Patent Publication Number: US-2023162996-A1

Title: Etching apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of co-pending U.S. patent application Ser. No. 16/441,579, filed Jun. 14, 2019, which claims benefit of U.S. provisional patent application Ser. No. 62/687,760, filed Jun. 20, 2018. Each of the aforementioned related patent applications is herein incorporated by reference. 
    
    
     BACKGROUND 
     Field 
     Embodiments of the present disclosure generally relate to apparatus for etching a substrate. More specifically, embodiments described herein relate to methods and apparatus for electron beam reactive plasma etching. 
     Description of the Related Art 
     In the semiconductor manufacturing industry, various technological advances have enabled production of increasingly complex devices at advanced technology nodes. For example, device feature sizes have been reduced to the nanometer scale and the geometric complexity of such features has grown increasingly complex. Etching processes used to fabricate such devices are often a limiting factor in further development of advanced devices. 
     Reactive ion etching (RIE) is a conventional etching technique which utilizes ion bombardment to induce etching reactions on a substrate. With RIE it is possible to generate anisotropic etching profiles, however, certain ion energy thresholds are often necessary to induce desired etching reactions and to control the etching profile. The ion energy thresholds often reduce etch selectivity and may damage the structure being etched. 
     Electron beams are another technology commonly used in the semiconductor manufacturing industry. Electrons beams, when utilized with suitable etching gas chemistries, can induce etching on a substrate. However, conventional electron beam etching apparatus typically emit an electron beam with a cross section on the micrometer scale which is not practical for forming nanometer scale advanced devices. In addition, conventional electron beam technology is typically unsuitable for fabrication of advanced optical devices and the like which employ complex topographical features. 
     Thus, what is needed in the art are improved etching apparatus. 
     SUMMARY 
     In one embodiment, a substrate processing apparatus is provided. The apparatus includes a chamber body defining a volume, a pedestal disposed in the volume, and a ceiling coupled to the chamber body opposite the pedestal. An electrode is disposed in the volume between the pedestal and the ceiling. At least one of the electrode or the pedestal is movable to orient a surface of the electrode facing a surface of the pedestal in a non-parallel orientation. 
     In another embodiment, a substrate processing apparatus is provided. The apparatus includes a chamber body defining a volume, a ceiling coupled to the chamber body, an electrode coupled to the ceiling, and a pedestal disposed in the volume and having a surface facing a surface of the electrode. An actuator is coupled to the pedestal and configured to position a surface of the pedestal facing the surface of the electrode in a non-parallel orientation relative to the surface of the electrode. 
     In yet another embodiment, a substrate processing apparatus is provided. The apparatus includes a chamber body defining a volume, an electrode for performing electron beam reactive plasma etching disposed in the volume, and a pedestal coupled to a support shaft, the pedestal being disposed in the volume opposite the electrode. A conductive mesh is disposed in the pedestal, a plurality of shafts is coupled to either the electrode or the pedestal, and one or more ball screw actuators are coupled to the shafts. A first gas injector is coupled to the chamber body adjacent to the electrode and a second gas injector is coupled to the chamber body adjacent to the pedestal. 
    
    
     
       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 exemplary embodiments and are therefore not to be considered limiting of its scope, and may admit to other equally effective embodiments. 
         FIG.  1    schematically illustrates an electron beam reactive plasma etching (EBRPE) apparatus according to an embodiment described herein. 
         FIG.  2    schematically illustrates an EBRPE apparatus according to another embodiment described herein. 
         FIG.  3    illustrates an actuator assembly of an EBRPE apparatus according to an embodiment described herein. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments described herein relate to apparatus for performing electron beam reactive plasma etching (EBRPE). In one embodiment, an apparatus for performing EBRPE processes includes an electrode formed from a material having a high secondary electron emission coefficient. In another embodiment, an electrode is movably disposed within a process volume of a process chamber and capable of being positioned at a non-parallel angle relative to a major axis of a pedestal opposing the electrode. In another embodiment, a pedestal is movably disposed with a process volume of a process chamber and capable of being positioned at a non-parallel angle relative to a major axis of an electrode opposing the pedestal. Electrons emitted from the electrode are accelerated toward a substrate disposed on the pedestal to induce etching of the substrate. 
       FIG.  1    schematically illustrates an electron beam reactive plasma etching (EBRPE) chamber  100 . The chamber  100  has a chamber body  102  which defines a process volume  101 . In one embodiment, the chamber body  102  has a substantially cylindrical shape. In other embodiments, the chamber body  102  has a polygonal shape, such as a cubic shape or the like. The chamber body  102  is fabricated from a material suitable for maintaining a vacuum pressure environment therein, such as metallic materials, for example aluminum or stainless steel. 
     A ceiling  106  is coupled to the chamber body  102  and bounds one side of the process volume  101 . In one embodiment, the ceiling  106  is formed from an electrically conductive material, such as the materials utilized to fabricate the chamber body  102 . An electrode  108  is coupled to the ceiling  106  and disposed within the process volume  101 . A plurality of actuators  184 ,  186  couple the electrode  108  to the ceiling  106 . In one embodiment, the actuators  184 ,  186  are disposed within recesses formed on a surface  185  of the ceiling  106  which faces and is exposed to the process volume  101 . The actuators  184 ,  186 , which may be electrical, pneumatic, mechanical, and/or hydraulic in nature of actuation, are coupled by shafts  188 ,  190 , which extend from respective actuators  184 ,  186 , to the electrode  108 . In one embodiment, the actuators  184 ,  186  are stepper motors. 
     In one embodiment, the shaft  188  is disposed between the actuator  184  and the electrode  108  and movably couples the electrode  108  to the ceiling  106 . Similarly, the shaft  190  is disposed between the actuator  186  and the electrode  108  and movably couples the electrode  108  to the ceiling  106 . The actuators  184 ,  186  separately and independently control the movement of the shafts  188 ,  190  to enable positioning of the electrode  108  at various angles relative to the ceiling  106 . For example, as illustrated in  FIG.  1   , the shaft  188  extends farther than the shaft  190  from the ceiling  106  to orient the electrode  108  at a non-parallel (i.e., at an angle) relative to the ceiling  106  within the process volume  101 . In one embodiment, the shafts  188 ,  190  are lead screws or ball screws. 
     Each of the shafts  188 ,  190  is coupled to the electrode  108  by a respective joint  187 ,  189 . For example, the shaft  188  is coupled to the electrode by the joint  187  and the shaft  190  is coupled to the electrode  108  by the joint  189 . The joints  187 ,  189  are rotational type joints that allow the electrode  108  to move independently of the shafts  188 ,  190 . Examples of suitable joint types include ball and socket joints, pivot joints, hinge joints, saddle joints, universal joints, and the like. 
     In one embodiment, the electrode  108  is formed from a process-compatible material having a high secondary electron emission coefficient, such as silicon, carbon, silicon carbon materials, or silicon-oxide materials. Alternatively, the electrode  108  is formed from a metal oxide material such as aluminum oxide, yttrium oxide, or zirconium oxide. A dielectric ring  109 , which is formed from an electrically insulating material, is coupled to the chamber body  102  and surrounds the ceiling  106 , thus electrically isolating the ceiling  106  from the chamber body  102 . As illustrated, the dielectric ring  109  is disposed between the chamber body  102  and the ceiling  106  and supports the electrode  108  which extends from the ceiling  106 . In one embodiment, the dielectric ring  109  is optional if the electrode  108  is otherwise electrically isolated from the chamber body  102 . 
     A pedestal  110  is disposed in the process volume  101  below the electrode  108 . The pedestal  110  supports a substrate  111  thereon during processing and has a substrate support surface  110   a  oriented parallel to the ceiling  106 . In one embodiment, the pedestal  110  is movable in the axial direction by a lift servo  112 . The lift servo  112  may optionally rotate the pedestal  110 . During operation, the substrate support surface  110   a  is maintained at a distance of between about 1 inch and about 15 inches from the electrode  108 . In one embodiment, the pedestal  110  includes an electrostatic chuck (ESC)  142  which forms the substrate support surface  110   a . A conductive mesh  144  is disposed inside the ESC  142 , and coupled to a chucking voltage supply  148 . Power supplied to the mesh  144  generates an electrostatic force that chucks the substrate  111  to the surface  110   a . Additionally, a base layer  146  underlying the ESC  142  has internal passages  149  for circulating a thermal transfer medium (e.g., a gas and/or a liquid) from a circulation supply  145 . In one embodiment, the circulation supply  145  includes a heat sink. In another embodiment, the circulation supply  145  includes a heat source. In one embodiment, a temperature of the pedestal  110  is maintained between about −20° C. and about 1000° C. 
     A first RF power generator  122  having a frequency below the VHF range or below the HF range (e.g., in the MF or LF range, e.g., between about 100 kHz and about 60 MHz, such as about 2 MHz) is coupled to the electrode  108  through an impedance match circuit  124  via an RF feed conductor  123 . A second RF power generator  120  having a frequency in the MF or LF range may also be coupled to the electrode  108  through the impedance match circuit  124  via the RF feed conductor  123 . In one embodiment, the first RF power generator  122  has a frequency of about 2 MHZ and the second RF power generator  120  has a frequency of about 60 MHz. In one embodiment, the impedance match circuit  124  is adapted to match an impedance of a plasma formed in the process volume  101  at the different frequencies of the RF power generators  120  and  122 , as well as filtering to isolate the power generators from one another. Output power levels of the RF power generators  120 ,  122  are independently controlled by a controller  126 . As will be described in detail below, power from the RF power generators  120 ,  122  is coupled to the electrode  108 . 
     In one embodiment, the ceiling  106  is electrically conductive and is in electrical contact with the electrode  108 . Power from the impedance match circuit  124  is conducted through the ceiling  106  to the electrode  108 , for example, through the shafts  188 ,  190  or other conductor. In one embodiment, the chamber body  102  is maintained at ground potential. In one embodiment, grounded internal surfaces (i.e. chamber body  102 ) inside the chamber  100  are coated with a process compatible material such as silicon, carbon, silicon carbon materials, or silicon-oxide materials. In an alternative embodiment, grounded internal surfaces inside the chamber  100  are coated with a material such as aluminum oxide, yttrium oxide, or zirconium oxide. 
     With the two RF power generators  120 ,  122 , radial plasma uniformity in the process volume  101  can be controlled by selecting a distance between the electrode  108  and pedestal  110 . In this embodiment, the RF power generators  120 ,  122  produces an edge-high radial distribution of plasma ion density in the process volume  101  and a center-high radial distribution of plasma ion density. With such a selection, the power levels of the two RF power generators  120 ,  122  are capable of generating a plasma with a substantially uniform radial plasma ion density. 
     As shown, a cable passage  192  is formed at least partially through the electrode  108  and normal to a bottom surface  199  of the electrode  108 . The RF feed conductor  123  and other cables or conductors are disposed through the cable passage  192 . A cable insulator  170  in the cable passage  192  if configured to prevent capacitive coupling of the RF feed conductor  123  to a cooling plate  175 . In one embodiment, the cable insulator  170  is fabricated from a dielectric material. The cooling plate  175  includes a material suitable for transferring thermal energy, such as metallic materials, for example aluminum or stainless steel. 
     In one embodiment, the electrode  108  includes an electrode plate  150 . A D.C. blocking capacitor  156  is connected in series with the output of the impedance match circuit  124 . In one embodiment, the RF feed conductor  123  is directly coupled to the electrode plate  150  through the ceiling  106  and the cable passage  192 . In this embodiment, a portion of the RF feed conductor  123  which is disposed in the process volume  101  is flexible in nature to accommodate movement of the electrode  108 . In one embodiment, the RF feed conductor  123  from the impedance match circuit  124  is connected to the ceiling  106  rather than being directly connected to the electrode  108 . In such an embodiment, RF power from the RF feed conductor  123  is capacitively coupled from the ceiling  106  to the electrode  108 . 
     In one embodiment, the electrode  108  includes an insulating plate  174  formed from an electrically insulating material and coupled to an insulator pipe  176 . The insulator pipe  176  may be formed of the same or similar material as the insulating plate  174 . The insulating plate  174  and the insulator pipe  176  electrically isolate and prevent capacitive coupling between the electrode plate  150  and the ceiling  106 . 
     In one embodiment, the electrode  108  includes a silicon plate  158  disposed on the electrode plate  150 . The silicon plate  158  is positioned by and held adjacent to the electrode plate  150  via an insulator clamp  172 . The insulator clamp  172  is fabricated from an electrically insulating material, such as quartz or aluminum oxide. The silicon plate  158  functions to protect a surface  199  of the silicon plate  158  from corrosive species which are generated in the process volume  101  during processing of the substrate  111  or cleaning of the chamber body  102 . 
     In one embodiment, internal passages  178  for conducting a thermally conductive liquid and/or gas inside the cooling plate  175  are connected to a thermal media circulation supply  180 . The thermal media circulation supply  180  may also function as a heat sink or a heat source. In one embodiment, the electrode  108  is encased, at least partially, in a protective member  182 . The protective member  182  surrounds the electrode  108  such that the surface  199  of the silicon plate  158  is exposed within the process volume  101  and other surfaces of the electrode  108  are covered by the protective member  182 . In one embodiment, the protective member  182  is formed from an electrically insulating material, such as quartz or polytetrafluoroethylene. In one embodiment, a grounding material, such as aluminum or the like, is disposed on the protective member  182  when the protective member  182  is formed from an electrically insulating material. In another embodiment, the protective member  182  is fabricated from a metallic material, such as aluminum or stainless steel. The protective member  182  functions to protect various surfaces of the electrode  108  from corrosive species which are generated in the process volume  101  during processing of the substrate  111  or cleaning of the chamber body  102 . In the illustrated embodiment, the joints  187 ,  189  are coupled to the protective member  182 , however, it is contemplated that the joints  187 ,  189  may be coupled to other regions of the electrode  108  depending upon the desired implementation. 
     In one embodiment, upper gas injectors  130  provide process gas into the process volume  101  through a first valve  132 . Lower gas injectors  134  provide process gas into the process volume  101  through a second valve  136 . The upper gas injectors  130  and the lower gas injectors  134  are disposed in sidewalls of the chamber body  102 . Gas is supplied from a plurality of process gas supplies  138  through a plurality of valves  140  which may include the first and second valves  132  and  136 . In one embodiment, the selection of gas species and the rates at which gas is delivered into the process volume  101  are independently controllable. For example, the type and/or rate of gas flowing through the upper gas injectors  130  may be different from the type and/or rate of gas flowing through the lower gas injectors  134 . The controller  126  controls the state of the valves  140 . 
     In one embodiment, an inert gas, such as argon or helium, is supplied into the process volume  101  through the upper gas injectors  130  and a process gas is supplied into the process volume  101  through the lower gas injectors  134 . In this embodiment, the inert gas delivered to the process volume  101  adjacent the electrode  108  functions to buffer the electrode  108  from a reactive plasma formed in the process volume  101 , thus increasing the useful life of the electrode  108 . In another embodiment, process gas is supplied to the process volume  101  through both the upper gas injectors  130  and the lower gas injectors  134 . 
     In one embodiment, plasma is generated in the process volume  101  by various bulk and surface processes, for example, by capacitive coupling. In one embodiment, plasma generation is also facilitated by energetic ion bombardment of the surface  199  of the top electron-emitting electrode  108 . In one example, the electrode  108  is biased with a substantially negative charge, such as by application of voltage form the voltage supply  154 . In one embodiment, bias power applied to the electrode  108  is between about 1 KW and about 10 KW with a frequency of between about 400 kHz and about 200 MHz. It is believed that ions generated by a capacitively coupled plasma are influenced by an electric field that encourages bombardment of the electrode  108  by the ions generated from the plasma. 
     The ion bombardment energy of the electrode  108  and the plasma density are functions of both RF power generators  120  and  122 . The ion bombardment energy of the electrode  108  is substantially controlled by the lower frequency power from the RF power generator  122  and the plasma density in the process volume  101  is substantially controlled (enhanced) by the VHF power from the RF power generator  120 . It is believed that ion bombardment of the electrode  108  heats the electrode  108  and causes the electrode  108  to emit secondary electrons. Energetic secondary electrons, which have a negative charge, are emitted from the surface  199  of the electrode  108  and accelerated away from the electrode  108  due to the negative bias of the electrode  108 . 
     The flux of energetic electrons from the surface  199  of the electrode  108  is believed to be an electron beam, and may be oriented substantially perpendicular to the interior surface of the electrode  108 . A beam energy of the electron beam is approximately equal to the ion bombardment energy of the electrode  108 , which typically can range from about 10 eV to 5000 eV. In one embodiment, the plasma potential is greater than the potential of the electrode  108  and the energetic secondary electrons emitted from the electrode  108  are further accelerated by a sheath voltage of the plasma as the secondary electrons traverse through the plasma. 
     At least a portion of the electron beam, comprised of the secondary electron flux emitted from electrode  108  due to energetic ion bombardment of the electrode surface  199 , propagates through the process volume  101  and reacts with process gases near the substrate  111 . With utilization of suitable process gases, such as chlorine containing materials, fluorine containing materials, bromine containing materials, oxygen containing materials, and the like, the electron beam induces etching reactions on the substrate  111 . It is believed that the electron beams, in addition to the capacitively generated plasma, generate chemically reactive radicals and ions which adsorb to the surface of the substrate and form a chemically reactive polymer layer on the surface of the substrate  111 . 
     In one embodiment, an RF bias power generator  162  is coupled through an impedance match  164  to the conductive mesh  144  or other electrode of the pedestal  110 . In a further embodiment, a waveform tailoring processor  147  may be connected between the output of the impedance match  164  and the conductive mesh  144 . The waveform tailoring processor  147  changes the waveform produced by the RF bias power generator  162  to a desired waveform. The ion energy of plasma near the substrate  111  is controlled by the waveform tailoring processor  147 . In one embodiment, the waveform tailoring processor  147  produces a waveform in which the amplitude is held during a certain portion of each RF cycle at a level corresponding to a desired ion energy level. The controller  126  controls the waveform tailoring processor  147 . 
     Accordingly, the electron beam induces chemical reactions to liberate gas phase volatile products and etch the substrate  111 . Etching of the substrate  111  is also influenced by other factors, such as pressure. In one embodiment, a vacuum maintained in the process volume  101  during electron beam etching of the substrate  111  is between about 0.1 Torr and about 10 Torr. The vacuum is generated by a vacuum pump  168  which is in fluid communication with the process volume  101 . The pressure within the process volume  101  is regulated by a throttle valve  166  which is disposed between the process volume  101  and the vacuum pump  168 . 
     Other factors which influence etching characteristics of the substrate  111  include the angle ⊖ at which the surface  199  of the electrode  108  is disposed relative to the substantially horizontal orientation of the surface  110   a  of pedestal  110  and the substrate  111  disposed thereon. In one embodiment, the angle ⊖ is between about 1° and about 45°, such as between about 5° and about 30°, for example, between about 10° and about 20°. As a result of the tilting of the electrode  108  to an orientation that is non-parallel to the ceiling  106  and surface  110   a  of the pedestal  110 , secondary electrons contact the substrate  111  at substantially non-perpendicular angles which enable the substrate  111  to be etched with slanted features. Slanted etching is believed to enable advanced feature formation and can advantageously be implemented in the formation of various optical devices and the like. 
       FIG.  2    schematically illustrates another embodiment of the EBRPE apparatus  100 . In the illustrated embodiment, the electrode  108  and the ceiling  106  are maintained in a parallel and substantially horizontal position. The support surface  110   a  of the pedestal  110  is capable of being positioned in a non-horizontal orientation relative to a substantially horizontal orientation of the electrode  108 . In other words, the pedestal  110  is movable such that the surface  110   a  of the pedestal  110  can be positioned in a non-parallel orientation relative to the surface  199  of the electrode  108 . Aspects of the embodiment illustrated in  FIG.  2    which are common to the embodiment of  FIG.  1    are described above. 
     The ceiling  106  is coupled to and supports the electrode  108  within the process volume  101 . In one embodiment, the electrode  108  is coupled by mechanical clamping to the ceiling  106  such that the surface  199  of the electrode  108  is exposed to the process volume  101  and faces the support surface  110   a  of the pedestal  110 . In this embodiment, the ceiling  106  is a support for the electrode  108  which includes an insulating layer  150  containing a conductive mesh  152  facing the surface  199 . A D.C. blocking capacitor  156  is connected in series with the output of the impedance match circuit  124 . In one embodiment, the RF feed conductor  123  form the impedance match circuit is connected to the conductive mesh  152 . In another embodiment, the RF feed conductor  123  from the impedance match circuit  124  is connected to the electrode support or ceiling  106  rather than being directly connected to the electrode  108 . In such an embodiment, RF power from the RF feed conductor  123  is capacitively coupled from the electrode support to the electrode  108 . 
     In one embodiment, internal passages  178  for conducting a thermally conductive liquid and/or gas inside the ceiling  106  are connected to a thermal media circulation supply  180 . The thermal media circulation supply  180  acts as a heat sink or a heat source. The mechanical contact between the electrode  108  and the ceiling  106  is sufficient to maintain high thermal conductance between the electrode  108  and the ceiling  106 . 
     The pedestal  110  is coupled to a support shaft  212  by a joint  210 . The joint  210  rotatably couples the pedestal to the support shaft  212  to enable movement of the pedestal  110  between one or more angles G. The joint  210  is disposed between the base layer  146  of the pedestal  110  and a topmost portion of the support shaft  212 . Examples of suitable joint types for the joint  210  include ball and socket joints, pivot joints, hinge joints, saddle joints, universal joints, and the like. A topmost portion of the support shaft  212  has a tapered surface  214 . The tapered surface  214  extends from the joint  210  with an increasing radius down the support shaft  212 . As such, a radius of the support shaft  212  at the joint  210  is less than the radius of the support shaft  212  elsewhere along a length of the support shaft  212 . Thus, the tapered surface  214  enables the pedestal  110  to be positioned at various angle magnitudes without interference from the support shaft  212 . It is also contemplated that conduits extending from one or more of the voltage supply  148 , the impedance match  164 , and the circulation supply  145  extend through the support shaft  212  and the joint  210  to the pedestal  110 . 
     In one embodiment, a plurality of actuators  202 ,  204  are coupled to the chamber body  102  in the process volume  101 . In another embodiment, the plurality of actuators  202 ,  204  are disposed outside of the process volume  101 . The actuators  202 ,  204  which may be electrical, pneumatic, mechanical, and/or hydraulic in nature of actuation, are coupled to shafts  206 ,  208  which extend from respective actuators  202 ,  204  to the pedestal  110 . In one embodiment, the actuators  202 ,  204  are linear motors or stepper motors. In one embodiment, the shafts  206 ,  208  are leads screws or ball screws. In embodiments where the actuators  202 ,  204  are disposed outside of the process volume  101 , the shafts  206 ,  208  are configured to extend from the actuators  202 ,  204  through the chamber body  102  to the pedestal  110 . In this embodiment, sealing apparatus may be disposed at regions of the chamber body  102  where the shafts  206 ,  208  extend through the chamber body  102 . 
     In one embodiment, the shaft  206  is disposed between the actuator  202  and the pedestal  110  and movably actuates the pedestal  110  about the support shaft  212 . Similarly, the shaft  208  is disposed between the actuator  204  and the pedestal and movably actuates the pedestal  110  about the support shaft  212 . The shafts  206 ,  208  may be telescopic to enable different magnitudes of travel to facilitate an angled positioning of the pedestal. For example, as illustrated in  FIG.  2   , the shaft  206  is extended to a greater degree than the shaft  208  to orient the surface  110   a  of the pedestal  110  at a non-zero angle relative to the surface  199  of the electrode  108  within the process volume  101 . 
     Each of the shafts  206 ,  208  is coupled to the pedestal  110  by a respective joint  218 ,  216 . For example, the shaft  206  is coupled to the pedestal  110  by the joint  218  and the shaft  208  is coupled to the pedestal  110  by the joint  216 . The joints  216 ,  218  are rotational type joints that allow the pedestal  110  to move independently of the shafts  206 ,  208 . Examples of suitable joint types for the joints  216 ,  218  include ball and socket joints, pivot joints, hinge joints, saddle joints, universal joints, and the like. 
     The ability to angle the surface  110   a  of the pedestal  110  with respect to the surface  199  of the electrode  108  provides for the ability to perform slanted etching on the substrate  111 . The angle ⊖ at which the surface  110   a  of the pedestal  110  is disposed relative to the substantially horizontal orientation of the surface  199  of the electrode  108  influences etching characteristics of the substrate  111 , among other factors. In one embodiment, the angle ⊖ is between about 1° and about 45°, such as between about 5° and about 30°, for example, between about 10° and about 20°. As a result of the angled disposition of the pedestal  110 , secondary electrons contact the substrate  111  at substantially non-perpendicular angles which enable the substrate  111  to be etched with slanted features. Slanted etching is believed to enable advanced feature formation and can advantageously be implemented in the formation of various optical devices and the like. 
     In operation, the pedestal  110  is positioned in a substantially horizontal orientation during placement of the substrate  111  on the pedestal  110 . After the substrate  111  is secured to the pedestal  110 , the surface  110   a  of the pedestal  110  is tilted to the desired angle ⊖ by extension of the shafts  206 ,  208  by the actuators  202 ,  204 . An EBRPE process is performed while the pedestal  110  is in the tilted orientation and the pedestal  110  is returned to a substantially horizontal orientation after EBRPE processing has stopped. 
       FIG.  3    illustrates an actuator assembly  316  of the EBRPE apparatus  100  according to an embodiment described herein. The actuator assembly  316  is configured to extend or retract either of the shafts  188 ,  190  into the process volume  101 . The actuator assembly  316  includes a shaft  304 , a link  310 , and a motor  308 . The motor  308  is disposed on a motor base plate  318  and supported by the link  310 . A power supply  320  supplies electrical power to the motor  318 . 
     A brace  302  is coupled to the chamber body  102  and supports the actuator assembly  316 . A first end of the shaft  304  is coupled to the brace  302  via a connector  306 . A second end of the shaft  304  opposite the first end is coupled to the chamber body  102  via the connector  306 . The link  310  is moveably coupled to the shaft  304 . For example, the shaft  304  and link  310  may comprise a ball screw and ball nut, respectively. 
     The link  310  is configured to transfer linear or rotational energy from the motor  308  to the shaft  304 . In one embodiment, the shaft  304  is stationary and the motor  308  is configured to move the link  310  along the shaft  304 . In another embodiment, the motor  308  may be disposed on the brace  302  and configured to move the shaft  304  with a link  310  that is fixably coupled to the motor base plate  318 . 
     The actuator assembly  316  is fluidly sealed from the process volume  101  by bellows  312  and an seal  314 . The shaft  190  moveably couples the electrode  108  to the motor base plate  318 .  FIG.  3    depicts a portion of the chamber body  102  and the electrode  108 . While a single actuator assembly  316  is shown in  FIG.  3   , it is contemplated that one or more additional actuator assemblies may couple the electrode  108  to the chamber body  102 . 
     By utilizing electron beams generated in accordance with the embodiments described above, reactive species which are not readily obtained with conventional etching processes may be generated. For example, reactive species with high ionization and/or excitation/dissociation energies may be obtained with the EBRPE methods and apparatus described herein. It is also believed that the EBRPE methods described herein provide for etching rates equivalent to or greater than conventional etching processes, but with improved material selectivity. 
     For example, EBRPE methods are believed to provide improved etch selectivity due to the separation of threshold electron beam energies used to induce etching reactions. For example, with certain polymerizing gas chemistries, the threshold energy utilized to etch silicon oxide materials is much greater than the threshold energy utilized to etch silicon. As a result, it is possible to achieve etch selectivities of about 5:1 or greater. In one embodiment, EBRPE is believed to enable about 5:1 silicon:silicon oxide etch selectivity. In another embodiment, EBRPE is believed to enable about 5:1 tungsten:silicon nitride etch selectivity. 
     The kinetic energy of electrons is also much less than that of ions. As a result, substrate damage is reduced because the potential for sputtering is reduced. Moreover, by controlling the electron beam energy, such as by application of RF power to the electrode, EBRPE is believed to provide a “softer” etch than conventional etching processes. With improved control, EBRPE is able to produce tapered etch profiles, such as etching profiles utilized in certain shallow trench isolation applications. Moreover, by enabling slant etching by either tilt positioning of the electrode or the pedestal, advanced etching profiles and operations may be performed. 
     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, and the scope thereof is determined by the claims that follow.