Patent Publication Number: US-2020294789-A1

Title: Methods for selectively forming a silicon nitride film on a substrate and related semiconductor device structures

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Divisional of, and claims priority to and the benefit of, U.S. patent application Ser. No. 15/589,849, filed May 8, 2017 and entitled “METHODS FOR SELECTIVELY FORMING A SILICON NITRIDE FILM ON A SUBSTRATE AND RELATED SEMICONDUCTOR DEVICE STRUCTURES,” which is hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure generally relates to methods for selectively forming a silicon nitride film on a substrate and related semiconductor device structures including a selective silicon nitride film. 
     BACKGROUND OF THE DISCLOSURE 
     In the field of semiconductor device technology silicon nitride films may be utilized during the fabrication of semiconductor integrated circuitry. For example, silicon nitride films may be utilized as an insulating material during the fabrication of semiconductor device structures, such as, for example, transistors, memory cells, logic devices, memory arrays, etc. 
     There is a need in the field of semiconductor device technology for low temperature deposition processes for high quality silicon nitride films; such low temperature deposition processes should also provide precise control of the film thickness, thickness uniformity and conformality. 
     Common silicon nitride film deposition processes require high temperature deposition, i.e., around 600° C. to 800° C., to attain the reaction between precursors such as dichlorosilane (DCS) and ammonia (NH 3 ). State of the art device structures may not be able to withstand such a high thermal budget which may further result in a deterioration of device performance and may cause device integration problems. 
     An alternative solution to high temperature deposition processes may be to utilize a plasma to activate the precursors which may in turn allow for low temperature reactions and reduced deposition temperatures for silicon nitride films. However, plasma based deposition processes may be limited in deposition performance, i.e., step coverage, uniformity of film quality achievable for high aspect ratio structures and plasma based deposition processes may damage the underlying device structures. 
     In some applications it may be desirable to form silicon nitride films only in certain areas of a substrate. Typically, such a result is achieved by depositing a continuous film and patterning it using subsequent lithography and etch steps. Such processing is time consuming and expensive, and does not offer the precision required for many applications. A possible solution is the use of selective deposition processes whereby the material is deposited only in the desired areas thereby eliminating the need for subsequent patterning steps. 
     Therefore low temperature selective deposition processes for silicon nitride films and semiconductor device structures including such selective silicon nitride films may be needed to improve semiconductor device performance. 
     SUMMARY OF THE DISCLOSURE 
     In accordance with at least one embodiment of the disclosure, a method for selectively forming a silicon nitride film a on substrate comprising a first metallic surface and a second dielectric surface by a cyclical deposition process is provided. The method may comprise, contacting the substrate with a first reactant comprising a silicon halide source, contacting the substrate with a second reactant comprising a nitrogen source, wherein the incubation delay for the first metallic surface is less than the incubation delay for the second dielectric surface. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the invention, the advantages of embodiments of the disclosure may be more readily ascertained from the description of certain examples of the embodiments of the disclosure when read in conjunction with the accompanying drawing, in which: 
         FIG. 1  illustrates a process flow for a method of forming a selective silicon nitride film on a substrate as described in the embodiments of the disclosure; 
         FIG. 2  illustrates the deposition thickness versus number of cyclical deposition cycles for silicon nitride films formed according to the embodiments of the disclosure; 
         FIG. 3  illustrates another process for a method of forming a selective silicon nitride film on a substrate as described in the embodiments of the disclosure; 
         FIG. 4  illustrates an exemplary reaction system configured to perform the embodiments of the disclosure; 
         FIG. 5  illustrates an example semiconductor device structure which includes a silicon nitride film formed by the embodiments of the disclosure. 
     
    
    
     It will be appreciated that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of illustrated embodiments of the present disclosure. 
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below. 
     As used herein, the term “metallic surface” may refer to a surface including metal ions and may further include, but is not limited to, metals, metal alloys, metal salts, metal oxides, metal silicides, metal borides, semi-metals and metal nitrides. 
     As used herein, the term “cyclic deposition” may refer to the sequential introduction of precursors (reactants) into a reaction chamber to deposit a layer over a substrate and includes processing techniques such as atomic layer deposition and cyclical chemical vapor deposition. 
     As used herein, the term “incubation period” may refer to the number of cyclical deposition cycles in the initial stages of a cyclical deposition in which no discernable deposition is observed. 
     As used herein, the term “atomic layer deposition” (ALD) may refer to a vapor deposition process in which deposition cycles, preferably a plurality of consecutive deposition cycles, are conducted in a process chamber. Typically, during each cycle the precursor is chemisorbed to a deposition surface (e.g., a substrate surface or a previously deposited underlying surface such as material from a previous ALD cycle), forming a monolayer or sub-monolayer that does not readily react with additional precursor (i.e., a self-limiting reaction). Thereafter, if necessary, a reactant (e.g., another precursor or reaction gas) may subsequently be introduced into the process chamber for use in converting the chemisorbed precursor to the desired material on the deposition surface. Typically, this reactant is capable of further reaction with the precursor. Further, purging steps may also be utilized during each cycle to remove excess precursor from the process chamber and/or remove excess reactant and/or reaction byproducts from the process chamber after conversion of the chemisorbed precursor. Further, the term “atomic layer deposition,” as used herein, is also meant to include processes designated by related terms such as, “chemical vapor atomic layer deposition”, “atomic layer epitaxy” (ALE), molecular beam epitaxy (MBE), gas source MBE, or organometallic MBE, and chemical beam epitaxy when performed with alternating pulses of precursor composition(s), reactive gas, and purge (e.g., inert carrier) gas. 
     As used herein, the term “cyclical chemical vapor deposition” may refer to any process wherein a substrate is sequentially exposed to two or more volatile precursors, which react and/or decompose on a substrate to produce a desired deposition. 
     As used herein, the term “substrate” may refer to any underlying material or materials that may be used, or upon which a device, a circuit or a film may be formed. Substrate may comprise a wafer, such as a silicon wafer, a glass substrate or any other type of substrate. The substrate may also comprise completely or partially fabricated semiconductor device structures including metallic surfaces and dielectric surfaces. 
     A number of materials and their chemical formula are given in this disclosure, such materials and their chemical formula should not be construed as limiting the stoichiometry of a given material or material surface. 
     The embodiments of the disclosure may include methods for selectively forming a silicon nitride film on a substrate and particularly for forming a high quality selective silicon nitride film on a substrate at reduced deposition temperatures. As a non-limiting example embodiment of the disclosure a method of forming a selective silicon nitride film on a substrate may include an atomic layer deposition process or a cyclical chemical vapor deposition process. In particular embodiments the substrate may comprise a first metallic surface and a second dielectric surface and methods for forming the selective silicon nitride may favor deposition on the first metallic surface over deposition on the second dielectric surface. 
     The methods of the disclosure may be understood with reference to  FIG. 1  which illustrates a non-limiting example embodiment of a method  100  for selectively forming a silicon nitride film on a substrate, the substrate comprising a first metallic surface and a second dielectric surface. For example,  FIG. 1  may illustrate a method  100  for selectively forming a silicon nitride film on a substrate by a cyclical deposition process. In more detail the cyclical deposition process for forming the selective silicon nitride may comprise an atomic layer deposition process or alternatively may comprise a cyclical chemical vapor deposition process. A non-limiting example embodiment of a cyclical deposition process may include ALD, wherein ALD is based on typically self-limiting reactions, whereby sequential and alternating pulses of reactants are used to deposit about one atomic (or molecular) monolayer of material per deposition cycle. The deposition conditions and precursors are typically selected to provide self-saturating reactions, such that an adsorbed layer of one reactant leaves a surface termination that is non-reactive with the gas phase reactants of the same reactant. The substrate is subsequently contacted with a different reactant that reacts with the previous termination to enable continued deposition. Thus, each cycle of alternated pulses typically leaves no more than about one monolayer of the desired material. However, as mentioned above, the skilled artisan will recognize that in one or more ALD cycles more than one monolayer of material may be deposited, for example if some gas phase reactions occur despite the alternating nature of the process. 
     In an ALD-type process for depositing a selective silicon nitride film, one ALD cycle may comprise exposing the substrate to a first reactant, as illustrated in process block  104  of  FIG. 1 , removing any unreacted first reactant and reaction byproducts from the reaction space and exposing the substrate to a second reactant, as illustrated by process block  106  of  FIG. 1 , followed by a second removal step. The first reactant may comprise a silicon halide source and the second reactant may comprise a nitrogen source. 
     Precursors may be separated by inert gases, such as argon (Ar) or nitrogen (N 2 ), to prevent gas-phase reactions between reactants and enable self-saturating surface reactions. In some embodiments, however, the substrate may be moved to separately contact a first vapor phase reactant and a second vapor phase reactant. Because the reactions self-saturate, strict temperature control of the substrates and precise dosage control of the precursors is not usually required. However, the substrate temperature is preferably such that an incident gas species does not condense into monolayers or multimonolayers nor thermally decompose on the surface. Surplus chemicals and reaction byproducts, if any, are removed from the substrate surface, such as by purging the reaction space or by moving the substrate, before the substrate is contacted with the next reactive chemical. Undesired gaseous molecules can be effectively expelled from a reaction space with the help of an inert purging gas. A vacuum pump may be used to assist in the purging. 
     Reactors capable of being used to deposit selective silicon nitride films can be used for the deposition. Such reactors include ALD reactors, as well as CVD reactors equipped with appropriate equipment and means for providing the precursors. According to some embodiments, a showerhead reactor may be used. 
     Examples of suitable reactors that may be used include commercially available single substrate (or single wafer) deposition equipment such as Pulsar® reactors (such as the Pulsar® 2000 and the Pulsar® 3000 and Pulsar® XP ALD), and EmerALD® XP and the EmerALD® reactors, available from ASM America, Inc. of Phoenix, Ariz. and ASM Europe B.V., Almere, Netherlands. Other commercially available reactors include those from ASM Japan K.K. (Tokyo, Japan) under the tradename Eagle® XP and XP8. In some embodiments the reactor is a spatial ALD reactor, in which the substrates moves or rotates during processing. 
     In some embodiments a batch reactor may be used. Suitable batch reactors include, but are not limited to, Advance® 400 Series reactors commercially available from ASM Europe B.V (Almere, Netherlands) under the trade names A400 and A412 PLUS. In some embodiments a vertical batch reactor is utilized in which the boat rotates during processing, such as the A412. Thus, in some embodiments the wafers rotate during processing. In other embodiments, the batch reactor comprises a minibatch reactor configured to accommodate 10 or fewer wafers, 8 or fewer wafers, 6 or fewer wafers, 4 or fewer wafers, or 2 wafers. In some embodiments in which a batch reactor is used, wafer-to-wafer uniformity is less than 3% (1 sigma), less than 2%, less than 1% or even less than 0.5%. 
     The deposition processes described herein can optionally be carried out in a reactor or reaction space connected to a cluster tool. In a cluster tool, because each reaction chamber is dedicated to one type of process, the temperature of the reaction chamber in each module can be kept constant, which improves the throughput compared to a reactor in which the substrate is heated up to the process temperature before each run. Additionally, in a cluster tool it is possible to reduce the time to pump the reaction chamber to the desired process pressure levels between substrates. 
     A stand-alone reactor can be equipped with a load-lock. In that case, it is not necessary to cool down the reaction space between each run. In some embodiments a deposition process for depositing a selective silicon nitride film may comprise a plurality of ALD cycles. 
     In some embodiments the cyclical deposition processes are used to form the selective silicon nitride film on a substrate and the selective deposition process may be an ALD type process. In some embodiments the cyclical deposition may be a hybrid ALD/CVD or cyclical CVD process. For example, in some embodiments the deposition rate of the ALD process may be low compared with a CVD process. One approach to increase the deposition rate may be that of operating at a higher substrate temperature than that typically employed in an ALD process, resulting in a chemical vapor deposition process, but still taking advantage of the sequential introduction of precursors, such a process may be referred to as cyclical CVD. 
     According to some embodiments, ALD processes are used to form a selective silicon nitride film on a substrate, such as an integrated circuit workpiece. In some embodiments of the disclosure each ALD cycle comprises two distinct deposition steps or phases. 
     In a first phase of the cyclical deposition process (“the silicon phase”), the substrate surface on which deposition is desired is contacted with a first vapor phase reactant (process block  104  of  FIG. 1 ) comprising a silicon precursor which chemisorbs onto the substrate surface, forming no more than about one monolayer of reactant species on the surface of the substrate. It should be appreciated that in some embodiments, each contacting step may be repeated one or more times prior to advancing on to the subsequent processing step, i.e., prior to a subsequent contacting step or removal/purge step. 
     In some embodiments, a silicon precursor, also referred to herein as the “silicon compound” may comprise a silicon halide source. In some embodiments, the first reactant may comprise a silicon halide source and may further comprise at least one of silicon tetraiodide (SiI 4 ), silicon tetrabromide (SiBr 4 ), silicon tetrachloride (SiCl 4 ), hexachlorodisilane (Si 2 Cl 6 ), hexaiododisilane (Si 2 I 6 ), octoiodotrisilane (Si 3 I 8 ). In embodiments wherein the silicon halide source comprises silicon tetraiodide (SiI 4 ) the silicon tetraiodide source may be preheated to provide sufficient vapor pressure for delivery to the reaction chamber, for example, in some embodiments the silicon tetraiodide precursor source may be preheated to a temperature of between approximately 90° C. and approximately 125° C., or in some embodiments the silicon tetraiodide may be preheated to a temperature of approximately 100° C. 
     In some embodiments, exposing the substrate to a silicon halide source may comprise pulsing the silicon precursor (e.g., the silicon tetraiodide (SiI 4 )) over the substrate for a time period of between about 0.5 seconds and about 30 seconds, or between about 0.5 seconds and about 10.0 seconds, or between about 0.5 seconds and about 5.0 seconds. In addition, during the pulsing of the silicon halide source over the substrate the flow rate of the silicon halide source may be less than 2000 sccm, or less than 1000 sccm, or less than 500 sccm, or less than 250 sccm or even less than 100 sccm. 
     Excess silicon halide source and reaction byproducts (if any) may be removed from the substrate surface, e.g., by purging with an inert gas. For example, in some embodiments of the disclosure the methods may include a purge cycle wherein the substrate surface is purged for a time period of less than approximately 5.0 seconds. Excess silicon halide source and any reaction byproducts may be removed with the aid of a vacuum generated by a pumping system. 
     In a second phase of the selective cyclical deposition (“the nitrogen phase”), the substrate is contacted with a second vapor phase reactant comprising a nitrogen source (process block  106  of  FIG. 1 ). In some embodiments of the disclosure, methods may further comprise selecting the nitrogen source to comprise at least one of ammonia (NH 3 ), hydrazine (N 2 H 4 ) or an alkyl-hydrazine, wherein the alkyl-hydrazine may refer to a derivative of hydrazine which may comprise an alkyl functional group and may also comprise additional functional groups, non-limiting example embodiments of an alkyl-hydrazine may comprise at least one of tertbutylhydrazine (C 4 H 9 N 2 H 3 ), methylhydrazine (CH 3 NHNH 2 ) or dimethylhydrazine ((CH 3 ) 2 N 2 H 2 ). 
     In some embodiments, exposing the substrate to the nitrogen source may comprise pulsing the nitrogen source (e.g., ammonia (NH 3 )) over the substrate for a time period of between about 0.5 seconds to about 30.0 seconds, or between about 0.5 seconds to about 10 seconds, or between about 0.5 second to about 5 seconds. During the pulsing of the nitrogen source over the substrate the flow rate of the nitrogen source may be less than 4000 sccm, or less than 2000 sccm, or less than 1000 sccm, or less than 500 sccm, or even less than 250 sccm. 
     The second vapor phase reactant comprising a nitrogen source may react with silicon-containing molecules left on the substrate surface. In some embodiments, the second phase nitrogen source may react with the silicon-containing molecules left on the substrate surface to deposit a silicon nitride film over selective portions of the substrate. 
     Excess second source chemical and reaction byproducts, if any, may be removed from the substrate surface, for example by a purging gas pulse and/or vacuum generated by a pumping system. Purging gas is preferably any inert gas, such as, without limitation, argon (Ar), nitrogen (N 2 ) or helium (He). A phase is generally considered to immediately follow another phase if a purge (i.e., purging gas pulse) or other reactant removal step intervenes. 
     Although as illustrated in method  100  of  FIG. 1 , the selective deposition process  102  may comprise contacting the substrate with a first reactant  104  followed subsequently by contacting the substrate with a second reactant  106  it should be appreciated that embodiments of the disclosure may reverse the contacting sequence and the substrate may be first contacted with the second reactant  106  subsequently followed by contacting the substrate with the first reactant  104 . It should also be appreciated that the substrate may be contacted multiple times with the first reactant prior to contacting the substrate with the second reactant and vice versa. 
     Embodiments of the disclosure may further comprise heating the substrate during the selective deposition process  102 . In some embodiments methods may comprise heating the substrate to a temperature of between approximately 200° C. and approximately 350° C. In some embodiment methods may comprise heating the substrate to a temperature of less than approximately 250° C., or to a temperature of less than approximately 225° C., or even to a temperature of less than approximately 200° C. In some further embodiments methods may comprise heating the substrate to a temperature of approximately 250° C. 
     Embodiments of the disclosure may further comprise reducing the pressure in the reaction chamber utilized for depositing the selective silicon nitride. For example, in some embodiments the selective deposition may be performed at a reaction chamber pressure of less than 50 Torr, or at a reaction chamber pressure of less than 25 Torr, or at a reaction chamber pressure of less than 10 Torr, or even at a reaction chamber pressure of less than 5 Torr. 
     In some embodiments of the disclosure the substrate may comprise a first metallic surface and a second dielectric surface. The incubation period, i.e., the number of cyclical deposition cycles in the initial stages of the selective cyclical deposition process where no discernable deposition occurs, may be altered by controlling the process parameters and reactant chemistries utilized in the selective cyclical deposition process. Therefore the embodiments of the current disclosure provide methods for controlling the incubation period of the first metallic surface and the second dielectric surface to enable selective silicon nitride film deposition process. Therefore, in some embodiments the incubation period for the first metallic surface may be less than the incubation period for the second dielectric surface, i.e., the selective cyclical deposition may, in the initial stages of the selective cyclical deposition process, favor deposition on the first metallic surface. 
       FIG. 2  illustrates the selective deposition of silicon nitride films on a native silicon oxide surface in comparison to deposition on a clustered titanium nitride (TiN) surface and an oxidized titanium nitride surface. In more detail,  FIG. 2  illustrates the thickness of the silicon nitride deposited at the center of the sample versus the number of selective cyclical deposition cycles, wherein the data labelled as  202  illustrates the deposition of silicon nitride on native silicon oxide, the data as labelled  204  illustrates the deposition of silicon nitride on oxidized titanium nitride and the data labelled as  206  illustrates the deposition of silicon nitride on clustered titanium nitride. The incubation period for a particular deposition process may be determined by the intercept of the deposition data with the y=0 axis. The incubation period for the silicon nitride deposition on native silicon oxide is labelled  208  and illustrates a number of cycles of approximately 100, therefore in some embodiments of the disclosure the incubation period for the second dielectric surface is approximately less than 100 cycles. The incubation periods for the silicon nitride deposition on the clustered titanium nitride and on the oxidized titanium nitride are substantially equal and are labelled as  210  in  FIG. 2  and demonstrate an incubation period of approximately 20 cycles. Therefore, in some embodiments the incubation period for the first metallic surface is less than the incubation period for the second dielectric surface and further in some embodiments the nucleation rate of the silicon nitride film is higher on the first metallic surface than on the second dielectric. 
     After the initial incubation period is over the silicon nitride deposition proceeds at a substantially fixed rate on both the first metallic surface and on the second dielectric surface. The deposition rate of the selective silicon nitride film, which is typically presented as Å/pulsing cycle, depends on a number of factors including, for example, on the number of available reactive surface sites or active sites on the surface and bulkiness of the chemisorbing molecules. In some embodiments, the deposition rate of such films may range from about 0.1 to about 5.0 Å/pulsing cycle. In some embodiments, the deposition rate can be about 0.1, 0.2, 0.3, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 Å/pulsing cycle. 
     The selective deposition process for forming a selective silicon nitride film on a substrate comprising a first metallic surface and a second dielectric surface may be repeated one or more times until the desired thickness of the selective silicon nitride is achieved. Referring back to  FIG. 1  process block  108  illustrates a decision gate for determining if the selective deposition process should or should not be repeated, the decision gate being determined by the desired thickness of the selective silicon nitride film. For example, in some embodiments forming the selective silicon nitride film on the substrate by the selective deposition process comprises forming the selective silicon nitride film with a thickness of between approximately 10 Angstroms and approximately 40 Angstroms. In some embodiments the methods may comprise forming the selective silicon nitride film on the substrate with a thickness of less than 50 Angstroms, or less than 40 Angstroms, or less than 30 Angstroms, or less than 20 Angstroms, or even less than 10 Angstroms. 
       FIG. 2  illustrates that during the incubation period for the selective deposition of the silicon nitride film on the native silicon oxide surface that there is substantially no deposition on the native silicon oxide surface whilst there is significant deposition on both the clustered titanium nitride surface and the clustered titanium nitride surface. It should be noted that the selectivity of the deposition process may be expressed as the ratio of the amount of material formed on the first metallic surface (A) minus the amount of material formed on the second dielectric surface (B) to the amount of material formed on the first metallic surface (A) (i.e., selectivity can be given as a percentage calculated by [(deposition on first metallic surface)-(deposition on second dielectric surface)/(deposition on the first metallic surface) or [(A−B)/A]. In some embodiments the selectivity may be above about 70%, or may be above about 80%, or may be above about 90%, or may be above about 95%, or may be above about 98%, or may be above about 99% or may be about 100%. In some cases, selectivity above 80% may be acceptable for certain applications. In some cases, selectivity above 50% may be acceptable for certain applications. In some embodiments, the deposition temperature may be selected such that the selectivity is above about 90%. In some embodiments, the deposition temperature may be selected such that a selectivity of about 100% may be achieved. As a non-limiting example, (and with reference to  FIG. 2 ) during the incubation period of the native silicon oxide surface (i.e., the second dielectric surface) the selective silicon nitride deposition process is 100% selective to deposition on the first metallic surface (i.e., on the clustered titanium nitride surface or on the oxidized titanium nitride surface). As illustrated in  FIG. 2 , during the incubation of the second dielectric surface (e.g., the native oxide surface) it is possible to deposit approximately less than 25 Angstroms of silicon nitride on the first metallic surface (e.g., on the clustered titanium nitride surface or the oxidized titanium nitride surface) with 100% selectivity. 
     In some embodiments of the disclosure it may be desired to deposit thicker silicon nitride films on the first metallic surface without any or substantially any silicon nitride formation on the second dielectric surface.  FIG. 3  illustrates method  300  which may comprise methods for selectively forming thicker silicon nitride films on the first metallic surface than on the second dielectric surface. Method  300  may start with a selective cyclical deposition process as outlined previously for method  100  and may include one or more deposition cycles (such as ALD cycles) comprising contacting the substrate with a first reactant comprising a silicon halide source  304  and contacting the substrate with a second reactant comprising a nitrogen source  306 . The selective cyclical deposition process  302  may be repeated until a desired thickness of a silicon nitride film is deposited. In such embodiments the selective cyclical deposition process may be operated beyond the incubation period for the second dielectric surface such that the silicon nitride film is deposited both on the first metallic surface and the second dielectric surface. Therefore embodiments of the disclosure may further comprise forming the silicon nitride film to a first thickness over the first metallic surface and forming the silicon nitride film to a second thickness over the second dielectric surface, wherein the first thickness is greater than the second thickness. 
     Upon formation of the silicon nitride to a desired thickness on both the first metallic surface and the second dielectric surface, the substrate and overlying silicon film may be exposed to an etching process to remove a portion of the silicon nitride film, as shown as process block  310  in  FIG. 3 . In some embodiments the reaction chamber for performing the selective cyclical deposition process and the reaction chamber for performing the etching process may be the same. In other embodiments the substrate is transferred from a first reaction chamber configured for selective cyclical silicon nitride deposition to a second reaction chamber configured for etching the silicon nitride film. The first reaction chamber and the second reaction chamber may be part of the same semiconductor processing apparatus and may comprise a cluster tool equipped with a transfer chamber having controlled environmental conditions, thereby preventing exposure of the substrate to ambient conditions. In some embodiments the second reaction chamber configured for etching a portion of the silicon nitride film may be configured for at least one of reactive ion etching, inductively coupled plasma etching or electron cyclotron resonance etching. In some embodiments the second reaction chamber configured for etching a portion of the silicon nitride film may be configured for atomic layer etching (ALE). 
     Once the substrate is situated in a reaction chamber configured for etching a portion of the silicon nitride film the methods may comprise etching the silicon nitride film over the second dielectric surface until it is substantially removed and simultaneously etching the silicon nitride film over the first metallic surface until it is partially removed. As a non-limiting example, the silicon nitride film may be etched utilizing at least one of a chlorine based etch chemistry or a fluorine based etch chemistry. Therefore any excess silicon nitride which was deposited over the second dielectric surface may be removed whilst leaving a portion of the silicon nitride film on the first metallic surface. 
     Upon completion of the etch process the thickness of the silicon nitride on the first metallic surface may be determined (process block  312  of  FIG. 3 ) and if additional silicon nitride is required on the first metallic surface the substrate may be transferred to the reaction chamber configured for selective cyclical silicon nitride film deposition. Therefore in some embodiments the processes of etching and selectively forming a silicon nitride film are repeated two or more times i.e., the method  300  is repeated two or more times until a desired thickness of silicon nitride is deposited over the first metallic surface at which point the method may exit (process block  314  of  FIG. 3 ). 
     In some embodiments a substrate is provided comprising a first metallic surface and a second dielectric surface. In some embodiments a substrate is provided that comprises a first metal oxide surface, a first metal nitride surface, a first metal silicide surface, a first metal boride surface, or a first semi-metal surface. In some embodiments the second dielectric surface may comprise —OH groups. In some embodiments the second dielectric surface may be a SiO 2  based surface. In some embodiments the second dielectric surface may comprise Si—O bonds. In some embodiment the second dielectric surface may comprise a SiO 2  based low-k material. In some embodiments the second dielectric surface may comprise more than about 30%, or in some cases more than about 50% of SiO 2 . In further embodiments the second dielectric surface may comprise a silicon nitride surface or a silicon oxynitride surface. In some embodiments the second dielectric surface may comprise GeO 2 . In some embodiments the second dielectric surface may comprise Ge—O bonds. 
     In some embodiments of the disclosure the methods may comprise selecting the first metallic surface to comprise at least one of titanium nitride, titanium silicon nitride (TiSiN), tantalum nitride (TaN), tantalum silicon nitride, tungsten (W), molybdenum (Mo), silicon (Si), silicon germanium (SiGe), germanium antiomony tellurium (GeSbTe), cobalt (Co), tantalum silicide (TaSi), titanium silicide (TiSi), gallium arsenide or gallium nitride. 
     In some embodiments of the disclosure the methods may comprise selecting the second dielectric surface to comprise at least one of a silicon oxide, a silicon nitride, a silicon oxynitride, carbon, hafnium oxide (HfO), zirconium oxide (ZrO), aluminum oxide (AlO), titanium oxide (TiO) or silicon oxycarbide (SiOC). 
     One of skill in the art will recognize that the processes described herein are applicable to many contexts, including the fabrication of semiconductor device structures, such as, but not limited to, memory devices, device liners, device spacers, sacrificial layers, diodes including light emitting diodes and transistors including planar devices as well as multiple gate transistors, such as FinFETs. As a non-limiting example,  FIG. 5  illustrates a semiconductor device structure  500  which may comprise a portion of an interconnection device structure for electrically connecting one or more semiconductor devices. The semiconductor device structure  500  may comprise an interlayer dielectric  502 , a copper interconnect  504  disposed within the interlayer dielectric  502  and a diffusion barrier layer  506  disposed between the copper interconnect  504  and the interlayer dielectric  502 . In some embodiments, the interlayer dielectric  502  may comprise a silicon oxide and/or a low-k dielectric material and the diffusion barrier layer  506  may comprise tantalum, tantalum nitride, tungsten or tungsten nitride. As shown in  FIG. 5  the copper interconnect  504  may be capped with a silicon nitride capping layer  508  and the silicon nitride capping layer  508  may be selectively deposited over surface  504 A of the copper interconnect  504  utilizing the selective deposition processes of the current disclosure, such that the silicon nitride material is deposited selectively over the surface  504 A of the copper interconnect  504  without any or substantially any silicon nitride deposition on the interlayer dielectric surface  502 A. 
     Embodiments of the disclosure may also include a reaction system configured for selectively forming the silicon nitride films of the present disclosure. In more detail,  FIG. 4  schematically illustrates a reaction system  400  including a reaction chamber  402  that further includes mechanism for retaining a substrate (not shown) under predetermined pressure, temperature, and ambient conditions, and for selectively exposing the substrate to various gases. A precursor reactant source  404  may be coupled by conduits or other appropriate means  404 A to the reaction chamber  402 , and may further couple to a manifold, valve control system, mass flow control system, or mechanism to control a gaseous precursor originating from the precursor reactant source  404 . A precursor (not shown) supplied by the precursor reactant source  404 , the reactant (not shown), may be liquid or solid under room temperature and standard atmospheric pressure conditions. Such a precursor may be vaporized within a reactant source vacuum vessel, which may be maintained at or above a vaporizing temperature within a precursor source chamber. In such embodiments, the vaporized precursor may be transported with a carrier gas (e.g., an inactive or inert gas) and then fed into the reaction chamber  402  through conduit  404 A. In other embodiments, the precursor may be a vapor under standard conditions. In such embodiments, the precursor does not need to be vaporized and may not require a carrier gas. For example, in one embodiment the precursor may be stored in a gas cylinder. The reaction system  400  may also include additional precursor reactant sources, such precursor reactant source  406  which may also be couple to the reaction chamber by conduits  406 A as described above. 
     A purge gas source  408  may also be coupled to the reaction chamber  402  via conduits  408 A, and selectively supplies various inert or noble gases to the reaction chamber  402  to assist with the removal of precursor gas or waste gasses from the reaction chamber. The various inert or noble gasses that may be supplied may originate from a solid, liquid or stored gaseous form. 
     The reaction system  400  of  FIG. 4 , may also comprise a system operation and control mechanism  410  that provides electronic circuitry and mechanical components to selectively operate valves, manifolds, pumps and other equipment included in the reaction system  400 . Such circuitry and components operate to introduce precursors, purge gasses from the respective precursor sources  404 ,  406  and purge gas source  408 . The system operation and control mechanism  410  also controls timing of gas pulse sequences, temperature of the substrate and reaction chamber, and pressure of the reaction chamber and various other operations necessary to provide proper operation of the reaction system  400 . The operation and control mechanism  410  can include control software and electrically or pneumatically controlled valves to control flow of precursors, reactants and purge gasses into and out of the reaction chamber  402 . The control system can include modules such as a software or hardware component, e.g., a FPGA or ASIC, which performs certain tasks. A module can advantageously be configured to reside on the addressable storage medium of the control system and be configured to execute one or more processes. 
     Those of skill in the relevant arts appreciate that other configurations of the present reaction system are possible, including different number and kind of precursor reactant sources and purge gas sources. Further, such persons will also appreciate that there are many arrangements of valves, conduits, precursor sources, purge gas sources that may be used to accomplish the goal of selectively feeding gasses into reaction chamber  402 . Further, as a schematic representation of a reaction system, many components have been omitted for simplicity of illustration, and such components may include, for example, various valves, manifolds, purifiers, heaters, containers, vents, and/or bypasses. In some embodiments, reaction system  400  may include two or more reaction chambers wherein each reaction chamber may be configured for a desired process, for example, a first reaction chamber may be configured for selective cyclical deposition processes and a second reaction chamber may be configured for etching process. In addition, the reaction system  400  may comprise a transfer chamber for transferring substrate from a first reaction chamber to a second reaction chamber under controlled conditions. 
     The example embodiments of the disclosure described above do not limit the scope of the invention, since these embodiments are merely examples of the embodiments of the invention, which is defined by the appended claims and their legal equivalents. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the disclosure, in addition to those shown and described herein, such as alternative useful combination of the elements described, may become apparent to those skilled in the art from the description. Such modifications and embodiments are also intended to fall within the scope of the appended claims.