US3723276A

US3723276A - Article coating method

Info

Publication number: US3723276A
Application number: US00829906A
Authority: US
Inventors: G Lane; C Cartwright; K Elmslie
Original assignee: Warner Lambert Co LLC
Current assignee: Warner Lambert Co LLC
Priority date: 1969-06-03
Filing date: 1969-06-03
Publication date: 1973-03-27
Anticipated expiration: 1990-03-27
Also published as: NL7008076A; NL169349C; ES380347A1; DE2027301B2; NL169349B; CA949021A; JPS5136236B1; FR2049889A5; DE2027301A1; DE2027301C3; GB1318771A; JPS5313591B1

Abstract

AN APPARATUS AND METHOD FOR COATING ARTICLES OR SUBSTRATES, PARTICULARLY RAZOR BLADES OR OTHER CUTTING INSTRUMENTS, IN WHICH MEANS ARE PROVEDED 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. VARIOUS MECHANICAL HANDLING AND PROTECTIVE DEVICES ARE DESCRIBED FOR CARRING OUT THE OPERATIONS IN A SINGLE VACUUM CHAMBER. PREFERABLY, THE SUBSTRATE IS FIRST CLEANED BY SO-CALLED REVERSE SPUTTING (USING THE INTENDED SUBSTRATE AS A TARGET) OR GLOW DISCHARGE CLEANING, OR SPUTTING ETCHING, THEN PROTECTED AGAINST CONTAMINATION WHILE THE TARGET IS CLEARED, WITH THE SUBSTRATE THEREAFTER BEING EXPOSED TO COATING BY SPUTTERING. IN ANOTHER EMBODIMENT, SIMULATANEOUS 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.

Description

- March 27, 1973 c; Q LANE ETAL ARTICLE COATING METHOD 5 Sheets-Sheet Filed June 1'), 1969 E S H L Y RM S OLRM T T WL T g VGMW N RC H [0 T BY H March 27, 1973 e. c. LANE ET AL ARTICLE COATING METHOD 5 Sheets-Sheet 2 Filed June 5, 1969 March 27, 1973 G. c. LANE ET AL ARTICLE COATING METHOD 5 Sheets-Sheet 4.

Filed June 5, 1969 March 27, 1973 G. c. LANE ET AL ARTICLE COATING METHOD 5 Sheets-Sheet 5 Filed June 3, 1969 r' 3,723,276 Ice Patented Mar- 27, 1973 United States Patent 1 2 3,723,276 Nevertheless, as is the case with many mass produced A ICLE CQATING METHO articles, there is still room for further improvement, par- D George C. Lane, Danbury, Cyril A. Cartwright, Monroe, ticularly by way of methods and apparatus which make and Keith W. Elmslie, Guilford, Conn., assignors to higher production speed and even better quality control Warner-113mm y, Morris Plains, possible, as well as those which tend to make material Flled i- 73 handling and the like simpler and more foolproof. There U S 0 204,192 c 9 Claims is also a need for systems which are improved in regard to simplifying pretreatment of the substrate to be coated and which aiford greater versatility and reliability in use.

ABSTRACT OF THE DISCLOSURE 10 There is also a need for simplified apparatus which make practical the practice of a process having a plurality of An apparatus and method for coating articles or substeps within a single unit of apparatus.

strates, particularly razor blades or other cutting instruments, in which means are provided for establishing a In View of 'E needs Set e it is an Obieet radio frequency alternating electrical field bet of the present invention to provide an improved product ween electrodes within a vacuum chamber for sputtering a coating g g ggg ggi' g z g gf gi g gszgg a g appafrom a target having the coating material thereon to the article, or substrate to be coated. The described apparatus which P e for Pleamng Substrate Prior coating by sequential or simultaneous operations carried includes means for providing preliminary cleamng o t e out within a single evacuated chamber so that the operasubstrate as well as the target before coating, such cleaning operation being capable of operating in any one of Hons may be f' i wlthout breekmg the .vacuum several different Operational modes various mechanical necessary to obtain conditions under which sputtering takes handling and protective devices are described for carrying out the operations in a single vacuum chamber. Prefere obleet 15 PYeVlde e apparatus cleaning ably, the substrate is first cleaned by so-calle revel-Se an article to be coated, for cleaning the target which serves sputtering (using the intended substrate as a target) or as a Source glow discharge cleaning, or sputter etching, 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 the blade to a h g Vacuum m operations either simultaneously or in sequence on a p ue e l of the mventlen 15 9 PYOVlde an effp rality of articles at one or more stations without breaking Yams 1n Whleh e reverse eputtefmg y be ut lhled the vacuum in the evacuated chamber, or allowing as amethed of cleaning the article to be coated prior to tamination of the article, substrate or target between eoalmg thereo? cleaning and coating operations. Another object is to provide an apparatus in which cleaning of an article or substrate by glow discharge, or

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 tar- 0 reverse sputtering, a sputter etching may be carried out, BA KGRO OF THE INVENTION followed by coating the same article or substrate with a It is we known that it is highly desirable, in the sputtered coating material, all being carried out within terest of durability and economy, to obtain extremely thin, the Same apparatushighly pure continuous metal, alloy, or like hard coating by v v g g fira ggst Si eth;1 lfsllvcaltiar algal: gig/322a; (111133;);

on the sharpened edges of cutting instruments such as i conditions of high vacuum without breaking the vacuur between steps of the method.

to cutting surfaces such as blade or knife edges are now b1 ge gg g e zlgsfig il l stlli gigs gfirgpggg sgl gg tg u ethods and a aratus bein describe u 2 known S ch as m pp g be coated in the same atmosphere, and may be protectr t' n Ser Nos. 680,794, and 680,- for example m apphca 10 5 against atmospheric or like contamination between clea 926, both filed Nov. 6, 1967. (Ending instruments made ing and coating.

in this manner possess coatings of about 50 to 800 angstrorns (A.) and preferably 100 to Ziflt) A., which are thick g sg i ggg b ga g g ggil g z z g z gi z enough to protect the cuttmg edge mm premature wear and coated in a desired sequence, or simultaneously ii and corrosion, but still thin enough to prevent rapid dullhi h vacuum environment ing of the edge of me A Principal adiantage A still further ob'ect is to rovide a cleaning and coat of using the sputtering deposition methods described in apparatus which iniludes ayacuum chamber means m these applications is that the cutting instrument may be in for pp g a plurality of articles to {De coated finish ground, honed and stropped to a desired degree 0 for advancin them in succession ast a coafm Sta sharpness and thereafter coated bprotecgifizh wliitlh a lilar after a fi g Operation is perfgrmed and u u t e e i g rs} 3 3? 222 g 223 3 z g f includes means for establishing a high frequency elect a field either alternately or simultaneously between the or to sharpen an edge previously imparted to an instrumeut after the edge has been hardened. Edge surfaces at and the groufld and the aftlcles f ceated am so coated may also readily be coated with lubricous coatground for cleemng and eoatmg the article 111 the de ing materials such as plastic materials, silicone lubricants, mannernow known A further ob ect of the invention is to provide ai or the like, in any known manner. It is that articles made with the use of the apparatus an paratus in which the means for supporting and m methods referred to above possess heretofore unsurpassed the articles to be coated about within the vacuum c ity consistent with reasonable economy and outstandber includes means for maintaining the edges of thc qual ing useful life. cles approximately parallel to a surrounding surfac ing the time they are being cleaned, and which includes given axis to reverse the orientation thereof at a desired means for rotating one or more article holders to a depoint in the apparatus; and sired extent about its own axis within a relatively small is a fragmentary plan view of a portion of the portion of the motion cycle of the article holder and for article protective device of the invention, showing the olding it against axial rotation during a relatively larger mo e of operation and an alternate position thereof in portion of its rotating cycle. phantom lines.

Another Object IS to provide an apparatus IH- OF THE cludes means, preferably single means, for exposing ar- MENTS OF THE INVENTION ticles to be coated to coating material being sputtered from the target in one position of said means, and for pro- 1 The invention l now be d s ribed With reference tecting the articles against contamination sputtered from to Partlchlar ehlhodlmems thereof, In h first f which the target durmg cleanmg th f m another posmon f c caning of all the articles to be coated takes place before such means, as well as serving as means for aiding target any of the articles, groups of artlcles, a ate cleaning prior to the time the target material is sputtered F emhg how the drawings In greater etai and onto the articles to b Coated. particularly to FIGS. 1 and 2, this form of the invention 0t er object is to provide a method in which a radio may be seen to be di in a combination article requency 1s Impressed both on a target and on an arm cleaning and coating apparatus 10 whic is somewhat dicle to be coated, the target and article are allowed to agrammahcahy Q t0 1110111618 8 rame or base 12, reach differing electrical potentials so that there is a signifimeans P estahhshlhfe ah evachated r 8 h rm f cant potential between the two, in which minute quantities an exterior, q h hght houslflg Which is mounted of an inert gas are introduced at least into an evacuated means for recelvlhg and handling arhcles t e c ated, 1n region between the articles and the target, whereby atoms the form of F assembly 16 Comprised of a lower ring ionized by the electrons flowing in the chamber strike stand 18, an Insulator r1113 20 a IOWer earing race 22 a collision of an ionized atom with the article or the target 25 a drive? ring 28 which adapted to Support a P sputtering off one or more surface atoms, thereof, to prorahtY P amcle holdhr means the f m 0 bayonet as vide simultaneous lower rate surface cleaning of the arsembheF 30 f holdlhg a plurality of rt s 32 thereon. ticle and higher rate sputtering of the coating onto the ar- The driven rmg 28 mc1udeS external rlhg ge teeth 34 ticle, and an apparatus for carrying out the method. adflpted to mesh Wlth the teeth 36 on a P1111011 gear These and other objects of the invention are achieved 30 dnven by Stub shaft Eilch bayonet assembly Q by providing a vacuum apparatus having means for cludeswertically disposed tines 42 which are received porting a plurality of articles or groups or articles within a clrcular holder member 44 havmg a lower exten an evacuated chamber or other region target means Com sion 46 rotatably mounted for iotation in bearings 48 and taining a coating material, means for moving the articles further Includes a bottom g 50 fixedly attached h f about in the chamber, means for supplying high frequency i 52 .arespmvlded on h gear for recelvmg electrical energy to the articles for one mode of operation, C am T e 4 also has Pomohs thereof ehgflgmg and to the target In another mode and Control means for teeth 56 on the outer periphery of a central, fixed sprocket causing these operations to take place simultaneously or 8 mqunted on a hub 60 Protected by Insulator 62 from in a desired sequence of Operation to provide Coated electrical contact therew th. The bearings 48 engage the tides made by the method and apparatus outer surface of a plurality of sleeves 64 disposed in the 2 y The exact manner in which these and other ob ects of 1 en ring 8 an m use rotation of the mug 28 about of the car 50, and conse uent rotat'o f when they are considered in COHJUIICUOH with the apg q l n 0 each bayonet tation of the ring 28 about its axis causes rotawhich reference is made to the accompanying drawings, Thus m w erein like reference numerals indicate corresponding of each bayonet assembly 30 about Its Own so t at a given part thereof, for example an edge 66 of the parts throughout b ade or other article 32 held on the bayonet assembly BRIEF DESCRIPTION OF THE DRAWINGS FIG 1 is a vertical sectional View, taken through a alternately for each full revolution of the ring 28. In other portion fth vacuum chamber fth apparatus fth words, t e exterior circumference of the sprockets and vention, and illustrating certain principal portions of the gears 50, 58 may be selected so as to turn the bayonet ,pparams; assembly 30 one-half turn for each complete turn of the FIG. 2 is a top plan view, partly in plan and partly in Tlhg ection, with portions broken away, showing the appara- In the embodiment shown in FIGS- 1 and a motor Us of FIG 1; 68 is provided having a shaft 70 thereon containing a driv- FIG 3 is a schematic View of a simplified form of the en bevel gear 74 which is fixedly attached t0 the stub lectrical circuitry of the invention; shaft 40. Thus, the ring 28 and the parts associated there- F G. 4 is a schematic view of another portion of the with are rotated by the manner set forth above. ectrical circuit of the invention showing a power sup- As shown in FIGS. 1 and 2, means are provided for y, an alternating current source and an impedance protecting the articles 32 held on the bayonets 30 or other atching network; article holding devices against undesired contamination, F 5 is a schematic view showing the operation of and for assisting in the cleaning of such articles, in the Jortion of the electrical circuit of the apparatus in one form of an article shroud assembly 76 defining, on the dc of operation for cleaning the blade; inside thereof, a cylindrical passageway 78. The shroud E is a schematic view showing the circuit of the assembly 76 includes an outer wall portion 80, an inner iaratus in another mode of operation thereof, for cleanwall portion 82, a top wall portion 84, and on an insulatthe blades or the like by another process; ing support 86 which is fixedly attached to the roof por- G 7 is a top view, partly in horizontal section, and tion 88 of the chamber 14. The bottom edge 90 of the l portions broken away, showing another form of the shroud assembly 76 is closely spaced apart from the iratus of the invention; upper surface of the ring 28, so that the articles 32 held on is a vertical sectional view, on a greatly enthe tines of 42 of the bayonets 30 are substantially comis for orienting groups of articles to be coated in a rotation of the ring 28. ed position of use, and for rotating them about a 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 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 surface of 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 110 of the chamber 14.

Referring again to FIG. 1, it is shown that each wall 80, 83 comprises respectively an outer surface 112, 114, 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 ap paratus 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 130, 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 134 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 148 and its associated driving gear 150 will move the arm 134 straight forward a given distance 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 defined 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 assembl 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 in 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 inert 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 renerator 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 generator 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 21-8, 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 fixed 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 frequency, and this impedance is matched in the manner shown, or in an 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 element 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 flow.

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 14, 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 10- millimeters (mm.) of mercury (torr). The shield 98 is moved to the closed position so that two continuous inwardly facing

surfaces

116, 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

116, 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 1 10- to 1 10 torr. Under these conditions, a current of about 500 milliamperes (ma.) will be developed, and the resulting glOW discharge will cause ionization of argon atoms and impingment thereof onto the blade edges to a degree sufficient 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 1 l0- torr as a background pressure, RF energy at 13.56 megacycles or megahertz (me. or mHz.) is supplied to the target electrode 126, and argon is leaked through the valve 204 until a pressure of approximately 6 to 9X10- 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 field are attracted to the target 126 by the DC bias thereon with consequent sputtering of 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 methods 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 final 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 changing electrical conditions and manipulating the vacuum level and inert gas leak valve controls, but without exposing 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 2 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 182, 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 10- 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, 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 are 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 10- 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 may 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 supply 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 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 10 is evacuated to a background pressure of about 1x10- 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 9X 1O 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 1 up to about 10 to 1, preferably between 2 to 1 and 3 to 1. 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 10 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 possible. This is not ordinarily a problem, however, since a crystal oscillator having a definite, fixed 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 all 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 functionally 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 1n 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 specifically 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

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 248 plus a slight working clearance.

Referring now to FIG. 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, 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, 250 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 244, 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. Since the holder 252 is rotated about its own axis, the trailing pin 250 is moved to the right of a motion line parallel tto 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 the cam element 254 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 for receiving the

pins

248, 250. A bearing assembly 276 locates the holder 252 and mounts it and its associated components for rotation about its vertical axis. A snap ring 278 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 256 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 310 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 connected with Example. 1.

However, the means for driving the ring 282 are somewhat difierent, comprising the ring gear 288 and pinion gear 304 with its associated mechanism, instead of the 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. 1 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 and perpendicular to radial planes defined by the longitudinal axis of the shroud 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 are preferred where it is desired to maintain an edge 322 of an article 316 parallel to a given surface 318 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 edge blades, or where only one side of an article is desired to be cleaned and coated, rotation of each bayonet 30 or holder 252 about its own axis is not necessary, and portions of the mechanisms, such as the cam surface 260 and the outer cam elementt 254 may be done away with, as might the chain and gear assembly described in connection with FIGS. 1 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 1 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 1 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 13 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.

We claim:

1. In a method of cleaning a plurality of cutting instruments each having at least one cutting edge and of depositing a thin continuous coating on the cutting edges; wherein said method is performed in a sputtering chamber comprising at least one target having a coating material thereon, shroud means for enclosing said instruments comprising a pair of spaced concentric cylindrical inner surfaces having a longitudinal axis, and shutter means for opening said shroud means to expose the cutting edges of said instruments to said at least one target; the steps comprising:

(a) disposing said cutting instruments in a plurality of arrays within said shroud means, each of said arrays having the instruments therein arranged with the cutting edges parallel to said inner surfaces and perpendicular to a radial plane passing through said longitudinal axis,

(b) evacuating said chamber,

() establishing an electrical potential difference between said shroud means and said arrays,

(d) moving said arrays between said inner surfaces in a circular direction while maintaining the relative array arrangements of step (a),

(e) introducing minute quantities of an inert gas into said chamber to clean the cutting edges by removing atoms therefrom,

(f) establishing an electrical potential difference between said at least one target and said arrays, and

(g) actuating said shutter means to open said shroud means and sequentially expose said at least one target to each of said arrays, thereby sputtering said coating material to the cutting edges of said instruments.

2. A method as defined in claim 1 further including the step of cleaning said at least one target by removing a portion of the surface thereof by sputtering prior to p (e)- 3. A method as defined in claim 1 in which said at least one target is cleaned of surface contamination by sputtering prior to step (g).

4. A method as defined in claim 1 wherein step (0) includes applying a direct current bias to said arrays.

5. A method as defined in claim 1 in which step (c) includes applying a high frequency alternating current to said arrays to establish a direct current bias on said arrays with respect to ground.

6. A method as defined in claim 1 in which said atoms removed from the cutting edges in step (e) include atoms of organic contaminants and atoms of gases adsorbed on said surface.

7. A method as defined in claim 1 in which said atoms removed from the cutting edges in step (e) include portions of the cutting edges and atoms of oxide coatings formed on the cutting edges.

8. A method as defined in claim 1 in which said coating material comprises substantially pure metallic chromium.

9. In a method of cleaning a plurality of razor blades each having at least one cutting edge and of depositing a thin continuous coating on the cutting edges; wherein said method is performed in a sputtering chamber comprising at least one target having a coating material thereon, shroud means for enclosing said blades comprising a pair of spaced concentric cylindrical inner surfaces having a longitudinal axis, and shutter means for opening said shroud means to expose the cutting edges of said blades to said at least one target; the steps comprising:

(a) disposing said blades in a plurality of arrays between said inner surfaces, each of said arrays having the blades therein arranged with the cutting edges perpendicular to a radial plane passing through said longitudinal axis,

(b) evacuating said chamber,

(c) establishing an electrical potential difference between said shroud means and said arrays,

(g) actuating said shutter means to open said shroud means and sequentially expose said at least one target to each of said arrays, thereby sputtering said coating material to the cutting edges of said blades.

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 6/ 196 7 Laegreid et al. 204-192 3,451,912 6/1969 Dheurle et al. 204-192 3,480,535 11/1969 Bloom 204-192 3,479,269 11/1969 Byrnes et al. 204-192 3,515,663 6/ 1970 Bodway 204-192 3,528,906 9/1970 Cash et al. 204-192 3,562,140 2/ 1971 Skinner et al. 204-192 JOHN H. MACK, Primary Examiner S. S. KA NTER, Assistant Examiner US. Cl. X.R. 1204-298