Power modulation for etching high aspect ratio features

A method of etching a substrate is described. The method includes disposing a substrate having a surface exposing a first material and a second material in a processing space of a plasma processing system, and performing a modulated plasma etching process to selectively remove the first material at a rate greater than removing the second material. The modulated plasma etching process comprises a power modulation cycle having sequential power application steps that includes: applying a radio frequency (RF) signal to the plasma processing system at a first power level, applying the RF signal to the plasma processing system at a second power level, and applying the RF signal to the plasma processing system at a third power level. Thereafter, the power modulation cycle is repeated at least one more cycle, wherein each modulation cycle includes a modulation time period.

FIELD OF INVENTION

The invention relates to a method for selectively etching one material on a substrate relative to another material on the substrate using plasma.

DESCRIPTION OF RELATED ART

The need to remain competitive in cost and performance in the production of semiconductor devices has caused a continuous increase in device density of integrated circuits. To accomplish higher integration and miniaturization in a semiconductor integrated circuit, miniaturization of a circuit pattern formed on a semiconductor wafer must also be accomplished.

Plasma etching is a standard technique used to manufacture semiconductor integrated circuitry by transferring geometric shapes and patterns from a lithographic mask to underlying layers of a semiconductor wafer. With increasing aspect ratios and more complex materials, the need for state-of-the-art etching processes that meet selectivity and profile control requirements is becoming increasingly critical.

SUMMARY OF THE INVENTION

Embodiments of the invention relate to a method for selectively etching one material on a substrate relative to another material on the substrate using plasma.

According to one embodiment, a method of etching a substrate is described. The method includes disposing a substrate having a surface exposing a first material and a second material in a processing space of a plasma processing system, and performing a modulated plasma etching process to selectively remove the first material at a rate greater than removing the second material. The modulated plasma etching process comprises a power modulation cycle having sequential power application steps that includes: applying a radio frequency (RF) signal to the plasma processing system at a first power level, applying the RF signal to the plasma processing system at a second power level, and applying the RF signal to the plasma processing system at a third power level. Thereafter, the power modulation cycle is repeated at least one more cycle, wherein each modulation cycle includes a modulation time period.

DETAILED DESCRIPTION OF SEVERAL EMBODIMENTS

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of a processing system, descriptions of various components and processes used therein. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.

Similarly, for purposes of explanation, specific numbers, materials, and configurations are set forth in order to provide a thorough understanding of the invention. Nevertheless, the invention may be practiced without specific details. Furthermore, it is understood that the various embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

“Substrate” as used herein generically refers to the object being processed in accordance with the invention. The substrate may include any material portion or structure of a device, particularly a semiconductor or other electronics device, and may, for example, be a base substrate structure, such as a semiconductor wafer or a layer on or overlying a base substrate structure such as a thin film. The substrate may be a conventional silicon substrate or other bulk substrate comprising a layer of semiconductive material. As used herein, the term “bulk substrate” means and includes not only silicon wafers, but also silicon-on-insulator (“SOI”) substrates, such as silicon-on-sapphire (“SOS”) substrates and silicon-on-glass (“SOG”) substrates, epitaxial layers of silicon on a base semiconductor foundation, and other semiconductor or optoelectronic materials, such as silicon-germanium, germanium, gallium arsenide, gallium nitride, and indium phosphide. The substrate may be doped or undoped. Thus, substrate is not intended to be limited to any particular base structure, underlying layer or overlying layer, patterned or un-patterned, but rather, is contemplated to include any such layer or base structure, and any combination of layers and/or base structures. The description below may reference particular types of substrates, but this is for illustrative purposes only and not limitation.

During pattern etching, a dry plasma etching process can be utilized, wherein plasma is formed from a process gas by coupling electromagnetic (EM) energy, such as radio frequency (RF) power, to the process gas in order to heat electrons and cause subsequent ionization and dissociation of the atomic and/or molecular constituents of the process gas. Furthermore, the coupling of electromagnetic energy can be used to control the energy level of charged species incident on the exposed substrate surface. Through control of various plasma properties, including charged specie density, charged specie flux, charged specie energy, chemical flux, etc., a desired end result for the plasma etching process can be achieved according to embodiments described herein. In particular, embodiments are provided that achieve target etch selectivity and profile control.

As described above, materials, typically employed in semiconductor device manufacturing, are selectively removed relative to one another using modulated plasma etching. Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,FIGS. 1A, 1B, and 2illustrate a method for etching a material on a microelectronic workpiece according to an embodiment. The method is pictorially illustrated inFIGS. 1A and 1B, and presented by way of a flow chart200inFIG. 2. As presented inFIG. 2, the flow chart200begins in212with disposing a substrate110having a surface exposing a first material (130) and a second material (140) in a processing space of a plasma processing system.

As shown inFIG. 1A, the substrate110can include a patterned layer140overlying a film stack, including one or more layers120,130to be etched or patterned. The patterned layer140can define an open feature pattern150overlying one or more additional layers. The substrate110further includes device layers. The device layers can include any thin film or structure on the substrate into which a pattern is to be transferred, or a target material is to be removed.

Layers130and140can be any material utilized in the manufacture of electronic devices, including semiconductor devices, electro-mechanical devices, photovoltaic devices, etc. However, to selectively etch one layer (e.g., layer130of a first material) relative to another layer (e.g., layer140of a second material), the material composition of the two layers is inherently different, such that each layer exhibits a different etch resistance when exposed to an etchant. Layers130,140can be organic or inorganic materials. Layers130,140can be silicon-containing material, germanium-containing material, carbon-containing material, or metal-containing material. For example, silicon-containing materials can include amorphous silicon (a-Si), polycrystalline silicon (poly-Si), single crystal silicon, doped silicon, silicon oxide (SiOx), silicon nitride (SiNy), silicon carbide (SiCz), silicon oxynitride (SiOxNy), silicon oxycarbide (SiOxCz), silicon-germanium alloy (SixGe1-x), etc. Metal-containing materials can include a metal, a metal alloy, a transition metal (e.g., Ti, Ta, W, Ru, Co, Ni, Hf, etc.), transition metal oxide (e.g., titanium oxide (TiOx)), transition metal nitride (e.g., titanium nitride (TiNy)), carbides, chalcogenides, etc. Layers130,140can include organic resists, anti-reflective coatings, or planarization layers, or silicon-containing resists, anti-reflective coatings, or planarization layers with varying degrees of silicon content. The above materials may be deposited using vapor deposition techniques, or spin-on deposition techniques.

InFIG. 1Band in214ofFIG. 2, the open feature pattern150overlying one or more additional layers is extended into layer130by performing a modulated plasma etching process to selectively remove the first material (130) at a rate greater than removing the second material (140). The modulated plasma etching process includes a power modulation cycle having sequential power application steps. The sequential power application steps involve applying a radio frequency (RF) signal to the plasma processing system at a first power level, applying the RF signal to the plasma processing system at a second power level, and applying the RF signal to the plasma processing system at a third power level, wherein the first, second, and third power levels differ in value from one another. As necessary to complete the etch process to meet target specifications, the modulation cycle is repeated at least one more cycle, wherein each modulation cycle includes a modulation time period. The modulation cycle can include a periodic modulation cycle.

Referring now toFIG. 3, a modulated plasma etching process300is illustrated. In one embodiment, the modulated plasma etching process300includes modulation of the radio frequency (RF) power delivered to a substrate holder or susceptor upon which the substrate is positioned. The substrate holder can position the substrate facing an RF powered electrode, such as a capacitive coupling element or inductive coupling element (to be described below). Alternatively, the substrate holder can position the substrate facing a slotted plane antenna, wherein power at a microwave frequency is coupled to the slotted plane antenna, for example. Exemplary systems are depicted inFIGS. 4 through 6. While the modulation of the RF power delivered to the substrate holder or susceptor is described, it can alternatively be coupled to other power coupling elements in the plasma processing system.

The modulated plasma etching process depicts a modulation cycle310with a first power level (P1)312, a second power level (P2)314, and a third power level (P3)316. As shown inFIG. 3, the first power level312exceeds the second power level314, and the second power level314exceeds the third power level316. The third power level316can include a power-off state, or relatively low power state. According to one embodiment, the order of the power level sequence is shown inFIG. 3; however, the power level sequence can be different (e.g., P3-P2-P1, P2-P3-P1, P2-P1-P3, etc.).

The second power level314can range from 20% to 80% of the first power level312. Alternatively, the second power level314can range from 40% to 60% of the first power level312. The third power level316can range from 0% to 50% of the second power level314. Alternatively, the third power level316can range from 0% to 20% of the second power level314.

As illustrated inFIG. 3, the modulation cycle310can include a periodic modulation cycle. The modulation cycle310can include a modulation frequency that ranges from 1 Hz to 100 kHz. Alternatively, the modulation frequency can range from 5 Hz to 50 Hz. Alternatively yet, the modulation frequency can be equal to or greater than 1 kHz. The applying the RF signal at the first RF power level can range from 5% to 20% (indicated as322) of the time period of the modulation cycle310. The applying the RF signal at the second RF power level314can range from 30% to 50% (indicated as324) of the time period of the modulation cycle. The applying the RF signal at the third RF power level316can range from 30% to 60% (indicated as326) of the time period of the modulation cycle.

The inventors surmise that the first power level312can be used to ‘break-through’ passivating layers (e.g., native oxide, etc.), reaction byproduct, residue, etc. in preparation of, during, or following the etching of layer130(FIGS. 1A and 1B) or steps during the etching of layer130. The inventors also surmise that the second power level314can be used to selectively etch layer130(relative to layer140) and optionally passivate various surfaces to impact selectivity and profile control. The inventors further surmise that the third power level316can be used to exhaust and/or purge byproduct from the process space.

During the modulated plasma etching process, at least one property of the modulation cycle may be adjusted. The at least one property may include a power amplitude, a modulation frequency, a modulation duty cycle, a modulation waveform, or a modulation phase (relative to other modulated properties, such as gas flow, source and/or bias power, etc.).

In one embodiment, the modulated plasma etching process may comprise a process parameter space that includes: a chamber pressure ranging up to about 1000 mtorr (millitorr) (e.g., up to about 200 mtorr, or up to about 50 to 150 mtorr), a halogen-containing gas flow rate ranging up to about 2000 sccm (standard cubic centimeters per minute) (e.g., up to about 1000 sccm, or about 1 sccm to about 200 sccm), a polymerizing gas flow rate ranging up to about 2000 sccm (e.g., up to about 1000 sccm, or about 1 sccm to about 100 sccm), an optional noble gas (e.g., He or Ar) flow rate ranging up to about 2000 sccm (e.g., up to about 1000 sccm), an upper electrode/antenna power ranging up to about 2000-to-5000 W (watts) (e.g., up to about 1000 W, or up to about 600 W), and a lower electrode power ranging up to about 1000-to-2000 W (e.g., up to about 600 W, or up to about 100 W, or up to 50 W). Also, the upper electrode/antenna frequency can range from about 0.1 MHz to about 3 GHz. In addition, the lower electrode RF frequency can range from about 0.1 MHz to about 100 MHz, e.g., about 2 MHz.

One or more of the methods for etching a substrate described above may be performed utilizing a plasma processing system, such as the one the systems described inFIGS. 4 through 6. However, the methods discussed are not to be limited in scope by this exemplary presentation. The method of etching a substrate according to various embodiments described above may be performed in other plasma processing systems not specifically described below. Furthermore, various componentry described inFIGS. 4 through 6can be utilized, replaced with, or complemented by other componentry not described. While one or more RF or microwave power sources of various electromagnetic frequency are described, multiple sources above, below, or surrounding the substrate W are contemplated.

FIG. 4is a schematic cross-sectional view of a microwave plasma processing apparatus in accordance with embodiments herein. The microwave plasma processing apparatus can be configured to perform plasma processing, such as plasma etching, plasma enhanced chemical vapor deposition (PECVD), plasma enhanced atomic layer deposition (PEALD), etc., via surface wave plasma excitation at microwave frequencies using, for example, a flat, plate-type slot antenna. Plasma processing can be executed within processing chamber401, which can be a cylindrical vacuum chamber composed of a machined or cast metal, such as aluminum or stainless steel. The processing chamber401is electrically grounded using, for example, ground wire402. The processing chamber401defines a processing vessel providing a process space PS for plasma generation. An inner wall of the processing vessel can be coated with a protective barrier, such as alumina, yttria, or other protectant.

At a lower, central area within the processing chamber401, a susceptor412(which can be disc-shaped) can serve as a mounting table on which, for example, a substrate W to be processed (such as a semiconductor wafer) can be mounted. Substrate W can be moved into the processing chamber401through loading/unloading port437and gate valve427. An electrostatic chuck436is provided on a top surface of the susceptor412. Clamp electrode435is electrically connected to DC (direct current) power source439. The electrostatic chuck436attracts the substrate W thereto via an electrostatic force generated when a DC voltage from the DC power source439is applied to the clamp electrode435so that substrate W is securely mounted on the susceptor412.

A high-frequency power source429for applying a RF (radio frequency) bias is electrically connected to the susceptor412, or bias electrode through an impedance matching unit428(to match impedance or minimize reflected power) and a power feeding rod424. The high-frequency power source429can output a high-frequency voltage in a range from, for example, 0.2 MHz to 20 MHz, e.g., 13.56 MHz. Applying a high frequency bias power attracts ions, generated by the plasma in the processing chamber401, to substrate W. Power source429can include a signal generator and amplifier for modulating the amplitude and power output from the power source429according to the modulation cycle described above. A focus ring438is provided radially outside the electrostatic chuck436to surround the substrate W.

A coolant flow path444can extend, for example, in a circumferential direction, within susceptor412and can be configured to receive circulated coolant to assist with controlling a processing temperature of substrate W on the electrostatic chuck436. Additionally, a heat transfer gas from a heat transfer gas supply unit (not illustrated) can be supplied to a space between a top surface of the electrostatic chuck436and a rear surface of the substrate W through a gas supply line445.

An exhaust path433can be formed along an outer periphery of support unit414and/or conductive support unit416and an inner wall of the processing chamber401in which an annular baffle plate434is attached to the top or inlet of the exhaust path433and an exhaust port432(or multiple exhaust ports), which is provided in a bottom portion of the exhaust path433. A gas exhaust unit430is connected to each exhaust port432through gas exhaust line431, which can have multiple exhaust lines. The gas exhaust unit430can include a vacuum pump such as a turbo molecular pump configured to decompress the plasma processing space within the processing chamber401to a desired vacuum condition.

An upper portion of the microwave plasma processing apparatus will now be described. A dielectric window457is arranged to seal an upper portion of the processing chamber401, through which electromagnetic radiation at microwave frequencies can propagate to the process space PS. A space just below the dielectric window457within the processing chamber401serves as a plasma generation space as process space PS. The dielectric window457can be made of a microwave-permeable dielectric material, such as quartz or ceramic, including aluminum oxide, and can have a thickness of, for example, about 20 mm (millimeters) or sufficient thickness to mechanically resist the pressure difference between an interior of the processing chamber401and the ambient environment. The dielectric window457can be provided with a slot plate454which can be a conductor attached to, or disposed on, a top surface of the dielectric window457. The slot plate454can have a plurality of slot pairs that are configured to irradiate microwaves distributed concentrically in a rotationally symmetric arrangement, though other geometric configurations can be used. On the slot plate454, a dielectric plate456can shorten the wavelength of microwaves propagated inside the slot plate454. The slot plate454is electromagnetically coupled to a microwave transmission line458. A slot antenna455, which can be a flat plate-type slot antenna, for example, or a disc-shaped, radial line slot antenna, can include the slot plate454, the dielectric plate456, and an antenna rear plate (not shown) provided to be opposite to the slot plate454.

The microwave transmission line458is a line configured to propagate or transmit electromagnetic waves at microwave frequencies or other frequencies, for example, microwaves of 2.45 GHz, which are output from a microwave generator460at a predetermined power level, to the slot antenna455. The microwave transmission line458can include a waveguide462, a waveguide-coaxial line converter464, and a coaxial line466. The waveguide462can be, for example, a rectangular waveguide configured to transmit microwaves from the microwave generator460to the waveguide-coaxial line converter464. The coaxial line466extends from the waveguide-coaxial line converter464to the central portion of the top of the processing chamber401and a terminal end of the coaxial line466is coupled to the slot antenna455through the dielectric plate456. An outer conductor469and an inner conductor468can define a space for wave transmission. A connector unit479is connected to the lower end of the inner conductor468.

In addition, as electromagnetic waves propagate radially through the dielectric plate456, the wavelength shortens, and the wave mode transitions to plane waves of circular polarization having two orthogonal polarization components from each slot pair of the slot antenna455that are radiated toward the inside of the processing chamber401. Process gas in the vicinity of the surface of the dielectric window457is then ionized by the electric fields of surface waves (microwave electric fields) propagated in the radial direction along the surface of the dielectric window457and, as a result, high-density and low-electronic temperature plasma is generated.

The dielectric plate456can include a cooling jacket plate442, which can serve as an antenna rear plate to cover a top of the processing chamber401. The cooling jacket plate442can be configured to absorb heat (radiating) of dielectric loss, which is generated from the dielectric window457and the dielectric plate456. To provide cooling, a coolant can be circulated in a flow path443, and fed and removed through conduit446and conduit448.

The microwave plasma processing apparatus can include two routes for process gas introduction. Upper gas introduction section481includes a gas flow path provided in the dielectric window457, and a side gas introduction section487that includes a gas flow path provided in a side wall of the processing chamber401, as a gas introduction mechanism configured to introduce a processing gas into the processing chamber401.

In the upper gas introduction section481, a gas flow path488is provided in the inner conductor468of the coaxial line466to extend in an axial direction through the inside of the inner conductor468. Additionally, a first gas supply line484from a process gas supply system480is connected to the upper end of the inner conductor468and the gas flow path488of the coaxial line466. The connector unit479can have a plurality of internal flow paths which are bored and radially branched from a common inlet. The connector unit479can be made of a conductor, and can be electrically grounded. The dielectric window457can be formed with inner flow paths connected to the terminal ends of a branched gas supply paths such as for process gas to vertically pass through the dielectric window457to face the plasma generation space within the processing chamber401.

In the upper gas introduction section481, a processing gas, which is communicated from the process gas supply system480at a predetermined pressure (for example, an etching gas or a film-forming gas), flows through the first gas supply line484, the gas flow path488of the coaxial line466, and is ejected from each gas jet port453at the terminal end. A mass flow controller (MFC)486and corresponding valve can be used for opening/closing and metering process gas flow in first gas supply line484.

The side gas introduction section487is placed at a position lower than a bottom surface of the dielectric window457, and can include a buffer chamber489(manifold), sidewall gas jet ports459, and a second gas supply line485extending from the process gas supply system480to the buffer chamber489. A mass flow controller483and corresponding valve can be used for opening/closing and metering process gas flow in second gas supply line485. Process gas from side gas introduction section487can be jetted in a substantially horizontal flow from the respective sidewall gas jet ports459to be diffused in the process space PS.

Components of the plasma processing apparatus can be connected to, and controlled by, a control unit450, which in turn can be connected to a corresponding storage unit452and user interface451. Control unit450can include a microcomputer configured to control operation of each of the components within the microwave plasma processing apparatus such as, for example, the gas exhaust unit430, the high-frequency power source429, DC power source439for the electrostatic chuck436, microwave generator460, the upper gas introduction section481, the side gas introduction section487, the process gas supply system480, and a heat transfer gas supply unit (not illustrated) or the operations of the entire apparatus. Various plasma processing operations can be executed via the user interface451, and various plasma processing recipes and operations can be stored in the storage unit452. Accordingly, a given substrate can be processed within the plasma processing chamber with various microfabrication techniques.

FIG. 5is a schematic cross-sectional view of a capacitively coupled plasma processing apparatus in accordance with embodiments herein. This apparatus can be used for multiple operations including ashing, etching, deposition, cleaning, plasma polymerization, plasma-enhanced chemical vapor deposition (PECVD), and so forth. Plasma processing can be executed within processing chamber501, which can be a vacuum chamber composed of a metal, such as aluminum or stainless steel. The processing chamber501is grounded using, for example, a ground wire502. The processing chamber501defines a processing vessel providing a process space PS for plasma generation. An inner wall of the processing vessel can be coated with alumina, yttria, or other protectant. The processing vessel can be cylindrical in shape, or have other geometric configurations.

At a lower, central area within the processing chamber501, a susceptor512(which can be disc-shaped) can serve as a mounting table on which, for example, a substrate W to be processed (such as a semiconductor wafer) can be mounted. Substrate W can be moved into the processing chamber501through loading/unloading port537and gate valve527. Susceptor512forms part of a lower electrode520(lower electrode assembly) as an example of a second electrode acting as a mounting table for mounting substrate W thereon. Specifically, the susceptor512is supported on a susceptor support515, which is provided at substantially a central region of a bottom portion of processing chamber501via an insulating plate517. The susceptor support515can be cylindrical. The susceptor512can be formed of an aluminum alloy, for example.

Susceptor512can be provided with an electrostatic chuck536(as part of the lower electrode assembly) for holding the substrate W. The electrostatic chuck536is provided with a clamp electrode535. Clamp electrode535is electrically connected to DC (direct current) power source539. The electrostatic chuck536attracts the substrate W thereto via an electrostatic force generated when a DC voltage from the DC power source539is applied to the clamp electrode535so that substrate W is securely mounted on the susceptor512. A high-frequency power source529for applying a RF (radio frequency) bias is electrically connected to the susceptor512, or bias electrode through an impedance matching unit528(to match impedance or minimize reflected power). The high-frequency power source529(a second power source) can output a high-frequency voltage in a range from, for example, 0.2 MHz to 20 MHz. Applying a high frequency bias power attracts ions, generated by the plasma in the processing chamber501, to substrate W. Power source529can include a signal generator and amplifier for modulating the amplitude and power output from the power source529according to the modulation cycle described above. A focus ring538is provided radially outside the electrostatic chuck536to surround the substrate W.

An inner wall member519, which can be cylindrical and formed of quartz, for example, can be attached to the outer peripheral side of the electrostatic chuck536and susceptor support515. The susceptor support515includes a coolant flow path544(for flowing chilled or heated fluid). The coolant flow path544communicates with a chiller unit (not shown), installed outside the processing chamber501. Coolant flow path544is supplied with coolant (cooling or heating liquid, such as water or dielectric fluid) circulating through corresponding lines. Accordingly, a temperature of the substrate W mounted on/above the susceptor512can be accurately controlled. A gas supply line545, which passes through the susceptor512and the susceptor support515, is configured to supply heat transfer gas to an upper surface of the electrostatic chuck536. A heat transfer gas (also known as backside gas), such as helium (He), can be supplied between the substrate W and the electrostatic chuck536via the gas supply line545to assist in heating substrate W.

An exhaust path533can be formed along an outer periphery of inner wall member519and an inner sidewall surface of the processing chamber501. An exhaust port532(or multiple exhaust ports) is provided in a bottom portion of the exhaust path533. A gas exhaust unit530is connected to each exhaust port via gas exhaust line531. The gas exhaust unit530can include a vacuum pump such as a turbo molecular pump configured to decompress the plasma processing space within the processing chamber501to a desired vacuum condition. The gas exhaust unit530evacuates the inside of the processing chamber501to thereby depressurize an inner pressure thereof up to a desired degree of vacuum.

An upper electrode570(that is, an upper electrode assembly), is an example of a first electrode that is positioned vertically above the lower electrode520to face the lower electrode520(as parallel plate electrodes, for example). The plasma generation space, or process space PS, is defined between the lower electrode520and the upper electrode570. The upper electrode570can include an inner upper electrode571having a disk shape, for example, and an outer upper electrode572having an annular shape, for example, that surrounds a periphery of the inner upper electrode571. The inner upper electrode571also functions as a processing gas inlet for injecting a specific amount of processing gas into the process space PS above substrate W mounted on the lower electrode520. The upper electrode570thereby forms a shower head.

More specifically, the inner upper electrode571includes electrode plate575(which is typically circular) having gas injection openings582. Inner upper electrode571also includes an electrode support578detachably supporting an upper side of the electrode plate575. The electrode support578can be formed in the shape of a disk having substantially the same diameter as the electrode plate575(when electrode plate575is embodied as circular in shape). In alternative embodiments, electrode plate575can be square, rectangular, polygonal, etc. The electrode plate575can be formed of a conductor or semiconductor material, such as Si, SiC, doped Si, aluminum, and so forth. The electrode plate575can be integral with upper electrode570, or detachably supported by electrode support578for convenience in replacing a given plate after surface erosion. The upper electrode570can also include a cooling plate or cooling mechanism (not shown) to control temperature of the electrode plate575.

The electrode support578can be formed of, e.g., aluminum, and can include a buffer chamber589. Buffer chamber589is used for diffusing process gas and can define a disk-shaped space. Processing gas from a process gas supply system580supplies gas to the upper electrode570. The process gas supply system580can be configured to supply a processing gas for performing specific processes, such as film-forming, etching, and the like, on the substrate W. The process gas supply system580is connected with a gas supply line584forming a processing gas supply path. The gas supply line584is connected to the buffer chamber589of the inner upper electrode571. The processing gas can then move from the buffer chamber589to the gas injection openings582at a lower surface thereof. A flow rate of processing gas introduced into the buffer chamber589can be adjusted using a mass flow controller, for example. Further, the processing gas introduced is uniformly discharged from the gas injection openings582of the electrode plate575(showerhead electrode) to the process space PS. The inner upper electrode571then functions in part to provide a showerhead electrode assembly.

A dielectric576, having a ring shape, can be interposed between the inner upper electrode571and the outer upper electrode572. An insulator506, which can be a shield member having a ring shape and being formed of, e.g., alumina, is interposed between the outer upper electrode572and an inner peripheral wall of the processing chamber501in an air tight manner.

The outer upper electrode572is electrically connected with a high-frequency power source560(first high-frequency power source) via a power feeder565, an upper power feed rod561, and a matching unit566. The high-frequency power source560can output a high-frequency voltage having a frequency of 40 MHz (megahertz) or higher (e.g., 60 MHz), or can output a very high frequency (VHF) voltage having a frequency of 3-300 MHz. This power source can be referred to as the main power supply as compared to a bias power supply. The power feeder565can be formed into a substantially cylindrical shape, for example, having an open lower surface. The power feeder565can be connected to the outer upper electrode572at the lower end portion thereof. The power feeder565is electrically connected with the lower end portion of the upper power feed rod561at the center portion of an upper surface thereof. The upper power feed rod561is connected to the output side of the matching unit566at the upper end portion thereof. The matching unit566is connected to the high-frequency power source560and can match load impedance with the internal impedance of the high-frequency power source560. Note, however, that outer upper electrode572is optional and embodiments can function with a single upper electrode.

Power feeder565can be covered on an outside thereof by a ground conductor567, which can be cylindrical having a sidewall whose diameter is substantially the same as that of the processing chamber501. The ground conductor567is connected to the upper portion of a sidewall of the processing chamber501at the lower end portion thereof. The upper power feed rod561passes through a center portion of the upper surface of the ground conductor567. An insulating member564is interposed at the contact portion between the ground conductor567and the upper power feed rod561.

The electrode support578is electrically connected with a lower power feed rod563on the upper surface thereof. The lower power feed rod563is connected to the upper power feed rod561via a connector. The upper power feed rod561and the lower power feed rod563form a power feed rod for supplying high-frequency electric power from the high-frequency power source560to the upper electrode570. A variable capacitor562is provided in the lower power feed rod563. By adjusting the capacitance of the variable capacitor562, when the high-frequency electric power is applied from the high-frequency power source560, the relative ratio of an electric field strength formed directly under the outer upper electrode572to an electric field strength formed directly under the inner upper electrode571can be adjusted. The inner upper electrode571of the upper electrode570is electrically connected with a low pass filter (LPF)591. The LPF591blocks or filters high frequencies from the high-frequency power source560while passing low frequencies from the high-frequency power source529to ground. A lower portion of the system, the susceptor512, forming part of the lower electrode520, is electrically connected with a high pass filter (HPF)592. The HPF592passes high frequencies from the high-frequency power source560to ground.

Components of the plasma processing apparatus can be connected to, and controlled by, a control unit550, which in turn can be connected to a corresponding storage unit552and user interface551. Various plasma processing operations can be executed via the user interface551, and various plasma processing recipes and operations can be stored in storage unit552. Accordingly, a given substrate can be processed within the plasma processing chamber with various microfabrication techniques. In operation, the plasma processing apparatus uses the upper and lower electrodes to generate a plasma in the processing space PS. This generated plasma can then be used for processing a target substrate (such as substrate W or any material to be processed) in various types of treatments such as plasma etching, chemical vapor deposition, treatment of glass material and treatment of large panels such as thin-film solar cells, other photovoltaic cells, and organic/inorganic plates for flat panel displays, etc.

High-frequency electric power in a range from about 3 MHz to 300 MHz, is applied from the high-frequency power source560to the upper electrode570. A high-frequency electric field is generated between the upper electrode570and the susceptor512or lower electrode. Processing gas delivered to process space PS can then be ionized and dissociated to form a reactive plasma. A low frequency electric power in a range from about 0.2 MHz to 20 MHz can be applied from the high-frequency power source529to the susceptor512forming the lower electrode. In other words, a dual or tri-frequency system can be used. As a result, ions in the plasma are attracted toward the susceptor512with sufficient energy to anisotropically etch features via ion assistance. Note that for convenience,FIG. 5shows the high-frequency power source560supplying power to the upper electrode570. In Alternative embodiments, the high-frequency power source560can be supplied to the lower electrode520. Thus, both main power (energizing power) and the bias power (ion acceleration power) can be supplied to the lower electrode.

FIG. 6is a schematic cross-sectional view of an inductively coupled plasma processing apparatus in accordance with embodiments herein. This apparatus can be used for multiple operations including ashing, etching, deposition, cleaning, plasma polymerization, plasma-enhanced chemical vapor deposition (PECVD), and so forth. Plasma processing can be executed within processing chamber601, which can be a vacuum chamber composed of a metal, such as aluminum or stainless steel. The processing chamber601is grounded using, for example, a ground wire602. The processing chamber601defines a processing vessel providing a process space PS for plasma generation. An inner wall of the processing vessel can be coated with alumina, yttria, or other protectant. The processing vessel can be cylindrical in shape, or have other geometric configurations.

At a lower, central area within the processing chamber601, a susceptor612(which can be disc-shaped) can serve as a mounting table on which, for example, a substrate W to be processed (such as a semiconductor wafer) can be mounted. Substrate W can be moved into the processing chamber601through loading/unloading port637and gate valve627. Susceptor612forms part of a lower electrode620(lower electrode assembly) as an example of a second electrode acting as a mounting table for mounting substrate W thereon. Specifically, the susceptor612is supported on a susceptor support625, which is provided at substantially a central region of a bottom portion of processing chamber601. The susceptor support625can be cylindrical. The susceptor612can be formed of an aluminum alloy, for example.

Susceptor612can be provided with an electrostatic chuck636(as part of the lower electrode assembly) for holding the substrate W. The electrostatic chuck636is provided with a clamp electrode635. Clamp electrode635is electrically connected to DC (direct current) power source639. The electrostatic chuck636attracts the substrate W thereto via an electrostatic force generated when a DC voltage from the DC power source639is applied to the clamp electrode635so that substrate W is securely mounted on the susceptor612.

The susceptor612can include an insulating frame613and be supported by susceptor support625, which can include an elevation mechanism. The susceptor612can be vertically moved by the elevation mechanism during loading and/or unloading of the substrate W. A bellows626can be disposed between the insulating frame613and a bottom portion of the processing chamber601to surround support625as an airtight enclosure. Susceptor612can include a temperature sensor and a temperature control mechanism, including a coolant flow path (for flowing chilled or heated fluid), a heating unit such as a ceramic heater or the like (all not shown) that can be used to control a temperature of the substrate W. The coolant flow path communicates with a chiller unit (not shown), installed outside the processing chamber601. Coolant flow path is supplied with coolant (cooling or heating liquid, such as water or dielectric fluid) circulating through corresponding lines. A focus ring (not shown), can be provided on an upper surface of the susceptor612to surround the electrostatic chuck636and assist with directional ion bombardment.

A gas supply line645, which passes through the susceptor612, is configured to supply heat transfer gas to an upper surface of the electrostatic chuck636. A heat transfer gas (also known as backside gas), such as helium (He) can be supplied between the substrate W and the electrostatic chuck636via the gas supply line645to assist in heating substrate W.

A gas exhaust unit630, including a vacuum pump and the like, can be connected to a bottom portion of the processing chamber601through gas exhaust line631. The gas exhaust unit630can include a vacuum pump, such as a turbo molecular pump, configured to decompress the plasma processing space within the processing chamber601to a desired vacuum condition during a given plasma processing operation.

The plasma processing apparatus can be partitioned into an antenna chamber603and a processing chamber601by a window655. Window655can be a dielectric material, such as quartz, or a conductive material, such as metal. For embodiments in which the window655is metal, the window655can be electrically insulated from processing chamber601, e.g., insulators606. In this example, the window655forms a ceiling of the processing chamber601. In some embodiments, window655can be divided into multiple sections, with these sections optionally insulated from each other.

Provided between sidewall604of the antenna chamber603and sidewall607of the processing chamber601is a support shelf605projecting toward the inside of the processing apparatus. A support member609serves to support window655and also functions as a shower housing for supplying a processing gas. When the support member609serves as the shower housing, a gas channel683, extending in a direction parallel to a working surface of a substrate W to be processed, is formed inside the support member609and communicates with gas injection openings682for injecting process gas into the process space PS. A gas supply line684is configured to be in communication with the gas channel683. The gas supply line684defines a flow path through the ceiling of the processing chamber601, and is connected to a process gas supply system680including a processing gas supply source, a valve system and the corresponding components. Accordingly, during plasma processing, a given process gas can be injected into the process space PS.

In antenna chamber603, a high-frequency antenna662(radio frequency) is disposed above the window655so as to face the window655, and can be spaced apart from the window655by a spacers667made of an insulating material. High-frequency antenna662can be formed in a spiral shape or formed in other configurations.

During plasma processing, a high frequency power having a frequency ranging from a few MHz to hundreds of MHz, e.g., 13.56 MHz, to generate an inductive electric field can be supplied from a high-frequency power source660to the high-frequency antenna662via power feed members661. A matching unit666(impedance matching unit) can be connected to high-frequency power source660. The high-frequency antenna662in this example can have corresponding power feed portion664and power feed portion665connected to the power feed members661, as well as additional power feed portions depending on a particular antenna configuration. Power feed portions can be arranged at similar diametrical distances and angular spacing. Antenna lines can extend outwardly from power feed portion664and power feed portion665(or inwardly depending on antenna configuration) to an end portion of antenna lines. End portions of antenna lines can be connected to the capacitors668, and the antenna lines are grounded via the capacitors668. Capacitors668can include one or more variable capacitors.

With a given substrate mounted within processing chamber601, one or more plasma processing operations can be executed. By applying high frequency power to the high-frequency antenna662, an inductive electric field is generated in the processing chamber601, and processing gas supplied from the gas injection openings682is excited to form plasma in the presence of electrons heated by the inductive electric field. The plasma can then be used to process a given substrate, such as performing processes for etching, ashing, depositing, etc.

A high-frequency power source629for applying a RF (radio frequency) bias is electrically connected to the susceptor612, or bias electrode through an impedance matching unit628(to match impedance or minimize reflected power). The high-frequency power source629(a second power source) can output a high-frequency voltage in a range from, for example, 0.2 MHz to 20 MHz, e.g., 3.2 MHz. Applying a high frequency bias power attracts ions, generated by the plasma in the processing chamber601, to substrate W. Power source629can include a signal generator and amplifier for modulating the amplitude and power output from the power source629according to the modulation cycle described above.

Components of the plasma processing apparatus can be connected to, and controlled by, a control unit650, which in turn can be connected to a corresponding storage unit652and user interface651. Various plasma processing operations can be executed via the user interface651, and various plasma processing recipes and operations can be stored in storage unit652. Accordingly, a given substrate can be processed within the plasma processing chamber with various microfabrication techniques.

Although only certain embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.