Showerhead-cooler system of a semiconductor-processing chamber for semiconductor wafers of large area
Proposed is a showerhead-cooler system of a semiconductor-processing chamber with uniform distribution of plasma density. The showerhead has a plurality of through gas holes that are coaxial with respective channels of the gas-feeding cooler plate. On the gas inlet side, the though passages of the showerhead are provided with unequal conical nozzles characterized by a central angle that decreases from the peripheral part of the showerhead to the showerhead center. Such design provides uniformity of plasma density. Furthermore, in order to protect the walls of the nozzle and the walls of the gas holes from erosion that may be caused by the hollow-cathode phenomenon, these areas are coated with a thin protective coating that is resistant to electrical breakdown and chemical corrosion.
1. A showerhead-cooler system of a semiconductor-processing chamber of a CCP plasma processing apparatus intended for processing of objects with a plasma process, comprising: a showerhead having a plurality of through gas holes; a gas-feeding cooler plate that is connected to an RF power supply, has electrical contact with the showerhead, and forms with the showerhead a gas-accumulation reservoir that communicates with the through gas holes of the showerhead; a gas-feeding cooler plate has a plurality of through gas-feeding passages that communicate with the gas-accumulating reservoir; a showerhead having a front side that faces the semiconductor-processing chamber, a back side that faces the cooler plate, a peripheral portion, which is in said electrical contact with the cooler plate, and a central area which has a showerhead center C; on the back side of the showerhead the through gas holes of the showerhead having conical nozzles with a cone angle θ that decreases in the direction from the peripheral portion to the showerhead center; the object being a semiconductor wafer, each through gas hole has a diameter d H , a length I H , and being located at a predetermined radial distance R from the showerhead center and wherein the following relationship exists between the cone angle θ of the conical nozzle of a through gas hole and a radial distance R of the gas hole from the showerhead center:
1+ bR )=[1−1/{1−[(2 I H tan θ/ d H ]} 4 ] −1/2 (1)
where “b” is a coefficient that depends on the parameters of the plasma process.
2. The showerhead-cooler system of claim 1 , wherein the cone angle of each nozzle decreases in the direction from the peripheral portion to the central area of the showerhead from 120° to 0°.
3. The showerhead-cooler system of claim 1 , wherein the cone angle of the conical nozzles linearly decreases in the direction from the peripheral portion to the showerhead center.
4. The showerhead-cooler system of claim 3 , wherein the cone angle of each nozzle decreases in the direction from the peripheral portion to the showerhead center from 120° to 0°.
5. The showerhead-cooler system of claim 1 , wherein the surfaces of the conical nozzles and at least a part of the walls of the gas holes in the area adjacent to the conical nozzles have a protective coating resistant to electrical breakdown and chemical corrosion.
6. The showerhead-cooler system of claim 5 , wherein the protective coating is an yttrium oxide coating.
7. The showerhead-cooler system of claim 6 , wherein the cone angle of each nozzle decreases in the direction from the peripheral portion to the of the showerhead center from 120° to 0°, the through gas-feeding passages of the cooler plate being coaxial with the gas holes of the showerhead.
8. The showerhead-cooler system of claim 1 , wherein the wafer has a diameter of 450 mm.
9. The showerhead-cooler system of claim 7 , wherein the surfaces of the conical nozzles and at least a part of the walls of the gas holes in the area adjacent to the conical nozzles have a protective coating resistant to electrical breakdown and chemical corrosion.
10. The showerhead-cooler system of claim 9 , wherein the protective coating is an yttrium oxide coating.
11. The showerhead-cooler system of claim 10 , wherein the cone angle of each nozzle decreases in the direction from the peripheral portion to the central area of the showerhead from 120° to 0°.