JP2002252276A - Method and device for measuring self bias, and electrostatic attraction device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure a self bias voltage of a object to be processed accurately in a short time and hold the object stably with the required electrostatic attraction. SOLUTION: A circular electrostatic chuck sheet 30 is crowned on the upper surface of a mounting stage 18, which is provided at the central part of a processing container 10. A semiconductor wafer W is mounted on the electrostatic chuck sheet 30. The electrostatic chuck sheet 30 is constituted by sealing a thin conducting film 36, which comprises, e.g. a copper coil as an electrode for electrostatic attraction, between a thin film 32 and an insulating film 34 comprising, e.g. polyimide. The thin film 32 has the function of, e.g. a resistor, and comprises a dielectric, e.g. SiC. The conductive film 36 is connected to the output terminal of a variable DC power supply 46 through an ammeter 44. The ammeter 44 detects the leaking current between the semiconductor wafer W and the conducting film 36. The variable DC power supply 46 outputs the variable DC voltage V0 under the control of a control part 50.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for measuring a self-bias voltage of an object to be processed in a plasma processing apparatus, and an electrostatic chuck for holding an object to be processed on a mounting table with an electrostatic attraction force. Related to the device.

[0002]

2. Description of the Related Art In the manufacture of semiconductor integrated circuits, for example, plasma is used in various processes such as ashing, etching, CVD, and sputtering to promote the ionization and chemical reaction of a processing gas. In a general plasma processing apparatus, a pair of electrodes are vertically arranged opposite to each other in a vacuum processing container, an upper electrode is connected to a ground potential, and a high-frequency voltage is applied to a lower electrode (mounting table). During this time, plasma is generated by electric discharge, and electrons, ions, etc. in the plasma are pulled into a target object, for example, a semiconductor wafer on the mounting table by an electric field, so that a predetermined plasma process is performed on the surface of the semiconductor wafer. ing.

In such a plasma processing apparatus, since a high-frequency voltage is applied to the lower electrode (mounting table) via a capacitor, the object to be processed on the mounting table has a DC negative potential, that is, a self-bias voltage. Clamped. That is,
In the half cycle in which the high frequency voltage becomes a positive voltage, electrons (negative charges) in the plasma are attracted to the object to be processed, and in the half cycle in which the high frequency voltage becomes a negative voltage, ions (positive charges) in the plasma are drawn to the object to be processed. The electrons are attracted more because the mass of the electrons is smaller than that of the ions and they are easier to move. As a result, the capacitor is constantly charged, and the object to be processed has a substantially constant DC negative potential (self-voltage). Bias voltage).

[0004] The self-bias voltage affects the energy of ions incident on the object to be processed. If the energy is too large, problems such as damage to an oxide film on the surface of the object to be processed occur.
For this reason, in the plasma processing apparatus, it is necessary to measure the self-bias voltage and adjust it to a desired value. However, it is practically impossible to directly measure the self-bias voltage by applying a probe or the like to the object in the processing container. Therefore, conventionally, the potential of the lower electrode (mounting table) has been measured via a voltage sense line or the like, and the self-bias voltage has been estimated from the measured value.

Incidentally, a recent plasma processing apparatus is provided with an electrostatic chuck which holds an object to be processed on a mounting table by electrostatic attraction without using mechanical holding means such as a clamp. The initial type of this type of electrostatic chuck has an insulating coating formed by oxidizing the surface of a mounting table made of, for example, aluminum, and applying a high DC voltage to the mounting table to remove the insulating coating on the mounting table surface. The polarization is such that static electricity is generated at a boundary surface with the object to be processed, and the object to be processed is held on the mounting table by its electrostatic attraction force (Coulomb force). However, such an electrostatic chuck mechanism cannot obtain sufficient polarization of the insulating film on the mounting table surface,
The electrostatic attraction force was not enough. Today, the mainstream is an electrostatic chuck having a structure in which an electrostatic chuck sheet in which a conductive film (electrostatic attraction electrode) is sealed in an insulating film is placed on the upper surface of a mounting table.

[0006]

As described above, the conventional self-bias measurement method is a method of measuring the potential of the lower electrode (mounting table) and estimating the self-bias voltage from the measured value. However, an electrostatic chuck sheet or an insulating film is interposed between the lower electrode and the object to be processed, and the resistance or capacitor acts accordingly, so that the potential of the lower electrode and the electric potential of the object to be processed (self-bias voltage). Is not good. For this reason, the conventional method has many measurement errors and cannot obtain a highly accurate self-bias voltage measurement value.

Conventionally, the value of the DC voltage applied to the electrostatic chucking electrode has been determined independently of the self-bias voltage. Therefore, not only is it time-consuming to set or adjust the DC applied voltage for obtaining the required electrostatic attraction force, but also after the adjustment, the self-adjustment due to a change in processing conditions (for example, a change in high-frequency power for plasma generation). When the bias voltage was changed, the electrostatic attraction force was also changed, and the condition was bad.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and provides a self-bias measuring method and apparatus capable of accurately measuring the self-bias voltage of an object to be processed in a plasma processing apparatus in a short time. With the goal.

Further, according to the present invention, in a plasma processing apparatus, an object to be processed can be held at a desired electrostatic attraction force, and the electrostatic attraction force is stably maintained at a set value with respect to a change in a self-bias voltage. It is an object of the present invention to provide an electrostatic attraction device capable of performing the above.

[0010]

In order to achieve the above object, a first self-bias measuring method of the present invention is provided by a method of electrostatically attracting and holding a mounting table in a processing vessel of a plasma processing apparatus. In the self-bias measuring method for measuring the self-bias voltage of the object, a variable DC voltage is applied to the electrostatic chucking electrode of the mounting table, and the object and the electrostatic force are changed while changing the value of the DC voltage. A method of detecting a DC leakage current between the attraction electrode and a method of obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the voltage value of the DC voltage and the current value of the DC leakage current. .

Further, a first self-bias measuring device of the present invention is a self-bias measuring device for measuring a self-bias voltage of an object to be processed held by an electrostatic attraction force on a mounting table in a processing vessel of a plasma processing apparatus. In the apparatus, a variable DC voltage generating means for applying a variable DC voltage to the electrostatic attraction electrode of the mounting table, and a leakage current detection for detecting a DC leakage current between the object to be processed and the electrostatic attraction electrode Means for variably controlling the DC voltage applied to the electrostatic chucking electrode of the mounting table from the variable DC voltage generating means, wherein the DC value detected by the voltage value of the DC voltage and the leakage current detecting means is provided. Self-bias voltage detecting means for obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the current value and the current value.

A second self-bias measuring method according to the present invention comprises:
In a self-bias measurement method for measuring a self-bias voltage of an object to be processed which is held on a mounting table by an electrostatic attraction force in a processing vessel of a plasma processing apparatus, a variable DC voltage is applied to the electrostatic adsorption electrode of the mounting table. To detect a DC leakage current between the object to be processed and the electrostatic chucking electrode while changing the value of the DC voltage, and the value of the DC voltage when the DC leakage current becomes substantially zero. Is used as the measured value of the self-bias voltage.

Further, a second self-bias measuring device of the present invention is a self-bias measuring device for measuring a self-bias voltage of an object to be processed which is held by an electrostatic attraction force on a mounting table in a processing vessel of a plasma processing apparatus. In the apparatus, a variable DC voltage generating means for applying a variable DC voltage to the electrostatic chucking electrode of the mounting table, and a leak current detecting a DC leak current between the object to be processed and the electrostatic chucking electrode Detecting means for variably controlling the DC voltage applied to the electrostatic chucking electrode of the mounting table from the variable DC voltage generating means, wherein the current detection value of the DC leakage current obtained by the leakage current detecting means is substantially Self-bias voltage detecting means for setting the DC voltage when the voltage becomes zero as a measured value of the self-bias voltage.

According to the present invention, there is provided an electrostatic attraction apparatus for holding an object to be processed on a mounting table in a processing vessel of a plasma processing apparatus by an electrostatic attraction force. An electrostatic attraction electrode provided on the mounting table to exert an electroadhesive force; a variable DC voltage generating means for applying a variable DC voltage to the electrostatic attraction electrode; A leakage current detecting means for detecting a DC leakage current between the electrode for electrostatic adsorption, a voltage value of a variable DC voltage applied to the electrode for electrostatic attraction by the variable DC voltage generating means and a voltage value detected by the leakage current detecting means. Self-bias voltage detection means for obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the current value of the DC leakage current and
A voltage substantially equal to the sum or difference between the measured value of the self-bias voltage obtained by the self-bias voltage detection means and the voltage difference between the object to be processed and the electrode for obtaining a desired electrostatic attraction force. And a voltage control means for controlling the variable DC voltage generating means so as to apply the voltage to the electrostatic attraction electrode during the processing of the object to be processed.

In the first self-bias measuring method or the self-bias measuring apparatus of the present invention, a variable DC voltage is applied to the electrostatic chucking electrode of the mounting table, and the object to be processed is changed while changing the value of the variable DC voltage. A DC leakage current flowing between the electrode and the electrostatic chucking electrode is detected, and a measured value of the self-bias voltage is obtained based on the voltage-current characteristics of the variable DC voltage and the DC leakage current. Generally, this voltage-current characteristic is represented as a symmetric curve centered on the value of the self-bias voltage. Therefore, in the second self-bias measurement method or the self-bias measurement device of the present invention, the value of the variable DC voltage when the DC leakage current becomes substantially zero is used as the measured value of the self-bias voltage.

In the electrostatic chuck according to the present invention, the voltage difference between the object to be processed and the electrode for electrostatic chuck is determined based on the measured value of the self-bias voltage obtained by the self-bias measuring method according to the present invention. So that the voltage difference for obtaining the electroadsorption force
A predetermined variable DC voltage is applied to the electrostatic attraction electrode. Since the voltage control means controls and adjusts the electrostatic attraction force,
Even if the self-bias voltage changes, the variable DC voltage is automatically adjusted to stably maintain the electrostatic attraction force at the set value.

[0017]

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

FIG. 1 is a sectional view showing the structure of a plasma etching apparatus according to one embodiment of the present invention.

Processing container 1 of this plasma etching apparatus
Numeral 0 is formed as a closed cylindrical chamber made of, for example, aluminum at both ends. An object to be processed, for example, a semiconductor wafer W, is placed on the side wall of the processing vessel 10.
There is provided a gate valve 11 for carrying in / out the inside.

A cylindrical, electrically conductive outer support frame 12 is erected on the bottom surface of the processing container 10, and a bottomed, cylindrical, insulated inner support frame 14 is fitted inside the outer support frame 12. ing. A cylindrical support table 1 is provided on the inner bottom of the inner support frame 14.
6, and a disc-shaped mounting table 1 on the support 16.
8 is fixed by bolts (not shown). Both the support table 16 and the mounting table 18 are made of a conductive metal such as aluminum. The cooling jacket 20 is provided inside the support base 16, and the cooling liquid supplied to the cooling jacket 20 through the introduction pipe 22 is discharged to the outside of the apparatus through the discharge pipe 24. The support table 16 and the mounting table 18 are formed with through holes 16a, 18a for supplying a heat exchange gas, for example, a helium gas, to the back surface of the semiconductor wafer W on the mounting table 18. A high frequency power supply 28 is connected via a capacitor 26 to the mounting table 18 functioning as a lower electrode.

A circular electrostatic chuck sheet 30 is mounted on the upper surface of the mounting table 18, and a semiconductor wafer W is mounted on the electrostatic chuck sheet 30. The electrostatic chuck sheet 30 is formed by laminating a dielectric such as SiC, which also has a function as a resistor, on a thin film 32 made of, for example, SiC, and an insulating film 34 made of polyimide, for example. The electrodes are formed by enclosing a thin conductive film 36 made of, for example, copper foil. Also in this electrostatic chuck sheet 30, a vent hole 30a for supplying helium gas for heat exchange to the back surface of the semiconductor wafer W on the mounting table 18 is formed.

The conductive film 36 of the electrostatic chuck sheet 30 is
Insulating coated conductive wire 38 penetrating mounting table 18, support table 1
6, a power supply rod 40 penetrating the inner support frame 14 and the outer support frame 12, a coil 42 provided outside the processing container 10, and an ammeter 44, which are connected to the output terminal of a variable DC power supply 46.

The coil 42 cooperates with a capacitor 48 to constitute a low-pass filter for removing high-frequency noise induced or mixed into the DC circuit. Ammeter 4
Reference numeral 4 denotes a current flowing through the DC circuit, that is, the semiconductor wafer W (workpiece) and the conductive film 36 of the electrostatic chuck sheet 30.
(Electrode for electrostatic attraction), and outputs a leakage current detection signal ML indicating the detected current value to the control unit 50. The variable DC power supply 46 is configured to output an arbitrary DC voltage V0 specified by the voltage control signal ES from the control unit 50. The control unit 50 includes, for example, a microcomputer, and controls the self-bias voltage measurement and the control and adjustment of the electrostatic attraction force in the present embodiment as described later.

A gas introduction chamber 52 is provided above the mounting table 18. The etching gas introduced into the gas introduction chamber 52 through the gas supply pipe 54 is discharged or directed toward the semiconductor wafer W at a uniform pressure and flow rate from the large number of ventilation holes 52b of the porous plate 52a facing the mounting table 18. It is injected. The gas introduction chamber 52 also serves as an upper electrode and is grounded. An exhaust port 56 is provided on a side wall near the bottom of the processing container 10.
A vacuum pump (not shown) is connected to the exhaust port 56 via an exhaust pipe 58.

In the plasma etching apparatus having such a configuration, plasma etching is performed as follows. For example, 380 KHz, 15 KW from a high frequency power supply 28 via a capacitor 26 to a lower electrode (mounting table) 18
Under a state in which the processing vessel 10 is evacuated to a predetermined degree of vacuum by a vacuum pump through an exhaust port 54 and an exhaust pipe 56, and passes through the gas supply pipe 54 and the gas introduction chamber 52. Etching gas
It is supplied within 0. Then, the gas molecules of the etching gas are ionized by the energy of the high-frequency power immediately below the gas introduction chamber 52, and plasma is generated. Electrons, ions, active species, and the like in the plasma enter the surface (processed surface) of the semiconductor wafer W on the mounting table 18 almost perpendicularly and cause a chemical reaction with a workpiece on the wafer surface, thereby performing etching. Done. The reaction product vaporized by the etching is exhausted from the exhaust port 56.

During such etching, a variable DC power supply 46 is applied to the conductive film 36 of the electrostatic chuck sheet 30.
A more constant DC voltage is applied, the dielectric film 32 is polarized by the DC voltage, and a positive charge,
Negative charges are induced on the back surface of the semiconductor wafer W, and the semiconductor wafer W is suction-held on the mounting table 18 by the Coulomb force between the positive charges and the negative charges.

A high-frequency voltage is applied from a high-frequency power supply 28 to a mounting table 18 as a lower electrode via a capacitor 26, and plasma is stored just above the semiconductor wafer W. A self-bias voltage is induced. According to this embodiment, as described below, the self-bias voltage is accurately measured, and the semiconductor wafer W is placed on the mounting table 18 during plasma etching based on the self-bias voltage measurement value. A DC voltage for holding by suction force is applied to the conductive film 36 of the electrostatic chuck sheet 30 from the variable DC power supply 46.

The method of measuring the self-bias according to the present embodiment will be described with reference to FIGS. FIG. 2 is a circuit diagram of a portion related to the measurement of the self-bias in the present embodiment. Dielectric film 32 of electrostatic chuck sheet 30
Is the intermediate resistivity between the conductor and the insulator (1 × 10 ⁸ to 1
(× 10 ¹² Ω · cm), which can be regarded as a resistor. Since the resistance of the resistor 32 is considerably large, the variable DC power supply 46
The resistance values of the conductors (42, 40, 38, etc.) can be neglected. The space between the upper electrode 52 and the semiconductor wafer W is a conductive space because ions and electrons in the plasma PR move.

Therefore, as shown in FIG. 2, between the output terminal of the variable DC power supply 46 and the ground, the ammeter 44, the resistor (dielectric film) 32, the semiconductor wafer W, the plasma PR
And an electric circuit in which the upper electrode 52 is connected in series. In a steady state, the voltage distribution (potential) in the plasma PR is constant and stable, and the potential of the semiconductor wafer W is clamped to the self-bias voltage VSB with respect to the upper electrode 52 (earth potential). Therefore, assuming that the output voltage of the variable DC power supply 46 is V0, the resistance value of the resistor 32 is R, and the voltage drop in the ammeter 44 can be ignored, the DC current flowing in this electric circuit, that is, the semiconductor wafer W and the conductive film The leakage current iL between the (electrostatic attraction electrodes) 36 is expressed by the following equation. iL = (V0-VSB) / R (1)

In the above equation (1), the self-bias voltage V
Although the SB is constant, the resistance R of the resistor 32 is equal to the voltage V0,
It is a value that changes depending on the temperature, the state of the back surface of the semiconductor wafer W, for example, the oxidation state, and the like.

In this embodiment, under the control of the control unit 50, the leakage current iL is detected by the ammeter 44 while changing the value of the output voltage V0 of the variable DC power supply 46. Then, a voltage-current characteristic as shown in FIG. 3 is obtained between V0 and the absolute value | iL | of iL. In this voltage-current characteristic,
When V0 is almost equal to VSB (self-bias voltage) |
iL | becomes substantially zero, and | iL | increases parabolically as the difference (absolute value) between V0 and VSB increases.
When V0 is larger than VSB, iL flows from the conductive film (electrostatic attraction electrode) 36 side to the semiconductor wafer W side, and V0 becomes VSB.
When it is smaller than iL, iL flows from the semiconductor wafer W side to the conductive film 36 side. A measured value of the self-bias voltage can be obtained based on the voltage-current characteristics.

According to the preferred self-bias measurement method of this embodiment, | iL | is based on the voltage-current characteristic that | iL | becomes substantially zero when V0 is substantially equal to VSB.
Is almost zero, the value of V0 is the self-bias voltage V
It is the measured value of SB. The control unit 50 outputs from the ammeter 44 |
leakage current detection value M indicating that iL | is almost zero
The value of the output voltage V0 of the variable DC power supply 46 when L is received is determined as the measured value of the self-bias voltage VSB. The control unit 50 can also give the measured value of the self-bias voltage VSB obtained in this way to a display device or a recording device (not shown) to display or record.

According to the second self-bias measurement method, V 0 and V
Based on the above-mentioned voltage-current characteristic that | iL | increases in a parabolic manner as the difference in SB increases, the value of V0 when the current values iLa and iLb of the leakage current iL having the opposite polarity and the same absolute value are obtained is obtained. The intermediate value of the values V0a and V0b (V0a + V0
b) / 2 is the measured value of the self-bias voltage VSB. In this case, the control unit 20 fetches the measured value of iL for each value of V0 into a storage unit (not shown), and determines the measured values iLa and iLb having opposite polarities and equal absolute values by a comparison operation,
Consequently, the value V0 of V0 corresponding to each of the measured values is obtained.
0a and V0b are determined, and a measured value of the self-bias voltage VSB is calculated from the voltage values V0a and V0b.

In this embodiment, the control unit 50 controls the output voltage V0 of the variable DC power supply 46 in an open loop. However, if necessary, a voltage detection means for detecting V0 may be provided. The value of V0 can be monitored or controlled with high accuracy, and a measured value of the self-bias voltage VSB can be obtained with higher accuracy.

In the self-bias measurement method according to the present embodiment, when V0 approaches VSB, the applied voltage (voltage difference) between the semiconductor wafer W and the conductive film (electrostatic attraction electrode) 36 is increased.
And the electrostatic attraction force is reduced. Since the gas for heat exchange is supplied to the back surface of the semiconductor wafer W, if the electrostatic attraction force is reduced, the semiconductor wafer W may be displaced from the mounting table 18 due to the pressure of the gas for heat exchange. Therefore, when the self-bias measurement method is performed in the plasma etching apparatus of FIG. 1, it is necessary to use a dummy semiconductor wafer W and hold it with an appropriate jig. In this respect, in the second self-bias measurement method, since it is possible to determine the measured values iLa and iLb having opposite polarities and the same absolute value without bringing V0 close to VSB, the semiconductor which is actually subjected to the etching process is obtained. The self-bias voltage VSB can be measured for the wafer W.

The electrostatic chuck according to this embodiment includes an electrostatic chuck sheet 30, a variable DC power supply 46, an ammeter 44,
It comprises a control unit 50. The control unit 50 calculates the measured value of the self-bias voltage VSB of the semiconductor wafer W based on the voltage-current characteristic between the output voltage V0 of the variable DC power supply 46 and the leakage current iL detected by the ammeter 44 as described above. In addition to functioning as the required self-bias voltage detection means, the semiconductor wafer W
Also functions as a voltage control means for controlling the variable DC power supply 46 so as to apply a DC voltage to the conductive film (electrode for electrostatic attraction) 36 to hold a DC voltage on the mounting table 18 with a desired electrostatic attraction force.

That is, there is a proportional relationship between the applied voltage VF between the semiconductor wafer W and the conductive film (electrostatic attraction electrode) 36 and the electrostatic attraction force F as shown in FIG. ) Are obtained as theoretical or experimental values. Control unit 50
Is, if the required electrostatic attraction force Fs is set, this F
The measured value of the self-bias voltage VSB is added to the value VFS of the applied voltage VF corresponding to s, and the variable DC power supply 46 outputs an output voltage V0 equal to the sum (VFS + VSB).

In this embodiment, for example, the high frequency power supply 28
When the self-bias voltage VSB changes due to the change of the output of the control circuit 50, the control unit 50 can measure the value of the new self-bias voltage VSB as described above. Output voltage V of DC power supply 46
By adjusting 0, the electrostatic attraction force F can be stably maintained at the set value Fs.

While the preferred embodiment has been described above,
The present invention is not limited to the above embodiments,
Various modifications and changes are possible within the scope of the technical idea.

For example, the electrode for electrostatic attraction may be one which is disposed opposite to the object to be processed via a film or plate having both dielectric properties and electric leakage, and its shape, structure and size may be arbitrarily selected. Is possible. Therefore, configurations other than the electrostatic chuck sheet are possible.

The ammeter 44 and the variable DC power supply 46
The circuit configuration and software of the control unit 50 can be arbitrarily modified and changed. The control unit 50
May not be provided, the measured value of the ammeter 44 may be displayed, and the operator may variably adjust the output voltage of the variable DC power supply 46 by manual operation while viewing the measured current value.

Although the above embodiment relates to a plasma etching apparatus, the present invention is applicable to other plasma processing apparatuses such as a plasma ashing apparatus and a plasma CVD apparatus. The present invention is also applicable to a processing object such as an LCD substrate.

[0043]

According to the self-bias measuring method and apparatus of the present invention, the leakage current between the object to be processed and the electrostatic attraction electrode is detected while changing the value of the DC voltage applied to the electrostatic attraction electrode, Since the measured value of the self-bias voltage was obtained based on the voltage-current characteristics of the applied DC voltage and the leakage current,
A highly accurate self-bias voltage measurement value with few errors can be easily obtained in a short time.

According to the electrostatic attraction device of the present invention, the voltage difference between the object to be processed and the electrode for electrostatic attraction is based on the measured value of the self-bias voltage and the voltage difference for obtaining the desired electrostatic attraction force. Since a predetermined variable DC voltage is applied to the electrostatic attraction electrode, the electrostatic attraction force can be stably maintained at the set value even when the self-bias voltage changes.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating an overall configuration of a plasma etching apparatus according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram for explaining the operation of the self-bias measurement method in the embodiment.

FIG. 3 is a diagram illustrating a voltage-current characteristic between a variable DC voltage and a leakage current used in the self-bias measurement method according to the embodiment.

FIG. 4 is a diagram showing characteristics between an applied voltage and an electrostatic attraction force used in the electrostatic attraction device according to the embodiment.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 processing container 18 mounting table 30 electrostatic chuck sheet 32 dielectric film (resistor) 34 insulating film 36 conductive film (electrode for electrostatic attraction) 44 ammeter 46 variable DC power supply 50 control unit W semiconductor wafer

Claims (5)

[Claims] 1. A self-bias measuring method for measuring a self-bias voltage of an object to be processed held on a mounting table by an electrostatic attraction force in a processing vessel of a plasma processing apparatus, the method comprising: A variable DC voltage is applied to the DC voltage, and a DC leakage current between the object to be processed and the electrostatic chucking electrode is detected while changing the value of the DC voltage, and the voltage value of the DC voltage and the DC leakage current are detected. A self-bias voltage measurement value obtained based on a voltage-current characteristic between the self-bias voltage value and the current value. 2. A self-bias measuring device for measuring a self-bias voltage of an object to be processed held on a mounting table by an electrostatic attraction force in a processing vessel of a plasma processing apparatus. A variable DC voltage generating means for applying a variable DC voltage to the electrode; a leakage current detecting means for detecting a DC leakage current between the object to be processed and the electrostatic chucking electrode; and the variable DC voltage generating means. The DC voltage applied to the electrostatic chuck electrode of the mounting table is variably controlled, and a voltage-current characteristic between a voltage value of the DC voltage and a current value of the DC leakage current detected by the leakage current detection unit is obtained. A self-bias voltage detecting device for obtaining a measured value of the self-bias voltage based on the self-bias voltage. 3. A self-bias measuring method for measuring a self-bias voltage of an object to be processed held on a mounting table by an electrostatic attraction force in a processing vessel of a plasma processing apparatus. Applying a variable DC voltage to the DC voltage, detecting a DC leakage current between the object to be processed and the electrostatic chucking electrode while changing the value of the DC voltage, when the DC leakage current becomes substantially zero. A self-bias measurement method, wherein the value of the DC voltage is a measured value of the self-bias voltage. 4. A self-bias measuring device for measuring a self-bias voltage of an object to be processed held on a mounting table by an electrostatic attraction force in a processing vessel of a plasma processing apparatus. A variable DC voltage generating means for applying a variable DC voltage to the leakage current detecting means for detecting a DC leakage current between the object to be processed and the electrostatic chucking electrode; and The DC voltage applied to the electrostatic chucking electrode of the mounting table is variably controlled, and the DC voltage when the current detection value of the DC leakage current obtained by the leakage current detection means becomes substantially zero is the self-bias. A self-bias voltage measuring device for measuring a voltage; 5. An electrostatic attraction device for holding an object to be processed on a mounting table with an electrostatic attraction force in a processing vessel of a plasma processing apparatus, wherein the electrostatic attraction force is applied to the object to be processed. The electrostatic chucking electrode provided on the mounting table, a variable DC voltage generating means for applying a variable DC voltage to the electrostatic chucking electrode, and a DC voltage between the workpiece and the electrostatic chucking electrode. A leak current detecting means for detecting a leak current; a voltage value of a variable DC voltage applied to the electrostatic chucking electrode by the variable DC voltage generating means; and a current of the DC leak current detected by the leak current detecting means. Self-bias voltage detecting means for obtaining a measured value of the self-bias voltage based on a voltage-current characteristic between the self-bias voltage and a desired electrostatic attraction. Power The variable DC voltage generating means such that a voltage substantially equal to a sum or a difference value between a voltage difference between the object to be processed and the electrode to be obtained is applied to the electrostatic attraction electrode during processing of the object to be processed. And a voltage control means for controlling the voltage.