Method of selectively deglazing P205
A method of forming a transistor is disclosed, in which gate-to-substrate leakage is addressed by forming and maintaining a conformal oxide layer overlying the transistor gate. Using the method disclosed for an n-type device, the conformal oxide layer can be formed as part of the source-drain doping process. Subsequent removal of residual phosphorous dopants from the surface of the oxide layer is accomplished without significant erosion of the oxide layer. The removal step uses a selective deglazing process that employs a hydrolytic reaction, and an acid-base neutralization reaction that includes an ammonium hydroxide component.
1. A method of forming a field effect transistor, the method comprising:
forming a gate dielectric layer overlying a silicon substrate;
forming a gate electrode overlying and directly in contact with the gate dielectric;
forming a dopant film layer overlying the silicon substrate adjacent to the gate dielectric;
incorporating dopants from the dopant film into the substrate to create doped source and drain regions of the transistor;
growing a silicon oxide layer over the source and drain regions, in direct contact with the silicon semiconductor substrate; and
removing the dopant film using a deglazing process that is selective to the silicon oxide layer.
2. The method according to claim 1 , wherein the gate is made of polysilicon.
3. The method according to claim 1 , wherein the step of incorporating includes heating the substrate.
4. The method according to claim 1 , wherein the dopant film includes phosphorous and the transistor is an n-type transistor.
5. The method according to claim 1 , wherein the dopant film includes arsenic and the transistor is an n-type transistor.
6. The method according to claim 1 , wherein the step of removing includes a hydrolytic reaction and an acid-base neutralization reaction.
7. The method according to claim 6 , wherein the acid-base neutralization reaction includes ammonium hydroxide.
8. The method according to claim 7 wherein the acid-base neutralization reaction further includes hydrogen peroxide.
9. A method of forming an n-type field effect transistor on a substrate, comprising:
forming a gate on the substrate, including a gate oxide;
using the gate as a mask, doping portions of the substrate with an n-type dopant layer to form n-type source and drain regions;
growing a conformal oxide layer in contact with the gate oxide; and
removing residual amounts of the n-type dopant layer using a hydrolytic reaction that is selective to the oxide layer.
10. The method of claim 9 , wherein the doping step and the step of growing a conformal oxide layer are executed as sequential parts of the same processing recipe.
11. The method according to claim 9 , further comprising neutralizing an acidic product of the hydrolytic reaction.
12. The method according to claim 11 , wherein the neutralizing includes ammonium hydroxide as a reactant.
13. The method according to claim 12 , wherein the neutralizing further includes hydrogen peroxide as a reactant.
14. The method of claim 9 , wherein the n-type dopant is phosphorous.
15. The method of claim 9 , wherein the n-type dopant is arsenic.
16. The method of claim 9 , wherein the substrate is silicon and the gate is polysilicon.