Apparatus for generating etchant for remote plasma processing

Abstract

A remote plasma source (RPS) for generating etchant utilizes a symmetric hollow cathode cavity to increase etchant rate. The RPS includes: 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, where the first hollow cavity is symmetric to the second hollow cavity; the first gap is positioned between the upper electrode and the lower electrode and electrically separates the upper electrode from the lower electrode; and an annular dielectric cap directly contacting the lower electrode in the first gap and forming a second gap between an uppermost surface of the annular dielectric cap and a lowermost surface of the upper electrode. The annular dielectric cap fills about 50% to about 95% of a height of the first gap.

Description

Technical Field

[0001] Embodiments of the present principles relate generally to semiconductor chambers used in semiconductor processing. Background Art

[0002] Some processing chambers may include a remote plasma source (RPS) for forming a plasma away from the processing chamber, into which free radicals and / or ionized species are transported. Typically, the RPS is connected to the processing chamber via a mixing container for mixing a processing gas flow provided by the RPS with a diluent (or carrier) gas or other fluid before being transported to the chamber. The ions or free radicals may then be dispersed into a processing space of the processing chamber to perform processes such as etching or cleaning. The RPS may include an RF electrode having hollow cavities and a ground electrode consisting of a flat ground plate. The RF electrode having a hollow cavity generates a hollow cathode mode that enhances electron impact ionization within the hollow cavity. The ground electrode having a flat ground plate generates a glow discharge mode. The inventors have observed that if a sinusoidal drive system is used for such an RPS, particles may be generated during the glow discharge mode, resulting in defects on the wafer being processed.

[0003] Thus, the inventors provide improved apparatus for generating a remote plasma with increased etch rate and reduced particle generation. Summary of the invention

[0004] Provided herein are apparatus for increasing etch rates and reducing particle generation during remote plasma generation.

[0005] In some embodiments, an apparatus for processing a substrate may include: a processing chamber having a chamber body surrounding a processing space, a remote plasma source (RPS) having a plasma source, the plasma source having an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetrical with hollow cavities, the hollow cavities being configured to induce a hollow cathode effect within the hollow cavities, wherein the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover positioned within the first gap, wherein the annular dielectric cover is in direct contact with the lower electrode and forms a second gap between an uppermost surface of the annular dielectric cover and a lowermost surface of the upper electrode, wherein the annular dielectric cover fills about 50% to about 95% of a height of the first gap, and wherein the RPS is configured to provide free radicals or ions into the processing space, and a radio frequency (RF) power source configured to provide symmetrical driving waveforms on 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] In some embodiments, the apparatus may further include: wherein the annular dielectric cover is a ceramic material, wherein the annular dielectric cover has an outermost edge and an innermost edge, the outermost edge has a first thickness, the innermost edge has a second thickness less than the first thickness, wherein the second thickness is about 1 mm to about 2 mm and the first thickness is less than about 95% of the height of the first gap, wherein the first thickness slopes downward to a third thickness equal to the second thickness before reaching the innermost edge, wherein the inner diameter of the annular dielectric cover is greater than the outer edge of the opening of the hollow cavity, wherein the inner diameter of the annular dielectric cover is less than the outer edge of the opening of the hollow cavity, wherein the innermost edge of the annular dielectric cover at least partially extends into the opening, wherein capillaries are spaced apart near the innermost edge of the annular dielectric cover, wherein the diameter of the capillaries is less than twice the thickness of the sheath of the plasma to be generated using the RPS, wherein the upper electrode and the lower electrode are plated with electroless nickel (electroless nickel) nickelplating), wherein a yttria coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode, and / or wherein a yttria coating is applied to plasma exposed surfaces having a first gap and the plasma exposed surfaces are near openings of the hollow cavities of the upper electrode and the lower electrode.

[0007] In some embodiments, an apparatus for processing a substrate may include: a remote plasma source (RPS) having a plasma source, the plasma source having an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetrical with a hollow cavity, the hollow cavity being configured to induce a hollow cathode effect within the hollow cavity, wherein the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, wherein the annular dielectric cover is in direct contact with the lower electrode and forms a second gap between an uppermost surface of the annular dielectric cover and a lowermost surface of the upper electrode, wherein the annular dielectric cover fills about 50% to about 95% of a height of the first gap, and wherein the RPS is configured to provide free radicals or ions, and a radio frequency (RF) power source, the radio frequency (RF) power source being configured to provide symmetrical driving waveforms on 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] In some embodiments, the apparatus may further include: wherein the annular dielectric cover has an outermost edge and an innermost edge, the outermost edge has a first thickness, the innermost edge has a second thickness less than the first thickness, and wherein the second thickness is about 1 mm to about 2 mm and the first thickness is less than about 95% of the height of the first gap, wherein the first thickness slopes downward to a third thickness equal to the second thickness before reaching the innermost edge, wherein the inner diameter of the annular dielectric cover is greater than the outer edge of the opening of the hollow cavity, or wherein the inner diameter of the annular dielectric cover is less than the outer edge of the opening of the hollow cavity, wherein the innermost edge of the annular dielectric cover extends at least partially into the opening, wherein capillaries are spaced apart near the innermost edge of the annular dielectric cover, and wherein the diameter of the capillaries is less than twice the thickness of a sheath of a plasma to be generated using the RPS, and / or wherein the upper electrode and the lower electrode are plated with electroless nickel, and wherein a yttrium oxide coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode on the electroless nickel.

[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, the first hollow cavity being configured to induce a hollow cathode effect in the first hollow cavity; a lower electrode having a second hollow cavity, the second hollow cavity being configured to induce a hollow cathode effect in the second hollow cavity, wherein the first hollow cavity is symmetrical to the second hollow cavity; a first gap, the first gap being positioned between the upper electrode and the lower electrode and electrically separating the upper electrode from the lower electrode; and an annular dielectric cover, the annular dielectric cover directly contacting the first hollow cavity. The invention relates to a method for manufacturing a second hollow cavity and a method for manufacturing a second hollow cavity. The method comprises: forming a first hollow cavity and a second hollow cavity between the lower electrode in a gap and forming 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 fills about 50% to about 95% of the height of the first gap, wherein the annular dielectric cover has an inner diameter smaller than an outer edge of an opening of the second hollow cavity, the inner diameter of the annular dielectric cover at least partially extending into the opening while directly contacting a surface of the second hollow cavity, and wherein capillary pores are spaced apart near the innermost edge of the annular dielectric cover and the diameter of the capillary pores is less than twice the thickness of a sheath of a plasma to be generated using the RPS.

[0010] In some embodiments, the apparatus may further include: wherein the upper electrode and the lower electrode are plated with electroless nickel, and a yttrium oxide coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode above the electroless nickel.

[0011] Other and further embodiments are disclosed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The embodiments of the present principles, which have been briefly summarized above and will be discussed in more detail below, can be understood by referring to the illustrative embodiments of the present principles depicted in the accompanying drawings. However, the accompanying drawings depict only typical embodiments of the present principles, and since the present principles may allow other equally effective embodiments, the accompanying drawings are not to be considered as limiting the scope of the present disclosure.

[0013] Figure 1 Depicted is a cross-sectional view of a processing chamber with a remote plasma source, according to some embodiments of the present principles.

[0014] Figure 2 Depicted is a cross-sectional view of a plasma source with symmetric electrodes, according to some embodiments of the present principles.

[0015] Figure 3 Depicted is a cross-sectional view of a plasma source with symmetric electrodes and plasma generation, according to some embodiments of the present principles.

[0016] Figure 4Depicted is a cross-sectional view of a plasma source with symmetric electrodes and lid, according to some embodiments of the present principles.

[0017] Figure 5 Depicted is an isometric view of a cover for a remote plasma source, according to some embodiments of the present principles.

[0018] Figure 6 Depicted is an isometric view of a cover having an inclined surface for a remote plasma source, according to some embodiments of the present principles.

[0019] Figure 7 Depicted is a cross-sectional view of a cover profile having an inclined surface for a remote plasma source, according to some embodiments of the present principles.

[0020] Figure 8 Depicted is a cross-sectional view of a cover profile having an inclined surface and an extension for a remote plasma source, according to some embodiments of the present principles.

[0021] Fig. 9 Depicted is a cross-sectional view of a cover profile having an inclined surface and an extension with a capillary hole for a remote plasma source, according to some embodiments of the present principles.

[0022] Fig.10 Depicted is a bottom-up view of a cover having an inclined surface and an extension with a capillary hole for a remote plasma source, according to some embodiments of the present principles.

[0023] Fig.11 Depicted is a cross-sectional view of a plasma source having symmetric electrodes with yttria coatings and a cover with sloped surfaces, according to some embodiments of the present principles.

[0024] Fig.12 Graph depicting a symmetrical drive waveform according to some embodiments of the present principles.

[0025] Fig.13 Depicted is a hollow cathode effect chamber, according to some embodiments of the present principles.

[0026] Fig.14 Depicted is a bottom-up view of a cover for a remote plasma source having an inclined surface and an extension with an alternative capillary pattern, according to some embodiments of the present principles.

[0027] For ease of understanding, the same reference numerals are used to designate the same elements common to the drawings, where possible. 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 description. DETAILED DESCRIPTION

[0028] The device provides an improved remote plasma source (RPS) having a symmetrical hollow electrode that produces a hollow cathode effect mode for anode and cathode cycles of a symmetrical RF drive system. The improved RPS eliminates the glow discharge mode of the anode cycle in a typical RPS system, which can cause particles to be generated in the processing chamber, resulting in wafer defects and reduced wafer yield. The method and device of the present principle use a symmetrical electrode configuration together with a symmetrical drive voltage waveform to produce a hollow cathode discharge mode. The symmetrical electrode and drive configuration can use higher power without generating particles and having a higher etching rate. In addition, eliminating the glow discharge mode can extend the service life of the RF system by preventing accumulation on the gap surface between the electrodes. The symmetrical cavity electrode can be used with an RF power system with a symmetrical drive waveform to achieve a hollow cathode effect mode for both cathode and anode cycles, and the frequency of the symmetrical drive waveform ranges from tens of kilohertz (10's of kilohertz) to hundreds of kilohertz (100's of kilohertz). The inventors have found that a symmetrical waveform has the benefit of neutralizing charged particles accumulated in previous cycles. The symmetrical waveform may include, but is not limited to, a sinusoidal waveform or a square waveform, etc.

[0029] Some processing chambers have an asymmetric electrode configuration that provides two different discharge modes, including a hollow cathode mode and a glow discharge mode for cathode and anode cycles. The inventors have found that the glow discharge mode causes electrode sputtering to produce particles due to high-energy ion impacts. The particles produced may fall on the wafer and affect the performance of the semiconductor. It was found that for higher RF powers, the particle performance is even worse, which severely limits the yield because the RF power must be reduced to improve particle performance and reduce particle generation. The inventors have found that the performance of the symmetrical hollow cavity electrode can be further improved by utilizing a ceramic cover placed above the bottom electrode and in the gap between the electrodes to increase the etching rate by enhancing the hollow cathode effect. In some embodiments, the dielectric (e.g., ceramic, etc.) cover and the dielectric (e.g., ceramic, etc.) separator can be combined into a single unitary piece or assembly. In some embodiments, the inventors have found that a mixed coating of electroless nickel (ENP) and yttrium oxide (Y2O3) on the electrode and / or capillary pores on the dielectric cover can also be used to generate improved plasma (higher density) without any ignition failure. The use of a ceramic cap has the advantageous benefit of applying more power to the hollow cathode discharge region to significantly increase the etch rate.

[0030] Hollow cathode discharge plasmas are more efficient in etchant generation than plasmas generated in the gap region between symmetrical hollow cavity electrodes. The inventors have found that by covering the gap region between the electrodes with a dielectric material, the impedance can be increased and help reduce the power losses that occur in the gap. The dielectric material can be a thin ceramic or film such as yttrium oxide, which also prevents any underlying electrode material (such as but not limited to nickel, etc.) from sputtering during plasma generation. The inventors have also found that covering the electrodes with a dielectric makes plasma ignition more difficult. In order to reduce ignition failures, the shape of the dielectric should be optimized. Capillaries can be added to the cover or unit assembly to help ignite the plasma more easily.

[0031] The method and apparatus can be used in different types of processing chambers, such as pre-cleaning chambers or etching chambers. As an example chamber, Figure 1 A cross-sectional view of a processing chamber 100 with a remote plasma source 164 is depicted according to some embodiments. The processing chamber 100 is a vacuum chamber that is suitable for maintaining a sub-atmospheric pressure within an interior space 102 during substrate processing. In some embodiments, the processing chamber 100 can maintain a pressure of about 1 mTorr to 100 Torr. The processing chamber 100 includes a chamber body 106 that surrounds a processing space 108 positioned in an upper half of the interior space 102. The chamber body 104 can be made of a metal such as aluminum. The chamber body 104 can be grounded to a ground 110 via a coupling.

[0032] The substrate support 112 is disposed within the interior space 102 to support and hold a substrate 114 (such as, for example, 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 formed of an aluminum-based material or a ceramic-based material, among others. A pedestal formed of a ceramic-based material may be used for high temperature processes. The hollow support shaft 118 provides a conduit to provide, for example, 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 about the pedestal 116 to enhance process uniformity 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. Ceramic-based materials facilitate high pressure process capabilities. A slit valve 122 may be coupled to the chamber body 104 to facilitate moving the substrate 114 into and out of the interior space 102.

[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 susceptor 116 between an upper processing position and a lower transfer position. The substrate lift 126 may include lift pins 128 mounted on a platform 130 that is connected to a shaft 132 that is 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 susceptor 116. The susceptor 116 may include through holes to receive the lift pins 128. The hollow support shaft 118 provides a path for a gas conduit 194 to couple a backside gas supply 136 and / or an RF power supply 138 to the susceptor 116. In some embodiments, the RF power supply 138 provides bias power to the susceptor 116 through a matching network 140 to a power conduit 142. In some embodiments, the RF energy provided by RF power supply 138 may have a frequency of about 2 MHz or higher. In some embodiments, RF power supply 138 may have a frequency of about 13.56 MHz.

[0034] In some embodiments, a 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, allowing the gas to interact with the back side of the substrate 114 to maintain a given temperature. The gas channel 144 is configured to provide a backside gas (such as nitrogen (N), argon (Ar), or helium (He)) to the upper surface 146 of the pedestal 116 to serve as a heat transfer medium. The gas channel 144 is fluidly connected to the backside gas supply 136 via a gas conduit 194 to control the temperature and / or temperature distribution of the substrate 114 during use. For example, the backside gas supply 136 can supply gas to cool and / or heat the substrate 1114 during use. In some embodiments, the substrate 114 can be heated from about 60 degrees Celsius to about 450 degrees Celsius.

[0035] The processing chamber 100 includes a processing kit that circumscribing various chamber components to prevent unwanted reactions between these components and contaminants. The processing kit includes an upper shield 148. In some embodiments, the upper shield 148 can be made of a metal, such as aluminum. In some embodiments, the processing kit can be composed of quartz. In some embodiments, a mixing container 156 is coupled to the processing space 108 and is in fluid communication with the processing space 108. The mixing container 156 is also fluidly connected to the RPS 164. The mixing container 156 allows the plasma gas to mix with other gases provided by the gas delivery system 150. The flow rate of the other gases from the gas delivery system 150 can be controlled by a first flow valve 188.

[0036] The showerhead 158 is located above the processing volume 108 and below the ceiling 162 of the chamber body 104. The showerhead 158 includes a through hole 160 to allow gas to flow from the mixing container 156 into the processing volume 108. The RPS 164 is fluidly connected to the mixing container 156 to allow ionized gas to flow from the RPS 164 into the mixing container 156, through the showerhead 158, and into the processing volume 108. Plasma is generated in the RPS 164 by a plasma RF power supply 166 that provides RF energy to the RPS 164. The process gas used to form the plasma is supplied by the process gas source 170 and controlled by the second flow 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 processing the substrate 114.

[0037] The pump port 172 is configured to facilitate the removal of particles and gases from the interior space 102. The processing chamber 100 is coupled to and in fluid communication with a vacuum system 174, which includes a throttle valve (not shown) and a pump (not shown) for exhausting the processing chamber 100. 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 inside the processing 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 about 1900 liters per second to about 3000 liters per second. In some embodiments, the vacuum system 174 can be used to facilitate regulating the substrate temperature.

[0038] In some embodiments, the controller 178 is used for the operation of the processing chamber 100. The controller 178 can use direct control of the processing chamber 100, or alternatively, use indirect control of the processing chamber 100 by controlling a computer (or controller) associated with the processing chamber 100. In operation, the controller 178 can collect data and feedback from the processing chamber 100 to optimize the performance of the processing chamber 100. The controller 178 generally includes a central processing unit (CPU) 180, a memory 182, and a support circuit 184. The CPU 180 can be any form of general-purpose computer processor that can be used in an industrial environment. The support circuit 184 is generally coupled to the CPU 180 and may include caches, clock circuits, input / output subsystems, power supplies, etc. A software routine (as described below) can be stored in the memory 182, and when the CPU 180 executes the software routine, the software routine converts the CPU 180 into a special-purpose computer (controller 178). The software routine can also be stored and / or executed by a second controller (not shown) located remote from the processing chamber 100.

[0039] The memory 182 is in the form of a computer-readable storage medium containing instructions, which, when executed by the CPU 180, are used to facilitate the operation of semiconductor processes and equipment. The instructions in the memory 182 are in the form of a program product, such as a program product that performs the method of the present principles. The program code may conform to any of a number of different programming languages. In one example, the present disclosure may be implemented as a program product stored on a computer-readable storage medium for use with a computer system. The program(s) of the program product define the functions of aspects (including the methods described in this specification). Illustrative computer-readable storage media include, but are not limited to: non-writable storage media on which information can be permanently stored (e.g., a read-only memory device within a computer, such as 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); and writable storage media on which information can be stored (e.g., a floppy disk within a disk drive or hard drive or any type of solid-state random access semiconductor memory). When these computer-readable storage media carry computer-readable instructions that direct the functions of the methods described herein, these computer-readable storage media are aspects of the present principles.

[0040] Figure 2 A cross-sectional view of a plasma source 200 having an upper symmetrical electrode 202A and a lower symmetrical electrode 202B is depicted in accordance with some embodiments. During operation of the RPS 164, gas enters the gas port 210 and plasma-related products exit through the diffuser hole 208 into the mixing vessel 156. The diffuser hole 208 may have a diameter of about 0.1 inches to about 0.2 inches. The upper symmetrical electrode 202A and the lower symmetrical electrode 202B have corresponding upper symmetrical hollow cavities 204A and corresponding lower symmetrical hollow cavities 204B configured to produce a hollow cathode effect. The upper symmetrical electrode 202A and the lower symmetrical electrode 202B are separated by a gap 206. The gap 206 is an annular region and electrically separates the upper symmetrical electrode 202A and the lower symmetrical electrode 202B by a height 252 of about 0.2 inches to about 0.5 inches. The gap 206 has a width 254 defined by the distance at which the upper symmetrical electrode 202A and the lower symmetrical electrode 202B remain parallel to each other. The upper symmetrical hollow cavity 204A and the lower symmetrical hollow cavity 204B have a tapered shape 1302, such as Fig.13 isometric view of the . Fig.13 A hollow cathode effect chamber 1300 is depicted according to some embodiments.

[0041] exist Fig.13, the cone 1302 has a vertical axis 1304 at the center. At the first end 1310 is an opening that is fluidly connected to a gas supply (e.g., a processing gas source 170). The opening at the first end 1310 may have a diameter of about 0.1 inches to about 0.2 inches. At the second end 1312 is a larger flared opening that is fluidly connected to the gap 206 between the upper symmetric electrode 202A and the lower symmetric electrode 202B. In some embodiments, the cone 1302 may have a first cone portion 1314 that has a first angle 1306 of about 5 degrees to about 30 degrees. The inventors have found that a smaller angle (e.g., less than about 10 degrees) helps to increase the etching rate by promoting a denser plasma formation in the hollow cavity. In some embodiments, the first cone portion 1314 has a first angle 1306 of about 8 degrees. In some embodiments, the cone 1302 may have a second cone portion 1316 having a larger flared opening or rounding, with a second angle 1308 of about 10 degrees to about 60 degrees. The second cone portion 1316 smoothly blends 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 1302 may be about 1.5 inches to about 2 inches.

[0042] like Fig.12 As shown in the graph 1200 of FIG. 1 , the plasma RF power supply 166 generates a symmetrical drive waveform 1202 (e.g., a sinusoidal waveform is shown as a non-limiting example). During the cathodic period 1206, the hollow cathode mode caused by the upper symmetrical hollow cavity 204A forms the plasma 212. During the anodic period 1204, the hollow cathode mode caused by the lower symmetrical hollow cavity 204B forms the plasma 212. In a conventional system with a ground plate for the lower electrode, the anodic period 1204 instead produces a glow discharge mode due to the ground plate, which produces particles that are detrimental to semiconductor performance. Using the upper symmetrical electrode 202A and the lower symmetrical electrode 202B of the present principles, the particle performance is significantly improved. During testing, the inventors discovered that when upper symmetrical hollow cavity 204A and lower symmetrical hollow cavity 204B are configured to produce a hollow cathode effect, RPS 164 has superior particle performance compared to an RPS having flat planar electrodes that produce a glow discharge for both anode and cathode cycles of symmetrical drive waveform 1202 .

[0043] The inventors discovered during testing that when using an upper electrode as a hollow cavity and a lower electrode as a plate electrode that is grounded (i.e., an "asymmetric electrode"), two different plasma modes are generated when the plasma source is driven with a symmetrical waveform. During the anode cycle 1204, a thin plasma is formed just on top of the plate electrode that is grounded. During the cathode cycle 1206, a strong hollow cathode effect occurs in the center of the hollow cavity of the top electrode, forming a plasma at the center ("hollow cathode effect"). The inventors found that the hollow cathode mode improves etching performance. When the drive waveform is changed so that only a cathode cycle (half-sine waveform) exists, the inventors found that etching performance is improved, but also found a negative side effect of material accumulation in the gap separating the top and bottom electrodes of the plasma source.

[0044] When the electrodes become parallel flat electrodes with a gap between them, a glow discharge mode is generated for both the anode and cathode cycles, resulting in a decrease in etching performance and a considerable amount of particles. The inventors have found that the use of a symmetrical electrode with a hollow cavity configured to generate a hollow cathode effect mode for both the anode and cathode cycles significantly improves etching performance compared to a single conical hollow electrode. The improved etching rate is as follows Figure 3 300 of FIG. 300 shows the result of an increased plasma portion 310A of plasma 308 formed in the upper symmetrical hollow cavity 204A and an increased plasma portion 310B of plasma 308 formed in the lower symmetrical hollow cavity 204B. The increased plasma increases the etching rate by about 20% compared to a single hollow cavity design. An annular isolator 302 may surround the symmetrical hollow cavities to isolate the electrodes and provide a gap 206 between the symmetrical electrodes 202A, 202B. In some embodiments, the annular isolator 302 may be positioned above the lower symmetrical electrode or the upper symmetrical electrode ( Figure 3 3. An annular spacer 302 having a thickness 304 is depicted above the lower electrode. In some embodiments, the annular spacer 302 may extend and surround both the lower electrode and the upper electrode, such as Figure 3 304, as shown by the increased thickness 306. Compared to thickness 304, the greater thickness 306 provides a significantly reduced capacitance between the upper and lower electrodes due to the increased distance between the upper and lower electrodes.

[0045] Although the etching rate is increased compared to the single hollow cavity design, the inventors have found that a large percentage of the plasma 308 extends 314 into and fills the gap 206 between the upper symmetrical electrode 202A and the lower symmetrical electrode 202B, as shown in FIG. Figure 3 The inventors have discovered that by reducing the electric field strength across gap 206, more power supplied to the electrodes can be used in the hollow cavity region. Figure 4In some embodiments depicted in view 400 of FIG. 4 , a cover 402 formed of a dielectric material is positioned over the lower symmetric electrode 202B or the upper symmetric electrode 202A to reduce the electric field strength in the gap 206, thereby causing a significant increase in 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 to about three times (300%) compared to a symmetric hollow cavity electrode without a cover on one of the symmetric electrodes.

[0046] Figure 5 Depicts a cover 402 having a rectangular cross-section (also as Figure 4 500 of the embodiment shown in FIG. 402. The cover 402 is annular and is positioned within the gap 206 between the upper symmetrical electrode 202A and the lower symmetrical electrode 202B. The cover 402 and all covers described herein are defined as an annular dielectric material that fills the gap 206 with dielectric material from about 5% of the height 252 of the gap 206 to about 95% of the height 252 of the gap 206 (see FIG. 50). Figure 2 ). The cap discussed herein does not completely fill the gap 206 (from the bottom electrode surface to the top electrode surface) to provide a space 406 to allow accumulation 404 of process residues. When the electrodes are composed of nickel material, the nickel material often sputters during processing, and the re-sputtered nickel particles form accumulation 404 on the surface of the cap. Leaving a space 406 between the cap and one or more electrodes allows the particles to accumulate, thereby increasing the time between RPS maintenance intervals. In addition, the space 406, while increasing the maintenance interval, also prevents short circuits or arcing when metal residues (such as re-sputtered nickel) short circuit or metal residues are in close contact with two electrodes in the RPS.

[0047] The width 514 of the cover 402 may cover about 80% to about 100% of the width 254 of the gap 206. Figure 5 As can be seen in FIG. 5 , cut line AA 522 produces a rectangular cross section having an outer edge 512 with a first thickness 506 and an inner edge 510 with a second thickness 508 equal to the first thickness 506. In some embodiments, the first thickness 506 can be about 80% to 95% of the height 252 of the gap 206. During testing, the inventors found that igniting the plasma within the hollow cavity could be problematic if the inner edge 510 of the cover 402 was the same thickness as the outer edge 512 of the cover. The lower electric field strength near the hollow cavity produces weaker plasma ignition and is generally unable to ignite the plasma to a sustainable level.

[0048] exist Figure 6600, a cover 602 is depicted having an inner edge 610 with a reduced second thickness 608. The second thickness 608 of the inner edge 610 can be about 5% to about 50% of the first thickness 606 of the outer edge 612 and the top surface 616. In some embodiments, the second thickness 608 can be from about 1 mm to about 2 mm. The inventors have discovered that while it is desirable that the second thickness 608 be as thin as possible to promote easier plasma ignition, the cover 602 is composed of a ceramic material and the structural integrity of the cover 602 can dictate how thin the ceramic material can be for a given RPS. If the second thickness 608 is too thick, the plasma in the hollow cavity is enhanced but ignition of the plasma becomes very difficult or impossible. The width 614 of the cover 602 can be changed or remain unchanged compared to the width 514 of the cover 402.

[0049] The altered profile of the cover 602 is shown at cut line AA 622. The width 620 of the top surface 616 can extend from about 30% to about 80% of the width 614 of the cover 602 before the angled surface 618 begins. The inventors have discovered that the thinner inner edge 610 of the cover 602 provides enhanced plasma ignition performance while still providing increased plasma in a symmetrical hollow cavity (e.g., maintaining high etch rate performance). Figure 7 In view 700 of FIG. 6 , another profile along cut line AA 622 is depicted as having a modified inclined surface 718. Inclined surface 718 has a sharper initial angle and then slopes downward from first thickness 606 to second thickness 608. Modified inclined surface 718 creates a larger area for increasing electric field strength (compared to Figure 6 The thinner portion of the cover has a larger area and a higher electric field strength) to ignite the plasma while still providing a reduced electric field strength for generating plasma mostly in the upper symmetric electrode and the lower symmetric electrode. It will be appreciated by those skilled in the art that other inclined surfaces and shapes of the cover profile may provide sufficient plasma ignition while generating most of the plasma in the upper symmetric electrode and the lower symmetric electrode.

[0050] The inventors have discovered that the plasma within the symmetrical electrode can be further enhanced by adding an extension 802 to the cover 602, which extends the cover 602 further to the position shown in FIG. Figure 8 The mouth or second cone portion 1316 of at least the lower symmetrical hollow cavity of the lower symmetrical electrode shown in view 800 (see, for example, Fig.13 ). The extension 802 follows the contour of the surface 1320 of the second conical portion 1316. The extension 802 further enhances the plasma in the symmetrical electrode, but makes the ignition of the plasma more difficult. The inventors have found that if the capillary 902 surrounds the extension 802 (such as Fig. 9 900 of the view 900 of the symmetrical electrode) are equally spaced, the ignition of the plasma is significantly enhanced while maintaining a higher performance plasma inside the symmetrical hollow cavity of the symmetrical electrode. The capillary 902 exposes the top surface of the lower symmetrical electrode so that the increased electric field strength at the exposed position can more easily ignite the plasma. If the diameter 908 of the capillary 902 is less than 2 times the thickness of the plasma sheath, the plasma can be easily ignited due to the electrode surface exposed through the capillary 902, but the plasma will not be able to be maintained through the capillary 902 because the plasma sheath is too thick to allow the plasma to form in the capillary 902 (the plasma sheath needs to bend into the capillary, and this will require a hole with a diameter of twice the thickness of the sheath or more to maintain the plasma in the hole).

[0051] Under high pressure conditions, the thickness of the plasma sheath will be less than under low pressure conditions. The size of the diameter of the capillary 902 will depend on the operating conditions (e.g., pressure, etc.) of the particular RPS design. The distance 906 between the inner edge of the cover 602 with the extension 802 and the center point of the diameter 908 of the capillary 902 can be as small as possible while still allowing the plasma to be ignited in the symmetrical hollow cavity of the symmetrical electrode. If the distance 906 is too large, the plasma ignited near the capillary 902 will not be close enough to ignite the plasma in the hollow cavity of the electrode. Fig.10 The capillary holes 902 are depicted in bottom view 1000 as being equally spaced around the inner edge of the cover 602 having the extension 802. In some embodiments, the number of capillary holes 902 can be eight or more. The more capillary holes 902 there are, the easier it is to ignite the plasma. However, manufacturability may limit the number of capillary holes that can be made in a given ceramic material. A large number of holes may allow the wall thickness 910 between the capillary holes 902 to be thinned until a loss of integrity occurs or the ceramic material becomes too thin to maintain integrity under operating conditions. Fig.14 , a first bottom-up view 1400A depicts a first annular row 1402 of capillary holes and a second annular row 1404 of capillary holes radiating 1410 outward from a center point 1406 of a cover 1408. In some embodiments, the cover 1408 may have more than two annular rows of capillary holes. Fig.14In the second view 1400B, the capillary holes of the first annular row 1402 are offset from the capillary holes of the second annular row 1404 to allow the holes to be more densely distributed closer to the inner edge 1412 of the cover 1408. 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 multiple annular rows with a mixture of offset and radially aligned capillary holes. In some embodiments, each annular row may have capillary holes of different diameters. In some embodiments, a single annular row may have capillary holes of different diameters.

[0052] like Fig.11 The upper symmetric electrode 202A and the lower symmetric electrode 202B shown in view 1100 of can be formed of an aluminum material with electroless nickel plating (ENP). The ENP process forms a layer of nickel on the surface of the electrode to prevent chemical reactions during etching or other processes. The chemical reactions may include, but are not limited to, fluorine-based reactions (such as aluminum fluoride) produced by etching process gases (such as, but not limited to, nitrogen trifluoride (NF3) and the like). However, nickel coatings typically produce particles that may eventually land on the substrate and cause performance issues with substrate features. The inventors have discovered that by applying an additional yttrium oxide (Y2O3) coating 1104 on the ENP on the high electric field region of the symmetric electrode RPS, the yttrium oxide coating 1104 will increase the impedance of the gap 206 to allow more power to be supplied to the hollow cathode discharge while preventing nickel sputtering that may be deposited on top of the ceramic surface within the gap 206, thereby reducing the impedance of the gap 206. The yttrium oxide coating 1104 also helps prevent chemical reactions that occur during etching or other processes, such as, but not limited to, fluorine-based reactions produced by etching process gases such as, but not limited to, nitrogen trifluoride (NF3). In some embodiments, the thickness 1110 of the yttrium oxide coating 1104 is about 100 mils.

[0053] Because the yttrium oxide coating 1104 extends at least partially down into the mouth of the hollow cavity, the plasma performance is further enhanced, such as increasing the etch rate, etc., depending on how the RPS is used. If yttrium oxide-based particles are generated, they will not cause arcing and short circuits by accumulating in the gap area because yttrium oxide particles are not as conductive as nickel particles. In the case of Fig.11 In some embodiments shown, the yttrium oxide coating 1104 is applied to the surface 1320 of the second cone portion 1316 (see Fig.13), and is applied to at least a portion of the parallel surface 1106 of the gap 206 that will be exposed to the plasma during operation. In some embodiments, the yttria coating 1104 may extend to cover most or all of the parallel surface 1106 to facilitate the manufacture of the coated electrode. The inventors have found that the yttria coating 1104 may extend 1108 to the first conical portion surface 1322A of the upper symmetrical hollow cavity 204A (see Fig.13 ) and the first cone portion surface 1322B of the lower symmetrical hollow cavity 204B. By extending the yttria coating 1104 into the hollow cavity, the yttria coating 1104 will prevent nickel sputtering from occurring inside the hollow cavity and improve the particle performance of the RPS (i.e., reduce the number of particles generated), especially nickel-based particles.

[0054] In some embodiments, the cover, the cover with the extension, or the cover with the extension and the capillary hole can be used with the same Fig.11 In some embodiments, the yttrium oxide coating 1104 is used in combination with the yttrium oxide coating 1104 depicted in FIG. Fig.11 The illustrated unit cell assembly 1102 can be used in an RPS with or without the yttria coating 1104. The unit cell assembly 1102 incorporates the cover and the insulator into a single unitary component for ease of placement and assembly. The unit cell assembly 1102 is also cheaper to manufacture as a single component. Although the unit cell assembly 1102 is illustrated as having a separator portion extending only into the lower symmetric electrode 202B, as shown in FIG. Figure 3 As shown, in some embodiments, cell assembly 1102 may include separator portions extending into both upper symmetric electrode 202A and lower symmetric electrode 202B.

[0055] While the foregoing is directed to embodiments of the present principles, other and further embodiments of the present principles may be conceived without departing from the basic scope thereof.

Claims

1. An apparatus for processing a substrate, comprising: a processing chamber having a chamber body surrounding a processing space; a remote plasma source (RPS) having a plasma source having an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetrical with a hollow cavity, the hollow cavity being configured to induce a hollow cathode effect within the hollow cavity, wherein the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, wherein the annular dielectric cover is in direct contact with the lower electrode and forms a second gap between an uppermost surface of the annular dielectric cover and a lowermost surface of the upper electrode, wherein the annular dielectric cover fills about 50% to about 95% of a height of the first gap, and wherein the RPS is configured to provide radicals or ions into the processing space; as well as A radio frequency (RF) power supply is configured to provide symmetrical driving waveforms on 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.

2. The device of claim 1, wherein the annular dielectric cover is a ceramic material.

3. The apparatus of claim 1, wherein the annular dielectric cover has an outermost edge and an innermost edge, the outermost edge having a first thickness, and the innermost edge having a second thickness that is less than the first thickness. 4 . The device of claim 3 , wherein the second thickness is about 1 mm to about 2 mm, and the first thickness is less than about 95% of the height of the first gap.

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

6. The device of claim 1, wherein the inner diameter of the annular media cover is larger than the outer edge of the opening of the hollow cavity.

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

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

9. The apparatus of claim 8, wherein the capillary hole has a diameter less than twice the thickness of a sheath of plasma to be generated by the RPS.

10. The device of claim 1, wherein the upper electrode and the lower electrode are plated with chemical nickel.

11. The apparatus of claim 10, wherein a yttria coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode.

12. The apparatus of claim 10, wherein a yttria coating is applied to a plasma exposed surface having a first gap and adjacent openings of the hollow cavities of the upper and lower electrodes.

13. An apparatus for processing a substrate, comprising: a remote plasma source (RPS) having a plasma source having an upper electrode and a lower electrode, wherein the upper electrode and the lower electrode are symmetrical with a hollow cavity, the hollow cavity being configured to induce a hollow cathode effect within the hollow cavity, wherein the upper electrode and the lower electrode are electrically separated by a first gap, an annular dielectric cover is positioned within the first gap, wherein the annular dielectric cover is in direct contact with the lower electrode and forms a second gap between an uppermost surface of the annular dielectric cover and a lowermost surface of the upper electrode, wherein the annular dielectric cover fills about 50% to about 95% of a height of the first gap, and wherein the RPS is configured to provide free radicals or ions; and A radio frequency (RF) power supply is configured to provide symmetrical driving waveforms on 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.

14. The apparatus of claim 13, wherein the annular dielectric cover has an outermost edge and an innermost edge, the outermost edge having a first thickness, the innermost edge having a second thickness less than the first thickness, and wherein the second thickness is about 1 mm to about 2 mm and the first thickness is less than about 95% of the height of the first gap.

15. The device of claim 14, wherein the first thickness slopes downwardly to a third thickness equal to the second thickness before reaching the innermost edge.

16. The apparatus of claim 13, wherein the inner diameter of the annular dielectric cover is larger than the outer edge of the opening of the hollow cavity, or wherein the inner diameter of the annular dielectric cover is smaller than the outer edge of the opening of the hollow cavity, and wherein the innermost edge of the annular dielectric cover at least partially extends into the opening.

17. The apparatus of claim 16, wherein capillary holes are spaced about the innermost edge of the annular dielectric cover, and wherein a diameter of the capillary holes is less than twice the thickness of a sheath of a plasma to be generated by the RPS.

18. The apparatus of claim 13, wherein the upper electrode and the lower electrode are plated with electroless nickel, and wherein a yttria coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode on the electroless nickel.

19. An apparatus for providing a remote plasma source (RPS) for generating an etchant, comprising: 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 symmetrical; a first gap positioned between the upper electrode and the lower electrode and electrically separating the upper electrode from the lower electrode; as well as an annular dielectric cover directly contacting the lower electrode in the first gap and forming a second gap between an uppermost surface of the annular dielectric cover and a lowermost surface of the upper electrode, wherein the annular dielectric cover fills about 50% to about 95% of the height of the first gap, wherein the annular dielectric cover has an inner diameter smaller than an outer edge of an opening of the second hollow cavity, the inner diameter of the annular dielectric cover at least partially extending into the opening while directly contacting a surface of the second hollow cavity, and wherein capillary pores are spaced apart near an innermost edge of the annular dielectric cover and a diameter of the capillary pores is less than twice the thickness of a sheath of a plasma to be generated using the RPS.

20. The apparatus of claim 19, wherein the upper electrode and the lower electrode are plated with electroless nickel, and a yttria coating is applied to plasma exposed surfaces of the upper electrode and the lower electrode above the electroless nickel.

Images