JP2004259832A - Plasma process equipment and dust removal method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide plasma process equipment for plasma processing having a means which has high dust elimination efficiency when a large wafer substrate is used and ejects surely once eliminated dust to the outside of the system, and to provide a dust removal method. <P>SOLUTION: The plasma process equipment is provided with a first electrode for generating a plasma and a second electrode for moving dust. The first and the second electrodes are arranged in the direction parallel to the surface of a substrate 11 to be treated. A high frequency voltage and a polyphase AC voltage are applied to a substrate holder 10 for holding the substrate 11. While a plasma treatment is performed, the dust is carried by using a traveling wave electric field which the potential distribution by the polyphase AC voltage forms. The dust is ejected from inside the treatment chamber 7 by using a venting means. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a plasma processing apparatus and a dust removing method, and more particularly, to a plasma process in a plasma process such as a film forming step, an etching step, and an ashing step using plasma excited by an electromagnetic wave or the like in manufacturing a semiconductor or a liquid crystal display element. The present invention relates to an apparatus and a dust removing method.
[0002]
[Prior art]
2. Description of the Related Art In a manufacturing process of a liquid crystal display device, a semiconductor device, or the like, a plasma process device using plasma is used in a film forming process, an etching process, an ashing process, and the like. This process is performed by introducing a processing gas into a processing container provided with a holder on which a wafer or a substrate is placed, and supplying electric energy to the processing gas in the form of, for example, an electromagnetic wave to form a plasma.
[0003]
Hereinafter, a conventional example in which processing is performed by a plasma processing apparatus using microwaves will be described with reference to FIGS.
[0004]
FIG. 25 is a cross-sectional view of a plasma processing apparatus using microwave excitation. In FIG. 25, an upper lid 101 and a dielectric window 104 made of a dielectric material such as alumina are arranged on a chamber 102, and the inside of the processing chamber 107 can be maintained in a vacuum state by O-rings 105 and 106. A rectangular waveguide 103 that supplies microwaves into the processing chamber 107 is disposed on the upper lid 101, and the rectangular waveguide 103 is connected to a microwave oscillator 113 via a waveguide 112. ing. A metal slot antenna plate 108 having a plurality of slots 109 is provided between the dielectric window 104 and the rectangular waveguide 103. Here, the microwave oscillated by the microwave oscillator 113 is radiated into the processing chamber 107 via the waveguide 112, the rectangular waveguide 103, the slot 109, and the dielectric window 104. When the microwaves are radiated into the processing chamber 107, the processing gas introduced into the processing chamber 107 is excited from the gas supply system 114 to generate plasma, and the substrate 111 placed on the substrate holder 110 is heated. Is subjected to a plasma process. In the substrate holder 110, the surface on the substrate side is covered with a dielectric (not shown). The substrate holder 110 has a lower electrode (not shown) to which a high-frequency voltage is applied below the dielectric.
[0005]
When, for example, an etching process or an ashing process is performed as the plasma process, a reaction product is generated due to a reaction between an excited gas in the plasma and a substrate surface material. Most of the reaction product is discharged from the system through the exhaust port 115 through the exhaust pipe 116 by the exhaust pump 117. However, some reaction products remain in the processing chamber 107, and adhere to and deposit on the inner wall of the chamber 102 and the surface of the dielectric window 104. For example, even when a film forming process such as CVD (Chemical Vapor Deposition) is performed, molecules that are not formed on a wafer or a substrate adhere to the inner wall of the chamber 102 or the surface of the dielectric window 104 in the same manner as described above.
[0006]
The deposits are deposited and grown over time, and are separated from the wall surface by collision of the radicals and ions in the plasma with the wall surface. The exfoliated matter becomes dust and falls on a wafer or a substrate. Dust dropped in this way causes serious problems concerning product quality and yield, such as deterioration of patterning accuracy, insulation failure due to pinholes in the formation of an insulating film, and deterioration of characteristics of a semiconductor film.
[0007]
In order to solve the above problems, the following behavior of dust in plasma has been conventionally used as an effective means having a small influence on a wafer, a substrate, and an apparatus.
[0008]
During the plasma processing, a bulk plasma 140 exists between the dielectric window 104 and the substrate 111 as shown in FIG. At the interface between the bulk plasma 140 and the substrate 111, a sheath region 141 is formed in which the electrons having higher mobility than the ions jump from the bulk plasma 140 to the surface of the substrate 111, and the potential drops sharply toward the surface of the substrate 111. You. Therefore, when the substrate 111 is grounded, the surface to be processed of the substrate 111 has a negative potential. Dust that passes through the plasma is also negatively charged as described above due to the difference in mobility between ions and electrons. Here, due to the balance between gravity that causes the dust to fall on the surface of the substrate 111 and the electric repulsive force due to the electric field in the sheath region 141, the dust is confined and floats in the sheath region 141 above the substrate 111. However, when the supply of power energy such as microwaves is cut off and the plasma disappears, the surface of the substrate 111 to be processed is no longer charged through the discharge of the capacitor to the ground potential, so that the dust falls on the substrate 111.
[0009]
As a method of catching dust using the behavior of dust as described above, for example, Japanese Patent Publication No. 7-111959 (conventional example 1), Japanese Patent Application Laid-Open No. 7-106307 (conventional example 2), and No. 091247 (conventional example 3).
[0010]
In the first conventional example, a concave groove or a portion lower than the substrate supporting region is formed around the substrate supporting region of the substrate holder, and a portion having a large potential difference is formed, thereby capturing negatively charged fine particles.
[0011]
In Conventional Example 2, a dust collecting electrode is disposed in a processing container, and a small foreign substance floating in the processing container is electrostatically attracted to the dust collecting electrode by applying a DC voltage to the collecting electrode. Captured.
[0012]
In Conventional Example 3, a ring body is provided around a mounting table of a semiconductor wafer so as to be substantially at the same height as the mounting surface of the mounting table, and an electrode is embedded in a surface portion of the ring body. A positive voltage is applied to this electrode to draw particles into the electrode.
[0013]
On the other hand, as a conventional method of transporting charged particles, for example, as described in JP-A-10-250846 (conventional example 4) and JP-A-2001-139144 (conventional example 5), a traveling wave electric field is used. Is used.
[0014]
The method shown in Conventional Example 4 and Conventional Example 5 is a method of transporting particles using a so-called electric field curtain, in which a power supply for applying a polyphase alternating voltage is periodically applied to a linearly formed electrode. By connecting and applying alternating voltages (alternating voltages) having different phases from each other, a traveling-wave alternating electric field (a traveling-wave electric field) is generated, and the charged particles are conveyed.
[0015]
[Patent Document 1]
Japanese Patent Publication No. 7-111959
[0016]
[Patent Document 2]
JP-A-7-106307
[0017]
[Patent Document 3]
JP 2000-91247 A
[0018]
[Patent Document 4]
JP-A-10-250846
[0019]
[Patent Document 5]
JP 2001-139144 A
[0020]
[Problems to be solved by the invention]
However, in the dust removing methods in Conventional Examples 1 to 3 described above, since the dust collecting mechanism is provided in a fixed state, the relative position between the wafer or the substrate and the collecting mechanism is not changed. The area that can be removed is limited to the surroundings where the dust collecting mechanism is provided. Therefore, the effect decreases as the distance from the dust collecting mechanism increases. In particular, when the size of the substrate is large, such as a glass substrate for a TFT (Thin Film Transistor) liquid crystal display device, dust is not completely removed from the entire surface of the substrate.
[0021]
Further, the dust removing methods in Conventional Examples 1 to 3 do not include a mechanism for reliably discharging the dust once collected to the outside of the system. Therefore, there is a possibility that dust that has been collected but not discharged may adhere to the substrate at the moment when the plasma is stopped or during the transportation of the substrate.
[0022]
Furthermore, since the dust removing means in the conventional examples 2 and 3 is a method of attaching negatively charged dust to the surface of the positively charged electrode, the dust collecting means of the collecting mechanism gradually increases as the collection is continued. The capacity is reduced, and maintenance such as replacement of the electrode and cleaning after removing the electrode is required. This causes an increase in the manufacturing cost of the semiconductor element.
[0023]
Further, in the particle transport mechanism using the traveling-wave electric field described in Conventional Example 4 and Conventional Example 5, only the AC voltage or the AC voltage and the DC voltage are applied to each transport electrode. On the other hand, in a plasma processing apparatus, it is necessary to apply a high-frequency voltage to the entire surface of a substrate to be processed.
[0024]
Here, when the carrier electrode structures described in Conventional Examples 4 and 5 are superimposed on a high-frequency electrode to which a high-frequency voltage is applied, the high-frequency voltage is blocked by a traveling-wave electric field, and thus does not function as a plasma processing apparatus. . Further, when a high-frequency electrode is superimposed on the above-mentioned carrier electrode structure, the traveling-wave electric field is interrupted by a high-frequency voltage, and thus has no dust removing function.
[0025]
The present invention has been made in view of such circumstances, and an object of the present invention is to have a high dust removal effect even when a large wafer or substrate is used, and to reliably remove dust once removed from the system. To provide a plasma processing apparatus for a plasma process and a dust removing method having means for discharging the dust.
[0026]
[Means for Solving the Problems]
A plasma processing apparatus according to the present invention includes a processing chamber for performing a plasma process, an exhaust unit for exhausting the processing chamber, a gas supply unit for supplying a gas into the processing chamber, a plasma generation unit for exciting the gas with plasma, and an electrode. A substrate holder on which the substrate to be processed is placed, and a voltage applying means connected to the electrode portion, wherein the electrode portion is a first electrode for applying a voltage to the plasma and a first electrode for moving dust. The first electrode and the second electrode are arranged so as to be arranged in a direction parallel to a surface to be processed of the substrate to be processed, and the first and second electrodes are insulated from each other. This makes it possible to reliably remove dust floating on the substrate to be processed.
[0027]
Here, it is preferable that an insulating material or a gap be provided between the first electrode and the second electrode. This makes it possible to reliably remove dust floating on the substrate to be processed.
[0028]
In one aspect, the voltage applying means includes a high-frequency voltage applying means and a multi-phase AC voltage applying means, wherein the first electrode is connected to the high-frequency voltage applying means, and the second electrode is connected to the high-frequency voltage applying means and the polyphase AC voltage applying means. Preferably, it is connected to AC voltage applying means. Thus, dust can be removed while performing plasma processing on the substrate to be processed.
[0029]
In another aspect, the voltage application unit includes a high-frequency voltage application unit and a multi-phase AC voltage application unit, the second electrode is arranged in a matrix, and the first and second electrodes, the high-frequency voltage application unit, and the multi-phase voltage application unit. It is preferable to include a switch for switching a connection state with the phase AC voltage applying unit. Thereby, the dust transport path can be changed without changing the electrode arrangement.
[0030]
The insulating material on the surfaces of the first and second electrodes is preferably formed by an anodic oxidation method. Thus, an insulating film can be easily formed at low cost, and the insulating property between the first electrode and the second electrode can be secured.
[0031]
The multi-phase AC voltage is preferably applied with a phase delayed from the center to the outer periphery of the substrate holder. Thereby, the conveying distance of the dust is shortened, and the dust can be efficiently removed in a short time.
[0032]
Preferably, the first and second electrodes include a straight shape. This allows the dust to be conveyed to the outer periphery of the substrate holder over the shortest distance.
[0033]
Further, the first and second electrodes may be arranged so as to surround a part of the outer periphery of the substrate holder. Further, the first electrode is arranged to surround the central portion of the substrate holder, and the second electrode is arranged along the outer periphery of the substrate holder, the first portion being arranged to surround the central portion of the substrate holder. And a second portion for conveying dust along the outer periphery of the substrate holder. Thereby, the transported dust can be collected on a part of the outer periphery of the substrate holder.
[0034]
It is preferable that the plasma processing apparatus further includes a controller connected to the multi-phase AC voltage application unit, and the controller activates the multi-phase AC voltage application unit at least immediately after the start and immediately before the end of the plasma processing. Thus, in the film forming step, the etching step, the ashing step, and the like, dust can be removed at the point where dust falls on the substrate becomes the most problematic, so that dust can be removed efficiently.
[0035]
It is preferable that the plasma processing apparatus include a valve between the processing chamber and the exhaust unit, and a dust collecting unit between the valve and the exhaust unit. By providing the valve, the inside of the processing chamber is opened to the atmosphere when the filter on the side of the exhaust means for collecting dust is mainly exchanged, so that dust is not mixed.
[0036]
The dust removal method according to the present invention is a dust removal method inside a processing chamber of a plasma processing apparatus, wherein a multi-phase AC voltage is applied to a substrate holder that holds a substrate during plasma excitation, and a potential by the multi-phase AC voltage is applied. The method includes a step of transporting dust using a traveling wave formed by the distribution, and an exhaust step of removing dust from inside the processing chamber using an exhaust unit. Accordingly, plasma processing can be performed without dropping dust on the substrate to be processed.
[0037]
Here, it is preferable that the traveling wave travels from the central portion of the substrate holder toward the outer periphery, and the dust is transported from the central portion of the substrate holder to the outer periphery. Thereby, the conveying distance of the dust is shortened, and the dust can be efficiently removed in a short time.
[0038]
Further, it is preferable that the traveling wave is converged to two or less portions on the outer periphery of the substrate holder, and the dust is transported to two or less portions on the outer periphery of the substrate holder. Accordingly, it is not necessary to provide a large number of discharge ports, and it is possible to efficiently transport dust from the discharge section to the discharge ports.
[0039]
The evacuation step is preferably performed under the condition that the Knudsen number in the processing chamber is less than 1 and the plasma gas stay time in the processing chamber is 10 seconds or less on average. As a result, the dust is discharged from the exhaust port without delay.
[0040]
It is preferable that the transporting step and the exhausting step are performed at least one of immediately after the start and immediately before the end of the plasma processing. Thus, in the film forming step, the etching step, the ashing step, and the like, dust can be removed at the point where dust falls on the substrate is the most problematic, so that dust can be removed efficiently.
[0041]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of a plasma processing apparatus and a dust removal method according to the present invention will be described.
[0042]
(Embodiment 1)
1 to 5 are views showing a plasma processing apparatus and a dust removing method according to the first embodiment.
[0043]
The dust removing method according to the present embodiment is a dust removing method in a processing chamber 7 of a plasma processing apparatus, which applies a high-frequency voltage and a multi-phase AC voltage to a substrate holder 10 holding a substrate 11 to be processed. A process in which only a multi-phase AC voltage is applied during processing or during plasma excitation to transport dust using a traveling wave in which a potential distribution formed by the multi-phase AC voltage is formed, and an exhaust pump 35 as an exhaust unit is provided. And an exhaust step of removing dust from the inside of the processing chamber 7 by using the exhaust gas. Thus, plasma processing can be performed without dropping dust on the substrate 11 to be processed.
[0044]
FIG. 1 is a sectional view of a plasma processing apparatus according to the present embodiment.
As shown in FIG. 1, the plasma processing apparatus includes a processing chamber 7 for performing plasma processing, exhaust pumps 17 and 35 serving as an exhaust unit for exhausting the processing chamber 7, and a gas supply for supplying gas into the processing chamber 7. A gas supply system 14 as a means, a microwave oscillator 13 as a plasma generating means for plasma-exciting a gas, a substrate holder 10 having an electrode portion 26 and on which the substrate 11 to be processed is mounted, and connected to the electrode portion 26 And a high-frequency power supply 24 as a voltage application means.
[0045]
An upper lid 1 is provided on the chamber main body 2 via an O-ring 6 so as to vacuum seal the inside of the processing chamber 7. A substrate holder 10 is provided on the bottom surface of the chamber body 2 so as to face the upper lid 1, and a substrate 11 to be processed is placed on the substrate holder 10. A dielectric window 4 made of a dielectric such as alumina is buried in the upper lid 1, and an O-ring 5 is provided between the upper lid 1 and the dielectric window 4 to vacuum seal the inside of the processing chamber 7. is set up.
[0046]
A rectangular waveguide 3 made of an aluminum material is arranged on the upper lid 1, and the rectangular waveguide 3 is connected to a microwave oscillator 13 via a waveguide 12. A slot antenna plate 8 made of a thin aluminum plate having a plurality of slots 9 is provided between the dielectric window 4 and the rectangular waveguide 3. The slot antenna plate 8 distributes a high frequency wave such as a microwave introduced into the rectangular waveguide 3 and supplies it to the inside of the processing chamber 7.
[0047]
Further, the substrate holder 10 has a dielectric 23 on the surface on the side of the substrate 11 to be processed, a lower part 27 of the substrate holder on the opposite side, and an electrode part 26 in the middle.
[0048]
The microwave oscillated by the microwave oscillator 13 passes through the waveguide 12, the rectangular waveguide 3, and the slot 9, is introduced into the processing chamber 7 through the dielectric window 4, and is introduced from the gas supply system 14. The reaction gas is turned into plasma. The plasma-converted reaction gas reaches the substrate 11 to be processed, and promotes etching and ashing by a radical reaction promoting effect and physical collision of electrons and ions. In the case of CVD, a gas is decomposed by plasma to deposit a thin film of silicon or the like.
[0049]
Although a microwave plasma process apparatus is assumed in FIG. 1, a basic structure of the apparatus is based on a plasma method such as ECR (Electron Coupling Resonance) plasma, ICP (Inductively Coupled Plasma), and remote plasma. The same applies to a device, a parallel plate type RIE (Reactive Ion Etching) device, and the like.
[0050]
An exhaust port 15 is provided on the lower surface of the chamber body 2. The exhaust port 15 (for pressure adjustment) is connected to an exhaust pump 17 via an exhaust pipe 16. An exhaust port 30 (for dust removal) provided on a side wall of the main body 2 is connected to an exhaust pump 35 via an exhaust pipe 31. Here, the wall surface of the exhaust pipe 31 has a structure that can be heated. The exhaust pipe 31 is provided with a filter 33 (for backflow prevention), an exhaust valve 34, and a filter 32 (for dust removal) in order from the processing chamber 7 side.
[0051]
During the plasma processing, electrons having a higher mobility than the ions jump from the bulk plasma into the surface of the substrate 11 to be processed, so that the sheath region 41 containing excessive ions is formed, and at the same time, the surface of the substrate 11 to be processed is negative. Charge. Dust in the processing chamber 7 is also negatively charged by the same mechanism as the substrate, and the gravity acting on the dust and the electric repulsion acting between the substrate 11 and the dust are balanced. Therefore, dust is confined in the sheath region 41 during the plasma processing.
[0052]
Next, a process of transporting the dust trapped in the sheath region 41 will be described.
2 and 3 are cross-sectional views of the substrate holder and dust floating above the substrate holder. (The substrate 11 to be processed is not shown in FIGS. 2 and 3.) As shown in FIGS. 2 and 3, the electrode portion 26 formed under the dielectric 23 applies a voltage to the plasma for applying a voltage to the plasma. The first electrode 20 and the second electrodes 21a, 21b, and 21c for moving dust are provided. The first electrode 20 and the second electrodes 21a, 21b, and 21c are parallel to the surface of the substrate 11 to be processed. It is arranged so that it may line up in the direction. In the electrode section 26, the first electrodes 20 and the second electrodes 21a, 21b, 21c are alternately arranged. However, the present invention is not limited to this arrangement mode. For example, two adjacent first electrodes 20 are arranged adjacent to each other. The arrangement in which the second electrodes 21a, 21b, 21c are installed may be adopted.
[0053]
An insulating film 25 as an insulating material is formed around the first electrode 20, and the first electrode 20 and the second electrodes 21a, 21b, 21c are insulated. This insulating film 25 is formed by performing anodic oxidation on the surface of the first electrode 20. By using the anodic oxidation method, an insulating film can be easily formed at low cost. Further, the insulating film may be formed on the surface of the second electrode or on both surfaces of the first and second electrodes. Here, in FIGS. 2 and 3, the thickness of the insulating film 25 is exaggerated for the sake of explanation.
[0054]
The first electrode 20 is connected to a high-frequency power supply 24, and the second electrodes 21a, 21b, 21c are connected to the high-frequency power supply 24 and the polyphase AC power supplies 22a, 22b, 22c. By applying a high-frequency voltage to both the first and second electrodes during the plasma processing, a voltage can be applied to the plasma from the entire surface of the substrate holder, and the plasma processing can be uniformly performed on the substrate surface. Can be. Further, an alternating AC voltage and a high-frequency voltage can be applied to the second electrodes 21a, 21b, 21c in a superimposed manner. (The high-frequency power supply 24 is not shown in FIGS. 2 and 3.) Here, the polyphase AC power supplies 22a, 22b, and 22c apply alternating voltages having different phases from each other.
[0055]
The alternating voltages applied by the polyphase AC power supplies 22a, 22b, 22c are each shifted in phase by 120 degrees. For example, the alternating voltage from the power supply 22b has a phase delayed by 120 degrees from the alternating voltage from the power supply 22a. Similarly, the alternating voltage by the power supply 22c is adjusted so that the phase is delayed by 120 degrees with respect to the alternating voltage by the power supply 22b. That is, the multi-phase AC voltage is applied with a delayed phase from the center to the outer periphery of the substrate holder 10, and each power supply voltage is expressed as follows.
V ₁ = V _m1 ・ Sinωt
V ₂ = V _m2 ・ Sin (ωt-2π / 3)
V ₃ = V _m3 ・ Sin (ωt-4π / 3)
Where V ₁ , V ₂ , V ₃ Are the alternating voltages of the power supplies 22a, 22b and 22c, respectively. V _m1 , V _m2 , V _m3 Is the maximum value of each power supply voltage. _m1 = V _m2 = V _m3 It is.
[0056]
By applying the alternating voltage as described above, a traveling-wave alternating electric field (a traveling-wave electric field) is formed in the direction of the arrow shown in FIG.
[0057]
At this time, if the dust 42 of the negatively charged sheath region 41 is present in the traveling wave-like alternating electric field, a strong electric field portion on the surface of the second electrodes 21a, 21b, 21c (the lower electrode at the higher voltage position). (Directly above).
[0058]
Here, since the potential peak temporally forms a traveling wave, the negatively charged dust 42 is supplied to the power source having the highest voltage in each phase (the power source 22a in the phase shown in FIG. 2 and the power source 22b in the phase shown in FIG. 3). ) (The power supply 21a in the phase shown in FIG. 2 and the power supply 21b in the phase shown in FIG. 3). Thus, the dust 42 transitions in the space immediately above the substrate 11 to be processed, and is transported in the direction of the arrow shown in FIG.
[0059]
With the above configuration and operation, a high-frequency voltage for performing the plasma processing can be applied from the entire surface of the substrate holder 10 by the high-frequency power supply 24, and at the same time, the dust 42 confined in the sheath region 41 is transported in a predetermined direction. be able to.
[0060]
Here, depending on conditions, the multi-phase AC voltage may be applied while the high-frequency voltage is being applied, or may be applied after the high-frequency voltage is stopped.
[0061]
In the case where a physical reaction is performed mainly for the purpose of performing the plasma process, ions in the plasma are attracted to the substrate surface, and the high-frequency voltage is increased to promote physical collision. On the other hand, when a chemical reaction is mainly performed, the high-frequency voltage is reduced.
[0062]
Here, when performing a plasma process for the purpose of a physical reaction, it is preferable to apply a multi-phase AC voltage after stopping the high-frequency voltage. This does not affect the plasma process.
[0063]
On the other hand, when performing a plasma process for the purpose of a chemical reaction, if the high-frequency voltage is stopped and then a multi-phase AC voltage is applied to remove dust, the reaction proceeds during that time. Therefore, when performing a plasma process for the purpose of a chemical reaction, it is preferable to remove dust by applying a polyphase AC voltage while applying a high-frequency voltage.
[0064]
As the waveform of the polyphase AC voltage, either a pulse waveform or a sine waveform, or any combination thereof may be used. In addition, the polyphase referred to here is an alternating current of at least three phases. In the present embodiment, the number of phases of the AC voltage is three, and the phase shift of each AC voltage is 120 degrees, but these are not necessarily limited to the above values.
[0065]
Next, the timing of performing the above-described transport step will be described.
In a surface processing such as etching or ashing or a surface modification process, there is a problem that dust falls on the substrate after the plasma processing is completed. In order to prevent this, it is most efficient and preferable to perform the dust removal operation immediately before the end of the plasma processing. In a film forming process such as CVD, it is necessary to perform dust removal work both immediately after the start of the plasma processing and immediately before the end of the plasma processing in order to prevent impurities from being mixed into the film in addition to dust falling after the plasma processing. preferable.
[0066]
On the other hand, as shown in FIG. 1, the plasma processing apparatus according to the present embodiment has an arithmetic processing unit 52 as a controller connected to the multi-phase AC power supplies 22a, 22b, 22c, And an optical sensor 51 capable of recognizing light emission by plasma. The arithmetic processing unit 52 operates the multi-phase AC power supplies 22a, 22b, and 22c at least immediately after the start and immediately before the end of the plasma processing to perform the dust transporting step and the exhausting step.
[0067]
Next, a determination method immediately after the start and immediately before the end of the plasma processing will be described.
The optical sensor 51 recognizes the start of the plasma processing based on the emission of the plasma, and feeds the result back to the arithmetic processing unit 52 for use in determining the start of dust removal.
[0068]
When performing the etching process, an EPD (End Point Detector) that recognizes the end point of the etching can be used to determine the start of dust removal immediately before the end of the plasma process. The EPD detects the light intensity of a specific wavelength emitted when the gas used in the etching is excited into a plasma state, and the consumption of the gas used decreases after the end of the etching. The end point of the etching can be recognized by detecting the change in the intensity.
[0069]
In the present embodiment, dust is removed at the same time as overetching by performing overetching for several seconds after determining the end point of the etching by the EPD and feeding back the result of the end point determination to the arithmetic processing unit 52.
[0070]
The arithmetic processing unit 52 is also connected to the microwave oscillator 13 and the gas supply system 14. By inputting conditions in advance, the microwave is applied at the start of the plasma processing and simultaneously the multi-phase AC power supplies 22a and 22b , 22c and the gas supplied to the processing chamber 7 can be changed, and simultaneously, the polyphase AC power supplies 22a, 22b, 22c can be operated.
[0071]
If the plasma is not stopped when changing the gas, the gas used for maintaining the plasma when removing dust may be changed to an inert gas such as Ar.
[0072]
Next, an exhaust step of discharging the transported dust from the processing chamber 7 will be described.
The dust transported in the above transport step is adsorbed by the viscous gas and is discharged together with the gas from the exhaust port 30 shown in FIG. This evacuation step is preferably performed under the condition that the Knudsen number Ku inside the processing chamber 7 is less than 1 and the plasma gas stay time τ in the processing chamber is 10 seconds or less on average. As a result, the dust is discharged from the exhaust port without delay. It is preferable that the Knudsen number Ku and the plasma gas stay time τ in the processing chamber be as small as possible. However, in view of the current state of the art, Ku is 2.0 × 10 ^-3 The lower limit of about 0.8 is considered to be about 0.8.
[0073]
Here, for example, gas (N ₂ ) Is λ (m) = 6.6 × 10 ^-3 / P (Pa), 1 (SCCM) = 1.69 × 10 ^-3 (Pa · m ³ / S), the volume V = 0.300 (m ³ ), An exhaust port having a diameter L = 0.200 (m) is provided, and the processing pressure P = 2.0 (Pa) and the gas flow rate Q = 50 (SCCM).
Ku = λ / L = 0.0165 <1
τ = PV / Q = 7.09 <10
And the above condition is satisfied.
[0074]
Focusing on the pump displacement, the volume V = 0.300 (m ³ ), The pumping speed V ₀ = 6.00 × 10 ^-2 (M ³ / S), τ = V / V ₀ = 5.00 <10
And the above condition is satisfied.
[0075]
As described above, by selecting the exhaust pump having the capacity of the processing chamber and the exhaust capacity (the processing pressure, the gas flow rate, and the exhaust speed) according to the volume, the dust is discharged from the exhaust port without delay.
[0076]
Here, the vertical installation position of the exhaust port 30 is determined in consideration of the vertical position of the dust floating on the substrate 11 to be processed and the areas of the first and second electrodes. However, it is usually provided slightly below the surface of the substrate 11 to be processed. The installation position in the plane direction is provided corresponding to the carry-out portion where the dust is carried out of the region of the substrate holder. An auxiliary transport mechanism for further collecting dust may be provided between the discharge section and the exhaust port. Thus, dust carried by the traveling wave electric field can be more reliably discharged out of the system, and the suction force of the exhaust pump 35 can be used most effectively.
[0077]
The dust 42 discharged from the exhaust port 30 passes through the exhaust pipe 31 shown in FIG. 1 and is collected by the filter 32 (for dust removal). Here, since the inner wall surface of the exhaust pipe 31 is heated, it is possible to prevent the discharged dust from adhering.
[0078]
The plasma processing apparatus includes an exhaust valve 34 between the processing chamber 7 and the exhaust pump 35, and dust collecting means is provided between the processing chamber 7 and the exhaust valve 34 and between the exhaust valve 34 and the exhaust pump 35. Are provided as filters 32 and 33. Here, when dust is removed, the filter 33 (for backflow prevention) is not inserted.
[0079]
Since the exhaust valve 34 is provided, even when the filter 32 on the exhaust pump 35 side is replaced, the inside of the processing chamber 7 is opened to the atmosphere, so that dust is not mixed.
[0080]
Further, by providing the filters 32 and 33 on both sides of the exhaust valve 34, there is a pressure difference between the inside of the processing chamber 7 and the exhaust pump 35 via the exhaust valve 34, and when the exhaust valve 34 is opened, the filter 32 If there is a possibility that dust trapped in (for dust removal) or dust adhering to the inner wall of the exhaust pipe 31 may enter the inside of the processing chamber 7, a filter 33 (for backflow prevention) is inserted. Dust flowing back can be collected. Inserting such a backflow prevention filter 33 according to the situation is effective in a case where a backflow from the exhaust pump 35 side is considered.
[0081]
The filter 32 and the filter 33 may be used not only when opening and closing the exhaust valve 34 but also when removing dust. In such a case, it is necessary to select an appropriate type of the filters 32 and 33 according to the situation. it can. That is, large dust is trapped in the filter 33 on the processing chamber 7 side using a relatively coarse HEPA filter, and dust that has passed through the HEPA filter is trapped in the filter 32 on the exhaust pump 35 side using an ULPA filter. Thus, fine dust can be trapped while the maintenance cycle of the filters 32 and 33 is lengthened.
[0082]
Next, the planar arrangement of the first and second electrodes on the substrate holder 10 will be described.
[0083]
FIG. 4 is a plan view of the substrate holder 10. As shown in FIG. 4, the first electrode 20 and the second electrodes 21a, 21b, 21c have a linear shape, and are all arranged in parallel. Here, regarding the length of one side of the substrate holder 10 and the lengths of the first and second electrodes provided inside the substrate holder 10, the length of one side of the substrate to be processed or the length of the wafer Designed to be larger than the diameter. According to the above configuration, the dust can be transported to the outer periphery of the substrate holder at the shortest distance.
[0084]
More specifically, with respect to the substrate holder 10 shown in FIG. ₁ , V ₂ , V ₃ Is applied, the multi-phase AC voltage is applied with a phase delayed from the center to the outer periphery of the substrate holder 10. As a result, the traveling wave electric field travels from the center of the substrate holder 10 toward the outer periphery, and conveys the dust from the center of the substrate holder 10 to the outer periphery.
[0085]
FIG. 5 shows that the substrate holder 10 shown in FIG. ₁ , V ₂ , V ₃ FIG. 6 is a plan view when dust 42 is removed by applying a pressure. By applying a voltage with a phase delayed from the center toward the outside, the distance of dust transport is shortened, and dust can be efficiently removed in a short time. In addition, since the dust is conveyed separately to the left and right, the dust can be efficiently conveyed from the outer periphery of the substrate 11 to the exhaust port 30. Further, the left and right transfer start positions are started from the electrode located at the center of the substrate so that the transfer of dust does not leak.
[0086]
(Embodiment 2)
FIG. 6 is a cross-sectional view of the substrate holder according to the second embodiment. In the first embodiment, an insulating film as an insulating material is used as a method for providing insulation between the first electrode and the second electrode. However, a method for securing insulation is not necessarily used. It is not limited to. In this embodiment, as shown in FIG. 6, the first electrode and the second electrode are arranged so as to be arranged in a direction parallel to the surface to be processed of the substrate to be processed and with a gap provided between the electrodes. Have been. Here, in FIG. 6, the width of the gap 43 is exaggerated for the sake of explanation. The width of the gap 43 is desirably adjusted so that processing can be performed uniformly over the entire substrate when a high-frequency voltage is applied to both the first and second electrodes to perform a plasma process.
[0087]
(Embodiment 3)
7 to 10 are plan views showing the arrangement of the first and second electrodes in the third embodiment. The arrows shown in FIGS. 7 to 10 indicate the directions in which the dust is conveyed.
[0088]
In the dust removing method according to the present embodiment, the traveling wave is converged to two or less portions on the outer periphery of the substrate holder 10 and the dust is transported to two or less portions on the outer periphery of the substrate holder 10.
[0089]
7 and 8, the first and second electrodes are arranged so as to surround a part of the outer periphery of the substrate holder 10.
[0090]
In FIG. 7, the direction in which the dust is conveyed is adjusted by the curved electrodes surrounding the central portions of the left and right outer peripheries of the substrate holder 10, so that the dust can be collected at the central portions of the left and right outer peripheries.
[0091]
In FIG. 8, a U-shaped electrode is arranged so as to surround the central part of the left and right outer peripheries of the substrate holder 10, and dust is conveyed toward the opening of the U-shape, whereby the substrate holder Dust can be collected at the center of the outer periphery on the left and right sides of 10.
[0092]
9 and 10, the first and second electrodes are provided along a first portion arranged to surround a central portion of the substrate holder 10 and an outer periphery of the substrate holder 10. And a second portion that conveys dust along the outer periphery of the substrate holder 10.
[0093]
Here, when the size of the substrate 11 to be processed does not reach the annular electrode formed on the outermost periphery, a high-frequency voltage is applied to the electrode portion (second portion) arranged along the outermost periphery. No need. Therefore, the first electrode may not be arranged in this portion, and may be constituted only by the second electrode.
[0094]
In FIG. 9, a substantially rhombus-shaped electrode is arranged at the center, and annular electrodes are arranged continuously so as to surround the outer periphery thereof. Electrodes are arranged.
[0095]
In FIG. 10, a rectangular electrode is arranged at the center, and an annular electrode is continuously arranged so as to surround the outer periphery. Dust is conveyed along the outermost periphery of the annular electrode, and the electrodes are collected at one place. Is arranged.
[0096]
In the present embodiment, by adopting the electrode arrangement as described above, in any case, the conveyed dust can be collected at a limited carry-out portion on the outer periphery of the substrate holder, and the dust collection efficiency can be increased. Thus, it is not necessary to provide a large number of discharge ports, and dust can be more efficiently removed.
[0097]
(Embodiment 4)
11 to 22 are plan views showing the arrangement and connection of the electrodes and the direction in which dust is conveyed in the fourth embodiment.
[0098]
In the plasma processing apparatus according to the present embodiment, the second electrodes are arranged in a matrix, and switch the connection state between the first and second electrodes and high-frequency power supply 24 and multiphase AC power supplies 22a, 22b, and 22c. It has a switch.
[0099]
As shown in FIG. 11, the shape of the electrode is, for example, a rectangular shape, and the electrodes are arranged in a matrix. Further, a switch lower base 28 (fixed type) is connected so that a voltage can be applied to the electrode at a desired timing. Here, a switch circuit (non-fixed type) may be used instead of the switch lower base.
[0100]
FIG. 12 shows that the first electrode 20 for applying a high-frequency voltage and the second electrodes 21a, 21b, and 21c for applying a polyphase AC voltage in addition to the high-frequency voltage are linearly formed by operating a switch. And a plan view in which they are alternately arranged in parallel. Thereby, the same dust removing effect as in the first embodiment can be obtained.
[0101]
In the present embodiment, even when the same electrode is used, the direction of the dust removal can be changed by switching the switch circuit or replacing the switch base.
[0102]
FIG. 13 to FIG. 16 are plan views showing a modification of the electrode arrangement with respect to FIG. 13, FIG. 14, FIG. 15, FIG. 15, and FIG. 16 show the same electrode arrangement and dust transport direction as in FIG. In any case, the conveyed dust can be collected at a limited carry-out portion on the outer periphery of the substrate holder.
[0103]
In the present embodiment, with the above configuration, dust collection efficiency can be improved as in the third embodiment. Thus, it is not necessary to provide a large number of discharge ports, and dust can be more efficiently removed.
[0104]
17 to 22 show still another modification of the matrix arrangement of the second electrodes in the present embodiment.
[0105]
As the matrix arrangement of the electrodes in the present embodiment, for example, as shown in FIGS. 17 to 21, a hexagon (FIG. 17), a two-way triangle (FIG. 18), a cross (FIG. 19), and a three-direction A rhombus (FIG. 20), a quadrilateral (FIG. 21) in which one quadrangle and four trapezoids surrounding the quadrilateral, and the like may be arranged in a matrix. Further, for example, as shown in FIG. 22, a form in which second electrodes such as circles and polygons are arranged in a matrix in the spread of the first electrodes may be employed.
[0106]
(Embodiment 5)
FIG. 23 is a sectional view of a plasma processing apparatus including the plasma processing apparatus according to the fifth embodiment.
[0107]
In FIG. 23, exhaust systems such as an exhaust port 30 for dust removal and an exhaust pump 35 are provided on both sides of the chamber main body 2 in the dust transport direction. This is to discharge the transported dust out of the system more efficiently and reliably. The configuration other than the above is the same as that of the first embodiment.
[0108]
(Embodiment 6)
FIG. 24 is a sectional view of a plasma processing apparatus including the plasma processing apparatus according to the sixth embodiment.
[0109]
In FIG. 24, the exhaust pump 35 serves both as an exhaust pump for removing dust and a vacuum pump for adjusting pressure, and the apparatus configuration is simple. The configuration other than the above is the same as that of the first embodiment.
[0110]
As described above, the embodiments of the present invention have been described. However, the embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
[0111]
【The invention's effect】
According to the present invention, it is possible to provide a plasma processing apparatus and a dust removal method capable of efficiently and reliably discharging dust floating on a processing target substrate while performing plasma processing.
[Brief description of the drawings]
FIG. 1 is a sectional view of a plasma processing apparatus according to a first embodiment of the present invention.
FIG. 2 is an enlarged view showing a substrate holder and dust floating above the substrate holder according to the first embodiment of the present invention.
FIG. 3 is an enlarged view showing a state in another phase of dust floating above the substrate holder according to the first embodiment of the present invention.
FIG. 4 is a plan view of the substrate holder according to Embodiment 1 of the present invention.
FIG. 5 is a plan view of the inside of the processing chamber during dust removal according to Embodiment 1 of the present invention.
FIG. 6 is an enlarged view showing a substrate holder according to Embodiment 2 of the present invention.
FIG. 7 is a plan view showing an arrangement of electrodes and a direction of conveying dust according to Embodiment 3 of the present invention.
FIG. 8 is a plan view showing a modification of the arrangement of electrodes and the direction in which dust is transported according to Embodiment 3 of the present invention.
FIG. 9 is a plan view showing still another modified example of the arrangement of electrodes and the direction of conveying dust according to Embodiment 3 of the present invention.
FIG. 10 is a plan view showing still another modified example of the arrangement of the electrodes and the conveying direction of the dust according to the third embodiment of the present invention.
FIG. 11 is a plan view of a substrate holder illustrating an arrangement and circuits of electrodes according to Embodiment 4 of the present invention.
FIG. 12 is a plan view showing an example of a form of an electrode that can be formed on the substrate holder shown in FIG.
FIG. 13 is a plan view showing a modification of the connection of the electrodes according to the fourth embodiment of the present invention and a direction in which dust is conveyed.
FIG. 14 is a plan view showing still another modified example of the electrode form according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 15 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention and a direction in which dust is conveyed.
FIG. 16 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 17 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 18 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention and a direction in which dust is conveyed.
FIG. 19 is a plan view showing still another modified example of the electrode configuration according to the fourth embodiment of the present invention and a direction in which dust is conveyed.
FIG. 20 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 21 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 22 is a plan view showing still another modified example of the electrode configuration according to Embodiment 4 of the present invention, and a direction in which dust is conveyed.
FIG. 23 is a sectional view of a plasma processing apparatus including a plasma processing apparatus according to Embodiment 5 of the present invention.
FIG. 24 is a sectional view of a plasma processing apparatus including a plasma processing apparatus according to Embodiment 6 of the present invention.
FIG. 25 is a sectional view of a conventional plasma processing apparatus.
FIG. 26 is a sectional view of the inside of a processing chamber when plasma is generated in a conventional plasma processing apparatus.
[Explanation of symbols]
1, 101 upper lid, 2, 102 chamber main body, 3, 103 rectangular waveguide, 4, 104 dielectric window, 5, 6, 105, 106 O-ring, 7, 107 processing chamber, 8, 108 slot antenna plate, 9 , 109 slot, 10, 110 substrate holder, 11, 111 substrate to be processed, 12, 112 waveguide, 13, 113 microwave oscillator, 14, 114 gas supply system, 15, 115 exhaust port (for pressure adjustment), 16 , 116 exhaust pipe, 17, 117 exhaust pump (for pressure adjustment), 20 first electrode (for high-frequency power supply), 21 second electrode (for polyphase AC power supply), 22 polyphase AC power supply, 23 dielectric, 24 High frequency power supply, 25 Insulating film, 26 Electrode part, 27 Substrate holder lower part, 28 Switch base, 30 Exhaust port (for dust removal), 31 Exhaust pipe, 32 Filter (for dust removal), 33 F Filter (for backflow prevention), 34 exhaust valve, 35 exhaust pump (for dust collection), 41, 141 sheath area, 42 dust, 43 gap, 51 optical sensor, 52 arithmetic processing unit, 140 bulk plasma.

Claims (16)

A processing chamber for performing plasma processing,
Exhaust means for exhausting the processing chamber;
Gas supply means for supplying gas into the processing chamber,
Plasma generating means for plasma-exciting the gas,
A substrate holder having an electrode portion and on which the substrate to be processed is placed;
Voltage applying means connected to the electrode unit,
The electrode unit has a first electrode that applies a voltage to plasma and a second electrode that moves dust,
A plasma processing apparatus, wherein the first electrode and the second electrode are arranged so as to be arranged in a direction parallel to a processing surface of the processing substrate, and the first and second electrodes are insulated. 2. The plasma processing apparatus according to claim 1, wherein an insulating substance or a gap is provided between the first electrode and the second electrode. The voltage applying unit includes a high-frequency voltage applying unit and a multi-phase AC voltage applying unit,
The first electrode is connected to the high-frequency voltage applying means,
3. The plasma processing apparatus according to claim 1, wherein the second electrode is connected to the high-frequency voltage application unit and the multi-phase AC voltage application unit. 4. The voltage applying unit includes a high-frequency voltage applying unit and a multi-phase AC voltage applying unit,
The second electrodes are arranged in a matrix,
3. The plasma processing apparatus according to claim 1, further comprising a switch configured to switch a connection state between the first and second electrodes and the high-frequency voltage application unit and the multi-phase AC voltage application unit. 4. The plasma processing apparatus according to claim 2, wherein the insulating material on the surfaces of the first and second electrodes is formed by an anodic oxidation method. The plasma processing apparatus according to any one of claims 1 to 5, wherein the multi-phase AC voltage is applied with a phase delayed from a central portion of the substrate holder toward an outer periphery. The plasma processing apparatus according to claim 1, wherein the first and second electrodes have a linear shape. The plasma processing apparatus according to claim 1, wherein the first and second electrodes are arranged so as to surround a part of an outer periphery of the substrate holder. The first electrode is arranged to surround a central portion of the substrate holder,
The second electrode is
A first portion arranged to surround a central portion of the substrate holder;
The plasma processing apparatus according to any one of claims 1 to 6, further comprising a second portion provided along an outer periphery of the substrate holder and configured to transport the dust along the outer periphery of the substrate holder. The plasma processing apparatus further includes a controller connected to the multi-phase AC voltage applying unit,
The plasma processing apparatus according to any one of claims 1 to 9, wherein the controller activates the multi-phase AC voltage applying unit immediately at least immediately before and after the start of the plasma processing. The plasma processing apparatus includes a valve between the processing chamber and the exhaust unit,
The plasma processing apparatus according to any one of claims 1 to 10, further comprising dust collecting means between the valve and the exhaust means. A method for removing dust in a processing chamber of a plasma processing apparatus,
Applying a polyphase AC voltage to the substrate holder that holds the substrate during plasma excitation, and transporting the dust using a traveling wave that forms a potential distribution by the polyphase AC voltage,
An exhausting step of removing the dust from the inside of the processing chamber using an exhausting means. The traveling wave travels from the center of the substrate holder toward the outer periphery,
The dust removing method according to claim 12, wherein the dust is transported from a central portion of the substrate holder to an outer periphery. Converging the traveling wave to two or less portions on the outer periphery of the substrate holder,
14. The dust removing method according to claim 12, wherein the dust is transported to two or less portions on an outer periphery of the substrate holder. The method according to any one of claims 12 to 14, wherein the exhausting step is performed under the condition that the Knudsen number in the processing chamber is less than 1 and the plasma gas stays in the processing chamber for an average of 10 seconds or less. Dust removal method. 16. The dust removing method according to claim 12, wherein the transporting step and the exhausting step are performed at least one of immediately after the start and immediately before the end of the plasma processing.

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