US20110240598A1

US20110240598A1 - Plasma processing apparatus and plasma processing method

Info

Publication number: US20110240598A1
Application number: US13/129,607
Authority: US
Inventors: Nobuyuki Okayama; Naoki Matsumoto
Original assignee: Tokyo Electron Ltd
Current assignee: Tokyo Electron Ltd
Priority date: 2008-11-18
Filing date: 2009-08-25
Publication date: 2011-10-06
Also published as: CN102217044A; JP5360069B2; KR101266890B1; WO2010058642A1; CN102217044B; TWI442837B; TW201028052A; KR20120098931A; KR20110081296A; JPWO2010058642A1; KR101341371B1

Abstract

A plasma processing apparatus 11 includes a reactant gas supply unit 13 for supplying a reactant gas for a plasma process into a processing chamber 12. The reactant gas supply unit 13 includes a first reactant gas supply unit 61 provided at a center of a dielectric plate 16 and configured to supply the reactant gas in a directly downward direction toward a central region of a processing target substrate W held on a holding table 14; and a second reactant gas supply unit 62 provided at a position directly above the holding table 14 but not directly above the processing target substrate W held on the holding table 14 and configured to supply the reactant gas toward a center of the processing target substrate W held on the holding table 14.

Description

TECHNICAL FIELD

The present invention relates to a plasma processing apparatus and a plasma processing method; and, more particularly, to a plasma processing apparatus and a plasma processing method for generating plasma by using a microwave as a plasma source.

BACKGROUND ART

A semiconductor device such as a LSI (Large Scale Integrated circuit) is manufactured by performing various processes such as etching, CVD (Chemical Vapor Deposition), sputtering or the like on a semiconductor substrate (wafer) as a processing target substrate. A processing method using plasma as an energy source, i.e., plasma etching, plasma CVD or plasma sputtering may be used to perform the etching, the CVD or the sputtering process. There are known various kinds of plasma such as parallel plate type plasma, ICP (Inductively-Coupled Plasma) and ECR (Electron Cyclotron Resonance) Plasma, and plasma generated by various apparatuses is used for a plasma process.
When the plasma etching or the like is performed on the processing target substrate, a reactant gas for processing the processing target substrate needs to be supplied into a processing chamber for generating plasma therein. Here, a technology for supplying the reactant gas into the processing chamber during the plasma process of the processing target substrate is described in Japanese Patent Laid-open Publication No. 2004-165374 (Patent Document 1) or Japanese Patent Laid-open Publication No. H6-112163 (Patent Document 2). In the Patent Document 1, an annular gas ring is provided between a mounting table for mounting thereon a processing target object and a main coil in a plasma processing apparatus using ECR plasma. The gas ring has a diameter larger than that of the mounting table. The reactant gas is supplied by the gas ring. In the Patent Document 2, a gas inlet for a deposition gas is provided in the vicinity of a sample holding table in a plasma processing apparatus using ECR plasma.
Patent Document 1: Japanese Patent Laid-open Publication No. 2004-165374
Patent Document 2: Japanese Patent Laid-open Publication No. H6-112163

DISCLOSURE OF THE INVENTION

[Problems to Be Solved by the Invention]
When processing a processing target substrate, it may be desirable to process the processing target substrate uniformly over the entire surface thereof. When a reactant gas is supplied into the processing chamber, the reactant gas may be supplied from a multiple number of places in order to improve uniformity of the plasma process within the surface of the processing target object. FIG. 21 is a schematic cross sectional view illustrating a part of a plasma processing apparatus 101 in which two reactant gas supply units for supplying reactant gases into a processing chamber are provided at two different positions. In the plasma processing apparatus 101 shown in FIG. 21, in order to supply a reactant gas to a central region of a circular plate-shaped processing target substrate W, a first reactant gas supply unit 104 is provided in a central portion of a dielectric plate 103 which introduces a microwave into a processing chamber 102. The first reactant gas supply unit 104 discharges the reactant gas toward the central region of the processing target substrate W. Further, in order to supply the reactant gas to an edge region of the processing target substrate W, a second reactant gas supply unit 106 is provided in an upper portion of a sidewall 105 of the processing chamber 102. In the plasma processing apparatus 101 during a plasma process, evacuation is performed in a downward direction by a gas exhaust unit (not shown) located at a lower side of FIG. 21.
In the plasma processing apparatus 101 in which the two reactant gas supply units are provided at the two different positions as described above, when the reactant gas is supplied into the processing chamber 102 at a pressure range (equal to or larger than about 50 mTorr) of a viscous flow, the reactant gas supplied from the second reactant gas supply unit 106 is affected by the first reactant gas supply unit 104 and flows toward the central portion, as indicated by an arrow X of FIG. 21. That is, the reactant gas from the second reactant gas supply unit 106 flows along the same supply path as that of the reactant gas from the first reactant gas supply unit 104. Accordingly, an effect of supplying the reactant gas from the second reactant gas supply unit 106 is not much. The reactant gas supplied to the central region of the processing target substrate W is diffused in a radial direction from the central region toward the edge region of the processing target substrate. As the reactant gas flows toward the edge region, the reactant gas is consumed and a reaction product increases. As a result, distribution of a processed state on the processing target substrate W is not uniform in a diametric direction of the processing target substrate W, resulting in non-uniformity of a processed surface.
Meanwhile, at a pressure range (equal to or less than about 50 mTorr) of a molecular flow, the reactant gas supplied from the second reactant gas supply unit 106 flows in a downward direction, as indicated by an arrow Y of FIG. 21, due to the evacuation by the gas exhaust unit. Accordingly, the reactant gas supplied from the second reactant gas supply unit 106 is exhausted without reaching the processing target substrate W. As a result, only the reactant gas from the first reactant gas supply unit 104 may reach the processing target substrate W. Thus, as in the aforementioned case, the processed state of the processing target substrate W may be become non-uniform within the surface thereof.
As stated above, in the plasma processing apparatus 101 having the above-described configuration, even if a supply amount of the gas from the second reactant gas supply unit 106 is adjusted by varying an internal pressure of the processing chamber 102, the reactant gas may not be uniformly supplied to the processing target substrate W. Thus, it may be difficult to achieve uniformity of the plasma process within the surface of the processing target substrate W. In the plasma processing apparatuses described in Patent Document 1 and Patent Document 2, the above-mentioned problem may be encountered.
Here, in case that the second reactant gas supply unit is provided in a position directly above the processing target substrate W so as to supply the reactant gas to the processing target substrate W uniformly, the following problems may be caused. FIG. 22 is a schematic cross sectional view showing a part of a plasma processing apparatus 111 having such a configuration, and FIG. 22 corresponds to the cross section illustrated in FIG. 21. As shown in FIG. 22, in the plasma processing apparatus 111, a first reactant gas supply unit 113 is provided in a central portion of a dielectric plate 112, and a ring-shaped second reactant gas supply unit 115 is provided in a position directly above a processing target substrate W held on a holding table 114. A reactant gas is supplied to an edge region of the processing target substrate W in a directly downward direction by the second reactant gas supply unit 115.
In this configuration, however, the reactant gas supplied from the first reactant gas supply unit 113 and the reactant gas supplied from the second reactant gas supply unit 115 may collide with each other in a region 116 between the central region and the edge region of the processing target substrate W in a diametric direction. In FIG. 22, the region 116 is marked by a dashed line. The reactant gas may stay in this region 116, thus resulting in stay of a deposit (reaction product).
Further, as shown in FIG. 22, if the second reactant gas supply unit is provided in the position directly above the processing target substrate W, the second reactant gas supply unit may become a plasma shield that blocks a flow of plasma above the processing target substrate W. Such a plasma shield may cause non-uniformity of the plasma process on the processing target substrate W.
Due to the stay of the deposit and the presence of the plasma shield as mentioned above, an etching rate of the processing target substrate W in the region 116 and an etching rate of the processing target substrate W in the central region or the edge region become different, resulting in deterioration of uniformity of the plasma process within the surface of the processing target substrate W.
The present invention provides a plasma processing apparatus capable of improving uniformity of a plasma process within a surface of a processing target substrate.
The present invention also provides a plasma processing method capable of improving uniformity of a plasma process within a surface of a processing target substrate.
[Means for Solving the Problems]
In accordance with one aspect of the present invention, there is provided a plasma processing apparatus including a processing chamber configured to perform therein a plasma process on a processing target substrate; a holding table provided within the processing chamber and configured to hold the processing target substrate thereon; a plasma generating unit configured to generate plasma within the processing chamber; and a reactant gas supply unit configured to supply a reactant gas for the plasma process into the processing chamber. The reactant gas supply unit includes a first reactant gas supply unit configured to supply the reactant gas in a directly downward direction toward a central region of the processing target substrate held on the holding table; and a second reactant gas supply unit provided at a position directly above the holding table but not directly above the processing target substrate held on the holding table, and configured to supply the reactant gas toward a center of the processing target substrate held on the holding table.
In accordance with this plasma processing apparatus, the reactant gas can be uniformly supplied to the entire processing target substrate by both the first reactant gas supply unit configured to supply the reactant gas in the directly downward direction toward the central region of the processing target substrate W and the second reactant gas supply unit configured to supply the reactant gas toward the center of the processing target substrate. Further, since the reactant gases supplied from the first and second reactant gas supply units do not stay on the processing target substrate, stay of deposits (reaction products) can be suppressed. Furthermore, the second reactant gas supply unit does not block a flow of plasma toward the processing target substrate. Accordingly, uniformity of the plasma process within the surface of the processing target substrate can be improved. Further, the “the position directly above the processing target substrate” refers to a vertically upper region of the processing target substrate, and the “the center of the processing target substrate” refers to the central region of the processing target substrate and a vertically upper region of the central region of the processing target substrate.
Desirably, the second reactant gas supply unit may be provided in the vicinity of the holding table.
More desirably, the second reactant gas supply unit may be configured to supply the reactant gas in an inclined direction toward a central region of the processing target substrate held on the holding table.
Further, the second reactant gas supply unit may be configured to supply the reactant gas in a horizontal direction toward the center of the processing target substrate held on the holding table.
More desirably, the second reactant gas supply unit may include a ring-shaped member, and the ring-shaped member may be provided with a supply hole through which the reactant gas is supplied.
More desirably, the processing target substrate may be of a circular plate shape, the ring-shaped member may be of a circular ring shape, and an inner diameter of the ring-shaped member may be larger than an outer diameter of the processing target substrate.
Moreover, the processing chamber may include a bottom positioned under the holding table and a sidewall upwardly extending from a periphery of the bottom, and the second reactant gas supply unit may be embedded within the sidewall.
More desirably, the sidewall may include an inwardly projecting protrusion, and the second reactant gas supply unit may be embedded within the protrusion.
Further, in a desirable embodiment, the plasma generating unit may include a microwave generator capable of generating a microwave for exciting plasma and a dielectric plate positioned to face the holding table and configured to introduce the microwave into the processing chamber, and the first reactant gas supply unit may be provided at a central portion of the dielectric plate.
More desirably, the plasma processing apparatus may further include a first temperature controller configured to control a temperature of the central region of the processing target substrate held on the holding table; and a second temperature controller configured to control a temperature of an edge region of the processing target substrate held on the holding table.
More desirably, at least one of the first and second temperature controllers may be divided into a plurality of members.
Further, in a desirable embodiment, the first and second temperature controllers may be provided within the holding table.
More desirably, the processing chamber may include a bottom positioned under the holding table and a sidewall upwardly extending from a periphery of the bottom, and the plasma processing apparatus may further include a sidewall temperature controller configured to control a temperature of the sidewall.
More desirably, the sidewall temperature controller may be provided within the sidewall.
In accordance with another aspect of the present invention, there is provided a plasma processing method for performing a plasma process on a processing target substrate. The plasma processing method includes holding the processing target substrate on a holding table provided within the processing chamber; generating a microwave for exciting plasma; introducing the microwave into the processing chamber through a dielectric plate; and supplying a reactant gas in a directly downward direction from a central portion of the dielectric plate toward a central region of the processing target substrate, and supplying the reactant gas in an inclined direction toward the processing target substrate from a position directly above the holding table but not directly above the processing target substrate held on the holding table.
In accordance with still another aspect of the present invention, there is provided a plasma processing apparatus including a holding table configured to hold a processing target substrate thereon; a processing chamber configured to perform therein a plasma process on the processing target substrate, and having a bottom positioned under the holding table and a ring-shaped sidewall upwardly extending from a periphery of the bottom; a plasma generating unit configured to generate plasma within the processing chamber; and a reactant gas supply unit configured to supply a reactant gas for the plasma process into the processing chamber. The reactant gas supply unit includes a first reactant gas supply unit configured to supply the reactant gas in a directly downward direction toward a central region of the processing target substrate held on the holding table; and a second reactant gas supply unit having a ring-shaped member provided at an upper position of the holding table and at a position deviated from a vertically upper region of the processing target substrate held on the holding table and at an inside position of the sidewall, and configured to supply the reactant gas toward a center of the processing target substrate held on the holding table.
Desirably, the ring-shaped member may be provided at an outside position of the holding table.
More desirably, the plasma processing apparatus may include a first temperature controller configured to control a temperature of the central region of the processing target substrate held on the holding table; and a second temperature controller configured to control a temperature of an edge region of the processing target substrate held on the holding table.
More desirably, the first and second temperature controllers may be provided within the holding table.
More desirably, at least one of the first and second temperature controllers may be divided into a plurality of members.
[Effect of the Invention]
In accordance with the plasma processing apparatus and the plasma processing method of the present invention, the reactant gas can be uniformly supplied to the entire processing target substrate by both the first reactant gas supply unit for supplying the reactant gas in the directly downward direction toward the processing target substrate and the second reactant gas supply unit for supplying the reactant gas toward the processing target substrate in the inclined direction. Further, since the reactant gases supplied from the first and second reactant gas supply units do not stay on the processing target substrate, stay of deposits (reaction products) can be suppressed. Furthermore, the second reactant gas supply unit does not block a flow of plasma toward the processing target substrate. Accordingly, uniformity of the plasma process within the surface of the processing target substrate can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with an embodiment of the present invention;

FIG. 2 is a diagram illustrating the vicinity of a circular ring-shaped member of a second reactant gas supply unit of the plasma processing apparatus shown in FIG. 1, when viewed from a direction of an arrow II of FIG. 1;

FIG. 3 is an enlarged view of a part III in the plasma processing apparatus shown in FIG. 1;

FIG. 4 is a schematic diagram illustrating flows of reactant gases from a first reactant gas supply unit and the second reactant gas supply unit;

FIG. 5 illustrates a relationship between a film thickness and a position on a processing target substrate W in a case of setting an angle θ for supplying the reactant gas from the second reactant gas supply unit to be about 42° in the plasma processing apparatus in accordance with the embodiment of the present invention;

FIG. 6 illustrates a relationship between a film thickness and a position on a processing target substrate W in a case of setting an angle θ for supplying the reactant gas from the second reactant gas supply unit to be about 24° in the plasma processing apparatus in accordance with the embodiment of the present invention;

FIG. 7 illustrates an X axis, a Y axis, a V axis and a W axis shown in FIGS. 5 and 6 on a processing target substrate W;

FIG. 8 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with another embodiment of the present invention and FIG. 8 corresponds to FIG. 1;

FIG. 9 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with still another embodiment of the present invention and FIG. 9 corresponds to FIG. 1;

FIG. 10 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with still another embodiment of the present invention and FIG. 10 corresponds to FIG. 1;

FIG. 11 is a diagram showing a part of a second reactant gas supply unit of the plasma processing apparatus of FIG. 10, when viewed from a direction of an arrow XI of FIG. 10.

FIG. 12 is an enlarged view of a part of a second reactant gas supply unit of the plasma processing apparatus of FIG. 10;

FIG. 13 is a graph showing a relationship between an etching rate normalized value and a lot number of processing target substrates respectively processed by the plasma processing apparatus shown in FIG. 10 and by the plasma processing apparatus shown in FIG. 21;

FIG. 14 is a graph showing a relationship between the number of particles and a lot number of processing target substrates processed by the plasma processing apparatus shown in FIG. 10;

FIG. 15 is a graph showing a relationship between a center/edge flow rate ratio and a non-uniformity of a plasma process on a processing target substrate processed by the plasma processing apparatus of FIG. 10;

FIG. 16 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed by the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio indicated by an arrow G₁of FIG. 15;

FIG. 17 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed in the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio indicated by an arrow G₂of FIG. 15;

FIG. 18 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed in the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio indicated by an arrow G₃of FIG. 15;

FIG. 19 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with still another embodiment of the present invention and FIG. 19 corresponds to FIG. 1;

FIG. 20 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with still another embodiment of the present invention and FIG. 20 corresponds to FIG. 1;

FIG. 21 is a schematic cross sectional view illustrating a part of a conventional plasma processing apparatus in which two reactant gas supply units for supplying reactant gases into a processing chamber are provided at two different positions; and

FIG. 22 is a schematic cross sectional view showing a part of a conventional plasma processing apparatus in which a second reactant gas supply unit is provided directly above a processing target substrate W and FIG. 22 corresponds to FIG. 21.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in accordance with an embodiment of the present invention. As depicted in FIG. 1, a plasma processing apparatus 11 may include a processing chamber 12 for performing therein a plasma process on a processing target substrate W; a reactant gas supply unit 13 for supplying a reactant gas for the plasma process into the processing chamber 12; a circular plate-shaped holding table 14 for holding the processing target substrate W thereon; a microwave generator 15 capable of generating a microwave for plasma excitation; a dielectric plate 16 positioned to face the holding table 14 and configured to introduce the microwave generated by the microwave generator 15 into the processing chamber 12; and a controller (not shown) capable of controlling the entire plasma processing apparatus 11. The controller controls processing conditions for performing the plasma process on the processing target substrate W, such as a gas flow rate in the reactant gas supply unit 13 and an internal pressure of the processing chamber 12.
The processing chamber 12 may include a bottom 17 positioned under the holding table 14 and a sidewall 18 extending upward from the periphery of the bottom 17. The sidewall 18 has a cylindrical shape. A gas exhaust hole 19 for gas exhaust is provided in the bottom 17 of the processing chamber 12. A top of the processing chamber 12 is opened and the processing chamber 12 can be hermetically sealed by a dielectric plate 16 provided at the top of the processing chamber 12 and by an O-ring 20 as a sealing member provided between the dielectric plate 16 and the processing chamber 12.
The microwave generator 15 having a matching unit 21 is connected to an upper portion of a coaxial waveguide 24 for introducing a microwave via a mode converter 22 and a waveguide 23. For example, a microwave of a TE mode generated by the microwave generator 15 is converted to a TEM mode by the mode converter 22 after it passes through the waveguide 23. Then, the microwave of the TEM mode propagates through the coaxial waveguide 24. The coaxial waveguide 24 may include a central conductor 25 provided at a center thereof in a diametric direction; and an external conductor 26 provided at the outside of the central conductor 25 in the diametric direction. An upper end of the central conductor 25 is connected to a ceiling partition wall of the mode converter 22. A frequency of the microwave generated by the microwave generator 15 is, for example, about 2.45 GHz. Further, the waveguide 23 may have a circular or a rectangular cross section.
The dielectric plate 16 is of a circular plate shape and is made of a dielectric material. A ring-shaped tapered recess 27 is provided on a bottom surface of the dielectric plate 16 to facilitate generation of a standing wave by the introduced microwave. Due to the recess 27, plasma can be efficiently generated under the dielectric plate 16 by the microwave. Further, the dielectric plate 16 may be made of a material such as, but not limited to, quartz or alumina.
Further, the plasma processing apparatus 11 may include a wavelength shortening plate 28 for propagating the microwave introduced through the coaxial waveguide 24; and a thin circular slot plate 30 for introducing the microwave to the dielectric plate 16 through a multiple number of slot holes 29. The microwave generated by the microwave generator 15 is propagated to the wavelength shortening plate 28 through the coaxial waveguide 24 and is then introduced to the dielectric plate 16 through the slot holes 29 provided in the slot plate 30. The microwave transmitted through the dielectric plate 16 generates an electric field directly under the dielectric plate 16. As a result, plasma is generated within the processing chamber 12.
The holding table 14 also serves as a high frequency electrode and is supported by a cylindrical insulating support 31 extending vertically upward from the bottom 17. A ring-shaped gas exhaust passageway 33 is formed between the sidewall 18 of the processing chamber 12 and a cylindrical conductive support 32 extending vertically upward from the bottom 17 along the outer periphery of the cylindrical support 31. A ring-shaped baffle plate 34 provided with a multiple number of through holes is fixed to an upper portion of the gas exhaust passageway 33. A gas exhaust unit 36 is connected to a bottom portion of the gas exhaust hole 19 via a gas exhaust pipe 35. The gas exhaust unit 36 has a vacuum pump such as a turbo molecular pump. The inside of the processing chamber 12 can be depressurized to a desired vacuum level by the gas exhaust unit 36.
The holding table 14 is electrically connected with a high frequency RF bias power supply 37 via a matching unit 38 and a power supply rod 39. The high frequency power supply 37 outputs a high frequency power of a certain frequency, e.g., about 13.56 MHz, suitable for controlling energy of ions attracted into the processing target substrate W. The matching unit 38 has a matcher for matching impedance on the side of the high frequency power supply 37 with impedance on the side of a load such as an electrode, plasma and the processing chamber 12. A blocking capacitor for generation of self-bias is included in the matcher.
An electrostatic chuck 41 configured to hold the processing target substrate W by an electrostatic attracting force is provided on a top surface of the holding table 14. Further, a focus ring 42 is provided at a periphery of the electrostatic chuck 41 in a diametric direction to surround the processing target substrate W in a ring shape. The electrostatic chuck 41 may include an electrode 43 made of a conductive film sandwiched between a pair of insulating films 44 and 45. The electrode 43 is electrically connected with a high voltage DC power supply 46 via a switch 47 and a coated line 48. The processing target substrate W can be attracted to and held on the electrostatic chuck 41 by a Coulomb force generated by a DC voltage applied from the DC power supply 46.
A ring-shaped coolant path 51 extending in a circumferential direction of the holding table 14 is provided within the holding table 14. A coolant of a preset temperature, e.g., cooling water is supplied into and circulated through the coolant path 51 from a chiller unit (not shown) via pipes 52 and 53. A processing temperature of the processing target substrate W on the electrostatic chuck 41 can be controlled by adjusting the temperature of the coolant. Further, a heat transfer gas from a heat transfer gas supply unit (not shown), e.g., a He gas is supplied to between a top surface of the electrostatic chuck 41 and a rear surface of the processing target substrate W via a gas supply pipe 54.
Now, a detailed configuration of the reactant gas supply unit 13 for supplying a reactant gas for the plasma process into the processing chamber 12 will be explained. The reactant gas supply unit 13 may include a first reactant gas supply unit 61 for supplying the reactant gas in a directly downward direction toward the central region of the processing target substrate W; and a second reactant gas supply unit 62 for supplying the reactant gas toward the processing target substrate W in an inclined direction. To elaborate, the first reactant gas supply unit 61 supplies the reactant gas in a direction indicated by an arrow F₁of FIG. 1, while the second reactant gas supply unit 62 supplies the reactant gas in a direction indicted by an arrow F₂of FIG. 1. Here, the second reactant gas supply unit 62 supplies the reactant gas toward a center of the processing target substrate W, i.e., toward the central region of the processing target substrate W. The same kind of reactant gas is supplied to the first and second reactant gas supply units 61 and 62 from a single reactant gas supply source (not shown).
A configuration of the first reactant gas supply unit 62 will be first elaborated. The first reactant gas supply unit 61 is provided at a center of the dielectric plate 16 in a diametric direction and is located at an upper position of the dielectric plate 16 from a bottom surface 63 of the dielectric plate 16 facing the holding table 14. The dielectric plate 16 is provided with an accommodation part 64 for accommodating the first reactant gas supply unit 61 therein. An O-ring 65 is provided between the first reactant gas supply unit 61 and the accommodation part 64 so as to secure airtightness of the inside of the processing chamber 112.
The first reactant gas supply unit 61 is provided with a multiple number of supply holes 66 through which the reactant gas is discharged in a directly downward direction toward the central region of the processing target substrate W. The supply holes 66 are provided in an area of the wall surface 67 facing the holding table 14 and the area is exposed to the inside of the processing chamber 12. Further, the wall surface 67 is flat. The supply holes 66 are provided in the first reactant gas supply unit 61 to be located at the center of the dielectric plate 16 in the diametric direction.
The plasma processing apparatus 11 is provided with a gas flow path 68 formed through the central conductor 25 of the coaxial waveguide 24, the slot plate 30 and the dielectric plate 16 to reach the supply holes 66. A gas supply system 72 including an opening/closing valve 70 and/or a flow rate controller 71 such as a mass flow controller is connected to a gas inlet 69 formed at an upper end of the central conductor 25. The reactant gas is supplied while its flow rate is controlled by the gas supply system 72.
Now, a configuration of the second reactant gas supply unit 62 will be elaborated. FIG. 2 is a diagram illustrating a circular ring-shaped member 73 included in the second reactant gas supply unit 62 shown in FIG. 1 and its vicinity, when viewed from a direction of an arrow II of FIG. 1. As depicted in FIGS. 1 and 2, the second reactant gas supply unit 62 may include the ring-shaped member 73 and holding members 74 that hold the ring-shaped member 73 from a higher position of the sidewall 18 than the ring-shaped member 73. The ring-shaped member 73 is of a pipe shape and the inside of the ring-shipped member 73 serves as a flow path of the reactant gas. The ring-shaped member 73 is positioned between the holding table 14 and the dielectric plate 16 within the processing chamber 12.
Now, the ring-shaped member 73 will be elaborated. FIG. 3 is an enlarged view of the ring-shaped member 73 indicated by a part III of FIG. 1. As depicted in FIGS. 1 to 3, the ring-shaped member 73 may include a wall 79 a straightly extending in a vertical direction and located at an inner circumference of the ring-shaped member 73; a wall 79 b straightly extending in a vertical direction and located at an outer circumference of ring-shaped member 73; a wall 79 c straightly extending in a left-right direction and located on the side of the holding table 14; and a wall 79 d straightly extending in a slant direction so as to connect a lower end of the wall 79 a with an inner end of the wall 79 c.
The ring-shaped member 73 is provided with a multiple number of supply holes 75 through which the reactant gas is discharged in an inclined direction toward the processing target substrate W. Each supply hole 75 has a circular shape. The supply holes 75 are provided in the wall 79 d extending in the slant direction. To elaborate, each supply hole 75 is formed by opening a part of the wall 79 d in a direction orthogonal to the wall 79 d. An inclination angle of the supply hole 75 may be selected depending on the direction for supplying the reactant gas. Here, the inclination angle of the supply hole 75 is the same as an angle of the inclined direction for supplying the reactant gas by the second reactant gas supply unit 62 and is defined as an angle θ between a straight line (indicated by a dashed dotted line of FIG. 3) extending in a left-right direction through a vertical center 78 of the ring-shaped member 73 and a straight line 79 e (indicated by a dashed triple-dotted line of FIG. 3) extending in the direction orthogonal to the wall 79 d. The supply holes 75 are arranged at a same distance from each other along a circumference of the ring-shaped member 73. In the present embodiment, eight (8) supply holes 75 are provided.
The holding member 74 is of a pipe shape. The reactant gas supplied from the outside of the processing chamber 12 reaches the ring-shaped member 73 through the inside of the holding member 74. The holding member 74 has a substantially L-shaped cross section and is inwardly protruded from an upper portion of the sidewall 18 and vertically extended in a downward direction. An end portion 76 of the holding member 74 extended in the downward direction is connected with the ring-shaped member 73. A gas supply system (not shown) including an opening/closing valve and a flow rate controller as mentioned above may also be installed outside the holding member 74.
In this embodiment, the second reactant gas supply unit 62 is located in a position directly above the holding table 14 but not located directly above the processing target substrate W held on the holding table 14. Specifically, if an inner diameter of the ring-shaped member 73 is denoted by D₁and an outer diameter of the processing target substrate W is denoted by D₂, the inner diameter D₁of the ring-shaped member 73 is set to be larger than the outer diameter D₂of the processing target substrate W. Further, the holding member 74 is also located at a position which is not directly above the processing target substrate W.
Desirably, the second reactant gas supply unit 62 may be located at the vicinity of the holding table 14. Specifically, the ring-shaped member 73 may be provided in a so-called downflow region which is not affected by the reactant gas supplied from the first reactant gas supply unit 61 and in which a plasma density is low. A distance L₁from a top surface 77 of the processing target substrate W held on the holding table 14 to the center 78 of the ring-shaped member 73 indicated by the dashed dotted line of FIG. 1 may be set to a preset value within about 90 mm.
Now, a method for performing a plasma process on a processing target substrate W by the plasma processing apparatus 11 in accordance with the embodiment of the present invention will be explained.
First, the processing target substrate W is held on the electrostatic chuck 41 of the holding table 14 installed in the processing chamber 12. Then, a microwave for exciting plasma is generated by the microwave generator 15, and, then, the microwave is introduced into the processing chamber 12 through the dielectric plate 16 or the like. Then, a reactant gas is supplied in a directly downward direction from a central portion of the dielectric plate 16 toward a central region of the processing target substrate W through the supply holes 66 of the first reactant gas supply unit 61. Further, the reactant gas is also supplied in an inclined direction toward the central region of the processing target substrate W through the supply holes 75 of the ring-shaped member 73 of the second reactant gas supply unit 62. In this way, a plasma process is performed on the processing target substrate W.
In accordance with the plasma processing apparatus 11 and the plasma processing method as described above, the reactant gas can be uniformly supplied to the entire processing target substrate W by the first reactant gas supply unit 61 that supplies the reactant gas in the directly downward direction toward the central region of the processing target substrate W and by the second reactant gas supply unit 62 that supplies the reactant gas in the inclined direction toward the central region of the processing target substrate W. Furthermore, since the reactant gases supplied by the first and second reactant gas supply units 61 and 62 do not stay on the processing target substrate W, stay of deposits on the processing target substrate W can be suppressed. Moreover, the second reactant gas supply unit 62 does not block a flow of plasma toward the processing target substrate W. Accordingly, uniformity of the plasma process within a surface of the processing target substrate W can be improved.
Here, flows of the reactant gases supplied from the first reactant gas supply unit 61 and the second reactant gas supply unit 62 of the plasma processing apparatus 11 having the above-described configuration will be elaborated. FIG. 4 is a schematic diagram illustrating the flows of the reactant gases supplied from the first and second reactant gas supply units 61 and 62. In FIG. 4, each component of the plasma processing apparatus 11 is illustrated in a simplified manner. As can be seen from FIG. 4, the reactant gas from the first reactant gas supply unit 61 is supplied in the directly downward direction toward the central region of the processing target substrate W as indicated by an arrow F₁of FIG. 4 and then tends to flow upward after bouncing one time at a position 80 in the vicinity of the central region of the processing target substrate W marked by a dashed line of FIG. 4. Since, however, the reactant gas from the second reactant gas supply unit 62 is supplied in a direction indicated by an arrow F₂, the reactant gas from the first reactant gas supply unit 61 is suppressed from flowing upward after being bounced. Instead, the reactant gas supplied from the first reactant gas supply unit 61 flows toward an edge region of the processing target substrate W in a direction indicated by an arrow F₃. Due to this mechanism, stay of the reactant gas as illustrated in FIG. 22 may be suppressed.
FIGS. 5 and 6 are graphs showing a relationship between a film thickness and a position on the processing target substrate W when a film is formed on the processing target substrate W by the plasma processing apparatus 11 in accordance with the embodiment of the present invention. In FIGS. 5 and 6, a vertical axis represents a film thickness Å, and a horizontal axis indicates a distance mm from a center O. Further, FIG. 7 illustrates an X axis, a Y axis, a V axis and a W axis shown in FIGS. 5 and 6 on the processing target substrate W. FIGS. 5 and 6 illustrate cases in which an angle θ for supplying the reactant gas from the second reactant gas supply unit 62 is varied. FIG. 5 illustrates a case in which the angle θ for supplying the reactant gas from the second reactant gas supply unit 62 is about 42°, and FIG. 6 illustrates a case in which the angle θ for supplying the reactant gas from the second reactant gas supply unit 62 is about 24°. In the cases of FIGS. 5 and 6, an inner diameter of the ring-shaped member 73 is about 400 mm, and a distance L₁as shown in FIG. 1 is about 90 mm. Further, FIG. 6 illustrates a case of using the plasma processing apparatus 11 configured as shown in FIG. 1 and the angle corresponds to an angle for supplying the reactant gas from the second reactant gas supply unit 62 toward the central region of the processing target substrate W held on the holding table 14. In FIG. 5, a ratio between a gas supply amount from the first reactant gas supply unit 61 and a gas supply amount from the second reactant gas supply unit 62 is about 32:68. Further, in FIG. 6, a ratio between a gas supply amount from the first reactant gas supply unit 61 and a gas supply amount from the second reaction gas supply unit 62 is about 27:73.
As can be seen from FIG. 5, in case that the angle for supplying the reactant gas from the second reactant gas supply unit 62 is about 42°, although film thicknesses on the central region and the edge region of the processing target substrate W are slightly larger than film thicknesses on regions between the central and edge regions and the graph of FIG. 5 is of a substantially W shape, the film thicknesses are almost stabilized and uniform. That is, uniformity of the plasma process in the surface of the processing target substrate W is improved. Further, as can be seen from FIG. 6, in case that the angle θ for supplying the reactant gas from the second reactant gas supply unit 62 is about 24°, film thicknesses on the entire processing target substrate W are substantially uniformed. That is, uniformity of the plasma process in the surface of the processing target substrate W is further improved.
In the plasma processing apparatus 11 having the above-described configuration, the uniformity of the plasma process in the surface of the processing target substrate W can be improved by supplying the reactant gas from the second reactant gas supply unit 62 in the inclined direction. Meanwhile, in the conventional plasma processing apparatus as depicted in FIG. 22, uniformity of a plasma process in the surface of the processing target substrate W cannot be improved by, for example, adjusting a ratio of gas supply amounts. That is, in the conventional plasma processing apparatus as configured in FIG. 22, a processing degree in the surface of the processing target substrate W hardly changes even if the ratio of the gas supply amounts is adjusted.
Moreover, in the plasma processing apparatus in accordance with the embodiment of the present invention, since respective components of the second reactant gas supply unit 62 are provided at positions other than directly above the processing target substrate W, fatigue of each component of the second reactant gas supply unit 62 due to plasma can be reduced. Thus, lifetime of the second reactant gas supply unit 62 can be increased.
In addition, although the embodiment has been described for the case that the second reactant gas supply unit includes the ring-shaped member and the holding members for holding the ring-shaped member from a higher position of the sidewall than the ring-shaped member, the present invention may not be limited thereto. By way of example, the second reactant gas supply unit may include the ring-shaped member and supporting members straightly extended from the sidewall of the processing chamber inwardly in a diametric direction.
FIG. 8 is a schematic cross sectional view illustrating major components of a plasma processing apparatus having such supporting members and FIG. 8 corresponds to FIG. 1. In FIG. 8, the same parts as those described in FIG. 1 will be assigned same reference numerals and redundant description thereof will be omitted. As illustrated in FIG. 8, a second reactant gas supply unit 92 included in a plasma processing apparatus 91 and configured to supply a reactant gas in an inclined direction toward a processing target substrate W may include a ring-shaped member 93 that is supported by supporting members 94 straightly extended from a sidewall 18 of the processing chamber 12 inwardly in a diametric direction. The supporting member 94 has a hollow shape. The reactant gas supplied from the outside of the plasma processing apparatus 91 is introduced into a processing chamber 12 through supply holes 95 of the ring-shaped member 93 via the inside of the supporting member 94. With this configuration, the same effect as mentioned above can also be achieved.
Moreover, although this embodiment has been described for the case that the second reactant gas supply unit includes the ring-shaped member and the holding members for holding the ring-shaped member from a higher position of the sidewall than the ring-shaped member, the present invention may not be limited thereto. By way of example, the second reactant gas supply unit for supplying the reactant gas in the inclined direction toward the processing target substrate W may be embedded in a sidewall of the processing chamber.
Furthermore, in the plasma processing apparatus, the sidewall of the processing chamber may include an inwardly projecting protrusion, and the second reactant gas supply unit may be embedded in the protrusion.
FIG. 9 is a schematic cross sectional view illustrating major components of a plasma processing apparatus having such a protrusion and FIG. 9 corresponds to FIG. 1. In FIG. 9, the same parts as those described in FIG. 1 will be assigned same reference numerals and redundant description thereof will be omitted. As illustrated in FIG. 9, a sidewall 82 of a plasma processing apparatus 81 may include a protrusion 83 that is projected inward, particularly, that is projected inward in a diametric direction. The protrusion 83 is of a circular ring shape. A ring-shaped member 84 of a second reactant gas supply unit for supplying a reactant gas in an inclined direction toward a processing target substrate W is embedded in the protrusion 83. A multiple number of supply holes 85 provided in the ring-shaped member 84 is exposed and opened in a wall surface 86 of the protrusion 83 extended in an inclined direction. In this embodiment, the protrusion 83 is located at a position directly above the holding table 14 but not directly above the processing target substrate W. To elaborate, an inner diameter of the protrusion 83, i.e., a distance D₃between two opposite points on a wall surface 88 of the protrusion 83 in a diametric direction is larger than an outer diameter D₂of the processing target substrate W. Further, a gas flow path 89 is formed within the sidewall 82 so as to be connected to the ring-shaped member 84 from the outside of a processing chamber 87. With this configuration, the same effect as described above can also be achieved.
In such a case, the processing chamber 87 may have a bottle neck structure as an overall shape in which an inner diameter of the sidewall 82 above the ring-shaped member 84 is smaller than an inner diameter of the sidewall 82 below the ring-shaped member 84.
Furthermore, in the above-described embodiment, each supply hole of the ring-shaped member has a circular shape. However, the present invention may not be limited thereto, and the supply hole may have an elongated shape extending in a circumferential direction or in a diametric direction. Moreover, in the above-described embodiment, although the number of the supply holes is 8, the present invention may not be limited thereto.
Besides, in the above-described embodiment, the ring-shaped member includes a multiple number of walls respectively extending in the vertical direction, the left-right direction and the slant direction. However, the present invention may not be limited thereto, and the ring-shaped member may have, but not limited to, a curved wall portion. Further, in the cross sectional view of FIG. 3, the ring-shaped member may have a circular ring-shaped wall portion.
Furthermore, in the above-described embodiment, the second reactant gas supply unit includes the ring-shaped member. However, the present invention may not be limited thereto, and the second reactant gas supply unit may not include the ring-shaped member. By way of example, supply holes may be provided in lower ends of a multiplicity of holding members, and the reactant gas may be supplied in an inclined direction toward the processing target substrate W through these supply holes.
Moreover, in the above-described embodiment, the second reactant gas supply unit supplies the reactant gas in the inclined direction toward the central region of the processing target substrate W held on the holding table. However, the present invention may not be limited thereto, and the second reactant gas supply unit may be configured to supply the reactant gas in a horizontal direction toward the center of the processing target substrate W held on the holding table. To be more specific, referring to FIG. 3, an angle θ for supplying the reactant gas from the second reactant gas supply unit may be set to be θ=0. By setting the angle θ in this way, the same effect as described above can also be achieved. That is, the reactant gas can be uniformly supplied to the entire processing target substrate W. Further, the reactant gases supplied from the first and second reactant gas supply units may not stay on the processing target substrate W, so that stay of deposits can be suppressed.
Such a case will be elaborated with reference to the accompanying drawings. FIG. 10 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in such a case and FIG. 10 corresponds to FIG. 1. In FIG. 10, the same parts as those illustrated in FIG. 1 will be assigned same reference numerals and redundant description thereof will be omitted. FIG. 11 is a diagram showing a part of a second reactant gas supply unit of the plasma processing apparatus of FIG. 10, when viewed from a direction of an arrow XI of FIG. 10. FIG. 12 is an enlarged view of a part marked by XII of FIG. 10. A cross section depicted in FIG. 10 corresponds to a diagram taken along a line X-X of FIG. 11.
Referring to FIGS. 10 to 12, a plasma processing apparatus 201 in accordance with still another embodiment of the present invention may include a second reactant gas supply unit 202 configured to supply a reactant gas in a horizontal direction toward a center of a processing target substrate W held on a holding table 14. The second reactant gas supply unit 202 may include a circular ring-shaped member 208 and three protrusions 211 a, 211 b and 211 c that are projected outward from an outer surface of the circular ring-shaped member 208 in a diametric direction. The three protrusions 211 a to 211 c are arranged at a regular distance in a circumferential direction of the ring-shaped member 208. To be specific, the three protrusions 211 a to 211 c are formed at an interval of about 120°.
The second reactant gas supply unit 202 may be formed by joining a flat ring-shaped first member 209 a provided with protrusions corresponding to the protrusions 211 a to 211 c and a ring-shaped second member 209 b having a substantially one-side-opened rectangular cross section and provided with protrusions corresponding to the protrusions 211 a to 211 c. As shown in FIG. 12, the second reactant gas supply unit 202 has a substantially rectangular cross section. That is, a gas flow path 210 formed by joining the first member 209 a and the second member 209 b is a space having a substantially rectangular cross section. Further, the first and second members may be made of, but not limited to, quartz.
The second reactant gas supply unit 202 is provided with thirty six (36) supply holes 215 through which the reactant gas is supplied into a processing chamber 12. The supply holes 215 are formed so as to supply the reactant gas in a straightly diametric direction toward an inside of the ring-shaped member 208. To elaborate, each supply hole 215 is formed through an inner wall of the second member 209 b of the second reactant gas supply unit 202. The supply holes 215 are formed at substantially midway positions of the ring-shaped member 208 in a vertical direction. Each supply hole 215 has a circular shape having a size of, e.g., about φ0.5 mm. The supply holes 215 are opened by, e.g., laser. The thirty six (36) supply holes 215 are arranged at a regular distance on an inner surface 216 of the second reactant gas supply unit 202 in a circumferential direction thereof.
The second reactant gas supply unit 202 is installed in the processing chamber 12 by being supported by three supports 212 a, 212 b and 212 c provided at a sidewall 18 of the processing chamber 12. To elaborate, inner surfaces 214 a, 214 b and 214 c of the three supports 212 a, 212 b and 212 c inwardly extended from the sidewall 18 in a diametric direction at an interval of about 120° are joined to outer surfaces 213 a, 213 b and 213 c of the three protrusions 211 a, 211 b and 211 c of the second reactant gas supply unit 202, respectively. With regard to an installation position of the ring-shaped member 208 in a vertical direction, the ring-shaped member 208 is installed in a so-called downflow region.
Here, the support 212 a has a hollow shape, and the gas can be supplied into the gas flow path 210 of the second reactant gas supply unit 202 through the support 212 a from the outside of the processing chamber 12. Meanwhile, the other two supports 212 b and 212 c have solid shapes without allowing an inflow/outflow of the gas. That is, in the second reactant gas supply unit 202, the gas is introduced into the gas flow path 210 from the outside of the processing chamber 12 through the support 212 a and the protrusion 211 a and then is discharged into the processing chamber 12 toward a center of the processing target substrate W through the 36 supply holes 215.
Further, the plasma processing apparatus 201 illustrated in FIG. 10 may include a temperature control unit 203 embedded in the holding table 14 and configured to control a temperature of the processing target substrate W held on the holding table 14. The temperature control unit 203 may include a first temperature controller 204 for controlling a temperature of a central region of the processing target substrate W held on the holding table 14; and a second temperature controller 205 for controlling a temperature of an edge region of the processing target substrate W held on the holding table 14. Specifically, the first and second temperature controllers 204 and 205 are, for example, heaters of which temperatures are independently adjusted. The first temperature controller 204 may be provided in a center of the holding table 14 in a diametric direction. The second temperature controller 205 is of a ring-shape and is positioned outside the first temperature controller 204 while a gap is provided between the first and second temperature controllers in a diametric direction. The temperatures of the central region and the edge region of the processing target substrate W can be set to different temperatures by the first and second temperature controllers 204 and 205. In this way, by controlling the temperatures of the central and edge regions of the processing target substrate W independently by the first and second temperature controllers 204 and 205, uniformity of a plasma process within a surface of the processing target substrate W can be further improved. Besides, the first and second temperature controllers 204 and 205 are separately controlled, and they may be configured to control the temperatures by flowing a coolant, as in the plasma processing apparatus 11 depicted in FIG. 1.
Moreover, in the plasma processing apparatus 201 illustrated in FIG. 10, temperature controllers 206 and 207 may be provided within the cylindrical sidewall 18 of the processing chamber 12 and within a cover 217 provided on top of the sidewall 18, respectively. Temperatures of the sidewall 18 and the cover 217 can be adjusted by the temperature controllers 206 and 207. Accordingly, an internal temperature of the processing chamber 12 can be stabilized and more uniform plasma process is enabled. The temperature controllers 206 and 207 may be heaters or configured to flow a coolant.
In accordance with the plasma processing apparatus 201 having the above-described configuration, the same effects as described above can also be achieved. That is, uniformity of the plasma process within the surface of the processing target substrate W can be obtained.
In accordance with sill another embodiment, since the ring-shaped member 208 of the second reactant gas supply unit 202 is configured as a separate member from the sidewall 18 or the cover 17 and is supported within the processing chamber 12 by the three supports 212 a to 212 c, the ring-shaped member 208 is kept away from the temperature controllers 206 and 207 and, thus, a temperature of the ring-shaped member 208 can be maintained stable. Accordingly, the ring-shaped member 208 may not be affected by the temperature control by the temperature controllers 206 and 207, and, thus, a gas supply amount through the supply holes 215 of the second reactant gas supply unit 202 can be stabilized.
FIG. 13 is a graph showing etching rate normalized values when 40 lots are processed by the plasma processing apparatus shown in FIG. 10 and in the conventional plasma processing apparatus shown in FIG. 21. A horizontal axis represents a lot number, and a vertical axis represents an etching rate normalized value. Here, a first substrate of every lot is measured. An etching rate normalized value is an index that indicates a degree of variation of each etching rate from an average etching rate of all etching samples when the average etching rate is defined as 1. In FIG. 13, circles and a solid line represent the case of the plasma processing apparatus of FIG. 10, and squares and a dashed line represent the case of the conventional plasma processing apparatus of FIG. 21.
Referring to FIG. 13, in case of the plasma processing apparatus shown in FIG. 10, the etching rate normalized value varies within a range equal to about 1.00 and less than about 1.01 between the lots. In contrast, in case of the conventional plasma processing apparatus shown in FIG. 21, the etching rate normalized value fluctuates within a range from about 0.98 to about 1.02. That is, as compared to the case of the plasma processing apparatus of FIG. 10 in which non-uniformity of the etching rate normalized value is less than about 0.01, non-uniformity of the etching rate normalized value in case of the plasma processing apparatus of FIG. 21 is larger than about 0.04. Thus, the graph shows that the non-uniformity of etching rate normalized values between the lots is greatly reduced in the plasma processing apparatus of FIG. 10.
FIG. 14 is a graph showing a relationship between the number of particles and a lot number of processing target substrates processed by the plasma processing apparatus shown in FIG. 10. A horizontal axis represents a lot number, and a vertical axis represents the number of particles. The lot numbers in FIG. 14 are equal to the lot numbers in FIG. 13. Here, particles having a diameter of about 130 nm are counted by a particle monitor (SP1) (product of KLA-Tencor Corporation).
As can be seen from FIG. 14, a maximum value of the number of particles in the plasma processing apparatus of FIG. 10 is 5, and the number of particles is mostly less than 5 at each lot and sometimes even zero. That is, the number of particles is greatly reduced. In the plasma processing apparatus shown in FIG. 21, since the dielectric plate is located in the vicinity of supply holes, the supply holes may be exposed to strong plasma and particles may be generated from an inner wall surface in which the supply holes are provided. In contrast, in the plasma processing apparatus shown in FIG. 10, since the ring-shaped member is provided in the downflow region, the supply holes are not exposed to strong plasma and particles may not be generated much.
FIG. 15 is a graph showing a relationship between a center/edge flow rate ratio and a non-uniformity of a plasma process on a processing target substrate processed by the plasma processing apparatus of FIG. 10. A horizontal axis represents a center/edge flow rate ratio (%), and a vertical axis represents a process non-uniformity (%). Here, a center/edge flow rate ratio refers to a ratio of a gas supply amount to an edge of the processing target substrate with respect to a gas supply amount to a center of the processing target substrate, i.e., a ratio of a gas supply amount from the second reactant gas supply unit with respect to a gas supply amount from the first reactant gas supply unit. To elaborate, a flow rate ratio 0% means that a gas is supplied only from the first reactant gas supply unit, and a flow rate ratio 70% means that the gas supply amount from the first reactant gas supply unit is 70% of a total gas supply amount and the gas supply amount from the second reactant gas supply unit is about 30% of the total gas supply amount. Furthermore, a process non-uniformity refers to a value obtained by dividing a difference between a maximum etching amount and a minimum etching amount in a surface of the processing target substrate by a multipoint average value. As will be described below, in case of a center-fast distribution, the process non-uniformity becomes a plus value, whereas, in case of an edge-fast distribution, the process non-uniformity becomes a minus value.
FIG. 16 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed by the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio of about 0%, as indicated by an. arrow G₁of FIG. 15. FIG. 17 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed by the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio of about 70%, as indicated by an arrow G₂of FIG. 15. FIG. 18 is a graph showing a relationship between a film thickness and a position on the processing target substrate W when the processing target substrate W is processed by the plasma processing apparatus of FIG. 10 at a center/edge flow rate ratio of about 20%, as indicated by an arrow G₃of FIG. 15. Vertical axes and horizontal axes on the graphs depicted in FIGS. 16 to 18 are the same as those depicted on the graphs of FIGS. 4 and 5, and redundant description thereof will be omitted.
Referring to FIG. 15, when the center/edge flow rate ratio is about 0%, a process non-uniformity is about (−) 33% and a so-called center-fast distribution is shown. That is, as depicted in FIG. 16, a center of the processing target substrate W is greatly etched and a film thickness at the center is thin, whereas an etching amount at an edge of the processing target substrate W is reduced and a film thickness at the edge is thick. As the center/edge flow rate ratio increases, the process non-uniformity approaches 0%, and if the center/edge flow rate ratio finally reaches about 70%, a so-called edge-fast distribution is shown. That is, as illustrated in FIG. 17, the process non-uniformity becomes about (+) 15%, and the edge of the processing target substrate W may be more etched than the center thereof.
This result shows that the process non-uniformity can be changed from the edge-fast distribution to the center-fast distribution. On these graphs, it may be easy to adjust the process non-uniformity to about 0% by varying the center/edge flow rate ratio, i.e., by varying the gas supply amounts from the first and second reactant gas supply units. On the graph shown in FIG. 15, a process non-uniformity distribution as depicted in FIG. 18 may be obtained by setting the center/edge flow rate ratio to about 20%. In contrast, in the plasma processing apparatus shown in FIG. 21, a graph may be shown on a position distanced away from 0%, and maintained substantially parallel to a horizontal axis, and it becomes very difficult to achieve a process non-uniformity of 0% even if the center/edge flow rate ratio is adjusted.
Further, in this embodiment, although each supply hole is described to have a circular shape, the present invention may not be limited thereto, and the supply hole may have, by way of example, an elongated shape, an oval shape or a polygonal shape. Furthermore, a vertical position for forming the supply holes may not be limited to the midway position, but the supply holes may be formed at an upper portion or a lower portion of the ring-shaped member 208 in a vertical direction. Moreover, an opening size of each supply hole may be varied as required, and the number of the supply holes is not limited to the mentioned example. By way of example, 8 or 16 supply holes may be provided. In addition, the cross section of the ring-shaped member may have a circular or polygonal cross section.
Moreover, although this embodiment has been described for the case that the second reactant gas supply unit includes the first and second members and supported by the three supports, the present invention may not be limited thereto, and the second reactant gas supply unit for discharging the gas in the horizontal direction may be embedded in a sidewall of the processing chamber, as in the plasma processing apparatus shown in FIG. 9.
FIG. 19 is a schematic cross sectional view illustrating major components of a plasma processing apparatus in such a case and FIG. 19 corresponds to FIG. 1. In FIG. 19, the same parts as those described in FIG. 1 will be assigned same reference numerals, and redundant description thereof will be omitted.
Referring to FIG. 19, a plasma processing apparatus 221 may include a second reactant gas supply unit 222 configured to supply a reactant gas in a horizontal direction toward a center of a processing target substrate W held on a holding table 14. A temperature control unit 223 provided within the holding table 14 may include a first temperature controller 224 located at a center of the holding table 14 in a diametric direction and a circular ring-shaped second temperature controller 225 positioned outside the first temperature controller 224.
A part of a sidewall 82 of a processing chamber 12 of the plasma processing apparatus 221 is projected inward in a diametric direction. This protrusion 229 is of a circular ring shape. Further, gas supply holes 231 are opened through an inner surface 228 of the protrusion 229 in a horizontal direction. Further, a gas flow path 230 extended from the outside of the processing chamber 12 to the supply holes 231 is provided within the sidewall 82. Each supply hole 231 is opened in a circular shape and the supply holes 231 are arranged at a regular distance in a circumferential direction. In addition, as in the plasma processing apparatus shown in FIG. 10, temperature controllers 226 and 227 may be provided within a lower part and an upper part of the sidewall 82 with the gas flow path 230 located therebetween. With this configuration, the same effects as described above can also be achieved.
Moreover, in the above-described embodiments, although the second reactant gas supply unit of the plasma processing apparatus is located at a position directly above the holding table but not directly above the processing target substrate W, the present invention may not be limited thereto, and the plasma processing apparatus may be configured as follows.
That is, the plasma processing apparatus may include a holding table configured to hold the processing target substrate thereon; a processing chamber configured to perform therein a plasma process on the processing target substrate, and having a bottom positioned under the holding table and a ring-shaped sidewall upwardly extending from a periphery of the bottom; a plasma generator configured to generate plasma within the processing chamber; and a reactant gas supply unit configured to supply a reactant gas for the plasma process into the processing chamber. Further, the reactant gas supply unit may include a first reactant gas supply unit configured to supply the reactant gas in a directly downward direction toward a central region of the processing target substrate held on the holding table; and a second reactant gas supply unit having a ring-shaped member provided at an upper position of the holding table and at a position deviated from a direct region of the processing target substrate held on the holding table and at an inside position of the sidewall, and configured to supply the reactant gas toward a center side of the processing target substrate held on the holding table. FIG. 20 illustrates a. plasma processing apparatus 241 having a configuration same as the configuration of the plasma processing apparatus of FIG. 10 excepting that a ring-shaped member of a second reactant gas supply unit 242 is provided at a position deviated from a vertically upper region of a processing target substrate W held on a holding table 14, i.e., at an outside position from a vertically upper region of the holding table 14 and an inside position from a sidewall 18. To elaborate, the ring-shaped member is provided at a position outside from an edge of the holding table 14. That is, the ring-shaped member may be provided at an outside position from a vertically upper region of the holding table 14. With this configuration, the same effects as described above can also be achieved.
Further, in the plasma processing apparatuses shown in FIGS. 10, 19 and 20, the first and second temperature controllers are provided within the holding table. However, the present invention may not be limited thereto, and the first and second temperature controllers may be provided at an outside of the holding table. Moreover, the first and second temperature controllers may be divided in a diametric direction, in a circumferential direction or in a vertical direction. That is, each of the first and second temperature controllers may be composed of a multiple number of members. In addition, the first and second temperature controllers may be formed as a single body. By way of example, a single-body type heater capable of controlling temperatures of a center and an edge independently may be used. Furthermore, the first and second temperature controllers may not be provided, and the temperature controllers provided in the sidewall and the like may also be omitted. Further, it may be also possible to provide temperature controllers in the plasma processing apparatus shown in FIG. 1 or FIG. 9 if necessary.
In the above-described embodiments, although a wall surface of the first reactant gas supply unit facing the holding table is flat, the present invention may not be limited thereto, and a part of the first reactant gas supply unit in which the supply holes are provided may be protruded toward the holding table.
Further, in the above-described embodiments, although the same kind of reactant gas is supplied from the first and second reactant gas supply units, the kinds of gases from the first and second reactant gas supply unit may be different.
Moreover, the second reactant gas supply unit may be configured to supply the gas in a directly downward direction in consideration of an apparatus configuration, particularly, in consideration of dimensions of various components of the apparatus such as a size of the processing chamber, a position of the holding table, a size of the processing target substrate and so forth.
Furthermore, in the above-described embodiments, the plasma processing apparatus is of a type that uses a microwave as a plasma source, the present invention may not be limited thereto. By way of example, the present invention may also be applicable to a plasma processing apparatus using ICP (Inductively-Coupled Plasma), ECR (Electron Cyclotron Resonance) plasma, parallel plate type plasma or the like as a plasma source.
While various aspects and embodiments have been described herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for the purposes of illustration and are not intended to be limiting. Therefore, the true scope and spirit of the invention is indicated by the appended claims rather than by the foregoing description, and it shall be understood that all modifications and embodiments conceived from the meaning and scope of the claims and their equivalents are included in the scope of the invention.

INDUSTRIAL APPLICABILITY

A plasma processing apparatus and a plasma processing method in accordance with the present invention may be effectively used to improve uniformity of a plasma process within a surface of a processing target substrate.
[Explanation of Codes]
11, 81, 91, 201, 221, 241: Plasma processing apparatus
12, 87: Processing chamber
13: Reactant gas supply unit
14: Holding table
15: Microwave generator
16: Dielectric plate
17: Bottom
18, 22: Sidewall
19: Gas exhaust hole
20, 65: O-ring
21: Matching unit
22: Mode converter
23: Waveguide
24: Coaxial waveguide
25: Central conductor
26: External conductor
27: Recess
28: Wavelength shortening plate
29: Slot hole
30: Slot plate
31,32: Cylindrical support
33: Gas exhaust passageway
34: Baffle plate
35: Gas exhaust pipe
36: Gas exhaust unit
37: High frequency power supply
38: Matching unit
39: Power supply rod
41: Electrostatic chuck
42: Focus ring
43: Electrode
44, 45: Insulating film
46: DC power supply
47: Switch
48: Coated line
51: Coolant path
52, 53: Pipe
54: Gas supply pipe
61: First reactant gas supply unit
62, 92, 202, 222, 242: Second reactant gas supply unit
63: Bottom surface
64: Accommodation part
66, 75, 85, 95, 215, 231: Supply hole
67, 86, 88: Wall surface
68, 89, 210, 230: Gas flow path
69: Gas inlet
70: Opening/closing valve
71: Flow rate controller
72: Gas supply system
73, 84, 93, 208: Ring-shaped member
74: Holding member
76: End portion
77: Top surface
78: Center
79 a, 79 b, 79 c, 79 d: Wall
79 e: Straight line
80: Position
83, 229: Protrusion
94, 212 a, 212 b, 212 c: Supporting member
203, 204, 205, 206, 207, 223, 224, 225, 226, 227:
Temperature control unit
209 a: First member
209 b: Second member
211 a, 211 b, 211 c: Protrusion
213 a, 213 b, 213 c: Outer surface
214 a, 214 b, 214 c, 216, 228: Inner surface
217: Cover

Claims

1. A plasma processing apparatus comprising:

a processing chamber configured to perform therein a plasma process on a processing target substrate;

a holding table provided within the processing chamber and configured to hold the processing target substrate thereon;

a plasma generating unit configured to generate plasma within the processing chamber; and

a reactant gas supply unit configured to supply a reactant gas for the plasma process into the processing chamber,

wherein the reactant gas supply unit comprises:

a first reactant gas supply unit configured to supply the reactant gas in a directly downward direction toward a central region of the processing target substrate held on the holding table; and

a second reactant gas supply unit provided at a position directly above the holding table but not directly above the processing target substrate held on the holding table, and configured to supply the reactant gas toward a center of the processing target substrate held on the holding table.

2. The plasma processing apparatus of claim 1, wherein the second reactant gas supply unit is provided in the vicinity of the holding table.

3. The plasma processing apparatus of claim 1, wherein the second reactant gas supply unit is configured to supply the reactant gas in an inclined direction toward a central region of the processing target substrate held on the holding table.

4. The plasma processing apparatus of claim 1, wherein the second reactant gas supply unit is configured to supply the reactant gas in a horizontal direction toward the center of the processing target substrate held on the holding table.

5. The plasma processing apparatus of claim 1, wherein the second reactant gas supply unit comprises a ring-shaped member, and

the ring-shaped member is provided with a supply hole through which the reactant gas is supplied.

6. The plasma processing apparatus of claim 5, wherein the processing target substrate is of a circular plate shape,

the ring-shaped member is of a circular ring shape, and

an inner diameter of the ring-shaped member is larger than an outer diameter of the processing target substrate.

7. The plasma processing apparatus of claim 1, wherein the processing chamber comprises a bottom positioned under the holding table and a sidewall upwardly extending from a periphery of the bottom, and

the second reactant gas supply unit is embedded within the sidewall.

8. The plasma processing apparatus of claim 7, wherein the sidewall comprises an inwardly projecting protrusion, and

the second reactant gas supply unit is embedded within the protrusion.

9. The plasma processing apparatus of claim 1, wherein the plasma generating unit comprises a microwave generator capable of generating a microwave for exciting plasma and a dielectric plate positioned to face the holding table and configured to introduce the microwave into the processing chamber, and

the first reactant gas supply unit is provided at a central portion of the dielectric plate.

10. The plasma processing apparatus of claim 1, further comprising:

a first temperature controller configured to control a temperature of the central region of the processing target substrate held on the holding table; and

a second temperature controller configured to control a temperature of an edge region of the processing target substrate held on the holding table.

11. The plasma processing apparatus of claim 10, wherein the first and second temperature controllers are provided within the holding table.

12. The plasma processing apparatus of claim 10, wherein at least one of the first and second temperature controllers is divided into a plurality of members.

13. The plasma processing apparatus of claim 1, wherein the processing chamber comprises a bottom positioned under the holding table and a sidewall upwardly extending from a periphery of the bottom, and

the apparatus further comprises a sidewall temperature controller configured to control a temperature of the sidewall.

14. The plasma processing apparatus of claim 12 13, wherein the sidewall temperature controller is provided within the sidewall.

15. A plasma processing method for performing a plasma process on a processing target substrate, the method comprising:

holding the processing target substrate on a holding table provided within the processing chamber;

generating a microwave for exciting plasma;

introducing the microwave into the processing chamber through a dielectric plate; and

supplying a reactant gas in a directly downward direction from a central portion of the dielectric plate toward a central region of the processing target substrate, and supplying the reactant gas in an inclined direction toward the processing target substrate from a position directly above the holding table but not directly above the processing target substrate held on the holding table.

16. A plasma processing apparatus comprising:

a holding table configured to hold a processing target substrate thereon;

a processing chamber configured to perform therein a plasma process on the processing target substrate, and having a bottom positioned under the holding table and a ring-shaped sidewall upwardly extending from a periphery of the bottom;

wherein the reactant gas supply unit comprises:

a second reactant gas supply unit having a ring-shaped member provided at an upper position of the holding table and at a position deviated from a vertically upper region of the processing target substrate held on the holding table and at an inside position of the sidewall, and configured to supply the reactant gas toward a center of the processing target substrate held on the holding table.

17. The plasma processing apparatus of claim 16, wherein the ring-shaped member is provided at an outside position of the holding table.

18. The plasma processing apparatus of claim 16, further comprising:

19. The plasma processing apparatus of claim 18, wherein the first and second temperature controllers are provided within the holding table.

20. The plasma processing apparatus of claim 18, wherein at least one of the first and second temperature controllers is divided into a plurality of members.