Patent Publication Number: US-2021166946-A1

Title: Apparatus and techniques for substrate processing using independent ion source and radical source

Description:
RELATED APPLICATIONS 
     This application claims priority to U.S. provisional patent application Ser. No. 62/942,430, filed Dec. 2, 2019, entitled APPARATUS AND TECHNIQUES FOR SUBSTRATE PROCESSING USING INDEPENDENT ION SOURCE AND RADICAL SOURCE, and incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This disclosure relates to substrate processing and more particularly to processing using multiple different sources to generate ions and radicals. 
     BACKGROUND 
     Processing of substrates to form devices, such as electronic devices, optical devices, mechanical devices, and so forth, often involves the use of energetic species, such as ions and radicals. In known etching or deposition systems, for example, a substrate may be exposed to a processing plasma to perform a given deposition or etching operation. In some variants, a processing ion beam may be extracted from a plasma and directed to the substrate. Notably, the processing plasma or processing ion beam may include excited species in the form of ions and radicals. Both ions and radicals may influence the properties of a substrate being processed. For example, ions and radicals may both contribute to etching or deposition. Notably, ions may tend to generate etching, while radicals may tend to generate deposition. However, the relative concentration of ions and radicals may be difficult to control, as well as the trajectories of such species. 
     With respect to these and other considerations, the present embodiments are provided. 
     BRIEF SUMMARY 
     In one embodiment, a system a substrate stage to support a substrate; a plurality of beam sources, comprising: an ion beam source, the ion beam source arranged to direct an ion beam to the substrate; and a radical beam source, the radical beam source arranged to direct a radical beam to the substrate. The system may include a controller configured to control the ion beam source and the radical beam source to operate independently of one another, in at least one aspect, wherein the at least one aspect includes beam composition, beam angle of incidence, and relative scanning of a beam source with respect to the substrate. 
     In another embodiment, a method may include providing a substrate in a process chamber, and directing an ion beam to the substrate from an ion beam source. The method may also include directing a radical beam to the substrate from a radical beam source, separate from the ion beam source, wherein the ion beam differs from the radical beam in at least one aspect, the at least one aspect including beam composition, beam angle of incidence, relative scanning of a beam source with respect to the substrate. 
     In a further embodiment, a processing system may include a housing, a substrate stage disposed within the housing, an ion beam source, the ion beam source arranged within the housing, to direct an ion beam to the substrate stage; and a radical beam source, the radical beam source arranged within the housing to direct a radical beam to the substrate. The processing system may further include a controller configured to control the ion beam source and the radical beam source to operate independently of one another, in at least one aspect, wherein the at least one aspect includes beam composition, beam angle of incidence, and relative scanning of a beam source with respect to the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate exemplary approaches of the disclosure, including the practical application of the principles thereof, as follows: 
         FIG. 1A  and  FIG. 1B  show a side view and top plan schematic view of an exemplary system. 
         FIG. 2  presents an exemplary process flow. 
     
    
    
     The drawings are not necessarily to scale. The drawings are merely representations, not intended to portray specific parameters of the disclosure. The drawings are intended to depict exemplary embodiments of the disclosure, and therefore are not be considered as limiting in scope. In the drawings, like numbering represents like elements. 
     DETAILED DESCRIPTION 
     The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, where some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout. 
     The present embodiments provide novel apparatus and techniques for substrate processing. Various embodiments employ a combination of separate ion beam source(s) and separate radical beam source(s) to perform substrate processing, where a radical beam source is independently adjustable with respect to an ion beam source. Radicals may include a variety of components produced by a plasma, not including electrons for example, while ions may include charged particles produced in a plasma, again, not including electrons. Non-limiting examples of ions may include inert gas ions, hydrogen ions, oxygen ions, nitrogen ions, reactive ions, ions based upon carbon, ions based upon hydrocarbons, ions based upon fluorocarbons, and so forth. Non-limiting examples of radicals may include radicals based upon carbon, hydrocarbons, fluorocarbons, chlorocarbons, hydrogen, oxygen, nitrogen, or other suitable gaseous species. According to various embodiments, an apparatus or system may arrange a radical beam source and ion beam source to process a substrate in a sequential manner, or alternatively, in a concurrent manner. In particular embodiments, a substrate may be processed independently by a radical beam source and ion beam source, where the processing may include any suitable combination of etching, deposition, implantation, doping, or other processing technique associated with energetic particles, such as ions and radicals. 
     In accordance with some embodiments, an ion beam as disclosed herein, may be provided as a mass analyzed ion beam, or as a non-mass analyzed ion beam. The ion beam may be provided as a ribbon ion beam or as a spot beam, in different embodiments. In various embodiments, the ion beam may be provided as a convergent ion beam, a collimated ion beam, or a divergent ion beam. The ion beam may be provided as a directional beam, where an average angle of incidence of the ion beam may be fixed or adjustable. In some embodiments, the ion beam source may be arranged to direct an ion beam along a perpendicular (normal) to a main plane of a substrate, such as a main surface of a semiconductor wafer. In other embodiments, the ion beam source may be arranged to direct an ion beam off-normal, meaning at a non-zero angle of incidence with respect to the normal to the main plane of the substrate. 
     Likewise, in various embodiments a radical beam may be directed to a substrate, independently of an ion beam, where the angle of incidence of the radical beam may be along a normal to a substrate plane, or may directed off normal to the substrate. Because the radical beam may be supplied from a radical beam source, separated from an ion beam source, the chemistry and accordingly radical species, directed to a substrate, may be independently controlled with respect to the species provided in an ion beam, including ions. 
     In accordance with various non-limiting embodiments, a radical generator used to generate radicals for a radical beam source may be an RF plasma source, a thermal source, an electron beam source, or a hot cathode source. The radical beam source may be configured to provide a radical beam as a spot beam, or alternatively as a ribbon radical beam. 
     In accordance with various non-limiting embodiments, an apparatus or system as disclosed herein may include a scanning system, arranged with any suitable combination of substrate scanner, ion beam source scanner, and radical beam source scanner. The system may accordingly generate a suitable relative motion of a substrate with respect to an ion beam source and/or radical beam source. In accordance with various embodiments, a scanning system may be arranged with an air bearing, SCARA (Selective Compliance Assembly Robot Arm) robot, or conventional robot, or other known scanning components. 
     In various embodiments of the disclosure, a control system is provided to separately control the output conditions of a radical beam source and the output conditions of an ion beam source. The separate control may include coordination of the output of a radical beam source and an ion beam source so as to provide a targeted combination of radical beam treatment and ion beam treatment to a substrate. 
     In some embodiments, the substrate may be arranged in a common process chamber where processing by both a radical beam source and an ion beam source takes place. In particular embodiments, a barrier, such as a gas curtain or septum may be provided within a processing chamber or processing station, to provide at least partial isolation of ion beam processing from radical beam processing. 
       FIG. 1A  depicts a system  100 , arranged in accordance with embodiments of the disclosure. The system  100  may include multiple beam sources, including an ion beam source  104  and a radical beam source  106 , where in some embodiments, the multiple beam sources may be arranged within a common structure or housing, shown as housing  102 . The ion beam source  104  may generate an ion beam  110  so as to impact a substrate  122 , to perform a given substrate processing operation. The ion beam source  104  may include an ion chamber, such as a plasma chamber, where a plasma is generated by known methods, including RF excitation, hot cathode, indirectly heated cathode, or other known technique. The ion beam source  104  may further include known extraction components to extract and direct the ion beam  110  to the substrate  122 . 
     The radical beam source  106  may generate a radical beam  112  to impact the substrate  122  so as to process the substrate  122  independently of the processing of the substrate  122  that is performed by the ion beam  110 . In accordance with some non-limiting embodiments, the radical beam source  106  may incorporate or may be coupled to a radical generator (not separately depicted) arranged to generate radicals for the radical beam source  106 , where the radical generator is an RF plasma source, a thermal source, an electron beam source, or a hot cathode source. 
     The system  100  further may include a substrate stage  120 , to support a substrate  122 , where the substrate stage  120  may be disposed in a process chamber. In the embodiment of  FIG. 1A  the process chamber is generally defined by the housing  102 , while other configurations are possible. A controller  150  is also provided in the system  100 , to control operation of various components of the system  100 , detailed below. For example, the controller  150  may control the ion beam source  104  and radical beam source  106  to operate independently of one another in at least one aspect. As an example, the controller  150  may control gas species provided to ion beam source  104  and radical beam source  106  so that the beam composition differs between the ion beam source  104  and radical beam source  106 . The controller  150  may control the ion beam source  104  to generate a same angle of incidence or a different angle of incidence for the ion beam  110 , as compared to the angle of incidence of radical beam  112 . In addition, the controller  15  may send control signals to adjust the relative scanning of a beam source, such as the ion beam source  104  or radical beam source  106 , with respect to the substrate  122 . 
     In different embodiments the relative scanning may be accomplished using a scan component of the substrate stage  120  (not separately shown) to scan the substrate  122  while the ion beam source  104  and radical beam source  106  are stationary. In other embodiments, the ion beam source  104 , radical beam source  106 , or both beam sources may be translated or scanned with respect to the substrate  122  while the substrate stage is stationary, using a scan component  130  or scan component  132 , respectively. Notably, in some implementations, the controller  150 , in conjunction with the scan component  130  and scan component  132 , may generate independent movement of the ion beam source  104  and radical beam source  106  with respect to one another. In other implementations, the controller  150  may control the ion beam source  104  and radical beam source  106  to scan in concert with one another with respect to the substrate  122 . In still further embodiments, the ion beam source  104  may be scanned in conjunction with simultaneous scanning of the substrate stage  120 , the radical beam source  106  may be scanned in conjunction with simultaneous scanning of the substrate stage  120 , or both ion beam source  104  and radical beam source  106  may be scanned in conjunction with simultaneous scanning of the substrate stage  120 . 
     In various embodiments, the ion beam source  104  may generate a spot shaped ion beam (spot beam), while in other embodiments the ion beam source  104  may generate the ion beam  110  as a ribbon ion beam as shown in  FIG. 1B . To generate a ribbon ion beam, an extraction assembly may include rectangular and elongated extraction apertures to generate the ion beam  110 , having a generally rectangular cross-section, as shown in  FIG. 1B . The aspect ratio of the extraction apertures, as well as the ion beam (X-dimension/Y-dimension) may be 2/1, 3/1, 5/1, 10/1, 50/1 or greater according to various non-limiting embodiments. Similarly, the radical beam source  106  may generate the radical beam  112  as a spot beam or as a ribbon shaped radical beam, as shown in  FIG. 1B . According to some embodiments, a substrate  122  may be scanned (along the Y-axis of the Cartesian coordinate system shown, to sequentially expose the same area of a substrate  122  to the ion beam  110  and radical beam  112 . Notably, the substrate stage  120  may be provided with rotational capability, to rotate the substrate about an axis normal to the main plane of the substrate stage (in the configuration of  FIG. 1A  the main plane is represented by the X-Y plane and the normal by the Z-axis). In the case of a spot beam system, the relative scanning may be two dimensional rather than linear, consisting of motion in the X-Y plane rather than purely along the Y axis. For example, the substrate stage  120  may be scanned within a scan plane (such as the X-Y plane) in a combination of movement in both an X-direction and Y-direction with respect to a spot shaped ion beam. The substrate stage  120  may also be scanned in a combination of movement in in both an X-direction and Y-direction with respect to a spot shaped radical bean. Moreover, an ion bean source generating a spot beam and/or a radical source generating a spot beam, may be translated with respect to a substrate stage  120  in both an X-direction and Y-direction. 
     Its various non-limiting embodiments, the ion beam source  104  may include either a noble gas, nitrogen, oxygen, hydrogen, hydrocarbons C y H x , halogen containing molecules ((C x F y , NF x , SF x , etc), or any combination of the above. In various implementations, the ion beam source  104  may be biased with respect to the substrate  122  at a given extraction potential, to generate a given ion energy to the ion beam  110 . In various embodiments, the ion beam source  104  may be rotatable to direct the ion beam  110  along a trajectory forming a given angle of incidence (θ I ) with respect to a perpendicular (Z-axis) to the main plane (X-Y) of the substrate stage  120  and substrate  122 , which plane therefore is defined by the main surface of a substrate  122 , such as a wafer surface. The value of this angle of incidence may range from zero degrees (meaning that the beam trajectory is along the Z-axis) to 85 degrees in various non-limiting embodiments. 
     In various embodiments, the radical beam  112  may include neutrals. The radicals of radical beam  112  may include reactive radicals generated from a plasma, including halogen containing molecular gases (C x F y , NF x ; SF x , etc), in addition to a mix of other gases (noble gases, oxygen, nitrogen, hydrogen, hydrocarbons C y H x , etc), depending on the processing application for radical beam source  106 . The radical beam source  106  may include an aperture so as to direct the radical beam  112  along a given angle of incidence with respect to the perpendicular (Z-axis). The value of the angle of incidence ((θ R )) for radical beam  112  may be set by the controller  150  to be the same as the angle θ I  of ion beam  110 , or different from the angle of ion beam  110 . 
     Similarly to ion beam  106 , the radical beam  112  may be elongated along the X-axis in some embodiments, as shown in  FIG. 1B . According to various embodiments of the disclosure, because the radical beam source  106  may be separately powered and separately supplied with gas from the ion beam source  104 , the ratio of radical flux to ion flux directed to the substrate  122  in a given processing operation may be independently controlled, providing a tunable process for directing radicals and ions. Generally, the radical beam  112  may include mostly reactive neutrals with some fraction of ions. For example, the input gas may be CF 4  (carbon tetrafluoride). By itself CF 4  is very inert (like inert argon or N 2 ), but when dissociated in the plasma (by the plasmas energetic electrons) the parent CF 4  will be broken up into daughter fragments such as CF 3 , CF 2 , CF, F, C. The fluorine containing daughter fragments that now have an open bond are chemically reactive and useful for a surface etching process. In addition to generating neutral CFx radicals, there will also be ionized radicals like CFx +  as well, while the overall flux is mostly neutrals in various embodiments. 
     In various embodiments, the substrate  122  may be scanned along the Y axis of the Cartesian coordinate system shown, where the main substrate surface is arranged parallel to the X-Y plane during scanning. In the illustration of  FIG. 1A , the substrate  122  scans horizontally (along the Y-axis) through a flux of ions and radicals impinging at different non-zero angles of incidence. However, the relative orientation of the radical beam  112  and ion beam  110  with respect to one another is shown merely to illustrate that the different beams may be independently controlled and may define different angles of incidence. In other embodiments, the apparatus of  FIG. 1A  may be oriented wherein the substrate  122  scans vertically, with the various components depicted in  FIG. 1A  arranged to have the same relative orientation to one another. The outputs of both the ion beam source  104  and the radical beam source  106  are accordingly directed co-linearly along the same non-zero angle with respect to a substrate scan direction (Y-axis), and are thus able to achieve an isocentric process (allowing for a spread of angles about a mean non-zero angle of incidence). 
     As noted, to generate an ion beam at a non-zero angle of incidence with respect to the Z-axis (perpendicular to substrate plane or scan plane), in one embodiment, an entire ion beam source, such as ion beam source  104 , may be tilted with respect to the scan plane (X-Z plane), as suggested in  FIG. 1A . number of electrodes). 
     Regarding the radical beam source  106 , a nozzled structure or other similar configuration may be included to provide collimation of the radical beam  112 , so that the flux of radicals from radical beam  112  may define an average angle of incidence, where the individual trajectories of radicals do not diverge substantially from one another. In other words, the angular spread about the angle of incidence θ R  may be limited to a few degrees, 10 degrees or 20 degrees in different non-limiting embodiments. 
     Thus, the system  100  provides a combination of components to increase flexibility in substrate processing with energetic species, by decoupling ion beam treatment from radical beam treatment, where the composition and geometry of radical beam and ion beam are independently controllable. This configuration facilitates new capabilities, including better control of reactive ion etching processes, reactive deposition processes, ion implantation processes, as well as more precise control of treatment of three dimensional structures in a substrate. 
       FIG. 2  presents an exemplary process flow  200 . At block  202 , a substrate is provided in a process chamber. At block  204 , an ion beam is directed to the substrate from an ion beam source. The ion beam source may be coupled to generate ions of any suitable species, and may be movable so as to adjust the angle of incidence of the ion beam with respect to the substrate. At block  206  a radical beam is directed to the substrate from a radical beam source, separate from the ion beam source. Notably, the radical beam source may be used in conjunction with the ion beam source to process the substrate, for an operation such as etching, deposition, implantation, and the like. At block  208 , the substrate is scanned with respect to the ion beam source, radical beam source, or both, while the radical beam and ion beam are directed to the substrate. For example, during the scanning of the substrate, the substrate may be scanned along a horizontal direction, such as a Y-axis, while a separation between the substrate and the radical beam source and ion beam source along a vertical direction, such as a Z-axis, remains constant. As such, the ion beam and radical beam may differ in beam composition, beam including beam angle of incidence, relative motion with respect to the substrate during processing, or a combination of the above. 
     The present embodiments provide at least the following advantages. The present embodiments allow ion and radical treatment for a substrate to be tuned separately and independently to achieve the best process. For instance, in the case where the best ion source output is achieved at a relatively lower pressure and the best radical beam treatment is achieved at a relatively higher pressure, the present embodiments enable both of these conditions to be met without compromise. The present embodiments have the further advantage of providing the ability to perform substrate processing in a common system, using very different source types, such as a RF based-radical source and hot cathode-based ion source is can be employed. A further advantage to the present embodiments is the ability to match the output of a radical beam source and ion beam source, where the radical treatment or the ion beam treatment may otherwise be rate limiting in a system lacking two independent sources. 
     While certain embodiments of the disclosure have been described herein, the disclosure is not limited thereto, as the disclosure is as broad in scope as the art will allow and the specification may be read likewise. Therefore, the above description is not to be construed as limiting. Instead, the above description is merely as exemplifications of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.