Patent Application
20140315392
The present invention relates to components of semiconductor plasma processing chambers, and more specifically for a barrier coating for components of semiconductor plasma processing chambers.
In the field of semiconductor material processing, semiconductor plasma processing chambers including vacuum processing chambers are used, for example, for etching and deposition, such as plasma etching or plasma enhanced chemical vapor deposition (PECVD) of various materials on substrates. Some of these processes utilize corrosive and erosive process gases and plasma in such processing chambers. It is desirable to minimize chamber component wear, and particle and/or metal contamination of substrates processed in the chambers. Accordingly, it is desirable that plasma-exposed components of such apparatuses be resistant to corrosion when exposed to such gases and plasma.
Disclosed herein is a cold spray barrier coated component of a semiconductor plasma processing chamber. The cold spray barrier coated component of a semiconductor plasma processing chamber comprises a substrate having at least one metal surface wherein a portion of the metal surface is configured to form an electrical contact, and a cold spray barrier coating formed from a thermally and electrically conductive material on at least the metal surface configured to form the electrical contact. Further, the cold spray barrier coating may be on a portion of the metal surface exposed to plasma and/or process gas.
Also disclosed herein is a process for cold spray barrier coating at least one metal surface forming an electrical contact of a component of a semiconductor plasma processing chamber. The process for cold spray barrier coating the electrical contact of a component of a semiconductor plasma processing chamber comprises cold spraying an electrically conductive cold spray barrier on at least portion of at least one metal surface of a substrate, wherein the portion of the metal surface is configured to form an electrical contact.
Further disclosed herein is a semiconductor plasma processing apparatus. The semiconductor plasma processing apparatus, comprises a plasma processing chamber in which semiconductor substrates are processed. The apparatus further comprises a process gas source in fluid communication with the plasma processing chamber for supplying a process gas into the plasma processing chamber, and an RF energy source is adapted to energize the process gas into the plasma state in the plasma processing chamber. The semiconductor plasma processing apparatus comprises at least one cold spray barrier coated component.
Also disclosed herein is a method of plasma processing a semiconductor substrate in a semiconductor plasma processing apparatus comprising at least one cold spray barrier coated component. The method comprises supplying the process gas from the process gas source into the plasma processing chamber, applying RF energy to the process gas using the RF energy source to generate plasma in the plasma processing chamber, and plasma processing a semiconductor substrate in the plasma processing chamber.
Disclosed herein is a component of a semiconductor plasma processing chamber comprising an electrically conductive barrier coating, wherein the barrier coating is formed with a cold spray barrier coating technique and is corrosion resistant. The semiconductor plasma processing chamber preferably includes a vacuum chamber, and may be a plasma etching or deposition chamber (herein referred to as “plasma chamber”) of a semiconductor plasma processing apparatus. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present embodiments. It will be apparent, however, to one skilled in the art that the present embodiments may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail in order not to unnecessarily obscure the present embodiments.
Components described herein include a substrate having at least one metal surface, such as an aluminum or aluminum alloy substrate, and an electrically conductive cold spray barrier coating on a portion of the metal surface which is configured to form an electrical contact of the substrate. The portion of the metal surface which is configured to form an electrical contact of the substrate may be a surface of the component configured to mate with a surface of an adjacent component (i.e. mating surface). The electrically conductive cold spray barrier coating may additionally be formed on a plasma exposed and/or process gas exposed metal surface of the substrate. The component to be cold spray barrier coated is preferably an aluminum or aluminum alloy electrical contact within the plasma chamber, such as mating surfaces between a gas distribution plate 226 and an electrode 224 (see
During plasma processing, such as an etching processes, process gases can be halogen-containing species, e.g., CxFy, CxHyFz, HBr, NF3, HCl, SiCl4, Cl2, and BCl3 (wherein x≧1, y≧1, and z≧0), which are corrosive with respect to aluminum and aluminum alloy surfaces. Therefore, the cold spray barrier coating may be preferably applied to aluminum or aluminum alloy surfaces. Such application may be in the form of a replaceable dense aluminum cold spray barrier coating, or more preferably a corrosion resistant cold spray barrier coating formed from a material, such as tantalum, on aluminum or aluminum alloy surfaces. Tantalum may be preferred due to its resistance to halogen corrosion and its thermal and electrical properties.
Components which include the electrically conductive cold spray barrier coating can be used in apparatuses for performing various processes including plasma etching of semiconductor substrates and deposition of materials (e.g., ALD, PECVD and the like) used for manufacturing various substrates including, e.g., semiconductor wafers, flat panel display substrates, and the like. Depending on the type and construction of an apparatus, the component(s) having at least one metal surface wherein a portion of the metal surface is configured to form an electrical contact, which is to be cold spray coated, can be, e.g., chamber walls, chamber liners, baffles, gas distribution plates, gas distribution rings, substrate supports, edge rings, gas nozzles, fasteners, shrouds, confinement rings, gaskets, RF straps, electrically conductive connecting members, and the like. For example the components may include an aluminum or aluminum alloy surface wherein the surface is exposed to process gas and/or plasma wherein a portion of the aluminum or aluminum alloy surface is configured to form a contact with another component such that electrical current (either RF or DC) may pass through both components during plasma processing of a semiconductor wafer. The cold spray barrier coating may be applied to the exposed aluminum or aluminum alloy surface of the component and the electrical contact portion of said component, such that the surface may exhibit a barrier coating (e.g. an aluminum cold spray barrier coating), or corrosion resistant barrier coating (e.g. a tantalum cold spray barrier coating) while maintaining electrical and thermal conductivity. The components can include one or more exterior and/or interior surfaces coated with the electrically conductive cold spray barrier coating which is preferably corrosion resistant. In some embodiments, the entire exterior surface of the component may include the cold spray barrier coating.
A cold spray coated component 100 according to an exemplary embodiment is shown in
The cold spray barrier coating 120 is preferably formed by cold spraying a metal, ceramic, or a metal ceramic compound onto the at least one metal surface 112 forming an electrical contact of the substrate 110. Cold spraying is a kinetic spray process utilizing supersonic jets of compressed gas to accelerate near-room temperature powder particles (here, preferably of high purity aluminum, or alternatively tantalum) at high velocities, wherein the particles traveling at speeds between about 450 to 1,500 msec impact with the substrate (here, the metal component or other product being cold spray barrier coated) to create a coating. In one embodiment, the particles plastically deform and consolidate on the substrate upon impact. Cold spray may also be referred to as gas dynamic spray, supersonic spray, and/or kinetic spray. The basis of the cold spray process is the gas-dynamic acceleration of particulates (from high purity metal powders) to supersonic velocities (450-1500 m/sec), and hence high kinetic energies, so that solid-state plastic deformation and fusion occur on impact to produce dense coatings, with refined microstructure, without the feedstock material being significantly heated. For example, pure aluminum which has been wrought (fully worked) may have a Brinell Hardness Scale value between about 40 and 45, whereas cold sprayed pure aluminum may have a Brinell Hardness scale value between about 55 and 60. In one embodiment, this may be achieved using convergent-divergent de Laval nozzles, high pressures (up to 500 psi or 3.5 MPa) and flow rates (up to 90 m3/hr) of compressed gases such as helium, argon, or nitrogen. In another embodiment, the gases may be pre-heated to (below the melting point of many metals, preferably below 120° C.) increase the velocity of the particles of the coating material. In one embodiment, the particles of the metallic bonding material (here, the high purity aluminum) may have a particle diameter ranging from about 1 to about 50 microns, and a particle density ranging from about 2.5 g/cm3 to about 20 g/cm3.
As the gas with which the metal powder forms a gas-powder mixture there is generally used an inert gas. Inert gas according to the embodiments herein includes, but is not limited to argon, helium, or relatively non-reactive nitrogen or mixtures of two or more thereof. In particular cases, air may also be used. If safety regulations are met, the use of mixtures of hydrogen with other gases can be considered and can be used advantageously due to hydrogen's extremely high sonic velocity. In fact hydrogen's sonic velocity is 30% greater than that of helium which in turn is approximately 3 times that of nitrogen. Air's sonic velocity is 344 m/s at 20 C and 1 atmosphere (atm), while hydrogen with a lower molecular weight (about 2.016 as compared to air's molecular weight of 28.96) has a sonic velocity of 1308 m/s. For example, a gas mixture of helium and 4% hydrogen may be utilized.
The cold spray barrier coating forming the electrically conductive coating is preferably formed from a metallic material, wherein the metallic material is preferably corrosion resistant to halogen containing gas species. The coating can be formed niobium, tantalum, tungsten, tungsten carbide, molybdenum, titanium, zirconium, nickel, cobalt, iron, chromium, aluminum, silver, copper, stainless steel, WC-Co, or mixtures thereof. Preferably, the cold spray barrier coating is formed from aluminum and is formed to coat an aluminum surface which functions as an electrical contact in the plasma chamber. During processing the previously applied aluminum cold spray barrier coating formed on the aluminum surface which functions as an electrical contact may be eroded, and in such an instance, a new aluminum cold spray barrier coating may be applied on the electrical contact such that the life of the electrical contact in the plasma chamber may be extended.
In one embodiment, the cold spray deposition may be performed in an inert chamber atmosphere, such as a vacuum chamber comprising argon, in order to prevent the oxidation of the substrate, for example an aluminum substrate, that is to be sprayed. On the other hand, in another embodiment, the cold spray deposition may be performed in air (e.g., in the room atmosphere), thereby allowing the spraying process to occur in a continuous, in-line fashion (i.e., without the substrate leaving the manufacturing line). An in-line spraying process may reduce the total amount of time and cost associated with the manufacture of the high purity spray coated substrates according to the teachings of one embodiment of the present disclosure.
The cold spray barrier coating forming the electrically conductive cold spray barrier coating 120 can have a thickness of about 1 micrometer to about 10,000 micrometers, such as about 2 micrometers to about 15 micrometers. Preferably, the thickness of the cold spray barrier coating is substantially uniform over the surface 112 of the substrate 110. In general, the cold spray barrier coating has a purity of at least 99%, such as 99.5% or 99.7%, 99.9%, advantageously has a purity of at least 99.95%, based on metallic impurities, especially of at least 99.995% or of at least 99.999%, in particular preferably of at least 99.9995%.
The cold spray barrier coating is preferably very dense with less than about 5% by volume porosity. In more preferable embodiments, the cold spray barrier coating has less than about 2% by volume porosity, or less than about 1% by volume porosity, such as a porosity of less than about 0.5%, 0.1%, 0.01%, 0.001%, and 0.0001% i.e., has a density that approaches the theoretical density of the coating material. The cold spray barrier coating is preferably also free of defects. A low porosity level can minimize contact of aggressive plasma etch (e.g., plasma formed from fluorocarbon, fluorohydrocarbon, bromine, and chlorine containing etch gases) atmospheres with the underlying substrate. Accordingly, the cold spray barrier coating protects against physical and/or chemical attack of the substrate by such aggressive atmospheres.
In general if an alloy is used instead of a pure metal for the cold spray barrier coating, then preferably the alloy as a whole, has high purity, so that a corresponding highly pure coating can be produced. In one of the embodiments disclosed herein the total content of non-metallic impurities in powders, such as oxygen, carbon, nitrogen or hydrogen, should advantageously be less than 1,000 ppm, preferably less than 500 ppm, and more preferably less than 150 ppm. In one of the embodiments disclosed herein, the oxygen content is 50 ppm or less, the nitrogen content is 25 ppm or less and the carbon content is 25 ppm or less. The content of metallic impurities is advantageously 500 ppm or less, preferably 100 ppm or less and most preferably 50 ppm or less, in particular 10 ppm or less. The oxygen content of the cold spray barrier coating is largely dependent on the oxygen content of the original powder used to perform the cold spraying as opposed to the cold spraying process.
The cold spray barrier coating forming the electrically conductive and preferably corrosion resistant coating 120 preferably has good adhesion strength to the surfaces 112 of the substrate 110 (i.e. fails cohesively). The cold spray barrier coating can be formed directly on the substrate 110 without having previously roughened the substrate surface 112. In an alternate embodiment the substrate surface 112 may be roughened before the cold spray barrier coating is applied. In a preferred embodiment, the cold spray barrier coating provides suitable adherence without prior roughening of the substrate surface 112, which obviates additional process steps. Preferably, the cold spray barrier coating has a sufficiently-high adhesive bond strength to the surface(s) 112 of a substrate 110 on which the coating is formed such that when a tensile bond strength test is performed on the component 100, the cold spray barrier coating fails cohesively (i.e., in the substrate bulk of the component) and not adhesively (i.e., at the substrate/coating interface).
In order to ensure good adhesion of the cold spray barrier coating to the substrate 110, the substrate surface 112 should be thoroughly cleaned from oxide scale and/or grease, prior to cold spraying. This cleaning can be carried out by agitating the substrate 110 in a solution of dilute hydrochloric acid, or sulfuric acid, or in a degreasing solvent.
Embodiments of the cold spray coated component may be used in plasma etch chambers or deposition chambers of semiconductor plasma processing apparatuses, such as dielectric etch chambers, capacitively coupled plasma etching chambers, inductively coupled plasma etching chambers, PECVD (plasma enhanced chemical vapor deposition) chambers, and ALD (atomic layer deposition) chambers for example. In these chambers, substrate surfaces can be exposed to plasma and/or process gases. In certain etching processes, these process gases can be halogen-containing species, e.g., CxFy, CxHyFz, HBr, NF3, HCl, SiCl4, Cl2, and BCl3, which are corrosive with respect to certain materials, such as aluminum and aluminum alloy surfaces. The cold spray barrier coating, however, can be used to coat the plasma-exposed and/or process gas exposed aluminum or aluminum alloy surfaces to provide corrosion resistance from the plasma and process gases. The cold spray barrier coating may be used to provide, for example, a dense aluminum coating, wherein the coating may be replaced periodically after being eroded and/or corroded to a predetermined point. Alternatively, the cold spray barrier coating may be used to provide a dense tantalum coating. Tantalum is preferred due to its resistance to corrosive gas attacks at high temperature and pressure as well as for desired electrical and thermal conductivity properties. Preferably the plasma-exposed and/or process gas exposed aluminum or aluminum alloy surfaces in the plasma processing apparatus include the cold spray barrier coating wherein a portion of the coated surfaces can form electrical and thermal contact surfaces wherein electrical current and thermal energy may be conducted therethrough. The cold spray barrier coating may provide corrosion resistance to the exposed surfaces while not inhibiting electrical conduction or interfering with an RF return path provided by the component in a semiconductor plasma processing apparatus.
Although the cold spray barrier coating is applicable to any type of component having a metal surface forming an electrical contact, for ease of illustration, the coating will be described in more detail with reference to the apparatus described in commonly-assigned U.S. Published Application No. 2009/0200269 which is incorporated herein by reference in its entirety.
The upper electrode assembly 225 preferably includes an upper showerhead electrode 224 and a gas distribution plate 226. The upper electrode assembly 225 may also optionally include an outer electrode 224a surrounding the upper showerhead electrode 224 as well as an optional gas distribution ring 226a surrounding the gas distribution plate 226. The upper showerhead electrode 224 and gas distribution plate 226 include gas passages for distributing process gas into the gap 232 defined between the upper showerhead electrode 224 and the lower electrode assembly 215. The upper electrode assembly 225 may further optionally include a gas distribution system such as one or more baffles (not shown) including gas passages for distributing process gas into the gap 232 defined between the upper showerhead electrode 224 and the lower electrode assembly 215. An exemplary embodiment of an upper electrode assembly which includes baffles can be found in commonly-assigned U.S. Pat. No. 8,313,665, which is hereby incorporated by reference in its entirety. The upper electrode assembly 225 can include additional components such as RF gasket 320, a heating element 121, gas nozzle 122, and other parts. The chamber housing 202 has a gate (not shown) through which a substrate 214, is unloaded/loaded into the chamber 200. For example, the substrate 214 can enter the chamber through a load lock as described in commonly-assigned U.S. Pat. No. 6,899,109, which is hereby incorporated by reference in its entirety.
The upper showerhead electrode 224 is preferably formed from a semiconductor compatible material such as single crystal silicon or polysilicon. The gas distribution plate is preferably formed from aluminum or an aluminum alloy. Preferably, the gas distribution plate 226 and showerhead electrode 224 are configured such that they may conduct heat and direct RF current therethrough. Aluminum or aluminum alloy surfaces on the gas distribution plate 226 which interface with the silicon upper showerhead electrode 224 form electrical contacts therebetween. The portions of the aluminum or aluminum alloy surfaces of the gas distribution plate 226 are preferably coated with the cold spray barrier coating to provide a metal coated component exhibiting good electrical and thermal conductivity. In an embodiment, an electrically conductive member, such as RF gasket 320 is in direct contact with the gas distribution plate 226 and showerhead electrode 224. The RF gasket 320 is mounted near the peripheral edge of the gas distribution plate 226 and showerhead electrode 224 to improve RF conduction. Additionally, the RF gasket 320 improves DC conduction between the gas distribution plate 226 and showerhead electrode 224, preventing arcing between these two components. Preferably, the RF gasket 320 is flexible, such that it can accommodate the contraction and expansion due to thermal cycling of the upper electrode assembly 225. The RF gasket 320 is preferably a spiral metallic gasket, and is preferably made of stainless steel, aluminum, an aluminum alloy, or the like. The RF gasket 320 is preferably cold sprayed with the cold spray barrier coating such as to farm a corrosion resistant and electrically conductive cold spray barrier coated component which may conduct heat as well.
In some exemplary embodiments, the upper electrode assembly 225 is adjustable in up and down directions (arrows A and A′ in
The RF return strap 248 provides a conductive RF return path between the upper electrode assembly 225 and the upper chamber wall 204 to allow the electrode assembly 225 to move vertically within the chamber 200. The strap includes two planar ends connected by a curved section. The curved section accommodates movement of the upper electrode assembly 225 relative to the upper chamber wall 204. Depending on factors such as the chamber size, a plurality (2, 4, 6, 8, 10 or more) RF return straps 248 can be arranged at circumferentially spaced positions around the upper electrode assembly 225. Additionally, a plurality (2, 4, 6, 8, 10 or more) RF return straps 246 can be arranged at circumferentially spaced positions around the lower electrode assembly 215
For brevity, only one gas line 236 connected to gas source 234 is shown in
In other exemplary embodiments, the lower electrode assembly 215 may move up and down (arrows B and B′ in
If desired, the movable lower electrode assembly 215 can be grounded to a wall of the chamber by at least one lower RF strap 246 which electrically couples an outer edge ring (ground ring) 222 to an electrically conductive part, such as a chamber wall liner 252 and provides a short RF return path for plasma, while allowing the lower electrode assembly 215 to move vertically within the chamber 200 such as during multistep plasma processing wherein the gap is set to different heights.
In the embodiment shown in
For example, as illustrated in
Referring back to
The bottom of the upper chamber wall 204 is coupled to a vacuum pump unit 244 for exhausting gas from the chamber 200. Preferably, the confinement ring assembly 206 substantially terminates the electric fields formed within the gap 232 and prevents the electric fields from penetrating an outer chamber volume 268. The confinement ring assembly 206 can be grounded to a wall of the chamber by at least one flexible RF strap 250 which electrically couples the confinement ring assembly 206 to an electrically conductive part such as upper chamber wall 204.
Process gas injected into the gap 232 is energized to produce plasma to process the substrate 214, passes through the confinement ring assembly 206, and into outer chamber volume 268 until exhausted by the vacuum pump unit 244. Since plasma chamber parts in the outer chamber volume 268 can be exposed to plasma and reactive process gas (radicals, active species) during operation, aluminum or aluminum alloys forming a surface of said chamber part may preferably include the electrically conductive cold spray barrier coating that can withstand the plasma and reactive process gas. Preferably the cold spray barrier coating is formed from a corrosion resistant metal, such as tantalum. Alternatively the cold spray barrier coating may be formed from dense, highly pure aluminum.
In an embodiment the RF power supply 240 supplies RF power to the lower electrode assembly 215 during operation, the RF power supply 240 delivers RF energy via shaft 260 to the lower electrode 210. The process gas in the gap 232 is electrically excited to produce plasma by the RF power delivered to the lower electrode 210.
Plasma chamber substrates, which have at least one metal surface wherein a portion of the metal surface is configured to form an electrical contact, such as a portion of an aluminum or aluminum alloy surface(s) forming an electrical contact surface for gas distribution plate 226, gas distribution ring 226a, one or more optional baffles, the lower electrode assembly 215, edge rings, the annular shroud 401, and the chamber liner 252, upper chamber wall 204, chamber housing 202, RF gasket 320, electrically conductive connecting members 270, and fasteners may be cold spray barrier coated components. Any other substrate in the semiconductor plasma processing apparatus having a metal surface such as an aluminum or aluminum alloy surface, wherein a portion of the metal surface is configured to form an electrical contact may also include the cold spray barrier coating. Preferably, the cold spray barrier coating is applied to bare (nonanodized) aluminum surfaces of the aluminum components. The cold spray barrier coating can be coated on some or all of the plasma exposed and/or process gas exposed surfaces of the components. In an embodiment, the cold spray barrier coated aluminum components may have an outer oxide coating formed thereon.
While the invention has been described in detail with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made, and equivalents employed, without departing from the scope of the appended claims.
