Pulsed plasma with low wafer temperature for ultra thin layer etches

Abstract

Ultrathin material layers are plasma etched with an etch system configured for cryogenic cooling of a substrate to reduce the diffusion coefficients of foreign and intrinsic stop layer atoms (e.g., of the bombarded crystal lattice), and further configured for plasma pulsing to reduce the energy of the impinging ions with cryogenic wafer temperatures. Substrate temperatures of −50° C. or more are employed to reduce the susceptibility of a stop layer material to damage associated with ion impact. Ion energy is reduced to below the threshold where stop layer lattice atoms are displaced or ions are implanted into the bulk lattice. In embodiments, a plasma of an etchant gas having ion energies less than 10 eV are achieved through plasma pulsing, which when directed at the low temperature substrate may controllably etch ultra-thin material layers.

Dependencies are inferred from the claim text.