JP2016115818A - Plasma processing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a plasma processing apparatus that is improved in yield of processing by making a state of adsorption of a sample stabler.SOLUTION: A plasma processing apparatus comprises: a sample table which is arranged in a processing chamber in a vacuum container and has a sample to be processed placed on its upper surface; a dielectric-made film which comprises a film-like electrode for attraction constituting a surface, where the sample is placed, of the sample table and generating electrostatic force for attracting and holding the sample inside; and a sample table internal electrode arranged in the sample table and supplied with high-frequency electric power having high output and low output alternately at a predetermined frequency. Further, the plasma processing apparatus comprises a control part which switches the electric power from a DC power source to be supplied to the electrode for attraction between a plurality of power supply paths differing in capacity, in accordance with the output level fluctuation of the high-frequency electric power supplied to the sample table internal electrode with the sample held on the dielectric-made film.SELECTED DRAWING: Figure 1

Description

The present invention relates to a semiconductor manufacturing apparatus for manufacturing a semiconductor device, and in particular, a dry etching technique for etching a semiconductor material such as silicon or a silicon oxide film according to a mask pattern shape formed of a resist material using plasma. About.

In plasma processing represented by dry etching, a raw material gas is introduced into a vacuum vessel having a vacuum exhaust means, and the raw material gas is converted into plasma by electromagnetic waves and exposed to the sample to be processed, except for the mask portion on the surface of the sample to be processed. This is a semiconductor micromachining method for obtaining a desired shape by etching. For the plasma generation, an inductive coupling method, an electron cyclotron resonance method, and a parallel plate method (including a magnetron method) are mainly used.

13.56 MHz is mainly used for inductively coupled plasma generation, and 2.45 GHz electromagnetic waves are mainly used for electron cyclotron resonance. These inductive coupling method and electron cyclotron resonance method have a structure in which an electromagnetic wave in the RF band is applied to the sample to be processed for the purpose of controlling the energy of incident ions on the surface of the sample to be processed separately from plasma generation.

On the other hand, in the parallel plate method, electromagnetic waves of 13.56 MHz have been widely used for plasma generation in the past, but in recent years, electromagnetic waves in the VHF band (30 MHz to 300 MHz) have been used. Similar to the cyclotron resonance method, RF band electromagnetic waves that independently control the energy of incident ions on the surface of the workpiece are also used separately from plasma generation.

These plasma processing apparatuses generally have a structure in which a workpiece sample is electrostatically adsorbed on a workpiece sample placement means and helium gas is allowed to flow between the workpiece sample and the workpiece sample placement means in order to keep the temperature of the workpiece sample with high accuracy. It is used for. As the electrostatic adsorption method, two methods of a single electrode and a bipolar electrode are mainly used.

The electrostatic adsorption is performed by applying a DC voltage between the metal electrode and the sample to be processed through a thin insulating film made of ceramic or the like. In addition, a high frequency voltage is applied to the sample to be processed because ions from plasma are accelerated and incident. Therefore, the potential difference between the metal electrode that controls the electrostatic attraction force and the sample to be processed is a voltage difference between a DC voltage applied to the metal electrode and a self-bias voltage generated between the sample to be processed and the plasma by applying a high frequency. .

If the self-bias voltage is sufficiently small compared to the DC voltage applied to the metal electrode, the adsorption power can be almost equal to the DC power supply voltage, but the high-frequency bias voltage applied to the workpiece is large and the self-bias voltage is less than the DC voltage. When the size is not negligible, the attractive force changes due to the applied high-frequency voltage and is not stable. In addition, when the high frequency bias voltage is very high, there is a possibility that the electrostatic chucking portion is destroyed when the withstand voltage of the thin insulating film disposed between the metal electrode and the sample to be processed is exceeded.

Japanese Patent Application Laid-Open No. 2006-210726 (Patent Document 1) discloses a technique for coping with the case where the self-bias voltage generated by the high-frequency voltage has a greater influence than the DC power supply voltage. In this prior art, in order to avoid the influence of the self-bias voltage generated in response to the high-frequency voltage on the electrostatic adsorption voltage, the high-frequency bias voltage is monitored and the DC power supply voltage is controlled in accordance with the high-frequency voltage. It is disclosed.

JP 2006-210726 A

The above-described conventional technique has a problem because the following points are insufficiently considered.

That is, the prior art discloses a technique for controlling the output value of a DC voltage power supply for electrostatic attraction with reference to a monitor value of a high frequency bias voltage applied to a workpiece. This technique can only cope with a case where the control speed of the DC power supply voltage is relatively slow (for example, 0.1 seconds or more).

However, among those that apply high-frequency bias power to a substrate-like workpiece such as a semiconductor wafer, ON / OFF at intervals of several tens of milliseconds to 1 millisecond (frequency of several tens of Hz to several kHz) There is a case where high frequency (Radio Frequency: RF) power of a predetermined frequency is applied by repeating high amplitude and low amplitude (hereinafter referred to as TM: Time Modulation or time modulation). In the case of controlling the voltage of the DC power supply by the conventional technique, it is difficult to increase or decrease the value corresponding to the TM operation repeated at such a high frequency.

For this reason, in the conventional technique, there is a problem that in the case of TM operation, the stability of the electrostatic adsorption force and the application of excessive voltage to the insulating material for electrostatic adsorption cannot be prevented. For this reason, the conventional technique has not taken into consideration that the result of the processing of the sample deviates from the expected allowable range and the processing yield is impaired. It was.

An object of the present invention is a case where the high-frequency voltage for bias formation applied to the sample is a value that is not negligible with respect to the DC power supply voltage used for electrostatic adsorption, and the voltage of the high-frequency power is reduced to several tens. An object of the present invention is to provide a plasma processing apparatus that can stabilize the state of sample adsorption and improve the processing yield even when performing a modulation operation that is turned ON / OFF at a frequency of Hz to several kHz. It is another object of the present invention to provide a plasma processing apparatus capable of preventing an excessive voltage application to the electrostatic adsorption insulating material.

The purpose is to arrange a sample stage on the upper surface of the vacuum chamber, on which a sample to be processed is placed, and a surface on which the sample is placed, and to adsorb and hold the sample inside. A dielectric film provided with a film-like adsorption electrode for generating electrostatic force, and a sample which is arranged inside the sample table and which is supplied with high frequency power that repeats high and low output at a predetermined frequency And supply to the adsorption electrode according to the repetition of the output of the high-frequency power supplied to the sample stage electrode in a state where the sample is held on the dielectric film. This is achieved by a plasma processing apparatus including a control unit that switches electric power from a direct current power source between a plurality of power supply paths each having a different capacity.

According to the present invention, in addition to the control of the DC voltage for electrostatic attraction corresponding to the value of the high frequency bias voltage (when the high frequency bias is ON), it is switched ON / OFF by switching to the DC voltage application circuit in the path through the capacitor at high speed. It is possible to control the electrostatic chucking voltage corresponding to a large change in application of a high-frequency bias voltage. As a result, even when the high frequency bias voltage is TM-operated, it is possible to secure a stable attracting force and prevent application of excessive voltage to the electrostatic attracting insulating material.

It is a longitudinal section showing an outline of composition of a sample stand of a plasma processing apparatus concerning an example of the present invention typically. For bipolar electrostatic adsorption disposed on the sample stage when a time-continuous high-frequency voltage is supplied from the high-frequency power source 12 included in the conventional plasma processing apparatus to the sample stage or its base material It is a timing chart showing operation | movement of this electrode. For bipolar electrostatic adsorption disposed on the sample stage when a time-continuous high-frequency voltage is supplied from the high-frequency power source 12 included in the conventional plasma processing apparatus to the sample stage or its base material It is a timing chart showing operation | movement of this electrode. For bipolar electrostatic adsorption disposed on the sample stage when a time-continuous high-frequency voltage is supplied from the high-frequency power source 12 included in the conventional plasma processing apparatus to the sample stage or its base material It is a timing chart showing operation | movement of this electrode. For bipolar electrostatic adsorption disposed on the sample stage when a time-continuous high-frequency voltage is supplied from the high-frequency power source 12 included in the conventional plasma processing apparatus to the sample stage or its base material It is a timing chart showing operation | movement of this electrode. The operation of the electrode for bipolar electrostatic adsorption disposed on the upper part of the sample stage when a high frequency voltage is supplied from the high frequency power source of the plasma processing apparatus according to the embodiment shown in FIG. It is a timing chart showing. FIG. 1 shows the operation of the bipolar electrostatic chucking electrode disposed on the sample stage when a high frequency voltage is supplied from the high frequency power source of the plasma processing apparatus according to the embodiment of FIG. It is a timing chart showing another example. It is a longitudinal cross-sectional view which shows typically the outline of the structure of the sample stand of the plasma processing apparatus which concerns on the modification of the Example shown in FIG. The operation of the unipolar ESC electrode disposed on the sample stage when a high frequency voltage is supplied from the high frequency power source of the plasma processing apparatus according to the modification shown in FIG. It is a timing chart to represent. The basic block diagram of Example 3 in this invention. The basic block diagram of Example 4 in this invention.

Embodiments of the present invention will be described below with reference to the drawings.

A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view schematically showing an outline of a configuration of a sample stage of a plasma processing apparatus according to an embodiment of the present invention. In this figure, a sample stage disposed inside a vacuum vessel constituting the plasma processing apparatus and a plurality of circuits electrically or physically connected to the sample stage are schematically shown.

In this figure, a sample stage 100 according to the present invention is disposed in a processing chamber disposed inside a vacuum vessel (not shown), and has a mounting surface on which a sample to be processed is mounted. ing. The sealed processing chamber inside the vacuum vessel is connected to a vacuum pump such as a turbo molecular pump (not shown) disposed below the vacuum vessel, and the gas in the space in the processing chamber is exhausted by the operation of the vacuum pump, and the processing chamber is predetermined. The pressure is reduced to a degree of vacuum. The sample stage 100 is disposed below the space inside the processing chamber, and the upper space is supplied with processing gas supplied in a decompressed state for processing the sample 4 and supplied from outside the vacuum vessel. This is a space in which plasma 16 is formed by exciting atoms or molecules of the processing gas by the action of the applied electric field or magnetic field.

The sample stage 100 of the present embodiment has a circular shape in which the upper surface is placed and held on a substrate-like sample 4 such as a semiconductor wafer, or a shape approximated to the extent that it can be regarded as this, and a circle that is symmetric with respect to the central axis in the vertical direction. It has a shape that approximates to a level that can be regarded as a plate or a cylinder or these. The main constituent members include a base material portion 1 having a shape similar to a cylinder having heat conduction or conductivity such as metal or the like, and a ceramic such as aluminum oxide or yttrium oxide covering the upper surface thereof. A dielectric film is formed.

The upper surface of the film constitutes the mounting surface of the sample 4, and DC power is supplied to the inside of the film to cause the sample 4 to be electrostatically generated between the charges formed on the surface of the dielectric material and the back surface of the sample 4. A film-like ESC electrode 3 adsorbed on the upper surface of the film is disposed. That is, the dielectric film constitutes the ESC film 2, and the internal ESC electrode 3 comprises a plurality of films provided with different polarities to constitute a bipolar electrostatic adsorption electrode. In particular, the ESC electrode 3 is composed of an even number of films, and is arranged in the ESC film so that the total areas of the films to which the respective polarities are imparted are equal.

In the present embodiment, two ESC electrodes 3 shown in the drawing are electrically connected to separate DC power sources 5 and supplied with DC power to be given the desired polarity. One end of each DC power source 5 is connected to a grounded earth, and the other end is connected to the ESC electrode 3 via a low-pass filter (LPF) 6 and a semiconductor switch unit 7. As shown in the figure, each of the two ESC electrodes 3 is supplied with a DC voltage of different polarity and in the absence of the plasma 16, the sample 4 is electrostatically adsorbed to the ESC film 2 by the potential difference of the DC voltage applied to each of them. The

The semiconductor switch unit 7 has a function of a switch for switching the electrical connection between each ESC electrode 3 and the low-pass filter 6 to one that does not pass through the capacitor 8. The time of the switching operation and the interval between the connections are adjusted by a signal from the control unit 9 configured to communicate signals with the DC power supply 5 and the semiconductor switch 7.

In this embodiment, the capacitor 8 has a capacitance comparable to the capacitance between each ESC electrode 3 and the sample 4. Further, in this embodiment, one end side is electrically connected to a place grounded or grounded, and the other end is connected to Ti via a high-frequency voltage detector 10 and a high-frequency matching unit 11. Or the high frequency power supply 12 electrically connected with the metal base part 1 which contains this as a component is provided. In a state where the sample 4 is placed on the ESC film 2 above the sample stage 100 and is adsorbed and held, the high frequency power from the high frequency power source 12 is applied to the base portion 1, and a bias is applied above the upper surfaces of the ESC film 2 and the sample 4. A potential is formed.

A refrigerant flow path 13 is disposed inside the base member 1 and is connected to a temperature controller such as a chiller unit (not shown) via a conduit, and the refrigerant flowing out of the temperature controller returns through the refrigerant flow path 13. A road is constructed. The temperature of the base material part 1 is suitable for processing and operation of the apparatus by exchanging heat with the member of the base material part 1 constituting the refrigerant at a predetermined temperature while flowing in the refrigerant flow path 13. It is adjusted to the desired value within the temperature range. Furthermore, a gas supply path 14 that penetrates the base material 100 and the ESC film 2 and is connected to a storage unit that is a gas source (not shown) is disposed at or near the central axis of the sample stage 100 having a cylindrical shape. ing.

The opening at the center of the ESC film 2, which is the upper end of the gas supply path 14, faces the gap between the back surface of the sample 4 and the upper surface of the ESC film 2 with the sample 4 placed on the ESC film 2. The helium gas that has flowed from the gas source through the gas supply path 14 through this opening is introduced into the gap, and the helium gas adjusted to have a pressure within a predetermined range is used for the sample 4 and the ESC film 2. The heat conduction between is high.

The high-frequency power source 12 and the control unit 9 of the present embodiment are communicably connected to the control unit 15 and operate based on a command signal from the control unit 15 for adjusting these operations. The control units 9 and 15 described below include a storage device in which software and data for operating the arithmetic unit are recorded and stored in accordance with an algorithm described as an arithmetic unit such as a semiconductor microprocessor. And an interface for connecting the communication between these and the arithmetic unit, the storage device, and a communication path for connecting the interfaces so that they can communicate with each other. It is comprised so that a signal can be exchanged between.

A conventional technique of the plasma processing apparatus according to the present embodiment will be described with reference to FIGS. FIG. 2 shows a bipolar system arranged on the upper part of the sample stage when a time-continuous high-frequency voltage is supplied from the high-frequency power source 12 included in the plasma processing apparatus according to the prior art to the sample stage or its base part. It is a timing chart showing operation | movement of the electrode for electrostatic attraction.

In the prior art of such bipolar electrostatic adsorption, a plurality of metal films for electrostatic adsorption arranged in a dielectric film constituting the mounting surface which is the upper surface of the sample stage, A DC voltage having a different polarity is applied from a DC power source to a plurality of electrodes each having an area close to 1: 1 or a value approximated to such an extent. FIG. 2 shows an example in which +2000 V is applied to the electrode C constituting the electrostatic chucking electrode corresponding to the ESC electrode 3 of the embodiment of FIG. 1 and −2000 V is applied to the electrode D.

In this state, under the condition that the plasma 16 is not ignited above the sample stage in the processing chamber and the high-frequency power is not supplied from the high-frequency power source to the base material part, the potentials formed on the sample are respectively The potential applied is an intermediate potential of the voltage of the DC power having the opposite polarity (0 V in the example of FIG. 2 or a value close thereto), and the potential difference between the sample and the electrostatic adsorption electrodes C and D was applied respectively. The value is the same as or close to the sum of the DC voltages. In this state, even if the plasma 16 is ignited, the potential difference between the electrodes CD is kept equal to that before the plasma 16 is formed in a state where a high frequency voltage is not applied.

However, when a high-frequency power voltage is applied, a self-bias voltage (Vdc) corresponding to the amplitude of the high-frequency voltage is generated in the sample. Vdc is a negative potential, and the potential of the sample to be processed is the value of Vdc.

When a voltage that causes a significant difference between Vdc and the DC voltage applied to each ESC electrode C and D is generated, an ESC electrode to which a positive DC voltage is applied by a DC power source as shown in FIG. The potential difference between C and the sample to be processed is a value obtained by adding | Vdc | to a DC voltage applied by a DC power source. On the other hand, the potential difference between the ESC electrode D to which a negative potential is applied from the DC power source and the sample to be processed is a value obtained by subtracting | Vdc | from the voltage applied by the DC power source.

The electrostatic attraction force depends predominantly on the potential difference between the ESC electrodes C and D and the sample placed on the dielectric film. Therefore, when the high frequency voltage shown in FIG. 2 is applied, the ESC electrode While the adsorption force increases between C and the sample, the adsorption force decreases between the ESC electrode D and the sample. Therefore, the adsorption force of the ESC electrode D occupying 1/2 of the area where the electrostatic adsorption force is generated is reduced, so that the adsorption force of the sample to be processed is reduced as a whole. In addition, since a potential difference higher than the DC voltage applied to the ESC electrode C is generated, the withstand voltage of the ESC films C and D may be exceeded depending on the value of Vdc.

Therefore, as shown in FIG. 3, in the conventional technique, the voltage of the high frequency power applied to the sample is detected, and the voltage of the DC power applied to each ESC electrode C, D is adjusted according to the detected value. doing. For example, in the example shown in FIG. 3, +2000 V and −2000 V are applied to the ESC electrodes C and D, respectively, in a state where the plasma 16 is not ignited (the plasma 16 is not formed) and no high frequency voltage is applied. . When the plasma 16 is ignited and a high frequency voltage is applied to an internal metal electrode such as the base portion of the sample stage, a constant constant (conventionally 0.3 to 0.5) is applied to the amplitude Vpp of the high frequency voltage. The direct current voltage multiplied by the degree is adjusted to the voltage applied to each ESC electrode.

Specifically, the voltage (+2000 V) of the ESC electrode C to which a positive DC voltage is applied is decreased, and the voltage of the ESC electrode D to which a negative DC voltage (−2000 V) is applied is adjusted to increase. . For example, when the high-frequency voltage amplitude Vpp is 5000 V and the constant for estimating Vdc is 0.4, the applied voltage of the ESC electrode C to which +2000 V was applied before the plasma 16 ignition is 0 V, and similarly the plasma 16 ignition is performed. The applied voltage of the ESC electrode D to which −2000V was previously applied is −4000V. By doing this, even after a high frequency voltage is applied, fluctuations in the potential difference between the ESC electrodes C and D and the sample are suppressed, and an excessive potential difference is formed between the adsorption force stabilization and the ESC films. Is suppressed.

In the process of a sample such as a semiconductor wafer for manufacturing a semiconductor device in recent years, not only a case where a high-frequency voltage is continuously applied as in the example of FIGS. As described above, the high-frequency voltage may repeat ON / OFF or high output and low output at a specific interval or frequency as time elapses. In this embodiment, the supply of high-frequency power for forming such a bias potential is hereinafter referred to as a modulation bias application method, particularly time modulation (Time Modulation method: TM method).

In the example shown in FIGS. 4 and 5, the supply of high-frequency power to the electrodes in the sample table is turned on / off as time passes, while the plasma 16 in the space above the sample table in the processing chamber is supplied. Generation is performed continuously.

In the case of the TM method, when a constant ESC DC voltage is applied to each of the ESC electrodes C and D as in FIG. 1, as shown in FIG. Is a potential difference higher than the DC voltage, and the potential difference between the ESC electrode D and the sample is a value lower than the DC voltage during the period of the high-frequency voltage On. For this reason, in the example of FIG. 4 as well, in the period when the high-frequency voltage is On, there is a possibility that the adsorption force of the ESC electrode D is insufficient and an excessive voltage is applied to the ESC electrode C.

FIG. 5 shows a case where the value of the DC voltage supplied to the ESC electrodes C and D is adjusted according to the value of the high-frequency voltage Vpp, as in the example shown in FIG. The example in this figure also aims to stabilize the adsorption force similar to that in FIG. 2 and suppress the occurrence of an excessive potential difference between the ESC films. However, in general, it is technically difficult to increase or decrease the value of the DC voltage to a predetermined value corresponding to ON / OFF of the high frequency. This is because if a high direct current voltage necessary for electrostatic attraction of the sample is adjusted according to the TM cycle and frequency, a power capacity corresponding to the reactive current is required, resulting in a larger power supply and a complicated application circuit. Will be invited.

Further, in the DC power supply for supplying power to the ESC electrodes C and D on the sample stage in this example, there is a possibility that a part of the high frequency power applied to the electrodes in the sample stage leaks and flows. In order to protect the direct current power supply against a large amount of power, a low pass filter is generally disposed between the direct current power supply and the ESC electrode. Since such a low-pass filter has a band that also takes into account voltage fluctuations due to TM modulation, the DC power supply supports high-speed modulation of the high-frequency power for bias formation (time increase / decrease in value). Even if it can be increased or decreased, this is prevented by the low-pass filter.

For this reason, as shown in FIG. 5, when the control is performed with a value corresponding to the high-frequency voltage amplitude Vpp when the high-frequency voltage is ON, the potential difference between the ESC electrode C and the sample during the high-frequency voltage off period is The potential difference between the ESC electrode D and the sample becomes excessive. As shown in FIGS. 4 and 5, it is difficult to control the output from the DC power supply in accordance with the TM method, and it is difficult to increase / decrease with the conventional technique, ensuring a stable electrostatic attracting force and excess potential difference applied to the ESC film. It was difficult to deter.

Next, the operation of the first embodiment will be described with reference to FIGS. FIG. 6 shows a bipolar type disposed on the sample stage 100 when a high frequency voltage is supplied from the high frequency power supply 12 of the plasma processing apparatus according to the embodiment shown in FIG. 6 is a timing chart showing the operation of the ESC electrode 3 for electrostatic adsorption.

In the example of FIG. 6, before the plasma 16 is ignited and before the radio frequency (RF) voltage is applied, the ESC electrode C is + 2000V and the ESC electrode D is applied to the ESC electrode D, as in the conventional technique shown in FIGS. A DC voltage of −2000 V is supplied from the DC power source 5, and the sample 4 is adsorbed and held on the ESC film 2 by the electrostatic force formed between the ESC film 2 and the sample 4. At this time, the potential difference between the sample 4 and each of the ESC electrodes C and D is 2000 V or a value approximated to the extent that it can be regarded as this.

Next, the plasma 16 is ignited to form the plasma 16 in the processing chamber, and high frequency (RF) power from the high frequency power source 12 is supplied to the base portion 1 of the sample stage 100 to form a bias potential above the surface of the sample 4. The As described above, in this example, high-frequency power is time-modulated (TM), turned on / off at a predetermined frequency (interval), and supplied from the high-frequency power source 12 to the base member 1. At this time, the plasma 16 of this example is continuously formed (discontinuously formed) in time, and among them, a high-frequency power for forming a bias applied to the sample 4 via the base member 1. Only that voltage operates in TM mode.

In this example, simultaneously with the application of the high-frequency voltage, the voltage at the time when the high-frequency voltage is turned on is detected by a voltage sensor (not shown), and the DC voltage of the ESC electrode D to which a negative voltage is applied according to the detection result. To change. Specifically, the DC voltage applied from the DC power source 5 to the ESC electrode D is a coefficient (this example) arbitrarily determined by the high-frequency voltage amplitude (Vpp) detected in the same manner as the prior art shown in FIGS. In this case, the value is increased by a factor of 0.3 to 0.5).

For example, when Vpp is 5000V and the coefficient is 0.4, the voltage of the ESC electrode D to which a negative voltage is applied decreases from −2000V to −4000V. At this time, the semiconductor switch unit 7 connected to the ESC electrode C to which a positive voltage is applied corresponds to the command signal from each control unit 9 and the A switch shown in FIG. The connection is made on the contact side, and the voltage of the DC power supply 5 is applied to the ESC electrode C without passing through the capacitor 8. On the other hand, the semiconductor switch unit 7 connected to the ESC electrode D to which a negative voltage is applied is on the B contact side, and the voltage of the DC power supply 5 is applied to the ESC electrode D via the capacitor 8. The power supply path from the DC power supply 5 switched to the B contact side and connected to the ESC electrode D has an impedance corresponding to the capacitance of the capacitor 8 from the power supply path when the semiconductor switch unit 7 is switched to the A contact side. Or the capacitance is increased.

On the other hand, when the high-frequency voltage is OFF, contrary to the ON period, the semiconductor switch unit 7 connected to the ESC electrode C to which a positive voltage is applied has a B contact side (DC power supply via the capacitor 8). 5 is applied to the ESC electrode C), and the semiconductor switch unit 7 connected to the ESC electrode D to which a negative voltage is applied has a contact A side (the voltage of the DC power supply 5 is directly applied to the ESC electrode D). To be applied). By such an operation, it is possible to avoid a decrease in adsorption voltage and application of excessive voltage, which are problems in the prior art, due to the high-frequency voltage ON / OFF.

The state when the high-frequency voltage is ON in the above operation will be described. When the plasma 16 is ignited and a high frequency voltage is applied to the base member 1, the potential on the upper surface of the sample 4 becomes a self-bias potential. This potential is a negative value and is usually about 0.3 to 0.5 times the amplitude Vpp of the high-frequency voltage.

Therefore, the potential difference between the ESC electrode C to which the positive voltage is applied and the sample 4 is increased by the self-bias voltage during the high-frequency voltage ON period when the output value of the DC power supply 5 is not changed by the semiconductor switch unit 7 or the like. It will be. For this reason, a large potential difference is formed between the two ESC films 2, and the potential difference between the ESC electrode D and the sample 4 to which a negative voltage is applied is reduced by the self-bias voltage and the adsorption force is reduced. descend.

Therefore, in this embodiment, the semiconductor switch unit 7 is switched to the A contact side during the high-frequency voltage ON period, so that the capacitance or impedance corresponding to the capacitance of the capacitor 8 is reduced from the DC power source 5 through the power supply path. By supplying electric power to the ESC electrode D having a negative value, the voltage supplied from the DC power source 5 to the ESC electrode D by the amount corresponding to the self-bias potential corresponding to the value of Vpp is shown in FIG. As shown, change to reduce. With such a configuration, a change in potential difference between the ESC electrode D to which a negative voltage is applied and the sample 4 is suppressed, and a change in adsorption force is reduced.

On the other hand, the semiconductor switch unit 7 is operated so that an excessive potential difference does not occur in the ESC electrode C to which a positive voltage is applied, so that the power supply path from the DC power supply 5 to the ESC electrode C is statically connected to the capacitor 8. Switch to the one on the B side where the capacity or impedance of the electric capacity is relatively increased (solid switch C). In this example, the capacitor 8 of the semiconductor switch unit 7 is configured to have a value similar to the capacitance between the ESC electrode D and the sample 4 (for example, about 9000 pF). As a result, the voltage applied to the ESC electrode C is divided by the capacitance ratio, and the potential difference between the ESC electrode C and the sample 4 is about half that when no capacitor is interposed. As a result, the ESC electrode An increase in potential difference between C and sample 4 can be suppressed and stabilized.

Next, the operation when the high frequency voltage is OFF will be described. When the high frequency voltage is turned off in the state where the plasma 16 is formed, the potential of the sample 4 becomes a potential determined by the floating potential of the plasma 16, which is about 10 to several tens V, which is around 0V. Therefore, the voltage is applied with an excessive potential difference between the ESC electrode D and the sample 4 under the condition of supplying power from the DC power source 5 in the high-frequency voltage ON state shown in FIG.

However, in the conventional technique, it is difficult to change the voltage value of the DC power supply 5 following the periodic ON / OFF of the voltage of the power from the high-frequency power supply 12, so that the high-frequency voltage is ON. In general, a configuration is determined by referring to a value of a certain period. In the embodiment shown in FIG. 6, during the period when the high-frequency voltage is OFF, the semiconductor switch unit 7 switches to the B contact side and switches the power supply from the DC power supply 5 to the ESC electrode D to the path via the capacitor 8.

Further, the path for supplying DC power from the DC power supply 5 to the ESC electrode C is switched to the A contact side in the semiconductor switch unit 7, and the power supply from the DC power supply 5 to the ESC electrode C is switched to a path not via the capacitor 8. . With this configuration, the DC voltage applied to the ESC electrode D is divided into the ESC film and the capacitor 8 in the same manner as the ESC electrode C in the state of the high-frequency voltage ON described above. The potential difference with the sample 4 can be stabilized.

In the present embodiment, the switching operation of the semiconductor switch unit 7 is performed during the period from the start to the end of the process of processing the film to be processed among the film layers previously disposed on the upper surface of the sample 4. This is carried out following or synchronizing with the period in which the voltage is periodically turned ON / OFF. As a result, during the processing of the sample 4, the voltage value of the DC power supplied to the ESC electrodes C and D is changed corresponding to the high-frequency voltage changed by the TM method, so that the voltage between these electrodes and the sample 4 is changed. The fluctuation of the potential difference can be suppressed, whereby the electrostatic attraction force can be stabilized and the dielectric breakdown accompanying excessive voltage application can be suppressed.

In the embodiment shown in FIG. 1, the capacitance value of the capacitor 8 is set to be approximately the same as the capacitance sandwiching the ESC film 2 between the ESC electrode 3 connected to the DC power source 5 and the sample 4. However, a similar result can be obtained by arranging a capacitor in a range of 1/4 to 4 times the capacitance between the ESC electrode 3 and the sample 4. In general, the potential difference VESC between the ESC electrode 3 and the sample 4 is determined by the following equation (1) based on the capacitance (C1) between the ESC electrode 3 and the sample 4 and the capacitance (C2) of the capacitor 8. it can.

VESC = C2 × VG / (C1 + C2) (1)

According to this equation, when the capacitance value (C2) of the capacitor 8 is set to a range of 1/4 to 4 times the capacitance (C1) between the ESC electrode 3 and the sample 4, the ESC electrode 3 It can be seen that the potential difference with the sample 4 can be adjusted within the range of 0.2 to 0.8 of the output value (VG) of the DC power supply 5.

In the embodiment of FIG. 1, there is one type of capacitor 8, and it is necessary to select the capacitor 8 under a voltage dividing condition that can most suppress fluctuations with respect to the use conditions. In order to deal with a wide range of high-frequency voltages in a series of processing, it is possible to further stabilize the adsorption voltage by using the configuration of the modified example described later, and improve the stability of the adsorption force and the suppression accuracy of excessive voltage application. be able to.

The operation of the ESC electrode 3 different from the embodiment of FIG. 1 will be described with reference to FIG. 7 shows a bipolar type disposed on the sample stage 100 when a high frequency voltage is supplied from the high frequency power supply 12 of the plasma 16 processing apparatus according to the embodiment of FIG. It is a timing chart showing another example of operation of the electrode for electrostatic attraction.

In this example, under the condition that the plasma 16 is not ignited and the high frequency voltage is not applied to the ESC electrode 3, DC voltages of +2000 V and −2000 V are respectively applied to the ESC electrodes C and D from the DC power source 5 as in FIG. 6. The sample 4 is supplied and electrostatically adsorbed on the ESC film. Next, when the plasma 16 is ignited, the plasma 16 is formed, and radio frequency (RF) power is applied, the voltage supplied to the ESC electrode D in accordance with this is changed from a negative value of −2000 V to a positive value. Change to + 2000V.

In this state, +2000 V of DC power is applied to both the electrodes C and D, and the sample 4 is substantially adsorbed by the monopolar method. Based on this state, the power supply path between the DC power source 5 and each of the electrodes C and D is a semiconductor switch unit 7 connected to the electrodes C and D during the period when the high-frequency voltage is ON. In FIG. 2, the path is switched to the B contact side having a relatively large capacity or impedance via the capacitor 8 and switched to the A contact side path to which a DC voltage is applied without passing through the capacitor 8 during a period when the high frequency voltage is OFF.

The switching operation of the semiconductor switch section 7 is performed and repeated in accordance with periodic ON / OFF of high-frequency power voltage or repetition of high output and low output. With this operation, also in the example of FIG. 7, fluctuations in the potential difference between the ESC electrode and the sample 4 can be suppressed, and electrostatic attraction force can be stabilized and excessive voltage application to the ESC film can be suppressed. Also in the example of this figure, the electrostatic capacity of the capacitor 8 is the same as in the examples of FIGS. 1 and 6, and the static electricity sandwiching the ESC film 2 between the ESC electrode 3 connected to the DC power source 5 and the sample 4. The value is in the range of 1/4 to 4 times the capacitance between the ESC electrode 3 and the sample 4, including the same level as the capacitance.

Modification 1

A modification of the embodiment shown in FIG. 1 will be described below with reference to FIGS. FIG. 8 is a longitudinal sectional view schematically showing the outline of the configuration of the sample stage of the plasma processing apparatus according to the modification of the embodiment shown in FIG. FIG. 9 shows a single electrode disposed on the sample stage 800 when a high frequency voltage is supplied from the high frequency power source 12 of the plasma processing apparatus according to the modification shown in FIG. 4 is a timing chart showing the operation of the ESC electrode 3 of the equation.

The embodiment described with reference to FIGS. 1, 6, and 7 includes a bipolar ESC electrode 3 in a dielectric film constituting the upper surface of the sample stage 100. The examples shown in FIGS. 8 and 9 are provided with a monopolar ESC electrode 3 in a dielectric film constituting the upper surface of the sample stage 100. That is, in the modification of FIG. 8, the ESC electrode 3 has a single polarity with respect to the sample 4, and the DC power source 5 that supplies DC power to the sample 4 and the DC power source 5 and the ESC film 3 In order to provide the same polarity, the power supply path that electrically connects them, and the low-pass filter 6 and the semiconductor switch unit 7 or the capacitor 8 disposed on the power supply path cooperate with each other as one or a plurality of sets. It becomes the operation of.

The other configuration of the sample stage 800 according to this modification is the same as that of the embodiment shown in FIG. 1, and the voltage of the high-frequency power supplied from the high-frequency power source 12 to the metal substrate 1 is also predetermined. The same is true in that the voltage of the frequency is periodically ON / OFF with time, or time-modulated (TM) in which high output with a large amplitude and low output with a small amplitude are repeated.

FIG. 9 shows a specific example of the operation of the ESC film 3 of the sample stage 800 according to the modification shown in FIG. Also in this example, Vpp is detected using the detection result of the high-frequency voltage detector 10 during the period when the voltage of the high-frequency power from the high-frequency power source 12 is ON, and the DC power source 5 is based on this result. The DC power supplied to the ESC film 3 is supplied with a DC voltage having a value that is increased or decreased by a self-bias voltage generated in the sample 4 by the high-frequency power.

More specifically, when Vpp is 5000 V and the estimated self-bias voltage constant is 0.4, the DC power supply 5 supplies the ESC electrode 3 when a high frequency (RF) power voltage is supplied. The voltage is reduced to the negative side of 2000V (when the initial adsorption voltage is -2000V, it is set to -4000V). At this time, the semiconductor switch unit 7 in the DC power supply path is connected to the A side, which is a power supply path not passing through the capacitor 8.

Next, when the high-frequency voltage is OFF, the semiconductor switch unit 7 has the capacitor 8 whose capacitance is set in a range of 1/4 to 4 times the capacitance between the ESC electrode 3 and the sample 4. Switch to the B side, which is the route to supply via As described above, also in the present modification, the voltage value of the DC power is adjusted according to the magnitude of the self-bias voltage, and the power supply path is switched in synchronization with or following the periodic ON / OFF of the high-frequency power by the TM. By repeating the above, even in the unipolar method, the fluctuation of the potential difference between the ESC electrode 3 and the sample 4 is suppressed, the electrostatic attraction force is stabilized, and the excessive voltage is applied to the ESC film 2.

Modification 2

Another modification of the embodiment shown in FIG. 1 will be described with reference to FIG. FIG. 10 is a longitudinal sectional view schematically showing an outline of the configuration of the sample stage 1000 of the plasma processing apparatus according to another modification of the embodiment shown in FIG. 11 shows a single electrode disposed on the sample stage 1000 when a high-frequency voltage is supplied from the high-frequency power source 12 of the plasma processing apparatus according to the modification shown in FIG. 4 is a timing chart showing the operation of the ESC electrode 3 of the equation.

In the embodiment shown in FIGS. 1, 6, and 7 and the modification shown in FIGS. 8 and 9, the capacitor 8 that controls the potential difference between the ESC electrode 3 and the sample 4 in the semiconductor switch unit 7 is a single static. It has electric capacity. For this reason, the frequency range of the high frequency which can suppress the fluctuation | variation of the high frequency voltage in the case where it switches to the B side in the semiconductor switch part 7 and makes the electric power feeding path from the direct-current power supply 5 the path | route via the capacitor | condenser 8 is relatively. There was a problem of being small.

Therefore, in this example, the semiconductor switch unit 7 is provided with a capacitor array 17 in which a plurality of capacitors having different capacities are arranged in parallel, and according to the value of Vpp of the high-frequency power detected using the detection result of the high-frequency voltage detection unit 10. Thus, a configuration is provided in which one of the capacitors array 17 is selected by a semiconductor switch and switched to a power feeding path through the capacitor. With this configuration, the DC power is supplied to the ESC film 3 in synchronization with or following the supply of the high frequency (RF) power that is periodically turned ON / OFF by the TM or the high output and the low output. It is possible to expand the application range of the high-frequency voltage that can be adjusted by increasing / decreasing to stabilize the adsorption force and suppress the application of excessive voltage to the ESC film 3.

In this example, the value of each capacitor of the capacitor array 17 of FIG. 10 is 1/4 to 4 times the electrostatic capacity sandwiching the ESC film 2 between the ESC electrode 3 and the sample 4 described in the first embodiment. Has been in range.

FIG. 11 shows a configuration of the modification of FIG. 10 applied to a sample stage equipped with a monopolar ESC electrode. Also in the unipolar ESC electrode 3 in this example, the Vpp of the high frequency power from the high frequency power supply 12 is detected using the result detected by the high frequency voltage detection unit 10, and an appropriate capacitor of the capacitor array 17 is determined according to this value. By expanding the range of application of the high-frequency voltage that can stabilize the adsorption force and suppress the application of excessive voltage to the ESC film 3 even when time-modulated high-frequency power is supplied to the substrate 1. can do. Similarly to FIG. 10, the value of each capacitor of the capacitor array 8 is set to a range of ¼ to 4 times the capacitance between the ESC electrode 3 and the sample 4 described in the first embodiment.

The present invention relates to a semiconductor device manufacturing apparatus, and more particularly to a plasma etching apparatus that performs an etching process of a semiconductor material using a pattern drawn by a lithography technique as a mask. Usually, the plasma etching apparatus maintains the processing accuracy by performing high-accuracy temperature control by electrostatically adsorbing the processing sample to the processing sample setting means. The present invention relates to this electrostatic adsorption, and the high frequency voltage amplitude applied to the sample to be processed is as high as several kV, and in the TM operation in which the voltage application is turned ON / OFF at a period of several tens to several kHz. It is possible to stabilize the electrostatic attraction force of the workpiece to be processed and to suppress the application of excessive voltage to the electrostatic adsorption film.

  DESCRIPTION OF SYMBOLS 1 ... Base material part, 2 ... ESC film | membrane, 3 ... ESC electrode, 4 ... Sample, 5 ... DC power supply, 6 ... Low-pass filter, 7 ... Semiconductor switch part, 8 ... Capacitor, 9 ... Control part, 10 ... High frequency Voltage detector, 11... High-frequency matching unit, 12... High-frequency power source, 13... Refrigerant path, 14.

Claims (6)

A processing chamber that is disposed inside the vacuum vessel and in which plasma is formed inside, a sample table that is disposed in the processing chamber and on which a sample to be processed using the plasma is placed, and the sample on the sample table includes A dielectric film having a film-like adsorption electrode for generating an electrostatic force that constitutes a surface to be placed and adsorbs and holds the sample inside, and is disposed inside the sample stage and is in the process A sample stage electrode that is supplied with high-frequency power in which a high output and a low output are repeated at a predetermined frequency;
Power from a DC power source that is supplied to the adsorption electrode in accordance with repetition of the output of the high-frequency power that is supplied to the sample stage electrode while the sample is held on the dielectric film And a controller that switches between a plurality of power supply paths each having a different capacity.
The plasma processing apparatus according to claim 1,
The adsorption electrode comprises a plurality of film-like electrodes, each having a different polarity and constituting a bipolar adsorption electrode that adsorbs the sample,
The bipolar type adsorption electrode to which different polarities are given according to repetition of the output of the high-frequency power supplied to the electrode in the sample stage in a state where the sample is held on the dielectric film. And a control unit that reversely switches power from a DC power source supplied to each of the power supply paths having a large capacity and a power supply path having a small capacity among the plurality of power supply paths.
The plasma processing apparatus according to claim 2,
In the period when the high-frequency power is high output, the control unit passes the power feeding path with a small capacity to the adsorption electrode to which a positive polarity is given, and then supplies the adsorption electrode to which a negative polarity is given. The electric power is supplied through the large-capacity power supply path, and during the period when the high-frequency power is low output, the negative electrode has a negative polarity passing through the large-capacity power supply path to the adsorption electrode provided with a positive polarity. The plasma processing apparatus which switches the said electric power feeding path so that the said electric power may be supplied to the provided said electrode for adsorption | suction through the said electric power feeding path with a small capacity | capacitance.
A plasma processing apparatus according to any one of claims 1 to 3,
The plasma processing apparatus, wherein the switch unit that switches the power supply path selects and switches a plurality of power supply paths in which capacitors each having a different capacitance are arranged according to the voltage value of the high-frequency power.
The plasma processing apparatus according to any one of claims 1 to 4,
The plasma processing apparatus in which the capacitance of the plurality of capacitors in the switch unit is in a range of ¼ to four times the capacitance between the adsorption electrode and the sample with the dielectric film interposed therebetween.
The plasma processing apparatus according to claim 4 or 5, wherein
The plasma processing apparatus which selects the said electric power feeding path according to the maximum value of the voltage of the said high frequency electric power.