JP7202641B2 - Plasma processing apparatus and plasma processing method - Google Patents

Description

The present invention relates to a plasma processing apparatus capable of continuously performing a plurality of plasma processing steps.

Patent Document 1 discloses a plate-shaped high-frequency antenna conductor attached so as to airtightly cover an opening provided in a wall surface of a vacuum vessel, and a high-frequency antenna conductor at one end in the longitudinal direction of the antenna conductor. A plasma processing apparatus that feeds power, directly grounds the other end to flow a high-frequency current, generates plasma by an induced electromagnetic field generated in the vicinity of an antenna conductor, and plasma-processes a substrate to be processed using the plasma. is disclosed. Further, Patent Document 2 discloses a plasma processing apparatus provided with two antenna conductors, one for each antenna conductor.

Japanese Patent Application No. 2010-512945 JP 2016-149287 A

The plasma processing process of a substrate material by a plasma processing apparatus includes a plurality of plasma processing processes such as a substrate surface cleaning process, an ion implantation process, or a diamond-like carbon (hereinafter also referred to as DLC) film forming process. In these steps, the substrate to be processed needs to be at a negative potential with respect to the plasma potential of the discharge plasma while being irradiated with ions. In the plasma processing apparatuses described in Patent Documents 1 and 2, ion irradiation is performed by applying a negative DC voltage or a negative pulse voltage with respect to the plasma potential to the substrate to be processed. However, for example, in a plasma processing apparatus having a plurality of plasma processing steps by a roll-to-roll method, it is necessary to apply a negative high voltage to the entire substrate and transfer system, which makes the apparatus complicated and expensive, making it practically unusable. untargetable.
A main object of the present invention is to provide a low-cost and safe plasma processing apparatus capable of performing plasma processing while maintaining a substrate to be processed and a transfer system at ground potential, and capable of continuously performing a plurality of plasma processing steps with different processing conditions. to provide.

The present invention provides a plasma processing chamber (hereinafter simply referred to as processing chamber) in which a substrate to be processed is accommodated, and an inductively coupled antenna unit (hereinafter simply referred to as antenna unit) for generating plasma in the plasma processing chamber. ), a driving power supply for supplying driving power to the antenna unit, an evacuation means for evacuating the inside of the processing chamber, and a gas introduction means for introducing a working gas, wherein the induction A coupled antenna unit includes a rectangular dielectric lid and an inductively coupled antenna conductor (hereinafter simply referred to as an antenna conductor) attached to the surface of the lid, and is formed on the wall surface of the processing chamber. The antenna conductor is mounted so as to block the opening, the feed terminal provided in the center in the longitudinal direction of the antenna conductor is connected to the driving power supply, and the ground terminals provided at both ends in the longitudinal direction are grounded via a capacitor. characterized by

When both ends in the longitudinal direction of the antenna conductor are grounded via capacitors in this way, they act as low impedance to high-frequency voltages and high impedance to DC voltages or low-frequency voltages. By appropriately choosing the capacitance of the capacitor, the antenna conductor can be electrically floated in a conductive state for high frequency voltages and in an insulated state for low frequency voltages. A high-frequency power of, for example, 13.56 MHz is applied to the power supply terminal to excite a high-frequency discharge plasma, and a low-frequency pulse voltage of, for example, 30 kHz can be superimposed and applied. By applying a positive low-frequency pulse voltage to the antenna conductor, the surface of the substrate to be processed can be irradiated with ions. In this specification, an AC voltage with a frequency of 300 kHz or more is described as a high-frequency voltage, and an AC voltage or pulse voltage with a frequency of less than 300 kHz is described as a low-frequency voltage.

The capacitors provided at both ends in the longitudinal direction of the antenna conductor may be external single capacitors. can be configured. It is desirable that the capacitance of the capacitor is 0.1 nF (nanofarad) or more and 30 nF or less.
With such a configuration, both ends of the antenna conductor are substantially grounded against high-frequency current, and are in a floating state against low-frequency current, so that the potential of the antenna conductor can be arbitrarily controlled. can be done.

The antenna unit uses, for example, a machinable ceramics material as a material for the lid, and the antenna conductor, the feeding terminal, and the ground terminal are formed and integrated on the lid by metallizing or the like.
Such an integrated antenna unit can be easily attached to and detached from an opening formed in the wall surface of the processing chamber, so that maintenance of the antenna unit is easy. Also, the heat generated in the antenna conductor can be dissipated.

The antenna conductor surface is covered with an inorganic material containing any one of silicon, silicon compounds, carbon, and carbon compounds. This can suppress scattering of metal impurities from the surface of the antenna conductor.

The drive power source can superimpose a high-frequency voltage and a low-frequency voltage, or a bias voltage such as a positive pulse voltage and supply power to the power supply terminal. By applying a low-frequency voltage or a positive pulse voltage, the plasma potential can be made positive with respect to the ground potential, and plasma processing can be performed while irradiating the substrate at the ground potential with ions.

A plurality of openings are formed in the wall surface of the processing chamber in parallel, and the antenna unit can be attached to each opening.
With such a configuration, the plurality of antenna units can be attached to different openings, so the size of the opening can be made smaller than when a plurality of antenna units are attached to one opening. This reduces the mechanical strength required for the lids that close the openings. The manufacturing cost of the antenna unit can be reduced.

The antenna conductor (hereinafter also referred to as forward antenna conductor) formed on the inner surface of the lid (the inner surface of the processing chamber) and the electrode member (hereinafter referred to as the antenna conductor) formed on the outer surface thereof (the outer surface of the processing chamber). The antenna conductor and the electrode member are electrically connected at both ends in the longitudinal direction, and the other end of the electrode member is grounded via a capacitor to connect the antenna conductor to the antenna conductor. The structure constitutes a reciprocating circuit for the high-frequency current fed to the central portion in the longitudinal direction.
With such a configuration, the inductance of the antenna conductor can be reduced. Therefore, a plasma processing apparatus capable of constructing a long antenna unit and capable of plasma processing a large area can be put into practical use.

Further, the plasma processing apparatus comprises at least one plasma processing chamber according to any one of claims 1 to 7, and a load chamber and an unload chamber for storing the substrate to be processed before and after the processing chamber. A cassette-to-cassette system or roll-to-roll system in-line plasma processing apparatus provided with transport means for transporting substrates to be processed is constructed. If necessary, a plurality of processing chambers are connected so that a plurality of processing steps can be performed continuously.

Plasma potential can be controlled by supplying power to the center of the inductively coupled antenna conductor in the longitudinal direction and grounding both ends through capacitors. This makes it possible to perform plasma processing while irradiating high-energy ions without applying high-frequency voltage or pulse voltage to the substrate to be processed which is at ground potential. In particular, in a roll-to-roll type plasma processing apparatus having a plurality of processing steps, different plasma processing can be performed for each processing chamber. By grounding the substrate to be processed and the transfer system as a whole, the manufacturing cost of the plasma processing apparatus can be reduced and the handling safety can be significantly improved.

1 is a schematic cross-sectional view showing one embodiment of a plasma processing apparatus according to the present invention; FIG. It is a schematic drawing which shows other embodiment of the antenna unit which concerns on this invention. FIG. 4 is a schematic drawing showing another embodiment of an antenna unit; FIG. It is a schematic drawing which shows other embodiment of the plasma processing apparatus which concerns on this invention.

An embodiment of a plasma processing apparatus according to the present invention will be described below with reference to the drawings.

The plasma processing apparatus of the present embodiment employs a so-called inductively coupled plasma (ICP) system, in which discharge plasma is generated using an electromagnetic field generated by applying a high frequency current to an inductively coupled antenna unit. .

Specifically, as shown in FIG. 1, this plasma processing apparatus 100 includes a processing chamber 11 for accommodating a substrate 12 to be processed, an antenna unit 10 for generating plasma in an internal space S of the processing chamber 11, and an antenna unit 10. A high-frequency power supply 22 for supplying high-frequency power, a matching device 21, a bias power supply 23 for supplying a positive pulse voltage, vacuum evacuation means (not shown), working gas introducing means (not shown), and the like are provided.

Specifically, the processing chamber 11 has an opening 112 formed in its wall surface. Here, for example, a rectangular opening 112 is formed in the upper wall portion 111 of the processing chamber 11 when viewed from above. A cover 14 constituting the antenna unit 10 is detachably provided in the opening 112 , and the cover 14 closes the opening 112 to seal the internal space S. As shown in FIG.

In the processing chamber 11, the antenna unit and the substrate 12 to be processed are arranged so as to face the antenna unit. The substrate 12 to be processed is mounted on a substrate holder 18 and grounded through the substrate holder. Also, the substrate temperature can be controlled as needed. The internal space S of the processing chamber 11 is maintained at a predetermined degree of vacuum by evacuation means and gas introduction means. A mixed gas of, for example, argon and hydrogen is introduced into the processing chamber 11 at a predetermined pressure (for example, 1 Pa), and high-frequency power is supplied from a high-frequency power supply 22 to the antenna conductor 13 via a matching box 21, thereby causing discharge. A plasma is excited.

The antenna unit 10 includes a cover 14 made of an insulating plate and an antenna conductor 13 attached to the inner surface of the cover. It has ground terminals 16 at both ends 13a and 13b in the longitudinal direction. The ground terminal is grounded through a capacitor 17. Although the antenna unit 10 of this embodiment includes one antenna conductor 13, it includes a plurality of antenna conductors connected in parallel. It can be anything.

The antenna conductor 13 having, for example, a length of 50 cm or more and a width of about 1 to 10 cm is attached to the inner surface of the lid 14. For example, the lid 14 has a flat plate-like shape having a length of 50 cm or more and a width of about 5 to 20 cm. There is an insulating plate. Further, the thickness dimension of the lid body 14 is required to be strong enough to withstand the atmospheric pressure, and the thickness is about 1 to 3 cm. However, it is not specified by this dimension.

The lid 14 is mounted so as to hold the vacuum seal member 19 and cover the opening 112 provided in the upper wall portion 111. Its size is larger than that of the antenna conductor 13 in the width direction and width of the vacuum seal portion. It has a long dimension in the longitudinal direction. The cover 14 fixes the antenna conductor and at the same time keeps it in an electrically insulated state, and is preferably made of a ceramic material such as alumina, Macor, or photoveil. Further, the lid body 14 may be made of a heat-resistant organic material such as peak resin (PEEK) or fluorine-based resin (PTFE).

The antenna conductor 13 is fed with, for example, a high frequency power of 13.56 MHz and a positive bias voltage, and the antenna conductor is preferably made of a metal material with low resistivity, such as copper or aluminum alloy.

As a method for attaching the antenna conductor to the lid, the antenna conductor can be fixed to the inner surface of the lid 14 with screws or the like. Alternatively, it may be formed on the inner surface of the lid 14 by a metallizing method. Specifically, first, a hole for the power supply terminal 15 and a hole for the ground terminal 16 are formed in the cover 14 made of alumina or the like. After that, a metal layer is formed by applying a Mo--Mn paste to the antenna conductor formation portion of the lid and the inner surface of the terminal hole and firing the paste. An antenna conductor 13 having a thickness of about 30 to 40 μm, for example, is formed thereon by Ni plating or the like. Kovar pins having a coefficient of thermal expansion close to that of the alumina cover 14 are inserted into the terminal holes as the power supply terminals 15 and the ground terminals 16, and the electrode terminals are brazed using silver brazing or the like.
With such a configuration, not only can the antenna conductor 13 be directly attached to the surface of the lid, but heat generated in the antenna conductor can be radiated to the lid.

In this embodiment, since the antenna conductor is exposed to the discharge plasma, the antenna conductor metal may be sputtered and scattered by ion bombardment, contaminating the surface of the substrate to be processed. It is desirable to cover the surface of the antenna conductor with a material that can be scattered. Depending on the purpose of the plasma treatment, carbon-based or silicon-based materials are preferred. Specific examples include silicon, silicon carbide, silicon oxide, silicon nitride, DLC, titanium carbide, and zirconium carbide.

A feature of the plasma processing apparatus 100 of the present embodiment is that a high-frequency voltage of, for example, 13.56 MHz is supplied to the central portion in the longitudinal direction of the antenna conductor to excite high-density ICP plasma in the vicinity of the antenna conductor. The plasma potential can be made higher than the ground potential by superimposing a positive pulse voltage or a low-frequency AC voltage. As a result, plasma processing can be performed while irradiating high-energy ions accelerated by an ion sheath electric field formed on the surface of the substrate to be processed.

The high-frequency power source 22 excites discharge plasma in the vicinity of the antenna conductor, and generally uses high-frequency power with a frequency of 13.56 MHz, but is not limited to this frequency. A high frequency voltage of 300 kHz or higher as used herein is preferred. A bias power supply 23 is for controlling the potential of the high-density plasma excited in the vicinity of the antenna conductor, and is a power supply capable of supplying a positive bias voltage. For example, it is preferable to supply a positive pulse voltage, a positive AC voltage, or a half-wave rectified bias voltage. If the pressure of the working gas is several Pa or more, the discharge plasma can be excited only by a pulse voltage or a low-frequency AC voltage. In this case, the high frequency power supply 22 and the matching box 21 are unnecessary.

In order to control the plasma potential by applying a low-frequency bias voltage, the ground ends 13a and 13b of the antenna conductor should be grounded through the capacitor 17. FIG. A sufficient high-frequency current is passed through the antenna conductor to excite the discharge plasma, and a positive bias voltage is applied to the antenna conductor to control the plasma potential. The density of the plasma excited by the high-frequency discharge is highest near the antenna conductor and attenuates with increasing distance from the antenna conductor. Therefore, applying a positive bias voltage to the antenna conductor to control the plasma potential is a very effective control method, and the plasma potential is also modulated in accordance with the bias voltage. An ion sheath corresponding to the bias voltage is formed on the surface of the substrate to be processed, which is at ground potential, and ions accelerated by this ion sheath enter the substrate.

A suitable capacitance of the capacitor is 0.1 nF to 30 nF so that a sufficient high-frequency current can flow through the antenna conductor and a low-frequency pulse voltage can be applied. A more preferred range is 0.5 nF to 15 nF. For example, if the capacitance is 3 nF, the impedance to a high frequency voltage of 13.56 MHz is about 3Ω, and the impedance to a low frequency voltage of 30 kHz is about 1800Ω. Therefore, although it is in a conductive state for high frequency current, it becomes high impedance for low frequency current, the antenna conductor is placed in an electrically floating state, and the plasma potential can be controlled by applying a pulse voltage.
In addition, if the capacitance of the capacitor is less than 0.1 nF, the impedance against the high-frequency current becomes large and sufficient high-frequency current cannot flow. On the other hand, when the capacitance is 30 nF or more, the impedance to the low-frequency current is low and the power loss increases.

An antenna unit 20, which is another embodiment of the antenna unit, will be described with reference to FIG. As shown in FIG. 1, the capacitor 17 can be an individual capacitor externally attached, but as shown in FIG. 17 may be formed. A dielectric layer 25 can be formed on the surface of the antenna conductor 13 , a ground terminal 16 can be formed on the surface, and grounded to the upper wall portion 111 via a ground wire 26 .

The capacitance of a multilayer capacitor is determined by the area of the electrodes and the dielectric constant and thickness of the dielectric layers. As the material for the dielectric layer, it is desirable to use a dielectric having a large dielectric constant and excellent withstand voltage characteristics, such as zirconia ceramics. For example, if the electrode area is 10 cm ² , the dielectric constant is 30, and the thickness is 0.3 cm, then a multilayer capacitor of about 1 nF can be formed.

Furthermore, another embodiment of the antenna unit will be described with reference to FIG. The antenna unit 30 shown in FIG. 3 further includes the antenna conductor 13 formed on the inner surface of the lid 14 and the electrode member Z formed on the outer surface.
Here, in order to make the explanation easier to understand, the antenna conductor 13 formed on the inner surface of the lid 14 is referred to as the outgoing antenna conductor 13, and the electrode member Z formed on the outer surface is referred to as the return antenna conductor Z. do.

The inbound antenna conductor Z is provided substantially facing the longitudinal direction of the outbound antenna conductor 13, and both ends Za and Zb of the inbound antenna conductor 13 are connected to both ends 13a and 13b of the outbound antenna conductor 13 via conductors Xa and Xb passing through the lid, respectively. are electrically connected. The other end Zc of the return antenna conductor is grounded via a capacitor 17 .

With such a configuration, the high-frequency current supplied to the central portion 13c in the longitudinal direction of the outward antenna conductor 13 flows through the one end portion 13a and the other end portion 13b of the outward antenna conductor 13, and then passes through the connecting ends Za and Zb to the return antenna. It flows into one end of the conductor Z, and flows into the other end Zc of the return antenna conductor Z. As a result, the direction of the high-frequency current flowing through the outward antenna conductor 13 and the direction of the high-frequency current flowing through the return antenna conductor Z are reversed. In other words, the outward antenna conductor 13, the connection ends Za and Zb, and the return antenna conductor Z form a round-trip circuit for the high-frequency current fed to the central portion 13c of the antenna conductor 13 in the longitudinal direction. Mutual inductance occurs between the two reciprocating antenna conductors in such a reciprocating circuit. The impedance of the antenna conductor with respect to the high-frequency current has the effect of being reduced by canceling out the mutual inductance. Therefore, a large high-frequency current can flow with respect to the same high-frequency voltage, and a long antenna unit can be put into practical use.

In addition, the inductance of the parallel plate reciprocating antenna conductor is proportional to the length and spacing of the reciprocating antenna conductor and inversely proportional to the width. That is, the inductance decreases when the reciprocating antenna conductors are brought close to each other, and increases when they are separated from each other. Further, by increasing the width of the central portion of the antenna conductor and decreasing the width of both ends, the inductance of the central portion can be reduced and the inductance of both ends can be relatively increased.

The impedance in the longitudinal direction of the antenna unit can be changed by arbitrarily changing the electrode width at any position in the longitudinal direction of the outgoing antenna conductor and the return antenna conductor. When a high-frequency current is passed through the antenna conductor, high-frequency power is consumed at a portion of the antenna conductor with high impedance, and electromagnetic field energy near the antenna conductor also increases. Thereby, the plasma density distribution in the longitudinal direction of the antenna conductor of the plasma excited in the processing chamber can be controlled.

In the case of the reciprocating antenna conductor according to the present invention, the impedance in the longitudinal direction of the antenna unit 30 can be changed by arbitrarily changing the width at any position in the longitudinal direction. By increasing the conductor width in the central region of the antenna conductor and decreasing the conductor width in both end regions, it is possible to compensate for the reduction in plasma density due to plasma diffusion in the end regions of the antenna conductor. The plasma density in the longitudinal direction of the antenna unit can be made uniform.

Another embodiment according to the present invention will be described with reference to FIG. FIG. 4 is a conceptual diagram of an in-line plasma processing apparatus 200 based on the roll-to-roll system using the principle of the plasma processing apparatus 100 shown in FIG. FIG. 4 is a schematic cross-sectional view seen from above. The plasma processing apparatus 100 has a load chamber 31 and an unload chamber 32 on the left and right sides of the processing chamber 11 of the plasma processing apparatus 100 . In the load chamber 31, a substrate to be processed 13, for example, an aluminum foil for a capacitor, is wound around an unwinding roll 33 and stored. processed by means. The substrate to be processed 12 that has been processed is taken up by the transfer means on a take-up roll 34 stored in the unload chamber 32 and stored, and is periodically carried out to the outside as a product.

The in-line plasma processing apparatus 200 shown in FIG. 4 has three processing chambers C1, C2, C3. For example, the surface of the substrate to be processed is cleaned by ion irradiation in the first processing chamber C1, a thin film such as DLC is formed in the second processing chamber C2, and functional surface treatment is performed in the third processing chamber C3. It can be carried out. Of course, it could also be a single processing chamber.

The load chamber 31, each processing chamber, and the unload chamber 32 are maintained at high vacuum by exhaust means (not shown). A working gas is introduced into each processing chamber by working gas introduction means (not shown), and is adjusted to a predetermined gas pressure, for example, 1 Pa.

When performing a plurality of plasma processing processes in succession in this manner, a plurality of processing chambers may be connected as shown in FIG. 4, and different plasma processing can be performed for each processing chamber. That is, the substrate 12 to be processed is grounded, a working gas required for each processing chamber is introduced to adjust the gas pressure, and a driving voltage different for each processing chamber is supplied to the antenna unit 10 to perform a plurality of plasma processes. can be done simultaneously and consecutively. Since a dedicated processing chamber and processing conditions can be set for each plasma processing step, productivity and product quality can be improved.

Furthermore, each processing chamber can be arbitrarily designed in terms of the size of the processing chamber, the number of mounted antenna units, the size of the antenna conductor, etc., depending on the content of plasma processing.

In the in-line plasma processing apparatus 200 according to the present invention, the substrate to be processed can be transferred between the processing chambers through the substrate transfer slit 36 provided in the partition plate 37 . Since each processing chamber is equipped with working gas introduction means and evacuation means, the working gas pressure difference between adjacent chambers can be set to several Pa or less. Therefore, since the pressure difference of the working gas is several Pa or less and the gas conductance of the substrate transfer slit 36 can be made sufficiently small, it is not necessary to consider the mixing of the working gas between the processing chambers.

Although the representative embodiments have been described above, the present invention is not limited to the above embodiments unless the gist of the invention is changed.

100 plasma processing apparatus 10 antenna unit 11 plasma processing chamber 111 upper wall 112 opening 13 antenna conductor 14 lid 17 capacitor 20 other antenna unit 200 other plasma processing apparatus 21 matching box 22 high frequency power supply 23 bias power supply 25 dielectric plate 30 Other antenna unit 33 Unwinding roll 34 Winding roll 35 Transport roll

Claims (8)

A plasma processing chamber accommodating a substrate to be processed, an inductively coupled antenna unit for generating plasma in the plasma processing chamber, a driving power supply for supplying driving power to the inductively coupled antenna unit, and the plasma processing. A plasma processing apparatus comprising: evacuation means for evacuating a chamber; and gas introduction means for introducing a working gas,
The inductively coupled antenna unit comprises a rectangular dielectric lid and an inductively coupled antenna conductor attached to the surface of the lid, and closes an opening formed in a wall surface of the plasma processing chamber. attached to the
a power supply terminal provided at a central portion in the longitudinal direction of the inductively coupled antenna conductor is connected to the driving power supply;
A plasma processing apparatus, wherein ground terminals provided at both ends in a longitudinal direction are grounded via a capacitor. 2. The capacitor is formed by sandwiching a dielectric member between the inductive coupling antenna conductor and a ground terminal at both longitudinal ends of the inductive coupling antenna conductor. 3. The plasma processing apparatus according to . 3. A plasma processing apparatus according to claim 1, wherein said capacitor has a capacitance of 0.1 nF to 30 nF. 4. The inductively coupled antenna conductor according to any one of claims 1 to 3 , wherein the surface of the inductively coupled antenna conductor is coated with an inorganic material containing any one of silicon, a silicon compound, carbon, and a carbon compound. Plasma processing equipment. 5. The apparatus according to any one of claims 1 to 4 , wherein a plurality of openings are formed in a wall surface of said plasma processing chamber substantially parallel to each other, and said inductively coupled antenna unit is attached to each of said openings. The plasma processing apparatus described. The inductively coupled antenna conductor serving as a forward path for high-frequency current is attached to the inner surface of the lid, and the electrode member serving as a return path is attached to the outer surface of the lid,
The inductively coupled antenna conductor serving as the outward path and the electrode member serving as the return path are electrically connected at both ends in the longitudinal direction, and the other end of the electrode member serving as the return path is grounded via a capacitor. 6. The plasma processing apparatus according to any one of claims 1 to 5 , wherein a reciprocating circuit for the high-frequency current fed to the central portion of the inductively coupled antenna conductor in the longitudinal direction is formed. The plasma processing apparatus comprises at least one plasma processing chamber according to any one of claims 1 to 6 , and a load chamber and an unload chamber for storing the substrate to be processed before and after the plasma processing chamber. A plasma processing apparatus of a cassette-to-cassette system or a roll-to-roll in-line system comprising transport means for transporting the substrate to be processed. 8. The plasma processing apparatus according to any one of claims 1 to 7 , wherein a potential of said inductively coupled antenna conductor is controlled by superimposing high-frequency power and a positive bias voltage on said feeding terminal. A plasma processing method characterized by:

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