| 摘要 |
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.
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