Silicon film formation by chemical transport in atmospheric-pressure pure hydrogen plasma

Abstract

To prepare polycrystalline silicon (poly-Si) films at low temperatures (<400°C) with high deposition rate, we propose a chemical transport method using atmospheric-pressure pure hydrogen plasma, called the atmospheric-pressure enhanced chemical transport method. In this method, high-pressure (200–760Torr) stable glow plasma of pure hydrogen was generated by a 150MHz very high frequency power between the two parallel electrodes less than 2mm apart. One of the electrodes is composed of the cooled Si solid source and the other the heated substrate (200–400°C). According to the temperature dependence of hydrogen etching rate of Si, SiHx species are mainly generated at the cooled Si solid source by hydrogen atoms. These species are again decomposed in the plasma, transported to the substrate to form Si films. In the present experiments on poly-Si film formation, a high deposition rate of 300nm∕min was achieved at 400°C, and nearly ideal utilization efficiencies (>93%) of Si solid source was realized in every condition. Si grains formed on a (001) Si substrate revealed anisotropic morphology elongated along ⟨110⟩ directions, and most of them had columnar structures epitaxially grown to the thickness of 2μm even at 200°C.

High‐rate preparation of thin Si films by atmospheric‐pressure plasma enhanced chemical transport

“…This implies that the part of Si grain has the same orientation as substrate. From the above results, the Si film morphology on Si substrate reveals the same structure as previous report, [5] even if the R d increases to 15 nm/s. This means that the poly-Si film could be prepared independently of R d by APECT.…”

“…[5] This method needs no source gas because SiH x molecules are generated in the hydrogen plasma by the etching of solid Si source, and a high deposition rate of 5 nm/s has been attained. Generally, it is well-known that the crystalline fraction of Si film decreases with increasing deposition rate in low-temperature process.…”

Purified Silicon Film Formation from Metallurgical-Grade Silicon by Hydrogen-Plasma-Induced Chemical Transport

“…[12][13][14][15][16] In this review article, we describe two new processes to produce purified Si material directly from MG-Si based on the APECT principle. One is the formation of purified Si films using a 150 MHz very high frequency (VHF) H 2 plasma, which is generated in a narrow plasma gap (proximity-type APECT).…”

“…One is the formation of purified Si films using a 150 MHz very high frequency (VHF) H 2 plasma, which is generated in a narrow plasma gap (proximity-type APECT). [12][13][14][15] The other is a new process of SiH 4 gas formation directly from MG-Si using 2.45 GHz microwave H 2 plasma (remote-type APECT). 16,17) Although the experiments were performed in the H 2 pressure range from 100 to 760 Torr, the acronym ''APECT'' is used throughout this article.…”

High rate synthesis of crystalline silicon films from SiH4+He using high density microwave plasma

“…Many efforts have been explored for this aim, ranging from the use of high-pressure-depletion conditions and multiholecathode electrode structure to the investigations of new plasma sources such as the microwave plasma, the expanding thermal plasma, and the atmospheric pressure plasmas. [14][15][16][17][18][19] Quite some knowledge has been obtained about the crystalline Si film deposition process and the optimum plasma chemistry for high quality film fabrication. It is commonly considered that SiH 3 is the main precursor responsible for the film growth and atomic hydrogen H plays an essential role for the film crystallization.…”