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AssigneeApplied Materials, Inc.
InventorsPadmapani Nallan, Hakeem Oluseyi
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The present invention relates to a method of etching tungsten or tungsten nitride in semiconductor structures, and particularly to the etching of gate electrodes which require precise control over the etching process. We have discovered a method of etching tungsten or tungsten nitride which permits precise etch profile control while providing excellent selectivity, of at least 175:1, for example, in favor of etching tungsten or tungsten nitride rather than an adjacent oxide layer. Typically, the oxide is selected from silicon oxide, silicon oxynitride, tantalum pentoxide, zirconium oxide, and combinations thereof. The method appears to be applicable to tungsten or tungsten nitride, whether deposited by physical vapor deposition (PVD) or chemical vapor deposition (CVD). In particular, an initial etch chemistry, used during the majority of the tungsten or tungsten nitride etching process (the main etch), employs the use of a plasma source gas where the chemically functional etchant species are generated from a combination of sulfur hexafluoride (SF6) and nitrogen (N2), or in the alternative, from a combination of nitrogen trifluoride (NF3), chlorine (Cl2), and carbon tetrafluoride (CF4). Toward the end of the main etching process, a second chemistry is used in which the chemically functional etchant species are generated from Cl2 and O2. This final portion of the etch process may be referred to as an “overetch” process, since etching is carried out to at least the surface underlying the tungsten or tungsten nitride. However, this second etch chemistry may optionally be divided into two steps, where the plasma source gas oxygen content and plasma source power are increased in the second step.
A method of plasma etching tungsten or tungsten nitride, wherein an etch selectivity of greater than about 75:1 is obtained relative to an adjacent silicon oxide layer by using a plasma source gas comprising chemically functional etchant species which are generated from Cl2 and O2, wherein the volumetric percentage of O2 in said plasma source gas is at least 35%, and wherein a plasma density is at least 1.6×1011 e−/cm3.
A method of selectively etching tungsten or tungsten nitride relative to an underlying oxide layer in semiconductor structures, comprising:
A method of selectively etching tungsten or tungsten nitride relative to an underlying oxide layer in semiconductor structures, comprising:
A method of selectively etching tungsten nitride relative to silicon oxide during the etching of semiconductor structures, comprising:
A method of plasma etching tungsten or tungsten nitride, wherein an etch selectivity of greater than about 75:1 is obtained relative to an adjacent tantalum pentoxide layer by using a plasma source gas comprising chemically functional etchant species which are generated from Cl2 and O2, wherein the volumetric percentage of O2 in said plasma source gas ranges from about 20% to about 50%, and wherein a plasma density ranges from about 2.0×1010 e−/cm3 to about 1.8×1011 e−/cm3.
A method of selectively etching tungsten nitride relative to tantalum pentoxide during the etching of semiconductor structures, comprising:
A semiconductor gate structure comprising a layer of tungsten and an underlying layer of tantalum pentoxide, deposited on a silicon substrate, wherein said tantalum pentoxide layer has thickness of less than about 100 Å.
Dependencies are inferred from the claim text.