Coating processes – Electrical product produced – Integrated circuit – printed circuit – or circuit board
Patent
1988-10-28
1990-01-16
Pianalto, Bernard
Coating processes
Electrical product produced
Integrated circuit, printed circuit, or circuit board
427237, 427253, 4272552, B05D 306
Patent
active
048942561
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for reactive deposition of tubular metal bodies on a tubular substrate from a flowing gas phase containing a metal halide, a glow discharge being generated between an inner electrode and an outer electrode, one of which is of tubular construction and serves as substrate.
A process of this type is known from European Published Application No. 204,356 which corresponds to U.S. Pat. No. 4,713,259. In the process described therein, a controlled reciprocating movement of the inner electrode relative to the outer electrode takes place. Between the inner electrode and the outer electrode, a locally limited glow discharge zone is produced which is maintained during the deposition. At the same time, steps are taken to prevent the formation of electrically conducting layers on electrically insulating structural parts in the reaction chamber. The temperature in the substrate region is kept constant at a low value at which the thermal deposition rate is small compared with the glow discharge deposition rate.
In the known process, mass flows of tungsten fluoride of up to 50 sccm, i.e. up to 50 cm.sup.3 /min, referred to standard conditions (0.degree. C., 10.sup.5 Pa), are used. The known process has the disadvantage that in some cases an unexpectedly low yield of the metal deposition is obtained.
The invention is based on the object of ensuring a high metal deposition.
This object is achieved, according to the invention in that, in a process of the type mentioned in the introduction, the reactive deposition from the gas phase is carried out in the high plasma resistance range.
A preferred technique for establishing the high plasma resistance is to adjust the absolute mass flow of the metal halide to at least 60 sccm. An increase in absolute mass flow of the metal halide is limited only by the flow cross section in the mass flow regulator used in the particular case.
Additional advantageous measures for achieving a high metal deposition, in some cases even 100%, consist in, 0.4 A and/or molybdenum or rhenium and also, additionally, an inert gas and hydrogen, and/or contains at least one organometallic compound of an element of group IIIb of the periodic system (scandium group and actinides) as a further component, and/or molecular ratio H.sub.2 :WF.sub.6 =6 to 8:1, and/or serving as a substrate and an inner electrode, the length of the part of the inner electrode which projects into the glow discharge being equal to the inside diameter of the outer electrode or greater than the inside diameter thereof.
The process according to the invention has the advantage that, as a result of the high yield achieved, the waste disposal problem has decreased at the same time.
Processes for reactive deposition of layers and shaped bodies from a gas phase are known as CVD processes. Processes in which the deposition reaction is activated by a plasma are known as PCVD processes.
The teaching of using a high plasma resistance in a PCVD process in which electrically conducting layers are deposited is based on investigations of the direct current glow discharge in a gas mixture composed of tungsten hexafluoride (WF.sub.6), hydrogen (H.sub.2) and argon (Ar) in which novel and hitherto unexpected properties of the plasma were found, the knowledge of which is necessary for an optimum process control and process yield. It was established that, depending on the absolute WF.sub.6 mass flow, two different plasma states of the WF.sub.6 +H.sub.2 +Ar plasma exist which differ primarily in the plasma resistance. Depending on the geometry and process parameters such as pressure, temperature and glow-discharge current, either a fairly abrupt or a continuous transition between the two states is obtained in a plot, shown in the drawing, of the voltage drop U.sub.p1 between cathode and anode against the absolute WF.sub.6 mass flow Q.sub.abs (WF.sub.6) with otherwise constant conditions. In this connection, the high plasma resistance state is reached at an absolute WF.sub.6 mass flow or flow rate of about 60 sccm. However,
REFERENCES:
patent: 4713259 (1989-12-01), Gartner et al.
Gartner Georg F.
Janiel Peter A.
Pianalto Bernard
Spain Norman N.
U.S. Philips Corporation
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