Auxiliary plasma source for robust ignition and reignition in plasma chambers - Patents.com

Abstract

The semiconductor processing system may include a semiconductor processing chamber configured to execute a recipe on a semiconductor wafer. The system may include a first plasma source that supplies a plasma to the semiconductor processing chamber and operates in a duty cycle during execution of the recipe. The system may also include a second plasma source configured to maintain a plasma in the semiconductor processing chamber while the first plasma source operates in the duty cycle.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of and priority to U.S. Non-Provisional Application No. 17 / 551,698, filed December 15, 2021, entitled "AUXILIARY PLASMA SOURCE FOR ROBUST IGNITION AND RESTRIKES IN A PLASMA CHAMBER," the entire contents of which are incorporated herein by reference.

[0002]

[0002] The present disclosure relates generally to auxiliary plasma sources for use in semiconductor manufacturing. More specifically, the present disclosure describes techniques for ensuring more uniform ignition and reignition of a plasma in a main plasma chamber during complex duty cycles using multiple plasma sources. [Background technology]

[0003] To generate plasmas used in semiconductor manufacturing processes, energy is typically added to neutral gases at a level that ionizes atoms in the semiconductor processing chamber. For example, argon (Ar) has an ignition or "ignition" requirement of 500 W to reach a plasma state and may require 15 W of energy at 40 MHz to maintain the plasma state. Current semiconductor manufacturing techniques may use duty cycles, which may include multiple power levels, each characterized by the energy delivered to the plasma, during which there are periods when the plasma source is in an on state and periods when the plasma source is in an off state during which the plasma can be quenched in the chamber. During a duty cycle, a power ranging from about 30 W to 8000 W may be applied at the beginning of each on cycle. As manufacturing techniques require more complex duty cycles and / or duty cycles with longer off periods between on periods, the plasma in the chamber will have a longer cooling time during the off periods to quench the plasma. This results in greater variability in plasma generation and a higher incidence of manufacturing defects. Summary of the Invention

[0004] In some embodiments, a method of supplying plasma to a semiconductor processing chamber may include processing a semiconductor wafer in the semiconductor processing chamber according to a recipe. Processing the semiconductor wafer may include maintaining the semiconductor processing chamber at a constant pressure. The method may also include operating a first plasma source according to a recipe. The first plasma source may be coupled to the semiconductor processing chamber and configured to operate in a duty cycle during execution of the recipe. The first plasma source may supply plasma to the semiconductor processing chamber. The first plasma source may operate in a duty cycle between a plurality of power levels. The plurality of power levels may include a first power level that causes the first plasma source to ignite a plasma in the semiconductor processing chamber. The plurality of power levels may also include a second power level that quenches the plasma in the semiconductor processing chamber and transitions the plasma from a plasma state to a gas state. A third power level may reignite the plasma in the semiconductor processing chamber and transition the plasma from a gas state to a plasma state. The third power level may use less energy than the first power level. The plasma may include argon. The method may include operating a second plasma source configured to maintain a plasma while the first plasma source is operating at a duty cycle during execution of the recipe. The second plasma source may provide a supply of electrons to the first plasma source. The second plasma source may also, or alternatively, provide a supply of high energy electrons to the semiconductor processing chamber.

[0005] In some embodiments, the semiconductor processing system may include a semiconductor processing chamber configured to execute a recipe for processing a semiconductor wafer. The system may include a first plasma source configured to provide a plasma to the semiconductor processing chamber. The first plasma source may also be configured to operate with a duty cycle during execution of the recipe. The recipe executed on the semiconductor wafer may be characterized by a duty cycle that requires cycling the first plasma source between a plurality of power levels. The duty cycle may operate in a range of about 5% to 95%. The system may also include a second plasma source configured to maintain a plasma in the semiconductor processing chamber while the first plasma source operates with the duty cycle. The second plasma source may be a microwave coaxial resonator. The microwave coaxial resonator may be configured as an electron flood gun. The second plasma source may be a toroidal plasma source. The toroidal plasma source may be configured as an electron flood gun. The second plasma source may be a surface wave plasma source. The surface wave plasma source may generate the plasma using capacitive coupling or using inductive coupling.

[0006] In some embodiments, a semiconductor processing system may include a semiconductor processing chamber configured to execute a recipe for processing a semiconductor wafer. The system may include a plasma source configured to provide a plasma to the semiconductor processing chamber. The plasma source may also be configured to operate with a duty cycle during execution of the recipe. The plasma source may include a toroidal plasma source or a coaxial resonator. The system may include a surface wave plasma source configured to maintain a plasma in the semiconductor processing chamber during execution of the recipe on the semiconductor wafer. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 illustrates an example of a semiconductor manufacturing system according to some embodiments. [Diagram 2]FIG. 1 illustrates an example of a semiconductor processing system having an auxiliary plasma source according to some embodiments. [Diagram 3] FIG. 1 illustrates a system for generating plasma ignition using a radio frequency (RF) coaxial resonator configured as an electron flood gun, according to some embodiments. [Figure 4] FIG. 1 illustrates a toroidal plasma source configured as a toroidal electron flood gun according to some embodiments. [Diagram 5] FIG. 1 illustrates a surface wave plasma source according to some embodiments. [Figure 6] FIG. 1 illustrates a semiconductor processing system using a surface wave plasma source as an auxiliary plasma source according to some embodiments. [Figure 7] FIG. 2 shows a flowchart of a method for providing a plasma to a semiconductor processing chamber, according to some embodiments. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008]

[0014] As mentioned above, current techniques used in semiconductor manufacturing may require more complex duty cycles that may often have frequencies ranging from about 5 Hz to 5000 Hz. In other embodiments, the frequency may range from 0.01 Hz to 200 Hz. The duty cycle may vary the energy level of the plasma according to the recipe being executed on the semiconductor wafer. The recipe may vary the energy level at multiple levels, for example, from 300 W to 600 W, depending on the pressure in the chamber.

[0009]

[0015] Generally, the pressure required to ignite a plasma is higher than the pressure required to maintain the plasma in the chamber at a given energy level. For example, igniting an argon plasma at 25 mTorr may require 500 W of inductively coupled power (ICP), while the desired operating pressure in a semiconductor processing chamber may be in the range of 1 mTorr to 400 mTorr. Thus, the pressure in a semiconductor processing chamber is raised and lowered many times according to the recipe.

[0010]

[0016] However, increasing the pressure in a semiconductor processing chamber to allow for consistent ignition and re-ignition of the plasma can cause manufacturing problems. For example, increasing the pressure in a semiconductor processing chamber to re-ignite can result in undesirable polymer deposition. When a recipe requires multiple ignitions and re-ignitions, additional periods of high pressure are added, increasing the opportunity for unwanted polymer deposition and other process variations.

[0011]

[0017] The embodiments described in this disclosure solve these and other technical problems by adding an additional auxiliary plasma source to the chamber. Two plasma sources (sometimes called a "primary" plasma source and an "auxiliary" plasma source, or a "first" plasma source and a "secondary" plasma source) work together to ignite and maintain a constant plasma in the chamber. The primary plasma source is configured to provide and maintain the plasma and can operate during the execution of a recipe on a semiconductor wafer. The primary plasma source can be cycled between different power levels, including a level at which the plasma is quenched and the primary plasma source is in an "off" state. For example, to maintain the plasma, depending on the recipe and the design of the primary plasma source, only 15 W of energy at 40 MHz may be required, compared to 500 W and frequencies in the GHz range used to ignite or reignite the plasma.

[0012]

[0018] The auxiliary plasma source or secondary plasma source may be configured to maintain the plasma provided by the primary plasma source in the semiconductor processing chamber. The secondary plasma source may operate throughout the execution of a wafer recipe. In some configurations, the auxiliary plasma source may reduce the maintenance power required by the primary plasma source. The auxiliary plasma source may be configured to generate a "leak" plasma that is diffused into the chamber, or may be configured to pump plasma into the semiconductor processing chamber by creating a potential difference with respect to the chamber body and provide a supply of electrons to the chamber.

[0013]

[0019] The second plasma source may be implemented using a number of different technological solutions, including surface wave plasma sources such as surfatron devices that use surface waves to generate plasma. A microwave coaxial resonator plasma source may be used and may be configured as an electron flood gun. A toroidal plasma source may also be used and may be configured as an electron flood gun. In some embodiments, two or more auxiliary plasma sources may be used, which may provide a more consistent plasma density within the semiconductor processing chamber.

[0014]

[0020] By using an auxiliary plasma source to provide an electron source to a semiconductor chamber, the main plasma source can be cycled between power levels and / or turned off during the execution of a recipe. Because the auxiliary plasma source maintains the plasma in the chamber during the duty cycle of the main plasma source, it is not necessary to reignite the plasma every time the duty cycle of the main plasma source enters an on state. Even if reignition is required, the power from the main plasma source can be reduced when working with the auxiliary plasma source. Furthermore, when reignition is performed using the auxiliary plasma source, the pressure and other environmental characteristics in the chamber do not need to be changed. Instead, the environmental characteristics of the chamber can be maintained during reignition, thereby reducing process variations during the duty cycle of the main plasma source. The embodiments of the present disclosure can thereby reduce the power required to maintain the plasma in a semiconductor processing chamber and eliminate the need to adjust the pressure, power, and capacitive matching network for reignition required during the duty cycle.

[0015]

[0021] 1 illustrates an example of a semiconductor manufacturing system according to some embodiments. The system 100 may include a semiconductor processing chamber 102 and a primary plasma source 104. The primary plasma source 104 may include, for example, an inductively coupled plasma source having a first coil 110, a second coil 112, an alternating current (AC) power supply 114, a power divider 111, a controller 118, and a gas source 116. The primary plasma source 104 may also include a capacitively coupled plasma source.

[0016]

[0022] The semiconductor processing chamber 102 may include a wafer platform 106 that supports a semiconductor wafer 108. A recipe may be executed on the semiconductor wafer 108 during a semiconductor manufacturing process. As used herein, a "recipe" may refer to a set of instructions that control the operation of the semiconductor processing chamber 102. For example, a recipe may include time-sequential set points for environmental conditions, such as pressure, temperature, gas concentrations, gas flow rates, and / or other conditions. A recipe may also include voltages, currents, power settings, duty cycles, and other electronic stimuli that may be applied to various components of the semiconductor processing chamber 102 to generate a plasma, deposit a film or layer on the semiconductor wafer 108, polish or etch a layer on the semiconductor wafer 108, and / or perform other processes on the semiconductor wafer 108.

[0017]

[0023] The controller 118 can cause gas to be supplied from the gas source 116 to the semiconductor processing chamber 102 according to a recipe. The controller 118 can also cause current to be output by the AC power supply 114 according to a recipe. The power splitter 111 can divide the current between the coils 110 and 112. The current can be supplied at a power level and frequency sufficient to ionize the gas with the resulting electromagnetic field and ignite a plasma in the semiconductor processing chamber 102. The plasma can fill the semiconductor processing chamber 102 by diffusion effects or can be driven by a potential difference between the plasma source 104 and the semiconductor processing chamber 102.

[0018]

[0024] The recipe may include a duty cycle that causes the controller 118 to turn the AC power source 114 on and off and / or vary the power level output by the AC power source 114. Thus, the main plasma source 104 may be in an ON state characterized by one or more power levels, or the main plasma source may be in an OFF state. In some embodiments, the ON state may include multiple power levels. A first power level may enable the first plasma source to ignite a plasma in the semiconductor processing chamber 102. A second power level may enable the plasma in the semiconductor processing chamber 102 to quench or transition back to a gaseous state. A third power level may reignite the plasma in the semiconductor processing chamber 102 and transition the plasma from a gaseous state to a plasma state. The third power level may use less energy than the first power level.

[0019]

[0025] In situations where a recipe causes the main plasma state to be turned off for a portion of the recipe, it may be necessary to reignite or "relight" the plasma when required by the duty cycle. In that case, the main plasma source 104 may use more power to reignite the plasma than is required to maintain the plasma. An increase in the operating pressure within the semiconductor processing chamber 102 may also be required to reignite the plasma. The increase in pressure required to reignite the plasma may lead to manufacturing defects, such as unwanted deposition or generation of polymers on the semiconductor wafer 108.

[0020]

[0026] Furthermore, because only the primary plasma source 104 supplies plasma to the semiconductor processing chamber 102, the plasma may not fill the semiconductor processing chamber 102 uniformly. Thus, the amount of plasma to which the semiconductor wafer 108 is exposed may vary, which may lead to additional manufacturing defects.

[0021]

[0027] 1, the main plasma source 104 is illustrated as an inductively coupled plasma source, however, many well-known types of main plasma sources can be used, including capacitively coupled plasma sources, and other types of sources. This list is not exhaustive, and any plasma source can be used as the main plasma source 104. Additionally, although the main plasma source 104 is illustrated external to the semiconductor processing chamber 102, other configurations are possible, including where the main plasma source 104 is internal to the semiconductor processing chamber 102 and a plasma is formed inside the semiconductor processing chamber 102 instead of filling the chamber.

[0022]

[0028] 2 illustrates an example of a semiconductor processing system having an auxiliary plasma source, according to some embodiments. The system 200 may include a semiconductor processing chamber 202, a primary plasma source 204, and an auxiliary plasma source 220. In some embodiments, the semiconductor processing chamber 202 and the primary plasma source 204 may be similar to the primary plasma source 104 depicted in FIG. 1. Thus, the labeled components 202-218 may function similarly to the corresponding components 102-118 in FIG. 1. As in FIG. 1, the primary plasma source 204 is illustrated as an inductively coupled power supply, however, a capacitively coupled power supply, or any other type of plasma source, may be used instead of or in addition to the inductively coupled power supply.

[0023]

[0029] The auxiliary plasma source 220 may be configured to maintain a plasma in the semiconductor processing chamber 202 while the primary plasma source is operating at a duty cycle during the execution of a recipe. The auxiliary plasma source 220 may be on for the duration of the recipe executed on the semiconductor wafer 208. In some embodiments, the auxiliary plasma source may be held at a single power level for the duration of the recipe executed on the semiconductor wafer 208. The auxiliary plasma source 220 may include any type of plasma source, including surface wave generated plasma sources such as surfatrons, microwave coaxial resonators of various configurations, toroidal plasma generators, and the like. The auxiliary plasma source may also include a coaxial resonator with a quartz reactor. Additionally, although only one auxiliary plasma source is illustrated, any number of auxiliary plasma sources may be arranged in any configuration. For example, multiple auxiliary plasma sources may be distributed around the semiconductor processing chamber 202 to maintain a more uniform plasma density. Furthermore, the auxiliary plasma source 220 may be added to a semiconductor manufacturing system, such as the system 100 of FIG. 1, after the semiconductor manufacturing system is manufactured in which the primary plasma source 204 is an integral part of the semiconductor processing system.

[0024]

[0030] The auxiliary plasma source 220 can maintain a plasma in the semiconductor processing chamber 202 by providing a supply of electrons to the semiconductor processing chamber 202. In some embodiments, the electrons can be provided by the auxiliary plasma source 220 as a "leak" plasma that enters the semiconductor processing chamber 202 by diffusion effects. In other embodiments, the auxiliary plasma source can be configured as an electron flood gun, and the electrons can enter the semiconductor processing chamber 202 as an electron beam. Any type of plasma source, some of which are described in more detail below, can be configured to provide a leak plasma or can be configured as an electron flood gun.

[0025]

[0031] In some embodiments, the auxiliary plasma source 220 operates at microwave frequencies (3×10 8 From 3×10 11Hz). By operating at microwave frequencies, the auxiliary plasma source 220 can be physically smaller than the main plasma source 204. Additionally, the power used by the auxiliary plasma source 220 can be less than the power used by the main plasma source 204. In other embodiments, the auxiliary plasma source can be as low as 3×10 5 From 3×10 8 It may be configured to operate in the radio frequency (RF) range, such as 50 Hz.

[0026]

[0032] The system 200 can be used to execute a recipe on a semiconductor wafer 208. The primary plasma source is configured to provide a plasma to the semiconductor processing chamber 202 and can be configured to operate on a duty cycle during execution of the recipe. The recipe can include a duty cycle that requires the primary plasma source 204 to alternate between multiple power levels. In some embodiments, a first power level can cause the first plasma source to ignite a plasma in the semiconductor processing chamber 202. A second power level can cause the plasma in the semiconductor processing chamber 102 to quench or transition to a gaseous state. A third power level can reignite the plasma in the semiconductor processing chamber 102 and transition the plasma from a gaseous state to a plasma state. The third power level can use less energy than the first power level.

[0027]

[0033] In some embodiments, the first power level may ignite a plasma in the semiconductor processing chamber 202. The second power level may be characterized by a decrease in the energy of the plasma, where the auxiliary plasma source 220 may maintain the plasma in the semiconductor processing chamber 202. The third power level may cause the main plasma source 204 to increase the energy of the plasma. Because the plasma may be maintained by the auxiliary plasma source 220, it may not be necessary to reignite the plasma.

[0028]

[0034] The supply of electrons provided by the auxiliary plasma source 220 may enable the main plasma source 204 to transition directly from one power level to another. The supply of electrons may act as seed electrons and allow the plasma to transition to an energy dictated by a recipe instead of a higher power level that may be required to reignite the plasma. In other words, the auxiliary plasma source 220 acts as an ignition source for the main plasma source 204 while simultaneously maintaining the plasma in the semiconductor processing chamber 202 and allowing the main plasma source to change power levels without reignition.

[0029]

[0035] Additionally, the semiconductor processing chamber 202 may be held at a constant pressure. Because the plasma in the semiconductor processing chamber 202 may be maintained by the auxiliary plasma source 220, the pressure in the semiconductor processing chamber 202 may be held at a desired operating pressure instead of being raised to re-ignite the plasma during execution of a recipe. Manufacturing defects, such as unwanted polymer deposition, may be mitigated without having to raise the pressure in the semiconductor processing chamber 202 to a higher re-ignition pressure.

[0030]

[0036] FIG. 3 illustrates a system for plasma ignition using a radio frequency (RF) coaxial resonator configured as an electron flood gun, according to some embodiments. The coaxial resonator allows for the transmission of a narrow band of EM waves. For example, a common configuration of a coaxial resonator is a λ / 4 resonator that transmits only EM waves whose wave wavelength is ¼ (or a multiple thereof) of the length of the coaxial resonator. The coaxial resonator generates a strong electromagnetic (EM) field when a current characterized by the resonant frequency of the coaxial resonator is carried by the inner body of the coaxial resonator. At sufficient power levels, a plasma can form at the end of the coaxial resonator.

[0031]

[0037] The system 300 may include a main plasma source body 302 and a direct current (DC) coaxial resonator including an outer DC resonator body 304, an inner DC resonator body 306, a DC connection 308, and a DC source 310. The system 300 may also include an RF coaxial resonator including an outer RF resonator body 312, an inner RF resonator body 314, and a DC insulation block 316. The system 300 may also include an insulator 322 and a chamber window 320. The chamber window 320 may lead to a semiconductor processing chamber, such as the semiconductor processing chamber 102 of FIG.

[0032]

[0038] A DC source 310 may supply current to the inner DC resonator body 306 via a DC connection 308. The current may then return through the outer DC resonator body 304. An electromagnetic field may be formed between the inner DC resonator body 306 and the outer DC resonator body 304. When a frequency with sufficient power is applied to the inner DC resonator body, a plasma may be formed near the chamber window 320.

[0033]

[0039] The internal RF resonator body may be connected to an alternating current (AC) power source 318. In some embodiments, the AC power source 318 is in the microwave range (3×10 8 From 3×10 11 A current utilizing a frequency of about 100 Hz can be supplied to the inner RF resonator body 314. The inner RF resonator body can extend into the outer DC resonator body 304, allowing electrons to enter the DC coaxial resonator. When the AC power source 318 supplies a current near the resonant frequency of the RF coaxial resonator, a plasma can be formed at the end of the inner RF resonator body 314.

[0034]

[0040] The external RF resonator body may be in electrical contact with the main plasma source body 302. In some embodiments, the main plasma source body 302 may be electrically grounded. Thus, the RF coaxial resonator is at a lower potential than the DC coaxial resonator, and electrons may be pumped into the DC coaxial resonator. The RF coaxial resonator configuration may be referred to as an electron flood gun since it provides an electron beam.

[0035]

[0041] To prevent undesired electromagnetic effects from altering the RF coaxial resonator, the RF coaxial resonator may be isolated from DC currents. The DC isolation block connector 316 may isolate the AC coaxial resonator from the DC currents in the DC coaxial resonator. In some embodiments, the DC isolation block connector 316 may include ceramic, along with other suitable materials.

[0036]

[0042] The DC coaxial resonator may serve as the primary plasma source for the semiconductor processing chamber, instead of the primary plasma source 104 in FIG. 1. As in FIG. 1, the power of the DC coaxial resonator may vary according to a recipe executed by one or more processors. In some embodiments, the DC coaxial resonator may have a supply of high energy electrons provided by the RF coaxial resonator via an internal RF resonator body 314, which may serve as an auxiliary plasma source as described above. The supply of high energy electrons allows the DC coaxial resonator to use less power to reignite the plasma or to maintain the plasma at various power levels. Furthermore, by using the RF coaxial resonator as an ignition source for the DC coaxial resonator, the plasma may be formed more stably compared to conventional methods.

[0037]

[0043] Additionally, although the RF coaxial resonator has been shown as supplying electrons to the DC coaxial resonator, other configurations are possible. For example, the RF coaxial resonator can be used as an auxiliary plasma source 220 in FIG. 2 mounted in the process chamber rather than as the primary plasma source. In that case, the RF coaxial resonator can provide a supply of electrons to the semiconductor process chamber 202 and can sustain a plasma directly within the semiconductor process chamber 202.

[0038]

[0044] Although system 300 illustrates a DC coaxial resonator that is ignited or sustained by an RF coaxial resonator, in other embodiments, alternative plasma sources can be used. For example, the DC coaxial resonator can be replaced with any plasma source, including a surface wave generated plasma source such as a surfatron, a coaxial resonator of various configurations (e.g., with a quartz reactor), a toroidal plasma generator, and / or other alternatives. Other plasma sources can also be configured as electron flood guns.

[0039]

[0045] 4 illustrates a toroidal plasma source configured as a toroidal electron flood gun, according to some embodiments. Although the toroidal electron flood gun 400 is illustrated separately, the toroidal electron flood gun 400 may be applied to any of the embodiments herein. For example, the toroidal electron flood gun 400 may be the auxiliary plasma source 220 of FIG. 2. In another embodiment, the toroidal electron flood gun may be used in place of or in addition to the RF coaxial resonator of FIG. 3.

[0040]

[0046] The toroidal electron flood gun 400 may include a flood gun body 402. A toroidal chamber 404 may be included within the flood gun body 402. A gas inlet 406 may pass through the flood gun body 402 to deliver gas to the toroidal chamber 404. The toroidal chamber may also be electrically grounded. A plasma exhaust 408 may be connected at a first end to the toroidal chamber 404. In some embodiments, the plasma exhaust 408 may be connected at a second end to a semiconductor processing chamber, such as the semiconductor processing chamber 202 of FIG. 2. In some embodiments, the second end may be connected to another plasma source, such as the DC coaxial resonator of FIG. 3.

[0041]

[0047] The toroidal flood gun 400 may also include an alternating current (AC) power source 410 electrically connected to the conductors 412a and 412b via AC path 414. In some embodiments, the AC power source is in the microwave range (3×10 8From 3×10 11 Hz). In another embodiment, the AC power source 410 can supply current in the RF range (3×10 5 From 3×10 8 A current with a frequency of 100 Hz can be provided through the conductors 412a and 412b. The current can flow through the conductors 412a and 412b, creating a magnetic field that is alternately directed toward and away from the toroidal chamber 404. The current can also create a toroidal electric field around the conductors 412a and 412b. The changing magnetic and toroidal electric fields can drive gas around the toroidal chamber 404, creating a plasma.

[0042]

[0048] In some embodiments, the flood gun body 402 may be connected to a DC source 416 via a DC path 418. The DC source 416 may provide a current that creates a voltage between the toroidal electron flood gun 400 and a semiconductor processing chamber or plasma source that may be attached to the second end of the plasma exhaust 408. This voltage may cause electrons to be pumped from the toroidal electron flood gun 400 into a semiconductor processing chamber or plasma source that may be attached to the second end of the plasma exhaust 408. Thus, the toroidal electron flood gun 400 may be used as an auxiliary plasma source, such as the auxiliary plasma source 220 of FIG. 2, or in place of or in addition to the RF coaxial resonator of FIG. 3.

[0043]

[0049] 5 is a diagram illustrating a surface wave generated plasma source 500 according to some embodiments. The surface wave plasma source 500 may include a plasma source housing 502. The plasma source housing 502 may include an inner tube 504 and a launching plate 508. There may be a launching gap 510 between the inner tube 504 and the launching plate 508. A dielectric tube 506 may be inside the inner tube 504, and a radio frequency (RF) power source 514 may be in contact with the inner tube 504.

[0044]

[0050] During operation, the RF power source 514 may supply an alternating current to the inner tube 504. In some embodiments, the alternating current may be supplied at a frequency range of about 10 MHz to 3 GHz. The alternating current may be supplied at a power level of about 1 W to 2000 W. The alternating current flows across the inner tube 504 and creates an electric field around the inner tube 504. The electric field may be along the axial direction of the dielectric tube 506.

[0045]

[0051] Also during operation, a gas such as argon or helium may be supplied to the dielectric tube 506 through the gas port 516. In some embodiments, an alternating current supplied through inductive coupling to the inner tube 504 may be supplied at a sufficient level to cause the gas to become a plasma as it moves through the dielectric tube 506 and the electric field. In other embodiments, an alternating current supplied through capacitive coupling to the inner tube 504 may be supplied at a sufficient level to cause the gas to become a plasma as it moves through the dielectric tube 506 and the electric field. The alternating current may also form a surface wave that propagates from the launching gap 510 into the plasma. The surface wave sends electrons toward the launching gap 510 along the propagation direction, forming an ionization front that leads to the plasma.

[0046]

[0052] When the surface wave is emitted from the launching gap 510, the plasma and the ionization front may be propelled towards the launching plate 508. In some embodiments, the launching plate 508 may be fabricated from a metal. The potential difference between the plasma and the launching plate 508 may drive the ionization front and the plasma further towards the axial direction of the dielectric tube 506.

[0047]

[0053] In some embodiments, the launching plate 508 can be configured to direct the ionization front and plasma toward a semiconductor processing chamber, such as the semiconductor processing chamber 202 of FIG. 2. In other embodiments, the launching plate can be in contact with a primary plasma source, such as the DC coaxial resonator of FIG. 3. In this manner, the surface wave plasma source 500 can be used as a supplemental plasma source configured to deliver a supply of high energy electrons to a semiconductor processing chamber and / or another plasma source. Because the surface wave plasma source 500 can deliver a supply of electrons, the surface wave plasma source 500 can be used to ignite or sustain plasma generated from other sources, allowing the other sources to be operated at lower power and changed according to a recipe.

[0048]

[0054] 6 illustrates a semiconductor processing system using a surface wave plasma source as an auxiliary plasma source, according to certain embodiments. System 600 can include a semiconductor processing chamber 602, a primary plasma source 604, and an auxiliary plasma source 620. In some embodiments, semiconductor processing chamber 602 and primary plasma source 604 can be similar to those depicted in FIG. 1. Thus, labeled components 602-618 can function similarly to corresponding components 102-118 in FIG. 1. As in FIG. 1, primary plasma source 604 is shown as an inductively coupled plasma source, however, primary plasma source 604 can be any type of plasma source, including a capacitively coupled plasma source, or any other plasma source.

[0049]

[0055] The system 600 may also include a surface wave plasma source 650. The surface wave plasma source 650 may include an outer wall 620. In some embodiments, the outer wall 620 may be fabricated from a metal. The outer wall 620 may also be electrically grounded. The outer wall 620 may house an inner tube 622 that surrounds a dielectric tube 624. In some embodiments, the inner tube 622 may be fabricated from aluminum. The dielectric tube 624 may be fabricated from quartz. The dielectric tube 624, the inner tube 622, and the outer wall 620 may include a gas port 630 that allows gas to enter the dielectric tube 624.

[0050]

[0056] The surface wave plasma source 650 may also include an RF power source 626 that delivers alternating current to the inner tube 622 via an AC path 628. In some embodiments, the alternating current may be provided at a frequency range of about 10 MHz to 3 GHz. The alternating current may further be provided at a power level of about 1 W to 2000 W.

[0051]

[0057] In some embodiments, the semiconductor processing chamber 602 may be configured to execute a recipe for processing a semiconductor wafer 608. The primary plasma source 604 supplies a plasma to the semiconductor processing chamber 602 and may be configured to operate on a duty cycle during execution of a recipe. The surface wave plasma source 650 may be configured to maintain a plasma in the semiconductor processing chamber 602 throughout the execution of a recipe. In some embodiments, the surface wave plasma source 650 may function as the surface wave plasma source 500 described in FIG. 5. Similar to the surface wave plasma source 500, the surface wave plasma source 650 may provide a supply of electrons to the semiconductor processing chamber 602.

[0052]

[0058] 6 shows only one surface wave plasma source 650, system 600 may include any number of surface wave plasma sources. A surface wave plasma source may be smaller than a different type of plasma source having the same operating frequency because a surface wave plasma source does not necessarily have a minimum length determined by the wavelength associated with the operating frequency. Therefore, it may be practical to include additional surface wave plasma sources in a single system such as system 600.

[0053]

[0059] 7 illustrates a flow chart of a method for providing a plasma to a semiconductor processing chamber, according to some embodiments. In block 702, the method may include processing a semiconductor wafer in the semiconductor processing chamber according to a recipe. In some embodiments, the semiconductor processing chamber is held at a constant pressure.

[0054]

[0060] At block 704, the method 700 may include operating a first plasma source according to a recipe, the plasma source being coupled to the semiconductor processing chamber. The first plasma source may also be configured to operate on a duty cycle during execution of the recipe. The first plasma source may provide plasma to the semiconductor processing chamber. In some embodiments, the first plasma source may be a primary plasma source, such as the primary plasma source 204 of FIG. 2. The plasma may include argon, helium, or other similar plasma gas. The first plasma source may be an inductively coupled plasma source, a capacitively coupled plasma source, or any other type of plasma source.

[0055]

[0061] In block 706, the method 700 may include operating a second plasma source configured to maintain a plasma in the semiconductor processing chamber. The second plasma source may maintain a plasma during the execution of the recipe while the first plasma source operates at a duty cycle. The second plasma source may include a surface wave generated plasma source such as a surfatron, a coaxial resonator of various configurations, a toroidal plasma generator, etc., along with other configurations. In some embodiments, the second plasma source may be an auxiliary plasma source, such as the auxiliary plasma source 220 of FIG. 2. In some embodiments, the second plasma source may be turned on before operating the first plasma source in block 704. The second plasma source may assist the first plasma source in initial plasma ignition and then remain on to maintain the plasma while the first plasma source operates at a duty cycle throughout the execution of the recipe.

[0056]

[0062] In some embodiments, the second plasma source can provide a supply of electrons to the semiconductor processing chamber. The second plasma source can provide electrons to the semiconductor processing chamber by diffusion effects as a leak plasma or by pumping plasma. For example, the second plasma source can pump plasma into the semiconductor processing chamber using an electric potential, such as with an electron beam or electron flood gun.

[0057]

[0063] In some embodiments, the first plasma source may be duty cycled between a plurality of power levels. The first power level may cause the first plasma source to ignite a plasma in the semiconductor processing chamber. The second power level may quench the plasma in the semiconductor processing chamber and transition it to a gaseous state. The third power level may reignite the plasma in the semiconductor processing chamber and transition the plasma from the gaseous state to a plasma state. The third power level may use less energy than the first power level. The duty cycle may operate in a range of about 5% to 95%. In other embodiments, the second power level may be characterized by a decrease in the energy of the plasma. The auxiliary plasma source may then maintain the plasma in the semiconductor processing chamber. The third power level may cause the primary plasma source to increase the energy of the plasma. It may not be necessary to reignite the plasma because the plasma is maintained by the auxiliary plasma source.

[0058]

[0064] In some embodiments, the second plasma source can provide a supply of energetic electrons to the first plasma source. The second plasma source can provide electrons to the first plasma source by diffusion effects as a leak plasma or by pumping plasma. For example, the second plasma source can pump plasma into the first plasma source using an electric potential, such as with an electron beam or electron flood gun.

[0059]

[0065] It should be understood that the specific steps of FIG. 7 provide a particular method of providing a plasma to a semiconductor processing chamber according to various embodiments. Other sequences of steps may be performed according to alternative embodiments. For example, alternative embodiments may perform the steps outlined above in a different sequence. Additionally, individual steps illustrated in FIG. 7 may include multiple sub-steps that may be performed in various sequences as appropriate for the individual step. Additionally, additional steps may be added or removed depending on the particular application. Many variations, modifications, and alternatives are within the scope of the present disclosure.

[0060]

[0066] In the above description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various embodiments. However, it will be apparent that some embodiments may be practiced without some of these specific details. In other instances, well-known structures and devices are shown in block diagram form.

[0061]

[0067] The above description provides only exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the above description of various embodiments provides an enabling disclosure for implementing at least one embodiment. It should be understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope of the several embodiments as defined in the appended claims.

[0062]

[0068] It is also noted that the particular embodiments may be described as a process that is depicted as a flowchart, a flow diagram, a data flow diagram, a structure diagram, or a block diagram. While a flowchart may describe steps as a sequential process, many of the steps may be performed in parallel or simultaneously. Moreover, the order of the steps may be rearranged. A process terminates when the step is completed, but may have additional steps not included in the diagram. A process may correspond to a method, a function, a procedure, a subroutine, a subprogram, etc. When a process corresponds to a function, its termination may correspond to a return of the function to the calling function or the main function.

Claims

1. 1. A method for providing a plasma to a semiconductor processing chamber, comprising: processing a semiconductor wafer in a semiconductor processing chamber according to a recipe; operating a first plasma source according to the recipe, the first plasma source configured to supply a plasma to the semiconductor processing chamber and to operate with a duty cycle during execution of the recipe; operating a second plasma source, the second plasma source configured to be in an on state while the first plasma source is operating at a duty cycle; A method comprising:

2. 10. The method of claim 1 , wherein the first plasma source is configured to operate in a duty cycle between a plurality of power levels including a first power level that causes the first plasma source to ignite a plasma in the semiconductor processing chamber and a second power level at which the plasma is maintained in the semiconductor processing chamber.

3. The method of claim 1 , wherein processing the semiconductor wafer comprises duty cycling the first plasma source between a plurality of power levels.

4. 4. The method of claim 3, wherein the plurality of power levels include a first power level that causes the first plasma source to ignite a plasma in the semiconductor processing chamber, a second power level that quenches the plasma in the semiconductor processing chamber and transitions it to a gas state, and a third power level that re-ignites the plasma in the semiconductor processing chamber and transitions it from a gas state to a plasma state, the third power level using less energy than the first power level.

5. The method of claim 1 , wherein operating the second plasma source comprises providing a supply of electrons to the first plasma source.

6. The method of claim 1 , wherein operating the second plasma source provides a supply of electrons to the semiconductor processing chamber.

7. The method of claim 1 , wherein processing the semiconductor wafer comprises maintaining the semiconductor processing chamber at a constant pressure.

8. 1. A semiconductor processing system comprising: a semiconductor processing chamber configured to execute a recipe for processing a semiconductor wafer; a first plasma source configured to provide a plasma to the semiconductor processing chamber and to operate in a duty cycle while executing the recipe; a second plasma source configured to maintain a plasma in the semiconductor processing chamber while the first plasma source is operating at a duty cycle during execution of the recipe; A semiconductor processing system comprising:

9. 10. The semiconductor processing system of claim 8, wherein a recipe performed on the semiconductor wafer is characterized by a duty cycle that cycles the first plasma source between a plurality of power levels, and the second plasma source is configured to be turned on before the first plasma source initially ignites a plasma in the semiconductor processing chamber.

10. 10. The semiconductor processing system of claim 9, wherein said duty cycle operates at a frequency range of 5 Hz to 5000 Hz.

11. The semiconductor processing system of claim 8 , wherein the second plasma source comprises a microwave coaxial resonator.

12. The semiconductor processing system of claim 11 , wherein the microwave coaxial resonator is configured as an electron flood gun.

13. 10. The semiconductor processing system of claim 8, wherein the second plasma source comprises a toroidal plasma source configured as an electron flood gun.

14. The semiconductor processing system of claim 8 , wherein the second plasma source comprises a surface wave plasma source.

15. 15. The semiconductor processing system of claim 14, wherein the surface wave plasma source generates the plasma using capacitive coupling.

16. 15. The semiconductor processing system of claim 14, wherein the surface wave plasma source generates the plasma using inductive coupling.

17. 10. The semiconductor processing system of claim 8, wherein said semiconductor processing chamber and said first plasma source are integrated parts of said semiconductor processing system, and said second plasma source is installed after manufacture of said semiconductor processing system.

18. 1. A semiconductor processing system comprising: a semiconductor processing chamber configured to execute a recipe for processing a semiconductor wafer; a plasma source configured to deliver a plasma to the semiconductor processing chamber and to operate in a duty cycle while executing the recipe; a surface wave generated plasma source configured to maintain a plasma in the semiconductor processing chamber throughout execution of the recipe on the semiconductor wafer; A semiconductor processing system comprising:

19. 20. The semiconductor processing system of claim 18, wherein the plasma source comprises a toroidal plasma source.

20. 20. The semiconductor processing system of claim 18, wherein the plasma source comprises a coaxial resonator.

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