Techniques for forming angled structures for reduced defects in heteroepitaxy of semiconductor films

A method for forming a semiconductor device, comprising:

• forming a non-crystalline layer over a first crystalline material in a substrate;
• providing a reactive ambient around the substrate;
• directing ions from a plasma to the substrate at a non-zero angle of incidence with respect to a perpendicular to a plane of the substrate,
• etching the non-crystalline layer using the ions and reactive ambient to form an angled trench through the non-crystalline layer, wherein a portion of the first crystalline material at a bottom of the angled trench is exposed, the angled trench forming a non-zero angle of inclination with respect to the perpendicular;
• and
• growing a second crystalline material from the bottom of the angled trench by epitaxial growth, wherein the second crystalline material fills the angled trench, and wherein the first and second crystalline materials have mismatched lattice dimensions.

A method for forming a semiconductor device, comprising:

• forming a dielectric layer over a silicon-containing crystalline substrate;
• forming an angled trench by etching the dielectric layer using ions in combination with a reactive ambient, to expose a portion of the silicon-containing crystalline substrate at a bottom of the angled trench, wherein an angle of inclination between sidewalls of the angled trench and a top surface of the silicon-containing crystalline substrate is greater than
• tan
• -
• 1
• ⁢
• h
• w
• ,
• where h represents a thickness of the dielectric layer, and w represents a width of the angled trench along the top surface of the silicon-containing crystalline substrate;
• etching the exposed silicon-containing crystalline substrate at the bottom of the angled trench to produce a surface along (111) crystal plane direction;
• and
• forming a crystalline material comprising a Group III element and a Group V element in the angled trench by epitaxial growth.

A method for etching a substrate, comprising:

• providing a reactive ambient around the substrate when a non-crystalline layer is disposed over a first crystalline material in the substrate;
• generating a plasma in a plasma chamber;
• modifying a shape of a plasma sheath boundary of the plasma;
• extracting ions from the plasma;
• directing the ions to the substrate at a non-zero angle of incidence with respect to a perpendicular to a plane of the substrate, wherein the ions and reactive ambient are effective to form an angled trench through the non-crystalline layer to expose a portion of the first crystalline material at a bottom of the angled trench, the angled trench forming a non-zero angle of inclination with respect to the perpendicular;
• and
• adjusting a separation of the substrate from the plasma chamber, from a first separation to a second separation greater than the first separation during the directing the ions, wherein the ions and reactive ambient provide a first degree of physical etching of the non-crystalline layer when the substrate is arranged at the first separation, and a second degree of physical etching that is greater than the first degree when the substrate is arranged at the second separation.