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The Laser-assisted Discharge Plasma (LDP) Technology
In the LDP architecture, liquid tin plays multiple roles. Tin is:
- the fuel
- the electrode (the wheels are not; they are merely conductors)
- a protector (protecting the rotating wheels from laser ablation)
- a conductor (a liquid bath of tin)
- a coolant.
In LDP, the plasma is generated between two rotating discs.
Partially immersed in baths filled with liquid tin, the discs are wetted and covered with a thin layer of liquid tin.
A pulsed laser beam focused one of the discs evaporates a small amount of tin, generating a tin cloud between the two discs.
Next, a capacitor bank (which is connected to the discs via the liquid tin) discharges and converts the tin cloud into a plasma.
Pinched by the high current, the plasma emits EUV radiation.
This process is repeated several thousand times per second.
The resulting heat load is cooled by the liquid tin, which is kept at a constant temperature by an external cooler.
A grazing incidence mirror is used to focus the produced EUV light into the scanner.
Because the tin plasma generates tin debris, in the form of droplets, clusters, neutrals and ions, it is critical to protect the highly sensitive EUV optics.
XTREME technologies uses a foil-trap in combination with an inert buffer gas. Due to collisions with the gas, the tin is redirected to the foils.
A very long collector lifetime (in excess of one year) has already been demonstrated, enabling high equipment uptime and a low Cost of Ownership.
To prevent tin contamination of the scanner, baffles are installed between the collector and the wall of the vacuum chamber. No tin is found after the Intermediate Focus (IF).
