Patent Publication Number: US-11654460-B2

Title: Megasonic clean with cavity property monitoring

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 63/270,525, filed Oct. 21, 2021, which is herein incorporated by reference in its entirety. 
    
    
     FIELD 
     Embodiments of the present disclosure generally relate to a substrate processing equipment. 
     BACKGROUND 
     Megasonic clean chambers are used in the semiconductor industry for cleaning various types of substrates. Megasonic clean chambers generally use acoustic energy to create cavity implosions in a cleaning fluid directed at the substrate. However, large cavities in the cleaning fluid may damage substrates during cleaning. 
     Accordingly, the inventors have provided improved apparatus and methods for cleaning substrates in a megasonic clean chamber. 
     SUMMARY 
     Embodiments of megasonic cleaning chambers are provided herein. In some embodiments, a megasonic cleaning chamber includes: a chamber body defining an interior volume therein; a substrate support to support a substrate disposed in the interior volume; a supply tube comprising a transparent material configured to direct a cleaning fluid to the substrate support; a megasonic power generator coupled to the supply tube to provide megasonic power to the cleaning fluid; a megasonic transducer coupled to the megasonic power generator and the supply tube to create megasonic waves in the cleaning fluid and to form cavities in the cleaning fluid, wherein the megasonic transducer is configured to direct the megasonic waves and cavities toward the substrate support; and one or more sensors configured to generate a signal indicative of a property of the cavities in the cleaning fluid. 
     In some embodiments, a method of cleaning a substrate in a megasonic cleaning chamber includes: flowing a cleaning fluid through a supply tube in a megasonic cleaning chamber towards a substrate; using a megasonic transducer to generate megasonic waves through the cleaning fluid and create cavities in the cleaning fluid; and using one or more sensors to determine properties of the cavities in-situ based on emissions received from the cavities. 
     In some embodiments, a non-transitory computer readable medium having instructions stored thereon that, when executed, causes a method of cleaning a substrate in a megasonic cleaning chamber to be performed, the method including: flowing a cleaning fluid through a supply tube in a megasonic cleaning chamber towards a substrate; using a megasonic transducer to generate megasonic waves through the cleaning fluid, creating cavities in the cleaning fluid; and using one or more sensors to determine properties of the cavities in-situ based on emissions received from the cavities. 
     Other and further embodiments of the present disclosure are described below. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present disclosure, briefly summarized above and discussed in greater detail below, can be understood by reference to the illustrative embodiments of the disclosure depicted in the appended drawings. However, the appended drawings illustrate only typical embodiments of the disclosure and are therefore not to be considered limiting of scope, for the disclosure may admit to other equally effective embodiments. 
         FIG.  1    depicts a schematic side view of a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. 
         FIG.  2    depicts a schematic top view of a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. 
         FIG.  3    depicts a schematic side view of a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. 
         FIG.  4    depicts a schematic side view of a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. 
         FIG.  5    depicts a flow chart of a method of cleaning a substrate in a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. 
     
    
    
     To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. The figures are not drawn to scale and may be simplified for clarity. Elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation. 
     DETAILED DESCRIPTION 
     Embodiments of megasonic cleaning chambers are provided herein. The megasonic cleaning chambers provided herein are configured to characterize cavities formed in the cleaning fluids in-situ. The cavities may be characterized by properties such as size, temperature, energy, shape, or the like. For example, the megasonic cleaning chamber may include one or more sensors that facilitate monitoring properties of the cavities or facilitate monitoring and control of the properties of the cavities. The megasonic cleaning chamber may include a controller configured to change one or more parameters of the megasonic cleaning chamber to control, for example, cavity sizes, temperatures, or cavity energies. By controlling the properties of the cavities within the cleaning fluid, the megasonic cleaning chamber can advantageously form cavities that are large enough to provide adequate cleaning force and small enough to prevent damage of substrates to be cleaned. 
       FIG.  1    depicts a schematic side view of a megasonic cleaning chamber, or cleaning chamber  100 , in accordance with at least some embodiments of the present disclosure. The cleaning chamber  100  generally includes a chamber body  102  defining an interior volume  110  therein. The chamber body  102  may be made of any suitable material. A substrate support  116  may be disposed in the interior volume  110  to support a substrate  112  disposed in the interior volume  110 . The substrate support  116  may be coupled to a motor  160  to facilitate rotational movement of the substrate support  116 . The substrate  112  may be any substrate suitable for use in semiconductor applications. 
     The cleaning chamber  100  further includes a supply tube  118  disposed in the interior volume  110  to direct a cleaning fluid  114  to the substrate  112 . The supply tube  118  is generally made of transparent material. In some embodiments, the supply tube  118  is made of quartz. In some embodiments, the supply tube  118  is a vertical tube extending orthogonal to an upper surface of the substrate  112 . In some embodiments, the supply tube  118  may be extend at an angle less than ninety degrees with respect to the upper surface of the substrate  112 . 
     In some embodiments, a fluid supply  124  is coupled to the supply tube  118  to hold and supply cleaning fluid to the supply tube  118 . In some embodiments, the cleaning fluid comprises a liquid-gas mixture. In some embodiments, the cleaning fluid comprises a liquid such as water, ammonium hydroxide, hydrogen peroxide, or the like. In some embodiments, the cleaning fluid comprises a gas such as hydrogen (H2), oxygen (O2), helium (He), nitrogen (N2), argon (Ar), or a combination thereof. In some embodiments, the cleaning fluid may include a surfactant. In some embodiments, the fluid supply  124  is coupled to the supply tube  118  through a sidewall of the supply tube  118 . A drain system  140  may be coupled to the chamber body  102  to drain cleaning fluids and contaminants. The drain system  140  may include one or more valves (not shown) to control a pressure in the interior volume  110  and one or more pumps (not shown). 
     The cleaning chamber  100  includes a megasonic power generator  120  coupled to the supply tube  118  to provide megasonic power to the cleaning fluid  114 . In some embodiments, a megasonic transducer  126  is coupled to the megasonic power generator  120  and the supply tube  118  to create megasonic waves  132  in the cleaning fluid  114 . The megasonic waves  132  in the cleaning fluid  114  lead to the formation of cavities  134  in the cleaning fluid  114 . The megasonic transducer  126  is configured to direct the megasonic waves  132  and cavities  134  toward the substrate  112  to clean the substrate  112 . In some embodiments, the megasonic waves have a frequency range of about 0.4 MHz to about 6.0 MHz. 
     The cleaning chamber  100  includes one or more sensors  142  configured to facilitate determining properties of the cavities  134  in the cleaning fluid  114 . For example, the one or more sensors  142  may generate a signal indicative of a property of the cavities  134  or may generate a signal to determine a property of the cavities  134 . In some embodiments, the properties of the cavities  134  may be cavity size. In some embodiments, the cleaning chamber  100  further includes a laser source  162  disposed in the interior volume  110 . In some embodiments, the laser source  162  and the one or more sensors  142  are configured to sense light from the laser source  162  to determine a size of the cavities  134  based on a measured diffraction of a laser beam from the laser source  162  after the laser beam passes through the cavities  134 . In some embodiments, the one or more sensors  142  are a plurality of sensors disposed along a vertical position  164  of the supply tube  118 .  FIG.  2    depicts a schematic top view of portions of a cleaning chamber  100  in accordance with at least some embodiments of the present disclosure. In some embodiments, the plurality of sensors  142  are detectors. In some embodiments, the plurality of sensors  142  are disposed along a plurality of radial positions along an arcuate path  210  about the supply tube  118 . In some embodiments, the plurality of sensors  142  are disposed about halfway or 180 degrees around the supply tube  118 . 
     Referring back to  FIG.  1   , the supply tube  118 , the megasonic transducer  126 , and the one or more sensors  142  may collectively be referred to as an upper assembly  150 . The upper assembly  150  may be configured to translate across the substrate support  116  in a lateral direction  156  so that an entire upper surface of the substrate  112  may be cleaned. The one or more sensors  142  may be coupled to the supply tube  118  via a mounting frame or other suitable coupling apparatus. 
     The cleaning chamber  100  may include a controller  170  to control the operation of the cleaning chamber  100 . The controller  170  generally includes a central processing unit (CPU)  172 , a memory  174 , and a support circuit  176 . The CPU  172  may be one of any form of a general-purpose computer processor that can be used in an industrial setting. The support circuit  176  is conventionally coupled to the CPU  172  and may comprise a cache, clock circuits, input/output subsystems, power supplies, and the like. Software routines, such as processing methods as described above may be stored in the memory  174  and, when executed by the CPU  172 , transform the CPU  172  into a controller  170 . The software routines may also be stored and/or executed by a second controller (not shown) that is located remotely from the cleaning chamber  100 . 
     In operation, the controller  170  enables data collection and feedback from the cleaning chamber  100  to optimize performance of the cleaning chamber  100  and provides instructions to system components. For example, the controller  170  may be configured to use the one or more sensors  142  or signals from the one or more sensors  142  to determine sizes of cavities  134  or other cavity properties and modify one or more parameters of the cleaning chamber  100  to change the size or other cavity properties of the cavities  134 . The memory  174  can be a non-transitory computer readable storage medium having instructions that when executed by the CPU  172  (or controller  170 ) perform the methods described herein. 
     Embodiments in accordance with the present disclosure may be implemented in hardware, firmware, software, or any combination thereof. Embodiments may also be implemented as instructions stored using one or more computer readable media, which may be read and executed by one or more processors. A computer readable medium may include any mechanism for storing or transmitting information in a form readable by a machine (e.g., a computing platform or a “virtual machine” running on one or more computing platforms). For example, a computer readable medium may include any suitable form of volatile or non-volatile memory. In some embodiments, the computer readable media may include a non-transitory computer readable medium. 
       FIG.  3    depicts a schematic side view of a megasonic cleaning chamber in accordance with at least some embodiments of the present disclosure. In some embodiments, the cleaning chamber  100  comprising a light source  310  directed at the supply tube  118 . The one or more sensors  142  may comprise a camera  320  having a high-speed photographic sensor configured to capture images of the cavities  134  illuminated by photons  330  from the light source  310  to determine the size of the cavities  134 . 
       FIG.  4    depicts a schematic side view of a megasonic cleaning chamber  100  in accordance with at least some embodiments of the present disclosure. The megasonic cleaning chamber of claim  1 , wherein the one or more sensors  142  comprise an optical emission spectrometer  410  to determine the wavelength and intensity of sonoluminescence emissions, or optical emission spectrum (OES), due to the cavities  134  in the cleaning fluid  114 . For example, OES of the gas in the cavities  134 . Based on the OES data, cavity properties such as cavity temperature, energy, cleaning performance, and possible propensity to damage the substrate  112  can be estimated. The OES emissions from the cavities  134  may be generated by the megasonic waves  132  passing through the cleaning fluid  114 . 
       FIG.  5    depicts a flow chart of a method  500  of cleaning a substrate in a megasonic cleaning chamber (e.g., cleaning chamber  100 ) in accordance with at least some embodiments of the present disclosure. At  502 , the method  500  includes flowing a cleaning fluid (e.g., cleaning fluid  114 ) through a supply tube (e.g., supply tube  118 ) in a megasonic cleaning chamber towards a substrate (e.g., substrate  112 ). 
     At  504 , the method  500  includes using a megasonic transducer (e.g., megasonic transducer  126 ) to generate megasonic waves (e.g., megasonic waves  132 ) through the cleaning fluid and create cavities (e.g., cavities  134 ) in the cleaning fluid. In some embodiments, the megasonic waves have a frequency range of about 0.4 MHz to about 6.0 MHz. 
     At  506 , the method  500  includes using one or more sensors (e.g., one or more sensors  142 ) to determine cavity properties in-situ based on emissions received by the one or more sensors from the cavities. Properties such as cavity size may be determined from any suitable sensing technique, such as laser diffraction, optical, spectroscopy, or acoustic methods. For example, in some embodiments, using one or more sensors to determine sizes of the cavities based on emissions received from the cavities comprises: directing a laser (e.g., laser source  162 ) to the supply tube, detecting scattered laser light (e.g., scattered laser light  148 ) via the one or more sensors, and determining sizes of the cavities based on the detected scattered laser light. 
     In some embodiments, using one or more sensors to determine sizes of the cavities comprises using optical methods such as cameras for high-speed photography. For example, optical methods may include directing a light source (e.g., light source  310 ) to the supply tube, using a camera (e.g., camera  320 ) having the one or more sensors configured for generating images of the cavities, and determining sizes of the cavities based on the images. The light source may advantageously provide better contrast between a background and the cavities. 
     In some embodiments, using one or more sensors to determine cavity properties based on emissions received from the cavities comprises using an optical emission spectrometer (e.g., optical emission spectrometer  520 ) having the one or more sensors configured to detect light emissions from the cavities that are caused by the megasonic waves to determine, for example, cavity temperature and cavity energy. The cavity temperature and cavity energy may refer to the temperature or energy of the gas within the cavities. Based on the data from the optical emission spectrometer, cleaning performance, and possible damages can be estimated. In some embodiments, a controller (e.g., controller  170 ) may take OES data from the optical emission spectrometer to determine cavity sizes based on the OES data. 
     In some embodiments, the method  500  includes adjusting a parameter of the megasonic cleaning chamber if the determined properties, such as cavity size, cavity temperature, or cavity energy are outside of a desired range. In some embodiments, the parameter comprises one or more of power provided to the megasonic transducer by the megasonic generator, frequency of the megasonic waves, gas concentration in the cleaning fluid, or temperature of the cleaning fluid. For example, if the cavities are too small, one or more of: the power provided to the megasonic transducer by the megasonic generator, gas concentration in the cleaning fluid, or temperature of the cleaning fluid may be increased. If the cavities are too large, one or more of: the power provided to the megasonic transducer by the megasonic generator, gas concentration in the cleaning fluid, or temperature of the cleaning fluid may be decreased. In some embodiments, the desired range of the size of the cavities are about 1 micron to about 20 microns in diameter. In some embodiments, the parameters may be adjusted via an end user, via a controlled method using a controller, or artificial intelligence (AI) controlled method which is based on using a controller and data processing using any suitable AI technique. 
     In some embodiments, the method  500  includes rotating the substrate while flowing the cleaning fluid. In some embodiments, the method  500  includes moving the supply tube across the substrate while flowing the cleaning fluid to clean an entirety of the substrate. 
     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.