JP2007250860A - Plasma processor and electrode assembly therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrode assembly for a plasma processor and the plasma processor, wherein a plasma density can be intended to make uniform without causing a generation of an abnormal discharge or a complication of an assembly and maintenance, and a plasma processing can be carried out with an excellent in-plane uniformity. <P>SOLUTION: The electrode assembly for the plasma processor is constituted of an electrode surface member 32, a spacer 37, a cleaning plate 34, and an electrode support 33. At least one of these electrode surface member 32, spacer 37, and cleaning plate 34 is made of a metal composite material; and is formed as a plate-shaped member having such a distribution of an electric resistance value that its center part has a higher electric resistance value than its periphery. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electrode assembly for a plasma processing apparatus and a plasma processing apparatus for performing plasma processing such as plasma etching.

  In a manufacturing process of a semiconductor device, a liquid crystal display device, or the like, plasma processing that performs various types of processing using plasma is frequently used. As a plasma processing apparatus that performs such plasma processing, for example, a so-called parallel plate type plasma processing apparatus that generates a plasma by forming a high-frequency electric field between a pair of opposing electrodes arranged in a processing chamber. Are known.

  In recent semiconductor device manufacturing processes and the like, the diameter of a semiconductor wafer as a substrate to be processed is gradually increased in order to improve productivity and the like. For this reason, in the parallel plate type plasma processing apparatus as described above, it is necessary to generate plasma having a uniform plasma density in a wide area range to improve the in-plane uniformity of the plasma processing.

The plasma density as described above tends to increase at the center of the electrode and decrease at the periphery. For this reason, in the electrode assembly for a plasma processing apparatus, an electrode surface member (for example, composed of silicon or the like) that constitutes an exposed surface exposed in the processing chamber, a spacer that is a member disposed on the back surface side, or the like In order to make the plasma density uniform, a gap is formed only near the center of the electrode. There is also known a technique in which the electrode surface member and the like are formed of different members having different electrical resistances from the central portion and the peripheral portion to achieve uniform plasma density (see, for example, Patent Document 1).
JP 2000-323456 A

  Among the above-described conventional techniques, the technique of providing a gap between the electrode surface member and the spacer disposed on the back side of the electrode has a problem that abnormal discharge may occur in the gap. In addition, in the technology in which the electrode surface member and the like are configured by separate members having different electrical resistances from the central portion and the peripheral portion, the number of constituent members is increased, and assembly and maintenance of the electrode assembly for the plasma processing apparatus is complicated. There are challenges.

  The present invention has been made in response to the above-described conventional circumstances, and it is possible to achieve uniform plasma density without incurring abnormal discharge and intricate assembly and maintenance. It is an object of the present invention to provide an electrode assembly for a plasma processing apparatus and a plasma processing apparatus that can perform favorable plasma processing.

  The electrode assembly for a plasma processing apparatus according to claim 1 is an electrode assembly for a plasma processing apparatus for generating a plasma by generating a high-frequency electric field in a processing chamber in which a substrate to be processed is accommodated. Thus, a plate-like member having a distribution of electrical resistance values in which the central portion has a higher electrical resistance value than the peripheral portion is provided.

  The electrode assembly for a plasma processing apparatus according to claim 2 is the electrode assembly for a plasma processing apparatus according to claim 1, wherein the plate-like member is an electrode surface member constituting an exposed surface exposed in the processing chamber. It is characterized by that.

  The electrode assembly for a plasma processing apparatus according to claim 3 is the electrode assembly for a plasma processing apparatus according to claim 1, wherein the plate-shaped member is a back surface of an electrode surface member that constitutes an exposed surface exposed in the processing chamber. It is a member arrange | positioned at the side, It is characterized by the above-mentioned.

  The electrode assembly for a plasma processing apparatus according to claim 4 is the electrode assembly for a plasma processing apparatus according to any one of claims 1 to 3, wherein the plate-shaped member is interposed between the central portion and the peripheral portion. And an intermediate portion having an intermediate electrical resistance value between the electrical resistance value of the central portion and the electrical resistance value of the peripheral portion.

  A plasma processing apparatus according to a fifth aspect comprises the electrode assembly for a plasma processing apparatus according to any one of the first to fourth aspects, and is configured to supply high-frequency power to the electrode assembly for the plasma processing apparatus. And

  A plasma processing apparatus according to a sixth aspect includes the electrode assembly for a plasma processing apparatus according to any one of the first to fourth aspects, and is configured such that the electrode assembly for the plasma processing apparatus is set to a ground potential. And

  According to the present invention, plasma processing that can achieve uniform plasma density and can perform plasma processing with good in-plane uniformity without causing abnormal discharge or complicated assembly and maintenance. An electrode assembly for a device and a plasma processing apparatus can be provided.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an overall cross-sectional configuration of a plasma etching apparatus as a plasma processing apparatus according to the present embodiment, and FIG. 2 shows a cross-sectional configuration of the main part thereof.

  The plasma etching apparatus 1 is configured as a capacitively coupled parallel plate etching apparatus in which electrode plates are opposed in parallel in the vertical direction and a power source for plasma formation is connected.

  The plasma etching apparatus 1 has a processing chamber (processing container) 10 formed of, for example, aluminum whose surface is anodized and formed into a cylindrical shape, and the processing chamber 10 is grounded. A substantially cylindrical susceptor support 12 for placing an object to be processed, for example, a semiconductor wafer W, is provided on the bottom of the processing chamber 10 via an insulating plate 11 such as ceramic. Further, a susceptor 13 constituting a lower electrode is provided on the susceptor support 12. A high pass filter (HPF) 62 is connected to the susceptor 13.

  A refrigerant chamber 19 is provided inside the susceptor support 12. In this refrigerant chamber 19, refrigerant is introduced and circulated through the refrigerant pipes 20 a and 20 b, and the cold heat is transmitted to the semiconductor through the susceptor 13. Heat is transferred to the wafer W, whereby the semiconductor wafer W is controlled to a desired temperature.

  On the susceptor 13, an electrostatic chuck 14 having substantially the same shape as the semiconductor wafer W is provided. The electrostatic chuck 14 includes an electrode plate 15 made of a conductive film and a pair of insulating layers or insulating sheets sandwiching the electrode plate 15, and a DC power supply 16 includes a connection terminal 58 and a movable power supply rod, which will be described later, on the electrode plate 15. 67 is electrically connected. The electrostatic chuck 14 sucks and holds the semiconductor wafer W by a Coulomb force or a Johnson-Rahbek force caused by a DC voltage applied by the DC power supply 16.

  A plurality of pusher pins 56 are provided inside the susceptor 13 so as to protrude from the upper surface of the electrostatic chuck 14. The pusher pins 56 are driven by a drive mechanism including, for example, a motor and a ball screw, and the semiconductor wafer W is lifted onto the electrostatic chuck when the semiconductor wafer W is transferred to and from a transfer robot or the like. Support with.

  An annular focus ring 17 is disposed on the susceptor 13 so as to surround the periphery of the electrostatic chuck 14. The focus ring 17 is made of silicon or the like and has an effect of improving etching uniformity. A cover ring 54 that protects the side of the focus ring 17 is disposed around the focus ring 17. A cylindrical inner wall member 18 made of, for example, quartz is provided on the side surfaces of the susceptor 13 and the susceptor support 12.

  The insulating plate 11, the susceptor support 12, the susceptor 13, and the electrostatic chuck 14 are provided with a gas passage 21 for supplying a heat transfer medium (for example, He gas) on the back surface of the semiconductor wafer W. The cold heat of the susceptor 13 is transmitted to the semiconductor wafer W via the heat transfer medium so that the semiconductor wafer W is maintained at a predetermined temperature.

  An upper electrode 22 is provided above the susceptor 13 so as to face the susceptor 13 in parallel. A space between the susceptor 13 and the upper electrode 22 functions as a plasma generation space S. The upper electrode 22 includes an annular outer upper electrode 23 and a disk-shaped inner upper electrode 24 disposed inside the outer upper electrode 23. A dielectric 25 made of, for example, quartz is disposed between the inner upper electrode 24 and the outer upper electrode 23, and these are insulated. A capacitor is formed by inserting a dielectric 25 between the inner upper electrode 24 and the outer upper electrode 23. The capacitance of the capacitor is set to a desired value according to the size of the gap between the inner upper electrode 24 and the outer upper electrode 23 and the dielectric constant of the dielectric 25. Between the outer upper electrode 23 and the side wall of the processing chamber 10, for example, an annular insulating shielding member 26 made of alumina or yttria is disposed in an airtight manner.

  The outer upper electrode 23 is made of, for example, silicon. As shown in FIG. 2, a first high-frequency power source 31 is electrically connected to the outer upper electrode 23 via a matching unit 27, a power feeding rod 28, a connector 29, and a power feeding cylinder 30. The first high frequency power supply 31 outputs a high frequency of 13.5 MHz or higher, for example, a high frequency voltage of 60 MHz. The power supply cylinder 30 is made of a substantially cylindrical or conical conductive plate, for example, an aluminum plate or a copper plate, and the lower end is continuously connected to the outer upper electrode 23 in the circumferential direction, and the upper end is connected to the power supply rod 28 via the connector 29. Is electrically connected. Outside the power supply cylinder 30, the side wall of the processing chamber 10 extends upward from the height position of the upper electrode 22 to constitute a cylindrical ground conductor 10 a. The upper end portion of the cylindrical ground conductor 10 a is electrically insulated from the power feeding rod 28 by a cylindrical insulating member 63. In this configuration, in the load circuit viewed from the connector 29, a coaxial line having the power supply tube 30 and the outer upper electrode 23 as a waveguide is formed by the power supply tube 30, the outer upper electrode 23, and the cylindrical ground conductor 10a.

  The inner upper electrode 24 has a large number of gas holes 32a and an electrode surface member 32 constituting an exposed surface exposed in the processing chamber. A cooling plate 34 having a large number of gas holes 34 a is provided on the back surface side of the electrode surface member 32, and a spacer 37 having a number of gas holes 37 a between the cooling plate 34 and the electrode surface member 32. Is provided. The cooling plate 34 is provided with a refrigerant circulation mechanism (not shown) and can be set to a desired temperature.

  The electrode surface member 32, the spacer 37, and the cooling plate 34 are integrally supported by an electrode support 33. The electrode surface member 32 is fastened to the electrode support 33 by a bolt (not shown), and the head portion of the bolt is protected by an annular shield ring 53 disposed under the electrode surface member 34.

  Inside the electrode support 33, a buffer chamber into which a processing gas to be described later is introduced is formed. The buffer chamber is divided into a central buffer chamber 35 and a peripheral buffer chamber 36 separated by an annular partition member 43 made of an O-ring or the like. Consists of.

  In the present embodiment, the electrode surface member 32, the spacer 37, the cooling plate 34, and the electrode support 33 constitute an electrode assembly for a plasma processing apparatus, and these are integrally replaced during maintenance of the plasma etching apparatus 1 or the like. It is possible. Then, at least one of the electrode surface member 32, the spacer 37, and the cooling plate 34 is made of a metal matrix composite material, and has a plate-like shape having a distribution of electric resistance values in which the central portion has a higher electric resistance value than the peripheral portion. It is a member. As such a metal matrix composite (MMC (Metal Matrix Composites)), for example, a metal matrix composite manufactured by Nippon Ceratech Co., Ltd. can be used.

  In such a metal matrix composite, it is possible to constitute an integral member having regions having different electric resistance values by adjusting the content ratio of the ceramic with respect to the metal. The spacer 37 and the cooling plate 34 can be manufactured as an integral plate-like member having a higher resistance value in the central part than in the peripheral part. In addition, when comprising the electrode surface member 32 from a metal matrix composite material, it is preferable to comprise from the thing which uses silicon | silicone as a base material. When the spacer 37 and the cooling plate 34 are made of a metal matrix composite material, the spacer 37 and the cooling plate 34 can be made of an aluminum alloy or the like as a base material.

  As described above, at least one of the electrode surface member 32, the spacer 37, and the cooling plate 34 constituting the electrode assembly for the plasma processing apparatus is made of a metal matrix composite material, and the central portion has a higher electrical resistance value than the peripheral portion. By using a plate-like member having a distribution of electrical resistance values, for example, the same effect as when a gap is provided only at the center between the electrode surface member 32 and the spacer 37, that is, the plasma density at the center is reduced. It is possible to suppress the increase, and plasma processing with good in-plane uniformity can be performed. Further, since no gap is formed, abnormal discharge can be prevented from occurring in the gap portion. Furthermore, by constituting from an integral plate-like member, it is possible to prevent the structure from becoming complicated and the assembly and maintenance from becoming complicated as in the case of being constituted from a plurality of members. The electrical resistance value distribution may be divided into two regions, a central portion 100a and a peripheral portion 100b as schematically shown in FIG. 3, and as schematically shown in FIG. An intermediate region 100c having an intermediate resistance value may be provided between the portions 100b and divided into three regions. Further, it may be divided into a larger number of regions.

  The metal matrix composite as described above can also be used for other components of the plasma etching apparatus 1. For example, the processing chamber 10 is made of a metal matrix composite material, and a heater layer and an insulating layer surrounding the heater layer are provided inside, and the surface layer is a conductor layer, so that an integrated chamber with a built-in heater is provided. Can also be configured. With such a configuration, the temperature of the wall surface of the processing chamber 10 can be controlled, and handling at the time of cleaning or the like can be easily performed as compared with a case where a heater or a Peltier element is separately attached.

  The first high frequency power supply 31 is electrically connected to the electrode support 33 of the inner upper electrode 24 via the matching unit 27, the power feeding rod 28, the connector 29, and the upper power feeding cylinder 44. A variable capacitor 45 capable of variably adjusting the capacitance is disposed in the middle of the upper feeding cylinder 44.

  As shown in FIG. 1, a processing gas supply source 38 is disposed outside the processing chamber 10. A processing gas can be supplied from the processing gas supply source 38 to the central buffer chamber 35 and the peripheral buffer chamber 36 at a desired flow rate ratio. That is, the gas supply pipe 39 from the processing gas supply source 38 branches into the branch pipes 39a and 39b on the way, and is connected to the central buffer chamber 35 and the peripheral buffer chamber 36 via the flow rate control valves 40a and 40b. Further, a mass flow controller (MFC) 41 and an opening / closing valve 42 are inserted in the gas supply pipe 39.

  An exhaust port 46 is provided at the bottom of the processing chamber 10, and an automatic pressure control valve (APC valve) 48 and a turbo molecular pump (TMP) 49 are connected to the exhaust port 46 via an exhaust manifold 47. The automatic pressure control valve 48 and the turbo molecular pump 49 cooperate with each other so that the inside of the processing chamber 10 can be evacuated to a predetermined reduced pressure atmosphere, for example, a predetermined pressure of 1 Pa or less. An annular baffle plate 50 having a plurality of air holes is disposed between the exhaust port 46 and the plasma generation space S so as to surround the susceptor support 12. The baffle plate 50 prevents plasma leakage from the plasma generation space S to the exhaust port 46.

  Further, a loading / unloading port 51 for the semiconductor wafer W is provided on the side wall of the processing chamber 10, and a gate valve 52 is provided here. Then, with the gate valve 52 opened, the semiconductor wafer W is transferred to and from an adjacent load lock chamber (not shown) through the loading / unloading port 51. A shutter 55 is disposed between the loading / unloading port 51 and the plasma generation space S as a slide valve that moves up and down by air pressure. The shutter 55 shuts off the loading / unloading port 51 from the plasma generation space S when the gate valve 52 is opened during loading / unloading of the semiconductor wafer W into / from the plasma generation space S, so that the plasma leaks through the loading / unloading port 51. To prevent.

  A second high-frequency power source 59 is connected to the susceptor 13 serving as the lower electrode via a lower feeding cylinder 57 and a matching unit 58. The frequency of the second high frequency power supply 59 is preferably in the range of 2 to 27 MHz. A movable feeding rod 67 that is connected to the electrode plate 15 of the electrostatic chuck 14 and has an end portion of the connection terminal 58 that passes through the susceptor 13 is exposed in the inner space of the lower feeding cylinder 57 and moves up and down in the inner space. Has been placed. When the DC power supply 16 applies a DC voltage to the electrode plate 15, the movable power supply rod 67 rises and contacts the connection terminal 58. When the DC power supply 16 does not apply a DC voltage to the electrode plate 15, the movable power supply rod 67 It descends and leaves the connection terminal 58.

  The movable power supply rod 67 has a flange at the bottom, and the lower power supply cylinder 57 also has a flange protruding toward the inner space. Between the flange of the movable power supply rod 67 and the flange of the lower power supply cylinder 57, a spring 60 made of silicon nitride (SiN) as an insulator for restricting the vertical movement of the movable power supply rod 67 is disposed. By configuring the spring 60 from an insulator in this way, electromagnetic induction due to high frequency power does not occur, and the spring 60 does not reach a high temperature, so that deterioration can be prevented.

  The inner upper electrode 24 is connected to a low pass filter (LPF) 61 that does not pass high-frequency power from the first high-frequency power supply 31 to the ground but passes high-frequency power from the second high-frequency power supply 59 to the ground. On the other hand, the susceptor 13 is connected to a high-pass filter (HPF) 62 for passing high-frequency power from the first high-frequency power supply 31 to the ground.

  When plasma etching of the semiconductor wafer W is performed by the plasma etching apparatus 1 having the above-described configuration, the semiconductor wafer W is transferred from the load lock chamber (not shown) into the processing chamber 10 after the gate valve 52 is opened, and electrostatically charged. It is placed on the chuck 14. Then, a DC voltage is applied from the DC power supply 16 to the electrode plate 15 of the electrostatic chuck 14, whereby the semiconductor wafer W is electrostatically attracted onto the electrostatic chuck 14. Next, the gate valve 52 is closed, and the inside of the processing chamber 10 is evacuated to a predetermined vacuum level by the APC valve 48 and the TMP 49.

  Thereafter, the on-off valve 42 is opened, and a predetermined processing gas (etching gas) from the processing gas supply source 38 is adjusted in flow rate by the mass flow controller 41, and the processing chamber 10 is passed through the central buffer chamber 35 and the peripheral buffer chamber 36. It is introduced into the plasma generation space S.

  Then, the pressure in the processing chamber 10 is maintained at a predetermined pressure. Thereafter, high frequency power having a predetermined frequency is applied to the upper electrode 22 from the first high frequency power supply 31. As a result, a high-frequency electric field is generated between the upper electrode 22 and the susceptor 13 as the lower electrode, and the processing gas is dissociated into plasma.

  On the other hand, high frequency power having a frequency lower than that of the first high frequency power supply 31 is applied from the second high frequency power supply 59 to the susceptor 13 serving as the lower electrode. Thereby, ions in the plasma are attracted to the susceptor 13 side, and the anisotropy of etching is enhanced by ion assist.

  At this time, in the inner upper electrode 24, since the ratio of the processing gas ejection flow rate can be arbitrarily adjusted by the central shower head and the peripheral shower head facing the semiconductor wafer W on the susceptor 13, the spatial distribution of the gas molecule or radical density can be adjusted. It is possible to arbitrarily control the spatial distribution of etching characteristics based on radicals by controlling in the radial direction of the wafer W.

  Further, in the upper electrode 22, the outer upper electrode 23 is mainly used as a high-frequency electrode for plasma generation, the inner upper electrode 24 is used as a subordinate, and the first high-frequency power supply 31 and the second high-frequency power supply 59 are directly below the upper electrode 22. The ratio of the electric field strength given to the electrons can be adjusted. Therefore, the spatial distribution of ion density can be controlled in the radial direction, and the spatial characteristics of reactive ion etching can be controlled arbitrarily and finely.

  Furthermore, in the inner upper electrode 24, at least one of the electrode surface member 32, the spacer 37, and the cooling plate 34 is made of a metal matrix composite material, and the central portion has an electric resistance value that is higher than the peripheral portion. A plate-like member having a distribution is used. As a result, the high-frequency electric field in the central portion becomes strong, and the plasma density in this portion can be prevented from increasing, and plasma processing with good in-plane uniformity can be performed.

  When the plasma etching is completed, the supply of the high frequency power and the supply of the processing gas are stopped, and the semiconductor wafer W is unloaded from the processing chamber 10 by a procedure reverse to the procedure described above.

  As described above, according to the present embodiment, the plasma density can be made uniform without causing the occurrence of abnormal discharge and the complexity of assembly and maintenance, and the plasma treatment with good in-plane uniformity can be performed. It can be carried out.

  In addition, this invention is not limited to said embodiment, Various deformation | transformation are possible. For example, the plasma etching apparatus is not limited to the parallel plate type upper and lower high-frequency application type shown in FIGS. 1 and 2, and for example, as shown in FIG. 5, the first high-frequency power supply 31 is connected to the lower electrode (susceptor 13). In addition, the present invention can be similarly applied to the lower two-frequency application type plasma etching apparatus 1a to which the second high-frequency power source 59 is connected.

  In addition, about the plasma etching apparatus 1a of FIG. 5, the code | symbol corresponding to the part corresponding to the plasma etching apparatus 1 shown in FIG. Are electrically connected to the ground and are set to the ground potential. The electrode surface member 32 or the like constituting the upper electrode is a plate-shaped member made of a metal matrix composite material and having a distribution of electrical resistance values with a central portion having a higher electrical resistance value than a peripheral portion. The same effect can be obtained. In the plasma etching apparatus 1a of FIG. 5, a rotatable magnet 70 is provided outside the processing chamber 10, and a plasma can be controlled by forming a magnetic field in the processing chamber 10.

1 is a diagram showing an overall configuration of a plasma etching apparatus according to an embodiment of the present invention. The figure which shows the principal part structure of the plasma etching apparatus of FIG. The figure for demonstrating the state of distribution of resistance value. The figure for demonstrating the state of other distribution of resistance value. The figure which shows the whole structure of the plasma etching apparatus which concerns on other embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Plasma etching apparatus, 10 ... Processing chamber, 22 ... Upper electrode, 32 ... Electrode surface member, 33 ... Electrode support, 34 ... Cooling plate, 37 ... Spacer, W ... Semiconductor wafer.

Claims (6)

An electrode assembly for a plasma processing apparatus for generating a plasma by forming a high-frequency electric field in a processing chamber in which a substrate to be processed is accommodated,
An electrode assembly for a plasma processing apparatus, comprising a plate-like member made of a metal matrix composite and having a distribution of electric resistance values with a central portion having a higher electric resistance value than a peripheral portion. An electrode assembly for a plasma processing apparatus according to claim 1,
The electrode assembly for a plasma processing apparatus, wherein the plate member is an electrode surface member constituting an exposed surface exposed in the processing chamber. An electrode assembly for a plasma processing apparatus according to claim 1,
The electrode assembly for a plasma processing apparatus, wherein the plate-shaped member is a member disposed on the back side of an electrode surface member that constitutes an exposed surface exposed in the processing chamber. An electrode assembly for a plasma processing apparatus according to any one of claims 1 to 3,
The plate-like member has an intermediate portion that is located between the central portion and the peripheral portion and has an intermediate electric resistance value between the electric resistance value of the central portion and the electric resistance value of the peripheral portion. An electrode assembly for a plasma processing apparatus. An electrode assembly for a plasma processing apparatus according to any one of claims 1 to 4, comprising:
A plasma processing apparatus configured to supply high-frequency power to the electrode assembly for the plasma processing apparatus. An electrode assembly for a plasma processing apparatus according to any one of claims 1 to 4, comprising:
A plasma processing apparatus characterized in that the electrode assembly for the plasma processing apparatus is configured to have a ground potential.

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