Abstract:
A method of performing in-situ cleaning of a substrate includes inserting a gas cluster ion beam into a processing chamber containing a substrate, the gas cluster ion beam includes a broad gas cluster ion bean that reaches an entire surface of the substrate. The entire surface of the substrate becomes substantially uniform after an exposure to the gas cluster ion beam.

Description:
BACKGROUND 
       [0001]    The present invention generally relates to semiconductor manufacturing and more particularly to low-temperature silicide film growth. 
         [0002]    Complementary metal-oxide-semiconductor (CMOS) technology is commonly used for fabricating field effect transistors (FETs) as part of advanced integrated circuits (IC), such as CPUs, memory, storage devices, and the like. Most common among these may be metal-oxide-semiconductor field effect transistors (MOSFETs). In a typical MOSFET, a gate structure may be energized to create an electric field in an underlying channel region of a substrate, by which charge carriers are allowed to travel through the channel region between a source region and a drain region. As ICs continue to scale downward in size, the use of high carrier mobility materials in the channel region may be considered to boost device performance for the 14 nm node and beyond. Group III-V materials, such as gallium arsenide (GaAs) and indium gallium arsenide (InGaAs), may be potential candidates to replace silicon (Si) as the channel material. 
       SUMMARY 
       [0003]    The ability to conduct low temperature silicide film growth as well as in-situ pre-clean of a substrate may facilitate implementing new generation Group III-V channel materials in current CMOS technology. 
         [0004]    According to an embodiment of the present disclosure, a method of performing in-situ cleaning of a substrate may include inserting a gas cluster ion beam into a processing chamber containing a substrate, the gas cluster ion beam may include a broad gas cluster ion bean that reaches an entire surface of the substrate, the entire surface of the substrate becomes substantially uniform after an exposure to the gas cluster ion beam. 
         [0005]    According to another embodiment of the present disclosure, a method of performing in-situ cleaning of a substrate may include supplying an etchant gas to a cluster formation chamber to form a gas cluster, moving the gas cluster to an ionization-acceleration chamber to form a gas cluster ion beam, injecting the gas cluster ion beam into a processing chamber, the processing chamber containing the substrate, and bombarding an entire surface of the substrate with the gas cluster ion beam. 
         [0006]    According to another embodiment of the present disclosure, a method of performing in-situ cleaning of a substrate may include supplying an etchant gas to a cluster formation chamber to form a gas cluster, moving the gas cluster to an ionization-acceleration chamber to form a gas cluster ion beam, injecting the gas cluster ion beam into a processing chamber via an opening, the processing chamber containing the substrate, and bombarding an entire surface of the substrate with the gas cluster ion beam, a width of the opening allows a size of the gas cluster ion beam to be increased such that the entire surface of the substrate is reached by the gas cluster ion beam. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0007]    The following detailed description, given by way of example and not intended to limit the invention solely thereto, will best be appreciated in conjunction with the accompanying drawings, in which: 
           [0008]      FIG. 1  is a cross-sectional view of a gas cluster ion beam (GCIB) device, according to an embodiment of the present invention; 
           [0009]      FIG. 2  is a cross-sectional view of a GCIB device depicting forming a gas cluster ion beam and injecting a precursor gas to form a silicide film on a substrate, according to an embodiment of the present invention; and 
           [0010]      FIG. 3  is a cross-sectional view of a GCIB device depicting forming a broad gas cluster ion beam and injecting a precursor gas to form a silicide film on a substrate, according to an alternate embodiment of the present invention. 
       
    
    
       [0011]    The drawings are not necessarily to scale. The drawings are merely schematic representations, not intended to portray specific parameters of the invention. The drawings are intended to depict only typical embodiments of the invention. In the drawings, like numbering represents like elements. 
       DETAILED DESCRIPTION 
       [0012]    Detailed embodiments of the claimed structures and methods are disclosed herein; however, it may be understood that the disclosed embodiments are merely illustrative of the claimed structures and methods that may be embodied in various forms. This invention may, however, be embodied in many different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of this invention to those skilled in the art. 
         [0013]    In the following description, numerous specific details are set forth, such as particular structures, components, materials, dimensions, processing steps, and techniques, in order to provide a thorough understanding of the present invention. However, it will be appreciated by one of ordinary skill of the art that the invention may be practiced without these specific details. In other instances, well-known structures or processing steps have not been described in detail in order to avoid obscuring the invention. It will be understood that when an element as a layer, region, or substrate is referred to as being “on” or “over” another element, it may be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” or “directly over” another element, there are no intervening elements present. It will also be understood that when an element is referred to as being “beneath,” “below,” or “under” another element, it may be directly beneath or under the other element, or intervening elements may be present. In contrast, when an element is referred to as being “directly beneath” or “directly under” another element, there are no intervening elements present. 
         [0014]    In the interest of not obscuring the presentation of embodiments of the present invention, in the following detailed description, some processing steps or operations that are known in the art may have been combined together for presentation and for illustration purposes and in some instances may have not been described in detail. In other instances, some processing steps or operations that are known in the art may not be described at all. It should be understood that the following description is rather focused on the distinctive features or elements of various embodiments of the present invention. 
         [0015]    As the semiconductor industry continues to scale down the size of devices, a new generation of high carrier mobility channel materials have been considered to further improve device performance. Group III-V materials, such as GaAs and InGaAs, may be potential candidates to replace Si as the channel material. However, fabricating low resistance contacts on source and drain regions formed in these Group III-V materials may pose challenges to their implementation. One possible challenge may include forming a low resistance silicide on a complex material such as InGaAs. In such cases, the physical properties of the Group III-V materials may require a deposition temperature lower than 400° C. when forming a silicide, which may in turn limit the choice of silicide materials. Therefore, formation of self-aligned silicide contacts using traditional methods, which may include metal film deposition and high temperature annealing, may not be compatible with silicide film growth on Group III-V materials. 
         [0016]    Current technologies, such as gas cluster ion beam (GCIB) processes, may exhibit unique nonlinear effects that may be valuable for surface processing applications, and in particular, low-temperature silicide film formation. By adding an injection device to a processing chamber of a GCIB device, embodiments of the present disclosure may, among other potential benefits, conduct a low-temperature anisotropic deposition such that a highly conductive silicide film may be grown directly on a surface of the Group III-V material. This low-temperature anisotropic deposition may reduce silicide contact resistance and potentially improve device performance. 
         [0017]    The present invention generally relates to semiconductor manufacturing and more particularly to low-temperature silicide film growth. A low-temperature silicide film deposition may be conducted by modifying a GCIB device. One way to modify the GCIB device to conduct low-temperature silicide film growth may include adding an injection device to a processing chamber of the GCIB device. One embodiment by which to form the silicide film on a Group III-V material surface using the modified GCIB device is described in detail below by referring to the accompanying drawings in  FIGS. 1-2 . 
         [0018]    Referring now to  FIG. 1 , a gas cluster ion beam (GCIB) device  100  is shown, according to an embodiment of the present disclosure. In the depicted embodiment, the GCIB device  100  may include a cluster formation chamber  102 , an ionization-acceleration chamber  108  and a processing chamber  110  in which a substrate  126  may be placed to be processed. An aperture  114  may control the size of a subsequently formed gas cluster ion beam. The aperture  114  may have a width capable of creating a collimated gas cluster ion beam as described in  FIG. 2 . 
         [0019]    The GCIB device  100  may be configured to produce a gas cluster ion beam suitable for treating the substrate  126 . In the depicted embodiment, the substrate  126  may include a semiconductor wafer made from any of several known semiconductor materials including, but not limited to, silicon, germanium, silicon-germanium alloy, carbon-doped silicon, carbon-doped silicon-germanium alloy, and compound (e.g. Group III-V and Group II-VI) semiconductor materials. Non-limiting examples of compound semiconductor materials include GaAs, InAs and/or InGaAs. In one exemplary embodiment, the substrate  126  may include GaAs. 
         [0020]    The GCIB device  100  may further include an injection device  120  located on a top portion of the processing chamber  110 . The injection device  120  may be positioned relative to the substrate  126 . More specifically, the position of the injection device  120  may allow directional injection of a subsequently inserted precursor gas for localized treatment of the substrate  126 . In one embodiment, the injection device may be positioned on an angle of approximately 45° with respect to the plane of the substrate  126 . However, it should be noted that the injection device  120  may be positioned at any inclination angle that may allow localized treatment of areas of the substrate  126 . The injection device  120  may include, for example, a showerhead device having a plurality of openings through which the precursor gas may flow. 
         [0021]    Referring now to  FIG. 2 , a source gas  204  may be supplied to the cluster formation chamber  102  to form a gas cluster beam (not shown) that may be subsequently ionized and accelerated in the ionization-acceleration chamber  108  to form a gas cluster ion beam  208  (hereinafter “GCIB”). The GCIB  208  may be used to form a silicide film  230  on the substrate  126  contained in the processing chamber  110 . 
         [0022]    The processing steps involved in the formation of the GCIB  208  are well known to those skilled in the art and may include forming a gas cluster in the cluster formation chamber  102  by expansion of the source gas  204  at high pressure through a room temperature nozzle (not shown) into vacuum. Then, gas clusters may enter the ionization-acceleration chamber  108  located downstream of the cluster formation chamber  102 . Once in the ionization-acceleration chamber  108 , a second vacuum stage may take place where gas clusters may be ionized by electron bombardment and then accelerated to a high potential ranging from approximately 1 keV to approximately 100 keV. The energy range of the GCIB  208  may vary according to the envisioned use for the GCIB device  100 . For the purpose of silicide film growth, the GCIB  208  may have an energy range varying from approximately 10 keV to approximately 60 keV. 
         [0023]    In some embodiments, magnetic filtering of the GCIB  208  may be conducted prior to a subsequent vacuum stage performed in the processing chamber  110  in order to reduce monomer ion contamination. The resulting beam may include cluster ions with a size distribution that may range from a few hundred atoms to several thousand atoms. In one embodiment, the GCIB  208  size distribution may vary between approximately 100 atoms/cluster to approximately 20,000 atoms/cluster. In another embodiment, the GCIB  208  size distribution may vary between approximately 5,000 atoms/cluster to approximately 10,000 atoms/cluster. 
         [0024]    At this point, a neutralizer assembly (not shown) connected to the processing chamber  110  may inject low energy electrons into the GCIB  208  in order to decrease space charge blow-up and to avoid charge build-up on nonconductive substrates. When the GCIB  208  enters the processing chamber  110 , mechanical scanning may be used for uniform treatment of the substrate  126 . In some embodiments, a Faraday current monitor (not shown) may be used for dose control of the GCIB  208 . The dose of GCIB  208  may range from approximately 1 e 12  clusters/cm 2  to approximately 1 e 18  clusters/cm 2 . 
         [0025]    Depending upon the application, the gas clusters may be produced from a variety of gases. For the purpose of silicide film growth, the source gas  204  may include any metal or silicon-containing gas suitable for silicide formation. In one embodiment, the source gas  204  may include a silicon-source gas such as SiH 2 Cls (DCS), Si 2 H 6 , SiCl 4  and SiHCl 3 . In another embodiment, the source gas  204  may include a metal-source gas such as TiCl 4 , WF 6 , and metal amidinates, including cobalt and nickel based amidinates. 
         [0026]    With continued reference to  FIG. 2 , a precursor gas  210  may be introduced into the processing chamber  110  through the injection device  120 . The precursor gas  210  may be directionally injected in order to reach a surface of the substrate  126 . The precursor gas  210  may include any metal or silicon containing gas suitable for silicide formation. In one embodiment, the precursor gas  210  may include a silicon-source gas such as SiH 2 Cls (DCS), Si 2 H 6 , SiCl 4  and SiHCl 3 . In another embodiment, the precursor gas  210  may include a metal-source gas such as TiCl 4 , WF 6 , and metal amidinates, including cobalt and nickel based amidinates. 
         [0027]    It should be understood that if the source gas  204  includes a silicon-source gas, the precursor gas  210  may include a metal-source gas and vice versa. 
         [0028]    In one embodiment, the precursor gas  210  and the GOB  208  may be simultaneously injected into the processing chamber  110  for processing of the substrate  126 . In this embodiment, simultaneous cluster ion bombardment and precursor gas exposure may occur on the substrate  126 , adhesion of atoms (or molecules) of the precursor gas  210  on the substrate  126  may be predominantly facilitated by the energetic cluster ions which may induce a chemical reaction at the substrate surface to promote growth of the silicide film  230 . Therefore, the growth rate of the silicide film  230  may be controlled by the GCIB  208  flux. 
         [0029]    It should be noted that, in embodiments where the precursor gas  210  and the GCIB  208  may be simultaneously injected into the processing chamber  110 , the precursor gas  210  and the GCIB  208  may collide prior to reaching the substrate  126 . These collisions may cause the gas clusters to lose energy before reaching the substrate  126  which may affect the deposition process. In order to reduce collisions between the precursor gas  210  and the GCIB  208 , pressure in the processing chamber  110  may be kept low enough such that collisions are minimized. For example, pressure in the processing chamber  110  may be kept in a range varying from approximately 10 −6  Torr to approximately 10 −2  Torr in order to minimize collisions between the precursor gas  210  and the GCIB  208  prior to reaching the substrate  126 . 
         [0030]    In another embodiment, the precursor gas  210  may be introduced to the processing chamber  110  in cycles of precursor gas injection followed by GCIB injection and vice versa. Stated differently, a cyclic deposition in which pulses of precursor gas  210  injection followed by GCIB  208  bombardment may be conducted to form the silicide film  230  on the substrate  126 . It should be noted that growth of the silicide film  230  may occur layer by layer. In this embodiment, one or more monolayers of the precursor material on the substrate surface may react with the incoming energetic gas cluster ions, which may result in growth of the silicide film  230 . The thickness of the silicide film  230  may be controlled by the number of precursor gas  210  and GCIB  208  pulses. 
         [0031]    The processing chamber  110  may further include a mechanical scanning system which may allow the substrate  126  to move in different directions so that the entire surface of the substrate  126  may be reached by the GCIB  208  and the precursor gas  210 . As a result, a silicide film  230  having a substantially even thickness may be formed on the substrate  126 . 
         [0032]    It should be understood that the terms “growth and/or deposition” and “formed and/or grown” mean the growth of a material on a deposition surface such as the substrate  126 . 
         [0033]    The GCIB  208  together with the precursor gas  210 , injected via the injection device  120  in the processing chamber  110 , may provide a low-temperature thin-film deposition process that may facilitate the formation of a silicide film on the substrate  126  with enhanced density, adhesion, smoothness, crystallinity, and electrical characteristics that silicide films deposited by typical deposition techniques may not exhibit. Also, because the GCIB process is anisotropic, the silicide film may be substantially deposited in surfaces perpendicular to the direction of the GCIB  208 , having minimal impact on surfaces of the substrate  126  that are parallel to the GCIB  208 . 
         [0034]    In another embodiment, the GCIB  208  may be used to conduct an in-situ pre-clean of the substrate  126  prior to forming the silicide film  230 . Pre-cleaning of the substrate  126  may remove contaminants and produce a uniform substrate surface which may benefit further processing steps, including the formation of the silicide film  230 . In this embodiment, the source gas  204  may include any suitable etchant gas such as, for example, NF 3 . 
         [0035]    Another embodiment by which to modify the GCIB device to conduct low-temperature silicide film growth on a Group III-V material is described in detail below by referring to the accompanying drawing in  FIG. 3 . The present embodiment may include modifying an aperture of the processing chamber and adding an injection device to the processing chamber of the GCIB device. 
         [0036]    Referring now to  FIG. 3 , a broad GCIB  320  may be formed in the GCIB device  300 , according to an alternate embodiment of the present disclosure. In this embodiment, the aperture  114  ( FIG. 2 ) may be modified such that it has a width capable of increasing the cluster distribution size to form the broad GCIB  320 . By doing so, the broad GCIB  320  may reach a substantially larger area of the substrate  126  than the GCIB  208  ( FIG. 2 ). In an embodiment, the aperture  114  ( FIG. 2 ) may remain in place, but may be widened to form the broad GCIB ( FIG. 2 ). In the depicted embodiment, the aperture  114  ( FIG. 2 ) may be removed entirely to form the broad GCIB  320  which may be able to bombard the entire surface of the substrate  126 . In embodiments where the broad GCIB  320  may be formed, mechanical scanning of the substrate  126  may not be required to achieve a uniform treatment of the substrate  126 . It should be understood that the broad GCIB  320  may be formed from a source gas similar to the source gas  204  described above with reference to  FIG. 2 . 
         [0037]    Furthermore, different pressure and nozzle size combinations may be required to increase the broad GCIB  320  intensity and achieve a larger distribution size. In one embodiment, the broad GCIB  320  size distribution may vary between approximately 100 atoms/cluster to approximately 20,000 atoms/cluster. In another embodiment, the GCIB  320  size distribution may vary between approximately 5,000 atoms/cluster to approximately 10,000 atoms/cluster. 
         [0038]    In the depicted embodiment, the broad GCIB  320  may include an energy range varying from approximately 10 keV to approximately 60 keV and may be injected in doses ranging from approximately 1 e 12  clusters/cm 2  to approximately 1 e 18  clusters/cm 2 . 
         [0039]    An injection device  340  may be added to the processing chamber  110 . Similarly to the injection device  120  shown in  FIG. 1 , the injection device  340  may be located on a top portion of the processing chamber  110 . The injection device  340  may be positioned relative to the substrate  126 . However, unlike the injection device  120  ( FIG. 1 ), the injection device  340  may not necessarily allow directional injection of a subsequently inserted precursor gas  360  for treatment of the substrate  126 . 
         [0040]    Next, a precursor gas  360  may be introduced into the processing chamber  110  via the injection device  340 . The precursor gas  360  may include any metal or silicon containing gas suitable for silicide formation. In one embodiment, the precursor gas  360  may include a silicon-source gas such as SiH 2 Cls (DCS), Si 2 H 6 , SiCl 4  and SiHCl 3 . In another embodiment, the precursor gas  360  may include a metal-source gas such as TiCl 4 , WF 6 , and metal amidinates, including cobalt and nickel based amidinates. 
         [0041]    In one embodiment, the precursor gas  360  and the broad GCIB  320  may be simultaneously injected into the processing chamber  110  for processing of the substrate  126 . In another embodiment, the precursor gas  360  may be introduced to the processing chamber  110  in cycles of precursor gas injection followed by GCIB injection and vice versa. 
         [0042]    In embodiments where the precursor gas  360  and the broad GCIB  320  may be simultaneously injected into the processing chamber  110 , the precursor gas  360  may be injected until reaching a pressure at which the broad GCIB  320  and the precursor gas  360  may collide. Since collisions may cause the gas clusters to lose energy before reaching the substrate  126 , pressure in the processing chamber  110  may be maintained low enough such that collisions between the precursor gas  360  and the broad GCIB  320  may be reduced. For example, in one embodiment, the pressure in the processing chamber  110  may be kept in a range varying from approximately 10 −2  Torr to approximately 10 −1  Torr in order to minimize the collisions between the precursor gas  360  and the broad GCIB  320  prior to reaching the substrate  126 . 
         [0043]    In another embodiment, the broad GCIB  320  may be used to conduct an in-situ pre-clean of the substrate  126  prior to forming a silicide film  380 . Pre-cleaning of the substrate  126  may remove contaminants and produce a uniform substrate surface which may benefit further processing steps, including the formation of the silicide film  380 . In this embodiment, the source gas  204  may include any suitable etchant gas such as, for example, NF 3 . 
         [0044]    Therefore, by adding an injection device to a processing chamber of a GICB device, low temperature silicide growth may be conducted to form a highly conductive silicide film on a substrate that may include Group III-V materials. As a result, electrical resistance may be reduced, thereby enhancing device performance and potentially increasing product yield and reliability. Additionally, in-situ pre-clean of the substrate may be conducted to improve surface conditions prior to deposition of the silicide film. 
         [0045]    The descriptions of the various embodiments of the present invention have been presented for purposes of illustration, but are not intended to be exhaustive or limited to the embodiments disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The terminology used herein was chosen to best explain the principles of the embodiment, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand the embodiments disclosed herein.