Laser processing

Abstract

A controlled, switched laser system for vaporizing a target structure on a substrate includes a diode-pumped, solid-state laser for producing a laser output, a controllable switch for controlling the on/off state and power level of the laser, and a wavelength shifter. The wavelength shifter shifts the wavelength of the laser output from a conventional wavelength to a wavelength beyond the absorption edge of the substrate but shorter than 1.2 μm in order to obtain a decrease in absorption of the laser output by the substrate due to the shift in the wavelength of the laser output. The wavelength shifter is removably insertable into the switched laser system so as to enable the switched laser system to operate at the conventional wavelength and at the wavelength beyond the absorption edge of the substrate. Heating of the substrate and hence damage to the substrate is limited due to the wavelength being beyond the absorption edge of the substrate. Good depth of focus of the laser beam output is maintained relative to spot size of the laser beam output due to the wavelength being less than about 1.2 μm.

1 - 56 . (canceled)  
     
     
         57 . A laser-based link blowing system for vaporizing and removing a thin metal or polysilicon target link structure on a semiconductor wafer, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, comprising: 
 a laser assembly configurable to produce a laser beam having an operating repetition rate of 10 kilohertz or higher and a wavelength of less than 1.2 microns;    a computer programmed to control timing signals synchronized with position of the laser beam relative to a thin metal or polysilicon target link structure supported on a silicon substrate, the substrate being part of a semiconductor memory device; and    an optical switch that is controllably switchable based on the timing signals so as to transmit an output pulse of the laser beam to the target link structure on demand, the output pulse having a pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, and short enough to avoid unacceptable damage to the substrate or adjacent link structures, the output pulse rate being controllable by controlling the optical switch, the laser assembly being configured to focus the output pulse onto the target link structure into a spot diameter;    whereby the spot size and depth of focus is improved relative to a longer wavelength greater than 1.2 microns, and the output pulse width limits damage to the substrate.    
     
     
         58 . The system of  claim 57  wherein the laser assembly is configurable to produce a laser beam having a pulse width less than 10 nanoseconds.  
     
     
         59 . The system of  claim 57  wherein the wavelength of less than 1.2 microns is about 1.047 microns.  
     
     
         60 . The system of  claim 57  wherein the wavelength of less than 1.2 microns is about 1.064 microns.  
     
     
         61 . The system of  claim 57  wherein the laser assembly comprises a neodymium vanadate laser.  
     
     
         62 . A controlled, switched laser-based link blowing system for vaporizing and removing a thin metal or polysilicon target link structure on a silicon substrate, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, comprising: 
 a diode-pumped, solid-state laser assembly configurable to produce a laser beam output having an operating repetition rate of 5 kilohertz or higher and a wavelength shorter than 1.2 microns;    a controllable switch for controlling the on/off state and power level of the laser assembly; and    a computer programmed to control the laser assembly, the computer being programmed to cause the laser beam output to be directed at the thin metal or polysilicon target link structure on the silicon substrate to vaporize and remove the target link structure, the laser beam output having a pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, and short enough to avoid unacceptable damage to the substrate or adjacent link structures;    whereby heating of the silicon substrate and hence damage to the silicon substrate is limited due to the output pulse width being sufficiently short.    
     
     
         63 . The system of  claim 62  wherein the laser assembly is configurable to produce a laser beam having a pulse width less than 10 nanoseconds.  
     
     
         64 . The system of  claim 62  wherein the laser assembly is configurable to produce a laser beam having an operating repetition rate of 10 kilohertz or higher.  
     
     
         65 . The system of  claim 62  wherein the wavelength shorter than 1.2 microns is about 1.047 microns.  
     
     
         66 . The system of  claim 62  wherein the wavelength shorter than 1.2 microns is about 1.064 microns.  
     
     
         67 . The system of  claim 62  wherein the laser assembly comprises a neodymium vanadate laser.  
     
     
         68 . A laser-based link blowing system for vaporizing and removing a thin metal or polysilicon target link structure on a silicon substrate, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, comprising: 
 a diode-pumped, q-switched, solid-state laser assembly;    a computer programmed to control the laser assembly to cause the laser assembly to produce a laser beam output;    the laser assembly being configurable to produce the laser beam output at an operating repetition rate of about 5 kilohertz or higher and a wavelength shorter than 1.2 microns, and being configured to focus the output pulse onto the thin metal or polysilicon target link structure into a spot diameter, the laser beam output having a pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, and short enough to avoid unacceptable damage to the substrate or adjacent link structures.    
     
     
         69 . The system of  claim 68  wherein the laser assembly is configurable to produce a laser beam having a pulse width less than 10 nanoseconds.  
     
     
         70 . The system of  claim 68  wherein the laser assembly is configurable to produce a laser beam having an operating repetition rate of 10 kilohertz or higher.  
     
     
         71 . The system of  claim 68  wherein the wavelength shorter than 1.2 microns is about 1.047 microns.  
     
     
         72 . The system of  claim 68  wherein the wavelength shorter than 1.2 microns is about 1.064 microns.  
     
     
         73 . The system of  claim 68  wherein the laser assembly comprises a neodymium vanadate laser.  
     
     
         74 . A laser-based method of vaporizing and removing a thin metal or polysilicon target link structure on a semiconductor wafer comprising the steps of: 
 providing a thin metal or polysilicon target link structure supported on a silicon substrate, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, the substrate being part of a semiconductor memory device;    producing a laser beam having an operating repetition rate of 5 kilohertz or higher and a wavelength less than 1.2 microns;    generating timing signals under control of a computer, synchronized with position of the laser beam relative to the target link structure;    using the computer to controllably switch an optical switch based on the timing signals so as to transmit an output pulse of the laser beam to the target link structure on demand, the output pulse rate being controlled by controlling the optical switch, the output pulse having a pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure and short enough to avoid unacceptable damage to the substrate or adjacent link structures;    focusing the output pulse onto the target link structure into a spot diameter;    whereby the spot size and depth of focus is improved relative to a longer wavelength greater than 1.2 microns, and the output pulse width limits damage to the substrate.    
     
     
         75 . The method of  claim 74  wherein the laser beam has a pulse width less than 10 nanoseconds.  
     
     
         76 . The method of  claim 74  wherein the laser beam has an operating repetition rate of 10 kilohertz or higher.  
     
     
         77 . The method of  claim 74  wherein the wavelength less than 1.2 microns is about 1.047 microns.  
     
     
         78 . The method of  claim 74  wherein the wavelength less than 1.2 microns is about 1.064 microns.  
     
     
         79 . The method of  claim 74  wherein laser beam is produced by a neodymium vanadate laser.  
     
     
         80 . A method of vaporizing and removing a thin metal or polysilicon target link structure on a silicon substrate, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, comprising the steps of: 
 providing a diode-pumped, q-switched, solid-state laser assembly under control of a computer;    producing a laser beam output having an operating repetition rate of about 5 kilohertz or higher and a wavelength shorter than 1.2 microns, the laser beam output having an output pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, and short enough to avoid unacceptable damage to the substrate or adjacent link structures; and    focusing the output pulse onto the target link structure into a spot diameter, the output pulse being positioned with accuracy of less than 3/10 of a micron.    
     
     
         81 . The method of  claim 80  wherein the laser beam has a pulse width less than 10 nanoseconds.  
     
     
         82 . The method of  claim 80  wherein the laser beam has an operating repetition rate of 10 kilohertz or higher.  
     
     
         83 . The method of  claim 80  wherein the laser wavelength is about 1.047 microns.  
     
     
         84 . The method of  claim 80  wherein the laser wavelength is about 1.064 microns.  
     
     
         85 . The method of  claim 80  wherein laser beam output is produced by a neodymium vanadate laser.  
     
     
         86 . The method of  claim 80  wherein the solid state laser system further comprises an optical switch positioned beyond the laser cavity and external to the laser cavity and wherein the method further comprises controllably switching the optical switch based on computer controlled timing signals so as to transmit an output pulse of the laser beam to the target link structure on demand, the output pulse rate and pulse spacing being controlled by the controlling the optical switch.  
     
     
         87 . The method of  claim 80  wherein the output pulse width is less than 10 nanoseconds.  
     
     
         88 . A semiconductor memory device produced by a laser-based method of vaporizing and removing a thin metal or polysilicon target link structure on a semiconductor wafer, the method comprising the steps of: 
 providing a thin metal or polysilicon target link structure supported on a silicon substrate, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, the substrate being part of the semiconductor memory device;    producing a laser beam having an operating repetition rate of 5 kilohertz or higher and a wavelength less than 1.2 microns;    generating timing signals under control of a computer, synchronized with position of the laser beam relative to the target link structure;    using the computer to controllably switch an optical switch based on the timing signals so as to transmit an output pulse of the laser beam to the target link structure on demand, the output pulse rate being controlled by controlling the optical switch, the output pulse having a pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure and short enough to avoid unacceptable damage to the substrate or adjacent link structures;    focusing the output pulse onto the target link structure into a spot diameter;    whereby the spot size and depth of focus is improved relative to a longer wavelength greater than 1.2 microns, and the output pulse width limits damage to the substrate.    
     
     
         89 . A semiconductor device produced by a method of vaporizing and removing a thin metal or polysilicon target link structure on a silicon substrate, the substrate being a part of the semiconductor device, the target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, the method comprising the steps of: 
 providing a diode-pumped, q-switched, solid-state laser assembly, under control of a computer;    producing a laser beam output having an operating repetition rate of about 5 kilohertz or higher and a wavelength shorter than 1.2 microns, the laser beam output having an output pulse width long enough to impart sufficient energy to cleanly remove the thin metal or polysilicon target link structure having a width no greater than 1 micron and a thickness no greater than about ⅓ micron, without and short enough to avoid unacceptable damage to the substrate or adjacent link structures; and    focusing the output pulse onto the target link structure into a spot diameter, the output pulse being positioned with accuracy of less than 3/10 of a micron.