Process for low temperature, dry etching, and dry planarization of copper

Abstract

The subject invention pertains to a method and apparatus for etching copper (Cu). The subject invention can involve passing a halide gas over an area of Cu such that CuX, or CuX and CuX 2 , are formed, where X is the halide. Examples of halides which can be utilized with the subject matter include, but are not necessarily limited to, Cl, Br, F, and I. Once the CuX, or CuX and CuX 2 , are formed the subject invention can then involve passing a reducing gas over the area of Cu for a sufficient time to etch away at least a portion of the CuX, or CuX 2 , respectively. With respect to a specific embodiment in which CuX and CuX 2 are produced when the halide gas is passed over the area of Cu, the reducing gas can be passed until essentially all of the CUX 2 is etched and at least a portion of the CuX is etched. Examples of reducing gases which can be utilized with the subject invention include, but are not necessarily limited to, hydrogen gas and hydrogen gas plasma. The subject invention can accomplish the etching of Cu by passing the reducing gas over the Cu so as to be on a CuX 2 —Cu 3 X 2 metastable line when etching CuX 2 and to be a CuY—CuX metastable line, where Y is the reducing gas element, when etching CuX. FIGS. 5, 6 , and 8, show such metastable lines for Cu, with X being Cl, from temperatures ranging from 50° C. to 200° C. These can be extrapolated to other temperatures, for other halides, and/or other reducing gases. The subject invention can be used to, for example, etch partial into a layer of Cu, through a layer of Cu, or to smooth a Cu surface.

1 . A method for etching copper, comprising: 
 passing a halide gas over an area of Cu, wherein when the halide gas is passed over the area of Cu, CuX, and CuX 2  are formed on the area of Cu, wherein when the halide gas is passed over the area of Cu, the Cu is at a temperature of less than about 100° C.; and    passing a reducing gas over the area of Cu for a sufficient time to etch away at least a portion of the CUX 2 .    
   
   
       2 . The method according to  claim 1 , wherein passing a reducing gas over the area of Cu is accomplished so as to be on a CuX 2 —Cu 3 X 3 (g) metastable line.  
   
   
       3 . The method according to  claim 1 , wherein X is selected from the group consisting of: Cl, F, Br, and I.  
   
   
       4 . The method according to  claim 1 , wherein the halide gas is a chlorine gas.  
   
   
       5 . The method according to  claim 1 , wherein the halide gas passed over the area of Cu is at a pressure between about 20 milliTorr and about 400 milliTorr.  
   
   
       6 . The method according to  claim 1 , wherein the halide gas is a chlorine gas wherein the chlorine gas is a chlorine gas plasma, wherein the chlorine gas plasma is produced via a plasma system selected from the group consisting of: RIE, ICP, and ECR.  
   
   
       7 . The method according to  claim 1 , wherein when the halide gas is passed over the area of Cu, the Cu is at a temperature of less than about 25° C.  
   
   
       8 . The method according to  claim 4 , wherein when the chlorine gas is passed over the area of Cu, the Cu is at a temperature of less than about 50 C.  
   
   
       9 . The method according to  claim 4 , wherein when the chlorine gas is passed over the area of Cu, the Cu is at a temperature of less than about 0 C.  
   
   
       10 . The method according to  claim 4 , wherein when the chlorine gas is passed over the exposed area of Cu, the Cu is at a temperature of less than about −100 C.  
   
   
       11 . The method according to  claim 4 , wherein when the chlorine gas is passed over the exposed area of Cu, the Cu is at a temperature of less than about −150 C.  
   
   
       12 . The method according to  claim 4 , wherein when the chlorine gas is passed over the exposed area of Cu, the Cu is at a temperature of less than about −200 C.  
   
   
       13 . The method according to  claim 1 , wherein passing a halide gas over the area of Cu comprises passing a halide gas plasma over the area of Cu.  
   
   
       14 . The method according to  claim 4 , wherein the chlorine gas comprises a chlorine radical.  
   
   
       15 . The method according to  claim 14 , wherein the chlorine radical is selected from the group consisting of: Cl 2 , Cl, Cl − , and Cl + .  
   
   
       16 . The method according to  claim 1 , wherein the reducing gas comprises a reducing gas plasma.  
   
   
       17 . The method according to  claim 4 , wherein the chlorine gas passed over the area of Cu is at a pressure which allows the formation of CuCl and CuCl 2 .  
   
   
       18 . The method according to  claim 1 , wherein the halide gas comprises a mixture of halides.  
   
   
       19 . The method according to  claim 1 , wherein the reducing gas is a hydrogen plasma.  
   
   
       20 . The method according to  claim 1 , wherein the reducing gas is passed over area of the Cu for a sufficient time to etch essentially all of the CuX 2 .  
   
   
       21 . The method according to  claim 1 , wherein prior to passing a halide gas over the area of Cu, further comprising: masking a layer of Cu such that the area of Cu is unmasked.  
   
   
       22 . The method according to  claim 1 , wherein a surface of the area of Cu is smoothed.  
   
   
       23 . A method for etching copper, comprising; 
 passing a halide gas over an area of Cu, wherein when the halide gas is passed over the area of Cu, CuX is formed on the area of Cu, where X is the halide;    passing a reducing gas over the area of Cu for a sufficient time to etch away at least a portion of the CuX.    
   
   
       24 . The method according to  claim 23 , wherein passing a reducing gas over the area of Cu is accomplished so as to be on a CuX—CuY(g) metastable line, where Y is the reducing gas element.  
   
   
       25 . The method according to  claim 23 , wherein the reducing gas is hydrogen gas, wherein passing a reducing gas over the area of Cu is accomplished so as to be on a CuX—CuH(g) metastable line.  
   
   
       26 . The method according to  claim 23 , wherein the reducing gas is hydrogen gas plasma, wherein the reducing gas is hydrogen gas, wherein passing a reducing gas over the area of Cu is accomplished so as to be on a CuX—CuH(g) metastable line.  
   
   
       27 . The method according to  claim 23 , wherein the halide, X, is selected from the group consisting of: Cl, F, Br, and I.  
   
   
       28 . The method according to  claim 23 , wherein the reducing gas is hydrogen gas.  
   
   
       29 . The method according to  claim 23 , wherein the reducing gas is hydrogen gas plasma.  
   
   
       30 . The method according to  claim 1 , wherein when the halide gas is passed over the area of Cu, the CuX and CuX 2  formed on the area of Cu are formed as layers.  
   
   
       31 . The method according to  claim 20 , wherein the reducing gas is passed over the area of the Cu for a sufficient time to etch at least a portion of the CuX after essentially all of the CuX 2  is etched.  
   
   
       32 . The method according to  claim 23 , wherein the reducing gas is passed over the area of Cu for sufficient time to etch essentially all of the CuX.  
   
   
       33 . The method according to  claim 1 , wherein the halide gas is a chlorine gas plasma.  
   
   
       34 . The method according to  claim 13 , wherein the halide gas passed over the area of Cu is at a pressure that allows the formation of solid CuX and solid CuX 2 .