Patent Application
20100050938
The present application is based on and claims priority of Japanese patent application No. 2008-216344 filed on Aug. 26, 2008, the entire contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a plasma processing apparatus including a detecting means for detecting the plasma condition of the plasma processing apparatus and a detecting method thereof, and more specifically, relates to a plasma processing apparatus having a detecting means for detecting the plasma condition in detail without causing heavy metal contamination, so as to stably control the plasma condition.
2. Description of the Related Art
Recently, processing apparatuses using plasma have been applied widely in the processes of manufacturing not only semiconductor devices but also other products such as flat displays. In plasma processing apparatuses, reactive gases or deposition film material gases are discharged via microwaves or high frequency waves, depending on the aim of the process through which samples are processed. At this time, high energy electrons, ions and active radicals excited by the discharge cause the inner walls and the components of the vacuum processing chamber to be chipped via sputtering or chemically consumed, causing various drawbacks such as mixing of particles to the sample to be processed and heavy metal contamination of the wall surface material. Especially, as the semiconductor devices become highly integrated and the transistor structure becomes minute, the distance between circuit wiring becomes even smaller than 0.1 μm, so that even very minute particles may cause short circuit and other problems. Further, even if a small amount of heavy metal is mixed to the transistor circuit, the electric property thereof is varied and the yield of the products is deteriorated. According to such circumstances, the recent plasma processing apparatuses have a large portion of the surface of the inner wall of the vacuum processing chamber covered with chemically stable material or covered with quartz components. Further, in order to prevent generation of particles by reaction products formed during processing, stepped structures and observation ports on the inner wall of the vacuum processing chamber to which reaction products are easily attached and deposited are reduced.
On the other hand, along with the miniaturization of the semiconductor devices, the manufacturing processes thereof have become more complex and requires higher accuracy, so that there are increasing needs to constantly monitor the status of plasma processing and to control the same to determined values. The various parameters regarding plasma processing include discharge power and processing gas pressure that can easily be monitored and controlled as control parameters of the processing apparatus, but in general, it is difficult to monitor the change of distribution of plasma temperature or plasma density that directly influence the status of processing. A Langmuir measurement method in which a probe of a needle-like electrode is inserted to the plasma is known as the method for measuring the electron temperature and density of plasma, but in the plasma processing apparatuses used for manufacturing semiconductor devices, heavy metal contamination caused by the probe electrode will affect the performance of the semiconductor device, and the variation of processing properties caused by inserting a probe to the plasma causes deterioration of product yield.
Therefore, the plasma processing apparatuses used for manufacturing semiconductor devices widely adopt a method for observing the emission of plasma through an observation window formed on the side wall of the plasma processing apparatus as a means for monitoring the processing condition, as disclosed in the prior art example of Japanese patent application laid-open publication No. 05-259250 (patent document 1). Upon monitoring the plasma emission, it is necessary to form a dielectric window made for example of quartz with an inner diameter of approximately 10 mm on the wall surface of the plasma processing chamber at a position where plasma can be observed, and it is possible to adopt an arrangement in which metal components are not exposed to plasma, so that no heavy metal contamination is caused, and by placing the observation window away from the plasma, it becomes possible to suppress the influence that the window has on the processing conditions. The observed plasma emission data is used for controlling the process by extracting the signals reflecting the change of radical composition within the plasma or the variation of plasma condition based on the emission spectrum of various radicals.
According to the prior art disclosed in Japanese patent application laid-open publication No. 06-188220 (patent document 2) providing a temperature sensor on the inner wall of the plasma processing chamber to control the inner wall of the plasma processing chamber to a constant temperature so as to maintain a constant amount of reaction products caused by etching to be attached to the inner wall of the plasma processing chamber so as to improve the reproducibility of processing. A temperature sensor is relatively easily disposed, such as by forming a small hole from the atmospheric-pressure side of the inner wall made of metal of the processing chamber and inserting and attaching a small thermocouple thereto. Further, since the arrangement does not have any influence on the inner side of the plasma processing chamber, there are no concerns of the arrangement affecting the plasma or causing heavy metal contamination.
Japanese patent application laid-open publication No. 08-222396 (patent document 3) discloses a prior art of measuring a portion of the radio frequency discharge current via a measurement electrode serving as an earth electrode which is positioned in a flange or a recessed portion on a side wall of a reactor in an asymmetric radio-frequency low pressure plasma, wherein the measured signals are converted into digital signals to evaluate the plasma parameter via a mathematical algorithm.
However, according to the prior art plasma processing apparatuses, it is necessary to provide flanges having sensors for detecting the discharge current at positions coming in contact with plasma to measure the plasma condition, or provide observation windows at positions capable of directly observing the emission of plasma. In order to perform highly accurate plasma processing, it is preferable to increase the number of measurement points so as to measure the plasma condition in detail in order to control the processing apparatus with high accuracy, but it is difficult to provide multiple observations ports or flanges having a size of a few centimeters on the side wall of the vacuum processing chamber having a height of approximately 10 to 20 cm, and particles may be increased by providing projected or recessed structures on the inner wall of the vacuum processing chamber. Further, if a sensor is to be arranged within the conductor wall of the vacuum processing chamber, the physical quantity capable of being measured is restricted to the temperature or the like of the wall.
The present invention aims at solving the problems of the prior art by providing a plasma processing apparatus capable of controlling plasma with high accuracy without providing disturbance to the plasma condition, without causing increase of particles, and without damaging the means for detecting the plasma condition.
The first aspect of the present invention provides a plasma processing apparatus including a vacuum processing chamber, a plasma generating means having a plasma-generating high frequency power supply and a magnetic coil to generate plasma in the vacuum processing chamber so as to subject a sample disposed in the vacuum processing chamber to plasma processing, the apparatus comprising: a sheet-like electrode disposed in the interior of the vacuum processing chamber for receiving a high frequency signal from an electric field or a magnetic field indicating the condition of plasma; a signal line connected to the sheet electrode; a signal output means for outputting the signal from the sheet-like electrode to the exterior of the vacuum processing chamber; and a control means comprising a physical quantity detecting unit for detecting a target physical quantity from the high frequency signal from the electric field or the magnetic field indicating the condition of plasma of the vacuum processing chamber, a measurement data storage unit for storing a past measurement data, a standard value and a new measurement data, a measurement processing unit for comparing the past measurement data and the standard value stored in the measurement data storage unit and the new measurement data detected by the physical quantity detecting unit so as to output a signal corresponding to the positional variation or overall density variation of plasma and to output a warning signal when the variation exceeds the standard value, and a control unit for controlling apparatus parameters such as the output of the plasma-generating high frequency power supply and the coil currents of the magnetic coils in response to the variation signal, the positional variation or the overall density variation of plasma from the measurement processing unit so as to stabilize the plasma condition; wherein the sheet-like electrode and the signal line are formed between at least two or more layers of dielectric protection film formed on a surface of an inner wall of the vacuum processing chamber in contact with plasma or on a surface of an inner cylinder having a metal base material arranged between the inner wall of the vacuum processing chamber and the plasma; and wherein the sheet-like electrode either receives or detects the electric field or the magnetic field from the plasma.
Further according to the plasma processing apparatus of the first aspect of the invention, the dielectric protection film is formed via a spray film of dielectric such as an oxide of aluminum or yttrium.
Moreover, according to the plasma processing apparatus of the first aspect of the invention, the sheet-like electrode is arranged on a surface of a dielectric film having a thickness of 10 to 300 μm formed on a surface of the inner wall of the vacuum processing chamber or on a surface of a base material conductor of an inner cylinder arranged within the vacuum processing chamber, and further having a dielectric sprayed film formed on the surface of the sheet-like electrode to a thickness of 10 to 300 μm.
According further to the plasma processing apparatus of the first aspect of the invention, the sheet-like electrode is a planar conductor capacitively coupled with plasma to detect the electric field, a spiral-shaped conductor having one end grounded for detecting the magnetic field, or an antenna for transmitting and receiving electromagnetic waves.
According further to the plasma processing apparatus of the first aspect of the invention, sheet-like electrodes are disposed at least at two locations on the inner wall coming in contact with plasma, high frequency current or voltage flowing in through the plasma to the inner wall of the vacuum processing chamber from the biasing high frequency power applied to the sample are detected at multiple varying locations, and the control means performs control so as to stabilize the condition of plasma based on the information regarding variation of plasma distribution from signals detected by the plurality of sheet-like electrodes.
Further according to the plasma processing apparatus of the first aspect of the invention, the signal output means comprises an output unit connected to the signal line and exposed to an exterior of the dielectric protection film, and an output signal line connected to a vacuum introduction terminal attached to a vacuum wall of the vacuum processing chamber via a connector, so as to output the detection signal detected by the sensing electrode to the exterior of the vacuum processing chamber.
According further to the plasma processing apparatus of the first aspect of the invention, the signal output means is composed of a first antenna such as a coil antenna or a dipole antenna connected to the signal line, and a second antenna such as a coil antenna or a dipole antenna connected to a vacuum introduction terminal attached to a vacuum wall of the vacuum processing chamber for receiving signals from the first antenna; and the sheet-like electrode and the physical quantity detecting means are connected to output the detection signal to the exterior of the vacuum processing chamber.
According further to the plasma processing apparatus of the first aspect of the invention, an IC chip connected to the sheet-like electrode and an antenna for outputting the detection signal to an external circuit are formed within the dielectric protection film at a location where it does not come in contact with high-density plasma, and management data stored in the IC chip such as individual identification information and operation time of components are output to the exterior of the vacuum processing chamber via the antenna, and stored in the measurement data storage unit.
According further to the plasma processing apparatus of the first aspect of the invention, the plasma processing apparatus includes a vacuum processing chamber, and a plasma generating means having a plasma-generating high frequency power supply and a magnetic coil to generate plasma in the vacuum processing chamber by introducing processing gas so as to subject a sample disposed in the vacuum processing chamber to plasma processing, wherein an electric circuit disposed in the interior of the vacuum processing chamber is covered with a dielectric protection film disposed on a surface of an inner wall of the vacuum processing chamber coming in contact with the plasma or on a surface of an inner cylinder formed of a metal base material disposed between the inner wall of the vacuum processing chamber and the plasma so that the electric circuit is not directly exposed to plasma, further comprising a first electrode disposed in the interior of the vacuum processing chamber and connected to the electric circuit for outputting signals from the electric circuit to an exterior of the vacuum processing chamber and a second electrode connected to a control means for controlling plasma generating conditions disposed in the exterior of the vacuum processing chamber, wherein the first electrode and the second electrode transmit and receive the signals via capacitive coupling or inductive coupling.
Now, the preferred embodiments for carrying out the present invention will be described with reference to
In
The vacuum processing chamber 1 for generating plasma and processing samples to be processed has surrounding walls formed of base material such as aluminum and stainless steel, and is connected to an evacuation means 7 for evacuating the vacuum processing chamber 1. A wafer 8, which is the sample to be processed, is held via electrostatic force by an electrostatic chuck 10 at the lower area of the vacuum processing chamber 1. A biasing high frequency power supply 9 is connected to the wafer 8 for applying high frequency to the wafer 8 so as to accelerate ions and promote irradiation. The details of the feeder connected to the electrostatic chuck 10 and the biasing high frequency power supply 9 or the cooling mechanism of the wafer 8 are not shown in the drawing, but the supporting unit of the wafer 8 is formed of many components.
A vacuum window 4 formed of dielectric material for introducing plasma-generating high frequency waves and a gas discharge panel 3 also formed of dielectric material are provided at the upper portion of the vacuum processing chamber 1. The plasma-generating high frequency waves are output from the plasma-generating high frequency power supply 13 with a frequency of tens of MHz to approximately 500 MHz, and via the coaxial pipe 12, are irradiated toward the inner side of the vacuum processing chamber 1 from the high frequency electrode 11. The high frequency electrode 11 is a metal disk-shaped member fixed via an insulating supporting member to a metal casing using screws or the like. Magnetic field coils 14 and a yoke 15 are arranged so as to surround the metal casing including the high frequency electrode 11 at the upper portion of the vacuum processing chamber 1, and by controlling the coil current of each of the magnetic field coils 14, a magnetic field is applied to the whole area of the vacuum processing chamber 1.
Plasma 2 is generated by ionizing the processing gas supplied through the gas discharge panel 3 using the mutual action of the high frequency electric field from the high frequency electrode 11 and the magnetic field. The generated plasma 2 has high temperature and high density near the high frequency electrode 11 having a strong high frequency electric field and in a magnetic field region where the high frequency electric field and magnetic field resonate, which may lead to damage of the inner walls of the vacuum processing chamber 1. Therefore, a dielectric protection film 6 formed of a substance having resistance to plasma and reactive radicals is formed on the inner wall of the vacuum processing chamber 1. Possible materials of the dielectric protection film 6 include a dielectric protection film formed by subjecting the surface of an aluminum base metal to a lumite processing, oxides of aluminum and yttrium, and polymer materials. Further, if reaction products generated during processing are attached and gradually deposited on the inner wall of the vacuum processing chamber 1, deposits detached therefrom become particles, possibly causing defective products.
Therefore, the inner wall of the vacuum processing chamber 1 must be cleaned periodically, so an inner cylinder 5 that can easy be removed and cleaned is disposed inside the vacuum processing chamber 1. Thus, the dielectric protection film 6 on the surface of the inner cylinder 5 exposed to the plasma 2 must have the highest strength, formed for example by thermally spraying yttria Y2O3 to a thickness of 0.1 mm to 0.5 mm on the surface of the aluminum base material.
A plurality of sensing electrodes 21a, 21b and 21c are formed on the inner side of the dielectric protection film 6 for measuring plasma 2. The positions and shapes of the sensing electrodes 21a, 21b and 21c are varied depending on the object of measurement, but the embodiment of
The basic structure of a sensing electrode is illustrated with reference to the cross-section of
The configuration of a sensing electrode seen from plasma 2 will be described with reference to
The detected high frequency signals are transmitted to the exterior of the vacuum processing chamber from the second signal line 33 of
Another embodiment for taking out the detected signals to the exterior of the vacuum processing chamber will be described with reference to
Another embodiment of a sensing electrode will be described with reference to
The high frequency signals detected by the spiral sensing electrode 21s of
According to the embodiment of
A measurement example of the high frequency current measured via the sensing electrodes 21 is illustrated in
Next, we will describe an embodiment in which an IC chip disposed within the vacuum processing chamber is used to manage the identification information of components and the operating time thereof. According to the present embodiment, an IC chip connected to a sheet-like electrode and an antenna for outputting the detection signals to an external circuit are disposed within a dielectric protection film at a position where it is not exposed to high-density plasma within the vacuum processing chamber. The IC chip stores management data including the individual identification information of components such as the surrounding wall of the vacuum processing chamber 1 or the inner cylinder 5 and the operating time thereof. The plasma processing apparatus transmits the management data via an antenna to the exterior, which can be read in a noncontact manner, and the conditions of the components can be managed by storing the management data in the measurement data storage unit, so that it becomes possible to clean the inner wall or the inner cylinder of the vacuum processing chamber at appropriate timings.
According to the plasma processing apparatus of the above-mentioned embodiments, sensing electrodes are arranged within the layers of the dielectric protection film, so that it becomes possible to provide a plurality of sensing electrodes or a large-sized sensing electrode for sensing the plasma status on the inner wall of the vacuum processing chamber without causing heavy metal contamination of the sample being processed. Further, since the sensing electrodes and signal lines are formed within the dielectric protection film, they will not be damaged by plasma or deteriorated by corrosion due to reactive gas, and stable measurement can be performed for a long period of time. Further, by arranging a plurality of sensing electrodes at arbitrary positions on the inner wall of the vacuum processing chamber, the plasma position or density changes can be measured with higher accurately. As a result, the plasma processing apparatus can be controlled via correct measurement data, so that highly accurate and stable plasma processing is enabled.
The present invention is especially useful in detecting and monitoring the status of a plasma processing apparatus especially applied to manufacturing semiconductors, enabling stable processing to be performed for a long period of time.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-216344 | Aug 2008 | JP | national |
