Patent Publication Number: US-10770350-B2

Title: Method of separating a back layer on a singulated semiconductor wafer attached to carrier substrate

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation application of co-pending U.S. application Ser. No. 16/352,218 filed on Mar. 13, 2019 and issued as U.S. Pat. No. 10,553,491 on Feb. 4, 2020, which is a continuation application of U.S. application Ser. No. 15/977,608 filed on May 11, 2018 and issued as U.S. Pat. No. 10,269,642 on Apr. 23, 2019, which is a continuation of U.S. application Ser. No. 15/384,646 filed on Dec. 20, 2016 and issued as U.S. Pat. No. 10,014,217 on Jul. 3, 2018, which is a continuation application of U.S. application Ser. No. 14/808,729 filed on Jul. 24, 2015 and issued as U.S. Pat. No. 9,564,365 on Feb. 7, 2017, which is a divisional application of U.S. application Ser. No. 14/057,756 filed on Oct. 18, 2013 and issued as U.S. Pat. No. 9,136,173 on Sep. 15, 2015, which claims the benefit of priority from: U.S. Provisional Application No. 61/723,548, which was filed on Nov. 7, 2012, from U.S. Provisional Application No. 61/750,520, which was filed on Jan. 9, 2013, and from U.S. Provisional Application No. 61/774,081, which was filed on Mar. 7, 2013, all of which are fully incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates, in general, to electronics and, more particularly, to methods and apparatus for forming semiconductors. 
     In the past, the semiconductor industry utilized various methods and equipment to singulate individual semiconductor die from a semiconductor wafer on which the die was manufactured. Typically, a technique called scribing or dicing was used to either partially or fully cut through the wafer with a diamond cutting wheel along scribe grids or singulation lines that were formed on the wafer between the individual die. To allow for the alignment and the width of the dicing wheel each scribe grid usually had a large width, generally about one hundred fifty (150) microns, which consumed a large portion of the semiconductor wafer. Additionally, the time required to scribe each singulation line on the semiconductor wafer could take over one hour or more. This time reduced the throughput and manufacturing capacity of a production facility. 
     Other methods, which have included thermal laser separation (TLS), laser ablation dicing, and plasma dicing, have been explored as alternatives to scribing. Plasma dicing is a promising process compared to scribing and other alternative processes because it supports narrower scribe lines, has increased throughput, and can singulate die in varied and flexible patterns. However, plasma dicing has had manufacturing implementation challenges. Such challenges have included non-compatibility with wafer backside layers, such as back metal layers, because the etch process has been unable to effectively remove or separate the backside layers from the singulation lines. Removing or separating the backside layers from the scribe lines is necessary to facilitate subsequent processing, such as pick-and-place and assembly processes. 
     Accordingly, it is desirable to have a method of singulating die from a semiconductor wafer that removes or separates the backside layers from within the singulation lines. It would be beneficial for the method to be cost effective and to minimize any damage to or contamination of the separated die. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a reduced plan view of an embodiment of a wafer in accordance with the present invention; 
         FIGS. 2-5  illustrate partial cross-sectional views of an embodiment of a the wafer of  FIG. 1  at various stages in a process of singulating die from the wafer in accordance with an embodiment of the present invention; 
         FIG. 6  illustrates a cross-sectional view of the wafer of  FIG. 1  at a stage of processing within an apparatus in accordance with another embodiment of the present invention; 
         FIG. 7  illustrates a partial cross-sectional view of an embodiment of the wafer of  FIG. 5  or  FIG. 6  at a later stage of processing in accordance with an embodiment of the present invention; 
         FIG. 8  illustrates a cross-sectional view of a wafer in accordance with a second embodiment of the present invention; 
         FIG. 9  illustrates a top view of the second embodiment after subsequent processing in accordance with the present invention; 
         FIG. 10  illustrates a cross-sectional view of the second embodiment after subsequent processing in accordance with the present invention; 
         FIG. 11  illustrates a cross-sectional view of the second embodiment after additional processing in accordance with the present invention; 
         FIG. 12  illustrates a cross-sectional view of the second embodiment after further processing in accordance with the present invention; 
         FIG. 13  illustrates a cross-sectional view of the second embodiment at a later stage of fabrication in accordance with the present invention; 
         FIG. 14  illustrates a cross-sectional view of the second embodiment in accordance with an alternative manufacturing process; 
         FIG. 15  illustrates the wafer of  FIG. 10  in accordance with an additional embodiment of the present invention; 
         FIG. 16  illustrates a cross-sectional view of the additional embodiment after further processing in accordance with the present invention; 
         FIG. 17  illustrates a cross-sectional view of the additional embodiment at a later stage of fabrication in accordance with the present invention; and 
         FIG. 18  illustrates a flowchart of a process for singulating back layer material in accordance with a further embodiment of the present invention. 
     
    
    
     For simplicity and clarity of the illustration, elements in the figures are not necessarily drawn to scale, and the same reference numbers in different figures denote the same elements. Additionally, descriptions and details of well-known steps and elements are omitted for simplicity of the description. For clarity of the drawings, certain regions of device structures, such as doped regions or dielectric regions, may be illustrated as having generally straight line edges and precise angular corners. However, those skilled in the art understand that, due to the diffusion and activation of dopants or formation of layers, the edges of such regions generally may not be straight lines and that the corners may not be precise angles. Furthermore, the term “major surface” when used in conjunction with a semiconductor region, wafer, or substrate means the surface of the semiconductor region, wafer, or substrate that forms an interface with another material, such as a dielectric, an insulator, a conductor, or a polycrystalline semiconductor. The major surface can have a topography that changes in the x, y and z directions. 
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a reduced plan view that graphically illustrates a wafer  10  at a later step in fabrication. In one embodiment, wafer  10  can be a semiconductor substrate. Wafer  10  includes a plurality of semiconductor die, such as die  12 ,  14 ,  16 , and  18 , that are formed on or as part of semiconductor wafer  10 . Die  12 ,  14 ,  16 , and  18  are spaced apart from each other on wafer  10  by spaces in which singulation lines are to be formed or defined, such as scribe lines or singulation lines  13 ,  15 ,  17 , and  19 . As is well known in the art, all of the semiconductor die on wafer  10  generally are separated from each other on all sides by areas where scribe lines or singulation lines, such as singulation lines  13 ,  15 ,  17 , and  19  are to be formed. Die  12 ,  14 ,  16 , and  18  can be any kind of electronic device including semiconductor devices such as, diodes, transistors, discrete devices, sensor devices, optical devices, integrated circuits or other devices known to one of ordinary skill in the art. In one embodiment, wafer  10  has completed wafer processing including the formation of a backside layer described hereinafter. 
       FIG. 2  illustrates an enlarged cross-sectional view of wafer  10  at an early step in a die singulation method in accordance with a first embodiment. In one embodiment, wafer  10  is attached to a carrier substrate, transfer tape, or carrier tape  30  that facilitates supporting the plurality of die after they are singulated. Such carrier tapes are well known to those of skill in the art. In one embodiment, carrier tape  30  can be attached to a frame  40 , which can include frame portions or portions  401  and  402 . As illustrated, carrier tape  30  can be attached to surface  4010  of frame portion  401  and to surface  4020  of frame portion  402 . 
     In the cross-section illustrated, wafer  10  can include a bulk substrate  11 , such as a silicon substrate, which can include opposing major surfaces  21  and  22 . In other embodiments, bulk substrate  11  can comprise other semiconductor materials such as heterojunction semiconductor materials. In one embodiment, contact pads  24  can be formed along, in, on, or above portions of major surface  21  to provide for electrical contact between structures formed within substrate  11  and next levels of assembly or external elements. For example, contact pads  24  can be formed to receive bonding wires or clips that may be subsequently be attached to contact pads  24 , or contact pads  24  can be formed to receive a solder ball, bump or other type of attachment structure. Contact pads  24  generally can be a metal or other conductive material. Typically, a dielectric material  26  such as, a blanket deposited dielectric layer can be formed on or overlying major surface  21  to function as a passivation layer for wafer  10 . In one embodiment, dielectric material  26  can be a material that etches at a slower rate than that of substrate  11 . In one embodiment, dielectric material  26  can be a silicon oxide, silicon nitride, or polyimide when substrate  11  is silicon. 
     In one embodiment, openings can be formed in dielectric material  26  (and other dielectric layers that can be formed underneath dielectric material  26 ) to expose underlying surfaces of contact pads  24  and surfaces of substrate  11  where singulation lines  13 ,  15 ,  17 , and  19  are to be formed. In one embodiment, a patterned photoresist layer can be used for the openings using an etching process. As illustrated in  FIG. 2  and in accordance with the present embodiment, wafer  10  further includes a layer of material  28  formed on or overlying major surface  22  of wafer  10 . In one embodiment, layer  28  can be a conductive back metal layer. In one embodiment, layer  28  can be a multi-layer metal system such as, titanium/nickel/silver, titanium/nickel/silver/tungsten, chrome/nickel/gold, copper, copper alloys, gold, or other materials known to those skilled in the art. In another embodiment, layer  28  can be a wafer backside coating (WBC) film, such as a die-attach coating or film. In one embodiment, layer  28  can be formed having or provided with gaps, spaces, or channels between at least some adjacent die. In a further embodiment, the gaps are substantially aligned with corresponding spaces on the opposite side of wafer  10  where singulation lines  13 ,  15 ,  17 ,  19  will be formed. In another embodiment, layer  28  is separated from edges of least some of the die. 
       FIG. 3  illustrates an enlarged cross-sectional view of wafer  10  at a subsequent step during a singulation process. In  FIG. 3 , a plasma or dry etch singulation process is illustrated. It is understood that other singulation processes can be used. In one embodiment, wafer  10  can be mounted on carrier tape or film  30  and then can be placed within an etch apparatus  300 , such as a plasma etch apparatus. In one embodiment, substrate  11  can be etched through the openings to form or define singulation lines or openings  13 ,  15 ,  17 , and  19  extending from major surface  21 . The etching process can be performed using a chemistry (generally represented as arrows  31 ) that selectively etches silicon at a much higher rate than that of dielectrics and/or metals. In one embodiment, wafer  10  can be etched using a process commonly referred to as the Bosch process. In one embodiment, wafer  10  can be etched using the Bosch process in a deep reactive ion etch system. In one embodiment, the width of singulation lines  13 ,  15 ,  17 , and  19  can be from about five microns to about twenty microns. Such a width is sufficient to ensure that the openings that form singulation lines  13 ,  15 ,  17 , and  19  can be formed completely through substrate  11  stopping proximate to or on layer  28  because of the etch selectivity as generally illustrated in  FIG. 4 . In one embodiment, layer  28  can be used as a stop layer for the plasma etch singulation process. In one embodiment, singulation lines  13 ,  15 ,  17 , and  19  can be formed in about five to about thirty minutes using the Bosch process. 
       FIG. 5  illustrates a cross-sectional view of wafer  10  at a subsequent process step. In one embodiment, frame  40  can be placed onto a holding device  63  or support structure  63 . In one embodiment, support structure  63  can include pedestal(s) or standoff(s)  631  that is configured to provide a gap  632 , depression  632 , or well  632  or another structure that allows wafer  10  and tape  30  to expand without contacting support structure  63  during subsequent processing. In one embodiment, frame  40  can be reversibly attached to support structure  63  using vacuum or a clamping structure. 
     In one embodiment, layer  28  is separated by a mechanical device  61 , such as a stylus  610  or a rotating wheel  620  as illustrated in  FIG. 5 . In one embodiment, surface  21  is free floating (i.e., well  632  is an air gap) as illustrated in  FIG. 5 . In another embodiment, surface  21  can be in contact with a flexible support structure such as polyimide or any number of flexible polymers. In one embodiment, mechanical device  61  is configured to provide a reduced area or localized pressure point  623  onto wafer  10 . In one embodiment, mechanical device  61  can be configured to have a radius that is approximately half the width of die  12 ,  14 ,  16 , and  19 . In another embodiment, mechanical device  61  can be configured to have a radius that is approximately equal to a width of die  12 ,  14 ,  16 , and  19 . In one embodiment, the radius of mechanical device  61  can be selected to be approximately double the size of die  12 ,  14 ,  16 , and  19  or greater. Mechanical device  61  can be configured with pressure, speed, and alignment control. Also, mechanical device  61  can be configured with a quick disconnect device  611  to allow for simplified removal of mechanical device  61  from a main apparatus, which improves process flexibility. Mechanical device  61  can be made of a metal, rubber, organic solid material (for example, a plastic), ceramic, composite material, combinations thereof, or other materials known to those of ordinary skill in the art. In the embodiment illustrated, rotating wheel  620  can be passed along tape  30  with sufficient pressure applied to separate layer  28  while minimizing any detrimental effects to die  12 ,  14 ,  16 , and  19 . In one embodiment, more than one mechanical device  61  can be used to separate layer  28 . 
       FIG. 6  illustrates a cross-sectional view of wafer  10  at subsequent process step as an alternative embodiment to  FIG. 5 . In one embodiment, multiple mechanical devices  71  can be formed on a plate structure  710 . Mechanical devices  71  can be similar to mechanical devices  61 . In one embodiment, mechanical devices  71  can be styluses configured to provide localized pressure points onto wafer  10 . In one embodiment, plate structure  710  can be placed against tape  30  with sufficient pressure applied to separate layer  28 . In one embodiment, plate structure  710  can rotate as illustrated by arrow  712 . In another embodiment, frame  40  can be rotated over plate structure  710  as illustrated by arrow  714  or moved horizontally back-and-forth over plate structure  710  as illustrated by arrows  716  and  718  to separate layer  28 . In a subsequent step, die  12 ,  14 ,  16 , and  18  can be removed from carrier tape  30  as part of a further assembly process using, for example, a pick-and-place apparatus  81  as generally illustrated in  FIG. 7 . In one embodiment, carrier tape  30  can be exposed to a UV light source prior to the pick-and-place step to reduce the adhesiveness of the tape. 
       FIG. 8  illustrates a partial cross-sectional view of a wafer  100  in accordance with a second embodiment. In one embodiment, substrate  100  can be a semiconductor wafer similar to semiconductor wafer  10 , and can have a plurality of die or semiconductor die  12 ,  14 ,  16 , and  18 . Die  12 ,  14 ,  16 , and  18  are spaced apart from each other on substrate  100  by spaces in which singulation lines are to be formed or defined, such as scribe lines or singulation lines  13 ,  15 ,  17 , and  19 . Die  12 ,  14 ,  16 , and  18  can be any kind of electronic device including semiconductor devices such as, diodes, transistors, discrete devices, sensor devices, optical devices, integrated circuits or other devices known to one of ordinary skill in the art. 
     In one embodiment, wafer  100  has completed wafer processing including the formation of a backside layer  281 . In one embodiment, backside layer  281  is a continuous film. The method in accordance with the present embodiment is configured for processing wafers having thicker layers or materials on the backside of wafer  100 . It was found in some wafers with thicker backside materials that the cracks that form during the separation process can undesirably propagate or wander into the active areas of the die, which can lead to device failures. In one embodiment, layer  281  can be a wafer backside coating or WBC formed using, for example stencil, screen printing, and/or spin coating techniques. By way of example, the WBC can be a die attach adhesive material having a thickness from about 5 microns to about 50 microns. In one embodiment, the WBC can be a die attach adhesive material having a thickness of about 20 microns. Layer  281  can be configured to facilitate the attachment of die  12 ,  14 ,  16 , and  18  to a next level of assembly, such as a leadframe or a printed circuit board. In another embodiment, layer  281  can be a back metal layer having a thickness greater than about 2 microns or 3 microns. In one embodiment, layer  281  can be a titanium/nickel/gold/tin (Ti/Ni/Au/Sn) back metal structure having a thickness greater than about 3 microns. As those skilled in the art appreciate, whether the present embodiment is used can depend on not only thickness of the materials present, but also the kinds materials present. In one embodiment, layer  281  can be formed having or provided with gaps, spaces, or channels between at least some adjacent die. In a further embodiment, the gaps are substantially aligned with corresponding spaces on the opposite side of wafer  10  where singulation lines  13 ,  15 ,  17 ,  19  will be formed. In another embodiment, layer  281  is separated from edges of least some of the die. 
       FIG. 9  illustrates a top view of wafer  100  after subsequent processing in which singulation lines or openings  13 ,  15 ,  17 , and  19  are formed. In one embodiment, wafer  100  can be mounted on carrier tape  30  with layer  281  against carrier tape  30 . In one embodiment, carrier tape  30  is mounted to frame  40 . Wafer  100  can then be placed into the etch apparatus as described in  FIG. 3  to form or define singulation lines  13 ,  15 ,  17 , and  19 .  FIG. 10  illustrates a cross-sectional view of wafer  100  after singulation lines  13 ,  15 ,  17  and  19  are defined. In one embodiment, singulation lines  13 ,  15 ,  17  and  19  end or terminate adjacent or proximate to or stop on layer  281 . 
       FIG. 11  illustrates a cross-sectional view of wafer  100  after additional processing. In one embodiment, a carrier film or substrate  310  is placed overlying the front surface or the surface opposite to layer  281 . In one embodiment, carrier film  310  can be a carrier tape with characteristics similar to carrier tape  30 , a carrier tape with lighter adhesive compared to carrier tape  30 , a protective film, or other materials as known to those of ordinary skill in the art. In one embodiment, carrier film  310  overlaps onto carrier  40  as illustrated in  FIG. 11 . Carrier tape  30  can be removed to expose layer  281 . In an optional step, a mechanical tool  365 , such as a scribe can be used to form scribe lines  267 , which are generally aligned with singulation lines  13 ,  15 ,  17 , and  19 . 
       FIG. 12  illustrates a cross-sectional view of wafer  100  at a subsequent process step. In one embodiment, frame  40  can be placed onto a holding device  63  or support structure  63 . In one embodiment, support structure  63  can include pedestal(s) or standoff(s)  631  that is configured to provide a gap  632 , depression  632 , or well  632  or another structure that allows wafer  100  and film  310  to expand without contacting support structure  63  during subsequent processing. In one embodiment, frame  40  can be reversibly attached to support structure  63  using vacuum or a clamping structure. 
     In one embodiment, layer  281  is separated by a mechanical device  61 , such as a stylus  610  or a rotating wheel  620  as illustrated in  FIG. 12 . In one embodiment, layer  281  is free floating as illustrated in  FIG. 12 . In another embodiment, surface  281  can be in contact with a flexible support structure such as polyimide or any number of flexible polymers. In one embodiment, mechanical device  61  is configured to provide a reduced area or localized pressure point  623  onto wafer  10 . In one embodiment, mechanical device  61  can be configured to have a radius that is approximately half the width of die  12 ,  14 ,  16 , and  19 . In another embodiment, mechanical device  61  can be configured to have a radius that is approximately equal to a width of die  12 ,  14 ,  16 , and  19 . In one embodiment, the radius of mechanical device  61  can be selected to be approximately double the size of die  12 ,  14 ,  16 , and  19 . Mechanical device  61  can be configured with pressure, speed, and alignment control. Also, mechanical device  61  can be configured with a quick disconnect device  611  to allow for simplified removal of mechanical device  61  from a main apparatus, which improves process flexibility. Mechanical device  61  can be made of a metal, rubber, organic solid material (for example, a plastic), ceramic, composite material, or combinations thereof. In the embodiment illustrated, rotating wheel  620  can be passed along tape  301  with sufficient pressure applied to separate layer  281  while minimizing any detrimental effects to die  12 ,  14 ,  16 , and  19 . In one embodiment, more than one mechanical device  61  can be used to separate layer  281 . 
       FIG. 13  illustrates a cross-sectional view of wafer  100  at a subsequent fabrication step. In one embodiment, a carrier tape  320  is placed on the back surface or the surface adjacent layer  281  and carrier film  310  can be removed from the opposite side. In one embodiment, carrier tape  320  overlaps onto frame  40 . In one embodiment, frame  40  with carrier tape  320  and wafer  100  can be placed within a mechanical device that helps spread-out or expand carrier tape  320  to better facilitate, for example, a pick and place step. In one embodiment, frame  40  can be placed between clamp portions  816  and  818  as generally illustrated in  FIG. 13 . In one embodiment, step or stand-off portions  821  can be placed or attached onto clamp portions  818  to provide a structure for expanding or stretching carrier tape  320 . This expansion effect can increase the distance between adjacent die on wafer  100  to better facilitate the removal of the individual die from carrier tape  320 . In one embodiment, carrier tape  320  can be exposed to UV light to reduce the adhesive characteristics of the tape to make removal of the die easier. 
       FIG. 14  illustrates a cross-sectional and perspective view of wafer  100  at subsequent process step as an alternative embodiment to  FIG. 12 . In one embodiment, multiple mechanical devices  71  can be formed on a plate structure  710 . Mechanical devices  71  can be similar to mechanical devices  61 . In one embodiment, mechanical devices  71  can be styluses configured to provide localized pressure points onto wafer  100 . In one embodiment, plate structure  710  can be placed against film  310  with sufficient pressure applied to separate layer  281 . In one embodiment, plate structure  710  can rotate as illustrated by arrow  712 . In another embodiment, frame  40  can be rotated over plate structure  710  as illustrated by arrow  714  or moved horizontally back-and-forth over plate structure  710  as illustrated by arrows  716  and  718  to separate layer  281 . In a subsequent step, die  12 ,  14 ,  16 , and  18  can be removed from the carrier tape as part of a further assembly process using, for example, the method described and generally illustrated in  FIG. 13 . In one embodiment, the carrier tape can be exposed to a UV light source prior to the pick-and-place step to reduce the adhesiveness of the tape. It is understood that prior to pick and place an additional carrier tape can be placed adjacent layer  281  and carrier film  310  can be removed. 
       FIG. 15  illustrates a cross-sectional view of wafer  100  as an alternative embodiment after processing described in conjunction with  FIG. 10 . In one embodiment, carrier film  310  is placed overlying the front surface or the surface opposite to layer  281 . In one embodiment, carrier film  310  overlaps onto carrier  40  as illustrated in  FIG. 15 . In the present embodiment, carrier tape  30  is left in place for additional processing. It should be noted that  FIG. 15  represents an idealized image and that carrier film  310  and carrier tape  30  may come into contact with each other; optionally an additional release layer (not shown) may be added between carrier film  310  and carrier tape  30 . 
       FIG. 16  illustrates a cross-sectional view of wafer  100  at a subsequent process step. In one embodiment, frame  40  can be placed onto a holding device  731  or support structure  731 . In one embodiment, support structure  731  can be configured to include a gap  732 , depression  732 , or well  732  or another structure that allows wafer  100  and tape  30  to expand without contacting support structure  731  during subsequent processing. Support structure  731  may be heated or cooled to heat or cool layer  30 . Support structure  731  may have adjustable vacuum or air pressure against layer  30 . In one embodiment, frame  40  can be reversibly attached to support structure  731  using vacuum or a clamping structure. In an optional embodiment, a compressive layer  733  can be placed within well  732  to provide additional elastic, resistive, or reactive force during the singulation of layer  281 . In one embodiment, compressive layer  733  can be a rubber pad or a pressurized membrane structure. 
     In one embodiment, layer  281  is separated by mechanical device  81 , such as a stylus  810  as illustrated in  FIG. 16 , which is applied to the front side of wafer  100  through film  310 . In accordance with the present embodiment, the singulation of layer  281  is carried out with wafer  100  placed between tape  30  and film  310 . Mechanical device  81  is configured to provide a mechanical force along the front side of wafer  100  sufficient to propagate separation lines or cracks within singulation lines  13 ,  15 ,  17 , and  19 . In one embodiment, mechanical device  81  is configured to provide a reduced area or localized pressure point  823  onto wafer  100 . In one embodiment, stylus  810  can be configured to have a radius that is approximately half the width of die  12 ,  14 ,  16 , and  18 . In another embodiment, stylus  810  can be configured to have a radius that is approximately equal to a width of die  12 ,  14 ,  16 , and  18 . In one embodiment, the radius of stylus  810  can be selected to be approximately double the size or greater of die  12 ,  14 ,  16 , and  18 . Mechanical device  81  can be configured with pressure, speed, and alignment control. Also, mechanical device  81  can be configured with a quick disconnect device  811  to allow for simplified removal of mechanical device  81  from a main apparatus, which improves process flexibility. Mechanical device  81  can be made of a metal, rubber, organic solid material (for example, a plastic), ceramic, composite material, combinations thereof, or other materials as known to those of ordinary skill in the art. In one embodiment, more than one mechanical device  81  can be used to separate layer  281 . 
       FIG. 17  illustrates a cross-sectional view of wafer  100  at a subsequent fabrication step. In one embodiment, carrier film  310  can be removed from the front side of wafer  100  leaving carrier tape  30  in place. In one embodiment, frame  40  with carrier tape  30  and wafer  100  can be placed into a mechanical device that helps spread-out or expand carrier tape  30  to better facilitate, for example a pick and place step. In one embodiment, frame  40  can be placed between clamp portions  816  and  818  as generally illustrated in  FIG. 17 . In one embodiment, step or stand-off portions  821  can be placed or attached onto clamp portions  818  to provide a structure for expanding or stretching carrier tape  320 . This expansion effect can increase the distance between adjacent die on wafer  100  to better facilitate the removal of the individual die from carrier tape  30 . In one embodiment, carrier tape  30  can be exposed to UV light to reduce the adhesive characteristics of the tape to make removal of the die easier. 
       FIG. 18  illustrates a flow chart for singulating thick backside material in accordance with another embodiment.  FIG. 18  will be described using wafer  100  embodiment starting at  FIG. 10  after wafer  100  has been singulated. It is understood that such singulation can be by any method where the singulation terminates proximate to backside layer  281 . In step  1300  carrier film  310  is applied or attached to the front side of wafer  100  with carrier tape  30  adjacent to layer  281 . In the present embodiment, carrier film  310  can be selected to have a higher adhesive strength between carrier film  310  and wafer  100  compared to the adhesive strength between carrier tape  30  and wafer  100 . In one embodiment, the difference in adhesive strengths can be selected to better maintain the die in place while carrier tape  30  is subsequently removed after layer  281  is singulated or separated. Carrier tape  30  is selected to have an adhesive strength sufficient to remove material from the singulation lines without pulling the die away from carrier film  310  or damaging the remaining layer  281  material on the individual die. 
     In optional step  1301 , a localized pressure is applied to at least one side of wafer  100  to initiate cracks, crack lines, or separation lines in layer  281  within the singulation lines. In one embodiment, stylus  611  can be used. In another embodiment, a pressurized liquid or gas can be used. In one embodiment, the localized pressure can be applied the front side of wafer  100 . In another embodiment, the localized pressure can be applied to the backside of wafer  100 . In a further embodiment, the localized pressure can be applied to both sides of wafer  100 . 
     In step  1302 , carrier tape  30  can be optionally exposed to a UV light source and then removed from wafer  100 . In one embodiment, the removal of carrier tape  30  during step  1302  removes material from singulation lines  13 ,  15 ,  17 , and  19 , which is facilitated by the differences in adhesive strengths between carrier film  310  and carrier tape  30 . In one embodiment, the removal of the material can be facilitated without having to stretch the carrier tape or use the stylus to separate the back metal or back layer, although removal of the metal will require less adhesive force if separated by the stylus prior to the removal of carrier tape  30 . 
     In step  1303 , a new carrier tape can be applied to the backside of wafer  100 , and then carrier film  310  can be removed from the front side of wafer  100  in step  1304 . Wafer  100  can then be subjected to further processing. 
     It was found that the present embodiments produce improved results compared to methods using carrier tapes on one side of the wafer only. In accordance with the present embodiment, carrier tape layers are placed on both sides of the wafer during the singulation of the backside material. The present embodiment improves the quality of the singulated backside material and reduces yield loss due to singulation lines propagating into die active areas. 
     From all of the foregoing, one skilled in the art can determine that, according to one embodiment, a method of singulating a wafer (for example, elements  10 ,  100 ) comprises providing a wafer having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the wafer and separated from each other by spaces, wherein the wafer has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed along the second major surface. The method includes placing the wafer onto a first carrier substrate (for example, element  30 ), wherein the layer of material is adjacent the first carrier substrate. The method includes singulating the wafer through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein singulating includes stopping in proximity to the layer of material. The method includes applying a localized pressure (for example, element  61 ,  71 ,  710 ,  81 ) to at least one of the first major surface or the second major surface to separate the layer of material in the singulation lines. 
     From all of the foregoing, one skilled in the art can determine that, according to another embodiment, a method of singulating die from a wafer (for example, elements  10 ,  100 ) comprises providing a wafer having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the wafer and separated from each other by spaces, wherein the wafer has first and second opposing major surfaces (for example, elements  21 ,  22 ) and wherein a layer of material (for example, elements  28 ,  281 ) is formed along the second major surface. The method includes placing the wafer onto a first carrier substrate (for example, element  30 ), wherein the layer of material is adjacent the first carrier substrate; singulating the wafer through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein the singulation lines terminate before penetrating completely through the layer of material. The method includes placing the wafer onto to a second carrier substrate (for example, element  310 ), wherein the layer of material is opposite to the second carrier substrate. The method includes moving a mechanical device along the second carrier substrate to separate the layer of material in the singulation lines. 
     In one embodiment of the foregoing method, placing the wafer onto the first carrier substrate can include placing the wafer onto a first carrier tape, and placing the wafer onto the second carrier substrate can include placing the wafer onto a second carrier tape. In another embodiment, moving the mechanical device can include moving at least one stylus. In an additional embodiment, providing the wafer can include providing a semiconductor wafer having a wafer backside coating layer overlying the second major surface. In a further embodiment, singulating the wafer can include plasma etching the wafer. 
     From all of the foregoing, one skilled in the art can determine that, according to an additional embodiment, a method of singulating a substrate (for example, elements  10 ,  100 ) comprises providing a substrate having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the substrate and separated from each other by spaces, wherein the substrate has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed overlying the second major surface. The method includes placing a carrier tape (for example, element  30 ) onto the layer of material. The method includes plasma etching the substrate through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein the singulation lines terminate in proximity to the layer of material. The method includes placing a carrier film (for example, element  310 ) onto the substrate opposite to the layer of material. The method includes applying a localized pressure to the first major surface using a mechanical device to separate the layer of material. 
     In one embodiment of the foregoing method, applying a localized pressure can include applying a localized pressure with at least one stylus. In another embodiment providing the substrate includes providing a semiconductor wafer having a wafer backside coating layer formed overlying the second major surface. 
     From all of the foregoing, one skilled in the art can determine that, according to further embodiment, a method of forming an electronic device comprises providing a wafer (for example, elements  10 ,  100 ) having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the wafer and separated from each other by spaces, wherein the wafer has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed along the second major surface, and wherein the layer of material is placed on a first carrier substrate. The method includes singulating the wafer through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ). The method includes placing the wafer onto a second carrier substrate (for example, element  310 ), wherein the layer of material is opposite to the second carrier substrate. The method includes moving a mechanical device along one of the first or second carrier substrates to separate the layer of material in the singulation lines. 
     In one embodiment of the foregoing method, placing the wafer onto the first carrier substrate can include placing the wafer onto a first carrier tape, and placing the wafer onto the second carrier substrate can include placing the wafer onto a second carrier tape. In another embodiment, moving the mechanical device can include moving the mechanical device with both the first carrier substrate and the second carrier substrate attached to the wafer. In an additional embodiment, moving the mechanical device can include moving at least one carrier substrate. In a further embodiment, moving the mechanical device can include moving at least one stylus along the second carrier substrate. In a still further embodiment, moving the mechanical device can include moving the mechanical device while the first carrier tape is placed against a compressive layer. In another embodiment, placing the wafer onto the second carrier substrate can include placing the wafer onto the second carrier substrate, wherein the second carrier substrate has a higher adhesive strength than the first carrier substrate. In an additional embodiment, one or more of the foregoing methods can further include removing the first carrier substrate after moving the mechanical device, wherein removing the first carrier substrate removes portions of the layer of material in the singulation lines. In one embodiment, removing the first carrier substrate can include removing the first carrier substrate without stretching either the first or the second carrier tapes before the first carrier tape is removed. 
     From all of the foregoing, one skilled in the art can determine that, according to a still further embodiment, an apparatus for separating die (for example, elements  12 ,  14 ,  16 ,  18 ) from a wafer (for example, elements  10 ,  100 ) comprises a structure for holding the wafer on a carrier substrate, wherein the semiconductor wafer has a plurality of singulation lines that terminate proximate to a layer of material on the wafer; and a structure for applying a localized pressure (for example, elements  61 ,  71 ,  81 ) to the wafer through the carrier substrate. 
     In one embodiment of the foregoing apparatus the semiconductor wafer has a plurality of singulation lines etched through the semiconductor wafer. In another embodiment, the singulation lines are plasma etched through the semiconductor wafer. In an additional embodiment, the structure for applying the localized pressure can be configured to move in relation to the wafer. In a further embodiment, the structure for applying the localized pressure can be configured to rotate. In a still further embodiment, the structure for applying the localized pressure comprises more than one stylus. In one embodiment, the structure for holding can include a compressive layer (for example, element  733 ). In another embodiment, the compressive layer comprises a pressurized membrane structure. 
     From all of the foregoing, one skilled in the art can determine that, according to another embodiment, a method of singulating a substrate comprises providing a substrate (for example, elements  10 ,  100 ) having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the substrate and separated from each other by spaces, wherein the substrate has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed overlying the second major surface. The method includes placing a carrier tape (for example, element  30 ) onto the layer of material. The method includes plasma etching the substrate through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein the singulation lines terminate in proximity to the layer of material. The method includes applying a localized pressure to the second major surface using a mechanical device (for example, elements  61 ,  71 ,  81 ) to separate the layer of material. 
     From all of the foregoing, one skilled in the art can determine that, according to an additional embodiment, a method of singulating a substrate comprises providing a substrate (for example, elements  10 ,  100 ) having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the substrate and separated from each other by spaces, wherein the substrate has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed overlying the second major surface. The method includes placing a first carrier tape (for example, element  30 ) onto the layer of material. The method includes plasma etching the substrate through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein the singulation lines terminate in proximity to the layer of material. The method includes placing a second carrier tape (for example, element  310 ) onto the substrate opposite to the layer of material; and removing the first carrier tape to separate the layer of material in singulation lines. 
     From all of the foregoing, one skilled in the art can determine that, according to further embodiment, a method of singulating a substrate comprises providing a substrate (for example, elements  10 ,  100 ) having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the substrate and separated from each other by spaces, wherein the substrate has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed overlying the second major surface. The method includes placing a first carrier tape (for example, element  30 ) onto the layer of material. The method includes plasma etching the substrate through the spaces to form singulation lines (for example, elements  13 ,  15 ,  17 ,  19 ), wherein the singulation lines terminate in proximity to the layer of material. The method includes placing a second carrier tape (for example, element  310 ) onto the substrate opposite to the layer of material. The method includes applying a localized pressure to one major surface of the substrate using a mechanical device (for example,  61 ,  71 ,  81 ) to separate the layer of material in the singulation lines while substrate is attached to both the first and second carrier tapes. 
     From all of the foregoing, one skilled in the art can determine that, according to a still further embodiment, a method of singulating a substrate comprises providing a substrate (for example, elements  10 ,  100 ) having a plurality of die (for example, elements  12 ,  14 ,  16 ,  18 ) formed on the substrate and separated from each other by spaces, wherein the substrate has first and second opposing major surfaces (for example, elements  21 ,  22 ), and wherein a layer of material (for example, elements  28 ,  281 ) is formed overlying the second major surface. The method includes placing a first carrier tape (for example, element  30 ) onto the layer of material. The method includes plasma etching the substrate through the spaces to form singulation lines, wherein the singulation lines terminate in proximity to the layer of material. The method includes placing a second carrier tape (for example, element  310 ) onto the substrate opposite to the layer of material. The method includes removing the first carrier tape to separate the layer of material in singulation lines. 
     In view of all of the above, it is evident that a novel method and apparatus are disclosed. Included, among other features, is placing a substrate having a layer of material on a major surface of the substrate onto a carrier tape, and forming singulation lines through the substrate to expose portions of the layer of material within the singulation lines. A second carrier tape is applied to the front side of the substrate, and a mechanical device that provides a localized pressure to the front side of the substrate is used to separate the layer of material from the back side of the substrate while the substrate has carrier tape layers on both sides. The method provides, among other things, an efficient, reliable, and cost effective process for singulating substrates that include back layers, such as thicker back metal layers or WBC layers. 
     While the subject matter of the invention is described with specific preferred embodiments and example embodiments, the foregoing drawings and descriptions thereof depict only typical embodiments of the subject matter, and are not therefore to be considered limiting of its scope. It is evident that many alternatives and variations will be apparent to those skilled in the art. For example, other forms of removable support materials can be used instead of carrier tapes. 
     As the claims hereinafter reflect, inventive aspects may lie in less than all features of a single foregoing disclosed embodiment. Thus, the hereinafter expressed claims are hereby expressly incorporated into this Detailed Description of the Drawings, with each claim standing on its own as a separate embodiment of the invention. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and meant to form different embodiments as would be understood by those skilled in the art.