Polysilicon layer and method of forming the same
View Patent ↗The method of forming a polysilicon layer is provided. A first polysilicon layer with a first grain size is formed on a substrate. A second polysilicon layer with a second grain size is formed on the first polysilicon layer. The first grain size is smaller than the second grain size. The first polysilicon layer with a smaller grain size can serve as a base for the following deposition, so that the second polysilicon layer formed thereon has a flatter topography, and thus, the surface roughness is reduced and the Rs uniformity within a wafer is improved.
1. A method of forming a polysilicon layer, comprising:
forming a first polysilicon layer on a substrate, wherein the first polysilicon layer is formed by introducing a silicon-containing gas and an inhibitive gas, and the inhibitive gas is for inhibiting a decomposition rate of the silicon-containing gas; and
forming a second polysilicon layer on the first polysilicon layer, wherein the second polysilicon layer is formed by introducing the silicon-containing gas only,
wherein the silicon-containing gas comprises silane or disilane, and the inhibitive gas comprises hydrogen, and
wherein a flow rate ratio of the silicon-containing gas to the inhibitive gas is from about 1:50 to about 1:60.
2. The method of claim 1 , wherein the first polysilicon layer is amorphous while the second polysilicon layer is crystallized.
3. The method of claim 1 , wherein the first polysilicon layer has a first grain size, the second polysilicon layer has a second grain size, and the first grain size is smaller than the second grain size.
4. The method of claim 1 , wherein a flow rate of the silicon-containing gas is about 50-60 sccm, and a flow rate of the inhibitive gas is about 2,500-3,600 sccm.
5. The method of claim 1 , wherein a flow rate of the silicon-containing gas keeps the same, and a flow rate of the inhibitive gas keeps the same or increases over time.
6. The method of claim 1 , wherein the first polysilicon layer and the second polysilicon layer are formed at the same temperature of about 700-750° C.
7. The method of claim 1 , wherein a temperature of forming the first polysilicon layer is lower than a temperature of forming the second polysilicon layer.
8. The method of claim 7 , wherein the temperature of forming the first polysilicon layer is about 550-650° C., and the temperature of forming the second polysilicon layer is about 700-750° C.
9. The method of claim 1 , wherein a thickness of the first polysilicon layer is smaller than a thickness of the second polysilicon layer.
10. The method of claim 9 , wherein a thickness ratio of the first polysilicon layer to the second polysilicon layer is from about 1:2.5 to about 1:6.
11. The method of claim 10 , wherein the thickness of the first polysilicon layer is about 100-200 Å, and the thickness of the second polysilicon layer is about 500-600 Å.
12. The method of claim 1 , further comprising performing a first ion implantation process after the step of forming the second polysilicon layer to dope the second polysilicon layer.
13. The method of claim 12 , further comprising performing a second ion implantation process before the step of performing the first ion implantation process, so as to form a barrier layer in the second polysilicon layer to prevent dopants from diffusing to the first polysilicon layer.