KR100226556B1 - Vhf/uhf reactor - Google Patents

Abstract

The present invention utilizes an equiaxed, integrated transmission line structure 32 of a low loss, very short transmission line that delivers alternating current power 30 to the plasma chamber 33, thereby enabling effective use of the VHF / UHF frequency for plasma generation. Post the treatment reactor 10. The use of VHF / UHF frequencies in the 50-800 MHz range provides viable throughput (separation or simultaneous etching and deposition) and allows for a reduced external voltage compared to conventional frequencies such as 13.56 MHz. Thus, the loss for small geometry devices that are sensitive to electricity is reduced.

Description

VHF / UHF (Ultra High Frequency / Ultra High Frequency) Reactor System

1 is a schematic representation of a UHF / VHF plasma reactor system according to the present invention.

2 is a schematic equivalent diagram of a transmission line structure included in the reactor of FIG.

3 is a schematic circuit diagram of a matching network.

4 is a schematic diagram showing an actual equivalent circuit of the schematic circuit of FIG.

Explanation of symbols for main parts of the drawings

10 plasma treatment reactor 11 housing

12 sidewall of plasma chamber 15 wafer

18: throttle belt 21: controlled radial flow

23 outlet branch 24 conductive screen

27: gas inlet branch pipe 30: power supply source

31 matching network 32 coaxial integrated transmission line structure

32C: wafer support electrode, center conductor, cathode

32I: Insulator 32O: External Conductor

33: plasma chamber 53: rear electrode

C1: variable shunt capacitor C2: variable series capacitor

The present invention relates to an RF plasma processing reactor and, more particularly, to a plasma reactor that uses UHF / VHF energy to generate a plasma.

Conventional semiconductor processing systems, such as chemical vapor deposition (CVD) and reactive ion etching (RIE) reactor systems, utilize RF energy with high frequencies of about 13.56-40.68 MHz at low frequencies of about 10-500 KHz. Below about 1 MHz, ions and electrons are accelerated by the vibration of the electric field or by any steady-state electric field in the plasma. At this relatively low frequency, the electrode sheath voltage on the wafer is typically up to one or more kilovolt peaks, which is well above the damage threshold of 200-300 volts. Above a few MHz, the electrons can still respond to changes in the electric field. Heavier ions cannot match the change in the electric field, but are accelerated by the steady state electric field. In this frequency range (and actual gas pressure and power levels), the steady state sheath voltage is in the range of hundreds to 1000 volts or more.

Preferred methods of reducing the bias voltage in an RF system include applying a magnetic field to the plasma. This B field confines electrons to the region near the wafer surface, increasing ion current and ion flux density, and thus reducing the need for voltage and ion energy. By comparison, the non-magnetic RIE process for etching silicon dioxide is based on RF energy applied at 13.56 MHz, 10-15 L asymmetric system, 50 millitorr pressure and about 8-10 to 1 anode area to wafer support cathode area. And can generate about 800 volts of wafer (cathode) sheath voltage. Applying a 60 gauss magnetic field can reduce the bias voltage from about 25-30%, or from 800 volts to about 500-600 volts, while increasing the etch rate by about 50%.

However, application of a normal field B parallel to the wafer results in an E × B ion / electron drift and a plasma density gradient in the wafer radial direction. Plasma inclination results in non-uniform etching, deposition and other film properties throughout the wafer. Non-uniformity can be achieved by rotating the magnetic field around the wafer, typically by using a pair of electromagnetic coils driven by a phase difference of 90 ° by mechanical movement of the permanent magnet, or by instantaneously adjusting the coil pair's current in steps or adjusting the magnetic field. Can be reduced by moving in proportion. However, although the non-uniform tilt can be reduced by rotating this magnetic field, some non-uniformity usually remains.

In addition, the magnetic field has a natural inherent disadvantage that is variable due to the presence of windows, slit valves, hardware and other discontinuities. Therefore, in order to use the magnetic field, it is necessary to design the chamber very carefully in consideration of the geometry of the magnetic field and the effects of various parts.

Finally, it is difficult to obtain a compact system by filling two pairs, or more, of coils, in particular one chamber, which is particularly self-reinforcing reactor surrounding the Helm Holtz coil structure and / or common load locks. This is even more true when using a chamber's multi-chamber system.

United States Patent No. 4,842,683 to inventor, et al. Discloses a specific reactor system that has the ability to temporarily and selectively change the field strength and direction and is designed for compact multi-chamber reactor systems.

Other known reactor systems use microwave energy at frequencies above 800 MHz, typically 2.45 GHz, to generate the plasma. This technique produces high density plasma and low particle energy, minimizing damage to the device by electrical induction. However, in many processes, such as the RIE of silicon dioxide, the minimum reaction threshold energy of the reaction must be exceeded. In this process, low-frequency power is supplied in addition to the microwave power to generate a voltage high enough to overcome the energy barrier. Thus, the resulting reactor system requires two power sources and a matching network, making it an expensive and complex system.

Although the relatively high frequency VHF / UHF energy of about 50 to 800 MHz has the potential to reduce the voltage that the wafer exhibits during plasma processing, this frequency of energy is not used in any semiconductor processing reactor on a commercial scale. In part, this failure is due to the need for very short transmission lines at frequencies in this range and, in general, because of the strict system design needed to effectively transfer energy into the chamber.

[Summary of invention]

It is a main object of the present invention to provide a plasma reactor that uses high frequency AC (AC) energy to generate plasma.

Another object of the present invention is to provide a plasma reactor that uses VHF / UHF energy to generate plasma.

It is yet another object of the present invention to provide a plasma reactor system that meets stringent VHF / UHF design requirements for applying VHF / UHF energy to the system's vacuum chamber to generate plasma.

It is still another object of the present invention to provide a plasma reactor in which the reactor itself is formed as a transmission line in order to effectively apply high frequency energy such as VHF / UHF energy to the plasma chamber of the reactor.

Another object of the present invention is a plasma reactor system that effectively applies VHF / UHF energy to a vacuum chamber to generate a treatment plasma while providing commercially viable deposition and etch rates for various conductors, insulators and semiconductor materials. In order to prevent electrical induced damage to semiconductor devices during processing, a plasma reactor system is characterized by a sufficiently low electrode sheath voltage of, for example, 200-300 volts.

According to one aspect, the present invention, which achieves the above object, is realized by a plasma processing reactor formed of a transmission line structure for directly applying AC energy to a plasma chamber.

According to another feature, the present invention is implemented by an RF power plasma processing reactor comprising a wafer chamber and a wafer support electrode configured to simulate a coaxial transmission line structure that applies AC energy to the plasma chamber to form a plasma.

The transmission line structure is preferably suitable for applying AC energy of about 50-800 MHz frequency to the chamber.

The transmission line structure (a) shorter than _^1/4 of the wavelength at the frequency of interest length or (b) _^1/2 multiple of the wavelength at the frequency of interest (n = 1, 2 ...) an effective electrical length selected from It is desirable to provide.

According to another feature, the present invention is a housing forming a plasma chamber; Cylindrical wafer support electrode means located within the housing; A gas inlet manifold located within the housing for providing the reaction gas to the plasma chamber; And an integrated transmission line structure suitable for applying AC energy of a selected frequency from an external source to the plasma chamber. The transmission line structure comprises a cylindrical positive electrode means, an outer conductor surrounding the cylindrical electrode means and an insulator between the cylindrical electrode means and the outer conductor, applying AC energy to the plasma chamber along the cylindrical electrode means, such as a coaxial cable, AC energy is applied from the chamber to the outer conductor via the chamber housing. Preferably, the plasma processing reactor has an annular discharge branch which surrounds the external electrode means. The branch tube has a conductive pumping screen surrounding the cylindrical electrode means. The exhaust gas flows radially from the periphery of the wafer support position through the pumping screen to the vacuum pumping means in a controlled manner. The pumping screen also electrically connects the chamber wall and the outer conductor to complete the current path to the outer conductor.

The invention also includes a matching network suitable for effectively applying external AC energy to the transmission line structure. In a preferred coupling arrangement, the cylindrical electrode means comprises or is connected to the rear electrode, the outer conductor comprises or is connected to the peripheral electrode, and the matching network is connected in series between the rear electrode and the peripheral electrode. Capacitors and variable shunt capacitors.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1. Overview of Reactor System (1)

A high frequency VHF / UHF plasma processing reactor 10 embodying the present invention is shown in FIG. According to one of several features to be described later, part of the reactor itself is formed in a transmission line structure for applying high frequency plasma generating energy from the matching network to the plasma chamber 33 (reference numeral 33 denotes the chamber and the plasma therein). ). This unique integrated transmission line structure satisfies very short transmission line requirements between the matching network and the load at the primary frequency of interest of 50-800 MHz. This makes it possible to effectively adjust the high frequency plasma generating energy to the plasma electrode to generate commercially acceptable etch rates and deposition rates under low ion energy and low sheath voltage. This voltage is low enough to prevent damage to electrically sensitive semiconductor devices. In addition, the VHF / UHF system of the present invention compensates for the disadvantages of the prior art, such as ECR reinforcement technology and magnetic reinforcement technology.

The reactor 10 is formed of aluminum or other suitable material and includes a vacuum chamber housing 11 having a side wall 12, an upper wall 13 and a lower wall 14. A vacuum seal 34, such as an O-ring, is inserted between the various mating surfaces to maintain a vacuum-tight seal. The interior of the chamber housing 11 is evacuated by a vacuum system 16 having one or more pumps. For example, the vacuum system 16 includes a turbomolecular pump 17 supported by a root blower (not shown) and a mechanical pump (not shown), and a throttle valve 18 for regulating pressure regardless of flow rate. It communicates with the chamber 33 through). Of course, other changes are possible and other devices may be used. For example, the turbo molecular pump 17 may be omitted in many high pressure dedicated systems.

The reactant gas is supplied from the one or more sources of pressurized gas to the chamber housing 11 via a path 19 via a computer controlled flow controller (not shown) and through the gas inlet branch 27 to the plasma chamber 33. Enter The branch tube may be of another suitable design for supplying the etching gas and / or deposition gas to the plasma chamber 33 to generate an etching and / or deposition plasma by applying a shower head or high frequency RF energy. Preferably, high frequency AC energy, such as VHF / UHF energy, at a frequency of 50-800 MHz is applied to the electrode 32C (commonly referred to as the system cathode), the top surface of the support wafer 15, and the sidewall 12 of the reactor chamber typically. , A second electrode (ie, system anode) comprising an upper wall 13 and / or branching pipe 27. Other embodiments are also possible. For example, if an electrode region ratio of high pressure and / or about 1: 1 (anode region: cathode region = 1: 1) is desired, electrically insulating the chamber wall from the plasma, two electrodes insulated from the chamber wall It may be preferable to use rather than to use the chamber wall as an anode.

Other features that the reactor chamber system 11 may have include the use of a fluid heat transfer medium to maintain the internal and / or external temperature of the gas inlet branch 27 above a certain value, below, or within a certain range; The use of a fluid heat transfer medium to heat or cool the cathode 32C; Resistive heating of the cathode 32C; The use of a gas heat transfer medium between the wafer 15 and the cathode 32C; And mechanical or electrostatic means for clamping the wafer 15 to the cathode 32C. This feature is disclosed in US Pat. No. 4,872,947, filed Oct. 10, 1989 and US Pat. No. 4,842,683, filed June 27, 1989.

The chamber of the present invention is useful for both high and low pressure operations, and the space d between the wafer support cathode 32C and the gas inlet branch 27 can be tailored for high and low pressure operation. For example, in the high pressure operation of 500 millitorr to 50 Torr, the space d is preferably about 5 cm or less, and in the low pressure operation of 2 to 500 millitorr, the space d is preferably about 5 cm or more. The chamber may comprise a fixed space d as shown, or may use a variable space, such as an exchangeable stretchable chamber top. The reactor 10 includes high pressure and low pressure deposition of materials such as silicon oxide and silicon nitride; Low pressure anisotropic RIE of materials such as silicon dioxide, silicon nitride, silicon, polysilicon and aluminum; High pressure plasma etching of the above materials; It is useful for performing CVD faceting, which involves co-deposition and etching of the above materials. Examples of such and other processes in which reactor 10 may be used are disclosed in US patent applications such as Collins, which is named VHF / UHF PLASMA PROCESS FOR USE IN FORMING INTEGRATED CIRCUIT STRUCTURES ON SEMICONDUCTOR WAFERS.

Preferably, the gas flow from the gas inlet branch 27 is pumped radially outward from the wafer 15 after downwardly directed toward the wafer 15. To this end, an annular vacuum discharge branch 23 is formed for the cathode transmission line structure 32, one side of the chamber wall 12, the other side of the outer transmission line conductor 320, and the bottom of the chamber bottom wall ( 14, and the upper portion is defined between the conductive pumping screen 24. The screen 24 is inserted between the outlet branch 23 and the plasma chamber 33 to provide a conductive path between the outer conductor 320 of the transmission line structure 32 and the chamber sidewall 12. The outlet branch 23 forms an annular pumping channel for uniformly radially pumping the exhaust gas from around the wafer 15. The outlet branch 23 communicates to the exhaust gas system 16 via one or more holes 26 in the bottom wall. All gas is along the path 19 to the gas inlet branch 27, from the inlet branch to the wafer 15 along the path 20, radially outward along the path 21 from the edge around the wafer, and It flows through the screen 24 to the gas outlet branch 23 and then from the outlet branch 23 along the path 22 to the exhaust system 16.

Referring to FIGS. 1 and 2, high frequency VHF / UHF energy with a frequency of 50-800 MHz from the power supply 30 is input to the matching network 31 and transmitted to the chamber 33 by the transmission line structure 32. Is applied to the plasma.

2. Transmission line requirements

The transmission line structure 32 is a coaxial transmission line with very low loss and a very short coaxial transmission line to minimize deformation of the load impedance Z _L such that the matching network 31 does not exhibit an impedance different from the load impedance.

The characteristic impedance Z ₀ of the coaxial transmission line structure 32 is as follows:

Where μ = μο.μr (permeability);

μr = 1 (for nonmagnetic material);

μo = 4π × 10 ⁻⁷ H / m;

∈ = ∈o. R (dielectric constant);

∈r = relative dielectric constant;

O = 8.85 × 10 ⁻¹² F / m;

r ₀ = inner radius of the outer conductor;

r _i = radius of the inner conductor.

If the transmission line structure is terminated with a plasma in the chamber, the input impedance Z _in (the impedance seen in the matching network) of the transmission line structure is a function of the characteristic impedance Z ₀ :

Where Z _L = load impedance of the plasma;

l = actual length of the transmission line;

β (phase constant) = 2π / λ _m , λ _m = wavelength in the material of interest;

λ _m = , ε _r = relative dielectric constant, μ _r = specific permeability,

λ _fs (wavelength in free space) = 300 × 10 ⁶ (m / sec) / frequency (Hz).

According to equation (2), if Z _{0 =} Z _L , the same impedance is seen in the matching network regardless of the length of the transmission line. However, if Z ₀ ≠ Z _L , then the impedance of the transmission line transforms the load impedance Z _L to any new impedance of λ / 2 periods. To minimize distortion, the transmission line should be very short, ie 1/10 to 1/20 of the AC energy wavelength at the highest frequency used. For example, for the prior art frequency 13.56 MHz, λ _fs is much shorter, about 1 m. Thus, at high frequency of 300 MHz, the transmission line structure between the matching network and the plasma load should be 0.05-0.1 m or less so as not to exceed the maximum length requirement.

3. Transmission line structure (32)

A suitable high frequency coaxial transmission line design requires a supply path through the short transmission line with low characteristic impedance from the matching network to the wafer and a return path along the transmission line. This design surrounds the cathode 32C, the annular concentric conductors 32O, and the cathodes 32C and insulates the cathode from the annular concentric conductors 32O, as shown in FIGS. It is preferably made by a transmission line structure 32 comprising a low loss non-porous insulator 32I that displaces (or otherwise breaks down). For example, Teflon ^™ or quartz materials are preferred because they have high dielectric strength and low relative permittivity and low losses. The input side of this structure is connected to the matching network by the method described below. Insulated cathode 32C and external conductor 3300 provide separate current paths between matching network 31 and plasma 33. The first reversible current path 37 runs from the matching network along the outer periphery of the cathode 32C to the plasma sheath of the upper electrode surface. The second reversible current path 38 runs from the plasma chamber 33 along the upper inside of the gas inlet branch 27 and the chamber wall 12, along the conductive exhaust branch screen 24, to the outer conductor 32 O. ) To the matching network. It should be noted that the outlet branch screen 24 is part of the uniform radiant gas pumping system and the return path for the RF current.

During the application of alternating energy, the RF current path alternates between the direction shown and the reverse direction. Since the structure of the transmission line structure 32 is a coaxial cable type, the internal impedance of the cathode 32C is high (compared to the outside), and the impedance is high toward the outside of the conductor 3300 (compared to the inside), and thus the RF Current is concentrated in the coaxial transmission line on the outer surface of the cathode 32C and on the inner surface of the outer conductor 3300. At high VHF / UHF operating frequencies of about 50-800 MHz, these currents are concentrated to skin thicknesses of tenths of a millimeter deep. For example, the use of larger wafers 4-8 inches in diameter with proportional diameter cathodes 32C and outer conductors 32O provides a large effective cross-sectional area and a low impedance current path along the transmission line structure. .

If the coaxial transmission line structure 32 is terminated with a pure resistance, such as characteristic impedance Z ₀ , as shown in equation (2) above, the matching network will show a constant impedance Z ₀ regardless of the length of the transmission line. This is not the case here, however, because the plasma is operated at a constant pressure, power and frequency range and contains various gases, which collectively changes the load impedance Z _L appearing at the ends of the transmission line 32. . Since the load Z _L does not match the non-ideal (non-lossless) transmission line 32, standing waves present in the transmission line increase resistance loss and dielectric loss between the transmission line and the matching network 31, and the like. Although the matching network 31 can be used to eliminate the standing wave and thus the loss from the input of the matching network to the amplifier or power supply 30, the matching network, the transmission line structure 32 and the plasma in the chamber are responsible for the resonant system. As a result, the resistance loss and dielectric loss between the transmission line structure 32 and the matching network 31 are increased. In summary, the load impedance Z _L is not matched due to loss, but the loss is smallest when Z _L ≒ Z _O. To reduce the losses due to mismatching of the load, the coaxial transmission line structure 32 is designed to have a characteristic impedance Z _O that is most suitable for the range of load impedances involved in plasma operation. Typically, in the above operating parameters and materials, the series equivalent RC load impedance Z _L represented by the plasma on the transmission line includes a resistance of about 1 to 30 ohms and a capacitance of about 50 to 400 picofarads. Therefore, the optimal value selects the characteristic impedance Z _O of the transmission line centered on the load impedance range of about 10 to 15 ohms.

As shown in equation (2), the transmission line line 32 needs to be very short to prevent deformation of the plasma impedance seen in the matching network. Preferred transmission lines should be smaller than λ / 4, which is a quarter wavelength, and more preferably about 0.05λ to 0.1λ. More generally, it is not possible to place the matching network at a distance shorter than 1/4 wavelength to the load, but it is an integer multiple of half wavelength (λ / 2) (n / 2λ, n = 1, 2, 3, ... That is, by using transmission line lengths corresponding to λ / 2, λ, 3 / 2λ, etc., a half-wavelength period can be used in connection with impedance deformation. More precisely, preferred values are λ / 2 to λ / 2 + 0.05λ; λ to λ + 0.05λ: 3 / 2λ to 3 / 2λ + 0.05λ and so on. Under this condition, the matching network should not be located in odd multiples of (1/4) wavelengths (λ / 4, 3 / 4λ, 5 / 4λ) because of the quarter wavelength portion (i.e., when n is odd). This is because Z _L is modified such that 4λ) is Z _in = Z ₀ ² / Z _L , and Z _in is very large because Z _L is small. Thus, the matching network cannot match the plasma load, making it difficult to deliver power to the plasma without undesirable system resonance and power loss.

In addition, in order to effectively transfer power, the inner diameter (cross section size) of the outer conductor 3200 should not be much larger than the outer diameter (cross section size) of the central conductor 32C.

In summary, the chamber includes a transmission line structure that delivers VHF or UHF power of about 50 to 800 MHz from the matching network 31 to the plasma 33. This transmission line structure (a) is very short compared to 1/4 wavelength at the frequency of interest to avoid undesired deformation of the plasma impedance, or alternatively corresponds to an integer multiple of approximately half wavelength; (b) has a characteristic Z ₀ selected to suppress losses due to standing waves present in the transmission line between the plasma and the matching network; (c) The central conductor has an outer conductor path cross sectional size that is not substantially larger than the cross sectional size.

4. Matching Network

By keeping the actual length of the transmission line structure shorter than 1/4 wavelength, i.e., less than 1/10 or 1/20 of the wavelength or slightly greater than the integer multiple of the aforementioned 1/2 wavelength, when the load is a typical low series RC impedance Some inductive impedance components are provided in the transmission line network. Usually, to match resistive loads, L-type networks require an inductance in series with the capacitance. However, the very short transmission line structure 32 terminates with very low resistance and low impedance loads, thus showing inductive components as well as resistive components in the matching network. Although the plasma 33 is an RC load, the inductive component is present so that no inductance is needed inside the matching network. This enables a simple matching network with two variable capacitors.

3 and 4, a preferred matching network 31 is connected between the input of the matching network and the output of the matching network and the shunt capacitor C ₁ connected between the input and ground of the matching network. L-type network with series capacitor C ₂ directly coupled to the input of 32). The matching network arrangement of FIGS. 3 and 4 is suitable when the output resistance impedance of a typical source is 50 ohms and the resistive impedance component of a conventional plasma 33 is 1 to 50 ohms, and generally the output resistance component of the source is Suitable when larger than the resistance component of the load. If the resistance portion of the plasma load impedance Z _L exceeds the output resistance impedance of the source, the connection of the input and output of the matching network is reversed.

The capacitors C ₁ and C ₂ are typically air capacitors having a fixed conductor plate and a processed conductor plate formed of a copper plate or a silver plated copper plate. The fixed conductor plate 58 of the capacitor C ₁ is the case or housing 50 of the matching network and is connected to ground. Referring together to FIG. 1, the plate 57 is connected to an input 50 from a power source 30 and is controlled by a motor M ₁ under the control of the system computer 60 based on real time Z _in or reflected power. Run along path 62. This input is used to adjust the capacitance of the capacitor by adjusting the spacing of the plates in a known manner. Teflon ^™ or other suitable low loss high dielectric constant material thin plate 61 is inserted between capacitor plate 57 and capacitor plate 58 to prevent arcing. In FIG. 1 the computer 60 (or discrete computer) is conveniently used to control the operation of the power source 30 and to select a suitable frequency within the range of interest to select the desired voltage and power combination for a given process. The ability to control the voltage and power at high frequencies of 50-800 MHz provides a very large process window.

Similarly configured series capacitor C ₂ is connected to an insulating arc-resistant plate 59 made of a material such as Teflon ^TM and to the input 50 and in the same way as in the case of capacitor C ₁ to change the capacitance of C ₂ . And a leg 56 which is moved along the path 63 by the motor M ₂ . The stationary leg 55 is connected to the output 52 of the matching network, which includes a clip 54 coupled with the pillar 53 of the conductor extending downward. Pillar 530 is part of cathode 32C or is electrically connected to the cathode.

Typically two movable capacitor legs are electrically connected to input 50 by conductor straps formed of a material such as copper. The annular electrode 64 between the bottom of the reactor chamber housing 12 and the top of the matching network case 35 connects the matching network 31 and the outer conductor 3300 with the same potential, ie, system ground, and the matching net. The required coaxial cable coupling or termination is established between the matching network 31 and the transmission line structure 32 together with the output 52 of the work. This structure also capacitively couples the matching network to the transmission line structure to prevent direct current bias when the sheath voltages are different.

For a plasma RC impedance of 50 to 400 picoferrets in series with typical process variables and 1-30 ohms, C ₁ and C ₂ will vary over a range of about 10 to 400 picofarads. Of course, if very short transmission line conditions are not met, the inductor needs to be connected in series with C ₂ . Those skilled in the art will readily be able to derive and use other standard matching network arrangements suitable for the system of the present invention. For example, in low frequency operation, any inductor can be used in series with C ₂ . In addition, the matching network may have a separate DC blocking capacitor.

Claims (17)

A plasma processing reactor, comprising: (a) a housing having a wall defining a plasma chamber; (b) wafer supported cylindrical electrode means in the plasma chamber defining a wafer support position; (c) a gas inlet branch located in the housing for supplying a reaction gas to the plasma chamber; (d) vacuum pump means; And (e) an integrated transmission line structure for applying AC energy of a selected frequency from said external source to said plasma chamber, said integrated transmission line structure comprising: (i) said cylindrical electrode means; (Ii) an outer conductor surrounding said cylindrical electrode means; (Iii) electrical connection means for electrically connecting said outer conductor to said plasma chamber wall; And (iii) an insulator between the cylindrical electrode means and the external conductor, wherein AC energy applied to the transmission furnace structure is coaxially connected to the plasma chamber along the cylindrical electrode means and from the plasma chamber. And a plasma processing reactor connected to the external conductor. 2. The plasma processing reactor of claim 1, further comprising a matching network for contacting the electrode means and the external conductor to couple the AC energy to the transmission line structure. 3. The first variable capacitor of claim 2, wherein the cylindrical electrode means is electrically connected to the pillar electrode, the outer conductor is connected to the peripheral electrode, and the matching network is connected between the pillar electrode and the peripheral electrode. A plasma processing reactor comprising two variable capacitors. 4. The plasma processing reactor of any one of claims 1 to 3, wherein the length of the transmission line structure is less than 1/4 wavelength at a selected frequency. 4. A method according to any one of claims 1 to 3, wherein the frequency of the external AC energy is in the range of about 50 to 800 MHz and the length of the transmission line structure is less than 1/4 wavelength at the selected frequency. Plasma treatment reactor. The transmission line structure according to any one of claims 1 to 3, wherein the length of the transmission line structure is (nλ) / 2, where n = 1, 2, 3, ..., and Plasma treatment reactor, characterized in that the wavelength of the AC energy. 4. The method of any one of claims 1 to 3, wherein the frequency of the AC energy is selected within the range of about 50 to 800 MHz, wherein the length of the transmission line structure is (nλ) / 2, where n = 1, 2, 3, etc., wherein λ is a wavelength at a selected frequency. The plasma processing reactor of claim 1, wherein the AC energy is applied to the transmission line structure through a matching network including a first variable capacitor and a second variable capacitor. 9. The plasma processing reactor of claim 8, wherein the matching network further comprises an inductor connected in series with the second variable capacitor. A plasma processing reactor comprising: (a) a chamber; And (b) an electrode in the chamber, the electrode comprising: (i) a central conductor providing a first reversible path for connecting high frequency AC energy from an energy source to a plasma in the chamber; (Ii) a coaxial concentric outer conductor providing a second reversible path for connecting the high frequency AC energy from the energy source to a plasma in the chamber; And (iii) a coaxial concentric dielectric interposed between the center conductor and the outer conductor, wherein the electrode has a characteristic transfer impedance substantially equal to the chamber load impedance. 11. The plasma processing reactor of claim 10, further comprising a matching network that optimally connects the high frequency AC energy from the energy source to the electrode. 11. The plasma processing reactor of claim 10, wherein the central conductor further comprises a wafer support. 11. The plasma processing reactor of claim 10, wherein the electrode further comprises a transmission line having an impedance of 5 to 50 ohms. 11. The plasma processing reactor of claim 10, wherein the high frequency AC energy is selected in the range of 50 to 800 MHz. 14. The plasma processing reactor of claim 13, wherein the length of the transmission line is less than a quarter wavelength at a selected AC energy frequency. 14. The plasma treatment of claim 13, wherein the length of the transmission line is (nλ) / 2, where n = 1, 2, 3, etc., and λ is a wavelength at a selected AC energy frequency. Reactor. 12. The system of claim 11, wherein the matching network comprises: (a) a variable shunt capacitor; And (b) a variable series capacitor.