Semiconductor device manufacturing: process – Formation of semiconductive active region on any substrate – Amorphous semiconductor
Patent
1996-05-17
1998-12-22
Dutton, Brian
Semiconductor device manufacturing: process
Formation of semiconductive active region on any substrate
Amorphous semiconductor
438485, H01L 2120, H01L 2136, C30B 0000
Patent
active
058519041
DESCRIPTION:
BRIEF SUMMARY
RELATED APPLICATION
This application is a 35 U.S.C. .sctn. 371 application of PCT/DE94/01158, filed on Sep. 29, 1994.
BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates to a method of manufacturing microcrystalline layers from elements of the fourth principal group of the periodic system, such as silicon, germanium or tin, and to a method of manufacturing luminescent silicon structures, solar cells and transistors.
The invention further relates to the layers or products manufactured according to these methods.
Microcrystalline layers, particularly of silicon, due to their optical and electronic properties and also due to the possibility of separating the layers at lower temperatures (200.degree. to 300.degree. C.) are becoming increasingly important. Preferred fields of application for such layers are solar cells and thin layer transistors like LEDs.
A conventional method for separating microcrystalline silicon (.mu.c-Si) is the CVD method. Manufacture of the layers in this case is undertaken by using SiH.sub.4 in hydrogen as a process gas. SiH.sub.4 is used in an intensely diluted form in hydrogen (less than 5% by volume) (T. Hamasaki, H. Kurata, M. Hirose, Ul. Osaka, Appl. Phys. Lett. 37 (1980) 1084). The low temperature formation of the crystalline phase may in this case be understood to be an equilibrium between the silicon deposition and the removal of the regions with unsequenced Si-Si bonds by the atomic hydrogen. This process is termed hydrogen etching (C. C. Tsai, G. B. Anderson, R. Thompson, B. Wacker, J. Non-Cryst. Sol. 114 (1989) 151). A problem of this conventional PE-CVD is that the growth of the sequenced microcrystalline Si layer requires mild plasma conditions, in comparison to which the production of the required atomic hydrogen requires for hydrogen etching a high pressure and a high power of the hydrogen plasma. Another problem is that the deposition rate is very low at 0.5 to 1 nm/min (5 to 10 .ANG./min).
In order to solve this problem, in the interim a plurality of cyclic methods of manufacturing .mu.c-Si:H and related layers such as .mu.c-Si:Ge:H have been proposed, all of which provide for a separation into two process steps. According to this, in a first step, for example, an amorphous SiH layer is deposited under the conditions favorable for Si deposition, and then in a second step the hydrogen etching is undertaken under the conditions necessary for hydrogen etching (A. Asano, T. Ichimura, H. Sakai, J. Appl. Phys. 65 (1989) 2439. A. Asano, Appl. Phys. Lett. 56 (1990) 533). Hydrogen treatment is carried out in such a way that a constant flow of hydrogen is passed into the CVD reactor over the substrate.
It has however become apparent that even this cyclic method does not provide satisfying results as regards the deposition rate. A further disadvantage is that the step of hydrogen etching is extremely difficult to control.
Proceeding from this prior art the object of the present invention is to propose a new cyclic method for a deposition of microcrystalline layers from elements of the IVth principal group, by means of which it is possible better to control the step of hydrogen etching and to achieve clearly higher deposition rates than were previously possible. A further object of the present invention is to propose applications of interest with such layers.
It has become surprisingly apparent that, when the conventional method for manufacturing the microcrystalline layers, in the second process step, i.e., during hydrogen treatment, is so converted that the hydrogen treatment is carried out in a closed system, clearly higher deposition rates are achieved. The microcrystalline layers produced in this way are particularly characterized in that the microcrystalline layer has a crystallite proportion of 20 to 95%, so called element dots, i.e., spatially defined crystallites, being formed.
The procedure in the hydrogen treatment according to the invention is such that, after deposition of the amorphous layer, with conventional process gases and under conventional condit
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Fischer Thomas
Koynov Svetoslav
Schwarz Reinhard
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