Abstract:
This invention relates to a semiconductor having protruding contacts comprising, a first semiconductor substrate having at least one interconnect located substantially within the first substrate, and a second semiconductor substrate having at least one protruding contact point that substantially contacts at least one interconnect.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates to a semiconductor having protruding contacts comprising, a first semiconductor substrate having at least one interconnect located substantially within the first substrate, and a second semiconductor substrate having at least one protruding contact point that substantially contacts at least one interconnect.  
         [0003]     2. Description of the Related Art  
         [0004]     Prior to the present invention, as set forth in general terms above and more specifically below, it is known in the semiconductor art, that two semiconductor substrates can be joined together at low temperatures by using well-known plasma-enhanced bonding processes. These low-temperature substrate joining techniques can be used to package MEMS (microelectromechanical systems) or NEMS (nanoelectromachanical systems) devices hermetically as well as 3-D wafer stacking. With respect to these low-temperature substrate joining techniques, the surface of the substrates to be joined need to be flat and very smooth (&lt;20 A rms surface roughness over 2 μm×2 μm). Consequently, the surfaces are usually planarized with chemical mechanical polishing (CMP).  
         [0005]     It is well known that the CMP planarization process creates some unique challenges for wafer-to-wafer interconnect applications since it is difficult to planarize the interconnect plug (or contact points) and the surrounding area evenly. The interconnect between two substrates may fail if dishing on the plugs occurs during the CMP process. Also, plasma-enhanced bonding may fail if the plugs surfaces are higher than the surrounding area, which prevents the two substrates from contacting at the atomic level.  
         [0006]     It is also known, in the semiconductor art, that compliant intermediate layers (such as BCB (benzocyclobutene)) are often used to adhere two substrates together as well as to form an interconnect at the same time. This approach works fine for many 3-D interconnect applications, but does not work when both 3-D interconnect and hermetic packaging are required since BCB is not hermetic.  
         [0007]     It is further known, in the semiconductor art, that Au bump or solder ball techniques can be used to flip-chip bond one substrate to another. However, none of these techniques provide both a good electrical interconnect between the substrates and hermetic packaging at the wafer level as the bumps or balls tend to cause a standoff between the circuits or substrates. The interconnect density is also limited with this approach.  
         [0008]     Finally, it is known, in the interconnect art, to bond the interconnect to the pad of the circuit device. Typical techniques involve heat, eutectic bonding, electrical bonding, and/or mechanical bonding. However, many of these techniques do not provide an adequate bond for a variety of reasons.  
         [0009]     It is apparent from the above that there exists a need in the semiconductor art for a semiconductor construction technique that works with both 3-D interconnect and hermetic packaging, but which at the same time allows the two substrates to be efficiently bonded so that they contact each other at the atomic level. It is a purpose of this invention to fulfill this and other needs in the art in a manner more apparent to the skilled artisan once given the following disclosure.  
       SUMMARY OF THE INVENTION  
       [0010]     Generally speaking, an embodiment of this invention fulfills these needs by providing a semiconductor having protruding contacts comprising, a first semiconductor substrate having at least one interconnect located substantially within the first substrate, and a second semiconductor substrate having at least one protruding contact point that substantially contacts at least one interconnect.  
         [0011]     In certain preferred embodiments, the first semiconductor substrate includes a CMOS (complementary metal oxide semiconductor) circuit on a top surface and through-silicon interconnect plugs. Also, the first semiconductor substrate may include an optical MEMS or NEMS device. Also, the surface of the interconnect that contacts the protruding contact point of the second substrate may be thinned and chemically mechanically polished.  
         [0012]     In another further preferred embodiment, the second semiconductor substrate may include CMOS or other high density (nanotechnology devices) circuitry and at least one protruding contact point. Also, the contact point is formed by layering various metal and dielectric films, including a compressive dielectric film, wherein etching is employed to cause the compressive dielectric film to bow up slightly and create a protruding contact point.  
         [0013]     The preferred semiconductor, according to various embodiments of the present invention, offers the following advantages: ease of assembly; excellent electrical contact characteristics; and good durability. In fact, in many of the preferred embodiments, these factors of ease of assembly and excellent electrical contact characteristics are optimized to an extent that is considerably higher than heretofore achieved in prior, known semiconductor devices.  
         [0014]     The above and other features of the present invention, which will become more apparent as the description proceeds, are best understood by considering the following detailed description in conjunction with the accompanying drawings, wherein like characters represent like parts throughout the several views and in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIGS. 1   a  and  1   b  are a schematic illustrations of a semiconductor substrate having a through-silicon interconnect with  FIG. 1   b  illustrating a detailed view of the end of the through-silicon interconnect, according to one embodiment of the present invention;  
         [0016]      FIG. 2  is a schematic illustration of a second semiconductor substrate with CMOS circuitry and contact points, to be bonded to the first substrate, according to the ongoing embodiment of the present invention;  
         [0017]      FIG. 3  is a schematic illustration of a patterned sacrificial film prior to forming a contact pad, according to the ongoing embodiment of the present invention;  
         [0018]      FIG. 4  is a schematic illustration of a deposited compressive film that will form a contact pad, according to the ongoing embodiment of the present invention;  
         [0019]      FIGS. 5   a  and  5   b  are schematic illustrations of a planarized contact pad prior to release, wherein  FIG. 5   a  is the cross sectional view and  FIG. 5   b  is the top-down view, according to the ongoing embodiment of the present invention;  
         [0020]      FIGS. 6   a  and  6   b  are schematic illustrations of a patterned photoresist that will define the contact pads during a subsequent etching process, wherein  FIG. 6   a  is the cross sectional view and  FIG. 6   b  is the top-down view, according to the ongoing embodiment of the present invention;  
         [0021]      FIGS. 7   a  and  7   b  are schematic illustrations of a released contact pad after removal of the sacrificial layer wherein  FIG. 7   a  is the cross sectional view and  FIG. 7   b  is the top-down view, according to the ongoing embodiment of the present invention;  
         [0022]      FIGS. 8   a  and  8   b  are schematic illustrations of the final interconnect assembly formed by plasma bonding substrates one and two together, wherein  FIG. 8   b  illustrates a detailed view of a contact point between substrates one and two, according to the ongoing embodiment of the present invention;  
         [0023]      FIG. 9  is a schematic illustration of face-to-face bonding with an optical MEMS device, according to another embodiment of the present invention; and  
         [0024]      FIG. 10  is a schematic illustration of face-to-back wafer bonding with high density circuitry, according to still another embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     With reference first to  FIG. 1 , there is illustrated one preferred embodiment for use of the concepts of this invention.  FIG. 1  illustrates a first semiconductor substrate  2 . Substrate  2  includes, in part, complementary metal oxide semiconductor (CMOS)  6 , and through silicon interconnect plugs  8 . Preferably, substrate  2  may be conventionally thinned and chemically mechanically polished (CMP) on the backside to prepare the plugs  8  for bonding. Also, through silicon interconnect plugs can be constructed of any suitable material such as tungsten, copper, gold or the like. Finally, each substrate  2  and  20  ( FIG. 2 ) may not contain through silicon interconnect plugs  8  and the two substrates can be bonded together face-to-face.  
         [0026]     With respect to  FIG. 1   b , a detailed view of the dished surface  10  of the through silicon interconnect plug  8  is illustrated. The dished surface  10  typically results from the CMP process. It is to understood that the dished surface  10  that opposes the protruding contact point  26  ( FIG. 2 ) does not have to be recessed, it can be recessed, flat or a released compressively stressed protruding contact, as well.  
         [0027]     With respect to  FIG. 2 , a second semiconductor substrate  20  is illustrated. Substrate  20  includes, in part, substrate backside  22 , CMOS  24 , and contact points  26 . The details of how contact points  26  are fabricated will be discussed in relation to  FIGS. 3-8 .  
         [0028]     With respect to  FIG. 3 , patterned semiconductor substrate  20  is illustrated. Substrate  20  includes, in part, CMOS  24 , and sacrificial, film  32 . As shown in  FIG. 3 , CMOS  24  and sacrificial film  32  are conventionally patterned to form a contact pad. Also, sacrificial film  32 , preferably, is a silicon film. It is to be understood that the sacrificial layer can be any material that can be selectively etched and removed relative to other layers or materials in the device.  
         [0029]     With respect to  FIG. 4 , semiconductor wafer  20  is illustrated with compressive and contact films deposited. Wafer  20  includes, in part, CMOS  24 , sacrificial film  32 , compressive dielectric film  42 , and metallic contact film  44 . As shown in  FIG. 4 , compressive dielectric film  42  and metallic contact film  44  are conventionally deposited on top of sacrificial layer  32  and CMOS  24 . Also, compressive dielectric film  42 , preferably, is constructed of Si 3 N 4 . It is to be understood that the compressive film  42  can also be other materials as long as it is compressively stressed in the final device. Finally, metallic contact film  44 , preferably, is constructed of any suitable metallic material such as a noble metal (for example, gold) various solder materials, or typical multi-metal layer contact structures such as Cu/Au and Cu/Ni/Au. Finally, it is to be understood that the metal layer  44  could, with the proper materials set, theoretically be the compressive layer, as well.  
         [0030]     With respect to  FIGS. 5   a  and  5   b , semiconductor wafer  20  is illustrated. After contact layers have been deposited on semiconductor wafer  20  ( FIG. 4 ), it is planarized according to a conventional CMP process, such as the Damascene process. As can be seen in  FIG. 5   a , at this point wafer  20  includes, in part, CMOS  24 , sacrificial film  32 , compressive dielectric film  42 , and metallic contact film  44 . As can be seen in  FIG. 5   b , only CMOS  24  and metallic film  44  are exposed after the planarization process.  
         [0031]     With respect to  FIGS. 6   a  and  6   b , semiconductor wafer  20  is illustrated with patterned photoresist prior to etching to define the contacts. After semiconductor wafer  20  ( FIG. 5 ) has been planarized, it is patterned and etched, according to conventional techniques. Semiconductor wafer  20  at this point includes, in part, CMOS  24 , sacrificial film  32 , compressive dielectric film  42 , metallic contact film  44 , patterning film  62 , and contact point  64 . Preferably, patterning film  62  is constructed of any suitable material such as any suitable polymeric material for patterning via photo-imaging, embossing, imprinting or other common techniques. As can be seen in  FIG. 6   a , patterning film  62  is conventionally deposited on metallic film  44 . Compressive dielectric film  42  and metallic film  44  are then conventionally patterned and etched to form contact point  64 . During this patterning and etching process, sacrificial film  32  is also exposed, as shown in  FIG. 6   b . It is to be understood that the contact points can be patterned in other shapes, in addition to rectangular.  
         [0032]     With respect to  FIGS. 7   a  and  7   b , semiconductor wafer  20  is illustrated after removal of sacrificial layer  32 . After semiconductor wafer  20  ( FIG. 6 ) has been patterned and etched ( FIG. 6 ), it is again etched, according to conventional techniques, such as XeF 2  or SF 6  plasma etching. Semiconductor wafer  20  at this point includes, in part, substrate CMOS  24 , compressive dielectric film  42 , metallic contact film  44 , and released contact pad  72 . As can be seen in  FIG. 7   a , released contact pad  72  is formed after sacrificial film  32  is etched away underneath compressive dielectric film  42  and metallic contact film  44 . Once the contact points are released, compressive dielectric film  42  causes released contact pad  72  to bow up slightly and protrude from the planarized surface. The patterning film  62  ( FIG. 6 ) is then conventionally stripped.  FIG. 7   b  shows a top-down view of semiconductor wafer  20  with CMOS  24  and released contact pad  72  exposed.  
         [0033]     With respect to  FIGS. 8   a  and  8   b , completed semiconductor interconnect assembly  80  is illustrated. After semiconductor wafer  20  ( FIG. 7 ) has been completed, it is then contacted with semiconductor substrate  2  ( FIG. 2 ) in order to form semiconductor interconnect assembly  80 . Semiconductor interconnect assembly  80  includes, in part, CMOS  6 , through silicon interconnect plugs  8 , CMOS  24 , and contact points  26 . As can be seen in  FIG. 8   a , semiconductor substrate  2  and semiconductor wafer  20  are conventionally plasma treated (such as in N 2 , O 2  or Ar plasma) and bonded together. It is to be understood that interconnect assembly  80  maybe located on the top side, the back side or multiple sides of each substrate  2  ( FIG. 1 ) and  20  ( FIG. 2 ).  
         [0034]     With respect to  FIG. 8   b , contact pad  72  of semiconductor wafer  20  protrudes upwards towards dished surface  10  of plug  8  on semiconductor substrate  2 . In this manner, an excellent interconnect is insured even when the surfaces of the through silicon interconnect plugs  8  are slightly dished.  
         [0035]     With respect to  FIG. 9 , semiconductor  90  is illustrated. Semiconductor  90  includes, in part, glass substrate  92 , CMOS  93 , interconnects  94 , an optical MEMS or NEMS devices  95 , CMOS  96  and released contact pads  97 . As illustrated in  FIG. 9 , a face-to-face bonding of the glass substrate and the MEMS device is achieved through a conventional plasma enhanced bonding process. In this manner, released contact pads  97  protrude upward towards interconnect  94  in order to form an excellent interconnect between the two devices in a similar manner as discussed above with respect to  FIGS. 1-8 .  
         [0036]     Finally, with respect to  FIG. 10 , semiconductor  100  is illustrated. Semiconductor  100  includes, in part, substrate backside or lid  102 , through silicon interconnect plugs  104 , substrate backside  106 , high density circuitry devices  108 , and released contact pads  110 . High density circuitry devices  108  can be, preferably, nanotechnology devices. As illustrated in  FIG. 10 , lid  102  will not only provide a cap over substrate  106  and high density circuitry devices  108 , but also increase the number of input-output counts.  
         [0037]     While the present invention has been illustrated with respect to particular semiconductor devices, it is to be understood that the present invention can also be utilized in other devices such as, but not limited to, non-CMOS devices (JetMOS, sensors, etc), NEMS devices, photonics devices, various medical devices, FLEX circuits, PCBs (Printed Circuit Boards), any type of protruding contacts to flat contacts, any type of protruding contacts to protruding contacts, and various multi-layer (2 or more) substrate stacks without deviating from the scope of the present invention.  
         [0038]     Also, the present invention can be embodied in any computer-readable medium for use by or in connection with an instruction-execution system, apparatus or device such as a computer/processor based system, processor-containing system or other system that can fetch the instructions from the instruction-execution system, apparatus or device, and execute the instructions contained therein. In the context of this disclosure, a “computer-readable medium” can be any means that can store, communicate, propagate or transport a program for use by or in connection with the instruction-execution system, apparatus or device. The computer-readable medium can comprise any one of many physical media such as, for example, electronic, magnetic, optical, electromagnetic, infrared, or semiconductor media. More specific examples of a suitable computer-readable medium would include, but are not limited to, a portable magnetic computer diskette such as floppy diskettes or hard drives, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory, or a portable compact disc. It is to be understood that the computer-readable medium could even be paper or another suitable medium upon which the program is printed, as the program can be electronically captured, via, for instance, optical scanning of the paper or other medium, then compiled, interpreted or otherwise processed in a single manner, if necessary, and then stored in a computer memory.  
         [0039]     Those skilled in the art will understand that various embodiment of the present invention can be implemented in hardware, software, firmware or combinations thereof. Separate embodiments of the present invention can be implemented using a combination of hardware and software or firmware that is stored in memory and executed by a suitable instruction-execution system. If implemented solely in hardware, as in an alternative embodiment, the present invention can be separately implemented with any or a combination of technologies which are well known in the art (for example, discrete-logic circuits, application-specific integrated circuits (ASICs), programmable-gate arrays (PGAs), field-programmable gate arrays (FPGAs), and/or other later developed technologies. In preferred embodiments, the present invention can be implemented in a combination of software and data executed and stored under the control of a computing device.  
         [0040]     It will be well understood by one having ordinary skill in the art, after having become familiar with the teachings of the present invention, that software applications may be written in a number of programming languages now known or later developed.  
         [0041]     Once given the above disclosure, many other features, modifications or improvements will become apparent to the skilled artisan. Such features, modifications or improvements are, therefore, considered to be a part of this invention, the scope of which is to be determined by the following claims.