Process of making a thin film

The film-forming apparatus includes a gas introduction tube for introducing an inert gas into a vacuum chamber, a vapour source and a target, and forms a thin film by depositing sputtered particles and evaporated particles on the surface of a substrate, the sputtered particles being liberated by sputtering the target using ion energy of plasma generated around the target while the evaporated particles being obtained by evaporating a vapour source by heating and ionising evaporated components using the plasma. This apparatus comprises a substrate holder for holding the substrate so that its film-forming surface faces the side wall of the vacuum chamber; a rotating table for rotating the substrate holder within the vacuum chamber; a target arranged in the side wall of the vacuum chamber so that its sputtering surface faces the inside of the vacuum chamber; a shield detachably fitted in a through hole formed approximately through the centre of the target and having a hollow space therein; a gas introduction tube for introducing the inert gas into the hollow space of the shield; and a vapour source provided in the hollow space near the gas exit of the gas introduction tube. This apparatus is employed in the film-forming method of the present invention.

BACKGROUND OF THE INVENTION 
The present invention relates to an apparatus for forming a thin film 
provided with a sputtering target and a vapour source, and a method for 
producing a thin film using the apparatus. 
Formation of a relatively thick (about 1 .mu.m), uniform film of multiple 
components should be carried out in a short period of time in order to 
obtain a film of high precision. For example, Japanese Patent Application 
Laid-open No. 94473/1980 (JP-A-55-94473) discloses an ion-plating 
apparatus provided with a sputtering target and a vapour source to form a 
multi-component film. 
This apparatus, as shown in FIG. 3, comprises a substrate 46 fixed inside a 
vacuum chamber 41, a vapour source 45 disposed in the lower part of the 
vacuum chamber 41, a target 42 and a sputtering electrode 43 each placed 
between the substrate 46 and the vapour source 45, an anode 44 disposed on 
the side of the vapour source 45, and a hot cathode 47 provided on the 
side of the substrate 46 to generate gas-discharge plasma. In the vacuum 
chamber 41 of this apparatus, where gas is introduced from a gas supply 
source 48, a film is formed by evaporating the vapour source 45 at a 
constant rate through heating and then ionising the particles of the 
evaporated components in gas-discharge plasma, as well as applying a 
high-frequency magnetic field to the sputtering electrode 43 for 
sputtering the target 42. The film formed on the substrate 46 is composed 
of the evaporated component and the sputtered component. 
This ion-plating apparatus, however, fails to produce a uniform film on a 
large substrate, which is in great demand recently. In the vacuum chamber 
41, while the vapour source 45 faces the substrate 46, the target 42 is 
arranged approximately perpendicular to the substrate 46 in the vicinity 
thereof. This structure prevents particles sputtered out of the target 42 
from uniformly reaching the surface of a large substrate to give a uniform 
layer. 
Besides, the substrate 46 and the vapour source 45 are spaced at such a 
distance that the ionised evaporated particles cannot reach the substrate 
in a short time. This causes degradation of the precision of a film. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to solve the above 
problems, specifically by providing a method for forming a uniform and 
highly-precise film and an apparatus for the same. 
The film-forming method of the present invention comprises the steps of 
introducing an inert gas into a vacuum chamber and depositing, on the 
surface of a substrate, sputtered particles liberated by sputtering a 
target using ion energy of plasma generated around the target and 
evaporated particles obtained by evaporating a vapour source by heating 
and ionising thus evaporated components using the above plasma, and the 
method is characterised in arranging the target in the side wall of the 
vacuum chamber so that its sputtering surface (the surface to be 
sputtered) faces the inside of the vacuum chamber; conducting sputtering 
of the target and heating of the vapour source simultaneously or 
separately, while introducing the inert gas through a hollow space of a 
shield which is detachably fitted in a through hole formed approximately 
through the centre of the target, with keeping the surface of the 
substrate opposite to the sputtering surface of the target; and carrying 
thus yielded sputtered particles and evaporated particles, simultaneously 
or separately, to the surface of the substrate with a jet of the inert 
gas, thereby to form a thin film. 
Moreover, the film-forming method of the present invention may use 
different materials respectively for the target and the vapour source. 
Further, the film-forming method of the present invention may comprise a 
plurality of the targets and the vapour sources and fit the shield 
detachably in each target so that the inert gas can be introduced into the 
hollow space of the shield. 
According to the film-forming method of the above structure, it is possible 
to conduct the sputtering step of supplying a voltage to a target 
electrode and the vapour source heating step simultaneously or separately, 
while ejecting the inert gas through the hollow space of the shield which 
is fitted approximately in the centre of the target. Owing to a jet of the 
inert gas, the sputtered particles and the ionised evaporated particles 
can reach the substrate in a shorter time, thus uniformly forming a film 
on the whole surface of the substrate. 
A multi-component film can be also formed by preparing the target and the 
vapour source of different materials. 
Further, arrangement of plural targets and vapour sources is effective to 
form a uniform and highly precise film on a large substrate and plural 
substrates. 
The film-forming apparatus of the present invention, comprising a gas 
introduction tube for introducing an inert gas into the vacuum chamber, a 
vapour source and a target, is employed in the above method for forming a 
thin film on the substrate by depositing sputtered particles liberated by 
sputtering the target using ion energy of plasma generated around the 
target and evaporated particles obtained by evaporating a vapour source by 
heating and ionising thus evaporated components using the plasma. The 
film-forming apparatus is characterised in comprising a holding part for 
holding the substrate so that its film-forming surface faces the side wall 
of the vacuum chamber, a rotating table for rotating the holding part 
within the vacuum chamber, a target arranged in the side wall of the 
vacuum chamber with its sputtering surface facing the inside of the vacuum 
chamber, a shield detachably fitted in a through hole formed approximately 
through the centre of the target and having a hollow space therein, a gas 
introduction tube for introducing the inert gas into the hollow space of 
the shield, and a vapour source provided in the hollow space near a gas 
exit of the inert gas introduction tube. 
Moreover, the film-forming apparatus may comprise two vapour sources 
provided in the hollow space near the gas exit of the inert gas 
introduction tube and composed of the same element or more than one 
elements, and a change-over switch for selectively supplying power to heat 
either of the two vapour sources. 
Further, the film-forming apparatus may comprise a plurality of integrated 
units, each of which comprises the shield having a hollow space equipped 
with the gas introduction tube and the vapour source as well as the target 
and arranged in or in the vicinity of the side wall of the vacuum chamber, 
and may allow the holding part to hold plural substrates. 
The film-forming apparatus of the present invention is designed to carry 
out the aforesaid film-forming method. A uniform and highly precise thin 
film can be formed all over the surface of a substrate, because the 
sputtered particles and the ionised evaporated particles derived from the 
vapour source near the inert gas exit are both carried with a jet of the 
inert gas onto the substrate, and the film-formation process is conducted 
with rotating the substrate. 
The two vapour sources function as follows: when both vapour sources are of 
the same element, one is reserved until the other is consumed, whereas 
vapour sources of different elements can provide a multi-component thin 
film. The vapour source may also be in boat plate-type or crucible-type. 
Additionally, the vapour source may be in the form of a wire or a powder 
and fed from the outside of the vacuum chamber for a continuous long-time 
operation. These vapour sources are switchable to each other, as required, 
by a change-over switch. 
Further, the integrated unit of the vapour source-mounted shield and the 
target facilitates installment of plural shields and targets. Arrangement 
of the plural integrated units ensures uniform and highly precise 
formation of a thin film not only on a large substrate but also on a 
plurality of substrates at the same time.

DETAILED DESCRIPTION OF TEE PREFERRED EMBODIMENTS 
Referring to the drawings, embodiments of the present invention are 
hereinafter described. FIG. 1 illustrates a schematic view of the 
fundamental construction of a film-forming apparatus of an embodiment of 
the present invention, and FIG. 2 is a schematic view of an entire 
construction of the film-forming apparatus. 
A vacuum chamber 1 is connected to a vacuum pump (not shown) which creates 
a vacuum of a predetermined degree in the vacuum chamber 1. A plurality of 
first sputtering units 10 and second sputtering units 20 are vertically 
installed respectively on the side wall of the vacuum chamber 1. As shown 
in FIG. 1, the first sputtering unit 10 comprises a copper target 3 
disposed so that its sputtering surface faces the inside of the vacuum 
chamber 1, a permanent magnet 6 provided outside the vacuum chamber 1 via 
the target 3 and a target electrode 3a, and a yoke 9 mounted in contact 
with the permanent magnet 6. A cylindrical shield 2 is fitted in a through 
hole formed approximately through the centre of the target 3, with one end 
thereof opening outwardly to form an inclined portion 2a. The shield 2 is 
equipped with a gas introduction tube 4 for introducing an inert gas into 
the vacuum chamber 1, and two vapour sources 5 filled in vapour source 
containers 5b placed near a gas exit 4a of the gas introduction tube 4. 
The vapour sources 5 are evaporated by heating the containers 5b with 
coils 5a wound around the side walls thereof. Power is selectively 
supplied to either of the coils 5a by a switch 7c. In the embodiment, 
copper is used as the vapour source. The voltage supplied to the target 
electrode 3a is prepared by superimposing a voltage transmitted from an 
alternating-current RF power source 8a through an impedance matching box 
7a and a voltage transmitted from a direct voltage source 8b for 
sputtering connected in series with a low-pass filter circuit 7b. 
The second sputtering unit 20 comprises a chromium target 23, and a 
permanent magnet 26 disposed outside the vacuum chamber 1 via a target 
electrode 23a. Direct current is supplied to the target electrode 23a. 
In the vacuum chamber 1, substrates S.sub.1, S.sub.2 are held by substrate 
holders 12, with keeping their film-forming surfaces face-to-face with the 
targets 3, 23, respectively. The substrate holders 12 are mounted on a 
rotating table 11 which is driven by a motor (not shown) and rotates in 
the vacuum chamber 1. 
Now, using the above film-forming apparatus, a thin film (Cr--Cu--Cr layer 
film) is formed on the surfaces of the substrates S.sub.1, S.sub.2, 
according to the manner hereinafter disclosed. 
The substrates S.sub.1, S.sub.2, as the base for forming thin films, are 
brought into the vacuum chamber 1 from a door (not shown) which is 
evacuated in advance to a predetermined degree of vacuum, and mounted on 
the substrate holders 12. Then, the substrate S (hereinafter, S indicates 
both S.sub.1 and S.sub.2) is shifted to a position opposite to the target 
23 by rotating the rotating table 11 by a motor. At this position, a 
voltage is supplied to the target electrode 23a for the sputtering of the 
target 23, whereby Cr particles are deposited on the substrate S to form a 
Cr layer. 
Next, the Cr-layered substrate S is brought opposite to the target 3. At 
this position, while inert Ar gas is introduced into the vacuum chamber 1, 
sputtering of the target 3 is conducted, on the one hand, by supplying a 
superimposed voltage composed of a voltage from the RF power source 8a 
connected through the matching box 7a to the target electrode 3a and a 
voltage from the direct voltage source 8b connected in series with the 
low-pass filter circuit 7b. Through this process, Cu particles are 
liberated and deposited on the substrate S. On the other hand, 
simultaneously, the vapour source 5 is heated by a voltage supplied from a 
power source 8c through a terminal 7d to the coil 5a. Then, the Cu 
particles evaporated out of the vapour source 5 are thrown towards the 
substrate S with a jet of an inert gas ejected nearby, and deposited 
thereon. The Cu particles derived from these steps provide a Cu layer, 
thus giving a thin two-layer Cr--Cu film on the substrate S. 
Thereafter, the substrate S is again moved opposite to the target 23. Cr 
particles are likewise deposited to give a three-layer film of Cr--Cu--Cr. 
The present embodiment employs a large-sized substrate as the substrate S. 
Nevertheless, a thin film obtained herein is uniform and very precise. In 
comparison with the conventional technology, the sputtered particles and 
the evaporated particles can cover a larger area as a result of the 
vertical arrangement of the plural sputtering units 10, 20 on the side 
wall of the vacuum chamber 1. In addition, introduction of an inert gas 
helps these particles reach the substrate S in a short time and thus 
ensures the precision of the film. 
In the present embodiment, both of the two vapour sources are made of the 
same element (Cu). When one vapour source is consumed, a change-over 
switch 7c switches the power supply to the other vapour source, so that Cu 
particles are evaporated continuously. 
The present embodiment is directed to the formation of a Cr--Cu--Cr film. 
However, thin films of other compositions are also obtainable in 
accordance with the combinations of the target 23, the target 3, and the 
vapour source 5. 
By way of example, the combination of a titanium target 23, a tungsten 
target 3 and an aluminium vapour asource 5 provides a Ti--Al(W)--Ti film. 
The present invention should not be limited to the combined use of the 
first sputtering unit 10 and the second sputtering unit 20, as described 
in the above embodiment. Independent use of the first sputtering unit 10 
can also provide a multi-component thin film. For example, a TiN film is 
formed by using a first sputtering unit 10 composed of a titanium target 3 
and a titanium vapour source 5 and ejecting a reactive gas of nitrogen or 
ammonium. In addition, a Cr--Cu--Cr film is obtainable with the 
independent use of first sputtering unit 10 by constituting one vapour 
source 5 with chromium and the other with copper and appropriately 
operating the change-over switch 7c. 
When the target 3 and the vapour source 5 are made of different materials, 
the structure of a multi-component thin film is controlled by conducting 
the sputtering of the target and the ejection of the evaporated particles 
at separate timings. 
As exemplified above, various film-forming conditions can be achieved not 
only by proper combination of the target material, vapour source material 
and inert gas, but also by proper control of the timing and duration of 
releasing respective particles. 
Incidentally, the positions and directions of the first sputtering units 10 
and the second sputtering units 20 are not limited to the definition of 
the present embodiment. These factors may be arranged to suit the size and 
number of the substrate. 
Further, the vapour source 5 may be a boat plate-type or crucible-type 
vapour source. Alternatively, an evaporation material can be fed from the 
outside of the vacuum chamber either in the form of a wire through a 
wire-feeding device or in the form of a powder through a pipe. This 
structure enables continuous feeding of the evaporation material for a 
long time.