Dielectric isolation bipolar transistor
AssigneeSGS-Thomson Microelectronics S.A.
InventorsYvon Gris, Jocelyne Mourier, Germaine Troillard
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Abstract
The present invention relates to a method of forming deep trenches in a BICMOS-type integrated circuit wherein the formation of a bipolar transistor includes the steps of depositing a base polysilicon layer, depositing a protection oxide layer, forming an emitter-base opening, and etching the silicon oxide protection layer and the base polysilicon layer outside the bipolar transistor areas. The formation of the trenches includes the steps of opening the protection oxide and base polysilicon layers above a thick oxide region while the emitter-base opening is being made, etching the thick oxide layer while the protection oxide layer is being etched, and etching the silicon under the thick oxide while the base polysilicon is being etched.
Claims12
A method of forming deep isolation trenches in a BICMOS-type integrated circuit wherein the formation of a bipolar transistor and an isolation trench includes the following steps:
- depositing a base polysilicon layer;
- depositing a protection oxide layer;
- forming an emitter-base opening through the protection oxide layer and the base polysilicon layer and simultaneously forming an opening through the protection oxide layer and the base polysilicon layer above a thick oxide layer;
- depositing an emitter polysilicon layer and etching this layer;
- simultaneously etching the thick oxide layer and the protection oxide layer outside emitter and base areas of the bipolar transistor;
- and
- simultaneously etching a silicon layer under the thick oxide layer to define the isolation trench and etching the base polysilicon layer outside the emitter and base areas of the bipolar transistor.
A method of forming a BICMOS-type integrated circuit with isolation trenches, including forming an isolation trench and forming a bipolar transistor by simultaneously forming both an emitter opening and an isolation trench opening through a protection oxide layer and a base silicon layer;
- simultaneously etching a thick oxide layer and the protection oxide layer outside emitter and base areas of the bipolar transistor;
- and simultaneously etching epitaxial silicon under the thick oxide layer to form the isolation trench and etching the base silicon layer outside the emitter and base areas of the bipolar transistor.
Dependencies are inferred from the claim text.