Plasma processing apparatus and plasma generating apparatus
The invention provides an ICP source plasma processing apparatus having improved the uniformity and ignition property of plasma. A plasma processing apparatus for generating plasma in a vacuum processing chamber to subject a sample to plasma processing, comprising multiple sets (7-1 through 7-4 and 7′-1 through 7′-4) of high frequency induction antennas for forming an induction electric field rotating in a right direction on an ECR plane of the magnetic field formed in the vacuum processing chamber, wherein the phases of currents supplied to the respect sets of high frequency induction antenna elements 7-1 through 7-4 and 7′-1 through 7′-4 are controlled so that the corresponding elements are provided with currents of the same phase, according to which plasma is generated via electron cyclotron resonance (ECR).
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The present application is based on and claims priorities of PCT international application No. PCT/JP2009/050428 filed Jan. 15, 2009 and Japanese patent application No. 2009-091761 filed on Apr. 6, 2009, the entire contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION1. Field of the Invention
The present invention relates to a plasma processing apparatus and a plasma generating apparatus using inductively coupled electron cyclotron resonance plasma. Specifically, the present invention characterizes in the structure of a high frequency induction antenna and the structure of a plasma reactor of the plasma processing apparatus and the plasma generating apparatus using inductively coupled electron cyclotron resonance plasma.
2. Description of the Related Art
In response to the miniaturization of semiconductor devices, the process conditions for realizing a uniform processing result within the wafer plane (process window) in plasma processing has become narrower year after year, and there are demands to control the process conditions more accurately in current plasma processing apparatuses. In order to respond to these demands, an apparatus capable of controlling the distribution of plasma, the dissociation of process gas and the surface reaction within the reactor with extremely high accuracy is required.
Currently, the typical plasma source used for such plasma processing apparatus is an inductively coupled plasma (hereinafter referred to as ICP) source. According to the ICP source, at first, a high frequency current I supplied to the high frequency induction antenna generates an induction magnetic field H around the antenna, and the induction magnetic field H creates an induction electric field E. At this time, when electrons exist in the space in which plasma should be generated, the electrons are driven by the induction electric field E, so as to ionize the gas atoms (molecules) and generate ion-electron pairs. The electrons thus formed are re-driven with the original electrons by the induction electric field E, by which further ionization is promoted. Finally, electron avalanche of the ionization phenomenon occurs, and plasma is generated. The area in which the density of plasma is highest is the space within the plasma generation space where the induction magnetic field H and the induction electric field E are strongest, that is, the space nearest the antenna. Further, the intensity of induction magnetic field H and induction electric field E attenuates by double the distance from a path of the current I flowing in the high frequency induction antenna. Therefore, the intensity distribution of the induction magnetic field H or the induction electric field E, consequently the plasma distribution, can be controlled via the shape of the antenna.
As described, the ICP source generates plasma by the high frequency current I flowing in the high frequency induction antenna. Generally when the number of turns of the high frequency induction antenna is increased, the inductance will rise and the current will drop, but the voltage will rise. When the number of turns is reduced, the voltage will drop but the current will rise. In designing the ICP source, the preferable level of current and voltage is determined not only from the viewpoint of uniformity, stability and generation efficiency of plasma, but also from various viewpoints of mechanical and electrical engineering. For example, the increase of current causes problems such as heating, power loss, and current-proof property of the variable capacitor used in the matching circuit. On the other hand, the increase of voltage causes problems such as abnormal discharge, influence of capacitive coupling of the high frequency induction antenna and plasma, and the dielectric-strength property of the variable capacitor. Therefore, designers of ICP sources must take into consideration the current-proof property and the dielectric-strength property of the electric elements such as the variable capacitors used in the matching circuit, the cooling of the high frequency induction antenna and the abnormal discharge thereof, upon determining the shape and number of turns of the high frequency induction antenna.
Such ICP source is advantageous in that the intensity distribution of the induction magnetic field H and induction electric field E created by the antenna, that is, the distribution of plasma, can be controlled via the turns and shapes of the high frequency induction antenna. Various design efforts of ICP sources have been provided.
One practical example is a plasma processing apparatus capable of processing a substrate placed on a substrate electrode using the ICP source. In the disclosed plasma processing apparatus, a portion of or all the high frequency induction antenna is formed of a multi-spiral shaped antenna so as to achieve a more uniform plasma, and deterioration of power efficiency via a matching parallel coil of the matching circuit for the high frequency induction antenna is minimized so as to reduce temperature rise (refer for example to patent document 1).
Further, an arrangement in which a plurality of identical high frequency induction antennas are disposed in parallel at fixed angular intervals has been proposed. For example, three high frequency induction antennas are disposed at angles of 120°, according to which the circumferential uniformity can be improved (refer for example to patent document 2). The disclosed high frequency induction antennas are wound vertically, wound in a plane, or wound around a dome. As disclosed in patent document 2, when a plurality of identical antenna elements are connected in parallel in the electric circuit, there is an advantage in that the total inductance of the high frequency induction antennas composed of a plurality of antenna elements is reduced.
Further, the high frequency induction antenna is arranged by connecting two or more identical antenna elements in parallel in the electric circuit, and the center of the antenna elements is arranged concentrically or radially so that their center coincide with the center of the object being processed, and the input terminals of the respective coil elements are disposed at fixed angular intervals obtained by dividing 360° by the number of coil elements, wherein the coil elements have three-dimensional structures extending in the radial and height direction (refer for example to patent document 3).
With respect to the ICP source, an electron cyclotron resonance (hereinafter referred to as ECR) plasma source is a plasma generating apparatus utilizing the resonant absorption of electromagnetic waves via electrons, characterized in that it has high absorption efficiency of electromagnetic energy, superior ignition property, and that a high density plasma can be obtained. Currently, apparatuses utilizing microwaves (2.45 GHz) or electromagnetic waves in the UHF or VHF band are developed. In many cases, radiation of electromagnetic waves into the discharge space is performed by adopting non-electrode discharge using waveguides for microwaves (2.45GHz), and adopting parallel plate capacitively coupled discharge applying capacitive coupling of plasma and electrodes radiating electromagnetic waves for UHF and VHF.
A plasma source utilizing the ECR phenomenon adopting high frequency induction antennas is also proposed. According to this plasma source, plasma is generated via waves called whistler waves which are a type of waves accompanying ECR phenomenon. Whistler waves are also called helicon waves, and the plasma source utilizing such waves is also called a helicon plasma source. One example of the arrangement of a helicon plasma source includes winding a high frequency antenna around the side wall of a cylindrical vacuum reactor, and applying a relatively low frequency, such as a high frequency power of 13.56 MHz, to the antenna, and further applying a magnetic field. At this time, the high frequency induction antenna generates electrons rotating in a right direction during a half cycle of the single cycle of 13.56 MHz, and generates electrons rotating in a left direction during the remaining half cycle. Of the two types of electrons, the mutual action between electrons rotating in the right direction and the magnetic field causes ECR phenomenon. However, the helicon plasma source is not suited for industrial use, since it has the following drawbacks: the time in which the ECR phenomenon occurs is limited to the half cycle of the high frequency, the place in which ECR occurs is diffused and the absorption length of the electromagnetic waves is long, so that a long cylindrical vacuum reactor is required, making it difficult to obtain uniform plasma, and the plasma property changes in steps in addition to the use of a long vacuum reactor, so that it is difficult to control the plasma to have a desirable plasma property (such as the electron temperature and the dissociation of gas).
A vertically long vacuum reactor specific for use with a helicon plasma source has been proposed (for example, refer to patent document 5). However, according to the art disclosed in the document, there is no use of high frequency induction antennas, and the helicon waves are generated via a method for controlling the phase of the voltage applied to a patch electrodes capacitively coupled with plasma. Further, in order to compensate for the drawback of the above-mentioned controllability of plasma distribution, two or more groups of electrodes are disposed along the vertically long vacuum reactor with an interval therebetween corresponding to the function of the helicon wave wavelength. However, regardless of whether an inductively coupled antenna or capacitively coupled patch electrodes are used, as long as helicon waves are used, the vertically long vacuum reactor must be used, by which the controllability of the plasma is deteriorated. This drawback is reflected clearly in patent document 5. In order to improve the controllability of plasma using the vertically long vacuum reactor, it is necessary to provide an extremely complex electrode and magnetic field arrangement, which is also reflected clearly in patent document 5.
There are many ways to create a rotating electric field in order to generate electrons rotating in the right direction. A simple method using patch antennas as disclosed in patent document 5 has been known for a long time, wherein n-number of (for example, 4) patch-like (small planes having circular or rectangular shapes) antennas are arranged on a circumference, and voltages having a frequency of the electromagnetic waves to be irradiated are supplied to the antennas so that the phases thereof are sequentially displaced by n/n (for example, n/4); according to which circularly polarized electromagnetic waves rotating in the right direction cab be irradiated.
At first, a method for actively generating an electric field rotating in the right direction will be described. When an active antenna exists, both a near field (both the electric field and the magnetic field) and a far field (electromagnetic waves) are formed around the antenna. The type and the intensity of the fields to be generated depends on the design and the way of use of the antenna. At this time, when the plasma and the antenna are capacitively coupled, the main process of power transportation to the plasma will be the electric field (near field). Further, when the plasma and the antenna are inductively coupled, the main process of power transportation to the plasma will be the magnetic field (near field). If neither capacitive coupling nor inductive coupling are performed actively, the main process of power transportation to the plasma will utilize far field. The following illustrates a method for generating an electric field rotating in the right direction using an electromagnetic wave radiation, an electric field and a magnetic field.
- (1) Electromagnetic Wave Radiation (Far Field)
Far field refers to electromagnetic waves that can be propagated to a far distance. This method includes a case where an electromagnetic field having actively circularly-polarized waves rotated in the right direction is discharged into the generation space of plasma, and a case where the electromagnetic field does not have actively circularly-polarized waves rotated in the right direction but utilizes the circularly-polarized waves rotating in the right direction included in the electromagnetic waves. The method for arranging n-number of patch antennas as described is an example of the former case, and the prior art non-electrode ECR discharge using microwaves is an example of the latter case. The plasma and the antenna are not actively coupled so that the near field will not get in the way. The irradiated electromagnetic waves are simply entered to the plasma. General antennas such as patch antennas and dipole antennas (refer to patent document 4: however, the art does not actively rotate the electromagnetic field in the right direction) can be used. According to this method, the following (A), (B) and (C) can be said.
- (A) Power is applied to the antenna (electrode). In order to enhance the radiation efficiency of the electromagnetic field, in many cases, the resonance of antenna is utilized actively. When resonance is not used, the radiation efficiency of electromagnetic waves is not good, so it is not preferable for practical use. The radiated electromagnetic waves do not actively head toward the plasma (basically, the electromagnetic waves are propagated to a far distance, so that they are oriented to various directions), so they are not efficiently absorbed by plasma, and they cannot be used to transfer a large amount of power. In order to transfer a large amount of power, a waveguide in which the direction of propagation of the electromagnetic waves is restricted is mainly used. However, the size of the waveguide is determined by the wavelength of the electromagnetic waves, so that when a frequency smaller than microwaves is used, the size of the waveguide will be too large, so the application of waveguides is limited.
- (B) When an electrode (antenna) is used instead of the waveguide, a terminal for applying power to the electrode is provided. A terminal for grounding the electrode may or may not be provided. This is determined by the method in which the resonance of antennas is generated.
- (C) Regardless of whether antennas are provided, the limit of penetration of electromagnetic waves radiated into plasma is determined by the cutoff density nc (m−3), and in this case, the electromagnetic waves penetrate through the plasma to the skin depth. The skin depth is 138 mm when the frequency is 200 MHz and the resistivity of plasma is 15 ωm, which is greater by some digits than the sheath (which is a few mm or smaller). In other words, it penetrates further into the plasma compared to the case of capacitive coupling mentioned later.
The relationship between the frequency f of electromagnetic waves and the cutoff density nc is illustrated in
- (2) Electric Field (Near Field)
In order to generate an electric field, an active electrode generating near field (electric field) is required, such as patch electrodes (refer for example to patent document 5) and parallel plate electrodes. In this case, the electric field (voltage generated in the electrode) must be strong (high), so the load of the electrode must be set to high impedance. In other words, the electrode used here must be designed to be capacitively coupled with plasma, but to not be coupled with earthed components as much as possible. In other words, it is generally not possible to earth even a portion of the electrode, or to earth the same by connecting a capacitor or a coil thereto. The electric field is a near field, so by devising the positional relationship between the electrode and plasma, it is possible to transfer a large amount of power efficiently to plasma, but in order to enhance capacitive coupling, it must have a sufficiently large area (a large electrostatic capacity) with respect to plasma. The capacitive coupling of the electrode and plasma is used, so not only antennas (electrodes capable of irradiating electromagnetic waves) but electrodes (equivalent to electrodes of a capacitively coupled parallel plate plasma source) simply generating an electric field (near field) can be used even when its ability to radiate electromagnetic waves is weak.
The following can be said with respect to this method.
- (A) A voltage is applied to the electrode. When the circularly-polarized waves rotating in the right direction is actively used, the voltage must be phase-controlled.
- (B) The electrode only includes a terminal for applying voltage, and does not include other terminals such as a terminal for grounding the electrode.
- (C) The capacitively coupled electric field is shielded by the collective motion of electrons (sheath). In order to reduce such shield, a magnetic field perpendicular to the electric field in a sheath must be applied to restrict the electron motion. In other words, by restricting the electron motion, the wavelength of the electric field within the plasma is extended.
- (D) According to the art disclosed in patent document 5, it can be concluded that an electrode capacitively coupled with plasma is used, based on the following arguments.
- (D-1) Voltage is utilized as high frequency signals. This means that the high frequency energy is converted directly to voltage or electric field and transmitted to the plasma. This means that the electrode is capacitively coupled with plasma. Further, when inductive coupling is used, current must be used as high frequency. This is because inductive coupling is performed via induction magnetic field, and the induction magnetic field is generated not via voltage but via high frequency current.
- (D-2) The document discloses a shielding phenomenon caused by electron motion, which means that the electrode is capacitively coupled with plasma. This describes that the shielding can be reduced via static magnetic field, which is possible only when the electrode is capacitively coupled with plasma. This is because it is impossible to change the skin depth via static magnetic field. High frequency induction magnetic field can only be reduced via high frequency induction magnetic field, and cannot be reduced via static magnetic field. This is because a magnetic field has a physical quantity capable of being subjected to addition and subtraction, but it is impossible to reduce the high frequency induction magnetic field (in other words, a variable value) via a static magnetic field (in other words, a constant value). The skin effect of plasma itself is the shielding effect of high frequency magnetic field components included in the electromagnetic field, and the skin effect itself is brought about by the high frequency induction magnetic field (which has an opposite polarity as the induction magnetic field being applied via current, so through addition, it reduces the induction magnetic field being generated by current) generated in the plasma.
- (D-3) It is disclosed that the electrode used in patent document 5 is not an antenna. This means that the electrode being used mainly utilizes a near field. In other words, it is either an induction electric field or an induction magnetic field described hereafter.
- (D-3-1) Patent document 5 discloses using patch-like electrodes having small areas in which the efficiency of radiating electromagnetic waves is not good. This means that the used electrode mainly utilizes the near field, and therefore, it is either an induction electric field or an induction magnetic field described hereafter. However, in the case of an electric field, a wide area (large electrostatic capacity) is required to increase the coupling with plasma, whereas in the case of a magnetic field, a path for supplying current must be provided longitudinally in parallel with plasma in order to realize transformer-coupling (inductive coupling). Patent document 5 only realizes capacitive coupling based on the shape of the electrode. There is no description nor drawing indicating that the patched electrodes are earthed. As described in (D-3-2), the size of the patch-like electrode is shorter than the wavelength of the high frequency, and the voltage generated in the patch-like electrode is varied by the frequency of the applied high frequency, but instantaneously, a constant voltage not being influenced by the wavelength is generated through the whole electrode, and a constant current is flown therein. The patch electrodes create as near field both intense induction electric field and weak induction magnetic field, but in that case, the induction electric field has an area capacitively coupled strongly with plasma, but the patch electrodes do not have a path length enabling to perform transformer-coupling strongly with plasma.
- (D-3-2) An example using 13.56 MHz is disclosed, but the wavelength of 13.56 MHz is approximately 22 m, and the patched electrodes in the drawing cannot be considered as being resonant with this wavelength (if it is resonating, the size of the electrode must be ½ or ¼ of the wavelength, and resonance will not occur if no active resonating means as shown in patent document 4 is applied. Further, there is a description that the electrode is not an antenna, so the patch electrode cannot be considered to be resonating). Further, there is no plasma processing apparatus capable of performing determined processes for forming semiconductor devices requiring such a large electrode. This means that the utilized electrodes mainly use near field (either induction electric field or induction magnetic field described later). However, in the case of electric fields, a wide area (large electrostatic capacity) is required to enhance coupling with plasma, whereas in the case of magnetic fields, a path for supplying current must be formed longitudinally in parallel with plasma for realizing transformer-coupling (inductive coupling). The shape of the electrodes is patch-like, and there is no current path for realizing the transformer-coupling with plasma. In other words, the patch-like electrodes are capacitively coupled with plasma.
- (D-3-3) Further, there is no description that the patch-like electrode is earthed. According thereto, the current flowing through the patch-like electrodes is flown via the plasma to an earth. In other words, plasma is the load of the patch-like electrodes, and the current varies greatly by the impedance of the generated plasma. As known well, in inductively coupled plasma, current is basically supplied to one end of the path being inductively coupled with plasma, while the other end is earthed. Accordingly, current flowing in the path is mainly directly supplied to the earth, and a large current is generated by the earth (low impedance of load). The large current is used to generate the induction magnetic field, through which power can be transferred efficiently to plasma. Of course, it is possible to separate the earth end from the earth and to insert a capacitor, but it still offers power to be transferred efficiently to plasma by generating an intense induction magnetic field by the large current generated by devising electric circuits. In other words, since the document lacks to provide any description nor drawings that the patched electrodes are earthed, it means that the patched electrode is mainly capacitively coupled with plasma.
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- [Patent document 1] Japanese patent application laid-open publication No.08-083696
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- [Non-Patent Documents]
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Regarding the prior art of generating an electric field rotating in the right direction, there has not been an art to create an electric field actively rotating in the right direction using an induction magnetic field (near field). Even further, there has not been developed an art to cause ECR phenomenon using the induction electric field actively rotating in the right direction crated via an induction magnetic field. The induction magnetic field is generated via current, so a completely reverse design with respect to using electric field is required. In other words, the use of induction magnetic field requires an active electrode for generating an intense near field (magnetic field), and the current must be strong, so that the load of the electrode must be of low impedance. In other words, the electrode used here must be inductively coupled (transformer-coupled) with plasma, and it must be actively earthed or earthed via capacitors or coils. The use of induction magnetic field is near field, so by devising the positional relationship with plasma, a large power can be transferred efficiently to plasma. According to this method, in order to strengthen inductive coupling, a path length (coil length) sufficient for coupling with plasma is required. This method utilizes the induction coupling of electrode and plasma (transformer-coupling), so it is possible to use not only antennas (electrodes capable of radiating electromagnetic waves) but also electrodes (coils) merely generating magnetic field (near field) having a weak ability to irradiate electromagnetic waves. The following can be said for the present method.
- (A) A phase-controlled current is applied to the electrode.
- (B) The electrode has a terminal for applying current and another terminal for actively supplying a large current from the electrode to an earth portion. This terminal is either earthed directly or earthed via capacitors or coils.
- (C) The inductively coupled electric field is shielded via skin effect similar to far field. This shield cannot be prevented via static magnetic field.
In an ICP source, when a high frequency current I is circulated around a high frequency induction antenna, it is flown into the plasma or earth via floating capacity and causes loss. This can cause the induction magnetic field H to have various intensity distributions in the circumferential direction, and as a result, a phenomenon where the uniformity of plasma in the circumferential direction is deteriorated may become significant. This phenomenon, which is a wavelength shortening phenomenon that appears as a reflected wave effect or a skin depth effect, not only influenced by the permittivity of the space surrounding the high frequency induction antenna but the magnetic permeability thereof. This phenomenon is a general phenomenon that occurs also in normal high frequency transmission cables such as coaxial cables, but when the high frequency induction antenna is either inductively coupled or capacitively coupled with plasma, the wavelength shortening effect thereof will appear more significantly. Further, not only in ICP sources but in general plasma sources such as the ECR plasma sources or the parallel plate capacitively coupled plasma sources, the traveling waves traveling toward the antenna or the interior of the vacuum reactor and the reflected waves are superposed to generate standing waves in the space surrounding the antenna irradiating high frequencies. This is caused by the reflected waves being reflected from the antenna terminal portion, the plasma and many portions in the vacuum reactor in which the high frequencies are irradiated. The standing waves also relate significantly to the wavelength shortening effect. In this state, in the case of ICP sources, even if a frequency of 13.56 MHz having a long wavelength of approximately 22 m is used as the radio frequency of the RF power supply, if the high frequency induction antenna length exceeds 2.5 m, standing waves accompanying a wavelength shortening effect are generated in the antenna loop. Therefore, the current distribution within the antenna loop becomes uneven, and the plasma density distribution also becomes uneven.
In an ICP source, the high frequency current I flowing in the antenna has its phase or direction of flow reversed periodically, and along therewith, the direction of the induction magnetic field H (induction electric field E), that is, the direction in which the electrons are driven, is also reversed. In other words, the electrons temporarily stop and then are accelerated in the opposite direction per every half cycle of the applied high frequency. According to such condition, when electron avalanche ionization during a certain half cycle of the high frequency is insufficient, it is difficult to obtain a sufficiently high density plasma when the electrons are temporarily stopped. This is because when the electrons are decelerated and temporarily stopped, the generation efficiency of plasma drops. Generally, as described earlier, the ignition property of plasmas not good according to the ICP source compared to the ECR plasma source or the capacitively coupled parallel plate plasma source. The generation efficiency of plasma is deteriorated every half cycle of high frequency waves in the same manner also according to a helicon plasma source using inductive coupling without being phase-controlled.
As described, there are many devices for improving the plasma uniformity using the ICP source, but the devising thereof causes the arrangement of the high frequency induction antenna to become complex, and will not work out as industrial apparatus. Further, the prior art is not intended to significantly improve the ignition property of plasma while maintaining a good plasma uniformity, and therefore, the problem of inferior ignition property is not solved.
On the other hand, the ECR plasma source has a shortwave length, and a complex electric field distribution is easily generated within the apparatus, so it is difficult to achieve a uniform plasma.
Since the wavelength of microwaves (2.45 GHz) is short, in large-scale ECR plasma source, the microwaves are propagated within the discharge space via various high order propagation modes. Thus, electric fields are locally concentrated at various locations within the plasma discharge space, and high density plasma occurs at these portions. Further, microwaves reflected at the interior of the plasma apparatus and returning thereto are superposed with the electric field distribution by the high order propagation mode of incident microwaves by which standing waves are generated, so that the electric field distribution within the apparatus may become more complex. By the above two reasons, it is generally difficult to obtain a uniform plasma property within a large diameter area. Further, once such complex electric field distribution occurs, it is actually impossible to control the electric field distribution and to change the same to an electric field distribution preferable for processing. This is because the structure of the apparatus must be changed so as not to cause high order propagation modes or to prevent reflected waves reflected and returning from the interior of the apparatus from forming a complex electric field distribution. A single apparatus structure almost never corresponds suitably to various discharge conditions. Further, in order to generate ECR discharge via microwaves (2.45 GHz), a magnetic field as intense as 875 Gauss is required, and the structure including power consumed by the coils generating such magnetic field and yoke becomes extremely large.
Further, regarding magnetic field intensity, relatively weak magnetic field is required for UHF and VHF, so that the significance of the problem is relieved. However, even by using UHF or VHF having a relatively long wavelength, the problem of standing waves is serious, wherein the electric field distribution within the discharge space becomes uneven, the generated plasma density distribution becomes uneven, and the process uniformity becomes a problem. Regarding this problem, theoretical and experimental studies are still performed (for example, refer to non-patent document 1).
As described, according to prior art ICP sources, means for generating plasma with advantageous uniformity have been examined, but such means will require a complex antenna structure, and will deteriorate the ignition property of plasma. On the other hand, ECR plasma sources have advantageous ignition property, but the high-order propagation mode of the electromagnetic waves and the plasma uniformity via standing waves are not good.
The present invention aims at solving the above problems, by providing a plasma processing apparatus using an ICP source in which the ECR discharge phenomenon can be utilized. Thereby, the antenna structure can be optimized via minimum schemes, by which the uniformity of plasma is improved and the ignition property of plasma is significantly improved.
In other words, the present invention provides a uniform plasma source with superior ignition property even in a plasma processing apparatus having a large diameter.
As a first step for solving the problems mentioned above, the present invention provides a plasma processing apparatus comprising a vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a power supply for supplying power to the magnetic field coil having high frequency current supplied to the high frequency induction antenna from the high frequency power supply and having a magnetic field applied thereto so as to turn the gas supplied into the vacuum processing chamber into plasma for subjecting the sample to plasma processing, wherein the vacuum processing chamber comprises a vacuum processing chamber top member fixed air tightly to an upper portion of the vacuum reactor, the vacuum processing chamber top member composed of dielectric material having a planar shape, a hollow semi spherical shape, a rotated trapezoidal shape, or a cylindrical shape with a bottom, and the high frequency induction antenna being divided into n-number (n being an integer of n≧2) of high frequency induction antenna elements, the divided high frequency induction antenna elements being arranged tandemly on a circumference, wherein high frequency currents sequentially delayed by λ (wavelength of the high frequency power supply)/n in a fixed direction with respect to the direction of the line of magnetic force are supplied to the respective high frequency induction antenna elements arranged tandemly. Thereby, a rotating induction electric field E rotating in a right direction with respect to the direction of line of magnetic force of a magnetic field B formed by supplying power to the magnetic field coil is created via the high frequency current, and by the rotating induction electric field, the electrons in the plasma are rotated in the right direction with respect to the direction of the line of magnetic force. At this time, the rotation frequency of the rotation induction electric field E and the electron cyclotron frequency via the magnetic field B are designed to correspond to each other, and plasma is generated by arranging a plurality of antennas and a magnetic field so that the induction electric field E and the magnetic field B arbitrarily satisfy a relationship of E×B≠0.
The second step for solving the problems of the prior art is to further apply a magnetic field B to the electrons rotating in the right direction, to thereby cause Larmor motion of the electrons. Larmor motion is a motion in the right rotational direction based on E×B drift, and in order for this motion to occur, the induction electric field E and the magnetic field B must satisfy a relationship of E×B≠0. The direction of application of the magnetic field B is the direction in which the induction electric field E rotates in the right direction with respect to the direction of the line of magnetic force of the magnetic field B. When these conditions are satisfied, the rotating direction of the induction electric field E in the right direction and the direction of rotation of the Larmor motion correspond. Further, this change of magnetic field B must have a variation frequency fB satisfying a relationship of 2πfB<<ωc with respect to the rotation frequency (electron cyclotron frequency ωc) of the Larmor motion. In addition to applying the magnetic field B, by causing an electron cyclotron resonance phenomenon to occur by having the electron cyclotron frequency ωc of the magnetic field intensity and the rotation frequency f of the rotating induction electric field E corresponding so as to satisfy 2πf=ωc, the above-mentioned problems can be solved.
In order to solve the problems mentioned above, the present invention provides a plasma processing apparatus comprising a cylindrical vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a power supply for supplying power to the magnetic field coil, wherein high frequency current is supplied to the high frequency induction antenna from the high frequency power supply so as to turn the gas supplied into the vacuum processing chamber into plasma for subjecting the sample to plasma processing, wherein the high frequency induction antenna being divided into n-number (n being an integer of n≧2) of high frequency induction antenna elements are arranged tandemly along a circumference being concentrically disposed with the vacuum reactor, high frequency currents sequentially delayed by λ (wavelength of the high frequency power supply)/n are supplied in a fixed direction to the tandemly arranged high frequency induction antenna elements, and power is supplied to the magnetic coil so as to form a magnetic field, by which plasma is generated and the sample is subjected to plasma processing.
Further, the present invention provides a plasma processing apparatus comprising a cylindrical vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a magnetic field coil power supply for supplying power to the magnetic field coil, wherein the high frequency induction antenna being divided into n-number (n being an integer of n≧2) of high frequency induction antenna elements are arranged tandemly along a circumference being concentrically disposed with the vacuum reactor, wherein high frequency currents sequentially delayed by λ (wavelength of the high frequency power supply)/n are supplied in a fixed direction to the tandemly arranged high frequency induction antenna elements, and high frequency currents are supplied to the high frequency induction antenna from the high frequency power supply, so as to turn the gas supplied into the vacuum processing chamber to plasma and to subject the sample to be processed to plasma processing, wherein the high frequency induction antenna and the magnetic field are arranged to satisfy a relationship of E×B≠0 between the induction electric field E generated by the antenna and the magnetic field B.
Further, the present invention provides a plasma processing apparatus comprising a cylindrical vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a magnetic field coil power supply for supplying power to the magnetic field coil, wherein the high frequency induction antenna being divided into n-number (n being an integer of n≧2) of high frequency induction antenna elements are arranged tandemly along a circumference being concentrically disposed with the vacuum reactor, wherein high frequency currents sequentially delayed by λ (wavelength of the high frequency power supply)/n are supplied in a fixed direction to the tandemly arranged high frequency induction antenna elements, and high frequency currents are supplied to the high frequency induction antenna from the high frequency power supply, so as to turn the gas supplied into the vacuum processing chamber to plasma and to subject the sample to plasma processing, wherein the rotation frequency f of the rotating induction electric field E and the electron cyclotron frequency ωc by the magnetic field B are set to correspond so-that 2πf=ωc. Thereby, electrons are capable of absorbing high frequency power by electron cyclotron resonance, and the problems of the prior art can be solved.
Next, the present invention provides a plasma processing apparatus comprising a cylindrical vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a magnetic field coil power supply for supplying power to the magnetic field coil, wherein the high frequency induction antenna being divided into n-number (n being an integer of n≧2) of high frequency induction antenna elements are arranged tandemly along a circumference being concentrically disposed with the vacuum reactor, wherein high frequency currents sequentially delayed by λ (wavelength of the high frequency power supply)/n are supplied in a fixed direction to the tandemly arranged high frequency induction antenna elements, and high frequency currents are supplied to the high frequency induction antenna from the high frequency power supply, so as to turn the gas supplied into the vacuum processing chamber to plasma and to subject the sample to plasma processing, wherein the high frequency induction antenna and the magnetic field are designed so that the direction of rotation of the induction electric field E generated by the antenna is rotated in the right direction with respect to the line of magnetic force of the magnetic field B formed by the magnetic field coil.
Further, the present invention provides a plasma generating apparatus comprising a vacuum processing chamber, and a plurality of high frequency induction antennas disposed outside the vacuum processing chamber to which high frequencies are supplied, wherein the induction electric field distribution formed within the vacuum processing chamber via the plurality of antennas rotates in a fixed direction within a magnetic field having a finite value.
Further, the present invention provides a plasma generating apparatus comprising a vacuum processing chamber, and a plurality of high frequency induction antennas disposed outside the vacuum processing chamber to which high frequencies are supplied, wherein the plurality of antennas are arranged in axial symmetry, the magnetic field distribution has an axially symmetric distribution, the axis of the plurality of antennas and the axis of the magnetic field distribution correspond, and the induction electric field distribution formed within the vacuum processing chamber rotates in a fixed direction.
The present invention further provides a plasma generating apparatus, wherein the direction of rotation of the induction electric field distribution that rotates in the fixed direction is a right direction rotation with respect to the direction of the line of magnetic force of the magnetic field.
The present invention further provides a plasma generating apparatus, wherein the plurality of antennas and the magnetic field are designed so that the induction electric field E formed via the plurality of antennas and the magnetic field B satisfy a relationship of E×B≠0.
The present invention further provides a plasma generating apparatus, wherein the rotation frequency f of the rotating induction electric field E formed via the plurality of antennas and the electron cyclotron frequency ωc via the magnetic field B correspond so that 2πf=ωc.
Further according to the present invention, according to the plasma processing apparatus, the magnetic field B can either be a static magnetic field or a varying magnetic field, but when it is a varying magnetic field, the variation frequency fB thereof must satisfy a relationship of 2πfB<<ωc with the rotation frequency (electron cyclotron frequency ωc) of the Larmor motion.
The plasma processing apparatus according to the present invention is not-restricted to application in the field of semiconductor device fabrication, and it can be applied to various fields of plasma processing, such as for manufacturing liquid crystal displays, for depositing various materials, and for treating surfaces. Here, we will illustrate preferred embodiments of the invention, taking the plasma etching apparatus for manufacturing semiconductor devices as an example.
The outline of the structure of the plasma processing apparatus to which the present invention is applied will be described with reference to
The vacuum reactor 11 is, for example, a vacuum vessel formed of an aluminum having its surface treated with alumite (anodized aluminum) processing or a stainless steel, which is electrically earthed. Further, it is also possible to perform surface treatments other than alumite processing, such as through use of other substances having high plasma resisting property (such as yttria: Y2O3). The vacuum processing chamber 1 comprises an evacuation means 13, and a transfer system 2 with a gate valve for carrying semiconductors W to be processed into and out of the chamber. In the vacuum processing chamber 1 is disposed an electrode 14 for placing thereon a semiconductor wafer W concentrically with the cylindrical vacuum reactor 11, which is positioned concentrically within the cylindrical vacuum reactor 11. The wafer W having been carried into the vacuum processing chamber through the transfer system 2 is carried onto the electrode 14, and fixed to the electrode 14. A bias high frequency power supply 41 is connected via a bias matching box 42 to the electrode 14 with the aim to control the energy of ions being incident on the semiconductor wafer W during plasma processing. The gas to be used for the etching process is introduced into the vacuum processing chamber 1 via the gas inlet port 3.
On the other hand, high frequency induction antenna elements 7-1 (not shown), 7-2, 7-3 (not shown) and 7-4 are disposed in an atmospheric area at a position opposing to the semiconductor wafer W via the vacuum reactor top member 12 formed of a planar insulating material such as quartz or alumina ceramics. The high frequency induction antenna elements 7-1 through 7-4 are disposed concentrically so that the center thereof corresponds to the center of the semiconductor wafer W. Although not shown in
Delay means 6-2, 6-3 (not shown) and 6-4 for delaying the phase of the current flowing to the respective high frequency induction antenna elements 7-1 through 7-4 are disposed between the high frequency induction antenna elements 7-1 through 7-4 and the plasma generating matching box 52.
A refrigerant flow path for cooling means not shown is disposed on the vacuum reactor top member 12, wherein cooling is performed by passing fluids such as water, Fluorinert (registered trademark), air and nitrogen through the refrigerant flow path. The antenna, the vacuum reactor 11 and the wafer stage 14 are also objects of cooling and temperature control.
Embodiment 1With reference to
On the right side of
Now, we will describe what type of induction electric field E is generated in the plasma by the high frequency induction antenna according to the present invention. The description is based on induction electric field E, but a shown in expression (1), the induction electric field E and the induction magnetic field H are mutually exchangeable physical quantities, and are equivalent. First,
Next, we will describe the induction electric field E created by the antenna of the present invention. First, a current state as shown in
As described, the present invention generates an induction electric field distribution having a local peak, but the uniformity of the generated plasma is not deteriorated thereby. First, the induction electric field distribution on the X axis of
Here, through use of upper and lower magnetic field coils 81 and 82 and a yoke 83 illustrated in
The remaining condition is to apply a magnetic field B wherein E×B≠0 with respect to the induction electric field E. This condition of E×B≠0 must be satisfied at some area within the space in which plasma is to be generated, but it is not required to be satisfied in all the space in which plasma is to be generated. There are various methods for applying magnetic field, but unless a magnetic field having a locally complex structure is used, this condition of “E×B≠0” is included in the above-mentioned first condition. According to this condition “E×B≠0”, the electrons perform a rotary motion called a Larmor motion having the line of magnetic force as the guiding center. This Larmor motion is not a rotary motion by the rotating induction electric field mentioned earlier, but is a motion called an electric cyclotron motion. The rotating frequency thereof is called an electron cyclotron frequency ωc, and can be expressed by the following expression (3). In the following expression (3), q represents the elementary charge of electrons, B represents the magnetic field intensity, and mere presents the mass of electrons. The characteristics of the electron cyclotron motion is that the frequency thereof is determined only by the magnetic field intensity.
Expression 3
Now, when the rotation frequency f of the rotating induction electric field E is set to correspond to 2πf=ωc of the cyclotron frequency ωc, electron cyclotron resonance occurs, and the high frequency power supplied to the high frequency induction antenna is absorbed resonantly via the electrons, by which high density plasma can be generated. However, the condition that “the rotation frequency f of the rotating induction electric field E is set to correspond to the cyclotron frequency ωc” is required to be satisfied at some area in the space that plasma is to be generated, but it is not required to be satisfied throughout the whole space in which plasma is to be generated. The generation condition of ECR is represented by the following expression (4) as mentioned earlier.
Expression 4
2πf=ωc (4)
The magnetic field B applied here can be a static magnetic field or a varying magnetic field. However, in the case of a varying magnetic field, the variation frequency fB must satisfy the relationship of 2πfB<<ωc with respect to the Larmor motion rotation frequency (electron cyclotron frequency ωc). What is meant by this relationship is that based on a single cycle of an electron performing electron cyclotron motion, the change of the varying magnetic field is sufficiently small, and that it can be regarded as a static magnetic field.
As described above, the plasma generating ability of electrons can be improved significantly by adopting a plasma heating method called electron cyclotron (ECR) heating. However, considering the desired plasma characteristics in industrial application, it is desirable to optimize the antenna structure so as to control the intensity and distribution of the induction electric field E, and to subject the intensity distribution of the magnetic field B to variable control, in order to create a space satisfying the conditions of the magnetic field B and the frequency at a necessary location within a necessary area, so as to control the plasma generation and the diffusion thereof.
Further, the method for enabling ECR discharge in an ICP source according to the present invention does not depend on the frequency of the used high frequency or the magnetic field intensity, and is adoptable if the conditions described heretofore are satisfied. Of course, regarding engineering applications, there will be limitations on the used frequency and the magnetic field intensity based on actual limitations such as the size of the reactor of the plasma. For example, if the radius rL of the Larmor motion shown in the following expression is greater than the reactor in which the plasma is to be confined, the electrons will collide against the reactor wall without performing cyclic motion, and ECR phenomenon will not occur. In expression (5), v represents the velocity of electrons in the direction horizontal to the plane of the electric field shown in
In this case, of course, it is necessary to increase the frequency of the used high frequency and to increase the magnetic field intensity so that ECR phenomenon occurs. However, the selection of the frequency and magnetic field intensity should be done freely based on the object, and the principle of the present invention itself will not be lost.
Now, the following four points are the necessary and sufficient conditions of the principle enabling ECR discharge to be performed using an ICP source. The first point is to create a distribution of induction electric field E that constantly rotates in the right direction with respect to the direction of the line of magnetic force of the magnetic field B applied to the space in which plasma is to be generated. The second point is to apply a magnetic field B satisfying E×B≠0 with respect to the distribution of induction electric field E that rotates in the right direction with respect to the magnetic field B and the direction of the line of magnetic force thereof. The third point is to match the rotation frequency f of the rotating induction electric field E and the electron cyclotron frequency ωc by the magnetic field B. The fourth point is that the change of magnetic field B is sufficiently small and that it can be regarded as a static magnetic field with respect to a single cycle of electrons performing electron cyclotron motion. The embodiment satisfying the above four points is illustrated in
In
However, from the viewpoint of industrial applicability, the shape of the vacuum reactor top member and the antenna position with respect to the top member have important meanings, since a uniform processing must be performed within the plane of the object W to be processed. In other words, the components of gas species constituting the plasma such as ions and radicals used for processing must form a uniform distribution on the plane of the object W to be processed.
Plasma is generated by the process gas being dissociated, excited and ionized by high energy electrons. The radicals and ions being generated at this time have strong electron energy dependency, and not only the amount of generation but the distribution of generation thereof differ between radicals and ions. Therefore, it is actually impossible to generate radicals and ions with identical distributions. Further, the generated radicals and ions spread via diffusion, but the diffusion coefficients vary between various types of radicals and ions. Especially, the diffusion coefficient of ions is normally greater by a few digits compared to the diffusion coefficient of neutral radicals. In other words, it is actually impossible to realize using diffusion to create a uniform distribution of radicals and ions simultaneously above the object W to be processed. Even further, upon generating plasma using process gas composed of molecules or formed by mixing a large variety of gases, multiple varieties of radicals and ions are generated, so it is even more impossible to realize uniform distribution of all radicals and ions. However, what is important in performing uniform processing is the variety of gas species contributing to advancing the plasma-applied process. For example, if the reaction is mainly progressed via a specific radical, it is important that the distribution of the specific radical becomes uniform. On the other hand, if the reaction is mainly progressed via ion sputtering, it is important that the distribution of the specific ion becomes uniform. Further, the reaction may be progressed by the competition of radicals and ions. In order to cope with such various processes, it is required that the process is advanced by realizing a more desirable uniformity by controlling the distribution and diffusion of the generated plasma.
The present invention provides two types of solutions for the above-mentioned demands. Since according to the present invention, the energy of electrons for generating plasma is determined by E×B, that is, the induction electric field E and the magnetic field B. The first solution relates to the induction electric field E, wherein the shape of the vacuum reactor top member 12 formed of insulating material and the position of the antenna with respect thereto are optimized per process. As mentioned earlier, according to the present invention, the distribution of the generated plasma is determined by the arrangement of the antenna, similar to normal ICP sources. This is because the strongest induction electric field E is formed near the antenna. Furthermore, the distribution of generated radicals and ions can be controlled by the spread of the space defined by the vacuum reactor top member, the object to be processed and the vacuum reactor. This is also closely related to the magnetic field B regarding the second solution, but here, the magnetic field will not be taken into consideration so as to simplify description.
Such control of distribution is enabled by changing the shape of the vacuum reactor top member 12 formed of insulating material.
In the drawing, it is shown that the distributions of ions above the object W to be processed are the same shapes according to
At first, the probability of ions vanishing within the space is extremely small, and the main cause of vanishing is the charge emission at the surface of the wall. In order for ions to vanish in the space, an extremely rare reaction such as colliding against two electrons at the same time (triple collision) is required. Further, there is a limitation that the collision of ions against the wall must be of equal quantity with electrons (quasi-neutrality condition of plasma). However, radicals are neutral excited species, and they lose the inactive energy easily by colliding with a single electron or with other molecules. The opposite case is also possible. Radicals also collide against walls and lose their excitation energy, but the flow-in thereof is unrelated to the quasi-neutrality condition of plasma, and is merely determined by the amount of diffusion to the wall. Of course, as mentioned earlier, the diffusion coefficients of ions and radicals differ greatly. In other words, by changing the volume of the space defined by the vacuum reactor top member 12 formed of insulating material and the vacuum reactor 11 and the surface area thereof, the level of generation area, diffusion and disappearance of radicals with respect to ions can be varied further. As described above, compared to the change from
The second solution is related to the magnetic field B, so as to optimize the generation and diffusion of plasma by variably controlling the shape of the vacuum reactor top member 12 formed of insulating body and the magnetic field distribution thereof. According to the embodiment shown in
An isomagnetic field plane is formed on a plane perpendicular to the line of magnetic force. There are a large number of isomagnetic field planes, one of which is shown as an example in
Next, the effect of combining the variation of the ECR plane and the shape of the vacuum reactor top member is described with reference to
Further, when an ECR plane is formed, the state of diffusion varies compared to when there is no magnetic field. In other words, since the ions and electrons in the plasma are charged particles, they are easily diffused along the magnetic field, and are not easily diffused perpendicularly with respect to the magnetic field. Electrons are diffused along the line of magnetic force in a state where they are wound around the line of magnetic force via Larmor motion, and the ions are diffused in the same direction as the electrons according to the requirement of the quasi-neutrality of plasma. However, since radicals are neutral particles, the diffusion thereof is not affected by the magnetic field. In other words, it can be recognized that the formation of the ECR plane not only changes the area in which the ions and radicals are generated, but also influences the distribution shape of ions and radicals via diffusion. Thus, the magnetic field is an extremely efficient means for controlling the plasma generation distribution and diffusion.
There is one more thing that can be recognized from
As described, the present invention has three kinds of devices for generating, diffusing and extinguishing plasma, that are (1) the antenna structure, (2) the structure of the vacuum reactor top member 12 formed of insulating material, and (3) the magnetic field. These characteristic features were not easily obtained according to prior art plasma sources such as the ICP source, the ECR plasma source or the parallel plane plasma source. Especially, even after determining the apparatus structure such as the antenna structure and the shape of the vacuum reactor top member 12 formed of insulating material, the magnetic field can be changed by varying the currents supplied to the upper and lower magnetic field coils 81 and 82 so as to control the generation area of plasma and the diffusion thereof even more dynamically.
With reference to
A third example of the shape of a vacuum processing chamber top member will be described with reference to
The fourth example of the shape of the vacuum processing chamber top member will be described with reference to
The functions according to these deformation examples are the same as those of the embodiment illustrated in
The following is a description on the shape and the arrangement of the high frequency induction antenna. In
In
In
In
The above-mentioned feature can be utilized to simplify the arrangement of
In
The variation of the power supply arrangement and high frequency induction antenna arrangement is not restricted to such example. For example, the application of the arrangements illustrated in
The next embodiment illustrated in
In other words, the present embodiment relates to a plasma processing apparatus comprising a vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna disposed outside the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, a power supply for supplying power to the magnetic field coil having high frequency current supplied to the high frequency induction antenna and a power supply for supplying power to the magnetic field coil, wherein high frequency power is supplied to the high frequency induction antenna from the high frequency power supply so as to turn the gas supplied into the vacuum processing chamber into plasma for subjecting the sample to plasma processing, characterized in that the high frequency induction antenna is divided into s-number (s being a positive even number) of high frequency induction antenna elements, the respective divided high frequency induction antenna elements being arranged in tandem on a circumference, the tandemly arranged high frequency induction antenna elements receiving supply of high frequency currents that are respectively delayed by λ (wavelength of high frequency power supply)/s in advance by s/2 number of high frequency power supplies sequentially in order from the first high frequency induction antenna element to the s/2nd high frequency induction antenna element, the s/2+1st high frequency induction antenna element to the sth high frequency induction antenna element sequentially receiving supply of high frequency currents with the same phases as the first to s/2nd high frequency induction antenna elements opposed thereto, the high frequency induction antenna elements being arranged so that the direction of currents supplied to the high frequency induction antenna elements is reversed, by which an electric field rotating in a fixed direction is formed to subject the sample to plasma processing, according to which the plasma for subjecting the sample to plasma processing is generated by forming an electric field rotating in a certain direction by supplying currents that are sequentially delayed in the right direction with respect to the direction of the line of magnetic force of the magnetic field formed by supplying power to the magnetic field coils.
As described, though the arrangements disclosed in
As described, when the division number n of the high frequency induction antenna is n=2, the induction electric field E formed via the high frequency induction antenna rotates in the right direction with respect to the direction of the line of magnetic force by applying a magnetic field B satisfying the second content of the aforementioned necessary and sufficient conditions. According to this embodiment, high frequency waves having λ/2 phase differences are supplied to the two high frequency induction antenna elements. The basic arrangement of the present embodiment is shown in
Therefore, as shown in
By adding the effect of
For example, patent document 6 discloses at least three linear conductors arranged radially and at even intervals from the center of the antenna, wherein each linear conductor has one end earthed and the other end connected to an RF high frequency power supply.
In
According to the present invention, the induction electric field E formed via the high frequency induction antenna rotates in the right direction with respect to the direction of the line of magnetic force of the magnetic field. The shape of the rotation plane is determined by the structure of the high frequency induction antenna, and can be circular or oval. Therefore, a center axis of rotation always exists. In industrial application, the magnetic field B, the object to be processed (such as circular wafers and rectangular glass substrates), the vacuum reactor, the gas injection port, the electrode on which the object to be processed is placed, and the evacuation port have center axes. According to the present invention, however, there is no need for the center axes to correspond, and they are not necessary conditions, since they are not related to the aforementioned necessary and sufficient conditions. However, when the uniformity of processing of the surface of the object to be processed (such as etching rate, deposition rate, or profile) becomes an issue, the center axes should preferably correspond.
As described, since according to the present invention a high frequency induction magnetic field for driving currents is constantly formed in the processing chamber, it is possible to improve the ignition property of plasma and to obtain high density plasma. Further according to the present invention, the length of the high frequency induction antenna can be controlled so as to correspond to demands for larger diameters, and to improve the uniformity of plasma in the circumferential direction.
The structure of the high frequency induction antenna from embodiments 1 through 7 can be applied to any shape of the second to fourth vacuum reactor top members 12.
Now, anther embodiment of the present invention will be described. According to the following embodiment of the present invention, multiple sets of high frequency induction antennas composed of a plurality of high frequency induction antenna elements are provided. Here, the number of sets of antennas composed of a plurality of high frequency induction antenna elements constituting a rotating induction electric field E is referred to as m. In the present invention, m can be any natural number. In other words, the antenna divided into multiple parts can be disposed not only on two circumferences but on three or more circumferences.
Embodiment 8 will now be described with reference to
According to the present invention, in a single high frequency induction antenna set, the phase of currents within the set of high frequency induction antennas must be controlled, for example as described in
Embodiment 9 will now be described with reference to
The arrangement of
There are two methods for making the plasma distribution in the circumferential direction more uniform. One method is to earth the earth end B via a capacitor C instead of directly as shown in
Another method is to displace the positions in the circumferential direction of the of the power feed end A and the earth end B of the inner antenna with respect to the circumferential positions of the power feed end A and the earth end B of the outer antenna, in other words, to provide phase angles thereto. In
Embodiment 10 will now be described with reference to
The method for forming a more smooth rotating electric field using the outer antenna 7 and the inner antenna 7′ was described with reference to
Embodiment 11 will be described with reference to
Similar to the example of a planar vacuum reactor top member 12, even if the vacuum reactor top member 12 formed of insulating material has a rotated trapezoidal shape, a hollow semispherical shape or dome shape, or a cylindrical shape with a bottom, the high frequency induction antennas can be disposed at the inner circumference or the outer circumference thereof, or at vertical or oblique positions. As described with reference to
The descriptions regarding
Embodiment 12 of the present invention will be described with reference to
Embodiment 13 of the present invention will be described with reference to
Claims
1. A plasma processing apparatus comprising a vacuum reactor constituting a vacuum processing chamber for housing a sample, a gas supply port for introducing a processing gas into the vacuum processing chamber, a high frequency induction antenna for forming an induction electric field into the vacuum processing chamber, a magnetic field coil for forming a magnetic field within the vacuum processing chamber, a plasma generating high frequency power supply for supplying high frequency current to the high frequency induction antenna, and a power supply for supplying power to the magnetic field coil, wherein high frequency current from the high frequency power supply is supplied to the high frequency induction antenna so as to turn the gas supplied to the vacuum processing chamber into plasma for subjecting the sample to plasma processing, wherein
- the vacuum processing chamber comprises a vacuum processing chamber top member composed of dielectric material fixed air-tightly to an upper portion of the vacuum reactor; and
- the high frequency induction antenna is divided into n (n being an integer of n≧2) high frequency induction antenna elements, the divided high frequency induction antenna elements being arranged tandemly, wherein multiple sets of tandemly arranged high frequency induction antenna elements are provided, high frequency currents sequentially delayed in a fixed direction by λ (wavelength of the high frequency power supply)/n are supplied to the respective high frequency induction antenna elements included in the respective sets of high frequency induction antennas, so as to form via the high frequency currents a rotating induction electric field E rotating in a right direction with respect to a direction of line of magnetic force of a magnetic field B formed by supplying power to the magnetic field coil, the rotating induction electric field E having a rotation frequency corresponding to an electron cyclotron frequency of the magnetic field B, and the multiple sets (number of sets being a natural number of m≧1) of high frequency induction antennas and the magnetic field are arranged so that the induction electric field E and the magnetic field B satisfy a relationship of E×B≠0 so as to generate plasma, the plasma being used to subject the sample to plasma processing.
2. The plasma processing apparatus according to claim 1, wherein
- the vacuum processing chamber top member has a planar shape, a hollow semispherical shape, a rotated trapezoidal shape, or a cylindrical shape with a bottom, and
- the multiple sets of high frequency induction antenna elements are all disposed outside the vacuum processing chamber top member.
3. A plasma generating apparatus comprising a vacuum processing chamber having a vacuum processing chamber top member formed of insulating material on the upper portion thereof, multiple sets (number of sets being a natural number of m≧1) of a plurality of high frequency induction antenna elements through which high frequency for forming an induction electric field in the vacuum processing chamber is supplied, the plurality of respective high frequency induction antenna elements of the plurality of sets of high frequency induction antenna elements are arranged on a single plane and symmetric with respect to an axis orthogonal to said plane, a magnetic field distribution having a symmetric distribution with respect to an axis crossing said plane and orthogonal to said plane, the axes of the respective plurality of sets of the multiple high frequency induction antennas corresponding to the axis of the magnetic field distribution, wherein the multiple antennas and the magnetic field are arranged so that the rotation frequency of said rotating induction electric field E formed by the multiple sets f high frequency induction antenna elements is set to correspond to the electron cyclotron frequency of the magnetic field B so that the induction electric field distribution formed in the vacuum processing chamber rotates in a fixed direction, and the induction electric field E formed by the multiple sets of the plurality of high frequency induction antenna elements and the magnetic field B satisfy a relationship of E×B≠0.
4. The plasma generating apparatus according to claim 3, wherein
- the vacuum processing chamber top member has a planar shape, a rotated trapezoidal shape, a hollow semispherical shape, or a cylindrical shape with a bottom, and
- the multiple sets of high frequency induction antenna elements are all disposed outside the vacuum processing chamber top member.
5. The plasma generating apparatus according to claim 3, wherein
- the rotating direction of the induction electric field distribution rotating in a fixed direction is a right direction with respect to the direction of the line of magnetic force of the magnetic field.
6. The plasma generating apparatus according to claim 3, wherein
- the rotation frequency of the rotating induction electric field E formed via the multiple sets of a plurality of high frequency induction antenna elements being is set to correspond to the electron cyclotron frequency of the magnetic field B.
7. The plasma generating apparatus according to claim 3, wherein
- a variation frequency fB of the magnetic field B is set to satisfy a relationship of 2πfB<<ωc with respect to a rotation frequency (electron cyclotron frequency ωc) of Larmor motion.
Type: Application
Filed: Aug 27, 2009
Publication Date: Jul 15, 2010
Applicant:
Inventor: Ryoji Nishio (Kudamatsu-shi)
Application Number: 12/461,891
International Classification: C23F 1/08 (20060101);