CA2175678A1

CA2175678A1 - Ablative imaging by proximity lithography

Info

Publication number: CA2175678A1
Application number: CA002175678A
Authority: CA
Inventors: Jeffrey B. Hill; Robert S. Jackson; Douglas S. Dunn; Daniel P. Stubbs; Andrew J. Ouderkirk
Original assignee: Individual
Current assignee: 3M Co
Priority date: 1993-12-17
Filing date: 1994-10-31
Publication date: 1995-05-22
Also published as: DE69407620D1; EP0734325A1; KR960706405A; JPH09506565A; DE69407620T2; WO1995016570A1; US5633123A; CN1057731C; US5501944A; EP0734325B1; CN1136792A

Abstract

The present invention includes a method of creating a shaped image (13) in a workpiece (10) using a high energy source (12), with the method comprising positioning a layer (16) proximate the workpiece such that the layer prevents debris from the workpiece from dispersing, and directing radiation from the high energy source through the layer to the workpiece, the layer substantially transparent to radiation emitted by the high energy source such that the high energy source is capable of forming the shaped image.

Description

wo 95/16570 2 1 7 5 ~ 7 ~ PCT/US94/12487 _.

ABLATIVE IMAGING
BY PROXIMIl'Y LITHOGRAPHY
BACKGROUND OF THE INVENlION
The present invention generally relates to a method of forming a shaped image in a workpiece. More specifically, the present invention relates to a method of forming a shaped image in a workpiece using a high energy source and a layer disposed proximate the workpiece such that the layer prevents debris from the workpiece from dispersing away from the workpiece.
Techniques for forming a shaped image in a workpiece are many. Such techniques are widely used in the manufacture of many types of electronic devices such as magnetic data storage disks with optical servo tracks, memory card circuits, and flexible circuits. Related techniques are also employed to mark various devices with information such as bar-codes, to create printing elements, such as lithographic plates, and to generate orn~m~nt~l designc Stamping is one technique for creating a shaped image in a workpiece. For example, presses with stamping dies create optically readable servo stitches in m~gnPtic data storage disks. One problem with the stamping technique is that stamping dies have relatively short life spans. Also, the elastic nature of the disks causes changes in the geol,ltLly of stamped stitches over time.
Chemical etching is another example of a technique for creating a shaped image in a workpiece. In this technique, photoresist is applied to a substrate and patterned in a known manner. Developed portions of the resist are then removed by chemical etching to leave the shaped image. The ch~m~ ls which perform the etch are not entirely beneficial. For instance, the chemicals tend to undercut undeveloped portions of the workpiece. This undercutting limits the size and location of the shaped image which may be formed in the workpiece.
Other well-known ~locesses for creating a shaped image in a workpiece include electron-beam, ion beam, corona, and plasma treatment. These methods are either continuous or long pulse length etching processes which, due to their low energy flux, yield a low heat transfer rate. The low heat transfer rates are detrimental when etching surface coatings such as polymer-based coa~ings. Specifically, the low heat transfer rates create an undesirable thermal treatment effect in areas of the coating other than the etched areas.
Laser-based techniques are also useful for creating a shaped image in a workpiece. One technique utilizes an Argon/Ion laser to directly burn optically-readable servo stitches one by one into a m~En~ic data storage disk. The laser beam is optically switched on and off while the disk is spinning and a final lens objective is tr~ncl~t~d.
U.S. Patent No. 4,323,755 to Ni~w~bel~; concems a method of producing a m~rhinP
readable coded marking in a surface of a workpiece, such as a glass faceplate panel of a television picture tube, by vaporizing parallel areas of similar width in the panel surface using a CO2 laser. U.S. Patent No. 4,515,867 to Rl~her et al. illustrates a technique for directly marking a glass funnel of a television picture tube by ablating image features into a pigmen~ed inorganic coating placed on the funnel. U. Sowado, H.-J. Kahlert & D. Basting, in "Excimer Laser Processing of Thin Metallic Films On Dielectric Substrates," 801 High Power Lasers 163-167 (1987), comment upon patteming metal co~tinEc of polymer ~lbSLlaLeS using ablation.
U.S. Patent No. 5,204,517 to Cates et al. discloses a method of removing p~unt co~tinEc from metal and polymer substrates using an eY~imçr laser. The laser has a relatively long pulse width on the order of 0.2 microsecQn~C during which the energy density is in the range of 1-5 J/cm2. The method involves control of a paint removal process by monitoring spectral emissions of the paint coating.
U.S. Patent No. 5,061,604 to Ouderkirk et al. describes irradiation of a surfacelayer of semi-crystalline polymer with an excimer laser to create an imagewise distribution of quasi-amorphous polymer within the surface layer has been mentioned.
A reactive ion etching process is then utilized to ~,~ferentially remove the semi-crystalline polymer after irradiation of the surface layer.
U.S. Patent Nos. 4,822,451 to Ouderkirk et al., 4,868,006 to Yorkgitis et al, and 4,879,176 to Ouderkirk et al. also concern irradiation of a surface layer of semi-crystalline polymer with an excimer laser to render portions of the surface layer quasi-amorphous. It has been noted that the presence of the quasi-amorphous layer tends to enhance bonding of the semi-crystalline polymer to other materials generally, including adhesive materials. It has also been noted that the presence of the quasi-amorphous layer reduces optical reflectance and increases optical tr~n~mi~sion of the semi-crystalline WO 95116570 2 1 7 ~ 6 7 8 PCT/US94/12487 polymer, increases coating adhesion to the semi-crystalline polymer, and reduces the coefficient of friction of the surface of the semi-crystalline polymer.
Such direct laser formation of individual shaped image features may be desirablefor some workpieces with small numbers of image feaLules and for some projects with 5 relatively small nul,lbel~ of workpieces. However, direct laser formation of individual features is not entirely without problems. For example, ablation typically yields high energy fragments of debris which often splash onto optical equipment ~ccoci~t~d with the laser. Cleaning the debris fr~gm~ntc from the optical eluil~,llcnt is disruptive and impractical in industrial applir~tionc One potential solution to the debris problem involves moving the final optical surfaces some added lict~nce away from the workpiece. However, this solution isundesirable for a variety of reasons. For instance, laser beam control and orientation relative to the workpiece is more tec~nir~lly challenging and less economically efficient when the optical surfaces are moved further from the workpiece. Additionally, space 15 con~iderations som~otimt~s prevent movement of the optical s~rf~ces away from the wolk~;~e.
U. S. Patent No. 4,032,743 to I~rbach et al. discloses a rotating cylindrical drum and a plurality of stationary lasers for boring closely spaced holes through foil strips mounted on the drum using a single pulse of a laser for each hole. A strip of film is 20 connecled to fixed-rate supply and take-up reels and is positioned between the foil and a lens of the laser to protect the lens from vaporized material. The film is transparent to the radiation wavelength of the laser.
Another consideration is that, though direct formation of individual image features is sometirnes ben~-fici~l for workpieces with fewer image features and for 25 smaller batches of wolky;~es, direct feature formation is not alwavs an optimum choice.
For example, direct laser formation of image features, one at a time. requires much more time than if the laser operated on multiple images or image features arranged about the workpiece.
Technological advances have been developed which allow laser operation on more 30 than one image or image feature at a time. For example, U.S. Patent No. 4,877,480 to Das discloses a contact lithographic technique for forming shaped images in a Wo 95/16570 PCT/USg4/12487 wu-kll -ce, such as an ~lumin~-coated ceramic substrat~ According to Das, a mask of m~t~ri~l that is highly reflective in the wavelengths of the sel~ted laser is placed in contact with the ~lumin~ coating. Radiation from a CO2 laser is applied to the mask to remove portions of the alumina coating which are not m~c'r~d The reflective surface 5 of the mask reflects the laser r~ tion away from areas of the workpiece covered by the mask.
M. (~allthi~r, R. Bourret, E. Adler, & Cheng-Kuei Jen, in "FY~imPr Laser Thin Metallic film P~ ing On Polyvinyledene Difluoride," 129 Materials Research Society S~ )osiu", ~loc~l;"p~, 399~04 (1989), discu~Ps a technique for ablating metal 10 co~tin~s located on the front and back sides of a polymer film using an excimer laser and a mask to form pat~...s in each of the metal co~tingc. The laser first ablates a pattern in the coating on the front side in a single pulse. The laser then ablates a pattern in the coating on the rear side in a single pulse by passing radiation through the front side of the polymer film toward the coating on the rear side.
A mask which is placed in relation with a workr~ e, as in the Das patent, may be a sul ~ulled or an un.",l,~,Led mask. An un.,upl)ol~ed mask is a mask which does not include underlying .,e~-h~nit ~l suppon for transparent window ponions of the mask which shape the areas to be removed from the wolh~;ece. The use of unsùppol~d masks may be disadvantageous for many reasons. For example, unsul~pol Led masks tend 20 to absorb heat which may cause mask shape distonion. Also, due to the inability of an unsuppol~ed mask to support isolated areas of mask material, it is not possible to make certain image features, such as an X-Y pattern or the center of the letter "O", using an un~,u~ ed mask. It is also difficult under some m~nllf~tllring tolerance extremes to ."~inl~;n an un.,uppol~ed mask in intimate contact with the worhpiece being imaged.
25 This may impair resolution and create ~lignmtont problems.
A ~,u~ ed contact mask includes me~h~nical suppon for all areas of the mask and avoids many problems ~Ssoci~ted with unsupported masks. However, it has beenfound that even the use of a supl)ol~d mask in combination with a laser is not entirely .s~ti sfactctry for creating patterned images in workpieces. One major problem is fragment 30 debris created by im~ging processes, such as ablation. Specifically, debris ohen splashes onto the mask. Cleaning the mask after each use is not practical in industrial wo 95/16~70 2 1 7 5 6 7 8 PCT/USg4/12487 ~ppli~ n~ Also, debris may cause spots in transparent window areas of the mask during the im~ing process. Such spots cause diffr~c~ion of the laser beam and may prevent accurate image feature creation.
One po~ ial solution to the debris problem is to move the mask away from the S workpiece. In some applit~tionc~ projection lithography inco.~ol~les a mask position~d away from the wu-kl.:e~e. J. R. Lankard & G. Wolbold, in "FYCjm~r Laser Ablation of Polyimide in a Manufacturing Facility," 54 Apvlied Physics A - Solids and Surfaces, 355-359 (1987), discuss application of projection lithography in conne~ion with laser ablation of polymer-coated suba~ld~es.
Projection lithography has a number of limit~tions, though, including high equipment costs and low laser beam throughput. Also, projection lithography may only expose small workpiece areas at a time. This small field size complicates imaging of large area, non-,cpe~;ng shaped images since the mask must be repeatedly and precisely moved in relation to the imaged areas. Movement of the mask away from the workpiece may also decrease the resolution of image features in the workpiece and may cause image blooming b~l~.~n the mask pattern and the workpiece.

SUMMARY OF THE INVENTION
The present invention includes a method of creating a shaped image in a workpiece using a high energy source. The method comprises positioning a layer proximate the wulk~iece, sl~ch that the layer prevents debris from the workpiece from dispersing away from the workpiece, and directing radiation from the high energy source through the layer to the workpiece, the layer being substantially transparent to radiation emitted by the high energy source such that the high energy source is capable of forming the shaped image. The present invention also inrhlde5 a method of preventing debris from the workpiece from dispersing away from the workpiece and a system for preventing debris from dispersing away from the wclk~;ece.

BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a perspective view of the system of the present invention.
Figure 2 is a side elevation view of one embodiment of the workpiece and buffer wo 95/16570 2 1 7 5 6 78 PCT/US94/12487 layer of the present invention.
Figure 3 is a side elevation view of another embodiment of the workpiece and buffer layer of the present invention.
Figure 4 is a ~ e view of another embolimPnt of the system of the 5 present invention.
Figure 5 is a p~ e view of another embodiment of the system of the present invention.
Figure 6 is a graph of percent r~ ti- n tr~n~mitt~nce versus a range of radiation wavelengths for a 25 ~m thick sheet of c~p~rjtor grade biaxially oriented polypropylene 10 film.
Figure 7 is a side elevation view of another embodiment of the system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention includes a method of forming a shaped image in a workpiece using a high energy source and a method of preventing debris from the workpiece from dispersing away from the workpiece. The present invention also includes a system for preventing debris from the workpiece from dispersing away from the workpiece and a kit for forming the shaped image in the workpiece using the high 20 energy source.
In acco,dance with the method and system of the present invention. energy output11 from a high energy source 12, as in a batch staging system 23 illustrated in Figure 1, is directed toward a workpiece 10 to form a shaped image, such as a three dimensional pattern 13, in the workpiece 10. Any of a variety of optical elements 14, 25 such as lenses and mirrors, may be positioned to adjust the energy output 11 of the high energy source 12.
Under certain conditions, the energy output 11 may force debris away from the workpiece 10. A buffer layer 16 is disposed proximate the workpiece 10 to prevent debris from dispersing away from the workpiece 10 and to prevent debris from 30 contacting any final optical element (not shown) located proximate the workpiece 10.
The buffer layer 16 may also prevent debris from redepositing on areas of the workpiece Wo 95/16570 2 1 7 5 6 7 8 PCT/USg4/12487 10 that are located a~ Pnt the pattern 13 of the w~l~.cce. (In Figure 1, the buffer layer 16 is shown spaced away from the workpiece 10 for pul~oses of clarity only).
F.cc-~n~i~lly, the buffer layer 16 is a debris blocking layer which acts as a physical barrier to movement of debris away from the pattern 13 and the wul~.cce 10. The buffer layer 5 16 is also useful for preventing cont~min~tion of "clean room" enviror""er,t~ by trapping debris plu~ lale the workpiece 10.
W~.l~ieces 10 of particular interest, as in Figure 2, include a substrate 19. One or more sides of the ~.lb~L,dte 19 may include a coating 20. If the substrate 19 does not include the coating 20, the s-lbsl-dle 19 in~ dPc a boundary portion (not shown) instead of the coating 20. The pattern 13 is preferably created in the coating 20, if the substrate 19 includes the coating 20, or in the boundary portion, if the s.-bsL,dte 19 does not include the coating 20.
The substrate 19 may be made of many organic or inorganic materials, in~ rling silicon, metal, or polymers, such as polyester, polycdll,onate, polyethylene, polyamide, 15 polyethylene ler~ tp or polyimide. The boundary portion is made of the same material as the substrate. The coating in~ludes a surface coating layer (not shown), and may include additional coating layers (not shown). The coating layers may be arranged in any desired order. The pattem 13 may be formed in any of the coating layers, as desired, so long as the desired coating layer is visible to a s~ffi~ient amount of the 20 energy output 11 to form the pattem 13.
Organic and inorganic m~tPri~1~ may be included in the coating layers to providedesired operative, structural, identifying, and aesthetic features. For in.~t~nce, one or more of the coating layers may be made of a conductive metal to provide desired conductive characteristics. ~xamples of conductive metals of interest include copper, 25 silver, nickel, ch~ollliulll, and alloys of these, such as indium tin oxide. Also, one or more of the coating layers may be made of a m~gn~tic colll~uulld to provide desired magnetic characteristics. The magnetic co",l,vund, for purposes of this disclosure, is an elemental metal or a metal co"-~ùund that possesses magnetic properties. The magnetic colllpo~lnd may be the sole component of a particular coating layer or may be 30 a single component of several components making up the particular coating layer, such as magnetic particles distributed within the particular coating layer. Examples of wo 95/16570 2 1 7 5 6 7 8 pcTluss4ll2487 m~nPtic metals include iron, iron oxide, barium ferrite, cobalt nickel, cobalt phosphorous, cobalt chrome, and oxides of cobalt.
Examples of potential workpieces include sul,sL,~hs coated with m~gnPtic metal or m~gnPtic material, such as a m~gnPtic data storage disk, sometimPs referred to as a 5 floppy disk. In one e",bo~ Pnt the pattem 13 takes the form of a servo path, such as a spiral track, of the m~nPtic storage disk. In another elllbo~ t the pattem 13,namely the servo path, inrllld~Ps a plurality of conre ,I.ic optical servo tracks formed in the m~gnPtic storage disk. Other examples of potential wu,~ eces include substrates coated with conductive metal, such as memory card circuits and touch screen circuits.
10 Additional examples of po~enlial workpieces include polymer-coated subsL,~tes, such as objects on which bar code information is placed.
Preferably, the energy output ll. as in Figure 1, has both high energy density, high energy per unit area, high fluence, and high energy density per pulse, to assure c~icf~ctnry im~ging. Other variables affecting high energy source selection include 15 substrate ch~~ ;cti~s~ coating char~rteric~ics, and pattem characteristics, such as pattem line width and spacing, overall pattern size, and pattern depth. Potential high energy sources include monochromatic devices such as lasers and short pulse length, bro~b~nd sources such as surface discharge mP~h~nicmc and fl~chl~mps.
In one embodiment (not shown), the buffer layer 16 comprises the substrate 19 of the workpiece 10. A coated side (not shown) of the ~ub~LIdte 19 includes the coating 20. The substrate also includes a non-coated side (not shown). The coated and non-coated sides oppose each other. In this embodiment, the high energy source 12 islocated on the non-coated side of the substrate 19. The energy output 11 of the high energy source 12 enters the non-coated side of the substrate 19 and passes through the substrate 19. The energy output 11 contacts the coating 20 on a side (not shown) of the coating 20 that is in contact with the substrate 19 and creates the pattern 13 in the coating 20 of the workpiece 10.
In more p-efelled embodiments, the buffer layer 16 is either a web of film (not shown) or, as in Figure 1, a sheet of film 18 positioned to isolate the workpiece 10. All comments about the buffer layer 16 apply to the sheet of film 18, the web of film, and the substrate (when the substrate is the buffer layer 16), unless otherwise indicated. The 21 75b78 Wo 9s/l6570 PCT/U$94/12487 buffer layer 16 is durable enough to provide ade~uate h~nrlling characteristics and strong enough to prevent passage of debris liberatPd from the workpiece 10.
The high energy source 12 and the buffer layer 16 are preferably SPlP~tPd to assure optimum image shaping in the coating or the buw-d~u y portion (not shown) of the S workpiece 10 and to assure effi~iPnt use of the energy output 11. The energy output 11 lc lui-cd at the coating or the boundary portion depPn~c on the wavelength distribution of the energy output 11 and on Wt~ characterictirs~ in~lu~ing charaçte~icti~s of the substrate, the coating and the pattern 13 to be formed. The wavelength distribution and workpiece characteristics, s~lbstAntiAlly deterrnine the absorption characteristics of the 10 coating or the boundary portion, and thus the ablation results.
The energy output 11 actually reaching the coating or the boundary portion depentic on the L,Anc...iL~Ailre of the energy output 11 through the buffer layer 16. A
higher LIA~ An~e through the buffer layer 16 decreases the required input energy to the high energy source 12 and decreases absorptive heating of the buffer layer 16. The 15 trAncmittAnce of the buffer layer 16 is highly depen~lP-nt upon the material the buffer layer 16 is made of and the thi~knPcc of the buffer layer 16.
The buffer layer 16 is sufficiently transparent to the energy output 11 of the high energy source 12 such that the energy output 11, after passing through the buffer layer 16, has sufficient ,c~ ining energy to form the pattern 13 in the coating or the boundary 20 portion of the wolkl~;ece 10. The buffer layer 16 is p,erc,dbly highly transparent to the energy output 11 such that the high energy source 12 efficiently develops the pattern 13 in the coating or the boundary portion. Preferably, the buffer layer 16 is sufficiently lldnS~Cnt to the energy output 11 to allow at least about fifty percent (50%), and mor p~cÇ~dbly at least about eighty percent (80%), of the energy output 11 to pass through 25 the buffer layer 16.
The high energy source 12 and the buffer layer 16 are preferably SPI~t-P~ to assure optimum image shaping in the coating or the boundary portion. Image shaping d~PpPn(is on the geometric changes in the energy output 11, such as sc~ g and diffraction of the output 11, due to passage of the output 11 through the buffer layer 16.
30 The geometric changes in the energy output 11 are created by buffer layer 16 manufacturing defects, such as extrusion lines, surface irregularities and caliper non-wo 95/16570 PCT/USg4/12487 UlliÇul,,,ity. Preferably, the buffer layer 16 has minim~l m~nuf~rt--nng defects and is of sufficient ~uality to produce desirable image resolution in the coating or the boundary portion.
The tr~ncmitt~nG~P of the buffer layer 16 and the geG"l~tlic changes i~pose~
5 upon the energy output 11 depend upon the m~tPri~l the buffer layer 16 is made of, the thir~nPs5 of the buffer ~ayer 16, and m~nuf~rtllring defects present in the buffer layer 16. It has been discovered that some organic polymer films, such as particular grades of pol~yroyylene film, are particularly conducive to opL.",ll", image shaping and effi~iPnt use of energy output 11 from the high energy source 12, under certain circumct~nres It is generally desirable to place the buffer layer 16 yluAilllate the coating or the boundary portion so that the final optical element (not shown), such as a projection lens (not shown) used in projection lithography, may be placed close to the workpiece lO.
Close spacing of the final optical element (not shown) and the coating or the boundary portion may produce more favorable im~ging economics and improved pattem 13 char~rtPricti~s Close spacing also limits cont~-.-in~l;on of non-imaged portions 21 of the pattem 13 located outside the pattem features. When the buffer layer 16 is in intimate contact with the coating 20, as in Figure 2, debris 22 does not spread to the non-imaged portions 21 of the pattern 13. When the buffer layer 16 is slightly spaced apart from the coating 20, as in Figure 3, debris 22 does spread outside the pattern feature and co~ -.n~ s the non-imaged portion 21 of the pattern 13.
However, the degree of close contact desired between the buffer layer 16 and thecoating 20 or the boundary portion, may also depend upon workpiece variables, such as the roughness of the coating or the boundary portion of the workpiece 10. For e~mple, some coating.c 20 have rougher surfaces than other coatings 20. It is believed that if the buffer layer 16 is in intim~te contact with a rough surface such that the buffer layer conforms to the rough surface, the pattern 13 created by the energy source will likely have somewhat poorer resolution. It is believed that the poorer resolution will arise due to dispersion and diffraction effects created when the energy output passes through the buffer layer 16 at other than a substantially perpendicular orientation.
Referring back to Figure 1, close spacing of the buffer layer 16 and the coatingor the boundary portion may be obtained by laying the buffer layer 16 against the coating or the buund~u.y portion such that the buffer layer 16 and the workpiece 10 are in fixed contact with each other. (In Figure 1, the buffer layer 16 is shown spaced away from the wulk~:e~e 10 for pul~ses of clarity only.) Also, close spacing of the buffer layer 16 and the coating is inherently present when the sul~slldte is the buffer layer 16.
Altematively, as in Figure 4, the workpiece 10 and the buffer layer 16 may be placed in dynamic rel~tionchip using a continuûus staging system 24 such that the buffer layer 16 and the coating or the boundary portion of the workpiece 10 are in contact with each other, but are not fixed to each other. (For pullJoses of clarity only, the pattem 13 is not shown in Figure 4.) Here, the workpiece 10 takes the form of a workpiece web 25 and the buffer layer 16 takes the fomm of a buffer web 26.
The wc.,hy;cce web 25 extends from a supply roller 28, around two positioning rollers 30, 32, to a take-up roller 34. The buffer web 26 extends from a supply roller 36 to a take-up roller 38 such that the buffer web 26 is in contact with the workpiece web 25 between the positioning rollers 30, 32. Preferably, the workpiece web 25 and the buffer web 26 are tr~ncl~ed in the same direction at e~ual linear speeds such that the workpiece web 25 and the buffer web 26 are subst~nti~lly stationary with respect to each other.
Referring back to Figure 1, a template, such as a SUPPO1 ted mask 40 with a guide shape (not shown), may be positioned plu~illlate the workpiece 10. The guide shape of the mask 40 comprises eCcPnti~lly one or more shaped windows (nût shown) which direct the energy output 11 of the high energy source 12 toward the workpiece lO in the form of the pattern 13 as the energy output 11 and the workpiece 10 move relative to each other. The workpiece 10 is located on one side of the mask 40, and the high energy source 12 is located on the other side of the mask 40. The buffer layer 16 is positioned between the mask 40 and the coating or boundary surface of the workpiece 10 to prevent debris from dispersing away from the workpiece 10 and to prevent debris from cont~ting the mask 40. The buffer layer 16 may also prevent debris from redepositing on areas of the workpiece 10 that are located adjacent the pattern 13 of the workpiece.
The buffer layer 16 acts as a physical, impermeable barrier that prevents movement of debris away from the workpiece 10, and thus prevents debris from contacting and soiling the mask 40. If the buffer layer 16 were not present, debris wo 95/16570 2 1 7 5 h 7 8 PCT/US94/12487 would contact and adhere to the mask 40 within the shaped windows. ClP~ning of the debris from the mask 40 or re~!~c~PmPnt of the mask 40 would be needed to prevent dispersion and diffraction of the energy output 11 and undesirable im~ging effects.
Debris clP~ning is disruptive and mask 40 repl~PmPnt is expensive.
The wavelength characteristics of the high energy source 12 and the reflectivityof the mask 40 are two factors conci~lPred when sPIecting the mask 40. High reflectivity to the output wavelengths of the high energy source 12 is desirable outside the guide shape of the mask 40 where it is desired to block the energy output 11. High reflectivity minimi7Ps etching of the mask 40 in areas outside the windows.
In other c~.bod;.~ s, the buffer layer 16 and the mask 40 are integrally connP~tPA In one embo iimPnt the mask 40 is integral with any side of the buffer layer 16 such that the mask 40 is capable of guiding the energy output 11 of the high energy source 12 to form the pattern 13 in the workpiece 10. In another embodiment, the mask is formed within the buffer layer 16. The integrally connect~PA buffer layer 16 and mask 40 are positioned p~uAillla~e the coating or boundary surface of the workpiece 10 to prevent debris from dispersing away from the workpiece 10. The integrally conn~;~d buffer layer 16 and mask 40 may also prevent debris from redepositing on areas of the workpiece 10 that are located adjacent the pattern 13 of the wu~klJ;~e.
In another embodiment, the template is an ink formation (not shown) placed on or proximate the coating or boundary portion of the workpiece 10. The ink formation is substituted for the mask 40. The ink formation serves as a guide for the energy output 11 of the high energy source 12 as the energy output 11 and workpiece 10 move relative to each other. The ink formation is positionPd belwæn the buffer layer 16 and the workpiece 10 if the ink formation is applied directly to the workpiece 10.
Otherwise, the buffer layer 16 is positioned between the ink formation and the workpiece 10. In one embodiment, the ink formation is formed on the buffer layer 16 using known printing techniques. The ink formation may be formed on any side of the buffer layer 16 so long as the ink formation is capable of guiding the energy output 11 of the high energy source 12 to form the pattern 13 in the workpiece 10.
When used with the ink formation, the buffer layer 16 acts as a physical, impermeable barrier that prevents movement of the debris away from the workpiece 10, wo 95/16570 2 1 7 ~ 6 7 8 PCT/USg4/12487 and thus ~ nL~ debris from cont~rtin~ the final optical c~ t (not shown). If thebuffer layer 16 were not present, debris would contact and adhere to the final optical element. Cle~nin~ of the debris from the final optical f`~ or repl~rf mf nt of the final optical element would be needed to prevent dispersion and diffraction of the energy 5 output 11 and undesirable im~ging effects. Debris cle~ning is disruptive and optical element repl~mPnt is expensive.
In one prcfcl,cd embodiment of the inventive method, the high energy source 12 selectively removes the coating or the bol-nd~r portion in the form of the pattern 13 by a well known process called ablative deco...l~s;L;sn, he.~;nafLer lcfcl~ed to as ablation.
10 It is known that ablation leads to high energy fr~gf ~ ;on of debris. It is believed that fr~gmentc of debris travel on the order of one or two cçntim~ters from the workpiece lO. Ablation of the coating or the boundary portion may be accomplished with or without the mask 40 or ink formation.
The high energy source 12 used in the ablation process, as in Figure 1, is preferably a laser 42 in one embodiment. The energy output 11 :~Ccoci~tf~d with the laser 42 is a laser beam 44. Preferably, the laser 42 is an excimer laser. The excimer laser produces a short pulse length (e.g., 20 n~noseconds) beam with s~ffici~nt energy density (approximately 0.5 Jlcm2) for effective ablation in the wo,~iece 10. Short pulses of relatively high density energy assure that a subst~nti~l amount of heat is generated in the coating or the boundary portion of the wo,~iece 10 in a very short time period such that the generated heat stays in the coating or the boundary portion during the short time increments of the ablation process.
The short pulse length, high density energy available from the excimer laser is believed to concentrate in the pattem of the coating or the boundary portion rather than bleeding away from the pattem or out of the coating or boundary portion. Additionally, the high densitv energy of the excimer laser is available over a relatively large area, as colllp~ed to other lasers. The large beam 44 area coupled with the guide shape of the mask 40 mav allow the excimer laser to desirably ablate more than one pattem or pattem feature at a time.
It has been found that a 248 nm wavelength beam from the excimer laser provides high pattem resolution and relatively high energy absorbance in some selected WO95/16570 2 1 7 5 6 ~8 PCT/US94/12487 surface coating layers. Also, in some surface coating layers, a 308 nm wavelength beam from the excimer laser was found to produce good pattern resolution, acceptably high surface coating layer absollJallce, and potenlially cignifir~nt operation and m~intPn~nce economies, as co~ d to the 248 nm UV wavelength. The 248 nm wavelength beam 5 was obtained from the excimer laser using a mixture of krypton, fluorine, neon, and helium in a select ratio. Ultraviolet wavelength emi~cionc of 308 nm from the excimer laser require a mixture of xenon, hydrogen c~lori~e, neon, and helium. Proper beam geo,..ell~ is an illlpul~nt p~dlllet~r when using the eYçimçr laser and the mask 40 in the ablation process. Particularly illl~l ~It beam geometry variables for the excimer laser 10 include beam shape, beam ~lignmPnt, beam focal length, and beam width and height.
The emitted beam from the excimer laser is approximately rectangular in shape with about a 3:1 aspect ratio. In one embo-limPnt, the optical elements 14 include a collimator (not shown) oriented for ~ligning the beam of the excimer laser. The collimator includes front surface alul~-irlulll or dielectric type mirrors with coatings 15 al ~ropate for beams with SPIPctpd energy dPncitiPs Other parameters of interest when uti1i7ing the excimer laser and the mask 40 inthe ablation process are the amount of beam overlap of succec~ive laser pulses and the amount of beam gap between succes~ive laser pulses. It may be desirable to minimize beam overlap, while also avoiding beam gaps btlwæn successive laser pulses. Beamoverlap may cause unc~ti~f~r~ory ablation results, such as unwanted variations within the pattern 13 undesirable thermal effects within the workpiece 10, and detrimental changes in debris formation. Beam gap may cause incomplete formation of the pattern 13.
Beam overlap and beam gap may be controlled by varying the translation speed of the beam relative to the workpiece 10. Beam overlap and beam gap may also be controlled by varying the pulse repetition rate of the excimer laser. Control of beam overlap and beam gap may depend on a variety of beam factors, such as beam focal length and beam energy density distribution profile. Beam overlap control and beam gap control may also depend on workpiece variables, such as absorption and ablation characteristics of the workpiece.
The optical elements 14 preferably include a cylindrical converging lens (not shown) and a cylindrical diverging lens (not shown). The cylindrical converging lens Wo 95/l6s70 2 1 7 5 6 7 8 PCT/US94l12487 sets the focal length of the beam. In one embo~iim~ont of the mPt~od, the converging lens has a 106.68 cm focal length. The cylindrical diverging lens sets the horizontal spread of the beam ~ e.~ing from the converging lens. In one embodimPnt of the methQd, the diverging lens has a 15.24 cm focal length. The converging and diverging 5lenses are made of high UV tr~ncmicsion m~tPri~hc such as fused silica, commonly known as synthetic quartz.
By adjusting the relative ~iict~ncPs between the converging lens, the diverging lens, and the wo,~;cce 10, the width and the height of the beam 44 are selectively adjustable to provide the desired beam energy density and the desired beam spread 10app.up,iate for particular template tlimPnsions and workpieces. It has been found that the beam 44 of the excimer laser, with a width of approximately 200 mm and a height ranging between 0.5 mm and 4.0 mm, is particularly a~r~p~ia~e for use with the mask 40 for forming the pattern in the coating or the boundary portion of the workpiece 10.
In another emb~iiment, the high energy source 12 is a fl~chl~mp 46, as in Figure155. Preferably, the flashlamp 46 is a short pulse linear fl~chl~mp that includes a spalci)t, quartz lamp tube (not shown) with a wall thir~nPcs on the order of about 1 mm. The lamp tube has an internal bore (not shown) with a ~ n~ tl ~ in the applo~i",ate range of 3-20 mm. The length of the fl~chl~mp 46 pl~feldbly is manycentimPters, such as about 30 cm. Electrodes, preferably made of tnngcten, are sealed 20into the ends of the lamp tube. The lamp tube is filled with a noble gas, preferably xenon for efficiency reasons.
The flashlamp 46 is pulsed in the range of 1-20 Hz by applying a high voltage in the range of 5-40 KV to the electrodes using a c~p~ritQr bank. The charge ionizes the xenon atoms to form a plasma which emits a bro~db~nd of radiation ranging from 25about 200 nm to about 800 nm. The fl~chl~ p 46 includes a reflector 48 that is placed over the fl~chi~rnr 46 to shape and guide the radiation. The reflector 48 is shaped to direct the radiation, at the required density and fluence, toward the template and the coating or boundary portion of the workpiece 10.
Linear fl~chl~mps are capable of producing high intensity, high fluence energy 30output at shorter wavelengths in relatively short pulses on the order of 5 ~sec. Short pulses of relatively high density energy assure that a substantial amount of heat is WO 9S/16570 2 i 7 5 6 7 8 PCT/US94/12487 g~n~ d in the coating or the boundary portion in a very short time period such that the gellG~a~ed heat stays in the coating or the b~ul~d~ portion during the short time incl~"ltnls of im~in~ plucesses such as ablation. For eY~mple, it has been found that a xenon linear fl~chl~mp, with a bro~1b~n~ spectral output provides an energy density at the template of bel~., about 1.0 and 1.5 J/cm2 during a pulse of belw~n about 2 and 6 ~secs and is capable of suitably forrning the pattem 13 in some workpieces using some tel"plates. Additionally, the energy of the linear fl~hl~mp is available over a relatively large area, as co,npa~ed to other high energy sources. The large radiation coverage area coupled with the guide shape of the mask 40 allows the linear fl~chl~mps to desirably create multiple patterns 13 or pattern features at â time.
Referring back to Figure 1, the mask 40 is placed b~l~n the high energy source 12 and the workpiece 10 such that the energy output 11 ablates the pattern 13 in the coating or boundary portion of the workpiece 10. Preferably, the mask 40 is made of a base material (not shown) with high transparency to the energy output 11 of the high energy source 12, such as the ultraviolet wavelength emissions of the excimer laser.
The base material of the mask 40 is coated with a plutecti~e overlay (not shown) that is highly reflective to the wavelengths of interest. In one embodiment, the base m~tPri~l of the mask 40 is made of synthetic fused silica, and the p,u~;Li~e overlay is al,l,.,in~
The aluminum is preferably vacuum deposited onto the fused silica base material to a depth of a~",luAi-l-ately 600 nm. The guide shape of the mask 40 is formed in the protective overlay, the aluminum, by standard semiconductor industry photolithographic and wet etch pl~es~h~g techniques.
The buffer layer 16 is positionP~ between the mask 40 and the workpiece 10 such that the mask 40 is in close working relationship with the workpiece 10. (In Figure 1, 2~ the mask 40, buffer layer 16, and workpiece 10 are shown spaced apart for pu,l,oses of clarity only.) In this orientation, the buffer layer 16 prevents movement of debris away from the workpiece 10 and prevents debris from contacting the mask 40. The buffer layer 16 mav also prevent debris from redepositing on areas of the workpiece 10 that are located adjacent the pattem 13 of the workpiece. It is generally desirable to position the buffer layer 16 in intimate contact with both the mask 40 and the workpiece 10 to minimize spread of the beam 44 after the beam 44 passes through the mask 40.

21 7567~
Wo 95/16570 PCT/US94/12487 However, the desired level of intim~tç contact between the buffer layer 16 and the workpiece 10, as previously noted, deppnAc upon wolhl~;~e 10 variables, such as the roughness of the coating or boundary portion.
The buffer layer 16, preferably the sheet of film, may be made of co,l,,,,clcia 5 grades of polymer film, such as commercial grade polypropylene and commercial grade polyethylene. However, commercial grades of polymer film are not IJlcfcllcd because co"""e,~;;al grades of polymer film typically have l-,anur~cluling defects, such as extrusion lines, surface irregul~ntiPs and caliper non-unifol ",ity. These defects introduce irregularities into the energy output 11, such as the laser beam 44, as the laser 10 beam 44 passes through the sheet of film. ~dAition~lly, co"""ercial grades of polymer films with these defects tend to absorb energy from the energy output 11. This causes the polymer film to heat up and decreases the durability and useful life of the polymer film.
If co"""e.~;al grades of polymer films are non~thPl~cc sPlP~ted, it has been found 15 that commercial grade polyethylene, relative to co"""cl,_;al grade polypropylene, is significantly less transparent to some wavelengths of interest. Coll~ ~ndingly, the power supplied to the high energy source 12 for creating an identir~l pattern in an idcntir~l workpiece is increased for a particular source emitting a par~icular wavelength energy through co"""~ .c;al grade polyethylene, as co",~ d to a similar source emitting 20 the particular wavelength energy through commercial grade polypropylene.
Preferably, the buffer layer 16 is made of capacitor grade biaxially-oriented polypropylene (BOPP). It has been found that c~p~ritQr grade polypropylene provides a high tr~nC-nitt~nce to 248 nm ultraviolet light, as ill~ çd graphically in Figure 6.
Additionally, the c~p~citor grade polypropylene has a smooth finish, uniform thickness, 25 and minim~l defects, such as casting marks. These qualities minimi7ç energy output 11 absorption and spread as the energy output 11 passes through the sheet of film, thereby preserving pattern resolution and extending film life.
The buffer layer 16, preferably the sheet of film, may be positioned in relationto the workpiece 10 in a variety of ways. For incpnce, the sheet of film may be laid 30 on or over the coating or boundary portion of the workpiece 10. The mask 40 may then be placed in working relation with the workpiece 10 such that the sheet of film is W O 95/16570 PCTrUS94/12487 rli~pose~ bel~n the mask 40 and the wulkl~iece 10. AS another exarnple, the sheet of film may be extruded or l~min~tP~ onto the coating of the workpiece 10 using convention~l extrusion or l~min~tion equipment and techniques.
AILGI~ Ve1Y~ referring to the batch staging system 23 of Figure 1, the mask 40 may be ~t~rh~d to the workpiece 10 such that the workpiece 10, buffer layer 16 and mask 40 are in fixed contact, with the buffer layer 16 located bel~n the workpiece 10 and the mask 40. (The mask, buffer layer 16, and workpiece 10 are shown spaced apart in Figure 1 for pu~yOSeS of clarity only.) The staging system 23 also includes an X-Y
translation stage 52. The workpiece 10 is fixed against the tr~nCl~tion stage 52 and the mask 40 is fixed to face away from the tr~nCl~tion stage 52. The stage 52 is tn~nCI~t~d through the laser beam 44 to scan the energy output 11 over the guide shape of the mask 40 to ablate the pattern 13 in the wnrkT-ie~e 10.
Another option for positioning the buffer layer 16 includes the continuous staging system 24, as in Figure 4, which ~ ir.~i.in~ the buffer web 26 in a close, coo..linated and dynamic relationship with the workpiece web 25 and the mask 40. The mask 40 is att~rhed to a mask translation frame (not shown). A conventional plugld---mable controller (not shown) tr~n~l~tes the frame and the mask 40, between a starting position 54 and an ending position 56.
The mask 40 is tr~ncl~t~d in the same direction and at the same speed as the workpiece web 25 and the buffer web 26 to scan the mask 40 through the laser beam 44, between the starting and ending positions 54, 56, thereby ablating the pattern 13 in the workpiece web 25. After each pattern is completed, the mask 40 is reset to the starting position 54, the workpiece 10 and the buffer layer 16 are replaced and the mask 40 is again tr~ncl~t~d through the laser beam 44 in a repe~l;n~ cycle. The continuous staging system m~int~ins the workpiece web 25, the buffer web 26, and the mask 40 in contact and fixed relation with each other during imaging of the pattem in the workpiece, though the workpiece web 25, the buffer web 26 and the mask 40 are not fixed to each other.
Alternatively, the sheet of film may be extruded or l~min~t~ onto the coating orboundary portion of the workpiece 10 prior to the im~ein~ process to make an im~ein~
kit (not shown). In kit form, the sheet of film protects the coating or the boundary portion during storage and transportation of the workpiece 10. Kits may also be -p~ d at a c~ntr~i7pd loc~tinn to realize film pl~pment econol, i.,s.
After the pattem 13 is created in the workpiece 10, the buffer layer 16 is removed from the worlcyiece 10. Signifi~nt amounts of debris are typically removed with the sheet of film when the buffer layer 16 is made of biaxially-oriente~
S polypropylene. SUbS~1~S that include the coating or the bound~u.y portion may be cleaned of ~ ning debris using a convention~l carbon dioxide snow blasting process.
According to the snow blasting process, carbon dioxide at approxim~tPly 59.76 kg/cm2 is mixed with ambient air to produce cryst~lli7ed carbon dioxide snow granules. The crys~lli7Pd snow granules are projected at the coating or the boundary portion of the 10 w~lky;ece 10 in "sand blast" fashion using a commercially available blasting gun.
Although many embodimentc may be practiced in accordance with this invention, the invention is demonstrated by the following illustrative but non-limiting examples.

EXAMPLE:S
15 Example 1 The batch staging system 23 of Figure 1 is l~resen~Li~/e of the setup used in Example 1. The laser 42 was a Model LPX 315 150 Watt Excimer Laser available from Lambda Physik of Acton, Massachusetts. The Model LPX 315 laser was capable of selective beam energy output ranging from 400 to 800 mJ at up to a 150 Hz pulse rate.
20 The Excimer Laser was optimized for fluorine and produced ultraviolet radiation with a wave length of 248 nm.
The workpiece 10 was a metal-coated substrate. The substrate was made of 25 ~m thick polyethylene, and the coating was copper. The copper coating was deposited to a thi~nec.c of 100 nm by evd~ ing the copper onto the polyethylene substrate using 25 a standard E-beam evaporation technique within a vacuum chamber.
The base m~tPri~l of the mask 40 was made of a 2.3 mm thick synthetic fused silica plate, and the base material was coated with alu..,inll.,,. The aluminum was vacuum deposited on the fused silica plate to a depth of approximately 600 nm. The guide shape was formed in the mask 40 by standard semiconductor industry 30 photolithographic and wet etch plocesc;ng techniques.
The buffer layer 16 was a 50 ~m thick sheet of co,lll"ercial grade polypropylene.

Wo gS/16570 2 ~ 7 5 6 7 8 PCT/US94/12487 The buffer layer 16 was placed in contact with and b. l-. ~n the mask 40 and the copper coating of the workpiece 10 by fixing the mask 40, the buffer layer 16, and the workpiece 10 to the X-Y tr~nCl~tinn stage 52.
The optical c4 ..~ 14include~d a cylindrir~l converging lens with a 106.68 cm 5 focal length and a cylinrlrit~l diverging lens with a 15.24 cm focal length. The ~ict~n~es btlwcen the converging lens and the workpiece 10 and bcl~. ~en the converging lens and the diverging lens were adjusted to provide the co"lbination of beam width, height, and energy density lc4uilcd for ablation of the copper coating of the workpiece 10.
The X-Y tr~nCl~tion stage 52 was tr~ncl~t~d through the laser beam 44 to scan 10 the guide shape of the mask 40 to create the pattern 13 in the copper coating. The X-Y
translation stage 52 was tr~ncl~t~.d in the Y direction at a linear rate of 250 cm/min.
The laser 42 produced an energy density of 125 mJ/cm2 at the workpiece 10. The energy density was measured by an apelLuled Model ED-500 Jo~llen ~er available from Gentech of Ste-Fog, Quebec, Canada. The meter was placed the same tiict~nce from the laser 42 as existed bel~.- the laser 42 and the workpiece 10.
After the pattern 13 was ablated in the copper coating of the workpiece 10, the buffer layer 16 was removed and discarded. The buffer layer 16 prevented debris from contacting the mask 40 as the mask 40 was free of debris after the buffer layer 14 was removed. The pattern 13 formed in the copper coating had good resolution and was free 20 of shorts bclwæn pattern features.

Example 2 Example 2 utilized the ~ldnge,llent ~epi~led in Figure 5. The high energy source 12 was the fl~chl~mp 46. The fl~chl~mp 46 was a Part No. ILCT-18 fl~chl~mp 25 available from ILC Technology, Inc. of Sunnyvale, California. The fl~chl~mp 46 had an arc length of 8.9 cm included the quartz lamp tube with the 6 mm ~ meter internal bore and also included the t~ngcten electrodes sealed into the ends of the tube. The tube was filled with xenon gas at a gauge plessult: of 400 mm of Hg(0C). The fl~chl~mp 46 had a pulse width of 6 ~sec FWHM with an input energy of 100 joules per pulse.
30 The flashlamp 46 operated at a pulse repetition rate of approximately 1 Hz. Pulse radiation from the fl~chl~mp was directed toward the workpiece 10 by the reflector 48, Wo 95/16570 2 1 7 5 6 7 8 PCT~Sg4/12487 which was ellirti~ y-shaped~ through a 5.0 cm reflector a~llulL.
The wolhl,;ece 10 was the substrate coated with metal. The substrate was made of 50 ~Lm thick polyethylene ~r~h~ AtP The coating was a 75 nm thick layer of copper that was vacuum deposited onto the polyethylene ~r~ht~Al~tP subsllAtP. The S buffer layer 16 was a sheet of 25 ,um thick c~paritor grade polypropylene available from Bollmet Industries of Dayville, Conne~ticut The mask 40 was subst~ntiAlly similar to the mask 40 ~esrnbed in Example 1. R ~I;At;On from the flAchlAmp 46 was directedthrough the mask 40 and through the buffer layer 16 to ablate the pattern 13 in the coating of the workpiece 10. I2A~IiAtion from the flAchlAmr 46 ablated approximately 14 cm2 area of copper from the polyethylene t~lC~ tl~Al~t~p- substrate. The buffer layer 16 was removed and discarded after imAging of the pattern 13 in the workpiece 10. The resolution of the pattern 13 was good with no shorts between pattern features. The pattern features included lines as small as 100 ~m wide with 50 ~m line to line spacing.

Example 3 For this Example, a trAnCl~ting mirror set-up 58, illustrated in Figure 7, was utilized. The t Ai~lAI;ng mirror set-up 58 includçd the wolh~.ece 10, the buffer layer 16, the mask 40, and the laser 42. Additionally, the trAnCl~ting mirror set-up 58 included a linear translation stage/servo 60 with a flat mirror 62 mounted on the stage/servo 60 such that the laser beam 44 of the laser 42 was directed through the mask 40 and the buffer layer 16 to create the pattern 13 in the workpiece 10.
The laser 42 was the Model LPX 315 I Ambd~ Physik Fxçim~r Laser described in Example 1. The optical elements 14 comprised the cylindrical converging lens and the cylindrical diverging lens of Example 1 alldnged as described in Example 1 The workpiece 10 of this Example was a nominal 8.89 cm mAgnçtic data storage disk, generally Icf~lcd to as a floppy disk 64. The floppy disk 64 was made of apolyethylene ~l~hl~lAlAte substrate layered with a mAgnetic coating conci.cting of mAgnetic particles dispersed within a 0.7 ~m polymeric binder. The buffer layer 16 was made of capacitor grade biaxially oriented polypropylene film available from Bollmet Industries of Dayville, Connecti~ut. The buffer layer 16 was 25 ,um thick and, referring to Figure 6. had a tr~ncmittAnce of about eighty-two percent (82%) to 248 nm radiation.

WOg5/16570 2 1 7 ~ ~ 7a . PCT/US94/12487 Tr~n~miccion was ~ d using a Model T ~mhA~-9 W/viS Sp~;llu?holu...~r available from Perkin Elmer Co. of Eden Prairie, Minnt~!~ The mask 40 was s"b,l~ ~ti~lly similar to the mask 40 described in Example 1. In addition, the guide shape of the mask 40 was capable of use in fo,---ing the pattern 13 in the m~E~ti~
5 coating of the floppy disk 64. The pattern 13 inrluded a plurality of concentric optical servo tracks. Each servo track inrlu~led a plurality of stitches arranged end to end in single file fashion. Each stitch was appr~im~t~ly 5 ~m wide and beLwæn about 40 to 80 ~m long. Overall, the pattern 13 included approximately 1.5 million stitches.The floppy disk 64 included a standard central hub portion 66 with a central locating feature 68. A mask centering hub 70 with a cenleling pin 72 was ~tt~rhPd to the center of the mask 40.
The buffer layer 16 was then placed onto the mask 40 such that the buffer layer 16 fully covered the guide shape of the mask 40. The floppy disk 64 was then placed onto the mask 40 such that the buffer layer 16 was disposed between the mask 40 and 15 the floppy disk 64. The floppy disk 64 was precisely aligned to the guide shape of the mask 40 using the cent~l locating feature 68 and the mask centering hub 70. A
weighted contact mat 74 was then placed on the floppy disk 64 to minimi7e disk 64 distortion and assure inl;..-~tP contact belween the floppy disk 64 and the buffer layer 16 and between the buffer layer 16 and the mask 40. (The mask 40, buffer layer 16, floppy disk 64, and contact mat 74 are shown spaced apart in Figure 7 for purposes of clarity only.) The mask 40, the buffer layer 16, and the floppy disk 64 were fixed relative to the linear translation stage/servo 60 such that the laser beam 44 emerging from the diverging lens of the optical elements 14 reflected off the flat mirror 62 and scanned the guide shape of the mask 40 to form the pattern 13 of optical servo tracks in the m~gnetic coating of the woll~iece 10 as the stage/servo 60 moved. A standard programmablecontroller in combination with a DC servo motor 78 directed linear movement of the stage/servo 60, and thus the flat mirror 62, with respect to the mask 40 at a rate of approximately one hundred inches per minute (254 cm/minute).
The laser 42 produced an energy density of approximately 125 mJ/cm2 at a pulse repetition rate of 140 Hz. After ablation was completed, the buffer layer 16 was -~...ov~d. The m~grletir, coating was then cleaned using the carbon dioxide snowblasting process at a carbon dioxide pl~,S;~Ilc of apl"oAi-llalely 59.76 kg/cm2. Atomic Force Micç~scope (AFM) measurements showed minim~l ~liffr~rtion effects were created in the pattern 13 of optical servo tracks due to the buffer layer 16 or the mask 40. Several S hundred floppy disks 64 were succe~fully imaged without any in~ir~tion of degradation of the guide shape of the mask 40. Signifir~nt ~mounts of debris were evident on the buffer layers 16 after ~ ;Li~e buffer layers 16 were se~dld~ed from ~e~ecli~e floppy disks 64.

10 Exam~le 4 The batch staging system 23 of Figure 1 was utilized in Example 4. The details about the laser 42 and the optical elements 14 were substantially similar to those described in F-~mple 1. Multiple workpieces with differing patterns 13 formed in the coating in each r~ e workpiece 10 lltili7ing different buffer layers 16 at different 15 laser pulse repetition rates and different X-Y translation stage 52 translation speeds were included in the work of Example 4, as ~u.. ~.i7Pd in the following table:

Wor~piece 10 Pul e TnNblion (Co ling 20\Subur le 19) P tlem 13 Buffer l~yer 16 (Hz) Specd (cm/minu~e) lOOnm Niclcel/50~ m Polye-ler Grid of 121 m SO~Lm L ' gredc linee on ~ , yl. _ 50 203 2 250um cenler~
I OOnm Nic~el/25~1m Grid of 12~m S-me liner on S~me 45 250Um cenlerr IOOnm Niclcel/175~m Per llel 12~1m Pul~ ' wide liner on Seme 45 S~me 500um cenlerr lOOnm Copper/25~ m Grid of 12~un F~ e~' ~1. ,c linec on S~me 40 Seme 250um cenlerr ISOnm Copper/175~m P r llel 121 m Pul~ ' wide liner on S-me 45 Srmc 500~m cenler~
IOOnm ('I 'SO~m Grid of 12um 30 Polye~er iiner on S-me45 S-me 250/~m cenler~
SO~m Polyerler (no co bng~ Memory C-rd 25um c~p~cilor g~de 254 Circui~ l"`'r~ 75 WO 95/16570 2 1 7 5 Ç ~ PCT/US94/12487 The laser 42 supplied an energy density of ~p-u~ Ply 125 mJ/cm~ to the c~qtingc of the fe.,~cli~re workr-iP~es 10 to form the ,.,~ e patterns 13 in the.e~ ive cs~tingc or boundary portion. After each pattern 13 was formed, the buffer layer 16 was removed and the pattern 13 of the le~ e workpiece 10 was inspe~ted Though pattern quality varied among the rci~;live workpieces 10, the laser 42 5qticfqctorily formed each of the patterns 13 in the ~~ e coq*ngc and boundary portion of the wo.~:~es 10.

Example 5 The batch staging system 23 of Figure 1 was utilized in Example 5. The laser 42, the optical e1P~ Pn~C 14, the wo~kl~icce 10, the buffer layer 16, and the mask 40 were as described in Example l. The pattern 13 formed in the coating of the workpiece 10 was a grid of 12 ~Lm wide lines on 250 ~m centers. The pattern 13 was formed in the workpiece lO, as desc.ibed in FYqmrle 1, in over 150 samples of the workpiece 10using the same mask 40. The mask 40 rc4uilcd no special h~n-1ling other then periodic clP~ning with TcAwipcs~ and isopropyl alcohol. In each of the 150 samples, the pattern 13 formed in the workpiece 10 had good resolution.
If the buffer layer 16 had not been used, the life ~;A~c~Cy of the mask 40 would have been ~I,luAh..a~ely 10 samples. Instead, use of the buffer layer 16 allowed use of the mask 40 on 150 samples to date, without significant degradation of the guide shape of the mask 40, and is expected to allow continued use of the mask 40 on additional samples of the workpiece 10 in the future.
Although the present invention has been described with reference to plcfcllcd embodiments, workers skilled in the art will recognize that ch~ngPs may be made in form and detail without departing from the spirit and scope of the invention.

Claims

AMENDED CLAIMS

1. A method of preventing debris from a workpiece (10) from dispersing away from the workpiece, the debris being created by a high energy source (12) used to ablate a shaped image (13) in the workpiece, the method comprising:
positioning a mask (40) proximate the workpiece;
positioning a debris blocking layer (16) between the mask and the workpiece, the layer being substantially transparent to radiation emitted by the high energy source such that the high energy source is capable of ablating the shaped image;
directing radiation from the high energy source through the mask, through the debris blocking layer, and toward the workpiece;
ablating the workpiece with the radiation, thereby forming the shaped image;
and separating the debris blocking layer from the workpiece, whereby the debris blocking layer minimizes degradation of the mask, thereby minimizing g the need to clean the mask and prolonging the useful life of the mask.

2. A method of preventing debris from workpieces (10) from dispersing away from the workpieces, the debris created by a high energy source (12) used to ablate a shaped image (13) in the workpieces, the method comprising:
(1) positioning a mask (40) proximate a first workpiece;
(2) positioning a first portion of a debris blocking layer (16) between the mask and the workpiece, the layer being substantially transparent to radiation emitted by the high energy source such that the high energy source is capable of ablating the shaped image;
(3) directing radiation from the high energy source through the mask, through the debris blocking layer, and toward the workpiece;
(4) ablating the workpiece with the radiation, thereby forming the shaped image;

(5) separating the first portion of the debris blocking layer from the first workpiece;
(6) repositioning the mask proximate a second workpiece;
positioning a second portion of the debris blocking layer between the mask and the second workpiece;
(8) repeating steps (3) and (4); and (9) separating the second portion of the debris blocking layer from the second workpiece, whereby the shaped image may be formed in a plurality of workpieces while minimizing degradation of the mask, thereby minimizing the need to clean the mask and prolonging the useful life of the mask.

3. The method of claims 1 or 2, wherein the workpiece comprises a substrate with a coating, and wherein the shaped image is formed in the coating.

4. The method of claims 1 or 2, wherein the debris blocking layer comprises capacitor grade biaxially oriented polypropylene.

5. The method of claim 2, further comprising step (10), wherein steps (6)-(9) are repeated over 100 times with third, fourth, fifth, ... workpieces and third, fourth, fifth, ... portions of the debris blocking layer, whereby the mask is used over 100 times before cleaning or replacement of the mask is required.

6. A method of making a data storage disk (64) using a laser (42) which emits radiation, the method comprising:
providing a substrate coated with a magnetic coating;
placing a debris blocking layer (16) in contact with the coating, the layer being substantially transparent to ultraviolet radiation;
placing a mask (40) in contact with the debris blocking layer such that the layer is disposed between the mask and the coated substrate (64);
directing ultraviolet radiation of the laser through the mask and the debris blocking layer;

ablating the coating with the radiation, thereby forming a pattern (13) in the coating; and separating the debris blocking layer from the coated substrate, whereby the debris blocking layer minimizes degradation of the mask, thereby minimizing the need to clean the mask and prolonging the useful life of the mask.

7. The method of claim 6, wherein the pattern comprises a plurality of optical servo tracks arranged in spiral or concentric form.

8. The method of claim 7, wherein the servo tracks comprise a plurality of stitches spaced in single file, end-to-end fashion, each stitch being less than about 10 µm wide.

9. The method of claim 7, further comprising forcing the coated substrate and the mask together to force the magnetic coating against the debrisblocking layer and to force the mask against the debris blocking layer.

10. The method of claim 6, wherein the debris blocking layer comprises polypropylene, polyethylene, polycarbonate, or polymethylmethacrylate.