Abstract:
A method for forming a device wafer with a recyclable support by providing a wafer having first and second surfaces, with at least the first surface of the wafer comprising a semiconductor material that is suitable for receiving or forming electronic devices thereon, providing a supporting substrate having upper and lower surfaces, and providing the second surface of the wafer or the upper surface of the supporting substrate with void features in an amount sufficient to enable a connecting bond therebetween to form a construct wherein the bond is formed at an interface between the wafer and the substrate and is suitable to maintain the wafer and supporting substrate in association while forming or applying electronic devices to the first surface of the wafer, but which connecting bond is severable at the interface due to the void features to separate the substrate from the wafer so that the substrate can be reused.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a division of application Ser. No. 11/736,809 filed Apr. 18, 2007. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is directed to a method of forming a device wafer and, in particular, a method of attaching and separating a reusable supporting substrate to a wafer to form a device. 
       BACKGROUND OF THE INVENTION 
       [0003]    Wafers are used as the base of integrated circuit chips. As wafers increase in size, the thickness of the wafers have been increased for mechanical stability of the wafer during device processing. For example, when producing a 200 mm wafer, the wafer thickness is about 725 microns and when producing a 300 mm wafer, the wafer thickness is about 775 microns. The increase in wafer size results in an increase in the amount of a silicon bulk material which is consumed for each usable wafer area. With wafers sizes approaching 450 mm, effective utilization of a single crystalline bulk material to produce the wafer is of critical importance, especially in view of the increasing expense of raw materials as well as increased competition for polysilicon from the photovoltaic industry. 
         [0004]    In order to reduce the thickness of a wafer, standard device processing is usually finished by mechanically grinding of the back side of a wafer. This enables the thin layer to be as close as possible to the heat sink or other heat dissipation component of the wafer. The grinding step may be performed before separation/cutting the wafer into die and finalizing of individual devices. Grinding results in the loss of a significant amount (more than 50%) of silicon (i.e., silicon which is not included in the final integrated circuit chip). 
         [0005]    In order to maintain the wafer on a supporting surface or substrate, it is necessary to have a bond which is strong enough to survive device fabrication but weak enough to be separated from the supporting surface without causing damage to the wafer or supporting substrate. Existing techniques for forming a weaker bond require that an SiO2 layer of the wafer may be chemical or dry plasma etched. Such etching results in roughness which would make the bond weaker than a perfectly smooth surface. If the surface, however, is too rough, the wafer may delaminate during device fabrication. For example, during a wet treatment step, liquid may flow at the level of the interface between the wafer and the supporting substrate and cause uncontrolled detachment/debonding during further process steps. 
         [0006]    It is desirable to have a wafer which requires a minimal amount of material and which may be attached to and non-destructively removed from a supporting substrate that provides the required mechanical properties during device fabrication. In this way, the substrate may be conserved for reuse with other wafers to form further devices. 
       SUMMARY OF THE INVENTION 
       [0007]    The invention relates to a method for forming a device wafer with a recyclable support which includes providing a wafer having first and second surfaces, with at least the first surface of the wafer comprising a semiconductor material that is suitable for receiving or forming electronic devices thereon. The method further comprises providing a supporting substrate having upper and lower surfaces, and providing the second surface of the wafer or the upper surface of the supporting substrate with void features in an amount sufficient to enable a connecting bond therebetween to form a construct wherein the bond is formed at an interface between the wafer and the substrate and is suitable to maintain the wafer and supporting substrate in association while forming or applying electronic devices to the first surface of the wafer, but which connecting bond is severable at the interface due to the void features to separate the substrate from the wafer so that the substrate can be reused. 
         [0008]    In one embodiment, the voids are provided by forming a plurality of holes through the supporting substrate, wherein the plurality of holes are configured to receive at least one loosening agent therethrough for weakening the connecting bond between the wafer and the substrate at the interface. Generally, the holes have diameters between about 25 microns and about 100 microns and may be separated from each other by a distance of between about 100 microns and about 1 mm. The holes may be formed by selective etching of the substrate. Preferably, the selective etching includes dry etching. 
         [0009]    The method may further include applying at least one loosening agent through the holes to weaken the connecting bond between the wafer and substrate. Preferably, the loosening agent is an acid or gas applied in a quantity sufficient to deteriorate the connecting bond to assist in the separation of the wafer from the substrate. In some embodiments, the method may include holding the construct and applying a pressure differential to the interface through the holes of the substrate in an amount sufficient to detach the wafer from the supporting substrate. For this embodiment, the supporting substrate can be coated with a thin layer of material after providing the holes therein to prevent premature loosening or separation during device fabrication. The coating can be removed by etching prior to applying the loosening agent. 
         [0010]    In another embodiment, the void features are provided by forming depressions in the upper surface of the supporting substrate or on the second surface of the wafer prior to forming the connecting bond therebetween. Generally, the depressions are formed by etching. 
         [0011]    The void features may be provided by forming bumps on the upper surface of the substrate or the second surface of the wafer prior to forming the connecting bond therebetween, with the void features comprising portions adjacent to the bumps. In one embodiment, the bumps are formed by epitaxial deposition, while in another embodiment the bumps are formed by oxidizing the second surface of the wafer or the upper surface of the supporting substrate. 
         [0012]    The method may further include applying mechanical forces to pull apart and separate the wafer and supporting substrate. Preferably, the mechanical forces are applied by a mechanical device that includes a blade, or by a jet of gas or liquid. The method may further comprise positioning the wafer and substrate in a vacuum to further weaken the connecting bond between the wafer and the substrate at the interface. 
         [0013]    In one embodiment, the method further includes forming or applying components on the first surface of the wafer to form electronic devices thereon prior to separating the wafer from the supporting substrate. Preferably, for this embodiment, the method further comprises separating the wafer from the substrate and, thereafter, cutting the wafer into a plurality of pieces. In some embodiments, the wafer is a SOI wafer. 
         [0014]    In the preferred embodiment, the method further comprises separating the wafer from the supporting substrate for recycling and re-use for supporting another wafer, and further comprises removing oxides from the upper surface of the separated supporting substrate; reoxidizing that surface of the substrate to form void features thereon; and connecting the supporting substrate to another wafer. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The present invention can be better understood by reference to the following drawings, wherein like references numerals represent like elements. The drawings are merely exemplary to illustrate certain features that can be used singularly or in combination with other features and the present invention should not be limited to the embodiments shown. 
           [0016]      FIG. 1  is a perspective view of an exemplary embodiment of a wafer being separated from bulk material; 
           [0017]      FIG. 2  is a cross-sectional view of an alternative exemplary embodiment of a wafer being separated from bulk material; 
           [0018]      FIG. 3  is a perspective view of another exemplary embodiment of a wafer being separated from a starter wafer; 
           [0019]      FIG. 4  is a cross-sectional view of an exemplary embodiment of a supporting substrate; 
           [0020]      FIG. 5  is a cross-sectional view of an alternative exemplary embodiment of a supporting substrate; 
           [0021]      FIG. 6  is a cross-sectional view of an exemplary embodiment of a wafer connected to an exemplary embodiment of a supporting substrate; 
           [0022]      FIG. 7  is a cross-sectional view of an exemplary embodiment of a wafer connected to an alternative exemplary embodiment of a supporting substrate; 
           [0023]      FIG. 8  is a perspective view of an exemplary embodiment of a processed wafer having components formed thereon. 
           [0024]      FIG. 9  is a cross-sectional view of the structure of  FIG. 6  with a loosening agent acting thereon; 
           [0025]      FIG. 10  is a perspective view of a portion of the processed wafer of  FIG. 8  positioned on a holding member; 
           [0026]      FIG. 11  is a perspective view of exemplary devices formed from the processed wafer of  FIG. 8 ; 
           [0027]      FIG. 12  is a cross-sectional view of a device of  FIG. 11  in an operational housing; 
           [0028]      FIG. 13  is a cross-sectional view of an exemplary embodiment of a wafer connected to an exemplary embodiment of a supporting substrate with the walls and bottom of the holes coated with a thin layer of material; 
           [0029]      FIG. 14  is a cross-sectional view of the structure of  FIG. 13  with a thin layer of material coated on the walls and bottom of the holes being removed by wet or dry etch steps; and 
           [0030]      FIG. 15  is a cross-sectional view of the structure of  FIG. 13  with a loosening agent acting thereon, after removing the thin layer of material by wet or dry etch steps. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0031]    The method of forming a device  14  ( FIG. 11 ) may comprise providing a wafer  16  and a base or supporting substrate  18 , and forming a feature  20 ,  22  ( FIGS. 4 ,  5 ) in/through the supporting substrate  18  for separating the wafer  16  and the supporting substrate after processing the wafer. It should, however, be understood that those of ordinary skill in the art will recognize many modifications and substitutions which may be made to various steps for forming a device  14 . 
         [0032]    As shown in  FIG. 1 , one preferred method for obtaining a wafer  16 , such as a bulk silicon wafer or a SOI (silicon on insulator) wafer, is to cut the wafer  16  from an ingot or bulk material  24 . A wafer  16  is cut from the bulk material  24  using, for example, a wire impregnated with abrasives such as silicon carbide or an annular saw. The resultant wafer  16  may have a first surface  16   a  and a second surface  16   b  and may have a thickness  26  between about 100 microns to about 500 microns. While the wafer  16  is illustrated as a circular shape, it will be appreciated that wafer  16  may be any shape (e.g., ellipse, oval, square, rectangular, or other polygon). Furthermore, the wafer  16  can have a rounded edge or side  16   c  ( FIG. 6 ). 
         [0033]    In another method, as illustrated in  FIG. 2 , a wafer  16  may be cut from the bulk material  24  using the SMART-CUT® method. The SMART-CUT® method is known per se to the skilled person (see, for example, G. Celler, Frontiers of Silicon-on-Insulator, Journal of Applied Physics, Vol. 93, no. 9, May 1, 2003, pages 4955-4978), and is incorporated herein by reference. In order to obtain a wafer  16  from a bulk material  24  using the SMART-CUT® method, atomic species  28  may be implanted into the bulk material  24 . For example, as shown in  FIG. 2 , helium and/or hydrogen may be implanted in the bulk material  24 , thereby forming a zone of weakness  30 . The bulk material  24  then has a first portion  32  above the zone of weakness  30  and a second portion  34  below the zone of weakness  30 . In order to separate the first and second portion  32  and  34 , the bulk material  24  is molecularly bonded to a stiffener or handle substrate of an insulator material. To further fragilize the zone of weakness, the bonded components may be heat treated by annealing. Once heat treatment is completed, the first portion  32  is separated from the second portion  34  at the zone of weakness  30 , thereby transferring the first portion of the bulk material to the stiffener or handle substrate to thus form a silicon on insulator (SOI) wafer  16  for use as the starting material. 
         [0034]    The SMART-CUT® process can be used in the present invention with the only difference being that the handle substrate in the SOI wafer (the region below the buried oxide or BOX) should be thinner than usual, for instance 100 to 400 microns instead of 775 in a typical 300 mm SOI. Fabrication of these thin SOI wafers would consume less silicon than in a conventional case, and this would lead to a reduction in the amount of silicon in the handle substrate or stiffener. 
         [0035]    It should be noted that a wafer  16  can be cut from a thicker, starting wafer  36 . Multiple wafers could then be made out of a single one for economy and conservation of silicon material. For example, as shown in  FIG. 3 , a 300 mm wafers having a thickness of 775 microns or a planned 450 mm wafer anticipated to have a thickness of  800 + microns can be starting wafers  36  which are cut to obtain a wafer  16  having a thickness  26  of between about 100 microns and about 500 microns. It will be appreciated, however, that a wafer  16  may be cut by any method from a starting wafer or a bulk material. 
         [0036]    Similar to the wafer  16 , the supporting substrate  18  may also be cut from a bulk material by, for example, wires or saws as noted above The supporting substrate  18  can have an upper surface  18   a  and a lower surface  18   b  and may be made of, for example, silicon carbide or polycrystalline silicon. Those of ordinary skill in the art will appreciate that other materials can be used, however, it is preferred that the supporting substrate  18  has thermal properties (e.g., a thermal expansion coefficient, a heat dissipation property, etc.) which are similar to the wafer  16 . In this way, when heated during processing, the wafer  16  and supporting substrate  18  expand and/or contract at the same/similar rates, thereby preventing damage to the wafer  16  or supporting substrate  18  and/or premature separation (e.g., before processing is completed) of the wafer  16  from the supporting substrate  18 . In addition, the supporting substrate  18  can be made of a material that does not contaminate the wafer  16  (e.g., one that does not release material or particles into the wafer  16 ). 
         [0037]    The substrate  18  is preferably circular, but can be any suitable shape and may be the same or different size or shape as the wafer  16 . Furthermore, the supporting substrate can have a rounded edge or side  18   c  ( FIG. 6 ). In one embodiment, as shown in  FIG. 4 , a feature such as one or more holes  20  (e.g., an array of holes  20 ) may be formed through the supporting substrate  18  from the upper surface  18   a  to the lower surface  18   b.  These holes can be formed by a variety of processes, with dry etching methods such as, for example, the Bosch process, preferred for forming the holes  20  through the supporting substrate  18 . 
         [0038]    The Bosch process is described in U.S. Pat. No. 5,501,893 to Laermer et al., which is incorporated herein by reference thereto. The Bosch process involves alternating etch and deposition steps, in an inductively coupled reactive ion etching system. The etch part of the cycle typically produces etching to a depth of 2 to 3 μm of a silicon substrate per etching step, and uses, for example, a mixture of sulfur hexafluoride SF2 and argon Ar. In the deposition step, a mixture of, for example, trifluoromethane CHF3 and argon Ar, is used to generally deposit a 50 nm thick Teflon-like polymer layer on the side walls or on the etching base of the silicon substrate. During the following etching step, the side walls of the structure to be etched in remain protected by the polymer applied during the deposition step, as positively-charged cations are accelerated toward the silicon substrate by means of the electric prestress, and fall nearly vertically onto the substrate surface. The repetitive alternation of the etch and deposition steps results in an anisotropic etching at rates of between 2 to 20 μm/min, depending on the recipe and machine. This process is particularly useful in etching high aspect ratio holes at high etching rate and these are eminently suitable for use in the present invention. 
         [0039]    In particular, holes  20  may be formed by dry plasma etching. Each hole  20  may have a dimension  38  of between about 25 microns and about 100 microns and the holes  20  may be a distance  40  apart of between about 100 microns to 1 mm. Stated another way, the holes  20  can cover between about 0.05% and about 5% of the surface area of the supporting substrate  18 . Any size hole  20  and spacing of holes  20 , however, is envisioned so long as the holes  20  can be used to separate the wafer  16  and the supporting substrate  18  (for example, so that a liquid (e.g., a loosening agent such as acid) and/or gas (e.g., pressurized air) may pass therethrough) as will be described herein. Preferably, the holes do not overlap or form a honeycomb type structure. 
         [0040]    In another embodiment, as shown in  FIG. 5 , a surface feature  22  (e.g., one or more dimples or shallow depressions) may be formed on the upper surface  18   a  of a supporting substrate  18  so as to reduce surface contact. Each surface feature  22  may have a dimension  42  of between about 5 microns and about 100 microns and the surface features  22  may be a distance  44  apart of between about 10 microns to 0.5 mm) so that the surface features can cover between about 1% and about 50% of the surface area of the supporting substrate  18 . The surface features may be in the form of “bumps” with the number of bumps not being too excessive to cause loss of strength so that the construct cannot withstand conventional processing. Such a configuration reduces the surface area of the supporting substrate  18  which is connected/bonded to the wafer  16 , thus resulting in a bond between the wafer  16  and supporting substrate  18  that is weaker than the bond that would have been formed had there been no such bumps or surface features  22 . The surface feature  22  may be formed by lithography and/or wet silicon (Si) etching. In such an embodiment, bonding of the wafer  16  to the supporting substrate  18  may be performed in a vacuum or at a reduced pressure. 
         [0041]    In another embodiment, instead of forming surface features  22  in the supporting substrate  18 , a substance such as acid may be used to etch or remove a portion of the layer (e.g., oxide layer) bonding the wafer  16  and the supporting substrate  18 . This is done before bonding so that a roughened surface is provided. Such etching or removal may have the same effect as the surface features  22 , reducing the surface area of the supporting substrate  18  which is connected/bonded to the wafer  16  While only a limited number of holes and surface features  20 ,  22  are illustrated in  FIGS. 4 ,  5 ,  6 ,  7  and  9 , those skilled in the art will recognize that there will considerably more holes or surface features  20 ,  22  than are shown. Moreover, while the holes and surface features  20 ,  22  are shown as having a circular cross section, the holes and surface features  20 ,  22  may be any shape such as, for example, oval or polygonal. In one embodiment, the surface features  22  can be elongated slots or depressions (not shown) extending partially along the upper surface  18   a  of the supporting substrate  18 . In another embodiment, the elongated slots may extend along substantially the entire length of the upper surface  18   a.  Optionally, the slots can intersect at least one edge or side  18   c,  but they generally will be formed to not intersect. The lower surface of the substrate and the walls and bottom of the holes  20  may be coated with a thin layer of material  80  after bonding the wafer, as shown in  FIGS. 13 and 14 , so that the bond interface is better protected from premature loosening during device fabrication in the wafer. When separation of the substrate from the wafer is intended, a wet or dry etch steps  90  would then precede the application of the loosening agent  60 , as shown in  FIGS. 14 and 15 . For example, a coating of less than 1 micron of polycrystalline or amorphous silicon would protect oxide at the bond interface from damage during device fabrication. Even without intentional coating, some deposits may form in the holes  20  during processing that would require wet or dry etching  90  before application of the loosening agent  60 . 
         [0042]    In a preferred embodiment, as shown in  FIG. 6 , the wafer  16  may be connected/bonded to a supporting substrate  18  prior to separating the wafer  16  therefrom. Connecting/bonding the wafer  16  to the supporting substrate  18  permits proper wafer handling throughout the entire process of forming a device  14 . In a preferred embodiment, by using the method described herein, the thickness  46  of the wafer  16  and supporting substrate  18  may be equal to or less than the thickness of current wafers by itself. For example, when attached the wafer  16  and supporting substrate  18  may have a thickness  46  of about 650 to 1000 microns and approximately 725 microns for a 200 mm wafer, 775 microns for a 300 mm wafer or approximately 800 or more microns for the anticipated 450 mm wafer. As such, the thickness  48  of the supporting substrate  18  will vary depending on the thickness  26  of the wafer  16 . The wafers generally have a thickness of between 150 and 350 microns, and the supporting substrate would have a thickness of between 300 and 850 microns. For example, when the wafer  16  is a 300 mm wafer and has a thickness  26  of about 200 microns, the supporting substrate  18  has a thickness of about 575 microns. In this example, the total thickness  46  is about 775 microns. The same size relationships are true when the wafer is an SOI wafer. The total thickness  46  may be any thickness so long as the combined wafer  16  and supporting substrate  18  can withstand processing without breaking or being damaged. Another factor which may be important for determining total thickness  46  is the ability of the combined wafer  16  and supporting substrate  18  to be held in machines which are configured to process standard wafer sizes. The skilled artisan can select the best combination of thicknesses for a particular application. 
         [0043]    In another embodiment, a supporting substrate  18  having an array of holes  20  may be used to temporarily support a layer of material adapted for epitaxial deposition. After epitaxial deposition, the supporting substrate  18 , the layer and the deposited epitaxial layer may be bonded to a final support. Thereafter, the supporting substrate  18  may be detached and reused. In yet other embodiments, the supporting substrate  18  can be used only for intermediate steps performed on the first surface  16   a  of the wafer  16  in processing a wafer  16  (e.g., epitaxial deposition, bonding of other layers, etching, etc.) rather than being used through the entire processing of the wafer  16 . 
         [0044]    Using a wafer  16  bonded to a supporting substrate  18  may provide significant advantages over using a standard size wafer (e.g., 200 mm/725 microns or 300 mm/775 microns). For example, during processing a standard 300 mm wafer having a starting thickness of 775 microns, may be thinned down or reduced by about 50% to 75% using, for example, a grinding wheel. A significant amount of material is essentially wasted or thrown away during processing. Starting with a wafer  16  with a thickness  26  which is less than a standard thickness (e.g., 775 microns) enables more of the starting wafer or bulk material to be conserved. Moreover, since the wafer  16  is bonded to the supporting substrate  18  and forms a structure having a thickness which is substantially the same as the thickness of a standard wafer, the resultant structure is capable of being processed in machines designed to hold standard wafers. 
         [0045]    Various methods may be used in order to form a bond between the wafer  16  and the supporting substrate  18 . The bond should be strong enough to prevent damage to/fracture of the wafer  16  during fabrication/processing of a device  14  but weak enough so that the wafer  16  can be separated from the supporting substrate  18  at the end of a fabrication/processing sequence of a device  14 . It should be noted that, in some methods, it may be desirable for the bond to be weak enough so that the wafer  16  can be separated from the supporting substrate  18  at some point during the fabrication/processing sequence. In a preferred embodiment, bond may be accomplished by depositing an oxide  50  onto at least a portion of the surface of the wafer  16  and/or supporting substrate  18 . In particular, the oxide  50  may be formed by being grown or deposited on the second surface  16   b  of the wafer  16  and/or the upper surface  18   a  of the supporting substrate  18 . In this way, the oxide  50  can be positioned between the wafer  16  and supporting substrate  18  to form an interface  52 , therefore, forming a resultant structure  54 . A strong bond can be formed between the wafer  16  and the supporting substrate  18  by annealing/heating the oxide at a high temperature and a weaker bond can be formed by using a lower temperature. In a preferred embodiment, temperatures that are generally between about 400° C. and about 1200° C. are used for bonding. In one embodiment, before bonding the wafer  16  and supporting substrate  18 , at least a portion of the resultant structure  54  may be coated with a material which may assist in bonding the wafer  1  and the substrate  2 . 
         [0046]    The resultant structure  54  may subsequently be processed to make devices (e.g., circuit chips) as known by those skilled in the art. The material of the wafer, whether for the entire thickness or just for the thin useful layer in the case of a SOI wafer, is a semiconductor material that is suitable for forming such devices. For example, as illustrated in  FIG. 8 , a plurality of components  56 ,  58  can be fabricated by conventional methods in the wafer  16 . 
         [0047]    After the resultant structure  54  is processed, in a preferred embodiment, as illustrated in  FIG. 9 , an amount of at least one loosening agent  60  such as an acid (e.g., hydrofluoric acid (HF)), pressurized acid, or gas (e.g., pressurized air) can be applied to the lower surface  18   b  of the supporting substrate  18  (i.e., the portion of the substrate  18  which does not contact the wafer  16 ). The first surface  16   a  of the wafer  16  (i.e., the surface of the wafer  16  which is not positioned against the supporting substrate  18 ) may be protected from the loosening agent  60  by any means known to those skilled in the art (e.g., by applying a protective coating on the surface  16   a  or sealing the surface in a chamber (not shown)). The loosening agent  60  may penetrate through one or more holes  20  of the supporting substrate  18  and may flow to the interface  52  between the wafer  16  and the supporting substrate  18 . 
         [0048]    In an embodiment where the loosening agent  60  is acid and an oxide  50  is used for bonding, the loosening agent  60  may partially remove the oxide  50  to form voids or weakened areas  62 . This may result in a reduction in the bond strength per unit area at the interface  52 . Moreover, etching with acid may be performed over a long period of time so that enough oxide  50  is removed to enable the wafer  16  to be separated from the supporting substrate  18  without using any further loosening agent  60  such as pressurized air. 
         [0049]    With the bond weakened, the wafer  16  and supporting substrate  18  can be separated by various means. In a preferred embodiment, as shown in  FIG. 9 , after etching is performed, a second loosening agent  60  such as pressurized gas (e.g., high pressure air) may be passed through the holes  20  to provide the additional force needed to separate the wafer  16  from the supporting substrate  18 . The wafer  16  and/or substrate  18  may be held by the fixture at at least one edge or side  16   c,    18   c.  When using pressurized air, the wafer  16  and/or supporting substrate  18  may be held by a fixture  64 ,  66 , respectively (e.g., a circular fixture) which may fit tightly around the edges or sides  16   c,    18   c  of the wafer  16  or substrate  18 , respectively. In addition or alternatively, the wafer  16  can be held by a supported member  68 . At least fixture  66  may provide a seal around the wafer  16  so that air does not move around the edge or side  16   a  of the wafer  16 . As air moves through the holes, the wafer  16  may separate or disconnect from the supporting substrate  18 . The fixture  66  and/or supporting member  68  may hold the wafer  16  steady as the wafer  16  is separated from the supporting substrate  18  (e.g., so that the wafer  16  does not “pop” off the supporting substrate  18 ). 
         [0050]    In another embodiment, the wafer  16  and substrate  18  can be separated by a pressure differential. The wafer  16  and substrate  18  may separate two closed chambers (not shown) (i.e., positioned between two chambers), one chamber may be at a higher pressure than the other chamber. The pressure differential may be transmitted through one or more holes  20  in the substrate  18  to the interface  52  between the wafer  16  and supporting substrate  18 . The pressure may provide the force necessary to separate/detach the wafer  16  and the substrate  18 . In another embodiment, separation of the wafer  16  and the supporting substrate  18  may be initiated from the edge or side  70  of the resultant structure  54  by a mechanical means (e.g., a razor blade type device) or a fine jet of gas or liquid. In such an embodiment, the wafer  16  and supporting substrate  18  can be separated/pulled apart by providing suction to at least one of the wafer  16  or supporting substrate  18 . 
         [0051]    In other embodiments, no etchant may be used and pressurized gas may be used to apply forces on the wafer  16  through the holes  20  to separate the wafer  16  from the supporting substrate  18 . In yet another embodiment, a gaseous or liquid etchant can be put under pressure to etch the interface  52  as well exert the necessary forces to separate the wafer  16  from the supporting substrate  18  so that a secondary loosening agent  60  is unnecessary. 
         [0052]    As shown in  FIG. 7 , one or more holes  20  can each have depression  63 . Depression  63  can allow more loosening agent  60  to contact the interface  52 . The depression  63  can be larger than the dimension of the holes  20  and can be the same or different shape as the holes  20 . In one embodiment, the depression  63  can be between about 1.5 and 5 times larger than the holes. Such a configuration increases the surface area of the interface  52  which is exposed to the loosening agent  60  while, at the same time, providing enough surface area to hold the wafer  16  so that the wafer  16  does not break, become damaged or detach from the supporting substrate  18 . In another embodiment, one or more curvaceous or linear depression channels radiate outwardly from a hole wherein the channels direct loosening agent  60  to contact interface  52 . The particular shape and size of these channels may depend on the desired bond strength between the wafer  16  and substrate  18 . Generally, the total area covered by these channels is between about 5% and about 25% of total wafer  16 —substrate  18  bonding surface. 
         [0053]    Before or after the wafer  16  and supporting substrate  18  are separated, they be rinsed and dried to remove any contaminants such as dust, etchant, etc. from the resultant structure  54 . 
         [0054]    After detachment, the supporting substrate  18  may be recycled and reused for processing another wafer  16 . In one embodiment, after separation of the wafer  16  and the substrate  18 , all oxide may be stripped from the substrate  18 . The substrate  18  may then be reoxidized and joined/bonded/connected to another wafer  16 . The substrate  18  may be recycled or reused for multiple wafers  16 . Removing the oxide and reoxidizing may be useful to prevent contamination (e.g., particles, metals) that may be present in or on the substrate  18 . If the substrate  18  is not stripped of oxide between uses, contaminants may propagate and/or accumulate during the reuse of the substrate  18 . 
         [0055]    A fully processed wafer  16 , after being detached from the supporting substrate  16 , can be placed on a holding member  72  such as an elastic plate ( FIG. 10 ) and cut into die or separate devices  14  as shown in  FIG. 11 . As shown in  FIG. 12 , one or more connection members  74  can then be operably associated with the device  14  and the device  14  can be positioned in a housing  76  which may be made of, for example, plastic. 
         [0056]    While the foregoing description and drawings represent a preferred embodiment of the present invention, it will be understood that various additions, modifications and substitutions can be made therein without departing from the spirit and scope of the present invention as defined in the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention can be embodied in other specific forms, structures, arrangements, proportions, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. One skilled in the art will appreciate that the present invention can be used with many modifications of structure, arrangement, proportions, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, and not limited to the foregoing description.