Apparatus for generating an etchant for a remote plasma process

Abstract

A remote plasma source (RPS) for generating an etchant utilizes a symmetric hollow cathode cavity to improve the etching rate. The RPS includes an upper electrode having a first hollow cavity configured to induce a hollow cathode effect within the first hollow cavity, and a lower electrode having a second hollow cavity configured to induce a hollow cathode effect within the second hollow cavity, wherein the first hollow cavity and the second hollow cavity are symmetric, a lower electrode, a first gap positioned between the upper electrode and the lower electrode and electrically separating the upper electrode and the lower electrode, and an annular dielectric cover that directly contacts the lower electrode within the first gap and forms a second gap between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode. The annular dielectric cover occupies from about 50% to about 95% of the height of the first gap.

Description

Technical Field

[0001]

[0001] Embodiments of the present principle generally relate to semiconductor chambers used in semiconductor processes.

Background Art

[0002]

[0002] Some process chambers may include a remote plasma source (RPS) for forming plasma remotely from the process chamber where radicals and / or ionized species are to be delivered. Conventionally, the RPS is connected to the process chamber through a mixing reservoir for mixing the process gas stream supplied by the RPS with a diluent (or carrier) gas or other fluid before being delivered to the chamber. Thereafter, ions or radicals can be dispersed into the processing region of the process chamber to perform processes such as etching or cleaning. The RPS may include an RF electrode having a hollow cavity and a ground electrode consisting of a flat ground plate. The RF electrode having a hollow cavity forms a hollow cathode mode that promotes electron impact ionization within the hollow cavity. The ground electrode consisting of a flat ground plate generates a glow discharge mode. The inventors have observed that when a sine wave drive system is used for the above RPS, particles may be generated during the glow discharge mode, which may cause defects in the wafers being processed.

[0003]

[0003] Accordingly, the inventors have provided an improved remote plasma generation apparatus that improves etching speed and reduces particle generation.

Summary of the Invention

[0004]

[0004] Provided herein is an apparatus for improving etching speed and reducing particle generation during remote plasma generation.

[0005]

[0005] In some embodiments, an apparatus for processing a substrate includes a process chamber having a chamber body surrounding a processing region, and a remote plasma source (RPS) having a plasma source with an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetric and have a hollow cavity configured to induce a hollow cathode effect within the hollow cavity, the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, the annular dielectric cover is in direct contact with the lower electrode, a second gap is formed between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode, the annular dielectric cover occupies from about 50% to about 95% of the height of the first gap, the RPS is configured to supply radicals or ions into the processing region, and a radio frequency (RF) power source configured to supply a symmetric drive waveform to the upper electrode and the lower electrode to generate an anode cycle and a cathode cycle of the RPS, wherein the anode cycle and the cathode cycle operate in a hollow cathode effect mode.

[0006]

[0006] In some embodiments, the apparatus has an annular dielectric cover that is a ceramic material, the annular dielectric cover having an outermost edge with a first thickness and an innermost edge with a second thickness that is less than the first thickness, the second thickness being from about 1 millimeter to about 2 millimeters, the first thickness being less than about 95% of the height of the first gap, the first thickness tapering downward to a third thickness equal to the second thickness before reaching the innermost edge, the annular dielectric cover having an inner diameter greater than the outer edge of the opening of the hollow cavity and an inner diameter less than the outer edge of the opening of the hollow cavity, the innermost edge of the annular dielectric cover extending at least partially into the opening, capillary holes being spaced apart proximate to the innermost edge of the annular dielectric cover, the capillary holes having a diameter less than twice the thickness of the sheath of the plasma generated by the RPS, the upper and lower electrodes being plated with electroless nickel plating, and an yttria coating being applied to the plasma-exposed surfaces of the upper and lower electrodes and / or an yttria coating being applied to the plasma-exposed surfaces having the first gap and proximate to the openings of the hollow cavities of the upper and lower electrodes.

[0007]

[0007] In some embodiments, an apparatus for processing a substrate is a remote plasma source (RPS) having a plasma source with an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetric with a hollow cavity configured to induce a hollow cathode effect within the hollow cavity, the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, the annular dielectric cover is in direct contact with the lower electrode, a second gap is formed between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode, the annular dielectric cover occupies from about 50% to about 95% of the height of the first gap, the RPS is a remote plasma source configured to supply radicals or ions, and a radio frequency (RF) power source configured to supply a symmetric drive waveform to the upper electrode and the lower electrode to generate an anode cycle and a cathode cycle of the RPS, wherein the anode cycle and the cathode cycle operate in a hollow cathode effect mode.

[0008]

[0008] In some embodiments, the apparatus further includes that the annular dielectric cover has an outermost edge with a first thickness and an innermost edge with a second thickness smaller than the first thickness, the second thickness is from about 1 millimeter to about 2 millimeters, the first thickness is less than about 95% of the height of the first gap, the first thickness slopes downward to a third thickness equal to the second thickness before reaching the innermost edge, the annular dielectric cover has an inner diameter larger than the outer edge of the opening of the hollow cavity, or the annular dielectric cover has an inner diameter smaller than the outer edge of the opening of the hollow cavity, the innermost edge of the annular dielectric cover extends at least partially within the opening, capillary holes are spaced adjacent to the innermost edge of the annular dielectric cover, the capillary holes have a diameter less than twice the thickness of the sheath of the plasma generated by the RPS, and / or the upper electrode and the lower electrode are plated with electroless nickel plating and an yttria coating is applied over the electroless nickel plating on the plasma-exposed surfaces of the upper electrode and the lower electrode.

[0009]

[0009] In some embodiments, an apparatus for providing a remote plasma source (RPS) for generating an etchant may include an upper electrode having a first hollow cavity configured to induce a hollow cathode effect within the first hollow cavity, a lower electrode having a second hollow cavity configured to induce a hollow cathode effect within the second hollow cavity, wherein the first hollow cavity and the second hollow cavity are symmetric, the lower electrode, a first gap positioned between the upper electrode and the lower electrode and electrically separating the upper electrode and the lower electrode, and an annular dielectric cover that directly contacts the lower electrode within the first gap and forms a second gap between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode, wherein the annular dielectric cover occupies from about 50% to about 95% of the height of the first gap, the annular dielectric cover has an inner diameter smaller than an outer edge of an opening of the second hollow cavity and extends at least partially into the opening while directly contacting a surface of the second hollow cavity, and capillary holes are spaced proximate to an innermost edge of the annular dielectric cover and have a diameter less than twice the thickness of a sheath of plasma generated by the RPS.

[0010]

[0010] In some embodiments, the apparatus may further include that the upper electrode and the lower electrode are plated with electroless nickel plating and a yttria coating is applied over the electroless nickel plating of the plasma-exposed surfaces of the upper electrode and the lower electrode.

[0011]

[0011] Other further embodiments are disclosed below.

[0012]

[0012] By referring to the exemplary embodiments of the present principle shown in the accompanying drawings, the embodiments of the present principle summarized above and described in more detail below can be understood. However, the accompanying drawings merely show typical embodiments of the present principle and should not be regarded as limiting the scope. The present principle may also admit other equally effective embodiments.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 12

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Figure 14

DETAILED DESCRIPTION OF THE INVENTION

[0014]

[0027] For ease of understanding, wherever possible, the same reference numbers are used to denote the same elements common to the drawings. The drawings are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated into other embodiments without further elaboration.

[0015]

[0028] The present device provides an improved remote plasma source (RPS) having a symmetric hollow electrode that generates a hollow cathode effect mode for the anode and cathode cycles of a symmetric RF drive system. The improved RPS eliminates the glow discharge mode for the anode cycle found in typical RPS systems that causes particle generation in the process chamber leading to wafer defects and reduced wafer yield. The methods and devices of the present principle use a symmetric electrode configuration with a symmetric drive voltage waveform to generate a hollow cathode discharge mode. The symmetric electrode and drive configuration allows for higher power to be used without generating particles, resulting in a higher etching rate. Further, by eliminating the glow discharge mode, the life of the RF system is extended by preventing accumulation on the gap surface between the electrodes. The symmetric hollow cavity electrode can be used with an RF power system having a symmetric drive waveform with a frequency in the range of a few tens of kilohertz to a few hundred kilohertz to enable the hollow cathode effect mode in both the cathode and anode cycles. The inventors have discovered that the symmetric waveform has the advantage of neutralizing charged particles accumulated in the previous cycle. The symmetric waveform may include, but is not limited to, a sine wave waveform or a rectangular wave waveform.

[0016]

[0029] Several process chambers have an asymmetric electrode configuration that provides two different discharge modes consisting of a hollow cathode mode and a glow discharge mode for cathode and anode cycles. The inventors have found that in the glow discharge mode, particles are generated from sputtering of the electrodes by high energy ion bombardment. The generated particles fall onto the wafer and can affect the performance of the semiconductor. It has been found that the particle performance deteriorates further as the RF power is increased, and the throughput is significantly limited because the RF power has to be reduced in order to improve the particle performance and suppress the generation of particles. The inventors have discovered that the performance of the symmetric hollow cavity electrode can be further improved by using a ceramic cover disposed on top of the bottom electrode and in the gap between the electrodes, which can increase the etching rate by promoting the hollow cathode effect. In some embodiments, a dielectric (e.g., ceramic, etc.) cover and a dielectric (e.g., ceramic, etc.) isolator can be integrated into a single unitary device or assembly. In some embodiments, the inventors have also found that a hybrid coating of electroless nickel plating (ENP) and yttria (Y2O3) on the capillary holes on the electrodes and / or the dielectric cover can be used to generate an improved plasma (higher density) without ignition failure. The use of the ceramic cover has the advantageous benefit of injecting more power into the hollow cathode discharge region to significantly increase the etching rate.

[0017]

[0030] A hollow cathode discharge plasma has a higher etchant generation efficiency than a plasma generated in a gap region between symmetric hollow cavity electrodes. The inventors have discovered that covering the gap region between the electrodes with a dielectric material increases the impedance and helps reduce the power loss occurring within the gap. The dielectric material may be a thin ceramic or a thin film such as yttria, and can prevent any underlying electrode material such as nickel from being sputtered during plasma generation. Further, the inventors have found that covering the electrodes with a dielectric makes plasma ignition more difficult. In order to reduce ignition failure, it is necessary to optimize the shape of the dielectric. To facilitate plasma ignition, a capillary hole can be added to the cover or the integrated assembly.

[0018]

[0031] The present method and apparatus can be used in different types of process chambers such as a pre - cleaning chamber or an etching chamber. As an example of the use of the chamber, FIG. 1 shows a cross - sectional view of a process chamber 100 having a remote plasma source 164 according to some embodiments. The process chamber 100 is a vacuum chamber adapted to maintain a sub - atmospheric pressure within an internal region 102 during substrate processing. In some embodiments, the process chamber 100 can maintain a pressure from about 1 mTorr to 100 Torr. The process chamber 100 includes a chamber body 106 surrounding a processing region 108 located in the upper half of the internal region 102. The chamber body 104 may be made of a metal such as aluminum. The chamber body 104 may be grounded through a connection to ground 110.

[0019]

[0032] For example, a substrate support 112 is disposed within the internal region 102 to support and hold a substrate 114 such as a semiconductor wafer or other such substrate. The substrate support 112 may generally include a pedestal 116 and a hollow support shaft 118 for supporting the pedestal 116. The pedestal 116 may be made of an aluminum-based material or a ceramic-based material, etc. A pedestal formed of a ceramic-based material can be used in high-temperature processes. The hollow support shaft 118 provides, for example, conduits for supplying backside gas, process gas, fluid, coolant, power, etc. to the pedestal 116. In some embodiments, the substrate support 112 includes a focus ring 120 disposed around the pedestal 116 to enhance the uniformity of the process at the edge of the substrate 114. In some embodiments, the focus ring 120 is made of a quartz-based material. In some embodiments, the focus ring 120 is made of a ceramic-based material. The ceramic-based material enhances the high-pressure process capability. A slit valve 122 can be coupled to the chamber body 104 to facilitate the transfer of the substrate 114 in and out of the internal region 102.

[0020]

[0033] In some embodiments, the hollow support shaft 118 is coupled to a lift actuator 124, such as a motor, that provides vertical movement of the pedestal 116 between an upper processing position and a lower transfer position. The substrate lift 126 may include a lift pin 128 attached to a platform 130 connected to a shaft 132 coupled to a second lift actuator 134 for raising and lowering the substrate lift 126 so that the substrate 114 can be placed on or removed from the pedestal 116. The pedestal 116 may include a through hole for receiving the lift pin 128. The hollow support shaft 118 provides a passage for a gas conduit 194 to couple a backside gas supply 136 and / or an RF power supply 138 to the pedestal 116. In some embodiments, the RF power supply 138 supplies bias power to a power conduit 142 to the pedestal 116 via a matching network 140. In some embodiments, the RF energy supplied by the RF power supply 138 may have a frequency of about 2 MHz or greater. In some embodiments, the RF power supply 138 may have a frequency of about 13.56 MHz.

[0021]

[0034] In some embodiments, the backside gas supply 136 is disposed outside the chamber body 104 and supplies gas to the pedestal 116. In some embodiments, the pedestal 116 includes a gas channel 144 that enables gas to interact with the backside of the substrate 114 to maintain a predetermined temperature. The gas channel 144 supplies a backside gas, such as nitrogen (N), argon (Ar), or helium (He), to the upper surface 146 of the pedestal 116 and is configured to act as a heat transfer medium. The gas channel 144 is in fluid connection with the backside gas supply 136 via a gas conduit 194 to control the temperature and / or temperature profile of the substrate 114 in use. For example, the backside gas supply 136 can supply a gas for cooling and / or heating the substrate 114 in use. In some embodiments, the substrate 114 can be heated from about 60 degrees Celsius to about 450 degrees Celsius.

[0022]

[0035] The process chamber 100 includes a process kit that surrounds such components to prevent unwanted reactions between the various chamber components and contaminants. The process kit includes an upper shield 148. In some embodiments, the upper shield 148 may be made of a metal such as aluminum. In some embodiments, the process kit may be made of quartz. In some embodiments, a mixing reservoir 156 is coupled to and in fluid communication with the processing region 108. The mixing reservoir 156 is also in fluid connection with the RPS 164. The mixing reservoir 156 enables the mixing of the plasma gas and other gases supplied by the gas delivery system 150. The flow rate of the other gases from the gas delivery system 150 can be controlled by the first flow rate valve 188.

[0023]

[0036] The showerhead 158 is above the processing region 108 and is located below the ceiling 162 of the chamber body 104. The showerhead 158 includes through holes 160 for flowing gas from the mixing reservoir 156 into the processing region 108. The RPS 164 is in fluid connection with the mixing reservoir 156 such that ionized gas can flow from the RPS 164 into the mixing reservoir 156, through the showerhead 158, and into the processing region 108. Plasma is generated in the RPS 164 by a plasma RF power supply 166 that supplies RF energy to the RPS 164. The process gas used to form the plasma is supplied by a process gas source 170 and is controlled by a second flow rate valve 186. The plasma gas supplied by the process gas source 170 may include, but is not limited to, hydrogen, helium, and / or argon, etc. The RPS 164 generates ions and radicals of the process gas to facilitate the processing of the substrate 114.

[0024]

[0037] The pump port 172 is configured to facilitate the removal of particles and gas from the internal region 102. The process chamber 100 is coupled to a vacuum system 174 that includes a throttle valve (not shown) and a pump (not shown) used to evacuate the process chamber 100 and is in fluid communication with the vacuum system 174. In some embodiments, the vacuum system 174 is coupled to the pump port 172 disposed on the bottom surface 176 of the chamber body 104. The pressure within the process chamber 100 can be adjusted by adjusting the throttle valve and / or the vacuum pump. In some embodiments, the pump has a flow rate of from about 1900 liters per second to about 3000 liters per second. In some embodiments, the vacuum system 174 can be used to facilitate the adjustment of the substrate temperature.

[0025]

[0038] In some embodiments, a controller 178 is used in the process of the process chamber 100. The controller 178 can use direct control of the process chamber 100 or, alternatively, can use indirect control of the process chamber 100 by controlling a computer (or controller) associated with the process chamber 100. In the process, the controller 178 enables data collection and feedback from the process chamber 100 to optimize the performance of the process chamber 100. The controller 178 generally includes a central processing unit (CPU) 180, a memory 182, and support circuitry 184. The CPU 180 can be any form of general-purpose computer processor usable in an industrial environment. The support circuitry 184 is conventionally coupled to the CPU 180 and may include a cache, a clock circuit, an input / output subsystem, a power supply, and the like. When software routines such as methods as described below are stored in the memory 182 and executed by the CPU 180, the CPU 180 can be converted into a special-purpose computer (controller 178). The software routines may also be stored and / or executed by a second controller (not shown) located remotely from the process chamber 100.

[0026]

[0039] When executed by the CPU 180, the memory 182 is in the form of a computer-readable storage medium that includes instructions for facilitating the operation of semiconductor processes and devices. The instructions in the memory 182 are in the form of a program product such as a program for implementing the method of this principle. The program code can conform to any one of a number of different programming languages. In one example, the present disclosure can be implemented as a program product stored in a computer-readable storage medium for use with a computer system. The program(s) of the program product define the functions of the aspects (including the methods described herein). Exemplary computer-readable storage media include non-writable storage media in which information is permanently stored (e.g., a CD-ROM disk readable by a CD-ROM drive, a flash memory, a ROM chip, or any type of solid-state non-volatile semiconductor memory such as a read-only memory device in a computer), and writable storage media in which changeable information is stored (e.g., a floppy disk in a diskette drive or a hard disk drive, or any type of solid-state random access semiconductor memory), but are not limited thereto. Such a computer-readable storage medium is an aspect of this principle when it carries computer-readable instructions that direct the functions of the methods described herein.

[0027]

[0040] FIG. 2 is a cross-sectional view showing a plasma source 200 having an upper symmetric electrode 202A and a lower symmetric electrode 202B according to some embodiments. During operation of the RPS 164, gas enters through gas port 210, and plasma-related products exit into mixing reservoir 156 through diffuser holes 208. The diffuser holes 208 may have a diameter from about 0.1 inch to about 0.2 inch. The upper symmetric electrode 202A and the lower symmetric electrode 202B each have a respective upper symmetric hollow cavity 204A and a respective lower symmetric hollow cavity 204B configured to provide a hollow cathode effect. The upper symmetric electrode 202A and the lower symmetric electrode 202B are separated by a gap 206. The gap 206 is an annular-shaped region that electrically separates the upper symmetric electrode 202A and the lower symmetric electrode 202B by a height 252 from about 0.2 inch to about 0.5 inch. The gap 206 has a width 254 defined by the distance at which the upper symmetric electrode 202A and the lower symmetric electrode 202B remain parallel to each other. The upper symmetric hollow cavity 204A and the lower symmetric hollow cavity 204B have a frustum shape 1302 as shown in the isometric view of FIG. 13. FIG. 13 shows a hollow cathode effect cavity 1300 according to some embodiments.

[0028]

[0041] In FIG. 13, the cone shape 1302 has a vertical axis 1304 at its center. The first end 1310 has an opening for fluid connection to a gas supply (e.g., a process gas source 170). The opening at the first end 1310 may have a diameter of from about 0.1 inch to about 0.2 inch. The second end 1312 is a larger flare-shaped opening that is in fluid connection with the gap 206 between the upper symmetric electrode 202A and the lower symmetric electrode 202B. In some embodiments, the cone shape 1302 may have a first cone portion 1314 having a first angle 1306 of from about 5 degrees to about 30 degrees. The inventors have found that the smaller the angle (e.g., less than about 10 degrees), the more conducive it is to the formation of a high-density plasma in the hollow cavity and helps to increase the etching rate. In some embodiments, the first cone portion 1314 has a first angle 1306 of about 8 degrees. In some embodiments, the cone shape 1302 may have a second cone portion 1316 with a larger flare-shaped opening or a rounded shape having a second angle 1308 of from about 10 degrees to about 60 degrees. The second cone portion 1316 smoothly merges the first cone portion 1314 into the gap region between the upper symmetric electrode 202A and the lower symmetric electrode 202B. In some embodiments, the height 1318 of the cone shape 1302 may be from about 1.5 inches to about 2 inches.

[0029]

[0042] As shown in graph 1200 of FIG. 12, the plasma RF power supply 166 generates a symmetric drive waveform 1202 (e.g., a sine wave is shown as a non-limiting example). During the cathode period 1206, the hollow cathode mode by the upper symmetric hollow cavity 204A forms the plasma 212. During the anode period 1204, the hollow cathode mode by the lower symmetric hollow cavity 204B forms the plasma 212. In a conventional system having a ground plate for the lower electrode, the anode period 1204 instead generates a glow discharge mode due to the ground plate, generating particles harmful to semiconductor performance. With the upper symmetric electrode 202A and the lower symmetric electrode 202B of this principle, the particle performance is greatly improved. During the test, the inventors found that when the upper symmetric hollow cavity 204A and the lower symmetric hollow cavity 204B are configured to provide a hollow cathode effect, the RPS 164 has excellent particle performance compared to an RPS having parallel plane electrodes that generate glow discharge for both the anode and cathode periods of the symmetric drive waveform 1202.

[0030]

[0043] During the test, the inventors found that when the upper electrode having a hollow cavity and the bottom electrode which is a plate electrode are used as the ground (i.e., "asymmetric electrodes"), when the plasma source is driven by a symmetric waveform, two different plasma modes are generated. During the anode period 1204, a thin plasma is formed directly above the plate electrode used as the ground. During the cathode period 1206, a strong hollow cathode effect occurs at the center of the hollow cavity of the upper electrode and plasma is formed at the center ("hollow cathode effect"). The inventors found that the hollow cathode mode improves the etching performance. When the drive waveform is changed so that only the cathode period exists (half-sine wave waveform), the inventors found that the etching performance is improved, but a negative side effect of material accumulation in the gap separating the upper and bottom electrodes of the plasma source was also found.

[0031]

[0044] When the electrodes are changed to parallel plate electrodes having a gap therebetween, a glow discharge mode occurs in both the anode period and the cathode period, resulting in a decrease in etching performance and the generation of a significant number of particles. The inventors have discovered that by using a symmetric electrode having a hollow cavity configured to generate a hollow cathode effect mode in the anode period and the cathode period, the etching performance is significantly improved compared to a single conical-shaped hollow electrode. The etching rate was improved as a result of the increased plasma portions 310A of the plasma 308 formed in the upper symmetric hollow cavity 204A and the increased plasma portions 310B of the plasma 308 formed in the lower symmetric cavity 204B, as shown in FIG. 300 of FIG. 3. The increased plasma resulted in an approximately 20% increase in the etching rate compared to a single hollow cavity design. The symmetric hollow cavity can be surrounded by an annular isolator 302 to separate the electrodes and form a gap 206 between the symmetric electrodes 202A, 202B. In some embodiments, the annular isolator 302 may be positioned on top of the lower symmetric electrode or the upper symmetric electrode (FIG. 3 shows the annular isolator 302 on top of the lower electrode having a thickness 304). In some embodiments, the annular isolator 302 may extend to and surround both the lower electrode and the upper electrode, as shown by the increased thickness 306 in FIG. 3. The larger thickness 306 increases the distance between the upper electrode and the lower electrode compared to the thickness 304, resulting in a significant decrease in the capacitance between the upper electrode and the lower electrode.

[0032]

[0045] The etching rate was increased compared to a single hollow cavity design, but the inventors found that a large proportion of the plasma 308 extends (314) into and occupies the gap 206 between the upper symmetric electrode 202A and the lower symmetric electrode 202B, as shown in FIG. 3. The inventors discovered that by reducing the strength of the electric field across the entire gap 206, more of the power supplied to the electrodes becomes available in the hollow cavity region. As shown in FIG. 400 of FIG. 4, in some embodiments, a cover 402 formed of a dielectric material is positioned over the lower symmetric electrode 202B or the upper symmetric electrode 202A, reducing the electric field strength in the gap 206, and as a result, significantly increasing the plasma 408 in the hollow cavity region. In some embodiments, the cover is formed of a ceramic material. The inventors have found that using such a configuration increases the etching rate by up to about 3 times (300%) compared to a symmetric hollow cavity electrode without a cover on one of the symmetric electrodes.

[0033]

[0046] FIG. 5 shows a view 500 of a cover 402 (also shown in FIG. 4) having a rectangular cross-section. The cover 402 is annular and is positioned in the gap 206 between the upper symmetric electrode 202A and the lower symmetric electrode 202B. The cover 402, and all covers described herein, are defined as an annular dielectric material that fills the gap 206 with a dielectric material from about 5% to about 95% of the height 252 of the gap 206 (see FIG. 2). The covers described herein do not completely fill the gap 206 (from the lower electrode surface to the upper electrode surface) to provide a space 406 that allows for the accumulation 404 of process residues. When the electrodes are composed of a nickel material, the nickel material is often sputtered during processing, and the re-sputtered nickel particles cause the accumulation 404 on the cover surface. Leaving a space 406 between the cover and one or more electrodes allows for the accumulation of particles and increases the maintenance interval of the RPS. Further, the space 406 increases the maintenance interval while preventing the occurrence of a short circuit or arc discharge if metal residues such as re-sputtered nickel short-circuit or adhere to both electrodes within the RPS.

[0034]

[0047] The width 514 of the cover 402 can cover from about 80% to about 100% of the width 254 of the gap 206. As can be seen from FIG. 5, the cutting line A-A522 creates a rectangular cross-section having an outer edge 512 of the first thickness 506 and an inner edge 510 of the second thickness 508 equal to the first thickness 506. In some embodiments, the first thickness 506 may be from about 80% to 95% of the height 252 of the gap 206. During testing, the inventors found that when the inner edge 510 of the cover 402 is the same thickness as the outer edge 512 of the cover, plasma ignition in the hollow cavity becomes a problem. Due to the low electric field strength near the hollow cavity, plasma ignition is weak and often cannot ignite the plasma to a sustainable level.

[0035]

[0048] FIG. 600 of FIG. 6 shows a cover 602 having an inner edge 610 with a reduced second thickness 608. The second thickness 608 of the inner edge 610 may be from about 5% to about 50% of the first thickness 606 of the outer edge 612 and the upper surface 616. In some embodiments, the second thickness 608 may be from about 1 mm to about 2 mm. The inventors found that the second thickness 608 is desirably as thin as possible to facilitate easier plasma ignition, but since the cover 602 is composed of a ceramic material, the structural integrity of the cover 602 determines how thin the ceramic material can be made for a given RPS. If the second thickness 608 is too thick, the plasma in the hollow cavity is enhanced, but plasma ignition becomes very difficult or impossible. The width 614 of the cover 602 may be changed or remain unchanged compared to the width 514 of the cover 402.

[0036]

[0049] The modified profile of the cover 602 is shown by the cutting line AA622. The width 620 of the upper surface 616 may extend from about 30% to about 80% of the width 614 of the cover 602 up to in front of the angled surface 618. The inventors have found that by making the inner edge 610 of the cover 602 thinner, the plasma ignition performance is improved while the plasma in the symmetric hollow cavity still remains increased (for example, the etching rate performance remains high). In FIG. 700 of FIG. 7, another profile along the cutting line AA622 is shown together with the modified angled surface 718. The angled surface 718 has a sharper initial angle and then slopes from the first thickness 606 to the second thickness 608. The modified angled surface 718 creates a larger region (the region of the thinner part is larger than the profile of the cover in FIG. 6 and has a high electric field strength) where the electric field strength for igniting the plasma is increased, while the electric field strength is kept low so that the plasma is mainly generated at the upper and lower symmetric electrodes. Those skilled in the art can understand that with other angled surfaces and shapes of the cover profile, sufficient plasma ignition can be obtained while generating most of the plasma in the upper and lower symmetric electrodes.

[0037]

[0050] As shown in FIG. 800 of FIG. 8, the inventors have found that by adding an extension 802 to the cover 602 that further extends the cover 602 into the mouth of at least the lower symmetric hollow cavity of the lower symmetric electrode or into the second cone portion 1316 (see, for example, FIG. 13), the plasma in the symmetric electrode can be further enhanced. The extension 802 follows the contour of the surface 1320 of the second cone portion 1316. The extension 802 further enhances the plasma in the symmetric electrode, but makes plasma ignition more difficult. The inventors have found that when capillary holes 902 are equally spaced around the inner edge 904 of the cover 602 having the extension 802, as shown in FIG. 900 of FIG. 9, plasma ignition is significantly improved while maintaining a higher performance plasma in the symmetric hollow cavity of the symmetric electrode. The capillary holes 902 expose the upper surface of the lower symmetric electrode, and when the electric field strength at the exposed position increases, plasma ignition becomes easier. When the diameter 908 of the capillary hole 902 is less than twice the thickness of the plasma sheath, the plasma can be easily ignited by the electrode surface exposed through the capillary hole 902. However, since the plasma sheath is too thick and the plasma is not formed in the capillary hole 902, the plasma cannot be maintained through the capillary hole 902 (the plasma sheath needs to bend into the capillary hole, and in that case, a hole having a diameter more than twice the thickness of the sheath is required to maintain the plasma in the hole).

[0038]

[0051] Under high-pressure conditions, the sheath of the plasma has a smaller thickness than under low-pressure conditions. The diameter size of the capillary hole 902 depends on the operating conditions (e.g., pressure, etc.) of a specific RPS design. The distance 906 between the inner edge of the cover 602 having the extension 802 and the center point of the diameter 908 of the capillary hole 902 can be made as small as possible while enabling plasma ignition within the symmetric hollow cavity of the symmetric electrode. If the distance 906 is too large, the plasma ignited near the capillary hole 902 will not be close enough to ignite the plasma within the hollow cavity of the electrode. In the bottom view 1000 of FIG. 10, the equal spacing of the capillary holes 902 around the inner edge of the cover 602 having the extension 802 is shown. In some embodiments, the number of capillary holes 902 may be 8 or more. The larger the number of capillary holes 902, the easier it is for plasma ignition. However, due to manufacturability, the number of capillary holes that may be made of a given ceramic material may be limited. With a large number of holes, the wall thickness 910 between the capillary holes 902 becomes thin, and there is a possibility that integrity is lost, or the ceramic material is too thin to maintain integrity under operating conditions. In the first bottom view 1400A of FIG. 14, a first annular row 1402 and a second annular row 1404 of capillary holes extending radially outward 1410 from the center point 1406 of the cover 1408 are shown. In some embodiments, the cover 1408 may have more than two annular rows of capillary holes. In the second view 1400B of FIG. 14, the first annular row 1402 of capillary holes and the second annular row 1404 of capillary holes are offset, and the distribution of the holes closer to the inner edge 1412 of the cover 1408 may be denser. In some embodiments, the cover 1408 may have more than two offset annular rows of capillary holes. In some embodiments, the cover 1408 may have a plurality of annular rows in which offset capillary holes and radially aligned capillary holes are mixed. In some embodiments, each of the annular rows may have capillary holes of different diameters. In some embodiments, a single annular row may have capillary holes of different diameters.

[0039]

[0052] The upper symmetric electrode 202A and the lower symmetric electrode 202B shown in FIG. 1100 of FIG. 11 may be formed of an aluminum material plated with electroless nickel plating (ENP). The ENP process forms a layer of nickel on the surface of the electrode to prevent chemical reactions that occur during etching or other processes. Chemical reactions include, but are not limited to, fluorine-based reactions such as aluminum fluoride caused by an etching process gas such as nitrogen trifluoride (NF3). However, nickel coatings often generate fine particles that can accumulate on the substrate and cause performance problems with substrate features. The inventors have found that by applying an additional yttria (Y2O3) coating 1104 on the ENP over the high electric field region of the symmetric electrode RPS, the yttria coating 1104 can increase the impedance of the gap 206 while preventing nickel sputtering that could deposit on the ceramic surface within the gap 206 and reduce the impedance of the gap 206, enabling more power to be supplied by hollow cathode discharge. Also, the yttria coating 1104 facilitates preventing chemical reactions that occur during etching or other processes, including, but not limited to, fluorine-based reactions caused by an etching process gas such as nitrogen trifluoride (NF3). In some embodiments, the yttria coating 1104 has a thickness 1110 of about 100 mils.

[0040]

[0053] Since the yttria coating 1104 extends at least partially to the mouth of the hollow cavity, the plasma performance is further improved, such as an increase in the etching rate, depending on how the RPS is used. Since yttria particles are not conductive like nickel particles, even if yttria-based particles are generated, they cannot accumulate in the gap region and cause arc discharge and short circuit. In some embodiments as shown in FIG. 11, the yttria coating 1104 is applied to at least a portion of the surface 1320 of the second cone portion 1316 (see FIG. 13) and the plane 1106 of the gap 206 that will be exposed to the plasma during the process. In some embodiments, the yttria coating 1104 may extend to cover most or all of the plane 1106 to facilitate the manufacture of the coated electrode. The inventors have found that the yttria coating 1104 may be extended 1108 over the first cone surface 1322A of the upper symmetric hollow cavity 204A (see FIG. 13) and over the first cone surface 1322B of the lower symmetric hollow cavity 204B. By extending the yttria coating 1104 into the hollow cavity, the yttria coating 1104 prevents nickel sputtering from occurring within the hollow cavity and improves the particle performance of the RPS, particularly the particle performance of nickel-based particles (i.e., reduces the number of particles generated).

[0041]

[0054] In some embodiments, as also shown in FIG. 11, a cover, a cover having an extension, or a cover having an extension and a capillary hole may be used with the yttria coating 1104. In some embodiments, an integrated assembly 1102 as shown in FIG. 11 may be used in the RPS with or without the yttria coating 1104. The integrated assembly 1102 incorporates a cover and an insulator into a single integrated device to facilitate placement and assembly. The integrated assembly 1102 is also low-cost to manufacture as a single component. Although FIG. 3 shows the integrated assembly 1102 with only an insulator portion extending to the lower symmetric electrode 202B, in some embodiments, the integrated assembly 1102 may include an insulator portion extending to both the upper symmetric electrode 202A and the lower symmetric electrode 202B.

[0042]

[0055] While the foregoing is directed to embodiments of the principle, other and further embodiments of the principle may be devised without departing from its basic scope.

Claims

1. An apparatus for processing a substrate, comprising: a process chamber having a chamber body surrounding a processing region; and a remote plasma source (RPS) having a plasma source with an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetric and have a hollow cavity configured to induce a hollow cathode effect within the hollow cavity, the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, the annular dielectric cover is in direct contact with the lower electrode, a second gap is formed between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode, the annular dielectric cover occupies from about 50% to about 95% of the height of the first gap, and the RPS is configured to supply radicals or ions into the processing region; a radio frequency (RF) power source configured to supply a symmetric drive waveform to the upper electrode and the lower electrode to generate an anode cycle and a cathode cycle of the RPS, wherein the anode cycle and the cathode cycle operate in a hollow cathode effect mode; The apparatus comprising the above.

2. The apparatus according to claim 1, wherein the annular dielectric cover is a ceramic material.

3. The apparatus according to claim 1, wherein the annular dielectric cover has an outermost edge with a first thickness and an innermost edge with a second thickness smaller than the first thickness.

4. The apparatus according to claim 3, wherein the second thickness is from about 1 millimeter to about 2 millimeters, and the first thickness is less than about 95% of the height of the first gap.

5. The apparatus according to claim 3, wherein the first thickness slopes downward to a third thickness equal to the second thickness before reaching the innermost edge.

6. The apparatus according to claim 1, wherein the annular dielectric cover has an inner diameter larger than an outer edge of an opening of the hollow cavity.

7. The apparatus according to claim 1, wherein the annular dielectric cover has an inner diameter smaller than an outer edge of an opening of the hollow cavity, and the innermost edge of the annular dielectric cover at least partially extends into the opening.

8. The apparatus according to claim 7, wherein capillary holes are spaced adjacent to the innermost edge of the annular dielectric cover.

9. The capillary hole has a diameter less than twice the thickness of the sheath of the plasma generated by the RPS, and the device according to claim 8.

10. The upper electrode and the lower electrode are plated by electroless nickel plating, and the device according to claim 1.

11. The yttria coating is applied to the plasma-exposed surfaces of the upper electrode and the lower electrode, and the device according to claim 10.

12. The yttria coating is applied to a plasma-exposed surface having a first gap and in the vicinity of the openings of the hollow cavities of the upper electrode and the lower electrode, and the device according to claim 10.

13. An apparatus for processing a substrate, A remote plasma source (RPS) having a plasma source including an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetric with a hollow cavity configured to induce a hollow cathode effect in the hollow cavity, the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, the annular dielectric cover is in direct contact with the lower electrode, a second gap is formed between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode, the annular dielectric cover occupies from about 50% to about 95% of the height of the first gap, and the RPS is configured to supply radicals or ions, a remote plasma source (RPS); A high-frequency (RF) power source configured to supply a symmetric drive waveform to the upper electrode and the lower electrode to generate an anode cycle and a cathode cycle of the RPS, wherein the anode cycle and the cathode cycle operate in a hollow cathode effect mode, an RF power source An apparatus comprising.

14. The annular dielectric cover has an outermost edge having a first thickness and an innermost edge having a second thickness smaller than the first thickness, the second thickness is from about 1 millimeter to about 2 millimeters, and the first thickness is less than about 95% of the height of the first gap, and the device according to claim 13.

15. The first thickness slopes downward to a third thickness equal to the second thickness before reaching the innermost edge, and the device according to claim 14.

16. The annular dielectric cover has an inner diameter greater than the outer edge of the opening of the hollow cavity, or the annular dielectric cover has an inner diameter smaller than the outer edge of the opening of the hollow cavity, and the innermost edge of the annular dielectric cover extends at least partially into the opening. The apparatus according to claim 13.

17. Capillary holes are spaced apart close to the innermost edge of the annular dielectric cover, and the capillary holes have a diameter less than twice the thickness of the sheath of the plasma generated by the RPS. The apparatus according to claim 16.

18. The upper electrode and the lower electrode are plated by electroless nickel plating, and an yttria coating is applied over the electroless nickel plating on the plasma-exposed surfaces of the upper electrode and the lower electrode. The apparatus according to claim 13.

19. An apparatus for providing a remote plasma source (RPS) for generating an etchant, An upper electrode having the first hollow cavity configured to induce a hollow cathode effect within the first hollow cavity, A lower electrode having the second hollow cavity configured to induce a hollow cathode effect within the second hollow cavity, wherein the first hollow cavity and the second hollow cavity are symmetric. The lower electrode, A first gap positioned between the upper electrode and the lower electrode and electrically separating the upper electrode and the lower electrode, An annular dielectric cover that directly contacts the lower electrode within the first gap and forms a second gap between the uppermost surface of the annular dielectric cover and the lowermost surface of the upper electrode. The annular dielectric cover occupies from about 50% to about 95% of the height of the first gap. The annular dielectric cover has an inner diameter smaller than the outer edge of the opening of the second hollow cavity and extends at least partially into the opening while directly contacting the surface of the second hollow cavity. Capillary holes are spaced apart close to the innermost edge of the annular dielectric cover and have a diameter less than twice the thickness of the sheath of the plasma generated by the RPS. The annular dielectric cover An apparatus comprising.

20. The device according to claim 19, wherein the upper electrode and the lower electrode are plated by electroless nickel plating, and the yttria coating is applied on the electroless nickel plating of the plasma exposure surfaces of the upper electrode and the lower electrode.

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