Abstract:
The invention provides a semiconductor multi-chip package including a substrate, a first semiconductor chip mounted on the substrate and a second semiconductor chip disposed directly above the first semiconductor chip. The package further includes a spacer disposed between the substrate and the second semiconductor chip to maintain a vertical interval between the first and second semiconductor chips and electrically connect the second semiconductor chip to the substrate. The invention minimizes noise generated through a bonding wire connecting the substrate with the chip to ensure stable operation of the chip, and reduces the size of the substrate and the number of mounted components, thereby achieving miniaturization of the package.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims the benefit of Korean Patent Application No. 2005-60380 filed on Jul. 5, 2005, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a multi-chip package with at least two semiconductor chips packaged therein, and more particularly, to a semiconductor multi-chip package which is designed to minimize noise generated through a bonding wire connecting a substrate with a chip to ensure stable operation of the chip, and to reduce the size of a substrate and number of components mounted thereon, thereby achieving miniaturization.  
         [0004]     2. Description of the Related Art  
         [0005]     Electronic devices are becoming more miniaturized and multi-functional to meet the needs arising from recent developments in the semiconductor industry and the users. Multi-chip packaging technology, which is developed to meet such needs, packages a single type or different types of semiconductor chips in a single unit package.  
         [0006]     This is more advantageous in terms of package size, weight or mounting area compared with packaging each semiconductor chip in one package. Thus, the multi-chip packaging technology is extensively applied to mobile phones and the like that require miniaturization and light weight in order to reduce mounting area and weight thereof.  
         [0007]     In general, to package a plurality of semiconductor elements such as chips or dies in a single package, the semiconductor elements are either arranged in a stacked structure or aligned in parallel. In the case of the former, the stacked structure complicates the manufacturing process in a limited thickness. In the case of the latter, at least two semiconductor chips are disposed on the same plane, which renders it difficult to achieve miniaturization of the package.  
         [0008]     In general, semiconductor chips are stacked in a package that needs to be miniaturized and light-weighted. Such an exemple of a conventional multi-chip package is described hereunder.  
         [0009]      FIG. 1  is a sectional view illustrating the conventional multi-chip package. The multi-chip package  1  shown in  FIG. 1  includes a first semiconductor chip  10  mounted on a substrate  2 , a second semiconductor chip  20  disposed above the first semiconductor chip  10  in a predetermined interval and a spacer  30  having a predetermined height. The spacer  30  is disposed between the second semiconductor chip  20  and the substrate  2  to maintain a predetermined interval between the first and second semiconductor chips  10  and  20 .  
         [0010]     Each of the semiconductor chips  10  and  20  is adhered by a surface opposite of the active surface that has an integrated circuit formed thereon. The active surfaces of the semiconductor chips  10  and  20  face the same direction.  
         [0011]     The first semiconductor chip  10  is electrically connected to the substrate  2  with chip pads thereof wire-bonded to bonding pads  43  of the substrate  2  by bonding wires  44 . The second semiconductor chip  20  is electrically connected to the substrate  2  with chip pads thereof wire-bonded to bonding pads  41  of the substrate  2  by bonding wires  42 .  
         [0012]     In addition, plastic encapsulating material such as epoxy molding compound completes the package body in the upper part of the substrate  2  where at least one electric component is mounted by sealing the first and second semiconductor chips  10  and  20  and mounted components  15  to protect them from the external environment. Solder balls (not shown) may be provided on the lower surface of the substrate  2  as external terminals for electric connection to the outside.  
         [0013]     In the meantime, a supplementary spacer  35  is disposed between the first and second semiconductor chips  10  and  20 . The substrate  2  is a ceramic substrate manufactured in Low Temperature Co-fired Ceramic (LTCC) process to have passive elements such as a resistor, a capacitor and a coil embedded therein.  
         [0014]     However, in such a configuration of the conventional multi-chip package  1 , the second bonding wire  42  connecting the second semiconductor chip  20  and the substrate  2  is longer than the first bonding wire  44  electrically connecting the first semiconductor chip  10  and the substrate  2 . This entails higher incidence of noise during transmission of signals and greater bonding inductance, and thus the operation is unstable.  
         [0015]     In addition, as the second bonding wire  42  has an end connected to the second semiconductor chip  20  and the other end directly bonded to the substrate  2 , a horizontal length L between the bonding locations of the second bonding wire  42  is longer, thus limiting reduction of the size of the substrate  2  for miniaturization.  
       SUMMARY OF THE INVENTION  
       [0016]     The present invention has been made to solve the foregoing problems of the prior art and therefore an object of certain embodiments of the present invention is to provide a semiconductor multi-chip package which can minimize noise generated through a bonding wire connecting a substrate with a chip and reduce the size of the substrate and number of components mounted thereon, thereby achieving miniaturization.  
         [0017]     According to an aspect of the invention for realizing the object, there is provided a semiconductor multi-chip package including: a substrate; a first semiconductor chip mounted on an upper surface of the substrate; at least one second semiconductor chip disposed directly above the first semiconductor chip; and a spacer disposed between the substrate and the second semiconductor chip to maintain a predetermined interval between the first and second semiconductor chips and electrically connect the second semiconductor chip to the substrate.  
         [0018]     Preferably, the first semiconductor chip is wire-bonded onto the substrate.  
         [0019]     Preferably, the first semiconductor chip is flip-chip bonded onto the substrate.  
         [0020]     Preferably, the second semiconductor chip is wire-bonded onto the spacer.  
         [0021]     Preferably, the spacer comprises a Low Temperature Co-fired Ceramic (LTCC) substrate having at least one passive element therein.  
         [0022]     Preferably, the spacer has a portion of an upper surface adhered to a lower surface of the second semiconductor chip with an adhesive, and has an undersurface adhered to the substrate via solder balls therebetween.  
         [0023]     Preferably, the semiconductor multi-chip package according to the present invention further includes an encapsulant that covers the first and second semiconductor chips on the substrate.  
         [0024]     Preferably, the semiconductor multi-chip package according to the present invention further includes a supplementary spacer between the first semiconductor chip and the second semiconductor chip, and preferably, the supplementary spacer is made of insulation material. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0025]     The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:  
         [0026]      FIG. 1  is a sectional view illustrating a semiconductor multi-chip package according to prior art;  
         [0027]      FIG. 2  is a sectional view illustrating a semiconductor multi-chip package according to the present invention; and  
         [0028]      FIG. 3  is a plan view illustrating the semiconductor multi-chip package according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]     Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.  
         [0030]      FIG. 2  is a sectional view illustrating a semiconductor multi-chip package according to the present invention, and  FIG. 3  is a plan view illustrating the semiconductor multi-chip package according to the present invention.  
         [0031]     As shown in  FIGS. 2 and 3 , according to a preferred embodiment of the present invention, the semiconductor multi-chip package  100  achieves miniaturization of a final product by reducing the number of components and the size of a substrate. The semiconductor multi-chip package  100  includes a substrate  101 , first and second semiconductor chips  110  and  120  and a spacer  130 .  
         [0032]     That is, the substrate  101 , which is a ceramic substrate with at least one ceramic layer stacked, has various circuits pattern-printed thereon, a plurality of bonding pads  103  for wire-bonding, and a plurality of components  105  mounted in accordance with the circuits on an upper surface thereof.  
         [0033]     In addition, the substrate  101  has lower terminals  107  on an undersurface thereof and the lower terminals  107  have solder balls (not shown) for electrical connection with a main substrate. Thereby, the substrate  101  can be mounted on the main substrate with the solder balls (not shown) therebetween.  
         [0034]     Herein, the substrate  101  is a Low Temperature Co-fired Ceramic (LTCC) substrate. The LTCC substrate is obtained by first, forming passive elements R, L and C (filter, balun and coupler) for configuring the circuits on a plurality of green sheets made of glass-ceramics, via screen printing and photo patterning using highly conductive Ag, Cu, etc. With these green sheets stacked on one another, ceramic and metal conductors are fired simultaneously at a temperature of 1000° C. or lower to obtain the LTCC substrate.  
         [0035]     Thereby, the passive elements such as a capacitor, a resistor and an inductor are embedded in the substrate  101  in the form of patterns.  
         [0036]     The first semiconductor chip  110  is a chip component which is mounted on an upper surface of the substrate  101  to be electrically connected to the circuits pattern-printed on an upper surface of the substrate  101 . As shown in  FIGS. 2 and 3 , adhered to the substrate  101  by an adhesive  109 , the first semiconductor chip  110  can be wire-bonded onto the substrate  101  by a plurality of first wires  141 .  
         [0037]     Each of the first bonding wires  141  is a conductive member having one end bonded to a chip pad  112  formed on an upper surface of the first semiconductor chip  110  and the other end bonded to the bonding pad  103  formed on the substrate  101 .  
         [0038]     However, the first semiconductor chip  110  is not limited to the above, and alternatively can be flip-chip bonded to an upper surface of the substrate  101 , with ball pads (not shown) and a plurality of solder balls (not shown) formed on a lower surface thereof.  
         [0039]     In addition, the second semiconductor chip  120  is composed of at least one chip component disposed directly above the first semiconductor chip  110  in a predetermined interval. The second semiconductor chip  120  is not directly connected to the substrate  101  but stacked in parallel and above the substrate  101  with a spacer  130  having conductive lines formed therein disposed therebetween.  
         [0040]     The first and second semiconductor chips  110  and  120  may be ones selected from a group consisting of a memory chip such as SRAM and DRAM, a digital integrated circuit chip, an RF integrated circuit chip and a base band chip.  
         [0041]     In addition, the spacer  130  has upper and lower ends thereof connected respectively to an upper surface of the substrate  101  and a lower surface of the second semiconductor chip  120 , and having a thickness greater than the height of the first semiconductor chip  110  mounted on the substrate  101 , in order to maintain a vertical interval between the first and second semiconductor chips  110  and  120 .  
         [0042]     Herein, the spacer  130  is composed of at least two LTCC substrates with at least one passive elements R, L and C (filter, balun and coupler) embedded therein, and disposed along the outer peripheral portions of the second semiconductor chip  120  to electrically connect the second semiconductor chip  120  with the substrate  101 .  
         [0043]     Thus, the passive elements such as a decoupling capacitor or Electrostatic Discharge (ESD) device that may be required depending on the operation of the second semiconductor chip  120  can be embedded in the spacer  130  without being mounted on the substrate  101 , thereby reducing the number of components mounted on the substrate  101 .  
         [0044]     The second semiconductor chip  120  is bonded to the spacer  140  by second bonding wires  142 . Each of the second bonding wires  142  has an end bonded to a chip pad  122  formed on an upper surface of the second semiconductor chip  120  and the other end bonded to a bonding pad  133  formed on an upper surface of the spacer  130 . The bonding pads  133  are electrically connected to the passive elements R, L and C (filter, balun and coupler) through vias or patterns.  
         [0045]     Here, the spacer  130  is fixedly adhered to a lower surface of the second semiconductor chip  120  with an insulating adhesive  139 .  
         [0046]     The spacer  130  has a plurality of solder pads on a lower surface thereof to be electrically connected to the pattern circuits formed on the substrate  101  via solder balls  136 .  
         [0047]     Thereby, the second semiconductor chip  120  is electrically connected to the substrate  101  by the second bonding wires  142  and the solder balls  136 .  
         [0048]     Further, a horizontal length L 1  measured between the chip pad  122  and the bonding pad  133  connected, respectively, to each end of the second bonding wire  142  is shorter than a horizontal length L (see  FIG. 1 ) measured between the chip pad and the bonding pad  41  of the substrate  2  connected, respectively, to each end of the second bonding wire  42  in the conventional package. Thus, the second bonding wire  142  can be formed in a shorter length, and also the substrate  101  where the first and second semiconductor chips  110  and  120  are mounted can be designed smaller.  
         [0049]     As the second bonding wires  142  are formed in a shorter length, noise of signals transmitted therethrough can be reduced, thereby minimizing occurrence of parasitic component due to bonding inductance.  
         [0050]     In the meantime, an encapsulant  150  made of plastic encapsulating material such as epoxy molding compound is formed on the substrate  101  to protect the mounted components  105 , the first and second semiconductor chips  110  and  120  and the first and second bonding wires  141  and  142  from being damaged or corroded by the outside environment, thereby completing the package.  
         [0051]     In addition, a supplementary spacer  135  made of insulation material such as silicone can be additionally disposed between the first semiconductor chip  110  mounted on the substrate  101  and the second semiconductor chip  120  adhered to the spacer  130 , thereby stably maintaining an interval between the first and second semiconductor chips  110  and  120 .  
         [0052]     Herein, it is preferable that the supplementary spacer  135  is formed in a shape substantially the same as those of the first and second semiconductor chips  110  and  120 , and formed smaller than an upper surface area of the first semiconductor chip  110 .  
         [0053]     According to a preferred embodiment of the invention as set forth above, the passive elements involved in the operation of the second semiconductor chip can be embedded in the LTCC spacer disposed between the first and second semiconductor chips instead of being mounted on the substrate. This allows reducing the number of components mounted on the substrate and the size of the substrate, thereby miniaturizing the final product.  
         [0054]     Further, the second bonding wires can be formed in a length smaller than that in the prior art, thus reducing noise of a signal transmitted therethrough and occurrence of parasitic component due to bonding inductance. Thereby, the stable operation of the package is ensured to enhance reliability of the package and attain stable electric characteristics.  
         [0055]     While the present invention has been shown and described in connection with the preferred embodiments, it will be apparent to those skilled in the art that modifications and variations can be made without departing from the spirit and scope of the invention as defined by the appended claims.