Ultrathin chemically grown oxide film as a dopant diffusion barrier in semiconductor devices
View Patent ↗The invention is a chemically grown oxide layer which prevents dopant diffusion between semiconductor layers. The chemically grown oxide layer may be so thin that it does not form a barrier to electrical conduction, and thus may be formed within active devices such as diodes or bipolar transistors. Such a chemically grown oxide film is advantageously used to prevent dopant diffusion in a vertically oriented polysilicon diode formed in a monolithic three dimensional memory array.
1. A method for forming a semiconductor device, the method comprising:
forming a first semiconductor layer;
growing a chemically grown oxide on the first semiconductor layer in a liquid ambient;
forming a second semiconductor layer directly on the chemically grown oxide,
wherein the first semiconductor layer or the second semiconductor layer is doped with a first conductivity-enhancing dopant; and
subjecting the first semiconductor layer, the chemically grown oxide layer, and the second semiconductor layer to a temperature exceeding about 700 degrees C.,
wherein the chemically grown oxide inhibits diffusion of the first conductivity-enhancing dopant between the first and second semiconductor layers.
2. The method of claim 1 wherein the first semiconductor layer is at least 80 atomic percent silicon.
3. The method of claim 1 wherein the growing step comprises exposing the first semiconductor layer to a solution containing H 2 O 2 .
4. The method of claim 1 wherein the growing step comprises exposing the first semiconductor layer to a solution containing a component capable of providing nitrogen.
5. The method of claim 4 wherein the solution contains NH 4 OH.
6. The method of claim 1 wherein the growing step takes place at a temperature less than about 180 degrees C.
7. The method of claim 1 wherein the first conductivity-enhancing dopant is an n-type dopant.
8. The method of claim 7 wherein the first conductivity-enhancing dopant is phosphorus.
9. The method of claim 1 wherein the first conductivity-enhancing dopant is a p-type dopant.
10. The method of claim 9 wherein the first conductivity-enhancing dopant is boron.
11. The method of claim 1 wherein the first or the second semiconductor layer is doped by in situ doping.
12. The method of claim 1 wherein the first or the second semiconductor layer is doped by ion implantation.
13. The method of claim 1 further comprising passing a current between the first and second semiconductor layers.
14. The method of claim 1 wherein the first semiconductor layer and the second semiconductor layer are portions of a diode.
15. The method of claim 14 wherein the diode is a p-i-n diode.
16. The method of claim 14 wherein the diode is a p-n diode.
17. The method of claim 1 wherein the step of forming the first semiconductor layer comprises depositing in situ doped silicon or a silicon alloy.
18. The method of claim 17 wherein the step of forming the second semiconductor layer comprises depositing undoped silicon, germanium, or a silicon-germanium alloy.
19. The method of claim 17 wherein the step of forming the second semiconductor layer comprises depositing semiconductor material doped with a second conductivity-enhancing dopant opposite the conductivity type of the first conductivity-enhancing dopant.
20. The method of claim 1 wherein the step of forming the first semiconductor layer comprises depositing undoped silicon or a silicon alloy.