Wafer support table and RF rod
A wafer support table includes a ceramic base having a wafer placement surface and including an RF electrode and a heater electrode embedded, the RF electrode being closer to the wafer placement surface; a hole extending from a surface of the ceramic base opposite the wafer placement surface toward the RF electrode; and an RF rod through having a top end joined to the RF electrode or joined to a conductive member connected to the RF electrode, wherein the RF rod is a hybrid rod including a first rod member that is made of Ni and constitutes a portion of the RF rod from the top end to a predetermined position and a second rod member that is joined to the first rod member and constitutes a portion of the RF rod from the predetermined position to the base end and is made of a non-magnetic material.
1. A wafer support table comprising:
a ceramic base having a wafer placement surface and including an RF electrode and a heater electrode embedded, the RF electrode being closer to the wafer placement surface;
a hole extending from a surface of the ceramic base opposite the wafer placement surface toward the RF electrode; and
an RF rod through which radio-frequency power is supplied to the RF electrode and having a top end joined to the RF electrode exposed to a bottom of the hole or joined to a conductive member connected to the RF electrode, wherein
the RF rod is a hybrid rod including a first rod member that is made of Ni and constitutes a portion of the RF rod from the top end to a predetermined position located between the top end and a base end and a second rod member that is joined to the first rod member and constitutes a portion of the RF rod from the predetermined position to the base end, and
the second rod member is made of a non-magnetic material.
2. The wafer support table according to claim 1 , wherein
the predetermined position is determined by using a rod made of Ni, instead of the hybrid rod, and is a position where T (x) represented by T (x)=Ts−(□T/L)*x is greater than or equal to Curie temperature of Ni and lower than or equal to oxidation temperature of the non-magnetic material, where Ts [° C.] is a temperature of the heater electrode (provided that Ts exceeds the Curie temperature of Ni), L [cm] is a length of the rod made of Ni, □T [° C.] is a difference in temperature between ends of the rod made of Ni, x [cm] is a length of the rod made of Ni from the top end to the predetermined position, and T (x) [° C.] is a temperature of the rod made of Ni at the predetermined position.
3. The wafer support table according to claim 1 , wherein the second rod member has at an end thereof a protrusion tapered to gradually decrease in width toward the base end of the RF rod, and
the protrusion of the second rod member fits in a recess at an end of the first rod member to form the RF rod.
4. The wafer support table according to claim 1 , wherein the first rod member has at an end thereof a protrusion tapered to gradually decrease in width toward the top end of the RF rod, and
the protrusion of the first rod member fits in a recess at an end of the second rod member to form the RF rod.
5. The wafer support table according to claim 1 , wherein the second rod member is made of tungsten.
6. The wafer support table according to claim 1 , wherein the RF rod has a hollow section.
7. The wafer support table according to claim 6 , wherein
the second rod member has the hollow section, and
a peripheral wall defining the hollow section is made of tungsten ribbon or tungsten mesh.
8. The wafer support table according to claim 1 , wherein the first rod member has a narrow portion near a top end thereof.
9. An RF rod that is a hybrid rod comprising:
a first rod member that is made of Ni and constitutes a portion of the RF rod from a top end to a predetermined position located between the top end and a base end and a second rod member that is joined to the first rod member and constitutes a portion of the RF rod from the predetermined position to the base end, wherein
the second rod member is made of a non-magnetic material.