System and methods for surface cleaning

Abstract

A system for removing photoresist from semiconductor wafers is disclosed. The system utilizes a solid-state laser having wavelengths in the near-visible and visible portions of the electromagnetic spectrum to remove photoresist without requiring hazardous gases or wet solutions. In addition, the system does not damage the substrate being cleaned, nor leave a carbon residue requiring further processing to remove. The system uses photon energy, oxygen, water vapor and ozone to interact with contaminants on a surface, forming a gas reaction zone (GRZ). The GRZ reacts and completely removes the photoresist or other unwanted contamination.

1 .- 66 . (canceled)  
   
   
       67 . A wafer cleaning system comprising: 
 a wafer handling module configured and arranged to: 
 provide a dirty wafer to a cleaning chamber, the dirty wafer including a residue on an upper surface of the dirty wafer, and  
 receive a clean wafer from the cleaning chamber, the clean wafer being substantially free of the residue;  
   a gas delivery module configured and arranged to: 
 make a gas mixture available to the cleaning chamber at a substantially constant flow rate, the gas mixture comprising: 
 a first portion containing oxygen,  
 a second portion containing water vapor, and  
 a third portion containing ozone at a concentration of 15% by weight, where the ozone concentration is sufficient to absorb a pulsed optical energy so as to prevent the pulsed optical energy from removing the residue from the dirty wafer unless the first portion containing oxygen and the second portion containing water vapor are present in quantities sufficient to form a gas reaction zone with the third portion containing ozone on at least a portion of the upper surface of the dirty wafer that is illuminated by the pulsed optical energy, the gas reaction zone causing the residue on the upper surface of the dirty wafer to be converted from a substantially solid state to a substantially gaseous state in a presence of the pulsed optical energy;  
 
   an optics module configured and arranged to: 
 generate near-visible radiation using a solid-state laser configured and arranged to: 
 produce a 1 millijoule (mJ) pulse at the surface of the dirty wafer when the dirty wafer is exposed to the gas mixture in the cleaning chamber, the solid-state laser further providing the 1 mJ pulse at a wavelength of 355 nanometers (nm), the solid-state laser further providing the 1 mJ pulse at a pulse rate of 10 kilo-Hertz (kHz);  
 
   a heating module configured and arranged to: 
 heat the dirty wafer to a first temperature of substantially 90° centigrade (C.), the heating of the dirty wafer to 90° C. facilitating conversion of the residue from the substantially solid state to the substantially gaseous state in the presence of the gas mixture and the pulsed optical energy, the first temperature remaining below a temperature threshold that is associated with a second temperature that identifies a temperature value capable of causing damage to the dirty wafer; an exhaust module configured and arranged to:  
 remove residue in the gaseous state,  
 remove an unconsumed portion of the gas mixture, and  
 make the residue in the gaseous state and the unconsumed portion of the gas mixture available to a gas outlet, the gas outlet removing the residue in the gaseous state and the unconsumed portion of the gas mixture from the wafer cleaning system; and  
   a reaction chamber operating as the cleaning chamber, the reaction chamber configured and arranged to: 
 receive the dirty wafer from the wafer handling module,  
 receive the gas mixture from the gas delivery module,  
 receive the pulsed optical energy from the optics module,  
 maintain a pressure of approximately 500 Torr while the residue is exposed to the gas mixture and the pulsed optical energy,  
 make the residue in the gaseous state and the unconsumed portion of the gas mixture available to the gas exhaust module, and  
 provide the clean wafer to the wafer handling module.  
   
   
   
       68 . The wafer cleaning system of  claim 67 , wherein the gas delivery module is further configured to: 
 maintain a gas flow for the gas mixture at a rate in the range of 4 standard liters per minute (slm) to 15 slm.    
   
   
       69 . The wafer cleaning system of  claim 68 , wherein the residue comprises a hard-baked photoresist.  
   
   
       70 . An apparatus for cleaning a surface of a semiconductor substrate, the apparatus comprising: 
 means for holding the substrate in a cleaning position, the cleaning position making the surface available to optical energy configured to clean the substrate;    means for heating the substrate while the substrate is cleaned, the heating means maintaining the substrate at a temperature of 90° C. while the substrate is cleaned;    means for maintaining an environment around the substrate while the substrate is cleaned;    means for providing a gas mixture to the maintaining means, the providing means providing the gas mixture at a rate of 4 standard liters per minute (slm) to 15 slm, the gas mixture comprising: 
 a first gas including oxygen,  
 a second gas including ozone at a concentration of at least 15% by weight, and  
 water vapor;  
   means for removing a portion of the gas mixture that is not consumed when the substrate is cleaned in the environment; and    means for providing the optical energy to the surface of the substrate at: 
 a wavelength of approximately 355 nanometers (nm),  
 a pulse rate of approximately 10 kilo-Hertz (kHz), and  
 a pulse energy of approximately 1 millijoule (mJ); and  
   wherein the gas mixture and the optical energy cooperatively operate to form a gas reaction zone on the surface of the substrate and wherein the gas reaction zone operates to facilitate cleaning the surface of the substrate.    
   
   
       71 . A system for removing residue from the surface of a substrate maintained at a temperature in the range of 85° C. to 100° C., the system comprising: 
 a first device configured to provide a gas mixture comprising oxygen gas, ozone gas having a concentration in the range of 12% to 17% by weight, and water vapor; and    a second device configured to provide optical energy having a wavelength of about 355 nanometers (nm) and a pulse energy of 1 millijoule (mJ) at the surface of the substrate, the gas mixture and the optical energy causing the residue to change state from a solid phase to a gaseous phase without damaging the surface of the substrate.    
   
   
       72 . The system of  claim 71 , wherein the gas mixture further includes at least one of a gas selected from alcohols or alcohol pre-cursors.  
   
   
       73 . The system of  claim 71 , wherein the second device provides optical energy at a pulse repetition rate of 10 kHz.  
   
   
       74 . The system of  claim 71 , wherein the second device provides optical energy at a pulse repetition rate of 1 kHz to 100 kHz.  
   
   
       75 . The system of  claim 74 , wherein the second device includes a solid-state laser having a primary beam containing near-visible wavelength optical energy at about the 355 nm wavelength and a residual beam having visible wavelength optical energy in the range of about a 532 nm wavelength.  
   
   
       76 . A system for removing residue from a surface of a substrate without damaging the substrate, the system comprising: 
 a laser having a pulse energy of 1 millijoule (mJ) and a pulse repetition rate in the range of 1 kilo-Hertz (kHz) to 100 kHz, the laser outputting a wavelength in a range of 300 nanometers (nm) to 780 nm, the 1 mJ pulse illuminating the residue to facilitate residue removal;    a gas delivery module for delivering a gas mixture at a rate in a range of 4 standard liters per minute (slm) to 15 slm, the gas mixture comprising: 
 oxygen gas,  
 ozone gas having a concentration in a range of 10% to 20% by weight, and  
 water vapor; and  
   a chamber comprising: 
 a retaining device to retain the substrate in a determined position while the residue is removed therefrom,  
 a heating device to maintain the substrate at a temperature in the range of 20° C. to 100° C. while the residue is removed therefrom,  
 a device to maintain an environment surrounding the surface of the substrate while the residue is removed therefrom, and  
 a window to facilitate maintaining the environment around the surface of the substrate and to allow the residue to be illuminated in the presence of the gas mixture to form a gas reaction zone that causes the residue to change from a solid state to a gaseous state, the change from the solid state to the gaseous state removing the residue from the substrate without damaging the substrate.  
   
   
   
       77 . The system of  claim 76 , wherein the device maintains the environment at a pressure in a range of 5 Torr to 760 Torr while the residue is removed from the substrate.  
   
   
       78 . The system of  claim 76 , wherein the device maintains the environment at a positive pressure in the range of 0.5 pounds-per-square-inch (psi) to 5,000 psi.  
   
   
       79 . The system of  claim 76 , wherein the gas mixture further comprises: 
 methane.    
   
   
       80 . The system of  claim 76 , wherein the gas mixture further comprises: 
 hydrogen peroxide.    
   
   
       81 . The system of  claim 76 , wherein the gas mixture further comprises at least one of an alcohol or an alcohol pre-cursor.  
   
   
       82 . The system of  claim 76 , wherein the laser is a yttrium—aluminum—garnet (YAG) laser.  
   
   
       83 . The system of  claim 76 , wherein the laser has a pulse repetition rate of 10 kHz and a wavelength of 355 nm.  
   
   
       84 . The system of  claim 76 , wherein the residue includes hard-baked photoresist.  
   
   
       85 . The system of  claim 76 , wherein the residue includes a hard-baked photoresist that has been processed through an ion implantation process.  
   
   
       86 . The system of  claim 76 , wherein the residue includes a hard-baked photoresist that has been processed through a semiconductor etch process.