Film formation process

A process of forming a film on a substrate, which comprises bringing a substrate into contact with a plasma zone formed by generating, by use of a discharge electrode or discharge electrodes, high temperature or quasi-high temperature plasma of a gas containing at least one carbon containing compound, wherein said electrode comprises a sheet-like electrode provided with a slit having a linear portion and connected to a microwave electric source; or wherein said plasma zone is formed by forcing a high temperature or quasi-high temperature plasma generated in an arc between said electrodes by DC discharge, to move by applying a magnetic field. The process enables formation of films on substrate surfaces in a high energy efficiency.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a process of forming a plasma polymerized film on 
a substrate surface by using a plasma of an organic compound gas, or a 
process of forming a film on a substrate surface by using an inorganic 
compound gas, as exemplified by plasma CVD. More particularly. it is 
concerned with a film formation process that can form the above every sort 
of film on a substrate in a high energy efficiency and is particularly 
suited for forming a film comprising a diamond-like substance. 
2. Description of the Prior Art 
Hitherto utilized in forming films by using every sort of plasma are 
methods in which parallel plate electrodes, hollow cathode cylindrical 
electrodes (which are for use in direct current, low frequency or 
high-frequency electric sources), coils (for use in high-frequency 
electric sources), microwave cavities (for use in microwave electric 
sources) or the like are used to generate plasma. 
Such conventional methods of forming films by using plasma, however, can 
not treat substrate surfaces having a relatively large area. and moreover 
these methods have the problem that they can achieve only a low energy 
efficiency. 
More specifically, when, for example, the microwave cavities are used, the 
plasma that can be generated has inherently such a small volume that they 
are not suited for treating surfaces having a large area. Other plasma 
generating systems enable generation of plasma with a large volume. Since, 
however, only part of the plasma that comes into contact with the 
substrate, can substantially contribute to the formation of films on 
substrate surfaces, it often occurs that almost all part of the large 
volume plasma plays no part in the formation of films, resulting in a low 
energy efficiency. In particular, in instances in which the formation of 
films is carried out in a high-temperature plasma zone, the plasma has 
such a high energy density that making plasma having a large volume may 
bring about a remarkable increase in consumption of the electric power 
necessary for excitation. Thus, this is a great problem in practical 
viewpoints. 
In particular, films comprising a diamond-like substance are expected to be 
put into practical use as diamond tools such as throw-away tips and saws, 
all sorts of sliding parts, heat dissipation plates used in devices such 
as semiconductor lasers, IC packages and hybrid ICs, etc. For that 
purpose, however, it is strongly required to make it possible to prepare a 
diamond-like substance having a large area, and to improve productivity 
and enhance economical merits. However, in the above conventional method 
utilizing microwave plasma, the plasma that can be generated has 
inherently a small volume since there is used a microwave cavity. Hence, a 
film obtainable by making treatment once can have only a film area as 
small as several square centimeters, and can be applied with difficulty 
when substrates have a large substrate surface as in large tools, large 
machine parts, etc. Also, even when the substrates to be treated are of 
small size, it is impossible to treat a large number of substrates in one 
time, bringing about the problem that there can be achieved low 
productivity and economical merits. Moreover, an attempt to make large the 
microwave cavity may result in a lowering of energy absorption efficiency, 
making it impossible to generate a high temperature plasma necessary for 
the formation of films. 
SUMMARY OF THE INVENTION 
Accordingly, an object of this invention is to provide a process that can 
form every sort of film in a high energy efficiency. 
As a means for achieving the above object, this invention provides a 
process of forming a film on a substrate, comprising; 
bringing a substrate into contact with a plasma zone formed by generating 
by use of a discharge electrode a high temperature or quasi-high 
temperature plasma of a gas containing at least one selected from the 
group consisting of an organic compound and an inorganic compound; 
wherein said electrode comprises a sheet-like electrode provided with a 
slit having a linear portion and connected to a microwave electric source 
(hereinafter called "the first process"). 
As another means for achieving the above object, this invention also 
provides a process of forming a film on a substrate, comprising: 
bringing a substrate into contact with a plasma zone formed by generating 
by use of discharge electrodes, a high temperature or quasi-high 
temperature plasma of a gas containing at least one selected from the 
group consisting of an organic compound and an inorganic compound; 
wherein said plasma zone is formed by forcing a high temperature or 
quasi-high temperature plasma generated in the form of an arc between said 
electrodes by DC discharge, to move by applying a magnetic field 
(hereinafter called "the second process"). 
The above processes of this invention enables formation of films on 
substrate surfaces in a high energy efficiency. In particular, the first 
process enables formation of films in a high energy efficiency, on 
substrate surfaces having a large area, and the second process enables 
formation of films in a large film formation rate and with a uniform 
thickness even with use of a relatively low energy.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Of the compounds usable as a component of the gas subjected to the 
electrical discharge in the first process and second process of this 
invention, the organic compound may include, for example, chain or cyclic 
saturated hydrocarbons such as methane, ethane, propane, butane, pentane, 
octane and cyclohexane; unsaturated hydrocarbons containing a double bond 
or triple bond, such as ethylene, propylene, butadiene, benzene, styrene, 
acetylene and allene; halogenated alkanes such as monofluoromethane, 
difluoromethane, trifluoromethane, tetrafluoromethane, monochloromethane, 
dichloromethane, trichloromethane, tetrachloromethane, 
monofluorodichloromethane, monofluoroethane, trifluoroethane, 
tetrafluoroethane, pentafluoroethane, hexafluoroethane, dichloroethane, 
tetrachloroethane, hexachloroethane, difluorodichloroethane, 
trifluorotrichloroethane, monofluoropropane, trifluoropropane, 
pentafluoropropane. perfluoropropane, dichloropropane, tetrachloropropane, 
hexachloropropane, perchloropropane, difluorodichlropropane, 
tetrafluorodichloropropane, bromomethane, methylene bromide, bromoform, 
carbon tetrabromide, tetrabromoethane, pentabromoethane, methyl iodide, 
diiodomethane, monofluorobutane, trifluorobutane, tetrafluorobutane, 
octafluorobutane, difluorobutane, monofluoropentane, pentafluoropentane, 
octachloropentane, perchloropentane, trifluorotrichloropentane, 
tetrafluorohexane, nonachlorohexane, pentafluorotrichlorohexane, 
tetrafluoroheptane, hexafluoroheptane, trifluoropentachloroheptane, 
difluorooctane, pentafluorooctane, difluorotetrafluorooctane, 
monofluorononane, hexafluorononane, decachlorononane, 
heptafluorohexachlorononane, difluorodecane, pentafluoodecane, 
tetrachlorodecane, tetrafluorotetrachlorodecane and octadecachlorodecane; 
nitrogen-containing organic compounds such as allylamine, methylamine, 
ethylamine, pyidine, pyrimidine, purine, picoline and acrylamide; 
sulfur-containing organic compounds such as carbon disulfide, methyl 
mercaptan and ethyl mercaptan; alcohols such as methanol, ethanol, 
propanol; phenol compounds such as phenol and crezole; aldehyde compounds 
such as holmaldehyde and acetaldehyde; ketone compounds such as acetone 
and methyl ethyl ketone; and fatty acids such as formic acid, acetic acid 
and propionic acid; alkyl esters such as methyl ester, ethyl ester and 
butyl ester of these fatty acids: etc. 
The inorganic compounds usable in the first process and second process of 
this invention may include carbon monoxide, carbon dioxide and 
diazomethane. 
The gases of these organic compounds and inorganic compounds may also be 
mixed with rare gases such as helium, argon and xenon or gases such as 
hydrogen, oxygen and nitrogen. These gases may be used alone or in 
combination of two or more. 
To prepare the film comprising a diamond-like substance according to the 
first and second processes of this invention, used are carbon-containing 
organic compounds among the above, but preferred are carbon-containing 
organic compounds having 1 to 4 carbon atoms, such as methane, ethane, 
propane, butane, ethylene, propylene, butadiene, allylamine, methylamine, 
ethylamine, carbon disulfide, methanol, ethanol, formaldehyde and 
acetaldehyde, methyl ethyl ketone, formic acid, ethyl acetate, etc. 
To prepare the film comprising a diamond-like substance, it is also 
required to mix hydrogen into the carbon-containing organic compounds, 
where hydrogen and carbon-containing organic compounds may preferably be 
used in the proportion of from 0.1 to 5 mol, more preferably from 0.2 to 2 
mol, of carbon-containing organic compounds per 100 mol of hydrogen. Here, 
an overly small proportion of the carbon-containing organic compound tends 
to make slow the growth rate of the diamond like substance, and an overly 
large proportion of the same tends to result in formation of a 
diamond-like substance containing amorphous carbon in a large quantity. 
In the processes of this invention, the high temperature or quasi-high 
temperature plasma is used. Here, the high temperature plasma is known to 
refer to a plasma of Te/Tg.perspectiveto.1, assuming the electron 
temperature of plasma as Te and the gas temperature as Tg. The quasi-high 
temperature plasma is known to refer to a plasma of 1&lt;Te/Tg&lt;10. 
In the first process, used as the discharge electrode is a sheet-like 
electrode provided with a slit having a linear portion and connected to a 
microwave electric source (hereinafter referred to merely as "sheet-like 
electrode"). 
The slit provided in the sheet like electrode may have a turned shape, or 
may be partly turned drawing an arc, but has at least one substantially 
linear portion satisfying the condition expressed by the equation: 
EQU 1=n.times..lambda./2 
wherein 1 is the length of said linear portion and is a wavelength of a 
microwave, and n is an integer of 1 or more, preferably 1 to 8, and more 
preferably 1 to 4 (hereinafter called "effective linear portion"). Absence 
of the effective linear portion in the slit may result in no normal 
microwave discharge, making it impossible to excite plasma in a desired 
state. 
This slit may further preferably be provided in such a manner that the 
whole length of the effective linear portions may be 0.1 to 6 cm/cm.sup.2 
with respect to the area of the substrate surface on which a film is 
intended to be formed or the area of the sheet-like electrode. 
The slit usually have a width of generally not less than 1 mm and less than 
.lambda./2. 
FIG. 1 is a perspective view illustrating an example of the sheet-like 
electrode, in which a sheet-like electrode has a slit formed by making a 
out from an outer edge into the inside. This sheet-like electrode 1 
comprises a conductive material, and is constituted of a flat sheet which 
is rectangular as a whole. On one of the longer sides of this sheet like 
electrode 1, a slit 3 is cut from a start point (cutting-in part) 2 
nearest to its one end in parallel to a shorter side 4. and the slit 3 
turns plural times at a right angle until it reaches an end point at a 
point 5 inside the sheet-like electrode. 
In FIG. 1, the slit 3 is constituted of six relatively long effective 
linear portions A.sup.1 parallel to the shorter side 1 and six relatively 
short linear portions which are not effective linear portions (hereinafter 
called "non-effective linear portion(s)") B.sup.1 parallel to the longer 
side, and is a single slit continuous from the start point 2 to the end 
point 5. Connected respectively to two points (the numerals 6 and 7 in the 
figure) interposing the slit 3 in the vicinity of the start point of the 
slit 3 are two lead wires 8a and 8b extending from a coaxial tube 8. 
FIG. 2 is a perspective view illustrating another example of the sheet-like 
electrode, which is a sheet-like electrode having the slit in plurality. 
This sheet-like electrode 21 also comprises a conductive material, and is 
constituted of a flat sheet which is rectangular as a whole. The slit 23 
of the sheet-like electrode 21 comprises slits that form effective linear 
portions A.sup.2 in parallel to shorter sides 24a and 24b of the 
sheet-like electrode 21, and the respective slits are separated. This 
sheet-like electrode 21 also has coaxial tube connecting portions 22a and 
22b on its shorter sides 24a and 24b, which portions are respectively 
connected to coaxial tubes 28a and 28b. 
There is no particular limitation on the shape of the slit formed in the 
sheet-like electrode so long as it has at least one effective linear 
portion, and, besides the example illustrated in FIG. 1 or FIG. 2, may 
include, for example, the shapes as illustrated in FIG. 3 to FIG. 8. In 
the example of FIG. 3, a slit 32 is provided in a sheet-like electrode 31 
in such a fashion that a plurality of effective linear portions A.sup.3 
only are continuously connected with each other through angles .alpha.. ln 
the example of FIG. 4, a slit 42 is provided in a sheet-like electrode 41 
in such a fashion that sets of two effective linear portions A.sup.4 
connected with each other through angles .beta. are repeated in some 
number with the interposition of shorter non-effective linear portion 
B.sup.4. In the example of FIG. 5, a slit cut in from the middle 52 of a 
longer side 51 is branched at the position of a point 54, and thereafter 
turns like that in FIG. 1 to form a plurality of effective linear portions 
A.sup.5 before they respectively stop at end points 55 and 56. In the 
example of FIG. 6, a plurality of slits 61, 62, 63, etc. each constituting 
the effective linear portion are provided in parallel to each other and at 
an angle .gamma. with respect to a longer side 65 of a sheet-like 
electrode 64. 
In the first process, it is also possible to use, besides the above, the 
sheet-like electrode having the shapes as illustrated in FIG. 7 and FIG. 
8. 
In FIG. 7, a sheet-like electrode 70 is formed of two supporting rods 71a 
and 71b comprising a conductive material, and rods 72, 73, 74, 75, 76 and 
77 comprising a conductive material provided across the supporting rods 
71a and 71b in equal intervals in the form of a ladder. Small, rectangular 
spaces 78, 79, etc. surrounded by the rods correspond to the slit 
described above, and the length A.sup.7 of the rectangular space in the 
longitudinal direction constitutes the effective linear portion. In the 
example of FIG. 8, a plurality of blades comprising a conductive material 
are arranged in the same plane on the part at which only an inner guide 
tube 81 of a coaxial tube is bared, in such a fashion that the length 1 
defined between both ends of blades opposing through the inner guide tube 
may correspond to the length of the effective linear portion. 
There is no limitation on the shape of the sheet-like electrode, and its 
outline may be of any shape including a rectangular shape, as well as a 
circular shape. 
The sheet-like electrode may not particularly be required to be flat, and 
may have a curved surface as a whole or in part or may have convexes or 
concaves, corresponding to the three-dimensional shape of the substrate 
surface to be treated. 
FIG. 9 is a cross section illustrating a sheet-like electrode 93 suited to 
form a film on a spherical surface 92 of a substrate 91, where said 
electrode 93 is made to have an undersurface 94 formed in a concave 
surface in agreement with the spherical surface 92 of the substrate 91. 
FIG. 10 also is a cross section illustrating a sheet-like electrode 104 
suited to form a film on a surface 103 of a substrate 102 having a 
rectangular convex 101, where said electrode 104 is formed with a 
rectangular concave in agreement with the convex 101 of the substrate 102, 
and is so designed that a film can be evenly formed on the whole top 
surface 103 of the substrate 102 as a whole. FIG. 11 is a cross section 
illustrating a sheet-like electrode 114 suited to form a film 
simultaneously on the surfaces 112 and 113 of a sheet-like substrate, 
where said electrode 114 is turned in U-shape and so designed that films 
can be formed on the whole of both surfaces 112 and 113 of the substrate 
111. 
The sheet-like electrode may also be provided in plurality and in parallel 
with appropriate spacing, thereby making it possible to form films 
simultaneously on both surfaces of the substrate. 
Methods of introducing microwaves to the sheet-like electrode used in the 
first process may include, for example, a method in which an end of a 
coaxial cable or coaxial tube connected at the other end to a waveguide is 
connected to the sheet-like electrode, a method in which an end of a 
coaxial cable or coaxial tube connected at the other end to a waveguide is 
connected to one end of a parallel wire line and thereafter the other end 
of the parallel wire line is connected to the electrode, and a method in 
which an antenna provided in a waveguide and an antenna provided for the 
electrode are used. 
Methods of introducing microwaves to the sheet-like electrode may also 
include a method in which a microwave is introduced to one end of the 
sheet-like electrode and, at the same time, another microwave is also 
introduced to the other end thereof, and a method in which a microwave is 
introduced to one end of the sheet-like electrode and a coaxial tube or 
waveguide is connected to the other end thereof, which is then connected 
to a termination (i.e., dummy load). These methods enable introduction of 
a microwave to the sheet-like electrode in a good efficiency, and are 
effective for obtaining stabler plasma. Specific examples of such methods 
of introducing the microwave to the sheet-like electrode may include (a) a 
method in which slits are arranged in the sheet-like electrode in a 
point-symmetrical or line-symmetrical fashion, and microwaves are 
introduced to symmetrically related two points on the electrode from 
respectively independent electric sources, and (b) a method in which slits 
are arranged in the sheet-like electrode in a point-symmetrical or 
line-symmetrical fashion, and microwaves are introduced to one of 
symmetrically related two points on the electrode, to the other of which a 
coaxial tube or waveguide is connected, which is then connected to a 
termination. Here, the termination is a device to let microwaves having 
not been consumed in generating plasma escape in a liquid such as water or 
oil through a waveguide or coaxial tube. 
In the first process of this invention, it is further possible to form 
stabler plasma by applying a magnetic field to the sheet like electrode. 
In this instance, the magnetic flux density in the vicinity of the sheet 
like electrode may preferably be maintained at from 500 to 2,000 gauss, 
and an electromagnet, for example, can be used as a means for applying the 
magnetic field. 
In the first process of this invention, a plasma zone in the form of mat 
(hereinafter called mat-like plasma zone) is so formed that it may cover 
the surface of the sheet-like electrode. The thickness represented by L in 
mm and the area represented by S in mm.sup.2 of the mat-like plasma zone 
may preferably have a relation of: 
EQU S/L&gt;200 
and also said plasma zone has an average energy density of 10 W/cm.sup.3 or 
more. The value of S/L otherwise 200 or less may result in formation of a 
plasma zone having a small two dimensional breadth, making it impossible 
to make large so much the area on which a film can be formed. The plasma 
zone may preferably have a thickness of usually from 1 to 40 mm, 
preferably from 3 to 20 mm. 
The plasma zone may also preferably have an energy density of 10 W/cm.sup.3 
or more on average, preferably from 10 to 1,000 W/cm.sup.3. The energy 
density otherwise less than 10 W/cm.sup.3 on average may result in a 
lowering of the rate of film formation on a large-area substrate surface. 
There is no particular limitation on the material for the sheet-like 
electrode so long as it is a conductive material, and, specifically, there 
can be used any materials having a conductivity of 10.sup.2 ohm.sup.-1 
cm.sup.-1 or more at room temperature and usually having a good thermal 
resistance at 600.degree. C. or more. Such materials may include, for 
example, transition metals such as iron, cobalt, nickel, manganese, 
chromium, vanadium, titanium, copper, zinc, yttrium, ruthenium, zirconium, 
niobium, molybdenum, rhodium, palladium, silver, tantaium, tungsten, 
rhenium, platinum, gold, thallium, lead and bismuth; aluminum; alloys of 
the above transition metals or aluminum, such as stainless steel, brass, 
bronze and super alloy; dispersion reinforce alloys comprising metal 
oxides dispersed in a metal, such as copper-alumina, copper-silicon oxide, 
silver-alumina, silver-cadmium oxide and nickel yttrium oxide; carbon 
materials such as carbon and graphite; and preferred among these are 
materials having a conductivity of 10.sup.5 ohm.sup.-1 cm.sup.-1 or more, 
including copper, silver, aluminum, copper alloys and copper-alumina 
dispersion reinforced alloys. Surfaces of these materials may also be 
covered with electrical insulators or semiconductive materials such as 
glass, ceramics, silicon and diamond. The sheet-like electrode is fixed in 
a reaction vessel to be used, with an electrical insulator. The electrical 
insulator that can be used may include, for example, inorganic materials 
such as alumina, boron nitride, quartz glass, silicon nitride and 
zirconium oxide; and organic polymers such as nylon and polyethylene. 
However. inorganic materials must be used in the case of a high 
temperature. 
In the first process, a gas containing at least one selected from the group 
consisting of an organic compound and an inorganic compound is positioned 
in the reaction vessel. Flow rate of these gases may range generally from 
0.1 to 100,000 cc(STP)/min per 100 lit. of inner volume of the reaction 
vessel. Average pressure in the reaction vessel may range usually from 0.5 
to 760 Torr, preferably from 1 to 200 Torr. These are expressed as general 
ranges, and may be selected depending on the type of films to be formed. 
For example, in instances in which films comprising the diamond-like 
substance are formed, the carbon-containing organic compound and hydrogen 
are used, where the gas flow rate of the carbon-containing organic 
compound may range usually from 0.01 to 10,000 cc(STP)/min per 100 lit. of 
inner volume of the reaction vessel, and the flow rate of hydrogen may 
range from 0.1 to 10,000 cc(STP)/min per 100 lit. of inner volume of the 
reaction vessel. 
In forming films comprising the diamond-like substance, hydrogen and the 
carbon-containing organic compound may be separately fed to the reaction 
zone and then subjected to microwave discharge while mixing, or may be fed 
to the reaction zone in the form of a previously mixed gas and then 
subjected to the microwave discharge. In either case, a rare gas such as 
helium, argon or xenon may be mixed into the hydrogen, carbon-containing 
organic compound, or the mixed gas of these. There is no particular 
limitation on the proportion of the rare gas, but it may preferably be 80 
mol or less per 100 mol of hydrogen. 
Under the above conditions, the mat-like plasma usually with a thickness of 
1 to 20 mm in approximation is generated over the whole surface of the 
sheet-like electrode. A substrate may be so disposed previously or 
thereafter that the substrate surface to be treated may come into contact 
with the plasma thus excited, so that the desired film comprising the 
diamond-like substance can be formed on the substrate surface. Here, when, 
for example, the sheet like electrode has an area of 10,000 mm.sup.2, an 
applied electric power of about 1.5 kW results in excitation of plasma of 
about 5 mm in thickness on the surface of the electrode. Lowering of the 
applied electric power to 0.8 kW results in a plasma thickness lessened to 
about 2 mm, but the desired film comprising the diamond-like substance can 
be formed by bringing the substrate to come near to the electrode surface. 
In the second process of this invention, the plasma of the gas containing 
at least one selected from the group consisting of an organic compound and 
inorganic compound, is generated by DC discharge and force to move by 
applying a magnetic field. The plasma generated by DC discharge comprises 
a high temperature or quasi-high temperature plasma generated in the form 
of an arc (hereinafter simply called "arced plasma"). 
To generate the arced plasma in the second process, used are, for example, 
the electrodes as illustrated in FIGS. 12A to 12C or FIG. 13. 
FIG. 12A illustrates discharge electrodes comprising a pair of rod-like 
electrodes 121 connected to a DC electric source, and the two electrodes 
121 are fixed so as to give a space, for example, of from 1 to 10 mm by 
use of an insulator 122 comprising aluminum or the like. The arced plasma 
is generated at part between the discharge electrodes, and forced to move 
in the longitudinal direction of the rod-like electrodes, as shown by 
arrow X in the figure, by applying a magnetic field formed by a magnet 
(not shown). The arced plasma generated at part between the discharge 
electrodes comes to be in the state that it protrudes up and down the 
discharge electrodes, so that a film can be formed on a substrate set near 
to the discharge electrodes. 
FIG. 12B illustrates an example of the discharge electrodes comprised of 
three or more rod-like electrodes 121 similar to those shown in FIG. 12A, 
which is suited to form films having a larger area. 
FIG. 12C illustrates an example in which a disc-like electrode 123 and 
electrodes 124, 126 and 126 comprised of ring shaped flat sheets are 
concentrically arranged and circular slits 127 are respectively formed 
therebetween, where the respective electrodes 123 to 126 are connected to 
a DC electric source as shown in the figure. The arced plasma is generated 
at part of each circular slit 127 and moves along the circular slit 127 by 
the effect of the magnetic field formed by an electromagnet (not shown). 
The arced plasma generated at part of each circular slit 127 comes to be 
in the state that it protrudes up and down the ring-shaped electrodes, and 
forced to move along the circular slit 127 by application of a magnetic 
field formed by an electromagnet, for instance, so that a film can be 
formed on a substrate set near to the discharge electrodes. In the 
embodiments, in FIG. 12A to FIG. 12C, a refrigerant may preferably be 
channeled inside the discharge electrodes to effect cooling. 
Materials for the discharge electrodes used in the second process may 
include the same conductive materials process. 
To generate the arced plasma in the second process, a voltage of from 10 to 
900 volt is applied between the electrodes by using a DC electric source. 
In the second process also, a gas containing at least one selected from the 
group consisting of an organic compound and an inorganic compound is 
flowed in the reaction vessel, and flow rate of these gases usually ranges 
from 100 to 100,000 cc(STP)/min per 100 lit. of inner volume of the 
reaction vessel. 
In particular, in the second process, the gas may preferably be positioned 
between the electrodes in the form of a jet flow so that the arced plasma 
is forced to jet from the discharge electrodes like a plasma jet. Thus, 
gas flow velocity between the electrodes, necessary for generating the 
arced plasma like a jet, may preferably be set to from 0.01 to 600 m/sec, 
particularly preferably from 0.05 to 100 m/sec. 
Average pressure in the reaction vessel may range usually from 10 to 760 
Torr, and energy density of the plasma may range usually from 10 to 1,000 
W/cm.sup.3 on time average. 
Methods by which the gas is fed to the reaction zone in the second process 
of this invention may include the same methods as in the first process. In 
particular, to flow the gas in the form of a jet flow between the 
discharge electrodes, available is a method in which, for example, a pipe 
131 as illustrated in FIG. 13 is set on the discharge electrodes 132 and a 
gas is fed through this pipe 131. This pipe 131 is provided with a 
gas-jetting slit 133 in the manner that the slit may face the discharge 
electrodes 132 and be positioned between two adjacent discharge 
electrodes, so that the gas can be fed from this gas-jetting slit to 
between the two adjacent discharge electrodes in the form of a jet flow. 
In the second process, the generated arced plasma is forced to move by 
applying a magnetic field. This magnetic field is applied in the direction 
perpendicular to the direction of the flow of electric discharge current 
caused by DC discharge. Magnitude of magnetic flux density ranges usually 
from 80 to 2,000 gauss. To produce this magnetic field an electromagnet 
for forming a magnetic field in the direction perpendicular to the 
direction of the flow of electric discharge current caused by DC discharge 
is placed, for example, at the upper and lower parts or right and left 
parts of the discharge electrodes as exemplified in the above. 
The position of the discharge between the discharge electrodes can be moved 
by applying this electric field, and, when, for example, the discharge 
electrodes as shown in FIG. 12A or FIG. 12C are used, a plasma sensor 
having the function to give a command to reverse the direction of the 
magnetic field at every time when it detects the plasma may be provided at 
both ends of a section in which the arced plasma reciprocates, thus 
enabling the reversal of the direction of movement. This reversal of the 
direction of the magnetic field may also be achieved by previously 
measuring the velocity of movement of the arced plasma, and automatically 
reversing the direction of the electric current for the electromagnet 
according to a period, for example, of about 1 second or less, determined 
on the basis of the measurements. 
The first and second processes of this invention is carried out in a 
reaction vessel, but there is no particular limitation on the type of the 
reaction vessel to be used, and may be included bell jar reaction vessels, 
as well as those exemplified by rectangular parallelepiped reaction 
vessels. There is also no particular limitation on a vacuum exhaust system 
connected to the reaction vessel, and there can be used those of various 
types commonly used. 
The first and second processes of this invention may also optionally 
provided with, for example, a substrate-supporting means such as a 
substrate stand, a substrate-heating means and a substrate cooling means. 
Particularly when the film comprising a diamond-like substance is formed, 
the substrate temperature may preferably be maintained at 600.degree. to 
900.degree. C. When it is necessary to heat the substrate, an infrared 
image furnace or a resistance heater can be used as the substrate stand, 
and, when it is necessary to cool the substrate, a water-cooling type 
cooling stand can be used as the substrate stand. 
On the substrate on which a film can be formed by the first or second 
process of this invention, there is no particular limitation so long as it 
has thermal resistance, and there may be included ceramics such as 
alumina, tungsten carbide and titanium nitride: semiconductors such as 
silicon, germanium and gallium arsenic; metals such as molybdenum, 
tungsten, tantalum. copper and iron; dispersion reinforced alloys 
comprising metal oxide particles dispersed in copper or copper alloys; and 
quartz glass. 
These substrates may be used as they are, or may be used after surfaces are 
scratched using a diamond paste or the like to make it easier to form 
films. 
EXAMPLES 
The process of this invention will be described below in greater detail by 
way of Examples. 
EXAMPLE 1 
Using the apparatus schematically illustrated in FIG. 14, formation of 
films comprising a diamond-like substance was carried out on substrates. 
This apparatus is equipped with a sheet-like electrode 142 fixed 
horizontally in a bell jar reaction vessel 141, and the electrode 142 is 
connected to a microwave electric source for introducing a microwave with 
a wavelength of 122 mm through a coaxial cable 143 and a 
microwave-introducing terminal 144. 
A substrate stand 145 made of alumina, provided in the reaction vessel is 
equipped with an infrared image furnace, which can heat to a desired 
temperature a substrate 146 placed on the substrate stand. Connected to 
the bottom of the reaction vessel are an exhaust tube 147 connected to a 
vacuum exhaust system, and a gas inlet tube for introducing a gas used for 
generating plasma to which valves 147 and 148 are respectively provided. 
The sheet-like electrode 142 is made of copper and comprised of two sheets 
of the sheet like electrode exemplified in FIG. 5, which are arranged and 
connected to the coaxial cable 143 as illustrated in FIG. 15 and are 
rectangular sheet-like electrodes having a dimension of 
160.times.180.times.1 mm when the two sheets are put side by side. A slit 
151 has a slit width of 4 mm, twenty-two (22) effective linear portions 
whose length X shown in FIG. 15 is 61 mm, and non-effective linear 
portions which keep every two adjacent effective linear portions apart by 
a distance of 15 mm as shown by Y in FIG. 15. 
Used as the substrate 146 was a silicon wafer having a diameter of 2 
inches. This substrate was placed in a beaker together with diamond 
particles having an average particle diameter of 3 micrometers, maintained 
for 10 minutes in an ultrasonic washer filled with water together with the 
whole beaker to carry out a pretreatment to make scratches on the 
substrate surface, and thereafter placed on the substrate stand. The top 
surface of the substrate and the sheet-like electrode was held 4 mm apart. 
For Test Nos. 1 to 14, kind of gas used for generating plasma, pressure, 
energy density of plasma and substrate temperature were varied as shown in 
Table 1, and treatments of the tests were carried out for 2 hours under 
the conditions respectively shown in Table 1. The energy density is 
expressed by a value obtained by dividing the applied microwave electric 
power by the volume of generated plasma. Also, the substrate temperature 
was measured by using an alumel-chromel thermocouple fixed to the 
substrate, making control by adjusting the electric power for the infrared 
image furnace. At the time of the measurement, however, the application of 
the microwave electric power was stopped for a short time. 
(1) Average thickness, scattering of thickness and crystallinity of the 
films comprising a diamond-like substance thus obtained on the substrate 
are shown together in Table 1. Here, the average thickness was determined 
by observing cross sections of the substrates on which films comprising a 
diamond-like substance were formed, with use of a scanning electron 
microscope. The scattering of thickness is expressed by an arithmetical 
mean of the differences between the thicknesses of ten samples selected at 
random and the average thickness thereof. Also, the crystallinity is 
indicated by hd/ha which is the ratio of the height hd at a peak around 
1,330 cm.sup.-1 in the Ramman spectrum (the one inherent in crystal 
diamond) and the height ha at a peak around 1500.sup.-1 in the same (the 
one inherent in amorphous caron). It can be evaluated that the greater 
this ratio is, the higher the diamond formation is. 
TABLE 1 
__________________________________________________________________________ 
Aver- 
Film 
Sub- Plasma age thick- 
Plasma 
strate 
zone film 
ness 
Kind of gas energy 
temper- 
thick- thick- 
scat- 
Test 
& gas flow rate 
Pressure 
density 
ature 
ness ness 
tering 
Crystal- 
No. 
cc(STP)/min 
(Torr) 
(W/cm.sup.3) 
(.degree.C.) 
(mm) 
S/L 
(.mu.m) 
(.mu.m) 
linity 
__________________________________________________________________________ 
1 CH.sub.4 (10) + 
20 16 800 12 2,400 
4 &lt;1 &gt;10 
H.sub.2 (1,000) 
2 CH.sub.4 (10) + 
100 24 780 4 7,200 
6 &lt;1 &gt;10 
H.sub.2 (1,000) 
3 CH.sub.3 OH(15) + 
10 12 750 14 2,057 
5 &lt;1 &gt;10 
H.sub.2 (1,000) 
4 CH.sub.3 OH(15) + 
80 19 850 6 4,800 
12 4 &gt;10 
H.sub.2 (1,000) 
5 CH.sub.3 NH.sub.2 (10) + 
5 13 810 14 2,057 
5 &lt;1 &gt;10 
H.sub.2 (800) 
6 CH.sub.3 NH.sub.2 (10) + 
100 27 740 4 7,200 
7 &lt;1 &gt;10 
H.sub.2 (800) 
7 CS.sub.2 (8) + H.sub.2 (700) 
10 14 820 16 1,800 
8 &lt;1 5 
8 CS.sub.2 (8) + H.sub.2 (700) 
90 22 840 4 7,200 
9 2 7 
9 CO.sub.2 (10) + 
40 21 830 10 2,880 
1 &lt;1 6 
H.sub.2 (1,200) 
10 CO.sub.2 (10) + 
80 35 910 6 4,800 
2 &lt;1 7 
H.sub.2 (1,200) 
11 CH.sub.3 F(10) + 
20 16 820 12 2,400 
7 &lt;1 &gt;10 
H.sub.2 (1,000) 
12 CH.sub.3 F(10) + 
100 24 840 4 7,200 
9 2 &gt;10 
H.sub.2 (1,000) 
13 CF.sub.4 (10) + 
15 20 830 12 2,400 
8 &gt;1 8 
H.sub.2 (1,000) 
14 CF.sub.4 (10) + 
40 27 870 10 2,880 
10 3 7 
H.sub.2 (1,000) 
__________________________________________________________________________ 
(2) In Test Nos. 15, 16 and 17, films comprising a diamond-like substance 
were obtained on molybdenum plates under the same plasma-generating 
conditions as in Test Nos. 5, 7 and 11, respectively, and deposited on 
their surfaces were gold electrodes 161 in spots with a diameter of 1 mm 
at eighteen positions as shown in FIG. 16. Each gold electrode was 
numbered as shown in the figure, and measured was electrical resistance 
between each electrode and molybdenum plate. Results obtained are shown in 
Table 2. Here, since the magnitude of the electrical resistance is 
proportional to the film thickness of the diamond like substance, the 
results shown in Table 2 tell that films comprising a diamond like 
substance were uniformly formed on the molybdenum sheets. 
TABLE 2 
______________________________________ 
(Unit: ohm) 
Measure 
point Test 15 Test 16 Test 17 
______________________________________ 
1 5 .times. 10.sup.11 
5 .times. 10.sup.11 
7 .times. 10.sup.11 
2 6 .times. 10.sup.11 
7 .times. 10.sup.11 
8 .times. 10.sup.11 
3 6 .times. 10.sup.11 
8 .times. 10.sup.11 
8 .times. 10.sup.11 
4 6 .times. 10.sup.11 
8 .times. 10.sup.11 
8 .times. 10.sup.11 
5 6 .times. 10.sup.11 
7 .times. 10.sup.11 
7 .times. 10.sup.11 
6 4 .times. 10.sup.11 
6 .times. 10.sup.11 
7 .times. 10.sup.11 
7 4 .times. 10.sup.11 
7 .times. 10.sup.11 
8 .times. 10.sup.11 
8 6 .times. 10.sup.11 
8 .times. 10.sup.11 
7 .times. 10.sup.11 
9 6 .times. 10.sup.11 
9 .times. 10.sup.11 
8 .times. 10.sup.11 
10 6 .times. 10.sup.11 
9 .times. 10.sup.11 
8 .times. 10.sup.11 
11 6 .times. 10.sup.11 
8 .times. 10.sup.11 
8 .times. 10.sup.11 
12 4 .times. 10.sup.11 
6 .times. 10.sup.11 
7 .times. 10.sup.11 
13 5 .times. 10.sup.11 
5 .times. 10.sup.11 
8 .times. 10.sup.11 
14 5 .times. 10.sup.11 
7 .times. 10.sup.11 
8 .times. 10.sup.11 
15 6 .times. 10.sup.11 
8 .times. 10.sup.11 
7 .times. 10.sup.11 
16 6 .times. 10.sup.11 
8 .times. 10.sup.11 
7 .times. 10.sup.11 
17 6 .times. 10.sup.11 
7 .times. 10.sup.11 
8 .times. 10.sup.11 
18 5 .times. 10.sup.11 
7 .times. 10.sup.11 
7 .times. 10.sup.11 
______________________________________ 
EXAMPLE 2 
Using the apparatus schematically illustrated in FIG. 17, formation of 
films comprising a diamond-like substance was carried out on substrates. 
The same components as those in the apparatus illustrated in FIG. 14 are 
denoted by the same numerals. This apparatus has the same constitution as 
the apparatus illustrated in FIG. 14 except that the apparatus illustrated 
in FIG. 14 is additionally provided with a coil 171a above the sheet-like 
electrode 172 and also a coil 171b beneath the substrate stand 145, and 
further a sheet-like electrode 172 made of molybdenum having the same 
shape and dimension was used in place of the sheet-like electrode 142 made 
of copper. 
Used as the substrate 146 was the same as in Example 1, and the top surface 
of the substrate 146 and the sheet-like electrode 172 were held 4 mm 
apart. The magnetic field produced by the coils 171a and 171b were set so 
as to give 875 gauss in the vicinity of the substrate 146. 
For Test Nos. 19 to 22, kind of gas used for generating plasma, pressure, 
energy density of plasma and substrate temperature were varied as shown in 
Table 3, and treatments of these tests were carried out for 2 hours under 
the conditions respectively shown in Table 3. Average thickness, 
scattering of thickness and crystallinity of the resulting films 
comprising a diamond-like substance were measured in the same manner as in 
Example 1, and the results obtained are shown in Table 3. 
EXAMPLE 3 
Formation of films comprising a diamond-like substance was carried out on 
substrates, using the same apparatus as the apparatus schematically 
illustrated in FIG. 17 and used in Example 2, except that the sheet-like 
electrode 172 used therein was replaced by a sheet-like electrode having 
the slits as exemplified in FIG. 2, having a rectangular shape of 
100.times.80.times.1 mm and made of molybdenum, in which five silts having 
a length of 61 mm at the effective linear portion A.sup.2 and a slit width 
B.sup.2 of 12 mm are provided at intervals of 7 mm. 
For Test Nos. 23 to 26, kind of gas use for generating plasma, pressure, 
energy density of plasma and substrate temperature were varied as shown in 
Table 3, and treatments of these tests were carried out for 2 hours under 
the conditions respectively shown in Table 3. Average thickness, 
scattering of thickness and crystallinity of the resulting films 
comprising a diamond-like substance were measured in the same manner as in 
Example 1, and the results obtained are shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
Aver- 
Film 
Sub- Plasma age thick- 
Plasma 
strate 
zone film 
ness 
Kind of gas energy 
temper- 
thick- thick- 
scat- 
Test 
& gas flow rate 
Pressure 
density 
ature 
ness ness 
tering 
Crystal- 
No. 
cc(STP)/min 
(Torr) 
(W/cm.sup.3) 
(.degree.C.) 
(mm) 
S/L 
(.mu.m) 
(.mu.m) 
linity 
__________________________________________________________________________ 
19 CH.sub.4 (10) + 
20 30 820 18 3,600 
5 &lt;2 &gt;10 
H.sub.2 (1,000) 
20 CH.sub.4 (10) + 
100 42 810 10 2,880 
7 &lt;2 &gt;10 
H.sub.2 (1,000) 
21 CH.sub.3 OH(15) + 
10 28 820 20 1,440 
6 &lt;2 &gt;10 
H.sub.2 (1,000) 
22 CH.sub.3 OH(15) + 
80 38 810 12 2,400 
14 &lt;5 &gt;10 
H.sub.2 (1,000) 
23 CH.sub.4 (10) + 
20 29 820 18 444 
5 &lt;1 &gt;10 
H.sub.2 (1,000) 
24 CH.sub.4 (10) + 
100 43 815 10 800 
8 &lt;2 &gt;10 
H.sub.2 (1,000) 
25 CH.sub.3 OH(15) + 
10 28 815 20 400 
6 &lt;2 5 
H.sub.2 (1,000) 
26 CH.sub.3 OH(15) + 
80 39 810 12 667 
15 &lt;5 7 
H.sub.2 (1,000) 
__________________________________________________________________________ 
EXAMPLE 4 
Using the apparatus schematically illustrated in FIG. 18, formation of 
films comprising a diamond-like substance was carried out on substrates. 
This apparatus is equipped with discharge electrodes 182 internally 
holding a cooling refrigerant pipe (not shown) and fixed horizontally in a 
bell ar reaction vessel 181, and said electrodes 182 are connected to a DC 
electric source 186. A substrate stand 183 made of alumina and provided 
inside the reaction vessel is equipped therein with an infrared image 
furnace and a cooling refrigerant pipe (not shown), so that a substrate 
184 placed on said substrate stand can be maintained at a desired 
temperature. Electromagnets 185a and 185b are further provided above the 
discharge electrodes 12 and beneath the substrate stand 184, respectively, 
in such a manner that the electromagnets may sandwich these. The 
electromagnets 185a and connected to an electric source 187 provided 
outside the reaction vessel, and can form electric field in the direction 
perpendicular to the electric current flowing between the electrodes. 
Provided at the bottom of the reaction vessel are an exhaust tube, a gas 
inlet tube and so forth in the same manner as in the apparatus illustrated 
in FIG. 14. These are denoted in FIG. 18 with the same numerals as in FIG. 
14. 
The discharge electrodes 182 correspond to the electrodes of the type shown 
in FIG. 12B, and are comprised of five rod-like electrodes with a 
dimension of 10.times.10.times.200 mm each, which are so arranged that 
anodes and cathodes may alternate. Of these, the electrodes serving as 
anodes are made of copper, and the electrodes serving as cathodes are made 
of tungsten. Electrodes adjacent to each other have a spacing of 5 mm, and 
both ends of each discharge electrode are fixed with insulators 122 made 
of alumina. 
As the substrate 184, a silicon wafer of 70.times.200.times.0.3 mm was 
placed on the substrate stand 183. 
The top surface of the substrate and the discharge electrodes were held 5 
mm apart. Voltage of the electric source 187 was adjusted so that electric 
field produced by the electromagnets 185a and 185b may come to be about 
400 gauss in the vicinity of the discharge electrodes 182, thus forcing 
the arced plasma to move. Plasma sensors (not shown) were further provided 
on both ends of the discharge electrodes 182 to reverse the electric 
current of the electric source 187 at every time when the arced plasma 
reaches extremities of the discharge electrodes 182. 
For Test Nos. 27 to 34, kind of was used for generating plasma, pressure, 
energy density of plasma and substrate temperature were varied as shown in 
Table 4, and treatments of these tests were carried out for 1 hour under 
the conditions respectively shown in Table 4. The energy density is 
expressed by a value obtained by dividing the applied microwave electric 
power by the whole volume over the area in which the plasma was generated 
and moved. The substrate temperature was also measured in the same manner 
as in Example 1. Average thickness, scattering of thickness and 
crystallinity of the resulting films comprising a diamond-like substance 
were measured in the same manner as in Example 1, and the results obtained 
are shown in Table 4. 
TABLE 4 
__________________________________________________________________________ 
Aver- 
Film 
Sub- age thick- 
Plasma 
strate 
film 
ness 
Kind of gas 
Average 
energy 
temper- 
thick- 
scat- 
Test 
& gas flow rate 
pressure 
density 
ature 
ness 
tering 
Crystal- 
No. 
cc(STP)/min 
(Torr) 
(W/cm.sup.3) 
(.degree.C.) 
(.mu.m) 
(.mu.m) 
linity 
__________________________________________________________________________ 
27 CH.sub.4 (10) + 
20 90 800 22 3 &gt;10 
H.sub.2 (1,000) 
28 CH.sub.4 (10) + 
100 200 600 14 2 8 
H.sub.2 (1,000) 
29 CH.sub.3 OH(15) + 
10 80 550 12 2 6 
H.sub.2 (1,000) 
30 CH.sub.3 OH(15) + 
80 170 750 18 
3 8 
H.sub.2 (1,000) 
31 CH.sub.3 NH.sub.2 (10) + 
5 50 850 16 2 &gt;10 
H.sub.2 (800) 
32 CH.sub.3 NH.sub.2 (10) + 
100 170 700 20 3 7 
H.sub.2 (800) 
33 CO.sub.2 + H.sub.2 (1,200) 
40 100 800 14 2 &gt;10 
34 CO.sub.2 + H.sub. 2 (1,200) 
80 180 650 7 &lt;1 7 
__________________________________________________________________________ 
EXAMPLE 5 
Using the apparatus schematically illustrated in FIG. 19, formation of 
films comprising a diamond-like substance was carried out on substrates. 
The same components as in FIG. i3 and FIG. 18 are denoted by the same 
numerals. This apparatus is the same as the apparatus illustrated in FIG. 
18 and used in Example 4, except that four pipes 133 having a gas-jetting 
slit 133 from which a plasma generating was is flowed into between the 
discharge electrodes in the form of a jet flow, as exemplified in FIG. 13, 
was set between the discharge electrodes 182 and the electromagnet 185a 
positioned above the discharge electrodes 182. This gas jetting slit 133 
is 1 mm wide and 200 mm long, and provided in the manner that it may face 
the center of the slit between electrodes as described with reference to 
FIG. 13. The gas jetting slit 133 and the discharge electrodes 182 are 
held 5 mm apart. The pipe 131 is connected to a gas inlet tube 192 for 
introducing plasma generating gas, provided at the bottom of a reaction 
vessel 191. An exhaust tube 193 is also connected to the bottom of the 
reaction vessel 191. 
For Test Nos. 35 to 42, kind of gas used for generating plasma, pressure, 
energy density of plasma and substrate temperature were varied as shown in 
Table 5, and treatments of these tests were carried out for 1 hour under 
the conditions respectively shown in Table 5. 
Average thickness, scattering of thickness and crystallinity of the 
resulting films comprising a diamond-like substance were measured in the 
same manner as in Example 1, and the results obtained are shown in Table 
5. 
TABLE 5 
__________________________________________________________________________ 
Gas flow Aver- 
Film 
velocity Sub- age thich- 
between 
Plasma 
strate 
film 
ness 
Kind of gas 
Average 
discharge 
energy 
temper- 
thick- 
scat- 
Test 
& gas flow rate 
pressure 
electrodes 
density 
ature 
ness 
tering 
Crystal- 
No. 
cc(STP)/min 
(Torr) 
(m/sec) 
(W/cm.sup.3) 
(.degree.C.) 
(.mu.m) 
(.mu.m) 
linity 
__________________________________________________________________________ 
35 CH.sub.4 (10) + 
20 3.2 120 850 60 5 &gt;10 
H.sub.2 (1,000) 
36 CH.sub.4 (10) + 
100 0.6 300 620 42 4 7 
H.sub.2 (1,000) 
37 CH.sub.3 OH(15) + 
10 6.4 100 600 55 3 7 
H.sub.2 (1,000) 
38 CH.sub.3 OH(15) 
80 1.1 200 800 67 4 
&gt;10 
H.sub.2 (1,000) 
39 CH.sub.3 NH.sub.2 (10) + 
5 10.3 80 900 47 2 &gt;10 
H.sub.2 (800) 
40 CH.sub.3 NH.sub.2 (10) + 
100 1.2 250 780 60 4 8 
H.sub.2 (800) 
41 CO.sub.2 (10) + H.sub.2 (1,200) 
40 1.9 150 870 47 3 &gt;10 
42 CO.sub.2 (10) + H.sub.2 (1,200) 
80 0.95 330 710 33 &lt;1 9 
__________________________________________________________________________