JP2017028092A - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of realizing in-plane uniformity associated with plasma processing and desired distribution adjustment for an etching rate, etc. with respect to a plasma processing apparatus.SOLUTION: A plasma processing apparatus includes a mounting electrode for mounting a substrate to be processed, a first electrode at an inner peripheral portion and a second electrode at an outer peripheral portion as electrodes provided inside the mounting electrode, a power supply unit for supplying high-frequency bias power to apply a high frequency bias voltage to the mounting electrodes and an electrode, applying a first voltage to the first electrode as a high frequency bias voltage, applying a second voltage to the second electrode, and applying a third voltage to the mounting electrodes, a monitor unit for monitoring the first voltage and the second voltage, a resistivity calculation unit for calculating the resistivity of the substrate to be processed based on a monitor value of the monitor unit, and a correction unit for determining a correction value related to the high frequency bias voltage according to the resistivity and controlling the driving of the power supply unit so as to achieve the correction value.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a plasma processing technique. The present invention also relates to a technique for controlling high-frequency bias power for plasma processing.

  In general, in a process of manufacturing a semiconductor integrated circuit element or the like, a plasma processing apparatus is used to perform processing such as etching using plasma, which is suitable for processing, on a target substrate such as a wafer. There are various methods related to the processing of the plasma processing apparatus. As one method, there is a method in which a high-frequency bias voltage for acting on plasma is applied to an electrode of a holding unit that holds a substrate to be processed in a processing chamber.

  Along with the improvement in the degree of device integration, there is a demand for improvement in microfabrication accuracy, and at the same time, there is a demand for improvement in uniformity within the wafer surface in processing such as plasma etching. For example, it is required to improve in-plane uniformity regarding the etching rate and the critical dimension of the etching pattern shape.

  The in-plane uniformity is affected by the distribution of plasma density, gas flow, temperature, reaction product, incident ion energy, and the like. For example, when the plasma density distribution is non-uniform in the radial direction in the plane, the etching rate or the like can be non-uniform in the plane due to the influence. For example, even if a uniform rate of the film to be etched is obtained, an in-plane shape difference between the inner peripheral portion and the outer peripheral portion in the surface may occur due to the retention or deposition of the reaction product. Further, even if the in-plane etching depth is adjusted, the in-plane selection ratio is different, and therefore the hard mask height may be different in the in-plane.

  Therefore, the conventional plasma processing apparatus has a distribution adjustment function for adjusting electrical problems around the wafer, particularly plasma density distribution and ion energy distribution, in order to improve or control in-plane non-uniformity related to the etching rate and the like. There is something.

  Japanese Patent No. 5396568 (Patent Document 1) is given as an example of the prior art relating to the realization of in-plane uniformity in the processing of a plasma processing apparatus. A plasma processing apparatus described in Patent Document 1 includes a lower electrode and an upper electrode as electrodes, a first power source that applies power of a first frequency to the electrodes, and power of a second frequency that is applied to the lower electrode. , A bias distribution control electrode provided at the peripheral edge of the lower electrode, and a power supply that applies a rectangular wave voltage of the third frequency to the bias distribution control electrode.

Japanese Patent No. 5396568

  As in Patent Document 1, as a conventional plasma processing apparatus, a high-frequency bias voltage is applied to the electrode of the holding unit of the wafer according to distribution adjustment, thereby achieving in-plane uniformity related to plasma processing. There is something.

  However, according to the study by the present inventors, when a distribution adjustment function of a conventional plasma processing apparatus is used and a high frequency bias voltage is applied and a predetermined distribution adjustment control is executed during plasma processing of a wafer. There are the following problems. For example, even when the desired distribution adjustment control is executed so as to obtain a flat distribution in the radial direction in the plane, a desired result such as a uniform etching rate may not be obtained unlike the intended case. It has been found that when the desired distribution adjustment control is executed, the effect of the distribution adjustment may change due to the influence of the resistivity of the wafer during plasma processing.

  An object of the present invention is to provide a technique capable of realizing desired distribution adjustments such as in-plane uniformity related to plasma processing and an etching rate with respect to a plasma processing apparatus.

  A typical embodiment of the present invention is a plasma processing apparatus having the following configuration.

  A plasma processing apparatus according to an embodiment includes an electromagnetic wave generating unit that generates an electromagnetic wave, and a process in which plasma processing is performed as a process for a substrate to be processed held in a holding unit based on plasma generated based on the electromagnetic wave. A chamber, a mounting electrode for mounting the substrate to be processed, and an electrode provided inside the mounting electrode, in a plane corresponding to the mounting electrode; And the second electrode on the outer periphery, and the high frequency bias power for applying the high frequency bias voltage to the placement electrode and the electrode are supplied to the first electrode as the high frequency bias voltage. A power supply unit that applies a first voltage, applies a second voltage to the second electrode, and applies a third voltage to the placement electrode, and a monitor unit that monitors the first voltage and the second voltage And said Based on the monitor value of the nita unit, a resistivity calculation unit that calculates the resistivity of the substrate to be processed, and a correction value related to the high-frequency bias voltage is determined according to the resistivity so that the correction value is obtained. A correction unit that drives and controls the power supply unit.

  According to a typical embodiment of the present invention, it is possible to achieve desired distribution adjustments such as in-plane uniformity and etching rate related to plasma processing in a plasma processing apparatus.

It is a figure which shows the structure of the plasma processing apparatus of Embodiment 1 of this invention. FIG. 3 is a diagram illustrating a configuration of a processing chamber and a power supply unit in the first embodiment. FIG. 3 is a diagram illustrating a characteristic graph representing a relationship between an inductance value and a voltage value in the first embodiment. FIG. 3 is a diagram showing a sequence of high-frequency bias voltage control during plasma processing in the first embodiment. 6 is a diagram illustrating characteristics of high-frequency bias voltage control and etching rate distribution adjustment according to resistivity in Embodiment 1. FIG. 6 is a diagram illustrating an example of DB data in the first embodiment. FIG. 6 is a diagram illustrating an example of monitor values according to Embodiment 1. FIG. 6 is a diagram illustrating an example of a control table in Embodiment 1. FIG. 6 is a diagram illustrating correction of distribution adjustment in the first embodiment. FIG. It is a figure which shows the structure of the process chamber and electric power supply part in the plasma processing apparatus of Embodiment 3 of this invention. FIG. 11 is a diagram illustrating a relationship between resistivity and voltage value in the third embodiment. FIG. 10 is a diagram illustrating an example of a control table in the third embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that components having the same function are denoted by the same reference symbols throughout the drawings for describing the embodiment, and the repetitive description thereof will be omitted.

(Embodiment 1)
A plasma processing apparatus and a plasma processing method according to Embodiment 1 of the present invention will be described with reference to FIGS. The plasma processing method of the first embodiment is a method including a step executed by the plasma processing apparatus of the first embodiment.

  As described above, when a distribution adjustment function of a conventional plasma processing apparatus is used to perform a desired distribution adjustment control by applying a high frequency bias voltage during plasma processing of a wafer, the wafer being processed is processed. The effect of distribution adjustment may change due to the influence of resistivity. As a result, unlike the intention, the etching rate may be non-uniform in the radial direction within the surface.

  The reason why such a case occurs is considered as follows. In the electrode holding the wafer, for example, it is assumed that a first voltage is applied to the inner peripheral electrode and a second voltage is applied to the outer peripheral electrode. However, power propagates between the inner peripheral electrode and the outer peripheral electrode through the path between the electrodes. As a result, the wafer surface approaches the voltage value between the first voltage and the second voltage, and the power difference is reduced. It is considered that the reduction in power difference between the electrodes and the degree of propagation are determined mainly depending on the resistivity of the wafer.

  The basic resistivity of the wafer is determined by the impurity concentration, the plane orientation of the Si crystal of the wafer, and the like. However, wafers undergoing actual plasma etching processing reflect the processing conditions, processing conditions, etc., and are affected by the gas and plasma conditions near the wafer, resulting in a resistivity that differs from the basic resistivity. ing. The actual resistivity during this process may vary due to various factors such as the temperature at and near the wafer, the surface condition, the sample stack, deposits, and the electrostatic attraction between the wafer and the electrode.

  The plasma processing apparatus of the first embodiment has a function of calculating the resistivity of the wafer being processed in consideration of the above factors and performing control including suitable distribution adjustment according to the resistivity.

[Plasma processing equipment (1)]
FIG. 1 shows a functional block configuration of the plasma processing apparatus of the first embodiment. The plasma processing apparatus of the first embodiment includes a processing chamber 10, a power supply unit 20, a monitor unit 30, an electromagnetic wave generation unit 40, and a control unit 50.

  The processing chamber 10 includes a holding unit 2 and a substrate 3 to be processed held by the holding unit 2. The substrate to be processed 3 is a material to be processed such as a wafer and has a disk shape. The holding unit 2 includes a placement electrode 4 and a conductor film 5 that is an upper surface portion of the placement electrode 4. The processing chamber 10 has a substantially cylindrical shape. The mounting electrode 4 is an electrode for mounting the substrate 3 to be processed, and has a disk shape corresponding to the substrate 3 to be processed such as a wafer. The center axis of the placement electrode 4 and the substrate 3 to be processed in the processing chamber 10 is indicated by a one-dot chain line.

  The mounting electrode 4 is connected to the high frequency bias power source 24 of the power supply unit 20 through a power supply line. A third power P3, which is a high-frequency bias power supply, is supplied from the high-frequency bias power supply 24 to the mounting electrode 4, whereby a third voltage V3, which is a high-frequency bias power supply voltage, is applied.

  The conductor film 5 has a first electrode 6 and a second electrode 7 as electrodes. The conductor film 5 includes a first electrode 6 and a second electrode 7 as conductor films provided in two regions. These two electrodes are electrostatic adsorption electrodes (ESC: Electro Static Chuck) which are bipolar electrodes for electrostatic adsorption. The first electrode 6 is an inner peripheral portion ESC, and is an electrode disposed on the inner peripheral portion in the vicinity of the central axis on the disk-shaped surface. The second electrode 7 is an outer peripheral portion ESC, and is an electrode disposed on the outer peripheral portion on the disk-shaped surface.

  The first electrode 6 and the second electrode 7 are each connected to the power supply unit 20 through a power supply line. The first voltage V1 that is the first high-frequency bias voltage is applied to the first electrode 6 from the power supply unit 20 based on the supply of the first power P1 that is the first high-frequency bias power. The second voltage V2 that is the second high-frequency bias voltage is applied from the power supply unit 20 to the second electrode 7 based on the supply of the second power P2 that is the second high-frequency bias power.

  The power supply unit 20 includes a switch 21, an LC resonance circuit 22, a control circuit 23, a high frequency bias power source 24, and the like. The switch 21 is connected to the LC resonance circuit 22, the first electrode 6 and the second electrode 7, a first state connected to the first electrode 6, and a second state connected to the second electrode 7. The switch is switchable between a third state not connected to any electrode.

  The LC resonance circuit 22 is a damping circuit, and includes a circuit in which a variable inductance by a coil and a fixed capacitance by a capacitor are connected in series, and an inductance value can be controlled. By controlling the inductance value as a control value, the high-frequency bias voltage value applied to the first electrode 6 and the second electrode 7 can be variably controlled.

  The control circuit 23 controls the operation and state of the circuit in the power supply unit 20 according to the drive control value C1 from the control unit 50. The control circuit 23 includes a circuit that variably controls the state of the switch 21 and the inductance value that is the control value of the LC resonance circuit 22.

  The high frequency bias power source 24 is a power source that supplies high frequency bias power source power. The high-frequency bias power supply power is power for applying a high-frequency bias voltage to the electrode of the holding unit 2. The high frequency bias voltage is a voltage for acting on the plasma in the processing chamber 10.

  During the plasma processing, the monitor unit 30 constantly monitors the voltage value related to the high-frequency bias voltage of the electrode of the holding unit 2, the inductance value that is the control value of the LC resonance circuit 22 of the power supply unit 20, and the like. This is given to the resistivity calculator 51 of the controller 50. The monitor unit 30 measures and monitors the first voltage V1 of the first electrode 6, the second voltage V2 of the second electrode 7, and the third voltage V3 of the placement electrode 4 as voltage values.

  The first voltage V1, the second voltage V2, and the third voltage V3 are peak-to-peak voltages (represented by Vpp) corresponding to the difference between the maximum value and the minimum value of the AC power amplitude.

  The electromagnetic wave generation unit 40 is a known element, but is a part that generates an electromagnetic wave and propagates it to the processing chamber 10.

  The control unit 50 includes a resistivity calculation unit 51, a correction unit 52, a DB unit 53, and a processing condition management unit 54. The control unit 50 controls the entire plasma processing apparatus including the electromagnetic wave generation unit 40, the processing chamber 10, the power supply unit 20, and the monitor unit 30. The control unit 50 controls the plasma processing for the substrate to be processed 3 in the processing chamber 10 according to the processing conditions and processing sequence of the plasma processing. The control unit 50 can be configured by a computer or a circuit board, for example.

  The processing condition management unit 54 manages processing conditions and processing sequences for plasma processing. The processing sequence includes a plurality of steps. The plurality of processes include various processes such as a transfer process, a wafer holding process, an electromagnetic wave generation process, a gas supply and evacuation process, and a high frequency bias voltage application process, depending on processing conditions. Each process has a drive control value according to processing conditions, for example, a gas pressure value, a voltage value, and the like. The processing condition management unit 54 sets or changes processing conditions based on an operator's operation, and performs settings relating to the distribution adjustment function, registration of DB data in the DB unit 53, and the like.

  The control unit 50 controls the transfer of the substrate to be processed 3 into the processing chamber 10 and the holding of the substrate 3 to be processed in the holding unit 2 when controlling the sequence of the plasma processing. In addition, the control unit 50 performs control such as generation and introduction of electromagnetic waves into the processing chamber 10, gas supply and evacuation, and application of a high-frequency bias voltage.

  The control unit 50 has a distribution adjustment function and uses the electrode of the holding unit 2 and the power supply unit 20 so that the plasma state, the etching rate, and the like are uniform in the plane during the plasma etching process. Then, control including desired distribution adjustment is performed. This distribution adjustment is to adjust the plasma density and ion energy distribution in the in-plane radial direction corresponding to the wafer or the like to a desired distribution such as a flat distribution, a concave distribution, or a convex distribution. . The control unit 50 performs power control so that different high frequency bias voltages are applied to the first electrode 6 in the inner peripheral portion and the second electrode 7 in the outer peripheral portion so as to obtain a desired etching rate.

  The resistivity calculation unit 51 inputs a monitor value from the monitor unit 30 during the plasma processing. The resistivity calculation unit 51 calculates the actual resistivity of the substrate 3 being processed based on the voltage value and the control value that are monitor values at that time. This resistivity is distinguished from the basic resistivity as the first resistivity (indicated by R1). At this time, the resistivity calculation unit 51 calculates the first resistivity R1 using the DB data of the DB unit 53. The resistivity calculation unit 51 provides information including the calculated first resistivity R1 to the correction unit 52. The first resistivity R1 is a value reflecting a processing condition, a processing state, and the like.

  The DB unit 53 is configured by a storage device or the like, and holds a DB in which data used for calculation of resistivity and control information used for correction control are stored. The DB of the DB unit 53 is registered in advance, and data can be updated through the processing condition management unit 54.

  In the DB of the DB unit 53, information representing the relationship between a plurality of variable values is stored as a table. The plurality of variable values include the resistivity of the substrate to be processed 3, the inductance value that is the control value of the LC resonance circuit 22, and the high-frequency bias voltage value of each electrode of the first electrode 6 and the second electrode 7. The DB data includes a table representing the relationship between the control value and the high-frequency bias voltage value of each electrode for each resistivity at a plurality of representative resistivity values for a plurality of sample wafers.

  The correction unit 52 uses the first resistivity R1 calculated by the resistivity calculation unit 51 to determine a voltage correction value that is a suitable correction value of the high-frequency bias power value corresponding to the desired distribution adjustment. Further, the correction unit 52 determines a control correction value that is a correction value of the control value corresponding to the voltage correction value. The correction unit 52 operates the power supply unit 20 using the correction value including the determined voltage correction value and control correction value. The correction unit 52 drives and controls the power supply unit 20 using the drive control value C1 corresponding to the correction value.

  As a result, the power supply unit 20 operates an internal circuit or the like according to the drive control value C1, and corresponds to the correction value from the power supply unit 20 to the first electrode 6 and the second electrode 7 that are the electrodes of the holding unit 2. The corrected high frequency bias voltage is applied. Thereby, control including suitable distribution adjustment in accordance with the first resistivity R1 of the substrate 3 to be processed is performed. As a result, the distribution of ion energy and the like can be suitably controlled between the inner and outer peripheral portions in the surface, stable plasma processing with high uniformity can be realized, and as a result, the etching rate can be made uniform in the surface, etc. The effect is obtained.

  As described above, the plasma processing apparatus according to the first embodiment calculates the first resistivity R1 based on the monitor value during the plasma etching process of the wafer, and preferably uses a high frequency according to the first resistivity R1. Real-time control such as correcting the bias voltage value is performed.

  In order to achieve in-plane uniformity related to plasma processing, the plasma processing apparatus directly controls the state of distribution such as the incident ion energy distribution on the wafer surface with high accuracy and controls it. If possible, it is more preferable. However, it may be technically difficult to directly measure and monitor the in-plane distribution with high accuracy. In the configuration of the first embodiment, instead of directly measuring the distribution in the plane, the state is measured at a plurality of positions in the radial direction in the plane. In particular, in this configuration, the monitor unit 30 has a voltage value in a state in which a high-frequency bias voltage is applied to the two electrodes of the holding unit 2 including the first electrode 6 on the inner periphery and the second electrode 7 on the outer periphery. The first voltage V1 and the second voltage V2 are measured.

  Then, the control unit 50 calculates the first resistivity R1 of the wafer being processed based on the voltage value of the monitor, and calculates the in-plane radial distribution based on the first resistivity R1. The high frequency bias voltage of each electrode is corrected so as to obtain a distribution corresponding to the distribution adjustment, for example, a flat distribution.

[Plasma processing equipment (2)]
FIG. 2 shows the configuration of the plasma processing apparatus of the first embodiment. The plasma processing apparatus of the first embodiment is an etching apparatus having a function of performing a plasma etching process using microwave electron cyclotron resonance (ECR).

  The processing chamber 10 is a vacuum container whose upper part in the Z direction is open. A vacuum exhaust device (not shown) is connected to the processing chamber 10 via a vacuum exhaust port 110. A shower plate 102 and a window portion 103 are provided in the upper portion of the processing chamber 10. The shower plate 102 has holes and is made of, for example, quartz. A gas for plasma etching supplied from the gas supply mechanism 125 is introduced into the processing chamber 10 through the holes. A window 103 is provided on the shower plate 102 with a gap for gas supply. The window portion 103 transmits electromagnetic waves from above and encloses it in the processing chamber 10. The window 103 uses a dielectric material such as quartz as a material.

  On the window 103, a cavity 104 is provided for distribution adjustment. The upper part of the cavity 104 is open, and a waveguide 105 extending in the Z direction is connected thereto. A waveguide converter 106 is connected to the top of the waveguide 105, and a waveguide 107 extending in the X direction is connected to the end of the waveguide converter 106 in the X direction. Yes. The waveguide converter 106 also serves as a corner that bends the direction of the waveguide and the electromagnetic wave by 90 degrees. The waveguide 105, the waveguide 107, and the like are oscillation waveguides that propagate electromagnetic waves. A source power source 108 is connected to an end portion of the waveguide 107 in the X direction.

  The source power source 108 is a power source for generating electromagnetic waves, and generates electromagnetic waves based on control from the control unit 50. In the first embodiment, a microwave of 2.45 GHz is used as the frequency of the electromagnetic wave. An electromagnetic wave generated by the source power supply 108 propagates in the Z direction through the waveguide 107, the waveguide converter 106, and the waveguide 105, and passes through the cavity 104, the window 103, and the shower plate 102 to enter the processing chamber 10. To be introduced.

  A magnetic field generating coil 109 is provided on the outer periphery of the upper portion of the processing chamber 10. The magnetic field generation coil 109 generates a magnetic field in the processing chamber 10 during ECR processing. The power oscillated from the source power supply 108 generates high-density plasma in the processing chamber 10 by interaction with the magnetic field formed by the magnetic field generating coil 109.

  A holding part 2 is provided below the processing chamber 10 so as to face the window part 103. The holding unit 2 holds the substrate 3 to be processed placed on the upper surface. The central axes of the waveguide 105, the holding portion 2 of the processing chamber 10, and the substrate 3 to be processed are the same. The holding unit 2 is mainly composed of the placement electrode 4. The mounting electrode 4 is made of aluminum or titanium as a material. A conductive film 5 is provided on the upper surface which is a part of the mounting electrode 4. Note that a thermal spray film (not shown) made of alumina ceramic or the like is provided on the upper surface of the conductive film 5 of the mounting electrode 4.

  A first electrode 6 and a second electrode 7 are formed inside the conductive film 5 of the mounting electrode 4 as a dielectric film which is an electrode divided into two regions of an inner peripheral portion and an outer peripheral portion. . The first electrode 6 and the second electrode 7 are used for electrostatic attraction of the substrate 3 to be processed and for application of a high frequency bias voltage.

  The power supply unit 20 includes a switch 21, an LC resonance circuit 22, a control circuit 23, a high frequency bias power supply 24, a matching box 210, a high frequency filter 220, DC power supplies 221 and 222, a first voltage detector 201, and a second voltage detector 202. And a third voltage detector 203.

  The placement electrode 4, the first electrode 6, and the second electrode 7 of the holding unit 2 are connected to the power supply unit 20. The mounting electrode 4 is connected to the high-frequency bias power source 24 through the third voltage detector 203 and the matching box 210. The first electrode 6 is connected to the LC resonance circuit 22 through the first voltage detector 201 and the first terminal of the switch 21. The second electrode 7 is connected to the LC resonance circuit 22 through the second voltage detection unit 202 and the second terminal of the switch 21. A DC power source 221 and a DC power source 222 are connected to the first electrode 6 and the second electrode 7 via a high frequency filter 220.

[Outline of plasma processing]
The outline of the plasma processing in the plasma processing apparatus of Embodiment 1 is as follows. The substrate 3 to be processed such as a wafer is transferred into the processing chamber 10 based on the transfer control of the control unit 50 and mounted on the conductor film 5 of the mounting electrode 4 of the holding unit 2. Then, the placed substrate 3 is placed on the first electrode 6 by a positive voltage and the second electrode 7 by a DC power source 221, 222. It is electrostatically attracted and held at a predetermined position on the electrode 4.

  Thereafter, the processing chamber 10 is in a vacuum state in which the inside is depressurized based on gas supply control and vacuum exhaust control from the control unit 50. In this case, specifically, a gas for plasma etching is supplied from the gas supply mechanism 125 via a mass flow controller (not shown). Then, the gas passes through the gap between the window portion 103 and the shower plate 102 and is introduced into the processing chamber 10 from the hole of the shower plate 102. The control unit 50 maintains the inside of the processing chamber 10 at a predetermined pressure while controlling the vacuum exhaust device.

  The control unit 50 generates an electromagnetic wave from the source power supply 108 based on the electromagnetic wave generation control, and generates a plasma in the processing chamber 10 based on the electromagnetic wave introduced into the processing chamber 10 in a vacuum state.

  At that time, the control unit 50 applies a high-frequency bias voltage to each of the first electrode 6 and the second electrode 7 that are electrodes of the holding unit 2 in the processing chamber 10 based on power control for the power supply unit 20. The high frequency bias voltage causes an action of drawing ions from the plasma to the substrate 3 to be processed.

  More specifically, high frequency bias power is supplied from the high frequency bias power supply 24 to the mounting electrode 4, and a high frequency bias voltage is applied to the mounting electrode 4. Further, high frequency bias power is supplied to the first electrode 6 and the second electrode 7 based on the switching control of the switch 21 of the LC resonance circuit 22, and a high frequency bias voltage is applied to each electrode.

  Thereby, the plasma etching process is performed on the surface of the substrate 3 to be processed. At this time, reaction products generated by gas and etching are exhausted through the vacuum exhaust port 110 at the bottom of the processing chamber 10.

[Power supply section]
Next, a circuit configuration of the power supply unit 20 and a mechanism for applying different high-frequency bias voltages to the first electrode 6 and the second electrode 7 of the holding unit 2 from one high-frequency bias power supply 24 will be described.

  The switch 21 is connected to the first state connected to the first electrode 6 by the first terminal, the second state connected to the second electrode 7 by the second terminal, and connected to both the first electrode 6 and the second electrode 7. The three types of states, which are not performed, can be switched according to the input of the control terminal.

  The LC resonance circuit 22 includes a series connection of a fixed capacitance by the capacitor 22a and a variable inductance by the coil 22b, and is grounded. Capacitance is indicated by C and inductance is indicated by L. Let the inductance value, which is a variable control value, be the L value.

  A voltage detector is provided at each of the first electrode 6, the second electrode 7, and the outlet of the high-frequency bias power source 24. That is, the outlet of the first electrode 6 has the first voltage detector 201 in the middle of the power supply line, and the outlet of the second electrode 7 has the second voltage detector 202 in the middle of the power supply line. Have In addition, a third voltage detector 203 is provided at the exit of the matching box 210 of the high frequency bias power supply 24 in the middle of the power supply line to the mounting electrode 4. Each voltage detector is composed of an A / D converter or the like, and detects the voltage and its Vpp value with high time resolution.

  The first voltage detector 201 detects Vpp of the first voltage V <b> 1 that is the first high-frequency bias voltage applied to the first electrode 6. The second voltage detector 202 detects Vpp of the second voltage V <b> 2 that is the second high-frequency bias voltage applied to the second electrode 7. The third voltage detector 203 detects Vpp of the third voltage V3 that is the third high-frequency bias voltage applied to the placement electrode 4.

  Each voltage detector is connected to the monitor unit 30 of FIG. The first voltage detector 201 outputs the detected value of the first voltage V1 to the monitor unit 30. The second voltage detector 202 outputs the detected value of the second voltage V2 to the monitor unit 30. The third voltage detector 203 outputs the detected value of the third voltage V3 to the monitor unit 30.

  The L value of the variable inductance of the LC resonance circuit 22 is controlled by the control unit 50 through the control circuit 23 as a control value. By controlling the L value, the magnitudes of the first voltage V1 and the second voltage V2 that are high-frequency bias voltages can be variably controlled. The variable control of the L value can be realized, for example, by changing the rotation angle of the coil 22b by driving a motor (not shown) connected to the coil 22b having the inductance L. Thereby, the L value can be variably controlled at high speed.

  The control circuit 23 includes a drive mechanism such as a motor, and is connected to the coil 22 b of the inductance L of the LC resonance circuit 22. The operation of the control circuit 23 is controlled by the drive control value C1 from the correction unit 52 of the control unit 50. The control circuit 23 variably controls the L value of the inductance L of the LC resonance circuit 22 in accordance with the drive control value C1 from the correction unit 52. Further, the L value can be monitored from the monitor unit 30 through the control circuit 23. The control circuit 23 outputs the L value to the monitor unit 30.

  The monitor unit 30 receives the voltage values {V1, V2, V3} which are detection values from each voltage detector of the power supply unit 20, and also inputs the L value from the control circuit 23 and needs these values. The monitor value including those values is output to the resistivity calculation unit 51 of the control unit 50.

  The control circuit 23 is connected to the control terminal of the switch 21. The control circuit 23 controls switching of the switch 21 in accordance with the drive control value C1 from the correction unit 52. In the first state in which the switch 21 is connected to the first terminal, the capacitor C and the inductance L of the LC resonance circuit 22 are connected to the first electrode 6. In the second state where the switch 21 is connected to the second terminal, the capacitance C and the inductance L of the LC resonance circuit 22 are connected to the second electrode 7. In the third state in which the switch 21 is not connected to either the first terminal or the second terminal, the LC resonance circuit 22 is not connected to the first electrode 6 and the second electrode 7.

  By controlling the switch 21 and the L value, the first voltage V1 of the first electrode 6 and the second voltage V2 of the second electrode 7 are controlled to be voltage values corresponding to the L value. The power supply unit 20 can variably control the L value and the magnitude of the high-frequency bias power supply voltage based on the control from the control unit 50, and accordingly, the magnitudes of the first voltage V1 and the second voltage V2 can be set. It can be variably controlled.

  Let LZ be the L value at which the LC resonance circuit 22 becomes the LC series resonance point. However, the capacitance component of the LC resonance circuit 22 includes the mounting electrode 4 and the plasma capacitance component in addition to the fixed capacitance C. The maximum value of the control range for the L value is about 1.1 times the value LZ. In Embodiment 1, the minimum value of the L value is defined as 0% and the maximum value is defined as 100%. The value LZ serving as the LC series resonance point is about 90%.

  The matching box 210 is an impedance matching unit, and matches the impedance between the input-side high-frequency bias power supply 24 and the output-side placement electrode 4.

  It is assumed that a certain amount of power PA (unit: watts) is supplied to the mounting electrode 4 as the high frequency bias power source power output from the high frequency bias power source 24. In this case, the third voltage detector 203 measures, for example, 300 V (unit: volt) as the third voltage V3 that is the high-frequency bias voltage generated by the high-frequency bias power supply. When the switch 21 is in the third state, the first voltage V1 of the first electrode 6 and the second voltage V2 of the second electrode 7 are both measured by the first voltage detector 201 and the second voltage detector 202. Is done. In this state, the high frequency bias voltage is applied uniformly within the plane corresponding to the substrate 3 to be processed.

  When the switch 21 is connected to the first electrode 6 and the L value is close to the LC series resonance point (for example, the value LZ = 80%), the impedance of the LC resonance circuit 22 approaches zero. The impedance viewed from the high frequency bias power supply 24 is lowered. As a result, Vpp of the first voltage V1 of the first electrode 6 decreases from the above 250V. At this time, Vpp of the second voltage V2 of the other second electrode 7 also decreases from the above 250V.

  Between the first electrode 6 and the second electrode 7, there are two paths through the placement electrode 4 and the conductor film 5 of the holding unit 2 and the inside of the substrate 3 to be processed. Since a current flows through the path, the second voltage V2 of the second electrode 7 is dragged by the first voltage V1 of the first electrode 6, and both voltages approach an intermediate value. Therefore, both the first voltage V1 and the second voltage V2 are reduced as described above.

[Inductance characteristics]
FIG. 3A is a characteristic showing the relationship between the Vpp of the first voltage V1 of the first electrode 6 and the second voltage V2 of the second electrode 7, which are monitor voltage values, and the L value of the variable inductance L. A graph is shown. The characteristic of this graph is called inductance characteristic. In this characteristic, V2> V1 as the setting Vpp.

  The controller 50 increases the L value from zero to a value LZ corresponding to the resonance point. Then, (V2−V1), which is the difference value (V1−V1) of Vpp between the first voltage V1 and the second voltage V2, gradually increases and both Vpp of V1 and V2 decrease. When the L value becomes the value LZ, the impedance becomes almost zero and V1 becomes minimum, but the difference value D1 becomes maximum.

  FIG. 3B relates to the characteristics of FIG. 3A, and shows the high-frequency bias power supply voltage and the first voltage V1 and the second voltage V2 that are monitor voltage values when the L value is fixed to a certain value. The graph of the characteristic showing the relationship with Vpp is shown. The high-frequency bias power supply voltage corresponds to the third voltage V3 that is a voltage based on the output power of the high-frequency bias power supply 24 described above. In this graph, V1 and V2 increase as V3 increases.

  That is, from FIG. 3, the first electrode 6 and the second electrode 7 have different high-frequency bias voltages having different magnitudes by controlling two parameters of the third voltage V3 and the L value, which are high-frequency bias power supply voltages. The voltage V1 and the second voltage V2 can be applied. The first voltage V1 and the second voltage V2 have a predetermined relationship with the third voltage V3 and the L value. The desired distribution adjustment can be realized by changing the first voltage V1 and the second voltage V2 by controlling the third voltage V3 and the L value.

  Conversely, even in the second state where the switch 21 is connected to the second electrode 7 side, the inductance characteristics do not change except for the positive / negative relationship compared to the case of the first state. This is because the two regions of the first electrode 6 and the second electrode 7 are designed to have approximately the same area in order to ensure uniform electrostatic adsorption by the ESC. By switching the switch 21, it is possible to change the magnitude relationship between Vpp of the first voltage V1 and the second voltage V2.

  As a premise, when the first voltage V1 and the second voltage V2 are both 250V, the distribution of the etching rate is, for example, a convex distribution. In this case, it is assumed that the distribution adjustment is controlled so as to obtain an etching rate with better uniformity, that is, close to a flat distribution. As this control, for the high-frequency bias voltage, the first voltage V1 is set to 200V, and the second voltage V2 is set to 300V. When performing this control, the power supply unit 20 first sets the switch 21 to the first state, outputs the high-frequency bias power supply power at PA × 1.5 W, thereby setting the third voltage V3 to 400 V, and the L value To 60%.

  However, the inductance characteristics vary depending on the conditions and state of plasma processing, the magnitude of the high frequency bias voltage, and the like. Therefore, if the Vpp of the first voltage V1 and the second voltage V2 is determined in advance from the beginning, the L value and the high-frequency bias power value of an appropriate magnitude are not determined at one point. In particular, as described above, the actual resistivity of the wafer varies depending on the conditions and state of plasma processing and the influence of various factors. And the control effect and controllability regarding distribution adjustment change according to the resistivity.

  It is desirable to perform control including distribution adjustment by determining an appropriate L value and high-frequency bias power value according to the plasma processing conditions and states. Therefore, the first embodiment has a function of calculating an actual resistivity of a wafer during plasma processing and determining an L value that is a power value or a control value according to the resistivity.

[Control sequence]
FIG. 4 shows a time-series sequence when performing control to apply a high-frequency bias voltage to the electrode during the plasma etching process in the plasma processing apparatus of the first embodiment. This control example is a control example in a case where 200 V is applied to the first electrode 6 as the first voltage V1 and 300 V is applied to the second electrode 7 as the second voltage V2 in accordance with various conditions. 4A shows the high-frequency bias power source power output from the high-frequency bias power source 24. FIG. (B) shows the L value of the variable inductance of the LC resonance circuit 22. (C) shows the detected value of the third voltage V3 which is a high frequency bias power supply voltage based on the power of (a). (D) shows the detected value of the second voltage V2 of the outer peripheral portion ESC. (E) shows the detected value of the first voltage V1 of the inner periphery ESC. (F) shows (V2−V1) which is a difference value D1 between the first voltage V1 and the second voltage V2.

  The control unit 50 performs the following control on the power supply unit 20. First, in a third state in which the switch 21 is not connected to any electrode, the high-frequency bias power supply power in (a) is set to a predetermined power PA [W], and the third voltage V3 in (c) is set to 300V. Then, the second voltage V2 in (d) and the first voltage V1 in (e) both become 250V.

  Next, at the time point t1, the control unit 50 sets the switch 21 to the first state connected to the first electrode 6 side having the lower setting Vpp, and the L value in (b) is changed from 0% which is the initial value. Increase to larger. Then, as described above, while the difference value D1 = (V2−V1) in (f) increases, as a basic characteristic, both the first voltage V1 and the second voltage V2 decrease. On the other hand, in this control, adjustment is performed while increasing the high-frequency bias power supply power in (a) so that the average value of the first voltage V1 and the second voltage V2 (V1 + V2) / 2 is kept constant. Accordingly, the second voltage V2 of (d) is increased to 300V and the first voltage V1 of (e) is decreased to 200V in the period up to time t2.

  At the time of this adjustment control, the adjustment of the high-frequency bias power source power in (a) is performed while calculating the average value of the first voltage V1 and the second voltage V2 through the monitor unit 30 and the control unit 50. . Or about the said adjustment, the 3rd voltage V3 of the 3rd voltage detector 203 is monitored, and the said adjustment is performed so that the 3rd voltage V3 may be maintained constant like (c).

  The L value is changed until the difference value D1 in (f) reaches the set difference value Dx. The set difference value Dx is a value corresponding to a desired distribution adjustment. After the application of the high-frequency bias voltage from the time point t1, the adjustment of the high-frequency bias voltage is completed at a time point t2 after about several seconds have elapsed, and the first voltage V1 and the second voltage V2 are set to desired Vpp, for example, 200V and 300V. be able to. At time t2, the L value becomes a predetermined value Lx.

  In the period after time t2, the high-frequency bias power supply voltage, the L value, the first voltage V1, and the second voltage V2 are maintained constant unless correction occurs.

  According to the above control sequence, the first voltage V1 and the second voltage V2 are the same Vpp, and the distribution of ion energy and the like in the surface is a flat distribution without significantly deviating from the average etching rate of the reference condition. Only the distribution of the etching rate can be changed. In other words, the control sequence of the first embodiment has an advantage that the distribution adjustment and the plasma processing can be suitably realized based on the reference condition without adversely affecting other elements.

[Characteristics of high-frequency bias voltage control according to resistivity]
FIG. 5 shows the characteristics of the high-frequency bias voltage control and the etching rate distribution adjustment control corresponding to the difference in resistivity in the plasma processing apparatus of the first embodiment. The etching rate depends on the high-frequency bias voltage Vpp. Further, the etching rate varies depending on the resistivity.

  FIG. 5A shows characteristics relating to the distribution of the etching rate in the in-plane radial direction when the resistivity of the wafer as the substrate to be processed 3 is 10 Ω · cm. In the graph of this characteristic, the horizontal axis indicates the radial position (x) in the surface of the wafer, and the vertical axis indicates the etching rate corresponding to the high-frequency bias voltage value of the plasma etching process for the wafer. This resistivity = 10 Ω · cm is a reference resistivity of a typical sample wafer. Regarding the position x, the position indicated by the alternate long and short dash line corresponds to the inner peripheral portion including the central axis of the wafer, and both sides thereof correspond to the outer peripheral portion.

  A curve K1 is a curve when the first voltage V1 at the inner peripheral portion is 250V and the second voltage V2 at the outer peripheral portion is also 250V as the first control of the distribution adjustment, and has a convex distribution. A curve K2 is a curve when the first voltage V1 at the inner peripheral portion is 200V and the second voltage V2 at the outer peripheral portion is 300V as the second control of the distribution adjustment, and has a substantially flat distribution. The second control corresponds to a condition for setting (V2−V1), which is the difference value D1, to 100V.

  In contrast to the first control, as in the second control, the rate is higher in the outer peripheral portion where Vpp is increased by 50V, and the rate is lower in the inner peripheral portion where Vpp is reduced by 50V. Further, the rate in the vicinity of the boundary between the inner peripheral portion and the outer peripheral portion is a substantially intermediate value between the inner peripheral portion and the outer peripheral portion. That is, when the reference resistivity is 10 Ω · cm, the in-plane radial characteristic in the etching rate distribution is smoothed from the convex distribution to the flat distribution in the second control with respect to the first control. The rate of the part is higher and the in-plane uniformity is improved.

  Next, similarly, FIG. 5B shows characteristics when the resistivity is 1 Ω · cm, and FIG. 5C shows characteristics when the resistivity is 100 Ω · cm.

  When the resistivity in FIG. 5B is 1 Ω · cm, the etching rate distribution is not sufficiently controlled and the degree of improvement in uniformity is small compared to FIG. 5A. A curve K3 in FIG. 5B is the same as the curve K1 in FIG. 5A, which has a different resistivity but has a convex distribution. The curve K4 is basically the same as the curve K2 of the second control in FIG. 5A, but has a convex distribution which is a different distribution due to the different resistivity.

  The curves K2 and K4 under the condition that the difference value D1 is 100V are compared with the curves K1 and K3 under the condition where the first voltage V1 and the second voltage V2 are the same. Then, when the resistivity is relatively high, the distribution of the etching rate changes greatly as shown by the curve K1 to the curve K2, and approaches a flat distribution. Specifically, the Vpp difference between the curve K1 and the curve K2 at the position of the central axis in FIG. 5A is relatively large, whereas the curve K3 at the position of the central axis in FIG. And the difference in Vpp between the curve K4 is relatively small. The same applies to the position of the outer peripheral portion. The curve K4 is slightly improved with respect to the convex distribution of the curve K3, but does not reach the flat distribution of the curve K2.

  Similarly, when comparing the first voltage V1 and the second voltage V2 with the same L value, the Vpp difference at each electrode position is smaller when the resistivity is lower than the reference resistivity. Become.

  That is, in the range of 1 to 10 Ω · cm, it can be said that the higher the resistivity, the higher the controllability of the distribution adjustment relating to the etching rate. When the resistivity is low, such as 1 Ω · cm in FIG. 5B, the high-frequency bias power is more likely to propagate in the radial direction of the wafer than on the plasma side immediately above the wafer. As described above, high-frequency bias currents propagate between the electrodes through the paths between the electrodes. Thereby, the 1st voltage V1 and the 2nd voltage V2 approach both average value by an inner peripheral part and an outer peripheral part. Therefore, the controllability of the rate at each position of the inner peripheral portion and the outer peripheral portion becomes smaller than the case of 10 Ω · cm which is the reference resistivity as described above.

  On the other hand, when the resistivity is high, such as 100 Ω · cm in FIG. 5C, the degree of propagation of the high-frequency bias power in the radial direction of the wafer is suppressed, and the first voltage V1 on the inner peripheral portion and the outer peripheral portion are reduced. The second voltage V2 is maintained on the wafer and propagates to the plasma immediately above. Therefore, the controllability becomes high, and the controllability appears as a difference in the resulting etching rate.

  The curve K5 in FIG. 5C has the same conditions as the curve K1 in FIG. 5A, and the curve K6 is basically the same as the curve K2 in FIG. Depending on the difference in rate, the distribution is a concave distribution. That is, in the curve K6, the difference in Vpp at each position of the inner peripheral portion and the outer peripheral portion is larger than that of the curve K5, thereby forming a concave distribution.

  Similarly, in the range of 10 to 100 Ω · cm, it can be said that the higher the resistivity, the higher the controllability of the distribution adjustment. Similarly, when the first voltage V1 and the second voltage V2 are compared with the same L value, the Vpp difference at the position of each electrode is larger when the resistivity is larger than the reference resistivity. Become.

  By the plasma processing, the sheath thickness directly above the wafer is thin at the inner peripheral portion where the first voltage V1 is low, thick at the outer peripheral portion where the second voltage V2 is high, and the impedance to the plasma side is also reduced at the inner peripheral portion. It becomes larger at the outer periphery. The LC resonance circuit 22 is connected to the first electrode 6 on the inner periphery, and the impedance of the first electrode 6 is small. These mutual effects increase the Vpp difference at the position of each electrode. As a result, the curve K6 has a concave distribution beyond the flat distribution of the curve K2.

  Whether the high-frequency bias power is likely to propagate in the plasma immediately above the electrode or in the radial direction of the wafer depends on the ratio between the impedance and the resistance value depending on the sheath thickness. For example, when the wafer diameter is 300 mm and the resistivity is uniformly 1 Ω · cm, the resistance in the in-plane circumferential region between the position of 50 mm and 100 mm from the central axis in the radial direction of the wafer. Is about 2Ω. The magnitude of this resistance is directly proportional to the resistivity.

  For example, when the sheath voltage formed with a high frequency bias power of 400 kHz and a Vpp of about 200 V is 100 V, the sheath thickness is calculated from the Debye length, and is about 0.4 mm. The capacity in this case is about 1500 PF, and the impedance per unit area of 1 cm 2 is about 0.4Ω.

  When the resistivity of the wafer is as low as about 0.1 Ω · cm, the impedance and the resistance value due to the sheath thickness are almost in the same order, and the degree of high-frequency bias power propagating in the radial direction becomes considerably high. As a result, the controllability regarding the distribution adjustment is considerably lowered. Since the sheath thickness depends on the magnitude of the high-frequency bias voltage, the controllability related to the distribution adjustment varies depending on the magnitude of the high-frequency bias voltage.

  As for the inductance characteristics, the resistivity is an element that determines the Q value (Quality factor value representing the sharpness of resonance) in an RLC series circuit in which resistance is added to the LC resonance circuit. Therefore, the inductance characteristic changes according to the resistivity.

  As described above, the controllability, characteristics, and effects in high-frequency bias voltage control and distribution adjustment control differ depending on the difference in resistivity of the substrate 3 to be processed. Therefore, it is effective to correct the contents of the control according to the actual resistivity of the substrate 3 to be processed.

[Resistivity calculation unit and DB]
Based on the above recognition, a method of calculating the actual resistivity of the substrate 3 to be processed during plasma processing by the resistivity calculation unit 51 of the control unit 50 in the plasma processing apparatus of the first embodiment will be described.

  FIG. 6 shows a configuration example of DB data of the DB unit 53 used for calculation of resistivity. In this DB, information on the above-described inductance characteristics is organized for each of a plurality of typical resistivity values for a reference sample wafer for each same plasma processing condition based on experiments and the like in advance. Has been stored. This DB stores a table of inductance characteristics representing the relationship between the L value and the high frequency bias voltage value of each electrode according to the magnitude of the high frequency bias power supply as data for each resistivity. For example, a plurality of representative values may be set for the magnitude of the high-frequency bias power supply power and the power supply voltage.

  In FIG. 6, four values of 100, 10, 1, 0.1 Ω · cm are shown as typical resistivity examples. For example, as data when resistivity = 100 Ω · cm, Tables 601 to 602 are provided as tables of a plurality of inductance characteristics corresponding to a plurality of values obtained by changing the value of the high-frequency bias power supply power from small to large. Table 601 shows a table of inductance characteristics in the case where the high-frequency bias power supply power has a small predetermined value. Table 602 shows a table of inductance characteristics in the case where the high-frequency bias power supply power has a large predetermined value. As data in the case of resistivity = 10 Ω · cm, Tables 611 to 612 are provided as tables of a plurality of inductance characteristics according to the value of the high frequency bias power supply power. Similarly, data is provided for each resistivity.

  For example, by performing plasma processing on a sample dummy wafer in advance, inductance characteristics at each resistivity {0.1, 1, 10, 100 Ω · cm} and each power source power can be obtained. The information is stored in the DB in advance.

  The resistivity calculator 51 calculates a first resistivity R1 that is an actual resistivity of the wafer being processed, using the processing conditions, the monitor value, and the DB data during the plasma processing. The resistivity calculation unit 51 obtains, from the monitor value, the first voltage V1 at the inner periphery, the second voltage V2 at the outer periphery, and the L value that is the control value for the wafer being processed. The resistivity calculator 51 compares the values {V1, V2, L value} with corresponding data in the DB to calculate the first resistivity R1. The resistivity calculator 51 refers to at least the first voltage V1 and the second voltage V2.

  In FIG. 6, four values are used as the resistivity. However, the present invention is not limited to this, and the actual resistivity can be calculated with higher accuracy by providing the DB with more detailed data on a plurality of resistivity values. is there.

[Monitor value]
FIG. 7 shows an example of a monitor value during plasma processing of a wafer as an example of a monitor value of the monitor unit 30 for calculating the resistivity. In the table of FIG. 7, the column includes time (T), inductance (L), outer periphery ESC voltage value (V2), inner periphery ESC voltage value (V1), power supply voltage value (V3), and power output ratio. . “Time (T)” indicates a time corresponding to an elapsed time from the start of the plasma processing. “Inductance (L)” indicates the aforementioned L value. The “outer peripheral part ESC voltage value (V2)” indicates the detection value of the second voltage V2 of the second electrode 7 described above. The “inner circumference ESC voltage value (V1)” indicates the detected value of the first voltage V1 of the first electrode 6 described above. “Power supply voltage value (V3)” indicates a detection value of the third voltage V3 based on the power of the high-frequency bias power supply 24 described above. “Power supply output ratio” indicates the ratio of the output of the high-frequency bias power supply 24 to the predetermined power PA.

[Comparison verification process]
The resistivity calculation unit 51 calculates the first resistivity R1 by using the monitor value as shown in FIG. 7 and the DB data as shown in FIG. As monitor values, for example, at time Tx, L value = Lx, V2 = V2x, V1 = V1x, V3 = V3x, and the like are obtained. The resistivity calculation unit 51 compares the monitor value with the DB data, and determines and extracts the closest data to the monitor value from the DB data. For example, the resistivity calculation unit 51 may search the DB data using the monitor value as a search condition during the comparison and determination process, or the proximity of the monitor value and the DB data value as described below. May be calculated, and the nearest data may be determined based on the index value E.

  The resistivity calculation unit 51 calculates, for example, an index value E that represents the proximity between the monitor value and the inductance characteristic table. This index value can be calculated by applying various known methods. As an example, the resistivity calculation unit 51 calculates, as the index value E, a difference value or a ratio between the monitor value Lx and the L value in the table. Similarly, the resistivity calculation unit 51 calculates a difference value or ratio between the monitor value V1x and the table V1, and calculates a difference value or ratio between the monitor value V2x and the table V2. In addition, the resistivity calculation unit 51 may perform a predetermined calculation using the difference value or ratio thereof, for example, addition or selection of a minimum value. The resistivity calculating unit 51 extracts a table of inductance characteristics having the smallest index value E as the closest data.

  As a result of the above comparison and determination, it is assumed that, as data closest to the DB, for example, one inductance characteristic table with a resistivity = 100 Ω · cm and a high-frequency bias power supply having a predetermined value is obtained. That is, the combination of the monitor values Lx, V1x, and V2x is the closest to the specific combination of the L value and V1, V2 in the inductance characteristic table.

  The resistivity calculation unit 51 calculates the first resistivity R1 using the data in the closest table and the index value E, and the high-frequency bias power supply value associated therewith or the L value that is a control value. Etc. are calculated. The resistivity calculating unit 51 refers to values such as resistivity, power supply power value, L value, etc. in the data of the nearest table, and reflects a predetermined index value E representing the proximity to those values. Calculations such as multiplication are performed. The resistivity calculator 51 obtains the first resistivity R1 as a result of the calculation. Similarly, the resistivity calculator 51 obtains an L value, a high-frequency bias power supply power value, and the like related to the first resistivity R1.

  In addition, although it was set as the some table | surface stored in DB in FIG. 6 as a structure of the information used for resistivity calculation, it is applicable not only to this. For example, a plurality of variable value relationships as shown in FIG. 6 arranged in one table may be provided. In addition to the table, a calculation formula representing a relationship between a plurality of variable values may be defined and used. In that case, the resistivity calculator 51 substitutes the input value into the calculation formula to obtain the first resistivity R1 as the output value.

  The correction unit 52 uses the first resistivity R1 calculated by the resistivity calculation unit 51 and the like to perform correction processing related to control including plasma processing and distribution adjustment for the wafer being processed by processing such as predetermined calculation. decide. The correction unit 52 determines a correction value for the high frequency bias power and voltage and a correction value for the L value as the correction value.

  Furthermore, the data for each time (T) corresponding to the elapsed time of the plasma processing or the data for each processing step of the plasma processing may be stored in the DB in the same manner. In that case, the resistivity calculation unit 51 uses, as one of the monitor values, the time (T) during the plasma processing or information indicating the processing step, refers to the data corresponding to the time or the processing step from the DB, The first resistivity R1 is determined in the same manner as described above.

[Correction section]
In the case of the above processing example, since the control L value and the power supply voltage value are obtained from the resistivity calculation unit 51 together with the first resistivity R1, the correction unit 52 determines the correction value using the information. The correction unit 52 determines the drive control value C1 to be given to the power supply unit 20 using the first resistivity R1, the L value, and the power supply voltage value. The correction unit 52 determines correction values for the first voltage V1 and the second voltage V2, which are high-frequency bias voltages to be applied to the respective electrodes, in accordance with desired distribution adjustment such as a concave distribution, a flat distribution, and a convex distribution. To do.

  For example, when the distribution adjustment is controlled so that the etching rate has a flat distribution as shown by a curve K2 in FIG. The correction unit 52 adjusts the second control corresponding to the curve K2 and the first voltage V1 = 200V and the second voltage V2 = 300V at the resistivity = 10 Ω · cm to the first resistivity R1 before correction. The corrected first voltage V1 and second voltage V2 are determined. For example, the correction unit 52 multiplies V1 = 200V and V2 = 300V by a correction value according to the ratio between the first resistivity R1 and 10 Ω · cm. Thereby, the correction values of the first voltage V1 and the second voltage V2 can be obtained.

  The correction unit 52 determines the L value and the high-frequency bias power supply power value in the drive control value C1 based on the relationship between a plurality of variable values from the correction values obtained as described above.

  FIG. 8 shows a control table which is an example of information used for correction processing for obtaining a correction value from the first resistivity R1 by the correction unit 52. The control table is stored in advance in the DB unit 53, for example, and the correction unit 52 performs correction processing with reference to the control table. This control table stores in advance information representing the relationship between typical resistivity corresponding to FIG. 6, controllability related to distribution adjustment, correction voltage value, and the like.

  In the table of FIG. 8, the row number indicated by #, “Resistivity”, “Controllability ratio”, “Necessary correction Vpp difference (flat distribution)”, “Voltage after correction of inner ESC (V1)” , “Peripheral part ESC corrected voltage (V2)”. “Resistivity” is a typical resistivity value in the DB, and here, 10 Ω · cm corresponding to (A) of FIG. 5 is specified as the reference resistivity. The “controllability ratio” is a ratio representing controllability related to the above-described distribution adjustment of the etching rate, and is set to 1 in the case of 10 Ω · cm. “Necessary correction Vpp difference (flat distribution)” indicates a value of a Vpp difference necessary as a correction when the control is performed so that a flat distribution is obtained as one of the distribution adjustments, that is, a uniform rate. This value is a difference value between the inner periphery ESC corrected voltage and the outer periphery ESC corrected voltage. “Inner circumference ESC corrected voltage (V1)” indicates the corrected first voltage V1, and “Outer circumference ESC corrected voltage (V2)” indicates the corrected second voltage V2.

  In the table of FIG. 8, the third row shows that when the resistivity is 10 Ω · cm as the reference value, the controllability ratio = 1, the correction required Vpp difference = 100 V, and the corrected first voltage V1 is 200V, indicating that V2 after correction is 300V. The correction required Vpp difference is (300−200) = 100. This corresponds to the second control curve K2 in FIG.

  The second row shows the controllability ratio = 0.5 when the resistivity = 1 Ω · cm, the correction required Vpp difference = 200 V, the corrected first voltage V1 is 150 V, and the corrected second voltage. Indicates that V2 is 350V. The correction required Vpp difference is (350−150) = 200. This corresponds to correcting the curve K4 in FIG. 5B to a curve K7 in FIG. 9A described later. The corrected curve K7 approaches a flat distribution.

  The fourth row shows that when the resistivity = 100 Ω · cm, the controllability ratio = 1.6, the correction required Vpp difference = 60 V, the corrected first voltage V1 is 220 V, and the corrected second voltage. It shows that V2 is 280V. The correction required Vpp difference is (280−220) = 60. This corresponds to correcting the curve K6 in FIG. 5C to a curve K8 in FIG. 9B described later. The corrected curve K8 approaches a flat distribution.

  The first row is the case where the resistivity = 0.1 Ω · cm. As described above, when the resistivity is small to some extent, the controllability regarding the radial distribution in the surface is small, and correction is necessary. The difference in Vpp becomes large, for example, 1000V. In this case, the effectiveness of the distribution adjustment control is low.

  The control table is not limited to the information on the four resistivities described above, and information on a plurality of resistivities that are more finely divided may be stored.

  The correction unit 52 refers to the information in the control table from the first resistivity R1, and corrects the value according to the magnitude of the first resistivity R1, thereby correcting the high-frequency bias voltage value after correction. Etc. can be obtained. Thereby, the drive control value C1 for the control including a desired suitable distribution adjustment can be obtained.

  Not limited to the above processing example, the correction unit 52 calculates a correction value by reflecting the index value E representing the above-mentioned proximity to the reference resistivity and the power value related thereto by multiplication or the like. May be. The correction unit 52 may calculate the correction value using a predetermined calculation formula. Alternatively, the resistivity calculation unit 51 and the correction unit 52 may be integrated into one, and the drive control value C1 may be determined from the input monitor value.

  The correction unit 52 immediately supplies the drive control value C1 corresponding to the correction value to the control circuit 23 of the power supply unit 20 and the like during the plasma processing. Thereby, the first voltage V1 of the first electrode 6 and the second voltage V2 of the second electrode 7 which are electrodes in the processing chamber 10 are set to the corrected high-frequency bias voltage value from the power supply unit 20. it can. As a result of this plasma treatment, a more favorable etching rate, for example, a flat distribution can be obtained than before correction. An example of the above distribution adjustment is a case where the distribution is flat. However, in the case where it is desired to control the distribution to be a concave distribution or a convex distribution as another distribution adjustment, it can be realized in the same manner as described above. The DB control table is provided with information corresponding to the case of the concave distribution or the case of the convex distribution as in FIG.

[Control after correction]
FIG. 9 shows the control characteristics after correction with respect to the case where FIG. 5 is the control characteristics before correction. FIG. 9A shows the case where the resistivity = 1 Ω · cm. A curve K7 shows a curve after correction with respect to the curve K4 in FIG. 5B, where the corrected first voltage V1 at the inner peripheral portion is 150V and the corrected second voltage V2 at the outer peripheral portion is 350V. This correction content corresponds to the second row in FIG.

  FIG. 9B shows the case where resistivity = 100 Ω · cm. A curve K8 shows a curve after correction with respect to the curve K6 in FIG. 5C, where the first voltage V1 after correction of the inner peripheral portion is 220V, and the second voltage V2 after correction of the outer peripheral portion is 280V. This correction content corresponds to the fourth row in FIG.

  The corrected etching rate is closer to a flatter distribution in both the curve K7 and the curve K8. In the curve K7, the Vpp value is smaller at the position of the inner peripheral portion than the curve K4, the Vpp value is larger at the position of the outer peripheral portion, and both values are close to each other. In the curve K8, the Vpp value is larger at the position of the inner peripheral portion than the curve K6, and the Vpp value is smaller at the position of the outer peripheral portion.

  Regarding (A) of FIG. 9, in the control of the curve K4 before correction, the difference value D1 (V2−V1) is 100V. At the position of the inner periphery, the Vpp difference between the standard control V1 value and the control V1 value is (200−250) = − 50V. Similarly, at the position of the outer peripheral portion, the Vpp difference between the standard control V2 value and the control V2 value is (300−250) = 50V.

  On the other hand, in the control of the corrected curve K7, the difference value D1 (V2−V1) is 200V. At the position of the inner periphery, the Vpp difference between the standard control V1 value and the control V1 value is (150−250) = − 100V. Similarly, the Vpp difference between the V2 value of the standard control and the V2 value of the control at the position of the outer peripheral portion is (350−250) = 100V.

  That is, in the control curve K7 after the correction, the difference value D1 and the Vpp difference at each position are twice as large as the control curve K4 before the correction. In this way, by increasing the difference value D1 and the Vpp difference at each position by correction, the distribution can be made closer to a flat distribution from the convex distribution.

  Regarding (B) in FIG. 9, in the control of the curve K6 before correction, the difference value D1 (V2−V1) is 100V. At the position of the inner periphery, the Vpp difference between the standard control V1 value and the control V1 value is (200−250) = − 50V. Similarly, at the position of the outer peripheral portion, the Vpp difference between the standard control V2 value and the control V2 value is (300−250) = 50V.

  On the other hand, in the control of the corrected curve K8, the difference value D1 (V2−V1) is 60V. At the position of the inner periphery, the Vpp difference between the standard control V1 value and the control V1 value is (220−250) = − 30V. Similarly, at the position of the outer peripheral portion, the Vpp difference between the standard control V2 value and the control V2 value is (280−250) = 30V.

  That is, in the control curve K8 after correction, the difference value D1 and the Vpp difference at each position are 0.6 times smaller than the control curve K6 before correction. In this way, by reducing the difference value D1 and the Vpp difference at each position by correction, the distribution can be made closer to the flat distribution from the concave distribution.

  When the resistivity of the wafer being processed is low, for example, 1 Ω · cm, it is necessary to increase the Vpp difference to some extent at each position between the first electrode 6 and the second electrode 7. As a correction corresponding to this, the correction unit 52 sets the L value to 80%, sets the high frequency bias power supply power for the third voltage V3 to PA × 2.0 W with respect to the predetermined power PA, and sets the first voltage V1 to 150 V. The second voltage V2 is set to 350V. As a result, the in-plane rate can be made close to uniform as shown by the curve K7 in FIG.

  When the resistivity of the wafer being processed is high, for example, 100 Ω · cm, it is necessary to reduce the Vpp difference to some extent at each position between the first electrode 6 and the second electrode 7. As a correction corresponding to this, the correction unit 52 sets the L value to 30%, sets the high-frequency bias power supply power for the third voltage V3 to PA × 1.2 W with respect to the predetermined power PA, and sets the first voltage V1 to 220V. The second voltage V2 is 280V. As a result, the in-plane rate can be made closer to uniform as shown by the curve K8 in FIG.

[Effects]
As described above, according to the plasma processing apparatus of the first embodiment, it is possible to achieve desired distribution adjustment such as in-plane uniformity related to plasma processing and etching rate. According to the first embodiment, the distribution of incident ion energy in the plasma etching process can be controlled with high accuracy. According to the first embodiment, suitable etching can be realized by applying an optimum high-frequency bias voltage according to the resistivity of the substrate to be processed.

  In a plurality of processing steps of the plasma etching sequence, the actual resistivity of the wafer changes during the processing step. Factors include changes in the temperature of the wafer, etching of the conductive film of the laminated film of the wafer, adhesion of deposits on the wafer, and the like in addition to the conditions for each processing step.

  The plasma processing apparatus of the first embodiment performs plasma processing by applying different high-frequency bias voltages to the respective electrodes, and the voltage of each electrode is also applied to changes in the resistivity of the wafer as the processing steps during the processing progress. Is constantly monitored to detect the resistivity and its change immediately. And a plasma processing apparatus correct | amends the high frequency bias voltage corresponding to distribution adjustment according to the resistivity in process and its change. Thereby, when the resistivity of the wafer is not too low, for example, when it is about 1 Ω · cm or more, the distribution of the etching rate in the radial direction in the surface can be made to be uniform, for example.

[Modification]
The following is given as a modification of the plasma processing apparatus of the first embodiment. The configuration of the LC resonance circuit 22 may be a combination of a variable capacitance and a fixed inductance. In that case, the control value is a capacitance value.

  The DB data of the DB unit 53 includes information obtained by experiments in advance. As a modification, the plasma processing apparatus records and accumulates the result of plasma processing of the wafer as data including the resistivity and voltage value information at that time in the DB of the DB unit 53, and in subsequent plasma processing May be used. That is, the plasma processing apparatus may be provided with a function of automatically updating the DB data.

  In the plane corresponding to the mounting electrode 4 of the holding part 2, not only the two electrodes of the inner peripheral part and the outer peripheral part but also a form in which three or more electrodes are provided may be used. The plasma processing apparatus monitors each voltage value of three or more electrodes, calculates a resistivity using the monitored value, and performs control such as correction.

  The method relating to the calculation of the first resistivity R1 and the determination of the correction value is not limited to the method for finely calculating the values such as the first resistivity R1 and the voltage correction value. For example, the resistivity and the voltage correction value are set in the DB in advance as a plurality of roughly divided values. As the plurality of resistivity values, for example, {1, 2,..., 9, 10 Ω · cm}, {10, 20,. The resistivity calculation unit 51 selects the closest one of the plurality of resistivity values based on the determination of the monitor value. The correction unit 52 selects a voltage correction value related to the selected resistivity value. In the case of this form, the speed of the real-time processing can be increased instead of slightly reducing the control accuracy.

(Embodiment 2)
A plasma processing apparatus according to the second embodiment of the present invention will be described. The basic configuration of the second embodiment is the same as the configuration of the first embodiment, and the following description will be made on portions of the configuration of the second embodiment that are different from the configuration of the first embodiment.

  The plasma processing apparatus according to the second embodiment performs a predetermined control by calculating the resistivity of the wafer to be processed before the plasma etching process is performed on the wafer that is the substrate 3 to be processed. The configuration of the second embodiment is the configuration of FIGS. 1 and 2, and the processing content of the control unit 50 is different from that of the first embodiment.

  First, a sequence example of the conventional plasma etching process is as follows. After the wafer is transferred to the processing chamber, the wafer is electrostatically attracted to the electrode and held at a predetermined position of the holding unit by applying a DC voltage from the DC power source to the electrode. Next, an etching gas is introduced into the processing chamber, an electromagnetic wave is generated by applying a voltage to the source power supply, and an electromagnetic wave propagated through a waveguide or the like is introduced into the processing chamber, and plasma is generated in the processing chamber. Thereafter, a high-frequency bias voltage for causing plasma to act is applied to the electrode of the processing chamber by power supply control.

  In the second embodiment, the following plasma etching process sequence is performed. In the processing chamber 10, after holding the wafer by electrostatic attraction by applying DC voltage from the DC power sources 221 and 222 to the electrodes, the following processing steps are performed before generating plasma from electromagnetic waves. In the processing step, on the basis of the control of the power supply unit 20 from the control unit 50, the high-frequency bias power is applied to the electrodes of the holding unit 2 with a predetermined low power, for example, about 5 seconds for a few seconds in the absence of plasma. Apply in time. At that time, the power supply unit 20 increases the L value of the LC resonance circuit 22 from 0% to 100% in the first state in which the switch 21 is connected to the first electrode 6 side.

  In this case, a characteristic close to the characteristic of FIG. 3A corresponding to the inductance characteristic in the case of no plasma in Embodiment 1 is obtained. The monitor unit 30 monitors the value {L value, V1, V2, V3, etc.} relating to the characteristic at the time of the processing step. Based on the monitor value, the resistivity calculation unit 51 compares the characteristic with an inductance characteristic created in advance and stored in the DB. Thereby, the resistivity calculation unit 51 obtains a schematic resistivity of the wafer before processing as the resistivity before processing. Let the resistivity before processing be the second resistivity R2. This pre-process resistivity is obtained as a value close to the actual resistivity of the wafer being processed. The correction unit 52 performs control such as predetermined correction using the obtained pre-processing resistivity.

  In the plasma processing apparatus of the second embodiment, the approximate resistivity of the wafer can be obtained before the plasma processing. Therefore, the control unit 50 can perform the following control before processing. The correction unit 52 of the control unit 50 has a function of performing the control.

  First, when the pre-processing resistivity is as low as a certain value, for example, 0.1 Ω · cm, the control unit 50 outputs an alert such as caution or cancels the plasma processing as specific control. . The control unit 50 compares the calculated pre-process resistivity with a predetermined threshold value, and applies the specific control when it is equal to or less than the threshold value.

  As described above, for example, in a wafer having a low resistivity such as resistivity = 0.1 Ω · cm, the controllability of distribution adjustment can be achieved even when different high-frequency bias voltages are applied to the first electrode 6 and the second electrode 7. Small and weak effect. Further, it is necessary to supply a considerably large high-frequency bias power supply, and it is necessary to pay attention to power efficiency. That is, in this case, the effectiveness of the control is low.

  In this case, before executing the plasma processing, the control unit 50 outputs an alert such as a caution to the operator based on the calculation and determination of the pre-processing resistivity, and then executes the processing. The alert content is, for example, a notice that the etching rate distribution cannot be sufficiently controlled by the resistivity of the wafer. The operator confirms the alert and continues processing as necessary. As another control example, the control unit 50 outputs an alert and cancels the process. The content of the alert is, for example, a notice that the processing is canceled because the resistivity of the wafer cannot sufficiently control the etching rate distribution.

  As the second control, the control unit 50 determines the first voltage V1, the second voltage V2, and the like for obtaining a uniform rate or the like in the processing based on the calculation and determination of the pre-processing resistivity before the plasma processing. The range of values such as L value and high frequency bias power supply is narrowed to some extent. The correction unit 52 drives and controls the power supply unit 20 based on the narrowed range. As a result, the accuracy of the high-frequency bias voltage can be increased during processing, and the time required for control and correction can be shortened.

  Conventionally, there is an example in which the wafer resistivity is measured in advance using a commercially available wafer resistance measuring device. However, as described above, the wafer resistivity changes under the influence of various factors such as the temperature of the wafer, the electrostatic adsorption state, the state of the front and back surfaces of the wafer, and the wafer sample film type. Therefore, as in the second embodiment, immediately before the plasma processing, by detecting and controlling the resistivity of the wafer in the state immediately before the processing, a desirable effect can be obtained compared to the conventional case. When calculating the pre-processing resistivity, the resistivity calculating unit 51 calculates the pre-processing resistivity in consideration of processing conditions and monitor values in the plasma processing apparatus. And the control part 50 can perform control more suitable than before using the resistivity before a process.

(Embodiment 3)
A plasma processing apparatus according to the third embodiment of the present invention will be described with reference to FIG. The basic configuration of the third embodiment is the same as the configuration of the first embodiment, and hereinafter, the difference in the configuration of the third embodiment from the configuration of the first embodiment will be described. In the third embodiment, the configuration of the power supply unit 20 is mainly different from the configuration of FIGS. 1 and 2 of the first embodiment.

  FIG. 10 mainly shows the configuration of the processing chamber 10 and the power supply unit 20 in the plasma processing apparatus of the third embodiment. In the configuration of the power supply unit 20 in FIG. 10, the line extending from the high-frequency bias power supply 24 and the matching box 210 is different from the configuration in FIG. 2 between the placement electrode 4 and the second electrode 7 that is the outer peripheral portion ESC. A switch 301 is connected to each other.

  The switch 301 can be switched between a first state connected to the placement electrode 4 side and a second state connected to the second electrode 7 by a control terminal. The first terminal of the switch 301 is connected to the mounting electrode 4 through a power supply line, and the second terminal is connected to the second terminal through the capacitor 302 and the power supply line to which the second voltage detector 202 is connected. Connected to the electrode 7. A capacitor 302 is inserted in the line between the switch 301 and the second electrode 7. The capacitor 302 is an element for cutting the DC voltage of the ESC.

  The switch 301 is a switch for applying a high-frequency bias power supply voltage to the placement electrode 4 in the first state and to only one of the first electrode 6 and the second electrode 7 in the second state. The first state of the switch 301 is the same as the circuit configuration of the first embodiment. Switching of the control terminal of the switch 301 is controlled by the control circuit 23, for example.

  In the third embodiment, the second electrode 7 is used as one electrode to which the switch 301 is connected. However, in the modification, the first electrode 6 may be used as one electrode. In this case, a high frequency bias power supply voltage is applied to the first electrode 6.

  As in the first embodiment, the plasma processing apparatus according to the third embodiment calculates the first resistivity R1 of the substrate 3 to be processed during the plasma etching process, and performs correction or the like according to the resistivity. Take control. In addition, the plasma processing apparatus of the third embodiment calculates the pre-processing resistivity of the substrate to be processed 3 before processing, and performs control according to the pre-processing resistivity.

  The sequence of the plasma etching process in the third embodiment includes the following processing steps. First, a wafer as the substrate 3 to be processed is transferred into the processing chamber 10, and in the first state of the switch 301, a DC voltage from the DC power sources 221 and 222 is applied to the electrodes of the holding unit 2, and the wafer is electrostatically charged. Adsorbed. Thereafter, based on the control of the power supply unit 20, the control unit 50 sets the switch 301 to the second state in which the switch 301 is connected to the second electrode 7 before generating plasma in the processing chamber 10. In a third state where no connection is made. In this state, the power supply unit 20 supplies the high frequency bias power from the high frequency bias power supply 24 to the second electrode 7 with a predetermined low power, for example, 5 W. As a result, a high frequency bias power supply voltage is applied to the second electrode 7. At this time, the second voltage detector 202 detects this high frequency bias power supply voltage as the second voltage V2. The third voltage detector 203 detects this high frequency bias power supply voltage as the third voltage V3.

  At this time, for example, when the resistivity of the wafer is 10 Ω · cm, the first electrode 6 which is the other electrode to which the high frequency bias power supply voltage is not applied is applied to the second electrode 7 through the path between the electrodes. A voltage about 1/10 of the voltage is applied. The first voltage detector 201 measures and detects the voltage as the first voltage V1.

  When the resistivity of the wafer to be processed is low, the second voltage V2 of the second electrode 7 in the outer peripheral portion tends to increase, and conversely, when the resistivity is high, the second voltage V2 tends to decrease. is there.

  The monitor unit 30 monitors the first voltage V1, the second voltage V2, and the third voltage V3 during the processing step. The resistivity calculation unit 51 uses the data based on the monitor value to compare and collate with the data of the voltage value for each typical resistivity stored in the DB in advance. The resistivity before processing, which is resistivity, is calculated. This processing content can be realized in the same manner as in the first embodiment.

  In the third embodiment, as in the first embodiment, the resistivity of the wafer can be calculated even under conditions with plasma, that is, during plasma processing. This is realized as follows, for example. The power supply unit 20 supplies predetermined power as high-frequency bias power to the first electrode 6 on the inner periphery, and applies a first voltage V1 corresponding to the predetermined power.

  FIG. 11 shows the resistance regarding the first voltage V1 of the first electrode 6 at the inner peripheral portion and the second voltage V2 of the second electrode 7 at the outer peripheral portion when the third voltage V3 by the high frequency bias power supply power is about 100V. Shows rate dependency. The horizontal axis represents the wafer resistivity, and the vertical axis represents the monitor voltage values {V1, V2, V3}. A curve 901 indicates a V1 value, a curve 902 indicates a V2 value, and a curve 903 indicates a V3 value. As shown by the curves 901 and 902, when the resistivity is low, the difference value (V2−V1) of Vpp between the first voltage V1 at the inner peripheral portion and the second voltage V2 at the outer peripheral portion becomes small, and the resistivity is reduced. If it is high, the difference value becomes large.

  On the other hand, with respect to the third voltage V3 corresponding to the high frequency bias power supply voltage, the influence of impedance matching of the matching box 210 is large, the influence of resistivity is small, and the voltage value hardly appears. Therefore, it is difficult to calculate the resistivity from the third voltage V3 corresponding to the high frequency bias power supply voltage.

  For each voltage and Vpp difference value to be measured, a difference is caused between a resistance factor and another factor such as plasma. Therefore, the monitor unit 30 monitors the three voltage values. The resistivity calculator 51 uses the monitor value to divide, for example, the Vpp difference value between ESCs (V2−V1) by the third voltage V3 that is Vpp of the high-frequency bias power supply voltage, and is the value. The resistivity during processing is calculated from (V2-V1) / V3. Thereby, the accuracy of calculation of resistivity during processing can be increased.

  Then, the plasma processing apparatus of the third embodiment performs control for suitably correcting the high-frequency bias power and the voltage value during the processing by the correction unit 52 using the calculated resistivity as in the first embodiment. Do. At this time, for example, after the resistivity and the power correction value are determined, the correction unit 52 switches the switch 301 in FIG. 10 to the first state connected to the placement electrode 4 side. And the correction | amendment part 52 applies the corrected high frequency bias electric power to the 1st electrode 6 and the 2nd electrode 7 as the state which switches the switch 21 between a 1st state and a 2nd state similarly to Embodiment 1. FIG. To control.

  FIG. 12 shows an example of a control table in the third embodiment. In the table of FIG. 12, the columns include resistivity, outer peripheral ESC voltage value (V2), internal ESC voltage value (V1), power supply voltage value (V3), and (V2−V1) / V3.

  “Resistivity” has a plurality of typical resistivities as in the control table of FIG. The “outer periphery ESC voltage value (V2)” indicates the second voltage V2 corresponding to the resistivity. “Internal ESC voltage value (V1)” indicates the first voltage V1 corresponding to the resistivity. “Power supply voltage value (V3)” indicates the third voltage V3. “(V2−V1) / V3” indicates the calculated value.

  In the DB unit 53, the control table is created and stored in advance. The resistivity calculation unit 51 calculates each resistivity by referring to the control table from the monitor value before and during the process. In addition, when there are a plurality of processing conditions for plasma processing, information may be similarly prepared for each processing condition and used.

  The present invention has been specifically described above based on the embodiments. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the invention.

  The substrate to be processed 3 is not limited to a silicon (Si) oxide film, but a poly Si film, a photoresist film, an antireflection organic film, a silicon nitride oxide film, a silicon nitride film, a low-k material, a high- k Materials, amorphous carbon films, Si substrates, etc. are also applicable.

  Treatment gases include chlorine, hydrogen bromide, tetrafluoromethane, trifluoromethane, difluoride methane, argon, helium, oxygen, nitrogen, carbon dioxide, carbon monoxide, hydrogen, ammonia, octafluoride Propane, nitrogen trifluoride, sulfur hexafluoride, methane, silicon tetrafluoride, silicon tetrachloride, and the like can be applied.

  The plasma processing apparatus and its discharge method are not limited to the etching apparatus using microwave ECR discharge, but also apply to dry etching apparatuses using magnetic field UHF discharge, capacitively coupled discharge, inductively coupled discharge, magnetron discharge, etc. Is possible.

  The present invention is suitable for an etching apparatus using microwave ECR discharge and its processing. The present invention is not limited to this, and can be widely applied to a device having a high-frequency bias power supply for ion attraction, which has a difference in rate due to the high-frequency bias, that is, a process having a correlation between ion energy and rate.

  DESCRIPTION OF SYMBOLS 2 ... Holding part, 3 ... Substrate to be processed, 4 ... Mounting electrode, 5 ... Conductor film, 6 ... 1st electrode, 7 ... 2nd electrode, 10 ... Processing chamber, 20 ... Power supply part, 21 ... Switch, DESCRIPTION OF SYMBOLS 22 ... LC resonance circuit, 23 ... Control circuit, 24 ... High frequency bias power supply, 30 ... Monitor part, 50 ... Control part, 51 ... Resistivity calculation part, 52 ... Correction part, 53 ... DB part, 54 ... Processing condition management part .

Claims (14)

A plasma processing apparatus,
An electromagnetic wave generator for generating electromagnetic waves;
Based on the plasma generated based on the electromagnetic wave, a processing chamber in which plasma processing is performed as processing for the substrate to be processed held in the holding unit;
In the holding portion, as a placement electrode for placing the substrate to be processed and an electrode provided inside the placement electrode, a first electrode located on the inner periphery in a plane corresponding to the placement electrode. One electrode and a second electrode on the outer periphery;
A high-frequency bias power for applying a high-frequency bias voltage to the placement electrode and the electrode is supplied, a first voltage is applied to the first electrode, and a second voltage is applied to the second electrode as the high-frequency bias voltage. Applying a third voltage to the placement electrode, a power supply unit;
A monitor for monitoring the first voltage and the second voltage;
A resistivity calculation unit that calculates the resistivity of the substrate to be processed based on the monitor value of the monitor unit;
According to the resistivity, a correction value for the high-frequency bias voltage is determined, and a correction unit that drives and controls the power supply unit so as to be the correction value;
A plasma processing apparatus. The plasma processing apparatus according to claim 1,
The power supply unit includes a high-frequency bias power source and an LC resonance circuit connected to the first electrode and the second electrode via a switch, and the switch and the LC resonance circuit during execution of the processing. The first voltage is applied to the first electrode, the second voltage is applied to the second electrode by controlling a variable control value of
The monitoring unit monitors the voltage value including the first voltage and the second voltage, and the control value during the execution of the process,
The resistivity calculation unit uses the first voltage, the second voltage, and the control value during the execution of the process, and uses the first voltage corresponding to the state during the process as the resistivity. Calculate the resistivity,
The correction unit determines the control value corresponding to the correction value based on the first resistivity during the execution of the process, and drives and controls the power supply unit using the control value. ,
Plasma processing equipment. The plasma processing apparatus according to claim 2, wherein
In the processing, the correction unit sets the control value of the LC resonance circuit to a first value, supplies predetermined power from the high-frequency bias power source, and thereafter, the first voltage and the second voltage in a subsequent period. The control value is changed to the second value until the difference value between the first voltage and the second voltage reaches a predetermined value while maintaining the average value of
Plasma processing equipment. The plasma processing apparatus according to claim 2, wherein
The correction unit holds, as a plurality of variable values, control information representing a relationship between a resistivity related to the substrate to be processed and a voltage value including the first voltage and the second voltage related to the high-frequency bias voltage. And referring to the control information based on the voltage value of the monitor value to calculate a resistivity related to the voltage value of the monitor value;
Plasma processing equipment. The plasma processing apparatus according to claim 4, wherein
Having a DB section for holding the DB;
In the DB, information indicating the relationship between the first voltage and the voltage value including the second voltage is stored for each resistivity in a plurality of resistivity as the control information,
The resistivity calculation unit compares the voltage value of the monitor value with the voltage value of the DB to obtain the closest voltage value and the associated resistivity, and the resistivity or the A resistivity obtained by correcting the resistivity according to proximity is obtained as the first resistivity.
Plasma processing equipment. The plasma processing apparatus according to claim 2, wherein
The power supply unit applies the first voltage and the second voltage by supplying the high-frequency bias power in response to in-plane distribution adjustment corresponding to the substrate to be processed with respect to the processing rate,
The correction unit determines a correction value including the first voltage and the second voltage in correspondence with the distribution adjustment;
Plasma processing equipment. The plasma processing apparatus according to claim 6, wherein
When the first resistivity is smaller than a reference resistivity, the correction unit converts the voltage values of the first voltage and the second voltage to be the correction values in the case of the reference resistivity. When the first resistivity is larger than the reference resistivity, the first voltage and the second voltage as the correction values are corrected. Each voltage value is corrected to be smaller than the voltage value applied in the case of the reference resistivity.
Plasma processing equipment. The plasma processing apparatus according to claim 7, wherein
The correction unit corrects each voltage value of the first voltage and the second voltage as the correction value with a magnitude according to the proximity between the first resistivity and the reference resistivity,
Plasma processing equipment. The plasma processing apparatus according to claim 1,
The power supply unit includes a high-frequency bias power source and an LC resonance circuit connected to the first electrode and the second electrode via a switch, and the substrate to be processed is placed on the placement electrode. Thereafter, before the execution of the processing, the first voltage is applied to the first electrode and the second voltage is applied to the second electrode by controlling variable control values of the switch and the LC resonance circuit. Applied,
The monitor unit monitors the voltage value including the first voltage and the second voltage, and the control value before the execution of the process,
The resistivity calculation unit uses the first voltage, the second voltage, and the control value before the execution of the process, and uses a second value corresponding to a state of the substrate to be processed before the process is executed. Calculate the resistivity,
The correction unit determines the control value corresponding to the correction value based on the second resistivity before executing the process, and drives and controls the power supply unit using the control value. ,
Plasma processing equipment. The plasma processing apparatus according to claim 9, wherein
The correction unit determines the magnitude of the second resistivity, outputs an alert according to the magnitude of the second resistivity, and cancels the process.
Plasma processing equipment. The plasma processing apparatus according to claim 9, wherein
The correction unit determines a magnitude of the second resistivity, and narrows down a range of the correction value used in the process according to the magnitude of the second resistivity;
Plasma processing equipment. The plasma processing apparatus according to claim 1,
The power supply unit includes: an LC resonance circuit connected to the first electrode and the second electrode via a first switch; and the placement electrode and one electrode of the first electrode and the second electrode A high-frequency bias power source connected to the first high-frequency bias power source, and a voltage detector connected to an outlet of the high-frequency bias power source,
Prior to execution of the processing, the second switch is connected to the one electrode, and the first switch is not connected to any electrode. Is supplied to the one electrode,
The monitoring unit monitors the voltage value including the first voltage and the second voltage before the execution of the processing,
The resistivity calculation unit calculates the resistivity corresponding to the state before the execution of the process using the voltage value before the execution of the process,
The correction unit performs control related to the processing using the resistivity before the execution of the processing.
Plasma processing equipment. The plasma processing apparatus according to claim 12, wherein
During execution of the process, the second switch is connected to the placement electrode, and a variable control value of the first switch and the LC resonance circuit is controlled, thereby controlling the first electrode. Applying the first voltage, applying the second voltage to the second electrode;
The monitor unit monitors the voltage value and the control value during the execution of the process,
The resistivity calculation unit calculates a resistivity corresponding to a state during execution of the process during the execution of the process,
The correction unit performs control related to the process using the resistivity during the execution of the process.
Plasma processing equipment. A plasma processing method in a plasma processing apparatus,
The plasma processing apparatus includes:
An electromagnetic wave generator for generating electromagnetic waves;
Based on the plasma generated based on the electromagnetic wave, a processing chamber in which plasma processing is performed as processing for the substrate to be processed held in the holding unit;
In the holding portion, as a placement electrode for placing the substrate to be processed and an electrode provided inside the placement electrode, a first electrode located on the inner periphery in a plane corresponding to the placement electrode. One electrode and a second electrode on the outer periphery;
With
The plasma processing method is performed by the plasma processing apparatus as a step.
A high-frequency bias power for applying a high-frequency bias voltage to the placement electrode and the electrode is supplied, a first voltage is applied to the first electrode, and a second voltage is applied to the second electrode as the high-frequency bias voltage. Applying and applying a third voltage to the placement electrode;
Monitoring the first voltage and the second voltage;
Calculating a resistivity of the substrate to be processed based on a monitor value of the monitor;
Determining a correction value for the high-frequency bias power in accordance with the resistivity, and driving and controlling the correction value to be the correction value;
A plasma processing method.

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