A structure for forming a laser circuit having low penetration ohmic contact providing impurity gettering and the resultant laser circuit

Abstract

A novel contact structure and method for a multilayer gettering contact metallization is provided utilizing a thin layer of a pure metal as the initial layer formed on a semiconductor cap layer. During formation of the contact structure, this thin metal layer reacts with the cap layer and the resulting reacted layer traps mobile impurities and self-interstitials diffusing within the cap layer and in nearby metal layers, preventing further migration into active areas of the semiconductor device. The contact metallization is formed of pure metal layers compatible with each other and with the underlying semiconductor cap layer such that depth of reaction is minimized and controllable by the thickness of the metal layers applied. Thin semiconductor cap layers, such as InGaAs cap layers less than 200 nm thick, may be used in the present invention with extremely thin pure metal layers of thickness 10 nm or less, thus enabling an increased level of integration for semiconductor optoelectronic devices. In addition, because pure metal layers are used in the ohmic contact, fewer impurities are introduced in the formation of the contact than with prior art alloy contacts.

1 . A multilayer gettering contact metallization, comprising: 
 a semiconductor cap layer; and    a low-penetration electrical contact formed on said cap layer including a plurality of metal layers, at least one of which reacts with said cap layer to remove mobile impurities and self-interstitials from said cap layer.    
     
     
         2 . The contact metallization of  claim 1  wherein said metal layers are annealed layers.  
     
     
         3 . The contact metallization of  claim 1  wherein said metal layers are electron-beam evaporated layers.  
     
     
         4 . The contact metallization of  claim 1  wherein said cap layer is a compound semiconductor doped with Zinc.  
     
     
         5 . The contact metallization of  claim 1  wherein said cap layer is a compound semiconductor doped with Carbon.  
     
     
         6 . The contact metallization of  claim 1  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Zinc.  
     
     
         7 . The contact metallization of  claim 1  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Carbon.  
     
     
         8 . The contact metallization of  claim 1  wherein said cap layer has a thickness of between about 30 nm and 500 nm.  
     
     
         9 . The contact metallization of  claim 1  wherein said cap layer has a thickness greater than about 30 nm and less than about 200 nm.  
     
     
         10 . The contact metallization of  claim 1  wherein said cap layer has a thickness of about 50 nm.  
     
     
         11 . The contact metallization of  claim 1  wherein said plurality of metal layers includes at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         12 . The contact metallization of  claim 1  wherein said plurality of metal layers includes a first layer of Gold formed on said cap layer, a second layer of Titanium formed on said first layer, a third layer of Platinum formed on said second layer, and a fourth layer of Gold formed on said third layer.  
     
     
         13 . The contact metallization of  claim 12  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         14 . The contact metallization of  claim 12  wherein said first layer has a thickness of between about 1 nm to 11 nm, said second layer has a thickness of between about 30 nm to 70 nm, said third layer has a thickness of between about 30 nm to 70 nm, and said fourth layer has a thickness of between about 50 nm to 300 nm.  
     
     
         15 . The contact metallization of  claim 1  wherein said cap layer is reacted with said at least one metal layer whereby said plurality of metal layers includes a first layer containing at least Gold and Indium and a second layer containing at least Titanium and Gold.  
     
     
         16 . The contact metallization of  claim 1  wherein said mobile impurities include Zinc.  
     
     
         17 . The contact metallization of  claim 1  wherein said self-interstitials include atoms of Indium or Gallium.  
     
     
         18 . The contact metallization of  claim 1  wherein said mobile impurities and self-interstitials include atoms of at least one of the group selected from Copper, Zinc, Indium and Gallium.  
     
     
         19 . The contact metallization of  claim 1  further comprising a barrier metallization formed on said plurality of metal layers including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         20 . The contact metallization of  claim 19  further comprising a bonding metallization formed on said barrier metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.  
     
     
         21 . An optoelectronic integrated circuit, comprising: 
 a semiconductor device including a plurality of semiconductor device layers; and    at least one multilayer gettering contact metallization formed on said plurality of device layers, comprising: 
 a semiconductor cap layer;  
 a low-penetration electrical contact formed on said cap layer including 
 a plurality of metal layers, at least one of which reacts with said cap layer to remove mobile impurities and self-interstitials from said cap layer.  
 
   
     
     
         22 . The optoelectronic integrated circuit of  claim 21  wherein said metal layers are annealed layers.  
     
     
         23 . The optoelectronic integrated circuit of  claim 21  wherein said metal layers are electron-beam evaporated layers.  
     
     
         24 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer is a compound semiconductor doped with Zinc.  
     
     
         25 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer is a compound semiconductor doped with Carbon.  
     
     
         26 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Zinc.  
     
     
         27 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Carbon.  
     
     
         28 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer has a thickness of between about 30 nm and 500 nm.  
     
     
         29 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer has a thickness greater than about 30 nm and less than about 200 nm.  
     
     
         30 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer has a thickness of about 50 nm.  
     
     
         31 . The optoelectronic integrated circuit of  claim 21  wherein said plurality of metal layers includes at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         32 . The optoelectronic integrated circuit of  claim 21  wherein said plurality of metal layers includes a first layer of Gold formed on said cap layer, a second layer of Titanium formed on said first layer, a third layer of Platinum formed on said second layer, and a fourth layer of Gold formed on said third layer.  
     
     
         33 . The optoelectronic integrated circuit of  claim 32  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         34 . The optoelectronic integrated circuit of  claim 32  wherein said first layer has a thickness of between about 1 nm to 11 nm, said second layer has a thickness of between about 30 nm to 70 nm, said third layer has a thickness of between about 30 nm to 70 nm, and said fourth layer has a thickness of between about 50 nm to 300 nm.  
     
     
         35 . The optoelectronic integrated circuit of  claim 21  wherein said cap layer is reacted with said at least one metal layer whereby said plurality of metal layers includes a first layer containing at least Gold and Indium and a second layer containing at least Titanium and Gold.  
     
     
         36 . The optoelectronic integrated circuit of  claim 21  wherein said mobile impurities include Zinc.  
     
     
         37 . The optoelectronic integrated circuit of  claim 21  wherein said self-interstitials include atoms of Indium or Gallium.  
     
     
         38 . The optoelectronic integrated circuit of  claim 21  wherein said mobile impurities and self-interstitials include atoms of at least one of the group selected from Copper, Zinc, Indium and Gallium.  
     
     
         39 . The optoelectronic integrated circuit of  claim 21  further comprising a barrier metallization formed on said plurality of metal layers including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         40 . The optoelectronic integrated circuit of  claim 39  further comprising a bonding metallization formed on said barrier metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.  
     
     
         41 . A multiple-quantum-well semiconductor laser, comprising: 
 a multiple-quantum-well semiconductor device including a plurality of semiconductor device layers; and    at least one multilayer gettering contact metallization formed on said plurality of device layers, comprising: 
 a semiconductor cap layer;  
 a low-penetration electrical contact formed on said cap layer including 
 a plurality of metal layers, at least one of which reacts with said cap layer to remove mobile impurities and self-interstitials from said cap layer.  
 
   
     
     
         42 . The laser of  claim 41  wherein said metal layers are annealed layers.  
     
     
         43 . The laser of  claim 41  wherein said metal layers are electron-beam evaporated layers.  
     
     
         44 . The laser of  claim 41  wherein said cap layer is a compound semiconductor doped with Zinc.  
     
     
         45 . The laser of  claim 41  wherein said cap layer is a compound semiconductor doped with Carbon.  
     
     
         46 . The laser of  claim 41  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Zinc.  
     
     
         47 . The laser of  claim 41  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Carbon.  
     
     
         48 . The laser of  claim 41  wherein said cap layer has a thickness of between about 30 nm and 500 nm.  
     
     
         49 . The laser of  claim 41  wherein said cap layer has a thickness greater than about 30 nm and less than about 200 nm.  
     
     
         50 . The laser of  claim 41  wherein said cap layer has a thickness of about 50 nm.  
     
     
         51 . The laser of  claim 41  wherein said plurality of metal layers includes at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         52 . The laser of  claim 41  wherein said plurality of metal layers includes a first layer of Gold formed on said cap layer, a second layer of Titanium formed on said first layer, a third layer of Platinum formed on said second layer, and a fourth layer of Gold formed on said third layer.  
     
     
         53 . The laser of  claim 52  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         54 . The laser of  claim 52  wherein said first layer has a thickness of between about 1 nm to 11 nm, said second layer has a thickness of between about 30 nm to 70 nm, said third layer has a thickness of between about 30 nm to 70 nm, and said fourth layer has a thickness of between about 50 nm to 300 nm.  
     
     
         55 . The laser of  claim 41  wherein said cap layer is reacted with said at least one metal layer whereby said plurality of metal layers includes a first layer containing at least Gold and Indium and a second layer containing at least Titanium and Gold.  
     
     
         56 . The laser of  claim 41  wherein said mobile impurities include Zinc.  
     
     
         57 . The laser of  claim 41  wherein said self-interstitials include atoms of Indium or Gallium.  
     
     
         58 . The laser of  claim 41  wherein said mobile impurities and self-interstitials include atoms of at least one of the group selected from Copper, Zinc, Indium and Gallium.  
     
     
         59 . The laser of  claim 41  further comprising a barrier metallization formed on said plurality of metal layers including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         60 . The laser of  claim 59  further comprising a bonding metallization formed on said barrier metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.  
     
     
         61 . An electroabsorption modulated laser (EML), comprising: 
 an electroabsorption modulated semiconductor device including a plurality of semiconductor device layers; and    at least one multilayer gettering contact metallization formed on said plurality of device layers, comprising: 
 a semiconductor cap layer;  
 a low-penetration electrical contact formed on said cap layer including 
 a plurality of metal layers, at least one of which reacts with said cap layer to remove mobile impurities and self-interstitials from said cap layer.  
 
   
     
     
         62 . The laser of  claim 61  wherein said metal layers are annealed layers.  
     
     
         63 . The laser of  claim 61  wherein said metal layers are electron-beam evaporated layers.  
     
     
         64 . The laser of  claim 61  wherein said cap layer is a compound semiconductor doped with Zinc.  
     
     
         65 . The laser of  claim 61  wherein said cap layer is a compound semiconductor doped with Carbon.  
     
     
         66 . The laser of  claim 61  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Zinc.  
     
     
         67 . The laser of  claim 61  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Carbon.  
     
     
         68 . The laser of  claim 61  wherein said cap layer has a thickness of between about 30 nm and 500 nm.  
     
     
         69 . The laser of  claim 61  wherein said cap layer has a thickness greater than about 30 nm and less than about 200 nm.  
     
     
         70 . The laser of  claim 61  wherein said cap layer has a thickness of about 50 nm.  
     
     
         71 . The laser of  claim 61  wherein said plurality of metal layers includes at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         72 . The laser of  claim 61  wherein said plurality of metal layers includes a first layer of Gold formed on said cap layer, a second layer of Titanium formed on said first layer, a third layer of Platinum formed on said second layer, and a fourth layer of Gold formed on said third layer.  
     
     
         73 . The laser of  claim 72  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         74 . The laser of  claim 72  wherein said first layer has a thickness of between about 1 nm to 11 nm, said second layer has a thickness of between about 30 nm to 70 nm, said third layer has a thickness of between about 30 nm to 70 nm, and said fourth layer has a thickness of between about 50 nm to 300 nm.  
     
     
         75 . The laser of  claim 61  wherein said cap layer is reacted with said at least one metal layer whereby said plurality of metal layers includes a first layer containing at least Gold and Indium and a second layer containing at least Titanium and Gold.  
     
     
         76 . The laser of  claim 61  wherein said mobile impurities include Zinc.  
     
     
         77 . The laser of  claim 61  wherein said self-interstitials include atoms of Indium or Gallium.  
     
     
         78 . The laser of  claim 61  wherein said mobile impurities and self-interstitials include atoms of at least one of the group selected from Copper, Zinc, Indium and Gallium.  
     
     
         79 . The laser of  claim 61  further comprising a barrier metallization formed on said plurality of metal layers including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         80 . The laser of  claim 79  further comprising a bonding metallization formed on said barrier metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.  
     
     
         81 . An optoelectronic communications system, comprising: 
 a semiconductor laser;    an optoelectronic receiver; and    an optical link connecting said laser and said receiver,    wherein at least one of said laser, said link, and said receiver includes a multilayer gettering contact metallization, comprising: 
 a semiconductor cap layer; and  
 a low-penetration electrical contact formed on said cap layer including 
 a plurality of metal layers, at least one of which reacts with said cap layer to remove mobile impurities and self-interstitials from said cap layer.  
 
   
     
     
         82 . The system of  claim 81  wherein said metal layers are annealed layers.  
     
     
         83 . The system of  claim 81  wherein said metal layers are electron-beam evaporated layers.  
     
     
         84 . The system of  claim 81  wherein said cap layer is a compound semiconductor doped with Zinc.  
     
     
         85 . The system of  claim 81  wherein said cap layer is a compound semiconductor doped with Carbon.  
     
     
         86 . The system of  claim 81  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Zinc.  
     
     
         87 . The system of  claim 81  wherein said cap layer is a compound semiconductor including Indium, Gallium and Arsenic and is doped with Carbon.  
     
     
         88 . The system of  claim 81  wherein said cap layer has a thickness of between about 30 nm and 500 nm.  
     
     
         89 . The system of  claim 81  wherein said cap layer has a thickness greater than about 30 nm and less than about 200 nm.  
     
     
         90 . The system of  claim 81  wherein said cap layer has a thickness of about 50 nm.  
     
     
         91 . The system of  claim 81  wherein said plurality of metal layers includes at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         92 . The system of  claim 81  wherein said plurality of metal layers includes a first layer of Gold formed on said cap layer, a second layer of Titanium formed on said first layer, a third layer of Platinum formed on said second layer, and a fourth layer of Gold formed on said third layer.  
     
     
         93 . The system of  claim 92  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         94 . The system of  claim 92  wherein said first layer has a thickness of between about 1 nm to 11 nm, said second layer has a thickness of between about 30 nm to 70 nm, said third layer has a thickness of between about 30 nm to 70 nm, and said fourth layer has a thickness of between about 50 nm to 300 nrn.  
     
     
         95 . The system of  claim 81  wherein said cap layer is reacted with said at least one metal layer whereby said plurality of metal layers includes a first layer containing at least Gold and Indium and a second layer containing at least Titanium and Gold.  
     
     
         96 . The system of  claim 81  wherein said mobile impurities include Zinc.  
     
     
         97 . The system of  claim 81  wherein said self-interstitials include atoms of Indium or Gallium.  
     
     
         98 . The system of  claim 81  wherein said mobile impurities and self-interstitials include atoms of at least one of the group selected from Copper, Zinc, Indium and Gallium.  
     
     
         99 . The system of  claim 81  further comprising a barrier metallization formed on said plurality of metal layers including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         100 . The system of  claim 99  further comprising a bonding metallization formed on said barrier metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.  
     
     
         101 . A method of producing a multilayer gettering contact metallization in a laser semiconductor device having a cap layer, comprising the acts of: 
 forming a dielectric barrier layer on said cap layer;    removing portions of said dielectric barrier layer according to a pattern to expose portions of said cap layer;    forming a plurality of pure metal layers on said exposed cap layer portions, at least one of which is capable of gettering mobile impurities and self-interstitials present in said cap layer; and    heating said plurality of pure metal layers to cause mobile impurities and self-interstitials in at least said cap layer to be gettered in said plurality of pure metal layers.    
     
     
         102 . The method of  claim 101  wherein said forming of said dielectric barrier layer includes forming said barrier layer using an oxide or a nitride.  
     
     
         103 . The method of  claim 101  wherein said forming of said pure metal layers includes electron-beam evaporation in a vacuum.  
     
     
         104 . The method of  claim 101  wherein said act of heating includes heating said metal layers at a temperature of about 350 degrees Celsius for between about 0.25 minutes to 7 minutes.  
     
     
         105 . The method of  claim 101  wherein said forming of said pure metal layers includes forming at least one layer of Gold, at least one layer of a low-electronegativity metal, and at least one layer of a high-electronegativity metal.  
     
     
         106 . The method of  claim 101  wherein said forming of said pure metal layers includes forming a first layer of Gold on said cap layer, a second layer of Titanium on said first layer, a third layer of Platinum on said second layer, and a fourth layer of Gold on said third layer.  
     
     
         107 . The method of  claim 106  wherein said first layer reacts with said cap layer, and said second layer reacts with said cap layer, said first layer, and said third layer.  
     
     
         108 . The method of  claim 106  wherein said forming of said first, second, third and fourth layers includes forming said first layer to a thickness of between about 1 nm to 11 nm, said second layer to a thickness of between about 30 nm to 70 nm, said third layer to a thickness of between about 30 nm to 70 nm, and said fourth layer to a thickness of between about 50 nm to 300 nm.  
     
     
         109 . The method of  claim 101  wherein said cap layer reacts with said plurality of metal layers to form at least a first layer and a second layer, said first layer containing at least Gold and Indium and said second layer containing at least Titanium and Gold.  
     
     
         110 . The method of  claim 101  wherein said metal layers react with a controlled amount of said cap layer, said controlled amount determined by a thickness of said metal layers formed on said cap layer, a time for which said metal layers are heated, and a temperature at which said metal layers are heated.  
     
     
         111 . The method of  claim 101  wherein said act of heating causes mobile impurities to be gettered including at least Zinc.  
     
     
         112 . The method of  claim 101  wherein said act of heating causes self-interstitials to be gettered including at least atoms of Indium or Gallium.  
     
     
         113 . The method of  claim 101  wherein said act of heating causes mobile impurities and self-interstitials to be gettered including atoms of at least one of the group consisting of Copper, Zinc, Indium and Gallium.  
     
     
         114 . The method of  claim 101  further comprising forming a barrier metallization on said plurality of metal layers, said barrier metallization including a first barrier layer of a low-electronegativity metal, a second barrier layer of a high-electronegativity metal, and a third barrier layer of Au.  
     
     
         115 . The method of  claim 114  further comprising forming a bonding metallization on said barrier metallization, said bonding metallization including a first bonding layer of Au, a second bonding layer of Pt, and a third bonding layer of Au.