METHOD FOR ISOLATING ACTIVE REGIONS IN GERMANIUM-BASED MOS DEVICE

摘要

Disclosed herein is a method for isolating active regions in a germanium-based MOS device. A surface of a germanium-based substrate is covered by a thin polysilicon layer or a poly-SiGe layer, and an isolation structure of germanium dioxide covered by a silicon dioxide layer or a SiGe oxide layer on top is formed by means of two steps of oxidation in a case of the active regions are protected. Such two steps of oxidation using the polysilicon layer or the poly-SiGe layer as a sacrificial layer is advantageous to improve the isolation quality of a fabricated germanium dioxide and to reduce a beak effect occurred during a local field oxygen oxidation so as to dramatically elevate the performance of the germanium device.

主权项

1. A method for isolating active regions in a germanium-based MOS device, comprising the following steps:
1) Cleaning a germanium-based semiconductor substrate and removing a natural oxide layer on a surface of the substrate; 2) Passivating the surface of the substrate; 3) Depositing a polysilicon layer or a poly-SiGe layer as a sacrificial layer on the surface of the substrate; 4) Depositing a silicon nitride layer on the sacrificial layer; 5) Coating a photoresist on the silicon nitride layer, defining an active region through a photolithography process, and forming a mask of the photoresist above the active region; 6) Etching and removing the silicon nitride layer above an isolation region by using the photoresist as the mask, and removing the mask of the photoresist; 7) Forming an isolation structure of germanium dioxide covered by a silicon dioxide layer or an SiGe oxide layer on top by means of oxidation; and 8) Etching and removing the silicon nitride layer and the sacrificial layer above the active region.