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FIELD OF THE INVENTION
The present invention relates to a vacuum processing method and apparatus
and, more specifically, to a method of and an apparatus for processing
substrates in vacuum chamber, such as a chemical vapour deposition (CVD).
BACKGROUND OF THE INVENTION
In a conventional vacuum processing apparatus such as a CVD illustrated in
FIG. 1 of the accompanying drawings, one or more substrates A are mounted
on the surface of a substrate holder B which is disposed in a vacuum
chamber C, and is intended to be rotated by a motor D via a rotation
transmitting mechanism E. Around the substrate holder B there is provided
an earth shield F which is electrically isolated from the substrate holder
B by an insulator member G. The substrate holder B is supplied with DC or
RF power from a DC or RF power feeder H which may be of a rotating contact
type, a capacitor coupling type or the like. Vacuum seal assembly I is
provided on the opening of the chamber wall for preventing a rotating
shaft and vacuum seal from vibrating during operation of the substrate
holder B. The vacuum rotation seal assembly I may comprise O ring seal,
Wilson's seal or magnetic fluid seal. The substrate holder B is provided
with either or both of a heater or cooling channel into which a power or
cooling water is fed by feeding means J such as a rotary joint.
FIG. 2 illustrates an other conventional CVD apparatus in which the same
reference characters are used to designate the components corresponding to
those in FIG. 1, and a heating mechanism K is, separated from the
substrate holder B and is secured to the vacuum chamber C.
In the conventional CVD apparatus as shown in FIG. 1 or 2, a plasma is
produced in the vacuum chamber by applying a suitable RF power so as to
the substrate holder to generate a glow discharge in the vacuum chamber.
In order to vary DC bias to be effectively generated at the surface of the
substrate (this DC bias to be generated at the surface of the substrate is
strictly more or less different from that to be generated at the surface
of the substrate holder, but it is assumed herein that the former is the
same as the latter), the RF power itself should be controlled or the RF
power should be electrically controlled, for example, by providing a
mechanism (for example, a capacitor, a coil, a resistor or the like) for
varying an impedance in the whole substrate holder mechanism in the RF
power transmitting circuit. For the DC or RF power feeding mechanism,
there should be used means for introducing the power into the rotating
mechanism, and thus this leads to difficulty in a maintenance or checking.
Further, since the capacitor, coil or resistor to be used for varying the
impedance have variable characteristics, it is difficult to make a fine
adjustment of the DC bias.
Where the conventional apparatus shown in FIG. 1 or 2 is employed for
forming a thin film on the substrate or etching the substrate, in the
apparatus illustrated in FIG. 1 a film forming material, a reactive gas or
the like may be adhered and deposited not only on the surface of the
substrate holder, but also on the whole surface of the earth shield and
the chamber wall, and in the case of the apparatus illustrated in FIG. 2
such film forming material or reactive gas may be adhered and deposited on
the back side of the substrate holder and the surface of the heater
assembly. Cleaning of the portions contaminated by such film forming
material or reactive gas becomes troublsome.
In the case of the apparatus shown in FIG. 1, even if the cleaning of the
contaminated portions is carried out by a plasma which is generated by
introducing a suitable reactive gas or inert gas into the vacuum chamber
and applying RF or DC power to the substrate holder, the surface of the
substrate holder and the portions fully exposed to the plasma may be
cleaned, but it is difficult to clean down the portions which are not
exposed and not fully exposed to the plasma.
Furthermore, in the apparatus illustrated in FIG. 1, since the substrate
holder is rotated together with the earth shield, the weight of the
components to be rotated becomes heavy and then it is necessary to use a
motor having a larger rotating torque. Complication of the substrate
holder and the feeding means for the heater power and the cooling water
can not be avoided, and the removement or maintenance of these components
become troublesome.
It is, therefore, an object of the present invention to provide a vacuum
processing method in which the drawbacks of the above-mentioned
conventional system can be overcome and a DC bias to be applied to
substrates can be mechanically and easily controlled with excellent
reproducibility.
Another object of the present invention is to provide a vacuum processing
apparatus in which the drawbacks of the above-mentioned conventional
system can be overcome and a DC bias to be applied to substrates can be
mechanically and easily controlled with excellent reproducibility.
Still another object of the present invention is to provide a method of
cleaning substrate holder or susceptor and other components in a vacuum
chamber, in which the susceptor and other components can be easily cleaned
with maintaining a required evacuated condition in the vacuum chamber.
Still another object of the present invention is to provide a vacuum
processing apparatus in which the susceptor and other components in the
vacuum chamber can be easily cleaned with maintaining required evacuated
condition and a desired processing performance in the vacuum chamber.
A further object of the present invention is to provide a vacuum processing
apparatus which comprises a substrate-electrode mechanism which is
functionally excellent and has no above-mentioned drawbacks of the
conventional system.
A still further object of the present invention is to provide a CVD
apparatus in which the construction can be simplified and an excellent
function can be obtained.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, there is provided a
vacuum processing method comprising changing the distance between an
electrode member which is electrically insulated from a wall of a vacuum
chamber and supplied with an AC voltage for generating a plasma by a glow
discharge in said vacuum chamber and a member for supporting at least one
substrate to be processed by said plasma, thereby controlling a DC bias to
be generated on the surface of said supporting member or the surface of
the substrate in respect to said AC voltage.
According to a second aspect of the present invention, there is provided a
vacuum processing apparatus comprising an electrode member which is
electrically insulated from a wall of a vacuum chamber and is supplied
with an AC voltage for generating a plasma by a glow discharge in said
vacuum chamber, a drive shaft which is arranged to slidably pass through
said chamber wall or said electrode member, a supporting member fixed to
the end portion of said driving shaft positioned in said vacuum chamber
and intended to support at least one substrate to be processed by said
plasma, and a mechanism for driving said drive shaft along the axis
thereof, the distance between said electrode member and said supporting
member being adjusted so that a DC bias generated on the surface of said
supporting member or said substrate is varied in respect to said AC
voltage.
The distance between the electrode member and the supporting member may be
adjusted by displacing the supporting member in respect to the electrode
member.
The AC voltage may be applied only to the electrode member or may be
applied to both of the electrode member and supporting member.
When the distance between the electrode member and the supporting member is
smaller than a predetermined value, the plasma may be produced in the
space on the opposite side of the supporting member to the electrode
member or above the supporting member, thereby cleaning the supporting
member and the portions positioned in the vicinity thereof. When the
distance between the electrode member and the supporting member is larger
than said predetermined value, the plasma may be transferred therebetween,
thereby cleaning the back side of the supporting member, the electrode
member and the portions positioned in the vicinity thereof.
The drive mechanism may comprise means for linearly driving the drive shaft
along the axis thereof and means for rotating the driving shaft around the
axis thereof.
According to a third aspect of the present invention, there is provided a
CVD apparatus comprising an electrode member fixed to a wall of a pressure
reduced chamber, a drive shaft adapted to slidably and rotatably pass
through the electrode member, a substrate holder mounted on the end
portion of the drive shaft positioned in the pressure reduced chamber, a
first linear drive means for moving the drive shaft along the axis
thereof, a rotary drive means for rotating the drive shaft, a plurality of
pins being arranged to be slidably inserted into a plurality of holes
provided on the electrode member for lifting each substrate, a second
linear drive means for driving the substrate lifting pins along the axes
thereof, and a plurality of openings provided on the substrate holder to
align with said holes and into which said substrate lifting pins can be
inserted.
The rotary drive means may be fixed on a vacuum seal member for sealing in
vacuum tight and rotatably supporting the drive shaft, and the first and
second linear drive means may be provided on a common base plate which is
coupled with the electrode member or the wall of the pressure reduced
chamber by guide members. Each of the guide members may be slidably
supported on linear bearings.
The drive shaft may be hollow, through which a cooling or heating medium
may be circulated via a rotary joint mechanism.
In the CVD apparatus according to the present invention, there may be
provided supporting arms each of which has one end mounted perpendicularly
on the one end of the associated lifting pin, and the other end of the
each supporting arm is extended into a slot formed on the outer peripheral
portion of the electrode member and is moved through a slot formed on the
outer peripheral portion of the substrate holder and positioned in
alignment with the other end of the arm.
The above and other objects and advantages of the invention will become
more apparent from the following description and accompany drawings
forming part of the present invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGS. 1 and 2 are respectively sectional views showing conventional CVD
apparatuses;
FIG. 3 is an elevation view of the apparatus embodying the present
invention with portions thereof broken away to illustrate the internal
structure thereof;
FIG. 4 is a cross-sectional view of FIG. 3 taken along the line IV--IV
thereof;
FIG. 5 a longitudinal sectional view of FIG. 4 taken along the line V--V
thereof;
FIG. 6 is a cross-sectional view of FIG. 5 taken along the line VI--VI
thereof;
FIG. 7 is a cross-sectional view of FIG. 5 taken along the line VII--VII
thereof;
FIG. 8 is a longitudinal sectional view of FIG. 7 taken along the line
VIII--VIII thereof;
FIG. 9 is a perspective view of the essential portions of the CVD apparatus
according to the present invention;
FIG. 10 is a schematic view to explain the operation of the illustrated
embodiment;
FIG. 11 is a longitudinal sectional view of showing a modified embodiment
of the present invention;
FIG. 12 is a plane view of the apparatus of FIG. 11.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to the drawings and more specifically FIGS. 3 to 9, there is
shown a CVD apparatus according to the first embodiment of the present
invention. The apparatus comprises a vacuum chamber 1 which has one side
wall provided with a reactive gas feeding nozzle 2 and a bottom wall
provided with an evacuating port 3. This evacuating port 3 is connected to
an evacuating device not shown such as a vacuum pump through an evacuating
pipe 4 and a duct 5. The vacuum chamber has also a front wall provided
with an opening 6 for loading the substrate to be processed into the
vacuum chamber 1 and unloading the processed substrate from the vacuum
chamber 1. This opening 6 should be provided with a suitable gate valve
which is not shown.
Under the vacuum chamber 1 there is disposed a lifting and rotating
mechanism 7 which is enclosed with a casing 8. The lifting and totating
mechanism 7 and the casing 8 are secured to the vacuum chamber 1. The
vacuum chamber 1 is fixed on a framework 9 by clamp members only one of
which is shown at 10 in FIG. 3.
In the vacuum chamber 1 there is provided a circular susceptor or substrate
holder 11 for supporting a substrate to be processed, under which an
electrode body 12 is disposed. The susceptor 11 and the electrode body 12
are surrounded with an annular earth shield 13 which has an inner
periphery vacuum tightly secured to the outer flange of the electrode body
12 via an insulating member 14 and seal rings 15 by clamp screws only one
of which is shown at 16 in FIG. 5. The outer periphery or flange of the
earth shield 13 is vacuum tightly secured to the bottom wall la of the
vacuum chamber 1 by clamp screws only one of which is shown at 17 in FIG.
5. To the top surface of the earth shield 13 there is attached an annular
member 18 which may be made of a quartz.
The susceptor 11 has a central portion intergratedly fixed to a rotating
shaft 9 which extends through the central bore 12a of the electrode body
12 and is tightly and rotatably supported by a vacuum rotating seal
assembly 20 having bellows 21 and a pair of bearings 22 and 23. The
bearings 22 and 23 are mounted on a casing 24 which has a lower end
secured to an intermediate mounting plate 25.
The rotating shaft 19 is provided with a pulley 26 near the lower end
portion thereof. Under the intermediate mounting plate 25 there is
disposed a lower mounting plate 27 to which a motor 28 is secured by a
retainer member 29. As shown in FIGS. 5 and 7, the retainer member 29 has
an upstanding portion 29a to which L-shaped member 30 is secured by screws
31. The L-shaped member 30 is also secured to the lower mounting plate 27.
The motor 28 is provided with a output rotating shaft 28a on which a
pulley 32 is fixed by a key 33 and a clamp screw 34. A timing belt 35 is
engaged with both of the pulley 32 and the pulley 26.
Under the lower mounting plate 27 there is disposed a base plate 36 which
as shown in FIGS. 5, 6 and 7 is secured to the electrode body 12 by three
guide rods 37 being positioned at an equal angular position. Each of the
guide rods 37 has an upper end 37a screwed on the electrode body 12 and a
lower screwed end 37b fixed to the base plate 36 by a nut 38. Each of the
guide rods 37 is slidably supported by a lower linear ball bearing 39
mounted between the intermediate mounting plate 25 and the lower mounting
plate 27, and an upper linear ball bearing 40 mounted on an upper mounting
plate 41. Therefore, the upper, intermediate and lower mounting plates 41,
25 and 27 can be exactly moved upwards and downwards by the guide rods 37.
An air cylinder device 42 is provided on the base plate 36. This air
cylinder device 42 comprises a drive rod 43 which is secured to the lower
mounting plate 27 by a nut 44.
The lower end portion of the rotating shaft 19 is passed through the
opening 27a of the lower mounting plate 27 and is connected to a cooling
water feeding device 45 which may be a rotary union and from which cooling
water is fed through a feed channel of the rotating shaft 19 and flows out
of the rotating shaft 19 through a return channel thereof. The electrode
body 12 is provided with a separated cooling water supply which is not
shown.
On the upper mounting plate 41 there are provided three substrate lifting
pins 46. Each pin 46 has a lower end portion secured to the upper mounting
plate 41 and an upper end portion extended through the associated one of
bores 12b which are formed on the periphery of the electrode body 12.
Between the electrode body 12 and the upper mounting plate 41 bellows 47
surround the pins 46 to shut off these pins from the atmosphere.
As shown in FIGS. 8 and 9, a substrate lifting pin driving device 48 is
provided on the base plate 36. This substrate lifter driving device 48
includes a driving rod 49 the upper end of which is coupled with the upper
mounting plate 41 via a link member 50.
The susceptor 11 is provided with three slots 11a which are positioned at
120.degree. intervals about the center thereof to receive the substrate
lifting pins 46. The susceptor 11 may be rotated by means of the motor 28
so that the slots 11a are aligned with the respective substrate lifting
pins 46 as shown in FIG. 4. The angular positioning of the susceptor 11
against the respective lifting pins 46 may be controlled by a position
sensor 51 which is attached to the pulley 26.
The substrate, not shown, placed on the susceptor 11 may be lifted by
moving the respective lifting pins 46 upwards through the slots 11a of the
susceptor 11 by means of the upper mounting plate 41 which is driven by
the driving device 48.
As shown in FIG. 8, from the electrode body 12 is suspended a sensor
supporting rod 52 which supports a sensor 53 for detecting the lifted
position of the lower mounting plate 27 and therefore the susceptor 11,
and a sensor 54 for detecting the lifted position of the upper mounting
plate 41 and therefore the lifting pins 46.
The electrode body 12 is supplied with RF power from RF power supply 55
through a circuit 56 as shown in FIG. 5.
The operation of the illustrated apparatus will now be described.
The substrate to be processed is positioned on the susceptor 11 in the
vacuum chamber 1, the vacuum chamber 1 is evacuated so that it has a
predetermined pressure, and a suitable gas is introduced into the vacuum
chamber 1 for generating the plasma by a glow discharge.
When the cylinder device 42 is operated, the drive rod 43 is moved upwards,
and then the lower mounting plate 27, the intermediate mounting plate 25
and the rotating shaft 19 are lifted. Therefore, the susceptor 11 is
raised so that the distance d between the susceptor 11 and the electrode
body 12 is increased.
FIG. 10 shows the relation of the distance d to the potential V which is
generated on the surface of the susceptor 11 or substrate S.
As shown in FIG. 10-A, when the distance d is a small, that is d1, DC bias
voltage becomes large value V1, and the plasma P is generated on the
substrate S.
When the distance d is increased as shown at d2 in FIG. 10-B, DC bias
voltage is decreased to the value V2. In this case, the plasma to be
generated is maintained above the substrate S. When the distance d is more
increased as shown at d3 in FIG. 10-C, DC bias voltage is decreased to the
value V3 which is lower than V2, and the plasma is transferred into the
space defined between the susceptor 11 and the electrode body 12. It is,
therefore, appreciated that the potential on the susceptor 11 and DC bias
voltage can be varied and the area where the plasma is to be produced can
be changed in response to the position of the susceptor 11.
In sputtering, etching, Plasma CVD or the like, generally, RF bias is
applied to the substrates to be processed and a suitable DC bias voltage
is applied to the substrates in order to improve the property of a thin
film to be formed on the substrate, step coverage, anisotropy of an
etching or the like. For this end, in the conventional system, an
electrical control has been utilized.
In accordance with the illustrated embodiment of the present invention,
however, DC bias voltage can be easily changed by adjusting the position
of the susceptor 11 in respect to the electrode body 12.
In the illustrated embodiment, therefore, the position of the susceptor 11
can be adjusted in view of the property of the thin film to be formed on
the surface of the substrate on the susceptor 11 and the other
characteristics. The intermediate mounting plate 25 and the lower mounting
plate 27 are guided and lifted along the guide rod 37. Thus, the rotating
shaft 19 may be exactly raised without shaking. When the rotating shaft 19
is moved to a predetermined raised position, the sensor 53 attached to the
supporting rod 52 feeds the output signal to the air cylinder device 42,
and therefore the air cylinder device 42 is deenergized, thereby stopping
the susceptor 11 at the desired distance from the electrode body 12.
Then, the motor 28 is energized so that the rotating shaft 19 is rotated
through the timing belt 35 and the pulley 26, and the susceptor 11 is
rotated. From the reactive gas feeding nozzle 2 a reactive gas is
introduced into the vacuum chamber 1. On the surface of the substrate
positioned on the susceptor 11 there can be uniformly formed a thin film
which includes the components of the reactive gas.
When the thin film having a predetermined thickness is formed on the
surface of the substrate, the feeding of the reactive gas into the vacuum
chamber 1 is stopped and the motor 28 is deenergized so that the susceptor
11 is stopped. And then the air cylinder device 42 is energized so that
the drive rod 43 is moved downwards to down the susceptor 11 to the
position as shown in FIG. 5. When the susceptor 11 reaches that position,
the sensor 53 applies the output signal to the air cylinder device 42 to
stop it. When the motor 28 is deenergized, the susceptor 11 is stopped so
that the slots 11a are aligned with the respective lifting pins 46 by
means of the position sensor 51.
With the energizing of the substrate lifter driving device 48, the upper
mounting plate 41 is moved upwards, and then the lifting pins 46 are
passed through the respective slots 11a in the susceptor 11 to push the
substrate upwards. A suitable carrier fork not shown is inserted into the
vacuum chamber 1 through the opening 6 so as to receive the substrate
raised by the lifting pins 46, and the substrate is carried out of the
vacuum chamber 1 by this fork.
Next substrate to be processed is placed on the carrier fork, is introduced
into, the vacuum chamber 1, through the opening 6 and is positioned on the
raised lifting pins 46.
Thereafter, with the energizing of the cylinder device 48, the lifting pins
46 is fallen to the position as shown in FIG. 5 so that the substrate is
mounted on the susceptor 11. In this case, the downward movement of the
lifting pins 46 can be detected by the sensor 54 which feeds a control
signal to the cylinder device 48 to stop the operation thereof. In this
way, the operation of the system may be sequentially repeated for
processing successive substrates.
In the cleaning operation of the illustrated apparatus, the susceptor 11
has no substrate mounted thereon. In order to clean the surface of the
susceptor 11 and the portions in the vicinity thereof, for example,
chamber wall, the susceptor is set to the position as shown in FIG. 10-A
or 10-B. Therefore, these portions may be cleaned by the bombardment of
the plasma which is produced in the space above the susceptor. In this
case, since the produced plasma penetrates little into the area between
the susceptor 11 and the electrode body 12, the rear portion of the
susceptor 11 and the surface of the electrode 12 can not substantially be
cleaned. The rear surface of the susceptor 11 and the surface of the
electrode body 12 can be cleaned by raising the susceptor 11 with the
operation of the air cylinder device 42 and forming the plasma between the
susceptor 11 and the electrode body 12 as shown in FIG. 10-C.
A modified embodiment of the invention is illustrated in FIGS. 11 and 12 in
which the same numerals are used to denote the elements corresponding to
those in FIGS. 3 to 9.
On the atmospheric side of an electrode body 57 heater assemblies 58 are
attached by a mounting member 59. The heater assemblies 58 are arranged at
equal angular intervals. Each of the heater assemblies 58 comprises an
infrared lamp 60. The electrode body 57 is provided with a plurality of
openings 61 which are opposite to the respective heater assemblies 58. In
each opening 61 of the electrode body 57 there is tightly fitted a window
member 62 which may be made of a transparent material having a low
infrared absorption, for example quartz. A linear bearing 40 is secured to
a mounting plate 63 which is provided with equally spaced three
extensions, only one of the extensions being shown at 63a in FIG. 11. On
each extension 63a there is provided a substrate lifting pin 64 which is
surrounded with bellows 65, and has a top end 64a tightly and slidably
passed through the bottom wall 1a of a vacuum chamber and positioned in
the vacuum chamber. To the top end 64a of the pin 64 is attached one end
of a horizontal arm 66, the other end 66a of the horizontal arm 66 being
extended into the associated one of recesses 57a which are provided on the
periphery of the electrode body 57. Susceptor 67 fixed on the driving
shaft 19 is provided with recesses 67a at the periphery thereof. The
recesses 67a of the susceptor 67 are positioned at the same angular
intervals as that of the recesses 57a of the electrode body 57 so that the
recesses 67a may be aligned with the recesses 57a as shown in FIG. 12. The
susceptor 67 may be angularly positioned in respect to the electrode body
57 by means of a position sensor as in the first embodiment. It should be
understood that the substrate S has an outer periphery positioned over the
ends 66a of the horizontal arms 66. It should be also understood that the
other arrangement is substantially similar to the first embodiment.
In the operation of the apparatus illustrated in FIGS. 11 and 12, A thin
film can be uniformly formed on the surface of the substrate S while it is
rotated. Upon the forming of the thin film, the substrate S is heated by
the infrared ray from the heater assemblies 58. In this connection, if the
susceptor 67 is made of transparent material, the substrate S may be
directly heated by the infrared beam, but if does not so, the substrate S
may be heated with the heat transfer.
When the thin film having a desired thickness is formed on the surface of
the substrate S, the rotation of the susceptor 67 is stopped so that the
recesses 67a thereof may be aligned with the recesses 57a of the electrode
body 57 by the position sensor as in the first embodiment, and then the
susceptor 67 is moved to the position shown in FIG. 11 by raising or
lowering the drive shaft 19.
Thereafter, the mounting plate 63 is lifted to move the lifting pins 64 and
therefore the horizontal arms 66 upwards. Thus, the substrate S is raised
to the loading or unloading position by the arms 66 being moved upwards.
It should be appreciated that in this modified embodiment the cleaning
operation and the controlling of DC bias may be performed in the same
manner as that of the first embodiment.
Further, it should be understood that in this embodiment, the electrode
body 57, the heater assemblies 58 and the portions which are to be cooled
may be cooled by suitable cooling means.
According to the present invention as described above, the DC bias to be
produced on the surface of the substrate can be mechanically controlled,
and the susceptor and the other components in the vacuum chamber can be
easily cleaned while maintaining the desired evacuated condition in the
vacuum chamber,.
The present invention has also advantages of reducing the load of the
rotary drive mechanism, and assembling and disassembling easily the rotary
drive mechanism.
While the present invention has been described in detail with respect to
certain now preferred embodiments, it will be understood that various
changes and modifications may be made within the scope of the claimed
invention. For example, the present invention may be equally applied to
sputtering, plasma etching, plasma CVD or other surface processing
apparatus.
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