Plasma radiation source, method of forming plasma radiation, apparatus for projecting a pattern from a patterning device onto a substrate and device manufacturing method

An apparatus to project a pattern from a patterning device onto a substrate, the apparatus comprising:

• a plasma radiation source comprising:
• an anode and a cathode defining a region in which to produce a plasma current, wherein the anode has a first major annular surface and the cathode has a second major annular surface which is facing the first major annular surface of the anode such that the anode and the cathode do not overlap each other, and
• a magnet disposed substantially around the anode and the cathode to externally induce an initial magnetic field in a discharge gap between the anode and the cathode, wherein, in use, the magnetic field in the region has an axial component directed along a direction of the plasma current;
• and
• an illumination system configured to form a radiation beam from radiation emitted from the region.

A method of producing radiation, comprising:

• generating a plasma current in a plasma region in a direction between an anode and a cathode;
• applying a magnetic field in the plasma region with an axial component directed along the direction of the plasma current;
• and
• emitting radiation from the plasma region,
• wherein the anode has a first major annular surface, the cathode has a second major annular surface which faces the first major annular surface of the anode such that the anode and the cathode do not overlap each other, and a magnet is disposed substantially around the anode and the cathode to externally induce an initial magnetic field in a discharge gap between the anode and the cathode.

A device manufacturing method comprising:

• generating a plasma current in a plasma region in a direction from an anode to a cathode;
• applying a magnetic field in the plasma region with an axial component directed along the direction of the plasma current;
• and
• using a reflective optical element to form a radiation beam from radiation emitted from the plasma region,
• wherein the anode has a first major annular surface, the cathode has a second major annular surface which faces the first major annular surface of the anode such that the anode and the cathode do not overlap each other, and a magnet is disposed substantially around the anode and the cathode to externally induce an initial magnetic field in a discharge gap between the anode and the cathode.

A plasma radiation source comprising:

• an anode and a cathode defining a region in which to produce a plasma current;
• and
• an electromagnet magnet configured to receive an electric current that induces an initial magnetic field of a sufficient strength in a discharge gap between the annular anode and the annular cathode such as to limit the collapse of a Z-pinch region of the plasma,
• wherein the magnetic field in the region has an axial component directed along a direction of the plasma current,
• wherein the anode is an annular anode having a first major annular surface and the cathode is an annular cathode having a second major annular surface which faces the first major annular surface of the annular anode such that the annular anode and the annular cathode do not overlap each other.