Antenna, plasma processing device and plasma processing method

A plasma processing method performed by a plasma processing apparatus having an antenna, the plasma processing method comprising:

• heating a dielectric window of the antenna by using a heater, the antenna including the dielectric window having a first surface and a second surface extending on a side opposite to the first surface, the second surface having an annular recessed surface extending around a central axis and recessed toward the first surface, and a flat surface surrounded by the annular recessed surface, a slot plate provided on the first surface, a dielectric plate provided on the slot plate, a heat transfer member made of metal, having an upper surface and a lower surface opposing to each other, and sandwiching the dielectric plate between the lower surface and the slot plate, a cooling jacket provided on the heat transfer member;
• and the heater provided between the heat transfer member and the cooling jacket, the upper surface including a plurality of first regions and a second region, the cooling jacket being mounted on the plurality of first regions, the second region being recessed further toward the lower surface than the plurality of first regions, the heater being mounted on the second region, and each of the plurality of first regions being provided at a position at least partially overlapping the flat surface when viewed in a direction parallel to the central axis;
• and
• plasma-processing a workpiece while cooling the dielectric window by using the cooling jacket, after the heating of the dielectric window by the heater is stopped.