Low pressure arc plasma immersion coating vapor deposition and ion treatment

A coating system includes a vacuum chamber and a coating assembly. The coating assembly includes a vapor source, a substrate holder, a remote anode electrically coupled to the cathode target, and a cathode chamber assembly. The cathode chamber assembly includes a cathode target, an optional primary anode and a shield which isolates the cathode target from the vacuum chamber. The shield defines an opening for transmitting an electron emission current of a remote arc discharge from the cathode target to the remote anode that streams along the target face long dimension. A primary power supply is connected between the cathode target and the primary anode while a secondary power supply is connected between the cathode target and the remote anode. Characteristically, a linear remote anode dimension and a vapor source short dimension are parallel to a dimension in which an arc spot is steered along the cathode target.

FIELD OF THE INVENTION

The present invention relates to plasma assisted deposition systems and related methods.

BACKGROUND OF THE INVENTION

Physical vapor deposition (PVD) and low pressure Chemical vapor deposition (CVD) sources are used for deposition of coatings and surface treatment. Conventional metal vapor sources such as electron beam physical vapor deposition (EBPVD) and magnetron sputtering (MS) metal vapor sources can provide high deposition rates. However, the low energy of the metal vapor atoms and the low ionization rate of these processes result in coatings with low density, poor adhesion, poor structure and morphology. It is well established that assistance of the coating deposition process with bombardment by energetic particles dramatically improves coatings by densifying the depositing materials, reducing the grain size and improving coating adhesion. In these processes, the surface layer is affected by a high rate of bombardment by energetic ions which modifies the mobility of depositing metal vapor atoms and, in many cases, creates metastable structures with unique functional properties. Moreover, ion bombardment of the coating surface influences gas adsorption behavior by increasing the sticking coefficient of gases such as nitrogen and changing the nature of adsorption sites from lower energy physic-sorption sites to higher energy chemi-sorption sites. This approach is especially productive in the deposition of nanostructured composite coatings with ultra-fine or glass-like amorphous structures.

There are two different approaches to provide ion bombardment assistance during PVD or CVD processes. Ion beam assisted deposition (IBAD) is a method which holds great promise for forming dense ceramic coatings on polymers and other temperature sensitive materials. The IBAD process is typically carried out under vacuum (˜1×10−5Torr) in which a ceramic is thermally evaporated onto a substrate and simultaneously bombarded with energetic ions. The ion beam causes the deposited atoms to mix with the substrate, creating a graded layer, which can improve coating adhesion and reduce film stress. The impinging ions also produce a “shot-peening effect” which compacts and densifies the layer thereby reducing or eliminating columnar growth.

For example, during the IBAD processing of diamond-like carbon (DLC) films, carbon is evaporated by an electron beam source or sputtered by a magnetron source. Ion bombardment is provided by an independent broad-aperture ion beam source such as an argon ion beam. Such argon ion beams do not change the chemistry of the growing films and only influences its structure, morphology, binding energy and atom-to-atom bonding by lattice network modification. Addition of an appropriate gaseous precursor to the ion beam results in doping of the growing DLC films thereby providing a chemical vapor assistance during the IBAD process. An example of such silicon doping of DLC films are deposited from an Ar+SiH4ion beam. Fluoride can be added to the films via an Ar and fluorohydrocarbon ion beam, nitrogen can be added by using an Ar and N2ion beam, and boron can be added by using Ar+BH4ion beam. IBAD is a flexible technological process which allows control of coating properties in a broadened area by variation of the processing parameters: the ion beam composition, ion energy, ion current and the ion-to-atom arrival ratio.

Although the IBAD process works reasonably well, it has limitations due to its line-in-sight nature which is detrimental to achieving uniform coating distribution over complex shape components when the conformity of the coating deposition process is important. In addition, the IBAD process has limited scale up capability. The plasma immersion ion deposition (PIID) process overcomes some of these limitations by providing a low pressure plasma environment which effectively envelops the substrates to be coated within the uniform plasma cloud. This results in a highly uniform rate of ion bombardment over both 3-D complex shape substrates and large loads. The PVD or CVD process is used to generate vapor species for treatment of the substrate surface. In contrast to IBAD, the PIID is a non-line-of-sight process capable of treating complex surfaces without manipulation. PIID utilizes plasma generated from a gas discharge that fills in the entire processing chamber thereby allowing complex compositions and architectures to be coated. Examples of plasma immersion ion treatment include ionitriding, carbonitriding, ion implantation and other gaseous ion treatment processes that may be performed by immersing a substrate to be coated in a nitrogen containing plasma under negative bias. In addition, the electron current extracted from the plasma when substrates are positively biased can be used for pre-heating and heat treatment processes. Clearly, the non-line-of-sight processing feature presents numerous advantages over the line-of-sight processing, particularly for the efficient processing of a large quantity of 3-D objects. The ionized gaseous environment used during the PIID processes can be generated by applying different types of plasma discharges, such as glow discharge, RF discharge, micro-wave (MW) discharge and low pressure arc discharge. Low pressure arc discharge is particularly advantageous in that it provides a dense, uniform highly ionized plasma over large processing volumes at low cost. In the arc discharge plasma assisted coating deposition or ion treatment processes, substrates are positioned between the arc cathode and the remote arc anode within the arc discharge plasma area. Thermionic filament cathodes, hollow cathodes, vacuum arc evaporating cold cathodes, and combinations thereof can be used as electron emitters for generating a gaseous low pressure arc plasma discharge environment. Alternatively, the conductive evaporative material itself can be used as a cathode or an anode of an ionizing arc discharge. This latter feature is provided in the vacuum cathodic arc deposition processes or in various arc plasma enhanced electron beam and thermal evaporation processes.

Deposition of a reacted coating like CrN may be accomplished by various physical vapor deposition techniques such as cathodic arc deposition, filtered arc deposition, electron beam evaporation and sputter deposition techniques. Electron beam physical vapor deposition (EBPVD) technology, both conventional and ionized, has been used in many applications, but is generally not considered a viable manufacturing technology in many fields because of batch-processing issues, difficulties of scaling up to achieve uniform coating distribution across large substrates and because of the difficulty of multi-elemental coating composition control due to thermodynamically driven distillation of the elements with different vapor pressures. In contrast, magnetron sputtering (MS) based PVD is used for a wide variety of applications due to the high uniformity of magnetron coatings at acceptable deposition rates, precise control of multi-elemental coating composition and the ability of the MS process to be easily integrated in fully automated industrial batch coating systems. Cathodic and anodic arc enhanced electron beam physical vapor deposition (EBPVD) processes dubbed hot evaporated cathode (HEC) and hot evaporated anode (HEA) respectively have demonstrated increased ionization rate, but suffer from arc spots instabilities and non-uniform distribution of the ionization rate across the EBPVD metal vapor flow. In these processes, the arc discharge is coupled with evaporation process making it difficult to provide independent control of ionization and evaporation rates in HEA and HEC processes. Therefore, it is extremely difficult to integrate PA-EBPVD processes in fully automated industrial batch coating systems.

Sputter techniques are well known in the art as being capable of cost effectively depositing thick reacted coatings although films beyond about one micron tend to develop haziness due to crystallization. The crystallization phenomenon or columnar film growth is associated with the inherent low energy of depositing atoms in sputter deposition techniques thereby creating an opportunity for energetically favored crystal structures. These crystal structures may have undesired anisotropic properties specific for wear and cosmetic applications. Various approaches have been developed over the last decade to enhance the ionization rate in a magnetron sputtering process. The main goal of these approaches is to increase the electron density along the pass of the magnetron sputtering atoms flow thereby increasing ionization of metal atoms by increasing the frequency of electron-atom collisions. The high power impulse magnetron sputtering (HIPIMS) process uses high power pulses applied to the magnetron target concurrently with DC power to increase electron emission and consequently increase the ionization rate of metal sputtering flow. This process demonstrates improved coating properties in the deposition of nitride wear resistant coatings for cutting tools. In the HIPIMS process, improved ionization is achieved only during short pulse times, while during pauses, the ionization rate is low as in conventional DC-MS processes. Since the pulse parameters are coupled with magnetron sputtering process parameters in the HIPIMS process, the sputtering rate, which is found to be almost three times lower than that of the conventional DC-MS process, can be adversely affected. Moreover, the high voltage pulses in the HIPIMS process may induce arcing on magnetron targets resulting in contamination of the growing films.

In order to generate a highly ionized discharge in a vicinity of magnetron targets, an inductively coupled plasma (ICP) source can be added in the region between the cathode and the substrate. A non-resonant induction coil is then placed parallel to the cathode in essentially a conventional DC-MS apparatus, immersed or adjacent to the plasma. The inductive coil is generally driven at 13.56 MHz using a 50Ω rf power supply through a capacitive matching network. The rf power is often coupled to the plasma across a dielectric window or wall. Inductively coupled discharges are commonly operated in the pressure range of 1-50 mTorr and applied power 200-1000 W resulting in an electron density in the range of 1016-1018m−3which is generally found to increase linearly with increasing applied power. In a magnetron sputtering discharge, metal atoms are sputtered from the cathode target using dc or rf power. The metal atoms transit the dense plasma, created by the rf coil, where they are ionized. A water cooled inductive coil placed between the magnetron target and substrates to be coated adversely affects the metal sputtering flow. The MS setup is therefore much more complicated, expensive, and difficult to integrate into existing batch coating and in-line coating system. These disadvantages are also true for the microwave assisted magnetron sputtering (MW-MS) process. In the MW-MS process, the vacuum processing chamber layout must be re-designed to allow the metal sputtering flow crossing an ionization zone. However, the RF, MW and ICP approaches to ionizing the PVD process experience difficulties with plasma distribution uniformity over a large processing area, which is an obstacle for integration into large area coating deposition systems.

Another prior art technique for producing energetic ions is plasma enhanced magnetron sputtering (PEMS) which has a thermionic hot filament cathode (HF-MS) or hollow cathode (HC-MS) as a source of ionized electrons to increase the ionization rate in the DC-MS process. In the HF-MS process, a distant thermionic filament cathode is used as a source of ionizing electrons making this process similar to the HC-MS process. However, this process typically exhibits plasma non-uniformity and is difficult to integrate in industrial large area coating systems. Moreover, both hot filaments and hollow arc cathodes are sensitive and degrade quickly in the reactive plasma atmosphere. The disadvantages of these plasma generating processes are overcome by utilizing a cold evaporative vacuum arc cathode as a source of electrons for ionization and activation of a vapor deposition processing environment.

The cosmetic appearance of the conventional cathodic arc deposited films includes particulates of un-reacted target material called macros that renders the deposited film with defects undesired in applications requiring specific wear, corrosion and cosmetic properties. However, arc deposited films do not have a crystalline character unlike sputtered films because the arc evaporation process produces highly ionized plasma with a high energy of depositing atoms believed to effectively randomize crystal structures in the developing film.

Accordingly, there is a need for additional techniques of producing energetic particles in coating processes to produce improved film properties.

SUMMARY OF THE INVENTION

The present invention solves one or more problems of the prior art by providing in at least one embodiment a system for coating a substrate. The coating system includes a vacuum chamber and a coating assembly positioned within the vacuum chamber. The coating assembly includes a vapor source that provides material to be coated onto a substrate, a substrate holder to hold substrates to be coated such that the substrates are positioned in front of the vapor source, a cathode chamber assembly, and a remote anode. The cathode chamber assembly includes a cathode target, an optional primary anode and a shield which isolates the cathode from the vacuum chamber. The shield defines openings for transmitting an electron emission current from the cathode into the vacuum chamber. The vapor source is positioned between the cathode chamber assembly and the remote anode while the remote anode is electrically coupled to the cathode. The coating system also includes a primary power supply connected between the cathode target and the primary anode and a secondary power supply connected between the cathode target and the remote anode. Characteristically, the remote anode has a linear remote anode dimension, the vapor source has a linear vapor source dimension, the cathode target has a linear cathode target dimension, and the substrate holder has a linear holder dimension such that the linear remote anode dimension, the linear vapor source dimension, the linear cathode target dimension, and the linear holder dimension are parallel to each other, with the linear remote anode dimension being equal to or greater than the linear cathode target dimension and the linear vapor source dimension such that a confined plasma streams from the cathode target to the remote anode.

In another embodiment, a method of coating a substrate in the coating system set forth above is provided. The method includes a step of generating a primary arc in the electron emitting cathode source between the cathode target and the primary anode. A confined remote arc in a coating area is generated between the cathode chamber assembly and the remote anode such that metal vapor flow from the vapor source is generated toward at least one substrate to be coated. In still another embodiment, a coating system having a directed arc spot is provided. The coating system includes a vacuum chamber and a coating assembly positioned within the vacuum chamber. The coating assembly includes at least one sputtering source, a substrate holder to hold substrates to be coated such that the substrates are positioned in front of the sputtering source, and a plasma duct defining a first exit opening and a second exit opening. The coating assembly includes a cathode target for generating a metal plasma positioned in the plasma duct, a remote anode electrically coupled to the cathode target, a primary power supply for powering the cathode, and a secondary power supply connected between the cathode target and the remote anode. The sputtering source is positioned between the cathode target and the remote anode. A duct coil surrounds the plasma duct such that activation of the duct coil creating a transporting magnetic field within the plasma duct that is substantially parallel to an evaporating surface of the cathode target to direct the plasma away from the plasma duct extending to the sputtering source and/or substrates on the substrate holder during film deposition. A duct coil power supply activates the duct coil while a first trim electromagnet and a second trim electromagnet are positioned adjacent to opposite non-evaporating opposite sides of the cathode target where they generate a magnetic field above a surface of the cathode target.

In still another embodiment, a coating system having a remote anode is provided. The coating system includes a vacuum chamber and a coating assembly. The coating assembly includes a vapor source having a target face with a vapor source long dimension and a vapor face short dimension and a substrate holder to hold substrates to be coated such that the substrates are positioned in front of the vapor source. The substrate holder has a linear holder dimension. The coating assembly further includes a remote anode electrically coupled to the cathode target. The remote anode has a linear remote anode dimension. The coating assembly further includes a cathode chamber assembly having a cathode target, an optional primary anode and a shield which isolates the cathode target from the vacuum chamber. The cathode target having a linear cathode target long dimension and a linear cathode target short dimension. The shield defines at least one opening for transmitting an electron emission current of a remote arc discharge from the cathode target to the remote anode that streams along the target face long dimension. A primary power supply is connected between the cathode target and the primary anode while a secondary power supply is connected between the cathode target and the remote anode. Characteristically, the linear remote anode dimension and the vapor source short dimension are parallel to a dimension in which an arc spot is steered along the cathode target.

In still another embodiment, a method of coating a substrate in the coating systems herein is provided. The method includes steps of the generating a primary arc in the electron emitting cathode source between the cathode target and the primary anode; generating a confined remote arc in a coating area between the cathode chamber assembly and the remote anode; and generating metal vapor flow from the vapor source toward at least one substrate to be coated.

DESCRIPTION OF THE INVENTION

With reference toFIGS. 1A, 1B, 1C and 1D, a coating system that uses a remote arc discharge plasma is provided.FIG. 1Ais an idealized side view of the coating system.FIG. 1Bis a front view perpendicular to the view ofFIG. 1A.FIG. 1Cis a schematic of the coating system including electrical wiring. The system of this embodiment is particularly useful for arc plasma enhancement of large area magnetron sputtering coating deposition processes. Coating system10includes vacuum chamber12with a coating assembly positioned therein. The coating assembly includes vapor source16, cathode chamber assembly18positioned in vacuum chamber12, and substrate holder20to hold substrates22to be coated.FIGS. 1Aand1B depict a variation in which vapor source16is a magnetron sputtering source so that the coating process of system10is a remote arc assisted magnetron sputtering (RAAMS) process. Such magnetron sputtering sources include a target Ts, a power supply Ps, and an anode As. It should be appreciated that other types of vapor sources may be utilized for vapor source16. Examples of such vapor sources include, but are not limited to, thermal evaporators, electron beam evaporators, cathodic arc evaporators, and the like. Substrates22are positioned in front of the vapor source16during coating and move along direction d1during deposition of the coating. In a refinement, substrates may be continuously introduced from a load-lock chamber at the right of vacuum chamber12and received by an output chamber at the left of vacuum chamber12inFIG. 1A. Cathode chamber assembly18includes a cathode enclosure24with openings26defined therein, electron emitting cathode28, an optional separate primary anode34and shield36. Shield36isolates electron emitting cathode28from vacuum chamber12. In a refinement, optional separate anode34, cathode enclosure24, shield36, or a ground connection operate as the primary cathode-coupled anode.

Cathode chamber assembly18operates as an electron emitting cathode source in the context of the present embodiment. In a refinement, a primary arc is generated in the electron emitting cathode source between cathode28and the primary anode. The cathode enclosure24can serve both as an independent primary anode connected to the positive pole of the primary arc power supply48and as a grounded anode, when it is connected to the ground34. Shield36defines openings38for transmitting electron emission current40from cathode28into vacuum chamber12. The shield can be floating or it can be connected to the positive pole of either primary arc power supply48or an additional power supply (not shown). In another refinement, cathode28is a cathodic arc cathode and the grounded primary anode34is a cathodic arc anode. Any number of different cathodes may be used for electron emitting cathode28. Examples of such cathodes include, but are not limited to, cold vacuum arc cathodes, hollow cathodes, thermionic filament cathodes, and the like, and combinations thereof. Typically, the cathode target is made of metal having a gettering capability including titanium and zirconium alloys. In a refinement, the shield of the cathode chamber is water cooled and negatively biased in relation to the cathode target wherein the bias potential of the shield ranges from −50 volts to −1000 volts. In still another refinement, cathode chamber assembly18includes a cathode array having a plurality of cathode targets installed therein with the height of cathode target array being substantially the same height of the remote anode and the height of a deposition area. Separation from the top of the cathode chamber assembly or vapor source16to substrates22(i.e., top of the substrates) is such that the plasma streaming from cathode28to remote anode44is confined. Typically, separation distance from the shield36of the cathode chamber assembly or from the evaporation surface of the vapor source16or from the remote anode44to substrates22is from about 2 inches to about 20 inches, which result in a formation of a narrow corridor for confinement of the remote arc plasma between the cathode28in a cathode chamber18and the remote anode44. When the width of this corridor is less than 2 inches it creates high impedance in plasma leading to plasma instabilities and eventually extinguishing of the remote arc discharge. When the width of this corridor is greater than 20 inches the plasma density in the remote arc discharge is not increasing enough to ionize the metal sputtering flow. In a particularly useful refinement, a large area cathode target having a shape of plate or bar is installed in the cathode chamber assembly18. Typically, such a large area cathode target has a height that is substantially equal to the height of the anode and the height of a deposition area. In a refinement, the cathode target can be made of the metal having a gettering capability such as for example titanium alloy or zirconium alloy. In this case the shielded cathode electron emitting source can also serve as a vacuum gettering pump which can improve pumping efficiency of the coating system. To further improve the gettering pumping efficiency the shield36facing the evaporating surface of the cathode target28in the cathode chamber18can be water cooled and optionally connected to high voltage bias power supply. When the water cooled shield36is biased to high negative potential ranging from −50V to −1000V in relation to the cathode target28, it will be subjected to intense ion bombardment by metal ions generating by the cathodic arc evaporating process. Condensation of metal vapor under conditions of intense ion bombardment is favorable for pumping noble gases such as He, Ar, Ne, Xe, Kr as well as hydrogen.

System10also includes remote anode44electrically coupled to cathode28, primary power supply48connected between cathode28and the primary cathode-coupled anode. Remote anode44is positioned in vacuum chamber12such that vapor source16is positioned between cathode chamber assembly18and the remote anode. In a refinement, a plurality of vapor sources is positioned between cathode chamber assembly18and remote anode44as set forth below in more detail. System10also includes secondary power supply52which electrically couples cathode28to remote anode44. Low pass filter54is also depicted inFIG. 1Awhich includes resistor R and capacitor C. Typically, vapor source16is positioned between cathode chamber assembly18and remote anode44. System10further includes pumping system56for maintaining a reduced pressure and gas system58for introducing one or more gases (e.g., argon, nitrogen, helium, etc.) into deposition chamber12. In a refinement, secondary power supply52, which powers the distant arc discharge in coating chamber12is installed between cathode chamber assembly18and remote anode44and provides at least 20% higher open circuit voltage than primary power supply48.

Still referring toFIGS. 1A, 1B, 1C, and 1D, a primary arc is initiated by arc igniter60in a cathode chamber24isolated from the discharge chamber by shield36with openings38for transmission of the electron current40. Typically, the plasma potential near the screen is low, close to the plasma potential in cathode chamber assembly18, while in the remote arc discharge plasma, the electric potential is high, close to the electrical potential of remote anode44.FIG. 2provides a typical distribution of the plasma potential between the screen and the remote anode obtained by finite element modeling. Surprisingly, the present coating system is found to produce a confined plasma arc that streams from cathode chamber assembly18to remote anode44.FIG. 1Dprovides a schematic illustration showing the movement of the plasma density between remote anode44and cathode28. A confined plasma streams (i.e., a plasma jet) between the remote anode and the cathode through the coating region. The ends of the confined plasma move along direction d4as set forth inFIG. 1D. An arc spot66forms on cathode28along with erosion zone68The plasma field62at remote anode44and the plasma field64at cathode28are confined dimensionally in a space from about 1 to 5 inches along direction d4. In one refinement, magnetic fields are used to accomplish the rastering movement along d4. In other refinement, this rastering movement is accomplished by mechanically moving cathode28along direction d4. In still other refinements, an emission filament bombarding cathode with electrons is moved along d4. In still other refinements as shown inFIG. 1E, the cathode includes a plurality of cathode elements281-6which are sequentially activated in order to form a plasma jet moving along d4. The confinement of the plasma arc results in a high density and hot plasma jet connecting cathodic arc spots at the primary cathode with an associated area at the remote anode running through a relatively narrow corridor created between the chamber walls (with primary cathodes, anodes and magnetrons attached) and substrate holder. This results in a high current density in the moving plasma jet connecting the cathode and remote anode. In a refinement, the current density in RAAMS plasma within this narrow corridor is from 0.1 mA/cm2up to 100 A/cm2. Typically, the electron density nein the background remote arc plasma ranges from about ne˜108cm−3to about ne˜1010cm−3while within the confined arc plasma jet area the electron density ranges from about ne˜1010cm−3to about ne˜1013cm−3. The confinement creating the plasma jet is a result of the physical dimensional relations between the components as set forth below as well as the application of magnetic fields. In particular, the discharge operates at very high plasma potential which corresponds to a high energy of ion bombardment (i.e., the ion bombardment energy is the difference between the plasma potential (vs. ground) and the substrate bias potential (vs. ground)). Even at floating and grounded substrates, ions with 50-70 eV are obtained because the plasma potential is above 50 V. In a refinement, the plasma potential is from 5V to 500V.

With reference toFIGS. 1A and 1B, an aspect of the relative sizing of various components of coating system10is provided. Remote anode44has a linear remote anode dimension Da. Vapor source16has a linear vapor source dimension Dv. Cathode target Ts has a linear cathode target dimension Dc. Substrate holder20has a linear holder dimension Dh. In a refinement, the linear remote anode dimension Da, the linear vapor source dimension Dv, the linear cathode target dimension Dc. and the linear holder dimension Dhare parallel to each other. In another refinement, the linear remote anode dimension Dais greater than or equal to the linear vapor source dimension Dvwhich is greater than or equal to the linear cathode target dimension Dcwhich is greater than or equal to the linear holder dimension Dh.

In a variation of the present embodiment, several remote anodes are associated with (i.e., electrically coupled to) at least one arc cathode positioned in the shielded cathodic chamber assembly18. The remote anodes are positioned at strategic positions within the coating chamber.

In another variation, the perpendicular distances between each of the vapor sources (e.g., vapor source16) and substrates22to be coated is substantially equal. Moreover, in a further refinement, the distance between cathode28and remote anode44is less than the distance at which breakdown occurs when an applied voltage of secondary power supply52exceeds 1.2 to 30 times the applied voltage of primary power supply48.

In still another refinement of the present embodiment, plasma probes are installed between the cathode28and remote anode44to measure plasma density. Such measurements provide a feedback so that the second power supply52is adjusted to provide adjusting a remote anode current to remote anode44to obtain a uniform distribution of the plasma density between cathode chamber assembly18and remote anode44.

Remote arc plasma modeling of the present embodiment is characterized by the electric potential distribution between cathode chamber assembly18and remote anode44and by the plasma density in the remote arc discharge plasma. The plasma potential in the remote arc discharge plasma and the anode potential increase as the remote discharge current increases. The plasma density in the remote arc discharge plasma increases almost proportional to the discharge current. This result is verified by optical emission spectroscopy of the remote arc discharge plasma.FIG. 3shows the intensity of the radiation emitted by excited argon atoms (spectral line ArI 739.79 nm) from the remote arc discharge plasma versus discharge current. It can be seen that the intensity of light emission from the argon atoms excited by direct electron impact is nearly proportional to the discharge current. This phenomenon is explained by the direct proportional relationship between electron concentration in the remote arc plasma and the remote arc discharge current. The ion concentration in the remote arc discharge is nearly equal to the electron concentration such that plasma quasi-neutrality is maintained.

With reference toFIGS. 4A, 4B and 4C, variations of the present embodiment with a chain of magnetron sputtering sources installed inline between a shielded cathode chamber assembly on one side and a distant arc anode on the other side is provided. In this context, the term “inline” means that the components are linearly arranged such that the substrates may pass over the components while moving in a linear direction.FIG. 4Aprovides a schematic of a coating system having additional remote anodes positioned between the magnetron sputtering source with additional shielded cathode chamber assemblies added to secure the uniformity and high ionization of gaseous plasma environment. Deposition system70includes vacuum chamber72with associated vacuum and gas supply systems as set forth above. Deposition system70also includes vapor sources76and78, cathode chamber assemblies80and82, and substrate holder84to hold substrates22to be coated.FIG. 4Adepicts a variation in which vapor sources76,78are magnetron sputtering sources. The substrates are positioned in front of the vapor sources during coating. Typically, substrates22move along direction d1during deposition of the coating. Cathode chamber assemblies80and82, respectively, include cathode enclosures90and92with openings94and96defined therein, cathodes98and100, optional primary anodes102and104, and shields106,108. Shields106,108respectively isolate cathodes98,100from vacuum chamber72. Shields106,108each define openings for transmitting electron emission currents into vacuum chamber72. In a refinement, cathodes98,100are cathodic arc cathodes and primary anodes102,104are cathodic arc anodes. System70also includes remote anodes110,112, respectively, electrically coupled to cathodes98,100. In a refinement as depicted inFIG. 4A, the shielded cathode chamber assemblies, the vapor sources (e.g., magnetron targets) and the remote anodes are aligned along the straight line which is suitable for the in-line coating systems.

FIG. 4Bprovides a schematic illustration of a coating system which includes variable resistors installed between a master anode and each of a plurality of slave anodes. In this refinement, coating system120includes vacuum chamber122and cathode chamber assembly124which is of the general design set forth above. Cathode chamber assembly124includes cathode chamber126, cathode128, arc igniter130, shield132defining a plurality of openings therein, and optional primary anode134. System120also includes primary power supply136which connects cathode128and primary anode134and magnetron sputtering sources136,138,140. Each magnetron sputtering source has a target Ts, a power supply Ps and an associated counter-electrode system120which also includes remote anode142with secondary power supply144providing a voltage potential between cathode128and remote anode142. System120also includes slave anodes146,148,150,152which are at intermediate voltage potentials established by variable resistors R1, R2, R3, and R4. In this refinement, the density of the plasma distribution can be controlled by changing the current through each of the slave anodes using variable resistors R1, R2, R3, and R4. The distances between the slave anodes and the distance between the slave anode closest to the master anode and the master anode cannot be greater than the minimal distance of the plasma discharge interruption in a processing gas composition and pressure.

FIG. 4Cprovides a refinement in which a resistor in parallel with a capacitor is used to set the voltage potentials of the intermediate anode. In this refinement, resistor R5in parallel with C5sets the voltage potential for anode146, resistor R6in parallel with C6sets the voltage potential for anode148, resistor R7in parallel with C7sets the voltage potential for anode150, and resistor R8in parallel with C8sets the voltage potential for anode152. In this refinement, the capacitors are used to extend the RAAMS process along the large distance by pulse igniting of the remote arc discharges between the cathode in a cathode chamber and each of the slave anodes positioned between the cathode in a cathode chamber and the master anode. It is appreciated that slave anodes can be also provided with additional independent power supplies; each of the slave anode power supply can be installed between the cathode128and the corresponding slave anode. The open circuit voltage of each secondary power supply connected either to the master anode or to the slave anode exceeds at least 1.2 times the open circuit voltage of the primary arc power supply136.

In still another variation of the invention, an inline modular configuration of the RAAMS setup is provided inFIG. 5. Such an inline system may include any number of deposition stations and/or surface treatment stations (e.g., plasma cleaning, ion implantation carburizing, nitriding, etc.). In the variation depicted inFIG. 5, coating system154includes modules156-164which are aligned inline. Modules156-164are separated from the neighboring module by load-lock gate valve166-176. Modular RAAMS surface engineering system154includes module156which is a chamber-module having a shielded cathodic arc chamber178and a remote anode180positioned along one wall of the chamber as set forth above. An optional set of magnetic coils182,184which create a longitudinal magnetic field ranging from 1 to 100 Gs along the coating chamber is also shown in this Figure. This module156performs the following operations: substrate loading; ion etching or ion cleaning of the substrates by high energy (typically E>200 eV) ion bombardment in an argon with a remote anode arc discharge (RAAD) plasma generated between the cathode in a shielded cathode chamber and a remote anode; and conditioning of the substrates to be coated by soft ion bombardment (typically E<200 eV) in an argon RAAD plasma generated between the cathode in a shielded cathode chamber and a remote anode. Second module158ionitrides the substrate surfaces to be coated in nitrogen or argon-nitrogen mix RAAD plasma generated between the cathode in a shielded cathode chamber and remote anode. The rate of plasma immersion ionitriding of HSS, M2 and 440C steel in the RAAD plasma immersion ionitriding process reaches 0.5 to 1 μm/min at pressures from 0.1 mtorr to 200 mtorr and a remote anode current ranging from 10 to 300 amps, but typically within the pressure range 0.2-100 mtorr and remote anode range from 10 to 200 amps. The RAAD plasma immersion ionitriding is a low temperature treatment where substrate temperature typically does not exceed 350° C. In this process, the substrates may be floating, grounded or biased at very low negative bias voltages (e.g. below −100V). Ionitriding at such low bias voltages is due to the high positive RAAD plasma potential causing the plasma ions to receive excessive energy from the high plasma potential which exceeds the grounded substrate potential. Alternatively, a low energy ion implantation of such elements as nitrogen, phosphorus, silicon, carbon from the gaseous RAAD plasma can be also performed at relatively low substrate bias voltages typically ranging from −200 to −1500 volts. The diagram of potential distribution in RAAD plasma processing is illustrated inFIG. 6. In a typical RAAD plasma process, the primary cathode has potential ranging from −20 to −50 volts relative to the ground primary anode. In a refinement, the floating substrate potential ranges from −10 to −50 volts relative to the primary cathode. The biased substrate potential in ionitriding, carburizing and other ion diffusion saturation processes is typically from −10 to −200 V relative to the primary cathode, while in the RAAD plasma immersion low energy ion implantation process, the substrate bias is typically from −200 to −1500 volts.

It is appreciated that the modular chamber layout ofFIG. 5can also be used to perform remote anode arc plasma assisted CVD (RAACVD) processes in gaseous RAAD plasma chambers (for instance, modules156,158and164inFIG. 5). For example, this low pressure plasma immersion CVD process setup can be used for deposition of polycrystalline diamond coatings in the plasma-creating gas atmosphere consisting of 0.1-1% methane and balance hydrogen or hydrogen-argon mix. RAAD plasma acts as a powerful activator of the reactive atmosphere with high density of atomic hydrogen and HC radicals which are contributing to formation of polycrystalline diamond coating. In this process the substrate to be coated can be either grounded, floating or biased to the negative potential not below −100 volts vs. the primary cathode. Independent radiation heater array can be used to maintain substrate temperature in the range from 200° C. to 1000° C. as necessary for the deposition of polycrystalline diamond coating in the plasma enhanced low pressure CVD processes.

In another embodiment, a coating system having plasma sources aligned along curvilinear walls is provided.FIG. 7Aprovides a schematic top view of a batch coating system with a centrally located shielded cathode chamber.FIG. 7Bprovides a schematic perspective view of the batch coating system ofFIG. 7A. Coating system190includes vacuum chamber192, cathode chamber194which includes cathode196, and shield198. Vacuum chamber192has a substantially circular cross section. System190also includes primary power supply170which sets the voltage potential between cathode196and primary anode202. System190also includes magnetron sputtering sources204-210each of which includes target Ts, power supply Ps, and anode As. In a refinement, magnetron sputtering sources204-210are arranged along a circle having the same center as the cross section of vacuum chamber192. System190also includes remote anodes212and214which are set at a voltage potential relative to cathode194by power supplies216and218. In this embodiment, substrates22move axially along a circular direction d2as they are coated. In each of the variations ofFIGS. 7A and 7B, the plasma streams between cathode196and the remote anodes. This streaming is confined by the separation between the remote anode (or sputtering sources) and the substrates (i.e., top of the substrates) which is typically 2 to 20 inches. The confinement persist through the coating zone Moreover, the plasma is rastered along the cathode in a direction perpendicular to the movement of the substrates as set forth above with respect toFIG. 1D.

As set forth above, remote anodes212and214have a linear remote anode dimension Da. Magnetron sputtering sources204-210have linear source dimension Ds. Cathode target196has a linear cathode target dimension Dc. Substrate holder20has a linear holder dimension Dh. In a refinement, the linear remote anode dimension Da, the linear cathode target dimension Dc. and the linear holder dimension Dhare parallel to each other. In another refinement, the linear remote anode dimension Dais greater than or equal to the linear cathode target dimension Dcwhich is greater than or equal to the linear holder dimension Dh.

It is appreciated that an external magnetic field can be applied in a coating chamber for the embodiments set forth above to further enhance the plasma density during arc plasma enhanced magnetron sputtering coating deposition processes. The preferable magnetic field will have magnetic field lines aligned generally parallel to the cathodic arc chamber and/or remote anode. This will contribute to the increase of the arc discharge voltage and, consequently, to the electron energy and arc plasma propagation length along the coating chamber. For example, the external magnetic field can be applied along the coating chambers in the inline coating system shown inFIG. 5.

A uniform plasma density distribution in the coating chambers set forth above can be achieved by appropriately distributing both remote anodes and the electron emitting surface of the shielded vacuum arc cathode targets to evenly cover the coating deposition area. For example, if coating deposition area is 1 m high then both electron emitting surfaces of the shielded cathode target and electron current collecting remote anode surfaces have to be distributed to evenly cover this 1 m high coating deposition area. To achieve these requirements, several small cathode targets can be installed in a shielded cathode chamber, each of the cathode targets is connected to the negative pole of the independent power supply. The cathode targets are distributed generally evenly so the electron flows emitted by each of the cathode targets overlap outside the shielded cathode chamber providing a generally even distribution of electron density over the coating deposition area. The positive poles of the remote arc power supplies can be connected to one large anode plate having the height generally the same as a height of the coating deposition area and facing the substrate holder with substrates to be coated as shown inFIGS. 1 and 4-6. The set of anode plates, each connected to the positive pole of the remote arc power supplies, can be used to provide even distribution of electron density over the coating deposition area. Similarly, instead of using a set of small cathode targets in a shielded cathode chamber, a single large cathode target having a linear dimension similar to the linear dimension of the coating deposition area can be used as a cathode of remote arc discharge. In this case, electron emission spots (i.e., cathodic arc spots) are rastered over the cathode target to provide a generally even distribution of electron emission current over the coating deposition area. The rastering of the cathodic arc spots over a large cathode target area can be achieved, for example, by magnetic steering of the cathodic arc spots over the arc evaporating area of the cathode target or by mechanical movement.

With reference toFIGS. 8A-8H, schematic illustrations depicting a refinement of coating system ofFIGS. 7A and 7Bwhich uses a magnetically steered cathodic arc spot is provided. The present variation incorporates features from U.S. Pat. No. 6,350,356, the entire disclosure of which is hereby incorporated by reference. Referring toFIG. 8A, system190′ includes duct magnetic coil270surrounding plasma duct272which is formed within cathode chamber194between the two opposite sides of the housing274. Coil270includes winding270afacing side196aof the cathode target196and an opposite winding270bfacing side196bof the cathode target196. Cathode target196is generally bar shaped with a long dimension dA. Duct coil270generates a magnetic field along the duct272with magnetic force lines generally parallel to the sides196aand196bof the cathode target196. When cathodic arc spot278is ignited on the evaporating surfaces196aor196b, arc spot278moves along a long side of the bar-cathode196. At the end of the bar, arc spot278switches sides and continues its movement in the opposite direction at the opposite side of the bar. Isolation ceramic plates (not shown) attached to the sides of the cathode bar perpendicular to the magnetic force lines prevent the arc spot escaping from the evaporating surface of the cathode196. Shields198are optionally installed at the ends of the plasma duct272facing the coating area in the coating chamber192. In a refinement, shields198are movable to permit opening and closing the plasma duct272depending on the stage of the coating process. When shields198are closed the RAAMS process can be conducted with enhance ionization of the magnetron sputtering environment by the RAAD plasma. When the ends of the duct272are opened, the cathodic arc plasma flows along the magnetic force lines generated by duct coil270toward substrates22to be coated which results in deposition of cathodic arc coatings from the cathodic arc metal vapor plasma which is magnetically filtered from undesirable neutral metal atoms and macroparticles. The filtered cathodic arc coating deposition may be conducted as a single process phase or in conjunction with magnetron sputtering by the magnetron sputtering sources204-210. The ionization and activation of the plasma environment by the remote arc discharge established between the cathode196in the cathode chamber194and the remote anodes210,214improves the density, smoothness and other physic-chemical and functional properties of the coatings.

Referring toFIGS. 8B and 8C, schematic illustrations depicting the mechanism of magnetic steering of the cathodic arc spots around an elongated rectangular bar cathode are provided. Rectangular bar-shaped cathode196is positioned between two portions of duct coil windings270. Left winding270aand right winding270bface the evaporating sides of the cathode196. Cathode side196afaces duct coil winding side270awhile cathode side196bfaces duct coil winding side270b. The magnetic field B generated by the duct coil windings270is parallel to the sides of the cathode196facing the duct coil winding and at the same time is perpendicular to the axis dAof the elongated cathode196(i.e. the long sides of the cathode target196). When cathodic arc spot278is ignited on a side of the cathode196facing the duct coil winding arc, current Iarcis generated perpendicular to the surface of the cathode target196and, therefore, perpendicular to the magnetic force lines B generated by duct coil270. In this case, the cathode arc spot moves along the long side of the cathode with the average velocity Varc, which is proportional to the Ampere force defined by a product of arc current Iarcand magnetic field B, following the well-known Ampere law:
Varc.=(−/+)c*Iarc*B,(1)

where c is a coefficient which is defined by the cathode material. The direction of the arc spot movement (the sign in the parenthesis in the above formulae) is also determined by the cathode target material since the magnetic field generated by the duct coil270is parallel to four sides of the cathode target (i.e., long in the same direction around the evaporative sides of cathode target196). For example, when the cathode arc spot278ais created on cathode side196afacing the duct coil winding270a, the arc spot moves down the cathode target196along the long side196a. At the end of the cathode bar, the arc spots turn to the short side196dfollowed by turning to the long side196band then continuing up along long side196b, etc.

FIG. 8Cdepicts the arc spots moving along the evaporative sides196a,196b,196cand196dof the cathode target196, which are parallel to the magnetic force lines280generated by the duct coil270. The duct coil is energized by the duct coil power supply282while arc power supply284is connected to the cathode target196. The duct coil includes coils270aand270bconnected by an electric circuit including current conductors286,288,290and290. The sides of the cathode target196perpendicular to the magnetic force lines are covered by the isolation plates294which prevent arc spots from escaping the evaporative surface of cathode target196. Cathodic arc plasma is trapped by the magnetic force280generated by the duct coils270aand270bwhich prevent plasma diffusion across magnetic force lines280, while plasma can freely move along the magnetic force lines280.

FIG. 8Dprovides additional details regarding the steering of cathodic spots by the duct coil. The magnetic field generated by the duct coil270steers the cathodic arc spots along the sides of the cathode target bar196parallel to the magnetic field force lines as set forth above. The direction of the movement of the cathodic arc spots is shown by the arrows AD. The ends of the plasma duct272are opened which allows the cathodic metal vapor plasma to flow along magnetic force lines toward substrates22installed on substrate holder20in the coating chamber. The neutrals and macroparticles are trapped within the cathode chamber on the inner walls of the duct272yielding near 100% ionized metal vapor plasma to enter in the coating area outside of the plasma duct272. This design of the cathode chamber is essentially that of a filtered cathodic arc metal vapor plasma source capable of getting rid of macroparticles and neutrals in the outcoming metal vapor plasma and yielding nearly 100% atomically clean ionized metal vapor for deposition of advanced coatings. The RAAD plasma established between the cathode196and the remote anodes212,214enhances ionization and activation of the plasma environment in the RAAMS coating deposition process, resulting in improved coating properties. In this design, the hybrid coating deposition processes can be conducted as a single cathodic arc or magnetron coating deposition or as a hybrid process combining cathodic arc metal vapor plasma with magnetron metal sputtering flow immersed in a highly ionized remote arc plasma environment.

Still referring toFIG. 8D, the issue of arc plasma enhancement of large area magnetron sputtering coating deposition process and hybrid processes is addressed by positioning at least one remote arc anode off line-in-sight with the cathode target bar196. In this variation, at least one substrate22held by substrate holder20′ and magnetron sputtering sources204-210are positioned in a coating chamber region outside of the plasma duct272. The present RAAMS process effectively immerses the metal sputtering flow generated by conventional magnetron sources in the dense and highly ionized remote anode arc discharge (RAAD) gaseous plasma. The remote arc power supply (not shown) which powers the RAAD plasma is installed between the arc cathode target196and the at least one remote anode212. The remote anodes212,214provide at least 20% higher open circuit voltage than the power supply which powers the primary arc discharge in a cathode chamber which is ignited between the arc cathode196and the proximate anode. The proximate anode can be an inner wall of the plasma duct enclosures296a,296bor, optionally, an independent anode electrode within plasma duct272. In another refinement, several additional remote anodes, each of them associated with at least one arc cathode positioned within plasma duct272, may be utilized. The remote anodes are positioned at strategic positions within the coating chamber between the end-openings of the plasma duct272off line-in-sight from cathode196. The minimal distance between the end-openings of the plasma duct272and the remote anodes212,214must be less than the plasma discharge breakdown distance when the voltage applied between the cathode and remote anode exceeds 1.2 to 10 times the voltage drop between the cathode and the primary (proximate) anode, which can be either electrically grounded or isolated.

FIG. 8Edepicts a variation of the coating system ofFIG. 8A-8Dwhich utilizes a macroparticle filter are provided. The design of this variation incorporates the advanced macroparticles filter of U.S. Pat. No. 7,498,587 and EU Pat. Application No. EP 1 852 891 A2, the entire disclosures of which are hereby incorporated by reference. System190′ includes trimming coils300aand300bpositioned adjacent to the opposite sides of the cathode target196and facing opposite sides of the plasma duct272. The inner walls of the opposite ducts296aand296bare provided with grooves or, optionally with baffles for trapping macroparticles. Duct coil272surrounds duct272with winding portion270abeing parallel to the long side of the cathode target196awhile facing duct side296a. Similarly, winding portion270bis parallel to the long side of the cathode target196band faces duct side296b. Trimming coils300a,300binclude magnetic cores302which are surrounded by electromagnetic coils304. The cathodic arc spots move along the evaporation sides196aand196bof the cathode target196under influence of the Ampere force according to the expression (1) set forth above. The sides of the cathode target196perpendicular to the plane of symmetry of the duct272are covered by ceramic isolation plates294aand294bto prevent arc spots from escaping the evaporating surface of the cathode target196. The direction of the magnetic field generated by the trimming coils300a, bcoincides with the direction of the magnetic field generated by the duct coil270. However, in the vicinity of the evaporating surfaces of the cathode target196aor196b, the magnetic force lines generated by trimming coils300a, bare arch-shaped thereby allowing confinement of the cathodic arc spots within the evaporation area of the cathode target as require by the well-known acute angle rule (see for example, R. L. Boxman, D. M. Sanders, and P. J. Martin,Handbook of Vacuum Arc Science and Technology. Park Ridge, N.J.: Noyes Publications, 1995 pgs. 423-444).

FIGS. 8F, 8G and 8Hprovide schematics illustrating the mechanism of arc confinement by the magnetic field generated by the trimming coils300a, b. Cathodic arc spots278are located under a top point of the arch-shaped magnetic force lines as required by the acute-angle rule of arc spot confinement. The magnetic field with the arch-shaped configuration above the evaporating surface of the cathode target196is generated between the South pole of the trimming coil300aand the North pole of the trimming coil300bon both sides of the cathode target196facing the duct272. The configuration of the magnetic field within plasma duct272is evaluated using numerical calculation. The magnetic field with plasma duct272, when both duct coil270and trimming coils300are turned ON, generates a magnetic field in the same direction is shown inFIG. 8G. This figure demonstrates that the magnetic force lines are directed in the same direction while still having an arch-shaped configuration in the vicinity of the evaporation surface of the cathode target196. In this mode, the cathodic arc plasma magnetically filtered from the neutral metal atoms and macroparticles flows along the magnetic force lines away from the plasma duct272toward substrates to be coated (not shown) in the coating area of the coating chamber outside of the plasma duct272. In this filtered cathodic arc deposition mode, the nearly 100% ionized metal vapor plasma with little, if any, neutral metal atoms or macroparticles is deposited onto substrates thereby creating defect-free coatings with superior properties. The magnetron sputtering coatings can also be deposited during this mode of operation by the magnetrons positioned on the outer walls of the plasma duct272. Additional ionization and activation of the coating deposition plasma environment during this mode of operation is provided by the remote arc discharge established between cathode196and remote anodes212,214positioned next to the magnetrons on the outer wall of the plasma duct272or, alternatively, on the inner wall of the coating chamber opposite to the magnetron sources (not shown). Referring toFIG. 8H, the magnetic field force lines are shown to switch directions within the plasma duct when duct coil270is turned “OFF”. However, when both trimming coils300a, bare turned “ON” an arch-shaped magnetic field is generated above the evaporative surface of cathode target196. Depending on the operating mode, the deflecting magnetic field generated by deflecting duct coil270can be turned “ON” or “OFF”. When the magnetic field of the deflecting duct coil270is turned “ON”, the metal vapor plasma generated by the cathode target196is transported bi-directionally throughout the plasma duct272towards substrates20. When the deflecting duct coil270is turned “OFF”, the metal vapor plasma generated by the cathode target196does not transport towards substrates20, although the cathode arc spots continue their movement around the target bar196driven by the steering magnetic field generated by trim coils300a, b. In this variation, the duct coil works as a magnetic shutter eliminating the need in a mechanical shutter or shield as shown inFIG. 7A. When the magnetic shutter is “ON,” the metal vapor is transported through the plasma duct toward substrates20in the processing chamber. When the magnetic shutter is “OFF”, the magnetic shutter is closed and metal vapor does not reach substrates20.FIG. 7Hshows the distribution of the magnetic field in plasma duct272is zero when the current of the duct coil is set to zero and the trim coils current set to 0.1 amperes and duct coil current is zero. It can be seen that when the magnetic field of duct coil270is zero, there is no magnetic field to transport metal vapor plasma away from the plasma duct272, although trim coils300a,300bstill generate a magnetic field with an arch-shaped geometry that is sufficient both for confinement of the arc spots278within evaporating area of the target196(magnetic arch configuration at the evaporating target surface) and for steering the arc spot movement around the cathode bar196. In this latter operation mode, when cathodic arc metal vapor plasma is trapped within the plasma duct, the electrons still flow away from the plasma duct toward remote anodes positioned outside of the plasma duct272in the coating chamber. The resulting remote arc discharge is established between cathode196in the plasma duct272and the remote anodes (not shown) which can be positioned in the outer wall of the plasma duct272or in the wall of the coating chamber in a position opposite to the magnetron sources (not shown). The RAAD plasma enhances ionization and activation of the coating deposition processing environment in the coating chamber, resulting in deposition of advanced coatings with superior properties.

When the magnetic shutter is closed, cathode target196still generates a large electron current which can be extracted toward remote anodes to establish a remote arc assisted discharge plasma in the processing chamber. The RAAD plasma is characterized by high density, ranging from 1010-1013cm−3, high electron temperature ranging from 3 to 20 eV, and high plasma potential which generally resembles the potential of the remote anode. An experimental study confirms that the magnetic shutter can seal the plasma duct272thereby preventing metal vapor plasma from reaching the substrates20when the magnetic shutter is closed. Cathode target bar196used in these experiments was made of stainless steel. The silicon wafers which are used as substrates20are installed on substrate holding shafts of the round table substrate holder which is rotated at 5 RPM during 2 hours of the coating deposition process. The current of trim coils300is set at 0.2 A while the duct coil270current is set to zero. The argon pressure is 1.5 mtorr while the current of the primary arc is 140 amperes. After a two hour exposure, the substrates are unloaded and the coating thickness is measured by means of optical interferometry using Veeco NT3300 Optical Profiler. The results are presented in Table 1 below.

From the results presented in Table 1, it follows that the deposition rate on a rotating substrate holder does not exceed 6 nm/hr when the magnetic shutter is closed. The average coating thickness produced in a coating deposition process, either by filtered cathodic arc deposition or magnetron sputtering sources, typically exceeds 1 μm/hr. In this case, leakage of the metal vapor does not increase doping elements in a coating over the usual level of impurity of the cathode targets used in industrial coating deposition processes.

The following processes can be conducted in a remote arc assisted surface engineering (RAASE) chamber:

1. ion cleaning/etching in dense RAAD plasma (magnetic shutter is closed);

2. low temperature ion nitriding or oxi-nitriding, plasma carburizing. The temperature of substrates during this process can be as low as 150° C. The ionitriding rate of M2 steel in RAAD nitrogen plasma is typically ranging from 0.1 to 0.5 μm/min. (magnetic shutter is closed);

3. deposition of filtered arc coatings (magnetic shutter is open;

4. deposition of magnetron sputtering coating by remote arc assisted magnetron sputtering (RAAMS) process (magnetic shutter is closed); and

5. deposition of magnetron sputtering coatings modulated by filtered arc coatings (magnetic shutter OFF/ON as per duty cycle to achieve a required coating modulation period).

With reference toFIG. 9A-E, schematics of a filtered arc assisted magnetron sputtering (“FAAMS”) hybrid filtered arc-magnetron bi-directional system having additional magnetron sources are provided. In this variation, additional magnetron sputtering sources310-316are positioned adjacent to the arc cathode chamber194magnetically coupled with filtered arc source196and having the magnetron targets forming an open angle in the range from 10 degrees to 80 degrees. This opening angle Ao assists in focusing the magnetron sputtering flow toward the substrates. In this filtered arc assisted magnetron sputtering hybrid coating deposition process, the filtered arc metal plasma flows along the magnetic field lines of the transporting magnetic field created by the duct coil270. Moreover, the magnetic field lines diverge at the exit of the plasma duct272. This results in metal ions from the filtered arc cathode passing by the magnetron sputtering target area close to the target surface and crossing a magnetron discharge area with large close-loop magnetic field topology. A substantial portion of these metal ions are trapped in the magnetron magnetic field and contribute to the sputtering of the magnetron target, which can occur even without sputtering gas (argon or other noble gas) and within a broadened pressure range from 10−6to 10−2torr. Another portion of the metal ions generated by filtered arc cathodes continue towards substrates22where they mix with the focusing magnetron sputtering flow, providing an ionized metal fraction of the magnetron sputtering coating deposition process. It is well-known that increasing the ionization rate of the metal vapor improves coating adhesion, density, and other mechanical properties, and smoothness.

FIG. 9Bprovides additional features of the FAAMS hybrid filtered arc-magnetron bi-directional source. Optional additional focusing magnetic coils320are positioned opposite to the exit opening of the plasma duct which provides additional improvement of the plasma density and controls mixing of the magnetron sputtering flow with filtered arc metal plasma flow focusing toward substrates to be coated in a coating chamber (not shown). In addition, optional focusing magnetic coils324are positioned about magnetron targets310-316at the exit portion of the plasma duct272. Focusing coils324improve the concentration of the plasma density near the magnetron targets. The direction of the magnetic force lines generated by these coils at the side adjacent to the duct coil have the same direction as the transporting magnetic field generated by the duct coil.FIG. 9Cprovides a schematic illustration of a refinement of the system ofFIG. 9B. In this refinement, pairs of magnetic focusing coils328are positioned at the exit portion of the plasma duct surrounding the plasma duct on both sides of the magnetron sources.FIG. 9Dprovides a top cross section of the coating systems ofFIGS. 9A-C, in which the remote arc plasma (F1), the magnetron sputtering flows (F2), and the filtered arc plasma stream (F3) are depicted. The direction of the magnetic field generated by these focusing coil coincide with the direction of the transporting magnetic field generated by the duct coil.FIG. 9Eprovides yet another variation of a coating system.FIG. 9Edepicts a section coating chamber192outline with the rotating substrate holding turntable22with substrates to be coated20. The cathode chamber194is positioned opposite to the substrates to be coated20in the coating chamber192. The primary arc discharge in a cathode chamber194is ignited by the striker440on cathode target196which are enclosed within the housing274. The housing274has a shield198with openings which are not transparent for heavy particles such as ions, atoms and macroparticles emitted from the surface of cathode target196, but allow electrons to flow freely toward the remote anodes in the coating chamber192. The magnetron targets310,312are positioned adjacent to the cathode chamber shield198so that the sputtering flow emitted from the magnetron targets is coupled with highly ionized plasma in front of the shield198and focusing toward substrates20in the coating chamber192. In this arrangement the cathodic portion of the remote arc plasma generating in front of the cathode shield198is coupled with magnetron sputtering flow resulting in substantial increase of ionization and activation of the metal-gaseous plasma generating by the magnetron targets310,312which contributes to further improvement of coating adhesion, density, smoothness, reduction of the defects and improvement of their functional properties for different applications.

The FAAMS surface engineering system can operate in the following modes:

1. RAAD plasma immersion ion cleaning, ion nitriding, low energy ion implantation. In this mode the cathodic arc source is operating, both trim coils are ON, but the plasma transporting duct coil is OFF. Turning OFF the duct coil effectively prevents the metal plasma generated by the cathode positioned in a center of the plasma duct for reaching out of the plasma duct toward substrates to be coated in a coating chamber, but the gaseous dense and highly ionized RAAD plasma is filling the entire processing chamber including the interior of the plasma duct and the area in a chamber where substrates to be coated are positioned on the substrate holder. This dense gaseous plasma provides a highly ionized environment for plasma immersion ion cleaning, ion nitriding (as well as ion carburizing, oxi-carburizing, boronizing and other ion saturation processes) and low energy ion implantation. It can also be used for remote arc assisted CVD (RAACVD) processes, including deposition of a diamond-like carbon (DLC) coating when the hydrocarbon contained gaseous atmosphere is created in a coating chamber. In this mode, the remote arc plasma assisted CVD process can be conducted. Moreover, it is possible to deposit polycrystalline diamond coatings when substrates are heated to a deposition temperature ranging from 500 to 1000° C. (depending on type of substrate). In such a process, the gas pressure is typically ranging from 1 to 200 mTorr, the gas atmosphere typically includes 0.1-2% of methane in hydrogen at a hydrogen flowrate ranging from 50 to 200 sccm depending on pumping system capability with the balance being argon. The duct coil works as a magnetic shutter, effectively closing the way out of the metal plasma generated by the cathode in a plasma duct, while opening the way for the RAAD generated gaseous plasma.

2. When the duct coil is OFF (magnetic shutter is closed) and RAAD plasma is created within the coating chamber between the cathode in plasma duct and remote anode(s) in a coating deposition area outside of the plasma duct, the highly ionized plasma environment can be used for plasma assistant magnetron sputtering (RAAMS) processes. In this case, the magnetron sources positioned outside of the plasma duct in a coating area are turned ON and magnetron sputtering process is conducted in a highly ionized RAAD plasma environment. In this process, the productivity of the magnetron sputtering increases more than 30% and the coating is densified by the ion bombardment of the substrate surface by gaseous plasma-born ions.

3. When the plasma duct coil is ON, the magnetic shutter is open and metal plasma generated by the cathode in a plasma duct is flowing into the coating deposition area along the magnetic force lines of the transporting magnetic field generated by the duct coil. The filtered arc metal plasma can be used for deposition of the variety of coatings, including superhard hydrogen free tetrahedral amorphous carbon (ta-C) coating when graphite bar is used as a cathode target in a plasma duct. When magnetron sources positioned in the exit portion of the plasma duct and having their targets facing the substrates are turned ON, the hybrid filtered arc assisted magnetron sputtering (FAAMS) process starts. In this case, the filtered arc metal plasma which is 100% ionized is passing the magnetron sources mixing with the magnetron sputtering atomic metal flow which generally has a low ionization rate of <5%. The mixed filtered arc metal plasma and magnetron sputtering atomic metal flow is directed toward substrates in a coating area in front of the exit of the plasma duct, which provide hybrid filtered arc assisted magnetron sputtering coating deposition with high and controllable concentrations of the depositing metal atoms flow.

FIG. 10provides a schematic description of the physical processes which are involved in the bi-directional remote arc discharge of the present invention. The primary arc is initiated by an arc igniter on a surface of cathode target196isolated from the discharge chamber by the pair of trimming coils300. This source can work in two modes: first, in a coating deposition mode when the arc vapor plasma is transported along the magnetic force lines of the longitudinal magnetic field created by the duct coil270force; and second, in electron emission mode, when the duct coil is turned off and arc plasma is confined and magnetically isolated from the processing chamber by the magnetic field created by a pair of trimming coils300. The plasma potential within the plasma duct272is low, close to the potential of the proximate anode, which is in most cases grounded, while in the remote arc discharge plasma the electric potential is high, close to the potential of the remote anode214. The typical distribution of the plasma potential between the plasma duct272and the remote anode214, obtained by finite element modeling is shown inFIG. 2.

With reference toFIG. 11, a schematic of a batch coating system with a peripherally located shielded cathode chamber assembly is provided. Coating system330includes vacuum chamber332, cathode chamber assembly334, which includes cathode chamber336, cathode338and shield340. System330also includes primary power supply342which sets the voltage potential between cathode338and primary anode344. System330also includes magnetron sputtering sources356-366each of which includes target Ts, power supply Ps, and anode As. System330also includes remote anode360which is set at a voltage potential relative to cathode338by power supply362. In this embodiment, substrates22move axially along direction d3as they are coated.

FIG. 12illustrates a further variation providing a shielded cathodic arc electron emission source located in the center of the coating chamber. In particular, the present variation provides a circular batch coating system380with cathode chamber assembly382located in its central area. The cathode384is positioned within the cathode chamber assembly382generally along the axes of the coating system380. Cathode chamber assembly382, respectively, include cathode enclosures388with openings390and392defined therein, cathode384, optional primary anodes (not shown), and shields396,398. The enclosure388and shields396,398respectively isolate cathode384from vacuum chamber400and can also serve as a primary anode for the arc discharge ignited in a cathode chamber382. The primary arc power supply is also provided between the cathode384and the anode-enclosure388(not shown). The enclosure388and shields396,398each define openings for transmitting electron emission currents into vacuum chamber400, while at the same time serving as a barrier stopping the heavy particles such as metal vapor atoms, ions and macroparticles, emitted from the cathode384to reach substrates20to be coated in the coating chamber400. The magnetron sputtering sources402,404, and406are attached to the wall408of the chamber400. The remote anodes410,412and414are positioned next to the corresponding magnetron sources, preferably surrounding these sputtering sources. The substrates20are positioned on rotary table platform420at the distance d1between the cathode chamber and magnetron sputtering targets. The distance from the magnetron target surface to the substrates20is typically ranging from 4 to 10 inches. The remote arc power supplies424,426, and428are installed between the remote anodes410,412and414and the central cathode384in the cathode chamber382. The cathode384can be a thermionic filament cathode, but preferably the cold evaporative vacuum arc cathode can be used, which is not sensitive to the reactive plasma processing environment which can contain chemically aggressive gases such as methane, oxygen and nitrogen for coating deposition of carbides, oxides and nitrides. Cathode384is either elongated thermionic filament or a cold cathode in a form of elongated metal bar or rod. Moreover, cathode384is positioned within the cathode chamber382along the axes of the coating chamber400with its electron emission zone length parallel and generally dimensionally equal to the height of the substrate20loading zone. Moreover, cathode384has a long dimension that is either less than or equal to the height of the remote anodes310,312and314. The heights of the magnetron targets are also either less than or equal to the height of the remote anodes.

In a refinement, the magnetrons402,404,406shown inFIG. 12, can be replaced with planar heaters. The substrates to be coated can be placed at the heater surface, facing the center of the chamber where the shielded cathode chamber382is positioned with the cathode384. In this case the substrates can be heated to 900° C. while at the same time highly ionized remote anode arc plasma can be established in the chamber380by remote anode arc discharge between the cathode384in a cathode chamber382and the remote anodes536,538,540positioned at the wall of the chamber380. In this process, when gas atmosphere in a chamber380is composed of a mixture of methane, hydrogen and argon at the pressure range from 1 mTorr to 200 mTorr and methane concentration in hydrogen ranging from 0.1 to 2 at. weight % the polycrystalline diamond coatings can be deposited on substrates positioned at the heated surface of the heaters, heated to the deposition temperature ranging from 700 to 1000° C.

With reference toFIG. 13, schematic illustrations of a system incorporating an electron emitting vacuum arc cold cathode source are provided. In particular, the present variation adopts the design of the electron emitting vacuum arc cold cathode source of the system of U.S. Pat. No. 5,269,898, the entire disclosure of which is hereby incorporated by reference. Rod-shaped cathode430is mounted within cathode chamber432, which serves as a primary anode for the vacuum cathodic arc discharge powered by the primary arc power supply434. Cathode430is connected to the negative output of an arc power supply434, and the enclosure436of the cathode chamber432is connected to the positive output of arc power supply434. The positive output of the primary arc can be optionally grounded as shown by the dashed line inFIG. 7D. An arc is struck repetitively by a striker440, located at the end of cathode430that is opposite the connection to arc power supply434. A helical electromagnet coil442is mounted coaxially with the cathode430and serves to generate a solenoidal magnetic field with flux lines substantially parallel to the cathode430axis, and having a magnitude proportional to the current furnished by a coil power supply446. One or more substrates20, upon which a coating is to be deposited, are disposed surrounding the cathode chamber432and optionally mounted on a substrate holding turntable platform (not shown) which will provide rotation of the substrates during deposition, if necessary, to achieve a uniform coating thickness distribution thereon. An arc spot450and a typical trajectory452thereof resulting from the influence of the applied magnetic field are also depicted. Arc spot travels all or part of the length of the cathode430toward the connection to arc power supply434before being re-struck. The insulator454prevents movement of the arc spot450off the desired evaporable surface of cathode430. Electromagnet coil442may be electrically isolated from the arc circuit, or it may comprise a part of the anode by connection thereto as indicated by the dotted line458. The electromagnetic coil442may alternatively serve as the sole primary anode for the primary arc discharge in the cathode chamber432, in which case the electromagnetic coil442is isolated electrically from the chamber430and connected to the positive output of primary arc power supply434, which is disconnected from the cathode chamber432. One or more magnetron sputtering sources460are mounted along the walls462of the chamber466surrounded by the remote anodes470. The remote anodes are connected to the positive output of the remote arc power supply472, while its negative output is connected to the cathode430in the cathode chamber432. The enclosure436of the cathode chamber430has openings476covered by shields478to prevent the heavy particles (ions, neutral atoms and macroparticles) emitted by the cathode430from reaching the deposition area outside of the cathode chamber432, but the electrons are able to freely penetrate into the coating area throughout the openings476between the enclosure436and shields478. The remote arc current is conducting between the cathode430within the cathode chamber432and remote anodes470surrounding the magnetron sputtering sources460at the wall of the coating chamber466. The remote anode is connected to the positive output of the remote arc power supply472, while the negative output of the remote arc power supply472is connected to the cathode430in the cathode chamber432. The remote arc ionizes and activates the plasma environment during the magnetron sputtering coating deposition process, but can also serve as a source of ionization and creation of plasma environment in a coating area during preliminary ion cleaning of the substrates before the coating process starts, as well as for the plasma immersion ion implantation, ionitriding and plasma assisted low pressure CVD coating deposition processes.

With reference toFIGS. 14A-14C, a schematic illustrations of a variation of a coating system incorporating a macroparticle filter are provided. In this variation, the design of the cathode chamber of U.S. Pat. Application No. 2012/0199070 is adopted, the entire disclosure of this patent application is hereby incorporated by reference. System480includes cathode chamber484which is configured as a macroparticles filter. Cathode chamber484includes an even number of duct assemblies symmetrically positioned around elongated cathode486. The variation set forth inFIGS. 14A and 14Bincludes four duct assemblies, i.e., duct assemblies488,490,492,494, which effectively form an enclosure496around the cathode486. The duct assemblies488,490,492,494define ducts500,502,504,506through which positively charged ions are guided from cathode target486to substrates20. Duct assemblies488,490,492,494define a magnetic field for guiding a plasma. Duct assemblies each include support component510and baffle component512for blocking macroparticles. In a refinement, baffle component512includes protrusions514for enhancing the ability of filtering out macroparticles. Electrical posts516,518are used to connect to the filter power supply so that the duct assemblies are electrically biased for repelling positively charged ions. When the duct assemblies488,490,492,494are positively biased in relationship to the cathode486it is also serving as a primary anode for the primary arc discharge established within the cathode chamber484. The duct assemblies488,490,492,494can also be isolated and have a floating potential. In this case the arc steering electromagnetic coil (not shown) can serve as a primary anode to the cathode486for igniting the primary arc discharge in the cathode chamber484as was explained above in relation to the embodiment of the invention shown inFIG. 14B. With reference toFIG. 14Ca schematic perspective view of a cathode chamber enclosure-filter assembly496is provided. Filter assembly-cathode chamber enclosure496is made of a set of duct assemblies488,490,492,494, which are parallel to the cathode486, preferably having a shape of a rod but which can also be made as a bar with any polygonal cross-section. During the filtered cathodic arc coating deposition process the filter is electrically activated by passing a current along the duct assemblies488,490,492,494to establish a magnetic field.

Still referring toFIGS. 14A-14C, a magnetic field is optionally created by passing a current through the duct assemblies so as to create a magnetic field. In particular, adjacent duct assemblies generate magnetic fields with opposite magnetic polarities. Arrows520,522,524,526indicate an example of the directions that current may flow to create such magnetic fields. The arrows show that the directions of the currents in the neighboring duct assemblies are opposite to each another. The magnetic field generated in this manner has an orientation normal to an elongated cathode surface and strength conductive to plasma guidance produced by passing current through the duct assemblies. In this filtered arc deposition mode, the metal vapor plasma emitted from the cathode486passes through the ducts between the duct assemblies thereby allowing undesirable macroparticles and neutral metal vapor constituencies to be eliminated and to deliver 100% ionized metal vapor plasma to the substrates.

In the remote anode arc plasma discharge (RAAD) mode, the current does not conduct through the duct assemblies488,490,492,494and the metal vapor plasma extracting magnetic field is not generating. In this duct-passive mode, the electrons emitted from the surface of the cathode486can pass freely through the ducts500,502,504,506which conduct the RAAD current between the cathode486in the cathode chamber484and the remote anodes530,532and534which surround the magnetron sources536,538and540which are positioned along the chamber wall506of the coating system380. At the same time, the duct assemblies488,490,492,494serve as a barrier which stops the heavy particles such as metal vapor atoms, ions and macroparticles, emitted from the cathode486to reach substrates. The RAAD plasma ionizes and activates the plasma processing environment in a processing area of the system380where the substrates are positioned. This results in the ability to conduct ion plasma cleaning, ion implantation ionitriding and remote arc assisted magnetron sputtering (RAAMS) yielding advanced properties of plasma processing products.

With reference toFIGS. 15A and 15B, a schematic illustration of a variation of the RAAMS system is provided.FIG. 15Ais a schematic side view of the RAAMS system whileFIG. 15Bis a schematic side view perpendicular to the view ofFIG. 15A. System530includes chamber532, substrate holder534with substrates536to be coated, primary cathodes538a, b, magnetrons540a, band remote anodes542a, b. Cathodes538a, bare located at side544(i.e., the bottom) of the chamber532in a cathode section548separated from the coating section550of the chamber532by chevron shield552, which is impermeable for heavy particle but allows the electrons to go through toward the remote anodes542a, bin coating section550. Shield552can be electrically floating or it can be connected to the positive terminal of either primary arc power supply554or an additional power supply (not shown). The primary arc anode556is located at the middle of the cathode chamber548between two arc cathodes: the cathode538ain a left compartment of the cathode chamber548and the cathode538bin a right compartment of the cathode chamber548. The substrate holder534with substrates536to be coated is located between magnetrons540a, b. The substrates face magnetron540aon left side and magnetron540bon right side. The remote anodes542a, bare located above magnetrons540a, band are separated from one another by an optional separation baffle560. Separating anode556, substrate holder534with substrates536to be coated and optional separation baffle560effectively divide chamber532into two sides (i.e., a left side and right side) thereby preventing hot jet562aassociated with cathode538alocated on left side of chamber532from flowing through the right side of chamber532toward remote anode542bfrom flowing into the left side of the chamber532toward remote anode542a. Remote anode542ais coupled with arc cathode538aon left side of substrate holder534and remote anode542bis coupled with the cathode538bon right side of the substrate holder534. Anode556, substrate holder534and optional separating baffle560effectively divide coating chamber550into two sections: a left section housing left cathode538a, left magnetron540aand left remote anode542aand a right section housing the right cathode538b, right magnetron540band right remote anode542b. This division forms two narrow discharge gaps or discharge corridors: a left gap separating left magnetron540aand substrate holder534on the left side of the coating section550and a right gap separating the right magnetron540band substrate holder534on right side of the coating section550. The width of the separating discharge gaps ranges from 2 to 20 inches.

In a refinement, the cathode target can be made of a metal having a gettering capability such as titanium alloy or zirconium alloy. In this case the shielded cathode electron emitting source also serves as a vacuum gettering pump which improves pumping efficiency of coating system530. To further improve the gettering pumping efficiency, shield552facing the evaporating surface of the cathode target538ain the cathode chamber550can be water cooled and optionally connected to high voltage bias power supply. When water cooled shield552is biased to high negative potential ranging from −50V to −1000V relative to cathode targets538aand538b, shield552is subjected to intense ion bombardment by metal ions generating by the cathodic arc evaporating process. Condensation of metal vapor under conditions of intense ion bombardment is favorable for pumping noble gases such as He, Ar, Ne, Xe, Kr as well as hydrogen. Moreover, water cooled primary anode556facing cathode targets538a, balso contributes to the pumping capacity by increasing the metal vapor condensation/gettering area.

Still referring toFIGS. 15A and 15B, it can be seen that several magnetron sources540are located above cathode chamber548in coating section550. Substrate holder534with substrates536moves along chamber532passing magnetrons562. Cathodic arc spot564moves along cathode target566of arc cathode538while being steered by magnetic steering coil570or other steering means. Experimental investigation of this system revealed that narrow plasma jet562has a high plasma density ranging from 1011to 1013cm−3and an electron temperature exceeding 2 eV (typically ranging from 3 to 20 eV). The majority of the remote anode arc discharge current flows along the narrow hot plasma jet562and has an arc current density ranging from 0.1 mA/cm2to 100 A/cm2. The rest of the coating section is filled by the cold and rare plasma with electron temperature typically below 3 eV and plasma density ranging from 108to 1011cm−3. The width of hot plasma jet562is typically from 1 to 5 cm while moving with the same speed as cathodic arc spot564which follows the steering movement of the cathodic arc spot564on cathode target566. It is believed that the most of the remote arc current conducts between cathode538in cathode chamber548and remote anode542throughout hot plasma jet562. It can be also seen fromFIG. 15Athat two hot plasma jets562aand562bform within the narrow discharge gaps between left magnetron540aand substrate holder534on left side of the coating section550and between right magnetron540band substrate holder534on the right side of the coating section550. Left jet562abridges left cathode538ain a left compartment of the cathode chamber548and left remote anode542aon the left side of the coating section550. Right jet562bbridges right cathode538bin a right compartment of the cathode chamber548with right remote anode542bon right side of the coating section550.

With reference toFIG. 16, a schematic illustration of a variation ofFIGS. 15A and 15Bwith a cathode in one of the compartments of the cathode chamber and with two cathodic arc spots is provided. In this variation, two plasma jets562aand562bformed between chevron baffle552and remote anode542above each of cathodic arc spots576aand576bbridge the current connections between cathode538and remote anode542. The direction of the remote arc current along jets562aand562bassociated with cathodic arc spots576aand576bare shown by the vertical arrows on these jets. The plasma distribution has maximums578aand578bnear each of the cathodic arc spots576aand576bmoving along the erosion corridor580on cathode target566either by a steering magnetic field created by a steering coil located beyond the target582(not shown) or by other means as described below. In this variation, the dimensions of the high ionization area is Ai˜L(magnetron)×W(jet). In horizontally aligned systems set forth above, the ionization area is only Ai˜W(magnetron)×W(jet). The increase of the magnetron sputtering flow ionization area by vertical alignment of arc jet562(parallel to the long side of the magnetron540) vs. horizontal alignment of the arc jet562(parallel to the short side of the magnetron540as in the parent case) is approximately L(magnetron)/W(magnetron).

Still referring toFIG. 16, a confined plasma streams (i.e., a plasma jet) bridging the discharge gap between remote anode542and cathode target566through coating region550, moves along direction d4while remaining parallel to the long side of the magnetrons540. The ends of confined plasma jets562move along direction d4as set forth inFIG. 16. Arc spot576forms on cathode580along the erosion zone578. The plasma field584at remote anode542and the plasma field578at cathode target580are confined dimensionally in a space from about 1 to 5 inches along direction d4. In one refinement, magnetic steering fields are used to accomplish the rastering movement along d4. In other refinements, this rastering movement is accomplished by mechanically moving cathode580along direction d4. In still other refinements, a thermionic filament cathode with secondary emission electrons moves along d4.

With reference toFIGS. 15A, 15B, and 16, an aspect of the relative sizing of various components of coating system530is provided. Remote anode542has a linear remote anode dimension Da parallel to the cathode target538. The horizontal area of location of vapor sources538(i.e., the four magnetrons shown inFIG. 15B) is also relevant. The area along the direction parallel to the short side of the magnetrons538has a linear vapor source dimension Dv. Cathode target566has a linear cathode target dimension Dc parallel to the remote anode542and also parallel to the short side of the magnetrons538. In a refinement, the linear remote anode dimension Da, the linear vapor source dimension Dv, and the linear cathode target dimension Dc are parallel to each other. In another refinement, the linear remote anode dimension Da is greater than or equal to the linear cathode target dimension Dc which is greater than or equal to the linear vapor source dimension Dv.

FIG. 17provides an alternative configuration of the remote plasma system utilizing a coaxial batch coating chamber layout with planar magnetron sources540a, blocated at the chamber walls and substrates to be coated536attached to the rotating carousel substrate holder592. Coating chamber590includes carousel substrate holder592with substrates536to be coated and a set of the planar magnetron sputtering sources540a, battached to the walls of the coating chamber590facing the substrates to be coated. Coating chamber590also includes cathode chamber600with primary cathode538and coaxial primary anode556located at the bottom of the chamber590and remote anode-ring596located at the top of the chamber590.

Cathode chamber600includes shield-housing598with openings598a,598bfacing toward the gap between the magnetrons540and the substrate holder592. Optional separation baffle560in the form of a cylinder is also installed in the rotating substrate holder592. Anode556, substrate holder592, and optional separation baffle560create a narrow coaxial gap within the chamber590between the magnetrons540and the substrate holder592to confine hot jets562and secure their position parallel to the axes of the chamber590. Openings598may be located coaxial to the substrate holder592. Cathode540has the shape of a ring coaxial with coating chamber590and with primary cylindrical anode556. Alternatively, several primary cathodes540are installed coaxially to the primary anode556in a cathode chamber548. The primary anode can also serve as a condensation surface to improve the pumping speed by gettering effect effectively absorbing the residual gases within a film forming on a surface of the anode556by condensation of the vapor plasma generated by the cathode538. This configuration increases the remote arc plasma density thereby providing a more intense ion bombardment assistance rate during magnetron sputtering. In this configuration, a denser zone of the remote arc discharge plasma is created in the gap between the magnetron target and substrates to be coated.

With reference toFIGS. 18A and 18B, a refinement with separate primary cathode chambers548for each magnetron sputtering source540is provided. In theFIG. 18A, cathode chamber548is positioned under coating chamber550. Magnetron540is positioned in coating chamber550immediately above the shield552separating cathode chamber548from the coating chamber550. Cathodic arc source538as a powerful electron emitter is positioned below the magnetron540. The size of the cathode target, which defines the dimension of arc spot steering zone, is ranging from ¼ to 2 times of the width of the magnetron target, but preferably within the range from 0.5 to 1.5 times the width of the magnetron target. Primary anode556is positioned above the cathode target566and has a dimension generally smaller or equal to cathodic arc target566. Magnetic steering coil570is optionally positioned under the cathode538for steering arc spots at the surface of cathodic arc target566. Remote anode542is positioned in a coating chamber550above the magnetron540providing that cathode538, magnetron540and anode542are aligned generally along the same line. High density plasma jet562forms within coating chamber550between shield552and anode542along the surface of the magnetron540above the cathodic arc spot602which is moving over the surface of the cathode target566by the magnetic steering effect provided by the steering magnetic field of steering coil570. Cathodic arc spots602and plasma jet562are aligned along a single vertical line parallel to the long side of the magnetron540bridging the discharge gap toward remote anode542. In this arrangement, the steering of the cathodic arc spots602at the surface of the cathode target566provides a corresponding steering of the high density plasma jet562with remote anode arc current directed along the direction parallel to the long side of the magnetron540, while the axes of the jet562is parallel to the long side of the magnetron540. Plasma jet562crosses the magnetron discharge in front of the magnetron target bridging the distance between the shield and the remote anode542and ionizes the sputtering metal atoms flow and gaseous environment in front of the magnetron sputtering source540within the area where the plasma jet562crosses the magnetron discharge. The increase of ionization and activation of the metal sputtering atoms and gaseous species in front of magnetron540is distributed evenly both along the direction parallel to the long side of the magnetron540and along the direction parallel to the short side of the magnetron540. The uniformity of the ionization ability of the plasma jet562along the direction parallel to the long side of the magnetron540is achieved by the uniform distribution of the plasma density and the electron temperature along the plasma jet562. The uniformity of the ionization ability of plasma jet562along the direction parallel to the short side of the magnetron540is achieved by repeatedly moving the jet562back and forth across the magnetron discharge from one end of magnetron540to another by magnetically steering displacement of the cathodic arc spot602on cathodic arc target566.

In a typical example, the primary arc discharge between the cathode538in the cathode chamber548and the primary anode556is powered by the power supply554a. The remote anode arc discharge between cathode538and remote anode542is powered by power supply608. Ballast resistor610is installed between remote anode542and grounded coating chamber550, which allows control of the voltage drop between remote anode542and grounded chamber550. When the micro-arcing occurs at the coating chamber550walls, electronic switch612will be closed thereby short circuiting remote anode542to the ground and effectively eliminating arcing, followed by re-ignition of the remote arc when the position of electronic switch612is open. Switch612may be also open during the time of igniting of the RAAD plasma. Ignition of the RAAD can be provided by applying high voltage negative potential either to magnetron540which starts the magnetron discharge or, alternatively, by applying high negative voltage to the substrate holder534establishing the glow discharge across the discharge gap between cathode chamber548and remote anode542. The high voltage discharge as a means for ignition of the RAAD can be used in either DC or pulse discharge mode. The dimensions of the magnetron sputtering target of the magnetron540are typically 10 cm width×100 cm tall. The dimension of the cathodic arc target566is typically about 10 cm, nearly equal to the width of the magnetron540target. The width of the plasma jet562is about 3 cm. The magnetically steered moving velocity of the arc spot602over the surface of the cathode target566is approximately 1000 cm/s. In this case, the repetition frequency of the plasma jet steering across the magnetron discharge zone will be approximately 50 Hz. Assuming the improved ionization rate within the area of the magnetron discharge crossed by the plasma jet56ais ˜30% the average ionization rate of the magnetron discharge plasma by the plasma jet562will reach ˜10%, which is at least an order of magnitude higher than that of the conventional magnetron sputtering flow. The improved ionization rate of the magnetron sputtering flow results in increased intensity of ion bombardment assistance during magnetron sputtering coating deposition process which yields coatings having nearly theoretical high density, low defects, high smoothness, and superior functional properties. The inline vacuum coating system utilizing a plurality of magnetron sources, each provided with a separate cathode chamber, is shown inFIG. 18B.

With reference toFIG. 19A, a further advanced variation of the systems ofFIG. 14-18is provided. Intermediate electrode-grid622is installed in front of the magnetron540, which effectively limits the area of the confinement of the high density plasma jet562in front of the magnetron sputtering target540. In this arrangement, cathode chamber548is enclosed within the enclosure628. Although enclosure628can be electrically grounded, it is preferable that it is insulated from the grounded chamber providing that there is no direct electrical coupling between the primary and the remote arc discharges. Enclosure628has opening630facing the discharge gap or plasma corridor632between the magnetron target634and the electrode-grid622. The length of opening630is generally equal to that of the width of the magnetron target634while the width of the opening630is less than the width d of the discharge gap632. Electrode-grid622can be composed of thin wires638made of refractory metals chosen from the group of W, Ta, Nb, Hf, Ti, Mo, and stainless steel. The diameters of the wires are typically from 0.01 mm to 2 mm. A diameter less than 0.01 mm may result in melting of the wire in a contact with RAAD plasma. A diameter thicker than 2 mm will absorb too much coating material from the sputtering flow. Wires638can be arranged in a screen of different patterns or as an array of single wires parallel to each another. Grid electrode622must be transparent to the sputtering metal flow with transparency better than 50%. The distance between the neighboring wires638in a screen or grid electrode622is typically from 0.5 mm to 10 mm. Distances between neighboring wires in grid electrode622less than 0.5 mm are impractical and can affect the transparency of grid electrode622. Distances between neighboring wires638in grid electrode622greater than 10 mm may not have enough plasma confining properties to confine plasma jet562within the discharge gap or the plasma corridor632. The distance d between the magnetron target634and the grid electrode622is typically from 10 mm to 100 mm. Distances less than 10 mm are too small to confine the arc jet562a, while distances greater than 10 cm are too large to provide a narrow corridor which can squeeze the plasma jet, effectively increasing its electron density, electron temperature, and the metal sputtering flow ionization rate.

Grid electrode622generally functions as an intermediate anode. However, it may also serve as a remote discharge plasma igniting electrode. In this latter case, switch642connects the negative pole of high voltage DC or pulse power supply644to grid-electrode622. When a negative high voltage DC or pulse bias potential is applied to the grid electrode622, it ignites the glow discharge providing the initial ionization within the remote anode arc plasma discharge gap632thereby initiating the RAAD plasma. After the RAAD plasma is ignited, switch642can connect the positive pole of the intermediate anode power supply646to the electrode-grid622transferring the electrode grid622in the intermediate anode mode when the electrode-grid622becomes an intermediate anode of the remote anode arc discharge. In this case, grid electrode622is connected to the positive pole of the power supply646, while the negative pole is connected to the cathode538. In a refinement, the electrode-grid can be connected to the negative pole of the power supply644during operation of the RAAD plasma, while the positive pole is connected to the cathode538. In this case, the potential of the electrode grid622will be negative in relation to the cathode538, but the potential of the electrode grid622cannot be lower than the cathode538more than two times of the voltage drop between the cathode538and the primary anode556. Electrode grid622can be also isolated from the other components of the coating chamber setup. In such cases, the potential of the electrode-grid622will be set at floating potential value determined by the plasma density and electron temperature in the RAAD plasma. The plasma density within the discharge gap632can be increased to the extremely high level by reducing the width of the discharge gap and increasing the remote anode arc current. This allows using sputtering target540ain the diode sputtering process without magnetic enhancement as required in the magnetron sputtering process.

The remote arc current density in jet562the remote arc discharge gap defined between the anode grid622and the magnetron540is ranges from 0.1 to 500 A/cm2. A remote current density less than 0.1 A/cm2 is not enough to provide a desirable level of ionization of the magnetron sputtering flow. The remote arc current densities more than 500 A/cm2 requires too much power of the remote arc discharge power supply which is not practical for the applications. High current density of the remote arc discharge (i.e., jet (562) within the discharge gap defined between the anode grid622and magnetron540can be achieved by using a DC power supplies646and/or608which can provide a DC currents ranging from 10 to 2000 A to remote anode542and/or the grid anode622or, alternatively, by using a pulse power supplies which can apply a positive voltage pulses to the remote anode542and/or grid anode622. The positive voltage pulses can range from 500 to 10,000 V and the associated current pulses can range from 1000 to 50,000 A.

With reference toFIG. 19B, a variation of the system ofFIG. 19Ais provided. Wires638in the grid-electrode array622are positioned parallel to each other and to the short side of the magnetron540. Each wire638is connected to the remote anode542via capacitor640and shunt resistor642while the diodes secure the direction of the current toward wire element638. During operation, before the remote discharge is ignited, capacitors640are charged to the maximum open circuit voltage of the remote anode arc power supply608. This arrangement triggers the cascade ignition of the remote arc discharge by igniting the remote arc, first between the cathode538and first single wire638positioned closest to the cathode538, followed by propagation of the remote arc discharge sequentially via all intermediate single wire electrodes638of the electrode grid array622toward remote anode542. After the ignition phase, capacitors640will be discharged and the potential of each wire638and of the entire electrode grid array622will be determined by shunt resistors642. If the remote anode arc discharge is extinguished, capacitors640will be charged again to the maximum open circuit voltage of the power supply608with the cascade ignition automatically repeated. Alternatively, the ignition is initiated by the control system. This approach can be also applied to the multi-magnetron system similar to that shown inFIGS. 16 and 18B. In this case the intermediate ignition electrodes of the cascade ignition arrangement can be positioned between within the gaps between the respective magnetron sputtering sources.

With reference toFIG. 19C, an additional advanced of the coating system ofFIG. 19Ais provided. Capacitively coupled RF electrodes648,650are positioned at both cathode end652and remote anode end654of the remote arc discharge column562. The RF generator and the matching network are installed in series with RF electrodes648to activate the plasma jet562by superimposing the RF oscillations along plasma jet562. The frequency of the oscillations can range from 10 kHz to 500 MHz. In a refinement, the frequency of the generator ranges between 500 kHz and 100 MHz. The commonly used 13.56 MHz RF generator is suitable for this purpose. When intense RF oscillations are created within the plasma jet562the plasma density, electron temperature and, subsequently, the ionization rate of the magnetron sputtering and gaseous plasma increase thereby resulting in an increase in the remote anode arc discharge ionization efficiency and activation capabilities. This further improves the properties and performance of the coatings and plasma treated surfaces by RAAMS discharge plasma. In another variation as illustrated inFIG. 19C, a pulsed high voltage generator or pulsed RF generator656is used instead of a continuous-wave RF generator thereby providing high voltage unipolar or RF pulses for ignition of RAAMS discharge as well as superimposed high voltage high current pulses during the coating deposition process. The repetition frequency of the high voltage high current or RF pulses range from 1 Hz to 100 kHz.

FIG. 19Dprovides a perspective view of the RAAMS module with an electrode grid. Cathode chamber548with the primary cathode (not shown) and the primary anode (not shown) is positioned under the magnetron sputtering magnetrons540. The electrode grid622is positioned in front of the magnetron540. The remote arc discharge, i.e., jet562, is ignited between the primary cathode (not shown) in a cathode chamber548and remote anode542. The remote arc jet562enters from an opening in the cathode chamber548into the remote arc discharge gap created between the grid electrode622and the sputtering surface of magnetron540.

With reference toFIG. 19E, a schematic of a system of another remote anode coating system is provided. Remote anode arc plasma cage622can be created in front of the magnetron target634of the magnetron vapor source540as shown illustratively inFIG. 19E. The remote arc discharge can be established between the primary arc cathode (not shown) in a cathode chamber548and the anode cage (i.e., grid622) and/or the top remote anode542. In this embodiment of the invention the remote anode arc plasma is streaming from the opening630in the cathode chamber548along the long side of the magnetron target634toward the grid anode622and/or the top remote anode542. Although the cage-grid remote anode622can be made of wires aligned in many different patterns the embodiment of the invention shown inFIG. 19Eutilizes the remote anode cage622composed of array of straight wires parallel to the long side of the magnetron target634.

With reference toFIG. 19F, which is a transversal cross-section of the system shown inFIG. 19E, a schematic of a system using an array of wires is provided. This array of the parallel wires consists of the outer array of wires622aforming an outer boundary of the remote anode grid-cage622. The remote anode arc plasma jet is confined within the anode cage formed by this outer array of anode cage wire622a. It can also optionally consist of the array of the inner wires622bwhich are positioned within the anode grid-cage622. When the positive DC or pulse potential is applied to the anode grid-cage in reference to the cathode in the cathode chamber548, the anodic plasma sheath is forming around each of the wire of the array of outer wires622aand the inner wires622b. The ionization efficiency within the anodic plasma sheath is greater than that of the background plasma which results in the improvement of the ionization rate of the magnetron sputtering flow hence contributing to further improvement of the coating properties. The role of the inner wires622bis also to divert the charged particles such as electrons and positive ions curling their trajectories, creating a pendulum effect, increasing the length of the trajectories of charged particles, and effectively trapping the charged particles within the anode grid-cage622hence increasing the ionization probabilities of the magnetron sputtering flow. This approach to plasma confinement can be also used along without a need of magnetic confinement. This allows using the sputtering target in a diode sputtering mode without magnets while the high density remote anode arc plasma is confined electrostatically within the anode grid-cage622. The characteristic distance between the neighboring wires in the anode grid-cage622shown inFIG. 19Eranges from 0.5 mm to 30 mm. The thickness of each wire is typically ranges from 50 micrometers to 3000 micrometers. The remote anode arc current density streaming along the target634parallel to its long side from the cathode chamber opening634ranges from 0.1 to 500 A/cm2. The remote anode arc current can be provided either by DC power supplies or pulse power supplies. The cross-section of the magnetron sputtering source540surrounding by the anode grid cage622is shown illustratively inFIG. 19F. The magnetron discharge647is established above the magnetron target7ainflicting a magnetron sputtering metal atomic flow649. The anode cage consists of the outer array622aand the inner anodic wire array622b. When wire is energized by applying the positive potential vs. the cathode in a cathode chamber (not shown), the anodic plasma sheath with enhanced ionization rate is established around each of the wires of the anode grid-cage622. The trajectories of charged particles (electrons and positive ions)651are diverting when the particle is approaching the anodic plasma sheath surrounding the array of the wires622a,b. In a refinement the wires of the anode grid-cage622is made of refractory metals such as W or Ta and their temperature is maintained in a range of 500-2500° C., which allows effectively re-evaporate the metal atoms of the magnetron sputtering flow which can stick to the surface of the wire. It is believed that high ionization rate within the anode grid-cage will make it possible to operate the sputtering vapor source in a pressure range below 0.5 mtorr and even without noble gas such as argon or krypton which thereby eliminating detrimental inclusions of the noble gas atoms in a coating lattice

With reference toFIG. 20, a variation in which the electron emission cathodic arc source with a non-consumable cathode is provided. Cathode assembly660includes a water-cooled cathode with a cylindrical shape or rectangular cavity. Rectangular cavity662includes an internal evaporating and electron emission surface664and the primary anode666generally consisting of a cylindrical or a rectangular insert668attached to the anode plate670. Anode insert668is extended within the cathode cavity662. Anode666is made of refractory metals chosen from the group of W, Ta, Nb, Hf, Ti, Cr, Mo and stainless steel. Anode plate670is isolated from the cathode by ceramic spacers672. Primary anode666is attached to the water-cooled plasma transfer vessel676via the spacers678, having small cross section providing high thermal resistance between the plasma vessel676and the primary anode666. The plasma vessel676includes opening680with facing the cathode538throughout the tubular anode insert668on side of the cathode538and the opening682facing the discharge gap between the electrode—grid622and the magnetron source540on the side of the coating chamber550. The length of the opening682is generally equal to that of the width of the magnetron target634while the width of the opening682is less than the width d of the discharge gap632. The spacers678can be made of refractory metal. In this case the plasma vessel676is electrically connected to the primary anode666. Alternatively, the spacers678can be made of non-conductive ceramic, making the plasma vessel676electrically isolated from the primary anode666. In any case the spacers678must have a small cross section providing a high thermal resistivity between the water-cooled plasma vessel662and the primary anode668. In operation the primary anode is heated by the arc current reaching the temperature when the re-evaporation of the metal transferred from the cathode occurs effectively recycling the cathode metal evaporating from the internal cathode surface669in the cathodic arc discharge.

Cathode vessel662is typically formed from a metal with a relatively low melting temperature and high saturating vapor pressure. Examples of such metals include, but are not limited to, Cu, Al, bronze and other low temperature alloys. Alternatively, cathode vessel662can be made of copper, but its internal evaporating and electron emission surface669should be covered by a thin layer of a metal with low boiling temperature (e.g., Zn, Cd, Bi, Na, Mg, Rb). Low temperature evaporating metals are easily re-evaporated by the hot primary anode when its temperature is from 600 to 1100 deg. C. The water-cooled internal surface of the plasma vessel676may also function as a condensation surface effectively preventing the flux of cathode atoms to flow into the coating chamber section550. It is should be appreciated that the variations ofFIGS. 18-20can be also used without electrode-grid622. In this case the opening in the cathode chamber548facing the coating chamber550should be positioned close to the surface of the magnetron target634, facing the area of the magnetron discharge where the density of the sputtering atoms is higher.

FIGS. 21A and 21Bprovide alternative configurations of remote plasma systems. With reference toFIG. 21A, coating system670includes substrate holder672positioned between magnetron sputtering source674and anode676. Coating system670also includes cathode chamber678which is of the design set forth above. This configuration increases remote arc plasma density thereby providing a higher ion bombardment assistance rate during magnetron sputtering. With reference toFIG. 21B, coating system680includes anode682which is composed of thin wires. Anode682is installed between magnetron target684and substrate holder686. Coating system680also includes cathode chamber688as set forth above. In this latter configuration, a denser zone of the remote arc discharge plasma is created in the gap between the magnetron target and substrates to be coated.

In another embodiment, a coated article formed by the methods and systems set forth above is provided. With reference toFIG. 22A, coated article726comprises substrate728having surface730and coating732disposed over surface730. In a refinement, the coating is a protective coating. Typically, the coating has a dense microstructure and a characteristic color. In a refinement, the coating includes a refractory metal reacted with nitrogen, oxygen and/or carbon to form a refractory metal nitride, oxide, or carbide. Examples of suitable refractory metals include, but are not limited to, chromium, hafnium, tantalum, zirconium, titanium and zirconium-titanium alloy. Chromium nitride is an example of a particularly useful coating made by the methods set forth above. In a refinement, the coating has a thickness from about 1 to about 6 microns. With reference toFIG. 22B, a variation of a chromium nitride coating, which is a multilayer structure formed by the methods set forth above, is provided. Coated article834includes thin layer836of an unreacted chromium layer disposed over substrate728and a thick stoichiometric chromium nitride layer838disposed over unreacted chromium layer736. In a further refinement, the multilayer structure further includes layer740of intermediate stoichiometric chromium nitride layer disposed over the stoichiometric chromium nitride layer738. Intermediate stoichiometric chromium nitride240has a stoichiometry given by CrN(1-x)where x is a number between 0.3 and 1.0. In a refinement, the thickness of the unreacted chromium layer736is between 0.05 and 0.5 microns, the thickness of the thick chromium nitride layer738is from 1 to 3 microns, and the intermediate stoichiometric chromium nitride740is from 0.5 to 1 micron.