JP2012185948A - Plasma processing device, and control method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing device capable of controlling the ratio of currents of inductive coupling antennas over a wide range with stability, and a control method therefor.SOLUTION: The plasma processing device has two or more lines of inductive coupling antennas, and a capacitive coupling antenna. In the device, the inductive coupling antennas and the capacitive coupling antenna are electrically connected in series. The plasma processing device comprises: a first regulator circuit operable to regulate RF currents flowing through the inductive coupling antennas; a second regulator circuit operable to regulate the ratio of RF currents flowing through the inductive coupling antennas and the capacitive coupling antenna; sensors operable to measure the RF currents flowing through the inductive coupling antennas respectively; and control means operable to control the ratio of currents flowing through the inductive coupling antennas to make the ratio constant while performing the monitoring for an excessive current toward the first regulator circuit based on signals from the sensors.

Description

The present invention relates to a plasma processing apparatus and a control method thereof.

  As a conventional plasma processing apparatus, for example, in Patent Document 1, in plasma processing using an inductively coupled antenna, grounding is performed via a load capable of changing the magnitude of impedance between the inductively coupled antenna and the capacitively coupled antenna. In addition, it is described that the adhesion of the reaction product to the inner wall of the vacuum vessel is suppressed by adjusting the magnitude of the impedance of the load. In addition, branching from a single power supply to the two systems of inductively coupled antennas, and by arranging a variable load on one antenna side, the current ratio of the two inductively coupled antennas is adjusted, and the plasma distribution is controlled. Things are known.

  Also, Patent Document 2 discloses a method for distributing power from a single power source to a plurality of coils disposed on a processing chamber that provides controllable plasma uniformity across a wafer disposed in the processing chamber. Methods and apparatus are described. An apparatus for distributing power from a power source to two or more coils disposed on a processing chamber includes a connection between the power source and the first coil, a series variable capacitor connected between the power source and the second coil. , And a device that performs power distribution control using a parallel variable capacitor connected to a node between a second coil and a power source.

JP 2000-323298 A JP-T-2004-53856 Publication

  In the prior art of Patent Document 1, in the combination of an inductively coupled antenna and a capacitively coupled antenna, consideration is given to the fact that the plasma state changes due to current control of the capacitively coupled antenna, and the current ratio of a plurality of inductively coupled antennas varies. There wasn't. That is, there has been a problem that the current ratio of the inductively coupled antenna changes with the change of plasma.

  Although there is a conventional technique such as Patent Document 2 for controlling the current ratio to a plurality of inductively coupled antennas, sufficient consideration is given to stably controlling the current ratio of a plurality of inductively coupled antennas over a wide range. It wasn't. That is, there is a problem of overcurrent generation to a variable load that is a means for adjusting the current ratio of the inductively coupled antenna. Therefore, the present invention provides a plasma processing apparatus and a control method therefor that can stably control the current ratio of a plurality of inductively coupled antennas over a wide range.

  The present invention includes two or more systems of inductively coupled antennas disposed with respect to a surface surrounding a region where plasma is formed, and a capacitively coupled antenna disposed with respect to a surface surrounding a region where plasma is formed. In the plasma processing apparatus in which the inductively coupled antenna and the capacitively coupled antenna are electrically connected in series, a first adjustment circuit for adjusting a magnitude of a high-frequency current flowing through each inductively coupled antenna, and each inductive coupling A second adjustment circuit for adjusting a ratio of the high-frequency current flowing through the antenna and the capacitive coupling antenna; a sensor for measuring the magnitude of each high-frequency current flowing through each inductive coupling antenna; and a signal from the sensor. And control means for controlling the ratio of the current flowing through each inductively coupled antenna to be constant in parallel with the overcurrent monitoring to the first adjustment circuit. It is a plasma processing apparatus.

  Further, the present invention provides two or more systems of inductively coupled antennas arranged with respect to a surface surrounding a region where plasma is formed, and an electrical connection between the induction antenna and the surface surrounding a region where plasma is formed. A capacitive coupling antenna connected in series, a first adjustment circuit for adjusting a magnitude of a high frequency current flowing through each inductive coupling antenna, and a ratio of a high frequency current flowing through each inductive coupling antenna and the capacitive coupling antenna In a control method using a plasma processing apparatus comprising a second adjustment circuit that adjusts the frequency and a sensor that measures the magnitude of each high-frequency current flowing through each inductively coupled antenna, the control method using the signal from the sensor In the control method, the ratio of the current flowing through each inductive coupling antenna is controlled to be constant in parallel with the overcurrent monitoring to the first adjustment circuit.

  With the configuration of the present invention, the current ratio of a plurality of inductively coupled antennas can be stably controlled over a wide range.

It is a schematic sectional drawing of the plasma processing apparatus which shows one Example of this invention. 3 is a longitudinal sectional view of the vacuum vessel 2. FIG. It is an equivalent circuit diagram of the discharge part 2a and the matching device 3. It is a characteristic view of the maximum allowable current with respect to the capacitance of the variable load. FIG. 6 is a diagram showing the relationship between the capacitance of the variable load 16 and the current flowing through the second inductively coupled antenna 1b and the variable load 16. It is a figure which shows an antenna current ratio control and an overcurrent detection circuit.

  An embodiment of the present invention will be described below with reference to FIG. FIG. 1 shows a schematic cross-sectional view of a plasma processing apparatus according to an embodiment of the present invention. In this case, the vacuum vessel 2 mounts a discharge part 2a made of an insulating material (for example, non-conductive material such as quartz or ceramic) that forms a plasma generation part therein, and a sample, for example, a wafer 13, which is an object to be processed. The electrode 5 for placing it is composed of a processing section 2b installed inside. The processing unit 2b is grounded to the ground, and the electrode 5 is attached to the processing unit 2b via an insulating material. A first inductive coupling antenna 1a and a second inductive coupling antenna 1b, which are two types of coiled dielectric coupling antennas, are disposed outside the discharge part 2a. Further, a Faraday shield 8 that is a disk-shaped capacitively coupled antenna that is capacitively coupled to the plasma 6 is provided on the atmosphere side of the discharge part 2a. The first inductively coupled antenna 1 a, the second inductively coupled antenna 1 b, and the Faraday shield 8 are connected in series to the first high frequency power supply 10 via the impedance matching circuit 12 in the matching unit 3. In addition, a variable load 16 whose impedance magnitude is variable is connected in series to the second inductively coupled antenna 1b, and a variable variable load 17 connected in parallel to the Faraday shield 8 is connected to the coil 18. Is grounded through the ground. Furthermore, the first inductive coupling antenna 1a and the second inductive coupling antenna 1b are connected to the antenna current ratio control / overcurrent detection circuit 15 via the first current sensor 14a and the second current sensor 14b. The Faraday shield 8 is connected to the FSV detection / control circuit 19. Here, FSV (Faraday Shield Voltage) is a high-frequency voltage applied to the Faraday shield, and is hereinafter referred to as FSV. A processing gas is supplied from the gas supply device 4 into the vacuum vessel 2, and the inside of the vacuum vessel 2 is evacuated to a predetermined pressure by the exhaust device 7. A second high frequency power source 11 is connected to the electrode 5.

  In the apparatus configured as described above, the process gas is supplied into the vacuum vessel 2 by the gas supply device 4, and the first inductively coupled antenna 1a, the second inductively coupled antenna 1b, and the Faraday shield 8 which is a capacitively coupled antenna. The processing gas is turned into plasma by the action of the electric field generated by. The plasma-ized processing gas is exhausted by the exhaust device 7. For example, high-frequency power generated by the first high-frequency power supply 10 such as 13.56 MHz, 27.12 MHz, 40.68 MHz, or a higher frequency VHF band is supplied to the first inductively coupled antenna 1a and the second inductive coupling antenna 1a. By supplying the inductive coupling antenna 1b and the Faraday shield 8, an induction magnetic field or electric field for plasma generation is obtained. In order to suppress reflection of power, the impedance of the antenna is first set using an impedance matching circuit 12. It is made to correspond to the output impedance of the high frequency power source 10. As the impedance matching circuit 12, a circuit using two variable capacitors that can change the capacitance, which is also called a general inverted L type, is used. The wafer 13 to be processed is placed on the electrode 5, and a bias voltage is applied to the electrode 5 by the second high frequency power supply 11 in order to draw ions in the plasma into the wafer 13.

  In the apparatus configured as shown in FIG. 1, the plasma distribution can be controlled by controlling the magnitude of the high-frequency current flowing in the two systems of the first inductively coupled antenna 1a and the second inductively coupled antenna 1b. . Hereinafter, a method for controlling the plasma distribution will be described.

  FIG. 2 is a longitudinal sectional view of the vacuum vessel 2. Regions 24a and 24b are regions where the induction magnetic field generated by the first inductively coupled antenna 1a and the second inductively coupled antenna 1b, which are two types of inductively coupled antennas, is strong. The region where the electric field generated by the Faraday shield 8 is strong is 24c. Plasma is generated in a region where these induction magnetic field and electric field are strong. The discharge part 2a of the vacuum vessel 2 has a different diameter in the region 24a and in the region 24b by decreasing the diameter upward. In this case, the diameter of the region 24a is smaller than the diameter of the region 24b. Along with this, the plasma produced by the first inductively coupled antenna 1a becomes a plasma having a high density at the center, and the plasma produced by the second inductively coupled antenna 1b becomes a plasma having a high density at the outer periphery. Therefore, the plasma distribution can be controlled by adjusting the ratio of the current flowing through the first inductively coupled antenna 1a and the second inductively coupled antenna 1b which are inductively coupled antennas.

  Next, a method for adjusting the ratio of the high-frequency current flowing through the first inductively coupled antenna 1a and the second inductively coupled antenna 1b will be described. FIG. 3 shows an equivalent circuit of the discharge unit 2a and the matching unit 3 of FIG. In FIG. 1, the first inductively coupled antenna 1a is equivalently shown as a load 9a, the second inductively coupled antenna 1b as a load 9b, and the Faraday shield 8 as a load 22. Assuming that the magnitude of the impedance of the load 9a is Za and the magnitude of the impedance obtained by combining the load 9b and the variable load 16 variable is Zb, the magnitude of the high-frequency current flowing through the load 9a and the load 9b is 1 / Za and 1 Proportional to / Zb. The inductively coupled antenna has a positive reactance, but the current can be controlled by changing Zb from a positive value to zero with a variable capacitor having a negative reactance.

  The first current sensor 14a detects the high-frequency current flowing through the load 9a and the second current sensor 14b through the load 9b, and the antenna current ratio control / overcurrent detection circuit 15 controls the current to have an arbitrary current ratio.

  FIG. 4 shows the relationship between the capacitance of a variable load generally used in a plasma processing apparatus and the maximum allowable current. Although the capacitance of the variable load can be varied within the specification range, it can be seen that the maximum allowable current decreases as the capacitance decreases below a certain capacitance. For this reason, even if the current is less than the maximum allowable current as a specification, if the capacitance is low, an overcurrent may flow through the variable load, resulting in a decrease in the life of the variable load or a failure of the variable load.

  FIG. 5 shows the relationship between the capacitance of the variable load 16 and the current flowing through the second inductively coupled antenna 1 b and the variable load 16. The current flowing through the variable load 16 is greatest when the capacitance of the variable load is the lowest, and decreases as the capacitance increases. Therefore, when the variable load 16 has a low capacitance, an overcurrent may flow. To prevent failure due to overcurrent, it is only necessary to change the capacitance of the variable load in a region where the maximum allowable current does not change. However, since the variable range of the capacitance becomes narrow, the range of the controllable current ratio is limited. Will be. In the present invention, an antenna current ratio control / overcurrent detection circuit 15 is provided to stably control the current ratio of the inductively coupled antenna over a wide range.

  FIG. 6 shows the configuration of the antenna current ratio control / overcurrent detection circuit. The antenna current ratio controller / overcurrent detector 23 calculates the current ratio of the inductively coupled antenna from the values obtained from the first current sensor 14a and the second current sensor 14b. The deviation is detected by comparing with an arbitrary current ratio set in advance, and a signal is sent to the stepping motor drive circuit 25 so that the stepping motor 26 of the VC 4 is driven in a direction in which the deviation decreases. By repeating the above operation until the above deviation falls within a preset deviation, the current ratio of the currents flowing through the two induction antennas can be maintained at a desired current ratio.

  Further, in the overcurrent detection unit, when the overcurrent to the variable load is detected based on the current value obtained from the second current sensor 14b, the output from the first high frequency power supply 10 is interrupted. Abnormal signal transmission. The current value determined as an overcurrent in this case is set as follows. First, information indicating where the electrostatic capacity of the variable load is in the variable range is sent from the position detector 21 to the antenna current ratio control unit / overcurrent detection unit 23, and the variable load is based on this information. Is calculated. Next, based on the characteristic of the maximum allowable current with respect to the capacitance of the variable load 16 as shown in FIG. 4, the maximum allowable current value is calculated according to the calculated value of the capacitance, and this calculated The maximum allowable current value is set to a current value for determining an overcurrent. Since the overcurrent is set in this manner, an appropriate overcurrent current value can be set according to the capacitance of the variable load. For this reason, even when the capacitance of the variable load is low, the allowable current is not exceeded, and the current ratio can be stably controlled over a wide range.

  As described above, the present invention prevents the overcurrent to the antenna current ratio control / overcurrent detection circuit 15 which is likely to occur in the range where the capacitance of the variable load is small, and the current ratio of the plurality of inductively coupled antennas. Therefore, the current ratio of the plurality of inductively coupled antennas can be stably controlled over a wide range.

DESCRIPTION OF SYMBOLS 1a 1st inductive coupling antenna 1b 2nd inductive coupling antenna 2 Vacuum vessel 2a Discharge part 2b Processing part 3 Matching device 4 Gas supply device 5 Electrode 6 Plasma 7 Exhaust device 8 Faraday shield 9a, 9b, 20, 22 Load 10 1st One high-frequency power source 11 Second high-frequency power source 12 Impedance matching circuit 13 Wafer 14a First current sensor 14b Second current sensor 15 Antenna current ratio control / overcurrent detection circuits 16, 17 Variable load 18 Coil 19 FSV detection / control Circuit 21 Position detector 23 Antenna current ratio control unit / overcurrent detection unit 24a, 24b, 24c Region 25 Stepping motor drive circuit 26 Stepping motor

Claims (2)

  Two or more inductive coupling antennas arranged with respect to a surface surrounding a region where plasma is formed, and a capacitively coupled antenna arranged with respect to a surface surrounding a region where plasma is formed, the inductive coupling In a plasma processing apparatus in which an antenna and the capacitively coupled antenna are electrically connected in series, a first adjustment circuit for adjusting a magnitude of a high-frequency current flowing through each of the inductively coupled antennas, each of the inductively coupled antennas and the capacitor A second adjustment circuit for adjusting a ratio of a high-frequency current flowing through the coupling antenna; a sensor for measuring a magnitude of each high-frequency current flowing through each inductive coupling antenna; and the first based on a signal from the sensor. Characterized in that it has a control means for controlling the ratio of the current flowing through each inductively coupled antenna to be constant in parallel with the overcurrent monitoring to the adjustment circuit of Management apparatus. Two or more systems of inductively coupled antennas arranged with respect to the surface surrounding the region where plasma is formed, and electrically connected in series with the induction antenna disposed over the surface surrounding the region where plasma is formed A capacitive coupling antenna; a first adjustment circuit for adjusting a magnitude of a high-frequency current flowing through each inductive coupling antenna; and a second adjustment circuit configured to adjust a ratio of a high-frequency current flowing through each inductive coupling antenna and the capacitive coupling antenna. In a control method using a plasma processing apparatus comprising an adjustment circuit and a sensor for measuring the magnitude of each high-frequency current flowing through each inductive coupling antenna,
A control method characterized in that the ratio of the current flowing through each inductively coupled antenna is controlled to be constant in parallel with monitoring of the overcurrent to the first adjustment circuit based on a signal from the sensor.

Images