WO2012069943A1

WO2012069943A1 - Plasma processing apparatus

Info

Publication number: WO2012069943A1
Application number: PCT/IB2011/054859
Authority: WO
Inventors: Joachim Mai; Patrik Wolf; Hermann Schlemm
Original assignee: Roth & Rau Ag
Priority date: 2010-11-24
Filing date: 2011-11-02
Publication date: 2012-05-31
Also published as: DE102010060762B4; DE102010060762A1; CN103229272B; TW201230892A; TWI448215B; CN103229272A; DE102010060762A9

Abstract

The present invention relates to a plasma processing apparatus for processing at least one planar substrate in a substrate continuous installation, wherein the plasma processing apparatus has: at least one substrate carrier electrode, on which the substrate lying thereon can be transported through the substrate continuous installation and which is routed in a manner insulated from ground potential in terms of DC current; an areally designed radiofrequency electrode, which has an AC voltage potential applied to it and is provided at a distance above the at least one substrate lying on the substrate carrier electrode, a dark space shielding which is formed in a pot-shaped manner above the substrate carrier electrode, wherein the open region of the pot-shaped dark space shielding is directed at the at least one substrate, and the pot-shaped dark space shielding has an edge which outwardly widens the dark space shielding and which is arranged tightly above the substrate carrier electrode and parallel to the surface thereof, and wherein a plasma space for forming a low-pressure plasma is provided during the operation of the plasma processing apparatus between the substrate carrier electrode or substrate(s), radiofrequency electrode and dark space shielding; at least one electrically conductive second electrode arranged on the rear side and parallel to the substrate carrier electrode; and a gas supply for introducing process gas into the plasma space. The object of the present invention is to develop a plasma processing apparatus of the generic type cited above with as little technical expenditure as possible such that, given defined substrate transportation and advantageous gas supply and gas discharge even with substrates with a large surface area or substrate carriers with a large number of individual substrates, high-energy interaction of ions from the plasma space with the substrate surface is possible. The object is achieved by a plasma processing apparatus of the generic type cited above in which the second electrode is a ground electrode at ground potential, wherein the substrate carrier electrode can be coupled capacitively to the ground electrode, and the gas supply has at least one gas inlet provided in the radiofrequency electrode and/or the dark space shielding and at least one gas outlet provided in the dark space shielding.

Description

Plasma processing apparatus

The present invention relates to a plasma processing apparatus for processing at least one planar substrate in a continuous substrate system, wherein the plasma processing apparatus comprises: at least one substrate carrier electrode, on which the substrate is transportable lying through the substrate flow system and which is DC-guided insulated from ground potential; a surface-trained high-frequency electrode, which rests against an AC potential and is provided at a distance above the at least one substrate resting on the substrate carrier electrode; a dark space shield formed above the substrate carrier electrode, the open area of the cup-shaped dark space shield being directed onto the at least one substrate and the cup-shaped dark space shield having an outwardly widening edge extending darkly above the substrate carrier electrode and parallel to its surface, and wherein, in the operation of the plasma processing apparatus between substrate carrier electrode or substrate (s), high-frequency electrode and dark space shield, a plasma space for the formation of a low-pressure plasma is provided; at least one electrically conductive second electrode arranged on the rear side and parallel to the substrate carrier electrode; and a gas supply for introducing process gas into the plasma chamber.

The large-scale plasma processing of surfaces has gained a high status in today's industrial production and will continue to gain in importance in the future. Examples of this are plasma technologies such as plasma etching, plasma pretreatment or plasma-enhanced chemical vapor deposition, also abbreviated to PECVD for short. Depending on the technology requirements, different devices for producing plasmas or also different arrangement variants are selected between the devices for producing plasmas and the location of the plasma processing. Demands such as good process stability, high system availability, low media consumption, short maintenance times, etc., are becoming more and more important for mass production in addition to technological requirements. Often there is also the question of the possibility for scaling up the process or the devices for the processing of large areas and / or the processing of the largest possible number of samples in the shortest processing time. Linearly scalable devices for the plasma processing of surfaces are particularly advantageous since, for example, the requirement for good homogeneity of the processing in the direction of the linear expansion can be realized more easily here. For homogeneous processing of large areas, these are then preferably moved through the processing area.

Thus, for example, in-line coating systems are known in which a defined number of linear microwave plasma sources are used. Such microwave plasma sources are preferably operated with an excitation frequency of 2.45 GHz and are distinguished by a particularly high achievable plasma density and are therefore particularly suitable for the high-rate deposition of thin layers. Due to the very low plasma edge layer potentials of such microwave plasma sources in relation to the substrate surface, only low-energy ion bombardment occurs during plasma processing. This is a great advantage when working on sensitive surfaces. Often, however, a high coating speed also leads to porous and less dense layers and the occurrence of stacking defects or of non-saturated bonds is great. Therefore, a compromise between high coating speeds and the achievable layer properties often has to be addressed.

Plasma sources operated at low excitation frequencies are again characterized by a low plasma density, but by a high ion energy and ion density in the surface treatment. Especially parallel plate arrangements are a good example for this. In the case of the asymmetrically operated parallel plate arrangement, one electrode is connected to ground potential and another connected to the power supply. Depending on the excitation frequency used and the area ratio of the electrodes as well as the set process conditions, different energetic conditions of the incident ions on the electrodes result. Depending on the choice of one of the two electrodes as a substrate carrier electrode, therefore, there are also different processing conditions. Plasma processing systems in the form of substrate throughput systems in which substrate carriers are used, which are moved during surface processing or even to be transported through the processing area, represent a major technical challenge. Especially when a defined electrical potential is to be achieved at the substrate carrier , it must be able to carry eg a defined equal or high frequency current during the movement.

The publications described below disclose different solutions.

The document DE 43 01 189 C2 describes a plasma processing apparatus of the above-mentioned type. It is based on the task of coupling energy through a substrate carrier into a plasma chamber in an in-line or through-flow system without causing parasitic plasmas. It is essential that the capacitive coupling of RF energy is applied over a large area to moving substrates. The plasma chamber is formed by a cup-shaped shielding of a first electrode, wherein a gas inlet is provided in the plasma chamber. The pot-shaped shield has an edge which is arranged closely above the substrate carrier and parallel to the surface thereof. On the back of the substrate carrier, a further high-frequency electrode is arranged with Dunkelraumabschirmung at a defined distance. Thus, high frequency energy can be coupled into the substrate carrier. The capacitance of the first electrode relative to the substrate carrier should be as large as possible, while the mass of the electrode should be as small as possible in order to be able to build up an efficient DC potential at the substrate carrier.

The disadvantage here is that the dark space shield must be continued over the area of the electrode arrangement in order to avoid parasitic plasmas. Furthermore, it is not disclosed how the gas extraction from the reaction area of the plasma processing should take place. The removal of spent gases can take place here only by the remaining gap between the edge of the shield and the substrate carrier. This is also disadvantageous because it causes further undefined processing on the substrate surfaces. The publication WO 02/056338 A2 discloses a further apparatus for plasma-assisted processing of surfaces of planar substrates. The authors of this document set themselves the task of proposing a cost-effective device, with the relatively large-sized substrate surfaces at an increased frequency, preferably in the frequency range above 30 MHz, can be edited. The device described uses a chamber, which may also be a vacuum chamber. At least one mass tunnel is arranged in this chamber. In this mass tunnel, a discharge space which is essentially closed relative to the chamber volume is formed. In this discharge space, an HF / VHF electrode is arranged at a smaller distance and parallel to the respective substrate surface, so that the generated plasma is formed predominantly between the electrode and the substrate surface. In the mass tunnel are also two diametrically opposed slots formed whose width and height has been selected according to the substrate to be processed or the substrate with a substrate carrier.

The substrate or the substrate with substrate carrier can be moved translationally through these slots through the mass tunnel and consequently also through the discharge space. The mass tunnel is closed except for these slots on all sides. Through the mass tunnel, a process gas supply into the discharge space and a process gas discharge from the discharge space is performed. The coupling of the electric current takes place between substrate with substrate carrier and mass tunnel on capacitive paths. The substrate carrier is guided electrically insulated from the mass tunnel. The mass tunnel, the HF / VHF electrode and their power supply are electrically insulated from the chamber wall by insulators.

The disadvantage here is the very large technical effort. The mass tunnel must have walls arranged exactly parallel to the substrate carrier, which are arranged at a very small distance from the substrate carrier. Especially when the mass tunnel is also to be tempered, it comes to thermal expansion of the mass tunnel and the substrate carrier and the technical feasibility for a defined substrate transport, which must also be done electrically isolated by the mass tunnel, is very challenging. When processing large-area substrates or substrate carriers with a large number of individual substrates, it is difficult to In addition, the electrode assembly then has a large width perpendicular to the transport direction, and therefore the mass tunnel also has to be widely extended in the transport direction and on both sides of the high-frequency electrode arrangement in order to be able to achieve sufficient capacitive coupling of the substrate carrier to the ground tunnel. Another disadvantage is that due to the small necessary distance between the substrate carrier and the walls of the mass tunnel results in a gas-filled space that can be pumped difficult.

It is therefore the object of the present invention to develop a plasma processing apparatus of the abovementioned type with the least possible technical outlay such that, with defined substrate transport and advantageous gas supply and removal even with large-area substrates or substrate carriers with a plurality of individual substrates, a high-energy interaction of ions from the plasma space with the substrate surface is possible.

The object is achieved by a plasma processing apparatus of the abovementioned type, in which the second electrode is a ground electrode lying at ground potential, wherein the substrate carrier electrode is capacitively coupled to the ground electrode, and the gas supply at least one provided in the high-frequency electrode and / or the dark space shield Gas inlet and at least one provided in the dark space shield gas outlet.

The device according to the invention serves for the defined generation of low-pressure plasmas in a working pressure range of about 1 Pa to a few hundred Pascals. The excitation frequency should preferably be 13.56 MHz. Higher and lower excitation frequencies can be used according to the technical characteristics of the device and the technological requirements. In practice, a frequency range of about 50 kHz to about 100 MHz may be interesting.

According to the invention, since the second electrode is used as the ground electrode and the substrate electrode is conducted in a DC-insulated manner with respect to the ground potential, a capacitive voltage divider is formed between the high-frequency electrode, the substrate carrier electrode and the ground electrode. For a given excitation frequency and defined discharge conditions of the low pressure plasma decides the Size of each capacitance of this capacitive voltage divider across the level of voltage drops across these capacitances. Due to a high capacitance between the substrate carrier electrode and the ground electrode, the substrate carrier electrode is at an AC potential lying close to the ground potential of the ground electrode. As a result, the ions are accelerated from the plasma space with high energy in the direction of the substrate carrier electrode or substrate, which leads to high-quality processing results.

Thus, since high frequency plasma sources have a distinct advantage over microwave plasma sources in the potential provision of higher energy ions during surface processing of substrates, this advantage can be exploited using the plasma processing apparatus of the invention to deposit denser layers, for example. However, with the aid of the device according to the invention, it is also possible to eliminate certain stoichiometry errors during layer growth or to also change bond conditions in the layer in a defined manner. Further advantages may lie in the selective etching or in the substrate pretreatment.

With the plasma processing device according to the invention, the moving substrate carrier electrode, on which a defined number of individual substrates can be arranged in a suitable manner, can be capacitively coupled before an RF discharge. Furthermore, the proposed device has a Plasmabox-like structure. This results in new advantageous possibilities of process management, for example, in continuous systems for silicon nitride deposition on solar cell substrates. In addition, the device according to the invention is suitable for effecting, in combination with a microwave plasma source, advantageous successive arrangements of RF discharges and microwave discharges.

In order to enable a suitable capacitive coupling of the substrate carrier electrode, the substrate carrier electrode is preferably formed from an electrically conductive material.

So that the at least one substrate lying on the substrate carrier electrode can be continuously passed through the substrate flow system under the plasma source and processed, the substrate carrier electrode in the gap between the substrate mige dark space shield having high-frequency electrode assembly and the ground electrode movable back and forth or transported through this gap.

In an advantageous embodiment of the present invention, with a defined effective area of the high-frequency electrode, the distance between the substrate carrier electrode and the ground electrode and / or the size of the Substratträgerelektrodenflä- che against the ground electrode adapted to the under discharge conditions between the high-frequency electrode to the Ground electrode flowing high-frequency displacement current does not provide for plasma ignition suitable voltage drop between the substrate carrier electrode and the ground electrode.

According to a favorable variant of the invention, the high-frequency electrode has an encircling raised edge region, so that the high-frequency electrode has the shape of a turned-over "U." This can be used to define the effective area ratio between the effective ground surface and the active high-frequency electrode surface.

According to a further embodiment of the present invention, the high-frequency electrode arrangement having the high-frequency electrode and the dark space shield is linearly scaled perpendicular to the transport direction of the substrate carrier electrode. With this geometry, a homogeneous substrate processing along a line transverse to the substrate transport direction can be realized by the substrate flow system, wherein the substrates can be moved under this line.

It has proved to be particularly advantageous according to the invention when the high-frequency electrode and the dark space shield having high-frequency electrode assembly is operated with an excitation frequency of about 50 kHz to about 100 MHz. At these frequencies, layers of high quality can be produced when using the device according to the invention for layer deposition.

To improve the high-frequency power distribution, in a further proposed embodiment of the present invention, in particular in the case of long-length high-frequency electrode arrangements, a plurality of high-frequency feeders are used for supplying high-frequency energy to the high-frequency electrode. Particularly advantageous processing results can be achieved by the present invention, when the high-frequency electrode assembly with the dark space shield can be heated and / or cooled.

The cooling and / or heating of the high-frequency electrode arrangement can be implemented particularly well if appropriate channels for temperature control are provided in the high-frequency electrode with a suitable heat carrier, wherein the heat carrier is preferably supplied by at least one of the existing high-frequency supply, which with at least a tempering device is connected or are.

If according to a preferred embodiment of the present invention, a suitable frame-like flow device is attached to the substrate-facing side of the dark space shield, a defined gas flow resistance can be achieved between the flow guide device and the substrate carrier electrode.

According to a likewise advantageous variant of the present invention, the area of the substrate carrier electrode is at least equal to or greater than the area which is formed by the opening area of the dark space shield.

Preferably, in the present invention, the area of the ground electrode is greater than or equal to the area of the substrate support electrode.

It has also proved to be particularly favorable when the ground electrode is provided with a coating of a suitable dielectric material.

In a further advantageous embodiment of the present invention, an additional suitable plate of dielectric material is arranged on the side of the ground electrode facing the substrate carrier electrode. Thereby, the capacitance of the electrical capacitor formed between the substrate carrier electrode and the ground electrode is increased.

A large ground electrode area can be achieved in the plasma processing apparatus according to the invention in that a plurality of individual ground electrodes are subsequently detected. are arranged one another, so that they together can form a relative to the substrate support electrode electrically effective ground electrode.

It may also be advantageous if a radiant heater is installed in the ground electrode.

In a particularly favorable embodiment of the present invention, the wall of the vacuum chamber forms the ground electrode, so that it is possible to dispense with a separate ground electrode in this variant.

A particularly preferred embodiment of the plasma processing apparatus according to the invention is designed so that the high-frequency electrode contains at least its own suitable gas shower and that at the same time in at least one wall of the dark space shield an additional gas shower is present, the respective opposite to the gas shower wall of Dunkelraumabschirmung contains at least one pump opening ,

A likewise advantageous gas supply and gas discharge can also be achieved if a single or multiple gas shower is provided in a wall of the dark space shield and at least one suitable pump opening is provided in the wall of the dark space shield opposite thereto. In this variant, no gas inlet is provided in the high-frequency electrode. This results in front of the high-frequency electrode, a cross-flow of the gases admitted.

In a further alternative of the plasma processing apparatus according to the invention, a single or multiple gas shower is provided in a wall of the dark space shield, and suitable pump openings are provided in the wall of the dark space shield opposite thereto, wherein the pump openings are guided vacuum-tight out of the vacuum chamber and connected to a separate pump system.

Conveniently, the plasma chamber is provided with an additional inner wall lining, which can be exchanged in a simple manner, whereby these inner wall surfaces are exchangeable. clothing contains all the necessary pump grids and gas outlet openings for the gas supply and gas removal.

In a further development of the present invention, a plate made of a suitable dielectric material is applied directly in front of the high-frequency electrode and completely covers the latter against the plasma space.

It is further possible according to the invention to arrange a plurality of high-frequency electrode arrangements with dark space shields in the direction of movement of the substrate carrier electrode successively in a vacuum chamber.

In order to always be able to ensure sufficient capacitive ground coupling of the substrate carrier electrode, in a variant of the present invention, further ground electrodes are provided between the adjacent vacuum chambers for transporting the substrate carrier electrode.

According to a further efficient example of the invention, a plurality of substrate carrier electrodes are successively movable through the discharge zone of the plasma processing apparatus, the distance of which from each other being adjusted so that plasma ignition between the individual substrate carrier electrodes is not possible.

Finally, in one embodiment of the present invention, it is also possible to use a continuous electrically conductive tape as the substrate carrier electrode, for which typically a substrate carrier is used.

Preferred embodiments of the present invention, their structure, function and advantages are explained in more detail below with reference to figures, wherein

Figure 1 shows schematically an embodiment of a plasma processing apparatus according to the invention with a gas inlet in the form of a provided in the high-frequency electrode gas shower and lateral, guided through the walls of the dark space shield gas outlets in a sectional side view; Figure 2 shows schematically a further embodiment of a plasma processing apparatus according to the invention with provided in the dark space shield gas inlets and outlets in a sectional side view;

Figure 3 shows schematically a modified variant of the embodiment of a plasma processing apparatus according to the invention from Figure 2 with an additional, interchangeable inner wall lining of the plasma chamber in a sectional side view; and

FIG. 4 schematically shows a further possible embodiment of a plasma processing device according to the invention with gas inlets and outlets provided in the dark space shield, the gas outlet being connected to a pumping port, in a sectional side view.

FIG. 1 schematically shows an embodiment of a plasma processing apparatus according to the invention for large-area plasma processing of surfaces of substrates. The plasma processing apparatus is installed in a vacuum chamber. The walls of the vacuum chamber 20 are at ground potential. The vacuum chamber 20 is provided with pump ports 21 and 22 for the connection of pumping systems. Both sides of the vacuum chamber 20 opening gaps 23, 24 are present. Here, for example, vacuum valves or adjacent vacuum chambers can be connected. The opening geometry of these opening gaps 23, 24 is designed so that a substrate carrier electrode 27 can be transported through unhindered. On the substrate support electrode 27 individual substrates 28 may be arranged.

On the side of the substrate carrier electrode 27 facing the vacuum chamber bottom, there is a ground electrode 25, which can be embodied simultaneously as a radiant heater. The ground electrode 25 is thermally decoupled from the vacuum chamber bottom by radiation shields 26 and is suitably connected to ground potential. The high-frequency electrode assembly of the plasma processing apparatus shown consists essentially of a dark space shield 1, a high-frequency electrode 2, which is embedded here for example in dielectric insulator 4, 17, 18, and at least one high-frequency supply 3. As insulation materials, for example, alumina ceramic, quartz glass or Also plastic materials such as PEEK or Teflon can be used. The high-frequency electrode 2 is coupled to a high-frequency supply device 30, as a result of which an alternating-voltage potential can be applied to the high-frequency electrode 2. The high-frequency supply device 30 is connected to the ground potential on which the walls of the vacuum chamber 20 are located. In the high-frequency electrode 2, a gas shower 15 with a defined hole arrangement is provided, which can supply a plasma chamber 5 of the plasma processing apparatus as homogeneously as possible with process gases. The gas shower 16 is connected via a gas buffer volume 16 and at least one gas supply 14 with a gas supply system. It is advantageous if the gas supply 14 is the same with the high-frequency supply 3, since this is already connected to the high-frequency electrode 2.

The dark space shield 1 is guided beyond the high-frequency electrode 2, approximately to the substrate support electrode 27 and thus forms together with the high-frequency electrode 2 an electrically sealed plasma chamber 5. The distance between the front of the high-frequency electrode 2 and the substrate support electrode 27 is adapted to the technological requirements. It is in practice about 10 mm to about 30 mm.

Immediately at the opening of the plasma chamber 5, which is bounded by the walls of the dark space shield 1, there is a frame-like designed flow guide 6 in the form of a Strömungswertleitbleches. This is broadened beyond the outer dimensions of the dark space shield 1, so that a defined gas flow resistance can be achieved at a defined distance between this flow guiding device 6 and the substrate carrier electrode 27. This makes it possible to define the gas flow out of the plasma chamber 5 mainly in the direction of the pump openings 7, 8. In FIG. 1, on both sides of the dark space shield 1, at least one pump opening 7, 8 is present in each case. For more homogeneous suction of the plasma chamber 5, it is more advantageous if several Pump openings 7, 8 along the respective side of the dark space shield 1 are present. The pump openings 7, 8 are covered with so-called pump grids 9, 10. These pump grids 9, 10 are made of a highly electrically conductive material and have adapted gas-permeable openings such as slots or holes. As a result, the plasma chamber 5 is bounded on all sides with good electrically conductive walls and still contains the possibility of a defined gas discharge.

As already mentioned above, the high-frequency electrode 2 has at least one high-frequency supply 3. This is preferably carried out coaxially. In this way, higher excitation frequencies can also be used for the supply of high-frequency energy without appreciable current or voltage losses occurring in the line system. The high-frequency feeder 3 is connected to the high-frequency supply device 30 according to the prior art. For electrical power adjustment of the complex resistance of the plasma and the impedance of the generator output, a so-called match box is usually interposed as a function of the generator frequency used.

The high-frequency electrode arrangement can also be tempered if suitable technical devices are used for this purpose. This can be done either by means of suitable electrical heating devices or via the heat exchange of suitable heat transfer media. For example, 2 channels or holes for guiding and transporting a suitable heat carrier can be provided in the high-frequency electrode. This heat transfer medium should preferably be supplied via at least one of the existing high-frequency feeders 3. The dark space shield 1 is either tempered with the vacuum chamber 20 or even has a suitable device for temperature control.

The high frequency electrode assembly is operated asymmetrically. This means that the ground potential is used as the reference potential for the generator voltage used. As a result, the electric fields emanating from the high-frequency electrode 2 will also form predominantly with the ground electrode 25. If its field strengths reach the breakdown field strength of the gases used and an ignitable working pressure is present, a low-pressure plasma is ignited in the plasma chamber 5. The walls of the dark space shield 1 are defined at ground potential. The substrate carrier electrode 27 is direct current, isolated from ground potential, insulated. If an alternating voltage of suitable frequency is used for the plasma excitation, an alternating current also flows from the high-frequency electrode 2 to the substrate carrier electrode 27 and from there to near mass surfaces, but essentially to the ground electrode 25. This arrangement thereby forms a capacitive voltage divider. Given the excitation frequency and the defined discharge conditions of the low-pressure plasma, the size of the individual capacitances then determines the magnitude of the voltage drops across these capacitances. A substantial capacity is formed by the substrate carrier electrode 27 with the ground electrode 25. This capacity should be as large as possible because at the same time a small AC voltage drop is connected. As a result, the alternating voltage potential of the substrate carrier electrode 27 is also closer to the ground potential, and the interaction of the low-pressure plasma with the substrate carrier electrode 27 then corresponds more closely to the conditions of a discharge to an electrode lying at ground potential. The size of the capacitance between the substrate support electrode 27 and ground electrode 25 becomes maximum when the distance to each other becomes minimum, and the area of the ground electrode 25 is equal to or larger than the area of the substrate support electrode 27. For technical reasons, it may be necessary for the ground electrode 25 to become necessary must be composed of several individual ground electrodes. Especially when the ground electrode 25 is also to be used as radiant heating, the temperature gradient occurring within the substrate carrier electrode 27 can be counteracted by dividing the heat radiation into a plurality of mass electrodes which can be independently temperature-controlled.

The capacitance between substrate carrier electrode 27 and ground electrode 25 can also be increased by arranging a plate made of a suitable dielectric material in the intermediate space. This plate should preferably be enlarged beyond the dimensions of the ground electrode 25, whereby inhomogeneous electric fields that could form from the edge region of the substrate carrier electrode 27 to the ground electrode 25 can be reduced. The danger of the formation of parasitic plasmas is therefore also lower. If the ground electrode 25 is also designed as a radiation heater at the same time, then the effectiveness of the heat transfer to the Substratträgerelekt- Rode 27 are increased when this dielectric plate is made of a material with a high emissivity. Highly suitable materials are mainly ceramic materials such as alumina ceramic.

Within the scope of the technical possibilities and depending on the required dimensions of the substrate carrier electrode 27, the dimensions of the high-frequency electrode arrangement, in particular the area size of the high-frequency electrode 2 and its distance from the substrate carrier electrode 27, can be adapted to the capacitive voltage divider between the high-frequency electrode 2 and the ground electrode 25 for good capacitive ground coupling of the substrate support electrode 27 to optimize. An additional capacitance for ground coupling of the substrate carrier electrode 27 can also be achieved with the flow guide device 6, since this is defined at ground potential. Depending on the defined area and distance of the Strömungsleitwertbleches used as Strömungsleitwertbleches to the substrate support electrode 27, this Strömungsleitwertblech contribute a more or less large proportion of the capacitive coupling of the substrate support electrode 27 to the ground potential.

Plasma boundary layers are formed by the interaction of the charge carriers generated in the plasma with the surrounding walls. The plasma sand layer potential for the respective wall is always more positive than the electrical potential of the wall itself. The height of the boundary layer potentials also largely depends on the area ratio of the electrode surfaces used. Thus, a small high-frequency electrode 2 leads to a large ground electrode 25 to form a negative electrode potential at the high-frequency electrode 2. This negative DC potential is superimposed on the high-frequency voltage and is also referred to as RF bias. Very high RF bias can increase the risk that the electrode material will be eroded by an increased ion impact, which can contaminate the processing process.

Figure 2 shows an advantageous embodiment of the high-frequency electrode 2 with a peripheral raised edge 29. Thus, the effective effective electrode area of the high-frequency electrode 2 can be increased in proportion to the effective ground surface under plasma conditions. The use of the terms effective electrode area and effective ground area should be understood to mean that under plasma conditions can distinguish geometric surfaces of electrically effective surfaces. The shape and dimensions of the raised edge 29 can be adapted to the technical and electrical requirements.

Compared to FIG. 1, FIG. 2 shows a modified gas supply for the plasma chamber 5. The gas supply no longer takes place via the high-frequency electrode 2, but with the aid of a hole arrangement 32 in the dark space shield 1. At least one gas connection 31 is connected to a gas buffer volume 37 which supplies the hole arrangement 32 with gas. Pump openings 7 with pump grids 9 are located in the wall of the dark space shield 2 opposite the hole arrangement 32. As a result, a cross flow of process gas upstream of the high-frequency electrode 2 is achieved under process conditions. In rare cases, it may be advantageous if, in addition to the gas shower in the dark room screen 1, a gas shower is also present in the high-frequency electrode 2.

Figure 3 shows schematically an advantageous development of the arrangement in Figure 2 with an additionally existing and interchangeable inner wall lining 33, 34, 35 and 36. Except for the dielectric plate 36, this inner wall lining consists of interconnected, electrically conductive sheets, which are the inner side walls of the plasma chamber 5 and the flow guide 6 cover. Advantageously, necessary pump grids 33 in front of the pump openings 7 should be incorporated into the inner wall lining. Also in the area of the illustrated hole arrangement 32, adapted hole arrangements 34 are present in the inner wall lining. The dielectric plate 36 is adapted to the technological requirements and consists for example of alumina ceramic, quartz glass or other suitable materials. If the high-frequency electrode assembly attached to a removable or tiltable lid of the vacuum chamber 20, so can the inner wall lining exchange very comfortable and the maintenance of the high-frequency electrode assembly is thus low.

FIG. 4 shows a further apparatus for large-area plasma processing of surfaces of substrates 28, in which the lateral pump openings 38 with the pump grids 9 do not open into the vacuum chamber 20 but are connected in a vacuum-tight manner to the vacuum chamber 20 with at least one pump connection 40 present. they are. The pumping port or ports 40 are advantageously connected to at least one suitable pumping system. It is advantageous if several pumping ports 38 are connected to their own pumping ports 40 and these in turn with a common pump distributor, not shown. If a suitable pumping system is connected to this pump distributor, a particularly uniform pumping out of the plasma chamber 5 is achieved. With the opposite of the vacuum chamber 20 independent pumping out of the plasma chamber 20 so that the carryover of process gases from the plasma chamber 5 in the vacuum chamber 20 can be greatly reduced.

Depending on the technological requirements, a single plasma processing apparatus according to the invention can also be combined with the partially different features of the embodiments shown in FIGS. 1 to 4.

If necessary, several devices with the features of Figures 1 to 4 can be arranged in a common vacuum chamber 20 and combined.

If a plurality of process chambers and lock chambers are to be interconnected to form a complete in-line processing system, it is also necessary to ensure adequate mass coupling of the substrate carrier electrode 27 during transport in the intermediate regions to the adjacent chambers. Advantageously, individual substrate carrier electrodes 27 are to be transported one after the other and with as small a distance as possible from one another through the processing area of the existing high-frequency electrode arrangements. Thus, the discharge conditions of the individual generated low-pressure plasmas can be stabilized and the risk of plasma ignition in the gap between individual substrate support electrodes 27 can be reduced.

Claims

Plasma processing apparatus for processing at least one planar substrate (28) in a substrate continuous flow system, the plasma processing apparatus comprising:

at least one substrate carrier electrode (27), on which the substrate (28) can be transported lying on the substrate throughput system and which is conducted in a DC-isolated manner with respect to ground potential;

a planar-shaped high-frequency electrode (2) which bears against an alternating voltage potential and is provided at a distance above the at least one substrate (28) resting on the substrate carrier electrode (27); a dark space shield (1) formed cup-shaped over the substrate carrier electrode (27),

wherein the open area of the cup-shaped dark space shield (1) is directed onto the at least one substrate (28) and the pot-shaped dark space shield (1) has a dark space shield (1) outwardly widening edge (6), which lies close above the substrate carrier electrode (27 ) and is arranged parallel to the surface thereof, and

wherein a plasma chamber (5) for forming a low-pressure plasma is provided between the substrate support electrode (27) or substrate (s) (28), high-frequency electrode (2) and dark space shield (1) during operation of the plasma processing apparatus;

at least one electrically conductive second electrode (25) arranged on the rear side and parallel to the substrate carrier electrode (27); and

a gas supply for introducing process gas into the plasma chamber (5), characterized

that the second electrode is a ground electrode (25) lying at ground potential, wherein the substrate carrier electrode (27) is capacitively coupled to the ground electrode (25), and

the gas supply comprises at least one gas inlet (14, 15, 16, 31, 37, 32, 34) provided in the high-frequency electrode (2) and / or the dark space shield (1) and at least one gas outlet (10) provided in the dark space shield (1) , 8, 9, 7, 9, 38, 40).

2. Plasma processing apparatus according to claim 1, characterized in that at a defined effective area of the high-frequency electrode (2) the distance between the Substratträgerelektrode (27) and the ground electrode (25) and / or the size of the Substratträgerelektrodenfläche relative to the ground electrode (25) so is adapted that the under high-frequency displacement current flowing under discharge conditions between the high-frequency electrode (2) to the ground electrode (25) provides no voltage drop suitable for plasma ignition between the substrate substrate (27) and the ground electrode (25).

3. Plasma processing apparatus according to claim 1 or 2, characterized in that the high-frequency electrode (2) has a peripheral raised edge region (29).

4. Plasma processing apparatus according to at least one of claims 1 to 3, characterized in that the high-frequency electrode (2) and the dark space shield (1) having high-frequency electrode assembly is linearly scaled perpendicular to the transport direction of the substrate carrier electrode (27).

5. Plasma processing apparatus according to at least one of claims 1 to 4, characterized in that the high-frequency electrode (2) and the dark space shield (1) having high-frequency electrode assembly is operated with an excitation frequency of 50 kHz to 100 MHz.

6. Plasma processing apparatus according to at least one of claims 1 to 5, characterized in that the high-frequency electrode (2) has a plurality of high-frequency supply lines (3) for the supply of high-frequency energy.

7. Plasma processing apparatus according to at least one of claims 1 to 6, characterized in that the high-frequency electrode assembly with the dark space shield (1) can be heated and / or cooled.

8. plasma processing apparatus according to at least one of claims 1 to 7, characterized in that in the high-frequency electrode (2) is provided at least one channel for temperature control with a heat carrier, wherein the Heat transfer medium is supplied by at least one high-frequency supply (3) connected to at least one tempering device.

9. plasma processing apparatus according to at least one of claims 1 to 8, characterized in that on the substrate side facing the dark space shield (1) a frame-like flow guide (6) is mounted.

10. Plasma processing apparatus according to at least one of claims 1 and 9, characterized in that the surface of the substrate carrier electrode (27) is at least equal to or larger than the area formed by the opening area of the dark space shield (1).

1 1. A plasma processing apparatus according to at least one of claims 1 to 10, characterized in that the surface of the ground electrode (25) is greater than or equal to the surface of the substrate carrier electrode (27).

12. Plasma processing apparatus according to at least one of claims 1 to 1 1, characterized in that the ground electrode (25) has a coating of a dielectric material.

13. Plasma processing apparatus according to at least one of claims 1 to 12, characterized in that on the substrate carrier electrode (27) facing side of the ground electrode (25) a plate of dielectric material is arranged.

14. Plasma processing apparatus according to at least one of claims 1 to 13, characterized in that the substrate carrier electrode (27) electrically effective ground electrode (25) is formed of a plurality of individual successively arranged ground electrodes.

15. Plasma processing apparatus according to at least one of claims 1 to 14, characterized in that in the ground electrode (25) is provided a radiant heater.

16. Plasma processing apparatus according to at least one of claims 1 to 15, characterized in that at least one wall of the vacuum chamber (20) forms the ground electrode (25).

17. Plasma processing apparatus according to claim 1, characterized in that the high-frequency electrode (2) contains at least one own gas shower (16) and that at least one pump opening (7, 8) is provided on one or both sides in the dark space shield (1) ), which is covered with at least one electrically conductive pump grid (9, 10) and opens into the space of the vacuum chamber (20).

18. Plasma processing apparatus according to at least one of claims 1 to 16, characterized in that the high-frequency electrode (2) contains at least one gas shower (16) and that at the same time in at least one wall of the dark space shield (1) an additional gas shower (32) is, wherein each of the gas shower (32) opposite wall of the dark space shield (1) contains at least one pump opening (7).

19. A plasma processing apparatus according to at least one of claims 1 to 16, characterized in that in a wall of the dark space shield (1) a single or multiple gas shower (16) is provided and in the opposite wall of the dark space shield (1) at least one pump opening (7 ) is provided.

20. Plasma processing apparatus according to claim 1, characterized in that a single or multiple gas shower (32) is provided in a wall of the dark space shield (1) and that at least one pump opening (1) is provided in the wall of the dark space shield (1) opposite thereto. 38) is provided, wherein the at least one pump opening (38) leads vacuum-tight from the vacuum chamber (20) and is connected to its own pumping system (40).

21. Plasma processing apparatus according to at least one of claims 1 to 20, characterized in that the plasma chamber (5) has a replaceable inner wall lining (33, 34, 35, 36), said inner wall lining (33, 34, 35, 36) pumping grid and gas outlet openings for the Gas supply and gas removal to and from the plasma chamber (5) contains.

22. Plasma processing apparatus according to at least one of claims 1 to 21, characterized in that immediately before the high-frequency electrode (2) a plate made of a suitable dielectric material is applied, which covers them completely opposite the plasma chamber (5).

23. Plasma processing apparatus according to at least one of claims 1 to 22, characterized in that a plurality of high-frequency electrode assemblies with dark space shields (1) in the direction of movement of the substrate carrier electrode (27) through the substrate flow system are successively arranged in a vacuum chamber (20).

24. Plasma processing apparatus according to at least one of claims 1 to 23, characterized in that further mass electrodes (25) are provided in the direction of movement of the substrate carrier electrode (27) through the substrate flow system between adjacent vacuum chambers (20).

25. Plasma processing apparatus according to claim 1, characterized in that the plasma processing apparatus has a plurality of substrate carrier electrodes (27) which are movable in succession through the discharge zone, the spacing of these substrate carrier electrodes (27) from each other being set such that no plasma ignition occurs between the individual substrate carrier electrodes (27) is possible.

26. Plasma processing apparatus according to at least one of claims 1 to 25, characterized in that a continuous electrically conductive strip is used as substrate carrier electrode (27).