Patent Publication Number: US-2022238333-A1

Title: Doped or undoped silicon carbide deposition and remote hydrogen plasma exposure for gapfill

Description:
INCORPORATION BY REFERENCE 
     An Application Data Sheet is filed concurrently with this specification as part of the present application. Each application that the present application claims benefit of or priority to as identified in the concurrently filed Application Data Sheet is incorporated by reference herein in their entireties and for all purposes. 
     BACKGROUND 
     Fabrication of devices such as semiconductor devices may involve deposition of various dielectric, conductive, or semiconductive films in recessed features of a substrate. Various techniques for filling such features exist, but as devices shrink and features become smaller, feature fill without voids or seams becomes increasingly challenging. 
     The background provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent that it is described in this background, 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. 
     SUMMARY 
     Provided herein is a method of depositing a doped or undoped silicon carbide (SiC x O y N z ) film in one or more features of a substrate. The method includes depositing a first thickness of the SiC x O y N z  film in the one or more features of the substrate, exposing the SiC x O y N z  film to a remote hydrogen plasma under conditions that increase a size of an opening near a top surface of each of the one or more features, and depositing a second thickness of the SiC x O y N z  film on the first thickness of the SiC x O y N z  film, where x has a value greater than zero, y has a value equal to or greater than zero, and z has a value equal to or greater than zero. 
     In some implementations, the method further includes repeating operations of exposing the SiC x O y N z  film to the remote hydrogen plasma and depositing a new thickness of the SiC x O y N z  film in the one or more features until the one or more features are substantially filled. In some implementations, the conditions of the remote hydrogen plasma include a treatment time, a treatment frequency, a treatment power, and/or remote plasma gas composition, where the treatment time, the treatment frequency, the treatment power, and/or the remote plasma gas composition are controlled so that the size of the opening near the top surface of each of the one or more features is increased more than a size of an opening near a bottom surface of each of the one or more features. The treatment time of exposure to the remote hydrogen plasma may be between about 0.5 seconds and about 120 seconds. The treatment frequency may be 10 Å or less of the SiC x O y N z  film per cycle of depositing the SiC x O y N z  film and exposing the SiC x O y N z  film to remote hydrogen plasma. The remote plasma gas composition of the remote hydrogen plasma may include the remote hydrogen plasma having a concentration between about 10% and about 50% by volume of hydrogen. In some implementations, each of the first thickness and the second thickness is between about 0.5 Å and about 4.5 Å. In some implementations, depositing the first thickness of the SiC x O y N z  film includes flowing one or more silicon-containing precursors into a reaction chamber, and introducing one or more hydrogen radicals generated from a remote plasma source and towards the substrate in the reaction chamber, where the one or more hydrogen radicals react with the one or more silicon-containing precursors to deposit the first thickness of the SiC x O y N z  film. In some implementations, at least 90% of the hydrogen radicals are hydrogen radicals in the ground state. In some implementations, the conditions of the remote hydrogen plasma increase the size of the opening near the top surface of each of the one or more features by at least about 5%. In some implementations, the conditions of the remote hydrogen plasma increase the size of the opening near the top surface of each of the one or more features when an atomic concentration of carbon of the first thickness of the SiC x O y N z  film is between about 10% and about 30%. In some implementations, operations of depositing the first thickness of the SiC x O y N z  film and exposing the SiC x O y N z  film to the remote hydrogen plasma occur without introducing a vacuum break. In some implementations, the method further includes introducing a time interval between depositing the first thickness of the SiC x O y N z  film and exposing the first thickness of the SiC x O y N z  film to remote hydrogen plasma in order to modulate gapfill performance. 
     Another aspect involves an apparatus. The apparatus includes a reaction chamber, a substrate support for supporting a substrate in the reaction chamber, the substrate having one or more features, and a controller. The controller is configured with instructions for performing the following operations: depositing a first thickness of a doped or undoped silicon carbide (SiC x O y N z ) film in the one or more features of the substrate, exposing the SiC x O y N z  film to a remote hydrogen plasma under conditions that increase a size of an opening near a top surface of each of the one or more features, depositing a second thickness of the SiC x O y N z  film on the first thickness of the SiC x O y N z  film, where x has a value greater than zero, y has a value equal to or greater than zero, and z has a value equal to or greater than zero. 
     In some implementations, the controller is further configured with instructions for performing the following operation: repeating operations of exposing the SiC x O y N z  film to the remote hydrogen plasma and depositing a new thickness of the SiC x O y N z  film in the one or more features until the one or more features are substantially filled. In some implementations, the conditions of the remote hydrogen plasma include a treatment time, a treatment frequency, a treatment power, and/or a remote plasma gas composition, where the treatment time, the treatment frequency, the treatment power, and/or remote plasma gas composition are controlled so that the size of the opening near the top surface of each of the one or more features is increased more than a size of an opening near a bottom surface of each of the one or more features. The remote plasma gas composition of the remote hydrogen plasma may include the remote hydrogen plasma having a concentration between about 10% and about 50% by volume of hydrogen. In some implementations, each of the first thickness and the second thickness is equal to or less than about 10 Å. In some implementations, the controller is further configured with instructions for performing the following operation: introducing a time interval between depositing the first thickness of the SiC x O y N z  film and exposing the first thickness of the SiC x O y N z  film to remote hydrogen plasma in order to modulate gapfill performance. 
     These and other aspects are described further below with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a cross-sectional schematic of an example feature of a substrate. 
         FIGS. 2A-2C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using dep-etch-dep processing. 
         FIGS. 3A-3C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using inhibition chemistry. 
         FIG. 4  illustrates a cross-sectional schematic of different gapfill materials in an example substrate according to some implementations. 
         FIGS. 5A-5C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using remote plasma chemical vapor deposition and remote hydrogen plasma exposure operations according to some implementations. 
         FIG. 6  illustrates a schematic diagram of an example plasma processing apparatus with a remote plasma source according to some implementations. 
         FIG. 7  illustrates a schematic diagram of an example plasma processing apparatus with a remote plasma source according to some other implementations. 
         FIG. 8  shows a TEM image of an SiC x O y N z  film deposited in a plurality of features of a substrate according to some implementations. 
         FIG. 9  shows a TEM image of an SiC x O y N z  film deposited in a plurality of features of a substrate according to some implementations. 
     
    
    
     DETAILED DESCRIPTION 
     In the present disclosure, the terms “semiconductor wafer,” “wafer,” “substrate,” “wafer substrate,” and “partially fabricated integrated circuit” are used interchangeably. One of ordinary skill in the art would understand that the term “partially fabricated integrated circuit” can refer to a silicon wafer during any of many stages of integrated circuit fabrication. A wafer or substrate used in the semiconductor device industry typically has a diameter of 200 mm, or 300 mm, or 450 mm. The following detailed description assumes the present disclosure is implemented on a wafer. However, the present disclosure is not so limited. The work piece may be of various shapes, sizes, and materials. In addition to semiconductor wafers, other work pieces that may take advantage of the present disclosure include various articles such as printed circuit boards and the like. 
     Substrates may include “features” or “trenches.” “Features” as used herein may refer to non-planar structures of a substrate, typically a surface being modified in a semiconductor device fabrication operation. Examples of features, which may also be referred to as “negative features” or “recessed features,” include trenches, holes, vias, gaps, recessed regions, and the like. These terms may be used interchangeably in the present disclosure. One example of a feature is a hole or via in a semiconductor substrate or in a layer on the substrate. Another example is a trench in a substrate or layer. A feature typically has an aspect ratio (depth to lateral dimension). A feature may be characterized by one or more of narrow and/or re-entrant openings, constrictions within the feature, and high aspect ratios. A feature having a high aspect ratio can have a depth to lateral dimension aspect ratio equal to or greater than about 10:1, equal to or greater than about 15:1, equal to or greater than about 20:1, equal to or greater than about 25:1, equal to or greater than about 30:1, equal to or greater than about 40:1, equal to or greater than about 50:1, or equal to or greater than about 100:1. In various embodiments, the feature may have an under-layer, such as a barrier layer or adhesion layer. Non-limiting examples of under-layers include dielectric layers and conducting layers, e.g., silicon oxides, silicon nitrides, undoped silicon carbides, oxygen-doped silicon carbides, nitrogen-doped silicon carbides, metal oxides, metal nitrides, metal carbides, and metal layers. 
     Features of a substrate can be of various types. In some embodiments, a feature can have straight sidewalls, positively sloped sidewalls, or negatively sloped sidewalls. In some embodiments, a feature can have sidewall topography or sidewall roughness, which may occur as a result of an etch process to form the feature. In some embodiments, a feature can have a feature opening that is greater at the top of the feature than at the bottom, or a feature can have a feature opening that is greater at the bottom of the feature than at the top. In some embodiments, a feature can be partially filled with material or have one or more under-layers. Gapfill of features such as any of foregoing embodiments can depend on feature type and profile. Semiconductor fabrication processes often include gapfill processes or dielectric gapfill processes. Typically, chemical vapor deposition (CVD) and/or atomic layer deposition (ALD) methods are used to fill features. Conventional techniques, however, often result in formation of undesirable seams or voids within the feature. In some embodiments, the presence of seams and/or voids in gapfill may lead to high resistance, contamination, loss of filled materials, degraded performance, and even device failure. 
     As the aspect ratio of features increases, mass transport limitations of CVD gas phase reactions may cause “bread-loafing” deposition effects that show thicker deposition at top surfaces and thinner deposition at recessed surfaces, which causes the top of a feature opening to close before the feature can be completely filled. Unlike CVD processes, ALD processes use surface-mediated deposition reactions to deposit films on a layer-by-layer basis, and such films are typically conformal. Although ALD can deposit highly conformal films, deposition of films into high aspect ratio features can be challenging. The step coverage and uniformity of film along the sidewall depends on, for example, transport of the deposition precursor, reactant ions and/or radicals, and byproducts. As the lateral dimension of the feature is reduced or the depth of the feature is increased, transport and diffusion of the deposition precursor and/or reactant species becomes increasingly difficult in the feature. Thus, the top of the feature is exposed to more precursor and reactant species and the bottom of the feature is exposed to fewer precursor and reactant species due to diffusion limitations. This can lead to the formation of seams and/or voids in high aspect ratio features. 
       FIG. 1  illustrates a cross-sectional schematic of an example feature of a substrate. A substrate  100  has a feature  101  that is filled using a conventional CVD, plasma-enhanced CVD (PECVD), ALD, or plasma-enhanced ALD (PEALD) technique. A seam  106  forms where gapfill material  102  deposited along sidewalls of the feature  101  meets. If ALD or PEALD techniques are used, the opening at the top of the feature  101  closes and molecular transport becomes progressively difficult, which causes the seam  106  to form near the top of the feature  101  and leave a void  108  in the feature  101 . If CVD or PECVD techniques are used, the gapfill material  102  will tend to build up faster at the edges of the feature  101  than along sidewalls of the feature so that the top of the feature  101  closes off and is “pinched” at the seam  106  before the feature  101  is filled, thereby leaving a void  108  in the feature  101 . 
     In addition to the formation of voids and seams, the film deposited within the feature may have a different and more degraded film quality than the film deposited near the top of the feature. Without being limited by any theory, this may be because the number and distribution of reactant species reaching the bottom of the feature is different from and less than at the top. In some embodiments, film quality can be evaluated by etching the deposited film and observing and comparing the etch rates at the top of the feature, at the bottom of the feature, and at the sidewalls of the feature. 
     To improve gapfill performance in CVD, PECVD, ALD, or PEALD processes, one of many approaches are generally implemented. 
     In some embodiments, the deposition rate for CVD, PECVD, ALD, or PEALD gapfill can be slowed down. Slowing down deposition rate can fine tune the deposition profile in the gapfill structure and improve gapfill performance. For example, more cycles can be performed in ALD or PEALD processes before a feature is closed off. In addition or in the alternative, a longer duration during initial cycles may allow diffusion of precursor and/or reactant species to reach the bottom and sidewalls of the features. However, slowing down the deposition rate to improve gapfill decreases overall throughput and generally is more applicable to low aspect ratio features and/or features with large openings. 
     In some embodiments, dep-etch-dep (deposition, etch, deposition) techniques are employed to fill features. The dep-etch-dep technique involves deposition of gapfill material, followed by etching some of the gapfill material back to open the feature opening, and followed by re-depositing some of the same gapfill material to complete the gapfill or advance the gapfill process.  FIGS. 2A-2C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using dep-etch-dep processing.  FIG. 2A  shows an example of a feature  201  of a substrate  200  where material  202   a  is deposited in the feature  201 . The material  202   a  may be deposited conformally along a top surface, sidewalls, and a bottom surface of the feature  201 . In some embodiments, the material  202   a  may be deposited using ALD or PEALD. A typical ALD cycle may include: (i) dosing that delivers and adsorbs precursor material onto a substrate surface, (ii) purging excess precursor material from the chamber and leaving a self-limited monolayer on the substrate surface, (iii) delivery of reactant material to react with the adsorbed precursor material, and (iv) purging of unreacted reactant material or reaction byproducts from the chamber. The dose step may adsorb precursor material in a self-limiting manner such that once active sites are occupied by the precursor material, little or no additional precursor material will be adsorbed on the substrate surface. The reactant material may likewise react with the precursor material in a self-limiting or adsorption-limiting manner. Purge steps may be optionally performed to remove excess precursor material, reaction byproducts, and/or unreacted reactant material from the chamber, thereby completing an ALD cycle.  FIG. 2B  shows an example of the feature  201  of the substrate  200  where the material  202   a  is etched back. For example, as shown in  FIG. 2B , the material  202   a  can be etched back and result in a tapered profile. Thus, more of the material  202   a  is removed near the top of the feature  201  than at the bottom of the feature  201 . The etch operation performed in  FIG. 2B  reshapes the deposited material  202   a  so that more material can be filled in the feature  201 . When a subsequent deposition operation is performed that deposits more material near the top of the feature  201  than at the bottom of the feature  201 , the feature  201  can be filled with smaller or no voids.  FIG. 2C  shows an example of the feature  201  of the substrate  200  where material  202   b  is deposited in the feature  201 . The material  202   b  includes the material  202   a  from  FIGS. 2A and 2B . As shown in  FIG. 2C , the material  202   b  may substantially fill the feature  201  following deposition and etch operations. Deposition of the material  202   b  may result in formation of a void  203 , but the void  203  may be smaller by interrupting deposition operations with one or more etch operations. While dep-etch-dep techniques may mitigate the formation of voids and/or seams, etch operations during dep-etch-dep may etch underlying materials, which often leads to device instability and possible device failure. Furthermore, dep-etch-dep techniques often involve multiple rounds of dep-etch-dep and/or multiple wafer transfers between deposition and etch chambers, which lowers overall throughput. 
     In some embodiments, inhibition chemistry can be used so that gapfill material grows or otherwise forms in the feature in a topographically different manner. For example, an inhibitor can react with a material and create a passivated surface to inhibit growth. A surface of a substrate can be more passivated in field and upper regions of a feature and less passivated as a distance into the feature increases. That way, deposition at the top of a feature is selectively inhibited and deposition in lower portions of the feature can proceed with less inhibition or without being inhibited. As a result, bottom-up fill is enhanced.  FIGS. 3A-3C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using inhibition chemistry.  FIG. 3A  shows an example of a feature  301  of a substrate  300  where at least a field region and upper regions of the feature  301  are exposed to a reactant that inhibits deposition/growth of gapfill material. The reactant reacts with a material to form a passivated layer  305  on the substrate  300 . By way of an example, nitrogen gas (N 2 ) or ammonia (NH 3 ) may be used to form the passivated layer  305  that is made of a nitride. Gapfill material, such as ALD silicon dioxide (SiO 2 ), nucleates at a slower rate on nitride surfaces. In  FIG. 3B , gapfill material  302   a  is deposited in the feature  301 . The gapfill material  302   a  may be deposited along a top surface, sidewalls, and a bottom surface of the feature  301 . The passivated layer  305  selectively inhibits deposition/growth of the gapfill material  302   a  in the field region and upper regions of the feature  301  so that deposition/growth of the gapfill material  302   a  in other regions of the feature  301  proceeds with less inhibition or without inhibition. In  FIG. 3C , gapfill material  302   b  is deposited to substantially fill the feature  301 . Deposition of the gapfill material  302   b  may result in the formation of a void  303 , but the void  303  may be smaller by virtue of the inhibition chemistry promoting bottom-up filling in the feature  301 . While inhibition chemistry may mitigate the formation of voids and/or seams, inhibition chemistries are limited to certain types of chemistries and processes. In other words, different processes require different inhibition chemistries. Certain inhibition chemistries may not be suitable for limiting deposition/growth of SiC x O y N z  films, or deposition/growth of SiC x O y N z  films using a particular deposition technique (e.g., remote plasma CVD), or deposition/growth of SiC x O y N z  films with desired properties (e.g., high etch selectivity to oxide and nitride). Thus, application of inhibition chemistry in gapfill may be limited to certain chemistries, deposition techniques, and film properties. 
     The present disclosure relates to deposition of doped or undoped silicon carbide film for gapfill using remote plasma CVD and remote plasma exposure. One or more high aspect ratio features are filled or at least substantially filled with doped or undoped silicon carbide gapfill material. In some embodiments, the doped or undoped silicon carbide gapfill material is silicon oxycarbide (SiCO). In some embodiments, the doped or undoped silicon carbide gapfill material is silicon nitricarbide (SiCN). A source gas including hydrogen gas is provided into a remote plasma source that may cause the source gas to dissociate and generate ions and radicals in an excited energy state. After excitation, the radicals in the excited energy state relax to substantially low energy state radicals or ground state radicals in a reaction chamber. One or more silicon-containing precursors are provided in the reaction chamber, where bonds in the one or more silicon-containing precursors are selectively broken by the substantially low energy state radicals or ground state radicals to form the doped or undoped silicon carbide gapfill material in the one or more high aspect ratio features. Gapfill occurs by alternating deposition and treatment operations, where the deposition operation includes depositing a certain thickness of doped or undoped silicon carbide gapfill material by remote plasma CVD and where the treatment operation includes exposing the doped or undoped silicon carbide gapfill material to remote hydrogen plasma. Remote hydrogen plasma treatment conditions are controlled so that a size of an opening near a top surface of each of the high aspect ratio features is increased after treatment. In some instances, the size of the opening near the top surface is increased more than a size of an opening near a bottom surface of each of the high aspect ratio features after treatment. In some embodiments, the remote hydrogen plasma treatment conditions are controlled by controlling treatment time, treatment frequency, treatment power, and/or remote plasma gas composition. Various time intervals can be introduced in between plasma deposition and plasma treatment to modulate the gapfill performance. 
     Silicon carbide films are frequently used in semiconductor devices. As used herein, the term “silicon carbide” includes undoped or doped silicon carbides, such oxygen doped silicon carbide or silicon oxycarbide (SiCO), nitrogen doped silicon carbide or silicon nitricarbide (SiCN), and nitrogen and oxygen doped silicon carbide or silicon oxynitricarbide (SiOCN). For many, doped silicon carbides have at most about 50% atomic of dopant atoms, whether those atoms are oxygen, nitrogen, or atoms of another element. The doping level provides desired film properties. As used herein, reference to “doped or undoped silicon carbide” refers specifically to “SiC x O y N z ,” where x has a value greater than zero, y has a value equal to or greater than zero, and z has a value equal to or greater than zero. 
     Doped or undoped silicon carbide films may be employed as metal diffusion barriers, etch stop layers, hard mask layers, gate spacers for source and drain implants, encapsulation barriers for magnetoresistive random-access memory (MRAM) or resistive random-access memory (RRAM), and hermetic diffusion barriers at air gaps, among other applications. In some embodiments, doped or undoped silicon carbide films may be used as gapfill material in high aspect ratio features of transistor devices. 
       FIG. 4  illustrates a cross-sectional schematic of different gapfill materials in an example substrate according to some implementations. A semiconductor device  400  may include first electrically conductive structures  402  and second electrically conductive structures  404 . In some embodiments, the semiconductor device  400  is a transistor device. Spacers  420  may separate the first electrically conductive structures  402  and the second electrically conductive structures  404 . A first gapfill material forms a first insulating cap layer  412  over the first electrically conductive structures  402 , and a second gapfill material forms a second insulating cap layer  414  over the second electrically conductive structures  404 . The first insulating cap layer  412  may have a different etch selectivity than the second insulating cap layer. For example, the first gapfill material of the first insulating cap layer  412  may have an etch selectivity of at least 7:1 under dry etch or wet etch conditions against the second gapfill material of the second insulating cap layer  414 . The first gapfill material may have excellent electrical properties including high breakdown voltages and low leakage currents. Moreover, the first gapfill material may have a low dielectric constant (low-k), where the effective dielectric constant of the first gapfill material is about 4.0 or lower, about 3.5 or lower, about 3.0 or lower, or about 2.5 or lower. In some embodiments, the first gapfill material is SiCO formed by a remote plasma CVD process of the present disclosure. The second gapfill material may be a nitride or oxide, such as silicon nitride or silicon oxide. In some embodiments, the first electrically conductive structures  402  include source/drain contacts in a transistor device, and the second electrically conductive structures  404  include a gate stack having a gate electrode layer and a gate dielectric layer in the transistor device. Having the first gapfill material be SiCO formed by the remote plasma CVD process of present disclosure not only provides good electrical properties, low dielectric constant, and high etch selectivity against other gapfill materials, but also provides good step coverage and gapfill performance that does not leave a significant seam and/or void. 
     Features of a substrate may be filled or at least substantially filled with doped or undoped silicon carbide gapfill material using a process that involves alternating operations of remote plasma CVD and remote hydrogen plasma exposure. In other words, a certain thickness of doped or undoped silicon carbide gapfill material may be deposited by remote plasma CVD followed by a controlled remote hydrogen plasma exposure, and the steps may be repeated until the features are filled or at least substantially filled. As used herein, substantially filled may refer to having the feature filled to at least 98% by volume. 
       FIG. 5A-5C  are cross-sectional schematic illustrations of a feature of an example substrate undergoing gapfill using remote plasma chemical vapor deposition and remote hydrogen plasma exposure operations according to some implementations. Operations  500   a - 500   c  of a process  500  shown in  FIGS. 5A-5C  may include additional, fewer, or different operations. The operations  500   a - 500   c  of the process  500  shown in  FIGS. 5A-5C  may be performed by any one of the plasma processing apparatuses as described in  FIGS. 6 and 7 . 
     At operation  500   a  of the process  500 , a first thickness of a SiC x O y N z  film  506  is deposited in a feature  504  of a substrate  502 . Though the substrate  502  shows only a single feature  504  in  FIGS. 5A-5C , it will be understood that the substrate  502  may have one or more features  504 . In some embodiments, the SiC x O y N z  film  506  includes silicon oxycarbide (SiCO). The first thickness of the SiC x O y N z  film  506  is deposited by a remote plasma CVD process. The remote plasma CVD process deposits the first thickness of the SiC x O y N z  film  506  on the surface of the substrate  502  under relatively mild conditions adjacent to the substrate  502 . 
     Depositing the first thickness of the SiC x O y N z  film  506  includes flowing one or more silicon-containing precursors into a reaction chamber and introducing one or more hydrogen radicals generated from a remote plasma source towards the substrate  502  in the reaction chamber, where the one or more hydrogen radicals react with the one or more silicon-containing precursors to deposit the first thickness of the SiC x O y N z  film  506 . The one or more silicon-containing precursors can include a silicon-containing precursor with one or more silicon-hydrogen (Si—H) bonds and/or silicon-silicon (Si—Si) bonds. In some embodiments, the silicon-containing precursor can have one or more silicon-carbon (Si—C) bonds. In some embodiments, the silicon-containing precursor can have one or more silicon-oxygen (Si—O) bonds. In some embodiments, the silicon-containing precursor can have one or more silicon-nitrogen (Si—N) bonds. Examples of silicon-containing precursors are discussed in further detail below. 
     During the deposition process, the Si—H bonds and/or Si—Si bonds are broken and serve as reactive sites for forming bonds between the silicon-containing precursors in the deposited SiC x O y N z  film  506 . The broken bonds can also serve as sites for cross-linking during thermal processing conducted during or after deposition. Bonding at the reactive sites and cross-linking can form a primary backbone or matrix collectively in the resulting SiC x O y N z  film  506 . In some embodiments, the relatively mild conditions can preserve or substantially preserve Si—C bonds and, if present, Si—O bonds and Si—N bonds in the as-deposited layer of the SiC x O y N z  film  506 . Accordingly, the reaction conditions adjacent to the substrate  502  provide for the selective breaking of Si—H and/or Si—Si bonds, e.g., extracting hydrogen from the broken Si—H bonds, but the reaction conditions do not provide for extracting oxygen from Si—O bonds, nitrogen from Si—N bonds, or carbon from Si—C bonds. However, introduction of a co-reactant such as oxygen may extract carbon from Si—C bonds. Generally, the described reaction conditions exist at the exposed face of the substrate  502  (the face where the SiC x O y N z  film  506  is deposited). They may further exist at some distance above the substrate  502 , e.g., about 0.5 micrometers to about 150 millimeters above the substrate  502 . In effect, activation of the silicon-containing precursors can happen in the gas phase at a substantial distance above the substrate  502 . Typically, the pertinent reaction conditions will be uniform or substantially uniform over the entire exposed face of the substrate  502 , although certain applications may permit some variation. 
     In addition to the silicon-containing precursors, the environment adjacent to the substrate  502  includes one or more radicals that are in a substantially low energy state or ground state. The one or more radicals can include one or more hydrogen radicals, which may also be referred to as hydrogen atom radicals or hydrogen radical species. In some embodiments, all, or substantially all, or a substantial fraction of the hydrogen radicals adjacent to the substrate  502  are in the ground state, e.g., at least about 90% or 95% of the hydrogen radicals adjacent to the substrate  502  are in the ground state. As an example, hydrogen gas (Hz) may be provided in an inert carrier gas such as helium in a remote plasma source. Hydrogen radicals are generated in the remote plasma source and introduced into the reaction chamber. Once generated in the remote plasma source, the hydrogen radicals are in an excited energy state. For example, hydrogen in an excited energy state can have an energy of at least 10.2 eV (first excited state). Excited hydrogen radicals may cause unselective decomposition of a silicon-containing precursor, easily breaking Si—H, Si—Si, Si—N, Si—O, and Si—C bonds, which can alter the composition or physical or electrical characteristics of the SiC x O y N z  film  506 . This can lead to films with high dielectric constants, low breakdown voltages, high leakage currents, and poor conformality. Process conditions are controlled so that the hydrogen radicals lose their energy or relax when they encounter the substrate  502  without recombining. The process conditions are controlled so that the hydrogen radicals are in a substantially low energy state or ground state at the environment adjacent to the substrate  502 , where hydrogen radicals in a substantially low energy state or ground state can be capable of selectively breaking Si—H and Si—Si bonds while generally preserving Si—O, Si—N, and Si—C bonds. For example, the plasma processing apparatus or associated components may be designed so that a residence time of hydrogen radicals diffusing from the remote plasma source to the substrate  502  is greater than the energetic relaxation time of an excited hydrogen atom radical. The plasma processing apparatuses shown in  FIGS. 6 and 7  may be configured to produce a mild state in which a substantial fraction of the hydrogen radicals in the environment adjacent to the substrate  502  are in a ground state. 
     The source gas for the hydrogen radicals may be delivered with other species, including carrier gas. The silicon-containing precursors may be delivered with other species, including carrier gas. Example carrier gases include but are not limited to argon (Ar), helium (He), neon (Ne), krypton (Kr), and xenon (Xe). The concentration of carrier gas can be substantially greater than the concentration of the source gas. As used herein, “substantially greater” with respect to the concentration of carrier gas relative to source gas can refer to a percentage by volume that is at least three times greater. By way of an example, hydrogen gas may be provided in a helium carrier gas at a concentration of about 1-50% hydrogen. The presence of the carrier gas can contribute to increased ionization of the source gas and reduced recombination. Though lower pressure typically facilitates increased ionization of the source gas and reduced recombination, the presence of the carrier gas can serve the same effect. That way, even at a higher pressure, a substantial fraction of radicals may be generated with minimal recombination when a carrier gas such as helium is flowed with the source gas. Higher pressure in the reaction chamber during deposition may improve the conformality of the SiC x O y N z  film  506 . Higher pressure in the reaction chamber may correspond to a pressure greater than about 3 Torr or greater than about 5 Torr, such as about 7 Torr. 
     In some embodiments, the silicon-containing precursors are introduced as a mixture having major and minor species. The minor species may not contribute significantly to the composition or structural features of the SiC x O y N z  film  506 . In some embodiments, the silicon-containing precursors provide essentially all of the mass of the deposited SiC x O y N z  film  506 , with small amounts of hydrogen or other element from the remote plasma providing less than about 5 atomic percent or less than about 2 atomic percent. In some embodiments, the deposition reaction includes a co-reactant other than the silicon-containing precursors and the hydrogen radicals, which may or may not contribute to the composition of the deposited SiC x O y N z  film  506 . Thus, the co-reactant may tune the composition of the first thickness of the SiC x O y N z  film  506 . Examples of co-reactants include carbon dioxide (CO 2 ), carbon monoxide (CO), water (H 2 O), methanol (CH 3 OH), oxygen (O 2 ), ozone (O 3 ), nitrogen (N 2 ), nitrous oxide (N 2 O), ammonia (NH 3 ), diazene (N 2 H 2 ), methane (CH 4 ), ethane (C 2 H 6 ), acetylene (C 2 H 2 ), ethylene (C 2 H 4 ), diborane (B 2 H 6 ), and combinations thereof. Such materials may be used as nitriding agents, oxidizers, reductants, etc. Depending on the choice of the co-reactant, the co-reactant may increase or decrease the carbon, oxygen, or nitrogen content of the SiC x O y N z  film  506 . In some embodiments, the co-reactant may be introduced into the reaction chamber along the same flow path as the hydrogen radicals. The co-reactant may be introduced upstream of the silicon-containing precursors, where the co-reactant may be at least partially converted to radicals and/or ions. In some embodiments, the co-reactant may be introduced into the reaction chamber along the same flow path as the silicon-containing precursors. In such instances, the co-reactant may be introduced downstream of the hydrogen radicals, typically without direct exposure to plasma. In some embodiments, the co-reactant may be present in the process gases at about 0.05% or less by mass, or at about 0.01% or less by mass, or at about 0.001% or less by mass. In some embodiments, the co-reactant may be present at higher concentrations, such as about 2% or less or about 0.1% or less by mass. In some embodiments, the co-reactant is present at even higher concentrations, such as about 10% or more or about 20% or more by mass. In some embodiments, bonds in a co-reactant may be selectively broken by the hydrogen radicals to activate the co-reactant. 
     Process conditions for depositing the first thickness of the SiC x O y N z  film  506  can be controlled. In some embodiments, a temperature in the environment adjacent to the substrate  502  can be largely controlled by the temperature of a pedestal on which the substrate  502  is supported during deposition of the SiC x O y N z  film  506 . In some embodiments, the operating temperature can be between about 50° C. and about 500° C. or between about 250° C. and about 400° C. Increasing temperature can lead to increased cross-linking on the substrate surface. In some embodiments, a pressure in the reaction chamber can be controlled to facilitate production of reactive radicals. In some embodiments, chamber pressure can be about 35 Torr or lower, between about 10 Torr and about 20 Torr in some applications, or between about 0.2 Torr and about 5 Torr in some other applications. 
     The silicon-containing precursors used in forming the SiC x O y N z  film  506  may each contain at least one Si—H and/or at least one Si—Si bond. The silicon-containing precursors may optionally each contain at least one Si—O bond, Si—N bond, and/or Si—C bond. In some embodiments, the silicon-containing precursors each do not contain O—C or N—C bonds; e.g., the precursors contain no alkoxy (—O—R), where R is an organic group such as a hydrocarbon group, or amine (—NR 1 R 2 ), where R 1  and R 2  are independently hydrogen or organic groups. Without being limited by any theory, it is believed that such groups may impart high sticking coefficients to the precursors or fragments on which they reside. 
     The silicon-containing precursors employed in the deposition reaction may be limited to a particular chemical class or mixtures of the chemical classes. In some embodiments, the silicon-containing precursors include siloxanes. The siloxanes may be cyclic, three-dimensional or caged, or linear. In some embodiments, the silicon-containing precursors include alkyl silanes or other hydrocarbon-substituted silanes. For example, the silicon-containing precursor can include an alkylcarbosilane. In some embodiments, the silicon-containing precursors include alkoxy silanes. In some embodiments, the silicon-containing precursors include silazanes. The silazanes may be cyclic or linear. Specific examples of the chemical classes of silicon-containing precursors are described in U.S. patent application Ser. No. 14/616,435 to Varadarajan et al., filed Feb. 6, 2015, titled “CONFORMAL DEPOSITION OF SILICON CARBIDE FILMS,” which is incorporated herein by reference in its entirety and for all purposes. 
     In depositing the SiC x O y N z  film  506 , multiple silicon-containing precursors can be present in the process gas, where some of the silicon-containing precursors are different. For example, a siloxane and an alkyl silane can be used together, or a siloxane and an alkoxy silane can be used together. The relative proportions of the individual precursors can be chosen based on the chemical structures of the precursors chosen and the application of the resulting SiC x O y N z  film  506 . For example, an amount of siloxane can be greater than an amount of silane in molar percentages to produce a more porous film. 
     In some embodiments when depositing silicon oxycarbide films, the silicon-containing precursors may include siloxanes such as cyclic siloxanes or linear siloxanes. In some embodiments when depositing silicon oxycarbide films, the silicon-containing precursors may include alkyl silanes. An oxygen-containing co-reactant may be introduced to react with the alkyl silanes. 
     The silicon-containing precursors may be chosen to produce a highly conformal SiC x O y N z  film  506 . Conformality may be calculated by comparing the average thickness of a deposited film on a bottom, sidewall, or top of a feature  504  to the average thickness of a deposited film on a bottom, sidewall, or top of a feature  504 . For example, conformality may be calculated by dividing the average thickness of the deposited film on the sidewall by the average thickness of the deposited film at the top of the feature  504  and multiplying it by  100  to obtain a percentage. It is believed that silicon-containing precursors having low sticking coefficients are capable of producing highly conformal films. “Sticking coefficient” is a term used to describe the ratio of the number of adsorbate species (e.g., fragments or molecules) that adsorb/stick to a surface compared to the total number of species that impinge upon that surface during the same period of time. The symbol S c  is sometimes used to refer to the sticking coefficient. The value of Se is between 0 (meaning that none of the species stick) and  1  (meaning that all of the impinging species stick). Various factors affect the sticking coefficient including the type of impinging species, surface temperature, surface coverage, structural details of the surface, and the kinetic energy of the impinging species. 
     At operation  500   a  of the process  500 , the first thickness of the SiC x O y N z  film  506  may have a conformality of at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 98%. The first thickness of the SiC x O y N z  film  506  may be equal to or less than about 10 Å, or may be equal to or less than about 5 Å. In some embodiments, the first thickness of the SiC x O y N z  film  506  may be between about 0.5 Å and about 5 Å, or between about 0.5 Å and about 4.5 Å. 
     The first thickness of the SiC x O y N z  film  506  can be deposited according to a predetermined deposition time to achieve a desired thickness. In some embodiments, the deposition time can be between about 1 second and about 200 seconds, or between about 5 seconds and about 100 seconds. The first thickness can be controlled to enable sufficient penetration of a subsequent remote plasma treatment to densify and shrink the first thickness of the SiC x O y N z  film  506 . Moreover, the first thickness can be controlled according to a desired treatment frequency of the subsequent remote plasma treatment operations. 
     The first thickness of the SiC x O y N z  film  506  is deposited in the feature  504  of the substrate  502 , where the feature  504  can take the shape of a trench, recess, or hole. The feature  504  can have a depth to lateral dimension aspect ratio of at least about 5:1, at least about 10:1, at least about 15:1, at least about 20:1, at least about 30:1, at least about 40:1, at least about 50:1, or at least about 100:1. For example, features having a high aspect ratio may be at least 10:1. The lateral dimension may be a width or diameter at the top of the feature  504 . In some embodiments, the lateral dimension of the feature  504  may be less than about 200 nm, less than about 100 nm, between about 2 nm and about 100 nm, or between about 2 nm and about 50 nm. In some embodiments, the depth of the feature  504  may be between about 0.1 μm and about 100 μm, between about 0.5 μm and about 50 μm, between about 0.5 μm and about 25 μm, or between about 1 μm and about 25 μm. 
     The composition of the SiC x O y N z  film  506  may affect an amount that the first thickness of the SiC x O y N z  film  506  shrinks in a subsequent remote plasma exposure operation. In some implementations, the composition of the SiC x O y N z  film  506  can have an atomic concentration of carbon between about 10% and about 40% or between about 10% and about 30%. In some implementations, the atomic concentration of carbon may be controlled by adjusting deposition parameters such as choice of precursors, flow rate of the precursors, choice of co-reactant, and flow rate of a co-reactant such as oxygen. For example, increasing the presence oxygen in the deposition of the SiC x O y N z  film  506  can extract more carbon from the SiC x O y N z  film  506 . In some implementations, the atomic concentration of carbon in the SiC x O y N z  film  506  is controlled during operation  500   a  so that conditions of remote hydrogen plasma exposure increase a size of an opening near a top surface of the feature  504  during operation  500   b.    
     At operation  500   b  of the process  500 , the SiC x O y N z  film  506  is exposed to a remote hydrogen plasma under conditions that increase a size of an opening near a top surface of the feature  504 . The remote hydrogen plasma is used to treat the first thickness of the SiC x O y N z  film  506  so that the first thickness of the SiC x O y N z  film  506  shrinks near the top surface of the feature  504 . How much the first thickness of the SiC x O y N z  film  506  shrinks near the top surface of the feature  504  can depend on the first thickness and composition of the SiC x O y N z  film  506 . How much the first thickness of the SiC x O y N z  film  506  shrinks near the top surface of the feature  504  can also depend on the remote plasma conditions. 
     A remote plasma source for generating radicals of a source gas during deposition may also serve to generate radicals of the source gas during treatment to shrink the first thickness of the SiC x O y N z  film  506  near the top surface of the feature  504 . Accordingly, SiC x O y N z  film deposition may occur in the same reaction chamber as SiC x O y N z  film treatment. This allows alternating deposition and treatment cycles to be performed in the same tool. As a result, depositing the first thickness and exposing the first thickness of the SiC x O y N z  film  506  to remote hydrogen plasma can occur without introducing a vacuum break (e.g., air break). A vacuum break can reduce throughput and introduce oxidation in the substrate  502 , which can lead to higher electrical resistance and decreased performance. 
     Exposing the first thickness of the SiC x O y N z  film  506  to the remote hydrogen plasma occurs without delivery of silicon-containing precursors. In other words, while depositing the first thickness of the SiC x O y N z  film  506  involves flowing one or more silicon-containing precursors to react with hydrogen radicals of the remote hydrogen plasma, exposing the first thickness of the SiC x O y N z  film  506  ceases the flow of silicon-containing precursors. A source gas including hydrogen gas can be provided with an inert carrier gas such as helium. In some embodiments, the source gas can include hydrogen, nitrogen, N—H containing species such as NH 3 , oxygen, oxygen-containing species such as H 2 O, CO 2 , or N 2 O, or combinations thereof. The source gas is provided in the remote plasma source, where hydrogen radicals are generated in the remote plasma source and introduced into the reaction chamber and towards the substrate  502 . Once generated in the remote plasma source, the hydrogen radicals are in an excited energy state. The hydrogen radicals lose their energy or relax when they encounter the substrate  502  without recombining. The first thickness of the SiC x O y N z  film  506  is exposed to a remote hydrogen plasma such that at least a substantial fraction of the hydrogen radicals are in a substantially low energy state or ground state. In some embodiments, at least 90% of the radicals of the source gas are hydrogen radicals in the ground state. Such hydrogen radicals of the remote hydrogen plasma are used to densify and shrink the first thickness of the SiC x O y N z  film  506  near the top surface of the feature  504 . Due at least in part to the minimal concentration of ions and the low energy state of the hydrogen radicals, exposing the SiC x O y N z  film  506  to the remote hydrogen plasma does not generally cause damage to underlying layers of the substrate  502 . 
     The thickness of the SiC x O y N z  film  506  can be deposited according to a treatment frequency of each remote hydrogen plasma treatment. Thus, how much SiC x O y N z  film  506  is deposited per deposition-treatment cycle is controlled to improve gapfill performance. At operation  500   a , the first thickness of the SiC x O y N z  film  506  is equal to or less than about 10 Å, equal to or less than about 5 Å, or between about 0.5 Å and about 4.5 Å. Accordingly, a thickness equal to or less than about 10 Å, equal to or less than about 5 Å, or between about 0.5 Å and about 4.5 Å of SiC x O y N z  film  506  is deposited per deposition-treatment cycle. A higher treatment frequency corresponds to smaller thicknesses of SiC x O y N z  film  506  deposited per cycle, where a higher treatment frequency may provide better gapfill performance. 
     The composition of the SiC x O y N z  film  506  can be deposited so that the remote hydrogen plasma treatment has a greater effect on shrinking the first thickness of the SiC x O y N z  film  506 . Specifically, an atomic concentration of carbon in the SiC x O y N z  film  506  can be tuned at operation  500   a , where the atomic concentration of carbon is between about 10% and about 40% or between about 10% and about 30%. In some implementations, the increase in the size of the opening near the top surface of the feature  504  is greater when the atomic carbon concentration in the SiC x O y N z  film  506  is lower. Where the atomic concentration of carbon is controlled, the size of the opening near the top surface of the feature  504  may be increased using the conditions of the remote hydrogen plasma. This can improve gapfill performance. 
     The conditions of the remote hydrogen plasma can be controlled to preferentially treat the first thickness of the SiC x O y N z  film  506  near the top surface than near a bottom surface of the feature  504 . The first thickness of the SiC x O y N z  film  506  near the top surface of the feature  504  may be exposed to more hydrogen radicals of the remote hydrogen plasma than near the bottom surface. In some embodiments, treatment time and/or treatment frequency may be controlled so that diffusion or transport of the hydrogen radicals of the remote hydrogen plasma towards the bottom surface of the feature  504  is limited. For example, shorter treatment times may limit diffusion/transport of the hydrogen radicals from reaching the bottom surface of the feature  504 . In some embodiments, the treatment time of exposure to the remote hydrogen plasma is between about 0.5 seconds and about 120 seconds, between about 1 second and about 30 seconds, between about 2 seconds and about 20 seconds, or between about 5 seconds and about 15 seconds. In some embodiments, the treatment time of exposure to the remote hydrogen plasma is about 10 seconds. It will be understood that the treatment time may vary depending on the aspect ratio of the feature  504 , where the treatment time is long enough to densify and shrink the first thickness of the SiC x O y N z  film  506  but short enough to limit diffusion and transport of hydrogen radicals to the bottom surface of the feature  504 . 
     The conditions of the remote hydrogen plasma can be controlled to increase the size of the opening near the top surface of the feature  504 . In some embodiments, the size of the opening near the top surface of the feature  504  is increased more than a size of an opening near the bottom surface of the feature  504 . Exposure to the remote hydrogen plasma can densify the SiC x O y N z  film  506  by extracting hydrogen and promoting cross-linking so that more Si—O—Si and Si—C—Si bonds may form. Moreover, exposure to the remote hydrogen plasma can shrink the thickness of the SiC x O y N z  film  506  under suitable conditions. In some embodiments, a treatment power can be controlled to facilitate densifying and shrinking the thickness of the SiC x O y N z  film  506 . In some embodiments, RF power of an inductively-coupled plasma can be tuned to control treatment power, where the RF power can be between about 300 Watts and 10 Kilowatts, between about 1 Kilowatt and about 8 Kilowatts, or between about 2 Kilowatts and about 6 Kilowatts. The RF power applied to the remote plasma source during treatment can be adjusted to increase generation of hydrogen radicals of the source gas. In some embodiments, the treatment power can be correlated at least in part with remote plasma gas composition. The remote plasma gas composition can include a concentration of source gas relative to carrier gas, where a greater concentration of source gas contributes to increased generation of radicals, thereby leading to a higher treatment power. In some embodiments, a concentration of a source gas (e.g., hydrogen gas) is at least 10% by volume with a balance of inert carrier gas, at least 15% by volume with a balance of inert carrier gas, at least 20% by volume with a balance of inert carrier gas, at least 25% by volume with a balance of inert carrier gas, between about 10% and about 50% by volume with a balance of inert carrier gas, or between about 10% and about 30% by volume with a balance of inert carrier gas. Specifically, a gas mixture can include hydrogen gas with a balance of an inert carrier gas such as helium, where the gas mixture includes at least 10% by volume hydrogen gas with the balance of helium, at least 15% by volume hydrogen gas with the balance of helium, at least 20% by volume hydrogen gas with the balance of helium, at least 25% by volume hydrogen gas with the balance of helium, between about 10% and about 50% by volume hydrogen gas with the balance of helium, or between about 10% and about 30% by volume hydrogen gas with the balance of helium. In contrast, typical gas mixtures include hydrogen gas at a concentration of 1-10% by volume with a balance of helium. Treatment power and remote plasma gas composition may be adjusted depending on the composition of the SiC x O y N z  film  506 . In some embodiments, treatment power may be reduced and/or hydrogen source gas concentration may be reduced in the remote hydrogen plasma treatment and still achieve an increase in the size of the opening near the top surface of the feature  504  where an atomic concentration of carbon in the SiC x O y N z  film  506  is reduced. 
     The size of the opening near the top surface of the feature  504  can be measured using a lateral distance (e.g., diameter) along the top surface of the feature  504 . Specifically, the size of the opening can be measured by a distance between opposite corners of the top surface of the feature  504  minus the thickness of the SiC x O y N z  film  506  at the corners of the top surface of the feature  504 . In some embodiments, the size of the opening near the top surface of the feature  504  after operation  500   b  can be increased by a percentage amount that is at least about 1%, at least about 5%, at least about 10%, at least about 20%, at least about 50%, at least about 100%, between about 1% and about 100%, between about 5% and about 100%, between about 1% and about 50%, or between about 5% and about 50%. By way of an example, the size of the opening near the top surface of the feature  504  can increase from 20 nm to an amount greater than 30 nm after operation  500   b , which represents an increase of at least 50%. 
     In some embodiments, the size of the opening near the top surface of the feature  504  is increased more than the size of the opening near the bottom surface of the feature  504 . The size of the opening near the bottom surface of the feature  504  can be measured using a lateral distance (e.g., diameter) along the bottom surface of the feature  504 . Specifically, the size of the opening can be measured by a distance between opposite corners of the bottom surface of the feature  504  minus the thickness of the SiC x O y N z  film  506  at the corners of the bottom surface of the feature  504 . The bottom surface of the feature  504  refers to the lowest exposed surface as the feature  504  is filled by the SiC x O y N z  film  506 . After operation  500   b , the size of the opening near the bottom surface of the feature  504  does not increase or increases by an amount less than the opening near the top surface of the feature  504 . 
     In some embodiments, the conditions of the remote hydrogen plasma can be controlled so that the SiC x O y N z  film  506  shrinks more at a top opening than at a bottom opening. The hydrogen radicals and/or ions of the remote plasma can be isotropic or substantially isotropic in nature so that treatment occurs preferentially at the top opening than at the bottom opening of the feature  504 . Treatment frequency, treatment time, treatment power, and/or remote plasma gas composition can be controlled so that the size of the opening near the top surface of the feature  504  is increased more than the opening near the bottom surface of the feature  504 . Composition and thickness of the SiC x O y N z  film  506  can be controlled so that the size of the opening near the top surface of the feature  504  is increased more than the opening near the bottom surface of the feature  504 . 
     It will be understood that parameters other than treatment frequency, treatment time, treatment power, remote plasma gas composition, composition of the SiC x O y N z  film  506 , and thickness of the SiC x O y N z  film  506  can be controlled to shrink the SiC x O y N z  film  506  at the top opening. Other tunable parameters include but are not limited to timing, gas composition, gas flow rates, chamber pressure, chamber temperature, substrate temperature, time interval between deposition and plasma treatment, and substrate position. These parameters can be tuned during exposure to the remote hydrogen plasma to influence the characteristics of the remote plasma, which can affect the size of the opening near the top surface of the feature  504 . In some embodiments, the chamber pressure can be between about 0.2 Torr and about 5 Torr, or between about 1 Torr and about 3 Torr. In some embodiments, the chamber pressure can be greater than 3 Torr or greater than 5 Torr, where other process conditions (e.g., inert carrier gas) cause sufficient ionization and reduced residence times. In some embodiments, the source gas can be flowed with one or more co-reactants, such as CO 2 , CO, H 2 O, CH 3 OH, O 2 , O 3 , N 2 , N 2 O, NH 3 , N 2 H 2 , CH 4 , C 2 H 6 , C 2 H 2 , C 2 H 4 , B 2 H 6 , or combinations thereof. Depending on the choice of the co-reactants, the one or more co-reactants can increase or decrease oxygen, nitrogen, or carbon content of the SiC x O y N z  film  506 . In some embodiments, the one or more co-reactants may include CO 2 , O 2 , N 2 , NH 3 , or combinations thereof. The presence of oxygen gas or oxygen radicals tends to extract carbon from Si—C bonds, thereby converting carbide to oxide. 
     In some embodiments, a time interval may be introduced between depositing the first thickness of the SiC x O y N z  film  506  at operation  500   a  and exposing the first thickness of the SiC x O y N z  film  506  to remote hydrogen plasma treatment at operation  500   b . During the time interval, plasma is turned off and some gases continue to flow into the reaction chamber. In some embodiments, the gases may include the silicon-containing precursors flowed during deposition at operation  500   a . During the time interval where plasma is turned off, residue deposition does not occur that may adversely affect gapfill performance. In some implementations, the time interval may be between about 1 second and about 30 seconds, such as about 5 seconds, about 10 seconds, or about 20 seconds. 
     At operation  500   c  of the process  500 , a second thickness of the SiC x O y N z  film  506  is deposited in the feature  504  of the substrate  502 . The second thickness can be deposited on or over the first thickness of the SiC x O y N z  film  506 . Aspects of depositing the second thickness of the SiC x O y N z  film  506  can be identical or at least similar to aspects of depositing the first thickness of the SiC x O y N z  film  506 . Specifically, where depositing the first thickness includes flowing one or more silicon-containing precursors into the reaction chamber and introducing hydrogen radicals generated from the remote plasma source to react with the one or more silicon-containing precursors during the operation  500   a , depositing the second thickness includes repeating the aforementioned operation  500   a  in operation  500   c . Deposition time, film thickness, chamber pressure, chamber temperature, substrate temperature, RF power levels, gas flow, gas composition, and other parameters in operation  500   c  may be the same or different than in operation  500   a . The first thickness of the SiC x O y N z  film  506  is deposited by a remote plasma CVD process, and the second thickness of the SiC x O y N z  film  506  is deposited by a remote plasma CVD process, where the remote plasma CVD process deposits the second thickness of the SiC x O y N z  film  506  on the surface of the substrate  502  under relatively mild conditions adjacent to the substrate  502 . Such relatively mild conditions are described in operation  500   a.    
     In some embodiments, the second thickness of the SiC x O y N z  film  506  may have a conformality of at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, or at least about 98%. The second thickness of the SiC x O y N z  film  506  may be equal to or less than about 10 Å, or equal to or less than about 5 Å. In some embodiments, the second thickness of the SiC x O y N z  film  506  may be between about 0.5 Å and about 5 Å, or between about 0.5 Å and about 4.5 Å. 
     Deposition of the second thickness of the SiC x O y N z  film  506  may occur in the same reaction chamber as treatment of the SiC x O y N z  film  506  and deposition of the first thickness of the SiC x O y N z  film  506 . As a result, depositing the second thickness of the SiC x O y N z  film  506  can occur without introducing a vacuum break (e.g., air break) between operations. 
     The operation  500   c  of the process  500  may further include repeating operations of  500   b  and  500   a  until the feature  504  is filled or substantially filled. As used herein, “substantially filled” with respect to filling the feature  504  can refer to having the SiC x O y N z  film  506  occupy at least 98% of a volume the feature  504 . Seams and/or voids  508  may form when the feature  504  is substantially filled with the SiC x O y N z  film  506 . However, deposition by remote plasma CVD and remote hydrogen plasma exposure as described in the present disclosure can eliminate formation of seams and/or voids  508  or at least minimize the sizes of seams and/or voids  508 . 
     Repeating operations of  500   b  and  500   a  in operation  500   c  can include repeating: (i) exposing the SiC x O y N z  film  506  to remote hydrogen plasma so that a size of an opening at the top surface of the feature  504  is increased and (ii) depositing a new thickness of the SiC x O y N z  film  506  in the feature  504 . In some embodiments, treatment frequency, treatment time, treatment power, and/or remote plasma gas composition are identical in operation  500   c  to the treatment frequency, treatment time, treatment power, and/or remote plasma gas composition in operations  500   b  and  500   a . For example, a treatment frequency of 5 Å or less per deposition-treatment cycle, a treatment time of between about 0.5 seconds and 120 seconds, a treatment power of an applied RF power between about 1 Kilowatt and about 8 Kilowatts, and a remote plasma gas composition having a concentration between about 10% and about 50% by volume of hydrogen with a balance of helium can be provided until the feature  504  is filled or at least substantially filled. The conditions of the remote hydrogen plasma during repeated operations  500   b  in operation  500   c  are controlled so that the size of the opening near the top surface of the feature  504  is increased. In some embodiments, the size of the opening near the top surface of the feature  504  is increased more than the opening near the bottom surface of the feature  504  when repeating operations  500   b  in operation  500   c . Gapfill is completed when one of the repeated operations  500   a  in operation  500   c  closes off the opening of the feature  504 . 
     In some embodiments, a time interval may be introduced between depositing the second thickness of the SiC x O y N z  film  506  at operation  500   c  and repeating operation  500   b  (i.e., plasma treatment). During the time interval, plasma is turned off and some gases continue to flow into the reaction chamber. In some embodiments, the gases may include the hydrogen gas, inert carrier gas, and/or co-reactant gas flowed during plasma treatment at operation  500   b . During the time interval where plasma is turned off, residue deposition does not occur that may adversely affect gapfill performance. In some implementations, the time interval may be between about 1 second and about 30 seconds, such as about 5 seconds, about 10 seconds, or about 20 seconds. Generally speaking, various time intervals may occur between plasma deposition and plasma treatment operations to modulate gapfill performance. This means that the time intervals may occur in a transition from deposition to plasma treatment, and/or in a transition from plasma treatment back to deposition. 
     In some embodiments, parameters of treatment frequency, treatment time, treatment power, and/or remote plasma gas composition may be adjusted depending on the geometry of the feature  504 . Depending on an aspect ratio of the feature  504 , the treatment frequency, treatment time, treatment power, and/or remote plasma gas composition may vary. The treatment frequency, for example, can be flexibly tuned based on an incoming feature geometry to reshape the filling of the feature  504  and improve gapfill performance. That way, how much thickness of the SiC x O y N z  film  506  is deposited per deposition-treatment cycle can be tuned to minimize formation of seams and/or voids  508  while maintaining reasonable throughput. 
     The SiC x O y N z  film  506  deposited by remote plasma CVD in the present disclosure has high etch selectivity to both oxide and nitride materials, where the SiC x O y N z  film  506  has an etch selectivity of at least 7:1 under dry etch or wet etch conditions against oxide and nitride materials. The SiC x O y N z  film  506  may have excellent electrical properties including high breakdown voltages and low leakage currents. In addition, the SiC x O y N z  film  506  may have a low dielectric constant (low-k), where the effective dielectric constant of the SiC x O y N z  film  506  is about 4.0 or lower, about 3.5 or lower, about 3.0 or lower, or about 2.5 or lower. 
     One aspect of the disclosure is an apparatus configured to accomplish the methods described herein. A suitable apparatus includes hardware for accomplishing the process operations and a system controller having instructions for controlling process operations in accordance with the present disclosure. In some embodiments, the apparatus for performing the aforementioned process operations can include a remote plasma source. A remote plasma source provides mild reaction conditions in comparison to a direct plasma. An example of a suitable remote plasma apparatus is described in U.S. patent application Ser. No. 14/062,648 to Varadarajan et al., filed Oct. 24, 2013, titled “GROUND STATE HYDROGEN RADICAL SOURCES FOR CHEMICAL VAPOR DEPOSITION OF SILICON-CARBON-CONTAINING FILMS,” which is incorporated herein by reference in its entirety and for all purposes. 
       FIG. 6  presents a schematic diagram of a remote plasma apparatus according to certain embodiments. The device  600  includes a reaction chamber  610  with a showerhead  620 . Inside the reaction chamber  610 , a substrate  630  rests on a stage or pedestal  635 . In some embodiments, the pedestal  635  can be fitted with a heating/cooling element. A controller  640  may be connected to the components of the device  600  to control the operation of the device  600 . 
     For example, the controller  640  may contain instructions for controlling process conditions for the operations of the device  600 , such as the temperature process conditions and/or the pressure process conditions. In some embodiments, the controller  640  may contain instructions for controlling the flow rates of precursor gas, co-reactant gas, source gas, and carrier gas. The controller  640  may contain instructions for controlling the treatment frequency, treatment time, treatment power, and remote plasma gas composition of remote hydrogen plasma. A more detailed description of the controller  640  is provided below. 
     During operation, gases or gas mixtures are introduced into the reaction chamber  610  via one or more gas inlets coupled to the reaction chamber  610 . In some embodiments, two or more gas inlets are coupled to the reaction chamber  610 . A first gas inlet  655  can be coupled to the reaction chamber  610  and connected to a vessel  650 , and a second gas inlet  665  can be coupled to the reaction chamber  610  and connected to a remote plasma source  660 . In embodiments including remote plasma configurations, the delivery lines for the precursors and the radical species generated in the remote plasma source  660  are separated. Hence, the precursors and the radical species do not substantially interact before reaching the substrate  630 . It will be understood that in some implementations the gas lines may be reversed so that the vessel  650  may provide precursor gas flow through the second gas inlet  665  and the remote plasma source  660  may provide ions and radicals through the first gas inlet  655 . 
     One or more radical species may be generated in the remote plasma source  660  and configured to enter the reaction chamber  610  via the second gas inlet  665 . Any type of plasma source may be used in remote plasma source  660  to create the radical species. This includes, but is not limited to, capacitively coupled plasmas, inductively coupled plasmas, microwave plasmas, DC plasmas, and laser-created plasmas. An example of a capacitively coupled plasma can be a radio frequency (RF) plasma. A high-frequency plasma can be configured to operate at 13.56 MHz or higher. An example of such a remote plasma source  660  can be the GAMMA®, manufactured by Lam Research Corporation of Fremont, Calif. Another example of such a RF remote plasma source  660  can be the Astron®, manufactured by MKS Instruments of Wilmington, Mass., which can be operated at 440 kHz and can be provided as a subunit bolted onto a larger apparatus for processing one or more substrates in parallel. In some embodiments, a microwave plasma can be used as the remote plasma source  660 , such as the Astex®, also manufactured by MKS Instruments. A microwave plasma can be configured to operate at a frequency of 2.45 GHz. Gas provided to the remote plasma source  660  may include hydrogen, nitrogen, oxygen, and other gases as mentioned elsewhere herein. In certain embodiments, hydrogen is provided in a carrier such helium. As an example, hydrogen gas may be provided in a helium carrier at a concentration of about 1-50% by volume during deposition operations, and hydrogen gas may be provided in a helium carrier at a concentration of at least about 10% by volume during treatment operations. 
     The precursors can be provided in vessel  650  and can be supplied to the showerhead  620  via the first gas inlet  655 . The showerhead  620  distributes the precursors into the reaction chamber  610  toward the substrate  630 . The substrate  630  can be located beneath the showerhead  620 . It will be appreciated that the showerhead  620  can have any suitable shape, and may have any number and arrangement of ports for distributing gases to the substrate  630 . The precursors can be supplied to the showerhead  620  and ultimately to the substrate  630  at a controlled flow rate. 
     The one or more radical species formed in the remote plasma source  660  can be carried in the gas phase toward the substrate  630 . The one or more radical species can flow through a second gas inlet  665  into the reaction chamber  610 . It will be understood that the second gas inlet  665  need not be transverse to the surface of the substrate  630  as illustrated in  FIG. 6 . In certain embodiments, the second gas inlet  665  can be directly above the substrate  630  or in other locations. The distance between the remote plasma source  660  and the reaction chamber  610  can be configured to provide mild reactive conditions such that the ionized species generated in the remote plasma source  660  are substantially neutralized, but at least some radical species in substantially low energy states remain in the environment adjacent to the substrate  630 . Such low energy state radical species are not recombined to form stable compounds. The distance between the remote plasma source  660  and the reaction chamber  610  can be a function of the aggressiveness of the plasma (e.g., determined in part by the source RF power level), the density of gas in the plasma (e.g., if there&#39;s a high concentration of hydrogen atoms, a significant fraction of them may recombine to form H 2  before reaching the reaction chamber  610 ), and other factors. In some embodiments, the distance between the remote plasma source  660  and the reaction chamber  610  can be between about 1 cm and 30 cm, such as about 5 cm or about 15 cm. 
     In some embodiments, a co-reactant, which is not the primary silicon-containing precursor or a hydrogen radical, is introduced during the deposition reaction. In some implementations, the device  600  is configured to introduce the co-reactant through the second gas inlet  665 , in which case the co-reactant is at least partially converted to plasma. In some implementations, the device  600  is configured to introduce the co-reactant through the showerhead  620  via the first gas inlet  655 . Examples of the co-reactant include oxygen, nitrogen, ammonia, carbon dioxide, carbon monoxide, and the like. 
       FIG. 7  illustrates a schematic diagram of an example plasma processing apparatus with a remote plasma source according to some other implementations. The plasma processing apparatus  700  includes the remote plasma source  702  separated from a reaction chamber  704 . The remote plasma source  702  is fluidly coupled with the reaction chamber  704  via a multiport gas distributor  706 , which may also be referred to as a showerhead. Radical species are generated in the remote plasma source  702  and supplied to the reaction chamber  704 . One or more silicon-containing precursors are supplied to the reaction chamber  704  downstream from the remote plasma source  702  and from the multiport gas distributor  706 . The one or more silicon-containing precursors react with the radical species in a chemical vapor deposition zone  708  of the reaction chamber  704  to deposit a SiC x O y N z  film on a surface of a substrate  712 . The chemical vapor deposition zone  708  includes an environment adjacent to the surface of the substrate  712 . 
     The substrate  712  is supported on a substrate support or pedestal  714 . The pedestal  714  may move within the reaction chamber  704  to position the substrate  712  within the chemical vapor deposition zone  708 . In the embodiment shown in  FIG. 7 , pedestal  714  is shown having elevated the substrate  712  within the chemical vapor deposition zone  708 . The pedestal  714  may also adjust the temperature of the substrate  712  in some embodiments, which can provide some selective control over thermally activated surface reactions on the substrate  712 . 
       FIG. 7  shows a coil  718  arranged around the remote plasma source  702 , where the remote plasma source  702  includes an outer wall (e.g., quartz dome). The coil  718  is electrically coupled to a plasma generator controller  722 , which may be used to form and sustain plasma within a plasma region  724  via inductively coupled plasma generation. In some implementations, the plasma generator controller  722  may include a power supply for supplying power to the coil  718 , where the power can be in a range between about 1 and 6 kilowatts (kW) during plasma generation. In some implementations, electrodes or antenna for parallel plate or capacitively coupled plasma generation may be used to generate a continuous supply of radicals via plasma excitation rather than inductively coupled plasma generation. Regardless of the mechanism used to ignite and sustain the plasma in the plasma region  724 , radical species may continuously be generated using plasma excitation during film deposition and treatment. In some implementations, hydrogen radicals are generated under approximately steady-state conditions during steady-state film deposition, though transients may occur at the beginning and end of film deposition and treatment. 
     A supply of hydrogen radicals may be continuously generated within the plasma region  724  while hydrogen gas or other source gas is being supplied to the remote plasma source  702 . Excited hydrogen radicals may be generated in the remote plasma source  702 . If not re-excited or re-supplied with energy, or re-combined with other radicals, the excited hydrogen radicals lose their energy, or relax. Thus, excited hydrogen radicals may relax to form hydrogen radicals in a substantially low energy state or ground state. 
     The hydrogen gas or other source gas may be diluted with one or more additional gases. These one or more additional gases may be supplied to the remote plasma source  702 . In some implementations, the hydrogen gas or other source gas is mixed with one or more additional gases to form a gas mixture, where the one or more additional gases can include a carrier gas. Non-limiting examples of additional gases can include helium, neon, argon, krypton, and xenon. The one or more additional gases may support or stabilize steady-state plasma conditions within the remote plasma source  702  or aid in transient plasma ignition or extinction processes. In some implementations, diluting hydrogen gas or other source gas with helium, for example, may permit higher total pressures without concomitant plasma breakdown. Put another way, a dilute gas mixture of hydrogen gas and helium may permit higher total gas pressure without increasing plasma power to the remote plasma source  702 . As shown in  FIG. 7 , a source gas supply  726  is fluidly coupled with the remote plasma source  702  for supplying the hydrogen gas or source gas. In addition, an additional gas supply  728  is fluidly coupled with the remote plasma source  702  for supplying the one or more additional gases. The one or more additional gases may also include a co-reactant gas as described above. While the embodiment in  FIG. 7  depicts the gas mixture of the source gas and the one or more additional gases being introduced through separate gas outlets, it will be understood that the gas mixture may be introduced directly into the remote plasma source  702 . That is, a pre-mixed dilute gas mixture may be supplied to the remote plasma source  702  through a single gas outlet. 
     Gases, such as excited hydrogen and helium radicals and relaxed gases/radicals, flow out of the remote plasma source  702  and into the reaction chamber  704  via multiport gas distributor  706 . Gases within the multiport gas distributor  706  and within the reaction chamber  704  are generally not subject to continued plasma excitation therein. In some implementations, the multiport gas distributor  706  includes an ion filter and/or a photon filter. Filtering ions and/or photons may reduce substrate damage, undesirable re-excitation of molecules, and/or selective breakdown or decomposition of silicon-containing precursors within the reaction chamber  704 . Multiport gas distributor  706  may have a plurality of gas ports  734  to diffuse the flow of gases into the reaction chamber  704 . In some implementations, the plurality of gas ports  734  may be mutually spaced apart. In some implementations, the plurality of gas ports  734  may be arranged as an array of regularly spaced apart channels or through-holes extending through a plate separating the remote plasma source  702  and the reaction chamber  704 . The plurality of gas ports  734  may smoothly disperse and diffuse exiting radicals from the remote plasma source  702  into the reaction chamber  704 . 
     Typical remote plasma sources are far removed from reaction vessels. Consequently, radical extinction and recombination, e.g., via wall collision events, may reduce active species substantially. In contrast, in some implementations, dimensions for the plurality of gas ports  734  may be configured in view of the mean free path or gas flow residence time under typical processing conditions to aid the free passage of radicals into the reaction chamber  704 . In some implementations, openings for the plurality of gas ports  734  may occupy between about 5% and about 20% of an exposed surface area of the multiport gas distributor  706 . In some implementations, the plurality of gas ports  734  may each have an axial length to diameter ratio of between about 3:1 and 10:1 or between about 6:1 and about 8:1. Such aspect ratios may reduce wall-collision frequency for radical species passing through the plurality of gas ports  734  while providing sufficient time for a majority of excited state radical species to relax to ground state radical species. In some implementations, dimensions of the plurality of gas ports  734  may be configured so that the residence time of gases passing through the multiport gas distributor  706  is greater than the typical energetic relaxation time of an excited state radical species. Excited state radical species for hydrogen source gas may be denoted by .H* in  FIG. 7  and ground state radical species for hydrogen source gas may be denoted by .H in  FIG. 7 . 
     In some implementations, excited state radical species exiting the plurality of gas ports  734  may flow into a relaxation zone  738  contained within an interior of the reaction chamber  704 . The relaxation zone  738  is positioned upstream of the chemical vapor deposition zone  708  but downstream of the multiport gas distributor  706 . Substantially all or at least 90% of the excited state radical species exiting the multiport gas distributor  706  will transition into relaxed state radical species in the relaxation zone  738 . Put another way, almost all of the excited state radical species (e.g., excited hydrogen radicals) entering the relaxation zone  738  become de-excited or transition into a relaxed state radical species (e.g., ground state hydrogen radicals) before exiting the relaxation zone  738 . In some implementations, process conditions or a geometry of the relaxation zone  738  may be configured so that the residence time of radical species flowing through the relaxation zone  738 , e.g., a time determined by mean free path and mean molecular velocity, results in relaxed state radical species flowing out of the relaxation zone  738 . 
     With the delivery of radical species to the relaxation zone  738  from the multiport gas distributor  706 , one or more silicon-containing precursors and/or one or more co-reactants may be introduced into the chemical vapor deposition zone  708 . The one or more silicon-containing precursors may be introduced via a gas distributor or gas outlet  742 , where the gas outlet  742  may be fluidly coupled with a precursor supply source  740 . The relaxation zone  738  may be contained within a space between the multiport gas distributor  706  and the gas outlet  742 . The gas outlet  742  may include mutually spaced apart openings so that the flow of the one or more silicon-containing precursors may be introduced in a direction parallel with gas mixture flowing from the relaxation zone  738 . The gas outlet  742  may be located downstream from the multiport gas distributor  706  and the relaxation zone  738 . The gas outlet  742  may be located upstream from the chemical vapor deposition zone  708  and the substrate  712 . The chemical vapor deposition zone  708  is located within the interior of the reaction chamber  704  and between the gas outlet  742  and the substrate  712 . 
     Substantially all of the flow of the one or more silicon-containing precursors may be prevented from mixing with excited state radical species adjacent to the multiport gas distributor  706 . Relaxed or ground state radical species mix in a region adjacent to the substrate  712  with the one or more silicon-containing precursors. The chemical vapor deposition zone  708  includes the region adjacent to the substrate  712  where the relaxed or ground state radical species mix with the one or more silicon-containing precursors. The relaxed or ground state radical species mix with the one or more silicon-containing precursors in the gas phase during CVD formation of an SiC x O y N z  film. However, the relaxed or ground state radical species do not mix with any silicon-containing precursors in the gas phase during densification and shrinkage of the SiC x O y N z  film. 
     In some implementations, a co-reactant may be introduced from the gas outlet  742  and flowed along with the one or more silicon-containing precursors. The co-reactant may be introduced downstream from the remote plasma source  702 . The co-reactant may be supplied from the precursor supply source  740  or other source (not shown) fluidly coupled to the gas outlet  742 . In some implementations, a co-reactant may be introduced from the multiport gas distributor  706  and flowed along with the radical species generated in the remote plasma source  702  and into the reaction chamber  704 . This may include radicals and/or ions of a co-reactant gas provided in the remote plasma source  702 . The co-reactant may be supplied from the additional gas supply  728 . 
     The gas outlet  742  may be separated from the multiport gas distributor  706  by a sufficient distance to prevent back diffusion or back streaming of the one or more silicon-containing precursors. In some implementations, the gas outlet  742  may be separated from the plurality of gas ports  734  by a distance between about 0.5 inches and about 5 inches, or between about 1.5 inches and about 4.5 inches, or between about 1.5 inches and about 3 inches. 
     Process gases may be removed from the reaction chamber  704  via an outlet  748  configured that is fluidly coupled to a pump (not shown). Thus, excess silicon-containing precursors, co-reactants, radical species, and diluent and displacement or purge gases may be removed from the reaction chamber  704 . In some implementations, a system controller  750  is in operative communication with the plasma processing apparatus  700 . In some implementations, the system controller  750  includes a processor system  752  (e.g., microprocessor) configured to execute instructions held in a data system  754  (e.g., memory). In some implementations, the system controller  750  may be in communication with the plasma generator controller  722  to control plasma parameters and/or conditions. In some implementations, the system controller  750  may be in communication with the pedestal  714  to control pedestal elevation and temperature. In some implementations, the system controller  750  may control other processing conditions, such as RF power settings, frequency settings, duty cycles, pulse times, pressure within the reaction chamber  704 , pressure within the remote plasma source  702 , gas flow rates from the source gas supply  726  and the additional gas supply  728 , gas flow rates from the precursor supply source  740  and other sources, temperature of the pedestal  714 , and temperature of the reaction chamber  704 , among others. 
     Aspects of the controller  750  of  FIG. 7  described below also apply to the controller  640  of  FIG. 6 . The controller  750  may contain instructions for controlling process conditions for the operation of the plasma processing apparatus  700 . The controller  750  will typically include one or more memory devices and one or more processors. The processor may include a CPU or computer, analog and/or digital input/output connections, stepper motor controller boards, etc. Instructions for implementing appropriate control operations are executed on the processor. These instructions may be stored on the memory devices associated with the controller  750  or they may be provided over a network. 
     In certain embodiments, the controller  750  controls all or most activities of the plasma processing apparatus  700  described herein. For example, the controller  750  may control all or most activities of the plasma processing apparatus  700  associated with depositing an SiC x O y N z  film and, optionally, other operations in a fabrication flow that includes the SiC x O y N z  film. The controller  750  may execute system control software including sets of instructions for controlling the treatment frequency, treatment time, treatment power, and remote plasma gas composition of remote plasma conditions for gapfill operations. The controller  750  may also execute system control software including sets of instructions for controlling timing, time interval between deposition and plasma treatment operations, gas composition, gas flow rates, chamber pressure, chamber temperature, substrate position, and/or other parameters. Other computer programs, scripts, or routines stored on memory devices associated with the controller  750  may be employed in some embodiments. To provide relatively mild reactive conditions at the environment adjacent to the substrate  712 , parameters such as the RF power levels, gas flow rates to the plasma region  724 , gas flow rates to the chemical vapor deposition zone  708 , and timing of the plasma ignition can be adjusted and maintained by controller  750 . Additionally, adjusting the substrate position may further reduce the presence of high-energy radical species at the environment adjacent to the substrate  712 . In a multi-station reactor, the controller  750  may comprise different or identical instructions for different apparatus stations, thus allowing the apparatus stations to operate either independently or synchronously. 
     In some embodiments, the controller  750  may include instructions for performing operations such depositing a first thickness of a SiC x O y N z  film in one or more features of the substrate  712 , exposing the SiC x O y N z  film to a remote hydrogen plasma under conditions that increase a size of an opening near a top surface of each of the one or more features, and depositing a second thickness of the SiC x O y N z  film is deposited in the one or more features of the substrate  712 . In depositing the first thickness and the second thickness of the SiC x O y N z  film, the controller  750  may include instructions for flowing one or more silicon-containing precursors into the reaction chamber  704  and introducing one or more hydrogen radicals generated from the remote plasma source  702  and towards the substrate  712  in the reaction chamber  704 , where the one or more hydrogen radicals react with the one or more silicon-containing precursors to deposit the SiC x O y N z  film. In some embodiments, the controller  750  may further include instructions for controlling an atomic concentration of the SiC x O y N z  film so that the conditions of the remote hydrogen plasma increase the size of the opening near the top surface of each of the one or more features. In some embodiments, the controller  750  may further include instructions for repeating operations of exposing the SiC x O y N z  film to the remote hydrogen plasma and depositing a new thickness of the SiC x O y N z  film in the one or more features of the substrate  712  until the one or more features are filled or at least substantially filled. In some embodiments, the conditions of the remote hydrogen plasma include a treatment frequency, treatment time, treatment power, and/or remote plasma gas composition being controlled so that the size of the opening near the top surface of each of the one or more features is increased more than a size of an opening near a bottom surface of each of the one or more features. In some embodiments, the treatment power of the remote hydrogen plasma includes a concentration between about 10% and about 50% by volume of hydrogen, or a concentration between about 10% and about 30% by volume of hydrogen. In some embodiments, the first thickness and the second thickness of the SiC x O y N z  film is each between about 0.5 Å and about 10 Å, or between about 0.5 Å and about 4.5 Å. 
     In some embodiments, the apparatus  700  may include a user interface associated with controller  750 . The user interface may include a display screen, graphical software displays of the apparatus  700  and/or process conditions, and user input devices such as pointing devices, keyboards, touch screens, microphones, etc. 
     The computer program code for controlling the above operations can be written in any conventional computer readable programming language: for example, assembly language, C, C++, Pascal, Fortran, or others. Compiled object code or script is executed by the processor to perform the tasks identified in the program. 
     Signals for monitoring the process may be provided by analog and/or digital input connections of the system controller. The signals for controlling the process are output on the analog and digital output connections of the processing system. 
     In general, the methods described herein can be performed on systems including semiconductor processing equipment such as a processing tool or tools, chamber or chambers, a platform or platforms for processing, and/or specific processing components (a wafer pedestal, a gas flow system, etc.). These systems may be integrated with electronics for controlling their operation before, during, and after processing of a semiconductor wafer or substrate. In general, the electronics are referred to as the controller, which may control various components or subparts of the system or systems. The controller, depending on the processing requirements and/or the type of system, may be programmed to control any of the processes disclosed herein, including the delivery of processing gases, temperature settings (e.g., heating and/or cooling), pressure settings, vacuum settings, power settings, RF generator settings, RF matching circuit settings, frequency settings, flow rate settings, fluid delivery settings, positional and operation settings, wafer transfers into and out of a tool and other transfer tools and/or load locks connected to or interfaced with a specific system. 
     Broadly speaking, the controller may be defined as electronics having various integrated circuits, logic, memory, and/or software that receive instructions, issue instructions, control operation, enable cleaning operations, enable endpoint measurements, and the like. The integrated circuits may include chips in the form of firmware that store program instructions, digital signal processors (DSPs), chips defined as application specific integrated circuits (ASICs), and/or one or more microprocessors, or microcontrollers that execute program instructions (e.g., software). Program instructions may be instructions communicated to the controller in the form of various individual settings (or program files), defining operational parameters for carrying out a particular process on or for a semiconductor wafer or to a system. The operational parameters may, in some embodiments, be part of a recipe defined by process engineers to accomplish one or more processing steps during the fabrication of one or more layers, materials (e.g., silicon carbide), surfaces, circuits, and/or dies of a wafer. 
     The controller, in some implementations, may be a part of or coupled to a computer that is integrated with, coupled to the system, otherwise networked to the system, or a combination thereof. For example, the controller may be in the “cloud” or all or a part of a fab host computer system, which can allow for remote access of the wafer processing. The computer may enable remote access to the system to monitor current progress of fabrication operations, examine a history of past fabrication operations, examine trends or performance metrics from a plurality of fabrication operations, to change parameters of current processing, to set processing steps to follow a current processing, or to start a new process. In some examples, a remote computer (e.g. a server) can provide process recipes to a system over a network, which may include a local network or the Internet. The remote computer may include a user interface that enables entry or programming of parameters and/or settings, which are then communicated to the system from the remote computer. In some examples, the controller receives instructions in the form of data, which specify parameters for each of the processing steps to be performed during one or more operations. It should be understood that the parameters may be specific to the type of process to be performed and the type of tool that the controller is configured to interface with or control. Thus as described above, the controller may be distributed, such as by comprising one or more discrete controllers that are networked together and working towards a common purpose, such as the processes and controls described herein. An example of a distributed controller for such purposes would be one or more integrated circuits on a chamber in communication with one or more integrated circuits located remotely (such as at the platform level or as part of a remote computer) that combine to control a process on the chamber. 
     In addition to the doped or undoped silicon carbide deposition and treatment described herein, example systems may include a plasma etch chamber or module, a deposition chamber or module, a spin-rinse chamber or module, a metal plating chamber or module, a clean chamber or module, a bevel edge etch chamber or module, a physical vapor deposition (PVD) chamber or module, a chemical vapor deposition (CVD) chamber or module, an atomic layer deposition (ALD) chamber or module, an atomic layer etch (ALE) chamber or module, an ion implantation chamber or module, a track chamber or module, and any other semiconductor processing systems that may be associated or used in the fabrication and/or manufacturing of semiconductor wafers. 
     As noted above, depending on the process step or steps to be performed by the tool, the controller might communicate with one or more of other tool circuits or modules, other tool components, cluster tools, other tool interfaces, adjacent tools, neighboring tools, tools located throughout a factory, a main computer, another controller, or tools used in material transport that bring containers of wafers to and from tool locations and/or load ports in a semiconductor manufacturing factory. 
     The apparatus/process described hereinabove may be used in conjunction with lithographic patterning tools or processes, for example, for the fabrication or manufacture of semiconductor devices, displays, LEDs, photovoltaic panels and the like. Typically, though not necessarily, such tools/processes will be used or conducted together in a common fabrication facility. Lithographic patterning of a film typically includes some or all of the following operations, each operation enabled with a number of possible tools: (1) application of photoresist on a workpiece, i.e., substrate, using a spin-on or spray-on tool; (2) curing of photoresist using a hot plate or furnace or UV curing tool; (3) exposing the photoresist to visible or UV or x-ray light with a tool such as a wafer stepper; (4) developing the resist so as to selectively remove resist and thereby pattern it using a tool such as a wet bench; (5) transferring the resist pattern into an underlying film or workpiece by using a dry or plasma-assisted etching tool; and (6) removing the resist using a tool such as an RF or microwave plasma resist stripper. 
       FIG. 8  shows a TEM image of an SiC x O y N z  film deposited in a plurality of features of a substrate according to some implementations. The SiC x O y N z  film serves as gapfill material in the plurality of features. The SiC x O y N z  film may include silicon oxycarbide. The SiC x O y N z  film may be deposited by alternating remote plasma CVD and remote hydrogen plasma exposure operations. The treatment frequency is greater than about 10 Å per deposition-treatment cycle, the treatment power of the remote hydrogen plasma has a concentration of between 1-5% hydrogen by volume with a balance of helium, and the treatment time of the remote hydrogen plasma exposure is at least 10 seconds. Voids are formed in each of the plurality of features in  FIG. 8 . 
       FIG. 9  shows a TEM image of a SiC x O y N z  film deposited in a plurality of features of a substrate according to some implementations. The SiC x O y N z  film serves as gapfill material in the plurality of features. The SiC x O y N z  film may include silicon oxycarbide. The SiC x O y N z  film may be deposited by alternating remote plasma CVD and remote hydrogen plasma exposure operations. Various time intervals may be introduced between remote plasma CVD and remote hydrogen plasma exposure operations to modulate gapfill performance. However, the remote hydrogen plasma exposure conditions are controlled to limit the sizes of the voids formed in  FIG. 9 . The treatment frequency is equal to or less than 5 Å per deposition-treatment cycle, the treatment power of the remote hydrogen plasma is between about 2 Kilowatts and about 6 Kilowatts, and the remote plasma gas composition has a concentration of between about 10% and about 50% by volume of hydrogen with a balance of helium, and the treatment time of the remote hydrogen plasma exposure is between about 0.5 seconds and about 120 seconds. Voids are formed in each of the plurality of features in  FIG. 9 , but the voids are significantly smaller compared to  FIG. 8 . 
     In the foregoing description, numerous specific details are set forth to provide a thorough understanding of the presented embodiments. The disclosed embodiments may be practiced without some or all of these specific details. In other instances, well-known process operations have not been described in detail to not unnecessarily obscure the disclosed embodiments. While the disclosed embodiments are described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments. 
     Although the foregoing embodiments have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatus of the present embodiments. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the embodiments are not to be limited to the details given herein.