US20070000870A1 - Plasma processing method - Google Patents

Abstract

The present invention is a plasma processing method including: a step of introducing a substrate into a processing container, a metal or metallic compound film being formed on a surface of the substrate; a step of supplying a noble gas and an H₂gas into the processing container; and a step of generating plasma in the processing container while the noble gas and the H₂gas are supplied, so that a natural oxide film formed on a surface of the metal or metallic compound film is removed by means of the plasma. According to the invention, the noble gas and the H₂gas are supplied into the processing container, the plasma is generated in the processing container, and the plasma acts on the natural oxide film formed on a surface of the metal or metallic compound film. Thus, active hydrogen in the plasma reduces the natural oxide film, and active species of the noble gas etch the natural oxide film. As a result, the natural oxide film can be removed with a satisfactory selective ratio.

Description

FIELD OF THE INVENTION
• The present invention relates to a plasma processing method that is used to remove a natural oxide film formed on a metal film or a metallic compound film, in particular on a CoSi₂film, of a surface of a substrate.
DESCRIPTION OF THE RELATED ART
• In a semiconductor manufacturing process, a Ti film is deposited on a bottom of a contact hole formed in a silicon wafer as an object to be processed. A barrier layer such as TiN is formed on a TiSi layer, which is formed by interdiffusion of the Ti film and the silicon wafer. In addition, an Al layer, a W layer, a Cu layer or the like is formed on the barrier layer. Thereby, filling of the contact hole and forming of wirings are carried out. Conventionally, a metal-deposition system having a plurality of chambers is used for carrying out the above successive steps. In such a metal-deposition system, in order to obtain good electrical contacts, prior to the deposition process, a process for removing a natural oxide film formed on the silicon wafer, that is, a pre-clean process is carried out.
• The pre-clean process is a process wherein plasma of a process gas is generated in a chamber assembled in the metal-deposition system and wherein the natural oxide film formed on the silicon wafer is removed by the plasma. According to the pre-clean process, the natural oxide film can be removed in an in-line manner and relatively easily.
• On the other hand, recently, miniaturization of semiconductor devices has been advanced. For example, if the diameter of a hole is 0.15 μm or smaller, it is desired to further lower the resistance of wiring contact portions. Conventionally, TiSi is used as a material for the contact portions. Recently, instead of TiSi, a CoSi₂film, whose resistance is low, is formed on Si, and then Ti is formed thereon. In that case, a natural oxide film may be formed on a surface of the CoSi₂film. The natural oxide film may cause higher resistance of the contact portions. Thus, if a pre-clean process is conducted to efficiently remove the natural oxide film on the surface of the CoSi₂film without giving any damage and with a good selective ratio, this is very advantageous in the semiconductor manufacturing process.
• However, when the natural oxide film on the CoSi₂film is removed by the conventional pre-clean process, the etching selective ratio may not be sufficient. In addition, in a method of removing the natural oxide film on the CoSi₂film by means of a process such as a wet processing by an HF aqueous solution, the whole exposed surface and the lateral wall of the hole or the like are subjected to an isotropic etching. Thus, it is difficult to use this method for recent miniaturized devices.
• Thus, it is required to achieve a plasma process wherein the natural oxide film on the CoSi₂film is efficiently removed with a high selective ratio while less damage is given to the CoSi₂film.
• In addition, with respect to a natural oxide film on a surface of any metal or metallic compound film other than the CoSi₂film as well, if the natural oxide film can be efficiently removed with a high selective ratio by means of a pre-clean process by plasma, this is very advantageous in the semiconductor manufacturing process.
SUMMARY OF THE INVENTION
• This invention is developed by focusing the aforementioned problems in order to resolve them effectively. An object of the present invention is to provide a plasma processing method wherein a natural oxide film on a metal or metallic compound film, in particular a CoSi₂film, can be efficiently removed with a sufficient selective ratio.
• The present invention is a plasma processing method comprising: a step of introducing a substrate into a processing container, a metal or metallic compound film being formed on a surface of the substrate; a step of supplying a noble gas and an H₂gas into the processing container; and a step of generating plasma in the processing container while the noble gas and the H₂gas are supplied, so that a natural oxide film formed on a surface of the metal or metallic compound film is removed by means of the plasma.
• According to the present invention, the noble gas and the H₂gas are supplied into the processing container, the plasma is generated in the processing container, and the plasma acts on the natural oxide film formed on a surface of the metal or metallic compound film. Thus, active hydrogen in the plasma reduces the natural oxide film, and active species of the noble gas etch the natural oxide film. As a result, the natural oxide film can be removed with a satisfactory selective ratio.
• The metal or metallic compound may consist of any of CoSi₂, Co, W, WSi, Cu, Si, Al, Mo, MoSi, Ni and NiSi. It is preferable that an etching selective ratio of the natural oxide film with respect to the metal or metallic compound film is 3 or more.
• It is preferable that the plasma is one of inductive coupling plasma, helicon wave plasma and microwave plasma. Such plasma can be generated independently from a bias-voltage control of a lower electrode for drawing-in the plasma. Thus, the natural oxide film can be removed while less damage is given to the metal or metallic compound film by ions.
• In addition, the present invention is a plasma processing method comprising: a step of introducing a substrate into a processing container, a CoSi₂film being formed on a surface of the substrate; a step of supplying a noble gas and an H₂gas into the processing container; and a step of generating inductive coupling plasma in the processing container and applying a bias voltage to the substrate while the noble gas and the H₂gas are supplied, so that a natural oxide film formed on a surface of the CoSi₂film is removed by means of the plasma.
• According to the present invention, the noble gas and the H₂gas are supplied into the processing container, the inductive coupling plasma is generated in the processing container, and the plasma acts on the natural oxide film formed on a surface of the CoSi₂film. Thus, active hydrogen in the plasma reduces the natural oxide film, and active species of the noble gas etch the natural oxide film. As a result, the natural oxide film formed on the surface of the CoSi₂film can be removed with a satisfactory selective ratio and without giving any damage by ions to the CoSi₂film. In the case, it is preferable that an etching selective ratio of the natural oxide film with respect to the CoSi₂film is 3 or more.
• Preferably, in the step of supplying a noble gas and an H₂gas into the processing container, the H₂gas is supplied in such a manner that an amount of the H₂gas is 20% or more with respect to a total amount of the noble gas and the H₂gas. Further preferably, in the step of supplying a noble gas and an H₂gas into the processing container, the H₂gas is supplied in such a manner that an amount of the H₂gas is 40 % or more with respect to a total amount of the noble gas and the H₂gas.
• In addition, preferably, the noble gas is at least one of Ar, Ne, He, Kr and Xe.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a schematic structural view showing a metal-deposition system including a pre-clean processing unit wherein a plasma processing method according to an embodiment of the present invention is carried out;
• FIG. 2 is a schematic sectional view of the pre-clean processing unit shown inFIG. 1;
• FIG. 3 is a graph showing a relationship between outputs of a high-frequency electric power source and etching selective ratios of an SiO₂film with respect to a CoSi₂film;
• FIG. 4 is a graph showing a relationship between ratios of a flow amount of H₂gas with respect to the total flow amount and etching selective ratios of an SiO₂film with respect to a CoSi₂film; and
• FIG. 5 is a graph showing a relationship between pressures in the processing container and etching selective ratios of an SiO₂film with respect to a CoSi₂film.
DESCRIPTION OF THE PREFERRED EMBODIMENT
• Hereinafter, embodiments of the present invention will be described with reference to the attached drawings.
• FIG. 1 is a schematic structural view showing a metal-deposition system including a pre-clean processing unit wherein a plasma processing method according to an embodiment of the present invention is carried out. In the metal-deposition system1, atransfer chamber10 is arranged at a central position thereof. Twocassette chambers11 and12, adegassing chamber13, a Ti depositingunit14, apre-clean processing unit15, aTiN depositing unit16, an Al depositingunit17 and acooling chamber18 are provided around thetransfer chamber10. That is, the metal-deposition system1 is a multi-chamber type of cluster-tool system.
• In the metal-deposition system1, a barrier layer is formed on a CoSi₂film on a silicon wafer W (hereinafter, which is referred to as merely a wafer), the silicon wafer W having a contact hole or a via hole, the CoSi₂film being formed on the hole portion (contact portion). In addition, an Al (aluminum) layer is formed on the barrier layer. Thereby, filling of the hole and forming of an Al wiring are carried out. Specifically, a single wafer W is taken out from thecassette chamber11 by means of atransfer arm19, and then introduced into thepre-clean processing unit15 through thetransfer chamber10. Thepre-clean processing unit15 removes a natural oxide film formed on the CoSi₂film at the contact portion (which is described below in detail). The wafer W is then transferred to thedegassing chamber13 by thetransfer arm19. A degassing process is carried out to the wafer W in thedegassing chamber13. Alternatively, without the degassing process in thedegassing chamber13, the wafer W may be directly transferred to the Ti depositingunit14.
• Then, the wafer W is introduced into the Ti depositingunit14. The Ti depositingunit14 deposits a Ti film on the CoSi₂film by means of, for example, a plasma CVD process using an H₂gas, an Ar gas and a TiCl₄gas. After the Ti film is deposited, the wafer W is introduced into theTiN depositing unit16. TheTiN depositing unit16 deposits a TiN film by means of, for example, a plasma CVD process using an N₂gas or an NH₃gas, an Ar gas and a TiCl₄gas, in order to form a barrier layer. Alternatively, the TiN film may be deposited by means of a thermal CVD process using an N₂gas, an NH₃gas and a TiCl₄gas. Then, theAl depositing unit17 forms an Al layer on the barrier layer. By the above steps, a predetermined depositing process is completed. Then, the wafer W is cooled in the coolingchamber18, and sent to thecassette chamber12.
• The arrangement of thechambers14 to17 is freely determined. The number of respective chambers is determined taking into consideration the number of processes to the wafer and throughput thereof. For example, thechambers14 and15 may be pre-clean chambers, thechamber16 may be a Ti depositing chamber, and thechamber17 may be a TiN depositing chamber. Alternatively, thechamber14 may be a pre-clean chamber, thechambers15 and16 may be Ti depositing chambers, and thechamber17 may be a TiN depositing chamber.
• As described above, a semiconductor device can be manufactured, the semiconductor wafer including, for example, a wafer W having a contact hole reaching an impurity diffusion region and provided with an interlayer insulating film, a CoSi₂film formed on the impurity diffusion zone in the contact hole, a barrier layer formed on the CoSi₂film, and a metal layer formed on the barrier layer to electrically communicate with the impurity diffusion region on a substrate.
• In the metal-deposition system1 of the present embodiment, a vacuum state is maintained in thetransfer chamber10. Thus, after the natural oxide film on the CoSi₂film is removed by thepre-clean processing unit15, the wafer W can be subjected to the deposition process of the Ti film in theTi depositing unit14 without being exposed to the atmospheric air. That is, a natural oxide film can not be formed again on the CoSi₂film before the Ti film is deposited. Thereby, the interface between the Ti film deposited by theTi depositing unit14 and the CoSi₂film is formed satisfactorily, which may improve electrical characteristics thereof.
• Next, thepre-clean processing unit15 included in the above metal-deposition system1 is explained in detail.FIG. 2 is a schematic sectional view of thepre-clean processing unit15. Thepre-clean processing unit15 is formed as an inductive coupling plasma (ICP) etching unit.
• As shown inFIG. 2, thepre-clean processing unit15 includes aprocessing container20 having: acylindrical chamber21 that has a bottom but whose upper end is open, and acylindrical bell jar22 that has a lid, thebell jar22 being arranged continuously on thechamber21 via agas supplying member45 and agasket46.
• In thechamber21, a susceptor (stage for a substrate)23 for horizontally supporting the wafer W as an object to be processed thereon is supported by acylindrical supporting member32. Aconcave portion24 that has substantially the same shape as the wafer W is formed on a surface of asusceptor body27 of thesusceptor23. The wafer W is adapted to be placed on theconcave portion24. Under theconcave portion24, a disk-like meshylower electrode25 is buried. A bias voltage may be applied to thelower electrode25. In addition, aheating member26 consisting of W, Mo or the like is buried below thelower electrode25. Thesusceptor body27 consists of an insulating material such as ceramics, for example, AlN, Al₂O₃or the like. Thus, thesusceptor body27 and theheating member26 form a ceramics heater. A direct-current power source41 is connected to theheating member26. When thepower source41 supplies electric power to theheating member26, theheating member26 is heated and the wafer W may be heated to a predetermined temperature.
• In addition, above thesusceptor23, acircular shadow ring30 made of an insulating material such as quartz, AlN, Al₂O₃or the like is arranged so as to cover the edge of the wafer W placed on theconcave portion24. Theshadow ring30 is connected to acircular member34 via a supporting pillar33 that is connected to a lower surface of theshadow ring30. Thecircular member34 is connected to an elevatingmechanism37 via arod member36. When therod member36 is moved up and down by the elevatingmechanism37, thecircular member34, the supporting pillar33 and theshadow ring30 are integrally moved up and down. Therod member36 is surrounded by abellows35. Thus, it is prevented that the atmosphere in theprocessing container20 leaks outside from a vicinity of therod member36.
• Theshadow ring30 have a function to mask the edge of the wafer W and a function as a focus ring for generating density-uniform plasma above the surface of the wafer W. Theshadow ring30 is moved up to a predetermined position when the wafer W is transferred into thechamber21 and passed onto wafer supporting pins (not shown) that extend through thesusceptor23 and can be moved up and down. On the other hand, after the wafer W is passed on the wafer supporting pins, when the wafer W is placed onto thesusceptor23, theshadow ring30 is moved down together with the wafer supporting pins.
• The abovelower electrode25 is connected to a high-frequencyelectric power source39 of a frequency of for example 13.56 MHz, via amatching unit38. When the high-frequencyelectric power source39 supplies electric power to thelower electrode25, a predetermined bias voltage is adapted to be applied to the lower electrode25 (that is, finally the wafer W).
• The circulargas supplying member45 and thegasket46 are provided between thechamber21 and thebell jar22, in order to maintain airtightness. A plurality of gas-discharging holes is formed in thegas supplying member45 at a substantially even arrangement over the whole circumference thereof. A gas is supplied from agas supplying mechanism60 into theprocessing container20 through the gas-discharging holes.
• In addition, anopening47 is provided in a lateral wall of thechamber21. A gate valve48 is mounted at a position corresponding to theopening47 outside thechamber21. Thus, while the gate valve48 is opened, the wafer W is adapted to be transferred between a load-lock chamber (not shown) and thechamber21 through thetransfer chamber10.
• Thebell jar22 is made of an electrical insulating material such as quartz or ceramics. Aninductive coil42 as an antenna, which is plasma generating means, is wound around the outside periphery of thebell jar22. Thecoil42 is connected to a high-frequencyelectric power source44 of a frequency of 450 kHz to 600 MHz, preferably 450 kHz, via amatching unit43. When the high-frequencyelectric power source44 supplies high-frequency electric power to thecoil42 via thematching unit43, inductive coupling plasma (ICP) is adapted to be generated in thebell jar22.
• Thegas supplying mechanism60 has an Argas supplying source61 that supplies an Ar gas, and an H₂gas supplying source62 that supplies an H₂gas. The Argas supplying source61 is connected to agas line63. On the way of thegas line63, an open-close valve65, a mass-flow controller67 and an open-close valve69 are provided in the order. In addition, the H₂gas supplying source62 is connected to agas line64. On the way of thegas line64, an open-close valve66, a mass-flow controller68 and an open-close valve70 are provided in the order. Thegas lines63,64 are connected to agas line71, and thegas line71 is connected to thegas supplying member45.
• A bottom wall of thechamber21 is connected to anexhaust pipe50. Theexhaust pipe50 is connected to an exhaust unit51 including a vacuum pump. When the exhaust unit51 is driven, a vacuum of a predetermined level can be maintained in theprocessing container20.
• Then, an operation of removing a natural oxide film formed on a wafer W by using the abovepre-clean processing unit15 is explained.
• At first, the gate valve48 is opened, and a wafer W is introduced into thechamber21 by means of thetransfer arm19 provided in thetransfer chamber10 of the metal-deposition system1. Then, in a state wherein theshadow ring30 has been moved up, the wafer W is passed onto the wafer supporting pins (not shown) projecting from thesusceptor23. Then, the wafer supporting pins and theshadow ring30 are moved down, so that the wafer W is placed on thesusceptor23 and theshadow ring30 masks the outside peripheral edge of the wafer W.
• After that, the gate valve48 is closed, and the atmosphere in theprocessing container20 is discharged by the exhaust system51 to a predetermined reduced-pressure state. In the reduced-pressure state, the Ar gas and the H₂gas are introduced at respective predetermined flow rates from the Argas supplying source61 and the H₂gas supplying source62 into theprocessing container20. At the same time, the high-frequencyelectric power source44 starts to supply high-frequency electric power to thecoil42, so that inductive coupling plasma is generated in thebell jar22. Thus, active species of Ar, H₂and so on are generated. In addition, the high-frequencyelectric power source39 supplies high-frequency electric power of for example 450 kHz to 60 MHz, preferably 13.56 MHz, to thesusceptor23. That is, a self-bias voltage is applied to the wafer W. This makes it easier for the active species to be drawn to the wafer W, that is, the reduction and etching process is more efficiently carried out.
• In the above state, in order to enhance the reduction force, theheating member26 is heated by electric power from theelectric power source41 so that the wafer W is heated to 200 to 500° C. Thus, a pre-clean process wherein a natural oxide film on a CoSi₂film formed at a contact portion of the wafer W is reduced, etched and removed is carried out.
• Then, a gas-discharging amount by the exhaust system51 and gas-supplying amounts from the Argas supplying source61 and the H₂gas supplying source62 are adjusted so that theprocessing container20 is returned to the same vacuum level as thetransfer chamber10. Then, the supporting pins project from thesusceptor23 to lift up the wafer W. When the gate valve48 is opened, thetransfer arm19 goes into thechamber21 and takes out the wafer W. Then, the steps at thepre-clean processing unit15 are completed.
• According to the above pre-clean process, the natural oxide film on a CoSi₂film may be properly removed. In the case, if the ratio between the Ar gas as a noble gas and the H₂gas is properly adjusted, an etching selective ratio of the natural oxide film with respect to the CoSi₂film can be sufficiently enhanced and damage given to the CoSi₂film as a base layer can be reduced. It is preferable that the etching selective ratio, that is, a ratio between an etching rate of the CoSi₂film and an etching rate of the natural oxide film is 3 or more.
• In addition, in the present embodiment, inductive electromagnetic field is generated in thebell jar22, the inductive coupling plasma that causes less ion-damage to the base layer is generated, and the natural oxide film is removed by the inductive coupling plasma. Thus, damage by ions to the CoSi₂film as the base layer can be further reduced.
• Regarding the above pre-clean process, experiments were carried out for investigating effects of process conditions on the etching selective ratio of the SiO₂film with respect to the CoSi₂film. In the experiments, the process conditions were as follows: the Ar gas flow rate and the H₂gas flow rate were 0.008 L/min and 0.012 L/min (8 sccm and12 sccm); the pressure in theprocessing container20 was 0.655 Pa; the temperature of the heated wafer W was 500° C.; the electric power of the high-frequencyelectric power source39 was 200 W; the electric power of the high-frequencyelectric power source44 was 1000 W; and the time of the pre-clean process was 60 second. While the above values were used as a reference process condition, any of the output of the high-frequencyelectric power source39, the H₂gas flow rate and the pressure in theprocessing container20 was variously changed and respective etching selective ratios of the SiO₂film with respect to the CoSi₂film (ratio of SiO₂/CoSi₂) were measured. The results are shown in FIGS.3 to5.FIG. 3 is a graph on which the abscissa represents the output of the high-frequency electric power source39 (bias power) and the ordinate represents the etching selective ratio.FIG. 4 is a graph on which the abscissa represents the ratio of the H₂gas flow rate with respect to the total gas flow rate and the ordinate represents the etching selective ratio.FIG. 5 is a graph on which the abscissa represents the pressure in theprocessing container20 and the ordinate represents the etching selective ratio.
• Taking into consideration the results of the experiments, preferable process conditions for the pre-clean process are explained below.
• Even if the H₂gas flow rate supplied into theprocessing container20 is very small, if the processing time is short, the natural oxide film can be removed with less damage to the CoSi₂film. However, in view of effectively removing the natural oxide film with less damage to the CoSi₂film, the ratio of the H₂gas supplied into theprocessing container20 is preferably 20% or more, more preferably 40 % or more. In addition, when the ratio of the H₂gas is higher, the etching selective ratio of the natural oxide film is also higher. When the ratio of the H₂gas is 80%, the etching selective ratio of the natural oxide film is 20 or more. However, when the ratio of the H₂gas is higher than 80%, it is difficult to obtain a desired etched amount (2 nm or more) of the natural oxide film within a short time. Therefore, it is preferable that the ratio of the H₂gas is not higher than 80%.
• It is preferable that the pressure in theprocessing container20 is 0.133 to 6.55 Pa (1 to 50 mTorr). More preferably, the pressure is 0.133 to 2.66 Pa (1 to 20 mTorr).
• The total flow amount of the gases is 30 sccm or lower, preferably 20 sccm or lower.
• The bias electric power supplied from the high-frequencyelectric power source39 to the susceptor is preferably 20 to 700 W. More preferably, it is 100 to 500 W.
• The time of the pre-clean process is preferably 10 to 180 second in view of etching in-plane uniformity. More preferably, it is 10 to 120 second.
• When any process condition satisfying the above ranges is adopted, the natural oxide film formed on the CoSi₂film can be properly removed.
• In addition, the present invention is not limited to the above embodiment, but may be variously modified. For example, in the above embodiment, the natural oxide film is removed by the inductive coupling plasma. However, this invention is not limited thereto, and helicon wave plasma, microwave plasma such as microwave remote plasma, and high-density plasma that may cause less damage by ions can be preferably used. Of course, any other plasma can be also used. In addition, in the above embodiment, the natural oxide film on the CoSi₂film formed on the contact portion of the wafer W is removed. However, this invention is not limited thereto, and a natural oxide film formed on a surface of any other metal or metallic compound film can be removed with a high selective ratio. Such a metal or metallic compound film may be a Co film, a W film, a WSi film, a Cu film, a Si film, an Al film, a Mo film, a MoSi film, a Ni film and a NiSi film. In addition, the present invention can be also used for removing an oxide formed after a polishing step by means of CMP in a wiring-forming process. In addition, in the above embodiment, the Ar gas is used as a noble gas, but Ne, He, Kr and Xe may be also used.

Claims (25)

1-37. (canceled)

38. A plasma processing method comprising;

a step of introducing a substrate into a processing container, a metal or metallic compound or Si film being on a surface of the substrate,

a step of supplying an Ar gas into the processing container, and

a step of generating inductive coupling plasma in the processing container while the Ar gas is supplied, so that a natural oxide film existing on a surface of the metal or metallic compound or Si film is removed by means of the plasma, wherein

a gas flow rate of the Ar gas is 30 sccm or lower,

an etching selective ratio of the natural oxide film with respect to the metal or metallic compound or Si film is 3 or more,

a frequency for generating the inductive coupling plasma is 450 kHz, and

a frequency of the high-frequency bias voltage is 13.56 MHz.

39. A plasma processing method according toclaim 38, further comprising:

a step of heating the substrate to 200 to 500° C., after the step of supplying an Ar gas into the processing container.

40. A plasma processing method according toclaim 38, wherein the metal or metallic compound consists of any of CoSi₂, Co, W, WSi, Cu, Al, Mo, MoSi, Ni and NiSi.

41. A plasma processing method comprising:

a step of introducing a substrate into a processing container, a CoSi₂film being on a surface of the substrate,

a step of supplying an Ar gas into the processing container, and

a step of heating the substrate to 200 to 500° C.,

a step of generating inductive coupling plasma in the processing container and applying a high-frequency bias voltage to the substrate while the Ar gas is supplied, so that a natural oxide film existing on a surface of the CoSi₂film is removed by means of the plasma, wherein

a gas flow rate of the Ar gas is 30 sccm or lower,

an etching selective ratio of the natural oxide film with respect to the CoSi₂film is 3 or more,

a frequency for generating the inductive coupling plasma is 450 kHz, and

a frequency of the high-frequency bias voltage is 13.56 MHz.

42. A plasma processing method according toclaim 38, wherein the high-frequency bias voltage to the substrate is 20 to 700 W.

43. A plasma processing method according toclaim 41, wherein the high-frequency bias voltage to the substrate is 20 to 700 W.

44. A plasma processing method according toclaim 38, wherein the high-frequency bias voltage to the substrate is 10 to 500 W.

45. A plasma processing method according toclaim 41, wherein the high-frequency bias voltage to the substrate is 10 to 500 W.

46. A plasma processing method according toclaim 38, wherein a pressure in the processing container is 0.133 to 6.55 Pa.

47. A plasma processing method according toclaim 41, wherein a pressure in the processing container is 0.133 to 6.55 Pa.

48. A plasma processing method according toclaim 38, wherein a pressure in the processing container is 0.133 to 2.66 Pa.

49. A plasma processing method according toclaim 41, wherein a pressure in the processing container is 0.133 to 2.66 Pa.

50. A plasma processing method according toclaim 38, wherein the time of the step of removing the natural oxide film is 10 to 180 seconds.

51. A plasma processing method according toclaim 41, wherein the time of the step of removing the natural oxide film is 10 to 180 seconds.

52. A plasma processing method according toclaim 38, wherein the time of the step of removing the natural oxide film is 10 to 120 seconds.

53. A plasma processing method according toclaim 41, wherein the time of the step of removing the natural oxide film is 10 to 120 seconds.

54. A plasma processing method according toclaim 38, further comprising:

a step of covering an edge of the substrate by means of a circular member, after the step of supplying an Ar gas into the processing container.

55. A plasma processing method according toclaim 41, further comprising:

a step of covering an edge of the substrate by means of a circular member, after the step of supplying an Ar gas into the processing container.

56. A plasma processing method according toclaim 38, wherein

the processing container has a chamber whose upper end is open and a bell jar is arranged on the chamber,

an inductive coil is wound around an outside periphery of the bell jar,

a susceptor for placing the substrate thereon is arranged in the processing container,

a lower electrode is buried in the susceptor, and

the chamber is connected to an exhaust unit.

57. A plasma processing method according toclaim 41, wherein

the processing container has a chamber whose upper end is open and a bell jar is arranged on the chamber,

an inductive coil is wound around an outside periphery of the bell jar,

a susceptor for placing the substrate thereon is arranged in the processing container,

a lower electrode is buried in the susceptor, and

the chamber is connected to an exhaust unit.

58. A plasma processing method comprising:

a step of introducing a substrate into a processing container, a metal or metallic compound or Si film being on a surface of the substrate,

a step of supplying an Ar gas into the processing container,

a step of generating inductive coupling plasma in the processing container while the Ar gas is supplied, so that a natural oxide film existing on a surface of the metal or metallic compound or Si film is removed by means of the plasma,

a step of forming a Ti film on the substrate, and

a step of forming a TiN film on the Ti film, wherein

a gas flow rate of the Ar gas is 30 sccm or lower,

an etching selective ratio of the natural oxide film with respect to the metal or metallic compound or Si film is 3 or more,

a frequency for generating the inductive coupling plasma is 450 kHz, and

a frequency of the high-frequency bias voltage is 13.56 MHz.

59. A plasma processing method according toclaim 58, wherein

the step of forming a Ti film is conducted by a plasma CVD process using a TiCl₄gas, an H₂gas and an Ar gas.

60. A plasma processing method according toclaim 58, wherein

the step of forming a TiN film is conducted by a CVD process using a gas including a TiCl₄gas and an NH₃gas.

61. A plasma processing method according toclaim 59, wherein

the step of forming a TiN film is conducted by a CVD process using a gas including a TiCl₄gas and an NH₃gas.

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