Patent Publication Number: US-2022230913-A1

Title: Method for fabricating semiconductor device with covering liners

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. Non-Provisional application Ser. No. 16/902,692 filed Jun. 16, 2020, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a semiconductor device with covering liners. 
     DISCUSSION OF THE BACKGROUND 
     Semiconductor devices are used in a variety of electronic applications, such as personal computers, cellular telephones, digital cameras, and other electronic equipment. The dimensions of semiconductor devices are continuously being scaled down to meet the increasing demand of computing ability. However, a variety of issues arise during the scaling-down process, and such issues are continuously increasing. Therefore, challenges remain in achieving improved quality, yield, performance, and reliability and reduced complexity. 
     This Discussion of the Background section is provided for background information only. The statements in this Discussion of the Background are not an admission that the subject matter disclosed in this section constitutes prior art to the present disclosure, and no part of this Discussion of the Background section may be used as an admission that any part of this application, including this Discussion of the Background section, constitutes prior art to the present disclosure. 
     SUMMARY 
     One aspect of the present disclosure provides a substrate, a porous insulating layer positioned above the substrate, a first conductive feature positioned in the porous insulating layer, and covering liners including two top segments and two side segments. The two side segments are positioned on sidewalls of the first conductive feature, and the two top segments are positioned on top surfaces of the porous insulating layer. 
     In some embodiments, the semiconductor device includes supporting liners positioned between the two side segments of the covering liners and the porous insulating layer and between the porous insulating layer and the substrate. 
     In some embodiments, a thickness of supporting liners is between about 2 nm and about 20 nm. 
     In some embodiments, a thickness of the two side segments of the covering liners is gradually decreased toward the substrate. 
     In some embodiments, a thickness of the two top segments of the covering liners is between about 1 angstrom and about 30 angstroms. 
     In some embodiments, a porosity of the porous insulating layer is between about 10% and about 50%. 
     In some embodiments, the covering liners are formed of metal oxide. 
     In some embodiments, an aspect ratio of the first conductive feature is between about 1:3 and about 1:15. 
     In some embodiments, the semiconductor device includes a first barrier layer positioned between the two side segments of the covering liners and the first conductive feature and between the porous insulating layer and the substrate. 
     In some embodiments, a thickness of the first barrier layer is between about 10 angstroms and about 15 angstroms. 
     In some embodiments, bottommost points of the two side segments of the covering liners are at a vertical level lower than a bottom surface of the porous insulating layer. 
     Another aspect of the present disclosure provides a method for fabricating a semiconductor device including providing a substrate, forming a sacrificial structure above the substrate, forming a supporting liner covering the sacrificial structure, forming an energy-removable layer covering the supporting liner, performing a planarization process until a top surface of the sacrificial structure is exposed, performing an etch process to remove the sacrificial structure and concurrently form a first opening in the energy-removable layer, forming covering liners on sidewalls of the first opening and on a top surface of the energy-removable layer, forming a first conductive feature in the first opening, and applying an energy source to turn the energy-removable layer into a porous insulating layer. 
     In some embodiments, the supporting liner is formed of silicon nitride. 
     In some embodiments, the energy-removable layer includes a base material and a decomposable porogen material. 
     In some embodiments, the base material includes methylsilsesquioxane, low-dielectric materials, or silicon oxide. 
     In some embodiments, the energy source is heat, light, or a combination thereof. 
     In some embodiments, the covering liners are formed of metal oxide. 
     In some embodiments, the step of forming the sacrificial structure above the substrate includes forming a bottom sacrificial layer above the substrate, forming a top sacrificial layer on the bottom sacrificial layer, performing a photolithography-etch process to remove portions of the bottom sacrificial layer and portions of the top sacrificial layer and concurrently form the sacrificial structure. 
     In some embodiments, the bottom sacrificial layer is formed of silicon carbon. 
     In some embodiments, the method for fabricating the semiconductor device includes a step of forming a first barrier layer in the first opening before the step of forming the first conductive feature in the first opening. 
     Due to the design of the semiconductor device of the present disclosure, the porous insulating layer may reduce the parasitic capacitance between conductive features of the semiconductor device. In addition, with the assistant of the covering liner, the first conductive feature may be formed without any void. Therefore, the yield of the semiconductor device may be improved. 
     The foregoing has outlined rather broadly the features and technical advantages of the present disclosure in order that the detailed description of the disclosure that follows may be better understood. Additional features and advantages of the disclosure will be described hereinafter, and form the subject of the claims of the disclosure. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures or processes for carrying out the same purposes of the present disclosure. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure as set forth in the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It should be noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion. 
         FIG. 1  illustrates, in a flowchart diagram form, a method for fabricating a semiconductor device in accordance with one embodiment of the present disclosure; 
         FIGS. 2 to 8  illustrate, in schematic cross-sectional view diagrams, a flow for fabricating the semiconductor device in accordance with one embodiment of the present disclosure; 
         FIG. 9  illustrates, in a schematic cross-sectional diagram, a semiconductor device in accordance with another embodiment of the present disclosure; 
         FIG. 10  illustrates, in a close-up schematic cross-sectional diagram, part of the semiconductor device in accordance with another embodiment of the present disclosure; 
         FIG. 11  illustrates, in a close-up schematic cross-sectional view diagram, a semiconductor device in accordance with another embodiment of the present disclosure; 
         FIG. 12  illustrates, in a schematic cross-sectional diagram, a semiconductor device in accordance with another embodiment of the present disclosure; 
         FIG. 13  illustrates, in a close-up schematic cross-sectional view diagram, a semiconductor device in accordance with another embodiment of the present disclosure; 
         FIG. 14  illustrates, in a flowchart diagram form, a method for fabricating a semiconductor device in accordance with another embodiment of the present disclosure; 
         FIGS. 15 to 31  illustrate, in schematic cross-sectional view diagrams, a flow for fabricating the semiconductor device in accordance with another embodiment of the present disclosure; 
         FIGS. 32 to 35  illustrate, in schematic cross-sectional diagrams, part of a flow of fabricating a semiconductor device in accordance with another embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. 
     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. 
     It should be understood that when an element or layer is referred to as being “connected to” or “coupled to” another element or layer, it can be directly connected to or coupled to another element or layer, or intervening elements or layers may be present. 
     It should be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. Unless indicated otherwise, these terms are only used to distinguish one element from another element. Thus, for example, a first element, a first component or a first section discussed below could be termed a second element, a second component or a second section without departing from the teachings of the present disclosure. 
     Unless the context indicates otherwise, terms such as “same,” “equal,” “planar,” or “coplanar,” as used herein when referring to orientation, layout, location, shapes, sizes, amounts, or other measures do not necessarily mean an exactly identical orientation, layout, location, shape, size, amount, or other measure, but are intended to encompass nearly identical orientation, layout, location, shapes, sizes, amounts, or other measures within acceptable variations that may occur, for example, due to manufacturing processes. The term “substantially” may be used herein to reflect this meaning. For example, items described as “substantially the same,” “substantially equal,” or “substantially planar,” may be exactly the same, equal, or planar, or may be the same, equal, or planar within acceptable variations that may occur, for example, due to manufacturing processes. 
     In the present disclosure, a semiconductor device generally means a device which can function by utilizing semiconductor characteristics, and an electro-optic device, a light-emitting display device, a semiconductor circuit, and an electronic device are all included in the category of the semiconductor device. Specifically, semiconductor devices of embodiments of the present disclosure may be dynamic random-access memory devices. 
     It should be noted that, the term “about” modifying the quantity of an ingredient, component, or reactant of the present disclosure employed refers to variation in the numerical quantity that can occur, for example, through typical measuring and liquid handling procedures used for making concentrates or solutions. Furthermore, variation can occur from inadvertent error in measuring procedures, differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods, and the like. In one aspect, the term “about” means within 10% of the reported numerical value. In another aspect, the term “about” means within 5% of the reported numerical value. Yet, in another aspect, the term “about” means within 10, 9, 8, 7, 6, 5, 4, 3, 2, or 1% of the reported numerical value. 
     It should be noted that, in the description of the present disclosure, above (or up) corresponds to the direction of the arrow of the direction Z, and below (or down) corresponds to the opposite direction of the arrow of the direction Z. 
       FIG. 1  illustrates, in a flowchart diagram form, a method for fabricating a semiconductor device  1 A in accordance with one embodiment of the present disclosure.  FIGS. 2 to 8  illustrate, in schematic cross-sectional view diagrams, a flow for fabricating the semiconductor device  1 A in accordance with one embodiment of the present disclosure. 
     With reference to  FIGS. 1 to 3 , at step S 11 , sacrificial structures  603  may be formed on a substrate  101 . 
     With reference to  FIG. 2 , a bottom sacrificial layer  603 - 1 , a top sacrificial layer  603 - 3 , and a first mask layer  605  may be sequentially formed on the substrate  101 . The bottom sacrificial layer  603 - 1  may be formed of, for example, silicon carbon, or the like. The top sacrificial layer  603 - 3  may be a hard mask layer including silicon nitride, silicon oxynitride, or silicon nitride oxide. In some embodiments, the top sacrificial layer  603 - 3  may be a single layer including a dielectric anti-reflective coating layer, an organic dielectric anti-reflective coating layer, or a bottom anti-reflective coating layer. The first mask layer  605  may be a single layer including a photoresist layer. A photolithography process may be performed to pattern the first mask layer  605  and define the positions of the sacrificial structures  603 . With reference to  FIG. 3 , an etch process, such as an anisotropic dry etch process, may be performed to remove portions of the top sacrificial layer  603 - 3  and portions of the bottom sacrificial layer  603 - 1  and concurrently form the sacrificial structures  603 . After the etch process, the first mask layer  605  may be removed. 
     With reference to  FIG. 1  and  FIGS. 4 to 6 , at step S 13 , supporting liners  303  and energy-removable layer  401  may be formed on the substrate  101 , and first openings  607  may be formed in the energy-removable layer  401 . 
     With reference to  FIG. 4 , the supporting liner  303  may be formed to cover the sacrificial structures  603 . The supporting liner  303  may be formed of, for example, silicon nitride. Subsequently, an energy-removable layer  401  may be formed to cover the supporting liner  303 . The energy-removable layer  401  may include a material such as a thermal decomposable material, a photonic decomposable material, an e-beam decomposable material, or a combination thereof. With reference to  FIG. 5 , a planarization process, such as chemical mechanical polishing, may be performed until the top surfaces of the sacrificial structures  603  are exposed to provide a substantially flat surface for subsequent processing steps. With reference to  FIG. 6 , an etch process may be performed to remove the sacrificial structures  603  and concurrently form the first openings  607  at the places where the sacrificial structures  603  previously occupied. 
     With reference to  FIGS. 1, 7, and 8 , at step S 15 , covering liners  305 , a first barrier layer  307 , and first conductive features  301  may be formed in the first openings  607 , and an energy treatment may be performed to turn the energy-removable layer  401  into a porous insulating layer  403 . 
     With reference to  FIGS. 7 and 8 , the covering liners  305  may be conformally formed on the top surface of the energy-removable layer  401 , on the top surfaces of the supporting liner  303 , and on the sidewalls of the first openings  607 . The covering liners  305  may be formed by a deposition process such as an atomic layer deposition method precisely controlling an amount of a first precursor of the atomic layer deposition method. The covering liners  305  may be formed of, for example, aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium nitride, tungsten nitride, silicon nitride, or silicon oxide. The first barrier layer  307  may be conformally formed on the covering liners  305  and in the first opening  607 . The first barrier layer  307  may be formed of, for example, titanium nitride. A layer of first conductive material  609  may be deposited into the first opening  607  by a deposition process. The layer of first conductive material  609  may include doped polysilicon, a metal, or a metal silicide. 
     After the deposition process, a planarization process, such as chemical mechanical polishing, may be performed until the top surfaces of the covering liners  305  are exposed to remove excess material, provide a substantially flat surface for subsequent processing steps, and concurrently form the first conductive features  301  in the first opening  607 . Subsequently, an energy source may be applied to the intermediate semiconductor device to turn the energy-removable layer  401  into the porous insulating layer  403 . 
     The first conductive feature  301  may be employed as contacts, bit line contacts, vias, through-substrate vias, conductive lines, bit lines, capacitor contacts, landing pads, or other suitable conductive elements. 
       FIG. 9  illustrates, in a schematic cross-sectional diagram, a semiconductor device  1 B in accordance with another embodiment of the present disclosure.  FIG. 10  illustrates, in a close-up schematic cross-sectional diagram, part of the semiconductor device  1 B in accordance with another embodiment of the present disclosure. 
     With reference to  FIGS. 9 and 10 , the semiconductor device  1 B may include a substrate  101 , an isolation layer  103 , impurity regions  107 , two word line structures  201 , a first conductive feature  301 , supporting liners  303 , covering liners  305 , a first barrier layer  307 , a second conductive feature  309 , second barrier layers  311 , third conductive features  313 , a porous insulating layer  403 , insulating layers  405 ,  407 ,  409 , and capacitor structures  501 . 
     With reference to  FIGS. 9 and 10 , the substrate  101  may be formed of for example, silicon, germanium, silicon germanium, silicon carbon, silicon germanium carbon, gallium, gallium arsenide, indium arsenide, indium phosphorus or other IV-IV, III-V or II-VI semiconductor materials. 
     With reference to  FIGS. 9 and 10 , the isolation layer  103  may be disposed in an upper portion of the substrate  101 . The isolation layer  103  may be formed of, for example, an insulating material such as silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, or fluoride-doped silicate. The isolation layer  103  may define an active area  105  of the substrate  101 . The active area  105  may be in the isolation layer  103 . 
     It should be noted that, in the present disclosure, silicon oxynitride refers to a substance which contains silicon, nitrogen, and oxygen and in which a proportion of oxygen is greater than that of nitrogen. Silicon nitride oxide refers to a substance which contains silicon, oxygen, and nitrogen and in which a proportion of nitrogen is greater than that of oxygen. 
     With reference to  FIGS. 9 and 10 , the two word line structures  201  may be disposed in the upper portion of the active area  105 . Each of the two word line structures  201  may include a word line dielectric layer  203 , a word line electrode  205 , and a word line capping layer  207 . For convenience of description, only one word line structure  201  is described. 
     With reference to  FIGS. 9 and 10 , the word line dielectric layer  203  may be inwardly disposed in the upper portion of active area  105 . The word line dielectric layer  203  may be formed of an insulating material having a dielectric constant of about 4.0 or greater. (All dielectric constants mentioned herein are relative to a vacuum unless otherwise noted.). The insulating material having a dielectric constant of about 4.0 or greater may be hafnium oxide, zirconium oxide, aluminum oxide, titanium oxide, lanthanum oxide, strontium titanate, lanthanum aluminate, yttrium oxide, gallium (III) trioxide, gadolinium gallium oxide, lead zirconium titanate, barium strontium titanate, or a mixture thereof. Alternatively, in another embodiment, the insulating material may be silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, or the like. The word line dielectric layer  203  may have a thickness between about 0.5 nm and about 10 nm. 
     With reference to  FIGS. 9 and 10 , the word line electrode  205  may be disposed on the word line dielectric layer  203 . The word line electrode  205  may be formed of a conductive material such as doped polysilicon, silicon germanium, metal, metal alloy, metal silicide, metal nitride, metal carbide, or a combination including multilayers thereof. The metal may be aluminum, copper, tungsten, or cobalt. The metal silicide may be nickel silicide, platinum silicide, titanium silicide, molybdenum silicide, cobalt silicide, tantalum silicide, tungsten silicide, or the like. The word line electrode  205  may have a thickness between about 50 nm and about 500 nm. In some embodiments, a word line barrier layer (not shown) may be disposed between the word line dielectric layer  203  and the word line electrode  205 . The word line barrier layer may be formed of, for example, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, and combination thereof. The word line barrier layer may be employed to prevent the word line electrode  205  from flaking or spalling from the word line dielectric layer  203 . 
     With reference to  FIGS. 9 and 10 , the word line capping layer  207  may be disposed on the word line electrode  205 . The top surface of the word line capping layer  207  may be even with the top surface of the substrate  101 . The word line capping layer  207  may be formed of, for example, silicon oxide, silicon nitride, silicon oxynitride, silicon nitride oxide, fluoride-doped silicate, or the like. In some embodiments, the word line capping layer  207  may be formed of a stacked layer including a bottom capping layer (not shown) and a top capping layer (not shown). The bottom capping layer may be disposed on the word line electrode  205 . The top capping layer may be disposed on the bottom capping layer. The bottom capping layer may be formed of an insulating material having a dielectric constant of about 4.0 or greater. The top capping layer may be formed of a low dielectric-constant material such as silicon oxide, fluoride-doped silicate, or the like. The top capping layer formed of the low dielectric-constant material may reduce electric field at the top surface of the substrate  101 ; therefore, leakage current may be reduced. 
     With reference to  FIGS. 9 and 10 , the impurity regions  107  may be disposed in the active area  105  of the substrate  101 . The impurity regions  107  may be doped with a dopant such as phosphorus, arsenic, or antimony. The impurity regions  107  may include a first impurity region  107 - 1  and two second impurity regions  107 - 3 . The first impurity region  107 - 1  may be disposed between the two word line structures  201 . The two second impurity region  107 - 3  may be disposed between the two word line structures  201  and the isolation layer  103 . 
     With reference to  FIGS. 9 and 10 , the porous insulating layer  403  may be disposed above the substrate  101 . A porosity of the porous insulating layer  403  may be between about 10% and about 50%. The porous insulating layer  403  may have a dielectric constant less than 3.0. The porous insulating layer  403  may include a skeleton and a plurality of empty spaces disposed among the skeleton. The plurality of empty spaces may connect to each other and may be filled with air. The skeleton may include, for example, silicon oxide, low-dielectric materials, or methylsilsesquioxane. The plurality of empty spaces of the porous insulating layer  403  may be filled with air. As a result, a dielectric constant of the porous insulating layer  403  may be significantly lower than a layer formed of, for example, silicon oxide. Therefore, the porous insulating layer  403  may significantly reduce the parasitic capacitance between the first conductive feature  301  and the third conductive features  313 . That is, the porous insulating layer  403  may significantly alleviate an interference effect between electrical signals induced or applied to the first conductive feature  301  and the third conductive features  313 . 
     With reference to  FIGS. 9 and 10 , the first conductive feature  301  may be disposed in the porous insulating layer  403 . The first conductive feature  301  may be formed of, for example, doped polysilicon, a metal, or a metal silicide. The first conductive feature  301  may be electrically coupled to the first impurity region  107 - 1 . In the embodiment depicted, the first conductive feature  301  may be employed as a bit line contact but is not limited thereto. In some embodiments, an aspect ratio of the first conductive feature  301  may be between about 1:3 and about 1:15. 
     With reference to  FIGS. 9 and 10 , the first barrier layer  307  may be disposed on sidewalls of the first conductive feature  301  and the bottom surface of the first conductive feature  301 . In other words, the first barrier layer  307  may be disposed between the first conductive feature  301  and the porous insulating layer  403  and between the first conductive feature  301  and the first impurity region  107 - 1 . Specifically, the first barrier layer  307  may include a bottom segment  307 B and two side segments  307 S. The bottom segment  307 B may be disposed on the bottom surface of the first conductive feature  301 . The two side segments  307 S may connect to the two ends of the bottom segment  307 B and may be respectively correspondingly disposed on sidewalls of the first conductive feature  301 . In some embodiments, the first barrier layer  307  may have a thickness T 1  between about 10 angstroms and about 15 angstroms. In some embodiments, the thickness T 1  of the first barrier layer  307  may be between about 11 angstroms and about 13 angstroms. The first barrier layer  307  may be formed of, for example, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, or combination thereof. The first barrier layer  307  may be employed to prevent conductive material of the first conductive feature  301  from diffusing into the porous insulating layer  403 . The first barrier layer  307  may be electrically coupled to the first impurity region  107 - 1  and the first conductive feature  301 . 
     With reference to  FIGS. 9 and 10 , the covering liners  305  may be respectively correspondingly disposed on the two side segments  307 S of the first barrier layer  307 , disposed on the top surface of the porous insulating layer  403 , and disposed on the top surfaces of the supporting liners  303 . Specifically, the covering liners  305  may include two side segments  305 S and two top segments  305 T. One end of each of the two top segments  305 T may connect to corresponding one of the two side segments  305 S. For convenience of description, only one side segment  305 S and one top segment  305 T are described. 
     With reference to  FIGS. 9 and 10 , the side segment  305 S of the covering liner  305  may be disposed on the upper portion of the side segment  307 S of the first barrier layer  307 . In other words, the side segment  305 S of the covering liner  305  may be disposed between the side segment  307 S of the first barrier layer  307  and the porous insulating layer  403 . In some embodiments, a thickness T 2  of the side segment  305 S of the covering liner  305  may gradually decrease along the direction Z toward the substrate  101 . In some embodiments, the bottommost point  305 BP of the side segment  305 S may be at a vertical level higher than a vertical level of the bottom surface  403 BS of the porous insulating layer  403 . In some embodiments, the bottommost point  305 BP of the side segment  305 S may be at a vertical level even with a vertical level of the bottom surface  403 BS of the porous insulating layer  403 . 
     With reference to  FIGS. 9 and 10 , the top segment  305 T of the covering liner  305  may be disposed on the top surface of the porous insulating layer  403  and disposed on the top surfaces of the supporting liners  303 . In some embodiments, a thickness T 3  of the top segment  305 T of the covering liner  305  may be between about 1 angstrom and about 30 angstroms. 
     In some embodiments, the covering liners  305  may be formed of, for example, aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium nitride, tungsten nitride, silicon nitride, or silicon oxide. The covering liners  305  may serve as a protection layer for the porous insulating layer  403  during subsequent semiconductor processes and may avoid void produced during formation of the first conductive feature  301 . 
     With reference to  FIGS. 9 and 10 , the supporting liners  303  may be disposed between the porous insulating layer  403  and the substrate  101 , between the covering liners  305  and the porous insulating layer  403 , and between the first barrier layer  307  and the porous insulating layer  403 . The supporting liners  303  may have a thickness T 4  between about 2 nm and about 20 nm. Specifically, the supporting liners  303  may include two side segments  303 S and two bottom segments  303 B. For convenience of description, only one side segment  303 S and one bottom segment  303 B are described. 
     With reference to  FIGS. 9 and 10 , the bottom segment  303 B of the supporting liner  303  may be disposed on the substrate  101  and disposed under the porous insulating layer  403 . In other words, the bottom segment  303 B of the supporting liner  303  may be disposed between the porous insulating layer  403  and the substrate  101 . The upper portion of the side segment  303 S of the supporting liner  303  may be disposed on the side segment  305 S of the covering liner  305 . The lower portion of the side segment  303 S of the supporting liner  303  may be disposed on the lower portion of the side segment  307 S of the first barrier layer  307 . The lower portion of the side segment  303 S of the supporting liner  303  may connect to one end, which is adjacent to the first conductive feature  301 , of the bottom segment  303 B of the supporting liner  303 . 
     In some embodiments, the supporting liners  303  may be formed of, for example, silicon nitride, silicon oxynitride, or the like. The supporting liners  303  may provide structural support for the porous insulating layer  403  and the first conductive feature  301 . 
     With reference to  FIGS. 9 and 10 , the insulating layers  405 ,  407 ,  409  may be sequentially stacked on the covering liners  305 . The insulating layers  405 ,  407 ,  409  may be formed of, for example, silicon nitride, silicon oxide, silicon oxynitride, flowable oxide, undoped silica glass, borosilica glass, phosphosilica glass, borophosphosilica glass, fluoride silicate glass, carbon-doped silicon oxide, or a combination thereof, but are not limited thereto. The insulating layers  405 ,  407 ,  409  may be formed of a same material but are not limited thereto. 
     With reference to  FIGS. 9 and 10 , the second conductive feature  309  may be disposed in the insulating layer  405  and disposed on the first conductive feature  301 . The second conductive feature  309  may be electrically coupled to the first conductive feature  301 . The second conductive feature  309  may be formed of, for example, a conductive material such as tungsten, aluminum, copper, nickel, or cobalt. In the embodiment depicted, the second conductive feature  309  may be employed as a bit line but is not limited thereto. In some embodiments, insulating spacers (not shown) may be disposed on sidewalls of the second conductive feature  309  to improve the process tolerance for the third conductive features  313  which will be fabricated later. 
     With reference to  FIGS. 9 and 10 , the third conductive features  313  may be respectively correspondingly disposed on the two second impurity regions  107 - 3  and disposed penetrating the covering liners  305 , the porous insulating layer  403 , the supporting liners  303 , and the insulating layers  405 ,  407 . The third conductive features  313  may be electrically coupled to the two second impurity regions  107 - 3 . In some embodiments, the sidewalls  313 S of the third conductive features  313  may have a slanted cross-sectional profile. In some embodiments, a width of the third conductive features  313  may gradually become wider from bottom to top along the direction Z. In some embodiments, an angle α between the top surface  313 TS of the third conductive features  313  and the sidewall  313 S of the third conductive features  313  may be between 83 degree and about 90 degree. The third conductive features  313  may be formed of, for example, doped polysilicon, titanium, titanium nitride, tantalum, tantalum nitride, tungsten, copper, aluminum or aluminum alloy. In some embodiments, an aspect ratio of the third conductive features  313  may be between about 1:3 and about 1:15. In the embodiment depicted, the third conductive features  313  may be employed as capacitor contacts. 
     With reference to  FIGS. 9 and 10 , the second barrier layers  311  may be respectively correspondingly disposed on the sidewalls  313 S of the third conductive features  313  and the bottom surfaces of the third conductive features  313 . Specifically, each of the second barrier layers  311  may include a bottom segment  311 B and side segments  311 S. The bottom segment  311 B of the second barrier layer  311  may be disposed on the substrate  101  and on the bottom surface of the third conductive feature  313 . The bottom segment  311 B of the second barrier layer  311  may be disposed between the substrate  101  and the third conductive features  313 . The side segments  311 S of the second barrier layer  311  may connect to the two ends of the bottom segment  311 B of the second barrier layer  311 . The side segments  403 S of the second barrier layer  311  may be disposed on the sidewalls  313 S of the third conductive features  313 . The second barrier layers  311  may have a thickness T 5  between about 10 angstroms and about 15 angstroms. In some embodiments, the thickness T 5  of the second barrier layers  311  may be between about 11 angstroms and about 13 angstroms. 
     In some embodiments, the second barrier layers  311  may be formed of, for example, titanium, titanium nitride, titanium silicon nitride, tantalum, tantalum nitride, tantalum silicon nitride, or combination thereof. The second barrier layers  311  may be employed to prevent conductive material of the second barrier layers  311  from diffusing into the insulating layers  405 ,  407 , the covering liners  305 , the porous insulating layer  403 , and the supporting liners  303 . 
     With reference to  FIGS. 9 and 10 , the capacitor structures  501  may be disposed in the insulating layer  409  and respectively correspondingly disposed on the third conductive features  313 . The capacitor structures  501  may be electrically coupled to the third conductive features  313 . The capacitor structures  501  may include capacitor bottom electrodes  503 , a capacitor dielectric layer  505 , and a capacitor top electrode  507 . 
     With reference to  FIGS. 9 and 10 , the capacitor bottom electrodes  503  may be inwardly disposed in the insulating layer  409 . The bottoms of the capacitor bottom electrodes  503  may respectively correspondingly contact the top surfaces  313 TS of the third conductive features  313 . The capacitor bottom electrodes  503  may be formed of, for example, doped polysilicon, metal, metal nitride, or metal silicide. The capacitor dielectric layer  505  may be disposed on the capacitor bottom electrodes  503  and cover the top surface of the insulating layers  409 . The capacitor dielectric layer  505  may be formed of a single layer including an insulating material having a dielectric constant of about 4.0 or greater. The capacitor dielectric layer  505  may have a thickness between about 1 angstrom and about 100 angstroms. Alternatively, in some embodiments, the capacitor dielectric layer  505  may be formed of a stacked layer consisting of silicon oxide, silicon nitride, and silicon oxide. Alternatively, in some embodiments, the capacitor dielectric layer  505  may be formed of a stacked layer consisting of zirconium oxide, aluminum oxide, and zirconium oxide. The capacitor top electrode  507  may be disposed on the capacitor dielectric layer  505 . The capacitor top electrode  507  may be formed of, for example, doped polysilicon, silicon germanium alloy, or metal. 
       FIG. 11  illustrates, in a close-up schematic cross-sectional view diagram, a semiconductor device  1 C in accordance with another embodiment of the present disclosure.  FIG. 12  illustrates, in a schematic cross-sectional diagram, a semiconductor device  1 D in accordance with another embodiment of the present disclosure.  FIG. 13  illustrates, in a close-up schematic cross-sectional view diagram, a semiconductor device  1 E in accordance with another embodiment of the present disclosure. 
     With reference to  FIG. 11 , in the semiconductor device  1 C, the bottommost points  305 BP of the side segments  305 S of the covering liners  305  may contact the first impurity region  107 - 1 . The side segment  307 S of the first barrier layer  307  may be opposite to the side segment  303 S of the supporting liner  303  with the side segment  305 S of the covering liner  305  interposed therebetween. 
     With reference to  FIG. 12 , in the semiconductor device  1 D, the adjustment layers  315  may be disposed between the third conductive features  313  and the side segments  311 S of the second barrier layers  311 . Specifically, the adjustment layers  315  may be respectively correspondingly disposed on upper portions of the side segments  311 S of the second barrier layers  311 . The bottommost points  315 BP of the bottommost points  315 BP may be at a vertical level higher than a vertical level of the bottom segment  311 B of the second barrier layers  311 . 
     In some embodiments, the adjustment layers  315  may be formed of any suitable metal, metal oxide, metal carbide, metal nitride, or combination thereof. For example, the adjustment layers  315  may be formed of aluminum carbide, aluminum nitride, tungsten carbide, or tungsten nitride. In some embodiments, the adjustment layers  315  may be formed of, for example, aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium nitride, tungsten nitride, silicon nitride, or silicon oxide. 
     With reference to  FIG. 13 , in the semiconductor device  1 E, the bottommost points  315 BP of the adjustment layers  315  may contact the bottom segments  311 B of the second barrier layers  311 . 
     With the presence of the adjustment layers  315 , the third conductive features  313  may be formed without any void. Therefore, the yield of the semiconductor device  1 D/ 1 E may be improved. 
       FIG. 14  illustrates, in a flowchart diagram form, a method  20  for fabricating a semiconductor device  1 B in accordance with another embodiment of the present disclosure.  FIGS. 15 to 31  illustrate, in schematic cross-sectional view diagrams, a flow for fabricating the semiconductor device  1 B in accordance with another embodiment of the present disclosure. 
     With reference to  FIGS. 14 and 15 , at step S 21 , a substrate  101  may be provided and an isolation layer  103 , an impurity region  107  may be formed in the substrate  101 , and two word line structures  201  may be formed in the substrate  101 . 
     With reference to  FIG. 15 , the isolation layer  103  may be formed in the substrate  101  and define an active area  105 . An implantation process may be performed to dope a dopant into the upper portion of the active area  105  and concurrently form the impurity region  107  in the active area  105 . The dopant may be phosphorus, arsenic, or antimony. The two word line structures  201  may divide the impurity region  107  into a first impurity region  107 - 1  and two second impurity region  107 - 3 . 
     With reference to  FIGS. 14, 16, and 17 , at step S 23 , a sacrificial structure  603  may be formed on the substrate  101 . 
     With reference to  FIG. 16 , a bottom sacrificial layer  603 - 1  and a top sacrificial layer  603 - 3  may be sequentially formed on the substrate  101 . In some embodiments, the bottom sacrificial layer  603 - 1  may be formed of, for example, silicon carbon, or the like. In some embodiments, the top sacrificial layer  603 - 3  may be a hard mask layer including silicon nitride, silicon oxynitride, or silicon nitride oxide. In some embodiments, the top sacrificial layer  603 - 3  may be a single layer including a dielectric anti-reflective coating layer, an organic dielectric anti-reflective coating layer, or a bottom anti-reflective coating layer. A thickness of the top sacrificial layer  603 - 3  may be between about 240 angstroms and about 630 angstroms. In some embodiments, the top sacrificial layer  603 - 3  may be a stacked layer including, form bottom to top, a dielectric anti-reflective coating layer and a bottom anti-reflective coating layer. 
     With reference to  FIG. 16 , a first mask layer  605  may be formed on the top sacrificial layer  603 - 3 . In some embodiments, the first mask layer  605  may be a single layer including a photoresist layer. In some embodiments, the first mask layer  605  may be a stacked layer including, form bottom to top, a photoresist layer and a top anti-reflective coating layer. A photolithography process may be performed to pattern the first mask layer  605  and define the position of the sacrificial structure  603 . 
     With reference to  FIG. 17 , an etch process, such as an anisotropic dry etch process, may be performed to remove portions of the top sacrificial layer  603 - 3  and portions of the bottom sacrificial layer  603 - 1  and concurrently form the sacrificial structure  603  on the first impurity region  107 - 1 . The first mask layer  605  may be removed after the etch process. 
     With reference to  FIG. 14  and  FIGS. 18 to 20 , at step S 25 , supporting liners  303  and energy-removable layer  401  may be formed on the substrate  101 , and a first opening  607  may be formed in the energy-removable layer  401 . 
     With reference to  FIG. 18 , the supporting liner  303  may be formed on the top surface of the substrate  101 , on the sidewalls of the sacrificial structure  603 , and on the top surface of the sacrificial structure  603 . Subsequently, an energy-removable layer  401  may be formed to cover the supporting liner  303 . The energy-removable layer  401  may include a material such as a thermal decomposable material, a photonic decomposable material, an e-beam decomposable material, or a combination thereof. For example, the energy-removable layer  401  may include a base material and a decomposable porogen material that is sacrificially removed upon exposure to an energy source. The base material may include a methylsilsesquioxane based material. The decomposable porogen material may include a porogen organic compound that provides porosity to the base material of the energy-removable material. 
     With reference to  FIG. 19 , a planarization process, such as chemical mechanical polishing, may be performed until the top surface of the sacrificial structure  603  is exposed to provide a substantially flat surface for subsequent processing steps. After the planarization process, the supporting liner  303  formed on the top surface of the top sacrificial layer  603 - 3  may be removed, and the supporting liner  303  may be divided into multiple portions. 
     With reference to  FIG. 20 , an etch process may be performed to remove the sacrificial structure  603  and concurrently form the first opening  607  at the place where the sacrificial structure  603  previously occupied. The top surface of the impurity region  107 - 1  may be exposed through the first opening  607 . 
     With reference to  FIG. 14  and  FIGS. 21 to 24 , at step S 27 , covering liners  305 , a first barrier layer  307 , and a first conductive feature  301  may be formed in the first opening  607 . 
     With reference to  FIG. 21 , the covering liners  305  may be conformally formed on the top surface of the energy-removable layer  401 , on the top surfaces of the supporting liners  303 , and on the sidewalls of the first opening  607 . The supporting liners  303  and the covering liners  305  may provide structural support for the energy-removable layer  401 . The covering liners  305  may also employed as a protection layer for the energy-removable layer  401  during subsequent semiconductor processes. 
     In some embodiments, the covering liners  305  may be formed by a deposition process such as an atomic layer deposition method precisely controlling an amount of a first precursor of the atomic layer deposition method. The covering liners  305  may be formed of, for example, aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium nitride, tungsten nitride, silicon nitride, or silicon oxide. When the covering liners  305  are formed of aluminum oxide, the first precursor may be trimethylaluminum and a second precursor may be water or ozone. When the covering liners  305  are formed of hafnium oxide, the first precursor may be hafnium tetrachloride, hafnium tert-butoxide, hafnium dimethylamide, hafnium ethylmethylamide, hafnium diethylamide, or hafnium methoxy-t-butoxide and the second precursor may be water or ozone. When the covering liners  305  are formed of zirconium oxide, the first precursor may be zirconium tetrachloride and the second precursor may be water or ozone. When the covering liners  305  are formed of titanium oxide, the first precursor may be titanium tetrachloride, tetraethyl titanate, or titanium isopropoxide and the second precursor may be water or ozone. When the covering liners  305  are formed of titanium nitride, the first precursor may be titanium tetrachloride and ammonia. When the covering liners  305  are formed of tungsten nitride, the first precursor may be tungsten hexafluoride and ammonia. When the covering liners  305  are formed of silicon nitride, the first precursor may be silylene, chlorine, ammonia, and/or dinitrogen tetrahydride. When the covering liners  305  are formed of silicon oxide, the first precursor may be silicon tetraisocyanate or CH 3 OSi(NCO) 3  and the second precursor may be hydrogen or ozone. 
     With reference to  FIG. 22 , the first barrier layer  307  may be conformally formed on the covering liners  305  and in the first opening  607 . A stabilization process, which includes a tilted aluminum implantation process and an oxidation process, may be optionally performed on the first barrier layer  307 . The tilted aluminum implantation process may insert aluminum into the first barrier layer  307 . The oxidation process may oxidize the aluminum inserted into the first barrier layer  307  and may stabilize the first barrier layer  307 . 
     With reference to  FIGS. 23 and 24 , a layer of first conductive material  609  may be deposited into the first opening  607  by a deposition process. The layer of first conductive material  609  may include doped polysilicon, a metal, or a metal silicide. After the deposition process, a planarization process, such as chemical mechanical polishing, may be performed until the top surfaces of the covering liners  305  are exposed to remove excess material, provide a substantially flat surface for subsequent processing steps, and concurrently form the first conductive feature  301  in the first opening  607 . It should be noted that, the first conductive feature  301  may completely fill the first opening  607 . 
     With reference to  FIG. 14  and  FIGS. 25 to 29 , at step S 29 , a second conductive feature  309  may be formed on the first conductive feature  301 , and third conductive features  313  may be formed on the substrate  101 . 
     With reference to  FIG. 25 , an insulating layer  405  may be formed on the covering liners  305  and the first conductive feature  301 . The second conductive feature  309  may be formed on the first conductive feature  301  by a damascene process. 
     With reference to  FIG. 26 , an insulating layer  407  may be formed on the insulating layer  405 . A photolithography process and a subsequent etch process may be performed to form second openings  611  so as to penetrate the supporting liners  303 , the energy-removable layer  401 , the covering liners  305 , and the insulating layers  405 ,  407 . The two second impurity regions  107 - 3  may be exposed through the second openings  611 . 
     With reference to  FIG. 27 , a second barrier layer  311  may be conformally formed in the second openings  611 . A stabilization process similar with that illustrated in  FIG. 22  may be optionally performed on the second barrier layer  311 . 
     With reference to  FIG. 28 , a layer of second conductive material  613  may be deposited over the intermediate semiconductor device illustrated in  FIG. 27  and completely fill the second openings  611 . The layer of contact material  717  may be deposited by atomic layer deposition, chemical vapor deposition, or other conformal deposition method. 
     With reference to  FIG. 29 , a planarization process, such as chemical mechanical polishing, may be performed until the top surface of the insulating layer  407  is exposed to remove excess material, provide a substantially flat surface for subsequent processing steps, and concurrently form the third conductive features  313  in the second openings  611 . 
     With reference to  FIGS. 14 and 30 , at step S 31 , an energy treatment may be performed to turn the energy-removable layer  401  into a porous insulating layer  403 . 
     With reference to  FIG. 30 , the energy treatment may be performed to the intermediate semiconductor device in  FIG. 29  by applying an energy source thereto. The energy source may include heat, light, or a combination thereof. When heat is used as the energy source, a temperature of the energy treatment may be between about 800° C. and about 900° C. When light is used as the energy source, an ultraviolet light may be applied. The energy treatment may remove the decomposable porogen material from the energy-removable layer  401  to generate empty spaces (pores), with the base material remaining in place. After the energy treatment, the energy-removable layer  401  may be turned into the porous insulating layer  403 . The base material may be turned into a skeleton of the porous insulating layer  403  and the empty spaces may be distributed among the skeleton of the porous insulating layer  403 . 
     With reference to  FIGS. 14 and 31 , at step S 33 , capacitor structures  501  may be formed on the third conductive features  313 . 
     With reference to  FIG. 31 , an insulating layer  409  may be formed on the insulating layer  407  by a deposition process. A photolithography process may be performed to define positions of the capacitor structures  501 . After the photolithography process, an etch process, such as an anisotropic dry etch process, may be performed to form capacitor openings  615  in the insulating layer  409 . The third conductive features  313  may be exposed through the capacitor openings  615 . Capacitor bottom electrodes  503  may be respectively correspondingly formed in the capacitor openings  615 . A capacitor dielectric layer  505  may be formed on the capacitor bottom electrodes  503  in the capacitor openings  615  and formed on the top surface of the insulating layer  409 . A capacitor top electrode  507  may be formed on the capacitor dielectric layer  505  and may fill the capacitor openings  615 . The capacitor bottom electrodes  503 , the capacitor dielectric layer  505 , and the capacitor top electrode  507  together form the capacitor structures  501 . 
       FIGS. 32 to 35  illustrate, in schematic cross-sectional diagrams, part of a flow of fabricating a semiconductor device  1 D in accordance with another embodiment of the present disclosure. 
     With reference to  FIG. 32 , an intermediate semiconductor device as illustrated in  FIG. 27  may be fabricated. The second barrier layer  311  may include bottom segments  311 B, side segments  311 S, and top segments  311 T. The bottom segments  311 B and the side segments  311 S of the second barrier layer  311  may be respectively correspondingly formed on the sidewalls and the bottom surfaces of the second openings  611 . The top segments  311 T of the second barrier layer  311  may be formed on the top surfaces of the insulating layer  407 . 
     With reference to  FIG. 32 , adjustment layers  315  may be conformally formed on the top segments  311 T of the second barrier layer  311  and the upper portions of the side segments  311 S of the second barrier layer  311 . 
     In some embodiments, the adjustment layers  315  may be formed of, for example, aluminum oxide, hafnium oxide, zirconium oxide, titanium oxide, titanium nitride, tungsten nitride, silicon nitride, or silicon oxide. The adjustment layers  315  may be formed by a procedure similar with the formation of the covering liner  305  illustrated in  FIG. 21 . 
     In some embodiments, adjustment layers  315  may be formed of metal nitride or metal carbide. For example, the adjustment layers  315  may be formed of aluminum carbide, aluminum nitride, tungsten carbide, or tungsten nitride. In some embodiments, the adjustment layers  315  may be formed by conformally deposited a metal in the second openings  611 . Due to the geometry of the second openings  611  may prevent the metal from reaching the bottom surfaces of the second openings  611 . Thus, the metal may deposit faster on the side segments  311 S of the second barrier layer  311  than on the bottom segment  311 B of the second barrier layer  311 . Subsequently, a plasma treatment using a nitrogen-containing or carbon-containing gas may be applied to transform the metal into a metal nitride or a metal carbide. In some embodiments, the adjustment layers  315  may be conformally formed on the side segments  311 S and the bottom segments  311 B of the second barrier layer  311 . An anisotropic etching process may be applied to remove the adjustment layers  315  formed on the bottom segments  311 B of the second barrier layer  311 . 
     With reference to  FIG. 33 , a layer of second conductive material  613  may be deposited over the intermediate semiconductor device illustrated in  FIG. 32  and completely fill the second openings  611 . The layer of second conductive material  613  may be deposited by atomic layer deposition, chemical vapor deposition, or other conformal deposition method. Due to the presence of the adjustment layers  315 , the deposition rate of the second conductive material  613  on the sidewalls of the second openings  611  may be reduced. Hence, the deposition rate of the second conductive material  613  on the sidewalls of the second openings  611  and the deposition rate of the second conductive material  613  on the bottom surfaces of the second openings  611  may become close to each other. As a result, the second openings  611  may be filled without any void formation near the bottom surfaces of the second openings  611 . The yield of the semiconductor device  1 D may be improved. 
     With reference to  FIG. 34 , a planarization process, such as chemical mechanical polishing, may be performed to remove excess material, the top segments  315 T of the adjustment layers  315 , and the top segments  311 T of the second barrier layer  311 . The layer of second conductive material  613  may be turned into the third conductive features  313  after the planarization process. 
     With reference to  FIG. 35 , the porous insulating layer  403 , the capacitor structures  501 , and the third insulating layer  409  may be formed a procedure similar to that illustrated in  FIGS. 30 and 31 . In some embodiments, the energy treatment may be performed after the formation of the capacitor structures  501 . 
     One aspect of the present disclosure provides a semiconductor device including a substrate, a porous insulating layer positioned above the substrate, a first conductive feature positioned in the porous insulating layer, and covering liners including two top segments and two side segments. The two side segments are positioned on sidewalls of the first conductive feature, and the two top segments are positioned on top surfaces of the porous insulating layer. 
     Another aspect of the present disclosure provides a method for fabricating a semiconductor device including providing a substrate, forming a sacrificial structure above the substrate, forming a supporting liner covering the sacrificial structure, forming an energy-removable layer covering the supporting liner, performing a planarization process until a top surface of the sacrificial structure is exposed, performing an etch process to remove the sacrificial structure and concurrently form a first opening in the energy-removable layer, forming covering liners on sidewalls of the first opening and on a top surface of the energy-removable layer, forming a first conductive feature in the first opening, and applying an energy source to turn the energy-removable layer into a porous insulating layer. 
     Due to the design of the semiconductor device of the present disclosure, the porous insulating layer  403  may reduce the parasitic capacitance between conductive features (e.g., the first conductive feature  301  and the third conductive features  313 ) of the semiconductor device  1 A. In addition, with the assistant of the covering liners  305 , the first conductive feature  301  may be formed without any void. Therefore, the yield of the semiconductor device  1 A may be improved. 
     Although the present disclosure 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 disclosure as defined by the appended claims. For example, many of the processes discussed above can 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 disclosure, 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 disclosure. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, and steps.