Abstract:
A stationary vacuum deposition machine for use in a method for processing substrates to make magnetic hard disks includes a series of stations and a transport. The series of stations includes an entrance station for receiving substrates into the machine and a predetermined station. The transport operates in a cycle with each cycle including a transport phase and a stationary phase. The transport causes all the substrates that are in the machine to be moved during the transport phase, and be temporarily held stationary during the stationary phase, such that during each stationary phase a predetermined one of the stations is occupied by one of the substrates while each of a plurality of others of the stations is occupied by a respective one of a plurality of others of the substrates. The machine further includes a plurality of vacuum deposition stations and a scanning beam generator. Each vacuum deposition station operates during each stationary phase such that each station causes a thin film to be deposited on a respective one of the substrates. The scanning beam generator directs a scanning beam at the substrate occupying the predetermined station while the substrate is held stationary to produce a textured pattern.

Description:
This application is a division of application Ser. No. 08/920,170, filed Aug. 27, 1997, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to processing of a substrate in making a disk to be used in a fixed-disk disk drive. More particularly, it relates to using a vacuum deposition machine to laser texture an inner annular region or landing zone of a substrate. 
     2. Description of the Prior Art and Related Information 
     The overall cost and performance of a contemporary fixed-disk disk drive, such as a magnetic hard disk drive, depend significantly on the cost and performance of each magnetic disk within the drive. 
     The cost of manufacturing magnetic disks depends in part on the cost and efficiency of operation of various machines used to carry out numerous processes involved in manufacturing the disks. These processes include texturing processes. Typically, one machine is used for “full-surface” texturing and another machine is used for landing zone texturing. An example of a machine for landing zone texturing is a standalone laser texturing machine which includes a rotating and translating spindle that rotates a substrate while a stationary pulsed laser beam is directed at the rotating substrate causing bumps to be formed in the landing zone of the substrate. 
     The standalone machine typically laser textures one substrate at a time and its throughput may be severely limited by factors such as the substrate handling time. Also, the cost of the laser texturing machine may constitute a significant portion of the overall cost of manufacturing the disks. 
     The manufacturing of magnetic disks also typically involves the use of a stationary vacuum deposition machine. (In this art, a stationary vacuum deposition machine is commonly called a stationary sputtering machine, and the two different terms are used interchangeably herein.). An alternate machine is an in-line sputtering machine. Either type of machine is used to, among other things, deposit a succession of thin film layers on a substrate. The thin film layers may include an underlayer, a magnetic layer, and a carbon overcoat layer. A typical stationary sputtering machine includes a series of stations. The series of stations includes a load station, a plurality of sputtering stations, a cooling station, a heating station, and an unload station. Each station has a per-stage processing time of typically approximately 5 to 7 seconds. The sputtering stations are used to sputter the succession of thin film layers on a substrate; typically, both sides of the substrate are sputtered with the succession of thin film layers. Among the series of stations, a plurality of spare stations are also usually included. The cost of a sputtering machine adds a significant portion to the overall cost of manufacturing the disks. 
     The performance of a fixed-disk disk drive depends in part on structures that affect the startup of operation of the drive. In a typical disk drive, a slider lands in the landing zone when the disk drive is powered down. Texturing of the landing zone reduces the effective contact area between the slider and the surface of the landing zone thereby reducing the static friction forces (“stiction”) that must be overcome to separate the slider from the surface of the landing zone when the disk drive is powered on. Such a reduction of static friction forces improves the performance of the disk drive. 
     A need exists in the art to reduce the costs of manufacturing the disks. 
     SUMMARY OF THE INVENTION 
     This invention can be regarded as a method for using a stationary vacuum deposition machine to process a substrate to make a magnetic hard disk. The machine has a controllable transport means and a series of stations. The series of stations includes stations to which the controllable transport means sequentially moves the substrate and at each of which a thin film layer is deposited onto the substrate. The method includes the steps of loading the substrate into the machine and controlling the transport means to cause the substrate to be moved into, and then be temporarily held stationary in, a predetermined one of the series of stations. The method also includes the step of directing a scanning beam at the substrate while it is held stationary in the predetermined station to produce a textured pattern. 
     This invention can also be regarded as a method for using a stationary vacuum deposition machine to process substrates to make magnetic hard disks in a pipeline process. The machine has a controllable transport means, a series of stations through which the controllable transport means sequentially moves each of the substrates, and a controllable plurality of station vacuum deposition means. The method includes the steps of sequentially loading the substrates into the machine and controlling the transport means to operate in a cycle with each cycle including a transport phase and a stationary phase such that the transport means causes all the substrates that are in the machine to be moved during the transport phase, and be temporarily held stationary during the stationary phase, such that during each stationary phase a predetermined one of the stations is occupied by one of the substrates while each of a plurality of others of the stations is occupied by a respective one of a plurality of others of the substrates. The method also includes the steps of controlling the plurality of station vacuum deposition means to operate during each stationary phase such that each station vacuum deposition means causes a thin film to be deposited on a respective one of the substrates, and also during each stationary phase, directing a scanning beam at the substrate occupying the predetermined station while the substrate is held stationary to produce a textured pattern. 
     This invention can also be regarded as a stationary vacuum deposition machine for use in a method for processing substrates to make magnetic hard disks. The machine includes a series of stations and a transport means. The series of stations includes an entrance station for receiving substrates into the machine and a predetermined station. The transport means operates in a cycle with each cycle including a transport phase and a stationary phase. The transport means causes all the substrates that are in the machine to be moved during the transport phase, and be temporarily held stationary during the stationary phase, such that during each stationary phase a predetermined one of the stations is occupied by one of the substrates while each of a plurality of others of the stations is occupied by a respective one of a plurality of others of the substrates. The machine further includes a plurality of station vacuum deposition means and a scanning beam generating means. Each station vacuum deposition means operates during each stationary phase such that each station vacuum deposition means causes a thin film to be deposited on a respective one of the substrates. The scanning beam generating means directs a scanning beam at the substrate occupying the predetermined station while the substrate is held stationary to produce a textured pattern. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of a stationary sputtering machine which incorporates an embodiment of this invention; 
     FIG. 2 is the general construction of a laser texturing apparatus that is incorporated in the machine of FIG. 1 and a representative substrate; preferably, one of the stations shown in FIG. 1 includes such laser texturing apparatus for each of the sides of the substrate; 
     FIG. 3 is a graph of a differential error signal versus the out-of-focus distance of a substrate when a laser beam strikes the substrate; 
     FIG. 4A is a plan view of a substrate such as the substrate shown in FIG. 2, with a landing zone textured by laser texturing; 
     FIG. 4B schematically represents various possible positions that a substrate can occupy relative to a scan lens when the substrate is initially transferred into a station such as station  116  of the machine shown in FIG.  1 . 
     FIG. 5 is a perspective view of a portion of a substrate having a rim only bump formed in a landing zone of the substrate shown in FIG. 4A; 
     FIG. 6A is an intensity contour map of a laser beam according to another embodiment of this invention; 
     FIG. 6B is a cross section view of an energy distribution of the intensity contour map shown in FIG. 6A; 
     FIG. 6C is an intensity contour map of a laser beam according to another embodiment of this invention; 
     FIG. 6D is a cross section view of an energy distribution of the intensity contour map shown in FIG. 6C; 
     FIG. 7A schematically represents a portion of a station, such as station  112  shown in FIG. 1, used to preheat both sides of a substrate; 
     FIG. 7B schematically represents a portion of a station, such as station  114  shown in FIG. 1, used to light sputter etch one side of a substrate; 
     FIG. 8A schematically represents a portion of a station, such as station  120  shown in FIG. 1, used to deposit an underlayer on both sides of a substrate; and 
     FIG. 8B schematically represents a portion of a station, such as station  122  shown in FIG. 1, used to deposit a magnetic layer on both sides of a substrate. 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a machine  100 , referred to herein interchangeably as either a stationary vacuum deposition machine or a stationary sputtering machine, includes a robot  102 , a series of stations  110  to  132 , and a transport means such as a centrically beared wheel  106 . Wheel  106  includes radially disposed grippers such as gripper  108 , a portion of which is shown in FIG. 1. A wall  104  separates series of stations  110  to  132  from a cleanroom  134 . 
     In operation, cassettes (not shown) of substrates made from metal, glass, or ceramic are positioned in front of robot  102  in cleanroom  134 ; an example of a metal substrate is an aluminum substrate which is typically plated with a layer of nickel-phosphorous. Robotic arms (not shown) within robot  102  load each substrate in sequence, one at a time, from a cassette into an entrance station  110 . From entrance station  110 , each substrate is transported by wheel  106  in a pipeline process to each station for per stage processing. 
     Wheel  106  is controlled by operating in a cycle where each cycle includes a transport phase and a stationary phase. During the transport phase, wheel  106  rotates counter-clockwise such that gripper  108  transports the substrate in entrance station  110  to one of a succession of predetermined stations, such as a station  112 . Concurrently, robot  102  loads another substrate from the cassette into entrance station  110 . The process of loading each substrate into entrance station  110  as wheel  106  rotates counter-clockwise continues until all of the substrates from each cassette have been loaded into entrance station  110 . 
     During the stationary phase, station  112  performs per-stage processing such as preheating the substrate while it is temporarily held stationary in the station by gripper  108 . The preheating occurs for a period of time allocated for per-stage processing within machine  100 , typically approximately 5 to 7 seconds per stage. The substrate, such as substrate  230  (FIG.  4 A), is heated to a predetermined start temperature, e.g., 230 degrees C as shown in FIG.  7 A. As shown, heaters  900  and  902  are positioned on each side of substrate  230 . 
     The substrate is then transported or moved to a station  114 . With reference to FIG. 7B, station  114  contains a light sputter etch means such as an ion gun  908  which directs a stream of ions represented by a dashed line  910  to a landing zone  400  of a surface, e.g. top surface  904 , of substrate  230  to perform a light sputter etch of the surface. The light sputter etch removes a plurality of monolayers from the surface, preferably in the range of 1 to 1000 monolayers. A second ion gun (not shown) may be positioned on the other side of substrate  230  such that its bottom surface  906  is also light sputter etched. Alternatively, plasma etching may be used to perform the light sputter etch. 
     Significantly, the per stage processing which occurs in stations  112  and  114  allows the height of the bumps to be controlled when the bumps are formed in station  116 . The preheating of the substrate controls the melt duration which influences the height of the bumps. For example, if the predetermined start temperature is higher, the resolidification time increases which gives additional time for capillary forces to try to restore a flat surface, i.e., the bump height should be reduced. The light sputter etch removes surface oxides from the substrate which may reduce the effects of chemicapillary flow in the formation of bumps. Hence, the formation of bumps may be influenced primarily by thermocapillary flow which results in greater control of the bump height. 
     After the light sputter etch, the substrate is transported to station  116  by wheel  106 . At station  116 , a scanning beam generating means such as a laser texturing apparatus  201  (FIG. 2) directs a scanning beam such as a laser beam  202  (FIG. 2) at the substrate while it is held stationary in the station. This texturing operation will be described in more detail below with reference to FIG.  2 . The substrate is then transported to a station  118  where it is heated for a second period of time. Alternatively, both per-stage heating processes can occur after or before the laser zone texturing operation. The substrate is next transported to a succession of stations  120  and  122 , each of which contains a station sputtering means such as the structure shown in FIGS. 8A and 8B, respectively; each structure is controlled to operate during each stationary phase of wheel  106 . 
     With reference to FIG. 8A, a thin film such as an underlayer  1004  is deposited on both sides of substrate  230  by an underlayer sputtering mechanism generally indicated by  1000  in station  120 . Mechanism  1000  includes a plurality of magnets  1008  and a target  1010  positioned on each side of the substrate. Suitably, the magnets can be either permanent magnets or electromagnets, and the targets are chromium-vanadium targets with each target biased at a negative voltage. In FIG. 8B, a magnetic layer sputtering mechanism generally indicated by  1002  deposits a thin film magnetic layer  1006  above underlayer  1004  on both sides of the substrate in station  122 . Mechanism  1002  includes a plurality of magnets  1012  and a target  1014  positioned on both sides of the substrate. Each target is biased at a negative voltage. Suitably, the targets are cobalt alloy targets. 
     Continuing with FIG. 1, wheel  106  transports the substrate to a spare station  124  and to a station  126  which is used to cool the substrate. At stations  128  and  130 , a thin film layer of carbon is deposited above the magnetic layer in each station. Again, both sides of the substrate are deposited, e.g., by sputtering, with the thin film layers of carbon. The substrate is transported to an exit station  132  where robot  102  unloads the substrate. Other types of processing may be applied to the substrate in the course of making a magnetic hard disk, such as adding a lubricant to the thin film layers of carbon. Also, other types of vacuum deposition techniques may be used in machine  100  such as Ion Beam Deposition, chemical vapor deposition (“CVD”), and plasma-enhanced chemical vapor deposition (“PECVD”). 
     With reference to FIG. 2, a laser texturing apparatus  201  includes a plurality of components  200 - 250 . Substrate  230  does not form a part of apparatus  201 . A laser  200 , such as a Spectra-Physics V70 or B10 vanadate laser, generates laser beam  202 . Suitably, laser beam  202  has a Gaussian shaped energy distribution. Laser beam  202  passes through a Faraday isolator  204 , a mechanical variable attenuator  206 , and a beam expander  208 . Faraday isolator  204  changes the polarization of laser beam  202  to protect laser  200  when a portion of laser beam  202  reflects back from a surface of substrate  230 . Attenuator  206  may be used to attenuate laser beam  202 . Beam expander  208  expands the size of laser beam  202  by a suitable amount such as 3× or 6× its size depending on the laser used. Laser beam  202  then passes through another beam expander  210 , a variable retarder  212 , and a polarizer  214 . Beam expander  210  such as a Rodenstock beam expander is used to expand laser beam  202  to a suitable amount, e.g., 2 to 8× the size of the laser beam received at its input. Variable retarder  212  and polarizer  214  are used to electronically control the attenuation of the power of laser beam  202 . Laser beam  202 , denoted by L 1 , is received at the input of a polarizing beamsplitter  216 . 
     Beamsplitter  216  splits laser beam L 1  such that most of it, denoted by L 3 , passes through to strike substrate  230  via elements  218  to  228  while a small portion of it, denoted by L 2  passes through to an average power detector  236  and pulse width detector  238  via elements  232  and  234 . Element  232  is a best form singlet lens and element  234  is a non-polarizing beamsplitter. Average power detector  236  detects the average power of laser beam L 2  while pulse width detector  238  detects its pulse width, suitably in nanoseconds. Laser beam L 3  passes through a variable retarder  218  such as a ferroelectric liquid crystal retarder and a polarizer  220  which together form a fast shutter; alternatively, a mechanical shutter may be used. Laser beam L 3  then passes through a quarter wave retarder  222 , a scan mechanism  224 , a scan lens  226  within a moveable module  225 , and a window  228  to strike landing zone  400  of substrate  230 . Scan lens  226  is suitably mounted on a computer-controlled stage which includes a translation stage and a two-axis tilt stage. Retarder  222  allows most of the reflected laser beam, denoted by L 4 , to be directed to an auto-focus sensor  250 . Suitably, scan mechanism  224  may be an x-y galvo scanner and scan lens  226  may comprise a plurality of lens in series having a focal length of approximately 100 millimeters (mm). Also, the minimum distance between window  228  and substrate  230  is suitably approximately 25 mm. 
     A portion of the incident laser beam L 3  is reflected back from substrate  230  and passes through window  228 , scan lens  226 , scan mechanism  224 , retarder  222 , polarizer  220 , and retarder  218 . The reflected portion, denoted by L 4 , is reflected off beamsplitter  216  such that a portion of laser beam L 4 , denoted by L 5 , passes to auto-focus sensor  250  which is used to focus the laser beam onto the substrate. Auto focus sensor  250  includes a half wave retarder  240 , a polarizer  242 , a spherical lens  244 , a cylindrical lens  246 , and a focus detector  248 . Retarder  240  and polarizer  242  function as a variable attenuator. Suitably, focus detector  248  may be a four quadrant detector. Spherical lens  244  provides most of the focusing power while cylindrical lens  246  adds astigmatism. The astigmatism causes rays from sagittal and meridian sections to focus at different axial locations. At the tangential and sagittal foci, the images are horizontal and vertical lines, respectively. When the laser beam is optimally focused, the image is a circle halfway between the tangential and sagittal foci. The focus is adjusted by controlling the position of scan lens  226  via module  225  until the output of the horizontal and vertical quadrants are matched. A second apparatus  201  (not shown) may be positioned on the other side of substrate  230  in station  116  such that both sides of substrate  230  are laser textured simultaneously; in that embodiment, each apparatus  201  may have a dedicated laser such as laser  200  or a single laser may be used for both apparatuses. 
     The operation of apparatus  201  will now be explained primarily with reference to FIGS. 2-4B. Prior to the actual texturing of substrate  230 , suitably, laser beam  202  is focused on substrate  230  via an autofocus operation, the scanning direction of laser beam  202  is determined, and the vibration of substrate  230  is attenuated; the above three operations are collectively referred to as control operations. The vibration of substrate  230  may occur when the substrate is transported to station  116  by wheel  106 . 
     In an autofocus operation, the scan lens such as scan lens  226  is preferably moved while the substrate such as substrate  230  is held stationary. Moreover, laser beam  202  scans the substrate in a circle at least once at reduced laser power to prevent the laser beam from texturing the substrate. When the scanning occurs, substrate  230  may assume one of several possible positions relative to an optical axis  406  of scan lens  226 , three positions of which are shown in FIG.  4 B. 
     The first position, denoted by a dashed line  408 , represents an“in-focus” or focused condition of the laser beam; in this condition, laser beam  202  strikes the substrate at an angle which is perpendicular to a surface of the substrate and scan lens  226  is at a suitable distance from the surface. The second and third positions each represent an“out-of-focus” or unfocused condition of the laser beam. For example, when the substrate is in the second position, the laser beam scans the substrate at points such as points a to d as shown in FIGS. 4A and 4B. Each of points a to d in FIG. 4B correspond to points a to d on dashed circular line  404  in FIG.  4 A. At points a and c, the substrate is too close and too far, respectively from scan lens  226 . At points b and d, the substrate is at an in-focus distance from the scan lens. 
     Based on a reflected portion of laser beam  202  which is detected by focus detector  248 , focus detector  248  generates an error signal. For example, if a four quadrant detector was used as focus detector  248 , then the error signal is generated based on an equation such as (A-B)+(C-D) where A,B,C, D are consecutive quadrants in the four quadrant detector. An error signal such as the differential error signal shown in FIG. 3 is generated by focus detector  248 . Error signals  306  and  304  approximately correspond to points c and a, respectively, as shown in FIGS. 4A and 4B. Error signal  302  approximately corresponds to points b and d, respectively, as shown also in FIGS. 4A and 4B. Error signal  302  represents the in-focus condition. The output of focus detector  248  is then used to adjust the position of scan lens  226  to correct for the focus error. For example, scan lens  226  is adjusted in the pitch and/or yaw directions by moving the two-axis tilt stage to correct for the focus error. When the substrate is in the third position, scans lens  226  is moved or translated towards the substrate by moving the translation stage as well as making the pitch and/or yaw adjustments to correct the focus error. Scans lens  226  can also be translated away from the substrate. Once laser beam  202  is focused on the substrate, the scanning direction is determined. 
     The scanning direction is determined such that the scan of the laser beam during texturing occurs concentric about the center of hole  402  in substrate  230 . An offset between optical axis  406  and the center of hole  402 , represented by the intersection of the x-y axis, is detected by scanning laser beam  202  in the x and y directions at reduced laser power. An x-y galvoscanner is used as scanning mechanism  224  in this example. When the laser beam is scanned in the x direction or horizontally, focus detector  248  receives a portion of the reflected laser beam such that a signal representing the reflected laser beam is generated. The signal contains a null where the laser beam is not reflected such as at hole  402  in substrate  230 . Based on this signal, focus detector  248  determines the horizontal offset of the center of hole  402  relative to optical axis  406 . Likewise, the vertical offset or the offset in the y direction is determined. The x-y galvoscanner is then suitably programmed to scan the substrate based on the determined horizontal and vertical offsets such that the scanning occurs substantially concentric to the center of hole  402 . The auto-focus and the scanning direction determination operations are conducted each time a substrate is transferred to station  116 . After the substrate is transferred out of station  116 , scan lens  226  is returned to a default position. 
     The vibration of substrate  230  is attenuated by employing dampening fingers or other suitable mechanical means. After the control operations are completed, the texturing of landing zone  400  commences at an increased laser power such that bumps are formed as shown in FIG.  5 . The texturing occurs such that the scanning of laser beam  202  is a concentric spiral about hole  402 . Landing zone  400  can also be located in other annular regions of the substrate such as the outer annular region. 
     With reference to FIG. 5, landing zone  400  includes a plurality of bumps, only one of which is shown, formed by apparatus  201  shown in FIG. 2. A bump such as bump  500  typically includes a rim  502  and a cavity  504 . 
     With reference to FIG. 6A, a laser beam, which is different than the typical Gaussian shaped laser beam used in the prior art to laser texture landing zones, includes an intensity contour map  700 . Contour map  700  includes a plurality of annular portions concentric about an axis  704 . The energy of the laser beam is concentrated in one of the annular portions, annular portion  702 . With reference to FIG. 6B, a cross section  800  of contour map  700  defines an energy distribution which is characterized by a plurality of maximum energy peaks such as peaks  802  and  804 . Peaks  802  and  804  correspond to annular portion  702 . The laser beam having such a cross section may be implemented within the apparatus shown in FIG. 2 in conjunction with the machine shown in FIG.  1 . The light sputter etch performed in station  114  (FIG.  1 )“turns off” chemicapillary flow when a substrate is laser textured in station  116  (FIG.  1 ). Hence, in station  116 , the bumps formed by the laser having cross section  700  stem from thermocapillary flow alone. Each bump includes a central protrusion surrounded by a cavity and a rim. 
     Other laser beams having different energy distributions may be used to form bumps similar to the ones formed by the laser beam represented by FIGS. 6A and 6B. For example, a laser beam having the intensity contour map and cross section shown in FIGS. 6C and 6D, respectively, may be used. In FIG. 6C, substantially most of the energy of the laser beam is concentrated in the central portions  806  of intensity contour map  810 . In FIG. 6D, a cross section  808  of contour map  810  defines an energy distribution such that each peak corresponds to a central portion  806 . The laser beams represented in FIGS. 6A and 6C may be generated by an apparatus using suitable Fourier optics techniques. Suitably, a 2-D addressable spatial light modulator may be positioned between beam expanders  208  and  210  in the apparatus shown in FIG. 2 to generate such laser beams. 
     Significantly, this invention takes advantage of the relatively high throughput of a stationary sputtering machine by conducting laser zone texturing of substrates in one of the spare stations. By doing so, a separate standalone laser zone texturing machine is eliminated in the making of magnetic hard disks which reduces the capital equipment costs.