IL194401A - Pulsed laser-arc source of uniform filtered carbon/metal plasma - Google Patents

Description

WOVlWK ¾Wp ΊΓ^ Ύΐρ» Pulsed Laser-Arc Source of Uniform Filtered Carbon/Metal Plasma FILD OF THE INVENTION The present invention is related to the systems and methods for coating deposition on the substrate in vacuum, wherein plasma is generated by means of a pulsed vacuum arc on the cathode-target, and plasma ions form layers on the substrate. That method has long been successfully employed in a wide spectrum of physical vapor deposition processes (PVD).

To be more exact, the present invention is related to the field of laser-induced cathodic-arc discharge plasma sources and, particularly, it is related to the field of laser-arc sources with effective 100% plasma filtration for the utilization in various fields, wherein particle-free plasma is required.

The present invention can be used in cases, wherein a high output, the plasma uniform flux and low consumable material loss are required, and can be used for highly productive deposition of isotropic zero-defect coatings on the product surfaces.

BACKGROUND OF THE INVENTION The problem of thin film coating deposition, wherein scientific aspects of physics, chemistry and mechanics are interlacing, is probably one of the most significant among current trends of the technology and material science.

Semiconductor and optical industries are the example of the importance of thin film coating application. High rate of these scientific industries development requires the coating continuous quality increase and the thin film production techniques continuous improvement.

A number of papers have been devoted to some experimental and commercial applications in microelectronics, microtribology and biomedical technologies [1].

Such coatings are also used in sensors, display panels (autoelectronic emitters) and photodiodes. Among the thin film deposition methods for superhard high quality DLC, the most successful should be mentioned - pulsed laser ablation (PLA), pulsed laser deposition (PLD) and deposition by filtered cathodic vacuum arc (FCVA).

FCVA usually provides high quality coating deposition. At present, FCVA is also extensively used for metal nitride films production (TiN, ZrN, CrN, TiAlN...). For instance, TiN film is employed for product decoration in imitation gold, as a protective coating on medical implants, in automobile industry, to increase cutting tool wear resistance.

FCVA process is also effectively used in industry for advanced ceramic film production because of its relative ease and simplicity. Another example of the process application is ultrathin silver film deposition, since these films possess unique properties and attract continuous attention of both industry experts and researchers. The ultrathin silver films are usually part of multilayer film structures.

Mentioned above and other applications require films having preset structural, electrical, optical and other characteristics. To achieve these characteristics, perfect FCVA sources are required able to control ion-plasma process effect on the film parameters and properties, which is a necessary step for producing coatings with new functional properties.

Arc technology is a conventional PVD technology for hard coating deposition [2] is characterized by a number of indisputable advantages: ■ high evaporation rate and high coating deposition output, ■ deposition technology high efficiency (efficiency itself, economical efficiency, profitableness), ■ high plasma excitation (activation) - almost stripped plasma and a high particle kinetic energy. The stationary vacuum arc discharge plasma as well as pulsed and quasistationary discharge plasma is characterized by a high amount of ions traveling from the cathode towards the anode with the energy (in eV) that exceeds the discharge voltage value (in V).

On the other hand, the arc technology has significant disadvantages, limiting its industrial application: ■ unreliable operation of the vacuum arc triggering (misfire), ■ low resource of the triggering devices, particularly, in pulsed and heavy current plasma sources, ■ the discharge instability, ■ random and interrupted arc discharge, ■ random and uncontrollable cathode spot travel, ■ the cathode surface non-uniform erosion (non-uniform wear), ■ deposited coating irregular surface features, ■ non-uniform film thickness, ■ macroparticle emission, and as a result, deterioration of the film produced, macro-inclusions and/or other coating defects (for example, micro-channels), ■ significant plasma flux loss at filtration and/or in plasma carrying duct.

There are some ways to eliminate the arc technology disadvantages without losing commercial efficiency, in particular: ■ laser-induced vacuum arc; ■ the cathode spot travel control; ■ prevention of overheating and melting in the cathode local points; ■ the macroparticle size and amount reduction in the arc discharge before the filter; ■ the increase in the cathode spot retrograde travel velocity; ■ arc firing time restriction (pulsed operation mode); ■ macroparticle separation from the plasma, that is, cathodic-arc plasma filtration (FCAD) ensuring macroparticle complete removal.

In vacuum arc coating deposition systems, the arc discharge triggering unit plays a significant part.

The triggering unit must not only strike the arc, which triggers the plasma generation process, but it is also required to "re-trigger" the process, if, for any reason, the arc discharge between the cathode and the anode is terminated. In the vacuum arc coating deposition process, the vacuum arc multiple interruption (extinction) is a common phenomenon, and on any of such occasion, the vacuum arc regeneration is required by means of the triggering device.

It should be particularly noted that the pulsed sources have some disadvantages concerning fast wear of the triggering devices whose operation is based on the arc discharge striking proximate to the cathode effective surface. The stable operation resource of such triggers is relatively small. The triggering devices in heavy current plasma sources, being affected by intensive erosion and rapid dust loading with the material of the eroding cathode, fail particularly fast.

One of the simplest ways of vacuum arc initiation is using mechanical devices, wherein the triggering electrode is forced to contact the cathode material surface for a moment and to let the current run through the electrode and the cathode. As soon as the triggering electrode is drawn away from the cathode surface, the electric arc strikes, being then maintained between the cathode and the anode electrodes within the chamber [3, 4]. The mechanical devices are awkward and prone to "welded grabbing" between the electrode and the cathode and contaminate the plasma at the moment of triggering. Besides, the mechanical devices are too slow (sluggish) and that is why, are unacceptable for a pulsed operation.

Some arc discharge triggering devices use the phenomenon of the transition of a high voltage glow discharge into a vacuum arc.

For instance, according to the invention of US Patent 4,673,477 [5], to trigger a heavy current arc discharge between the cathode and the anode, weak current glow discharge plasma is used, generated in a magnetic field proximate to the cathode at pulsed inert gas leak-in to the chamber; the inert gas pressure (argon or krypton) within the chamber being set from 0.1 to 500 mTorr, the cathode being supplied with a negative electrical potential of 100 to 3,000 V relative to the anode. In the electronic trap in crossed electric and magnetic fields, a discharge with closed electron drift strikes and above the disk cathode effective surface, dense annular plasma is produced.

So, the combination of a high voltage from a weak current power supply and a low voltage from a heavy current power supply, connected parallel to the discharge gap (to the cathode and anode) causes glow discharge plasma generation, which, in its turn, ignites the required heavy current low voltage arc discharge. As soon as the arc strikes, the high voltage power supply is switched off and the inert gas supply is terminated. The magnetic field is not switched off and is used in the arc discharge to stabilize and control the cathode spot travel.

The disadvantage of the method is that plasma flux at the initiation moment has unsatisfactory energy characteristic for coating deposition, and the coating produced at that very moment can negatively affect the result of the entire technological process. Besides, a slow arc discharge triggering, since it is impossible to start the inert gas supply immediately, is extremely inconvenient for pulsed operation and makes the arc discharge stable "re-triggering" difficult.

In US Pat. 6,936,145 [6], paper [7] and Pat. SU 1812240 [8], an electric break-down on the insulator surface was used to trigger the vacuum arc. The triggering device operation is based on the formation of spark discharges proximate to the cathode effective surface. A positive high voltage pulse is supplied between the triggering electrode and the cathode from an additional power supply. As a result of the break-down on the insulator surface, cathode spots are formed on the cathode and after that, the discharge is maintained between the cathode and the anode by means of the base power supply in a pulsed or stationary operation (DC). The initiation time may be within the range of tens of nanoseconds to milliseconds and is selected within the limits depending on the base arc discharge current acceleration time, that is, the base power supply lag. To evaporate the material stored in the cathode, that is, to wear the resource, the triggering system has to withstand up to 106 operating pulses without reducing the wear reliability during the operation.

An experimentally developed triggering device based on beryllium oxide ceramics [7] meets the requirement. Utilizing the ceramics having a high thermal conductivity makes it possible to avoid the insulator failure by high voltage break-down during its entire service life. The disadvantage of the method is the utilization of ecologically unacceptable ceramics and deterioration of the initiation conditions during the operation.

The disadvantage of all the ignition methods described is related to the fact that a large size cathode can cause the arc discharge occasional extinction in a random point on the cathode spot travel path. At retriggering, the cathode spots will start their travel from the same fixed point on the cathode where the arc discharge strikes. That may cause the coating deposition non-uniformity with large size cathodes and large area substrates.

So, a conclusion may be made that none of the vacuum arc striking methods described meets the requirements of the cathode unit reliable operation, provides the cathode material uniform wear and a large resource of the cathode-target material, reliably confines the cathode spots on the effective surface and provides a high resource of the cathode operation. The laser induced vacuum arc method is completely deprived of the above mentioned disadvantages.

The measures taken in order to remove macroparticles from the plasma flux are determined by their specific properties stated below.

Experimentally proved that the emission of the vacuum arc eroding cathode substance flux is accounted for the processes in the cathode spot, and that the main cathode mass is consumed due to the generation of the two particle flows: ion flow and the cathode material splashes (macroparticles) [9]; the cathode mass consumption in the ion phase per unit of the discharge carried being a constant value for the given material, whereas the erosion in the droplet phase depends on the peculiarities of the cathodic arc plasma source, particularly on the cathode heat condition [10].

Another important characteristic of the macroparticle generation process is that for different cathode materials, the lower the material melting point and the higher the cathode operating temperature, the larger the erosion droplet fraction. It has been found [11] that the cathode material mass consumption in the droplet phase increases several times when the temperature rises from 100°C to 500-650°C.

Therefore, to reduce the amount of macroparticles in the erosive plasma flux, the plasma source design should be provided with the cathode efficient forced cooling (as a rule with running water). The melt content in the cathode spot and, consequently, the droplet formation intensity are determined by the heat removal from the cathode spot active area to the surrounding cathode material mass and the mass temperature.

There are another two reasons for more intensive splashing at a heavy current and, consequently, at a large amount of the cathode spots and small size cathode effective surface (for example, on Ti cathode, when the average current density on the entire cathode surface exceeds 1 OA/cm2).

First, increases the probability that randomly traveling cathode spots reach the regions locally been heated up to the melting temperature by the neighboring cathode spots, thus increasing splashing.

Second, at a heavy current (>200 A), the cathode spot bunches are formed, which travel slower and that also increases splashing. These spots may be long confined in a local point, forming deep craters. The deepening of the craters enhances large size macroparticle (10-25 μπι) formation.

At a quite fast travel, the cathode spot stays at a given point of its path on the cathode surface just a short period of time. As a result, the spot local temperature does not have enough time to reach the level typical for stationary operation. While the cathode spot travels, the melt amount in its active area reduces and so does the amount of the material ejected by the cathode spot as droplets (macroparticles).

Therefore, the majority of the papers describe the methods which force the cathode spots to travel fast along the cathode surface.

The macroparticle formation is also accounted for the fact that microscopic projections (protrusions) formed during the arc discharge and exist on the graphite cathode surface can explode because of the high electric current running through them and heating them rapidly. It is especially true for porous graphite cathodes.

Some inventions have provided specific measures to avoid graphite protrusion formation, one of the possible sources of the macroparticle generation.

Negative consequence of the droplet flux formation is the fact that the base portion of the macroparticles scatters from the cathode spot at an acute angle with the cathode eroding surface. Since the maximum of the large particle flux density angular distributions are within the range of several degrees, protrusions, surface irregularities and solid droplets are formed on the cathode neighboring sections that, in its turn, also increase the macroparticle emission during the cathode travel onto the sections.

The macroparticle emission weakening due to shortening the time of the cathode spot staying at the same point is also achieved at the pulsed arcing. Paper [12] stresses a significant reduction of the macroparticle amount in the pulsed operation comparing to the vacuum arc constant operation. One hundred time reduction for the macroparticle of ~0.1 μιη and ten time reduction for the macroparticles of ~10 μιη.

Alongside with the main advantage of the macroparticle content reduction in the plasma generated, the coating formation by means of the pulsed arc discharge in vacuum has a number of other advantages.

In the pulsed sources at appropriate discharge current pulse amplitude and its relative duration, the electrode forced cooling becomes easier and the cathode spot local temperature decreases owing to the heat removal in the intervals between the pulses. So, there is no principal lower bound of the average discharge current value (unlike the direct current arc, which cannot exist at the current lower than a certain level). Actually, there is no problem of the cathode spot confining on the cathode effective surface.

The average discharge current value determining the average ion current on the substrate is controlled by selecting the pulse amplitude and relative duration. The average ion current, in its turn, affects the film deposition rate and the substrate heat demand. However, under the conditions of commercial production, the source high output is the key requirement; therefore, powerful plasma sources are of the principle interest. It should be noted, that to make the average current in conventional pulsed sources higher than the current in the stationary plasma sources is impossible because of the cooling problem in the pulsed sources.

However, it is possible to increase the pulse discharge current significantly and it is very important duririg dielectric coating deposition (diamond-like), since the ion energy in the plasma flux generated can be controlled by the arc current within rather wide limits. That makes it possible to do without employing a rather complex system of negative bias applying onto the substrate.

Still another cathode erosion property in the arc discharge should be taken into account. The neutral atom fluxes emitted by the cathode spots are small. However, hot macroparticles emitted by the cathode are additionally heated since their surfaces the ions and, evaporating, are served as the main source of neutral vapor within the discharge gap volume [13]. It is understandable, that as a result of it, the neutral atom angular distribution, to some extent, follows the droplet distribution in the discharge gap volume [14].

Owing to the macroparticle emission peculiarities and their interaction with plasma in the interelectrode gap, a number of methods and devices have been developed to reduce the macroparticle flux intensity in the low pressure arc discharge erosive plasma in the filter-free coating deposition systems. Although these methods of the macroparticle suppression do not provide the complete plasma cleaning, they are rather important.

Some designs use the systems, wherein the object to be plasma affected (substrate) is disposed within the line-of-sight range from the cathode effective surface emitting macroparticles, as filter- free systems. In other words, there are no system elements between the substrate and the cathode which can be a mechanical obstacle for the macroparticles traveling towards the substrate.

According to the invention of US Pat. 5,401,543 [15], instead of the macroparticle side deflection or filtration, the cathode is made of the material which does not generate macroparticles in the arc discharge. Using cathodes of vitreous carbon or pyrolytic graphite makes it possible to produce the coating characterized by the particle reduced content. However, it is clear that this method does not ensure complete absence of the macroparticles in the films.

An example of the most efficient pulsed carbon source is a plasma source with an annular anode able to control the ion energy. First, the source has been presented by Maslov and others [16]. Plasma was generated at a capacitor bank discharge between the cathode and the anode. The plasma flux was focused by a solenoid connected in series to the discharge gap. The arc was drawn by an annular igniter on the cathode effective face. The cylindrical cathode and the coaxial anode were made of pure graphite; the cathode having the diameter of 30mm was surrounded by 110mm aperture. Typical operational parameters were (100— 500)V- the discharge voltage of the capacitance of 2000 μΡ, the pulse repetition rate was (0.1— 35)Hz.

That design has proved the possibility of plasma ion additional acceleration up to (60— 100)eV. Sometimes, that type of plasma accelerator is referred to as a face carbon plasma accelerator or source.

Besides the absence of the macroparticle filtration, another disadvantage of the source is a substantial macroparticle starting flow since there is no retrograde travel of the cathode spots at the arc discharge heavy current, small cathode effective region and at a poor heat removal from the region. It requires frequent cleaning of the plasma carrying duct. High quality coatings can only be produced at the source low output.

The cathode material neutral atoms are not involved in the process of film deposition and can deteriorate the film quality (for instance, in case of diamond-like coating, they can increase SP2 fraction). In addition, due to the collisions with charged particles, the cathode material neutral atoms can change the primary plasma flux characteristics. As a result of the atom self-recharging, the neutral vapor higher concentration in the region proximate to the cathode causes the reduction of the fast ion amount and formation of slow ions in the plasma. Besides, the neutral atoms are ionized at the collisions with electrons, also forming lower energy ions than the ions traveling from the cathode spot. That can deteriorate the film quality since the low energy ions pass through the filter and hit the substrate.

The macroparticles trapped by the filter as well as the neutral atoms constitute the loss of the cathode material which clogs the anode and the plasma carrying duct. Accumulating in the filter, they decrease the filter capacity, requiring labor-consuming non-productive operations for periodic shut-downs and maintenance of the commercial systems. Therefore, some measures should be taken to reduce the neutral atom and macroparticle flow from the cathode spots on the cathode surface and before entering the filter.

So, it is advisable to give preference to the sources with "suppressed" macroparticle emission even in the situation when they are designed for the operation as part of the systems provided with efficient magnetic filters. Then, the plasma flux generated by the arc cathode spot is undergone double cleaning - at the stage of formation in the plasma source itself and then passing through the filter.

The above mentioned is first and foremost true for forming pure carbon plasma fluxes in high quality diamond-like coating deposition.

The essence of the technology for depositing coatings on tools, semiconductor elements, implants, decorative or optical products and its industrial applicability require the solution of some problems, the most important of which are ■ confining the cathode spots on the cathode effective surface, ■ uniform cathode material wear during long-term operations, ■ macroparticle filtration without the plasma flux significant loss, ■ high source output, ■ long-term and reliable operation, requiring no labor-consuming shut-downs, cleaning and the consumable cathode replacement.

Spontaneous arcing represents the cathode spots, traveling randomly. The random travel may cause the discharge instability, if the cathode spots travel on the cathode to the regions, wherein the arc discharge cannot be sustained. Additionally, during their random travel, the cathode spots can travel beyond the edges of the cathode effective surface and damage the cathode mount or the current contact jaw and insulator elements.

Another disadvantage caused by the cathode spot uncontrollable random travel is the cathode surface non-uniform erosion (non-uniform wear), and as a consequence, non-uniform substrate coating deposition.

US Pat. 5,451,308 [17] describes a planar cathodic-arc plasma source. The vacuum arc cathode spots are forced to perform a retrograde travel along the cathode-target by a transverse magnetic field of the current, passing through the cathode. The current is running from the cathode spot instant position to the current contact jaws. The cathode spot travel along the cathode effective surface according to any required time law is controlled by means of the cathode spot instant position sensors and controllable switches on the current contact jaws. The cathode spot travel control by means of electric signals does not depend on the arc current and the cathode length. The arc spot travel rate along the cathode-target exceeds 10 cm/sec, thanks to which the macroparticle amount and size in the coating have notably reduced. Besides, that source provides decrease in the production and operation cost as a result of replacing several local arc evaporators with a single planar one.

The basic disadvantage of the device is the switching key complexity and a short service life and also impossibility of the arc re-triggering at the point, wherein the arc discharge was extinct, and as a consequence, the coating non-uniformity.

In the previous technology, a lot of attempts have been made to solve the problems regarding the cathode spot tendency to stay rather long at some certain points of the target, which is especially characteristic of plane cathodes. That so-called arc dwelling increases the macroparticle flow and causes deep erosion in those points on the cathode surface that results in non-uniform coating and losses due to the wall deposition, the necessity of the cathode frequent replacement, increases downtime and makes the maintenance more complex. The arc dwelling in certain points of the cathode is a common problem of the previous technology, which is solved by using magnetic fields causing the cathode spot directed travel. That solution also provides the macroparticle flow reduction. The macroparticle level in the vapor flow generally depends on the cathode spot travel rate and on the arc current value.

To control the cathode spot longitudinal travel in order to improve the coating uniformity and the cathode uniform wear (deposition rate, quality cost), some designs use different methods of supplying different points of the cathode with and switching current running along the cathode from the point of the cathode spot localization to the current contact jaw. The current magnetic fields force the cathode spots to perform retrograde travel along the cathode towards the negative contact jaw having a power supply unit. In that case, the current was switched directly by a mechanical switch, electromechanical, electromagnetic, electronic and other switching devices were used for current switching between the contacts.

Controlling the cathode spot travel, in other words, forcing them to travel in a certain direction, it is possible to obtain the cathode more uniform erosion, less splashing and, consequently, more uniform high quality substrate deposition, which is impossible to produce at the cathode spot random travel. These methods employ sensors to detect, stop and force the cathode spots to travel in the opposite direction in case they come close to the cathode edge.

The methods mentioned work relatively well, but they are expensive and rather complex. They require additional power supplies and a lot of complex electronic devices, sometimes prone to HF interferences produced by the vacuum arc. The designs may be hard to maintain and repair in case of failures. Besides, at high speed and heavy current used in the methods according to the inventions, the switches are very complex and expensive.

According to US Pat. 5,269,898 [18], some devices are used to produce on the cathode surface a closed loop magnetic field similar to the magnetron magnetic field, in order to control the cathode spot travel on extended plane cathodes; said devices are disposed under the cathode. According to one of the embodiments of the invention, a solenoid is used as the magnetic field generator, producing a transverse magnetic field above the cathode. However, while traveling in such a magnetic field, the cathode spots wore out a deep narrow slot along their way, that is, caused the cathode non-uniform erosion. Therefore, the invention provides special means for alternating switching on/off the closed loop magnetic field. During the arc discharge, the solenoid is supplied with short-term pulses alternating with long intervals. When the solenoid is supplied with the current short-term pulse, the cathode spots perform a short distance directed retrograde travel in the transverse magnetic field along the magnetic channel. During the intervals, that is, without magnetic field, the cathode spots travel randomly, diffusely moving off the central region. So, owing to short directed and long random motions, the cathode evaporates uniformly in the arc discharge.

Other embodiments of the invention use a few windings and more complex current commutation by utilizing pulsed or sinusoidal current, making it possible to combine transverse, longitudinal and random travel of the cathode spots to produce the cathode uniform wear and the uniform coatings. The disadvantages of the invention are a low output a large macroparticle flow since the cathode spots are localized in one small region of the extended cathode, and at a heavy current, as described above, it may cause a strong splashing.

According to paper [19], a stationary Ti evaporator is developed, comprising three rods connected as a three-beam star. The cathode spots are confined on the evaporator-cathode effective surface and Ti is consumed uniformly by the cathode spot retrograde travel in the magnetic field of the currents alternately running towards three symmetrically disposed current contact jaws. The magnetic field accelerates the cathode spot travel thus reducing the macroparticle generation, since there is a decrease in the average time, the cathode spot stays in each crater on the way of its travel. Negative leads of three-phase (or six-phase) rectifier diodes, feeding the arc discharge, are not connected in one point (as in the conventional rectifier) but connected individually to the current contact jaws. The positive rectifier diode leads are connected (as usual) in one point and then to the anode (the vacuum chamber walls).

After striking the arc by means of the igniter in the centre of the star, the cathode spots travel along one of the rods in the magnetic field of the current flowing from the cathode spots to the current contact connected to the rectifier diode which is conducting at that moment. The next moment, according to the three-phase rectifier operation mode, another diode is conducting, and the cathode spots travel to another current contact, then to the following one and so on. This way, each of the three current contacts is alternately connected to the rectifier for a period of time equal to 1/3 of the supply line period. The rod length, depending on the discharge current, is selected so as to let the cathode spots cover the distance between the rod ends for 1/3 of the supply line period. The cathode spots successively run over the rod surfaces uniformly evaporating Ti in all the directions. A significant decrease in the macroparticle flow has been noticed. It has appeared advisable to employ a three-phase current contact jaws to feed a disk evaporator having a face region of Ti evaporation. In comparison with one current contact jaw, the cathode material wear gets more uniform. Crater and hole formation on the effective surface is completely eliminated. Evaporators shaped as torus with tree symmetrical current contact jaws have also been tested. The disadvantage of that device is that it is impossible to vary the cathode dimensions in a wide range.

US Pat. 6,926,811 [20] describes a cathodic-arc source for substrate coating deposition by using water cooled cathodes of the material deposited, having a cylindrical tubular shape and rotating about their cylindrical axis during the deposition process. Magnetic field sources, a permanent magnet and an electromagnet coil, are disposed inside each of the cathodes and travel up and down during the deposition process causing the arc cathode spots to migrate up and down according to "magnetic field maximum" law. Alternatively, that magnetic field configuration also provides the cathode spot travel round the cylindrical cathode. Conventionally, in the coating deposition process, the magnets are moved up and down along the cathode length.

The disadvantage of the invention is its low output.

US Pat. 5,895,559 [21] describes an attempt to confine the cathode spots on the cathode effective surface by using heavy current resistors between the cathode two outputs for spontaneous control of the cathode spot travel. Electrical connection to the cathode opposite sides is accomplished via two or more resistors having a small resistance value and a high temperature coefficient of resistance. The two resistors are alternately heated by the arc current and cooled by the cooling system so as to force the arc current to switch from the hot resistor to the cold one according to Kirchhoff s laws. The cycle is periodically repeated because of the heating-cooling process lag. The resistor positions, the resistance value and the value of the temperature coefficient of resistance are selected so that during the switching time, the cathode spots travel along the entire cathode surface. The resistors are preferably to have a low resistance and a high temperature coefficient of resistance at the cathode current of ~300 A. However, the design having resistors cannot efficiently control the cathode spot travel rate and path, and as a result, the arc tends to hang up on the idle side of the cathode. That hanging-up causes the cathode material accumulation in the discharge gap, rapid damage to the insulation and untimely failure of the entire system.

According to the invention of US Pat. 6,936,145 [6], a cathode provided with the external mechanical lever current switching between two or more electric contacts on the cathode was designed. A rotary cylindrical collector with alternating sector inserts of copper and insulator and brush contacts disposed round the cylinder was used as the switch. The switching rate could be controlled by varying the cylinder rotation rate by changing the electric motor revolutions or by means of a reduction gear.

According to the invention, a preliminary mechanical treatment of the cylindrical cathode surface in the form of spiral slots or thread winds was employed. Different cathode shapes were used, such as internal cylindrically profiled cathode as a rod or a tube to deposit coatings on the internal surface of the product to be deposited; cylindrical, toroidal or annular cathode to deposit coatings on the external surface of the product to be deposited. According to the invention, the device can also utilize the cathode at currents up to 600A. In addition, the invention employs an anode/cathode layout, wherein both the anode and the cathode are arranged within one assembly and there is no need to use the chamber body as the anode. The layout helps to avoid undesirable arc discharges on the cathode idle sections as well as between the current conducting elements and the chamber walls, as it occurs using the previous technology, when the vacuum chamber is connected to the anode.

Considerable success has recently been achieved and many methods utilizing laser sources for PLD (pulsed laser deposition) and/or VAD (vacuum arc deposition) have been experimentally tested.

US Pat. 6,110,291 [22] describes a plurality of design embodiments able to form uniform high quality thin films on large areas by PLD, without damaging the substrate, and also presents some methods for controlling and adjusting the film properties during the coating deposition.

In particular a plurality of methods for controlling the laser beam pulses and the laser spot, scanning on the target surface; a design variant using a rotatable multiangular mirror, providing the laser beam direction change; a design variant using an acoustic optical element controlling the light beam direction by means of a sound wave; a design variant using vibrating or rotating mirrors for turning the laser beam; a method for controlling the laser beam repetition rate/the laser spot travel rate ratio so that the same point on the target cannot be irradiated by the laser beam twice or by a greater number of pulses; a method and possibility of irradiation of the plurality of different regions on the target by a sequence of laser beams producing a thin film on a large area without moving the substrate; a method and the possibility of dividing one laser beam into a plurality of beams directed onto different regions on the target surface; a design variant, wherein one laser beam alternately irradiates a plurality of targets, and a method for moving the plurality of targets; a method and the possibility of dividing one laser beam into a plurality of beams in order to treat different regions of the target with the corresponding individual laser beams. That provides an effective and simultaneous coating deposition on the entire target surface without increasing the amount of the laser sources; one of the film quality laser control methods; one of the design variants and the possibility of a magnetic field generation in the space between the target and the substrate to force the plume electrons and ions to propagate along the magnetic lines of force. The plume spreads radially and so, a uniform thin film can be formed on a larger substrate surface by a single plume; a design variant, wherein the laser beam is incident normal to the target surface through the opening in the substrate; the transverse expansion of the plume irradiated by the target getting larger, thus providing a more uniform film; according to another design variant, the transverse expansion of the plume irradiated by the target is achieved by focusing the beam on the target surface and by increasing the energy density on the target surface; a design variant, wherein a sequence of lasers are used to increase the number of the plumes generated simultaneously. That makes the formation of uniform film on a wider region easier. A larger amount of lasers causes an increase in the film formation rate and output. In the design, mirrors, targets and substrates can travel providing a uniform film production. The device controlling the motion of these elements provides random travel, simple rotation and differential rotation, ■ the design variants with a transverse or longitudinal magnetic field are used to separate and eject ions from the plume and to prevent the ions from hitting the substrate surface. This method is used for specific coatings that need just neutral particles, ■ the variants described use targets of different shapes - cylindrical, plane and fragmentary.

So, the object of producing a uniform film on large areas is achieved by complicating the movable optical devices and by increasing the number of the lasers. However, the cathode small sizes and the alternating switching of the laser ablation pulses cannot provide sufficient output for industrial application.

In the light of the problem described, the most advanced is the laser induced arc discharge method.

The results obtained in paper [23] show that tribotechnical and mechanical properties of a-C and CNX actually do not depend on the method they are produced, PLD (pulsed laser deposition) or VAD (vacuum arc deposition). Therefore, these methods can be considered interchangeable for growing a-C and CNX films. This fact, in its turn, makes it possible to substitute commercial coatings produced by the laser method with the similar coating produced by a cheaper and more productive vacuum-arc method.

Even though, as described above, for a wide spectrum of technologies, pulsed laser deposition (PLD) has been successfully employed, but for industrial application, plasma generation by vacuum arc deposition (VAD) is more efficient. In addition to such factors as ion kinetic energy and plasma ionization, plasma formation efficiency, characteristic of plasma assisted coating deposition processes, is of great importance for practical applications.

Unlike plasma, produced by a laser beam, having ion (10-1000)eV and neutral spectrum depending on the power density, arc-discharge plasma is characterized by stripped plasma having average ion energy of more than 20 eV, depending on the arc pulsed current. DLC films deposited by VAD reach SP3 content (up to 85%), the result comparable with the films deposited by mono-energy ion beams [24].

Comparing to the arc discharge in continuous operation, which is hard to control, laser induced and laser controlled pulsed vacuum-arc deposition (laser arc) is a method for controlling the material erosion process and for decreasing the macroparticle emission. The laser arc combines the advantages of PLD perfect controllability and VAD plasma structure high output. Regarding the control flexibility and plasma parameters high reproducibility from pulse to pulse, sources with laser ignition [25] are of great interest.

The principles of laser-induced vacuum arc vapor formation (laser arc) are described and analyzed in detail in [26, 27). Nd-YAG pulsed laser radiation is focused on the cathode surface into a spot of 150 μπι at the edge of the plane anode, disposed at a distance of 3-5mm from the cathode. On the cathode, a unipolar arc strikes, which then goes into the principle discharge between the cathode and the anode, the cathode erosion region is located symmetrically about the ignition point. For the cathode uniform erosion (burning-out), its surface scanning by the laser beam is provided. In the device described, the cathode is shaped as a cylinder having the possibility to rotate and simultaneously be scanned by the laser beam along the element. The selection of high repetition rate of the discharge pulses (up to 500Hz) at their short length provides a significant decrease in the macroparticle amount and size in the plasma, the macroparticle size being not more than 1 μπι.

The vacuum discharge was induced by the laser radiation focused on the target into a spot of 200μπι in diameter by means of Nd glass systems (wave length 4=1.06 μιη) in mode synchronization operation (output radiation energy JR>=\3, light pulse duration r=27ps, the target power density ~1014W/cm2).

Paper [28] and US Pat. 6,338,778 [29] describe the utilization of arc sources disposed in a vacuum chamber as cylindrical cathodes of different materials and plate anodes disposed at a distance of 5mm from the cathode cylinder. The cylinder may be tens of centimeters high and of the same size as the product to be deposited. The cathode diameter may be large enough to provide a long service life before replacement. The substrate holder is positioned in a vacuum chamber and electrically insulated. The substrate holder design provides its rotation, water cooling or heating and the possibility to be connected to the negative bias pulsed source. The basic assemblies are an oscillating beam pulsed laser (Nd-YAG Q-switching laser), a pulsed current generator, a pulsed bias supply, gas flow system and computer control system of all the components and technological steps.

The basic process comprises a pulsed cathodic vacuum arc induced by concentrated laser pulses. At the arc pulse length between 20 and 100 μβ, the cathode spot evaporates just a certain region surrounding the ignition point, the laser focus. So, the cathode material local overheating causing the macroparticle emission, an inherent drawback of the conventional vacuum arc, has been actually decreased: the arc spot position is controlled by the laser focus shift (scanning) on the rotating cylindrical cathode, making possible its orderly evaporation. Using cathodes made of different materials, it is possible to produce multilayer structures with easily changeable variations.

According to paper [26], the material was evaporated in a vacuum chamber at a pressure about lO^Pa, plasma was produced by a pulsed vacuum arc discharge triggered between the cathode, comprising the materials used for coating deposition, and the anode (water cooled); the cathode spot travel was time and position controlled by the laser pulse. A commercial Nd- YAG Q-switching pulsed laser ensuring the power density of more than 5xl08W/cm2 with a repetition rate of lkHz was used. The material erosion in the cathode spot was mainly obtained by the arc discharge pulse. Specially designed pulsed power supply provided the arc current of (20— 100)μ8 duration, max. current of 1000 A and the repetition rate up to lkHz.

The laser control, the laser beam travel and the cathode rotation have made it possible to obtain a uniform erosion of the entire barrel surface during the entire period of operation.

As a whole, the experience of practicing the laser induced vacuum arc devices has shown that: ■ The laser arc systems for industrial coating deposition are an alternative method for increasing the arc discharge controllability and simultaneously achieving commercially acceptable output. The laser induced arc method can provide the increase in coating deposition rate up to the value of the order of ΙΟμιη/h, using maximal current of lkA, the pulse length of 20 to 100 μβ and the repetition rate up to lkHz.

■ Very hard hydrogen-free a-C film coatings, both simple layers and metal layer combinations (multilayer structures) are characterized by high hardness, high Young module, high wear resistance and high chemical resistance. The laser arc method is preferable for thin film deposition at temperatures lower than 100°C and high coating deposition rates, and also for the substrate material prone to temperature.

■ Laser arc source can be adapted to the existing equipment and can also be combined with other conventional deposition methods.

The entire cathode surface material uniform wear is provided by systematic controlled scanning (the laser beam oscillations) and the cathode rotation.

The material erosion occurs only around the point where the arc is induced by the pulsed vacuum arc discharge controlled by the laser, therefore, the longer the vacuum arc pulse, the longer the cathode spots travel randomly, which can cause the macroparticle higher emission. However, it is impossible to reduce the vacuum arc pulse duration with respect to the laser pulse length for the reasons described above.

The macroparticle emission was greatly reduced by preventing a local overheating as a result of the cathode spot existence time and travel limitation controlled by the laser spot. However, the method does not eliminate the macroparticle flow on the substrate.

A significant disadvantage of the laser induced arc discharge method (as well as the laser ablation method) is dust loading of the beam input window to the chamber. The transparency of the window decreases by 60% after two-second period of the source operation with a graphite cathode due to a carbon film deposition. Conventionally, the glass is cleaned by the same laser beam. For the cleaning, it is necessary to consume part of the laser beam power. That means that the laser power should be higher than required for vacuum arc striking (or for producing the required amount of the laser plasma).

To protect the window from dust loading, a film of transparent polymer material can be placed before the window. During the source operation, the film moves before the window, continuously renewing its transparency. It complicates the design and is not always acceptable, for instance, at a long-term operation without opening; the protective film reserve inside the vacuum chamber should be too large.

Close to the present invention is the device according to DE patentl 9850218 [30] and US patent 6,533,908 [31]. According to these inventions, the plasma flux is generated by a laser induced pulsed arc source. The system described uses an additional absorbing electrode, unlike the design of the previous plasma filters, wherein the plasma flux is controlled by crossed electric and magnetic fields. There is no magnetic field, and the additional electrode has electric positive potential with respect to the plasma. The additional electrode produces an electric field. The plasma ions and electrons travel through the electric field, as a result of which negatively charged particles, mainly the electrons are absorbed by the absorbing electrode, whereas positively charged particles, mainly, the ions are ejected and reach the substrate. Neutral particles and the particles having a high mass/charge ratio due to their sizes are slightly affected; therefore, they can be separated from the plasma flux. According to the final variant of the invention, the deflecting electrode is served as an anode. It should be noted that not only electrons, but also some amount of macroparticles and clusters are precipitated on the electrode because, as mentioned above, they have a negative potential with respect to the plasma potential.

A significant disadvantage of the device is that since there is no magnetic field, the deflecting electrode potential required to affect the plasma flux ions is achieved at very heavy currents on the electrode, the currents exceeding the arc current between the cathode and the anode. Actually, it means that the plasma flux loss is rather great.

The present invention is the development and improvement of the efficient cathodic arc filtered plasma source described in papers [32, 33, 34]. The source has a high efficiency factor, 7.5%. The source is based on the principle of forming a stable current-carrying Hall layer in an arched, toroidal or barrel transverse magnetic field in a vacuum arc discharge on the cathodic-arc plasma boundary. The Hall layer is over the cathode surface, follows the magnetic field configuration and is normal to the plasma flux direction from the cathode spots. The plasma boundary in its one projection coincides with the magnetic field and in its other projection has the shape similar to cardioid. That provides maximal ion reflection in the electric field of the Hall layer towards the deposition area, while undesirable macroparticles, not affected by the magnetic fields and electrostatic forces are unable to reach the workpieces to be deposited. The anode is disposed away from the cathode at a distance nearly equal to the cardioid radius and has an orientation at which the discharge current, running along the anode shaped a rod or as a structure of strips, produces an additional magnetic field aligned with the arched magnetic field generated by permanent magnets or electromagnets. The cathode spots travel along the cathode efficient surface and are confined on it during an operating pulse length also by the magnetic field arched configuration [34].

The ion source based on that principle usually comprises a few cathode units disposed orderly in a circle or in a row. Each cathode unit comprises a cathode of consumable material (metal or graphite) and a magnetic system. Each cathode is arranged so that its so-called effective surface with cathode spots thereon, being the cathodic-arc plasma sources, is turned to the closed side of the chamber beyond the line of sight range from the region, wherein the products to be deposited can be arranged.

The source is designed for pulsed operation. During the pulse time, said cathode spots are forced to perform retrograde travel in the magnetic field from the ignition point on the one end of the cathode towards the other end of the cathode, where a current-carrying electrode is positioned; the arc discharge being alternately induced on each of the cathodes [33].

A vacuum arc filtered plasma source with a conical cathode and a toroidal magnetic field designed for stationary and quasi-stationary operation is also based on the concept of the current-carrying Hall layer in a transverse magnetic field. According to that design, the conical cathode is aligned with the source axis, the magnetic system generates a toroidal magnetic field in the cathode region, the anode is shaped as a truncated cone divided into strips by slots so that the anode current transverse magnetic fields are normal to the permanent magnet magnetic field close to the cathode surface [33].

The disadvantages of the source stem from the disadvantages of the electron triggering used, that is, for a strong material wear proximate to the ignition local point. Second, during their travel in the arched transverse magnetic field, the cathode spots wear a deep narrow slot along the cathode path, that is, cause the cathode non-uniform erosion, as known from a plurality of practical data, mentioned, for instance, in US Pat. 4,724,058 [18]. It is aggravated by the small size of the cathode effective region.

All these reasons cause a sufficient starting flux of the macroparticles before the filter. It means that the cathode material consumption is increased, whereas the macroparticles clog the anode and the walls of the plasma carrying duct. It involves expensive and labor consuming measures for the equipment periodic shut-downs and maintenance.

The same filtration method is used in Israel Pat. Pending 178522 [35], wherein a combined plasma source is described, characterized in that its vacuum chamber comprises a filtered source of cathodic-arc metal plasma aligned with an argon ion source with closed drift anode layer plasma acceleration.

The disadvantage of the combined source is that a plurality of cathodes disposed discretely, even though close enough to one another, is not able to provide the plasma flux high uniformity.

The primary object of the present invention is an improved system, possessing the advantages of the previous laser plasma and laser-arc plasma sources and devoiding of their disadvantages, namely, high macroparticle starting flow, the plasma flux great losses at filtration and transportation towards the substrate (small plasma efficiency factor), the window dust loading and the laser power loss for the glass cleaning involved.

Another object of the present invention is an effective system, reliable in operation, providing the cathode-target starting material uniform consumption and, as a whole, capable for a long-term large-size industrial application for highly productive coating deposition, first of all, for producing uniform high quality superhard, protective, bio-compatible, low friction, including composite, coatings (for instance, diamond-like, TiN, TiAIN, TiAlBN) on extended large area surfaces of large-size products as well as on a plurality of small products.

SUMMARY OF THE INVENTION According to one embodiment, the object stated is achieved by the design offered - a pulsed filtered cathodic-arc plasma source with a rotatable conical cathode, a stationary magnetic field and a laser induced vacuum arc.

According to other embodiments of the present invention, the object stated is achieved by the design offered - a pulsed filtered cathodic-arc plasma source with a stationary conical or annular cathode, a traveling magnetic field and the laser scanning of the vacuum arc striking points.

The design offered is characterized by the following important aspects, which help describe the basic structure of the present invention: ■ Vacuum arc pulses are induced by concentrated laser pulses. The laser pulse is focused on the cathode surface and produces a small plasma cloud, from which the arc discharge develops between the cathode and the anode.

The laser arc efficiency and reliability depends, to a great extent, on the probability of the laser induced vacuum arc discharge. High reliability of the vacuum arc striking (p>50%) on metal or graphite is ensured at laser power density in the active zone of ~108 W/cm2, that can be realized with a cheap pulsed Nd-YAG laser [25].

■ The system of magnets or electromagnets forms an arched transverse magnetic field on the cathode surface. The macroparticles are filtered directly within the arc discharge gap by using the effect of the Hall layer formation on the plasma boundary at the arc discharge in the arched transverse magnetic field, reflecting at which, the ions change their path so that they can travel from said cathode effective surface to the area, wherein the products to be deposited are arranged.

The design offered is characterized by a complete filtration of cathodic-arc plasma from macroparticles, droplets and neutral atoms. And owing to high plasma efficiency of the method, the working material loss in the plasma carrying duct is significantly reduced.

■ During the vacuum arc pulse length, the cathode spots perform a retrograde travel in the transverse magnetic field from the striking point along the cone generator.

The laser pulse length is less than 100ns, that is, two-three orders of magnitude less than the arc discharge duration equal to the cathode spot retrograde travel time along the cone generator. So, the laser pulse energy (some mJ) is much lower than the energy of an arc discharge pulse (~20J). Therefore, the cathode material erosion occurs in the cathode spot mainly due to the arc discharge pulse. Any electrically conductive material (for example, graphite, Ti, copper) can be used as the cathode-target.

The cathode spot retrograde travel from the laser-induced arc point, according to the present invention, (unlike conventional laser arc devices, characterized by the cathode random travel proximate to the laser-induced arc point), provides the reduction of the macroparticle starting flow from the cathode since an orderly motion in the transverse magnetic fields used is faster than the random one.

■ The anode design has a comb structure shaped as narrow sections electrically connected to the anode cooled annular body via ballast resistors.

■ Outside the discharge gap, a second annular anode is disposed as well as the windings producing a longitudinal magnetic field along the source axis parallel to the plasma current- free flux. The second annular anode and the longitudinal magnetic field form a plasma carrying duct for the plasma flux transport towards the substrate. That system not only prevents ion flow loss, but also increases the arc discharge stability in the arched transverse magnetic field.

The ability of cathodic-arc plasma to improve the deposited coating quality (properties) can be significantly extended, if some methods are developed to control the particle energy spectrum used for forming films. It is true just for the plasma ion component.

In the well-known conventional sources based on vacuum-arc discharge, a plasma jet emitted from the cathode surface travels towards the anode and passing through it, gets into other parts of the vacuum system (for example, into the extractor). Usually, the discharge gap is located inside the solenoid, producing a magnetic field along the discharge axis. In a strong magnetic field, the plasma jet diameter is sufficiently less than the diameter of the anode opening and the cathode substance (ions) actually does not hit the annular anode; the current closing occurs because of the fast electron escape (having a large Larmor radius) from the plasma boundary surface onto the annular anode. Thus, between the cathode and the anode, a current carrying jet is realized and behind the anode cut, the jet gets currentless. The calculations presented in paper [36] have shown that outside the anode, the currentless plasma jet preserves high temperature and electron density values, if there is a strong axial magnetic field. Therefore, in ion sources based on the vacuum arc, for producing high energy ions, the magnetic field is applied not only to the cathode-anode gap, but also to the currentless portion of the plasma jet in order to prevent its expansion and cooling. This experience has been taken into account in the present invention, wherein current closing occurs due to electron drift onto the anode in the Hall layer on the plasma boundary in crossed ExB fields [34]. The Hall layer shape follows the magnetic field configuration. The cathode substance (ions) is reflected at the Hall layer so that only a small fraction of it hit the anode. A current carrying plasma flux is realized between the cathode and anode, whereas outside the discharge gap the plasma flux becomes currentless.

When there are no magnetic fields, the average carbon ion energy in the cathodic-arc plasma is about (20-25)eV [37]. According to the present invention and in the cathodic-arc plasma source with a magnetic field across the discharge axis described in paper [34], the voltage across the discharge gap is monotonously increasing with the increase in the magnetic field strength. In the region of the arc discharge stable existence, the discharge voltage sufficiently exceeds a typical voltage of the vacuum arc (up to 80V instead of 20V without the magnetic field). The increased voltage across the discharge gap means that much more energy is invested into the plasma. It leads to the electron temperature rise and higher values of the average ion energy as well as to increased negative self-bias on the substrates. The increased self-bias, in the long run, causes the energy increase in ions reaching the substrate.

According to the present invention, another annular anode is disposed in the magnetic field guided along the ring axis parallel to the plasma currentless flux, that is, normal to the magnetic field within the discharge gap to form a plasma carrying duct outside the discharge gap. The magnetic field in the currentless fraction of the plasma jet not only prevents the ion flow loss by confining the plasma flux from expansion and cooling, but also increases the arc discharge stability in a wide range of the arched transverse magnetic field variations.

That makes it possible to control the arc discharge voltage by varying the magnetic field within the discharge gap without reducing the ignition reliability or causing the arc discharge instability and without reducing the plasma efficiency. With the magnetic field increase, the voltage across the discharge gap also increases, thus providing the electrons heating during their drift in the crossed fields, causing the ion kinetic energy increase. In the long run, it permits to select the ion energy suitable to provide higher quality DLC or other deposited coatings. In other words, additional acceleration of the plasma ion component is achieved by the possibility to obtain a higher voltage within the discharge gap with a transverse magnetic field in the presence of a longitudinal magnetic field in the currentless fraction of the plasma jet.

Three embodiments of the present invention are based on the principle structure described above.

According to the first embodiment, the rotatable cathode made of the material for coating deposition is shaped as a hollow truncated cone. Stationary permanent magnets are arranged inside the cone and produce an arched magnetic field over the cathode surface within the discharge gap.

The cathode rotation and cooling and the current contact jaws for the vacuum arc pulsed power supply is accomplished through a rotation input, well-known from conventional techniques.

The cathode is disposed so that its so-called effective surface with the cathode spots thereon being the source of cathodic plasma is located beyond the line-of-sight range from the region, wherein the products to be deposited are arranged.

The laser beams and the permanent magnets inside the conical cathode are oriented so that the laser induced vacuum arc point on the cathode is aligned with the arched magnetic field symmetry axis. In the field, as mentioned above, on the plasma boundary, during the arc discharge a Hall layer is formed, reflected at which the ions change their path so that they can travel from said cathode effective surface towards the region, wherein the products to be deposited are arranged. The anode is shaped as several (for example, three) narrow stripped sections electrically connected to the annular cooled anode body via ballast resistors.

The discharge current, running in the sections, produces a magnetic field aligned with the arched magnetic field generated by said magnetic system. That provides the formation of the stable Hall layer ensuring a high plasma efficiency of the macroparticle filtration system.

Owing to the cathode rotation, the cathode spot retrograde motion as well as the cathode spot random travel during their retrograde motion, the entire cathode effective surface is worn in a systematic and uniform manner.

The first embodiment design provides the cathode effective surface uniform evaporation, the reliable pulsed vacuum arc triggering, the cathode material large reserve and a high output as a result of the laser ignition, the conical cathode rotation and the cathode spot retrograde travel along the cone generator in the transverse magnetic field.

According to the second embodiment of the present invention, the conical cathode is stationary and the vacuum arc striking point as well as the arc discharge existence region with the Hall layer are moved relative to the cathode surface by simultaneous rotation of the permanent magnets inside the conical cathode and the system of the laser beam reflecting elements.

The cathodic-arc plasma source has an axially symmetrical design.

The entire cathode effective surface is worn in a systematic and uniform manner by the laser beam circular scanning of the ignition point in step with the arched magnetic field rotation, the cathode spot retrograde travel on the cone generator and the cathode spot random motion in the process. The laser beam from one pulsed laser source is guided along the rotation axis. The system comprising a reflecting semi-transparent mirror and a reflecting glass insert divides the laser beam into two beams guided in opposite directions. After having been fully reflected inside the glass ring and penetrated through the annular window into the vacuum chamber, the laser beams simultaneously induce two vacuum arcs on both sides of the conical cathode.

The anode is designed as a comb structure in the shape of narrow strips (sections) or rods electrically connected to a common anode via ballast resistances.

The arc discharge current is uniformly distributed between the two arc discharges and the ballast resistance value is selected so as to make one discharge current be sufficient for providing the arc stable existence during the operating pulse length of about 1ms (for example, discharge current in cell Je>150A for graphite, 7e>80A for Ti). On the other hand, the current of one arc discharge should not be too heavy (for example, /e<400A for graphite, /„<300Α for Ti) since the existence of several cathode spots on a small area causes a higher generation of macroparticles. The operating pulse total current is twice as great and can reach 800A.

Unlike the first embodiment of the present invention, the anode temperature condition is not so hard since at the circle scanning by two laser beams, the arc discharge current is alternately applied to a plurality of the anode sections and so, the heat demand is distributed.

Similar to the first embodiment of the present invention, the discharge current running alternately in these sections produces a magnetic field aligned with the arched magnetic field generated by the rotatable magnetic system. That provides the formation of the stable Hall layer, ensuring the macroparticle filtration system high plasma efficiency.

The third embodiment of the present invention is characterized by the following.

The anode is arranged in the centre along the cylindrical chamber axis. The anode is designed as a conical comb-shaped structure of narrow sections electrically connected to the annular cooled anode body via the ballast resistances.

The annular large size cathode is positioned proximate to the cylindrical vacuum chamber wall. The electromagnet system surrounds the annular cathode and is arranged outside the vacuum chamber. The electromagnet three-phase power supply system forms an alternating structure of the magnetic field arched configurations (arched magnetic cells) traveling along the annular cathode surface in step with the scanning laser beams inducing vacuum arc discharges simultaneously in said arched magnetic fields.

The laser induced vacuum arc is synchronized with the traveling arched magnetic field by rotating the disk with the system of reflecting mirrors splitting the laser beam into several beams.

In the arched magnetic field, as mentioned above, during the arc discharge, the Hall layer is formed on the plasma boundary, reflected at which the ions change their path so that they can travel from said cathode effective surface towards to the region, wherein the products to be deposited are arranged.

The annular cathode is positioned so that its so-called effective surface with the cathode spots thereon being the cathodic plasma sources is disposed beyond the line-of-sight range from the region, wherein the products to be deposited are arranged.

So, on the one hand, the arched magnetic field is employed for the plasma flux filtration.

On the other hand, the periodic structure of the magnetic field configurations (arched magnetic cells) is used to disperse and uniformly distribute the cathode spots among the cells on the entire length of the cathode and to prevent the cathode spots from concentrating in the same point on the cathode. The arc discharge current is uniformly distributed among the arched magnetic cells. The identical ballast resistance magnitudes on the anode are selected so that the discharge current is sufficient to ensure the arc stable existence in each individual cell during the operating pulse. However, the arc discharge current in a cell should not be too great since the presence of several cathode spots on a small area leads to the macroparticle higher generation. The total operating pulse current is determined by the number of cells.

That solution provides a multiple increase in the total discharge current and the source output, whereas the current density (the number of cathode spots in a local point within one arched cell) remains small, therefore, the macroparticle starting flow and the cathode splashes decreases.

Unlike the first and the second embodiments, the third embodiment of the present invention is characterizes by a higher output, a larger cathode size and so, by the increased cathode material reserve providing the cathode effective surface uniform evaporation and the uniform substrate coating deposition.

As has been noted, a significant disadvantage of the laser induced arc discharge method (as well as the laser ablation method) is the dust loading of the laser beam input window to the chamber and as a result, the laser beam power loss. The specific feature of the present invention is the absence of that disadvantage since the plasma flux or the entire target-cathode material substance flow does not pass towards the window because it is reflected at the Hall layer [34] and, according to the practice, the dust loading of the surfaces "protected" with the Hall layer is insignificant. Therefore, there is no need to increase the laser beam power for cleaning the laser beam input window to the chamber.

A significant reduction of the starting macroparticle flow from the cathode before the filter, comparing to the conventional methods, and high plasma efficiency help avoid the vacuum chamber and plasma carrying duct clogging with the cathode material, thus increasing the source trouble-free operation time.

The present invention realizes the advantages of the cathodic-arc plasma filtered in the arched magnetic field (stripped plasma flux, high plasma efficiency and the macroparticle and splash elimination) combined with the advantages of the laser induced vacuum arc.

In the source offered, a guided plasma flux is formed able to propagate an acceptable distance towards the substrate region without significant side expansion and without the losses stemmed from the expansion.

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is explained by the drawings, wherein Fig. 1 is sectional view taken on line BB (Fig. 2) of the first embodiment of the present pulsed laser-arc plasma source; Fig. 2 is a sectional view taken on line AA (Fig. 1) of the first embodiment of the present pulsed laser-arc plasma source; Fig. 3 is an axonometric drawing of the first embodiment of the pulsed laser-arc plasma source with a sectional view taken on plane BB (Fig. 2); Fig. 4 is an axonometric drawing of the first embodiment of the pulsed laser-arc plasma source with a sectional view taken on plane CC (Fig. 2); Fig. 5 is a sectional view taken on line COC (Fig. 6) of the second embodiment of the pulsed laser-arc plasma source; Fig. 6 is a sectional view taken on line AA (Fig. 5) of the second embodiment of the pulsed laser- arc plasma source; Fig. 7 is a sectional view taken on line BB (Fig. 5) of the second embodiment of the pulsed laser- arc plasma source; Fig. 8 is an axonometric drawing of the second embodiment of the pulsed laser-arc source with a sectional view on the plane DD (Fig. 7).

Fig. 9 is a sectional view taken on line EE (Fig. 10) of the third embodiment of the pulsed laser- arc plasma source; Fig. 10 is the electromagnet three-phase power supply and a periodic structure of the magnetic field arched configurations (arched magnetic cells) realized by the third embodiment of the present invention, a sectional view taken on line FF (Fig. 9); Fig. 11 is an axonometric drawing of the third embodiment of the pulsed laser-arc plasma source with a sectional view on the plane EE (Fig. 10).

DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present pulsed laser-arc source of uniform filtered carbon/metal plasma in an arched transverse magnetic field comprises: ■ a cooled rotatable conical cathode unit with a bushing insulator and a shield system; the cathode being made of consumable material for coating deposition; ■ a stationary magnetic system (permanent magnets) inside the rotatable conical cathode; ■ a laser induced vacuum-arc device; ■ a cooled comb-shaped first anode made of narrow strips; ■ second annular anode embraced by a coil (winding) and forming plasma flux transportation duct; said anode providing the combination and harmonization of the arched transverse magnetic field within the discharge gap with the longitudinal magnetic field within the plasma flux transportation duct.

The pulsed annular cathodic-arc filtered plasma source is mounted on flange 1 and disposed in the vacuum chamber of source 2 (Fig. 1, 3 and 4). The source chamber is, in its turn, attached to large size vacuum chamber 3 having region 4 (Fig. 1), wherein a large size product is arranged or there is a plurality of products to be deposited Cooled cathode unit 5 (Fig. 1, 2, 3) comprises hollow conical cathode 6 of the material for coating deposition, for instance, graphite, made rotatable about its axis.

The conical cathode is fixed on metal non-magnetic sleeve 7 having cavity 8 for arranging therein magnetic system 9 as well as for cooling.

The cathode rotation, cooling and feeding as well as the internal magnetic system cooling are accomplished through a rotary vacuum input well-known from the conventional technique.

Hollow rotary shaft 10 (Fig. 1, 4) is joined to sleeve 7 by means of screws 11. Vacuum seal 12 is used to make cavity 8 (Fig 2) vacuum-tight. Screws 13 and bush 14 are served to provide and maintain electric and heat conductive contact between conical cathode 6 and conical sleeve 7. Stationary magnetic system 9 (Fig. 1-4) comprises permanent magnets 15 (Fig. 2, 3, 4), magnetic poles 16 and magnetic core 17.

Fig 2 shows the arched magnetic field configuration produced by magnetic system 9. The magnetic field structure presents an alternation of the arched configurations having "right" magnetic field Bc, that is, the field, wherein it is possible to create a stable Hall layer ejecting the plasma flux in the required direction, with an opposite magnetic field, which is not used.

The cathode unit 5 (Fig. 1, 3) is cooled by a running water flow, shown with arrows 18 through unions 19 and stationary pipe 20 inside hallow rotary shaft 10. Stationary pipe 20 is mounted on flange 21, which is at the cathode potential and is insulated from the body by means of fabric-based laminate washers 22 and ring 23. Heavy current pulsed power supply from flange 21 to the rotatable cathode is realized by means of brushes 24, such as used, for example, in the design according to patent [6].

The rotary vacuum input comprises bearing-race 25 (Fig. 4) for ball bearings 26, rotary seal 27, insulators 28 and vacuum seals 29. The rotation is geared from electric motor 30. Driven gear 31 (Fig. 1, 3) with disc 32 of insulating material between the gear rim and the hub is mounted on shaft 10. Shields 33 and 34 (Fig. 1) are at a floating potential. The shields protect all the cathode idle surfaces avoiding arc discharges, which shunt the main arc discharge and may cause damage to the bushing insulator and the rotary input, on which the cathode assembly is mounted.

The cathode may be of quite a big diameter to provide the cathode long-term operation.

The cathode spots are induced by two laser beams 35 and 36 at points 37 and 38, correspondingly (Fig. 1, 2, 3) and during the arc discharge pulse perform a retrograde travel as far as shield 34 (Fig. 1) on the opposite end of cathode 6. The retrograde travel rate for different material and different transverse magnetic fields lies within the range of (4-70)m/s. For example, for a dense graphite cathode, at the arc discharge current of 400A and the magnetic field of 600G, the retrograde travel rate is equal to 50m/s. The conical cathode generator length determines the cathode spot retrograde travel duration and, consequently, the arc discharge pulse length. From the cathode geometry and the discharge gap peculiarities, it can be inferred that the generator length may be within the range of (3— 6)cm, therefore, (l-2)ms arc discharge pulses are used. Since the operating voltage across the voltage gap is 70V, arc discharge pulse energy is (30— 60)J.

During the arc discharge pulse, the cathode spots perform not only retrograde travel, but also a random motion. The cathode spot random shift during the retrograde travel is in proportion to square root of the arc discharge time and, during the pulse, reaches (2-4)mm. During the cathode rotation, its surface moves, whereas the cathode spot retrograde motion path remains within the arched magnetic field region. So, at the above mentioned three types of the cathode spot travel relative to the surface, the entire cathode effective surface may be exposed to uniform erosion.

The laser induced vacuum arc device includes two pulsed laser sources 39 and 40 (Fig. 1, 3). The laser beams are reflected inside glass prisms 41 and 42 owing to the total internal reflection and pass through glass windows 43 and 44 into the vacuum chamber.

The cathode shape varies as the cathode material is wearing and at the end of the operation acquires the shape marked with dash line 45 (Fig. 1). Therefore, laser beams 35 and 36 travel gradually during the operation up to positions 35' and 36' by moving reflecting glass prisms 41 and 42 along arrows / and ^.

Cooled anode (Fig. 1, 2, 3) consists of two combs 46 and 47 made of narrow strips 48. Owing to that fact, discharge current Ia running on the strips generates magnetic field Ba (Fig. 2) having the same direction as arched magnetic field Bc produced by said magnetic system 9, as shown in Fig. 2. The anode is cooled with running water, flowing through cavity 49 inside annular body 50 (Fig. 1, 3). The cooling and the power supply are accomplished through busing insulating inputs (not shown in the drawing) in flange 1.

Each section comprises plane thin ceramic insulator 51, having high thermal conductivity (Fig. 1) and graphite plate 52. Plane insulator 51 provides heat contact with anode poles 48, whereas graphite plates 52 serve as ballast resistances in the discharge circuit and determine the arc discharge current uniformly distributed between the two arc discharges; ballast resistance 52 is selected so that the current of one discharge is sufficient to provide the arc stable existence during an operating pulse of about 1ms and, on the other hand, the current of one arc discharge should not be too high to avoid an enhanced macroparticle generation. The operating pulse total current is twice as high and can reach 800A.

Second annular anode 53 (Fig. 1, 3, 4) is embraced by magnetic coils (windings) 54 having pot core 55 and forms a duct for the plasma flux further transport in a longitudinal (100— 300)G magnetic field towards region 4 (Fig. 1), wherein products/workpieces to be deposited ate arranged. The second anode is supplied with a positive voltage of (100— 250)V, relative to the cathode. Anode 53 walls are parallel to longitudinal magnetic field BL lines of force (Fig. 1). Since the plasma flux electrons are magnetized, the second anode current is (0-10)% of the discharge current, therefore, that region of the plasma flux can be considered currentless. The plasma electrons are confined from escaping onto the walls by the longitudinal magnetic field, whereas the ions are confined from escaping onto the walls by the transverse electric field. Rings 56 and 57 are at a floating potential.

As a whole, the present design prevents the plasma flux loss in the plasma carrying duct, which could have been quite significant because of a large angular spread of starting plasma flux 58 at the output of the discharge gap.

In addition, as stated before, the harmonization and a smooth transition of the transverse magnetic field into a longitudinal one provide the Hall layer stability. That happens even in case when transverse magnetic field BC (Fig. 2) is so great that without the harmonization with longitudinal field BL (Fig. 3), the arc discharge cannot be sustained at all. Therefore, it becomes possible to vary the arched transverse magnetic field within a wide range without the arc discharge quenching and interrupting and without reduction of the triggering reliability.

For example, at the magnetic field within the range of 2^(300-^500)0 in the region of the cathode spot existence on the graphite cathode, the voltage across the discharge gap becomes (90— 160)V that increases the ion energy significantly and ensures higher quality DLC or other coatings deposited.

The arc discharge is fed by pulsed power supply 59 (Fig. 1) providing pulsed power supply to the first and the second anodes, having the following characteristics: the first anode no-load voltage is +(200— 400) V, the total current of the two vacuum arcs is (200— 800) A, the second anode voltage is +(100— 300)V, the second anode current is (50— 100)A.

According to the present embodiment, the coating deposition average rate is controlled, first, by varying the arc discharge current power supply 59, second, by varying the laser induced vacuum arc frequency.

The cathode uniform erosion is provided or corrected by varying the cathode circular rotation rate.

According to the second embodiment of the present invention, the source of filtered plasma with pulsed arc discharge in the arched transverse magnetic field is characterized in that the conical cathode is stationary, whereas the laser induced vacuum arc point and the arc discharge with the Hall layer region are moved relative to the cathode surface by means of simultaneous synchronous rotation of the permanent magnets inside the conical cathode and the system of reflecting elements for the laser beam (Fig. 5— 8). That provides integrally uniform plasma flux of circular section. The source according to the second embodiment comprises: ■ a cooled stationary conical cathode of consumable material for coating deposition having a bushing insulator and a shield system; ■ a magnetic system of permanent magnets rotatable inside the conical cathode; ■ a laser induced vacuum arc device provided with the laser beam reflection, splitting and circular scanning system; ■ a cooled conical comb-shaped first anode made of narrow sections; ■ second annular anode embraced by a coil (winding) and forming the plasma flux transportation duct; said anode providing the combination and harmonization of the traveling arched transverse magnetic field within the discharge gap with the longitudinal magnetic field in the plasma flux transportation duct.

Similar to the first embodiment of the present invention, the pulsed annular cathodic arc plasma source is mounted on flange 1 and disposed inside the source vacuum chamber 2 (Fig 5, 7, 8). The source chamber is, in its turn, attached to large size vacuum chamber 3 having region 4 (Fig. 5), wherein large size product or a plurality of products/workpieces to be deposited are arranged.

Cooled cathode unit 60 (Fig. 5, 7 and 8) includes hollow conical cathode 61 of the coating deposition material mounted on metal non-magnetic sleeve 7 having cavity 8 (Fig. 6) for arranging therein magnetic system 62 (Fig. 6, 7 and 8) and also for cooling. Sleeve 7 is connected to cathode body 63 with screws 11. To make cavity 8 vacuum tight, vacuum seal 12 is used (Fig. 5). Screws 13 and bush 14 are served to produce and maintain an electric and heat conductive contact between conical cathode 61 and sleeve 7.

The cathode feeding and cooling as well as internal magnetic system 62 rotation is accomplished through rotary shaft 64, whereon the two laser beam circular scanning system is also mounted. The rotary assembly comprises ball-bearings 26 (Fig. 8) and rotary shaft water sealing collars 65, 66, 67 (Fig. 5, 8). Along the shaft 64, there are channels for cooling water supply 68 and removal 69 (Fig. 5).

Similar to the first embodiment of the present invention, the rotation is transmitted from electric motor 30 via gearing. Driven gear 31 having disc 32 of insulating material between the gear rim and the hub is mounted on shaft 64.

Flange 70 is at the cathode potential and is insulated from the body by fabric-based laminated washer 22 and ring 23. Heavy current pulsed contact from flange 70 to rotary shaft 64 and from the shaft to cathode body 63 is realized by means of brushes 71 and 72, well-known from the conventional technology [6].

Pulsed laser source 73 is served as a laser induced vacuum arc device. The laser beam is guided along the shaft rotation axis. At the beginning, starting laser beam 74 is semi- reflected at mirror plate 75 [22], and reflected beam 741, carrying half of the starting beam light power, passes through focusing lens 76 towards stationary glass ring 77 having conical surface 78. Straight beam 742 undergoes total internal reflection at glass insert beveled surface 79 and through focusing lens 80 also passes towards stationary glass ring 77 having conical surface 78. This way, the laser beam is splitted into two beams having half of the starting laser power each. Reflected at surface 78, laser beams 74i and 742 pass through glass annular window 81 in vacuum towards the conical cathode. Window 81 is sealed by vacuum seals 82 and 83, internal 84 and external 85 ring flanges. Annular window 81 has another function; it is served as an insulator between cathode body 63 and flange 1.

The cathode shape changes as the cathode material wears, and at the end of the operation gets the shape defined by dash line 45 (Fig. 5). Therefore, laser beams 74i and 742 are gradually moved during the operation up to positions 74 f and 742' by moving reflecting glass ring 77 to position 77' (defined by a dash line) along arrow F3.

The cooled anode (Fig. 5, 7 and 8) is shaped as conical comb structure 85 of narrow sections 86. Owing to that fact, discharge current Ia running through these sections (Fig. 5) forms magnetic field Ba (Fig. 7) aligned with arched magnetic field Bc produced by magnetic system 62, as shown in Fig.7. The anode is cooled with water running through cavity 49 in ring 50 (Fig. 5, 8). The anode cooling and feeding is accomplished through bushing insulator 87 in flange 1.

Each section comprises plane thin ceramic insulator 51, having high thermal conductivity, and graphite plate 52. Plane insulator 51 provides heat contact with anode structure 85, whereas graphite washers 52 are served as ballast resistances in the discharge circuit and determine the discharge current.

Second annular anode 53 (Fig. 5, 8) is embraced by coils (windings) 54, having pot core 55, and forms a duct for further transport of the plasma flux in a longitudinal 100-300 G magnetic field towards region 4 (Fig. 5), wherein the products to be deposited are arranged. The second anode is supplied with a positive voltage of 100-250 V relative to the cathode. Second anode walls 53 are parallel to longitudinal magnetic field BL lines of force (Fig. 5). Since the plasma flux electrons are magnetized, the second anode current is (0— 10)% of the discharge current, therefore, this plasma flux region may be considered currentless. The plasma electrons are confined from escaping onto the walls by the longitudinal magnetic field and ions are confined from escaping onto the walls by a transverse electric field. Rings 56 and 57 are at floating potential.

As a whole, that design prevents the plasma flux loss in the plasma-carrying duct, which could have been rather significant due to a large angular spread of starting plasma flux 58 ions at the output of the discharge gap.

Besides, as stated above, harmonization and smooth transition of the transverse magnetic field into a longitudinal one provide the Hall layer stability. It occurs even when transverse magnetic field 5c(Fig. 7) is so strong that without harmonization with longitudinal field EL (Fig. 5), the arc discharge cannot be sustained at all. So, it becomes possible to vary the arched transverse magnetic field without the arc discharge break-downs and interruptions or without reduction of the triggering reliability.

For example, at the magnetic field in the region of the cathode spot existence on the graphite cathode surface within the range of -βα~(300— 500)G, a voltage across the discharge gap assumes a value of (90— 160)V providing a significant increase in the ion energy and high quality DLC or any other coating deposited.

The arc discharge is fed by pulsed power supply 59, providing pulsed power supply to the first and the second anodes, having the following characteristics: the first anode no-load voltage is +(200— 400) V, the total current of the two vacuum arcs is (200— 800)A, the second anode voltage is +(100— 300)V, the second anode current is (50— 100)A.

Average coating deposition rate in the present embodiment is controlled, first, by varying the arc discharge current in power supply 59, secondly, by varying the laser induced vacuum arc frequency.

The cathode erosion uniformity may be ensured or corrected by varying the traveling magnetic field velocity and the rate of the laser beam circular scanning, that is, by varying shaft 64 rotation speed.

According to the third embodiment of the present invention, the source of filtered plasma with a pulsed arc discharge in the arched transverse magnetic field is characterized by a higher output, a larger cathode size and, consequently, by an increased cathode material reserve, providing a uniform evaporation of the cathode effective surface and uniform substrate coating deposition. The annular large size cathode is made stationary, whereas the laser induced vacuum arc point and the region of the arc discharge having the Hall layer travel relative to the cathode surface is accomplished by the rotation of the laser beam reflecting system simultaneously and in step with the traveling magnetic field.

That provides integrally uniform plasma flux of circular section.

The source according to the third embodiment comprises: ■ a cooled unit of a stationary annular large size cathode of consumable material for coating deposition with the shield system; ■ an electromagnet system embracing the annular cathode and forming an alternating structure of the magnetic field arched configurations (arched magnetic cells) traveling along the annular cathode surface; said electromagnet system being disposed outside the vacuum chamber; ■ a laser induced vacuum arc discharge device in said vacuum arc arched magnetic fields provided with a laser beam circular scanning device; ■ a cooled anode shaped as a conical comb-shaped structure embracing the conical cathode; ■ second annular anode embraced by a coil (winding) and forming the plasma flux transportation duct providing the combination and harmonization of the traveling arched transverse magnetic field within the discharge gap with the longitudinal magnetic field in said plasma flux transportation duct.

Similar to the first embodiment of the present invention, the pulsed annular cathodic-arc plasma source is mounted on flange 1 placed in the vacuum chamber of source 2 (Fig. 9, 11). The source chamber is fixed, in its turn, to large size vacuum chamber 3, having region 4, wherein a large size product or a plurality of products/workpieces to be deposited are arranged.

Fig. 10 shows an alternating structure of the magnetic field arched configurations (arched magnetic cells), traveling along the internal surface of annular cathode 88 and realized in the third embodiment by means of electromagnets 89, magnetic core 89' and three-phase power supply 90. The magnetic field structure presents the alternation of the arched configurations having the right magnetic field direction Bc 911, 912, 913, 914, that is, the direction, wherein it is possible to form a stable Hall layer ejecting the plasma flux in the required direction, and cells having an opposite magnetic field 921, 922, 923, 924, which are not used. The number of cells may be equal to 4 (as in Fig. 10) or more, depending on the selected cathode diameter. The cathode diameter may be large enough to provide high coating deposition output and the cathode long-term operation.

The laser induced vacuum-arc device is presented by laser source 93 (Fig. 9, 11). Initial laser beam 94 is guided along shaft 64 rotation axis and is splitted into four laser beams 941, 942, 943, 944 by the mirror system, said four laser beams inducing cathode spots on the annular cathode in points 95l5 952, 953, 954 (Fig. 10).

The laser beam splitting and reflecting unit comprises a set of mirrors 961, 962, 963, reflecting a quarter, a third or a half of the inputting laser beam power, respectively, and element for total internal reflection 964. Fig. 9 and 11 show two 971 and 974 of the four lenses used for focusing four laser beams on the laser induced vacuum arc points. The same figures show two 98i and 984 of the four total internal reflection glass elements used to re-guide the four laser beams towards the annular cathode.

The set of mirrors, lenses and reflecting elements is arranged inside cylindrical body 99 able to rotate together with shaft 64 providing the synchronization of the laser induced vacuum arc and the traveling arched magnetic field.

Double reflected laser beams 94ls 942, 943, and 944, performing circular scanning, pass into vacuum through glass window 81. Window 81 is sealed by vacuum seals 82 and 83, internal 84 and external 85 annular flanges. Annular window 81 is also served as an insulator between anode body 100 and flange 1.

According to Fig. 9, 10 and 11, the cathode spots are induced by laser beams in points 951, 952, 953, 954 and, during the arc discharge pulse, perform retrograde travel along the conical cathode generator. The generator length determines the cathode spot retrograde travel duration, and so the arc discharge pulse length. It can be inferred from the cathode geometry and the discharge gap peculiarities that the generator length may be within the range of 3-6 cm; therefore, arc discharge pulses of less than 2 ms are used. In addition to the retrograde travel, the cathode spots are involved into a random motion during the arc discharge pulse length.

The cathode shape changes as the cathode material wears and at the end of the operation gets the shape shown with dash line 88' (Fig. 9). Therefore, during the operation, laser beams 94i, 942, 943 and 944 are gradually moved to position 94 , 942', 943' and 944' by moving cylindrical body 98 to position 98' (marked with a dash line) along arrow F4.

Annular cathode 88 is mounted on non-magnetic sleeve 101 with screws 102 and bush 103, providing electric and heat conducting contact. The sleeve is connected to setting ring 104 with screws 105. The cathode is cooled with running water, flowing through cavity 106 between sleeve 101 and ring 104 (Fig. 9, 11). The feeding and cooling are accomplished through bushing insulators 107. All the ineffective surfaces of the cathode unit are protected by the shield at floating potential 108 and 109.

Cooled anode (Fig. 9, 11) is presented by a conical comb-shaped structure 110 made of narrow strips 111. Similar to the previous embodiments, the discharge current /„, running on the strips, produces a magnetic field Ba having the same direction as arched magnetic field Bc (Fig. 10) of electromagnets 89 does.

Each section comprises plane thin ceramic insulator having high thermal conductivity 51 and graphite plate 52. Plane insulator 51 provides anode body 100 heat contact with anode strips 111, whereas graphite plates 52 are served as ballast resistances in the discharge circuit and determine the discharge current in each of magnetic cells 911-9I4.

The anode power supply and cooling is accomplished through rotary shaft 64, whereon, as stated above, the laser beam circular scanning system is mounted.

The rotary unit comprises ball-bearings 26 (Fig. 9, 11) and water sealing collars 65, 66, 67 of the rotary shaft 64. The cooling is accomplished with running water flowing through cavity 112 in anode body 100 (Fig. 9, 11). Water supply and removal channels 68 and 69 are arranged along the rotary shaft.

Similar to the previous embodiments of the present invention, the rotation is transmitted from electric motor 30 via gear transmission (Fig. 9). Driven gear 31 having disc 32 of insulating material is disposed between the gear rim and the hub. Flange 70 is at the anode potential and insulated from the body with fabric-based laminate washers 22 and ring 23. Heavy current pulsed power is supplied from flange 70 to rotary shaft 64 and from the shaft to anode body 63 by means of brushes 71 and 72.

Second annular anode 53 (Fig. 9, 11), just as well as in the first and the second embodiments of the present invention, is embraced by coils (windings) 54 having pot core 55 and forms a channel for further plasma flux transport in a longitudinal magnetic field of (100— 300)G towards region 4 (Fig. 9). The second anode is supplied with a positive voltage of 100-250 V relative to the cathode. Second anode 53 walls are parallel to longitudinal magnetic field Bi lines of force (Fig.9). Since the plasma flux electrons are magnetized, the second anode current makes up (0— 15)% of the discharge current. The plasma electrons are confined from escaping onto the walls by the longitudinal magnetic field, whereas ions are confined from escaping onto the walls by the transverse electric field. Rings 56 and 57 are at a floating potential.

As a whole, that design permits to prevent the plasma flux loss in the plasma carrying duct, which could have been rather significant due to large angular spread of starting plasma flux 58 ions at the output of the discharge gap.

As stated above, the harmonization and smooth transition of the transverse magnetic field into a longitudinal one provides the Hall layer stability. Owing to that fact, it becomes possible to vary the arched transverse magnetic field within a wide range without neither the arc discharge breakdowns and interruptions nor reduction of the triggering reliability. For example, at the magnetic field in the cathode spot existence region on the graphite cathode within the range of 2fc~(300— 500)G, a voltage across the discharge gap acquires a value of 90-160 V, providing a substantial increase in the ion energy and high quality of DLC and other coatings deposited.

The arc discharge is fed by pulsed power supply 112 which provides the first and second anodes with pulsed power supply (Fig.9). The power supply unit specifications are: no-load voltage across the first anode is +(200— 400)V, the total current of the two vacuum arcs is (400— 1600) A, voltage across the second anode is +( 100-300) V, current across the second anode is (50— 200)A.

The average coating deposition rate can be controlled in two ways.

First, by varying the arc discharge current on power supply 112, second, by varying the laser induced vacuum arc frequency.

The arched magnetic field traveling along the cathode effective surface is synchronized with the laser beam circular scanning by means of device 113 (Fig.9). The device reads control marks 114 on gear 32 and controls three-phase power supply system 90.

The cathode erosion uniformity can be provided and corrected by varying the traveling magnetic field velocity by changing three-phase power supply 90 frequency simultaneously with synchronous change of the laser beam circular scanning, that is, shaft 64 rotation speed.

Taking into consideration the above mentioned, the present invention advantages are: • Total 100% filtration of plasma flux in a multi-cell arched magnetic field. Macroparticles, clusters and neutral particles cannot pass through the filter. That filtration method ensures plasma efficiency of more than 70%.

• The annular source high output. On the one hand, the arched magnetic field is utilized for the plasma flux filtration, on the other hand, it provides uniform distribution of the cathode spots, and consequently, the whole arc discharge over the entire annular cathode surface, whereas the annular anode body via ballast resistances.

• Possibility of controlling the annular plasma source output within a wide range. It leads to a significant power reduction at some stages of coating deposition • Small cathode material loss in plasma carrying duct. It eliminates a significant disadvantage of the conventional industrial systems, wherein labor-consuming cleaning operations are required with periodic shut-downs and maintenance.

• Long-term operation without changing the cathode, cleaning the plasma carrying duct and troubleshooting.

• Uniform coating deposition on large size and annular products/workpieces.

• Laser beam control and scanning ensures that the entire cathode surface is worn in a systematic and uniform manner.

• Possibility of controlling the energy spectrum of the particles used to form films by varying the arched cell magnetic field, affecting the value of voltage across the discharge gap.

• The laser source power is not required for cleaning the laser beam input window to the chamber. The window is not dust-loaded, since it is protected by the Hall layer both at pulsed laser deposition and at arc discharge. It makes it possible to use a cheap laser source of lower power for laser induced vacuum arc.

• In the source of filtered plasma, a guided plasma flux is formed, able to propagate at an acceptable distance towards the substrate.

Therefore, it becomes possible to build in a gate-type slide valve in the plasma carrying duct and arrange the vacuum system of a few vacuum chambers (source chambers and a chamber for positioning the products/workpieces to be deposited) having individual evacuation.

• The filtered source of the second and third embodiments may not necessarily be made annular. Slightly changing the laser scanning design, it is possible to use an extended configuration, for instance, of racetrack, oval or rectangular configurations.

The annular source may be employed in systems for coating deposition, ion doping or ion cleaning.

Coatings produced according to the present invention can be used in the following fields: wear resistant coatings, low friction coatings, super-hard coatings; cutting tools, drill bits; tools and devices for biomedicine and its applications; biological implants; chemically resistant coatings; optics and coatings on transparent substrates, display screens, architectural glass panels; electronic elements; nanotechnology.

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Applicant: LUMIKS P.T Author: Efim Bender 45

Claims (2)

t is claimed is:

1. Pulsed laser-arc source of uniform filtered carbon/metal plasma, comprising: • a cylindrical vacuum chamber for positioning an annular plasma source therein, having a live flange for plasma flux outlet towards the region, wherein products/workpieces to be deposited are arranged, • a cooled cathode unit, • a cooled anode unit, • laser beam input window/windows disposed on the side opposite the flange for plasma flux outlet, • a laser induced vacuum arc device, comprising laser source/sources and a device for laser beam reflecting and focusing on vacuum arc striking points on the cathode surface, • an anode-cathode discharge gap power supply, c h a r a c t e r i z e d in that • the cooled cathode unit is shaped as a conical ring; • outside the vacuum chamber, a magnetic system of a sequence of magnets/electromagnets is disposed for producing a plurality of arched magnetic fields over the cathode surface within the discharge gap; • the cooled anode unit has a comb-shaped structure made as narrow sections electrically connected to the anode via ballast resistances to provide the same direction of the anode section current magnetic fields and the arched magnetic field within the discharge gap; • along the source axis, the second annular anode is disposed embraced by coils and forming the plasma flux transport duct, combining and harmonizing the arched transverse magnetic field within the discharge gap and the longitudinal magnetic field within the duct; • it comprises the second power supply for applying a positive pulsed voltage to the second anode, relative to the cathode.

2. The plasma source as defined in claim 1 , wherein • said cooled cathode unit comprises a rotary conical cathode of a consumable material for coating deposition having a holder and a system of shields, the cathode effective surface being located beyond the line-of-sight range from the region, wherein products/workpieces to be deposited are arranged, 40 • said magnetic system for producing arched magnetic fields over the cathode surface comprises stationary permanent magnets inside the rotary conical cathode, • the anode of said anode unit comprises two combs disposed in two regions having arched magnetic field, • said laser device comprises two pulsed laser sources and two glass prisms for laser beam reflection to the vacuum arc striking points on the cathode surface. The plasma source as defined in claim 1, wherein • said cooled cathode unit comprises a stationary conical cathode of a consumable material for coating deposition having a holder and a system of shields; the cathode effective surface being located beyond the line-of-sight range from the region, wherein products/workpieces to be deposited are arranged; • said magnetic system having permanent magnets producing a traveling arched magnetic field over the cathode effective surface is mounted on the rotary shaft; • the anode of said cooled anode unit is shaped as a conical comb structure embracing the conical cathode; • said laser device comprises a pulsed laser source, a laser beam reflecting, splitting and circular scanning device mounted on the same rotary shaft as said magnetic system. The plasma source as defined in claim 1 , wherein • said cooled cathode unit comprises a stationary annular large size cathode of a consumable material for coating deposition, a system of shields and bushing insulators for current contact and cooling; the cathode effective surface is oriented beyond the line- of-sight range f om the region, wherein products/workpieces to be deposited are arranged; • said magnetic system comprises electromagnets embracing the annular cathode and forming an alternating structure of arched magnetic cells traveling along the annular cathode effective surface; said electromagnets being disposed outside the vacuum chamber; • said laser induced vacuum arc device within said arched magnetic cells comprises a laser beam reflecting, splitting and circular scanning device mounted on the same rotary shaft as said magnetic system; • the anode of said cooled anode unit is shaped as a conical comb structure disposed inside the annular cathode; 41 means for the synchronization of the traveling arched magnetic field along the cathode effective surface with the laser beam circular scanning are provided on the rotary shaft. 42