Method of etching ferroelectric layers

Abstract

A method of etching a ferroelectric layer comprises etching a ferroelectric layer using boron trichloride gas and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas. The carbon-containing gas may include CHF 3 or C 2 H 4 . The nitrogen-containing gas may include N 2 or NF 3 . The method reduces side etching of ferroelectric layers, and in particular, PZT-based ferroelectric layers and thereby improves electrical performance and reliability of devices made therefrom.

1 . A method of etching a ferroelectric layer, the method comprising: 
 providing a substrate comprising a ferroelectric layer; and    supplying a process gas comprising boron trichloride and at least one auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas.    
     
     
         2 . The method of  claim 1  wherein the process gas comprises boron trichloride, a carbon-containing gas and a nitrogen-containing gas.  
     
     
         3 . The method of  claim 2  wherein the carbon-containing gas has a flow rate that is substantially equal to a flow rate of the nitrogen-containing gas.  
     
     
         4 . The method of  claim 1 , wherein a flow rate of the at least one auxiliary gas is not less than 1 sccm and not greater than 10 sccm.  
     
     
         5 . The method of  claim 1 , wherein a flow rate of the at least one auxiliary gas is not less than 1% by mole and not greater than 10% by mole with respect to a total flow rate of process gas supplied during etching.  
     
     
         6 . The method of  claim 1 , wherein the carbon-containing gas is selected from the group consisting of CHF 3  and C 2 H 4 .  
     
     
         7 . The method of  claim 1 , wherein the nitrogen-containing gas is selected from the group consisting of N 2  and NF 3 .  
     
     
         8 . The method of  claim 1 , wherein the process gas further comprises argon.  
     
     
         9 . The method of  claim 1  wherein hard masks are used to etch the ferroelectric layer.  
     
     
         10 . The method of  claim 1  wherein the ferrorelectric material is lead zirconate titanate (PZT).  
     
     
         11 . A method of forming a capacitor, comprising: 
 forming a multi-layer film comprising a first conductive layer, a ferroelectric layer, and a second conductive layer;    etching the first conductive layer to form first electrodes;    etching the ferroelectric layer with a process gas comprising boron trichloride and an auxiliary gas selected from the group consisting of a carbon-containing gas and a nitrogen-containing gas; and    etching the second conductive layer to form the second electrodes.    
     
     
         12 . The method of  claim 11 , wherein the first conductive layer and the second conductive layer include a material selected from the group consisting of precious metals and conductive oxides.  
     
     
         13 . The method of  claim 11 , wherein the first conductive layer and the second conductive layer include a material selected from the group consisting of iridium, platinum and ruthenium, iridium oxide (lrO 2 ), and ruthenium oxide (RuO 2 ).  
     
     
         14 . The method of  claim 11  wherein the process gas comprises boron trichloride, a carbon-containing gas and a nitrogen-containing gas.  
     
     
         15 . The method of  claim 11 , wherein the at least one auxiliary gas has a flow rate not less than 1 sccm and not greater than 10 sccm.  
     
     
         16 . The method of  claim 11 , wherein the at least one auxiliary gas has a flow rate not less than 1% by mole and not greater than 10% by mole with respect to a total flow rate of process gas supplied during etching.  
     
     
         17 . The method of  claim 11 , wherein the carbon-containing gas is selected from the group consisting of CHF 3  and C 2 H 4 .  
     
     
         18 . The method of  claim 11 , wherein the nitrogen-containing gas is selected from the group consisting of N 2  and NF 3 .  
     
     
         19 . The method of  claim 11 , wherein the process gas further comprises argon.  
     
     
         20 . The method of  claim 11  wherein the ferroelectric material is lead zirconate titanate (PZT).  
     
     
         21 . The method of  claim 11  further comprising: 
 forming hard masks on the second conductive layer; and  
 using the hard masks to etch the second conductive layer, the ferroelectric layer, and the first conductive layer.