Localized annealing of metal-silicon carbide ohmic contacts and devices so formed

Abstract

A contact for a semiconductor device can be formed by forming a metal on a Silicon Carbide (SiC) substrate and annealing an interface location of the metal and the SiC substrate to form a metal-SiC material thereat and avoiding annealing at a location on the SiC substrate to avoid forming the metal-SiC material thereat.

1 . A method of forming an ohmic contact for a semiconductor device, comprising: 
 forming a metal on a Silicon Carbide (SiC) layer; and    annealing an interface location of the metal and the SiC layer to form a metal-SiC material thereat and avoiding annealing at a location on the SiC layer to avoid forming the metal-SiC material thereat.    
   
   
       2 . A method according to  claim 1  wherein the SiC layer comprises a SiC substrate.  
   
   
       3 . A method according to  claim 2  wherein annealing comprises: 
 annealing at the interface location; and    annealing according to a pattern to avoid annealing at the location.    
   
   
       4 . A method according to  claim 2 , wherein the interface location comprises a first interface location and the location on the SiC substrate comprises a second interface location of the metal and the SiC substrate, wherein annealing comprises: 
 impinging laser light through an opening in a mask layer onto the metal layer at the first interface location and blocking the laser light with the mask layer opposite the second interface location to avoid annealing at the second interface location.    
   
   
       5 . A method according to  claim 1  wherein annealing comprises: 
 activating a laser opposite the interface location to impinge laser light onto the metal layer at the interface location; and    de-activating the laser opposite the location to avoid annealing at the location.    
   
   
       6 . A method according to  claim 2  wherein forming a metal comprises: 
 forming the metal on the SiC substrate to form the location, wherein the location is spaced-apart from the SiC substrate.    
   
   
       7 . A method according to  claim 2  wherein the metal is formed in a pattern to expose a portion of the SiC substrate at the location, wherein annealing comprises: 
 activating a laser opposite the interface location to impinge laser light onto the metal layer at the interface location; and    maintaining activation of the laser opposite the location.    
   
   
       8 . A method according to  claim 2  wherein the metal-SiC material at the interface location comprises a metal ohmic contact on a back side of the substrate opposite a front side of the substrate having an epitaxial layer thereon.  
   
   
       9 . A method according to  claim 1  wherein annealing comprises: 
 impinging laser light on the interface location to form at least one ohmic contact including opposing ohmic contact boundaries having a non-ohmic contact region therebetween.    
   
   
       10 . A method according to  claim 9  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a striped pattern forming an oblique angle with a side of the device.  
   
   
       11 . A method according to  claim 6  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a striped pattern parallel to a side of the device.  
   
   
       12 . A method according to  claim 6  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a circular pattern.  
   
   
       13 . A method according to  claim 2 , wherein the interface location comprises a first interface location and the location on the SiC substrate comprises a second interface location of the metal and the SiC substrate, wherein annealing comprises: 
 impinging an electron beam on the interface location and blocking the electron beam from impinging the second interface location.    
   
   
       14 . A method of forming an ohmic contact for a semiconductor device, comprising: 
 forming a metal on a Silicon Carbide (SiC) layer; and    laser annealing interface locations of the metal and the SiC layer according to a pattern to form a metal-SiC material thereat corresponding to the pattern.    
   
   
       15 . A method according to  claim 14  wherein the SiC layer comprises a SiC substrate.  
   
   
       16 . A method according to  claim 15  wherein forming a metal comprises forming a blanket metal on the substrate, wherein laser annealing comprises: 
 impinging laser light on the interface locations through openings in a mask, that defines the pattern, to form the metal-SiC material thereat; and    blocking the laser light with the mask opposite other interface locations of the metal and the SiC substrate.    
   
   
       17 . A method according to  claim 14  wherein forming a metal comprises forming a blanket metal on the substrate, wherein laser annealing comprises: 
 activating a laser opposite the interface locations, according to the pattern, to impinge laser light onto the blanket metal layer at the interface location; and    de-activating the laser opposite other interface locations to avoid annealing at the other locations.    
   
   
       18 . A method according to  claim 14  wherein the metal comprises nickel, platinum, or titanium.  
   
   
       19 . A method according to  claim 15  wherein laser annealing comprises impinging laser light on the interface locations at an energy and wavelength sufficient to form a silicide of the metal and the SiC substrate.  
   
   
       20 . A method according to  claim 19 , wherein the SiC substrate comprises 6H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 2.8 joules/cm 2  in a single pulse having a duration of about 30 nanoseconds.  
   
   
       21 . A method according to  claim 19 , wherein the SiC substrate comprises 4H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 4.2 joules/cm 2  in about five pulses each having a duration of about 30 nanoseconds.  
   
   
       22 . A method according to  claim 19  wherein the laser light comprises photon energies above a bandgap of the SiC substrate.  
   
   
       23 . A method according to  claim 19  wherein the laser light comprises pulsed or continuous wave laser light.  
   
   
       24 . A method of forming an ohmic contact for a semiconductor device, comprising: 
 forming a metal on a Silicon Carbide (SiC) layer according to a pattern so that portions of the layer are exposed; and    impinging laser light on the exposed portions of the SiC layer and on interface locations of the metal and the Si-C layer to form a metal-SiC material thereat corresponding to the pattern.    
   
   
       25 . A method according to  claim 24  wherein the SiC layer comprises a SiC substrate.  
   
   
       26 . A method according to  claim 24  wherein the metal comprises nickel, platinum, or titanium.  
   
   
       27 . A method according to  claim 25  wherein laser annealing comprises impinging laser light on the interface locations at an energy and wavelength sufficient to form a silicide of the metal and the SiC substrate.  
   
   
       28 . A method according to  claim 25  wherein the SiC substrate comprises 6H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 2.8 joules/cm 2  in a single pulse having a duration of about 30 nanoseconds.  
   
   
       29 . A method according to  claim 25  wherein the SiC substrate comprises 4H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 4.2 joules/cm 2  in about five pulses each having a duration of about 30 nanoseconds.  
   
   
       30 . A method according to  claim 25  wherein the laser light comprises photon energies above a bandgap of the SiC substrate.  
   
   
       31 . A method according to  claim 25  wherein the laser light comprises pulsed or continuous wave laser light.  
   
   
       32 . A method of forming an ohmic contact for a semiconductor device, comprising: 
 forming a photoresist on a SiC layer according to a pattern to expose first portions of the SiC layer and to cover second portions of the substrate;    forming a blanket metal on the first portions and on the photoresist;    impinging laser light on interface locations of the blanket metal and the SiC layer corresponding to the first portions to form a metal-SiC material thereat and avoiding impinging laser light on the blanket metal corresponding to the second portions to avoid forming the metal-SiC material thereat.    
   
   
       33 . A method according to  claim 32  wherein the SiC layer comprises a SiC substrate.  
   
   
       34 . A method according to  claim 32  further comprising: 
 removing metal from the photoresist so that metal-SiC material remains;    forming an overlay on the metal-SiC material; and    removing the photoresist from the SiC substrate.    
   
   
       35 . A method according to  claim 32  further comprising: 
 forming an overlay on the metal-SiC material and on the photoresist; and    removing the photoresist from the SiC layer.    
   
   
       36 . A method according to  claim 32  further comprising: 
 lifting-off the photoresist and the metal thereon leaving the metal-SiC material; and    forming an overlay on the metal-SiC material.    
   
   
       37 . A method according to  claim 32  wherein the metal comprises nickel, platinum, or titanium.  
   
   
       38 . A method according to  claim 32  wherein laser annealing comprises impinging laser light on the interface locations at an energy and wavelength sufficient to form a silicide of the metal and the SiC layer.  
   
   
       39 . A method according to  claim 33  wherein the SiC substrate comprises 6H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 2.8 joules/cm 2  in a single pulse having a duration of about 30 nanoseconds.  
   
   
       40 . A method according to  claim 33  wherein the SiC substrate comprises 4H SiC, wherein laser annealing comprises impinging laser light having a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 4.2 joules/cm 2  in about five pulses each having a duration of about 30 nanoseconds.  
   
   
       41 . A method according to  claim 33  wherein the laser light comprises photon energies above a bandgap of the SiC substrate.  
   
   
       42 . A method according to  claim 32  wherein the laser light comprises pulsed or continuous wave laser light.  
   
   
       43 . A method of forming a contact for a light emitting device (LED), comprising: 
 impinging laser light on an interface location between a metal and a Silicon Carbide (SiC) layer to form a metal-SiC material to provide at least one ohmic contact on the LED including opposing ohmic contact boundaries having a non-ohmic contact region therebetween.    
   
   
       44  A method according to  claim 43  wherein the SiC layer comprises a SiC substrate.  
   
   
       45 . A method according to  claim 43  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a striped pattern forming an oblique angle with a side of the device.  
   
   
       46 . A method according to  claim 43  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a striped pattern parallel to a side of the device.  
   
   
       47 . A method according to  claim 43  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining a circular pattern.  
   
   
       48 . A method according to  claim 44  wherein the SiC substrate comprises 6H SiC, wherein the laser light comprises a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 2.8 joules/cm 2  in a single pulse having a duration of about 30 nanoseconds.  
   
   
       49 . A method according to  claim 44  wherein the SiC substrate comprises 4H SiC, wherein the laser light comprises a wavelength of about 248 nanometers to about 308 nanometers at an energy of about 4.2 joules/cm 2  in about five pulses each having a duration of about 30 nanoseconds.  
   
   
       50 . A method according to  claim 44  wherein the laser light comprises photon energies above a bandgap of the SiC substrate.  
   
   
       51 . A method according to  claim 43  wherein the laser light comprises pulsed or continuous wave laser light.  
   
   
       52 . A method of forming an ohmic contact for a semiconductor device, comprising: 
 forming a metal on a Silicon Carbide (SiC) layer;    laser annealing the metal and the SiC layer to form a metal-SiC material at interface locations of the metal and the SiC layer; and    removing portions of the metal-SiC material to expose the SiC layer according to a pattern to provide at least one ohmic contact on the semiconductor device.    
   
   
       53 . A method according to  claim 52  wherein the SiC layer comprises a SiC substrate.  
   
   
       54 . A contact in a semiconductor device, comprising: 
 at least one metal-Silicon Carbide (SiC) ohmic contact on a SiC layer, the at least one metal-SiC ohmic contact including opposing ohmic contact boundaries having a non-ohmic contact region therebetween.    
   
   
       55 . A contact according to  claim 54  wherein the SiC layer comprises a SiC substrate.  
   
   
       56 . A contact according to  claim 54  wherein the opposing ohmic contact boundaries are separated by about 10 um.  
   
   
       57 . A contact according to  claim 54  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining stripes in a striped pattern forming oblique angles with a side of the device.  
   
   
       58 . A contact according to  claim 54  wherein the stripes are separated about 106 um.  
   
   
       59 . A contact according to  claim 54  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining stripes a striped pattern parallel to a side of the device.  
   
   
       60  A contact according to  claim 54  wherein the striped pattern defines a substantially circular shape having a diameter of about 95 um, wherein the stripes are separated by distance of about 4.0 um to about 5.0 um.  
   
   
       61 . A contact according to  claim 54  wherein the at least one ohmic contact comprises a plurality of ohmic contacts including respective opposing ohmic contact boundaries defining rings of a concentric circular pattern.  
   
   
       62 . A contact according to  claim 54  wherein the rings are separated by a distance of about 4.0 um to about 5.0 um.  
   
   
       63 . A contact according to  claim 54  wherein, the device comprises a light emitting diode.