Energy-efficient, laser-based method and system for processing target material

Abstract

An energy-efficient method and system for processing target material such as microstructures in a microscopic region without causing undesirable changes in electrical and/or physical characteristics of material surrounding the target material is provided. The system includes a controller for generating a processing control signal and a signal generator for generating a modulated drive waveform based on the processing control signal. The waveform has a sub-nanosecond rise time. The system also includes a gain-switched, pulsed semiconductor seed laser for generating a laser pulse train at a repetition rate. The drive waveform pumps the laser so that each pulse of the pulse train has a predetermined shape. Further, the system includes a laser amplifier for optically amplifying the pulse train to obtain an amplified pulse train without significantly changing the predetermined shape of the pulses. The amplified pulses have little distortion and have substantially the same relative temporal power distribution as the original pulse train from the laser. Each of the amplified pulses has a substantially square temporal power density distribution, a sharp rise time, a pulse duration and a fall time. The system further includes a beam delivery and focusing subsystem for delivering and focusing at least a portion of the amplified pulse train onto the target material. The rise time (less than about 1 ns) is fast enough to efficiently couple laser energy to the target material, the pulse duration (typically 2-10 ns) is sufficient to process the target material, and the fall time (a few ns) is rapid enough to prevent the undesirable changes to the material surrounding the target material.

1 .- 83 . (canceled)  
     
     
         84 . A laser system for modifying target material, the system comprising: 
 a signal generator that provides an electrical drive waveform having an on state and an off state;    a seed laser that receives the electrical drive waveform and has an output comprising a sequence of variable width pulses with a wavelengths;    an optical fiber amplifier that receives the output of the seed laser and amplifies the output to produce a sequence of amplified pulses including at least one amplified pulse that is directed toward the target material; and    a subsystem that receives the output of the fiber amplifier for controlling the level of optical energy incident on the material, and for selectively directing, based on position information, the at least one amplified pulse to the target material so that the target material is selectively modified.    
     
     
         85 . The system as claimed in  claim 84 , wherein the seed laser is a semiconductor laser diode.  
     
     
         86 . The system as claimed in  claim 84 , wherein the wavelength is less than an absorption edge of the target material.  
     
     
         87 . The system as claimed in  claim 84 , wherein the at least one amplified pulse has a substantially square temporal pulse shape.  
     
     
         88 . The system as claimed in  claim 84 , further comprising a shifter that controls a changeable, time-varying characteristic of the at least one amplified pulse.  
     
     
         89 . The system claimed in  claim 84 , wherein the target material is part of a microelectronic device.  
     
     
         90 . The system as claimed in  claim 89 , wherein the microelectronic device is a microelectromechanical device.  
     
     
         91 . The system as claimed in  claim 84 , wherein pulse duration of each pulse of the sequence of variable width pulses corresponds to a duration wherein a fluence threshold for material processing is substantially proportional to the square root of the pulse duration whereby the target material is processed in a thermal manner.  
     
     
         92 . The system as claimed in  claim 84 , wherein each of the amplified pulses has at least 0.1 and up to 3 microjoules of energy.  
     
     
         93 . The system as claimed in  claim 84 , wherein the seed laser includes a modified Q-switched system.  
     
     
         94 . The system as claimed in  claim 84 , wherein the target material has a specific dimension and wherein the specified dimension is less than the wavelength.  
     
     
         95 . The system as claimed in  claim 84 , wherein the subsystem includes an optical switch and a computer coupled to the optical switch for selecting material processing pulses of the sequence of amplified pulses and to control position of the selected pulses relative to the target material.  
     
     
         96 . The system as claimed in  claim 84 , wherein a lower bound of the variable width is at least several picoseconds.  
     
     
         97 . The system as claimed in  claim 84 , wherein an upper bound of the variable width is 10 nanoseconds.  
     
     
         98 . The system as claimed in  claim 84 , wherein the at least one amplified pulse creates a feature from the target material.  
     
     
         99 . The system as claimed in  claim 84 , wherein the at least one amplified pulse removes a feature from the target material.