A spiral wave plasma generating device

Abstract

The invention discloses a spiral wave plasma generating device, comprising a quartz glass tube sealed at one end, an inductor coil, a spiral wave antenna, a constant magnetic field coil or a magnet, and a vacuum chamber made of metal. The open end of the quartz glass tube is sealed and connected to the vacuum chamber made of metal, and together with vacuum pumping, gas filling and pressure measuring components, a vacuum system for plasma discharge is formed. The radio frequency antenna located at the sealed end of the quartz glass tube and the inductor coil located at the open end of the quartz glass tube are connected in series to a radio frequency power source, forming a power drive system. The invention utilizes the spiral wave antenna to generate two wave modes in weakly magnetized plasma, one of which is only propagated in the edge region of the plasma due to ion Landau damping in the plasma, thereby improving the energy and density of the boundary plasma, and greatly improving the spatial distribution uniformity of the density and energy of the plasma.

Description

Technical Field

[0001] The invention relates to the technical field of plasma generation, and in particular to a helicon wave plasma generating device. Background Art

[0002] In 1962, Professor Peter Toneman of the Harwell Atomic Energy Laboratory in the United Kingdom discovered the helical wave (H-mode), which is a wave in a steady magnetic field plasma [1]. The helical wave is an electromagnetic wave that propagates in a magnetized plasma. It propagates along the direction of the magnetic field, is circularly polarized, and its cyclotron direction is the same as the cyclotron direction of the carriers in the magnetic field. This wave disturbs the magnetic field lines and turns them into spiral lines, so it is called a helical wave. The helical wave is dispersive, and its phase velocity and group velocity are proportional to the square root of the frequency. The frequency of the helical wave is between the low mixing frequency (ω c Ω c ) 1 / 2 and ion plasma oscillation frequency Ω p between ω and ω, which is much lower than the electron cyclotron frequency ω c , which belongs to the radio frequency band. The spiral wave in the plasma is a low-frequency electrostatic wave with a "spiral" waveform. Therefore, a special antenna can be used to emit spiral waves to produce plasma, namely spiral wave plasma. Although the spiral waves are excited by the induction antenna, these "spiral" waves are largely electrostatic and therefore not propagable. Taking into account the factor of electron mass, Boswell discovered a second wave in the edge region of the plasma, which was named the Trivelpiece–Gould (TG-mode) wave mode [2].

[0003] The plasma excited by the helicon wave is called helicon wave plasma. The most prominent advantage is that when the helicon wave propagates in the plasma, it can heat a large area of ​​electrons, the electron density is high and uniform, and the required confinement magnetic field is not strong. It is worth noting that under the same power, compared with other RF source discharge plasmas, such as capacitive coupled discharge (CCP) and inductive coupled discharge (ICP), the helicon wave discharge can produce high-density and spatially uniform plasma. Uniform plasma is a technology urgently needed by the semiconductor manufacturing industry to improve the yield of products, especially when the wafers are getting bigger and bigger, uniform plasma technology is particularly important. However, helicon wave plasma is not easy to produce under low pressure conditions. It needs to be produced under high pressure (>30mTorr) and then reduced to a low pressure state [3]. This undoubtedly hindered the application of helicon wave plasma in semiconductor manufacturing, and commercialization did not develop further.

[0004] Patent CN103898458A discloses a method for preparing silicon nanocrystalline thin film by spiral wave plasma sputtering technology, and patent CN1121303A discloses a spiral wave plasma processing method and device. Neither of them involves the key technical problem that plasma is not easy to generate under low pressure conditions.

[0005] References:

[0006] [1] Lehane JA and Thonemann PC 1965 Proc. Phys. Soc. 85 301;

[0007] [2] Boswell RW 1984 Plasma Phys. Control. Fusion 26 1147;

[0008] [3] Francis F Chen Plasma Sources Sci. Technol. 24 (2015) 014001(25pp). Summary of the invention

[0009] The helicon wave plasma generating device proposed in the present invention can solve at least one of the above-mentioned technical problems.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] A spiral wave plasma generating device includes a quartz glass tube sealed at one end, an inductor coil, a radio frequency antenna, a constant magnetic field coil or a magnet, and a metal vacuum chamber; the open end of the quartz glass tube is sealed and connected to the metal vacuum chamber, and together with the vacuum pumping, gas filling and pressure measurement components, forms a vacuum system for plasma discharge; the radio frequency antenna located at the sealed end of the quartz glass tube and the inductor coil located at the open end of the quartz glass tube are connected in series to a radio frequency power supply to form a power drive system; the constant magnetic field is generated by a DC power supply to a DC coil placed outside the radio frequency antenna, or by a permanent magnet, to provide a magnetic field system for exciting spiral waves. These three systems constitute a generating device capable of generating high-density uniform plasma under low pressure, and processing semiconductor devices (such as wafers) placed below the open end of the quartz tube in the vacuum chamber.

[0012] Furthermore, the plasma generating device uses a quartz tube with a low electromagnetic wave absorption rate and one end sealed, the inner diameter of the tube is no more than 10 cm, and the open end of the quartz tube is sealed and connected to a vacuum chamber made of metal.

[0013] Furthermore, the inductor coil is placed outside the quartz tube near the sealing end, the number of turns of the coil is more than 3 turns, and the inner diameter is slightly larger than the outer diameter of the quartz tube.

[0014] Furthermore, the radio frequency antenna sleeve is placed outside the quartz tube near the opening end, and the distance from the inductor coil is greater than 5 cm. The length of the antenna is ≧5 cm.

[0015] Furthermore, a constant magnetic field coil or magnet is placed in the RF antenna sleeve and placed in the RF antenna to provide a constant magnetic field of more than 50 Gauss in the plasma discharge region.

[0016] Furthermore, the radio frequency antenna is connected in series with the inductor coil and is powered by a radio frequency power supply through impedance matching.

[0017] Furthermore, the RF antenna is composed of two parallel metal closed loops connected 180° symmetrically by two conductive wires, one end of one of the conductive wires is open-circuited to the metal closed loop for series connection with the inductor coil and the input of the RF power supply.

[0018] Furthermore, the radio frequency antenna connected in series with the inductor coil may also be an antenna of other structures, such as a Boswell antenna, a half-wavelength right-helical antenna, a Nagoya type III antenna, and the like.

[0019] Furthermore, the pressure threshold of plasma operation extends toward low pressure to below mTorr.

[0020] It can be seen from the above technical scheme that the present invention discloses a spiral wave plasma generating device, which belongs to the application technology field of low-temperature plasma and is used to generate plasma with uniform density and energy distribution to meet industrial needs. A spiral wave plasma generating technology described in the present invention is to connect the inductor coil and the radio frequency antenna in series, and generate plasma under the condition of lower vacuum degree in a steady magnetic field under the drive of the radio frequency power supply; the generating device is composed of a quartz glass tube vacuum cavity, an inductor coil, a radio frequency antenna and a DC coil or a magnet that generates a steady magnetic field. The inductor coil generates plasma in a wider range of gas pressures, which makes up for the limitation that the spiral wave plasma can only discharge under higher gas pressures. The radio frequency antenna generates two wave modes in the weakly magnetized plasma, one of which is only propagated in the edge area of ​​the plasma due to the ion Landau damping in the plasma, which improves the energy and density of the boundary plasma, so that the spatial distribution uniformity of the density and energy of the plasma is greatly improved, which makes up for the limitation of the uneven distribution of the inductively coupled discharge plasma. The present invention can be widely used in industrial fields such as plasma cleaning, etching, degumming, material surface modification, and coating.

[0021] The helicon wave plasma generator of the present invention has the following beneficial effects:

[0022] The present invention utilizes the advantage of inductively coupled discharge plasma (ICP) having a wide pressure range to make up for the limitation that spiral wave plasma can only discharge at higher pressures; uses radio frequency antennas to generate two wave modes in weakly magnetized plasma, one of which is only propagated in the edge area of ​​plasma due to ion Landau damping in the plasma, thereby increasing the energy and density of the boundary plasma, greatly improving the spatial distribution uniformity of the density and energy of the plasma, and making up for the limitation of uneven distribution of inductively coupled discharge plasma. The present invention can be widely used in industrial fields such as plasma cleaning, etching, degumming, material surface modification, and coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0024] Figure 2a 1 is a schematic structural diagram of a helicon wave plasma source formed by a radio frequency antenna and an inductor coil connected in series according to an embodiment of the present invention;

[0025] Figure 2b yes Figure 2a Equivalent current loop diagram;

[0026] Figure 3a It is a schematic diagram of the structure of a helical wave plasma source consisting of a half-wavelength right-helical antenna and an inductor coil connected in series;

[0027] Figure 3b yes Figure 3a Equivalent current loop diagram;

[0028] Figure 4a It is a schematic diagram of the structure of a helical wave plasma source consisting of a Boswell antenna and an inductor coil connected in series;

[0029] Figure 4b yes Figure 4a Equivalent current loop diagram;

[0030] Figure 5a It is a schematic diagram of the structure of a helical wave plasma source consisting of a Nagoya III antenna and an inductor coil connected in series;

[0031] Figure 5b yes Figure 5a Equivalent current loop diagram;

[0032] In the figure: 1. Quartz glass tube; 2. Inductor coil; 3. Radio frequency antenna; 4. Steady magnetic field coil or permanent magnet; 5. Metal vacuum chamber. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments.

[0034] Embodiment 1

[0035] like Figure 1 The structure diagram of a spiral wave plasma generation technology and device is shown as follows; an inductor 2 is sheathed on the near closed end of a quartz glass tube 1 that is closed at one end, a radio frequency antenna 3 is sheathed on the near open end of the quartz glass tube 1, a DC power supply is sheathed on the outside of the radio frequency antenna 3, and a constant magnetic field coil 4 that supplies power is used to generate the magnetic field B0 required to excite the spiral wave. Since a very high external magnetic field strength B0 is not required, the spiral wave can be effectively excited between 50 and 500 Gauss, and a permanent magnet can be used to replace the constant magnetic field coil 4. In order to reduce the end face loss of the plasma and the mutual inductance between the inductor 2 and the radio frequency antenna 3, the closed end face of the quartz glass tube 1 and the inductor 2, the inductor 2 and the radio frequency antenna 3, and the inductor 2 and the open end face of the quartz glass tube 1 are all kept at a distance of more than 5 cm. The open end face of the quartz glass tube 1 is sealed and connected to a metal vacuum chamber 5, and the vacuum exhaust, air intake unit and vacuum measurement system are connected to the metal vacuum chamber 5 to provide an air pressure environment for generating plasma. The inductor 2 and the radio frequency antenna 3 are connected in series to a radio frequency power supply with automatic impedance matching. A device for generating helicon wave plasma under low pressure was built.

[0036] This low-pressure helicon wave plasma technology is applicable to the RF antenna structure in the following embodiments.

[0037] Embodiment 2

[0038] Figure 2a It is a structural schematic diagram of a radio frequency antenna of the present invention. The radio frequency antenna 3 of the present invention is composed of two parallel metal closed loops connected by two conductive wires 180° symmetrically, one end of one of the conductive wires is open to the metal closed loop, which is the input point g of the radio frequency power supply. The current is evenly divided from point g to point d, flows through the wire to point e of another metal closed loop, and then evenly divided to point f and flows through the series induction coil 2, and flows out from the other end of the induction coil. Figure 2b The quartz glass tube 1, the induction coil 2, and the radio frequency antenna 3 are implemented according to the first embodiment to build a low-pressure spiral wave plasma generating device.

[0039] Experimental results show that when the steady magnetic field B0 is in the range of 50 gauss to 800 gauss and the discharge pressure is in the range of 0.1 mtorr to 1000 mtorr, radially uniform plasma can be generated using inert gas, nitrogen, oxygen, hydrogen or their mixed gas pressures.

[0040] Embodiment 3

[0041] Figure 3a , Figure 4a , Figure 5a The radio frequency antenna 3 in the embodiment is one of the three radio frequency antennas introduced in reference [3]. According to the steps and methods of the first embodiment, Figure 1 The RF antenna 3 in the Figure 3a , Figure 4a , Figure 5a The RF antenna 3 in the figure is replaced, and the others remain unchanged, to construct three types of helicon wave plasma generating devices. Figure 3b , Figure 4b , Figure 5b is an equivalent current loop diagram, corresponding to the structural schematic diagram Figure 3a , Figure 4a , Figure 5a .

[0042] In Example 2 and Example 3, a quartz glass tube with an inner diameter of Ø60 is used, and the RF power frequency is 13.56MHz and 27MHz respectively, the power is adjustable, and the maximum output power is 1kw. The steady magnetic field B0 is in the range of 50 gauss to 800 gauss. The experimental results show that both Example 2 and Example 3 can discharge normally under low pressure (mtorr), and the plasma density reaches 10 12 —10 13 cm -3 , which is one to two orders of magnitude higher than the density of inductively coupled plasma (ICP) and capacitively coupled plasma (CCP). Under the same power conditions, the plasma density of 27MHz discharge is higher than that of 13.56MHz discharge.

[0043] The spiral wave plasma generation technology and device can be widely used in industries such as semiconductor electronic chips, new energy, new materials, etc. that rely on high-density uniform plasma processing, such as plasma cleaning, etching, thin film deposition, surface modification, etc.

[0044] In summary, the embodiment of the present invention discloses a spiral wave plasma generating device, which belongs to the application technology field of low-temperature plasma, and is used to generate plasma with uniform density and energy distribution to meet industrial needs. A spiral wave plasma generating technology described in the present invention is to connect the inductor coil and the radio frequency antenna in series, and generate plasma under the condition of lower vacuum degree in a steady magnetic field under the drive of the radio frequency power supply; the generating device is composed of a quartz glass tube vacuum cavity, an inductor coil, a radio frequency antenna, and a DC coil or magnet that generates a steady magnetic field. The inductor coil generates plasma in a wider range of gas pressures, which makes up for the limitation that the spiral wave plasma can only discharge under higher gas pressures. The radio frequency antenna generates two wave modes in the weakly magnetized plasma, one of which is only propagated in the edge area of ​​the plasma due to the ion Landau damping in the plasma, which improves the energy and density of the boundary plasma, so that the spatial distribution uniformity of the density and energy of the plasma is greatly improved, which makes up for the limitation of the uneven distribution of the inductively coupled discharge plasma. The present invention can be widely used in industrial fields such as plasma cleaning, etching, degumming, material surface modification, and coating.

[0045] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A helicon wave plasma generating device, comprising a quartz glass tube sealed at one end and an inductor coil, characterized in that: It also includes a radio frequency antenna, a constant magnetic field coil or a magnet, and a vacuum chamber made of metal; The open end of the quartz glass tube is sealed and connected to a vacuum chamber made of metal material, and together with the vacuum pumping, filling and pressure measurement components, forms a vacuum system for plasma discharge; The radio frequency antenna located at the sealed end of the quartz glass tube and the inductor coil located at the open end of the quartz glass tube are connected in series to the radio frequency power supply to form a power drive system; The steady magnetic field is generated by a DC power supply to a DC coil placed outside the radio frequency antenna, or by a permanent magnet, providing a magnetic field system for exciting spiral waves; The radio frequency antenna is composed of two parallel metal closed loops connected by two conductive wires with a 180° symmetry, wherein one end of one of the conductive wires is open-circuited to the metal closed loop for connecting the inductor coil and the input of the radio frequency power supply in series.

2. The helicon wave plasma generator according to claim 1, characterized in that: The plasma generating device adopts a quartz tube with one end sealed at a low electromagnetic wave absorption rate, the inner diameter of the tube is less than or equal to 10 cm, and the open end of the quartz tube is sealed and connected to a vacuum chamber made of metal material.

3. The helicon wave plasma generator according to claim 1, characterized in that: The inductor coil sleeve is placed outside the quartz tube near the sealing end, the number of coil turns is more than 3 turns, and the inner diameter is larger than the outer diameter of the quartz tube.

4. The helicon wave plasma generator according to claim 1, characterized in that: The radio frequency antenna sleeve is placed outside the quartz tube near the opening end, with a distance greater than 5 cm from the inductor coil, and the length of the antenna is ≧5 cm.

5. The helicon wave plasma generator according to claim 1, characterized in that: The constant magnetic field coil or magnet is placed in the RF antenna sleeve and placed on the RF antenna to provide a constant magnetic field of more than 50 Gauss in the plasma discharge region.

6. The helicon wave plasma generator according to claim 1, characterized in that: The radio frequency antenna is connected in series with the inductor coil and is powered by a radio frequency power supply through impedance matching.

7. The helicon wave plasma generator according to claim 1, characterized in that: The radio frequency antenna connected in series with the inductor coil is one of a Boswell antenna, a half-wave right-hand helical antenna, and a Nagoya III type antenna.

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