US 3740327 A
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June 19, 1973 G. c. LANE ET AL 3,740,327
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June 19, 1973 G. c:A LANE ET AL 3,740,327
SPUTTER COATING APPARATUS WITH SHROUDING MEANS Original Filed June 3, 1969 5 Sheets-Sheet 2 June 19, 1973 G. C, LANE ET AL 3,740,327
SPUTTER COATING APPARATUS WITH SHROUDING MEANS Original Filed June 5, 1969 5 Sheets-Sheet 5 I| SU PPLY |78 92 rTo ne nq 98 23a 3,4% Rf. |94 |96 .f\` SUPPLY T ,I *M /me 24o \234 236 VL j |24 j |28 Rf -Tl' GNERAToR 'G |64 vAcuuM 22e E 204 20e l: INERT GAS y 4 202/ SOURCE June 19, 1973 G, Q LANE ET AL 3,740,327
SPUTTER COATING APPARATUS WITH SHROUDING MEANS Original Filed June I5. 1969 5 Sheets-Sheet 4 June 19, 1973 SPUTTER GOATING APPARATUS WITH SHROUDING MEANS G. C. LANE ET AL original Fiied June 3, 1969 5 Sheets*Sheet b United States Patent O 3,740,327 SPU'ITER COATlNG APPARATUS WITH SHROUDING MEANS George C. Lane, Danbury, Cyril A. Cartwright, Monroe, and Keith W. Elmslie, Madison, Conn., assignors to Warner-Lambert Company, Morris Plains, NJ. Original application .lune 3, 1969, Ser. No. 829,906. Divided and this application Nov. 5, 1971, Ser. No. 196,054
Int. Cl. C23c 15/00 U.S. Cl. 204-298 9 Claims ABSTRACT OF THE DISCLOSURE An apparatus and method for coating articles or substrates, particularly razor blades or other cutting instruments, in which means are provided for establishing a radio frequency alternating electrical field between electrodes within a vacuum chamber for sputtering a coating from a target having the coating material thereon to the article or substrate to be coated. The described apparatus includes means for providing preliminary cleaning of the substrate as well as the target before coating, such cleaning operation being capable of operating in any one of several different operational modes. Preferably, the substrate is iirst cleaned by so-called reverse sputtering, then protected against contamination While the target is cleaned, with the substrate thereafter being exposed to coating by sputtering. In another embodiment, simultaneous substrate cleaning and deposition takes place, as the target and the substrate are maintained at different potentials While having radio frequency alternating voltages impressed thereon. The apparatus provides a means of performing these operations either simultaneously or in sequence on a plurality of articles at one or more stations without breaking the vacuum in the evacuated chamber, or allowing contamination of the article, substrate or target between cleaning and coating operations.
CROSS-REFERENCE TO RELATED APPLICATION This patent application is a division of copending U.S. patent application Ser. No. 829,906, led June 3, 1969.
BACKGROUND OF THE INVENTION It is well known that it is highly desirable, in the interest of durability and economy, to obtain extremely thin, highly pure continuous metal, alloy, or like hard coating on the sharpened edges of cutting instruments such as razor blades, for example. Methods and apparatus for applying such thin coating economically and reproducibly to cutting surfaces such as blade or knife edges are now known, such as methods and apapratus being described, for example, in applications Ser. Nos. 680,794, and 680,926, both tiled Nov. 6, 1967. Cutting instruments made in this manner possess coatings of about 50 to 800 angstroms (A.) and preferably 100 to 200 A., which are thickenough to protect the cutting edge from premature wear and corrosion, but still thin enough to prevent rapid dulling of the edge of the instrument. A principal advantage of using the sputtering deposition methods described in these applications is that the cutting instrument may be finish ground, honed and stropped to a desired degree of sharpness and thereafter coated protectively with a hard metal or alloy coating without being dulled. Thus, there is no need to form an edge on a hard coating material, or to sharpen an edge previously imparted to an instrument after the edge has been hardened. Edge surfaces so coated may also readily be coated with lubricous coating materials such as plastic materials, silicone lubricants, or the like, in any known manner. It is now well known that articles made with the use of the apparatus and methods 3,740,327 Patented June 19 1973 ICC referred to above possess heretofore unsurpassed quality consistent with reasonable economy and outstanding useful life.
Nevertheless, as is the case with many mass produced articles, there is still room for further improvement, particularly by way of methods and apparatus which make higher production speeds and even better quality control possible, as well as those which tend to make material handling and the like simpler and more foolproof. There is also a need for systems which are improved in regard to simplifying pretreatment of the substrate to be coated and which afford greater versatility and reliability in use. There is also a need for simplified apparatus which make practical the practice of a process having a plurality of steps within a single unit of apparatus.
In View of the needs set forth above, it is an object of the present invention to provide an improved product cleaning and coating apparatus and method.
A further object is to provide a sputter coating apparatus which provides for cleaning a substrate prior to coating by sequential or simultaneous operations carried out within a single evacuated chamber so that the operations may be performed without breaking the vacuum necessary to obtain conditions under which sputtering takes place.
Another object is to provide an apparatus for cleaning an article to be coated, for cleaning the target which serves as a source of coating material while simultaneously protecting the article from contamination by the material cleaned from the target, and thereafter coating the article by exposing it to coating material sputtered from the target.
A further object is to provide an apparatus in which `cleaning of a blade or other substrate prior to coating thereof by sputtering may be accomplished by subjecting the blade to a glow discharge in a high vacuum chamber.
Another object of the invention is to provide an apparatus in which so-called reverse sputering may be utilized as a method of cleaning the article to be coated prior to coating thereof.
Another object is to provide an apparatus in which cleaning of an article or substrate by glow discharge, or reverse sputtering, a sputter etching may be carried out, followed by coating the same article or substrate with' a sputtered coating material, all being carried out within the same apparatus.
Another object of the invention is to provide a method by which a substrate may be cleaned and coated under conditions of high vacuum Without breaking the vacuum between steps of the method.
A still further object is to provide an apparatus in which blades may be cleaned in a high vacuum atmosphere, may be coated in the same atmosphere, and may be protected against atmospheric or like contamination between cleaning and coating.
A still further object is to provide an apparatus and method by which a plurality of articles may be cleaned and coated in a desired sequence, or simultaneously in a high vacuum environment.
A still further object is to provide a cleaning and coating apparatus which includes a vacuum chamber, means therein for supporting a plurality of articles to be coated and for advancing them in succession past a coating station after a cleaning operation is performed, and in which includes means for establishing a high frequency electrical field either alternately or simultaneously between the target and the ground and the articles to be coated and the ground for cleaning and coating the article in the desired manner.
A further object of the invention is to provide an apparatus in which the means for supporting and moving the articles to be coated about Within the vacuum chamber includes means for maintaining the edges of the articles approximately parallel to a surrounding surface during the time they are being cleaned, and which includes means for rotating one or more article holders to a desired extent about its own axis Within a relatively small portion of the motion cycle of the article holder and for holding it against axial rotation during a relatively larger portion of its rotating cycle.
Another object is tov provide an apparatus which includes means, preferably single means, for exposing articles to be coated to coating material being sputtered from the target in one position of said means, and for protecting the articles against contamination sputtered from the target during cleaning thereof in another position of such means, as Well as serving as means for aiding target cleaning prior to the time the target material is sputtered onto the articles to be coated;
Another object is to provide a method in which a radio frequency is impressed both on a target and on an article to be coated, the target and article are allowed to reach differing electrical potentials so that there is a significant potential between the two, in which minute quantities of an inert gas are introduced at least into an evacuated region between the articles and the target, whereby atoms ionized by the electrons owing in the chamber strike both the substrate and the target, at different rates, each collision of an ionized atom with the article or the target sputtering olf one or more surface atoms, thereof, to provide simultaneous lower rate surface cleaning of the article and higher rate sputtering of the coating onto the article, and an apparatus for carrying out the method.
These and other objects of the invention are achieved by providing a vacuum apparatus having means for supporting a plurality of articles or groups of articles within an evacuated chamber or other region, target means containing a coating material, means for moving the articles about in the chamber, means for supplying high frequency electrical energy to the articles for one mode of operation, and to the target in another mode, and control means for causing these operations to take place simultaneously or in a desired sequency of operation to provide coated articles made by the method and apparatus.
The exact manner in which these and other objects of the invention are attained will become more apparent when they are considered in conjunction with the appended claims, and the following detailed description in which reference is made to the accompanying drawings, wherein like reference numerals indicate corresponding parts throughout.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view, taken through a portion of the vacuum chamber of the apparatus of the invention, and illustrating certain principal portions of the apparatus;
FIG. 2 is a top plan view, partly in plan and partly in section, with portions broken away, showing the apparatus of FIG. 1;
FIG. 3 is a schematic view of a simpliied form of the electrical circuitry of the invention;
FIG. 4 is a schematic view of another portion of the electrical circuit of the invention showing a power supply, an alternating current source, and an impedance matching network;
FIG. 5 is a schematic view showing the operation of a portion of the electrical circuit of the apparatus in one mode of operation for cleaning the blade;
FIG. 6 is a schematic view showing the circuit of the apparatus in another mode of operation thereof, for cleaning the blades or the like by another process;
FIG. 7 is a top view, partly in horizontal section, and with portions broken away, showing another form of the apparatus of the invention;
FIG. 8 is a vertical sectional view, on a greatly enlarged scale, showing the operation of a portion of the means for orienting groups of articles to be coated in a desired position of use, and for rotating them about a lgiven axis to reverse the orientation thereof at a desired point in the apparatus; and
FIG. 9 is a fragmentary plan view of a portion of the article protective device of the invention, showing the mode of operation and an alternate position thereof in phantom lines.
DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION The invention will now be described with reference to particular embodiments thereof, in the first of which cleaning of all the articles to be coated takes place before any of the articles, or groups of articles, are coated.
Referring now to the drawings in greater detail, and particularly to FIGS. 1 and 2, this form of the invention may be seen to be embodied in a combination article cleaning and coating apparatus 10 which is somewhat diagrammatically shown to include a frame or base |12, means for establishing an evacuated region in the form of an exterior, vacuum tight housing 14, in which is mounted means for receiving and handling articles to be coated, in the form of an assembly 16 comprised of a lower ring stand 18, an insulator ring 20, a lower bearing race 22, a plurality of ball bearings 24, an upper bearing race 26, and a driven ring 28 which is adapted to support a plurality of article holder means in the form of bayonet assemblies 30` for holding a plurality of articles 32 thereon. The driven ring 28 includes external ring gear teeth 54 adapted to mesh with the teeth 36 on a pinion gear 38 driven by a stub shaft 40. Each bayonet assembly 30 includes vertically disposed tines 42 which are received in a circular holder member 44 having a lower extension y46 rotatably mounted for rotation in bearings 48, and further includes a bottom gear 50 fixedly attached thereto. External teeth 52 are provided on the gear for receiving a chain 54. The chain 54 also has portions thereof engaging teeth 56 on the outer periphery of a central, xed sprocket 58 mounted on `a hub 60 protected by a insulator 62. from electrical contact therewith. The bearings 48 engage .the outer surface of a plurality of sleeves 64 disposed in the driven ring 28, and in use, rotation of the ring 28 about the axis of the sprocket 58 will cause an epicyclic rotation of the gears 50, and consequent rotation of each bayonet assembly 30 about its own axis.
Thus, rotation of the ring 28 about its axis causes rotation of each bayonet assembly 30 about its own axis so that a given part thereof, for example an edge 66 of the blade or other article 32 held on the bayonet assembly 30 is presented in a parallel relation to a given point alternately for each full revoution of the ring 26. In other words, the exterior circumference of the sprockets and gears 50, 58 may be selected so as to turn the bayonet assembly 30 one-half turn for each complete turn of the ring 23.
In the embodiment shown in FIGS. 1 and 2, a motor 68 is provided having a shaft 701 thereon containing a driving lbevel gear 72 in eng-agement with a driven bevel .gear 74 which is iixedly attached to the stub shaft 40.
Thus, the ring 28 and the parts associated therewith are rotated by the manner set forth above.
As shown in FIGS. l and 2, means is provided for protecting the articles 32 held on the bayonets 30 or other article holding devices against undesired contamination, and for assisting in the cleaning of soch articles, in the form of an article shroud assembly 76 defining, on the inside thereof, a cylindrical passageway 78. The shroud assembly 76 includes an outer wall portion 80, an inner wall portion 82, a top wall portion 84, and an insulating support 86 which is fixedly attached to the roof portion 88 of the chamber 14. The bottom edge 90 of the shroud assembly 76 is closely spaced apart from the upper surface of the ring 28, so that the article 32 held on the tines 42 of the bayonets 30 are substantially completely enclosed, except at the bottom thereof, during rotation of the ring 28.
Referring now particularly to FIG. 2, it will be seen that an opening 92 is provided in a part of the exterior wall 80 of the shroud 76, and that this opening 92, which is defined by oppositely facing end surfaces 94, 96 of the wall 80 includes means in the form of a movable Shield 98 in the shroud opening 92 for protecting the articles 32 against contamination which might enter through the opening 92. The shield 98 is adapted to be removably received in a relatively snug relation within the opening 92., that is, with the edges 100, 102 of the shield 98 engaging the end surfaces 94, 96. Means in the form of pins 104, 106 are provided for locating the shield 98 and for establishing the path of movement thereof in a manner which will be described in greater detail herein. As shown in the phantom lines in FIG. 2, the shutter or shield 98 may be moved from the closed position to an open position lying closely along the outer surfaceof the wall 80, thereby exposing the articles 32 to any particles which may be sputtered from the target assembly .108 received in a target housing portion 1'10` of the chamber 14.
Referring again to FIG. 1, it is shown that each wall 80, 82 comprises respectively an outer surface 112, 1114, an inner surface 116, 118, and intermediate heater units 120, 122, the construction and function of Which will be described in further detail herein. Referring now to `another principal portion of the cleaning and coating apparatus 10, it will be seen that the target assembly 108 includes a dark space shielding assembly 124, a target plate 126, and a backing plate 128 which will be described in further detail herein. A co-axial lead-in assembly 2130, details which will be set forth further herein, extends through a rear wall portion 132 of the housing portion 110.
Referring now to FIG. 9, the construction of one form of the shield 98 and its associated operating components are shown. Thus, FIG. 9 shows that a support arm 134 is fixedly attached to the rear surface 136 of the shield 98, and the support arm 135 includes a driving gear sector 138, a pair of elongated slots 140 receiving respectively a guide pin 142 and a guide and pivot pin 144. Teeth `146 are arranged on the sector 138 so that rotation of the shaft 4148 and its associated driving gear 150 will move the arm y134 straight forward a given ydistance as shown in the phantom lines, until further rotation of the gear 150 will cause a swinging of the shield 98 to the fully opened position shown in phantom lines in FIG. 9. Reversing the direction of the shaft 148 and its associated gear 150 will cause the shield 98 to swing back to its original extended position and then be retracted to a position wherein the opening 92 dened by the end walls 94, 96 of the outside wall 80 is closed. Suitable insulators (not shown) are provided for insuring that the shield 92 and its associated mechanism are of the same electrical potential as the remaining portions of the shroud assembly 76.
Referring now to FIG. 3, additional details of the leadin assembly 130, the target assembly 108 and certain of the electrical components are shown. The backing plate 128 contains a continuous tube 152 having the near end thereof communicating with the interior passage 154 of an outer coolant tube 156, inside which is co-axially disposed an inner coolant tube 158, the interior 160 of which communicates with the far end of the tube 152. Water or like coolant passes in the direction of the arrows, that is, into the backing plate 128 of the target assembly 108 through the outer tube 156 and thence circuitously through the tube 152 within the backing plate 128 and out the exit opening 162 of the inner tube 158.
A wire lead 164 is attached to the outer surface of the outer tube 156, which serves as the connection to the radio frequency generator, shown schematically at 166.
A ceramic insulator 168 and gasket assembly 170 are provided to provide electrical and vacuum insulation, and, being conventional and not forming per se a novel part of the present invention, further description thereof is omitted. The target plate 126 is disposed in electrical as well as intimate heat exchange contact with the backing plate 128, and typically is a pure chromium metal or other metal or alloy to be deposited on the article or substrate. The backing plate 128 is preferably copper or other like electrically and thermally conductive material. The dark space shielding assembly 124 surrounds these components in the illustrated manner.
Again making reference to FIG. 3, a direct current (DC) supply 172 is schematically illustrated for connection at a terminal 174 to a movable pole 176 of a switch 178 so that, in one position of the switch 178, communication may be established between the direct current source or supply 172, which has one terminal thereof grounded, as by lead 180, and the article 32 to be coated. A radio frequency (RF) supply 182 having a grounded lead 184 on one terminal thereof has an opposite terminal 186 connected to a lead 188, so that connection may also be established between this supply 182 and the articles 32. Another terminal 190 is grounded by lead 192 so that the articles 32 may be grounded by moving the switch 178 to an appropriate position. Means in the form of a lead 194 are provided for grounding the shield 98 through the switch 196 if desired. As the description proceeds, it will more clearly appear that, in some embodiments, the RF generator 166 and the RF supply 182 may be the same unit, and may be different units in other embodiments. At any rate, FIG. 3 shows that an RF connection may be established between the generator 166 and the target and backing plate 126, 128, that the shield 98 may or may not be grounded, and that the blade or other articles 32 may alternately be floating grounded, or connected to a DC supply or to an RF supply, as desired. The exact connections and the sequences in which they are made will be set forth below in connection with a description of the operation of the apparatus.
Referring now to FIG. 4, there are shown somewhat schematically a vacuum chamber 198, having a target electrode 200 therein, in a spatially communicating relation with an insert gas source 202 by means of a leak valve 204 disposed in the connector line 206, and in electrical communication or contact with the tunable RF generator and amplifier assembly 208 and the tunable pi matching network 210, through the coaxial lead-in assembly 130. These components, the construction and arrangement of which are generally known to those skilled in the art, will be described briefly, although the detailed construction features of these elements do not per se form a novel part of the present invention.
Thus, the tunable genertor and amplifier assembly 208 is schematically shown in the form of lead 212 adapted for connection to an oscillator or other radio frequency source (not shown), and a tube 214 which is connected thereto so as to amplify the RF signal to the desired intensity, an inductor 216 and a pair of grounded variable capacitors 218, 220 being connected to either terminal of the inductor 216 for establishing a resonant condition of the electrical circuit, typically at a frequency of 13.56 megacycles. The pi matching network 210 includes a grounded iixed capacitor 222 and a variable capacitor 224 in parallel with each other, and further includes an inductor 226 and a second variable capacitor 228 between the inductor 226 and the target electrode 200. The matching network 210 is adapted to match the impedance of the output circuit, including the amplifier tube 214 and its associated circuitry with the impedance of the target electrode 200. In other words, the target electrode 200, which is isolated from the ground, together with its inductor 226 and variable capacitor 228, is an open circuit to direct current but has a definite AC impedance at a given fre- 7 quency, and this impedance is matched in the manner shown, or in any other suitable manner, to the impedance of the output circuit furnishing the signal. Typically, the output circuit has a 50 ohm impedance, and the target assembly should be tuned so as to have the same impedance. The capacitor 228 also serves to couple the output circuit to the target electrode 200 capacitively, so that direct current bias may be built up on the target electrode 200.
Referring now to FIG. 5, the connection between the DC supply 172 and the articles 32 are shown, it being apparent that the blade is separated by a high vacuum gap 230 from a grounded elements 232, which is shown as being disposed parallel to the edges 66 of the blade or other articles 32. Thus, as will be described in further detail herein, under proper conditions, a glow discharge may be developed in the space 230 between the grounded element 232 and the blade 32, in the presence of a minute amount of inert gas leaked into the space 230 over a background of very high vacuum (low pressure), and ionized by high energy current ow.
FIG. 6 shows an RF supply 182 connected to the article 32 and also shows the grounded element 232 being spaced apart from the articles 32, and with the edges 66 of the articles 32 and the element 232 being generally parallel. As will be described further herein, a reverse sputtering or sputter etching may take place under these conditions if an inert gas is leaked in minute quantity into the space 230 between the article 32 and the element 232, over a background of high vacuum, and ionized.
Referring now to the operation of the embodiments of the invention shown in FIGS. 1 and 2, the articles 32 to be coated are razor blades, and the process may be carried out as follows.
Example 1 The vacuum tight housing i14, including the roof portion 88 thereof, is lifted vertically from the base 12, and a plurality of razor blades 32 are disposed in a stack in parallel relation to each other with the central apertures` thereof in registry with the tines 42 on the bayonet assemblies 30. Each bayonet assembly 30 is loaded with a stack of blades, with each stack containing up to several thousand blades. When all the bayonet assemblies 30 are fully loaded and inserted with the holder members 44 thereof in position of use, the housing 14 is aligned and placed over the base 12, so that the blades are surrounded by the shroud 76 in the manner shown in FIG. 1.
Thereupon, a roughing vacuum pump (not shown) is operated to draw an initial vacuum inside the unit 10, and thereafter, the vacuum is increased to a level approximately 1 10r6 millimeters (mm.) of mercury (torr). The shield 98 is moved to the closed position so that two continuous inwardly facing surfaces 1'16, 118 are presented to the blades. As shown in FIG. 5, the shroud assembly 76 may be grounded, so that the element 232 in FIG. 5, in this mode of operation, would be one or both of the surfaces i116, 118 of the shroud 76. A potential of from about 500 to 3000 volts DC, and preferably about 1000 volts is impressed on the blades, such as from the DC source 172. At this point, argon or like inert gas is leaked through the valve 204 by a source 202 (FIG. 4) until the pressure reaches a level from about 1x10"2 to 1 103 torr. Under these conditions, a current of about 500 milliamperes (ma.) will be developed, and th'e resulting glow discharge will cause ionization of argon atoms and impingment thereof onto the blade edges to a degree sucient to remove surface contaminants, particularly organic material and adsorbed gases. Preliminary vaporization of such volatile contaminants, and elimination of adsorbed material may be aided by activating the heater units 120, 122 so as to heat the blades 32 to a temperature well below their annealing point, but high enough to aid in removing these contaminants. Typically,
the blade edges may reach a temperature of 300 to 400 F.
After the glow discharge has proceeded for one or two complete revolutions of the ring 28, which might typically take three to six minutes or more, the DC supply is disconnected from the blades or articles 32, the ground connection to the shroud 76 is removed so that it is insulated from the ground, and the ring 28 and associated components, including the articles 32 are then grounded. The vacuum is then again reduced to the level of about 1x10-6 torr as a background pressure, RF energy at 13.56 megacycles or megahertz (mc. or mI-Iz.) is supplied to the target electrode `126, and argon is leaked through the valve 204 until a pressure of approximately 6 to 9x10*4 torr is reached, while the shield `98 remains in the closed position. The electrode 126 becomes the cathode in this mode of operation, and the argon or other inert gas atoms which are ionized in the RF eld are attracted to the target 126 by the DC bias thereon with consequent sputtering 4of surface atoms from the target 126. The major portion of these sputtered atoms of coating material fall on the outer surface of the shield 98, which is interposed between the articles '32 and the target 126. After a minute or more of operation in this mode, the surface of the target 126, which would normally have contained a certain amount of contamination such as oxides, adsorbed gases, or the like will become completely clean and pure, free from any contamination. Thereupon, the shield 98 is moved to the position shown in phantom lines in FIGS. 2 and 9, and as the ring 28 continues to rotate, each blade or article passes by the target 126 with its edges 66 generally parallel thereto and in a facing relation to the target 126. After each bayonet assembly 30 has passed the target 126 twice, both edges of the articles 32 contained thereon have been exposed for coating for the desired time, and the coating operation is complete.
Thus, it will be seen that the apparatus and method just described provides means and method for glow discharge cleaning under vacuum conditions to clean the surface of the articles to be coated, following which the articles are protected during vacuum cleaning of the target, whereupon the 4final step of coating the clean blades with material deposited from the cleaned target is accomplished. All of these steps are carried out in the same apparatus, merely by chan-ging electrical conditions and manipulating the vacuum level and inert gas leak valve controls, but withoutsexposing the articles to any atmospheric contamination by breaking the vacuum during any of the operational cycles. The blades cleaned and coated by the use of this method and apparatus have proved to be outstanding in coating integrity and uniformity.
The same apparatus, or a different but similarly constructed apparatus may be used in a somewhat different but related mode of operation, as will now be set forth.
Example 12 A method was performed as set forth above, differing significantly only in the respects set forth below. Following loading of the articles within the apparatus and establishment of the described Vacuum, articles 32 were connected to an RF supply such as the supply 1182, having one terminal thereof grounded, and the other terminal 186 thereof in electrical communication with the bayonet 30 and the articles 32 contained thereon. The shield 98 remains in the closed position, and the shroud assembly 76 may be grounded. Argon or like inert gas is leaked through the valve 204 to establish a pressure of about 1 to 3 1f03 torr. The blades, at a power setting of the RF supply sufficient to cause a current flow of about 50 ma., achieve a DC bias of up to about 3000 volts, and as the argon ionized atoms bombard the blade edges, any oxide layer thereon, and small amounts of the metal surface itself, are removed by this bombardment,
amasar to insure that the blade surface to be coated is completely free of contamination, including atmospheric contamination.
After several minutes, the cleaning operation, which can be characterized as reverse sputtering, that is, using the intended substrate or article as a target, is complete. Thereafter, the RF supply is connected to the target 126, the blades or articles 32 are electrically grounded, and the surface of the target 126 is cleaned in the manner set forth in connection with Example 1. Thereafter, the shield 98 is moved to the open position, and the blades or other articles 32, which vare at ground potential, are coated, also in the same manner as set forth above in Example 1. The blades cleaned and coated by the use of this method and apparatus have also proved to be outstanding in coating integrity and uniformity.
Example 3 Blades were cleaned and coated in the manner set forth in Example 2, except that a cleaning operation, in this case is characterized as a sputter etching operation, instead of reverse sputtering. This operation was accomplished by applying approximately 1000 Watts of RF power at 13.56 mHz. to the blades, which attained a DC bias of from about 4000 to about 5000 volts. Cleaning was carried out under an argon pressure of from about 6 to about 9 10F4 torr, for a period of several minutes. In this mode, less argon or other inert gas was used than in the foregoing examples, and the distance between the blade or other articles 32 and the grounded terminal is preferably somewhat greater than under the conditions set forth in Example 2. This operation rnay be suitably carried out in an apparatus in which the shroud 76 has the walls 116, 118 thereof spaced farther from the edges 66 of the articles 32 than would be the case where glow discharge cleaning is used. The target cleaning and blade coating is carried out in the same manner as in the foregoing Examples 1 and 2. Excellent results were obtained.
Example 4 An apparatus substantially the same as that described above was used to carry out the following method of the invention, in which the blades or other articles 32, were cleaned and coated simultaneously. In this case, the inner surfaces 116, 118 of the outer and inner walls 80, 82 of the shroud 76 Were made with a substantial thickness of article coating material thereon, that is, typically, with a relatively thick coating of pure metallic chromium thereon. Blades were loaded in the manner set forth in the above examples, and the shield 98 was moved to the closed position. An RF 234, having one terminal 236 thereof grounded, has the other terminal 238 thereof connected, as by a switch 240, to the inner surface 116, 118 of the shroud 76, and to the inner surface 136 of the shield 98. An RF supply such as the supply 182 is connected to the ring 28 and thus to the bayonet 30 and the articles 32 supported thereon. The RF supply may be a single unit having one lead attached to the shroud 76 and to the other to the articles 32, or two individual RF supplies, one for the shroud and one for the articles, may be used.
After connections have been made as set forth above, the interior of the apparatus is evacuated to a bac-kground pressure of about 1x10'-6 torr, and the walls 116, 118 of the shroud 76 are supplied with a 13.56 megacycle RF, the shroud 76 being electrically isolated, as by the insulator 86, from the ground. A power of about 5000 watts is applied and a voltage of about 5000 volts DC may be developed as argon is leaked through the valve 204 until a pressure of about 6 to 9 104 is reached. The blades or articles 32 to be coated are also supplied with an RF of the same frequency, and the insulator 20 or the like insures that the ring 28 and parts of the apparatus 10 operatively associated therewith are isolated from the ground. A power of from about 800 to 1000 watts is supplied to the blades, which develop a DC bias of about 2000 volts. In this circuit the articles 32 or blades form one electrode of one RF supply and the ground the other electrode. In the other RF circuit, the shroud 76 forms one electrode, and the ground is the other electrode. Under the above conditions, the ionized inert gas atoms will strike both the DC biased articles 32 and the target, which in this case comprises the interior surfaces 116, 118 of the shroud 76. However, since a greater bias is developed on the target than on the articles, more sputtering will take place at the target than on the articles, for example, in the relative ratio of from about 2 to l up to about l0 to 1, preferably between 2 to l and 3 to l. In this manner, the surface of the articles will be cleaned by a reverse sputtering or sputter etching process while target material is sputtered onto the article at a greater rate than sputtering therefrom takes place. Any contamination of either the target or the blade will thus become diffused rather than remaining in one or two, near-surface layers, and, since a thickness of 1.0l to 30 atomic diameters of surface coating is ultimately built up on the blade or other articles, such contaminants, even if present, do not damage the quality or integrity of the coating. In this case, a certain incidental amount of coated material is resputtered back to the target, but the overall effect is that of simultaneously reducing the target thickness and placing a high quality coating on the articles.
Although it is not necessary that the two RF circuits be in exact resonance, the frequencies should be as nearly the same as possi-ble. This is not ordinarily a problem, however, since a crystal oscillator having a definite, xed frequency is commonly employed for generating such RF signals for amplification. In this case, vacuum and electrical conditions are maintained the same as from the outset of the process, until completion of the coating. Thus, this form of the apparatus also has al1 the advantages of the methods set forth in Examples 1 through 3 above, although the particulars of the apparatus and method are somewhat different. In this embodiment, the shield 98 need not be movable, and the target assembly 108 and the housing may be eliminated, although it is possible to operate the apparatus in the form shown herein according to the method described in this example, the target and housing not being function-ally involved, but not being required to be removed for operation. Thus, with the proper electrical connections, the apparatus illustrated herein may be used in these different modes of operation without alteration, or an apparatus according to the invention may be constructed so as to be useful in all modes but to favor a particular mode of operation in use.
Referring now to FIGS. 7 and 8, portions of another form of the apparatus of the invention are shown, these elements being adapted to receive a plurality of articlesupporting elements thereon for handling in a manner and for purposes which will now be set forth.
Referring now specically to FIGS. 7 and 8, a cam track assembly 242 is shown to include a circular continuous cam body 242 having an outer surface 246 adapted to guidingly receive thereon a front bayonet drive pin 248 and a rear bayonet drive pin 250, each pin 248, 250 being operatively associated with an article holder 252. A second, outer cam element 254 for effecting rotation of each of the holders 252 about its axis is disposed on a ring and cam support plate 256 which also supports the body 244, with the profiled inner surface 258 of the element 254 facing a complementary shaped outwardly facing surface 260 on the body 244, and spaced apart therefrom by approximately the diameter of a pin 258 plus a slight working clearance.
Referring now to F-IG. 8, the disposition of the pins 248, 250 between the surface 260 of the cam body 244 and the inner surface 258 of the outer cam element 254 is shown. As further shown in FIG. 7, the two pins 248,
l l 250 ride with their inner surfaces in a sliding relation to the outer surface 246 of the cam body 244, thereby maintaining the holders 252 and any articles disposed thereon substantially in a fixed orientation with respect to the circular body 244. That is, for example, the articles are supported so that a line extending between the pins 248, 2'50 would always be substantially perpendicular to a radius of a circle disposed co-axially with relation to the cam body 244. Assuming the holders 252 to be in circular motion in the path defined by the surface 246 of the cam body 2'44, as the pair of pins 248, 250 are moved counterclockwise as shown in FIG. 7, a point will be reached where the leading pin 248 engages the nose portion 262 of the cam element 254, thereby causing the lead pin 248 to be moved inwardly and thereby counterclockwise about the axis of the holder 252, that is, to the left as it is moved between the surfaces 258, 260 which define a channel 264. lSince the holder 252 is rotated about its own axis, the trailing pin 250 is moved to the right of a motion line parallel to the outer surface 246 of the cam 244. Thus, this pin 250 rides along or outside of the outer surface 244 of the cam element 244, While following the profile of the cam channel 264 causes the lead pin 248 to begin lagging 'behind in respect to the trailing pin 250 as the holder 252 continues movement, until their positions are reversed, as shown in FIG. 7 where the pins 248, 250 are emerging from the channel 264 and passing the end of cam element 2'54 in FIG. 7. Thus, a holder 252 will maintain an orientation with a part of the articles mounted thereon facing inwardly toward the center of the cam track 244 for about 300 to 330 of revolution, for example, after which, by engagement with the cam mechanism just described, it will rotate one-half turn about its own axis to present an opposite face of a supported article to the side, or toward the center of revolution.
Referring now to FIG. 8, other portions of the mechanism, including another form of the means for supporting and rotating the article holders within the apparatus as well as about their own axes, are shown. As seen in FIG. 8, each article holder 252 includes a lower extension portion 268 held by a fastener 270 in fixed relation to a base 272, which includes openings 274 for receiving the pins 248, 250. A bearing assembly 2761 locates the holder 252 and mounts it and its associated components for rotation about its -vertical axis. A snap ring 278y retains the bearing assembly 276 in position within the opening 282 in the rotatable ring 282. Fasteners 284, 286 respectively secure an internally toothed ring gear 288 and a bearing plate 290 to the ring 282. The ring and cam support plate 256 supports a lower bearing race 292 having a groove 294 therein in which is received a plurality of ball bearings 296 for supporting the plate 290. Another bearing assembly 298 on an inner surface 300 of the plate 2-56 includes a ring driving stub shaft 302 having on one end thereof a pinion gear 304 for engagement with the ring gear 288, and a bevel gear 306 on the other end thereof for engagement with a matched driving bevel gear 308 supported on a driven shaft 310. A motor (not shown) drives the shaft 3'10 through an outer output shaft 312 and a flexible coupling 314. A bearing assembly 316 supports the driven shaft 310 and the gear 308 in rotatable relation to the bottom support 318 for the plate 256. An insulator 320 is disposed between the support 318 and a lower portion 322 of the cleaning and coating apparatus 10.
The operation of this form of article supporting and handling means is similar to the operation of the form shown in FIGS. 1 and 2, and described in connection with Example l.
However, the means for driving the ring 282 are somewhat ditferent, comprising the ring gear 288 and pinion gear 304 with its associated mechanism, instead of the 12 chain 58 and the gears 50, 58 illustrated in connection with the description of FIGS. 1 and 2.
The resulting motion of the supported articles is different in the embodiment shown in FIGS. 7 and 8 than it is in the embodiments shown in FIGS. l and 2, for example. Thus, the provision of the pins 248, 250 riding on the exterior surface 246 of the cam body 244 serves to maintain the edges 322 of any article 316 parallel to an inner surface 318 of a shroud or the like 320 during an entire revolution of the ring 282, except where the cam track assembly 242 acts to rotate each holder 252 about its own vertical axis. In the embodiment shown in FIGS. 1 and 2, on the other hand, the bayonet assemblies 30 were rotated continuously one degree about their own axes for each two degrees of revolution of the ring 28.
Therefore, the embodiments shown in FIGS. 7 and 8 is preferred where it is desired to maintain an edge 322 of an article 316 parallel to a given surface 3118 so that the potential drop between the edge 322 and the surface 318 is relatively the same at all points along the edge 322. Accordingly, in some modes of operation, the manner of supporting the blades and manipulating them shown in FIGS. 7 and 8 is preferred.
The above examples have been described generally making reference to the articles 32 or 316 being double edge razor blades. However, where the articles are single edges blades, or where only one side of an article is desired to be cleaned and coated, rotation of each bayonet 30 or holder 2'52 about its own axis is not necessary, and portions of the mechanisms, such as the cam surface 260 and the outer cam element 254 may be done away with, as might the chain and gear assembly described in connection with FIGS. l and 2. In such case, it is also obvious that only one surface of a shroud need be charged if the glow discharge or sputtering were to take place with respect to only one edge or surface of a supported article.
EXAMPLE 5 A plurality of blades 316 or like articles were placed on the holder 252, and the blades were cleaned by any of the methods set forth in the foregoing Examples l through 3, and were coated by sputtering a chromium coating from the target 324 disposed within a shield unit 326 in the same manner as described in connection with the above Examples 1 through 3. The apparatus shown in FIGS. 7 and 8 also operated in a manner just described, that is, with the ring 232 rotating about its axis and aligning the plurality of holders 252 such that the edges 322 of the articles 316 disposed thereon are kept parallel to the inner surface 318 of the shroud 320 for about 330 of revolution of the ring 282, and then rotated 180 about their own axes as set forth above. The electrical connections were made in the same manner as set forth in connection with Examples l through 3, and the unit described was effective to coat razor blades with a thin but continuous, uniform coating having outstanding integrity and adhesion. The apparatus was operative to produce substantially equal results when cleaning was effected by the glow discharge method, the sputter etching method, or the reverse sputtering method.
The apparatus described is also Operative to produce excellent blades when modified and operated in the manner set forth in connection with the description of the embodiment of Example 4.
summarizing the method and apparatus referred to above, it will be particularly noted that the provision of the shield 98 serves the dual function of providing means for shielding the blades or articles against contamination during the time the target is cleaned by sputtering the first several layers of surface material therefrom, and also the function of protecting the target from sputtered contamination during the time the blades are being cleaned by glow discharge, sputter etching, or reverse sputtering.
The illustrated apparatus includes support means for the article holders in the form of the solid rings shown, but it will be appreciated that the articles might be moved past the target by other means, such as by mounting the holders on links of a continuous belt or chain, for example. One sputtered material illustrated herein is metallic chromium, but it will be understood that other metals, metal alloys, and compounds such as metal carbides or the like may also be sputtered onto the coated articles. In the event that an article is desired to be covered with two or more overlying layers or successive coatings following cleaning, it is obvious that additional target means may be provided, suitable connections may be made to supply high frequency energy to them in any desired sequence.
A commonly inert gas used in the sputtering operation is argon, but other inert gases such as neon or krypton may also be used. Details of the electrical circuitry may be altered by those skilled in the art, but a typical means of establishing a connection between relatively movable parts in a high vacuum is by the use of a gold brush or the like such as that shown in FIG. 1.
It will therefore be seen, by reference to the foregoing description, that the present invention provides a new and useful article coating method and apparatus having a number of advantages and characteristics, including those pointed out herein and others which are inherent in the invention.
What is claimed is:
1. An apparatus for cleaning the surface of an article and for coating the surface so cleaned, comprising, in combination, means for establishing an evacuated region, means for supplying controlled amounts of an inert gas into said evacuated region, and, disposed within said evacuated region, means for supporting at least one article to be coated, means for shrouding said supporting means and any articles supported thereon, means for establishing differing electrical potentials on said shrouding means and on said supporting means including any articles associated therewith, portions of said shrouding means forming a movable article shield movable between at least two positions and an opening for receiving said shield, one of said positions being an open position thereof to establish spatial communication between the exterior of said shrouding means and said supporting means including any articles associated therewith when said supporting means within shrouding means disposed in a position of registry with said opening, and the other position being a closed position thereof to shield articles inside said shroud from material entering through said opening, target means disposed outside said shroud and in facing relation to the outer surface of said shield in the closed position thereof, and means for supplying a high frequency alternating voltage to said target including means for establishing an electrical potential on said target.
2. An apparatus as defined in claim 1 in which said means for supporting at least one article comprises a plurality of individual means each adapted to receive at least one article to be coated.
3. An apparatus as delined in claim 1 in which said means for supporting at least one article comprises a 14 plurality of individual means as adapted to support at least one article to be coated, and which further includes means for moving said supporting means within said shroud past said opening for exposure to said target when said shield is in said open position thereof.
4. An apparatus as defined in claim 3 in which said means for moving said supporting means further includes means for disposing a given portion of said articles in a given relation to said shrouding means, and for maintaining said relation throughout at least a substantial portion of the movement cycle of said means for moving said supporting means.
5. An apparatus as defined in claim 3 in which said means for moving said article holders further includes said means for aligning a given portion of said articles in a given relation to a given portion of said shrouding means, and for maintaining said relation through a substantial portion of the movement cycle of said means for moving said supporting means, and which further includes means for rotating said supporting means about their axes within a relatively small portion of the movement cycle of said means for moving said holders, whereby said articles are maintained in a given alignment in relation to said shroud during a substantial portion of the movement thereof and are moved so as to assume a changed alignment in respect to said shroud during another p0rtion of said movement cycle.
6. An apparatus as defined in claim 3 in which said supporting means comprise a plurality of bayonets removably mounted in said means for moving said supporting means.
7. An apparatus as defined in claim 3 in which said means for moving said supporting means comprises a continuous ring having motorized driving means associated therewith.
8. An apparatus as defined in claim 6 in which said bayonets are mounted for rotation about the vertical axis thereof.
9. An apparatus as defined in claim 6 in which each of said bayonets includes actuators thereon for engagement with a guiding surface, and which said means for rotating said supporting means includes a cam element adapted to engage said actuators and thereby initiate rotation of said bayonets about said vertical axes thereof.
References Cited UNITED STATES PATENTS 3,458,426 7/ 1969 Rausch et al 204-298 3,021,271 2/ 1962 Wehner 204-192 3,121,852 2/1964 Boyd et al. 204-192 3,324,019 l6/ 1967 Laegreid et al 204-298 3,451,912 6/ 1969 DHeurle et al. 204-192 3,480,535 11/1969 Bloom 204-298 3,479,269 l1/ 1969 Byrnes et al. 204--298 3,515,663 6/1970 Bodway 204-192 3,528,906 9/1970 Cash et al. 204--298 3,562,140 2/1971 Skinner et al. 204-192 JOHN H. MACK, Primary Examiner S. S. KANTER, Assistant Examiner