JP2013243135A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize an RF power loss and its machine difference (variation among devices) in a filter circuit for attenuating undesired high-frequency noise, and to improve reproducibility and reliability for process performance.SOLUTION: In this plasma etching device, first stage air-core coil units A(1) and A(2) of two systems provided on first and second power feeding lines are concentrically attached to a bobbin 114A. That is, coil lead wires respectively configuring both air-core coil units A(1) and A(2) are wound in spiral at an equal coil length while overlapping with each other and being translated in an axial direction. Similarly, respective coil lead wires of second stage air-core coil units B(1) and B(2) are wound in spiral at an equal coil length while overlapping with each other and being translated in the axial direction.

Description

  The present invention relates to a plasma processing apparatus that performs plasma processing on an object to be processed using high frequency, and more particularly to a plasma processing apparatus that includes a filter circuit for attenuating unwanted high frequency noise.

  In microfabrication for manufacturing semiconductor devices using plasma or FPD (Flat Panel Display), control of plasma density distribution on the substrate to be processed (semiconductor wafer, glass substrate, etc.) and control of substrate temperature or temperature distribution. Is very important. If the temperature control of the substrate is not properly performed, process uniformity on the substrate surface cannot be secured, and the manufacturing yield of the semiconductor device or the display device is lowered.

  Generally, a mounting table or susceptor for mounting a substrate to be processed in a chamber of a plasma processing apparatus, particularly a capacitively coupled plasma processing apparatus, functions as a high-frequency electrode that applies a high frequency to a plasma space, and electrostatically attracts the substrate. And a function of a temperature control unit for controlling the substrate to a predetermined temperature by heat transfer. Regarding the temperature control function, it is desired that the distribution of heat input characteristics to the substrate due to non-uniformity of radiant heat from plasma and chamber walls and the heat distribution by the substrate support structure can be corrected appropriately.

  Conventionally, in order to control the temperature of the upper surface of the susceptor (and thus the temperature of the substrate), a refrigerant passage for flowing a refrigerant is provided inside the susceptor or the susceptor support base, and the temperature-controlled refrigerant is circulated and supplied to the refrigerant passage. The method is heavily used. However, such a chiller method has a weak point that it is difficult to change the temperature of the refrigerant rapidly and the temperature control response is low, so that the temperature switching or raising / lowering temperature cannot be performed at high speed. In the field of recent processes such as plasma etching, a method of continuously processing a multilayer film on a substrate to be processed in a single chamber is required instead of the conventional multi-chamber method. In order to realize this single-chamber method, a technique that enables high-speed temperature rising and cooling of the mounting table has become essential. Under such circumstances, a heater system that incorporates a heating element that generates heat upon energization in the susceptor and controls the Joule heat generated by the heating element to control the susceptor temperature and, in turn, the substrate temperature at high speed and high is being reviewed again.

  By the way, when the lower high-frequency application method that connects a high-frequency power source to the susceptor from the surface of plasma control and the heater method as described above in which a heating element is provided on the susceptor from the surface of temperature control are applied to the susceptor from the high-frequency power source If a part of the generated high frequency enters the heater power supply through the heating element and the heater power supply line as noise, the operation or performance of the heater power supply may be impaired. In particular, the heater power supply capable of high-speed control uses semiconductor switching elements such as SSR (Solid State Relay) to perform high-sensitivity switching control or ON / OFF control, so malfunctions easily occur when high-frequency noise enters. Easy to wake up. Therefore, it is usual to provide a filter circuit for sufficiently attenuating undesired high frequencies in the heater power supply line.

  In general, this type of filter circuit has an LC low-pass filter composed of one coil (inductor) and one capacitor connected in multiple stages in a ladder shape. For example, assuming that the attenuation rate per stage of the LC low-pass filter is 1/10, the high-frequency noise can be attenuated to 1/100 in the two-stage connection and can be attenuated to 1/1000 in the three-stage connection.

JP 2006-286733 A

  As described above, in the conventional plasma processing apparatus, the function of the filter circuit provided on the heater power supply line enters from the high frequency power source via the susceptor from the viewpoint of maintaining normal operation or performance on the heater power source side. The main focus is on attenuating high-frequency noise, and a low-inductance coil and a large-capacitance capacitor are used for the LC low-pass filter at each stage in the filter circuit.

  However, the present inventor has been developing and evaluating a plasma processing apparatus that uses both a low-frequency application method and a heater method for a susceptor, and the conventional filter circuit as described above has a problem in terms of process performance. I noticed that there was. That is, there is a certain correlation between the high-frequency power loss applied to the susceptor from the high-frequency power source and the process performance (for example, the etching rate) (the relationship that the process performance decreases as the RF power loss increases). As is known, it has been found that conventional filter circuits cause a significant amount of RF power loss that is not negligible in terms of process performance. Moreover, it was also found that even in the same type of plasma processing apparatus, there was a variation (machine difference) in the amount of RF power loss for each unit, which led to a difference in process performance. And as a result of repeated experiments and diligent researches under such problem awareness, the present invention has been achieved.

  That is, the present invention solves the problems of the prior art as described above, and in a plasma processing apparatus including a filter circuit for attenuating undesired high frequency noise, the amount of RF power loss in the filter circuit In addition, the object is to improve the reproducibility and reliability of process performance by minimizing machine differences (variations between apparatuses) as much as possible.

  In order to achieve the above object, a plasma processing apparatus according to a first aspect of the present invention provides a first high-frequency power source that outputs a first high-frequency to a first electrode disposed in a depressurizable processing container. And high-frequency noise coming from the heating element on the first and second power supply lines for electrically connecting the heating element provided on the first electrode and the heater power supply. A first and second air-core coils in the first stage of the filter circuit as viewed from the heating element on the first and second power supply lines. Are provided, and the first and second air-core coils are coaxial with each other and have substantially the same winding length.

  In the above device configuration, the first stage coil of the filter circuit is an air-core coil. Therefore, by setting the inductance to a very large value, compared to a coil with a small inductance or a magnetic core such as ferrite. High-frequency power loss can be significantly reduced. Furthermore, since the first and second air-core coils constituting the first stage coil are coaxial with each other and have substantially the same winding length, an indefinite increase in the frequency characteristic of the actual resistance component in the filter circuit appears. It can be prevented or suppressed, thereby improving the reproducibility of the process performance.

  In the above apparatus configuration, the ratio of the winding lengths of the first and second air-core coils is preferably closer to 1, and is most preferably 1 strictly. Further, it is preferable to make the diameters of both air core coils equal in order to obtain the same self-inductance between the first and second air core coils, and in order to obtain the maximum mutual inductance, both air core coils are concentric. It is preferable to arrange in a shape.

  According to the plasma processing apparatus of the present invention, in the plasma processing apparatus having the filter circuit for attenuating undesired high-frequency noise by the above-described configuration and operation, the RF power loss amount in the filter circuit and the function thereof Differences (variations between devices) can be minimized to improve process performance reproducibility and reliability.

It is sectional drawing which shows the structure of the plasma processing apparatus in one Embodiment of this invention. It is a figure which shows the circuit structure of the electric power feeding part for supplying electric power to the heat generating body of a susceptor in embodiment. It is a figure which shows the structural example of the heat generating body in embodiment. It is a figure which shows the circuit structure of the first stage coil in embodiment. It is a top view which shows the main structures in the filter unit in embodiment. It is a schematic sectional drawing which shows the main structures in the filter unit in embodiment. It is a perspective view which shows the coil winding structure of the air core coil of 2 systems with which the common bobbin is mounted | worn in embodiment. It is a partial cross section perspective view which shows the coil winding structure in embodiment. It is a figure which shows the relationship between the inductance and stray capacitance of a first stage coil, and filter power loss rate (%) in embodiment. It is a figure which shows the frequency characteristic of the impedance when the coil winding ratio of the first stage coil is 0.6 in the coil winding structure of the embodiment. It is a figure which shows the frequency characteristic of the actual resistance component when the coil winding ratio of the first stage coil is 0.6 in the coil winding structure of the embodiment. It is a figure which shows the frequency characteristic of an impedance and an actual resistance component when the coil winding ratio of the first stage coil is set to 0.8 in the coil winding structure of the embodiment. It is a figure which shows the frequency characteristic of an impedance and an actual resistance component when the coil winding ratio of the first stage coil is set to 0.9 in the coil winding structure of the embodiment. It is a figure which shows the frequency characteristic of an impedance and a real resistance component when the coil winding ratio of the first stage coil is set to 1 in the coil winding structure of embodiment. It is a figure which shows the frequency characteristic of an impedance and a real resistance component when the coil winding ratio of the first stage coil is 1.1 in the coil winding structure of embodiment. It is a figure which shows the frequency characteristic of an impedance and an actual resistance component when the coil winding ratio of the first stage coil is set to 1.2 in the coil winding structure of the embodiment. It is a figure which shows the modification of the coil winding structure by this invention. It is a figure which shows another modification of the coil winding structure by this invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 shows the configuration of a plasma processing apparatus according to an embodiment of the present invention. This plasma processing apparatus is configured as a capacitively coupled plasma etching apparatus of an upper and lower two frequency application system, and has a cylindrical chamber (processing container) 10 made of metal such as aluminum or stainless steel. The chamber 10 is grounded for safety.

  In the chamber 10, for example, a disk-shaped susceptor 12 on which a semiconductor wafer W is placed as a processing object is horizontally disposed as a lower electrode. The susceptor 12 is made of aluminum, for example, and is supported ungrounded by an insulating cylindrical support 14 made of ceramic, for example, extending vertically upward from the bottom of the chamber 10. An annular exhaust path 18 is formed between the conductive cylindrical support portion 16 extending vertically upward from the bottom of the chamber 10 along the outer periphery of the insulating cylindrical support portion 14 and the inner wall of the chamber 10. An exhaust port 20 is provided at the bottom of the path 18. An exhaust device 24 is connected to the exhaust port 20 via an exhaust pipe 22. The exhaust device 24 includes a vacuum pump such as a turbo molecular pump, and can reduce the processing space in the chamber 10 to a desired degree of vacuum. A gate valve 26 that opens and closes the loading / unloading port of the semiconductor wafer W is attached to the side wall of the chamber 10.

  A first high frequency power supply 28 is electrically connected to the susceptor 12 via an RF cable 30, a lower matching unit 32, and a lower power feed rod 34. Here, the high frequency power supply 28 outputs a first high frequency of a predetermined frequency, for example, 13.56 MHz, which mainly contributes to the drawing of ions into the semiconductor wafer W on the susceptor 12. The RF cable 30 is made of a coaxial cable, for example. The lower matching unit 32 accommodates a matching circuit for matching between the impedance on the high frequency power supply 28 side and the impedance on the load (mainly electrodes and plasma) side, and also includes an RF sensor and a controller for auto matching. A stepping motor is also provided.

  The susceptor 12 has a diameter or diameter that is slightly larger than that of the semiconductor wafer W. The main surface, that is, the upper surface of the susceptor 12 is radiused to a central region that is substantially the same shape (circular) and substantially the same size as the wafer W, that is, a wafer placement portion, and an annular peripheral portion that extends outside the wafer placement portion. The semiconductor wafer W to be processed is placed on the wafer placement portion, and a focus ring 36 having an inner diameter slightly larger than the diameter of the semiconductor wafer W is formed on the annular peripheral portion. It is attached. The focus ring 36 is made of, for example, any one of Si, SiC, C, and SiO 2 depending on the material to be etched of the semiconductor wafer W.

  On the wafer mounting portion on the upper surface of the susceptor 12, an electrostatic chuck 38 and a heating element 40 for wafer adsorption are provided. The electrostatic chuck 38 encloses, for example, a mesh-like conductor 44 in a film-like or plate-like dielectric 42 that is integrally formed on or integrally fixed to the upper surface of the susceptor 12. An external DC power supply 45 disposed outside is electrically connected via a switch 46, a high-resistance resistor 48, and a DC high-voltage line 50. The semiconductor wafer W can be attracted and held on the electrostatic chuck 38 by a Coulomb force by a high-voltage DC voltage applied from the DC power supply 45. Note that the DC high-voltage line 50 is a covered wire, passes through the cylindrical lower power feed rod 34, penetrates the susceptor 12 from below, and is connected to the conductor 44 of the electrostatic chuck 38.

  The heating element 40 is composed of, for example, a spiral resistance heating wire enclosed in a dielectric 42 together with the conductor 44 of the electrostatic chuck 38. In this embodiment, as shown in FIG. 3, the radial direction of the susceptor 12 is formed. 2 is divided into an inner heating wire 40 (IN) and an outer heating wire 40 (OUT). Among these, the inner heating wire 40 (IN) is a dedicated wire disposed outside the chamber 10 via the insulation-coated power supply conductor 52 (IN), the filter unit 54 (IN), and the electric cable 56 (IN). It is electrically connected to the heater power source 58 (IN). The outer heating wire 40 (OUT) is a dedicated heater power source which is also disposed outside the chamber 10 via the insulation-coated power supply conductor 52 (OUT), the filter unit 54 (OUT) and the electric cable 56 (OUT). 58 (OUT) is electrically connected. Among these, the filter units 54 (IN) and 54 (OUT) are main features in this embodiment, and the internal configuration and operation will be described in detail later.

  Inside the susceptor 12, for example, an annular refrigerant passage 60 extending in the circumferential direction is provided. A refrigerant having a predetermined temperature supplied from an external chiller unit (not shown) through a pipe flows through the refrigerant passage 60. The temperature of the semiconductor wafer W on the electrostatic chuck 38 can be controlled by the temperature of the coolant. Further, in order to further increase the accuracy of the wafer temperature, a heat transfer gas such as He gas from a heat transfer gas supply unit (not shown) is passed through the gas supply pipe and the gas passage 62 inside the susceptor 12 through the electrostatic chuck 38. And the semiconductor wafer W.

  On the ceiling of the chamber 10, there is provided a shower head 64 that is parallel to the susceptor 12 and also serves as an upper electrode. The shower head 64 includes an electrode plate 66 facing the susceptor 12 and an electrode support 68 that detachably supports the electrode plate 66 from the back (upper side) thereof. A gas chamber 70 is provided inside the electrode support 68. A number of gas discharge holes 72 penetrating from the gas chamber 70 to the susceptor 12 side are formed in the electrode support 68 and the electrode plate 66. A space S between the electrode plate 66 and the susceptor 12 is a plasma generation space or a processing space. A gas supply pipe 76 from the processing gas supply unit 74 is connected to the gas introduction port 70 a provided in the upper part of the gas chamber 70. The electrode plate 66 is made of, for example, Si, SiC, or C, and the electrode support 68 is made of, for example, anodized aluminum.

  A ring-shaped insulator 78 made of alumina, for example, is airtightly sealed between the shower head 64 and the upper surface opening edge of the chamber 10. The shower head 64 is attached to the chamber 10 in an electrically floating state, that is, ungrounded. It has been. A second high frequency power supply 80 is electrically connected to the shower head 64 via an RF cable 82, an upper matching unit 84, and an upper power feed rod 86. Here, the high frequency power supply 80 outputs a second high frequency of a predetermined frequency, for example, 60 MHz, mainly contributing to plasma generation. The RF cable 82 is made of, for example, a coaxial cable. The matching unit 84 accommodates a matching circuit for matching between the impedance on the high frequency power supply 80 side and the impedance on the load (mainly electrodes and plasma) side, as well as an RF sensor, a controller for auto-matching, A stepping motor and the like are also provided.

  Each part in this plasma etching apparatus, for example, exhaust device 24, high frequency power supplies 28 and 80, switch 46 of DC power supply 45, heater power supplies 58 (IN) and 58 (OUT), chiller unit (not shown), heat transfer gas supply section Individual operations such as (not shown) and the processing gas supply unit 74 and the operation (sequence) of the entire apparatus are controlled by an apparatus control unit (not shown) including a microcomputer, for example.

  In order to perform etching in this plasma etching apparatus, first, the gate valve 26 is opened, and the semiconductor wafer W to be processed is loaded into the chamber 10 and placed on the electrostatic chuck 38. Then, an etching gas (generally a mixed gas) is introduced into the chamber 10 from the processing gas supply unit 74 at a predetermined flow rate, and the pressure in the chamber 10 is set to a set value by the exhaust device 24. Further, the first and second high frequency power supplies 28 and 80 are turned on to output the first high frequency (13.56 MHz) and the second high frequency (60 MHz) at predetermined powers, respectively, and these high frequencies are output to the RF cables 30 and 82. The susceptor (lower electrode) 12 and the shower head (upper electrode) 64 are supplied to the susceptor (lower electrode) 12 and the power supply rods 34 and 86, respectively. Further, the switch 46 is turned on, and the heat transfer gas (He gas) is confined in the contact interface between the electrostatic chuck 38 and the semiconductor wafer W by the electrostatic adsorption force. Then, while supplying cooling water adjusted to a constant temperature from the chiller unit to the refrigerant passage 60 in the susceptor 12, the heater power sources 58 (IN) and 58 (OUT) are turned on to turn on the inner heating element 40 (IN ) And the outer heating element 40 (OUT) are heated by independent Joule heat, and the temperature or temperature distribution on the upper surface of the susceptor 12 is controlled to a set value. The etching gas discharged from the shower head 64 is turned into plasma by high-frequency discharge between the electrodes 12 and 64, and the film on the main surface of the semiconductor wafer W is etched into a predetermined pattern by radicals and ions generated by the plasma. .

  This capacitively coupled plasma etching apparatus applies a relatively high frequency second high frequency suitable for plasma generation of 60 MHz to the shower head 64 to increase the density of the plasma in a preferable dissociated state, and even under lower pressure conditions. High density plasma can be formed. At the same time, a highly selective anisotropic etching is performed on the semiconductor wafer W on the susceptor 12 by applying a first high frequency of 13.56 MHz, which is a relatively low frequency suitable for ion attraction, to the susceptor 12. be able to. Normally, any frequency of 40 MHz or higher can be used for the second high frequency.

  Further, in this capacitively coupled plasma etching apparatus, chiller cooling and heater heating are simultaneously applied to the susceptor 12, and the heater heating is controlled independently at the central portion and the edge portion in the radial direction. Switching or raising / lowering temperature is possible, and the profile of the temperature distribution can be controlled arbitrarily or in various ways.

  Next, with reference to FIGS. 2 to 15, the configuration and operation of the filter units 54 (IN) and 54 (OUT), which are the main characteristic portions of this embodiment, will be described.

  FIG. 2 shows a circuit configuration of a power feeding unit for supplying power to the heating element 40 provided in the susceptor 12. In this embodiment, individual power feeding units having substantially the same circuit configuration are connected to each of the inner heating wire 40 (IN) and the outer heating wire 40 (OUT) of the heating element 40, and the inner heating wire 40. The heat generation amount or the heat generation temperature of (IN) and the outer heating wire 40 (OUT) are controlled independently. In the following description, the configuration and operation of the power feeding unit for the inner heating wire 40 (IN) will be described. The configuration and operation of the power feeding unit for the outer heating wire 40 (OUT) are exactly the same.

  The heater power source 58 (IN) is an AC output type power source that performs a commercial frequency switching (ON / OFF) operation using, for example, an SSR, and is connected to the inner heating element 40 (IN) by a closed loop circuit. More specifically, of the pair of output terminals of the heater power supply 58 (IN), the first output terminal is the first of the inner heating line 40 (IN) via the first power supply line (power supply line) 100 (1). The second output terminal is electrically connected to the second terminal b of the inner heating line 40 (IN) via the second power supply line (power supply line) 100 (2). It is connected.

  The filter unit 54 (IN) includes first and second power line filters 102 (1) and 102 (2) provided in the middle of the first and second power supply lines 100 (1) and 100 (2), respectively. Have. Both power supply line filters 102 (1) and 102 (2) have substantially the same circuit configuration, and in the illustrated example, the first-stage LC low-pass filter 104 (1) is viewed from the inner heating line 40 (IN) side. ), 104 (2) and LC low-pass filters 106 (1), 106 (2) in the next stage are cascaded in a ladder shape.

  More specifically, the first stage LC low-pass filters 104 (1) and 104 (2) are series circuits of first stage coils 108 (1) and 108 (2) and first stage capacitors 110 (1) and 110 (2), respectively. It is configured. One terminal of the first stage coils 108 (1), 108 (2) or the filter terminals T (1), T (2) are connected to both terminals a of the inner heating wire 40 (IN) via a pair of power supply conductors 52 (IN). , B, and first stage capacitors 110 (1), 110 (2) are respectively connected between the other terminals of the first stage coils 108 (1), 108 (2) and the ground potential portion.

  The next-stage LC low-pass filters 106 (1) and 106 (2) are configured by a series circuit of the next-stage coils 112 (1) and 112 (2) and the next-stage capacitors 114 (1) and 114 (2). Yes. One terminal of the next stage coils 112 (1) and 112 (2) is a connection point m (1) between the first stage coils 108 (1) and 108 (2) and the first stage capacitors 110 (1) and 110 (2). , M (2), and next stage capacitors 114 (1) and 114 (2) are connected between the other terminals of the next stage coils 112 (1) and 112 (2) and the ground potential part, respectively. ing. The connection points n (1) and n (2) between the next stage coils 112 (1) and 112 (2) and the next stage capacitors 114 (1) and 114 (2) are electric cables (pair cables). The heater power supply 58 (IN) is connected to the first and second output terminals of the heater power supply 58 (IN) via 56 (IN), respectively.

  In the power supply unit configured as described above, the current output from the heater power supply 58 (IN) is the first power supply line 100 (1), that is, the electric cable 56 (IN), and the next coil 112 (1) in the positive polarity cycle. , Through the first stage coil 108 (1) and the feed conductor 52 (IN), enter the inner heating wire 40 (IN) from one terminal a, and generate Joule heat by energization at each part of the inner heating wire 40 (IN). After exiting from the other terminal b, it passes through the second feed line 100 (2), that is, the feed conductor 52 (IN), the first stage coil 108 (2), the next stage coil 112 (2), and the electric cable 56 (IN). And return. In the negative cycle, a current flows through the same circuit in the opposite direction. Since the heater AC output current is a commercial frequency, the impedance or voltage drop in the first stage coils 108 (1) and 108 (2) and the next stage coils 112 (1) and 112 (2) is negligibly small. The leakage current that escapes to the ground through the capacitors 110 (1) and 110 (2) and the next stage capacitors 114 (1) and 114 (2) is negligibly small.

  One of the features of this embodiment is that the first stage coils 108 (1) and 108 (2) of the first stage LC low-pass filters 104 (1) and 104 (2) are air core coils from the viewpoint of preventing heat generation, and the installation space. In order to reduce the size (especially in the vertical space), preferably a plurality of, for example, two air-core coils [A (1), B (1)], [ A (2), B (2)]. A further feature is that the plurality of single air-core coils [A (1), B (1)], [A (2), B (2)] are coiled as shown in FIGS. The filter unit 54 (IN) has a line structure.

  As shown in FIG. 4, two air-core coils A (1) and B (1) constituting the first-stage coil 108 (1) in the first-stage LC low-pass filter 104 (1) of the first feed line 100 (1). 1) is electrically connected in series in this order when viewed from the inner heating wire 40 (IN) side, and the air-core coil unit A (1) is electrically connected to the first stage position, that is, to the physical terminal T (1). In the nearest position. The two air-core coils A (2) and B (2) constituting the first-stage coil 108 (2) in the first-stage LC low-pass filter 104 (2) of the second feeder line 100 (2) are also arranged on the inner side. When viewed from the heating wire 40 (IN) side, they are electrically connected in series in this order, and the air-core coil unit A (2) is the closest position to the first stage, that is, the electrical terminal T (1). It is in.

  5 and 6, the filter unit 54 (IN) has a box-shaped cover or casing 120 made of a conductive plate, and the casing 120 accommodates all the filter components. In particular, the two air-core coils constituting the first stage coils 108 (1) and 108 (2) respectively [A (1), B (1)], [A (2), B (2)] The first stage capacitors 110 (1) and 110 (2) and the next stage LC low pass filters 106 (1) and 106 (2) are arranged in a small space at one corner. As a material of the casing 120, stainless steel having high magnetic shielding ability and excellent rust prevention and high relative permeability is suitable.

  Each single-core coil [A (1), B (1)], [A (2), B (2)] is sufficiently large from the heater power supply 52 (IN) to the inner heating wire 40 (IN) (for example, In order to obtain a very large inductance with an air core without having a magnetic core such as ferrite from the viewpoint of preventing heat generation (power loss) in addition to the function of a power supply line for flowing current (30A), It has a coil size (e.g., a diameter of 22 to 45 mm, a length of 150 to 250 mm) that is contrary to common sense.

  In this embodiment, two single air-core coils [A (1), B (1)], [A (2), B (2)] in the casing 120 as a whole are both spatially and functionally. Installed efficiently. More specifically, the first stage air-core coils A (1) and A (2) of the first and second power supply lines 100 (1) and 100 (2) are connected to each other in the circumferential direction of the casing 120. It is mounted concentrically on a cylindrical or columnar bobbin 114A made of an insulator, such as a resin, standing up close to the side surface.

  Here, the winding structure between the two air-core coils alone A (1) and A (2) is characteristic. That is, the coil conductors constituting the air-core coils A (1) and A (2) are equal to each other while being translated along the outer peripheral surface of the common bobbin 114A so as to overlap in the bobbin axial direction as shown in FIG. It is wound spirally with the winding length. As shown in FIG. 8, the coil conductors of both air-core coils alone A (1) and A (2) are preferably made of a thin plate or a flat copper wire having the same cross-sectional area. In order to prevent this, the coil conductor of one air-core coil unit A (2) is covered with an insulating coating such as a Teflon (registered trademark) tube 120.

  On the other hand, the second-stage air-core coils B (1) and B (2) of the two power supply lines 100 (1) and 100 (2) are separated from each other by another support shaft that is erected substantially at the center in the casing 120. 114B is mounted concentrically. The winding structure between both air core coils B (1) and B (2) is the same as the winding structure between both air core coils A (1) and A (2). The coil conductors are spirally wound with the same winding length while overlapping and translating along the bobbin axial direction along the outer peripheral surface of the common bobbin 114B.

  As shown in FIG. 6, filter terminals T (1), T (2) are attached to the upper ends of the first-stage air-core coils A (1), A (2), and the first-stage air-core coils A ( 1), A (2) and the second stage air-core coil unit B (1), B (2) are connected via a connector conductor 122 on the lower end side. Also, the second stage air-core coils B (1), B (2) and the first stage capacitors 110 (1), 110 (2) are connected via the connector conductor 124 at the upper end side. For the connector conductors 122 and 124, coil conductors constituting each coil unit may be used as they are.

  As described above, in this embodiment, the spiral direction of the coil winding is the same between the two air-core coils mounted on the common bobbin. That is, the first stage air-core coil unit A (1) of the first system or the first power supply line 100 (2) and the second system or the second power supply line 100 (2) mounted together on the bobbin 114A. The direction of the spiral of the coil winding constituting them is the same as that of the first stage air-core coil unit A (2). As a result, both the air-core coils alone A (1) and A (2) have a high frequency on the two power supply lines propagating from the susceptor 12 through the inner heating wire 40 (IN) and the power supply conductor 52 (IN). Current flows in the same direction with the same spiral direction. In this case, that is, when a high-frequency current flows simultaneously in both air-core coils alone A (1) and A (2), there is a relationship that the magnetic fluxes penetrating both coils are directed in the same direction. A mutual inductance with a positive coupling constant is obtained between 1) and A (2). Similarly, between the second stage air-core coils B (1) and B (2) mounted together on the bobbin 114B, the direction of the spiral of the coil winding constituting them is the same, and the coupling constant is A positive mutual inductance is obtained.

  Further, the coil diameter and the winding length are equal between the two systems of air-core coils mounted on a common bobbin. That is, the first stage air-core coils A (1) and A (2) mounted on the bobbin 114A are made of conducting wires of the same material and the same size (thickness and length), both of which are bobbins 114A. It has a coil diameter defined by the outer diameter. In addition, in each of the air-core coils A (1) and A (2), the coil conductors are alternately overlapped in the bobbin axis direction. The second-stage air core coils B (1) and B (2) mounted on the bobbin 114B are also made of the same material and the same size (thickness and length), both of which are the outer diameter of the bobbin 114B. The coil conductors are alternately overlapped in the bobbin axis direction.

  In such a coil winding structure, the self-inductance is equal to each other and the maximum mutual inductance is obtained between the first-stage air-core coils A (1) and A (2). Similarly, the self-inductance is equal to each other and the maximum mutual inductance is obtained between the second stage air-core coils B (1) and B (2). As will be described later, this is important in reducing the RF power loss in the filter unit 120 and further reducing the difference in RF power loss.

  Further, in this embodiment, between the bobbins 114A and 114B adjacent to each other in the horizontal direction, the direction of the spiral of the coil winding is made opposite to the direction of the axial magnetic field generated at the center of each coil. . For example, when the magnetic field lines penetrate from the top to the bottom in the axial direction in the air core coils A (1) and A (2), the magnetic field lines in the adjacent air core coils B (1) and B (2). Pierce from bottom to top in the axial direction. As a result, the first stage air-core coil unit A (1) and the second stage air-core coil unit B (1) connected in series and the first stage air-core coil unit A (2) and the second stage There is a relationship in which a high-frequency current flows in the opposite direction in the direction of the opposite spiral in space with the single-stage air-core coil unit B (2). A mutual inductance having a positive coupling constant can also be obtained between A (2) and the single coil B (1), B (2) on the bobbin 114B side. This also contributes to reducing the RF power loss in the filter unit 120.

  Thus, the air-core coils alone [A (1), B (1)], [A (2), B (2)] housed in the casing 120 have a large self-inductance and a maximum mutual inductance. Thus, a combined inductance of 5 μH or more can be easily realized in the first stage coils 108 (1) and 108 (2) constituted by these air-core coils alone.

  In the present invention, from the viewpoint of reducing the RF power loss as much as possible, it is particularly preferable that the first stage air-core coils A (1) and A (2) have a large inductance. For this reason, as shown in FIG. 6, the number of windings of the first stage air-core coil unit A (1), A (2) is set to the number of windings of the subsequent stage air-core coil unit B (1), B (2). There are more than numbers.

  The first stage coils 108 (1) and 108 (2) actually have stray capacitance and loss (resistance) as a matter of course. It is important to reduce the stray capacitance as much as possible in order to reduce the power loss of the first stage coil 108. From this point of view, in this embodiment, the air-core coils constituting the first stage coils 108 (1), 108 (2) alone [A (1), B (1)], [A (2), B (2)] Are separated from the inner wall surface (ground potential surface) of the casing 120 by 10 mm or more, so that the combined stray capacitance between the first stage coils 108 (1) and 108 (2) and the ground potential portion, that is, the combined ground stray capacitance is 30 pF or less. I try to suppress it.

  If the sum of the inductances of multi-stage connected air-core coils [A (1), B (1)], [A (2), B (2)] is the same, The larger the number of turns of a single air-core coil unit A (1), A (2), the smaller the total ground capacitance. In addition, the total ground floating capacity of the air core coil unit [A (1), B (1)], [A (2), B (2)] of the multi-stage connection is the same. In this case, the smaller the stray capacitance of the first stage air-core coils A (1) and A (2) is, the smaller the total stray capacitance is. This has been confirmed by the present inventors through simulations and experiments.

  As described above, increasing the number of windings of the first stage air-core coils A (1) and A (2), or reducing their ground stray capacitance, makes the first stage coils 108 (1), 108 (2) It is most effective in reducing the total synthetic ground capacitance. In that sense, for example, it is preferable to set a particularly large separation distance between the first-stage air-core coils A (1), A (2) and the casing 120, for example. Alternatively, it is preferable that the number of turns of the first-stage air core coils A (1) and A (2) be as large as possible than the number of turns of the subsequent air-core coils B (1) and B (2).

  As shown in FIGS. 5 and 6, a box 126 made of resin, for example, is attached to the side wall of the casing 120 in the vicinity of the second stage air-core coils B (1) and B (2). The next-stage LC low-pass filters 106 (1) and 106 (2) are all housed in the interior, and the first-stage capacitors 110 (1) and 110 (2) are arranged below the box 126. Between the second stage air-core coil unit B (1), B (2) and the box 126, a ground potential conductor plate 128 serving also as an electromagnetic shield is provided, and the first stage capacitor 110 (1) is provided on the conductor plate 128. 110 (2) are implemented.

  In the plasma etching apparatus of this embodiment, a part of the high frequency applied from the first high frequency power source 28 to the susceptor 12 is transmitted from the inner heating element 40 (IN) to the first and second power supply lines 100 (1), 100. The signal passes through (2) and enters the filter circuits 102 (1) and 102 (2). The high-frequency current that has entered the filter circuits 102 (1) and 102 (2) is attenuated to, for example, 1/10 or less by the first-stage LC low-pass filters 104 (1) and 104 (2), and the next-stage LC low-pass filter 106 ( The high-frequency current flowing into 1) and 106 (2) is very small. For this reason, the power loss of the next-stage coils 112 (1) and 112 (2) is almost negligible, and the next-stage coils 112 (1) and 112 (2) may be configured with small magnetic core-containing coils. it can. However, it is not desirable that the next stage coils 112 (1) and 112 (2) be magnetically coupled to the second stage air core coils B (1) and B (2) adjacent to the next stage coils 112 (1) and 112 (2). It is shielded with. The conductor plate 128 may be made of the same material as the casing 120.

  As described above, most of the high-frequency waves that enter the filter circuits 102 (1) and 102 (2) from the susceptor 12 side through the feed lines 100 (1) and 100 (2) are first-stage LC low-pass filters 104 (1). , 104 (2) attenuates and disappears, and accordingly, most of the RF power loss in the filter circuits 102 (1), 102 (2) occurs in the first-stage LC low-pass filters 104 (1), 104 (2). .

  In the plasma etching apparatus of this embodiment, the present inventor uses the combined inductance (L) and combined ground floating capacitance (C) of the first stage coils 108 (1) and 108 (2) as the horizontal axis and the vertical axis, respectively. The ratio of the RF power loss generated in 102 (1) and 102 (2) to the total high frequency power (the output power of the high frequency power supply 28), that is, the filter power loss rate (%), is obtained by simulation as shown in FIG. A contour map was obtained. The combined inductance (L) and the combined ground stray capacitance (C) are the apparent combined inductance and combined ground stray capacitance of the first stage coils 108 (1) and 108 (2) when viewed from the heating element 40 side. .

  As shown in FIG. 9, the larger the value of inductance (L) and the smaller the value of stray capacitance (C), the smaller the filter power loss rate (%), and L is 5 μH or more and C is 30 pF or less. It can be seen that the filter power loss rate (%) is always less than 4% even if the values of L and C fluctuate in the region (the region indicated by the dotted line frame). On the other hand, outside of the above region, it is not only difficult or impossible to keep the filter power loss rate (%) below 4%, but also the filter power loss rate (%) with respect to small changes in L or C. It changes a lot.

  By the way, in general plasma etching, the tolerance of the reproducibility of the etching rate, which is a typical index of process performance, has a variation of approximately 2% or less, and for that purpose, the filter power loss rate (%) is twice that. In other words, it should be less than 4%. Therefore, if the inductance (L) of each of the first-stage coils 108 (1) and 108 (2) is 5 μH or more and the stray capacitance (C) is 30 pF or less, the etching rate reproducibility tolerance can be surely cleared. .

  In this embodiment, the filter unit 54 (IN) is configured as described above to satisfy the numerical conditions of L and C. In particular, in the first stage LC low-pass filters 104 (1) and 104 (2), a pair of air-core coils alone [A (1), A (2)], [B ( 1), B (2)], a coil winding structure is employed in which the self-inductance is equal and the mutual inductance is maximized.

  In the plasma etching apparatus of this embodiment, the inventor of the present application provides a gap between the first stage coil 108 (1) of the first power supply line 100 (1) and the first stage coil 108 (2) of the second power supply line 100 (2). And the combined impedance (Z) and actual resistance component (R) of both coils 108 (1) and 108 (2) when the winding length ratio is changed within the range of 0.6 to 1.2. As a result of simulation, results as shown in FIGS. 10 to 15 were obtained.

  It can be seen from the simulation results that there is a significant difference in the frequency characteristics of the actual resistance component (R) between the case where the winding length ratio is 1 and the other cases. That is, the winding length ratio is other than 1, that is, 0.6 (FIG. 10B), 0.8 (FIG. 11), 0.9 (FIG. 12), 1.1 (FIG. 14), 1.2 (FIG. 15). In the case, the characteristic (Q) in which the actual resistance component (R) abnormally increases in the shape of a square (n) uniformly in the vicinity of 9 MHz is seen, whereas the winding length ratio is 1 (FIG. 13). No such abnormal increase (Q) of the actual resistance component (R) is observed. However, the degree of abnormal increase (Q) of the actual resistance component (R) in the vicinity of 9 MHz increases as the winding length ratio becomes farther than 1, so that the abnormal increase (Q ) Will gradually decrease. In addition, in the example shown in the figure, the frequency region where the abnormal increase (Q) of the actual resistance component (R) appears when the winding length ratio is other than 1 is around 9 MHz. The present inventor has also confirmed through experiments and the like that the frequency characteristics vary, that is, there is a machine difference.

  In the frequency characteristics of the simulation (FIGS. 10 to 15), the actual resistance component (R) increases in a square shape around 16 MHz regardless of the winding length ratio. This is a natural phenomenon for (1) and 108 (2) to have parallel resonance characteristics, and not indefinite (abnormal) characteristics.

  When the first-stage coils 108 (1) and 108 (2) in the filter unit 54 (IN) have an indefinite abnormal increase (Q) with the above-described machine difference in the frequency characteristics of the actual resistance component (R) The filter power loss rate fluctuates in an indefinite manner, and the process performance reproducibility decreases. However, in this embodiment, since the coil winding structure that stably satisfies the condition of the winding length ratio 1 in the first stage coils 108 (1) and 108 (2) is adopted as described above, the actual resistance component (R ) Can be reliably prevented from appearing in the frequency characteristics, and the filter power loss rate can be suppressed to an allowable value or less to improve the reproducibility of the process performance.

  As mentioned above, although preferred embodiment was described, this invention is not limited to the said embodiment, A various deformation | transformation is possible within the range of the technical idea.

  For example, FIGS. 16 and 17 show modifications of the coil winding structure according to the present invention. The coil winding structure shown in FIG. 16 is the above implementation in that two coils A and B are mounted on the common bobbin 114 with the same coil diameter and the winding length ratio of both coils A and B is 1. Although the configuration is the same, the coil conductors of the coils A and B are not configured to alternately overlap in the bobbin axis direction, and the maximum mutual inductance cannot be obtained between the coils A and B. The coil winding structure shown in FIG. 17 is the same as the above embodiment in that two coils A and B are mounted on a common bobbin 114 and the winding length ratio of both coils A and B is 1. However, the diameters of the coils A and B are different from each other, and the coil conductors are not alternately overlapped in the bobbin axis direction. For this reason, the self-inductance of both the coils A and B is not the same, and the mutual inductance is not the maximum.

  Since the coil winding structure as shown in FIGS. 16 and 17 lacks some of the requirements to be satisfied in the above embodiment, the frequency characteristics of the actual resistance component (R), the filter power loss rate, and thus the process performance reproducibility are improved. The effect of improving is reduced or halved.

  Further, in the plasma etching apparatus of the above-described embodiment, the heating element 40 provided in the susceptor 12 is divided into the inner heating line 40 (IN) and the outer heating line 40 (OUT) in the radial direction of the susceptor. An integrated type is also possible. In this case, only one heater power source and power supply line are required.

  In the above-described embodiment, in the filter units 54 (IN) and 54 (OUT), the first stage coils 108 (1) and 108 (2) are each made up of two air-core coils alone [A (1), B (1 )], [A (2), B (2)]. However, the first stage coils 108 (1), 108 (2) are, for example, three air core coils alone [A (1), B (1), C (1)], [A (2), B (2), C (2)] can be divided, respectively, or can be constituted by only one air-core coil unit A (1), A (2).

  Also, the circuit configurations of the filter circuits 102 (1) and 102 (2) can be variously modified. For example, a third stage is provided after the LC low-pass filters 106 (1) and 106 (2) of the next stage. A configuration in which LC low-pass filters are cascaded is also possible.

  In the above-described embodiment, the second high frequency (60 MHz) for plasma generation is applied to the shower head (upper electrode) 64, but the lower portion where the second high frequency is superimposed on the first high frequency (13.56 MHz) and applied to the susceptor 12. The present invention can also be applied to a two-frequency application method. Furthermore, a lower one-frequency application method in which only the first high frequency (13.56 MHz) is applied to the susceptor 12 without applying a high frequency to the upper electrode 64 is also possible. Further, the first high frequency applied to the susceptor 12 is not limited to 13.56 MHz, and other frequencies can be used. The casing 120 used for the filter unit 52 is not limited to a sealed housing structure, and a part thereof may be opened.

  In the above-described embodiment, a pair of heater power supply lines 100 (1) and 100 (2) that electrically connect the heating element 40 provided on the susceptor 12 in the chamber 10 and the heater power supply 58 installed outside the chamber 10 are used. ) Relates to a filter circuit for attenuating the first high-frequency noise for ion attraction. However, the present invention is not limited to such a power line filter, and a predetermined electrical component provided in the chamber and an electric power system or signal system external circuit provided outside the chamber are electrically connected. The present invention can be applied to any filter circuit provided on a pair of lines to be connected. Therefore, the high frequency to be attenuated or cut off by the filter circuit can be arbitrarily selected. For example, it may be a high frequency that mainly contributes to plasma generation, or a harmonic or intermodulation distortion (IMD) generated from plasma as a nonlinear circuit. distortion).

  The present invention is not limited to a plasma etching apparatus, but can be applied to other plasma processing apparatuses such as plasma CVD, plasma oxidation, plasma nitridation, and sputtering. Further, the substrate to be processed in the present invention is not limited to a semiconductor wafer, and various substrates for flat panel displays, photomasks, CD substrates, printed substrates, and the like are also possible.

10 chamber (processing vessel)
12 Susceptor (lower electrode)
24 Exhaust device 28 First high frequency power supply 40 Heating element 40 (IN) Inner heating wire 40 (OUT) Outer heating wire 54 (IN), 54 (OUT) Filter unit 58 (IN), 58 (OUT) Heater power supply 64 Shower Head (upper electrode)
74 Process gas supply unit 100 (1) First power supply line 100 (2) Second power supply line 102 (1) First power line filter 102 (2) Second power line filter 104 (1), 104 ( 2) First stage LC low pass filter 106 (1), 106 (2) Next stage LC low pass filter 108 (1), 108 (2) First stage coil 110 (1), 110 (2) First stage capacitor A (1), A (2) First stage air-core coil unit B (1), B (2) Second stage air-core coil unit

In order to achieve the above object, a plasma processing apparatus according to a first aspect of the present invention provides a first high-frequency power source that outputs a first high-frequency to a first electrode disposed in a depressurizable processing container. And a high-frequency wave that enters the first and second power supply lines for electrically connecting the heating element provided in the first electrode and the heater power supply via the heating element. A plasma processing apparatus provided with a filter circuit for attenuating noise, wherein the first and second air cores are provided in the first stage of the filter circuit when viewed from the heating element on the first and second power supply lines. Coils are provided, and the first and second coil conductors constituting the first and second air-core coils , respectively, are spirally wound with substantially the same winding length while being translated coaxially with each other, The first and The second air-core coil, a high frequency current on the propagated from the heating element the first and second feed line flows in the same direction.
In the plasma processing apparatus according to the second aspect of the present invention, for plasma processing using a high frequency in a depressurizable processing container, predetermined electrical components provided in the processing container are provided via first and second lines. And an external circuit of a power system or a signal system that is provided outside the processing container, and the high-frequency noise that enters the first and second lines via the electrical component is A plasma processing apparatus for attenuating by a filter circuit provided on a first line and a second line, wherein the first and second stages are disposed on the first stage of the filter circuit as viewed from the electrical component on the first line and the second line. air-core coil are respectively provided, first and second coil conductors constituting the first and second air-core coil respectively, spirally wound at a substantially equal winding length while translate coaxially of In which, in the first and second air-core coil, a high frequency current on the first and second feed line having propagated from the electrical component flows in the same direction.

In the above device configuration, the first stage coil of the filter circuit is an air-core coil. Therefore, by setting the inductance to a very large value, compared to a coil with a small inductance or a magnetic core such as ferrite. High-frequency power loss can be significantly reduced. In addition, the first and second coil conductors constituting the first and second air-core coils constituting the first stage coil are spirally wound with substantially the same winding length while being translated coaxially with each other. In addition, it is possible to prevent or suppress the occurrence of indefinite abnormal increase in the frequency characteristic of the actual resistance component in the filter circuit, thereby improving the reproducibility of the process performance.

Claims (1)

A first high-frequency power source that outputs a first high frequency is electrically connected to a first electrode that is disposed in a depressurizable processing container, and a heating element and a heater power source that are provided in the first electrode; A plasma processing apparatus provided with a filter circuit for attenuating high-frequency noise entering from the heating element on the first and second power supply lines for electrically connecting
First and second air-core coils are provided in the first stage of the filter circuit as viewed from the heating element on the first and second power supply lines, respectively.
The plasma processing apparatus, wherein the first and second air-core coils are coaxial with each other and have substantially the same winding length.

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