Abstract:
A substrate bonding apparatus comprises a platen and a press. The press is movable relative to the platen for pressing at least one substrate stack between the press and platen. In one embodiment, a consumable compliant member is disposed between the press and the platen. In another embodiment, the apparatus further comprises a substrate carrier adapted for holding and carrying more than one substrate stack in and out of the apparatus. A method for bonding substrates is also described.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority from U.S. Provisional Patent Application No. 60/644,806, filed Jan. 18, 2005, which is incorporated herein by reference in its entirety. 
     
    
     BACKGROUND  
       [0002]     1. Field  
         [0003]     The present invention relates to substrate processing apparatus and, more particularly, to a substrate bonding tool.  
         [0004]     2. Brief Description of Related Developments  
         [0005]     Consumers desire ever cheaper electrical and electronic devices. A major part of the cost in producing consumer electrical and electronic devices is the cost of the semiconductor devices that provide the very features that make the electronic devices so desired by consumers. Manufacturers of the semiconductor devices thus continue to seek ways to lessen manufacturing costs of the semiconductors. Increasing manufacturing throughput, thereby reducing unit cost, is one way semiconductor manufacturers seek to achieve their goal. By way of example, various types of semiconductor devices have an architecture formed by bonding more than one substrate or wafer to each other. Conventional bond tools generally perform the bond operation one wafer stack at a time. To improve throughput, some conventional bond tools have a cluster of bond chambers, each of which is capable of bonding a stack of wafers at a time. Though bond cluster tools do provide throughput improvements over non-cluster bond tools, it may be readily realized that conventional bond cluster tools are more costly than non-cluster tools due to the multiplicity of substantially identical components and systems in the cluster tool as well as the greater demands on the automated control system to perform the operation with the cluster tool. Further, conventional cluster tools suffer an inherent throughput penalty arising from the time spent in moving wafers to and from different tool chambers or modules (i.e. different destinations) when loading and unloading the tool. By comparison, in a non-cluster tool the movement of wafers is but to and from a single chamber or module (i.e. a common destination) when loading and unloading the tool, thereby eliminating repositioning of the transport apparatus for different transport paths with a commensurate reduction in transport times. The present invention overcomes the problems of conventional tools as will be described in greater detail below with reference to exemplary embodiments.  
       SUMMARY  
       [0006]     In one embodiment, a substrate bonding apparatus comprises a frame and a platen connected to the frame. The platen is adapted for supporting thereon at least one stack of substrates. A press is movably connected to the frame, the frame being movable relative to the platen for pressing the at least one stack between the press and the platen. A compliant member is disposed between the press and platen so that the press pressing the at least one stack presses the compliant member against the at least one stack.  
         [0007]     In another embodiment, a substrate bonding apparatus comprises a frame and a platen connected to the frame, the platen being adapted for supporting thereon at least one stack of substrates. A press is movably connected to the frame, the press being movable relative to the platen for pressing the at least one substrate stack between the press and the platen. The apparatus further comprises a substrate carrier adapted for holding and carrying more than one substrate stack in and out of the apparatus, the substrate carrier being separably connectable to at least one of the platen or the press to position the more than one substrate stack between the press and platen so that the press and platen substantially simultaneously press the more than one substrate stack to effect bonding between substrates of each of the more than one substrate stack substantially simultaneously.  
         [0008]     In yet another embodiment, a method for bonding substrates comprises providing a substrate bonding apparatus with a platen and a press movable relative to each other. The method further comprises positioning multiple substrate stacks in the apparatus between the platen and the press. The method still further comprises providing a consumable member and placing the consumable member between the platen and press so that the consumable member is seated against more than one of the multiple substrate stacks. And, the method further comprises pressing the multiple substrate stacks with the press wherein pressing presses the consumable member against the more than one of the substrate stacks to effect substantially simultaneous bonding between stacked substrates of each of the more than one substrate stacks. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing aspects and other features of the present invention are explained in the following description, taken in connection with the accompanying drawings, wherein:  
         [0010]      FIG. 1  is an exploded partial perspective view of a processing tool incorporating features in accordance with an exemplary embodiment of the present invention, and two wafers S 1 , S 2 ;  
         [0011]      FIG. 2  is an enlarged exploded perspective view of a carrier section, wafer alignment section and pressure applicator section of the processing tool in  FIG. 1  and the two wafers S 1 , S 2 ;  
         [0012]      FIG. 3  is a plan view of the wafer alignment section; and  
         [0013]      FIG. 4  is an enlarged partial view of the wafer alignment section shown in  FIG. 3 .  
     
    
     DETAILED DESCRIPTION  
       [0014]     In the embodiment shown in  FIG. 1 , the tool  10  is illustrated as a bond tool for example purposes, though the features of present invention as will be described below with specific reference to the exemplary embodiments are equally applicable to other semiconductor substrate and flat panel processing tools. Although the present invention will be described with reference to the embodiment shown in the drawings, it should be understood that the present invention can be embodied in many alternate forms and embodiments. In addition, any suitable size, shape or type of elements or materials could be used.  
         [0015]     The bond tool  10 , operates generally as a clamp. The tool  10  may have opposing clamping blocks, in this embodiment an upper pressure head or press  20  and opposing lower pressure block or platen  22 . The tool  10  has a carrier section  24 , a pressure applicator section  26  and an alignment section  28 . The carrier section  24 , pressure applicator section  26  and alignment section  28  may be placed as a sandwich stack (i.e. the alignment section sandwiched between the carrier section and pressure applicator section) between the opposing pressure head  20  and pressure block  22 . The carrier section  24  may be position or otherwise placed on the lower pressure block  22 . The pressure applicator section  26  may be disposed against the upper pressure head  20 . Multiple stacks of wafers (only one set of wafers S 1 , S 2  forming on stack ST 1  is shown in  FIG. 1  for example purposes) may be positioned in the wafer alignment section  28 . The upper pressure head  20  and the lower pressure block  22  are moved together to apply suitable bonding pressure on the multiple wafer stacks, similar to stack ST, and effect bonding between interfacing wafers, similar to wafers S 1 , S 2 , in each stack bonding pressure on the multiple stacks is simultaneously delivered by the carrier section  24  and pressure applicator section  26  the pressure applicator section provides a substantially uniform pressure distribution on all wafer stacks being pressed in the tool  10  regardless of variances in height of different stacks as will be described in greater detail below.  
         [0016]     The wafers or substrates S 1 , S 2  may be of any suitable type. For example, the substrates S, S 2  may be 200 mm, or 300 mm diameter semiconductor substrates, or other type of flat panel such as flat panels for display screens. In the embodiment shown, the wafers S 1 , S 2  are substantially similar to each other. In alternate embodiments, the stack ST may comprise different types of wafers. Stack ST is shown in  FIG. 1  as having two wafers S 1 , S 2  for example purposes. As may be realized, stack ST may include any desired number of wafers being bonded together.  
         [0017]     Still referring to  FIG. 1 , and in greater detail, bond tool  10  may include a chamber or housing  12 . The chamber  12  may be closed or otherwise configured to have a controlled atmosphere, such as an inert gas, or may be held in vacuum conditions. In alternate embodiments, the tool may not include a chamber. As seen in  FIG. 1 , the chamber  12  may include an access port  14 . The port  14  may have a door for closing the port if desired. The access port  14  may be sized to allow placement and removal of the carrier section  24 , pressure applicator section  26 , wafer alignment section  28  as well as the wafers S 1 , S 2  and/or bonded stacks into the chamber  12 . A transport device (not shown), such as a transport arm or slide, that may be automated or otherwise manually operated, may be used to move the carrier section  24 , applicator section  26 , alignment section  28  and wafers/stacks into and out of the chamber  12 . The carrier section  24 , applicator section  26 , alignment section  28 , wafers/stacks may be moved in or out of the chamber  12  individually or together as a unit as will be described in greater detail below. As seen in  FIG. 1  at least one of the upper pressure head  20  and/or the lower pressure block  22  is movably held in the chamber  12 . In the embodiment shown in  FIG. 1 , the pressure head  20  and opposing block  22  are depicted in a vertical clamping configuration. In alternate embodiments, the opposing pressure head and pressure block may be arranged in any other desired clamping orientation (i.e. horizontally clamping). In the exemplary embodiment, the upper pressure head  20  is movable back and forth in the direction indicated by arrow P 1 . The head  20  may be actuated in direction P 1  by any suitable means such as electrical, pneumatic or hydraulic drive (not shown). A suitable example of the bonding tool may be the SB series of bonding tools from Suss MicroTec. Accordingly, the pressure head  20 , as well as the pressure block  22  and the peripheral systems supporting or effecting the function of head  20  and block  22  may be generally similar to corresponding portions of the SB series bonding tools. Movement of pressure head  20  in direction P 1  may be controlled by a suitable tool controller (not shown). Stroke of the pressure head  20  may be sized as desired to generate suitable bonding pressure on the wafer stack. The pressure head  20  may have a seating surface  20 S. The seating surface  20 S may be oriented so that the direction of head movement P 1  is substantially normal to the seating surface. The seating surface, or the head may have heat control (i.e. may be heated and/or cooled). The heat control may be provided by any suitable thermal controller (not shown).  
         [0018]     The tool  10  may be configured to perform any desirable substrate bond process, such an anodic, eutectic, adhesive, fusion, and thermocompression bond processors for wafer to wafer bonding. Accordingly, the tool controller (not shown) may suitably control the operation parameters of the upper pressure head  20  (e.g. head/seating temperature, stroke, chamber atmosphere) in accordance with the desired bond process being performed. The seating surface is made from a suitably hard material such as SiC.  
         [0019]     As seen in  FIG. 1 , the lower pressure block  22  is generally similar to the upper pressure head  20 . In this embodiment, the lower block  22  may be fixed relative to chamber  12 . In alternate embodiments, the pressure block may be movable relative to the chamber in the direction indicated by arrow P 1  in  FIG. 1  (i.e. similar but opposite to the upper pressure head). The block  22  may include thermal control. The block  22  may have a seating surface  22 S for seating the carrier section  24 . The seating surface  24  is aligned within a very close degree of parallelity with the plane of the seating surface  20 S on the upper head  20 . The block  22  may also have holding and alignment features  30  for effecting alignment and holding of the carrier section  24  on the seating surface  22 S. In this embodiment, the alignment features  30  may include keys  30 K (one key  30 K is visible in  FIG. 1 ) for engagement with conformal features on the carrier section as will be described further below. For example, there may be three keys  30 K, equally spaced around the center of the seating surface  22 S to lock the position of the carrier section  24  on the seating surface in the horizontal plane (defined by the X and Z axes). In the embodiment shown, the keys  30 K may project from the seating surface. The keys  30 K may be passive (i.e. are positionally fixed). In alternate embodiments the keys may provide an active grip of (may be actuated to open or close on) the carrier section  24 . In other alternate embodiments, the lower pressure block may have any other suitable coupling and interface for the carrier section.  
         [0020]     Referring now also to  FIG. 2 , there is shown an enlarged perspective view of the alignment section  28 , pressure applicator section  26  and carrier section  24  (as well as wafers S 1 , S 2  for stack ST). As seen in  FIG. 2 , carrier section  24  may include a flat plate  24 P made from a hard material such as SiC, though in alternate embodiments, any other suitable material may be used. Plate  24 P may be of unitary construction or may be an assembly. The plate  24 P has upper and lower surfaces  24 S,  24 M that are substantially parallel. The lower surface  24 M of the plate forms a mating surface for mating the carrier section  24  to the seating surface  22 S of the lower pressure block  22 . The upper surface  24 S of the plate  24 P provides a seating surface for the wafer alignment section  28 . The upper surface  24 S in this embodiment also provides a seating surface for wafer stacks (similar to stack ST) located in the alignment section  28 . In this embodiment, the carrier section  24  facilitates transport of (i.e. may be used as a carrier for) the alignment section and wafer stacks (similar to stack ST) as will be described below. In alternate embodiments, for example where the alignment section and wafer stacks may be transported, individually or together, by other carrying means into the chamber, the carrier section may be integral to the seating section of the lower pressure block. In the embodiment shown in  FIGS. 1-2 , the plate  24 P of the carrier section  24  has a coupling  24 C for coupling the carrier section  24  to the seating surface  22 S. The coupling  24 C may comprise complementing recesses (in this embodiment there are three recess  24 C, though only two are visible in  FIG. 2 ) for keys  30 K on the seating surface  22  (see also  FIG. 1 ). The recesses  24 C are shown formed in the outer perimeter of plate  24 P, and have a general scallop shape conformal to the shape of the corresponding keys  30 K. When the carrier section  24  is mated to the seating surface  22 S, the keys  30 K are received into recesses  24 C providing a positive coupling between carrier section  24  and seating surface  22 . In alternate embodiments, any other desired type of coupling may be used on the carrier section to mate with the pressure block of the tool. As noted before, the upper seating surface  24 S of the carrier section is sized and shaped to provide suitable seating for the wafer alignment section, as well as wafer stacks that may be located in the wafer alignment section. It is noted, that wafer stacks may not populate all stack holding locations of the alignment section. In the embodiment shown, the carrier section and wafer alignment section are shown as having a generally circular shape, though in alternate embodiments the carrier and wafer alignment section may have any other desired shape.  
         [0021]     In this embodiment, the wafer alignment section  28  generally includes a plate  28 P. The plate may be made from any suitable material, such as a non-reactive metal or plastic. The wafer alignment section  28  may not be subjected to compressive pressure during bonding operation, as will be seen below, and hence the plate  28 P may be made from a relatively soft material. The plate  28 P may be of unitary construction, though in alternate embodiments the plate may be made of multiple pieces assembled or otherwise joined together. The plate  28 P may have a lower seating surface  28 S for seating against the upper seating surface  24 S of carrier section  24 . The alignment section  28  may also include suitable coupling features (not shown) such as projecting pins mating into conformal recesses, to positively couple the alignment section  28  to the carrier section  24  during transport and bonding operation. In alternate embodiments, frictional interface may be used for coupling alignment and carrier sections. As seen in  FIGS. 2 , and  3 - 4 , the plate  28 P has openings  28 O forming locations for holding stacked wafers, similar to wafers S 1 , S 2  in the alignment section as will be described in greater detail below. The thickness of the plate  28 P is established in order to allow sufficient pressure during bonding operation to be applied to stacked wafers, in the holding locations of the alignment section, for adequate wafer to wafer bonding to take in each stack of wafers. Hence, the thickness of the plate  28 P is dependent on wafer stack height as well as any deflection or yield in the wafer stack expected to occur during bonding. The thickness of the plate  28  P is thus set so that under lowest tolerance stack up of the wafer stack (i.e. the wafers, S 1 , S 2  making up the wafer stack ST are as thin as SEMI standard tolerances allow, generating a short stack) the uppermost wafer surface extends sufficiently above the upper surface of plate  28 P, and remains raised above the upper surface throughout the bonding operation, so that the clamping pressure from the head  20  and block  22  remains imparted on the wafer stack and not the alignment section.  
         [0022]      FIG. 3  shows a plan view of the plate  28 P of the alignment section, and  FIG. 4  shows a partial plan view of the plate around one wafer stack holding location  28 O. In the embodiment shown, the plate  28 P has seven wafer stack holding locations formed by six equally distributed outer openings  28 O, and an inner opening  240 . The shown arrangement and number of holes in plate  28 P is merely exemplary. In alternate embodiments, there may be any desired number of holes providing wafer stack locations. In alternate embodiments also, the holes may be disposed in any desired arrangement such as in a row and column type of arrangement. Holes  28 O are through holes, and bottom wafers (similar to wafer S 1 ) located in the holes  28 O are seated against the upper surface  24 S of the carrier section plate  24 P. As seen best in  FIG. 4 , the perimeter of the holes  28 O is shaped to form a close clearance fit with the wafers S 1 , S 2 . In the exemplary embodiment, the hole perimeter may also include a flat edge that cooperates with the fiducial flat on the wafer edge of each wafer to align the wafers S 1 , S 2  in the holding locations with respect to each other.  
         [0023]     Referring now back to  FIG. 2 , the pressure applicator section  26  generally comprises a foil  26 F capable of transmitting and evenly distributing desired pressure from the upper pressure head  20  onto the wafer stacks (similar to stack ST) disposed in the alignment section  28  when located between head  20  and block  22 , regardless of the number and spacing of the stack as well as the height variance of the stacks relative to each other. In this embodiment, the foil  26 F may be made from graphite, or polymer material, or any other desired material, and may be a one piece member of unitary construction. In alternate embodiments, the foil of the pressure applicator section may be made of any other suitable compliant material that has a substantially flat compression modulus (i.e. pressure is substantially constant as compression deflection/deformation increases). As seen in  FIG. 2 , the foil  26 F is sized to cover the wafer stacks in all the location holes of the alignment section. Upper surface  26 U of the foil is disposed to seat against seating surface  20 S of the head  20 . The lower surface  26 L may bare directly against the uppermost surface of the wafer stack. In alternate embodiments, the pressure applicator section  26  may include a shield foil  14  (not shown) non reactive material (for example a gold foil) that would be positioned between foil  26 F and the wafer stack tops to control particulate from being deposited on the wafers.  
         [0024]     Referring now again to  FIG. 1 , in this embodiment, the wafer alignment section  28  may be placed on the carrier section  24 , and the wafers S 1 , S 2  may be loaded into the alignment section  28 , to form stacks ST in the desired number of locations, when the carrier section  24  is located outside the chamber. The foil  26 F may then be positioned over the wafer stacks in the alignment section, and the carrier section  24 , carrying the alignment section, wafer stacks and pressure applicator section borne as a unit into the chamber. In alternate embodiments, the pressure applicator section and foil may be positioned over the wafer stacks after the carrier section and wafer stacks are placed in the chamber. The carrier section  24  may be coupled to the seating surface  22 S of the block  22 , as described before. In alternate embodiments, the pressure applicator section may be positioned on seating surface  20 S independent from transport of carrier section  24  into the chamber. When the carrier section is seated, the upper head is actuated to press the pressure applicator section  26  against the wafer stacks in alignment section  28 , compressing the wafer stacks between pressure applicator  26  and seating surface of carrier section  24 . As noted before, the pressure applicator section  26  delivers, via compliant foil  26 F in this embodiment, substantially even pressure distribution across all wafer stacks ST in the alignment section, to provide substantially simultaneous wafer to wafer bonding in each of the multiple wafer stacks. Upon completion of the bonding operation, the bonded stacks may be removed, for example by removal of the carrier section  24  with the stacks, alignment section  28 , and foil  26 F as a unit. As may be realized, foil  26 F may be consumable and may be discarded after the bonding operation if desired. The wafer stacks may be removed from the alignment section and carrier section, new wafer stacks may then be seated on the carrier section and within the alignment section, and a new foil  26 F positioned over the stacks for a subsequent bonding process.  
         [0025]     It should be understood that the foregoing description is only illustrative of the invention. Various alternatives and modifications can be devised by those skilled in the art without departing from the invention. Accordingly, the present invention is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.