Patent Publication Number: US-2022238349-A1

Title: Polymerization protective liner for reactive ion etch in patterning

Description:
INCORPORATION BY REFERENCE 
     A PCT Request Form 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 PCT Request Form is incorporated by reference herein in its entirety and for all purposes. 
    
    
     BACKGROUND 
     Many semiconductor fabrication processes involve patterning schemes that include etching vias and trenches. However, as devices shrink and selected materials change, etching vias and trenches introduces challenges that include patterning loading and undercut of materials. 
     The background description provided herein is for the purposes of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     SUMMARY 
     Provided herein are methods and apparatuses for processing semiconductor substrates. One aspect involves a method including: providing a semiconductor substrate to a chamber, the semiconductor substrate having a target layer having a thickness t and a metallization layer underlying the target layer with at least one region including metal; forming a lower patterned mask layer over the target layer by etching a lower mask layer; and forming a polymerization protective liner over the lower patterned mask layer without breaking vacuum. Some embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods. 
     Implementations may include one or more of the following features. In some embodiments, the method further includes forming an upper mask layer over the polymerization protective liner; patterning the semiconductor substrate using the upper mask layer to form at least one via aligning with the at least one region including metal; and after patterning the semiconductor substrate using the upper mask layer, patterning the target layer using reactive ion etch. 
     In some embodiments, the polymerization protective liner is deposited nonconformally and reduces reactive ion etch lag by at least 5-10%. In some embodiments, the lower patterned mask layer includes one or more corners exposed during patterning of the semiconductor substrate using the upper mask layer to form the at least one via. In some embodiments, the at least one via has a critical dimension of between about 10 nm and about 30 nm. 
     In some embodiments, the upper mask layer is formed by extreme ultraviolet lithography. In various embodiments, the lower patterned mask layer is formed by extreme ultraviolet lithography. In some embodiments, the polymerization protective liner is a sacrificial film. 
     The method may include forming of the polymerization protective liner and patterning of the lower patterned mask layer performed in the same chamber. In some embodiments, the thickness of the polymerization protective liner in features of different sizes is etched at the same rate during reactive ion etch. In some embodiments, less than SA of the lower patterned mask layer is etched during the patterning of the semiconductor substrate using the upper mask layer as a result of the polymerization protective liner on the lower patterned mask layer. 
     In some embodiments, the polymerization protective liner is deposited using silicon tetrachloride and methane. In some embodiments, the lower patterned mask layer includes material selected from the group including titanium nitride, titanium oxide, and tungsten-containing materials. 
     In some embodiments, the lower patterned mask layer includes negative features having a critical dimension between about 10 nm and about 30 nm. In some embodiments, the lower patterned mask layer includes spaced apart positive features with wide and narrow negative features between positive features; and where thickness of the polymerization protective liner deposited at bottoms of wide negative features is greater than thickness of the polymerization protective liner deposited at bottoms of narrow negative features. In some embodiments, the metallization layer includes copper. In some embodiments, patterning the semiconductor substrate using the upper patterned mask layer results in less than 2 nm of undercut in the target layer. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. 
     One aspect involves a method including: providing a semiconductor substrate having a lower patterned mask layer over a target layer having a thickness t and a metallization layer underlying the target layer with at least one region including metal; forming a polymerization protective liner over the lower patterned mask layer; forming an upper mask layer over the polymerization protective liner; patterning the semiconductor substrate using the upper mask layer to form at least one via aligning with the at least one region including metal; and after patterning the semiconductor substrate using the upper mask layer, patterning the target layer using reactive ion etch. Some embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods. 
     Implementations may include one or more of the following features. In some embodiments, forming of the polymerization protective liner and patterning of the semiconductor substrate using either the lower patterned mask layer or the upper mask layer are performed without breaking vacuum. In some embodiments, the semiconductor substrate further includes a second region of the target layer with no lower patterned mask layer overlying it. In some embodiments, patterning the target layer etches the second region and the target layer to the same thickness remaining on the semiconductor substrate. In some embodiments, the difference in thickness of the second region and the target layer not in the second region after patterning the target layer is less than 5 nm. In some embodiments, the target layer is patterned to preserve a thickness of the target layer less than t and greater than 0 on regions of the target layer not underlying the lower patterned mask layer. In some embodiments, the target layer includes ultra-low k dielectric material. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. 
     One aspect involves an apparatus for processing a semiconductor substrate, the apparatus including: one or more process chambers, where at least one process chamber includes a pedestal for holding the semiconductor substrate; a plasma generator; one or more gas inlets into the process chambers and associated flow-control hardware; and a controller having at least one processor and a memory, where the at least one processor and the memory are communicatively connected with one another, the at least one processor is at least operatively connected with the flow-control hardware, and the memory stores computer-executable instructions for controlling the at least one processor to at least control the flow-control hardware by: (i) causing a lower mask layer on the semiconductor substrate to be etched to form a patterned lower mask layer; and (ii) after causing the lower mask layer to be etched, causing introduction of silicon tetrachloride and methane to form a polymerization protective liner over the patterned lower mask layer. Some embodiments of this aspect include corresponding computer systems, apparatus, and computer programs recorded on one or more computer storage devices, each configured to perform the actions of the methods. 
     Implementations may include one or more of the following features. In some embodiments, the plasma generator is inductively coupled. Implementations of the described techniques may include hardware, a method or process, or computer software on a computer-accessible medium. A system of one or more computers can be configured to perform particular operations or actions by virtue of having software, firmware, hardware, or a combination of them installed on the system that in operation causes or cause the system to perform the actions. One or more computer programs can be configured to perform particular operations or actions by virtue of including instructions that, when executed by data processing apparatus, cause the apparatus to perform the actions. 
     These and other aspects are described further below with reference to the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1-6  are schematic illustrations of example drawings of substrates in a patterning scheme. 
         FIG. 7  is a process flow diagram depicting operations for an example method performed in accordance with certain disclosed embodiments. 
         FIGS. 8-13  are schematic illustrations of example drawings of substrates in a patterning scheme in accordance with certain disclosed embodiments. 
         FIG. 14  is a schematic diagram of an example process chamber for performing certain disclosed embodiments. 
         FIG. 15  is a schematic diagram of an example process tool for performing certain disclosed embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In the following 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 will be described in conjunction with the specific embodiments, it will be understood that it is not intended to limit the disclosed embodiments. 
     Semiconductor fabrication involves various patterning schemes for forming a variety of structures. Some patterning processes involve fabricating vias for later metallization operations, and processes may involve maintaining the integrity of the via profile to form high performing structures. 
     Such structures are formed by exposing materials to particular etching chemistries using masking and selectivity to form the desired structures. However, the combination of the exposed material and etching chemistry can pose challenges when the some exposed material is susceptible to tapering or undercut when exposed to etch chemistries used to etch other regions of a substrate. Example techniques for reducing this effect include modifying either the materials that are susceptible to etch or the material to be etched, or changing the etch chemistry used during etch. 
     Some patterning processes involve reactive ion etching (RIE) of dielectric material on a patterned substrate having different sized negative features. However, an effect referred to as “RIE lag” may occur—that is, etching in one feature is faster, or slower, than etching in another feature due to the size of the feature. This is also referred to as “pattern loading.” 
     Some patterning processes can also affect critical dimension of features etched therein, which may be due to angled bombardment of ions that cause undercut during etch and thereby etch in areas that are not desired. 
     An example patterning scheme is provided in  FIGS. 1-6 . These figures show an example of a problem that can occur during a patterning process. As described below, these figures show a patterning scheme involving a lower and upper mask to etch vias and trenches. 
       FIG. 1  shows an example substrate with various layers. In various embodiments, the substrate is a semiconductor substrate. The substrate may be a silicon wafer, e.g., a 200-mm wafer, a 300-mm wafer, or a 450-mm wafer, including wafers having one or more layers of material, such as dielectric, conducting, or semi-conducting material deposited thereon. In various embodiments, the substrate is patterned. A patterned substrate may have “features” such as pillars, poles, trenches, via or contact holes, which may be characterized by one or more of narrow and/or re-entrant openings, constrictions within the feature, and high aspect ratios. The feature(s) may be formed in one or more of the above described layers. One example of a feature is a pillar or pole in a semiconductor substrate or a layer on the substrate. Another example is a trench in a substrate or layer. 
     It will be understood that additional layers not shown may also be present on the substrate. The substrate includes a first layer  101  which includes metal contacts  102  and dielectric material  104 , such that dielectric material  104  is between the metal contacts  102  and thicknesses of the metal contacts  102  and dielectric material  104  are the same and top surfaces of metal contacts  102  and dielectric material  104  are flush. In some embodiments, metal contacts  102  include copper. A first etch stop layer  106  is depicted as being directly on top of the first layer  101 . On top of the first etch stop layer  106  is an ultra-low k dielectric layer  108 . The k value of the ultra-low k dielectric layer  108  may be between about 2 and about 2.7. The ultra-low k dielectric layer  108  is between about 40 nm and about 100 nm thick and is used as material for a sidewall of a future via to the metal contacts  102 . “Future via” used herein refers to a via that will be etched on the substrate following patterning operations. In various embodiments, a future via is selected to align over one of the metal contacts  102 . 
     On top of the ultra-low k dielectric layer  108  is a second etch stop layer  110 . The second etch stop layer  110  may be silicon nitride material or silicon oxide material or both. In some embodiments, the second etch stop layer  110  is deposited using tetraethyl orthosilicate (TEOS). In various embodiments, the second etch stop layer  110  is a blanket layer having a thickness between about SA and about 20 Å. In this example, a lower patterned mask  113  is directly on top of the second etch stop layer  110 . This lower patterned mask  113 , will be referred to herein as the “lower” mask, in reference to the location of the mask relative to a later, “upper” mask described below. 
     The lower patterned mask  113  includes both a titanium nitride hard mask layer  111 , as well as a TEOS layer  112 , which may be silicon oxide used to protect the titanium nitride hard mask layer  111  during etch. The lower patterned mask  113  may have a feature height of about 20 nm to about 50 nm, or about 50 nm, such that the height includes both titanium nitride hard mask layer  111  and TEOS layer  112 . The substrate provided in  FIG. 1  may be a substrate that was previously exposed to etching chemistry to “open” the titanium nitride hard mask layer  111  and thereby pattern it. 
     Patterning results in forming the lower patterned mask  113 , which as described herein, includes two materials (that is, each lower mask positive features  113   a ,  113   b ,  113   c , and  113   d  is a stack of two materials—the TEOS material and titanium nitride material). It will be understood that, in some cases, a lower patterned mask  113  may include only one material or more than two materials. First lower mask positive feature  113   a  includes first titanium nitride hard mask  111   a  and first TEOS material  112   a ; second lower mask positive feature  113   b  includes second titanium nitride hard mask  111   b  and second TEOS material  112   b ; third lower mask positive feature  113   c  includes third titanium nitride hard mask  111   c  and third TEOS material  112   c ; and fourth lower mask positive feature  113   d  includes fourth titanium nitride hard mask  111   d  and fourth TEOS material  112   d.    
     Between lower mask positive features are lower mask negative features  113   x ,  113   y , and  113   z . Lower mask negative feature  113   z  may have a critical dimension between about 100 nm and about 1 μm. Although four positive features and three negative features are depicted in this example, it will be understood that a substrate may include any number of positive and negative features. Each positive feature includes a particular thickness of titanium nitride hard mask layer  111  and TEOS layer  112 , and sidewalls of the feature are such that the surface of titanium nitride hard mask layer  111  and TEOS layer  112  are flush. In some embodiments, the width of each positive feature may be the same. In some embodiments, the widths of the positive features are different. 
     First lower mask negative feature  113   x  is the space between the first lower mask positive feature  113   a  and second lower mask positive feature  113   b . Second lower mask negative feature  113   y  is the space between the second lower mask positive feature  113   b  and third lower mask positive feature  113   c . Third lower mask negative feature  113   z  is the space between the third lower mask positive feature  113   c  and fourth lower mask positive feature  113   d . Additionally, the negative features defined by the spaces between the four positive features in  FIG. 1  have different sizes. The space between positive features may also be different; that is they may not be equally spaced on the substrate and thus first lower mask negative feature  113   x , second lower mask negative feature  113   y , and third lower mask negative feature  113   z  may have different critical dimensions. For example, first lower mask negative feature  113   x  has an aspect ratio of about 1:1, and second lower mask negative feature  113   y  has an aspect ratio of about 1:3, and third lower mask negative feature  113   z  has an aspect ratio of about 1:10. While the drawing shows three different aspect ratios, it will be understood that any suitable number of aspect ratios can be present. Likewise, positive features may also have different aspect ratios. 
     The distance between positive features, and/or the aspect ratio of negative features between the positive features, may vary over the surface of the substrate. An example range of distances between positive features is between about 10 nm and about 30 nm or between about 20 nm and about 30 nm. The pattern formed by the lower patterned mask  113  is used in part to form later formed vias. 
       FIG. 2  shows an example schematic illustration of a substrate after a spin-on carbon layer is deposited and an upper mask is formed. Like  FIG. 1 ,  FIG. 2  includes the first layer  101  including metal contacts  102  and dielectric material  104 ; first etch stop layer  106 ; ultra-low k dielectric layer  108 ; second etch stop layer  110 ; titanium nitride hard mask layer  111 ; and TEOS layer  112 . A spin-on carbon layer  114  is formed over the patterned substrate, filling the first lower mask negative feature  113   x , second lower mask negative feature  113   y , and third lower mask negative feature  113   z  of the lower patterned mask  113  depicted in  FIG. 1 . A third etch stop layer  116  is deposited over the spin-on carbon layer  114  (which also may be referred to as an organic polymerizing layer), and carbon-containing photoresist material is deposited and patterned to form the upper patterned mask  118 . The third etch stop layer  116  may be an anti-reflective layer. 
     The pattern of the upper patterned mask  118  is different from that of the lower patterned mask  113  such that the upper patterned mask  118  can be used to form trenches while the lower patterned mask  113  can be used to form vias as desired. In this example, the upper patterned mask  118  includes four upper patterned mask positive features  118   a ,  118   b ,  118   c , and  118   d , spaced apart with three upper patterned mask negative features  118   x ,  118   y ,  118   z  between them such that first upper patterned mask negative feature  118   x  of the upper patterned mask  118  overlaps partially with the now filled first lower mask negative feature  113   x  of the lower patterned mask  113 ; second upper patterned mask negative feature  118   y  and third upper patterned mask negative feature  118   z  in the upper patterned mask  118  overlap with the second lower patterned mask negative feature  113   y  of the lower patterned mask  113 , and the third lower mask negative feature  113   z  of the lower patterned mask  113  does not overlap with any negative feature (and is thus directly under a positive feature) of the upper patterned mask  118 . 
       FIG. 3  shows an example of a substrate where corners may be etched during etching of the spin-on carbon layer  114 . During this operation, the substrate may be exposed to a fluorine-containing plasma to etch the third etch stop layer  116 . Additionally, the substrate may be further exposed to a non-fluorine-containing gas including nitrogen, hydrogen, oxygen, carbon monoxide, or combinations thereof, to pattern the spin-on carbon layer  114 . 
     As shown, in  FIG. 3 , the upper patterned mask  118  is used to etch the spin-on carbon layer  114  and form patterned spin-on carbon layer  314  such that the pattern of upper patterned mask  118  is transferred to the spin-on carbon layer  114 . During this operation, the third etch stop layer  116  is patterned to form patterned third etch stop layer  316 , which includes first patterned third etch stop layer  316   a , second patterned third etch stop layer  316   b , third patterned third etch stop layer  316   c , and fourth patterned third etch stop layer  316   d . Etching is performed to the second etch stop layer  110 . 
     Etching species travel into upper patterned mask negative features  118   x ,  118   y , and  118   z  as shown in  FIG. 2  to form first via  318   x , second via  318   y , and third via  318   z , each of which align with one of each of the metal contacts  102 . During etch, first degraded corner  313   i , second degraded corner  313   j , and third degraded corner  313   j  of first TEOS material  312   a , second TEOS material  312   b , and third TEOS material  313   c , respectively, of the lower patterned mask  113  are exposed to the etching thereby resulting in degraded lower patterned mask positive features  313   a ,  313   b , and  313   c , respectively. Such degradation affects the profile of the lower patterned mask  313 . The top surface of a corner prior to etching may have a dimension of about 2 nm to about 5 nm; however, such exposed corners may be degraded due to etching as shown in  FIG. 3 . 
     In  FIG. 4 , the ultra-low k dielectric layer  108  is etched using the lower patterned mask  314   a ,  314   b ,  314   c  and  314   d  as a mask to thereby form vias  418   x ,  418   y , and  418   z . During this operation, a fluorocarbon gas may be introduced with a second gas which may include one or more of oxygen, nitrogen, and argon. 
     Etching species flow into vias  318   x ,  318   y , and  318   z  of  FIG. 3 , etching through second etch stop layer  110  to form patterned etch stop layer  410 , which includes first patterned etch stop material  410   a , second patterned etch stop material  410   b , third patterned etch stop material  410   c , and fourth patterned etch stop material  410   d . During etch, etching species flow into vias  318   x ,  318   y , and  318   z  of  FIG. 3 , but the species then hit the uneven profile of the degraded corners  313   i ,  313   j , and  313   k  at an angle, such that the trajectory causes etching species to undercut sidewalls of patterned ultra-low k dielectric layer  408 . Undercut refers to a sidewall of a feature being curved, or may refer to features where negative features have nonuniform etching on the sidewalls, where the critical dimension of the feature throughout the depth of the feature varies by ±2 to 4 nm. 
     For example, first trajectory  4181  shows an example of a path that an etching species may take when etching species hits first degraded corner  313   i  and sidewall of second patterned ultra-low k dielectric material  408   b . Another example second trajectory  418   m  shows an example path of an etching species such that the etching species hits second degraded corner  313   j , thereby etching sidewall of third patterned ultra-low k dielectric material  408   c . Third trajectory  418   n  is yet another example path of an etching species such that the etching species hits third degraded corner  313   k , thereby etching the other sidewall of third patterned ultra-low k dielectric material  408   c . In some cases, trajectories such as those described herein may also affect other sidewalls of the patterned ultra-low k dielectric layer  408 , such as on sidewalls of the first patterned ultra-low k dielectric material  408   a  and fourth patterned ultra-low k dielectric material  408   d . During etching, the upper patterned mask  118  may degrade and reduce in thickness to leave etched upper patterned mask  418 . 
     In  FIG. 5 , stripping the patterned spin-on carbon layer  314  leaves vias  518   x ,  518   y , and  518   z , which penetrate down to the patterned ultra-low k dielectric material  408 . However, vias  518   x ,  518   y , and  518   z  have a degraded profile due to the undercut caused by prior etching and during stripping of the patterned spin-on carbon layer  314 , plasma used to etch the spin-on carbon will cause further degradation. However, due to the degradation and undercut, the resulting via has an undesirable profile. Removal of the patterned spin-on carbon layer  314  also leaves trench  513   z.    
     In  FIG. 6 , TEOS material is etched from the substrate. During this operation, first TEOS material  312   a  and second TEOS material  312   b  are selectively removed from the substrate, leaving exposed first titanium hard mask  111   a  with underlying first patterned second etch stop material  610   a  and second titanium nitride hard mask  111   b  with underlying second patterned second etch stop material  610   b , respectively. In this example, second etch stop layer  610  material is the same TEOS material as TEOS layer  312 ; as a result, third patterned etch stop layer  410   c  is removed from the surface of third patterned ultra-low k dielectric material  408   c . Third TEOS material  312   c  and fourth TEOS material  312   d  are also selectively removed, leaving third titanium nitride hard mask  111   c  and fourth titanium nitride hard mask  111   d , respectively. Since fourth etch stop material  410   d  is exposed during etch, fourth etch stop material  410   d  is etched using the third titanium nitride hard mask  111   c  and fourth titanium nitride hard mask  111   d  as a mask, leaving third patterned second etch stop material  610   d  underlying third titanium nitride hard mask  111   c  and fourth patterned second etch stop material  610   e  underlying fourth titanium nitride hard mask  111   d.    
     In various embodiments, patterning of this structure further includes etching third patterned ultra-low k dielectric material  408   c  and fourth patterned ultra-low k dielectric material  408   d ; although the width of these two regions is different, in some cases etching is desired such that both regions are etched to leave the same thickness of material on the substrate; likewise, the same thickness is etched from the tops of third patterned ultra-low k dielectric material  408   c  and fourth patterned ultra-low k dielectric material  408   d . However, due to pattern loading effects, chemistry used to etch the material during this operation etches the smaller width, third patterned ultra-low k dielectric material  408   c  faster than fourth patterned ultra-low k dielectric material  408   d , resulting in different remaining thicknesses of the degraded third patterned ultra-low k dielectric material  608   c  and degraded fourth patterned ultra-low k dielectric material  608   d.    
     To etch the fourth patterned ultra-low k dielectric material  408   d  to sufficient thickness, exposure is prolonged, resulting in degraded third patterned ultra-low k dielectric material  608   c  having degraded corners  608   i  and  608   j , with a thickness t 1  that is much smaller than remaining thickness t 3  of degraded fourth patterned ultra-low k dielectric material  608   d . For example, the difference between t 1  and t 3  may be about 5 nm. For example, t 1  may be about 10 nm while t 3  may be about 15 nm. Further, etching of fourth patterned ultra-low k dielectric material  408   d  results in a degraded fourth patterned ultra-low k dielectric material  608   d  having uneven thickness on the surface between the third titanium nitride hard mask  111   c  and fourth titanium nitride hard mask  111   d  such that the smallest thickness remaining of degraded fourth patterned ultra-low k dielectric material  608   d  is t 3  and the thickest thickness remaining of degraded fourth patterned ultra-low k dielectric material  608   d  is Li where the difference between t 3  and Li may range from 3 nm to 15 nm. During etch, first patterned ultra-low k dielectric material  608   a  and second patterned ultra-low k dielectric material  608   b  are not affected as they are protected by mask  623 . The degraded profiles formed in  FIG. 6  are a result of RIE lag and pattern loading issues. Etching results in vias  618   x ,  618   y , and  618   z  and trench  613   z  and the patterned ultra-low k dielectric layer  608 . 
     The patterning scheme provided in  FIGS. 1-6  result in features having degraded or tapered profiles, which may not be desirable in some embodiments. 
     Provided herein are methods for protecting a future location of a via and a field region during reactive ion etch (RIE) or similar patterning schemes by forming a polymerization protective liner in situ after forming the lower mask and prior to forming the upper mask. In many embodiments, such patterning schemes involve two mask layers at different levels—an upper and a lower level—to achieve the desired pattern. Disclosed embodiments reduce the RIE lag while maintaining critical dimension control for a via ultimately etched to align with underlying metal contacts. 
     Certain disclosed embodiments involve depositing a polymerization deposited layer after opening a hard mask in a lower mask layer. The polymerization deposited layer acts both as a protection layer for protecting the field region during etching of the ultra-low k dielectric layer to reduce RIE lag, but also for preserving corners and sidewall integrity during patterning of the via. Additionally, the polymerization deposited layer can be deposited to a thin thickness sufficient to protect the corners, sidewalls, and field regions as appropriate without sacrificing critical dimension of the via, and can also be a sacrificial layer that is ultimately removed. 
       FIG. 7  is a process flow diagram depicting operations that may be performed in accordance with certain disclosed embodiments. In operation  702 , a patterned substrate having a lower patterned mask layer is provided. 
     The patterned substrate includes a lower patterned mask layer. The mask layer may be a dielectric layer in some embodiments. For example, in some embodiments, the lower patterned mask layer is a silicon-containing layer, such as silicon oxide. In some embodiments, the lower patterned mask layer is a layer deposited using TEOS. The term “lower” in this context refers to a position relative to another mask layer later described below with respect to operation  706 . An example of a substrate that may be provided in operation  702  is described above with respect to  FIG. 1 . 
     In operation  704 , a polymerization protective liner is deposited over the lower patterned mask layer. 
       FIG. 8  shows a substrate having a polymerization protective liner  890  deposited over the substrate shown in  FIG. 1 . That is, polymerization protective liner  890  is deposited over exposed surfaces that include top surfaces and sidewalls of the lower patterned mask  813 , which includes TEOS layer  812  and titanium nitride hard mask  811  over second etch stop layer  810 . Each lower mask positive feature  813   a ,  813   b ,  813   c , and  813   d  in the lower patterned mask  813  is a stack of two materials—the TEOS material  812   a ,  812   b ,  812   c ,  812   d , respectively, and titanium nitride material  811   a ,  811   b ,  811   c ,  811   d , respectively. The polymerization protective liner  890  also deposits over exposed surfaces of the second etch stop layer  810 . Between lower mask positive features  813   a ,  813   b ,  813   c , and  813   d  are lower mask negative features  813   x ,  813   y , and  813   z . Underlying second etch stop layer  810  is ultra-low k dielectric layer  808 , which may be the same as ultra-low k dielectric layer  108  described above with respect to  FIG. 1 . Underlying the ultra-low k dielectric layer  808  is first etch stop layer  806 , which may be the same as first etch stop layer  106  of  FIG. 1 . Underlying the first etch stop layer  806  is a first layer  801  including metal contacts  802  and dielectric material  804  which may be the same as first layer  101  having metal contacts  102  and dielectric material  104 , respectively, as discussed above with respect to  FIG. 1 . 
     Polymerization protective liner  890  may be formed by implementing silicon tetrachloride and methane polymer deposition. In various embodiments, the polymerization protective liner is deposited in situ; that is, in some embodiments the polymerization protective liner is deposited in the same chamber as the etch chamber used during etching operations. While such material may be used in front end of line processes for gate control and critical dimension increase, such material may be suitable in back end of line processing over a titanium nitride hard mask. Extra polymerization at the end of titanium nitride hard mask open operations can be used to add an extra layer. Deposition may not necessarily be uniform as the thickness of the amount polymerized on the field regions may be greater than the material deposited between titanium nitride lines; however, such deposition can still preserve corners and reduce RIE lag as desired, by tailoring the amount of deposition and toggling process conditions. In various embodiments, the polymerization protective liner  890  is nonconformal, having thicker deposition in larger features and thinner deposition in smaller features. 
     Polymerization protective liner  890  may be a polymerizing layer of silicon oxide material. In some embodiments, polymerization protective liner  890  is an oxide having a structure different from that of TEOS layer  812  or second etch stop layer  810 . In some embodiments, polymerization protective liner  890  may be a low quality silicon oxide having chlorine impurities and/or other impurities. In various embodiments, the polymerization protective liner  890  is less dense than the TEOS layer  812 . In some embodiments, the polymerization protective liner  890  is less dense than the second etch stop layer  810 . In some embodiments, the polymerization protective liner  890  is less dense than both the TEOS layer  812  and the second etch stop layer  810 . In various embodiments, the thickness of the polymerization protective liner  890  is between about 1 nm and about 4 nm. In some embodiments, the polymerization protective liner  890  is deposited and not subsequently annealed, thereby resulting in a lower quality silicon oxide film. In contrast, TEOS layer  812  may be deposited using TEOS followed by annealing at a temperature between about 300° C. and about 400° C. to densify the film. 
     Polymerization protective liner  890  may not be deposited conformally in various embodiments. For example, in some embodiments, more polymerization may occur in large features of the lower patterned mask  813  such that the thickness of films deposited on the surface of the second etch stop layer  810  is thicker in some regions than the film being deposited on the exposed surface of the second etch stop layer  810  in other regions. In some embodiment, deposition of aspect ratio-dependent. 
     Polymerization protective liner  890  may be deposited to a thickness between about 3 and about 7 nm in features having a large feature opening between about 50 and about 500 nm. Polymerization protective liner  890  may be deposited to a thickness between about 1 and about 3 nm in features having a small feature opening between about 10 and about 40 nm. 
     In some embodiments, conformality of the film being deposited can be modulated by varying the pressure of the chamber, during deposition. In some embodiments, a low pressure may be between about 1 mTorr and about 100 mTorr, or less than about 8 mTorr, or between about 5 mTorr and about 80 mTorr. 
     In various embodiments, polymerization protective liner  890  may be deposited by polymerization involving exposing the substrate to a vapor phase polymerization deposition precursor. The polymerization protective liner  890  may be deposited using a silicon-containing or a carbon-containing precursor. One example silicon-containing precursor is a silicon chloride (SiCl 4 ) precursor. One example carbon-containing precursor is methane (CH 4 ). The conformality of the film being deposited can be modulated by varying the gas ratio between silicon-containing and carbon-containing gases. Polymerization may be performed in a reactive ion etch chamber used for subsequent or prior etching operations. 
     In alternative embodiments, the polymerization protective liner  890  is deposited using a deposition process such as atomic layer deposition (ALD) and/or plasma-enhanced atomic layer deposition (PEALD). In some embodiments, polymerization protective liner  890  is deposited using chemical vapor deposition (CVD) and/or plasma-enhanced chemical vapor deposition (PECVD). Plasma may be used in some embodiments. In some embodiments where plasma is used to deposit the polymerization protective liner  890 , a lower power may be used to modulate conformality of films. For example, in some embodiments, a plasma may be generated using a power of less than about 300 W, or less than about 250 W, for a single wafer. 
     In some embodiments, a bias may be applied to the substrate during deposition. For example, in some embodiments, a bias voltage of about 140V may be applied to the substrate during deposition. 
     Polymerization protective liner  890  may be difficult to deposit in narrow gaps such that other materials may be inadvertently etched during polymerization. For example, ultra-low k dielectric material or titanium nitride material may be susceptible to etching during this deposition process. As a result, particular chemistries may be selected to deposit the polymerization protective liner  890 . For example, some examples include halogen such as silicon tetrachloride (SiCl 4 ) (having a flow rate of about 5 to about 40 sccm), chlorine (Cl 2 ) (having a flow rate of about 5 to about 50 sccm), hydrogen bromide (HBr) (having a flow rate of about 30 to about 300 sccm), with dilution gases such as oxygen (O), nitrogen (N 2 ), argon (Ar), and helium (He). In various embodiments, a halogen-containing deposition chemistry is used to deposit the polymerization protective liner  890 . 
     The polymerization protective liner  890  may be modulated such that deposition is only on regions to be protected. For example, in an embodiment where it is desired to preserve corners such as further described below, the polymerization protective liner  890  can be used to polymerize at corners such as corners having a size of about 5 nm to about 7 nm. Such deposition may, for example, be deposited on titanium nitride or silicon oxide material. In another embodiment where it is desirable to reduce RIE lag, the polymerization protective liner  890  may be deposited on field regions of a surface without depositing on sidewalls by modulating process conditions including but not limited to temperature, plasma conditions, process gases, and process chamber pressure. 
     In some embodiments, after the polymerization protective liner  890  is deposited, the substrate may be subject to a short “flash” cleaning involving exposure to an oxygen and argon plasma. For example, this may be particularly useful for cleaning in smaller features while not affecting larger features. 
     In various embodiments, the polymerization protective liner  890  is deposited nonconformally such that thicker deposition is formed in larger features (such as features having an aspect ratio greater than 1:10 or features having a feature opening greater than 50 nm) and thinner deposition is formed in smaller features (such as features having an aspect ratio smaller than 1:4 or features having a feature opening less than 30 nm). In various embodiments, thicker polymerization is formed at the bottoms of features than on the sidewalls. 
     Returning to  FIG. 7 , in operation  706 , an upper mask layer is formed over the polymerization protective liner. Prior to operation  706 , a carbon-containing material may be deposited over the polymerization protective liner prior to forming the upper mask. An example substrate having an upper mask formed over a polymerization protective liner is shown in  FIG. 9 .  FIG. 9  depicts a substrate having first layer  801 , which includes metal contacts  802  and dielectric material  804 . Metal contacts  802  include first metal contact  802   a , second metal contact  802   b , and third metal contact  802   c . Overlying first layer  801  is first etch stop layer  806 , and overlying first etch stop layer  806  is ultra-low k dielectric layer  808 . On top of ultra-low k dielectric layer  808  is second etch stop layer  810 , with lower patterned mask  813  over second etch stop layer  810 , where lower patterned mask  813  includes titanium nitride hard mask  811  and TEOS layer  812 . Polymerization protective liner  890 , as previously deposited over lower patterned mask  813 , is depicted in  FIG. 9 . Additionally, spin-on carbon layer  914  is formed over polymerization protective liner  890 , followed by third etch stop layer  916  deposition. Upper patterned mask  918  is formed and patterned (or lithographically defined) to form an upper pattern. Upper patterned mask  918  includes first upper patterned mask positive feature  918   a , second upper patterned mask positive feature  918   b , third upper mask positive feature  918   c , and fourth upper mask positive feature  918   d  after patterning. Between first upper patterned mask positive feature  918   a  and second upper patterned mask positive feature  918   b  is first upper mask negative feature  918   x ; between second upper patterned mask positive feature  918   b  and third upper mask positive feature  918   c  is second upper patterned mask negative feature  918   y ; and between third upper mask positive feature  918   c  and fourth upper mask positive feature  918   d  is third upper patterned mask negative feature  918   z . First upper mask negative feature  918   x  may align with first metal contact  802   a ; second upper patterned mask negative feature  918   y  may align with second metal contact  802   b ; and third upper patterned mask negative feature  918   z  may align with third metal contact  802   c . First upper patterned mask positive feature  918   a  may largely overlap with first lower patterned mask positive feature  813   a ; second upper patterned mask positive feature  918   b  may overlap with at least some of second lower patterned mask positive feature  813   b ; third upper mask positive feature  918   c  may be positioned between second lower patterned mask positive feature  813   b  and third lower patterned mask positive feature  813   c ; and fourth upper mask positive feature  918   d  may overlap with at least some of third lower patterned mask positive feature  813   c  and fourth lower patterned mask positive feature  813   d . Forming of upper mask layer in operation  706  may involve depositing spin-on carbon layer  914 ; depositing third etch stop layer  916 ; depositing upper patterned mask  918 ; and patterning upper patterned mask  918 . 
     In some embodiments, after depositing the polymerization protective liner, an optional plasma flash operation may be performed to remove some unevenly deposited regions and smoothen them. A plasma flash operation may involve introducing carbon tetrafluoride and generating a plasma using a low pulsed bias, pulsed between 0V and 50V using plasma generated using a power between about 150 W and about 250 W at 130V. 
     Returning to  FIG. 7 , in operation  708 , vias are etched in the substrate using the upper mask layer as a mask. Vias may be etched to a critical dimension between about 10 nm and about 30 nm or between about 20 nm and about 30 nm. 
     An example is provided in  FIG. 10 .  FIG. 10  shows a substrate from  FIG. 9  whereby first via  1018   x , second via  1018   y , third via  1018   z  are formed by etching vertically through third etch stop layer  916  and spin-on carbon layer  914  using upper patterned mask  918  ultra-low k dielectric layer  808  as a mask having first upper patterned mask positive feature  918   a , second upper patterned mask positive feature  918   b , third upper patterned mask positive feature  918   c , and fourth upper patterned mask positive feature  918   d . Third etch stop layer  916  is thereby patterned to form patterned third etch stop layer  1016  having first patterned third etch stop material  1016   a , second patterned third etch stop material  1016   b , third patterned third etch stop material  1016   c , and fourth patterned third etch stop material  1016   d  consistent with upper patterned mask  918  having first upper patterned mask positive feature  918   a , second upper patterned mask positive feature  918   b , third upper patterned mask positive feature  918   c , and fourth upper patterned mask positive feature  918   d , respectively. Likewise, spin-on carbon layer  914  is patterned to form first patterned spin-on carbon material  1014   a , second patterned spin-on carbon material  1014   b , third patterned spin-on carbon material  1014   c , and fourth patterned spin-on carbon material  1014   d . Due to the presence of polymerization protective liner  1090 , first preserved corner  1013   i , second preserved corner  1013   j , and third preserved corner  1013   k  are protected; and the underlying first TEOS material  812   a , second TEOS material  812   b , and third TEOS material  812   c , respectively, maintain their profiles such that first lower mask positive feature  1013   a , second lower mask positive feature  1013   b , and third lower mask positive feature  1013   c  of lower mask  813  can be effectively used as a mask in subsequent operations. 
     Operation  708  of  FIG. 7  may involve etching using one or more of the following etching gases: carbon monoxide, nitrogen, oxygen, hydrogen, argon, and fluorocarbon such as CF 4 , C 4 F 8 , CH 2 F 2 , C 4 F 6  for example, and combinations thereof. Additionally, plasma may be used in some embodiments such that the plasma is generated using a power between about 50 and about 500 W including an optional bias that if applied, may be powered at a bias power of 50V to about 300V. 
     Vias are etched using the upper patterned mask layer as a mask. An example is provided in  FIG. 11 , whereby first via  1118   x , second via  1118   y , and third via  1118   z  are formed using first lower mask positive feature  1013   a , second lower mask positive feature  1013   b , and third patterned lower mask positive feature  1013   c  as a mask. First via  1118   x , second via  1118   y , and third via  1118   z  are formed such that second etch stop layer  810  is patterned to form patterned second etch stop layer  1110  having first patterned second etch stop material  1110   a , second patterned second etch stop material  1110   b , third patterned second etch stop material  1110   c , and fourth patterned second etch stop material  1110   d;    
     likewise, ultra-low k dielectric layer  808  is patterned to form patterned ultra-low k dielectric layer  1108 , which includes first patterned ultra-low k dielectric material  1108   a , second patterned ultra-low k dielectric material  1108   b , third patterned ultra-low k dielectric material  1108   c , and fourth patterned ultra-low k dielectric material  1108   d . First etch stop layer  806  prevents further etching to underlying layers. As a result of polymerization protective liner  1090 , no tapered corners exist on the substrate as first preserved corner  1013   i , second preserved corner  1013   j , and third preserved corner  1013   k  are protected; accordingly etching species used to form patterned ultra-low k dielectric layer  1108  does not result in undercut in first patterned ultra-low k dielectric material  1108   a , second patterned ultra-low k dielectric material  1108   b , third patterned ultra-low k dielectric material  1108   c , and fourth patterned ultra-low k dielectric material  1108   d.    
     In operation  710 , trenches are etched using the lower patterned mask layer as a mask. An example is provided in  FIG. 12 . As shown, the substrate provided in  FIG. 11  is exposed to etching gases to remove patterned spin-on carbon layer  1014 , patterned third etch stop layer  1016 , and upper patterned mask layer  918 . During this operation, polymerization protective liner  1090  is exposed to the trench etches. During this operation, some exposed regions of  1090  are removed but titanium nitride hard mask  811  is used as a hard mask to prevent etching in regions underlying titanium nitride hard mask  811 , including first, second, third, and fourth patterned second etch stop material  1310   a ,  1310   b ,  1310   c , and  1310   d , respectively, in the patterned second etch stop layer  1110 . First patterned ultra-low k dielectric material  1308   a  and second patterned ultra-low k dielectric material  1308   b  are protected by exposed first titanium hard mask  811   a  with underlying first patterned second etch stop material  1310   a  and second titanium nitride hard mask  811   b  with underlying second patterned second etch stop material  1310   b , respectively. Third patterned ultra-low k dielectric material  1308   c  and fourth patterned ultra-low k dielectric material  1308   d  are etched such that the remaining thicknesses Li and is are within about 3 Å of each other thereby reducing RIE lag. That is,  1108   d  in  FIG. 13  is etched such that an amount d is etched from the surface of  1308   d . In some embodiments, d is at least between about 30% and about 60% of the total thickness of patterned ultra-low k dielectric layer  1308 . Due to the presence of polymerization protective liner  1090 , first preserved corner  1308   i  and second preserved corner  1308   j  are provided. Etching results in vias  1318   x ,  1318   y , and  1318   z  and trench  1313   z  and the patterned ultra-low k dielectric layer  1308 . 
     Although specific examples are provided herein, it will be understood that a polymerization protective liner can have many applications. Since the liner deposition can be tailored using two knobs such as the SiCl 4  ratio over Cl 2 :HBr and the pressure and/or power conditions to adjust the thickness mostly to achieve various thicknesses over a patterned substrate and can be easily removed during a patterning scheme, the polymerization protective liner described herein can be used to reduce RIE lag, preserve feature profiles and reduce undercut, or both as appropriate and desired. 
     Apparatus 
     Disclosed embodiments may be performed in any suitable deposition and/or etching chamber or apparatus, which may be available from Lam Research Corporation of Fremont, Calif. 
     Deposition of a polymerization protective liner as described herein may be performed in any suitable apparatus. In various embodiments, the polymerization protective liner is performed in an etch chamber used for reactive ion etch. 
     Any suitable etch chamber may be used for etching operations described herein. Further description of plasma etch chambers may be found in U.S. Pat. Nos. 6,841,943 and 8,552,334, which are herein incorporated by reference in their entireties. 
     Disclosed embodiments are performed in an inductively coupled plasma (ICP) reactor. One example is provided in  FIG. 14 . Such ICP reactors have also been described in U.S. Pat. No. 9,362,133 issued Jun. 7, 2016, filed Dec. 10, 2013, and titled “METHOD FOR FORMING A MASK BY ETCHING CONFORMAL FILM ON PATTERNED ASHABLE HARDMASK,” hereby incorporated by reference for the purpose of describing a suitable ICP reactor for implementation of the techniques described herein. Although ICP reactors are described herein, in some embodiments, it should be understood that capacitively coupled plasma reactors may also be used. An example chamber or apparatus may include a chamber having chamber walls, a chuck for holding a substrate or wafer to be processed which may include electrostatic electrodes for chucking and dechucking a wafer and may be electrically charged using a radio frequency (RF) power supply, an RF power supply configured to supply power to a coil to generate a plasma, and gas flow inlets for inletting gases as described herein. In some embodiments, an apparatus may include more than one chamber, each of which may be used to etch, deposit, or process substrates. The chamber or apparatus may include a system controller for controlling some or all of the operations of the chamber or apparatus such as modulating the chamber pressure, inert gas flow, plasma power, plasma frequency, reactive gas flow (e.g., etching gas, etc.), bias power, temperature, vacuum settings, and other process conditions. The chamber may also be used to deposit carbon-containing material onto a substrate. 
       FIG. 14  schematically shows a cross-sectional view of an inductively coupled plasma integrated etching and deposition apparatus  1400  appropriate for implementing certain embodiments herein, an example of which is an inductively coupled plasma reactor, produced by Lam Research Corp. of Fremont, Calif. The inductively coupled plasma integrated etching and deposition apparatus  1400  includes a processing chamber  1401  structurally defined by chamber walls and a window  1411 . The chamber walls may be fabricated from stainless steel or aluminum. The window  1411  may be fabricated from quartz or other dielectric material. An optional internal showerhead  1450  divides the processing chamber  1401  into an upper sub-chamber  1402  and a lower sub-chamber  1403 . The showerhead may include one hole, or may include multiple holes for delivering and distributing gases and/or plasma species to lower sub-chamber  1403 . In most embodiments, showerhead  1450  may be removed, thereby utilizing a chamber space made of upper sub-chambers  1402  and  1403 . A chuck  1417  is positioned within the lower sub-chamber  1403  near the bottom inner surface. The chuck  1417  is configured to receive and hold a semiconductor wafer  1419  upon which the etching and deposition processes are performed. The chuck  1417  can be an electrostatic chuck for supporting the wafer  1419  when present. In some embodiments, an edge ring (not shown) surrounds chuck  1417 , and has an upper surface that is approximately planar with a top surface of a wafer  1419 , when present over chuck  1417 . The chuck  1417  also includes electrostatic electrodes for chucking and dechucking the wafer. A filter and DC clamp power supply (not shown) may be provided for this purpose. Other control systems for lifting the wafer  1419  off the chuck  1417  can also be provided. The chuck  1417  may be movable along an axis substantially parallel to the sidewalls of the chamber whereby the surface of the chuck  1417  is substantially parallel to the ground. If a showerhead is used, the distance between the wafer  1419  and the showerhead (not shown) may be between about 0.5 inches and about 3.0 inches. The chuck  1417  can be electrically charged using an RF power supply  1423 . The RF power supply  1423  is connected to matching circuitry  1421  through a connection  1427 . The matching circuitry  1421  is connected to the chuck  1417  through a connection  1425 . In this manner, the RF power supply  1423  is connected to the chuck  1417 . 
     Elements for plasma generation include a coil  1433  is positioned above window  1411 . In various embodiments, a coil is not used in disclosed embodiments. The coil  1433  is fabricated from an electrically conductive material and includes at least one complete turn. The example of a coil  1433  shown in  FIG. 14  includes three turns. The cross-sections of coil  1433  are shown with symbols, and coils having an “X” extend rotationally into the page, while coils having a “0” extend rotationally out of the page. Elements for plasma generation also include an RF power supply  1441  configured to supply RF power to the coil  1433 . In general, the RF power supply  1441  is connected to matching circuitry  1439  through a connection  1445 . The matching circuitry  1439  is connected to the coil  1433  through a connection  1443 . In this manner, the RF power supply  1441  is connected to the coil  1433 . An optional Faraday shield  1449  is positioned between the coil  1433  and the window  1411 . The Faraday shield  1449  is maintained in a spaced apart relationship relative to the coil  1433 . The Faraday shield  1449  is disposed immediately above the window  1411 . The coil  1433 , the Faraday shield  1449 , and the window  1411  are each configured to be substantially parallel to one another. The Faraday shield may prevent metal or other species from depositing on the dielectric window of the processing chamber  1401 . 
     Process gases (e.g. oxygen-containing gases, halogen-containing gases, etc.) may be flowed into the processing chamber  1401  through one or more main gas flow inlets  1460  positioned in the upper chamber  1402  and/or through one or more side gas flow inlets  1470 . Likewise, though not explicitly shown, similar gas flow inlets may be used to supply process gases to a capacitively coupled plasma processing chamber. A vacuum pump, e.g., a one or two stage mechanical dry pump and/or turbomolecular pump  1440 , may be used to draw process gases out of the processing chamber  1401  and to maintain a pressure within the processing chamber  1401 . A valve-controlled conduit may be used to fluidically connect the vacuum pump to the processing chamber  1401  so as to selectively control application of the vacuum environment provided by the vacuum pump. This may be done employing a closed-loop-controlled flow restriction device, such as a throttle valve (not shown) or a pendulum valve (not shown), during operational plasma processing. Likewise, a vacuum pump and valve controlled fluidic connection to the capacitively coupled plasma processing chamber may also be employed. 
     During operation of the apparatus, one or more process gases may be supplied through the gas flow inlets  1460  and/or  1470 . In certain embodiments, process gas may be supplied only through the main gas flow inlet  1460 , or only through the side gas flow inlet  1470 . In some cases, the gas flow inlets shown in the figure may be replaced more complex gas flow inlets, one or more showerheads, for example. The Faraday shield  1449  and/or optional grid or showerhead  1450  may include internal channels and holes that allow delivery of process gases to the processing chamber  1401 . Either or both of Faraday shield  1449  and optional grid  1450  may serve as a showerhead for delivery of process gases. In some embodiments, a liquid vaporization and delivery system may be situated upstream of the processing chamber  1401 , such that once a liquid reactant or precursor is vaporized, the vaporized reactant or precursor is introduced into the processing chamber  1401  via a gas flow inlet  1460  and/or  1470 . 
     Radio frequency power is supplied from the RF power supply  1441  to the coil  1433  to cause an RF current to flow through the coil  1433 . The RF current flowing through the coil  1433  generates an electromagnetic field about the coil  1433 . The electromagnetic field generates an inductive current within the upper sub-chamber  1402 . The physical and chemical interactions of various generated ions and radicals with the wafer  1419  selectively etch features of and deposit layers on the wafer. 
     If the plasma grid is used such that there is both an upper sub-chamber  1402  and a lower sub-chamber  1403 , the inductive current acts on the gas or gases present in the upper sub-chamber  1402  to generate an electron-ion plasma in the upper sub-chamber  1402 . The optional internal plasma grid  1450  limits the amount of hot electrons in the lower sub-chamber  1403 . In some embodiments, the apparatus is designed and operated such that the plasma present in the lower sub-chamber  1403  is an ion-ion plasma. 
     Both the upper electron-ion plasma and the lower ion-ion plasma may contain positive and negative ions, though the ion-ion plasma will have a greater ratio of negative ions to positive ions. Volatile etching and/or deposition byproducts may be removed from the lower-sub-chamber  1403  through port  1422 . The chuck  1417  disclosed herein may operate at elevated temperatures ranging between about 200° C. and about 500° C. The temperature will depend on the process operation and specific recipe. 
     Processing chamber  1401  may be coupled to facilities (not shown) when installed in a clean room or a fabrication facility. Facilities include plumbing that provide processing gases, vacuum, temperature control, and environmental particle control. These facilities are coupled to processing chamber  1401 , when installed in the target fabrication facility. Additionally, processing chamber  1401  may be coupled to a transfer chamber that allows robotics to transfer semiconductor wafers into and out of processing chamber  1401  using typical automation. 
     In some embodiments, a system controller  1430  (which may include one or more physical or logical controllers) controls some or all of the operations of a processing chamber. The system controller  1430  may include one or more memory devices and one or more processors. In some embodiments, the apparatus includes a switching system for controlling flow rates and durations when disclosed embodiments are performed. In some embodiments, the apparatus may have a switching time of up to about 500 ms, or up to about 750 ms. Switching time may depend on the flow chemistry, recipe chosen, reactor architecture, and other factors. 
     The processing chamber  1401  or apparatus may include a system controller. For example, in some embodiments, a controller  1430  is part of a system, which may be part of the above-described examples. Such systems can include semiconductor processing equipment, including 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. The electronics may be referred to as the “controller,” which may control various components or subparts of the system or systems. The controller  1430 , depending on the processing specification 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, radio frequency (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  1430  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, metals, oxides, silicon, silicon dioxide, surfaces, circuits, and/or dies of a wafer. 
     The controller  1430 , 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  1430  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 including 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. 
     Without limitation, 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  1430  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 processing chamber  1401  may be integrated in a multi-station tool such as shown in  FIG. 15 . Each station may be used to process different operations. For example, one station may be used to perform pre-oxidation while another station is used to perform selective etching of the metal-doped carbon-containing material. Disclosed embodiments may be performed without breaking vacuum and may be performed in the same apparatus. 
       FIG. 15  depicts a semiconductor process cluster architecture with various modules that interface with a vacuum transfer module (VTM)  1538 . The arrangement of transfer modules to “transfer” wafers among multiple storage facilities and processing modules may be referred to as a “cluster tool architecture” system. Airlock module  1530 , also known as a loadlock or transfer module, is shown in VTM  1538  with four processing modules  1520   a - 1520   d , which may be individual optimized to perform various fabrication processes. By way of example, processing modules  1520   a - 1620   d  may be implemented to perform substrate etching, deposition, ion implantation, wafer cleaning, sputtering, and/or other semiconductor processes. One or more of the substrate etching processing modules (any of  1520   a - 1620   d ) may be implemented as disclosed herein, i.e., for performing deposition of the polymerization protective liner, etching to form vias and/or trenches, and other suitable functions in accordance with the disclosed embodiments. Airlock module  1530  and process module  1520  may be referred to as “stations.” Each station has a facet  1536  that interfaces the station to VTM  1538 . Inside each facet, sensors  1 - 18  are used to detect the passing of wafer  1526  when moved between respective stations. 
     Robot  1522  transfers wafer  1526  between stations. In one embodiment, robot  1522  has one arm, and in another embodiment, robot  1522  has two arms, where each arm has an end effector  1524  to pick wafers such as wafer  1526  for transport. Front-end robot  1532 , in atmospheric transfer module (ATM)  1540 , is used to transfer wafers  1526  from cassette or Front Opening Unified Pod (FOUP)  1534  in Load Port Module (LPM)  1542  to airlock module  1530 . Module center  1528  inside process module  1520  is one location for placing wafer  1526 . Aligner  1544  in ATM  1540  is used to align wafers. 
     In an exemplary processing method, a wafer is placed in one of the FOUPs  1534  in the LPM  1542 . Front-end robot  1532  transfers the wafer from the FOUP  1534  to an aligner  1544 , which allows the wafer  1526  to be properly centered before it is etched or processed. After being aligned, the wafer  1526  is moved by the front-end robot  1532  into an airlock module  1530 . Because airlock modules have the ability to match the environment between an ATM and a VTM, the wafer  1526  is able to move between the two pressure environments without being damaged. From the airlock module  1530 , the wafer  1526  is moved by robot  1522  through VTM  1538  and into one of the process modules  1520   a - 1520   d . In order to achieve this wafer movement, the robot  1522  uses end effectors  1524  on each of its arms. Once the wafer  1526  has been processed, it is moved by robot  1522  from the process modules  1520   a - 1620   d  to an airlock module  1530 . From here, the wafer  1526  may be moved by the front-end robot  1532  to one of the FOUPs  1534  or to the aligner  1544 . 
     The computer controlling the wafer movement can be local to the cluster architecture, or can be located external to the cluster architecture in the manufacturing floor, or in a remote location and connected to the cluster architecture via a network. A controller as described above with respect to  FIG. 14  may be implemented with the tool in  FIG. 15 . 
     CONCLUSION 
     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.