Abstract:
Plasma processing chamber having a bottom electrode assembly is disclosed. The assembly has an inner bottom electrode for supporting a substrate and an outer bottom electrode disposed outside of the inner bottom electrode. The outer bottom electrode defines a region for chamber cleaning, and the outer bottom electrode includes a conductive ring and an inductive coil placed under the conductive ring. Further included is a dielectric material disposed between the inner bottom electrode and the outer bottom electrode, and the dielectric material separates the inner bottom electrode from the outer bottom electrode. A switch is provided for connecting radio frequency (RF) power to either the inner bottom electrode or the outer bottom electrode. The chamber also includes a top electrode assembly with a top electrode. The top electrode is disposed above both the inner and outer bottom electrodes.

Description:
CLAIM OF PRIORITY 
       [0001]    This application is a continuation application claiming priority under 35 U.S.C. 120 of U.S. patent application Ser. No. 13/191,402, filed on Jul. 26, 2011, and entitled “Methods for Plasma Cleaning an Internal Peripheral Region of a Plasma Processing Chamber, which claims priority as a divisional under 35 U.S.C. 120 of U.S. patent application Ser. No. 11/355,458, filed on Feb. 15, 2006, and entitled “Plasma Processing Reactor With Multiple Capacitive and Inductive Power Sources.” The disclosure of these applications are incorporated herein by reference in their entirety for all purposes. 
     
    
     BACKGROUND 
       [0002]    In the fabrication of semiconductor based devices (e.g. integrated circuits or flat panel displays), layers of material may alternately be deposited onto and etched from a substrate surface (e.g., the semiconductor wafer or the glass panel). As is well known in the art, the etching of the deposited layer(s) may be accomplished by a variety of techniques, including plasma-enhanced etching. In plasma-enhanced etching, the actual etching of the substrate takes place inside a plasma processing chamber. During the etching process, a plasma is formed from a suitable etchant source gas to etch areas of the workpiece that are unprotected by the etch mask, leaving behind the desired pattern. 
         [0003]    During plasma etching of a substrate, etch byproduct, which is made of polymers formed by photoresist or etched material layer with etching chemistry, is mainly deposited on the peripheral chamber hardware. The deposited byproduct accumulates with subsequent substrate etching. To improve device yield of substrate manufacturing, it is important to maintain a reproducible chamber, which can be achieved by performing a chamber cleaning process periodically after one or more substrate has been etched. Typically, chamber cleaning is performed after etching every substrate. 
         [0004]    Capacitively coupled vacuum plasma systems are frequently employed to etch dielectric material from a semiconductor substrate. The capacitive systems have the advantages of causing low plasma damage and having higher selectivity to the underlayer and photoresist layer. However, when a capacitively coupled plasma is used to clean the chamber after substrate etching, the capacitively coupled plasma, which has relatively high ion energy, would bombard the exposed electrostatic chuck. The electrostatic chuck is used to support the substrate during substrate etching, and bombarding the exposed electrostatic chuck results in electrostatic chuck lifetime degradation and particle generation. In addition, the capacitively coupled plasma generated by the top and bottom electrodes in the chamber is mainly concentrated in the center region above the electrostatic chuck and is not effective in cleaning the peripheral chamber hardware. In order to fully clean the peripheral chamber hardware, extended cleaning time is needed, which impacts the manufacturing throughput. In current capacitively coupled plasma reactors, the chamber clean after processing (or etching) each substrate is generally optimized within the constraints mentioned above. 
         [0005]    In view of the foregoing, there is a need for a method and apparatus that provides an improved chamber cleaning mechanism to increase electrostatic chuck lifetime, to improve substrate yield, and to increase manufacturing throughput. 
       SUMMARY 
       [0006]    Broadly speaking, the embodiments of the present invention fill these needs by providing an improved chamber cleaning mechanism. In addition, the embodiments of the present invention provide additional knobs to tune the etch processes. It should be appreciated that the present invention can be implemented in numerous ways, including as a process, an apparatus, or a system. Several inventive embodiments of the present invention are described below. 
         [0007]    In one embodiment, a plasma processing chamber is disclosed. The chamber includes a bottom electrode assembly. The bottom electrode assembly includes an inner bottom electrode for supporting a substrate and defining a center region for substrate etching. Also included in the bottom electrode assembly is an outer bottom electrode disposed outside of the inner bottom electrode. The outer bottom electrode defining a region for chamber cleaning, and the outer bottom electrode includes a conductive ring and an inductive coil placed under the conductive ring. Further included is a dielectric material disposed between the inner bottom electrode and the outer bottom electrode, and the dielectric material separates the inner bottom electrode from the outer bottom electrode. A switch is provided for connecting radio frequency (RF) power to either the inner bottom electrode or the outer bottom electrode. The chamber also includes a top electrode assembly with a top electrode. The top electrode is disposed above both the inner and outer bottom electrodes. 
         [0008]    In another embodiment, a plasma processing chamber is disclosed. The chamber includes bottom electrode assembly defined by, (i) an inner bottom electrode for supporting a substrate and defining a center region for substrate etching, the inner bottom electrode having a connection to a first RF power; (ii) an outer bottom electrode disposed outside of the inner bottom electrode, the outer bottom electrode defining a region for chamber cleaning, wherein the outer bottom electrode includes a conductive ring connected to ground; and (iii) a dielectric material disposed between the inner bottom electrode and the outer bottom electrode, the dielectric material separating the inner bottom electrode from the outer bottom electrode. The chamber also includes a top electrode assembly having a first top electrode disposed above the inner bottom electrode and a second top electrode that surrounds the first top electrode and is disposed above the outer bottom electrode of the bottom electrode assembly, second top electrode defined by, (i) an inductive coil buried in a dielectric material; (ii) a Faraday shield placed below the dielectric material; and (iii) a dielectric ring is placed below the Faraday shield, the dielectric ring is configured to face the region for chamber cleaning. 
         [0009]    Other aspects and advantages of the invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will be readily understood by the following detailed description in conjunction with the accompanying drawings, and like reference numerals designate like structural elements. 
           [0011]      FIG. 1A  shows a schematic diagram of one embodiment of a substrate etching system. 
           [0012]      FIG. 1B  shows a process flow of generating a cleaning plasma in a plasma system. 
           [0013]      FIG. 1C  shows a process flow of generating an etching plasma in a plasma system. 
           [0014]      FIG. 2  shows a schematic diagram of another embodiment of a substrate etching system. 
           [0015]      FIG. 3A  shows a schematic diagram of another embodiment of a substrate etching system. 
           [0016]      FIG. 3B  shows a process flow of generating a cleaning plasma in a plasma system. 
           [0017]      FIG. 3C  shows a process flow of generating an etching plasma in a plasma system. 
           [0018]      FIG. 4  shows a schematic diagram of yet another embodiment of a substrate etching system. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Several exemplary embodiments for an improved and more effective and more flexible chamber cleaning and etching system, method and apparatus will now be described. It will be apparent to those skilled in the art that the present invention may be practiced without some or all of the specific details set forth herein. 
         [0020]    As described earlier, a reproducible chamber wall surface condition after etching each substrate would improve the yield. An effective in-situ chamber clean has become a key feature for next generation plasma etch reactor. One embodiment of the present invention provides a second plasma source surrounding the substrate support. The second plasma source, which is placed near the periphery of the process chamber, can be initiated during a chamber clean operation after substrate etching to clean the peripheral chamber hardware that has accumulated etching byproduct during substrate etching.  FIG. 1A  shows a cross-sectional view of a plasma processing apparatus  100  that has a second plasma source surrounding the substrate support. This embodiment includes a bottom electrode  131  that is composed of a conductive material, which is operatively coupled to a RF (radio frequency) match  138  and a RF power supply  139 . The bottom electrode  131  is also a substrate support and is part of a bottom electrode assembly  130 . In one embodiment, the RF power supply  139  is a multiple frequency power supply. For example, the power source can have a mixture of frequencies in the range between about 400 kHz to about 60 MHz. Plasma is generated when RF power is delivered from the bottom electrode  131  to the gas inside the process chamber. In one embodiment, the RF power supply delivers RF power levels of up to about 1 Watt to about 10 Watts. 
         [0021]    In one embodiment, the bottom electrode assembly  130  has a built-in cooling mechanism (not shown) that can cool the substrate to be in the temperature range between about −20° C. to about 70° C. Surrounding the substrate support is a conductive ring  133  that provides additional grounding path for plasma during substrate processing. Between the bottom electrode  131  and the conductive ring  133 , there is a dielectric ring  132  that insulate the substrate support and the conductive ring  133 . 
         [0022]    By way of example and not of limitation, the bottom electrode  131  has an area that is adapted to receive a 300 mm substrate. In one embodiment, the powered bottom electrode  131  is configured to receive a substrate (not shown) and is configured to clamp the substrate to the bottom electrode  131  during substrate etching operation. The substrate is electrostatically clamped or “chucked” to the bottom electrode using well-known systems and methods. These well-known systems and methods include coating the bottom electrode  131  with a dielectric material that incorporates high-voltage electrodes (not shown) for chucking and dechucking purposes. The plasma processing apparatus  100  includes chamber walls  140  which are grounded through a ground  135 . The ground  135  is separated from the bottom electrode  131  by a dielectric material  136 . 
         [0023]    A first top electrode  111  is disposed a short distance above the bottom electrode  131 . Generally, the top electrode  111  is made from a material that is compatible with the substrate to avoid contamination. The first top electrode  111  is part of a top electrode assembly  110 , which is connected to a ground  148  and provides a complete electrical circuit for the RF power. The first top electrode  111  has a surface area that may vary from that of the bottom electrode  131 . The top electrode assembly  110  is coupled to the chamber cover  117 , which is grounded through ground  118 . By way of example and not of limitation, the first top electrode  111  is composed of a conductive material such as silicon or silicon carbide. Additionally, by way of example and not of limitation, the first top electrode  111  is located about 2 cm to about 3 cm from the bottom electrode. 
         [0024]    Surrounding the top electrode  111  is a second top electrode  112 , made of an inductive coil  112 . The inductive coil  112  is buried in a dielectric material  113 . The coil  112  is coupled to a RF match  126 , which is coupled to a RF power source  127 . In one embodiment, the RF power source  127  can supply a mixed frequency power. The frequency of power the RF power source  127  can be single or multiple in the range between about 400 kHz to about 27 MHz. In one embodiment, the power to create the inductively coupled plasma is between about 0 watts to about 2000 watts. 
         [0025]    A Faraday shield  114  is placed below the dielectric material  113 . Surrounding the dielectric material  113  is a conductive block  115 , which makes electrical contact with the Faraday shield  114  to provide a grounding path for RF power from the bottom electrode  131 . Below and surrounding the outer edge of the Faraday shield  114  is a recessed dielectric ring  116 . In one embodiment, the dielectric ring  116  is composed of quartz. 
         [0026]    The Faraday shield  114  provides a RF grounding path to the RF power coming from any of the electrodes. The Faraday shield  114  also helps to maintain an area ratio between the grounding area and powering area in the process chamber so the voltage-drops in the chamber during capacitively coupled plasma processing do not change with the introduction of the inductive coil  112 . Maintaining the same area ratio allows the etching processes to remain consistent even with the introduction of the inductive coil  112 . In addition, the Faraday shield  114  blocks electrical field from the inductive source to minimize capacitive coupling of from the inductive coils  112  during inductive plasma processing to avoid sputtering of chamber components. Details of how to design Faraday shield can be founded in co-assigned U.S. patent application Ser. No. 10/232,564, filed on Aug. 30, 2002, entitled “Faraday Shield Disposed within an Inductively Coupled Plasma Etching Chamber,” and U.S. patent application Ser. No. 10/345,582, filed on Jan. 15, 2003, entitled “Dual Interleaved Faraday Shields For An Inductively Coupled Plasma Etching Chamber.” Both patent applications are incorporated herein by reference in their entirety for all purposes. During chamber clean, the coil  112  is powered by the RF power source  127  to produce inductively coupled plasma in region  150 . During chamber clean, the conductive ring  133  is grounded and the bottom electrode is floating; therefore, the inductively coupled plasma in region  150  is mainly concentrated between the inductive coil  112  and the conductive ring  133 . 
         [0027]    Surrounding the first top electrode  111  and the second top electrode  112  is an insulator  120 . Below the insulator  120  are plasma confinement rings  121 ,  122 ,  123 . It should be appreciated that here could be one or more plasma confinement rings. The confinement rings  121 ,  122 ,  123  provide confinement to the plasma that is generated within the processing chamber. In one embodiment, the confinement rings  121 ,  122 , and  123  are composed of quartz. Details about the plasma confinement rings can be founded in co-assigned U.S. Pat. No. 6,744,212, issued on Jun. 1, 2004, entitled “Plasma Processing Apparatus And Method For Confining An RF Plasma Under Very High Gas Flow and RF Power Density Conditions,” and U.S. Pat. No. 6,872,281, issued on Mar. 29, 2005, entitled “Chamber Configuration For Confining A Plasma.” Both patents are incorporated herein by reference. 
         [0028]    A gas feed  128  is coupled to the center of the top electrode assembly  110 . The gas supplied by the gas feed  128  into the process chamber plenum  180  can be a single gas or a gas mixture of more than one gas. In one embodiment, once the gas reaches the top electrode assembly  110 , the gas feed  128  supplies the gas to the process chamber from both the center and the edge of the first top electrode  111 . In one embodiment, the first top electrode  111  is also a gas distribution showerhead. By way of example and not of limitation, the total gas flow rate is up to 1500 sccm. In one embodiment, the top electrode assembly  110  also has a heater plate (not shown) that can be used to maintain the temperature of the top electrode  111  to be between about 22° C. to about 200° C. 
         [0029]    As described earlier, the top electrode  111  is grounded through ground  148 . The top electrode  111  can also be coupled to a RF power source (not shown) or a DC power source (not shown). The power source for the capacitively coupled plasma between the first top electrode  111  and the bottom electrode  131  can come from the power source coupled to the first top electrode  111 , instead of the bottom electrode  131 . When the power is supplied from the top electrode  111 , the bottom electrode  131  is grounded. In addition, the top and bottom electrodes can supply RF power source alternatively. For example, the RF power source for the first top electrode  111  can also have a mixture of frequencies at 2 MHz, 27 MHz, and 60 MHz. 
         [0030]    The inductive plasma source can create a high density plasma in the peripheral region  150  without any significant sputtering of the chamber wall materials. As described earlier, sputtering of the chamber wall materials which could contaminate the chamber or decrease the lifetime of the parts. The inductive plasma source can effectively clean polymer (or etch byproduct) deposited on the peripheral chamber hardware, which comes in contact with the etch process plasma. 
         [0031]      FIG. 1B  shows an embodiment of a process flow for creating a chamber cleaning plasma. At operation  161 , chamber cleaning gas, such as O 2 , CF 4 , etc., is supplied to the plasma process chamber. At operation  163 , RF power is supplied to the inductive coil  112  of the plasma process chamber plenum  180  to generate the chamber cleaning plasma. The chamber cleaning plasma can then be used to clean the chamber. During chamber cleaning, the bottom electrode  131  is floating. The chamber cleaning plasma in region  150  is away from the bottom electrode  131  and is mainly disposed between the inductive electrode  112  and the conductive ring  133  of  FIG. 1A . 
         [0032]    Typical parallel plate capacitive coupled plasma shows a drop in plasma density near the edge of the substrate (or wafer) during etching process. The inductive plasma source provides a radial uniformity control knob. The inductive plasma can be turned on during an etching process to provide additional plasma density at the edge of the substrate without affecting the RF ground path of the main capacitive powers. It should be appreciated that the RF grounding path is not affected due to the usage of the Faraday shield. In addition, the inductive source plasma can also provide plasma to processes that require high plasma density and very low ion energy on the substrate, for example photoresist stripping for low-k dielectric etch. Consequently, usage of the inductive source plasma can increase the etch process window of the reactor. 
         [0033]      FIG. 1C  shows an embodiment of a process flow for generating an etching plasma. At operation  171 , etching gas(es), such as AR, C 4 F 8 , and O 2  for high aspect ratio contact etch (HARC), or Ar, CF 4 , CHF 3 , and O 2  for oxide tech, is supplied to the plasma processing chamber. After the etching gas enters the process chamber, RF power is supplied to the capacitive electrode and the inductive electrode to generate an etching plasma at operation  173 . The etching plasma generated has a capacitive component and an inductive component. The inductive component near the substrate edge can increase the plasma density at the substrate edge to make up for the drop of plasma density at the edge of the substrate, as described above. Therefore, the etching plasma can become more uniform across the substrate surface by the addition of the inductive component at the edge of the substrate. 
         [0034]      FIG. 2  shows a variation  200  of the previous embodiment  100  of  FIG. 1A . Two sets of inductive coils  212 A,  212 B are placed in the top electrode assembly  210 . The two set of inductive coils are made of one inner coil  212 A and one outer coil  212 B. The Faraday shield  214  is placed over the entire top electrode  211  to cover both the inner coil  212 A and the outer coil  212 B. Faraday shield  214  has similar functions as the Faraday shield  114  of  FIG. 1A  described above. Both sets of coils  212 A,  212 B are coupled to a RF match  226 , which is coupled to a RF power supply  227 . Due to the placement of the two sets of coils  212 A,  212 B, the process gas is supplied to the top electrode  211 , which may also be a showerhead, through a center gas feed  228 B and an edge gas feed  228 A. Other components in  FIG. 2  are similar to those already mentioned in  FIG. 1A . 
         [0035]    During chamber cleaning, both inductive coils  212 A and  212 B can be powered, or only the outer coil  212 B is powered, to create a cleaning plasma. If both coils are powered during chamber clean, a percentage of the power can be supplied to the inner coil, for example 0% to 50%, while the remaining power is supplied to the outer coil  112 B, for example 50% to 100%. It should be appreciated that the soft inductive plasma would not damage the electrostatic chuck during cleaning. It should be further appreciated that the additional inner inductive coil provides an additional processing tuning knob for the chamber cleaning process. The inner and outer coils can be powered at a different frequency or frequency mixture. Under such a circumstance, the inner and outer coils would need separate power supplies. Additional power supply would be added. 
         [0036]    In one embodiment, an inductive plasma in region  250  is created by first supplying a cleaning gas (or a cleaning gas mixture) into the plasma process chamber and then powering the inductive coils  212 A and  212 B by supplying all the power to coil  212 B. During chamber cleaning operation, the bottom electrode  231  may be kept floating and the conductive ring  233  is grounded. 
         [0037]    As described above, the inductive plasma source can create high-density plasma in the peripheral area without any significant sputtering of the chamber wall materials, which could contaminate the chamber or decrease the lifetime of the parts. The inductive plasma source can effectively clean polymer (or etch byproduct) deposited on the peripheral chamber hardware, which comes in contact with the etch process plasma. 
         [0038]    Both or one of the inductive coils  212 A,  212 B can also be powered, as well as the capacitive plasma power, to tune the etch plasma uniformity. In addition to the capacitively coupled plasma generated between the top electrode  211  and the bottom electrode  231 , the inductive power sources  212 A,  212 B can also be turned on to created inductive plasma, and can be tuned to improve plasma uniformity across the substrate during an etching process. Typically for capacitively coupled plasma, the plasma density is low at the edge of the substrate. The inductive coil(s)  112  in  FIG. 1A  and the outer coil(s)  212 B in  FIG. 2  can help raise the ion density at the edge of the substrate. The inner coil(s)  212 A and outer coil(s)  212 B of  FIG. 2  can also be used simultaneously to tune the plasma density. As mentioned above, a percentage of the power can be supplied to the inner coil(s)  212 A, and the remainder supplied to the outer coil(s)  212 B. The inner and outer coils  212 A,  212 B in  FIG. 2  provides additional process tuning knobs for etching processes. For some applications, only inductive power from the inductive coils (inner, outer, or both) is utilized to generate inductive plasma. 
         [0039]    By using Faraday shield  214 , the RF grounding path is not affected. In addition, the inductive source plasma can provide plasma to processes that require high plasma density and very low ion energy on the substrate, such as photoresist stripping or low-k dielectric etch. Therefore, the usage of the two sets of inductive coils would increase the process windows for etch processes. The process flow to generate an etching plasma by the embodiment shown in  FIG. 2  is similar to the process flow of  FIG. 1C , except that the single inductive electrode is replaced with double inductive electrodes (coils  212 A,  212 B). The etching plasma generated has a capacitive component and an inductive component. The inductive component can be tuned to increase the plasma uniformity across the substrate. 
         [0040]    Another embodiment  300  of the current invention is shown in  FIG. 3A . In  FIG. 3A , an outer bottom electrode  335  is placed under a conductive ring  333 , in addition to the inner bottom electrode  331 . The inner bottom electrode  331  is configured to support a substrate. The outer bottom electrode  335  can be coupled to the same RF power source  339  as the inner bottom electrode  331 , which is part of the bottom electrode assembly  330 . RF power source  339  can supply single frequency or multiple frequencies in the range between about 400 kHz to about 60 MHz. The RF power source  339  supplies power to the inner bottom electrode  331  and to the outer bottom electrode  335 , and is connected to a RF match  338 . In one embodiment, switch  336  controls application of the RF power to the electrodes. During substrate etching, switch  336  controls the RF power to be supplied to the inner bottom electrode  331 . During this process, the outer bottom electrode  335  could be coupled to ground  337  or to a RF tuning block kit  357 . The RF tuning block kit  357  allows selective grounding of certain frequency of the RF power supplied by power supply  339  to the inner bottom electrode  331 . For example, if the RF power supplied to the inner bottom electrode  331  includes 2 MHz, 27 MHz and 60 MHz. Selective grounding by the RF tuning block kit  357  allows grounding of one or two particular frequencies, such as 60 MHz, to tune the etching processing uniformity. 
         [0041]    Separate power sources can also be used to supply power simultaneously or alternately to the inner bottom electrode  331  and to the outer bottom electrode  335 . Other components in  FIG. 3A  are similar to those already mentioned in  FIG. 1A . During chamber cleaning, the power is supplied to the outer bottom electrode  335  to provide a capacitively coupled plasma in region  350  to clean the peripheral chamber. The capacitively coupled plasma in region  350  is generated between the top electrode  311  and the outer bottom electrode  335 . During the cleaning process, the bottom electrode may be floating; therefore, the capacitively coupled cleaning plasma, and its destructive effects are kept away from the exposed inner bottom electrode  331  (or electrostatic chuck). In turn, the cleaning plasma does not bombard the inner bottom electrode (or electrostatic chuck), and hence extends the lifetime of the inner bottom electrode (or electrostatic chuck). In addition, not as many particles are generated as using the capacitively coupled plasma from the bottom electrode  331  as compared to prior cleaning technologies. 
         [0042]    The peripheral capacitive plasma source creates high-density plasma in the peripheral region  350 . It should be appreciated that the capacitive plasma source can effectively clean polymer (or etch byproduct) deposited on the peripheral chamber hardware, which comes in contact with the etch process plasma. 
         [0043]      FIG. 3B  shows an embodiment of a process flow for creating a chamber cleaning plasma. At operation  361 , chamber cleaning gas, such as O 2 , CF 4 , etc., is supplied to the plasma process chamber. At operation  363 , RF power is supplied to the outer bottom electrode of the plasma process chamber to generate the chamber cleaning plasma. The chamber cleaning plasma can then be used to clean the chamber. During chamber cleaning, the inner bottom electrode is kept floating. The chamber cleaning plasma in the peripheral region is substantially away from the bottom electrode and is mainly disposed between the outer bottom electrode and the top electrode. 
         [0044]    In addition, the peripheral capacitive plasma source provides the ability to include a radial uniformity control knob. The peripheral capacitive plasma can be turned on during etching process to improve the etch plasma uniformity near the edge of the electrodes for the main capacitively coupled plasma. 
         [0045]      FIG. 3C  shows an embodiment of a process flow for generating an etching plasma. At operation  371 , etching gas(es), such as AR, C 4 F 8 , and O 2  for high aspect ratio contact etch (HARC), or Ar, CF 4 , CHF 3 , and O 2  for oxide etch, is supplied to the plasma processing chamber. At operation  373 , RF power is supplied to the inner bottom electrode ( 331 ) and the outer bottom electrode ( 335 ) to generate an etching plasma. It should be appreciated that the outer bottom electrode helps to increase the plasma density near the edge of the substrate. 
         [0046]    Another embodiment of the current invention is shown in  FIG. 4 . In  FIG. 4 , a second bottom electrode  435 , formed by an inductive coil, is placed under the conductive ring  433  and a Faraday shield  414 . The second bottom electrode  435  can be coupled to the same RF power source at the first bottom electrode  431 . The RF power source  439  supplies RF power to the first bottom electrode  431  or to the second bottom electrode  435  and is controlled by a switch  436 . RF power source  439  can supply single frequency or multiple frequencies in the range between about 400 kHz to about 60 MHz. The RF power source  439  supplies power to the inner bottom electrode  431  and to the outer bottom electrode  335 , and is connected to a RF match  438 . In one embodiment, switch  436  controls application of the RF power to the electrodes. During substrate etching, switch  436  controls the RF power to be supplied to the inner bottom electrode  431 . During this process, the outer bottom electrode  335  could be coupled to ground  437  or to a RF tuning block kit  457 . Separate RF power supplies can also be used to provide RF power to the bottom electrode  431  and to the second bottom electrode  435 . During substrate etching, the power is supplied to the bottom electrode  431 . Other components in  FIG. 4  are similar to those already mentioned in  FIG. 1A . 
         [0047]    During chamber cleaning, the cleaning gas is first supplied to the plasma process chamber. Afterwards, the power is supplied to the second bottom electrode  435  to provide inductively coupled plasma in region  450  to clean the peripheral chamber hardware. The inductively coupled plasma in region  450  is generated between the top electrode  411  and the second bottom electrode  435  and exists mainly near the edge of the chamber. Since the plasma is near the edge of the chamber and is generated from an inductive source (low ion energy), the plasma does not bombard the bottom electrode (or electrostatic chuck) as much and extends the life-time of the bottom electrode, or electrostatic chuck. Additionally, the plasma does not create as many particles as using the capacitively coupled plasma from the first bottom electrode  431 . 
         [0048]    As described above, the inductive plasma source can create high-density plasma in the peripheral area without any significant sputtering of the chamber wall materials, which could contaminate the chamber or decrease the lifetime of the parts. The inductive plasma source can effectively clean polymer (or etch byproduct) deposited on the peripheral chamber hardware, which comes in contact with the etch process plasma without the deleterious effects of prior art techniques. 
         [0049]    Typical parallel plate capacitive coupled plasma shows a drop in plasma density near the edge of the chamber during etching process. The inductive plasma source mentioned above provides a radial uniformity control knob. The inductive plasma can be turned on during etching process to provide additional plasma density at the edge of the electrodes without affecting the RF ground path of the main capacitive powers. In addition, the inductive source plasma can provide plasma to processes that require high plasma density and very low ion energy on the substrate, for example photoresist stripping or low-k dielectric etch. Therefore, usage of the extra peripheral electrode can increase the process windows for etching processes as well as more effectively clean the chamber between etch operations. 
         [0050]    The plasma process chamber described above provides a range of plasma density, ion energy, and chemistry control for a wide range of process application, such as dual damascene multi-step processes, high aspect ratio contact etch (HARC), strip, etc., along with effective chamber clean by a combination of capacitive and inductive plasma sources. In one embodiment, the effective chamber clean can be applied for next generation particle control to improve yield and to extend the life-time of the electro-static chucks used in the etching chamber. 
         [0051]    The plasma process chamber described above provides knobs to control radial uniformity of process parameters on the substrate. The process applications that use multi-step recipes involve a range of process pressure, RF power, and chemistries that produce a wide range of center to edge uniformity. The availability of in-situ control knobs provides flexibility for maintaining tight uniformity control for the process applications that use multi-step recipes as feature sizes continue to shrink. 
         [0052]    Although the foregoing invention has been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. Accordingly, the present embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein, but may be modified within the scope and equivalents of the appended claims.