Patent Publication Number: US-2021166915-A1

Title: Electrostatic chuck with multiple radio frequency meshes to control plasma uniformity

Description:
BACKGROUND 
     Field 
     Embodiments disclosed herein generally relate to apparatus and methods for tuning a plasma in a semiconductor substrate manufacturing process, more specifically, apparatus and methods for tuning a plasma near an edge of a semiconductor substrate. 
     Description of the Related Art 
     In the manufacture of integrated circuits and other electronic devices, plasma processes are often used for deposition or etching of various material layers. Plasma-enhanced chemical vapor deposition (PECVD) process is a chemical process wherein electro-magnetic energy is applied to at least one precursor gas or precursor vapor to transform the precursor into a reactive plasma. Plasma may be generated inside the processing chamber, i.e., in-situ, or in a remote plasma generator that is remotely positioned from the processing chamber. This process is widely used to deposit materials on substrates to produce high-quality and high-performance semiconductor devices. 
     In the current semiconductor manufacturing industry, transistor structures have become increasingly complicated and challenging as feature size continues to decrease. To meet processing demands, advanced processing control techniques are useful to control cost and maximize substrate and die yield. Normally, the dies at the edge of the substrate suffer yield issues such as contact via misalignment, and poor selectivity to a hard mask. On the substrate processing level, there is a need for advancements in process uniformity control to allow fine, localized process tuning as well as global processing tuning across the whole substrate. 
     Therefore, there is a need for methods and apparatus to allow fine, localized process tuning at the edge of the substrate. 
     SUMMARY 
     Embodiments disclosed herein generally relate to an apparatus and method for plasma tuning near a substrate edge. In one implementation, a method for tuning a plasma in a chamber is disclosed. The method includes providing a first radio frequency power to a central electrode embedded in a substrate support assembly, providing a second radio frequency power to an annular electrode embedded in the substrate support assembly at a location different than the central electrode, wherein the annular electrode is spaced from the central electrode and circumferentially surrounds the central electrode, monitoring parameters of the first and second radio frequency power, and adjusting one or both of the first and second radio frequency power based on the monitored parameters. 
     In another embodiment, a semiconductor processing chamber is disclosed. The semiconductor processing chamber includes a pedestal disposed in the chamber having a first electrode and a second electrode circumferentially surrounding the first electrode, a high frequency power source and a low frequency power source coupled to both of the first electrode and the second electrode, a power splitter disposed between the high frequency power source and the low frequency power source, and the first electrode and the second electrode, and an electrode tuning circuit coupled to both of the first electrode and the second electrode. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this disclosure and are therefore not to be considered limiting of its scope, for the disclosure may admit to other equally effective embodiments. 
         FIG. 1  illustrates a cross sectional view of a processing chamber, according to one aspect of the disclosure. 
         FIG. 2  illustrates a top view of a substrate assembly, according to one aspect of the disclosure. 
         FIG. 3  illustrates a partial perspective view of a substrate assembly, according to one aspect of this disclosure. 
         FIG. 4  is a schematic diagram of one embodiment of a power filter that may be utilized with the processing chamber of  FIG. 1 . 
         FIG. 5  is a schematic diagram of another embodiment of a power filter that may be utilized with the processing chamber of  FIG. 1 . 
         FIGS. 6A-6D  are schematic diagrams showing various embodiments of tuning circuits for tuning the first pedestal electrode and the second pedestal electrode. 
         FIG. 7  and  FIGS. 8A-8C  are schematic diagrams depicting various power splitting circuits that may be used with the power filters as described herein. 
         FIG. 9  is a schematic diagram depicting a circuit configured to counter inductance by the rods in the stem of the pedestal. 
         FIG. 10  is a schematic diagram depicting a power divider circuit according to another embodiment. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. 
     DETAILED DESCRIPTION 
     The present disclosure generally relates to methods and apparatus for controlling a plasma sheath near a substrate edge. The disclosure provides radio frequency (RF) circuits and methods to adjust the distribution of RF power to more than one mesh embedded in a substrate support or pedestal that also functions as an electrostatic chuck. The methods and apparatus described herein apply whether the embedded meshes are a source of RF power (e.g., a powered electrode or powered electrodes), or whether the meshes are the destination for RF power (e.g., a ground electrode or ground electrodes). Embodiments disclosed herein allow the modulation of the plasma profile uniformity above a substrate. Changing the plasma distribution leads to improved uniformity of film parameters on the substrate, for example, deposition rate, film stress, refractive index, as well as other parameters. 
     Conventional plasma control techniques to modulate plasma include top and bottom tuners which only weakly modify the plasma properties at the edge of a substrate relative to the rest of the substrate. This disclosure provides tuning elements to affect the plasma profile at the substrate edge as well as affecting other regions of the substrate other than the edge. Previous approaches to modulate the plasma at the edge of a substrate involved different process kits or edge rings. However, these are generally process specific, and when more than one film is deposited (for example, silicon oxide and silicon nitride) in the same chamber, it can be difficult to optimize the uniformity for both processes using the same set of hardware. The present disclosure provides the ability to change the plasma profile without changing hardware. 
     The present disclosure provides a pedestal having a plurality of meshes embedded therein, and one of the meshes functions as a chucking electrode to chuck a substrate thereon. A voltage divider is utilized to control and/or adjust the RF power to different meshes, or the RF power to different mesh segments. The voltage division is done with a capacitive voltage divider, a series resonance divider, or a parallel resonance divider. The variable element in the circuit is a capacitor, but the resonance based dividers can use fixed circuit elements and employ a variable frequency generator to modulate the power division. The different legs following the divider may require additional filtering elements either to block one frequency and pass another, or to compensate for subsequent circuit elements intrinsic to the pedestal configuration. The power division hardware applies whether the embedded meshes are a source of RF power (e.g., an electrode or electrodes), or whether the meshes are the destination for RF power (e.g., ground). 
       FIG. 1  is a cross sectional view of a processing chamber  100 , according to one aspect of the disclosure. As shown, the processing chamber  100  is an etch chamber suitable for etching a substrate, such as substrate  125 . Examples of processing chambers that may be adapted to benefit from exemplary aspects of the disclosure are Producer® Etch Processing Chamber, and Precision™ Processing Chamber, commercially available from Applied Materials, Inc., located in Santa Clara, Calif., It is contemplated that other processing chambers, including those from other manufacturers, may be adapted to benefit from aspects of the disclosure. 
     The processing chamber  100  may be used for various plasma processes. In one aspect, the processing chamber  100  may be used to perform dry etching with one or more etching agents. For example, the processing chamber may be used for ignition of plasma from a precursor C x F y  (where x and y represent known compounds), O 2 , NF 3 , or combinations thereof. In another implementation the processing chamber  100  may be used for plasma enhanced chemical vapor deposition (PECVD) with one or more precursors. 
     The processing chamber  100  includes a chamber body  102 , a lid assembly  106 , and a pedestal  104 . The lid assembly  106  is positioned at an upper end of the chamber body  102 . The pedestal  104  is disposed inside the chamber body  102 , and the lid assembly  106  coupled to the chamber body  102  and enclosing the pedestal  104  in a processing volume  120 . The chamber body  102  includes a transfer port  126 , which may include a slit valve, formed in a sidewall thereof. The transfer port  126  is selectively opened and closed to allow access to the processing volume  120  by a substrate handling robot (not shown) for substrate transfer. 
     An electrode  108  is provided as a portion of the lid assembly  106 . The electrode  108  may also function as a gas distributor plate  112  having a plurality of openings  118  for admitting process gas into the processing volume  120 . The process gases may be supplied to the processing chamber  100  via a conduit  114 , and the process gases may enter a gas mixing region  116  prior to flowing through the openings  118 . The electrode  108  is coupled to a source of electric power  142 , such as an RF generator. DC power, pulsed DC power, and pulsed RF power may also be used. An isolator  110 , which may be a dielectric material such as a ceramic or metal oxide, for example aluminum oxide and/or aluminum nitride, contacts the electrode  108  and separates the electrode  108  electrically and thermally from the chamber body  102 . A heater  119  is shown coupled to the gas distributor plate  112 . The heater  119  is coupled to an AC power source  121 . 
     The pedestal  104  is coupled to a lift mechanism through a shaft  144 , which extends through a bottom surface of the chamber body  102 . The lift mechanism may be flexibly sealed to the chamber body  102  by a bellows that prevents vacuum leakage from around the shaft  144 . The lift mechanism allows the substrate support  180  to be moved vertically within the chamber body  102  between a transfer position and a number of process positions to place the substrate  125  in proximity to the electrode  108 . 
     The pedestal  104  may be formed from a metallic or ceramic material, for example a metal oxide or nitride or oxide/nitride mixture such as aluminum, aluminum oxide, aluminum nitride, or an aluminum oxide/nitride mixture. A first pedestal electrode  122  and a second pedestal electrode  124  are provided in the pedestal  104 . The first pedestal electrode  122  and the second pedestal electrode  124  may be embedded within the pedestal  104  or coupled to a surface of the pedestal  104 . The first pedestal electrode  122  and the second pedestal electrode  124  may be a plate, a perforated plate, a mesh, a wire screen, or any other distributed arrangement. One or both of the first pedestal electrode  122  and the second pedestal electrode  124  may be a tuning electrode, and may be coupled to a tuning circuit  136  by a conduit  146 , for example a cable having a selected resistance such as 50Ω, disposed in a shaft  144  of the pedestal  104 . The tuning circuit  136  may have a sensor  138  and an electronic controller  140 , which may be a variable capacitor. The sensor  138  may be a voltage or current sensor, and may be coupled to the electronic controller  140  to provide further control over plasma conditions in the processing volume  120 . The first pedestal electrode  122  may also be a chucking electrode. 
     The first pedestal electrode  122  and the second pedestal electrode  124  are coupled to a power source  150 . The power source  150  may illustratively be a source of up to about 1000 W (but not limited to about 1000 W) of RF energy at a frequency of, for example, approximately 13.56 MHz, although other frequencies and powers may be provided as desired for particular applications. The power source  150  may be capable of producing AC power in multiple frequencies, such as 13.56 MHz and 2 MHz. The power source  150  may also produce either or both of continuous or pulsed DC power that may be utilized to chuck the substrate  125 . A mesh tuner  148  is shown coupled between the power source  150  and the first pedestal electrode  122  and the second pedestal electrode  124 . 
     An RF match  152  is coupled to each of the first pedestal electrode  122  and the second pedestal electrode  124  and the power source  150 . The RF match  152  includes a power splitter  154 . One or both of the RF match  152  and the mesh tuner  148  comprises a power filter (described below) for controlling power to the first pedestal electrode  122  and the second pedestal electrode  124 , 
       FIG. 2  illustrates a top view of a pedestal  104 , according to one aspect of the disclosure. The pedestal  104  includes a plurality of electrodes. The first pedestal electrode  122  and the second pedestal electrode  124  are a mesh, or a wire screen. The first pedestal electrode  122  and the second pedestal electrode  124  may be formed from aluminum or copper, or other electrically conductive metals or materials. 
     In one implementation, the second pedestal electrode  124  has a greater surface area than the first pedestal electrode  122 . In one implementation, the second pedestal electrode  124  has a greater diameter than the first pedestal electrode  122 . The second pedestal electrode  124  may surround the first pedestal electrode  122 . In one implementation, the first pedestal electrode  122  may function as a chucking electrode while also functioning as a first RF electrode. The second pedestal electrode  124  may be a second RF electrode that together with the first pedestal electrode  122  tunes the plasma. The first pedestal electrode  122  and the second pedestal electrode  124  may apply power at the same frequency or at different frequencies. The RF power to one or both of the first pedestal electrode  122  and the second pedestal electrode  124  may be varied in order to tune the plasma. For example, a sensor (not shown) may be used to monitor the RF energy from one or both of the first pedestal electrode  122  and the second pedestal electrode  124 . Data from the sensor device may be communicated and utilized to vary power applied to the RF power source for the first pedestal electrode  122  and/or the RF power source for the second pedestal electrode  124 . 
       FIG. 3  illustrates a partial perspective view of a pedestal  104 , according to one aspect of this disclosure. In this implementation, the second pedestal electrode  124  is disposed laterally adjacent the substrate  125  within the pedestal  104 . The second pedestal electrode  124  is disposed above the first pedestal electrode  122 , closer to the substrate  125 . 
       FIG. 4  is a schematic diagram of one embodiment of a power filter  400  that may be utilized with the processing chamber  100  of  FIG. 1 . In this embodiment, RF power for the processing chamber is provided from the bottom. For example, the gas distributor plate  112  is grounded and RF power for plasma formation is provided by the first pedestal electrode  122  and the second pedestal electrode  124 . 
     The power filter  400  includes the mesh tuner  148 , which may function as a power splitter. The power filter  400  includes a first circuit  405  and a second circuit  410 . Both of the first circuit  405  and the second circuit  410  are positioned between the power source  150  and the first pedestal electrode  122  and the second pedestal electrode  124 . In this embodiment, the power source  150  includes a high frequency RF generator  415  and a low frequency generator  420 . 
     The first circuit  405  includes an inductor  425  coupled between the low frequency generator  420  and a filter main lead  430 . The filter main lead  430  is coupled to both of the high frequency RF generator  415  and the low frequency generator  420 , and each of the first pedestal electrode  122  and the second pedestal electrode  124 . The filter main lead  430  is also coupled to the high frequency RF generator  415  and a first capacitor  435  is positioned therebetween The high frequency RF generator  415  is coupled to the filter main lead  430  and the second circuit  410 . The low frequency generator  420  and the first circuit  405  are coupled to the filter main lead  430  by the inductor  425 . 
     The second circuit  410  includes a second capacitor  440  and a third capacitor  445 . The third capacitor  445  is a variable capacitor. The third capacitor  445  functions as a tuning knob. The first circuit  405  and the second circuit  410  are coupled to the first pedestal electrode  122  by the filter main lead  430 . The first circuit  405  and the second circuit  410  are coupled to the second pedestal electrode  124  at a node  450 . The second circuit  410  is also coupled to the filter main lead  430  at a node  452 . The filter main lead  430  is coupled to the first pedestal electrode  122  by a rod  455 . The second pedestal electrode  124  is coupled to the power filter  400  by a rod  460 . Both of the rod  455  and the rod  460  are positioned in the shaft  144 , 
       FIG. 5  is a schematic diagram of another embodiment of a power filter  500  that may be utilized with the processing chamber  100  of  FIG. 1 . In this embodiment, RF power for the processing chamber is provided from the top. For example, the gas distributor plate  112  is coupled to the high frequency RF generator  415  and the low frequency generator  420  by the RF match  152 . In this embodiment, the power filter  500  is utilized to vary the ground path for both of the first pedestal electrode  122  and the second pedestal electrode  124 . The power filter  500  may be used to vary plasma properties of the first pedestal electrode  122  and the second pedestal electrode  124  by varying the ground path thereto, while the gas distributor plate  112  may be electrically floating. 
     The power filter  500  according to this embodiment includes a first capacitor  505 , a second capacitor  510 , and a third capacitor  515 . The first capacitor  505  and the second capacitor  510  are variable capacitors while the third capacitor  515  is a fixed capacitor. The first capacitor  505  and the second capacitor  510  may be utilized as tuning knobs that vary the path to ground for one of both of the first pedestal electrode  122  and the second pedestal electrode  124 . 
     The power filter  500  includes a first circuit  520  comprising the first capacitor  505  and the filter main lead  430 . The filter main lead  430  is coupled to the first pedestal electrode  122  by the rod  455 . The first capacitor  505  is coupled to ground. The power filter  500  also includes a second circuit  525  which includes the second capacitor  510  and the third capacitor  515 . The second circuit  525  is coupled to the second pedestal electrode  124  by the node  450  and the rod  460 , The second circuit  525  is also coupled to the filter main lead  430  at the node  452 . 
       FIGS. 6A-6D  are schematic diagrams showing various embodiments of tuning circuits for tuning the first pedestal electrode  122  and the second pedestal electrode  124 . A portion of the power filter  400  of  FIG. 4  is shown in  FIGS. 6A-6D . 
     In  FIG. 6A , signals from the high frequency RF generator  415  and the low frequency generator  420  are separated and then combined independently. In  FIG. 6B , signals from the high frequency RF generator  415  and the low frequency generator  420  are separated and then combined dependently. 
       FIGS. 6C and 6D  show application of signals from the high frequency RF generator  415  and the low frequency generator  420  that are split and then provided to each of the first pedestal electrode  122  and the second pedestal electrode  124  as desired. 
     In  FIG. 6C , high frequency signals are provided to the first pedestal electrode  122  and the second pedestal electrode  124  while low frequency signals are only provided to the first pedestal electrode  122 . Thus, the low frequency signals are not provided to the second pedestal electrode  124  in  FIG. 6C . 
     In  FIG. 6D , low frequency signals are provided to the first pedestal electrode  122  and the second pedestal electrode  124  while high frequency signals are only provided to the first pedestal electrode  122 . Thus, the high frequency signals are not provided to the second pedestal electrode  124  in  FIG. 6D . 
       FIG. 7  and  FIGS. 8A-80  are schematic diagrams depicting various power splitting circuits that may be used with the power filter  400  or the power filter  500 , as well as the power splitter  154 , as described above, 
       FIG. 7  depicts a capacitive voltage divider  700 . The capacitive voltage divider  700  of  FIG. 7  receives a power input signal  705  that is RF power at a fixed frequency. The third capacitor  445  provides a low impedance, and may be adjusted to provide the same voltage to the first pedestal electrode  122  and the second pedestal electrode  124 . A sensor  710  is coupled to both of the first pedestal electrode  122  and the second pedestal electrode  124 . The sensor  710  monitors power (e.g., voltage, current and/or phase) to each of the first pedestal electrode  122  and the second pedestal electrode  124 . Tuning of the first pedestal electrode  122  and the second pedestal electrode  124  is adjusted based on the information from the sensor  710 . 
       FIG. 8A  depicts a voltage divider circuit  800  that comprises the second capacitor  440  and the third capacitor  445  connected in series. An inductor  805  is positioned between the second capacitor  440  and the third capacitor  445 . The third capacitor  445  may be adjusted to vary voltage between the first pedestal electrode  122  and the second pedestal electrode  124 . The voltage divider circuit  800  comprises a series resonance circuit in one embodiment. 
       FIG. 8B  depicts a voltage divider circuit  810  that comprises the second capacitor  440  and the third capacitor  445 . An inductor  815  is connected in parallel to the second capacitor  440  and the third capacitor  445 . The third capacitor  445  may be adjusted to vary voltage between the first pedestal electrode  122  and the second pedestal electrode  124 . The voltage divider circuit  800  comprises a parallel resonance circuit in one embodiment. The inductor  815  may provide a higher impedance. 
       FIG. 8C  depicts a voltage divider circuit  820  that comprises the second capacitor  440  (a first fixed capacitor) and a fourth capacitor  825  (a second fixed capacitor) connected in series. The inductor  805  is positioned between the second capacitor  440  and the fourth capacitor  825 . 
       FIG. 8D  depicts a voltage divider circuit  830  that comprises the second capacitor  440  (a first fixed capacitor) and a fourth capacitor  825  (a second fixed capacitor) connected in parallel. The inductor  815  is positioned between the second capacitor  440  and the fourth capacitor  825 . 
     In  FIGS. 8C and 8D , the circuits are coupled to a power input signal  835  that provides RF power in various frequencies. Each of the voltage divider circuit  820  and the voltage divider circuit  830  contain no variable capacitor, and are utilized to adjust RF frequencies to the respective circuits to tune the first pedestal electrode  122  and the second pedestal electrode  124 . 
       FIG. 9  is a schematic diagram depicting a circuit  900  configured to counter inductance by the rods  455  and  460 . The circuit  900  is provided between a voltage divider (e.g., the power dividing circuits described above) and the first pedestal electrode  122  and the second pedestal electrode  124 . The circuit  900  includes an inductor  910  and an inductor  915  coupled to the rod  455  and the rod  460 , respectively. The circuit  900  also includes an intermesh capacitor  920  coupled to each of the inductors. The circuit  900  also includes a pair of LC circuits  925 , each consisting of an inductor  930  and a fixed capacitor  935 . The LC circuits  925  allow low frequency power to pass with low impedance but provide capacitance to cancel inductance from one or both of the rods  455  and  460 . The circuit  900  may use one of the capacitors to cancel inductance of the rods  455  and  460  for high frequency power and block low frequency power. The inductors may be utilized to block high frequency power and pass low frequency power. 
       FIG. 10  is a schematic diagram depicting a power divider circuit  1000  according to another embodiment. The power divider circuit  1000  includes the circuit  900  and the second circuit  410 . The power divider circuit  1000  also includes a filter circuit  1005 . Each of the filter circuits  1005  include an inductor  1020  (utilized to pass low frequency power with low inductive impedance) and a capacitor  1025  (to pass high frequency power with a capacitance that cancels out inductance of the rods  455  and  460  (not shown)). Each of the filter circuits  1005  are configured as parallel LC circuits. 
     Benefits of the present disclosure include increased control of plasma adjacent edges of a substrate. Increasing the plasma control results in increased plasma uniformity. 
     While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.