Profile tailored trench etch using a SF.sub.6 -O.sub.2 etching composition wherein both isotropic and anisotropic etching is achieved by varying the amount of oxygen
First Claim
1. A method for profile tailoring sidewalls of a trench in forming a semiconductor device on a silicon substrate, comprising:
- forming an insulative layer on an upper surface of the substrate;
patterning the insulative layer to define an outline characteristic;
forming an opening in the insulative layer wherein the upper surface of the silicon is exposed within an area of the defined outline characteristic;
plasma etching the exposed silicon preferentially within the opening to form a trench, with a gas mixture that includes an etching gas, a non-chlorinated sidewall passivating gas comprising oxygen, and an ionized inert gas;
maintaining the gas mixture in a pressure range of 0.7 to 1.1 Torr; and
selecting a passivating gas ratio in the mixture to determine the relative anisotropy of the etch wherein both isotropic and anisotropic etching can be achieved.
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Accused Products
Abstract
A dopant-opaque layer of polysilicon is deposited on gate oxide on the upper substrate surface to serve as a pattern definer during fabrication of the device. It provides control over successive P and N doping steps used to create the necessary operative junctions within a silicon substrate and the conductive structures formed atop the substrate. A trench is formed in the upper silicon surface and a source conductive layer is deposited to electrically contact the source region as a gate conductive layer is deposited atop the gate oxide layer. The trench sidewall is profile tailored using a novel O2 -SF6 plasma etch technique. An oxide sidewall spacer is formed on the sides of the pattern definer and gate oxide structures, before depositing the conductive material. A planarizing layer is applied and used as a mask for selectively removing any conductive material deposited atop the oxide spacer. The polysilicon layer on the oxide is reduced in thickness during trenching so that any conductive material deposited atop the spacers protrude upward for easy removal of excess, conductive material. The sidewall spacers can be sized, either alone or in combination with profile tailoring of the trench, to control source-region width (i.e., parasitic pinched base width) and proximity of the source conductor to the FET channel. Electrical contact between the source conductive layer and the source regions is enhanced by forming a low-resistivity layer between them.
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Citations
23 Claims
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1. A method for profile tailoring sidewalls of a trench in forming a semiconductor device on a silicon substrate, comprising:
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forming an insulative layer on an upper surface of the substrate; patterning the insulative layer to define an outline characteristic; forming an opening in the insulative layer wherein the upper surface of the silicon is exposed within an area of the defined outline characteristic; plasma etching the exposed silicon preferentially within the opening to form a trench, with a gas mixture that includes an etching gas, a non-chlorinated sidewall passivating gas comprising oxygen, and an ionized inert gas; maintaining the gas mixture in a pressure range of 0.7 to 1.1 Torr; and selecting a passivating gas ratio in the mixture to determine the relative anisotropy of the etch wherein both isotropic and anisotropic etching can be achieved. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A method for profile tailoring sidewalls of a trench in a single crystal silicon substrate comprising:
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forming an insulative layer on an upper surface of a single crystal silicon substrate; patterning the insulative layer to define an outline characteristic; forming an opening in the insulative layer wherein the upper surface of the substrate is exposed within an area of the defined outline characteristic; forming a trench within the opening by plasma etching the exposed silicon surface with a gas mixture consisting essentially of oxygen, an inert gas, and an etchant gas selected from the group consisting of SF6 and NF3 ; and controlling the relative anisotropy of the etch by controlling the amount of oxygen in the gas mixture wherein both isotropic and anisotropic etching can be achieved. - View Dependent Claims (18, 19, 20, 21, 22, 23)
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Specification