Semiconductor laser mounting with intact diffusion barrier layer

Abstract

A first contact surface of a semiconductor laser chip can be formed to a target surface roughness selected to have a maximum peak to valley height that is substantially smaller than a barrier layer thickness. A barrier layer that includes a non-metallic, electrically-conducting compound and that has the barrier layer thickness can be applied to the first contact surface, and the semiconductor laser chip can be soldered to a carrier mounting along the first contact surface using a solder composition by heating the soldering composition to less than a threshold temperature at which dissolution of the barrier layer into the soldering composition occurs. Related systems, methods, articles of manufacture, and the like are also described.

Claimed is: 
     
         1 . A method for frequency stabilization of semiconductor lasers comprising:
 forming a first contact surface of a semiconductor single-frequency laser chip for a tunable laser-based trace gas analyzer to a target surface roughness;   applying a metallization layer comprising 600·10 −10  m of titanium to the first contact surface;   applying a metallic diffusion barrier layer to the first contact surface over the metallization layer, the metallic diffusion barrier layer including multiple layers of differing materials, wherein applying the metallic diffusion barrier layer includes:
 applying a first metallic diffusion barrier layer, the first metallic diffusion barrier layer comprising platinum; and 
 applying a second metallic diffusion barrier layer underlaying the first metallic diffusion barrier layer, the second metallic diffusion barrier layer includes palladium, nickel, tungsten, molybdenum, titanium, tantalum, zirconium, cerium, gadolinium, chromium, manganese, aluminum, beryllium, or yttrium; 
   applying a solder preparation layer to the first contact surface subsequent to applying the metallic diffusion barrier layer and prior to soldering, wherein the solder preparation layer includes an approximately 2000 to 5000·10 −10  m thickness of gold; and   soldering the laser chip along the first contact surface to a carrier mounting using a solder composition, wherein the soldering includes melting the solder composition by heating the solder composition to less than a threshold temperature at which dissolution of the metallic diffusion barrier layer into the solder composition occurs,   wherein subsequent to the soldering, the metallic diffusion barrier layer remains contiguous and intact such that no direct contact occurs between semiconductor materials of the laser chip and the solder composition, such that no direct path exists by which constituents of any of the laser chip, the solder composition and the carrier mounting can diffuse across the metallic diffusion barrier layer.   
     
     
         2 . The method of  claim 1 , wherein, subsequent to the soldering, the solder composition has substantially temporally stable electrical and thermal conductivities. 
     
     
         3 . The method of  claim 1 , further comprising providing the solder composition as at least one of a solder preform that is substantially non-oxidized and a deposited layer that is substantially non-oxidized. 
     
     
         4 . The method of  claim 1 , wherein the soldering includes melting the solder composition under at least one of a reducing atmosphere and a non-oxidizing atmosphere. 
     
     
         5 . The method of  claim 1 , wherein the solder composition is selected from a group consisting of gold germanium, gold silicon, gold tin, silver tin, silver tin copper, silver tine lead, silver tin lead indium, silver tin antimony, tin lead, lead, silver, silicon, germanium, tin, antimony, bismuth, indium, and copper. 
     
     
         6 . The method of  claim 1 , wherein the forming of the first contact surface includes polishing the first contact surface to achieve the target surface roughness prior to applying the metallic diffusion barrier layer. 
     
     
         7 . The method of  claim 6 , wherein the target surface roughness is less than approximately 100·10 −10  m RMS, and/or wherein the target surface roughness is less than approximately 40·10 −10  m RMS. 
     
     
         8 . The method of  claim 1 , wherein the threshold temperature is less than approximately 400° C. 
     
     
         9 . The method of  claim 8 , wherein the threshold temperature is less than approximately 370° C. 
     
     
         10 . The method of  claim 9 , wherein the threshold temperature is less than approximately 340° C. 
     
     
         11 . The method of  claim 1 , further comprising applying another barrier layer to a second contact surface of the carrier mounting, and soldering the laser chip to the carrier mounting along the second contact surface. 
     
     
         12 . The method of  claim 1 , further comprising applying a solder facilitation layer between the first contact surface and a second contact surface on the carrier mounting prior to the soldering, the solder facilitation layer including a metal that is not a component of the solder preparation layer on either the first contact surface or the second contact surface. 
     
     
         13 . The method of  claim 12 , wherein applying the solder facilitation layer includes at least one of placing a sheet of the metal between the first contact surface and the second contact surface prior to the soldering, and depositing a layer of the metal that is not a component of the solder composition onto one or both of the first contact surface and the second contact surface prior to the soldering. 
     
     
         14 . The method of  claim 1 , further comprising matching a first thermal expansion characteristic of the carrier mounting to a second thermal expansion characteristic of the semiconductor laser chip. 
     
     
         15 . A tunable laser-based trace gas analyzer, comprising:
 a semiconductor single-frequency laser chip including:
 a first contact surface having a target surface roughness; 
 a metallization layer of 600·10 −10  m of titanium applied to the first contact surface; 
 a metallic diffusion barrier layer applied to the metallization layer, wherein the metallic diffusion barrier layer includes multiple layers of differing materials; and 
 a solder preparation layer applied to the metallic diffusion barrier layer, wherein the solder preparation layer includes an approximately 2000 to 5000·10 −10  m thickness of gold; and 
   a carrier mounting to which the laser chip is soldered along the first contact surface of the laser chip using a solder composition, wherein the solder composition is heated to less than a threshold temperature at which dissolution of the metallic diffusion barrier layer into the solder composition occurs, and   wherein the metallic diffusion barrier layer is contiguous such that the solder composition does not directly contact semiconductor materials of the laser chip, such that there is no direct path by which constituents of any of the laser chip, the solder composition and the carrier mounting can diffuse across the metallic diffusion barrier layer.   
     
     
         16 . The tunable laser-based trace gas analyzer of  claim 15 , wherein the tunable laser-based trace gas analyzer is a tunable diode laser absorption spectrometer. 
     
     
         17 . The tunable laser-based trace gas analyzer of  claim 15 , wherein the metallic diffusion barrier layer includes a first metallic diffusion barrier layer including platinum and a second metallic diffusion barrier layer underlaying the first metallic diffusion barrier layer, the second metallic diffusion barrier layer including palladium, nickel, tungsten, molybdenum, titanium, tantalum, zirconium, cerium, gadolinium, chromium, manganese, aluminum, beryllium, or yttrium. 
     
     
         18 . The tunable laser-based trace gas analyzer of  claim 15 , wherein the target surface roughness is less than approximately 100·10 −10  m RMS, and/or wherein the target surface roughness is less than approximately 40·10 −10  m RMS. 
     
     
         19 . The tunable laser-based trace gas analyzer of  claim 15 , further comprising a solder facilitation layer between the first contact surface and a second contact surface on the carrier mounting, the solder facilitation layer including a metal that is not a component of the solder preparation layer on either the first contact surface or the second contact surface. 
     
     
         20 . The tunable laser-based trace gas analyzer of  claim 15 , further comprising another barrier layer applied to a second contact surface of the carrier mounting, wherein the laser chip is soldered to the carrier mounting along the second contact surface.