Process of manufacturing Trench gate semiconductor device having gate oxide layer with multiple thicknesses
First Claim
1. A process of manufacturing a trench gate semiconductor device comprising:
- providing a semiconductor material;
forming a trench at a surface of the semiconductor material;
placing the semiconductor material in a reaction chamber;
producing charged particles of a dielectric within the chamber;
creating an electric field in the reaction chamber, the electric field causing the charged particles to move towards the semiconductor material such that the dielectric is deposited at a greater thickness on a bottom of the trench than on a sidewall of the trench;
depositing a conductive material in the trench to form a gate electrode; and
removing the dielectric from the sidewall of the trench.
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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.
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Citations
27 Claims
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1. A process of manufacturing a trench gate semiconductor device comprising:
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providing a semiconductor material;
forming a trench at a surface of the semiconductor material;
placing the semiconductor material in a reaction chamber;
producing charged particles of a dielectric within the chamber;
creating an electric field in the reaction chamber, the electric field causing the charged particles to move towards the semiconductor material such that the dielectric is deposited at a greater thickness on a bottom of the trench than on a sidewall of the trench;
depositing a conductive material in the trench to form a gate electrode; and
removing the dielectric from the sidewall of the trench. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A process of manufacturing a trench gate semiconductor device comprising:
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providing a semiconductor material;
forming a trench at a surface of the semiconductor material;
placing the semiconductor material in a reaction chamber;
producing charged particles of a dielectric within the chamber;
creating an electric field in the reaction chamber, the electric field causing the charged particles to move towards the semiconductor material such that the dielectric is deposited at a greater thickness on a bottom of the trench than on a sidewall of the trench;
depositing a conductive material in the trench to form a gate electrode; and
forming a second trench in the semiconductor material, wherein the electric field causes the charged particles to move towards the semiconductor material such that the dielectric is deposited at a greater thickness on a bottom of the second trench than on a sidewall of the second trench. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A process of manufacturing a trench gate semiconductor device comprising:
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providing a semiconductor material;
forming a trench at a surface of the semiconductor material;
placing the semiconductor material in a reaction chamber;
producing charged particles of a dielectric within the chamber;
creating an electric field in the reaction chamber, the electric field causing the charmed particles to move towards the semiconductor material such that the dielectric is deposited at a greater thickness on a bottom of the trench than on a sidewall of the trench;
depositing a conductive material in the trench to form a gate electrode;
and further comprising, before forming the trench;
depositing at least one layer on the surface of the semiconductor materal, the at least one layer comprising a hard layer;
removing a portion of the at least one layer to expose an area of the surface of the semiconductor material, leaving exposed edges of the at least one layer;
depositing a nitride layer, the nitride layer covering the at least one hard layer, the exposed area of the surface of the semiconductor material, and the exposed edges of the at least one hard layer; and
etching the nitride layer anisotropically so as to remove the nitride layer from a top surface of the at least one hard layer and a portion of the exposed area of the surface of the semiconductor material while leaving a portion of the nitride layer covering the exposed edges of the at least one hard layer. - View Dependent Claims (26, 27)
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Specification