Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based on and claims priority of Japanese Patent Application No. 2004-290142 filed on Oct. 1, 2004, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a method of manufacturing a substrate with through electrodes and, more particularly, a method of manufacturing a substrate with through electrodes having such a structure that upper and lower sides of the substrate can be connected electrically via the through electrodes passing through the substrate in a thickness direction.  
         [0004]     2. Description of the Related Art  
         [0005]     In the prior art, there is provided a substrate with through electrodes having the structure in which the through electrodes are formed in the substrate along a thickness direction to connect electrically upper and lower sides of the substrate. In Patent Literature 1 (Patent Application Publication (KOKAI) Hei 7-73920), there is recited a method of manufacturing an electrical connecting device having such a structure that conductors passing through a resin film are formed by making bump conductors formed on a supporting sheet or a copper foil pass through the resin film.  
         [0006]     Also, in Patent Literature 2 (Patent Application Publication (KOKAI) Hei 7-231163) and Patent Literature 3 (Patent Application Publication (KOKAI) Hei 6-342977), there is recited a method of inserting conductive bumps into a synthetic resin sheet along a thickness direction by forming the conductive bumps on the synthetic resin sheet, then placing a wear plate on upper and lower sides respectively, and then heating/pressurizing them.  
         [0007]     By the way, recently a substrate with through electrodes having such a structure that the through electrodes are formed in a semiconductor substrate (silicon, or the like) has been developed. Such substrate with through electrodes is arranged between a circuit substrate and a semiconductor chip to be packaged on this board, for example, and the semiconductor chip is connected electrically to the circuit substrate via the substrate with through electrodes. Alternately, there are some cases where the through electrodes are provided in the semiconductor substrates so as to stack and connect electrically semiconductor substrates on which semiconductor elements are formed.  
         [0008]     As the first method of manufacturing such substrate with through electrodes, first a semiconductor substrate in which through holes are formed is covered with an insulating layer, and then a metallic foil is pasted on a bottom surface of the semiconductor substrate. Then, through electrodes are formed in the through holes by the electroplating using the metallic foil as the plating power-supply layer, and then the through electrodes are obtained by removing the metallic foil.  
         [0009]     Also, as the second method of manufacturing such substrate, first blind vias which do not pass through the substrate are formed in a semiconductor substrate, and also an insulating layer is formed on a surface of the semiconductor substrate by oxidizing the substrate. Then, a seed layer is formed on the upper surface of the semiconductor substrate by the CVD method, and also a metal layer is formed by the electroplating to fill the blind vias. Then, the metal layer on the lower side of the blind vias is exposed by grinding the semiconductor substrate from the back surface side, and then the through electrodes are obtained by removing the metal layer on the upper side of the silicon substrate.  
         [0010]     However, in the first method of manufacturing such substrate, such a problem exists that heights of the through electrodes are varied in the substrate upon forming the through electrodes by the electroplating. A method of grinding top portions of the through electrodes by the polishing, or the like to planarize them may be considered. In this case, when semiconductor elements are formed on the semiconductor substrate, there is a possibility that such semiconductor elements are damaged.  
         [0011]     Also, in the second method of manufacturing such substrate, a seed layer must be formed on one surface of a thin semiconductor substrate (e.g., almost 200 μm or less) by the CVD method at a relatively high temperature (350° C. or more). Therefore, it is possible that such annealing causes a warp of the semiconductor substrate or inflicts damage on the semiconductor elements.  
         [0012]     In this event, according to the manufacturing methods in above Patent Literatures 1 to 3, it is difficult to form the through electrodes in the semiconductor substrate.  
       SUMMARY OF THE INVENTION  
       [0013]     It is an object of the present invention to provide a method of manufacturing a substrate with through electrodes, capable of forming the through electrodes in a semiconductor substrate, or the like not to cause any defect.  
         [0014]     The present invention is related to a method of manufacturing a substrate with through electrodes, which comprises the steps of forming a metal post over a temporal substrate in a state that the metal post can be peeled from the temporal substrate, placing a normal substrate in which a through hole is provided in a position corresponding to the metal post over the temporal substrate, whereby inserting the metal post on the temporal substrate into the through hole in the normal substrate, and obtaining a through electrode which is formed of the metal post passing through the normal substrate by peeling the temporal substrate from the metal post.  
         [0015]     In one preferred mode of the present invention, the peelable layer and the seed metal layer (metallic foil) are formed in sequence on the temporal substrate, and the metal post is formed on the seed metal layer by the electroplating. Then, the normal substrate (such as the semiconductor substrate on an overall surface of which an insulating layer is formed, or the like) in which the through hole is provided in a position corresponding to the metal post is positioned over the temporal substrate, and then the metal post is inserted into the through hole of the normal substrate. Then, the temporal substrate is peeled along an interface between the peelable layer and the seed metal layer, and then the seed metal layer is removed or the seed metal layer is patterned to be connected to the through electrode. The normal substrate (semiconductor substrate) in which the through electrode is formed may be formed of an element substrate on which the semiconductor elements are formed or a simple substrate on which no semiconductor element is formed.  
         [0016]     In this way, in the preferred mode of the present embodiment, the metal post is formed on the seed metal layer formed on the temporal substrate via the peelable layer, then the metal post is inserted into the through hole in the normal substrate, and then the temporal substrate is peeled and abandoned. By employing such method, there is no need to form the seed metal layer on the semiconductor substrate, in which the through electrodes are formed, by the CVD including the annealing, and thus the semiconductor substrate can be kept at a room temperature. As a result, such a problem can be avoided that a warp of the thin semiconductor substrate is generated or the semiconductor elements formed on the semiconductor substrate are damaged.  
         [0017]     Also, since the metal post is formed previously on the temporal substrate, there is no need to form directly the metal post in the through hole in the semiconductor substrate by the electroplating. Therefore, a reduction in a time and labor required in the manufacturing method can be achieved.  
         [0018]     In addition, even when heights of the metal posts are varied, the leveling can be applied by polishing the upper portions of the metal posts on the temporal substrate, or the like. Therefore, in case the semiconductor elements are formed on the semiconductor substrate, such semiconductor elements are not damaged upon leveling the metal post.  
         [0019]     The substrate with through electrodes of the present invention may be employed as the interposer that aligns the semiconductor chip with the circuit substrate by providing the through electrode in the semiconductor substrate, or a structure in which a plurality of semiconductor devices are stacked three-dimensionally and are connected mutually via the through electrode by providing the through electrode in the semiconductor substrate on which the semiconductor elements are formed. Otherwise, the substrate with through electrodes of the present invention may be applied to the packaging substrate in which the movable portion of the MEMS device is fit in the recess portion and packaged by providing the recess portion in the major center portion of the substrate with through electrodes. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIGS. 1A  to  1 L are sectional views showing a method of manufacturing a substrate with through electrodes according to a first embodiment of the present invention;  
         [0021]      FIG. 2  is a sectional view showing an example in which the substrate with through electrodes according to the first embodiment of the present invention is applied to an interposer;  
         [0022]      FIG. 3  is a sectional view showing an example in which semiconductor devices to which the substrate with through electrodes according to the first embodiment of the present invention is applied are stacked three-dimensionally and connected mutually;  
         [0023]      FIGS. 4A  to  4 F are sectional views showing a method of manufacturing a substrate with through electrodes according to a second embodiment of the present invention;  
         [0024]      FIG. 5  is a sectional view showing an example in which the substrate with through electrodes according to the second embodiment of the present invention is applied to a MEMS device packaging substrate; and  
         [0025]      FIG. 6  is a sectional view showing a method of forming metal posts in the method of manufacturing a substrate with through electrodes according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]     Embodiments of the present invention will be explained with reference to the accompanying drawings hereinafter.  
       First Embodiment  
       [0027]      FIGS. 1A  to  1 L are sectional views showing a method of manufacturing a substrate with through electrodes according to a first embodiment of the present invention in sequence. In the method of manufacturing the substrate with through electrodes in the first embodiment, as shown in  FIG. 1A , first a temporal substrate  10  is prepared, and a peelable layer  12  is formed on the temporal substrate  10 . As the temporal substrate  10 , a semiconductor substrate (a silicon wafer, a silicon chip, or the like) is used preferably. As the peelable layer  12 , a heat peeled tape having such a characteristic that can be pasted onto a seed metal layer formed on the temporal substrate  10  and the peelable layer  12  at an ordinary temperature but can be peeled from an interface of the seed metal layer by applying heat is used preferably.  
         [0028]     Then, as shown in  FIG. 1B , a seed metal layer  14  is formed on the peelable layer  12 . As the seed metal layer  14 , a metallic foil made of copper (Cu), or the like is used preferably, and pasted onto the peelable layer  12 . Then, as shown in  FIG. 1C , a resist film  16  is formed on the seed metal layer  14 . As the method of forming the resist film  16 , a resist coating liquid may be formed by the spin coating, or the like, or a dry film resist may be pasted.  
         [0029]     Then, as shown in  FIG. 1D , opening portions  16   x  are formed in the resist film  16  by exposing/developing the resist film  16 .  
         [0030]     Then, as shown in  FIG. 1E , metal posts  18   a  made of Cu, or the like are formed in the opening portions  16   x  in the resist film  16  by the electroplating utilizing the seed metal layer  14  as the plating power-supply layer. Then, the resist film  16  is removed by the remover or the dry ashing. Thus, as shown in  FIG. 1F , the metal posts  18   a  provided to stand upright on the seed metal layer  14  formed on the temporal substrate  10  are exposed. The metal posts  18   a  act later as the through electrodes that are provided to pass through the semiconductor substrate.  
         [0031]     In the case where a variation in heights of the metal posts  18   a  become a problem, top portions of the metal posts  18   a  may be polished by the CMP, or the like after the step in  FIG. 1E  (before the resist film  16  is removed). Thus, a variation in heights can be reduced by leveling the metal posts  18   a.  In this case, since no semiconductor element is formed on the temporal substrate  10 , there is no possibility that such polishing causes damage on the semiconductor elements.  
         [0032]     Then, as shown in  FIG. 1G , a semiconductor substrate  20  (a silicon wafer, a silicon chip, or the like whose thickness is 200 μm or less, for example) in which through holes  20   x  are formed is prepared as a normal substrate in which the through electrodes are formed. Then, an insulating layer  22  formed of a silicon oxide layer is formed on both surfaces of the semiconductor substrate  20  and inner surfaces of the through holes  20   x  by thermally oxidizing the semiconductor substrate  20 . The through holes  20   x  in the semiconductor substrate  20  are formed by the dry etching (RIE, or the like) using the resist film as a mask, in which opening portions are provided on the semiconductor substrate  20 . Also, the through holes  20   x  in the semiconductor substrate  20  are formed in positions that correspond to the metal posts  18   a  formed on the temporal substrate  10 . The semiconductor substrate  20  may be formed of an element substrate on which the semiconductor elements, etc. are formed or a simple substrate on which no semiconductor element is formed.  
         [0033]     Then, as also shown in  FIG. 1G , the semiconductor substrate  20  is positioned over the temporal substrate  10  in a condition that the through holes  20   x  in the semiconductor substrate  20  are aligned to correspond to the metal posts  18   a  formed on the temporal substrate  10 . Thus, as shown in  FIG. 1H , the metal posts  18   a  are inserted into the through holes  20   x  in the semiconductor substrate  20 . At this time, because a thickness of the semiconductor substrate  20  is set thinner than the height of the metal posts  18   a,  the metal posts  18   a  are inserted into the through holes  20   x  in the semiconductor substrate  20  to have projection portions  18   b  that are projected from the upper surface of the semiconductor substrate  20 .  
         [0034]     Then, as shown in  FIG. 1I , a resultant structure in  FIG. 1H  is placed on a lower die  24   b,  and then the projection portions  18   b  of the metal posts  18   a  projected from the upper surface of the semiconductor substrate  20  are crashed by pressing the resultant structure by means of an upper die  24   a.  Thus, as shown in  FIG. 1J , the projection portions  18   b  of the metal posts  18   a  are extended in the lateral direction, and thus upper connection portions  18   x  are formed. In addition, since the metal posts  18   a  in the through holes  20   x  in the semiconductor substrate  20  are extended in the lateral direction, clearances between the through holes  20   x  and the metal posts  18   a  are filled, whereby the metal posts  18   a  are fixed in the through holes  20   x  in the semiconductor substrate  20 .  
         [0035]     Then, as shown in  FIG. 1K , the temporal substrate  10  is peeled along an interface between the peelable layer  12  and the seed metal layer  14  by annealing the resultant structure at a temperature of 100 to 200° C. Then, the temporal substrate  10  onto which the peelable layer  12  is pasted is abandoned.  
         [0036]     Then, as shown in  FIG. 1L , the seed metal layer  14  is removed selectively from a resultant structure in  FIG. 1K . This seed metal layer  14  is removed by the wet etching or the polishing.  
         [0037]     In this fashion, the metal posts  18   a  formed on the temporal substrate  10  act as through electrodes  18  provided in the through holes  20   x  in the semiconductor substrate  20 , and also lower connection portions  18   y  are exposed on bottom portions of the through electrodes  18 . Accordingly, a substrate  1  with through electrodes of the present embodiment can be obtained.  
         [0038]     In the above embodiment, the seed metal layer  14  is removed. But wiring patterns connected to the through electrodes  18  may be formed on the lower surface of the semiconductor substrate  20  as the lower connection portions, by patterning the seed metal layer  14  by means of the photolithography and the etching.  
         [0039]     As explained above, according to the method of manufacturing the substrate with through electrodes of the present embodiment, first the peelable layer  12  and the seed metal layer  14  are formed on the temporal substrate  10 , and then the resist film  16  in which the opening portions  16   x  are provided in predetermined portions is formed on the seed metal layer  14 . Then, the metal posts  18   a  are formed in the opening portions  16   x  in the resist film  16  by the electroplating using the seed metal layer  14  as the plating power-supply layer, and then the resist film  16  is removed.  
         [0040]     Then, the semiconductor substrate  20  in which the through holes  20   x  are provided in the portions corresponding to the metal posts  18   a  and an overall surface of which is covered with the insulating layer  22  is prepared. Then, the semiconductor substrate  20  is arranged over the temporal substrate  10 , and then the metal posts  18   a  are inserted into the through holes  20   x  in the semiconductor substrate  20 . Then, the projection portions  18   b  of the metal posts  18   a  projected from the upper surface of the semiconductor substrate  20  are crashed by the press, so that the upper connection portions  18   x  are formed and simultaneously the metal posts  18   a  are fixed in the metal posts  18   a.    
         [0041]     Then, the temporal substrate  10  is peeled along an interface between the peelable layer  12  and the seed metal layer  14 , then the temporal substrate  10  on which the peelable layer  12  is pasted is abandoned, and then the seed metal layer  14  is removed. Accordingly, the bottom surfaces of the metal posts  18   a  are exposed, and the metal posts  18   a  constitute the through electrodes  18  that pass through the semiconductor substrate  20 . Then, the upper and lower sides of the through electrodes  18  constitute the upper connection portions  18   x  and the lower connection portions  18   y  respectively. In this manner, the through electrodes  18  that can connect electrically the upper and lower sides of the semiconductor substrate  20  are formed in the through holes  20   x  in the semiconductor substrate  20 . A plurality of through electrodes  18  are insulated electrically by the insulating layer  22  that is formed on both surfaces of the semiconductor substrate  20  and the inner surfaces of the through holes  20   x.    
         [0042]     In this way, in the present embodiment, the metal posts  18   a  are formed by the electroplating using the seed metal layer  14  formed on the temporal substrate  10  as the plating power-supply layer. Therefore, there is no need to form the seed metal layer on the semiconductor substrate  20 , into which the through electrodes  18  are inserted, by the CVD including the annealing, and thus the semiconductor substrate  20  can be maintained at a room temperature. As a result, there is no possibility that a warp of the thin semiconductor substrate  20  is generated. In addition, even when the semiconductor elements are formed on the semiconductor substrate  20 , the annealing is not applied to the semiconductor substrate  20 . As a result, there is no possibility that the semiconductor elements are damaged.  
         [0043]     Further, even when a variation in heights of the metal posts  18   a  is reduced by leveling the metal posts  18   a  after the step in  FIG. 1H , the semiconductor elements are not formed on the temporal substrate  10 . Therefore, it is not possible that the semiconductor elements are damaged, and various leveling methods can be employed.  
         [0044]     Besides, the step of forming the metal posts  18   a  in the opening portions  16   x  of the resist film  16  by the electroplating needs a relatively long time. In this case, if the metal posts  18   a  are formed previously on the temporal substrate  10 , a time and labor required to form the through electrodes  18  in the semiconductor substrate  20  can be shortened, and also a reduction of an delivery date of a product can be achieved.  
         [0045]     In  FIG. 2 , an example in which the substrate  1  with through electrodes of the first embodiment of the present invention is applied to an interposer that aligns the semiconductor chip with the circuit substrate is shown.  
         [0046]     As shown in  FIG. 2 , in a circuit substrate  30 , via posts  38  are provided in a resin substrate  32  to pass through, and wiring patterns  34  formed on an upper surface of the resin substrate  32  are connected to external connection terminals  36 , which are formed on the lower surface side of the resin substrate  32 , via the via posts  38 .  
         [0047]     Then, the lower connection portions  18   y  of the through electrodes  18  of the substrate  1  with through electrodes of the present embodiment are connected to the wiring patterns  34  of the circuit substrate  30  via bumps  42   a.  Then, a semiconductor chip  40  is connected to the upper connection portions  18   x  of the through electrodes  18  of the substrate  1  with through electrodes via bumps  42   b.    
         [0048]     In this manner, the substrate  1  with through electrodes of the present embodiment is arranged between the circuit substrate  30  and the semiconductor chip  40  (CPU, or the like), and the terminals of the semiconductor chip  40  are connected electrically to the terminals of the circuit substrate  30  with alignment or grid conversion.  
         [0049]     Also, as shown in  FIG. 3 , as the substrate with through electrodes of the present invention, a semiconductor element substrate  1   a  with through electrodes (semiconductor chip, or the like) on which the semiconductor elements, and the like are formed may be employed. More particularly, a plurality of semiconductor element substrates  1   a  with through electrodes of the present embodiment are stacked three-dimensionally and packaged onto the similar circuit substrate  30  to that in  FIG. 2 , and the through electrodes  18  are connected to the wiring patterns  34  of the circuit substrate  30  respectively in a condition that such through electrodes  18  are connected mutually via bumps  42 . Then, a plurality of semiconductor element substrates  1   a  with through electrodes are sealed with a sealing resin  44 .  
         [0050]     If doing so, wiring lengths between a plurality of semiconductor element substrates can be shortened. Therefore, the present embodiment can deal with an increase in an operating frequency and also the chip laminated type module responding to the high density packaging can be manufactured at a low cost with a high yield.  
       Second Embodiment  
       [0051]      FIGS. 4A  to  4 F are sectional views showing a method of manufacturing a substrate with through electrodes according to a second embodiment of the present invention. In the second embodiment, such a mode is shown that the substrate with through electrodes of the present invention is applied to the MEMS (Micro Electro Mechanical Systems) device packaging substrate (silicon cap).  
         [0052]     In the method of manufacturing the substrate with through electrodes of the second embodiment, as shown in  FIG. 4A , first the peelable layer  12  and the seed metal layer  14  are formed on the temporal substrate  10  by the same method as the first embodiment, and the metal posts  18   a  which stand upright are formed on the seed metal layer  14 . Then, as shown in  FIG. 4B , the semiconductor substrate  20  in which the through holes  20   x  are provided is prepared, and then the insulating layer  22  is formed on both surfaces of the semiconductor substrate  20  and inner surfaces of the through holes  20   x.  In the second embodiment, a substrate having such a structure that a projection portion  20   a  is formed on a peripheral portion of the substrate by providing a recess portion  20   b  in a major center portion is used as the semiconductor substrate  20 .  
         [0053]     Then, as also shown in  FIG. 4B , the semiconductor substrate  20  is positioned over the temporal substrate  10  to direct upwardly its surface on which the projection portion  20   a  of the semiconductor substrate  20  is provided in a condition that the through holes  20   x  in the semiconductor substrate  20  are aligned with the metal posts  18   a  on the temporal substrate  10 . Thus, as shown in  FIG. 4C , the metal posts  18   a  on the temporal substrate  10  are inserted into the through holes  20   x  in the semiconductor substrate  20  to have the projection portions  18   b.    
         [0054]     Then, as shown in  FIG. 4D , like the first embodiment, the resultant structure in  FIG. 4C  is put between the upper die  24   a  and the lower die  24   b  and pressed (pressurized). Thus, as shown in  FIG. 4E , the projection portions  18   b  of the metal posts  18   a  projected from the upper surface of the semiconductor substrate  20  are crashed, so that the upper connection portions  18   x  are formed and at the same time the metal posts  18   a  are fixed in the through holes  20   x  in the semiconductor substrate  20 .  
         [0055]     Then, as shown in  FIG. 4F , like the first embodiment, the temporal substrate  10  on which the peelable layer  12  is pasted is abandoned by peeling the temporal substrate  10  along an interface between the peelable layer  12  and the seed metal layer  14 . Then, the seed metal layer  14  on the lower surface of the semiconductor substrate  20  is patterned by the photolithography and the etching. Accordingly, the metal posts  18   a  are shaped into the through electrodes  18  and also the lower connection portions  18   y  connected to the through electrodes  18  are formed under the through electrodes  18 .  
         [0056]     With the above, a substrate  1   b  with through electrodes according to the second embodiment can be obtained.  
         [0057]     In the substrate  1   b  with through electrodes of the second embodiment, as shown in  FIG. 5 , external connection terminals  52  are provided to the lower connection portions  18   y  of the through electrodes  18 . Then, a MEMS device  50  (acceleration sensor) having a movable portion  56  is prepared, and connection portions (not shown) of the MEMS device  50  are connected to the upper connection portions  18   x  of the through electrodes  18  via bumps  54 . The MEMS device  50  can be manufactured by the micromachining technology, and also a pressure sensor, a switch, or the like may be employed in addition to the acceleration sensor. In this way, the movable portion  56  of the MEMS device  50  is fit in the recess portion  20   b  (cavity) of the substrate  1   a  with through electrodes in packaging.  
         [0058]     According to the method of manufacturing the substrate with through electrodes of the second embodiment, the advantages similar to the first embodiment can be achieved and also the packaging substrate (silicon cap) for the MEMS device having the movable portion can be easily manufactured.  
       Other Embodiment  
       [0059]      FIG. 6  is a sectional view showing a method of forming metal posts in the method of manufacturing a substrate with through electrodes according to other embodiment of the present invention.  
         [0060]     In the foregoing first and second embodiments, the metal posts  18   a  are formed on the seed metal layer  14  on the temporal substrate  10  by the electroplating. In this case, as shown in  FIG. 6 , ball bumps  19  may be formed on the seed metal layer  14  on the temporal substrate  10  by the wire bonding method. In other words, a metal wire made of gold, or the like is pulled out from a capillary of a wire bonder by a predetermined length, then a top end portion of this metal wire is rounded into a spherical shape by the discharge, then the spherical top end portion of the metal wire is brought into contact with the seed metal layer  14  by bringing down the capillary, and then such top end portion is bonded to the seed metal layer  14  by applying the heat and the ultrasonic vibration. Then, the metal wire is torn off by fixing the metal wire by a clamper, while pulling up the capillary. The ball bumps  19  shown in  FIG. 6  are formed by carrying out these steps plural times. Since later steps are similar to those in the first and second embodiments, their explanation will be omitted herein.

Technology Category: h