Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Diffusing a dopant
Reexamination Certificate
1999-12-21
2001-12-25
Christianson, Keith (Department: 2813)
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Diffusing a dopant
Reexamination Certificate
active
06333245
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention generally describes a method for introducing dopants into a semiconductor device. More specifically this invention describes a method for diffusing dopants into a substrate from a doped germanium oxide sacrificial layer on a semiconductor substrate.
2. Description of Relevant Art
The processing of a semiconductor, such as a CMOS dual work function device, typically requires doping p+ or n+ dopants into the semiconductor substrate. A patent to Frenette et al., in U.S. Pat. No. 5,770,490, entitled “Method for Producing Dual Work Function CMOS Device” describes the introduction of a dopant from a solid source, involving deposition of a solid layer containing the dopant onto the semiconductor substrate, then diffusing the dopant from the layer into the substrate by heating.
Both silicon dioxide and germanium solid sources have heretofore used strong acids to remove the silicon dioxide or germanium after the diffusion of the dopant into the semiconductor. Unfortunately, etching with strong acids may result in the removal of the silicon dioxide gate oxide and silicon dioxide used to fill standard isolation structures. This may provide paths for charge leakage between regions of different conductivity, resulting in semiconductor device degradation and failure.
SUMMARY OF THE INVENTION
According to a first aspect of the present invention, a method for forming a semiconductor device is provided. The method includes the following steps: forming a doped germanium oxide sacrificial layer on a substrate, wherein the doped germanium oxide sacrificial layer is doped with one of a p+ and n+ dopant; diffusing the dopants into the substrate; and removing the doped germanium oxide sacrificial layer.
According to a second aspect of the present invention, a method for forming a semiconductor device is provided. The method includes the following steps: providing a substrate; forming a germanium oxide sacrificial layer on the substrate; defining a first and second region in the germanium oxide sacrificial layer by forming a protective layer on the second region; doping the first region with one of a p+ and n+ dopant; removing the protective layer on the second region; forming a protective layer on the first region in the germanium oxide sacrificial layer; doping the second region with a second dopant wherein the second dopant is one of a p+ and n+ dopant, and wherein the second dopant is not the same type as the first dopant; removing the protective layer on the first region in the germanium oxide sacrificial layer; diffusing the first and second dopants into the substrate; and removing the doped germanium oxide sacrificial layer.
According to a third aspect of the present invention, a method for forming a semiconductor device is provided. The method includes the following steps: providing a substrate; forming a first doped sacrificial layer of germanium oxide on the substrate wherein the first dopant is one of a p+ and n+ dopant; defining a first and second region in the doped germanium oxide sacrificial layer by forming a protective layer on the first region; removing the second region in the doped germanium oxide sacrificial layer and forming an exposed substrate under the second region; removing the protective layer on the first region in the doped germanium oxide sacrificial layer; forming a second doped sacrificial layer of germanium oxide over the first region and over the exposed substrate wherein the second doped sacrificial layer contains a second dopant and wherein the second dopant is a different type than the first dopant; diffusing the first and second dopants into the substrate; removing the doped germanium oxide sacrificial layers.
According to a fourth aspect of the present invention, a method for forming a semiconductor device is provided. The method includes the following steps: providing a substrate; forming a first doped sacrificial layer of germanium oxide on the substrate wherein the first dopant is one of a p+ and n+ dopant; defining a first and second region in the doped germanium oxide sacrificial layer by forming a protective layer on the first region; removing the second region in the doped germanium oxide sacrificial layer and forming an exposed substrate under the second region; removing the protective layer on the first region in the doped germanium oxide sacrificial layer; doping with one of a second dopant from the group of p+ and n+ dopants into the exposed substrate, wherein the second dopant is different than the first dopant; diffusing the first and second dopants into the substrate; and removing the doped germanium oxide sacrificial layer.
It is therefore an advantage of the present invention to provide a method for forming semiconductor devices using sequential doping of defined regions of a sacrificial film with more than one dopant, and then causing the dopants to diffuse into the appropriate regions of a substrate using a singular anneal. A second advantage of the present invention is that defining only one region of a first doped sacrificial layer and overlaying a second doped sacrificial layer enables dopants to diffuse into the appropriate regions of a substrate with a singular anneal.
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Furukawa Toshiharu
Hakey Mark C.
Holmes Steven J.
Horak David V.
Ma William H.
Christianson Keith
International Business Machines - Corporation
Sabo William D.
Schmeiser Olsen & Watts
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