Alpha Omega Semiconductor Inc.

Zengyi He

Mengyu Pan

Kaiyu Chen

A method for preventing gate oxide damage of a trench MOSFET during wafer processing while adding an ESD protection module atop the trench MOSFET includes fabricate numerous trench MOSFETs on a wafer; add a Si3N4 isolation layer, capable of preventing the LTO patterning process from damaging the gate oxide, atop the wafer; add numerous ESD protection modules atop the Si3N4 isolation layer.

Method for preventing gate oxide damage of a trench MOSFET during wafer processing while adding an ESD protection module atop

A device structure is disclosed for preventing gate oxide damage of a trench MOSFET during wafer processing while adding an ESD protection module atop the trench MOSFET. The ESD protection module has a low temperature oxide (LTO) bottom layer whose patterning process was found to cause the gate oxide damage before. The present invention structure includes a semiconductor substrate having an active area and a termination area; numerous trench MOSFET cells disposed in the active area; numerous electrostatic discharge (ESD) diodes disposed above the semiconductor substrate in the termination area; and an insulation layer comprising Oxide/Nitride/Oxide (ONO) sandwiched between the ESD diodes and the semiconductor substrate. In one embodiment, the active area does not contain the ONO insulation layer.

Trench MOSFET with an ONO insulating layer sandwiched between an ESD protection module atop and a semiconductor substrate

A method and device structure are disclosed for preventing gate oxide damage of a trench MOSFET during wafer processing while adding an ESD protection module atop the trench MOSFET. The ESD protection module has a low temperature oxide (LTO) bottom layer whose patterning process is found to cause the gate oxide damage. The method includes: a) Fabricate numerous trench MOSFETs on a wafer. b) Add a SiNisolation layer, capable of preventing the LTO patterning process from damaging the gate oxide, atop the wafer. c) Add numerous ESD protection modules atop the SiNisolation layer. d) Remove those portions of the SiNisolation layer that are not beneath the ESD protection modules. In one embodiment, hydrofluoric acid is used as a first etchant for patterning the LTO while hot phosphoric acid is used as a second etchant for removing portions of the SiNisolation layer.

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Shanghai, China

Zengyi He