JP5651041B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

  An object of the present invention is to suppress an inrush current generated when a DC voltage required for electrostatic adsorption is applied, stably operate a plasma processing apparatus, reduce product defects, and improve process performance.

  In a plasma processing apparatus that performs thin film formation, plasma etching, and the like in a semiconductor manufacturing process, electrostatic adsorption is used as a method of holding a substrate to be processed such as a silicon wafer on a stage. The electrostatic adsorption does not require mechanical contact with the substrate, and can generate an electrostatic adsorption force on the entire back surface of the substrate. In particular, electrostatic attraction using the Johnson Rahbek effect can provide a large electrostatic attraction force. The Johnson Rabeck effect is a large electrostatic charge that accumulates charges in a narrow space at the interface by passing a current (hereinafter referred to as an “ESC (Electrostatic Chuck) current”) through the interface between the electrostatic adsorption film and the substrate on the stage surface. It is what gains adsorption power.

  The electrostatic adsorption by the Johnson Rahbek effect has a strong temperature dependency although a large electrostatic adsorption force can be obtained. This is because the electrostatic adsorption film in contact with the substrate has a strong temperature dependence. For example, when the stage temperature is increased to around 160 ° C., the resistance value of the electrostatic adsorption film decreases to about 1/1000 compared to the resistance value at room temperature. Therefore, the ESC current also increases as the stage temperature increases.

  On the other hand, a phenomenon occurs in which an ESC current larger than an ESC current flowing in a steady state flows at the moment when an adsorption voltage required for adsorption is applied after plasma ignition. An ESC current that is generated at the moment when the adsorption voltage is applied and that is much larger than the ESC current that flows in a steady state is called an inrush current. When the stage temperature is raised, the resistance value of the electrostatic adsorption film decreases, so that the generated inrush current takes a larger value than the inrush current flowing at normal temperature.

  Excessive ESC current flowing during processing creates a serious problem in operating the device. After the plasma is ignited, the ESC current flows into the plasma, so that the plasma potential rises. When an excessive ESC current is supplied to the plasma and the plasma potential rises significantly, local discharge may occur at the minute protrusions in the processing chamber. Local discharge in the processing chamber causes the generation of foreign matter. In addition, excessive ESC current may flow through the substrate, which may affect device characteristics on the substrate.

  FIG. 1 is an enlarged view of a contact surface between a stage 4 installed in a processing chamber of the plasma processing apparatus and a substrate 3 installed on the stage 4. FIG. 1 shows an equivalent circuit of the electrostatic adsorption film 15 and the substrate 3 relating to the ESC current.

  The principle of electrostatic attraction by the Johnson Rahbek effect and generation of inrush current will be described with reference to FIG. The stage 4 on which the substrate is installed is configured by laminating a conductor and an insulating electrostatic adsorption film 15. The electrostatic adsorption film 15 is made of a dielectric. Since the surface of the electrostatic adsorption film 15 has surface roughness, there are actually minute irregularities, and a space 16 exists between the substrate and the surface of the electrostatic adsorption film 15.

  Since the surface finishing accuracy of the back surface of the substrate is better than that of the surface of the electrostatic adsorption film 15, it can be modeled by contact between the unevenness of the electrostatic adsorption film 15 and the plane of the back surface of the substrate 3. In terms of an equivalent circuit, it is formed by a parallel circuit of the resistance Rb and the capacitance Cb of the electrostatic adsorption film 15, the contact resistance Rg of the convex part of the electrostatic adsorption film 15 and the back surface of the substrate, the unevenness of the electrostatic adsorption film 15, and the back surface of the substrate. The parallel circuit of the capacitance Cg of the space and the parallel circuit of the resistance Rw and the capacitance Cw of the substrate 3 can be modeled as a circuit connected in series.

  The electrostatic adsorption utilizing the Johnson Rahbek effect is characterized in that a minute ESC current is allowed to flow between the surface of the electrostatic adsorption film 15 and the substrate 3. When an ESC current is passed through the electrostatic adsorption film 15 and the substrate 3, charges are stored in the capacitors Cw, Cg, and Cb. In particular, since the space 16 between the surface of the electrostatic adsorption film 15 and the back surface of the substrate 3 is a very narrow space formed by the surface roughness, the capacitor Cg can store a large amount of charge. Therefore, by applying an adsorption voltage of several hundred volts, an ESC current flows between the substrate 3 and the stage 4 to obtain an adsorption force.

  However, immediately after the adsorption voltage is applied, no charge is accumulated in any of the capacitors Cw, Cg, and Cb. Alternatively, even if charges are accumulated by the self-bias voltage, the charges are very small, and no charges are accumulated in the capacitors Cw, Cg, and Cb. Therefore, immediately after the adsorption voltage is applied, a large current flows until charges are accumulated in the capacitors Cw, Cg, and Cb. This is the cause of the inrush current.

In a circuit constituted by a resistor and a capacitor as shown in FIG.

In the equation (1), E is a voltage output from the DC power supply 9, R is a combined impedance of the circuit, and C is a combined capacitance. The DC power supply 9 itself has a time constant. The voltage E output from the DC power supply 9 is expressed by equation (2).

In the equation (2), τ is a time constant of the DC power supply 9, and E ₀ is a steady voltage of the DC power supply 9. Therefore, the ESC current flowing in the circuit is expressed as follows.

  As a countermeasure against the occurrence of an inrush current, there is a technique described in Patent Document 1. This optimizes the time constant τ of the DC power supply 9 in accordance with the characteristics of the electrostatic adsorption film 15 on the stage 4 and prevents the inrush current by applying the adsorption voltage in a slope shape.

  On the other hand, there is a technique described in Patent Document 2 for controlling the ESC current. This sets the value of the ESC current necessary for electrostatic adsorption, and maintains the adsorption voltage so that the ESC current flowing during the process maintains the set value. According to Patent Document 2, if the technique of Patent Document 2 is used, the ESC current is controlled within a set range even when the processing conditions such as the stage temperature are changed.

JP-A-8-181118 JP 2007-48986 A

  However, the above-described technique is insufficient as a countermeasure against an increase in ESC current due to an increase in stage temperature, particularly an increase in inrush current.

  The technique described in Patent Document 1 proposes to reduce the inrush current I (t) by optimizing the time constant τ in the equation (3). However, since the resistance value of the electrostatic adsorption film 15 (included in R in the equation (3)) has a strong temperature dependency, the time constant τ needs to be optimized every time the stage temperature is changed. In an actual plasma processing apparatus, it is difficult to accurately measure the synthetic impedance R and the synthetic capacitance C of the circuit.

  The technique of Patent Document 2 has insufficient measures against inrush current. When the inrush current does not exceed the set value of the ESC current in Patent Document 2, there is a possibility that the ESC current flowing in a steady state after the occurrence of the inrush current becomes small and the electrostatic attraction necessary for processing cannot be obtained. There is. On the contrary, when the ESC current that flows in a steady state is controlled so as not to exceed the set value of the ESC current in Patent Document 2, the inrush current may exceed the set value of the ESC current. A method of applying the adsorption voltage stepwise has also been proposed, but introduction of heat transfer gas has not been studied as described below.

  The introduction of heat transfer gas to the back surface of the substrate 3 in the plasma processing apparatus will be described. The plasma processing apparatus currently in operation employs a method of improving the heat conduction between the stage 4 and the substrate 3 by introducing a heat transfer gas such as helium into the back surface of the substrate 3 being processed and controlling the temperature of the substrate 3. Has been. By introducing the heat transfer gas to the back surface of the substrate 3, pressure is generated in the space 16 formed by the substrate 3 and the electrostatic adsorption film 15 (hereinafter referred to as “back surface pressure”).

  This back surface pressure must be smaller than the electrostatic attracting force generated on the back surface of the substrate 3 and the electrostatic attracting film 15. If the back surface pressure exceeds the electrostatic attraction force, the substrate 3 may be peeled off from the stage, and serious problems such as displacement of the substrate 3 and damage to the substrate 3 may occur. In order to prevent such a problem, it is essential that an electrostatic attraction force equal to or higher than the back surface pressure is generated when the heat transfer gas is introduced. However, Patent Document 1 and Patent Document 2 do not consider introduction of heat transfer gas to the back surface of the substrate.

  When the technique of Patent Document 1 is used, there is a possibility that the heat transfer gas is introduced into the back surface of the substrate 3 while the adsorption voltage is applied in a slope shape. If the adsorption voltage necessary for electrostatic adsorption is not applied at the time when the heat transfer gas is introduced, the generated electrostatic adsorption force is less than the back pressure and the substrate 3 may be peeled off from the stage 4. Is expensive.

  The technique of Patent Document 2 proposes a method of gradually increasing the ESC current by applying an adsorption voltage stepwise as a method of controlling the ESC current. However, if the heat transfer gas is introduced while the adsorption voltage is being applied stepwise, if a sufficient electrostatic adsorption force is not generated between the substrate 3 and the electrostatic adsorption film 15, the substrate 3 is likely to peel off.

  In view of the above, it is possible to respond to changes in operating conditions such as stage temperature changes, prevent inrush currents and excessive ESC currents from flowing, and at the time of introducing heat transfer gas, the electrostatic adsorption force that exceeds the back pressure It is necessary to have a technology that makes it necessary to have

  In Patent Documents 1 and 2, the suppression of the inrush current until the heat transfer gas starts to be supplied is not considered. For this reason, this invention provides the plasma processing apparatus which can suppress an inrush current while fully ensuring the electrostatic attraction force of a sample.

  The objective of this invention is providing the plasma processing apparatus and the plasma processing method which solved the said subject.

  In order to achieve the above object, a plasma processing apparatus of the present invention includes a processing chamber, a sample stage provided in the processing chamber, on which a sample is placed, and the sample on the surface of the sample stage via an electrostatic adsorption film. A plasma processing apparatus for plasma-treating the sample, the current flowing between the sample stage and the sample via the electrostatic adsorption film Current measuring means for measuring the voltage, and voltage control for controlling the DC power supply so that the DC voltage is applied stepwise to the sample stage until the current value measured by the current measuring means falls within a preset range. Means, and when the measured current value reaches a preset range, the temperature of the coolant for adjusting the temperature of the sample flowing in a groove provided in the sample table is transferred to the sample, The sample and the static Characterized by a control unit for starting supply between said groove heat transfer gas supplied to the sample between the groove provided in the adsorption film.

  In addition, the plasma processing method of the present invention includes a processing chamber, a sample table provided in the processing chamber, on which a sample is placed, and a DC voltage for adsorbing the sample on the surface of the sample table via an electrostatic adsorption film. A plasma processing method of a plasma processing apparatus for plasma processing the sample, the current measuring means flowing between the sample stage and the sample through the electrostatic adsorption film Measuring the current, and controlling the direct current power source so that the direct current voltage is applied to the sample stage step by step until the current value measured by the current measuring means falls within a preset range by the voltage control means; When the measured current value reaches a preset range by the control unit, the temperature of the temperature adjusting refrigerant flowing in the groove provided in the sample table is transferred to the sample, Said Charges and wherein the initiating supply between said groove heat transfer gas supplied to the sample between the groove provided in the electrostatic adsorption film.

  According to the present invention, it is possible to prevent an excessive ESC current from flowing until the heat transfer gas starts to be supplied when the adsorption voltage is applied.

FIG. 1 is a diagram for explaining an equivalent circuit of a stage according to an embodiment of the present invention. FIG. 2 is a schematic view for explaining the structure of the plasma processing apparatus according to the embodiment of the present invention. FIG. 3 is a flowchart at the time of plasma ignition in the present invention. FIG. 4 is a timing chart at the time of plasma ignition in the present invention. FIG. 5 shows a measurement system of Test Example 1 in the present invention. FIG. 6 shows the results of Test Example 3 in the present invention.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 2 is a view showing a plasma etching apparatus used when performing the plasma processing method of the present invention. The inside of the processing chamber of the present plasma etching apparatus can electrostatically adsorb the discharge unit 2 made of quartz or ceramic non-conductive material forming the plasma generation unit, the substrate 3 to be processed, and the substrate 3. A stage 4 having an electrostatic adsorption film 15 and an exhaust port 5 for evacuating the processing chamber to a predetermined pressure.

  The discharge unit includes a plasma generating antenna 1, a high frequency power source 6, and a matching unit 7. The stage 4 includes a high-frequency power source 8, a DC power source 9 that outputs an adsorption voltage, a current sensor 10, a heat transfer gas inlet 11 that supplies heat transfer gas to the back surface of the substrate, and a high frequency applied to the substrate 3. It has a Vpp sensor 12 that detects a peak-to-peak value of bias power (hereinafter referred to as Vpp) and a control unit 13.

  In plasma etching, first, the processing chamber is controlled to a predetermined pressure by evacuation. Next, electromagnetic waves are introduced into the processing chamber from the high frequency power source 6 through the matching unit 7 and the antenna 1. The introduced electromagnetic wave turns the gas in the processing chamber into plasma. Etching is performed using the plasma 14. A high frequency bias is applied from a high frequency power supply 8 to the stage 4 on which the substrate 3 is placed for the purpose of controlling the processing shape.

  The current sensor 10 measures an ESC current flowing through a circuit formed by the DC power supply 9, the stage 4, the substrate 3, the plasma 14, and the wall of the processing chamber. The Vpp sensor 12 detects Vpp on the substrate 3 and sends data to the control unit 13. The control unit 13 calculates a self-bias voltage from the value of Vpp sent based on the equation (4). The control unit 13 determines the value from the value of the ESC current and the calculated value of the self bias voltage and controls the adsorption voltage.

  A first embodiment of the present invention will be described with reference to the flowchart of FIG. 3 and the timing chart of FIG. Example 1 is a case where a single layer film is etched using the present invention.

  Before starting plasma etching by this apparatus, it is necessary to set the control range of the ESC current, the initial value of the suction voltage, the change width of the suction voltage, the change interval of the suction voltage, and the self-bias ratio.

  A detailed description of the above five items will be given below. The ESC current control range, adsorption voltage change value, and adsorption voltage change interval can be used in common for changing the stage temperature, changing the etching gas, and changing the output value of the high-frequency power supply. Is possible.

  The control range of the ESC current is a range of the ESC current value controlled during the etching of the substrate 3. The ESC current must be capable of obtaining an electrostatic adsorption force that can sufficiently withstand the back surface pressure caused by the heat transfer gas introduced to the back surface of the substrate 3.

  The initial value of the adsorption voltage is the value of the adsorption voltage that is output first after plasma ignition. Since this value is applied for the purpose of suppressing the inrush voltage when the adsorption voltage is applied, the self-bias voltage or 0 is set.

  The change width of the suction voltage is a value of the suction voltage that is changed by one change when the suction voltage is changed stepwise as shown in FIG. When this value is large, a large peak appears in the ESC current value at the moment when the adsorption voltage is changed. It is better that the change width of the ESC current is as small as possible so that no peak occurs in the ESC current value.

  The change interval of the adsorption voltage refers to the time from the change of the adsorption voltage to the change when the adsorption voltage is changed stepwise as shown in FIG.

The self-bias ratio is a coefficient used when calculating the self-bias voltage from the value of Vpp on the substrate 3. The self-bias voltage, Vpp, and self-bias ratio are in the relationship of equation (4).

  After completing the above settings, plasma etching is started. A method for controlling the application of the adsorption voltage and the introduction of heat transfer gas during etching will be described with reference to FIG.

  First, the processing chamber is controlled to a predetermined pressure by evacuation. Thereafter, the current sensor 10 and the Vpp sensor 12 transmit the ESC current value and the Vpp monitor value to the control unit 13 as needed. After confirming that the processing chamber has a predetermined pressure, in step S301, electromagnetic waves are introduced from the high frequency power source 6 through the matching unit 7 and the antenna 1 to ignite plasma. A high frequency bias is applied from the high frequency power supply 8 to the stage 4 simultaneously with the plasma ignition or after the ignition (FIG. 4-T1).

  After starting the application of the high frequency bias, in step S302, the Vpp sensor 12 detects Vpp after the application of the high frequency bias and sends a Vpp monitor value to the control unit 13. In step S303, the control unit 13 calculates a self-bias voltage from the Vpp monitor value. The calculation formula to be calculated is formula (4). At the stage where the self-bias voltage is calculated, in step S304, the initial value of the adsorption voltage is output from the DC power source 9 (FIG. 4-T2).

  After applying the adsorption voltage initial value, the current sensor 10 detects the value of the ESC current flowing through the circuit in step S305. The control unit 13 inputs an ESC current value from the current sensor 10. In step S306, the control unit 13 determines whether the value of the input ESC current is within the control range of the ESC current input in advance or out of the control range.

  In step S306, when the value of the ESC current is outside the control range (No), in step S307, the control unit 13 sends a signal to the DC power supply 9 so as to apply the adsorption voltage stepwise. The DC power supply 9 receives a signal from the control unit 13 and changes the suction voltage stepwise. For example, if the value of the ESC current input by the control unit 13 is below the control range, the adsorption voltage is applied stepwise so as to increase the ESC current. Conversely, if the value of the ESC current input by the control unit 13 exceeds the control range, the adsorption voltage is applied stepwise so as to reduce the ESC current. (FIG. 4-T3-T5).

  Note that the ESC current value, which is a determination material when changing the adsorption voltage, is desirably data acquired after at least 10 ms has elapsed since the adsorption voltage was changed. This is because, as described in the timing chart of FIG. 4, there is a possibility that a peak occurs in the ESC current slightly at the moment when the adsorption voltage is changed.

  In step S306, after the control unit 13 confirms that the ESC current is within the control range (Yes), in step S308, introduction of the heat transfer gas to the back surface of the substrate 3 is started (FIG. 4-T6). At this point, a sufficient electrostatic attraction force is generated between the substrate 3 and the electrostatic adsorption film 15 on the stage 4 to withstand the introduction of the heat transfer gas to the back surface. For this reason, even if the heat transfer gas is introduced into the back surface of the substrate 3, the substrate 3 is not peeled off.

  The controller 13 records the voltage difference ΔV between the adsorption voltage and the self-bias voltage of the substrate 3 when the ESC current is controlled within the set range. The following etching is performed while controlling the adsorption voltage in accordance with the variation of Vpp so as to maintain the voltage difference ΔV recorded by the control unit 13 in step S309.

  By executing the control method as described above and applying the adsorption voltage stepwise, the ESC current is gradually increased and the inrush current is reduced. In addition, by applying the suction voltage while detecting the ESC current, it is possible to automatically derive the best suction voltage for electrostatic suction.

In order to demonstrate the usefulness of the present invention, the inventors conducted tests. In addition, in the following test examples, a substrate to be processed is placed on a stage on which an electrostatic adsorption film having a thickness of 0.6 mm, a surface roughness of 0.8 μm, and a resistivity of 8.0 × 10 ¹¹ Ω · cm is placed. An 8-inch silicon wafer is installed and tested.

  In Test Examples 1 and 2, the ESC current necessary for obtaining the electrostatic adsorption force was estimated, and the control range of the ESC current in the present invention was examined.

[Test Example 1]
Test Example 1 is an examination of the value of the ESC current that can obtain a sufficient electrostatic attraction force. FIG. 5 shows the measurement system used in Test Example 1. A test apparatus 17 is prepared outside the vacuum container. The conducting wire 18 is connected to the stage shaft 19 from the test apparatus 17. The stage shaft 19 and the stage 4 are equipotential. An 8-inch silicon wafer is set as the substrate 3 on the stage 4. A conductive wire 20 is pasted on the substrate 3 with Al tape. The conducting wire 20 goes out of the vacuum vessel through the connector 21 and is connected to the test apparatus 17. The test device 17 applies an adsorption voltage and detects an ESC current flowing in a circuit constituted by the test device 17, the conducting wire 18, the stage shaft 19, the substrate 3, and the conducting wire 20.

  After assembling the above circuit, the test apparatus 17 is started and an adsorption voltage is applied. After the adsorption voltage is applied and the substrate 3 is electrostatically adsorbed, the heat transfer gas is introduced from the heat transfer gas inlet 11 at a flow rate of 5 ml / min. Note that helium was used as the heat transfer gas. At this time, the back pressure generated in the pipe into which the heat transfer gas is introduced and in the space 16 between the electrostatic adsorption film 15 and the substrate 3 is measured by the pressure gauge 22. As the heat transfer gas is introduced, the back pressure increases.

  However, when the back surface pressure becomes larger than the electrostatic attraction force, the substrate 3 is peeled off from the stage 4, and the back surface pressure suddenly decreases at that moment. A value obtained by subtracting the weight of the substrate 3 from the back surface pressure immediately before the decrease in the back surface pressure is the electrostatic adsorption force generated between the substrate 3 and the electrostatic adsorption film 15. The weight of the substrate 3 is about 0.5 kPa according to the inventors' tests.

  Table 1 shows the relationship between the ESC current generated when the adsorption voltage of Test Example 1 is applied and the electrostatic adsorption force. Since no self-bias voltage is generated in this test, the voltage difference ΔV is the same as the adsorption voltage. The temperature of the stage 4 is controlled at 90 ° C. In Test Example 1, it is considered that a sufficient electrostatic attraction force is generated when the back pressure reaches 2.5 kPa, and the measurement is stopped.

From Table 1, it can be seen that an ESC current of 0.05 mA or more is necessary to obtain an electrostatic attraction force of 2.5 kPa or more.

[Test Example 2]
Test Example 2 shows the relationship between the ESC current and the stage temperature. Table 2 shows the test conditions of Test Example 2, and Table 3 shows the results of Test Example 2. The reason why the voltage difference ΔV in this test was set to 600 V reflects the result of Test Example 1, and the safety factor doubled from 300 V, which is a voltage difference ΔV capable of obtaining an electrostatic adsorption force of 2.5 kPa or more. It is a thing.

As shown in the results of Table 3, the higher the stage temperature, the larger the ESC current. From Table 2, when the condition for obtaining an optimal ESC current at a stage temperature of 40 ° C. is used at a stage temperature of 180 ° C., an excessive ESC current flows. On the other hand, when the condition for obtaining an optimal ESC current at a stage temperature of 180 ° C. is used at a stage temperature of 40 ° C., there is a high possibility that a sufficient electrostatic attraction force will not be generated. From this result, it can be seen that it is necessary to reset the condition for the optimum ESC current to flow every time the stage temperature is changed.

  From the results of Test Examples 1 and 2, as an example of the ESC current control range, a minimum value of 0.05 mA and a maximum value of 0.3 mA can be considered. The minimum value of 0.05 mA is an ESC current value at which an electrostatic attraction force of 2.5 kPa is obtained in Test Example 1. The maximum value of 0.3 mA was examined based on the ESC current of 0.26 mA that flows when the stage temperature is 140 ° C. in the test results of Table 3.

[Test Example 3]
Next, Test Example 3 is described. Test Example 3 verifies that an inrush voltage is generated at the moment when the adsorption voltage is applied, and that the inrush voltage can be reduced by applying the adsorption voltage stepwise. The test conditions are shown in Table 4, and the test results are shown in FIG. In Test Example 3, with the substrate 3 placed on the stage 4, the adsorption voltage was changed while maintaining the plasma 14, and the state of the ESC current at that moment was observed. This simulates the method of applying the adsorption voltage in the present invention.

  In this test, the adsorption voltage was controlled so that the voltage difference ΔV changed from 300V to 600V. In Test Example 3, the test is performed while introducing a heat transfer gas to the back surface of the substrate 3. The heat transfer gas is controlled to maintain a back pressure of 1.0 kPa. If the electrostatic attracting force generated by applying the attracting voltage is smaller than the back surface pressure, the substrate 3 is peeled off from the stage 4 and cannot be tested. Therefore, the adsorption voltage is controlled so that the voltage difference ΔV is 300 V or more so that an electrostatic adsorption force of 2.5 kPa or more is always generated between the substrate 3 and the stage 4. This setting prevents the substrate 3 from being peeled off from the stage 4 to prevent accurate measurement.

  In the four graphs of FIG. 6, the horizontal axis represents time, and the vertical axis represents adsorption voltage and ESC current. For each measurement, the adsorption voltage was changed at intervals of 300 V in FIG. 6A, at intervals of 100 V in FIG. 6B, at intervals of 50 V in FIG. 6C, and at intervals of 10 V in FIG.

In FIG. 6A, the ESC current increases instantaneously at the moment when the adsorption voltage is changed. However, as can be seen from FIGS. 6B, 6C, and 6D, the instantaneous increase in the ESC current can be reduced by applying the adsorption voltage stepwise. Moreover, if the change width of the adsorption voltage is small, the effect is high against an instantaneous increase in the ESC current.

  Based on the results of this test, an example of the change width and change interval of the adsorption voltage is examined. When the change width of the suction voltage is 10 V and the change interval is 40 ms, the suction voltage 300 V can be obtained approximately 1.5 seconds after the suction voltage initial value is output. Naturally, the smaller the change width of the adsorption voltage, the more effective as a countermeasure against the inrush current. It is desirable to set the change width and change interval of the suction voltage in consideration of the processing time, the performance of the DC power supply 9, and the like.

  In the present invention, the generation of the inrush voltage is suppressed by applying the adsorption voltage stepwise as in the test examples of FIGS. 6B, 6C, and 6D. In addition, by having a mechanism that automatically obtains the optimum adsorption voltage while detecting the ESC current, it prevents the occurrence of inrush current in response to the temperature change of the stage 4 and is only necessary for electrostatic adsorption of the substrate 3. ESC current can flow. By using the present invention to prevent an excessive ESC current from flowing, it is possible to prevent damage to foreign objects due to the occurrence of local discharge and devices on the substrate 3.

  Example 2 using the present invention is a case where a multilayer film is etched. In the etching of the multilayer film, the plasma 14 is once stopped every time each processing layer is etched. The plasma 14 is stopped, the processing conditions such as the processing gas, high frequency power, and stage temperature are changed, and the plasma 14 is ignited again to perform etching. When performing such etching, Vpp on the substrate 3 may fluctuate due to differences in processing layers and processing conditions. Therefore, the value of the ESC current required for electrostatic attraction and the attraction voltage also change. In such etching, introduction of heat transfer gas and application of adsorption voltage are stopped when plasma is stopped.

  In this case, every time the plasma 14 is ignited, there is a risk that the heat transfer gas is introduced in a state where the adsorption voltage is not applied to the stage and the substrate is peeled off from the stage. Therefore, the control method of the present invention is always performed when the plasma is ignited. When the plasma is ignited, the control method of the present invention is always performed, so that etching can be performed while obtaining the optimum adsorption voltage in each processing layer, and the substrate 3 is formed when the heat transfer gas is introduced. It is possible to prevent peeling from the stage 4.

  Example 3 using the present invention is a case where a multilayer film is etched at once. In the etching of the multilayer film, unlike the method described in the second embodiment, there is a method of etching each processing layer without stopping the plasma. In this case, the adsorption voltage is always applied to the stage 4 until the plasma is ignited and the processing layers are etched and the plasma is stopped. The heat transfer gas also flows intermittently so that the back pressure is controlled within a set range until the plasma is ignited and then stopped. An example of the present invention when performing such etching is as follows.

  The control method from the time of evacuation before plasma ignition to the time when the heat transfer gas is introduced is the same as that of the first embodiment of the present invention. The adsorption voltage is controlled so that the voltage difference ΔV obtained at this time is maintained for all the subsequent processing layers. This is because there is a risk that the heat transfer gas is introduced in a state where the adsorption voltage is not applied to the stage 4 and the substrate 3 is peeled off from the stage 4 only at the time of ignition.

  In the case of this embodiment, when the processing layer and processing conditions change, a phenomenon in which the value of the ESC current increases or decreases may occur. However, in many cases, the ESC current required for electrostatic attraction and the increase / decrease in the ESC current due to changes in the processing layer and processing conditions are larger than the value of the ESC current that may affect the generation of foreign matter and device characteristics on the substrate 3. There is no problem because it is small. In order to suppress the increase and decrease of the ESC current due to changes in the processing layer and processing conditions, it is effective to reduce the delay in the follow-up of the adsorption voltage with respect to the change in Vpp.

  In the present invention, it is also possible to input the correlation between the ESC current and the voltage difference ΔV into the apparatus in advance. In this case, the operator of the apparatus inputs the voltage difference ΔV instead of the ESC current before etching.

  The present invention is applied to an electrostatic chucking method in which the electrostatic chucking force generated on the substrate to be processed and the stage on which the substrate to be processed is strongly dependent on the current flowing between the substrate to be processed and the stage on which the substrate to be processed is placed. To do.

  The scope of application of the present invention is that if the substrate to be processed is installed by an electrostatic adsorption method that strongly depends on the current flowing between the substrate to be processed and the stage on which the substrate to be processed is installed, The thickness / area of the substrate to be processed, the stage temperature, the processing pressure, the frequency / output of the high frequency power supply, the output of the DC power supply, the type of the processing gas, etc. are not limited.

DESCRIPTION OF SYMBOLS 1 Antenna 2 Discharge part 3 Board | substrate 4 Stage 5 Exhaust port 6 High frequency power source 7 Matching device 8 High frequency power source 9 DC power source 10 Current sensor 11 Gas introduction port for heat transfer 12 Vpp sensor 13 Control unit 14 Plasma 15 Electrostatic adsorption film 16 Space 17 Test device 18 Conductor 19 Stage shaft 20 Conductor 21 Connector 22 Pressure gauge

Claims (4)

A processing chamber in which the sample is a plasma treatment, a plasma generating means for generating the plasma in the processing chamber, a sample stage where the sample is arranged Ru is placed into the processing chamber, the static by Johnson-Rahbek effect a DC power source for applying a DC voltage for electrostatically adsorbing the sample on the sample stage surface via a chucking layer on the sample stage, during the sample table and the sample through the electrostatic adsorption film a current detecting means for detecting a current flowing in the plasma processing apparatus Ru and a control unit for controlling the DC voltage in which the DC power is applied to the sample stage,
The control unit detects the value of the detected current so that the value of the current detected by the current detection means reaches a preset range each time the DC voltage applied to the sample stage is changed. after said sensed current value reaches the range of the preset, for heat transfer, which is supplied to the groove formed on the electrostatic adsorption film with stepwise increasing or decreasing the DC voltage on the basis of to initiate the supply of gas,
The current value of the range to the preset, when the heat transfer gas is supplied to the groove, and wherein the current value der Rukoto the specimen is sufficiently electrostatically adsorbed to the sample stage surface Plasma processing equipment. The plasma processing apparatus according to claim 1,
A high-frequency power supply for supplying high-frequency power to the sample stage;
The control unit includes a self-bias voltage at the start of the heat transfer gas supply obtained based on Vpp which is a value from a peak value to a peak value of the high frequency voltage applied to the sample stage, and the heat transfer gas. A plasma processing apparatus , wherein a DC power supply is controlled so as to maintain a difference from the DC voltage at the start of supply . A processing chamber in which the sample is a plasma treatment, a plasma generating means for generating the plasma in the processing chamber, a sample stage where the sample is arranged Ru is placed into the processing chamber, the static by Johnson-Rahbek effect a DC power source for applying a DC voltage for electrostatically adsorbing the sample on the sample stage surface via a chucking layer on the sample stage, during the sample table and the sample through the electrostatic adsorption film a current detecting means for detecting a current flowing in the plasma processing method using a plasma processing apparatus Ru and a control unit for controlling the DC voltage in which the DC power is applied to the sample stage,
Each time the DC voltage applied to the sample stage is changed, the current is detected by the current detection means,
Increasing or decreasing the DC voltage stepwise based on the detected current value such that the detected current value reaches a preset range;
After said sensed current value reaches the range of the previously set to start supply of the heat transfer gas supplied to the formed electrostatic adsorption film groove,
The current value of the range to the preset, when the heat transfer gas is supplied to the groove, and wherein the current value der Rukoto the specimen is sufficiently electrostatically adsorbed to the sample stage surface Plasma processing method. In the plasma processing method of Claim 3,
The plasma processing apparatus further includes a high frequency power source for supplying high frequency power to the sample stage,
The self-bias voltage at the start of the heat transfer gas supply obtained based on Vpp which is a value from the peak value to the peak value of the high frequency voltage applied to the sample stage, and the heat transfer gas supply start time. A plasma processing method comprising performing plasma processing after the start of supplying the heat transfer gas while applying the DC voltage to the sample stage so as to maintain a difference from the DC voltage .

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