Diffusing dopants into a semiconductor wafer
AssigneeMotorola, Inc.
InventorBohumil Lojek
Life of this patent
Estimating the term…
Abstract
Dopants from a diffusion source (16) are diffused into a product wafer (14) to form a uniform doping concentration within the product wafer (14). The source (16) has a thermal conductivity that is approximately equal to a thermal conductivity of the wafer (14). The source (16) is positioned near the wafer (14) thereby forming a space (23) between the source (16) and the wafer (14). Gas flow (26) through the space (23) is limited to a predetermined value in order to prevent disturbing dopant diffusion. The source (16) is heated to a predetermined temperature, then the wafer (14) is heated. Subsequently, the wafer (14) and the source (16) are cooled at substantially equal rates.
Claims20
A method of diffusing dopants into a semiconductor wafer comprising:
- forming a dopant layer on a first surface of a diffusion source by applying a spin-on dopant to the first surface, the diffusion source having a first thermal conductivity;
- positioning the diffusion source a predetermined distance from a product wafer having substantially the first thermal conductivity thereby creating a space between the dopant layer and the product wafer wherein the product wafer is smaller than the diffusion source and a first surface of the product wafer faces the dopant layer;
- limiting a flow of a gas through the space to a predetermined flow rate while permitting the gas to flow across a second surface of the product wafer and across a second surface of the diffusion source;
- heating the diffusion source to a predetermined temperature wherein the predetermined temperature causes dopants to diffuse from the dopant layer into the space;
- maintaining the diffusion source at substantially the predetermined temperature until the diffusion source reaches thermal equilibrium;
- heating the product wafer to substantially the predetermined temperature and diffusing the dopants from the space a predetermined depth into the product wafer thereby forming a doped area having a predetermined doping concentration variation across the product wafer;
- and
- cooling the diffusion source and the product wafer at substantially equal rates.
A method of forming uniform shallow diffusions in a semiconductor wafer comprising:
- providing a product wafer having a predetermined thermal conductivity;
- positioning a diffusion source having substantially the predetermined thermal conductivity a predetermined distance from the product wafer thereby creating a space between the product wafer and the diffusion source;
- limiting a flow of a gas through the space to a predetermined gas flow rate while forming a higher gas flow rate outside of the space;
- heating the diffusion source to a predetermined temperature;
- maintaining the diffusion source at substantially the predetermined temperature until the diffusion source substantially reaches thermal equilibrium;
- heating the product wafer substantially to the predetermined temperature thereby diffusing dopants from the doping source a predetermined distance into the product wafer;
- and
- cooling the diffusion source and the product wafer at substantially equal rates.
A method of diffusing dopants into a semiconductor wafer comprising:
- providing a product wafer having a predetermined thermal conductivity;
- positioning a diffusion source having substantially the predetermined thermal conductivity a predetermined distance from the product wafer thereby creating a space between the product wafer and the diffusion source;
- limiting gas flow through the space to a predetermined value;
- heating the diffusion source to a predetermined temperature;
- maintaining the diffusion source at the predetermined temperature until reaching thermal equilibrium;
- heating the product wafer;
- and
- cooling the diffusion source and the product wafer at substantially equal rates.
Dependencies are inferred from the claim text.