Laser processing

Abstract

The invention provides a system and method for vaporizing a target structure on a substrate. According to the invention, a calculation is performed, as a function of wavelength, of an incident beam energy necessary to deposit unit energy in the target structure. Then, for the incident beam energy, the energy expected to be deposited in the substrate as a function of wavelength is calculated. A wavelength is identified that corresponds to a relatively low value of the energy expected to be deposited in the substrate, the low value being substantially less than a value of the energy expected to be deposited in the substrate at a higher wavelength. A laser system is provided configured to produce a laser output at the wavelength corresponding to the relatively low value of the energy expected to be deposited in the substrate. The laser output is directed at the target structure on the substrate at the wavelength corresponding to the relatively low value of the energy expected to be deposited in the substrate, in order to vaporize the target structure.

1 - 11 . (canceled)  
     
     
         12 . A semiconductor device comprising a silicon substrate, the semiconductor device being produced by a method of vaporizing a target structure on the silicon substrate, the method comprising the steps of: 
 providing a laser system configured to produce a laser output at a wavelength below an absorption edge of the silicon substrate and below about 0.55 microns; and    directing the laser output at the target structure on the silicon substrate at the wavelength and at an incident beam energy, in order to vaporize the target structure, the silicon substrate being positioned beneath the target structure with respect to the laser output;    generating computer-controlled timing signals synchronized with the position of the pulsed laser beam relative to the target structure;    controllably switching an optical switch based on the timing signals so as to cause output pulses of the pulsed laser beam to be transmitted to the target structure;    wherein the incident beam energy at which the target structure is vaporized is reduced relative to an incident beam energy necessary to deposit unit energy in the target structure sufficient to vaporize the target structure at a higher wavelength below the absorption edge of the silicon substrate.    
     
     
         13 . The semiconductor device of  claim 12  wherein the identified wavelength corresponding to a relatively low value of the energy expected to be deposited in the silicon substrate is within a visible region of spectrum.  
     
     
         14 . The semiconductor device of  claim 13  wherein the identified wavelength corresponding to a relatively low value of the energy expected to be deposited in the silicon substrate is within a green region of spectrum.  
     
     
         15 . The semiconductor device of  claim 12  wherein the laser output at the incident beam energy comprises short pulses.  
     
     
         16 . The semiconductor device of  claim 12  wherein the laser system comprises a neodymium vanadate laser.  
     
     
         17 . The semiconductor device of  claim 12  wherein, at the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns, a spot size of the laser output at the target structure is reduced relative to a spot size obtainable at the higher wavelength below the absorption edge of the silicon substrate.  
     
     
         18 . The semiconductor device of  claim 12  wherein the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns is identified by: 
 calculating, as a function of wavelength, an incident beam energy necessary to deposit unit energy in the target structure sufficient to vaporize the target structure;    calculating, for the incident beam energy, energy expected to be deposited in the silicon substrate as a function of wavelength; and    identifying a wavelength below an absorption edge of the silicon substrate, the wavelength corresponding to a relatively low value of the energy expected to be deposited in the silicon substrate, the low value being substantially less than a value of the energy expected to be deposited in the silicon substrate at a higher wavelength below the absorption edge of the silicon substrate.    
     
     
         19 . A semiconductor device comprising a silicon substrate, the semiconductor device being produced by a method of vaporizing a target structure on the silicon substrate, the method comprising the steps of: 
 providing a laser system configured to produce a laser output at a wavelength below an absorption edge of the silicon substrate and below about 0.55 microns; and    directing the laser output at the target structure on the silicon substrate at the wavelength and at an incident beam energy, in order to vaporize the target structure, the silicon substrate being positioned beneath the target structure with respect to the laser output, wherein the laser output at the incident beam energy comprises short pulses;    generating computer-controlled timing signals synchronized with the position of the pulsed laser beam relative to the target structure; and    controllably switching an optical switch based on the timing signals so as to cause output pulses of the pulsed laser beam to be transmitted to the target structure.    
     
     
         20 . The semiconductor device of  claim 19  wherein the laser system comprises a neodymium vanadate laser.  
     
     
         21 . The semiconductor device of  claim 19  wherein, at the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns, a spot size of the laser output at the target structure is reduced relative to a spot size obtainable at the higher wavelength below the absorption edge of the silicon substrate  
     
     
         22 . The semiconductor device of  claim 19  wherein the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns is identified by: 
 calculating, as a function of wavelength, an incident beam energy necessary to deposit unit energy in the target structure sufficient to vaporize the target structure;    calculating, for the incident beam energy, energy expected to be deposited in the silicon substrate as a function of wavelength; and    identifying a wavelength below an absorption edge of the silicon substrate, the wavelength corresponding to a relatively low value of the energy expected to be deposited in the silicon substrate, the low value being substantially less than a value of the energy expected to be deposited in the silicon substrate at a higher wavelength below the absorption edge of the silicon substrate.    
     
     
         23 . A semiconductor device comprising a silicon substrate, the semiconductor device being produced by a method of vaporizing a target structure on the silicon substrate, the method comprising the steps of: 
 providing a laser system configured to produce a laser output at a wavelength below an absorption edge of the silicon substrate and below about 0.55 microns; and    directing the laser output at the target structure on the silicon substrate at the wavelength and at an incident beam energy, in order to vaporize the target structure, the silicon substrate being positioned beneath the target structure with respect to the laser output;    generating computer-controlled timing signals synchronized with the position of the pulsed laser beam relative to the target structure;    controllably switching an optical switch based on the timing signals so as to cause output pulses of the pulsed laser beam to be transmitted to the target structure;    wherein the incident beam energy at which the target structure is vaporized is reducible relative to an incident beam energy necessary to deposit unit energy in the target structure sufficient to vaporize the target structure at a higher wavelength below the absorption edge of the silicon substrate.    
     
     
         24 . The semiconductor device of  claim 23  wherein, at the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns, a spot size of the laser output at the target structure is reduced relative to a spot size obtainable at the higher wavelength below the absorption edge of the silicon substrate  
     
     
         25 . The semiconductor device of  claim 23  wherein the wavelength below the absorption edge of the silicon substrate and below about 0.55 microns is identified by: 
 calculating, as a function of wavelength, an incident beam energy necessary to deposit unit energy in the target structure sufficient to vaporize the target structure;    calculating, for the incident beam energy, energy expected to be deposited in the silicon substrate as a function of wavelength; and    identifying a wavelength below an absorption edge of the silicon substrate, the wavelength corresponding to a relatively low value of the energy expected to be deposited in the silicon substrate, the low value being substantially less than a value of the energy expected to be deposited in the silicon substrate at a higher wavelength below the absorption edge of the silicon substrate.