Abstract:
A method for handling and supporting a device wafer during a wafer thinning process and the resulting device are provided. Embodiments include forming a plurality of solder bumps on a first surface of a substrate having a first and a second surface; removing a portion from a periphery of the first surface of the substrate; forming a temporary bonding material on a first carrier; bonding the first surface of the substrate with the temporary bonding material of the first carrier; affixing the second surface of the substrate to a second carrier; and removing the temporary bonding material.

Description:
TECHNICAL FIELD 
     The present disclosure relates to handling of a device wafer, e.g., a complementary metal-oxide-semiconductor (CMOS) wafer, and more particularly to a wafer support system for 3D packaging. 
     BACKGROUND 
     Handling and supporting device wafers during a wafer thinning process poses a challenge. A known approach for handling device wafers during the thinning process involves seven steps: 1) trimming; 2) coating; 3) bonding; 4) thinning; 5) treating; 6) affixing; and 7) debonding, as illustrated in  FIGS. 1A through 1G , respectively. During the trimming step ( FIG. 1A ), a portion from a periphery of a first surface of a device wafer  101 , having a plurality of solder bumps  103 , is removed. The device wafer  101  is then coated with a bonding material  105 , e.g. a glue material, and a carrier  107  is treated at  109  to allow bonding only around an outer edge, as shown in  FIG. 1B . Next, the device wafer  101  is bonded to the carrier  107 , as illustrated in  FIG. 1C . Then, as illustrated in  FIG. 1D , a second surface of the device wafer  101  is thinned. Once the desired thickness of the device wafer  101  is reached, a chemical edge treatment is performed on the bonding material  105 , as illustrated at element  105 ′ in  FIG. 1E . Next, the second surface of the device wafer  101  is affixed to a film frame or other substrate  111  and the device wafer  101  is separated from the carrier  107 , as shown in  FIG. 1F . Thereafter, the bonding material  105  and  105 ′ is removed from the device wafer  101  as illustrated in  FIG. 1G . However the bonding material  105 / 105  may cause contamination of the wafer  101 , and cleaning the bonding material  105 / 105 ′ from the front side of the device wafer  101 , for example after the wafer  101  is on the film frame  111 , is required. 
     Another known approach (not shown for illustrative convenience) involves creating separate zones, e.g., stiction/non-stiction, to prevent bonding of a full wafer, e.g., a 300 millimeter (mm) wafer, to a carrier wafer. However, this approach causes additional processing complexities and also requires cleaning of the front side of the thin wafer after the wafer is transferred to the film frame. 
     A need therefore exists for methodology for handling and supporting a device wafer during wafer thinning without a need for special treatment of the carrier and extra cleaning of the device wafer and without bonding material causing the front side of the wafer to become contaminated, and the resulting device. 
     SUMMARY 
     An aspect of the present disclosure is a method of handling and supporting a device wafer during a wafer thinning process. 
     Another aspect of the present disclosure is a device including a bumped device wafer attached to a film frame. 
     Additional aspects and other features of the present disclosure will be set forth in the description which follows and in part will be apparent to those having ordinary skill in the art upon examination of the following or may be learned from the practice of the present disclosure. The advantages of the present disclosure may be realized and obtained as particularly pointed out in the appended claims. 
     According to the present disclosure, some technical effects may be achieved in part by a method of fabricating a semiconductor device, the method including: forming a plurality of solder bumps on a first surface of a substrate having a first and a second surface; removing a portion from a periphery of the first surface of the substrate; forming a temporary bonding material on a first carrier; bonding the first surface of the substrate with the temporary bonding material of the first carrier; affixing the second surface of the substrate to a second carrier; and removing the temporary bonding material. 
     Aspects of the present disclosure include forming the plurality of solder bumps by: forming a bump metallization pad on the first surface of the substrate; forming a photoresist template with a plurality of openings on top of the bump metallization pad; and forming a solder bump on the bump metallization pad at each of the openings of the photoresist template. Further aspects include removing the periphery of the first surface of the substrate by: mechanical dicing. Another aspect includes, removing 50 μm to 500 μm of depth and 0.5 mm to 10 mm of width of the periphery of the first surface of the substrate. Other aspects include forming the temporary bonding material only on a circumference of the first carrier. Additional aspects include forming the temporary bonding material from a thermoplastic or a temporary glue material. Further aspects include the first carrier being flat, and forming the temporary bonding material to a thickness of 100 μm to 600 μm. Another aspect includes the first carrier being recessed, and forming the temporary bonding material to a thickness of 5 μm to 50 μm. Other aspects include bonding the first surface of the substrate to the temporary bonding material of the first carrier only at the circumference. Additional aspects include removing a portion of the second surface of the substrate prior to affixing the second surface of the substrate to the second carrier. Further aspects include removing the portion of the second surface of the substrate by: mechanical grinding. Another aspect includes removing exposed temporary bonding material. Other aspects include affixing the second surface of the substrate to the second carrier with dicing tap. Additional aspects include removing the photoresist template and exposed bump metallization by: laser ablation, chemical etch and/or thermal process. 
     Another aspect of the present disclosure is a device including: a substrate having a first surface and a second surface; a bump metallization pad on the first surface of the substrate; a plurality of solder bumps on the bump metallization pad; and a tape frame attached to the second surface of the substrate. Aspects of the device include the tape frame being attached to the second surface of the substrate with dicing tape. 
     Another aspect of the present disclosure is a method including: removing a portion from periphery of first surface of a substrate by mechanical dicing; forming a plurality of bump metallization pads on the first surface of the substrate; forming a solder bump on each of the bump metallization pads; forming a temporary bonding material only on a circumference of a carrier; bonding the first surface of the substrate with the temporary bonding material only at the circumstance of the first carrier; thinning a second surface of the substrate by mechanical grinding; affixing the thinned second surface of the substrate to a tape frame; removing the temporary bonding material; and removing the photoresist template and exposed bump metallization material. 
     Additional aspects and technical effects of the present disclosure will become readily apparent to those skilled in the art from the following detailed description wherein embodiments of the present disclosure are described simply by way of illustration of the best mode contemplated to carry out the present disclosure. As will be realized, the present disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects, all without departing from the present disclosure. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawing and in which like reference numerals refer to similar elements and in which: 
         FIGS. 1A through 1G  schematically illustrate sequential steps of a background method of handling and supporting a device wafer during wafer thinning; and 
         FIGS. 2A through 2G  schematically illustrate sequential steps of a method of handling and supporting a device wafer during a wafer thinning process, in accordance with an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of exemplary embodiments. It should be apparent, however, that exemplary embodiments may be practiced without these specific details or with an equivalent arrangement. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring exemplary embodiments. In addition, unless otherwise indicated, all numbers expressing quantities, ratios, and numerical properties of ingredients, reaction conditions, and so forth used in the specification and claims are to be understood as being modified in all instances by the term “about.” 
     The present disclosure addresses and solves the current problems of device wafer contamination and the need for special treatment of the carrier and extra cleaning of the device wafer attendant upon handling device wafers during thinning processes. Moreover, the present disclosure also addresses and solves the alternative problem of having to create separate zones to prevent bonding of full wafers to a wafer carrier. 
     Methodology in accordance with embodiments of the present disclosure includes forming a plurality of solder bumps on a first surface of a substrate having a first and a second surface. A portion from a periphery of the first surface of the substrate is removed along the periphery. A temporary bonding material is formed on a first carrier. The first surface of the substrate is bonded with the temporary bonding material of the first carrier. The second surface of the substrate is affixed to a second carrier. The temporary bonding material is removed from the substrate. 
     Still other aspects, features, and technical effects will be readily apparent to those skilled in this art from the following detailed description, wherein preferred embodiments are shown and described, simply by way of illustration of the best mode contemplated. The disclosure is capable of other and different embodiments, and its several details are capable of modifications in various obvious respects. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as restrictive. 
     Adverting to  FIG. 2A , a plurality of solder bumps  201 , e.g., of lead-tin, tin-silver (SnAg), or copper (Cu) pillars, are formed on a first surface of a substrate  203 , for example by electronic chemical deposition (ECD). More specifically, a bump metallization pad  205 , e.g., of titanium tungsten/copper (TiW/C), is formed on the first surface of the substrate  203 . Thereafter, a photoresist template  207  with a plurality of openings is formed on the bump metallization pad  205 . Next, a solder bump  201  is formed on the bump metallization pad  205  at each of the openings of the photoresist template  207 . 
     Once the plurality of solder bumps  201  are formed on bump metallization pad  205 , 50 μm to 500 μm of depth and 0.5 mm to 10 mm of width of the periphery of the first surface of the substrate  203  and the bump metallization pad  205  are removed by mechanical dicing, as illustrated in  FIG. 2B . Alternatively, the periphery of the first surface of substrate  203  may be removed prior to forming the plurality of solder bumps  201 . 
     Next, a temporary bonding material  209 , e.g., of a thermoplastic material or a temporary glue material, is formed on a circumference of a first carrier  211  as shown in  FIG. 2C . For a flat carrier  211 , the temporary bonding material  209  is formed to a thickness of 100 μm to 600 μm. Alternatively, if the carrier  211  is recessed, the temporary bonding material  209  is formed to a thickness of 5 μm to 50 μm. In particular, a thinner amount of temporary bonding material  209  may produce better total thickness variation (TTV) control across the substrate  203 . 
     Adverting to  FIG. 2D , the periphery of the first surface of the substrate  203  is bonded with the temporary bonding material  209  of the carrier  211 . In particular, the photoresist template  207  is intended to protect the plurality of solder bumps  201  from coming into contact with the carrier  211 . Next, a portion of the second surface of the substrate  203  is removed by mechanical grinding as illustrated in  FIG. 2E , thinning the substrate  203 . Thereafter, the second surface of the substrate  203  is affixed to a second carrier  213 , e.g., a film frame, using dicing tape (not shown for illustrative convenience) as shown in  FIG. 2F . 
     Subsequent to affixing the substrate  203  to the second carrier  213 , an edge treatment is applied to dissolve the temporary bonding material  209 . For example, the temporary bonding material  209  is removed from the first surface of the substrate  203  with room temperature, a UV release, a laser release, a chemical release, or a thermal release as illustrated in  FIG. 2G . Last, the photoresist template  205  and exposed bump metallization pad  205  is removed by laser ablation, chemical etch, and/or thermal processing. Then, conventional processing, such as dicing, stacking, wafer reconstruction, e.g. for 3D packaging, may proceed. 
     The embodiments of the present disclosure can achieve several technical effects, including not requiring special treatment and extra cleaning to be performed on the device wafer, the front of the device wafer remains contamination free, and the disclosed process is less expensive compared to the known approaches. Embodiments of the present disclosure enjoy utility in various industrial applications as, for example, microprocessors, smart phones, mobile phones, cellular handsets, set-top boxes, DVD recorders and players, automotive navigation, printers and peripherals, networking and telecom equipment, gaming systems, and digital cameras. The present disclosure enjoys industrial applicability in any of 3D wafer packaging applications, for example, packaging wafers after fabricating TSV 3D interconnects. 
     In the preceding description, the present disclosure is described with reference to specifically exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the present disclosure, as set forth in the claims. The specification and drawings are, accordingly, to be regarded as illustrative and not as restrictive. It is understood that the present disclosure is capable of using various other combinations and embodiments and is capable of any changes or modifications within the scope of the inventive concept as expressed herein.