Patent Publication Number: US-2018053659-A1

Title: Methods and apparatus for deposition processes

Description:
FIELD 
     Embodiments of the present disclosure generally relate to methods for selective dielectric deposition using self-assembled monolayers. 
     BACKGROUND 
     Selective atomic layer deposition (ALD) and chemical vapor deposition (CVD) processes can advantageously reduce the number of steps and cost involved in conventional lithography while keeping up with the pace of device dimension shrinkage. Selective silicon based dielectric deposition in a metal dielectric pattern is of high potential value in back-end of line (BEOL) applications. Some alternative selective silicon based dielectric deposition techniques that have emerged are template-controlled growth, holographic based lithography, and the like. However, none of these alternative techniques provide a complete solution due to limitations like throughput, scale, defect issues, etc. 
     Accordingly, the inventors have developed improved methods and apparatus for selective dielectric deposition using self-assembled monolayer as sacrificial and nucleation inhibition layer. 
     SUMMARY 
     Methods for selective deposition using self-assembled monolayer (SAM) are provided herein. In some embodiments, a method of selectively depositing a low-k dielectric layer atop a substrate having an exposed silicon surface and an exposed silicon-containing surface, includes: (a) growing an organosilane based self-assembled monolayer atop the exposed silicon-containing surface, wherein the organosilane based self-assembled monolayer is thermally stable at a first temperature of greater than about 300 degrees Celsius; and (b) selectively depositing a low-k dielectric layer atop the exposed silicon surface of the substrate, wherein the organosilane based self-assembled monolayer inhibits deposition of the low-k dielectric layer atop the silicon-containing surface. 
     In some embodiments, a method of selectively depositing a layer atop a substrate having an exposed metal surface and an exposed silicon-containing surface, includes: (a) growing a first self-assembled monolayer atop the exposed metal surface; (b) growing a second self-assembled monolayer atop the exposed silicon-containing surface, wherein the second self-assembled monolayer is organosilane based; (c) heating the substrate to a temperature of about 200 to about 300 degrees Celsius to remove the first self-assembled monolayer from atop the exposed metal surface; (d) selectively depositing a layer atop the exposed metal surface, wherein the layer is a low-k dielectric layer or a metal layer; and (e) heating the substrate to a temperature of about 500 to about 1000 degrees Celsius to remove the second self-assembled monolayer from atop the exposed silicon-containing surface. 
     Other and further embodiments of the present disclosure are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. The appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of the scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  depicts a process chamber suitable for performing a chemical vapor deposition process or atomic layer deposition process in accordance with some embodiments of the present disclosure. 
         FIG. 2  depicts a flowchart of a method of selective deposition in accordance with some embodiments of the present disclosure. 
         FIGS. 3A-3D  are illustrative cross-sectional views of the substrate during different stages of the processing sequence of  FIG. 2  in accordance with some embodiments of the present disclosure. 
         FIG. 4  is a flow diagram of a method of selective deposition in accordance with some embodiments of the present disclosure. 
         FIGS. 5A-5F  are illustrative cross-sectional views of the substrate during different stages of the processing sequence of  FIG. 4  in accordance with some embodiments of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Methods for selective dielectric deposition using self-assembled monolayer (SAM) are provided herein. In some embodiments, the inventive methods described herein advantageously provide an innovative method of selective dielectric deposition or selective metal deposition using self-assembled monolayers. Self-assembled monolayers (SAM) can selectively grow on patterned substrate and enable selective deposition by inhibiting nucleation selectively. 
       FIG. 2  is a flow diagram of a method  200  of processing a substrate having an exposed silicon surface and an exposed silicon-containing surface in accordance with some embodiments of the present disclosure.  FIGS. 3A-3D  are illustrative cross-sectional views of the substrate during different stages of the processing sequence of  FIG. 2  in accordance with some embodiments of the present disclosure. The inventive methods may be performed in process chambers configured for atomic layer deposition (ALD) or chemical vapor deposition (CVD), such as the process chamber discussed below with respect to  FIG. 1 . 
     The method  200  is performed on a substrate  300 , as depicted in  FIG. 3A , having an exposed silicon surface  302  and an exposed silicon-containing surface  304 . The silicon-containing surface  304  is not the same as silicon surface  302 . The silicon-containing surface  304 , may be silicon dioxide, silicon nitride, or silicon oxynitride (SiON). In some embodiments, the substrate  300  may be a semiconductor wafer, such as a 200 or 300 mm semiconductor wafer. Other size and geometry substrates may also be used. 
     The method  200  begins at  202  and as depicted in  FIG. 3B , by depositing an organosilane based self-assembled monolayer (self-assembled monolayer  306 ) atop the exposed silicon-containing surface  304 . The self-assembled monolayer  306  is chosen to be thermally stable at a first temperature of greater than about 300 degrees Celsius, for example about 300 to about 500 degrees Celsius. By selecting a self-assembled monolayer  306  that is thermally stable at the first temperature, a subsequent deposition of the dielectric layer, via a chemical vapor deposition (CVD) or atomic layer deposition (ALD) process, typically performed at a temperature of less than 300 degrees Celsius will not decompose the self-assembled monolayer  306 . 
     Growing the organosilane based self-assembled monolayer  306  comprises exposing the substrate  300  to a solution comprising a liquid organosilane. Suitable organosilanes have long alkyl chains to form a compact, defect free, thermally stable, and chemically inert barrier which can be removed cleanly at a later stage. Suitable organosilanes have C-8 to C-30 chains, including all the corresponding homologues with C-8 to upward of C-30 chains. Exemplary suitable organosilanes include, but are not limited to, octadecyltrichlorosilane (ODTS), trimethoxy(octadecyl)silane (ODTMS), chloro(dimethyl)octadecylsilane (CDODS), or trichloro(1H, 1H, 2H, 2H-perfluorooctyl)silane (PFTS). One of the criteria listed above of choosing the organosilane molecule is the thermal stability of the self-assembled monolayer. Selecting a self-assembled monolayer that is thermally stable at the deposition temperature of the subsequently deposited dielectric layer avoids decomposition of the self-assembled monolayer  306  at the deposition temperature of the subsequently deposited dielectric layer. For example, the thermal stability of ODTS on silicon dioxide (SiO 2 ) is at least up to 500 degree Celsius. Accordingly, an ODTS self-assembled monolayer will not decompose during the deposition of dielectric material such as silicon dioxide (SiO 2 ) or silicon nitride (SiN) via an ALD process. Thus, the thermal stability of ODTS-SiO2 SAM expands the temperature compatibility limit. 
     The solution further comprises a solvent, such as toluene, hexane, cyclohexane, or diethylether. In some embodiments, the solution comprises the solvent having about 1 millimol to about 10 millimol of organosilane. The substrate  300  is dipped in the solution for about 2 to about 3 hours to form the self-assembled monolayer  306  atop the exposed silicon-containing surface  304 . The organosilane molecules have a chemical affinity (i.e. are reactive and selective) to the oxide in a silicon oxide (SiO 2 ) surface, or the nitride in a silicon nitride (SiN) surface or the oxide and nitride in a silicon oxynitride (SiON) surface. Thus, the self-assembled monolayer  306  will only form on the exposed silicon-containing surface  304  but not on the exposed silicon surface  302 . The substrate  300  is rinsed with a solvent, for example a solvent listed above, after depositing the self-assembled monolayer  306  to remove any unabsorbed organosilane molecules. 
     In some embodiments, the exposed silicon surface  302  may have a native oxide layer formed atop the exposed silicon surface  302 . In some embodiments, the native oxide layer is removed prior to depositing the self-assembled monolayer  306 . In embodiments where a native oxide layer is to be removed from the substrate, a SICONI™ Pre-clean process may be performed in a suitable chamber, such as a process chamber that utilizes SICONI™ technology available from Applied Materials, Inc., of Santa Clara, Calif. In such embodiments, the substrate  300  may be exposed to a fluorine containing precursor and a hydrogen containing precursor in a two part dry chemical clean process. In some embodiments, the fluorine containing precursor may comprise nitrogen trifluoride (NF 3 ), hydrogen fluoride (HF), diatomic fluorine (F 2 ), monatomic fluorine (F) and fluorine-substituted hydrocarbons, combinations thereof, or the like. In some embodiments, the hydrogen containing precursors may comprise atomic hydrogen (H), diatomic hydrogen (H2), ammonia (NH3), hydrocarbons, incompletely halogen-substituted hydrocarbons, combinations thereof, or the like. In some embodiments, the first part in the two part process may comprise using a remote plasma source to generate an etchant species (e.g., ammonium fluoride (NHF 4 )) from the fluorine containing precursor (e.g., nitrogen trifluoride (NF 3 )) and the hydrogen containing precursor (e.g., ammonia (NH 3 )). By using a remote plasma source, damage to the substrate may be minimized. The etchant species are then introduced into the pre-clean chamber and condensed into a solid by-product on the substrate surface through a reaction with native oxide layer. An in-situ anneal may then be performed to decompose the by-product. The by-product then sublimates and may be removed from the substrate surface via a flow of gas and pumped out of the pre-clean chamber. 
     Next, at  204  and as depicted in  FIG. 3C , a low-k dielectric layer  308  is selectively depositing atop the exposed silicon surface  302  of the substrate  300 . In some embodiments, the low-k dielectric layer is deposited via any suitable atomic layer deposition process or a chemical layer deposition process. The presence of the self-assembled monolayer  306  atop the silicon-containing surface  304  inhibits formation of the low-k dielectric layer on the silicon-containing surface  304  while the thermal stability of the self-assembled monolayer  306  prevents decomposition of the self-assembled monolayer  306  at the deposition temperatures of the low-k dielectric layer (e.g. less than about 300 degrees Celsius). The low-k dielectric layer  308  may include any low-k dielectric material suitable for semiconductor device fabrication. For example, in some embodiments, the low-k dielectric layer  308  may comprise a silicon containing material, for example, such as silicon oxide (SiO2). As used herein, the low-k dielectric layer  308  may have a low-k value of less than about 3.9 (for example, about 2.5 to about 3.5). 
     Next, and as depicted in  FIG. 3D , the substrate  300  is heated to a temperature of greater than about 500 degrees Celsius, for example about 500 to about 1000 degrees Celsius, to remove the self-assembled monolayer  306  from atop the exposed silicon-containing surface  304 . Following removal of the self-assembled monolayer  306  the method  200  ends and the substrate may undergo further processing as necessary for completion of a semiconductor device, such as a field effect transistor (FET), a fin field effect transistor (FinFET), a flash memory device, a 3D FINFET device, or the like. 
       FIG. 4  is a flow diagram of a method  400  of processing a substrate having an exposed metal surface and an exposed silicon-containing surface in accordance with some embodiments of the present disclosure.  FIGS. 5A-5F  are illustrative cross-sectional views of the substrate during different stages of the processing sequence of  FIG. 4  in accordance with some embodiments of the present disclosure. The inventive methods may be performed in process chambers configured for atomic layer deposition (ALD) or chemical vapor deposition (CVD), such as the process chamber discussed below with respect to  FIG. 1 . 
     The method  400  is performed on a substrate  500 , as depicted in  FIG. 5A , having an exposed metal surface  502  and an exposed silicon-containing surface  504 . The exposed metal surface  502  may be copper or cobalt. The silicon-containing surface  504  may be silicon dioxide, silicon nitride, or silicon oxynitride (SiON). In some embodiments, the substrate  500  may be a semiconductor wafer, such as a 200 or 300 mm semiconductor wafer. Other size and geometry substrates may also be used. 
     The method begins at  402  and as depicted in  FIG. 5B  by growing a first self-assembled monolayer  506  atop the exposed metal surface  502 . Growing the first self-assembled monolayer  506  comprises dipping the substrate  500  in a solution for about 2 to about 3 hours to form the first self-assembled monolayer  506  atop the exposed metal surface  502 . The solution comprises a solvent and long chain (i.e. C-8 to C-30 chains, including all the corresponding homologues with C-8 to upward of C-30 chains) alkyl thiols, long chain organophosphonic acids, or long chain sulfonic acids (i.e. SAM precursors). Exemplary suitable SAM precursors include, but are not limited to, octadecylthiol, octadecylphosphonic acid, and octadecylsulfonic acid. Exemplary solvents include, but are not limited to, ethanol or tetrahydrofuran (THF). In some embodiments, the solution comprises the solvent having about 1 millimol to about 10 millimol of SAM precursors. The SAM precursor molecules have a chemical affinity (i.e. are reactive and selective) to the metal surface and, thus, will only form the first self-assembled monolayer  506  on the exposed metal surface  502  but not on the exposed silicon-containing surface  504 . The substrate  500  is then rinsed with a solvent, for example a solvent listed above, after depositing the first self-assembled monolayer  506  to remove any unabsorbed SAM precursor molecules 
     Next, at  404  and as depicted in  FIG. 5C , a second self-assembled monolayer  508  is depositing atop the exposed silicon-containing surface  504 . The second self-assembled monolayer  508  is organosilane based as described above with respect to method  200 . The second self-assembled monolayer  508  is deposited as described above with respect to method  200 . However, the second self-assembled monolayer  508  is not selective to just the silicon-containing surface  504  and can react with the exposed metal surface  502 . Accordingly, the presence of the first self-assembled monolayer  506  prevents reaction of the second self-assembled monolayer  508  with the exposed metal surface  502 . 
     Next, at  406  and as depicted in  FIG. 5D , the substrate  500  is heated to a temperature of about 200 to about 300 degrees Celsius to remove the first self-assembled monolayer  506  from atop the metal surface  502 . The second self-assembled monolayer  508  is thermally stable at a higher temperature than the first self-assembled monolayer  506 . Accordingly, the second self-assembled monolayer  508  will not decompose at the temperature at which the first self-assembled monolayer  506  is removed from atop the metal surface  502 . 
     Next, at  408  and as depicted in  FIG. 5E , a layer  510 , is selectively depositing atop the exposed metal surface  502 . In some embodiments, the layer  510  is a low-k dielectric layer. The low-k dielectric layer may include any low-k dielectric material suitable for semiconductor device fabrication. For example, in some embodiments, the low-k dielectric layer may comprise a silicon containing material, for example, such as silicon oxide (SiO2). As used herein, the low-k dielectric layer  308  may have a low-k value of less than about 3.9 (for example, about 2.5 to about 3.5). In some embodiments, the layer  510  is a metal layer such as copper, tungsten, titanium or nickel. In some embodiments, the layer  510  is deposited via any suitable atomic layer deposition process or a chemical layer deposition process. The presence of the second self-assembled monolayer  508  atop the silicon-containing surface  504  inhibits formation of the layer  510  on the silicon-containing surface  504  while the thermal stability of the second self-assembled monolayer  508  prevents decomposition of the second self-assembled monolayer  508  at the deposition temperatures of the layer  510 . 
     Next, at  410  and as depicted in  FIG. 5F , the substrate  500  is heating to a temperature of about 500 to about 1000 degrees Celsius to remove the second self-assembled monolayer  508  from atop the silicon-containing surface  504 . Following removal of the second self-assembled monolayer  508  the method  400  ends and the substrate may undergo further processing as necessary for completion of a semiconductor device, such as a field effect transistor (FET), a fin field effect transistor (FinFET), a flash memory device, a 3D FINFET device, or the like 
       FIG. 1  depicts a schematic diagram of an illustrative apparatus  100  of the kind that may be used to practice embodiments of the disclosure as discussed herein. The apparatus  100  may comprise a controller  150  and a process chamber  102  having an exhaust system  120  for removing excess process gases, processing by-products, or the like, from the inner volume  105  of the process chamber  102 . Exemplary process chambers may include any of several process chambers configured for atomic layer deposition (ALD) or chemical vapor deposition (CVD), available from Applied Materials, Inc. of Santa Clara, Calif. Other suitable process chambers from other manufacturers may similarly be used. 
     The process chamber  102  has an inner volume  105  that may include a processing volume  104 . The processing volume  104  may be defined, for example, between a substrate support  108  disposed within the process chamber  102  for supporting a substrate  110  thereupon during processing and one or more gas inlets, such as a showerhead  114  and/or nozzles provided at predetermined locations. In some embodiments, the substrate support  108  may include a mechanism that retains or supports the substrate  110  on the surface of the substrate support  108 , such as an electrostatic chuck, a vacuum chuck, a substrate retaining clamp, or the like (not shown). In some embodiments, the substrate support  108  may include mechanisms for controlling the substrate temperature (such as heating and/or cooling devices, not shown) and/or for controlling the species flux and/or ion energy proximate the substrate surface. 
     For example, in some embodiments, the substrate support  108  may include an RF bias electrode  140 . The RF bias electrode  140  may be coupled to one or more bias power sources (one bias power source  138  shown) through one or more respective matching networks (matching network  136  shown). The one or more bias power sources may be capable of producing up to 1200 W or RF energy at a frequency of about 2 MHz to about 60 MHz, such as at about 2 MHz, or about 13.56 MHz, or about 60 Mhz. In some embodiments, two bias power sources may be provided for coupling RF power through respective matching networks to the RF bias electrode  140  at respective frequencies of about 2 MHz and about 13.56 MHz. The at least one bias power source may provide either continuous or pulsed power. In some embodiments, the bias power source alternatively may be a DC or pulsed DC source. 
     The substrate  110  may enter the process chamber  102  via an opening  112  in a wall of the process chamber  102 . The opening  112  may be selectively sealed via a slit valve  118 , or other mechanism for selectively providing access to the interior of the chamber through the opening  112 . The substrate support  108  may be coupled to a lift mechanism  134  that may control the position of the substrate support  108  between a lower position (as shown) suitable for transferring substrates into and out of the chamber via the opening  112  and a selectable upper position suitable for processing. The process position may be selected to maximize process uniformity for a particular process. When in at least one of the elevated processing positions, the substrate support  108  may be disposed above the opening  112  to provide a symmetrical processing region. 
     The one or more gas inlets (e.g., the showerhead  114 ) may be coupled to a gas supply  116  for providing one or more process gases through a mass flow controller  117  into the processing volume  104  of the process chamber  102 . In addition, one or more valves  119  may be provided to control the flow of the one or more process gases. The mass flow controller  117  and one or more valves  119  may be used individually, or in conjunction to provide the process gases at predetermined flow rates at a constant flow rate, or pulsed (as described above). 
     Although a showerhead  114  is shown in  FIG. 3 , additional or alternative gas inlets may be provided such as nozzles or inlets disposed in the ceiling or on the sidewalls of the process chamber  102  or at other locations suitable for providing gases to the process chamber  102 , such as the base of the process chamber, the periphery of the substrate support, or the like. 
     The apparatus  100  may utilize capacitively coupled RF energy for plasma processing. For example, the process chamber  102  may have a ceiling  142  made from dielectric materials and a showerhead  114  that is at least partially conductive to provide an RF electrode (or a separate RF electrode may be provided). The showerhead  114  (or other RF electrode) may be coupled to one or more RF power sources (one RF power source  148  shown) through one or more respective matching networks (matching network  146  shown). The one or more plasma sources may be capable of producing up to about 3,000 W, or in some embodiments, up to about 5,000 W, of RF energy at a frequency of about 2 MHz and/or about 13.56 MHz or a high frequency, such as 27 MHz and/or 60 MHz. The exhaust system  120  generally includes a pumping plenum  124  and one or more conduits that couple the pumping plenum  124  to the inner volume  105  (and generally, the processing volume  104 ) of the process chamber  102 . 
     A vacuum pump  128  may be coupled to the pumping plenum  124  via a pumping port  126  for pumping out the exhaust gases from the process chamber via one or more exhaust ports (two exhaust ports  122  shown). The vacuum pump  128  may be fluidly coupled to an exhaust outlet  132  for routing the exhaust to appropriate exhaust handling equipment. A valve  130  (such as a gate valve, or the like) may be disposed in the pumping plenum  124  to facilitate control of the flow rate of the exhaust gases in combination with the operation of the vacuum pump  128 . Although a z-motion gate valve is shown, any suitable, process compatible valve for controlling the flow of the exhaust may be utilized. 
     To facilitate control of the process chamber  102  as described above, the controller  150  may be any form of general-purpose computer processor that can be used in an industrial setting for controlling various chambers and sub-processors. The memory, or computer-readable medium,  156  of the CPU  152  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 support circuits  154  are coupled to the CPU  152  for supporting the processor in a conventional manner. These circuits include cache, power supplies, clock circuits, input/output circuitry and subsystems, and the like. 
     The inventive methods disclosed herein may generally be stored in the memory  156  as a software routine  158  that, when executed by the CPU  152 , causes the process chamber  102  to perform processes of the present disclosure. The software routine  158  may also be stored and/or executed by a second CPU (not shown) that is remotely located from the hardware being controlled by the CPU  152 . Some or all of the method of the present disclosure may also be performed in hardware. As such, the disclosure 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  158  may be executed after the substrate  110  is positioned on the substrate support  108 . The software routine  158 , when executed by the CPU  152 , transforms the general purpose computer into a specific purpose computer (controller)  150  that controls the chamber operation such that the methods disclosed herein are performed. 
     The disclosure may be practiced using other semiconductor substrate processing systems wherein the processing parameters may be adjusted to achieve acceptable characteristics by those skilled in the art by utilizing the teachings disclosed herein without departing from the spirit of the disclosure. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof.