Method for obtaining regions of dielectrically isolated single crystal silicon
AssigneeSiliconix Incorporated
InventorRichard A. Blanchard
Life of this patent
Estimating the term…
Abstract
A method of forming single crystal islands (30) by epitaxial growth from a monocrystalline substrate (10). A <100> or other suitable low index surface is preferentially etched to void an inverted pyramid section (16) with <111> or other suitable low index sidewalls (18). The <100> bottom (17) of the pyramid section is covered with insulation (20) and island refill material (24) is grown epitaxially from the sidewalls (18). The islands (30) are laterally isolated (25, 28) from the sidewalls (13) and the structure is finished to provide a substrate on which to form various IC devices.
Claims14
The process for forming a dielectrically-isolated single-crystal island in a monocrystalline wafer substrate comprising the steps of:
- providing a monocrystalline semiconductor wafer having a top surface in a low crystal index plane;
- masking the top surface mask material, leaving the surface exposed in a window area with rectangular sides parallel to the lattice of said crystal plane in the top surface;
- etching the exposed wafer surface preferentially normal to the top surface plane, to remove an inverted pyramid section having a flat bottom surface and with sidewall surfaces converging towards the bottom surface;
- providing a dielectric layer on the bottom surface only of the pyramid section;
- refilling the pyramid section with semiconductor refill above the dielectric;
- providing that the semiconductor refill is epitaxial with the monocrystalline semiconductor material of the sidewalls, to constitute a single crystal refill;
- and
- laterally isolating the single crystal between its surface and the dielectric layer,
- wherein the step of providing a dielectic layer includes:
- providing that at least the bottom surface of the pyramid section is heavily doped with phosphorus;
- forming a layer of dielectric on the pyramid section surface, substantially thicker on the bottom surface than on the sidewall surfaces;
- and
- nonpreferentially etching the layer of dielectric so that there is dielectric on the bottom surface but no dielectric on the sidewalls.
The process for forming a semiconductor device comprising the steps of:
- providing a monocrystalline semiconductor wafer having a top surface in a low crystal index plane;
- masking the top surface with mask material, leaving the surface exposed in a window area with rectangular sides parallel to the lattice of said crystal plane in the top surface;
- etching the exposed wafer surface preferentially normal to the top surface plane, to remove an inverted pyramid section having a flat bottom surface and with sidewall surfaces converging toward the bottom surface;
- providing that at least the bottom surface of the pyramid section is heavily doped with phosphorus;
- growing a layer of dielectric on the pyramid section surface, substantially thicker on the bottom surface than on the sidewall surfaces;
- nonpreferentially etching the layer of dielectric so that there is dielectric on the bottom surface but no dielectric on the sidewalls.
The process for forming a dielectrically-isolated single-crystal island in a monocrystalline wafer substrated comprising the steps of:
- providing a monocrystalline semiconductor wafer having a top surface;
- masking the top surface with mask material, leaving the surface exposed in a window area;
- etching the exposed wafer surface to thereby form a groove in said window area, said groove having sidewalls and a bottom surface;
- providing a dielectric layer on the bottom surface only of the groove;
- refilling the groove with semiconductor refill above the dielectric;
- providing that the semiconductor refill is epitaxial with the monocrystalline semiconductor material of the sidewalls of the groove, to constitute a single crystal refill;
- laterally isolating the single crystal between its surface and the dielectric layer,
- wherein the step of providing a dielectric layer includes:
- providing that at least the bottom surface of the groove is heavily doped with an oxidation rate enhancing impurity;
- forming a layer of dielectric on the surface of the groove, substantially thicker on the bottom surface than on the sidewalls;
- and
- nonpreferentially etching the layer of dielectric so that three is dielectric on the bottom surface but no dielectric on the sidewalls.
Dependencies are inferred from the claim text.