Patent Publication Number: US-11387167-B2

Title: Semiconductor structure and manufacturing method for the same

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of prior-filed provisional application with application No. 62/579,030, filed Oct. 30, 2017, the benefit of prior-filed non-provisional application with application Ser. No. 15/841,945, filed Dec. 14, 2017, and the benefit of prior-filed non-provisional application with application Ser. No. 16/228,585, filed Dec. 20, 2018. 
    
    
     BACKGROUND 
     The semiconductor integrated circuit (IC) industry has experienced rapid growth. Technological advances in IC materials and design have produced generations of ICs where each generation has smaller and more complex circuits than the previous generation. However, these advances have increased the complexity of processing and manufacturing ICs and, for these advances to be realized, similar developments in IC processing and manufacturing are needed. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. 
     As a part of the semiconductor fabrication, conductive elements may be formed to provide electrical interconnections for the various components for an IC. For example, conductive vias for interconnecting different metal layers may be formed by etching openings in an interlayer dielectric (ILD) and filling the openings with a conductive material. However, as semiconductor fabrication technology nodes continue to evolve, critical dimensions and pitches are becoming smaller and smaller, and the process windows are becoming tighter. Consequently, overlay errors (e.g., misaligned via) may occur, which may lead to problems such as reduced reliability test margin or poor device performance. 
     Therefore, while conventional via formation processes have been generally adequate for their intended purposes, they have not been entirely satisfactory in every aspect. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout. The drawings are not to scale, unless otherwise disclosed. 
         FIG. 1  is a cross sectional view showing an interconnect of a semiconductor structure, in accordance with some embodiments of the present disclosure. 
         FIG. 2  is a cross sectional view showing an interconnect of a semiconductor structure, in accordance with some embodiments of the present disclosure. 
         FIG. 3  is a cross sectional view showing an interconnect of a semiconductor structure, in accordance with some embodiments of the present disclosure. 
         FIG. 4  is a cross sectional view showing an interconnect of a semiconductor structure, in accordance with some embodiments of the present disclosure. 
         FIG. 5  is a cross sectional view showing an interconnect of a semiconductor structure, in accordance with some embodiments of the present disclosure. 
         FIG. 6  is a top view showing an interconnect pattern structure of two adjacent layers, in accordance with some embodiments of the present disclosure. 
         FIG. 7  is atop view showing an interconnect pattern structure of two adjacent layers, in accordance with some embodiments of the present disclosure. 
         FIG. 8  is a top view showing an interconnect pattern structure of two adjacent layers, in accordance with some embodiments of the present disclosure. 
         FIG. 9  is a top view showing an interconnect pattern structure of two adjacent layers, in accordance with some embodiments of the present disclosure. 
         FIG. 10  to  FIG. 14  are cross sectional views of a semiconductor structure at various manufacturing operations, in accordance with some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     The making and using of the embodiments of the disclosure are discussed in detail below. It should be appreciated, however, that the embodiments provide many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific ways to make and use the embodiments, and do not limit the scope of the disclosure. Throughout the various views and illustrative embodiments, like reference numerals are used to designate like elements. Reference will now be made in detail to exemplary embodiments illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts. In the drawings, the shape and thickness may be exaggerated for clarity and convenience. This description will be directed in particular to elements forming part of, or cooperating more directly with, an apparatus in accordance with the present disclosure. It is to be understood that elements not specifically shown or described may take various forms. Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. It should be appreciated that the following figures are not drawn to scale; rather, these figures are merely intended for illustration. 
     Further, spatially relative terms, such as “beneath,” “below,” “lower.” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly. 
     As a part of semiconductor fabrication, electrical interconnections need to be  3   o  formed to electrically interconnect the various microelectronic elements (e.g., source/drain, gate, etc.) of the semiconductor device. Generally, this involves forming openings in layers (such as in electrically insulating layers), and subsequently filling these openings with an electrically conductive material. The electrically conductive material is then polished to form the electrical interconnections such as metal lines or vias. 
     However, as semiconductor technology generations continue the scaling-down process, accurate alignment or overlay may become problematic due to the ever-decreasing trench sizes. For example, it may be more difficult for vias to be accurately aligned with the desired metal lines above or below. When via misalignment or overlay problems occur, conventional methods of fabrication may lead to undesirable over-etching of a dielectric material (e.g., ILD) below the via opening. When the via opening is later filled with a metal material, its shapes resembles a tiger tooth. Such “tiger tooth” vias may lead to poor device performance. Tighter process windows may need to be used to avoid these problems, but that may degrade device performance as well. 
     On the other hand, with the ever-decreasing technology node, different interconnect components shrink at different rate. For example, in technology node greater than or equal to 20 Nth metal (N20 and above), a through silicon via (TSV) having a width about or greater than 2.4 micrometer is in contact with the metal lines of a first metal layer. As described herein, the first metal layer is the first metal line layer in the back-end-of-line operation. Conventionally, a thickness of the first metal layer is greater than 1.5 μm, and a top view pattern of the first metal layer is solid without dielectric features. However, when advancing the technology node to sub 20 nm (N16 or N7), the width of the TSV remains substantially the same but the thickens of the first metal layer decreases to about 0.8 μm with an additional design rule of having a dimension of continuous metal feature in the first metal layer no greater than 2 μm. The continuous metal feature is defined by a particular metal area without any interruption, or cutting off, by materials other than metal, for example, dielectrics (interlayer dielectric ILD or inter metal dielectric IMD). The measure of distance in that particular metal area is the dimension of continuous metal feature. Illustration of continuous metal feature is presented in following figures of this disclosure. 
     Clearly, in N16 or N7, a width of the TSV at the first metal layer (e.g., 2.4 μm) is greater than the dimension of the continuous metal feature (e.g., 2 μm) in the first metal layer, hence, a first set of tiger tooth structure previously discussed occurs at the TSV/first metal layer interface. While the metal portion of the first metal layer functions as an etch stop with respect to the formation of TSV trench, the metal during TSV plating operation penetrates through the first metal layer at the boundary of the continuous metal feature as the etchant easily removes materials other than metal, for example, dielectrics. Moreover, with the reduced thickness of the first metal layer and the total thickness variation of the semiconductor substrate to be about 1 μm, the TSV trench etching operation could overetch the first metal layer and punch through the metal portion of the first metal layer, rendering the formation of a second set of tiger tooth structure. The extent of penetration for second set of tiger tooth structure may be less severe than that of the first set of tiger tooth structure. Illustration of the first set and the second set of tiger tooth structure are presented in following figures of this disclosure. 
     To mitigate the formation of tiger tooth structure which leads to various device performance concerns, such as signal damage due to TSV short with undesired metal layer, present disclosure proposes a novel structure and method utilizing the patterning of adjacent metal layers to enlarge the process window without sacrificing performance. The various aspects of the present disclosure will now be discussed in more detail with reference to  FIGS. 1-14 . 
     Referring to  FIG. 1 ,  FIG. 1  is a cross sectional view showing an interconnect of a semiconductor structure  10 , in accordance with some embodiments of the present disclosure. The semiconductor structure  10  includes a substrate  100  having an active side  100 A and a passive side  100 B opposite to the active side  100 A. Active components such as transistors and memories are formed in proximity to the active side  100 A. In the technology node N14 and beyond, a total thickness variation (TTV) in the substrate  100  is about 1 μm. The existence of TTV is prone to impact the precision of subsequent etching operation of a through substrate trench, as will be further discussed in the manufacturing operations below. In some embodiments, the semiconductor substrate  100  includes silicon. Alternatively, the substrate  100  may include other elementary semiconductor such as germanium in accordance with some embodiments. In some embodiments, the substrate  100  additionally or alternatively includes a compound semiconductor such as silicon carbide, gallium arsenic, indium arsenide, and indium phosphide. In some embodiments, the substrate  100  includes an alloy semiconductor such as silicon germanium, silicon germanium carbide, gallium arsenic phosphide, and gallium indium phosphide. 
     The substrate  100  may include an epitaxial layer formed on the active side  100 A, such as an epitaxial semiconductor layer overlying a bulk semiconductor wafer. In some embodiments, the substrate  100  includes a semiconductor-on-insulator (SOI) structure. For example, the substrate may include a buried oxide (BOX) layer formed by a process such as separation by implanted oxygen (SIMOX). In various embodiments, the substrate  100  includes various p-type doped regions and/or n-type doped regions, such as p-type wells, n-type wells, p-type source/drain features and/or n-type source/drain features, formed by a process such as ion implantation and/or diffusion. The substrate  100  may include other functional features such as a resistor, a capacitor, diode, transistors, such as field effect transistors (FETs). The substrate  100  may include lateral isolation features configured to separate various devices formed on the substrate  100 . The substrate  100  may further include a portion of a multilayer interconnection (MLI) structure. The multilayer interconnection structure includes metal lines in a plurality of metal layers. The metal lines in different metal layers may be connected through vertical conductive features, which are referred to as via features. The multilayer interconnection structure further includes contacts configured to connect metal lines to gate electrodes and/or doped features on the substrate  100 . The multilayer interconnection structure is designed to couple various devices features (such as various p-type and n-type doped regions, gate electrodes and/or passive devices) to form a functional circuit. 
     As shown in  FIG. 1 , an insulating layer  101  is disposed over the first side  100 A and sandwiched between the substrate  100  and an interconnect layer  102 . The interconnect layer  102  further includes a first metal layer  1021 , a first via layer  1022 , and dielectric  1013  surrounding the first metal layer  1021  and the first via layer  1022 . In some embodiments, the insulating layer  101  is composed of the same materials as the dielectric  1013 . In the N14 technology node, a thickness T1 of the first metal layer  1021  is lower than 1 μm, for example, 800 Angstrom, as compared to 1.5 μm in N20 and larger technology node. 
     With reference to the top view interconnect pattern  60 A of the first metal layer  1021  in  FIG. 6 , a continuous metal feature  103  can be defined by a particular metal area without any interruption, or cutting off, by materials other than metal, for example, dielectrics (interlayer dielectric ILD or inter metal dielectric IMD). The measure of distance in that particular metal area is the dimension of continuous metal feature  103 . As illustrated in  FIG. 1  and  FIG. 6 , starting from a center of the interconnect pattern  60 A toward the periphery of the pattern, the continuous metal feature  103  is cut off by a first dielectric feature  104 , and a dimension of the continuous metal feature  103  can be a width W enclosed by the first dielectric feature  104 . Referring back to  FIG. 1 , the dimension W1 of the continuous metal feature  103 , in some embodiments, is less than 2 μm as far as technology node N14 is concerned. The dimension of the continuous metal feature is set as a design rule in metal pattern design. Metal layers following this rule shall obtain benefits from various design consideration including appropriate release of stress in the metal layer. As shown in the top view interconnect pattern  60 A of the first metal layer  1021  in  FIG. 6 , the first dielectric feature  104  appears to have a broken band structure. Several metal bridges  1031  are connecting the continuous metal feature  103  inside the first dielectric feature  104  and the continuous metal feature  103  outside the first dielectric feature  104 . Although not shown in the top view pattern  60 A, the continuous metal feature outside the first dielectric feature  104  also follows the less than 2 μm design rule as discussed above. 
     Referring to  FIG. 1 , a through substrate via (TSV)  105  extends from a passive side  100 B of the substrate  100  toward the active side  100 A and further in contact with the first metal layer  1021 . TSVs are typically formed in a semiconductor IC die to facilitate the formation of a three dimensional (3D) stacking die structure. The TSVs may be utilized to provide electrical connections between components in different dies of the 3D stacking die structure. As previously discussed, a width W3 of the TSV  105  does not shrink at the same pace as the interconnect layer  102 , therefore, the width W3 is greater than the dimension W1 of the continuous metal feature  103  in technology node N14. For example, the width W3 can be equal to or greater than 2.4 μm, whereas the dimension W1 shall be smaller than 2 μm. The overlap region between the TSV  105  and the first metal layer  1021  is a hot spot for tiger tooth formation. Although may not appear in the final product, a first set of tiger tooth  107  penetrating the first dielectric feature  104  is illustrated with dotted lines in  FIG. 1 . In some embodiments, a second set of tiger tooth  109  penetrating the first metal layer  1021  within the continuous metal feature  103  is also illustrated with dotted lines in  FIG. 1 . People having ordinary skill in the art would understand that the tiger tooth  107 ,  109  are illustrated for demonstration purpose and is not intended to be a limitation in the final interconnect layer of the semiconductor structure  10 . 
     Referring to  FIG. 2 ,  FIG. 2  is a cross sectional view showing an interconnect of a semiconductor structure  20 , in accordance with some embodiments of the present disclosure. In  FIG. 2 , the interconnect layer  102  further include a second metal layer  1031  and a second via layer  1032 , which are both disposed at the active side  100 A of the semiconductor substrate  100 A and more distant from the active side  100 A than the first  3   o  metal layer  1021 . 
     With reference to the top view interconnect pattern  60 B of the second metal layer  1031  in  FIG. 6 , a continuous metal feature  103 ′ can be defined by a particular metal area without any interruption, or cutting off, by materials other than metal, for example, dielectrics (interlayer dielectric ILD or inter metal dielectric IMD). The measure of distance in that particular metal area is the dimension of continuous metal feature  103 ′. As illustrated in  FIG. 2  and  FIG. 6 , starting from an inner portion of the second dielectric feature  104 ′ toward the periphery of the pattern, the continuous metal feature  103 ′ is cut off by an outer portion of the second dielectric feature  104 ′, and a dimension of the continuous metal feature  103 ′ can be a width W2 measured between the inner portion and the outer portion of the second dielectric feature  104 ′. Referring back to  FIG. 2 , the dimension W2 of the continuous metal feature  103 ′, in some embodiments, is less than 2 μm as far as technology node N14 is concerned. The dimension of the continuous metal feature is set as a design rule in metal pattern design. Metal layers following this rule shall obtain benefits from various design consideration including appropriate release of stress in the metal layer. As shown in the top view interconnect pattern  60 B of the second metal layer  1031  in  FIG. 6 , the second dielectric feature  104 ′ appears to have a broken band structure. Several metal bridges  1031 ′ are connecting the continuous metal feature  103 ′ inside the inner portion of the second dielectric feature  104 ′ and the continuous metal feature  103 ′ outside the inner portion of the second dielectric feature  104 ′, so on and so forth. Although not shown in the top view pattern  60 B, the continuous metal feature inside the inner portion of the second dielectric feature  104 ′ also follows the less than 2 μm design rule as discussed above. 
     As shown in  FIG. 2 , the second dielectric feature  104 ′ and the first dielectric feature  104  are disposed staggerly from each other. That is to say, the vertical projection of the first dielectric feature  104  at the first metal layer  1021  is not overlapping with the second dielectric feature  104 ′ at the second metal layer  1031 . Such stagger arrangement of the first dielectric feature  104  and the second dielectric feature  104 ′ effectively prevent the first set of tiger tooth  107  from penetrating to metal layers further away from the active side  100 A. 
     Referring to  FIG. 3 ,  FIG. 3  is a cross sectional view showing an interconnect of a semiconductor structure  30 , in accordance with some embodiments of the present disclosure. In  FIG. 3 , the interconnect layer  102  further includes a third metal layer  1041  and a third via layer  1042 , which are both disposed at the active side  100 A of the semiconductor substrate  100 A and more distant from the active side  100 A than the second metal layer  1031 . 
     As shown in  FIG. 3 , the third metal layer  1041  can be a continuous metal feature without any interruption, or cutting off, by the dielectric feature. In the technology node greater than N20, the first metal layer is often adopted a solid metal layer without dielectric patterns. In the technology node N14 and beyond, as discussed herein, the third metal layer  1041  starts adopting the solid metal layer. In addition, a thickness of the third metal layer  1041  can be greater than that of the first metal layer  1021 . For example, the thickness of the third metal layer  1041  can be twice as thick as that of the first metal layer  1021 . In some embodiments, the third metal layer  1041  does not have to follow the less than 2 μm design rule as discussed above. 
     Referring to  FIG. 4 ,  FIG. 4  is a cross sectional view showing an interconnect of a semiconductor structure  40 , in accordance with some embodiments of the present disclosure. In  FIG. 4 , the interconnect layer  102  further includes a third metal layer  1041  and a third via layer  1042 , which are both disposed at the active side  100 A of the semiconductor substrate  100 A and more distant from the active side  100 A than the second metal layer  1031 . 
     As shown in  FIG. 4 , the third metal layer  1041  can have a continuous metal feature  103 ″ and a third dielectric feature  104 ″ both identical to that of the continuous metal feature  103  and the first dielectric feature  10  of first metal layer  1021 . In addition, the thickness of the third metal layer  1041  can be identical to that of the first metal layer  1021 . In some embodiments, the third metal layer  1041  also follow the less than 2 μm design rule as discussed above. Even if the third metal layer  1041  and the first metal layer  1021  share substantially identical continuous metal feature and dielectric feature, those features are both staggerly disposed with respect to the second metal layer  1031  between the first and the third metal layer. Present disclosure provides that the adjacent metal layers would have to apply stagger patterns while non-adjacent metal layers do not have to be limited by this rule. 
     Referring to  FIG. 5 ,  FIG. 5  is a cross sectional view showing an interconnect of a semiconductor structure  50 , in accordance with some embodiments of the present disclosure. In  FIG. 5 , the interconnect layer  102  further include a fourth metal layer  1051  and a fourth via layer  1052 , which are both disposed at the active side  100 A of the semiconductor substrate  100 A and more distant from the active side  100 A than the third metal layer  1041 . 
     As shown in  FIG. 5 , the continuous metal feature  103 ″ and the third dielectric feature  104 ″ of the third metal layer  1041  are different from that of the continuous metal feature  103 ′ and the second dielectric feature  104 ′ of second metal layer  1031 . In addition, the continuous metal feature  103 ′″ and the third dielectric feature  104 ″ of the fourth metal layer  1051  are different from those of the third metal layer  1041 . In some embodiments, the thickness of the fourth metal layer  1051  can be identical to that of the first metal layer  1021 . In some embodiments, the fourth metal layer  1051  also follow the less than 2 μm design rule as discussed above. Although not illustrated in  FIG. 5 , in some embodiments, the continuous metal feature  103 ″ and the third dielectric feature  104 ″ of the third metal layer  1041  can be substantially identical to those of the first metal layer  1021 , and the continuous metal feature  103 ′″ and the fourth dielectric feature  104 ′″ of the fourth metal layer  1051  can be substantially identical to those of the second metal layer  1031 . In the present embodiment, a fifth metal layer (not shown) further away from the active side  100 A can have a solid metal pattern and a design rule greater than 2 μm as previously discussed. 
     The less than 2 μm design rule discussed above is made under the premises of technology node N14 and beyond. However, in technology node N7, the design rule for the metal layer could be, for example, less than 0.5 μm. In other words, the dimension of the continuous metal feature in meal layers following the design rule shall be smaller than 0.5 μm as far as technology node N7 is concerned. 
     Referring to  FIG. 6 ,  FIG. 6  is a top view showing two interconnect pattern structures  60 A,  60 B of two adjacent layers, in accordance with some embodiments of the present disclosure. As previously discussed, interconnect pattern structure  60 A is a top view of the first metal layer  1021  as shown in  FIG. 1  and  FIG. 2 , and interconnect pattern structure  60 B is a top view of the second metal layer  1021  as shown in  FIG. 2 . Numeral labels identical to those addressed previously represent substantially identical components and are not repeated here for brevity. Pattern structures  60 A and  60 B are illustrated with alignment dotted lines showing the first dielectric feature  103  is downwardly projected to a continuous metal feature  103 ′ of the second metal layer  1031 . On the other hand, an inner portion and the outer portion of the second dielectric feature  104 ′ are upwardly projected to a continuous metal feature  103  of the first metal layer  1021 . The stagger disposition of the first dielectric feature  104  and the second dielectric feature  104 ′ can be clearly observed in  FIG. 6 . Furthermore, the first via layer  1022  and the second via layer  1032  is also shown from a top view perspective in  FIG. 6 . As previously discussed, the first dielectric feature  104  and the second dielectric feature  104 ′ possess a broken band. 
     Referring to  FIG. 7 ,  FIG. 7  is a top view showing two interconnect pattern structures  70 A,  70 B of two adjacent layers, in accordance with some embodiments of the present disclosure. As previously discussed, interconnect pattern structure  70 A is a top view of the first metal layer  1021  as shown in  FIG. 1  and  FIG. 2 , and interconnect pattern structure  70 B is a top view of the second metal layer  1021  as shown in  FIG. 2 . In some embodiments, the first dielectric feature  104  and the second dielectric feature  104 ′ appear to have a closed band structure. No metal bridge is connecting the continuous metal feature  103  inside the first dielectric feature  104  and the continuous metal feature  103  outside the first dielectric feature  104 . Similarly, no metal bridge is connecting the continuous metal feature  103 ′ inside the inner portion of the second dielectric feature  104 ′ and the continuous metal feature  103 ′ outside the inner portion of the second dielectric feature  104 ′. Pattern structures  70 A and  70 B are illustrated with alignment dotted lines showing the first dielectric feature  103  is downwardly projected to a continuous metal feature  103 ′ of the second metal layer  1031 . On the other hand, an inner portion and the outer portion of the second dielectric feature  104 ′ are upwardly projected to a continuous metal feature  103  of the first metal layer  1021 . Although not shown in the top view pattern  60 B, the continuous metal feature inside the inner portion of the second dielectric feature  104 ′ also follows the less than 2 μm design rule as discussed above. 
     Referring to  FIG. 8 ,  FIG. 8  is a top view showing an interconnect pattern structures  80 A,  80 B of two adjacent layers, in accordance with some embodiments of the present disclosure. As previously discussed, interconnect pattern structure  80 A is a top view of the first metal layer  1021  as shown in  FIG. 1  and  FIG. 2 , and interconnect pattern structure  80 B is a top view of the second metal layer  1021  as shown in  FIG. 2 . In some embodiments, the first dielectric feature  104  appears to have an open band structure. Several dielectric bridges are connecting the first dielectric feature  103  to another portion of the first dielectric feature  103  (not shown). However, in order to maintain the stagger feature between adjacent metal layers, the second dielectric feature  104 ′ appears to have a closed band structure. Pattern structures  80 A and  80 B are illustrated with alignment dotted lines showing the first dielectric feature  103  is downwardly projected to a continuous metal feature  103 ′ of the second metal layer  1031 . On the other hand, an inner portion and the outer portion of the second dielectric feature  104 ′ are upwardly projected to a continuous metal feature  103  of the first metal layer  1021 . 
     Referring to  FIG. 9 ,  FIG. 9  is a top view showing an interconnect pattern structures  90 A,  90 B of two adjacent layers, in accordance with some embodiments of the present disclosure. As previously discussed, interconnect pattern structure  90 A is a top view of the first metal layer  1021  as shown in  FIG. 1  and  FIG. 2 , and interconnect pattern structure  90 B is a top view of the second metal layer  1021  as shown in  FIG. 2 . In some embodiments, the first dielectric feature  104  appears to have a broken band structure. Several metal bridges  1031  are connecting the continuous metal feature  103  inside the first dielectric feature  104  and the continuous metal feature  103  outside the first dielectric feature  104 . In order to maintain the stagger feature between adjacent metal layers, the second dielectric feature  104 ′ appears to have an open band structure. Pattern structures  90 A and  90 B are illustrated with alignment dotted lines showing the first dielectric feature  103  is downwardly projected to a continuous metal feature  103 ′ of the second metal layer  1031 . On the other hand, an inner portion and the outer portion of the second dielectric feature  104 ′ are upwardly projected to a continuous metal feature  103  of the first metal layer  1021 . 
       FIG. 10  to  FIG. 14  are cross sectional views of a semiconductor structure  30  at various manufacturing operations, in accordance with some embodiments of the present disclosure. In  FIG. 10 , a semiconductor substrate  100  having an active side  100 A and a passive side  100 B is received. As previously discussed, active components such as memories or transistors are located in proximity to the active side  100 A, an insulating layer  101 , such as a shallow trench isolation, for separating different active regions are also formed in the substrate in proximity to the active side  100 A. Subsequently, a dielectric layer  101  such as an inter-layer dielectric (ILD) can be formed over the insulating layer  101  and the substrate  100 . Over the dielectric layer  101 , the interconnect  102  of the device is manufactured with previously discussed patterns of each metal layers. In the embodiment illustrated in  FIG. 10 , three metal layers and via layers are formed. In some embodiments, the metal layers are a metal feature, such as a metal line, a metal via feature or a metal contact feature. 
     For example, the first metal layer  1021  is formed by a damascene process, which is further described below. The first dielectric material layer is formed on the dielectric layer  101 . Alternatively, an etch stop layer (not shown) is formed on the dielectric layer  101  and the first dielectric material layer is formed on the etch stop layer. In some embodiments, the first dielectric material layer includes a dielectric material such as silicon oxide, silicon nitride, a low dielectric constant (low k) material, or a combination thereof. The low k material may include fluorinated silica glass (FSG), carbon doped silicon oxide, Black Diamond® (Applied Materials of Santa Clara, Calif.), Xerogel, Aerogel, amorphous fluorinated carbon, Parylene, bis-benzocyclobutenes (BCB), SiLK (Dow Chemical. Midland. Mich.), polyimide, porous polymer and/or other suitable materials as examples. A process of forming the first dielectric material layer may utilize chemical vapor deposition (CVD), a spin-on coating or other suitable deposition technology. The etch stop layer includes a material different from the first dielectric material layer designed to provide etch selectivity such that a subsequent etching process is able to substantially etch the first dielectric material layer and stops on the etch stop layer. For example, the etch stop layer includes silicon nitride, silicon oxide, silicon oxynitride, silicon carbide or other suitable material that functions to stop the etching of the subsequent etching process. The etch stop layer may be formed by CVD or other suitable technology. After the deposition of (the etch stop layer and) the first dielectric material layer, the first dielectric material layer may be further planarized by a technique, such as chemical mechanical polishing (CMP). 
     Thereafter, a mask layer (not shown) for the first metal layer  1021  is patterned by a lithography process, thereby forming a patterned mask layer having one (or more) opening to define a region (or regions) for metal line (or metal lines), as illustrated in  FIGS. 6-9 . In some embodiments, the opening of the patterned mask layer corresponds to the locations of the continuous metal feature  103  in the first metal layer  1021 , and the covered region of the patterned mask layer corresponds to the locations of the first dielectric feature  104  in the first metal layer  1021 . The metal line refers to a metal line in an upper metal layer to be formed. In some embodiments, the mask layer is a resist layer, the patterning process is a lithography procedure that includes spin-on coating, exposure and developing. In some embodiments, the mask layer is a hard mask, the patterning process includes forming a patterned resist layer on the hard mask using a lithography process; and etching the hard mask through the opening of the patterned resist layer using the patterned resist layer as an etch mask. After the formation of the patterned hard mask, the patterned resist layer may be removed by plasma ashing or wet stripping. 
     The formation of the first via layer  1022  can be referring to previously discussed section regarding the formation of the first metal layer  1021  and is not repeated here for brevity. Of course, the patterning of the first via layer  1022  changes correspondingly with the pattern of the first metal layer  1021 . The formation of the second metal layer  1031  can be referring to previously discussed section regarding the formation of the first metal layer  1021  and is not repeated here for brevity. The pattern of the second metal layer  1031  includes a continuous metal feature  103 ′ and a second dielectric feature  104 ′, as previously described. The first dielectric feature  104  in the first metal layer  1021  is designed to dispose staggerly from the second dielectric feature  104 ′ in the second metal layer  1031 . Furthermore, in  FIG. 10 , the formation of the third metal layer  1041  can be referring to previously discussed section regarding the formation of the first metal layer  1021  and is not repeated here for brevity. In some embodiments, the third metal layer  1041  can be a continuous metal feature without any interruption, or cutting off, by the dielectric feature. 
     In some embodiments, the substrate  100  may be then thinned from a passive side  100 B through known techniques, such as back grinding, etching, CMP, or the like, and a thick passivation layer  100 ′, for example, an oxide layer, is formed over the thinned surface on the passive side  100 B. 
     In  FIG. 11 , a through substrate via (TSV) recess  105 ′ is partially formed from the passive side  100 B of the substrate  100  via a first etching operation. The first etching operation removes the substrate  100  from the passive side  100 B until the insulating layer  303  is reached. In some embodiments, the first etching operation utilize an etching chemistry suitable for removing substrate materials. TSV recesses  105 ′ are formed after the CMOS device formations in proximity to the active side  100 A of the substrate  100  and after the metallization process of forming metal layers, for example, at least M1-M3, in the interconnect layer  102 . In an IC fabricated with advanced processing technology, inter-metal dielectric (IMD) layers  1013  are typically formed with dielectric materials having low dielectric constant (low-k) or extremely low dielectric constant in an effort to reduce inter-metal layer parasitic capacitance, thus increasing signal speed and enhance signal integrity. As an example, a low-k dielectric material has a dielectric constant less than 2.9, and is formed with a porous organic dielectric material. 
     In  FIG. 12 , a through substrate via (TSV) recess  105 ″ is completely formed from the passive side  100 B of the substrate  100  via a second etching operation. The second etching operation removes the remaining insulating layer  303 , the dielectric layer  303 , and until the first metal layer  1021  is reached. In some embodiments, the second etching operation utilizes an etching chemistry different from that of the first etching operation, for example, the second etching operation utilizes chemistry suitable for removing dielectric materials. It is the ability to control the second etching that determines the tiger tooth formation. For instance, if the second etching is considered over-etch, it is likely that the IMD layer  1013  at first metal layer  1021  level and the first via layer  1022  being removed by the etchant, providing a tiger tooth pocket for the subsequent metallic materials to fill. The IMD layer  1013  at first metal layer  1021  level corresponds to the first dielectric feature  104  as previously discussed. 
     This TSV recess  105 ″ formation process creates a number of problems in advanced processing technologies. One of the problems is that the formation of the TSV recesses  105 ″ in the inter-metal dielectric layers typically involves multiple etch processes; the wafers under processing often stand in queue for the various etch process to be completed. During processing, moisture or other chemical agents in a wafer processing facility may leach into the low-k inter-metal dielectric layers from the side wall of the TSV recesses and diffuse throughout the inter-metal dielectric layers, which may lead to undesired characteristic change of the low-k dielectric materials. Due to the large exposed surface area of the TSV recesses, this detrimental effect can be significant and cause serious device performance degradation and yield loss. The first and the second etching provided here provides a method to reduce the characteristic change of the IMD layer  1013  by exposing the low-k IMD layer  1013  in the last etching operation of TSV recess  105 ″ formation. 
     The TSV recesses  105 ″ formed in the IMD layers and in the substrate  100  are subsequently filled with conductive metallic materials by a metallization process, such as a metallic chemical vapor deposition process (CVD) or a metal electroplating process. Metallization process, such as metallic CVD or metal plating, may be subsequently performed on the passive side  100 B of the substrate  100 , filling copper (Cu) or the suitable conductive materials in the TSV recesses  105 ″ to form TSVs  105  in substrate  100 . Other suitable conductive materials, such as aluminum (Al), tungsten (W), cobalt (Co), gold (Au), silver (Ag), platinum (Pt), silicon (Si) and other suitable deposition processes may be also used to form TSVs  105 . 
     In  FIG. 13 , a CMP operation may be performed afterwards on the passive side  100 B of the substrate  100  to remove excess TSV materials and provide the desired flat substrate surface for the subsequent processing operations. Optionally, a barrier layer, such as a titanium nitride (TiN) layer and/or a metal seed layer (not shown), may be formed conformally in the TSV recesses  105 ″ by suitable processes, such as CVD or physical vapor deposition (PVD), prior to the metallization process of forming TSVs  105 . A barrier layer in TSV recesses  105 ″ may prevent any conducting TSV material from leaching into any active portions of the circuitry at the active side  100 A of the substrate  100 . Also shown in  FIG. 13 , the first set of tiger tooth  107  are illustrated with dotted lines to show the possible locations, and how the second metal layer  1031  can effectively prevent the first set of tiger tooth  107  from further penetration toward higher metal layers. 
     In  FIG. 14 , passive side  100 B of the substrate  100  may be further processed to form insulating layer  116 , dielectric layer (not shown), conductive interface (not shown), bonding pads (not shown) with similar materials and processing techniques used for the similar features formed previously over the active side  100 A of the substrate  100 . Substrate  100  thus processed may be bonded to other integrated circuit wafers and dies from both sides. Also shown in  FIG. 14 , after the metallization process, a width W3 of the TSV  105  in proximity to the first metal layer  1021  is greater than a dimension of the first dielectric feature  104  of the first metal layer  1021 . Since the “tiger tooth” via punch through is no longer a problem, the process windows for forming the TSVs  105  can be relaxed, and the device performance may be improved as well. 
     Some embodiments provide a semiconductor structure, including a semiconductor substrate, a first metal layer, and a through substrate via (TSV). The semiconductor substrate has an active side. The first metal layer is closest to the active side of the semiconductor substrate, and the first metal layer has a first continuous metal feature. The TSV is extending from the semiconductor substrate to the first continuous metal feature. A width of the TSV at the first metal layer is wider than a width of the first continuous metal feature. 
     Some embodiments provide an interconnect pattern structure, including a first metal layer, a second metal layer, and a through substrate via (TSV). The first metal layer has a first continuous metal feature. The second metal layer is over the first metal layer, and has a second continuous metal feature. The TSV is extending from the semiconductor substrate toward the first metal layer and in contact with the first continuous metal feature. The TSV includes a first set of tiger tooth. The first set of tiger tooth penetrates from the semiconductor substrate toward the second metal layer through the first metal layer. 
     Some embodiments provide a method for manufacturing a semiconductor structure. The method includes the following steps: receiving a semiconductor substrate having an active side; forming a first metal layer closest to the active side of the semiconductor substrate; and forming a through substrate via (TSV) extending from the semiconductor substrate to the first metal layer. Forming the TSV includes forming a tiger tooth penetrating the first metal layer, in which the tiger tooth is a continuous portion of the TSV. 
     Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. For example, many of the processes discussed above cancan be implemented in different methodologies and replaced by other processes, or a combination thereof. 
     Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed, that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps.