Patent Application
20170175247
The present invention relates to the art of depositing layers by physical vapor deposition, commonly known as PVD. One type of PVD is sputter deposition. Thereby, one type of the sputter deposition technology is so-called “magnetron sputtering”. Under sub-atmospheric conditions a material plate, called target, is bombarded by ions exhibiting an energy >>1 eV. Material is sputtered off the target at its sputtering surface, for subsequent deposition on a substrate. Magnetron sputtering relies on a glow plasma discharge which is generated by an electric field between the target, acting as a cathode, and an anode which is often realized by grounded parts of the vacuum recipient wherein the magnetron sputtering process is performed. The plasma is localized and retained close to the sputtering surface of the target by means of a magnet arrangement generating upon the sputtering surface a closed loop of tunnel-shaped magnetic field. This magnetic field forces the electrons of the plasma in a closed loop. Therefore, the magnetron magnetic field is often called “electron trap” and the magnetic field “magnetron tunnel”. Because of the fact that the plasma is localized and retained close to the surface all along the magnetron tunnel and electrons are trapped in the magnetron tunnel, the sputtering surface of the target is predominantly eroded by sputtering along the magnetron tunnel. Thereby, on one hand the target is purely exploited and, on the other hand, on the substrate surface to be coated, there occurs an uneven coating distribution, which “pictures” the magnetron tunnel. Additionally, as the erosion depth of the target increases, deposition on the substrate surface becomes more and more focused, which additionally contributes to uneven coating distribution along the surface of the substrate to be coated.
This disadvantage of magnetron sputtering with stationary magnetron tunnels is avoided if the magnetron tunnel is moved along the sputtering surface of the target, which may be achieved by moving the magnetron tunnel generating magnet arrangement along the backside of the target.
Magnetron sputter coating flat, plate-shaped substrates of an electrically isolating material having vias along at least one of the two-dimensionally extended plate surfaces in a manner that on one hand the thickness distribution of the coating along the addressed extended plate surface is at least substantially homogeneous, and, on the other hand, the surfaces of the vias, including sidewalls and bottom surface, become coated without that by such coating of the vias, voids are generated within the vias in that the vias become closed at their entrance is a difficult task and becomes the more difficult the larger that the aspect ratio of the uncoated vias, i.e. the ratio of depth to diameter, is.
It is an object of the invention to improve a sputtering source arrangement, a sputtering system as well as a method of manufacturing metal coated plate-shaped substrates of electrically isolating material having vias along the metal coated plate surface being as well metal-coated, in view of the addressed problem.
This is achieved by a sputtering source arrangement, which comprises, around a geometric axis, a first magnetron sub-source with a first target of a material. The target has a first sputtering surface which defines a plane perpendicular to the addressed geometric axis.
When we address a plane which is defined by a surface, namely the sputtering surface, we address a plane which is defined by the two-dimensional locus with respect to which the average of the distance vectors from the surface points of the addressed surface is zero.
The first magnetron sub-source comprises a first magnet arrangement located adjacent a back surface of the first target. The first magnet arrangement is drivingly movable along the first sputtering surface so as to establish a moving close loop first magnetron magnetic field movable along the first sputtering surface.
The sputtering source arrangement further comprises a second magnetron sub-source with a closed, frame-shaped second target of the addressed material and along the periphery of and electrically isolated from the first target. Thus in fact, the second target surrounds the first target along the first target periphery, whereby, considered in radial direction to the geometric axis, the second target frame may overlap the first sputtering surface or may be dimensioned not to overlap the addressed first sputtering surface.
The second target has a second sputtering surface around the geometric axis.
The second magnetron sub-source comprises a second magnet arrangement along and adjacent a back-surface of the second target so as to establish a second magnetron magnetic field along the second sputtering surface.
In one embodiment of the sputtering source, which may be combined with any of the subsequently addressed embodiments of the source, unless in contradiction, the first target is plane and/or circular. Thereby, the addressed sputtering source may exploit the most commonly used shapes of targets also in view of a common shape of substrates with vias which have to be sputter-coated by the source.
In a further embodiment of the sputtering source arrangement, which may be combined with any of the preaddressed embodiments and embodiments of the source arrangement still to be addressed, unless in contradiction, the second sputtering surface defines, in cross-sectional planes which contain the geometric axis, a pair of substantially straight lines.
In a further embodiment of the sputtering source arrangement, which may be combined with any of the preaddressed embodiments and embodiments still to addressed of the arrangement, unless in contradiction, the second sputtering surface defines around the geometric axis a surface which is parallel to the geometric axis and thus e.g. a cylindrical surface around the addressed geometric axis or which is perpendicular to the geometric axis and thereby especially facing away from the first sputtering surface, or is cone-shaped, opening in a direction along the geometric axis and away from the first sputtering surface.
In a further embodiment of the source arrangement, which may be combined with any of the preaddressed embodiments and embodiments of the arrangement still to be addressed, unless in contradiction, the sputtering source arrangement comprises a metal frame between the first sputtering surface and the second sputtering surface, which extends along the periphery of the first sputtering surface and along the second sputtering surface. The metal frame which thus is disposed between the first sputtering surface and the second sputtering surface is operable as an anode and thus electrically isolated from the first as well as from the second targets. Alternatively, the metal frame is operable electrically on a floating potential and is thus electrically isolated from the first as well as from the second targets. In a third alternative, the addressed metal frame is electrically connectable to the second target.
In a further embodiment of the sputtering source arrangement, which may be combined with any of the preaddressed embodiments and embodiments of the arrangement still to be addressed, unless in contradiction, the arrangement comprises a frame-shaped anode which is arranged, in a direction along the geometric axis and pointing away from the first sputtering surface, subsequent to and along the second sputtering surface.
According to a further embodiment of the sputtering source arrangement, which may be combined with any of the preaddressed embodiments and embodiments of the arrangement still to be addressed, unless in contradiction, the second magnet arrangement comprises a frame of magnets along the backside of the second target. The magnetic dipoles of these magnets are arranged in sectional planes which contain the geometric axis.
In an embodiment of the sputtering source arrangement which may be combined with any of the preaddressed embodiments and embodiments still to addressed of this arrangement, unless in contradiction, the second magnet arrangement is one of stationary with respect to the second sputtering surface and of drivingly movable with respect thereto. Thereby and in one embodiment the magnet arrangement is movable in directions which are in sectional planes containing the geometric axis as well as along the second sputtering surface in azimuthal direction with respect to the geometric axis.
In a good embodiment such movement is realized by a snake-like shaped moving, wobbling along the second sputtering surface, wobbling from one edge of the second sputtering surface to the other edge.
According to a further embodiment of the sputtering source arrangement, which may be combined with any of the preaddressed embodiments and embodiments of the arrangement still to be addressed, unless in contradiction, there is provided a cooling system which includes a pipe system for a cooling medium along the first and along the second target, which cooling system in one embodiment comprises a first cooling sub-system for the first target and a second cooling sub-system for the second target.
The sputtering system according to the present invention comprises a sputtering source arrangement, namely a sputtering source arrangement as was addressed above, possibly constructed according to one or more than one of the embodiments addressed above in context with the sputtering source arrangement. The sputtering system further comprises a power source arrangement which is operationally connectable to the first and to the second sub-sources, which is constructed to operate the first sub-source in a first mode, which is a pulsed DC mode and the second sub-source in a second mode.
We understand under a “pulsed DC” applying power in a pulsed manner. The resulting power pulse train has a DC-offset. Thereby, the DC offset may e.g. be half the pulse amplitudes, which results in a pulse train at which the pulse “off” level is at practical zero, irrespective of the duty cycle of the pulse train.
In one embodiment of the sputtering system, which may be combined with any embodiment of this system still to be addressed, unless in contradiction, the pulsed DC mode is a HIPIMS mode.
In an embodiment of the just addressed embodiment the power source arrangement operates the first target as follows: Adapted to the prevailing extent of the first sputtering surface so, that for an assumed extent of said first sputtering surface of 2240 cm2 there becomes valid:
In a further embodiment of the addressed sputtering system which may be combined with any of the preaddressed system embodiments as well as with such embodiments still to be addressed, unless in contradiction, the second mode in which the second sub-source is operated is a DC mode or a further pulsed DC mode.
In a further embodiment of the sputtering system which may be combined with any of the preaddressed system embodiments as well as with such embodiments still to be addressed, unless in contradiction, the second mode by which the second sub-source is operated is a HIPIMS mode.
In a further embodiment of the sputtering system which may be combined with any of the preaddressed system embodiments as well as with such embodiments still to be addressed, unless in contradiction, the power source arrangement is time-controllable so as to establish said first mode during a first timespan and the second mode during a second timespan, in one good embodiment thereof the addressed timespans are adjustable.
In a further embodiment of the just addressed embodiment the second timespan is started after starting of the first timespan.
In a further embodiment of that embodiments, wherein the power source arrangement is time-controllable to establish the respective first and second modes during the first timespan and the second timespan, the first and second timespans do not overlap.
In a further embodiment of the just addressed embodiment the time-controlled power source arrangement operates at least one of the second target as an anode, when the first mode is in enabled and of the first target as an anode, when the second mode is operated.
In a further embodiment of the system, which may be combined with any preaddressed system embodiment or with any such embodiment still to be addressed, unless in contradiction, one of the first and second targets is operated as an anode when the other of the first and second targets is operated as an anode and vice versa.
In a further embodiment of the sputtering system, which may be combined with any of the preaddressed system embodiments and system embodiments still to be addressed, unless in contradiction, the power source arrangement comprises a first power source operationally connected to first target and a second power source operationally connected to the second target.
In a further embodiment of the sputtering system, which may be combined with any of the preaddressed embodiments and embodiments of the system still to be addressed, unless in contradiction, the system further comprises a substrate holder for a plate-shaped substrate. The substrate holder is constructed to hold a plate-shaped substrate in a plane perpendicular to the geometric axis. The surface of a substrate held in the substrate holder and to be sputter coated facing towards the first and second targets.
In a further embodiment of the sputtering system in an embodiment as just addressed the system comprises a biasing power source, in a good embodiment an RF biasing power source which is operationally connectable to the substrate holder.
In a further embodiment of the sputtering system, which may be combined with any system embodiment already addressed and still to be addressed, unless in contradiction, and wherein a substrate holder is provided, the substrate holder is constructed to establish a distance d along the geometric axis and between the first sputtering surface and a surface to be sputter coated of a plate-shaped substrate on the substrate holder and with respect to a diameter D of a circle circumscribing the first sputtering surface, considered in a direction along the geometric axis, so that there is valid:
0.125 D≦d≦0.5 D.
In a further system embodiment, which may be combined with any such embodiment already addressed and still to be addressed, unless in contradiction, and which comprises a substrate holder, the first sputtering surface overlaps the periphery of a plate-shaped substrate on the substrate holder.
In a further system embodiment, which may be combined with any such embodiment already addressed, and which comprises a substrate holder, considered in a direction along the geometric axis, the second target is arranged subsequent the first target and a substrate, which is held by said substrate holder is arranged subsequent the second target.
The present invention is further directed on a method of manufacturing metal-coated, plate-shaped substrates of electrically isolating material having vias along the metal-coated plate surface, the vias being as well metal-coated. The addressed manufacturing method comprises coating a plate-shaped substrate of electrically isolating material having vias along at least one of the plate surfaces by means of a sputtering system as was addressed above and possibly such sputtering system according to one or more than one of the addressed embodiments.
In one variant of the addressed method, which may be combined with any method variant still to be addressed, unless in contradiction, the vias in the electrically isolating material plate-shaped substrate have an aspect ratio of at least 10:1 before being coated.
In a variant of the method, which may be combined with any of the preaddressed method variants and such variants still to be addressed, unless in contradiction, a plate-shaped substrate with vias is provided perpendicularly to the geometric axis, whereby the vias face the first sputtering surface. Then, the substrate is first magnetron sputter-coated with a metal by means of the first sputtering surface, whereby the first target is operated in a HIPIMS mode and the first magnet arrangement is moved in a driven manner along the first sputtering surface. The substrate is additionally second magnetron sputter-coated with the addressed metal by means of the second sputtering surface.
In one variant of the just addressed system variant, there is established the first sputter-coating during a first timespan T1, and there is established the second sputter-coating during a second timespan T2. The timespans T1 and T2 are thereby selected in one of the following modes:
In a further variant of the method, wherein first and second timespans are exploited, there is operated at least one of the first target during the first timespan T1 and of the second target during the second timespan T2 more than one time.
In a further variant of the method, which may be combined with any method variant already addressed and such variants still to be addressed, unless in contradiction, the second target is operated by one of DC mode, pulsed DC mode and HIPIMS mode.
In a variant of the method, which may be combined with any preaddressed method variant and such variants still to be addressed, unless in contradiction, the first and the second target are operated by an output-controllable common power source.
In one variant of the just addressed variant of the method, the common power source is operationally interconnected between the first and the second targets.
In one variant of the just addressed method variant, the common power source operates the first target in HIPIMS mode, the second target in one of DC mode, pulsed DC mode and HIPIMS mode.
In a variant of the just addressed variant, the common power source operates the second target in pulsed DC or in HIPIMS mode, thereby inverting pulse polarity when changing from sputter operating the first target to sputter operating the second target.
In a further variant of the method, which may be combined with any preaddressed method variant and such variants still to be addressed, unless in contradiction, the second target is exploited as a first anode in a timespan, during which the first target is sputter-operated, and the first target is exploited as a second anode in a timespan during which the second target is sputter-operated.
In a further variant of the method, which may be combined with any preaddressed method variant and such variant still to be addressed, unless in contradiction, during sputter-operating the first and the second target Rf bias power is applied to the substrate.
In one variant of the just addressed method variant, there is applied a different Rf bias power to the substrate for sputtering from the first target, then for sputtering from the second target.
In a further variant of the method, which may be combined with any preaddressed method variant and such variant still to be addressed, unless in contradiction, the thickness distribution of material deposited on said plate-shaped substrate of electrically isolating material and along the plate surface is adjusted by adjusting the ratio of a first timespan, during which said first target is sputtered and of a second timespan, during which the second target is sputtered.
In a further variant of the just addressed method variant, the addressed thickness distribution is adjusted during target life.
The invention under all its different aspects shall now be further explained with the help of examples and of figures. The figures show:
High-power impulse magnetron sputtering (HiPIMS, HIPIMS) is a method for physical vapor deposition—PVD—of thin films, which is based on magnetron sputter-deposition. HIPIMS utilizes extremely high power density of the order of kW.cm-2 in short pulses (impulses) of tenths of μsec extent at low duty cycle (ON/OFF time ration of <10%). A distinguishing feature of HIPIMS compared to common magnetron sputtering is its high degree of ionization of the sputtered off metal and high rate of molecular gas dissociation. With a conventional DC magnetron sputtering process the ionization of the sputtered-off material is increased by increasing the cathode power. The limit thereof is determined by the increased thermal load of the cathode and of the substrate to be coated. HIPIMS is applied at this point: The average cathode power remains low (1 to 10 kW) because of the small duty cycle. This allows the target to cool down during the OFF-times, resulting in an increased process stability. HIPIMS is a special type of pulsed DC magnetron sputtering.
The principle of HIPIMS (High-power Impulse Magnetron Sputtering) and its application for the material deposition into vias, especially TSV (Through Silicon Vias) has been described e.g. in WO 08/071734 A2, WO 08/071732 A2, WO 09/053479 A2 and in “Society of vacuum coaters 505/856-7188, 52nd annual technical conference proceedings, Santa Clara, Calif., May 9-14, 2009 ISSN 0737-5921”.
In the latter document it is described that for a given target, a given target to substrate distance and a given rotating magnet for generating the magnetron magnetic field the film thickness distribution develops from flat to dome-shaped when the pulse peak power HIPIMS discharge is increased.
There exists a need to provide a sufficiently thick layer, especially a sufficiently thick seed layer, in the bottom and along the sidewalls of vias as of TSV (Through Silicon Vias) with high aspect ratios between 5:1 and 10:1 or even higher, e.g. to enable later electro-plating. The deposition on the walls/bottom of the vias may thereby consist of an adhesion or barrier layer which may be of Ti or Ta, and a Cu seed layer, which is responsible for carrying the current for electro-plating into the via. With a DC magnetron sputtering setup working at a close target to substrate distance (TSD) it is practically impossible to provide material layers and thereby also the addressed seed layer in high aspect ratio vias as of TSVs due to the wide angular distribution of sputtered off material, customarily a metal. As a result later electro-plating will result in incomplete filling of the vias as depicted in
The HIPIMS process can provide a sufficiently high ion flux, in the addressed example sufficiently high Cu ion flux, to the substrate so that a complete electro-plating is possible as shown in
The present invention is to one part based on the experience that with a HIPIMS process, due to the limited target size, for a given magnetron sputter source with a uniform metal ion flux, the metal atom flux is stronger towards the center of the target and weaker towards the edge or periphery of the target. This is schematically shown in
Thus, according to
As a result the thickness profile on a substrate surface—i.e. in the field—becomes dome-shaped while deposition in the vias is uniform throughout the substrate surface or may even show thickened deposition in vias provided towards the edge or periphery of the substrate.
The present invention is further based on a second recognition. Departing from the explanations with respect to
The recognition is the disadvantageous fact that lacking plasma density in the center of the target of the magnetron source, less metal ions current flux is present in the center of the sputtering surface. This is shown in
As already discussed above, using a magnet system which allows for more erosion along the target edge or periphery improves the uniformity of coating thickness distribution along the extended surface of the substrate being coated, but has the disadvantage that the ion density profile concentrates more towards the target edge, which may lead to incomplete coverage of the surfaces of vias provided adjacent to the center of the substrate. Using a very small target to substrate distance (TSD) is not advisable, since there may come up interference between the high-density plasma adjacent the sputtering surface of the target and a bias of the substrate. Also for very high aspect ratios e.g. of 10:1 or more of vias, as of TSVs, one should use a target to substrate distance which is higher than for HIPIMS sputter coating flat substrates. This may be said “medium throw sputtering” compared to long-throw sputtering, where the directionality of material is given by narrow angle sputtering and not by the ionized material.
Another option to face the addressed recognition is to apply a target with a larger diameter with respect to the extent of a substrate with vias to be coated, which can also help to correct the uniformity of coating deposition on the substrate. The disadvantages of this option are:
With an eye on the metal ion and metal atom distribution as schematically shown in
In
Back to
The first target 703 may be plane, i.e. defining for a plane sputtering surface 705 before material has been sputtered off the target.
Further, the first target 703 may be in a view in direction along geometric axis A of any desired shape, but is in one embodiment circular. Then the second target 715 is ring-shaped.
Although the shape of the second sputtering surface 717 may be selected according to the respective application. In a today practiced embodiment the addressed sputtering surface 717 defines a pair of substantially straight lines in the sectional planes which contain the geometric axis A. In
Moreover, the second sputtering surface 717 may in one embodiment define, around geometric axis A, a surface which is parallel to the geometric axis A as is schematically shown in
Further, the second sputtering surface 717 may be perpendicular to the geometric axis A as schematically shown in
Alternatively, the second sputtering surface 717 may be cone-shaped as schematically shown in
Further embodiments of the sputter source arrangement as well as more details about the method of manufacturing shall be explained by the following examples and figures, which are more detailed, whereby all these examples and realization forms are based on the principle sputtering source arrangement as has been explained in context with
Specific features which will be described in context with the more detailed embodiments may be combined in any combination and applied to the embodiment of
In today's practiced forms of the sputtering source arrangement as of
Addressing a target 703 as of
0.125 D≦d≦0.5 D,
where D addresses the diameter of a circle which circumcises the first sputtering surface 705 as considered in direction of the geometric axis.
As already shown in
On the substrate S as of
A first setup of a sputtering system according to the invention, making use of a sputtering source arrangement as of the invention and in one of today's practiced modes is shown in
The first target 1203 is water-cooled 1241. The first magnet arrangement 1207 is rotated along the back surface 1209 of the first target 1203, as schematically shown by arrow w. A metal frame 1243 is provided all along the periphery of the first target 1203 and is electrically isolated therefrom. Operated on ground potential as shown in this embodiment, the metal frame 1243 acts as an anode with respect to both, the first sputtering sub-source 1201 as well as the second sputtering sub-source 1213.
The second magnetron sub-source 1213 is constructed as schematically shown in
The second target 1215 is cooled by a water cooling system 1245. The second magnet arrangement 1219 is stationary. The second target 1215 is operated with DC power from DC generator 1247.
In direction along axis A and pointing away from the first sputtering surface 1205, subsequent the second magnetron sub-source 1213, there is provided a further metal frame 1249 which is electrically isolated from the second target 1215 and, operated on ground potential, acts as well as an anode. The substrate S resides on a substrate holder 1251. Via substrate holder 1251 the substrate S is operated on Rf bias power by means of an Rf bias power unit 1253. Metal frame 1255 addresses in fact a remaining part co-defining the reaction space R for sputter-coating between substrate S and the two magnetron sub-sources 1201 and 1213.
Looking back on
The first target 703 may thus be operated at pulsed DC power and the second target 715 at DC power. Whereas the first magnet arrangement 707 is moved as was already addressed, the second magnet arrangement 719 may be stationary. Both targets 715 and 703 are cooled by a cooling system, thereby one embodiment each by a separate cooling system, as by a water cooling system.
The first magnetron source 1201 in the embodiment of
The second magnetron sub-source 1213 is run in DC magnetron mode. This is also one possibility to operate the second magnetron sub-source 713 of
The limited extension of the second target 1215 in the embodiment of
As was already addressed, in one embodiment the second target 715 as of
The embodiment as schematically shown in
The embodiment of
According to this embodiment, the second target 1415 is extended by the metal frame part 1443, with an eye on the embodiment of
Addressing the timespan during which the first sputtering source 1401 is sputter-operated as T1 and the timespan during which the second magnetron sub-source 1413 is sputter-operated as T2, this embodiment is especially suited, where the two timespans T1 and T2 do not overlap. Nevertheless, it might be possible to exploit the DC operated parts 1415 and 1443 as anode also when T1 and T2 do overlap. On a respective DC power level the second target 1415 and especially the metal frame part 1443 may also then act as an anode for sputter-operation of the first magnetron sub-source 1401, especially when operated in HIPIMS mode.
During timespans out of T2, in which only the second magnetron sub-source 1413 is operated, on one hand metal frame 1449 acts as an anode. Additionally the first target 1403 may then be operated so as to act as an anode for the second magnetron sub-source 1413.
The embodiment of
All the special features which have been described, especially with respect to the
Now the operating mode of the sputtering source arrangement and sputtering system according to the invention and operating the manufacturing method shall be addressed more in details. As has been addressed up to now especially with an eye on the
For a planar first target with a diameter of 400 m there is proposed to apply a pulse length of between 100 μsec and 200 μsec. The current pulses should be allowed to reach the maximum in approx. 100 μsec, which maximum should be in the range between 600 and 1000 A. The duty cycle should typically be in the range of 5 to 15%. If the target size differs from a 400 mm diameter circular shape, which accords with a surface of 2240 cm2, the respective parameters should be adapted to the prevailing surface extent so, that assumed the target surface was that of the 400 mm circular target, the addressed parameter values would be fulfilled.
The coating process, especially for coating plate-shaped substrates of electrically isolating materials having vias along the metal-coated plate surface and thereby especially when such vias have an aspect ratio of at least 10:1, is run in at least two steps. In a first step the first magnetron sub-source is operated in HIPIMS mode, in a second step the second sputtering sub-source is operated.
A first timespan T1 defines the operating timespan of the first step, sputter-operating the first magnetron sub-source, a second timespan T2 defines the extent of the second step, sputter-operating the second magnetron sub-source. The timespans T1, T2 may be of respectively desired length and may be staggered in time according to the specific application. Thus and according to
In analogy
During step 1 of time extent T1 the first magnetron sub-source as of 701 of
The advantages of the addressed two-step processing are:
By adjusting the ratio of the step times T1 and T2 the layer uniformity on the substrate can be adjusted. By controlling the ion Rf bias power, especially in the step 2, the amount of back sputtering can be adjusted to remove overhanging edges in the via opening. Since when operating the first magnetron sputtering sub-source during step T1 in HIPIMS high peak currents have to be achieved, usually a high process pressure is then preferred. In contrary, back sputtering process in step 2 is preferably run at a lower pressure, which can easily be established for DC magnetron sputtering.
In one embodiment, the first magnetron sub-source and the second magnetron sub-source can be used in combination and operated by one bipolar power supply 1940 as schematically shown in
This kind of bipolar power supply 1940 can be manufactured as a H-bridge and is available on the market. During step 1 the bipolar source 1940 is run in unipolar pulsed DC mode with a negative pole on the first target 703 and at an average power of P1—or at a voltage set point V1—for the timespan T1, followed by step 2 with a timespan T2 where the second target 715 is run in unipolar DC mode with a negative pole on target 715 at a different voltage or power set point P2 as shown in
Further, step 1 and step 2 can be run e.g. alternating several times. This can be advantageous if step 1 produces an overhanging edge in the via opening, which prevents further filling of the via, so that some intermittent back sputtering is necessary.
A sputtering source arrangement with a planar circular first magnetron sub-source is used with a target diameter of 400 mm. The target to substrate distance TSD is 140 mm. The substrate has a diameter of 300 mm. The ring-shaped second magnetron sub-source has a second target which, according to the embodiment of
The deposition uniformity has been calculated for a target to substrate distance TSD_R varying between 30 and 130 mm. For each individual radius from 0.0 to 150.0 mm on the substrate, the deposition contribution of the first magnetron sub-source dps (r) and of the second magnetron sub-source drs (r) can be superimposed to a resulting thickness dtotal (r). The deposition profile dtotal (r) can thus be optimized by a mixing factor F of the first and the second magnetron sub-sources:
d
total(r)=dps(r)+F*drs(r) (1)
Table 1 shows the calculated deposition profile together with the superposition factor F for the second magnetron sub-source source at different TSD_R. The uniformity profile is plotted in
The calculation above has been performed with a so-called cosine emission profile. As it is well-known to the skilled artisan, the sputter emission profile can be described by
I=[cos(∂)+C(2 cos(∂)−3 cos2(∂))]/π (2)
Therefore, the simulation has been repeated for a TSD_R of 30 mm and emission profiles with C between −1 and +1. The deposition uniformity profile is plotted in
Example 1 has shown that the superposition factor F for the second magnetron ring source seems to be quite high. The reason for this is a narrow erosion profile of the second magnetron sub-source of only approx. 18 mm, which bears the risk of a quite limited target life in relation to the target life of the first magnetron sub-source, which is a planar source.
Example 2 now uses the same first magnetron sub-source, a planar source with a target diameter of 400 mm and erosion profile as plotted in
surface of the ring target of the second magnetron sub-source, the erosion profile is approx. 46 mm. A wide erosion profile can usually be either achieved by moving magnets or by a magnet yoke design, which provides a flat magnetic field on the sputtering surface, therefore resulting in a wide erosion profile.
In Table 2 the calculated uniformity profile is listed for TSD_R varying between 60 mm and 100 mm as optimized by different superposition factors F for the second magnetron sub-source.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/076415 | 12/3/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61911630 | Dec 2013 | US |
