CA2184737A1 - Diamond-like carbon coated transducers for magnetic recording media - Google Patents

Abstract

A method is provided for manufacturing a diamond-like carbon coated magnetic transducer assembly with superior wear resistance, and improved lifetime. The invention discloses a magnetic transducer with a composite coating structure including an adhesion-enhancing a first interlayer containing silicon and an ion beam deposited DLC top layer. According to the method, the surface of the magnetic transducer substrate surface (3) is bombarbed with energetic ions from an ion source (4) to preform sputter etching, a silicon containing interlayer is deposited utilizing an ion beam source (7) and a target (10) to sputter deposit the interlayer, and following completion of the deposition of the interlayer a DLC top layer is deposited by ion beam deposition.

Description

wl~ss/23a7s 21 8 4 73 7 r ~ ~q DIAMOND-LIKE CARBON COATED TRANSDUCERS
FOR MAGNETIC RECORDING MEDIA
.
Field of the Invention This invention relates to transducer assemblies utilized in magnetic recording devices. More ~u i ' 'y, the invention relates to a trvnsducer for ug with magnetic rGcording mGdia e.g. thin film magnetic heads, ~ vtv~ e (MR) read heads, inductive heads, sliders, and tape heads.
Back~round of the Invention Amorphous diamond-like carbon (DLC) films are so-named because their properties re.emble, but do not duplicate, those of diamond. Some of these properties are high hardness (HV = about 1,000 to about 5,000 kg/mm2), low friction coefficient (ayylu~ tvly 0.1) and LlUII~yu-vl-~y across the majority of the vl~vvLlUlllU~ iC spectrum. At least some of the carbon atoms in DLC are bonded in chemical structures similar to that of diamond, but without long range crystal order. Although the term DLC was initially inoended to define a pure carbon material, the term DLC now used includes ar,~orphous, hard carbon materials containing up to 50 atomic percent of hydrogen. Other names for these hydrogen-containing DLC materials are "ulllUlyllUU~ lI,YVIIU,~ carbon", 11~yv111, ' ~ diamond-like carbon. or diarnond-like llyvllvvullvull. The structure of these hydro~en-containing hard carbon materials may be best described as a random covalent network of graphitic-type structures vull.~vv;vv1 by sp3 linkages, although the definitive structure of the films has yet to be universally accepted. In keeping with the majority of the previous literature and art, the term DLC is used in the present invention to refer to both the amorphous non h~ ' hard carbon materials, and the amorphous l~ ' hard carbon materials.
Many methods for directly depositing DLC films are known in the prior art, including (i) direct ion beam deposition, dual ion beam deposition, glow discharge, 30 radio frequency (RF) plasma, direct current (DC) plasm;3 or microwave plasma deposition from a carbon-containing gas or vapor which can also be mixed with hydrogen and/or inert gas, ~li) electron beam G~uyul~ , ion-assisted ~v~U~

wo 95/23878 2 1 8 4 7 3 7 P l/U~ r /60 magnetron sputtering, ion beam sputoering, or ion-assisted sputter deposition from a solid carbon target material, or (iii) cr~ ;r ~ of (i) and (ii).
DLC films are well known in the art and have been recognized as potential coatings to enhance the abrasion resistance of various substrate materials, including 5 recording media. The DLC coatings possess excellent mrr~ r~l properties such as high hardness and low coefficient of friction, and exhibit excellent re~istance to abrasion and chemical attack by nearly all known solvents, bases, and acids.
However, it has been found that the DLC coatings will impart improved wedr resistance to the substrate only if the adherence of the coating to the parent 10 substraoe is excellent.
The ~nost obvious and common approach to coating a substrate is to apply the DLC coating directly onto a clean surface which is free of residue. However,this approach often results in a DLC coating which displays inadequate adhesion,and therefore, poor wear resistance. DLC coatings are typically under significant 15 ~,UIIIIJlC~ iVC~ stress, on the order of 5 x 109 to d~ 5 x lol dynes/cm2.
This stress greatly affects the ability of the coating to remain adherent to thesubstraoe. Additionally, the surface of the sLbstrate to be coaoed often contains alkalj meta~s, oxides, and otherl. which can inhibit bonding of the DLC coating. Therefore, less obvious methods are required t~ produce a substrate20 with a highly adherent DLC coating which provides excellent abrasion resistance.
Magnetic transducers which include thin film magnetic heads, ..~ Li~, (MR) read heads, inductive heads, sliders, and tape heads, utilized in magnetic recording media have been known in the art for many years.
Their ~u~rrtih~ y to damage is also well known. One example of a magnetic 25 transducer used in recording media is a magnetic head slider. The slider supports a thin film magnetic read/wrioe head, which is formed by depositing layers of magnetic material, electrically conductive maoerial, and electrically insulatingmaoerial to form the magnetic pole pieces and magnetic gap which are necessary for the 30 . ' g, function with the magnetic coating on a magnetic recording medium.
After lapping the magnetic head to a ~ . t- -1~ d "throat height" dimension, a w095123878 2 8 4 7 3 7 P~.l/o... _. /o~i pattem of rails is produeed on the lapped surface to form an air bearing surfaeewhieh is used to "fly'- the magnetie head over tne magnetie reeording medium.
During operation, a magnetic head slider typieally flies with its air bearing surfaee less than a few .. ,.u;.. ,l.~,s (I microinch = 254 A) above the magnetie S reeording medium. The air bearing surface of the slider contacts the magnetic disk durillg start-up and shutdown of the disk rotation, and sometimes il~ad~ ly during operation. In cu..~, I sliders and recording media, this eontaet results in transfer of disk material (wear debris) to the slider, whieh degrades the a~,lU~IIallll,~ of the slider and inereases frietion. The presence of the wear debris 10 and the inereased frietion ean at times result in ca~a~ u~ ic failure and loss of stored i,.ru....dt;ul..
Tape heads used with magnetic recording tape also suffer failure due to wear and corrosion. In this case, the magnetic pole pieees are worn away by abrasive materials in magnetic tape. The magnetic materials on the transducer are 15 also degraded by ~,IIV;IUIIIII~,~n~ll eorrosion.
In addition to mcehanical wear, magnetic transducers such as thin film magnetie heads and ~ ,;u~u~;~LiY~ heads are fabrieated from materials that are attacked by -~ ,; . . such as moisture. Prolonged exposure of the transducer materials to dL-..~ ,l., often results in 1r~ ;,. of p~.r..,., - ,~ due 20 to oxidation and corrosion of the head materials.
Protective DLC overeoats for thin film metal alloy disks are well known. A
review of the field was presented by H. Tsai and D. Bogy in ~Cllal~ r ~ ;on of D;am~n~ Carbon Films and Their Applieation as Overeoats on Thin-film Media for Magnetic Recording", J. Vac. Sci. Teeh. AS (1987) 3287-3312. Illustrative 25 from the prior art are the following references:
Aine, U.S. Pat. No. Re 32,464 teaches a magnetic recording medium coated with a sputter-deposited graphitic carbon protective layer having thickness between 1-5 ~ u;-~h~s. Use of an adhesion-promoting carbide-fomming layer between the disk and the carbon film is disclosed and claimed. Additionally, "the magnetic 30 transducer head portion which occasionally sinks into contact with the rceord;ng medium is preferably formed of or coated with carbon, preferably in the form of graphite, to provide a low friction wear resistant contacting surface with the Wo 9sn3878 4 r~l,. . . /60 recording medium". The carbon layer may also be deposited by ion plating. Aine further states that the sputtering appaQtus allows the substQte surfaces and tlle surfaces of subsequent layers which are to be coated to be cleaned by bombardingsuch surfaces with ions for cleaning away any surface v.
Michihide et al., EP 216 079 Al, teach a method for n f~ g, a thin carbv~n film on the surface of a sliding member such as a hard disk of a magnetic recording device which contacts another member, in which the carbon thin film isformed by sputter deposition from a g~assy carbon sputtering target. Triode direct current sputtering. diode Qdio frequency glow discharge sputtering and magnetronsputtering are the methods disclosed for sputter deposition using the glassy carbon target material.
Howard, U.S. Pat. No. 4,778,582, describes a prior art sputler deposition technique for ~ ...r"~ of a thin film magnetic disk coated with amorphous llydl~ ~ I carbon. In this method, amorphous l~y~ b,vl carbon is 15 deposited by sputtering a carbon target in an atr~-srhP~ of argon and hydrogen.
The deposition rate is ~~ lLdt~,ly 6-7 ~/minute. A 100 ~ thick titanium layer isused as an adhesion layer.
Meyerson et al., U.S. Pat. No. 4,647,494, disclose an improved wear-resistant coating for metallic magnetic recording layers, where the improved 20 coating is a non-graphitic hard carbon layer strongly bound to the underlyingmetallic magnetic recording layer by an i,-~- . .". .I:~t~. Iayer of silicon, having a thickness less than 500 A. The silicon layer can be as thin as a few atomic layers.
The hard carbon layer has a thickness in the Qnge of about 25 A to I micron, Theprefcrred method for depositing both the silicon; ..~ layer and the hard 25 carbon layer is claimed to be plasma deposition. The patentees further teach that the silicon interfacia~ layer can be deposited by any known technique, e.g.
evapoQtion, sputtering, or plasma deposition. Plasma deposition is preferred because the same prvcessing equipment and steps can be used to form the silicon layer and the overlying hard carbon layer. Therefore, both the silicon layer and the 30 hard carbon layer can be formed by plasma deposition without breaking the vacuum in the system. Changing the source gasses, e.g., from silane to acetylene, are the only additional steps that are necessary. The patentees also state that hard . .

Wo 9sl23878 2; 8 4 7 3 7 1 ~ 60 carbon layer can be also deposited by sputtering and other methods. The patentees still further teach the silicon layer is exposed for 45 minutes to a hydrogen plasma - to provide both reactive and sputtered cleaning of the growth surface and also to further rGduce the native oxide layer on the silicon. rhis cleaning time is very 5 long, and ~ for industrial ~ ' It is further stated that the hydrogen plasma preclean does not, by itself completely remove the native oxide from the silicon substrate. Thus, improved methods of l/IG 1~ 'g the substrateprior to depositing the hard carbon coating are needed. The patentees also disclose difficulties in the use of plasma deposition of the hard carbon layer; see column 6, line 67 through column 7, line 3.
Japanese Laid Open Pat. Application (Kokai) No. 1-287819, Shinora, claims a magnetic recording medium (magnetic disk or magnetic tape) in which a diamond-form hard carbon thin film is located on a strongly magnetic metal thin film with a silicon or G ' layer, interposed between the two. Ion plating, high frequency sputterin~, and electron beam e~ )Ul~L~iUII are disclosed as methods for depositing silicon and i films, from thickness of 20 to 50 A. The diamond-like carbon film has a thickness between 50 and 100 A and can be formed by high frequency sputtering, ion beam deposition, or plasma ~ . Ir,,~ "
The diamond-like carbon layer is then overcoated with a lubricant to form the final product.
Endo et al., U.S. Pat. No. 4,774,130, discloses a magnetic recording medium composed of a magnetic film formed on the surface of a disk-shaped substrate and a protective film further formed on the surface of the magnetic film.
The protective film is composed of a first layer containing silicon, ~ or chromium oxide, and a second (top) layer of amorphous carbon or graphite-containing amorphous carbon. The first and second layers can be formed by a variety of sputtering techniques including magnetron sputtering, diode sputtering, and ion beam sputtering. The patentees teach that the first layer containing chromium oxide, silicon, and ~ermanium formed on the magnetic film excels in resistance to corrosion and weather conditions. The sGcond layer of amorphous carbon or graphite-containing amorphous carbon excels in lubricating property. The thickness of a first layer of elemental silicon is in the range of 100 Woss/23878 2 1 8 47 37 ~ .760 to 300 A. It is also taught that the second (carbon) layer is desired to have a thickness in the range of 200 to 700 A. If the tbickness is smaller than 200 ~, the ~rr~,~ of the second (carbon) layer in improving the lubricating propcrty is not sufficient. The patentees further state that if the resistance of the carbon layer 5 ~xceeds 10~ ohm-cm, the amorphous carbon assumes a texture ~ lldl..g the diamond structure and shows ~ Iubricating properties. In their exarnples, the patentees rll~r- that carbon films having properties which are more diamond-like than those in the claimed range perform much worse in contact-stop-start (CSS) tests than the amorphous carbon or graphite-conhining 10 amorphous carbon films of the patentees' invention. For example, the graphite-containing amorphous carbon layers provide resistance for 40,000-130.000 CSS cycles. whereas carbon films with the diamond-like structure provide resistance for 10,000-16,000 CSS cyc~es. In addition, it is shown that the graphite-containing amorphous carbon films are much more resistant to permeation15 by water than with the diamond-like structure.
Kurokawa et al., U.S. Pat. No. 4,717,622, discloses a magnetic recording medium with a protective layer of high hardness carbon ~yll~ .,J under a low r ' ~ and low pressure gas plasma. The magnetic recording medium is useful in a system where the magnetic head contacts the ma~netic recording 20 medium. The diamond-like carbon film has a Vicker's hardness of more than

2,000 kg/mm7, and a specific resistance of 10~ ohm-cm to 10~3 ohm-cm. The patentees refer to their diamond-like carbon coatings having properties in the dr~ ' range as "amorphous diamond". It is specifically stated that amorphous carbon films having a hardness in the range of 1,500 kglmm~ are "soft".
25 These "soft" carbon films are outside the critical teaching of this reference.
Nakamura et al., U.S. Pat. No. 4,804,590, teach an abrasion resistant magnetic recording member comprising a Cdlb~ surface protective film on a sutface of a magnetic film on the surface of a ~ ".:~ "- l ~ substrate. The protective film has a lower layer of ~;ull~ ud~ ly hard cr~lbOlidc~ film and an 30 upper layer of ~,ulllyd~dli~-,lY soft ~ ~ubol.d~,.,vu~ film. An ' layer of chromium, titanium, etc. may by used to improve the adhesion of the ~ "~
film to the magnetic film. The lower CdlbOlldC~VU:~ layer contains S atomic percent ~, , .

wossr23s7s 21 ~4 37 ~ 7O~
or less of hydrogen, fluorine, or a c~ . of hydrogen and fluorine, and the upper ..~u~ . Iayer contains 6 atomic peteent or more or hydrogen, fluorine.
or a c~mhinqti~n of hydrogen and fluorine. The lower ull~ull~ccuu~ layer may be a sputtered ~ r~o ~ film, and the upper layer may be a plasma chemical vapor deposited (PCVD) ~,Aui)ol~dcciuub film.
Additionally, protective DLC coatings on magnetic head sliders have been discussed in the prior att. Illustrative are the following references:
IBM Technical Disclosure Bulletin, Vol. 25, No. 7A (1982) page 3173 discusses a magnetic slider made of silicon which is coated with an extremely hard surface layer of silicon carbide or diamond-like carbon. The sufficient thickness of the silicon carbide or diamond-like carbon surface layer is in the range of 50 nm to 100 nm. The diamond-like carbon layer can be produced by ion beam or plasma deposition.
Bleich et al., U.S. Pat. No. 5,151,294, discloses a method for depositing a thin protective carbon film on the air bearing surface of a slider in a magneticrecording disk file by contacting the slider and a rotating magnetic disk for a time sufficient to cause transfer of the carbon from a carbon overcoated disk to the air bearing surface of the slider. The patentees teach that the carbon film formed on the slider is an essentially amorphous ll.ydl, ~ ' carbon film ~ 50 A in thiekrless.
Japanese Laid Open Pat. Application (Kokai) No. 3-25716, discloses a magnetic head slider, ~.llAU-u;uliL~i by the fact the head slider body is made of a sof; ceramic material, such as ferrite. and a hard ceramic membrane such as carbon, silicon, zirconium dioxide, aluminum oxide, or the like, which is bonded2s and molded onto at least the pressure-receiving surface of the slider which faces the magnetic disk. This disclosure is said to offer advantages in ' ~ of the slider, because softer ceramic substrate materials are used in processing. The hard ceramic membrane has a thickness in range of several hundred Angstroms, and may be made by a plasma chemical vapor deposition (PCVD) method.
Head et al., U.S. Pat. No. 4,130,847, describes a magnetic head slider having a protective coating preferably chromium over at least the magnetic head.

Wo 95/23878 2 1 8 4 7 3 7 ~I/U_. ~?760 ~

The coating is produced in a recess within the slider body to a thickness as small as 10 ~ u;.l~,h~,s.
Grill et al., U.S. Pat. No. 5,159,508, teaches a magnetic head slider coated with an adhesion layer and a protective diamond-like carbon layer. The coatulg is 5 fabricated onto the substrate after a lapping operation, but before patterning of the rails onto the slider, which protects the magnetic head during the fabrica~ion process. The slider has at least twû rails ûn the air bearing surface, and the rails have a protective coating comprising an adhesion layer, typically about 10 A to 50 A in thickness, and a thin layer of amorphous hydrog-enated carbon, less than about 10 250 ~ thick. Grill et al. teach that the two layers of the protective coating carl be deposited by any suitable technique, e.g. PACVD, ion beam or laser techniques.
The preferred technique is by the use of a DC biased substrate in an RF plasmd dcposition apparatus.
Chang et al., U.S. Pat. No. 5,175,658, claim a magnetic slider similar to that 15 disclosed in Gril~, et ol., U.S. Pat. No. 5,159,508, discussed above, but with an additional thin masking layer on top of the amorphous l~r~LuE~ dt~,~ carbon layer.
DC magnetron sputtering and RF magnetron sputtering are presented as preferred mcthods for depositing the amorphous l~y~LuL I carbon film.
Japanese Laid Open Pat. Application JP 58-150,122 describes a magnetic 20 head which has a thin film of a material, e.g. carbon, having a lubricating effect on the surface of the head which faces the magnetic recording medium. The thicknessof the film is disclosed to be in within the range of 200 A to 5000 i~.
German Pat. Application No. DE 3,714,787 describes a storage system in which the surface of a magnetic disk is coated with friction-reducing carbon and25 the rails of the magnetic head slider are coated with a friction reducing carbon.
The thickness of the carbon is 10 to looo A.
Published Pat. Application PCT/US88/00438 discloses a magnetic head slider havin~ a magnetic head which is built within one of the side rails. A wear layer is provided over the slider comprising a 50 A thick chromium layer and a 30 200 A thick carbon layer. Either component of the wear layer can be omitted.
The prior art methods for application of DLC co~tings on magnetic media transducers such as thin film heads and tape heads all suffer from one or more of . , _ , . . . .. .

wo ss/23s7s 2 8 4 7 3 7 r~ /60 the followin~ and ~I.ult~,u~ . (i) difficulty in pre-cleaning of substrates prior to depositiqn; (ii) adhesion of diamond-like carbon coating; (iii) - permeation of amorphous carbon films by water vapor and oxygen; (iv) fabrication of coherent, dense coatings which perform well at ~ ;.,c~ less than 200 ~; (v) 5 poor electrical resistivity of the coating due to the use of low resistivity Ti, Cr, or Si adhesion layers between the transducer and the DLC coadng, or a ~'graphitic",low resistivity DLC layer; (vi) control ûf DLC coating properties during a deposidon run and batch-to-batch variation of DLC coating, l, - ,,. ~ ;., (vii) DLC coatdng thickness control and l~ilJIu~luu;l~ y of thickness; (viii) part-to-part 10 and batch-to-batch control of DLC coatin~ uniformity; (ix) production readiness and ability to scale-up the deposition process for mass production; and (x) difficulty in coating transducer assembly substrates of cûmplex geometry or c~nfie~-r~ n These ~I~UILUUIII;~ are hi~hli~ ' ' in tlle following review of the two 15 preferred prior art methods for deposition of DLC coatings on magnetic media and magnetic LlfU~:~d~ . RF plasma deposition frûm a l~d~u~ ~ub~ gas, and magnetron sputter deposition from a carbon target using argon gas, or an fll fl~.~dlu~ gas ~ The first problem ~ cd by both methods is the difficulty in pre-cleaning the substrates prior to deposition of the adhesion 20 layer or carbon film. Typically subst.~ates are pre-cleaned in an inert gas or hydrogen glow discharge ~plasma) prior to deposition. This pre-cleaning technique suffers from low cleaning rate, and re-~u,,l~l,,.;,.-l;~n of the substrate by sputtered ~ which are deposited back onto the substrate.
It has been found that an adhesion-prqmoting interlayer is required to 25 achieve excellent adhesion between the magnetic transducer substrate and the protective DLC coating. In the prior art~ layers such as Ti, Cr, and Si, deposited by magnetron sputter deposition, ~,Yfl~)Ulfl~iUII, and plasma deposition have been used for this purpose. Achieving a highly dense (non-porous), adherent, adhesion-promoting layer still remains a problem with the prior art techniques.
30 Deposition of a silicon interfacial layer by plasma deposition such as disclosed in U.S. Pat. No. 4,647,494 as discussed above, has the additional di~,~lv,~ ; that the feed gas used is silane, which is an extremely flammable and toxic material.
_ _ . , . ,, . , _,, _,, _ _ .. ... . . .... .... ................ ... ...... ... ... ... .

WO95/23878 2 1 8 ~737 p~ /60 Feed gases of this nature are required by the plasma deposition technique for deposition of silicon layers of high purity.
One of the key ~ of the protectiYe DLC coating on magnetic transducers is the need to provide a barrier to moisture and oxygen. This requires 5 formation of a DLC structure with optimal atom packing density. This atom packing density is maximized by a high degree of ion ~ ' .11l..,... during film growth, which is not easily attainable or optimized by the magnetron sputter deposition or plasma deposition methods of the prior art. In addition, the difficulty in forming DLC films of maximum atom packing density by the magnetron sputter 10 deposition and plasma deposition methods of the prior art makes deposition ofcoherent, corrosion resistant pinhole-free films less than 200 ~ thick extremelydifficult.
For many designs of ma~netic Ll~lladu~ , it is critical for the protective coating to exhibit high electrical resistivity. This is specially true for 15 Illal;~..,t~ Li~, designs of tape heads or sliders. In these ma~ vl~ i designs, there are magnetic shields in the heads which shield the Illagl.~,Lol~;si~liv~
sensor from the other elements of the head. Those shields can be either groundedor at potential, but always at a different potential than the sensor. It is not allowable to provide a path for electrical conduction between tlle shields to the 20 sensor. Additionally, it is ~ot allowable to provide an electrically conductive path between the sensor to any other element in head which is maintained at a different electrical potential. Finally, there are situations in which it is deleterious to allow electtical charge to pass directly between the transducer and the recording medium when the transducer and recording medium come into direct contact. An 25 electrically non-conducting layer can protect against this problem.
Thus, it is often critical for the protective coating to be highly electrica~ly insulating. When a pure argon atmosphere is used, the electrical ~ viL~ of the sputter-deposited carbon film may be too high, causing electrical losses in the transducer. Electtical conduction paths can also be provided by low resistivity Ti, 30 Cr, or Si adhesion layers of the prior art. Clearly, for many magnetic transducer designs, there is a need for the production of a protective DLC coating in which WO 95113878 P~ /60 both the DLC layer and the adhesion-promoting interlayer are electrically non-ccm~lllrtin~
Regarding the control of DLC coating properties within a single deposition run, and from batch-to-batch, it is well known that control is difficult with the 5 plasma deposition methods, see Meyerson et al. in U.S. Pat. No. 4,647,494 discussed above. It is known in the prior art that as the hydrogen CU~ ;ull in hard carbon films increases, the film hardness decreases. Thus, the hard carbon film depûsited by the plasma depûsition method is nût uniform in ~
throughout its structure, the top surface ûf the film being softer than the portion of 10 th~ film in contact with the silicon layer. Softer DLC layers are d;~adv from the poirlt of view of higher wear rates.
Because the size ~nd shape of the part to be coated, and its method of fixturing infiuence the plasma uniformity and plasma density around a part, it is difficult to predict and control deposition thickness uniformity across multiple parts 15 coated within a single coating run using the plasma deposition methods of the prior art.
The depûsition rates of amorphous car.bon materials by magnetron sputter deposition from a carbon target are very low, on the order of 10 A/minuoe or less, see U.S. Pat No. 4,778,582 discussed above, resulting in ~A~ long 20 production times. While the plasma deposition methods offer much higher deposition raoes, it is difficult to reproducibly control deposition thickness, deposition raoe and deposition uniformity across large areas with plasma deposition methods. Due to their inherent high deposition rates, the plasma deposition methods (RF plasma, DC plasma and microwave plasma) are well-suited to5 fabrication of thick coatings of diamond-like carbon for many industrial c on wear parts. However, because of the ', ' of process variables such as pressure, gas flow rate, power, and substrate bias, accur~te control of deposition thickness is difficult. Thus, it is very difficult to ~ c;hard carbon layers as well as silicon adhesion layers with thickness less than 1,000 30 A with run-to-run thickness variation ûf less than ~I~,uluAill...,ul~ 10%. This is a significant di~.~dva~ , of the plasma deposition oechniques of the prior art for the deposition of DLC coatings on sliders where accurate control of thin (e.g. 200 A) wo 95123878 P~ . /60 protective layers is required. Very thin (< 200 A thick) protective layers is required for ultra-high recording density ap~li.,.l~iol.s in which the distance between the transducer and the magnetic medium needs to be less than several hundred Angstroms. The thickness of the DLC coating narrows this spacing.
Finally, because of the sensitivity of the plasma deposition processes to substrate geometry, it is often impossible to coat parts of complex geometry or r., r;~ Examples of complex geometry include sliders already mounted on their suspension systems, and tape heads or other transducers which have be~n packaged complete with electrical connectors (e.g. wires). Thus, the plasma 10 deposition methods are more conducive to application of the DLC coating whilesliders, for example are still joined on a chip as in U.S. Pat. Nos. 5,159,508 and 5,175,658 discussed above.
An improved ". ,..r;" I.,..,u- method would be very desired that allows the DLC coating to be applied to magnetic transducer assemblies of complex geornetry.
15 Additionally, an improved ~ method is needed that allows the DLC
coating to be deposited as the final step in the transducer ' p, process.
In this way, the DLC coating process could be readily integrated into current transducer assembly ~ ' g lines.
All of the difficulties described above combine to mak~ mass production of 20 DLC coatings on magnetic i ' by the plasma deposition process and other prior art methods very ulubL,.I~Li. indeed. Clearly, there is a strong need for an improved method for flexible, Ic~ludu~;blc, and high quality mass production of DLC coatings for magnetic i ~ W09SJ23878 2 1 8 4 7 3 7 F_~. /oO

SummarY of the Invention The invention provides a magnetic transducer assembly with superior wear resistance, and improved lifetime. More ,u~LiuuLI~lr, this invention provides an ion beam deposited DLC coating to the surface of a magnetic transducer which is S highly adherent, and exhibits greatly improved wear resistance and ~ vilUlll~ tal durability. This invention also provides a low cost and efficient process for mass-producing the diamond-like carbon cûated magnetic transducer with improved wear resistance and superior lifetime.
In the present invention, a magnetic transducer is provided with a composite 10 coating structu}e including an r ' ' enhancing first interlayer containing silicon and an ion beam deposited DLC top layer. The invention further provides a method fûr fabricating the protective DLC coating on the magnetic transducer.
In the method of the present invention, after completion of the lapping, or other operation to define the magnetic pole pieces, the surface of the magnetic 15 transducer substrate is chemically cleaned to remove c, ie. unwanted materials and other: In the second step, the substrate is inserted into a vacuum chamber, and the air in said chamber is evacuated. In the third step, the substrate surface is bombarded with energetic ions to assist in the removal of residual, i.e. I~yd~u~,culJu"., and surface oxides, and to activate the 20 surface. After the substrate surface has been sputter-etched, a silicon-containing interlayer material is deposited, preferably by ion beam sputter deposition.
Following completion of the deposition of the interlayer, a DLC outer layer is deposited by ion beam deposition. Once the chosen thickness of the DLC layer has been achieved, the deposition process on the transducer substrates is 25 terminated. the vacuum chamber pressure is increased to ~rl~ pressure, and the DLC-coated magnetic transducer substrates are removed from the vacuum chamber.
Brief Description of the Drawin~s Further features and advantages will become apparent from the fûllowing 30 and more particular description of the preferred ~ .l,~ ' of the invention, as illustrated by the lC ~ .y;l-g drawings, in which like reference characters generally refer to the same parts or elements, and in which:
... . .. . _ .. .... .... . . . ...... .. . .. . .. . . . . . .. . . . .

w0 95/23878 2 ~ 8 4 7 3 7 ~ o-/Ou FIG. 1 is an illustration of the ion beam deposition apparatus used to ~ DLC-coated magnetic hd.,sluc~,~ in accordance with the present invention;
FIG. 2A is a graph of frictional force versus the number of test revolutions 5 in a constant speed drag oest for an uncoated TiC/AI203 slider;
FIG. 2B is a graph of touch down velocity change versus the number of test revolutions in a constant speed drag test for an uncoated TiC/AI20l slider;
FIG. 2C is a graph of frictional force versus the number of test revolutions in a contact-start-stop test for an uncoated TiC/AI203 slider;
FIG. 2D is a graph of touch down velocity change versus the number of test revolutions in a contact-start-stop test for an uncoated TiC/AI203 slider;
FIG. 3A is a graph of frictional force versus the number of test revolutions in a constant speed drag test for a slider coated with lOOA of DLC according to the present invention;
FIG. 3B is a graph of touch down velocity change versus hhe number of test revolutions in a constant speed drag test for a slider coated with 100 A of DLC
according to the present invention;
FIG. 4A is a graph of frictional force versus the number of test revolutions in a conshant speed drag test for a slider coated with 50 A of DLC according to the 20 present invention;
FIG. 4B is a graph of touch down velocity change versus the number of test revolutions in a constant speed drag test for a slider coated wih'l 50 A of DLC
according to the present invention;
F~G. 5A is a graph of frictional force versus the number of test revolutions 25 in a contact-start-stop test for a slider coated with 100 A of DLC according to the prc-sent invention; and FIG. SB is a graph of touch down velocity change versus the number of test revolutions in a contact-start-stop test for a slider coated with 100 A of DLC
according to the present invention.

w0 951~3878 2 1 8 4 7 3 7 r~ 760 -15- ' Detailed Description of the Invention The method of the present invention substantially reduces or eliminates the di~lv~lllL~,i> and ~IU,IL,, _ associated with the prior art techniques by providing:
(1) an improved transducer assembly, e.g. slider, inductive head, . head, tape head, thin film head, and similar devices etc. for use with magnetic recording media, in which the transducer has improved lifetime, resistance to wear, and resistance to corrosion;
(2) for the l~ r~ulc of a transducer assembly for use with magnetic 10 recording media, in which the transducer has improved lifetime, resistance to wear, and resistance to corrosion;

(3) for the deposition of an amorphous DLC coating onto the surface of a transducer assembly, which surface faces the magnetic recording media, in which the amorphous DLC coating has the properties of high adhesion to the substrate.
;",1,. .I~ h;l;ly to ~.,v;., 1 elements such as waoer vapor and oxygen, high density, and extreme surface ~

(4) for the deposition of a thin amorphous DLC coating at layer thicknesses as small as 50 A or less onto the surface of a transducer assembly, which surface faces the magnetic recording media, in which the thin amorphous diamond-like carbon coating provides a protective surface for the transducer;

(5) for the deposition of a protective amorphous DLC coating onto the surface of a transducer assembly, which surface faces the magnetic recording media, in which the layer thickness and uniformity of the amorphous diamond-likecarbon coating are l~ ' ' ly controlled to a high degree of accuracy; and

(6) for the deposition of an amorphous DLC coating onto the surface of a transducer assembly, which surface faces the magnetic recording media, in which the protective amorphous ~' ~ ~~ ' like carbon coating is ~I c~ over large areas with high Ll,l. ~hl _ The ion beam deposited DLC coating protects the magnetic transducer assembly from wear and corrosion damage during normal operation and si~nificantly extends the lifetime of the magnetic transducer system. Additionally, the method for I r ' C of the ion beam deposited DLC coating substantially W095/23878 P_,/v,.. '/~`7760 21 8~737 reduees or eliminates the d;;.~J~ v and ~;,olt~,u.l i.l&~ of prior art DLC coating methods. It is not intended by the diseussion of a particular transducer assemb~y to limit the method of the present invention to any particu~ar type of tranCA,~r~rC, sliders, or tape heads.
S It has been ~n~ recr~Aly found that the ion beam deposition process for theDLC eoatings of the present invention produced remarkable p.,.~, on a variety of magnetic i ' and ma~netie transdueer assemblies sueh as sliders and tape heads. The remarkable ~. .'( compared to prior art techniques is the result of the .~ i.. of the critieal features and attributes listed beiow.
10 The method of the present invention is eapable of:
(I) Overcoming the diffieulties in obtaining an atomically clean surface by sputter-etching the substrates using an ion beam of controlled shape, current, and energy. The ion beam "shape" is controlled by focusin~ the beam with eL,~I.u~ ic or magnetic fields. In this way, the beam can be efficiently delivered 15 to the substrates to be processed, with maximum utilization. Control of ion beam current and beam energy to within 1% is routinely achieved which results in a highly repeatable and predictable rate of removal of surface residual l..~u~I,o,.s and other, layers. In addition, the ion beam sputter-etching process is conducted in hi&h vacuum conditions, such that oxidation or c.,..~ i.. of the 20 transducer surface with residual gases in the coating system is negligible. Finally, the apparatus geometry can be easily configured such that the sputtered c.,"~ deposit on the vacuum chamber walls, and do not re-deposit onto the surface of the part as it is being sputter-etched.
(2) Producing excellent adhesion of the protective ion beam deposited DLC
25 layer by generating an atomically clean surface prior to the oeposition of the coating, and via the use of silicon-containing adhesion-promoting interlayers between the DLC coating and the substrate. The silicon-containinv layers are preferably deposited by ion beam sputter deposition ' 'y upon completion of the ion beam sputter-etchin~ step to achieve maximum density and adhesion to 30 the substrate. Deposition of the adhesion-promoting interlayers i~ lvl;a~ly upon completion of the ion beam sputter-etching step minimizes the possibility for re- of the sputter-etched surface with vacuum chamber residual ~ases ~ W09sl23878 2 1 8 47 ~7 P~,1/lJ_,_ . /60 , .
or other ~v~ The silicon-containing layers are selected from the group consisting of amorphous silicon, silicon oxide, silicon nitride, silicon oxy-nitride, silicon carbide, silicon ca bvl~iLli~e~ the so-called silicon-doped DLC, mixtures thereof and chemical ,..,..l.:..-l;....~ thereof. Each of the silicon-containing5 interlayers may contain hydrogen.
(3) Producing highly dense ion beam deposited DLC coatings. This makes the coatings excellent barriers to water vapor and oxygen. The excellent barrierproperties of the thin ion beam deposited DLC coatings ~lc~ul~dbly result from the extremely high degree of ion b~.,..l., .l..,..,l during film growt:l, compared to prior 10 art methods. It has been found that DLC coatings prepared by direct ion beam deposition from methane gas in accordance with the present invention have extremely low permeability to water vapor and oxygen. It was r' ' that 250 A-thick direct ion beam deposited DLC films having hardness in the rdnge of a~ y 10-12 GPa decreased the oxygen permeability of pvly~ ylcll~ and 15 polyl,-v~lylc.l., plastic hlm sheets by greater than 50 times. DLC coatings as thin as 50 A provided similar results. The plastic sheet substrates for this test were chosen especially for ease of dc; of the permeability of the DLC
coatings to oxy~en and water vapor. In addition to their high density, the ion beam deposited DLC coatings of the present invention are also . ' ~'y 20 smooth, which produces a surface with high resistance to wear.
(4) Producing coherent, dense ion beam DLC coatings having thickness of 50 A or less and providing ma~netic Llal~sdu~ with excellent wedr proLection.
This result is also IJIc~ulllably due to the extremely high degree of ion bo~l-b~dl~.-L during film growth, compared to prior art methods. Ultra-low 25 thickness prooective layers are critically important for the newest technology of ulLra-high density magnetic recording media, in which the required dist_nce bctween the ma~n~-rirally active surface of the magnetic transducer material and the top surface of the recording medium can be as low as 100 A or less. The newest technology of direct contact tape heads is the most stringent example where thi~30 dimension is minimized.
(5) Producing highly electrically non-conducting DLC coatings as well as adhesion promoting inLerlayers which preferably are electrically non-: ' g wo 95/23878 2 ~ 8 4 7 3 7 P~ 60 Use of these electrically non-conducting interlayers provides improved ~ rul,..a..c~
of l..a~,~.."u,esi~livc sliders, .-I..E.,~,tv..,.,;~ive tape heads, and other ~rAnc~ r. rc, compared to prior art methods.
(6) Producing a coating in which its properties do not change with layer tbickness as is found for Ihe prior art RF plasma deposition processes. This attribute is achieved because the coating deposition step is preferably conducted with a charge neutralized ion beam. The use of charge neutralized ion beam deposition process also allows for coating of parts with complex geometry without r~,.cll.,C to the process. Parts of varying geometry can be coated within a single coating run with no adverse effect on the deposition conditions. Completeslider Acc~nnhli~c tape heads, or other transducer assemblies can be easily coated.
In addition, on substrales which con~ain electrically conducting and electrically insulating materials, all portions can be coated with the same high-quality DLC
coating. In the case of the plasma deposition methods, DLC coatings of differentproperties may be deposited on different locations of the same substrate, depending upon whether the area being coated is an electrical conductor or an electrical insulator, and the electtical onC between the substrates and the vacuum chamber. The lack of substrate geometry constraints of the present invention is in sharp contrast to the plasma deposition methods of the prior art.
(7~ Having magnetic transducer assemblies fixtured for coating with ease.
Because of the ease of fixturing transducer substrates of nearly any shape or c-,-~ri~--,-l-u.,, the ion beam process of the present invention can be used to apply a DLC coating to the transducer during any part of the magnetic transducer fabrication or assembly process. For example, the DLC coating can be applied during fabrication of the transducer element as in U.S. Pat. Nos. 5,159,508 and 5,175,658, after fabrication of the transducer element, but before completion of the final transducer assembly, or after completion of the final transducer assembly.(8) Obtaining minima~ batch-to-batch variation in the properties of the DLC
coatings. This is the case because process parameters such as ion energy, ion current density, gas flow rate, and deposition chamber pressure are largely de-coupled in the ion beam deposition method of the present invention, and because each of these process parameters can be accurately controlled and reproduced to a ~ W~9S123878 21 84737 P~~ g .5?

high degree of cer~ainty, often to within I %, In addition, the process endpointDLC coating thickness is easily defined and ICIIII ' ' (9) Producing high part-to-part thickness uniformity, e.g. a variation of less than 2% can be easily achieved. This is the case because of the comp~rihility ofS the method of the present invention with c~lmmrn-i~lly available substrate holders ill~ul~Julali,.6 motion, i.e. rotation aAd/or planetary motion.
(10) Being readily scaled-up to ~ .,. ' mass production because large scale ion beam sources are cullllll."u;dlly available. For example, C~ ,.u;dlly available 38 cm ion beam sources have been ~ased to de~osit DLC coatings ' 1~/ over four 18-inch diameter platens with a thickness variation across all parts of less than +/- 2%. Similar ion beam sources can be used to practice the process of the present invention. Plasma deposition systems for DLC coat;ngs arenot presently commercially available on this scale.
The apparatus for carrying out the preferred ~ ol~ form of the 15 invention is illustrated ,- h- ~ y in FIG.l. The coating process is carried out inside a high vacuum chamber I which is fabricated according to techniques known in the art. Vacuum chamber I is evacuated into the high vacuum region by first pumping with a rough vacuum pump (not shown) and then by a high vacuum pump 2. Pump 2 can be a diffusion pump, lulb.. ~.lr~ l,.l pump, cryogenic pump 20 (''~ UIJUllllJ"), or other high vacuum pumps known in the art. The use of cryopumps with carbon adsorbents is somewhat less adv ~3 ~ than other hi~h vacuum pumps because those cryopumps have a low capacity for hydrogen which is generated by the ion beam sources used in the present invention for the deposition of DLC. The low capacity for hydrogen results in the need to 25 frequently regenerate the adsorbent in the cryopumps.
It is understood that the process of the present invention can be carried out in a batch-type vacuum deposition system, in which the main vacuum chamber is evacuated and vented to a~llu~lJh~; after processing each batch of parts; a load-locked deposition system, in which the main vacuum deposition chamber is 30 maintained under vacuum at all times, but batches of parts to be coated are shuttled in and out of the deposition zone through vacuum-to-air load locks; or in-line processing vacuum deposition chambers in which parts are flowed constantly from _ _ _ _ _ _, , _, .. . ... .... .. .. ....... ... . .. ....... .... ... ... .....

Wo 95/23878 ~ l 8 4 7 3 7 ~ 7Go ~

~LI~u~l~ c, through differential pumping zones, into the deposition chamber, back through differential pumping zones, and retumed to ~ h . ;~ pressure.
Transducer substrates to be coated are mounted on substrate holder 3, which may il~cu~,u tilt, simple rotation, planetary motion, or Cf .~ C thereof.
5 The substrate holder can be in the vertical or horizontal f~n or at any angle in between. Vertical orientation is preferred to minimize particulate .
of the substrates, but if special IJI~,l..liVlls such as low turbulence vacuum pumping and careful chamber are practdced, the substrates can be mounted in the horizontal position and held in place by gravity. This horizontal10 mounting is a.lv~u.L~u~ from the point of view of easy hxturing of small substrates such as sliders which have just been separated from the chip. This horizontal geometry can be most easily visualized by rotating the illustration in FIG.l by 90 degrees.
Prior to deposition, the transducer substrates are ion beam sputter-etched lS with an energetic ion beam generated in ion beam source 4. Ion beam source 4 can be any ion source known in the prior art, including Kaufman-type direct current discharge ion sources, radio frequency or microwave frequency plasma discharge ion sources, each having one, two, or three grids, or gridless ion sources such as the End Hall ion source of U.S. Pat. No. 4,862,032. The ion source beam 20 is charge neutralized by o~ iùll of electrons into the beam using a neutra~izer (not shown), which may be a themmionic filament, plasma bridge, hollow cathode, or other types known in the prior art.
Ion source 4 is provided with inlets for i~LIudu~Liull of inert gases 5, such as argon. krypton. and xenon, for the sputter-etching, and l~yd~u~bùl~ gases 6.
25 such as methane. acetylene. and similar gas for the deposition of DLC. During the deposition of DLC, the l.~oc u ~u.~ gas can be mixed with an inert gas, and/or hydrogen or nitrogen (inlets not shown) to modify the properties of the resultant DLC coating. As in U.S. Pat. No. 4,490.229, an additional ion source (not shown)can be used to co-bombard the substrates during DLC deposition to alter the film30 properties.
An additional ion beam source 7, is also provided for ion beam sputter-deposition of interlayer materials onto the substrates. Ion beam source 7 is ~ W09sl23878 ~ 8~737 P~ ,.0 provided with inlets for operation on inert gases 8, such as argon, krypton, andxenon, and for reactive gases 9, such as nitrogell and oxygen. The ion beam fromsource 7 is directed onto a sputtering target 10, which can be silicon, silicon nitride, or silicon carbide. A silicon target is preferable. Reactive gases such as nitrogen, oxygen, and methane can be introduced into the vacuum chamber back~round during the reactive sputter deposition of the silicon nitride, silicon carbide, and silicon oxynitride to react with the depositing layer and modify its and properties.
According to the method of the present invention, after completion of the lapping, or other operation to define the magnetic pole pieces, the surface of the magnetic transducer substrate is first chemically cleaned to remove ~
Ultrasonic cleaning in solvents, or other de~ergents as known in the art is ofoen effective; details of the cleaning depend upon the nature of the ~ and residue remaining on the part after lapping and handling. It has been found that it lS is critical for this step to be effective in removing surface c~ and residues, or the resulting adhesion of the DLC coating will be poor. This is because in many transducer designs, only a very small amount, e.g. <lO0 A, of surface material can be removed during the subsequent in-vacuum cleaning by ion beam sputter-etching step in order to minimize pole recession.
In the second step, the substrate is inserted into a vacuum chamber, and the air in said chamber is evacuated. Typically, the vacuum chamber is evacuated to a pressure of about 1 x 10 5 Torr or less to ensure removal of water vapor and other ., from the vacuum system. However, the required level of vacuum which must be attained prior to initiatin~ the next step must be ~' ~ by ~ ;on The exact level of vacuum is dependent upon the nature of the substrate material, the sputter-etching rate, the c-.,.~ preænt in the vacuum chamber residual gas, and the details of the adhesion-promoting interlayer.
In the third step, the substrate surface is bombarded with energetic gas ions to assist in the removal of residual ~ e.g. any residual I..~'11.U..~I/OI~S, 30 surface oxides and other ~ and to activate the surface. This sputter-etching of the transducer substrate surface is required to achieve high adhesion of interlayer. The sputter-etching can be catried out with inert gases such as argon, krypton, and xenon. Additionally, hydrogen may be added to the ion beam to assist in activation of the surface. Typically, in order to achieve efficient and rapid ion sputter-etching, the ion beam energy is greater than 20 eV. Ion energies as high as 2000 eV can be used, but ion beam energies in the range of 5 about 20 to about 500 eV result in the least amount of atomic scale damage to the transaucer substrate.
Once the desired throat height dimension is achieved by the lapping or other process used in fabrication oE the transducer, this should not be S~ ;r~ yaffected by subsequent processing of the head. Due to the higher ion beam etch 10 rates of magnetic maoerials compared to ceramics, a r' . known as "pole recession" can occur if the ion beam sputter-etching process is operaoed at the incorrect condition, or for an extended period of time. ~Si..illli~illg the sputoer-etchin~ time to remove <100 A of material, operating with a beam of heavy inert gas (such as xenon) ions, and varying ion beam energy and angle can be used 15 to minimize the effects of differential etching and pole recession.
T " '~, afoer the transducer substrate surface has been sputter-etched, a silicon-containing interlayer material is deposited. It has been found that deposition of interlayer materials which contain silicon atoms onto the substrate prior to deposition of the DLC layer results in highly adherent DLC coatings with 20 ~ g wear resistance properties. It is currently believed that reaction between silicon atoms in the interlayer material and the carbon atoms in the DLClayer is essential for the DLC coating to exhibit excellent adhesion.
The thickness of the silicon-containing interlayer can be in the range of about 10 A to about 500 ~ in thickness. However, in order to provide the 25 minimum spacing between the magnetic transducer and the magnetic recording medium, thinner layers, e.g. about 10 ~ to about 50 ~, are preferred.
The silicon-containing interlayer can be deposioed by a variety of processes, including magnetron sputtering, plasma deposition, direct ion beam deposition, or ion beam sputter deposition. The silicon-containing interlayer is preferably 30 deposited by either direct ion beam deposition, or ion beam sputter deposition.
Direct ion beam deposition of interlayers containing silicon and one or more of the elements hydrogen, oxygen, carbon, and nitrogen can be perfommed by operating WO g5123878 2 1 8 4 7 3 7 r~ 75q ion source 4 on gases which contain these elements. For example, ion source 4 can be operated on d;~ /la;l~l~c gas to produce an interlayer containing silicon, carbon, and hydrogen. It is believed that the ion beam sputter deposition process produces silicon interlayers or interlayers containing silicon ar.d one or more of the 5 elements hydrogen, oxyyen, carbon, and nitrogen with high density and improved adhesion to the underlyin~ transducer substrate due to the high energy ion ... ,.. 1.~.,1..... : associated with this process.
It has been found that excellent adhesion of the DLC coating to the substrate can be obtained by using electrically non-conducting layers of 10 silicon-containing materials. Use of these layers is not known in the prior art.
These electrically non-conducting silicon-containing interlayers are adv for use in ~,-..L.I ~ ve sliders, Ill.~ ive tape heads, and other transducers for the reasons discussed above.
Examples of these electrically non-conducting silicon-containing layers 15 include silicon carbide, silicon nitride. silicon oxide, and silicon oxy-nittide, and mixtures thereof and chemical ~ ;O~c thereof, such as "silicon ~,~bullill;~
By "silicon carbide", it is meant to include materials which are composed of theelements silicon and carbon, and possibly hydrogen. S~ ic and non 1 .;. l.;.. l.;~ amounts of silicon and carbon are included in the definition of 20 this silicon carbide material. By "silicon nitride", it is meant to include materials which are composed of the elements silicon and nitro~en, and possibly hydrogen.
.Stoi~hiqm~tric and non-~r( ' ic amounts of silicon and nitrogen are included in the definition of this silicon nitride material. By "silicon oxide", it is meant to include materials which are composed of the elements silicon and oxygen, and 25 pocsibly hydrogen. The definition of silicon oxide includes only materials which have a higher atomic of silicon than does silicon dioxide, SiO~. It was found that attempts to use a sputtered silicon dioxide interlayer produced aDLC coating with poor adhesion. It is believed that a silicon oxide material having excess silicon atoms which are not fully bonded to oxygen is reo,uired to produce a 30 DLC coatin~ on magnetic L.. ~.ll.. ,.,.~ with optimum adhesion. By "silicon oxy-nitride", it is meant to include materials which are composed of the elements silicon, oxygen, and nitrogen, and possibly hydrogen. Materials falling under the , _, ... .. .. .. . . . . .. .. ..

Wo ss/23878 2 1 8 4 7 3 7 r~ v -2~
chemical formula SiO~NyH7 are considered to be within the definition of this silicon oxy-nitride material.
Following compleuon of the deposition of the silicon-containing interlayer to the desired thickness, a diamond-like carbon top ~ayer is deposited by ion beam 5 deposition. It is important to minimize the ume between compleuon of the silicon-containing interlayer, and the start of the deposiuon of the DLC layer.
Deposition of the DLC layer ' " 'y afoer completion of the inoerlayer deposiuon soep minimizes uhe possibility for re~ ";,.Al;nn of the interlayer surface with vacuum charnber residual gases or other C~ - ".. ~ The thickness 10 of the prooecuve ion beam deposioed DLC coaung is cnnct~in~.l to small ~lim^-^;on5 since the coating thickness adds directly to the spacing between themagnetic transducer and the magnetic recording medium. Depending on the design and operauon of the transducer, the DLC coating uhickness is typically in the range of about 2s h to about 2,000 h. Thicker DLC layers are generally preferable in 15 terms of providing increased protection against wear and corrosion, although u ~ e wear and corrosion resistance is a~so obtained by ion beam deposited DLC coatings at the low end of this thickness range. The actual thickness of theion beam deposited DLC layer is chosen in practice based on the maximum allowable increase in spacing between tl~e magneuc transducer and the magneuc 20 recording medium.
Several ion beam deposition methods may be used for the formation of the DLC co~tings of the present invention, including direct ion beam deposition, direct ion beam deposition with ion assist, i.e. "direct dual ion beam deposition", ionbeam sputter dcposition from a carbon target, and ion beam sputter deposition with 2s ior~ assist, i.e. "dual ion beam sputter deposition". Tl~e ion beam sputter deposition methods offer excellent control, uniformity, and flexibility of substrate geometry, but the deposition raoe is slower than that of the direct ion beam deposiuon process. To maximize the density and elecuical resisuvity of the ion beam sputoer-deposioed DLC coaung, bu~b_ld~ of the growing film by an additiol~al 30 ion beam ("ion assist") is normally required. Filtered carbon cathodic arc ion sources and la~cer ablauon (from a solid carbon target) ion sources can also be used as ion sources for generation of the carbon deposition flux for the DLC coatings of ~ W095/23878 2 1 84737 P~ o~

tne method of the present invention. In both of these ion sources, it is essentiai to perform some filtering of the beam to remove particles which degrade the coating.
These ion sources produce extremely hard diamond-like carbon coatings with very low hydrogen content. However, the coating stress level is high, so extreme care S in substrate chemicai cleaning, ion beam pre-cleaning, and interlayer deposition must be taken to obtain excellent coating adhesion.
For sake of process simplicity, rapid deposition, and ease of scale-up to mass ~., ' direct ion beam deposition from a ll~vlO~albu., gas source is the most preferred deposition process for this invention. ~ethane as the lly~l u~,~bvll source gas is preferred, but other I~Lu~,albul~ gases, such as acetylene, butane, and benzene can be used as well. Inert gases and hydrogen may be introduced into theion source plasma to modify the DLC film properties. The ion energy used in the DLC deposition process may be in the range of a~ln~ ' Iy 20 eV to a~ 'y 1000 eV. Ion energies in the range of about 20 eV to about 300 eV
are most preferred to minimize heating of the substrate during deposition.
Excellent wear resistance and iow p-rmP~ y have been ~ d by DLC
coatings having hardness in the range of about 10 to about IS GPa using direct ion beam deposition. This is in contrast to prior art references, e.g. U.S. Pat. No.4,717,622, which reL~iuire hardness in excess of a~lw~ lat~,ly 20 GPa (2,000 kg/mm2) to achieve high wear resistance. In addition to the ion beam for direct deposition, an ion assist beam, as in U.S. Pat. No. 4,490,229, can be utilized but is not rec~iuired.
Once the chosen thickness of the DLC layer has been achieved, the deposition process on the transducer substrates is i l, the vacuum chamber pressure is increased to: ,' ~ pressure, and the coated magnetic transducer substrates are removed from the vacuum chamber.
Examples The examples and discussion which follow further illustrate the superior p.,lrullllall~,e of the coated products of the method of this invention. The examples are for illustrative purposes and are not meant to limit the scope of the claims in any way.
Example I

woss/23878 2 1 8 4 7 3 7 T~ v /o~ ~

An Al,OJTiC slider (IBM 3380-type) was coated with ion beam deposited DLC by the following method. The sliders already mounted onto their suspension system were first chemically cleaned with isopropanol and blown dry with nitrogen. The cleaned sliders were then attached to a 6-inch diameter graphite S plate using adhesive tape. The graphite plate was then mounoed onto a rotary stage, and the vacuum chamber was evacuated to a pressure of 4.8 x 10~ Torr.
The slider was then sputter-etched using an argon ion beam from an 11 cm Kaufman-type ion source at an energy of 500 eV with a beam current of 137 mA
for 2 minuoes. The etch rate of a silicon witness coupon under these conditions 10 was ~ u~ t~ 300 A/minute. After this sputter-etching step, a 1000 eV, 100 mA argon ion beam was used to sputter-deposit a 25 A thick layer of silicon by ion beam sputter deposition from a silicon target. After deposition ot the silicDn ~ayer, a 100 A thick DLC layer was deposited by direct ion beam deposition usingtbe 1 I cm Kaufman-type ion source, operated at a beam energy of 75 eV and a 15 beam current of 175 mA.
Example 2 An AI~O3/TiC slider (IBM 3380-type) was coated with ion beam deposited DLC by the same procedure as in Example 1, except the Yacuum chamber was initially was evacuated to a pressure of 5.0 x 10~ Torr, and the thickness of the 20 DLC coating was 50 A.
Example 3 A ~ ,tUlG~ tape head was chemically cleaned, and mounted in an alur.linum fixture. The fixture was installed in a stainless steel vacuum chamber and the chamber was evacuated to a pressure of 3.0 x 10 6 Torr. The tape head 25 was then sputter-etched using an argon ion beam from an 1 I cm ICaufman-type ion sourcc at an energy of 500 eV with a beam current of 137 mA for 15 seconds.
The etch rate of a silicon witness coupon under these conditions was ~I~),.JlUAilll,.
300 A/minute. After this sputter-etching step, a 1500 eV, ~0 mA nitrogen ion beam was used ro sputter-deposit a 25 A thick layer of silicon nitride by reactive 30 ion beam sputter deposition from a silicon target. After deposition of the silicon nit~ide layer, a 225 A thick DLC layer was deposited by direct ion beam deposition -wo s~l_387s -27- r~ ^7760 using the 11 cm Kaufman-type ion source, operated at a beam energy of 75 eV and a beam current of 50 mA.
Example 4 Analog tape heads were cleaned with ;~u~-uu~l..ol and then blown dry with 5 nitrogen gas. The samples were mounted in an aluminum fixture and the fixture was installed into a stainless steel vacuum chamber which was evacuated to a pressure of 4.6 x 106 Torr. The tape heads were then sputter-etched for one minute using a 500 eV; 137 mA argon ion b~am generated by an 11 cm Kaufman type ion source. The etch rate of a silicon witness coupon under these conditions 10 was a~ y 300 A/minute. After this sputter-etchin~ step, a 1000 eV. 100 mA argon ion beam was used to sputter-deposit a 200 A thick layer of amorphous silicon by ion beam sputter deposition from a silicon tar~et. Afte} deposition of the silicon layer, a 1200 A thick DLC layer was d~posited onto the tape heads bydirect ion beam deposition using the 11 cm Kaufman-type ion source, operated at a 15 beam energy of 75 eV and a beam current of 100 mA.
The durability of the ion beam deposited DLC coating of the present invention was .1~ .1 by applying the coating to Al2OJTiC sliders used as with magnetic recording disks. The u ~ durability and p~,lru~ a~ . ' due to the DLC coating of the present invention were 20 determined by performing two types of accelerated wear tests: a constant speed drag test. and a contact-start-stop (CSS) test. The CSS test is used by the ma~netic disk recording industry as the ANSI standard method. A typical mode of failure in the tests is build-up of friction with revolutions of drag or cycles of CSS. Foruncoated sliders, the friction starts at a coefficient level of a~ y 0.2 and 25 builds up to three or four times that initial value with severai thousand cycles. The high levels of friction cause particle pullout with resulting abrasive wear and failure of the head-disk interface. Even if such wear does not occur, the high levels of friction are ~ ,~ C~ ,I., because the drive motor may not have sufficient torque to start the drive from the rest condition. Therefore, it is desirable to find a 30 c -".l, -~;.. of protective overcoat and lubricant to achieve a high level of CSS or dra~ revolutions without ~ friction build-up.

w095123878 21 84737 P~,/.,~ /60 Uncoated and DLC-coated sliders were measured on a standard tester developed by Hewlett Packard I ~ralr~n~c which consists of a computer-controlled spindle on which the disk is clamped and the slider ~.~Srl.nc;,.n assembly is attached to a strain gauge ' load beam to measure normal and 5 frictional forces on the slider. Tests were conducted in a class 100 clean hood in room air at 28C and 35% relative humidity. Standard ~ u;..lly available 95 mm diameter thin film disks with a 200-300 A thick layer amorphous carbon and a 20 A thick layer of lubricant were used in the tests.
The test procedure used was as follows. After the dis~ had been clamped 10 to the spindle and the slider is loaded on the disk, a single revolution is made at low rpm during which the friction force of the dragging slider is recorded. Then a single CSS is made and the friction is measured during the first revolution to reveal the peak static friction, called the "stiction". An additional indicator of failure is the touch-down velocity (TDV), defined as the speed at which friction15 reaches a threshold value upon landing of the slider as the spindle revolution speed is reduced from the normal operating speed.
Next, the tester was IJlU~lrlllUll~,d to perform either slûw speed drag tests orCSS tests while taking, .~,v. ' ' friction data reriodically, at 100 cycle intervals. These data are averaged, and the result is plotted as a function of 20 revolutions along with the TDV. An example of drag test data for an uncoated IBM 3380-ype Al2O3-TiC slider is presented in FIG. 2A, and 2B, and an example of CSS test data for an uncoated IBM 3380-type Al2O3- TiC slider is presented inFIG. 2C and 2D.
Note in FIG. 2A that the frictional force started at 2.07 gmf and increased 25 with the number of test revolutions to a value near 5 gmf at ~00 revolutions.Then, it remained nearly cûnstant until increasing to a maximum of 6 gmf at 'y 2600 revolutions. The test was stopped at 3300 revolutions whell the TDV showed two COII~G~UL;VG values 50% above the lowest value, a criterion chosen to maximize the accuracy of the ~ of u~ ;r~ on the 30 sliders by wea~ products. An increase of TDV is an indication that material has transferred from the disk to the slider. Similarly. in FIG. 2C, the frictional force statted at 1.93 gmf and increased to 5.2 gmf at dU~/I- ' ly 300 start/stops. It ~ wo ss/23878 2 1 8 ~ 7 3 7 . ~ o -29- `
reached a value near 7 gmf before the test was stopped after the TDV reached thecriteria 1200 start/stops. Microscopic ~r"min~tion of the sliders after tbese tests revealed that there was a significant amount of wear debris adhering to the rails of the sliders.
S IBM 3380-type Al~03-TiC sliders coated in Example I (100 A layer of DLC) and Example 2 (50 A layer of DLC) by the ion beam deposition l~rocess of the present invention were evaluated using the same test conditions used for theuncoated sliders. The tests on the DLC-coated sliders were set to terminate at 30,000 test reYolutions if not interrupted by the increase of the TDV. FIG. 3A and FIG. 3B show the drag test results for a slider coated with 100 A of DLC in Example 1. The test result is ' Ily different and improved relative to the uncoated sliders. In FIG. 3A, the frictional force rapidly increased from 1.61 gmf to about 3.2 gmf and remained essentially constant for 30,000 ~ . ' In FIG
3B, the TDV decreased from 3.51 meters/second to 2.8 m/s and remained essentially constant for the duration of the test. After 30,000 cycles was completed, only a small amount of wear maoerial was found on one rail of the slider. The rails were much cleaner than was the case for the tests of the uncoated sliders.
FIG. 4A and FIG. 4B show the drag test results for a slider coated with 50 A of DLC in Example 2. The test results were nearly identical to those found in FIG. 3A and FIG. 3B for the slider coated with 100 A of DLC in Example 1.
Again, there was only a very small amount of debris found on the rails of the slider for this test. The rails were much cleaner than was the case for the tests of the uncoated sliders.
FIG. 2C and FIG. 2D show the results of a CSS test for an uncoated TiVAI2O3 slider. It was found that the frictional force increased from an initial value of 1.93 gmf to 5.4 gmf at a~J~JlVAi~ ,ly 400 CSS cycles, then incr~ased more gradually until about 800 cycles, after which it became erratic and the test was terminated by the TDV criterion at 1,200 CSS cycles. After I of this CSS test, there was much more debris found on the rails of this slider than was found in the case of the previous drag tests on uncoated sliders.
_ Wo 95123878 ~ . 160 FIG. SA and FIG. SB show the results of CSS tests on the same slider (100 A DLC coating) used to obtain the data in FIG. 3A and FIG. 3B. The data show tbat the frictional force increased rapidly f}om 1.77 gmf to ~ 3.3 gmf and remained essentially constant for 8.000 CSS cycles. The TDV showed only 5 one instance of an increase, but otherwise showed a gradual decrease over the duration of the test.
These test results showed a ~ C difference in ~,~..rc.l.,~ ,c; of t~e ion beam DLC-coated slidèrs of the present invention compared to uncoated sli~ers inboth drag tests and CSS tests. Other coated and uncoated sliders were also tested 10 with similar results. In the dra~ tests, all of the uncoated sliders showed an increase of the friction to 6 gmf or more within the first 3,000 revolutions. This a 3-fold increase from the initial friction value. On the other hand, the tests with the DLC-coated sliders of the present invention showed a rapid inclease to slightly above 3 gmf, but the friction then remained constant for 30,000 15 revolutions. An increase to 6 gmf would be ~ l.l; even if the TDV &ilure criterion had not been met. However, an increase to 3 gmf is tolerable, and tl1eresults indicate that the tests could have pro~ressed to sig,.irl~,,."~ly higher number of revolutions before a further increase in friction would occur. If doubling ofinitial friction is set as the failure criterion in the drag tests, the uncoated sliders all 20 failed by 1,500 revolutions, while the ion beam DLC-coated sliders did not fail by 30,000 revolutions. Therefore, a factor of il~ of greater than 20 for the ion beam DLC-coated sliders was indicated by the drag tests.
Similarly, in the CSS tests, the uncoated sliders showed an increase of frictional force to 6 gmf by 1,000 cycles for three tests which were conducted. For 25 the case of the ion beam Dl,C-coated slider, the frictional force did not increase above 3.4 gmf at any time up to the point the test was terminated at 8,000 cycles.
Again, if doubling of the initial frictional force from 2 gmf to 4 gmf is set as the failure criterion, all of the uncoated sliders failed by 200 CSS cycles, whereas the ion beam DLC-coated slider did not yet fail by 8,000 cycles. Therefore, a factor of 30 il.",.~"_...~".l of greater than 40 for the ion beam DLC-coated sliders was indicated by the CSS tests.

~1VO 95/~3878 P_l~u~ /6/1 ~;rom the foregoin~ C~rirtif~n one of ordinary skill in the art can easily ascertain that the present invention provides an improved method for producing highly protective and wear resistant DLC coatings on magnetic ~ Highly important technical advantages of the method of the present invention include S ' ~, adhesion of the ion beam deposited DLC coating, and ease and flex;bility of mass production of DLC-coated magnetic ~
Without departing from the spirit and scope of this invention, one of ordinary skill in the art can make various changes and ..,~ to the invention to adapt it to various usa~es and conditions. As such, these changes and 10 ""~ are properly, equitably, and intended to be, within the full range of equivalents of the following claims.

Claims (19)

WHAT IS CLAIMED IS:

1. A method for producing a protective, wear resistant diamond-like carbon coating on the wear surface of a magnetic transducer comprising the steps of:
(a) chemically cleaning the surface of said magnetic transducer to remove contaminants;
(b) mounting said magnetic transducer in a deposition vacuum chamber and evacuating the air from said chamber;
(c) ion beam sputter-etching the surface of said magnetic transducer to further remove residual contaminants;
(d) ion beam sputter depositing an amorphous, electrically non-conducting adhesion-promoting interlayer selected from the group consisting of silicon, silicon carbide, silicon nitride, silicon oxide, silicon oxy-nitride, mixtures thereof and chemical combinations thereof;
(e) direct ion beam depositing an amorphous electrically non-conducting diamond-like carbon outer layer;
(f) increasing the vacuum chamber pressure to atmospheric pressure; and (g) recovering a diamond-like carbon coated magnetic transducer having improved wear and corrosion resistance.

2. The method of Claim 1 wherein said outer layer is deposited by direct ion beam deposition from a hydrocarbon gas.

3. The method of Claim 1 wherein said outer layer is deposited by direct ion beam deposition using ions generated by a cathodic are carbon ion source.

4. The method of Claim 1 wherein said outer layer is deposited by direct ion beam deposition using ions generated from a laser ablation carbon ion source.

5. The product manufactured by the method of Claim 1.

6. The product of Claim 5, wherein said magnetic transducer consists of a slider.

7. The product of Claim 5 wherein said magnetic transducer consists of a tape head.

8. The product of Claim 5, wherein said magnetic transducer consists of a magnetoresistive slider.

9. The product of Claim 5 wherein said magnetic transducer consists of a magnetoresistive tape head.

10. A transducer for use with magnetic recording media composed of a transducer assembly substrate, an amorphous, electrically non-conducting adhesion-promoting interlayer elected from the group consisting of silicon, silicon carbide, silicon nitride, silicon oxide, silicon oxy-nitride, mixtures thereof and chemical combinations thereof ion beam sputter deposited on and bonded to said substrate, and an amorphous, electrically non-conducting diamond-like carbon outer layer direct ion beam deposited on and bonded to said interlayer, whereby said transducer has improved wear and corrosion resistance.

11. The transducer of Claim 10 wherein said interlayer thickness is in the range of about 10 .ANG. to about 500 .ANG..

12. The transducer of Claim 10 wherein said interlayer thickness is in the range of about 10 .ANG. to about 50 .ANG..

13. The transducer of Claim 10 wherein said outer layer thickness is in the range of about 25 .ANG. to about 2000 .ANG..

14. The transducer of Claim 10 wherein said interlayer contains silicon.

15. The transducer of Claim 10 wherein said outer layer is deposited by direct ion beam deposition from a hydrocarbon gas.

16. The transducer of Claim 10 wherein said outer layer is deposited by direct ion beam deposition using ions generated by a cathodic arc carbon ion source.

17. The transducer of Claim 10 wherein said outer layer is deposited by direct ion beam deposition using ions generated from a laser ablation carbon ion source.

18. The transducer of Claim 10 consisting of a magnetoresistive slider.

19. The transducer of Claim 10 consisting of a magnetoresistive tape head.