Plasma processing method
A plasma processing method utilizing an apparatus comprising a processing chamber to which is connected an exhaust pump for decompressing the chamber, a gas feeding apparatus for feeding gas into the processing chamber, an object to be processed, a wafer electrode for mounting the object, an antenna electrode for generating plasma and opposed to the plate electrode, a plasma generating high frequency power supply connected to the antenna electrode, a first high frequency power supply connected to the wafer electrode, and a second high frequency power supply connected to the antenna electrode. The method includes setting the high frequencies applied from the first high frequency power supply and the second high frequency power supply to be equal and controlling the phase of the respective high frequencies.
The present invention relates to a plasma processing apparatus and plasma processing method, and more specifically, to a plasma processing apparatus and plasma processing method preferable for treating with plasma the surface of a sample such as a semiconductor element.
DESCRIPTION OF THE RELATED ARTWhen plasma is used to perform an etching treatment, process gas is ionized and activated to increase the process speed, and high frequency bias power is applied to the object to be etched so that the ions existing within the plasma are injected perpendicularly on the object, according to which highly accurate etching (for example, anisotropic etching) is made possible.
One example of a conventional plasma processing apparatus for etching consists of a vacuum vessel, a solenoid coil provided to the outer periphery of the exterior of the vacuum vessel, and a circular conductive plate arranged opposite to a sample stage provided within the vacuum vessel. It further consists of a UHF-band power supply and another high frequency power supply connected to the circular conductive plate and a high frequency power supply connected to the sample stage. The apparatus characterized in superposing and applying to the circular conductive plate an electric field of an UHF-band frequency generating plasma by the interaction between the electromagnetic wave from the UHF-band power supply and the magnetic field from the solenoid coil and an electric field of a frequency different from the UHF-band frequency, having the circular conductive plate (made for example of Si) react with plasma, thereby creating more active species that contribute to the etching process. The incident energy of ions to the wafer is controlled by high frequency power supply connected to the sample stage (refer for example to patent documents 1 or 2).
The conventional plasma processing apparatus comprises a processing chamber, as shown in
Above the antenna electrode 103 is provided a coaxial waveguide 108, and via the coaxial waveguide 108, a filter 109 and a matching unit 110, a UHF-band power supply 111 for generating plasma is connected to the electrode 103. Moreover, via the coaxial waveguide 108, a filter 112 and a matching unit 113, the other high frequency power supply 114 is connected to the antenna electrode 103.
A wafer electrode 115 for mounting the object 116 to be processed is located at the bottom of the vacuum vessel 101. The wafer electrode 115 is connected via a filter 117 and a matching unit 118 to a high frequency power supply 119. Moreover, the wafer electrode 115 is connected via a filter 120 to an electrostatic chuck power supply 121 for electrostatically chucking the object 116 to the electrode head.
Patent Document 1:
Japanese Patent Laid-Open Publication No. 9-321031
Patent Document 2:
U.S. Pat. No. 5,891,252
Recently, along with the increase of the integration of the semiconductor integrated circuit, the use of a large-diameter wafer (12 inches) is becoming more and more popular in the production site, so as to enhance throughput. Therefore, it has become an urgent task to improve the uniformity of the processing.
Moreover, in the conventional apparatuses, ions are accelerated by the electric field between the grounded vacuum vessel and the plasma potential. This may cause sputtering of the inner walls of the vacuum vessel by the ions, which results in increase of particles.
Further, along with the increase in the integration degree of semiconductor devices, there is increasing demand for improving the mask selectivity for high-precision surface treatment, and in order to do so, it is very important to create a desirable plasma composition.
SUMMARY OF THE INVENTIONThe first object of the present invention is to provide a plasma processing apparatus and plasma processing method capable of increasing the uniformity of the plasma processing.
The second object of the present invention is to provide a plasma processing apparatus and plasma processing method capable of reducing the amount of particles being generated.
The third object of the present invention is to provide a plasma processing apparatus and plasma processing method capable of providing a high-precision surface treatment.
The first object of the present invention is achieved by providing an electrode that opposes to the wafer electrode on which the sample is disposed, applying high frequency power for generating plasma on the opposing electrode, and applying to each of the electrodes, respectively, a high frequency power having a lower frequency than the high frequency power for generating plasma and with a controlled phase. Further, the phase difference of the high frequency applied to each of the electrodes ranges from 0° to 360°. Moreover, plasma is generated by the high frequency power and magnetic field. Even further, it is effective to switch the phase by multiple steps or to modulate the phase with time.
The second object of the present invention is achieved by providing an electrode that opposes to the wafer electrode on which the sample is disposed, applying high frequency power for generating plasma to the opposing electrode, and applying to each of the electrodes, respectively, a high frequency power having a lower frequency than the high frequency power for generating plasma and with a phase difference controlled to 180°±45°. Moreover, it is further effective to provide a cover and a film containing carbon to the inner walls of the processing chamber.
The third object of the present invention is achieved by providing an electrode that opposes to the wafer electrode on which the sample is disposed, applying high frequency power for generating plasma on the opposing electrode, and applying to each of the electrodes, respectively, a high frequency power having a lower frequency than the high frequency power for generating plasma and with a controlled phase. Further, the phase difference of the high frequency applied to each of the electrodes is in the range of 0° to 360°. Moreover, it is further effective to provide a cover and a film containing carbon to the inner walls of the processing chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
Now, the first preferred embodiment of the present invention will be explained with reference to
A coaxial waveguide 108 is provided above the antenna electrode 103, and via the coaxial waveguide 108, a filter 109 and a matching unit 110, a high frequency power supply 111 for generating plasma (having a frequency of 450 MHz, for example) is connected to the antenna electrode 103. Further, an antenna bias power supply (second high frequency power supply) 114 (having a frequency between 400 KHz and 4 MHz, for example) is connected to the antenna electrode 103 via the coaxial waveguide 108, a filter 112 and a matching unit 113. The filter 109 transmits the high frequency power supplied from the high frequency power supply 111 and effectively cuts the bias power from the antenna bias power supply 114. The filter 112 transmits the bias power supplied from the antenna bias power supply 114 and effectively cuts the high frequency power supplied from the high frequency power supply 111.
A wafer electrode 115 for mounting the object 116 to be processed is disposed to the lower portion of the vacuum vessel 101. A wafer bias power supply (first high frequency power supply) 119 (having a frequency of 400 kHz to 4 MHz, for example) is connected to the plate electrode 115 via a filter 117 and a matching unit 118. Further, an electrostatic chuck power supply 121 is connected to the wafer electrode 115 via a filter 120 for electrostatically attracting the object 116 to the plate electrode. The filter 117 transmits the bias power from the wafer bias power supply 119 and effectively cuts the high frequency power provided from the high frequency power supply 111. Normally, high frequency power is absorbed in the plasma and will not flow toward the wafer electrode 115. The filter 120 transmits the DC power supplied from the electrostatic chuck power supply 121, and effectively cuts the power from the high frequency power supply 111, the antenna bias power supply 114 and the wafer bias power supply 119.
The antenna bias power supply 114 and the wafer bias power supply 119 are connected to a phase controller 122, by which the phase of the high frequency output from the antenna bias power supply 114 and that output from the wafer bias power supply 119 can be controlled. In the example, the frequencies of the antenna bias power supply 114 and the plate bias power supply 119 are the same.
The phase controller 122 takes in voltage waveforms from between the filter 112 and matching unit 113 of the antenna bias power supply 144 and between the filter 117 and matching unit 118 of the plate bias power supply 119, and outputs small amplitude signals with a varied phase to the antenna bias power supply 114 and the wafer bias power supply 119 so that the voltage waveforms have a desired phase difference in the phase controller 122. In this case, the antenna bias power supply 114 and the wafer bias power supply 119 may only be equipped with an amplifying function.
If the phase controller 122 is designed to take in voltage waveforms from between the filter 112 and matching unit 113 of the antenna bias power supply 114 and between the filter 117 and matching unit 118 of the wafer bias power supply 119 but to only output trigger signals controlling the output timing of the power, the antenna bias power supply 114 and the wafer bias power supply 119 should be equipped with a function as an oscillator. In such case, it is possible to set the phase controller to control the output timings of both the high frequency power supplies or to control only the output timing of one power supply. Moreover, it is possible to set one high frequency power supply to have the function as an oscillator and the other high frequency power supply to have only the function as an amplifier, so that the phase controller 122 can supply to the high frequency power supply having only the amplifying function a small amplitude signal with varied phase based on the output signal of the high frequency power supply having the oscillator function.
In the above-explained apparatus, the interior of the processing chamber is depressurized by the exhaust pump 124, and then etching gas is fed into the processing chamber from the gas supplying apparatus 107 with pressure adjusted to a desired pressure level. The high frequency power having for example a frequency of 450 MHz oscillated by the high frequency power supply 111 is transmitted via the coaxial waveguide 108, through the upper electrode 103 and the dielectric window 104 and introduced to the processing chamber.
The electric field of the high frequency power introduced to the processing chamber interacts with the magnetic field created within the chamber by the magnetic field generating coil 105 (for example, a solenoid coil), and generates high density plasma within the chamber. Further, high frequency power (having a frequency of 400 kHz to 4 MHz, for example) is supplied from the antenna bias power supply 114 via the coaxial waveguide 108 to the antenna electrode 103. Furthermore, high frequency power (having a frequency of 400 kHz to 4 MHz, for example) is supplied from the plate bias power supply 119 to the object 116 to be processed mounted on the plate electrode 115, by which the object is subjected to surface processing (such as etching).
When a desirable material is used to form the antenna electrode 103, the application of high frequency voltage to the antenna electrode 103 by the antenna bias power supply 114 causes the material to react with the radicals within the plasma, thereby controlling the composition of the plasma being generated. For example, in etching an oxide film, Si is used as material of the antenna electrode 103 so as to control the amount of F radicals within the plasma that influences the etching performance of the oxide film.
According to the present apparatus, the high frequency power supply 111 with a frequency of 450 MHz is mainly used to generate plasma, the antenna bias power supply 114 is used to control the plasma composition or the plasma distribution, and the wafer bias power supply 119 is used to control the incident energy of the ions within the plasma to the object 116. Advantageously according to the present invention, the plasma generation (ion quantity) and the plasma composition (ratio of concentration of radicals) can be controlled independently.
According to the conventional system, plasma distribution was mainly adjusted by varying the magnetic field formation and changing the absorption efficiency of UHF electromagnetic waves to the plasma within the plane.
A semiconductor device is generally formed of multilayered films. Therefore, in an etching step, it is necessary to etch multiple layers either at once or by continuous steps. The gas, the ion energy and the ion quantity etc. suitable for etching varies according to the material of the object (films), so in order to etch various layers at once, step etching is performed where the gas and supplied power are varied in steps. When gas species and supplied power are varied, the plasma distribution is changed slightly, so it becomes necessary to control the magnetic field and the like according to each step. However, when magnetic field is used to control plasma distribution, the plasma distribution is varied greatly. According to
By modulating the phase difference of
Furthermore, in etching a high aspect ratio hole or a trench, the amount of radicals reaching the bottom of the hole or trench varies according to the aspect ratio and according to the radical species, with respect to the difference in the attachment coefficient of radicals generated in the plasma. The radicals themselves have a lifetime, so the uniformity of radicals on the wafer vary according to radical species. Since the plasma distribution can be varied by phase difference as shown in
When the side wall of the processing chamber is made of aluminum and the surface is treated with alumite (Al2O3) processing, by the use of a CF-system etching gas, the alumite film may be sputtered and damaged or AlF may be formed to the surface if the ion energy being incident on the side wall is high. The Al of the component of alumite being sputtered adheres to the wall surface of the processing chamber, reacts with F, and forms AlF. The AlF thus being formed has a low vapor pressure and is stable, so it is often accumulated gradually and becomes the source of particles. The particles caused by AlF are increased as the number of lot processes of the wafer increases and deteriorates the wafer yield factor, so when a certain management limit value is exceeded the processing chamber is released to the atmosphere, and processes such as exchange of parts and wet cleaning are performed. This leads to degraded apparatus operating rate and increases COC such as increased cost for exchange parts.
AlF particles can be reduced by not using Al for the inner wall surface of the processing chamber or by reducing the energy of ions being incident on the side walls so as to prevent sputtering thereof. Actual means to realize the former method and to reduce AlF particles is to cover or coat the side walls of the processing chamber with a material including carbon. According to the present embodiment, a polyimide cover and a polyimide coating are used considering their heat resistance. According to the conventional apparatus the plasma potential is high as shown in
Another method for not using Al as the inner wall surface of the processing chamber is to apply as coating a fluoride material having high vapor pressure to the surface of the wall. The material for coating may be an oxide of an element belonging to the III A family of the periodic table, such as scandium, yttrium, lanthanum, cerium, neodymium, ytterbium, dysprosium, and lutetium. Even if the oxide of any of the above element is used in the present invention (phase difference 180°), the opposing electrodes alternately function as earth, suppressing the plasma potential to a low value as shown in
According to the present invention, the high frequency voltage applied to two opposing electrodes is set to have a phase difference of 180°±30° so as to suppress the diffusion of plasma within the chamber, and the side walls of the chamber is coated with polyimide so as to reduce the deposition of particles on the side walls. Moreover, since according to the present invention the plasma potential is reduced compared to the conventional apparatus, the energy of ions being incident on the polyimide surface is small and causes very little sputtering. Therefore, the polyimide coating film has a long lifetime.
The second embodiment of the present invention will be explained with reference to
Moreover, according to the above embodiments the present invention is applied to an etching apparatus, but similar advantageous effects can be realized by applying the same to other plasma processing apparatuses such as ashing apparatus and plasma CVD apparatus where high frequency power is supplied to the wafer electrode.
According to the present invention where the plasma distribution is adjusted by controlling the phase of high frequency biases applied to the wafer electrode and to the electrode opposite thereto, the uniformity of etching can be effectively enhanced.
Even further, by controlling the phase of the high frequency bias, the impact of ions on the wall of the chamber can be controlled by the phase difference, by which the occurrence of particles from the inner wall of the apparatus can be reduced, which leads to longer cleaning cycles, and results in an improved throughput.
Moreover, the present invention controls the phase of the high frequency bias to thereby control the plasma composition, so high precision etching is made possible.
Claims
1-10. (canceled)
11. A plasma processing method utilizing a plasma processing apparatus comprising a processing chamber to which is connected an evacuator for decompressing the inner space of the processing chamber; a gas feeding apparatus for feeding gas into the processing chamber; a wafer electrode on which is mounted an object to be processed; an antenna electrode for generating plasma which is disposed so as to oppose to the wafer electrode; a plasma-generating high frequency power supply connected to the antenna electrode; a first high frequency power supply connected to the plate electrode; and a second high frequency power supply connected to the antenna electrode; wherein
- the plasma processing method comprises setting the frequency of the high frequency applied from the first high frequency power supply and that applied from the second high frequency power supply to be equal, and controlling the phase difference of the two high frequencies.
12. A plasma processing method according to claim 11, wherein the phase difference of the high frequencies is controlled within the range of 0° to 360°.
13. A plasma processing method according to claim 11, wherein the phase difference of the high frequencies is switched by steps while the object is being processed.
14. A plasma processing method according to claim 11, wherein the phase difference of the high frequencies is switched by steps within the range of 0° to 360° while the object is being processed.
15. A plasma processing method according to claim 11, wherein the phase difference of the high frequencies is varied with time.
16. A plasma processing method according to claim 11, wherein the phase difference of high frequencies is varied with time within the range of 0° to 360° while the object is being processed.
Type: Application
Filed: Jan 28, 2005
Publication Date: Jun 16, 2005
Inventors: Masahiro Sumiya (Kudamatsu-shi), Naoki Yasui (Kudamatsu-shi), Tomoyuki Tamura (Kudamatsu-shi)
Application Number: 11/043,971