Semiconductor device manufacturing: process – Formation of electrically isolated lateral semiconductive... – Implanting to form insulator
Reexamination Certificate
1998-03-24
2001-03-06
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Formation of electrically isolated lateral semiconductive...
Implanting to form insulator
Reexamination Certificate
active
06197656
ABSTRACT:
DESCRIPTION
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to semiconductor chip manufacture and more particularly to formation of lateral and vertical isolation structures.
2. Background Description SIMOX (Separation by IMplantation of OXygen) uses a high-dose oxygen implant to form a buried SiO
2
layer. As described by Leray et al. (“An Overview of Buried Oxides on Silicon: New Processes and Radiation Effects”,
J. Phys. III France
6 (1996) 1625-1646.), an insulating layer is obtained underneath the silicon surface by implantation of oxygen ions in a silicon wafer. The energy of the oxygen ions directly determines the range and profile of the implanted layer. Ion energy and oxygen fluence determine the thickness of buried oxide and top silicon layer over buried oxide.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an improved method for formation of planar isolation between devices.
The present invention is a method of forming a buried oxide layer wherein a masking layer, preferably a hard dielectricable to withstand the high temperature implantation and to resist the cleans during implantation, is applied and masked. Various thicknesses in the dielectric can be fabricated (e.g., by deposition followed by masked etching) to achieve various depths of the buried oxide layer, including oxide layers in contact with the surface, and no oxide layers at all. Optionally, to relieve stress and provide a continuous oxide film, an angled mask may be formed. However, sputtering during oxygen implantation may form an angle without additional processing. Optional annealing to round mask corners may form defects during the annealing step. Minimum buried oxide dimensions are determined by stress and lithography requirements and are independent of latchup or fill requirements. Buried devices may be formed beneath the buried oxide layer by deep dopant implantation after the buried oxide layer. Examples of such buried devices are buried resistors for improved power dissipation, lateral bipolar transistors, etc. In addition, fully isolated devices may be placed in regions where no buried oxide is formed (i.e., in substrate contact regions) allowing bulk devices to be fabricated simultaneously where required for improved thermal conductivity or to avoid the floating body effect of silicon on insulator (SOI) devices.
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Adkisson James W.
Lasky Jerome B.
Pastel Paul W.
Rankin Jed H.
Fourson George
International Business Machines - Corporation
McGuireWood LLP
Shkurko Eugene I.
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