Controlling multiple plasma processes

A power converter is capable to convert an electrical input power into a bipolar output power and to deliver the bipolar output power to at least two independent plasma processing chambers. The power converter includes: a power input port for connection to an electrical power delivering grid, at least two power output ports each for connection to one of the plasma processing chambers, and a controller configured to control delivering the bipolar output power to the power output ports, using at least one control parameter. The controller is configured to obtain a full set of desired values for the control parameter for the power output ports, calculate whether the power converter is capable of delivering every desired value to every output port, and if so, calculate a sequence of pulses of power delivery to the output ports to supply the power to plasma processes in the plasma processing chambers.

TECHNICAL HELD

The invention is directed to a power converter, plasma processing system and method of controlling multiple plasma processes.

BACKGROUND

Many plasma processing systems employ multiple independent plasma processing chambers where plasma processing is performed in parallel.

Such plasma process system is known from US 2014/0357064A1, US 2006/0156979A1, US2005/0034667A1, U.S. Pat. No. 7,396,759B1, US 2012/0101642 A1, U.S. Pat. Nos. 6,756,318B2, 6,495,392B2, 6,271,053B1. To this purpose these systems employ multiple independent power supplies connected to the individual chambers. In many instances the power delivered to all chambers is always less than the sum of the rated power installed on the machine through all independent power supplies. This excess in installed power creates high installation cost.

SUMMARY

One aspect of the invention features a power converter, which is capable to convert an electrical input power into a bipolar output power and to deliver the bipolar output power to at least two independent plasma processing chambers. The power converter comprises: one power input port for connection to an electrical power delivering grid, at least two, preferably more than two, power output ports, each for connection to one of the plasma processing chambers, and a controller configured to control the power converter to deliver the bipolar output power to the power output ports, using at least one of control parameters including: power, voltage, current, excitation frequency, or threshold for protective measures, by obtaining a full set of desired values for the parameters for the output ports. The controller is further configured to calculate whether the power converter is capable of delivering each desired value to each of the output ports, and if this is the case, to calculate a sequence of pulses of power delivery to the output ports to supply the power to the plasma processes.

In a further aspect, the controller may be configured to control the power converter such that at least one of the control parameters at a first power output port is different from the corresponding control parameter at a different power output port. In this way one single power converter with a given maximum power capability may be used instead of multiple power converters.

“bipolar output power” in this disclosure means an output power with an alternating current, where the current changes its direction with a frequency which may excite the plasma process (excitation frequency).

Control parameters may be measured values or set values of the mentioned parameters. The measured and set values may be absolute, actual, effective such as root mean square (rms), or extreme such as maximum or minimum values.

The input power may be an electrical power delivered from an AC power grid. It may be also a DC power line.

The controller may comprise a microcontroller with a software program running on it when the power unit is in use.

The controller may have multiple interfaces, such as data connections to external components, monitors, keyboards, connectable with wires or wireless.

The controller may have a computing part and a memory part. The memory part may be divided for multiple purposes such as monitor memory, ram, data memory, program memory.

A threshold value may be a value used for detecting ignition or breakdown of the plasma. It may be specified for each output port differently and changing in time.

The bipolar output power may be a power value more than 1 kW, preferably more than 10 kW.

The bipolar output power may be of a frequency more than 1 KHz, preferably more than 10 kHz, preferably more than 50 kHz.

In a further aspect, the power converter may comprise a first power converter stage configured to convert the input power to an intermediate power, preferable to DC link power.

In a further aspect, the power converter may comprise at least one further power converter stage configured to convert the intermediate power from the first power converter stage to the bipolar output power.

In a further aspect, the power converter may comprise at least two further power converter stages configured to convert the intermediate power from the first power converter stage to multiple bipolar output power signals and lead these powers to the power output ports.

In a further aspect, the controller may be configured to control the power converter stages such that, in use, the power converter delivers at a first time a first output power signal at the first output power port for a first time frame and at a second time a second power signal at the second output power port for a second time frame, where the first time is different from the second time and/or the first time frame is different from the second time frame.

In a further aspect, the power converter may comprise a switching circuitry between the power converter stage(s) and the output ports. The switching circuitry can include at least two switches each connected to a respective one of the output ports.

In a further aspect, the switches are controlled by the controller. Switches to switch between electrodes in only one plasma chamber may be embodied like the switches described in U.S. Pat. No. 6,620,299 B1.

In a further aspect, the switches may be configured to lead current into two opposite directions.

In a further aspect, the controller may be configured to activate a switch from a closed status into an open status only when the absolute value of current through the switch is lower than a current threshold, for example, one ampere, preferably zero.

In a further aspect, the controller may be configured to activate a switch from an open status into a closed status only when the absolute value of voltage along the open switch is lower than a voltage threshold, for example, 20 volts, preferably zero.

In a further aspect, at least one of the power converter stages comprises a bridge circuit, preferably a full bridge circuit.

One bridge circuit may be a rectifier bridge circuit capable of rectifying an AC power.

One bridge circuit may be a bipolar output power generating switching bridge circuit.

In a further aspect, the power converter may comprise a cabinet encompassing all other parts of the unit.

In a further aspect, the input port may be directly connected to the cabinet.

In a further aspect, the output ports may be directly connected to the cabinet.

Another aspect of the invention features a plasma processing system including: two, preferably more than two, plasma processing chambers, and one electrical power converter as described above.

Each plasma processing chamber may be connected to one of the power output ports of the power converter.

In a further aspect, at least one of the plasma processing chambers, preferably all plasma processing chambers, may be configured to process, in use, a plasma vapor deposition (PVD) process.

At least one of the plasma processing chambers, preferably all plasma processing chambers may be configured to process, in use, a plasma enhanced chemical vapor deposition (PECVD) process.

At least one of the plasma processing chambers, preferably all plasma processing chambers, may be configured to process, in use, an atomic layer deposition (ALD) process.

At least one of the plasma processing chambers, preferably all plasma processing chambers, may be configured to process, in use a plasma etching process.

A further aspect of the invention features a method of controlling multiple plasma processes in multiple plasma processing chambers with a controller by converting an electrical input power into a bipolar output power and delivering this output power to the plasma processing chambers, where the controller controls a power converter to deliver the bipolar output power to the power output ports, using at least one of control parameters including: power, voltage, current, excitation frequency, and threshold for protective measures (or protection threshold), by obtaining a full set of desired values for the parameters for the output ports, calculating whether the power converter is capable of delivering each desired value to each of the output ports, and if this is the case, calculating a sequence of pulses of power delivery to the output ports to supply the power to plasma processes in the plasma processing chambers.

In a further aspect of the method, the full set of desired values may be obtained via an interface connection, preferable from a control external from the power converter, where this external control controls also the plasma process in the plasma chambers.

In a further aspect of the method the calculation may comprise the calculation of the maximum desired power at all times and the comparison to the maximum power rating of the power converter.

In a further aspect of the method an error message may be given, in the case that the outcome of the calculation is, that there is no way of possible delivery the desired value to every of the output ports.

In a further aspect of the method may be given one or more options of changing the process with a new set of desired values in the case that the outcome of the calculation is, that there is no way of possible delivery the desired value to every of the output ports.

In a further aspect of the method the controller may control the power converter such that at least one of the control parameters at a first plasma chamber is different from the corresponding control parameter at a different plasma chamber.

Plasma processes in the different plasma chambers may be different or the same. They may be the same but in a different status, which means for example plasma process in a first plasma chamber is in a PECVD status where plasma process in a other plasma chamber at the beginning cleaning status, and the same PECVD status will be worked later, when plasma process in a first plasma chamber may be in an etching status. All these processes may be worked out simultaneously or in a time multiplexed manner or in a combination.

DETAILED DESCRIPTION

InFIG. 1a first plasma processing system19with a first power converter1is shown. The plasma processing system19comprises plasma processing chambers9a,9b. . .9n. each connected to a power output port3a,3b, . . .3n.

The power converter1comprises a power input port2for connection to an electrical power delivering grid7.

The power converter1further comprises a first power converter stage5configured to convert the input power at the input power port2to an intermediate power, preferably to DC link power12. Also multiple first power converter stages5configured to convert the input power at the input power port2to an intermediate power, preferably to DC link power12may be part of the power converter1and, preferably connected in parallel.

The power converter1further comprises one further power converter stage6connected downstream to the first power converter stage5configured to convert the intermediate power from the first power converter stage to the bipolar output power.

In between the power converter stage5and the further power converter stage6may be implemented an energy storing element (or energy saving element) such as an inductor or a capacitor for smoothing the current or voltage respectively.

The power converter1further comprises a switching circuitry including multiple switches8a,8b, . . .8nbetween the power converter stage6and the output ports3a,3b. . .3n.

The power converter1further comprises a controller4configured to control the power converter1to deliver the bipolar output power to the power output ports3a,3b, . . .3n, using at least one of control parameters including: power, voltage, current, excitation frequency, or threshold for protective measures (or protection threshold), such that at least one of the control parameters at a first power output port3ais different from the corresponding control parameter at a different power output port3b, . . .3n. In this example the controller4has connections to the power converter stages5,6and the switches8a,8b, . . .8n. Some of these connections may be optional, for example, the connection to the power converter stages5. The controller4may be configured to activate a switch8a,8b,8nfrom a closed status into an open status only when the absolute value of current through the switch is lower than a current threshold, for example, one ampere, preferably zero. This has the advantage that switches may be used which need not to be designed to switch higher currents. This makes the power converter even less expensive.

The plasma processing system19comprises a controller17external from the power converter1. This external controller17controls also the plasma process in the plasma chambers9a,9b, . . .9n.

The controller4may also be configured to activate a switch8a,8b, . . .8nfrom an open status into an closed status only when the absolute value of voltage along the open switch is lower than a voltage threshold, for example, 20 volts, preferably zero. This has the advantage that switches may be used which need not to be designed to switch higher voltages. This makes the power converter1even less expensive.

In the example switch, bipolar transistors81,82,91,92are used as shown inFIGS. 7 and 8. These bipolar transistors can be much cheaper than metal-oxide semiconductor field-effect transistors (MOSFETs). The bipolar transistors81,82,91,92may be insulated-gate bipolar transistors (IGBTs), which is a low cost transistor for leading high currents with low loss of energy. This makes the power converter1even less expensive, due to no need of expensive cooling devices.

InFIGS. 7 and 8additional diodes83,84,93,94are connected for leading current into the wanted direction and blocking current into unwanted direction.

The first power converter stage5may comprise a rectifier circuit, preferably a bridge rectifier circuit50as shown inFIG. 5. Four rectifying diodes52,53,54,55are connected in a bridge circuit to rectify AC power from the first port51to the second port56. The first port51may be additionally connected with at least one of the following: a filter, an overvoltage protection circuit, an overcurrent protection circuit. A filter may comprise one or more energy storing elements such as capacitors or inductors.

The second power converter stage6may comprise a switching bridge, preferably a full switching bridge60as shown inFIG. 6. This full bridge switching bridge60comprises four switches62,63,64,65. These switches may be transistors, bipolar transistors, IGBTs and most preferably MOSFETs. A filter circuit comprising one or multiple energy saving elements such as a capacitor61and/or inductors66,67may be at the input of the second power converter stage6. The full bridge switching bridge60may further comprise some diodes in the shown manner.

The power converter1may comprise a cabinet10encompassing all other parts of the power converter1. It may be of metal and therefore a good protection against electromagnetical (EM) disturbing waves. The input port2may be directly connected to the cabinet10. The output ports3a,3b, . . .3nmay also be directly connected to the cabinet (10).

In one power converter1the current leading capability of all of the switches8a,8b. . .8ntogether may be higher than the maximum power delivery possibilities of all the power converter stages5together.

InFIG. 2a second plasma processing system19′ with a second power converter1′ is shown. The second power converter1′ is an alternative to the first power converter1as shown inFIG. 1. All elements which are the same as inFIG. 1have the same reference numbers. The power converter1′ as shown inFIG. 2comprises instead of the switches8a,8b, . . .8nmultiple power converter stages6a,6b, . . .6nconfigured to convert the intermediate power12from the first power converter stage5to multiple bipolar output power signals and lead these powers to the power output ports3a,3h. . .3n. All power converter stages6a,6b, . . .6nare controllable by the controller4. All power converter stages6a,6b, . . .6nmay comprise full bridges60and filter elements61,66,67as shown inFIG. 6.

Measuring sensors for detecting voltage, current, frequency or power may be connected at the output ports3a,3b, . . .3n(not shown).

Also multiple first power converter stages5configured to convert the input power at the input power port2to an intermediate power, preferably to DC link power12may be part of the power converter1and, preferably connected in parallel.

FIG. 3shows a timing diagram of output power at a first output power port3a. The axis t is the time axis and the axis S30may be for example the voltage, current or power axis. As the axis S30is for the actual values of these parameters, the axis S31is for an effective value of these parameters. In the first diagram ofFIG. 3with the S30axis the bipolar signal is shown in two signal sequences31,32. The signal sequence31has an excitation frequency with a period of 2/11 of the time frame which begins at time point T31and ends at time point T32. The signal sequence32has an excitation frequency with a period of 2/11 of the time frame which begins at time point T33and ends at time point T34. In this example these frequencies are the same, but it is possible that these frequencies may be different. In the second diagram ofFIG. 3with the S31axis the effective values of the two signal sequences31,32are shown in two signal sequences33,34. Two threshold lines35,36are also shown in this diagram. They may be used to detect a plasma breakdown, such as an arc or an ignition of the plasma, when the effective value of one of the parameters power, voltage or current exceeds such a threshold. For example, if the signal sequence33is a current, the line35can be an arc detecting threshold line and the line36can be an ignition detecting threshold line. If the signal sequence33is a voltage, the line36can be an arc detecting threshold line, and an ignition detecting threshold line is not shown here. Line35has no specific meaning in this case.

In one power converter1′ the current leading capability of all of the power converter stages6a,6b,6ntogether may be higher than the maximum power delivery possibilities of all the power converter stages5together.

FIG. 4shows a timing diagram of output power at a different output power port3b, . . .3n. The axis t is the time axis and the axis S40may be for example the voltage, current or power axis. As the axis S40is for the actual values of these parameters, the axis S41is for an effective value of these parameters. In the first diagram ofFIG. 4with the S40axis the bipolar signal is shown in two signal sequences41,42. The signal sequence41has an excitation frequency with a period of 1/7 of the time frame which begins at time point T41and ends at time point T42. At time point T43a second pulse44starts the end of which cannot be seen in this diagram. It may be seen out of this example that the frequencies of the signals31,32and the signals41,42are different, and the frequency of the signals41,42is higher than the frequency of the signals31,32.

Additionally or alternatively to the exciting the frequency also power, voltage, current, or threshold for protective measures may be different between two different output ports3a,3b, . . .3nor at two different plasma chambers9a,9b, . . .9n.

Two threshold lines45,46are also shown in this diagram. They may be used to detect a plasma breakdown such as an arc or an ignition of the plasma, when the effective value of one of the parameters power, voltage or current exceeds such a threshold.

Various aspects of the invention work in a way of controlling multiple plasma processes in the multiple plasma processing chambers9a,9b,9nwith the controller4by converting an electrical input power into a bipolar output power as shown in the signal sequences31,32,41,42and deliver this output power to the plasma processing chambers9a,9b. . .9n. The controller4controls the power converter1to deliver the bipolar output power to the power output ports3a,3b, . . .3n, using at least one of control parameters: power, voltage, current, excitation frequency, or threshold for protective measures, by obtaining a full set of desired values for the parameters for the output ports3a,3b, . . .3n, calculating whether the power converter1,1′ is capable of delivering every desired parameter and/or desired values to every of the output ports3a,3b, . . .3n, and if this is the case, calculating a sequence of pulses of power delivery to the output ports3a,3b, . . .3nto supply the power to the plasma processes.

For that the controller4may control the power converter stages6,6a,6b, . . .6nor the switches8a,8b, . . .8nsuch that, in use, the power converter1delivers at a first time T31a first output power signal at the first output power port3afor a first time frame T31-T32and at a second time T41a second output power signal at a second output power port3b, . . .3nfor a second time frame T41-T42, where the first time T31, T41is different from the second time T32, T42and/or the first time frame T31-T32is different from the second time frame T41-T42.

A plasma system19like inFIG. 1and a plasma system19′ like inFIG. 2impose constraints on the simultaneous operation of more than one output port3a,3b, . . .3n. For plasma system19′ like inFIG. 2these constraints result when, for example, the total power or current handling capacity of the output stages connected to an input stage exceeds the power or current capacity of this input stage, so that the full output power cannot be supplied to all output ports3a,3b,3nsimultaneously. For plasma system19like inFIG. 1the full output power can only be supplied to one output port3a,3b, . . .3n, or a fraction of the full power to more than one output port3a,3b, . . .3n. For the case where independent operation of the different plasma processes is required, this can be achieved as long as the total duty cycle of all processes plus the time required to switch between outputs is smaller than the total cycle time.

These constraints create areas of possible operation and areas where no operation is possible within the space of the parameters enumerated above. For every request to the power supply to supply output power to an output or a set of output ports3a,3b, . . .3n, the location within or outside the possible area of operation has to be established. This leads to the need for a sequence controller.

A sequence controller14is part of the controller4. Its algorithm determines for every request to the power converter1to deliver output power to any of its output ports, or for a request to change one or more parameters of the output ports, whether this request lies in the possible area of operation. For a process as shown inFIGS. 3 and 4with power delivered to output ports3a,3b, . . .3n, where the different output ports3a,3b, . . .3nare driven with different power levels, different pulse duty cycles and different pulse frequencies, the sequence controller14ensures that:the pulse frequencies are integer multiples of each other, to avoid pulse overlaps (for plasma system19′ like inFIG. 2)for overlapping pulses the total requested output power and current do not exceed the possible maximum (for plasma system19′ like inFIG. 2)if possible maximums are exceeded at a limited period in the cycle, that a pattern is found without this limitation if possible (for plasma system19′ like inFIG. 2)the sum of the pulse on times plus the time to switch between outputs is smaller than the lowest frequency pulse cycle time (for plasma system19like inFIG. 1)a newly requested output pulse pattern on a particular output is activated at an appropriate time to fit into the pre existing active pulse pattern on the other outputs (for plasma system19like inFIG. 1)overall average power and current limits are not exceededa warning is issued to the user if the requested sequence is outside the possible areaa possible modified sequence is recommended to the user.