Trench semiconductor device having gate oxide layer with multiple thicknesses and processes of fabricating the same
First Claim
1. A process of fabricating a trench semiconductor device comprising:
- providing a semiconductor material;
forming a trench in said semiconductor material, said trench extending from a surface of said semiconductor material into said semiconductor material;
thermally growing an oxide lining on the sidewalls and bottom of said trench;
directionally depositing a thick oxide layer, said oxide layer depositing preferentially on horizontal surfaces so as to form a first thick portion over said oxide lining at a bottom of said trench and a thin portion on said oxide lining on said sidewall of said trench.
0 Assignments
0 Petitions
Accused Products
Abstract
The a trench semiconductor device such as a power MOSFET the high electric field at the corner of the trench is diminished by increasing the thickness of the gate oxide layer at the bottom of the trench. Several processes for manufacturing such devices are described. In one group of processes a directional deposition of silicon oxide is performed after the trench has been etched, yielding a thick oxide layer at the bottom of the trench. Any oxide which deposits on the walls of the trench is removed before a thin gate oxide layer is grown on the walls. The trench is then filled with polysilicon in or more stages. In a variation of the process a small amount of photoresist is deposited on the oxide at the bottom of the trench before the walls of the trench are etched. Alternatively, polysilicon can be deposited in the trench and etched back until only a portion remains at the bottom of the trench. The polysilicon is then oxidized and the trench is refilled with polysilicon. The processes can be combined, with a directional deposition of oxide being followed by a filling and oxidation of polysilicon. A process of forming a “keyhole” shaped gate electrode includes depositing polysilicon at the bottom of the trench, oxidizing the top surface of the polysilicon, etching the oxidized polysilicon, and filling the trench with polysilicon.
56 Citations
13 Claims
-
1. A process of fabricating a trench semiconductor device comprising:
-
providing a semiconductor material;
forming a trench in said semiconductor material, said trench extending from a surface of said semiconductor material into said semiconductor material;
thermally growing an oxide lining on the sidewalls and bottom of said trench;
directionally depositing a thick oxide layer, said oxide layer depositing preferentially on horizontal surfaces so as to form a first thick portion over said oxide lining at a bottom of said trench and a thin portion on said oxide lining on said sidewall of said trench. - View Dependent Claims (2)
-
-
3. A process of fabricating a trench semiconductor device comprising:
-
providing a semiconductor material;
forming a trench in said semiconductor material, said trench extending from a surface of said semiconductor material into said semiconductor material;
directionally depositing a thick oxide layer on said semiconductor material, said oxide layer depositing preferentially on horizontal surfaces so as to form a thick portion in a bottom of said trench and a thin portion on a sidewall of said trench;
depositing a photoresist layer;
removing all of said photoresist layer except for a remaining portion of said photoresist layer that overlies said thick portion of said thick oxide layer; and
removing said thin portion of said thick oxide layer from said sidewall of said trench. - View Dependent Claims (4, 5, 6)
-
-
7. A process of fabricating a trench semiconductor device comprising:
-
providing a semiconductor material;
forming a trench in said semiconductor material, said trench extending from a surface of said semiconductor material into said semiconductor material;
directionally depositing a thick oxide layer on said semiconductor material, said oxide layer depositing preferentially on horizontal surfaces so as to form a thick portion in a bottom of said trench and a thin portion on a sidewall of said trench;
depositing a polysilicon layer;
removing all of said polysilicon layer except for a remaining portion of said polysilicon layer that overlies said thick portion of said thick oxide layer;
oxidizing said remaining portion of said polysilicon layer; and
removing said thin portion of said thick oxide layer from said sidewall of said trench. - View Dependent Claims (8)
-
-
9. A process of fabricating a trench semiconductor device comprising:
-
providing a semiconductor material;
forming a mask layer on a surface of said semiconductor material;
forming a first opening in said mask layer, said first opening exposing an exposed are of said surface of said semiconductor material;
depositing a second layer on said mask layer and on said exposed area;
anisotropically etching said second layer so as to leave sidewall spacers on edges of said mask layer facing said first opening, the separation between said sidewall spacers forming a second opening narrower than said first opening;
forming a trench in said semiconductor material by etching said semiconductor material through said second opening;
forming a gate oxide layer on a sidewall of said trench;
directionally depositing a thick oxide layer, said thick oxide layer depositing preferentially on horizontal surfaces so as to form a first thick portion in a bottom of said trench and a second thick portion on said second layer; and
forming a polysilicon gate in said trench. - View Dependent Claims (10, 11, 12, 13)
-
Specification