Pecvd method and system and switching apparatus

Abstract

The present invention relates to a method (100) and a system (10) for plasma-enhanced chemical vapour deposition, and to a switching apparatus (40) for such a system (10). In said method, a plasma (P) for depositing a material on workpieces (70) held by a workpiece carrier (30) is intermittently generated in a process chamber (20) by means of the workpiece carrier (30). According to the invention, the workpiece carrier (30) is heated alternately with the plasma generation.

Description

[0001] PECVD process and system as well as switching device

[0002] The present invention relates to a method and a system for plasma-enhanced chemical vapor deposition and a switching device for such a system.

[0003] Plasma enhanced chemical vapor deposition (PECVD) is used to coat workpieces, particularly semiconductor substrates such as wafers. The deposition of a material from a process gas onto the workpieces takes place under plasma conditions at a process or working temperature. The plasma is usually generated by applying a high-frequency alternating voltage to the workpiece carrier. PECVD is usually used in tubular systems in which a tubular process chamber, also known as a process tube, is brought to the process temperature and kept there via an external heating cassette.

[0004] In a further development of such systems, the external heating cassette is replaced by a heatable workpiece carrier. The workpiece carrier can be used as a resistance heating element. In a heating phase, the workpieces are brought to the process temperature, and then the workpieces are coated in a plasma or process phase. The heatable workpiece carrier enables significantly higher heating rates and thus a shorter process time than external heating cassettes. However, dedicated heating is not possible during the process phase, as this requires different connections between the workpiece carrier and corresponding voltage sources.Cooling of the workpiece carrier by radiation and (inhibited) process gas convection during the process phase cannot usually be compensated due to the comparatively low heat generation during the burning of the plasma, which may lead to process impairments and inhomogeneities in the workpiece coating.

[0005] Against this background, it is an object of the present invention to further improve the PECVD process, in particular to keep a workpiece temperature substantially constant during a process phase of a PECVD process.

[0006] This object is achieved by a method and a system for plasma-assisted chemical vapor deposition and a switching device according to the independent claims.

[0007] Preferred embodiments are the subject of the dependent claims and the following description.

[0008] According to a first aspect of the invention, in the method for plasma-enhanced chemical vapor deposition, a plasma is intermittently generated in a process chamber by means of a workpiece carrier for depositing a material on workpieces, in particular wafers, held by the workpiece carrier. According to the invention, the workpiece carrier is heated, in particular repeatedly, alternating with the plasma generation. The heating preferably takes place directly, i.e., by applying a voltage, in particular a heating voltage, to the workpiece carrier.

[0009] Intermittent plasma generation within the meaning of the invention is preferably repetitive plasma generation which is limited in time (i.e. with each repetition). In other words, the plasma is expediently generated intermittently. Intermittent plasma generation is therefore preferably to be understood as repeated, in particular regular, plasma ignition. During intermittent plasma generation, a plasma is ignited again and again, in particular in rapid succession in the millisecond range. Intermittent plasma generation of this type is advantageous because, in the pauses between plasma ignitions, process gas exchange can take place in front of the workpieces to be coated. As a result, intermittent plasma generation enables the workpieces to be coated evenly.

[0010] Heating of the workpiece carrier in alternation with plasma generation, within the meaning of the invention, is preferably heating that occurs regularly after one or more plasma generations, i.e., between two or more plasma ignitions. Therefore, heating does not necessarily have to occur after each plasma generation; rather, the term "alternating" is intended to encompass cases in which heating always occurs, for example, after a predetermined number of plasma generations or ignitions.

[0011] One aspect of the invention is based on the approach of alternating workpiece carrier-supported plasma generation in a process chamber and dedicated workpiece carrier heating, for example over a predetermined process duration, such as during a process phase. The plasma generation and the workpiece carrier heating therefore preferably take place continuously and sequentially, expediently by applying appropriate voltages to the workpiece carrier. As a result, a process temperature in the process chamber can be kept essentially constant during the process phase, even without an additional heating device, for example an external heating cassette. In particular, cooling of the workpiece carrier can be prevented or at least slowed down. In this way, adverse process impairments, in particular inhomogeneities in the workpiece coating, can be reliably avoided.

[0012] In addition, this allows for effective use of the time between plasma ignitions. In particular, this time no longer has to pass unused as pure waiting time. If multiple process steps are planned, especially multiple process phases in which deposition on the workpieces is to take place, the process duration can also be shortened, since no heating phases are required between these process steps.

[0013] Preferred embodiments of the invention and their further developments are described below. These embodiments can be combined with each other and with the aspects of the invention described below, unless expressly excluded.

[0014] The plasma is preferably generated by appropriately applying a plasma voltage, in particular a high-frequency alternating voltage, to the workpiece carrier. As a result, the plasma can ignite between components of the workpiece carrier acting as electrodes, for example workpiece holders designed as graphite plates. In contrast, the workpiece carrier is preferably heated by appropriately applying a heating voltage, in particular a low-frequency alternating or direct voltage, to the workpiece carrier. Components of the workpiece carrier, in particular the workpiece holders, expediently serve as resistance heating elements. In this way, the plasma and heating voltage are effectively applied to the workpiece carrier intermittently. The plasma is preferably generated in regularly spaced plasma process sections during a process phase in which the material is deposited on the workpieces.As a result, the plasma can be ignited at regular, preferably predetermined, intervals. This operating mode is also referred to as blink mode. The workpiece carrier is expediently heated, particularly repeatedly, in heating process sections located between two plasma process sections. In these heating process sections, a portion of the process gas in the process chamber, particularly the process gas in the immediate vicinity of the workpieces or between the workpiece holders, for example, the graphite plates, can also be exchanged.

[0015] In order to increase the operating efficiency of a PECVD system, it is also conceivable to provide an additional workpiece carrier and to supply this intermittently with the plasma voltage. In particular, during the waiting time between two plasma ignitions, during which the workpiece carrier is heated up, material can additionally be deposited on workpieces held by the additional workpiece carrier. As a result, between two plasma process sections, in addition to a heating process section, a plasma is expediently generated by means of an additional workpiece carrier in a further plasma process section. In this way, a voltage source which provides the plasma voltage can advantageously be used again to provide the plasma voltage to the additional workpiece carrier during the waiting time between two plasma ignitions.

[0016] In order to achieve a homogeneous and reproducible plasma ignition

[0017] In order to be able to achieve deposition on the workpieces and to be able to introduce sufficient heating energy into the workpiece carrier, it is preferred that the length of the plasma process sections is 20 ms or less, in particular 10 ms or less, preferably 5 ms or less. For example, the length of the plasma process sections can be 2 ms to 20 ms, in particular 5 ms to 15 ms. In this way, breakdowns during plasma generation can be avoided. The length of the heating process sections between two plasma process sections is expediently between 20 ms and 200 ms, in particular between 40 ms and 150 ms, for example around 50 ms. In this way, sufficient time can be available to be able to maintain the desired process temperature of, for example, 300 ° C or more by heating the workpiece carrier.

[0018] In the interests of operational efficiency, it may also be advantageous to heat the workpiece carrier using a so-called plasma generator, which supplies the plasma voltage for generating the plasma. A plasma generator within the meaning of the invention is preferably a device which, in addition to a power supply, has further components, in particular circuits, for regulating the provided output voltage. By means of such a plasma generator, not only the level of the provided voltage but also, for example, its shape (sine, square, sawtooth, etc.) and / or frequency, can be specifically adjusted and regulated, at least within a certain range. When using the plasma generator as the source of the heating voltage, a dedicated heating voltage source can be dispensed with, at least for "intermediate heating" during the plasma phase.

[0019] Alternatively, it is of course also conceivable to provide a dedicated heating voltage source in addition to a plasma generator used for plasma generation. In order to be able to generate both the plasma and heating heat with the support of the tool carrier, the tool carrier expediently has two circuits, also referred to as heating strands. These circuits preferably run parallel at least in sections within the tool carrier, for example alternating through graphite plates arranged parallel to one another for holding the workpieces. Consequently, the tool carrier expediently has at least four power connections or inputs (at least two per circuit) via which it can be electrically connected to the heating voltage source and the plasma voltage source.

[0020] For the intermittent generation of plasma and the alternating heating of the workpiece carrier, i.e. for plasma generation in plasma process sections and for repeated heating of the workpiece carrier in heating process sections between two plasma process sections, preferably four outputs of a switching device are alternately connected in such a way that the two connected circuits in the workpiece carrier are each connected either to one of two poles of the plasma voltage source or to the two poles of the heating voltage source. The two circuits are integrated, by appropriate interconnection, thus expediently by means of the switching device, alternately into one plasma circuit or two heating circuits.

[0021] The switching device can be connected downstream of a plasma generator in the form of a distribution stage. In this case, the switching device can have four inputs, two for the dedicated heating voltage source and two for the plasma voltage source or the plasma generator. Alternatively, the switching device in the form of a distribution stage can also have only two inputs for the plasma generator if the plasma generator also supplies the heating voltage. In this case, it is also conceivable for the distribution stage to form part of the plasma generator, i.e., to be integrated into the plasma generator.

[0022] As an alternative to designing the switching device as a dedicated distribution stage, it is also conceivable to increase the number of outputs from an intermediate circuit of the plasma generator. Switching between the outputs can then take place directly at the intermediate circuit.

[0023] In any case, the connection is preferably purely electronic, for example, via appropriate power electronics. In contrast to the previously common switching between heating mode in a heating phase and plasma mode in a process phase, which is carried out using mechanical switches, a significantly faster switching between plasma and heating mode is now possible. In particular, a brief switch to heating mode can thus occur between two plasma ignitions.

[0024] In order to avoid reaching or exceeding a plasma ignition voltage between two adjacent components of the workpiece carrier that are at different potentials during heating, or at least to reduce the risk of this happening, it is advisable to limit the heating voltage. To do this, the voltage between two such components, for example two adjacent graphite plates for workpiece holding, should be prevented from reaching or exceeding the minimum of the Paschen curve during the heating process steps. The heating voltage is therefore expediently selected as a function of the desired process or workpiece temperature, the voltage drop in the circuits of the workpiece carrier, in particular at the workpiece holders serving as heating elements, the process gas, the distance between two adjacent workpiece holders and / or the like.

[0025] Preferably, at least a portion of the process gas in the process chamber is exchanged during heating of the workpiece carrier. As a result, fresh process gas, or at least a higher proportion of fresh process gas, can be available during subsequent plasma ignitions, thereby improving the homogeneity of the deposition or coating on the workpieces.

[0026] According to a second aspect of the invention, the system for plasma-assisted chemical vapor deposition comprises a process chamber and a workpiece carrier which can be arranged in the process chamber. According to the invention, a switching device is also provided for switching between a plasma operation of the workpiece carrier and a heating operation of the workpiece carrier. The switching can expediently be carried out in such a way that a plasma for depositing a material on workpieces held by the workpiece carrier is or can be generated intermittently in the process chamber by means of the workpiece carrier, and the workpiece carrier is or can be heated, in particular repeatedly, in alternation with the plasma generation.

[0027] Using the switching device, plasma generation and workpiece carrier heating can therefore occur continuously and sequentially. This allows the workpiece temperature to be kept essentially constant during the process phase, even without an additional heating device, such as an external heating cassette. In particular, cooling of the workpiece carrier can be prevented or at least slowed down. This reliably prevents adverse process impairments, particularly inhomogeneities in the workpiece coating.

[0028] Preferably, a plasma voltage source, in particular for providing the plasma voltage, and a heating voltage source, in particular for providing the heating voltage, are provided. In order to enable both plasma operation and heating operation to take place alternately, the workpiece carrier expediently has two, in particular parallel, circuits and the switching device has at least four outputs, via which the plasma voltage source and the heating voltage source can be electrically connected to the two circuits. The switching device is preferably designed for alternating connection of the four outputs such that the circuits connected to it are each connected or can be connected to one pole of the plasma voltage source or to the two poles of the heating voltage source. The two circuits can thus be integrated alternately in one plasma circuit or two heating circuits by means of the appropriate connection.

[0029] The switching device is preferably part of a plasma generator with a power supply for providing the plasma voltage and the heating voltage or is connected downstream of the plasma generator. In this case, the plasma voltage source and the heating voltage source can both be formed by the power supply, which provides an output voltage. The plasma generator expediently has further components, in particular circuits, for regulating the provided output voltage. The output voltage can thus be transformed into a high-frequency alternating voltage for plasma generation or a low-frequency alternating or even direct voltage for heating the workpiece carrier. The system can thus be designed efficiently; in particular, a dedicated heating voltage source can be dispensed with.

[0030] A cost-effective and uncomplicated switching device can be achieved by designing the switching device as a distribution stage of the plasma generator or as a distribution stage that can be connected downstream of the plasma generator. The switching device preferably has a circuit of, in particular, at least two, preferably at least eight, switching elements, for example bipolar transistors, with which each output of the switching device can be selectively connected to or separated from one of the two poles of the heating voltage source or one of the two poles of the plasma voltage source. If necessary, the plasma generator can also be retrofitted with such a distribution stage.

[0031] Alternatively, the switching device can also be formed as part of the plasma generator, upstream of a distribution stage of the same. In this case, the switching device is expediently arranged downstream of an intermediate circuit of the plasma generator.

[0032] Against this background, according to a third aspect of the invention, the switching device for supplying voltage to a workpiece carrier arranged in the process chamber of a system for plasma-enhanced chemical vapor deposition, in particular according to the second aspect of the invention, is designed to intermittently generate a plasma in a process chamber by means of a workpiece carrier for depositing a material on workpieces held by the workpiece carrier and to heat the workpiece carrier, in particular repeatedly, alternating with the plasma generation. By means of the switching device, the plasma generation and the workpiece carrier heating can therefore take place continuously and sequentially. As a result, a process temperature of the workpieces can be kept essentially constant during the process phase even without an additional heating device, for example an external heating cassette.In particular, cooling of the workpiece carrier can be prevented or at least slowed down. This reliably prevents adverse process impairments, especially inhomogeneities in the workpiece coating.

[0033] The invention is explained in more detail below with reference to figures. Where appropriate, elements with the same effect are provided with the same reference numerals. The invention is not limited to the exemplary embodiments shown in the figures - not even with regard to functional features. The previous description as well as the following description of the figures contains numerous features, some of which are summarized in the dependent claims. However, a person skilled in the art will also consider these features, as well as all other features disclosed above and in the following description of the figures, individually and combine them to form further useful combinations.In particular, all of the features mentioned can be combined individually and in any suitable combination with the method according to the first aspect of the invention, the system according to the second aspect of the invention and the switching device according to the third aspect of the invention.

[0034] They show, at least partly schematically:

[0035] Fig. 1 shows an example of a system for plasma-assisted chemical vapor deposition; Fig. 2 shows an example of a switching device by means of which two circuits in a workpiece carrier are connected for plasma operation;

[0036] Fig. 3 shows an example of a switching device by means of which two circuits in a workpiece carrier are connected for heating operation;

[0037] Fig. 4 shows an example of a switching device with a plurality of switching elements;

[0038] Fig. 5 shows an example of a workpiece carrier with two parallel circuits; and

[0039] Fig. 6 shows an example of a process for plasma-enhanced chemical vapor deposition.

[0040] Figure 1 shows an example of a system 10 for plasma-enhanced chemical vapor deposition, PECVD for short, with a process chamber 20, a workpiece carrier 30 that can be arranged in the process chamber 20, a switching device 40 for switching between a plasma operation of the workpiece carrier 30 and a heating operation of the workpiece carrier 30, a plasma voltage source 50, a heating voltage source 60, a pump 80 and a gas supply line 90.

[0041] The switching device 40 is designed to switch between the plasma operation and the heating operation of the workpiece carrier 30 such that a plasma for depositing a material on workpieces 70 held by the workpiece carrier 30 is intermittently generated in the process chamber 20 by means of the workpiece carrier 30, and the workpiece carrier 30 is repeatedly heated in alternation with the plasma generation. For this purpose, the switching device 40 preferably has a plurality of switching elements which can electrically connect two circuits in the workpiece carrier 30 - depending on the desired operating mode - to the plasma voltage source 50 or the heating voltage source 60. This is shown in Figures 2, 3, 4 and 5 and described in detail below.

[0042] For the electrical connection of the workpiece carrier 30 or its circuits to the switching device 40, the workpiece carrier 30 has a connection arrangement 32. The connection arrangement 32 is expediently arranged on an end face of the workpiece carrier 30. Upon complete insertion of the workpiece carrier 30 into the process chamber 20, for example through a closable opening 22, the connection arrangement 32 can consequently contact a complementary chamber connection arrangement 24, for example in the form of current lances, arranged on a rear wall opposite the opening 22. The chamber connection arrangement 24 is expediently connected to corresponding outputs of the switching device 40 (cf. Figure 4).

[0043] To generate the plasma, the process chamber 20 can be evacuated by means of the pump 80 after closing the opening 22, for example, until a pressure of less than 0.1 mbar prevails in the process chamber. At the same time, the workpiece carrier 30 can be heated by electrical connection to the heating voltage source 60 until it has reached a working temperature, for example, 300°C or more, and / or until this working temperature prevails in the process chamber 20. This is also referred to as the heating phase.

[0044] Subsequently, one or more process gases can be introduced into the process chamber 20 by means of the gas supply 90, for example silane SiH4 and dinitrogen monoxide N2O or ammonia NH3, until a working pressure of approximately 2.4 mbar is reached. The switching device 40 then connects the workpiece carrier 30, preferably alternately, to the plasma voltage source 50 and the heating voltage source 60. This is also referred to as the process phase. In this case, a plasma is alternately generated in the process chamber 20 and the workpiece carrier 30 is repeatedly heated in order to counteract a temperature drop due to radiation losses and process gas convection. The at least one process gas ionized in the plasma state can consequently react on the continuously hot surface of the workpieces 70 to form a desired layer.

[0045] The plasma voltage source 50 is expediently formed by a plasma generator, which can provide a corresponding plasma voltage, i.e., a high-frequency alternating voltage for generating the plasma. The switching device 30 is connected downstream of this plasma generator. In the present example, the heating voltage source 60 is designed as an independent voltage source, for example, as a heating transformer.

[0046] Figure 2 shows an example of a switching device 40, by means of which two circuits 34a, 34b, also referred to as heating strands, are interconnected in a workpiece carrier 30 for plasma operation. The switching device 40 connects each of the two circuits 34a, 34b to a respective pole A, B of a plasma voltage source 50. Consequently, each of the circuits 34a, 34b is effectively short-circuited by the switching device 40.

[0047] The circuits 34a, 34b run parallel in the workpiece carrier 30 at least in sections (cf. Figure 5) so that when a plasma voltage provided by the plasma voltage source 50, e.g. a high-frequency alternating voltage, is applied, a plasma P can be generated between them.

[0048] Figure 3 shows an example of a switching device 40, by means of which two circuits 34a, 34b, also referred to as heating strands, are interconnected in a workpiece carrier 30 for heating operation. For this purpose, the switching device 40 connects each of the two circuits 34a, 34b to the two poles A, B of a heating voltage source 60. Consequently, the two circuits 34a, 34b are effectively connected in parallel by means of the switching device 40.

[0049] The circuits 34a, 34b expediently comprise sections that heat up upon application of a heating voltage provided by the heating voltage source 60, e.g., a direct or low-frequency voltage. The circuits 34a, 34b thus serve, at least in sections, as (resistance) heating elements.

[0050] As an alternative to the configuration shown in Figure 3, it is also conceivable that the two circuits 34a, 34b can be connected in series by means of the switching device 40. This becomes clear in connection with Figure 4.

[0051] Figure 4 shows an example of a switching device 40 with a plurality of switching elements 42, of which only two are provided with a reference numeral for reasons of clarity. At least some of the switching elements 42 form a circuit 44 with which four outputs 46a, 46b, 46c, 46d of the switching device 40 can be selectively connected to or separated from one of the two poles A, B of a plasma voltage source 50 or a heating voltage source 60. For this purpose, in the present example, two of eight switching elements 42 are combined to form pairs 42a, 42b, 42c, 42d. Each of these pairs 42a-d is associated with exactly one output 46a-d. In a plasma operation or a heating operation of a workpiece carrier connected to the outputs 46a-d, one of the two switching elements 42 of each pair 42a-d can then be switched on, while the other switching element 42 of the pair 42a-d switches on the line between pole A or pole B.Pole B and output 46a-d separates.

[0052] In the present example, an optional switching element 42 is also shown, which can electrically connect two outputs 46b, 46c to one another when the switching elements 42 of the pairs 42b, 42c associated with the outputs 46b, 46c are both switched to be isolated. This allows, for example, two circuits, one of which is connected to the outputs 46a and 46b and the other to the outputs 46c and 46d, to be effectively connected in series for heating operation.

[0053] To enable high-frequency reconnection between the outputs 46a-d and the poles A, B, for example, in the millisecond range, the circuit 44 is preferably designed purely electronically. For this purpose, the switching elements 42 can be designed as bipolar transistors, or IGBTs for short, as in the present example. The switching elements 42 can thus be selectively controlled by means of an electrical control signal, for example, a control voltage ("gate voltage").

[0054] In the present example, the switching device 40 is connected downstream of a plasma generator 52. A power supply unit 54 of the plasma generator 52 serves both as a plasma voltage source 50 and as a heating voltage source 60. This is because a plasma generator 52 is usually designed to significantly modify a provided input voltage in order to provide a (high-frequency) plasma voltage. For this purpose, the plasma generator 52 can have further components, not shown in Figure 4, in particular circuits, which are connected downstream of the power supply unit 54. By means of these components, with appropriate configuration or control, not only the plasma voltage can be regulated on the basis of the provided output voltage, but a (low-frequency) heating voltage can also be provided.

[0055] As a result, the switching device 40 in the example shown has only two inputs 48a, 48b. Each of the inputs 48a, 48b is connected to one of the poles A, B.

[0056] Alternatively, the switching device 40 can also be part of the plasma generator 52 and form a corresponding distribution stage (not shown). In this case, the four outputs 46a-d of the switching device 40 form corresponding outputs of the plasma generator 52.

[0057] Optionally, the switching device 40 can also have additional outputs, which can also be selectively connected to the poles A, B by means of additional switching elements. These additional outputs can be used to generate a particularly uniform plasma during plasma operation of a workpiece carrier connected to the outputs 46a-d, as is clearly shown in Figure 5.

[0058] Figure 5 shows an example of a workpiece carrier 30 with two circuits 34a, 34b or heating strands that run parallel at least in sections. Each circuit 34a, 34b comprises several holders 36a, 36b connected electrically in series for holding workpieces to be coated. The holders 36b of one of the two circuits 34b are highlighted by hatching for clarity.

[0059] The workpiece carrier 30 has an input arrangement 32 with four inputs 32a, 32b, 32c, 32d, via which the circuits 34b can be electrically connected to a power source, essentially independently of one another. Two of the inputs 32a, 32c are assigned to one of the circuits 34a, and the other two of the inputs 32b, 32d are assigned to the other of the circuits 34b.

[0060] The connection to the power source can be made, for example, via a corresponding switching device with outputs 46a, 46b, 46c, 46d.

[0061] The holders 36a, 36b are arranged parallel to one another in at least one row 38, in such a way that the holders 36a of one of the circuits 34a are each adjacent to one or two holders 36b of the other of the circuits 34b. The holders 36a of one circuit 34a are therefore expediently arranged alternately or alternately with the holders 36b of the other circuit 34b. In plasma operation of the workpiece carrier 30, in which the inputs 32a, 32c are expediently connected to one pole of a plasma voltage source and the inputs 32b, 32d are connected to the other pole of the plasma voltage source, the holders 36a, 36b can therefore act as electrodes between which a plasma is generated.

[0062] In a heating operation of the workpiece carrier 30, however, in which the inputs 32a, 32b are expediently connected to one pole of a heating voltage source and the inputs 32c, 32d are connected to the other pole of the heating voltage source, the holders 36a, 36b can act as (resistance) heating elements.

[0063] For this purpose, the holders 36a, 36b can be designed, for example, as graphite plates.

[0064] To generate a more homogeneous plasma during plasma operation, additional inputs (shown in dashed lines) can optionally be provided between the inputs 32a, 32c and 32b, 32d. Particularly in the case of "long" circuits 34a, 34b, i.e., circuits 34a, 34b with a plurality of holders 36a and 36b, these inputs can be used to raise or lower the holders 36a and 36b evenly to the respective potential over the entire length of the respective circuit 34a and 34b.

[0065] Figure 6 shows an example of a method 100 for plasma-enhanced chemical vapor deposition, or PECVD for short. In a process phase 120, which expediently follows a heating phase 110, a plasma is alternately generated in a process chamber using a workpiece carrier to deposit a material onto workpieces held by the workpiece carrier, and the workpiece carrier is heated. The graph shown plots the power L used for plasma generation or heating over time t.

[0066] In process phase 120, the plasma is generated intermittently, particularly in plasma process sections 122. This means that the plasma generation occurs intermittently, or there is a pause between two plasma ignitions. The workpiece carrier is heated alternately with this plasma generation, i.e., in the pauses between two plasma ignitions. The heating of the workpiece carrier can occur, for example, in heating process sections 124 between two plasma process sections 122.

[0067] The heating of the workpiece carrier does not necessarily have to occur immediately after the plasma generation. For example, between the plasma generation and the heating, an available power L of a plasma voltage source, with which the plasma is generated in the plasma process sections 122, can be used to generate a plasma by means of a further workpiece carrier, possibly also in a further process chamber. The plasma generation by means of the further workpiece carrier expediently takes place in further plasma process sections 126, which are shown hatched for reasons of clarity.

[0068] Likewise, the heating of the workpiece carrier does not necessarily have to occur at the same frequency as the plasma generation. In other words, two or more plasma process phases 122 and / or further plasma process phases 126 can be provided between two heating process phases 124. Thus, heating of the workpiece carrier does not have to occur in every pause between two plasma process phases 122 and / or two further plasma process phases 126. For example, it is conceivable to alternately heat the workpiece carrier and another workpiece carrier, if necessary also in another process chamber, between successive plasma process phases 122 and / or further plasma process phases 126. The heating of the further workpiece carrier expediently takes place in further heating process sections 128, which are also shown hatched for reasons of clarity. List of reference symbols

[0069] 10 systems

[0070] 20 trial chamber

[0071] 22 Opening

[0072] 24 chamber connection arrangement

[0073] 30 workpiece carriers

[0074] 32 connection arrangement

[0075] 32a-d entrance

[0076] 34a, 34b circuit

[0077] 36a, 36b bracket

[0078] 38 row

[0079] 40 Switching device

[0080] 42 switching element

[0081] 42a-d Group

[0082] 44 circuit

[0083] 46a-d Exit

[0084] 48a, 48b entrance

[0085] 50 plasma voltage source

[0086] 52 plasma generator

[0087] 54 Power supply

[0088] 60 Heating voltage source

[0089] 70 workpiece

[0090] 80 pump

[0091] 90 gas supply line

[0092] 100 procedures

[0093] 110 Heating phase

[0094] 120 Process phase 122 Plasma process section

[0095] 124 Heating process section

[0096] 126 additional plasma process sections

[0097] 128 additional heating process section

[0098] P Plasma

[0099] L Power t Time

[0100] A, B Pole

Claims

Patent claims 1. A method (100) for plasma-assisted chemical vapor deposition, wherein a plasma (P) for depositing a material on workpieces (70) held by the workpiece carrier (30) is intermittently generated in a process chamber (20) by means of a workpiece carrier (30), characterized in that the workpiece carrier (30) is heated alternately with the plasma generation.

2. Method (100) according to claim 1, characterized in that - the plasma (P) is generated during a process phase (120) in which the material is deposited on the workpieces (70) in plasma process sections (122) spaced at regular intervals, and - the workpiece carrier (30) is heated in heating process sections (124) located between two plasma process sections (122).

3. Method (100) according to claim 2, characterized in that between two plasma process sections (122) in addition to a heating process section (124) in a further plasma process section (126) a plasma (P) is additionally generated by means of a further workpiece carrier.

4. Method (100) according to one of claims 2 or 3, characterized in that the length of the plasma process sections (122) is 15 ms or less, in particular 10 ms or less, and the length of the heating process sections (124) between two plasma process sections (122) is between 20 ms and 80 ms or less, in particular between 40 ms and 60 ms, preferably about 50 ms.

5. Method (100) according to one of the preceding claims, characterized in that the workpiece carrier (70) is heated by means of a plasma generator (52) which supplies a plasma voltage for generating the plasma (P).

6. Method (100) according to one of the preceding claims, characterized in that for the intermittent generation of the plasma (P) and the heating of the workpiece carrier (30) in alternation therewith, four outputs (46a, 46b, 46c, 46d) of a switching device (40) are alternately connected in such a way that two circuits (32a, 32b) connected thereto in the workpiece carrier (30) are each connected either to one of two poles (A, B) of a plasma voltage source (50) or to the two poles (A, B) of a heating voltage source (60) 7. Method (100) according to one of the preceding claims, characterized in that during the heating of the workpiece carrier (30) at least part of a process gas in the process chamber (20) is exchanged.

8. System (10) for plasma-assisted chemical vapor deposition, comprising a process chamber (20) and a workpiece carrier (30) which can be arranged in the process chamber (20), characterized by a switching device (40) for switching between a Plasma operation of the workpiece carrier (30) and a heating operation of the workpiece carrier (30) such that a plasma (P) for depositing a material on workpieces (70) held by the workpiece carrier (30) is intermittently generated in the process chamber (20) by means of the workpiece carrier (30) and the workpiece carrier (30) is heated alternately with the plasma generation.

9. System (10) according to claim 8, characterized by a plasma voltage source (50) and a heating voltage source (60), wherein the workpiece carrier (30) has two circuits (32a, 32b) and the switching device (40) has four outputs (46a, 46b, 46c, 46d) via which the plasma voltage source (50) and the heating voltage source (60) can be electrically connected to the two circuits (32a, 32b), wherein the switching device (40) is designed for alternately connecting the four outputs (46a, 46b, 46c, 46d) in such a way that the circuits (32a, 32b) connected thereto are each connected either to one pole (A, B) of the plasma voltage source (50) or to the two poles (A, B) of the heating voltage source (60).

10. System (10) according to claim 8 or 9, characterized in that the switching device (40) is part of a plasma generator (52) with a power supply (54) for providing a plasma voltage and a heating voltage or is connected downstream of the plasma generator (52).

11. System (10) according to one of claims 8 to 10, characterized in that that the switching device (40) has a circuit (44) of at least two switching elements (42) with which each output (46a, 46b, 46c, 46d) of the switching device (40) can be selectively connected to or separated from one of the two poles (A, B) of the heating voltage source (60) or one of the two poles (A, B) of the plasma voltage source (50).

12. System (10) according to one of claims 8 to 10, characterized in that the switching device (40) is formed by an intermediate circuit of the plasma generator (52).

13. Switching device (40) for supplying voltage to a workpiece carrier (30) arranged in a process chamber (20) of a system (10) for plasma-assisted chemical vapor deposition, which is designed for intermittent generation of a plasma (P) in the process chamber (20) by means of the workpiece carrier (30) for depositing a material on workpieces (70) held by the workpiece carrier (30) and for heating the workpiece carrier (30) alternately with the plasma generation.

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