Abstract:
An adhesive transfer method includes depositing an adhesive on a first substrate, transferring a layer of the adhesive from the first substrate to an intermediate substrate, and transferring adhesive from the layer of the adhesive to at least one area of a second substrate.

Description:
BACKGROUND  
       [0001]    Semiconductor die, wafers, and/or substrates may be joined to other semiconductor die, wafers, and/or substrates with an adhesive. Application of adhesive to the semiconductor die, wafers, and/or substrates to be joined, however, may be complicated by topography of the semiconductor die, wafers, and/or substrates. In addition, establishing a uniform layer of adhesive on the areas of the semiconductor die, wafers, and/or substrates to be joined may be challenging. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  schematically illustrates one example of an adhesive transfer and bonding process. 
           [0003]      FIG. 2  schematically illustrates another example of an adhesive transfer and bonding process. 
           [0004]      FIG. 3  illustrates one example of application of an adhesive transfer and bonding process. 
           [0005]      FIG. 4  illustrates one example of application of an adhesive transfer and bonding process. 
       
    
    
     DETAILED DESCRIPTION 
       [0006]    In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. In this regard, directional terminology, such as “top,” “bottom,” “front,” “back,” “leading,” “trailing,” etc., is used with reference to the orientation of the Figure(s) being described. Because components of examples of the present disclosure can be positioned in a number of different orientations, the directional terminology is used for purposes of illustration and is in no way limiting. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims. 
         [0007]      FIG. 1  schematically illustrates one example of an adhesive transfer and bonding process  100 . At  102 , process  100  includes reducing viscosity (i.e., increasing flowability) of an adhesive used in process  100 . An example of an adhesive used in process  100  includes a dual-cure adhesive such as EMS  405 - 57  from Engineered Materials Systems Inc. 
         [0008]    Reducing viscosity of the adhesive helps facilitate dispensing and depositing of the adhesive during subsequent processing. In one example, viscosity of the adhesive is reduced by diluting or thinning the adhesive with a solvent. An example of a solvent used for diluting or thinning the adhesive in process  100  includes cyclopentanone. 
         [0009]    At  104 , process  100  includes depositing the diluted adhesive on a dummy wafer or donor substrate  10 . More specifically, a layer of diluted adhesive  12  is deposited on a surface  11  of donor substrate  10 . In one example, adhesive  12  is deposited on surface  11  of donor substrate  10  by spin coating. 
         [0010]    Next, at  106 , process  100  includes transferring adhesive  12  from donor substrate  10  to an intermediate or carrier substrate  13 . An example of a material used for intermediate or carrier substrate  13  includes a flexible film including a polyester film such as Mylar. 
         [0011]    In one example, transferring adhesive  12  from donor substrate  10  to intermediate or carrier substrate  13  includes contacting or pressing a surface  14  of intermediate or carrier substrate  13  against adhesive  12  deposited on donor substrate  10 . As such, adhesive  12  is transferred to surface  14  of intermediate or carrier substrate  13  such that a layer  15  of adhesive  12  is formed on intermediate or carrier substrate  13  and remains on intermediate or carrier substrate  13  when intermediate or carrier substrate  13  is separated, peeled, or removed from donor substrate  10 . 
         [0012]    In one example, layer  15  of adhesive  12  is a substantially uniform layer, and has a thickness less than a total thickness of adhesive  12  deposited on donor substrate  10  such that a layer of adhesive  12  remains on donor substrate  10  after transferring adhesive  12  to intermediate or carrier substrate  13 . 
         [0013]    After transferring adhesive  12  to carrier substrate  1 . 3 , at  108 , process  100  includes removing the solvent from adhesive  12  of layer  15 . In one example, removing the solvent from adhesive  12  includes heating layer  15  of adhesive  12  and carrier substrate  13  at a predetermined temperature for a predetermined time so as to evaporate the solvent from adhesive  12 . 
         [0014]    In one example, at  110 , process  100  includes partially cross-linking or “B-staging” adhesive  12  as provided on carrier substrate  13 . In one example, partially cross-linking or “B-staging” adhesive  12  includes semi-curing adhesive  12  by exposing layer  15  of adhesive  12  to ultra-violet (UV) light. Partially cross-linking or “B-staging” adhesive  12  essentially “freezes” adhesive  12  in position to reduce wicking of adhesive  12 , and reduces a tack of adhesive  12  such that carrier substrate  13  with layer  15  of adhesive  12  may be “staged” or held for a period of time, and/or may be more easily handled during subsequent processing. 
         [0015]    At  112 , process  100  includes transferring adhesive  12  of layer  15  from carrier substrate  13  to a device wafer or substrate  16 . In one example, device wafer or substrate  16  includes a patterned substrate having a topography of raised portions or areas  17 . As such, transferring adhesive  12  of layer  15  from carrier substrate  13  to substrate  16  includes transferring adhesive  12  to raised portions or areas  17  of substrate  16 . 
         [0016]    In one example, transferring adhesive  12  from carrier substrate  13  to substrate  16  includes pressing layer  15  of adhesive  12  against substrate  16  and contacting raised portions or areas  17  of substrate  16  with layer  15  of adhesive  12 . As such, adhesive  12  from layer  15  is transferred to raised portions or areas  17  of substrate  16  and remains on raised portions or areas  17  of substrate  16  when carrier substrate  13  is separated, peeled, or removed from substrate  16 . Thus, a pattern of adhesive  12  transferred to substrate  16  follows and is aligned with a pattern of substrate  16  such that adhesive  12  transferred to substrate  16  is self-patterned and self-aligned. 
         [0017]    Partially cross-linking or “B-staging” adhesive  12  (as described, for example, at  110 ) reduces wicking of adhesive  12  so that adhesive  12 , after transfer at  112 , remains on raised portions or areas  17  of substrate  16  instead of wicking into recessed areas or regions among raised portions or areas  17  of substrate  16 . 
         [0018]    At  114  of process  100 , substrate  16  with self-patterned and self-aligned adhesive  12  is aligned with another substrate  18  for bonding with substrate  18  such that at  116  of process  100 , substrate  16  and substrate  18  are bonded together by adhesive  12 . In one example, substrate  16  and substrate  18  are bonded together by placing substrate  16  and substrate  18  in a thermal bonding machine at a predetermined temperature for a predetermined time. Thereafter, at  118  of process  100 , adhesive  12  is cured by heating substrates  16  and  18  at a predetermined temperature for a predetermined time. 
         [0019]      FIG. 2  schematically illustrates another example of an adhesive transfer and bonding process  200 . At  202 , process  200 , similar to process  100 , includes reducing viscosity of an adhesive used in process  200 . Similar to  102  of process  100 , viscosity of the adhesive is reduced by diluting or thinning the adhesive with a solvent. 
         [0020]    At  204 , process  200  includes depositing the diluted adhesive on a dummy wafer or donor substrate  20 . More specifically, a layer of diluted adhesive  22  is deposited on a surface  21  of donor substrate  20 . In one example, similar to  104  of process  100 , adhesive  22  is deposited on surface  21  of donor substrate  20  by spin coating. 
         [0021]    Next, at  206 , process  200  includes transferring adhesive  22  from donor substrate  20  to an intermediate or carrier substrate  23 . An example of a material used for intermediate or carrier substrate  23  includes a flexible film including a polyester film such a Mylar. 
         [0022]    In one example, similar to  106  of process  100 , transferring adhesive  22  from donor substrate  20  to intermediate or carrier substrate  23  includes contacting or pressing a surface  24  of intermediate or carrier substrate  23  against adhesive  22  deposited on donor substrate  20 . As such, adhesive  22  is transferred to surface  24  of intermediate or carrier substrate  23  such that a layer  25  of adhesive  22  is formed on intermediate or carrier substrate  23  and remains on intermediate or carrier substrate  23  when intermediate or carrier substrate  23  is separated, peeled, or removed from donor substrate  20 . 
         [0023]    In one example, similar to layer  15  of adhesive  12 , layer  25  of adhesive  22  is a substantially uniform layer, and has a thickness less than a total thickness of adhesive  22  deposited on donor substrate  20  such that a layer of adhesive  22  remains on donor substrate  20  after transferring adhesive  22  to intermediate or carrier substrate  23 . 
         [0024]    After transferring adhesive  22  to carrier substrate  23 , at  208 , process  200  includes removing the solvent from adhesive  22  of layer  25 . In one example, similar to  108  of process  100 , removing the solvent from adhesive  22  includes heating layer  25  of adhesive  22  and carrier substrate  23  at a predetermined temperature for a predetermined time so as to evaporate the solvent from adhesive  22 . 
         [0025]    At  210 , process  200  includes transferring adhesive  22  of layer  25  from carrier substrate  23  to a semiconductor die or substrate  26 . In one example, semiconductor die or substrate  26  includes a patterned substrate formed by a singulated wafer resulting in a topography of raised portions or areas  27  on a backing member (e.g., saw tape)  28 . As such, transferring adhesive  22  from carrier substrate  23  to substrate  26  includes transferring adhesive  22  to raised portions or areas  27  of substrate  26 . 
         [0026]    In one example, similar to  112  of process  100 , transferring adhesive  22  from carrier substrate  23  to substrate  26  includes pressing layer  25  of adhesive  22  against substrate  26  and contacting raised portions or areas  27  of substrate  26  with layer  25  of adhesive  22 . As such, adhesive  22  from layer  25  is transferred to raised portions or areas  27  of substrate  26  and remains on raised portions or areas  27  of substrate  26  when carrier substrate  24  is separated, peeled, or removed from substrate  26 . Thus, a pattern of adhesive  22  transferred to substrate  26  follows and is aligned with a pattern of substrate  26  such that adhesive  22  transferred to substrate  26  is self-patterned and self-aligned. 
         [0027]    In one example, at  212 , process  200  includes partially cross-linking or “B-staging” adhesive  22  as provided on substrate  26 . In one example, partially cross-linking or “B-staging” adhesive  22  includes semi-curing adhesive  22  by exposing adhesive  22  to ultra-violet (UV) light. Partially cross-linking or “B-staging” adhesive  22  essentially “freezes” adhesive  22  in position to reduce wicking of adhesive  22 , and reduces a tack of adhesive  22  such that substrate  26  with self-patterned and self-aligned adhesive  22  may be “staged” or held for a period of time, and/or may be more easily handled during subsequent processing. Partially cross-linking or “B-staging” adhesive  22  also reduces wicking of adhesive  12  into areas or regions between raised portions or areas  27  of substrate  26  or along edges of substrate  26  after transfer at  210 . 
         [0028]    At  214  of process  200 , substrate  26  with self-patterned and self-aligned adhesive  22  is stacked with another silicon or semiconductor die or substrate  29  for bonding to silicon or semiconductor die or substrate  29  with adhesive  22 . 
         [0029]      FIG. 3  illustrates one example of application of an adhesive transfer and bonding process as described herein. In one example, adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200  is used in fabrication of a fluid ejection device  300 . 
         [0030]    Schematically illustrated in cross-section in  FIG. 3 , one example of fluid ejection device  300  includes an electronics wafer or substrate  310 , a piezeoelectric wafer or substrate  320  attached to electronics wafer  310 , a piezoelectric element  330  supported by piezoelectric wafer  320 , a cap wafer or substrate  340  attached to piezoelectric wafer  320 , and a nozzle plate  350  attached to cap wafer  340 . 
         [0031]    In one example, piezoelectric wafer  320  is attached to electronics wafer  310  with an adhesive layer  360  formed using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 . In addition, in one example, cap wafer  340  is attached to piezoelectric wafer  320  with an adhesive layer  370  formed using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 , and nozzle plate  350  is attached to cap wafer  340  with an adhesive layer  380  also formed using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 . 
         [0032]    In one example, electronics wafer  310  includes a fluid (or ink) feed hole  312  communicated with a supply of fluid (or ink), and piezoelectric wafer  320  includes fluidic routing communicated with fluid feed hole  312  of electronics wafer  310  such that application of an electrical signal to piezoelectric element  330  deflects piezoelectric element  330  and ejects fluid (or ink) through cap wafer  340  and out a nozzle  352  of nozzle plate  350 . 
         [0033]    In one example, as illustrated in  FIG. 4 , fluidic routing of piezoelectric wafer  320  includes fluid channels  322  separated and formed by spaced ribs  324 , and includes pinch points  326  communicated with fluid channels  322  and formed by spaced posts  328 . Using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 , adhesive is applied to ribs  324  and posts  328  for bonding of piezoelectric wafer  320  to electronics wafer  310 . By using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 , a layer of self-patterned and self-aligned adhesive is applied to ribs  324  and posts  328  without blocking fluid channels  322  or spilling over the edges of ribs  324  to adjacent fluid channels  322 , and without blocking pinch points  326  or spilling over the edges of posts  328 . 
         [0034]    By using adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 , as described herein, a self-aligned and self-patterned adhesive layer may be formed on a semiconductor die, wafer, and/or substrate while minimizing wicking or flow of adhesive beyond edges of an intended application area for the adhesive. In addition, with adhesive transfer and bonding process  100  and/or adhesive transfer and bonding process  200 , a thin layer of adhesive of substantially uniform thickness providing for a thin bond line may be selectively applied to a semiconductor die, wafer, and/or substrate having a topography of small or narrow features. 
         [0035]    Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof.