Patent Abstract:
A debonder apparatus for debonding two via an adhesive layer combined with a release layer temporary bonded wafers includes a chuck assembly, a flex plate assembly and a contact roller. The chuck assembly includes a chuck and a first wafer holder configured to hold wafers in contact with the top surface of the chuck. The flex plate assembly includes a flex plate and a second wafer holder configured to hold wafers in contact with a first surface of the flex plate. The flex plate comprises a first edge connected to a hinge and a second edge diametrically opposite to the first edge, and the flex plate&#39;s first edge is arranged adjacent to a first edge of the chuck and the flex plate is configured to swing around the hinge and to be placed above the top surface of the chuck. The contact roller is arranged adjacent to a second edge of the chuck, which is diametrically opposite to its first edge. A debond drive motor is configured to move the contact roller vertical to the plane of the chuck top surface. In operation, a wafer pair, comprising a carrier wafer stacked upon and being bonded to a device wafer via an adhesive layer and a release layer, is placed upon the chuck so that the ubonded surface of the device wafer is in contact with the chuck top surface. Next, the flex plate swings around the hinge and is placed above the bottom chuck so that its first surface is in contact with the unbonded surface of the carrier wafer. Next, the contact roller is driven upward until it contacts and pushes the second edge of the flex plate up while the carrier wafer is held by the flex plate and the device wafer is held by the chuck via the second and first wafer holders, respectively. The contact roller push flexes the second edge of the flex plate and causes delamination of the wafer pair along the release layer.

Full Description:
CROSS REFERENCE TO RELATED CO-PENDING APPLICATIONS 
       [0001]    This application claims the benefit of U.S. provisional application Ser. No. 61/169,753 filed Apr. 16, 2009 and entitled “IMPROVED APPARATUS FOR TEMPORARY WAFER BONDING”, the contents of which are expressly incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to an apparatus for mechanically debonding temporary bonded semiconductor wafers, and more particularly to an industrial-scale mechanical debonder for debonding semiconductor wafers bonded via an adhesive layer combined with a release layer. 
       BACKGROUND OF THE INVENTION 
       [0003]    Several semiconductor wafer processes include wafer thinning steps. In some applications the wafers are thinned down to a thickness of less than 100 micrometers for the fabrication of integrated circuit (IC) devices. Thin wafers have the advantages of improved heat removal and better electrical operation of the fabricated IC devices. In one example, GaAs wafers are thinned down to 25 micrometers to fabricate power CMOS devices with improved heat removal. Wafer thinning also contributes to a reduction of the device capacitance and to an increase of its impedance, both of which result in an overall size reduction of the fabricated device. In other applications, wafer thinning is used for 3D-Integration bonding and for fabricating through wafer vias. 
         [0004]    Wafer thinning is usually performed via back-grinding and/or chemical mechanical polishing (CMP). CMP involves bringing the wafer surface into contact with a hard and flat rotating horizontal platter in the presence of a liquid slurry. The slurry usually contains abrasive powders, such as diamond or silicon carbide, along with chemical etchants such as ammonia, fluoride, or combinations thereof. The abrasives cause substrate thinning, while the etchants polish the substrate surface at the submicron level. The wafer is maintained in contact with the abrasives until a certain amount of substrate has been removed in order to achieve a targeted thickness. 
         [0005]    For wafer thicknesses of over 200 micrometers, the wafer is usually held in place with a fixture that utilizes a vacuum chuck or some other means of mechanical attachment. However, for wafer thicknesses of less than 200 micrometer and especially for wafers of less than 100 micrometers, it becomes increasingly difficult to mechanically hold the wafers and to maintain control of the planarity and integrity of the wafers during thinning. In these cases, it is actually common for wafers to develop microfractures and to break during CMP. 
         [0006]    An alternative to mechanical holding of the wafers during thinning involves attaching a first surface of the device wafer (i.e., wafer processed into a device) onto a carrier wafer and thinning down the exposed opposite device wafer surface. The bond between the carrier wafer and the device wafer is temporary and is removed upon completion of the thinning and any other processing steps. 
         [0007]    Several temporary bonding techniques have been suggested including using of adhesive compounds or using of adhesive tapes or layers. Thinned device wafers are debonded from the carrier wafers after processing by chemically dissolving the adhesive layer or by applying heat or radiation in order to decompose the adhesive layer or tape. Extreme care is needed during the debonding process in order to avoid fracture, surface damage, or warping of the extremely thin wafers, typically having a thickness of about 2-80 micrometers. It is desirable to provide an industrial-scale apparatus for debonding adhesively bonded semiconductor wafers that protects extremely thinned wafers from fracture, surface damage or warping. 
       SUMMARY OF THE INVENTION 
       [0008]    In general, in one aspect, the invention features a debonder apparatus for debonding two via an adhesive layer combined with a release layer temporary bonded wafers including a chuck assembly, a flex plate assembly and a contact roller. The chuck assembly includes a chuck and a first wafer holder configured to hold wafers in contact with the top surface of the chuck. The flex plate assembly includes a flex plate and a second wafer holder configured to hold wafers in contact with a first surface of the flex plate. The flex plate comprises a first edge connected to a hinge and a second edge diametrically opposite to the first edge, and the flex plate&#39;s first edge is arranged adjacent to a first edge of the chuck and the flex plate is configured to swing around the hinge and to be placed above the top surface of the chuck. The contact roller is arranged adjacent to a second edge of the chuck, the second edge of the chuck being diametrically opposite to its first edge. A debond drive motor is configured to move the contact roller vertical to the plane of the chuck top surface. In operation, a wafer pair, comprising a carrier wafer stacked upon and being bonded to a device wafer via an adhesive layer and a release layer, is placed upon the chuck so that the ubonded surface of the device wafer is in contact with the chuck top surface. Next, the flex plate swings around the hinge and is placed above the bottom chuck so that its first surface is in contact with the unbonded surface of the carrier wafer. Next, the contact roller is driven upward until it contacts and pushes the second edge of the flex plate up while the carrier wafer is held by the flex plate and the device wafer is held by the chuck via the second and first wafer holders, respectively. The contact roller push flexes the second edge of the flex plate and causes delamination of the wafer pair along the release layer. 
         [0009]    Implementations of this aspect of the invention may include one or more of the following features. The debonder may further include a hinge motor that drives the hinge. The first and second holders comprise vacuum pulling through the chuck and the flex plate, respectively. The wafer pair further includes a tape frame and the device wafer is held by the chuck by holding the tape frame via the vacuum pulled through the chuck. The debonder further includes a support plate supporting the chuck assembly, the flex plate assembly and the hinge. The debonder further includes a base plate supporting the support plate, the contact roller, the hinge motor and the debond drive motor. The flex plate assembly further includes a lift pin assembly designed to raise and lower wafers placed on the first surface of the flex plate. The flex plate further includes two independently controlled concentric vacuum zones configured to hold wafers having a diameter of 200 or 300 millimeters, respectively. The vacuum zones are sealed via one of an O-ring or suction cups. The chuck comprises a vacuum chuck made of porous ceramic materials. The debonder further includes an anti-backlash gear drive configured to prevent accidental back swing of the flex plate. 
         [0010]    In general, in another aspect, the invention features a method for debonding two via an adhesive layer combined with a release layer temporary bonded wafers. The method includes the following steps. First, providing a debond apparatus comprising a chuck assembly, a flex plate assembly and a contact roller. The chuck assembly comprises a chuck and a first wafer holder configured to hold wafers in contact with the top surface of the chuck. The flex plate assembly comprises a flex plate and a second wafer holder configured to hold wafers in contact with a first surface of the flex plate. The flex plate comprises a first edge connected to a hinge and a second edge diametrically opposite to the first edge, and the flex plate&#39;s first edge is arranged adjacent to a first edge of the chuck and the flex plate is configured to swing around the hinge and to be placed above the top surface of the chuck. The contact roller is arranged adjacent to a second edge of the chuck, the second edge of the chuck being diametrically opposite to its first edge. Next, providing a wafer pair comprising a carrier wafer stacked upon and being bonded to a device wafer via an adhesive layer and a release layer. Next, placing the wafer pair upon the chuck so that the ubonded surface of the device wafer is in contact with the chuck top surface. Next, swinging the flex plate around the hinge and placing it above the bottom chuck so that its first surface is in contact with the unbonded surface of the carrier wafer. Next, driving the contact roller upward until it contacts and pushes the second edge of the flex plate up while the carrier wafer is held by the flex plate and the device wafer is held by the chuck via the second and first wafer holders, respectively. Finally, the contact roller push flexes the second edge of the flex plate and causes delamination of the wafer pair along the release layer. 
         [0011]    The details of one or more embodiments of the invention are set forth in the accompanying drawings and description below. Other features, objects and advantages of the invention will be apparent from the following description of the preferred embodiments, the drawings and from the claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    Referring to the figures, wherein like numerals represent like parts throughout the several views: 
           [0013]      FIG. 1  is an overview schematic diagram of the improved temporary wafer bonder and debonder system according to this invention; 
           [0014]      FIG. 1A  is a schematic diagram of temporary wafer bonding process A and debonding process A performed in bonder module A and debonder A of  FIG. 1 , respectively; 
           [0015]      FIG. 1B  depicts a schematic cross-sectional view of the bonder module A of  FIG. 1  and a list of the process steps for performing the temporary wafer bonding process A of  FIG. 1A ; 
           [0016]      FIG. 2A  is a schematic diagram of temporary wafer bonding process B and debonding process B performed in bonder module B and debonder B of  FIG. 1 , respectively; 
           [0017]      FIG. 2B  depicts a schematic cross-sectional view of the bonder module B of  FIG. 1  and a list of the process steps for performing the temporary wafer bonding process B of  FIG. 2A ; 
           [0018]      FIG. 3A  is a schematic diagram of temporary wafer bonding process C and debonding process C performed in bonder module C and debonder C of  FIG. 1 , respectively; 
           [0019]      FIG. 3B  depicts a schematic cross-sectional view of the bonder module C of  FIG. 1 , and a list of the process steps for performing the temporary wafer bonding process C of  FIG. 3A ; 
           [0020]      FIG. 4  depicts a view of a fixture chuck; 
           [0021]      FIG. 5  depicts the temporary wafer bonder cluster of  FIG. 1 ; 
           [0022]      FIG. 6  depicts a closer view of the upper structure of the temporary wafer bonder cluster of  FIG. 5 ; 
           [0023]      FIG. 7  depicts a cross-sectional view of the upper structure of the temporary wafer bonder cluster of  FIG. 5 ; 
           [0024]      FIG. 8  depicts the hot plate module of the temporary wafer bonder cluster of  FIG. 7 ; 
           [0025]      FIG. 9  depicts a temporary bond module of the wafer bonder cluster of  FIG. 7 ; 
           [0026]      FIG. 10  depicts a schematic cross-sectional diagram of the temporary bonder module of  FIG. 9 ; 
           [0027]      FIG. 11  depicts a cross-sectional view of the temporary wafer bonder module of  FIG. 9  perpendicular to the load direction; 
           [0028]      FIG. 12  depicts a cross-sectional view of the temporary wafer bonder module of  FIG. 9  in line with the load direction; 
           [0029]      FIG. 13  depicts the top chuck leveling adjustment in the temporary wafer bonder module of  FIG. 9 ; 
           [0030]      FIG. 14  depicts a cross-sectional view of the top chuck of the temporary wafer bonder module of  FIG. 9 ; 
           [0031]      FIG. 15  depicts a detailed cross-sectional view of the temporary wafer bonder module of  FIG. 9 ; 
           [0032]      FIG. 16  depicts a wafer centering device with the pre-alignment arms in the open position; 
           [0033]      FIG. 17  depicts wafer centering device of  FIG. 16  with the pre-alignment arms in the closed position; 
           [0034]      FIG. 18A  depicts the pre-alignment of a 300 mm wafer; 
           [0035]      FIG. 18B  depicts the pre-alignment of a 200 mm wafer; 
           [0036]      FIG. 19A  depicts another wafer centering device for the pre-alignment of a 300 mm wafer; 
           [0037]      FIG. 19B  depicts the wafer centering device of  FIG. 19A  for the pre-alignment of a 200 mm wafer; 
           [0038]      FIG. 19C  depicts another wafer centering device for the pre-alignment of a wafer with the rotating arms in the open position; 
           [0039]      FIG. 19D  depicts the wafer centering device of  FIG. 19C  with the rotating arms in the closed position; 
           [0040]      FIG. 20A ,  FIG. 20B  and  FIG. 20C  depict the loading of the non-adhesive substrate and its transfer to the upper chuck; 
           [0041]      FIG. 21A ,  FIG. 21B  and  FIG. 21C  depict the loading of the adhesive substrate and its transfer to the lower chuck; 
           [0042]      FIG. 22A  and  FIG. 22B  depict bringing the adhesive substrate in contact with the non-adhesive substrate and the formation of a temporary bond between the two substrates; 
           [0043]      FIG. 23  depicts an overview diagram of the thermal slide debonder A of  FIG. 1 ; 
           [0044]      FIG. 24  depicts a cross-sectional view of the top chuck assembly of the debonder A of  FIG. 23 ; 
           [0045]      FIG. 25  depicts a cross-sectional side view of the debonder A of  FIG. 23 ; 
           [0046]      FIG. 26A ,  FIG. 26B  and  FIG. 26C  depict the thermal slide debonder A operational steps; 
           [0047]      FIG. 27  depicts an overview diagram of the mechanical debonder B of  FIG. 1 ; 
           [0048]      FIG. 28  depicts a cross-sectional side view of the debonder B of  FIG. 27 ; and 
           [0049]      FIG. 29  depicts the debonder B operational steps. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0050]    Referring to  FIG. 1 , an improved apparatus for temporary wafer bonding and debonding  100  includes a temporary bonder cluster  110  and a debonder cluster  120 . The temporary bonder cluster  110  includes temporary bonder module A, module B, module C, and module D,  210 ,  310 ,  410  and  510  respectively. Debonder cluster  120  includes a thermal slide debonder A  150 , a mechanical debonder B  250  and a radiation/mechanical debonder C  350 . Bonder cluster  110  facilitates the temporary bonding processes A, B, C, and D,  60   a ,  70   a ,  80   a  and  90   a , shown in  FIG. 1A ,  FIG. 2A ,  FIG. 3A , and  FIG. 4 , respectively, among others. Debonder cluster  120  facilitates the debonding processes A, B and C,  60   b ,  70   b , and  80   b , shown in  FIG. 1A ,  FIG. 2A  and  FIG. 3A , respectively. 
         [0051]    Referring to  FIG. 1A , temporary bond process A  60   a  includes the following steps. First, device wafer  20  is coated with a protective coating  21  ( 62 ), the coating is then baked and chilled ( 63 ) and then the wafer is flipped ( 64 ). A carrier wafer  30  is coated with an adhesive layer  31  ( 65 ) and then the coating is baked and chilled ( 66 ). In other embodiments, a dry adhesive film is laminated onto the carrier wafer, instead of coating an adhesive layer. Next, the flipped device wafer  20  is aligned with the carrier wafer  30  so that the surface of the device wafer with the protective coating  20   a  is opposite to the surface of the carrier wafer with the adhesive layer  30   a  ( 67 ) and then the two wafers are bonded ( 68 ) in temporary bonder module A, shown in  FIG. 1B . The bond is a temporary bond between the protective layer  21  and the adhesive layer  31 . In other embodiments, no protective coating is applied onto the device wafer surface and the device wafer surface  20   a  is directly bonded with the adhesive layer  31 . Examples of device wafers include GaAs wafers, silicon wafers, or any other semiconductor wafer that needs to be thinned down to less than 100 micrometers. These thin wafers are used in military and telecommunication applications for the fabrication of power amplifiers or other power devices where good heat removal and small power factor are desirable. The carrier wafer is usually made of a non-contaminating material that is thermally matched with the device wafer, i.e., has the same coefficient of thermal expansion (CTE). Examples of carrier wafer materials include silicon, glass, sapphire, quartz or other semiconductor materials. The diameter of the carrier wafer is usually the same as or slightly larger than the diameter of the device wafer, in order to support the device wafer edge and prevent cracking or chipping of the device wafer edge. In one example, the carrier wafer thickness is about 1000 micrometers and the total thickness variation (TTV) is 2-3 micrometers. Carrier wafers are recycled and reused after they are debonded from the device wafer. In one example, adhesive layer  31  is an organic adhesive WaferBOND™ HT-10.10, manufactured by Brewer Science, Missouri, USA. Adhesive  31  is applied via a spin-on process and has a thickness in the range of 9 to 25 micrometers. The spin speed is in the rage of 1000 to 2500 rpm and the spin time is between 3-60 second. After the spin-on application, the adhesive layer is baked for 2 min at a temperature between 100° C. to 150° C. and then cured for 1-3 minutes at a temperature between 160° C. to 220° C. WaferBOND™ HT-10.10 layer is optically transparent and is stable up to 220° C. After the thinning of the exposed device wafer surface  20   b  the carrier wafer  30  is debonded via the debond process A  60   b , shown in  FIG. 1A . Debond process A  60   b , includes the following steps. First heating the wafer stack  10  until the adhesive layer  31  softens and the carrier wafer  30  slides off from the thinned wafer ( 69 ). The WaferBOND™ HT-10.10 debonding time is less than 5 minutes. The thinned wafer  20  is then cleaned, any adhesive residue is stripped away ( 52 ) and the thinned wafer is placed in a dicing frame  25  ( 53 ) In some embodiments, a small rotational motion (twisting) of the carrier wafer takes place prior to the sliding translational motion. 
         [0052]    The temporary bonding ( 68 ) of the carrier wafer  30  to the device wafer  20  takes place in temporary bonder module A,  210 . Referring to  FIG. 1B , the device wafer  20  is placed in the fixture chuck  202  and the fixture chuck is loaded in the chamber  210 . The carrier wafer  30  is placed with the adhesive layer facing up directly on the bottom chuck  210   a  and the two wafers  20 ,  30  are stacked and aligned. The top chuck  210   b  is lowered down onto the stacked wafers and a low force is applied. The chamber is evacuated and the temperature is raised to 200° C. for the formation of the bond between the protective coating layer  21  and the adhesive layer  31 . Next, the chamber is cooled and the fixture is unloaded. 
         [0053]    The debond process A  60   b  is a thermal slide debond process and includes the following steps, shown in  FIG. 1A . The bonded wafer stack  10  is heated causing the adhesive layer  31  to become soft. The carrier wafer is then twisted around axis  169  and then slid off the wafer stack under controlled applied force and velocity ( 69 ). The separated device wafer  20  is then cleaned ( 52 ) and mounted onto a dicing frame  25  ( 53 ). 
         [0054]    Referring to  FIG. 2A , temporary bond process B  70   a  includes the following steps. First, a release layer  22  is formed onto a surface  20   a  of the device wafer  20  ( 72 ). The release layer is formed by first spin-coating a precursor compound onto the wafer device surface  20   a  and then performing Plasma Enhanced Chemical Vapor deposition (PECVD) in a commercially available PECVD chamber. In one example, the precursor for the release layer is SemicoSil™, a silicon rubber manufactured by Wacker, Germany. The coated device wafer is then spin coated with an adhesive ( 73 ) and then flipped ( 74 ). Next, a soft layer  32  is spin coated on a surface  30   a  of the carrier wafer  30  ( 76 ). In one example, soft layer  32  is a hot temperature cross-linking (HTC) silicone elastomer. Next, the flipped device wafer  20  is aligned with the carrier wafer  30  so that the surface  20   a  of the device wafer with the release layer  22  is opposite to the surface  30   a  of the carrier wafer with the soft layer  32  ( 77 ) and then the two wafers are bonded ( 78 ) in the temporary bonder module B, shown in  FIG. 2B . The temporary bond is formed under vacuum of 0.1 mbar, curing temperature between 150° C. to 200° C. and low applied bond force. 
         [0055]    Referring to  FIG. 2B , the device wafer  20  is placed in the fixture chuck  202  (shown in  FIG. 4 ) with the adhesive layer facing up. Next, spacers  203  are placed on top of the device wafer  20  and then the carrier wafer  30  is placed on top of the spacers and the assembled fixture chuck  202  is transferred to the bonder module B  310 . The chamber is evacuated, the spacers  203  are removed and the carrier wafer  30  is dropped onto the device wafer  20 . In some embodiments, the carrier wafer  30  is dropped onto the device wafer  20  by purging nitrogen or other inert gas through vacuum grooves formed in the upper chuck  222 . In other embodiments the upper chuck  222  is an electrostatic chuck (ESC) and the carrier wafer  30  is dropped onto the device wafer  20  by reversing the polarity of the ESC. Next, a low force is applied by purging the chamber with a low pressure gas and the temperature is raised to 200° C. for the formation of the bond. Next, the chamber is cooled and the fixture is unloaded. In other embodiments, the Z-axis  239  moves up and the stacked wafers  20 ,  30  are brought into contact with the upper chuck  222 . The upper chuck  222  may be semi-compliant or non-compliant, as will be described later. 
         [0056]    The debond process B  70   b  is a mechanical lift debond process and includes the following steps, shown in  FIG. 2A . The bonded wafer stack  10  is mounted onto a dicing frame  25  ( 54 ) and the carrier wafer  30  is mechanically lifted away from the device wafer  20  ( 55 ). The thinned device wafer  20  remains supported by the dicing frame  25 . 
         [0057]    Referring to  FIG. 3A , temporary bond process C,  80   a  includes the following steps. First, a surface of the device wafer  20  is coated with an adhesive layer  23  ( 82 ). In one example, adhesive layer  23  is a UV curable adhesive LC3200™, manufactured by 3M Company, MN, USA. The adhesive coated device wafer is then flipped ( 84 ). Next, a light absorbing release layer  33  is spin coated on a surface  30   a  of the carrier wafer  30  ( 86 ). In one example, light absorbing release layer  33  is a LC4000, manufactured by 3M Company, MN, USA. Next, the flipped device wafer  20  is aligned with the carrier wafer  30  so that the surface  20   a  of the device wafer with the adhesive layer  23  is opposite to the surface  30   a  of the carrier wafer  30  with the light absorbing release layer. The two surfaces  20   a  and  30   a  are brought into contact and the adhesive layer is cured with UV light ( 87 ). The two wafers are bonded ( 88 ) in temporary bonder module C  410 , shown in  FIG. 3B . The bond is a temporary bond between the light absorbing release layer  33  and the adhesive layer  23  and is formed under vacuum of 0.1 mbar and low applied bond force. The temporary bonding ( 88 ) of the carrier wafer to the device wafer occurs in temporary module C, shown in  FIG. 3B . 
         [0058]    Referring to  FIG. 3B , the carrier wafer  30  with the laser absorbing release layer LTHC layer is placed on the top chuck  412  and held in place by holding pins  413 . Next, the device wafer  20  is placed on the bottom chuck  414  with the adhesive layer  23  facing up. Next, the wafers  20 ,  30  are aligned, the chamber is evacuated, and the top chuck  412  with the carrier wafer  30  is dropped onto the device wafer  20 . A low force is applied for the formation of the bond between the release layer  33  and the adhesive layer  23 . Next, the bonded wafer stack  10  is unloaded and the adhesive is cured with UV light. 
         [0059]    Referring back to  FIG. 3A , the debond process C  80   b  includes the following steps. The bonded wafer stack  10  is mounted onto a dicing frame  25  ( 56 ) and the carrier wafer  30  is illuminated with a YAG laser beam. The laser beam causes the separation of the wafer stack along the release layer  33  ( 57 ) and the separated carrier wafer  30  is mechanically lifted away from the device wafer  20  ( 58 ). The adhesive layer is peeled away from the device wafer surface  20   a  ( 59 ) and the thinned device wafer  20  remains supported by the dicing frame  25 . 
         [0060]    Referring to  FIG. 5 , temporary bonder cluster  110  includes a housing  101  having an upper cabinet structure  102  stacked on top of a lower cabinet  103 . The upper cabinet  102  has a service access side  105  and the lower cabinet has leveling adjustments  104  and transport casters  106 . Within the upper cabinet structure  102  the configurable temporary bond process modules  210 ,  310 ,  410 ,  510  are vertically stacked, as shown in  FIG. 6 . Hot plate modules  130  and cold plate modules  140  are also vertically stacked on top, below or in-between the process modules  210 ,  310 , as shown in  FIG. 7 . Additional process modules may be included in order to provide further processing functionalities. Examples of the bond process modules include low applied force module, high applied force module, high temperature and low temperature modules, illumination (UV light or laser) modules, high pressure (gas) module, low (vacuum) pressure module and combinations thereof. 
         [0061]    Referring to  FIG. 9-FIG .  12 , temporary bond module  210  includes a housing  212  having a load door  211 , an upper block assembly  220  and an opposing lower block assembly  230 . The upper and lower block assemblies  220 ,  230  are movably connected to four Z-guide posts  242 . In other embodiments, less than four or more than four Z-guide posts are used. A telescoping curtain seal  235  is disposed between the upper and lower block assemblies  220 ,  230 . A temporary bonding chamber  202  is formed between the upper and lower assemblies  220 ,  230  and the telescoping curtain seal  235 . The curtain seal  235  keeps many of the process components that are outside of the temporary bonding chamber area  202  insulated from the process chamber temperature, pressure, vacuum, and atmosphere. Process components outside of the chamber area  202  include guidance posts  242 , Z-axis drive  243 , illumination sources, mechanical pre-alignment arms  460   a ,  460   b  and wafer centering jaws  461   a ,  461   b , among others. Curtain  235  also provides access to the bond chamber  202  from any radial direction. 
         [0062]    Referring to  FIG. 11 , the lower block assembly  230  includes a heater plate  232  supporting the wafer  20 , an insulation layer  236 , a water cooled support flange  237  a transfer pin stage  238  and a Z-axis block  239 . Heater plate  232  is a ceramic plate and includes resistive heater elements  233  and integrated air cooling  234 . Heater elements  233  are arranged so the two different heating zones are formed. A first heating zone  233 B is configured to heat a 200 mm wafer or the center region of a 300 mm wafer and a second heating zone  233 A is configured to heat the periphery of the 300 mm wafer. Heating zone  233 A is controlled independently from heating zone  233 B in order to achieve thermal uniformity throughout the entire bond interface  405  and to mitigate thermal losses at the edges of the wafer stack. Heater plate  232  also includes two different vacuum zones for holding wafers of 200 mm and 300 mm, respectively. The water cooled thermal isolation support flange  237  is separated from the heater plate by the insulation layer  236 . The transfer pin stage  238  is arranged below the lower block assembly  230  and is movable supported by the four posts  242 . Transfer pin stage  238  supports transfer pins  240  arranged so that they can raise or lower different size wafers. In one example, the transfer pins  240  are arranged so that they can raise or lower 200 mm and 300 mm wafers. Transfer pins  240  are straight shafts and, in some embodiments, have a vacuum feed opening extending through their center, as shown in  FIG. 15 . Vacuum drawn through the transfer pin openings holds the supported wafers in place onto the transfer pins during movement and prevents misalignment of the wafers. The Z-axis block  239  includes a precision Z-axis drive  243  with ball screw, linear cam design, a linear encoder feedback  244  for submicron position control, and a servomotor  246  with a gearbox, shown in  FIG. 12 . 
         [0063]    Referring to  FIG. 13 , the upper block assembly  220  includes an upper ceramic chuck  222 , a top static chamber wall  221  against which the curtain  235  seals with seal element  235   a , a 200 mm and a 300 mm membrane layers  224   a ,  224   b , and three metal flexure straps  226  arranged circularly at 120 degrees. The membrane layers  224   a ,  224   b , are clamped between the upper chuck  222  and the top housing wall  213  with clamps  215   a ,  215   b , respectively, and form two separate vacuum zones  223   a ,  223   b  designed to hold 200 mm and 300 mm wafers, respectively, as shown in  FIG. 14 . Membrane layers  224   a ,  224   b  are made of elastomer material or metal bellows. The upper ceramic chuck  222  is highly flat and thin. It has low mass and is semi-compliant in order to apply uniform pressure upon the wafer stack  10 . The upper chuck  222  is lightly pre-loaded with membrane pressure against three adjustable leveling clamp/drive assemblies  216 . Clamp/drive assemblies  216  are circularly arranged at 120 degrees. The upper chuck  222  is initially leveled while in contact with the lower ceramic heater plate  232 , so that it is parallel to the heater plate  232 . The three metal straps  226  act a flexures and provide X-Y-T (Theta) positioning with minimal Z-constraint for the upper chuck  222 . The clamp/drive assemblies  216  also provide a spherical Wedge Error Compensating (WEC) mechanism that rotates and/or tilts the ceramic chuck  222  around a center point corresponding to the center of the supported wafer without translation. In other embodiments, the upper ceramic chuck  222  positioning is accomplished with fixed leveling/locating pins, against which the chuck  222  is lashed. 
         [0064]    The loading and pre-alignment of the wafers is facilitated with the mechanical centering device  460 , shown in  FIG. 16 . Centering device  460  includes two rotatable pre-alignment arms  460   a ,  460   b  and a linearly moving alignment arm  460   c , shown in the open position in  FIG. 16  and in the closed position in  FIG. 17 . At the ends of each arm  460   a ,  460   b  there are mechanical jaws  461   a ,  461   b . The mechanical jaws  461   a ,  461   b  have tapered surfaces  462  and  463  that conform to the curved edge of the 300 mm wafer and 200 mm wafer, respectively, as shown in  FIG. 18A  and  FIG. 18B . The linearly moving arm  460   c  has a jaw  461   c  with a tapered curved inner surface that also conforms to the curved edge of circular wafers. Rotating arms  460   a ,  460   b  toward the center  465  of the support chuck  464  and linearly moving arm  460   c  toward the center  465  of the support chuck  464  brings the tapered surfaces of the mechanical jaws  461   a ,  461   b  and the tapered curved inner surface of jaw  461   c  in contact with the outer perimeter of the wafer and centers the wafer on the support chuck  464 . The three arms  460   a ,  460   b ,  460   c  are arranged at 120 degrees around the support chuck  464 . In another embodiment, the centering device  460  includes three rotatable pre-alignment arms, and at the ends of each arm there are mechanical jaws, as shown in  FIG. 18A  and  FIG. 18B . Rotating the arms toward the center of the support chuck  464  brings the tapered surfaces of the mechanical jaws in contact with the outer perimeter of the wafer and centers the wafer on the support chuck  464 . 
         [0065]    In another embodiment, the loading and pre-alignment of the wafers is facilitated with wafer centering device  470 , shown in  FIG. 19A  and  FIG. 19B . Wafer centering device  470  includes three centering linkages  471 ,  472 ,  473 . Centering linkage  471  includes a rectilinear mid-position air bearing or mechanical slide  471   a  that moves the wafer  30  in the Y-direction. Centering linkages  472 ,  473 , include rotating centering arms  472   a ,  473   a , that rotate clockwise and counterclockwise, respectively. The motions of the centering linkages  471 ,  472 ,  473 , are synchronized by the use of a cam plate  474  with two linear cam profiles  474   a ,  474   b . Cam profile  474   a  provides rectilinear motion for the mid-position centering arm  471  and cam profile  474   b  provides rectilinear motion for left and right centering arm push rods  472   b ,  473   b . The rectilinear motion of the push rods  472   b ,  473   b , is translated into rotary motion at the cam/cam follower interface at the centering arms  472   a ,  473   a , respectively. The cam plate is  474  fixed to a linear slide that is driven in a rectilinear motion (X-axis motion) by an electric motor or pneumatic actuation. A Linear Variable Differential Transformer (LVDT) or another electrical sensor at the mid-position centering arm  471  mechanism provides distance feedback, which indicates that the centering devices are stopped against the wafer edge. There is a spring preload on the centering device  471   a , and when the spring preload is overtaken the LVDT registers a displacement. 
         [0066]    In yet another embodiment, the loading and pre-alignment of the wafer  30  is facilitated with wafer centering device  480 , shown in  FIG. 19C  and  FIG. 19D . Wafer centering device  400  includes three centering linkages  481 ,  482 ,  483 . Centering linkage  481  includes a rectilinear mid-position air bearing or mechanical slide  481   a  that moves the wafer  30  in the Y-direction. Centering linkages  482 ,  483 , include rotating centering arms  482   a ,  483   a , that rotate clockwise and counterclockwise, respectively. The motions of the centering linkages  481 ,  482 ,  483 , are synchronized by the use of two plates  484 ,  485  that include linear cam profiles  484   a ,  484   b , respectively. Cam profiles  484   a ,  485   a  provide rectilinear motion for left and right centering arm push rods  482 ,  483 , respectively. The rectilinear motion of the push rods  482 ,  483 , is translated into rotary motion at the cam/cam follower interface at the centering arms  486   a ,  486   b , respectively. Plates  484 ,  485  are connected to linear slide  481   a  via rods  481   a ,  481   b , respectively. The linear motion of slide  481   a  in the Y direction is translated via the rods  486   a ,  486   b , into linear motion of plates  484 ,  485 , respectively, along the X-axis, as shown in  FIG. 19D . 
         [0067]    Referring to  FIG. 20A ,  FIG. 20B ,  FIG. 20C , the temporary bonding operation with the bonder module  210  includes the following steps. First, the non-adhesive substrate is loaded onto the transfer pins  240   a  by a robot end effector ( 350 ). In this case the substrate is a 300 mm wafer and is supported by the 300 mm pins  240   a , whereas the 200 mm pins  240   b  are shown to be slightly lower than the 300 mm pins  240   a . Next, the mechanical taper jaws  461   a ,  461   b , move into position around the wafer and the transfer pins  240   a  move down ( 352 ). The transfer pins have vacuum and purge functions. The purge function allows the wafer to float during the centering cycle and the vacuum function holds the wafer when the centering is complete. The tapered “funnel” jaws  461   a ,  461   b ,  461   c , drive the wafer to the center as it is lowered via the transfer pins  240   a . Jaws  461   a ,  461   b ,  461   c , are designed to accommodate and pre-align any size wafers, including 200 mm and 300 mm, shown in  FIGS. 19 and 18 , respectively. Next, the centering jaws  461   a ,  461   b ,  461   c  retract and the transfer pins move up to place the top substrate  20  on the upper vacuum chuck  222 , as shown in  FIG. 20C  ( 354 ). Next, a second adhesive coated substrate  30  is loaded face up onto the transfer pins  240   a  by the robot end effector ( 356 ), shown in  FIG. 21A  ( 356 ). Next, the mechanical taper jaws  460  move into position around the wafer  30  and the transfer pins  240   a  move down and then up ( 358 ), shown in  FIG. 21B . The centering jaws  461   a ,  461   b  retract and the transfer pins  240   a  move down to place the substrate  30  on the bottom vacuum chuck  232  ( 359 ), shown in  FIG. 21C . Next, the lower heater stage  230  moves up to form a close process gap between the top  20  and bottom  30  substrates and the curtain seal  235  is closed to form the temporary bonding chamber  202  ( 360 ), shown in  FIG. 22A . An initial deep vacuum is drawn (10-4 mbar) in the temporary bonding chamber  202  while the top substrate with  20  is held via mechanical fingers. Once the set vacuum level is reached the chamber pressure is raised slightly to about 5 mbar to generate a differential vacuum pressure that holds the top substrate  20  to the upper chuck  222 . The Z-axis stage  239  moves further up to bring the bottom substrate  30  in contact with the top substrate  20 , a shown in  FIG. 22B  ( 362 ). The top chuck  222  is lifted off from the stops  216  by this motion ( 362 ). Next, force is applied via the top membrane  224   a  and bottom top chuck  232  and the wafer stack  10  is heated to the process temperature ( 364 ). In one example, the applied force is in the range between 500 N to 8000N and the process temperature is 200 C. In cases where single sided heating is used, the wafer stack  10  is compressed with the membrane pressure to ensure good thermal transfer. After the end of the treatment, the bonded wafer stack  10  is cooled and unloaded with the help of the transfer pins and the robot end effector ( 366 ). 
         [0068]    In the above described case, the Z-axis moves up to contact the thin, semi-compliant upper chuck  222 /membrane  224  design. In this embodiment, the adhesive layer controls the TTV/tilt by applying pressure only in the direction perpendicular to the bond interface via the membranes/chuck flexures and by using a semi compliant chuck to conform to the adhesive topography. In other embodiments, the Z-axis moves up to contact a non-compliant chuck. In these cases the Z-axis motion controls the final thickness of the adhesive layer and forces the adhesive to conform to the rigid flat chuck  222 . The adhesive layer thickness may be controlled by using a Z-axis position control, pre-measured substrate thicknesses and known adhesive thicknesses. In yet other embodiments, a compliant layer is installed on the bottom chuck  232  and the adhesive is pre-cured or its viscosity is adjusted. In yet other embodiments, heat is applied both through the bottom and top chucks. 
         [0069]    Referring to  FIG. 23 , thermal slide debonder  150  includes a top chuck assembly  151 , a bottom chuck assembly  152 , a static gantry  153  supporting the top chuck assembly  151 , an X-axis carriage drive  154  supporting the bottom chuck assembly  152 , a lift pin assembly  155  designed to raise and lower wafers of various diameters including diameters of 200 mm and 300 mm, and a base plate  163  supporting the X-axis carriage drive  154  and gantry  153 . 
         [0070]    Referring to  FIG. 24 , the top chuck assembly  151  includes a top support chuck  157  bolted to gantry  153 , a heater support plate  158  in contact with the bottom surface of the top support chuck  157 , a top heater  159  in contact with the bottom surface of the heater plate  158 , a Z-axis drive  160  and a plate leveling system for leveling the upper wafer plate/heater bottom surface  164 . The plate leveling system includes three guide shafts  162  that connect the top heater  159  to the top support chuck  157  and three pneumatically actuated split clamps  161 . The plate leveling system provides a spherical Wedge Error Compensating (WEC) mechanism that rotates and/or tilts the upper wafer plate  164  around a center point corresponding to the center of the supported wafer without translation. The heater  159  is a steady state heater capable to heat the supported wafer stack  10  up to 350° C. Heater  159  includes a first heating zone configured to heat a 200 mm wafer or the center region of a 300 mm wafer and a second heating zone configured to heat the periphery of the 300 mm wafer. The first and second heating zones are controlled independently from each other in order to achieve thermal uniformity throughout the entire bond interface of the wafer stack and to mitigate thermal losses at the edges of the wafer stack. The heater support plate  158  is water cooled in order to provide thermal isolation and to prevent the propagation of any thermal expansion stresses that may be generated by the top heater  159 . 
         [0071]    Referring to  FIG. 25 , the bottom chuck  152  is made of a low thermal mass ceramic material and is designed to slide along the X-axis on top of the air bearing carriage drive  154 . The carriage drive  154  is guided in this X-axis motion by two parallel lateral carriage guidance tracks  156 . Bottom chuck  152  is also designed to rotate along its Z-axis  169 . A Z-axis rotation by a small angle (i.e., twisting) is used to initiate the separation of the wafers, as will be described below. The base plate  163  is vibration isolated. In one example, base plate is made of granite. In other examples base plate  156  has a honeycomb structure and is supported by pneumatic vibration isolators (not shown). 
         [0072]    Referring to  FIG. 26A ,  FIG. 26B ,  FIG. 26C , the debonding operation with the thermal slide debonder  150  of  FIG. 23  includes the following steps. First, the temporary bonded wafer stack  10  is loaded on the primary lift pins  155  arranged so that the carrier wafer  30  is on the top and the thinned device wafer  20  is on the bottom ( 171 ). Next, the wafer stack  10  is lowered so that the bottom surface of the thinned device wafer  20  is brought into contact with the bottom chuck  152  ( 172 ). The bottom chuck  152  is then moved along the  165   a  direction until it is under the top heater  159  ( 174 ). Next, the Z-axis  160  of the top chuck  151  moves down and the bottom surface  164  of the top heater  159  is brought into contact with the top surface of the carrier wafer  30  and then air is floated on top heater  159  and carrier wafer  30  until the carrier wafer stack  30  reaches a set temperature. When the set temperature is reached, vacuum is pulled on the carrier wafer  30  so that is held by the top chuck assembly  151  and the guide shafts  162  are locked in the split clamps  162  ( 175 ). At this point the top chuck  151  is rigidly held while the bottom chuck  152  is compliant and the thermal slide separation is initiated ( 176 ) by first twisting the bottom chuck  152  and then moving the X-axis carriage  154  toward the  165   b  direction away from the rigidly held top chuck assembly  151  ( 177 ). The debonded thinned device wafer  20  is carried by the X-axis carriage  154  to the unload position where it is lifted up by the pins ( 178 ) for removal ( 179 ). Next, the X-axis carriage  154  moves back along direction  165   a  ( 180 ). Upon reaching the position under the top chuck assembly  151 , the lift pins  155  are raised to contact the adhesive side of the carrier wafer  30  and air is purged onto the heater plate  159  to release the carrier wafer from it ( 181 ). The lift pins  155  are lowered to a height just above the bottom chuck plane so as to not contaminated the bottom chuck top surface with the adhesive ( 182 ) and the X-axis carriage  154  moves along  165   b  back to the unload position. The carrier wafer is cooled and then removed ( 183 ). 
         [0073]    Referring to  FIG. 2A , mechanical debonder B  250  debonds the carrier wafer  30  from the thinned device wafer  20  by mechanically lifting an edge  31  of the carrier wafer  30  away from the thinned device wafer  20 . Prior to the debonding process the temporary bonded wafer stack  10  is attached to a frame  25 , and upon separation the thinned wafer remains supported by the frame  25 . Referring to  FIG. 27  and  FIG. 28 , debonder  250  includes a flex plate  253  with a two zone circular vacuum seal  255 . Seal  255  includes two zones, one for a sealing a 200 mm wafer placed within the area surrounded by the seal and a second for sealing a 300 mm wafer within the area surrounded by the seal. Seal  255  is implemented either with an O-ring or with suction cups. A lift pin assembly  254  is used to raise or lower the separated carrier wafer  30  that is transported by the flex plate  253 . Debonder  250  also includes a vacuum chuck  256 . Both the vacuum chuck  256  and the flex plate  253  are arranged next to each other upon a support plate  252 , which in turn is supported by the base plate  251 . Flex plate  253  has an edge  253   b  connected to a hinge  263  that is driven by a hinge motor drive  257 . Vacuum chuck  256  is made of a porous sintered ceramic material and is designed to support the separated thin wafer  20 . Hinge motor drive  257  is used to drive the flex plate  253  upon the wafer stack  10  after the wafer stack  10  has been loaded on the vacuum chuck  256 . An anti-backlash gear drive  258  is used to prevent accidental backing of the flex plate  253 . A debond drive motor  259  is attached at the edge  251   a  of the base plate  251  and next to the edge of the chuck support plate  252   a . Debond drive motor  259  moves a contact roller  260  vertical to the plane of the base plate  251  in direction  261  and this motion of the contact roller  260  lifts the edge  253   a  of the flex plate  253  after the flex plate has been placed upon the loaded wafer stack  10 , as will be described below. 
         [0074]    Referring to  FIG. 29 , the debonding operation  270  with the debonder  250  includes the following steps. First, The tape frame  25  with the wafer stack  10  is loaded upon the vacuum chuck  256 , so that the carrier wafer  30  is on the top and the thinned wafer  20  is on the bottom ( 271 ). The tape frame  25  is indexed against the frame registration pins  262 , shown in  FIG. 28 , and the position of the tape frame  25  is locked. Next, vacuum is pulled through the porous vacuum chuck  256  to hold the tape frame adhesive film. Next, the hinge motor  257  is engaged to transport the flex plate  253  onto the loaded wafer stack, so that it is in contact with the back of the carrier wafer  30  ( 272 ). Upon reaching the position upon the carrier wafer  30 , vacuum is pulled on the carrier wafer top via the seal  255 . The torque of the hinge motor  257  is kept constant to maintain the flex plate  253  in this “closed position”. Next, the debond motor  259  is engaged to move the contact roller  260  up in the direction  261   a  and to push the edge  253   a  of the flex plate  253  up ( 273 ). This upward motion of the flex plate edge  253   a  bents (or flexes) slightly the carrier wafer  30  and cause the wafer stack  10  to delaminate along the release layer  32  and thereby to separate the carrier wafer  30  from the thinned wafer  20 . Silicon wafers break or cleave much easier along the (110) crystallographic plane than any other orientation. Therefore, the carrier wafer  30  is fabricated on a (110) plane so that its 110 direction is perpendicular to the push direction  261   a , thereby preventing breaking of the wafer  30  during delamination. The thinned wafer  20  remains attached to the tape frame  25 , which is held by the vacuum chuck  256 . Through this step the debond motor  259  is held constant in position. Next, the hinge motor drive  257  opens the flex plate  253  with the attached separated carrier wafer  30  in the “open position”, in a controlled manner ( 274 ). The flex plate vacuum is released thereby releasing the carrier wafer  30 . Next, the lift pins  254  are moved up to raise the carrier wafer  30  oriented so that the release layer  32  is facing up and then the carrier wafer  30  is removed. Next, the vacuum through the porous vacuum chuck  256  is released and the tape  25  with the attached thinned wafer  20  is removed. 
         [0075]    Several 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. Accordingly, other embodiments are within the scope of the following claims.

Technology Classification (CPC): 8