Patent Publication Number: US-2022231137-A1

Title: Metal cap for contact resistance reduction

Description:
TECHNICAL FIELD 
     Embodiments of the present disclosure generally relate to transistors and methods for forming transistors. In particular, transistor contacts, for example source/drain contacts, have reduced resistance. 
     BACKGROUND 
     Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors, and resistors on a single chip. In the course of integrated circuit evolution, functional density (i.e., the number of interconnected devices per chip area) has generally increased while geometry size (i.e., the smallest component (or line) that can be created using a fabrication process) has decreased. 
     Microelectronic devices are fabricated on a semiconductor substrate as integrated circuits in which various conductive layers are interconnected with one another to permit electronic signals to propagate within the device. An example of such a device is a complementary metal-oxide-semiconductor (CMOS) field effect transistor (FET) or MOSFET, including both planar and three-dimensional structures. An example of a three-dimensional structure is a FinFET device. 
     Drive current, and therefore speed, of a transistor is proportional to a gate width of the transistor. Faster transistors generally require larger gate width. There is a trade-off between transistor size and speed, and “fin” field-effect transistors (finFETs) have been developed to address the conflicting goals of a transistor having maximum drive current and minimum size. FinFETs are characterized by a fin-shaped channel region that greatly increases the size of the transistor without significantly increasing the footprint of the transistor. 
     An exemplary finFET or MOSFET includes a gate electrode on a gate dielectric layer on a surface of a semiconductor substrate. Source/drain regions are provided along opposite sides of the gate electrode. The source and drain regions are generally heavily doped regions of the semiconductor substrate. Usually a capped silicide layer, for example, titanium silicide capped by titanium nitride, is used to couple contacts, e.g., active and/or metal contacts, to the source and drain regions. Including a nitrogen-containing capping layer, however, can undesirably contribute to contact resistance. 
     Further, during middle-of-line (MOL) processes, a minimum via resistance for the MOL structures are targeted. A liner material (e.g., titanium nitride) is often required to improve adhesion of metals to dielectric materials to pass post-processing steps such as chemical-mechanical planarization (CMP) and to enhance CVD nucleation. However, the presence of the liner adds to the via resistance. 
     Therefore, there is a need in the art for transistors and MOL applications with decreased resistance. 
     SUMMARY 
     One or more embodiments are directed to a contact stack of a semiconductor device, which comprises: a source/drain region; a metal silicide layer above the source/drain region; a metal cap layer in direct contact with the metal silicide layer; and a conductor in contact with the metal cap layer. 
     Additional embodiments are directed to a semiconductor device comprising: a contact stack on the substrate, a dielectric layer adjacent to the contact stack, and a metal gate adjacent to the dielectric layer. The contact stack comprises: a source/drain region comprising: silicon, germanium, silicon-germanium, or a group III/V compound semiconductor; a metal silicide layer on the source/drain region, the metal silicide layer comprising: titanium silicide, cobalt silicide, ruthenium silicide, nickel silicide, molybdenum silicide, or alloys thereof; a metal cap layer directly on the metal silicide layer, the metal cap layer comprising: tungsten, ruthenium, molybdenum, or alloys thereof; and a conductor on the metal cap layer. 
     Further embodiments are directed to a method comprising: depositing a metal silicide layer in a feature of a substrate in a first processing chamber, the feature comprising a bottom wall and sidewalls; moving the substrate to a second processing chamber that is integrated with the first processing chamber such that there is not an air break between the first and second processing chambers; preparing a metal cap layer directly on the metal silicide layer; and depositing a conductor on the metal cap layer. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  is a cross-sectional view of a contact stack in accordance with one or more embodiments; 
         FIG. 2  is a cross-sectional view of a semiconductor device in accordance with one or more embodiments; 
         FIG. 3A  is a flowchart of a method for forming a contact stack according to  FIG. 1  in accordance with one or more embodiments; 
         FIG. 3B  is a flowchart of a method for forming a contact stack according to one or more embodiments; 
         FIGS. 4A-4H  illustrate various views of a stack during different stages of the method of  FIG. 3B ; and 
         FIG. 5  is a cluster tool accordance with one or more embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Before describing several exemplary embodiments of the disclosure, it is to be understood that the disclosure is not limited to the details of construction or process steps set forth in the following description. The disclosure is capable of other embodiments and of being practiced or being carried out in various ways. 
     As used in this specification and the appended claims, the term “substrate” refers to a surface, or portion of a surface, upon which a process acts. It will also be understood by those skilled in the art that reference to a substrate can also refer to only a portion of the substrate, unless the context clearly indicates otherwise. Additionally, reference to depositing on a substrate can mean both a bare substrate and a substrate with one or more films or features deposited or formed thereon. 
     A “substrate” as used herein, refers to any substrate or material surface formed on a substrate upon which film processing is performed during a fabrication process. For example, a substrate surface on which processing can be performed include materials such as silicon, silicon oxide, strained silicon, silicon on insulator (SOI), carbon doped silicon oxides, amorphous silicon, doped silicon, germanium, gallium arsenide, glass, sapphire, and any other materials such as metals, metal nitrides, metal alloys, and other conductive materials, depending on the application. Substrates include, without limitation, semiconductor wafers. Substrates may be exposed to a pretreatment process to polish, etch, reduce, oxidize, hydroxylate, anneal, UV cure, e-beam cure and/or bake the substrate surface. In addition to film processing directly on the surface of the substrate itself, in the present disclosure, any of the film processing steps disclosed may also be performed on an underlayer formed on the substrate as disclosed in more detail below, and the term “substrate surface” is intended to include such underlayer as the context indicates. Thus for example, where a film/layer or partial film/layer has been deposited onto a substrate surface, the exposed surface of the newly deposited film/layer becomes the substrate surface. 
     As used herein, the term “fin field-effect transistor (FinFET)” refers to a MOSFET transistor built on a substrate where the gate is placed on two or three sides of the channel, forming a double- or triple-gate structure. FinFET devices have been given the generic name FinFETs because the channel region forms a “fin” on the substrate. FinFET devices have fast switching times and high current density. 
     As used herein, “consists essentially of” with respect to composition of a layer means that the stated elements compose greater than 95%, greater than 98%, greater than 99% or greater than 99.5% of the stated material on an atomic basis. For the avoidance of doubt, no stoichiometric ratios are implied by the identification of materials disclosed herein. For example, a TiSi material contains titanium and silicon. These elements may or may not be present at a 1:1 ratio. 
     Embodiments herein relate to contact stacks, semiconductor devices, and methods of making the same, which advantageously offer reduced resistance in transistor contacts. Resistance is reduced by eliminating nitrogen-based layers, e.g., a nitride cap layer and/or a nitride liner layer. Use of a metal-based cap layer on top of a silicide layer at contact areas, e.g., source and drain, eliminates the use of a nitrogen-based barrier film between silicide and conductor, e.g., plug metal. Contact resistance is advantageously reduced by direct contact between the silicide and plug metal, e.g., direct contact of silicide with different low resistivity metals (W, Ru, Mo, . . . ). The metal-based cap layer advantageously inhibits silicide from alteration by process chemicals (O 2 , F, Cl 2 , and the like). 
     Contact resistance (Ω) provides a measure of the opposition to electric current flow due to contacting interfaces. In a contact stack, a nitride-based cap according to prior art contributed upwards of 25% of the stack&#39;s contact resistance. Experiments of embodiments herein where a nitride-based cap (TiN) was replaced with a metal cap (W) resulted in a reduction in contact resistance on the order of 20%. 
     Metal cap layers herein are effective to inhibit and/or eliminate diffusion of undesirable elements into and/or silicon out of the underlying metal silicide layer. For example, a tungsten metal cap layer, e.g., having a thickness of about 20 to 30 Angstroms, is effective to inhibit and/or eliminate diffusion of one or more of: oxygen, argon, fluorine, silicon. 
     Processes according to one or more embodiments eliminate an air break, which facilitates the removal of a nitrogen-based cap layer. Deposition of a metal cap layer is done using low energy physical vapor deposition (PVD) technology, which replaces the use of chemical vapor deposition (CVD) and eliminates the need for a nitrogen-based liner for CVD nucleation. Low energy PVD technology also advantageously reduces potential for damage to the metal silicide layer. 
     According to one or more embodiments, devices and methods of formation these devices are particularly useful in forming FinFET devices and will be described in that context. Other devices and applications are also within the scope of the invention. 
       FIG. 1  illustrates a cross-sectional view of an exemplary contact stack  101  suitable for a semiconductor device. Stack  101  comprises a source/drain region  110 . In some embodiments, the source/drain region  110  comprises silicon, germanium, silicon-germanium, or a group III/V compound semiconductor. Above the source/drain region  110  is a metal silicide layer  120 . In some embodiments, the metal silicide layer  120  comprises: titanium silicide, cobalt silicide, or ruthenium silicide. In direct contact with the metal silicide layer  120  is a metal cap layer  130 . In one or more embodiments, the contact stack  101  excludes a metal nitride layer in direct contact with the metal silicide layer. In one or more embodiments, the entire contact stack  101  excludes a metal nitride layer. In some embodiments, the metal cap comprises: tungsten, ruthenium, molybdenum, or alloys thereof. Above the metal cap layer is a conductor  140 . In one or more embodiments, the metal cap layer is in contact with conductor  140 . The conductor  140  may comprise a combination of layers to provide an active contact and/or a metal contact. In one or more embodiments, the conductor  140  comprises a metal selected from the group consisting of: tungsten, ruthenium, and cobalt. 
     In some embodiments, the metal silicide layer  120  comprises or consists essentially of TiSi. In some embodiments, the metal cap layer  130  comprises or consists essentially of tungsten (W). 
       FIG. 2  illustrates a cross-sectional view of a semiconductor device  200  comprising: a substrate  205 , a contact stack  201  on the substrate  205 , a dielectric layer  250 , and a metal gate  260 . The contact stack  201  comprises: a source/drain region  210 , a metal silicide layer  220  on the source/drain region  210 , a metal cap layer  230  in direct contact with the metal silicide layer  220 , and a conductor  240  above the metal cap layer  230 . In one or more embodiments, the conductor  240  is in contact with the metal cap layer  230 . In one or more embodiments, the conductor  240  is in direct contact with the metal cap layer  230 . 
     As shown in  FIG. 2 , in one or more embodiments, the source/drain region  210  is formed on the substrate  205 . In other embodiments, a source/drain region may be integral to and/or extend from a body of the substrate. 
     In some embodiments, the source/drain region  210  comprises silicon, germanium, silicon-germanium, or a group III/V compound semiconductor. In some embodiments, the metal silicide layer  220  comprises: titanium silicide, cobalt silicide, ruthenium silicide, nickel silicide, molybdenum silicide, or alloys thereof. In one or more embodiments, the contact stack  201  excludes a metal nitride layer on the metal silicide layer. In one or more embodiments, the entire contact stack  201  excludes a metal nitride layer. In some embodiments, the metal cap layer  230  comprises: tungsten, ruthenium, molybdenum, or alloys thereof. The conductor  240  may comprise a combination of layers to provide an active contact and/or a metal contact. In one or more embodiments, the conductor  240  comprises a metal selected from the group consisting of: tungsten, ruthenium, and cobalt. 
     The dielectric layer  250  insulates the contact stack  201  from the metal gate  260 . In one or more embodiments, the dielectric layer directly contacts the contact stack. In one or more embodiments, the semiconductor device  200  excludes a metal nitride layer between the contact stack  201  and the dielectric layer  250 . In one or more embodiments, the entire semiconductor device  200  excludes a metal nitride layer. In one or more embodiments, the dielectric layer  250  comprises a dielectric material, such as an oxide or a nitride, for example: SiOx (e.g., SiO 2 ), SiN, SiCN, or other suitable dielectric material. 
     In some embodiments, the metal silicide layer  220  comprises or consists essentially of TiSi. In some embodiments, the metal cap layer  230  comprises or consists essentially of tungsten (W). 
     In some embodiments, the metal silicide layer has a thickness of greater than or equal to 20 Å to less than or equal to 60 Å, and all values and subranges therebetween. In some embodiments, the metal silicide layer has a thickness of about 40 Å, which includes 40 Å±10%. In one or more embodiments, the metal silicide layer is a selectively deposited layer. In one or more embodiments, the metal silicide layer is a selective layer of TiSi. 
     In some embodiments, the metal cap layer has a thickness of greater than or equal to 10 Å to less than or equal to 50 Å, and all values and subranges therebetween. In some embodiments, the metal cap layer has a thickness of about 30 Å, which includes 30 Å±10%. In one or more embodiments, the metal cap layer is deposited by a PVD process. 
     Referring to  FIG. 3A , a general embodiment relates to a method  300  of manufacturing a contact stack of a semiconductor device. The method  300  starts at operation  310  by depositing a metal silicide layer in a feature of a substrate. At operation  320 , a metal cap layer is prepared directly on the metal silicide layer in the absence of an air break. For example, operation  310  is conducted in a first chamber that is integrated with a second chamber where operation  320  is conducted. At operation  330 , a conductor is deposited on the metal cap layer. In one or more embodiments, operation  330  is conducted in a third chamber. In one or more embodiments, the method comprises: depositing a metal silicide layer in the feature of a substrate in a first processing chamber; moving the substrate to a second processing chamber that is integrated with the first processing chamber such that there is not an air break between the first and second processing chambers; preparing a metal cap layer directly on the metal silicide layer; and depositing a conductor on the metal cap layer. 
     Referring to  FIGS. 3B to 4A-4H , another embodiment relates to a method  350  of manufacturing a contact stack of a semiconductor device  400 . The method  350  starts at operation  360  by depositing a metal silicide layer  420  in a feature  402  of a substrate  405  as shown in  FIG. 4A . In one or more embodiments, the feature  402  comprises a source/drain region  410  as a bottom wall  402   b , and sidewalls  402   s  comprising a dielectric material  450 . 
     The feature  402  may be formed by methods known in the art. As an example, the feature  402  may be a trench prepared by etching a dielectric layer to reach a source/drain region and there after by a pre-cleaning process (e.g., wet etch and/or dry etch) to remove contaminants. The wet etch process may utilize ammonia or hydrogen fluoride solution. The dry etch process may be a plasma etch process and may utilize a fluorine or hydrogen containing etchant. The pre-clean process would not substantially remove any portion of the source/drain region. 
     Reference to “ source/drain region” is a source region or a drain region or a merged source and drain region. In one or more embodiments, the source/drain region  410  is fabricated from a semiconductor material that is grown epitaxially on one or more surfaces of the substrate  405 . 
     In one or more embodiments, the metal silicide layer  420  is deposited selectively onto the bottom wall  402   b . In one or more embodiments, the metal silicide layer  420  is deposited by a selective epitaxial deposition process such that the metal silicide layer  420  is formed on the bottom  402   b  of the feature  402 , and not on sidewalls  402   s  of the feature  402  as a result of the selective epitaxial deposition process. 
     In general, any suitable precursors can be used for the metal silicide layer. For a titanium silicide layer, titanium precursors can include, but are not limited to TiCl 4 , TiBr 4 , Til 4 , TiF 4 , tetrakisdimethylamino titanium; silicon-based precursors can include but are not limited to silanes (e.g., silane(Si 1 H 4 ), disilane (Si 2 H 6 ), trisilane (Si 3 H 8 ), tetrasilane (Si 4 H 10 ), isotetrasilane, neopentasilane (Si 6 H 12 ), cyclopentasilane (Si 6 H 10 ), hexasilane (C 6 H 14 ), cyclohexasilane (Si 6 H 12 ) or, in general, Si z H a  where z=1 or more, and combinations thereof), organosilanes, and/or halosilanes (of Si g H h X i , where each X is a halogen independently selected from F, Cl, Br and I, g is any integer greater than or equal to 1, h and i are each less than or equal to 2 g+2 and h+i is equal to 2 g+2) as a co-reactant. 
     The order in which the substrate is exposed to the precursors can be varied. The exposures may repeat in a deposition cycle. Further, exposure to a precursor may be repeated within a single deposition cycle. 
     At operation  370 , a metal cap material  432  is deposited directly on the metal silicide layer  420 , as shown in  FIG. 4B , in the absence of an air break. In one or more embodiments, operations  360  and  370  are conducted in different processing chambers that are integrated. As such, transfer between the chambers is performed without breaking vacuum and/or without exposure to ambient air. 
     An exemplary process for depositing the metal cap material directly on the metal silicide layer is by a physical vapor deposition (PVD) process. In one or more embodiments, depositing the metal cap material directly on the metal silicide layer is conducted in (PVD) process chamber. In one or more embodiments, the conditions of the PVD process chamber are low energy. In one or more embodiments, the PVD process chamber is a RF-PVD process chamber. In one or more embodiments, temperature of the PVD chamber within a range of room temperature (e.g., 25° C.) to 600° C., including all values and subranges therebetween. In one or more embodiments, bias is in a range of 0 W to 400 W, including all values and subranges therebetween. In one or more embodiments, direct current is in a range of 0 W to 500 W. In one or more embodiments, radio frequency is in range of 1 kHz to 10 kHz. 
     In an embodiment, the PVD chamber has conditions of: a chamber temperature of 350° C. to 450° C.; a chamber pressure of 120 mT±50 mT; a bias in a range of 0 W to 200 W; a direct current (DC) in a range of 0 W to 500 W; and a radio frequency (RF) in a range of 1 kHz to 10 kHz. In one or more embodiments, the PVD chamber has conditions of: a chamber temperature of 400° C.±50° C.; a chamber pressure of 120 mT ±50 mT; a bias in a range of 0 W to 200 W; a direct current (DC) of 500 W±50 W; and a radio frequency (RF) of 3 kHz±1 kHz. In one or more embodiments, the PVD process is a plasma-enhanced PVD. In one or more embodiments, the plasma-enhanced PVD includes a pulsed radio frequency (RF) plasma. 
     According to one or more embodiments, deposition of the metal cap material  432  is by bottom fill as shown in  FIG. 4B , which requires further processing to prepare a metal cap layer  430  at operation  380  prior to deposition of a conductor at operation  390 . 
     In general, any suitable metal cap precursor can be used for the metal cap material and/or metal cap layer. 
     Operation  380  to prepare a metal cap layer includes  FIGS. 4C-4G . In  FIG. 4C , according to one or more embodiments, a material  434 , which may be a spin-on or gap-fill material, is deposited over the entirety of the device  400 . In one or more embodiments, the material  434  is a spin-on material, which is a carbon-based material. In one or more embodiments, the material  434  is a CVD gap-fill material, which is a dielectic material. 
       FIG. 4D , according to one or more embodiments, depicts etching of at least a portion of the material  434 . For spin-on material, etching may be conducted by a dry etch process, which may utilize a plasma etch process and may utilize a hydrogen or nitrogen or oxygen containing etchant. For tungsten material, etching may be conducted by a dry etch process, which may utilze oxidizing exposed tungsten followed by WF 6 . Alternatively, according to one or more embodiments, after depositing the material  434  shown in  FIG. 4C , a chemical mechanical polishing (CMP) of at least a portion of the material and the metal cap layer above the dielectric material may be applied followed by an etching of at least a portion of the material  434  in the trench. 
     In  FIG. 4E , the metal cap material  432  is etched to remove the metal cap material  432  from a portion of the sidewalls  402   s  above the material  434  and the top surfaces of the dielectric material  450 . 
     In  FIG. 4F , the remaining material  434  is etched away, leaving the metal cap material  432  exposed. 
     In  FIG. 4G , the exposed metal cap material  432  is etched (e.g., wet etch and/or dry etch) to form a metal cap layer  430 . An etching with oxygen-, fluorine-, or chlorine-based gas may be conducted, for example. 
     After formation of the metal cap layer  430 , at operation  390  and shown in  FIG. 4H , a conductor  440  is deposited on the metal cap layer  430 . The conductor  440  is fabricated from an electrically conductive material, such as a metal. In one or more embodiments, the conductor comprises a metal selected from the group consisting of: tungsten, ruthenium, and cobalt. Optionally, prior to deposition of the conductor  440  there is a pre-clean operation conducted. In one or more embodiments, the pre-clean operation prior to deposition of the conductor comprises a plasma treatment, e.g., hydrogen plasma. 
     In one or more embodiments, the conductor is deposited by a selective deposition method. In one or more embodiments, the conductor is deposited by a CVD process and/or a PVD process. 
     In general, any suitable precursor can be used for the conductor. For example, precursors of a tungsten conductor can include, but are not limited to WCl 6 , WBr 6 , Wl 6 , WF 6 . 
     Consistent with the foregoing, methods of this disclosure can be performed in the same chamber or in one or more separate processing chambers. In some embodiments, the substrate is moved from the first chamber to a separate, second chamber for further processing. The substrate can be moved directly from the first chamber to the separate processing chamber, or it can be moved from the first chamber to one or more transfer chambers, and then moved to the separate processing chamber. Accordingly, a suitable processing apparatus may comprise multiple chambers in communication with a transfer station. An apparatus of this sort may be referred to as a “cluster tool” or “clustered system,” and the like. 
     Generally, a cluster tool is a modular system comprising multiple chambers which perform various functions including substrate center-finding and orientation, annealing, deposition and/or etching. According to one or more embodiments, a cluster tool includes at least a first chamber and a central transfer chamber. The central transfer chamber may house a robot that can shuttle substrates between and among processing chambers and load lock chambers. The transfer chamber is typically maintained at a vacuum condition and provides an intermediate stage for shuttling substrates from one chamber to another and/or to a load lock chamber positioned at a front end of the cluster tool. Two well-known cluster tools which may be adapted for the present disclosure are the Centura® and the Endura®, both available from Applied Materials, Inc., of Santa Clara, Calif. However, the exact arrangement and combination of chambers may be altered for purposes of performing specific steps of a process as described herein. Other processing chambers which may be used include, but are not limited to, cyclical layer deposition (CLD), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), etch, pre-clean, chemical clean, thermal treatment such as RTP, plasma nitridation, anneal, orientation, hydroxylation and other substrate processes. By carrying out processes in a chamber on a cluster tool, surface contamination of the substrate with atmospheric impurities can be avoided without oxidation prior to depositing a subsequent film. 
     In some embodiments, the first processing chamber and the second processing chamber are part of the same, clustered, processing tool. Accordingly, in some embodiments, the method is an in-situ integrated method. 
     In some embodiments, the first processing chamber and the second processing chamber are different processing tools. Accordingly, in some embodiments, the method is an ex-situ integrated method. 
     According to one or more embodiments, the substrate is continuously under vacuum or “load lock” conditions, and is not exposed to ambient air when being moved from one chamber to the next. The transfer chambers are thus under vacuum and are “pumped down” under vacuum pressure. Inert gases may be present in the processing chambers or the transfer chambers. In some embodiments, an inert gas is used as a purge gas to remove some or all of the reactants. According to one or more embodiments, a purge gas is injected at the exit of the deposition chamber to prevent reactants from moving from the deposition chamber to the transfer chamber and/or additional processing chamber. Thus, the flow of inert gas forms a curtain at the exit of the chamber. 
     The substrate can be processed in single substrate deposition chambers, where a single substrate is loaded, processed and unloaded before another substrate is processed. The substrate can also be processed in a continuous manner, similar to a conveyer system, in which multiple substrate are individually loaded into a first part of the chamber, move through the chamber and are unloaded from a second part of the chamber. The shape of the chamber and associated conveyer system can form a straight path or curved path. Additionally, the processing chamber may be a carousel in which multiple substrates are moved about a central axis and are exposed to deposition, etch, annealing, and/or cleaning processes throughout the carousel path. 
     The substrate can also be stationary or rotated during processing. A rotating substrate can be rotated continuously or in discreet steps. For example, a substrate may be rotated throughout the entire process, or the substrate can be rotated by a small amount between exposures to different reactive or purge gases. Rotating the substrate during processing (either continuously or in steps) may help produce a more uniform deposition or etch by minimizing the effect of, for example, local variability in gas flow geometries. 
     With reference to  FIG. 5 , additional embodiments of the disclosure are directed to a processing system  900  for executing the methods described herein.  FIG. 5  illustrates a system  900  that can be used to process a substrate according to one or more embodiment of the disclosure. The system  900  can be referred to as a cluster tool. The system  900  includes a central transfer station  910  with a robot  912  therein. The robot  912  is illustrated as a single blade robot; however, those skilled in the art will recognize that other robot  912  configurations are within the scope of the disclosure. The robot  912  is configured to move one or more substrate between chambers connected to the central transfer station  910 . 
     At least one pre-clean/buffer chamber  920  is connected to the central transfer station  910 . The pre-clean/buffer chamber  920  can include one or more of a heater, a radical source or plasma source. The pre-clean/buffer chamber  920  can be used as a holding area for an individual semiconductor substrate or for a cassette of wafers for processing. The pre-clean/buffer chamber  920  can perform pre-cleaning processes or can pre-heat the substrate for processing or can simply be a staging area for the process sequence. In some embodiments, there are two pre-clean/buffer chambers  920  connected to the central transfer station  910 . 
     In the embodiment shown in  FIG. 5 , the pre-clean chambers  920  can act as pass through chambers between the factory interface  905  and the central transfer station  910 . The factory interface  905  can include one or more robot  906  to move substrate from a cassette to the pre-clean/buffer chamber  920 . The robot  912  can then move the substrate from the pre-clean/buffer chamber  920  to other chambers within the system  900 . 
     A first processing chamber  930  can be connected to the central transfer station  910 . The first processing chamber  930  can be configured as an epitaxy chamber for (selectively) depositing a metal silicide layer and may be in fluid communication with one or more reactive gas sources to provide one or more flows of reactive gases to the first processing chamber  930 . The substrate can be moved to and from the processing chamber  930  by the robot  912  passing through isolation valve  914 . 
     Processing chamber  940  can also be connected to the central transfer station  910 . In some embodiments, processing chamber  940  comprises physical vapor deposition (PVD) chamber for depositing a metal cap material and/or layer and is fluid communication with one or more reactive gas sources to provide flows of reactive gas to the processing chamber  940 . In some embodiments, processing chamber  940  is an RF-PVD chamber. The substrate can be moved to and from the processing chamber  940  by robot  912  passing through isolation valve  914 . 
     In some embodiments, processing chamber  960  is connected to the central transfer station  910  and is configured to act as a conductor deposition chamber. The processing chamber  960  can be configured to perform one or more different selective deposition (e.g., CVD or PVD) processes. 
     In some embodiments, each of the processing chambers  930 ,  940 , and  960  are configured to perform different portions of the processing method. For example, processing chamber  930  may be configured to perform the metal silicide layer deposition process, processing chamber  940  may be configured to perform the metal cap material and/or layer deposition process, and processing chamber  960  may be configured to perform a conductor deposition process. The skilled artisan will recognize that the number and arrangement of individual processing chamber on the tool can be varied and that the embodiment illustrated in  FIG. 5  is merely representative of one possible configuration. 
     In some embodiments, the processing system  900  includes one or more metrology stations. For example metrology stations can be located within pre-clean/buffer chamber  920 , within the central transfer station  910  or within any of the individual processing chambers. The metrology station can be any position within the system  900  that allows the distance of the recess to be measured without exposing the substrate to an oxidizing environment. 
     At least one controller  950  is coupled to one or more of the central transfer station  910 , the pre-clean/buffer chamber  920 , processing chambers  930 ,  940 , or  960 . In some embodiments, there are more than one controller  950  connected to the individual chambers or stations and a primary control processor is coupled to each of the separate processors to control the system  900 . The controller  950  may be one of any form of general-purpose computer processor, microcontroller, microprocessor, etc., that can be used in an industrial setting for controlling various chambers and sub-processors. 
     The at least one controller  950  can have a processor  952 , a memory  954  coupled to the processor  952 , input/output devices  956  coupled to the processor  952 , and support circuits  958  to communication between the different electronic components. The memory  954  can include one or more of transitory memory (e.g., random access memory) and non-transitory memory (e.g., storage). 
     The memory  954 , or computer-readable medium, of the processor may be one or more of readily available memory such as random access memory (RAM), read-only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. The memory  954  can retain an instruction set that is operable by the processor  952  to control parameters and components of the system  900 . The support circuits  958  are coupled to the processor  952  for supporting the processor in a conventional manner. Circuits may include, for example, cache, power supplies, clock circuits, input/output circuitry, subsystems, and the like. 
     Processes may generally be stored in the memory as a software routine that, when executed by the processor, causes the process chamber to perform processes of the present disclosure. The software routine may also be stored and/or executed by a second processor (not shown) that is remotely located from the hardware being controlled by the processor. Some or all of the method of the present disclosure may also be performed in hardware. As such, the process may be implemented in software and executed using a computer system, in hardware as, e.g., an application specific integrated circuit or other type of hardware implementation, or as a combination of software and hardware. The software routine, when executed by the processor, transforms the general purpose computer into a specific purpose computer (controller) that controls the chamber operation such that the processes are performed. 
     In some embodiments, the controller  950  has one or more configurations to execute individual processes or sub-processes to perform the method. The controller  950  can be connected to and configured to operate intermediate components to perform the functions of the methods. For example, the controller  950  can be connected to and configured to control one or more of gas valves, actuators, motors, slit valves, vacuum control, etc. 
     The controller  950  of some embodiments has one or more configurations selected from: a configuration to move a substrate on the robot between the plurality of processing chambers and metrology station; a configuration to load and/or unload substrates from the system; a configuration to deposit a metal silicide layer, which in one or more embodiments comprises TiSi; a configuration to deposit a metal cap layer, which in one or more embodiments comprises W, directly on the metal silicide layer; and/or a configuration to deposit a conductor, which in one or more embodiments comprises W. 
     Reference throughout this specification to “one embodiment,” “certain embodiments,” “one or more embodiments” or “an embodiment” means that a particular feature, structure, material, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of the phrases such as “in one or more embodiments,” “in certain embodiments,” “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the particular features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments. 
     Although the disclosure herein has been described with reference to particular embodiments, those skilled in the art will understand that the embodiments described are merely illustrative of the principles and applications of the present disclosure. It will be apparent to those skilled in the art that various modifications and variations can be made to the method and apparatus of the present disclosure without departing from the spirit and scope of the disclosure. Thus, the present disclosure can include modifications and variations that are within the scope of the appended claims and their equivalents.