JP2019040853A - Measuring device, measurement method, and plasma processing device - Google Patents

Abstract

To easily measure the self bias voltage Vof plasma.SOLUTION: There is provided a measuring device including: a switch that switches a connection of an electrode to which a direct current voltage is applied, the electrode being within an electrostatic chuck disposed in a plasma processing device; a member provided with electrostatic capacitance, the member being connected to the switch; and a measuring unit that measures a value corresponding to an electric charge amount accumulated in the member provided with the electrostatic capacitance.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a measuring apparatus, a measuring method, and a plasma processing apparatus.

  In plasma processing such as etching and film formation performed in a plasma processing apparatus, it is important to grasp the state of plasma in order to control the etching rate and film formation rate. Therefore, a method for measuring the self-bias voltage Vdc has been proposed to measure the plasma state (see, for example, Patent Documents 1 and 2).

  In Patent Document 1, the self-bias voltage Vdc is indirectly measured by a device that is not in direct contact with plasma. In Patent Document 1, a device is provided in a processing vessel wall, a voltage applied to an electrode insulated by a dielectric in the device is measured, and a self-bias voltage Vdc is calculated from the measured voltage in consideration of each parasitic capacitance. .

  In Patent Document 2, a self-bias voltage Vdc measurement circuit is incorporated in a matching device, the input resistance of the measurement circuit is set to a value sufficiently larger than the resistance value of the showerhead, and the self-bias voltage Vdc is measured by the measurement circuit. .

JP 2001-148374 A JP 2006-93342 A

  However, the above method requires a design change of the device or circuit, and the self-bias voltage Vdc cannot be easily measured. For example, in Patent Document 1, machining is performed on a processing container wall in order to provide a device in the processing container wall. Further, since the measurement probe is located at a position away from the plasma to be measured, the sensitivity and accuracy of measurement are lowered. In Patent Document 2, it is necessary to incorporate a measurement circuit for the self-bias voltage Vdc into the matching unit, which requires a design change of the plasma processing apparatus.

  As described above, in Patent Documents 1 and 2, in order to incorporate a probe and a measurement circuit for measuring the self-bias voltage Vdc, it is necessary to change the mechanical design of the plasma processing apparatus and the high-frequency circuit (matching unit). There may be a lack of versatility and simplicity of measurement.

  In view of the above problem, in one aspect, the present invention aims to easily measure the self-bias voltage Vdc of plasma.

  In order to solve the above problems, according to one aspect, an electrode in an electrostatic chuck disposed in a plasma processing apparatus, the switching unit switching connection of the electrode to which a DC voltage is applied, and There is provided a measuring apparatus including a member having a capacitance connected to the switching unit, and a measuring unit that measures a value corresponding to the amount of charge accumulated in the member having the capacitance.

  According to one aspect, the plasma self-bias voltage Vdc can be easily measured.

The figure for demonstrating a self-bias voltage. The figure which shows an example of the plasma processing apparatus and measuring apparatus which concern on one Embodiment. The figure for demonstrating the measurement timing of the self-bias voltage concerning one Embodiment. The figure which shows an example of the measurement sequence of the self-bias voltage concerning one Embodiment. The figure which shows an example of the measurement sequence of the self-bias voltage concerning one Embodiment. The figure which shows an example of the model used for calculation of the self-bias voltage which concerns on one Embodiment. The figure which shows an example of the equivalent circuit of the model which concerns on one Embodiment. The figure which shows an example of the measurement result of the self-bias voltage which concerns on one Embodiment. The figure which shows an example of the correlation information of the self-bias voltage and deposition time which concern on one Embodiment. The figure which shows an example of the measurement performed previously in order to collect the correlation information of FIG. The flowchart which shows an example of the measuring method which concerns on one Embodiment.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, in this specification and drawing, about the substantially same structure, the duplicate description is abbreviate | omitted by attaching | subjecting the same code | symbol.

[Self-bias voltage]
First, a direct current self-bias voltage of plasma (hereinafter referred to as “self-bias voltage Vdc”) will be described with reference to FIG. FIG. 1A schematically shows a part of the counter electrode in which the electrode A and the electrode K are arranged to face each other. Electrode A is a ground electrode that is grounded, the electrodes K are high-frequency electrodes connected to a high-frequency power supply (RF power supply) through the blocking capacitor C _B. Further, the area of the electrode K is smaller than the area of the electrode A.

  A high frequency power RF is applied to the electrode K to ionize and dissociate the gas, thereby generating plasma. Since the high frequency power RF in which the sign curve is symmetrical is applied to the electrode K, the potential of the electrode K becomes zero in total. Electrons and cations are generated from the generated plasma. As shown in FIG. 1B, electrons flow into the electrode K when the electrode K is at a positive potential with respect to the plasma, and cations when the electrode K is at a negative potential. Flows in.

  At this time, since the electrons have a small mass, they can follow the high-speed potential fluctuation of the electrode K. As a result, electrons flow into the electrode K. On the other hand, since the cation has a large mass, it cannot follow the high-speed potential fluctuation of the electrode K and moves in the average electric field according to the law of inertia. For this reason, the amount of ions flowing into the electrode K is constant and very small.

Since the electrodes K are floating from the ground by a blocking capacitor C _B, electrons flowing to the electrode K does not flow to the ground. Therefore, electrons flow into the electrode K and accumulate in a period (half cycle) in which the surface of the electrode K is at a positive potential with respect to the plasma. However, because of the accumulated electrons, the surface of the electrode K is negatively charged and a negative bias is generated with respect to the plasma. The negative bias causes cations to flow into the surface of the electrode K. As a result, a sheath is formed on the surface of the electrode K.

  Eventually, the surface of electrode K is positive with respect to the plasma for a very short time during one cycle. The DC component of the potential difference of the electrode K when the electrons flowing at that time and the positive ions steadily flowing due to a negative bias are balanced is the self-bias voltage Vdc.

  In order to control the etching rate, film formation rate, etc., which show the characteristics of plasma processing, it is necessary to grasp the plasma state. Therefore, in this embodiment, the self-bias voltage Vdc is measured in order to grasp the plasma state in the plasma processing apparatus 100.

[Configuration of plasma processing apparatus]
A plasma processing apparatus 100 according to this embodiment shown in FIG. 2 includes an apparatus main body, a relay box 6 and a measuring apparatus 10. The measuring apparatus 10 measures the voltage of the adsorption electrode 21 in the electrostatic chuck 2 a disposed in the processing container C of the plasma processing apparatus 100. The relay box 6 switches the connection destination of the adsorption electrode 21 between the DC power source 7 and the measuring device 10. When the adsorption electrode 21 and the measuring device 10 are connected, the measuring device 10 shows a value corresponding to the amount of charge accumulated in the acrylic plate 14 sandwiched between the copper disc 12 and the copper plate 13. measuring the voltage V ₂ between the disc 12 and the copper plate 13 as a DC component of the potential difference of the adsorption electrode 21 of the electrostatic chuck 2a, calculates a self-bias voltage Vdc on the basis of the measurement results. Thus, in the present embodiment, the self-bias voltage Vdc can be measured easily and accurately simply by adding the relay box 6 and the measuring device 10 to the existing plasma processing apparatus 100. Below, an example of a structure of the plasma processing apparatus 100 and the measuring apparatus 10 which concern on this embodiment is demonstrated.

(Configuration of plasma processing equipment)
The plasma processing apparatus 100 according to the present embodiment is a capacitively coupled parallel plate plasma processing apparatus, and includes a substantially cylindrical processing container C. The inner surface of the processing container C is subjected to alumite treatment (anodizing treatment). The inside of the processing vessel C is a processing chamber in which plasma processing such as etching processing and film formation processing is performed by plasma. A stage 2 is provided in the processing container C.

  The stage 2 is provided with an electrostatic chuck 2a for electrostatically adsorbing the wafer W on the base 2b. Base 2b is formed of, for example, aluminum (Al), titanium (Ti), silicon carbide (SiC), or the like. Stage 2 also functions as a lower electrode.

  The electrostatic chuck 2 a has a structure having the attracting electrode 21 in the dielectric layer 22. On the surface of the electrostatic chuck 2a, dot-shaped convex portions 22a are formed. The adsorption electrode 21 is connected to the relay box 6. When the switch 6a of the relay box 6 is switched to the DC power source 7 and a DC voltage is supplied from the DC power source 7 to the suction electrode 21, a wafer W, which is an example of a substrate, is attracted and held by the electrostatic chuck 2a by Coulomb force. The

  An annular focus ring 8 is placed on the outer peripheral side of the electrostatic chuck 2a so as to surround the outer edge of the wafer W. The focus ring 8 is formed of, for example, silicon, and functions to converge plasma toward the surface of the wafer W and improve the efficiency of plasma processing.

  A first high frequency power (HF) for plasma generation of a first frequency is applied from the first high frequency power source 3 to the stage 2, and a second frequency lower than the first frequency is applied from the second high frequency power source 4. A second high frequency power (LF) for generating a bias voltage having a frequency is applied. The first high-frequency power source 3 is electrically connected to the stage 2 via the matching unit 3a. The second high frequency power supply 4 is electrically connected to the stage 2 through the matching unit 4a. The first high frequency power supply 3 applies, for example, high frequency power HF of 40 MHz to the stage 2. For example, the second high frequency power supply 4 applies a high frequency power LF of 13.56 MHz to the stage 2. In the present embodiment, the first high frequency power is applied to the stage 2, but the first high frequency power may be applied to the gas shower head 1.

  The matching unit 3a matches the load impedance to the internal (or output) impedance of the first high-frequency power source 3. The matching unit 4a matches the load impedance to the internal (or output) impedance of the second high frequency power supply 4.

  The gas shower head 1 is attached so as to close the opening of the ceiling portion of the processing container C through a shield ring that covers the outer edge of the gas shower head 1. The gas shower head 1 is grounded. The gas shower head 1 may be formed of silicon. The gas shower head 1 functions as a counter electrode (upper electrode) facing the stage 2 (lower electrode).

  The gas shower head 1 is formed with a gas inlet 1a for introducing gas. Inside the gas shower head 1 is provided a diffusion chamber 1b for diffusing gas. The gas output from the gas supply unit 5 is supplied to the diffusion chamber 1b through the gas introduction port 1a, is diffused in the diffusion chamber 1b, and is introduced into the processing container C from a number of gas supply holes 1c.

  An exhaust port is formed in the bottom surface of the processing container C, and the inside of the processing container C is exhausted by an exhaust device 9 connected to the exhaust port. Thereby, the inside of the processing container C can be maintained at a predetermined degree of vacuum. A gate valve G is provided on the side wall of the processing container C. The gate valve G opens and closes when the wafer W is loaded and unloaded from the processing container C.

  When the processing gas is supplied from the gas supply unit 5 into the processing container C and the first and second high-frequency powers are applied to the stage 2 from the first high-frequency power source 3 and the second high-frequency power source 4, plasma is generated and applied to the wafer W. A predetermined plasma treatment is performed. In particular, when the second high frequency power is applied from the second high frequency power source 4 to the stage 2, ions in the plasma are attracted to the wafer W side.

  After the plasma processing, the DC power supply 7 supplies the suction electrode 21 with a DC voltage that is opposite in polarity to that at the time of chucking the wafer W, and charges on the wafer W are discharged. As a result, the wafer W is peeled off from the electrostatic chuck 2a and carried out of the processing container C through the gate valve G.

  The plasma processing apparatus 100 is provided with a control unit 200 that controls the operation of the entire apparatus. The control unit 200 includes a CPU (Central Processing Unit) 205, a ROM (Read Only Memory) 210, and a RAM (Random Access Memory) 215. The CPU 205 executes a desired process such as etching according to a recipe stored in a storage area such as the RAM 215. The recipe includes process time, pressure (gas exhaust), high frequency power and voltage, various gas flow rates, process vessel temperature (upper electrode temperature, process vessel side wall temperature, wafer W temperature), which are control information of the apparatus for process conditions. Electrostatic chuck temperature, etc.), refrigerant temperature, etc. are set.

Further, the control unit 200 switches the switch 6 a of the relay box 6 at a predetermined timing, and connects the adsorption electrode 21 to the measuring device 10. Voltage _{V 2} measuring device 10 is measured is transmitted to the control unit 200, thereby, the control unit 200, based on the voltage _{V 2,} to calculate the self-bias voltage Vdc.

  A program for executing these operations and a recipe indicating processing conditions may be stored in a hard disk or a semiconductor memory. Further, the recipe may be set at a predetermined position and read out while being stored in a portable computer-readable storage medium such as a CD-ROM or DVD.

(Configuration of measuring device)
Next, an example of the configuration of the measuring apparatus 10 will be described. The measuring device 10 includes a filter 11, a copper disk 12, a copper plate 13, an acrylic plate 14, a probe 15, a surface potential meter 16, and a signal recording device 17. The probe 15 and the surface electrometer 16 constitute a potential measurement system 18.

  In FIG. 2, the relay box 6 is illustrated separately from the measuring device 10 for convenience of explanation, but the measuring device 10 includes the relay box 6. The relay box 6 switches the connection of the adsorption electrode 21 between the DC power supply 7 and the member having the capacitance of the measuring device 10. The relay box 6 connects the switch 6a of the relay box 6 to the measuring device 10 at the timing of measuring the self-bias voltage Vdc. The relay box 6 is an example of a switching unit that switches the connection of the adsorption electrode 21 to which high-frequency power is applied to a member having capacitance. A member having an acrylic plate 14 sandwiched between the copper disk 12 and the copper plate 13 is an example of a member having capacitance. The member having an electrostatic capacity is not limited to the configuration of the copper disc 12, the copper plate 13, and the acrylic plate 14, but can be configured by an insulated conductor.

  In the potential measurement system 18, the potential generated in the acrylic plate 14 between the copper disk 12 and the copper plate 13 is measured by the surface potentiometer 16 using a probe 15 provided in a non-contact manner on the surface of the copper disk 12. The potential measurement system 18 is an example of a measurement unit that measures a value corresponding to the amount of charge accumulated in a member having capacitance. The probe 15 may be in contact with the copper disk 12 or may be non-contact as long as the potential difference between the copper disk 12 and the copper plate 13 can be measured.

A filter 11 that removes high-frequency power is provided between the relay box 6 and the member having the electrostatic capacity to prevent the high-frequency power from propagating to the measuring device 10 side. When switched to the side switch 6a of the relay box 6 is connected to the member having an electrostatic capacity of the measuring device 10 from the side which is connected to the DC power supply 7, the measurement of the voltage V ₂ generated in member having a capacitance, in other words, it is possible to measure the voltage V ₂ of the adsorption electrode 21 in a floating state.

Specifically, the copper plate 13 is grounded, and the potential measured by the surface potentiometer 16 using the probe 15 provided in a non-contact manner on the surface of the copper disc 12 is the voltage of the adsorption electrode 21 in the floating state. the V _2. In addition, although the diameter of the copper disc 12 may be about 100 mm, for example, it is not restricted to this.

The voltage V ₂ measured by the surface potential meter 16 is stored in a signal recording device 17 connected to the surface potential meter 16. The signal recording device 17 may be an electronic device having a memory such as a PC or a tablet terminal, or may be a cloud computer installed on the cloud. Measured voltage V ₂ which is recorded on the signal recording apparatus 17 is transmitted to the control unit 200 is used by the controller 200 to control the etching rate and the deposition rate or the like of the plasma processing apparatus 100.

The amount of charge accumulated in the member having capacitance is affected by moisture. For this reason, it is preferable that the copper disc 12, the copper plate 13, the acrylic plate 14, and the probe 15 are provided in a vacuum vessel. Copper disc 12, copper plate 13, by placing an acrylic plate 14 and the probe 15 in a vacuum environment, it is possible to accurately measure the voltage V ₂ without being affected by the disturbance due to environmental.

[Measurement timing]
FIG. 3 shows an example of a processing cycle for processing the wafer W in the plasma processing apparatus 100. When the processing is started, first, the wafer W is loaded from the gate valve G of the plasma processing apparatus 100 (step S1). Next, a predetermined DC voltage is supplied from the DC power source 7 to the adsorption electrode 21, and the wafer W is electrostatically adsorbed to the electrostatic chuck 2a (step S2). Next, high frequency power is applied to the stage 2 (adsorption electrode 21), the process gas supplied from the gas supply unit 5 is turned into plasma, and the wafer W is subjected to plasma processing such as etching (step S3). The etching process is an example of a substrate process using plasma. The high-frequency power may be either the high-frequency power HF output from the first high-frequency power supply 3 or the high-frequency power LF output from the second high-frequency power supply 4, or both.

  Next, the DC voltage applied to the adsorption electrode 21 in step S2 is supplied to the adsorption electrode 21 with the opposite polarity and the same magnitude, and the wafer W is detached from the electrostatic chuck 2a (step S4). W is carried out from the gate valve G of the plasma processing apparatus 100 (step S5). Next, a cleaning process is performed (step S6).

  At this time, the processing of one wafer W is completed, and one processing cycle is completed. When the processing cycle of the next wafer W is resumed, surface treatment (cleaning such as treatment) of the electrostatic chuck 2a is performed (step S6), the next wafer W is loaded (step S1), and the processing after step S1 is performed. repeat.

In (1) cleaning process (S6) and (2) etching process (S3) of the above cycle, the relay box 6 switches the connection of the adsorption electrode 21 to the measuring device 10. That is, the relay box 6 switches the connection of the adsorption electrode 21 to the measurement device 10 at the timing when the processing of the wafer W by plasma or the cleaning process is being performed, and the voltage V ₂ of the adsorption electrode 21 in the floating state in the potential measurement system 18. Measure.

[Measurement sequence]
Next, an example of a measurement sequence in (1) cleaning process and (2) etching process will be described with reference to the measurement sequence charts of FIGS. FIG. 4 shows an example of a measurement sequence in the cleaning process. FIG. 5 shows an example of a measurement sequence in the etching process. The control unit 200 controls the measurement sequence in the cleaning process and the etching process.

(1) Measurement Sequence in Cleaning Process The measurement sequence in the cleaning process shown in FIG. 4 is performed during waferless dry cleaning (WLDC) or waferless treatment (WLT). When this measurement sequence is started, the adsorption electrode 21 is off, that is, not connected to the DC power source 7 but connected to the ground (reference potential).

  In this state, the measurement sequence is started at I in FIG. 4, and the switch 6a of the relay box 6 is switched to the side connected to the measuring apparatus 10 at II. Thereby, the connection of the adsorption electrode 21 is switched to the measuring apparatus 10, and the adsorption electrode 21 will be in a floating state.

Thereafter, the high frequency power is turned on in III, and the voltage V ₂ of the copper disk 12 is measured by the surface potentiometer 16 using the probe 15 in the potential measuring system 18 and recorded in the signal recording device 17. Next, the high frequency power is turned off at IV, the switch 6a of the relay box 6 is switched to the side connected to the DC power source 7 at V, and the measurement sequence is completed. The above measurement sequence is repeated.

(2) Measurement Sequence in Etching Process The measurement sequence in the etching process shown in FIG. 5 is performed while the wafer W is placed on the electrostatic chuck 2a and during plasma processing such as etching. When this measurement sequence is started, the adsorption electrode 21 is on, that is, connected to the DC power source 7.

  In this state, the measurement sequence is started at I in FIG. 5, and the switch 6a of the relay box 6 is switched to the side connected to the measuring apparatus 10 at II. Thereby, the connection of the adsorption | suction electrode 21 is switched to the measuring apparatus 10, and the adsorption | suction electrode 21 will be in a floating state.

Thereafter, the high frequency power is turned on in III, and the voltage V ₂ of the copper disk 12 is measured by the surface potentiometer 16 using the probe 15 in the potential measuring system 18 and recorded in the signal recording device 17. Next, the high frequency power is turned off at IV, the switch 6a of the relay box 6 is switched to the side connected to the DC power source 7 at V, and the measurement sequence is completed. When the above measurement sequence is repeated, if the plasma processing is in progress, the direct current voltage HV is applied to the adsorption electrode 21 by VI and the wafer W is electrostatically adsorbed to the stage 2, and then the measurement sequence of VII to XI is performed. In step XII, the application of the DC voltage HV to the adsorption electrode 21 is turned off, and the adsorption of the wafer W is stopped. The measurement sequences of VII to XI are the same as the measurement sequences of II to V described above.

  Thus, the relay box 6 switches the connection of the adsorption electrode 21 between the DC power source 7 and the measuring device 10. When the switch 6 a of the relay box 6 is switched to the measuring device 10, the adsorption electrode 21 enters a floating state, and then high frequency power is applied, and the gas is turned into plasma in the plasma processing space of the plasma processing device 100.

After applying high-frequency power, the surface potential meter 16, the voltage V ₂ of the copper disc 12 was measured using the probe 15, the control unit 200, based on the voltage V ₂ measured, to calculate the self-bias voltage Vdc . Hereinafter, a method for calculating the self-bias Vdc based on the measured voltage V ₂ will be described.

[Calculation method of self-bias Vdc]
An example of a model used for calculating the self-bias Vdc according to the present embodiment is shown in FIG. As shown in the enlarged view of a part of the surface of the electrostatic chuck 2a in FIG. 6, the area of the upper surface of the dot-shaped convex portion 22a formed on the surface of the electrostatic chuck 2a is _defined as b _dot. The height of 22a is set to d _dot . Further, the height from the attracting electrode 21 to the upper surface of the dots is T, and the area ratio of the area of the upper surface of the convex portion 22a to the area of the surface of the electrostatic chuck 2a is _ael .

The capacitance of the space portion between the dot-shaped convex portions 22a of the electrostatic chuck 2a and C _11, the capacitance between the adsorption electrode 21 under the space between the convex portions 22a and C _12, the convex portion 22a the capacitance between the upper surface of the adsorption electrode 21 and C _13.

The capacitance _{C 11} is calculated from the following equation (1).

The capacitance _{C 12} is calculated from the following equation (2).

The capacitance _{C 13} is calculated from the following equation (3).

In the equations (1) to (3), ε ₀ indicates a vacuum dielectric constant, and ε _r is a relative dielectric constant, that is, a dielectric constant ε of the dielectric layer 22 of the electrostatic chuck 2a and a vacuum dielectric constant ε _0. Ratio (= ε / ε ₀ ), and S represents the area of the adsorption electrode 21.

Since the electrostatic capacitances C ₁₁ , C ₁₂ , and C ₁₃ are fixed values obtained from design parameters, the electrostatic capacitance C ₁ of the electrostatic chuck 2a is expressed by the following equations (4) as electrostatic capacitances C ₁₁ , C _12. , C ₁₃ is substituted as a fixed value.

The capacitance C ₁ of the calculated electrostatic chuck 2a, the charge q accumulated in the model of the voltage V ₁ and the electrostatic chuck 2a which is applied to the electrostatic chuck 2a shown in FIG. 7 is an equivalent circuit of FIG. 6 ₁ and the following equation (5) is established by Coulomb's law.

C ₁ V ₁ = q ₁ (5)
The capacitance between the copper disc 12 and the copper plate 13 (ground) and C _2, the capacitance of the filter 11 and C _3, the voltage applied between and filter 11 of the copper disc 12 and the copper plate 13 and V _2. Further, assuming that the charges accumulated between the copper disk 12 and the copper plate 13 and in the filter 11 are q _{2 and} q ₃ , the following equation (6) is established according to Coulomb's law.

Incidentally, C ₂ capacitance is determined by the configuration of the copper disc 12 and the copper plate 13 and the acrylic plate 14, which is a fixed value determined from the design parameters. Similarly, the capacitance C ₃ is a fixed value determined from design parameters, which is determined by the configuration of the filter 11. The capacitances C ₁ , C ₂ , and C ₃ can be determined not only from fixed values determined from design parameters, but also from measured values obtained through measurement.

(C ₂ + C ₃ ) V ₂ = q ₂ + q ₁ (6)
The charge q ₁ accumulated in the electrostatic chuck 2 a, the charge q ₂ accumulated between the copper disk 12 and the copper plate 13, and the charge q ₃ accumulated in the filter 11 are expressed by the following equation (7). Holds.
q ₁ − (q ₂ + q ₃ ) = 0 (7)
When formula (7) is transformed,
q ₁ = (q ₂ + q ₃ ) (8)
Substituting (5) and (6) into (8),
C ₁ V ₁ = (C ₂ + C ₃ ) V ₂ (9)
When formula (9) is transformed,
V ₁ = V ₂ × (C ₂ + C ₃ ) / C ₁ (10)
V ₂ = V ₁ × C ₁ / (C ₂ + C ₃ ) (11)
From the equations (10) and (11), the self-bias voltage V _{dc in} FIG. 7 is calculated by the equation (12).
V _dc = V ₁ + V ₂ (12)
Substituting (10) into (12),
V _dc = V ₂ × (C ₂ + C ₃ ) / C ₁ + V ₂ (13)
Substituting the voltage V ₂ measured by the measuring apparatus 10 and the fixed capacitances C ₁ , C ₂ , and C ₃ into the equation (13), the self-bias voltage V _dc is calculated. The capacitance C ₁ is a combined capacitance value of C ₁₁ , C ₁₂ , and C ₁₃ obtained from the equation (4). The capacitances C ₁ , C ₂ and C ₃ are fixed values determined from design parameters.

As described above, according to the measurement method according to the present embodiment, the self-bias voltage V _dc is based on the equation (13), the voltage V ₂ that is the measurement value of the surface potentiometer 16, and the electrostatic chuck 2a. The electrostatic capacity C ₁ , the electrostatic capacity C _{2 of the} member having the electrostatic capacity, and the electrostatic capacity C ₃ of the filter 11 can be derived easily and accurately.

[Measurement result]
8 shows the measurement results and the voltage V ₂ by the measuring apparatus 10 according to the present embodiment, an example of a self-bias voltage V _dc was calculated from the voltage V _2. The horizontal axis in FIG. 8 indicates the pressure in the processing container C of the plasma processing apparatus 100. 8, by changing the pressure in the processing container C, shows the voltage V ₂ measured by the measuring device 10 as a measurement value. Further, based on the equation (13), the self-bias voltage V _dc converted from the capacitances C ₁ , C ₂ , C ₃ and the measured voltage V ₂ is shown as a converted value.

According to this, regardless of the change in the pressure in the processing container C, the three measured values and the converted values correspond one-to-one. That is, the voltage of the attracting electrode 21 in the floating state is measured by the potential measuring system 18 using a member having capacitance, and the self-bias voltage V _dc can be accurately calculated using the measured voltage V _2. Recognize. Further, from the equation (13), as the electrostatic capacity C _{2 of the} member having electrostatic capacity and the electrostatic capacity C ₃ of the filter 11 are smaller, the measured voltage V ₂ (measured value) and the self-bias voltage V _dc ( Conversion value) asymptotically.

As described above, according to the present embodiment, the plasma self-bias voltage V _dc can be easily measured simply by providing the plasma processing apparatus with the switching unit and the measurement apparatus without changing the design of the plasma processing apparatus. Can be done.

[Measuring method]
The deviation or cracking of the wafer W is caused by charges remaining on the surface of the electrostatic chuck 2a. The voltage V ₂ indicating the residual adsorption state on the surface of the electrostatic chuck 2 a that causes the wafer W to be displaced or cracked, that is, the charge storage easiness or the charged state is measured by the measuring device 10, and the equation (13) Based on this, the self-bias voltage V _dc can be calculated.

The measurement and calculation of the self-bias voltage V _dc of the voltage V _2, carried out in a state before the electrostatic chuck 2a which wafer W is loaded. Then, according to the calculated self-bias voltage V _dc , the residual chucking state of the surface of the electrostatic chuck 2a at that time is determined, and the electrostatic chuck performed by opening the cleaning process time of the electrostatic chuck 2a and the processing container C The presence / absence of execution of 2a maintenance or the like is controlled. In this way, the residual adsorption state on the surface of the electrostatic chuck 2a is determined in advance based on the calculated self-bias voltage V _dc without placing the wafer W, so that the pusher pin rises when the wafer W is unloaded. The risk of breaking the wafer W can be eliminated.

In other words, in the past, the surface potential of the electrostatic chuck 2a was measured by checking the residual adsorption by checking the magnitude of pin torque when the pusher pin is raised when the wafer W is unloaded, or by inserting a probe or a sensor. On the other hand, according to the measurement method described above, while maintaining the risk of breaking the wafer W, the residual adsorption state on the surface of the electrostatic chuck 2a is determined according to the value of the self-bias voltage _Vdc , and maintenance is performed. It can be determined whether or not. Thereby, based on the determination result, it is possible to obtain a guideline for optimizing the operation method and improving the operation such as the frequency of cleaning performed according to the self-bias voltage V _dc , the cleaning processing time, and the execution timing of other maintenance. .

For example, an example of a measurement method according to an embodiment including the above determination will be described with reference to FIGS. FIG. 9 is a graph illustrating an example of correlation information between the self-bias voltage V _dc and the deposition time according to an embodiment. FIG. 10 is a diagram illustrating an example of a process performed in advance to collect correlation information illustrated in the graph of FIG. FIG. 11 is a flowchart illustrating an example of a measurement method according to an embodiment.

In FIG. 9, the correlation information between the accumulated value of the deposition time on the horizontal axis and the self-bias voltage V _dc on the vertical axis was derived based on the measured voltage V ₂ between the copper disk 12 and the copper plate 13. The accumulated value of the deposition time of the deposit on the horizontal axis is equal to the accumulated value of the application time of the high frequency power applied by supplying the deposition gas, and is proportional to the thickness of the deposit deposited on the surface of the electrostatic chuck 2a. . The accumulated value of the deposition time on the horizontal axis is an example of a value indicating the residual adsorption state of the electrostatic chuck 2a. However, the value indicating the residual adsorption state of the electrostatic chuck 2a is not limited to the accumulated value of the deposition time, and may be a measured value of the thickness of the deposit on the electrostatic chuck 2a, or the application time of the high-frequency power. May be a cumulative value.

Further, the self-bias voltage V _{dc on} the vertical axis is an example of a value corresponding to the measured charge amount. Value corresponding to the measured electric charge amount is not limited to the self-bias voltage V _dc was calculated from the voltage V _2, may be a voltage V ₂ measured.

In this embodiment, the correlation information between the accumulated value of the deposition time in FIG. 9 and the self-bias voltage V _dc is derived by the steps (a) to (i) in FIG. However, the graph indicating the correlation between the value corresponding to the measured charge amount and the value indicating the residual adsorption state of the electrostatic chuck 2a is not limited to a straight line.

For example, in the process of FIG. 10A, the measurement apparatus 10 places the wafer W on the electrostatic chuck 2a in a state where there is no deposit on the surface (that is, the deposition time is 0 second), and plasma of O ₂ gas. generated to measure the voltage V ₂ between the copper disc 12 and the copper plate 13. Based on the equation (13), the self-bias voltage V _dc indicating the residual adsorption state of the surface of the electrostatic chuck 2a at the initial time was calculated from the voltage V _{2 of the} measurement result. The data at this time is V _dc (= −70 V) when the deposition time in FIG. 9 is 0 (s), and this data is stored in the storage unit such as the RAM 215 of the control unit 200.

  Next, in the process of FIG. 10B, after unloading the wafer W, a high frequency power is applied for a predetermined time (in this embodiment, 30 seconds) while supplying a CF-based gas which is an example of a deposition gas. A plasma of a system gas was generated, and a deposit R, which is a CF-based polymer, was deposited on the surface of the electrostatic chuck 2a.

Next, in the step of FIG. 10C, the wafer W is placed on the electrostatic chuck 2a, plasma of O ₂ gas is generated, and the voltage V ₂ between the copper disk 12 and the copper plate 13 is measured. did. Based on the equation (13), a self-bias voltage V _dc indicating the residual adsorption state of the surface of the electrostatic chuck 2a at this time was calculated from the voltage V _{2 of the} measurement result. The data at this time is V _dc (= −68 V) when the deposition time in FIG. 9 is 30 seconds, and this data was stored in the storage unit such as the RAM 215 of the control unit 200.

  Next, in the process of FIG. 10D, after unloading the wafer W, high-frequency power is applied for a predetermined time (in this embodiment, another 30 seconds) while supplying the CF-based gas, thereby generating CF-based gas plasma. Then, a CF polymer deposit R was further deposited on the surface of the electrostatic chuck 2a.

Next, in the step of FIG. 10E, the wafer W is placed on the electrostatic chuck 2a, O ₂ gas plasma is generated, and the voltage V ₂ between the copper disc 12 and the copper plate 13 is measured. did. Then, based on the equation (13), a self-bias voltage V _dc (= −66 V) indicating a residual adsorption state on the surface of the electrostatic chuck 2 a at this time was calculated from the voltage V _{2 of the} measurement result. The data at this time is V _dc when the deposition time in FIG. 9 is 60 seconds (= 30 + 30), and this data is stored in the storage unit such as the RAM 215 of the control unit 200.

In the steps of FIGS. 10 (f) and (g), FIGS. 10 (h) and (i), the same operation as that of the steps of FIGS. 10 (c) and 10 (d) was repeated twice. That is, in the measurement of FIG. 10G, V _dc (= −64 V) when the deposition time of FIG. 9 is 90 seconds is calculated, and in the measurement of FIG. 10H, the deposition time of FIG. 9 is 120 seconds. V _dc (= −62 V) at this time was calculated, and these data were stored in a storage unit such as the RAM 215 of the control unit 200.

By performing such measurement in advance, the storage unit accumulates correlation information indicating the correlation between the deposition time and the self-bias voltage V _dc as shown in FIG. Note that the correlation information indicating the correlation between the deposition time and the self-bias voltage V _dc in FIG. 9 indicates a correlation between a value corresponding to the charge amount measured in advance and a value indicating the residual adsorption state of the electrostatic chuck 2a. It is an example of correlation information.

  The correlation information of FIG. 9 accumulated in this way is referred to in the measurement method according to the embodiment shown in FIG. The measurement method shown in FIG. 11 is performed by the control unit 200 before the wafer W is loaded, and includes a determination step for determining whether or not to perform maintenance such as a cleaning process. Thereby, according to the measurement method according to the present embodiment, in a predetermined case, since maintenance such as a cleaning process is performed before the wafer W is carried in, the wafer W due to residual adsorption on the surface of the electrostatic chuck 2a. Slippage and cracking can be prevented.

When the processing of FIG. 11 is started, the control unit 200 switches the switch 6 a of the relay box 6 and connects the adsorption electrode 21 to the measuring device 10. Measuring device 10 measures the voltage _{V 2} (step S10). Voltage _{V 2} measured is transmitted to the control unit 200, thereby, the control unit 200, based on the voltage _{V 2,} to calculate the self-bias voltage _{V dc} (step S12).

Next, the control unit 200 determines whether or not the calculated absolute value of the self-bias voltage V _dc exceeds a predetermined threshold Th ₁ (Step S14). When the control unit 200 determines that the calculated absolute value of V _dc does not exceed the predetermined threshold Th ₁ , the residual chucking state of the electrostatic chuck 2 a is such that the wafer W is cracked when the wafer W is discharged and unloaded. It is determined that it is not, and this processing ends.

On the other hand, in step S14, the control unit 200, the absolute value of the calculated self-bias voltage V _dc is determined to exceed the threshold value Th ₁ with a predetermined threshold value Th in which the absolute value of self-bias voltage V _dc is predetermined _It is determined whether it exceeds ₂ (step S16).

For example, the threshold Th ₁ and the threshold Th ₂ are in a relationship in which the absolute value of the threshold Th ₁ is smaller than the absolute value of the threshold Th ₂ as shown in FIG. For example, it the threshold Th _1, when the absolute value of self-bias voltage V _dc is greater than the threshold value Th ₁ is Pintoruku pusher pin is high, some degree of residual adsorption state that cracks on the wafer W occurs during neutralization It is an example of the parameter | index which shows.

Further, for example, the threshold Th ₂ is a residual adsorption state in which there is a high possibility that the wafer W will be cracked during static elimination when the absolute value of the self-bias voltage V _dc is larger than the threshold Th ₂ , and the processing container C is opened. It is an example of the parameter | index which shows that it is necessary to perform a maintenance.

Therefore, in step S16, when the control unit 200 determines that the absolute value of the self-bias voltage V _dc exceeds a predetermined threshold Th ₂ , the processing unit C is opened and the surface of the electrostatic chuck 2a is wiped with alcohol. Control is performed to perform maintenance, and this processing ends.

On the other hand, in step S16, the control unit 200 determines that the absolute value of self-bias voltage V _dc is not exceeded the threshold value Th ₂ predetermined, and the cleaning treatment time was longer than usual, the wafer-less dry cleaning The process is terminated. As an example of making the cleaning processing time longer than usual, for example, when the normal cleaning processing time is 20 seconds, there is a control of making the cleaning processing time longer to about 80 seconds.

According to this, with reference to the storage unit storing the correlation information between the self-bias voltage V _dc and the deposition time, the residual surface of the electrostatic chuck 2 a based on the self-bias voltage V _dc calculated from the measured voltage V _2. A determination step for determining the suction state is executed. In the determination step, when the absolute value of the measured calculated self-bias voltage V _dc is greater than at least one of the predetermined threshold Th _{1 and the} threshold Th ₂ with reference to the storage unit, the control unit 200 Then, it is determined that the cleaning process or other maintenance in the electrostatic chuck 2a or the processing container C is executed. In the determination step, the residual adsorbed state of the surface of the electrostatic chuck 2a based on the voltage V ₂ measured may be determined.

As a result, according to the calculated self-bias voltage V _dc , a guideline for optimizing the operation method and improving the operation, such as whether the cleaning frequency, the cleaning time, or the timing of performing maintenance of the electrostatic chuck 2a, etc., is obtained. be able to.

  As mentioned above, although the measuring apparatus, the measuring method, and the plasma processing apparatus were demonstrated by the said embodiment, the measuring apparatus, the measuring method, and plasma processing apparatus concerning this invention are not limited to the said embodiment, In the scope of the present invention. Various modifications and improvements are possible. The matters described in the above embodiments can be combined within a consistent range.

  The substrate processing apparatus according to the present invention is applicable to any type of capacitively coupled plasma (CCP), inductively coupled plasma (ICP), radial line slot antenna, electron cyclotron resonance plasma (ECR), and Helicon wave plasma (HWP). .

  In the present specification, the wafer W has been described as an example of the substrate. However, the substrate is not limited to this, and may be various substrates used in LCD (Liquid Crystal Display) and FPD (Flat Panel Display), a photomask, a CD substrate, a printed circuit board, and the like.

DESCRIPTION OF SYMBOLS 1 Gas shower head 2a Electrostatic chuck 2b Base 3 1st high frequency power supply 4 2nd high frequency power supply 5 Gas supply part 6 Relay box 8 Focus ring 9 Exhaust device 10 Measuring device 11 Filter 12 Copper disk 13 Copper plate 14 Acrylic plate 15 Probe 16 Surface Potential Meter 17 Signal Recording Device 18 Potential Measurement System 21 Adsorption Electrode 22 Dielectric Layer 100 Plasma Processing Device 200 Control Unit

Claims (14)

A switching unit that switches the connection of the electrode to which a DC voltage is applied, which is an electrode in an electrostatic chuck disposed in the plasma processing apparatus;
A member having a capacitance connected to the switching unit;
A measurement unit that measures a value corresponding to the amount of charge accumulated in the member having the capacitance;
Measuring device. The switching unit switches the connection of the electrode between the DC power source and the member having the capacitance,
The measuring apparatus according to claim 1. Between the switching unit and the member having the capacitance, a filter for removing high-frequency power is provided.
The measuring apparatus according to claim 1 or 2. The switching unit switches the connection of the electrode to a member having the capacitance while performing substrate processing or cleaning processing by plasma,
The measuring unit measures a value corresponding to an amount of charge accumulated in the member having the capacitance during the substrate processing or the cleaning processing;
The measuring apparatus as described in any one of Claims 1-3. The switching unit applies high-frequency power after switching the connection of the electrodes to the member having the capacitance.
The measuring apparatus as described in any one of Claims 1-4. Based on a value corresponding to the measured charge amount, a plasma self-bias voltage is measured.
The measuring apparatus as described in any one of Claims 1-5. The measurement unit has a probe provided in non-contact or contact with the surface of the member having the capacitance,
The member having the capacitance and the probe are provided in a vacuum container.
The measuring apparatus as described in any one of Claims 1-6. A switching step of switching connection of electrodes in the electrostatic chuck disposed in the plasma processing apparatus;
An application step of applying high frequency power to the electrostatic chuck;
A measurement step of measuring a value corresponding to the amount of charge accumulated in a member having a capacitance connected to the electrode by the switching;
Measuring method. In the switching step, the connection of the electrode is switched between a DC power source and the member having the capacitance.
The measurement method according to claim 8. After the switching step switches the connection of the electrodes to the member having the capacitance, the applying step applies high-frequency power.
The measurement method according to claim 8 or 9. In the switching step, the connection of the electrode is switched to the member having the capacitance during the substrate processing or the cleaning processing by plasma,
The measurement step measures a value corresponding to the amount of charge accumulated in the member having the capacitance during the substrate process or the cleaning process.
The measurement method according to claim 10. Based on a value corresponding to the measured charge amount, referring to a storage unit that stores correlation information between a value corresponding to the charge amount measured in advance and a value indicating the residual adsorption state of the electrostatic chuck. A determination step of determining the residual adsorption state;
The measuring method as described in any one of Claims 8-11. In the determination step, when it is determined that the absolute value of the value corresponding to the measured charge amount exceeds a predetermined threshold with reference to the storage unit, it is determined that the cleaning process or the electrostatic chuck maintenance is performed. To
The measurement method according to claim 12. A high frequency power supply for applying high frequency power;
A switching unit that switches the connection of the electrode to which a DC voltage is applied, which is an electrode in an electrostatic chuck disposed in the plasma processing apparatus;
A member having a capacitance connected to the switching unit;
A measurement unit that measures a value corresponding to the amount of charge accumulated in the member having the capacitance;
A plasma processing apparatus.

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