US20120216955A1

US20120216955A1 - Plasma processing apparatus

Info

Publication number: US20120216955A1
Application number: US13/401,115
Authority: US
Inventors: Hideo Eto; Makoto Saito; Hisashi Hashiguchi; Atsushi Ito; Michio Sato
Original assignee: Toshiba Corp; Toshiba Materials Co Ltd
Current assignee: Toshiba Corp; Toshiba Materials Co Ltd
Priority date: 2011-02-25
Filing date: 2012-02-21
Publication date: 2012-08-30
Also published as: JP2012191200A

Abstract

According to one embodiment, a plasma processing apparatus that includes a process target holding portion and a plasma generating unit in a chamber, and processes a process target by using generated plasma is provided. An yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber on a generation region side of the plasma. The yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more and 200 μm or less, has a film density of 90% or more, and is such that yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in area ratio.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2011-40190, filed on Feb. 25, 2011; the entire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a plasma processing apparatus.

BACKGROUND

Conventionally, in a micro-patterning process in manufacturing semiconductor devices, liquid crystal display devices, and the like, an RIE (Reactive Ion Etching) apparatus is used. In the RIE apparatus, etching is performed by setting the inside of a chamber in a low-pressure state and turning fluorine based gas or chlorine based gas introduced into the chamber into plasma. The inner wall and the internal structural members of such the RIE apparatus easily corrode by being exposed to plasma, so that a material having a high plasma resistance, such as yttrium oxide (yttria) and aluminum oxide (alumina), is coated thereon as a protective film.
However, even when the protective film such as yttrium oxide is coated on the inner wall and the internal structural members of the RIE apparatus, the protective film degrades due to shedding of particles, cracks, or the like.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating one example of a part mounted on a plasma processing apparatus in a first embodiment;

FIG. 2A is a tracing illustrating one example of an yttrium oxide film in the first embodiment;

FIG. 2B is a photograph illustrating one example of the yttrium oxide film in the first embodiment;

FIG. 3A is a tracing further magnifying a part in FIG. 2A;

FIG. 3B is a photograph further magnifying a part in FIG. 2B;

FIG. 4 is a diagram illustrating film forming conditions of yttrium oxide films formed by an impact sintering method (Examples 1 to 7) and a conventional thermal spray method (Comparison Example 1);

FIG. 5 is a diagram illustrating an evaluation result of an yttrium oxide film formed under each condition shown in FIG. 4;

FIG. 6 is a diagram illustrating an evaluation result of the plasma resistance;

FIG. 7 is a cross-sectional view schematically illustrating one example of a configuration of a plasma processing apparatus in a second embodiment;

FIG. 8A is a plan view illustrating one example of a configuration of a shower head coated with a protective film in the second embodiment;

FIG. 8B is a schematic cross-sectional view of the shower head coated with the protective film in the second embodiment near a gas ejection port formed region;

FIG. 9A and FIG. 9B are perspective views illustrating one example of a configuration of a deposition shield coated with the protective film in the second embodiment;

FIG. 10A is a perspective view illustrating one example of a configuration of an insulator ring coated with the protective film in the second embodiment;

FIG. 10B is a cross-sectional view illustrating one example of the configuration of the insulator ring coated with the protective film in the second embodiment;

FIG. 11 is a diagram illustrating a degree of a particle shedding rate of the protective film in the second embodiment; and

FIG. 12 is a diagram illustrating a degree of an etching rate of the protective film in the second embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a plasma processing apparatus that includes a process target holding portion that holds a process target in a chamber and a plasma generating unit that turns gas introduced into the chamber into plasma, and processes the process target by using generated plasma is provided. An yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber on a generation region side of plasma generated in the plasma generating unit. The yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more and 200 μm or less, has a film density of 90% or more, and is such that yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in area ratio and yttrium oxide particles, whose grain boundary is not confirmable, is 20 to 100% in area ratio.
A plasma processing apparatus according to the embodiments will be explained in detail below with reference to the accompanying drawings. The present invention is not limited to these embodiments.

First Embodiment

A plasma processing apparatus in the first embodiment is an apparatus on which parts for the plasma processing apparatus, which include an yttrium oxide film formed by an impact sintering method, are mounted. The yttrium oxide film is an yttrium oxide film (hereinafter, an yttrium oxide film in a semi-molten state) that includes yttrium oxide particles in which adjacent particles, at least the surfaces of which are in a molten state, are bonded and solidified and in which part of grain boundaries cannot be seen. This semi-molten-state yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more, has a film density of 90% or more, and includes yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary can be confirmed, by 0 to 80% in area ratio and includes yttrium oxide particles, whose grain boundary cannot be confirmed, by 20 to 100% in area ratio.
FIG. 1 is a diagram illustrating one example of a part mounted on the plasma processing apparatus in the first embodiment. FIG. 1 illustrates a part 1 for the plasma processing apparatus, an yttrium oxide film 2, and a substrate 3. Yttrium oxide has resistance to plasma attack and radical attack (for example, active F radical) and therefore has no problem, however, particularly, yttrium oxide having resistant to fluorine plasma is preferable.
Moreover, the purity of yttrium oxide particles is preferably 99.9% or more. A large amount of impurities in yttrium oxide particles causes contamination in a manufacturing process of semiconductors. Therefore, yttrium oxide particles whose purity is 99.9% or more are preferably used.
An yttrium oxide film includes yttrium oxide particles. For example, if the film is formed by a typical thermal spray method, the film is formed in a state where yttrium oxide particles are in a molten state. Therefore, the yttrium oxide particles are in flat shape. On the contrary, in the first embodiment, because yttrium oxide particles are not melted and thus do not have a flat shape, and the yttrium oxide film includes yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary can be identified, by 0 to 80% in area ratio and includes yttrium oxide particles, whose grain boundary cannot be identified, by 20 to 100% in area ratio.
Yttrium oxide particles whose grain boundary can be confirmed can be recognized in a magnified photograph. For example, the yttrium oxide particles can be recognized by taking a 5000-times-magnified photograph by an electron microscope. FIG. 2A is a tracing illustrating one example of the yttrium oxide film in the first embodiment and FIG. 2B is a photograph illustrating one example of the yttrium oxide film in the first embodiment. FIG. 3A is a tracing further magnifying a part in FIG. 2A and FIG. 3B is a photograph further magnifying a part in FIG. 2B. FIG. 2A is a diagram tracing the photograph in FIG. 2B and FIG. 3A is a diagram tracing the photograph in FIG. 3B. These figures illustrate yttrium oxide particles 4 whose grain boundary cannot be confirmed and yttrium oxide particles 5 whose grain boundary can be confirmed.
“Yttrium oxide particles whose grain boundary can be confirmed” are particles in which a grain boundary of each particle can be confirmed by a contrast difference in a magnified photograph. On the other hand, “yttrium oxide particles whose grain boundary cannot be confirmed” are particles in which adjacent particles are bonded and a grain boundary of each particle cannot be confirmed in a magnified photograph. Moreover, a unit area is 20 μm×20 μm and an area of each of “yttrium oxide particles whose grain boundary can be confirmed” and “yttrium oxide particles whose grain boundary cannot be confirmed” in an arbitrary predetermined number (for example, three) of the unit areas selected in a sample is measured, and the average thereof is set as the area ratio of each of “yttrium oxide particles whose grain boundary can be confirmed” and “yttrium oxide particles whose grain boundary cannot be confirmed”. In FIG. 2A to FIG. 3B, both the particle group of the “yttrium oxide particles 5 whose grain boundary can be confirmed” and the particle group of the “yttrium oxide particles 4 whose grain boundary cannot be confirmed” exist in a mixed state.
The impact sintering method is a film forming method of forming a film by spraying particles by combustion flame, and is a method of impacting particles onto a substrate at high speed (for example, sound speed or faster) and forming a film by sinter bonding the particles by crushing heat of the particles by the impact. Therefore, an yttrium oxide film including yttrium oxide particles having a crushed shape rather than a particle shape of raw powder tends to be formed. In the first embodiment, in such the impact sintering method, a film is formed by controlling such that the spray rate of yttrium oxide particles is accelerated in a state where the yttrium oxide particles are not melted or only the surface layer thereof is melted to be equal to or faster than a critical speed at which the particles start to deposit. An yttrium oxide particle whose surface layer is melted is bonded to an adjacent yttrium oxide particle by crushing heat when impacting onto the substrate, so that an yttrium oxide film including yttrium oxide particles whose grain boundary cannot be confirmed is formed. At this time, the entire yttrium oxide particle may be melted by crushing heat when the yttrium oxide particle impacts onto the substrate instead of only the surface layer. In this case also, a similar yttrium oxide film is formed. An yttrium oxide particle whose surface layer is not melted is melted in some cases at least in the surface layer thereof by crushing heat when impacting onto the substrate, so that an yttrium oxide film including yttrium oxide particles in which the grain boundary between adjacent yttrium oxide particles cannot be confirmed is formed. In this manner, with the use of a high-speed spraying, raw powder is not sprayed in a molten state as in a thermal spraying, so that yttrium oxide particles can be deposited in a state of substantially maintaining a powder form of the yttrium oxide particles as raw powder. Therefore, stress in a film is not generated, so that a dense (high film density) yttrium oxide film having a high bonding force can be formed.
In this manner, the impact sintering method is capable of high-speed spraying, so that a structure in which “yttrium oxide particles whose grain boundary can be confirmed” and “yttrium oxide particles whose grain boundary cannot be confirmed” exist in a mixed state can be easily obtained. When the sum of the area ratio of “yttrium oxide particles whose grain boundary can be confirmed” and “yttrium oxide particles whose grain boundary cannot be confirmed” is 100%, the area ratio of “yttrium oxide particles whose grain boundary can be confirmed” is 0 to 80% and the area ratio of “yttrium oxide particles whose grain boundary cannot be confirmed” is 20 to 100%.
If the area ratio of “yttrium oxide particles whose grain boundary can be confirmed” exceeds 80%, crushing heat by the impact is not sufficient, which causes a rapid cooling state in deposition, so that the density and the bonding force of a film decrease and a crack is generated in some cases. The area ratio of “yttrium oxide particles whose grain boundary can be confirmed” is preferably 0 to 50%. This is equivalent to that the area ratio of “yttrium oxide particles whose grain boundary cannot be confirmed” is preferably in a range of 50 to 100%.
Moreover, the film thickness of the yttrium oxide film is desirably 10 μm or more. If the film thickness is less than 10 μm, the effect of providing the yttrium oxide film is not sufficiently obtained and this may cause film separation. The upper limit of the film thickness of the yttrium oxide film is not particularly limited, however, if the film is too thick, no further effect can be obtained and moreover, a crack is easily generated due to accumulation of internal stress and this becomes a factor of cost increase. Therefore, the thickness of the yttrium oxide film is 10 to 200 μm and is more preferably, 50 to 150 μm.
Moreover, the film density needs to be 90% or more. The film density is an antonym of the porosity, and the film density being 90% or more is the same as the porosity being 10% or less. As a measuring method of the film density, an oxide film is cut in the film thickness direction, a magnified photograph (for example, 500 times) of its cross-sectional structure is taken by an optical microscope, and the area ratio of pores in the magnified photograph is calculated. Then, the film density is calculated by “film density (%)=100−area ratio of pores”. In the calculation of the film density, an area of a unit area 200 μm×200 μm is analyzed. When the film thickness is thin, the film density is measured at a plurality of locations until the total cross-sectional area becomes the unit area 200 μm×200 μm.
The film density is preferably 90% or more, more preferably 95% or more, and still more preferably 99% or more and 100% or less. When a lot of pores (voids) are present in the yttrium oxide film, corrosion, such as plasma attack, proceeds from the pores, which reduces the life of the oxide film. Specially, it is desirable that there are not many pores in the surface of the yttrium oxide film.
Moreover, the surface roughness Ra of the yttrium oxide film is preferably 3 μm or less. If the surface irregularity of the yttrium oxide film is large, plasma attack or the like is easy to concentrate, which may reduce the life of the film. The surface roughness Ra is measured according to JIS-B-0601-1994. Preferably, the surface roughness Ra is 2 μm or less.
Moreover, the average particle diameter of yttrium oxide particles whose grain boundary can be confirmed is preferably 2 μm or less and the average particle diameter of all yttrium oxide particles including yttrium oxide particles whose grain boundary cannot be confirmed is preferably 5 μm or less.
As will be described later, yttrium oxide powder as raw powder used in the impact sintering method preferably has an average particle diameter in a range of 1 to 5 μm. If the average particle diameter of yttrium oxide particles as raw powder exceeds 5 μm, when the particles impact, the particles are not crushed and scatter, so that a film is difficult to form and moreover, a film may be damaged by a blast action of the particles themselves and a crack may be generated. On the other hand, if the average particle diameter of yttrium oxide particles becomes 5 μm or less, when fine particles impact, crushing proceeds moderately and particle bonding is facilitated by heat generated by the crushing, so that a film is easily formed. This formed film has a large bonding force between particles, so that wear due to plasma attack and radical attack is reduced and particle generation is reduced, thereby improving the plasma resistance. A more preferred value of the particle diameter of particles is 1 μm or more and 3 μm or less, and if the particle diameter becomes less than 1 μm, it becomes difficult to proceed crushing of particles, so that although a film is formed, the film becomes a low density film and therefore the plasma resistance and the corrosion resistance decrease. Therefore, the range of application of the fine particle diameter is preferably 1 to 5 μm. However, if fine particles of less than 1 μm are less than 5% of all yttrium oxide particles, film formation is not degraded, so that powder containing fine particles of less than 1 μm may be used.
The average particle diameter is obtained by using a magnified photograph as shown in FIG. 2B. The longest diagonal line in particles in the photograph is set as the particle diameter of yttrium oxide particles whose grain boundary can be confirmed. For yttrium oxide particles whose grain boundary cannot be confirmed, a temporary circle of each particle is used and the diameter thereof is set as the particle diameter. This operation is performed for a predetermined number of particles for each particle group (for example, 50 particles, totally 100 particles) and the average thereof is set as the average particle diameter.
When an X-ray diffraction analysis (X-ray diffraction Technique: hereinafter, XRD analysis) is performed on the yttrium oxide film, and the resulting strongest peak of a cubical crystal (cubic) is Ic and the resulting strongest peak of a monoclinic crystal (monoclinic) is Im, the ratio Im/Ic is preferably 0.2 to 0.6. The XRD analysis is performed under the condition of a 2θ method, using a Cu as a target, setting a tube voltage to 40 kV, and setting a tube current to 40 mA.
The strongest peak of a cubical crystal is detected between 28 and 30°. Moreover, the strongest peak of a monoclinic crystal is detected between 30 and 33°. Normally, commercial yttrium oxide particles are a cubical crystal. Crystalline change occurs in some cases in part of the yttrium oxide particles by crushing heat in the impact sintering method, however, if crystalline change occurs in many yttrium oxide particles, the internal stress is generated and thus the film characteristics degrade. Therefore, Im/Ic is preferably in a range of 0.2 to 0.6.
Next, the manufacturing method of parts for a dry etching apparatus in the first embodiment is explained. The manufacturing method of the parts for the plasma processing apparatus, on which the yttrium oxide film is formed by the impact sintering method in the first embodiment, includes a process of supplying slurry containing yttrium oxide particles into combustion flame and a process of spraying yttrium oxide particles onto a substrate at a spray rate of 400 to 1000 m/sec. The average particle diameter of yttrium oxide particles is preferably 1 to 5 μm. Moreover, slurry containing yttrium oxide particles is preferably supplied to the center of combustion flame. The temperature of combustion flame at this time is desirably 3000° C. or less.
The impact sintering method is a film forming method of supplying slurry containing yttrium oxide particles into combustion flame and spraying yttrium oxide particles at high speed. A film forming apparatus that performs the impact sintering method includes a combustion source supply port from which a combustion source is supplied and a combustion chamber connected thereto. Combustion flame is generated in a combustion flame port by combusting the combustion source in the combustion chamber. A slurry supply port is provided near combustion flame and yttrium oxide particle slurry supplied from the slurry supply port is sprayed to the substrate from the combustion flame via a nozzle to form a film. The combustion source is oxygen, acetylene, heating oil, or the like and two of them may be used for a combustion source if needed.
When forming an yttrium oxide film by the impact sintering method, the spray rate of yttrium oxide particles is preferably in a range of 400 m/sec or more and 1000 m/sec or less. If the spray rate is low, crushing when particles impact becomes insufficient and a film having a high film density may not be obtained. Moreover, if the spray rate exceeds 1000 m/sec, the impact is too strong, so that the blast effect by yttrium oxide particles occurs and a desired film is difficult to obtain.
Moreover, when yttrium oxide particle slurry is supplied from the slurry supply port, the slurry is preferably supplied to the center of combustion flame. If yttrium oxide particle slurry is supplied to the outside of combustion flame, part of yttrium oxide particles is sprayed from the outside of the combustion flame and part thereof is sprayed after reaching the center of the combustion flame, so that the spray rate is not stabilized. Moreover, the temperature is slightly different between the outside and the inside in the same combustion flame, so that the film quality becomes inconsistent. On the contrary, if yttrium oxide particle slurry is supplied to the center of combustion flame, a film is formed at the same temperature and the same spray rate, so that the film quality becomes consistent and thus it becomes possible to control the structure of particles whose grain boundary can be confirmed and particles whose grain boundary cannot be confirmed.
Moreover, the impact sintering method is a film forming method of forming a film by spraying particles by combustion flame and is a method of forming a film by impacting particles at high speed and sinter bonding the particles by crushing heat of the particles by the impact. Therefore, an yttrium oxide film including yttrium oxide particles having a crushed shape rather than a particle shape of raw powder tends to be formed. Moreover, an yttrium oxide film having a high film density can be obtained by controlling such that the spray rate of yttrium oxide particles is accelerated in a state where the yttrium oxide particles are not melted or only the surface layer thereof is melted to be equal to or faster than a critical speed at which the particles start to deposit. The impact sintering method is capable of high-speed spraying, so that “particles whose grain boundary cannot be confirmed” can be easily obtained. Thus, it is possible to efficiently obtain the yttrium oxide film that includes yttrium oxide particles, whose grain boundary can be confirmed, by 0 to 80% in area ratio and yttrium oxide particles, whose grain boundary cannot be confirmed, by 20 to 100% in area ratio as in the first embodiment.
Moreover, it is effective to adjust a spray distance L from the nozzle to the substrate in a control of “particles whose grain boundary can be confirmed” and “particles whose grain boundary cannot be confirmed”. As described above, the impact sintering method is a method of spraying yttrium oxide particles at high speed by using combustion flame and sinter bonding and depositing the yttrium oxide particles by utilizing crushing heat of the particles at the time of the impact. In order to form a film without forming yttrium oxide particles, which are once heated by combustion flame, into a melted flat shape, the spray distance L is preferably 100 to 400 mm. The spray distance L of less than 100 mm is too close, so that oxide particles are not crushed and therefore a film in which particles are sinter bonded is hard to obtain. On the other hand, the spray distance L exceeding 400 mm is too far, so that the impact force becomes low and therefore a target oxide film is hard to obtain. Melted and unmelted structures can be controlled by controlling the spray rate and the oxide particle size as raw powder described above. Preferably, the spray distance L is 100 to 200 mm.
Moreover, yttrium oxide particle slurry is preferably slurry containing yttrium oxide particles having an average particle diameter of 1 to 5 μm as raw powder. Solvent to be slurried is preferably solvent that is relatively easy to volatilize, such as methyl alcohol and ethyl alcohol. Yttrium oxide particles are preferably mixed with solvent after being sufficiently crushed to be free from a coarse particle. For example, presence of a coarse particle of 20 μm or larger makes it difficult to obtain a uniform film. Moreover, yttrium oxide particles in slurry are preferably 30 to 80 vol %. Slurry having a moderate flowability is smoothly supplied to a supply port and therefore the supply is stabilized, so that a uniform film can be obtained.
With the use of such an impact sintering method, an yttrium oxide film can be formed without changing a crystal structure of raw powder (yttrium oxide particle slurry). For example, yttrium oxide is a cubical crystal at room temperature. If yttrium oxide is exposed to high temperature such as combustion flame in a thermal spray method, a crystal structure changes, however, yttrium oxide is not exposed to high temperature in the impact sintering method, so that yttrium oxide particles can form an yttrium oxide film while maintaining a stable cubical crystal.
The pars for the plasma processing apparatus as above can be applied to various plasma processing apparatuses. For example, micro-patterning of various thin films, such as a dielectric film, an electrode film, and a wiring film formed on an Si wafer or a substrate, can be performed by using an RIE (Reactive Ion Etching) apparatus that performs a process by using ions or radicals generated by turning halogen gas into plasma by a radio-frequency voltage applied between electrodes or an interaction between an electric field of microwaves and a magnetic field. The parts for the plasma processing apparatus in the first embodiment can be applied to any portion exposed to plasma. Therefore, they can be applied to any part exposed to plasma, such as an inner wall part, without being limited to a wafer arrangement member. Moreover, the substrate on which the yttrium oxide film is formed is not limited to quartz and the yttrium oxide film may be provided on a metal member or a ceramic member. Specially, although the technology can be applied to a deposition shield, an insulator ring, an upper electrode, a baffle plate, a focus ring, a shield ring, a bellows cover, and the like exposed to plasma among parts used in the plasma processing apparatus, the technology is not limited to a field of a semiconductor manufacturing apparatus and can be applied also to parts of the plasma processing apparatus such as a liquid crystal display device.
Moreover, the plasma resistance in the part for the plasma processing apparatus is improved significantly, so that particles can be reduced and the life of used parts can be prolonged. Therefore, according to the plasma processing apparatus using such parts for the plasma processing apparatus, particles during the plasma process can be reduced and the number of replacement times of the parts can be reduced.
Moreover, in an RIE apparatus utilizing high-density plasma, a dielectric member is used in some cases to ensure insulation against a radio-frequency voltage applied for generating plasma. As a protective film of a dielectric member exposed to plasma such as an upper electrode, bi-layer coating, which is formed by depositing a highly insulating aluminum oxide film (alumite) and then forming the yttrium oxide film thereon, is effective. In terms of insulation, thickness adjustment of an aluminum oxide film and formation of a high-density film are important, and specially, when an aluminum oxide film having an a structure is densely formed, a further effect is exerted, so that it is preferable to set the condition equivalent to formation of the yttrium oxide film.
An aluminum oxide film is used as a lower layer, however, other oxides or a mixture thereof may be used and it is preferable to select a material according to requisite characteristics. In the case of a double-layered structure with an aluminum oxide film, the upper limit thereof is preferably 500 μm or less.
Moreover, because particles are sprayed at high speed by the impact sintering method and particles are deposited by its impact energy, when depositing a film on a structural part, a blast treatment is not needed. Consequently, there is no residual blast member and generation of a surface defect, so that adhesion of a film improves. This is because a film is formed directly on a part surface by causing a surface oxide film of a structural member to be destroyed by a high-speed impact of particles and exposing an active surface and a film is formed by causing bonding to occur between particles by heat generation due to particle breakdown in the particle impact thereafter.
Therefore, generation of particles due to separation of attached matters deposited on the parts for the apparatus can be suppressed and the number of times of cleaning the apparatus and replacing the parts can be significantly reduced. Reduction of particle generation contributes largely to reduce defects at the time of an etching process and defects in a film at the time of various thin film formation in semiconductor manufacturing and moreover, to improvement in yield of parts and elements obtained by using it. Moreover, reduction in the number of times of cleaning the apparatus and replacing the parts and prolongation of the useful life of the parts contribute largely to improvement in productivity and reduction in running costs.
The first embodiment is explained in detail below with reference to examples.
FIG. 4 is a diagram illustrating film forming conditions of yttrium oxide films formed by the impact sintering method (Examples 1 to 7) and a conventional thermal spray method (Comparison Example 1). An yttrium oxide film is formed on an aluminum substrate (100 mm×200 mm) under the conditions shown in FIG. 4 by the impact sintering method using a combustion-flame type spraying apparatus to be the part for the plasma processing apparatus. In each example, ethyl alcohol is used as solvent of yttrium oxide particle slurry. Moreover, in each example, high-purity oxide particles with the purity of 99.9% or more are used as raw powder to be used. Furthermore, yttrium oxide (Y₂O₃) particles as raw powder are a cubic crystal, and yttrium oxide particles free from a coarse particle exceeding 20 μm by sufficient crushing and screening are used. Moreover, in Comparison Example 1, an yttrium oxide film is formed by a plasma thermal spray method.
FIG. 5 is a diagram illustrating an evaluation result of an yttrium oxide film formed under each condition shown in FIG. 4. For the yttrium oxide films in each example and the comparison example shown in FIG. 4, the film density, the area ratio of particles whose grain boundary can be confirmed and particles whose grain boundary cannot be confirmed, and the average particle diameter of particles whose grain boundary can be confirmed in an yttrium oxide film are measured and the crystal structure is analyzed by the XRD method.
In terms of the film density, a magnified photograph (500 times) is taken so that the total unit area in the film cross section becomes 200 μm×200 μm and the film density is obtained from a ratio of pores in the photograph. In terms of the area ratio of particles whose grain boundary can be confirmed and particles whose grain boundary cannot be confirmed, a magnified photograph (5000 times) of a unit area 20 μm×20 μm in the film surface is taken and the area ratio is obtained under the condition that particles in which a grain boundary of one yttrium oxide particle is confirmed are determined as “particles whose grain boundary can be confirmed” and particles in which grain boundaries are bonded and cannot be confirmed are determined as “particles whose grain boundary cannot be confirmed”. This operation is performed at arbitrary three locations and the average thereof is determined as the area ratio (%) of “particles whose grain boundary can be confirmed” and “particles whose grain boundary cannot be confirmed”. Moreover, the average particle diameter of “particles whose grain boundary can be confirmed” is obtained by using the same magnified photograph. Furthermore, the crystal structure is examined by the ratio Im/Ic of the strongest peak Ic of a cubic crystal and the strongest peak Im of a monoclinic crystal detected in the XRD analysis (using a Cu target, setting a tube voltage to 40 kV, and setting a tube current to 40 mA).
As is apparent from FIG. 5, in the yttrium oxide films according to the present examples, the film density is high and the ratio (area ratio) of “yttrium oxide particles whose grain boundary can be confirmed” is in a range of 0 to 80%. Moreover, with the use of the impact sintering method, the average particle diameter of “yttrium oxide particles whose grain boundary can be confirmed” is slightly smaller than the size (about 5 μm) of raw powder. Furthermore, because the particles are not melted more than necessary, the crystal structure is partially the same as raw powder (Im/Ic=0.2 to 0.6).
Moreover, although not shown in FIG. 5, the yttrium oxide films in Examples 1 to 6 have a surface roughness Ra of 3 μm or less. The surface roughness Ra of the yttrium oxide film in Example 7 is as large as 6.2 μm, and this is considered to be because the number of “particles whose grain boundary cannot be confirmed” is small and thus the surface irregularity becomes large. Furthermore, in Comparison Example 1, the surface roughness Ra of the yttrium oxide film is 3.4 μm.
Next, FIG. 6 is a diagram illustrating an evaluation result of the plasma resistance. Each yttrium oxide film in each example and the comparison example shown in FIG. 4 is arranged in the plasma processing apparatus and is exposed to plasma generated by a mixed gas of CF₄(80 sccm)+0 ₂(20 sccm)+Ar (100 sccm). The pressure in an RIE chamber is set to 20 mTorr and the RF output is set to 100 W, and after continuously operating for 12 hours (“30 minutes discharging→10 minutes cooling”×24 times), an amount of shed particles of the yttrium oxide film is examined by a peeling evaluation by a Scotch tape method. Specifically, after attaching Scotch tape to the yttrium oxide film, the tape is peeled, the tape is subjected to SEM (Scanning Electron Microscope) observation, and an area, in which shed particles are adhered, present in a field of view of 80 μm×60 μm is measured. Moreover, the weight of a member on which the yttrium oxide film is formed is measured by a precision balance before and after performing the above test and the weight loss is obtained.
FIG. 6 shows that, in the impact sintering method (Examples 1 to 7), the weight loss is smaller than the conventional thermal spray method (Comparison Example 1) and an amount of shed particles from the yttrium oxide film is also smaller by one or more orders of magnitude. Consequently, it is found that the parts for the RIE apparatus, on which the protective film is formed by the impact sintering method according to the present examples, are resistant to plasma attack and radical attack. Being resistant to plasma attack and radical attack means that generation of particles when using the RIE apparatus can be efficiently suppressed.
In each of the above examples, the yttrium oxide film by the impact sintering method is directly formed on the surface of each part as an example, however, an effect of improving also insulation as the parts can be exerted by forming at least one layer of a dielectric film, such as an aluminum oxide film, between a part surface and the yttrium oxide film and forming the yttrium oxide film by the impact sintering method on the outermost surface thereof.
As explained above, according to the parts for the RIE apparatus in the first embodiment, corrosion of a film due to radicals of corrosive gas can be suppressed, so that stability of each part and the film itself can be improved, enabling to suppress generation of particles from the parts or the film. Furthermore, because the life of used parts is prolonged and products generated by corrosion can be reduced, the number of times of cleaning the apparatus and replacing the parts can be reduced.

Second Embodiment

In the second embodiment, a specific example of applying the yttrium oxide film explained in the first embodiment to structural members of a plasma processing apparatus is explained.
FIG. 7 is a cross-sectional view schematically illustrating one example of the configuration of the plasma processing apparatus in the second embodiment. In this embodiment, as a plasma processing apparatus 10, an RIE apparatus is exemplified. The plasma processing apparatus 10 includes, for example, a sealed aluminum chamber 11. This chamber 11 is grounded.
A support table 21, which horizontally supports a wafer 100 as a process target and functions as a lower electrode, is provided in the chamber 11. On the surface of the support table 21, a not-shown holding mechanism, such as an electrostatic chuck mechanism that electrostatically adsorbs the wafer 100, is provided. An insulator ring 22 is arranged to cover the side surface and the peripheral portion of the bottom surface of the support table 21, and a focus ring 23 is provided on the outer periphery of the support table 21 above the portion covered by the insulator ring 22. This focus ring 23 is a member that adjusts an electric field so that the electric field is not biased with respect to a vertical direction (direction vertical to the wafer surface) in the peripheral portion of the wafer 100 when etching the wafer 100.
Moreover, the support table 21 is supported on a support portion 12, which projects vertically upward in a tubular shape from the bottom wall near the center of the chamber 11, via the insulator ring 22 to be positioned near the center in the chamber 11. A baffle plate 24 is provided between the insulator ring 22 and the side wall of the chamber 11. The baffle plate 24 includes a plurality of gas exhaust holes 25 penetrating in the thickness direction of the plate. Moreover, a feeder 31, which supplies radio-frequency power, is connected to the support table 21 and a blocking capacitor 32, a matching box 33, and a radio-frequency power source 34 are connected to this feeder 31. Radio-frequency power of a predetermined frequency is supplied from the radio-frequency power source 34 to the support table 21.
A shower head 41, which functions as an upper electrode, is provided above the support table 21 to face the support table 21 functioning as a lower electrode. The shower head 41 is fixed to the sidewall near the upper portion of the chamber 11 at a predetermined distance from the support table 21 to face the support table 21 in parallel therewith. With such a structure, the shower head 41 and the support table 21 configure a pair of parallel plate electrodes. Moreover, a plurality of gas ejection ports 42 penetrating in the thickness direction of the plate is provided in the shower head 41.
A gas supply port 13, from which process gas used in the plasma process is supplied, is provided near the upper portion of the chamber 11 and a not-shown gas supplying apparatus is connected to the gas supply port 13 via a pipe.
A gas exhaust port 14 is provided in the lower portion of the chamber 11 lower than the support table 21 and the baffle plate 24 and a vacuum pump as a not-shown exhausting unit is connected to the gas exhaust port 14 via a pipe.
Moreover, a deposition shield 45, which prevents adhesion of deposition generated in the plasma process to the sidewall of the chamber 11, is provided on the sidewall of the chamber 11 in a region partitioned between the baffle plate 24 and the shower head 41. Moreover, an opening 15 for moving the wafer 100 into and out of the chamber 11 is formed in the sidewall at a predetermined position of the chamber 11 and a shutter 46 is provided at the portion of the deposition shield 45 corresponding to this opening 15. The shutter 46 has a role of partitioning between the outside and the inside of the chamber 11, and when moving the wafer 100 into and out of the chamber 11, the shutter 46 is opened to connect the opening 15 and the inside of the chamber 11.
The region partitioned by the support table 21, the baffle plate 24, and the shower head 41 in the chamber 11 becomes a plasma processing chamber 61, the upper region in the chamber 11 partitioned by the shower head 41 becomes a gas supply chamber 62, and the lower region in the chamber 11 partitioned by the support table 21 and the baffle plate 24 becomes a gas exhaust chamber 63.
A summary of a process in the plasma processing apparatus 10 configured as above is explained. First, the wafer 100 as a process target is placed on the support table 21 and is fixed, for example, by an electrostatic chuck mechanism. Next, the inside of the chamber 11 is evacuated by a not-shown vacuum pump connected to the gas exhaust port 14. At this time, the gas exhaust chamber 63 and the plasma processing chamber 61 are connected through the gas exhaust holes 25 provided in the baffle plate 24, so that the inside of the whole chamber 11 is evacuated by the vacuum pump connected to the gas exhaust port 14.
Thereafter, when the inside of the chamber 11 reaches a predetermined pressure, because the plasma processing chamber 61 and the gas supply chamber 62 are connected through the gas ejection ports 42 of the shower head 41, process gas is supplied to the gas supply chamber 62 from the not-shown gas supplying apparatus and is supplied to the plasma processing chamber 61 via the gas ejection ports 42 of the shower head 41. When the pressure inside the plasma processing chamber 61 reaches a predetermined pressure, in a state where the shower head 41 (upper electrode) is grounded, a radio-frequency voltage is applied to the support table 21 (lower electrode) to generate plasma in the plasma processing chamber 61. Because a radio-frequency voltage is applied to the lower electrode, a potential gradient is formed between plasma and a wafer, so that ions in plasma gas are accelerated toward the support table 21, whereby an etching process is performed.
As described above, a surface of a structural member on a side in contact with a plasma generation region, that is, the surface of the structural member of the plasma processing chamber 61 is exposed to plasma and easily degraded, so that a protective film 50 is formed. Specifically, the protective film 50 including the yttrium oxide film in a semi-molten state explained in the first embodiment is formed on the surface of the support table 21 on the side on which the wafer 100 is placed, the surface of the insulator ring 22, the surface of the focus ring 23, the surface of the baffle plate 24 on the plasma processing chamber 61 side, the surface of the shower head 41 on the plasma processing chamber 61 side, the surface of the deposition shield 45 on the plasma processing chamber 61 side, and the surface of the shutter 46 on the plasma processing chamber 61 side.
FIG. 8A and FIG. 8B are diagrams illustrating one example of the configuration of the shower head coated with the protective film in the second embodiment, in which FIG. 8A is a plan view and FIG. 8B is a schematic cross-sectional view near a gas ejection port formed region. In this example, the shower head 41 as a gas supplying member has a disk shape and the gas ejection ports 42, which penetrate through the plate-shaped member in the thickness direction, are provided in a predetermined range from the center of the shower head 41. The entire surface of one main surface of the shower head 41, that is, the surface on the side exposed to plasma during the plasma process in the plasma processing apparatus 10 is coated with the protective film 50.
The gas ejection port 42 typically has a diameter of about a few hundred μm to a few mm and has a complex cross-sectional shape in a longitudinal direction of the hole so that process gas can be supplied uniformly and stably in the chamber 11. Therefore, if the protective film 50 is formed near the gas ejection ports 42, stress is concentrated in a portion having a large curvature, so that a crack is easily generated. Moreover, the shower head 41 also functions as an upper electrode, and when the gas ejection ports 42 are provided in such an electrode, an electric field is concentrated in a portion having a large curvature, so that a particularly-high plasma resistance is required.
Thus, the surface of the shower head 41 including the gas ejection ports 42 is coated with the protective film 50 formed of the yttrium oxide film formed by the impact sintering method shown in the first embodiment, so that the protective film 50, which has improved plasma resistance and is not easily peeled off, can be obtained on the surface of the shower head 41. Moreover, as explained in the first embodiment, the area ratio of yttrium oxide particles whose grain boundary cannot be confirmed is set to 20 to 100% and the area ratio of yttrium oxide particles whose grain boundary can be confirmed is set to 80 to 0%, so that adjacent particles are bonded together, enabling to obtain the dense protective film 50 in which particles do not shed easily.
The forming method of the protective film 50 onto the surface of the shower head 41 is similar to the forming method of the protective film 50 by the impact sintering method explained in the first embodiment, and the protective film 50 is formed on the shower head 41 as a processing target with the thickness of 10 to 200 μm. The gas ejection port 42 includes a first hole 421, which penetrates through the plate-like shower head 41 in its thickness direction with a predetermined diameter, and a second hole 422 whose opening diameter gradually increases toward the plasma processing chamber 61 side from the first hole 421, and the protective film 50 is formed from the surface (main surface) of the shower head 41 on the side facing the plasma processing chamber 61 to the inner wall of the second holes 422. However, the first holes 421 are approximately vertical to the formation surface of the gas ejection ports 42 of the shower head 41, so that substantially no protective film 50 is formed on the inner wall of the first holes 421. Moreover, the thickness of the protective film 50 formed on the surface of the second hole 422 gradually increases in a direction in which the opening diameter increases from near the boundary with the first hole 421 and becomes substantially a uniform thickness in a region in which the gas ejection port 42 is not formed.
FIG. 9A and FIG. 9B are perspective views illustrating one example of the configuration of the deposition shield coated with the protective film in the second embodiment. As shown in FIG. 9A, the deposition shield 45 as an inner wall protective member has a cylindrical shape to fit in the inner wall of the plasma processing chamber 61 portion of the chamber 11. A support member 451 fixable to the sidewall of the chamber 11 is provided on one end portion of the cylindrical member in a height direction. Moreover, an opening 452 is provided also in the deposition shield 45 to match the formation position of the opening 15 of the chamber 11. As shown in FIG. 9B, the shutter 46 is provided to fit in the opening 452. In this embodiment, the shutter 46 is configured to be slidable in the height direction of the cylindrical member. The protective film 50 is provided on the inner side surface of the deposition shield 45 including the shutter 46.
In this manner, the etching resistance of the deposition shield 45 improves by forming the protective film 50 on the deposition shield 45, so that the frequency of replacement of the deposition shield 45 can be reduced.
FIG. 10A and FIG. 10B are diagrams illustrating one example of the configuration of the insulator ring coated with the protective film in the second embodiment, in which FIG. 10A is a perspective view and FIG. 10B is a cross-sectional view. As shown in FIG. 10A and FIG. 10B, the insulator ring 22 is, for example, formed of quartz (SiO₂) having a circular ring shape. The insulator ring 22 includes a lower cutout portion 221, which is provided on the lower side to cover the outer periphery of the support table 21 and to be fixed at a step portion provided on the outer periphery of the support table 21, and an upper cutout portion 222 provided on the upper side to fix the focus ring 23. The protective film 50 is formed from an upper surface portion 223 to a side surface portion 224 excluding the upper cutout portion 222. For example, the protective film 50 can be provided from the upper surface portion 223 to the side surface portion 224 with a uniform thickness.
In FIG. 8A to FIG. 10B, the shower head 41, the deposition shield 45, and the insulator ring 22 are exemplified, however, the protective film 50 can be formed by the impact sintering method in the similar manner also on a portion exposed to plasma during the plasma process among structural members of the plasma processing apparatus.
FIG. 11 is a diagram illustrating the degree of the particle shedding rate of the protective film in the second embodiment. In this embodiment, after attaching Scotch tape to the protective film 50, the tape is peeled, the tape is subjected to SEM observation and an area of yttrium oxide particles forming the protective film 50 present in a field of view of 80 μm×60 μm is measured, and the particle area per unit area remained on the peeled side is obtained as the particle shedding rate. In this embodiment, measurement is performed on an yttrium oxide film A formed by the method in the first embodiment and an yttrium oxide film B formed by a thermal spray method. Consequently, whereas the particle shedding rate of the yttrium oxide film B formed by a thermal spray method as a typical method of forming an yttrium oxide film is 1.664%, the particle shedding rate of the yttrium oxide film A is 0.033%. That is, in the protective film 50 that uses the yttrium oxide film A in the present embodiment, adhesion to a film formation target is effectively improved compared with a thermally sprayed film.
FIG. 12 is a diagram illustrating the degree of the etching rate of the protective film in the second embodiment. Structural members on which the yttrium oxide films A and B are formed are arranged in an RIE apparatus, etching is performed for a predetermined time, and thereafter, an etching degree (for example, weight loss) is measured, thereby obtaining the etching rate of the protective film 50. In this embodiment, the etching rate with reference to the yttrium oxide film B is shown. As shown in this figure, it is found that in the protective film 50 in which the yttrium oxide film A in the present embodiment is used, the etching rate is low compared with the yttrium oxide film B formed by using a conventional thermal spray method, so that the etching resistance is improved.
As above, according to the second embodiment, adhesion and the etching resistance can be improved compared with a protective film by a conventional thermal spray method by applying the protective film 50 including yttrium oxide particles formed by the impact sintering method to structural members of the plasma processing apparatus. Consequently, the life of the structural members of the plasma processing apparatus can be prolonged, so that the effect of lowering the manufacturing cost of semiconductor devices manufactured by the plasma processing apparatus is obtained.
Moreover, an RIE apparatus is exemplified as the plasma processing apparatus in the above, however, it is not limited thereto and the protective film 50 in the above embodiments can be applied to any apparatus that performs a process by generating plasma or radicals, such as a plasma enhanced CVD (Chemical Vapor Deposition) apparatus.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

Claims

1. A plasma processing apparatus that includes a process target holding portion that holds a process target in a chamber and a plasma generating unit that turns gas introduced into the chamber into plasma, and processes the process target by using generated plasma, wherein

an yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber on a generation region side of plasma generated in the plasma generating unit, and

the yttrium oxide film includes yttrium oxide particles, has a film thickness of 10 μm or more and 200 μm or less, has a film density of 90% or more, and is such that yttrium oxide particles, which are present in a unit area 20 μm×20 μm and whose grain boundary is confirmable, are 0 to 80% in area ratio and yttrium oxide particles, whose grain boundary is not confirmable, is 20 to 100% in area ratio.

2. The plasma processing apparatus according to claim 1, wherein the plasma generating unit is a plate-like gas supplying member that is arranged to face the process target holding portion, supplies the gas to a side of the process target holding portion via a gas ejection port, and functions as an electrode that turns the gas into plasma.

3. The plasma processing apparatus according to claim 2, wherein

the gas supplying member includes a gas ejection port that includes a first hole having a first diameter and a second hole, which is connected to one end portion of the first hole, whose opening diameter increases from the end portion to be a second diameter larger than the first diameter, and which is provided on one main surface side of the gas supplying member, and

the yttrium oxide film is provided on a surface forming the second hole and the one main surface of the gas supplying member.

4. The plasma processing apparatus according to claim 1, further comprising a tubular inner wall protective member provided to be fitted in an inner wall of the chamber exposed to the plasma generation region, wherein

the yttrium oxide film is formed on a surface of the inner wall protective member on the plasma generation region side.

5. The plasma processing apparatus according to claim 4, wherein

the inner wall protective member includes a shutter that openably covers an opening provided to move the process target between an inside and an outside of the chamber, and

the yttrium oxide film is formed also on a surface of the shutter on the plasma generation region side.

6. The plasma processing apparatus according to claim 1, wherein

the process target holding portion includes

a support member that holds the process target and functions as an electrode that turns the gas into plasma, and

an insulator ring that is provided to cover a side surface of the support member and is formed of a dielectric material, and

the yttrium oxide film is provided on an upper surface and an outer peripheral portion of the insulator ring to be the plasma generation region side.

7. The plasma processing apparatus according to claim 6, wherein

the process target holding portion includes a focus ring that is arranged around the process target placed on the support member and is formed of a conductive material, and

the yttrium oxide film is provided on a surface of the focus ring on the plasma generation region side.

8. The plasma processing apparatus according to claim 1, further comprising a baffle plate that connects an outer periphery of the process target holding portion and a sidewall of the chamber, and includes a gas exhaust hole from which gas on the plasma generation region side is exhausted, wherein

the yttrium oxide film is provided on a surface of the baffle plate on the plasma generation region side.

9. The plasma processing apparatus according to claim 1, wherein the yttrium oxide particles are yttrium oxide particles whose purity is 99.9% or more.

10. The plasma processing apparatus according to claim 1, wherein the yttrium oxide film has a film thickness of 10 to 200 μm and a film density of 99% or more and 100% or less.

11. The plasma processing apparatus according to claim 1, wherein the yttrium oxide particles whose grain boundary is confirmable have an average particle diameter of 2 μm or less.

12. The plasma processing apparatus according to claim 1, wherein an average particle diameter of the yttrium oxide particles is 5 μm or less.

13. The plasma processing apparatus according to claim 1, wherein, when an XRD analysis is performed on the yttrium oxide film, a ratio Im/Ic is 0.2 to 0.6, where Ic is a strongest peak of a cubic crystal and Im is a strongest peak of a monoclinic crystal.

14. The plasma processing apparatus according to claim 1, wherein a surface roughness Ra of the yttrium oxide film is 3 μm or less.

15. The plasma processing apparatus according to claim 1, wherein the yttrium oxide film is formed on an inner wall of the chamber and a surface of a structural member in the chamber via an aluminum oxide film.

16. The plasma processing apparatus according to claim 15, wherein the aluminum oxide film has an a structure.