Abstract:
A micro-electromechanical systems (MEMS) disc drive includes high-precision and integrated components to allow for increased functionality, robustness and reduced size as compared to currently produced disc drives. Integrating multiple subcomponents of the disc drive using batch processing provides low manufacturing costs. Furthermore, using MEMS techniques, new features can be added to disc drives. For example, an environmental control component, an accelerometer and/or a thermometer may be integrated into the housing of the disc drive.

Description:
TECHNICAL FIELD 
       [0001]    The invention relates to disc drives. 
       BACKGROUND 
       [0002]    A disc drive typically includes a base to which various drive components are mounted. A cover connects with the base to form a housing that defines an internal, sealed environment. The components include a spindle motor, which rotates one or more discs at a constant high speed. Information is written to and read from tracks on the discs through the use of an actuator assembly. The actuator assembly includes one or more actuator arms, which extend towards the discs. Mounted on each of the actuator arms is a head, which includes one or more transducer elements to perform read operations, write operations or read and write operations. Heads generally include an air bearing slider enabling the head to fly in close proximity above the corresponding media surface of the associated disc. An air bearing slider does not necessarily need air to operate. For example, in some designs, the internal environment of a disc drive may be filled with a fluid other than air, e.g., helium. 
         [0003]    Increases in storage media density have allowed disc drive manufactures to produce disc drives with large capacities, but which are much smaller than disc drives generally found in desktop computers. For example, a five gigabyte disc drive having a smaller profile than a credit card, and a thickness less than a quarter-inch is currently available. Small disc drives are scaled versions of what has been developed for larger versions. 
         [0004]    However, smaller disc drive designs create new challenges. Current disc drive designs have begun to reach the limits of conventional manufacturing techniques. Smaller disc drives developed for consumer electronics, e.g., cell phones and PDAs, must withstand higher shocks than desktop or laptop computer disc drives. Manufacturing tolerances of the mechanical components of a disc drive are relatively crude in small form factor drives. For this reason, physical stops, e.g., gimbal limiters, used in conventional disc drives to prevent the actuator assembly from contacting the media surface are only effective for large displacement shocks. In another example, the minimum thickness of a disc drive can be limited because suitable rotary bearings for the actuator assembly become difficult to manufacture for disc drive design with a small height, e.g., a height of less than 3.5 millimeters (0.14 inches). Also, manufacturing tolerances for disc drive designs force the gap between the permanent magnet and the voice coil of the actuator assembly to be at least about 25 micrometers. A smaller gap would be preferred to provide greater force, require less energy to move the actuator assembly, and/or use a smaller actuation mechanism, which generally includes a permanent magnet and voice coil. These and other challenges must be met to develop even smaller disc drive designs. 
         [0005]    In a separate development, micro-electromechanical systems (MEMS) microstructures are manufactured in batch methodologies similar to computer microchips. The photolithographic techniques that mass-produce millions of complex microchips can also be used simultaneously to develop and produce mechanical sensors and actuators integrated with electronic circuitry. Most MEMS devices are built on wafers of silicon, but other substrates may also be used. MEMS manufacturing processes adopt micromachining technologies from integrated circuit (IC) manufacturing and batch fabrication techniques. 
         [0006]    Like ICs, the structures are developed in thin films of materials. The processes are based on depositing thin films of metal, insulating material, semiconducting material or crystalline material on a substrate, applying patterned masks by photolithographic imaging, and then etching the films to the mask. In addition to standard IC fabrication methods, in MEMS manufacturing a sacrificial layer is introduced—a material which keeps other layers separated as the structure is being built up but is dissolved in the very last step leaving selective parts of the structure free to move. 
         [0007]    Use of established “batch” processing of MEMS devices, similar to volume IC manufacturing processes, eliminates many of the cost barriers that inhibit large scale production using other less proven technologies. Although MEMS fabrication may consist of a multi-step process, the simultaneous manufacture of large numbers of these devices on a single wafer can greatly reduce the overall per unit cost. 
         [0008]    Surface micromachining, bulk micromachining and electroforming (lithography, plating and molding) constitute three general approaches to MEMS manufacturing. Surface micromachining is a process based on the building up of material layers that are selectively preserved or removed by continued processing. The bulk of the substrate remains untouched In contrast, in bulk micromachining, large portions of the substrate are removed to form the desired structure out of the substrate itself. Structures with greater heights may be formed because thicker substrates can be used for bulk micromachining as compared to surface micromachining. 
         [0009]    Electroforming processes combine IC lithography, electroplating and molding to obtain depth. Patterns are created on a substrate and then electroplated to create three-dimensional molds. These molds can be used as the final product, or various materials can be injected into them. This process has two advantages. Materials other than the wafer material, generally silicon, can be used (e.g. metal, plastic, ceramic) and devices with very high aspect ratios can be built. Electroforming can also be a cost-effective method of manufacturing due to, e.g., relatively inexpensive processing equipment. 
         [0010]    Another fabrication technique is wafer bonding. Wafer bonding can be used to bond micromachined silicon wafers together, or to other substrates, to form larger more complex devices. Examples of wafer bonding include anodic bonding, metal eutectic bonding and direct silicon bonding. Other bonding methods include using an adhesive layer, such as a glass, or photoresist. 
         [0011]    MEMS fabrication processes usually include deposition, etching and lithography. These processes are repeated in according to an ordered sequence to produce the layers and features necessary for the MEMS structure. Deposition refers to the deposit of thin films of material and includes depositions from chemical reactions and depositions from physical reaction. Depositions from chemical reactions include chemical vapor deposition, electrodeposition, epitaxy, and thermal oxidation. These processes use solid material created directly from a chemical reaction in gas/or liquid compositions or with the substrate material. Generally, the chemical reaction will also produce one or more byproducts, which may be gases, liquids and even other solids. Depositions from physical reactions include physical vapor deposition (e.g., evaporation or sputtering) and casting. In depositions from physical reactions a deposited material is physically placed on the substrate without creating a chemical byproduct. 
         [0012]    Etching is a process of removing portions of deposited films or the substrate itself. Two types of etching processes are wet etching and dry etching. Wet etching dissolves the material by immersing it in a chemical solution. Dry etching occurs by dissolving the material using reactive ions or a vapor phase etchant. 
         [0013]    Lithography in the MEMS context is typically the transfer of a pattern to a photosensitive material by selective exposure to a radiation source such as light. When a photosensitive material is selectively exposed to radiation, e.g. by masking some of the radiation, the radiation pattern on the material is transferred to the material exposed. In this manner, the properties of the exposed and unexposed regions differ. 
         [0014]    Deposition, etching and lithography processes may occur in combination repeatedly in order to produce a single MEMS structure. Lithography may be used to mask portions of a film or the substrate. Masked portions may be protected during a subsequent etching process to produce precise MEMS structures. Conversely, masked portions may themselves be etched. This process can be used to make a component or a mold for a component. For example, multiple layers of film can be deposited onto a substrate. Following each deposition step, a lithography step may be preformed to define a desired cross section of a MEMS structure through that layer. After a desired number of layers have been deposited and individually subjected to radiation patterns in lithography steps, portions of the layers defining the MEMS structure can be removed with a single etching process, leaving a mold behind for the desired MEMS structure. A compatible material may then be injected into the mold to produce the desired MEMS structure. As shown by this example, precise and complex structures may be produced using MEMS techniques. 
       SUMMARY 
       [0015]    In general, the invention is directed to disc drives that may be manufactured using MEMS techniques. According to one aspect of the invention, integrated components of a disc drive are manufactured using MEMS processes. For example, a complete disc drive may require processing one or more wafers. For example, one wafer may include a base, disc and actuator and another wafer may include a cover having an integrated environmental control component and integrated permanent magnet. In this example, after the two wafers are separately processed, the cover is bonded and sealed to the base to complete the disc drive manufacturing process. Furthermore, a wafer may contain integrated components for multiple disc drives. Including components for multiple disc drives on a single wafer provides reduced costs. In one embodiment, the invention is directed to a device comprising a housing, a rotatable media disc and an actuator including a head to communicate with the rotatable media disc. The housing, the rotatable media disc, the head and the actuator are manufactured from a single wafer substrate. 
         [0016]    In a different embodiment, the invention is directed to a device comprising a housing including a base and a cover, a MEMS rotatable media disc, and a MEMS actuator including a head to communicate with the rotatable media disc. The MEMS actuator is bonded to the base or the cover. 
         [0017]    In another embodiment, a device comprises a rotatable media disc, and a housing including a base. The rotatable media disc and the base form an integrated disc motor to rotate the rotatable media disc. The base and the rotatable media disc are manufactured as a single component from a single wafer substrate. 
         [0018]    Embodiments of the invention may provide one or more of the following advantages. For example, MEMS techniques allow integrated circuits to be integrated with structural components of a HDD. Furthermore, MEMS techniques may provide significantly reduced design tolerance requirements compared to disc drive designs using convention techniques. Furthermore, batch fabrication techniques similar to those used for integrated circuits applied to disc drives can reduce manufacturing costs, allow for complex integrated component designs and reduce require design tolerances as compared to conventional disc drive manufacturing techniques. 
         [0019]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0020]      FIGS. 1A-C  illustrate a disc dive manufactured using MEMS techniques. 
           [0021]      FIG. 2  is a cut-away illustration of a disc dive manufactured using MEMS techniques. 
           [0022]      FIG. 3  shows an exploded view of an integrated recordable disc and motor. 
           [0023]      FIG. 4  is a close-up view of an integrated recordable disc and motor. 
           [0024]      FIG. 5  illustrates an electromagnetic induction actuation mechanism for a recordable disc. 
           [0025]      FIG. 6  illustrates an electrostatic actuation mechanism for a recordable disc capable of capacitive disc sensing. 
           [0026]      FIG. 7  illustrates an electromagnetic actuation mechanism for a recordable disc. 
           [0027]      FIGS. 8A-C  are cross-section illustrations showing a disc dive including actuator electrodes integrated with the base of the disc drive. 
           [0028]      FIG. 9  illustrates a recordable disc centered on a hub including fluid bearings. 
           [0029]      FIG. 10  illustrates a recordable disc constrained by ring of fluid bearings at the outer diameter of the recordable disc. 
           [0030]      FIG. 11  illustrates a recordable disc centered on a hub including centering fingers with fluid bearings. 
           [0031]      FIG. 12  illustrates a recordable disc constrained by ring of centering fingers with fluid bearings at the outer diameter of the recordable disc. 
           [0032]      FIGS. 13A-B  illustrate a side view of a recordable compliant disc mounted on a center hub. 
           [0033]      FIG. 14  shows a recordable disc mounted on a center hub designed to provide radial and axial thrust bearing support. 
           [0034]      FIG. 15A  illustrates a recordable disc and disc drive housing including a multi-level support bearing with textured fluid bearing surfaces between the disc and disc drive housing. 
           [0035]      FIG. 15B  illustrates a single-level recordable disc and disc drive housing with textured fluid bearing surfaces between the disc and disc drive housing. 
           [0036]      FIG. 16  illustrates an electromagnetically levitating rotary bearing and exemplary micromachine process steps for its manufacture. 
           [0037]      FIG. 17  illustrates an annular chuck mechanism with an adjustable internal diameter. 
           [0038]      FIG. 18  illustrates a recordable disc and adjustable outer diameter fluid bearing. 
           [0039]      FIGS. 19A-C  illustrate exemplary process steps to produce a MEMS disc drive having a center hub to constrain the disc as it rotates. 
           [0040]      FIGS. 20A-C  illustrate exemplary process steps to produce a disc drive including a center hub on a single wafer substrate. 
           [0041]      FIGS. 21A-D  illustrate exemplary process steps to produce a MEMS disc drive having fluid bearing sliders at the outside diameter of the disc in lieu of a center hub to constrain the disc as it rotates. 
           [0042]      FIG. 22  illustrates a micromachined four-bar linkage actuator and suspension for a head. 
           [0043]      FIGS. 23A-B  illustrate techniques for manufacturing disc drive head actuators using MEMS techniques. 
       
    
    
     DETAILED DESCRIPTION 
       [0044]      FIGS. 1A-1C  illustrate disc dive  100  manufactured using MEMS techniques.  FIGS. 1A and 1B  are exploded peripheral views of disc drive assembly  100 .  FIG. 1C  shows a disc drive  100  as manufactured. Various components of disc drive assembly  100  are manufactured using MEMS fabrication techniques. Generally speaking, MEMS is the integration of mechanical elements, sensors, actuators, and/or electronics on a substrate using microfabrication technology. The term “substrate” is used generically used throughout this document. For example, the term substrate is synonymous for terms such as sheet, wafer, film, platen, platform, plate and base as commonly used by those of skill in the art. 
         [0045]    As an example, the substrate may be silicon commonly used to make integrated circuits (ICs). MEMS components of disc drive assembly  100  are fabricated using microfabrication process sequences. Micromechanical components, e.g., actuator assembly  112 , are fabricated using compatible “micromachining” processes that selectively etch away parts of the silicon wafer or add new structural layers to form the mechanical and electromechanical devices. Micromachining techniques include deposition, etching lithographic and electroplating techniques. 
         [0046]    Disc drive assembly  100  includes a base  102 , disc  104  and cover  106 . Disc drive  100  also includes a seal  122  between cover  106  and base  102  to prevent external contaminants from entering an internal environment of disc drive  100  through a seam formed between cover  106  and base  102 . Seal  122  also allows disc drive to contain a fluid. For example, in some embodiments the internal environment may hold helium, or in other embodiments a liquid. For example, an internal environment holding a liquid may be useful to provide a boundary layer between moving parts of disc drive assembly  100 . 
         [0047]    Electronics  120  and actuator assembly  112  are mounted to base  102 . Base  102  also includes integrated disc actuator electrodes  108 . Electrodes  108  interact with elements integrated into disc  104  to rotate disc  104  about bearing  110  electrostatically. Actuator assembly  112  includes head  118  to read and/or write or data from disc  104 . Actuator assembly  112  also includes coil  114 , e.g., coil  114  may be a voice coil, which interacts with permanent magnet  116  to actuate actuator assembly  112  to place head  118  in a desired position relative to disc  104 . Other embodiments use other actuation methods such as electromagnetic actuation. Integrated components of base  102  may be created using microfabrication processes performed on a single substrate wafer. In some embodiments, microfabrication processes may be used to form more than one of bases  102  on a single wafer. 
         [0048]    Like base  102 , cover  106  may include integrated components manufactured using a batch fabrication process, which may provide manufacturability, cost, and/or performance improvements. For example, permanent magnet  116  may be integrated with cover  106 . As shown if  FIG. 1B , cover  106  includes an integrated environmental control component  128 . Integrated environmental control component  128  may be a resistive element to heat disc drive  100  and/or a cooler, e.g., Peltier cooling system. Integrated environmental control component  128  provides a controlled environment for disc drive  100 . 
         [0049]    In other embodiments, as shown in  FIG. 2 , disc drive  100  may also include integrated sensors, such as a thermometer, gyroscope, position sensor, pressure sensor, or accelerometer. Such sensors may be used independently or in conjunction with integrated environmental control component  128 . Sensors and/or integrated environmental control component  128  can allow disc drive  100  to respond to changing environmental conditions and/or to shocks and other events. This may increase reliability of disc drive  100 , expand allowable operating conditions and/or control the effect of thermal expansion on components of disc drive  100 . 
         [0050]    As shown in  FIG. 1A , cover  106  also includes vias  124 , which provide connections between multiple disc drive  100   s  arranged in a stack or an array. For example, as shown in  FIG. 1A  vias  124  connect to electrodes  108 . With these connections, electrodes  108  may be activated simultaneously to rotate disc  104  with actuation electrodes  108  in one or more other disc drives  100 . Vias  124  may also connect electronics  120  between multiple disc drives  100 . In this manner, a device having only single disc drive interface may control a stack or an array of disc drives. Electrical studs  126  connect base  102  to vias  124  on cover  106 . In disc drive  100 , not all vias  124  are paired with one of electrical studs  128 , in other embodiments may include more or less vias  124  and/or more or less electrical studs  126 . 
         [0051]    Disc drive  100  may be manufactured according to a variety of micromachining operations. For example, in one embodiment, base  102  including integrated actuator assembly  112 , electronics  120  and disc actuator electrodes  108 , may be formed on a single wafer. Cover  106  may be formed on a second wafer. Disc  104  may be formed on the same wafer as cover  106  or base  102 , or on its own separate wafer. Assembly of the base and disc may occur before etching of sacrificial layers around disc  104  occurs. In some embodiments, each wafer may contain components for more than one disc drive. Also, separate components may be batch fabricated and assembled in a pick-and-place or batch transfer method. 
         [0052]      FIG. 2  illustrates an exemplary disc drive  140  manufactured using MEMS techniques. Disc drive  140  includes a base  164  and a cover  142  that form a sealed housing of disc drive  140 . Within the housing, integrated actuation electrodes  150  interact with disc  172  to rotate disc  172  about spindle  158 . For example, disc  172  may include integrated magnets or electrostatic elements to receive actuation forces from integrated actuation electrodes  150 . 
         [0053]    Disc  172  includes a media surface  156 , which may comprise, for example, magnetic particles. Disc  172  may optionally include a shield layer (not shown in  FIG. 2 ) below media surface  156  to protect media surface  156  from electromagnetic fields cause by actuation electrodes  150  of disc  172 . Disc  172  may also combine with base  164  to form a fluid bearing that creates a boundary layer to keep disc  172  from contacting base  164  during operation of disc drive  140 . As referred to herein, a fluid bearing includes two surfaces that support a pressurized layer of fluid between the two surfaces to limit or prevent contact between the two surfaces during movement of one surface relative to the other surface. For example, one of the two surfaces may be textured to produce a desirable pressurized boundary layer of fluid between the two surfaces during movement of one surface relative to the other surface. Spindle  158  may also include fluid bearings to prevent disc  172  from contacting spindle  158  during operation of disc drive  140 . In this manner, disc  172  is constrained not only by spindle  158 , but also by boundary layer fluid pressure forces from fluid bearings. The bearing fluid could be a liquid or a gas. 
         [0054]    Actuator arm  162  holds head  160  in close proximity to media surface  156 . Head  160  traverses media surface  156  of disc  172  to read from and/or write to media surface  156 . For example, actuator arm  162  may actuate head  160  with a stroke of at least 0.5 millimeters. The stroke is the maximum movement distance of head  160  in a plane parallel to media surface  156  provided by the range of motion of actuator arm  162 . As other examples, actuator arm  162  may actuate head  160  with a stroke of at least 1 millimeter, with a stroke of at least 3 millimeters, with a stroke of at least 5 millimeters, with a stroke of at least 10 millimeters, with a stroke of at least 15 millimeters, with a stroke of at least 20 millimeters, or with a stroke of at least 25 millimeters. 
         [0055]    Coil  170  interacts with magnet  152  to actuate actuator arm  162  about bearing  168 . MEMS techniques provide for very precise layer thicknesses such that smaller tolerances need to be taken into account in the design of disc drive  140 . For this reason, coil  170  may be located at a distance of less than 25 micrometers from magnet  152 . For example, coil  170  may be located at a distance of less than 20 micrometers from magnet  152 . As other examples, coil  170  may be located at a distance of less than 15 micrometers from magnet  152 , a distance of less than 10 micrometers from magnet  152 , or a distance of less than 5 micrometers from magnet  152 . In other embodiments, the locations of magnet  152  switched with coil  170  such that magnet  152  is part of actuator arm  162  and coil  170  is fixed to cover  142 . In other embodiments, magnet  152  may be replaced a coil that interacts with coil  170 . Such embodiments also allow for a gap between the two coils that is as small as the gap between coil  170  and magnet  152 . 
         [0056]    Disc drive  140  includes many features that would be difficult or even impossible to include in disc drive manufactured using conventional techniques. For example, disc drive  140  includes motion limiters  163 . Because MEMS techniques provide for very precise layers, motion limiters  163  are located in close proximity to actuator arm  162 . For example, motion limiters  163  may be located at a distance of less than 25 micrometers from actuator arm  162  or a distance of less than 20 micrometers from actuator arm  162 . As other examples, motion limiters  163  may be located at a distance of less than 15 micrometers from actuator arm  162 , a distance of less than 10 micrometers from actuator arm  162 , or a distance of less than 5 micrometers from actuator arm  162 . 
         [0057]    As another example, disc drive  140  includes an integrated sensor  146 . Integrated sensor  146  may be, e.g., a thermometer, gyroscope, position sensor, pressure sensor, humidity sensor or accelerometer. Integrated sensor  146  may measure ambient conditions within the drive which may be useful to, e.g., to control head-disc spacing. As another example, integrated sensor  146  may be used to detect shocks. For example, in the event of a shock, head  160  may be moved away from media surface  156  to prevent damage to media surface  156 . 
         [0058]    Disc drive  140  also includes an integrated environmental control component  154 , which may include one or both of a resistive heating element and/or a Peltier cooling system. Disc drive  140  may also include control circuitry integrated within its housing. In this manner, disc drive  140  does not require a separate printed circuit board to control its operation. However, disc drive  140  may mount to a printed circuit board as part of a larger device, e.g., a cell phone or other consumer electronic device. 
         [0059]    Disc drive  140  further includes vias  148  integrated into its housing; vias  148  include an electrically conductive paths  149 , which may allow multiple disc drive  140  provide an interface for another disc drive. For example, disc drive  140  may mount to a printed circuit board and another disc drive may mount on top of disc drive  140  using bond pads  144  and communicate with the printed circuit board through electrically conductive paths  149  of vias  148 . 
         [0060]      FIG. 3  shows an exploded view of integrated recordable disc and motor  260 . Integrated disc and motor  260  utilizes ability to pattern conductors, electrodes and/or magnets on or in disc  262  with exceptional precision using MEMS fabrication methods. Integrated disc and motor  260  is shown with disc  262 , case  263 , center hub  266 , actuation electrodes  264  and seal  267 . Other configurations of an integrated recordable disc and motor are also possible. For example, center hub  266  may not be required if fluid bearings axially constrain disc  262 , e.g., such fluid bearings may be located at the outside diameter of disc  262 . 
         [0061]    Integrated disc and motor  260  comprises a microfabricated disc actuation mechanism, which may be manufactured utilizing the batch microfabrication processes. Integrated disc and motor  260  may be a component of a small form factor disc drive, e.g., a disc drive having a form factor of one inch or less. Small form factor disc drive designs benefit from small and precise gaps, integrated features or components, and well aligned patterning provided by MEMS techniques. One actuation mechanism that could be implemented into integrated disc and motor  260  is an electrostatic media motor. In the media motor, electrical fields generated by voltages applied to actuation electrodes  264  interact with the bottom surface of disc  262 , which is a dielectric material such as glass, inducing charges in the dielectric material of the disc. The induced charges in the disc interact with the electric field from electrodes  264  to generate a force to rotate disc  262 . Actuation electrodes  264  also function as a textured fluid bearing surface support disc  262  as it spins. Hub  266  contains the position of disc  262  using fluid and mechanical bearing forces. Optionally, actuation electrodes  264  may provide an electrostatic actuation force on disc  262  to preload fluid bearings during rotation of disc  262 . While  FIG. 3  shows actuation electrodes acting only one side of disc  262  additional actuation electrodes may placed on both sides of the disc surface. 
         [0062]    A similar disc actuation mechanism to an electrostatic media motor is a capacitive electrostatic actuation motor. For a capacitive electrostatic actuation motor, disc  262  includes patterned electrodes on its surface. The location of electrodes on disc  262  may vary. For example electrodes may be positioned at the center of disc  262 , throughout the surface of disc  262 , only at the outside diameter of disc  262  or otherwise. 
         [0063]    For a capacitive electrostatic actuation motor, the electrodes on disc  262  are preferably kept at a set potential (e.g. ground) while actuation electrodes  264  are individually controlled to apply electrostatic attractive forces to rotate disc  262 . Voltages to subsets of actuation electrodes  264  are varied with a correctly chosen frequency to provide a constant torque on disc  262 . 
         [0064]    In another embodiment, integrated disc and motor  260  may combine to form a permanent magnet motor. For example, disc  262  may include integrated permanent magnets and may serve as the rotor for the permanent magnet motor, while actuation electrodes  264  are replaced by electromagnetic coils which function as the stator. 
         [0065]    Integrated disc and motor  260  may include additional features not shown in  FIG. 3  For example, disc  262  may include multiple layers to optimize actuation output or shield a media surface from a magnetic field created by electromagnetic coils or permanent magnets. Disc  262  and/or actuation electrodes  264  may, in addition to forming part of one or more fluid bearings, also include patterned geometry to optimize actuation output. Instead of, or in combination with fluid bearings, integrated disc and motor  260  may include magnetic layers for magnetic bearings at moving component interfaces. Disc  262  and/or actuation electrodes  264  may also include geometry, e.g., at the outer diameter of disc  262 , to enhance shock and disc run-out performance. For example, integrated shock mitigation features may include small-gap limiters or active or passive actuated locking mechanisms, e.g., a piezoelectric “disc clamp”, to minimize the effects of shock upon a sensed acceleration event. Described actuation mechanisms are merely exemplary and may be modified consistent with principles of the invention. For example, embodiments may utilize a combination of the described actuation mechanisms. 
         [0066]      FIG. 4  is a close-up view of integrated recordable disc and motor  270 . Integrated recordable disc and motor  270  includes a disc  274 , a base  276  with actuation electrodes  278 , and a cover  272 . Components of integrated recordable disc and motor  270  may formed using MEMS processes on a single wafer substrate or may be formed on multiple substrates and later assembled, e.g., using pick and place techniques. 
         [0067]    Disc  274  includes surface features that optimize actuation forces from actuation electrodes  278 ; these surface features may also form a textured fluid bearing surface. Actuation electrodes  278  can also form a textured fluid bearing surface, as does cover  272 . By providing fluid bearings, integrated recordable disc and motor  270  may achieve a rotational velocity of 100,000 revolutions per minute. As other examples, integrated recordable disc and motor  270  may achieve a rotational velocity of 25,000 revolutions per minute, 50,000 revolutions per minute, and/or 75,000 revolutions per minute. At high rotational velocity, the dynamics of fluid bearings change, which must be incorporated into the design of fluid bearing surfaces on base  276  and cover  272 . Additionally, this high rotational velocity allows multiple sampling of the same data from recordable disc  274 , which is useful for noise reduction. 
         [0068]    MEMS techniques that may be used to produce integrated recordable disc and motor  270  allow for high geometric tolerances. Specifically, integrated recordable disc and motor  270  may be produced using etching among other techniques. Etching techniques include oxidation smoothing of silicon, hydrogen annealing of silicon, controlled atomic layer deposition, and/or start-up burnish. 
         [0069]      FIG. 5  illustrates electromagnetic induction actuation mechanism  280  for recordable disc  282 . Disc  282  includes an integrated shield layer  284  and integrated induction coils  285 . Induction coils  285  are shown as figure-eight coils, but other arrangements may also be utilized consistent with principles of the invention. Electromagnetic induction actuation mechanism  280  further includes electromagnets  283 A and  283 B (“electromagnets  283 ”), which apply electromagnetic fields to induction coils  285  in order to rotate disc  282 . For example, electromagnets  283  may be coils through which current passes to produce a magnetic field. Shield layer  284  may protect a media surface of disc  282  from electromagnetic forces produced by electromagnets  283 . 
         [0070]    As shown in  FIG. 5 , induction coils  285  provide torque at the edge of disc  282 . Each induction coil  285  has two sides, say side A and side B. A change in magnetic flux through side A, e.g., caused by electromagnet  283 A, induces an electromotive force on side A of the loop. This causes a current in the induction coil  285 . The same current in side A occurs in side B. The current through loop B creates a magnetic field. Side B of the induction coil  285  can be treated as a magnetic dipole. Electromagnet  283 B applies a magnetic field gradient at side B, causing a tangential force at the outside diameter of disc  282 . This results in the rotational motion of disc  282 . 
         [0071]      FIG. 6  illustrates capacitive electrostatic actuation mechanism  288  for recordable disc  292  capable of capacitive disc sensing. Capacitive electrostatic actuation mechanism  288  includes capacitors  292 A and  292 B (“capacitors  292 ”) and recordable disc  292  with integrated conductive plates  293 . Plates  293  may be solid elements placed in cavities formed in the disc. In other embodiments, plates  293  may be thin films deposited on the surface, or in shallow recesses in the disc, with the film wrapping around the edge of the disc as shown, to electrically connect the top side plate to the bottom side plate. 
         [0072]    The general concept of capacitive electrostatic actuation mechanism  288  is as follows. A voltage applied to one of the capacitors, e.g., capacitor  292 A, tends to pull in the nearest conductive plate  293 , attempting to center plate  293  under capacitor  292 A to create the lowest energy condition. The spacing between plates  293  and capacitors  292 A and  292 B is selected so that when a plate is directly centered within one capacitor, another plate is not centered, but is offset from the other capacitor. This allows continuous rotation by properly timing the voltage pulses applied to the two capacitors, so that a torque in the desired direction is continuously generated. In practice, the number of capacitors is usually greater than two. The frequency and phase of voltage for capacitor  292 A and capacitor  292 B may be adjusted to control the rotational velocity of disc  290 . This type of actuator does not require the plates on the disc to be grounded for maximum performance. 
         [0073]      FIG. 7  illustrates electromagnetic actuation mechanism  294  for recordable disc  295 . Magnetic components  299  are integrated about the outer diameter of disc  295 . Magnetic components  299  may include a permanently magnetized “hard” magnetic material such as a Samarium-Cobalt alloy, or a high permeability “soft” magnetic material such as permalloy. If magnetic components  299  are permanent magnets, the magnetization direction is preferably radial. The direction of magnetization in each of magnetic components  299  may alternate with each of magnetic components  299  or each of magnetic components  299  may have the same direction of magnetization. Electromagnetic actuation mechanism  294  also includes electromagnets  297 , fixed about the outer perimeter of disc  295 . 
         [0074]    Similar to electromagnetic induction actuation mechanism  280  in  FIG. 5  and capacitive electrostatic actuation mechanism  288  in  FIG. 6 , disc  295  is rotated by a torque at its edges. However, other embodiments may apply a torque at other locations on disc  295 . Electromagnets  297  create a magnetic field gradient that reacts with magnetic components  299  integrated with disc  295 . For example, an external electric circuit may drive electromagnets  297 . Electromagnets  297  may be either single pole or multiple poles. The magnetic field gradient created by electromagnets  297  interacts with the magnetic fields of magnetic components  299  to create a force on disc  295 . The rotational velocity of disc  295  can be controlled by the applied currents to electromagnets  297 . 
         [0075]    Electromagnetic actuation mechanism  294  may be adapted to eliminate a need for a hub or spindle at the center of disc  295 . For example, electromagnets  297  may create a centering force on disc  295 . Furthermore, fluid bearings may be utilized to further constrain disc  295 . 
         [0076]      FIGS. 8A-B  illustrate disc dive  300  including actuator coils  308 A-C (coils  308 ) integrated within base  302 . Base  302  combines with cover  306  to form a housing of disc drive  300 . Disc  304  is situated within the housing. Disc drive  300  also includes other components not shown in  FIGS. 8A-B . For example, disc drive  300  may contain one or more of the following: electronic components, an actuator assembly including a voice coil, a head and an integrated environmental control component. 
         [0077]    Disc  304  is primarily composed of a disc material layer  303 , a substrate such as spin-on glass, but also includes a shield layer  307  and a media layer  305 . Permanent magnets  309 , which are magnetizable components, are integrated with disc  304 . Permanent magnets  309  may be evenly spaced on the bottom surface to disc  304  so that the mass of disc  304  is symmetric about its center. Permanent magnets  309  function to harness electromagnetic field energy created by actuator coils  308  in order to rotate disc  304 . In some embodiments, disc  304  may not include permanent magnets  309 ; e.g., permanent magnets  309  may be replaced with a set of coils or coils in conjunction with permanent magnets, or a magnetically soft permeable material may replace the permanent magnets to harness electromagnetic field energy created by actuator coils  308 . 
         [0078]    Shield layer  307  insulates media layer  305  from electromagnetic fields produced by permanent magnets  309  and/or actuator coils  308 . For example, if media layer  305  is a magnetic media layer, shield layer  307  may prevent undesirable degradation to data stored on media layer  305 . In other embodiments, media layer  305  may not be affected by electromagnetic fields produced by permanent magnets  309  and/or actuator coils  308  such that layer  307  may not be necessary. For example, media layer  305  may only be affected by electromagnetic fields of much greater strength than those by permanent magnets  309  and/or actuator coils  308 . 
         [0079]    Actuator coils  308  are arranged in sets, e.g., actuator coil sets  308 A-C. For example, actuator coils  308  may rotate disc  304  in the following manner. A current applied to actuator coil  308 A attracts the nearest magnet  309  on disc  304 . As disc  304  spins and magnet  309  moves past the center of actuator coil  308 A, current in actuator coil  308 A is turned off and current in actuator coil  308 B is turned on, pulling magnet  309  past actuator coil  308 A. Once magnets  309  reach actuator coil  308 B, current in actuator coil  308 B is turned off and current in actuator coil  308 C is turned on, pulling magnets  309  towards actuator electrodes  308 C. The cycle repeats indefinitely. 
         [0080]    Disc  304  rotates within a circular aperture formed by the walls of cover  306 . Disc  304  is constrained not only by the physical position of cover  306  and base  302 , but also by boundary layers of fluid, e.g., air, around the surfaces of disc  304 . Internal surfaces of base  302  and cover  306  may include textured fluid bearing surfaces to increase fluid pressure within boundary layers surrounding disc  304  to stabilize disc  304  as it rotates. At very high speeds, boundary layers fluid pressure surrounding disc  304  may prevent disc from contacting base  302  or cover  306 , even when disc drive  300  is subjected to a substantial shock. For example, disc  304  may achieve speeds of 100,000 rpm or greater. 
         [0081]    When disc drive  300  is not operating, actuator coils  308  may secure disc to base  302 , e.g., the position shown in  FIG. 8A . This may protect media surface of disc  304  to increase reliability of disc drive  300 . Furthermore, in the event of a severe shock, disc drive  300  may automatically secure disc  304  to base  302  in order to prevent damage to media surface  305 . Securing disc  304  to base  302  may temporarily interruption read/write processes of disc drive  300 . However, the operation of disc drive  300  may immediately be resumed following a severe shock. The interruption resulting from a shock may not be noticeable to a user of disc drive  300 . For example, data stored in a cache (not shown) may be sufficient to operate a device containing disc drive  300  until disc drive  300  releases disc  304  from actuator coils  308 . In addition, the high-precision of the drive manufacturing may allow for creation of mechanical limiters that would limit the deflection of components to prevent mechanical yielding or damage. 
         [0082]      FIG. 8C  illustrates an exemplary arrangement of permanent magnets  309  in disc  304 . As shown in  FIG. 8C , permanent magnets  309  are distributed among three concentric circles  310 . Permanent magnets  309  are equally spaced within each of concentric circles  310  such that the mass of disc  304  is symmetric about its center. 
         [0083]      FIGS. 9-12  illustrate recordable disc axially constrained by fluid bearings. In different embodiments, fluid bearings may operate using air, other gasses or liquids. In  FIG. 9  recordable disc  320  is centered on hub  322 . Axial bearing  324  includes fluid bearing features to form a controlled, non-contact pressurization when disc  320  rotates. For example Axial bearing  324  may comprise subtle or pronounced “fin” or “step” type structures to create a controlled fluid pressurization gap for a spinning disc. For example, axial bearing  324  may include grooved fluid dynamic thrust gas bearings. 
         [0084]      FIG. 10  illustrates recordable disc  328  constrained by ring of fluid bearings  332  at the outer diameter of recordable disc  328 .  FIG. 10  is similarly to  FIG. 9  except that it does not include a center hub utilizing outer fluid bearing features for radial support. Instead recordable disc  328  is constrained by fluid bearings  332  at its outer diameter. Fluid bearings  332  form a boundary layer that interact with base  330  to center disc  328 . 
         [0085]      FIG. 11  illustrates recordable disc  340  centered on hub  342  including centering fingers  344  with textured fluid bearing surfaces.  FIG. 11  includes a variation on the center hub design of  FIG. 14 . Center hub  342  includes “fingers”  344 , which have textured fluid bearing surfaces at contact points with disc  340 . Fingers  344  allow for adjustment, e.g., due to shocks or defects. 
         [0086]      FIG. 12  illustrates recordable disc  358  constrained by a ring of centering fingers  352  with fluid bearings at the outer diameter of recordable disc  358 .  FIG. 12  shows fingers  352  at the outer diameter of disc  358 . Fingers  352  are fixed to base  350  and include fluid bearings at the contact points with disc  358 . Fingers  352  provide radial support and allow for adjustment, e.g., due to shocks or defects. 
         [0087]      FIGS. 13A-B  are cross-section illustrations of disc dive  360  including actuators  368  integrated within base  362 . Disc drive  360  is also shown with recordable disc  366  on center hub  364 . Disc drive  360  includes additional features not shown in  FIG. 13 . For example, disc drive  360  includes a head mounted to an actuator (not shown) to read and/or write data to recordable disc  366 . In different embodiments, recordable disc  366  can be either a flexible or rigid recordable disc. In embodiments where recordable disc  366  is flexible, centripetal force may in whole or in part contribute to causing disc  366  to be substantially flat during operation of disc drive  360 . 
         [0088]      FIG. 13A  shows disc dive  360  while in operation. Actuators  368  provide electrostatic and/or electromagnetic forces on recordable disc  366  to rotate flexible recordable disc  366  about center hub  364 , an axial bearing for recordable disc  366 . 
         [0089]    If disc  366  is sufficiently compliant, when disc drive  360  is not operating, actuators  368  or a subset thereof may secure disc to base  362 , e.g., the position shown in  FIG. 13B . This may protect the media surface of disc  366  to increase reliability of disc drive  360 . Furthermore, in the event of a severe shock, disc drive  360  may automatically secure disc  366  to base  362  in order to prevent damage to the media surface. Securing disc  366  to base  362  may temporarily interruption read/write processes of disc drive  360 . However, the operation of disc drive  360  may immediately be resumed following a severe shock. The interruption resulting from a shock may not be noticeable to a user of disc drive  360 . For example, data stored in a cache (not shown) may be sufficient to operate a device containing disc drive  360  until disc drive  360  releases disc  366  from actuators  368 . In addition, in embodiments where recordable disc  366  is flexible, recordable disc  366  can provide a compliant surface while a head/suspension/actuator (not shown in  FIGS. 13A-B ) remains rigid. This is in contrast to a conventional disc drive designs that utilize a rigidly supported recordable disc and a compliant gimbal suspension structure. 
         [0090]    Center hub  364  may include textured fluid bearing surfaces to create a boundary layer between the rotatable portions of center hub  364  and the fixed spindle of center hub  364  during operation of disc drive  360 . During operation, disc  366  is constrained not only by center hub  364 , but also by boundary layers of fluid, e.g., air, around the surfaces of disc  366 . Furthermore, centripetal force may keep disc  366  substantially flat during operation. Base  362  may include fluid bearing surfaces to increase fluid pressure within boundary layers surrounding disc  366  to stabilize disc  366  as it rotates. At very high speeds, boundary layers fluid pressure surrounding disc  366  may prevent disc from contacting base  362 , even when disc  360  is subjected to a substantial shock. For example, disc  366  may achieve speeds of 100,000 rpm or greater. 
         [0091]      FIG. 14  shows disc drive  380  including recordable disc  386  mounted on center hub  384 , an axial bearing for recordable disc  366 . Center hub  384  is designed to provide radial and axial thrust bearing support for recordable disc  386  because its surface is at an angle relative to the rotational plane of disc  386 . A mechanical bearing that utilizes a small gap between stationary hub  384  and disc  386  during operation of disc drive  380 . For example, this gap may be fabricated with a thin sacrificial film. A protective coating over the interface of hub  386  and disc  386  may reduce wear, provide mechanical robustness or even lubrication. For example, a protective coating could be applied as a thin film in the regular process flow, or could be applied towards the back end of the processing. 
         [0092]    Axial bearing structures other than those shown in  FIGS. 13 and 14  are also possible. For example, an additional bearing element may be used to prevent static friction and resulting wear during very low speed operation as seen at start and prior to stop. For example, an INCABLOC™ type bearing element may be used. An additional bearing element may define a wider range of axial rotor location than the primary bearing elements that are effective close to nominal speed. 
         [0093]      FIG. 15A  illustrates disc drive  390  including recordable disc  392  and housing  393 . Housing  393  includes multi-level support fluid bearings  394 . Multi-level support fluid bearings  394  may be fabricated using multiple layers and MEMS processes, including wafer bonding, etc. Multi-level support fluid bearings  394  may provide stability to recordable disc  392  by having a large surface area and through multi-directional support of recordable disc  392 . 
         [0094]      FIG. 15B  illustrates disc drive  395  including recordable disc  396  and housing  397 . Disc drive  395  includes fluid bearings  398  and  399 . As shown in  FIG. 15B , fluid bearings  398  include a textured fluid bearing surface on recordable disc  396 , while fluid bearings  399  include a textured fluid bearing surface on housing  397 . Other embodiments may include fluid bearings with two opposing textured fluid bearing surfaces forming a single fluid bearing. 
         [0095]      FIG. 16  illustrates MEMS process steps I-V for the manufacture of levitating rotary bearing  418 . In step I, base wafer  400  is etched with cavity  401 . For example, base wafer may comprise silicon. In step II, electromagnet  402  patterned on top of cavity  401 . For example, electromagnet  402  may include coils and magnetic material. 
         [0096]    Step III requires multiple MEMS processes. First, sacrificial layer  406  is deposited with a constant thickness. Second, magnetic material  408  is deposited into what remains of cavity  401 . Third, disc material  410  is deposited. For example, disc material  410  may be a spin-on-glass. 
         [0097]    Step IV, also requires multiple MEMS processes. First, a sacrificial layer (not shown) is deposited on top of disc material  410 . The sacrificial layer may form fluid bearing geometry. Second, cover material  412  is deposited on the sacrificial layer. For example, cover material  412  may comprise the same substance as base wafer  400 . Cover material  412  takes the shape of the sacrificial layer, including fluid bearing features. Third, the sacrificial layer is etched along with sacrificial layer  406 , releasing disc material  410 . 
         [0098]    A Step V shows levitating rotary bearing  418  in operation. Electromagnet  402  creates forces  414  to levitate and axially constrain disc material  410 . An actuation mechanism (not shown) rotates disc material  410 . For example, an electrostatic or electromagnetic actuation mechanism may be used. Fluid bearings on cover material  412  create forces  416  to create a constant fly height. Because forces  416  oppose forces  414 , disc material  410  is constrained axially and vertically. In this manner, rotary bearing  418  does not require a central hub or fluid bearing features at the outer diameter of disc material  410 . 
         [0099]      FIG. 17  illustrates annular chuck mechanism  420  with an adjustable internal diameter. Chuck mechanism  420  provides adjustable geometry to reduce or eliminate the gap between hub  422  and chuck mechanism  420 . For example, chuck mechanism  420  may comprise piezoelectric, magnetostrictive, and/or thermal actuation structure. Chuck mechanism  420  couples to a recordable disc (not shown) and combines with hub  422  to form a bearing for the disc. Minimizing any gaps between hub  422  and chuck mechanism  420  increases the precision of rotational movement of the recordable disc. Precise rotational movement is required to increase track density on a magnetic media for example. Chuck mechanism  420  provides process robustness and allow greater tolerances manufactured gaps between hub  422  and chuck mechanism  420 . Even though there may be a large gap between hub  422  and chuck mechanism  420  after fabrication, the gap can be controlled by shrinking chuck mechanism  420 . Chuck mechanism  420  may also be used to minimize effects of shock by “locking down” or grabbing onto hub  422  during a sensed shock or acceleration event. 
         [0100]      FIG. 18  illustrates recordable disc  424  and adjustable outer diameter fluid bearing  426 . Adjustable outer diameter fluid bearing  426  provides adjustable geometry to reduce or eliminate the gap between recordable disc  424  and adjustable outer diameter fluid bearing  426 . For example, adjustable outer diameter fluid bearing  426  may comprise piezoelectric, magnetostrictive, and/or thermal actuation structure. Adjustable outer diameter fluid bearing  426  minimizes the gap at the outer diameter of disc  424 . Adjustable outer diameter fluid bearing  426  may provide many of the same advantages as chuck mechanism  420  shown in  FIG. 17 . Adjustable outer diameter fluid bearing  426  improves the precision of rotational movement of disc  424  by adjusting the outside diameter radial textured fluid bearing surface position relative to disc  424 . In this manner, adjustable outer diameter fluid bearing  426  optimize gaps between the textured fluid bearing surface and disc  424 . Adjustable outer diameter fluid bearing  426  may also be used to minimize effects of shock by “locking down” or grabbing onto disc  424  during a sensed shock or acceleration event. 
         [0101]      FIGS. 19A-C  illustrate exemplary process steps to produce MEMS disc drive  500  having a center hub to constrain the disc as it rotates.  FIG. 19A  shows MEMS process steps I-XI performed on a first wafer substrate  504  to create integrated base and disc  522 . FIG.  19 B shows cover  538  created on a second wafer substrate  530 .  FIG. 19C  shows cover  538  bonded to integrated base and disc  522  forming disc drive  500 . One or more manufacturing processes may be required between each step shown in  FIGS. 19A-C . 
         [0102]    As shown in  FIG. 19A , integrated base and disc  522  is produced from a single wafer using a series of MEMS processes. Steps I-III form the basic disc geometry of integrated base and disc  522 . In step I patterned sacrificial layer  502  is molded to substrate  504 . For example, patterned sacrificial layer  502  may be SiO 2 . Patterned sacrificial layer  502  may be shaped to create fluid bearings for the disc of integrated base and disc  522 . In step II, disc material  506  is deposited on top of patterned sacrificial layer  502 . For example, disc material  506  may be spun-on glass. In step III, disc material  506  is planarized. A deposition step (not shown) may be used to add a shield layer and/or media layer, e.g., a magnetic media layer, to disc material  506 . 
         [0103]    Steps IV-VII form the hub of integrated base and disc  522 . The hub constrains the disc as it rotates. In step IV hub geometry  510  is etched into disc material  506  and sacrificial layer  502 . For example, hub geometry  510  may contain fluid bearing sliders to increase boundary layer fluid pressure of the disc as disc drive  500  operates. In step V, hub sacrificial layer  512  is deposited and patterned. For example, sacrificial layer  512  may be the same material as patterned sacrificial layer  502 , e.g., SiO 2 . In step VI, hub material  514  is deposited. For example, hub material  514  may be polysilicon. For step VII, hub material  514  is planarized to complete the shape of the hub of integrated base and disc  522 . 
         [0104]    Steps VIII and IX form add the media surface to the disc of integrated base and disc  522  and finish the shape of the disc. In step VIII, media layer  516  is deposited and patterned. For example, media layer  516  may be a thin film magnetic media. For step IX, disc geometry is patterned by etching gap  518  through media layer  516 , disc material  506  and into patterned sacrificial layer  502 . 
         [0105]    Steps X and XI complete integrated base and disc  522 . In step X, sacrificial layer  520  is deposited and patterned as a protective layer in order to protect integrated base and disc  522  during back end processing steps, such as singulation of separate components. For example, sacrificial layer  520  may be the same material as sacrificial layer  512  and patterned sacrificial layer  502 , e.g., SiO 2 . In step XI, sacrificial layer  520 , sacrificial layer  512  and patterned sacrificial layer  502  are etched. For example, etching may be performed using anhydrous HF and alcohol vapor etch. After etching disc material  506  is released from substrate  504 , and the disc may rotate freely about the hub. 
         [0106]      FIG. 19B  shows cover  538  created on a second wafer substrate  530 . For example, substrate  530  may comprise silicon. Cover  538  may be created using bulk micromachining processes. Cover  538  also includes patterned bonding material  532 . Cover  538  may additionally include an integrated permanent magnet to interact with a voice coil of an actuator assembly and/or an environmental control component. 
         [0107]      FIG. 19C  shows cover  538  bonded to integrated base and disc  522  forming disc drive  500 . Cover  538  is held to the base of integrated base and disc  522  with bonding material  532 . Bonding material  532  creates a hermetic seal to contain fluids within disc drive  500 . For example fluids contained within disc drive  500  may be helium or other gaseous or liquid fluids. 
         [0108]    Processes other than those described, may also be used in the manufacture of disc drive  500 . For example, burnishing could be used to correct for small defects. Also, disc drive  500  may include additional features not shown in  FIGS. 19A-C . For example a protective coating may be added to hub  510  or elsewhere for lubrication or mechanical robustness. For example, disc drive  500  also includes an actuator assembly and may also include actuator electrodes integrated within its base and permanent magnets integrate within its disc. For example, disc drive  500  may include an integrated sensor, e.g., a thermometer, gyroscope or accelerometer. Disc drive  500  may also include an integrated environmental control component, e.g., a resistive heating element and/or a Peltier cooling system. Disc drive  500  may also include control circuitry integrated within its housing. Each of these features may be manufactured using MEMS techniques as part of the first wafer, the second wafer or one or more additional wafer(s). 
         [0109]    The techniques described with respect to  FIG. 19  for depositing the disc structure allow integration of disc and disc actuator including features such as electrodes or magnets. Alternatively, a disc may microfabricated out of a bulk material, e.g., silicon and used with other conventionally manufactured disc drive components. 
         [0110]      FIGS. 20A-C  illustrate disc drive  600  including a center hub formed from single wafer substrate  602  and micromachine process steps for its manufacture.  FIGS. 20A-C  illustrate steps I-XIII, each step representing a point in the manufacturing process of disc drive  600 . One or more manufacturing processes may be required between each step shown in  FIGS. 20A-C . 
         [0111]    Steps I and II, shown in  FIG. 20A , produce a base and disc actuation component for disc drive  600 . In step I, wafer vias  604  and sensor  607  are patterned in wafer substrate  602 . In this manner, wafer vias  604  and sensor  607  are integrated within the housing of disc drive  600 . For example wafer substrate  602  may be a silicon wafer substrate. Wafer vias  604  may provide electrical connections, e.g., power and/or data signal connections, for disc drive  600 . Additional electrical connection paths (not shown) may also be patterned in wafer substrate  602 . Sensor  607  may be, e.g., a thermometer, gyroscope or accelerometer. In step II, actuation electrodes  612  deposited and patterned. Spacer layer  608  is also deposited and patterned in step II. For example, spacer layer  608  may comprise silicon. Spacer layer  608  is patterned to integrate vias  604  within the housing of disc drive  600 . 
         [0112]    Steps III-V, shown in  FIG. 20A , produce a recordable disc of disc drive  600 . In step III, sacrificial layer  614  is deposited. For example, sacrificial layer  614  may comprise germanium. Sacrificial layer  614  is shown with fluid bearing features. In step IV, first disc material layer  616  is deposited. For example, disc material layer  616  may comprise spin-on glass. After disc material layer  616  is deposited, media surface  617  is deposited on top of disc material layer  616 . For example, media surface  617  may include magnetic particles. In step V, disc material layer  616  including media surface  617  is patterned and etched to form the shape of the recordable disc. The disc pattern may include textured fluid bearing surfaces. 
         [0113]    Steps VI and VII, shown in  FIG. 20B , produce center hub  610  for disc drive  600 . In step VI, sacrificial layer  618  is deposited. For example, sacrificial layer  618  may consist of the same substance as sacrificial layer  614 . For example, sacrificial layer  618  may comprise germanium. Sacrificial layer may include fluid bearing features (not shown) for center hub  610 . In step VII, center hub  610  is deposited on top of sacrificial layer  618 . 
         [0114]    Steps VIII and IX, shown in  FIG. 20B , produce actuator arm  621  for disc drive  600 . In step VIII, sacrificial layer  618  is etched. In step IX, actuator arm  621  is deposited and patterned on top of sacrificial layer  618 . Actuator arm  621  includes head  623  and coil  622 . 
         [0115]    The manufacturing process of disc drive  600  completes with steps X-XIII, as shown in  FIG. 20C . In step X, top sacrificial layer  627  is deposited. For example, top sacrificial layer  627  may consist of the same substance as sacrificial layers  614  and  618 . For example, top sacrificial layer  627  may comprise germanium. In step XI, environmental control component  631  and permanent magnet  629  are deposited and patterned. Environmental control component  631  may include one or both of a resistive heating element and/or a Peltier cooling system. When disc drive  600  is operational, coil  622  interacts with magnet  629  to actuate actuator arm  621 . In other embodiments, magnet  629  maybe replaced with a coil to interact with coil  622 . 
         [0116]    In Step VII, top layer  634  is deposited and planarized. For example, top layer  634  may consist of the same material as wafer substrate  602 , spacer layer  608  and center hub  610 . E.g., top layer  634  may comprise silicon. In step XII, sacrificial layers  614 ,  618  and  627  are removed. For example, sacrificial layers  614 ,  618  and  627  may be removed using liquid or vapor etching techniques. 
         [0117]    Disc drive  600  may include additional features not shown in  FIGS. 20A-C . For example, disc drive  600  may contain control circuitry integrated and additional electrical connection vias integrated within its housing. Each of these features may be manufactured using MEMS techniques. 
         [0118]      FIGS. 21  A-D illustrate exemplary process steps to produce MEMS disc drive  700  having fluid bearing sliders at the outside diameter of the disc to constrain the disc as it rotates.  FIG. 21A  shows cover  708  created on a first wafer substrate  702 .  FIG. 21B  shows MEMS process steps I and II performed on a second wafer substrate  710  to create integrated base and actuator electrodes  715 .  FIG. 21C  shows MEMS process steps I-V performed on a third wafer substrate  716  to create integrated disc and outer diameter fluid bearing  728 .  FIG. 21D  shows MEMS process steps I-III to combine cover  708 , integrated base and actuator electrodes  715  and integrated disc and outer diameter fluid bearing  728  to form disc drive  700 . One or more manufacturing processes may be required between each step shown in  FIGS. 21A-D . 
         [0119]      FIG. 21A  shows cover  708  created on a first wafer substrate  702 . For example, substrate  702  may comprise silicon. Cover  708  may be created using bulk micromachining processes. Cover  708  also includes patterned bonding material  704 . Cover  708  may additionally include an integrated permanent magnet to interact with a voice coil of an actuator assembly and/or an environmental control component. 
         [0120]      FIG. 21B  shows MEMS process steps I and II performed on a second wafer substrate  710  to create integrated base and actuator electrodes  715 . In step I, through-wafer electrical vias  712  are created through wafer substrate  710 . For example, substrate  710  may comprise silicon. In step II, actuator electrodes  714  are deposited and patterned using actuator electrode patterns  712 . 
         [0121]      FIG. 21C  shows MEMS process steps I-V performed on a third wafer substrate  716  to create integrated disc and outer diameter fluid bearing  728 . In step I, sacrificial layer  718  is deposited on wafer substrate  716 . For example, substrate  716  may comprise polished silicon. In step II, fluid bearing material  720  is deposited. For example, fluid bearing material  720  may be polysilicon. In step III, fluid bearing material  720  is patterned. For step IV, media layer  722  is deposited and patterned. For example, media layer  722  may be a thin film magnetic media. For step V, patterned bonding material  724  is added to the bottom of fluid bearing material  720 . 
         [0122]      FIG. 21D  shows MEMS process steps I-III to combine cover  708 , integrated base and actuator electrodes  715  and integrated disc and outer diameter fluid bearing  728  to form disc drive  700 . In step I, integrated disc and outer diameter fluid bearing  728  is bonded to integrated base and actuator electrodes  715 . In step II, sacrificial layer  718  is etched. For example, etching may be performed using anhydrous HF and alcohol vapor etch. Step II releases the disc from the fluid bearings. In step III, cover  708  is bonded integrated base and actuator electrodes  715  with bonding material  704 . Bonding material  704  creates a hermetic seal to contain fluids within disc drive  700 . For example fluids contained within disc drive  700  may be helium or liquid fluids. 
         [0123]    Disc drive  700  may include additional features not shown in  FIGS. 21A-D . For example, disc drive  700  also includes an actuator assembly and may also include actuator electrodes integrated within its base and permanent magnets integrate within its disc. Disc drive  700  may include an integrated sensor, an integrated environmental control component and/or integrated control circuitry. Each of these features may be manufactured using MEMS techniques as part of the first wafer, the second wafer or additional wafer(s). 
         [0124]      FIG. 22  illustrates micromachined four-bar linkage actuator  230  that supports head  236 . The suspension structure of actuator  230  includes beams  232  mounted to plates  234 , flexural bearings  238  and head  236 . Flexural bearings  238  provide, in combination with beams  232  and plates  234 , a single degree of motion for head  236 . Actuator  230  also includes head  236  and integrated electrical interconnects to drive coil  235  and head  236 . Actuator  230  is an integrated head suspension, actuation coil and bearing structure. 
         [0125]    Flexural bearings  238  have small heights as measured along their axis of rotation. For example, flexural bearings  238  may have heights of less than 5 millimeters. As other examples, flexural bearings  238  may have heights of less than 4 millimeters, of less than 3 millimeters, of less than 2 millimeters or of less than 1 millimeter. The small heights of flexural bearings  238  allow for a disc drive design with a lower Z-height. 
         [0126]    Actuator  230  moves using coil  235  by creating an electromagnetic field to interact with a permanent magnet fixed to a housing of a disc drive. Actuator  230  also includes secondary actuation mechanism  237  integrated with head  236  to provide fine positioning of the head  236  relative to a media surface of the disc drive. Secondary actuation mechanism  237  may include, for example, one or more piezoelectric crystals. 
         [0127]    A constant force is required to counteract the elasticity of flexural bearings  238  to hold actuator  230  in a position other than a centered position. While actuator  230  includes coil  235  for primary actuation, other embodiments may be actuated by different means. For example, thermal, electrostatic, piezoelectric and electro-active polymer actuation techniques may be used. In another example, coil  235  may be replaced with a magnet and interact with a fixed-position coil. Coil  235  may be formed by electroplating, winding or constructed as a flexible circuit and assembled onto actuator  230 . For example, assembly may includes pick and place techniques. 
         [0128]    Flexural bearings  238  may be made from multiple layers fabricated using MEMS techniques. Each of the layers in flexural bearings  238  only flexes a small portion of the total flexture of flexural bearings  238 . The multiples layer allow for high flexibility in flexural bearings  238 . The high flexibility of flexural bearings  238  reduces the actuation force required to move actuator  230 . 
         [0129]    Actuator  230  may be an actuator for a disc drive manufactured using MEMS and/or batch fabrication techniques. For example, actuator  230  may be fabricated from electroformed metal. MEMS processes allow a variety of complex features to be integrated as part of actuator  230 . For example, integrated conductive paths may be formed within structural components of actuator  230 , e.g., head  236  may be powered by and communicate through such conductive paths. Actuator  230  may also be formed as an integrated component of a disc drive, e.g., actuator  112  in  FIG. 1 . 
         [0130]    Actuator  230  also includes integrated sensor  239 . Integrated sensor  239  may be, e.g., a thermometer, gyroscope, position sensor, pressure sensor, or accelerometer. Integrated sensor  239  is located in a position that may be useful to detect external shocks which may result in head  236  contacting a media surface of a disc. To prevent damage to the media surface and to head  236 , in the event of a shock, head  160  may be moved away from media surface  156 . As another example, integrated sensor  1239  may measure ambient conditions within a disc drive of actuator  230  which may be useful to, e.g., to control head-disc spacing. 
         [0131]    Actuator  230  has many advantages. The four-bar design of actuator  230  may minimize skew and improve the performance of head  236  by maintaining a precise distance above a media surface in a disc drive (not shown). Furthermore, coil  235  may be plated at the same time as the corresponding permanent magnet, which allows for a very small gap between the permanent magnet and coil  235 . This small spacing increases the force that may be achieved to drive actuator  230 , or, alternatively, a much smaller permanent magnet and/or coil. This increase in efficiency allows for a disc drive design with a reduced package height. Also actuator  230  can incorporate a head gimbal assembly with slider motion limiters with very small tolerances. For example, tolerances of less then ten micrometers are possible. 
         [0132]    Beams  222  may be formed using electroplating and multiple pattern layers. For example, beams  222  may include an internal three-dimensional truss structure to increase strength and stiffness of beams  222 , while reducing weight. 
         [0133]      FIGS. 23A-B  illustrate techniques for manufacturing disc drive head actuator  630  and disc drive head actuator  632  using MEMS techniques. Actuators  630  and  632  may be the same as actuator  230  of  FIG. 22 . The viewpoint for  FIGS. 23A-B  is shown as line A-A in  FIG. 22 . Actuators  630  and  632  are formed in incremental layers on substrate  602 . Actuators  630  and  632  may include internal three-dimensional truss structures. 
         [0134]    Steps I, II, III, and IV, shown in  FIG. 23A , produce layer  622 , which is the first layer of structure for actuator  630 . In step I, plating seed layer  604  is deposited on substrate  602  and sacrificial structures  606  are patterned on plating seed layer  604 . For example, plating seed layer  604  may be copper. In step II, sacrificial layer  608  is plated on top of plating seed layer  604 . For example, sacrificial layer  608  may be copper. In step III, sacrificial structures  606  are removed and the first layer of structural material  610  is electroplated on top of the mold formed by sacrificial layer  608 . As an example, structural material  610  may be a Nickel alloy. In step IV, layer  622 A is completed by planarizing to produce the desired height of layer  622 A. 
         [0135]    The process of steps I-IV are repeated as shown in steps V-VII to produce layer  622 B, which is the second layer of structure for actuator  630 . In step V, sacrificial structures  612  are patterned layer  622 A and sacrificial layer  613  is plated on top of sacrificial structures  612  and patterned layer  622 A. For example, sacrificial layer  613  may be copper. In step VI, sacrificial structures  612  are removed and the second layer of structural material  614  is electroplated on top of the mold formed by sacrificial layer  613 . As an example, structural material  613  may be a Nickel alloy. In step VII, layer  622 B is completed by planarizing to produce the desired height of layer  622 B. 
         [0136]    These process steps are repeated again for each of layers  622 C- 622 H to produce the structure shown in step VIII. In step IX, the sacrificial material including sacrificial layer  608  and sacrificial layer  613  is removed using wet or dry etching. This releases actuator  630  from substrate  602 . 
         [0137]      FIG. 23B  illustrates process steps for adding an actuation coil to the structure of an actuator manufactures as shown in  FIG. 23A . Step I is the same as shown in step VIII of  FIG. 23A . In step II, insulative layer  640  is patterned on top of the actuator structure material. In step III, metal coil structures  644  is deposited or patterned on top of insulative layer  640 . In step, IV, insulative layer  646  is patterned on top metal coil structures  644  and insulative layer  640 . In step V, the sacrificial material is removed using wet or dry etching. This releases actuator  632  from substrate  602 . 
         [0138]    Actuators  630  and  632  may include additional features not shown in  FIGS. 23A-B . For example, actuators  630  and  632  may be integrated with a head used to read to or write from a media disc in a disc drive. Actuators  630  and  632  may also contain integrated control circuitry integrated and additional electrical connection vias. Each of these features may be manufactured using MEMS techniques. The same steps as illustrated in  FIGS. 23A-B  may also be used to manufacture more than one disc drive head actuator on a common substrate. 
         [0139]    A number of embodiments of the present invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, wafers used in the manufacture of MEMS disc drives may include components for more than one disc drive. Accordingly, these and other embodiments are within the scope of the following claims.