Plasma reactor with inductie excitation of plasma and efficient removal of heat from the excitation coil
View Patent ↗The plasma reactor of the invention is intended for treating the surfaces of objects such as semiconductor wafers and large display panels, or the like, with plasma. The main part of the plasma reactor is an array of RF antenna cells, which are deeply immersed into the interior of the working chamber. Each antenna cell has a ferromagnetic core with a heat conductor and a coil wound onto the core. The core and coil are sealed in the protective cap. Deep immersion of the antenna cells having the structure of the invention provides high efficiency of plasma excitation, while the arrangement of the plasma cells and possibility of their individual adjustment provide high uniformity of plasma distribution and possibility of adjusting plasma parameters, such as plasma density, in a wide range.
1. A plasma reactor with inductive excitation of plasma, comprising:
a working chamber that can be sealed and evacuated and that is provided with working gas supply channels, and a working gas outlet port, the working chamber comprising a sidewall and a chamber top;
a plurality of antenna cells immersed into the working chamber; and
an RF power source connected to the antenna cells for generation of plasma in the working chamber;
each antenna cell of the plurality of antenna cells comprising:
a ferromagnetic core;
at least one inductive coil wound onto the ferromagnetic core;
a cap made from a dielectric material that sealingly covers the ferromagnetic core and the inductive coil, the cap being connected to one of the working chamber sidewall or chamber top;
wherein the ferromagnetic core of the antenna cell has a tubular shape with a central opening, the antenna cell comprising a heat conductor made from a material of high thermal conductivity inserted into the central opening, wherein the heat conductor is in contact with a heat sink, the heat sink being spaced apart from both the working chamber sidewall and the chamber top; the heat sink being a separate structure from the cap, and the heat sink being in thermal communication with one of the working chamber sidewall or chamber top.
2. The plasma reactor of claim 1 , wherein the cap is made from a non-electrically conductive material of high thermal conductivity.
3. The plasma reactor of claim 1 , wherein the heat conductor of high thermal conductivity is made of a metal.
4. The plasma reactor of claim 1 , wherein each antenna cell is provided with an individual matching network for matching an impedance of each antenna cell with an impedance of the RF power source.
5. The plasma reactor of claim 4 , wherein each antenna cell of the plurality of antenna cells is connected to the RF power source via a parallel connection or a serial connection.
6. The plasma reactor of claim 4 , wherein a first end of the at least one inductive coil in each respective antenna cell is connected to a first balanced output of a matching network, a second end of the at least one inductive coil in the respective antenna cell is connected to a second balanced output of the matching network, wherein a first RF potential is applied to the first end of the at least one inductive coil in the respective antenna cell, a second RF potential is applied to the second end of the at least one inductive coil in the respective antenna cell, the first and second RF potentials being approximately equal and opposite in phase.
7. The plasma reactor of claim 4 , wherein each antenna cell comprises an additional coil bifilarly wound with the inductive coil around the ferromagnetic core, the inductive coil and the additional coil each having a first end at a first end of the bifilar winding and a second end at a second end of the bifilar winding.
8. The plasma reactor of claim 7 , wherein the first end of the inductive coil in each respective antenna cell is connected to an unbalanced output of a matching network, the first end of the additional coil and the second end of the conductive coil are connected to a ground of the matching network, the second end of the addition coil is coupled to an unbalanced output of the matching network, the RF potential applied to the first end of the inductive coil being equal in magnitude and opposite in phase to a second RP potential applied to the second end of the additional coil.
9. The plasma reactor of claim 1 , wherein the plurality of antenna cells are coupled to the RF power source through a common impedance matching network.
10. The plasma reactor of claim 9 , wherein the plurality of antenna cells is connected to the RF power source via a parallel connection or a serial connection.
11. The plasma reactor of claim 9 , wherein a first end of the at least one inductive coil in each respective antenna cell is connected to a first balanced output of a matching network, a second end of the at least one inductive coil in the respective antenna cell is connected to a second balanced output of the matching network, wherein a first RF potential is applied to the first end of the at least one inductive coil in the respective antenna cell, a second RF potential is applied to the second end of the at least one inductive coil in the respective antenna cell, the first and second RF potentials being approximately equal and opposite in phase.
12. The plasma reactor of claim 9 , wherein each antenna cell comprises an additional coil bifilarly wound with the inductive coil around the ferromagnetic core, the inductive coil and the additional coil each having a first end at a first end of the bifilar winding and a second end at a second end of the bifilar winding.
13. The plasma reactor of claim 12 , wherein the first end of the inductive coil in each respective antenna cell is connected to an unbalanced output of a matching network, the first end of the additional coil and the second end of the conductive coil are connected to a ground of the matching network, the second end of the addition coil is coupled to an unbalanced output of the matching network, the RF potential applied to the first end of the inductive coil being equal in magnitude and opposite in phase to a second RF potential applied to the second end of the additional coil.