JP3761474B2 - Plasma processing equipment - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus that processes an object to be processed using plasma.
[0002]
[Prior art]
When processing an object to be processed, particularly an insulating film, using plasma, for example, a parallel plate type plasma processing apparatus that applies two different RFs to opposing electrodes (conventional technique 1, for example, Japanese Patent Laid-Open No. 8-339984). Is used. In such an apparatus, the upper electrode and the lower electrode are disposed so as to face each other vertically in the processing chamber, and high frequency power is supplied to at least one of the electrodes to ionize and dissociate the processing gas introduced into the processing chamber. The wafer is processed using the ions and radicals generated in this way. The upper electrode is provided with a cooling plate made of aluminum and a refrigerant circulation path, and there is a diffusion member for introducing gas into the processing chamber, and a baffle plate for distributing the gas is provided therein. A plasma processing apparatus having a permanent magnet on the back surface of the RF electrode and arranging the permanent magnet in a ring shape is disclosed in Japanese Patent Application Laid-Open No. 8-28896 (Prior Art 2). Further, a plasma processing apparatus in which a planar antenna member is provided so as to face an electrode on which an object is placed, a μ wave is supplied to the antenna member, and a slit opening is provided on the front surface of the planar antenna member is disclosed in JP-A-9 -63793 (prior art 3). Japanese Patent Application Laid-Open No. 10-134995 describes a parallel plate type UHF-plasma device in which high frequency waves in the UHF band are supplied to a disk-shaped antenna by a coaxial cable, and the antenna diameter is set to a predetermined value n / 2 · λ ( A plasma processing apparatus set to n: integer) is disclosed (prior art 4).
[0003]
[Problems to be solved by the invention]
In the prior art 1, as the operating frequency is increased, the high frequency penetrates between the upper electrode and the metallic cooling plate or between the discharge port (gas blowing port). Since the penetration thickness is very thin (1 mm or less), a high electric field is generated in the meantime, and so-called abnormal discharge is likely to occur. Once an abnormal discharge occurs, the diameter of the blowout hole expands, and plasma is generated inside this time, causing the generation of foreign matter, or the upper electrode is scraped and the desired performance cannot be maintained. For this reason, since it is difficult to increase the density by high frequency, there is a problem that the processing speed (etching rate) cannot be increased.
[0004]
In Prior Art 2, a magnetic field is locally formed at a location limited to the size of the permanent magnet. If an attempt is made to increase the confinement effect by the magnetic field, the magnetic field strength in the vicinity of the magnet increases, and the plasma density increases in this portion. Further, since a bias is applied to the RF electrode and ions are attracted, sputtering occurs locally. For this reason, there is a problem that local consumption of the electrode is caused, foreign matter is increased, and device reliability is lowered.
[0005]
In prior art 3, the distribution is adjusted by providing a slit in the antenna section and adjusting the length of the slit to about (1/2 to 1/10) λ (λ: μ wave guide wavelength). As will be described later, what is important is that unless the slit position and the dimensions at the back of the antenna are specified, it is difficult to adjust the emission of the microwave and the electric field distribution therefrom.
[0006]
In Prior Art 4, since the center of the antenna corresponds to the antinode of the electric field and the end of the antenna corresponds to the node of the electric field, the electric field distribution immediately below the antenna is necessarily convex. Therefore, there is a problem that it is difficult to make the plasma uniform.
[0007]
SUMMARY OF THE INVENTION An object of the present invention is to provide a plasma processing apparatus that realizes high-density, high-uniform and stable plasma without abnormal discharge in a wide parameter region in a system for generating plasma using a high-frequency and magnetic field in the VHF band or UHF band. Is to provide.
[0008]
[Means for Solving the Problems]
According to one aspect of the present invention, the present invention provides a vacuum vessel, a processing chamber inside the vacuum vessel to which a gas is supplied, a support electrode provided in the processing chamber and supporting a processing object, A high frequency introduction means comprising a disk-shaped antenna for supplying a high frequency in the UHF or VHF band to the processing chamber, a radiation port composed of an insulator disposed beside the antenna, and a magnetic field forming means for forming a magnetic field in the processing chamber. And a shower plate electrode for introducing gas into the processing chamber, and in the antenna portion composed of the shower plate electrode and the disk-shaped antenna, a space made of a dielectric and a metal surrounding the antenna conductor portion ( (Referred to as an electric field control space). In this case, it is preferable that the dielectric constant of the dielectric used in the electric field control space is smaller than the dielectric constant of the member constituting the shower plate electrode.
[0009]
The antenna unit may be provided with a plurality of electric field control spaces made of a dielectric and a metal surrounding the dielectric. In this case, considering the symmetry in the circumferential direction, the electric field control space is preferably formed on concentric circles.
[0010]
A second ring-shaped metal that is in electrical contact with the antenna conductor portion is disposed between the antenna conductor and the shower plate in the electric field control space, and the electric field distribution is controlled by the diameter of the ring.
[0011]
Furthermore, a metal rod that is in electrical contact with the antenna conductor and a third disk-shaped conductor that is in electrical contact with the metal rod may be disposed at the center of the antenna. As a shower plate for supplying gas, a plate-like member made of Si, SiC, or C may be arranged, and a plasma apparatus for supplying a high frequency in the UHF or VHF band to the processing chamber via the plate-like member may be used.
[0012]
The state of the electric field distribution when a high frequency in the UHF band (f = 450 MHz) is introduced into the processing chamber will be described with reference to FIG. The high frequency supplied by the coaxial cable propagates in the coaxial mode between the antenna conductor and the outer conductor, and is supplied to the processing chamber through the dielectric next to the antenna. At the same time, it is supplied to the processing chamber through the shower plate electrode under the antenna conductor. Since the plasma density is usually higher than the cut-off density n = 2.5 × 10 ¹⁵ m ⁻³ for UHF: f = 450 MHz, it cannot propagate in the UHF wave plasma and propagates through the sheath formed between the electrode and the plasma. To do. Since the sheath is about 1 to several mm, the inside of the sheath has a high electric field. The shower plate electrode may be composed of Si, SiC, etc. In this case, UHF also penetrates into Si and SiC, so that this portion is also exposed to a high electric field. On the other hand, as in the prior art 1, it is also a gas outlet. For this reason, since the gas is exposed to a high electric field, plasma is generated there, and further accelerated by the electrode potential, so that ions enter the inside. As a result, abnormal discharge occurs inside, and it is considered that foreign matter is generated or damaged from the shower plate.
[0013]
Here, if an electric field control space surrounded by the dielectric and metal is provided on the shower plate, UHF propagates there. FIG. 8 shows the electric field distribution in the sheath when a disk-shaped dielectric having a radius r = 50 mm is embedded in the antenna conductor as the electric field control space. In addition to the effect of reducing the electric field due to the inclusion of the dielectric, the distance between the antenna conductor and the plasma is effectively increased, so the electric field strength is reduced. In addition, when the electric field control space is not provided, the electric field in the sheath has a convex shape in the form of a Bessel function to J ₀ (r). Can be changed locally. As a result, a uniform electric field is realized. Also, as shown in the figure, the UHF electric field clearly shows antinodes and nodes, but the electric field distribution can be relaxed by providing a plurality of electric field control spaces at the antinodes of the electric field in the radial direction. , Improve the radial uniformity. In addition, when the antenna is provided with a second metal ring positioned between the conductor and the shower plate, the waves appearing in the sheath propagate through the electric field control space as schematically shown in FIG. Thus, the wave reflected by the metal enclosure and the wave propagating through the shower plate electrode are superimposed. The electric field appearing in the sheath is controlled by changing the distribution and intensity of the wave (standing wave) propagating in the electric field control space by changing the diameter of the metal ring. Conversely, by providing a disk-shaped antenna at the center and providing an opening at the periphery, the strength of the electric field at that portion can be increased or decreased. The use of a metal having good thermal conductivity is preferable from the viewpoint of controlling (cooling) the temperature of the antenna and the shower plate, rather than a structure in contact with the shower plate via an insulator. Further, Si, SiC or C is desirable as a member of the shower plate electrode from the viewpoint of reducing foreign matters and metal contamination in the processing chamber and removing excess F generated from the fluorocarbon.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
The miniaturization and high integration of ULSI elements are rapidly progressing, and accordingly, the precision of etching technology and the large diameter are required. In particular, insulating film etching that processes oxide films and low-dielectric-constant insulating films needs to cope with the diversification of processed film types along with the complexity of device structures and the reduction in processing width. There is a demand for a high selectivity and vertical machining shape for Si ₃ N ₄ . However, when an attempt is made to obtain a high selectivity with respect to the base or resist, an “etch stop” or RIE-lag in which the etching reaction stops in the middle is likely to occur, and both high aspect vertical processing and high selectivity can be achieved. It is getting more and more difficult. In the insulating film etching, fluorocarbon gas containing carbon and fluorine is used, and an etching reaction proceeds by film deposition of fluorocarbon radicals (CxFy) decomposed by plasma and ion incidence. The selection ratio is manifested by the difference in film thickness and composition of the fluorocarbon film deposited on the oxide film, resist, and Si ₃ N ₄ . It is considered that a higher selectivity ratio is obtained when the density ratio CxFy / F of the fluorocarbon radical and the F radical is higher. On the other hand, when the amount of CxFy or the ratio of carbon increases, the etching reaction may stop. The composition of fluorocarbon radicals is governed not only by plasma density and electron temperature, but also by chemical reaction and recycling at the chamber wall. Moreover, the reaction product and its dissociated substance inhibit the etching. Therefore, in oxide film etching, it is necessary to control the density and temperature of plasma that governs dissociation of radicals and reaction products, and distribution control is necessary for large-diameter uniform processing. Further, in order to achieve a high throughput, that is, a high etching rate, it is essential to increase the density of plasma. Embodiments of the present invention for realizing these will be described below using reference examples and examples.
[0015]
A first embodiment of the present invention is shown in FIG. A processing chamber 2 of the plasma processing apparatus is formed in a processing container made of anodized aluminum or the like, and the processing chamber 2 is provided with a support (electrode) 5 for supporting an object (wafer) 4 to be processed. A gas 3 having a container 1 and introduced into the processing chamber is exhausted by an exhaust system 6. A susceptor 7 for placing a wafer is disposed on the support base. A ring-shaped focus ring 8 made of Si or the like is disposed on the susceptor 7, and the focus ring 8 is used to ensure uniformity near the edge of the wafer. A means for introducing a high frequency is placed on the upper part of the processing chamber 2. The high frequency of the UHF band or VHF band generated by the UHF / VHF generation source 9 is supplied to the antenna conductor 12 through the matching unit 10 and the transmission line 11. A dielectric 14 is filled between the antenna conductor 12 and the conductor wall 13, and high frequency is introduced into the processing chamber 2 through the radiation port 15. An RF generation source 16 that is different from the UHF or VHF generation source 9 is provided, and high frequency in the RF band is also supplied to the antenna conductor 12. Around the vacuum vessel 1, there is a magnetic field forming means 17 that forms a magnetic field in the processing chamber 2. A baffle plate 18 made of aluminum or the like is disposed on the antenna conductor 12 to disperse the gas. A shower plate electrode 19 is connected under the baffle plate and contacts the processing chamber 2. A gas hole 19a is formed in the shower plate electrode, and the gas 3 is supplied into the processing chamber 2 through the gas hole 19a. Below the antenna conductor 12 and the baffle plate 18 (on the processing chamber side), a dielectric 20 and a metal partition plate 21 are disposed so as to surround the dielectric 20 to form an electric field control space 22. The metal partition plate 21 is electrically connected to the antenna conductor 12 and the baffle plate 18. The dielectric constant of the dielectric 20 is preferably smaller than the dielectric constant of the shower plate electrode 19. A state of processing of the workpiece 4 when this embodiment is used will be described by taking oxide film etching as an example. The workpiece 4 is transported to the support base 5 in the processing chamber 2 by transport means (not shown). After the gas 3 composed of fluorocarbon gas, O ₂ , Ar, etc. is supplied to the processing chamber 2 and the internal pressure is set to a predetermined value, the UHF / VHF generation source 9 applies the antenna conductor 12 and the shower plate electrode 19. High frequency is supplied, and plasma and consequently various radicals are generated. Thereafter, high frequency power is supplied to the support 5 to generate an ion pulling voltage (bias) in the object to be processed, and the oxide film is etched by the incidence of the various radicals and ions. In this case, UHF and VHF can penetrate into the electric field control space 22 provided on the shower plate electrode 19, so that the electric field strength generated under the shower plate electrode 19 can be reduced. For example, if quartz is used as the dielectric 20 and the inner diameter of the electric field control space is about φ100 and the thickness is 5 t or more, the electric field strength in that range is reduced to about 2/3 to 1/2. The plasma density distribution in the central portion that originally exhibits the convex distribution can be made flat, and as a result, the etching rate of the insulating film is made uniform.
[0016]
A second embodiment of the present invention is shown in FIG. We focus on the structure of the antenna used in the plasma processing apparatus. The embodiment shown in FIG. 1 is characterized in that a plurality of electric field control spaces 22 including a dielectric 20 and a metal partition plate 21 surrounding the dielectric 20 are arranged in the antenna conductor portion 12 in the radial direction. For example, taking the electric field shown in FIG. For convenience, up to φ100 is called Center, φ100-200 is called Middle, and φ200-300 is called Edge. In this case, the electric field distribution is in the order of Center>Edge> Middle. φ0 to 100 (referred to as Center) is filled with 5t quartz as a dielectric, and in addition, about 4t quartz is filled in the range of φ220 to φ300 (Edge). Metal rings are arranged on φ100 to φ200 (Middle). Then, the electric field strength in the range of φ0 to 100 and the range of φ200 to 300 can be lowered and the electric field strength in the range of φ100 to 200 can be made uniform, so that the electric field in the range of φ300 can be made uniform. Here, for the sake of simplicity, the electric field control space is arranged at two locations, Center and Middle, but if the three locations or areas of Center, Middle, and Edge are subdivided, they may be arranged more than that. Further, there are arbitrary combinations of the thicknesses d and relative dielectric constants εr of the dielectrics arranged in each of them, but the value of εr / d of the dielectrics at the locations where the electric field strength is desired to be reduced may be made smaller than others. You may change that part.
[0017]
A third embodiment of the present invention is shown in FIG. A second metal ring 23 that is in electrical contact with the antenna conductor portion is disposed between the antenna conductor and the shower plate electrode. The electric field of UHF and VHF propagating through the side of the antenna conductor propagates through the sheath portion via the shower plate electrode, and a part thereof is composed of the dielectric 20, the metal partition plate 21, and the second metal ring 23. It also propagates in the electric field control space 22 and is reflected by the metal partition plate 21 surrounding the dielectric 20. The traveling wave propagating through the dielectric 20 interferes with the reflected wave to form a standing wave. This wave is again supplied into the sheath through the shower plate electrode 19 located below the electric field control space 22. Taking the above electric field distribution as an example, an example of flattening will be described. If quartz (relative permittivity 3.8) is used as the dielectric and Si (relative permittivity 11.8) is used as the shower plate electrode, the radius of the dielectric is 150 mm, the thickness is about 10 t, and the inner diameter of the second metal ring. Is preferably about 60 to 100 mm.
[0018]
A fourth embodiment of the present invention is shown in FIG. We focus on the structure of the antenna used in the plasma processing apparatus. In the embodiment shown in FIGS. 1 to 3, a second metal partition plate 24 is newly arranged on the inner side of the second metal ring 23 so as to be in electrical contact with the antenna conductor 12. The metal partition plate 24 is used to increase or decrease the electric field strength at the center, and the wave is strengthened or weakened at the opening between the partition plate and the second metal ring 23. Taking the electric field strength distribution as an example, an example of flattening will be described. First, in order to weaken the center, the inner diameter of the second metal partition plate 24 is about 50 mm.
In order to strengthen the middle portion, the distance between the second partition plate and the partition plate in the electric field control space is set to 1 / 4λ of the guide wavelength: f = 450 MHz, and about 88 mm in quartz. When the inner diameter of the second metal ring 23 is about 100 mm, the electric field in the radius of 50 to 100 mm can be strengthened. In this way, the electric field within a radius of 150 mm can be made relatively uniform, and plasma and etching can be made uniform.
[0019]
A fifth embodiment of the present invention is shown in FIG. We focus on the structure of the antenna used in the plasma processing apparatus. The embodiment shown in FIGS. 1 to 3 is characterized in that a third disk-shaped conductor 25 is arranged in the center of the electric field control space. The above-described electric field distribution will be described as an example. Assuming that quartz (relative dielectric constant 3.8) is used as the dielectric, the radius of the dielectric is 150 mm, the thickness is about 10 t, the diameter of the third disk-shaped conductor 25 is about 50 mm, and the inner diameter of the second metal ring 23. Is about 80 to 120 mm. Thus, by making an opening at r = 50 to 100, the electric field strength at that portion is increased. The electric field strength may be changed by changing the area of the opening, in other words, the diameter of the disk-shaped conductor 25 and the inner diameter of the second metal ring 23, or the dielectric constant of the dielectric. Moreover, the height (distance from the shower plate electrode) between the third third disk-shaped conductor 25 and the second metal ring 23 may be changed.
[0020]
A sixth embodiment of the present invention is shown in FIG. We focus on the structure of the antenna used in the plasma processing apparatus. A plate-like member 26 made of Si, SiC or C is disposed as the shower plate electrode 19. A high frequency of UHF or VHF is supplied to the processing chamber via the plate-like member 26. The dielectric constant can be written as ε = εr-jεi, and Si is taken as an example. Εr = 11.8, εi to ωε / η, where ω is an angular frequency and η is a resistivity. If the resistivity is selected so that εr >> εi, UHF or the like can be infiltrated. In the case of f = 450 MHz, if η = 1 to 10 Ωcm, it can be handled as a dielectric, and heat loss due to resistance is reduced. Further, since Si is used as an LSI member, there is no concern about contamination due to it. C and SiC are also suitable because the gas used is a fluorocarbon composed of C and F.
[0021]
In the embodiment of the present invention configured as described above, an electric field control space composed of an antenna conductor, a dielectric, a partition plate, and a metal disk is provided for the antenna portion for introducing UHF or VHF into the processing chamber. By adjusting the position of the partition plate and the metal disk, the electric field intensity at a desired position is changed and uniformized. 2) The abnormal discharge generated at the gas inlet is reduced by lowering the electric field strength generated at the shower plate electrode. The combination of the electric field control means and the magnetic field generation means makes it possible to control the plasma distribution in response to changes in process parameters such as pressure, gas type, and power.
[0022]
【The invention's effect】
According to the present invention, there is provided a plasma processing apparatus that realizes high-density, high-uniform plasma without abnormal discharge in a wide parameter region in a method of generating plasma using a high-frequency and magnetic field in the VHF or UHF band. it can. As a result, high processing speed and uniform processing of large-diameter wafers are realized.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a plasma processing apparatus according to a first embodiment of the present invention.
FIG. 2 is a diagram for explaining a second embodiment of the antenna configuration used in the present invention.
FIG. 3 is a diagram for explaining a third embodiment of the antenna configuration used in the present invention.
FIG. 4 is a diagram for explaining a fourth embodiment of the antenna configuration used in the present invention.
FIG. 5 is a diagram for explaining a fifth embodiment of the high-frequency radiation port used in the present invention.
FIG. 6 is a diagram for explaining a sixth embodiment of the high-frequency radiation port used in the present invention.
FIG. 7 is a diagram showing a UHF electric field distribution in a comparative example.
FIG. 8 is a diagram showing an electric field distribution comparison between a comparative example and the present invention.
FIG. 9 is a diagram showing the operation of the first exemplary embodiment of the present invention.
FIG. 10 is a diagram showing the effect of the first exemplary embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 2 ... Processing chamber, 3 ... Gas, 4 ... To-be-processed object, 5 ... Support stand (electrode), 6 ... Exhaust system, 7 ... Susceptor, 8 ... Focus ring, 9 ... UHF * VHF generation source, DESCRIPTION OF SYMBOLS 10 ... Matching device, 11 ... Transmission line, 12 ... Antenna conductor, 13 ... Conductor wall (waveguide), 14, 20 ... Dielectric, 15 ... High frequency introduction means (radiation port), 16 ... RF generation source, 17 ... Magnetic field Forming means, 18 ... baffle plate, 19 ... shower plate electrode, 19a ... gas hole, 19b, 26 ... plate member (Si, SiC, C), 21 ... metal partition plate, 22 ... electric field control space, 23 ... second Metal ring, 24 ... second metal partition plate, 25 ... third disk-shaped conductor.

Claims (5)

  A vacuum vessel, a processing chamber inside the vacuum vessel to which gas is supplied, a support electrode that is provided in the processing chamber and supports an object to be processed, and an antenna that supplies a high frequency in the UHF band or VHF band to the processing chamber A disk-shaped antenna conductor portion of the antenna portion comprising a disk-shaped antenna conductor portion and a shower plate for supplying gas. A plasma processing apparatus having a plurality of electric field control spaces each having a dielectric and a metal surrounding the dielectric.   2. The plasma processing apparatus according to claim 1, wherein a ring-shaped metal electrically connected to the metal is disposed in an electric field control space having the dielectric and the metal surrounding the dielectric. 3. The plasma processing apparatus according to claim 2, wherein a metal partition plate is newly disposed inside the ring-shaped metal so as to be electrically connected to the antenna conductor portion.   3. The plasma processing apparatus according to claim 1, wherein a metal rod electrically connected to the antenna conductor portion and a disk-shaped conductor electrically connected to the metal rod are arranged at a central portion of the antenna portion.   5. The shower plate for supplying gas according to claim 1, wherein a plate-like member made of at least one of Si, SiC, and C is disposed, and a UHF band or a VHF band is interposed through the plate-like member. Plasma processing equipment that supplies high-frequency waves to the processing chamber.

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