Process for filling deep trenches with polysilicon and oxide
First Claim
1. A process for fabricating a trench structure of a semiconductor device, said process comprising the steps of:
- forming a masking layer on a top surface of a silicon substrate;
patterning and etching away selected regions of said masking layer to form a plurality of spaced openings therein;
etching away portions of said silicon substrate which are located beneath said plural openings in said masking layer to form a trench in said silicon substrate;
removing said masking layer;
forming a first liner insulation layer on the interior walls and bottom surface of said trench and on said top surface of said silicon substrate;
etching away a portion of said first liner insulation layer that is atop said silicon substrate and that covers an upper portion of the interior walls of said trench, thereby removing any re-entrant structure in said upper portion of said first insulation layer and in said interior walls of said trench that is located at an entrance to said trench;
depositing a layer of polysilicon on said top surface of said substrate and in said trench such that said trench is filled; and
removing a portion of said polysilicon layer that is formed atop said top surface of said substrate.
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Accused Products
Abstract
A process for etching and filling a trench prevents the top opening of the trench from being closed off prior to the trench being completely filled. After a masking layer is deposited and patterned, the trench is etched and then the masking layer is removed. A first liner insulating layer is grown or deposited and is then etched anisotropically to remove the layer from the top surface of the substrate as well as from the top portion of the walls of the trench. A second, thinner liner layer is grown or deposited on the exposed portion of the walls of the trench to provide surface and edge protection. A polysilicon layer is then deposited to fill the trench and is planarized to remove the portion deposited on the top surface of the substrate. Alternatively, the thinner oxide liner can be omitted, and the polysilicon is removed by chemical mechanical polishing until the trench liner oxide appears on the top surface. An overlaying insulation layer is then deposited. A passivation layer may be subsequently deposited on the bottom surface. The process is particularly suited for etching and filling steps that leave a re-entrant profile at the top of the trench. The trench structure may provide dielectric isolation for the cells of a photovoltaic generator. An MOS-gated device may be integrated into the same chip and may be a lateral or vertical MOSFET or a lateral or vertical IGBT.
35 Citations
24 Claims
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1. A process for fabricating a trench structure of a semiconductor device, said process comprising the steps of:
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forming a masking layer on a top surface of a silicon substrate; patterning and etching away selected regions of said masking layer to form a plurality of spaced openings therein; etching away portions of said silicon substrate which are located beneath said plural openings in said masking layer to form a trench in said silicon substrate; removing said masking layer; forming a first liner insulation layer on the interior walls and bottom surface of said trench and on said top surface of said silicon substrate; etching away a portion of said first liner insulation layer that is atop said silicon substrate and that covers an upper portion of the interior walls of said trench, thereby removing any re-entrant structure in said upper portion of said first insulation layer and in said interior walls of said trench that is located at an entrance to said trench; depositing a layer of polysilicon on said top surface of said substrate and in said trench such that said trench is filled; and removing a portion of said polysilicon layer that is formed atop said top surface of said substrate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A process of forming a trench in a silicon wafer;
- said process comprising the steps of etching at least one opening into the surface of said wafer;
said opening having a pair of spaced walls and a bottom surface at a given depth;
forming an insulator layer on the walls and bottom surface of said opening and on a portion of the surface of said wafer that is adjacent to said walls of said opening;
selectively removing a portion of said insulation layer from said surface of said wafer and from an upper region of said walls of said opening, whereby any material of said insulation layer that has a re-entrantly thickened profile at the entrance to said opening is removed;
depositing polysilicon on said top surface of said substrate and in said trench so that said trench is filled; and
removing a portion of said polysilicon layer that is formed atop said top surface of said substrate. - View Dependent Claims (18, 19, 20, 21, 22, 23, 24)
- said process comprising the steps of etching at least one opening into the surface of said wafer;
Specification