Plasma processing apparatus and plasma processing method

There is provided a plasma processing apparatus capable of stably generating plasma by suppressing oscillation of a plasma potential, and capable of preventing contamination caused by sputtering a facing electrode made of metal. A high frequency bias power is applied to an electrode within a mounting table for mounting a target object thereon. An extended protrusion 60 is formed at an inner peripheral surface of a cover member 27. The extended protrusion 60 is formed toward a plasma generation space S and serves as a facing electrode facing an electrode 7 within a mounting table 5 with the plasma generation space S therebetween. A ratio of a surface area of the facing electrode with respect to that of an electrode for bias (facing electrode surface area/bias electrode area) is in a range of from about 1 to about 5.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Japanese Patent Application Nos. 2010-207772 and 2011-163750 filed on Sep. 16, 2010 and Jul. 26, 2011, respectively, the entire disclosures of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present disclosure relates to a plasma processing apparatus and a plasma processing method for performing a plasma process on a target object such as a semiconductor wafer.

BACKGROUND OF THE INVENTION

In a manufacturing process of a semiconductor device, various processes such as an etching process, an ashing process and a film forming process have been performed on a semiconductor wafer as a target object. In these processes, there has been used a plasma processing apparatus configured to perform a plasma process on the semiconductor wafer in a processing chamber capable of maintaining a vacuum atmosphere.

Recently, a semiconductor wafer has become larger and a device has become miniaturized. In response to this trend, it has been required to enhance efficiency (for example, a film forming rate) in a plasma process and uniformity of a process on a wafer surface. For this reason, attention is drawn to a method for performing a plasma process while a bias voltage is applied to a semiconductor wafer and a high frequency power is applied to an electrode embedded in a mounting table for mounting thereon a semiconductor wafer within a processing chamber of a plasma processing apparatus (for example, Patent Document 1).

If the high frequency power is applied to the electrode embedded in the mounting table, a conductive member, having a ground potential, positioned over a plasma generation space with respect to the electrode embedded in the mounting table may serve as a facing electrode. That is, if the high frequency bias power is applied to the electrode within the mounting table, there is formed a path of a high frequency current (a RF return circuit) from this mounting table to the facing electrode via plasma and from the facing electrode to an earth of a high frequency bias power supply via a wall of the processing chamber. If the path of the high frequency current is not formed stably, an oscillation amplitude of a plasma potential (Vp) generated within the processing chamber becomes large, and, thus, the plasma process cannot be performed stably. Further, if the oscillation amplitude of the plasma potential is large, particularly when a process is performed at a low pressure of several tens Pa or less, a surface of the facing electrode typically made of aluminum may be sputtered by the plasma, resulting in contamination. In order to suppress oscillation of the plasma potential, the facing electrode needs to have a sufficiently large area. However, in a conventional microwave plasma processing apparatus described in Patent Document 1, a microwave transmissive plate is provided at an upper region of the processing chamber. Thus, unlike a parallel plate type plasma processing apparatus, it is difficult for the facing electrode to have a sufficiently large area due to a design limitation of the apparatus.

In this regard, as a microwave plasma processing apparatus, there has been suggested a plasma processing apparatus capable of detachably attaching an annular facing electrode made of silicon or aluminum to a periphery of a microwave transmissive plate within a processing chamber (for example, Patent Documents 2 and 3). In a conventional technique described in Patent Documents 2 and 3, the facing electrode has a sufficiently large area. Thus, when a high frequency power is applied to a mounting table, a plasma potential (Vp) can be stabilized. However, since the facing electrode described in Patent Documents 2 and 3 is provided so as to closely come into contact with the microwave transmissive plate, an effective area for introducing a microwave becomes smaller and the microwave is introduced unstably. Thus, plasma may be generated unstably in the processing chamber. Further, in the microwave plasma processing apparatus, plasma is generated right below the microwave transmissive plate, and, thus, a temperature of electrons is the highest in the vicinity of the microwave transmissive plate. For this reason, if the facing electrode closely comes into contact with the microwave transmissive plate so as to protrude toward a processing space as described in Patent Documents 2 and 3, a front end of the facing electrode can be sputtered by the plasma easily and contamination may occur.Patent Document 1: PCT Publication No. WO2009/123198 A1Patent Document 2: Japanese Patent Laid-open Publication No. H09-266095Patent Document 3: Japanese Patent Laid-open Publication No. H10-214823

BRIEF SUMMARY OF THE INVENTION

In view of the foregoing circumstance, the present disclosure provides a plasma processing method capable of stably generating plasma by suppressing oscillation of a plasma potential, and capable of preventing contamination caused by sputtering on a facing electrode made of metal in a plasma processing apparatus configured to apply a high frequency bias power to the electrode within a mounting table for mounting a target object thereon.

In accordance with one aspect of the present disclosure, there is provided a plasma processing apparatus including a processing chamber having an opening at an upper portion thereof and configured to perform therein a process on a target object by plasma; a mounting table configured to mount the target object thereon within the processing chamber; a first electrode embedded in the mounting table and configured to apply a bias voltage to the target object; a dielectric plate configured to form a plasma generation space by closing the opening of the processing chamber and transmit a microwave so as to introduce the microwave into the processing chamber; a planar antenna provided above the dielectric plate and configured to introduce the microwave generated by a microwave generator into the processing chamber via the dielectric plate; an annular cover member provided on the processing chamber and including a contact support protruding toward the plasma generation space and configured to support an outer periphery of the dielectric plate on an upper surface of the contact support; an annular extended protrusion protruding from the processing chamber or the contact support toward the plasma generation space within the processing chamber with a gap between the dielectric plate and the annular extended protrusion and serving as a part of a second electrode facing the first electrode via the plasma generation space therebetween; and a space formed between an upper surface of the extended protrusion and a lower surface of the dielectric plate.

In the plasma processing apparatus, a gap between the upper surface of the extended protrusion and the lower surface of the dielectric plate may be in a range of from about 10 mm to about 30 mm.

In the plasma processing apparatus, a leading end of the extended protrusion may have a protruded length that does not reach an area above an edge of the target object mounted on the mounting table.

The plasma processing apparatus may further include a gas inlet for introducing a processing gas into the space between the dielectric plate and the extended protrusion.

In the plasma processing apparatus, the extended protrusion may be formed as a single body with the cover member. Alternatively, the extended protrusion may be formed as a single body with the processing chamber. Otherwise, the extended protrusion may be an auxiliary electrode member fixed to the cover member or may be an auxiliary electrode member fixed to the processing chamber.

In the plasma processing apparatus, a surface of the extended protrusion may have prominences and depressions.

In the plasma processing apparatus, a ratio of a surface area of the second electrode facing the plasma generation space to an area of an embedded range of the first electrode in the mounting table may be in a range of from about 1 to about 5.

In the plasma processing apparatus, a protective film may be formed on the surface of the extended protrusion. Here, the protective film may be made of silicon.

The plasma processing apparatus may further include an insulating plate provided along an inner wall of the processing chamber at a position lower than a mounting surface of the mounting table. Here, the insulating plate may be provided to reach an exhaust chamber connected to a lower region of the processing chamber.

In accordance with another aspect of the present disclosure, there is provided a plasma processing method for performing a process on a target object with plasma by a plasma processing apparatus including a processing chamber having an opening at an upper portion thereof and configured to perform therein the process on the target object by the plasma; a mounting table configured to mount the target object thereon within the processing chamber; a first electrode embedded in the mounting table and configured to apply a bias voltage to the target object; a dielectric plate configured to form a plasma generation space by closing the opening of the processing chamber and transmit a microwave so as to introduce the microwave into the processing chamber; a planar antenna provided above the dielectric plate and configured to introduce the microwave generated by a microwave generator into the processing chamber via the dielectric plate; an annular cover member provided on the processing chamber and including a contact support protruding toward the plasma generation space and configured to support an outer periphery of the dielectric plate on an upper surface of the contact support; an annular extended protrusion protruding from the processing chamber or the contact support toward the plasma generation space within the processing chamber with a gap between the dielectric plate and the annular extended protrusion and serving as a part of a second electrode facing the first electrode via the plasma generation space therebetween; and a space formed between an upper surface of the extended protrusion and a lower surface of the dielectric plate. The plasma processing method includes generating the plasma in the processing chamber; and performing the process on the target object with the generated plasma by the plasma processing apparatus. Here, a processing pressure may be about 40 Pa or less.

The plasma processing apparatus in accordance with the present disclosure may include the extended protrusion protruding from the processing chamber or the contact support toward the plasma generation space with the gap with respect to the dielectric plate. The extended protrusion may serve as a part of the second electrode facing the first electrode via the plasma generation space therebetween. Thus, the second electrode can have a sufficiently large area and oscillation of a plasma potential can be suppressed. Further, by increasing the second electrode surface area, it may be possible to suppress sputtering on the surface of the second electrode, and, thus, contamination can be prevented. Furthermore, since the second electrode has the sufficiently large area, a short circuit or an abnormal electric discharge in other portions can be suppressed. Moreover, since the extended protrusion may be spaced from the dielectric plate, it is not necessary to reduce an effective area of the dielectric plate, and plasma generated within the processing chamber can be stabilized by supplying the sufficient microwave power.

DETAILED DESCRIPTION OF THE INVENTION

First Embodiment

FIG. 1is a schematic cross sectional view showing a configuration of a plasma processing apparatus100in accordance with a first embodiment of the present disclosure.FIG. 2Ais a cross sectional view showing enlarged main parts ofFIG. 1.FIG. 2Bis a perspective view showing an external appearance of a cover as a component of the plasma processing apparatus100.FIG. 3Ashows a planar antenna of the plasma processing apparatus100ofFIG. 1.

The plasma processing apparatus100may be configured as a RLSA microwave plasma processing apparatus capable of generating microwave excitation plasma having a high density and a low electron temperature within the processing chamber by introducing a microwave into a processing chamber through a planar antenna having multiple slot holes, particularly a RLSA (Radial Line Slot Antenna). In the plasma processing apparatus100, a process can be performed by plasma having a plasma density in a range of from about 1×1010/cm3to about 5×1012/cm3, and a low electron temperature in a range of from about 0.7 eV to about 2 eV. Thus, by way of example, in manufacturing processes of various semiconductor devices, the plasma processing apparatus100can be used appropriately for forming a silicon oxide film (for example, a SiO2film) by oxidizing silicon of a target object or forming a silicon nitride film (for example, a SiN film) by nitriding the silicon of a target object.

The plasma processing apparatus100may be sealed airtightly and may include a substantially cylindrical processing chamber1configured to accommodate therein a semiconductor wafer (hereinafter, simply referred to as “wafer”) W as a target object. This processing chamber1may be grounded and made of a metal such as aluminum, aluminum alloy or stainless steel. Further, the processing chamber1may be configured to be divided into multiple sections instead of being a single chamber. At an upper region of the processing chamber1, a microwave inlet unit26may be provided so as to be opened and closed. That is, the microwave inlet unit26may be positioned at an upper end portion of the processing chamber1. Further, at a lower region of the processing chamber1, an exhaust chamber11may be connected. The processing chamber1may include a multiple number of cooling water paths3aconfigured to cool a wall of the processing chamber1. Thus, it is possible to suppress plasma damage or a position deviation of a contact surface with the microwave inlet unit26by thermal expansion caused by a plasma heat, and also prevent a decrease in a sealing property or particle generation.

Within the processing chamber1, a mounting table5configured to horizontally support the wafer W may be provided. The mounting table5may be supported by a cylindrical support4extended upwards from a central bottom portion of the exhaust chamber11. The mounting table5and the support4may be made of, for example, quartz or a ceramic material such as AlN or Al2O3and, particularly, AlN of high thermal conductivity may be desirable. Further, the mounting table5may have therein a resistance heater5a. By way of example, since the resistance heater5amay be supplied with a power from a heater power supply6as an AC power supply of about 200 V and may heat the mounting table5, the wafer W as the target object may be heated accordingly. At a power supply line6aconfigured to connect the heater5aand the heater power supply6, a filter box45configured to filter a RF (a high frequency) power may be provided. A temperature of the mounting table5may be measured by a non-illustrated thermocouple that is embedded in the mounting table5. Further, based on a signal from the thermocouple, the heater power supply6may be controlled. By way of example, the temperature can be stably controlled in a range of from room temperature to about 800° C.

Within the mounting table5, a bias electrode7serving as a first electrode may be embedded above the heater5a. This electrode7may be embedded in a region approximately corresponding to the wafer W mounted on the mounting table5. The electrode7may be made of a conductive material such as molybdenum and tungsten. The electrode7may be formed in, for example, a mesh shape, a grid pattern or a vortex shape. A cover8amay be provided so as to cover the upper surface and the entire surface of a sidewall of the mounting table5. The cover8amay prevent the mounting table5sputtered by plasma from being a cause of metal contamination. In an upper surface of the cover8a, a recess (a groove) having a size larger than a size of the wafer W and a depth substantially equivalent to a thickness of the wafer W may be formed in order to guide the wafer W. The wafer W may be positioned on this recess. Around the mounting table5, a baffle plate8bmade of quartz may be provided annularly in order to uniformly exhaust the inside of the processing chamber1. This baffle plate8bmay have a plurality of holes8cand may be supported by a supporting column (not illustrated). In the mounting table5, a multiple number of wafer supporting pins (not illustrated) configured to support and lift up/down the wafer W may be provided so as to protrude from and retract into the upper surface of the mounting table5.

At a substantially central portion in a bottom wall1aof the processing chamber1, a circular opening10may be formed. At the bottom wall1a, the exhaust chamber11extending downwards may be provided. The exhaust chamber11may communicate with the opening10and uniformly exhaust the inside of the processing chamber1. At a side wall of the exhaust chamber11, an exhaust port11bmay be formed, and an exhaust line23may be connected thereto. This exhaust line23may be connected to an exhaust device24including a vacuum pump. By operating this exhaust device24, an internal gas of the processing chamber1may be uniformly discharged into a space11aof the exhaust chamber11and exhausted through the exhaust line23. Thus, the inside of the processing chamber1can be quickly depressurized to a certain vacuum level, for example, about 0.133 Pa. The exhaust line23may be connected to a bottom surface of the exhaust chamber11. Further, the exhaust chamber11may be provided within the processing chamber1.

At a sidewall1bof the processing chamber1, a loading/unloading port configured to load and unload the wafer W and a gate valve configured to open and close this loading/unloading port may be provided (all not illustrated).

At an upper region of the processing chamber1, an opening may be formed, and the microwave inlet unit26may be provided airtightly so as to cover this opening. This microwave inlet unit26can be opened and closed by a non-illustrated opening/closing device. The microwave inlet unit26may include, as main components, a cover member27, a microwave transmissive plate28, a planar antenna31, a wavelength shortening member33in sequence upwardly from the mounting table5. Further, a conductive cover34made of, for example, SUS, aluminum, and aluminum alloy may be provided so as to cover the wavelength shortening member33. An outer periphery of the cover34may be fixed to the cover member27by an annular pressing ring35via a fixing member36.

The cover member27may be grounded and made of the same material as the processing chamber1. In the present embodiment, an opening may be formed at the annular cover member27. An inner periphery of the cover member27may be exposed to a plasma generation space S within the processing chamber1, and the cover member27may serve as a facing electrode (a second electrode) facing the electrode7(a lower electrode) within the mounting table5. An inner peripheral surface of the annular cover member27may be provided with a protrusion60protruding toward the plasma generation space S rather than an inner wall surface of the processing chamber1. As depicted inFIGS. 2A and 2B, the protrusion60may include a contact support60A and an extended protrusion60B. Here, the contact support60A may contact with the microwave transmissive plate28thereon and support the microwave transmissive plate28. Further, the extended protrusion60B may be configured to outstandingly protrude toward the plasma generation space S within the processing chamber1rather than the contact support60A. Since a step-shaped portion may be formed between the contact support60A and the extended protrusion60B, when the microwave transmissive plate28is positioned on the contact support60A, an annular space S1may be formed between the microwave transmissive plate28and the extended protrusion60B. In the present embodiment, the extended protrusion60B may play a major role in the facing electrode. Further, the space S1may constitute a portion of the plasma generation space S.

In an inner peripheral surface of the contact support60A of the cover member27, gas inlet openings15amay be formed uniformly at multiple positions (for example, about 32 positions). That is, at a wall of the contact support60A where the step-shaped portion is formed between the contact support60A and the extended protrusion60B, the multiple gas inlet openings15amay be annularly formed. Each gas inlet opening15amay be opened toward the space S1so as to respectively introduce a processing gas into the space S1. Each of gas inlet paths15bextended in a slated direction from each gas inlet opening15ainto the cover member27may be formed. Alternatively, the gas inlet path15bmay be formed horizontally. Each gas inlet path15bmay communicate with an annular path13horizontally formed between the cover member27and the upper portion of the processing chamber1. Thus, the processing gas can be supplied uniformly into the plasma generation space S and the space S1within the processing chamber1.

At a contact portion between the processing chamber1and the cover member27, sealing members9aand9bsuch as O-ring may be provided along the annular path13at the inside and the outside with respect to the annular path13. Thus, the contact portion may be airtightly maintained. That is, when the microwave inlet unit26is closed, a space between an upper end surface of the sidewall1bof the processing chamber1and the cover member27having an opening/closing function may be sealed by the sealing members9aand9b. The sealing members9aand9bmay be made of fluorine-based rubber material, for example, Kalrez (trade name; product of DuPont). Further, at an outer peripheral surface of the cover member27, a multiple number of coolant paths27amay be formed. The cover member27and an outer peripheral portion of the microwave transmissive plate28may be cooled by a coolant circulating through the coolant path27a. Thus, it is possible to prevent a position deviation of a contact surface between the cover member27and the microwave transmissive plate28due to thermal expansion caused by a plasma heat. Further, it is also possible to prevent a sealing property from being decreased or particles from being generated.

The microwave transmissive plate28as a dielectric plate may be made of a dielectric material such as quartz or ceramic such as Al2O3, AlN, sapphire and SiN. The microwave transmissive plate28may serve as a microwave inlet window for transmitting a microwave from the planar antenna31and introducing the transmitted microwave into the plasma generation space S within the processing chamber1. A lower surface (facing the mounting table5) of the microwave transmissive plate28may be not limited to a planar surface, and a recess or a groove may be formed thereon in order to make a microwave uniform and stabilize plasma, for example.

The outer peripheral portion of the microwave transmissive plate28may be airtightly supported on the contact support60A of the protrusion60of the cover member27via a sealing member29. Therefore, while the microwave inlet unit26is closed, the plasma generation space S may be formed by the processing chamber1and the microwave transmissive plate28, and the plasma generation space S may be maintained airtightly.

The planar antenna31may be formed in a circular plate shape and engaged with an outer periphery of the cover34above the microwave transmissive plate28. The planar antenna31may have a surface formed of a metal plate such as a gold- or silver-plated copper plate, an aluminum plate, a nickel plate or a brass plate and may have multiple slot holes32for radiating an electromagnetic wave such as a microwave. The slot holes32may pass through the planar antenna31and every two adjacent slot holes may make a pair and be arranged in a certain pattern.

By way of example, each of the slot holes32may be formed in an elongated groove shape as depicted inFIG. 3A, and, typically, adjacent two slot holes32may be arranged in a “T” shape. Further, these multiple slot holes32may be arranged concentrically. A length or arrangement gap of the slot holes32may be determined depending on a wavelength λg of a microwave within a waveguide37. By way of example, the slot holes32may be arranged such that a gap therebetween is set to be in a range of from about λg/4 to about λg. Further, inFIG. 3A, a gap between two pairs of the slot holes32arranged concentrically may be represented as Δr. Further, the slot holes32may have other shapes such as a circular shape or a circular arc shape. Furthermore, an arrangement shape of the slot holes is not specifically limited to a concentric circular shape, and, thus, the slot holes32may be arranged in, for example, a spiral shape or a radial shape.

The wavelength shortening member33may have a dielectric constant higher than that of a vacuum, and may be provided on an upper surface of the planar antenna31. The wavelength shortening member33may be made of quartz, ceramic, fluorine-based resin such as polytetrafluoroethylene, or polyimide resin. Since a wavelength of a microwave is increased in a vacuum state, the wavelength shortening member33may control plasma by shortening the wavelength of the microwave. Further, the planar antenna31may be closely contacted with or spaced apart from the microwave transmissive plate28. Moreover, the planar antenna31may be closely contacted with or spaced apart from the wavelength shortening member33. However, it is desirable that the planar antenna31may be closely brought into contact with the microwave transmissive plate28and the wavelength shortening member33.

Within the cover34, a coolant path34amay be formed and a coolant may flow through the coolant path34aso as to cool the cover34, the wavelength shortening member33, the planar antenna31, the microwave transmissive plate28and the cover member27. Therefore, it may be possible to prevent these components from being deformed or damaged, and also possible to generate stable plasma. The planar antenna31and the cover34may be grounded.

At a central portion of the cover34, an opening34bmay be formed, and the opening34bmay be connected to the waveguide37. An end of the waveguide37may be connected to a microwave generator39via a matching circuit38. Thus, a microwave having a frequency of, for example, about 2.45 GHz generated by the microwave generator39may be propagated to the planar antenna31through the waveguide37. As a frequency of the microwave, about 8.35 GHz or about 1.98 GHz may be employed.

The waveguide37may include a coaxial waveguide37ahaving a cylindrical cross-sectional shape and a rectangular waveguide37bconnected to the coaxial waveguide37aat an upper end of the coaxial waveguide37avia a mode converter40. The coaxial waveguide37amay be extended upwards from the opening34bof the cover34, and the rectangular waveguide37bmay be extended horizontally. The mode converter40between the coaxial waveguide37aand the rectangular waveguide37bmay convert a microwave propagated in a TE mode within the rectangular waveguide37binto a TEM mode. In a center of the coaxial waveguide37a, an internal conductor41may be extended from the mode converter40to the planar antenna31. A lower end of the internal conductor41may be connected and fixed to a central portion of the planar antenna31. Further, a flat waveguide may be formed by the planar antenna31and the cover34. Thus, the microwave may be introduced into the central portion of the planar antenna31via the internal conductor41of the coaxial waveguide37a, and then, the introduced microwave may be efficiently and uniformly propagated from the central portion of the planar antenna31in a radial direction.

Hereinafter, a gas supply mechanism of the plasma processing apparatus100will be explained. As depicted inFIG. 2A, at certain positions (for example, equi-spaced four positions) of the sidewall1bof the processing chamber1, multiple gas supply channels12vertically penetrating an inside of the sidewall1band the bottom wall1amay be formed. Each gas supply channel12may be connected to the annular path13formed at a contact surface between an upper end of the sidewall1bof the processing chamber1and a lower end of the cover member27. The annular path13may be connected to a gas supply unit16via the gas supply channel12and a gas supply pipe12a. Alternatively, the gas supply unit16may be connected to the annular path13at a side surface of the processing chamber1by horizontally forming the gas supply channel12.

The annular path13is a gas path formed by a step-shaped portion18and a step-shaped portion19at a contact portion between an upper end surface of the processing chamber1and a lower end surface of the cover member27. The step-shaped portion18may be positioned at a lower surface of the cover member27, and the step-shaped portion19may be positioned at an upper end surface of the sidewall1bof the processing chamber1. This annular path13may be provided annularly in a substantially horizontal direction so as to surround the plasma generation space S within the processing chamber1. Alternatively, the annular path13may be provided by forming a groove (a recess) in the upper end surface of the sidewall1bof the processing chamber1or in the lower surface of the cover member27. The annular path13may serve as a gas distribution unit capable of uniformly distributing and supplying a gas to each gas inlet path15b. That is, the annular path13may prevent the processing gas from being non-uniformly supplied into the processing chamber1by being supplied only to specific gas inlet openings15a. As described above, in the present embodiment, the processing gas from the gas supply unit16may be supplied uniformly into the plasma generation space S and the space S1within the processing chamber1from the gas inlet openings15athrough each gas supply channel12, the annular path13and each gas inlet path15b. For example, the gas inlet openings15aare provided at about thirty two (32) positions. Therefore, it may be possible to enhance uniformity of the plasma within the processing chamber1.

Hereinafter, there will be explained a bias voltage applying unit configured to apply a bias voltage to the wafer W mounted on the mounting table5. The electrode7embedded in the mounting table5may be connected to a high frequency power supply44for applying a bias power via a power supply line42penetrating the inside of the support4and a matching box (M.B.)43. The electrode7may be configured to apply a high frequency bias power to the wafer W. As described above, the filter box45may be provided at the power supply line6afor supplying a power from the heater power supply6to the heater5a. The matching box43and the filter box45may be connected with each other via a shield box46and may be positioned at a lower portion of the exhaust chamber11. The shield box46may be made of a conductive material such as aluminum and SUS. Within the shield box46, a conductive plate47made of, e.g., copper and connected to the power supply line42may be provided. Further, the conductive plate47may be connected to a matcher (not illustrated) within the matching box43. By using the conductive plate47, a contact area with respect to the power supply line42may be greatly increased and a contact resistance may be decreased. As a result, it is possible to reduce an electric current loss at the contact portion. As described above, in the plasma processing apparatus100in accordance with the present embodiment, the matching box43and the filter box45may be connected with each other via the shield box46as a unit and directly connected to the lower portion of the exhaust chamber11of the processing chamber1. Thus, it may be possible to reduce a loss of the high frequency power supplied to the electrode7from the high frequency power supply44, and also possible increase power consumption efficiency. Accordingly, power can be supplied stably. Since the high frequency bias power can be applied stably to the wafer W mounted on the mounting table5, the plasma generated within the processing chamber1may be stabilized and a uniform plasma process can be performed.

As described above, at the inner peripheral surface of the cover member27, the protrusion60including the contact support60A and the extended protrusion60B may constitute a part of the cover member27. Since the cover member27and the protrusion60are formed as a single body, thermal conductivity and electric conductivity can be secured. The extended protrusion60B of the protrusion60may include an upper surface60B1, a leading end surface60B2, and a lower surface60B3. This protrusion60may be formed toward the plasma generation space S and may serve as the facing electrode (second electrode) facing the electrode (first electrode) within the mounting table5with the plasma generation space S therebetween. To be specific, inFIG. 2A, a surface ranging from a position A indicated by a circle to a position B indicated by a circle and including an exposed surface of the protrusion60(i.e. a surface of the contact support60A and the upper surface60B1, the leading end surface60B2, and the lower surface60B3of the extended protrusion60B) may serve as the facing electrode. Here, the position A is an end of a contact portion between the contact support60A of the cover member27and the microwave transmissive plate28. Further, the position B is an end (i.e., an end contacted with an upper liner49a) of an exposed lower surface of the contact support60A. In the present embodiment, the inner peripheral surface of the annular cover member27ranging from the position A to the position B may be exposed to the plasma generation space S and may serve as the facing electrode of an annular shape. In this way, by providing an annular member serving as a facing electrode so as to protrude toward the plasma generation space, even in the RLSA-type plasma processing apparatus100in which it is difficult to provide a facing electrode right above the mounting table5due to the microwave transmissive plate28, the facing electrode may have a sufficiently large surface area.

In the plasma processing apparatus100in accordance with the present embodiment, the portion serving as the facing electrode facing the lower electrode may be exposed to the plasma generation space S and may be a conductive member having a ground potential. Further, as will be described below, since a protective film48can be formed on the surface of the facing electrode, “the portion exposed to the plasma generation space S” may include the portion on which the protective film48is formed. To define the facing electrode in more detail, by way of example, the facing electrode may have a surface, above a wafer mounting surface of the mounting table5, exposed toward the plasma generation space S. Further, the facing electrode may be a conductive member exposed to plasma having an electron density of about 1×1011/cm3or more when the plasma is generated within the processing chamber1. However, the electron density is just an example and it is not limited thereto. By way of example,FIG. 3Bshows measurement results of an electron density and an electron temperature at a region right below a central portion of the microwave transmissive plate28within the processing chamber1of the plasma processing apparatus100while varying a processing pressure and a gap G (a distance from a surface of the wafer W to the microwave transmissive plate28). An electron density and an electron temperature of plasma generated within the processing chamber1may vary depending on the processing pressure and the gap G. Thus, it is desirable to adjust a surface area of the facing electrode depending on the processing pressure and the gap G. By way of example, the gap G may be in a range of, desirably, from about 50 mm to about 150 mm, and, more desirably, from 70 mm to about 120 mm.

Hereinafter, an area of the portion (facing electrode) exposed to the plasma generation space S may be referred to as “facing electrode surface area” and an area of an embedded range of the electrode7in the mounting table5may be referred to as “bias electrode area”. Here, a ratio of the facing electrode surface area to the bias electrode area may be, desirably, about 1 or higher and, more desirably, in a range of from about 1 to about 5, and, still more desirably, in a range of from about 1 to about 4 and, still more desirably, in a range of from about 2 to about 4. If the ratio of the facing electrode surface area to the bias electrode area (facing electrode surface area/bias electrode area) is lower than about 1, oscillation of a plasma potential may be increased and stable plasma cannot be generated within the processing chamber1. Further, a surface of the facing electrode may be etched by strong sputtering by plasma in the vicinity of the facing electrode. This may cause aluminum contamination. The ratio of the facing electrode surface area to the bias electrode area may be desirable if it is as high as possible. However, it may be desirable to set an upper limit to be about 5, or, desirably, about 4 or lower considering a size and a configuration limitation of the apparatus. When the electrode7has an opening or a gap formed in, for example, a mesh shape, a grid pattern and a vortex shape, the area of the embedded range of the electrode7in the mounting table indicates an area of an entire planar surface of the electrode7assuming that the entire planar surface also includes the opening or the gap formed in the electrode7.

Desirably, a leading end (the leading end surface60B2of the extended protrusion60B) of the protrusion60serving as the facing electrode may have a protruded length which does not reach a region above the wafer W mounted on the mounting table5(i.e. a position PWEof a peripheral end of the wafer W). If the leading end of the protrusion60reaches an inner position than the position PWEof the peripheral end of the wafer W, a range of uniform plasma having a high density, generated within the processing chamber1, may be smaller than a size of the wafer W and a density of the plasma at a periphery of the wafer W may be decreased. As a result, there may be a possibility that a process is not uniformly performed at an outer periphery of the wafer W. At a side (on the sidewall1b's side of the processing chamber1) opposite to the leading end (the leading end surface60B2) of the protrusion60serving as the facing electrode, a contact end with the sidewall1bmay serve as a base end. However, in the present embodiment, it may be sufficient if the position B on the way to the base end is exposed to the plasma generation space S. That is, in the present embodiment, an end of the exposed lower surface60B3of the protrusion60serving as the facing electrode may be a contact point with respect to the upper liner49a. The contact point is indicated as the position B inFIG. 2A.

Further, the upper surface60B1(facing the space S1) of the extended protrusion60B may be spaced from the lower surface of the microwave transmissive plate28. That is, the extended protrusion60B may protrude toward the plasma generation space S with a gap L1with respect to the microwave transmissive plate28. In this way, since there is the gap L1between the microwave transmissive plate28and the extended protrusion60B, the facing electrode can have a sufficiently large surface area without reducing an effective area, through which a microwave is transmitted, of the microwave transmissive plate28. The space S1may become a portion of the plasma generation space S and plasma may also be generated in the space S1. Thus, plasma can be maintained stably within the processing chamber1. On the contrary, like a conventional plasma processing apparatus, if the microwave transmissive plate28and the extended protrusion60B are brought into contact with each other without the gap L1therebetween, in order for the facing electrode to have a large surface area within the processing chamber1, a protruded amount of the extended protrusion60B′ toward the center of the microwave transmissive plate28needs to be increased. In this case, when plasma is generated, the effective area of the microwave transmissive plate28may be decreased as much as a contact area with respect to the upper surface60B1of the extended protrusion60B. Therefore, a supply amount of a microwave power into the processing chamber1may be decreased. As a result, plasma may not be generated, or even if generated, the plasma may be unstable. In order to solve this problem, the processing chamber1needs to be larger, but an installation space and a manufacturing cost of the apparatus may be increased. Further, if the microwave transmissive plate28and the extended protrusion60B are closely brought into contact with each other, the facing electrode's surface in a vicinity of the contact point (i.e. the leading end of the extended protrusion60B) between the microwave transmissive plate28and the facing electrode may be sputtered by plasma having a high density, and, thus, metal contamination may easily occur.

The gap L1may be, desirably, greater than a thickness of a sheath between plasma generated right below the microwave transmissive plate28and the microwave transmissive plate28, and sufficiently greater than an electron mean free path. By way of example, in the plasma processing apparatus100depicted inFIG. 1, if a high frequency bias voltage of about 50 V is applied under a processing pressure of about 6.7 Pa, a thickness of a sheath may be about 0.25 mm and an electron mean free path may be about 8 mm. Therefore, by way of example, the gap L1may be, desirably, in a range of from about 10 mm to about 30 mm and, more desirably, in a range of from about 20 mm to about 25 mm. When the gap L1is in the range described above, plasma can be maintained stably within the processing chamber1. When the gap L1is smaller than about 10 mm, an abnormal electric discharge may occur within the space S1and the plasma may not be stabilized. In particular, if the gap L1is smaller than the thickness of the sheath, it may be difficult to generate plasma within the processing chamber1. When the gap L1is greater than about 30 mm, the extended protrusion60B may be too close to the electrode7in the mounting table5. Thus, it may be difficult for the extended protrusion60B to serve as the facing electrode, and the extended protrusion60B may be damaged by a heat of the mounting table5.

Likewise, in order to prevent the extended protrusion60B from being too close to the electrode7in the mounting table5, it may be desirable that an upper limit of a thickness L2(i.e. a distance between the upper surface60B1and the lower surface60B3) of the extended protrusion60B may be, for example, about 20 mm. However, if the thickness L2of the extended protrusion60B is too small, an effect of the extended protrusion60B as the facing electrode may be decreased. Thus, desirably, a lower limit of the thickness L2may be, for example, about 5 mm. Therefore, the thickness L2of the extended protrusion60B may be, desirably, in a range of from about 5 mm to about 20 mm and, more desirably, in a range of from about 7 mm to about 17 mm.

A distance L3from the lower surface60B3of the extended protrusion60B to the upper surface of the mounting table5(herein, a height difference between two components) may be, for example, desirably, in a range of from about 15 mm to about 60 mm and, more desirably, in a range of from about 20 mm to about 25 mm in order for the extended protrusion60B to serve as the facing electrode but not to be too close to the electrode7in the mounting table5.

In the plasma processing apparatus100in accordance with the present embodiment, the gas inlet openings15amay be positioned above the extended protrusion60B and the processing gas may be supplied to the space S1between the extended protrusion60B and the microwave transmissive plate28. With this configuration, it may be possible to promote a substitution and a discharge of the gas within the space S1right below the microwave transmissive plate28, and the processing gas may be activated easily. Therefore, it may be possible to efficiently generate plasma in the entire space S1right below the microwave transmissive plate28. Further, the space S1may be a portion of the plasma generation space S. As another effect, as described in the following experiments, by supplying the processing gas into the space S1right below the microwave transmissive plate28, it may be possible to promote a discharge of oxygen released from the microwave transmissive plate28made of quartz to an outside of the processing chamber1when a plasma nitridation process is performed in the plasma processing apparatus100. Therefore, it may be possible to suppress a decrease in a concentration of nitrogen contained in a formed nitride film. As the causes that the oxygen may be released from the microwave transmissive plate28, the following two cases may be considered. First, the oxygen previously existing in the microwave transmissive plate28made of quartz is released. Second, when a plasma process is performed on the wafer W previously having an oxide film in the plasma processing apparatus100, oxygen released from the wafer W may be attracted to the microwave transmissive plate28, and then, the oxygen may be released during the plasma nitridation process.

In the plasma processing apparatus100in accordance with the present embodiment, the protective film48may be formed on the exposed surface of the protrusion60of the cover member27serving as the facing electrode. That is, the cover member27may be made of metal such as aluminum or aluminum alloy, and, thus, the cover member27may be coated with the protective film48as depicted inFIG. 2Ain order to prevent metal contamination or particles generated when the cover member27is exposed to plasma and sputtered by the plasma. The protective film48may be formed on a surface of the contact support60A and the upper surface60B1, the leading end surface60B2and the lower surface60B3of the extended protrusion60B. Desirably, the protective film48may be made of silicon considering contamination or particles generated when the protective film48is sputtered. The silicon may be crystalline silicon such as single crystalline silicon or polycrystalline silicon or may be amorphous silicon. Even if the protective film48is formed on the protrusion60, the protrusion60can serve as the facing electrode and stable plasma can be generated, so that it may be possible to perform a uniform plasma process. The protective film48can suppress a short circuit or an abnormal electric discharge in other portion by efficiently forming a path of a high frequency current flowing from the mounting table5to the cover member27via the protrusion60as the facing electrode with the plasma generation space S therebetween. Further, the protective film48can protect the surface of the facing electrode from an oxidation reaction or sputtering with plasma, and prevent generation of contamination caused by metal such as aluminum which is a material of the facing electrode. When a silicon film serving as the protective film48is formed, even if the silicon film may be oxidized by an oxidation reaction with plasma and become a silicon dioxide film (a SiO2film), the SiO2film may be very thin, and the product of a dielectric constant and resistivity thereof may be low. Thus, the path of the current flowing from the mounting table5to the cover member27as the facing electrode with the plasma generation space S therebetween may rarely be interrupted. Accordingly, it may be possible to maintain the stable and appropriate path of the high frequency current.

Desirably, the silicon film as the protective film48may have low porosity in the film so as to be dense and have low resistivity. If porosity in the film is increased, volume resistivity may also be increased. Therefore, by way of example, if the porosity is in a range of from about 1% to about 10%, the volume resistivity may be, desirably, in a range of from about 5×104Ω·cm2to about 5×105Ω·cm2. Desirably, such a silicon film may be formed by, for example, a plasma spraying method. Further, by way of example, a thickness of the protective film48may be, desirably, in a range of from about 10 μm to about 800 μm and, more desirably, in a range of from about 50 μm to about 500 μm and, still more desirably, in a range of from about 50 μm to about 150 μm. If the thickness of the protective film48is smaller than about 10 μm, a protection effect cannot be sufficiently secured. If the thickness of the protective film48is greater than about 800 μm, cracks or peeling-off may easily occur due to stress.

The protective film48may be formed by a thin film forming method such as PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition) other than the plasma spraying method. Among these methods, a spraying method may be desirable in that since it is relatively cheap and easy to perform, it may be possible to form the protective film of which porosity and volume resistivity can be controlled to be in a satisfactory range. The spraying method may include a flame spraying method, an arc spraying method, a laser spraying method, and a plasma spraying method. Among these methods, the plasma spraying method may be desirable in that it is easy to control and a high purity film can be formed. The plasma spraying method may include an atmospheric plasma spraying method and a vacuum plasma spraying method and either of them may be employed.

In the plasma processing apparatus100in accordance with the present embodiment, a cylindrical liner made of quartz may be provided at an inner periphery of the processing chamber1. The liner may include the upper liner49aas a first insulating plate and a lower liner49bas a second insulating plate. The upper liner49ais configured to cover an inner surface of the upper portion of the processing chamber1, and the lower liner49bis connected to the upper liner49aand configured to cover an inner surface of the lower portion of the processing chamber1. The upper liner49aand the lower liner49bmay prevent a contact between a wall of the processing chamber1and plasma, and also prevent metal contamination caused by a material of the processing chamber1. Further, the upper liner49aand the lower liner49bmay prevent a short circuit or an abnormal electric discharge of the high frequency current from the mounting table5toward the sidewall1bof the processing chamber1. The lower liner49bpositioned to be adjacent to the mounting table5with a small gap therebetween may have a thickness much greater than that of the upper liner49a. Each of the upper liner49aand the lower liner49bmay have an enough thickness so as not to generate a short circuit or an abnormal electric discharge of the high frequency current, and the thickness may be set considering impedance. Desirably, the thickness of the lower liner49bmay be set to be larger than that of the upper liner49ain a range of, for example, from about 2 mm to about 30 mm.

The lower liner49bmay be provided so as to cover at least a part of inner surfaces, desirably almost entire surfaces, of the processing chamber1and the exhaust chamber11positioned lower than the mounting table5having therein the electrode7. The reason why the liner49bis provided as stated above is that since a distance between the mounting table5and the processing chamber1becomes shortest below the mounting table5, an abnormal electric discharge needs to be prevented in this region. The upper liner49aand the lower liner49bmay be made of, desirably, quartz. However, a dielectric material such as ceramic, for example, Al2O3, AlN and Y2O3may be employed. The upper liner49aand the lower liner49bmay be coated with the above-described materials. Further, by way of example, surfaces of the upper liner49aand the lower liner49bmade of aluminum may be coated with, for example, a SiO2film by the plasma spraying method.

Each component of the plasma processing apparatus100may be connected to and controlled by a control unit50including a computer. The control unit50may include, for example, a process controller51including a CPU, a user interface52connected to the process controller51, and storage53as depicted inFIG. 4. The process controller51may overall control components (for example, the heater power supply6, the gas supply unit16, the exhaust device24, the microwave generator39, the high frequency power supply44or the like) of the plasma processing apparatus100. The components are related to process conditions such as a temperature, a pressure, a gas flow rate, a microwave output and a high frequency power for applying a bias.

The user interface52may include a keyboard with which a process manager may input a command to operate the plasma processing apparatus100, or a display for visualizing and displaying an operational status of the plasma processing apparatus100. The storage53may store therein control programs (software) for executing various processes performed in the plasma processing apparatus100under control of the process controller51or recipes including process condition data or the like.

If necessary, when a command is received from the user interface52, the process controller51may retrieve a certain recipe from the storage53and execute it. Thus, a required process may be performed in the processing chamber1of the plasma processing apparatus100under control of the process controller51. The control programs or recipes including the process condition data can be read out from a computer-readable storage medium (for example, a CD-ROM, a hard disk, a flexible disk, a flash memory, a DVD, a blue ray disk or the like). Otherwise, the recipes may be received from another apparatus via, for example, a dedicated line.

In the plasma processing apparatus100configured as described above, a plasma oxidation process or a plasma nitridation process can be performed without damage on an underlying film or a substrate (wafer W) at a low temperature in a range of, for example, from room temperature (about 25° C.) to about 600° C. Further, in the plasma processing apparatus100, plasma may have high uniformity, and, thus, uniformity in a process can be secured for a large-diameter wafer W (target object).

Hereinafter, an operation of the plasma processing apparatus100will be explained. Above all, the wafer W may be loaded into the processing chamber1and mounted on the mounting table5. Then, a processing gas from the gas supply unit16may be introduced into the processing chamber1through the gas supply channels12, the annular path13and the gas inlet openings15a. As the processing gas, a rare gas such as Ar, Kr or He may be used. In addition to the rare gas, an oxidizing gas such as O2, N2O, NO, NO2or CO2in case of the plasma oxidation process or a nitrogen-containing gas such as N2or NH3in case of the plasma nitridation process may be supplied at a certain flow rate. Further, in case of the plasma oxidation process, H2may be added if necessary.

Subsequently, a microwave from the microwave generator39may be introduced to the waveguide37via the matching circuit38. The introduced microwave may pass through the rectangular waveguide37b, the mode converter40and the coaxial waveguide37ain sequence, and then, may be supplied into the planar antenna31via the internal conductor41. Thereafter, the microwave may be radiated into the processing chamber1from the slot holes32of the planar antenna31through the microwave transmissive plate28. In the meantime, the microwave may be propagated in a TE mode within the rectangular waveguide37b. Then, the microwave of the TE mode may be converted into a TEM mode by the mode converter40and propagated within the coaxial waveguide37atoward the planar antenna31. By the microwave radiated from the planar antenna31into the processing chamber1through the microwave transmissive plate28, an electromagnetic field may be generated in the processing chamber1and the processing gas may be excited into plasma.

Since the microwave may be radiated through the multiple slot holes32of the planar antenna31, this plasma may have a high density in a range of from about 1×1010/cm3to about 5×1012/cm3and a low electron temperature of about 1.5 eV in a vicinity of the wafer W. Therefore, by applying this plasma to the wafer W, a process can be performed while suppressing plasma damage.

In the present embodiment, during a plasma process, a high frequency power of a certain frequency may be supplied from the high frequency power supply44to the electrode7in the mounting table5. A frequency of the high frequency power supplied from the high frequency power supply44may be, desirably, in a range of, for example, from about 100 kHz to about 60 MHz and, more desirably, in a range of from about 400 kHz to about 13.5 MHz. By setting the frequency of the high frequency power to be in this range, a negative bias power can be efficiently applied to the mounting table5.

The high frequency power may be applied, as a power density per unit area of the wafer W, desirably, in a range of, for example, from about 0.2 W/cm2to about 2.3 W/cm2and, more desirably, in a range of from about 0.35 W/cm2to about 1.2 W/cm2. By setting the power density of the high frequency power to be in this range, the negative bias power can be efficiently applied to the mounting table5.

Further, the high frequency power may be, desirably, in a range of from about 200 W to about 2000 W and, more desirably, in a range of from about 300 W to about 1200 W. By setting the high frequency power to be in this range, the negative bias power can be efficiently applied to the mounting table5.

The high frequency power applied to the electrode7in the mounting table5may maintain the plasma at a low electron temperature, and attract ion species in the plasma toward the wafer W. Therefore, by supplying the high frequency power to the electrode7and applying the bias power to the wafer W, it is possible to increase a processing rate of the plasma oxidation process or the plasma nitridation process, and also possible to perform an uniform process on the wafer.

In this case, the high frequency power can be efficiently applied to the electrode7in the mounting table5from the high frequency power supply44, with a low power loss, via the high frequency power inlet unit (the matching box43and the conductive plate47within the shield box46) and the power supply line42. The high frequency power applied to the electrode7may be transmitted from the mounting table5to the cover member27including the protrusion60serving as the facing electrode via the plasma generation space S, and then, transmitted to the earth of the high frequency power supply44via the sidewall1bof the processing chamber1and a wall of the exhaust chamber11. The above-described transmitting route of the high frequency power may form the high frequency current path (the RF return circuit). In the present embodiment, by providing the extended protrusion60B, oscillation of the plasma potential Vp can be suppressed, and stable plasma can be generated within the processing chamber1. Further, it may be possible to prevent the surface of the facing electrode from being sputtered by the plasma and from being a cause of metal contamination.

Further, on the exposed surface, facing the plasma generation space S, of the protrusion60serving as the facing electrode, the conductive protective film48(a silicon film or a SiO2film formed by oxidizing silicon) may be formed. Thus, the surface of the facing electrode can be protected. Further, it is possible to form the high frequency current path, through which the high frequency current may flow appropriately from the mounting table5to the cover member27as the facing electrode with the plasma generation space S therebetween, without any interruption. Further, the upper liner49aand the lower liner49bhaving a thickness greater than that of the upper liner49amay be provided on the inner surface of the processing chamber1to be adjacent to the protective film48. Thus, a short circuit or an abnormal electric discharge can be surely prevented at these components. That is, the abnormal electric discharge and the metal contamination can be prevented by the protective film48.

As described above, in the plasma processing apparatus100in accordance with the present embodiment, by the extended protrusion60B of the protrusion60serving as the facing electrode, the facing electrode may have a sufficiently large surface area, and the appropriate high frequency current path may be formed. Therefore, it may be possible to enhance power consumption efficiency of the high frequency bias power supplied to the electrode7in the mounting table5for mounting the wafer W thereon. Further, by forming the space S1between the extended protrusion60B and the microwave transmissive plate28and providing the facing electrode so as to protrude toward the plasma generation space S, it may be possible to generate stable plasma in the plasma generation space S and the space S1. Furthermore, by preventing the abnormal electric discharge, it may be possible to perform an efficient and stableprocess. Moreover, since the extended protrusion60B may be provided with the gap L1with respect to the microwave transmissive plate28, it may not be necessary to reduce an effective area, through which the microwave is transmitted, of the microwave transmissive plate28. Accordingly, it may be possible to introduce a sufficient microwave power, and also possible to stabilize plasma generated within the processing chamber1.

Second Embodiment

Hereinafter, a plasma processing apparatus in accordance with a second embodiment of the present disclosure will be explained with reference toFIG. 5. A plasma processing apparatus101in accordance with the second embodiment is the same, except its features, as the plasma processing apparatus100in accordance with the first embodiment. Therefore, explanation (FIGS. 1,3A and4) of the whole configuration will be omitted. Some components illustrated inFIG. 5which are the same as the components illustrated inFIG. 2Awill be assigned same reference numerals and explanation thereof will be omitted.

In the plasma processing apparatus101in accordance with the present embodiment, at an inner peripheral surface of a cover member27, a protrusion61may constitute a part of the cover member27. Since the cover member27and the protrusion61are formed as a single body, thermal conductivity and electric conductivity can be secured. The protrusion61may include a contact support61A and an extended protrusion61B. The extended protrusion61B of the protrusion61may include an upper surface61B1, a leading end surface61B2, and a lower surface61B3. The protrusion61may be formed toward a plasma generation space S and may serve as a facing electrode (second electrode) facing an electrode7(first electrode) within a mounting table5with the plasma generation space S therebetween. To be specific, inFIG. 5, a surface ranging from a position A indicated by a circle to a position B indicated by a circle and including an exposed surface of the protrusion61(i.e. a surface of the contact support61A and the upper surface61B1, the leading end surface61B2, and the lower surface61B3of the extended protrusion61B) may serve as the facing electrode. Here, the position A is an end of a contact portion between the contact support61A of the cover member27and the microwave transmissive plate28. Further, the position B is an end (i.e., an end contacted with an upper liner49a) of an exposed lower surface of the contact support61A. In the present embodiment, the inner peripheral surface of the annular cover member27ranging from the position A to the position B may be exposed to the plasma generation space S and may serve as the facing electrode of an annular shape. In this way, by providing an annular member serving as a facing electrode so as to protrude toward the plasma generation space, even in the RLSA-type plasma processing apparatus101in which it is difficult to provide a facing electrode right above the mounting table5due to the microwave transmissive plate28, the facing electrode may have a sufficiently large surface area.

Further, in the plasma processing apparatus101in accordance with the present embodiment, a front surface (i.e. the upper surface61B1), the leading end surface61B2, the lower surface61B3of the extended protrusion61B of the protrusion61playing as a major role in the facing electrode may be formed to have a cross-sectional shape having prominences and depressions, and the facing electrode may have a sufficiently large surface area. With this shape of the extended protrusion61B serving as the facing electrode, the facing electrode may have a large area within a limited space of a processing chamber1. In the present embodiment, in order to generate stable plasma within the processing chamber1by suppressing the oscillation of the plasma potential and reduce sputtering by the plasma in a vicinity of the facing electrode, a ratio of the facing electrode surface area to a bias electrode area may be, desirably, about 1 or higher and, more desirably, in a range of from about 1 to about 5 and, still more desirably, in a range of from about 1 to about 4 and, still more desirably, in a range of from about 2 to about 4. The plasma processing apparatus101depicted inFIG. 5has the area ratio of about 5.

Desirably, the leading end surface61B2of the protrusion61serving as the facing electrode may have a protruded length which does not reach a position PWEof a peripheral end of the wafer W mounted on the mounting table5. If a leading end of the protrusion61reaches an inner position than the position PWEof the peripheral end of the wafer W, a range of plasma having a high density, generated within the processing chamber1, may be smaller than a size of the wafer W and a density of the plasma at a periphery of the wafer W may be decreased. As a result, there may be a possibility that a process is not uniformly performed at an outer periphery of the wafer W. At a side (on the sidewall1b's side of the processing chamber1) opposite to the leading end (the leading end surface61B2) of the protrusion61serving as the facing electrode, a contact end with the sidewall1bmay become a base end. However, in the present embodiment, it may be sufficient if the position B on the way to the base end is exposed to the plasma generation space S. That is, in the present embodiment, an end of the exposed lower surface of the contact support61A of the protrusion61serving as the facing electrode may be a contact point with respect to the upper liner49a. The contact point is indicated as the position B inFIG. 5.

Further, the upper surface61B1(facing the space S1) of the extended protrusion61B may be spaced from a lower surface of the microwave transmissive plate28. That is, the extended protrusion61B may protrude toward the plasma generation space S with a gap L1with respect to the microwave transmissive plate28. In this way, since there is the gap L1between the microwave transmissive plate28and the extended protrusion61B, the facing electrode may have a sufficiently large surface area without reducing an effective area, through which a microwave is transmitted, of the microwave transmissive plate28. The space S1may become a portion of the plasma generation space S and plasma may also be generated in the space S1. Thus, a plasma process can be performed uniformly on the wafer W. On the contrary, if the microwave transmissive plate28and the extended protrusion61B are brought into contact with each other without the gap L1therebetween, in order for the facing electrode to have a large surface area within the processing chamber1, a protruded amount of the extended protrusion61B toward a center of the microwave transmissive plate28needs to be increased. In this case, when plasma is generated, the effective area of the microwave transmissive plate28may be decreased as much as a contact area with respect to the extended protrusion61B. Therefore, a supply amount of a microwave power into the processing chamber1may be decreased. As a result, plasma may not be generated, or even if generated, the plasma may be unstable. In order to solve this problem, the processing chamber1needs to be larger, but an installation space and a manufacturing cost of the apparatus may be increased.

The gap L1may be, desirably, greater than a thickness of a sheath between plasma generated right below the microwave transmissive plate28and the microwave transmissive plate28, and sufficiently greater than a mean free path of electrons. By way of example, the gap L1may be, desirably, in a range of from about 10 mm to about 30 mm and, more desirably, in a range of from about 20 mm to about 25 mm. When the gap L1is smaller than about 10 mm, an abnormal electric discharge may occur within the space S1and the plasma may not be stabilized. In particular, if the gap L1is smaller than the thickness of the sheath, it may be difficult to generate plasma within the processing chamber1. When the gap L1is greater than about 30 mm, the extended protrusion61B may be too close to the electrode7in the mounting table5. Thus, it may be difficult for the extended protrusion61B to serve as the facing electrode, and the extended protrusion61B may be damaged by heat of the mounting table5.

Likewise, in order to prevent the extended protrusion61B from being too close to the electrode7in the mounting table5, it may be desirable that an upper limit of a thickness L2(i.e. a distance between the upper surface61B1and the lower surface61B3) of the extended protrusion61B may be, for example, about 20 mm. However, if the thickness L2of the extended protrusion61B is too small, an effect of the extended protrusion61B as the facing electrode may be decreased. Thus, desirably, a lower limit of the thickness L2may be, for example, about 5 mm. Therefore, the thickness L2of the extended protrusion61B may be, desirably, in a range of from about 5 mm to about 20 mm and more desirably, in a range of from about 7 mm to about 17 mm

A distance L3from the lower surface61B3of the extended protrusion61B to the upper surface of the mounting table5(herein, a height difference between two components) may be, for example, desirably, in a range of from about 15 mm to about 60 mm and more desirably, in a range of from about 20 mm to about 25 mm in order for the extended protrusion61B to serve as the facing electrode but not to be too close to the electrode7in the mounting table5.

In the plasma processing apparatus101in accordance with the present embodiment, gas inlet openings15amay be positioned at the contact support61A above the extended protrusion61B and a processing gas may be supplied to the space S1between the extended protrusion61B and the microwave transmissive plate28. With this configuration, it may be possible to promote a substitution and a discharge of a gas in the space S1(which serves as a portion of the plasma generation space S) right below the microwave transmissive plate28, and the processing gas may be activated easily. Therefore, it may be possible to efficiently generate plasma in the entire space S1right below the microwave transmissive plate28. As another effect, by supplying the processing gas into the space S1right below the microwave transmissive plate28, it may be possible to promote a discharge of oxygen released from the microwave transmissive plate28made of quartz when a plasma nitridation process is performed in the plasma processing apparatus101. Therefore, it may be possible to suppress a decrease in a concentration of nitrogen contained in a formed nitride film.

In the present embodiment, a protective film48may be formed on the exposed surface of the protrusion61. The protective film48may prevent the protrusion61from being exposed to plasma and sputtered by the plasma to generate metal contamination or particles. Even if the protective film48is formed on the protrusion61, the protrusion61can serve as the facing electrode and stable plasma can be generated, so that it may be possible to perform a uniform plasma process.

The prominences and depressions of the extended protrusion61B may be not limited to a shape as depicted inFIG. 5. In order for the extended protrusion61B to have a greater surface area, a certain shape such as a groove shape or a hole shape may be selected. However, in order to prevent an abnormal electric discharge or generation of particles on the surface of the extended protrusion61B protruding toward the plasma generation space S, it is desirable that angled portions of the extended protrusion61B may be formed in rounded shapes as depicted inFIG. 5. Further, it is not necessary to form the prominences and depressions on the entire surface of the extended protrusion61B. Instead, by way of example, the prominences and depressions may be formed only on the upper surface61B1or lower surface61B3of the extended protrusion61B.

Other configurations and effects of the present embodiment are the same as those of the first embodiment.

Third Embodiment

Hereinafter, a plasma processing apparatus in accordance with a third embodiment of the present disclosure will be explained with reference toFIG. 6. A plasma processing apparatus102in accordance with the third embodiment is the same, except its features, as the plasma processing apparatus100in accordance with the first embodiment. Therefore, explanation (FIGS. 1,3A and4) of the whole configuration will be omitted. Some components illustrated inFIG. 6which are the same as the components illustrated inFIG. 2Awill be assigned same reference numerals and explanation thereof will be omitted.

In the plasma processing apparatuses in accordance with the first and second embodiments, extended protrusions60B and61B may be respectively formed at protrusions60and61of a cover member27as the facing electrode. However, in the plasma processing apparatus102in accordance with the present embodiment, an extended protrusion62protruding inwards may be formed at an upper region of a processing chamber1as a part of the processing chamber1, so that an area serving as the facing electrode can be increased. Since the processing chamber1and the protrusion62are formed as a single body, thermal conductivity and electric conductivity can be secured. The extended protrusion62may be partially contacted with a contact support60′ of the cover member27and may be electrically connected to the contact support60′. The contact support60′ may support a microwave transmissive plate28.

The extended protrusion62may be formed at an upper end of a sidewall1bof the processing chamber1. The extended protrusion62may include a contact section62A in contact with a contact support60′ of the cover member27and an exposed portion62B including an exposed upper surface62B1, a leading end surface62B2and a lower surface62B3. The contact support60′ and the extended protrusion62may be formed toward a plasma generation space S and may serve as a facing electrode (second electrode) in pairs with respect to an electrode7(first electrode) within a mounting table5with the plasma generation space S therebetween. To be specific, inFIG. 6, an inner peripheral surface ranging from a position A indicated by a circle to a position B indicated by a circle and including an exposed surface of the contact support60′ and a surface of the extended protrusion62(i.e. the exposed upper surface62B1, the leading end surface62B2, and lower surface62B3of the extended protrusion62) may serve as the facing electrode. Here, the position A is an end of a contact portion between the contact support60′ of the cover member27and the microwave transmissive plate28. Further, the position B is an end (i.e., an end contacted with an upper liner49a) of an exposed lower surface of the extended protrusion62. In the present embodiment, the surface ranging from the position A to the position B may be exposed to the plasma generation space S and may serve as the facing electrode of an annular shape. In this way, the facing electrode can be formed by multiple components (the cover member27and the processing chamber1) having surfaces facing the plasma generation space S. By providing an annular member serving as a facing electrode so as to protrude toward the plasma generation space, even in the RLSA-type plasma processing apparatus102in which it is difficult to provide a facing electrode right above the mounting table5due to the microwave transmissive plate28, the facing electrode may have a sufficiently large surface area. Further, in the present embodiment, the extended protrusion62as an extended part of the facing electrode may be formed at the upper region of the processing chamber1, and, thus, it may be effective in reducing a distance (gap G; seeFIG. 1) from a surface of a wafer W mounting on the mounting table5to the microwave transmissive plate28.

In the present embodiment, in order to generate stable plasma within the processing chamber1by suppressing the oscillation of the plasma potential and reduce sputtering by the plasma in a vicinity of the facing electrode, a ratio of the facing electrode surface area to a bias electrode area may be, desirably, about 1 or higher and, more desirably, in a range of from about 1 to about 5 and, still more desirably, in a range of from about 1 to about 4 and, still more desirably, in a range of from about 2 to about 4.

Desirably, the leading end surface62B2of the extended protrusion62serving as the facing electrode may have a protruded length which does not reach a position PWEof a peripheral end of the wafer W mounted on the mounting table5. If a leading end of the extended protrusion62reaches an inner position than the position PWEof the peripheral end of the wafer W, a range of plasma having a high density, generated within the processing chamber1, may be smaller than a size of the wafer W and a density of the plasma at a periphery of the wafer W may be decreased. As a result, there may be a possibility that a process is not uniformly performed at an outer periphery of the wafer W. At a side (on the sidewall1b's side of the processing chamber1) opposite to the leading end (the leading end surface62B2) in the extended protrusion62serving as the facing electrode, an angled portion bending from the sidewall1bmay become a base end. However, in the present embodiment, it may be sufficient if the position B on the way to the base end is exposed to the plasma generation space S. That is, in the present embodiment, an end of the exposed lower surface of the extended protrusion62serving as the facing electrode may be a contact point with respect to the upper liner49a. The contact point is indicated as the position B inFIG. 6.

Further, the upper surface62B1(facing the space S1) of the extended protrusion62may be spaced from a lower surface of the microwave transmissive plate28. That is, the extended protrusion62may protrude toward the plasma generation space S with a gap L1with respect to the microwave transmissive plate28. In this way, since there is the gap L1between the microwave transmissive plate28and the extended protrusion62, the facing electrode may have a sufficiently large surface area without reducing an effective area, through which a microwave is transmitted, of the microwave transmissive plate28. The space S1may become a portion of the plasma generation space S and plasma may also be generated in the space S1. Thus, a plasma process can be performed uniformly on the wafer W. On the contrary, if the microwave transmissive plate28and the extended protrusion62are brought into contact with each other without the gap L1therebetween, in order for the facing electrode to have a large surface area within the processing chamber1, a protruded amount of the extended protrusion62toward a center of the microwave transmissive plate28needs to be increased. In this case, when plasma is generated, the effective area of the microwave transmissive plate28may be decreased as much as a contact area with the upper surface62B1of the extended protrusion62. Therefore, a supply amount of a microwave power into the processing chamber1may be decreased. As a result, plasma may not be generated, or even if generated, the plasma may be unstable. In order to solve this problem, the processing chamber1needs to be larger, but an installation space and a manufacturing cost of the apparatus may be increased.

The gap L1may be, desirably, greater than a thickness of a sheath between plasma generated right below the microwave transmissive plate28and the microwave transmissive plate28and by way of example, the gap L1may be, desirably, in a range of from about 10 mm to about 30 mm and more desirably, in a range of from about 20 mm to about 25 mm. When the gap L1is smaller than about 10 mm, an abnormal electric discharge may occur within the space S1and the plasma may not be stabilized. In particular, if the gap L1is equal to or smaller than the thickness of the sheath, it may be difficult to generate plasma within the processing chamber1. When the gap L1is greater than about 30 mm, the extended protrusion62may be too close to the electrode7in the mounting table5. Thus, it may be difficult for the extended protrusion62to serve as the facing electrode and the extended protrusion62may be damaged by heat of the mounting table5.

Likewise, in order to prevent the extended protrusion62from being too close to the electrode7in the mounting table5, it may be desirable that an upper limit of a thickness L2(i.e. a distance between the upper surface62B1and the lower surface62B3) of the extended protrusion62may be, for example, about 20 mm. However, if the thickness L2of the extended protrusion62is too small, an effect of the extended protrusion62as the facing electrode may be decreased. Thus, desirably, a lower limit of the thickness L2may be, for example, about 5 mm. Therefore, the thickness L2of the extended protrusion62may be, desirably, in a range of from about 5 mm to about 20 mm and more desirably, in a range of from about 7 mm to about 17 mm.

A distance L3from the lower surface62B3of the extended protrusion62to the upper surface of the mounting table5(herein, a height difference between two components) may be, for example, desirably, in a range of from about 15 mm to about 60 mm and more desirably, in a range of from about 20 mm to about 25 mm in order for the extended protrusion62to serve as the facing electrode but not to be too close to the electrode7in the mounting table5.

In the plasma processing apparatus102in accordance with the present embodiment, gas inlet openings15amay be positioned at the contact support60′ above the extended protrusion62and a processing gas may be supplied to the space S1between the extended protrusion62and the microwave transmissive plate28. With this configuration, it may be possible to promote a substitution and a discharge of a gas in the space S1(which serves as a portion of the plasma generation space S) right below the microwave transmissive plate28, and the processing gas may be activated easily. Therefore, it may be possible to efficiently generate plasma in the entire space S1right below the microwave transmissive plate28. As another effect, by supplying the processing gas into the space S1right below the microwave transmissive plate28, it may be possible to promote a discharge of oxygen released from the microwave transmissive plate28made of quartz when a plasma nitridation process is performed in the plasma processing apparatus102. Therefore, it may be possible to suppress a decrease in a concentration of nitrogen contained in a formed nitride film.

In the plasma processing apparatus102in accordance with present embodiment, a protective film48may be formed on surfaces of the contact support60′ and the extended protrusion62serving as the facing electrode. That is, as depicted inFIG. 6, the protective film48may be formed on a surface of the contact support60′ of the aluminum cover member27exposed to plasma. Further, the protective film48may be formed on a surface of the extended protrusion62exposed to plasma within the processing chamber1. The protective film48may prevent the contact support60′ and the extended protrusion62from being exposed to plasma and sputtered by the plasma to generate metal contamination or particles. Even if the protective film48is formed on the contact support60′ or the extended protrusion62, the contact support60′ or the extended protrusion62can serve as the facing electrode and stable plasma can be generated, so that it may be possible to perform a uniform plasma process.

Other configurations and effects of the present embodiment are the same as those of the first embodiment.

Fourth Embodiment

Hereinafter, a plasma processing apparatus in accordance with a fourth embodiment of the present disclosure will be explained with reference toFIG. 7. A plasma processing apparatus103in accordance with the fourth embodiment is the same, except its features, as the plasma processing apparatus100in accordance with the first embodiment. Therefore, explanation (FIGS. 1,3A and4) of the whole configuration will be omitted. Some components illustrated inFIG. 7which are the same as the components illustrated inFIG. 2Awill be assigned same reference numerals and explanation thereof will be omitted.

In the plasma processing apparatus103in accordance with the present embodiment, an extended protrusion63may be provided such that an annular auxiliary electrode member may detachably attach to a contact support60′ of a cover member27. In this way, an auxiliary member may be provided as a part or the whole of a facing electrode. Since the extended protrusion63is formed as a separate component from the cover member27or a processing chamber1, it may be easy to replace the extended protrusion63as consumables. The extended protrusion63may include an upper surface63a, a leading end surface63band a lower surface63c.

A material of the auxiliary electrode member of the extended protrusion63may be not limited if it is a conductive material. By way of example, it may be possible to employ a metal material such as aluminum, aluminum alloy or stainless steel, or also employ silicon. In particular, if the extended protrusion63is made of silicon, the silicon may have an advantage since it is not necessary to form a protective film on a surface of the extended protrusion63. The extended protrusion63may be fixed to an inner peripheral surface of the contact support60′ of the cover member27by, for example, a non-illustrated screw in a certain fixing direction.

Further, in the plasma processing apparatus103in accordance with the present embodiment, the extended protrusion63may be formed toward a plasma generation space S and may serve as a facing electrode (second electrode) facing an electrode7(first electrode) within a mounting table5with the plasma generation space S therebetween. To be specific, inFIG. 7, an inner peripheral surface ranging from a position A indicated by a circle to a position B indicated by a circle and including an exposed surface of the contact support60′ and an exposed surface of the extended protrusion63(i.e. the exposed upper surface63a, leading end surface63b, and lower surface63cof the extended protrusion63) may serve as the facing electrode. Here, the position A is an end of a contact portion between the contact support60′ of the cover member27and the microwave transmissive plate28. Further, the position B is an end (i.e., an end contacted with an upper liner49a) of an exposed surface of the contact support60′. In the present embodiment, the surface ranging from the position A to the position B may be exposed to the plasma generation space S and may serve as the facing electrode of an annular shape. In this way, the facing electrode may be formed by multiple components (the cover member27and an auxiliary electrode member of the extended protrusion63) having surfaces facing the plasma generation space S. By providing an annular member serving as a facing electrode so as to protrude toward the plasma generation space, even in the RLSA-type plasma processing apparatus103in which it is difficult to provide a facing electrode right above the mounting table5due to the microwave transmissive plate28, the facing electrode may have a sufficiently large surface area.

Further, in the present embodiment, by additionally attaching the extended protrusion63to the contact support60′ of the cover member27, the portion serving as the facing electrode can have a sufficiently large surface area. In this way, the facing electrode may be formed by combining the multiple components, and, thus, the facing electrode can have a sufficiently large area within a limited space of a processing chamber1. In the present embodiment, in order to generate stable plasma within the processing chamber1by suppressing the oscillation of the plasma potential and reduce sputtering by the plasma in a vicinity of the facing electrode, a ratio of the facing electrode surface area to a bias electrode area may be, desirably, about 1 or higher and, more desirably, in a range of from about 1 to about 5 and, still more desirably, in a range of from about 1 to about 4 and, still more desirably, in a range of from about 2 to about 4.

Desirably, a leading end (the leading end surface63b) of the extended protrusion63serving as the facing electrode may have a protruded length which does not reach a position PWEof a peripheral end of the wafer W mounted on the mounting table5. If the leading end of the extended protrusion63reaches an inner position than the position PWEof the peripheral end of the wafer W, a range of plasma having a high density, generated within the processing chamber1, may be smaller than a size of the wafer W and a density of the plasma at a periphery of the wafer W may be decreased. As a result, there may be a possibility that a process is not uniformly performed at an outer periphery of the wafer W. At a side opposite to the leading end (the leading end surface63b) in the extended protrusion63, a portion ranging from a contact portion between the extended protrusion63and the contact support60′ to the position B may also be exposed to the plasma generation space S. That is, in the present embodiment, an end of the exposed lower surface of the contact support60′ serving as the facing electrode may be a contact point with respect to an upper liner49a. The contact point is indicated as the position B inFIG. 7.

Further, the upper surface63aof the extended protrusion63may be spaced from a lower surface of the microwave transmissive plate28. That is, the extended protrusion63may protrude toward the plasma generation space S with a gap L1with respect to the microwave transmissive plate28. In this way, since there is the gap L1between the microwave transmissive plate28and the extended protrusion63, the facing electrode may have a sufficiently large surface area without reducing an effective area, through which a microwave is transmitted, of the microwave transmissive plate28. The space S1may become a portion of the plasma generation space S and plasma may also be generated in the space S1. Thus, a plasma process can be performed uniformly on the wafer W. On the contrary, if the microwave transmissive plate28and the extended protrusion63are brought into contact with each other without the gap L1therebetween, in order for the facing electrode to have a large surface area within the processing chamber1, a protruded amount of the extended protrusion63toward a center of the microwave transmissive plate28needs to be increased. In this case, when plasma is generated, the effective area of the microwave transmissive plate28may be decreased as much as a contact area with the upper surface63aof the extended protrusion63. Therefore, a supply amount of a microwave power into the processing chamber1may be decreased. As a result, plasma may not be generated, or even if generated, the plasma may be unstable. In order to solve this problem, the processing chamber1needs to be larger, but an installation space and a manufacturing cost of the apparatus may be increased.

The gap L1may be, desirably, greater than a thickness of a sheath between plasma generated right below the microwave transmissive plate28and the microwave transmissive plate28and by way of example, the gap L1may be, desirably, in a range of from about 10 mm to about 30 mm and more desirably, in a range of from about 20 mm to about 25 mm. When the gap L1is smaller than about 10 mm, an abnormal electric discharge may occur within the space S1and the plasma may not be stabilized. In particular, if the gap L1is equal to or smaller than the thickness of the sheath, it may be difficult to generate plasma within the processing chamber1. When the gap L1is greater than about 30 mm, the extended protrusion63may be too close to the electrode7in the mounting table5. Thus, it may be difficult for the extended protrusion63to serve as the facing electrode and the extended protrusion63may be damaged by heat of the mounting table5.

Likewise, in order to prevent the extended protrusion63from being too close to the electrode7in the mounting table5, it may be desirable that an upper limit of a thickness L2(i.e. a distance between the upper surface63aand the lower surface63c) of the extended protrusion63may be, for example, about 20 mm. However, if the thickness L2of the extended protrusion63is too small, an effect of the extended protrusion63as the facing electrode may be decreased. Thus, desirably, a lower limit of the thickness L2may be, for example, about 5 mm. Therefore, the thickness L2of the extended protrusion63may be, desirably, in a range of from about 5 mm to about 20 mm and more desirably, in a range of from about 7 mm to about 17 mm.

A distance L3from the lower surface63cof the extended protrusion63to the upper surface of the mounting table5(herein, a height difference between two components) may be, for example, desirably, in a range of from about 15 mm to about 60 mm and more desirably, in a range of from about 20 mm to about 25 mm in order for the extended protrusion63to serve as the facing electrode but not to be too close to the electrode7in the mounting table5.

In the plasma processing apparatus103in accordance with the present embodiment, gas inlet openings15amay be positioned at the contact support60′ above the extended protrusion63and a processing gas may be supplied to the space S1between the extended protrusion63and the microwave transmissive plate28. With this configuration, it may be possible to promote a substitution and a discharge of a gas in the space S1(which serves as a portion of the plasma generation space S) right below the microwave transmissive plate28, and the processing gas may be activated easily. Therefore, it may be possible to efficiently generate plasma in the entire space S1right below the microwave transmissive plate28. As another effect, by supplying the processing gas into the space S1right below the microwave transmissive plate28, it may be possible to promote a discharge of oxygen released from the microwave transmissive plate28made of quartz when a plasma nitridation process is performed in the plasma processing apparatus103. Therefore, it may be possible to suppress a decrease in a concentration of nitrogen contained in a formed nitride film.

A cross sectional shape of the extended protrusion63may not be limited to the shape as depicted inFIG. 7. In order for the extended protrusion63to have a greater surface area, a certain shape, for example, a L-shaped cross sectional shape may be selected. Otherwise, prominences and depressions or groove may be formed on a surface of the extended protrusion63. However, in order to prevent an abnormal electric discharge or generation of particles on the surface of the extended protrusion63protruding toward the plasma generation space S, it is desirable that angled portions of the extended protrusion63may be formed in rounded shapes as depicted inFIG. 7. In the present embodiment, a protective film48may be formed on the exposed surfaces of the contact support60′ and the extended protrusion63facing the plasma generation space S. The protective film48may prevent the contact support60′ and the extended protrusion63from being exposed to plasma and sputtered by the plasma to generate metal contamination or particles. Even if the protective film48is formed on the contact support60′ and extended protrusion63, the contact support60′ and extended protrusion63can serve as the facing electrode and stable plasma can be generated, so that it may be possible to perform a uniform plasma process. Further, if the entire extended protrusion63is made of silicon, the protective film may not be formed thereon.

Other configurations and effects of the present embodiment are the same as those of the first embodiment.

Fifth Embodiment

Hereinafter, a plasma processing apparatus in accordance with a fifth embodiment of the present disclosure will be explained with reference toFIG. 8. A plasma processing apparatus104in accordance with the fifth embodiment is the same, except its features, as the plasma processing apparatus100in accordance with the first embodiment. Therefore, explanation (FIGS. 1,3A and4) of the whole configuration will be omitted. Some components illustrated inFIG. 8which are the same as the components illustrated inFIG. 2Awill be assigned same reference numerals and explanation thereof will be omitted.

In the plasma processing apparatus103in accordance with the fourth embodiment, the extended protrusion63(auxiliary electrode member) may be provided at the cover member27. However, in the plasma processing apparatus104in accordance with the present embodiment, an extended protrusion64(annular auxiliary electrode member) may be provided so as to detachably attach to an upper region of a processing chamber1. In this way, an auxiliary member may be provided as a part or the whole of a facing electrode. Since the extended protrusion64is formed as a separate component from the cover member27or the processing chamber1, it may be easy to replace the extended protrusion64as consumables. The extended protrusion64may include an upper surface64a, a leading end surface64band a lower surface64c. At the upper surface64aof the extended protrusion64, a step-shaped portion may be formed corresponding to a shape of a contact support60′ of the cover member27. Further, the lower surface64cof the extended protrusion64may include multiple (two inFIG. 8) annular grooves64d.

A material of the extended protrusion64may be not limited if it is a conductive material. By way of example, it may be possible to employ a metal material such as aluminum, aluminum alloy or stainless steel, or also employ silicon. If the extended protrusion64is made of silicon, the silicon may have an advantage since it is not necessary to form a protective film on a surface of the extended protrusion64. The extended protrusion64may be fixed to an inner peripheral surface of a sidewall1bof the processing chamber1by, for example, a non-illustrated screw in a certain fixing direction.

Further, in the plasma processing apparatus104in accordance with the present embodiment, the extended protrusion64may be formed toward a plasma generation space S and may serve as a facing electrode (second electrode) facing an electrode7(first electrode) within a mounting table5with the plasma generation space S therebetween. To be specific, inFIG. 8, an inner peripheral surface ranging from a position A indicated by a circle to a position B indicated by a circle and including an exposed surface of the contact support60′ and an exposed surface of the extended protrusion64(i.e. the exposed upper surface64a, leading end surface64b, and lower surface64cof the extended protrusion64) may serve as the facing electrode. Here, the position A is an end of a contact portion between the contact support60′ of the cover member27and the microwave transmissive plate28. Further, the position B is an end (i.e., an end contacted with an upper liner49a) of an exposed lower surface of the extended protrusion64. In the present embodiment, the surface ranging from the position A to the position B may be exposed to the plasma generation space S and may serve as the facing electrode of an annular shape. In this way, the facing electrode may be formed by multiple components (the cover member27and the extended protrusion64) having surfaces facing the plasma generation space S. By providing an annular member serving as a facing electrode so as to protrude toward the plasma generation space, even in the RLSA-type plasma processing apparatus104in which it is difficult to provide a facing electrode right above the mounting table5due to the microwave transmissive plate28, the facing electrode may have a sufficiently large surface area.

Further, in the present embodiment, by additionally attaching the extended protrusion64to the contact support60′ of the cover member27, the portion serving as the facing electrode can have a sufficiently large surface area. In this way, the facing electrode may be formed by combining the multiple components, and, thus, the facing electrode can have a sufficiently large area within a limited space of a processing chamber1. In the present embodiment, in order to generate stable plasma within the processing chamber1by suppressing the oscillation of the plasma potential and reduce sputtering by the plasma in a vicinity of the facing electrode, a ratio of the facing electrode surface area to a bias electrode area may be, desirably, about 1 or higher and more desirably, in a range of from about 1 to about 5 and still more desirably, in a range of from about 1 to about 4 and still more desirably, in a range of from about 2 to about 4.

Desirably, a leading end (the leading end surface64b) of the extended protrusion64serving as the facing electrode may have a protruded length which does not reach a position PWEof a peripheral end of the wafer W mounted on the mounting table5. If the leading end of the extended protrusion64reaches an inner position than the position PWEof the peripheral end of the wafer W, a range of plasma having a high density, generated within the processing chamber1, may be smaller than a size of the wafer W and a density of the plasma at a periphery of the wafer W may be decreased. As a result, there may be a possibility that a process is not uniformly performed at an outer periphery of the wafer W. At a side opposite to the leading end (the leading end surface64b) in the extended protrusion64, a contact end with respect to a sidewall1bmay become a base end. However, in the present embodiment, the position B on the way to the base end is exposed to the plasma generation space S. That is, in the present embodiment, an end of the exposed lower surface of the extended protrusion64serving as the facing electrode may be a contact point with respect to an upper liner49a. The contact point is indicated as the position B inFIG. 8.

Further, the upper surface64aof the extended protrusion64may be spaced from a lower surface of the microwave transmissive plate28. That is, the extended protrusion64may protrude toward the plasma generation space S with a gap L1with respect to the microwave transmissive plate28. In this way, since there is the gap L1between the microwave transmissive plate28and the extended protrusion64, the facing electrode may have a sufficiently large surface area without reducing an effective area, through which a microwave is transmitted, of the microwave transmissive plate28. The space S1may become a portion of the plasma generation space S and plasma may also be generated in the space S1. Thus, a plasma process can be performed uniformly on the wafer W. On the contrary, if the microwave transmissive plate28and the extended protrusion64are brought into contact with each other without the gap L1therebetween, in order for the facing electrode to have a large surface area within the processing chamber1, a protruded amount of the extended protrusion64toward a center of the microwave transmissive plate28needs to be increased. In this case, when plasma is generated, the effective area of the microwave transmissive plate28may be decreased as much as a contact area with the upper surface64aof the extended protrusion64. Therefore, a supply amount of a microwave power supplied into the processing chamber1may be decreased. As a result, plasma may not be generated, or even if generated, the plasma may be unstable. In order to solve this problem, the processing chamber1needs to be larger, but an installation space and a manufacturing cost of the apparatus may be increased.

The gap L1may be, desirably, greater than a thickness of a sheath between plasma generated right below the microwave transmissive plate28and the microwave transmissive plate28and by way of example, the gap L1may be, desirably, in a range of from about 10 mm to about 30 mm and more desirably, in a range of from about 20 mm to about 25 mm. When the gap L1is smaller than about 10 mm, the plasma may not be stabilized. In particular, if the gap L1is equal to or smaller than the thickness of the sheath, it may be difficult to generate plasma within the processing chamber1. When the gap L1is greater than about 30 mm, the extended protrusion64may be too close to the electrode7in the mounting table5. Thus, it may be difficult for the extended protrusion64to serve as the facing electrode and the extended protrusion64may be damaged by heat of the mounting table5.

Likewise, in order to prevent the extended protrusion64from being too close to the electrode7in the mounting table5, it may be desirable that an upper limit of a thickness L2(i.e. a distance between the upper surface64aand the lower surface64c) of the extended protrusion64may be, for example, about 20 mm. However, if the thickness L2of the extended protrusion64is too small, an effect of the extended protrusion64as the facing electrode may be decreased. Thus, desirably, a lower limit of the thickness L2may be, for example, about 5 mm. Therefore, the thickness L2of the extended protrusion64may be, desirably, in a range of from about 5 mm to about 20 mm and more desirably, in a range of from about 7 mm to about 17 mm.

A distance L3from the lower surface64cof the extended protrusion64to the upper surface of the mounting table5(herein, a height difference between two components) may be, for example, desirably, in a range of from about 15 mm to about 60 mm and more desirably, in a range of from about 20 mm to about 25 mm in order for the extended protrusion64to serve as the facing electrode but not to be too close to the electrode7in the mounting table5.

In the plasma processing apparatus104in accordance with the present embodiment, gas inlet openings15amay be positioned at the contact support60′ above the extended protrusion64and a processing gas may be supplied to the space S1between the extended protrusion64and the microwave transmissive plate28. With this configuration, it may be possible to promote a substitution and a discharge of a gas in the space S1(which serves as a portion of the plasma generation space S) right below the microwave transmissive plate28, and the processing gas may be activated easily. Therefore, it may be possible to efficiently generate plasma in the entire space S1right below the microwave transmissive plate28. As another effect, by supplying the processing gas into the space S1right below the microwave transmissive plate28, it may be possible to promote a discharge of oxygen released from the microwave transmissive plate28made of quartz when a plasma nitridation process is performed in the plasma processing apparatus104. Therefore, it may be possible to suppress a decrease in a concentration of nitrogen contained in a formed nitride film.

The extended protrusion64shown inFIG. 8may include the annular double grooves64dat the lower surface64cof the extended protrusion64in order to secure a sufficient large surface area. However, a cross sectional shape of the extended protrusion64may not be limited to the shape as depicted inFIG. 8. In order for the extended protrusion64to have a greater surface area, for example, a multiple number of holes may be provided annularly. However, in order to prevent an abnormal electric discharge or generation of particles on the surface of the extended protrusion64protruding toward the plasma generation space S, it is desirable that angled portions may be formed in rounded shapes as depicted inFIG. 8. Further, althoughFIG. 8shows that the extended protrusion64may be in contact with the contact support60′ of the cover member27, the extended protrusion64may be spaced from the contact support60′.

In the present embodiment, a protective film48may be formed on the exposed surface of the contact support60′ facing the plasma generation space S. Meanwhile, the entire extended protrusion64may be made of, for example, silicon, and, thus, the protective film may not be formed thereon. However, if the extended protrusion64is made of a metal material such as aluminum, the protective film may be formed by, for example, coating the surface of the extended protrusion64with a SiO2film by means of a plasma spraying method. Even if the protective film48is formed on the contact support60′ and the extended protrusion64, the contact support60′ and the extended protrusion64can serve as the facing electrode and stable plasma can be generated, so that it may be possible to perform a uniform plasma process.

Other configurations and effects of the present embodiment are the same as those of the first embodiment.

Characteristic configurations explained in the first to fifth embodiments can be combined with each other. By way of example, in the extended protrusion60B in the first embodiment (FIGS. 1,2A and2B) or the extended protrusion in the third embodiment (FIG. 6), prominences and depressions may be additionally formed as described in the second embodiment, so that a surface area thereof may be increased. Likewise, in the extended protrusions63and64in the fourth embodiment (FIG. 7) and the fifth embodiment (FIG. 8), respectively, prominences and depressions may be additionally formed as described in the second embodiment, so that a surface area thereof may be increased.

Further, a protrusion serving as a facing electrode may be provided at both of the cover member27and the processing chamber1, or auxiliary electrode members (extended protrusions63and64) serving as facing electrodes may be provided at both of the cover member27and the processing chamber1.

Hereinafter, an effect of the present disclosure will be explained with reference to experimental data. In a plasma processing apparatus of the same configuration of the plasma processing apparatus100depicted inFIG. 1, if a potential of the mounting table5is measured when a high frequency voltage is applied to the electrode7in the mounting table5, AC waveforms are shown as schematically illustrated inFIGS. 9A and 9B.FIG. 9Ashows that a facing electrode surface area has an insufficient size with respect to a bias electrode area, andFIG. 9Bshows that a facing electrode surface area has a sufficient size with respect to a bias electrode area. InFIGS. 9A and 9B, Vmaxdenotes a maximum value of amplitude of the high frequency voltage at the mounting table5. Generally, a potential difference of Vmax-GND (ground potential) may correspond to oscillation amplitude of a plasma potential Vp. InFIG. 9Ashowing that the facing electrode surface area has an insufficient size with respect to the bias electrode area, the Vp may oscillate by a high frequency power, so that the Vmaxmay be increased. Meanwhile, inFIG. 9Bshowing that the facing electrode surface area has a sufficient surface size with respect to the bias electrode area, the plasma potential may be rarely changed and a self bias voltage Vdccan be generated.

FIG. 10shows a relationship between Vmaxand an amount of aluminum (Al) contamination generated when a plasma oxidation process is performed in the plasma processing apparatus while changing process conditions. The process conditions may be as follows. A processing pressure may be about 6.67 Pa, about 20 Pa or about 40 Pa. An Ar gas and an O2gas may be used as a processing gas, and a flow rate ratio of the oxygen gas to the processing gas may be about 0.5 volume %, about 1 volume %, about 25 volume % or about 50 volume %. Further, a frequency of a high frequency bias power supplied to the electrode7in the mounting table5may be about 13.56 MHz, and a high frequency power may be about 450 W, about 600 W or about 900 W. As can be seen fromFIG. 10, regardless of the above process conditions, as the Vmaxis increased, an amount of Al contamination may be increased in proportion thereto. The cause that Al contamination is generated may be that the cover member27made of aluminum has been sputtered. In order to suppress the Al contamination, it may be effective to reduce a value of the Vmax. By way of example, in order to suppress the Al contamination to be about 7×1010[atoms/cm2] or less, the Vmaxneeds to be about 70 V or less. Further, in order to suppress the Vmax, as depicted inFIG. 9B, it may be effective to make the facing electrode surface area greater than the bias electrode area.

An experiment has been conducted to measure a change in Vmaxwhen a facing electrode surface area is varied while a bias electrode area is fixed.FIGS. 11 to 16are graphs each showing a relationship between a facing electrode area ratio (horizontal axis) and Vmax(longitudinal axis) when a plasma oxidation process is performed under various process conditions by a plasma processing apparatus of the same configuration of the plasma processing apparatus100depicted inFIG. 1. Herein, the facing electrode area ratio means a value obtained by dividing the facing electrode surface area by the bias electrode area. Further, an Ar gas and an oxygen gas may be used as a processing gas. Furthermore, a frequency of a high frequency bias power supplied to the electrode7in the mounting table5may be about 13.56 MHz, and a high frequency power may be about 0 W (power not applied), about 300 W, about 450 W, about 600 W or about 900 W.

FIG. 11shows experimental data under conditions set at about 6.67 Pa for a processing pressure, about 0.5 volume % for a flow rate ratio of an oxygen gas, and about 1200 W for a microwave power for generating plasma.FIG. 12shows experimental data under conditions set at about 6.67 Pa for a processing pressure, about 50 volume % for a flow rate ratio of an oxygen gas, and about 3400 W for a microwave power for generating plasma.FIG. 13shows experimental data under conditions set at about 20 Pa for a processing pressure, about 0.5 volume % for a flow rate ratio of an oxygen gas, and about 1200 W for a microwave power for generating plasma.FIG. 14shows experimental data under conditions set at about 20 Pa for a processing pressure, about 50 volume % for a flow rate ratio of an oxygen gas, and about 3400 W for a microwave power for generating plasma.FIG. 15shows experimental data under conditions set at about 40 Pa for a processing pressure, about 0.5 volume % for a flow rate ratio of an oxygen gas, and about 1200 W for a microwave power for generating plasma.FIG. 16shows experimental data under conditions set at about 40 Pa for a processing pressure, about 50 volume % for a flow rate ratio of an oxygen gas, and about 3400 W for a microwave power for generating plasma. The facing electrode surface area may be about 500 cm2, 1400 cm2, 1800 cm2, 2200 cm2, or 3150 cm2, and the bias electrode area may be set to about 855 cm2.

It can be seen from the graphs ofFIGS. 11 to 16that as the facing electrode area ratio is increased, the Vmaxmay be decreased. Further, this tendency may be remarkable under the processing pressure of about 6.67 Pa. It has been found that an effect of suppressing the Vmaxwith an increase of the facing electrode area ratio can be achieved as the pressure becomes low. In the plasma processing apparatus of the same configuration of the plasma processing apparatus100depicted inFIG. 1, in order to surely obtain the effect of suppressing the Vmaxwith the increase of the facing electrode area ratio, it may be desirable to perform a plasma process under the processing pressure of about 40 Pa or less.

Based on the foregoing results, in a plasma processing apparatus of the same configuration of the plasma processing apparatus100depicted inFIG. 1, an amount of aluminum (Al) contamination generated when a plasma oxidation process may be performed while changing a facing electrode surface area has been examined. In this experiment, a facing electrode surface area may be set to about 2200 cm2(area ratio: large), about 1800 cm2(area ratio: medium) or about 500 cm2(area ratio: small), and a bias electrode area may be set to about 855 cm2. Further, a processing pressure may vary in a range of from about 6.67 Pa to about 40 Pa.FIG. 17shows the experimental results. InFIG. 17, numerals of “5.0 E10” and “1.8 E11” represent amounts of Al contamination of “5.0×1010” and “1.8×1011”, respectively. Based on the results, when the facing electrode surface area is 2200 cm2(area ratio: large) or about 1800 cm2(area ratio: medium), the Vmaxcan be suppressed to be about 70 V or less under the processing pressure of about 40 Pa or less (seeFIG. 10). Thus, the Al contamination can be suppressed sufficiently. However, when the facing electrode surface area is about 500 cm2(area ratio: small), the Vmaxcannot be suppressed to be about 70 V or less under the processing pressure of about 20 Pa or less (seeFIG. 10). Thus, the amount of Al contamination may be greatly increased. Accordingly, in order to suppress the Vmaxto be about 70 V or less, it may be effective to set the facing electrode surface area to be about 1800 cm2(area ratio: medium) or more. Therefore, it has been found that the facing electrode area ratio (the facing electrode surface area/the bias electrode area) may be, desirably, in a range of from about 1 to about 5 and, more desirably, in a range of from about 2 to about 5 and still more desirably, in a range of from about 2 to about 4.

Then, an experiment has been conducted to verify an effect of a difference in an inlet position of a processing gas in a plasma processing apparatus of the same configuration of the plasma processing apparatus100depicted inFIG. 1. In this experiment, during a plasma nitridation process, there has been made a comparison of an amount of oxygen in a silicon nitride film when the following two cases. That is, the first case is when a processing gas is introduced through the gas inlet openings15adepicted inFIG. 1(embodiment as illustrated inFIG. 1), and the second case is when a gas ring is provided annularly at the sidewall1bbelow the protrusion60and a processing gas is introduced (comparative example not illustrated). A processing target in the plasma nitridation process is silicon on a surface of a wafer W having a diameter of about 300 mm. An amount of oxygen in the silicon nitride film has been measured at a central area and a periphery of the wafer W by an X-ray photoelectron spectroscopy (XPS) apparatus.

Conditions of the plasma nitridation process are as follows, and a flow rate ratio of N2, a processing pressure and a high frequency bias power are varied.

FIG. 18Ashows a measurement result of an amount of oxygen in the silicon nitride film at the central area of the wafer W, andFIG. 18Bshows a measurement result of an amount of oxygen in the silicon nitride film at the periphery of the wafer W. In an experimental example of introducing the processing gas from the gas inlet openings15a, it can be seen that a concentration of oxygen in the silicon nitride film is decreased under the processing pressure in a range of from about 6.67 Pa to about 133 Pa as compared with the comparative example of introducing the processing gas from a position below the protrusion60. In the experimental example, the concentration of oxygen may be decreased regardless of whether or not a high frequency bias power is applied, and the same tendency can be seen at the central area and the periphery of the wafer W. According to the measurement results at the periphery, where the concentration of oxygen is high, of the wafer W under the processing pressure of about 133 Pa, a decrease of about 80 at most in the concentration of oxygen can be found in the experimental example as compared with the comparative example.

In a plasma processing apparatus, having the extended protrusion60B in order to increase the facing electrode area, of the same configuration as depicted inFIG. 1, the closed space S1between the extended protrusion60B and the microwave transmissive plate28may serve as a gas reservoir. As a result, the gas reservoir may easily cause an oxygen entrance into the silicon nitride film during the plasma nitridation process. The oxygen entrance means that oxygen existing in the microwave transmissive plate28is released to the plasma generation space S by plasma, and then, the released oxygen may enter into the silicon nitride film formed during the plasma nitridation process. In the comparative example, the processing gas is introduced from the position below the protrusion60, and, thus, the gas may stay in the space S1right below the microwave transmissive plate28. Accordingly, the oxygen released from the microwave transmissive plate28may stay in the space S1for a long time and it may be difficult for the oxygen to be discharged from the processing chamber1. As a result, there is a strong probability that the oxygen enters into the silicon nitride film on the surface of the wafer W. Meanwhile, in the experimental example, the processing gas is introduced from the gas inlet openings15ainto the space S1right below the microwave transmissive plate28. Thus, the oxygen released from the microwave transmissive plate28can be quickly moved from the space S1. Accordingly, since the oxygen can be efficiently discharged to the outside of the processing chamber1, it may be possible that the oxygen does not easily enter into the silicon nitride film on the wafer W.

As described above, plasma processing apparatuses in respective embodiments of the present disclosure may include extended protrusions60B,61B,62,63and64protruding from the processing chamber1or the cover member27toward the plasma generation space S with the gap L1with respect to the microwave transmissive plate28. Further, the extended protrusions60B,61B,62,63and64may serve as a part of a facing electrode facing the electrode7with a plasma generation space S therebetween. Thus, the facing electrode may have a sufficiently large area and oscillation of the plasma potential Vp can be suppressed. Furthermore, by increasing the facing electrode surface area, it may be possible to suppress sputtering on the surface of the facing electrode by plasma, and, thus, contamination can be prevented. Furthermore, since the facing electrode may have a sufficiently large area, a short circuit or an abnormal electric discharge in other portions can be suppressed. Moreover, since the extended protrusion60B,61B,62,63and64may be spaced from the microwave transmissive plate28, it is not necessary to reduce an effective area of the microwave transmissive plate28, and plasma generated within the processing chamber1can be stabilized by introducing a sufficient microwave power.

The embodiments of the present disclosure have been provided for the examples in detail, but the present disclosure is not limited to the above-described embodiments. By way of example, in the above-described embodiments, the cover member27for supporting the microwave transmissive plate28is a part of the microwave inlet unit26, but the cover member27for supporting the microwave transmissive plate28may be a part of the processing chamber1.

Further, in the above-described embodiments, the gas inlet openings15aare provided at the cover member27, but the gas inlet openings15amay be provided at other members other than the cover member27. By way of example,FIG. 19is a cross sectional view of main parts of a configuration of a plasma processing apparatus102A in a modification example of an aspect (the third embodiment; seeFIG. 6) in which an extended protrusion62is provided as a single body with the sidewall1bof the processing chamber1. As depicted inFIG. 19, the rectangularly annular path13A may be provided at the upper end of the sidewall1bof the processing chamber1, and the gas inlet path15bcommunicating with this annular path13A may be formed in the sidewall1b. Therefore, the gas inlet openings15amay be provided at the upper portion of the sidewall1b. With this configuration, a processing gas can be supplied from the gas inlet openings15ato the space S1between the microwave transmissive plate28and the extended protrusion62.

Further, in the above-described embodiments, a main body of the cover member27serving as a member to be exposed to plasma is made of aluminum. However, even if the cover member27is made of other metal such as stainless steel, the same effect can be obtained.

A shape of the extended protrusion is not limited to an annular shape, and multiple extended protrusions separated from each other may be provided so as to protrude toward the plasma generation space S.

The plasma process is not limited to the plasma oxidation process or the plasma nitridation process if the high frequency power is supplied to the electrode7in the mounting table5. By way of example, various plasma processes such as a plasma CVD process, an etching process or the like can be employed. Further, the target object is not limited to the semiconductor wafer, and other substrates such as a FPD glass substrate or the like can be employed.