Patent Application
20130149852
The present invention relates to semiconductor processing, and more particularly to a method for plasma processing a metal-containing gate electrode film to adjust the work function of the metal-containing gate electrode film.
In the semiconductor industry, the minimum feature sizes of microelectronic devices are approaching the deep sub-micron regime to meet the demand for faster, lower power microprocessors and digital circuits. The Si-based microelectronic technology is currently faced with major materials challenges to achieve further miniaturization of integrated circuit devices. A gate stack containing a SiO2 gate dielectric and a degenerately doped polycrystalline Si gate electrode, which has served the industry for several decades, will be replaced with a gate stack having a higher capacitance.
High-capacitance materials, known as high-k materials (where “k” refers to the dielectric constant of the material), feature a dielectric constant greater than that of SiO2 (k˜3.9). In addition, high-k materials may refer to dielectric materials that are deposited onto substrates (e.g., HfO2, ZrO2) rather than grown on the surface of the substrates (e.g., SiO2, SiOxNy). High-k materials may, for example, incorporate metallic silicates or oxides (e.g., Ta2O5 (k˜26), TiO2 (k˜80), ZrO2 (k˜25), Al2O3 (k˜9), HfSiO (k˜5-25), and HfO2 (k˜25)).
In addition to the gate dielectric layer, the gate electrode layer also represents a major challenge for future scaling of microelectronic devices. The introduction of metal-containing gate electrodes to replace the traditional doped poly-Si gate electrode can bring about several advantages. These advantages include elimination of the poly-Si gate depletion effect, reduction in sheet resistance, better reliability and potentially better thermal stability on the advanced high-k dielectric materials. In one example, switching from poly-Si to a metal-containing gate electrode can achieve a 2-3 Angstrom (Å) improvement in the effective or electrical thickness of the gate stack. This improvement occurs largely because the problem of poly-Si depletion at the interfaces with other materials is removed entirely.
Work function, resistivity, and compatibility with complementary metal oxide semiconductor (CMOS) technology are key parameters for the new gate electrode materials. One of the material selection criteria for the metal-containing gate electrode is that the work function be tunable. The work function of a material is the minimum energy needed to remove an electron from a solid to a point immediately outside the solid surface. Positive-channel Metal Oxide Semiconductor (PMOS) and the Negative-channel Metal Oxide Semiconductor (NMOS) transistor gate electrodes require different gate materials be used for the gate electrode to achieve acceptable threshold voltages; the latter having a Fermi level near the silicon valence band (E˜4 eV), and the former having a Fermi level near the conduction band (E˜5.1 eV).
High-energy implantation of dopant ions (e.g., nitrogen ions) into a metal gate electrode layer in a gate stack has been previously researched in order to lower the work function. However, ion implantation methods that include exposing the metal layer to high-energy ions can damage the gate stack, for example cause charging damage of the dielectric layer that can increase the leakage current and the reliability of the dielectric layer. The charging damage from exposure of high-energy ions is expected to increase as the minimum feature sizes get smaller and the different materials layers that form gate stacks get thinner. Therefore, new methods are needed for processing gate stacks and, in particular, new methods for tuning the work function of the gate stacks are needed.
Embodiments of the invention provide a method for manufacturing a semiconductor device containing a metal-containing gate electrode film with a tunable work function.
According to one embodiment of the invention, the method includes providing in a process chamber a metal-containing gate electrode film on a substrate, flowing a process gas consisting of hydrogen (H2) and optionally a noble gas into the process chamber, forming plasma excited species from the process gas by a microwave plasma source, and exposing the metal-containing gate electrode film to the plasma excited species to form a modified metal-containing gate electrode film having a lower work function than the metal-containing gate electrode film.
According to another embodiment, the method includes providing in a process chamber a metal-containing gate electrode film on a substrate, forming first plasma excited species from a first process gas by a microwave plasma source, and exposing the metal-containing gate electrode film to the first plasma excited species to form a first modified metal-containing gate electrode film and an unmodified metal-containing gate electrode film. The method can further include forming second plasma excited species from a second process gas by the microwave plasma source, and exposing the unmodified metal-containing gate electrode film to the second plasma excited species to form a second modified metal-containing gate electrode film.
In the drawings:
In the following description, in order to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of a plasma processing system and descriptions of various components. However, it should be understood that the invention may be practiced in other embodiments that depart from these specific details.
The dielectric layer 110 can contain a SiO2 (or SiOx) layer, a SiN (or SiNy) layer, a SiON (or SiOxNy) layer, or a high-k layer, or a combination of two or more thereof. The high-k layer can, for example, contain metal oxides and their silicates, including Ta2O5, TiO2, ZrO2, Al2O3, Y2O3, HfSiOx, HfO2, ZrO2, ZrSiOx, TaSiOx, SrOx, SrSiOx, LaOx, LaSiOx, YOx, or YSiOx, or combinations of two or more thereof. A thickness of the high-k layer can, for example, be between about 10 angstrom (Å) and about 200 Å or between about 20 Å and about 40 Å. In one example, the dielectric layer 110 can contain an interface layer (not shown) in direct contact with the substrate 105, for example an oxide layer (e.g., SiOx), a nitride layer (e.g., SiNx), or an oxynitride layer (e.g., SiOxNy), or a combination thereof. Integrated circuits containing a Si substrate commonly employ SiO2 and/or SiOxNy substrate interface layers that can have excellent electrical properties, including high electron mobility and low electron trap densities. Gate stacks containing a high-k layer formed on SiO2 and/or SiOxNy substrate interface layers can require the substrate interface layer to have a thickness of only about 5-10 Å.
The metal-containing gate electrode film 120 can include metals and metal-containing materials, including W, WN, Al, Mo, Ta, TaN, TaSiN, HfN, HfSiN, Ti, TiN, TiSiN, Mo, MoN, Nb, Re, Ru, or RuO2. A thickness of the metal-containing gate electrode film 120 can, for example, be between about 10 Å and about 500 Å or between about 20 Å and about 200 Å.
In 220, a process gas consisting of hydrogen (H2) and optionally a noble gas is flowed into the process chamber. In one example, the process gas can consist of H2. In another example, the process gas can consist of H2 and Argon (Ar). In yet another example, the process gas can consist of H2 and Helium (He). In still another example, the process gas can consist of H2, Ar, and He.
In 230, plasma excited species 130 are formed from the process gas by a microwave plasma source. According to one embodiment, the microwave plasma source can be a radial line slot antenna (RLSA) plasma source available from Tokyo Electron Limited, Akasaka, Japan. Exemplary microwave plasma sources are shown in
In 240, the metal-containing gate electrode film 120 is exposed to the plasma excited species 130 to form a modified metal-containing gate electrode film 140 that has a lower work function than the metal-containing gate electrode film 120. The plasma excited species may include reducing species with low kinetic energy that can selectively modify the metal-containing gate electrode film 120 (or only a surface layer of the metal-containing gate electrode film 120), while minimizing or eliminating charging damage in underlying films or layers. The modification of the metal-containing gate electrode film 120 may be substantially uniform through a thickness of the modified metal-containing gate electrode film 140, or alternately, the modification of the metal-containing gate electrode film 120 may be substantially non-uniform through a thickness of the modified metal-containing gate electrode film 140.
The exposure of the metal-containing gate electrode 120 to the plasma excited species 130 in 240 may be performed using processing parameters that result in a desired modification of the metal-containing gate electrode film 120. Process parameters for the exposure can be determined by direct experimentation and/or design of experiments (DOE). As one skilled in the art will readily appreciate, adjustable process parameters include, among others, plasma conditions (plasma power, process pressure, and process gas composition), process time, and substrate temperature.
The process 200 may further contain an annealing step for heat-treating one or more of the film stacks 100 and 101, and/or or the gate stack 102 following the exposure to the plasma excited species 130. The heat-treating can be performed to obtain the desired work function and material and electrical properties of the film stacks 100 and 101, and/or the gate stack 102. As would be appreciated by those skilled in the art, each of the steps or stages in the flowchart of
The dielectric layer 310 can contain a SiO2 (or SiOx) layer, a SiN (or SiNy) layer, a SiON (or SiOxNy) layer, or a high-k layer, or a combination of two or more thereof. The high-k layer can, for example, contain metal oxides and their silicates, including Ta2O5, TiO2, ZrO2, Al2O3, Y2O3, HfSiOx, HfO2, ZrO2, ZrSiOx, TaSiOx, SrOx, SrSiOx, LaOx, LaSiOx, YOx, or YSiOx, or combinations of two or more thereof. A thickness of the high-k layer can, for example, be between about 10 angstrom (Å) and about 200 Å or between about 20 Å and about 40 Å. In one example, the dielectric layer 310 can contain an interface layer (not shown) in direct contact with the substrate 305, for example an oxide layer (e.g., SiOx), a nitride layer (e.g., SiNx), or an oxynitride layer (e.g., SiOxNy), or a combination thereof. Integrated circuits containing a Si substrate commonly employ SiO2 and/or SiOxNy substrate interface layers that can have excellent electrical properties, including high electron mobility and low electron trap densities. Gate stacks containing a high-k layer formed on SiO2 and/or SiOxNy substrate interface layers can require the substrate interface layer to have a thickness of only about 5-10 Å.
The metal-containing gate electrode film 320 can include metals and metal-containing materials, including W, WN, Al, Mo, Ta, TaN, TaSiN, HfN, HfSiN, Ti, TiN, TiSiN, Mo, MoN, Re, or Ru. A thickness of the metal-containing gate electrode film 320 can, for example, be between about 10 Å and about 500 Å or between about 20 Å and about 200 Å.
According to some embodiments of the invention, the film stack 303 may be further processed in the manufacturing of a semiconductor device.
In 420, a first process gas is flowed into the process chamber. According to one embodiment of the invention, the first process gas can consist of hydrogen (H2) and optionally a noble gas. In one example, the first process gas can consist of H2. In another example, the first process gas can consist of H2 and Ar. In yet another example, the process gas can consist of H2 and He. In still another example, the first process gas can consist of H2, Ar, and He. According to another embodiment of the invention, the first process gas can consist of oxygen (O2) and optionally one or more gases selected from the group consisting of a noble gas, nitrogen (N2), H2, or a combination thereof. In one example, the first process gas can consist of O2. In another example, the first process gas can consist of O2 and Ar. In yet another example, the first process gas can consist of O2, N2, and optionally Ar. In still another example, the first process gas can consist of O2, Ar, and He.
In 430, first plasma excited species 330 are formed from the first process gas by a microwave plasma source. According to one embodiment of the invention, the first plasma excited species 330 may include reducing species formed by plasma excitation of the first process gas consisting of hydrogen (H2) and optionally a noble gas. According to another embodiment of the invention, the first plasma excited species may include oxidizing species formed by plasma excitation of a first process gas consisting of oxygen (O2) and optionally one or more gases selected from the group consisting of a noble gas, N2, H2, or a combination thereof. According to one embodiment, the microwave plasma source can be a radial line slot antenna (RLSA) plasma source available from Tokyo Electron Limited, Akasaka, Japan.
In 440, a first portion 322 of the metal-containing gate electrode film 320 is exposed to the first plasma excited species 330 to form a first modified metal-containing gate electrode film 350 and an unmodified metal-containing gate electrode film 324. In one embodiment, the first plasma excited species 330 may include reducing species and the first modified metal-containing gate electrode film 350 has a lower work function than the unmodified metal-containing gate electrode film 324. In another embodiment, the first plasma excited species 330 may include oxidizing species and the first modified metal-containing gate electrode film 350 has a higher work function than the unmodified metal-containing gate electrode film 324.
The exposure of the metal-containing gate electrode film 320 to the first plasma excited species 330 in 440 may be performed under processing parameters for a time period that result in a desired modification of the metal-containing gate electrode film 320. Process parameters for the exposure can be determined by direct experimentation and/or design of experiments (DOE). As one skilled in the art will readily appreciate, adjustable process parameters include, among others, plasma conditions (plasma power, process pressure, and process gas composition), process time, and substrate temperature.
Following the exposure to the first plasma excited species 330 in 440, the patterned film 340 may be removed using conventional wet or dry etching methods.
In 450, the film stack 303 may, as depicted in
The process 400 may further contain an annealing step for heat-treating one or more of the film stacks 301, 301 and 302, and/or or the gate stacks 304/306 following the exposure to the first plasma excited species 330. The heat-treating can be performed to obtain the desired work function and material and electrical properties of the gate stacks 304/306. As would be appreciated by those skilled in the art, each of the steps or stages in the flowchart of
According to some embodiments of the invention, the film stack 311 may be further processed in the manufacturing of a semiconductor device.
In 650, a second process gas is flowed into the process chamber. According to one embodiment of the invention, the second process gas can consist of oxygen (O2) and optionally one or more gases selected from the group consisting of a noble gas, nitrogen (N2), H2, or a combination thereof. In one example, the second process gas can consist of O2. In another example, the second process gas can consist of O2 and Ar. In yet another example, the second process gas can consist of O2, N2, and optionally Ar. In still another example, the second process gas can consist of O2, Ar, and He. According to another embodiment, the second process gas can consist of hydrogen H2 and optionally a noble gas. In one example, the second process gas can consist of H2. In another example, the second process gas can consist of H2 and Ar. In yet another example, the second process gas can consist of H2 and He. In still another example, the second process gas can consist of H2, Ar, and He.
In 660, second plasma excited species 672 are formed from the second process gas by a microwave plasma source. According to one embodiment, the second plasma excited species 672 may include oxidizing species formed by plasma excitation of a second process gas consisting of oxygen (O2) and optionally one or more gases selected from the group consisting of a noble gas, N2, H2, or a combination thereof. According to another embodiment, the second plasma excited species 672 may include reducing species formed by plasma excitation of the second process gas consisting of hydrogen (H2) and optionally a noble gas. According to one embodiment, the microwave plasma source can be a radial line slot antenna (RLSA) plasma source available from Tokyo Electron Limited, Akasaka, Japan.
In 670, the film stack 307 containing the unmodified metal-containing gate electrode film 324 is exposed to second plasma excited species 372 to form a second modified metal-containing gate electrode film 380. In one embodiment, the second plasma excited species 372 may include oxidizing species and the second modified metal-containing gate electrode film 380 has a higher work function than the first modified metal-containing gate electrode film 350. In another embodiment, the second plasma excited species 372 may include reducing species and the first modified metal-containing gate electrode film 350 has a higher work function than the first modified metal-containing gate electrode film 350.
The exposure of the unmodified metal-containing gate electrode film 324 to the second plasma excited species 372 in 670 may be performed under processing parameters that result in a desired modification of the unmodified metal-containing gate electrode film 324. Process parameters for the exposure can be determined by direct experimentation and/or design of experiments (DOE). As one skilled in the art will readily appreciate, adjustable process parameters include, among others, plasma conditions (plasma power, process pressure, and process gas composition), process time, and substrate temperature.
Following the exposure to the second plasma excited species 372 in 670, the patterned film 360 may be removed using conventional wet or dry etching methods.
In 680, the resulting film stack 311 may be further processed by patterning the first modified metal-containing gate electrode film 350, the second modified metal-containing gate electrode film 380 and the underlying dielectric film 310 to form a first gate stack 315 and a second gate stack 313. According to one embodiment, the first gate stack 315, containing gate electrode 352, has a lower work function than the second gate stack 313, containing gate electrode 382. In this embodiment, the gate electrode 352 can be a NMOS gate electrode and the gate electrode 382 can be a PMOS gate electrode. According to another embodiment, the first gate stack 315, containing gate electrode 352, has a higher work function than the second gate stack 313, containing gate electrode 382. In this embodiment, the gate electrode 352 can be a PMOS gate electrode and the gate electrode 382 can be a NMOS gate electrode. The first gate stack 315 and the second gate stack 313 may, for example, be formed by anisotropic etching of the film stack 311 shown in
The process 600 may further contain an annealing step for heat-treating one or more of the film stacks 307, 309 and 311, and/or or the gate stacks 313/315 following the exposure to the second plasma excited species 372. The heat-treating can be performed to obtain the desired work function and material and electrical properties of the gate stacks 313/315. As would be appreciated by those skilled in the art, each of the steps or stages in the flowchart of
In summary,
Gas lines 572 are located in the side wall of the upper portion of plasma processing chamber 550 below the top plate 554. In one example, the number of gas lines 572 can be 16 (only two of which are shown in
In the plasma processing system 515, microwave power is provided to the plasma processing chamber 550 through the top plate 554 via a slot antenna 560 having a plurality of slots 560A. The slot antenna 560 faces the substrate 525 to be processed and the slot antenna 560 can be made from a metal plate, for example copper. In order to supply the microwave power to the slot antenna 560, a waveguide 563 is disposed on the top plate 554, where the waveguide 563 is connected to a microwave power supply 561 for generating electromagnetic wave at a microwave frequency of about 2.45 GHz, for example. The waveguide 563 contains a coaxial waveguide 563A with a lower end connected to the slot antenna 560, a coaxial waveguide 563B connected to the upper surface side of the circular (coaxial) waveguide 563A, and a coaxial waveguide converter 563C connected to the upper surface side of the coaxial waveguide 563B. Furthermore, a rectangular waveguide 563D is connected to the input of the coaxial waveguide converter 563C and an output for the microwave power supply 561.
Inside the coaxial waveguide 563B, an axial portion 562 (or inner conductor) of an electroconductive material is coaxially provided with the outer conductor, so that one end of the axial portion 562 is connected to the central (or nearly central) portion of the upper surface of slot antenna 560, and the other end of the axial portion 562 is connected to the upper surface of the coaxial waveguide 563B, thereby forming a coaxial structure. The microwave power can, for example, be between about 0.5 W/cm2 (Watts per square centimeter) and about 4 W/cm2. Alternatively, the microwave power can be between about 0.5 W/cm2 and about 3 W/cm2. The microwave irradiation may contain a microwave frequency of about 300 MHz (mega-Hertz) to about 10 GHz (giga-Hertz, for example about 2.45 GHz, and the plasma may contain an electron temperature of less than or equal to 5 eV (electron volt), including 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 eV, or any combination thereof. In other examples, the electron temperature can be below 5 eV, below 4.5 eV, below 4 eV, or even below 3.5 eV. In some examples, the electron temperature can be between 1 and 1.5 eV, between 1.5 and 2 eV, between 2 and 2.5 eV, between 2.5 and 3 eV, between 3.0 and 3.5 eV, between 3.5 and 4.0 eV, or between 4.0 and 4.5 eV. The plasma may have a density of about 1×1011/cm3 (per cubic centimeter) to about 1×1013/cm3, or higher.
In addition, in the plasma processing chamber 550, a substrate holder 552 is provided opposite the top plate 554 for supporting and heating a substrate 525 (e.g., a wafer). The substrate holder 552 contains a heater 557 to heat the substrate 525, where the heater 557 can be a resistive heater. Alternatively, the heater 557 may be a lamp heater or any other type of heater. Furthermore the plasma processing chamber 550 contains an exhaust line 553 connected to the bottom portion of the plasma processing chamber 550 and to a vacuum pump 555. The substrate holder 552 can be maintained at a temperature greater than 200° C., greater than 300° C., or greater than 400° C. In some examples, substrate holder 552 can be maintained at a temperature of about 250° C., for example.
The plasma processing system 515 further contains a substrate bias system 556 configured to bias the substrate holder 552 and the substrate 525 for generating a plasma and/or controlling energy of ions that are drawn to a substrate 525. The substrate bias system 556 includes a substrate power source configured couple power to the substrate holder 552. The substrate power source contains a RF generator and an impedance match network. The substrate power source is configured to couple power to the substrate holder 552 by energizing an electrode in the substrate holder 552. A typical frequency for the RF bias can range from about 0.1 MHz to about 100 MHz, and can be 13.56 MHz. In some examples, the RF bias can be less than 1 MHz, for example less than 0.8 MHz, less than 0.6 MHz, less than 0.4 MHz, or even less than 0.2 MHz. In one example, the RF bias can be about 0.4 MHz. Alternatively, RF power is applied to the electrode at multiple frequencies. The substrate bias system 556 is configured for supplying RF bias power can be between 0 W and 100 W, between 100 W and 200 W, between 200 W and 300 W, between 300 W and 400 W, or between 400 W and 500 W. RF bias systems for plasma processing are well known to those skilled in the art. Further, the substrate bias system 556 includes a DC voltage generator capable of supplying DC bias between −5 kV and +5 kV to the substrate holder 552.
The substrate bias system 556 is further configured to optionally provide pulsing of the RF bias power the pulsing frequency can be greater than 1 Hz, for example 2 Hz, 4 Hz, 6 Hz, 8 Hz, 10 Hz, 20 Hz, 30 Hz, 50 Hz, or greater. Exemplary RF bias power can be less than 100 W, less than 50 W, or less than 25 W, for example. It is noted that one skilled in the art will appreciate that the power levels of the substrate bias system 556 are related to the size of the substrate 525 being processed. For example, a 300 mm Si wafer requires greater power consumption than a 200 mm wafer during processing.
Still referring to
A top portion of the plasma processing chamber 20 is open-ended. The plasma gas supply unit 30 is placed opposite to the substrate holder 21 and is sealed with the top portion of the plasma processing chamber 20 via sealing members, not shown in this figure, such as O rings. The plasma gas supply unit 30, which may also function as a dielectric window, is made of materials such as aluminum oxide or quartz, and its planar surface, which has a virtual disk shape, faces the substrate holder 21. A plurality of gas supply holes 31 are provided opposite to the substrate holder 21 on the planar surface of the plasma gas supply unit 30. The plurality of gas supply holes 31 communicate with a plasma gas supply port 33 via a gas flow channel 32. A plasma gas supply source 34 provides plasma gas such as Ar gas, or other inert gases, into the plasma gas supply port 33. The plasma gas is then uniformly supplied into the plasma generation region R1 via the plurality of gas supply holes 31.
The plasma processing system 10 further includes a process gas supply unit 40, which is located substantially at the center of the plasma processing chamber 20 between the plasma generation region R1 and the plasma diffusion region R2. The process gas supply unit 40 is made of conducting materials such as aluminum alloy including magnesium (Mg) or stainless steel. Similar to the plasma gas supply unit 30, a plurality of gas supply holes 41 are provided on a planar surface of the process gas supply unit 40. The planar surface of the process gas supply unit 40 is positioned opposite to the substrate holder 21 and has a disk shape.
The plasma processing chamber 20 further includes exhaust lines 26 connected to the bottom portion of the plasma processing chamber 20, a vacuum line 27 connecting the exhaust line to a pressure controller valve 28 and to a vacuum pump 29. The pressure controller valve 28 may be used to achieve a desired gas pressure in the plasma processing chamber 20.
A plan view of the process gas supply unit 40 is shown in
Further, a plurality of openings 44 are formed on to the process gas supply unit 40 such that the plurality of openings 44 pass through the process gas supply unit 40 in vertical direction. The plurality of opening 44 passes the plasma gas, e.g., argon (Ar) gas, helium (He) gas, or other inert gases, into the plasma diffusion region R2 on the side of the substrate holder 21. As shown in
The process gas flows through the grid-like gas flow channel 42 and are uniformly supplied into the plasma diffusion region R2 via the plurality of gas supply holes 41. The plasma processing system 10 further includes four valves (V1-V4) and four flow rate controller (MFC1-MFC4) for respectively controlling a supply of the gases into the plasma processing chamber 20.
An external microwave generator 55 provides a microwave signal (or microwave energy) of a predetermined frequency, e.g., 2.45 GHz, to the antenna unit 57 via a coaxial waveguide 54. The coaxial waveguide 54 may include an inner conductor 54B and an outer conductor 54A. The microwave from the microwave generator 55 generates an electric field just below the plasma gas supply unit 30, in the plasma generation region R1, which in turn causes excitation of the process gas within the plasma processing chamber 20.
A plurality of slots 56 is provided on the radial line slot plate 52 to generate a circular polarized wave. The plurality of slots 56 is arranged in a substantially T-shaped form having a slight gap there between, in a concentric circle pattern or a spiral pattern along a circumferential direction. Since the slots 56a and 56b are perpendicular to each other, a circular polarized wave containing two orthogonal polarized components is radiated, as a plane wave, from the radial line slot plate 52.
The dielectric plate 53 is made of a low loss dielectric material, e.g., aluminum oxide (Al2O3) or silicon nitride (Si3N4), which is located between the radial line slot plate 52 and the flat antenna main body 51. The radial line slot plate 52 is mounted on the plasma processing chamber 20 using sealing members (not shown), such that the radial line slot plate 52 is in close contact with a cover plate 23. The cover plate 23 is located on the upper surface of plasma gas supply unit 30 and is formed from a microwave transmissive dielectric material such as aluminum oxide (Al2O3).
An external high-frequency power supply source 22 is electrically connected to the substrate holder 21 via a matching network 25. The external high-frequency power supply source 22 generates an RF bias power of a predetermined frequency, e.g. 13.56 MHz, for controlling ions energy that are drawn to the substrate W. The power supply source 22 is further configured to optionally provide pulsing of the RF bias power the pulsing frequency can be greater than 1 Hz, for example 2 Hz, 4 Hz, 6 Hz, 8 Hz, 10 Hz, 20 Hz, 30 Hz, 50 Hz, or greater. The power supply source 22 is configured for supplying RF bias power can be between 0 W and 100 W, between 100 W and 200 W, between 200 W and 300 W, between 300 W and 400 W, or between 400 W and 500 W. It is noted that one skilled in the art will appreciate that the power levels of the power supply source 22 are related to the size of the substrate being processed. For example, a 300 mm Si wafer requires greater power consumption than a 200 mm wafer during processing. The plasma processing system 10 further includes DC voltage generator 35 capable of supplying DC voltage bias between about −5 kV and about +5 kV to the substrate holder 21.
During the modification of a metal-containing gate electrode film, the plasma gas, e.g., Ar gas, may be introduced into the plasma processing chamber 20 using the plasma gas supply unit 30. On the other hand, the process gas may be introduced into the plasma processing chamber 20 using the process gas supply unit 40.
A plurality of embodiments for modifying metal-containing gate electrode films for semiconductor devices using a microwave plasma source have been described. The foregoing description of the embodiments of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. This description and the claims following include terms that are used for descriptive purposes only and are not to be construed as limiting. For example, the term “on” as used herein (including in the claims) does not require that a film “on” a substrate is directly on and in immediate contact with the substrate; there may be a second film or other structure between the film and the substrate.
It should be understood that various modifications and variations of the present invention may be employed in practicing the invention. It is therefore to be understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
