RF capacitive coupled dual frequency etch reactor

In a capacitively coupled etch reactor, in which the smaller electrode is etched, the larger electrode is electrically supplied by a very high frequency supply signal and by a high frequency supply signal. The smaller electrode, acting as a substrate carrier, is connected to ground potential.

The present invention is directed to a two-electrode capacitive coupled RF etch reactor or apparatus and obeys substantially the law of Koenig as e.g. addressed in U.S. Pat. No. 6,248,219. In such a reactor or apparatus, the plasma space is in operational contact solely with an electrode arrangement which consists of a first electrode arrangement and of a second electrode arrangement facing the first electrode arrangement. The law of Koenig defines that the ratio of the drop of time averaged electrical potential adjacent to the electrode surfaces between which an Rf plasma discharge is generated, is given by the inverse ratio of respective electrode surface areas raised to the fourth power. The conditions for which the law of Koenig is valid are also addressed in the patent as mentioned. Therefrom results the skilled artisan's knowledge, that the smaller electrode surface exposed to the Rf plasma is predominantly sputtered off, in other words etched, the larger being predominantly sputter coated.

It is an object of the present invention to provide an improved etching apparatus, also called reactor, of the addressed type.

This is achieved by the capacitive coupled RF vacuum etching apparatus constructed for etch operation under predetermined conditions, including predetermined pressure conditions. Such apparatus comprises a vacuum recipient—also addressed as enclosure—.

In the vacuum recipient, a plasma space is provided which is in contact solely with one electrode arrangement consisting of a first electrode arrangement and of a second electrode arrangement, facing the first electrode arrangement.

Other members which are not electrically conductive or which are operated in an electrically floating manner may be in contact with the plasma space but are not to be considered as electrodes.

The fact, that the plasma is operated and influenced by only two electrodes is essential for a Koenig type reactor.

The first electrode arrangement defines a first electrode surface exposed to the plasma space.

The second electrode arrangement defines a second electrode surface exposed to the plasma space and comprises the surface of a workpiece carrier with a carrier surface.

The first electrode surface is larger than the second electrode surface.

The first electrode arrangement is electrically connected to and supplied from an output arrangement of a Rf generator arrangement via a match box arrangement.

The Rf generator arrangement generates at least one first plasmas supply signal at a very high frequency at the output arrangement and at least one second plasma supply signal, at a high frequency lower than the very high frequency, at the output arrangement.

The first electrode arrangement is electrically connected via the match box arrangement to the output arrangement and is electrically supplied, in operation, by the first and by the second plasma supply signals.

The second electrode arrangement is, at least during etching operation, electrically connected to a system ground tab and is thus operated on system ground potential. Due to the dual—or even multiple—Rf-frequency supply of the plasma in the plasma space, the plasma density and thus etching efficiency is significantly increased.

Nevertheless, the overall construction of the reactor or apparatus is significantly facilitated by the fact that only the first electrode arrangement is multiple Rf supplied and provided with a match box arrangement, whereas the second electrode arrangement is kept on electrical ground potential. As it is this second electrode arrangement which provides for the workpiece support, the construction of workpiece handling equipment is thereby substantially simplified as well.

In one embodiment of the apparatus according to the invention the first electrode arrangement comprises a metal body with a surrounding surface freely exposed to and immersed in the plasma space whereby the surrounding surface is a part of the first electrode surface.

When we address that the surrounding surface of the body is freely exposed to the plasma space, it is clear that some minor and neglectable parts of that surface are not freely exposed but are necessarily used to establish a mechanical mount for the body within the plasma space.

By means of such a body the effective surface of the first electrode arrangement is significantly enlarged.

In one embodiment of the apparatus according to the invention the metal body comprises a pattern of through openings and/or through slits tailored so that, in operation, plasma burns in the through openings at the predetermined conditions.

By such trough openings and/or through slits plasma distribution in the plasma space may be controlled and thus the distribution of etching effect on the workpiece or substrate.

In one embodiment of the apparatus according to the invention the first electrode surface comprises a first surface area extending along a first plane, a second surface area of said body, extending along a second plane, said first and second surface areas defining an interspace tailored so that, in operation, plasma burns in and along the interspace at the predetermined conditions.

If such body is constructed and mounted to just form an interspace with a width just large enough to allow plasma to burn therein but not significantly larger, the effective surface of the first electrode becomes significantly enlarged without significantly increasing the overall volume of the plasma space and thus of the vacuum recipient.

In one embodiment of the apparatus according to the invention the second electrode surface comprises a surface area extending along a third plane and said first, second and third planes are parallel planes.

Thus, the reactor is, in one embodiment and principally, a parallel electrode reactor.

In one embodiment, the metal body is a plate.

In one embodiment of the apparatus according to the invention the Rf generator arrangement is connected, via the match box arrangement, to the first electrode arrangement at more than one locally different contact points.

In one embodiment of the apparatus according to the invention the first plasma supply signal and the second plasma supply signal are connected, via the match box arrangement, to the first electrode arrangement at locally different contact points.

Both embodiments just addressed may improve plasma distribution in the plasma space and, especially for etching large workpieces or substrates, may contribute to reducing the occurrence of standing waves.

In one embodiment of the apparatus according to the invention there is valid:
10 MHz≤fvhf≤400 MHz,
or
10 MHz≤fvhf≤300 MHz
or
20 MHz≤fvhf≤300 MHz
or
20 MHz≤fvhf≤100 MHz
and:
0.01fvhf≤fhf≤0.5fvhf
or
0.05fvhf≤fhf≤0.5fvhf.

Thereby fhfstands for the frequency of the high frequency supply signal and fvhfstands for the frequency of the very high frequency supply signal.

In one embodiment of the apparatus according to the invention the workpiece carrier is drivingly movable towards and from the first electrode arrangement.

In one embodiment of the apparatus according to the invention the workpiece carrier is not movable towards and from the first electrode arrangement.

In one embodiment of the apparatus according to the invention the workpiece carrier is not movable towards and from the first electrode arrangement and the first electrode arrangement comprises a drivingly movable door for loading/unloading a workpiece.

In one embodiment of the apparatus according to the invention the enclosure is subdivided in a pumping compartment comprising a pumping port and in an etching compartment comprising the first electrode arrangement. The compartments are separate by a shroud or rim which has a pattern of through openings or through slits tailored so that, in operation, plasma does not burn therein at the predetermined etching conditions.

Such two-compartment structure allows to realize high pumping efficiency through a large pumping port although keeping the etching compartment small, just adapted to the specific workpiece or substrate and the electrode arrangements. The etching compartment volume may be fully exploited for the electrode arrangements without considering pumping port requirements.

In one embodiment of the apparatus according to the invention the enclosure is subdivided in a pumping compartment which comprises a pumping port and in an etching compartment, which comprises the first electrode arrangement. The compartments are separate by a shroud or rim. The shroud or rim holds a frame which defines a workpiece access opening to the etching compartment. The frame is held by the shroud or rim by means of a multitude of spokes which mutually define through-gaps between the pumping compartment and the etching compartment. The gaps are tailored so that, in operation, plasma does not burn therein. In a further embodiment, the frame is thereby held by the rim or shroud by means of the spokes in such a manner, that the frame may freely expand and retract under thermal loading.

In one embodiment of the apparatus according to the invention the enclosure is again subdivided in a pumping compartment comprising a pumping port and an etching compartment comprising the first electrode arrangement. The compartments are separate by a shroud or rim having a pattern of through openings or through slits tailored so, that, in operation, plasma does not burn therein at the predetermined etching conditions. The shroud or rim holds a frame which defines a workpiece access opening to the etching compartment. The workpiece carrier is drivingly movable from a load-/unload position into a processing position and vice versa. The frame acts as a downholding member for a workpiece or substrate on the workpiece carrier in the processing position.

The skilled artisan knows as to when a vacuum plasma will burn or will not burn in a void e.g. in a hole, in a slit in an interspace, when predetermined processing conditions are applied.

In one embodiment of the apparatus according to the invention the enclosure is again subdivided in a pumping compartment comprising a pumping port and in an etching compartment which comprises the first electrode arrangement. The compartments are separate by a shroud or rim. The shroud or rim holds a frame which defines a workpiece access opening to the etching compartment. The workpiece carrier is drivingly movable from a load-/unload position into a processing position and vice versa. The frame is constructed so as to act as a downholding member for a workpiece or substrate on the workpiece carrier in the processing position. The shroud or rim holds the frame by means of a multitude of spokes mutually defining through-gaps between the pumping and the etching compartments. The through-gaps are tailored so, that, in operation, plasma does not burn therein at the predetermined etching conditions. The frame is held by the rim or shroud by means of the spokes so that it may freely expand and retract under thermal loading.

In one embodiment of the apparatus according to the invention the spokes are constructed as compressible and/or bendable members and thus resiliently allow free expansion and retraction of the frame.

In one embodiment of the apparatus according to the invention at least a part of the spokes define a direction of length extent each and are mounted to the frame so, that the respective direction of length extent intersects the tangent on said frame at the locus of respective spoke fixation with an angle α for which there is valid:
90°>α≥0°.

In one embodiment of the apparatus according to the invention the workpiece carrier comprises a channel arrangement adapted to receive a liquid heating or cooling medium.

In one embodiment of the apparatus according to the invention the enclosure is subdivided in a pumping compartment comprising a pumping port and an etching compartment comprising the first electrode arrangement. The compartments are separate by a shroud or rim which has a pattern of through openings or through slits tailored so that, in operation, plasma does not burn therein at the predetermined etching conditions. The workpiece carrier is drivingly movable from a load-/unload position into a processing position and vice versa. A downholding member is provided tailored to mechanically hold a workpiece or substrate down on the workpiece carrier and in the processing position at and along the periphery of the workpiece- or substrate-surface which is exposed to the etching compartment. The workpiece carrier comprises a channel arrangement adapted to receive a liquid heating or cooling medium and a further channel arrangement adapted to receive a heat conduction gas. The further channel arrangement discharges by a bore- and/or slit-pattern at the carrier-surface of the workpiece carrier.

In one embodiment of the apparatus according to the invention the further channel arrangement and the bores and/or slits discharging at the carrier-surface are tailored so as to establish along the periphery of an interspace between said carrier-surface and a substrate or workpiece a pressure of heat conducting gas which is at least equal to the pressure in the and along the more central parts of said interspace.

In one embodiment of the apparatus according to the invention the enclosure is subdivided in a pumping compartment comprising a pumping port and in an etching compartment comprising the first electrode arrangement. The compartments are separate by a shroud or rim having a pattern of through openings and/or through slits which are tailored so that, in operation, plasma does not burn therein at said predetermined etching conditions. The shroud or rim is either a part of the enclosure or comprises a part of the enclosure and a part of the first electrode arrangement.

In one embodiment of the apparatus according to the invention the enclosure is subdivided in a pumping compartment comprising a pumping port and in an etching compartment comprising the first electrode arrangement. The compartments are separate by a shroud or rim which has a pattern of through openings and/or through slits. As was addressed bevor in different contexts, these openings and/or through slits are tailored so that, in operation, plasma is not burning therein at the predetermined etching conditions. The workpiece carrier is drivingly movable from a load-/unload position into a processing position and vice versa. The shroud or rim is electrically connected to the workpiece support in its processing position by distinct, distributed and resilient contact members.

In one embodiment of the apparatus according to the invention the generator arrangement generates the first plasma supply signal at 60 MHz, the second plasma supply signal at about 13 Mhz.

Please note that in all embodiments in which a very high frequency supply signal as well as a high frequency supply signal are applied to the first electrode arrangement these at least two supply signals are simultaneously applied at least during time intervals of the etching operation.

In one embodiment of the apparatus according to the invention the predetermined pressure condition for the etching is between 0.1 and 0.5 Pa, both limits included.

In one embodiment of the apparatus according to the invention in which the first electrode arrangement comprises a metal body with a surrounding surface freely exposed to and immersed in the plasma space a spacing between a first part of said surrounding surface of the metal body freely exposed to and immersed in the plasma space and a second part of the first electrode surface, facing the first part, is 10 mm to 40 mm, preferably 20 mm.

In one embodiment of the apparatus according to the invention, a spacing between a predominant part of the first electrode surface facing the workpiece carrier and a predominant part of the surface of the workpiece carrier is 40 mm to 80 mm, both limits included, is preferably 65 mm.

One embodiment of the apparatus according to the invention is shaped for rectangular or square substrates.

In one embodiment of the apparatus according to the invention the Rf generator arrangement is constructed to at least one of frequency modulating and of power modulating at least one of said first and of said second supply signals during operation.

In one embodiment of the apparatus according to the invention at least one of the following features prevails:The Rf generator arrangement is tailored to generate said very high frequency as an integer multiple of said high frequency;The Rf generator arrangement is tailored to phase lock said first supply signal with said second supply signal;The Rf generator arrangement is tailored for adjusting mutual phasing of said first and said second supply signals;The Rf generator arrangement is tailored to vary mutual phasing of the first and second supply signals during operation.

The invention is further directed on a workpiece or substrate processing plant comprising at least one capacitive coupled Rf apparatus according to the invention or one or more than one of its embodiments. In one embodiment, the plant is an inline plant, including a coil-to-coil foil processing plant. In an inline plant, workpieces are transported in a row from one treatment station to the next at a fixed rhythm. In a further embodiment, the plant is of the type in which the treatment stations are loaded and unloaded with at least one workpiece or substrate at a selectable rhythm, as by a handler, e.g. a central handler.

The invention is further directed to a method of etching workpieces or substrates or of manufacturing etched workpieces or substrates by making use of the capacitive coupled RF vacuum etching apparatus according to the invention or according to one or more than one of its embodiments, or of the plant according to the invention.

In one variant of the method according to the invention etching is performed in a reactive gas atmosphere, preferably containing oxygen or oxygen and fluorine. Thereby oxygen as well as fluorine may be provided by a gas containing oxygen, oxygen e.g. by N2O and, respectively fluorine, by a gas containing fluorine, as e.g. by CF4, SF6, NF3, C4F8 etc.

One or more than one of the embodiments of the capacitive coupled RF vacuum apparatus may be combined, if not contradictory.

The invention will now be further described by examples and with the help of figures.

We address throughout the present description and claims a frequency f as a very high frequency fvhfif there is valid:
10 MHz≤fvhf≤400 MHz,
or
10 MHz≤fvhf≤300 MHz
or
20 MHz≤fvhf≤300 MHz
or
20 MHz≤fvhf≤100 MHz.

We address throughout the present description and claims a frequency f as a high frequency fhfif there is valid:
0.01fvhf≤fhf≤0.5fvhf
or
0.05fvhf≤fhf≤0.5fvhf.

The apparatus1of the embodiment ofFIG. 1and according to the invention, which will also be called reactor, comprises a vacuum chamber within a metal enclosure3. Within the enclosure3a pumping compartment5is separate from an etching compartment7by a separating shroud or rim9having a dense pattern of through-holes and/or through-slits11. The lower compartment, the pumping compartment5, comprises a large pumping port13to which a pump arrangement15is connectable.

A metal workpiece support, also called substrate support,19has a first metal part19arigidly mounted and electrically connected to the metal enclosure3and a movable part19bdrivingly movable up and down, as shown by the double arrow W, with respect to the part19a. The movable part19bcarries a metal workpiece- or substrate-carrier19c. The drive for the parts19band19cis not shown inFIG. 1.

The part19cis, especially in its edging, upper position, electrically linked to ground e.g. via a metal bellow21to part19a.

As schematically shown, the metal enclosure3is electrically connectable to a system ground-G-connector as e.g. shown inFIG. 1at23.

The enclosure3is further electrically connected to shroud or rim9e.g. at25and is electrically connected to part19ae.g. at27. Part19bis electrically connected to substrate carrier19ce.g. at28.

Within the etching compartment7there is provided a first electrode arrangement29. The first electrode arrangement29which provides for the larger electrode surface of the reactor1, thus the electrode surface being predominantly sputter coated, comprises a jar- or pot-shaped electrode body31with a plate shaped basis33and frame like side walls35. The jar- or pot-shaped electrode body31resides close to and separate from and along the enclosure3. It may e.g. be mounted to the enclosure3via an electrically isolating layer or by electrically isolating members (not shown).

The first electrode arrangement29is electrically connected to a supply generator arrangement37, as shown by line38, via a matchbox arrangement39. Thereby the basis33of the electrode body31is, e.g. substantially centrally, connected to—according to one embodiment of the invention—at least two outputs41vhfand41hfof an output arrangement of the matchbox arrangement39. From the output41vhfa first plasma supply signal with a fvhffrequency supplies the first electrode arrangement29and, from output41hfa second plasma supply signal with a frequency fhf, superimposed on the first plasma supply signal, supplies the first electrode arrangement29. The first and second plasma supply signals are generated by the supply generator arrangement37, e.g. comprising a generator for the first plasma supply signal and a second generator for the second plasma supply signal. The generator arrangement37has an output40vhfas well as an output40hfto the matchbox.

The first and second plasma supply signals are simultaneously applied—superimposed—to the first electrode arrangement29, at least during a time interval within etch processing timespan, thereby even during a predominant time interval within the etch processing timespan, or even during the entire etch processing timespan.

The match box arrangement39is constructed to prevent that, due to superposition of the plasma supply signals, the vhf plasma supply signal loads the hf generator output and vice versa. As schematically shown inFIG. 1a band block filter43vhftuned on the fvhfgenerated at the output40vhfblocks signals from the output40vhfto load the output40hf. In analogy, a band block filter43hftuned on the fhfgenerated at the output40hfblocks signals from the output40hfto load the output40vhf. This is equivalent to supplying the electrode arrangement29, respectively, via band-pass filters.

The second electrode arrangement45comprises the workpiece carrier19cof the workpiece support19in its lifted-up position (b), which is the etching position for a plate shaped workpiece or substrate residing on the workpiece carrier19c.

As addressed above, the workpiece carrier19cis on system ground potential. This significantly simplifies overall construction of the reactor, e.g. with an eye on handling substrates to and from the reactor. As the substrate is therefore operated on ground potential, the electrode arrangement29is operated on a floating DC potential e.g. in that it is—normally in the matchbox arrangement39—decoupled from DC as by capacitive coupling to the supply generator arrangement37, as schematically shown by capacitor34.

Generically spoken, and in this embodiment, the larger electrode is supplied by different Rf frequencies and the substrate carrier, the smaller electrode, is operated on ground potential.

The shroud9, operated on ground potential, is, electrically, part of the second electrode arrangement45. The RF plasma PL is confined between the inner surface31iof the electrode body31, the upper surface9iof the shroud9and the surface19ciof the workpiece carrier19cexposed to the etching compartment7.

Between the outer surface310of the electrode body31and the enclosure3no plasma is generated, due to the fact that the interspace between the enclosure3and the outer surface310of the electrode body31is respectively conceived e.g. so, that the spacing is smaller than dark space distance at the predetermined operating etching conditions or e.g. due to the fact that the respective interspace is filled with a dielectric material spacing layer.

The through-openings or through slits11in the shroud9are dimensioned so small, that no plasma may burn therein at the addressed conditions. Through slits are narrower than the addressed dark space distance. The diameters of through holes as well are smaller than the addressed dark space distance. Nevertheless, the density of through bores or through slits is high enough to ensure a very low gas flow resistance from the etching compartment7to the pumping compartment5, ensuring a highly efficient pumping-off of etched off material. As the trough-bores or -slits11in the shroud9are dimensioned so that no plasma may burn therein, the surface increase of the second electrode arrangement45by such bores and/or slits does not influence sputtering/etching distribution between the electrode arrangements29and45.

The etching efficiency of a substrate47is significantly improved by substantially enlarging the electrode surface of the first electrode arrangement29. This is realized by providing at least one metal body50e.g. plate shaped, distant from the surface31iof the electrode body31. The e.g. plate shaped, metal body50has an overall surrounding surface50i, which, with the exception of some small areas for mounting and electrically feeding the body50, is freely exposed to the plasma space PL. Electrically RF-supplied e.g. by both plasma supply signals, as schematically shown at52and spaced from the surface31iby a distance d1larger than the dark space distance at the prevailing conditions for the etching process for the substrate47, the e.g. plate shaped body50becomes completely immersed in the Rf plasma. Its overall surface50iis part of the electrode surface of the first electrode arrangement29.

Thus according to the invention, a metal body is immersed in the plasma space and at the Rf electric potential of the larger electrode arrangement in a reactor substantially obeying the law of Koenig.

By means of a selected pattern of through openings and/or through slits54, dimensioned to allow plasma burning there through, the etch-rate distribution along the workpiece or substrate47may be adjusted, e.g. for dealing with border effects which may affect this distribution along the periphery of the substrate47. To do so it is proposed to provide an increased density of through openings along and in vicinity of a substantial extent-parts of the periphery of the plate shaped body50and/or to provide extended slits along and in vicinity of the addressed peripheral parts.

Blurring or picturing the through holes or through slits54in the plate shaped body50on the etch-rate distribution on the substrate47may be minimized by appropriately selecting the distance d2between the surface of the substrate47to be etched and the surface of the plate shaped body50large enough. In a good embodiment of the reactor1, the addressed through slits54are realized comprising or even consisting of elongated slits along the periphery of the plate shaped body50, neighboring the side wall35of the electrode body31.

So as to minimize Rf return impedance to system ground G, the shroud or rim9electrically contacts the workpiece carrier19ce.g. by resilient contact members56e.g. distributed all along the circumference of the workpiece—or substrate carrier19c. Thereby in the embodiment ofFIG. 1Rf current is led in parallel along the enclosure3and along the workpiece support19to the system ground G.

Gas, especially just an inert working gas as e.g. Ar, is fed by a gas feed line53into the plasma space PL. The reactor1may also be used for reactive plasma etching e.g. in an oxygen or oxygen plus fluorine containing atmosphere. In this case also the respective reactive gas or gas mixture is fed through a respective gas feed line to the plasma space.

Due to the fact, that a powerful pump arrangement15may be connected to the large pumping port13in the separate pumping compartment5, which may be dimensioned completely independently from dimensioning of the etching compartment7with the respective surface extent conditions for the first and second electrode arrangements29,45, and due to the fact that the plasma space PL is in gas-flow (not plasma) connection through a dense pattern of through openings or through slits11in the shroud9, a highly effective pumping removal of etched off material from the etching compartment7is achieved.

It is to be noted, that in the frame of the present invention, the substrate carrier19cneeds not be movable up and down towards and from the electrode arrangement29but may be provided stationary e.g. in the up position shown inFIG. 1at (b).

FIG. 2shows, again schematically and simplified, an example of the view through the embodiment ofFIG. 1, seen from A-A ofFIG. 1. The substrates to be etched are assumed rectangular or square. Thus, the shroud9frames the rectangular or square shaped handling opening55(FIG. 1) to which the substrate carrier19cis lifted into etching position (inFIG. 1(b)) or lowered towards substrate loading position (inFIG. 1(a)). The shroud or rim9is a metal plate comprising a dense pattern of through slits between spokes12. According to this example, in one half of the shroud plate11the slits11extend substantially in the direction of the one diagonal of the rectangular or square shroud, in the other half of the shroud or rim9in the direction of the other diagonal. The respectively directed slits are addressed inFIG. 2by11aand11b. There where the spokes12defining the slits11abut in the handling opening55there ends12eare free as shown inFIG. 3, freely supported in a ceramic material frame57. The slits are machined in the plate shaped shroud9.

Due to the fact that, in this example, the ends12eof the spokes12are free to expand relatively to the frame57as addressed by the double arrow V inFIG. 3, the parts of shroud9and the frame57, most exposed to thermal loading by the Rf etching process, may freely expand relative to one another, avoiding warpage of the shroud plate9and/or stressing, warping and possibly slightly displacing the ceramic material frame57.

The ratio of solid material surface to open space surface of the slits11is about 1:1 and the width d3of the slits is between 3 mm and 10 mm.

Good operating parameters as used today:

Ar operating pressure: 0.1 to 0.5 Pa

Power vhf supply signal<power of hf supply signal.

d1: larger than dark space distance at the addressed operating conditions: d1≥20 mm d2: larger than dark space distance at the addressed operating conditions: d2≥65 mm

As schematically shown inFIG. 4the superimposed vhf and hf plasma supply signals may be fed to the first electrode arrangement29at locally different contact points, C1to Cn at the jar shaped electrode body31and/or at contact points E1to En to metal body50.

As schematically shown inFIG. 5, the vhf plasma supply signal and the hf plasma supply signal may thereby be supplied separately to the first electrode arrangement29, electrode body31and/or metal body50, at respectively one or more than one locally different points C11to C1nand/or E11to E1nfor the vhf supply signal and C21to C2nand/or E21to E2nfor the hf supply signal. Only one C1xand/or E1xand/or only one C2xand/or E2xcontacting points are possible as well.

The electrode body31and/or the metal body50may be subdivided in mutually electrically isolated segments, each supplied with at least one of the first and second plasma supply signals.

The Rf generator arrangement may further generate as a vhf first plasma supply signal a signal which may be frequency modulated during etch operation with respect to fvhfand/or which may be power modulated. Additionally, or alternatively the generator arrangement may generate as a hf second plasma supply signal a signal which may be frequency modulated during etch operation with respect to fhf, or which may be power modulated.

The selected fvhfmay further be an integer multiple of the fhf, phase locked or not phase locked and possibly with adjustable, possibly time varying mutual phasing. More than one second plasma supply signals at different fhfmay be applied in superimposed manner to the first electrode arrangement29.

As schematically shown inFIG. 6the first electrode surface31imay further be increased by realizing an upper part of the shroud or rim9by a respective part319of the electrode body31and by spieling the bottom surface of the part319by a shield part39of the enclosure3, defining an interspace to the part319narrower than dark space distance at the intended etching conditions. Both, part319and39have aligned through openings or through slits1131and113respectively. Clearly the first electrode surface may further be significantly enlarged by shaping the plate shaped body50similar to body31jar- or pot-like and/or by providing more than one of the metal bodies50e.g. plate shaped and staggered by more than dark space distance.

In the embodiment ofFIG. 1the workpiece carrier19cis dynamically operated i.e. movable up and down. In its low handling position, it is loaded with a workpiece or substrate to be etched and an etch treated workpiece or substrate is unloaded e.g. through a bidirectional load-lock60. The workpiece carrier19cis moved from handling position (a) up into etching position (b) for a substrate to be etch treated and from etching position (b) down into handling position (a) to unload the etch treated substrate.

InFIG. 7, most schematically and simplified, an embodiment is shown where the workpiece or substrate carrier19cis stationary i.e. is not movable towards and from the first electrode arrangement. The electrode body31may comprises a door31dwhich may be opened and closed e.g. by a drive62. In closed position, the door may be a part of the electrode body31and still contributes to the inner surface31i. The workpiece or substrate is loaded on and unloaded from the workpiece or substrate carrier19ce.g. via bidirectional load-lock60.

The workpiece or substrate carrier may also be handled with a respective substrate or workpiece trough the load lock60and is thus in any case not liftable towards and retractable from the first electrode arrangement31.

Alternatively, the substrate or workpiece, with or without the workpiece or substrate carrier, may be loaded and unloaded pathing below the first electrode arrangement with the jar- or pot-like body31without providing a door as of door31din the body31.

InFIG. 8there is shown, most simplified and schematically, an capacitive coupled RF vacuum etching apparatus obeying the law of Koenig. The Rf plasma space is confined between a first, larger electrode arrangement829and a second, smaller electrode arrangement845. The first, larger electrode arrangement is operated with a Rf drive signal with at least one frequency and with respect to the metal enclosure803on a reference potential, e.g. on ground potential. Thus, there exists, in operation, a Rf potential difference between the metal enclosure803and the larger electrode arrangement829. The spacing d4between the outer surface831oof the electrode arrangement829and the inner surface of the enclosure803wall is decisive for the Rf power loss from the electrode arrangement829to the enclosure803. To minimize such Rf loss, d4should be selected as large as possible, minimizing the capacitance between the addressed surfaces, defining the interspace832. On the other hand, plasma generation in the addressed interspace832is to be excluded, which requires d4to be smaller than dark space distance at the prevailing etching conditions.

To resolve this problem, one or more than one electrically floating metal screens830are provided in the interspace832, all along the surface8310and the inner surface of the metal enclosure803. By such floating screens, the capacitance between the addressed surfaces is kept small but no plasma may ignite in the interspace832, due to the spacings d5between neighboring surfaces of the scree or screens and the surface831oas well as the inner surface of the metal enclosure803, respectively, being kept smaller than the dark space distance. The screens830may be mounted by means of electrically isolating distance holders834as schematically shown inFIG. 8.

The aspect explained byFIG. 8is to minimize Rf power loss through an interspace from a large Rf operated electrode to the surrounding metal enclosure of a vacuum process recipient and thereby avoiding Rf plasma generation in such interspace by providing one or more than one metal screens along and in the interspace and mounted in an electrically floating manner. All sub interspaces between such screens and between such screens, the electrode surface and the metal enclosure surface, are narrower than dark space distance at the processing parameters of the process to be operated in the vacuum enclosure. This aspect is considered possibly inventive per se.

InFIG. 9there is shown, most simplified and schematically, the measures according to the invention, to enlarge the effective surface of the first electrode arrangement of the capacitive coupled RF vacuum etching apparatus according to the invention, which obeys the law of Koenig.

The Rf plasma reaction space PL is confined between the larger first electrode arrangement929and the second, smaller electrode arrangement945in the vacuum enclosure903. The electrode arrangements929,945are fed with respect to one another by an Rf supply of one or more than one frequency. The surface of the first, larger electrode arrangement829is significantly enlarged, by providing at the electrode arrangement929, at least one metal body950, e.g. plate shaped or jar-shaped and immersed in the plasma reaction space PL and operated on the electric potential of the remainder of the electrode arrangement929.

FIG. 10shows, simplified and schematically the capacitive coupled RF vacuum etching apparatus which, similar to the embodiment ofFIG. 1, comprises a pumping compartment1005with a large pumping port1013and an etching compartment1007. Similar to the embodiment ofFIG. 1the second, smaller electrode arrangement1045, comprising the workpiece carrier1019cis operated on ground potential and electrically contacts the shroud1009with the pumping trough bores and/or trough slits (not shown inFIG. 10) once lifted in etching position by distributed resilient contact members1056. As the shroud1009is electrically connected to the metal enclosure1003, similarly to shroud9inFIG. 1to enclosure3, and the enclosure1003is operated on electric ground potential, the workpiece carrier1019cas well becomes tightly connected to ground potential.

In opposition to the grounding concept as addressed in context withFIG. 1according to which the Rf current return path is led via a pair of parallel impedances, namely via the enclosure3along the pumping compartment5and via the workpiece support19down to system ground G, according to the embodiment ofFIG. 10the Rf return path is selected to be as short as possible. The system ground tab1023to system ground G is provided centrally at the top of the etching compartment1007. The grounding concept shown inFIG. 1may be replaced by the grounding concept ofFIG. 10as in both cases the workpiece carrier, as the second, smaller electrode arrangement, is operated on ground potential and not on a biasing potential.

FIG. 11shows, simplified and schematically an embodiment of the apparatus which, similar to the embodiment ofFIG. 1comprises a pumping compartment1105with a large pumping port1113and an etching compartment1107. A handling opening1155is confined by the rim or shroud1109with the trough-bores or -slits1111. The handling opening1155is bordered by a frame1157, in a good variant made of a ceramic material.

In opposition to the interaction of the workpiece carrier19cand the workpiece or substrate47with the shroud or rim9as shown inFIG. 1, according to the form of realization according toFIG. 11the shroud1109with the frame1157acts as a stop for the workpiece or substrate1147so that in the etching position of the workpiece carrier1119cthe upper surface of the workpiece or substrate1147is positioned substantially flush with the rim or shroud1109. Thereby the workpiece or substrate1147in its etching position becomes firmly biased and held between the workpiece carrier1119cand the frame1157. Additionally,FIG. 11shows, that the resilient contact members1156may be mechanically coupled to the workpiece carrier1119cwhereas according toFIG. 1they are mechanically coupled to the shroud9. Both variants are possible and also a combination in which some of the resilient contact members56,1156are mechanically coupled to the movable workpiece carrier19c,1119c, some to the stationary rim or shroud9,1109.

Especially if, as addressed, the border of the shroud or rim mechanically interacts with the workpiece or substrate during the etching operation, it is important to maintain such interaction accurately constant during the processing. In the embodiment ofFIG. 11such interaction is biasing and holding the workpiece or wafer1147during etch processing. Thus, generically and especially in this case, high mechanical stability must be achieved also in spite of mutual thermal expansions of different materials and structures which could result in mutual shift and/or warpage of the frame and shroud with the respective effect on the substrate or workpiece, especially on a thin and large substrate.

In spite of the fact, that in the embodiment according toFIG. 3according toFIG. 3, different thermal expansions of the spokes12and of the frame57are well considered by the fact that the ends of the spokes12are not firmly linked to the frame57, thisFIG. 3embodiment is not optimal in the case, as ofFIG. 11, in which the frame mechanically interacts with the workpiece or wafer1147, as during etch processing.

FIG. 12shows most schematically and simplified and in a top view on the rim or shroud arrangement1209, the ring-shaped frame1257for a circular workpiece or substrate1247in an alternative construction to that shown inFIG. 3. It is tailored to exploit the frame1257as a mechanical stop and down-holding member for the substrate1247during etch processing. Nevertheless, it may also be applied if the substrate cattier is stationary as addressed above and no stop is in fact needed.

Only a few of the spokes1212are shown inFIG. 12. The one ends1212e1of the spokes1212are mechanically fixed to the frame1257, as e.g. by gluing, welding, soldering, screwing. The other ends1212e2are mechanically fixed relative to the enclosure1203, as represented inFIG. 12only schematically. All the spokes1212together form the rim or shroud1209with the through-slits1211which are narrow enough to prevent plasma burning therein.

The spokes1212act as leaf springs with respect to relative expansion E of the frame1257with respect to the enclosure1203. The spokes1212which might be curved or bent as schematically shown in dash line at1212′ define for a length direction D and are mounted to the frame1257so, that the directions D of length extensions intersect the tangent T on the frame1257at the locus of spoke fixation with an angle α which is not 90°, but smaller than 90° down to 0°. Because in the addressed angle range the angle α is not critical with respect to the general leaf-spring effect of the spokes1212, the spokes1212may be arranged mutually parallel over selected sections of the circumference of the frame1257, as schematically represented inFIG. 12at1212pin dash lines. In fact the spokes act as bendable members.

The frame1257becomes stably mounted by the multitude of spokes1212and may freely expand and retract upon thermal loading without any warpage, so that a highly accurate positioning and holding of the workpiece or substrate1247is achieved.

As shown inFIG. 12in at1212″ the spokes or some of the spokes, most generically being compressible or bendable, may also be arranged under α=90° if compressible as by “zig-zag”- or wave-shaped. They in fact then act as compressible members.

FIG. 13shows in a representation in analogy to that ofFIG. 3the rim or shroud1309and frame1357arrangement for large rectangular substrates or workpieces and constructed in agreement with the generic approach as was just addressed in context withFIG. 12.

FIG. 14shows in a partial cross-sectional representation along line B-B ofFIG. 13the interaction of the liftable and retractable workpiece carrier1419cwith the substrate or workpiece1447with the rim or shroud1309and frame1357arrangement as ofFIG. 13.

According toFIG. 13andFIG. 14, in analogy to the teaching of genericFIG. 12, the frame1357defines the square-shaped handling opening1355for a square substrate or workpiece.

As may be seen fromFIG. 14and in analogy toFIG. 12the one ends1312e1of the spokes1312are fixed to the frame1357. In the specific example, hey are glued at1358and biased between the frame1357and a frame counterpart1357ain a good embodiment both made of ceramic material as of aluminum oxide.

The other ends1357e2(seeFIG. 13) are rigidly connected directly or indirectly to the enclosure1303. Four sections I to IV of respectively directed spokes1312are provided separate by webs1358which are not fixed to the frame1357/1357aas being provided perpendicularly to the frame tangent at the locus of mutual intersection. In a good embodiment the spokes1312the webs1358and a surrounding frame like part1359of the overall shroud or rim1309are made of a unitary metal plate into which the slits between the spokes1312are machined.

As becomes apparent fromFIG. 14, the workpiece carrier1419cbypasses, when moved in edge-processing position1147u, the border of the frame counterpart1357a, so that the workpiece or substrate1447becomes biased towards the frame1357.

It has to be pointed out, that instead of making use of a substrate-holding frame as of frame1357, the substrate or workpiece may be held firmly on the workpiece carrier, as of1419c, differently, e.g. by making use of electro static forces, thus by means of an electro static chuck or by a vacuum chuck establishing below the substrate or workpiece a pressure, which is smaller than the vacuum exploited for the edging process. In such a case, thermal loading of the shroud or rim might be substantially less critical.

Differently tailored workpiece carriers or chucks may be exchangeably applied in the capacitive coupled RF vacuum etching apparatus according to the invention.

In one embodiment, the workpiece carrier is cooled. It comprises a system of channels for a liquid cooling medium as addressed in dashed lines inFIG. 14at1448and inFIG. 1in dashed lines as well, at20.

In embodiments as were addressed, the vacuum enclosure is separate in a pumping compartment and in an etching compartment and the substrate or workpiece is firmly biased and held on a workpiece carrier. Cooling of the workpiece or substrate is improved by establishing a cushion of heat conducting gas between the cooled workpiece carrier and the bottom surface of the workpiece or substrate. The heat conducting gas flows from the interspace between the cooled surface of the workpiece carrier and the bottom surface of the workpiece or substrate into the pumping compartment and only neglectably into the etching compartment.

This approach at an embodiment of the apparatus, is schematically shown inFIG. 15. The workpiece carrier1519cis cooled as by means of a system of channels1548for a liquid cooling medium. The workpiece carrier1519cfurther comprises a gas-channel system1550adjacent and along its upper surface1552. Bores or slits1554connect the gas channel system1550to the surface1552of the workpiece carrier1519c. The gas channel system1552is connected to a gas source for a heat conduction gas (not shown). The gas channel system1552and the slits or bores1554are tailored so as to establish along the bottom surface of the workpiece or substrate1547a substantially homogeneous pressure distribution at most with an increased pressure along the periphery of the workpiece carrier1519cand thus along the periphery of a substrate or workpiece1547. The skilled artisan knows how to establish a respective pressure distribution along the bottom surface of the workpiece or substrate by respectively tailoring the distribution of the flow resistances along the gas channel system1552and/or the distribution of the bores or slits1554and/or the distribution of the flow resistances of the bores or slits1554.

As schematically shown qualitatively over the radial extent r of the workpiece carrier1519c, the pressure p is established to be substantially constant along the surface of the workpiece carrier or with a respective maximum, as shown in dashed lines, along the periphery of the substrate or workpiece1547.

In those embodiments of the apparatus in which a shroud or rim divides the overall vacuum recipient or enclosure in an etching compartment and in a pumping compartment, the heat conducting gas flow may leave the interspace between the substrate or workpiece and the upper surface of the workpiece carrier merely into the pumping compartment as shown inFIG. 15at HG. Here the etching compartment1507is separate from the pumping compartment1505by the shroud or rim arrangement1509. During processing the workpiece or substrate1547, the workpiece or substrate1547is mechanically held e.g. by the frame1557and substantially seals the etching compartment from the pumping compartment. Thus the two compartments communicate with respect to gas flow and during processing merely through the bores or slits in the shroud or rim1509. Because the interspace between the upper surface of the cooled workpiece carrier1519cand the bottom surface of the workpiece or substrate1547is located, during processing, on the pumping compartment-1505-side of the frame1557, the heat conducting gas HG leaves the addressed interspace exclusively into the pumping compartment1505. Thereby, the edging compartment and the edging process is not influenced by the heat conducting gas HG as e.g. He.

One or more than one apparatus according to the invention may be exploited in a so called inline workpiece or substrate processing plant, wherein at least one workpiece or at least one batch of workpieces is transported from one processing station to the next in a fixed sequence of processing stations. Such a plant is schematically shown inFIG. 16.

A workpiece or substrate or a batch of workpieces or substrates1647is conveyed along a processing plant1600, comprising chain of treating stations16011,16012. . . . At least one of the treating stations is an apparatus according to the invention under at least one of its aspects. The treating station16011may e.g. be a degasser station, the treating station16012the addressed apparatus. In the plant1600according toFIG. 16one workpiece or substrate or one batch thereof is simultaneously treated in each of the treating stations1601nand one workpiece or substrate or one batch thereof is simultaneously conveyed from one treatment station to the next one. If we address a single workpiece or substrate also as a batch (just with one single workpiece or substrate) in the embodiment of the inline plant1600ofFIG. 16, the extent of batches conveyed and of batches treated is constant along the chain. The path of conveyance PC may thereby be linear or curved e.g. circularly bent as exemplified in dash line at PCF′. The apparatus provided and according to the invention may be constructed with a liftable workpiece carrier or with not-liftable workpiece carrier. If more than one such apparatus is provided, some may be constructed with liftable workpiece carrier, some with not-liftable workpiece carrier. They need not be constructed equally but may incorporate one or more than one different embodiments.

In theFIG. 17—embodiment of an inline plant1700incorporating at least one of the apparatus according to the invention and possibly realizing at least one embodiment thereof, the number of batches (possibly of just one workpiece or substrate) simultaneously treated in the treating stations17011,17012,17013is different. As an example, a degasser station17011simultaneously treats a number N of batches, a cooling station17012simultaneously treats a different number M of batches, whereas the apparatus according to the invention,17011, treats one batch simultaneously. The average rate of batches input to and of batches output from the treatment stations is equal. Thereby the number of batches simultaneously input to and simultaneously output from a treatment station considered may be different. The path of conveyance PC may be linear or curved e.g. circularly bent as exemplified in dash line at PC′. The apparatus provided and according to the invention may be constructed with a liftable workpiece carrier or with a not-liftable workpiece carrier. If more than one apparatus is provided, some may be constructed with liftable workpiece carriers, some with not-liftable workpiece carriers. They need not be constructed equally.

FIG. 18shows a specific example of an in-line plant1800incorporating one or more than one apparatus according to the invention.

The workpiece or substrate is a foil1847unwound from a coil1851and rewound on a coil1852. Between the coils the foil1847is passed through a vacuum processing plant1800incorporating at least one apparatus1801according to the invention. In this embodiment, the workpiece carrier of the apparatus1801is not-liftable.

According toFIG. 19least one apparatus according to the invention is integrated in a non-inline plant1900which may be said a cluster-plant. More than one treating stations18011,18012etc. are loaded and unloaded with one or more than one batch1947(the batch may comprise only one workpiece or substrate) by a central handler1950. The handler1950has at least one drivingly expandable and retractable arm1952with a support1954for the batch1947and is drivingly rotatable about the central axis A. In this plant which incorporates at least one of the reactors according to the invention, the sequence of treating stations to which a batch1947is fed, the number of batches1947simultaneously conveyed, the number of batches simultaneously treated in respective treating stations and the treatment durations in the respective treatment stations is selectable and variably controllable. The apparatus provided and according to the invention may be constructed with a liftable workpiece carrier or with a not-liftable workpiece carrier. If more than one apparatus are provided, some may be constructed with liftable workpiece carriers, some with not-liftable workpiece carriers. They need not be constructed equally.

Summarizing a Further Aspect of the Vacuum Apparatus as Described Considered Possibly Inventive Per Se:

A vacuum apparatus comprising an enclosure (3) and a workpiece carrier and wherein said enclosure (3) is subdivided in a pumping compartment (7) comprising a pumping port (13) and a treating compartment (5) said compartments (5,7) being separate by a shroud or rim (9) having a pattern of through openings or through slits (11), baring plasma at predetermined processing conditions, said workpiece carrier being drivingly movable from a load-/unload position into a processing position and vice versa, a workpiece or substrate on said workpiece carrier (19c) being mechanically held (57) on said workpiece carrier in said processing position by a downholding member (57) and all along the periphery of the workpiece or substrate surface exposed to said treating compartment, said workpiece carrier (19c) comprising a channel arrangement (20) adapted to hold a liquid heating or cooling medium and a further channel arrangement adapted to hold a heat conduction gas communicating by a bore- or slit-arrangement with an interspace between the surface of said workpiece or substrate opposite said surface being exposed to said treating compartment.