Radio frequency plasma generator based on transformer coupling

Abstract

The invention relates to the technical field of semiconductor manufacturing, and provides a radio frequency plasma generator based on transformer coupling, which comprises a power amplifier unit, a resonant transformer, a gas source, a resonant capacitor, an ignition transformer and an ignition switch, one end of the first winding is connected with a first access point of the power amplifier unit, one end of the resonant capacitor and one end of the ignition switch, the other end of the first winding is connected with a second access point of the power amplifier unit, the other end of the resonant capacitor and one end of the fourth winding, and one end of the third winding is connected with one end of the second winding. The other end of the third winding is grounded, and the other end of the fourth winding is connected with the other end of the ignition switch; when the second winding is in the standby state, the ignition switch is switched off, when the second winding is in the working state, the ignition switch is switched on, the gas source sprays gas to be ionized between the two ends of the second winding, the gas to be ionized is broken down and ionized, and therefore plasma is obtained. The invention provides a portable and reliable plasma source.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing, and in particular to a radio frequency plasma generator based on transformer coupling. Background Art

[0002] Plasma discharge can be used to excite gases, thereby producing activated gases containing ions, free radicals, atoms and molecules. Activated gases are used in many fields of industrial and scientific applications, such as plasma cleaning, sputtering coating, plasma enhanced chemical vapor deposition, etching, etc.

[0003] Plasma can be generated in a variety of ways, including direct current discharge, radio frequency discharge, and microwave discharge. Direct current discharge is achieved by applying a high voltage between two electrodes in a gas. Radio frequency discharge can be achieved by capacitive coupling or inductive coupling to plasma coupling, where parallel plates are usually used to electrostatically couple energy into the plasma and induction coils are used to induce current into the plasma. Microwave discharge can be achieved by coupling microwave energy directly to the reactant gas through a window.

[0004] DC discharge can produce high-energy ions and is suitable for situations where the material being processed is in direct contact with the plasma. RF discharge and microwave discharge plasma sources require expensive and complex power supply systems. These plasma sources require precise RF or microwave power sources and complex matching networks to match the impedance of the reaction chamber. In addition, precision instruments are usually required to determine and control the actual power reaching the plasma, making it inconvenient to use. Summary of the invention

[0005] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention provides a transformer-coupled radio frequency plasma generator to achieve low-cost plasma generation and control.

[0006] The present invention provides a transformer-coupling-based radio frequency plasma generator, comprising a power amplifier unit, a resonant transformer, a gas source, a resonant capacitor, an ignition transformer and an ignition switch; wherein one end of a first winding of the resonant transformer is connected to a first access point of the power amplifier unit, one end of the resonant capacitor and one end of the ignition switch, the other end of the first winding is connected to a second access point of the power amplifier unit, the other end of the resonant capacitor and one end of a fourth winding of the ignition transformer, both ends of the second winding of the resonant transformer are disconnected and the distance between the two ends is within the breakdown distance, a gas outlet of the gas source is aligned between the two ends of the second winding, one end of a third winding of the ignition transformer is connected to one end of the second winding, the other end of the third winding is grounded, and the other end of the fourth winding is connected to the other end of the ignition switch; When the second winding is in a standby state, the ignition switch is disconnected, and the power amplifier unit has no current output; when the second winding is in a working state, the ignition switch is closed, and the power amplifier unit outputs current alternately. The gas outlet sprays the gas to be ionized between the two ends of the second winding, and the gas to be ionized is broken down and ionized by the electric field of the second winding, thereby obtaining ionized gas. The ionized gas is used as plasma, and after the ionized gas begins to be generated, the ignition switch is disconnected.

[0007] According to a transformer-coupled RF plasma generator provided by the present invention, the power amplifier unit includes a first transistor, a second transistor, a third transistor, a fourth transistor, a first access point, and a second access point, wherein the drain of the first transistor is connected to the drain of the second transistor, the source of the second transistor is connected to the drain of the third transistor and the second access point, the source of the third transistor is connected to the source of the fourth transistor, and the drain of the fourth transistor is connected to the source of the first transistor and the first access point.

[0008] A transformer-coupled RF plasma generator according to the present invention comprises a first drive amplifier, a second drive amplifier, a third drive amplifier and a fourth drive amplifier, wherein the output end of the first drive amplifier is connected to the gate of the first transistor, the output end of the second drive amplifier is connected to the gate of the second transistor, the gate of the third drive amplifier is connected to the gate of the third transistor, and the fourth drive amplifier is connected to the gate of the fourth transistor; When the power amplifier unit alternately outputs current within a cycle, the cycle includes a first discharge time and a second discharge time. During the first discharge time, the first drive amplifier and the third drive amplifier output a high level, and the first transistor and the third transistor are turned on. During the second discharge time, the second drive amplifier and the fourth drive amplifier output a high level, and the second transistor and the fourth transistor are turned on.

[0009] A transformer-coupled RF plasma generator provided according to the present invention includes a control unit, which is connected to the input end of the first drive amplifier, the input end of the second drive amplifier, the input end of the third drive amplifier, and the input end of the fourth drive amplifier. The control unit controls the output levels of the first drive amplifier, the second drive amplifier, the third drive amplifier, and the fourth drive amplifier.

[0010] A transformer-coupled RF plasma generator provided according to the present invention includes a power supply unit, the power supply unit includes a high-voltage power supply unit and a low-voltage power supply unit, the high-voltage power supply unit supplies power to the power amplifier unit, the low-voltage power supply unit supplies power to the control unit and the first drive amplifier, the second drive amplifier, the third drive amplifier and the fourth drive amplifier, the power supply unit is connected to the control unit and is controlled by the control unit.

[0011] According to a transformer-coupled RF plasma generator provided by the present invention, the resonant transformer is a magnetic core transformer, the first winding of the resonant transformer and the resonant capacitor form a resonant circuit, and the resonant circuit achieves stabilization of the plasma by changing the relative phase of the voltage and current in the second winding.

[0012] According to a transformer-coupled radio frequency plasma generator provided by the present invention, a cavity shell is provided around the second winding and the gas outlet, and the material of the cavity shell is a ceramic material.

[0013] According to the present invention, a transformer-coupled radio frequency plasma generator includes a first voltage monitoring unit and a second voltage monitoring unit, wherein the first voltage monitoring unit is connected to the first access point and one end of the ignition switch, and the second voltage monitoring unit is connected to one end of the first winding and one end of the resonant capacitor, wherein the first voltage monitoring unit monitors the voltage, current and power supply frequency of the first access point, and the second voltage monitoring unit monitors the voltage, current and power supply frequency of the first winding.

[0014] According to a transformer-coupled radio frequency plasma generator provided by the present invention, the ignition switch is an air switch.

[0015] The above one or more technical solutions in the embodiments of the present invention have at least one of the following technical effects: The present invention provides a transformer-coupled RF plasma generator, which realizes alternate power supply and control of the second winding relatively simply by driving an amplifier to control the on and off of a transistor in a power amplifier module. A relatively stable plasma can be generated by adjusting the frequency of the power supply and by using a resonant capacitor and a resonant transformer, without the need for additional matching devices, RF lines, reaction chambers, etc., thereby realizing power control and precise regulation of a plasma source at a relatively low cost and in a relatively small volume.

[0016] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a structural schematic diagram of a transformer-coupled radio frequency plasma generator provided by the present invention.

[0019] Figure 2 It is a structural schematic diagram of a power supply unit of a transformer-coupled radio frequency plasma generator provided by the present invention.

[0020] Reference numerals: 11. resonant capacitor; 12. first winding; 13. second winding; 14. cavity shell; 15. gas source; 21. ignition switch; 22. fourth winding; 23. third winding; 24. equivalent inductance; 25. equivalent resistance; 31. first transistor; 32. second transistor; 33. third transistor; 34. fourth transistor; 35. first access point; 36. second access point; 41. first drive amplifier; 42. second drive amplifier; 43. third drive amplifier; 44. fourth drive amplifier; 51. high voltage power supply unit; 52. low voltage power supply unit; 53. power switch; 61. control unit; 62. first voltage monitoring unit; 63. second voltage monitoring unit. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present invention. The following embodiments are used to illustrate the present invention, but cannot be used to limit the scope of the present invention.

[0022] In the description of the embodiments of the present invention, it should be noted that the terms “first”, “second” and “third” are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0023] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "connected" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention can be understood according to specific circumstances.

[0024] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the embodiment of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0025] See also Figure 1 to Figure 2 , this embodiment provides a transformer-coupled RF plasma generator.

[0026] Combine the following Figure 1 A transformer-coupled RF plasma generator is described in an embodiment of the present invention, comprising a power amplifier unit, a resonant transformer, a gas source 15, a resonant capacitor 11, an ignition transformer and an ignition switch 21; wherein, one end of the first winding 12 of the resonant transformer is connected to the first access point 35 of the power amplifier unit, one end of the resonant capacitor 11 and one end of the ignition switch 21, the other end of the first winding 12 is connected to the second access point 36 of the power amplifier unit, the other end of the resonant capacitor 11 and one end of the fourth winding 22 of the ignition transformer, the two ends of the second winding 13 of the resonant transformer are disconnected and the distance between the two ends is within the breakdown distance, the gas outlet of the gas source 15 is aligned between the two ends of the second winding 13, one end of the third winding 23 of the ignition transformer is connected to one end of the second winding 13, the other end of the third winding 23 is grounded, and the other end of the fourth winding 22 is connected to the other end of the ignition switch 21.

[0027] Here, the resonant transformer is a magnetic core transformer. The structure of the first winding 12 is similar to that of an inductor and can be regarded as an inductor, thereby forming a resonant circuit with the resonant capacitor 11. The turns ratio of the first winding 12 and the second winding 13 is 4 to 1, and the turns ratio of the fourth winding 22 and the third winding 23 is 1 to 3.

[0028] When the second winding 13 is in standby mode, that is, when no plasma is generated, the ignition switch 21 is disconnected, and the power amplifier unit has no current output. When the second winding 13 is in working mode, the ignition switch 21 is first closed, and the first access point 35 and the second access point 36 of the power amplifier unit also alternately output alternating current, and current will pass through the fourth winding 22. Since the fourth winding 22 and the third winding 23 together form an ignition transformer, and the power amplifier unit is alternately discharged, the current flowing through the fourth winding 22 is alternating current, so the current will be transmitted to the third winding 23, and since the number of turns of the third winding 23 is large, the voltage of the third winding 23 is high, and the second winding 13 and the third winding 23 are connected, so the voltage across the second winding 13 is also high.

[0029] At the same time, the gas outlet of the gas source 15 sprays the gas to be ionized between the two ends of the second winding 13. Here, the gas to be ionized can be argon, helium, nitrogen, etc., or a mixed gas. Since the two ends of the second winding 13 are disconnected and the distance between the two ends is within the breakdown distance, that is, the voltage at the two ends of the second winding 13 is sufficient to break down the gas to be ionized between the two ends, the gas to be ionized is broken down and ionized by the electric field of the second winding 13, thereby obtaining ionized gas, and the ionized gas is used as plasma. At this time, the plasma is a conductor and can be regarded as an equivalent inductance 24 and an equivalent resistance 25 connected in series. The breakdown distance is determined according to the type of gas to be ionized and the voltage at the two ends of the second winding 13 during ignition.

[0030] After the ionized gas begins to be generated, the two ends of the second winding 13 are turned on and the resistance of the plasma is small. Therefore, only a small voltage is required to continuously generate plasma, and a small voltage is beneficial to the life of the equipment and the stable control of the plasma. Therefore, the ignition switch 21 is disconnected. Here, in order to ensure the stability and reliability of the ignition switch 21, the ignition switch 21 uses an air switch, and the air switch can also protect the circuit during the high-voltage ignition stage to avoid damage caused by short circuits.

[0031] After ignition is completed, the gas source continues to spray the gas to be ionized to both ends of the second winding 13. Since there is plasma at both ends of the second winding 13, as long as the power amplifier unit continues to supply power, the gas to be ionized that arrives later can be ionized into new plasma, and the previous plasma is blown away to meet the external needs for plasma. Since the second winding 13 continuously generates plasma, its surrounding environment is relatively harsh, and a relatively stable environment is required to generate plasma, so a cavity shell 14 is provided around the second winding 13 and the gas outlet. In order to cope with high-temperature plasma, the cavity shell 14 is made of ceramic material, and in this embodiment, yttrium aluminum garnet material is selected.

[0032] Since the first winding 12 and the resonant capacitor 11 form a resonant circuit, the alternating current entering the first winding 12 through the power amplifier unit will resonate. At this time, it is only necessary to change the frequency of the current input into the first winding 12 by the power amplifier unit to change the relative phase of the current and voltage of the first winding 12. The first winding 12 and the second winding 13 form a resonant transformer, and the ignition transformer is disconnected at this time, so the relative phase of the current and voltage of the second winding 13 will also change, thereby ensuring impedance matching by changing the relative phase of the current and voltage of the second winding 13, and realizing the control of the process of generating plasma, so as to stably generate plasma. The frequency of the current can be adjusted in real time according to the state of the plasma.

[0033] The power amplifier unit includes a first transistor 31, a second transistor 32, a third transistor 33, a fourth transistor 34, a first access point 35 and a second access point 36, wherein the drain of the first transistor 31 is connected to the drain of the second transistor 32, the source of the second transistor 32 is connected to the drain of the third transistor 33 and the second access point 36, the source of the third transistor 33 is connected to the source of the fourth transistor 34, and the drain of the fourth transistor 34 is connected to the source of the first transistor 31 and the first access point 35.

[0034] In addition, there are a first driving amplifier 41, a second driving amplifier 42, a third driving amplifier 43 and a fourth driving amplifier 44. The output end of the first driving amplifier 41 is connected to the gate of the first transistor 31, the output end of the second driving amplifier 42 is connected to the gate of the second transistor 32, the gate of the third driving amplifier 43 is connected to the gate of the third transistor 33, and the fourth driving amplifier 44 is connected to the gate of the fourth transistor 34.

[0035] When the power amplifier unit alternately outputs the alternating current in one cycle, one cycle of the alternating current includes a first discharge time and a second discharge time. In the first discharge time, the first drive amplifier 41 and the third drive amplifier 43 output a high level, so that the first transistor 31 and the third transistor 33 are turned on, and the second transistor 32 and the fourth transistor 34 are in the off state. The alternating current reaches the first winding 12 through the first transistor 31 and the first access point 35, and then flows out through the second access point 36 and the third transistor 33. In the second discharge time, the second drive amplifier 42 and the fourth drive amplifier 44 output a high level, so that the second transistor 32 and the fourth transistor 34 are turned on, and the first transistor 31 and the third transistor 33 are in the off state. The alternating current reaches the first winding 12 through the second transistor 32 and the second access point 36, and then flows out through the first access point 35 and the fourth transistor 34. The driving amplifier controls the on and off of the transistor by outputting high and low levels, thereby enabling the power amplifier module to output alternating current. In addition, the driving amplifier can also adjust the phase of the alternating current output by the power amplifier module by controlling the duration of its output high and low levels, thereby promoting the stability of plasma generation.

[0036] The present invention also includes a control unit 61, which includes a programmable logic unit and a processor. The control unit 61 is connected to the input end of the first driving amplifier 41, the input end of the second driving amplifier 42, the input end of the third driving amplifier 43 and the input end of the fourth driving amplifier 44. The control unit 61 controls the output levels of the first driving amplifier 41, the second driving amplifier 42, the third driving amplifier 43 and the fourth driving amplifier 44, thereby realizing the control of the output process of the alternating current of the power amplifier unit.

[0037] The present invention further comprises a power supply unit, Figure 2: is a schematic diagram of the structure of the power supply unit. The power supply unit includes a high-voltage power supply unit 51 and a low-voltage power supply unit 52. The high-voltage power supply unit 51 is connected to the power amplifier unit and supplies power to the power amplifier unit. In this embodiment, one end of the high-voltage power supply unit 51 is connected to the drain of the first transistor 31 and the drain of the second transistor 32, and the other end is connected to the source of the third transistor 33 and the source of the fourth transistor 34. The low-voltage power supply unit 52 is connected to the control unit and the drive amplifier, so as to supply power to the control unit 61 and the first drive amplifier 41, the second drive amplifier 42, the third drive amplifier 43 and the fourth drive amplifier 44. The high-voltage power supply unit 51 of the power supply unit is connected to the control unit 61. When the frequency of the current input to the first winding 12 of the power amplifier unit needs to be changed, the control unit 61 will change the frequency of the current input to the power amplifier unit by the high-voltage power supply unit 51 through its built-in frequency modulation algorithm. The power supply unit also includes a power switch 53 having one end connected to an external power supply and one end connected to the high voltage power supply unit 51 and the low voltage power supply unit 52. The power switch 53 is used to control the on and off of the external current. In this embodiment, the power switch 53 is an air switch.

[0038] The present invention also includes a first voltage monitoring unit 62 and a second voltage monitoring unit 63. The first voltage monitoring unit 62 is connected to the first access point 35 and one end of the ignition switch 21, and the second voltage monitoring unit 63 is connected to one end of the first winding 12 and one end of the resonant capacitor 11. The first voltage monitoring unit 62 monitors the voltage, current and power supply frequency of the first access point 35, and the second voltage monitoring unit 63 monitors the voltage, current and power supply frequency of the first winding 12. The first voltage monitoring unit 62 and the second voltage monitoring unit 63 are also connected to the control unit 61 to return the monitored voltage, current and power supply frequency to the control unit 61, so that the control unit 61 adjusts the frequency of the current input to the power amplifier unit by the high-voltage power supply unit 51 according to the frequency modulation algorithm, thereby ensuring the stability of the ignition and plasma generation process.

[0039] The present invention provides a light and low-cost plasma generator that does not require complicated matching devices, radio frequency lines, reaction chambers and other equipment, and realizes power control and precise regulation of a plasma source at a relatively low cost and in a relatively small volume.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. 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 transformer-coupled radio frequency plasma generator, characterized in that: It comprises a power amplifier unit, a resonant transformer, a gas source, a resonant capacitor, an ignition transformer and an ignition switch; wherein, one end of the first winding of the resonant transformer is connected to the first access point of the power amplifier unit, one end of the resonant capacitor and one end of the ignition switch, the other end of the first winding is connected to the second access point of the power amplifier unit, the other end of the resonant capacitor and one end of the fourth winding of the ignition transformer, the two ends of the second winding of the resonant transformer are disconnected and the distance between the two ends is within the breakdown distance, the gas outlet of the gas source is aligned between the two ends of the second winding, one end of the third winding of the ignition transformer is connected to one end of the second winding, the other end of the third winding is grounded, and the other end of the fourth winding is connected to the other end of the ignition switch; When the second winding is in a standby state, the ignition switch is disconnected, and the power amplifier unit has no current output; when the second winding is in a working state, the ignition switch is closed, and the power amplifier unit outputs current alternately. The gas outlet sprays the gas to be ionized between the two ends of the second winding, and the gas to be ionized is broken down and ionized by the electric field of the second winding, thereby obtaining ionized gas. The ionized gas is used as plasma, and after the ionized gas begins to be generated, the ignition switch is disconnected.

2. The transformer-coupled RF plasma generator according to claim 1, characterized in that: The power amplifier unit includes a first transistor, a second transistor, a third transistor, a fourth transistor, a first access point, and a second access point, wherein the drain of the first transistor is connected to the drain of the second transistor, the source of the second transistor is connected to the drain of the third transistor and the second access point, the source of the third transistor is connected to the source of the fourth transistor, and the drain of the fourth transistor is connected to the source of the first transistor and the first access point.

3. The transformer-coupled RF plasma generator according to claim 2, characterized in that: The invention comprises a first driving amplifier, a second driving amplifier, a third driving amplifier and a fourth driving amplifier, wherein the output end of the first driving amplifier is connected to the gate of the first transistor, the output end of the second driving amplifier is connected to the gate of the second transistor, the gate of the third driving amplifier is connected to the gate of the third transistor, and the fourth driving amplifier is connected to the gate of the fourth transistor; When the power amplifier unit alternately outputs current within a cycle, the cycle includes a first discharge time and a second discharge time. During the first discharge time, the first drive amplifier and the third drive amplifier output a high level, and the first transistor and the third transistor are turned on. During the second discharge time, the second drive amplifier and the fourth drive amplifier output a high level, and the second transistor and the fourth transistor are turned on.

4. The transformer-coupled RF plasma generator according to claim 3, characterized in that: It includes a control unit, which is connected to the input end of the first driver amplifier, the input end of the second driver amplifier, the input end of the third driver amplifier and the input end of the fourth driver amplifier, and the control unit controls the output levels of the first driver amplifier, the second driver amplifier, the third driver amplifier and the fourth driver amplifier.

5. The transformer-coupled RF plasma generator according to claim 4, characterized in that: It includes a power supply unit, which includes a high-voltage power supply unit and a low-voltage power supply unit. The high-voltage power supply unit supplies power to the power amplifier unit, and the low-voltage power supply unit supplies power to the control unit and the first drive amplifier, the second drive amplifier, the third drive amplifier and the fourth drive amplifier. The power supply unit is connected to the control unit and is controlled by the control unit.

6. The transformer-coupled RF plasma generator according to claim 1, characterized in that: The resonant transformer is a magnetic core transformer. The first winding of the resonant transformer and the resonant capacitor form a resonant circuit. The resonant circuit stabilizes the plasma by changing the relative phase of the voltage and current in the second winding.

7. The transformer-coupled RF plasma generator according to claim 1, characterized in that: A cavity shell is provided around the second winding and the gas outlet, and the material of the cavity shell is ceramic material.

8. The transformer-coupled RF plasma generator according to claim 1, characterized in that: The device comprises a first voltage monitoring unit and a second voltage monitoring unit, wherein the first voltage monitoring unit is connected to the first access point and one end of the ignition switch, and the second voltage monitoring unit is connected to one end of the first winding and one end of the resonant capacitor. The first voltage monitoring unit monitors the voltage, current and power supply frequency of the first access point, and the second voltage monitoring unit monitors the voltage, current and power supply frequency of the first winding.

9. The transformer-coupled RF plasma generator according to claim 1, characterized in that: The ignition switch is an air switch.

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