The present invention is generically directed to a method of manufacturing at least one sputter-coated substrate which comprises magnetic field enhanced sputter coating of the at least one substrate from a target arrangement which comprises at least one sputter target which has a sputtering surface.
The invention is further directed to a sputtering source which comprises at least one target which has a sputtering surface and magnetic field generating members so as to enhance sputtering.
In the art of coating substrates by means of a vacuum deposition process sputtering is known since long. Thereby, an electric field is applied between an anode and a target cathode, within a vacuum chamber, and a working gas, normally a noble gas as e.g. Argon, is inlet into the vacuum chamber. Simplified, the working gas is ionized by collision to form positive noble gas ions, which are accelerated by the addressed electric field towards the sputtering surface of the target, wherefrom target material is sputtered off into the vacuum atmosphere and deposited on one or more than one substrates which are to be coated. Replacing or adding to the working gas a reactive gas results in such reactive gas being activated in the plasma adjacent to the sputtering surface, and in substrate coating with reaction products of reactive gas and sputtered off target material.
The electrons which are freed by the gas ionizing process substantially contribute to the ongoing ionization.
Such sputtering process may be enhanced by applying a magnetic field adjacent the sputtering surface of the target with magnetic field components which are perpendicular to the electric field applied to the target cathode. The generic effect of applying such magnetic field is an additional acceleration especially of the light-weight electrons leading to an increased ionization rate of the gas molecules and thus to an increased plasma density in the area of the applied magnetic field.
The effect of magnetic field enhancing sputtering is further improved by shaping the addressed magnetic field, so as to result in a pattern of magnetic field lines which arc upon the sputtering surface considered in planes perpendicular to the sputtering surface and further form, considered in direction perpendicular to the addressed planes, a closed loop along the sputtering surface, often addressed in the respective art as a closed loop tunnel of magnetic field lines. This technique is generically known as magnetron sputtering. The effect of the closed loop tunnel of lines of magnetic field is that, due to mutual effect of such magnetic field and of the electric field, electrons are accelerated along and within the tunnel loop, leading there to a significantly increased plasma density. This results, in the loop area, in a significantly increased rate of sputtering. Due to the effect of the tunnel loop of magnetic field lines cooperating with the electric field, the tunnel area is often called “electron trap”. The effect on the target is an increased sputter rate in the area covered by the tunnel loop. The resulting loop shaped sputtering profile in the sputtering surface is often called “race track”.
The generic problem which is addressed by the present invention is that whenever magnetic field-enhanced sputtering is performed, some areas of the sputtering surface of the target are more sputter eroded than others. Clearly, whenever a target is locally more sputter eroded than other areas, target life is dictated by the time at which the target is consumed at the areas of increased erosion. Therefore, uneven sputter erosion distribution along the target significantly dictates the efficiency with respect to the percentage of material which may be exploited for sputter coating from a given target. Further, a locally pronounced sputter erosion deteriorates homogeneity of the deposition rate of sputtered off material along a substrate.
A multitude of different approaches are known to ameliorate the addressed effect of magnetic field enhanced sputtering which comprises on one hand tailoring of a stationary tunnel-shaped magnetic field so as to result in increased components of magnetic field lines which are parallel to the sputtering surface and thus perpendicular to the electric field and adjacent that surface.
Other approaches are dynamic and move the magnetic field along the sputtering surface, thereby equalizing sputter erosion of the target over the time.
From the JP 148642, FIG. 11, it is e.g. known to provide a first stationary and elongated arrangement of magnetic poles along a target. Distant from and along such stationary and elongated arrangement of magnetic poles there is provided, beneath the sputtering surface, a dynamic and elongated arrangement of magnetic poles realized by an elongated drum revolving about an axis parallel to and distant from the addressed stationary and elongated arrangement. An arcing magnetic field is generated between the magnetic poles at the drum and the magnetic poles of the stationary arrangement. Due to the fact that upon the addressed drum the magnetic poles are arranged in a helical pattern, seen from the sputtering surface of a target, these poles are moved linearly along the stationary and elongated arrangement of magnetic poles. The magnetic field enhancing the sputtering process thus arcs upon the sputtering surface of the target from the stationary and elongated arrangement of magnetic poles to the dynamic arrangement of linearly moved magnetic poles or vice versa.
Such an approach has several disadvantages. One thereof is that the resulting magnetic field is substantially governed by the strength of magnets on the dynamic arrangement. A second one is that the resulting magnetic field is in fact only parallel to the sputtering surface along a very limited central area between the dynamic arrangement and the stationary elongated arrangement of magnetic poles.
It is an object of the present invention to provide a different approach.
This is achieved, according to the present invention, by a method of manufacturing at least one sputter-coated substrate which method comprises magnetic field-enhanced sputter coating of the at least one substrate from a target arrangement which has at least one sputter target having a sputtering surface. Thereby, there is generated a time-varying magnetic field on the sputter surface which is done by a first stationary and elongated arrangement of magnetic poles and a second stationary and elongated arrangement of magnetic poles, whereby the first and the second stationary and elongated arrangements are disposed mutually spaced and one along the other. At least one of the addressed stationary and elongated arrangements is situated under the sputtering surface. The two arrangements of magnetic poles commonly generate a stationary magnetic field which has a pattern of magnetic field lines which are arcing above the sputtering surface as considered in respective planes perpendicular to the sputtering surface. The addressed pattern of magnetic field lines further is tunnel-like, namely considered in the direction perpendicular to the addressed planes. There is superimposed a modulating magnetic field to the stationary magnetic field just adjacent at least one of the first and of the second stationary and elongated arrangements of magnetic poles and along at least a predominant part of the length extent of the addressed one arrangement.
Definitions
- When we speak of the sputtering surface of a target and use such surface as a geometric entity to other geometric entities thereto, we understand the sputtering surface as a geometric plane or possibly a bent geometric surface, disregarding any unsteadiness of the practical sputtering surface as introduced by target mounting arrangements or and especially sputter erosion profiles.
- Whenever we speak of “adjacent” to a stationary and elongated arrangement of magnetic poles we understand such “adjacent” to define a position which is substantially closer to the addressed arrangement than to the other or others stationary and elongated arrangement(s) of magnetic poles.
By the fact that a stationary magnetic field with the tunnel-shaped pattern of magnetic field lines is generated by means of elongated arrangements of magnetic poles which are stationary on one hand the overall strength of the magnetic field is governed by stationary magnetic poles and thus respective magnet arrangements. The stationary magnetic field acts as working point field. On the other hand the option is opened to exploit stationarily measures to optimize magnetic field lines parallel to the sputtering surface.
By additionally superimposing a dynamic modulating magnetic field to the working point field adjacent the at least one of the stationary and elongated arrangements an increasing extent of the effect of magnetic field line components parallel to the sputtering surface is achieved adjacent to the addressed one stationary arrangement. Thereby, the magnetic poles which govern the overall strength of the magnetic field of tunnel-shaped pattern need not be dynamically moved by a drive.
In one embodiment of the method according to the present invention the addressed modulating is performed time- and location-dependent along the at least one stationary and elongated arrangement, leading to a wavelike modulation along the one stationary arrangement.
In a further embodiment the addressed modulating comprises moving a dynamic arrangement of one or of alternate polarity magnetic poles adjacent to, perpendicularly and/or along the one stationary and elongated arrangement of magnetic poles, whereby one polarity poles of the moved arrangement are mutually spaced in direction of moving.
In a further embodiment the addressed modulating comprises moving an arrangement of ferromagnetic shunt members adjacent to, perpendicularly to and/or along the at least one stationary and elongated arrangement of magnetic poles, whereby the shunt members are mutually spaced in direction of moving. Magnetic poles of both polarities and ferromagnetic shunt members may be combined in one and the same arrangement which is moved.
In a further embodiment, which is especially suited to be applied for magnetic field-enhanced sputtering of the magnetron type, the method comprises providing a third stationary and elongated arrangement of magnetic poles, thereby the second stationary arrangement of magnetic poles being disposed in between the first and the third stationary and elongated arrangements of magnetic poles and beneath the sputtering surface. The addressed modulating is performed adjacent to and along the second stationary and elongated arrangement of magnetic poles, i.e. at that arrangement which is provided in between the other two stationary and elongated arrangements of magnetic poles.
In one embodiment, the modulating magnetic field is selected to be stronger than the stationary magnetic field whereupon it is superimposed.
In another embodiment the superimposed modulating magnetic field is selected to be weaker than the stationary magnetic field it is superimposed to.
It is to be noted that along the one stationary and elongated arrangement of magnetic poles, in some segments of extent the modulating field may be stronger, in other segments weaker than the stationary magnetic field it is superimposed to.
In a further embodiment of the method according to the present invention the addressed modulating includes providing a drum which is rotatable about an axis and located adjacent to the addressed one stationary and elongated arrangement. The drum has a pattern of at least one of ferromagnetic members and of magnetic poles.
By revolving the drum ferromagnetic members and/or magnetic poles are moved towards and from the magnetic poles of the one stationary and elongated arrangement, and thus perpendicularly to the length extent of the stationary arrangement.
In a further embodiment, at least two targets are provided disposed one beside the other, whereby the one stationary and elongated arrangement of magnetic poles, i.e. that one whereat modulating is performed, is disposed substantially between the at least two targets. Thereby, the addressed modulation affects stationary magnetic fields on both targets.
Still in a further embodiment the method according to the present invention comprises flattening the stationary magnetic field by means of a stationary and elongated arrangement of magnetic dipoles arranged along and between the first and second stationary and elongated arrangements of magnetic poles. The dipole axes are thereby substantially parallel and beneath the sputtering surface of the target.
Still in a further embodiment departing from an embodiment with first, second and third stationary and elongated arrangements of magnetic poles, the stationary magnetic field is flattened between the third and second stationary and elongated arrangements of magnetic poles by means of stationary and elongated arrangements of magnetic dipoles arranged along and between the first and second and between the third and the second stationary and elongated arrangements of magnetic poles. The dipole axes are thereby substantially parallel and beneath the sputtering surface.
The present invention is further directed on a sputtering source which comprises
- at least one sputter target having a sputter surface,
- a first stationary and elongated arrangement of magnetic poles along said target,
- a second stationary and elongated arrangement of magnetic poles disposed mutually spaced and along said first stationary and elongated arrangement of magnetic poles.
At least one of the first and of the second stationary and elongated arrangements of magnetic poles is disposed beneath the sputtering surface. The first and second stationary and elongated arrangements commonly generate a stationary magnetic field which has a pattern of magnetic field lines which arc upon the sputtering surface as considered in respective planes perpendicular to the addressed sputtering surface. The pattern is further tunnel-like, namely when considered in a direction perpendicular to the addressed planes.
The sputtering source further comprises a dynamic arrangement of at least one spaced apart ferromagnetic members and of magnetic poles which is drivingly movable adjacent to one of the first and of the second stationary and elongated arrangements of magnetic poles.
Thereby, a further dynamic arrangement of spaced apart ferromagnetic members and/or of magnetic poles may be provided drivingly movable adjacent and along the other of said first and second stationary and elongated arrangements of magnetic poles.
Looking back on the method of manufacturing according to the present invention, clearly superimposing a modulating magnetic field to the stationary magnetic field may additionally be performed adjacent the other of the first and of the second stationary and elongated arrangements of magnetic poles. Nevertheless, one modulating magnetic field considered affects the stationary magnetic field substantially along one of the addressed first and second stationary and elongated arrangements of magnetic poles.
In an embodiment of the sputtering source according to the present invention the addressed dynamic arrangement is drivingly movable adjacent the one of the first and second stationary and elongated arrangements of magnetic poles and perpendicularly and/or along the just addressed one arrangement. Thereby, modulation of the stationary magnetic field may be performed in a wavelike manner time- and location-dependent along the addressed one stationary and elongated arrangement of magnetic poles.
In one embodiment of the sputtering source according to the invention the source comprises a third stationary and elongated arrangement of magnetic poles, whereby the second stationary and elongated arrangement is disposed between the first and the third stationary and elongated arrangements and beneath the sputtering surface. The one stationary and elongated arrangement of magnetic poles to which the dynamic arrangement is adjacent to is the second stationary arrangement of magnetic poles.
In one embodiment of the source according to the present invention the stationary magnetic field is stronger than a magnetic field which is generated with at least a part of said magnetic poles of the dynamic arrangement considered at a common locus along and adjacent the one stationary and elongated arrangement of magnetic poles to which the dynamic arrangement is associated.
In a further embodiment of the source the stationary magnetic field is weaker than a magnetic field generated with at least a part of the magnetic poles of the dynamic arrangement considered at a common locus along and adjacent the one stationary and elongated arrangement of magnetic poles.
Thereby, the embodiments just addressed may be combined so that along one part of the stationary magnetic field the latter is stronger, along another part weaker than the respectively associated magnetic field which is generated with the dynamic arrangement.
In one embodiment of the source according to the invention the dynamic arrangement comprises a drum which is drivingly rotatable about an axis and which comprises a pattern of the addressed at least one of ferromagnetic members and of magnetic poles.
In a further embodiment the just addressed pattern is a helical pattern around the surface of the drum.
In a further embodiment the source according to the present invention comprises at least two targets disposed one beside the other and the one stationary and elongated arrangement of magnetic poles which is associated to the dynamic arrangement as addressed is disposed substantially between the at least two targets.
In a further embodiment of the source according to the present invention there is provided a stationary and elongated arrangement of magnetic dipoles along and between at least the first and second stationary and elongated arrangements of magnetic poles, the axes of the dipoles being substantially parallel to the sputtering surface and disposed adjacent to and beneath the sputtering surface.
Under a further aspect of the present invention there is proposed a method of manufacturing at least one sputter-coated substrate which comprises magnetic field-enhanced sputter-coating the at least one substrate from a target arrangement which comprises at least one sputter target having a sputter surface. Thereby, there is generated a time-varying magnetic field on the surface of the sputter target by a first stationary and elongated arrangement of magnetic poles and a second stationary and elongated arrangement of magnetic poles. The first and the second stationary and elongated arrangement are disposed mutually spaced and one along the other. At least one of the addressed arrangements is located beneath the sputtering surface. The first and second stationary and elongated arrangements commonly generate a stationary magnetic field which has a pattern of magnetic field lines arcing above the sputtering surface as considered in respective planes perpendicular to the sputtering surface. The magnetic field lines are further tunnel-like patterned considered in a direction perpendicular to the addressed planes. The addressed stationary magnetic field is controllably unbalanced, so as to result in the time-varying magnetic field.
Under a further aspect of the present invention there is proposed a method of modulating plasma density which comprises generating a magnetic field in a plasma exclusively by a drum with a helical pattern of magnetic poles rotated about the axis of the drum.
The invention shall now further be explained by means of examples and respective figures.
The figures show:
FIG. 1 a schematic perspectivic view of a magnet arrangement as provided at a source according to the present invention and according to the method of this invention, for explaining the generic approach of the present invention;
FIG. 2 still schematically, a stationary magnetic field and the modulation thereof as exploited by the present invention;
FIG. 3 over the time axis, modulation of the stationary magnetic field as a working point defining field;
FIG. 4 a part of a magnet arrangement with applied wavelike modulation of the stationary magnetic field and as exploited in one embodiment of the source and method according to the present invention;
FIG. 5 schematically, a part of a magnet arrangement with a first embodiment of modulating the stationary magnetic field according to the present invention;
FIG. 6 a representation in analogy to that of FIG. 5 with a second embodiment of realizing the modulation of the stationary magnetic field as of the present invention;
FIG. 7 in a representation in analogy to that of the FIGS. 5 and 6, a third embodiment of modulating the stationary magnetic field according to the present invention;
FIGS. 8 to 10 still in representations in analogy to those of the FIG. 5 to 7, three further embodiments of modulating the stationary magnetic field according to the present invention;
FIG. 11 in a perspectivic, schematic representation, an embodiment for realizing a flattened stationary magnetic field as exploited in embodiments of the present invention;
FIG. 12 realizing modulation of a stationary magnetic field generated by an embodiment as of FIG. 11 in a magnetron-type pattern according to embodiments of the invention;
FIG. 13 the embodiment of FIG. 12 without modulating, showing the resulting, flattened stationary magnetic field;
FIG. 14a) to d) Departing from an embodiment according to FIG. 12, the development of magnetic field and sputter erosion profile along the sputtering surface when modulating the stationary magnetic field as of FIG. 13 according to the present invention;
FIG. 15 at the embodiment shown in FIG. 14, the resulting erosion profile along the sputtering surface of the target;
FIG. 16 a drum with a helical pattern of magnetic poles with the resulting magnetic field as exploited in some embodiments of the present invention for modulating the stationary magnetic field;
FIG. 17 the resulting areas of higher plasma density upon a sputtering target caused by a drum per se as shown in FIG. 16;
FIG. 18 an embodiment according to FIG. 12 in top view using a drum as shown in FIG. 16 with resulting moving electron traps when the stationary magnetic field is relatively low compared with the modulating magnetic field of the drum;
FIG. 19 in a representation similar to that of FIG. 18, the snakelike moving electron trap which results at the embodiment of FIG. 18 if, in opposition thereto, the stationary magnetic field is relatively strong compared with the modulating magnetic field of the drum;
FIG. 20 in a representation in analogy to that of FIG. 14, two embodiments with multiple targets and multiple modulations per target according to the present invention;
FIG. 21 a further embodiment of the present invention which makes use of ferromagnetic members for modulating the stationary magnetic field, realized in an embodiment according to FIG. 13;
FIG. 22 five examples of modulating drums as applied in some embodiments of the present invention with helical pattern of magnetic poles differently tailored along subsequent segments of the drums, considered along their length extent, and
FIG. 23 schematically, the stationary magnetic field as applied according to the present invention and the modulation thereof by controlled unbalancing.
In FIG. 1 there are shown schematically parts of a sputtering source according to the present invention for explaining the generic approach according to the invention. There is provided a target 1 shown in dashed lines having a sputtering surface 3. A first arrangement 5 of magnetic poles is extended in one direction y and presents magnetic poles of a dipole DP. The magnetic poles may be of specifically selected alternating polarity, but will normally at least along some extent of the arrangement 5 be of the same polarity, as indicated e.g. S. The arrangement 5 is mounted stationary with respect to the target 1.
There is provided a second arrangement 7 of magnetic poles of dipoles DP which is as well extended in direction y and which is spaced from the arrangement 5. The magnetic poles presented by the arrangement 7 may again be of different polarities, but, here too, are normally and at least along a part of the extent of the arrangement 7 equal, as indicated by N. At least one of the two stationary and elongated arrangements of magnetic poles 5, 7 is mounted beneath the sputtering surface 3 of target 1. By the two stationary and elongated arrangements 5 and 7 and in fact the associated dipoles DP there is generated a stationary magnetic field Hs. The magnetic field lines thereof are arcing between the two arrangements 5 and 7, in planes P1 perpendicular to the sputtering surface 3 and upon the sputtering surface 3. According to the representation of FIG. 1 these planes P1 are perpendicular to the direction y. In combination, the magnetic field lines form a tunnel arcing above the sputtering surface 3 and considered in y direction, i.e. in direction perpendicular to the planes P1.
In FIG. 2 there is schematically shown the part of the stationary magnetic field Hs impinging on the magnetic poles of the polarity S as of the arrangement 5 of FIG. 1. According to the invention and as shown in FIG. 2 schematically and enlarged, the stationary magnetic field HS has magnetic field components HSx parallel to the sputtering surface 3 as well as components HSz perpendicular to the sputtering surface 3. According to the invention there is applied adjacent to the stationary and elongated arrangement of magnetic poles a modulating magnetic field Hm which has a time-varying magnetic field component Hmx(t). Due to the superposition of the stationary magnetic field component parallel to the sputtering surface, HSx and of the time varying component Hmx of the modulating magnetic field Hm the resulting magnetic field component parallel to the sputtering surface 3 is time varying too.
In FIG. 3 there is shown over the time axis t the component HSx of the stationary magnetic field HS as a working point value of magnetic field and the modulating component Hmx(t) of magnetic field resulting in superposition result magnetic field H(t).
Thus, the stationary magnetic field HS, arcing from one arrangement 7 to the second one 5 and over the sputtering surface 3 of the target 1, may be said defining for the working point magnetic field on which the modulating time-variable magnetic field Hm is superimposed adjacent to and along the one stationary and elongated arrangement 5 of magnetic poles, according to FIG. 1. As shown in FIG. 1 in dashed lines the stationary magnetic field HS may also be modulated by a further superimposed modulating magnetic field adjacent to and along the second stationary and elongated arrangement of magnetic poles, 7, e.g. and as shown in FIG. 3 also in dashed lines in phase opposition.
In FIG. 4 there is shown in an enlarged representation the one stationary and elongated arrangement 5 of magnetic poles adjacent to which the stationary magnetic field HS is modulated by the modulating magnetic field Hm. In this embodiment the modulation adjacent to magnetic poles S1 . . . Sn along direction y are correlated with respect to phasing so that there is realized a modulation pattern Hmx(t,y) along the extent of arrangement 5 which propagates like a wave.
In FIG. 5 there is shown, in an enlarged representation, the one stationary and elongated arrangement 5 of magnetic poles according to FIG. 1, thereby the double arrows represent, as they also do in the other figures, the magnetic dipoles which result in the magnetic poles at the respective arrangements. The modulating magnetic field Mm according to the FIGS. 1 to 3 is realized by moving linearly, according to the arrow v, an arrangement of magnetic poles adjacent to and along the one stationary arrangement. As further shown in FIG. 5 the dynamic arrangement 9 in this embodiment provides for magnetic poles interacting with magnetic poles of the stationary arrangement 5 of equal polarity. If more than one magnetic pole is provided along arrangement 9 as shown in FIG. 5, the equal magnetic poles along the extent of the dynamic arrangement 9 are mutually spaced. By drivingly moving the dynamic arrangement 9 adjacent to and along the stationary and elongated arrangement 5 the stationary magnetic field (not shown in FIG. 5) is modulated at each of the magnetic poles of the stationary and elongated arrangement 5. Heuristically one may say that whenever two of the equal polarity magnetic poles of the arrangement 5 and 9 are aligned the magnetic field component HSx of the stationary magnetic field as of FIG. 2 are increased adjacent to the magnetic poles of the stationary and elongated arrangement 5 and thus adjacent to the respective area of the sputtering surface.
FIG. 6 shows in a representation equal to that of FIG. 5 the arrangement of the one stationary and elongated arrangement of magnetic poles 5 cooperating with a dynamic arrangement of magnetic poles 9a, whereby the magnetic poles of the dynamic arrangement 9a are of opposite polarity to the magnetic poles of the stationary and elongated arrangement 5. Again heuristically, whenever two magnetic poles respectively of the stationary and of the dynamic arrangements 5 and 9a are or come into alignment, this results in weakening the magnetic field component parallel to the sputtering surface, Hmx as of FIG. 2 adjacent to and above the sputtering surface.
FIG. 7 shows a representation in analogy to those of the FIGS. 5 and 6 with the exception that here the dynamic arrangement of magnetic poles has at least a pair of subsequent magnetic poles of alternate polarity. By moving the dynamic and elongated arrangement 9b adjacent to and along the stationary and elongated arrangement 5 of magnetic poles the magnetic field components parallel to the sputtering surface are increased and reduced alternatively and in phase opposition at subsequent areas of sputtering surface adjacent to the magnetic poles of the stationary and elongated arrangement 5.
With an eye on the embodiment according to the FIGS. 5 and 6 some or all of the magnetic poles and the respective magnetic dipole members as shown at 11 of FIG. 5 may be replaced by ferromagnetic members, resulting in shunting a part of the stationary magnetic field HS and thereby unbalancing the stationary magnetic field there where such ferromagnetic shunting member is momentarily adjacent a respective magnetic pole of the stationary and elongated arrangement 5 in a modulating manner. Further, such ferromagnetic shunting members may be applied in between the magnetic poles as of the FIG. 5, 6 or 7. By such ferromagnetic shunting members, the stationary magnetic field HS is modulated.
FIG. 8 shows in a representation similar to that of the FIGS. 5 to 7 a further embodiment for realizing modulation of the stationary magnetic field HS as of FIG. 1. Adjacent to and along the one stationary and elongated arrangement of magnetic poles 5, there is provided a drum drivingly rotated about an axis A which is oriented parallel to the stationary and elongated arrangement 5. In drum 13 there are provided magnetic dipole members 15 respectively aligned with the magnetic poles along the stationary and elongated arrangement 5. In the embodiment of FIG. 8 the dipoles of the members 15 are all aligned in direction and polarity. By rotating drum 13 the stationary magnetic field HS impinging upon the sputtering surface adjacent to the magnetic poles of stationary arrangement 5 are all equally and simultaneously modulated by the alternatingly effective polarities of the dipole members 15 along the revolving drum 13 which are here in fact moved towards and from the arrangement 5, along the x axis.
FIG. 9 shows an embodiment similar to that of FIG. 8 in an equal representation. The difference between the embodiment of FIG. 8 and that of FIG. 9 is that the drum 13a in the embodiment of FIG. 9 has dipole members 15 which are arranged along drum 13a with magnetic dipoles of alternating polarity. By this embodiment a modulation substantially equally to that as achieved by the embodiment of FIG. 7 is realized. Nevertheless and from a constructional point of view realization by means of a drivingly rotatable drum as of the embodiment of FIG. 9 is highly advantageous compared with realization by means of a linearly moved arrangement as of FIG. 7.
With an eye on the embodiments according to the FIGS. 5-7 it has to be emphasized that the length extent of the respective dynamic arrangements 9, 9a and 9b respectively needs by no means be equal to such length extent of the stationary and elongated arrangements 5. Thus, with an eye on the embodiments of FIGS. 5 and 6 the dynamic and elongated arrangement may be reduced to comprise just one member defining for one magnetic polarity. In the embodiment of FIG. 7 the addressed length may be reduced to comprise just a pair of opposite polarity pole pieces.
In FIG. 10 there is shown a further embodiment similar to those as shown in the FIGS. 8 and 9. The difference of the embodiment according to FIG. 10 to those of the FIGS. 8 and 9 is that the dipole members 15 are arranged along the drivingly rotatable drum 13b to form a screw-thread-like helical pattern of magnetic poles along the extent of drum 13b. Thereby, modulation of the stationary magnetic field HS is performed over time with defined phasing as considered from one dipole member 15 to the next. This results in a wave-like propagation of modulation as was addressed in context with the more generic FIG. 4. Clearly respective mutual phasing between subsequent dipole members 15, which in fact accords with the relative angular position of the dipole members with respect to axis A, may be selected freely to result in a huge number of different modulation patterns to be exploited.
Up to now we have specifically addressed different embodiments for modulating the stationary magnetic field HS as of FIG. 1, 2 or 3.
As was already addressed the principle according to the present invention has an advantage that the stationary magnetic field may be tailored with respect to shape and strength independently from the applied modulating magnetic field Hm. FIG. 11 shows in a representation in analogy to that of FIG. 1 an embodiment of the present invention whereat, specifically, the stationary magnetic field HS is tailored to have optimum magnetic field components HSx parallel to the sputtering surface. The stationary and elongated arrangement of magnetic poles 7a is polarized, as an example, in opposite direction compared with the arrangement 7 of FIG. 1. This is purely an example, the addressed polarization could be made exactly as shown in FIG. 1. There is again provided a first stationary and elongated arrangement of magnetic poles 5a which is spaced from the (not shown) target with the sputtering surface. The arrangements 5 and 7a are bridged by a ferromagnetic bridging member 17 which is provided in fact also in all other embodiments as of FIG. 1 to 10 for generating the arcing stationary magnetic field HS. Between the two stationary and elongated arrangements 5a and 7a there is situated a stationary and elongated dipole arrangement 19. The dipole direction is selected so that along the magnetic circuit with the arrangements 19, 5a, 17 and 7a no inversion of dipole polarity is established.
Advantageously, the dipole arrangement 19 is spaced slightly further from the sputtering surface (not shown) than the magnetic pole forming surfaces of the respective arrangements 7a and 5a. Due to this arrangement there is achieved, as schematically shown, a substantially flattened pattern of magnetic field lines still forming respective arcs and a tunnel as was described in context with FIG. 1. Thereby, the magnetic field components HSx parallel to the sputtering surface 3 as of FIG. 1 are substantially homogenized considered in direction x and compared with the embodiment as of FIG. 1. All the modulation embodiments as have been described with the help of the FIG. 1 to 10 may be applied to realize the modulation unit MOD 21 shown in FIG. 11.
All the embodiments as have been shown up to now do provide for one extended tunnel of stationary magnetic field HS which is modulated according to the present invention. The approach according to the invention is nevertheless highly suited to be applied for magnetic field enhanced sputtering of the magnetron type, whereat the stationary magnetic field forms a closed tunnel loop upon the sputtering surface and especially the central area of the sputtering surface inside the addressed tunnel loop is less eroded, thereby leading to non-optimum target exploitation and to non-optimum homogeneity of distribution of sputter deposition along the surface of a substrate to be sputter-coated.
FIG. 12 shows an embodiment of a sputtering source according to the present invention and operating according to the method of the invention for magnetron-type magnetic field enhanced sputtering. The embodiment according to FIG. 12 results in fact from doubling the embodiment shown in FIG. 11 mirror-symmetrically. An outermost left stationary and elongated arrangement of magnetic pole 7a1 cooperates with a more centrally arranged stationary and elongated arrangement of magnetic pole 5a1 via stationary and elongated dipole arrangement 191 and ferromagnetic bridging part 17. Thereby, the left-hand leg Hs1 of the stationary magnetic field HS considered in y direction as of FIG. 1 is generated. An outermost right stationary and elongated arrangement of magnetic pole 7ar cooperates with stationary and elongated dipole arrangement 19r and a more centrally located stationary and elongated arrangement of magnetic pole 5ar so as to generate the right-hand leg of the magnetic field tunnel according to HSr. Between the pair of more centrally located stationary arrangements 5a1 and 5ar, generically spoken, there resides the modulation unit.
As perfectly clear to the skilled artisan such modulation unit may be realized as was specifically described with the help of the FIG. 5 to 10. As shown in FIG. 12 such modulation unit 21a is here realized by means of a drum 13, 13a or 13b as of one of the FIGS. 8 to 10.
In FIG. 13 there is shown the embodiment according to FIG. 12 with no modulation of the stationary magnetic field HS1, HSr and with the resulting erosion profile in the sputtering surface 3 and especially the area F of the sputtering surface which is not eroded.
FIG. 14 (a) to (d) shows the embodiment of FIG. 13 with the modulation unit realized by drum 13 or 13a or 13b of the FIG. 8 to 10. Thereby, the specific FIGS. 14a to 14d show the time variation of the magnetic field resulting from superposition of the stationary magnetic field HS as of FIG. 13 with the modulating magnetic field Hm generated by the drivingly rotating drum 13, 13a, 13b. The drum with the magnetic dipole as indicated is thereby rotated by respective 90° in clock-wise direction from representation (a) to representation (d). There are further shown the erosion profiles in each of the drum positions in a shaded manner and the relative shift of the erosion-free area F upon the sputtering surface. For clearness reasons only few reference numbers are introduced in FIG. 14. During sputtering and sputter-coating of one or more than one substrates the drum is drivingly rotated with a constant or variable angular speed ω.
Instead or additionally to the magnetic dipole members arranged along the revolving drum according to one of the embodiments according to FIG. 8, 9 or 10 ferromagnetic material members may be provided at the drum. Whenever the drum is realized, as a good solution, according to the embodiment of FIG. 10, in one embodiment the number of turns of the thread-like, helical pattern along the extent of the drum 13b as of FIG. 10 is an integer number. Thereby, torque forces between the magnets arranged along the drum 13b and the stationary and elongated arrangements of magnetic pole 5a1 and 5ar are minimized.
As may be seen from FIG. 12 to 14 in the respective embodiments there is realized magnetron-type, magnetic field enhanced sputtering, by respectively closing the electron trap formed by the tunnel-like pattern of magnetic field on both ends of the legs of the addressed tunnel. The rotational speed of the drum 13b may be adjusted according to the processing time for sputter-coating one more than one substrate simultaneously. The revolution speed ω becomes only critical if the processing time is below the revolving period. It is proposed to perform at least one or several revolutions by the drum 13b per process time in order to achieve a good uniformity of sputter-deposited coating. As may be seen from FIG. 14a to 14d at any angle of rotation of drum 13b the magnetic field lines and the instant sputtering erosion profile on the sputtering surface 3 are different. If a revolving dipole is parallel to the dipoles of the stationary arrangements of magnetic poles, the left-hand and right-hand erosion profiles are symmetrical, but still different compared with sputtering without modulation as of FIG. 13.
Any other angle of the revolving dipole results in a smaller or larger lateral shift of the magnetic field pattern just adjacent to the two stationary and elongated arrangements of magnetic poles and of the erosion profiles to the left and to the right. Any unsputtered area F whereupon sputter material is redeposited substantially disappears. A resulting overall erosion profile is shown in FIG. 15.
In FIG. 16 there is schematically shown in more details an embodiment of drum 13b as of FIG. 10. Tunnels of field lines are formed between respective magnetic poles at the drum. Such a drum 13b may be used to modulate plasma density of a plasma discharge. By rotating the drum 13b the pattern of magnetic poles moves linearly in the direction of the axis A.
In FIG. 17 there are shown the resulting areas of increased plasma density resulting from applying the drum as of FIG. 16 beneath a plasma without additional magnetic fields.
In the embodiment of FIG. 12 making use of drum 13b with thread-like, helical pattern of magnetic poles and as shown in FIG. 18, there is generated on one hand a magnetron electron trap by the stationary and elongated arrangements of magnetic pole and the terminating arrangements 23 of such poles. Additionally, by the interaction of the modulating magnetic field realized by drum 13b with the adjacent stationary and elongated arrangements of magnetic poles 5a1 and 5ar according to FIG. 12, central electron traps as shown at T in FIG. 18 are generated which move in direction of the axis A of the revolving drum 13b.
Thereby and in the embodiment according to FIG. 18 the stationary magnetic field HS as of FIG. 12 is relatively weak, so e.g. 10 Gauss to 200 Gauss with a modulating magnetic field generated by drum 13b of 100 Gauss to 1000 Gauss.
Nevertheless the stationary magnetic field is thereby strong enough to form together with the modulating magnetic field the travelling closed tunnels of magnetic field resulting in the electron traps T as of FIG. 18.
When the relative strength of the stationary magnetic field HS relative to the modulating magnetic field Hm is changed so that the stationary magnetic field is relatively strong compared with the modulating magnetic field, the resulting pattern of electron traps as of FIG. 18 switches to the pattern as shown in FIG. 19. Thereby, the modulating magnetic field is selected in the range of 200 Gauss, whereas the stationary magnetic field in the range of about 250 Gauss. The stationary elongated arrangements of magnetic poles as shown in FIG. 18 are not shown in FIG. 19. There is formed a continuous snakelike moving electron trap as the drum 13b rotates.
In FIG. 20 there are shown, based on a representation according to that of FIG. 14, two embodiments a) and b) with two rods per target 1. In the embodiment according to FIG. 20(a) modulation by respective drums 13, 13a, 13b is performed between adjacent stationary and elongated arrangements of magnetic poles 7a1 and 7ar of neighbouring targets, thus in fact between these targets 1 and additionally and according to FIG. 12 between the respective stationary and elongated arrangements of magnetic pole 5a1 and 5ar which latter are not shown in FIG. 20. In the embodiment of FIG. 20(b) magnetic field modulation is performed, with an eye on FIG. 12, adjacent to the outer stationary and elongated arrangements of magnetic pole 7a1, 7ar of each of the multiple targets 1.
In analogy to the modulation of the stationary magnetic field HS by means of a modulating magnetic field which is realized by respective magnetic dipoles, it is possible to use ferromagnetic material to provide for the modulation. Such material does not generate its own magnetic field, but can modify existing magnetic fields in a similar way as is done by superimposing a modulating magnetic field.
According to the embodiment of FIG. 21 the stationary magnetic field is generated as has been explained in context with FIG. 12. Between the stationary and elongated arrangements 5a1 and 5ar of magnetic pole there is provided a drivingly rotatable drum 13c. Along drum 13c there are provided radially extending bars 25 of ferromagnetic material arranged equal to the dipoles at the respective drums of FIG. 8 to 10. The drum 13c revolves in a ferromagnetic pole shoe 27 by which the one-polarity poles of magnets 29 are collected. Thus, the ferromagnetic bars 25 present that magnetic poles (S) whenever such bars are adjacent to the pole shoe 27. In dependency of the angular position of the bars 25 modulation of the stationary magnetic fields at the left and at the right legs is realized very similar to the modulation which has been explained in context with FIG. 14.
Whenever performing modulation of the stationary magnetic field HS especially by means of a driven drum as has been addressed up to now, along such drum segments may be defined by which different modulations are performed. Thus, whenever making use of thread-like helical patterns, be it of magnetic poles and/or of ferromagnetic member surfaces along the surface of the drum, in different segments along the drum, different thread pitches may be applied, even different revolving speeds etc. In FIG. 22 five examples are shown of a drum provided with a helical pattern of magnetic poles and whereat the helical patterns are different in predetermined segments along the extent of the drum.
When looking back and having understood the present invention as generically explained e.g. with the help of the FIGS. 1 to 9 it may be seen that this invention may also be considered from a different point of view and under a further aspect. This shall be explained with the help of FIG. 23(a) to FIG. 23(c). FIG. 23(a) shows in a schematic representation the first and second arrangements of magnetic poles 5, 7 and the stationary magnetic field HS as was addressed to now. According to FIG. 23(b) the stationary magnetic field HS is controllably unbalanced as schematically shown by applying an auxiliary arrangement of magnetic poles 5a adjacent to the stationary and elongated arrangement of magnetic poles 5. According to FIG. 23(c) an auxiliary arrangement 7a is provided adjacent to the stationary and elongated arrangement of magnetic poles 5. As a function of the respective magnetic polarities S, N which are presented by the auxiliary arrangements 5a and 7a to the stationary magnetic field HS the addressed stationary magnetic field HS as of FIG. 23(a) is modulatingly unbalanced, thereby strengthening or weakening the tunnel-shaped and arcing stationary magnetic field HS adjacent to the mono-polarity stationary and elongated arrangement of magnetic poles, according to FIG. 23 arrangement 5.
As schematically shown by the control C of the auxiliary arrangement of magnetic poles, so as to alternatively present alternative magnetic poles to the addressed stationary and elongated arrangement 5 of magnetic poles, the stationary magnetic field HS is modulated adjacent to the one stationary and elongated arrangement of magnetic poles 5 according to the present invention.
The disclosure of the U.S. provisional application Ser. No. 60/753,144 is enclosed into the present application by reference.
Patent Application
20070175748
