Mis-il silicon solar cell with passivation layer to induce surface inversion

Abstract

The present invention relates generally to a photovoltaic solar cell device and more particularly, to a structure and method of inducing charge inversion in a silicon substrate by using a highly charged passivation layer on an upper side of the silicon substrate. A positively charged passivation layer comprising hafnium oxide may be formed on an insulating layer covering an upper surface of a p-doped silicon substrate and on a metal contact to induce a strong inversion layer in an upper portion of the p-doped silicon substrate.

What is claimed is: 
     
         1 . A method comprising:
 conformally forming a positively charged metal oxide layer on an upper surface of an insulating layer and covering a metal contact on the insulating layer, the positive charge of the positively charged metal oxide layer causes an n-type region to form in an upper portion of a substrate; and   forming a silicon nitride layer directly above the positively charged metal oxide layer.   
     
     
         2 . The method of  claim 1 , further comprising:
 tuning a thickness and charge density of the positively charged metal oxide layer to affect a depth and charge density of the n-type region formed in the upper portion of the substrate.   
     
     
         3 . The method of  claim 2 , wherein tuning the thickness and charge density of the positively charged metal oxide layer comprises:
 adjusting a deposition temperature and a duration of an atomic layer deposition process used to form the positively charged metal oxide layer.   
     
     
         4 . The method of  claim 1 , further comprising:
 forming a metal layer on a bottom surface of the substrate; and   annealing the substrate and the metal layer to form a p+ doped layer in a bottom portion of the substrate.   
     
     
         5 . The method of  claim 4 , wherein forming the metal layer on the bottom surface of the substrate comprising depositing a layer of copper, silver, gold, tungsten, aluminum, or alloys thereof. 
     
     
         6 . The method of  claim 4 , wherein the metal layer on the bottom surface of the substrate comprising copper, silver, gold, tungsten, aluminum, or alloys thereof. 
     
     
         7 . The method of  claim 1 , wherein the substrate comprises a silicon-on-insulator substrate or a silicon germanium-on-insulator substrate. 
     
     
         8 . The method of  claim 1 , wherein the substrate comprises p-doped silicon. 
     
     
         9 . The method of  claim 1 , wherein forming the insulating layer comprises depositing a layer of silicon oxide. 
     
     
         10 . The method of  claim 1 , wherein the insulating layer comprises silicon oxide. 
     
     
         11 . The method of  claim 1 , wherein forming the metal contact comprises using a screen printing process. 
     
     
         12 . The method of  claim 1 , wherein the metal contact comprises copper, silver, gold, tungsten, aluminum, or alloys thereof. 
     
     
         13 . The method of  claim 1 , wherein forming the positively charged metal oxide layer on the insulating layer and on the metal contact comprises depositing a layer of hafnium oxide or lanthanum oxide. 
     
     
         14 . The method of  claim 1 , wherein the positively charged metal oxide layer comprises hafnium oxide or lanthanum oxide. 
     
     
         15 . The method of  claim 1 , wherein the positively charged metal oxide layer has a thickness of approximately 0.1 nm to approximately 5 nm. 
     
     
         16 . The method of  claim 1 , wherein the n-type region in the upper portion of the substrate comprises a larger electron concentration than the remainder of the substrate. 
     
     
         17 . The method of  claim 1 , further comprising:
 forming an anti-reflective (AR) layer on the positively charged metal oxide layer.