Patent Publication Number: US-2022235464-A1

Title: Selective carbon deposition

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 62/865,566, filed on Jun. 24, 2019. The entire disclosure of the application referenced above is incorporated herein by reference. 
    
    
     FIELD 
     The present disclosure relates to selective carbon deposition in an atomic layer deposition substrate processing chamber. 
     BACKGROUND 
     The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     Substrate processing systems may be used to treat substrates such as semiconductor wafers. Examples of substrate treatments include etching, deposition, photoresist removal, etc. During processing, the substrate is arranged on a substrate support such as an electrostatic chuck and one or more process gases may be introduced into the processing chamber. 
     The one or more processing gases may be delivered by a gas delivery system to the processing chamber. In some systems, the gas delivery system includes a manifold connected by one or more conduits to a showerhead that is located in the processing chamber. In some examples, processes use atomic layer deposition (ALD) to deposit a thin film on a substrate. Various alternating etching and deposition cycles may be performed on a same substrate. 
     In other features, the at least one underlying layer comprises at least one of silicon, silicon dioxide, and silicon nitride. The substrate includes alternating oxide-nitride (ONON) layers formed on the at least one underlying layer and the carbon film is formed on the ONON layers. Forming the features includes forming ONON pillars in the ONON layers. The carbon film is an amorphous hard mask (AHM) film. The first thickness is less than or equal to 1 μm. 
     In other features, selectively depositing the carbon includes depositing the carbon using an atomic layer deposition (ALD) process. Performing the ALD process includes supplying at least one carbon-containing precursor gas into the processing chamber in a dosing step first period, purging the processing chamber in a purging step in a second period, and generating plasma in the processing chamber in a plasma step in a third period. Performing the ALD process includes repeatedly alternating the dosing step, the purging step, and the plasma step. Generating the plasma includes generating the plasma while supplying a plasma process gas into the processing chamber without supplying the at least one carbon-containing precursor gas. 
     In other features, depositing a carbon seed layer on the substrate and depositing the carbon film onto the carbon seed layer. The carbon seed layer comprises carbon fluoride (CF x ), wherein x is an integer. Depositing the carbon seed layer includes depositing the carbon seed layer using a CVD or PECVD process. Depositing the carbon seed layer includes supplying a carbon-contain precursor gas into the processing chamber. The carbon-containing precursor gas includes at least one of carbon tetrabromide (CBr 4 ), tribromomethane (CHBr 3 ), and tribromomethane (CH 2 Br 2 ). 
     A system configured to deposit carbon on a substrate in a processing chamber includes a gas delivery system configured to supply process gases into the processing chamber, a radio frequency (RF) plasma generating system configured to generate plasma in the processing chamber, and a controller. The substrate includes a carbon film having a first thickness formed on at least one underlying layer of the substrate. The controller is configured to, with the substrate arranged on a substrate support in the processing chamber, control the RF plasma generating system to perform a first etching step to etch the substrate to form features on the substrate, remove portions of the carbon film, and decrease the first thickness of the carbon film, control the gas delivery system to selectively deposit carbon onto remaining portions of the carbon film, and control the RF plasma generating system to perform at least one second etching step to etch the substrate to complete the forming of the features on the substrate. 
     In other features, the controller is configured to control the gas delivery system and the RF plasma generating system to perform an atom layer deposition (ALD) process to deposit the carbon. To perform the ALD process, the controller is configured to control the gas delivery system to supply at least one carbon-containing precursor gas into the processing chamber in a dosing step first period, purge the processing chamber in a purging step in a second period, and control the RF plasma generating system to generate plasma in the processing chamber in a plasma step in a third period. 
     In other features, the controller is configured to control the gas delivery system and the RF plasma generating system to deposit a carbon seed layer on the substrate and deposit the carbon film onto the carbon seed layer. Depositing the carbon seed layer includes supplying a carbon-contain precursor gas into the processing chamber to deposit the carbon seed layer using a CVD or PECVD process. The carbon-containing precursor gas includes at least one of carbon tetrabromide (CBr 4 ), tribromomethane (CHBr 3 ), and tribromomethane (CH 2 Br 2 ). 
     SUMMARY 
     A method for depositing carbon on a substrate in a processing chamber includes arranging the substrate on a substrate support in the processing chamber. The substrate includes a carbon film having a first thickness formed on at least one underlying layer of the substrate. The method further includes performing a first etching step to etch the substrate to form features on the substrate, remove portions of the carbon film, and decrease the first thickness of the carbon film, selectively depositing carbon onto remaining portions of the carbon film, and performing at least one second etching step to etch the substrate to complete the forming of the features on the substrate. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description, the claims and the drawings. The detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an example of a substrate processing system according to the present disclosure; 
         FIGS. 2A, 2B, 2C, and 2D  show an example carbon mask deposition process; 
         FIGS. 3A, 3B, 3C, 3D, 3E, and 3F  show an example selective carbon deposition process according to the present disclosure; 
         FIGS. 4A, 4B, 4C, 4D, and 4E  show another example selective carbon deposition process according to the present disclosure; 
         FIGS. 5A, 5B, and 5C  show an example conformal carbon ALD process according to the present disclosure; 
         FIGS. 6A, 6B, and 6C  show an example process for depositing a carbon protection layer according to the present disclosure; 
         FIGS. 7A and 7B  show an example process for reducing a pitch of features formed on a substrate according to the present disclosure; 
         FIGS. 8A, 8B, 8C, and 8D  show an example double patterning process using conformal carbon deposition according to the present disclosure; and 
         FIG. 9  illustrates steps of an example method of performing a selective carbon deposition process according to the present disclosure. 
     
    
    
     In the drawings, reference numbers may be reused to identify similar and/or identical elements. 
     DETAILED DESCRIPTION 
     Deposition processes may be used to deposit films (such as amorphous carbon films) on an underlying layer or substrate. In some examples, films may be deposited as a mask to protect features of the substrate during subsequent pattern etching steps. For example, in some patterning processes (e.g., memory hole or other oxide-nitride (ONON) patterning), an amorphous carbon hardmask (AHM) film may be deposited onto the substrate to protect features during an anisotropic etching step. 
     The AHM film protects tops of features (e.g., ONON pillars or stacks) formed on the substrate during selective etching steps. However, the etching steps also remove material from the AHM film. Accordingly, for deep etching (i.e., for taller ONON stacks), a thickness of the deposited AHM film must be increased to withstand longer etching periods. Increased weight associated with the thicker AHM film may cause bowing of the substrate and/or ONON features. In other examples, a photoresist film may be used to define a pitch of the pattern. However, when the photoresist film is used, further reducing the pitch may be difficult. 
     Systems and methods according to the present disclosure selectively deposit carbon (e.g., using atomic layer deposition, or ALD) onto a previously deposited carbon film. For example, the carbon film may be deposited on a substrate or underlying layer comprising silicon (Si), silicon dioxide (SiO 2 ), silicon nitride (SiN), etc. using chemical vapor deposition (CVD) and/or, in some examples, may be incidentally deposited as a result of etching a carbon-containing film in a previous step. Subsequent to a first etching period, carbon may be redeposited onto the carbon film in a selective carbon growth step (e.g., using ALD). For example, the selective carbon growth step may only deposit carbon onto the remaining portion of the previously deposited carbon film and not onto other (e.g., Si, SiO 2 , SiN, etc.) features. Any nominal amounts of carbon deposited onto other surfaces may be removed by isotropic etching. Additional deposition of carbon may be performed as needed. For example, alternating carbon deposition steps and etching steps may be performed. In this manner, an amount of etching protection provided by the carbon film may be extended for additional etching periods without increasing an initial thickness of a deposited AHM film. 
     Referring now to  FIG. 1 , an example substrate processing system  100  configured to perform selective carbon deposition according to the principles of the present disclosure is shown. The substrate processing system  100  includes a substrate support (e.g., a pedestal)  104  arranged within a processing chamber  108 . A substrate  112  is arranged on the substrate support  104  for processing. For example, processing including deposition and etching steps may be performed on the substrate  112 . 
     A gas delivery system  120  is configured to flow process gases into the processing chamber  108 . For example, the gas delivery system  120  includes gas sources  122 - 1 ,  122 - 2 , . . . , and  122 -N (collectively gas sources  122 ) that are connected to valves  124 - 1 ,  124 - 2 , . . . , and  124 -N (collectively valves  124 ) and mass flow controllers  126 - 1 ,  126 - 2 , . . . , and  126 -N (collectively MFCs  126 ). The MFCs  126  control flow of gases from the gas sources  122  to a manifold  128  where the gases mix. An output of the manifold  128  is supplied via an optional pressure regulator  132  to a gas distribution device such as a multi-injector showerhead  140 . 
     In some examples, a temperature of the substrate support  104  may be controlled using resistive heaters  160 . The substrate support  104  may include coolant channels  164 . Cooling fluid is supplied to the coolant channels  164  from a fluid storage  168  and a pump  170 . Pressure sensors  172 ,  174  may be arranged in the manifold  128  or the showerhead  140 , respectively, to measure pressure. A valve  178  and a pump  180  may be used to evacuate reactants from the processing chamber  108  and/or to control pressure within the processing chamber  108 . 
     A controller  182  controls gas delivery from the gas delivery system  120 . In some examples, the controller  182  may include a dose controller  184  that controls dosing provided by the multi-injector showerhead  140 . The controller  182  controls pressure in the processing chamber and/or evacuation of reactants using the valve  178  and the pump  180 . The controller  182  controls the temperature of the substrate support  104  and the substrate  112  based upon temperature feedback (e.g., from sensors (not shown) in the substrate support and/or sensors (not shown) measuring coolant temperature). The controller  182  according to the present disclosure is configured to control the gas delivery system  120  to perform selective carbon deposition as described below in more detail. 
     In some examples, the substrate processing system  100  may be configured to perform etching (e.g., responsive to the controller  182 ) on the substrate  112  within the same processing chamber  108 . Accordingly, the substrate processing system  100  may include an RF generating system  188  configured to generate and provide RF power (e.g., as a voltage source, current source, etc.) to one of a lower electrode (e.g., a baseplate of the substrate support  104 , as shown) and an upper electrode (e.g., the showerhead  140 ). The other one of the lower electrode and the upper electrode may be DC grounded, AC grounded, or floating. For example only, the RF generating system  188  may include an RF generator  192  configured to generate an RF voltage that is fed by a matching and distribution network  196  to generate plasma within the processing chamber  108  to etch the substrate  112 . In other examples, the plasma may be generated inductively or remotely. Although, as shown for example purposes, the RF generating system  188  corresponds to a capacitively coupled plasma (CCP) system, the principles of the present disclosure may also be implemented in other suitable systems, such as, for example only transformer coupled plasma (TCP) systems, CCP cathode systems, remote microwave plasma generation and delivery systems, etc. 
     Referring now to  FIGS. 2A, 2B, 2C, and 2D , an example carbon mask deposition process is shown.  FIG. 2A  shows an example substrate  200  provided for processing. For example, the substrate  200  may include one or more underlying layers  204 . The underlying layers  204  may comprise Si, SiO 2 , SiN, etc.  FIG. 2B  shows alternating ONON layers  208  deposited on the underlying layers  204 .  FIG. 2C  shows an AHM layer  212  (e.g., a carbon AHM film) deposited on the ONON layers  208 .  FIG. 2D  shows ONON features  216  (e.g., ONON pillars or stacks) formed by etching the ONON layers  208 . The AHM layer  212  protects tops of the ONON features  216  formed during selective etching steps. As shown, the initial AHM layer  212  is sufficiently thick (e.g., greater than 2 μm) to withstand etching until the etching of the ONON features  216  is completed. 
     Referring now to  FIGS. 3A, 3B, 3C, 3D, 3E, and 3F , an example selective carbon deposition process according to the present disclosure is shown.  FIG. 3A  shows an example substrate  300  provided for processing. For example, the substrate  300  may include one or more underlying layers  304 . The underlying layers  304  may comprise Si, SiO 2 , SiN, etc.  FIG. 3B  shows alternating ONON layers  308  deposited on the underlying layers  304 . 
       FIG. 3C  shows an AHM layer  312  (e.g., a carbon AHM film) deposited on the ONON layers  308  (e.g., using a CVD or plasma enhanced CVD (PECVD) process). In this example, a thickness of the AHM layer  312  is significantly less than a thickness of the AHM layer  212  shown in  FIG. 2C  (and as indicated at  320 ). For example, the thickness of the AHM layer  312  may be 50% or less than a thickness of the AHM layer  212  (e.g., 1 μm or less).  FIG. 3D  shows ONON features  316  formed by etching the ONON layers  308 . The AHM layer  312  protects tops of the ONON features  316  formed during selective etching steps. 
       FIG. 3E  shows additional carbon material redeposited onto the AHM layer  312  (e.g., using an ALD process as described below in more detail). In other words, subsequent to the initial etching performed in  FIG. 3D  and prior to completing the etching of the ONON features  316 , carbon is selectively redeposited onto the AHM layer  312  to increase the thickness of the AHM layer  312 . For example, carbon is selectively redeposited in a selective carbon growth step such that carbon is deposited onto remaining portions of the AHM layer  312  without being deposited onto the ONON features  316  or the ONON layers  308 . Any carbon deposited onto the ONON features  316  or the ONON layers  308  may be removed in subsequent anisotropic etching steps. 
     In this manner, the thickness of the AHM layer  312  is increased to compensate for material lost during etching.  FIG. 3F  shows the ONON features  316  subsequent to additional etching. The alternating redepositing of the carbon on the AHM layer  312  and the etching of the ONON features  316  as described in  FIGS. 3E and 3F  may be repeated as necessary to complete the etching of the ONON features  316  to a desired depth. 
     In one example, an ALD process is performed to selectively deposit the carbon of the AHM layer  312  by providing a dose of one or more carbon precursor gases (e.g., precursors including hydrocarbon species (C x H y ), such acetylene, or C 2 H 2 , gas) into the processing chamber  108  in a dosing step for a first period (e.g., for 5-20 seconds). A purging step (e.g., using argon, or Ar, gas) may be performed in a subsequent second period (e.g., for 1-10 seconds). An RF plasma step is performed in a third period (e.g., from 0.1 to 1.0 second) subsequent to the purging step. A plasma process gas (e.g., Ar gas) may be provided while the precursor gases are not provided during the RF plasma step. In other words, plasma may be generated in the processing chamber  108  while the Ar gas is being flowed but without providing additional precursor gases subsequent to the purging step. Accordingly, relatively small amounts of carbon (e.g., 1-2 angstroms) are deposited during the RF plasma step. A second purging step may be performed in a fourth period (e.g., from 1 to 10 seconds) to purge byproducts from the processing chamber  108 . 
     The dosing, purging, and RF plasma steps may be repeated multiple times (e.g., for 200-300 cycles) to selectively deposit carbon as shown in  FIGS. 3C and 3E . In some examples, this selective carbon deposition process results in deposition of 30-50 nm of carbon on the AHM layer  312  while only 0-3.0 nm of carbon is deposited on Si, SiO 2 , or SiN layers. 
       FIGS. 4A, 4B, 4C, 4D, and 4E  show another example selective carbon deposition process according to the present disclosure. In this example, a carbon nucleation or seed layer is deposited and additional carbon material is selectively deposited onto the carbon seed layer (e.g., using ALD).  FIG. 4A  shows an example substrate  400  including one or more underlying layers  404  (e.g., Si, SiO 2 , SiN, etc.), alternating ONON layers  408  deposited on the underlying layers  404 , and an AHM layer  412  (e.g., a carbon AHM film) deposited on the ONON layers  408 . For example, a carbon seed layer  414  is deposited on the ONON layers  408  and the AHM layer  412  is deposited on the carbon seed layer  414 . In some examples, the carbon seed layer  414  may correspond to a CF x  layer conformally deposited onto the ONON layers  408 . The carbon of the AHM layer  412  selectively deposits onto the CF x  layer. 
     In some examples, the carbon seed layer  414  may be deposited using a CVD or PECVD process. The carbon seed layer  414  may have a thickness of 0.5 to 2 angstroms. In one example, a carbon bromide precursor gas (e.g., carbon tetrabromide, or CBr 4 ) is flowed into the processing chamber  108  to deposit the carbon seed layer  414 . Other example precursor gases include, but are not limited to, tribromomethane (CHBr 3 ) and tribromomethane (CH 2 Br 2 ). 
     In some examples, carbon is selectively deposited (e.g., using ALD) on the carbon seed layer  414  to form the AHM layer  412  by flowing a C 2 H 2  precursor gas into the processing chamber  108  and generating plasma in an RF plasma step. For example, a plasma process gas such as Ar gas may be provided during the RF plasma step to cause selective deposition of carbon onto the carbon seed layer  414 . Optional purging steps may be performed prior and/or subsequent to performing the selective carbon deposition in a manner similar to that described in  FIGS. 3A-3F . 
       FIG. 4B  shows ONON features  416  formed by etching the ONON layers  408 . The AHM layer  412  protects tops of the ONON features  416  formed during selective etching steps.  FIG. 4C  shows an example where the etching has removed the AHM layer  412  down to the carbon seed layer  414 .  FIG. 4D  shows additional carbon material deposited onto the carbon seed layer  414  to reform the AHM layer  412 . In other words, subsequent to the initial etching performed in  FIG. 4B  and prior to completing the etching of the ONON features  416 , carbon is selectively redeposited onto the carbon seed layer  414  to increase the thickness of the AHM layer  312 . For example, carbon is selectively redeposited in a selective carbon growth step (e.g., using ALD) such that carbon is deposited onto the carbon seed layer  414  and/or remaining portions of the AHM layer  412  without being deposited onto the ONON features  416  or the ONON layers  408 . Any carbon deposited onto the ONON features  416  or the ONON layers  408  may be removed in subsequent anisotropic etching steps. 
       FIG. 4E  shows the ONON features  416  subsequent to additional etching. The alternating redepositing of the carbon on the carbon seed layer  414  and/or the AHM layer  412  and the etching of the ONON features  416  as described in  FIGS. 4D and 4F  may be repeated as necessary to complete the etching of the ONON features  416  to a desired depth. 
       FIGS. 5A, 5B, and 5C  show an example conformal carbon ALD process according to the present disclosure.  FIG. 5A  shows an example substrate  500  including one or more underlying layers  504  and pattern features (e.g., stacks or pillars)  508  formed on the underlying layers. The underlying layers  504  may comprise Si, SiO 2 , SiN, etc. For example only, the pattern features  508  may correspond to features comprising silicon, silicon nitride, silicon oxide, ONON layers, etc. 
       FIG. 5B  shows a carbon seed layer  512  deposited on the pattern features  508 . For example, carbon seed layer  512  may correspond a layer deposited using a PECVD process. In one example, the PECVD process includes flowing one or more precursor gases (e.g., CBr 4 ) into the processing chamber  108  and generating plasma while additionally flowing a plasma process gas such as helium (He), molecular hydrogen (H 2 ), etc. 
       FIG. 5C  shows a conformal carbon ALD layer  516  formed on the carbon seed layer  512 . For example, the conformal carbon ALD layer  516  is formed by selectively depositing carbon onto the carbon seed layer  512 . For example, carbon is selectively deposited on the carbon seed layer  512  by flowing a hydrocarbon precursor such as C 2 H 2  gas into the processing chamber  108  and generating plasma in an RF plasma step. For example only, a plasma process gas such as Ar gas may be provided during the RF plasma step to cause selective deposition of carbon onto the carbon seed layer  512 . 
       FIGS. 6A, 6B, and 6C  show an example process for depositing a carbon protection layer according to the present disclosure.  FIG. 6A  shows an example substrate  600  including one or more underlying layers  604 , ONON layers  608  formed on the underlying layers  604 , and ONON features  612  previously etched into the ONON layers  608 . The underlying layers  504  may comprise Si, SiO 2 , SiN, etc. As shown, remaining portions of a carbon mask layer (e.g., a carbon AHM, a metal-doped diamond-like carbon (MDLC) layer, etc.)  616  may be formed on the ONON features  612 . The carbon mask layer  616  protects upper surfaces of the ONON features  612  during etching. 
       FIG. 6B  shows a conformal carbon protection layer  620  selectively deposited on the carbon mask layer  616 , upper surfaces of the ONON layers  608 , and sidewalls  624  of the ONON features  612 . For example, the carbon protection layer  620  may correspond to a layer deposited using an ALD process. In one example, the ALD process includes flowing one or more precursor gases (e.g., CBr 4 ) into the processing chamber  108  and generating plasma while additionally flowing a plasma process gas such as helium (He), molecular hydrogen (H 2 ), etc. to conformally deposit the carbon protection layer  620 . In other examples, the carbon protection layer  620  is not deposited in a separate step. Rather, the carbon protection layer  620  may be formed by material from the carbon mask layer  616  being redeposited during etching steps. 
       FIG. 6C  shows the ONON features  612  subsequent to additional etching. Portions of the carbon protection layer  620  protecting the sidewalls  624  of the ONON features  612  were etched. Accordingly, the carbon protection layer  620  as shown in  FIG. 6C  is thinner relative to  FIG. 6B . The carbon protection layer  620  may be redeposited for additional etching steps. In this manner, alternating deposition of the carbon protection layer  620  and etching steps may be repeated until etching of the ONON features  612  is completed. 
       FIGS. 7A and 7B  show an example process for reducing a pitch of features formed on a substrate  700  according to the present disclosure.  FIG. 7A  shows an example of the substrate  700  including one or more underlying layers such as an AHM  704 , an etch stop layer (ESL)  708 , etc. and pattern features (e.g., mandrels or spacers)  712  formed on the underlying layers. The mandrels  712  may comprise any suitable sacrificial material (e.g., Si, SiO 2 , etc.) that may be removed in subsequent etching steps. The mandrels  712  are spaced according to a pitch  716 . 
       FIG. 7B  shows a conformal carbon layer  720  selectively deposited onto the mandrels  712 . For example, the conformal carbon layer  720  may correspond to a layer deposited using an ALD process as described above in other examples. The conformal carbon layer  720  reduces the spacing between the mandrels  712  to form new reduced pitch  724 . 
       FIGS. 8A, 8B, 8C, and 8D  show an example double patterning process using conformal carbon deposition according to the present disclosure.  FIG. 8A  shows an example of a substrate  800  including one or more underlying layers  804 , a buffer layer (e.g., an SiN or SiN 2  layer)  808 , and pattern features (e.g., mandrels or spacers)  812  formed on the underlying layers. The mandrels  812  may comprise any suitable sacrificial material (e.g., Si, SiO 2 , etc.) that may be removed in subsequent etching steps. 
       FIG. 8B  shows a conformal (e.g., amorphous) carbon layer  816  selectively deposited onto the mandrels  812 . For example, the conformal carbon layer  816  may correspond to a layer deposited using an ALD process as described above in other examples. As shown in  FIG. 8C , the conformal carbon layer  816  can then be selectively etched (i.e., relative to SiO 2 , SiN 2 , etc.) from the buffer layer  808  and upper surfaces of the mandrels  812  while sidewalls (e.g., sidewall spacers)  820  of the carbon layer  816  remain on the substrate  800 . In some examples, etching of the carbon layer  816  includes one or more ashing steps. 
     As shown in  FIG. 8D , additional etching steps are performed to remove the mandrels  812  from between the sidewall spacers  820 . The sidewall spacers  820  remain on the substrate  800  for additional processing steps. 
     In addition to the examples provided above, conformal carbon deposition may be used for other semiconductor processing steps. For example, a PECVD or other ALD process may be used to conformally deposit carbon on a substrate to fill (i.e., gap fill) voids in the substrate. 
     Referring now to  FIG. 9 , an example method  900  of performing a selective carbon deposition process according to the present disclosure begins at  904 . At  908 , a substrate is arranged in a processing chamber. For example, the substrate may include one or more underlying layers and alternating ONON layers deposited on the underlying layers. At  912 , an optional carbon nucleation or seed layer is deposited onto the ONON layers. At  916 , an AHM layer (e.g., a carbon AHM film) is deposited onto the ONON layers (and/or onto the carbon seed layer). At  920 , ONON features (e.g., stacks or pillars) are formed by etching the ONON layers. 
     At  924 , additional carbon material is selectively deposited onto the AHM layer to replace material removed during the etching step (e.g., using an ALD process). In one example, the selective carbon deposition of the AHM layer is performed by providing a dose of one or more carbon precursor gases (e.g., acetylene, or C 2 H 2 , gas) into the processing chamber in a dosing step for a first period (e.g., for 5-20 seconds). A purging step (e.g., using argon, or Ar, gas) may be performed in a subsequent second period (e.g., for 1-10 seconds). An RF plasma step is performed in a third period (e.g., from 0.1 to 1.0 second) subsequent to the purging step. A second purging step may be performed in a fourth period (e.g., from 1 to 10 seconds) to purge byproducts from the processing chamber. The dosing, purging, and RF plasma steps may be repeated multiple times to selectively deposit a desired amount of carbon. 
     At  928 , additional etching is performed to complete the ONON features. The alternating redepositing of the carbon on the AHM layer and the etching of the ONON features performed at  924  and  928  may be repeated as necessary to complete the etching of the ONON features to a desired depth. The method  900  ends at  932 . 
     The foregoing description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. The broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent upon a study of the drawings, the specification, and the following claims. It should be understood that one or more steps within a method may be executed in different order (or concurrently) without altering the principles of the present disclosure. Further, although each of the embodiments is described above as having certain features, any one or more of those features described with respect to any embodiment of the disclosure can be implemented in and/or combined with features of any of the other embodiments, even if that combination is not explicitly described. In other words, the described embodiments are not mutually exclusive, and permutations of one or more embodiments with one another remain within the scope of this disclosure. 
     Spatial and functional relationships between elements (for example, between modules, circuit elements, semiconductor layers, etc.) are described using various terms, including “connected,” “engaged,” “coupled,” “adjacent,” “next to,” “on top of,” “above,” “below,” and “disposed.” Unless explicitly described as being “direct,” when a relationship between first and second elements is described in the above disclosure, that relationship can be a direct relationship where no other intervening elements are present between the first and second elements, but can also be an indirect relationship where one or more intervening elements are present (either spatially or functionally) between the first and second elements. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A OR B OR C), using a non-exclusive logical OR, and should not be construed to mean “at least one of A, at least one of B, and at least one of C.” 
     In some implementations, a controller is part of a system, which may be part of the above-described examples. Such systems can comprise 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, 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, 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 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, in some implementations, may be a part of or coupled to a computer that is integrated with the system, 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. 
     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 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.