved by about two orders of magnitude.

When a substrate was used in which the substrate temperature during ion implantation was lowered from room temperature to liquid nitrogen temperature, leakage current was further improved by about 1/2 digit.

FIG. 2 is a longitudinal sectional view of another embodiment of the invention.

Silicon dioxide film 12 formed on silicon substrate 11
An opening 13 is provided in the polycrystalline silicon film 14 , and the polycrystalline silicon film deposited thereon is melted by the lamp light, forming a single crystal silicon film 14 .
It becomes. In such a structure, since the opening 13 serves as a seed during single crystallization, a silicon film 14 having the same orientation as the substrate is formed on the silicon dioxide film 12, but the defect density increases as the distance from the opening 13 increases. .

This silicon film 14 has a direction perpendicular to the substrate, that is, <001
> Inject silicon ions 15 from the direction with an energy of 200
KeV, the dose was 7 x 1014 an-'', and 7 anneals were performed at 1000°C for 1 hour in %N2. When the etch bit was taken out and observed, the defect density was significantly increased within a range of about 300 μm from the opening. A significant decrease was observed.

〔Effect of the invention〕

As explained above, the present invention has the effect of significantly reducing lattice defects remaining in a silicon single crystal film formed on a silicon dioxide film. This is because the silicon ions implanted along the low index axis intensively destroy the disordered parts of the crystal, that is, the parts where defects exist. Silicon ions pass through the single crystal part without causing much damage to the crystal, but when they reach the defective part, channeling is inhibited, causing damage to the crystal in the defective part, and if the dose is high to a certain extent, the silicon ion passes through the crystal without causing much damage. Only the crystalline material will be made amorphous. Thereafter, when solid phase growth is caused by annealing, single crystallization occurs without forming defects, except when strong stress is applied. Since channeling becomes more pronounced at lower temperatures, silicon implantation at liquid nitrogen temperature has a greater effect as shown in Example 1.

This method has the advantage of causing less damage to the single crystal region, and hardly impairs the characteristics of the final device. Furthermore, since channeling is used and the defect is destroyed in a self-aligned manner, it can be applied to a wide range of film thicknesses and a wide range of defect densities, as seen in the other embodiments.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view for explaining one embodiment of the present invention;
FIG. 2 is a longitudinal sectional view for explaining another embodiment of the present invention. ■・・・・・・(OO1) Silicon substrate, 2・・・・・・
・Silicon dioxide layer, 3... Single crystal silicon layer, 4... Silicon ion, 11... (
001) Silicon substrate, 12... Silicon dioxide layer, 13... Opening, 14... Silicon film, 15... Silicon ion.

Claims (1)

[Claims] A method for improving a silicon single crystal film, comprising the steps of implanting silicon ions into a silicon single crystal film formed on an insulating film along a low index crystal axis of the silicon single crystal film, and annealing the silicon single crystal film. .