Patent Publication Number: US-2023148354-A1

Title: Bit line structure, semiconductor structure and method of manufacturing bit line structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of International Application No. PCT/CN2022/071821, filed on Jan. 13, 2022, which claims the priority to Chinese Patent Application 202110844690.9, titled “BIT LINE STRUCTURE, SEMICONDUCTOR STRUCTURE AND METHOD OF MANUFACTURING BIT LINE STRUCTURE” and filed on Jul. 26, 2021. The entire contents of International Application No. PCT/CN2022/071821 and Chinese Patent Application 202110844690.9 are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates, but is not limited to, a bit line structure, a semiconductor structure and a method of manufacturing a bit line structure. 
     BACKGROUND 
     In a dynamic random access memory (DRAM) device, a bit line (BL) is connected to a transistor and a capacitor. During manufacture of the DRAM, polysilicon (referred to as poly) is deposited necessarily to form contact and conductive structures of the BL. The contact resistance of the BL determines an electrical conductivity of the BL and a magnitude of current of the device, thereby affecting a conductivity of the device. With miniaturization of integrated circuits (ICs), increasingly higher requirements are being put forward for the contact and conductive structures of the BL. 
     SUMMARY 
     An overview of the subject described in detail in the present disclosure is provided below. This overview is not intended to limit the protection scope of the claims. 
     The present disclosure provides a bit line structure, a semiconductor structure and a method of manufacturing a bit line structure. 
     A first aspect of the present disclosure provides a bit line structure, the bit line structure is provided on a substrate, and includes: 
     a contact portion, including a bottom surface connected to the substrate; 
     a barrier layer, including an extension portion, the extension portion covering a top surface and an outer sidewall surface of the contact portion; and 
     a conductive layer, covering a part of the barrier layer. 
     A second aspect of the present disclosure provides a semiconductor structure including the bit line structure of the present disclosure. 
     A third aspect of the present disclosure provides a method of manufacturing a bit line structure, including: 
     providing a base, the base including a substrate and a first initial dielectric layer covering the substrate; 
     forming an initial contact hole in the base, a bottom wall of the initial contact hole exposing the substrate, and the initial contact hole penetrating through the first initial dielectric layer; 
     forming, in the initial contact hole, a contact portion and a second initial dielectric unit covering an outer sidewall of the contact portion, a bottom surface of the contact portion being connected to the substrate, and a sidewall of the second initial dielectric unit being connected to the substrate and the first initial dielectric layer; 
     etching a part of the first initial dielectric layer, and forming a first dielectric layer, the first dielectric layer exposing a part of the sidewall of the second initial dielectric unit; 
     depositing a third initial dielectric layer and an initial laminated structure, wherein the third initial dielectric layer covers the first dielectric layer and the part of the sidewall of the second initial dielectric unit, as well as a top surface of the contact portion and a top surface of the second initial dielectric unit, the third initial dielectric layer and the second initial dielectric unit are connected as a whole, and the initial laminated structure covers the third initial dielectric layer; 
     etching the initial laminated structure, the third initial dielectric layer and the second initial dielectric unit, wherein a remaining part of the initial laminated structure forms a laminated structure; the laminated structure includes a conductive layer; a remaining part of the second initial dielectric unit and a remaining part of the third initial dielectric layer are connected as a whole and form a barrier layer; and a part of the remaining part of the second initial dielectric unit and a part of a remaining part of the third initial dielectric layer that cover the contact portion form an extension portion of the barrier layer; and 
     forming a fourth dielectric layer, the fourth dielectric layer covering the laminated structure and a part of the extension portion. 
     Other aspects of the present disclosure are understandable upon reading and understanding of the accompanying drawings and detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated into the specification and constituting a part of the specification illustrate the embodiments of the present disclosure, and are used together with the description to explain the principles of the embodiments of the present disclosure. In these accompanying drawings, similar reference numerals represent similar elements. The accompanying drawings in the following description illustrate some rather than all of the embodiments of the present disclosure. Those skilled in the art may obtain other accompanying drawings based on these accompanying drawings without creative efforts. 
         FIG.  1    is a sectional view of a bit line (BL) structure in a direction parallel to a word line (WL) according to an exemplary embodiment of the present disclosure; 
         FIG.  2    is a sectional view of a BL structure in a direction of a BL according to an exemplary embodiment of the present disclosure; 
         FIG.  3    illustrates projection of a contact portion of a BL structure on a substrate according to an exemplary embodiment; 
         FIG.  4    is a flowchart of a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  5    is a flowchart for forming, in an initial contact hole, a second initial dielectric unit covering an outer sidewall of a contact portion in a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  6    is a flowchart for forming, in an initial contact hole, a contact portion in a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  7    is a flowchart for depositing an initial laminated structure in a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  8    is a flowchart of a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  9    is a flowchart for etching an initial laminated structure, a third initial dielectric layer and a second initial dielectric unit in a method of manufacturing a BL structure according to an exemplary embodiment; 
         FIG.  10 A  is a sectional view of a base in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  10 B  is a sectional view of a base in a direction of a BL according to an exemplary embodiment; 
         FIG.  11 A  is a sectional view of a photoresist mask layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  11 B  is a sectional view of a photoresist mask layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  12 A  is a sectional view of an initial contact hole formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  12 B  is a sectional view of an initial contact hole formed in a base in a direction of a BL according to an exemplary embodiment; 
         FIG.  13 A  is a sectional view of a second initial dielectric layer deposited in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  13 B  is a sectional view of a second initial dielectric layer deposited in a direction of a BL according to an exemplary embodiment; 
         FIG.  14 A  is a sectional view of a second initial dielectric unit formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  14 B  is a sectional view of a second initial dielectric unit formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  15 A  is a sectional view of a contact dielectric layer deposited in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  15 B  is a sectional view of a contact dielectric layer deposited in a direction of a BL according to an exemplary embodiment; 
         FIG.  16 A  is a sectional view of a contact portion formed in a direction is parallel to a WL according to an exemplary embodiment; 
         FIG.  16 B  is a sectional view of a contact portion formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  17 A  is a sectional view of a first dielectric layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  17 B  is a sectional view of a first dielectric layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  18 A  is a sectional view of a third initial dielectric layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  18 B  is a sectional view of a third initial dielectric layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  19 A  is a sectional view of an initial conductive layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  19 B  is a sectional view of an initial conductive layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  20 A  is a sectional view of an initial isolation layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  20 B  is a sectional view of an initial isolation layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  21 A  is a sectional view of a mask layer formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  21 B  is a sectional view of a mask layer formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  22 A  is a sectional view of a laminated structure formed in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  22 B  is a sectional view of a laminated structure formed in a direction of a BL according to an exemplary embodiment; 
         FIG.  23 A  is a sectional view of a fourth dielectric layer deposited in a direction parallel to a WL according to an exemplary embodiment; 
         FIG.  23 B  is a sectional view of a fourth dielectric layer deposited in a is direction of a BL according to an exemplary embodiment; 
         FIG.  24    is a sectional view of a BL structure in a direction parallel to a WL′ according to an exemplary comparative embodiment; 
         FIG.  25    is a sectional view of a BL structure in a direction of a BL′ according to an exemplary comparative embodiment; and 
         FIG.  26    illustrates projection of a contact portion of a BL structure on a substrate according to an exemplary comparative embodiment. 
     
    
    
     REFERENCE NUMERALS 
       10 : photoresist mask layer,  11 : first pattern,  110 : substrate,  101 : initial contact hole,  102 : contact hole,  111 : active region,  120 : first initial dielectric layer,  121 : first dielectric layer,  130 : second initial dielectric unit,  131 : second initial dielectric layer,  140 : third initial dielectric layer,  150 : contact dielectric layer,  160 : initial conductive layer,  170 : initial isolation layer,  180 : mask layer,  190 : fourth dielectric layer,  200 : BL structure,  210 : contact portion,  211 : first part,  212 : second part,  220 : barrier layer,  221 : extension portion,  2211 : first outer sidewall part,  2212 : second outer sidewall part,  222 : main body portion,  230 : conductive layer,  240 : isolation layer,  300 : insulating structure,  310 : insulating portion,  400 : WL,  500 : initial laminated structure, and  600 : laminated structure; and 
       110 ′: substrate,  120 ′: insulating layer,  200 ′: BL structure,  210 ′: contact portion,  220 ′: barrier metal layer,  230 ′: conductive layer,  240 ′: isolation layer, and  300 ′: insulating structure. 
     DETAILED DESCRIPTION 
     The technical solutions in the embodiments of the present disclosure are described below clearly and completely with reference to the accompanying drawings in the embodiments of the present disclosure. Apparently, the described embodiments are merely some rather than all of the embodiments of the present disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of the present disclosure without creative efforts should fall within the protection scope of the present disclosure. It should be noted that the embodiments in the present disclosure and features in the embodiments may be combined with each other in a non-conflicting manner. 
     A contact portion of a BL structure is connected to a transistor and a capacitor through a conductive layer. A resistance of the contact portion has a largest impact on an electrical conductivity of the BL. In order to minimize the contact resistance of the BL, a barrier metal layer of a highly refractory metal or metal compound such as titanium nitride is further provided on a top surface of the contact portion. 
     As shown in  FIGS.  24 - 26   , referring to an orientation in  FIG.  26   ,  FIG.  24    is a sectional view of a BL structure in a direction parallel to a WL (namely the direction of the WL′ in  FIG.  26   ).  FIG.  25    is a sectional view of a BL structure in a direction of a BL (namely the direction of the BL′ in  FIG.  26   ).  FIG.  26    illustrates projection of a contact portion  210 ′ of a BL structure on a substrate  110 ′. In the related art, a BL structure  200 ′ is provided in a substrate  110 ′. The BL structure includes a contact portion  210 ′, a barrier metal layer  220 ′, a conductive layer  230 ′, and an isolation layer  240 ′. The contact portion  210 ′ is provided in the substrate  110 ′. The contact portion  210 ′ includes a bottom surface connected to the substrate  110 ′, and a top flush with an insulating layer  120 ′ on the substrate  110 ′. The barrier metal layer  220 ′ covers the top surface of the contact portion  210 ′. The conductive layer  230 ′ is located on the substrate  110 ′ and covers the barrier metal layer  220 ′. The isolation layer  240 ′ covers the conductive layer  230 ′. The BL structure  200 ′ is covered by an insulating structure  300 ′. 
     The top surface of the contact portion  210 ′ is electrically connected to the conductive layer  230 ′ through the barrier metal layer  220 ′. A contact area between the contact portion  210 ′ and the conductive layer  230 ′ is an area of the top surface of the contact portion  210 ′. However, during manufacture of the BL structure  200 ′, when an insulating portion is formed on a sidewall of the contact portion  210 ′, the sidewall of the contact portion  210 ′ is prone to oxidation to is increase a resistance of the contact portion  210 ′. 
     Moreover, while ICs are developed toward a higher level of integration and a higher density, there are smaller sizes of the ICs, smaller spacings between WLs in the ICs, smaller sizes of BLs, and smaller contact areas of contact portions. As a result, resistances of the BLs may be increased greatly. 
     As shown in  FIGS.  1 - 3   , an exemplary embodiment of the present disclosure provides a BL structure, which is provided in a substrate  110 .  FIG.  1    is a sectional view of the BL structure in a direction parallel to a WL in  FIG.  3    (namely an extension direction of the WL) according to the embodiment.  FIG.  2    is a sectional view of the BL structure in a direction of a BL in  FIG.  3    (namely an extension direction of the BL structure) according to the embodiment.  FIG.  3    illustrates projection of a contact portion  210  of the BL structure on the substrate  110  according to the embodiment. 
     As shown in  FIG.  1    and  FIG.  2   , the BL structure  200  includes: a contact portion  210  including a bottom surface connected to the substrate  110 , a barrier layer  220  covering a part of the contact portion  210 , and a conductive layer  230  covering a part of the barrier layer  220 . The barrier layer  220  includes an extension portion  221  covering a top surface and an outer sidewall surface of the contact portion  210 . 
     As shown in  FIG.  3   , the substrate  110  includes active regions  111  arranged in an array. The bottom surface of the contact portion  210  contacts and is connected to each of the active regions  111  in the substrate. The substrate  110  is a semiconductor substrate including a silicon-containing substance. For example, the semiconductor substrate may be a silicon substrate, a silicon-germanium substrate, or a silicon on insulator (SOI) substrate. The contact portion  210  includes poly. 
     The barrier layer  220  may be of a single-layer structure or a laminated structure. The barrier layer  220  includes one or more selected from the group consisting of conductive metal, conductive metal nitride, and conductive alloy. For example, the conductive metal may be titanium, tantalum, or tungsten. 
     The conductive layer  230  may be of a single-layer structure or a laminated structure. The conductive layer  230  includes one or more selected from the group consisting of conductive metal, conductive metal nitride, and conductive alloy. For example, the conductive metal may be titanium, tantalum, or tungsten. 
     As shown in  FIG.  1   ,  FIG.  2    and  FIG.  3   , as the barrier layer  220  covers the top and the outer sidewall of the contact portion  210 , the BL structure  200  in the embodiment prevents the top and the outer sidewall of the contact portion  210  from being oxidized in manufacture of the BL to increase the contact resistance. The BL structure in the embodiment reduces the contact resistance of the contact portion  210  to achieve better electrical performance. 
     According to an exemplary embodiment, most contents of the BL structure in the embodiment are the same as those in the foregoing embodiment. The embodiment differs from the foregoing embodiment in: As shown in  FIG.  1    and  FIG.  2   , the contact portion  210  includes a first part  211  and a second part  212 . The first part  211  is located in the substrate  110 . The second part  212  is located on the substrate  110 . The barrier layer  220  further includes a main body portion  222 . The second part  212  of the contact portion  210  penetrates through the main body portion  222  and extends into the conductive layer  230 . The conductive layer  230  covers the main body portion  222  of the barrier layer  220  and a part of a surface of the extension portion  221 . 
     Improvements are made to the BL structure in the embodiment. The first part  211  of the contact portion  210  is buried in the substrate  110 . The second part  212  of the contact portion  210  extends out of the substrate  110  and extends into the conductive layer  230 . A contact area between the contact portion  210  and the conductive layer  230  is a sum of an area of the top surface of the contact portion  210  and an area of a sidewall of the second part  212  of the contact portion  210  extending into the conductive layer  230 . Therefore, the contact area between the contact portion  210  and the conductive layer  230  is increased. 
     By increasing the contact area between the contact portion  210  and the conductive layer  230  in the embodiment, the contact resistance between the contact portion  210  and the conductive layer  230  is reduced. With higher electrical connection performance between the contact portion  210  and the conductive layer  230  in the BL, the current is conducted more rapidly, and thus the electrical performance of the device can be improved. 
     According to an exemplary embodiment, most contents of the BL structure in the embodiment are the same as those in the foregoing embodiment. The embodiment differs from the foregoing embodiment in: As shown in  FIG.  1    and  FIG.  2   , the main body portion  222  covers a first dielectric layer  121  on the substrate  110 . The second part  112  of the contact portion  210  penetrates through the first dielectric layer  121 . 
     Exemplarily, a material of the first dielectric layer  121  may include a material with desirable insulation performance such as silicon nitride or silicon oxynitride. The first dielectric layer  121  covers a surface of the substrate  110  to insulate and isolate a structure in the substrate  110 . 
     According to an exemplary embodiment, most contents of the BL structure in the embodiment are the same as those in the foregoing embodiment. The embodiment differs from the foregoing embodiment in: As shown in  FIG.  1    and  FIG.  2   , along a circumferential direction of the extension portion  221 , a first outer sidewall part  2211  of the extension portion  221  contacts and is connected to the substrate  110 , and a second outer sidewall part  2212  of the extension portion  221  is provided with an insulating portion  310 . 
     Along the circumferential direction of the extension portion  221 , the first outer sidewall part  2211  of the extension portion  221  is the extension portion  221  in a first circumferential direction of the contact portion  210 , and the second outer sidewall part  2212  of the extension portion  221  is the extension portion  221  in a second circumferential direction of the contact portion  210 . The second direction refers to the extension direction of the BL structure  200  (namely the direction of the BL in  FIG.  3   ). 
     By providing the insulating portion  310  to cover the second outer sidewall is part  2212  of the extension portion  221 , the contact portion  210  in the extension portion  221  is protected well. In the embodiment, the insulating portion  310  and the first dielectric layer  121  on the surface of the substrate are connected as a whole to better protect the second outer sidewall part  2212  of the extension portion  221 . 
     According to an exemplary embodiment, most contents of the BL structure in the embodiment are the same as those in the foregoing embodiment. As shown in  FIG.  3   , according to the BL structure  200  in the embodiment, a plurality of parallel WLs  400  are buried in the substrate  110 . The contact portion  210  is provided between adjacent ones of the WLs  400 . 
     As shown in  FIG.  3   , the WLs  400  are buried WLs. The WLs  400  are buried in the substrate  110 . The WLs  400  are intersected with the active regions  111 . A top of each of the WLs  400  is not higher than the surface of the substrate  110 . In the embodiment, the active regions  111  in the substrate  110  are arranged in an array. The plurality of WLs  400  in the substrate  110  are also arranged parallel in an array. Each of the WLs  400  is intersected with at least one of the active regions  111 . 
     The contact portion  210  is provided in the substrate  110  between the adjacent ones of the WLs  400 . The bottom surface of the contact portion  210  contacts and is connected to the active region  111 , such that a limited space of the substrate  110  is fully utilized. 
     In some embodiments of the present disclosure, projection of the extension portion  221  on the substrate  110  is of a square. With a plane parallel to the WLs  400  and perpendicular to the substrate  110  as a first section, the second outer sidewall part  2212  of the extension portion  221  and the first section are perpendicular to each other. 
     In the embodiment, the second outer sidewall part  2212  of the extension portion  221  and the first section are perpendicular to each other. The direction of the second outer sidewall part  2212  of the extension portion  221  refers to the extension direction of the BL structure  200  (namely the direction of the BL in is  FIG.  3   ). The extension direction of the BL  200  (namely the direction of the BL in  FIG.  3   ) is perpendicular to the extension direction of the WL  400  (namely the direction of the WL in  FIG.  3   ). 
     The projection of the extension portion  221  on the substrate  110  is of the square, namely the first direction in which the first outer sidewall part  2211  of the extension portion  221  is located is perpendicular to the second direction. In the embodiment, the first direction refers to the direction of the WL in  FIG.  3   . 
     In the embodiment, the limited space of the substrate  110  is fully utilized to provide more BL structures  200  and WLs  400 . 
     According to an exemplary embodiment, most contents of the BL structure  200  in the embodiment are the same as those in the foregoing embodiment. The embodiment differs from the foregoing embodiment in: As shown in  FIG.  1    and  FIG.  2   , a thickness of the first outer sidewall part  2211  of the extension portion  221  is greater than a thickness of the second outer sidewall part  2212  of the extension portion  221 . 
     In the foregoing embodiment, the projection of the extension portion  221  on the substrate  110  is of the square. The second direction in which the second outer sidewall part  2212  of the extension portion  221  is located refers to the extension direction of the BL structure  200  (namely the direction of the BL in  FIG.  3   ). The first direction in which the first outer sidewall part  2211  of the extension portion  221  is located is parallel to the extension direction of the WL  400  (namely the direction of the WL in  FIG.  3   ). 
     In the embodiment, the linear shape of the BL structure  200  is kept by thinning the second outer sidewall part  2212  of the extension portion  221 . 
     According to an exemplary embodiment, as shown in  FIGS.  1 - 3   , the BL structure  200  in the embodiment is provided in a substrate  110 . A first dielectric layer  121  covers the substrate  110 . Arrayed active regions  111  are arranged in the substrate  110 . The BL structure  200  includes: a contact portion  210  including a bottom contacting and connected to each of the active regions  111 , a barrier layer  220  covering a part of the contact portion  210 , a conductive layer  230  covering a part of the barrier layer  220 , and an isolation layer  240  covering a top of the conductive layer  230 . 
     A material of the isolation layer  240  may include a material with desirable insulation performance such as silicon nitride or silicon oxynitride. The isolation layer  240  covers the conductive layer  230  to protect the BL structure  200 . 
     As shown in  FIG.  1    and  FIG.  2   , the contact portion  210  includes a first part  211  buried in the substrate  110  and a second part  212  extending out of the substrate  110 . The barrier layer  220  includes an extension portion  221  covering a sidewall and a top surface of the contact portion  210 , and a main body portion  222  covering the first dielectric layer  121 . The second part  212  of the contact portion  210  penetrates through the main body portion  222  and extends into the conductive layer  230 . The extension portion  221  covering a sidewall of the first part  211  of the contact portion  210  is also buried in the substrate  110 . The extension portion  221  covering a sidewall of the second part  212  of the contact portion  210  and the second part  212  of the contact portion  210  extend into the conductive layer  230  together. The conductive layer  230  covers the main body portion  222  of the barrier layer  220  and extends into a surface of the extension portion  221  in the conductive layer  230 . 
     In the embodiment, the BL structure  200  is further covered by an insulating structure  300 . The insulating structure  300  covers two sidewalls of the BL structure  200  on the substrate  110 , a top of the isolation layer  240 , and a second outer sidewall part  2212  of the contact portion in the substrate  110 . 
     According to the BL structure  200  in the embodiment, by increasing the contact area between the contact portion  210  and the conductive layer  230 , the contact resistance between the contact portion  210  and the conductive layer  230  is reduced. With higher electrical connection performance between the contact portion  210  and the conductive layer  230 , the current of the BL structure is conducted more rapidly in an IC, and thus the electrical performance of the device is improved. Moreover, the BL structure in the embodiment is further protected by the isolation layer  240  and the insulating structure  300 , such that the BL structure is firmer and more stable. 
     An exemplary embodiment of the present disclosure provides a semiconductor structure. The semiconductor structure includes the BL structure  200  in the foregoing embodiment of the present disclosure. 
     The semiconductor structure according to the embodiment of the present disclosure may be included in a memory cell and a memory cell array. A read operation or a write operation is performed through the BL structure  200  in the embodiment of the present disclosure. According to the semiconductor structure in the embodiment of the present disclosure, the contact portion of the BL structure has a small contact resistance, such that the current is conducted more rapidly, the data reading and writing speeds of the semiconductor structure are faster, and both electrical performance and memory performance of the semiconductor structure are improved. 
     The memory cell and the memory cell array may be included in a memory device and the memory device may be used in a dynamic random access memory (DRAM). However, the memory device may alternatively be applied in a static random-access memory (SRAM), a flash memory (flash EPROM), a ferroelectric random-access memory (FeRAM), a magnetic random access memory (MRAM), a phase change random-access memory (PRAM), or the like. 
     An exemplary embodiment of the present disclosure provides a method of manufacturing a BL structure, as shown in  FIG.  4   .  FIG.  4    is a flowchart of a method of manufacturing a BL structure according to an exemplary embodiment of the present disclosure.  FIG.  10 A  to  FIG.  23 B  are schematic views of various stages in the method of manufacturing a BL structure. The method of manufacturing a BL structure is described below with reference to  FIG.  10 A  to  FIG.  23 B . 
     As shown in  FIG.  4   , the method of manufacturing a BL structure provided by the exemplary embodiment of the present disclosure includes: 
     S 110 : Provide a base, the base including a substrate and a first initial dielectric layer covering the substrate. 
       FIG.  10 A  is a sectional view of the base in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  10 B  is a sectional view of the base in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  10 A  and  FIG.  10 B , when the base  100  is provided, the substrate  110  is provided first and then the first initial dielectric layer  120  is deposited on the substrate  110 . The first initial dielectric layer  120  covers a top of the substrate  110  to form the base  100 . 
     The substrate  110  is a semiconductor substrate including a silicon-containing substance. For example, the semiconductor substrate may be a silicon substrate, a silicon-germanium substrate, or an SOI substrate. The substrate  110  includes active regions  111  arranged in an array (referring to  FIG.  3   ). As shown in  FIG.  10 A  and  FIG.  10 B , a plurality of parallel WLs  400  are further arranged in the substrate  100  (referring to  FIG.  3   ). The WLs  400  are buried WLs, and are buried in the substrate  100 . The WLs  400  extend along a first direction (referring to the direction of the WL in  FIG.  3   ). The WLs  400  are respectively intersected with the active regions  111  at a predetermined angle, rather than perpendicular to the active regions (referring to  FIG.  3   ). 
     A material of the first initial dielectric layer  120  includes a material with desirable insulation performance such as silicon nitride or silicon oxynitride. In the embodiment, the first initial dielectric layer  120  is made of silicon nitride. 
     S 120 : Form an initial contact hole in the base, a bottom wall of the initial contact hole exposing the substrate, and the initial contact hole penetrating through the first initial dielectric layer. 
       FIG.  11 A  is a sectional view of a photoresist mask layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  11 B  is a sectional view of a photoresist mask layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment.  FIG.  12 A  is a sectional view of the initial contact hole formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  12 B  is a sectional view of the initial contact hole formed in a direction of a BL (referring to  FIG.  3   ) according to the is embodiment. 
     As shown in  FIG.  12 A  and  FIG.  12 B , referring to  FIG.  11 A  and  FIG.  11 B , the photoresist mask layer  10  is formed on the first initial dielectric layer  120 . A first pattern  11  is defined on the photoresist mask layer  10 . Projection of the first pattern  11  on the substrate  100  falls between adjacent two of the WLs  400 . There is an overlapping region between the projection of the first pattern  11  on the substrate  100  and projection of the active region  111  (referring to  FIG.  3   ) on the substrate  100 . According to the first pattern  11 , the first initial dielectric layer  120  and a part of the substrate  110  are removed sequentially to expose the active region  111 , thereby forming the initial contact hole  101 . 
     S 130 : Form, in the initial contact hole, a contact portion and a second initial dielectric unit covering an outer sidewall of the contact portion, a bottom surface of the contact portion being connected to the substrate, and a sidewall of the second initial dielectric unit being connected to the substrate and the first initial dielectric layer. 
       FIG.  14 A  is a sectional view of the second initial dielectric unit formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  14 B  is a sectional view of the second initial dielectric unit formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  14 A  and  FIG.  14 B , the second initial dielectric unit  130  is formed in the initial contact hole  101 . The second initial dielectric unit  130  covers a sidewall of the initial contact hole  101 . 
       FIG.  16 A  is a sectional view of the contact portion formed in a second direction, namely a direction parallel to a WL in  FIG.  3    (referring to  FIG.  3   ), according to the embodiment.  FIG.  16 B  is a sectional view of the contact portion formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  16 A  and  FIG.  16 B , the second initial dielectric unit  130  is filled to form the contact portion  210 . The bottom surface of the contact portion  210  is in contact with the substrate  110 . A top of each of the second initial dielectric unit and the contact portion  210  is flush with a top surface of the first initial is dielectric layer  120 . The outer sidewall of the contact portion  210  is covered by the second initial dielectric unit  130 . 
     The second initial dielectric unit  130  may be deposited by atomic layer deposition (ALD). A material of the second initial dielectric unit  130  includes one or more selected from the group consisting of conductive metal, conductive metal nitride, and conductive alloy. For example, the conductive metal may be titanium, tantalum, or tungsten. In the embodiment, the second initial dielectric unit  130  is made of titanium nitride. 
     The contact portion  210  may be deposited by the ALD. The contact portion  210  may be made of poly. 
     S 140 : Etch a part of the first initial dielectric layer, and form a first dielectric layer, the first dielectric layer exposing a part of the sidewall of the second initial dielectric unit. 
       FIG.  17 A  is a sectional view of the first dielectric layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  17 B  is a sectional view of the first dielectric layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  17 A  and  FIG.  17 B , referring to  FIG.  16 A  and  FIG.  16 B , the first initial dielectric layer  120  may be re-etched for a predetermined thickness by dry etching or wet drying to form the first dielectric layer  121 . The first dielectric layer  121  is thinner than the first initial dielectric layer  120  by the predetermined thickness. The top surface of the contact portion  210  originally flush with the top surface of the first initial dielectric layer  120  forms a protrusive portion protruding from the top of the first dielectric layer  121  by a predetermined height, and the second initial dielectric unit  130  on a sidewall of the protrusive portion is exposed. 
     S 150 : Deposit a third initial dielectric layer and an initial laminated structure, where the third initial dielectric layer covers the first dielectric layer and the part of the sidewall of the second initial dielectric unit, as well as a top surface of the contact portion and a top surface of the second initial dielectric unit, the third initial dielectric layer and the second initial dielectric unit are connected as a whole, and the initial laminated structure covers the third initial dielectric layer. 
       FIG.  18 A  is a sectional view of the third initial dielectric layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  18 B  is a sectional view of the third initial dielectric layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. 
     As shown in  FIG.  18 A  and  FIG.  18 B , the third initial dielectric layer  140  may be deposited by the ALD. A material of the third initial dielectric layer  140  includes one or more selected from the group consisting of conductive metal, conductive metal nitride, and conductive alloy. For example, the conductive metal may be titanium, tantalum, or tungsten. The material of the third initial dielectric layer  140  may be the same as or different from that of the second initial dielectric unit. In the embodiment, both the third initial dielectric layer  140  and the second initial dielectric unit  130  are made of the titanium nitride. 
     The third initial dielectric layer  140  covers the protrusive portion of the contact portion  210  protruding from the first dielectric layer  121 , and is connected to the second initial dielectric unit  130  together such that all sidewall and top surface of the contact portion  210  are covered. 
       FIG.  19 A  is a sectional view of an initial conductive layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  19 B  is a sectional view of an initial conductive layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  19 A  and  FIG.  19 B , referring to  FIG.  18 A  and  FIG.  18 B , a thickness of the third initial dielectric layer  140  is less than a height of the protrusive portion of the contact portion  210 . Upon formation of the third initial dielectric layer  140 , the top of the protrusive portion is still higher than the top of the third initial dielectric layer  140  on the first dielectric layer  121 . Upon formation of the initial laminated structure  500 , the top surface of the contact portion  210  and the third initial dielectric layer  140  thereon extend to the initial laminated structure  500  together. A contact area between the contact portion  210  and the initial laminated structure  500  is a sum of an area of the top surface of the contact portion  210  and an area of a sidewall of the contact portion extending into the initial laminated structure  500 . 
     S 160 : Etch the initial laminated structure, the third initial dielectric layer and the second initial dielectric unit, where a remaining part of the initial laminated structure forms a laminated structure; the laminated structure includes a conductive layer; a remaining part of the second initial dielectric unit and a remaining part of the third initial dielectric layer are connected as a whole and form a barrier layer; and a part of the remaining part of the second initial dielectric unit and a part of the remaining part of the third initial dielectric layer that cover the contact portion form an extension portion of the barrier layer. 
     A material of the conductive layer  230  includes one or more selected from the group consisting of conductive metal, conductive metal nitride, and conductive alloy. For example, the material of the conductive metal may be titanium, tantalum, or tungsten. In the embodiment, the conductive layer  230  is made of the tungsten. 
       FIG.  22 A  is a sectional view of the laminated structure formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  22 B  is a sectional view of the laminated structure formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. 
     As shown in  FIG.  22 A  and  FIG.  22 B , the initial laminated structure  500 , the third initial dielectric layer  140  and the second initial dielectric unit  130  are partially etched, until the first dielectric layer  121  is exposed or the substrate  110  is exposed, thereby forming the laminated structure  600 . The laminated structure  600  is a linear structure extending along a second direction (the extension direction of the BL structure  200 , namely the direction of the BL in  FIG.  3   ). The second direction is perpendicular to a first direction in which the WL  400  extends (namely the direction of the WL in  FIG.  3   ). 
     Any section of the laminated structure  600  in the first direction (namely the direction of the WL in  FIG.  3   ) has a same width. Moreover, in the first direction (namely the direction of the WL in  FIG.  3   ), a width of the laminated structure  600  is greater than that of the contact portion  210 , and less than or equal to that of the initial contact hole  101 , to ensure that two sides of the contact portion  210  are covered by the barrier layer  220 . 
     S 170 : Form a fourth dielectric layer, the fourth dielectric layer covering the laminated structure and a part of the extension portion. 
       FIG.  23 A  is a sectional view of the fourth dielectric layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  23 B  is a sectional view of the fourth dielectric layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  23 A  and  FIG.  23 B , the fourth dielectric layer  190  may be deposited by the ALD. A material of the fourth dielectric layer  190  includes a material with desirable insulation performance such as silicon nitride or silicon oxynitride. In the embodiment, the fourth dielectric layer  190  is made of the silicon nitride. 
     According to the manufacturing method in the embodiment, a second initial dielectric unit covers a sidewall of an initial contact hole, and then a contact portion is formed. An outer sidewall of the contact portion is covered by the second initial dielectric unit. A third initial dielectric layer covering a top surface of the contact portion is formed. Therefore, the outer sidewall and top surface of the contact portion are covered. During manufacture of the BL, the outer sidewall and top surface of the contact portion are prevented from being oxidized by air to increase the contact resistance. Moreover, a first initial dielectric layer is re-etched to form a first dielectric layer. The top surface of the contact portion is protruded from the first dielectric layer, such that the top surface of the contact portion extends into a conductive layer of a laminated structure. A contact area between the contact portion and the conductive layer is a sum of an area of the top surface of the contact portion and an area of a sidewall of the contact portion extending into the conductive layer. By preventing an increase in oxidation resistance of the contact portion during manufacture, the manufacturing method in the embodiment increases the contact area between the contact portion and the conductive layer, and reduces is the contact resistance between the contact portion and the conductive layer. With higher electrical connection efficiency between the contact portion and the conductive layer in the BL structure, the current is conducted more rapidly, and the electrical performance of the device can be improved. 
     According to an exemplary embodiment, the embodiment is a description on the implementation of Step S 120  in the foregoing embodiment. As shown in  FIG.  5   ,  FIG.  5    is a flowchart of Step S 120  of forming, in an initial contact hole, a second initial dielectric unit covering an outer sidewall of a contact portion in a method of manufacturing a BL structure according to the embodiment. 
     The step of forming, in the initial contact hole, a second initial dielectric unit covering an outer sidewall of the contact portion includes: 
     S 121 : Deposit a second initial dielectric layer, the second initial dielectric layer covering the first initial dielectric layer as well as a sidewall and the bottom wall of the initial contact hole. 
       FIG.  13 A  is a sectional view of the second initial dielectric layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  13 B  is a sectional view of the second initial dielectric layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  13 A  and  FIG.  13 B , referring to  FIG.  12 A  and  FIG.  12 B , the second initial dielectric layer  131  may be deposited by the ALD. In the embodiment, the second initial dielectric layer  131  is made of the titanium nitride. 
     S 122 : Etch a part of the second initial dielectric layer covering the first initial dielectric layer to expose the first initial dielectric layer, and etch a part of the second initial dielectric layer covering the bottom wall of the initial contact hole to expose the substrate, thereby forming the second initial dielectric unit. 
     As shown in  FIG.  14 A  and  FIG.  14 B , referring to  FIG.  13 A  and  FIG.  13 B , the second initial dielectric layer  131  covering the top surface of the first initial dielectric layer  120  is removed by the dry or wet etching. The second initial dielectric layer  131  covering the bottom wall of the initial contact hole  101  is removed until the substrate  110  is exposed. The second initial dielectric layer  131  covering the sidewall of the initial contact hole  101  is retained to serve as the second initial dielectric unit  130 . The second initial dielectric unit  130  and the exposed bottom wall of the initial contact hole  101  are enclosed into a contact hole  102 . 
     In the embodiment, a sidewall of the contact hole  102  is enclosed by the second initial dielectric unit  130 . Consequently, the bottom surface of the contact portion  210  contacts the substrate  110 , and the sidewall of the contact portion  210  is connected to the second initial dielectric unit  130 , which prevents direct exposure of the sidewall of the contact portion  210  in the air, prevents the sidewall of the contact portion  210  from being oxidized by the air during manufacture of the BL, and prevents the increase of the resistance due to oxidation of the contact portion  210 . 
     According to an exemplary embodiment, the embodiment is a description on the implementation of Step S 130  in the foregoing embodiment. As shown in  FIG.  6   ,  FIG.  6    is a flowchart of Step S 130  of forming, in the initial contact hole, a contact portion in a method of manufacturing a BL structure according to the embodiment. 
     The step of forming, in the initial contact hole, a contact portion includes: 
     S 131 : Deposit a contact dielectric layer, the contact dielectric layer covering an inner wall of the second initial dielectric unit and the first initial dielectric layer, as well as a part of the substrate exposed by the initial contact hole. 
       FIG.  15 A  is a sectional view of the contact dielectric layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  15 B  is a sectional view of the contact dielectric layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  15 A  and  FIG.  15 B , referring to  FIG.  14 A  and  FIG.  14 B , the contact dielectric layer  150  may be deposited by the ALD. The contact dielectric layer  150  is filled in the contact hole  102  and covers the top surface of the first initial dielectric layer  120 . In the embodiment, the contact dielectric layer  150  is made of the titanium is nitride. 
     S 132 : Remove a part of the contact dielectric layer, and remain a part of the contact dielectric layer in the initial contact hole to form the contact portion, the top surface of the contact portion being flush with a top surface of the first initial dielectric layer. 
     As shown in  FIG.  16 A  and  FIG.  16 B , referring to  FIG.  15 A  and  FIG.  15 B , the contact dielectric layer  150  on the first initial dielectric layer  120  is removed by the dry or wet etching, until the top surface of the first initial dielectric layer  120  is exposed to form the contact portion  210 . The top surface of the contact portion  210  is flush with the top surface of the first initial dielectric layer  120 . 
     In the exemplary embodiment, by removing the contact dielectric layer on the top surface of the first initial dielectric layer to form the contact portion, the top contact dielectric layer oxidized by the air can be removed, and thus the contact portion has the smaller resistance and the better conductivity. 
     According to an exemplary embodiment, the embodiment is a description on the implementation of Step S 150  in the foregoing embodiment. As shown in  FIG.  7   ,  FIG.  7    is a flowchart of Step S 150  of depositing an initial laminated structure in a method of manufacturing a BL structure according to the embodiment. 
     The step of depositing an initial laminated structure includes: 
     S 151 : Deposit an initial conductive layer, the initial conductive layer covering the third initial dielectric layer. 
     As shown in  FIG.  19 A  and  FIG.  19 B , referring to  FIG.  18 A  and  FIG.  18 B , the initial conductive layer  160  may be deposited by the ALD. The initial conductive layer  160  covers the top surface of the first initial dielectric layer  120 , the sidewall of the second initial dielectric unit  130 , the top surface of the contact portion  210  and the top of the third initial dielectric layer  140 . Exemplarily, the initial conductive layer  160  is made of the tungsten. 
     S 152 : Deposit an initial isolation layer, the initial isolation layer covering the initial conductive layer. 
       FIG.  20 A  is a sectional view of the initial isolation layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  20 B  is a sectional view of the initial isolation layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  20 A  and  FIG.  20 B , referring to  FIG.  19 A  and  FIG.  19 B , the initial isolation layer  170  may be deposited by the ALD, and the initial isolation layer  170  covers the initial conductive layer  160 . In the embodiment, the initial isolation layer  170  is made of the titanium nitride. 
     As shown in  FIG.  20 A  and  FIG.  20 B , the initial laminated structure  500  includes a contact portion  210 , the second initial dielectric unit  130 , the third initial dielectric layer  140 , the initial conductive layer  160 , and the initial isolation layer  170  on the substrate. 
     In the embodiment, the deposited initial laminated structure includes the initial conductive layer and the initial isolation layer, such that the BL structure is firmer and more stable. 
     An exemplary embodiment of the present disclosure provides a method of manufacturing a BL structure. As shown in  FIG.  8   ,  FIG.  8    is a flowchart of a method of manufacturing a BL structure according to an exemplary embodiment. Step S 210  to Step S 250  in the embodiment are the same as Step S 110  to Step S 150  in the foregoing embodiment, Step S 270  in the embodiment is the same as Step S 160  in the foregoing embodiment, and Step S 280  in the embodiment is the same as Step S 170  in the foregoing embodiment. 
     As shown in  FIG.  8   , the embodiment differs from the foregoing embodiment in: after Step S 250  of depositing a third initial dielectric layer and an initial laminated structure, and before Step S 270  of etching the initial laminated structure, the third initial dielectric layer and the second initial dielectric unit, the method of manufacturing a BL structure in the embodiment further includes Step S 260 : Form a mask layer on the initial isolation layer. 
       FIG.  21 A  is a sectional view of the mask layer formed in a direction parallel to a WL (referring to  FIG.  3   ) according to the embodiment.  FIG.  21 B  is a is sectional view of the mask layer formed in a direction of a BL (referring to  FIG.  3   ) according to the embodiment. As shown in  FIG.  21 A  and  FIG.  21 B , referring to  FIG.  20 A  and  FIG.  20 B , the mask layer  180  is correspondingly provided on the initial isolation layer  170  on the contact portion  210 . The mask layer  180  is of a strip structure extending along the second direction (the extension direction of the BL structure  200 , namely the direction of the BL in  FIG.  3   ). In the first direction (namely the direction of the WL in  FIG.  3   ), a width of the mask layer  180  is greater than that of the contact portion  210 , and less than or equal to that of the initial contact hole  101 . Projection of the contact portion  210  on the substrate  110  falls within projection of the mask layer  180  on the substrate  100 . 
     In the embodiment, the width of the mask layer  180  is less than that of the initial contact hole  101 , and two sides of projection of the initial contact hole  101  on the substrate  100  extend from two sides of the projection of the mask layer  180  on the substrate  100 . 
     In the embodiment, the width of the mask layer is limited within a range greater than the width of the contact portion and less than the width of the initial contact hole, and portions exceeding the mask layer are respectively retained at two sides of the initial contact hole, which ensures that the BL structure etched according to the mask layer in the embodiment has a desirable linear shape. Moreover, a part of the sidewall of the extension portion of the barrier layer can be exposed, such that the subsequently deposited fourth dielectric layer can cover the exposed sidewall of the extension portion to better protect the contact portion. 
     According to an exemplary embodiment, the embodiment is a description on the implementation of Step S 270  in the foregoing embodiment. As shown in  FIG.  9   ,  FIG.  9    is a flowchart of Step S 270  of etching the initial laminated structure, the third initial dielectric layer and the second initial dielectric unit in a method of manufacturing a BL structure according to the embodiment. 
     The step of etching the initial laminated structure, the third initial dielectric layer and the second initial dielectric unit includes: 
     S 271 : Etch the initial isolation layer, a remaining part of the initial isolation layer corresponding to a pattern defined by the mask layer forming an isolation layer. 
     S 272 : Etch the initial conductive layer, a remaining part of the initial conductive layer corresponding to the pattern forming the conductive layer. 
     S 273 : Etch the third initial dielectric layer, one part of a remaining part of the third initial dielectric layer corresponding to the pattern serving as one part of the extension portion, and the other part of the remaining part of the third initial dielectric layer corresponding to the pattern serving as a main body portion of the barrier layer. 
     S 274 : Etch the second initial dielectric unit, a remaining part of the second initial dielectric unit corresponding to the pattern serving as the other part of the extension portion. 
     As shown in  FIG.  22 A  and  FIG.  22 B , referring to  FIG.  21 A  and  FIG.  21 B , the mask layer  180  is provided on the initial isolation layer  170 . The initial isolation layer  170  not covered by the pattern defined by the mask layer  180  is removed by the dry or wet etching, and the remaining part of the initial isolation layer  170  forms the isolation layer  240 . The pattern defined by the mask layer  180  is transferred to the initial conductive layer  160 , the initial conductive layer  160  not covered by the pattern defined by the mask layer  180  is removed by the dry or wet etching, and the remaining part of the initial conductive layer  160  forms the conductive layer  230 . The pattern defined by the mask layer  180  is transferred to the third initial dielectric layer  140 , the third initial dielectric layer  140  not covered by the pattern defined by the mask layer  180  is removed by the dry or wet etching, and the remaining part of the third initial dielectric layer  140  serves as the main body portion  222  of the barrier layer  220  and one part of the extension portion  221 . The pattern defined by the mask layer  180  is transferred to the second initial dielectric unit  130 , the second initial dielectric unit  130  not covered by the pattern defined by the mask layer  180  is removed by the dry or wet etching until the substrate  110  is exposed, and the remaining is part of the second initial dielectric unit  130  serves as the other part of the extension portion  221  of the barrier layer  220 . 
     In the exemplary embodiment, in Step S 280 , when the width of the laminated structure is less than that of the initial contact hole  101 , after a part of the second initial dielectric unit  130  is removed, two sidewalls of the initial contact hole  101  are exposed. As shown in  FIG.  22 A  and  FIG.  22 B , a protective space is formed at each of two sides of the extension portion  221  of the barrier layer  220 . When the fourth dielectric layer  190  is deposited subsequently, a part of the fourth dielectric layer  190  covers the laminated structure  600  on the substrate  100  (referring to  FIG.  1    and  FIG.  2   ), and a part of the fourth dielectric layer  190  is filled in the protective space at each of the two sides of the extension portion  221  to form an insulating portion  310 . The fourth dielectric layer  190  covering the laminated structure  600  on the substrate  100  and the insulating portion  310  at each of the two sides of the extension portion  221  jointly serve as an insulating structure  300 . The insulating structure  300  and the first dielectric layer  121  are connected as a whole to protect the BL structure well. 
     The embodiments or implementations of this specification are described in a progressive manner, and each embodiment focuses on differences from other embodiments. The same or similar parts between the embodiments may refer to each other. 
     In the description of this specification, the description with reference to terms such as “an embodiment”, “an exemplary embodiment”, “some implementations”, “a schematic implementation”, and “an example” means that the specific feature, structure, material, or characteristic described in combination with the implementation(s) or example(s) is included in at least one implementation or example of the present disclosure. 
     In this specification, the schematic expression of the above terms does not necessarily refer to the same implementation or example. Moreover, the described specific feature, structure, material or characteristic may be combined in an appropriate manner in any one or more implementations or examples. 
     It should be noted that in the description of the present disclosure, the terms such as “center”, “top”, “bottom”, “left”, “right”, “vertical”, “horizontal”, “inner” and “outer” indicate the orientation or position relationships based on the accompanying drawings. These terms are merely intended to facilitate description of the present disclosure and simplify the description, rather than to indicate or imply that the mentioned apparatus or element must have a specific orientation and must be constructed and operated in a specific orientation. Therefore, these terms should not be construed as a limitation to the present disclosure. 
     It can be understood that the terms such as “first” and “second” used in the present disclosure can be used to describe various structures, but these structures are not limited by these terms. Instead, these terms are merely intended to distinguish one structure from another. 
     The same elements in one or more accompanying drawings are denoted by similar reference numerals. For the sake of clarity, various parts in the accompanying drawings are not drawn to scale. In addition, some well-known parts may not be shown. For the sake of brevity, a structure obtained by implementing a plurality of steps may be shown in one figure. In order to understand the present disclosure more clearly, many specific details of the present disclosure, such as the structure, material, size, processing process, and technology of the device, are described below. However, as those skilled in the art can understand, the present disclosure may not be implemented according to these specific details. 
     Finally, it should be noted that the above embodiments are merely intended to explain the technical solutions of the present disclosure, rather than to limit the present disclosure. Although the present disclosure is described in detail with reference to the above embodiments, those skilled in the art should understand that they may still modify the technical solutions described in the is above embodiments, or make equivalent substitutions of some or all of the technical features recorded therein, without deviating the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present disclosure. 
     INDUSTRIAL APPLICABILITY 
     According to the BL structure provided by the embodiment of the present disclosure, a barrier layer covers a top surface and an outer sidewall surface of a contact portion. The barrier layer protects the sidewall of the contact portion from being oxidized, thereby reducing the contact resistance of the BL.