JP2010010231A - Plasma treatment device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a plasma treatment device improving throughput in processing by stably adsorbing a wafer. <P>SOLUTION: The plasma treatment device includes a treatment chamber where plasma in a vacuum container is formed, a sample stage which is arranged therein to hold a wafer on its upper surface by electrostatic adsorption, a first heater which is arranged on the upper surface of the sample stage to heat the wafer, a second heater arranged and surrounded by the outer peripheral side of the upper surface in a lower sample stage under the first heater in the sample stage, and an adjuster which adjusts the operation of the second heater so that the temperature of the lower part of the sample stage is higher at the outer peripheral side than at the central side by the second heater. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a plasma processing apparatus for processing a substrate-like sample such as a semiconductor wafer in a container using plasma, and in particular, while holding the sample on a sample table arranged inside the container, adjusting the temperature. The present invention relates to a plasma processing apparatus that performs processing such as etching.

  In the plasma processing apparatus for processing a sample using the above-described plasma, in order to improve processing throughput, the structure of a plurality of film layers arranged on the surface of the sample to form a circuit structure of a semiconductor device is continuously processed. It is considered. For example, a plurality of films composed of different kinds of materials such as a photoresist layer, an antireflection film layer, a hard mask layer, a polysilicon layer, and a metal layer, which are arranged on the upper surface of a substrate of a semiconductor wafer made of silicon, are continuously provided. Etching is required.

  In order to carry out such a process composed of a plurality of steps with high accuracy, the wafer temperature value and its distribution as etching conditions must be changed between these steps with high accuracy in a short time. Is required. In addition, it is required that an appropriate temperature can be realized in a wide range for performing etching on such different kinds of materials at high speed and with high accuracy.

  In order to realize such a requirement, conventionally, an electrostatic adsorption device that is a sample stage that adsorbs and holds a sample on the upper surface thereof has a configuration for cooling the electrostatic adsorption device and the sample thereon, for example, a refrigerant. It has been considered to have a heater for heating the electrostatic adsorption device and the sample together with a refrigerant passage through which the gas flows.

  As an example of such an electrostatic adsorption device with a heater, for example, as disclosed in Patent Document 1, a heater as a heating unit near the surface of the electrostatic adsorption device and a cooling unit in the substrate of the electrostatic adsorption device In addition, a technique for changing the temperature of the wafer in a short time by operating the heat generating means and the cooling means independently of each other is disclosed.

Further, as disclosed in Patent Document 2, an electrode having a specific pattern for electrostatic adsorption is formed on an upper portion of a support substrate (sample stage) that adsorbs a wafer, and electrostatic adsorption is performed on the back side of the support substrate. A technique for maintaining the flatness of the suction surface by offsetting the difference in thermal expansion between the suction surface of the support substrate and the back surface of the support substrate by installing a heater having a pattern having the same or similar shape to the electrode pattern for use is disclosed. Yes.
JP 2007-088411 A Japanese Patent Laid-Open No. 10-080168

  However, according to the above-mentioned Patent Document 1, although the temperature difference generated between the heater and the coolant groove increases and the time required for the temperature change of the wafer is shortened, the amount of thermal expansion generated between the front surface and the back surface of the base material Increase the difference. As the difference in thermal expansion increases, the electrostatic attraction device is bent upwards as a whole, and the difference in height between the center portion of the upper surface and the outer peripheral portion increases. When the degree of such deflection becomes larger than a predetermined value, the wafer, which is a sample placed on the upper surface of the electrostatic chuck, cannot be brought into contact with the upper surface and part or all of the wafer is peeled off from the upper surface. End up. In this case, even if a heat transfer gas is supplied between the wafer and the electrostatic chuck, the heat transfer is locally biased, making it impossible to achieve the desired temperature distribution. Or the height of the wafer surface becomes non-uniform with respect to plasma, and the wafer cannot be etched accurately. Such a point has not been considered in the prior art.

  Further, according to Patent Document 2, since the cooling substrate is not provided in the support substrate that is an electrostatic attraction device, the time for cooling the wafer becomes long. In other words, since the periphery of the electrostatic adsorption device is a vacuum, the heat dissipation path of the electrostatic adsorption device is a conduction heat transfer by contact with a member for installing the electrostatic adsorption device in a vacuum vessel, or a power supply line such as a heater. The heat transfer is limited to the heat transfer through the heat sink or the radiation heat transfer of the electrostatic adsorption device. In any of the paths, the heat dissipation rate obtained is small, and the temperature that can be changed in the time between steps of processing the wafer is small, so that the processing throughput is reduced.

  Further, even if the support substrate is made of metal and has a coolant groove as a cooling means inside, the wafer temperature is lowered from a high temperature to a low temperature in order to realize continuous processing steps. The response time at the time of switching to the time increases, the time between steps in the etching process becomes longer, and the throughput is impaired. The reason for this increase in response time is that the heater disposed on the back surface of the support substrate generates heat during the high-temperature processing step. As the amount of heat generated by the heater on the back surface increases, the average temperature of the support substrate increases. Because it will end up.

  Furthermore, the amount of thermal expansion of the support substrate in the radial direction of the support substrate accompanying the temperature change between steps is larger in the support substrate than in the wafer, so that the wafer placed on the support substrate increases as the temperature changes. It becomes impossible to follow the deformation of the base material. At this time, if slip occurs between the wafer and the upper surface of the support substrate, the back surface of the wafer or the adsorption surface of the support substrate is damaged by friction, and the resulting defect portion becomes a foreign substance in the processing chamber. The wafer may be contaminated and the yield may be impaired. Such a problem becomes more prominent as the diameter of the wafer increases. In addition, the increase in the average temperature of the base material described in the first problem promotes the problem caused by the slip of the wafer. For these reasons, even if the support substrate is simply provided with a cooling unit and a heating unit, there has been a problem in performing continuous processing of a wafer in a plurality of steps with high accuracy and high efficiency.

  The present invention has been made to improve such problems, and it is an object of the present invention to provide a plasma processing apparatus that stably adsorbs a wafer and improves the throughput of processing.

  The above-described object is to provide cooling means formed on the substrate of the electrostatic adsorption device, first heating means formed on the surface of the electrostatic adsorption device, that is, very close to the adsorption surface, and wafer adsorption of the electrostatic adsorption device. The plasma processing apparatus is provided with an electrostatic adsorption device having a second heating means formed outside the surface, and a radial temperature gradient at the outermost peripheral edge of the wafer on the back surface of the electrostatic adsorption device This is achieved by making it positive toward the outer periphery.

  The plasma processing apparatus of the present invention includes a processing chamber in which plasma inside a vacuum vessel is formed, a sample table disposed in the processing chamber for holding a wafer on the upper surface by electrostatic adsorption, and the upper surface side in the sample table A first heater that heats the wafer, and a second heater that surrounds the outer periphery of the upper surface of the sample table that holds the wafer in electrostatic adsorption under the first heater in the sample table. And an adjuster for adjusting the operation of the second heater so that the temperature on the outer peripheral side of the lower part of the sample stage is higher than the temperature on the center side by the second heater. Do

According to the present invention, when the electrostatic adsorption device is thermally expanded and becomes convex during the high temperature step, the radial curvature of the wafer adsorption surface is reduced at the outermost peripheral end due to the action of the second heating means. Then, the wafer is reliably adsorbed on the adsorption surface at the outermost peripheral end.
In addition, according to the present invention, since the wafer attracting surface of the electrostatic attracting apparatus is not affected by the second heating means, thermal expansion in the radial direction of the wafer attracting surface of the electrostatic attracting apparatus is suppressed, and The back surface of the wafer and the attracting surface of the electrostatic attracting device with which the wafer contacts are not damaged.

  Due to the above effects, according to the present invention, it is possible to provide an electrostatic chucking apparatus that can stably chuck a wafer and perform plasma etching processing when the wafer temperature is changed in a short time.

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

  1 to 5 are diagrams illustrating an embodiment of the present invention. FIG. 1 is a longitudinal sectional view schematically showing the configuration of a plasma processing apparatus according to an embodiment of the present invention.

  In this embodiment, the plasma processing apparatus uses a wafer 1 which is a substrate-like sample such as a semiconductor wafer held on a sample stage having an electrode disposed in a lower part of a space to be decompressed inside a vacuum vessel. Processing is performed using the plasma formed at the top. An electric field generating means for supplying an electric field and a magnetic field to the internal space and a magnetic field generating means are arranged above the vacuum vessel, and an exhaust means for exhausting the inside is arranged below. The processing chamber 3 that is a space inside the vacuum vessel of the plasma processing apparatus is a substantially cylindrical space inside a metal vacuum chamber 102 having a substantially cylindrical shape, and the upper portion of the vacuum chamber 102 is above the processing chamber 3. A quartz shower plate 103 and a quartz lid 101 are arranged.

  On the other hand, an opening is disposed at the bottom of the processing chamber 3 below the vacuum chamber 102, and this opening communicates with the vacuum pump 105 via a valve 104 disposed below the opening. Further, the electrostatic adsorption device 2 is connected to the bottom surface of the processing chamber 3 of the vacuum chamber 102 via an insulating member 106 and disposed at the lower portion of the processing chamber 3. The gap between these members is hermetically sealed from the outside of the vacuum chamber 102 by an appropriate sealing means such as an O-ring (not shown), and the inside of the processing chamber 3 is exhausted through the opening by the operation of the vacuum pump 105. The pressure inside the processing chamber 3 can be maintained at a high degree of vacuum up to about 1 / 10,000 Pa.

  The ceiling surface of the processing chamber 3 is constituted by a shower plate 103 arranged so as to cover from the upper center to the outer periphery of the cylindrical processing chamber 3. A gas reservoir 109 is disposed between the shower plate 103 and the lid 101 which is placed above the vacuum chamber 102 and airtightly partitions the inside and outside. The gaps between the constituent members of the gas reservoir 109 are hermetically connected by a sealing means such as an O-ring (not shown).

  A processing gas 108 introduced into the processing chamber 3 is introduced into a gas reservoir 109 from a gas source such as a tank (not shown) through a predetermined pipe line and from a gas introduction hole 107 disposed in the vacuum chamber 102. The processing gas 108 introduced into the gas reservoir 109 is disposed in a circular area having a predetermined radius around the center of the shower plate 103 having a disk shape by diffusing throughout the space in the gas reservoir 109. It is introduced into the processing chamber 3 through a large number of through holes 110. As will be described later, the region where the through hole 110 is disposed is located above the wafer 1 placed on the lower electrostatic attraction apparatus 2, and the processing gas 108 that has passed through the through hole 110 passes through the entire wafer 1. And diffused into the processing chamber 3. As the processing gas 109, a gas of a single substance or a gas in which a plurality of substances are mixed at a predetermined ratio and an optimum flow rate ratio is used for each process.

  An antenna 111 that is a disk-shaped conductive member is disposed above the lid 101 above the processing chamber 3. The antenna 111 is connected to a high-frequency power source 114, a switch 113 capable of turning on and off the high-frequency power from the high-frequency power source 114, and a matching unit 112 for matching impedance when the high-frequency power is applied. When high-frequency power is applied to the antenna 111, the electric field passes through the lid 101, which is a disk-shaped member made of a dielectric material such as quartz, and propagates through the shower plate 103 to enter the space inside the processing chamber 3. Can be generated.

  Further, a coil 115 is disposed above the lid 101 and to the side of the vacuum chamber 102 so as to surround the outer periphery of the processing chamber 3 and the electrostatic adsorption device 2 inside. A magnetic field is supplied into the processing chamber 3. Due to the interaction between the electric field introduced into the processing chamber 3 and the magnetic field generated by the coil 115, the substance of the processing gas 108 introduced into the processing chamber 3 is excited to form a high-density plasma in the processing chamber 3. Is done.

  As will be described later, the electrostatic adsorption device 2 serving as a sample stage has a member made of conductive metal inside, and this member is connected to a high-frequency power source 116 via a matching unit 117 that supplies high-frequency power as an electrode. It is connected. By supplying the high frequency power from the high frequency power supply 116 to the electrostatic chuck 2, a bias potential is formed on the upper surface of the wafer 1 placed on the upper surface and sucked, and the plasma formed in the processing chamber 3. The charged particles present in the plasma during processing are attracted to the wafer surface. The etching process of the wafer 1 is performed using the action of the charged particles colliding with the surface of the wafer 1 along the electric field and magnetic field distribution and the action of the highly reactive particles in the plasma.

  The electrostatic adsorption device 2 that is a sample stage is disposed on the upper surface side that holds the wafer 1 and is below the first heater 5 that heats the wafer 1 and the first heater 5 in the electrostatic adsorption device 2. The second heater 16 is provided so as to surround the outer periphery of the upper surface of the electrostatic chucking apparatus 2 that holds the wafer 1 by electrostatic chucking.

  FIG. 2 is a longitudinal sectional view showing an outline of the configuration of the electrostatic adsorption device 2 according to the embodiment shown in FIG. The electrostatic chuck 2 is connected to the bottom of the vacuum chamber 102 that constitutes the bottom surface of the processing chamber 3 via an insulating member 106. The electrostatic attraction apparatus 2 is a member having a substantially convex cross section with a central portion having a thickness larger than that of the outer peripheral portion, and has an axisymmetric shape around a central axis in the vertical direction in the drawing.

  Further, the electrostatic adsorption device 2 includes a titanium base material 4 having a disk shape with a substantially convex cross section constituting a main part, and a plurality of dielectric layers formed on the circular upper surface of the convex part. It has a body membrane. These dielectric films are joined together after formation to form a mounting surface of the wafer 1.

  The dielectric film is formed on the upper surface of the convex portion of the base material 4 by thermal spraying, and on the upper surface of the first ceramic layer 9 around the center of the electrostatic adsorption device 2 by thermal spraying. A heater 5 as a first heating means formed symmetrically, a second ceramic layer 8 covering the periphery of the heater 5 and formed on the upper surface of the first ceramic layer 9 by thermal spraying, and a second ceramic layer A ring-shaped adsorption electrode 6 formed symmetrically around the center of the electrostatic adsorption device 2 by thermal spraying on the upper surface of 8, and formed by thermal spraying on the upper surface of the second ceramic layer 8 covering the circumference of the adsorption electrode 6. And a third ceramic layer 7 in contact with the back surface of the wafer 1 placed on the top.

  The heater 5 as the first heating means of this embodiment includes an inner heater 5a and an outer heater 5b arranged concentrically, each of which is independently adjusted in operation, and each heater is connected to the power source 10. Has been. In addition, a plurality of electrodes 6 to which electric power for electrostatic attraction is supplied are provided. A ring-shaped or circular inner electrode 6 a disposed around the central axis of the electrostatic attraction apparatus 2, and an outer peripheral side thereof And an outer electrode 6b having a ring shape. These electrodes are of a so-called dipole type in which electric power having different polarities is supplied from a DC power supply 15 connected to each of the electrodes. By applying a voltage to each of the electrodes 6 from the DC power supply 15, the dielectric film and static electricity inside the wafer 1 are accumulated, and the wafer 1 is electrostatically adsorbed and held on the upper surface of the ceramic layer 7 by mutual electrostatic force. . In the present embodiment, the electrode 6 is a dipole type electrostatic adsorption device having two electrodes, the inner electrode 6a and the outer electrode 6b. However, the electrode 6 is not necessarily a dipole type and may be a monopole type. Absent. Further, an adsorption method other than electrostatic adsorption may be used.

  The titanium base material 4 includes a plurality of flow paths 11 through which a refrigerant flows as cooling means inside the disk portion, and the temperature of which is adjusted to a predetermined value by a temperature controller 12 such as a chiller. Are connected to each other to exchange heat with the substrate 4 and the electrostatic adsorption device 2 and eventually the wafer 1 held above to adjust the temperature thereof. The flow channel 11 of the present embodiment is a combination of concentric circles or arcs arranged in multiple locations around the center axis in the vertical direction inside the base material 4, or a passage arranged in a spiral shape. In addition, at least two independent refrigerant passages are formed in the central portion of the base material 4 and the outer peripheral side portion thereof. The central flow path 11 and the outer peripheral side flow path 11 are connected to a temperature controller 12 capable of adjusting the temperature of the refrigerant to a different temperature without being connected to each other. It is comprised so that adjustment is possible so that the center part of the apparatus 2 and an outer peripheral side part may become different temperature.

  As described above, the base material 4 is connected to the high-frequency power source 116 through the matching unit 117. By applying a bias voltage, the ions in the plasma are attracted to the wafer and collide with the anisotropy of the film layer on the surface. Etching is realized. The material of the substrate 4 is titanium in the present embodiment, but is not necessarily limited to titanium, and any metal having an appropriate strength can be used. For example, stainless steel, aluminum, An aluminum alloy or the like can be suitably used.

  A second heating means 16 for heating the lower part of the electrostatic adsorption device 2 from the periphery thereof is disposed on the outer peripheral side portion of the lower part of the electrostatic adsorption device 2. That is, a fourth ceramic layer formed by spraying a concave portion disposed in a ring shape on the lower surface of the outer peripheral portion of the convex portion of the base material 4 having a convex cross section is formed inside the concave portion. The heater 16 as the second heating means formed by spraying on the lower surfaces of the 18 and fourth ceramic layers 18 and the fifth covering the periphery of the heater 16 and formed on the exposed surface of the fourth ceramic layer 18 by spraying. And a ceramic layer 17. The heater 16 as the second heating means is connected to a power source 19 for supplying power thereto.

  Further, a recess is disposed in the vicinity of the upper surface of the convex portion of the base material 4, and a thermocouple 13 as a temperature measuring means is provided inside. Further, a plurality of thermocouples 20 are disposed on the lower surface of the substrate 4 in the present embodiment. One of these thermocouples 20a is arranged directly below the outer end of the upper surface of the circular convex portion in the radial direction from the central axis of the substrate 4 or inside the position directly below the outer peripheral end of the mounted wafer 1. Has been. On the other hand, another thermocouple 20b is installed outside a position directly below the outer end of the upper surface of the circular convex portion or just below the outer end of the wafer 1. With the outputs from these thermocouples 20a and 20b, the controller 14 of the plasma processing apparatus can be a device for detecting the temperature distribution and change in the lower part of the electrostatic adsorption apparatus 2.

  The temperature controller 12, the heater power supplies 10 and 19, and the thermocouples 13 and 20 are connected to the controller 14, and these outputs can be transmitted to the controller 14 during processing or non-processing of the wafer 1. Yes. In the present embodiment, the controller 14 feeds back and adjusts the operation of the temperature controller 12 and the heater power supplies 10 and 19 (and the heater 5) based on the results detected from the outputs of the thermocouples 13 and 20. The temperature value of the wafer 1 and its distribution are adjusted appropriately. Since the adjustment of the temperature of the wafer 1 disposed inside the processing chamber 3 is mainly performed by the electrostatic adsorption device 2, it is better that the thermal resistance between the two is small, and therefore, between the wafer back surface and the electrostatic adsorption device. The cooling gas 21 is introduced into a small gap (not shown) existing in FIG. 1 at a pressure of, for example, 1000 Pa to improve the heat transfer between the back surface of the wafer 1 and the upper surface of the electrostatic chuck 2. The type of the cooling gas 21 is not particularly limited as long as it does not affect the processing, and for example, helium can be preferably used.

  In the plasma processing apparatus having such a configuration, the etching process of the wafer 1 is performed as follows. First, the processing chamber 3 is placed between a vacuum chamber 102 and a transfer container (not shown) connected to the vacuum chamber 102 in a state where the pressure of the vacuum chamber 105 is set to a predetermined level of vacuum. The valve that opens and closes is opened. The wafer 1 held by a transfer robot (not shown) inside the transfer container is carried into the processing chamber 3 from the transfer container, and the wafer placed on the upper surface of the electrostatic chuck 2 serving as a sample stage. It is transported to a predetermined position above the dielectric film constituting one mounting surface.

  At this time, the electrostatic adsorption device 2 adjusts the temperature of each refrigerant in advance so that a temperature value suitable for performing the etching process of the wafer 1 and its distribution are realized on the upper surface and the surface of the wafer 1. The controller 14 adjusts the temperature of the refrigerant flowing through the flow path 11 at the center and the outer periphery of each temperature controller 12 and the outputs of the heaters 5 and 16. For example, the temperature value of the refrigerant and the heater so that the temperature of the central portion of the convex portion of the wafer 1 or the electrostatic adsorption device 2 is high and the outer peripheral portion is low according to the product distribution in the processing chamber 3 above the wafer 1. The output of 5a is adjusted to be large. Further, the output of the heater 16 is adjusted so as to suppress the deformation of the upper surface of the substrate 4 or the dielectric film. Such adjustment by feedback is also performed after plasma is formed and processing is started.

  A plurality of 22 pins housed in the electrostatic chuck 2 are driven by a driving device (not shown) to protrude above the dielectric film and lift the wafer 1 upward from the robot to receive it. The pin 22 is driven again after moving out of the processing chamber 3 and moved downward to be stored inside the electrostatic chuck 2. By such an operation, the wafer 1 is placed on the placement surface of the electrostatic chuck 2.

  Thereafter, the power is supplied to the electrode film for electrostatic attraction disposed inside the dielectric film, which will be described later, so that the wafer 1 is statically fixed by the electrostatic film formed inside the dielectric film and the wafer 1. It is adsorbed and held on the electroadsorption device 2. Further, in order to improve the efficiency of heat transfer between the wafer 1 and the electrostatic chuck 2 during processing, heat transfer gas is introduced from the gas inlet having an opening on a dielectric film (not shown) from the wafer 1 and It is supplied to the space between the dielectric film.

  A processing gas 108 is introduced downward from the processing chamber 3 through a through hole 110 located above the wafer 1. At this time as well, the vacuum pump 105 is operating, and the inside of the processing chamber 3 is adjusted to a predetermined pressure. In this state, high frequency power is supplied to the antenna 111, an electric field is supplied into the processing chamber 3, and a magnetic field generated by the coil 115 is supplied into the processing chamber 3. The particles of the substance constituting the processing gas are excited by the action of these electric and magnetic fields to form plasma.

  Along with the formation of plasma, high-frequency power for forming a bias potential on the upper surface of the wafer 1 is supplied to the electrodes in the electrostatic chuck 2, and the wafer 1 is etched. In the etching process of this embodiment, at least one film layer disposed on the upper surface of the wafer 1 is continuously processed under different conditions, and the upper surface of the electrostatic chuck 2 is processed between the processing steps of each condition. And the temperature condition of the upper surface of the wafer 1 is changed. For example, the temperature of the refrigerant and the outputs of the heaters 5a and 5b are adjusted so that the difference between the temperature of the central portion of the convex portion of the wafer 1 or the electrostatic adsorption device 2 and the temperature of the outer peripheral portion becomes low or equal. The Along with this, the output of the heater 16 is further adjusted to suppress the deformation of the upper surface of the substrate 4 or the dielectric film.

  When it is detected from the output of a sensor or detection device (not shown) that a predetermined number of steps have been completed, the supply of electric and magnetic fields and the formation of a bias potential are stopped and the plasma is extinguished. The supply is stopped and the wafer 1 is unloaded from the processing chamber 3 or the vacuum chamber 102 by the reverse procedure of loading. Thereafter, after the discharge of plasma and processing gas, another unprocessed wafer 1 is carried in and the etching process is resumed.

  FIG. 3 is a cross-sectional view schematically showing a heater arrangement pattern according to the electrostatic attraction apparatus shown in FIG. FIG. 3A is a cross-sectional view showing a pattern of the heater 5 disposed on the upper surface of the substrate 4, and FIG. 3B is disposed on the lower surface side of the substrate 4 which is the second heating means. It is a cross-sectional view showing a pattern of the heater 16. 3A and 3B, W indicates the distance (radius) from the center to the periphery of the upper surface of the base material 4 on which the heater 5 is disposed, and corresponds to the radius of the wafer 1. It is. r indicates the distance (radius) from the center of the heater 16 disposed on the lower surface side of the substrate 4 as the second heating means.

  In the present embodiment, the heater 5 as the first heating means includes an inner heater 5a disposed in a ring shape around an axis in the vertical direction (front and back direction in the drawing) of the substrate 4 or the electrostatic chuck 2. The outer heater 5b is concentrically arranged around the outer periphery of the inner heater 5a. These are arc-shaped concentrically arranged at locations other than the connector portion for connecting to the power supply 15 in the regions where the upper surfaces of the circular convex portions of the base material having a convex cross section are arranged. The horizontal lines that pass through are folded symmetrically and connected in multiples, and are arranged so that the temperature in each region is uniform.

The heater 16 as the second heating means is disposed on the lower surface of the protruding portion protruding outward on the lower outer peripheral side of the convex portion of the base material 4, that is, on the lower outer peripheral side of the convex shape of the base material 4. It is arrange | positioned in a dent part, when it sees from upper direction, it is located in the outer side of the outer peripheral end of a convex part, and is arrange | positioned in the ring shape surrounding this. The dent is coaxial with the central axis of the substrate 4, that is, an arc-shaped film arranged concentrically at a location excluding the connector for connecting to the power source 19 is arranged concentrically with the heater 5.

  In this embodiment, an adsorption test of the wafer 1 is performed, and a radius r from the vertical axis center indicating the installation position of the heater 16 as the second heating means on the lower surface of the electrostatic adsorption device 2 and the radius W of the wafer 1 are shown. The relationship between the relative position of the wafer 1 and the adsorption state of the wafer 1 was examined. The result is shown in FIG. FIG. 7 shows a test of the wafer adsorption state when the relative position between the radius r from the vertical axis center indicating the installation position of the second heating means on the lower surface of the electrostatic adsorption apparatus and the wafer radius W is changed. It is a table | surface which shows the result at the time of performing.

  Here, the state in which the wafer 1 can be attracted means that the wafer 1 is attracted and supported or fixed on the dielectric film of the electrostatic attraction apparatus 2 and the back surface of the wafer 1 and the dielectric film are supported. Assume that it is determined that the temperature of the wafer 1 can be adjusted to a desired value by the action of the cooling gas 21 supplied between the upper surface and the etching process. Further, the state in which the suction cannot be performed means a state in which the wafer 1 cannot be supported or fixed on the upper surface of the electrostatic chuck 2, that is, if it is determined that the etching process cannot be performed, or is supplied to the back surface of the wafer 1. It is assumed that the pressure of the cooling gas 21 is low and the temperature of the wafer 1 cannot be adjusted to a desired value by adjusting the temperature of the electrostatic adsorption device 2 and therefore it is determined that the etching process cannot be performed. .

  As shown in FIG. 7, according to the adsorption test, the wafer 1 can be adsorbed to the electrostatic adsorption apparatus 2 when r / W> 1, while the wafer 1 is electrostatic adsorption apparatus 2 when r / W ≦ 1. It became impossible to adsorb.

  As a result of the examination by the inventors, the reason why the state of adsorption of the wafer 1 by the electrostatic adsorption device 2 is affected by the value of the installation radius r of the heater 16 with respect to the radius W of the wafer 1 is that the adsorption of the electrostatic adsorption device 2 It was found that the shape of the surface of the dielectric film on the surface, that is, the upper surface of the convex portion constituting the mounting surface of the wafer 1 is affected by the above value. That is, as the shape of the upper surface of the outer peripheral end of the convex portion of the base material 4 on which the dielectric film constituting the attracting surface of the electrostatic attracting device 2 is arranged is the shape of the truncated cone, that is, toward the outer peripheral side. As a result of investigations, the inventors have studied that the state in which the wafer 1 is attracted to the electrostatic attracting device 2 is affected when the height is lowered, or when the rate of change in height is zero or more. Obtained as knowledge.

  The difference in the shape of the suction surface depending on the heater installation radius r is shown in FIG. FIG. 4 is a graph showing the shape and temperature distribution of the electrostatic adsorption device 2 according to the value of the position of the second heating means relative to the wafer radius. 4A shows a case where r / W> 1, and FIG. 4B shows a case where r / W ≦ 1.

  FIG. 4A shows a graph showing the position of the dielectric film surface of the electrostatic chuck 2 at each position in the radial direction of the wafer 1 and the temperature at each position. The position of the dielectric film (adsorption film) is a straight line in the region 401 between the arrows in the graph, and the adsorption surface is shown to be conical at the outer peripheral side end.

  On the other hand, in the case of r / W ≦ 1 shown in FIG. 4B, the profile of the height of the suction surface was conical at a location other than the outer peripheral end. In addition, when the heater 16 is not used, the distribution of the height position of the suction surface does not have a conical surface shape. That is, when the position of the heater 16 to be heated is on the inner side of the outer peripheral edge of the wafer 1, the height of the suction surface becomes a conical surface in a region 402 other than the outer peripheral edge, and further, the outer peripheral side of the electrostatic chuck 2. The rate of change in the radial direction of the height of the attracting surface in the region increases rapidly. In such a case, the wafer 1 cannot follow the shape of the suction surface.

  In particular, in this embodiment, the outer peripheral edge of the surface of the uppermost layer of the dielectric film constituting the attracting surface of the electrostatic attracting device 2 is a ring-shaped convex portion projecting upward from the surface of the central region. When the wafer 1 is sucked and held, the upper surface of the convex portion comes into contact with the back surface of the wafer 1 to partition the central side from the outer peripheral side and is supplied to the rear surface of the wafer 1 on the central side (inner peripheral side). The cooling gas is prevented from leaking outside to improve the efficiency and uniformity of heat transfer. For this reason, if the outer peripheral end portion of the adsorption surface is not adsorbed to the wafer 1, not only the heat transfer efficiency at the outer peripheral end of the wafer 1 is locally reduced but also the pressure of the cooling gas is reduced, and the temperature of the entire wafer 1 is controlled. It will not be possible to realize in the period.

  Further, there is a difference in the temperature distribution on the back surface of the base material 4 due to the installation radius r of the heater 16 during the high temperature step. In the case of r / W> 1 shown in FIG. 4A, the temperature of the wafer 1 increases from the central portion toward the outer periphery at the position of the radius W of the wafer 1, and has a positive temperature gradient. On the other hand, when r / W ≦ 1 shown in FIG. 4B or the second heater 16 is not used, the temperature of the wafer 1 decreases from the central portion toward the outer periphery at the position of the radius W and is negative. It has a temperature gradient. The heater 16 as the second heat generating means on the lower surface of the electrostatic chucking device is provided so that the radial position r, which is the installation position, satisfies the relationship of r / W> 1 with respect to the wafer radius W. By controlling the heat generating means and the cooling means so that the temperature gradient in the radial direction of the outermost peripheral edge (radial position W) of the wafer 1 on the back surface of the substrate 4 of the apparatus 2 is positive from the central portion toward the outer periphery, A region including the outer peripheral edge of the adsorption surface or the upper surface of the substrate 4 becomes a conical surface, and the wafer 1 is adsorbed on the adsorption film of the electrostatic adsorption device 2. It becomes possible to suppress that the pressure of cooling gas falls.

  FIG. 5 is a cross-sectional view schematically showing a heater arrangement pattern of an electrostatic attraction apparatus according to a comparative example for explaining the difference from the present invention. FIG. 5A is a cross-sectional view schematically showing a heater pattern in a dielectric film on the upper surface of the convex portion of the base material 4, and FIG. 5B is arranged on the lower back surface of the base material 4. It is a cross-sectional view showing a heater pattern. The heater 23 on the back surface in this comparative example is provided so that the installation position r <W in the radial direction. Further, the heater 23 on the back surface is configured to have two systems 23a and 23b, similarly to the front surface.

  For the embodiment shown in FIG. 3 and the comparative example shown in FIG. 5, a plurality of steps with different wafer temperatures are continuously performed, and the temperature of the electrostatic chucking device is changed step by step while the wafer is sucked to the electrostatic chucking device. And the amount of generated foreign matter was measured. FIG. 6 shows a relationship between the in-plane average temperature of the wafer 1 at the highest temperature step and the amount of foreign matter generated when the wafer 1 is continuously processed in a series of a plurality of processing steps.

  The amount of foreign matter was below a predetermined reference value N as an upper limit for etching processing at any wafer average temperature, and the wafer could be processed. On the other hand, in the comparative example, the amount of foreign matter increased as the wafer temperature increased and exceeded the reference value N. In the comparative example, most of the temperature of the base material is increased by the heater heating from the upper and lower surfaces, so that a difference occurs in the base material average temperature at the high temperature step and the low temperature step.

  The base material average temperature difference between steps causes the radial thermal expansion or contraction of the electrostatic adsorption device when the temperature is changed. In the comparative example, it is considered that the wafer slipped without following the expansion and contraction of the electrostatic adsorption device due to the above-mentioned difference in the average temperature of the substrate, and the back surface of the wafer and the adsorption surface with which the wafer contacted were damaged, resulting in increased foreign matter. . On the other hand, in this embodiment, the substrate temperature near the adsorption surface at the high temperature step is close to the wafer temperature, but the lower part of the substrate is cooled by the refrigerant and kept near the refrigerant temperature. The material average temperature difference is small and the amount of thermal deformation is small. That is, the slip on the contact surface as seen in the comparative example is not remarkable in this embodiment, and the back surface of the suction wafer and the suction surface thereof are not damaged. Therefore, there is no difference in the amount of foreign matter depending on the average wafer temperature.

  In the embodiment of the present invention, the heater 5 as the first heating means has two systems of the inner heater 5a and the outer heater 5b. However, it is not always necessary to have two systems, and one system or three or more systems. A plurality of systems may be used. In this embodiment, the thermal spray heater 5 is used as the first heating means. However, this heating means is not necessarily limited to the thermal spray heater, and any heating method can be used as long as the vicinity of the adsorption surface can be heated. For example, there may be a technique in which a second or third flow path for flowing a high-temperature fluid is provided in the vicinity of the adsorption surface in the base material, or a technique in which a heater is provided inside the base material. In this embodiment, five layers are formed on the surface of the substrate 4 by thermal spraying. However, it is not always necessary to form five layers. The first heating means and the wafer are electrostatically attracted in the vicinity of the wafer attracting surface. Any structure may be used as long as the heating means and the electrode are arranged so as to be insulated from the base material.

  In the embodiment of the present invention, the thermal spray heater 16 is installed as the second heating means on the back surface of the base material at the outermost peripheral edge. However, any heating method can be used as long as the outermost peripheral edge of the base material can be heated. In addition, the installation position of the second heating means is not limited to the back surface of the base material, and may be anywhere as long as the outer peripheral edge of the base material is outside the wafer suction surface. That is, the second heating means and the installation position thereof are not limited to the present embodiment, for example, a method in which a flow path for flowing a high-temperature fluid is provided at the outer peripheral edge of the base material, or a heater inside the base material at the outer peripheral edge of the base material. Or a method of installing a thermal spray heater on the side surface of the substrate.

  The temperature measuring means is thermocouples 13 and 20 in the embodiment of the present invention, but is not necessarily limited to the use of thermocouples. In addition to thermocouples, platinum resistors, fluorescent thermometers, radiation temperatures are used. A meter can be used.

  In the embodiment of the present invention, two temperature measuring means 20 are provided on the back surface of the electrostatic adsorption device, but any number is possible. Alternatively, it is not always necessary to provide the temperature measuring means on the back surface of the electrostatic adsorption device. In the case where this is not provided, for example, the power of the heater 5 as the first heating means and the flow rate of the temperature controller 12 as the cooling means. It is conceivable that the heat generation amount of the second heating means 16 that is optimal for the temperature setting is obtained in advance as a list, and the heat generation amount of the second heating means 16 is controlled based on the list. It is done. Alternatively, the temperature measuring means 20 is not provided on the back surface of the electrostatic adsorption device, but a laser-type displacement measuring device is provided instead, and the amount of heat generated by the second heat generating means can be determined from the output. The measurement position of the displacement measuring instrument in this case is not limited, but it is desirable to use the surface of the electrostatic adsorption device.

  The material of the thermal sprayed ceramics 7, 8, 9, 17, and 18 may be any material as long as it can maintain insulation and has plasma resistance. For example, alumina or yttria is used. Preferably used. In addition, the material of the heaters 5 and 16 and the electrode 6 may be any metal, but for example, tungsten or nickel is preferably used.

FIG. 1 is a longitudinal sectional view showing an outline of a configuration of a plasma processing apparatus according to an embodiment of the present invention. FIG. 2 is a longitudinal sectional view showing an outline of the configuration of the electrostatic adsorption device 2 according to the embodiment shown in FIG. FIG. 3 is a cross-sectional view schematically showing a heater arrangement pattern according to the electrostatic attraction apparatus shown in FIG. FIG. 4 is a graph showing the shape and temperature distribution of the electrostatic adsorption device 2 according to the value of the position of the second heating means relative to the wafer radius. FIG. 5 is a cross-sectional view schematically showing a heater arrangement pattern of an electrostatic attraction apparatus according to a comparative example for explaining the difference from the present invention. FIG. 6 is a graph showing the relationship between the in-plane average temperature of the wafer and the amount of foreign matter generated in the difference in which the wafer is processed successively in a plurality of processing steps. FIG. 7 shows a test of the wafer adsorption state when the relative position between the radius r from the vertical axis center indicating the installation position of the second heating means on the lower surface of the electrostatic adsorption apparatus and the wafer radius is changed. It is a table | surface which shows the result at the time.

Explanation of symbols

1 Wafer 2 Electrostatic chuck (sample stage)
3 Processing Chamber 4 Base Material 5 Surface Heater 6 Adsorption Electrode 7 Third Ceramic Layer 8 Second Ceramic Layer 9 First Ceramic Layer
DESCRIPTION OF SYMBOLS 10 Heater power supply 11 Refrigerant flow path 12 Refrigerant temperature controller 13 Thermocouple 14 Control apparatus 15 DC power supply 16 Back surface heater 17 Fifth ceramic layer 18 Fourth ceramic layer 19 Heater power supply 20 Thermocouple 21 Cooling gas 22 Wafer conveyance push-up Device 23 Back heater 101 Lid 102 Vacuum chamber 103 Shower plate 104 Valve 105 Vacuum pump 106 Insulating member 107 Gas introduction hole 108 Process gas 109 Gas pool 110 Through hole 111 Antenna 112 Matching device 113 Switch 114 High frequency power source 115 Coil 116 High frequency power source 117 Alignment vessel.

Claims (5)

  A processing chamber in which plasma inside the vacuum chamber is formed; a sample table disposed in the processing chamber for holding the wafer by electrostatic adsorption; and a wafer disposed on the upper surface side in the sample table to heat the wafer A first heater; a second heater disposed around the upper surface of the sample table for holding the wafer in electrostatic adsorption under the first heater in the sample table; and the second heater And a controller for adjusting the operation of the second heater so that the temperature on the outer peripheral side of the lower part of the sample stage is higher than the temperature on the center side by the heater.   2. The plasma processing apparatus according to claim 1, wherein the adjuster adjusts the operation of the second heater so that a gradient of a temperature distribution in a lower portion of the sample stage becomes positive toward the outer peripheral side. 3. A plasma processing apparatus.   3. The plasma processing apparatus according to claim 1, wherein a passage of a heat exchange medium that is disposed between the first heater and the second heater in the sample stage and adjusts the temperature of the sample stage is provided. A plasma processing apparatus comprising:   4. The plasma processing apparatus according to claim 1, wherein the temperature on the center side of the wafer can be adjusted to be higher than the temperature on the outer peripheral side.   5. The plasma processing apparatus according to claim 1, wherein a metal disk-shaped member having a convex central portion and an upper surface of the convex portion are disposed in the sample stage. A dielectric film, and the second heater surrounds the outer periphery of the convex portion, and is disposed below the convex portion and on the lower surface of the disk-shaped member. A plasma processing apparatus.

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