U.S. patent application number 13/213533 was filed with the patent office on 2012-01-12 for film forming method, film forming apparatus and control unit for the film forming apparatus.
This patent application is currently assigned to CANON ANELVA CORPORATION. Invention is credited to Shunsuke Yamamoto.
Application Number | 20120006675 13/213533 |
Document ID | / |
Family ID | 44319319 |
Filed Date | 2012-01-12 |
United States Patent
Application |
20120006675 |
Kind Code |
A1 |
Yamamoto; Shunsuke |
January 12, 2012 |
FILM FORMING METHOD, FILM FORMING APPARATUS AND CONTROL UNIT FOR
THE FILM FORMING APPARATUS
Abstract
The invention reduces generation of particles. An embodiment of
the preset invention includes a target holder (6) for holding a
target (4), a power source (12) for applying a power to the target
holder (6), a substrate holder (7), a first shutter (14) capable of
opening and closing between the target (4) and the substrate holder
(7), a second shutter (19) located closer to the substrate holder
(7) than to the first shutter (14), and capable of opening and
closing between the target holder (6) and the substrate holder (7),
and a controller (con) for controlling the power source (12) and
the first and second shutters (14), (19). The controller (con)
applies a first power to the target holder (6) in the state where
the first shutter (14) is closed, then opens the first shutter
(14), and further applies a second power higher than the first
power to the target holder (6) in the state where the second
shutter (19) is closed.
Inventors: |
Yamamoto; Shunsuke; (Tokyo,
JP) |
Assignee: |
CANON ANELVA CORPORATION
Kawasaki-shi
JP
|
Family ID: |
44319319 |
Appl. No.: |
13/213533 |
Filed: |
August 19, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/JP2011/051487 |
Jan 26, 2011 |
|
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13213533 |
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Current U.S.
Class: |
204/192.1 ;
204/298.11 |
Current CPC
Class: |
H01J 37/3405 20130101;
C23C 14/225 20130101; H01J 37/3447 20130101; C23C 14/564 20130101;
C23C 14/3492 20130101; C23C 14/35 20130101 |
Class at
Publication: |
204/192.1 ;
204/298.11 |
International
Class: |
C23C 14/34 20060101
C23C014/34; C23C 14/54 20060101 C23C014/54 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 26, 2010 |
JP |
2010-014236 |
Claims
1. A film forming method for forming a film on a substrate by
sputtering a target, the method comprising: a first step of
applying a first power to a target holder holding the target to
cause discharge in a first discharge space, the first power being
lower than a film forming power applied upon film formation from a
power source connected to the target holder; a second step of
changing the location of discharging from the first discharge space
to a second discharge space larger than the first discharge space
while continuing the discharge caused in the first step; a third
step of applying a second power higher than the first power to the
target holder from the power source in the second discharge space;
and a fourth step of exposing the substrate, which is shielded
against the second discharge space, to the second discharge
space.
2. The film forming method according to claim 1, wherein: the first
discharge space is formed when a first shielding member is located
at a first position, the first shielding member being movable
between the first position that shields between the target holder
and a substrate holder holding the substrate and a second position
that does not shield between the target holder and the substrate
holder; and in the second step, the first shielding member is moved
from the first position to the second position.
3. The film forming method according to claim 1, wherein: prior to
the fourth step, the substrate is shielded against the second
discharge space by a second shielding member which is movable
between a third position that shields between the target holder and
the substrate holder and a fourth position that does not shield
between the target holder and the substrate holder; and in the
fourth step, the second shielding member is moved from the third
position to the fourth position.
4. The film forming method according to claim 1, wherein in the
third step, a power applied to the target holder is increased from
the first power to the second power.
5. The film forming method according to claim 4, wherein in the
third step, the power applied to the target holder is increased
stepwise or continuously.
6. The film forming method according to claim 1, wherein after the
fourth step, the film is continuously formed on the substrate.
7. A film forming apparatus comprising: a target holder for holding
a target; a power applying means for applying a power to the target
holder; a substrate holder for holding a substrate; a shield which
is grounded, has a hollow portion formed so as to surround the
target holder, and has an opening formed for causing the hollow
portion to communicate with outside the shield; a first shielding
member configured to be movable between a first position that
shields between the target holder and the substrate holder by
covering the opening and a second position that does not shield
between the target holder and the substrate holder; a second
shielding member configured to be movable between a third position
that shields between the target holder and the substrate holder by
covering at least a substrate holding surface of the substrate
holder and a fourth position that does not shield between the
target holder and the substrate holder; and a control means for
controlling the power applying means and movement of the first and
second shielding members, wherein the control means controls the
power applying means so as to apply a first power lower than a film
forming power applied to the target holder upon film formation in a
state where the first shielding member is located at the first
position and the second shielding member is located at the third
position, then controls movement of the first shielding member so
as to move the first shielding member from the first position to
the second position in a state where the second shielding member is
located at the third position, and then controls the power applying
means so as to apply a second power higher than the first power to
the target holder.
8. The film forming apparatus according to claim 7, wherein: the
shield has conductivity; and a surface of a hollow portion of the
shield facing the target holder is coated with an insulating film
formed through thermal spray.
9. The film forming apparatus according to claim 7, wherein the
control means controls, when the second power is applied, the power
applying means so as to increase a power applied to the target
holder from the first power to the second power.
10. A control unit for controlling a film forming apparatus
provided with a target holder for holding a target, a power
applying means for applying a power to the target holder, a
substrate holder for holding a substrate, a shield which is
grounded, has a hollow portion formed so as to surround the target
holder, and has an opening for causing the hollow portion to
communicate with outside the shield; a first shielding member
configured to be movable between a first position that shields
between the target holder and the substrate holder by covering the
opening and a second position that does not shield between the
target holder and the substrate holder; and a second shielding
member configured to be movable between a third position that
shields between the target holder and the substrate holder by
covering at least a substrate holding surface of the substrate
holder and a fourth position that does not shield between the
target holder and the substrate holder, the control unit
comprising: a means for controlling the power applying means so as
to apply a first power lower than a film forming power applied to
the target holder upon film formation in a state where the first
shielding member is located at the first position and the second
shielding member is located at the third position; a means for
controlling movement of the first shielding member so as to move
the first shielding member from the first position to the second
position in a state where the second shielding member is located at
the third position by applying the first power to the target holder
while continuing discharge caused in a first discharge space
between the hollow portion and the first shielding member; and a
means for controlling the power applying means so as to apply a
second power higher than the first power to the target holder in a
state where the first shielding member is located at the second
position and the second shielding member is located at the third
position.
11. A computer program causing a computer to function as the
control unit according to claim 10.
12. A storage medium for storing a computer readable program, which
stores the computer program according to claim 11.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation application of
International Application No. PCT/JP2011/051487, filed Jan. 26,
2011, which claims the benefit of Japanese Patent Application No.
2010-014236, filed Jan. 26, 2010. The contents of the
aforementioned applications are incorporated herein by reference in
their entities.
TECHNICAL FIELD
[0002] The present invention relates to a film forming method and a
film forming apparatus (for example, sputtering apparatus) employed
for depositing material on a substrate in the step of manufacturing
a semiconductor device and a magnetic storage medium, and a control
unit for the film forming apparatus.
BACKGROUND ART
[0003] The practice for producing the thin film using sputtering
phenomenon and processing the thin film for application to the
device has been widely implemented in the industry. The sputtering
phenomenon is caused by making high energy ion incident onto the
target from which sputter particles (neutral particles) are
generated, so that the sputter particles are deposited on the
substrate.
[0004] Generally, the sputtering film forming apparatus is provided
with a shield called shutter capable of opening and closing between
the target and the substrate. The shutter is used to control the
timing for starting the film formation so as not to start the film
forming process until stabilization of the plasma state within the
vacuum vessel. Specifically, the shutter is kept closed until
stabilization of the plasma generated upon application of high
voltage to the target so that no film is formed on the substrate.
Upon stabilization of the plasma, the shutter is opened to start
the film formation. Controlling start of the film formation using
the shutter makes it possible to conduct well controlled film
formation on the substrate with stabilized plasma, resulting in the
film with high quality.
[0005] Patent Document 1 discloses the high frequency sputtering
apparatus and method capable of forming the thin film with
excellent reproducibility with respect to the film quality and film
thickness by opening the shutter disposed between the substrate and
the target upon stabilization of self bias while detecting the self
bias voltage induced in the target. Patent Document 2 discloses the
sputtering apparatus having the sputter cathode provided with a
tubular cathode cover which surrounds the side of the sputter
surface, and the shutter that can be opened and closed provided in
the open end portion of the cathode cover. The sputtering apparatus
disclosed in Patent Document 2 is capable of reducing turnaround of
the sputter particles upon discharge in the state where the shutter
is closed before starting the film formation such as the target
cleaning.
RELATED ART
Patent Document
[0006] [Patent Document 1] Japanese Unexamined Patent Application
Publication No. 4-218671 [0007] [Patent Document 2] Japanese
Unexamined Patent Application Publication No. 8-269705
SUMMARY OF INVENTION
[0008] The sputtering film forming apparatus and method disclosed
in Patent Document 1 allow formation of the thin film with
excellent reproducibility with respect to film quality and film
thickness by opening the shutter disposed between the substrate and
the target at a time point when the self bias is stabilized.
However, reduction of the particle onto the substrate is not
disclosed in the document. The film forming apparatus disclosed in
Patent Document 2 has also improved the turnaround of the sputter
particles when the shutter is closed. However, the problem relevant
to the particle onto the substrate resulting from formation of the
film when the shutter is opened is not described. Influence of the
particle on production of the semiconductor device and the magnetic
storage medium adapted for recent miniaturization and thin-film
formation has increased, and accordingly, suppression of the
particle has been increasingly demanded.
[0009] A first aspect of the present invention is a film forming
method for forming a film on a substrate by sputtering a target,
the method comprising: a first step of applying a first power to a
target holder holding the target to cause discharge in a first
discharge space, the first power being lower than a film forming
power applied upon film formation from a power source connected to
the target holder; a second step of changing the location of
discharging from the first discharge space to a second discharge
space larger than the first discharge space while continuing the
discharge caused in the first step; a third step of applying a
second power higher than the first power to the target holder from
the power source in the second discharge space; and a fourth step
of exposing the substrate, which is shielded against the second
discharge space, to the second discharge space.
[0010] A second aspect of the present invention is a film forming
apparatus comprising: a target holder for holding a target; a power
applying means for applying a power to the target holder; a
substrate holder for holding a substrate; a shield which is
grounded, has a hollow portion formed so as to surround the target
holder, and has an opening formed for causing the hollow portion to
communicate with outside the shield; a first shielding member
configured to be movable between a first position that shields
between the target holder and the substrate holder by covering the
opening and a second position that does not shield between the
target holder and the substrate holder; a second shielding member
configured to be movable between a third position that shields
between the target holder and the substrate holder by covering at
least a substrate holding surface of the substrate holder and a
fourth position that does not shield between the target holder and
the substrate holder; and a control means for controlling the power
applying means and movement of the first and second shielding
members, wherein the control means controls the power applying
means so as to apply a first power lower than a film forming power
applied to the target holder upon film formation in a state where
the first shielding member is located at the first position and the
second shielding member is located at the third position, then
controls movement of the first shielding member so as to move the
first shielding member from the first position to the second
position in a state where the second shielding member is located at
the third position, and then controls the power applying means so
as to apply a second power higher than the first power to the
target holder.
[0011] A third aspect of the present invention is a control unit
for controlling a film forming apparatus provided with a target
holder for holding a target, a power applying means for applying a
power to the target holder, a substrate holder for holding a
substrate, a shield which is grounded, has a hollow portion formed
so as to surround the target holder, and has an opening for causing
the hollow portion to communicate with outside the shield; a first
shielding member configured to be movable between a first position
that shields between the target holder and the substrate holder by
covering the opening and a second position that does not shield
between the target holder and the substrate holder; and a second
shielding member configured to be movable between a third position
that shields between the target holder and the substrate holder by
covering at least a substrate holding surface of the substrate
holder and a fourth position that does not shield between the
target holder and the substrate holder, the control unit
comprising: a means for controlling the power applying means so as
to apply a first power lower than a film forming power applied to
the target holder upon film formation in a state where the first
shielding member is located at the first position and the second
shielding member is located at the third position; a means for
controlling movement of the first shielding member so as to move
the first shielding member from the first position to the second
position in a state where the second shielding member is located at
the third position by applying the first power to the target holder
while continuing discharge caused in a first discharge space
between the hollow portion and the first shielding member; and a
means for controlling the power applying means so as to apply a
second power higher than the first power to the target holder in a
state where the first shielding member is located at the second
position and the second shielding member is located at the third
position.
[0012] The present invention makes it possible to realize reduction
of the particle onto the substrate upon film formation.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 schematically illustrates a sputtering apparatus
according to an embodiment of the present invention.
[0014] FIG. 2 is a flow of a film forming method according to an
embodiment of the present invention.
[0015] FIG. 3 is a chart representing each state of components
resulting from application of the film forming method according to
an embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
[0016] Referring to FIG. 1, a general structure of a sputter film
forming apparatus 1 according to an embodiment of the present
invention will be described. FIG. 1 schematically illustrates the
sputtering apparatus 1 according to an embodiment of the present
invention.
[0017] The sputter film forming apparatus 1 includes a vacuum
chamber 2 provided with a gate valve 42 and capable of vacuum
exhaust, an exhaust chamber 8 which is provided adjacent to the
vacuum chamber 2 via an exhaust port, and an exhaust unit for
exhausting the inside of the vacuum chamber 2 via the exhaust
chamber 8. The exhaust unit includes a turbo-molecular pump 48
connected to the exhaust chamber 8 via a main valve 47. The
turbo-molecular pump 48 of the exhaust unit is further connected to
a dry pump 49. The exhaust unit is provided below the exhaust
chamber 8 in order to minimize the footprint (occupied area) of the
apparatus as a whole.
[0018] A target holder 6 is provided within the vacuum chamber 2
for holding a target 4 via a back plate 5. Adjacent to the target
holder 6, a target shutter 14 with an opening is provided so as to
cover the target holder 6. The target shutter 14 formed of a
conductive metal, for example, Al and SUS, is grounded. The target
shutter 14 has a rotary shutter structure. The target shutter 14
functions as a shielding member that changes a state between a
closed state (shielded state) for shielding between a substrate
holder 7 and the target holder 6, and an open state (retracted
state) for not shielding between the substrate holder 7 and the
target holder 6. When the target shutter 14 is located at a first
position that shields between the target holder 6 and the substrate
holder 7, the target shutter 14 is in the closed state. When the
target shutter 14 is located at the first position, an opening of a
chimney 9 (an opening for connecting the hollow portion of the
chimney 9 with outside the chimney 9) is covered with the target
shutter 14, so that the target holder 6 is shielded against the
substrate holder 7. Meanwhile, when the target shutter 14 is
located at a second position that does not shield between the
target holder 6 and the substrate holder 7, it is in the open
state.
[0019] The opening of the target shutter 14 is positioned between
the target 4 placed on the target holder 6 and a substrate 10
mounted on the substrate holder 7 to bring the target shutter 14
into the open state. The target shutter 14 is provided with a
target shutter drive mechanism 33 for opening and closing the
target shutter 14. The chimney 9 as a tubular shield is provided
around the target holder 6 in the space between the target holder 6
and the target shutter 14 so as to surround periphery of the target
holder 6. A magnetron discharge space to the front of the sputter
surface of the target 4 attached to the target holder 6 is
surrounded with the chimney 9, and open to the opening of the
target shutter 14 in the open state of the shutter.
[0020] In the embodiment, the target shutter 14 is configured to be
rotatable. However, the target shutter 14 may be arbitrarily
configured so long as it is movable between the first and the
second positions so as to establish its closed state and the open
state. For example, the target shutter 14 may be configured to be
slidable and may be moved between the first and second positions by
sliding.
[0021] If the magnetron discharge space to the front of the sputter
surface of the target 4 attached to the target holder 6 is
surrounded with the chimney 9 and the gas introducing mechanism is
further provided toward the magnetron discharge space, gas is
introduced while bringing the target shutter 14 into the closed
state so as to immediately raise the pressure to the front surface
of the target. This makes it possible to quickly start discharging
under the low pressure, thus providing the effect for improving
throughput.
[0022] The sputter apparatus of off-set arrangement in the present
embodiment, intended to obtain good distribution in spite of a very
thin film allows use of a plurality of targets so as to be
switchable. In this case, the target shutter 14 and the chimney 9
are used for the purpose of preventing or suppressing cross
contamination of the plurality of targets. That is, the target
shutter 14 in this case serves to shield the other target holder
from the discharge space (space where the plasma discharge occurs)
between the target holder 6 and the substrate holder 7 in the open
state.
[0023] The chimney 9 is formed of the conductive material, for
example, Al, and grounded. Preferably, the chimney 9 has
concavo-convex portions formed on its surface facing the target
through blast process and thermal spray from the aspect of
retaining the adhered sputter particles. It is more preferable to
coat the surface of the chimney 9, which faces the target with at
least the insulating material, for example, alumina and yttria
through thermal spray. The surface of the chimney 9 as the member
for surrounding the target 4, which faces the target 4 is coated
through at least alumina thermal spray, so that the surface
potential of the chimney 9 becomes close to the plasma potential
compared to the case where it is not coated through alumina thermal
spray. In other words, the surface of the chimney 9, which faces
the target is coated with at least the insulating film (for
example, insulating film formed through alumina thermal spray) so
as to allow the surface potential of the chimney 9 to be close to
the potential of plasma generated in the magnetron discharge space
in the structure capable of forming the magnetron discharge space
in the hollow portion of the chimney 9. This may suppress
bombardment by the charged particles in plasma, thus further
reducing the particles. The surface of the chimney 9, which faces
the target, is coated through at least the alumina thermal spray to
suppress abnormal discharge generated between the chimney 9 and the
target 4, thus further reducing the particles. When the surface of
the chimney 9, which faces the target, is coated through thermal
spray of the insulating film with arbitrary method other than the
one according to the embodiment, the result of remarkable particle
reduction has been obtained compared to the case where the chimney
surface is merely coated through the metal thermal spray. According
to the embodiment, a film forming method for forming a film on a
substrate by sputtering a target includes a first step of causing
discharge in a first discharge space by applying a first power to a
target holder for holding the target, the first power being lower
than a film forming power applied upon film formation by a power
source connected to the target holder, a second step of changing
the location of discharging from the first discharge space to a
second discharge space larger than the first discharge space while
continuing the discharge caused in the first step, a third step of
applying a second power higher than the first power to the target
holder from the power source in the second discharge space, and a
fourth step of exposing the substrate shielded against the second
discharge space to the second discharge space. The effect of the
particle reduction may not be limited to the case by the
aforementioned method. The particle reduction effect may be
obtained when the surface of the chimney 9, which faces the target
4, is coated through at least the insulating film thermal spray in
the structure capable of forming the magnetron discharge space in
the hollow portion of the chimney 9. The above-described method may
further be combined with the power application method according to
the embodiment so as to obtain more remarkable effects.
[0024] A magnet 13 for realizing magnetron sputtering is provided
to the rear of the target 4 when seen from the sputter surface. The
magnet 13 held by a magnet holder 3 is rotatable by a not shown
magnet holder rotating mechanism. During discharge, the magnet 13
is rotated for making erosion of the target uniform. The target 4
is provided at a position (offset position) obliquely upward with
respect to the substrate 10. In other words, the center point of
the sputter surface of the target 4 deviates from the normal of the
center point of the substrate 10 by a predetermined dimension. The
target holder 6 is connected to a power source 12 for applying
power for sputter discharge. When the power source 12 applies
voltage to the target holder 6, discharge starts to deposit sputter
particles on the substrate. Assuming that the distance between the
point at which the plane that includes the upper surface of the
substrate holder 7 intersects the normal of the plane that passes
the center point of the target 4, and the center point of the
target 4 is defined as T/S distance (see FIG. 1), the T/S distance
of the embodiment is set to 240 mm. As RF power source is used as
the power source, a not shown matching box is provided between the
power source 12 and the target holder 6.
[0025] The target holder 6 is insulated by an insulator 34 from the
vacuum chamber 2 at the ground potential. It is formed of a metal
such as Cu which serves as the electrode upon application of power.
The target holder 6 is provided with a not shown water path inside
so as to be cooled by cooling water supplied from a not shown water
pipe arrangement. The target 4 contains the material component
intended to be used for forming a film on the substrate 10.
[0026] The back plate 5 provided between the target 4 and the
target holder 6 is formed of a metal such as Cu, and supports the
target 4.
[0027] A substrate holder 7 for mounting the substrate 10 thereon,
and a substrate shutter 19 provided between the substrate holder 7
and the target holder 6 are provided within the vacuum chamber 2.
The substrate shutter 19 is supported by a substrate shutter
support mechanism 20 which is connected to a substrate shutter
drive mechanism for driving the substrate shutter 19 to be opened
and closed. The substrate shutter 19 provided adjacent to the
substrate holder 7 serves as a shielding member for switching a
state between a closed state for shielding between the substrate
holder 7 and the target holder 6 and an open state for not
shielding between the substrate holder 7 and the target holder 6.
That is, when the substrate shutter 19 is located at a third
position that shields between the target holder 6 and the substrate
holder 7, the substrate shutter 19 is in the closed state. When the
substrate shutter 19 is located at the third position, it covers at
least the substrate holding surface on which the substrate of the
substrate holder 9 is held. The substrate 10 is shielded against
the side of the target shutter 14 (for example, second discharge
space to be described later). Meanwhile, when the substrate shutter
19 is located at a fourth position that does not shield between the
target holder 6 and the substrate holder 7, it is in the open
state.
[0028] In the embodiment, the substrate shutter is configured to be
rotatable. However, the substrate shutter 19 may be arbitrarily
configured so long as it is movable between the third and fourth
positions so as to establish its closed/open states. For example,
the substrate shutter 19 may be configured to be slidable and may
be moved between the third and fourth positions by sliding.
[0029] The inner surface of the vacuum chamber 2 is grounded. A
grounded chamber shield 40 is provided on the inner surface of the
vacuum chamber 2 between the target shutter 14 and the substrate
holder 7. The chamber shield is formed separately from the vacuum
chamber 2 for preventing direct adhesion of sputter particles
discharged from the target 4 onto the inner surface of the vacuum
chamber 2, and for protecting the inner surface of the vacuum
chamber. The chamber shield may be periodically replaced and
cleaned for reuse. The chamber shield 40 is positioned to surround
at least the space between the opening of the target shutter 14 and
the position which can be shielded by the substrate shutter 19. The
grounded chamber shield 40 is capable of acting as a ground
electrode to the target 4 and the target holder 6 to which the high
frequency power is applied. Further preferably, the chamber shield
40 is positioned to surround the space between the opening of the
target shutter 14 and the substrate holder 7 from the aspect of
stability of plasma.
[0030] A ring-like shielding member (hereinafter referred to as
"substrate peripheral cover ring 21") is provided on the surface of
the substrate holder 7 at outer edge side (outer circumference) of
the portion on which the substrate 10 is mounted. The substrate
peripheral cover ring 21 prevents or suppresses adhesion of the
sputter particles to the portion of the substrate 10 mounted on the
substrate holder 7 other than the film forming surface. The portion
other than the film forming surface includes the side surface and
back surface of the substrate 10 in addition to the surface of the
substrate holder 7 covered by the substrate peripheral cover ring
21. The substrate holder 7 is provided with a substrate holder
drive mechanism 31 for moving the substrate holder 7 up and down
and rotating it at a predetermined speed. The substrate holder
drive mechanism 31 is capable of moving the substrate holder 7 up
and down.
[0031] The vacuum chamber 2 is provided with a first gas inlet 15
for introducing inert gas into the vacuum chamber 2, a second gas
inlet 17 for introducing reactive gas, and a pressure gauge 41 for
measuring pressure of the vacuum chamber 2. The first gas inlet 15
is connected to piping for introducing the inert gas (for example,
argon, krypton, xenon, neon), a mass flow controller for
controlling flow rate of the inert gas, and valves for switching
on/off state of flow of the inert gas, and configured to introduce
the gas at the flow rate designated by a not shown control unit
into the vacuum chamber 2 stably. The first gas inlet 15 may be
connected to a decompression valve, filter and the like when
needed. The first gas inlet 15 is positioned adjacent to the target
4. The first gas inlet 15 is configured to introduce the inert gas
into the magnetron discharge space to the front surface of the
target 4.
[0032] The second gas inlet 17 is connected to piping for
introducing reactive gas (for example, nitrogen, oxygen), the mass
flow controller for controlling the flow rate of the reactive gas,
and valves for switching on/off state of flow of the reactive gas,
and configured to introduce the gas at the flow rate designated by
a not shown control unit into the vacuum chamber 2 stably. The
second gas inlet 17 may be connected to a decompression valve,
filter and the like when needed. The second gas inlet 17 is
positioned adjacent to the substrate 10.
[0033] The sputter film forming apparatus 1 is provided with a
controller con as a control means for controlling the drive
mechanisms 32, 33 for the shutters 14, 19 and the power source 12
so as to open/close the shutters 14, 19 at a predetermined timing
to increase/decrease the power. The controller con of the sputter
film forming apparatus 1 includes a storage unit 81 for storing the
program of the method according to the embodiment as shown in FIG.
2, for example, and an arithmetic processing unit 82 for executing
the arithmetic processing of the process control. The controller
con is capable of executing the method according to the embodiment
in accordance with the program shown in FIG. 2. The arithmetic
processing unit 82 may be formed of a personal computer (PC), PLC,
and microcomputer, for example.
[0034] FIG. 2 represents an exemplary flow of the film forming
method according to the embodiment. FIG. 3 represents the
respective states of components (timing chart) when applying the
method. Referring to FIGS. 2 and 3, the film forming method
according to the embodiment using the apparatus as shown in FIG. 1
will be described.
[0035] First, the target shutter 14 (which may be referred to as
"first shutter") is in the closed state. That is, the target
shutter 14 is located at the first position. So if the target
shutter 14 is in the open state, the controller con controls the
target shutter drive mechanism 33 to rotate the target shutter 14
into the closed state so as to shield between the target holder 6
and the substrate holder 7. In the embodiment, the target holder 6
is surrounded with the chimney 9, so that the space defined by the
target shutter 14, the chimney 9 and the target 4 in the closed
state serves as the first discharge space. The first discharge
space is made smaller than the discharge space upon subsequent film
formation (second discharge space to be described later) to promote
discharging at ignition.
[0036] The substrate shutter 19 (which may be also referred to as
"second shutter") is also closed. That is, the substrate shutter 19
is located at the third position. While the substrate shutter 19 is
in the open state, the controller con controls the substrate
shutter drive mechanism 32 to rotate the substrate shutter 19 into
the closed state so as to shield between the target holder 6 and
the substrate holder 7.
[0037] In first step S1, the controller con controls the power
source 12 to apply a first power (electric power) to the target
holder 6 for holding the target 4. Application of the first power
causes discharge in the first discharge space. The power (first
power) applied in first step S31 may be lower than the film forming
power so long as the discharge is stably started. In second step
S2, the controller con controls the target shutter drive mechanism
33 to open the first shutter (target shutter 14) capable of
switching open/closed state between the target 4 and the substrate
10 while continuing the discharge with power applied in first step
S1. That is, the target shutter drive mechanism 33 rotates the
first shutter so as to move the first shutter from the first
position to the second position. The target holder 6 (target 4) is
exposed to the side of the substrate holder 7 (the target shutter
14 is brought into the open state). The target shutter is thus
brought into the open state to allow discharge also in the region
between the target holder 6 and the substrate holder 7 in the
vacuum chamber 2, for example. Second step S2 changes the location
of discharging from the first discharge space to the second
discharge space larger than the first discharge space.
[0038] In third step S3, the controller con controls the power
source 12 to increase the power applied to the target holder 6 from
the first power to a second power higher than the first power. It
is preferable to increase the power applied in third step S3
(second power) to a film forming power for stable film formation on
the next substrate. Then in fourth step S4, the controller con
controls the substrate shutter drive mechanism to open the second
shutter (substrate shutter 19) which can be opened/closed at the
position closer to the substrate 10 than to the first shutter
(target shutter 14) for starting the film formation on the
substrate 10. That is, the substrate shutter drive mechanism 32
rotates the second shutter so as to move the second shutter from
the third position to the fourth position for exposing the
substrate holder 7 (that is, the substrate 10) to the side of the
target holder 6 (substrate shutter 19 is brought into the open
state). The substrate holder 7 is thus brought into the open state
to expose the substrate holder (that is, substrate 10) to the
second discharge space. This allows the sputter particles to reach
the substrate 10 on which the film is formed.
[0039] The aforementioned flow of the film forming process allows
remarkable reduction in the particles.
[0040] The flow for starting the film forming process, and
background of the remarkable particle reduction as a result of such
process will be described.
[0041] In the state where the discharge space to the front of the
target 4 is surrounded with the chimney 9 to make it advantageous
to start discharging, and the first shutter (target shutter 14) is
closed, gas is introduced into the discharge space (first discharge
space) to start discharging through application of high frequency
power to the target holder 6. In the aforementioned state, the
plasma is confined by the target 4, the chimney 9 and the target
shutter 14. As it is well known, even if the target is formed of
the insulating material, high frequency propagates to generate
plasma and self bias voltage. In the embodiment, since the chimney
9 and the target shutter 14 are grounded, the chimney 9 and the
target shutter 14 serve as the ground electrodes. As the target
shutter 14 is configured to be rotatable by the drive mechanism,
the chimney 9 may be considered to be grounded, which does not have
to be completely grounded at high frequency.
[0042] In this specification, the area of the surface of the target
4 facing the plasma via the sheath is set as high frequency applied
electrode area. When starting the discharge while closing the
target shutter 14 as described above, the grounded electrode area
is set as the total area of the inner wall surface of the chimney 9
and the surface of the target shutter 14 facing the target at a
maximum. In this way, if the grounded electrode area is relatively
small to the high frequency applied electrode area, the unignorable
voltage may be applied not only to the target 4 but also to the
chimney 9 and the target shutter 14. The voltage in this case is
caused by the potential difference between the plasma potential and
the electrode.
[0043] As the grounded electrode area becomes larger relative to
the high frequency applied electrode area, the potential difference
between the plasma potential and the ground electrode becomes
smaller. Meanwhile, if the grounded electrode area becomes close to
the high frequency applied electrode area, the voltage that is
substantially the same voltage applied to the high frequency
applied electrode (target 4 in this case) may be also applied to
the ground electrode. If the target shutter 14 is opened (the
target shutter 14 is brought into the open state), the plasma is
diffused in the region between the target shutter and the chamber
shield 40. While the high frequency applied electrode area is kept
constant, the grounded electrode area in view of plasma largely
changes depending on the state where the target shutter 14 is
closed (closed state), and the state where it is opened (open
state). In other words, in the embodiment, the relationship of
"high frequency applied electrode area/grounded electrode area"
becomes "closed target shutter 14 (closed state)>opened target
shutter 14 (open state)". Increase in the grounded electrode area
relative to the high frequency applied electrode area is effective
for decreasing the voltage to the ground electrode.
[0044] In case of large potential difference between the chimney 9
and plasma, ion in the plasma is made incident onto the inner
surface of the chimney 9 in accordance with the potential
difference between the chimney 9 and the plasma. If the potential
difference is large, ions incident onto the inner surface of the
chimney 9 sputter the surface of the chimney 9 and the surface of
the target shutter 14 facing the target to generate particles.
[0045] When starting discharge in the state where the target
shutter 14 is closed (second step S2), the relatively small first
discharge space is formed. The ground electrode becomes the chimney
9 and the target shutter 14 for comporting the first discharge
space. Accordingly, the grounded electrode area becomes relatively
small to the high frequency applied electrode area. However, if
discharge is started under the applied electric power (power) as
the first power as low as possible, the potential difference
between the chimney 9 as the ground electrode and the plasma
generated in the first discharge space may be made small. This
makes it possible to reduce particle generation owing to ion
bombardment against the surface of the chimney 9 and the surface of
the target shutter 14 facing the target.
[0046] Meanwhile, even if the applied power is increased after
opening the target shutter 14 (in third step S3), particles are not
increased. That is, when the target shutter 14 is in the open
state, the ground electrode includes the chimney 9, the target
shutter 14 and the chamber shield 40. When bringing the target
shutter 14 into the open state, the high frequency applied
electrode area is not changed. The discharge space becomes the
second discharge space larger than the first discharge space, thus
making the grounded electrode area large. This makes it possible to
reduce the potential difference between the plasma potential and
the ground electrode potential. This may further prevent incidence
of the ion with the energy which may cause problem on the inner
surface of the chimney 9 and the surface of the chamber shield 40.
When opening the substrate shutter 19 that has been in the closed
state, the change in the grounded electrode area ratio to the high
frequency applied electrode area is not as large as the case where
the target shutter 14 that has been in closed state is opened.
Accordingly, the problem relevant to increase in particles hardly
occurs.
[0047] The embodiment describes the sputter apparatus with offset
arrangement. However, such condition is not necessarily required
for obtaining the effect of the present invention. The effect of
the present invention may be obtained when establishing the
conditions where at least two shielding members (for example,
shutters) are needed, and at least one of the shielding members is
provided adjacent to the target, and at least one of the other
shielding members is provided adjacent to the substrate.
Particularly, in case of the long throw sputtering having long
distance between the target and the substrate, the distance between
the shielding member near the target and the shielding member near
the substrate, or the distance between the shielding member near
the target and the substrate mounted on the substrate holder
becomes large. As the ground area largely changes when opening the
shielding member near the target, great effect may be obtained.
[0048] The shield (for example, chimney) provided for the shielding
member (for example, shutter) near the target at the target side is
advantageous for improving start of discharge and suppression of
the cross contamination. The configuration of the shield is not
limited to the one described in the embodiment so long as the
function is ensured. That is, the shield such as the chimney may be
an arbitrary member so long as it surrounds the target holder,
which includes a hollow portion and an opening for causing the
hollow portion to communicate with the outside, and is allowed to
be grounded. The opening is selectively shielded by the shielding
member such as the target shutter.
[0049] The applied power when changing the target shutter 14 from
the closed state to the open state is an essential factor because
the smaller the applied power becomes, the more the particles may
be suppressed. It is thought to be related to the change in the
plasma state which becomes large as the applied power is large when
changing the state of the target shutter 14 in the closed state to
the open state.
[0050] Referring to the timing chart of FIG. 3, the horizontal axis
represents time, and the vertical axis represents the open/closed
state of the first shutter, open/closed state of the second
shutter, and the applied power state from the power source 12 to
the target holder 6.
[0051] At a time T1, the first power (for example, 100 W) lower
than the film forming power (second power), which allows stable
start of discharge is applied (first step S1). Then at a time T2,
the first shutter is opened (second step S2). The first power
applied at the time T2 has to be lower than the second power as the
film forming power, which allows stable start of discharge for the
purpose of suppressing particles. Then the applied power is
increased to the second power from the time T3 to T4 (third step
S3). Preferably, the second power is set as the film forming power
(for example, 800 W) used in the film forming step. At a time T5,
the second shutter is opened to start the film forming step (fourth
step S4).
[0052] Preferably, the applied power is increased in third step S3
(from time T3 to T4) stepwise or continuously at low rates. The
stepwise or continuous increase in the power at low rates allows
reduction in the load to the power source 12, and further allows
the matching box to stably perform matching. Impedance of the
plasma is different between the low power and high power. So the
matching box needs to have different parameters, respectively. The
parameters may be adjusted generally by automatically changing the
variable capacitor capacity by way of hardware. When the power is
largely changed, the change of the variable capacitor capacity is
also increased, which may cause the time lag until the optimum
value, thus making the plasma unstable. Especially in such a case,
it is preferable to increase the applied power stepwise or
continuously at low rates. The period required for the increase at
low rates may be arbitrarily set so long as it is in the range
allowed by the product throughput, and the performance of the
matching box is allowed to follow up.
[0053] It is essential to cause discharge while suppressing
particle generation in the first discharge space, and not to
increase the potential difference between the ground electrode
potential and the plasma potential in first step S1. So the first
power may be arbitrarily set so long as it is low enough to allow
stable start of discharge, and not to largely increase the
potential difference. If the aforementioned requirements are
satisfied, the first power may be stepwise or continuously
increased or decreased in the period from the time T1 to T2 in FIG.
3.
[0054] (Example) The apparatus shown in FIG. 1 was employed to
perform RF sputtering using Al.sub.2O.sub.3 as the target, and the
chimney (tubular shield) 9 having the surface facing the target and
coated through alumina thermal spray. Argon was used as the inert
gas which is introduced from the first gas inlet 15. The RF power
(second power) for forming the film on the substrate 10 was set to
800 W. The power for starting power application (first power) was
set to 100 W. After applying the power of 100 W (first power)
(first step S1), the first shutter was opened (second step S2).
After opening the first shutter, the applied power was increased to
800 W (second power) upon formation of the substrate (third step
S3). After increasing the power, the second shutter was opened, and
film formation on the substrate was started (fourth step S4). In
the example, the number of particles on the substrate having the
film formed thereon counted 19, indicating reduction of the number
of particles relative to the comparative example to be described
later.
Comparative Example
[0055] Likewise the example as described above, RF sputtering was
performed using Al.sub.2O.sub.3 as the target, and the chimney
(tubular shield) 9 having the surface facing the target and coated
through alumina thermal spray. Argon was used as the inert gas
likewise the aforementioned example. The RF power for forming the
film on the substrate 10 was set to 800 W. After setting the RF
power to 800 W, and applying the power, the first shutter was
opened, and then the second shutter was opened to form the film.
The number of particles on the substrate having the film formed
thereon counted 496.
Other Example
[0056] According to the present invention, the controller con as
the control unit for the sputter film forming apparatus 1 may be
built in the sputter film forming apparatus 1, or provided
separately from the sputter film forming apparatus 1. When it is
separately provided, the controller con and the sputter film
forming apparatus 1 may be locally connected through LAN, or
connected with wire or wirelessly connected via WAN connection such
as the Internet, so that the controller con is configured to be
communicated with the sputter film forming apparatus 1.
[0057] The processing method configured to store the program for
operating the structure of the embodiment to realize the functions
as described above in the storage medium, read the program stored
in the storage medium as codes, and execute the operations by the
computer is also included in the scope of the above embodiment. In
other words, the computer readable data storage medium is also
within the range of the example. Naturally, the storage medium for
storing the computer program and the computer program itself may be
included in the range of the example.
[0058] For example, Floppy.TM. disk, hard disk, optical disk,
magnetic optical disk, CD-ROM, magnetic tape, nonvolatile memory
card, and ROM may be employed as the data storage medium.
[0059] Besides execution of the process by the program by itself
stored in the aforementioned storage medium, the other one which is
operated on OS in association with the other software and add-in
board function may be included in the category of the
aforementioned embodiment.
* * * * *