Abstract:
Systems and methods deposit a film on a substrate by introducing a precursor gas into a reaction volume of a processing chamber. A substrate is arranged in the reaction volume. After a predetermined soak period, the precursor gas is purged from the reaction volume. The substrate is exposed with plasma gas using a remote plasma source.

Description:
FIELD 
       [0001]    The present disclosure relates to substrate processing systems, and more particularly to systems and methods for remote plasma atomic layer deposition. 
       BACKGROUND 
       [0002]    The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
         [0003]      FIG. 1  illustrates an example of a method for depositing a film on a substrate such as a semiconductor wafer using thermal atomic layer deposition (tALD). At  10 , a precursor is introduced into a reaction volume of a processing chamber to expose a substrate such as a semiconductor wafer. At  14 , the precursor is purged from the reaction volume. At  16 , a reactant gas is introduced into the reaction volume. For example, the reactant gas may be ammonia. At  18 , the reactant gas is purged. 
         [0004]    A resulting film on the substrate has negligible damage to an extreme low k (ELK) dielectric layer and conformal step coverage. However, the film has poor film density, typically around 8.8 g/cm 3 . This causes poor barrier performance in Cu thermal diffusion and moisture out-diffusion from the ELK dielectric layer. 
         [0005]    In contrast, ion-induced atomic layer deposition (iALD) or plasma-enhanced atomic layer deposition (PEALD) processes use a capacitively-coupled plasma (CCP) treatment with a combination of argon, hydrogen, and ammonia at  16  in  FIG. 1 . The resulting film has high film density (13 g/cm 3 ) and good step coverage. However, the film has significant ELK damage, yield loss, and high content of undesirable carbon impurity (for example, &gt;20 atomic %). 
       SUMMARY 
       [0006]    A method for depositing a film on a substrate includes introducing a precursor gas into a reaction volume of a processing chamber, wherein a substrate is arranged in the reaction volume; after a predetermined soak period, purging the precursor gas from the reaction volume; and exposing the substrate with plasma gas using a remote plasma source. 
         [0007]    In other features, the method further includes arranging a plasma dome above a dual plenum showerhead; locating the substrate on a pedestal in the reaction volume adjacent to the dual plenum showerhead; supplying the precursor gas to a first plenum defined between first and second plates of the dual plenum showerhead, wherein the precursor gas flows through first distribution holes in the dual plenum showerhead to the reaction volume; and supplying the plasma gas to a second plenum of the plasma dome The second plenum is defined between the plasma dome and the dual plenum showerhead. The plasma gas flows through second distribution holes in the dual plenum showerhead to the reaction volume. 
         [0008]    In other features, the plasma gas is generated remotely in the second plenum by supplying a process gas to the second plenum; arranging coils around the plasma dome; and supplying current to the coils to generate the plasma gas in the second plenum. 
         [0009]    In other features, the method further includes purging the plasma gas from the reaction volume. The precursor gas includes one of tantalum, nitrogen and carbon. The plasma gas includes one of argon and hydrogen (Ar/H 2 ), nitrogen and hydrogen (N 2 /H 2 ), nitrogen and ammonia (N 2 /NH 3 ), helium and hydrogen (He/H 2 ) and/or hydrogen (H 2 ). The plasma gas includes one of nitrogen and hydrogen (N 2 /H 2 ) and nitrogen and ammonia (N 2 /NH 3 ). 
         [0010]    In other features, the precursor gas and the plasma gas flow through the dual plenum showerhead using separate paths. The method further includes performing a post plasma treatment using the plasma gas. The method further includes purging the post plasma treatment. 
         [0011]    In other features, the method further includes, prior to the exposing the substrate with the plasma gas using the remote plasma source, introducing a reactant gas dose into the reaction volume and purging the reactant gas dose. 
         [0012]    In other features, the method further includes performing a post plasma treatment using the plasma gas. The method further includes purging the post plasma treatment. 
         [0013]    A substrate processing system for depositing a film on a substrate includes a processing chamber including a reaction volume. A substrate is arranged on a pedestal in the reaction volume. A dual plenum showerhead is arranged between the plasma dome and the reaction volume. A first plenum defined by the dual plenum showerhead and a second plenum is defined between the plasma dome and the dual plenum showerhead. Plasma gas is generated remotely in the second plenum. A precursor source supplies a precursor gas to the first plenum. The precursor gas flows through first distribution holes in the dual plenum showerhead to the reaction volume. The plasma gas flows through second distribution holes in the dual plenum showerhead to the reaction volume. A controller is configured to introduce the precursor gas into the reaction volume. After a predetermined period, the controller is configured to purge the precursor gas from the reaction volume. The controller is configured to expose the substrate to the plasma gas. 
         [0014]    In other features, the controller is configured to purge the plasma gas from the reaction volume. The precursor gas includes one of tantalum, nitrogen and carbon. The plasma gas includes one of argon and hydrogen (Ar/H 2 ), nitrogen and hydrogen (N 2 /H 2 ), nitrogen and ammonia (N 2 /NH 3 ), helium and hydrogen (He/H 2 ) and/or hydrogen (H 2 ). The plasma gas includes one of nitrogen and hydrogen (N 2 /H 2 ) and nitrogen and ammonia (N 2 /NH 3 ). The controller is configured to perform a post plasma treatment using the plasma gas. The controller is configured to purge the post plasma treatment. 
         [0015]    In other features, the controller is configured to, prior to the exposing the substrate with the plasma gas, introduce a reactant dose into the reaction volume and purge the reactant dose. The controller is configured to perform a post plasma treatment using the plasma gas. The controller is configured to purge the post plasma treatment. 
         [0016]    Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]    The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
           [0018]      FIG. 1  is a flowchart illustrating a method for performing thermal atomic layer deposition (tALD) according to the prior art; 
           [0019]      FIGS. 2A and 2B  are functional block diagrams of a reaction volume for remote plasma atomic layer deposition (RPALD) according to the present disclosure; 
           [0020]      FIG. 3  depicts an isometric section view of an example of a dual-plenum showerhead according to the present disclosure. 
           [0021]      FIG. 4  depicts an exploded, isometric section view of the example dual-plenum showerhead according to the present disclosure. 
           [0022]      FIG. 5  depicts an isometric, quarter-section view of the dual-plenum showerhead of  FIG. 4  according to the present disclosure. 
           [0023]      FIG. 6  is a flowchart illustrating an example of a method for performing RPALD according to the present disclosure; 
           [0024]      FIG. 7  is a flowchart illustrating an example of another method for performing RPALD according to the present disclosure; 
           [0025]      FIG. 8  is a flowchart illustrating an example of another method for performing RPALD according to the present disclosure; 
           [0026]      FIG. 9  is a graph illustrating etch rate as a function of plasma gas composition; and 
           [0027]      FIG. 10  is a graph illustrating minimum film thickness to pass Cu thermal diffusion as a function of various processes. 
       
    
    
       [0028]    In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
       DETAILED DESCRIPTION 
       [0029]    The present disclosure describes systems and methods for using remote plasma atomic layer deposition (RPALD) to deposit film such as tantalum nitride (TaN) film or another film where a remote plasma source is exposed in a plasma dose step or a post-plasma treatment step. In some examples, a dual plenum showerhead blocks the intermixing of precursor gas and reactant gas. Using the remote plasma source, the systems and methods described herein improve film density and produce film with fewer impurities (carbon, oxygen). The systems and methods also provide conformal step coverage and minimize extreme low dielectric (ELK) damage. 
         [0030]    The systems and methods described herein utilize a remote plasma source as a reactant and/or as a post-plasma treatment. The remote plasma source generates a high density of hydrogen-containing radicals involved in the reaction with the precursor gas. Most of the ions associated with ELK damage may be filtered during delivery to the substrate. In some examples, the precursor gas includes tantalum (Ta), nitrogen (N), and carbon (C). The precursor gas is introduced to a first plenum of a dual plenum showerhead. In some examples, process gases including argon and hydrogen (Ar/H 2 ), nitrogen and hydrogen (N 2 /H 2 ), nitrogen and ammonia (N 2 /NH 3 ), helium and hydrogen (He/H 2 ) and/or hydrogen (H 2 ) are supplied to a plasma dome to generate the remote plasma source. 
         [0031]    In some examples, the dual plenum showerhead delivers the remotely-generated plasma to the wafer. In some examples, gas compositions with N 2 /H 2  and N 2 /NH 3  are used to achieve desired film properties, although other gas compositions such as, but not limited to, those described herein can be used. Due to the high density and non-directionality of hydrogen radicals that are generated, the systems and methods described herein can be applied to various small features that require thin, continuous step coverage and minimal plasma damage. 
         [0032]    Referring now to  FIGS. 2A and 2B , examples of suitable substrate processing systems  50  include a reaction volume  51  and a plasma dome  52  arranged adjacent to and in fluid communication with the reaction volume  51 . In some examples, the plasma dome  52  may be made of quartz or another suitable material. A plurality of electromagnetic coils  54  may be arranged around an outside surface of the plasma dome  52 . A dual plenum showerhead  56  may be arranged between the plasma dome  52  and the reaction volume  51 . A substrate  58  may be arranged on a pedestal  60  in the reaction volume  51  below the dual plenum showerhead  56 . 
         [0033]    Process gases  62  are supplied via a mass flow controller  63  to a second plenum defined between the plasma dome  52  and the dual plenum showerhead  56 . A diffuser  65  may be used to diffuse the process gas. A remote plasma controller  82  is connected to electromagnetic coils  54 . The remote plasma controller  82  may include a current source to supply current to the coils  54 . Process gas is supplied to the second plenum and the plasma gas is remotely generated by an induced magnetic field and an electric field when the remote plasma controller  82  flows current along the coils  54  around the plasma dome  52 . Alternately, the plasma gas may be generated outside of the plasma dome  52  and delivered to the plasma dome  52 . 
         [0034]    In  FIG. 2A , carrier gas  72  and a precursor gas  74  are supplied via a mass flow controller  73  and a valve  76  to the dual plenum showerhead  56 . In  FIG. 2B , an alternate arrangement is shown where carrier gas  72  and a precursor gas  74  are supplied via a mass flow controller  73  and multiple valves  85 ,  87  and  89  to the dual plenum showerhead  56 . 
         [0035]    The first plenum is defined between upper and lower plates of the dual plenum showerhead  56  as will be described further below. A valve  79  and a pump  80  may be used to purge gas from the reaction volume  51 . 
         [0036]    The dual plenum showerhead  56  separately delivers precursor or plasma to the reaction volume. In other words, the precursor gas travels from the precursor source to the first plenum of the dual plenum showerhead  56  and through first distribution holes in the dual plenum showerhead  56  to the reaction volume  51 . In contrast, the plasma flows from the second plenum through a second set of distribution holes in the dual plenum showerhead  56  to the reaction volume  51 . A controller  90  may be used to control the process and may be connected to the valves  74  and  79 , the mass flow controller  76 , the pump  80 , and the remote plasma controller  82 . 
         [0037]    In some examples, the plasma dome  52  and the dual plenum showerhead  56  may be implemented in a manner similar to that described in commonly-assigned “Dual Plenum, Axi-Symmetric Showerhead with Edge-To-Center Gas Delivery”, U.S. patent application Ser. No. 13/531,254, filed on Jun. 22, 2012, which is hereby incorporated by reference in its entirety.  FIGS. 3-5  show further details of an example of the dual plenum showerhead  56 . 
         [0038]      FIG. 3  shows the plasma dome  52  arranged above the dual plenum showerhead  56 . An area between the plasma dome  52  and the dual plenum showerhead  56  defines the second plenum. The plasma dome  52  may include a mounting location  104  to introduce the process gases  62  (or plasma if the plasma is generated remotely from the plasma dome  52 ) that is located on a top portion of the plasma dome  52 . 
         [0039]      FIG. 3  also shows the pedestal  60  and a guard ring  100 , which are not components of the dual plenum showerhead  56 , but are depicted to provide additional context to illustrate how the dual plenum showerhead  56  may be positioned relative to the substrate  58  (or the pedestal  60 ) in the substrate processing system  50 . 
         [0040]      FIG. 4  shows an upper faceplate  112  and a lower faceplate  114  of the dual plenum showerhead  56 . Fasteners  116  such as screws may be used to attach the upper faceplate  112  to the lower faceplate  114 . The fasteners  116  may thread into an interface plate  111 , which mates with a flange on the upper faceplate  112 . The dual plenum showerhead  56  may be seated in a mounting ring  118 . The mounting ring  118  may have a slightly larger diameter than the diameter of the guard ring  108  to allow the mounting ring  118  to slide down and around the guard ring  108 . 
         [0041]    The dual plenum showerhead  56  may be made from any suitable material such as aluminum, ceramic, or other materials compatible with a semiconductor processing environment. While the upper faceplate  112  and the lower faceplate  114  are shown fastened together, they can be fabricated in other ways. For example, the upper faceplate  112  and the lower faceplate  114  may be bonded together, for example, with a diffusion bond or brazing. 
         [0042]      FIG. 5  shows a lower surface of the upper faceplate  112  resting on an upper surface of the lower faceplate  114 . A gap between the upper faceplate  112  and the lower faceplate  114  forms a gas distribution channel  136 . For example only, the gas distribution channel  136  may be annular. Gas feed inlets  120  may be in fluid communication with the gas distribution channel  136 . A faceplate O-ring  124  may prevent gas from the gas feed inlets  120  and the gas distribution channel  136  from escaping through an interface between the upper faceplate  112  and the lower faceplate  114 . 
         [0043]      FIG. 5  also shows first channels  138  that are formed by the faceplates  112  and  114  and that may extend in a substantially radial direction with respect to the center axis  126 . Other examples may feature other channel shapes, such as non-radial spoke channels, curving channels, pinwheel channels or other configurations. In some examples, the first channels  138  may generally extend towards the center axis  126  of the faceplates  112  and  114  from locations spaced about the periphery of the faceplates  112  and  114 . 
         [0044]    Second channels  140  may be formed within the faceplate  112  and may extend in a substantially circumferential direction with respect to the center axis  126 . The second channels  140  may have different nominal diameters and may be spaced apart such that they are distributed across the faceplate  112 . While the second channels  140  that are shown are concentric annular channels that extend through 360 degrees, other examples may feature other channel path shapes. For example, instead of multiple annular second channels  140 , one or multiple spiral second channels centered on the center axis  126  may be used in some examples. 
         [0045]    The faceplates  112  and  114  may feature two different sets of gas distribution holes, each serving to exhaust a different plenum volume. For example, the faceplates  112  and  114  may include first gas distribution holes  132  and second gas distribution holes  134 . The second gas distribution holes  134  may allow gas within the second plenum volume to escape towards the reaction volume  51 . 
         [0046]    The first plenum may be formed, at least in part, by volume defined by the first channels and the second channels. The first gas distribution holes  132  may allow gas within the first plenum to escape towards the reaction volume  51 . The first gas distribution holes  132  may be smaller than the second gas distribution holes  134 . The second gas distribution holes  134  may also extend completely through the faceplates  112  and  114 , i.e., from top surface  128  to bottom surface  130 . In some examples, since the remote plasma may be generated in the second plenum, it may be desirable to increase the number of free radicals that are released into the reaction volume  51 . The second gas distribution holes  134  may thus have a diameter that, within certain constraints, is configured to maximize, to the extent possible, the number of free radicals that pass into the reaction volume  51 . 
         [0047]      FIG. 6  illustrates an example of a method according to the present disclosure. At  204 , a precursor dose is introduced into a reaction volume. At  206 , the precursor dose is purged from the reaction volume. At  210 , a plasma dose is introduced into the reaction volume using a remote plasma source. At  214 , the plasma dose is optionally purged. 
         [0048]      FIG. 7  illustrates another example of a method according to the present disclosure. At  230 , a precursor dose is introduced into a reaction volume. At  236 , the precursor dose is purged from the reaction volume. At  240 , a reactant dose is introduced into the reaction volume. At  244 , the reactant dose is purged from the reaction volume. At  248 , a post-plasma treatment step is performed using remote plasma. At  252 , the post plasma treatment is optionally purged from the reaction volume. 
         [0049]    For example only, a method based on  FIG. 7  may include a thermal reaction followed by post-plasma treatment including a precursor dose, purge, an NH 3  reactant dose, purge, a remote plasma N 2 /NH 3  or N 2 /H 2  treatment, and then purge. 
         [0050]      FIG. 8  illustrates another example of a method according to the present disclosure. At  270 , a precursor dose is introduced into a reaction volume. At  276 , the precursor dose is purged from the reaction volume. At  280 , a plasma dose step is performed using remote plasma. At  284 , the plasma dose is optionally purged from the reaction volume. At  288 , a post-plasma treatment step is performed using remote plasma. At  292 , the post plasma treatment is optionally purged from the reaction volume. 
         [0051]    For example only, a method based on  FIG. 7  may include two different types of remote plasma gas treatment. The example includes a precursor dose, purge, a remote plasma N 2 /H 2  dose (or He/H 2 ), purge, a remote plasma He/H 2  (or N 2 /H 2 ) and then purge. 
         [0052]    Referring now to  FIGS. 9-10 , the ELK thickness loss, growth rate, film chemical composition, film density, and Cu thermal diffusion barrier test of RPALD TaN process were assessed and compared with iALD and tALD processes. Referring now to  FIG. 9 , an etch test on ELK blanket substrates (k=2.4) showed that the remote plasma source with H 2 /N 2  or NH 3 /N 2  had lower ELK thickness loss by a factor of approximately 5 as compared to the capacitively coupled plasma with Ar/H 2 . 
         [0053]    Referring now to Table 1 below, the RPALD processes described herein are expected to yield high growth rate of 1 A/cycle, almost stoichiometric TaN composition with reduced carbon impurity of 3 at. %, and improved film density of 11.2 g/cm 3 . The high growth rate might be attributed to the enhanced chemisorptions of precursor molecules on hydrogen radicals terminated surface. 
         [0000]    
       
         
               
               
               
               
             
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
                 TABLE 1 
               
             
             
               
                   
                   
               
               
                   
                   
                   
                 Chemical Composition 
               
               
                   
                 Growth Rate 
                 Film Density 
                 (at. %) 
               
             
          
           
               
                 Process 
                 (A/Cycle) 
                 (g/cm 3 ) 
                 Ta 
                 N 
                 C 
                 O 
               
               
                   
               
             
          
           
               
                 iALD 
                 0.4 
                 13 
                 49 
                 26 
                 23 
                 2 
               
               
                 RPALD 
                 1.0 
                 11.2 
                 48 
                 47 
                 3 
                 2 
               
               
                 tALD 
                 0.65 
                 8.8 
                 48 
                 41 
                 9 
                 2 
               
               
                   
               
             
          
         
       
     
         [0054]    Referring now to  FIG. 10 , plasma gas is shown where Cu  100 A film was deposited as a capping layer. The Cu thermal diffusion barrier performance of TaN film was evaluated at 400° C., 30 minutes in an oven under forming gas ambient. RPALD TaN process showed that minimum film thickness for passing the Cu thermal diffusion barrier test was approximately 13 A, which is in the middle of tALD and iALD TaN. 
         [0055]    RP ALD TaN provides the thin and conformal step coverage on small features due to non-directional distribution of radicals. RPALD TaN process with H 2 /N 2  or NH 3 /N 2  achieved the improved film properties such as chemical composition and film density with minimized ELK underlayer damage. 
         [0056]    The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical OR. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. 
         [0057]    In this application, including the definitions below, the term module may be replaced with the term circuit. The term module may refer to, be part of, or include an Application Specific Integrated Circuit (ASIC); a digital, analog, or mixed analog/digital discrete circuit; a digital, analog, or mixed analog/digital integrated circuit; a combinational logic circuit; a field programmable gate array (FPGA); a processor (shared, dedicated, or group) that executes code; memory (shared, dedicated, or group) that stores code executed by a processor; other suitable hardware components that provide the described functionality; or a combination of some or all of the above, such as in a system-on-chip. 
         [0058]    The term code, as used above, may include software, firmware, and/or microcode, and may refer to programs, routines, functions, classes, and/or objects. The term shared processor encompasses a single processor that executes some or all code from multiple modules. The term group processor encompasses a processor that, in combination with additional processors, executes some or all code from one or more modules. The term shared memory encompasses a single memory that stores some or all code from multiple modules. The term group memory encompasses a memory that, in combination with additional memories, stores some or all code from one or more modules. The term memory may be a subset of the term computer-readable medium. The term computer-readable medium does not encompass transitory electrical and electromagnetic signals propagating through a medium, and may therefore be considered tangible and non-transitory. Non-limiting examples of a non-transitory tangible computer readable medium include nonvolatile memory, volatile memory, magnetic storage, and optical storage. 
         [0059]    The apparatuses and methods described in this application may be partially or fully implemented by one or more computer programs executed by one or more processors. The computer programs include processor-executable instructions that are stored on at least one non-transitory tangible computer readable medium. The computer programs may also include and/or rely on stored data.