VACUUM SYSTEM AND METHOD TO DEPOSIT A COMPOUND LAYER

Abstract

A vacuum apparatus to deposit a compound layer on at least one plate shaped substrate by sputtering. The apparatus including a vacuum chamber with side walls around a central axis. The chamber includes at least one inlet for a process gas, at least one inlet for an inert gas, a substrate handling opening, a pedestal including an electrostatic chuck formed as a substrate support in a central lower area of a sputter compartment, a magnetron sputter source including the target at the frontside and a magnet-system at the backside of the source, an anode looping around the target and at least an upper part of the pedestal and a pump compartment connected to a bottom of the sputter compartment by a flow labyrinth. A vacuum pump system is connected to the pump compartment.

Claims

1) A vacuum apparatus to deposit a compound layer on at least one plate shaped substrate by sputtering comprising: a vacuum chamber (11) with side walls around a central axis (A), the chamber including at least one inlet (13) for a process gas; at least one inlet (14) for an inert gas; a substrate handling opening (15); a pedestal (5) comprising an electrostatic chuck (6) formed as a substrate (4) support in a central lower area of a sputter compartment (18), the pedestal (5) being mounted in an electrically isolated manner and connected to a first pole of a first voltage source (21), the pedestal (5) further being movable in a vertical direction towards and away from a target (1) from an upper position to a lower position and vice-versa when a sputter process is active; a magnetron sputter source (22) comprising the target (1) at the frontside and a magnet-system (23) at the backside of the source, the target (1) being mounted in a central area at the top (19) of the sputter compartment (18) of the chamber (11) in an electrically isolated manner and being connected to a first pole of a second voltage source (25); an anode (2) looping around the target (1) and at least an upper part of the pedestal (5) which comprises the substrate support and the electrostatic chuck (6) thereby forming the sidewalls (12) of the sputter compartment, the anode (2) being electrically connected to ground; and a pump compartment (17) being connected to a bottom (20) of the sputter compartment by a flow labyrinth (26), the flow labyrinth being designed to provide essentially the same flow conductance in the upper and lower position of the pedestal and in any position in between, and a vacuum pump system (16) connected to the pump compartment (17).

2) The apparatus according to claim 1, wherein the flow labyrinth is designed to have the same flow area during a movement from the upper to the lower position of the pedestal and in any position in between.

3) The apparatus according to claim 1, wherein the flow labyrinth comprises at least one annular pump channel (27) looping around the pedestal in an area below the substrate support and the electrostatic chuck.

4) The apparatus according to claim 3, wherein at least one characteristic distance (w.sub.ch) between at least two cylindrically or/and ring-shaped surrounding walls (2, 8, 9) of the pump channel is constant in the upper and lower position of the pedestal (5) and in any position in between.

5) The apparatus according to claim 1, wherein an electrically isolated target ring (3) is mounted looping around the circumference of the target (1) between the target and the anode.

6) The apparatus according to claim 5, wherein the target ring is made of a conductive material and is isolated from ground and target potential by at least one ceramic ring which is hidden from any line of sight towards the sputter compartment.

7) The apparatus according to claim 1, wherein a ring-shield (7) is mounted electrically isolated onto the pedestal surrounding the substrate support and a mounted substrate.

8) The apparatus according to claim 7, wherein the ring-shield (7) is connected to a third voltage source.

9) The apparatus according to claim 1, wherein at least one of a surface of the pedestal and a surface of the electrostatic chuck comprise an open channel (28, 29) connected to a respective back-gas inlet (30, 31).

10) The apparatus according to claim 9, wherein both surfaces comprise an open channel with a back-gas inlet.

11) The apparatus according to claim 10, wherein both back-gas inlets are connected to one common or respective separate feedthroughs (32) to a common or respective separate gas supplies.

12-14. (canceled)

15) The apparatus according to claim 1, wherein the anode is manufactured as a single piece anode.

16) The apparatus according to claim 1, wherein the gas supply means are mounted along or around an upper or a lower circumference of the anode.

17) The apparatus according to claim 16, wherein the gas supply means comprise at least one of a gas ring (33) with distribution openings allocated along its circumference and a channel structure (34) integrated in the anode with a circular distribution gap (35) or respectively allocated distribution openings and/or or further distribution channels.

18) The apparatus according to claim 1, wherein the first voltage source is a first RF power supply.

19) The apparatus according to claim 1, wherein the second voltage source (25) is a pulsed DC power supply, or a DC power supply and a second RF power supply whereby at least the DC power supply is connected by an adapter network to the sputter electrode.

20) The apparatus according to claim 19, wherein the apparatus comprises adjusting means (36) to adjust a phase relation between the first and the second RF source.

21) The apparatus according to claim 1, wherein the apparatus comprises control means (37) to control a flow of the reactive gas in dependency of at least one of the following process parameters: a target voltage, an intensity or a line pattern of a plasma emission measured at the active sputtering surface of the target, a gas composition.

22) The apparatus according to claim 1, wherein a dark space shield (8) being connected to ground is provided in dark space distance looping at least around a base (5′) of the pedestal (5).

23) The apparatus according to claim 22, wherein the dark space shield (8) forms one sidewall of the pump channel.

24. (canceled)

25) The apparatus according to claim 1, wherein the target consists of at least one of the following materials or a mixture thereof: aluminium (Al or AlMe), aluminium-scandium (AlSc or AlScMe), aluminium-chromium (AlCr or AlCrMe), magnesium-hafnium (AlMgHf or AlMgHfMe), whereas Me stands for at least one further metal in a concentration of 0.1 to 10 atomic percent with reference to the overall metal content of the respective layer and a mixture of two or three main metals as AlSc, AlCr or AlMgHf always comprises at least 1% of a main metal which is in lower concentration.

26) Multi-chamber vacuum system (MCS) to process at least one plate shaped substrate, comprising at least one load-lock chamber, transfer means (52), and at least three processing modules, whereby a first processing module is a physical vapor etching module (P1) configured to etch a surface of a substrate, a second processing module is a metal sputter module (P2) configured to deposit a metal layer by sputtering to the surface of the substrate, and a third processing module is a compound sputter module (P4) configured according to the apparatus of claim 1.

27) The MCS system according to claim 26, comprising a fourth process module that is an annealing module (P3) configured to heat a substrate to an annealing temperature T.sub.A between 550° C. and 900° C.

28) The MCS system according to claim 26, wherein the annealing module is configured to heat the substrate within 60 to 180 s to the annealing temperature T.sub.A.

29) The MCS system according to claim 26, wherein it comprises at least one further of at least one of a physical vapor etching module (P1′), a metal sputter module (P2′), and a compound sputter module (P4′).

30-32. (canceled)

33) Method to produce a piezoelectric coating on at least one side of at least one plate shaped substrate (4), the method comprising a sputter process carried out on an apparatus or an MCS according to one claim 1.

34) The method according to claim 33, wherein a piezoelectric AlN film or a respective AlN film comprising at least one minor metal Me.sub.m and/or Scandium is deposited, whereby the hexagonal structure of AlN is preserved.

35) The method according to claim 33, wherein the layer comprises or consists of at least one of the following materials or a mixture thereof: aluminium nitride (AlN, AlMeN), aluminium-scandium nitride (AlScN, AlScMeN), aluminium-chromium nitride (AlCrN) or magnesium-hafnium nitride (MgHfN, MgHfMeN), whereas Me stands for at least one further metal in a concentration of 0.1 to 10 atomic percent with reference to the overall metal content of the respective layer.

36-38. (canceled)

39) The method according to claim 33, wherein a film stress, a rocking curve, a full width half maximum, a loss angle δ, or a surface roughness of a substrate coated with the sputter deposited layer is optimized by at least one of the following process parameters: a power of the first voltage source; a power of the second voltage source; a quotient of the power of the DC-source and the second RF-source; a duty cycle of the pulsed DC-source; a distance between a substrate surface and a target surface; a defined (DC, RF) voltage applied to the isolated ring-shield; a high deposition temperature of the piezoelectric layer; an annealing step to anneal at least a seed and/or a metal (bottom) layer.

40) The method according to claim 39 wherein it comprises the following steps: providing a flat substrate into a sputter compartment (18) of vacuum processing chamber (11); etching one surface of the substrate by physical vapor etching (PVE); depositing a first metallic layer (Me1) on the etched substrate surface by sputtering in a first metal deposition step; annealing the metallic layer (Me1) in an annealing step at an annealing temperature T.sub.A at least 50° C. higher than a compound deposition temperature T.sub.COMP of a subsequent compound deposition step; depositing a first compound layer (Comp1) at temperature T.sub.COMP on the outer surface of the metallic layer (Me1) by reactive sputtering in a first compound deposition step; and depositing a second metallic layer (Me2) on the outer surface of the first compound layer by sputtering in a second metal deposition step.

41) The method according to claim 40, wherein a seed layer (Seed) is provided by metallic or reactive sputtering between the PVE-step and the first metal deposition step.

42) The method according to claim 40, wherein the annealing step is applied in a separate annealing oven.

43) The method according to claim 33, wherein a further processing step is applied in a separate processing system.

44) The method according to claim 43, wherein the further processing step comprises a structuring step of the metal layer (Me1) before the compound layer (Comp1) is deposited.

Description

EXAMPLES AND FIGURES

[0055] The invention shall now be further exemplified with the help of examples and figures. The figures are all drawn merely schematically and simplified, same reference numbers refer to features of the same or similar functionality. With reference to the terms top or bottom as with up, on, below and above or left and right it should be mentioned that such terms are used for ease of use or with reference to the figures only and not in a restricting way, so that a top and bottom configuration with wafer and target in an opposing horizontal position as present could be also applied e.g. to a left and right configuration or vice versa, if the same inventive concept should be applied to another apparatus type having both targets and substrate in a vertical or inclined position. The same refers to cylindrically and ring-like structures which result from the respective design of the examples as shown which could be transferred also to other chamber symmetries, e.g. (rect)angular geometries.

[0056] The figures show:

[0057] FIG. 1: An embodiment of an apparatus according to the invention;

[0058] FIG. 2: An embodiment of a flow labyrinth;

[0059] FIG. 3: A further embodiment of a flow labyrinth;

[0060] FIG. 4: A further embodiment of a flow labyrinth;

[0061] FIG. 5: Details of a flow labyrinth;

[0062] FIG. 6: A flow diagram;

[0063] FIG. 7: A pedestal with double cool/heat gas supply;

[0064] FIG. 8: A circularly arranged inventive MCS;

[0065] FIG. 9: A linearly arranged inventive MCS.

[0066] FIG. 1 shows an outline of an inventive sputter apparatus comprising a two-part vacuum chamber 10, split into a sputter compartment 18 and a pump compartment 17, both in terms of gas flow connected by a flow labyrinth 26. In this this embodiment the apparatus has an essentially cylindrical setup, round an apparatus axis A. Target diameter r.sub.t and inner diameter r.sub.a of the anode 2 which forms the sidewalls of the sputter compartment 17 can be chosen according to the substrate, for instance according to a wafer size. For a 200 mm wafer a target diameter r.sub.t can be chosen from 250 to 400 mm and an inner diameter r.sub.a from 300 to 450 mm. The sidewalls 11 are designed as a cathode 2 of the magnetron sputter source 22, on the top of the sputter compartment 18, which comprises the target 1 and the magnet system 23. Further on a target backplate 24 may be provided in case of expensive or mechanically week target material. Between the target 1 and the cathode 2 an isolated mounted however conductive target ring 3 is positioned on a ceramic isolator 43 in form of a ring or ceramic supports arranged in an upper circumference of the anode 2 around the target 3. The target ring 3 is on floating potential. The isolator 43 sits hidden against any line of sight towards the sputter compartment 17 within a channel structure 34 which together with the inlet gap 35, gives the inlet 13 for the process gas which can be a reactive gas, a mixture of different reactive gases with or without addition of a diluent inert gas. In the embodiment as shown in FIG. 1 the inlet gap 35 is formed between the anode and the target ring 3. An alternative or additional inlet for process gas can be provided in form of a gas ring 33 near a lower circumference of the anode. Thereby process gas and inert gas supply can be split, which can as an example help to prevent target poisoning when process gas is supplied only via the remote gas ring 33, which can be positioned in the pump compartment 17 as shown, and only inert sputter gas is provided to the upper inlet 13.

[0067] In the bottom of the sputter compartment 18 a vertically movable RF-pedestal, see reference number 5 and vertical double arrow, is mounted comprising a electrostatic chuck 6 to fix the wafer 4 and the pedestal base 5′. Together with the pedestal a ring-shield 7 and a dark space shield 8 can be moved up and down. Both ring-shield 7 and dark space shield 8 are electrically isolated against the RF-potential of the pedestal and/or in dark space distance to respective RF-supporting parts of the pedestal 5 and the pedestals base 5′. However, the dark space shield 8 is on ground potential, whereas the ring-shield 7 is on floating potential or provided with a separate voltage source to form a third electrode in the sputter compartment 18. Such a third electrode 7 surrounding the wafer circumference can be used in addition to other known measurements, like e.g. target power and substrate bias, to optimize stress and stress distribution within the layers of a piezoelectric active coating. Via respective feedthroughs 32, the pedestal is connected to RF-lines 41 and fluid lines 42 for heating and cooling of pedestal 5 and ESC 6. An optical temperature measurement device 40, e.g. a pyrometer is used to control the temperature at the backside of the wafer 4, which needs an additional optical feedthrough 32. At the bottom or a sidewall 11 of the pumping compartment 17 a pump socket is provided to connect to the high vacuum pump system 16.

[0068] FIG. 2 to 5 show different modifications of the flow labyrinth 26. All parts connected to the pedestal 5 or it's base 5′, like electrically isolated ring-shield 7 and dark space shield 8 move together with the pedestal, whereas anode 2 and channel shield 9 are stationary. For reasons of process stability it is important to keep pressure fluctuations as low as possible. Therefor it is important to have the same pumping speed provided at every process relevant position of the pedestal, which does not necessarily include a potential loading and deloading position, e.g. the lowest or alternatively the highest possible position. A typical process relevant travel of the pedestal over the whole target live may be in the range of 40 mm to 90 mm for thick targets, for usual 6 mm targets the travel will be from about 15 mm to 40 mm, therefor a travel of 15 mm to 90 mm would be sufficient for any needs. All types of labyrinths 26 comprise at least one annular pump channel 27.

[0069] It is important that during the travel a characteristic distance (w.sub.ch), e.g. a characteristic width of the channel within the labyrinth, which defines the smallest flow area does not change and stays constant. To exemplify the situation at hand of a simple flow labyrinth between a sputter compartment 18 and a pump compartment 17, in FIG. 5 some distances I, II, III, IV, which may become a characteristic distance during a certain travel distance of the pedestal are shown. In the present example the pedestal has an overall stroke of 95 mm and is designed for a process relevant travel of 40 mm (from 65 to 95 mm, the highest possible position of the pedestal). Under constant vacuum and pumping conditions defined by a 110 cm.sup.2 traverse section between dark space shield 8 and inner circumference r.sub.ai of the lowest part of the anode shield 2, see diagram in FIG. 6. Within this range distance I defines a constant characteristic distance w.sub.ch for the labyrinth and enables to move the wafer towards and away from the target surface to compensate for target erosion and/or to control layer stress in the respective layer stack of the coating. If it comes to lower travel values, distance II becomes the characteristic value of the flow labyrinth 26 as shown by the thick broken line of the characteristic graph V. Within this lower range however the flow area diminishes constantly as distance II becomes smaller when the pedestals fin comes near to the plane of the lower inner circumference of the anode (dashed line). At the end of the lower part of the travel (not shown in the diagram) distance Ill becomes the characteristic value before the pedestal comes to sit at the anode at zero mm travel. With FIG. 2 to 5 gas inlet 13 is integrated within the anode 2 instead between tha anode 2 and the target ring 3. However a similar construction could be also used with FIG. 2 to 5 or vice versa an anode integrated gas inlet with the embodiment of FIG. 1. The dashed horizontal line in FIG. 5 shows an alternative higher position of the upper surface of the ring shield 7, which can have some benefits with certain process parameters and can be again combined with any embodiment of the actual invention. Thereby the upper surface of the ring shield can be in plane with the chuck 6 or the substrate surface or anywhere between.

[0070] Similar considerations can be made with the labyrinths 26 as shown with FIGS. 3 and 4, which both comprise one, respectively two 180° turns within the flow channel and therefor very effectively prevent any plasma spill out from the sputter compartment to the pump compartment as long as slit width(s) at the entrance of the labyrinth comply to dark space distance needs according to the respective vacuum conditions or are covered with respectively dimensioned grids. With FIG. 3 the dark space shield 8 is formed trough-like with a channel shield 9 positioned in the center of the trough, together defining a U-like flow channel. With FIG. 4 the channels are integrated in the channel shield 9, which here forms a part of the anode 2. They are positioned between the anode radius r.sub.a within the sputter compartment and the lower anode radius r.sub.ai which in this case is at dark space distance to the dark space shield 8. The integration of parts of or the complete labyrinth 26 within the anode shield 2, e.g. as a one-piece device or at least as a close thermic coupling, has merits with reference to a more equal temperature distribution within the sputter compartment. With FIG. 4 a channel coming from the sputter compartment 18 is split sideways into two S-bends leaving into the pumping compartment 17. In this case characteristic distance w.sub.ch, =w.sub.ch1+w.sub.ch2, whereby w.sub.ch1,2 can be defined as the widths of respective sub-channels with curved flow arrows.

[0071] For a 30 liters volume of the sputter compartment as used with all types of labyrinths, a pumping speed of 500 to 700 l/s should be adjustable. This translates to a pumping speed of about 2000 l/s for the high vacuum pump system 16, e.g. comprising a turbo molecular pump, as connected to the pump socket 44 of the pumping compartment 17, due to the flow resistance of the respective labyrinth 26 as used.

[0072] FIG. 7 shows details of an inventive pedestal 5 provided with two inlets 16 for an inert heating/cooling gas, namely one back gas inlet 30 for the wafer when fixed to the ESC and one back gas inlet 31 for the ESC. Respective inlet channels 14 connect the gas inlets with feedthroughs 32 at the bottom of the pedestals base 5′. Such a configuration has some merits compared to a configuration with one inlet for both systems only, as back pressure for the ESC thereby can be risen to higher values whereas the backpressure for the wafer is highly limited, e.g. to a maximum of 5 sccm for a 200 mm wafer to avoid arcing which would occur with higher flows as only the wafer 4 separates the inlet 30 and channels 29 from the high vacuum of the sputter compartment. With such a configuration the ESC 6 can have a surface patterned by channels 29 open to the wafer to rise the flow resistance of the heating/cooling gas when flowing under the wafer from inlet 31 towards an outer region of the ESC 6, where it may escape into the high vacuum of the sputter compartment, see upper horizontal arrows. The surface pattern may be any type of labyrinth pattern, like a cobweb, a spiral, a meandering or mensa-like pattern of open channels 29, with very low aisle height of some μm or even lower to hold flow resistance high. Thereby an equal gas distribution at the backside of the wafer as well as an equal distribution of support points or areas for the wafer support can be achieved to avoid any mechanical stress due to electrostatic force of the ESC 6. Due to the combination of a high support area and the evenly spread shallow channel cavities providing short path ways for the gas molecules between the cool/hot ESC-surface wafer, eventually, e.g. for wafer sizes ≥200 mm, combined with severally inlets 30 at different points of the ESC surface, cooling and heating of the backside of the wafer can be performed most efficiently even with low back-gas flow and pressure.

[0073] The inlet channel 14 from the feedthrough 32 to the back-gas inlet 31 to cool/heat the lower side of the ESC ends in an open channel 28 which is here realized as back-gas chamber 28 between the pedestal and the ESC. From there, back-gas can flow off to the pumping compartment 17 via needle channels 48 and base channels 49, as symbolized by curved arrows and lower horizontal arrows, both providing a high flow resistance to enable a higher backpressure between pedestal 5 and ESC 6, which can be about from 0.1 to 1 hPa (10.sup.−1-10.sup.0 mbar). Heating of the chuck 5, made of an isolating ceramic material and comprising at least one RF-electrodes 47 is provided by a heater plate 46 on the base 5′ of the chuck. Alternatively or additionally a water-cooled chuck can be used.

[0074] A multichamber system MCS 50 comprising four process modules P.sub.1 to P.sub.4 and up to six pre- or post-processing modules pp.sub.12 to pp.sub.46, the latter pairwise positioned above and below a wafer handling level are shown in FIG. 8. All modules are arranged circular or polygonal round a central handler compartment 51 comprising a freely programmable handler 52 to transfer wafers from a pre-processing module to processing modules, transfer wafers between modules, and finally transfer back the wafer to a post-processing tool. Transfer in and out of the MCS is done by a loadlock 53 for incoming wafers and a loadlock 54 for outgoing wafers. At least one further handler transfers wafers from the loadlock chamber(s) 55, here realized as one load lock section, to preprocessing module pp.sub.12 and back again to the loadlock section from postprocessing module pp.sub.56. Pre- and postprocessing modules pp.sub.12, pp.sub.34, pp.sub.56 may comprise at least one of a buffer for wafers waiting to be processed or transferred, a heating station, a cooling station, and an aligner station. Process modules as present show a minimal configuration when annealing should be performed within the MCS. Therefor module P1 comprises a PVE-station, P2 a metal sputter station and P3 an annealing chamber comprising a flat carbon heater face to face to the substrate surface to be heated. The top and the bottom of the annealing compartment comprising cooled reflector surfaces whereby the substrate is hold near its outer circumference by a three fingers support. Finally, module P4 comprises an inventive compound sputtering apparatus 10 as described above. Further modules, e.g. a second compound sputter module to speed up overall process time by dividing in halves the sputter time for the thickest layer system of the coating, or a second metal sputter module for a layer system comprising two or more metal electrodes, can be connected via docks 56.

[0075] A system control unit 36 of the MCS, which may include the respective system units of the modules or a least control the timing of such units, controls wafer transfer as well as process details within every module by control means 38, adjusting means 37, measurement means 40, and sensors (not shown) which again may be included at least in part within the system control unit 36 or separate with respective modules to be controlled. An Input/Output unit 39 allows an operator to modify single process parameters and to load new processes automatically.

[0076] In FIG. 9 a MCS 50′ with a linear module arrangement is shown schematically. In this case for every process step a separate module is provided between a loadlock 53 for incoming wafers and a load-lock 54 for outgoing wafers with respectively dedicated load-lock chambers 55′ and 55″ which may comprise pre- and postprocessing modules or be connected to such modules also (see FIG. 8). When the substrate has been transferred from load-lock chamber 55′ to PVE-module 1′, the process starts with an etching of the clean blank wafer surface, followed by a sputter process in module P4′ to deposit a thin compound layer as a seed layer to which a first metal layer Me1 is applied in module P2. It follows the annealing step in module P3, a further PVE step in P1 to refine the metallic surface, a further compound sputter step to apply the functional piezoelectric layer Comp1 to the etched metal layer Me1 in module P4 and finally a second deposition of a second metal layer Me2 to complete the layer stack with a second electrode in module P2′, before the substrate is be locked out from vacuum via load lock 54. Wafer transfer between modules and between modules and load-lock chambers 55′, 55″ is performed by a linear handler 52′.

REFERENCE NUMBERS

[0077] 1 target, sputtered electrode [0078] 2 anode [0079] 3 floating target ring [0080] 4 wafer [0081] 5 RF pedestal [0082] 5′ base of the pedestal [0083] 6 electrostatic chuck (ESC) [0084] 7 ring-shield [0085] 8 darkspace shield [0086] 9 channel shield [0087] 10 sputtering apparatus [0088] 11 vacuum chamber [0089] 12 side wall(s) [0090] 13 inlet process gas [0091] 14 inlet channel inert heating/cooling gas [0092] 15 substrate handling opening [0093] 16 vacuum pump system [0094] 17 pump compartment [0095] 18 sputter compartment [0096] 19 top of the sputter compartment [0097] 20 bottom of the sputter compartment [0098] 21 first voltage source [0099] 22 magnetron sputter source [0100] 23 magnet-system [0101] 24 backplate [0102] 25 second voltage source [0103] 26 flow labyrinth [0104] 27 annular pump channel [0105] 28 open channel pedestal/ESC [0106] 29 open channel ESC/wafer [0107] 30 back gas inlet wafer [0108] 31 back gas inlet ESC [0109] 32 feedthrough [0110] 33 gas ring, inlet process gas [0111] 34 channel structure [0112] 35 inlet gap [0113] 36 central processing unit [0114] 37 adjusting means [0115] 38 control means [0116] 39 I/O-device [0117] 40 temperature measurement device [0118] 41 RF-line [0119] 42 heating and cooling line [0120] 43 isolator [0121] 44 pump socket [0122] 45 pedestals fin [0123] 46 heater plate [0124] 47 RF-electrode [0125] 48 needle channelcool/heat [0126] 49 base channelchuck heater [0127] 50 multichamber system (MSC) [0128] 51 handler compartment [0129] 52 handler [0130] 53 load-lock in [0131] 54 load-lock out [0132] 55 load-lock section [0133] 56 dock [0134] Me.sub.m minor metal [0135] Me (preferably minor) metals in a concentration of 0.1 to 10 atomic percent [0136] P.sub.1 . . . P.sub.4 process modules [0137] pp.sub.12 . . . pp.sub.56 pre- or post-processing modules [0138] r.sub.t target radius [0139] r.sub.a anode radius [0140] r.sub.al lower anode radius [0141] w.sub.ch width of pump channel