Methods of semiconductor processing involving forming doped polysilicon on undoped polysilicon
A number of methods are provided for semiconductor processing. One such method includes depositing a first precursor material on a surface at a particular temperature to form an undoped polysilicon. The method also includes depositing a second precursor material on a surface of the undoped polysilicon at substantially the same temperature, wherein the undoped polysilicon serves as a seed to accelerate forming a doped polysilicon.
1. A method of semiconductor processing comprising:
forming undoped polysilicon on an oxide surface of a trench, the undoped polysilicon formed via depositing a disilane (Si 2 H 6 ) precursor material on the oxide surface at a process temperature below 450° C. and sufficient to induce thermal decomposition of the disilane precursor material into the undoped polysilicon; and
forming a boron-doped polysilicon on a surface of the undoped polysilicon within the trench at a substantially the same process temperature below 450° C. to prevent void formation within the trench, the doped polysilicon formed via depositing a silane (SiH 4 ) precursor material and a boron dopant material on the surface of the undoped polysilicon;
wherein a nucleation time associated with forming the boron-doped polysilicon on the surface of the undoped polysilicon within the trench at the process temperature below 450° C. is less than two minutes.
2. The method of claim 1 , wherein depositing the disilane precursor material on the oxide surface includes depositing the disilane precursor material on the surface of a trench having a width in a range of 20-30 nanometers and a depth of at least 50 nanometers.
3. The method of claim 1 , wherein the method includes forming the undoped polysilicon by chemical vapor deposition at the process temperature and a pressure that induces nucleation at around 2 minutes.
4. The method of claim 3 , wherein the method includes forming the boron-doped polysilicon by chemical vapor deposition over the formed undoped polysilicon at the process temperature and the pressure by inducing nucleation of the boron-doped polysilicon at around 1 minute.
5. The method of claim 4 , wherein the method includes forming the boron-doped and undoped polysilicon with the process temperature and the pressure at levels selected to induce conformal deposition in a substantially amorphous configuration in order to reduce void formation in the trench.
6. The method of claim 1 , wherein the method includes filling the trench with the undoped polysilicon and the boron-doped polysilicon to serve as a control gate in a non-volatile memory cell.
7. A method of semiconductor processing comprising:
depositing a disilane (Si 2 H) precursor material on a silicon dioxide (SiO 2 ) surface of a trench at a process temperature below 450° C. to form an undoped polysilicon seed material on the silicon dioxide surface of the trench via thermal decomposition of the disilane; and
depositing a silane (SiH 4 ) precursor material and a boron-containing dopant on a surface of the undoped polysilicon at substantially the same process temperature below 450° C. to form a void-free boron-doped polysilicon within the trench;
wherein a nucleation time associated with forming the void-free boron-doped polysilicon within the trench at the process temperature below 450° C. is less than two minutes.
8. The method of claim 7 , wherein depositing the disilane precursor material includes depositing disilane (Si 2 H 6 ) that undergoes thermal decomposition to the undoped polysilicon in a temperature range of 380-450° C.
9. The method of claim 7 , wherein depositing the silane precursor material includes depositing silane (SiH 4 ) and the boron-containing dopant that undergo thermal decomposition to the boron-doped polysilicon in a temperature range of 380-450° C.
10. The method of claim 9 , wherein forming the boron-doped polysilicon includes forming a P-type semiconductor structure in combination with the undoped polysilicon.
11. The method of claim 7 , wherein the method of semiconductor processing includes reducing a nucleation time of the silane precursor material at multiple sites on the undoped polysilicon.
12. The method of claim 11 , wherein reducing the nucleation time includes reducing a length of time for formation of a boron-doped polysilicon as compared to formation of the boron-doped polysilicon in the absence of the undoped polysilicon.
13. The method of claim 7 , wherein the method of semiconductor processing includes utilizing chemical vapor deposition to partially fill an unfilled portion of the trench on the surface of a semiconductor structure with the undoped polysilicon to a substantially uniform thickness on walls and a bottom of the unfilled portion of the trench and to fill a remainder of the trench with the boron-doped polysilicon.
14. A method of semiconductor processing comprising:
depositing a gaseous disilane (Si 2 H 6 ) in a trench on a solid silicon dioxide (SiO 2 ) surface of the trench at a temperature below 450° C. that induces thermal decomposition of disilane into an undoped polysilicon to cover walls and a bottom of the solid SiO 2 surface of the trench;
depositing a gaseous silane (SiH 4 ) and a gaseous boron-containing dopant on a surface of the undoped polysilicon at substantially the same temperature below 450° C.; and
inducing nucleation of the gaseous silane (SiH 4 ) and the gaseous boron-containing dopant and accelerating conformal forming of a boron-doped polysilicon by the undoped polysilicon serving as a seed in order to reduce void formation in the trench;
wherein a nucleation time associated with forming the boron-doped polysilicon within the trench at the temperature below 450° C. is less than two minutes.
15. The method of claim 14 , wherein the method includes forming the undoped polysilicon on the walls and the bottom of the solid SiO 2 surface of the trench to a substantially uniform thickness in a range of 1-7 nanometers.
16. The method of claim 14 , wherein depositing the silane and the boron-containing dopant includes inducing thermal decomposition thereof to form the boron-doped polysilicon in a temperature range of 380-450° C.
17. The method of claim 14 , wherein the method includes utilizing chemical vapor deposition with a substantially stable temperature in a range of 380-450° C. and with a substantially stable pressure in a range of 0.2-0.5 Torr to induce a substantially amorphous configuration of the boron-doped polysilicon.
18. The method of claim 14 , wherein the method includes adjusting flow rates of the gaseous silane and the gaseous boron-containing dopant during chemical vapor deposition such that the boron atom density in the boron-doped polysilicon is in a range of 0.1-1.0% per cubic centimeter of the boron-doped polysilicon.