JP3923323B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing apparatus and a plasma processing method, and more particularly, a high-performance plasma processing apparatus capable of stabilizing effective power consumed in a plasma space and a plasma processing using the same. It concerns the method.
[0002]
[Prior art]
Conventionally, a single-frequency excitation type plasma processing apparatus shown in FIG. 3 is known as a plasma processing apparatus.
In the plasma processing apparatus shown in FIG. 3, the plasma chamber 76 is a single-frequency excitation type plasma processing chamber unit capable of performing plasma processing such as CVD (chemical vapor deposition) sputtering, dry etching, and ashing. As shown in the figure, a plasma excitation electrode 4 and a susceptor electrode 8 for exciting plasma composed of parallel plates are provided, and a high-frequency power source 1 connected to the plasma excitation electrode 4 via a power distribution body 3, and the plasma A matching circuit 2 </ b> A for obtaining impedance matching between the chamber 76 and the high-frequency power source 1 is provided.
[0003]
More specifically, the plasma chamber 76 is provided with a plasma excitation electrode (cathode electrode) 4 and a shower plate 5 connected to the high frequency power source 1 at an upper position of the chamber 60, and a shower plate 5 at the lower portion of the chamber 60. A susceptor electrode (opposite electrode) 8 also serving as a susceptor (support) for mounting the substrate 16 to be processed is provided. The plasma excitation electrode 4 is connected to the high frequency power supply 1 through the power distribution body 3 and the matching circuit 2A. The plasma excitation electrode 4 and the power distribution body 3 are covered with a chassis (shielding conductor) 21 and the matching circuit 2A is housed in a matching box 2 made of a conductor. The chassis 21 and the matching box 2 are connected to each other, and the matching box 2 is connected to a shield line (outer conductor) of the feeder 1A made of a coaxial cable.
[0004]
In the case of the plasma processing apparatus shown in FIG. 3, the plasma excitation electrode 4 has a circular shape with a contour shape of about 30 cm in diameter, and corresponds to a chamber 60 having a circular cross section in the direction of the plasma excitation electrode surface. Further, an annular convex portion 4a is provided below the plasma excitation electrode 4, and a shower plate 5 in which a large number of holes 7 are formed is provided in contact with the convex portion 4a. It has been. A space 6 is formed between the plasma excitation electrode 4 and the shower plate 5. A gas introduction pipe 17 is connected to the space 6 through the side wall of the chassis 21 and through the plasma excitation electrode 4.
[0005]
The gas introduction pipe 17 is made of a conductor, and an insulator 17a is inserted in the middle of the gas introduction pipe 17 at a position inside the chassis 21, so that the plasma excitation electrode 4 and the gas supply source are insulated.
The gas introduced from the gas introduction pipe 17 is supplied into the chamber 60 constituted by the chamber wall 10 through the numerous holes 7 of the shower plate 5. The chamber wall 10 and the plasma excitation electrode 4 are insulated from each other by an insulator 9.
On the other hand, a susceptor electrode 8 serving as a wafer susceptor on which a plate-like substrate 16 is placed is provided in the chamber 60.
[0006]
A shaft 13 is connected to the center of the lower portion of the susceptor electrode 8. The shaft 13 is provided through the chamber bottom 10 </ b> A, and the lower end of the shaft 13 and the center of the chamber bottom 10 </ b> A are sealed by the bellows 11. It is connected.
The susceptor electrode 8 and the shaft 13 can be moved up and down by the bellows 11, and the distance between the plasma excitation electrode 4 and the susceptor electrode 8 can be freely adjusted. The susceptor electrode 8, the shaft 13, the bellows 11, the chamber bottom 10A, and the chamber wall 10 are at the same potential in terms of DC. Furthermore, since the chamber wall 10 and the chassis 21 are connected, the chamber wall 10, the chassis 21, and the matching box 2 are all at the same potential in terms of DC.
[0007]
In this plasma processing apparatus, high frequency power is supplied only to the plasma excitation electrode 4 and the susceptor electrode 8 is grounded. Further, the susceptor electrode 8 and the chamber wall 10 are at the same potential in terms of DC. The exhaust system is not shown.
[0008]
The matching circuit 2A is provided between the high-frequency power source 1 and the power feeding plate 3 and is adjusted so as to obtain impedance matching between the high-frequency power source 1 and the plasma excitation electrode 4 in response to a change in the plasma state in the chamber 60. Therefore, many of them have a configuration including a plurality of passive elements. Specifically, in the example of FIG. 3, the passive capacitor 22 includes a load capacitor 22 made of a vacuum variable capacitor, a tuning coil 23, and a tuning capacitor 24 made of an air variable capacitor. Here, in the example of FIG. 3, one tuning coil 23 is connected between the load capacitor 22 and the tuning capacitor 24.
[0009]
When performing an etching process or a film forming process using the plasma processing apparatus as described above, it is important to maintain the uniformity of the process. For this purpose, it is necessary to stabilize the generated plasma. As means for stabilizing the plasma, for example, as disclosed in JP-A-7-302696, the grounding state can be positively controlled, and the amount of ions depending on the electrical characteristics can be controlled to improve the processing characteristics. Discloses a method for plasma processing by monitoring a ground line. FIG. 4 illustrates a method for performing plasma processing by monitoring the ground line.
[0010]
The plasma processing apparatus of FIG. 4 includes an etching apparatus main body 101 and a process control unit 102 that controls the supply of vacuum exhaust and etching gas in the etching apparatus main body 101 and high-frequency power for plasma formation. ing. The etching apparatus main body 101 includes a processing chamber 103 that is vacuum-sealed with a dielectric discharge tube to allow microwaves to pass through, and a sample stage 105 provided at the lower part of the processing chamber 103. A semiconductor wafer 104 as a sample is placed in an electrically insulated state.
[0011]
Further, a mirror magnetic field is applied from the processing chamber 103 to the semiconductor wafer 104 by a solenoid coil and a permanent magnet (both not shown). In this state, the processing chamber 103 is evacuated to a high vacuum, and then a process gas is supplied to a predetermined gas. Introduced at gas pressure. Furthermore, the microwave generated by the magnetron is introduced into the processing chamber 103 through a waveguide (not shown) and applied to a plasma excitation electrode (cathode electrode, not shown). This generates a microwave discharge, resulting in a plasma state. The microwave discharge uses a resonance phenomenon between electron cyclotron motion in a magnetic field and microwaves.
[0012]
Further, the processing chamber 103 as an object to be grounded in the etching apparatus main body 101 is actively dropped to the ground via a variable resistor (current control means) 111 and an ammeter (measurement means) 112. As a result, the ammeter 112 outputs the measured value of the ground line in the processing chamber 103, and this output is connected to the computer 113. The computer 113 is programmed to operate to control the resistance value of the variable resistor 111 to a desired value based on the measurement value obtained by the ammeter 112.
[0013]
In this case, ions in the plasma depending on the current value of the ground line disappear on the wall surface of the grounded processing chamber 103 and the surface of the components in the processing chamber 103, so that current flows through the ground line, and thus flows into the ground line. It is said that the amount of ions annihilated, that is, the amount of ions in plasma can be controlled by controlling the current.
[0014]
[Problems to be solved by the invention]
However, in the above method, as in FIG. 3, the high frequency power applied to the plasma excitation electrode is controlled so that the output of the high frequency power supply becomes a predetermined value at the outlet to the high frequency power supply. In addition, since a part of the current on the ground line side is led to the bypass circuit in the measurement of the plasma excitation current, the plasma excitation current is measured using a part of the entire current, for example, 2 to 3%. However, there is a drawback that the measurement error is large.
In the above method, a resistor is used for current measurement to form a bypass circuit. This causes a current loss due to the impedance of the bypass circuit, and accurately grasps the power used for plasma excitation. There are difficulties that cannot be done.
[0015]
Furthermore, in the conventional method, since the output of the high frequency power supply is adjusted to a predetermined value at the power supply output section, the power loss of the matching circuit due to the temperature rise of the conductor when a high frequency current is passed. Fluctuates, and the effective power actually consumed in the plasma space fluctuates. For example, when the temperature of the conductor rises, the impedance of the high-frequency power circuit rises, resulting in a decrease in effective power consumed in the plasma space. Furthermore, in an apparatus in which a plurality of plasma chambers are connected, there is a difficulty that a difference occurs in effective power consumed in the plurality of plasma spaces.
The present invention has been made in view of the above-described problems, and directly grasps the high-frequency power applied to the plasma excitation electrode (cathode electrode) accurately and controls the power to a predetermined value to be stable. An object of the present invention is to provide a plasma processing apparatus capable of performing uniform plasma processing.
[0016]
[Means for Solving the Problems]
In order to solve the above-described problems, a plasma processing apparatus of the present invention includes a plasma excitation electrode to which electric power for exciting plasma is supplied, and a plasma processing chamber having a susceptor electrode facing the plasma excitation electrode inside. A high frequency power source for supplying high frequency power to the plasma excitation electrode, and a matching circuit for obtaining impedance matching between the plasma processing chamber and the high frequency power source, and a substrate to be processed on the susceptor electrode A plasma processing apparatus for processing with plasma, wherein the matching circuit has an input terminal and an output terminal, and the high-frequency power feeder that supplies the high- frequency power to the matching circuit from the high-frequency power source to the input terminal is connected to the high-frequency power source via, the serial output terminal, a high frequency electric supply the high frequency power to the plasma excitation electrode from said matching circuit Via the distribution member is connected to the plasma excitation electrode, a coil and a capacitor between these input and output terminals are respectively one or more arrangements, a ground potential portion in conduction with the plasma processing chamber of the chamber walls of the capacitor A current detection means connected to one of the power distribution bodies and attached to the power distribution body for monitoring a current flowing through the power distribution body; and a current value detected by the current detection means and a preset value. The difference between the set value and the set value is detected, the change of the capacitance of one capacitor in the matching circuit in which the difference becomes zero is calculated, and the change amount is changed via the feedback circuit to the matching circuit. Feedback to the circuit, and changing the capacitance of the capacitor based on the control signal, the effective power applied to the electrode is Characterized by comprising and means for controlling so that the value.
[0017]
By using such a plasma processing apparatus, it is possible to accurately and accurately grasp the high-frequency power applied to the plasma excitation electrode and control it to a predetermined power to perform stable and homogeneous plasma processing.
[0018]
In the plasma processing apparatus of the present invention, the current detecting means is supplied with current from the first coil surrounding the power distribution body, the second coil for converting the current of the first coil, and the second coil. A bridge circuit can be used.
Thus, taken out by converting the current flowing through the first and second coils, Ru can control the effective power applied to the plasma excitation electrode since it detected by the bridge circuit.
[0019]
The plasma processing method of the present invention includes a plasma excitation electrode to which power for exciting plasma is supplied, a plasma processing chamber having a susceptor electrode facing the plasma excitation electrode therein, and the plasma excitation electrode. A plasma comprising: a high frequency power source for supplying high frequency power; and a matching circuit for obtaining impedance matching between the plasma processing chamber and the high frequency power source, and processing a substrate to be processed on the susceptor electrode with plasma. The matching circuit has an input terminal and an output terminal, and the high-frequency power source is connected to the input terminal via a high-frequency power feeder that supplies the high-frequency power from the high-frequency power source to the matching circuit. Connected to the output terminal via the high-frequency power distributor for supplying the high-frequency power from the matching circuit to the plasma excitation electrode. A plasma excitation electrode is connected, and one or a plurality of coils and capacitors are arranged between the input / output terminals, and a ground potential portion that is electrically connected to the chamber wall of the plasma processing chamber is interposed through one of the capacitors. Connected to the power distribution body and equipped with a plasma processing apparatus having a current detection means for monitoring the current flowing through the power distribution body, and the current value detected by the current detection means is preset. Detecting the difference with the set value, calculating the change in the capacitance of one capacitor in the matching circuit where the difference becomes zero, and changing the amount of change through the feedback circuit to the matching circuit The effective power applied to the electrode is fed back to the circuit and the capacitance of the capacitor is changed based on the control signal. The target substrate employing the method of plasma treatment while controlling so that the constant value.
[0020]
According to such a plasma processing method, it is possible to maintain uniformity of processing when performing etching processing, film formation processing, sputtering processing, or the like.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be specifically described with reference to the drawings .
FIG. 1 is a cross-sectional view showing a schematic configuration of a first embodiment of a plasma processing apparatus of the present invention.
The main configuration of the plasma processing apparatus of the present invention is the same as that of the conventional plasma processing apparatus shown in FIG. Therefore, parts having the same function are given the same numbers as in FIG. The plasma processing apparatus of the present invention is different from the conventional plasma processing apparatus shown in FIG. 3 in that a current detecting means is attached to a power distribution body to detect a high frequency current, and this is used to apply a high frequency power applied to the plasma excitation electrode. Is controlled to become a predetermined value. Therefore, this control circuit will be mainly described.
[0022]
As shown in FIG. 1, in the plasma processing apparatus of the present invention, a clamp meter 12 is attached to a power distribution body 3 for applying a high-frequency current to a plasma excitation electrode 4 for exciting plasma, and the magnitude of the current flowing through the power distribution body 3 is increased. The detected current is input to the control circuit 15.
The control circuit 15 calculates a difference between the detected current and a preset input value, generates a signal for increasing or decreasing the output of the high-frequency power supply 1 until the difference becomes zero (0), Feedback is provided to the power supply 1 or the matching circuit 2A. One method is to increase or decrease the output of the high frequency power supply 1 based on the signal fed back to the high frequency power supply 1. In another method, the high frequency power applied to the plasma excitation electrode 4 is adjusted by changing the capacitance of the load capacitor 22 or the tuning capacitor 24 of the matching circuit 2A based on the signal fed back to the matching circuit 2A.
In this way, the current detection and the feedback of the control signal are repeated, and control is performed so that the difference between the detected current and the preset current value becomes zero (0).
[0023]
An example of the configuration of the control circuit 15 is shown in FIG. In the example shown in FIG. 2, a clamp meter 12 including a coil 12 a is attached to the power distribution body 3. The clamp meter 12 may be a fixed type that is attached in advance, or may be a movable type that can be attached at a required time by opening and closing the coil 12a.
A coil 12b having a different number of turns is attached to the coil 12a, and the current of the coil 12a is converted and extracted and detected by the bridge circuit 18. The ammeter 19 of the bridge circuit 18 is controlled to be zero (0). A control circuit that generates a control signal according to an instruction from the ammeter 19 is provided, and the control signal is fed back to the high-frequency power source or the matching circuit.
[0024]
Next, a method for performing plasma processing using the plasma processing apparatus of the present invention will be described.
The plasma processing method of the present invention employs a method of processing while controlling so that the power applied to the electrode for exciting the plasma is maintained at a predetermined value. Specifically, the current flowing through the high frequency power distribution body applied to the electrode for exciting the plasma is monitored by the current detecting means, and the current detected by the current detecting means is set to a predetermined value. do.
In the plasma processing method of the present invention, since the high frequency power applied to the plasma excitation electrode is directly detected and controlled to be a set value, for example, the matching circuit is caused by a temperature rise of the conductor when a high frequency current is passed. Therefore, even if the effective power actually consumed in the plasma space fluctuates, the following compensation can be made. Furthermore, even in an apparatus in which a plurality of plasma chambers are connected, effective power consumed in the plurality of plasma processing spaces can be uniformly maintained.
According to such a plasma processing method, it is possible to maintain uniformity of processing when performing etching processing, film formation processing, sputtering processing, or the like.
[0025]
[Action]
The present invention provides a plasma processing apparatus capable of stable and homogeneous plasma processing by directly accurately grasping high-frequency power applied to a plasma excitation electrode (cathode electrode) and performing stable power control. .
[0026]
【The invention's effect】
According to the present invention, since the effective power consumed in the plasma space can be kept constant, it is possible to perform uniform and stable processing when performing etching processing, film formation processing, sputtering processing, and the like. It becomes.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing a schematic configuration of a plasma processing apparatus of the present invention.
FIG. 2 is a diagram for explaining an overview of a control method in the plasma processing apparatus of FIG. 1;
FIG. 3 is a cross-sectional view showing a schematic configuration of an example of a conventional plasma processing apparatus.
FIG. 4 is a cross-sectional view showing a schematic configuration of another example of a conventional plasma processing apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... High frequency power supply, 2 ... Matching box, 2A ... Matching circuit, 3 ... Power distribution body, 4 ... Plasma excitation electrode, 5 ... ········· Shower plate, 6 ··· Space, 7 ···· hole, 8 ·········· Susceptor electrode, 9 ····· Insulator ..Chamber wall, 11 ... Bellows, 12 ... Clamp meter, 13 ... Shaft, 15 ... Control circuit, 16 ... Substrate, 17 ... Gas introduction pipe, 18 ... Bridge circuit, 19 ... Ammeter, 22 ... Load capacitor, 23 ... Tuning coil, 24 ... Tuning capacitor, 60 ... Chamber, 75,76 ... Plasma char , 101... Etching apparatus main body, 102... Process control unit, 103... Processing chamber, 104.・ Variable resistor, 112 ・ ・ ・ ・ ・ ・ Ammeter.

Claims (3)

A plasma excitation electrode to which power for exciting the plasma is supplied;
To obtain a plasma processing chamber having a susceptor electrode facing the plasma excitation electrode, a high frequency power source for supplying high frequency power to the plasma excitation electrode, and impedance matching between the plasma processing chamber and the high frequency power source A plasma processing apparatus for processing a substrate to be processed on the susceptor electrode with plasma.
The matching circuit has an input terminal and an output terminal,
The high frequency power source is connected to the input terminal via a high frequency power feeder that supplies the high frequency power from the high frequency power source to the matching circuit ,
The plasma excitation electrode is connected to the output terminal via a high frequency power distribution body that supplies the high frequency power from the matching circuit to the plasma excitation electrode ,
One or a plurality of coils and capacitors are arranged between these input / output terminals, and a ground potential portion that is electrically connected to the chamber wall of the plasma processing chamber is connected via one of the capacitors ,
Current detection means attached to the power distribution body for monitoring the current flowing through the power distribution body;
Detecting a difference between the current value detected by the current detection means and a preset setting value, calculating a change in the capacitance of one capacitor in the matching circuit in which the difference becomes zero, and
Effective power applied to the electrode by changing the amount of change via a feedback circuit to the matching circuit, feeding back to the circuit, and changing the capacitance of the capacitor based on the control signal And a means for controlling so as to become a predetermined value . The current detection means includes a first coil surrounding the power distribution body, a second coil for converting the current of the first coil, and a bridge circuit to which current is supplied from the second coil. The plasma processing apparatus according to claim 1. A plasma excitation electrode to which electric power for exciting plasma is supplied; a plasma processing chamber having a susceptor electrode facing the plasma excitation electrode; and a high-frequency power source for supplying high-frequency power to the plasma excitation electrode; A plasma circuit that includes a matching circuit for obtaining impedance matching between the plasma processing chamber and the high-frequency power source, and that processes a substrate to be processed on the susceptor electrode with plasma, and the matching circuit includes: The high-frequency power source is connected to the input terminal via a high-frequency power feeder that supplies the high-frequency power from the high-frequency power source to the matching circuit, and the high-frequency power source is connected to the output terminal. The plasma excitation electrode is connected via a high frequency power distribution body that supplies power from the matching circuit to the plasma excitation electrode. One or a plurality of coils and capacitors are respectively disposed between the input / output terminals, and a ground potential portion that is electrically connected to the chamber wall of the plasma processing chamber is connected via one of the capacitors, and the power distribution body A plasma processing apparatus equipped with a current detection means for monitoring the current flowing through the power distribution body, and detecting a difference between a current value detected by the current detection means and a preset set value. Calculating a change in the capacitance of one capacitor in the matching circuit in which the difference is zero, changing the amount of change via a feedback circuit to the matching circuit, and feeding back to the circuit, While changing the capacitance of the capacitor based on the control signal and controlling the effective power applied to the electrode to a predetermined value Serial plasma processing method, wherein a substrate to be processed to a plasma treatment.

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