Etching of semiconductor structures that include titanium-based layers

摘要

Two-step process sequences uniformly etch both tungsten-based and titanium-based structures on a substrate. A sequence of wet etches using peroxide and heated nitric acid uniformly recesses a metal stack that includes W, TiN, and TiAl. W, TiN and TiC are uniformly recessed by a peroxide etch at ˜25 C followed by an acid solution with a very small amount of added peroxide at ˜60 C. TiC is etched without etching trench oxides or other metals in a work-function metal stack by either (1) highly-dilute of ultra-dilute HF at 25-35 C, (2) dilute HCl at 25-60 C, (3) dilute NH4OH at 25-60 C, or (4) solution (2) or (3) with small amounts of peroxide. Other metals in the stack may then be plasma-etched without being blocked by TiC residues.

主权项

1. A method of uniformly etching a plurality of structures of different materials on a substrate, the method comprising:
exposing the substrate to a first etch process until a first subset of the structures is etched to a first depth; exposing the substrate to a second etch process until a second subset of the structures is etched to a second depth; wherein the first subset of the structures comprises W; wherein the second subset of the structures comprises at least one of titanium nitride (TiN), titanium aluminide (TiAl), or titanium aluminum nitride (TiAlN); wherein the first etch process comprises a solution of H2O2 and an acid; and wherein the second etch process comprises a nitric acid (HNO3) solution heated to between 60 C and 95 C, wherein a weight percentage of HNO3 in the nitric acid solution is between about 65% and 75%, wherein, after being exposed to the first etch process and the second etch process, the first subset and the second subset of the structures are etched to within 15% of the same depth; wherein at least one of the first subset or the second subset of the structures comprises tungsten (W); wherein at least one of the first subset or the second subset of the structures comprises titanium (Ti); and wherein the first etch process comprises a solution containing hydrogen peroxide (H2O2).