Device and method for plasma treatment of electronic materials

Abstract

Plasma applications are disclosed that operate with argon and other molecular gases at atmospheric pressure, and at low temperatures, and with high concentrations of reactive species. The plasma apparatus and the enclosure that contains the plasma apparatus and the substrate are substantially free of particles, so that the substrate does not become contaminated with particles during processing. The plasma is developed through capacitive discharge without streamers or micro-arcs. The techniques can be employed to remove organic materials from a substrate, thereby cleaning the substrate; to activate the surfaces of materials, thereby enhancing bonding between the material and a second material; to etch thin films of materials from a substrate; and to deposit thin films and coatings onto a substrate; all of which processes are carried out without contaminating the surface of the substrate with substantial numbers of particles.

What is claimed is: 
     
         1 . An apparatus for producing an ionized gas plasma, comprising:
 a housing having an inlet for gas flow comprising argon and one or more molecular gases, an outlet for argon plasma comprising reactive neutral species, and a flow path within the housing for directing the gas flow;   a power electrode disposed within the housing having a powered electrode surface exposed to the gas flow;   a ground electrode disposed adjacent to the power electrode such that a grounded electrode surface is closely spaced from the power electrode surface and the gas flow is directed therebetween;   a power supply for delivering radio frequency power coupled to the power electrode and the ground electrode to ionize the gas flow and produce the argon plasma comprising the reactive neutral species;   an enclosure having the housing contained within and including an enclosure gas flow wherein the enclosure gas flow has been filtered to remove particles from the flow; and   a material substrate disposed within the enclosure near the outlet of the housing to receive the reactive neutral species in the gas flow from the ionized gas plasma.   
     
     
         2 . The apparatus of  claim 1 , wherein the argon plasma is produced by a capacitive discharge without substantially any streamers or micro-arcs. 
     
     
         3 . The apparatus of  claim 1 , wherein the reactive neutral species from the ionized gas plasma are used for cleaning organic contamination from the material substrate, activating the material substrate surface for adhesion, etching a thin film off of the material substrate, or depositing a thin film onto the material substrate, all substantially without the deposition of particles. 
     
     
         4 . The apparatus of  claim 1 , wherein the gas inside the enclosure is at atmospheric pressure. 
     
     
         5 . The apparatus of  claim 1 , wherein the gas flow through the housing is laminar. 
     
     
         6 . The apparatus of  claim 1 , wherein the gas flow from the outlet of the housing for the argon plasma is between 25 and 200° C. 
     
     
         7 . The apparatus of  claim 1 , wherein the outlet of the housing for argon plasma comprises a linear opening. 
     
     
         8 . The apparatus of  claim 7 , wherein the linear opening is at least as wide as the material substrate and the material substrate is passed at a constant speed relative to and contacting the reactive gas beam. 
     
     
         9 . The apparatus of  claim 1 , further comprising a means of translating the housing with the outlet for the ionized gas plasma relative to the surface of the material substrate such that the entire surface of the material substrate is uniformly treated with the reactive species from the ionized gas plasma. 
     
     
         10 . The apparatus of  claim 1 , wherein the power supply operates at a radio frequency of 13.56 or 27.12 MHz and includes an auto-tuning network that impedance matches the radio frequency power supply to the argon plasma to minimize reflected power. 
     
     
         11 . The apparatus of  claim 1 , wherein the one or more molecular gases are added to the argon gas flow at a concentration between 0.5 to 5.0 volume % and a fraction of the one or more molecular gases dissociates into atoms inside the argon plasma, and then flows out of the outlet, wherein the atoms are selected from the group consisting of O, N, H, F, C and S atoms. 
     
     
         12 . The apparatus of  claim 1 , wherein the enclosure gas flow is laminar. 
     
     
         13 . The apparatus of  claim 1 , wherein the enclosure includes no more than 100,000 particles larger than 0.1 micron per cubic meter of air. 
     
     
         14 . The apparatus of  claim 13 , wherein the enclosure comprises a cleanroom. 
     
     
         15 . A method of producing an ionized gas plasma comprising:
 directing gas flow comprising argon and one or more molecular gases from an inlet through a flow path within a housing to an outlet for argon plasma comprising reactive neutral species;   directing the gas flow within the housing between a powered electrode surface of a power electrode and a grounded electrode surface of a ground electrode, the grounded electrode surface closely spaced from the powered electrode surface;   delivering radio frequency power coupled to the power electrode and the ground electrode from a power supply to ionize the gas flow and produce the argon plasma comprising the reactive neutral species;   disposing the housing with the argon plasma within an enclosure including an enclosure gas flow wherein the enclosure gas flow has been filtered to remove particles from the flow; and   disposing a material substrate within the enclosure near the outlet of the housing to receive the reactive neutral species.   
     
     
         16 . The method of  claim 15 , wherein the argon plasma comprising the reactive neutral species is produced by capacitive discharge substantially without any streamers or micro-arcs. 
     
     
         17 . The method of  claim 15 , wherein the reactive neutral species from the ionized gas plasma are used for cleaning organic contamination from the material substrate, activating the material substrate surface for adhesion, etching a thin film off of the material substrate, or depositing a thin film onto the material substrate, all substantially without the deposition of particles. 
     
     
         18 . The method of  claim 15 , wherein the gas inside the enclosure is at atmospheric pressure. 
     
     
         19 . The method of  claim 15 , wherein the gas flow inside the housing is laminar. 
     
     
         20 . The method of  claim 15 , wherein the gas flow from the outlet of the housing for the argon plasma is between 25 and 200° C. 
     
     
         21 . The method of  claim 15 , further comprising a means of translating the housing with the outlet for the ionized gas plasma relative to the surface of the material substrate such that the entire surface of the material substrate is uniformly treated with the reactive species from the ionized gas plasma. 
     
     
         22 . The method of  claim 15 , wherein the radio frequency power is delivered at 13.56 or 27.12 MHz. 
     
     
         23 . The method of  claim 15 , wherein the one or more molecular gases are added to the argon gas flow at a concentration between 0.5 to 5.0 volume % and a fraction of the one or more molecular gases dissociates into atoms inside the argon plasma, and then flows out of the outlet, wherein the atoms are selected from the group consisting of O, N, H, F, C and S atoms. 
     
     
         24 . The method of  claim 23 , wherein the molecular gas added to the argon gas flow is dissociated into atoms selected from the group consisting of oxygen (O), nitrogen (N), and hydrogen (H). 
     
     
         25 . The method of  claim 15 , wherein the enclosure gas flow is laminar. 
     
     
         26 . The method of  claim 15 , wherein the enclosure includes no more than 100,000 particles larger than 0.1 micron per cubic meter of air. 
     
     
         27 . The method of  claim 15 , wherein the enclosure comprises a cleanroom. 
     
     
         28 . The method of  claim 15 , wherein the molecular gas is selected from the group comprising oxygen and nitrogen and the material substrate is a semiconductor wafer and the surface of the semiconductor wafer is cleaned of organic contamination with the plasma. 
     
     
         29 . The method of  claim 15 , wherein the molecular gas is hydrogen and the material substrate is a copper substrate and copper oxide on the copper substrate is etched away with the plasma. 
     
     
         30 . The method of  claim 29 , wherein the copper substrate is a lead frame strip.