Patent Publication Number: US-7584714-B2

Title: Method and system for improving coupling between a surface wave plasma source and a plasma space

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to co-pending U.S. patent application Ser. No. 10/953,802, entitled “Surface wave plasma processing system and method of using”, filed on even date herewith; co-pending U.S. patent application Ser. No. 10/953,801, entitled “Plasma processing system for treating a substrate”, filed on even date herewith; and co-pending U.S. patent application Ser. No. 10/954,086, entitled “Method for treating a substrate”, filed on even date herewith. The entire contents of all of those applications are herein incorporated by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and apparatus for improving coupling between a surface wave plasma (SWP) source and plasma and, more particularly, to a method and apparatus for improving the coupling between the SWP source and plasma using a mode scrambler. 
     2. Description of Related Art 
     Typically, during semiconductor processing, a (dry) plasma etch process is utilized to remove or etch material along fine lines or within vias or contacts patterned on a semiconductor substrate. The plasma etch process generally involves positioning a semiconductor substrate with an overlying patterned, protective layer, for example a photoresist layer, into a processing chamber. Once the substrate is positioned within the chamber, an ionizable, dissociative gas mixture is introduced within the chamber at a pre-specified flow rate, while a vacuum pump is throttled to achieve an ambient process pressure. Thereafter, a plasma is formed when a portion of the gas species present are ionized following a collision with an energetic electron. Moreover, the heated electrons serve to dissociate some species of the mixture gas species and create reactant specie(s) suitable for the exposed surface etch chemistry. Once the plasma is formed, any exposed surfaces of the substrate are etched by the plasma. The process is adjusted to achieve optimal conditions, including an appropriate concentration of desirable reactant and ion populations to etch various features (e.g., trenches, vias, contacts, etc.) in the exposed regions of substrate. Such substrate materials where etching is required include silicon dioxide (SiO 2 ), poly-silicon and silicon nitride, for example. 
     Conventionally, various techniques have been implemented for exciting a gas into plasma for the treatment of a substrate during semiconductor device fabrication, as described above. In particular, (“parallel plate”) capacitively coupled plasma (CCP) processing systems, or inductively coupled plasma (ICP) processing systems have been utilized commonly for plasma excitation. Among other types of plasma sources, there are microwave plasma sources (including those utilizing electron-cyclotron resonance (ECR)), surface wave plasma (SWP) sources, and helicon plasma sources. These conventional systems typically provide a single vacuum chamber space wherein the ionizable gas for creating the plasma is mixed with the dissociative gas used for processing. The present inventors have recognized, however, that these conventional plasma processing systems suffer from a number of deficiencies. 
     First, providing ionization and dissociative gas in a common chamber provides limited control of process chemistry (i.e., control of chemistry dissociation). Moreover, a common plasma and processing space exposes the plasma source to process gasses that may erode or deposit material on the plasma source thereby affecting the operation of the plasma source. Similarly, a common gas mixture space may cause substrate damage due to interaction of the substrate with energetic electrons and ions of the plasma. Still further, the inventor has recognized that the conventional systems are limited to conventional techniques for controlling substrate processing uniformity, such as controlling the temperature of the substrate to compensate for non-uniformity of the plasma and/or process gasses. 
     SUMMARY OF THE INVENTION 
     Accordingly, one object of an invention of the present application is to reduce or eliminate any or all of the above-described problems. 
     Another object of an invention of the present application is to provide a method and system for improving process chemistry control in a plasma processing system. 
     Another object of an invention of the present application is to provide a method and system for reducing damage to system components such as a plasma source, and/or to reduce the possibility of damage to a substrate being processed. 
     Yet another object of an invention of the present application is to provide a method and system for improving control of process uniformity to a substrate. 
     Any of these and/or other objects of the invention can be provided by a surface wave plasma (SWP) source having an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface of the EM wave launcher adjacent the plasma. A power coupling system is coupled to the EM wave launcher, and configured to provide the EM energy to the EM wave launcher for forming the plasma. A mode scrambler coupled to the plasma surface of the EM wave launcher, and configured to reduce mode jumping between the desired EM wave mode and another EM wave mode. 
     According to another aspect of the invention, a surface wave plasma (SWP) source includes an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface of the EM wave launcher adjacent the plasma. A power coupling system is coupled to the EM wave launcher, and configured to provide the EM energy to the EM wave launcher for forming the plasma, and a means for reducing mode jumping between the desired EM wave mode and another EM wave mode. 
     According to yet another aspect of the invention, a method of manufacturing a surface wave plasma (SWP) source includes providing an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface of the EM wave launcher adjacent the plasma, and providing a coupling structure configured to couple the EM energy to the EM wave launcher for forming the plasma. A mode scrambler is formed on the plasma surface of the EM wave launcher, the mode scrambler being configured to reduce mode jumping between the desired EM wave mode and another EM wave mode. 
     In still another aspect, a surface wave plasma (SWP) source includes an electromagnetic (EM) wave launcher configured to couple EM energy in a desired EM wave mode to a plasma by generating a surface wave on a plasma surface of the EM wave launcher adjacent the plasma. A power coupling system coupled to the EM wave launcher, and configured to provide the EM energy to the EM wave launcher for forming the plasma. The EM wave launcher includes a resonator plate containing the plasma surface on which the surface wave is generated, and the resonator plate includes a high dielectric constant material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  presents a simplified schematic representation of a plasma processing system according to an embodiment of the invention; 
         FIG. 2  presents a simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with one embodiment; 
         FIG. 3  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with another embodiment; 
         FIG. 4  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with another embodiment; 
         FIG. 5  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with yet another embodiment; 
         FIG. 6  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with another embodiment; 
         FIG. 7  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with a further embodiment; 
         FIG. 8  presents another simplified schematic representation of a plasma source that can be used for the plasma processing system depicted in  FIG. 1  in accordance with still another embodiment; 
         FIGS. 9A and 9B  provide schematic representations of electromagnetic wave propagation in a medium; 
         FIG. 10  provides an exploded view of a portion of a processing chamber according to an embodiment; 
         FIG. 11  provides an exploded view of a portion of a processing chamber according to another embodiment; 
         FIG. 12  provides an exploded view of a portion of a processing chamber according to another embodiment; 
         FIG. 13  illustrates a top view of a gas injection grid according to an embodiment; 
         FIG. 14  illustrates a top view of a gas injection grid according to another embodiment; 
         FIG. 15  provides a method of operating a plasma processing system according to an embodiment; and 
         FIG. 16  provides a method of controlling the uniformity in a plasma processing system according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     In the following description, to facilitate a thorough understanding of the invention and for purposes of explanation and not limitation, specific details are set forth, such as a particular geometry of the plasma processing system and various descriptions of the system components. However, it should be understood that the invention may be practiced with other embodiments that depart from these specific details. Nonetheless, it should be appreciated that, contained within the description are features which, notwithstanding the inventive nature of the general concepts being explained, are also of an inventive nature. 
     Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views,  FIG. 1  illustrates a plasma processing system  100  according to an embodiment. The plasma processing system  100  comprises a processing chamber  110  having an upper chamber portion  112  (i.e. a first chamber portion) configured to define a plasma space  116 , and a lower chamber portion  114  (i.e. a second chamber portion) configured to define a process space  118 . In the lower chamber portion  114 , the processing chamber  110  comprises a substrate holder  120  configured to support a substrate  125 . Therein, the substrate  125  is exposed to process chemistry in process space  118 . Furthermore, the plasma processing system  100  comprises a plasma source  130  coupled to the upper chamber portion  112 , and configured to form plasma in the plasma space  116 . 
     As seen in  FIG. 1 , the plasma processing system  100  comprises a grid  140  coupled to the upper chamber portion  112  and the lower chamber portion  114 , and located between the plasma space  116  and the process space  118 . While  FIG.1  shows the gas injection grid positioned centrally to divide the processing chamber such that the upper chamber portion  112  is substantially equal in size to the lower portion  114 , the invention is not limited to this configuration. For example, the gas injection grid can be located within 200 mm from the upper surface of the substrate and, desirably, the gas injection grid is placed within a range of approximately 10 mm to approximately 150 mm from the upper surface of the substrate. The grid is preferably a gas injection grid  140  configured to introduce a first gas  142  to the plasma space  116  for forming plasma, and to introduce a second gas  144  to the process space  118  for forming process chemistry. However, it is not necessary for the first and second gasses to be introduced to their respective chamber portions by way of the grid  140 . For example, the plasma source  130  may be configured to supply the first gas  142  to the plasma space  116 . In embodiment of  FIG. 1 , a first gas supply system  150  is coupled to the gas injection grid  140 , and it is configured to supply the first gas  142 . Moreover, a second gas supply system  160  is coupled to the gas injection grid  140 , and it is configured to supply the second gas  144 . The temperature of the gas injection grid  140  can be controlled using a temperature control system  170 , and the electric potential of the gas injection grid  140  can be controlled using an electric bias control system  175 . 
     Furthermore, the plasma processing system  100  includes a pumping system  180  coupled to the processing chamber  110 , and configured to evacuate the processing chamber  110 , as well as control the pressure within the processing chamber  110 . Optionally, the plasma processing system  100  further includes a control system  190  coupled to the processing chamber  110 , substrate holder  120 , plasma source  130 , gas injection grid  140 , the first gas supply system  150 , the second gas supply system  160 , the temperature control system  170 , the electric bias control system  175 , and the pumping system  180 . The control system  190  can be configured to execute a process recipe for performing at least one of an etch process, and a deposition process in the plasma processing system  100 . 
     Referring still to  FIG. 1 , the plasma processing system  100  may be configured to process 200 mm substrates, 300 mm substrates, or larger-sized substrates. In fact, it is contemplated that the plasma processing system may be configured to process substrates, wafers, or LCDs regardless of their size, as would be appreciated by those skilled in the art. Therefore, while aspects of the invention will be described in connection with the processing of a semiconductor substrate, the invention is not limited solely thereto. 
     As described above, the processing chamber  110  is configured to facilitate the generation of plasma in plasma space  116 , and generate process chemistry in process space  118  adjacent a surface of the substrate  125 . The first gas  142 , which is introduced to the plasma space  116 , comprises plasma forming gas, or an ionizable gas or mixture of gases. The first gas  142  can include an inert gas, such as a Noble gas. The second gas  144 , which is introduced to the process space  118 , comprises a process gas or mixture of process gases. For example, in an etch process, the process gas can include molecular constituents that when dissociated are reactive with the material being etched on the substrate surface. Once plasma is formed in the plasma space  116 , some of the plasma can diffuse into the process space  118  through the gas injection grid  140 . The heated electrons having diffused into the process space  118 , can collide with molecules in the process gas causing dissociation and the formation of reactive radicals for performing an etch process, for example. The present inventors have discovered that this separation of the plasma space from the process space by a grid can provide several advantages over the conventional systems described above. 
     First, separate plasma and process spaces such as that shown in exemplary plasma processing system of  FIG. 1  can provide improved process control over conventional systems. Specifically, the use of a gas injection grid  140 , as described above, can, for example, affect the formation of a dense, high temperature (electron temperature, T e ) plasma in the plasma space  116 , while producing a lower temperature plasma in the process space  118 . In doing so, the split injection scheme for the first and second gases can affects a reduction in the dissociation of the molecular composition in the second gas that is utilized for forming the process chemistry, which provides greater control over the process at the substrate surface. 
     Additionally, the configuration of exemplary  FIG. 1  can reduce damage to chamber components such as the plasma source  130 , by preventing process gasses from entering the plasma space  116 . For example, as an inert gas (first gas), such as argon (Ar), is introduced to the plasma space  116 , plasma is formed and neutral Ar atoms are heated. The heated Ar neutral atoms diffuse downwards through the gas injection grid  140 , and enter the cooler, process space proximate the substrate. This diffusion of neutral gas creates a gas flow into the process space  118  that can reduce or eliminate back-diffusion of the molecular composition in the process gas (second gas). 
     Still further, the configuration of  FIG. 1  can reduce substrate damage caused by ion and electron interaction with the substrate  125 . In particular, the diffusion of electrons and ions through the injection grid  140  into the process space  118  provides fewer electrons and ions in this space relative to the conventional chamber described above. Moreover, many of these electrons and ions give up their energy to the dissociation of the process gas. Thus, fewer electrons and ions are available to interact with the substrate and cause damage thereto this is particularly important for low temperature processes because damage to the substrate  125  may not be annealed by the required process temperature. 
     Thus, the present inventors have discovered that separation of plasma space from a process space by a grid may provide advantages over a mixed chamber configuration. It is to be understood however, that the present invention is not limited to providing all or any one of the above advantages. For example, the grid separation structure may provide unknown advantages that can be exploited to the exclusion of any one or all of the above described advantages. 
     Referring now to the plasma source  130  of  FIG. 1 , this source may be a parallel plate capacitively coupled plasma source, an inductively coupled plasma source, microwave plasma source (including those utilizing electron-cyclotron resonance (ECR), a helicon plasma source or a surface wave plasma (SWP) source, for example. As would be understood by one of ordinary skill in the art, other known plasma sources may be used.  FIG. 2  shows a SWP source that may be used as the plasma source  130  of  FIG. 1 . Referring now to  FIG. 2 , a plasma source  230  is illustrated comprising a slot antenna, such as a radial line slot antenna (RLSA), with a coaxial feed  238  having an inner conductor  240 , an outer conductor  242 , and insulation  241 . A fluid channel  256  can be used to flow a temperature control fluid for temperature control of the plasma source  230 . 
     Additionally, the plasma source  230  includes an electromagnetic (EM) wave launcher  243  comprising a slow wave plate  244 , a slot antenna  246  having slots  248 , and a resonator plate  250 . The number of slots, geometry of the slots, the size of the slots, and the distribution of the slots are all factors that can contribute to the spatial uniformity of the plasma formed in plasma space  116 . Thus, the design of the slot antenna  246  may be used to control the spatial uniformity of the plasma in the plasma space  116 . Moreover the exact dimensions of the resonator plate  250  (i.e., thickness, and diameter) can be calculated numerically for a desired microwave frequency. These critical dimensions of the resonator plate  250  make this component expensive to produce. 
     The wave launcher  243  includes a microwave launcher configured to radiate microwave power into plasma space  116 . The microwave launcher can be coupled to a microwave source, such as a 2.45 GHz microwave power source, wherein microwave power is coupled to the microwave launcher via the coaxial feed  238 . Microwave energy generated by the microwave source is guided through a waveguide (not shown) to an isolator (not shown) for absorbing microwave energy reflected back to the microwave oscillator, and thereafter it is converted to a coaxial TEM mode via a coaxial converter (not shown). A tuner may be employed for impedance matching, and improved power transfer. The microwave energy is coupled to the microwave launcher via the coaxial feed  238 , where another mode change occurs from the TEM mode in the coaxial feed  238  to a TM mode. Additional details regarding the design of the coaxial feed and the wave launcher can be found in U.S. Pat. No. 5,024,716, entitled “Plasma processing apparatus for etching, ashing, and film-formation”; the contents of which are herein incorporated by reference in its entirety. 
     Referring still to  FIG. 2 , the plasma source  230  is coupled to the upper chamber portion  112  of processing chamber  110 , wherein a vacuum seal can be formed between the upper chamber wall  252  and the plasma source  230  using a sealing device  254 . The sealing device  254  can include an elastomer O-ring, however, other known sealing mechanisms may be used. 
     In general, the inner conductor  240  and the outer conductor  242  of the coaxial feed  238  comprise a conductive material, such as a metal, while the slow wave plate  244  and the resonator plate  250  comprise a dielectric material. In the latter, the slow wave plate  244  and the resonator plate  250  preferably comprise the same material, however different materials may be used. The material selected for fabrication of the slow wave plate  244  and the resonator plate  250  is chosen to reduce the wavelength of the propagating electro-magnetic (EM) wave relative to the free-space wavelength, and the dimensions of the slow wave plate  244  and the resonator plate  250  are chosen to ensure the formation of a standing wave effective for radiating EM energy into the plasma space  116 . 
     In one embodiment, the slow wave plate  244  and the resonator plate  250  are fabricated from quartz (silicon dioxide). In particularl, when the plasma processing system is utilized for etch process applications, quartz is often chosen for compatibility with the etch process. However, the present inventors have observed several problems with using quartz as the material of the slow wave plate  244  and the resonator plate  250 . 
     The onset of the standing wave electric field must remain adjacent the quartz-plasma interface for low power plasma processes. The present inventors have observed that the use of a quartz resonator plate with the standing wave at the quartz-plasma interface can be prone to mode jumps as plasma parameters shift. Specifically, shifts in plasma parameters affect the decaying electric field in the quartz resonator. If the electric field strength in the dielectric resonator is not sufficiently larger than the change in the electric field due to the shift in plasma parameters, such a shift can cause a voltage standing wave ratio (VSWR) jump, or standing wave mode jump. Also, when using quartz as the material for the manufacture of the resonator plate and the slow wave plate, the design of the slot antenna (i.e., number of slots, their size, geometry and distribution) is less effective for affecting spatially uniform plasma in the plasma space  116 . Therefore, a special shape can be required for forming uniform plasma.  FIG. 3  shows a plasma source  231  that can further include one or more concentric grooves  260  configured to improve the spatial uniformity of plasma in the plasma space  116 . However, this configuration can increase the cost of the quartz resonator plate. 
     In another embodiment of the present invention, the slow wave plate  244  and the resonator plate  250  can be fabricated from a high dielectric constant (high-k) material. As used herein, “high dielectric constant” and “high-k” material refer to materials having a dielectric constant equal to or greater than that of silicon dioxide (approximately a value of 3.9). The present inventors have recognized that the use of a high-k material can, for example, lead to reduced risk of mode jumping due to shifts in plasma parameters relative to other materials such as quartz described above. Moreover, use of the high-k material causes the design of the slot antenna to have improved effectiveness in controlling the spatial uniformity of plasma formed in plasma space  116 . Still further, use of a high-k material can allow reduced dissociation of the molecular constituent in the process chemistry, thereby allowing greater process control as discussed above with respect to  FIG. 1 . In this regard, the present inventors have recognized that the use of a high-k material for the slow wave plate  244  and the resonator plate  250  can improve process control in conventional single chamber plasma chambers as well as the split chamber configuration of exemplary  FIG. 1 . 
     In one embodiment, the high-k material can include intrinsic crystal silicon, alumina ceramic, aluminum nitride, and sapphire. However, other high-k materials may be used in accordance with the present invention. Moreover, a particular high-k material may be selected in accordance with the parameters of a particular process. For example, when the resonator plate  250  is fabricated from intrinsic crystal silicon, the plasma frequency exceeds 2.45 GHz at a temperature of 45 C. Therefore, intrinsic crystal silicon is appropriate for low temperature processes (i.e., less than 45 C). For higher temperature processes, the resonator plate  250  can be fabricated from alumina (Al 2 O 3 ), or sapphire. 
     As described above, the resonator plate of the plasma source has critical dimensions, which makes the resonator plate expensive. This is true of quartz resonator plates as well as resonator plates made of the high-k materials described above. However, the erosive nature of plasma in plasma space  116  may cause the resonator plate  250  to deviate from its critical dimensions thereby requiring frequent replacement of the expensive resonator plate  250 . This is particularly true for conventional single chamber plasma systems wherein the resonator plate is exposed to process gasses as well as the plasma. The present inventors have recognized that, due to the erosive plasma and the requirement for maintaining critical dimensions of the resonator plate  250 , a cover plate can be used as a consumable component to protect the more expensive resonator plate  250 . 
     Thus, according to yet another example, a cover plate  265  is coupled to a lower surface of the resonator plate  250  as illustrated in  FIG. 4 . The cover plate thickness is selected to be sufficiently thin such that it does not support standing wave modes within it (i.e., the thickness is not electromagnetically critical); however, it is sufficiently thick for mechanical stability. For example, the cover plate  265  can include a quartz cover plate that is 1 to 5 mm in thickness, or desirably 2 to 3 mm in thickness. Furthermore, the lower surface (or contact surface) of the resonator plate  250  and the upper surface (or contact surface) of the cover plate  265  can be polished to ensure a good contact between the resonator plate  250  and the cover plate  265 . A thin film may also be deposited on the lower surface of the resonator plate  250 , and polished in order to provide a good contact. For instance, the thin film can include a thin film of SiO 2 , and it may include up to 2 micron thermal SiO 2 , or up to 6 micron physical vapor deposition (PVD) SiO 2 . As would be understood by one of ordinary skill in the art, the cover plate  265  is preferably coupled to the resonator plate by fasteners or some other mechanism for allowing removal and replacement of the cover plate  265 . 
     Notwithstanding the benefit of the cover plate  265  in providing erosion protection for the expensive resonator plate component, the present inventor has discovered that the cover plate may contribute to instability of the plasma in a plasma processing system, such as the plasma system of  FIG. 1  or conventional single chamber plasma systems.  FIG. 9A  shows an infinite slab model depicting a simple geometric interface for the resonator plate  250  and the cover plate  265 . Analytical expressions of the electric and magnetic fields can be determined using the homogeneous Helmholtz equation, viz. 
     
       
         
           
             
               
                 
                   
                     
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     where x, y, and z are the Cartesian coordinates as shown in  FIG. 9A , E z  is the electric field in the z direction, E x  is the electric field in the x direction, H y  is the magnetic field in the y direction, k 250  is the cut-off wave number in the resonator plate, κ 250  is the dielectric constant of the resonator plate material and Y 0  is the vacuum wave admittance (Y 0 =(ε 0 /μ 0 ) 1/2 =Z 0   −1 ). Also in the above equation, β is the propagation constant from the basic dispersion relation β 2 =k 2 −k c   2 =κ 250 k 0   2 −k 250   2 =κ 265 k 0   2 +h 2 , where κ 265  is the dielectric constant of the cover plate material, k is the medium wave number, k c  is the medium cut-off wave number, h is the field damping constant, k 0  is the vacuum wave number and k 265 =jh. Thus, where the resonator plate is fabricated from intrinsic crystal silicon and the cover plate is fabricated from silicon dioxide, the subscript “250” refers to the material properties of intrinsic crystal silicon, and the subscript “265” refers to the material properties of silicon dioxide. 
     As shown in  FIG. 9A , the primary surface wave exists between the resonator plate and cover plate interface, and the onset of the evanescent electric field occurs at this interface. Electromagnetic waves, represented by k 1  and k 2 , are depicted as two exemplary modes in  FIG. 9A . Waves k 1,2  and k 2,2  represent the surface waves at this interface, traveling with a phase velocity between the phase velocity in intrinsic crystal silicon (e.g., κ˜12, and λ Si ˜1 cm), and the phase velocity in silicon dioxide (κ˜4, and λ SiO2 ˜3 cm). If the thickness of the cover plate is much larger than the wavelength of the EM wave, then the infinite slab model field solutions for x&gt;s are: 
     
       
         
           
             
               
                 
                   
                     
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     (where kY=k 0 Y 0 , when in vacuum; and kY=κ 265 k 0 Y 0 , for a surface wave in the cover plate). 
     However, since the thickness of the cover plate is only a fraction of the wavelength and, hence, a smaller fraction of the decay depth of the electric field, the above set of solutions are incomplete. For instance, an additional reflection at the interface between the cover plate and the plasma will occur, and there will exist a different decay constant for x&gt;q. Since the propagation constant will have to be the same for the resonator plate, the cover plate, and the plasma, there will exist a new β. More importantly, the new β leads to a new phase velocity straddling that in the resonator plate, the cover plate, and the plasma. 
     Therefore, as a result of the cover plate, it is possible that plasma instability can occur as a result of a shift in plasma parameters. Although the dielectric constant for the plasma is approximately a value of unity for a wide range of plasma parameters, EM wave dispersion is strongly affected by the electron density (n e ), the electron temperature (T e ), etc. When the dispersion relation changes in the plasma, the surface wave propagation constant changes. Consequently, the field solutions change. The immediate consequence can include an increase in the VSWR, and a possible mode jump that reduces the stability of the plasma processing chamber thereby diminishing the repeatability of processing performed in the plasma processing system. While such mode hops may be present without a cover plate, the possibility of increased instability in the plasma might be a factor contributing to the current failure to use consumable cover plate on surface wave plasma sources. 
     However, the present inventors have discovered that a mode scrambler can be coupled to the plasma source in order to mitigate the effects of mode jumping. Specifically, the cavity mode in the wave launcher  243  can be dependent upon the geometry of the wave launcher cavity and the material properties of the wave launcher cavity, as well as upon the plasma parameters. The use of a mode scrambler reduces the effect of changes in the plasma parameters on the resultant cavity mode. In this regard, the mode scrambler may be provided to facilitate use of a protective cover  265  that may otherwise not be used due to the possibility of causing mode hops as discussed above. This is true for conventional plasma systems as well as the system of  FIG. 1  discussed above. Moreover, the mode scrambler may be used to suppress mode hopping for SWP sources having a cover plate or not having a cover plate. 
       FIG. 5  shows a mode scrambler coupled to a lower surface of the resonator plate according to one embodiment of a plasma source. As seen in this figure, the mode scrambler  270  comprises one or more gas holes  274  coupled to one or more gas plenums  272 . In the embodiment of  FIG. 5 , the gas plenums  272  are coupled to the plasma space  116  by the gas holes  274  such that a gas, such as the first gas or an inert gas, is introduced to the plasma space  116 . Although each of the gas holes  274  in  FIG. 5  are shown to be coupled to a gas plenum  272 , one or more of the one or more gas holes  274  may not be coupled to a gas plenum  272 . Further, in one embodiment, one or more of the one or more gas holes  274  can be evacuated. 
     Referring still to  FIG. 5 , the plasma source  233  is coupled to the upper chamber portion  116  of processing chamber  110 , wherein a vacuum seal can be formed between the upper chamber wall  252  and the plasma source  230  using a sealing device  254 . The sealing device  254  can include an elastomer O-ring, however, other known sealing devices may be used. Furthermore, a second and third sealing device,  255 A and  255 B, can be utilized to provide a vacuum seal in the coaxial feed  238 . 
       FIG. 6  illustrates a plasma source according to yet another example. As seen in this figure, a mode scrambler  270  is coupled to a lower surface of the resonator plate  250  in plasma source  233 . Herein, the mode scrambler  270  comprises one or more blind holes  276  formed at an interface of the cover plate  265  and the resonator plate  250 .  FIG. 9B  shows an infinite slab model depicting a simple geometric interface for blind holes  276  formed between the resonator plate  250  and the cover plate  265 . As seen in  FIG. 9B , electromagnetic waves, represented by k 1 , k 2 , and k 3 , are depicted as three exemplary modes. Surface waves k 1,2  (k 1,3 ) and k 2,2  (k 2,3 ) represent effective coupling of energy to plasma in plasma space  116 . However, wave k 3  does not contribute to plasma heating, and it is reflected by the plasma. The present inventors have determined that this reflection of certain modes of electromagnetic waves diminishes the possibility of mode hopping that may occur in the SWP source and may be enhanced by the cover plate  265 . 
     The number, geometry, distribution, and size of the one or more blind holes  276  can also be selected in order to provide uniform plasma in plasma space  116 . Thus, the mode scrambler can be used to provide additional control of plasma uniformity. Additionally, the one or more blind holes  276  can be opened to the plasma space  116  rather than sealed from the plasma as seen in  FIG. 6 . In such a configuration, however, the size of each blind hole, such as the width or diameter of each hole, should be sufficiently small so as to avoid the formation of plasma in the hole which can contribute to mode hopping. If plasma is permitted to form in one or more holes, then the one or more holes can be subjected to erosion by the plasma, hence, damaging the hole and changing the hole dimensions. These changes in the hole dimensions can lead to changes in the coupling of power between the plasma source and plasma. For example, the width or diameter of each blind hole can be less than or equal to 2 mm for process pressures less than 100 mTorr. As the pressure is increased, the size of the blind hole should be decreased in order to prevent the formation of plasma therein (e.g., when p=200 mTorr, the diameter should be less than or equal to 1 mm). Additionally, for example, a blind hole diameter of less than 1 mm can be effective for scrambling cavity modes for λ Si ˜1 cm. 
     The one or more blind holes can be fabricated using drilling or milling techniques, sonic milling, laser milling, or etching processes, or any combination thereof. The etching processes can include dry or wet etching processes that can be utilized for forming the blind hole in the resonator plate  250 . In one embodiment, a thin SiO 2  layer, such as a 2 micron layer of thermal SiO 2  or a 6 micron layer of physical vapor deposition (PVD) SiO 2 , can be deposited on the lower surface of the resonator plate  250 . Thereafter, the thin SiO 2  layer can be patterned using, for example, an etching process, and the pattern can be transferred into the resonator plate  250  using an etching process, whereby the thin SiO 2  layer serves as a hard mask and defines the geometry of the one or more blind holes. Furthermore, the remaining thin SiO 2  layer can serve to ensure a good interface between the resonator plate  250  and the cover plate  265 . 
     According to yet another example of the plasma source, the blind holes  276  of the mode scrambler depicted in  FIG. 6  can be filled with a material in order to prevent the formation of plasma within the holes. For example, referring to  FIG. 7 , a coating  278  can be applied to the lower surface of the resonator plate  250  in order to fill the one or more blind holes  276 . The coating  278  preferably comprises a material having a dielectric constant less than the dielectric constant of the resonator plate  250 . For example, where the resonator plate is a high-k material, the coating  278  can include SiO 2  having a dielectric constant of approximately 4. Alternatively, the coating can include a low dielectric constant (low-k) material, having a dielectric constant less than that of SiO 2 . Moreover, the coating  278  can preferably include a low-k material, having a coefficient of thermal expansion that is compatible with the expansion coefficient for the resonator plate in order to improve reliability of the interface between the resonator plate  250  and the cover plate  265 . For example, the low-k material can include at least one of an organic, inorganic, and inorganic-organic hybrid material. Furthermore, the low-k material can include a porous, or non-porous coating. 
     Additionally, for example, the coating  278  may include an inorganic, silicate-based material, such as oxidized organosilane (or organo siloxane), deposited using CVD techniques. Examples of such coatings include Black Diamond™ CVD organosilicate glass (OSG) films commercially available from Applied Materials, Inc., or Coral™ CVD films commercially available from Novellus Systems. The coating  278  can also include single-phase materials, such as a silicon oxide-based matrix having CH 3  bonds that are broken during a curing process to create small voids (or pores), and/or dual-phase materials such as a silicon oxide-based matrix having pores of organic material (e.g., porogen) that is evaporated during a curing process. Alternatively, the coating  278  may include an inorganic, silicate-based material, such as hydrogen silsesquioxane (HSQ) or methyl silsesquioxane (MSQ), deposited using SOD techniques. Examples of such coatings include FOx HSQ commercially available from Dow Corning, XLK porous HSQ commercially available from Dow Corning, and JSR LKD-5109 commercially available from JSR Microelectronics. Still alternatively, the coating  278  can include an organic material deposited using SOD techniques. Examples of such coatings include SiLK-I, SiLK-J, SiLK-H, SiLK-D, and porous SiLK semiconductor dielectric resins commercially available from Dow Chemical, and FLARE™, and Nano-glass commercially available from Honeywell. 
     The coating  278  can be formed, for example, using chemical vapor deposition (CVD) techniques, or spin-on dielectric (SOD) techniques such as those offered in the Clean Track ACT 8 SOD and ACT 12 SOD coating systems commercially available from Tokyo Electron Limited (TEL). The Clean Track ACT 8 (200 mm) and ACT 12 (300 mm) coating systems provide coat, bake, and cure tools for SOD materials. The track system can be configured for processing substrate sizes of 100 mm, 200 mm, 300 mm, and greater. Other systems and methods for forming a coating on a substrate are well known to those skilled in the art of both spin-on technology and vapor deposition technology. Once the coating  278  is applied, it can be polished in order to, for example, provide an improved interface with the cover plate  265 . The polishing process can, for instance, include chemical-mechanical polishing (CMP). 
     According to yet another example of a plasma source, the mode scrambler  270  having one or more blind holes  276  can be filled with a plasma arrester in order to prevent the formation of plasma in the blind holes. For example, referring to  FIG. 8 , the one or more blind holes  276  are filled with a spherical pellet  280 . The spherical pellets  280  can, for example, comprise SiO 2 , or a low-k material, as described above. Once the one or more blind holes are loaded with the spherical pellets  280 , each pellet is secured by press-fitting each pellet into each blind hole or by retaining each pellet within the blind hole by coupling the cover plate  265  to the resonator plate  250 . The pellet&#39;s physical presence reduces the accelerated free electron path (electrons collide into pellet), thus, inhibiting avalanche ionization. In one example, each blind hole  276  can include a 2 mm diameter by a 2 mm depth, and each pellet  280  can have a diameter of 2 mm, and less (such that it is sufficiently small to fit within the blind hole). Additionally, in order to ensure a good interface between the resonator plate  250  and the cover plate  265 , a thin SiO 2  layer, such as a 2 micron layer of thermal SiO 2  or a 6 micron layer of physical vapor deposition (PVD) SiO 2 , can be deposited on the contact surfaces of the resonator plate  250 . 
     As indicated above, the grid  140  of  FIG. 1  may be configured to control process uniformity in the plasma processing system. Specifically, the grid  140  may be implemented as a gas injection grid for introducing the first and second gasses.  FIG. 10  illustrates a portion of a processing system showing details of a gas injection grid in accordance with one embodiment. A processing chamber  310  is depicted comprising an upper chamber portion  312  that encloses a plasma space  316 , and a lower chamber portion  314  that encloses a process region  318 . A plasma source  330 , such as a surface wave plasma source as described above, is coupled to the upper chamber portion  312 , and is configured to form plasma in plasma space  316 . A gas injection grid  340  is coupled to the upper chamber portion  312  and the lower chamber portion  314 , and located between the plasma space  316  and the process space  318 . As illustrated in  FIG. 10 , the gas injection grid  340  is coupled to the upper chamber portion  312 , and it is sealed for use in vacuum using an upper sealing device  344 , such as an elastomer O-ring. Also, as illustrated in  FIG. 10 , the gas injection grid  340  is coupled to the lower chamber portion  314 , and it is sealed for use in vacuum using a lower sealing device  346 , such as an elastomer O-ring. 
     The gas injection grid  340  comprises one or more passageways  342  coupling the plasma space  316  to the process space  318  that allow plasma to diffuse into the process space  318 . In the embodiment of  FIG. 10 , gas injection grid  340  is configured to introduce a first gas to the plasma space  316  through one or more gas injection orifices (not shown) that are coupled to a first gas channel array  356 . The first gas channel array  356  can include one gas channel coupled to a first gas supply system, or a plurality of gas channels forming multiple zones in the gas injection grid  340  that are independently coupled to the first gas supply system. In the latter, the composition of the first gas, or the flow rate of the first gas, or both can be varied from one gas channel to the next. By such variation, a condition of the plasma in plasma space  316  can be spatially controlled to achieve spatial uniformity or non-uniformity as desired. For example, spatial uniformity of the plasma may be used to maintain process uniformity, and non-uniformity of the plasma may be used to compensate for other conditions in the processing system. 
     As also seen in the embodiment of  FIG. 10 , gas injection grid  340  is configured to introduce a second gas to the process space  318  through one or more gas injection orifices (not shown) that are coupled to a second gas channel array  366 . The second gas channel array  366  can include one gas channel coupled to a second gas supply system, or a plurality of gas channels independently coupled to the second gas supply system. In the latter, the composition of the second gas, or the flow rate of the second gas, or both can be varied from one gas channel to the next. As with the first gas, such variation can be used to provide spatial control of the process gas space to achieve spatial uniformity or non-uniformity as desired. 
     Also in the embodiment of  FIG. 10 , the temperature of the gas injection grid  340  can be controlled by circulating a heat transfer fluid through a fluid channel array  376  in order to transfer heat from the gas injection grid  340  to a heat exchanger (not shown) when cooling, or to transfer heat to the gas injection grid  340  from the heat exchanger when heating. The fluid channel array  376  can include one fluid channel coupled to a temperature control system, or a plurality of fluid channels independently coupled to the temperature control system. In the latter, the composition of the heat transfer fluid, or the temperature of the heat transfer fluid, or the flow rate of the heat transfer fluid, or any combination thereof can be varied from one fluid channel to the next. Thus, the fluid channel array  376  can also be used to provide spatial control of the plasma and process spaces. 
     As illustrated in  FIG. 10 , the first gas is coupled to the first gas channel array  356  via a first array of gas lines  354 . The first gas is coupled to the first array of gas lines  354  through a first array of gas fittings  352 , which permits a point for coupling a first gas supply system, such as the first gas supply system  150  depicted in  FIG. 1 . For example, the first array of gas fittings  352  can be located in the upper chamber portion  312 , and the first array of gas lines  354  can pass through the upper chamber portion  312  into the gas injection grid  340 , whereby a first array of gas sealing devices  358  are utilized to prevent leakage of the first gas. For example, the first array of gas sealing devices  358  can include one or more elastomer O-rings. 
     As illustrated in  FIG. 11 , the second gas is coupled to the second gas channel array  366  via a second array of gas lines  364 . The second gas is coupled to the second array of gas lines  364  through a second array of gas fittings  362 , which permits a point for coupling a second gas supply system, such as the second gas supply system  160  depicted in  FIG. 1 . For example, the second array of gas fittings  362  can be located in the upper chamber portion  312 , and the second array of gas lines  364  can pass through the upper chamber portion  312  into the gas injection grid  340 , whereby a second array of gas sealing devices  368  are utilized to prevent leakage of the second gas. For example, the second array of gas sealing devices  368  can include one or more elastomer O-rings. 
     Additionally, as illustrated in  FIG. 12 , the heat transfer fluid is coupled to the fluid channel array  376  via an array of fluid lines  374 . The heat transfer fluid is coupled to the array of fluid lines  374  through an array of fluid fittings  372 , which permits a point for coupling a temperature control system, such as the temperature control system  170  depicted in  FIG. 1 . For example, the array of fluid fittings  372  can be located in the upper chamber portion  312 , and the array of fluid lines  374  can pass through the upper chamber portion  312  into the gas injection grid  340 , whereby an array of fluid sealing devices  378  are utilized to prevent leakage of the heat transfer fluid. For example, the array of fluid sealing devices  378  can include one or more elastomer O-rings. 
     Thus, as discussed above, one embodiment of the gas injection grid allows the first gas channel array, second gas channel array and/or third gas channel array to be used to provide spatial control of conditions in the process chamber. This spatial control can be used to replace or augment the control techniques of conventional process chambers described above in order to improve spatial control of processes at the substrate surface.  FIGS. 13  and  14 , illustrate a top down view of a gas injection grid for providing improved spatial control in accordance with two embodiments of the invention. 
     In  FIG. 13 , a gas injection grid  340 A is depicted, wherein the gas injection grid comprises a rectangular distribution of passageways  342 A, however, different shape passageways can be used. In the example of  FIG. 13 , the first gas is independently coupled to three gas channels  356 A,  356 B, and  356 C via three separate gas lines  354 A,  354 B, and  354 C. Similarly, in  FIG. 14 , a gas injection grid  340 B is depicted, wherein the gas injection grid comprises a circular distribution of passageways  342 B. For example, as shown in  FIG. 14 , the first gas is independently coupled to three gas channels  356 A,  356 B, and  356 C via three separate gas lines  354 A,  354 B, and  354 C. Although not shown, a separate mass flow controller, or separate array of mass flow controllers can be coupled to each gas line in  FIGS. 13 and 14  to allow use of different gas compositions and/or flow rates across the gas injection grid  340 A. While  FIG. 13  shows closed rectangular loops and  FIG. 14  shows closed circular loops that are concentrically spaced and each provided with a gas supply, the present invention is limited to this configuration. For example, each side of the rectangular gas channels in  FIG. 13  may be provided with a separate gas supply in order to provide a greater degree of spatial control. Moreover, while  FIGS. 13 and 14  are upper views of the gas injection grid  340  showing the gas channels and gas lines of the first gas, the spatial configuration of  FIGS. 13 and 14  may be used for the second gas channel array or fluid channel array. In addition, different spatial control configurations can be used for each of these channel arrays if desired. 
     The gas injection grid  340  ( 340 A,  340 B), depicted in  FIGS. 10 through 14  can be fabricated from a metal, such as aluminum, or a ceramic, such as alumina. Alternatively, the gas injection grid  340  can be fabricated from quartz, silicon, silicon carbide, silicon nitride, aluminum nitride, or carbon. Additionally, the gas injection grid  340  can be protected with a coating. For example, the coating can comprise one of a surface anodization, a coating formed using plasma electrolytic oxidation, or a spray coating such as a thermal spray coating. In an example, the coating can comprise at least one of Al 2 O 3  and Y 2 O 3 . In another example, the coating comprises at least one of a III-column element (column III of periodic table) and a Lanthanon element. In another example, the III-column element comprises at least one of Yttrium, Scandium, and Lanthanum. In another example, the Lanthanon element comprises at least one of Cerium, Dysprosium, and Europium. In another embodiment, the compound forming the coating comprises at least one of Yttria (Y 2 O 3 ), Sc 2 O 3 , Sc 2 F 3 , YF 3 , La 2 O 3 , CeO 2 , Eu 2 O 3 , and DyO 3 . In another example, the coating can comprise Keronite (surface coating treatment commercially available from Keronite Limited, Advanced Surface Technology, PO Box 700, Granta Park, Great Abington, Cambridge CB1 6ZY, UK). In another example, the coating can comprise at least one of silicon, silicon carbide, alumina, Teflon, Vespel, or Kapton. 
     Referring again to  FIG. 1 , substrate  125  can be affixed to the substrate holder  120  via a mechanical clamping system, or an electrical clamping system, such as an electrostatic clamping system. Furthermore, substrate holder  120  can further include a cooling system including a re-circulating coolant flow that receives heat from substrate holder  120  and transfers heat to a heat exchanger system (not shown), or when heating, transfers heat from the heat exchanger system. Moreover, gas can be delivered to the back-side of substrate  125  via a backside gas system to improve the gas-gap thermal conductance between substrate  125  and substrate holder  120 . Such a system can be utilized when temperature control of the substrate is required at elevated or reduced temperatures. For example, the backside gas system can comprise a two-zone gas distribution system, wherein the helium gas gap pressure can be independently varied between the center and the edge of substrate  125 . In other embodiments, heating/cooling elements, such as resistive heating elements, or thermo-electric heaters/coolers can be included in the substrate holder  120 , as well as the chamber wall of the processing chamber  110  and any other component within the plasma processing system  100 . 
     Furthermore, substrate holder  120  can comprise an electrode through which radio frequency (RF) power is coupled to the processing plasma in process space  118 . For example, substrate holder  120  can be electrically biased at a RF voltage via the transmission of RF power from a RF generator (not shown) through an impedance match network (not shown) to substrate holder  120 . A typical frequency for the RF bias can range from about 0.1 MHz to about 100 MHz. RF bias systems for plasma processing are well known to those skilled in the art. Alternately, RF power is applied to the substrate holder electrode at multiple frequencies. Furthermore, impedance match network serves to improve the transfer of RF power to plasma in plasma processing chamber  10  by reducing the reflected power. Match network topologies (e.g. L-type, π-type, T-type, etc.) and automatic control methods are well known to those skilled in the art. 
     The temperature control system  170  of exemplary  FIG. 1  can include components necessary for controlling the temperature of the gas injection grid  130 . For example, the temperature control system  170  can include a heat exchanger for controlling the temperature of a heat transfer fluid, a pump and mass flow controller for delivering and controlling the flow rate of the heat transfer fluid to one or more channels in the gas injection grid  130 , temperature sensing devices, a controller, etc. 
     The electric bias control system  175  can include components necessary for electrically biasing the gas injection grid  130 . The electric bias can include a direct current (DC) electrical bias, or an alternating current (AC) electrical bias, or a combination thereof. For example, the electrical bias may include a radio frequency (RF) electric bias. The electric bias control system  175  can include a voltage/current source or power source, voltage or current or impedance measuring devices, a controller, etc. 
     The pumping system  180  of exemplary  FIG. 1  can include a turbo-molecular vacuum pump (TMP) capable of a pumping speed up to about 5000 liters per second (and greater) and a gate valve for throttling the chamber pressure. In conventional plasma processing devices utilized for dry plasma etch, a 1000 to 3000 liter per second TMP is generally employed. Moreover, a device for monitoring chamber pressure (not shown) can be coupled to the processing chamber  110 . The pressure measuring device can be, for example, a Type 628B Baratron absolute capacitance manometer commercially available from MKS Instruments, Inc. (Andover, Mass.). 
     Still referring to  FIG. 1 , control system  190  can comprise a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate and activate inputs to plasma processing system  100  as well as monitor outputs from plasma processing system  100 . Moreover, the controller  190  may be coupled to and may exchange information with the processing chamber  110 , substrate holder  120 , plasma source  130 , gas injection grid  140 , first gas supply  150 , second gas supply  160 , temperature control system  170 , electric bias control system  175 , and pumping system  180 . For example, a program stored in the memory may be utilized to activate the inputs to the aforementioned components of the plasma processing system  100  according to a process recipe in order to perform an etching process, or a deposition process. One example of the controller  190  is a DELL PRECISION WORKSTATION 610™, available from Dell Corporation, Austin, Tex. 
     The controller  190  may be locally located relative to the plasma processing system  100 , or it may be remotely located relative to the plasma processing system  100 . For example, the controller  190  may exchange data with the plasma processing system  100  using at least one of a direct connection, an intranet, the Internet and a wireless connection. The controller  190  may be coupled to an intranet at, for example, a customer site (i.e., a device maker, etc.), or it may be coupled to an intranet at, for example, a vendor site (i.e., an equipment manufacturer). Additionally, for example, the controller  190  may be coupled to the Internet. Furthermore, another computer (i.e., controller, server, etc.) may access, for example, the controller  190  to exchange data via at least one of a direct connection, an intranet, and the Internet. As also would be appreciated by those skilled in the art, the controller  190  may exchange data with the plasma processing system  100  via a wireless connection. 
     Referring now to  FIG. 15 , a method of operating a plasma processing system is described. The method includes a flow chart  500  beginning in  510  with disposing a substrate in a plasma processing system, such as the plasma processing system described in any of  FIGS. 1 through 14 . For example, a substrate can be disposed in a processing chamber having an upper chamber portion configured to define a plasma space and a lower chamber portion configured to define a process space. 
     In  520 , a first gas is introduced to the plasma space from a gas injection grid positioned between the upper chamber portion and the lower chamber portion as described above, or by alternative gas injection schemes. The first gas comprises plasma forming gas, or an ionizable gas. For example, the first gas can include an inert gas, such as a Noble gas (i.e., helium, argon, xenon, krypton, neon). In  530 , a second gas is introduced to the process space from the gas injection grid or any other gas injection scheme. The second gas comprises a process gas. For example, the second gas can include a halogen containing gas, such as Cl 2 , HBr, SF 6 , NF 3 , etc. Additionally, for example, the second gas can include a C x F y  containing gas, such as CF 4 , C 4 F 6 , C 4 F 8 , C 5 F 8 , where x and y are integers greater than or equal to unity. The first or second gas may be injected using spatial control techniques such as those described above. 
     In  540 , plasma is formed in the plasma space from the first gas using a plasma source coupled to the upper chamber portion. The plasma source may be any of the sources described above. In  550 , process chemistry is formed in the process space to treat the substrate by coupling the process space to the plasma space through a grid such as the gas injection grid, which allows diffusion of the plasma into the process space as described above. 
     Referring now to  FIG. 16 , a method of controlling the uniformity in a plasma processing system is provided according to an embodiment. The method comprises a flow chart  600  beginning in  610  with disposing a substrate in a plasma processing system, such as the plasma processing system described in any of  FIGS. 1 through 14 . For example, a substrate can be disposed in a processing chamber having an upper chamber portion configured to define a plasma space and a lower chamber portion configured to define a process space. 
     In  620 , a first gas is introduced to the plasma space from a gas injection grid positioned between the upper chamber portion and the lower chamber portion. Optionally, the introduction of the first gas into the plasma space occurs from multiple zones formed in the gas injection grid as described above. Each zone for introducing the first gas includes a gas channel formed in the gas injection grid having one or more injection orifices, and the gas channel is independently coupled to a first gas supply system. Each zone can, for example, be formed in the radial directions, as illustrated in  FIGS. 13 and 14 , however, other spatial distributions can be used as described above. Such configurations allow for different flow rates and/or gas compositions across the grid. 
     In  630 , a second gas is introduced to the process space from the gas injection grid. Optionally, the introduction of the second gas into the plasma space occurs from multiple zones formed in the gas injection grid as described above. Where the first gas is introduced without spatial control, the second gas is introduced with spatial control. It is only necessary that one of the first and second gasses is injected by a method for providing spatial control, however both gasses can be injected in this way. Moreover, spatial temperature control may be provided as discussed above. Each zone for introducing the second gas includes a gas channel formed in the gas injection grid having one or more injection orifices, and the gas channel is independently coupled to a second gas supply system. Each zone can, for example, be formed in the radial directions, similar to the scheme illustrated for the first gas in  FIGS. 13 and 14 . 
     In  640 , the flow of the first gas into the plasma space is adjusted in order to provide spatial control of processing of the substrate. In a preferred embodiment, spatially uniform processing is achieved at the substrate. The local flow rate of the first gas into the plasma space can either raise or lower the local plasma density. For example, during high power operation of the plasma source, the hot plasma can be super heated, and therefore an increase in flow rate can lead to an excess of ionization of the first gas (i.e., plasma density increases). Alternatively, for example, during low power operation of the plasma source, the hot plasma is sustaining itself, and an increase in the flow rate can lead to quenching of the electron temperature (i.e., quenching of the collisions between neutrals and electrons), thus leading to a reduction in the plasma density. In one example, the gas injection grid can include, as described above, multiple zones for introducing the first gas into the plasma space. The flow rate for each zone can be utilized within the process recipe, for an etch or deposition process, in order to achieve the optimal spatial distribution of the plasma density in the plasma space for the specific process. For instance, a design of experiment (DOE) can be performed to determine the optimal set of flow rates for each of the zones to produce the optimal results. 
     Optionally, the flow of the second gas into the process space is adjusted in order to provide spatially uniform processing of the substrate. 
     In  650 , plasma is formed in the plasma space from the first gas using a plasma source coupled to the upper chamber portion. In  650 , process chemistry is formed in the process space to treat the substrate by coupling the process space to the plasma space through the gas injection grid. 
     Although only certain exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.