Patent Publication Number: US-2023142204-A1

Title: Film and forming method thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of International Application No. PCT/CN2021/128070, filed on Nov. 2, 2021, which claims the priority to Chinese Patent Application No. 202110304036.9, titled “FILM AND FORMING METHOD THEREOF” and filed on Mar. 22, 2021. The entire contents of International Application No. PCT/CN2021/128070 and Chinese Patent Application No. 202110304036.9 are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present disclosure relates to, but is not limited to, a film and a forming method thereof. 
     BACKGROUND 
     A diamond-like carbon (DLC) film, as a metastable material generated by combining Sp3 hybrid bonds and Sp2 hybrid bonds, has the excellent characteristics of both diamond and graphite, and has relatively high hardness, high resistivity, a good optical property, and an excellent tribological property, and therefore is widely used in the semiconductor industry. Due to the relatively high hardness of the DLC film, in a semiconductor patterning process, the use of the DLC film can effectively reduce a thickness of a photoresist and avoid collapse caused by an excessively high photoresist. 
     However, the DLC film has a relatively high internal stress, which has serious impact on a transfer effect of a pattern and tends to cause warpage of a wafer. 
     SUMMARY 
     An overview of the subject matter detailed in the present disclosure is provided below, which is not intended to limit the protection scope of the claims. 
     Embodiments of the present disclosure provide a film and a forming method thereof. 
     According to a first aspect of the embodiments of the present disclosure, a method of forming a film is provided, including: providing a base; forming a DLC film on the base, where the DLC film has a carbon-hydrogen chemical bond; and performing photocatalytic treatment on the DLC film, to break at least some of the carbon-hydrogen chemical bonds and reduce content of hydrogen elements in the DLC film. 
     According to a second aspect of the embodiments of the present disclosure, a film is provided, including: a DLC film obtained after photocatalytic treatment, where content of carbon-hydrogen chemical bonds included in the DLC film accounts for less than 5% of all chemical bonds, the DLC film is doped with metal elements, and part of the DLC film is a first DLC film including group V elements. 
     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 is 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   ,  FIG.  3   ,  FIG.  5    and  FIG.  7    are schematic diagrams of structures corresponding to various steps of a method of forming a film according to an embodiment of the present disclosure; and 
         FIG.  2   ,  FIG.  4   ,  FIG.  6    and  FIG.  8    are schematic diagrams of partial microstructures corresponding to various steps of a method of forming a film according to an embodiment of the present disclosure. 
     
    
    
     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. 
     Because the DLC film has a large quantity of hydrogen elements, atomic arrangement in the DLC film is irregular, and the irregular atomic arrangement leads to low hardness of the DLC film. In addition, because the DLC film has a large quantity of Sp 3  hybrid bonds, a density of carbon atoms in a partial region of the DLC film is relatively high, and an average coordination number of most atoms in the DLC film is relatively high, causing a relatively high internal stress of the DLC film. When the DLC film is used in a semiconductor patterning process, the DLC film with a relatively high internal stress has an adverse effect on a transfer effect of a pattern, and tends to cause warpage of a wafer. 
     An embodiment of the present disclosure provides a film and a forming method thereof, to perform photocatalytic treatment on the DLC film to remove some of hydrogen elements in the DLC film, and then perform ion implantation treatment on the DLC film to reduce content of Sp 3  hybrid bonds in the DLC film, such that a density of carbon atoms in a partial region of the DLC film is reduced, thereby improving hardness of the DLC film and reducing an internal stress of the DLC film. 
     Referring to  FIG.  1   , a base  100  is provided, and a DLC film  110  is formed on the base  100 . 
     The base  100  may be made of a material including monocrystalline silicon, silicon-on-insulator (SOI), stacked silicon-on-insulator (SSOI), stacked silicon-germanium-on-insulator (S-SiGeOl), silicon-germanium-on-insulator (SiGePOl), and germanium-on-insulator (GeOl). In this embodiment, the base  100  is monocrystalline silicon. 
     As shown in  FIG.  1    and  FIG.  2   , in this embodiment, the DLC film  110  is formed by using a metal precursor and a carbon precursor as a reactant, such that the formed DLC film  110  is doped with metal elements, and the metal elements  103  include carbon-friendly metal elements such as a titanium element, a tungsten element, or a chromium element. The doped carbon-friendly metal elements form, with carbon elements, a carbide hard phase with a stable thermodynamic property, to enhance a mechanical property and wear resistance of the DLC film  110 . In addition, the doped metal elements have carbon-friendly characteristics. This is beneficial to improving structural stability of the formed DLC film  110 . 
     In another embodiment, the DLC film may be formed by using a carbon precursor and a doped gas as a reactant. 
     The metal elements exist in a form of a nanocrystal in the DLC film  110 , or in a form of a nanocrystal that forms a face-centered cubic structure with carbon elements. The formed DLC film  110  has a stable thermodynamic property and a relatively strong mechanical property and wear resistance. 
     The metal elements  103  account for 5% to 25%, for example, 10%, 15%, or 20%, of the mass of the DLC film  110 . Content of the metal elements  103  is kept within this range, to retain excellent properties of graphite to the maximum extent while improving physical properties, such as hardness and wear resistance, of the DLC film  110 . 
     In this embodiment, the DLC film  110  is formed by using a plasma chemical vapor deposition process  101 , which is beneficial to quickly forming the DLC film  110  in which different elements are uniformly distributed. 
     In another embodiment, a carbon-containing gas mixture may be provided above the base, and then a carbon-containing electrode disposed in a treatment chamber may be bombarded, to generate a secondary electron beam in the carbon-containing gas mixture, which in turn forms a DLC film on a surface of the base from elements of the gas mixture. 
       FIG.  2    is a schematic diagram of a microstructure of a region A in  FIG.  1   . Different elements in the DLC film  110  are uniformly arranged, and the elements in the DLC film  110  are described in detail by intercepting the region A as an example. 
     Referring to  FIG.  2   , in this embodiment, the DLC film  110  has carbon elements  102 , metal elements  103 , and hydrogen elements  104 , where the hydrogen element  104  and the carbon element  102  form a carbon-hydrogen chemical bond, different carbon elements  102  form a carbon-carbon chemical bond, and the metal element  103  and the carbon element  102  form a carbon-metal element chemical bond. 
     Referring to  FIG.  3   , photocatalytic treatment  105  is performed on the DLC film  110 , to break at least some of carbon-hydrogen chemical bonds and reduce content of the hydrogen elements  104  (refer to  FIG.  2   ) in the DLC film  110 . 
     In an example, after the photocatalytic treatment  105  is performed, content of the carbon-hydrogen chemical bonds included in the DLC film  110  accounts for less than 5% of all chemical bonds. a proportion of the carbon-hydrogen chemical bonds is smaller, and proportions of carbon-carbon chemical bonds and carbon-metal element chemical bonds are greater. This is beneficial to improving hardness of the DLC film  110 . 
     The photocatalytic treatment  105  breaks at least some of the carbon-hydrogen chemical bonds in the DLC film  110 , and the hydrogen elements  104  escape as a gas is from the DLC film  110 , to reduce content of the hydrogen elements  104  in the DLC film  110 . Since the hydrogen elements  104  in the DLC film  110  are reduced, a proportion of carbon elements  102  in the DLC film  110  increases, and the carbon elements  102  with a higher proportion enables atomic arrangement in the DLC film  110  to be more regular, thereby improving the hardness of the DLC film  110  and improving performance of the DLC film  110 . 
     In an example, process parameters of the photocatalytic treatment  105  include: a used light wavelength range of 200 nanometers to 400 nanometers, for example, 250 nanometers, 300 nanometers, or 350 nanometers, a process time length of 3 minutes to 8 minutes, for example, 4 minutes, 5 minutes, or 6 minutes, and a process temperature of 15 degrees Celsius to 60 degrees Celsius, for example, 30 degrees Celsius, 40 degrees Celsius, or 50 degrees Celsius. The photocatalytic treatment  105  is performed by using the process parameters, to provide sufficient energy to break the carbon-hydrogen chemical bonds, and ensure that the energy is not so large as to affect a structure of the DLC film  110 . 
       FIG.  4    is a schematic diagram of a microstructure of a region B in  FIG.  3   . Referring to  FIG.  4   , the broken carbon bond forms a carbon-metal element chemical bond with the metal element  103  after the carbon-hydrogen chemical bond is broken. A quantity of carbon-metal element chemical bonds in the DLC film  110  is increased. This is beneficial to improving physical properties, such as hardness and wear resistance, of the DLC film  110 . 
     Referring to  FIG.  5    and  FIG.  6   , after the photocatalytic treatment  105  is performed, the method may further include: performing ion implantation treatment  106  on the DLC film  110 , where the ion implantation treatment  106  reduces content of Sp 3  hybrid bonds in the DLC film  110 , such that a density of carbon atoms in a partial region of the DLC film  110  is reduced. 
     The ion implantation treatment  106  is performed on the DLC film  110 , to reduce the content of the Sp 3  hybrid bonds in the DLC film  110 , such that the density of the carbon atoms in the partial region of the DLC film  110  is reduced. That the density of the carbon atoms in the partial region of the DLC film  110  is reduced indicates that an average coordination number of atoms in part of the DLC film  110  is reduced, where the coordination number refers to a quantity of coordination atoms around an atom at a center of a chemical compound, such that an internal stress of the DLC film  110  is reduced. In addition, that the content of the Sp3 hybrid bonds in the DLC film  110  is reduced can improve toughness of the DLC film  110 , and effectively enhance mechanical tribological adaptability of the DLC film  110  in vacuum and an atmospheric environment. 
     The ion implantation treatment  106  is to implant group V elements  107  into the DLC film  110 . In this embodiment, the implanted group V element  107  is a nitrogen element. Raw materials of the nitrogen element come from a wide range of sources, including ammonia, nitrogen oxide, nitrogen, and the like. A price of the nitrogen element is inexpensive, and an exhaust gas generated after the implantation is harmless and easy to be processed. In another embodiment, group V elements such as a phosphorus element or an arsenic element may be implanted. 
     In this embodiment, energy provided by the ion implantation treatment  106  breaks a carbon-carbon chemical bond and a carbon-metal element chemical bond, to enable at least some of the carbon elements  102  to separate from the chemical bonds, and generate carbon free radicals, where the carbon free radicals and the group V elements  107  form Sp2 hybrid bonds. 
     The DLC film  110  is doped with nitrogen elements, and the nitrogen elements may reduce an internal stress of the DLC film  110  through crystalline grain dislocation slip strain, to improve toughness of the DLC film  110 , and effectively enhance mechanical tribological adaptability of the DLC film  110  in vacuum and an atmospheric environment; the nitrogen elements suppress formation of the Sp3 hybrid bonds, leading to reduction of a density of carbon atoms in a partial region, and finally causing the Sp3 hybrid bonds to transform into Sp2 hybrid bonds; content of the Sp2 hybrid bonds in the DLC film  110  is increased, and content of the Sp 3  hybrid bonds is reduced; compared with the Sp3 hybrid bond, the Sp2 hybrid bond has atoms with a smaller average coordination number, and an average coordination number of atoms in the entire DLC film  110  becomes smaller, such that the internal stress of the DLC film  110  is reduced. 
     Process parameters of the ion implantation treatment  106  include: implantation energy of 1 electron volt to 2 electron volts, for example, 1.2 electron volts, 1.4 electron volts, or 1.8 electron volts, an ion source implantation dose of 1011 ions per square centimeter to 1013 ions per square centimeter, and a process time length of 5 seconds to 200 seconds, for example, 20 seconds, 100 seconds, or 120 seconds. 
     In this embodiment, relatively low implantation energy and a relatively high implantation dose are used, to reduce damage to a surface of the DLC film  110  in the process of performing the ion implantation treatment  106 , thereby increasing a product yield. 
     After the ion implantation treatment  106  is performed, part of the DLC film  110  is a first DLC film  112  including the group V elements  107 , and the remaining part of the DLC film  110  serves as a second DLC film  111 . 
     In a direction perpendicular to the surface of the DLC film  110 , a thickness of the DLC film  110  is 150 nanometers to 170 nanometers, for example, 155 nanometers, 160 nanometers, or 165 nanometers. In the direction perpendicular to the surface of the DLC film  110 , a thickness of the first DLC film  112  is 20 nanometers to 50 nanometers, for example, 25 nanometers, 20 nanometers, or 40 nanometers. In the direction perpendicular to the surface of the DLC film  110 , a thickness of the second DLC film  111  is 100 nanometers to 150 nanometers, for example, 110 nanometers, 120 nanometers, or 130 nanometers. 
       FIG.  6    is a schematic structural diagram of a microstructure of a region C in  FIG.  5   . Referring to  FIG.  6   , after the ion implantation treatment  106  is performed, a lattice of the DLC film  110  is damaged, not only are some of the carbon elements  102  separated from chemical bonds to form carbon free radicals, but also some of the metal elements  103  and the group V elements  107  are separated from chemical bonds. 
     In another embodiment, the ion implantation treatment may alternatively not be performed on the DLC film. 
     Referring to  FIG.  7   , after the ion implantation treatment  106  is performed (referring to  FIG.  5   ), the method may further include: performing annealing treatment  108  on the DLC film  110 , to repair of the lattice damage to the DLC film  110  in the process of the ion implantation treatment  106 , where the metal elements and the group V elements also is diffuse in the process of the annealing treatment  108  and become part of the lattice of the DLC film  110 . 
     In this embodiment, process parameters of the annealing treatment  108  include: a process temperature of 300 degrees Celsius to 500 degrees Celsius, for example, 350 degrees Celsius, 400 degrees Celsius, or 450 degrees Celsius, and a process time length of 20 minutes to 30 minutes, for example, 23 minutes, 25 minutes, or 28 minutes. 
       FIG.  8    is a schematic diagram of a microstructure of a region D of  FIG.  7   . Referring to  FIG.  8   , in the annealing treatment  108  (referring to  FIG.  7   ), the metal elements  103  and the group V elements  107  diffuse in the DLC film  110 , and are integrated into the repaired lattice of the DLC film  110 , to form a DLC film  110  with a relatively small average coordination number. 
     According to the method of forming a film provided in this embodiment of the present disclosure, the photocatalytic treatment  105  is performed on the DLC film  110 , to remove some of the hydrogen elements in the DLC film  110  and improve hardness of the DLC film  110 ; and then the ion implantation treatment  106  is performed on the DLC film  110 , to reduce the content of the Sp3 hybrid bonds in the DLC film  110 , such that a density of carbon atoms in a partial region of the DLC film  110  is reduced, and an internal stress of the DLC film  110  is reduced. When the DLC film  110  is used in a semiconductor patterning process, the DLC film  110  with a relatively low internal stress has a good pattern transfer effect and can effectively avoid warpage of a wafer. 
     A second embodiment of the present disclosure provides a film, where the film may be formed according to the method of forming a film in the first embodiment. The film provided in the second embodiment of the present disclosure is described in detail below with reference to the accompanying drawings. 
     Referring to  FIG.  7   , the film provided in this embodiment includes: the DLC film  110  obtained after the photocatalytic treatment is performed. 
     In this embodiment, the DLC film  110  has carbon elements, metal elements, and hydrogen elements, where the hydrogen element and the carbon element form a carbon-hydrogen chemical bond, different carbon elements form a carbon-carbon chemical bond, and the metal element and the carbon element form a carbon-metal element chemical is bond. 
     Content of the hydrogen elements in the DLC film  110  is fewer, and content of carbon-hydrogen chemical bonds included in the DLC film  110  accounts for less than 5% of all chemical bonds; the hydrogen elements  104  in the DLC film  110  are fewer, and a proportion of carbon elements in the DLC film  110  is higher, where the carbon elements with a higher proportion cause atomic arrangement in the DLC film  110  to be more regular, such that hardness of the DLC film  110  is improved, thereby improving performance of the DLC film  110 . 
     In this embodiment, the metal elements include carbon-friendly metal elements such as a titanium element, a tungsten element, or a chromium element. The doped carbon-friendly metal elements form, with the carbon elements, a carbide hard phase with a stable thermodynamic property, to enhance a mechanical property and wear resistance of the DLC film  110 . In addition, the doped metal elements have carbon-friendly characteristics. This is beneficial to improving structural stability of the formed DLC film  110 . 
     The metal elements exist in a form of a nanocrystal in the DLC film  110 , or in a form of a nanocrystal that forms a face-centered cubic structure with carbon elements. The formed DLC film  110  has a stable thermodynamic property and a relatively strong mechanical property and wear resistance. 
     The metal elements account for 5% to 25%, for example, 10%, 15%, or 20%, of the mass of the DLC film  110 . Content of the metal elements is kept within this range, to retain excellent properties of graphite to the maximum extent while improving physical properties, such as hardness and wear resistance, of the DLC film  110 . 
     In this embodiment, part of the DLC film  110  is a first DLC film  112  including group V elements, and the remaining part of the DLC film  110  serves as a second DLC film  111 . In this embodiment, the group V element is a nitrogen element. Raw materials of the nitrogen element come from a wide range of sources, including ammonia, nitrogen oxide, nitrogen, and the like. A price of the nitrogen element is inexpensive, and an exhaust gas generated after the implantation is harmless and easy to be processed. In another embodiment, group V elements such as a phosphorus element or an arsenic element may be implanted. 
     The DLC film  110  is doped with nitrogen elements, and the nitrogen elements may reduce an internal stress of the DLC film  110  through crystalline grain dislocation slip strain, to improve toughness of the DLC film  110 , and effectively enhance mechanical tribological adaptability of the DLC film  110  in vacuum and an atmospheric environment; the nitrogen elements suppress formation of the Sp3 hybrid bonds, leading to reduction of a density of carbon atoms in a partial region, and finally causing the Sp3 hybrid bonds to transform into Sp2 hybrid bonds; content of the Sp2 hybrid bonds in the DLC film  110  is increased, and content of the Sp3 hybrid bonds is reduced; compared with the Sp3 hybrid bond, the Sp 2  hybrid bond has atoms with a smaller average coordination number, and an average coordination number of atoms in the entire DLC film  110  becomes smaller, such that the internal stress of the DLC film  110  is reduced. 
     In a direction perpendicular to the surface of the DLC film  110 , a thickness of the DLC film  110  is 150 nanometers to 170 nanometers, for example, 155 nanometers, 160 nanometers, or 165 nanometers. In the direction perpendicular to the surface of the DLC film  110 , a thickness of the first DLC film  112  is 20 nanometers to 50 nanometers, for example, 25 nanometers, 20 nanometers, or 40 nanometers. In the direction perpendicular to the surface of the DLC film  110 , a thickness of the second DLC film  111  is 100 nanometers to 150 nanometers, for example, 110 nanometers, 120 nanometers, or 130 nanometers. 
     Embodiments of the present disclosure provide a film, the content of the carbon-hydrogen chemical bonds included in the DLC film  110  accounts for less than 5% of all chemical bonds, the hydrogen elements  104  in the DLC film  110  are fewer, a proportion of carbon elements in the DLC film  110  is higher, and the carbon elements with a higher proportion cause atomic arrangement in the DLC film  110  to be more regular, such that hardness of the DLC film  110  is relatively high; part of the DLC film  110  is a first DLC film  112  including the group V elements, and because the DLC film  110  has the group V elements, the DLC film  110  has more Sp2 hybrid bonds, and the density of carbon atoms in a partial region of the DLC film  110  is relatively low; the relatively low density of carbon atoms in the partial region of the DLC film  110  indicates that an average coordination number of atoms in the DLC film  110  is relatively small, to form the DLC film  110  with a relatively low internal stress; in addition, the DLC film  110  with a relatively low internal stress has relatively high toughness, and has relatively good mechanical tribological adaptability in vacuum and an atmospheric environment. 
     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 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 
     Embodiments of the present disclosure provide a film and a forming method thereof, to help improve hardness of a DLC film and reduce an internal stress of the DLC film.