JP4246539B2 - Plasma processing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method, and more particularly to a plasma processing method for forming plasma in a vacuum chamber using a plurality of electrodes.
[0002]
[Prior art]
Examples of apparatuses using plasma include a sputtering apparatus, an ashing apparatus, an etching apparatus, and a surface modification apparatus.
[0003]
FIG. 3 shows a sputtering apparatus 101 of the prior art among these plasma apparatuses. The sputtering apparatus 101 has a vacuum chamber 108, and a cathode electrode 111 is provided in the vacuum chamber 108.
[0004]
A target 115 made of a material to be sputtered is attached to the cathode 111.
[0005]
A substrate electrode 113 is disposed at a position facing the target 115 inside the vacuum chamber 108. A space between the target 115 and the substrate electrode 113 is surrounded by the grid electrode 112.
[0006]
The cathode electrode 111, the grid electrode 112, and the substrate electrode 113 are connected to a cathode power source 121, a grid power source 122, and a bias power source 123, respectively.
[0007]
In such a sputtering apparatus 101, the inside of the vacuum chamber 108 is evacuated by the evacuation system 127, and a vacuum atmosphere of a predetermined pressure is formed. In this state, the substrate 116 is placed on the substrate electrode 113, a sputtering gas is introduced into the vacuum chamber 108 from the gas introduction system 128, the power supplies 121 to 123 are activated, and a negative DC high voltage is applied to the cathode electrode 111. When a positive DC low voltage is applied to the grid power source 112 and a high frequency voltage is applied to the substrate electrode 113, plasma is formed near the surface of the target 115, and the target 115 is sputtered.
[0008]
Positive ion target particles that have jumped out of the target are focused by the grid electrode 112 and reach the surface of the substrate 116.
[0009]
In the sputtering apparatus 101 as described above, when there is an abnormal situation such as a foreign substance mixed in the target 115 or an electric field concentrated on a part of the target surface, arc discharge may occur locally. There is.
[0010]
Once arc discharge occurs, it not only causes generation of particles, but the energy of arc discharge is large, and even the target may be damaged.
[0011]
In order to prevent this, each of the power supplies 121 to 123 is provided with an arc interrupt device, and is configured to stop the output when the occurrence of an arc is detected.
[0012]
However, since the plurality of power supplies 121 to 123 operate simultaneously as described above, even if any power supply detects arc discharge and shuts off the output, the other power supplies do not detect arc discharge and output Is maintained, arc discharge may not be extinguished.
[0013]
On the other hand, at the time of start-up or return from shut-off, the power supplies 121 to 123 influence each other, and the output may be cut off accidentally even though no arc discharge has occurred. It has become.
[0014]
[Problems to be solved by the invention]
The present invention was created to solve the above-described disadvantages of the prior art, and an object thereof is to provide a technique capable of reliably stopping arc discharge without causing a malfunction.
[0015]
[Means for Solving the Problems]
In order to solve the above problem, the invention according to claim 1 is capable of applying a voltage different from the first electrode, the first power source connected to the first electrode, and the first electrode. A plasma processing method using a plasma processing apparatus having a second electrode configured as described above and a second power source connected to the second electrode, wherein when the plasma is formed, the first electrode When operating a power supply, applying a voltage to the first electrode, forming plasma in a vacuum atmosphere, and maintaining the plasma, the first and second power supplies The first and second voltages are respectively applied to the electrodes, and the object to be processed disposed in the vacuum atmosphere is treated with the plasma, and the absolute value of the output voltage of the first power source is lower than a predetermined value. Or the output current of the second power source The case of detecting that the relative value is greater than a predetermined value, the first as the detection of the occurrence of arc discharge, the second electrode, the first, second voltage so as not applied the This is a plasma processing method for eliminating arc discharge.
A second aspect of the present invention is the plasma processing method according to the first aspect, wherein the absolute value of the second voltage is closer to the ground potential than the absolute value of the first voltage.
According to a third aspect of the present invention, the plasma processing apparatus includes a third electrode configured to be able to apply a voltage different from the first and second electrodes, and the third electrode includes The third voltage according to any one of claims 1 and 2 , wherein a third voltage is applied from the third power source to the third electrode when a third power source is connected and the plasma is maintained. In the plasma processing method, when the occurrence of the arc discharge is detected , the third voltage is not applied to the third electrode.
Fourth aspect of the present invention, a target disposed on the first electrode, and sputtering the target by the plasma, any one of claims 1 to 3 to form a thin film on the processed surface of the object It is a plasma processing method of description.
[0016]
The present invention is configured as described above, and plasma is generated by a voltage applied to at least one electrode, and the generated plasma is maintained by applying different voltages to two or more electrodes.
[0017]
When the occurrence of arc discharge is detected based on the state of any one of the power sources connected to each electrode, the voltage necessary for maintaining plasma is applied to the electrode connected to the power source. Is not applied. Accordingly, in the present invention, the voltage necessary for maintaining the plasma is not applied to the electrodes connected to other power sources.
[0018]
For example, when an arc discharge is detected depending on the state of one power supply, not only the output of the power supply is stopped, but also the output of another power supply in which no arc discharge is detected. Therefore, the arc discharge is not maintained when the power source that has not detected the arc discharge supplies the electrodes.
[0019]
Instead of stopping the output of the power supply, the electrode may be connected to the ground potential, or the connection between the power supply and the electrode may be interrupted. In short, it suffices if voltage application to the electrode is stopped.
[0020]
In addition, a high voltage is applied to the electrodes used for plasma formation, while a lower voltage is sufficient to be applied to the other electrodes. An electrode to which a low voltage is applied is easily affected by the voltage fluctuation of the electrode to which a high voltage is applied. Therefore, an electrode to which a low voltage is applied is an arc due to the influence of the voltage fluctuation of the electrode to which a high voltage is applied. Even if no discharge occurs, the voltage drops and may approach the ground potential rather than a predetermined arc detection voltage. Therefore, for the power source connected to the electrode to which the low voltage is applied, the occurrence of arc discharge is preferably detected from the change in the output current.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described.
FIG. 1 shows an example of a plasma apparatus in which the present invention is used, and has a vacuum chamber 8.
[0022]
In the vacuum chamber 8, a first electrode (cathode electrode) 11, a second electrode (grid electrode) 12, and a third electrode (substrate electrode) 13 are arranged. A target 15 made of a material to be sputtered is attached to the first electrode 11.
[0023]
The third electrode 13 is disposed at a position facing the target 15 inside the vacuum chamber 8. The second electrode 12 has a substantially cylindrical shape, and is disposed so as to surround the space between the target 15 and the third electrode 13.
[0024]
A first power source (cathode power source) 21, a second power source (grid power source) 22, and a third power source (bias power source 23) are disposed outside the vacuum chamber 8. The first to third electrodes 11 to 13 are connected to the first to third power sources 21 to 23, respectively, and the vacuum chamber 8 is connected to the ground potential.
[0025]
Each of the power supplies 21 to 23 is configured to output a constant voltage or a constant current according to control of a control circuit built in each of the power supplies 21 to 23, or to stop the operation and output no voltage or current.
An evacuation system 27 and a gas introduction system 28 are connected to the vacuum chamber 8.
[0026]
The thin film formation process on the surface of the object to be processed will be described using the plasma processing apparatus 1. The vacuum exhaust system 27 is operated in advance, and the inside of the vacuum chamber 8 is exhausted to a predetermined pressure to form a vacuum atmosphere. .
[0027]
Then, while maintaining a vacuum atmosphere, a processing object such as a substrate is carried into the vacuum chamber 8 and placed on the third electrode 13. Reference numeral 16 in FIG. 1 indicates a processing object placed on the third electrode 13.
[0028]
Next, a processing gas (in this case, sputtering gas) is introduced from the gas introduction system 28 into the vacuum chamber 8, the first power supply 21 is activated, and a starting voltage that is a negative DC high voltage is applied to the first electrode 11. Then, plasma is formed near the surface of the target 15.
[0029]
After the plasma is formed, the output voltage of the first power source 21 is set to the first voltage, and the second and third power sources 21 and 23 are activated, and the second and third electrodes 12 and 13 are respectively connected to the first and second electrodes 12 and 13. Second and third voltages are applied to keep the plasma stable.
[0030]
The first voltage output from the first power supply 11 is a negative DC high voltage of about −500 to −400V, and the second voltage output from the second power supply 12 is a positive DC constant voltage of about + 100V. It is. The third voltage output from the third power source 13 is an AC voltage of 13.56 MHz, and its VDC (VDC: self-biased DC component) is about several tens of volts.
[0031]
When the plasma is formed, the first to third power sources 21 to 23 are activated, the first to third voltages are output from the respective power sources 21 to 23, and applied to the first to third electrodes 11 to 13, respectively. May be.
[0032]
When the plasma is stably maintained, the target 15 is sputtered by the plasma, and target particles are ejected from the target.
[0033]
Some of the target particles become positive ions and are focused by the second electrode 22 to which the second voltage is applied. When the target particles reach the surface of the substrate 16, a thin film grows. At this time, a continuous dense film is formed on the uneven surface of the object 16 to be processed by the third voltage applied to the third electrode 23.
[0034]
When a stable plasma is maintained during the growth of the thin film, the impedance of the plasma is a constant value, and the first to third electrodes 11 to 13 are electrically connected to each other by the constant value impedance. Has been.
[0035]
On the other hand, when arc discharge occurs and the arc current flows, the impedance of the plasma becomes almost zero, and the potential of at least one of the first to third electrodes 11 to 13 is substantially equal to the ground potential. Become.
[0036]
In a plasma processing apparatus that performs sputtering, the potential of the first electrode 11 that applies a negative DC high voltage to the target becomes substantially the ground potential.
[0037]
When an arc discharge occurs and, as a result, the potential of the first electrode 11 exceeds a predetermined value and approaches the ground potential, or the potential of the first electrode 11 becomes the ground potential, the control circuit in the first power supply 21 Detects the occurrence of arc discharge by detecting that the potential of the first electrode 11 exceeds the predetermined value and approaches the ground potential, and stops the output of the first power source 11 and other power sources. A stop signal is output to (second and third power supplies 12, 13, etc.).
[0038]
The stop signal is input to a control circuit built in each of the power supplies 22 and 23. When the stop signal is input, the power supplies 22 and 23 stop outputting.
[0039]
As a result, the output of each of the power supplies 11 to 13 including itself is stopped only by the first power supply 11 detecting the arc discharge, whereby the arc discharge is quickly extinguished.
[0040]
Each of the power supplies 11 to 13 restarts after maintaining the output stop for a certain time, and when it returns to the state of outputting the first to third voltages, the plasma is regenerated.
[0041]
In the above example, the first power source 21 detects the occurrence of arc discharge, but there may be a detection error or a detection delay.
[0042]
In the present invention, even when the second power source 22 detects the occurrence of arc discharge, the output voltages of the second power source 22 and the other power sources 21 and 23 are stopped, and the first to third electrodes 11 to 11 are stopped. The first to third voltages are not applied to 13, so that the arc discharge is surely extinguished.
[0043]
In the above example, the first power source 21 detects the occurrence of arc discharge by voltage change. However, if each of the power sources 21 to 23 is set to detect the occurrence of arc discharge by voltage change, a detection error or recovery error will occur. May occur.
[0044]
For example, in the plasma processing apparatus 1, a high voltage is applied to the first electrode 11 and a low voltage is applied to the second electrode 12, and the potential of the second electrode 12 is greater than the potential of the first electrode 11. Is also close to ground potential.
[0045]
Since the first electrode 11 and the second electrode 12 are electrically coupled by the impedance of the formed plasma, even if arc discharge does not occur, when the potential of the first electrode 11 changes, Even if the ratio is small, the potential of the second electrode 12 may be lower than the second voltage set for a moment. When the second power source 22 is configured to stop the output of each of the power sources 21 to 23 on condition that the output voltage exceeds the set value and approaches the ground potential, no arc discharge occurs. The first to third voltages applied to the electrodes 11 to 13 are stopped, which is inconvenient.
[0046]
When the power supplies 21 to 23 are restarted, the potential of the first electrode 11 greatly changes from the ground potential to a negative high voltage, so that the potential of the second electrode 22 once approaches the ground potential. The potential of the second electrode 12 crosses a predetermined voltage. When the second power source 22 is configured to detect the occurrence of arc discharge by a voltage change, the second power source 22 detects the occurrence of arc discharge at the time of restart, and the second power source 22 is stopped. A stop signal is output to the other power supplies 21 and 23, and the output of each of the power supplies 21 to 23 may be stopped.
[0047]
Thus, if the power source connected to the electrode to which the low voltage is applied is also configured to stop due to voltage fluctuation, each power source 21 to 23 is stopped due to a malfunction, which is inconvenient.
[0048]
In the present invention, the second power source 22 that outputs a voltage closer to the ground potential than the first power source 21 detects the occurrence of arc discharge not by the fluctuation of the output voltage but by the fluctuation of the output current. Reference numeral 29 in FIG. 1 is a current sensor that detects an output current of the second power supply 22.
[0049]
That is, in the second power source 22, the magnitude of the output current is detected by the current sensor 29, and it is assumed that arc discharge has occurred when the magnitude of the output current exceeds a predetermined reference value. Therefore, if the output current is smaller than the reference value, even if the voltage at the output terminal of the second power source 22 crosses a predetermined voltage, it is not determined that arc discharge has occurred, and the output stop or stop of the second power source 22 is not performed. No signal is output.
[0050]
On the other hand, even when the voltage fluctuation of the first electrode 11 is small and the first power source 21 does not detect arc discharge, the second power source 22 detects the occurrence of arc discharge from the magnitude of the output current. Then, the output voltage of the second power source 22 is stopped and a stop signal is output to the other power sources (first and third power sources 21 and 23). As a result, the outputs of the power sources 21 to 23 are stopped. It has become so.
[0051]
The third power source 23 also has a current sensor. When the output current of the third power source 23 itself exceeds a predetermined value, the output is stopped and a stop signal is output to the other power sources 21 and 22. As a result, the output of each of the power supplies 21 to 23 is stopped.
[0052]
As described above, the first to third voltages are not applied to the first to third electrodes 11 to 13 by stopping the outputs of the power sources 21 to 23. The first to third voltages are applied to the first to third electrodes 11 to 13 by operating the switches while the power supplies 21 to 23 output the first to third voltages. It may not be applied.
[0053]
For example, FIG. 2A shows an example in which the first to third switches SW _{1 to} SW ₃ are connected in parallel to the first to third power supplies 21 to 23, and arc discharge is detected. The power supplies 21 to 23 are configured to output stop signals to the switches SW _{1 to} SW ₃ without stopping output.
[0054]
Each of the switches SW _{1 to} SW ₃ is closed when a stop signal is input, and connects the first to third electrodes 11 to 13 to the ground potential. As a result, the first to third electrodes 11 to 13 are not applied with the first to third voltages.
[0055]
FIG. 2B shows a case where the first to third switches SW _{1 to} SW ₃ are connected in series to the first to third power sources 21 to 23, and from the power source that detects arc discharge. When the stop signal to the switches SW ₁ to SW ₃ are inputted, the switches SW ₁ to SW ₃ becomes open state, the first to third electrode 11 to 13 first to third power supply 21 to 23 Disconnect from. Accordingly, the first to third voltages are not applied to the first to third electrodes 11 to 13.
[0056]
In the plasma processing apparatus 1, the second electrode 12 that is a grid electrode is cylindrical, but may be a square tube. Moreover, the 2nd electrode 12 should just surround the space between the 1st electrode 11 and the 3rd electrode 13, and is divided | segmented into the vertical direction or a horizontal essential point, and may be comprised by the some electrode. .
[0057]
Moreover, the case where the plasma apparatus of the present invention does not have a grid electrode is also included. In that case, the electrode for plasma generation to which a negative high voltage is applied becomes the first electrode, and the electrode for applying an AC or DC bias to the substrate becomes the second electrode.
[0058]
Moreover, although the said Example demonstrated the sputtering device among plasma processing apparatuses, the plasma apparatus of this invention includes the apparatus which processes a process target object using plasma. For example, in addition to a sputtering apparatus, an ashing apparatus using plasma, an etching apparatus, a surface modification apparatus, and the like.
[0059]
Further, the plasma apparatus of the present invention is not limited to one having three electrodes, but includes an apparatus having two electrodes and an apparatus having four or more electrodes.
[0060]
In the above, a DC voltage is applied to the first and second electrodes 11 and 12 and an AC voltage is applied to the third electrode 13, but the case where an AC voltage is applied to the first and second electrodes is also included. . Further, the case where a DC voltage is applied to the third electrode 13 is also included. Further, the AC voltage includes a DC biased AC voltage.
[0061]
In a power source that outputs an alternating voltage, arc discharge can be detected by detecting the impedance of the load of the power source smaller than a predetermined value in addition to the case of detecting arc discharge by a change in output current.
[0062]
【The invention's effect】
Even when one power source detects arc discharge, voltage application to all the electrodes is stopped, so that arc discharge can be reliably extinguished.
If the detection of arc discharge due to a voltage change and the detection of arc discharge due to a current change are used in combination, startup and restart of the power supply will not fail.
[Brief description of the drawings]
FIG. 1 is an example of a plasma apparatus that can use the present invention. FIGS. 2A and 2B are diagrams for explaining an example in which voltage application is stopped using a switch. FIG. Sputtering equipment 【Explanation of symbols】
DESCRIPTION OF SYMBOLS 1 ... Plasma processing apparatus 8 ... Vacuum chamber 11 ... 1st electrode 12 ... 2nd electrode 13 ... 3rd electrode 15 ... Target 16 ... Process target 21 ... 1st power supply 22 …… Second power supply 23 …… Third power supply

Claims (4)

A first electrode;
A first power source connected to the first electrode;
A second electrode configured to be able to apply a voltage different from the first electrode;
A plasma processing method using a plasma processing apparatus having a second power source connected to the second electrode,
When forming the plasma, operate the first power supply, apply a voltage to the first electrode, form a plasma in a vacuum atmosphere,
In the case of maintaining the plasma, the first and second voltages are applied to the first and second electrodes from the first and second power sources, respectively, and the processing object is disposed in the vacuum atmosphere. Is treated with the plasma,
When it is detected that the absolute value of the output voltage of the first power supply is lower than a predetermined value, or when it is detected that the absolute value of the output current of the second power supply is larger than a predetermined value The plasma processing method of extinguishing the arc discharge in such a manner that the first and second electrodes are not applied to the first and second electrodes as the occurrence of arc discharge is detected .   The plasma processing method according to claim 1, wherein an absolute value of the second voltage is closer to a ground potential than an absolute value of the first voltage. In the plasma processing apparatus, a third electrode configured to be able to apply a voltage different from the first and second electrodes is disposed,
A third power source is connected to the third electrode,
3. The plasma processing method according to claim 1, wherein, when maintaining the plasma, a third voltage is applied from the third power source to the third electrode.
A plasma processing method for preventing the third voltage from being applied to the third electrode when the occurrence of the arc discharge is detected . The plasma processing method according to any one of claims 1 to 3 , wherein a target is disposed on the first electrode, the target is sputtered by the plasma, and a thin film is formed on a surface of the processing object.

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