| 摘要 |
In a laser produced plasma (LPP) extreme ultraviolet (EUV) system, a droplet is irradiated by a laser pulse to produce a plasma in a chamber. This generates forces that cause the plasma to destabilize and subsequent droplets to have their flight trajectory and speed altered as they approach the plasma. This destabilization is detectable from oscillations in the amount of EUV energy generated. To reduce the oscillations by stabilizing the plasma and travel of the droplets, a proportional-integral (PI) controller algorithm is used to modify an energy of subsequent laser pulses based on the EUV energy generated in the chamber. By modifying the energy of subsequent laser pulses, the plasma stabilizes, which reduces effects on droplet flight and stabilizes the amount of EUV energy generated, allowing the plasma chamber to operate for longer intervals and to lower the amount of reserve power maintained by a laser source. |
| 主权项 |
1. A method comprising:
measuring, using an extreme ultraviolet (EUV) energy detector, an amount of EUV energy generated by a first laser pulse impacting a first droplet in a plasma chamber of a laser produced plasma (LPP) EUV system; calculating a first modified laser pulse energy, using an EUV controller, based on the measured amount of EUV energy generated by the first laser pulse impacting the first droplet in the plasma chamber; instructing, by the EUV controller, the laser source to deliver a second laser pulse having the calculated first modified energy thereby altering flight of a second droplet in the plasma chamber; measuring, using the EUV energy detector, an amount of EUV energy generated by the second laser pulse impacting the second droplet in the plasma chamber; calculating a second modified laser pulse energy, using the EUV controller, based on the measured amount of EUV energy generated by the second laser pulse impacting the second droplet in the plasma chamber; and, instructing, by the EUV controller, the laser source to deliver a third laser pulse having the calculated second modified energy thereby altering flight of a third droplet in the plasma chamber. |
