Abstract:
A semiconductor package using flip-chip mounting technique is disclosed. The semiconductor package includes: a semiconductor device provided with a plurality of first pads extending from the semiconductor device; a substrate provided with a plurality of second pads extending from the substrate at positions in registry with the location of the first pads of the semiconductor device; and an anisotropic conductive material interposed between the plurality of first pads and the plurality of second pads to electrically connect the first pads to associated second pads, the anisotropic conductive material positioned at discrete locations around the semiconductor device, thereby providing unobstructed clearance at desired locations between the semiconductor device and the substrate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates, in general, to semiconductor packages using flip-chip mounting techniques and, more particularly, to a semiconductor package in which a semiconductor device is mounted using both a flip-chip mounting technique and an anisotropic conductive material.  
         [0003]     2. Description of the Related Art  
         [0004]     In recent years, micromachining techniques, for producing micro-optical elements, micro-optical sensors, micro-bio-chips, and micro-radio-communication devices, such as micro-mirrors, micro-lenses and micro-switches, using semiconductor device manufacturing processes, have been actively studied.  
         [0005]     To use semiconductor devices, manufactured through the micromachining techniques, in practical applications, semiconductor packages must be manufactured.  
         [0006]     Semiconductor packaging techniques are complex techniques which include a variety of steps for producing the semiconductor devices and the final products. In recent years, semiconductor packaging techniques have been quickly and highly developed such that one million or more cells can be integrated in a package. Particularly, non-memory semiconductor devices are highly developed such that the devices have a great number of I/O pins, a large die size, a great heat dissipation capacity, highly improved electrical functions, etc. However, the conventional semiconductor packaging techniques for packaging the non-memory semiconductor devices cannot keep pace with the rapid development of semiconductor devices.  
         [0007]     The semiconductor packaging techniques are very important techniques which determine the operational performance, sizes, costs and operational reliability of final electronic products. Particularly, the semiconductor packaging techniques play a key role in the manufacture of recently developed electronic products which aim for high electronic performances, smallness/high density, low power consumption, multifunctionality, ultrahigh signal processing rates and permanent operational reliability of the products.  
         [0008]     To meet the above-mentioned recent trends, a flip-chip bonding technique, which is a kind of technique for electrically connecting a semiconductor chip to a substrate, has been actively studied, proposed and used. However, a conventional flip-chip bonding technique must execute complicated bonding processes using solder, which include applying solder flux onto a substrate, arranging a chip having solder bumps relative to the substrate having surface electrodes, executing the reflow of solder bumps, removing remaining flux, and applying and hardening underfill, thus increasing the costs of final products.  
         [0009]     Therefore, in an effort to simplify the complicated processes of the conventional flip-chip bonding techniques, a wafer-phase semiconductor packaging technique, in which a polymer material, functioning as both flux and underfill, is applied to a semiconductor wafer, has been actively studied and developed. Furthermore, a flip-chip bonding technique using a conductive adhesive, which is advantageous in that it can reduce production costs, provide microelectrode pitches, and can be environment-friendly because it does not use flux or lead, and in which processes are executed at low temperatures, has been actively studied and developed.  
         [0010]     Conventional conductive material layers are classified into two types: anisotropic conductive material layers and isotropic conductive material layers. A conductive material layer comprises conductive particles, such as Ni, Au/polymer, or Ag particles, and a base resin, such as a thermosetting resin, thermoplastic resin, or blend type insulating resin produced by mixing the properties of the thermosetting resin and the thermoplastic resin.  
         [0011]      FIG. 1A  is a sectional view illustrating a conventional anisotropic conductive film. As shown in  FIG. 1A , the conventional anisotropic conductive film  10  is a polymer resin-based film, with conductive particles  20  finely dispersed in the conductive film  10  to impart conductivity to the film. A releasing film  30  is attached to each surface of the anisotropic conductive film  10 .  
         [0012]      FIG. 1B  is a sectional view illustrating a conventional flip-chip bonding technique for producing a semiconductor package using the anisotropic conductive film of  FIG. 1A . As shown in the drawing, a first release film  30  is removed from one surface of the anisotropic conductive film  10  and the exposed surface of the anisotropic conductive film  10  is thermally compressed and adhered to a substrate  50 . Thereafter, a second release film  30  is removed from the other surface of the anisotropic conductive film  10 . An IC chip  40  having bumps  45  is placed on the exposed surface of the conductive film  10  such that the bumps  45  of the IC chip  40  are aligned with electrodes  55  of the substrate  50 . Thereafter, the anisotropic conductive film  10 , having the IC chip  40  and the substrate  50 , is subjected to thermal compression, so that the conductive particles in the anisotropic conductive film are plastically deformed, thus mechanically and electrically coupling the bumps  45  to the electrodes  55 .  
         [0013]     However, to use the flip-chip bonding technique, which can produce semiconductor packages using anisotropic conductive films, in the process of producing a semiconductor device using a micromachining technique, it is required to solve some technical problems in advance.  
       SUMMARY OF THE INVENTION  
       [0014]     Accordingly, the present invention has been made keeping in mind the above-mentioned requirements occurring in the related art, and an object of the present invention is to provide a semiconductor package which is manufactured using a flip-chip mounting technique capable of providing a reliable electrical connection between a semiconductor substrate and a transparent substrate.  
         [0015]     Another object of the present invention is to provide a semiconductor package which is manufactured using a flip-chip mounting technique capable of providing a desired joining strength between the semiconductor substrate and the transparent substrate even when a low temperature and a low compression load are used in the process of joining the semiconductor substrate to the transparent substrate.  
         [0016]     In order to achieve the above objects, there is provided a semiconductor package using flip-chip mounting technique, comprising: a semiconductor device provided with a plurality of first pads extending from the semiconductor device; a substrate provided with a plurality of second pads extending from the substrate at positions in registry with the location of the first pads of the semiconductor device; and an anisotropic conductive material interposed between the plurality of first pads and the plurality of second pads to electrically connect the first pads to associated second pads, the anisotropic conductive material positioned at discrete locations around the semiconductor device, thereby providing unobstructed clearance at desired locations between the semiconductor device and the substrate.  
         [0017]     The semiconductor package using flip-chip mounting technique according to the present invention preferably further comprises a plurality of bumps provided on the first pads of the semiconductor device, each of the bumps extending in the direction of a corresponding second pad.  
         [0018]     In the semiconductor package using flip-chip mounting technique according to the present invention, the substrate is preferably transparent to light. The transparent substrate is preferably provided with an anti-reflective coating on at least one of the surfaces thereof, thus increasing light transmissivity of incident light. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description when taken in conjunction with the accompanying drawings, in which:  
         [0020]      FIG. 1A  is a sectional view illustrating a conventional anisotropic conductive film;  
         [0021]      FIG. 1B  is a sectional view illustrating a conventional flip-chip bonding technique for producing a semiconductor package using the anisotropic conductive film of  FIG. 1   a;    
         [0022]      FIG. 2  is a sectional view of a semiconductor package manufactured using a flip-chip mounting technique according to an embodiment of the present invention; and  
         [0023]      FIG. 3  is a sectional view of a light modulator module package manufactured according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0024]     Herein below, a semiconductor package manufactured using a flip-chip mounting technique according to the present invention will be described in detail with reference to the accompanying drawings.  
         [0025]      FIG. 2  is a sectional view of a semiconductor package manufactured using a flip-chip mounting technique according to an embodiment of the present invention.  
         [0026]     As shown in  FIG. 2 , the semiconductor package  100  manufactured using the flip-chip mounting technique according to the present invention comprises a semiconductor substrate  110  provided with a plurality of upper pads  120  on a lower surface thereof, a transparent substrate  130  provided with a plurality of lower pads  140  on an upper surface thereof, and an anisotropic conductive material layer  160  interposed between each of the upper pads  120  and an associated lower pad  140 . The semiconductor package  100  manufactured using the flip-chip mounting technique according to the present invention preferably further comprises a bump  150  that is provided on each of the upper pads  120 . The bump  150  extends in the direction of a corresponding lower pad  140 . Furthermore, the semiconductor package  100  of the present invention may further comprise a bump (not shown) that is provided on each of the lower pads  140  of the transparent substrate  130 . This bump extends in the direction of a corresponding upper pad  120 .  
         [0027]     The semiconductor substrate  110  is integrated with micro-machines, such as micro-optical elements, micro-optical sensors, micro-bio-chips, and micro-radio-communication devices. For example, light modulators may be integrated in the lower surface of the semiconductor substrate  110 .  
         [0028]     Furthermore, because the semiconductor substrate  110  is provided with the plurality of upper pads  120  on the lower surface thereof, the semiconductor substrate  110  can receive control signals or electric signals through the upper pads  120 .  
         [0029]     The transparent substrate  130  is formed of an optically transparent material so that incident light can be transmitted through the transparent substrate  130 . To enhance the light transmissivity of the transparent substrate  130 , it is preferable to form an anti-reflective coating on at least one of opposite surfaces of the transparent substrate  130 .  
         [0030]     Furthermore, because the transparent substrate  130  is provide with the plurality of lower pads  140  on the upper surface thereof, the transparent substrate  130  can transmit control signals or electric signals to the semiconductor substrate  110  through the lower pads  140 , thus controlling the micro-machines integrated in the semiconductor substrate  110 .  
         [0031]     The bumps  150  are respectively formed on the upper pads  120  of the semiconductor substrate  110  and transmit the electric signals between the semiconductor substrate  110  and the transparent substrate  130 .  
         [0032]     In accordance with another embodiment of the present invention, micro-electro-mechanical systems (MEMS) may be integrated in the lower surface of the semiconductor substrate  110 . In the above case, the semiconductor package preferably requires a space defined therein to allow the MEMS to be actuated in the space. The bumps  150  preferably act as spacers to create the space in the semiconductor package.  
         [0033]     The anisotropic conductive material layers  160  are configured such that conductive particles  161 , such as metal-coated plastic particles or metal particles, are dispersed in an adhesive, such as epoxy.  
         [0034]     In the embodiment of the present invention, the anisotropic conductive material layers  160  are processed as follows to electrically connect the upper pads  120  to the lower pads  140 . The anisotropic conductive material layers  160  are primarily placed between the upper pads  120  of the semiconductor substrate  110  and the lower pads  140  of the transparent substrate  130 , and then heated at a low temperature and compressed with a low compression load. Thus, the conductive particles  161  dispersed in the anisotropic conductive material layers  160  are brought into close contact with the upper and lower pads  120  and  140 , thereby electrically connecting the upper pads  120  to the associated lower pads  140 . In the above case, parts of the anisotropic conductive material layers  160  located on uncompressed parts of the upper and lower pads  120  and  140  are not electrically connected to each other because the conductive particles  161  in the designated parts are spaced apart from each other.  
         [0035]     Therefore, in the semiconductor package  100  manufactured using a flip-chip mounting technique according to the present invention, the upper pads  120  of the semiconductor substrate  110  can be electrically connected to the lower pads  140  of the transparent substrate  130  using a low compression load at a low temperature. Thus, the upper pads  120  are electrically connected to the lower pads  140  through a thermal compression process using a low compression load that does not cause cracks in the transparent substrate  130 .  
         [0036]     In a preferred embodiment of the present invention, an anisotropic conductive film, processed such that part of the film to be brought into close contact with the upper pads  120  and the lower pads  140 ,  241 ,  242  and  243  remains, may be used as the anisotropic conductive material layer  160 .  
         [0037]     In another preferred embodiment of the present invention, an anisotropic conductive solution, prepared by mixing conductive particles  161 , such as metal-coated plastic particles or metal particles, with an adhesive  162 , such as epoxy, may be used as the anisotropic conductive material layer  160 . In the above case, the anisotropic conductive material layer  160  may be formed by shallowly dipping the upper pads  120  of the semiconductor substrate  110  (or the bumps  150  in the case of upper pads  120  having the bumps  150 ) in the anisotropic conductive solution. Alternatively, the anisotropic conductive material layer  160  may be formed by lightly stamping the upper pads  120  of the semiconductor substrate  110  (or the bumps  150  in the case of upper pads  120  having the bumps  150 ) onto a fabric laden with the anisotropic conductive solution.  
         [0038]      FIG. 3  is a sectional view illustrating a light modulator module package manufactured according to the present invention.  
         [0039]     As shown in  FIG. 3 , the light modulator module package  200  manufactured according to the present invention includes a transparent substrate  230 , a light modulator device  211 , and a plurality of drive integrated circuits  212  and  213 .  
         [0040]     The transparent substrate  230  is formed of an optically transparent material so that incident light can be transmitted through the substrate  230 . The light modulator device  211 , the plurality of drive integrated circuits  212  and  213 , and a plurality of lower pads  241 ,  242  and  243  to transceive electrical signals are formed on the surface of the transparent substrate  230 .  
         [0041]     The light modulator device  211  is a semiconductor device integrated with a refractive, reflective or transmissive light modulator  211   a  on the lower surface thereof. The light modulator device  211  modulates the incident light passing through the transparent substrate  230 , and then emits the modulated light to the outside. The light modulator device  211  is provided with a plurality of upper pads  221  on the lower surface thereof. The upper pads  221  of the light modulator device  211  are electrically connected to the associated lower pads  241  of the transparent substrate  230  by means of anisotropic conductive material layers  261 .  
         [0042]     The plurality of drive integrated circuits  212  and  213  are placed around the light modulator device  211  and provide drive voltage to drive the light modulator device  211 . In a manner similar to the light modulator device  211 , the drive integrated circuits  212  and  213  are each provided with a plurality of upper pads  222  or  223  on the lower surface thereof. The upper pads  222  and  223  of the drive integrated circuits  212  and  213  are electrically connected to the associated lower pads  242  and  243  of the transparent substrate  230  through anisotropic conductive material layers  262  and  263 .  
         [0043]     Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.  
         [0044]     As described above, the present invention provides a semiconductor package manufactured using a flip-chip mounting technique. In the semiconductor package according to the present invention, a reliable electrical connection between a plurality of upper pads of a semiconductor substrate and a plurality of lower pads of a transparent substrate can be accomplished through a thermal compression process using a low compression load at a low temperature.  
         [0045]     To produce the semiconductor package using the flip-chip mounting technique according to the present invention, a thermal compression process using a low compression load is executed so that the transparent substrate does not crack.  
         [0046]     Furthermore, in the semiconductor package using the flip-chip mounting technique according to the present invention, the electrical connection of the upper pads of the semiconductor substrate to the lower pads of the transparent substrate is easily accomplished, so that the process of manufacturing the semiconductor package is simplified, and accomplishes the recent trend of hyperfineness, high-functionality, smallness and compactness of semiconductor packages.