DE1694504C3 - Process for the epitaxial growth of silicon carbide - Google Patents

Description

The invention relates to a method for epitaxial viewing Growth of silicon carbide on a crystalline seed crystal of silicon carbide by pyrolytic Decomposition of gases containing silicon and carbon, with a chlorine-free silane and aliphatic Hydrocarbon-containing gas is used, according to patent 1,467,085.

In the process described in the main patent 1,467,085, a mixture of gaseous substances containing silicon and hydrocarbons is fed to the reaction vessel under normal pressure by means of a flowing inert tear gas. This process has various advantages over the older process in which silicon _{tetrachloride (SiCl 4} ) and carbon tetrachloride (CCl ₄ ) are reduced with hydrogen. The most important advantage is that the hydrogen and the harmful reaction products formed during pyrolytic decomposition only occur in such small quantities that they practically no longer attack the reaction vessel and the base of its nucleus.

The main patent achieved with the method according to J *., · Ι However, the growth rate of the monocrystalline layer is not much higher than that after the older method. An increase in the rate of growth but would be very desirable, for example with slow growth of the layers no pn junctions achieved with the desired sharpness because of the diffusion phenomena that occur can be. The object of the invention is therefore to apply the method of the main patent to this effect to improve that a higher growth rate is achieved.

In the method mentioned at the outset, this object is achieved according to the invention in that During the Aufwachsproztsses a negative pressure is maintained in the reaction vessel, which between one torr and one hundredth of a torr. Through this measure it was possible to do one about ten times to achieve a higher growth rate compared to the previous method. When growing polycrystalline SiC, for example, even growth rates of 100 u per minute have been achieved. A Another advantage of the process is that the silanes and hydrocarbons and the dopants containing gases are sucked into the reaction chamber by the negative pressure. This allows the previously used inert carrier gases, which, like all substances used, must be extremely pure and therefore make the process more expensive, omitted.

An advantageous embodiment of the method according to the invention is that the growth rate controlled by the size of the negative pressure will.

The invention is based on the in the figure

Schaubitdiich illustrated embodiment described.

The graphite or tantalum block 2 is arranged in the reaction vessel 1, which consists of quartz. The monocrystalline SiIi-

Zium carbide seed 4, on the surface in the epitaxial process a single crystal layer can be applied to rope. The block 2 and thus also the germ 4 are heated to a temperature of about 1400 ° C. by means of the induction coil 5.

A gas mixture consisting of monosilane (SiH ₄ ) and propane (C ₃ H ₈ ) is passed through the pipe 6 into the Rcaklionsgefäß, which is immediately above the surface of the SiC nucleus 4 heated to about 1400 ° C in silicon carbide and hydrogen epitaxial growth of SiC on the nucleus.

Gas mixtures with a doping effect are supplied through the pipe 7 and with that through the pipe 6 mixed gas supplied. For example, for

η-type impurity as the gaseous phosphorus hydride phosphine (PH.,) or nitrogen (N ₂₎ and for p-Doticrung as a gaseous boron hydride, diborane (B ₂ H ₀₎ or the aluminum borane compound Al (BHJ ₃ introduced into the reaction vessel.

While the growth process is being carried out, an is connected to the suction line 8 Pump to maintain a negative pressure in the reaction vessel, which is between one Torr and one hundredth of a Torr. As a result, the gases supplied via lines 6 and 7 are in the Reaction chamber sucked without the use of carrier gases is required. To influence the growth rate of the epitaxial layer is regulated by the negative pressure. He can use the the valves 9 and 10 of the pipes 6 and 7 attached micrometer screws 11 and 12 very can be set precisely.

1 sheet of drawings

Claims (2)

Patent claims: 1. Process for the epitaxial growth of silicon carbide on a crystalline seed crystal from silicon carbide by pyrolytic decomposition of silicon and hydrocarbons containing gases, one containing chlorine-free silanes and aliphatic hydrocarbons Gas is used according to patent 1,467,085, characterized by the fact that during the Growing process in the reaction vessel, a negative pressure is maintained between a Torr and one hundredth of a Torr. 2. The method according to claim 1, characterized in that the growth rate is controlled by the size of the negative pressure.