JP2010177137A - High-density plasma source, and forming method of high density plasma - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-density plasma source applicable to a wide working atmospheric pressure from a low atmospheric pressure to a high atmospheric pressure, and a forming method of high-density plasma. <P>SOLUTION: The high-density plasma source is provided with a constitution, such that a chamber 2; a first conductor 3 arranged inside the chamber 2; a second conductor 4 [4A, 4B, 4C] which is arranged opposed to the first conductor 3 inside the chamber 2 and which is coated by a plurality of dielectrics 5; an alternate current power source 7 impressing a high voltage low-frequency voltage or a high-voltage three-phase AC voltage, each of the same electric potential, to the plurality of second conductors 4; and a negative DC bias power source 6, impressing a DC bias voltage to the first conductor 3, thereby composite plasmas composed of a DC discharge between the chamber 2 and the first conductor 3 and a dielectric barrier discharge, between the first conductor 3 and the plurality of the conductors 4 are generated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a high-density plasma source and a high-density plasma generation method.

  High-density plasma sources include, for example, dry etching in the semiconductor manufacturing field, plasma CVD (chemical vapor deposition) for thin film formation, surface modification of materials or welding and fusing of steel materials, and in recent years treatment of eyes and teeth It is used in various places.

  Conventionally, as a high-density plasma source, a low-pressure operation high-density plasma source and an atmospheric-pressure operation high-density plasma source are known. For example, a magnetron type, an electron cyclotron resonance (ECR) type, and a low-pressure glow discharge type have been put to practical use as high-density plasma sources operating at low atmospheric pressure. Further, as a high-density plasma source operating at atmospheric pressure, for example, a dielectric barrier type, a hollow cathode type, a microwave discharge type, and the like are being actively developed.

  Patent Document 1 discloses a low-pressure glow discharge type and dielectric barrier discharge type plasma source.

Special table 2007-522914 gazette

  By the way, each of the above-mentioned various high-density plasma sources has a narrow optimum operating pressure and lacks versatility.

  In view of the above points, the present invention provides a high-density plasma source and a high-density plasma generation method that can cope with a wide operating pressure from low pressure to high pressure.

  A high-density plasma source according to the present invention includes a chamber, a first conductor disposed in the chamber, and a plurality of dielectrics disposed in the chamber and facing the first conductor. A coated second conductor, an AC power supply that applies a high-voltage low-frequency voltage or a high-voltage three-phase AC voltage to each of the plurality of second conductors, and a negative voltage applied to the first conductor A DC bias power supply for applying a DC bias voltage, a DC discharge between the chamber and the first conductor, and a dielectric barrier discharge between the first conductor and the plurality of second conductors. The present invention is characterized in that a composite plasma comprising:

  In the high-density plasma source of the present invention, a direct current discharge is generated between the first conductor and the chamber, and the dielectric barrier is formed between the first conductor and the second conductor covered with the dielectric. Discharge occurs. Therefore, a composite plasma composed of a direct current discharge and a dielectric barrier discharge, that is, a so-called hybrid plasma is generated in the space near the first conductor. With this hybrid plasma, an ion current density greater than the simple sum of DC discharge and dielectric barrier discharge can be obtained, and by increasing the power of dielectric barrier discharge, high-density plasma is generated at higher atmospheric pressure. .

  A high-density plasma generation method according to the present invention generates a DC discharge between a first conductor to which a negative DC bias voltage is applied and a chamber in a chamber, and a high voltage low frequency voltage having the same potential. Alternatively, a dielectric barrier discharge is generated between the first conductor and the second conductor covered with a plurality of dielectrics to which a high-voltage three-phase AC voltage is applied, and the first conductor A composite plasma comprising a direct current discharge and a dielectric barrier discharge is generated in a nearby space.

  In the high-density plasma generation method of the present invention, a composite plasma composed of a direct current discharge and a dielectric barrier discharge, so-called hybrid plasma, can be generated in the space near the first conductor. This hybrid plasma can produce an ion current density greater than the simple sum of DC discharge and dielectric barrier discharge, and can increase the power of dielectric barrier discharge to generate high-density plasma at higher atmospheric pressure. it can.

  According to the high-density plasma source and the high-density plasma generation method according to the present invention, high-density plasma can be generated in a wide atmospheric pressure range from low pressure to high pressure.

It is sectional drawing which shows schematic structure of the high-density plasma source which concerns on 1st Embodiment of this invention. It is a side view showing a schematic structure of a high-density plasma source concerning a 1st embodiment of the present invention. It is a schematic diagram which shows the coaxial direct current discharge of the discharge forms with which it uses for description of the high-density plasma source which concerns on 1st Embodiment. It is a schematic diagram which shows the dielectric barrier discharge of the discharge forms with which it uses for description of the high-density plasma source which concerns on 1st Embodiment. It is a schematic diagram which shows the hybrid discharge which is a discharge form of the high-density plasma source which concerns on 1st Embodiment. It is a characteristic view which compared the ion current density-atmospheric pressure characteristic of the high-density plasma source which concerns on 1st Embodiment with the case where each of coaxial DC discharge and dielectric barrier discharge is independent. It is a schematic block diagram of the high-density plasma source provided with the measurement circuit for a measurement of ion current density-atmospheric pressure characteristic. It is the schematic of the high-density plasma apparatus used for the measurement of ion current density-atmospheric pressure characteristic. It is sectional drawing which shows schematic structure of the high-density plasma source which concerns on 2nd Embodiment of this invention. It is a perspective view which shows schematic structure of the high-density plasma source which concerns on 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

[First Embodiment]
1 and 2 show a first embodiment of a high-density plasma source according to the present invention. The high-density plasma source 1 according to the first embodiment includes a first conductor 2 and a plurality of surfaces disposed opposite to the first conductor 3 in a chamber 2. And a coated second conductor 4 [4A, 4B, 4C]. In this example, the first conductor 3 is formed by one (one) linear body, and the second conductor 4 is formed by three (three) linear bodies. The chamber 2 has a cylindrical shape and is made of, for example, stainless steel.

  The three second conductors 4A, 4B, 4C are arranged so as to surround the first conductor 3 at equiangular intervals. The three second conductors 4A, 4B, and 4C are opposed to the first conductor 3 with a required equal gap length d and are arranged in parallel to the first conductor 3. The first conductor 3 is located at the center of the cylindrical chamber 2 and is arranged coaxially with the so-called cylindrical chamber 2.

  The second conductor 4 [4A, 4B, 4C] is preferably formed of a metal member, for example, formed of Cu or the like, and the surface dielectric 5 is preferably formed of a heat resistant member such as heat resistant glass. For example, it is formed of a Pyrex tube. The material of the first conductor 3 is selected according to the plasma processing member to be plasma processed.

  Further, the high-density plasma source 1 includes a negative DC bias power source 6 for applying a negative DC bias voltage to the first conductor 3 and a second conductor 4 [4A, 4B, 4C]. An AC power source 7 for applying a high-voltage low-frequency voltage or a high-voltage three-phase AC voltage having the same potential is included. The AC power source 7 is a so-called low frequency power source or a three-phase AC power source. Chamber 2 is grounded. The positive side of the DC bias power supply 6 is grounded. The negative DC bias power source 6 is connected to the first conductor, and more specifically, connected between the first conductor 3 and the chamber 2. The low-frequency power source 7 is connected to the plurality of second conductors 4 [4A, 4B, 4C], and more specifically, the first conductor 3 and the plurality of second conductors 4 [4A, 4B, 4C]. Connected between.

  As an example, the negative DC bias power supply 6 is configured to be variable in the range of 0 V to −1 kV. The AC power supply 7 is configured by a low-frequency power supply capable of supplying low-frequency power with a frequency of 60 Hz to 100 KHz, 1 kVpp to 10 kVpp, for example. Said frequency should just be below the ion plasma frequency proportional to the square root of plasma density.

  Next, the operation of the high-density plasma source 1 will be described together with a high-density plasma generation method. In the high-density plasma source 1, a negative DC bias voltage is applied to the first conductor 3 from the negative DC bias power supply 6, and the plurality of second conductors 4 [4A, 4B, 4C] are supplied from the AC power supply 7. A required low frequency voltage or a three-phase AC voltage is applied. By applying voltage from both power sources 6 and 7, a coaxial DC discharge is generated between the first conductor 3 and the wall of the chamber 2, and the first conductor 3 and the second conductor 4 [4A, 4B]. , 4C], a dielectric barrier discharge occurs. Therefore, a composite plasma consisting of a coaxial DC discharge and a dielectric barrier discharge, that is, a hybrid plasma, is generated in a space near the first conductor 3, that is, a space around the first conductor 3. In the first embodiment, since the three second conductors 4A, 4B, and 4C are arranged at equiangular intervals, so-called triangle plasma is generated.

  FIGS. 3 to 5 show three cases in which triangle plasma is generated in the chamber 2 using a low-frequency power source as the DC bias power source 6 and the AC power source 7 in the high-density plasma source 1 of the first embodiment. It is a schematic diagram of a discharge form. FIG. 3 shows the case where only a negative DC bias voltage is applied to the first conductor 3, and a coaxial DC discharge 8 is generated between the grounded wall of the chamber 2 and the first conductor 3. . FIG. 4 shows the case where only the low frequency voltage is applied to the three second conductors 4 [4A, 4B, 4C], and the second conductor 4 [4A, 4B, 4C] and the first conductors. 3, and between the second conductor 4 [4 A, 4 B, 4 C] and the wall of the chamber 2, a dielectric barrier discharge 9 is generated. FIG. 5 shows a case where both a DC bias voltage and a low frequency voltage are applied, and the hybrid discharge 10 of the present embodiment is generated by combining the coaxial DC discharge 8 of FIG. 3 and the dielectric barrier discharge 9 of FIG. The

  FIG. 6 shows an ionic current density Ji [that compares the case of the coaxial DC discharge alone, the case of the dielectric barrier discharge alone, and the case of the hybrid discharge of the present embodiment in which the coaxial DC discharge and the dielectric barrier discharge are combined. A / m2])-atmospheric pressure P [Pa] characteristics. The ion current density is obtained by measuring the ion current flowing into the first conductor 3, and is approximately proportional to the plasma density.

  As shown in FIG. 7, the ion current was measured by a measurement circuit in which a negative DC bias power source 6 was connected in series with a resistance R of 1 kΩ. That is, by measuring the voltage V across the resistor R, the ions drawn into the first conductor 3 by the negative bias voltage are measured, and the finally measured voltage value is divided by 1 kΩ to obtain the ion current. Asked.

  FIG. 8 shows a schematic apparatus for measuring a high-density plasma source. This apparatus 11 includes three second conductors 4 [4A, 4B, 4C] made of copper (Cu) wires covered with a dielectric 5 made of Pyrex glass tubes in a cylindrical chamber 2, and metal wires. The first conductor 3 is arranged and configured. The three linear second conductors 4 [4A, 4B, 4C] are inserted into the through holes 13A, 13B, 13C of the first holder 12 so that each of them is located at each vertex of the equilateral triangle. Is retained. The first conductor 3 is disposed so as to be inserted into the through hole 14 provided in the first holder 12 and corresponding to the center of gravity of the regular triangle. One end of the first conductor 3 is fixed to the second holder 15, and the other end is held by the third holder 16 via the spring 17 while maintaining a required tension.

  In this apparatus 11, the first conductor 12 supporting the second conductor 4 [4A, 4B, 4C] is replaced to replace the second conductor 4 [4A, 4B, 4C] and the first conductor. The gap length d with the body 3 can be variably set. In addition, the apparatus 11 uses argon (Ar) gas 18 and oxygen (O) gas 19 as the working gas, adjusts the gas flow rate by the mass flow controllers 21 and 22, controls the operating pressure by the rotary pump 23, and exhausts the gas. To do. Chamber 2 is grounded. As a discharge power source, a negative DC bias power source 6 that can be varied between 0 V and 1 kV connected to the first conductor 3, and 13 kHz connected to each second conductor 4 [4A, 4B, 4C], A low-frequency power source 7 having a variable 1 kVpp to 10 kVpp is used.

  6, the gap length d is 1.0 mm, the diameter of the first conductor (tungsten wire) 3 is 0.25 mm, and the second conductor (copper wire) 4 [4A, 4B, 4C], and the outer diameter of the dielectric 5 is 4.0 mm.

  A curve a (◯) is a characteristic of a coaxial DC discharge alone with a negative DC bias voltage of −360V. A curve b (●) shows the characteristics of the dielectric barrier discharge alone with the low frequency voltage set to 2 kVpp. A curve c is a characteristic of the hybrid discharge in which the negative DC bias voltage is −360 V and the low frequency voltage is 2 kVpp. Curve d shows the characteristics of hybrid discharge with a negative DC bias voltage of −360 V and a low frequency voltage of 8 kVpp.

  According to the characteristic diagram of FIG. 6, either the dielectric barrier discharge (curve b) or the coaxial direct current discharge (curve a) alone has a low ion current density incident on the first conductor 3, but discharges them simultaneously. In the hybrid discharge (curves c and d), a synergistic effect that can obtain an ionic current density larger than the simple sum of the two can be confirmed. Moreover, plasma can be generated at a higher atmospheric pressure by increasing the power of the hybrid discharge in the hybrid discharge.

  According to the high-density plasma source 1 according to the first embodiment described above, it is possible to generate high-density plasma in a wide atmospheric pressure range from low pressure to high pressure by hybrid discharge.

  In the high-density plasma source 1 of the first embodiment, the first conductor 3 can be a plasma processing member. At this time, the second conductor 4 is a so-called electrode, and the first conductor 3 facing the electrode is a workpiece to be surface-treated. In this configuration, high-density plasma generation in a wide atmospheric pressure range from low pressure to high pressure is possible, and high-speed processing, such as surface modification or surface coating, is performed on the plasma processing member by the first conductor 3. The surface treatment such as stripping (peeling) or coating of various functional films (so-called surface treatment) can be performed. In the coating of the functional film, a necessary source gas for forming the functional film in the chamber is introduced.

[Second Embodiment]
9 and 10 show a second embodiment of the high-density plasma source according to the present invention. The high-density plasma source 31 according to the second embodiment includes one first conductor 3 in the chamber 2 and three or more surrounding the first conductor 3 at equiangular intervals, three in this example. A combination of the second conductor 4 [4A, 4B, 4C] covered with one dielectric 5 is a unit 32, and a plurality of units are arranged. In this case, the plurality of units are arranged so that the second conductor 4 covered with the dielectric 5 is shared between the adjacent units 32.

  A common negative DC bias power source 6 (not shown) for applying a negative DC bias voltage is connected to the first conductor 3 in each unit 32, and the second conductor 4 in each unit 32. Are connected to a common low-frequency power source 7 (not shown) for applying a high-voltage low-frequency voltage or a high-voltage three-phase AC voltage so as to have the same potential. The other configuration is the same as that described in the first embodiment, and a duplicate description is omitted. The discharge form in each unit 32 is the same hybrid discharge as described in the first embodiment.

  According to the high-density plasma source 31 according to the second embodiment, a hybrid discharge can be simultaneously generated in each unit 32. Further, when the first conductor 3 of each unit 32 is a plasma processing member, the plasma processing members by the plurality of first conductors 3 can be simultaneously surface-treated at a high speed, and the processing time can be reduced. It can be shortened.

  In the first embodiment and the second embodiment, the configuration is such that one first conductor 3 is surrounded by three second conductors 4 arranged at equiangular intervals. As described above, in the first and second embodiments, one first conductor 3 may be surrounded by four or more second conductors 4 arranged at equiangular intervals. In this configuration, a more uniform hybrid discharge can be generated around the first conductor 3. However, the combination of the first conductor 3 and the second conductor 4 covered with the three dielectrics 5 can simplify the configuration.

[Third Embodiment]
Although not shown, the high-density plasma source according to the third embodiment includes a second conductor covered with one first conductor and two dielectrics sandwiching the first conductor from both sides in the chamber. The conductor is arranged. Similar to the first embodiment, a linear first conductor is arranged coaxially in a cylindrical chamber, and the wire is arranged so as to face the first conductor through a required gap length. The second conductor covered with two dielectrics can be arranged at symmetrical positions (at an interval of 180 degrees). The chamber is grounded, the first conductor is connected to a negative DC bias power source, and the second conductor is connected to a low frequency power source or a three-phase AC power source. The first conductor can also be composed of a plasma processing member.

  Also in the high-density plasma source according to the third embodiment, the hybrid discharge described above is generated in the space around the first conductor, as described in the first embodiment. When the first conductor is formed of a plasma processing member, the entire surface of the plasma processing member can be subjected to surface treatment with the generated hybrid plasma.

  In the above example, the first conductor 3 is formed of a linear body. However, the first conductor 3 may be formed of a flat plate, a flexible thin plate, a ribbon, or other members. For example, a semiconductor substrate can be used for the first conductive 3.

  The above-described high-density plasma source of the present invention can be used as a plasma source such as plasma etching or plasma CVD. For example, the high-density plasma source of the present invention can be applied to the surface treatment of saw wires used when a silicon wafer is cut out from a silicon ingot.

  A saw wire made of iron (Fe) with carbon (C) added has a brass plating (Cu: 65%, Zn: 35%) film on the surface. This brass plating is a plating process required for the drawing process of saw wires. When cutting a silicon wafer with saw wire, Cu, which is a main component of brass plating, is a substance having a large diffusion coefficient, and therefore Cu may be diffused into the silicon wafer. If Cu diffuses into the silicon wafer, the conductivity of the silicon changes, and when a circuit element is formed on the silicon substrate, it may cause a malfunction such as an inflow of current to a place other than where the circuit element should flow. is there.

  Therefore, a Cu-free saw wire is required. Currently, a wet process using sulfuric acid or hydrochloric acid is used as a process for removing the surface Cu-containing brass plating film from the saw wire. In this wet process, there are problems that the environmental load increases because ammonia water and hydrogen peroxide water are used, and that waste liquid treatment after use is difficult.

  A dry process using plasma is desired in which a high reaction rate is obtained at a low temperature instead of the above wet process, waste liquid treatment is unnecessary, and exhaust gas treatment after use is easier than waste liquid treatment. The above-described high-density plasma source according to the present invention can be applied to a dry process plasma source for removing the brass plating film of the saw wire. In this case, the first conductor becomes a saw wire to be surface-treated and is transferred through the high-density plasma source. At this time, in the dry process, the operation pressure is set to a high pressure to a medium pressure, and etching is performed without using chlorine gas or fluorine gas, which is usually used as an etching gas, as the operation gas. In the high-density plasma source of the present invention, for example, a mixed gas of argon (Ar) and oxygen (O) can be used as the operating gas. The above-described ion current density is substantially proportional to the etching rate.

  1, 31 .. High-density plasma source, 2 .. Chamber, 3 .. First conductor, 4 [4A, 4B, 4C] .. Second conductor, 5 .. Dielectric, 6. Bias power supply, 7 ·· Low frequency power supply, 8 ·· Coaxial DC discharge, 9 ·· Dielectric barrier discharge, 10 ·· Hybrid discharge, 11 ·· Equipment for high density plasma source measurement, 32 ·· 1 unit

Claims (12)

A chamber;
A first conductor disposed in the chamber;
A second conductor coated with a plurality of dielectrics disposed within the chamber and facing the first conductor;
An AC power supply for applying a high voltage low frequency voltage or a high voltage three-phase AC voltage of the same potential to each of the plurality of second conductors;
A DC bias power supply for applying a negative DC bias voltage to the first conductor;
A composite plasma comprising a DC discharge between the chamber and the first conductor and a dielectric barrier discharge between the first conductor and the plurality of second conductors is generated. A high-density plasma source. 2. The high-density plasma source according to claim 1, wherein two or more second conductors covered with the dielectric are arranged so as to surround the first conductor at equiangular intervals. The first conductor is a linear plasma processing member;
The high-density plasma source according to claim 2, wherein the second conductor covered with the dielectric is a linear body. A combination of one first conductor and a second conductor covered with three or more dielectrics surrounding the first conductor at equiangular intervals as one unit,
A plurality of units are arranged to share the second conductor covered with the dielectric between adjacent units,
The high-density plasma source according to claim 2, wherein the composite plasma is generated in each of the units. The high-density plasma source according to claim 1, wherein the second conductor covered with the plurality of dielectrics is disposed so as to sandwich the first conductor. The high-density plasma source according to claim 1, wherein the first conductor is a plasma processing member. In the chamber
A DC discharge is generated between the first conductor to which a negative DC bias voltage is applied and the chamber;
Dielectric barrier discharge between a first conductor and a second conductor covered with a plurality of dielectrics to which a high-voltage low-frequency voltage or a high-voltage three-phase AC voltage having the same potential is applied. Is generated,
A high-density plasma generation method, comprising: generating a composite plasma including the DC discharge and the dielectric barrier discharge in a space close to the first conductor. Three or more second conductors coated with the dielectric surround the first conductor at equiangular intervals, the second conductor coated with each dielectric, and the first conductor The high-density plasma generation method according to claim 7, wherein dielectric barrier discharge is generated between the conductors. The first conductor is a linear plasma processing member,
The high-density plasma generation method according to claim 8, wherein the second conductor covered with the dielectric is a linear body. A combination of one first conductor and a second conductor covered with three or more dielectrics surrounding the first conductor at equiangular intervals is defined as one unit. The second conductor covered with the dielectric is arranged to be shared between adjacent units;
The high-density plasma generation method according to claim 7, wherein the composite plasma is generated in each unit. The high-density plasma generation method according to claim 7, wherein the second conductor covered with the plurality of dielectrics is disposed so as to sandwich the first conductor. The high-density plasma generation method according to claim 7, wherein the first conductor is a plasma processing member.

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