Patent Publication Number: US-2009221149-A1

Title: Multiple port gas injection system utilized in a semiconductor processing system

Description:
BACKGROUND 
     1. Field of the Invention 
     Embodiments of the present invention generally relate to semiconductor processing systems. More specifically, embodiments of the invention relates to an apparatus having multiple port gas injection system in a semiconductor processing system. 
     2. Description of the Related Art 
     Reliably producing sub-half micron and smaller features is one of the key technologies for the next generation of very large scale integration (VLSI) and ultra large-scale integration (ULSI) of semiconductor devices. However, as the limits of circuit technology are pushed, the shrinking dimensions of interconnects in VLSI and ULSI technology have placed additional demands on processing capabilities. Reliable formation of device structures is important to VLSI and ULSI success and to the continued effort to increase circuit density and quality of individual substrates and die. 
     Etching is one of many processes used for fabricating device structures. One problem associated with a conventional etch process is the non-uniformity of etch rate across the substrate due to a substrate edge effect. For example, ion plasma distribution across the substrate during processing are typically asymmetrical, resulting in a center-high edge-low or a center-low edge-high etch rate distribution across the substrate. Non-uniformity of etch rate may result in features formed on the substrate having different profiles and dimensions across the substrate surface. Furthermore, lateral etch rate non-uniformity also results in non-uniform critical dimensions of the structures formed by the etch process. Herein lateral etch rate non-uniformity is defined as a ratio of a difference between the maximal and minimal lateral etch rate to the sum of such values across the substrate. In many etch processes, the lateral etch rate at peripheral locations (i.e., near an edge of the substrate) is higher than the etch rate near a center of the substrate. 
     During the etch process, non-volatile by-products may passivate the sidewalls of the structures being formed and, as such, reduce the etch rate. or cause growth of critical dimensions during etching. Non-uniformity of the passivation rate across the substrate maybe caused by a higher concentration of etch by-products near the center of the substrate as compared to the peripheral region. In operation, a generally concentric pattern of exhaust pumping in the etch process chamber results in low concentration of the by-products near the edge of the substrate and, correspondingly, in a high local lateral etch rate as compared to the center of the substrate. 
     As such, structures being formed using conventional etch processes are typically over-etched in the peripheral region as compared to the central region of the substrate and experience less growth or even loss of critical dimensions. A loss of accuracy for topographic dimensions (e.g., critical dimensions (CDs), or smallest widths) of the etched structures in the center or peripheral regions of the substrates may significantly affect performance and increase costs of fabricating the integrated circuits and micro-electronic devices. 
     Therefore, there is a need for improving etching rate uniformity across a substrate. 
     SUMMARY 
     Embodiments of the invention include an apparatus having a multiple gas injection port system for providing a high uniform etching rate across the substrate. In one embodiment, an apparatus includes a gas nozzle for a semiconductor processing chamber. The nozzle has a hollow cylindrical body having a first outer diameter defining a hollow cylindrical sleeve and a second outer diameter defining a tip. A longitudinal passage is formed through the hollow cylindrical sleeve and at least partially extending to the tip of the body. A lateral passage breaks through the tip to the longitudinal passage. The lateral passage extends outward from the longitudinal passage to an opening formed on an outer surface of the tip. 
     In another embodiment, a semiconductor processing system includes a processing chamber having a chamber wall and a chamber lid defining a process volume, an annular ring having a plurality of injection ports formed therein positioned above the chamber wall and below the chamber lid, a plurality of nozzles each inserted within the plurality of injection ports configured to inject processing gas to the process volume, wherein the nozzles have an opening angled downwardly relative to a center line of the nozzle configured to inject processing gas to a predetermined position of the process volume. 
     In yet another embodiment, a method of etching a substrate disposed in a processing chamber includes providing a substrate into a processing chamber, supplying a reacting gas to a center region of the substrate surface though first group of injection ports disposed in a center region of the processing chamber, and supplying a passivation gas to a periphery region of the substrate surface through a second group of injection ports, wherein respective one of the second group of injection ports has a respective nozzle disposed therein, the nozzle having an opening oriented downwardly to direct passivation gas to the substrate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. 
         FIG. 1  is a schematic cross sectional diagram of an exemplary semiconductor substrate processing apparatus comprising a multiple port gas injection system in accordance with one embodiment of the invention; 
         FIGS. 2A-2C  are a schematic top and cross sectional view of one embodiment of an annular ring having multiple gas passages formed therein; 
         FIG. 3A-B  are cross sectional views of different embodiments of a nozzle that may be used in the multiple port gas injection system of  FIG. 1 ; 
         FIG. 4  is a top view of a multiple port gas injection system; and 
         FIG. 5  is a perspective drawing of an exemplary semiconductor substrate processing apparatus having one embodiment of a multiple port gas injection system. 
     
    
    
     It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. 
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. 
     DETAILED DESCRIPTION 
     Embodiments of the present invention include an apparatus having a multiple injection port system for etching topographic structures in material layers on a substrate with high etching rate uniformity. In one embodiment, the multiple gas injection port may supply different gases, such as a passivation gas and a reacting gas, individually and respectively at center and edge of the processing chamber to a substrate surface, thereby efficiently adjusting etch rate distribution across the substrate surface. The apparatus is generally used during etching of semiconductor devices, circuits and the like. Although invention is illustratively described in a semiconductor substrate etching apparatus, such as, a DPS® etch reactor, available from Applied Materials, Inc. of Santa Clara, Calif., the invention may be utilized in other processing systems, including etch, deposition, implant and thermal processing, or in other application where high gas distribution uniformity across a substrate and/or a processing chamber is desired. 
       FIG. 1  depicts a schematic diagram of an exemplary processing chamber  100  having a multiple port gas injection system  110  that may illustratively be used to practice the invention. The particular embodiment of the processing chamber  100  shown herein is an etch reactor and is provided for illustrative purposes and should not be used to limit the scope of the invention. 
     A controller  140  including a central processing unit (CPU)  144 , a memory  142 , and support circuits  146  is coupled to the processing chamber  100 . The controller  140  controls components of the processing chamber  100 , processes performed in the processing chamber  100 , as well as may facilitate an optional data exchange with databases of an integrated circuit fab. 
     The processing chamber  100  generally includes a conductive body (wall)  130  and a removable lid  120  that enclose a process volume  122 . The removable lid  120  has a bottom surface that forms as a ceiling  128  of the processing chamber  100 . In the depicted embodiment, the removable lid  120  is a substantially flat dielectric member. Other embodiments of the processing chamber  100  may have other types of lids, e.g., a dome-shaped ceiling. Above the removable lid  120  is disposed an antenna  112  comprising one or more inductive coil elements (two co-axial coil elements  112 A and  122 B are illustratively shown). The antenna  112  is coupled, through a first matching network  170 , to a radio-frequency (RF) plasma power source  118 . A pumping system  135  is coupled to the processing chamber  100  to facilitate evacuation and maintenance of process pressure. A substrate support assembly  116  is disposed in a bottom portion of the processing chamber  100  readily to receive a substrate  150  disposed thereon. The multiple port gas injection system  110  is disposed on a top portion of the processing chamber  100  adjacent to the ceiling  128  facing an upper surface of the substrate support assembly  116 . The multiple port gas injection system  110  is coupled to a gas panel  138  utilized to supply process gasses to the process volume  122  of the chamber  100 . 
     In one embodiment, the multiple port gas injection system  110  has a plurality of injection ports  190 ,  196  configured to supply processing gas to the process volume  122 . A first group of the injection ports  190  is formed in an annular ring  192  disposed around top portion of the sidewall  130  and below the ceiling  128 . The annular ring  192  interfaces with and partially occludes an edge shoulder step  172  of the removable lid  120 . The injection ports  190  of the first group are evenly spaced about an interior surface of the annular ring  192  to facilitate supplying processing gas from gas panel  138  through a gas manifold  198  to the process volume  122 . Details of the annular ring  192  and the first group of injection ports  190  will be further discussed below with referenced to  FIGS. 2A-C . 
     A second group of injection ports  196  is disposed in the ceiling  128  below the removable lid  120 . The second group of injection ports  196  is coupled to the gas panel  138  through a gas supply line  194 . The gas supply line  194  may be disposed externally to the processing chamber  100  coupling the injection ports  196  to the gas panel  138 . Alternatively, the gas supply line  194  may be embedded within the removable lid  120 , as will be further discussed with referenced to  FIG. 5 . In one embodiment, the second group of injection ports  196  may be disposed in a center region of the ceiling  128  having one or more center injection ports injecting processing gas to a center portion/zone of the process volume  122 . In another embodiment, the second group of the injection ports  196  may be covered in a showerhead (not shown) attached to the ceiling  128  of the removable lid  120 . The showerhead may have one or more concentric zones. Each zone feeds by processing gases provided by one or more of the ports  196 . It is contemplated that different numbers, dimensions, profiles, and distributions of the ports  196  may be utilized to distribute different amount of processing gas into the process volume  122  across the substrate  150 . In the embodiment depicted in  FIG. 1 , the second group of injection ports  196  is formed in a center region/zone of the ceiling  128 . In one embodiment, the ports  196  include at least one port  196   c  facing downward and a plurality of ports  196   r  facing radially outward so that the ratio of processing gases flow toward the center and edge of the substrate  100  may be controlled. Optionally, the rates and/or types of the gases provided to each port  196   c ,  196   r  may be independently controlled. 
       FIG. 2A  is a schematic top and partial cross sectional view of the annular ring  192  of  FIG. 1  having the first group of injection ports  190  formed therein. An outer gas supply line  210  is coupled to the ring  192  to supply processing gas from the gas panel  138  to the injection ports  190 . The annular ring  192  has an inner surface  208  and an outer surface  220  defining an inner and an outer diameter of the ring  192 . An interior shoulder  202  formed in an upper portion of the inner surface  208  to receive the edge shoulder step  172  of the removable lid  120  so that the lid  120  rests on the annular ring  192 , as shown in  FIG. 1 . An exterior shoulder  204  is formed in a lower portion of the outer surface  220  and is configured to engage the chamber sidewall  130 . The annular ring  192  is sized and shaped to mate with the edge shoulder  172  of the removable lid  120  and the chamber sidewall  130  when installed in the processing chamber  100 . In one embodiment, the annular ring  192  may be fabricated from process compatible materials, such as ceramic, metal or other suitable material. Examples materials suitable for fabricating the annular ring  192  include anodized materials, such as Al 2 O 3  or anodized Al, yttrium containing material, such as Y 2 O 3 , or ceramic, such as Al 2 O 3  or silicon carbide, metallic materials and the like. 
     In one embodiment, a plurality of injection ports  190  are evenly spaced around the annular ring  192 . The number and locations of injection port  190  may be selected to provide a desired gas distribution. In the embodiment depicted therein, twelve injection ports are formed in the annular ring  192 . 
     Each injection port  190  has a radial cylindrical passage  206   a  configured to accept a nozzle  250 . The passage  206   a  may be machined or otherwise formed in within the annular ring  192 . The radial cylindrical passage  206   a  is sized to securely receive the nozzle  250 . 
     In one embodiment, the nozzle  250  includes a hollow cylindrical sleeve  254  and a tip  252 . The sleeve  254  comprises the main body of the nozzle  250  sized to fit within the passage  206   a . The tip  252  of the nozzle  250  extends from the sleeve  254  and projects radially inward from the inner surface  208  of the ring  192  into the volume  122  of the processing chamber  100 . The nozzle  250  is configured to be readily removable from the radial cylindrical passage  206   a  to facilitate ease of replacement. In one embodiment, the nozzle is fabricated from process compatible materials, such as ceramic or metal material. Examples suitable nozzle materials include, but not limited to, anodized materials, such as Al 2 O 3  or anodized Al, yttrium containing material, such as Y 2 O 3 , or other similar ceramic, such as Al 2 O 3  or silicon carbide, or other metallic materials. 
     In one embodiment, the radial cylindrical passage  206   a  may be formed substantially horizontal relative to a substrate surface disposed in the processing chamber  100  to receive the nozzle  250  in a substantially horizontal orientation. Upon supplying processing gases, the nozzle  250  injects the processing gas inward to a desired position of the substrate surface. Furthermore, the position of each nozzle  250  and/or the injection angle of each nozzle  250  relative to the substrate surface may be individually arranged so as to inject gas flow to a desired region or the substrate surface. For example, the radial cylindrical passage  206   a  formed in the annular ring  192  may have an injection angle below a horizontal plane. In the embodiment of a radial cylindrical passage  206   b  depicted in  FIG. 2B , the radical cylindrical passage  206   b  may be formed in the ring  192  at an angle downward relative to a horizontal plane to facilitate accurate injection of gases to a targeted region on the substrate surface. The injection angle and position of the nozzles  250  from which processing gases are directed to the substrate surface provide good control over lateral etching profile across the substrate. 
       FIG. 2C  depicts different trajectories  280 ,  282 ,  284  for the processing gases injected from the nozzles  250  disposed in radial cylindrical passages  206   c ,  206   b  and  206   a . Different angles of the processing gas trajectories  280 ,  282 ,  284  from nozzles  250  to the substrate surface result in different radial distances r 1 , r 2 , r 3  from the centerline of the substrate  150 . Accordingly, by selection of the angle which directs the processing gases to the substrate surface, different distribution profile of processing gases may be obtained across the substrate surface. As the gas flow distribution profile may be adjusted, the uniformity of the center-edge gas flow across the substrate surface may be efficiently improved, thereby assisting in controlling the etch results (e.g., etch rate, feature profile, microloading effect) across the substrate in an uniform manner and maintaining a desired topographic dimension of features formed on the substrate  150 . 
       FIG. 3A  depicts a cross sectional view of one embodiment of nozzle  250 . The nozzle  250  includes a hollow cylindrical body. The body has the hollow cylindrical sleeve  254  and the tip  252 . The tip  252  extends from the hollow cylindrical sleeve  254 . The hollow cylindrical sleeve  254  has a first outer diameter  304  and the tip  252  has a second outer diameter  308 . The second outer diameter  308  is smaller than the first outer diameter  304 , thereby defining the tip  252 . In one embodiment, the first outer diameter  304  is about 50 percent greater than the second outer diameter  308 . In one embodiment, the first outer diameter  304  is between about 15.5 mm and about 16 mm and the second outer diameter  308  is between about 7.0 mm and about 7.5 mm. 
     A face  362  is formed on the exterior of the nozzle  250  between the tip  252  and the sleeve  254 . The face  362  may be perpendicular to a central axis of the nozzle  250 . In one embodiment, an o-ring gland  260  (shown in phantom) may be formed in the face  362  to accommodate the o-ring which may be utilized to prevent leakage between the nozzle  250  and the ring  192 . 
     The nozzle  250  includes a longitudinal passage formed within hollow cylindrical sleeve  254  and the tip  252 . The longitudinal passage includes a first passage  302  and a second passage  306 . The first passage  302  originates from a first end  312  of the nozzle  250  and extends through the body of the hollow cylindrical sleeve  254 . The first passage  302  further extends at least partially into the tip  252 , connecting to the second passage  306 . The second passage  306  coaxially aligned with the first passage  304  and extends longitudinally from the end of the first passage  304  to an second end  314  of the tip  252  of the nozzle  250 . Upon supplying a processing gas, the processing gas is delivered from the first passage  302  to the second passage  306  and injected through the second passage  306  to the substrate surface. 
     In one embodiment, the first passage  302  has a first inner diameter  306  and the second passage  306  has a second inner diameter  318  that smaller than the first inner diameter  316 . The first inner diameter  316  in the first passage  302  may transition sharply into the second inner diameter  318  in the second passage  306 , for example, at about a 90 degree interface. In one embodiment, the second inner diameter  318  is about four times smaller than the first inner diameter  316 . In one embodiment, the first inner diameter  316  is between about 3.0 mm and about 3.5 mm and the second inner diameter  318  is between about 0.5 mm and about 1 mm. 
       FIG. 3B  depicts another embodiment of a nozzle  258  that may be utilized with the ring  192  of  FIGS. 2A-B . The nozzle  258  has a longitudinal passage  330  having a uniform inner diameter  332  formed through the hollow cylindrical sleeve  254  and extending at least partially to the tip  252 . The longitudinal passage  330  may be coaxial or parallel to a centerline of the nozzle  258 . The longitudinal passage  330  is held in an orientation substantially in a horizontal plane parallel to the substrate surface by the ring  192 . A lateral passage  320  is formed at the tip portion  252  of the nozzle  258  and connected to the longitudinal passage  330 . The lateral passage  320  extends outward from the longitudinal passage  330  to an opening  332  formed on an outer surface  334  of the tip  252 . In one embodiment, the opening  332  has a width between about 0.5 mm and about 1.0 mm. 
     In one embodiment, the lateral passage  320  forms an acute angle with the longitudinal passage  330 . The injection angle may be formed substantially from about 15 degree to about 90 degree relative to the longitudinal passage  330 . The injection angles defined by the lateral passage  320  relative to the longitudinal passage  330  sets the trajectory  322  of the processing gas injected to the substrate surface. Accordingly, by selection of the angle formed by lateral passage  320  relative to the substrate surface, locations where the processing gases is delivered to the substrate surface may be efficiently controlled as desired, thereby providing a desired gas distribution profile formed across the substrate surface. As the gas flow distribution profile may be set by using a nozzle  258  with a desired orientation of the lateral passage  320 , the center-to-edge gas flow uniformity across the substrate surface may be efficiently improved, thereby facilitating control of the etching results. Thus the substrate may be etched in an uniform manner while maintaining a desired topographic dimension of features formed on the substrate  150 . In the embodiment where this particular type of nozzle  258  is used, the radial cylindrical passage  206   a  of the ring  192  may be formed in a substantially perpendicular orientation relative to a centerline of the ring  192 , so that the opening  322  of the lateral passage  320  formed in the nozzle  258  is pointed downward at a desired angle relative to the substrate surface. 
     Therefore, not only by controlling the injection angle of the radial cylindrical passage  206   a ,  206   b  formed in the annular ring  192  as shown in  FIGS. 2A-C , the designs of the nozzles  250 ,  258  may be selected to adjust the injection angle of the processing gas to the substrate surface. By adjusting the angle of the radial cylindrical passage  206   a ,  206   b  formed in the annular ring  192  and/or lateral passage  320  formed in the nozzle  258 , the gas flow distribution profile across the substrate surface may be efficiently controlled to achieve desired etching profile on the substrate. 
       FIG. 4  depicts a top view of the multiple port gas injection system  110  utilized to control the gas injection through the first group of gas injection ports  190 . The first group of gas injection ports  190  are disposed in a polar array about the annular ring  192 . The injection ports  190  are connected to respective valves  350 . In one embodiment, the open state of each valve  350  is independently controlled. The valve  350  may be pneumatically controlled as shown in  FIG. 4 . The valve  350  includes an input flow-through port  350   a , an output flow-through port  350   b , a controlled gas outlet port  350   c , and a pneumatic pressure control input port  350   d . The outlet port  350   c  provides a controlled process gas flow to the corresponding nozzle  250  to inject processing gas to a predetermined position on the substrate surface. 
     During operation, processing gas supplied from the gas panel  138  flows through the outer gas supply line  210  through an input port  354  formed on the annular ring  192 . Gas supply outlet ports  356 - 1 ,  356 - 2  are formed in the annular ring  192  and are connected to the inlet port  354 . A series of disconnectable gas flow lines  358  serially connect the valves  350  to the outlet ports  356 - 1 ,  356 - 2  of the annular ring  192 . The gas flow lines  358  are connected to the gas supply outlet ports  356 - 1 ,  356 - 2  respectively to deliver the processing gas from the gas supply ports  356 - 1 ,  356 - 2  to a corresponding set of the valves  350  connecting to the gas injection ports  190 . The processing gas flows through the gas supply line  358  to the input flow-through port  350   a  of the valve  350 . The processing gas flows from the input flow-through port  350   a  to the output flow-through port  350   b . Compressed air pressure at the control input port  350   d  determines whether the process gas is provided to the gas outlet port  350   c . The remaining gas other than diverted to the gas outlet port  350   c  is passed through the output flow-through port  350   b  compressed to the flow lines  358  to the successive valve  350 . 
     Alternatively, the process gases ma be distributed recursively to the processing chamber  100  to ensure balanced flow to nozzle  250 . The gas line from introduction of the gas to each nozzle  250  exiting throughout to the interior volume  122  is substantially equal so that flow resistance is substantially equal for all gas lines  358 . 
     A valve configuration processor  360  controls on and off, or any combination, of all of the valves  350  via valve control links  362 . Each valve  350  has an on-off mode controlled by the valve configuration processor  360  to provide or terminate gas flow to each corresponding gas injection port  190 . When the valve  350  is switched to an “on” mode, the processing gas is individually and separately supplied to the corresponding gas injection port  190 . In contrast, when the valve  350  is switched to an “off” mode, the gas flow supplied to its corresponding gas injection port  190  is terminated without affecting the flow of gas to the other valves. In an embodiment wherein the valves  350  are pneumatic valves, the control links  362  are designed as pneumatic, e.g., air, tubes to avoid the presence of electrical conductors close to the coil antennas  112 A,  112 B. 
     An air compressor  364  furnishes a desired pressure to an array of solenoid (e.g., electrically controlled) valves  365  that control application of the pressurized air to pneumatic control inputs  350   a  of the respective pneumatic valves  350 . The gas flow through the series of the valves  350  in the left side of  FIG. 4  is counter-clockwise while gas flow through the serious of valves  350  in the right side of the  FIG. 4  is clockwise. Alternatively, the valves  350  may be controlled electronically or by other suitable manner in the conventional practice. 
       FIG. 5  depicts a perspective drawing of the semiconductor substrate processing chamber  100  having the multiple port gas injection system  110  implemented therein. Upon installation of the multiple port gas injection system  110 , the plurality of valves  350  connected by the gas flow lines  358  are disposed around periphery region outside of the processing chamber  100 . The second group of injection port  196  is located in the center region below the removable lid  120 . The second group of injection port  196  may be controlled by another separate and individual valve (not shown) similar to the valve  350  depicted in  FIG. 4 . The gas supply line  194  connects the second group of the injection port  196  to the outer gas supply line  210  further to the gas panel  138 . The gas supply line  194  coupled to the second group of injection port  196  may be embedded within the removable lid  120  or by any other suitable manner internal or external to the processing chamber  100 . 
     By utilizing the multiple port gas injection system  110 , the processing gases may be supplied to the processing chamber  100  through different injection ports  196 ,  190  across the substrate surface. 
     In one embodiment, a passivation gas may be dispersed into the processing chamber  100  through the first group of injection ports  190  during etching while a reacting gas may be supplied to the processing chamber  100  through the second group of injection ports  196 . The passivation gas supplied through the first group of injection ports  190  are dispersed predominantly to a periphery region of the substrate surface while the reacting gas is directed predominately to the center of the substrate. The flow rate of the passivation gas supplied through each individual injection port  190  may be selectively controlled to facilitate a high concentration of such gas in a certain peripheral region on the substrate surface. The reacting gas supplied from the second group of injection port  196  may be controlled at different gas flow rate to result different concentration of reacting gas between the center and the periphery region of the substrate. 
     During etching, a portion of the etchants gas and by-products from the etching process are pumped away. A remaining portion of the by-products are re-deposited on sidewalls of the structures formed on the substrate, thereby reducing lateral rate and increasing critical dimensions during etching. In some embodiment, the concentration of such by-products may be depleted in the peripheral region faster than in the center region of the substrate, thereby resulting in low concentration of the by-product in the peripheral region and causing an increase in the etch rate in the peripheral region and less growth or even loss in critical dimensions during etching. By supplying the passivation gas from the first group of injection ports  190  to the periphery region of the substrate, the passivation gas assists forming a passivation film on sidewalls of the structures being formed in the peripheral region of the substrate. The chemistry of the passivation gas is selected such that the greater degree of polymerization potential enhances higher amount of passivation film deposited on the sidewalls of the structures which is chemically similar to the by-product of the etching process. The flow rate and degree of plasma dissociation of the passivation gas may be selectively adjusted to compensate for depletion of the by-products of the process to reduce the lateral etch rate in the peripheral region of the substrate, thereby providing a substantially uniform etching rate and feature scale critical dimensions across the substrate surface. 
     In one exemplary embodiment, a gate structure having silicon containing layer may be etched utilizing this processing chamber  100  with the multiple port gas injection system  110 . The passivation gas that may be used in this etching process includes one or more fluorosilane (SiF 4 ), silane (SiH 4 ), silicon tetrachloride (SiCl 4 ), CHF 3 , CH 2 F 2 , CH 3 F, HBr or the like. The reacting gas includes halogen containing gas, such as Cl 2 , HBr, BCl 3 , CF 4  and the like. Some dilution gas, such as N 2 , He, Ar or the like, may also be supplied to the processing chamber  100  during etching. In one embodiment, the passivation gas may be supplied to the processing gas at a flow rate between about 0 sccm and about 200 sccm. The reacting gas may be supplied to the processing gas at a flow rate between about 100 sccm and about 500 sccm. The dilution gas may be supplied to the processing gas at a flow rate between about 0 sccm and about 200 sccm. 
     While the foregoing is directed to embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.