Anisotropic etch process for tungsten metallurgy

Claim 2

Method for anisotropically etching tungsten, comprising the step of exposing said tungsten to a gaseous plasma comprised of a chlorine-based gas and oxygen, wherein oxygen comprises approxi­mately 25%-45% of said binary mixture.

Claim 3

Method of claim 1, wherein exposed portions of a layer (30), of tungsten metal formed on a layer of glass (10) disposed on a substrate (1) are anisotropically etched, comprising the steps of: placing said substrate into an etch chamber; and generating a gaseous plasma comprised of chlorine gas and oxygen, wherein oxygen comprises approxi­mately 25%-45% of said binary mixture, said gaseous plasma removing exposed portions of the layer of tungsten metal without appreciably attacking said layer of glass.

Claim 4

Method of claim 2, wherein said chamber is held at a power of approximately 300-400 W.

Claim 5

Method for anisotropically etching a thick vapor deposited tungsten layer (30) overlying a thin underlayer (20), disposed on a layer of passi­vating glass (10) arranged on a substrate (1), comprising the steps of: forming an inorganic layer (40) on an exposed surface of said tungsten layer (30); forming a layer (50) of photosensitive polymer on said inorganic layer (40), and patterning said photosensitive polymer layer (50), so as to expose selective portions of said inorganic masking layer (40); removing said exposed portions of said inorganic masking layer (40) without appreciably attacking underlying portions of said tungsten layer (30); and exposing said tungsten layer (30) and said underlayer (20) to a binary plasma gas mixture comprised of chlorine gas and oxygen, wherein said oxygen comprises approximately 25%-45% of said binary gas mixture, so as to anisotropically etch both of said tungsten layer and said under­layer at a high rate that is substantially uniform across the substrate, without appreciably attacking said passivation layer (10).

Claim 6

Method for anisotropically etching a thick vapor deposited tungsten layer (30) overlying a thin underlayer (20), disposed on a layer of passi­vating glass (10) arranged on a substrate (1), comprising the steps of: forming an inorganic layer (40) on an exposed surface of said tungsten layer (30); forming a layer (50) of photosensitive polymer on said inorganic layer (40), and patterning said photosensitive polymer layer (50), so as to expose selective portions of said inorganic masking layer (40); removing said exposed portions of said inorganic masking layer (40) without appreciably attacking underlying portions of said tungsten layer (30); and exposing said tungsten layer (30) and said underlayer (20) to a binary plasma gas mixture comprised of chlorine gas and oxygen, wherein said oxygen comprises approximately 25%-45% of said binary gas mixture, so as to anisotropically etch both of said tungsten layer and said under­layer at a high rate that is substantially uniform across the substrate, without appreciably attacking said passivation layer (10).

Claim 7

Method of claim 4, wherein said passivating layer (10) is selected from the group consisting of boro-phosphosilicate glass, phosphosilicate glass, and silicon dioxide.

Claim 8

Method of claim 4, wherein said inorganic layer (40) is selected from the group consisting of silicon oxide, silicon nitride, and mixtures thereof.

Claim 9

Method of claim 6, wherein said inorganic layer is comprised of silicon nitride, and wherein said selective portions of said silicon nitride are removed by exposure to a plasma gas mixture selected from the group consisting of CHF₃ and O₂, CF₄ and O₂, and NF₃ and O₂.

Claim 10

Method of claim 7, wherein said tungsten layer (30) and said barrier layer (20) are etched in a chamber held at a pressure of approximately 120 µbar and a power of approximately 300-400 W.

Claim 11

Method of claim 4, wherein a thick layer (30), of LPCVD tungsten metal disposed above a thin layer (20) of titanium nitride disposed on a glass passivating layer (10) arranged on a processed semiconductor substrate (1) is anisotropically etched.