Patent Publication Number: US-2023162971-A1

Title: Method of forming sioc and siocn low-k spacers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application Ser. No. 63/283,163 filed Nov. 24, 2021 and titled METHOD OF FORMING SIOC AND SIOCN LOW-K SPACERS, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF INVENTION 
     The present disclosure generally relates to improved methods for depositing silicon oxycarbide (SiOC) and silicon oxycarbonitride (SiOCN) films. 
     BACKGROUND OF THE DISCLOSURE 
     During the manufacture of semiconductor devices, the need for improved techniques for forming integrated spacers increases as the devices are scaled down. A conformality above 95%, low dielectric constant (low-k), good electrical isolation, low wet etch rate (preferably below 1 Å/min in a 0.5% diluted hydrofluoric acid (HF) solution), and no metal oxidation when metals are pre-deposited before deposition of spacers are desired. Silicon nitride (SiN) is generally the most widely used integrated spacer due to its high thermal stability and good etch selectivity. However, the dielectric constant of SiN is around 7.5, which is undesirably high, and can result in suppressed resistance capacitance (RC) delay due to parasitic capacitance in smaller devices. In current logic applications, the moderate scaling of gate spacer thickness (6 to 4 nm) generally requires a low-k value below 3.5 for better intrinsic performance. Also, memory devices like DRAM generally require bit line (BL) spacers with a low-k value below 4.4 and a high thermal stability. 
     Silicon oxycarbide (SiOC) and silicon oxycarbide nitride (SiOCN) films can be deposited with high conformality. The Si—O bonds yields a dielectric constant around 3.9, and the additional Si—C bonding can dramatically reduce the wet etch rate (WER) for improved etch selectivity. 
     Different deposition methods have previously been shown to yield different SiOC film qualities. For example, PECVD has been shown to yield highly dense SiOC films with true Si—C bonding, but does not yield good conformality when the pitch is small. As another example, using O-free PEALD with H 2  plasma and alkoxide-containing Si precursors has been shown to form SiOC films with Si—C bonding, but the sidewall quality is not desirable due to a weak energetic ion-induced densification. Therefore, improved methods for forming low-k spacers are desired. 
     Any discussion of problems and solutions set forth in this section has been included in this disclosure solely for the purposes of providing a context for the present disclosure, and should not be taken as an admission that any or all of the discussion was known at the time the invention was made. 
     SUMMARY OF THE DISCLOSURE 
     Exemplary embodiments of this disclosure provide methods for depositing SiOC and SiOCN films. While the ways in which various embodiments of the present disclosure address drawbacks of prior methods are discussed in more detail below, in general, various embodiments of the disclosure provide methods for depositing low-k SiOC and SiOCN films using Si precursors containing iodine and alkoxide. 
     In accordance with examples of the disclosure, a method of depositing a material on a surface of a substrate comprises providing the substrate within a reaction chamber; providing a precursor represented by a chemical formula comprising silicon, at least one iodine, and at least one functional group comprising carbon and oxygen within the reaction chamber; and providing a plasma within the reaction chamber. 
     In various embodiments, the oxygen is bonded to the silicon and the carbon. In various embodiments, the at least one functional group comprising carbon and oxygen comprises one or more of a C1-C6 alkyl group and a C6 aryl group. In various embodiments, the precursor is represented by a general formula I: 
     
       
         
         
             
             
         
       
     
     wherein at least one of X 1 , X 2 , X 3 , and X 4  is iodine of the at least one iodine, and at least one of X 1 , X 2 , X 3 , and X 4  is a functional group comprising carbon and oxygen of the at least one functionals group comprising carbon and oxygen. In various embodiments, two of X 1 , X 2 , X 3 , and X 4  are iodine of the at least one iodine, and two of X 1 , X 2 , X 3 , and X 4  are a functional group containing carbon and oxygen of the at least one functional group comprising carbon and oxygen. In various embodiments, three of X 1 , X 2 , X 3 , and X 4  are iodine of the at least one iodine, and one of X 1 , X 2 , X 3 , and X 4  is a functional group containing carbon and oxygen of the at least one functional group comprising carbon and oxygen. 
     In various embodiments, the functional group comprising carbon and oxygen comprises a C1-C6 alkoxide, or a C1-C4 alkoxide, or a C1-C3 alkoxide. 
     In various embodiments, the precursor comprises one or more of triethoxyiodosilane, iodotriphenoxysilane, [(triiodosilyl)oxy]benzene, triiodopropoxysilane, ethoxytriiodosilane, triiodomethoxysilane, diiododiphenoxysilane, diiododipropoxysilane, diiododimethoxysilane, iodotripropoxysilane, and iodotrimethoxysilane. 
     In various embodiments, the step of providing the plasma does not comprise providing an oxidant to the reaction chamber. In various embodiments, the plasma is formed by flowing one or more of H 2 , N 2 , and NH 3  to the reaction chamber. 
     In various embodiments, the method comprises a plasma enhanced cyclic (e.g., atomic layer deposition) process. 
     In various embodiments, the method further comprises purging the reaction chamber after providing the precursor. In various embodiments, the method further comprises purging the reaction chamber after providing the plasma. In some embodiments, no RF power is provided to the reaction chamber while purging the reaction chamber. 
     In various embodiments, a temperature within the reaction chamber is between about 100 and about 500° C., between about 200 and about 400° C., or between about 250 and about 350° C. In various embodiments, a pressure within the reaction chamber is between about 300 and 1000 Pa, or between about 1000 and about 3000 Pa. 
     In various embodiments, the material comprises one or more of silicon oxycarbide and silicon oxycarbide nitride. 
     In various embodiments, the method forms a spacer on a substrate. 
     In accordance with further embodiments of the disclosure, a device structure is provided. The device structure can be formed according to a method as set forth herein. 
     In accordance with yet additional examples of the disclosure, a system configured to perform a method and/or form a device structure as described herein is provided. 
     These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures; the invention not being limited to any particular embodiment(s) disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       A more complete understanding of exemplary embodiments of the present disclosure can be derived by referring to the detailed description and claims when considered in connection with the following illustrative figures. 
         FIG.  1    illustrates a surface reaction mechanism in accordance with previously known methods. 
         FIG.  2    illustrates a film deposition method in accordance with at least one embodiment of the disclosure. 
         FIG.  3    illustrates a structure in accordance with at least one embodiment of the disclosure. 
         FIG.  4    illustrates a system in accordance with at least one embodiment of the disclosure. 
         FIG.  5    illustrates another structure in accordance with at least one embodiment of the disclosure. 
         FIG.  6    illustrates a timing sequence in accordance with at least one embodiment of the disclosure 
     
    
    
     It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses described herein and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below. 
     As used herein, the terms “substrate” may refer to a wafer or any underlying material or materials that may be used to form, or upon which, a device, a circuit, or a film may be formed. Further, the substrate can include various features, such as recesses, lines, and the like formed within or on at least a portion of a layer of the substrate. 
     In some embodiments, the terms “film” and “layer” may be used interchangeably and refer to a layer extending in a direction perpendicular to a thickness direction to cover an entire target or concerned surface, or simply a layer covering a target or concerned surface. In some embodiments, the terms “film” or “layer” refer to a structure having a certain thickness formed on a surface. A film or layer may be constituted by a discrete single film or layer having certain characteristics. Alternatively, a film or layer may be constituted of multiple films or layers, and a boundary between adjacent films or layers may or may not be clear and may or may not be established based on physical, chemical, and/or any other characteristics, formation processes or sequence, and/or functions or purposes of the adjacent films or layers. 
     In some embodiments, “gas” can include material that is a gas at normal temperature and pressure, a vaporized solid and/or a vaporized liquid, and may be constituted by a single gas or a mixture of gases, depending on the context. A gas can include a process gas, an etch gas or other gas that passes through the substrate processing device, such as through a susceptor, a shower plate, a gas distribution device, a gas supply apparatus, an electrode, or the like. 
     In some embodiments, the term “precursor” refers generally to a compound that participates in the chemical reaction that produces another compound, and particularly to a compound that constitutes a film matrix or a main skeleton of a film, whereas the term “reactant” refers to a compound, other than precursors, that activates a precursor, modifies a precursor, or catalyzes a reaction of a precursor, wherein the reactant may provide an element (such as H and/or N) to a film matrix and become a part of the film matrix, when RF power is applied. 
     Further, in this disclosure, any two numbers of a variable can constitute a workable range of the variable, and any ranges indicated may include or exclude the endpoints. Additionally, any values of variables indicated (regardless of whether they are indicated with “about” or not) may refer to precise values or approximate values and include equivalents, and may refer to average, median, representative, majority, etc. in some embodiments. Further, in this disclosure, the terms “including,” “constituted by” and “having” refer independently to “typically or broadly comprising,” “comprising,” “consisting essentially of,” or “consisting of” in some embodiments. In this disclosure, any defined meanings do not necessarily exclude ordinary and customary meanings in some embodiments. Percentages set forth herein are absolute percentages, unless otherwise noted. 
     It shall be understood that the term “comprising” is open ended and does not exclude the presence of other elements or components, unless the context clearly indicates otherwise. The term “comprising” includes the meaning of “consisting of.” The term “consisting of” indicates that no other features or components are present than those mentioned, unless the context indicates otherwise. 
     In a PEALD SiN process, I 2 SiH 2  precursor has been shown to form dense surface species on sidewalls at the precursor feed step at higher temperatures of 350-400° C. The surface reaction is shown in  FIG.  1   . The I 2 SiH 2  precursor is unique due to the instability of iodine at high temperatures. 
     Described herein are methods for depositing a material on a substrate using Si precursors which contain iodine and alkoxide. By using iodine, sidewall quality may be improved during the precursor feed step at a high temperature, e.g. 500° C. Moreover, alkoxide ligands avoid the utilization of oxidative plasma, thereby preventing metal-oxidations. In some embodiments, the methods form a spacer on a substrate. 
       FIG.  2    illustrates a method  200  of depositing a material on a surface of a substrate according to an embodiment of the disclosure. Method  200  includes the steps of providing a substrate within a reaction chamber (step  202 ), providing a precursor comprising silicon, iodine, carbon, and oxygen to the reaction chamber (step  204 ), purging excess precursor from the reaction chamber (step  206 ), providing a plasma within the reaction chamber (step  208 ), and purging excess reactive species from the reaction chamber (step  210 ). 
     During step  202 , a substrate is provided within a reaction chamber. A temperature within the reaction chamber can be brought to a temperature and pressure for subsequent processing. In various embodiments, the temperature within the reaction chamber is between about 100° C. and about 500° C., between about 200° C. and about 400° C., or between about 250° C. and about 350° C. In various embodiments, the pressure within the reaction chamber is between about 300 Pa and 1000 Pa, or between about 1000 Pa and about 3000 Pa. 
     During step  204 , a precursor comprising silicon, iodine, carbon, and oxygen is provided to the reaction chamber. In various embodiments, the precursor includes silicon, at least one iodine, and at least one functional group comprising carbon and oxygen. In various embodiments, the oxygen is bonded to the silicon and the carbon. In various embodiments, the at least one functional group comprising carbon and oxygen comprises one or more of a C1-C6 alkyl group and a C6 aryl group. In various embodiments, the precursor is represented by a general formula I: 
     
       
         
         
             
             
         
       
     
     wherein at least one of X 1 , X 2 , X 3 , and X 4  is iodine of the at least one iodine, and at least one of X 1 , X 2 , X 3 , and X 4  is a functional group comprising carbon and oxygen of the at least one functionals group comprising carbon and oxygen. In some embodiments, in general formula I, at least two of X 1 , X 2 , X 3 , and X 4  are iodine of the at least one iodine, and two of X 1 , X 2 , X 3 , and X 4  are a functional group containing carbon and oxygen of the at least one functional group comprising carbon and oxygen. In some embodiments, in general formula I, three of X 1 , X 2 , X 3 , and X 4  are iodine of the at least one iodine, and one of X 1 , X 2 , X 3 , and X 4  is a functional group containing carbon and oxygen of the at least one functional group comprising carbon and oxygen 
     A flow rate of the precursor during step  204  may be between about 50 and about 1000 sccm. A duration of step  204  can be between about 0.15 and about 4 seconds. 
     In some embodiments, the functional group comprising carbon and oxygen comprises a C1-C6 alkoxide, or a C1-C4 alkoxide, or a C1-C3 alkoxide. 
     In preferred embodiments, the precursor comprises one or more of the compounds shown in Table 1. 
     
       
         
           
               
               
             
               
                 TABLE 1 
               
               
                   
               
             
            
               
                 Triethoxyiodosilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Silane, iodotriphenoxy-   
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 [(Triiodosilyl)oxy]benzene 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Triiodopropoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Ethoxytriiodosilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Triiodomethoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Silane, diiododiphenoxy- 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Diiododipropoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Diiododimethoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Iodotripropoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
               
                 Iodotrimethoxysilane 
                 
                   
                     
                     
                         
                         
                     
                   
                 
               
               
                   
               
            
           
         
       
     
     During optional step  206 , excess precursor is purged from the reaction chamber. 
     During step  208 , a plasma is provided to the reaction chamber. In preferred embodiments, the plasma is an H 2  plasma, a N 2  plasma, an NH 3  plasma, or an N 2 +H 2  plasma. That is, the plasma is formed by providing a reactant gas comprising H 2 , N 2 , NH 3 , or a combination of N 2  and H 2  to the reaction chamber and forming a plasma using a plasma power. A flow rate of the reactant gas may be between about 10 and 6000 sccm. A plasma power may be between about 30 and 1500 W for a 300 nm substrate. 
     During optional step  210 , excess reactive species are purged from the reaction chamber. 
     Steps  204 - 210  may constitute a deposition cycle; the deposition cycle may be repeated until the deposited material reaches a desired thickness. 
       FIG.  3    illustrates a structure  300  in accordance in accordance with exemplary embodiments of the disclosure. Structure  300  includes substrate  304  and SiOC and/or SiOCN layer  302 . Layer  302  can be formed, at least in part, according to a method as described herein, such as method  200 . A SiOC layer is a layer which includes silicon, oxygen, carbon, and which may include impurities to the extent that such impurities do not materially change the characteristics of the SiOC layer. Similarly, a SiOCN layer is a layer which includes silicon, oxygen, carbon, nitrogen, and unavoidable impurities to the extent that such impurities do not materially change the characteristics of the SiOCN layer. 
       FIG.  5    illustrates a structure  500  in accordance with exemplary embodiments of the disclosure. Structure  500  includes substrate  504 , feature  506 , and SiOC and/or SiOCN spacers  502 . Spacers  502  may be formed, at least in part, according to a method as described herein, such as method  200 . Feature  506  may be, for example, a gate or a portion thereof, or other material deposited on substrate  504 . 
       FIG.  4    illustrates a system  400  in accordance with exemplary embodiments of the disclosure. System  400  can be used to perform a method as described herein and/or to form a structure, or portion thereof, as described herein. 
     System  400  includes a reaction chamber  402 , including a reaction space  404 , a susceptor  408  to support a substrate  410 , a gas distribution assembly  412 , a gas supply system  406 , a plasma power source  414 , and a vacuum source  420 . System  400  can also include a controller  422  to control various components of system  400 . 
     Reaction chamber  402  can include any suitable reaction chamber, such as a plasma enhanced atomic layer deposition (PEALD) or a plasma enhanced chemical vapor deposition (PECVD) reaction chamber. 
     Susceptor  408  can include one or more heaters to heat substrate  410  to a desired temperature, such as a temperature noted herein. Further, susceptor  408  can form an electrode. In the illustrated example, susceptor  408  forms an electrode coupled to ground  416 . 
     Gas distribution assembly  412  can distribute gas to reaction space  404 . In accordance with exemplary embodiments of the disclosure, gas distribution assembly  412  includes a showerhead, which can form an electrode. In the illustrated example, gas distribution assembly  412  is coupled to a power source  414 , which provides power to gas distribution assembly  412  to produce a plasma with reaction space  404  (between gas distribution assembly  412  and susceptor  408 ). Power source  414  can be, for example, an RF power supply. 
     Gas supply system  406  can include one or more gas sources  424  and  426 , and a precursor source  430 . Gas source  424  can include, for example, a vessel and a reactant gas as described herein. Precursor source  430  can include a vessel and a precursor as described herein. Vacuum source  420  can include any suitable vacuum pump, such as a dry pump. Vacuum source  420  can be coupled to reaction chamber  402  via line  418  and controllable valve  438 . 
     Controller  422  can include electronic circuitry and software to selectively operate valves, heaters, thermocouples, pumps, and the like of system  400 . Such circuitry and components operate to introduce precursors, reactants, and purge gases from sources  424 ,  426 , and  430 . Controller  422  can control timing of gas pulse sequences, temperature of the substrate and/or reaction chamber, pressure within the reaction chamber, and various other operations to provide proper operation of system  400 . Controller  422  can include control software to electrically or pneumatically control valves to control flow of precursors, reactants and purge gases into and out of reaction chamber  402 . Controller  422  can include modules such as a software or hardware component, e.g., a FPGA or ASIC, which performs certain tasks. A module can advantageously be configured to reside on the addressable storage medium of the control system and be configured to execute one or more processes. 
       FIG.  6    illustrates a timing sequence  600  suitable for use with method  200 . In timing sequence  600 , in source feed step  602 , a precursor is provided to the reaction chamber followed by a source purge step  604 . Plasma is then applied in RF ON step  606 , followed by post (plasma) purge step  608 . Sequence steps  602 - 608  may be repeated until the deposited material reaches a desired thickness. As illustrated in timing sequence  600 , reactant gas and a carrier/purge gas may be continuously flowed into the reaction space throughout the process. 
     In some embodiments, source feed step  602  corresponds to step  204 ; source purge step  604  corresponds to step  206 ; RF ON step  606  corresponds to step  208 ; and post purge step  608  corresponds to step  210  of method  200 . 
     The example embodiments of the disclosure described above do not limit the scope of the invention since these embodiments are merely examples of the embodiments of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternative useful combinations of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.