JP4134769B2 - Plasma processing method and apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a plasma processing method and apparatus for a micro area.
[0002]
[Prior art]
In general, a resist process is used when patterning is performed on an object typified by a substrate having a thin film formed on the surface. An example is shown in FIG. In FIG. 9, first, a photosensitive resist 26 is applied to the surface of the workpiece 25 (FIG. 9A). Next, the resist 26 can be patterned into a desired shape by developing after exposure using an exposure machine (FIG. 9B). Then, the workpiece 25 is placed in a vacuum vessel, plasma is generated in the vacuum vessel, and the workpiece 25 is etched using the resist 26 as a mask, whereby the surface of the workpiece 25 is patterned into a desired shape. (FIG. 9C). Finally, the resist 26 is removed with oxygen plasma, an organic solvent, or the like, thereby completing the processing (FIG. 9D).
[0003]
Since the resist process as described above is suitable for accurately forming a fine pattern, it has played an important role in the manufacture of electronic devices such as semiconductors. However, there is a drawback that the process is complicated.
[0004]
Therefore, a new processing method that does not use a resist process is being studied. As an example, FIG. 10 shows the configuration of the plasma processing apparatus used in the conventional example.
[0005]
FIG. 10 shows a configuration of a plasma processing apparatus in which a partial surface treatment can be performed in Patent Document 1. A voltage is applied from the power source 31 to one electrode 32. A substrate 35 as an object to be processed is disposed near the other electrode 33, and a mixed gas is supplied from a gas inlet 36 for introducing a processing gas into the solid dielectric container, so that plasma is generated in the solid dielectric container 34. Then, the active particles can be ejected from the gas blowing port 37 onto the substrate 35 to perform a partial processing of the substrate 35. That is, partial surface treatment can be performed without using a resist mask. Note that the jig 38 is for connecting one electrode 32 and another electrode 33.
[0006]
[Patent Document 1]
Japanese Patent Laid-Open No. 9-49083
[Problems to be solved by the invention]
However, the conventional plasma treatment has a problem that the active particles ejected from the gas blowing port 37 spread outward, and only a partial surface treatment in a wide range of approximately 1 mm or more can be performed.
[0008]
In view of the above-described conventional problems, an object of the present invention is to provide a plasma processing method and apparatus capable of performing plasma processing only on a very small region.
[0009]
[Means for Solving the Problems]
In the plasma processing method of the first invention of the present application, a pair of inner plates are arranged outside the electrode having a knife edge shape at the tip, a pair of outer plates are further provided outside the pair of inner plates, and the pair A plasma source that forms an outer gas jet port with the inner plate and the pair of outer plates, and forms an inner gas jet port with the electrode and the pair of inner plates. The outer gas plate is arranged to extend to the tip of the outer gas plate, and is selected from a reactive gas, an organosilane gas, oxygen, or nitrogen while supplying an inert gas to the inner gas jet port. A plasma processing method of processing a part of the object to be processed by supplying a voltage to the electrode or the object to be processed while supplying a gas while bringing the plasma source close to the object to be processed, Plasma source and said In a plasma is generated between the treated and voltage, ON time is characterized by being applied in a pulse form is 10μs from 0.1.
[0010]
In the plasma processing method of the first invention of the present application, it is preferable that the inert gas ejected from the inner gas ejection port is helium, neon, argon, krypton, xenon, or a mixed gas thereof.
[0011]
Preferably, the voltage ON time is 0.1 to 1 μs.
[0012]
Preferably, the voltage pulse is direct current, and positive and negative direct current pulses are supplied substantially alternately. Alternatively, f _AC > 1 / t _ON may be satisfied when the voltage pulse is AC, the ON time is t _ON , and the AC frequency is f _AC .
[0013]
In the plasma processing apparatus according to the second invention of the present application, a pair of inner plates are disposed outside the electrode having a knife edge shape at the tip, a pair of outer plates are further provided outside the pair of inner plates, and the pair A plasma source that forms an outer gas jet port with the inner plate and the pair of outer plates, and forms an inner gas jet port with the electrode and the pair of inner plates. And an inner gas supply device for supplying an inert gas to the inner gas outlet, and a reactive gas or an organosilane-based gas, oxygen, An external gas supply device for supplying a gas selected from nitrogen, and a power supply for supplying a pulse voltage having an ON time of 0.1 to 10 μs to an object to be processed disposed close to the electrode or the plasma source With this The features.
[0014]
In the plasma processing apparatus of the second aspect of the present invention, preferably, in the power supply, a voltage pulse DC, it is desirable to be able to supply each other with positive and negative DC pulse exchange. Alternatively, in the power supply, a voltage pulse AC, the ON time was tON, when the frequency of the alternating current was set to _{f AC, f AC> 1 /} tON may be possible to meet.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0016]
FIG. 1 shows an exploded view of the microplasma source. The microplasma source includes a ceramic outer plate 1, inner plates 2 and 3, and an outer plate 4. The outer plates 1 and 4 are provided with an outer gas flow path 5 and an outer gas outlet 6. And 3 are provided with an inner gas passage 7 and an inner gas outlet 8. The source gas of the gas ejected from the inner gas outlet 8 passes through the through hole 10 provided in the inner plate 2 from the inner gas supply port 9 provided in the outer plate 1 by an inner gas supply device (not shown). Through the inner gas flow path 7.
[0017]
The source gas of the gas ejected from the outer gas outlet 6 is passed through the outer gas supply device (not shown) from the outer gas supply port 11 provided in the outer plate 1 to the through hole provided in the inner plate 2. 12, the gas is guided to the outer gas flow path 5 through the through hole 13 provided in the inner plate 3. Needless to say, the outer gas outlet 6 is disposed outside the inner gas outlet 8. The electrode 14 to which the high frequency power is applied is inserted into the electrode fixing hole 15 provided in the inner plates 2 and 3, and wiring and cooling for supplying the high frequency power are performed through the through holes 16 provided in the outer plates 1 and 4. Done.
[0018]
FIG. 2 shows a plan view of the microplasma source as viewed from the gas outlet side. An outer plate 1, inner plates 2 and 3, and an outer plate 4 are provided, and an outer gas outlet 6 is provided between the outer plate 1 and the inner plate 2 and between the inner plate 3 and the outer plate 4. And 3, an inner gas outlet 8 is provided.
[0019]
FIG. 3 shows a cross section of the thin plate 17 and the microplasma source as objects to be processed cut by a plane perpendicular to the thin plate 17. The microplasma source includes a ceramic outer plate 1, inner plates 2 and 3, and an outer plate 4. The outer plates 1 and 4 are provided with an outer gas flow path 5 and an outer gas outlet 6. And 3 are provided with an inner gas passage 7 and an inner gas outlet 8. The electrode 14 to which the high frequency power is applied is wired and cooled with a power source 18 for supplying a high frequency voltage through a through hole 16 provided in the outer plates 1 and 4. The inner plates 2 and 3 have a tapered lowermost portion so that a finer linear region can be plasma-processed. The thickness of the fine line formed by the inner gas outlet 8 serving as the opening of the microplasma source is 0.1 mm. In this way, the processing is performed by bringing the plasma source close to the thin plate 17 as an object to be processed.
[0020]
As is clear from FIGS. 2 and 3, the microplasma source has an opening formed in a fine line, supplies gas to the outer gas flow path 5, communicates with the outer gas flow path 5, and The gas is blown out from the outer gas discharge port 6 shallower than the outer gas channel 5 toward the object to be processed 17, the gas is supplied to the inner gas channel 7, communicates with the inner gas channel 7, and the inner gas flow Microplasma is generated by supplying electric power to the electrode 14 while blowing gas from the inner gas discharge port 8 shallower than the path 7 toward the workpiece 17. By adopting such a system, the gas supplied from the gas supply device to the outer gas flow path 5 or the inner gas flow path 7 first enters the outer gas flow path 5 or the inner gas flow path 7 which is deep and has a large conductance. Then, it is guided into the outer gas outlet 6 or the inner gas outlet 8 which is shallow and has low conductance.
[0021]
In other words, as the pressure distribution, the pressure in the outer gas flow path 5 is higher than that in the outer gas discharge port 6, and the pressure in the inner gas flow path 7 is higher than in the inner gas discharge port 8. Therefore, compared with the case where there is no difference in depth, the amount and speed of the gas blown out from the outer gas outlet 6 or the inner gas outlet 8 are particularly effective. Note that the conductance of the flow path and outlet is expressed by the terms “deep” and “shallow”, but this is a direction approximately perpendicular to the fine line direction and approximately parallel to the surface of the workpiece. The width of the flow path or the discharge port is expressed as “deep”. Similarly, the flow path or the discharge port is oriented substantially perpendicular to the fine line direction and substantially parallel to the surface of the workpiece. The narrow width is expressed as "shallow".
[0022]
The high frequency power supply 18 can supply AC voltage pulses. As shown in FIG. 4, when the ON time is t _ON and the AC frequency is f _AC , f _AC > 1 / t _ON It is possible to set so as to satisfy. That is, it is possible to set so that at least one sine waveform is included in one pulse of voltage.
[0023]
The microplasma source can operate from several Pa to several atmospheres, but typically operates at a pressure in the range of about 10 ⁴ Pa to about 3 atmospheres. In particular, operation near atmospheric pressure is particularly preferable because a strict sealing structure and a special exhaust device are not required, and diffusion of plasma and active particles is moderately suppressed.
[0024]
In the plasma processing apparatus equipped with a micro-plasma source with such a structure helium (He) as an inert gas from the inner gas ejection port, sulfur hexafluoride as a reaction gas from outside the gas jet port (SF ₆₎ 4 was supplied to the electrode 14 as shown in FIG. At this time, t _ON was set to 0.5 μs (1 / t _ON = 2 MHz), and f _AC was set to 8 MHz. By performing the plasma treatment under such conditions, a minute linear region of the silicon thin plate 17 could be etched. The obtained linear groove width was 65 μm, and a very small region could be processed as compared with the conventional example.
[0025]
This is because the difference in the ease of discharge between helium and sulfur hexafluoride under atmospheric pressure (helium is much easier to discharge) makes it possible to produce an inner gas jet that has a high concentration of helium. Because the microplasma could be generated only in the vicinity of the outlet 8, and because the pulsed voltage was supplied, the plasma generation region became smaller than when the continuous wave AC voltage was supplied. is there. In other words, it can be said that stopping the supply of voltage in a transitional state before reaching a steady state when a continuous wave AC voltage is supplied produced a special effect not found in the conventional example.
[0026]
This will be described in detail with reference to FIG.
[0027]
FIG. 5A shows a state after 0.1 μs after supplying a continuous wave AC voltage to the electrode. Microplasma 19 is generated in the vicinity of the inner gas outlet 8. FIG. 5B shows a state after 0.5 μs after supplying a continuous wave AC voltage to the electrode. A microplasma 19 has developed to the vicinity of the thin plate 17. FIG. 5C shows a state after 10 μs after supplying a continuous wave AC voltage to the electrode. A microplasma 19 is formed between the tip of the microplasma source (tips of the inner plates 2 and 3) and the thin plate 17.
[0028]
It should be noted that the magnitude of the microplasma does not increase beyond 10 μs after supplying a continuous wave AC voltage to the electrode, and the state of FIG. 5C is a steady state when a continuous wave AC voltage is supplied. Is shown. In the present embodiment, since t _{ON is set} to 0.5 μs, the supply of voltage is stopped in a transient state as shown in FIG. 5B, which supplies a continuous wave AC voltage. This is a factor that the plasma generation region is smaller than that in the past, and it is considered that a much smaller region can be etched than the conventional example.
[0029]
Reference: Y.M. Honda et al. "Initial Growth Process of Barrier Discharge in Atmospheric Pressure Helium for Glow Discharge Formation", Japan Journal of Applied Physics. 41, Pt. 2, no. 11A (2002) pp. L1256-L1258 describes the result of considering the transient development of the discharge region in a parallel plate type atmospheric pressure plasma source by simulation.
[0030]
In FIG. 6 shown in this document, the horizontal axis represents the radial position of a circular parallel plate, and the vertical axis represents the electron density. As can be seen from FIG. 6, the plasma gradually spreads over 1.4 μs after the voltage supply is started. Although this research does not deny that it was a big hint to the present invention, this document does not mention the processing of a minute region at all, and the present invention limits the plasma generation region to a smaller region. In addition, an ingenuity of injecting an inert gas and a reactive gas from the inner and outer gas outlets, respectively, is also added, and the present invention can be easily made by combining this document with any other known technique. Is unthinkable.
[0031]
Also, Patent Document 1 described in the conventional example describes the application of a pulsed voltage, but this is exclusively for the purpose of preventing abnormal discharge (arc), and narrows the discharge region. There is no mention of that. That is, it cannot be considered that the present invention can be easily achieved by combining Patent Document 1 with any other known technique. Even if a pulse voltage is applied in the configuration of Patent Document 1, it is possible to prevent arc discharge, but the discharge area becomes wide and it is impossible to process only a very small area. The present invention relates to a technique that makes it possible to process an area of less than 1 mm, or even less than 0.1 mm.
[0032]
In the embodiment of the present invention described above, the case where four ceramic plates are used as the plasma source is exemplified. However, a capillary type such as a parallel plate capillary type or an inductively coupled capillary type, a microgap method, an induction Various plasma sources such as a coupled tube type can be used. In particular, in the type using the knife-edge electrode 24 as shown in FIG. 7, since the distance between the electrode and the object to be processed is short, extremely high density plasma is formed in a minute portion. Therefore, the present invention is particularly effective. In FIG. 7, the plasma source includes a ceramic outer plate 20, inner plates 21 and 22, an outer plate 23, and an electrode 24. The outer plates 20 and 23 have an outer gas flow path 5 and an outer gas outlet. 6 and the inner plates 21 and 22 are provided with an inner gas flow path 7 and an inner gas outlet 8. The lowermost part of the electrode 24 has a knife-edge shape so that a fine linear region can be plasma-processed.
[0033]
Moreover, although the case where the fine linear area | region was plasma-processed was illustrated, this invention is applicable also when processing a fine dotted area | region. In this case, the inner gas outlet is a minute dot or an annular shape surrounding a minute dot-like solid, and the outer gas outlet surrounds the inner gas outlet outside the inner gas outlet. What is necessary is just to provide in the annular | circular shape provided by.
[0034]
Further, by supplying a pulsed voltage to the object to be processed, it is possible to enhance the action of attracting ions in the plasma. In this case, the electrode may be grounded or the electrode may be kept at a floating potential. Alternatively, a second electrode may be provided on the opposite side of the plasma source across the object to be processed, the second electrode may be grounded, or a pulsed voltage may be supplied to the second electrode. Also good. The second electrode has an advantage of concentrating an electric field when the object to be processed is a dielectric, and an advantage that it is unnecessary to provide a contact point on the object to be processed when the object to be processed includes a conductor.
[0035]
Moreover, although the case where the plasma was generated using the pulsed high frequency (alternating current) voltage was illustrated, the frequency of the alternating voltage can use high frequency power from several hundred kHz to several GHz. However, the voltage needs to be pulsed with an ON time of 0.1 to 10 μs. In order to control the ON time to be less than 0.1 μs, there is an inconvenience that the circuit for voltage supply needs a special contrivance so that the waveform does not become distorted. However, the plasma cannot be generated in a limited manner. More preferably, the voltage ON time is 0.1 to 1 μs. When the ON time is 1 μs or less, plasma can be generated in a limited manner in a region that is particularly small compared to the steady state.
[0036]
Further, the voltage pulse is a direct current, and positive and negative direct current pulses can be supplied substantially alternately. Even in this case, the voltage needs to be pulsed with an ON time of 0.1 to 10 μs. More preferably, the voltage ON time is 0.1 to 1 μs. An example of the voltage waveform is shown in FIG. Note that DC pulses that are continuously positive or negative may be supplied, but since discharge occurs only at the first pulse whose polarity is reversed due to charging, in this case also, it is substantially positive and negative. It is considered that DC pulses are supplied alternately.
[0037]
Further, the OFF time of the pulse voltage is desirably set to be as short as possible to improve the processing speed and more than the time required for the generated plasma to be almost completely extinguished. The time is preferably about 0.5 μs to 100 μs. More preferably, the OFF time of the pulse voltage is preferably 1 μs to 10 μs.
[0038]
Moreover, although the case where helium gas is jetted toward the workpiece from the inner gas jet port is illustrated, the gas jetted from the inner gas jet port needs to be a gas mainly composed of an inert gas. This is because, in general, a gas mainly composed of an inert gas is more easily converted into plasma under a pressure near atmospheric pressure than other gases.
[0039]
Moreover, although the case where sulfur hexafluoride gas was jetted from the outer gas jet port was exemplified, a gas that is less likely to be discharged than the reactive gas or the gas jetted from the inner gas jet port is jetted from the outer gas jet port. is required. The method of supplying a pulse voltage has the property of easily generating a stable glow discharge, so if a gas that is easy to discharge, such as an inert gas, is ejected from the outer gas outlet, the plasma spreads over a wide range. There is inconvenience that it is easy to end up. The inert gas supplied from the inner gas outlet is preferably helium, neon, argon, krypton, xenon, or a mixed gas thereof. Helium gas is particularly preferable because it is easy to generate a stable glow discharge near atmospheric pressure. The gas supplied from the outer gas outlet is preferably a gas mainly composed of a gas other than helium, neon, argon, krypton or xenon, such as a halogen-containing etching gas such as fluorine, chlorine or bromine, TEOS, or the like. It is possible to select from a deposition gas typified by organic silane, a gas that is difficult to discharge, such as oxygen and nitrogen, according to the treatment.
[0040]
In addition, when the voltage pulse is AC, the ON time is t _ON , the AC frequency is f _AC , t _ON is 0.5 μs (1 / t _ON = 2 MHz), and f _AC is 8 MHz. However, it is preferable that f _AC > 1 / t _ON be satisfied. It is very difficult to form a waveform that does not satisfy f _AC > 1 / t _ON . More preferably, it is desirable to satisfy f _AC > 10 / t _ON . If f _AC is less than 10 / t _ON , it is difficult to achieve impedance matching because the sideband is generated far from the center frequency f _AC in the voltage when viewed as pulse-modulated _AC . In order to ensure good impedance matching and suppress reflected power, f _AC is better as it is larger than 1 / t _ON .
[0041]
【The invention's effect】
As is apparent from the above description, according to the plasma processing method of the first invention of the present application, a pair of inner plates are arranged outside the electrode having a knife edge shape at the tip, and further outside the pair of inner plates. A plasma source having a pair of outer plates and forming an outer gas jet port with the pair of inner plates and the pair of outer plates and forming an inner gas jet port with the electrodes and the pair of inner plates. A tip portion of the electrode extends to the tip portions of the pair of outer plates, and a reactive gas or an organic gas is supplied to the outer gas jet port while supplying an inert gas to the inner gas jet port. silane-based gas, oxygen, while supplying a gas selected from nitrogen, by supplying a voltage to the electrode or the object to be processed with said plasma source is brought close to the object to be treated, a part of the object to be processed Plasma processing In this method, when plasma is generated between the plasma source and the object to be processed, a voltage is applied in a pulse shape with an ON time of 0.1 to 10 μs, so that plasma processing is performed only in a very small region. be able to.
[0042]
Further, according to the plasma processing apparatus of the second invention of the present application, the pair of inner plates is disposed outside the electrode having a knife edge shape at the tip portion, and a pair of outer plates are further provided outside the pair of inner plates, And a pair of inner plates and the pair of outer plates that form an outer gas outlet and the electrode and the pair of inner plates form an inner gas outlet. Are arranged to extend to the front ends of the pair of outer plates, and supply an inert gas to the inner gas outlet, and a reactive gas or organosilane system to the outer gas outlet A pulsed voltage having an ON time of 0.1 to 10 μs is applied to an outer gas supply device that supplies a gas selected from gas, oxygen, and nitrogen, and an object to be disposed in the vicinity of the electrode or the plasma source. Supply power Because having a can be subjected to plasma processing only to a very small area.
[Brief description of the drawings]
FIG. 1 is an exploded view of a plasma source used in an embodiment of the present invention. FIG. 2 is a plan view of a plasma source used in an embodiment of the present invention. FIG. 4 is a diagram showing an AC voltage pulse waveform in the embodiment of the present invention. FIG. 5 is a sectional view showing a transient state of plasma generation. FIG. 6 is a simulation result of transient development of a discharge region. FIG. 7 is a cross-sectional view of the plasma processing apparatus used in the embodiment of the present invention. FIG. 8 is a diagram showing a DC voltage pulse waveform in the embodiment of the present invention. FIG. 10 is a sectional view of a plasma processing apparatus used in a conventional example.
DESCRIPTION OF SYMBOLS 1 Outer plate 2 Inner plate 3 Inner plate 4 Outer plate 5 Outer gas channel 6 Outer gas outlet 7 Inner gas channel 8 Inner gas outlet 14 Electrode 16 Through hole 17 Thin plate 18 Power supply

Claims (8)

A pair of inner plates are arranged outside the electrode having a tip edge of a knife edge shape, a pair of outer plates are further provided outside the pair of inner plates, and the pair of inner plates and the pair of outer plates A plasma source that forms an outer gas jet and forms an inner gas jet with the electrode and the pair of inner plates;
The tip of the electrode is arranged extending to the tip of the pair of outer plates, and a reactive gas or organosilane system is supplied to the outer gas outlet while supplying an inert gas to the inner gas outlet. A part of the object to be processed is processed by supplying a voltage to the electrode or the object to be processed by bringing the plasma source close to the object to be processed while supplying a gas selected from gas, oxygen, and nitrogen. A plasma processing method,
A plasma processing method, wherein, when generating plasma between the plasma source and the object to be processed, a voltage is applied in the form of a pulse having an ON time of 0.1 to 10 μs.   2. The plasma processing method according to claim 1, wherein the inert gas ejected from the inner gas ejection port is helium, neon, argon, krypton, xenon, or a mixed gas thereof.   2. The plasma processing method according to claim 1, wherein the voltage ON time is 0.1 to 1 [mu] s.   2. The plasma processing method according to claim 1, wherein the voltage pulse is a direct current, and positive and negative direct current pulses are supplied substantially alternately. The plasma processing method according to claim 1, wherein f _AC > 1 / t _ON is satisfied when the voltage pulse is AC, the ON time is t _ON and the AC frequency is f _AC . A pair of inner plates are arranged outside the electrode having a tip edge of a knife edge shape, a pair of outer plates are further provided outside the pair of inner plates, and the pair of inner plates and the pair of outer plates A plasma source that forms an outer gas jet and forms an inner gas jet with the electrode and the pair of inner plates;
The tip of the electrode is arranged to extend to the tip of the pair of outer plates, and is an inner gas supply device that supplies an inert gas to the inner gas outlet, and is reactive to the outer gas outlet. ON time is 0.1 to 10 μs for an outer gas supply device that supplies a gas or a gas selected from organosilane-based gas, oxygen, and nitrogen, and an object to be disposed close to the electrode or the plasma source A plasma processing apparatus comprising: a power supply for supplying a certain pulse voltage.   7. The plasma processing apparatus according to claim 6, wherein the voltage pulse is a direct current, and positive and negative direct current pulses can be supplied substantially alternately. 7. The power supply according to claim 6, wherein when the voltage pulse is alternating current, the ON time is t _ON , and the alternating frequency is f _AC , f _AC > 1 / t _ON can be satisfied. Plasma processing equipment.

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