U.S. patent application number 09/888923 was filed with the patent office on 2002-03-28 for magnetron sputtering source.
This patent application is currently assigned to Unaxis Trading AG. Invention is credited to Grunenfelder, Pius, Haag, Walter, Krassnitzer, Siegfried, Schlegel, Markus, Schwendener, Urs.
Application Number | 20020036133 09/888923 |
Document ID | / |
Family ID | 4244074 |
Filed Date | 2002-03-28 |
United States Patent
Application |
20020036133 |
Kind Code |
A1 |
Haag, Walter ; et
al. |
March 28, 2002 |
Magnetron sputtering source
Abstract
A sputter source has at least two electrically mutually isolated
stationar bar-shaped target arrangements mounted one alongside the
other and separated by respective slits. Each of the target
arrangements includes a respective electric pad so that each target
arrangement may be operated electrically independently from the
other target arrangement. Each target arrangement also has a
controlled magnet arrangement for generating a time-varying
magnetron field upon the respective target arrangement. The magnet
arrangements may be controlled independently from each others. The
source further has an anode arrangement with anodes alongside and
between the target arrangements and/or along smaller sides of the
target arrangements.
Inventors: |
Haag, Walter; (Grabs,
CH) ; Grunenfelder, Pius; (Wangs, CH) ;
Schwendener, Urs; (Buchs, CH) ; Schlegel, Markus;
(Azmoos, CH) ; Krassnitzer, Siegfried; (Feldkirch,
AT) |
Correspondence
Address: |
NOTARO & MICHALOS P.C.
Empire State Building
Suite 6902
350 Fifth Avenue
New York
NY
10118-6985
US
|
Assignee: |
Unaxis Trading AG
|
Family ID: |
4244074 |
Appl. No.: |
09/888923 |
Filed: |
June 25, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09888923 |
Jun 25, 2001 |
|
|
|
09587543 |
Jun 5, 2000 |
|
|
|
6284106 |
|
|
|
|
09587543 |
Jun 5, 2000 |
|
|
|
09026446 |
Feb 19, 1998 |
|
|
|
6093293 |
|
|
|
|
Current U.S.
Class: |
204/192.12 ;
204/298.07; 204/298.08; 204/298.12; 204/298.19 |
Current CPC
Class: |
C23C 14/35 20130101;
H01J 2237/3325 20130101; H01J 37/3452 20130101; H01J 37/3408
20130101 |
Class at
Publication: |
204/192.12 ;
204/298.19; 204/298.07; 204/298.08; 204/298.12 |
International
Class: |
C23C 014/35 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 17, 1997 |
CH |
2897/97 |
Claims
1. Magnetron sputtering source where at least two long target
arrangements (3) that are electrically insulated from each other
are arranged at a distance (d) that is significantly smaller than
the width dimension (B) of target arrangements (3) and where each
target arrangement (3) has a separate electrical connection (5),
and where further an anode arrangement (7) is provided.
2. Source according to claim 1 where the anode arrangement
comprises anodes on the longitudinal side between the target
arrangements and/or on the face side of the target arrangement, but
preferably on the longitudinal side.
3. Source according to claim 1 in which a stationary magnetron
arrangement (47) is provided which preferably comprises a frame
containing electrical and/or permanent magnets that encircles the
target arrangements, where the magnets of the frame or frames are
preferably permanent magnets.
4. Source according to claims 1 to 3 where below each target
arrangement magnet arrangements are provided, preferably in such a
way that they each form a time variation of the magnet field
pattern above the sputtering surfaces of the arrangements,
preferably by varying the apex of a tunnel-shaped, circular magnet
field and where the magnet arrangements are implemented with
selectively controlled and/or moved electromagnets and/or moved
permanent magnets, preferably by the latter, and particularly
preferred by at least two motor driven, pivot bearing mounted
magnet drums (43) with permanent and/or electric magnets,
preferably with permanent magnets positioned along the longitudinal
axis of the target arrangements.
5. Source according to one of the claims 1 to 4 where the target
arrangements (3) are mounted on a base (41) and on which for each
target arrangement (3) closed cooling medium channels (35) are
arranged where the surfaces facing the base are sealed against said
surface by means of foils (37) preferably in such a way that on the
base side facing the target arrangements, vacuum pressure and on
the opposite side of the base simultaneously atmospheric pressure
can be applied.
6. Source according to one of the claims 1 to 5 where the target
arrangements (3) as well as the anode arrangement (7) and possibly
also the stationary magnetron arrangement(s), preferably the magnet
frame(s) (47) and/or the magnet arrangements below the target
arrangements, preferably magnet drums, and/or the cooling medium
channels (35) are mounted in or on a part made of electrical
insulating material, preferably plastic, of a base (41) and where
the base is preferably designed in such a way that vacuum pressure
on the target side and atmospheric pressure on the outer side can
be simultaneously applied.
7. Source according to one of the claims 6 where the cooling medium
channels are limited on their base by a metal plate.
8. Source according to one of the claims 1 to 7 where gas outlet
openings (49) are provided, distributed along the longitudinal
sides of the target arrangements, which openings communicate with a
gas distribution system (64).
9. Source according to one of the claims 1 to 8 where the spacing
(d) between the longitudinal sides of target arrangements (4) is
maximum 15%, preferably maximum 10% preferably maximum 7% of their
width dimension (B).
10. Source according to one of the claims 1 to 9 where the target
arrangements (4) have a length (L) that is at least equal to but
preferably much longer than the width, where it preferably is 400
mm.ltoreq.L.ltoreq.2000 mm.
11. Source according to one of the claims 1 to 10 where the
longitudinal side of the target arrangements form a distance d of 1
mm.ltoreq.d.ltoreq.230 mm preferably 7 mm.ltoreq.d.ltoreq.20
mm.
12. Source according to one of the claims 1 to 11 where width B of
the target arrangements is: 60 mm.ltoreq.B.ltoreq.350 mm preferably
80 mm.ltoreq.B.ltoreq.200 mm.
13. Source according to one of the claims 1 to 11 where the virgin
surfaces of the target arrangements (3) are arranged in one
plane.
14. Source according to one of the claims 1 to 13 where measured in
a given spatial direction (Z) the strength of the magnet field (H)
along the longitudinal dimension of the target arrangements and
their longitudinal edge zone is locally different.
15. Source according to one of the claims 1 to 14 where the target
arrangements (3) are assigned jointly to preferably one permanent
magnet frame each, and where the position and/or strength of the
magnets of the frame(s) (47) differs locally along at least a part
of the longitudinal dimension of the target arrangements.
16. Source according to one of the claims 1 to 15 where below the
target arrangements (3) at least two longitudinal, motor driven
magnet drums (43) mounted on pivot bearings are provided and where
the strength and/or the position of the magnets differs locally
along at least a part of the drums (43) and the magnets of the
drums are preferably permanent magnets.
17. Source according to one of the claims 1 to 16 where the target
arrangements (3) are jointly or preferably individually surrounded
by a magnet frame (47) and where the strength and/or position of
the magnets in said frame differ locally along at least on a part
of the longitudinal sides of the target arrangements, that is,
specular symmetrical to one of the long target diagonals (Di) when
viewed on a given target arrangement, and where the magnets of the
frame(s) are preferably permanent magnets.
18. Source according to one of the claims 1 to 17 where the target
arrangements are fastened by means of linear bayonet catches (25,
32).
19. Source according to one of the claims 1 to 18 where more than
two, preferably five and more target arrangements are provided.
20. Sputter coating chamber with a magnetron sputtering source (10)
according to one of the claims 1 to 19 with a substrate holder (66)
for at least one substrate to be sputter coated, where said holder
is arranged at a distance relative to the magnetron sputtering
source and where the following formula applies to the ration
(V.sub.QS) of the sputtered source surface F.sub.Q to the coated
substrate surface FS: V.sub.QS.ltoreq.3 preferably
V.sub.QS.ltoreq.2 preferably 1.5.ltoreq.V.sub.QS.ltoreq.2.
21. Chamber according to claim 20 where the distance (D) between
the virgin magnetron sputtering source surface (10) and the
substrate is essentially equal to the width of the long target
arrangements (3), and is preferably: 60 mm.ltoreq.D.ltoreq.250 mm,
preferably 80 mm.ltoreq.D.ltoreq.160 mm.
22. Vacuum coating system with a chamber according to one of the
claims 20 or 21 where the target arrangements (3) are connected to
electrical generators (62) that can be controlled independently of
each other.
23. System according to claim 22 where more than two of the target
arrangements (3) are provided and where at least two of the target
arrangements (3) are connected to the outputs of a common AC
generator (15, 17).
24. System according to claim 22 where at least one of the
generators 9, 62) is a DC generator, an AC generator or a generator
for outputting AC superposed with DC, or where at least one of the
generators is a DC generator and is connected to target arrangement
(3) via a chopper unit.
25. System according to one of the claims 22 to 24 where the gas
outlet openings (49) are provided on the longitudinal side at least
between a part of the target arrangements, which outlets are
connected to a reactive gas tank and/or a working gas tank
(53).
26. System according to claim 25 where at least a part of the gas
outlets (49) provided along the target arrangements (3) can be
controlled independently of the others with respect to gas flow
(51, 64).
27. Process for operating a system according to one of the claims
22 to 26 with at least three long target arrangements (3), where
the target arrangements on the outer sides are operated with higher
sputtering power, preferably 5 to 35% higher sputtering power,
preferably 10 to 20% with respect to the inner target
arrangements.
28. Process for operating a system according to one of the claims
22 to 26 on which below each target arrangement a locally shiftable
and/or time controlled magnet arrangement, preferably implemented
with at least two driven, pivot bearing mounted permanent magnet
drums (43), is provided and where the magnet field generator on the
target arrangements varies in intervals of 1 to 4 Hz, and where
preferably both drums (43) are driven in pendulum motion with a
pendulum frequency of 1 to 4 Hz, preferably approx. 2 Hz,
preferably with a pendulum amplitude of .phi..ltoreq..pi./4
29. Process according to one of the claims 27 or 28 where film
thickness distribution on the substrate across its surface is
adjusted, preferably approximately homogeneously, by controlling
the electrical supply of each target arrangement and/or the gas
inlet distribution and/or the magnet field distribution.
30. Process according to one of the claims 27 to 29 where the
magnetron sputtering source is operated with a power density p of 1
W/cm.sup.2.ltoreq.p.ltoreq.30 W/cm.sup.2, and where for reactive
sputter coating from preferably metallic targets, in particular for
ITO sputter coating, p is selected as follows: 1
W/cm.sup.2.ltoreq.p.ltoreq.5 W/cm.sup.2, for metal sputter coating:
15 W/cm.sup.2.ltoreq.p.ltoreq.30 W/cm.sup.2.
31. Long magnetron source with an essentially rectangular target
arrangement with a time-variable, preferably moving magnet system
where the target arrangement preferably comprises a magnet frame
(47) and where the field strength of the magnet frame, measured in
a given spatial direction (Z) differs locally along the
longitudinal sides (x) of the target arrangements.
32. Source according to claim 31 where the field strength of the
two longitudinal sides of the target arrangements differs locally,
essentially specular symmetrically, to the diagonal of the
arrangement.
33. Source according to one of the claims 31 or 32 where the magnet
system below the target arrangement comprise at least two driven,
pivot bearing mounted magnet drums (43) that extend in the
longitudinal direction of the target arrangement.
34. Utilization of the magnetron sputtering source according to one
of the claims 1 to 19, or the chamber according to one of the
claims 20 or 21, or the system according to one of the claims 22 to
26, or the source according to one of the claims 31 to 33, for
reactive sputter coating, preferably from metallic targets, in
particular for such coating with Indium Tin Oxide (ITO).
35. Utilization of the magnetron sputtering source according to one
of the claims 1 to 19, or the chamber according to one of the
claims 20 or 21, or the system according to one of the claims 22 to
26, or the source according to one of the claims 31 to 33, for
coating flat panel display substrates, in particular TFT or PDP
panel substrates, e.g. made of glass, in particular with a
reactively deposited coating, in particular an ITO coating.
36. Utilization according to claim 35 for substrates with an area
F.sub.S to be coated of: F.sub.S.gtoreq.900 cm.sup.2.
Description
[0001] This invention relates to a magnetron sputtering source
according to claim 1 or 31, a vacuum chamber with such a source
according to claim 20, a vacuum coating system with such a chamber,
according to claim 22, and in addition a process technique for such
a system according to claim 27, as well as its utilization.
[0002] In essence the present invention is based on the need for
depositing on large-surface, in particular rectangular substrates
with an area of at least 900 cm.sup.2, a film having a homogenous
thickness distribution, by means of sputter coating, in particular
also reactive sputter coating. Such substrates are in particular
used in the manufacture of flat panels, normally on glass
substrates thinner than 1 mm, such as for TFT panels or plasma
display panels (PDP).
[0003] When magnetron sputter coating large surfaces, even larger
sputter surfaces and consequently larger targets are normally
required unless the sputtering source and the substrate are moved
relative to each other. However, this results in problems with
respect to
[0004] (a) uniformity of the process conditions on the
large-surface target, with particular severity in reactive sputter
coating
[0005] (b) erosion profile
[0006] (c) cooling
[0007] (d) strain on the large targets, in particular through
atmospheric pressure and coolant pressure.
[0008] In order to solve the mechanical strain problem (d)
relatively thick target plates have to be used which in turn
reduces the magnetic penetration and consequently the electron trap
effect for a given electrical input power. If the power is
increased this results in cooling problems (c), in particular
because elaborate methods are needed for achieving good contact
between the target and the cooling medium, and also because of the
obstruction resulting from the installations on the back for
accommodating the magnets. It is also known that in magnetron
sputtering, be it reactive or non-reactive, the target arrangement
normally consisting of a sputtering area defining target plate made
of the material to be sputtered and a bonded mounting plate, the
target is sputter eroded along so-called "race tracks". On the
sputter surface one or several circular erosion furrows are created
due to the tunnel-shaped magnet fields applied to the target along
specific courses, which produce circular zones with elevated plasma
density. These occur due to the high electron density in the area
of the tunnel-shaped circular magnetron fields (electron traps).
Due to these "race tracks" an inhomogenous film thickness
distribution occurs already on relatively small-surface coating
substrates arranged in front of the magnetron sputtering source. In
addition the target material is inefficiently utilized because the
sputter erosion along the "race tracks" removes little material
from target areas outside these tracks which results in a
wave-shaped or furrow-shaped erosion profile. Because of these
"race tracks" the actually sputtered surface even of a large target
is small relative to the substrate surface. For eliminating the
effect of said "race tracks" on the coating it would be possible to
move the sputtering source and the substrate to be coated relative
to each other, as mentioned above, however, this results in a lower
deposition rate per unit of time. If locally higher sputtering
power is used, cooling problems are incurred in systems using
relative motion.
[0009] In trying to achieve the desired goal basically four
complexes of problems (a), (b), and (c), (d) are encountered whose
individual solutions aggravate the situation with respect to the
others; the solutions are mutually contradictory.
[0010] The objective of the present invention is to create a
magnetron sputtering source through which said problems can be
remedied, that can be implemented in practically any size, and that
is capable of economically achieving a homogenous coating thickness
distribution on at least one large-surface substrate that is
stationary relative to the source. In addition to maintaining
highly uniform process conditions the source shall be suitable for
sensitive reactive processes with high deposition or coating rates.
In reactive processes, inhomogenous "race track" effects lead to
known, severe problems due to the large plasma density
gradients.
[0011] This is achieved by the magnetron sputtering source
according to the present invention in which at least two,
preferably more than two, electrically isolated long target
arrangements are placed parallel to each other at a distance that
is significantly smaller than the width of the target arrangement,
where each target arrangement has its own electrical connections,
and where in addition an anode arrangement is provided. The targets
of the target arrangements have preferably rounded corners,
following the "race track" paths.
[0012] On such a magnetron sputtering source according to the
invention with independently controllable electrical power input to
the individual target arrangements, the film thickness distribution
deposited on the substrate located above can already be
significantly improved. The source according to the invention can
be modularly adapted to any substrate size to be coated.
[0013] With respect to the overall arrangement the anode
arrangement can--unless it is temporarily formed by the target
arrangements themselves--be located outside the overall arrangement
but preferably comprises anodes that are installed longitudinally
between the target arrangements and/or on the face of the target
arrangement, but particularly preferred longitudinally.
[0014] Also preferred is a stationary magnetron arrangement on the
source; the latter is preferably formed by a magnet frame that
encircles all the target arrangements, or is preferably implemented
with one frame each encircling each target arrangement. Although it
may be feasible and reasonable to implement the magnets on the
frame(s), or on the stationary magnet arrangement at least
partially by means of controllable electric magnets, the magnets of
the arrangement or the frame are preferably implemented with
permanent magnets.
[0015] Through a corresponding design of said stationary magnet
arrangement, preferably the permanent-magnet frames with respect to
the magnet field they generate on the immediately adjacent target
arrangement, the aforementioned film thickness distribution on the
substrate and the utilization efficiency of the long targets can be
further enhanced through specific shaping of "race tracks".
[0016] Magnet arrangements are provided preferably below each of
the at least two target arrangements. These may be locally
stationary and be fixed over time in order to create the tunnel
shaped magnet field on each of the target arrangements. Preferably
they are designed in such a way that they cause a time-dependent
variation of the magnet field pattern on the target arrangements.
With respect to the design and the generation of the magnet field
pattern on each of the target arrangements according to the
invention, we refer to EP-A-0 603 587 or U.S. Pat. No. 5,399,253 of
the same application, whose respective disclosure content is
declared to be an integral part of the present description.
[0017] According to FIG. 2 of EPO-A-0 603 587 the location of the
magnet pattern and consequently the zones of high plasma density
can be changed as a whole, but preferably it is not changed, or
changed only insignificantly, whereas according to FIGS. 2 and 3 of
said application the location of the apex--the point of maximum
plasma density--is changed.
[0018] For changing the location of the zones or the apex on the
magnet arrangements, selectively controlled electric
magnets--stationary or movable--can be provided below each of the
target arrangements, but far preferably this magnet arrangement is
implemented with driven movable permanent magnets.
[0019] A preferred, moving magnet arrangement is implemented with
at least two magnet drums arranged longitudinally below the driven
and pivot bearing mounted target arrangements, again preferably
with permanent magnets as illustrated, for an individual target, in
FIGS. 3 and 4 of EP-A-0 603 587.
[0020] The magnet drums are driven with pendulum motion with a
pendulum amplitude of preferably .ltoreq..tau./4. With respect to
this technique and its effect we again refer fully to said EP-A-0
603 587 or U.S. Pat. No. 5,399,253 respectively which also in this
respect are declared to be an integral part of the present patent
application description.
[0021] In summary, at least two driven and pivot bearing mounted
permanent magnet drums extending along the longitudinal axis of the
target arrangement are preferably provided.
[0022] In the preferred manner
[0023] with the electrical target arrangement supply
[0024] the field of said stationary magnet arrangement, in
particular said frames
[0025] with the field/time-variable magnet arrangement below each
target arrangement, preferably the magnet drums
[0026] a set of influencing variables is available which in
combination allow extensive optimization of the deposited film
thickness distribution, in particular with respect to its
homogeneity. In addition a high degree of target material
utilization is achieved. Highly advantageous is that
preferably--with shift of the magnet field apex on the target
arrangement--the plasma zones are not shifted in a scanning manner
but that within the zones the plasma density is changed through
wobbling.
[0027] To allow maximum sputter power input the target arrangements
are optimally cooled by mounting them on a base where the target
arrangement surfaces facing the base are largely covered by cooling
media channels which are sealed against the base by means of foils.
Large-surface heat removal is achieved because the pressure of the
cooling medium presses the entire foil surface firmly against the
target arrangements to be cooled.
[0028] On the magnetron sputtering source according to the
invention a base, preferably made at least partially from an
electrically insulating material, preferably plastic, is provided
on which in addition to said target arrangements the anodes and, if
existing, the stationary magnet arrangement, preferably permanent
magnet frames, the magnet arrangement below the target
arrangements, preferably the moving permanent magnet arrangements,
in particular said drums, as well as the cooling medium channels,
are accommodated. The base is designed and installed in such a way
that it separates the vacuum atmosphere and the external
atmosphere. In this way the target arrangement can be more flexibly
designed with respect to pressure-induced mechanical strain.
[0029] Another optimization or manipulated variable for said
large-surface film thickness distribution is obtained by providing
gas outlet openings, distributed on the longitudinal side of the
target arrangement, which openings communicate with a gas
distribution system. This makes it possible to admit reactive gas
and/or working gas with specifically adjusted distribution into the
process chamber above the source according to the invention of a
vacuum treatment chamber or system according to the invention.
[0030] The rectangular target arrangements are preferably spaced
apart by max. 15%, preferably max. 10% or even more preferably max.
7% of their width.
[0031] In a preferred design the lateral distance between the
individual target arrangements d is
[0032] 1 mm.ltoreq.d.ltoreq.230 mm, where preferably
[0033] 7 mm.ltoreq.d.ltoreq.20 mm.
[0034] Width B of the individual target arrangements is
preferably
[0035] 60 mm.ltoreq.B.ltoreq.350 mm, more preferably
[0036] 80 mm.ltoreq.B.ltoreq.200 mm
[0037] and their length L preferably
[0038] 400 mm.ltoreq.L.ltoreq.2000 mm.
[0039] The length of the individual target arrangements relative to
their width is at least the same, preferably considerably longer.
Although the sputtering surfaces of the individual target
arrangements are flat or pre-shaped and preferably arranged along
one plane, it is feasible to arrange the lateral sputtering
surfaces closer to the substrate to be coated than the ones in the
middle, possible also inclined, in order to compensate any edge
effects on the film thickness distribution, if necessary.
[0040] The electrons of the magnetron plasma circulate along the
"race tracks" in a direction defined by the magnet field and the
electrical field in the target surface area. It has been observed
that the routing of the electron path or its influence upon it and
consequently the influence on the resulting erosion furrows on the
target surfaces can be specifically optimized by creating the
magnet field along the longitudinal axes of the target arrangements
and by varying the shape of said field not only with respect to
time but also location. With a magnet frame--preferably one each,
and also preferably one permanent magnet frame each--this is
preferably achieved by positioning and/or by the selected strength
of the magnets on the frame, and/or by providing magnet
arrangements each below the target arrangements, preferably said
permanent magnet drums, by correspondingly varying the strength
and/or relative position of the magnets on the magnet arrangement.
As the electrons move in a circular path in accordance with the
magnet field polarity, it has been observed that apparently due to
drift forces the electrons, in particular in the narrow side areas
of the target arrangements and in accordance with the direction of
their movement, the electrons in corner areas that are diagonally
opposite are forced outward. For this reason it is proposed that
with the provided magnet frame the field strength created by the
frame magnets which are specular symmetrical to the target
"rectangle" diagonal be preferably designed with a locally
different shape.
[0041] In a preferred design version of the source according to the
invention the target arrangements are fixed by means of linear
bayonet catches, in particular in combination with their cooling
via pressure loaded foils of the aforementioned type. In this way
the arrangements can be very easily replaced after the pressure in
the cooling medium channels has been relieved; the greater part of
the target arrangement back side remains accessible for cooling and
no target arrangement fixing devices are exposed toward the process
chamber.
[0042] A preferred source according to the invention features more
than two target arrangements, preferably five or more.
[0043] By using a magnetron sputtering source according to the
invention on a sputter coating chamber on which, with a clearance
from the latter, a substrate holder for at least one, preferably
planar substrate to be sputter coated is provided, it is possible
to achieve an optimally small ratio V.sub.QS between the sputtered
source surfaces F.sub.Q and the substrate surface F.sub.S to be
sputtered, where:
[0044] V.sub.QS.ltoreq.3, preferably
[0045] V.sub.QS.ltoreq.2, where particularly preferred
[0046] 1.5.ltoreq.V.sub.QS.ltoreq.2.
[0047] This significantly increases the utilization efficiency of
the source. In a sputter coating chamber according to the invention
with said source this is achieved to an even higher degree by
choosing the distance D between the virgin surface of the magnetron
sputtering source and the substrate in such a way that it is
essentially equal to the width of a longitudinal target
arrangement, preferably
60 mm.ltoreq.D.ltoreq.250 mm,
preferably 80 mm.ltoreq.D.ltoreq.160 mm
[0048] On a vacuum coating system according to the invention with a
sputter coating chamber according to the invention and consequently
the magnetron sputtering source according to the invention, the
target arrangements are each connected to an electrical generator
or current sources, where said generators can be controlled
independently of each other.
[0049] The sputter coating system according to the invention with
at least three long target arrangements is preferably operated in
such a way that the two outer target arrangements are operated with
5 to 35% more sputtering power, preferably with 10 to 20% more
sputtering power than the inner target arrangements. The
aforementioned "scanning" of the target arrangements with respect
to the position of the plasma zones and in particular the preferred
"wobbling" of the apex of the tunnel magnet fields and consequently
the plasma density distribution, preferably realized by means of
said magnet drums in pendulum operation, is preferably performed
with a frequency of 1 to 4 Hz, preferably approx. 2 Hz. The
pendulum amplitude of the drum is preferably .phi..ltoreq..pi./4.
The coating thickness distribution on the substrate is further
optimized through an appropriate design of the path/time profiles
of said shift in position.
[0050] It should be emphasized that for this purpose also the
generators connected to the target arrangements can be controlled
for outputting mutually dependent, time modulated signals.
[0051] In addition the electrical supply of the target arrangements
and/or the distributed gas inlets and/or the magnet field
distribution are controlled in such a way or modulated in time in
such a way that the desired, preferably homogenous, film thickness
distribution on the substrate is achieved.
[0052] The magnetron sputtering source is preferably operated with
a power density p of
[0053] 1 W/cm.sup.2.ltoreq.p.ltoreq.30 W/cm.sup.2,
[0054] in particular for reactive film deposition, preferably from
metallic targets, and in particular ITO films with
[0055] 1 W/cm.sup.2.ltoreq.p.ltoreq.5 W/cm.sup.2,
[0056] and for sputter coating metal films preferably with
[0057] 15 W/cm.sup.2.ltoreq.p.ltoreq.30 W/cm.sup.2.
[0058] As has been recognized in conjunction with the development
of said magnetron sputtering source according to the invention, it
is basically advantageous, in particular with target plate
arrangements that are significantly longer than wide, to design the
magnet field strength of the magnetron field, viewed in the
longitudinal direction of the target arrangements and in particular
their lateral areas, with a locally different shape.
[0059] However, this insight is generally applicable to long
magnetrons.
[0060] For this reason it is proposed for a long magnetron source
according to the invention which comprises a time-variable,
preferably moving magnet system, to assign a magnet frame to the
target arrangement, preferably a permanent magnet frame where the
field strength of the frame magnets measured in one given chamber
direction, is designed locally different along the longitudinal
side of the target arrangements. For compensating said drift forces
acting on the circulating electrons it is proposed to design this
field strength locally different essentially specular symmetrical
to the target diagonal.
[0061] The present invention under all its aspects is in particular
suited to sputter coating substrates, in particular large-surface
and preferably plane substrates by means of a reactive process,
preferably with an ITO film (Indium Tin Oxide). The invention is
also suited to coating substrates, in particular glass substrates,
used in the production of flat panel displays, in particular TFT or
PDP panels, where basically the possibility is opened to highly
efficiently sputter coat also large substrates, for example, also
semiconductor substrates, with minimal reject rates either by means
of a reactive or non-reactive process, but in particular also
reactive.
[0062] Especially in sputter coating processes, in particular in
ITO coating, low discharge voltages for achieving high film
quality, in particular low film resistances, also without tempering
steps, are essential. This is achieved by means of the source
according to the invention.
[0063] It also achieves effective suppression of arc
discharges.
[0064] The invention is subsequently explained based on illustrated
examples:
[0065] FIG. 1 Magnetron sputtering source according to the
invention, electrically operated in a first version;
[0066] FIG. 2 Schematic representation of the sputtering source
according to FIG. 1 in another electrical circuit
configuration;
[0067] FIG. 3 Another circuit configuration of the sputtering
source according to the invention, shown analogously to FIG. 1;
[0068] FIG. 4 Cross-sectional detail of a magnetron sputtering
source according to the invention;
[0069] FIG. 5 Top view of a linear bayonet catch is used preferably
on the source according to FIG. 4;
[0070] FIG. 6 Simplified top view of a detail of a magnetron source
according to the invention;
[0071] FIG. 7 Top view of a preferred design version of a permanent
magnet drum preferably provided according to Fig. A on the
magnetron sputtering source according to the invention;
[0072] FIG. 8 Schematic representation of a sputter coating system
according to the invention;
[0073] FIG. 9 Erosion profile on a target arrangement of the source
according to the invention;
[0074] FIG. 10 Distribution of the sputtered material, determined
on a source according to the invention with five target
arrangements;
[0075] FIG. 11 Film thickness relief pattern on a 530.times.630
mm.sup.2 glass substrate coated by a source according to the
invention.
[0076] FIG. 1 schematically shows a magnetron sputtering source 1
according to the invention in its basic configuration. It comprises
at least two, or as illustrated, for example, three long target
arrangements 3a to 3c. The additional devices to be provided on a
magnetron sputtering source, such as the magnet field sources,
cooling facilities, etc. are not shown in FIG. 1. Source 1 has
separate electrical connections 5 on each target arrangement. For
example, strip shaped anodes 7a, 7b are provided preferably between
the longitudinally spaced target arrangements 3.
[0077] Because the target arrangements 3 are electrically insulated
from each other and have separate electrical terminals 5,
independent electrical wiring as subsequently also described in
conjunction with FIGS. 2 and 3 is possible.
[0078] As shown in FIG. 1 each target arrangement 3 is connected to
a generator 9, each of which generators can be controlled
independently of each other and which do not necessarily have to be
of the same type. As shown schematically the generators can be all
of the same type or implemented in any mixed combination of DC
generators, AC generators, AC and DC generators, generators for
outputting pulsed DC signals, or DC generators with intermediate
generator output, and with the chopper unit for the corresponding
target arrangement. With respect to their design and operating
principle full reference is made to said EP-A-0 564 789 or U.S.
application Ser. No. 08/887 091.
[0079] Also with respect to the electrical operation of the anodes
7 there is complete freedom in that they are operated either with
DC, AC, DC with superposed AC or pulsed DC voltage, or possibly via
one of the said chopper units, or, as shown at 12a, connected to
reference potential. By varying the electrical cathode or target
arrangement mode and possibly also the electrical anode mode,
distributed across the source surface formed by the target
arrangements, the distribution of sputtered material and
consequently the distribution on a substrate (not shown) arranged
above the source can be adjusted.
[0080] Generators 9 can be time modulated with mutual dependence,
as shown by the modulation inputs MOD, in order to specifically
modulate in the form of a travelling wave, the electrical operating
conditions above the target arrangements.
[0081] FIGS. 2 and 3 show, with the same position symbols,
additional electrical wiring arrangements of source 1 according to
the invention at which (not shown) an anode arrangement is not
necessary.
[0082] As shown in FIG. 2 and 3 the target arrangements 3 are
connected in pairs to the inputs of AC generators 15a, 15b or 17a
17b respectively, where also here generators 15 or 17 can
optionally output AC superposed DC signals or pulsed DC signals.
Again, generators 15, 17 are modulated, if desired, for example an
AC output signal practically as carrier signal, with an amplitude
modulation.
[0083] Whereas according to FIG. 2 one target arrangement 3b each
is connected to an input of one of the generators 15a and 15b,
target arrangements 3 as shown in FIG. 3 are connected in pairs via
generators 17. As shown with dashed lines at 19 it is possible, in
the sense of "common mode" signals, as well as in the design
according to FIG. 2 as well as the one in FIG. 3, to jointly
connect individual target arrangement groups to different
potentials. If a wiring technique according to FIG. 2 or 3 is
chosen, the generators in a preferred design version are operated
with a frequency of 12 to 45 kHz. With respect to a "common mode"
potential, as for example, the mass potential shown in FIG. 2,
target arrangements connected in pairs to a generator are
alternately connected to positive and negative potentials.
[0084] As can be seen from the diagrams in FIGS. 1 to 3 the
magnetron source according to the invention allows very high
flexibility for electrically operating the individual target
arrangements 3 and consequently to specifically design the
distribution of the sputtered material in process chamber 10 and
the deposition on a substrate.
[0085] FIG. 4 is a cross-sectional detail of a magnetron sputtering
source according to the invention in a preferred version. As shown
in FIG. 4 the target arrangements comprise one target plate
3.sub.a1 or 3.sub.b1 each made of the material to be sputtered and
which are bonded to one backing plate each 3.sub.a2 or 3.sub.b2
respectively. With the aid of the linear bayonet catches 20 the
target arrangements 3 are fixed on their lateral periphery and/or
in their center area to a metallic cooling plate 23.
[0086] The design of the linear bayonet catches is illustrated in
FIG. 5 according to which a hollow rail is provided either on
target arrangement 3 or on cooling plate 23, which rail has a
U-shaped cross-section, with inwardly bent U-legs 27 on which
recesses 29 are created at a certain distance. On the other of the
two parts, preferably on target arrangement 3, a linear rail with a
T-shaped cross-section is provided on which the ends of the
cross-member 33 feature protrusions 34. By inserting the
protrusions 34 into the recesses 29 and by linear shifting in
direction S the two parts are interlocked. It is possible, of
course, in the sense of reversal, to create protrusions on the
hollow rails that engage into corresponding recesses on rail
31.
[0087] The target arrangements 3 are clamped to the cooling plate
23 only when pressure is applied by the cooling medium in cooling
channels 35 of cooling pate 23. These channels 35 extend along the
predominantly flat area of the target arrangement surface facing
cooling plate 23. Cooling channels 35, pressurized by a liquid
cooling medium under pressure as described above, are sealed
against the target arrangement by a foil type membrane 37, as is
described in detail, for example, in CH-A-687 427 of the same
applicant. Under pressure of the cooling medium foils 37 press
tightly against the bottom of plate 3.sub.a2 or 3.sub.b2
respectively. Only when the cooling medium is put under pressure
does the target arrangement become rigidly clamped in the bayonet
catch. For removing the target arrangement 3 the complete cooling
system or the corresponding cooling system section is pressure
relieved, as a result of which the target arrangements can be
easily pushed out and removed or replaced.
[0088] Anode strips 39 are positioned on the longitudinal side of
the target arrangements 3. The anode strips as well as cooling
plate 23 are mounted on a supporting base 41 which preferably is
made at least partially of insulating material, preferably plastic.
Base 41 separates the vacuum atmosphere in process chamber 10 from
the ambient or normal atmosphere in space 11.
[0089] On the atmosphere side of base 41, for example, two
permanent magnet drums 43, extending along the longitudinal
dimension of the target arrangement, are supported in a rotating
fashion and are driven with pendulum motion by motors (not shown).
In pendulum motion they preferably perform a 180.degree. angle
pendulum movement--.omega.43. In the permanent magnet drums 43,
permanent magnets 45 are mounted along the longitudinal drum
dimension, preferably diametrically.
[0090] Also on the atmosphere side of base 41 one permanent magnet
frame 47 for each target arrangement 3 is mounted which essentially
runs below and along the periphery of the corresponding target
arrangement 3, as shown in FIG. 6.
[0091] In particular along the longitudinal sides of the target
arrangements gas inlet lines 49 terminate as shown in FIG. 6, which
can be controlled completely independently of each other,
preferably in rows, with respect to the gas flow, as shown with
dashed lines in FIG. 4. This is schematically shown in FIG. 4 with
servo valves 51 that are provided in a connection between lines 49
and a gas tank arrangement 53 with working gas such as argon and/or
with a reactive gas.
[0092] With respect to the operation and design of the permanent
magnet drum 43 we again refer fully to the disclosure content of
EP-0 603 587 or U.S. Pat. No. 5,399,253 respectively.
[0093] FIG. 6 shows a simplified top view detail of a magnetron
source in FIG. 4 according to the invention. As already described
based on FIG. 4 a permanent magnet frame 47 is installed below each
target arrangement 3. Preferably the magnet frame 47 is designed in
such a way that when viewed in a chamber direction, for example
according to H.sub.z in FIG. 4, the magnet field generated by the
permanent magnet frame changes locally along the longitudinal sides
of the target arrangements 3, as shown in FIG. 6 with x. In a
preferred design the magnets arranged on the longitudinal legs
47L.sub.1 and 47L.sub.2 of frame 47 are subdivided in to zones, for
example, four zones as shown in FIG. 6. In the diagram of FIG. 6
the field strength of the permanent magnets in the individual zones
Zl to Z4 is qualitatively shown through coordinate x and thereby
the field strength distribution in the x direction. In addition the
permanent magnet dipole directions are shown in the corresponding
zones Z.
[0094] On legs 47L.sub.1,2 the same permanent magnet zones are
preferably provided, however, specular symmetrical with respect to
the diagonal D.sub.i of the long target arrangement 3.
[0095] Through a specific design of the local magnet field
distribution that is achieved through the permanent magnet frames
47 on the target arrangements 3 it is possible to optimize the path
of the circulating electrons and consequently the location and
shape of the erosion profiles on the individual target
arrangements. This in particular by taking into consideration the
path deformations caused by drift forces. On the broad sides of the
target frames 47 permanent magnet zones Z.sub.B are provided which
preferably correspond to zone Z.sub.2. As mentioned before also a
single-target source according to FIGS. 4, 6 and 7 is
inventive.
[0096] Magnet fields H which vary locally in the x direction above
the corresponding target arrangements 3 which varies also as a
function of the magnet drum pendulum motion and varies also in
time, is specifically designed by choosing the field strength of
the provided permanent magnets such as in zones Z.sub.1, Z.sub.2,
Z.sub.4 and/or through the spatial dipole orientation such as in
zone Z.sub.3, and/or in the position (distance from the target
arrangement).
[0097] As mentioned, at least two permanent magnet drums 43 are
preferably provided on each of the target arrangements 3 provided
on the sputtering source according to the invention. One such drum
is shown in FIG. 7.
[0098] Preferably different permanent magnet zones, for example,
Z'.sub.1, to Z'.sub.4 are provided also on drums 43. FIG. 7
qualitatively shows the progression of the locally varying
permanent magnet field H.sub.r (x) along the provided drums, in
accordance with the preferred design.
[0099] On the source according to the invention the location and
time distribution of the sputter rate is optimized through specific
location and/or time distribution of the electrical supply of the
individual target arrangements and/or specific location and/or time
variation of the magnetron magnet field on the individual target
arrangements and/or through specific location and/or time variation
or design of the gas inflow conditions on the inlet openings 49. In
the preferred design version that has been explained based on FIGS.
4 to 7, these variables are preferably exploited in combination in
order to specifically design, preferably homogeneously, the film
thickness distribution on a substrate to be sputter coated, in
particular a flat substrate.
[0100] FIG. 8 schematically shows a sputter coating system 50
according to the invention with a sputter coating chamber 60
according to the invention in which is also schematically shown a
magnetron sputtering source 10 according to the invention. The
schematically shown source 10 as implemented in a preferred version
features six target arrangements 3 and is also preferably designed
as has been explained based on FIGS. 4 to 7. The source according
to the invention with its target arrangements is operated with
independent electrical supplies that can possibly be modulated, as
shown in block 62. Further, the gas inflow conditions--which can
possibly be modulated, in particular along the longitudinal
dimensions of the target arrangements as shown with servo valve 64,
are selectively set in order to admit a working and/or reactive gas
from gas tank 53 into the process chamber.
[0101] With drive block 65 the drive--which can possibly be
path/time modulated--for the permanent magnet drums on the source
according to the invention is shown on which, preferably
selectively, the desired drum pendulum motions can be set.
[0102] In chamber 60 according to the invention a substrate holder
66 is provided, in particular for holding a flat substrate to be
coated. Based on the capabilities offered by the source according
to the invention of optimally setting the time and location
distribution of the material sputtered off by source 10, in
particular a uniform distribution that has been averaged over time,
in particular also in the edge zones of the source, it is possible
to make the ratio V.sub.QS of the sputtering surface F.sub.Q of the
source to the substrate surface F.sub.S to be coated astonishingly
small, preferably
[0103] V.sub.QS.ltoreq.3,
[0104] preferably
[0105] V.sub.QS.ltoreq.2,
[0106] and even more preferably
[0107] 1.5.ltoreq.V.sub.QS 2.
[0108] This ratio shows that the material sputtered off the source
is used very efficiently because only correspondingly little of the
sputtered material is not deposited on the substrate surface. This
efficiency is further enhanced because distance D--due to the
large-surface distributed plasma coating of the source--between the
substrate surfaces to be sputtered and the virgin surface of the
magnetron source 10, can be selected very small, essentially equal
to width B (see FIG. 4) of the sputter surfaces on target
arrangements 3 and preferably
[0109] 60 mm.ltoreq.D.ltoreq.250 mm
[0110] preferably
[0111] 80 mm.ltoreq.D.ltoreq.160 mm.
[0112] Through said small distances D a high deposition rate is
achieved with high sputtering efficiency which results in a highly
economical coating process.
[0113] On the system shown in FIG. 8 the outermost target
arrangements are preferably operated by generators 62 with higher
sputtering power, preferably 5 to 35% higher, and even more
preferably with 10 to 20% higher sputtering power than the inner
target arrangements. The permanent magnet drums provided on source
10 according to FIG. 4 are preferably operated in pendulum mode
with a pendulum frequency of 1 to 4 Hz, preferably with approx. 2
Hz.
[0114] The magnetron sputtering source, sputtering chamber or
system, in particular in preferred operation, are particularly
suitable for magnetron sputter coating large-surface, in particular
flat substrates, with a high-quality film, with desired
distribution of the film thickness, in particular a homogenous film
thickness distribution in combination with high process economy. A
significant contribution to this is made by the large-surface,
homogeneously distributed process conditions on the source
according to the invention. As a consequence the invention can be
used for coating large-surface semiconductor substrates, but in
particular for coating substrates of flat display panels, in
particular TFT or PDP panels. This invention is in particular used
for reactive coating of said substrates, in particular with ITO
films or for metal coating said substrates through non-reactive
sputter coating. In the subsequent examples preferred sizes of the
source according to the invention or the chamber or the system are
summarized.
[0115] 1. Geometry
[0116] 1.1 On the source
[0117] Lateral distance d according to FIG. 4: maximum 15%,
preferably maximum 10%, even more preferably maximum 7% of the
width dimension B of the target arrangements and/or
[0118] 1 mm.ltoreq.d.ltoreq.230 mm, preferably
[0119] 7 mm.ltoreq.d.ltoreq.20 mm.
[0120] Virgin surfaces of the target arrangements along one
plane;
[0121] Width B of the target arrangements:
[0122] 60 mm.ltoreq.B.ltoreq.350 mm, preferably
[0123] 80 mm.ltoreq.B.ltoreq.200 mm.
[0124] Length of the target arrangements L: at least B, preferably
considerably longer, preferably
[0125] 400 mm.ltoreq.L.ltoreq.2000 mm.
[0126] End area of the targets: e.g. semicircular.
[0127] 1.2 Source/substrate:
[0128] Ration V.sub.QS of the dimension of sputtering surface
F.sub.Q to the dimension of the substrate surface F.sub.S , to be
coated:
[0129] V.sub.QS.ltoreq.3, preferably
[0130] V.sub.QS.ltoreq.2, or preferably even
[0131] 1.5.ltoreq.V.sub.QS.ltoreq.2.
[0132] Smallest distance of the virgin source surfaces/coating
surfaces D:
[0133] 60 mm.ltoreq.D.ltoreq.250 mm, preferably
[0134] 80 mm.ltoreq.D.ltoreq.160 mm.
[0135] Substrate sizes: for example 750.times.630 mm, coated with a
source having a sputtering surface of: 920.times.900 mm, or
Substrate size: 1100.times.900 mm, with a source having a
sputtering surface of: 1300.times.1200 mm.
[0136] 1.3 Cooling:
[0137] Ratio sputtering surface to cooling surface V.sub.SK:
[0138] 1.2.ltoreq.V.sub.SK.ltoreq.1.5.
[0139] 2. Operating variables
[0140] Target temperature T:
[0141] 40.degree. C..ltoreq.T.ltoreq.150.degree. C.,
[0142] preferably
[0143] 60.degree. C..ltoreq.T.ltoreq.130.degree. C.
[0144] Sputter power per unit of sputtering surface: 10 to 30
W/cm.sup.2, preferably 15 to 20 W/cm.sup.2.
[0145] Outermost target arrangements on each side, preferably with
5 to 35% more sputter power, preferably 10 to 20% more sputter
power per unit of surface.
[0146] Pendulum frequency of the magnet drums: 1 to 4 Hz,
preferably approx. 2 Hz.
[0147] Results: The following deposition rates were achieved:
[0148] ITO: 20 .ANG./sec.
[0149] Al: 130 to 160 .ANG./sec.
[0150] Cr: 140 .ANG./sec.
[0151] Ti: 100 .ANG./sec.
[0152] Ta: 106 .ANG./sec.
[0153] FIG. 9 shows the erosion profile on a 15 cm wide sputtering
surface in a target arrangement on the source according to the
invention. Due to the extremely uniform erosion the "race tracks"
or erosion profiles are barely recognizable.
[0154] FIG. 10 shows the resulting coating rate distribution of ITO
sputtering, based on a source according to the invention with five
target arrangements, each with a sputtering surface width B of 150
mm. In this distribution, film thickness deviations of only
.+-.3.8% are achieved on a substrate arranged at a distance D of
120 mm from the source surface.
[0155] In FIG. 11 the resulting film thickness distribution on a
large-surface glass substrate is shown which has been coated as
follows:
1 Total sputtering power P.sub.tot: 2 kW Sputtering time: 100 sec.
Deposition rate R: 26 .ANG./sec., relative: 13 .ANG./sec. kW Source
with six target arrangements of which the outermost arrangements
have been operated with an elevated sputter power of 10 or 15%
respectively (p.sub.1, p.sub.6): Substrate size: 650 .times. 550
mm
[0156] In FIG. 11 the edge zones of the substrate that were above
the target arrangements operated with elevated sputter power are
marked. In the ITO coating process the film thickness deviation
relative to the mean film thickness of 267 nm was .+-.6.3%.
[0157] The present invention avoids the following disadvantages of
known sputtering sources, in particular with respect to the coating
of large-surface workpieces:
[0158] Because according to the invention a uniform distribution of
the process conditions over a large magnetron sputtering surface is
possible with high deposition rate and high sputter rate
utilization, high economy is achieved when coating large-surface
substrates, or possibly in the simultaneous coating of many
individual substrates.
[0159] Because on the source according to the invention
simultaneous sputtering over a large surface takes place, better
film thickness distribution on the substrate is achieved and arcing
is prevented.
[0160] As the problem of reactive gas distribution and/or target
erosion distribution is solved in a homogenizing sense, the
substrates to be coated can be positioned much closer to the source
and have much larger coating surfaces relative to the source
surface, which improves the economy of a sputter coating system
that is equipped with a source according to the invention.
[0161] The problem of plasma density differences between the target
center and target periphery occurring on large-surface targets due
to missing anodes in the target center is remedied.
[0162] The source can be adapted flexibly to the corresponding size
requirements by means of modular target arrangements.
[0163] The problem occurring with large-surface targets where there
is reactive process gas starvation in the middle of the target, is
solved because the gas inlets 49 are distributed across the actual
source surface.
[0164] Because (see FIG. 4) the base (41) is between process vacuum
and atmospheric pressure it is no longer necessary to provide a
heavy cooling plate (23) that can absorb this load. As a result the
source becomes less elaborate and better penetration of the fields
of the magnet arrangements (47, 43) located below the target
arrangement (3) is achieved.
[0165] Through the selective control of the following
distributions:
[0166] by time and/or location, electrical operation of the target
arrangements
[0167] by time and/or location, magnetic operation of the target
arrangements
[0168] by time and/or location, gas inlet
[0169] it is possible to optimally adjust the film thickness
distribution, especially homogeneously, of large-surface
substrates.
[0170] Due to the provided bayonet catches in conjunction with the
clamping of the target arrangements via the cooling media pressure
extremely simple and fast exchange of the target arrangements is
possible and large-surface, efficient cooling is achieved.
[0171] Due to the bayonet catches provided below the sputtering
surfaces no fixing elements, and in particular no fixing elements
made of non-sputtering material, are accessible from the process
chamber.
* * * * *