RF power supply architecture including switchable match and frequency tuning

Abstract

The power supply circuit includes a switchable match, a high voltage bus and a low voltage bus connectable to a load such that the load is in series between the buses, at least two capacitors having a fixed capacitance connectable between the high voltage bus and the low voltage bus, a number of solid-state switches equal to the number of capacitors having a fixed capacitance connectable between the high voltage bus and the low voltage bus, each switch constructed and arranged to electrically connect or disconnect one of the capacitors between the high voltage bus and the low voltage bus, and a variable frequency power supply including a high voltage output connection connected to the high voltage bus.

Description

[Technical field]

[0001] Embodiments of the present invention generally relate to a match circuit located between an AC power source, e.g., an RF frequency power source, and a load, such as a semiconductor or other processing chamber, including a processing chamber where the load includes an AC (alternating current) powered element or an AC powered element coupled to a plasma in the chamber. More particularly, embodiments herein relate to methods and apparatus for providing a match between a power supply and a load where the characteristics of the load change dynamically and the match can be efficiently switched between match circuit elements while the load is being powered, and where the frequency of the AC power signal can likewise be dynamically changed, allowing for minimal power reflection from the load while the characteristics of the load change with power applied. [Background technology]

[0002] In the match art, matches are known that utilize variable capacitors, where the capacitors have a certain range of capacitance values, and the various values ​​of capacitance are selected, for example, by physically modifying the characteristics of the capacitor by applying a motor torque to a shaft connected to the variable capacitor to change its capacitance value. These motor-driven capacitors have a limited life span and are relatively slow to respond to changes in the load characteristics that require a change in the capacitance value in the match. In addition, it is known to use variable frequency power supplies where fixed match components are placed between the power supply and the load, where slight changes in the load characteristics that affect the match of the power supply to the load can be addressed by changing the frequency of the power signal to the match. However, the range of change in the output frequency is limited and cannot adequately address problems that arise when the load characteristics change and the load starts to reflect power, or when the amount of reflected power increases significantly compared to the forward power delivered from the electrode supply. Summary of the Invention

[0003] Provided herein is a power supply circuit including a match. In one aspect, the power supply circuit includes a switchable match including a high voltage bus connectable to a load, a low voltage bus connectable to the load such that the load is in series between the high voltage bus and the low voltage bus, at least two capacitors having a fixed capacitance selectively connectable between the high voltage bus and the low voltage bus, and a number of solid-state switches equal to the number of capacitors having a fixed capacitance connectable between the high voltage bus and the low voltage bus, each switch configured and arranged to selectively connect or disconnect one of the capacitors having a fixed capacitance selectively connectable between the high voltage bus and the low voltage bus between the high voltage bus and the low voltage bus, and a variable frequency power supply including a high voltage output connection connected to the high voltage bus.

[0004] In another aspect, there is provided a match connectable between a variable frequency power supply and a load, the load having electrical characteristics that are dynamically changeable, the match including: a high voltage bus connectable to the load, a low voltage bus connectable to the load such that the load is in series between the high voltage bus and the low voltage bus, at least two capacitors having fixed capacitances selectively connectable between the high voltage bus and the low voltage bus, and a number of solid-state switches equal to the number of capacitors having fixed capacitances connectable between the high voltage bus and the low voltage bus, each switch constructed and arranged to selectively connect or disconnect electrically one of the capacitors having fixed capacitances selectively connectable between the high voltage bus and the low voltage bus, between the high voltage bus and the low voltage bus.

[0005] and providing a variable frequency power supply including a high voltage output connection connected to the high voltage bus.

[0013] Also provided is a method of matching a power supply to a load, the power supply being a variable frequency power supply, the method including providing a power supply circuit comprising a switchable match configured to change its electrical characteristics in response to a change in a load to which the switchable match is connected, the method further including providing a high voltage bus connectable to the load, a low voltage bus connectable to the load such that the load is in series between the high voltage bus and the low voltage bus, at least two capacitors having fixed value capacitance selectively connectable between the high voltage bus and the low voltage bus, and a plurality of solid state switches equal to the number of capacitors having fixed value capacitance connectable between the high voltage bus and the low voltage bus, each switch constructed and arranged to selectively connect or disconnect one of the capacitors having fixed value capacitance selectively connectable between the high voltage bus and the low voltage bus, between the high voltage bus and the low voltage bus, and providing a variable frequency power supply including a high voltage output connection connected to the high voltage bus.

[0006] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be made by reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the accompanying drawings depict only exemplary embodiments, and therefore should not be considered as limiting the scope of the present disclosure, which may also admit of other equally effective embodiments. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a plan view of a plasma power supply circuit including a switchable match, a DC-AC converter, and an RF amplifier for providing an RF power signal matched to the changing electrical characteristics of a processing chamber, where the switchable match is included in a different box shell than the AC-DC converter and the RF amplifier. [Diagram 2]FIG. 1 is a plan view of a plasma power supply circuit including a switchable match, a DC-AC converter, and an RF amplifier for providing an RF power signal matched to the changing electrical characteristics of a processing chamber, where the switchable match is located in a box shell shared with the RF amplifier, which is a separate box shell from the DC power supply and the DC-AC converter. [Diagram 3] FIG. 1 is a plan view of a plasma power supply circuit including a switchable match, a DC-AC converter, and an RF amplifier for providing an RF power signal matched to the changing electrical characteristics of a processing chamber, where the switchable match is in a different box shell than the DC power supply, the DC-AC converter, and the RF amplifier. [Figure 4] FIG. 1 is a plan view of a plasma power supply circuit including a switchable match, a DC-AC converter, and an RF amplifier for providing an RF power signal matched to the changing electrical characteristics of a processing chamber, where the switchable match is located in a box shell shared with the RF amplifier, which is a separate box shell from the DC power supply and the DC-AC converter. [Diagram 5] FIG. 1 is a plan view of a plasma power supply circuit including an RF power source and a switchable match disposed in series with an RF cable to provide an RF power signal matched to the changing electrical characteristics of the processing chamber. [Figure 6] FIG. 1 is a plan view of a plasma power supply circuit including an RF power source and a switchable match disposed in series with an RF cable to provide an RF power signal matched to the changing electrical characteristics of the processing chamber. [Figure 7] 1 is a schematic circuit illustrating a single DC power supply configured to power several separate sets of DC-AC converters, RF amplifiers, and match circuits, with each set of DC-AC converters, RF amplifiers, and match circuits coupled to a specific load. [Figure 8]1 is a schematic circuit illustrating a single DC power supply configured to power several separate sets of DC-AC converters, RF amplifiers, and match circuits, with each set of DC-AC converters, RF amplifiers, and match circuits coupled to a specific load. [Figure 9] 1 is a graphical representation showing the electrical response of a switchable match herein. [Figure 10] 13 is a further graphical representation of the electrical response of a switchable match herein; [Figure 11] 13 is a further graphical representation of the electrical response of a switchable match herein; [Figure 12] 2 is a schematic diagram of a control circuit for the power supply circuit of the present invention; [Figure 13] FIG. 1 is a schematic diagram of a power supply circuit incorporating a DC power supply and an RF stage. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] For ease of understanding, wherever possible, identical reference numerals have been used to designate identical elements common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0009] Provided herein is an alternating current, e.g., AC or RF power supply structure that includes both switchable match and frequency tuning to supply power to a plasma chamber at a consistent rate despite changes in the electrical characteristics of the coupled load, where, for example, the electrical characteristics of the switchable match are changed to accommodate changes in the electrical reactance and resistance of the chamber components to which the power source is connected, or changes in the plasma and its return or ground path, or changes in the electrical characteristics of the series combination of the above components, plasma, return or ground paths. By appropriately connecting individual components of the switchable match to its active match circuit, the electrical characteristics of the switchable match can be altered to more closely match the electrical characteristics of its upstream circuit element with respect to the reactance of the downstream component, i.e., with respect to the reactance of the load, which may consist of the chamber components to which it is connected, the plasma in the chamber, or both. By selectively connecting the match components to the match circuit, they are matched or close to matching the reactance of the downstream load. Furthermore, by adjusting the frequency of the RF signal arriving at the match, a matched reactance or a reactance very close to the downstream reactance can be achieved.

[0010] Here, the individual components selectively included in the match circuit are individual capacitors provided as "shunt" capacitors located between the match power supply and ground line or bus, and one or more of these capacitors can be selectively incorporated into the match circuit using a dedicated solid-state switch located in series with each capacitor between the match power supply and return or ground bus. Switchable L-configuration matches and switchable π-configuration matches are described herein. Each such switchable match can be configured to be located in series either between the RF generator and appropriate power and return path wiring and the process chamber or its components, or between the DC power supply, DC-AC converter, and RF amplifier and the process chamber or its components. In addition, with respect to Figs. 1-4, RF power is provided by individual components in separate packages or shell boxes, here by a DC power supply 110, a DC-AC (RF) converter 112, and an RF amplifier 114 connected to an AC source, i.e., a fab or factory AC source of sufficient wattage to power the DC power supply 110 at, for example, 200-480V, whereas in Figs. 5 and 6, RF power is provided by an integrated RF generator. In the configurations of Figs. 1-4, a single DC power supply may be connected to multiple process chambers 122 via switchable matches 102 or 102' dedicated to each chamber, as shown diagrammatically in Figs. 7 and 8. Furthermore, the DC power supply, the DC-AC converter 112 (oscillator), and the RF or AC amplifier 114 may be configured in a single enclosure or shell box, as shown diagrammatically in Fig. 12. In the embodiment of the present disclosure shown in Fig. 1, a power supply circuit 100 is shown that includes an L-type switchable match circuit 102. In Fig. 2, the power supply circuit 100 is the same as in Fig. 1, but the RF amplifier and the switchable match are provided in the same shell box. In the embodiment of the present disclosure shown in Fig. 3, the power supply circuit 100 is shown including a π-type switchable match 102'. In Fig. 4, the power supply circuit 100 is the same as in Fig. 3, but the RF amplifier 114 and the switchable match 102' are provided in the same shell box.

[0011] 1, an RF power supply device is depicted that includes a power supply circuit 100 that includes a switchable match 102 and frequency tuning that allows power to be supplied to a plasma chamber at a consistent rate despite changes in the electrical characteristics of a connected load, where the load is a component of a process chamber 122 that changes its electrical characteristics while being powered, or a component of a process chamber 122 and a plasma that is electrically coupled thereto or electrically coupled to a ground or return path, where the electrical characteristics change while being powered, or a combination of these. The power supply circuit 100 is here configured to allow one or more switchable matches 102 to be connected thereto. For example, the power supply circuit 100 can be used to supply high RF power to a processing chamber 122, or its components or plasma, where reflected power is minimized by using active solid-state switching to move components of the switchable match 102 in and out of the match circuit while power is being supplied, despite changes in reactance in the processing chamber 122 or its components or plasma connected to the switchable match 102, and further by adjusting the frequency of the RF signal if necessary.

[0012] As shown in Fig. 1, the power supply circuit 100 includes a series of box shells 116a-e, each of which includes a frame 70 of steel or other metal, each configured as a rectangular prism surrounded by a skin 72 connected to the frame 70 by screw fasteners or other fastening elements, thus holding the elements of the power supply circuit as separate modules therein. Each box shell 116a-e includes at least two connectors 117 (connectors 117a-p of some box shells 116 in Fig. 1) extending through the skin 72, allowing the connection of electrical components in the shell 116a to components outside it or to components in or on the plasma chamber. A connecting cable 120, e.g., an RF shielded cable, connects to each connector 117 and connects the electrical components in each shell 116 through the connectors 117 to other components in the other shells 116 or to components of the process chamber 122.

[0013] 1-4, where the power supply circuit 100 is composed of modular elements within a box shell 116, a DC power source 110 enclosed in a box shell 116a supplies DC power to the power supply circuit 100. The DC power source 110 is connected to the power supply circuit 100 by two connection cables 120a, 120b. The connection cable 120a is connected to the DC + side or DC high voltage side of the DC power source 110 by connector 117a, and the connection cable 120b is connected to the - side or ground side of the DC power source 110 by connector 117d.

[0014] The connecting cables 120a,b extend from the connectors 117a,b on the box shell 116a covering the DC power source 110 to two input connectors 117c,d extending from the outer plate 72 of the box shell 116b covering the DC-AC converter 112. The DC-AC converter 112 converts the direct current electrical signal (power) received via the connecting cables 120,b to alternating current using a solid-state oscillator circuit. Here, the AC output of the DC-AC converter 112 can be an RF frequency, i.e. 13.56 or multiples thereof, or other AC frequencies. The output of the DC-AC converter 112 is connected to the RF (or AC) amplifier 114 via the connecting cables 120c,120d. A connecting cable 120c extends between an output connector 117e of the DC-AC converter 112 and an input connector 117g of the RF amplifier on the high voltage RF output side of the DC-AC converter 112, and a connecting cable 120d extends between a return or ground connector 117f of the AC-DC converter and a return or ground connector 117h of the RF amplifier 114. The RF amplifier 114 is a solid-state amplifier connected to a power source, such as a 220V or 44V external electrical connection (not shown), and increases the peak-to-peak voltage of the AC signal output by the DC-AC converter to a value useful for the end use of the AC signal, such as for driving an electrode or coil in or on a plasma processing chamber as part of a plasma circuit in the chamber, or for driving other components in the chamber that are not directly part of the plasma circuit. For example, the output rms (root mean square) voltage may be on the order of 1000V, more typically 100-200V.

[0015] On the output side of the switchable match 102, connector 117m on the high voltage bus 132 is connected to the high voltage input connector 117o of the plasma chamber 122 and connects to components of that chamber via connecting cable 1206, and connector 117n is connected to the return path or ground bus 134 and to the return or ground side connector 117p of the processing chamber 122 via connecting cable 1208.

[0016] In FIG. 1, the match is configured as an “L” match, where a first variable capacitance consisting of up to four capacitors 150a-d is located between the high voltage bus 132 and the return or ground bus 134, and a second capacitance in the form of a fixed capacitor 118 and an inductor 119 is located in series with the high voltage bus 132 between the connection with the variable capacitance and connector 117m.

[0017] Here, the shunt capacitance, i.e., the capacitance in the "L" circuit between the high voltage bus 132 and the return or ground bus 134, is a variable capacitance configurable by four capacitors 150a-d, each having a fixed capacitance value, each of which can be selectively connected between or across the high voltage bus 132 and the return or ground bus 134 by selectively operating one of the switches 152a-d connected between the capacitor 150 and the high voltage bus 132. A smaller number, but at least two shunt capacitors 150, or a larger number of shunt capacitors, can be utilized to allow the match designer to create a match with a minimized range of load electrical conditions where power is reflected by switching the shunt capacitors in and out of the match circuit. To allow matching over a large range of load resistances and reactances, one or more of the capacitors 150a-d may be switched in and out of the match circuit, i.e., connected between or across the high voltage bus 132 and the return or ground bus 134. When each of the capacitors 150a-d is connected to the match circuit, it is electrically parallel with one another between or across the high voltage bus 132 and the return or ground bus 134. In addition, the match designer may avoid the need for any of the capacitors 150a-d to be connected between or across the high voltage bus 132 and the return or ground bus 134. The connection of any of the capacitors 150a-d between or across the high voltage bus 132 and the return or ground bus 134 is made by closing a corresponding one of the switches 150a-d that are between the capacitors 150a-d and the high voltage bus 132. Similarly, any of the capacitors 150a-d can be disconnected between the high voltage bus 132 and the return bus or ground bus 134 by opening a corresponding one of the switches 150a-d located between the capacitors 150a-d and the high voltage bus 132.Here, switches 152a-d are solid-state switches, such as PIN diodes, that can be switched while power is being applied, i.e., the capacitors connected to them can be connected or disconnected from the match circuit while power is entering the processing chamber 122 or its components via the switchable match 102.

[0018] In the switchable match 102 of FIG. 1, the capacitance between or across the high voltage bus 132 and the return or ground bus 134 is the sum of the capacitances of the capacitors 150a-d connected between or across the high voltage bus 132 and the return or ground bus 134. The value of the shunt capacitance, which is the sum of the individual capacitance values ​​of the capacitors 150a-d switched into the match circuit, electrically connected between or across the high voltage bus 132 and the ground or return bus 134, is adjusted to maximize the power transfer to the process chamber components or the plasma coupled thereto, i.e., to the load, even when the relative resistance and reactance of the load changes. Referring to FIG. 9, the impact on matching using the present method is illustrated for switching up to two shunt capacitors, e.g., switching capacitors 150a,b into or out of the match circuit.

[0019] In FIG. 9, the coupling or transfer of effective power to the load is shown with two example capacitances C, compared to the shunt capacitance value, the resistance and reactance of the load. Here, the shunt capacitance is based on the sum of the capacitances of fixed capacitors, here for example capacitors 150a,b, switched into the match circuit as the shunt capacitor. Here, fixed means the rated or actual value of the capacitance of the capacitor at a certain condition, for example at 20° C. and atmospheric pressure, and it should be understood that the capacitance of such a capacitor may drift slightly based on its operating conditions and aging. However, the capacitance is fixed in the sense that the capacitor cannot be intentionally manipulated to change its capacitance, as is done with variable capacitors. In FIG. 9, the Y-axis represents the reactance of the load, and the X-axis represents the resistance of the load. During processing in the processing chamber, both the reactance and resistance of the load may change, which may affect the percentage or amount of power leaving the RF amplifier that actually passes into the load (e.g., a component of the processing chamber or a component of the processing chamber that is electrically coupled to the plasma in the chamber). Line 154 encloses the range of load resistance and reactance within which no power (or a minimal amount of power) is reflected by the load when only a single capacitor C1, e.g., capacitor 150a, is switched into the match circuit between or across the high voltage bus 132 and the return or ground bus 134. In other words, within the range of values ​​of load reactance X and resistance R enclosed by points 150a-d, if capacitor 150a is the only capacitor switched into the match circuit between or across the high voltage bus 132 and the return or ground bus 134, 100% of the power leaving the RF amplifier (or the maximum possible value of that power) will reach the load. In addition, because the reactance and resistance of the load may change dynamically during use of the load, e.g., the load as an electrode and the plasma in the plasma circuit, values ​​of resistance R and reactance X outside the area enclosed by line 154 will begin to reflect more power by the load.For example, line 156 represents a series of values ​​of the resistance R and reactance X of the load where, when only capacitor 150a is switched into the match circuit, 10% of the power is reflected by the load. In other words, 90% of the power leaving the RF amplifier 114 is passed to the load. Similarly, line 158 represents a series of values ​​of the resistance R and reactance X where, when only capacitor 150a is switched into the match circuit, 20% of the power is reflected by the load. In other words, 80% of the power leaving the RF amplifier 114 is passed to the load. Although not shown, the further away the values ​​of the resistance R and reactance X of the load are from the area enclosed by line 154 with only capacitor 150a switched into the match circuit, the greater the percentage of the reflected power and the smaller the percentage of the power leaving the RF amplifier that reaches the load.

[0020] Since drift in the resistance and reactance of the load cannot be directly controlled during use of the process chamber, if only a single fixed capacitor is switched into the match circuit between or across the high voltage bus 132 and the return or ground bus 134, the percentage of power transferred to the load may be significantly worse. However, now, a second fixed capacitor, for example capacitor 150b, can be additionally switched into the match circuit between or across the high voltage bus 132 and the return or ground bus 134. In addition to capacitor 150a, capacitor 150b can be switched into the match circuit, or capacitor 150a can be switched out of the match circuit while capacitor 150b is switched into the match circuit. In this case, the match circuit will match a different range of values ​​of the resistance R and reactance X of the load. However, it is also possible to select the values ​​of capacitors 150a,b such that the range of matched resistance R and reactance X that allows 100% or the highest possible power transmission to the load using only capacitor 150a overlaps with the range of matched resistance R and reactance X that allows 100% or the highest possible power transmission to the load using both capacitors 150a and 150b. Similarly, it is also possible to select the capacitances such that the range of matched resistance R and reactance X that allows 100% or the highest possible power transmission to the load using only capacitor 150a overlaps with the range of matched resistance R and reactance X that allows 100% or the highest possible power transmission to the load using only capacitor 150b. For example, in FIG. 9 , curve 162 encircles the resistance and reactance values ​​at which, when both capacitors 150 and 150b are switched into a match circuit between or across the high voltage bus 132 and the return or ground bus 134, 100% (or the maximum possible amount) of the power out of the RF amplifier is transferred to the load.Line 164 represents a series of values ​​of resistance r and reactance X where, when capacitor 150a and capacitor 150b are switched into the match circuit, 10% of the power is reflected by the load. In other words, 90% of the power leaving RF amplifier 114 is passed to the load. Similarly, line 166 represents a series of values ​​of resistance r and reactance X where, when capacitor 150a and capacitor 150b are switched into the match circuit, 20% of the power is reflected by the load. In other words, 80% of the power leaving RF amplifier 114 is passed to the load. Here, it can be seen that there is an overlap region where the percentage of the power reaching the load when only capacitor 150a or both capacitors 150a and 150b are switched into the match circuit is within the same percentage range.

[0021] By appropriately selecting the capacitor values, it is possible to create a match where the reflected power can reach the desired maximum value of Pr (reflected power) that is acceptable for the application performed in the process chamber. For example, by making the capacitance values ​​of the capacitors 150a and 150b slightly smaller than the values ​​for the results shown in Figure 9, the area enclosed by the curve 162 shifts leftward and downward, i.e., to lower X and R values, so that there is a range of resistance R and reactance X where the match passes 100% (or the maximum possible amount) of power to the load using only the capacitors 150a or b or using the capacitors 150a and 150b together. Similarly, if the sum of the capacitances of the capacitors 150a and 150b is larger than the values ​​shown in Figure 9, the areas of 100% (or the maximum possible amount) of power transfer enclosed by the lines 154 and 162 will be further apart, and areas of less power transfer, i.e. areas of greater reflectance, will be in between. In addition, there is a region of 100% transmission and a corresponding region of low transmission surrounding the 100% (or maximum possible power transfer) region having higher X and R values ​​than curve 162, the region of low transmission being formed by switching a third capacitance, such as capacitor 150c, into the match circuit, as shown by curve 170 in Figure 10. Similarly, there is a region of 100% (or maximum possible power transfer) and a corresponding region of low transmission surrounding the 100% region having even higher X and R values ​​than curve 162, the region of low transmission being formed by switching a fourth capacitance, such as capacitor 150c, into the match circuit, as shown by curve 172 in Figure 10. exists.

[0022] The shunt capacitance provided by selectively switching capacitors 150a-d in and out of the match circuit allows for up to 16 different shunt capacitances to exist within the match circuit. Assuming that the capacitance values ​​of capacitors 150a-d are A, B, C, and D, respectively, the following total shunt capacitance values ​​are possible between or across the high voltage bus 132 and the ground or return bus 134: 0 (none of capacitors 150a-d are switched into the circuit), A, B, C, D, A+B, A+B+C, A+B+C+D, A+C, A+C+D, A+B+D, A+D, B+C, B+C+D, B+D, and C+D. The total number of different capacitance values ​​that can exist between the high voltage bus 132 and the ground or return bus 134 is 2 c where C is the total number of available capacitors that can be switched in or out of the match circuit between the high voltage bus 132 and the return or ground bus 134. Thus, with only two capacitors 152a,b, four such capacitances are possible. With three capacitors 152a-c, eight capacitances can be represented. The number of capacitors and their values ​​is a matter of design choice for the match designer depending on the desired range of X and R values ​​to match for high transmittance and the desired overlap of the transmittance regions of each possible capacitance, such as 100%, 90%, 80%, etc. The capacitance values ​​of the capacitors 152a-d may be different from each other, for example, if A is less than B, B is less than C, and C is less than D. The capacitance value of each capacitor 150a-d may be the same. Some of the capacitors 150a-d may have the same capacitance value, while others have different capacitance values. The capacitance value is selected based on the likely or calculable characteristics of the load so that the switchable match provides the closest match that can deliver the maximum amount of forward power to the load.

[0023] 10 and 11, regions of matched resistance R and reactance X load characteristics with four different total shunt capacitances are shown. Each region may represent a load value or resistance R and X that results in 100% transmission (or maximum possible transmission) of forward power to the load for one of the capacitors 150a-d switched into the match circuit, or one of four different combinations of them. FIG. 10 shows a region of reactance X and resistance R value pairs surrounded by line 154 that represents the presence of only capacitor 150a of the same value as shown in FIG. 9 in the match circuit, and a region of reactance X and resistance R value pairs surrounded by line 154 that represents the presence of both capacitors 150a and 150b of the same values ​​as shown in FIG. 9 in the match circuit. Additional curves are shown, such as a third curve 170 encircling a region of reactance X and resistance R value pairs where 100% transmission to the load occurs using three of the capacitors 150a-d, or different combinations thereof, such as the first capacitor 150a, the third capacitor 150c, switched into the match circuit, and a fourth curve 172 encircling a region of reactance X and resistance R value pairs where 100% transmission to the load occurs using different combinations of the four capacitors 150a-d switched into the match circuit. 10, the regions of X and R value pairs where 100% (or maximum possible) transmission occurs are spaced apart from one another, such that switching combinations of these four capacitors 150a-d in the match circuit will result in a match operation where power (or an amount greater than the minimum possible) is reflected by the load, where the R and X values ​​of the load are not within the region bounded by any of the curves 154, 162, 170, and 172. This would occur if the reactance and resistance values ​​of the load were outside the region bounded by lines 154, 162, 170, and 172, for example in regions 174, 176, and 178 between the above regions.Thus, as the value of the electrically characteristic load changes, a portion of the power delivered to the process chamber 122 or its components, or more than the minimum amount possible, will be reflected, and the value of the power as a percentage of the forward power from the RF amplifier 114 will depend on how close together the regions bounded by the curves or lines 154, 162, 170, and 172 are. The greater the spacing between the regions, the greater the percentage of power reflected from the load when operating within these regions. However, this may be acceptable behavior for certain applications.

[0024] Alternatively, the values ​​of the capacitors 150a-d or the combination of the capacitors can be changed, which results in an overlap region of pairs of reactance X and resistance R values ​​that result in 100% transmission to the load. Now, the curves 162', 170' and 172' obtained by lowering the capacitance values ​​of the matched capacitors 150b-d of FIG. 10 result in the region of 100% match being shifted to lower values ​​of resistance R and reactance X, so that the boundaries of the regions of 100% transmission, if not overlapping, at least coexist in the direction of the R value. As a result, there is a large region of pairs of reactance X and resistance R values ​​that result in 100% transmission to the load, which is continuous and does not have reflection regions.

[0025] 10 and 11 show the region of pairs of reactance X and resistance R values ​​that result in 100% transmission to the load for four possible shunt capacitance values ​​that can be combined by switching one or more of capacitors 150a-d into a match circuit between or across the high voltage bus 132 and the return or ground bus 134 of FIG. 1. However, as noted above, the number of shunt capacitance values, and therefore the number of pairs of reactance X and resistance R values ​​that result in 100% transmission to the load (or the maximum possible for a match), is approximately 2. cwhere C is the number of available capacitors that can be switched into the match circuit between or across the high voltage bus 132 and the return or ground bus 134. Thus, the match designer has great freedom to design a match with multiple ranges of 100% (or the minimum possible power reflected) to match the power driver to the load.

[0026] The switches 152a-d are configured as solid state PIN diodes, each configured to switch a corresponding one of the capacitors 150a-d into a match circuit between or across the high voltage bus 132 and the return or ground bus 134. This allows the switches 152a-d to be switched under load, i.e., while power is being driven through at least the high voltage bus 132, where at least one of the capacitors 152a-d is switched into the match circuit through the remainder of the switchable match circuit 102 and further into the load, allowing for a continuous, uninterrupted supply of power to the load, i.e., to the process chamber 122 or components thereof.

[0027] Here, the DC-AC converter is capable of a variable frequency output, i.e., its output frequency can be controllably changed. As a result, when power is being delivered to a load and the switchable match 102 is operating to minimize the value of the power reflected by the load, the frequency of the power signal, i.e., the AC frequency value of the power output, can be modified to reduce or change the value of the power reflection. In the example of a shunt capacitance between or across the high voltage bus 132 and the return or ground bus 134 shown in Figures 9 and 10, there exists a pair of values ​​of the load resistance R and the load reactance X at which reflection of power from the load occurs. Now, by adjusting the frequency of the delivered power, it is possible to change the load resistance R and the load reactance X at which reflection is minimal or does not occur, thereby reducing the value of the reflected power to a lower value or to zero. As shown in Figure 10, as the characteristics of the load change, the temporary values ​​of the load resistance R and the load reactance X at the temporary frequency of the delivered power at a given moment are values ​​that are between the values ​​of the switchable capacitance, where the match transfers 100% of the power delivered to the load. This is represented by point 180, which lies between the 100% transmission region bounded by lines 154, 162. However, by adjusting the frequency of the AC power signal output by the DC-AC converter to either a higher or lower value, the location of the resulting load resistance R and reactance X pair will be changed relative to the region bounded by curves 154, 162, 170 or 172, resulting in either point 180' or 180" which is within the 100% transmission region. Since the performance of any match is frequency dependent, changing the frequency can be viewed as moving the load resistance R and reactance X values, shifting the region bounded by curves 154, 162, 170 or 172 in the X and R directions, or both.Thus, when the switchable match 102 is combined with a variable frequency power supply, here configured as a DC power supply 110, a DC-AC converter 112, and an RF amplifier 114, it is possible to operate the match in such a way that the occurrence of 100% (or the maximum possible) transmission of the power supplied to the load is maintained. This is possible even if the switchable match 102 contains a pair of values ​​of the load resistance R and inductance X, which at a given power frequency at which the power is reflected, as shown in Fig. 10, occurs. However, by changing the frequency of the power signal arriving at the switchable match, it is possible to adjust one of the regions of the load resistance and reactance value pairs in the R and X directions, or to adjust the load resistance R and reactance X values ​​so that the occurrence of 100% (or the minimum possible) transmission to the load occurs.

[0028] With reference to Figure 2, the modularity of the power supply has changed slightly compared to Figure 1. Here, the RF amplifier 114 is contained within the same box shell 116x as the switchable match 102. In all other respects the power supply system is the same as that shown and described with reference to Figure 1 and operates in the same way.

[0029] 3, a further embodiment of the power delivery circuit 100 utilizing a modified switchable match 102' is shown, where the modified switchable match 102' is configured as a π-type switchable match circuit 102' and includes two sets of capacitors 150a-d and 152e-h and corresponding switches 152a-d and 152e-h configured to selectively connect the capacitors 150a-h electrically connected in series therewith between and across the high voltage bus 132 and the return or ground bus 134. Here, the inductor 119 and the capacitor 118 are inserted in series within the high voltage bus 132, i.e., between the region of the high voltage bus 132 to which the capacitors 150a-d can be connected by the switches 152a-d, and the region between the inductor 119 and the capacitor 118 and the process chamber 122, where the capacitors 150e-h can be connected to the high voltage bus 132 by the switches 152e-h. Here, each leg of the π match 102', i.e., the portion to one side of the inductor 119, includes four fixed capacitors 150a-d or 150e-h, each of which is selectively connectable or not connectable between or across the high voltage bus 132 and the return or ground bus 134 of the switchable π match 102'. There are fewer, but at least two, such capacitors 150 in at least one leg of the switchable π match 102', and corresponding switches 152 for switching them in and out of the match circuit. The modularity of the power supply circuit 100' of Figure 3 corresponds structurally to the power supply circuit 100 of Figure 1, but the L-match arrangement of the power supply circuit of Figure 1 is replaced by a switchable π-match 102'. Similarly, the modularity of the power supply circuit 100' of Figure 4 corresponds structurally to the power supply circuit 100 of Figure 2, but the L-match arrangement of the power supply circuit 100 of Figure 2 is replaced by a switchable π-match 102'.

[0030] The π-type switchable match circuit 102' of the power supply circuit 100' of Figures 3 and 4 has similar operating characteristics from a matching standpoint as the L-type match configuration of the power supply circuit of Figure 1. Here, when none of the capacitors 150e-h are switched into the match circuit as shunt capacitors, the power supply circuit 100 of Figure 3 corresponds structurally to the power supply circuit 100 of Figure 1. When none of the capacitors 150e-h of the π match 102' are switched into shunt capacitance between or across the high voltage bus 132 and the return or ground bus 134, the match 102' has the same performance characteristics as the L-type switchable match 102 of Figures 1 and 2, where the capacitances of the fixed capacitors 125a-d are the same as their values ​​in Figures 1 and 2. Similarly, switching one or more of capacitors 150e-h into a match circuit between or across the high voltage bus 132 and the return or ground bus 134 while switching capacitors 150a-d out of the match circuit results in similar performance characteristics to the switchable match of Figures 1 and 2, where the capacitances of fixed capacitors 125a-d are the same as their values ​​in Figures 1 and 2. Switching capacitors from the set of fixed capacitors 150a-d on one side of inductor 119 into the match circuit of switchable pi match 102' between or across the high voltage bus 132 and the return or ground bus 134, plus switching capacitors from the set of fixed capacitors 150e-f on the other side of inductor 119 into the match circuit of switchable pi match 102' between or across the high voltage bus 132 and the return or ground bus 134, results in a combined effect of two sets of parallel shunt capacitors similar to that shown and described with respect to Figures 9-11. In addition to changing the output frequency of the DC-RF converter, this allows the match designer to design a match with a minimum pairing of the load resistance r and reactance X, where the match does not result in 100% transmission of the power supplied to the power supply circuit 100 to the load.For example, if the load exhibits resistance R and reactance X values ​​that are not perfectly matched at the momentary, i.e., current, output frequency of the DC-AC converter 112 to prevent power reflection at that frequency, the DC-AC converter can change its frequency upward or downward to adjust the match and load characteristics to eliminate or minimize power reflection by the load. Additionally, here, each of the switches 152a-h has the same or similar configuration as the switches 152a-d of Figures 1 and 2, and is preferably configured as a solid-state PIN diode capable of hot switching, i.e., switching under load or under full power application. As a result, in a power supply circuit 100' incorporating the switchable pi match 102', like the power supply circuit 100 of FIGS. 1 and 2, each and any of the capacitors 152 can be switched in or out of the match circuit between or across the high voltage bus 132 and the return or ground bus 134 under full power, without the need to disconnect the switchable pi match 102' from the RF amplifier or load, thus providing continuous matching of the load even while the resistance R and reactance X characteristics of the load are changing. As a result, maximum forward power, i.e., minimum reflected power, is provided by selectively switching one of capacitors 150a-h into or out of the shunt capacitance (the capacitance between the high voltage bus 132 and the return or ground bus 134) while simultaneously adjusting the output frequency of the DC-AC converter as needed to maintain maximum transmission of forward power to the load, in this case the processing chamber, including components of the processing chamber or components of the processing chamber that are electrically coupled to the plasma therein.

[0031] 7 and 8, the power supply circuits 100, 100' of FIGS. 1 to 4 herein can be used in a modular manner, in other words a single DC-AC generator can be connected to multiple processing chambers 122 via multiple switchable matches 102, 102', each switchable match 102 or 102' configured for matching to a single such processing chamber or component therein.

[0032] FIG. 7 shows a schematic of a distributed power system in which the output of a single DC power supply 110 is connected to the input of multiple DC-AC converters 112, one for each process chamber that is powered using the single DC power supply 110. Here, four process chambers 122a-d are ultimately connected to one DC power supply 110, but more or fewer process chambers 122 may be powered by one DC power supply 110. Each process chamber 122a-d is connected to a switchable match 102 or 102', and each switchable match 102 or 102' is connected to a dedicated RF amplifier 114, and each RF amplifier is connected to a dedicated DC-AC converter 112. Here, the RF (AC) amplifier 114 and the DC-AC converter 112 are shown as separate components, but they may be combined into a single RF stage connected to a DC source, i.e., the DC power supply 110, as shown in FIG. 12. Again, as in each embodiment utilizing a DC power supply 110, the DC power supply 110 is powered by an alternating current source, e.g., a fab or factory mains supply providing power at a frequency of 50-60 Hz, e.g., 200-480 V. Alternatively, the power source for the DC power supply 110 may be an AC rack configured to power multiple components of a processing system, e.g., a processing system utilizing one or more processing regions, configured to connect to all components of the system requiring unmatched AC power, and a DC power supply that converts the AC power input to a DC power output that is then converted to the desired AC frequency and power level. Here, the output of the DC power supply is connected to each of four dedicated DC-AC converters 112, via RF amplifiers 114 and switchable match circuits 102 or 102', and finally to power the chambers 122a-d. Here, each of the DC power supply 110, DC-AC converter 112, RF amplifier 114, and switchable match 102 or 102' are housed within their own dedicated box shell 116 (FIGS. 1-4) so ​​that the components can be easily switched or replaced out of the way within the power supply circuit 100, 100'.Again, the DC-AC generator 112 provides a variable frequency output to allow a wide range of combinations of load resistance R and reactance X values ​​with minimal reflected power or high power delivery with no reflected power, along with switching the capacitors in and out of the shunt capacitance of the switchable match circuit 102, 102'. Referring to Figure 8, the power delivery components are configured as in Figures 2 and 4 herein, with the RF amplifier 114 and the switchable match 102 or 102' combined in a single box shell 116 as in Figures 2 and 4. Otherwise, the power delivery circuit 100 or 100' of Figure 8 is the same as the circuit of Figure 7.

[0033] 5, an additional RF power supply structure device with a switchable match and frequency tuning capability for supplying power to a process chamber, e.g., a plasma processing chamber, at a consistent value despite changes in resistance R and reactance X of the process chamber components or environment to which the power supply structure device is connected. The power supply circuit 100 is now configured to allow one or more switchable matches 102 or 102' to be connected thereto. For example, the resulting power supply circuit 100" can be used to supply high levels of RF power to a process chamber 105 despite changes in resistance R and reactance X of the load to which the switchable match 102 is connected, e.g., the process chamber 122 or process chamber components.

[0034] Here, the power supply circuit 100″ includes an RF generator 220 capable of supplying RF power at a desired amplitude (RMS voltage) and frequency, which is connected to the switchable match 102 via cabling (cables 221, 222) as described above with respect to FIG. 1. In this embodiment, the RF generator is a standard 50Ω generator 220 contained within a box shell 116a, with a high voltage connector 117a and a return or ground connector 117b extending from the same side wall of the box shell 116a. A first 50Ω cable 221 connects the high voltage 1 and 2. The switchable match 102 is now configured as and operates similarly to the switchable match of Figures 1 and 2. The return or ground bus 134 of the switchable match 102 extends through the match and connects to a return or ground connection on the process chamber 122, and the high voltage bus 132 extends across the four switch connection positions to an in-line capacitor 119 and inductor 119 in series with it, and then connects to the high voltage side of the process chamber 122.

[0035] In this embodiment, a single RF generator 220 is dedicated to a single process chamber 122. As in the embodiment of Figures 1 and 2 herein, the switchable match 102 is operable to selectively switch one or more of the fixed capacitors 152a-d into shunt capacitances between or across the high voltage bus 132 and the return or ground bus 134 to change the match characteristics of the switchable match 102 to correspond to a plurality of distinct ranges of pairs of process chambers 122 or process chamber components or components and values ​​of resistance R and reactance X of the plasma. As a result, over a wide range of values ​​of resistance R and reactance X of the process chambers 122 or process chamber components, the switchable match 102 provides little or no reflected power at the process chamber, i.e., provides a perfect or near perfect match to deliver 100% or nearly 100% of the power output from the RF generator to the load (process chamber or process chamber component). Additionally, for ranges of process chamber 122 or process chamber components or components and values ​​of plasma resistance R and reactance X where switchable match 102 does not provide maximum possible transmission (minimum reflection), RF generator 220 is configured as a variable frequency RF generator 220 such that the output frequency of its power signal is adjustable to move switchable match 102 closer to the load resulting in maximum power transfer to the load, e.g., 100% power transfer.

[0036] Referring to Figure 6, another RF power supply structure device including switchable match and frequency tuning that can supply power to a plasma chamber at a consistent rate despite load reactance and resistive reactance changes is shown. In Figure 6, RF generator 220 and RF cables 221, 222 are utilized, but the L-type switchable match of Figure 5 is replaced with a π-type switchable match circuit 102'. In all other respects, the power supply circuit is the same.

[0037] The system here includes a controller for selecting the appropriate one of the fixed capacitors 150a-d or 150a-h to be switched into the shunt capacitance taking into account the reflected power and the power signal frequency. Here, the circuit element providing the AC frequency, such as the RF frequency, includes a circuit for measuring the power output by the frequency generating circuit element, also known as a forward power analyzer 200, and a circuit for measuring the reflected power arriving back at the output terminal of the frequency generating circuit element using a reflected power analyzer 202, each electrically interposed in the high voltage connection between the AC-DC converter 112 and the RF amplifier 114 or incorporated in one of these components, or incorporated in the RF generator of Figures 5 and 6. Here, the frequency generating circuit is either the DC-AC converter 112 of Figures 1 to 4 or the RF generator 220 of Figures 5 and 6. Taking the RF generator 220 as an example, the generator includes a comparator circuit that compares the amount of reflected power to the forward power as a percentage of forward power or a ratio of power reaching the load (forward power minus reflected power), and a logic controller configured to change the output frequency of the RF generator 220 to obtain the maximum possible ratio or ratio. This also takes into account that it may not be possible to achieve 100% transmission of forward power to the load, but the maximum transmission, represented by the maximum ratio or ratio of power reaching the load to the forward power, is the desired outcome of the frequency tuning of the RF generator 220. Based on the relative ratio or ratio, the generator, under the control of the logic controller, changes its output frequency to determine the optimal momentary (instantaneous) ratio or ratio that represents the minimum reflection and maximum transmission of forward power to the load. The RF generator can perform frequency tuning autonomously, i.e., independently of any other control elements of the circuit.

[0038] Additionally, a controller 250 is provided and configured to control the operational settings of the PIN diode switch 152 and selectively include a capacitor in the shunt capacitance of the match circuit. The controller 250 includes a logic device in which the characteristics of the operational range of the switchable match 102 or 102' are programmed or set, including, for example, a field programmable array, a microcomputer, or the like. For example, the controller may be a recipe controller used to select a recipe, i.e., a set of RF or AC power and frequencies to be supplied to the plasma electrode or other components of the chamber, as well as the temperature of the substrate support, the electrode-to-substrate spacing, the gas mixture in the chamber environment, and other process variables that can be controlled or selected. Specifically, for a given process chamber, the match designer, with knowledge of the possible range of resistances and reactances of the load to which the match is connected, e.g., the process chamber or process chamber components and the plasma electrically coupled thereto, determines a desired set of individual shunt capacitance values ​​that will result in maximum transmission of power to the load, and therefore low reflection from the load. Additionally, the designer programs the controller 250 to select which of the switches 152a-d or 152a-h should be in the closed position and have the capacitors connected to them become part of the shunt capacitance of the switchable match 102 or 102'. Throughout, the shunt capacitance is the value of the total capacitance between or across the high voltage bus 132 and the return or ground bus 134 of the switchable match 102 or 102'. This value is the sum of the fixed capacitances of all the capacitors 150 connected between or across the high voltage bus 132 and the return or ground bus 134 of the switchable match 102 or 102'. The designer can then operate the load, i.e., here the chamber 122, in its normal operating environment or conditions to determine the power actually reflected from the chamber and the resulting pairs of values ​​of the load resistance R and reactance X that result in high transmission (low reflection) and relatively low transmission (high power reflection).With this information, the designer can change the capacitance value of the fixed capacitor 150 that may be switched into the shunt capacitance. The designer or user can then map the range of resistance R and reactance X value pairs where there is a maximum transmission (minimum reflection) between the power supply circuit and the load for each potential or actual shunt capacitance to obtain the results shown in Figures 9 to 11 for a non-zero integer multiple of the nominal output frequency of the RF generator 220 or DC-AC converter 112, e.g., 13.56 KHz, e.g., 27.12 MHz, as well as the maximum and minimum variation of the frequency of the generator or converter with respect to the output frequency. As a result, a designer can determine the matching characteristics of power delivery circuit 100, 100′ or 100″ when coupled to a load, including in combination with possible output frequency values ​​of RF generator 220 or DC-AC converter 112 at which the match will function adequately for its intended purpose within a range of shunt capacitance values ​​that can be achieved by selectively switching one or more of capacitors 150a-d or 150a-h (FIG. 6) into the shunt capacitance. This may or may not include an operating point at which less power reaches the load than the maximum possible power that can be delivered.

[0039] A range of power transmission rates for a range of values ​​of the load resistance R and reactance X is then programmed into the controller 250, which monitors the identity of the fixed capacitors 150a-d or 150a-h switched into the match circuit, and thus the operational status of the match. In one embodiment, if the ratio of reflected power to forward power starts to increase or the ratio of reflected power to forward power starts to decrease, the RF generator 220 or DC-AC converter 112 automatically changes the output frequency of the power signal to regain the maximum forward power reaching the load, i.e., the highest possible power transmission rate. The controller 250 monitors the output frequency of the RF generator or DC-AC converter 112. If the above frequency changes still result in a lower than possible or desired power transmission to the load (excessive reflection), then based on the output frequency of the RF generator 220 or DC-AC converter 112 and the known settings of the switches 152, and thus the identities of the fixed capacitors 150 currently included in the shunt capacitance, the controller 250 sends a signal to one or more of the switches 152 to change their operating settings while the load is being powered by the RF generator 220 or DC-AC converter 112, thereby changing the shunt capacitance to a value that results in a higher power transmission, preferably the highest possible transmission, for the current operating conditions, including those of the load. The controller continuously monitors the forward power, reflected power, and output frequency of the RF generator 220 or DC-AC converter 112 to control the switches 152, and thus establishes a value of the shunt capacitance that results in the highest possible power transmission.

[0040] In another embodiment, the controller may be programmed to select the switches 152a-d or 152a-h to be closed to include one or more of the fixed capacitors 150a-d or 150a-h in the shunt capacitance of the match circuit based on a process recipe executed in the chamber or processing environment. Here, the system designer determines the reactance and resistance values ​​of the load during each processing step, the capacitors 150a-d or 150a-h to be selectively switched into the shunt capacitance, measures the reflected power, or both, and determines the appropriate capacitance of the fixed capacitors 150a-d or 150a-h to be switched into the shunt capacitance to minimize the reflection at each processing step based on predicted or actual data. Here, the frequency of the power supply is controlled only by the power supply itself.

[0041] FIG. 13 is a schematic diagram of a power supply circuit incorporating a DC power supply 110 and an RF stage 254, where the RF stage combines the DC-AC converter 112 and AC or RF amplifier 114 of FIGS. 1 to 4 into a single unit. Here, AC power in the range of 200V to 480V is supplied to the DC power supply 110, which converts the AC input to a DC output that is supplied to the RF stage 254. The RF stage includes a DC-AC (RF) converter and at least one AC (RF) amplifier as its solid-state elements. To obtain a desired power output from the RF stage, more than one amplifier can be connected to the output of the DC-AC converter of the RF stage, the outputs of which are combined in a combiner (not shown). The AC or RF output of the RF stage 254 passes through a measurement unit 256, where values ​​of reflected powers Pr and Pi reflected from a load 260, e.g., a processing chamber component, are measured and transmitted from the measurement unit 256 to a power supply controller 258. The power supply controller 258 is configured to send control signals to the DC power supply 110 to change the value of the DV power output from the DC power supply 110 and to send control signals to the RF stage 254 to change its output frequency. The power supply controller 258 includes logic to measure the change in reflected power versus the output frequency of the RF stage and to set the frequency to a value that minimizes the reflected power of the load 260. As a result, the frequency of the power can be changed independently of the value of the shunt resistor in the switchable match 102, for example, when the value of the shunt capacitance is based on the expected reactance and resistance values ​​of the load based on the process recipe being executed in the process environment to which the load is exposed or of which the load forms a part.

[0042] Switchable matches operable under load, i.e., including hot switching of fixed capacitors in and out of the shunt capacitance, have been described herein along with variable frequency sources of AC or RF power, which allow a wide range of load resistance and reactance values ​​to be accommodated while minimizing forward power reflection by the load.

Claims

1. 1. A power supply circuit, comprising: A switchable match configured to change its electrical characteristics in response to a change in a load to which the switchable match is connected, the switchable match comprising: a high voltage bus connectable to said load; a low voltage bus connectable to a load such that the load is in series between the high voltage bus and the low voltage bus; at least two capacitors, each having a fixed value capacitance, selectively connectable between the high voltage bus and the low voltage bus; and a plurality of solid-state switches, the number of which corresponds to the number of the capacitors having a fixed capacitance connectable between the high-voltage bus and the low-voltage bus, each switch being constructed and arranged to selectively electrically connect or disconnect one of the capacitors having a fixed capacitance selectively connectable between the high-voltage bus and the low-voltage bus, between the high-voltage bus and the low-voltage bus. Including, The power supply circuit further comprises: a variable frequency power supply circuit including a variable frequency power supply operably connected to a high voltage output connection connected to the high voltage bus Equipped with The switchable match: a first fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the first fixed capacitance comprising the sum of the capacitances of one or more of the fixed capacitance capacitors, wherein with the first fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the switchable match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected to it over a first range of resistance and reactance values ​​of the load and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected to it over a second range of resistance and reactance values ​​of the load; a second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the second fixed capacitance including a sum of one or more of the capacitors of fixed capacitance different from the capacitor providing the first fixed capacitance, wherein with the second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the switchable match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a third range of resistance and reactance values ​​of the load different from the first range, and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a fourth range of resistance and reactance values ​​of the load; The power supply circuit may be configured to include:

2. 2. The power supply circuit of claim 1, wherein the variable frequency power supply circuit includes a DC power supply and a variable frequency output DC to AC converter.

3. 3. The power supply circuit of claim 2, wherein the variable frequency power supply circuit further comprises an amplifier.

4. 2. The power supply circuit of claim 1, wherein the variable frequency power supply is an RF generator.

5. The power supply circuit of claim 1 , wherein the switchable match is configured as an L match.

6. The power supply circuit of claim 1 , wherein the switchable match is configured as a π match.

7. 2. The power supply circuit of claim 1, wherein the range of resistance and reactance of the load in the second range and the range of resistance and reactance of the load in the fourth range overlap.

8. 2. The power supply circuit of claim 1, wherein the range of the resistance and reactance of the load in the first range overlaps with the range of the resistance and reactance of the load in the fourth range, or the range of the resistance and reactance of the load in the second range overlaps with the range of the resistance and reactance of the load in the third range.

9. 2. The power supply circuit of claim 1, wherein the low voltage bus is a ground bus.

10. 2. The power supply circuit of claim 1, wherein the solid-state switches are electrically interposed between corresponding ones of the fixed capacitance capacitors and the high voltage bus.

11. 1. A match connectable between a variable frequency power supply circuit and a load, the variable frequency power supply circuit including a variable frequency power supply operatively connected to the load, an electrical characteristic of the load being dynamically variable, the match comprising: a high voltage bus connectable to said load; a low voltage bus connectable to a load such that the load is in series between the high voltage bus and the low voltage bus; at least two capacitors, each having a fixed value capacitance, selectively connectable between the high voltage bus and the low voltage bus; and a plurality of solid-state switches, the number of which corresponds to the number of capacitors having a fixed capacitance connectable between the high-voltage bus and the low-voltage bus, each switch being constructed and arranged to selectively electrically connect or disconnect one of the capacitors having a fixed capacitance selectively connectable between the high-voltage bus and the low-voltage bus, between the high-voltage bus and the low-voltage bus. Including, The match a first fixed capacitance comprising a sum of the capacitances of one or more of the fixed capacitance capacitors electrically connected between the high voltage bus and the low voltage bus, wherein with the first fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a first range of resistance and reactance values ​​of the load and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a second range of resistance and reactance values ​​of the load; a second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the second fixed capacitance including a sum of one or more of the capacitors of fixed capacitance different from the capacitor providing the first fixed capacitance, wherein with the second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a third range of resistance and reactance values ​​of the load different from the first range, and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a fourth range of resistance and reactance values ​​of the load; ,match.

12. The match of claim 11 , wherein the match is configured as one of an L match and a π match.

13. 12. The match of claim 11, wherein the ranges of resistance and reactance of the load in the second range and the ranges of resistance and reactance of the load in the fourth range overlap.

14. 12. The match of claim 11, wherein the ranges of resistance and reactance of the load in the first range overlap with the ranges of resistance and reactance of the load in the fourth range, or the ranges of resistance and reactance of the load in the second range overlap with the ranges of resistance and reactance of the load in the third range.

15. 12. The match of claim 11, wherein the solid-state switches are electrically interposed between corresponding ones of the fixed capacitance capacitors and the high voltage bus.

16. 1. A method of matching a power supply to a load, comprising the steps of: providing a power supply circuit, the power supply circuit comprising: a switchable match configured to change its electrical characteristics in response to a change in the load to which the switchable match is connected, the switchable match comprising: a high voltage bus connectable to said load; a low voltage bus connectable to a load such that the load is in series between the high voltage bus and the low voltage bus; at least two capacitors, each having a fixed value capacitance, selectively connectable between the high voltage bus and the low voltage bus; and a plurality of solid-state switches, the number of which corresponds to the number of capacitors having a fixed capacitance connectable between the high-voltage bus and the low-voltage bus, each switch being constructed and arranged to selectively electrically connect or disconnect one of the capacitors having a fixed capacitance selectively connectable between the high-voltage bus and the low-voltage bus, between the high-voltage bus and the low-voltage bus. Including, The method further comprises: providing a variable frequency power supply circuit including a variable frequency power supply operably connected to a high voltage output connection connected to the high voltage bus; providing a first fixed capacitance comprising a sum of the capacitances of one or more of the fixed capacitance capacitors electrically connected between the high voltage bus and the low voltage bus, wherein with the first fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the switchable match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a first range of resistance and reactance values ​​of the load, and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a second range of resistance and reactance values ​​of the load; providing a second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the second fixed capacitance comprising a sum of one or more of the capacitors of fixed capacitance different from the capacitor providing the first fixed capacitance, wherein with the second fixed capacitance electrically connected between the high voltage bus and the low voltage bus, the switchable match is configured to transfer a greater percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a third range of resistance and reactance values ​​of the load different from the first range, and to transfer a lesser percentage of the power transferred to it by the variable frequency power supply to the load connected thereto over a fourth range of resistance and reactance values ​​of the load; A method comprising:

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