Device and Method for Stopping an Etching Process

Abstract

A method for etching a layer assembly, the layer assembly including an intermediate layer sandwiched between an etch layer and a stop layer, the method including a step of etching the etch layer using a first etchant and a step of etching the intermediate layer using a second etchant. The first etchant includes a first etch selectivity of at least 5:1 with respect to the etch layer and the intermediate layer. The second etchant includes a second etch selectivity of at least 5:1 with respect to the intermediate layer and the stop layer. The first etchant being is different from the second etchant.

What is claimed is: 
     
         1 . A method for manufacturing a semiconductor structure, the method comprising:
 forming a stop layer;   forming an intermediate layer over the stop layer, the intermediate layer having an intermediate layer thickness;   forming an etch layer over the intermediate layer, the etch layer having an etch layer thickness, wherein the etch layer comprises an inclusion and a first material; and   performing a first etching step with an etch selectivity,   wherein a ratio of the etch layer thickness to the intermediate layer thickness is at most 3 times the etch selectivity of the first etching step, wherein the intermediate layer comprise a second material, wherein the stop layer comprises a third material, and wherein the etching rate of the inclusion is greater than the etching rate of the first material when exposed to a fluorocarbon etchant.   
     
     
         2 . The method of  claim 1 , wherein forming the etch layer comprises forming the etch layer such that the etch layer thickness varies more than 10% around a mean value. 
     
     
         3 . The method of  claim 2 , wherein forming the intermediate layer comprises forming the intermediate layer such that the intermediate layer thickness exceeds the ratio of the etch layer thickness to the etch selectivity. 
     
     
         4 . The method of  claim 1 , wherein the first material comprises titanium nitride, wherein the second material comprises silicon oxynitride, and wherein the third material comprises an oxide material. 
     
     
         5 . A method of forming a semiconductor structure, the method comprising:
 forming a stop layer of a first material over a semiconductor substrate, the stop layer comprising a metallic layer and having a stop layer thickness;   forming an intermediate layer of a second material over the stop layer, the intermediate layer having an intermediate layer thickness; and   forming an etch layer of a third material over the intermediate layer, the etch layer having an etch layer thickness,   forming a via contact by etching the etch layer, the intermediate layer, and the stop layer, wherein the etch layer comprises an inclusion, wherein the inclusion has an etching rate different than the etching rate of the third material during the etching, and wherein the etching rate of the inclusion is greater than the etching rate of the third material when exposed to a fluorocarbon etchant.   
     
     
         6 . The method of  claim 5 , wherein the intermediate layer thickness is such that a ratio of the etch layer thickness to the intermediate layer thickness is at most 3 times a first etch selectivity, and wherein the first etch selectivity is the etching rate of the first material divided by an etching rate of the second material when exposed to a fluorocarbon etchant. 
     
     
         7 . The method of  claim 6 , wherein the first and second materials are such that the first etch selectivity for the fluorocarbon etchant between the first and second materials is at least a ratio of 5:1, and wherein the second and third materials are such that a second etch selectivity for a fluoro-methane etchant between the second and third materials is at least a ratio of 5:1. 
     
     
         8 . The method of  claim 7 , wherein a thickness of the intermediate layer is less than a product of the second etch selectivity and the stop layer thickness. 
     
     
         9 . The method of  claim 5 , wherein the inclusion comprises air. 
     
     
         10 . The method of  claim 5 , wherein the metallic layer comprises aluminum, wherein the first material comprises titanium nitride, wherein the second material comprises silicon oxynitride, and wherein the third material comprises an oxide material. 
     
     
         11 . The method of  claim 5 , wherein the etch layer comprises a first non-uniformity in a region to be etched for forming the via contact, and wherein the first non-uniformity extends substantially through the etch layer thickness. 
     
     
         12 . The method of  claim 11 , further comprising a second non-uniformity in the region to be etched for forming the via contact, and wherein the second non-uniformity extends only partially through the etch layer thickness. 
     
     
         13 . The method of  claim 12 , wherein a sidewall of the first non-uniformity intersects with a sidewall of the second non-uniformity. 
     
     
         14 . The method of  claim 13 , wherein the inclusion is disposed under the intersecting sidewalls of the first and second non-uniformities. 
     
     
         15 . The method of  claim 12 , wherein the etch layer has a minimum thickness at a bottom surface of the first non-uniformity. 
     
     
         16 . The method of  claim 12 , wherein sidewalls of the first non-uniformity are non-uniform, and wherein a bottom surface of the first non-uniformity is non-uniform.