Patent Publication Number: US-11043372-B2

Title: High-density low temperature carbon films for hardmask and other patterning applications

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. Provisional Patent Application Ser. No. 62/516,828, filed Jun. 8, 2017, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Field 
     Implementations of the present disclosure generally relate to the fabrication of integrated circuits. More particularly, the implementations described herein provide techniques for deposition of high-density films for patterning applications. 
     Description of the Related Art 
     Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors and resistors on a single chip. The evolution of chip designs continually requires faster circuitry and greater circuit density. The demands for faster circuits with greater circuit densities impose corresponding demands on the materials used to fabricate such integrated circuits. In particular, as the dimensions of integrated circuit components reduce to the sub-micron scale, it is now necessary to use low resistivity conductive materials as well as low dielectric constant insulating materials to obtain suitable electrical performance from such components. 
     The demands for greater integrated circuit densities also impose demands on the process sequences used in the manufacture of integrated circuit components. For example, in process sequences that use conventional photolithographic techniques, a layer of energy sensitive resist is formed over a stack of material layers disposed on a substrate. The energy sensitive resist layer is exposed to an image of a pattern to form a photoresist mask. Thereafter, the mask pattern is transferred to one or more of the material layers of the stack using an etch process. The chemical etchant used in the etch process is selected to have a greater etch selectivity for the material layers of the stack than for the mask of energy sensitive resist. That is, the chemical etchant etches the one or more layers of the material stack at a rate much faster than the energy sensitive resist. The etch selectivity to the one or more material layers of the stack over the resist prevents the energy sensitive resist from being consumed prior to completion of the pattern transfer. 
     As the pattern dimensions are reduced, the thickness of the energy sensitive resist is correspondingly reduced in order to control pattern resolution. Such thin resist layers can be insufficient to mask underlying material layers during the pattern transfer step due to attack by the chemical etchant. An intermediate layer (e.g., silicon oxynitride, silicon carbine or carbon film), called a hardmask, is often used between the energy sensitive resist layer and the underlying material layers to facilitate pattern transfer because of greater resistance to the chemical etchant. Hardmask materials having both high etch selectivity and high deposition rates are desirable. As critical dimensions (CD) decrease, current hardmask materials lack the desired etch selectivity relative to underlying materials (e.g., oxides and nitrides) and are often difficult to deposit. 
     Therefore, there is a need in the art for an improved hardmask layers and methods for depositing improved hardmask layers. 
     SUMMARY 
     Implementations of the present disclosure generally relate to the fabrication of integrated circuits. More particularly, the implementations described herein provide techniques for deposition of high-density films for patterning applications. In one implementation, a method of processing a substrate is provided. The method includes flowing a hydrocarbon-containing gas mixture into a processing volume of a process chamber having a substrate positioned on an electrostatic chuck. The substrate is maintained at a pressure between about 0.5 mTorr and about 10 Torr. The method further includes generating a plasma at the substrate level by applying a first RF bias to the electrostatic chuck to deposit a diamond-like carbon film on the substrate. The diamond-like carbon film has a density greater than 1.8 g/cc and a stress less than −500 MPa. 
     In another implementation, a method of processing a substrate is provided. The method includes flowing a hydrocarbon-containing gas mixture into a processing volume of a process chamber having a substrate positioned on an electrostatic chuck. The substrate is maintained at a pressure between about 0.5 mTorr and about 10 Torr and the hydrocarbon-containing gas mixture comprises acetylene (C 2 H 2 ). The method further includes generating a plasma at the substrate level by applying a first RF bias and a second RF bias to the electrostatic chuck to deposit a diamond-like carbon film on the substrate. The diamond-like carbon film has a density greater from about 1.8 g/cc to about 2.5 g/cc and a stress from approximately −600 MPa to approximately −300 MPa. 
     In yet another implementation, a method of processing a substrate is provided. The method includes flowing a hydrocarbon-containing gas mixture into a processing volume of a process chamber having a substrate positioned on an electrostatic chuck. The processing volume is maintained at a pressure between about 0.5 mTorr and about 10 Torr. The method further includes generating a plasma at the substrate level by applying a first RF bias and a second RF bias to the electrostatic chuck to deposit a diamond-like carbon film on the substrate. The diamond-like carbon film has a density greater from about 1.8 g/cc to about 2.5 g/cc and a stress from approximately −1000 MPa to approximately −100 MPa, for example from approximately −600 MPa to approximately −300 MPa. The method further includes forming a patterned photoresist layer over the diamond-like carbon film. The method further includes etching the diamond-like carbon in a pattern corresponding with the patterned photoresist layer. The method further includes etching the pattern into the substrate. The method further includes depositing a material into the etched portions of the diamond-like carbon film. 
     In yet another implementation, a film for use as an underlayer for a EUV lithography process is provided. The film has an sp 3  hybridized carbon atom content of between 40% and 90% based on the total amount of carbon atoms in the film; a density of between 1.8 g/cc and 2.5 g/cc; and an elastic modulus that is between 150 GPa and 400 GPa. In some implementations, the film has a density of between 2.0 g/cc and 2.5 g/cc and an elastic modulus that is between 180 GPa and 200 GPa. In some implementations, the film has a stress of −600 MPa; a refractive index that is between 2.0 and 3.0; and an extinction coefficient of between 0.2 and 0.3. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description of the implementations, briefly summarized above, may be had by reference to implementations, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical implementations of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective implementations. 
         FIG. 1A  depicts a schematic cross-sectional view of a deposition system that can be used for the practice of implementations described herein; 
         FIG. 1B  depicts a schematic cross-sectional view of another deposition system that can be used for the practice of implementations described herein; 
         FIG. 2  depicts a schematic cross-sectional view of an electrostatic chuck that may be used in the apparatus of  FIG. 1A  and  FIG. 1B  for the practice of implementations described herein; 
         FIG. 3  depicts a flow diagram of a method for forming a diamond-like carbon layer on a film stack disposed on a substrate in accordance with one or more implementations of the present disclosure; 
         FIGS. 4A-4B  depict one implementation of a sequence for forming a diamond-like carbon layer on a film stack formed on a substrate in accordance with one or more implementations of the present disclosure; 
         FIG. 5  is a graph depicting density as a function of bias power for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure; 
         FIG. 6  is a graph depicting stress as a function of bias power for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure; 
         FIG. 7  is a graph depicting density and stress as a function of pressure for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure; and 
         FIG. 8  depicts a flow diagram of a method of using a diamond-like carbon layer in accordance with one or more implementations of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one implementation may be beneficially incorporated in other implementations without further recitation. 
     DETAILED DESCRIPTION 
     The following disclosure describes techniques for deposition of diamond-like carbon films on a substrate. Certain details are set forth in the following description and in  FIGS. 1-7  to provide a thorough understanding of various implementations of the disclosure. Other details describing well-known structures and systems often associated with plasma processing and diamond-like carbon film deposition are not set forth in the following disclosure to avoid unnecessarily obscuring the description of the various implementations. 
     Many of the details, dimensions, angles and other features shown in the Figures are merely illustrative of particular implementations. Accordingly, other implementations can have other details, components, dimensions, angles and features without departing from the spirit or scope of the present disclosure. In addition, further implementations of the disclosure can be practiced without several of the details described below. 
     Implementations described herein will be described below in reference to a PECVD process that can be carried out using any suitable thin film deposition system. Examples of suitable systems include the CENTURA® systems which may use a DXZ® processing chamber, PRECISION 5000® systems, PRODUCER® systems, PRODUCER® GT™ systems, PRODUCER® XP Precision™ systems, PRODUCER® SE™ systems, Sym3® processing chamber, and Mesa™ processing chamber, all of which are commercially available from Applied Materials, Inc., of Santa Clara, Calif. Other tools capable of performing PECVD processes may also be adapted to benefit from the implementations described herein. In addition, any system enabling the PECVD processes described herein can be used to advantage. The apparatus description described herein is illustrative and should not be construed or interpreted as limiting the scope of the implementations described herein. 
     Current hardmask applications for memory and other devices largely make use of thick carbon films (e.g., 300 nanometers to 1.5 microns) that are amorphous in nature but their etch selectivity is no longer sufficient to meet the increasingly stringent requirements and the high-aspect ratio etch of the upcoming nodes. To achieve greater etch selectivity, the density and the Young&#39;s modulus of the film needs to be improved. One of the main challenges in achieving greater etch selectivity and improved Young&#39;s modulus is the high compressive stress of such a film making it unsuitable for applications owing to the resultant high wafer bow. Hence there is a need for carbon (diamond-like) films with high-density and modulus (e.g., higher sp 3  content, more diamond-like) with high etch selectivity along with low stress (e.g., &lt;−500 MPa). 
     Implementations described herein, include improved methods of fabricating carbon films with high-density (e.g., &gt;1.8 g/cc), high modulus (e.g., &gt;150 GPa), and low stress (e.g., &lt;−500 MPa). The carbon films fabricated according to the implementations described herein are amorphous in nature and have a higher etch selectivity with much greater modulus (e.g., &gt;150 GPa) along with lower stress (&lt;−500 MPa) than current patterning films. The carbon films fabricated according to the implementations described herein not only have a low stress but also have a high sp 3  carbon content. In general, the deposition process described herein is also fully compatible with current integration schemes for hardmask applications. 
     In some implementations, the diamond-like carbon films described herein may be formed by chemical vapor deposition (plasma enhanced and/or thermal) processes using hydrocarbon-containing gas mixtures including precursors such as but not limited to C 2 H 2 , C 3 H 6 , CH 4 , C 4 H 8 , 1,3-dimethyladamantane, bicyclo[2.2.1]hepta-2,5-diene (2,5-Norbornadiene), adamantine (C 10 H 16 ), norbornene (C 7 H 10 ), or combinations thereof. The deposition process may be carried out at temperatures ranging from −50 degrees Celsius to 600 degrees Celsius. The deposition process may be carried out at pressures ranging from 0.1 mTorr to 10 Torr in a processing volume. The hydrocarbon-containing gas mixture may further include any one of, or a combination of any of He, Ar, Xe, N 2 , H 2 . The hydrocarbon-containing gas mixture may further include etchant gases such as Cl 2 , CF 4 , and/or NF 3  to improve film quality. The plasma (e.g., capacitive-coupled plasma) may be formed from either top and bottom electrodes or side electrodes. The electrodes may be formed from a single powered electrode, dual powered electrodes, or more electrodes with multiple frequencies such as, but not limited to, 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz and 100 MHz, being used alternatively or simultaneously in a CVD system with any or all of the reactant gases listed herein to deposit a thin film of diamond-like carbon for use as a hardmask and/or etch stop or any other application requiring smooth carbon films. The high etch selectivity of the diamond-like carbon film is achieved by having higher density and modulus than current generation films. Not to be bound by theory but it is believed that the higher density and modulus are a result of the high content of sp 3  hybridized carbon atoms in the film, which in turn may be achieved by a combination of low pressure and plasma power. 
     In some implementations, hydrogen radical are fed through an RPS, which leads to selective etching of sp 2  hybridized carbon atoms thus increasing the sp 3  hybridized carbon atom fraction of the film further, thus further increasing the etch selectivity. 
     In some implementations, the diamond-like carbon film was deposited in a chamber with substrate pedestal maintained at 10 degrees Celsius and the pressure was maintained at 2 mTorr, with plasma generated at the wafer level by applying a bias of 2500 Watts (13.56 MHz) to the electrostatic chuck. In some implementations, an additional RF of 1000 Watts at 2 MHz was also delivered to the electrostatic chuck thus generating a dual-bias plasma at the wafer level. 
     In some implementations, a film for use as an underlayer for an EUV lithography process can be any film described herein. 
     In some implementations, a film for use as an underlayer for an EUV lithography process has an sp 3  hybridized carbon atom content of between 40% and 90% based on the total amount of carbon atoms in the film; a density of between 1.8 g/cc and 2.5 g/cc; and an elastic modulus that is between 150 GPa and 400 GPa. 
     In some implementations, a film for use as an underlayer for an EUV lithography process has a density of between 2.0 g/cc and 2.2 g/cc; and an elastic modulus that is between about 180 GPa and about 200 GPa. In some implementations, the film has a density of about 2.1 g/cc and an elastic modulus of about 195 GPa. 
     In some implementations, for use as an underlayer for an EUV lithography process has a stress of −600 MPa; a refractive index that is between 2.0 and 3.0; and an extinction coefficient of between 0.2 and 0.3. 
       FIG. 1A  depicts a schematic illustration of a substrate processing system  132  that can be used to perform diamond-like carbon layer deposition in accordance with implementations described herein. The substrate processing system  132  includes a process chamber  100  coupled to a gas panel  130  and a controller  110 . The process chamber  100  generally includes a top wall  124 , a sidewall  101  and a bottom wall  122  that define a processing volume  126 . A substrate support assembly  146  is provided in the processing volume  126  of the process chamber  100 . The substrate support assembly  146  generally includes an electrostatic chuck  150  supported by a stem  160 . The electrostatic chuck  150  may be typically fabricated from aluminum, ceramic, and other suitable materials. The electrostatic chuck  150  may be moved in a vertical direction inside the process chamber  100  using a displacement mechanism (not shown). 
     A vacuum pump  102  is coupled to a port formed in the bottom of the process chamber  100 . The vacuum pump  102  is used to maintain a desired gas pressure in the process chamber  100 . The vacuum pump  102  also evacuates post-processing gases and by-products of the process from the process chamber  100 . 
     The substrate processing system  132  may further include additional equipment for controlling the chamber pressure, for example, valves (e.g., throttle valves and isolation valves) positioned between the process chamber  100  and the vacuum pump  102  to control the chamber pressure. 
     A gas distribution assembly  120  having a plurality of apertures  128  is disposed on the top of the process chamber  100  above the electrostatic chuck  150 . The apertures  128  of the gas distribution assembly  120  are utilized to introduce process gases into the process chamber  100 . The apertures  128  may have different sizes, number, distributions, shape, design, and diameters to facilitate the flow of the various process gases for different process requirements. The gas distribution assembly  120  is connected to the gas panel  130  that allows various gases to supply to the processing volume  126  during processing. A plasma is formed from the process gas mixture exiting the gas distribution assembly  120  to enhance thermal decomposition of the process gases resulting in the deposition of material on a surface  191  of the substrate  190 . 
     The gas distribution assembly  120  and the electrostatic chuck  150  may form a pair of spaced apart electrodes in the processing volume  126 . One or more RF power source  140  provide a bias potential through a matching network  138 , which is optional, to the gas distribution assembly  120  to facilitate generation of plasma between the gas distribution assembly  120  and the electrostatic chuck  150 . Alternatively, the RF power source  140  and the matching network  138  may be coupled to the gas distribution assembly  120 , the electrostatic chuck  150 , or coupled to both the gas distribution assembly  120  and the electrostatic chuck  150 , or coupled to an antenna (not shown) disposed exterior to the process chamber  100 . In some implementations, the RF power source  140  may produce power at a frequency of 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz. In one implementation, the RF power source  140  may provide between about 100 Watts and about 3,000 Watts at a frequency of about 50 kHz to about 13.6 MHz. In another implementation, the RF power source  140  may provide between about 500 Watts and about 1,800 Watts at a frequency of about 50 kHz to about 13.6 MHz. 
     The controller  110  includes a central processing unit (CPU)  112 , a memory  116 , and a support circuit  114  utilized to control the process sequence and regulate the gas flows from the gas panel  130 . The CPU  112  may be of any form of a general-purpose computer processor that may be used in an industrial setting. The software routines can be stored in the memory  116 , such as random access memory, read only memory, floppy, or hard disk drive, or other form of digital storage. The support circuit  114  is conventionally coupled to the CPU  112  and may include cache, clock circuits, input/output systems, power supplies, and the like. Bi-directional communications between the controller  110  and the various components of the substrate processing system  132  are handled through numerous signal cables collectively referred to as signal buses  118 , some of which are illustrated in  FIG. 1A . 
       FIG. 1B  depicts a schematic cross-sectional view of another substrate processing system  180  that can be used for the practice of implementations described herein. The substrate processing system  180  is similar to the substrate processing system  132  of  FIG. 1A , except that the substrate processing system  180  is configured to flow processing gases from gas panel  130  across the surface  191  of the substrate  190  via the sidewall  101 . In addition, the gas distribution assembly  120  depicted in  FIG. 1A  is replaced with an electrode  182 . The electrode  182  may be configured for secondary electron generation. In one implementation, the electrode  182  is a silicon-containing electrode. 
       FIG. 2  depicts a schematic cross-sectional view of the substrate support assembly  146  used in the processing systems of  FIG. 1A  and  FIG. 1B  that can be used for the practice of implementations described herein. Referring to  FIG. 2 , the electrostatic chuck  150  may include a heater element  170  suitable for controlling the temperature of a substrate  190  supported on an upper surface  192  of the electrostatic chuck  150 . The heater element  170  may be embedded in the electrostatic chuck  150 . The electrostatic chuck  150  may be resistively heated by applying an electric current from a heater power source  106  to the heater element  170 . The heater power source  106  may be coupled through an RF filter  216 . The RF filter  216  may be used to protect the heater power source  106  from RF energy. The heater element  170  may be made of a nickel-chromium wire encapsulated in a nickel-iron-chromium alloy (e.g., INCOLOY®) sheath tube. The electric current supplied from the heater power source  106  is regulated by the controller  110  to control the heat generated by the heater element  170 , thus maintaining the substrate  190  and the electrostatic chuck  150  at a substantially constant temperature during film deposition. The supplied electric current may be adjusted to selectively control the temperature of the electrostatic chuck  150  between about −50 degrees Celsius to about 600 degrees Celsius. 
     Referring to  FIG. 1 , a temperature sensor  172 , such as a thermocouple, may be embedded in the electrostatic chuck  150  to monitor the temperature of the electrostatic chuck  150  in a conventional manner. The measured temperature is used by the controller  110  to control the power supplied to the heater element  170  to maintain the substrate at a desired temperature. 
     The electrostatic chuck  150  includes a chucking electrode  210 , which may be a mesh of a conductive material. The chucking electrode  210  may be embedded in the electrostatic chuck  150 . The chucking electrode  210  is coupled to a chucking power source  212  that, when energized, electrostatically clamps the substrate  190  to the upper surface  192  of the electrostatic chuck  150 . 
     The chucking electrode  210  may be configured as a monopolar or bipolar electrode, or have another suitable arrangement. The chucking electrode  210  may be coupled through an RF filter  214  to the chucking power source  212 , which provides direct current (DC) power to electrostatically secure the substrate  190  to the upper surface  192  of the electrostatic chuck  150 . The RF filter  214  prevents RF power utilized to form plasma within the process chamber  100  from damaging electrical equipment or presenting an electrical hazard outside the chamber. The electrostatic chuck  150  may be fabricated from a ceramic material, such as AlN or Al 2 O 3 . Alternately, the electrostatic chuck  150  may be fabricated from a polymer, such as polyimide, polyetheretherketone (PEEK), polyaryletherketone (PAEK), and the like. 
     A power application system  220  is coupled to the substrate support assembly  146 . The power application system  220  may include the heater power source  106 , the chucking power source  212 , a first radio frequency (RF) power source  230 , and a second RF power source  240 . Implementations of the power application system  220  may additionally include the controller  110 , and a sensor device  250  that is in communication with the controller  110  and both of the first RF power source  230  and the second RF power source  240 . 
     The controller  110  may also be utilized to control the plasma from the processing gas by application of RF power from the first RF power source  230  and the second RF power source  240  in order to deposit a layer of material on the substrate  190 . 
     As described above, the electrostatic chuck  150  includes the chucking electrode  210  that may function in one aspect to chuck the substrate  190  while also functioning as a first RF electrode. The electrostatic chuck  150  may also include a second RF electrode  260 , and together with the chucking electrode  210 , may apply RF power to tune the plasma. The first RF power source  230  may be coupled to the second RF electrode  260  while the second RF power source  240  may be coupled to the chucking electrode  210 . A first matching network and a second matching network may be provided for the first RF power source  230  and the second RF power source  240 , respectively. The second RF electrode  260  may be a solid metal plate of a conductive material as shown. Alternatively, the second RF electrode  260  may be a mesh of conductive material. 
     The first RF power source  230  and the second RF power source  240  may produce power at the same frequency or a different frequency. In some implementations, one or both of the first RF power source  230  and the second RF power source  240  may independently produce power at a frequency from about 350 KHz to about 100 MHz (e.g., 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz). In some implementations, the first RF power source  230  may produce power at a frequency of 13.56 MHz and the second RF power source  240  may produce power at a frequency of 2 MHz, or vice versa. RF power from one or both of the first RF power source  230  and second RF power source  240  may be varied in order to tune the plasma. For example, the sensor device  250  may be used to monitor the RF energy from one or both of the first RF power source  230  and the second RF power source  240 . Data from the sensor device  250  may be communicated to the controller  110 , and the controller  110  may be utilized to vary power applied by the first RF power source  230  and the second RF power source  240 . 
     The quantity/percentage of sp 3  hybridized carbon atoms in the as-deposited diamond-like carbon may vary from application to application. In various implementations of the present disclosure, the as-deposited diamond-like carbon film may contain at least 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 percent of sp 3  hybridized carbon atoms. The as-deposited diamond-like carbon film may contain up to 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 percent of sp 3  hybridized carbon atoms. The as-deposited diamond-like carbon film may contain from about 50 to about 90 percent of sp 3  hybridized carbon atoms. The as-deposited diamond-like carbon film may contain from about 60 to about 70 percent of sp 3  hybridized carbon atoms. 
     In general, the following exemplary deposition process parameters may be used to form the as-deposited diamond-like carbon layer. The wafer temperature may range from about −50° C. to about 350° C. (e.g., from about 10° C. to about 100° C.; or from about 10° C. to about 50° C.). The chamber pressure may range from a chamber pressure of about 0.5 mTorr to about 10 Torr (e.g., about 2 mTorr to about 50 mTorr; or between about 2 mTorr and about 10 mTorr). The flow rate of the hydrocarbon-containing gas mixture may be from about 10 sccm to about 1,000 sccm (e.g., from about 100 sccm to about 200 sccm, or from about 150 sccm to about 200 sccm). The flow rate of a dilution gas may individually range from about 50 sccm to about 50,000 sccm (e.g., from about 50 sccm to about 500 sccm; or from about 50 sccm to about 100 sccm). 
     
       
         
           
               
               
               
               
             
               
                 TABLE I 
               
               
                   
               
               
                 Deposition 
                   
                   
                   
               
               
                 Parameter 
                 Exemplary Range 
                 Exemplary Range 
                 Exemplary Range 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
               
               
               
            
               
                 Temperature (° C.) 
                 −50-350° 
                 C. 
                 10-100° 
                 C. 
                 10-50° 
                 C. 
               
            
           
           
               
               
               
               
            
               
                 Pressure (Torr) 
                 0.5 mTorr-10 Torr 
                 2 mTorr-50 mTorr 
                 2 mTorr-10 mTorr 
               
            
           
           
               
               
               
               
               
               
               
            
               
                 First RF Power 
                 100-3,000 
                 Watts 
                 2,000-3,000 
                 Watts 
                 2,500 
                 Watts 
               
               
                 (13.56 MHz) 
               
               
                 Second RF Power 
                 200-2,000 
                 Watts 
                 800-1,200 
                 Watts 
                 1,000 
                 Watts 
               
               
                 (2 MHz) 
               
               
                 Spacing 
                 1,000 to 15,000 
                 mils 
                 6,000 to 12,000 
                 mils 
                 8,000 to 12,000 
                 mils 
               
               
                 C 2 H 2  flow 
                 10-1,000 
                 sccm 
                 100-200 
                 sccm 
                 150 
                 sccm 
               
               
                 He flow 
                 50-5,000 
                 sccm 
                 50-100 
                 sccm 
                 100 
                 sccm 
               
               
                   
               
            
           
         
       
     
     The diamond-like carbon layer may be deposited to a thickness between about 5 Å and about 20,000 Å (e.g., between about 300 Å to about 5000 Å; between about 2000 Å and about 3000 Å, or between about 5 Å to about 200 Å). The above process parameters depicted in Table I provide examples of process parameters for a 300 mm substrate in a deposition chamber available from Applied Materials, Inc. of Santa Clara, Calif. 
     The as-deposited diamond-like carbon film may have a refractive index or n-value (n (at 633 nm)) greater than 2.0, for example, approximately 2.0 to approximately 3.0, such as 2.3. The as-deposited diamond-like carbon film may have an extinction coefficient or k-value (K (at 633 nm)) greater than 0.1, for example, approximately 0.2 to approximately 0.3, such as 0.25. The as-deposited diamond-like carbon film may have a stress (MPa) less than about −100 MPa, for example from approximately −1000 MPa to approximately −100 MPa, from approximately −600 MPa to approximately −300 MPa, from approximately −600 MPa to approximately −500 MPa, such as approximately −550 MPa. The as-deposited diamond-like carbon film may have a density (g/cc) of greater than 1.8 g/cc, for example approximately 2.0 g/cc or higher, approximately 2.5 g/cc or higher, such as from about 1.8 g/cc to about 2.5 g/cc. The as-deposited diamond-like carbon film may film has an elastic modulus (GPa) of greater than 150 GPa, for example, from about 200 to about 400 GPa. 
       FIG. 3  depicts a flow diagram of a method  300  for forming a diamond-like carbon layer on a film stack disposed on a substrate in accordance with one implementation of the present disclosure. The diamond-like carbon layer formed on a film stack may be utilized, for example, as a hardmask to form stair-like structures in the film stack.  FIGS. 4A-4B  are schematic cross-sectional views illustrating a sequence for forming a diamond-like carbon layer on a film stack disposed on a substrate according to the method  300 . Although the method  300  is described below with reference to a hardmask layer that may be formed on a film stack utilized to manufacture stair-like structures in the film stack for three dimensional semiconductor devices, the method  300  may also be used to advantage in other device manufacturing applications. Further, it should also be understood that the operations depicted in  FIG. 3  may be performed simultaneously and/or in a different order than the order depicted in  FIG. 3 . 
     The method  300  begins at operation  310  by positioning a substrate, such as a substrate  400  depicted in  FIG. 4A , into a process chamber, such as the process chamber  100  depicted in  FIG. 1A  or  FIG. 1B . The substrate  400  may be substrate  190  depicted in  FIG. 1A ,  FIG. 1B  and  FIG. 2 . The substrate  400  may be positioned on an electrostatic chuck, for example, the upper surface  192  of the electrostatic chuck  150 . The substrate  400  may be a silicon-based material or any suitable insulating material or conductive material as needed, having a film stack  404  disposed on the substrate  400  that may be utilized to form a structure  402 , such as stair-like structures, in the film stack  404 . 
     As shown in the exemplary implementation depicted in  FIG. 4A , the substrate  400  may have a substantially planar surface, an uneven surface, or a substantially planar surface having a structure formed thereon. The film stack  404  is formed on the substrate  400 . In one implementation, the film stack  404  may be utilized to form a gate structure, a contact structure or an interconnection structure in a front end or back end process. The method  300  may be performed on the film stack  404  to form the stair-like structures therein used in a memory structure, such as NAND structure. In one implementation, the substrate  400  may be a material such as crystalline silicon (e.g., Si&lt;100&gt; or Si&lt;111&gt;), silicon oxide, strained silicon, silicon germanium, doped or undoped polysilicon, doped or undoped silicon substrates and patterned or non-patterned substrates silicon on insulator (SOI), carbon doped silicon oxides, silicon nitride, doped silicon, germanium, gallium arsenide, glass, sapphire. The substrate  400  may have various dimensions, such as 200 mm, 300 mm, and 450 mm or other diameter substrates, as well as, rectangular or square panels. Unless otherwise noted, implementations and examples described herein are conducted on substrates with a 200 mm diameter, a 300 mm diameter, or a 450 mm diameter substrate. In the implementation wherein a SOI structure is utilized for the substrate  400 , the substrate  400  may include a buried dielectric layer disposed on a silicon crystalline substrate. In the implementation depicted herein, the substrate  400  may be a crystalline silicon substrate. 
     In one implementation, the film stack  404  disposed on the substrate  400  may have a number of vertically stacked layers. The film stack  404  may comprise pairs including a first layer (shown as  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n ) and a second layer (shown as  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n ) repeatedly formed in the film stack  404 . The pairs includes alternating first layer (shown as  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n ) and second layer (shown as  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n ) repeatedly formed until desired numbers of pairs of the first layers and the second layers are reached. 
     The film stack  404  may be a part of a semiconductor chip, such as a three-dimensional memory chip. Although three repeating layers of first layers (shown as  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n ) and second layers (shown as  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n ) are shown in  FIGS. 4A-4B , it is noted that any desired number of repeating pairs of the first and the second layers may be utilized as needed. 
     In one implementation, the film stack  404  may be utilized to form multiple gate structures for a three-dimensional memory chip. The first layers  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n , formed in the film stack  404  may be a first dielectric layer and the second layers  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n  may be a second dielectric layer. Suitable dielectric layers may be utilized to form the first layers  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n  and the second layer  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n  include silicon oxide, silicon nitride, silicon oxynitride, silicon carbide, silicon oxycarbide, titanium nitride, composite of oxide and nitride, at least one or more oxide layers sandwiching a nitride layer, and combinations thereof, among others. In some implementations, the dielectric layers may be a high-k material having a dielectric constant greater than 4. Suitable examples of the high-k materials include hafnium dioxide (HfO 2 ), zirconium dioxide (ZrO 2 ), hafnium silicon oxide (HfSiO 2 ), hafnium aluminum oxide (HfAlO), zirconium silicon oxide (ZrSiO 2 ), tantalum dioxide (TaO 2 ), aluminum oxide, aluminum doped hafnium dioxide, bismuth strontium titanium (BST), and platinum zirconium titanium (PZT), among others. 
     In one particular example, the first layers  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n  are silicon oxide layers and the second layers  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n  are silicon nitride layers or polysilicon layers disposed on the first layers  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n . In one implementation, the thickness of first layers  408   a   1 ,  408   a   2 ,  408   a   3 , . . . ,  408   a   n  may be controlled at between about 50 Å and about 1000 Å, such as about 500 Å, and the thickness of the each second layers  408   b   1 ,  408   b   2 ,  408   b   3 , . . . ,  408   b   n  may be controlled at between about 50 Å and about 1000 Å, such as about 500 Å. The film stack  404  may have a total thickness between about 100 Å and about 2000 Å. In one implementation, a total thickness of the film stack  404  is about 3 microns to about 10 microns and will vary as technology advances. 
     It is noted that the diamond-like carbon layer may be formed on any surfaces or any portion of the substrate  400  with or without the film stack  404  present on the substrate  400 . 
     At operation  320 , a chucking voltage is applied to the electrostatic chuck to clamp the substrate  400  to the electrostatic chuck. In some implementations, where the substrate  400  is positioned on the upper surface  192  of the electrostatic chuck  150 , the upper surface  192  provides support and clamps the substrate  400  during processing. The electrostatic chuck  150  flattens the substrate  400  closely against the upper surface  192 , preventing backside deposition. An electrical bias is provided to the substrate  400  via chucking electrode  210 . The chucking electrode  210  may be in electronic communication with the chucking power source  212  that supplies a biasing voltage to the chucking electrode  210 . In one implementation, the chucking voltage is between about 10 volts and about 3000 volts. In one implementation, the chucking voltage is between about 100 volts and about 2000 volts. In one implementation, the chucking voltage is between about 200 volts and about 1000 volts. 
     During operation  320 , several process parameters may be regulated the process. In one implementation suitable for processing a 300 mm substrate, the process pressure in the processing volume may be maintained at about 0.1 mTorr to about 10 Torr (e.g., about 2 mTorr to about 50 mTorr; or about 5 mTorr to about 20 mTorr). In one implementation suitable for processing a 300 mm substrate, the processing temperature and/or substrate temperature may be maintained at about −50 degrees Celsius to about 350 degrees Celsius (e.g., about 0 degrees Celsius to about 50 degrees Celsius; or about 10 degrees Celsius to about 20 degrees Celsius). 
     In one implementation, a constant chucking voltage is applied to the substrate  400 . In one implementation, the chucking voltage may be pulsed to the electrostatic chuck  150 . In some implementations, a backside gas may be applied to the substrate  400  while applying the chucking voltage to control the temperature of the substrate. Backside gases may include but are not limited to, helium (He), argon (Ar), or the like. 
     At operation  330 , a plasma is generated at the substrate level by applying a first RF bias to the electrostatic chuck. Plasma generated at the substrate level may be generated in a plasma region between the substrate and the electrostatic chuck. The first RF bias may be from about 10 Watts and about 3000 Watts at a frequency of from about 350 KHz to about 100 MHz (e.g., 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz). In one implementation, the first RF bias is provided at a power between about 2500 Watts and about 3000 Watts at a frequency of about 13.56 MHz. In one implementation, the first RF bias is provided to the electrostatic chuck  150  via the second RF electrode  260 . The second RF electrode  260  may be in electronic communication with the first RF power source  230  that supplies a biasing voltage to the second RF electrode  260 . In one implementation, the bias power is between about 10 Watts and about 3000 Watts. In one implementation, the bias power is between about 2000 Watts and about 3000 Watts. In one implementation, the bias power is between about 2500 Watts and about 3000 Watts. The first RF power source  230  may produce power at a frequency of from about 350 KHz to about 100 MHz (e.g., 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz). 
     In some implementations, operation  330  further comprises applying a second RF bias to the electrostatic chuck. The second RF bias may be from about 10 Watts and about 3000 Watts at a frequency of from about 350 KHz to about 100 MHz (e.g., 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz). In one implementation, the second RF bias is provided at a power between about 800 Watts and about 1200 Watts at a frequency of about 2 MHz. In one implementation, the second RF bias is provided to the substrate  400  via the chucking electrode  210 . The chucking electrode  210  may be in electronic communication with second RF power source  240  that supplies a biasing voltage to the chucking electrode  210 . In one implementation, the bias power is between about 10 Watts and about 3000 Watts. In one implementation, the bias power is between about 500 Watts and about 1500 Watts. In one implementation, the bias power is between about 800 Watts and about 1200 Watts. The second RF power source  240  may produce power at a frequency of from about 350 KHz to about 100 MHz (e.g., 350 KHz, 2 MHz, 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, or 100 MHz). In one implementation, the chucking voltage supplied in operation  320  is maintained during operation  330 . 
     In some implementations, during operation  330 , the first RF bias is provided to the substrate  400  via the chucking electrode  210  and the second RF bias may be provided to the substrate  400  via the second RF electrode  260 . In one implementation, the first RF bias is about 2500 Watts (13.56 MHz) and the second RF bias is about 1000 Watts (2 MHz). 
     During operation  340 , a hydrocarbon-containing gas mixture is flowed into the processing volume  126  to form the diamond-like carbon film on the film stack. The hydrocarbon-containing gas mixture may be flowed from the gas panel  130  into the processing volume  126  either through the gas distribution assembly  120  or via the sidewall  101 . The hydrocarbon-containing gas mixture may include at least one hydrocarbon compound. The hydrocarbon-containing gas mixture may further include an inert gas, a dilution gas, a nitrogen-containing gas, an etchant gas or combinations thereof. The hydrocarbon can be any liquid or gas, though the preferred precursor would be vapor at room temperature to simplify the hardware needed for material metering, control and delivery to the chamber. In some implementations, the chucking voltage supplied during operation  320  is maintained during operation  340 . In some implementations, the process conditions established during operation  320  and plasma formed during operation  330  are maintained during operation  340 . 
     In one implementation, the hydrocarbon compound is a gaseous hydrocarbon. In one implementation, the hydrocarbon compound has a general formula C x H y , where x has a range of between 1 and 20 and y has a range of between 1 and 20. Suitable hydrocarbon compounds include, for example, C 2 H 2 , C 3 H 6 , CH 4 , C 4 H 8 , 1,3-dimethyladamantane, bicyclo[2.2.1]hepta-2,5-diene (2,5-Norbornadiene), adamantine (C 10 H 16 ), norbornene (C 7 H 10 ), or combinations thereof. In one example, C 2 H 2  is preferable due to formation of more stable intermediate species, which allows more surface mobility. 
     In one implementation, the hydrocarbon compound is an alkane (e.g., C n H 2n+2 , wherein n is between 1 and 20). Suitable hydrocarbon compounds include, for example, alkanes such as methane (CH 4 ), ethane (C 2 H 6 ), propylene (C 3 H 6 ), propane (C 3 H 8 ), butane (C 4 H 10 ) and its isomer isobutane, pentane (C 5 H 12 ), hexane (C 6 H 14 ) and its isomers isopentane and neopentane, hexane (C 6 H 14 ) and its isomers 2-methylpentane, 3-methylpentane, 2,3-dimethylbutane, and 2,2-dimethyl butane, or combinations thereof. 
     In one implementation, the hydrocarbon compound is an alkene (e.g., C n H 2n , wherein n is between 1 and 20). Suitable hydrocarbon compounds include, for example, alkenes such as ethylene, propylene, butylene and its isomers, pentene and its isomers, and the like, dienes such as butadiene, isoprene, pentadiene, hexadiene, or combinations thereof. Additional suitable hydrocarbons include, for example, halogenated alkenes such as monofluoroethylene, difluoroethylenes, trifluoroethylene, tetrafluoroethylene, monochloroethylene, dichloroethylenes, trichloroethylene, tetrachloroethylene, or combinations thereof. 
     In one implementation, the hydrocarbon compound is an alkyne (e.g., C n H 2n-2 , wherein n is between 1 and 20). Suitable hydrocarbon compounds include, for example, alkynes such as acetylene (C 2 H 2 ), propyne (C 3 H 4 ), butylene (C 4 H 8 ), vinylacetylene, or combinations thereof. 
     In one implementation, the hydrocarbon compound is an aromatic hydrocarbon compound, such as benzene, styrene, toluene, xylene, ethylbenzene, acetophenone, methyl benzoate, phenyl acetate, phenol, cresol, furan, and the like, alpha-terpinene, cymene, 1,1,3,3,-tetramethylbutylbenzene, t-butylether, t-butylethylene, methyl-methacrylate, and t-butylfurfurylether, compounds having the formula C 3 H 2  and C 5 H 4 , halogenated aromatic compounds including monofluorobenzene, difluorobenzenes, tetrafluorobenzenes, hexafluorobenzene, or combinations thereof. 
     In some implementations, the hydrocarbon-containing gas mixture further comprises one or more dilution gases. Suitable dilution gases such as helium (He), argon (Ar), xenon (Xe). hydrogen (H 2 ), nitrogen (N 2 ), ammonia (NH 3 ), or combinations thereof, among others, may be added to the gas mixture, if desired. Ar, He, and N 2  are used to control the density and deposition rate of the diamond-like carbon layer. In some cases, the addition of N 2  and/or NH 3  can be used to control the hydrogen ratio of the diamond-like carbon layer, as discussed below. Alternatively, dilution gases may not be used during the deposition. 
     In some implementations, the hydrocarbon-containing gas mixture further comprises one or more nitrogen-containing gases. Suitable nitrogen-containing compounds include, for example, pyridine, aliphatic amine, amines, nitriles, ammonia and similar compounds. 
     In some implementations, the hydrocarbon-containing gas mixture further comprises an inert gas. In some implementations, an inert gas, such as argon (Ar) and/or helium (He) may be supplied with the hydrocarbon-containing gas mixture into the processing volume  126 . Other inert gases, such as nitrogen (N 2 ) and nitric oxide (NO), may also be used to control the density and deposition rate of the diamond-like carbon layer. Additionally, a variety of other processing gases may be added to the hydrocarbon-containing gas mixture to modify properties of the diamond-like carbon material. In one implementation, the other processing gases may be reactive gases, such as hydrogen (H 2 ), ammonia (NH 3 ), a mixture of hydrogen (H 2 ) and nitrogen (N 2 ), or combinations thereof. The addition of H 2  and/or NH 3  may be used to control the hydrogen ratio (e.g., carbon to hydrogen ratio) of the deposited diamond-like carbon layer. The hydrogen ratio present in the diamond-like carbon film provides control over layer properties, such as reflectivity. 
     In some implementations, the hydrocarbon-containing gas mixture further comprises an etchant gas. Suitable etchant gases include chlorine (Cl 2 ), carbon tetrafluoride (CF 4 ), nitrogen trifluoride (NF 3 ), or combinations thereof. Not to be bound by theory, but it is believed that the etchant gases selectively etch sp 2  hybridized carbon atoms from the film thus increasing the fraction of sp 3  hybridized carbon atoms in the film, which increases the etch selectivity of the film. 
     In some implementation, after the diamond-like carbon layer  412  is formed on the substrate during operation  340 , the diamond-like carbon layer  412  is exposed to hydrogen radicals. In some implementations, the diamond-like carbon layer is exposed to hydrogen radicals during the deposition process of operation  340 . In some implementations, the hydrogen radicals formed in an RPS and delivered to the processing region. Not to be bound by theory, but it is believed that exposing the diamond-like carbon layer to hydrogen radicals leads to selective etching of sp 2  hybridized carbon atoms thus increasing the sp 3  hybridized carbon atom fraction of the film, thus increasing the etch selectivity. 
     At operation  350 , after the diamond-like carbon layer  412  is formed on the substrate, the substrate is de-chucked. During operation  350 , the chucking voltage is turned-off. The reactive gases are turned-off and optionally purged from the processing chamber. In one implementation, during operation  350  RF power is reduced (e.g., ˜200 W). Optionally, the controller  110  monitors impedance change to determine whether electrostatic charges are dissipated to ground through the RF path. Once the substrate is de-chucked from the electrostatic chuck, the remaining gases are purged from the processing chamber. The processing chamber is pumped down and the substrate is moved up on the lift pins and transferred out of chamber. 
       FIG. 8  depicts a flow diagram of a method  800  of using a diamond-like carbon layer in accordance with one or more implementations of the present disclosure. After the diamond-like carbon layer  412  is formed on the substrate, the diamond-like carbon layer  412  may be utilized in an etching process as a patterning mask to form a three-dimensional structure, such as a stair like structure. The diamond-like carbon layer  412  may be patterned using a standard photoresist patterning techniques. At operation  810 , a patterned photoresist (not shown) may be formed over the diamond-like carbon layer  412 . At operation  820 , the diamond-like carbon layer  412  may be etched in a pattern corresponding with the patterned photoresist layer followed by etching the pattern into the substrate  400  at operation  830 . At operation  840 , material may be deposited into the etched portions of the substrate  400 . At operation  850 , the diamond-like carbon layer  412  may be removed using a solution comprising hydrogen peroxide and sulfuric acid. One exemplary solution comprising hydrogen peroxide and sulfuric acid is known as Piranha solution or Piranha etch. The diamond-like carbon layer  412  may also be removed using etch chemistries containing oxygen and halogens (e.g., fluorine or chlorine), for example, Cl 2 /O 2 , CF 4 /O 2 , Cl 2 /O 2 /CF 4 . The diamond-like carbon layer  412  may be removed by a chemical mechanical polishing (CMP) process. 
     EXAMPLES 
     The following non-limiting examples are provided to further illustrate implementations described herein. However, the examples are not intended to be all inclusive and are not intended to limit the scope of the implementations described herein. 
     In one implementation, a low stress, high-density diamond-like carbon film of the present disclosure was fabricated by flowing 150 sccm C 2 H 2  and 100 sccm He as process gases at a temperature of 10 degrees Celsius, applying 2500 Watts RF (13.56 MHz) power and 1000 Watts (2 MHz) through the substrate pedestal (electrostatic chuck) in a CVD reactor with Ar and/or He as diluting gas. The resultant diamond-like carbon film had a density of 1.94 g/cc and stress of −350 MPa and an etch selectivity greater than currently available amorphous carbon films. 
     
       
         
           
               
               
               
               
             
               
                 TABLE II 
               
               
                   
               
               
                   
                   
                 PVD 
                   
               
               
                   
                 Amorphous 
                 Diamond-Like 
                 PECVD 
               
               
                   
                 Carbon Film 
                 Carbon Film 
                 Diamond-like 
               
               
                 Film Type 
                 Reference 
                 Reference 
                 carbon film 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
               
            
               
                 Density (g/cc) 
                 1.75 
                 2.52 
                 ~2.00 
               
               
                 Stress (MPa) 
                 −50 
                 −350 
                 −600 
               
               
                 n @ 633 nm 
                 2.07 
                 &gt;2.3 
                 2.37 
               
               
                 k @ 633 nm 
                 0.63 
                 &gt;0.5 
                 0.30 
               
               
                 H content (% RBS) 
                 12 
                  &lt;1% 
                 25 
               
               
                 sp 3  % 
                 &lt;10% 
                 ~50% 
                 ~60% 
               
               
                 Modulus/Hardness 
                 53/5.8 
                 231/19 
                 180/20 
               
               
                 (GPa) 
               
               
                 Temperature 
                 635 
                 25 
                 10 
               
               
                   
               
            
           
         
       
     
       FIG. 5  is a graph  500  depicting density as a function of bias power for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure. The graph  500  depicts density as a function of bias power for diamond-like carbon films deposited at a frequency of 2 MHz and a frequency of 13.56 MHz. The y-axis represents the density (g/cc) of the deposited films and the x-axis represents the bias power (Watts). As illustrated in  FIG. 5 , for the most part, as bias power increases, the density of the as-deposited film increases. 
       FIG. 6  is a graph  600  depicting stress as a function of bias power for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure. The graph  600  depicts stress as a function of bias power for diamond-like carbon films deposited at a frequency of 2 MHz and a frequency of 13.56 MHz. The y-axis represents the stress (MPa) of the deposited films and the x-axis represents the bias power (Watts). As illustrated in  FIG. 6 , for the most part, as bias power increases, the stress of the as-deposited film increases. 
       FIG. 7  is a graph  700  depicting density and stress as a function of pressure for a diamond-like carbon layer formed in accordance with one or more implementations of the present disclosure. The y-axis represents the density (g/cc) and stress (MPa) of the deposited films and the x-axis represents the process pressure (mTorr). As illustrated in  FIG. 7 , lower pressure yields a slightly higher density and lower stress and higher pressure yields more compressive stress. 
     Extreme Ultraviolet (“EUV”) Patterning Schemes 
     The choice of underlayer is critical to preventing nanofailures (e.g., bridging defects and spacing defects) in semiconductor devices when using metal-containing photoresists in extreme ultraviolet (“EUV”) patterning schemes. Conventional underlayers for EUV patterning (lithography) schemes are spin on carbon (SOC) materials. However, during patterning, metals such as tin, for example, diffuse through the SOC material leading to nanofailures in the semiconductor devices. Such nanofailures act to reduce, degrade, and hamper semiconductor performance. 
     The high-density carbon films described herein, on the other hand, have superior film qualities such as improved hardness and density. Such hardness and density allow the high-density carbon film to act as a stronger barrier against metal infiltration and to prevent and at a minimum, reduce nanofailures to a greater extent than the conventional SOC films. 
     In some implementations, a film for use as an underlayer for an extreme ultraviolet (“EUV”) lithography process is provided. In some implementations, the film (and/or as-deposited film) has one or more of the following characteristics: 
     1) A quantity/percentage of sp 3  hybridized carbon atoms (i.e., a sp 3  hybridized carbon atom content) that is at least 40, 45, 50, 55, 60, 65, 70, 75, 80, or 85 percent based on the total amount of carbon atoms in the as-deposited film. In these or other implementations, the quantity/percentage of sp 3  hybridized carbon atoms is up to 45, 50, 55, 60, 65, 70, 75, 80, 85, or 90 percent based on the total amount of carbon atoms in the as-deposited film. In these or other implementations, the quantity/percentage of sp 3  hybridized carbon atoms is from about 50 to about 90 percent (such as from about 60 to about 70 percent) based on the total amount of carbon atoms in the as-deposited film. 
     2) A thickness that is between about 5 Å and about 20,000 Å (e.g., between about 300 Å to about 5000 Å, such as between about 2000 Å and about 3000 Å). Alternately, a thickness that is between about 5 Å to about 200 Å. 
     3) A refractive index or n-value (n (at 633 nm)) that is greater than 2.0, for example, approximately 2.0 to approximately 3.0, such as 2.3. 
     4) An extinction coefficient or k-value (K (at 633 nm)) that is greater than 0.1, for example, approximately 0.2 to approximately 0.3, such as 0.25. 
     5) A stress (MPa) that is less than about −300 MPa, for example from approximately −600 MPa to approximately −300 MPa, from approximately −600 MPa to approximately −500 MPa, such as approximately −550 MPa. 
     6) A density (g/cc) that is greater than 1.8 g/cc, for example approximately 2.0 g/cc or higher, approximately 2.5 g/cc or higher, such as from about 1.8 g/cc to about 2.5 g/cc. 
     7) An elastic modulus (GPa) that is greater than 150 GPa, for example, from about 200 to about 400 GPa. 
     In some implementations, a film for use as an underlayer for an EUV lithography process can be any film described herein. 
     In some implementations, a film for use as an underlayer for an EUV lithography process has an sp 3  hybridized carbon atom content of between 40% and 90% based on the total amount of carbon atoms in the film; a density of between 1.8 g/cc and 2.5 g/cc; and an elastic modulus that is between 150 GPa and 400 GPa. 
     In some implementations, a film for use as an underlayer for an EUV lithography process has a density of between 2.0 g/cc and 2.2 g/cc; and an elastic modulus that is between about 180 GPa and about 200 GPa. In some implementations, the film has a density of about 2.1 g/cc and an elastic modulus of about 195 GPa. 
     In some implementations, for use as an underlayer for an EUV lithography process has a stress of −600 MPa; a refractive index that is between 2.0 and 3.0; and an extinction coefficient of between 0.2 and 0.3. 
     Thus, methods and apparatus for forming a diamond-like carbon hardmask layer that may be utilized to form stair-like structures for manufacturing three-dimensional stacking of semiconductor devices are provided. By utilization of the diamond-like hardmask layer with desired robust film properties and etching selectivity, an improved dimension and profile control of the resultant structures formed in a film stack may be obtained and the electrical performance of the chip devices may be enhanced in applications for three-dimensional stacking of semiconductor devices. 
     In summary, some of the benefits of the present disclosure provide a process for depositing diamond-like hardmask films on a substrate. Typical PECVD hardmask films have a very low percent of hybridized sp 3  atoms and hence low modulus and etch selectivity. In some implementations described herein, low process pressures (mTorr vs. Torr) and bottom driven plasma enables fabrication of films with approximately 60% or greater hybridized sp 3  atoms, which results in an improvement in etch selectivity relative to previously available hardmask films. In addition, some of the implementations described herein are performed at low substrate temperatures, which enable the deposition of other dielectric films at much lower temperatures than currently possible, opening up applications with low thermal budget that could not be currently addressed by CVD. Additionally, some of the implementations described herein may be used as an underlayer for an EUV lithography process. 
     When introducing elements of the present disclosure or exemplary aspects or implementation(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements. 
     The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. 
     While the foregoing is directed to implementations of the present disclosure, other and further implementations of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.