WO2002059954A1 - Plasma processing apparatus and plasma processing method - Google Patents

Abstract

The current Id flowing through a line of a DC high-voltage power supply (HV) when a high-frequency power supply (RF) is turned on and integrated so as to determine the change of charge ΔQ. The voltage Vdc of the wafer (W) is determined from the change of charge ΔQ. Thus, the potential of a work in a plasma is accurately determined with a simple structure.

Description

 Technical Field Plasma processing apparatus and plasma processing method

 The present invention relates to a plasma processing apparatus and a plasma processing method, and is suitably applied to a case where a potential of an object to be processed in plasma is obtained. Background art

 With conventional plasma processing equipment, it is difficult to directly measure the potential of the object in the plasma.Therefore, by measuring the voltage V pp of the susceptor on the high-frequency power supply line, The estimated ion energy was estimated.

 However, since the ion energy incident on the object depends on the potential of the object, estimating the ion energy from the voltage V pp of the susceptor degrades the calculation accuracy of the ion energy. For this reason, there has been a problem that the workpiece is damaged by the ion bombardment and the processing accuracy of the workpiece is deteriorated.

 To cope with such a problem, for example, Japanese Patent Application Laid-Open No. 6-232088 discloses a technique of monitoring VDC by a monitor terminal installed completely independently of a power supply circuit. . However, in this case, it is necessary to form a signal path for an independent monitor, which may complicate the device configuration. Disclosure of the invention

Therefore, an object of the present invention is to provide a simple configuration in which the potential of an object to be processed in plasma is It is an object of the present invention to provide a plasma processing apparatus and a plasma processing method capable of accurately determining the value of the plasma processing apparatus.

 In order to solve the above-described problems, the present invention provides an electrostatic chuck that attracts an object to be processed, a DC voltage source that applies a DC voltage to the electrostatic chuck, and generates plasma on the object to be processed. A plasma generation unit, a charge amount calculation unit that calculates an amount of charge stored in the electrostatic chuck, and the object to be processed based on a change in the amount of charge stored in the electrostatic chuck before and after the generation of the plasma. And a potential calculating means for calculating the potential of the above.

 When a workpiece is placed on the electrostatic chuck, a capacitance is formed between the workpiece and the electrostatic chuck. When the potential of the workpiece changes, the amount of electric charge accumulated in the electrostatic chuck Fluctuates via this capacitance. The electric charge stored in the electrostatic chuck is supplied through a line of a DC voltage source. Therefore, for example, by measuring the current flowing through this line, the amount of charge accumulated in the electrostatic chuck can be easily calculated. Therefore, even when it is difficult to directly measure the potential of the object to be processed, the potential of the object in the plasma can be simply calculated by calculating the variation in the amount of charge accumulated in the electrostatic chuck. It can be obtained with high accuracy by the configuration.

 Further, the present invention is characterized by further comprising control means for controlling the DC voltage source based on the potential of the object to be processed calculated by the potential calculation means.

 This makes it possible to control the energy of ions incident on the object with high accuracy.

Also, the present invention provides a step of adsorbing an object to be processed on an electrostatic chuck; a step of generating plasma on the object to be processed; Calculation And a step of calculating an electric potential of the object to be processed based on the fluctuation of the calculated electric charge amount.

 Accordingly, even when it is difficult to directly measure the potential of the target object because the target object is exposed to the plasma, the potential of the target object can be easily obtained. In addition, it is possible to accurately estimate the ion energy incident on the object to be processed.

 Further, the present invention is characterized in that the change in the charge amount is calculated based on an integration result of a pulse current flowing in a DC voltage source connected to the electrostatic chuck.

 This makes it possible to calculate the change in the amount of charge accumulated in the electrostatic chuck by simply connecting the ammeter to the DC voltage source and integrating the current flowing through the ammeter before and after plasma generation. It is possible to easily obtain the potential of the object to be processed.

 Further, the present invention is characterized in that the method further comprises a step of controlling a DC voltage applied to the electrostatic chuck based on the calculated potential of the object to be processed.

 This makes it possible to control the energy of ions incident on the object with high accuracy. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is a sectional view showing a schematic configuration of a plasma processing apparatus according to one embodiment of the present invention.

 FIG. 2 is a diagram showing a potential change of each part before and after generation of plasma in the plasma processing apparatus according to one embodiment of the present invention.

FIG. 3 is a waveform diagram showing a change in the DC power supply current of the plasma processing apparatus according to one embodiment of the present invention, and FIG. 3 (a) shows a waveform of one entire process. FIG. 3 (b) is an enlarged view of portion B of FIG. 3 (a). BEST MODE FOR CARRYING OUT THE INVENTION

 Hereinafter, a plasma processing apparatus and a plasma processing method according to an embodiment of the present invention will be described with reference to the drawings.

 FIG. 1 is a sectional view showing a schematic configuration of a plasma processing apparatus according to one embodiment of the present invention. In this embodiment, a magnetron R IE will be described as an example of a plasma processing apparatus.

In FIG. 1, an upper electrode 2 and a susceptor 3 are provided in a processing chamber 1. This susceptor 3 also serves as the lower electrode. The upper electrode 2 is provided with a plurality of gas ejection holes 2 a for introducing a processing gas into the processing chamber 1. The susceptor 3 is supported on a susceptor 4, and the susceptor 4 is held in the processing chamber 1 via an insulating plate 5. High frequency power supply RF is connected to susceptor 3 via capacitor C1. Then, by turning on the high-frequency power supply RF, a plasma P is generated in the processing chamber 1 ₍ also, a resistor R 1 is connected to the line of the high-frequency power supply RF, and the voltage V pp across the resistor R 1 is applied. By measuring, the voltage of susceptor 3 can be measured.

 The processing chamber 1 is provided with a gas supply pipe 1a and an exhaust pipe 1b, and the gas supply pipe la is connected to a gas supply source (not shown). Further, the exhaust pipe 1b is connected to a vacuum pump (not shown), and the pressure in the processing chamber 1 can be adjusted by evacuating the processing chamber 1 with the vacuum pump. A horizontal magnetic field forming magnet 9 is provided around the processing chamber 1 to form a magnetic field in the processing chamber 1. This makes it possible to increase the density of the plasma and efficiently perform the etching.

An electrostatic chuck 6 is provided on the susceptor 3. This electrostatic The hole 6 has, for example, a structure in which a C11 electrode 7 is sandwiched between polyimide films 8a and 8b. A DC high voltage power supply HV is connected to the Cii electrode 7 via a coil L and a resistor R2. By applying a DC high voltage to the Cii electrode 7, a Coulomb force acts on the wafer W, and the wafer W can be electrostatically attracted to the electrostatic chuck 6. The coil L and the resistor R2 block high frequency components from the high frequency power supply RF. Therefore, the high-frequency component from the high-frequency power supply RF is not transmitted to the DC high-voltage power supply HV.

 The line of the DC high-voltage power supply HV is provided with charge amount calculation means 11. The charge amount calculating means 11 calculates the amount of charge stored in the electrostatic chuck 6.

 Further, the wafer potential calculation means 12 calculates the potential of the wafer W based on the change in the charge amount calculated by the charge amount calculation means 11.

 Further, the control means 13 controls the DC high-voltage power supply HV based on the potential of the wafer W calculated by the wafer potential calculation means 12. That is, the DC voltage applied from the DC high-voltage power supply HV to the electrostatic chuck 6 is adjusted based on the potential of the wafer W.

 The charge amount calculation means 11 can be configured using, for example, an ammeter A for measuring the current Id and a charge meter 10 for calculating the charge amount based on the current Id. In the example shown in FIG. 1, an ammeter A for measuring a current Id flowing through the DC high-voltage power supply HV is connected to the line of the DC high-voltage power supply HV. The ammeter A is connected to a charge meter 10.

Note that the charge amount calculating means 11 may be configured using an integrator for integrating the current Id in addition to the configuration shown in FIG. Further, the configuration may be such that storage means for storing the measurement value of the ammeter A and calculation means for calculating the charge amount by performing arithmetic processing on the measurement value stored in the storage means. FIG. 2 is a schematic diagram of a plasma processing apparatus according to an embodiment of the present invention. FIG. 3 (a) is a waveform diagram showing a change in DC power supply current of a plasma processing apparatus according to an embodiment of the present invention, and FIG. It is an enlarged view of B part of (a).

 In Fig. 2, when the wafer W is placed on the susceptor 3 (electrostatic chuck 6) and the DC high-voltage power supply HV is off, the electrostatic chuck 6, the wafer W, and the processing space of the plasma processing apparatus (space) The potential of the chamber inner wall (wall) is 0 V.

 Next, when the DC high-voltage power supply HV is turned on and, for example, a voltage V0 of 1.5 kV is applied to the Cu electrode 7 of the electrostatic chuck 6, the potential of the Cu electrode 7 becomes 1.5 kV. At this time, since the wafer W is insulated through the polyimide film 8a of the electrostatic chuck 6, it remains at 0V. Therefore, a voltage of V0 = 1.5 kV is applied between the wafer W and the Cu electrode 7. Therefore, as shown in FIG. 3, a current Id for inducing a charge Q0 corresponding to the capacitance C between the electrode W and the Cu electrode 7 flows like a pulse. The current Id for inducing the charge Q0 corresponds to the pulse P1 generated when the DC high-voltage power supply HV is turned on, and the pulse P2 generated several seconds later. The pulse P1 is a current flowing when the wafer W is floating from the electrostatic chuck 6. The pulse P2 is a current flowing when the wafer W comes into contact with the electrostatic chuck 6.

This charge Q0 is supplied via the line of the DC high-voltage power supply HV. Therefore, by measuring the current Id corresponding to the pulse P 1 s P2 with the ammeter A connected to the line of the DC high-voltage power supply HV, the charge Q0 can be obtained by integrating this current Id. . Since the capacitance C between the wafer W and the Cu electrode 7 is known, the charge Q0 obtained by integrating the current Id corresponding to the pulses PI and P2 is obtained from the relationship Q0 = C CV0. Matches the value given. Next, when the high-frequency power supply RF is turned on, as shown in FIG. 2, the potential of the Cu electrode 7 remains at 1.5 kV, but since the wafer W is in an electrically floating state, The voltage Vdc is applied to the wafer W under the influence of the generated plasma P. Therefore, the voltage between the wafer W and the Cu electrode 7 changes from V0 to V0 + Vdc, and the amount of charge induced between the wafer W and the Cu electrode 7 changes. Here, the amount of change ΔQ of the charge induced between the wafer W and the Cu electrode 7 is

 A Q = C (V0 + Vdc)-C-V0 = C-Vdc · · (1)

 When the amount of charge induced between the wafer W and the Cu electrode 7 changes, a current I d corresponding to the change amount ΔQ of the charge flows like a pulse. This current Id corresponds to the pulse P3 generated when the high-frequency power supply RF is turned on. For this reason, the current Id corresponding to the pulse P3 is measured by the ammeter A connected to the line of the DC high-voltage power supply HV, and the amount of change ΔQ in the charge can be obtained by integrating this current Id. .

 When the charge change amount ΔQ is obtained, the electrostatic capacitance C between the wafer W and the Cu electrode 7 has a specific value, so that the voltage Vdc of the wafer W can be obtained from equation (1).

 For example, it is assumed that when the DC high-voltage power supply HV is turned on and a voltage V0 of 1.5 kV is applied to the electrostatic chuck 6, a charge amount of 0.15 mA / sec flows. Next, it is assumed that when the high-frequency power supply RF is turned on, a charge amount of 0.06 mA * sec flows. In this case, since the capacitance C is constant, the voltage Vdc applied to the wafer W when the high frequency power supply RF is turned on becomes 600 V. .

As described above, when the voltage of the wafer W changes due to the capacitance C between the wafer W and the electrostatic chuck 6, the charge stored in the electrostatic chuck 6 changes. For this reason, when the high-frequency power supply RF is turned on (the The voltage V dc of the wafer W can be determined by calculating the amount of change in the applied charge.

 Since the electric charge stored in the electrostatic chuck 6 is supplied from the line of the DC high-voltage power supply HV, it can be easily calculated using the ammeter A provided in the DC high-voltage power supply HV. Therefore, even when it is difficult to directly measure the potential of the wafer W with a voltmeter, the voltage applied to the wafer W can be easily obtained.

 Therefore, it is possible to accurately estimate the ion energy incident on the wafer W, and the plasma processing of the wafer W can be performed stably and with high accuracy.

 Further, based on the potential of the wafer W calculated by the wafer potential calculation means 12, the control means 13 controls the voltage value applied to the electrostatic chuck 6 from the DC high-voltage power supply HV. This makes it possible to accurately control the energy of ions incident on the wafer W.

 Further, as the ammeter A, an ammeter attached to the DC high-voltage power supply HV in advance can be used, and the voltage Vdc of the wafer W can be easily obtained at low cost.

 In the above-described embodiment, a case has been described in which a magnetron: an IE device is used to generate plasma, but any plasma processing device may be used, and the present invention may be applied to a plasma CVD device, an asshing device, or the like. . It can also be applied to ECR (Electron Cyclotron Resonance) plasma processing equipment, HEP (Helicon Wave Excited Plasma) processing equipment, ICP (Inductively Coupled Plasma) processing equipment, TCP (Transfer Coupling Plasma) processing equipment, etc. Good.

Also, the wafer W has been described as an example of an object to be processed by the plasma processing apparatus, but the wafer W may be anything such as a semiconductor substrate or a glass substrate. Alternatively, the present invention may be applied to a semiconductor device, a liquid crystal display device, an optical component, a CSP (chip size package) or a magnetic head.

 Also, when the voltage V dc of the wafer W changes due to some other factor after the R f is turned on, the charge amount is obtained from the pulse current generated at that time, and based on the calculated charge amount, (C) The voltage Vdc of W can be calculated.

 Furthermore, in the above-described embodiment, the description has been given of the monopolar electrostatic chuck 6, but the present invention may be applied to a bipolar electrostatic chuck. In this case, the charge amount may be obtained from the current of one of the lines of the DC high-voltage power supply.The currents of both lines of the DC high-voltage power supply are monitored, and the charge amounts flowing through both lines are made equal. The voltage of each DC high-voltage power supply may be adjusted.

 As described above, according to the present invention, even when the object to be processed is exposed to plasma, the potential of the object to be processed can be easily and accurately obtained. Industrial applicability

 The plasma processing apparatus and the plasma processing method according to the present invention can be used in a semiconductor manufacturing industry or the like that manufactures semiconductor devices. Therefore, it has industrial applicability.

Claims

The scope of the claims 1. An electrostatic chuck for adsorbing the workpiece,  A DC voltage source for applying a DC voltage to the electrostatic chuck,  Plasma generation means for generating plasma on the object to be processed, charge amount calculation means for calculating the amount of charge stored in the electrostatic chuck, and the amount of charge stored in the electrostatic chuck before and after the plasma generation A plasma processing apparatus comprising: a potential calculating unit configured to calculate a potential of the object to be processed based on a change.  2. The plasma processing apparatus according to claim 1, further comprising control means for controlling the DC voltage source based on the potential of the object to be processed calculated by the potential calculation means.  3. The step of adsorbing the object to be processed on the electrostatic chuck;  Generating plasma on the object to be processed;  Calculating the variation in the amount of charge stored in the electrostatic chuck before and after the generation of the plasma; and  Calculating the potential of the object to be processed based on the change in the calculated amount of charge.  4. The plasma processing method according to claim 3, wherein the variation in the charge amount is calculated based on an integration result of a pulse current flowing in a DC voltage source connected to the electrostatic chuck.  5. The plasma processing method according to claim 3, further comprising a step of controlling a DC voltage applied to the electrostatic chuck based on the calculated potential of the object to be processed.