Liquid precursor for deposition of copper selenide and method of preparing the same

Abstract

Liquid precursors containing copper and selenium suitable for deposition on a substrate to form thin films suitable for semiconductor applications are disclosed. Methods of preparing such liquid precursors and methods of depositing a precursor on a substrate are also disclosed.

1 . A method of preparing a liquid precursor, said method comprising the steps:
 reducing elemental selenium with a stoichiometric amount of a nitrogen-containing reducing agent in the presence of a first solvent to yield a preliminary precursor solution; and   combining the preliminary precursor solution with a solution of a copper salt and a second solvent, which may be the same or different than the first solvent, to yield the liquid precursor.   
     
     
         2 . The method of  claim 1  wherein the nitrogen-containing reducing agent having a standard reduction potential less than the standard reduction potential of selenium. 
     
     
         3 . The method of  claim 1  wherein the nitrogen-containing reducing agent is hydrazine. 
     
     
         4 . The method of  claim 1  wherein the first and second solvents are each selected from the group consisting of primary amines, secondary amines, glycols and combinations thereof. 
     
     
         5 . The method of  claim 1  wherein the first and second solvents are each selected from the group consisting of ethylene diamine, pyridine, ethanolamine, diethylene triamine, ethylene glycol, and combinations thereof. 
     
     
         6 . The method of  claim 5  wherein the first and second solvents are ethylene diamine. 
     
     
         7 . The method of  claim 1  wherein the copper salt is selected from the group consisting of copper chloride, copper bromide, copper iodide, copper acetate, copper formate, copper nitrate, copper trifluoromethanesulfonate, and combinations thereof. 
     
     
         9 . The method of  claim 1  further comprising the step of separating any precipitate formed during the combining step. 
     
     
         10 . The method of  claim 9  wherein the separation step is carried out using a process selected from the group consisting of filtration, centrifugation, and combinations thereof. 
     
     
         11 . The method of  claim 1  wherein the liquid precursor comprises a copper concentration of from about 0.08 M to 0.10 M. 
     
     
         12 . A method of depositing a solid precursor on a substrate, said method comprising the steps of:
 applying the liquid precursor prepared by the method of  claim 1  to the substrate; and   heating the liquid precursor to a temperature and for a time sufficient to yield the deposited solid precursor on the substrate.   
     
     
         13 . The method of  claim 12  wherein the deposited solid precursor is a thin film. 
     
     
         14 . The method of  claim 12  wherein the temperature is at least 50° C. 
     
     
         15 . The method of  claim 14  wherein the temperature is from about 50° C. to about 275° C. 
     
     
         16 . The method of  claim 12  wherein the deposited solid precursor is copper selenide at least substantially in the form of CuSe 2 . 
     
     
         17 . The method of  claim 12  wherein the deposited solid precursor comprises elemental selenium. 
     
     
         18 . The method of  claim 12  wherein the deposited solid precursor is characterized by an X-ray diffraction pattern substantially as shown in  FIG. 2 . 
     
     
         19 . The method of  claim 12  wherein the applying step is implemented through a process selected from the group consisting of drop coating, dip coating, spin coating, spraying, brushing, air brushing, ink jet application, stamping, printing, pouring, wiping, smearing, spray deposition, slot coating, and combinations thereof. 
     
     
         20 . The method of  claim 12  wherein the liquid precursor comprises a copper concentration in the range of about 0.08 M to about 0.10 M. 
     
     
         21 . A liquid precursor comprising:
 a hydrazine-free solvent for a solute comprising copper and selenium; and   a solute comprising copper and selenium.   
     
     
         22 . The liquid precursor of  claim 21  wherein copper and selenium are present in a molar ratio of about 1:3. 
     
     
         23 . The liquid precursor of  claim 21  wherein the hydrazine-free solvent comprises solvent selected from glycols, amines, and combinations thereof. 
     
     
         24 . The liquid precursor of  claim 21  wherein the copper concentration is in the range of about 0.08 M to about 0.10 M.