Improvement of ignition for inductively coupled plasmas

Abstract

This system provides a way to prevent overheating of the dielectric tube while ensuring sufficient voltage to reliably ignite the inductively coupled plasma. [Solution] In one embodiment, the present disclosure relates to a system for generating inductively coupled plasma. The system includes a dielectric tube and an induction coil circuit. The induction coil circuit includes induction coils surrounding the dielectric tube and connected in series with each other. Intervening capacitors are switchedly coupled between the induction coils. A control circuit is configured to, when it determines that the plasma is to be ignited, switch at least one of the intervening capacitors to disconnect from the induction coil circuit during plasma ignition.

Description

Background Art

[0001] A substrate processing system can use inductively coupled plasma (ICP) to process a substrate. The processes performed by the system can be short, and thus require rapid and reliable ignition of the plasma. They may also require an ICP source to ignite the process gas under various chemical and pressure conditions. These requirements present various challenges. For example, in high-power applications, a continuous high voltage across the ICP coil can cause heating of the dielectric tube by ion bombardment. However, a high voltage is required to ignite the plasma in ICP applications.

Summary of the Invention

[0002] The present disclosure describes systems and methods for preventing overheating of a dielectric tube while ensuring a voltage sufficient to reliably ignite an inductively coupled plasma.

[0003] In one aspect, the present disclosure is a system including a dielectric tube, an inductive coil circuit surrounding the dielectric tube and including a plurality of inductive coils connected in series with each other, a plurality of intervening capacitors coupled between the plurality of inductive coils, each intervening capacitor including either one fixed capacitor or a plurality of fixed capacitors coupled in parallel, a plurality of switches operably connected to the plurality of intervening capacitors, and a control circuit configured to switch at least one of the plurality of switches to disconnect at least one of the fixed capacitors of the plurality of intervening capacitors from the inductive coil circuit during ignition of the plasma when it is determined that the plasma has been ignited.

[0004] In another embodiment, a method for improving plasma ignition includes surrounding a dielectric tube with induction coils of an induction coil circuit, wherein the induction coil circuit includes a plurality of induction coils connected in series with each other, a plurality of intervening capacitors coupled between the plurality of induction coils, each intervening capacitor comprising one or more fixed capacitors coupled in parallel, and a plurality of switches operably connected to the plurality of intervening capacitors; and, when it is determined that the plasma is ignited, causing at least one of the plurality of switches to switch off at least one of the fixed capacitors of the plurality of intervening capacitors from the induction coil circuit during the plasma ignition.

[0005] This disclosure will be better understood from the detailed description and accompanying drawings. [Brief explanation of the drawing]

[0006] [Figure 1] This is a block diagram of a semiconductor processing system according to one embodiment. [Figure 2] This is a block diagram of an inductively coupled plasma source according to one embodiment. [Figure 3] This is a schematic diagram of the first induction coil circuit according to the first embodiment. [Figure 4] This is a schematic diagram of a portion of the second induction coil circuit according to the second embodiment. [Figure 5] This is a schematic diagram of a portion of the third induction coil circuit according to the third embodiment. [Figure 6A] These are schematic diagrams of switches according to different embodiments. [Figure 6B] These are schematic diagrams of switches according to different embodiments. [Figure 6C] These are schematic diagrams of switches according to different embodiments. [Figure 7] Figure 7 is a flowchart of a method for improving plasma ignition according to one embodiment. [Modes for carrying out the invention]

[0007] The drawings illustrate one or more embodiments of the present invention and do not limit the scope of the invention.

[0008] The following description of preferred embodiments is essentially illustrative and is not intended to limit one or more of the inventions in any way. The description of exemplary embodiments is intended to be read in conjunction with the accompanying drawings and is considered to be part of the whole written description. The discussion herein describes and illustrates several possible non-limiting combinations of configurations that may exist alone or in combination with other configurations. Furthermore, where used in this disclosure, the term “or” is interpreted as a logical operator that yields true if one or more of its operands are true. Furthermore, where used in this disclosure, the phrase “based on” is interpreted as “based at least partially on,” and is therefore not limited to the interpretation “based entirely on.” Furthermore, when the term “each” is used in reference to each of a plurality of items, it is not necessary to refer to each of such items in the entire system or apparatus, but rather may simply refer to each of one or more such items specifically described in the system.

[0009] The range used throughout is a concise expression for describing all values ​​within the range. Any value within the range can be selected as the end of the range. In addition, all references cited herein are incorporated herein in their entirety by reference. In the event of any conflict between the definitions in this disclosure and the definitions in the cited references, this disclosure shall prevail.

[0010] In the following descriptions in which block diagrams or circuits are shown and described, those skilled in the art will recognize, for clarity, that not all peripheral components or circuits are shown in the diagrams or described in the specification. For example, common components such as memory devices and power supplies may not be considered herein because their roles will be readily understood by those skilled in the art. Furthermore, where two components are referred to as “coupled” or “operably coupled,” this includes components that are related in any way so that power or signal information can be transferred to each other (directly or indirectly), and therefore these terms do not require a direct connection between components without an intermediate part.

[0011] For clarity and convenience in describing similar components or configurations, the same or similar reference numerals may be used across different embodiments or figures in this disclosure. This does not imply that the components or configurations identified by a particular reference numeral must be identical across each embodiment or figure, but merely suggests that the components or configurations are similar in general function or identity.

[0012] The configuration of the present invention may be implemented in software, hardware, firmware, or a combination thereof. The computer programs described herein are not limited to any particular embodiment and may be implemented as an operating system, application programs, foreground or background processes, drivers, or any combination thereof. The computer programs may run on a single computer or server processor, or on multiple computers or server processors.

[0013] The processors described in this disclosure may be any central processing unit (CPU), microprocessor, microcontroller, computer, or programmable device or circuit configured to execute computer program instructions (e.g., code). Various processors may be embodied in any preferred type of computer and / or server hardware (e.g., desktop, laptop, notebook, tablet, mobile phone, etc.) and may include all the usual auxiliary components necessary to form a functional data processing device, including but not limited to buses, software, and data storage such as volatile and non-volatile memory, input / output devices, graphical user interfaces (GUIs), removable data storage, and wired and / or wireless communication interface devices such as Wi-Fi, Bluetooth, LAN, etc. As used in this disclosure, the term “processor” may refer to one or more processors.

[0014] The computer-executable instructions or programs (e.g., software or code) and data described herein may be programmed into and visibly embodied in non-temporary computer-readable media accessible to and readable by each processor as described herein, which configures and directs the processor to perform desired functions and processes by executing instructions coded within the medium. A device embodying such a programmable processor configured into non-temporary computer-executable instructions or programs may be called a “programmable device” or “device,” and a group of programmable devices in a state of mutual communication may be called a “programmable system.” Non-transient “computer-readable media” as described in this disclosure may include, but are not limited to, any suitable volatile or non-volatile memory, including random access memory (RAM) and various types thereof, read-only memory (ROM) and various types thereof, USB flash memory, and magnetic or optical data storage devices (e.g., internal / external hard disks, floppy disks, magnetic tapes, CD-ROMs, DVD-ROMs, optical discs, ZIP® drives, Blu-ray discs, and others) that may be written to and / or read by a processor operably connected to the media.

[0015] In certain embodiments, the present invention may be embodied in the form of computer implementation processes and devices such as processor-based data processing and communication systems, or computer systems for carrying out those processes. The present invention may also be embodied in the form of software or computer program code embodied in a non-temporary computer-readable storage medium, which, when loaded into and executed by a data processing and communication system or computer system, configures the processor to produce specific logic circuits configured to implement the processes.

[0016] As mentioned above, in high-power applications, a sustained high voltage across the ICP coil can cause heating of the dielectric tube due to ion bombardment. To solve this problem, for example, a capacitor may be inserted between the inductors of the ICP coil to reduce the voltage. The capacitor counteracts the voltage generated by the induction coil, keeping the overall voltage of the ICP coil low. This is the approach taken in U.S. Patent No. 10,541,114, which is incorporated herein by reference in its entirety. This approach is effective in preventing heating of the dielectric tube. However, in ICP applications, a high voltage is required across the ICP coil to reliably ignite the plasma. Therefore, reducing the voltage reduces the reliability of plasma ignition.

[0017] To address this low-voltage ignition problem, one could attempt to use a separate secondary induction coil structure and a separate generator attached to the ICP coil for ignition, through which a different frequency would be injected. However, these components add considerable cost. Alternatively, one could inject a short high-voltage DC pulse to start the plasma, but this approach similarly requires separate induction coil structures or separate electrodes on two sides, thus adding significant cost.

[0018] This disclosure describes a simpler and more cost-effective system and method that prevents heating of the dielectric tube while also ensuring sufficient voltage to ignite the plasma. Referring to the figures, Figure 1 is a block diagram of a system 100 for processing a substrate according to one embodiment. The system 100 includes an inductively coupled plasma (ICP) source (e.g., a remote plasma unit) that provides ICP 207 to a process chamber 300. The process chamber 300 is shown to include standard components such as a chuck 304 for holding the substrate 302. Note that process chambers are well known, and therefore their length is not considered here. For further details on the potential features of the process chamber, see, for example, U.S. Patent No. 10,541,114 (incorporated by reference).

[0019] Figure 2 is a block diagram of the ICP source 200, and Figure 3 is a schematic diagram of the first induction coil circuit 210 of the ICP source 200 according to one embodiment. The ICP source 200 is configured to generate an inductively coupled hydrogen plasma, such as (but not limited to) an inductively coupled hydrogen plasma. An exemplary process gas source 202 supplies process gas 203 to a dielectric tube 206. The dielectric tube 206 is surrounded by induction coils 211, 212, 213, and 214, which form part of an induction coil circuit 210 that receives radio frequency (RF) power from an RF power supply 204. The induction coils 211-214 are connected in series with each other. While four induction coils 211-214 are utilized, the present invention is not limited to any particular number of induction coils. Intermediate capacitors 221, 222, and 223 are coupled between inductor coils 211-214, and switches 231-233 are operably coupled to intermediate capacitors 221-223, allowing them to be switched to disconnect intermediate capacitors 221-223 from the inductor coil circuit 210 (by short-circuiting, in this embodiment). In this embodiment, each intermediate capacitor 221-223 is coupled between adjacent inductor coils 211-214 (for example, intermediate capacitor 221 is coupled between adjacent inductor coils 211 and 212), and intermediate capacitors 221-223 are in series with inductor coils 211-214.

[0020] It should be noted that when plasma is ignited within an inductively coupled coil, the coil's impedance changes significantly, largely due to the interaction between the plasma and the coil's electromagnetic fields. When the plasma is ignited, it becomes a conductive medium that interacts with the coil's magnetic field. This interaction induces an electric current within the plasma, thereby affecting the coil's impedance. The ignited plasma typically provides a path for the induced current, reducing the coil's inductive reactance and lowering the coil's impedance upon ignition. After ignition, the impedance stabilizes at a new value lower than the initial impedance. This new impedance depends on factors such as plasma density, temperature, and the frequency of the applied electromagnetic field.

[0021] When the control circuit 250 determines that the plasma 209 is ignited, it is configured to switch at least one of the switches 231-233 to disconnect at least one of the fixed capacitors 221-223 of the intervening capacitor from the induction coil circuit 210 during the ignition of the plasma 209. The exemplary control circuit 250 is further configured to switch at least one of the fixed capacitors switched from the induction coil circuit back to the induction coil circuit after the ignition of the plasma, thus enabling the induction coil circuit 210 to have two operating modes, one during the ignition period, one during the ignition period, and one during the non-ignition period. By enabling these two modes, the ICP source 200 can generate a high voltage across the induction coils 211-214 during ignition to assist ignition, and can also return the capacitor to the circuit to reduce the voltage of the induction coil and prevent overheating of the dielectric tube. Generating a high voltage across the induction coils 211-214 increases the resonant frequency of the induction coils 211-214. The frequency from the RF power source 204 may also be increased to further increase the voltage across the induction coils 211-214, and the load can be made resonant. When the plasma 209 is ignited and the capacitors 221-223 return to the circuit, the resonant frequency of the induction coils 211-214 decreases, and the frequency from the RF power source 204 may also decrease. The drive frequency of the RF power source 204 may be configured to vary, for example, from several hundred kilohertz to several megahertz. The RF power may also be configured to vary, for example, from several tens of watts to several tens of kilowatts.

[0022] There are several potential ways in which the control circuit 250 can determine that the plasma 209 is about to be ignited and therefore that at least one of the intervening capacitors 221-223 should be switched off and disconnected. For example, the control circuit 250 can determine that the RF power from the RF power supply 204 that may be supplied to the induction coil circuit 210 is off or in an off state. In response, the control circuit 250 can automatically switch off and disconnect at least one intervening capacitor in preparation for the next ignition. The control circuit 250 can know that the RF power is off based on a signal received from the RF power supply 204. For example, a matching network (not shown) coupled to the control circuit can receive an RF-on signal indicating matching (and therefore the control circuit) when the RF power is on or off. Alternatively, the presence of RF power can be detected using a VI sensor or direction coupler. Ignition may occur rapidly (e.g., every few hundred milliseconds) or at less rapid intervals (e.g., every 10 seconds).

[0023] In an exemplary embodiment, the control circuit 250 includes a processor. The processor may be any type of suitably programmed processing device such as a computer or a microprocessor configured to execute computer program instructions (e.g., code). The processor may be embodied in a computer and / or server hardware of any suitable type (e.g., desktop, laptop, notebook, tablet, mobile phone, etc.), and also includes all the usual auxiliary components necessary to form a functional data processing device, such as buses, software and data storage (volatile memory and non-volatile memory, etc.), input / output devices, graphical user interface (GUI), removable data storage, and wired and / or wireless communication interface devices including Wi-Fi, Bluetooth, LAN, etc., but not limited to these. The processor of the exemplary embodiment is configured with a specific algorithm that enables the ICP source 200 to perform the functions described in this disclosure.

[0024] Note that it should be noted that the induction coil circuit 210 may further include capacitors 241 and 242 connected to the RF power supply 204. In an exemplary embodiment, capacitor 241 is a first fixed capacitor coupled between the first output terminal (-V) of the RF power supply 204 and one end of the first induction coil circuit 210, and capacitor 242 is a second fixed capacitor coupled between the second output terminal (+V) of the RF power supply 204 and the opposite end of the first induction coil circuit 210. However, in other embodiments, these capacitors may be omitted.

[0025] In the embodiments illustrated in Figures 2 and 3, each intervening capacitor 221 to 223 comprises a single fixed capacitor. Furthermore, each single fixed capacitor 221 to 223 is coupled to a corresponding switch 231 to 233, the corresponding switch being configured to short-circuit the single fixed capacitor, thereby disconnecting it from the inductive coil circuit. For example, switch 231 is configured to short-circuit fixed capacitor 221.

[0026] In other embodiments, one or more of the intervening capacitors may be configured to include multiple fixed capacitors connected in parallel, for example, as shown in Figures 4 and 5. Figure 4 is a schematic diagram of a portion of the second inductive coil circuit 210B according to the second embodiment. In this embodiment, the first capacitor switching circuit 251 in Figure 3 is replaced by the second capacitor switching circuit 251B. This switching circuit 251B includes 221A, 221B, and 221C. Of these capacitors, capacitor 221A remains in the inductive coil circuit 210B at all times, including during ignition. The other two capacitors 221B and 221C may be configured to be switched off from switches 210B, 231B, and 231C, respectively, during ignition. In this approach, capacitor 221A may continuously provide a voltage reduction to reduce the voltage of the inductive coils 211-214 and reduce overheating of the dielectric tube 206, while the switching capacitors 221B and 221C may be switched off to assist in ignition.

[0027] Figure 5 provides a third inductive coil circuit 210C that uses a third capacitor switching circuit 251C. The difference from the switching circuit 251B described above is that the switching circuit 251C includes a switch 231A provided for the short-circuit capacitor 221A. In this configuration, all three capacitors 221A-C can be isolated from the inductive coil circuit 210C. Therefore, the circuit 210C has the ability to provide a more significant voltage reduction to assist ignition.

[0028] It should be noted that the present invention is not limited to any particular number of capacitors connected in parallel, or any number of switchable capacitors, or any particular method of switching capacitors to disconnect them from the induction coil circuit. Furthermore, adjacent inductors may be configured to use different capacitor switching circuits having different numbers of capacitors and different switching devices. Thus, in some cases, a particular intervening capacitor (e.g., intervening capacitor 221) between adjacent induction coils (e.g., coils 211, 212) may be completely switched to disconnect during ignition, while other intervening capacitors (e.g., intervening capacitor 222) may remain switched to connect during ignition. The number of intervening capacitors to be switched to disconnect may depend on the extent to which ignition support is required, including considerations such as the amount of voltage required for the induction coil, as well as the size and number of inductors.

[0029] The present invention is not limited to any particular type of switch used to switch between connecting and disconnecting an intervening capacitor or a fixed capacitor equipped with an intervening capacitor. For example, the present invention may be configured to use a PIN diode, a NIP diode, or a FET. Figures 6A–6C provide schematic diagrams of exemplary switches 601, 602, and 603 that may be available. Figure 6A shows a MOSFET switch, Figure 6B shows a JFET switch, and Figure 6C shows a PIN diode switch. The inductive coil circuit may use the same type of switch throughout the switch, or it may use different types of switches.

[0030] For clarity and convenience, it should be noted that more general characteristics of ICP sources are not described in detail in this disclosure. For further details on the potential characteristics of ICP sources, see, for example, U.S. Patent No. 10,541,114 (incorporated by reference above) and its different ICP generating systems.

[0031] Figure 7 is a flowchart of method 400 for improving plasma ignition according to one embodiment. In the first operation 401, the dielectric tube 206 may be configured to be surrounded by induction coils 211-214, for example, as shown in Figure 2. The induction coils 211-214 form part of the induction coil circuits such as the induction coil circuits 210, 210B, and 210C described above. In the second operation 402, it is determined that the plasma is ignited as described above. In operation 403, when it is determined that the plasma 209 is ignited, at least one of the switches 231-233 is switched to disconnect at least one of the fixed capacitors 221-223 of the intervening capacitor from the induction coil circuit 210 during the ignition of the plasma 209. It should be noted that method 400 is not limited to the embodiments discussed above.

[0032] While the present invention has been described in relation to specific embodiments including current preferred modes of execution, those skilled in the art will understand that there are numerous variations and rearrangements of the systems and techniques described above. It should be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the invention. Therefore, the spirit and scope of the invention should be interpreted broadly as set forth in the appended claims. [Explanation of symbols]

[0033] 100 Systems 200 ICP source 202 Process gas sources 203 Process gas 204 RF power supply 206 Dielectric tube 207 ICP 209 Plasma 210 Induction Coil Circuit 211 Induction Coil 212 Induction Coil 213 Induction Coil 214 Induction Coil 221 Intervening Capacitor 222 Intervening capacitor 223 Intervening capacitor 231 switches 232 switches 233 switches 241 Capacitors 242 Capacitors 250 Control circuits 251 Switching Circuits 300 process chambers 302 Base material 304 Chuck 601 Switch 602 switch 603 switch

Claims

1. It is a system, Dielectric tubes and It is an induction coil circuit, A plurality of induction coils surround the dielectric tube and are connected in series with each other, A plurality of intervening capacitors coupled between the plurality of induction coils, wherein each intervening capacitor includes either one fixed capacitor or multiple fixed capacitors coupled in parallel, Multiple switches operably connected to the aforementioned multiple intervening capacitors, When it is determined that the plasma is ignited, the control circuit is configured to switch at least one of the plurality of switches to disconnect at least one of the fixed capacitors of the plurality of intervening capacitors from the induction coil circuit during the plasma ignition, A system equipped with these features.

2. The system according to claim 1, wherein the control circuit is further configured to reconnect at least one of the plurality of fixed capacitors that have been disconnected from the induction coil circuit to the induction coil circuit after the plasma has been ignited.

3. The system according to claim 1, wherein each intervening capacitor is coupled between adjacent induction coils among the plurality of induction coils.

4. The system according to claim 1, wherein each intervening capacitor is a single fixed capacitor.

5. The system according to claim 4, wherein each single fixed capacitor is coupled to a corresponding switch among the plurality of switches, and the corresponding switch is configured to short-circuit the single fixed capacitor, thereby disconnecting the single fixed capacitor from the induction coil circuit.

6. The system according to claim 1, wherein at least one of the plurality of intervening capacitors comprises a plurality of fixed capacitors connected in parallel, and during plasma ignition, a portion of the plurality of fixed capacitors switches to disconnect from the induction coil circuit, and a portion of the plurality of fixed capacitors does not switch to disconnect from the induction coil circuit.

7. The system according to claim 1, wherein the induction coil circuit is configured to generate inductively coupled plasma.

8. The system according to claim 1, wherein the plurality of intervening capacitors are in series with the plurality of inductive coils, and the plurality of switches include PIN diodes, NIP diodes, or FETs.

9. The system according to claim 1, wherein the determination of whether the plasma is ignited includes the determination that the RF power supplied to the induction coil circuit by the RF power supply is turned off.

10. The system according to claim 1, The system further comprises an RF power supply that supplies RF power to the induction coil circuit, A system in which, upon deciding to ignite the plasma, the control circuit is further configured to reduce the frequency of the RF power supplied by the RF power supply.

11. A method to improve plasma ignition, This involves surrounding a dielectric tube with an induction coil of an induction coil circuit, wherein the induction coil circuit is Multiple induction coils connected in series with each other, A plurality of intervening capacitors coupled between the plurality of induction coils, each intervening capacitor comprising one or more fixed capacitors coupled in parallel, Enclosing, including a plurality of switches operably connected to the plurality of intervening capacitors, When it is determined that the plasma is ignited, at least one of the plurality of switches is switched to disconnect at least one of the fixed capacitors of the plurality of intervening capacitors from the induction coil circuit during the ignition of the plasma. Methods that include...

12. The method according to claim 11, further comprising reconnecting at least one of the fixed capacitors that was disconnected from the induction coil circuit to the induction coil circuit after the ignition of the plasma.

13. The method according to claim 11, wherein each of the plurality of intervening capacitors is coupled between adjacent induction coils of the plurality of induction coils.

14. The method according to claim 11, wherein each intervening capacitor is a single fixed capacitor.

15. The method according to claim 14, wherein each single fixed capacitor is coupled to one of the plurality of switches, and the corresponding switch is configured to short-circuit the single fixed capacitor, thereby disconnecting the single fixed capacitor from the induction coil circuit.

16. The method according to claim 11, wherein at least one of the plurality of intervening capacitors comprises a plurality of fixed capacitors connected in parallel, and during plasma ignition, a portion of the plurality of fixed capacitors is switched to disconnect from the induction coil circuit, and a portion of the plurality of fixed capacitors is not switched to disconnect from the induction coil circuit.

17. The method according to claim 11, wherein the induction coil circuit is configured to generate inductively coupled plasma.

18. The method according to claim 11, wherein the plurality of intervening capacitors are in series with the plurality of induction coils, and the plurality of switches include PIN diodes, NIP diodes, or FETs.

19. The method according to claim 11, wherein the determination that the plasma is ignited includes the determination that the RF power supplied to the induction coil circuit by the RF power supply is turned off.

20. The method according to claim 11, The system further comprises an RF power supply that supplies RF power to the induction coil circuit, A method for reducing the frequency of RF power supplied by an RF power supply when it is determined that the plasma is ignited.

Images