METHOD FOR FORMING A THICK BOTTOM OXIDE (TBO) IN A TRENCH MOSFET
First Claim
1. A method for forming a thick bottom oxide for a trench MOSFET comprising:
- forming a trench in a semiconductor substrate;
using a high density plasma chemical vapor deposition (HDPCVD) process to form silicon dioxide at least partially into the trench and on a top surface of said substrate;
removing the silicon dioxide from the top surface of the substrate; and
removing the silicon dioxide from the sidewalls of the trench.
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Accused Products
Abstract
A method for forming a thick bottom oxide in the bottom of a trench used in a vertical MOSFET. Initially, an n-type substrate has an n-type epitaxial layer grown thereon. A top portion of the n-type epitaxial layer is implanted with p-type dopants to provide a p-layer. A trench is then etched into the p- and n-type epitaxial layer. A high density plasma chemical vapor deposition (HDPCVD) process is used to either partially or fully fill the trench. Any oxide on the top surface of the p-layer is then removed, such as by using a chemical mechanical polishing step. Then, an isotropic etching step, such as a wet etch, is used to remove the silicon dioxide from the trench, while leaving a thick bottom oxide at the bottom of the trench. The HDPCVD process utilizes minimal thermal budget to form the thick bottom oxide.
10 Citations
26 Claims
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1. A method for forming a thick bottom oxide for a trench MOSFET comprising:
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forming a trench in a semiconductor substrate; using a high density plasma chemical vapor deposition (HDPCVD) process to form silicon dioxide at least partially into the trench and on a top surface of said substrate; removing the silicon dioxide from the top surface of the substrate; and removing the silicon dioxide from the sidewalls of the trench. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. A MOSFET trench with a thick bottom oxide comprising:
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a trench in a semiconductor substrate; and a thick bottom oxide formed in the bottom of the trench, the thick bottom oxided formed by; using a high density plasma chemical vapor deposition (HDPCVD) process to form silicon dioxide at least partially into the trench and on a top surface of said substrate; removing the silicon dioxide from the top surface of the substrate; and removing the silicon dioxide from the sidewalls of the trench. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 18)
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19. A method for forming a thick bottom oxide for a trench MOSFET comprising:
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forming an epitaxial layer atop of a semiconductor substrate, the epitaxial layer of same conductive type as the semiconductor substrate; forming a hard mask over said epitaxial layer and patterning said hard mask to define a trench area; forming a trench in said epitaxial layer by selectively etching said epitaxial layer and using said hard mask; using a high density plasma chemical vapor deposition (HDPCVD) process to form silicon dioxide at least partially into the trench and on a top surface of said hard mask; removing the silicon dioxide from the surface of the hard mask; and removing the silicon dioxide from the sidewalls of the trench. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A method for forming a thick bottom oxide for a trench MOSFET comprising:
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forming an epitaxial layer atop of a semiconductor substrate, the epitaxial layer of same conductive type as the semiconductor substrate; forming a hard mask over said epitaxial layer and patterning said hard mask to define a trench area; forming a trench in said epitaxial layer by selectively etching said epitaxial layer and using said hard mask; using a high density plasma chemical vapor deposition (HDPCVD) process to form silicon dioxide at least partially into the trench and on a top surface of said hard mask; removing the silicon dioxide from the sidewalls of the trench; forming a gate oxide on the sidewalls of the trench using thermal oxidation; depositing a polysilicon layer until the trench is substantially filled; performing a chemical mechanical polish until the polysilicon and silicon dioxide is removed from atop the hard mask; and using implantation to implant the epitaxial layer until a top portion of the epitaxial layer is of opposite conductivity than the epitaxial layer. - View Dependent Claims (26)
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Specification