Method and apparatus to process substrates with megasonic energy

Abstract

A variety of techniques may be employed, alone or in combination, to enhance contact between a processed substrate and applied megasonic energy. In accordance with one embodiment of the new invention, the vibration plate is brought into intimate contact with one surface of the substrate, while cleaning or processing fluid contacts the other. In accordance with an alternative embodiment of the present invention, a reflecting surface may be provided to cause emanated energy to be reflected back into the near field and make it more uniform. In accordance with another alternative embodiment of the present invention, energy may be transferred across a substrate bounded on both sides by liquid with incidence of megasonic energy that is either normal to the substrate surface or within a critical range of incident angles. In yet another embodiment, generated dilatational waves may be converted to surface waves prior to contacting the substrate.

1 - 91 . (canceled)  
     
     
         92 . A method of processing a substrate comprising: 
 varying at least one of frequency, power, and pulse width of ultrasonic energy applied from a first energy source to a substrate in contact with a processing fluid, such that a uniformity of energy in near field regions is improved by at least one of moving high energy node points and low energy null points, minimizing a difference between a magnitude of the high and low energy points, and retarding formation of high and low energy points.    
     
     
         93 . The method of  claim 92  wherein at least part of the substrate is contacted by a processing fluid comprising one of a liquid, a vapor, a gas, and a solid.  
     
     
         94 . The method of  claim 92  further comprising: 
 applying sonic energy from a second energy source to the substrate in contact with a processing fluid, such that a far-field of the energy from the second energy source overlaps near field regions from the first energy source.    
     
     
         95 . The method of  claim 92  wherein a frequency of a driving voltage applied to at least one vibration member is cycled about a frequency set point.  
     
     
         96 . The method of  claim 95  wherein cycling the driving voltage frequency varies a magnitude of a resulting sonic energy wave within a process tank.  
     
     
         97 . The method of  claim 95  wherein the frequency of the driving voltage is cycled about the frequency set point according to at least one of a sinusoidal signal, a randomly fluctuating signal, and a predetermined stepwise sequence.  
     
     
         98 . The method of  claim 92  wherein a magnitude of a driving voltage applied to at least one vibration member is varied about a voltage magnitude set point according to at least one of a sinusoidal signal, a randomly fluctuating signal, and a stepwise sequence.  
     
     
         99 . The method of  claim 92  wherein a pulse width of a driving voltage applied to at least one vibration member is varied by at least one of cycling the pulse width of the applied voltage about a pulse width set point by means of at least one of a sinusoidal signal, a randomly fluctuating signal, and a stepwise sequence.  
     
     
         100 . The method of  claim 92  wherein at least one of a magnitude and a character of the resulting sonic energy wave within a processing tank is varied by varying the pulse width of the driving voltage applied to at least one vibration member by varying the pulse width of the applied driving voltage about a pulse width set point by means of at least one of a sinusoidal signal, a randomly fluctuating signal, and a predetermined stepwise sequence.  
     
     
         101 . The method of  claim 92  wherein the processing is conducted at least one of less than, greater than, and equal to atmospheric pressure.  
     
     
         102 . The method of  claim 92  wherein at least two individual vibration elements are sequentially energized.  
     
     
         103 . The method of  claim 92  wherein at least two individual vibration elements are energized simultaneously.  
     
     
         104 . The method of  claim 103  wherein a phase angle between the driving voltage applied to the vibration elements varied about a phase angle set point according to at least one of a sinusoidal signal, a randomly fluctuating signal and a stepwise sequence.  
     
     
         105 . The method of  claim 104  wherein the phase angle set point is greater than 0° and less than 180°.  
     
     
         106 . The method of  claim 105  wherein the phase angle set point changes at a rate which it is greater than one-tenth hertz and less than 10 megahertz.  
     
     
         107 . The method of  claim 105  wherein at least one of a rate of change of frequency of the applied driving voltage, and a rate of change of the pulse width of the applied driving voltage, is greater than one-tenth hertz and less than 10 megahertz.  
     
     
         108 . The method of  claim 92  wherein the pulse width is greater than one picosecond.  
     
     
         109 . The method of  claim 92  further comprising applying microwave energy at least one of prior to, during, and subsequent to the application of sonic energy.  
     
     
         110 . A method of processing a substrate with megasonic energy, the method comprising: 
 disposing a substrate in contact with a processing fluid;    applying megasonic energy to the substrate to establish points of constructive and destructive interference proximate to a substrate surface; and    changing a position, a magnitude, or a character of the points of constructive and destructive interference in order to enhance uniformity of exposure of the substrate to sonic energy.    
     
     
         111 . The method of  claim 110  wherein the position of points of constructive and destructive interference is changed by varying at least one of frequency, power, phase angle, and pulse width of the applied megasonic energy.  
     
     
         112 . The method of  claim 111  wherein at least one of a magnitude, a frequency, a phase angle, and a pulse width of a driving voltage of a source of the megasonic energy is varied about a set point according to at least one of a sinusoidal signal, a randomly fluctuating signal, and a stepwise sequence.  
     
     
         113 . The method of  claim 111  wherein a rate of change of at least one of the frequency, power, phase angle, and pulse width of the megasonic energy is varied by a rate greater than about 0.1 Hz and less than about 10 MHz.  
     
     
         114 . The method of  claim 110  wherein the position, magnitude, or character of points of constructive and destructive interference is changed by varying an orientation of the substrate relative to a source of the applied megasonic energy.  
     
     
         115 . The method of  claim 110  wherein the position, magnitude, or character of points of constructive and destructive interference is changed by varying a distance of the substrate relative to a source of the applied megasonic energy.  
     
     
         116 . The method of  claim 110  wherein the position, magnitude, or character of points of constructive and destructive interference is changed in a near field region of a source of the megasonic energy.  
     
     
         117 . The method of  claim 110  wherein the position, magnitude, or character of points of constructive and destructive interference is changed in a far field region of a source of the megasonic energy.  
     
     
         118 - 208 . (canceled)