ONO formation method

Abstract

An ONO formation method comprises the following procedures. First, a bottom oxide layer is formed on a silicon substrate, and then a silicon-rich nitride layer is deposited on the bottom oxide layer. Then, an oxidation process is performed to react with silicon atoms in the silicon-rich nitride layer, so as to form a top oxide layer. Alternatively, the silicon-rich layer can be replaced with a combination of a nitride layer and a polysilicon layer. The oxidation process can consume the polysilicon layer into the top oxide layer, and proper oxygen is introduced into the nitride layer.

1 . A method of forming an oxide-nitride-oxide layer in a non-volatile memory device, comprising the steps of: 
 providing a silicon substrate;    forming a bottom oxide layer on the silicon substrate;    depositing a silicon-rich nitride layer on the bottom oxide layer; and    performing an oxidation process to react with silicon atoms in the silicon-rich nitride layer, so as to form a top oxide layer.    
   
   
       2 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 1 , wherein the bottom oxide layer is of a thickness between 10 and 100 angstroms.  
   
   
       3 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 1 , wherein the silicon-rich nitride layer is of a thickness between 10 and 200 angstroms.  
   
   
       4 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 1 , wherein the oxidation process is conducted at a temperature between 700 and 1100° C.  
   
   
       5 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 1 , wherein the top oxide layer is of a thickness between 20 and 200 angstroms.  
   
   
       6 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 1 , further comprising the step of depositing a first oxide layer on the silicon-rich nitride layer before the oxidation process is performed.  
   
   
       7 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 6 , wherein the first oxide layer is a part of the top oxide layer.  
   
   
       8 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 6 , wherein the first oxide layer is made of high-temperature oxide.  
   
   
       9 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 6 , wherein the first oxide layer is deposited by chemical vapor deposition.  
   
   
       10 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 6 , wherein the first oxide layer is of a thickness between 10 and 100 angstroms.  
   
   
       11 . A method for forming an oxide-nitride-oxide layer in a non-volatile memory device, comprising the steps of: 
 providing a silicon substrate;    forming a bottom oxide layer on the silicon substrate;    depositing a nitride layer on the bottom oxide layer;    depositing a polysilicon layer on the nitride layer; and    performing an oxidation process to react with the polysilicon layer, so as to form a top oxide layer.    
   
   
       12 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 11 , wherein the nitride layer is of a thickness between 10 and 200 angstroms.  
   
   
       13 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 11 , wherein the polysilicon layer is of a thickness between 10 and 100 angstroms.  
   
   
       14 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 11 , further comprising the step of depositing a first oxide layer on the polysilicon layer before the oxidation process is performed.  
   
   
       15 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 14 , wherein the first oxide layer is a part of the top oxide layer.  
   
   
       16 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 14 , wherein the first oxide layer is made of high-temperature oxide.  
   
   
       17 . A method for forming an oxide-nitride-oxide layer in a non-volatile memory device, comprising the steps of: 
 providing a silicon substrate;    forming a bottom oxide layer on the silicon substrate;    depositing a polysilicon layer on the bottom oxide layer;    depositing a nitride layer on the polysilicon layer; and    performing an oxidation process, so as to form a top oxide layer.    
   
   
       18 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 17 , further comprising the step of depositing a first oxide layer on the nitride layer before the oxidation process is performed.  
   
   
       19 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 18 , wherein the first oxide layer is a part of the top oxide layer.  
   
   
       20 . The method for forming an oxide-nitride-oxide layer in a non-volatile memory device of  claim 17 , wherein the nitride layer is of a thickness between 20 and 50 angstroms.