Patent Publication Number: US-2022230947-A1

Title: Backside power distribution network semiconductor architecture using direct epitaxial layer connection and method of manufacturing the same

Description:
CROSS-REFERENCE TO THE RELATED APPLICATION 
     This application is based on and claims benefit to U.S. Provisional Application No. 63/138,597 filed on Jan. 18, 2021 in the U.S. Patent and Trademark Office, the disclosure of which is incorporated herein in its entirety by reference. 
    
    
     BACKGROUND 
     1. Field 
     Example embodiments of the present disclosure relate to a backside power distribution network (BSPDN) semiconductor architecture and a method of manufacturing the same, and more particularly to a BSPDN semiconductor architecture including a back side through-silicon via (TSV) contacting an epitaxial layer of an active device of a front side semiconductor device and a method of manufacturing the same. 
     2. Description of Related Art 
     The BSPDN semiconductor architecture separates the signal wiring from the power distribution network (PDN) provided on a wafer by providing a semiconductor device such as an integrated circuit including active devices and signal wires for routing signals on a front side of the wafer and providing a PDN for supplying power on a back side of the wafer. The BSPDN semiconductor architecture may minimize the routing congestion and allow for down scaling of an area of the semiconductor architecture. A BSPDN semiconductor architecture may result in a ˜30% reduction and an improved current-resistance (IR) drop as compared to a PDN semiconductor architecture. 
     However, there may be difficulties in manufacturing a BSPDN semiconductor architecture which requires multilayers of elements to connect the PDN on a back side of the wafer with an active device included in the integrated circuit provided on a front side of the wafer. The multilayer elements and multiple interfaces provided between the multilayer elements may increase connection resistance of the BSPDN semiconductor architecture. In addition, inclusion of the multilayer elements may result in complex manufacturing process and increase in manufacturing cost. 
     Information disclosed in this Background section has already been known to the inventors before achieving the embodiments of the present application or is technical information acquired in the process of achieving the embodiments. Therefore, it may contain information that does not form the prior art that is already known to the public. 
     SUMMARY 
     One or more example embodiments provide a backside power distribution network (BSPDN) semiconductor architecture and a method of manufacturing the same. 
     One or more example embodiments also provide to a BSPDN semiconductor architecture including a back side TSV contacting an active device of a front side semiconductor device and a method of manufacturing the same. 
     According to an aspect of an example embodiment, there is provided a semiconductor architecture including a wafer, a first semiconductor device configured to route signals that is provided on a first surface of the wafer, the first semiconductor device including an active device that includes an epitaxial layer, a second semiconductor device configured to supply powers that is provided on a second surface of the wafer opposite to the first surface, and a through-silicon via (TSV) protruding from the second semiconductor device and connected to the epitaxial layer of the active device. 
     According to another aspect of an example embodiment, there is provided a method of manufacturing a semiconductor architecture, the method including providing a wafer, providing a first semiconductor device on a first surface of the wafer, the first semiconductor device including an active device that includes an epitaxial layer, providing a trench from a second surface of the wafer opposite to the first surface to a level of the epitaxial layer of the active device, providing a through-silicon via (TSV) in the trench such that the TSV is connected to the epitaxial layer of the active device, and providing a second semiconductor device on the second surface of the wafer. 
     According to another aspect of an example embodiment, there is provided a semiconductor architecture including a wafer, a first semiconductor device provided on a first surface of the wafer, the first semiconductor device including an active device that includes an epitaxial layer, a second semiconductor device provided on a second surface of the wafer opposite to the first surface, the second semiconductor device including a power rail configured to supply power, and a through-silicon via (TSV) protruding from the power rail and extending to a level of the epitaxial layer of the active device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and/or other aspects, features, and advantages of example embodiments of the disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a perspective view of a general PDN semiconductor architecture and a BSPDN semiconductor architecture according to an example embodiment; 
         FIG. 2  illustrates a BSPDN semiconductor architecture according to a related embodiment; 
         FIGS. 3A, 3B, and 3C  illustrate a method of manufacturing a BSPDN semiconductor architecture according to a related embodiment; 
         FIG. 4  illustrates a perspective view of a BSPDN semiconductor architecture according to an example embodiment; 
         FIG. 5  illustrates a cross-sectional view taken along line I-I′ of  FIG. 4  according to an example embodiment; 
         FIG. 6  illustrates a cross-sectional view taken along line I-I′ of  FIG. 4  according to another example embodiment 
         FIGS. 7A, 7B, 7C, and 7D  illustrate a method of manufacturing a BSPDN semiconductor architecture illustrated in  FIG. 5  according to an example embodiment; 
         FIGS. 8A, 8B, 8C, 8D, and 8E  illustrate a method of manufacturing a BSPDN semiconductor architecture illustrated in  FIG. 6  according to an example embodiment; 
         FIG. 9  illustrates a flowchart of a method of manufacturing a BSPDN semiconductor architecture according to an example embodiment; 
         FIG. 10  illustrates a flowchart of a method of manufacturing a BSPDN semiconductor architecture according to another example embodiment; 
         FIG. 11  illustrates a semiconductor architecture that may incorporate the BSPDN semiconductor architectures according to example embodiments; and 
         FIG. 12  illustrates a schematic block diagram of an electronic system that may incorporate the BSPDN semiconductor architecture according to example embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     The example embodiments described herein are examples, and thus, the present disclosure is not limited thereto, and may be realized in various other forms. Each of the example embodiments provided in the following description is not excluded from being associated with one or more features of another example or another example embodiment also provided herein or not provided herein but consistent with the present disclosure. For example, even if matters described in a specific example or example embodiment are not described in a different example or example embodiment thereto, the matters may be understood as being related to or combined with the different example or embodiment, unless otherwise mentioned in descriptions thereof. 
     In addition, it should be understood that all descriptions of principles, aspects, examples, and example embodiments are intended to encompass structural and functional equivalents thereof. In addition, these equivalents should be understood as including not only currently well-known equivalents but also equivalents to be developed in the future, that is, all devices invented to perform the same functions regardless of the structures thereof. 
     It will be understood that when an element, component, layer, pattern, structure, region, or so on (hereinafter collectively “element”) of a semiconductor device is referred to as being “over,” “above,” “on,” “below,” “under,” “beneath,” “connected to” or “coupled to” another element the semiconductor device, it can be directly over, above, on, below, under, beneath, connected or coupled to the other element or an intervening element(s) may be present. In contrast, when an element of a semiconductor device is referred to as being “directly over,” “directly above,” “directly on,” “directly below,” “directly under,” “directly beneath,” “directly connected to” or “directly coupled to” another element of the semiconductor device, there are no intervening elements present. Like numerals refer to like elements throughout this disclosure. 
     Spatially relative terms, such as “over,” “above,” “on,” “upper,” “below,” “under,” “beneath,” “lower,” “top,” and “bottom,” and the like, may be used herein for ease of description to describe one element&#39;s relationship to another element(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of a semiconductor device in use or operation in addition to the orientation depicted in the figures. For example, if the semiconductor device in the figures is turned over, elements described as “below” or “beneath” other elements would then be oriented “above” the other elements. Thus, the term “below” can encompass both an orientation of above and below. The semiconductor device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     As used herein, expressions such as “at least one of,” when preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list. For example, the expression, “at least one of a, b, and c,” should be understood as including only a, only b, only c, both a and b, both a and c, both b and c, or all of a, b, and c. Herein, when a term “same” is used to compare a dimension of two or more elements, the term may cover a “substantially same” dimension. 
     It will be understood that, although the terms “first,” “second,” “third,” “fourth,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Thus, a first element discussed below could be termed a second element without departing from the teachings of the present disclosure. 
     It will be also understood that, even if a certain step or operation of manufacturing an apparatus or structure is described later than another step or operation, the step or operation may be performed later than the other step or operation unless the other step or operation is described as being performed after the step or operation. 
     Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of the example embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, the example embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of the present disclosure. Further, in the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. 
     For the sake of brevity, general elements to semiconductor devices may or may not be described in detail herein. 
       FIG. 1  illustrates a perspective view of a general PDN semiconductor architecture and a BSPDN semiconductor architecture according to an example embodiment. 
     Referring to  FIG. 1 , a general PDN semiconductor architecture  1000 ′ includes a PDN/signal wiring device  1200   a ′ on a front side of the wafer  1100 . However, such configuration of the general PDN semiconductor architecture  1000 ′ causes routing congestion in the PDN/signal wiring device  1200   a ′ and increases a total area of the semiconductor architecture. In addition, a resistance of the general PDN semiconductor architecture  1000 ′ may be relatively high. 
     As illustrated in  FIG. 1 , according to an example embodiment, a BSPDN semiconductor architecture  1000  is configured to separate a first semiconductor device  1200   a  for signal wiring, to be provided a front side of the wafer  1100 , from a second semiconductor device  1200   b  for power distribution to be provided on a back side of the wafer  1100  opposite to the first semiconductor device  1200   a.  The BSPDN semiconductor architecture  1000  according to an example embodiment may reduce the routing congestion and the area of the semiconductor architecture by removing the PDN from the front side of the wafer, and hence may also improve an IR drop. For example, a total area of the semiconductor architecture may be reduced by 30% compared to the general PDN semiconductor architecture  1000 ′. However, embodiments are not limited thereto. 
       FIG. 2  illustrates a BSPDN semiconductor architecture according to a related embodiment. 
     Referring the  FIG. 2 , the semiconductor architecture  1000  may include a wafer  1100 , a first semiconductor device  1200   a  provided on a first surface of the wafer  1100 , and a second semiconductor device  1200   b  provided on a second surface of the wafer  1100 . The first semiconductor device  1200   a  may be an integrated circuit configured to route signals, and may include components such as, for example, active devices (for example, transistors), signal wires, and BPRs  120 , etc. For example, the active devices may include fins  150  and epitaxial layers  160  provided on the fins  150 . The epitaxial layers  160  and fins  150  may include silicon (Si). The active devices may also include epitaxial layers provided on nanosheets, nanowires, etc. The active devices may be provided in a front-end-of-line (FEOL) layer on the first surface of the wafer  1100 . In the middle-of-the-line (MOL) layer of the first semiconductor device  1200   a,  an epitaxial contact  190  may be provided to contact the epitaxial layer  160  and extend in a horizontal direction parallel to the first surface of the wafer  1100 . A via  180  may be provided on a surface of the epitaxial contact  190  facing the wafer  1100 , and a BPR  120  may be provided on the via  180  contacting the epitaxial contact  190 , and protrude toward the wafer  1100 . In the back-end-of-line (BEOL) layer of the first semiconductor device  1200   a,  metal layers  170  configured route signals may be provided. Vias  180  may be provided between the metal layers  170  to connect the metal layers  170 , and vias  180  may be provided between the epitaxial contact  190  and a metal layer  170  to connect the signal wiring layer to the active device. 
     The active devices may include a power tapping epitaxial layer and a non-power tapping epitaxial layer. The metal layers  170  are connected to the non-power tapping epitaxial layer of the active device for signal routing between the active devices. The BPR  120  is connected to the power tapping epitaxial layer of the active devices and are not connected to the metal layers  170 . The BPR  120  is configured to deliver power to the active devices. 
     The second semiconductor device  1200   b  may be an integrated circuit including a PDN. The back-end-of-line (BEOL) layer of the second semiconductor device  1200   b  may include a power rail metal layer  170 ′ configured to operate as VDD/VSS power rail that is provided on a second surface of the wafer  1100 . The BEOL layer may also include a metal layer  170  and vias  180  provided between the power rail metal layer  170 ′ and the metal layer  170 . In addition, a TSV  130  configured to operate as a power connecting structure may protrude from the power rail metal layer  170 ′ and penetrate the wafer  1100  to contact the BPR  120 . 
     As illustrated in  FIG. 2 , multiple layers are provided between the power rail metal layer  170 ′ included in the second semiconductor device  1200   b  and an epitaxial layer  160  of the active device included in the first semiconductor device  1200   a.  For example, a TSV  130 , a BPR  120 , a via  180 , and an epitaxial contact  190  may be provided between the power rail metal layer  170 ′ and the epitaxial layer  160 . 
     According to the BSPDN semiconductor architecture  1000  of a related embodiment, the multiple layers provided between the power rail metal layer  170 ′ and the epitaxial layer  160  may increase connection resistance. In addition, the manufacturing process of the BSPDN semiconductor architecture  1000  may become more complex and the manufacturing cost may increase. Further, a misalignment between the TSV  130  and the BPR  120  may occur which may increase the resistance of the BSPDN semiconductor architecture  1000  and lead to a device failure of the BSPDN semiconductor architecture  1000 . 
       FIGS. 3A through 3C  illustrate a method of manufacturing a BSPDN semiconductor architecture according to a related embodiment. 
     As illustrated in  FIG. 3A , the method may include providing a wafer  1100  including an etch stop layer  1500 . The etch stop layer  1500  may be included in the wafer  1100 . 
     A first semiconductor device  1200   a  may be provided on a first surface of the wafer  1100 . The first semiconductor device  1200   a  may be an integrated circuit including components such as, for example, active devices, signal wires, and BPRs  120 . The BPR  120  may be provided on a first surface of the wafer  1100 . 
     Referring to  FIG. 3B , a wafer-to-wafer bonding process may be carried out. For example, a second wafer  1300  may be provided on a first surface of the first semiconductor device  1200   a.  The second wafer  1300  may be bonded by an adhesive layer  1400  provided between the first semiconductor device  1200   a  and the second wafer  1300 . After the wafer-to-wafer bonding, the semiconductor architecture is flipped. 
     Referring to  FIG. 3C , a portion of the wafer  1100  opposite to the first surface may be removed to a level of the etch stop layer  1500 . The etch stop layer  1500  may be removed to expose a second surface of the wafer  1100 . 
     A second semiconductor device  1200   b  may be provided on the second surface of the wafer  1100 . The second semiconductor device  1200   b  may be an integrated circuit including PDN for power distribution. The BEOL layer of the second semiconductor device  1200   b  may include a power rail metal layer  170 ′ and a metal layer  170 . Vias  180  may be provided between the power rail metal layer  170 ′ and the metal layer  170 . In addition, a TSV  130  may protrude from the second semiconductor device  1200   b.  The TSV  130  be in contact with the power rail metal layer  170 ′ and penetrate the wafer  1100  to contact the BPR  120  included in the first semiconductor device  1200   a.    
     As illustrated in  FIG. 3C , multiple layers including a TSV  130 , BPR  120 , via  180 , epitaxial contact  190  are provided between the power rail metal layer  170 ′ protruding from the second semiconductor device  1200   b  provided on the second surface of the wafer  1100  and an epitaxial layer  160  of the active device included in the first semiconductor device  1200   a  provided on the first surface of the wafer  1100 . 
     The multiple layers provided between the power rail metal layer  170 ′ and the epitaxial layer  160  may increase connection resistance of the BSPDN semiconductor architecture  1000  according to the related embodiment. The manufacturing process of the BSPDN semiconductor architecture  1000  may become more complex and the manufacturing cost may increase. In addition, a misalignment between the TSV  130  and the BPR  120  may occur which may increase the resistance of the BSPDN semiconductor architecture and may lead to a device failure of the BSPDN semiconductor architecture  1000 . 
       FIG. 4  illustrates a perspective view of a BSPDN semiconductor architecture according to an example embodiment. 
     As illustrated in  FIG. 4 , the BSPDN semiconductor architecture  1  may include a wafer  100 , a first semiconductor device  200   a  provided on a first surface of the wafer  100 , and a second semiconductor device  200   b  provided on a second surface of the wafer  100  opposite to the first semiconductor device  200   a.  The first semiconductor device  200   a  and the second semiconductor device  200   b  may be integrated to each other and may form a BSPDN semiconductor architecture  1  according to an example embodiment. 
     The wafer  100  may include, for example, a Si substrate, a glass substrate, a sapphire substrate, etc. However, embodiments are not limited thereto. As illustrated in  FIG. 4 , the wafer  100  may be a circular panel, but the shape of the wafer  100  is not limited thereto. For example, the wafer  100  may be a tetragonal panel. The wafer  100  may include a single layer or multiple layers. 
       FIG. 5  illustrates a cross-sectional view taken along line I-I′ of  FIG. 4  according to an example embodiment. 
     According to the example embodiment, the BSPDN semiconductor architecture  1  includes a first semiconductor device  200   a  provided on a first surface of the wafer  100  and a second semiconductor device  200   b  provided on a second surface of the wafer  100 . 
     The first semiconductor device  200   a  may be an integrated circuit including an active device (for example, transistor) and signal wires. For example, the FEOL layer of the first semiconductor device  200   a  may include an active device including fins  50  and epitaxial layers  60  provided on the fins  50 . The epitaxial layers  60  and the fins  50  may include Si. However, embodiments are not limited thereto. For example, the active device may include epitaxial layers  60  provided on nanosheets, nanowires, etc. The active device may be provided on the first surface of the wafer  100 . The MOL layer of the first semiconductor device  200   a  may include an epitaxial contact  90  provided on the epitaxial layer  60  and extending in a horizontal direction parallel to the first surface of the wafer  100 . The BEOL layer of the first semiconductor device  200   a  may include metal layers  70  configured to route signals. The metal layers  70  may include a metal material with low resistance such as, for example, copper (Cu). However, embodiments are not limited thereto. Vias  80  may be provided between the metal layers  70  to connect the metal layers  70 , and vias  80  may be provided between the epitaxial contact  90  and a metal layer  70  to connect the signal wiring layer to the active device. 
     In comparison to the first semiconductor device  200   a  included in a BSPDN semiconductor architecture  1000  as illustrated in  FIG. 2 , the first semiconductor device  200   a  included in a BSPDN semiconductor architecture  1  according to an example embodiment does not include a BPR. 
     The second semiconductor device  200   b  may be an integrated circuit including PDN configured to distribute power. The BEOL layer of the second semiconductor device  200   b  may include a power rail metal layer  70 ′ configured to operate as VDD/VSS power rail that is provided on a second surface of the wafer  100 . The BEOL layer may also include a metal layer  70  and vias  80  provided between the power rail metal layer  70 ′ and the metal layer  70 . In addition, a TSV  30  configured to operate as a power connecting structure may protrude from the power rail metal layer  70 ′ and penetrate the wafer  100 . The TSV  30  may be provided to directly contact the epitaxial layer  60  included in an active device of the first semiconductor device  200   a  and the power rail metal layer  70 ′ of the second semiconductor device  200   b.    
     For example, as illustrated in  FIG. 5 , the TSV  30  extends vertically from a surface of the second semiconductor device  200   b  to the level of the epitaxial layer  60  of the first semiconductor device  200   a.  The height of the TSV  30  may vary depending on the thickness of the wafer  100 , and may range from around 200 nm to 500 nm. However, embodiments are not limited thereto. 
     According to the example embodiment as illustrated in  FIG. 5 , the TSV  30  is directly connected to the epitaxial layer  60 , and there are no additional elements provided between the TSV  30  and the epitaxial layer  60 . Accordingly, the connection resistance of the BSPDN semiconductor architecture  1  may be lowered. The manufacturing process of the BSPDN semiconductor architecture  1  may be simplified and the manufacturing cost may be reduced. In addition, there is no concern for a misalignment between the TSV  30  and a BPR which may lead to misalignment between the first semiconductor device  200   a  and the second semiconductor device  200   b.  Thus, the performance of the BSPDN semiconductor architecture  1  may be improved. 
       FIG. 6  illustrates a cross-sectional view taken along line I-I′ of  FIG. 4  according to another example embodiment. 
     According to the example embodiment, the BSPDN semiconductor architecture  1 ′ includes a first semiconductor device  200   a  provided on a first surface of the wafer  100  and a second semiconductor device  200   b  provided on a second surface of the wafer  100 . 
     The first semiconductor device  200   a  may be an integrated circuit including an active device (for example, transistor) and signal wires. For example, the FEOL layer of the first semiconductor device  200   a  may include an active device including fins  50  and epitaxial layers  60  provided on the fins  50 . However, embodiments are not limited thereto. For example, the active device may include epitaxial layers  60  provided on nanosheets, nanowires, etc. The active device may be provided on the first surface of the wafer  100 . The MOL layer of the first semiconductor device  200   a  may include an epitaxial contact  90  provided on the epitaxial layer  60  and extend in a horizontal direction parallel to the first surface of the wafer  100 . The BEOL layer of the first semiconductor device  200   a  may include metal layers  70  configured to route signals. The metal layers  70  may include a metal material with low resistance such as, for example, Cu. However, embodiments are not limited thereto. Vias  80  may be provided between the metal layers  70  to connect the metal layers  70 , and vias  80  may be provided between the epitaxial contact  90  and a metal layer  70  to connect the signal wiring layer to the active device. 
     In comparison to the first semiconductor device  200   a  included in a BSPDN semiconductor architecture  1000  as illustrated in  FIG. 2 , the first semiconductor device  200   a  included in a BSPDN semiconductor architecture  1 ′ according to an example embodiment does not include a BPR. 
     The second semiconductor device  200   b  may be an integrated circuit including PDN configured to distribute power. The BEOL layer of the second semiconductor device  200   b  may include an embedded power rail metal layer  70 ″ configured to operate as VDD/VSS power rail that is at least partially embedded in a second surface of the wafer  100 . For example, the embedded power rail metal layer  70 ″ may be provided to at least partially penetrate the second surface of the wafer  100 . The BEOL layer of the second semiconductor device  200   b  also includes a via  80  that is provided on the embedded power rail metal layer  70 ″ and a metal layer  70  provided on the via  80 . A TSV  30  protrudes from a surface of the embedded power rail metal layer  70 ″ and penetrates the wafer  100  to be connected the epitaxial layer  60  of the active device included in the first semiconductor device  200   a.  The TSV  30  may be provided to directly contact the epitaxial layer  60  included in an active device of the first semiconductor device  200   a  and the embedded power rail metal layer  70 ″ of the second semiconductor device  200   b.    
     As illustrated in  FIG. 6 , the TSV  30  extends from a first surface of the embedded power rail metal layer  70 ″ to a level of the epitaxial layer  60  of the first semiconductor device  200   a.  The height of the TSV  30  may vary depending on the thickness of the wafer  100  and may range from around 200 nm to 500 nm. However, embodiments are not limited thereto. 
     Similar to the example embodiment as illustrated in  FIG. 5 , according to the example embodiment as illustrated in  FIG. 6 , as the TSV  30  is directly connected to the epitaxial layer  60 , and there are no additional elements provided between the TSV  30  and the epitaxial layer  60 , the connection resistance of the BSPDN semiconductor architecture  1 ′ may be lowered. The manufacturing process of the BSPDN semiconductor architecture  1 ′ may be simplified and the manufacturing cost may be reduced. In addition, there is no concern for a misalignment between the TSV  30  and a BPR which may lead to misalignment between the first semiconductor device  200   a  and the second semiconductor device  200   b.  Thus, the performance of the BSPDN semiconductor architecture  1 ′ may be improved. 
     In addition, according to the example embodiment as illustrated in  FIG. 6 , a height of the TSV  30  may be reduced compared to a height of the TSV  30  according to the example embodiment in  FIG. 5 . Accordingly, the aspect ratio of the TSV  30  may be reduced which may further lower resistance and facilitate the manufacturing process of the TSV  30 . 
     A width of the TSV  30  may depend on the width of the embedded power rail metal layer  70 ″ and may be less than a width of the embedded power rail metal layer  70 ″. However, embodiments are not limited thereto. 
       FIGS. 7A through 7D  illustrate a method of manufacturing a BSPDN semiconductor architecture illustrated in  FIG. 5  according to an example embodiment. 
     Referring to  FIG. 7A , a wafer  100  including an etch stop layer  500  is provided. The wafer  100  may be a Si layer, and the etch stop layer may be a silicon germanium (SiGe) layer, but embodiments are not limited thereto. For example, the etch stop layer may be an oxide layer in a silicon-on-insulator (SOI) wafer. 
     A first semiconductor device  200   a  is provided on the first surface of the wafer  100 . Providing the first semiconductor device  200   a  includes by providing an active device including fins  50  and epitaxial layers  60  on the first surface of the wafer. However, embodiments are not limited thereto. For example, providing the active device may include providing epitaxial layers  60  on nanosheets, nanowires, etc. An epitaxial contact  90  may be provided on the epitaxial layer  60  that extends in a horizontal direction parallel to the first surface of the wafer  100 . A via  80  may be provided on the epitaxial contact  90 . Metal layers  70  configured to route signals may be provided on the via  80 , connected to the epitaxial contact  90 , to be connected to the active device. Vias  80  may be provided between the metal layers  70  to connect the metal layers  70 . 
     Referring to  FIG. 7B , a wafer-to-wafer bonding process may be carried out. For example, a second wafer  300  may be provided on a first surface of the first semiconductor device  200   a.  The second wafer  300  may be bonded to the first semiconductor device  200   a  by providing an adhesive layer  400  between the first semiconductor device  200   a  and the second wafer  300 . However, embodiments are not limited thereto. According to another example embodiment, the second wafer  300  may be directly provided on the first semiconductor device  200   a.  For example, the second wafer  300  may be directly bonded to the first semiconductor device  200   a  by a Si direct bonding without using an adhesive layer. After the wafer-to-wafer bonding, the semiconductor architecture may be flipped. 
     Referring to  FIG. 7C , a portion of a back side the wafer  100  from the second surface may be removed to a level of the etch stop layer  500 . The etch stop layer  500  may be removed to expose a second surface of the wafer  100 . A portion of the wafer  100  and the etch stop layer  500  may be removed by a grinding process including, for example, chemical-mechanical polishing (CMP) or dry etching. However, embodiments are not limited thereto. 
     Referring to  FIG. 7D , a TSV opening  31  may be formed on the exposed second surface of the wafer  100  to a level of the epitaxial layer  60  such that the TSV opening  31  exposes the epitaxial layer  60 . The TSV opening  31  may be a trench formed by, for example, dry etching or wet etching. However, embodiments are not limited thereto. The TSV opening  31  is filled with a conductive material with a relatively low resistance such as, for example, Cu to form a TSV  30 . However, the conductive material is not limited thereto. The TSV  30  is formed to be in direct contact with the epitaxial layer  60 . An upper surface of the TSV  30  may be coplanar with the exposed surface of the wafer  100 . 
     Referring to  FIG. 7D , a second semiconductor device  200   b  is provided on the exposed second surface of the wafer  100  and an exposed surface of the TSV  30 . Providing the second semiconductor device  200   b  includes providing a power rail metal layer  70 ′ configured to operate as a VDD/VSS power rail to supply power on the exposed surface of the wafer  100  and the TSV  30 . Vias  80  are provided on the power rail metal layer  70 ′ and a metal layer  70  may be provided on the vias  80 . 
       FIGS. 8A through 8E  illustrate a method of manufacturing a BSPDN semiconductor architecture illustrated in  FIG. 6  according to an example embodiment. 
     Referring to  FIG. 8A , a wafer  100  including an etch stop layer  500  is provided. 
     A first semiconductor device  200   a  is provided on the first surface of the wafer  100 . Providing the first semiconductor device  200   a  includes by providing an active device including fins  50  and epitaxial layers  60  provided on the fins  50  on the first surface of the wafer. However, embodiments are not limited thereto. For example, providing the active device may include providing epitaxial layers  60  on nanosheets, nanowires, etc. An epitaxial contact  90  may be provided on the epitaxial layer  60  that extends in a horizontal direction parallel to the first surface of the wafer  100 . A via  80  may be provided on the epitaxial contact  90 . Metal layers  70  configured to route signals may be provided on the via  80 , connected to the epitaxial contact  90 , to be connected to the active device. Vias  80  may be provided between the metal layers  70  to connect the metal layers  70 . 
     Referring to  FIG. 8B , a wafer-to-wafer bonding process may be carried out. For example, a second wafer  300  may be provided on a first surface of the first semiconductor device  200   a.  The second wafer  300  may be bonded to the first semiconductor device  200   a  by providing an adhesive layer  400  between the first semiconductor device  200   a  and the second wafer  300 . However, embodiments are not limited thereto. According to another example embodiment, the second wafer  300  may be directly provided on the first semiconductor device  200   a.  For example, the second wafer  300  may be directly bonded to the first semiconductor device  200   a  by a Si direct bonding without using an adhesive layer. After the wafer-to-wafer bonding, the semiconductor architecture may be flipped. 
     Referring to  FIG. 8C , a portion of a back side the wafer  100  from the second surface may be removed to a level of the etch stop layer  500 . The etch stop layer  500  may be removed to expose a second surface of the wafer  100 . A portion of the wafer  100  and the etch stop layer  500  may be removed by a grinding process including, for example, chemical-mechanical polishing (CMP) or dry etching. However, embodiments are not limited thereto. 
     Referring to  FIG. 8D , a metal opening  71  may be formed on the exposed surface of the wafer  100 . The metal opening may be a trench formed by, for example, dry etching or wet etching. However, embodiments are not limited thereto. The depth of the metal opening  71  may be less than a height of the wafer  100 . An TSV opening  31  may be formed from the metal opening  71  to a level of the epitaxial layer  60  included in the first semiconductor device  200   a  such that the TSV opening  31  exposes the epitaxial layer  60 . 
     Referring to  FIG. 8E , a conductive material with low resistance such as, for example, Cu may be filled in the TSV opening  31  to form the TSV  30 . The TSV  30  may be formed to be in direct contact with the epitaxial layer  60 . 
     A second semiconductor device  200   b  may be provided on the wafer  100  and TSV  30 . Providing the second semiconductor device  200   b  may include filling the metal opening  71  with a conductive material with low resistance such as, for example, Cu to form a power rail metal layer  70 ″ that is configured to supply power. The power rail metal layer  70 ″ may be formed to directly contact the TSV  30 . A via  80  is provided on the power rail metal layer  70 ″, and a metal layer  70  is provided on the via  80 . 
       FIG. 9  is a flowchart illustrating a method of manufacturing a BSPDN semiconductor architecture according to an example embodiment. 
     According to an example embodiment, a wafer including an etch stop layer is provided (S 110 ). The wafer may be a Si layer, and the etch stop layer may be a silicon germanium (SiGe) layer, but embodiments are not limited thereto. For example, the etch stop layer may be an oxide layer in a silicon-on-insulator (SOI) wafer. 
     A first semiconductor device is provided on a first surface of the wafer (S 120 ). Providing the first semiconductor device includes providing an active device including fins and epitaxial layers on the first surface of the wafer. An epitaxial contact is provided on the epitaxial layer, and a via is provided on the epitaxial contact. Metal layers are provided on the via connected to the epitaxial contact, and vias may be provided between the metal layers. 
     A second wafer may be provided on the first semiconductor device (S 130 ). The second wafer may be bonded to the first semiconductor layer by providing an adhesive layer between the first semiconductor device and the second wafer. According to another example embodiment, the second wafer may be directly provided on the first semiconductor device by, for example, a Si direct bonding without using an adhesive layer. The wafer-to-wafer bonded semiconductor architecture may be flipped. 
     A portion of a back side of the wafer and the etch stop layer may be removed (S 140 ). The etch stop layer may be removed to expose a second surface of the wafer. The wafer and the etch stop layer may be removed by a grinding process such as, for example, CMP or dry etching, but embodiments are not limited thereto. 
     A opening is provided in the wafer (S 150 ). The opening is formed to a level of the epitaxial layer of the first semiconductor device such that the opening exposes the epitaxial layer. The opening may be a trench formed by dry etching or wet etching a portion of the exposed second surface of the wafer. However, embodiments are not limited thereto. 
     A TSV is provided in the opening (S 160 ). A conductive material with relatively low resistance such as, for example, Cu is filled in the opening to form the TSV. The TSV is formed to be in direct contact with the epitaxial layer of the first semiconductor device. 
     A second semiconductor device is provided on the second surface of the wafer and the TSV (S 170 ). Providing the second semiconductor device may include providing a power rail metal layer configured to supply power on the second surface of the wafer and an exposed surface of the TSV. The power rail metal layer is provided to contact the TSV. Vias are provided on the power rail metal layer and a metal layer may be provided on the vias. 
       FIG. 10  is a flowchart illustrating a method of manufacturing a BSPDN semiconductor architecture according to an example embodiment. 
     According to an example embodiment, a wafer including an etch stop layer is provided (S 210 ). The wafer may be a Si layer, and the etch stop layer may be a silicon germanium (SiGe) layer, but embodiments are not limited thereto. For example, the etch stop layer may be an oxide layer in a silicon-on-insulator (SOI) wafer. 
     A first semiconductor device is provided on a first surface of the wafer (S 220 ). Providing the first semiconductor device includes providing an active device including fins and epitaxial layers on the first surface of the wafer. An epitaxial contact is provided on the epitaxial layer, and a via is provided on the epitaxial contact. Metal layers are provided on the via connected to the epitaxial contact, and vias may be provided between the metal layers. 
     A second wafer may be provided on the first semiconductor device (S 230 ). The second wafer may be bonded to the first semiconductor layer by providing an adhesive layer between the first semiconductor device and the second wafer. According to another example embodiment, the second wafer may be directly provided on the first semiconductor device by, for example, a Si direct bonding without using an adhesive layer. The wafer-to-wafer bonded semiconductor architecture may be flipped. 
     A portion of a back side of the wafer and the etch stop layer may be removed (S 240 ). The etch stop layer may be removed to expose a second surface of the wafer. The wafer and the etch stop layer may be removed by a grinding process such as, for example, CMP or dry etching, but embodiments are not limited thereto. 
     A first opening is provided in the wafer (S 250 ). The first opening may be formed to a depth that is less than the thickness of the wafer. The first opening may be a trench formed by, for example, dry etching or wet etching a portion of the wafer. A second opening may be formed from the first opening to a level of the epitaxial layer such that the second opening exposes the epitaxial layer of the first semiconductor device. The second opening may be a trench formed by, for example, dry etching or wet etching. 
     A TSV is formed in the first opening (S 260 ). A conductive material with relatively low resistance such as, for example, Cu is filled in the second opening to form the TSV. The TSV is formed to contact the epitaxial layer of the first semiconductor device. 
     A second semiconductor device is provided on the second surface of the wafer (S 270 ). A conductive material with relatively low resistance such as, for example, Cu is filled in the first opening to form a power rail metal layer that is configured to operate as a VDD/VSS power rail to supply power. The power rail metal layer is formed to contact the TSV. At least one via is provided on the power rail metal layer, and a metal layer is provided on the at least one via. The power rail metal layer, the at least one via, and the metal layer may form a second semiconductor device. 
     According to the example embodiments, a TSV protruding from a second semiconductor device that is provided on a second surface of a wafer is in direct contact with an epitaxial layer included in a first semiconductor device provided on a first surface of the wafer. As there are no additional elements provided between the TSV and the epitaxial layer, the connection resistance of the BSPDN semiconductor architecture according to example embodiments may be lowered. The manufacturing process of the BSPDN semiconductor architecture may be simplified and the manufacturing cost may be reduced. In addition, there is no concern for a misalignment between the TSV and a BPR which may lead to misalignment between the first semiconductor device and the second semiconductor device. Thus, the performance of the BSPDN semiconductor architecture according to example embodiments may be improved. 
       FIG. 11  illustrates a semiconductor package that may incorporate the BSPDN semiconductor architectures according to example embodiments. 
     Referring to  FIG. 11 , a semiconductor package  2000  according to an example embodiment may include a processor  2200  and semiconductor devices  2300  that are mounted on a substrate  2100 . The processor  2200  and/or the semiconductor devices  2300  may include one or more of BSPDN semiconductor architecture described in the above example embodiments. 
       FIG. 12  illustrates a schematic block diagram of an electronic system according to an example embodiment. 
     Referring to  FIG. 12 , an electronic system  3000  in accordance with an embodiment may include a microprocessor  3100 , a memory  3200 , and a user interface  3300  that perform data communication using a bus  3400 . The microprocessor  3100  may include a central processing unit (CPU) or an application processor (AP). The electronic system  3000  may further include a random access memory (RAM)  3500  in direct communication with the microprocessor  3100 . The microprocessor  3100  and/or the RAM  3500  may be implemented in a single module or package. The user interface  3300  may be used to input data to the electronic system  3000 , or output data from the electronic system  3000 . For example, the user interface  3300  may include a keyboard, a touch pad, a touch screen, a mouse, a scanner, a voice detector, a liquid crystal display (LCD), a micro light-emitting device (LED), an organic light-emitting diode (OLED) device, an active-matrix light-emitting diode (AMOLED) device, a printer, a lighting, or various other input/output devices without limitation. The memory  3200  may store operational codes of the microprocessor  3100 , data processed by the microprocessor  3100 , or data received from an external device. The memory  3200  may include a memory controller, a hard disk, or a solid state drive (SSD). 
     At least the microprocessor  3100 , the memory  3200  and/or the RAM  3500  in the electronic system  3000  may include BSPDN semiconductor architecture as described in the above example embodiments. 
     It should be understood that example embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each example embodiment should typically be considered as available for other similar features or aspects in other embodiments. 
     While example embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope as defined by the following claims.