Abstract:
A semiconductor device including a semiconductor chip having a plurality of electrodes on one surface thereof in a thickness direction, a resin layer overlapping the one chip surface to provide a rectangular mounting surface, a plurality of metal posts in the resin layer, where the metal posts are electrically connected to the electrodes, and solder terminals respectively connected to the metal posts. The resin layer has a groove formed therein at the mounting surface so as to surround an area on which the metal posts are provided. The semiconductor device is mounted on the mounting substrate with an underfill material filled in a space between the mounting surface and the mounting substrate.

Description:
[0001]    This is a Divisional of U.S. Application No. 11/798,938, filed on May 17, 2007, the subject matter of which is incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a semiconductor device, and particularly to a semiconductor device called a wafer level CSP (Chip Scale (or Size) Package). 
         [0004]    2. Description of Related Art 
         [0005]    As one form of a semiconductor device, there is one called a wafer level CSP or wireless CSP. 
         [0006]    The wafer level CSP is composed of a semiconductor chip provided with a plurality of electrodes on one surface thereof in a thickness direction, and a resin layer provided in an overlapping manner on the electrode arranged surface side of the semiconductor chip. This wafer level CSP is directly mounted on a mounting substrate without being contained in a conventional container called a package. 
         [0007]    In the resin layer, copper-made posts are embedded, and rewiring which electrically connects the posts to the electrodes of the semiconductor chip are embedded. Solder terminals are fitted to the posts, and the posts are electrically connected via the solder terminals to terminals provided in the mounting substrate. 
         [0008]    The gap between the resin layer and the mounting substrate is filled with an underfill material. Due to this underfill material, the solder terminals are sealed and the wafer level CSP is firmly mounted on the mounting substrate. 
         [0009]    However, as shown in  FIG. 8 , in some cases, a stress F caused by contraction of the underfill material  300  when it cures is applied to the resin layer  200  in contact with the underfill material  300 , the resin layer  200  separates from the semiconductor chip  100 , and disconnection occurs between the semiconductor chip  100  and the resin layer  200  or the semiconductor chip  100  itself is broken. In  FIG. 8 , the reference numeral  400  denotes the semiconductor terminal, and  500  denotes the mounting substrate. 
       SUMMARY OF THE INVENTION 
       [0010]    A semiconductor device of the present invention includes a semiconductor chip provided with a plurality of electrodes on one surface thereof in the thickness direction, and a resin layer provided in an overlapping manner on the one surface of the semiconductor chip. This semiconductor device is mounted on the mounting substrate with an underfill material filled between the mounting surface and the mounting substrate by using the surface of the resin layer as the mounting surface. In the mounting surface, a groove which divide the mounting surface into a plurality of surfaces are provided. 
         [0011]    Since the grooves are provided in the mounting surface of the resin layer, the grooves can reduce stress applied to the resin layer caused according to curing of the underfill material. Therefore, the resin layer can be prevented from separating from the semiconductor chip. As a result, disconnection between the semiconductor chip and the resin layer and breakage of the semiconductor chip itself can be prevented. 
         [0012]    In the resin layer, a plurality of metal posts to which solder terminals are respectively connected are provided, and it is preferable that the groove is provided along outer edges of the resin layer between the outer edges and the posts. In this case, even if the resin layer separates from the semiconductor chip due to a stress applied to the resin layer according to curing of the underfill material, the separation can be suppressed from spreading over the groove. Therefore, the functional parts of the semiconductor chip can be prevented from being damaged. In addition, since the underfill material enters the groove, the contact area between the resin layer and the underfill material increases, and the entering underfill material functions as an anchor, whereby the adhesion between the underfill material and the resin layer can be improved. 
         [0013]    When the mounting surface is in a rectangular shape; the grooves may be provided along four respective outer peripheral edges of the mounting surface, or may be provided along two outer peripheral edges adjacent to each other among the four outer peripheral edges of the mounting surface. In the latter case, while the number of grooves is minimized to minimize the burden of the groove formation, disconnection between the semiconductor chip and the resin layer and breakage of the semiconductor chip itself can be prevented. 
         [0014]    The grooves may be inclined at a predetermined angle with respect to the mounting surface. In this case, the stress applied to the resin layer according to curing of the underfill material can be more satisfactorily reduced. Therefore, separation of the resin layer from the semiconductor chip can be reliably prevented. As a result, disconnection between the semiconductor chip and the resin layer and breakage of the semiconductor chip itself can be reliably prevented. 
         [0015]    The groove may have a step formed by a portion grooved relatively shallowly and a portion grooved relatively deeply. In this case, the stress applied to the resin layer according to curing of the underfill material can be more satisfactorily reduced. Therefore, separation of the resin layer from the semiconductor chip can be reliably prevented. As a result, disconnection between the semiconductor chip and the resin layer and breakage of the semiconductor chip itself can be reliably prevented. 
         [0016]    The above-described and other objects, features, and effects of the present invention will be made clear from the following description of embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1(A)  is a bottom view of a semiconductor device according to an embodiment of the present invention, and  FIG. 1(B)  is a sectional view along the X-X line of  FIG. 1(A) ; 
           [0018]      FIG. 2  is a bottom view of a semiconductor device according to another embodiment; 
           [0019]      FIG. 3  is a sectional view showing a first modification example of a groove shape; 
           [0020]      FIG. 4  is a sectional view showing a second modification example of the groove shape; 
           [0021]      FIG. 5  is a sectional view showing a third modification example of the groove shape; 
           [0022]      FIG. 6  is a sectional view showing a fourth modification example of the groove shape; 
           [0023]      FIG. 7  is a sectional view showing a fifth modification example of the groove shape; and 
           [0024]      FIG. 8  is a sectional view for describing separation of a resin layer occurring in a conventional semiconductor device. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0025]    Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. 
         [0026]      FIG. 1(A)  is a bottom view of a semiconductor device according to an embodiment of the present invention.  FIG. 1(B)  is a sectional view along the section line X-X of the semiconductor device of  FIG. 1(A) . 
         [0027]    The semiconductor device A of this embodiment is composed of a semiconductor chip  10  provided with a plurality of electrodes  11  arranged on one surface  12  in the thickness direction, and a resin layer  20  provided so as to overlap the electrode arranged surface  12  provided with the electrodes  11 . 
         [0028]    In the resin layer  20 , copper-made posts  21  are embedded. In addition, in the resin layer  20 , rewiring  22  made of copper wiring for electrically connecting the posts  21  with the electrodes  11  of the semiconductor chip  10  is embedded. On the surface of the resin layer  20 , solder terminals  30  formed of solder balls connected to the respective posts  21  are arranged. 
         [0029]    The surface of the resin layer  20  is a mounting surface for mounting the semiconductor device A on a mounting substrate. In this mounting surface, grooves  23  which divide the mounting surface into a plurality of surfaces are formed. In  FIG. 1 , the grooves  23  divide the mounting surface of the resin layer  20  into nine surfaces. Herein, the mounting substrate means not only a general mounting substrate formed of a glass epoxy substrate but also a package used for hermetically sealing the semiconductor device A. 
         [0030]    By thus providing the grooves  23  in the mounting surface of the resin layer  20 , when a stress is applied to the resin layer according to curing of the underfill material, the stress can be dispersed and reduced by the grooves  23 , so that the resin layer  20  can be prevented from separating from the semiconductor chip  10 . Therefore, disconnection between the semiconductor chip  10  and the resin layer  20  due to separation of the resin layer  20  from the semiconductor chip  10  or breakage of the semiconductor chip  10  itself due to the separation can be prevented. 
         [0031]    It is desirable that, as shown in  FIG. 1(A) , the grooves  23  are provided along the outer edges  24  of the resin layer  20  in a rectangular shape in a plan view between the outer edges  24  and the posts  21 . As clearly shown in  FIG. 1(A) , the grooves  23  extend to the outer edges  24  of the resin layer  20 . 
         [0032]    By thus providing the grooves  23  as close as possible to the outer edges  24 , at the outer edge  24  portions of the resin layer  20  to which the greatest stress is applied according to curing of the underfill material, the stress can be reduced. In addition, even if the resin layer  20  separates from the semiconductor chip  10  due to the stress applied to the resin layer  20 , the resin layer  20  becomes thin and easy to bend at the groove  23  portions, so that the stress can be greatly reduced at the groove  23  portions. Therefore, spreading of the separation of the resin layer  20  into the inner side over the grooves  23  can be suppressed. As a result, disconnection between the electrodes  11  of the semiconductor chip  10  and the rewiring  22  of the resin layer  20  (damage to functional parts) can be prevented. 
         [0033]    In addition, since the underfill material enters the grooves  23 , the contact area between the resin layer  20  and the underfill material increases, and the underfill material entering the groove  23  portions functions as an anchor, whereby the adhesion between the underfill material and the resin layer  20  can be improved. 
         [0034]    The grooves  23  can be formed while the grooving depths are adjusted by using a dicing machine which is used for cutting and separating semiconductor chips from a wafer in a semiconductor chip production process. 
         [0035]    The grooves  23  may be provided on the four outer edges  24  of the resin layer  20  in a rectangular shape in a plan view, as shown in  FIG. 1(A) , or may be provided on two outer peripheral edges  24  adjacent to each other among the four outer peripheral edges  24 , as shown in  FIG. 2 . In other words, the grooves  23  may be provided along two outer peripheral edges  24  forming one corner among the four outer peripheral edges  24 . 
         [0036]    Normally, after the semiconductor device A is mounted on a mounting substrate, an underfill material is applied with a dispenser along two outer peripheral edges adjacent to each other of the semiconductor device A, and by using the surface tension, that is, the capillary phenomenon, of the underfill material, the underfill material is wet-spread between the resin layer  20  and the mounting substrate. This underfill material cures while contracting so as to be drawn to the underfill material applied portion side. At the underfill material applied portion, a sufficient amount of underfill material is present, so that a great stress does not occur when the underfill material cures. However, to the tip end of the underfill material wet-spread portion, due to a small amount of the underfill material, the greatest stress is applied. 
         [0037]    Therefore, by providing the grooves  23  along the two outer peripheral edges  24  of the resin layer  20  which become tip end sides of the wet-spreading and are adjacent to each other, the stress applied when the underfill material cures can be most effectively reduced. In addition, in comparison with the construction shown in  FIG. 1(A) , the amount of formation of the grooves  23  can be reduced by half, so that the time taken for forming the grooves  23  can be shortened by half, and the manufacturing efficiency can be improved. 
         [0038]    The grooves  23  may also be formed by laser cutting without using a dicing machine. 
         [0039]    Particularly, when the grooves  23  are formed in the resin layer  20  by laser cutting, as shown in  FIG. 3 , they may be inclined at a predetermined angle θ with respect to the mounting surface of the resin layer  20 . By thus forming the grooves inclined with respect to the mounting surface of the resin layer  20 , the outer peripheral edges  24  of the resin layer  20  can be made easy to bend. As a result, the stress reducing function can be improved. 
         [0040]    In this embodiment, the grooves  23  are inclined toward the center side of the resin layer  20 . However, they may be inclined toward the outside of the resin layer  20 . In this case, a portion of the resin layer  20  inward of the grooves  23  can be made easy to bend. As a result, the stress reducing function can be improved. 
         [0041]    As another embodiment, as shown in  FIG. 4 , grooves  23 ′ each provided with a step  25  so as to change in depth along the width direction may be formed in the resin layer  20 . Particularly, in the embodiment shown in  FIG. 4 , a first groove  23 ′−l with a predetermined width is formed first by using a diamond cutter that is used for dicing, and then a second groove  23 ′− 2  with a width smaller than that of the first groove  23 ′− 1  is formed at the center of the first groove  23 ′− 1 , whereby the step  25  is formed. 
         [0042]    When thus providing the step  25 , it becomes easy to fill the inside of the groove  23 ′ with the underfill material, and the adhesion between the underfill material and the resin layer  20  can be improved. In addition, it can be made easy to prevent the mixing of air when the underfill material is filled. 
         [0043]    Without limiting to the center of the first groove  23 ′− 1 , the second groove  23 ′− 2  may be formed close to the outer peripheral edge  24  side as shown in  FIG. 5 . 
         [0044]    As shown in  FIG. 6 , in the resin layer  20 , tapered grooves  23 ″ which are narrowed gradually along the depth direction may be formed. By thus tapering the grooves  23 ″, the underfill material can be smoothly filled, so that the mixing of air can be easily prevented. 
         [0045]    When it is demanded to increase the adhesion between the resin layer  20  and the underfill material, as shown in  FIG. 7 , grooves  26  may be formed in the resin layer  20  by using isotropic etching or the like, whereby hollow portions wider than the openings of the grooves  26  may be provided, and eaves-like projecting pieces  27  may be provided at the openings of the grooves  26 . 
         [0046]    Embodiments of the present invention are described in detail above, and these are only specific examples used for making the technical contents of the present invention clear, and the present invention should not be limited to these specific examples, and the spirit and scope of the present invention are limited only by the accompanying claims. 
         [0047]    The present application corresponds to Japanese Patent Application No. 2006-139622 filed on May 18, 2006 with the Japanese Patent Office, whole disclosure of which is incorporated herein by reference.