JP2972066B2 - Method for manufacturing porous silicon film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a porous silicon film, which shortens the wavelength of photoluminescence light from the porous silicon film and further increases the light emission luminance.

[0002]

2. Description of the Related Art When single-crystal silicon and a platinum plate are placed in a chemical conversion solution containing hydrofluoric acid as a main component, the single-crystal silicon is used as an anode, and the platinum plate is used as a cathode. When the density is higher than a certain value, a mirror-like electric field polishing occurs, but a porous silicon layer is formed. In this porous silicon, photoluminescence not observed in ordinary silicon is observed. As a method for shortening the wavelength of the photoluminescence light and increasing the emission luminance, it is once left in the air after formation and then immersed again in a hydrofluoric acid solution, so that the dangling bond of the porous silicon is hydrogen or oxygen. A method of terminating and further improving the crystallinity of the porous layer is known.

[0003]

However, with the conventional method, the crystallinity is not sufficiently improved, so that further reduction in the wavelength of photoluminescence light and increase in light emission luminance cannot be expected.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and comprises forming a porous silicon film by anodizing single crystal silicon in a hydrofluoric acid solution, followed by ion doping. 1 × 10 ¹⁵ atoms / at an acceleration voltage of 10 keV or more and 500 eV or less
An object of the present invention is to provide a method for manufacturing a porous silicon film in which hydrogen ions of not less than 1 cm ^{2 and not} more than 1 × 10 ¹⁷ atoms / cm ² are implanted.

Another object of the present invention is to provide a method for manufacturing a porous silicon film which does not require a new heat treatment immediately after the ion implantation step.

[0006]

As described above, by supplying hydrogen by the ion doping method, it is possible to further reduce the dangling bonds of the porous silicon, and it is not necessary to perform a heat treatment. It can be manufactured.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of a main part for explaining anodization. HF: H ₂ O = 1 filled in the reaction cell 4: 1
An anode composed of a p-type silicon substrate 1 and a cathode composed of a platinum electrode 2 are immersed in a 1 (by volume) hydrofluoric acid solution 3. When a constant current is passed at a current density of 20 mA / cm ² for about 2 minutes, an electrochemical reaction occurs, and a porous silicon layer having a thickness of 1 μm is formed on the surface layer of the p-type silicon substrate 1. Subsequently, hydrogen ions are implanted at 5 × 10 ¹⁵ atoms / cm ² at 100 keV using an ion doping apparatus to obtain porous silicon having a sufficiently terminated dangling board (sample 1). Generally, heat treatment is performed after ion doping, but is not performed in this embodiment.

As a comparative example, porous silicon formed by anodization (sample 2), after anodization, allowed to stand in the air for 2 hours, and immersed again in a solution having the same concentration as the hydrofluoric acid solution 3 for 10 minutes. 1. Prepare porous silicon (sample 3).

When the crystallinity of the porous layer of each of Samples 1, 2, and 3 was examined by the X-ray two-crystal method, the crystallinity was good in the order of Sample 1, Sample 2, and Sample 3. It was confirmed that the crystallinity of the porous layer was improved.

When the Si—H bond and the dangling board were examined by the Fourier transform infrared spectroscopy and the electron spin resonance method, as shown in FIG.
It was confirmed that there were many H bonds and few dangling boards.

Further, the cross-section of the porous layers of Samples 1, 2 and 3 has a wavelength of 488 nm, a power of 0.5 mW and a beam diameter of 1 μm.
By irradiating the sample with an argon laser and examining the wavelength and emission intensity of the photoluminescence light, as shown in FIG. 3, it was confirmed that the sample 1 was most able to shorten the wavelength of the photoluminescence light and to improve the emission intensity (FIG. 3). 12 is sample 1, 13 is sample 2, and 14 is sample 3).

In the above embodiment, the hydrogen ions are converted to 100 k
5 × 10 ¹⁵ atoms / cm ² at eV (As a result of SIMS analysis, the peak concentration was 5 × 10 ²² atoms / cm ² , but in this embodiment, 1 × 10 ¹⁵ atoms / cm 2 at an acceleration voltage of 10 keV or more and 500 keV or less. ² or more 1 × 1
It is necessary to keep it within the range of 0 ¹⁷ atoms / cm ² or less. Outside this range, the crystallinity of the porous silicon is impaired, and the emission intensity is reduced.

[0014]

According to the present invention, since the crystallinity of porous silicon is improved, it is possible to further shorten the wavelength of photoluminescence light and increase the emission luminance.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part for explaining anodization.

FIG. 2 is a view showing experimental results of one example of the present invention and a conventional example by an electron spin resonance method.

FIG. 3 is a diagram showing the wavelength and emission intensity of photoluminescence light according to one embodiment of the present invention and a conventional example.

[Explanation of symbols]

 Reference Signs List 1 p-type silicon substrate 2 platinum electrode 3 hydrofluoric acid solution 4 Teflon anodizing reaction cell 5 constant DC power supply

────────────────────────────────────────────────── ─── Continued on the front page (58) Fields surveyed (Int. Cl. ⁶ , DB name) H01L 33/00 H01L 21/02 JICST file (JOIS)

Claims (2)

(57) [Claims] After a porous silicon film is formed by anodizing single crystal silicon in a hydrofluoric acid solution, an ion doping method is performed at an acceleration voltage of 10 keV or more and 500 keV or less to 1 × 10 ¹⁵ atoms / cm ² or more. × 1
A method for producing a porous silicon film, comprising ion-implanting hydrogen of not more than 0 ¹⁷ atoms / cm ² . 2. A method for manufacturing a porous silicon film, wherein a new heat treatment is not required immediately after the step of ion implantation.