激光诱导放电等离子体极紫外光源的研究

Abstract

Objective With the continuous decrease in feature size in the semiconductor industry, extreme ultraviolet lithography (EUVL) is voltage increases from 7 kV to 15 kV, the total and EUV radiation powers both increase, and the highest EUV radiation power reaches 0.025 MW. The total radiation energy increases from 842.00 mJ to 3.85 J, and the total EUV radiation energy increases from 3.5 mJ to 65.0 mJ. The CE increases from 0.054% to 0.23%, and the SP increases from 0.42% to 1.69%. At a voltage of 7 kV, the maximum EUV radiation power density is 0.09 MW/cm 3 , and the EUV radiation is mainly concentrated near the anode (Fig. 7). When the voltage is 15 kV, the maximum EUV radiation power density can reach 0.3 MW/cm 3 , and the EUV radiation is mainly concentrated on both sides of the electrodes (Fig. 8). The average ionization degree of the plasma in the main area of EUV radiation is 10-12.Conclusions In this study, the EUV radiation emitted by the LDP and LPP is conducted experimentally and theoretically.Compared to that of the LPP source, the temperature of the LDP source is significantly higher, and more Sn 10+ , Sn 11+ , and Sn 12+ ions are present. Transitions between multiple excited states gradually replace those between single excited and ground states. However, the plasma size of the LDP source is very large, resulting in a low radiation power density. The light source for mask inspection requires strong brightness; therefore, further research on the Zpinch mechanism is required to reduce the plasma size and improve brightness. The discharge voltage significantly influences the inband EUV radiation of the LDP source. This phenomenon demonstrates the major advantage of the LDP light source: the extreme ultraviolet output power can be increased by increasing the injection of electrical energy. However, CE and SP still need to be improved by increasing the current rise rate. Shortening the current rise time and reducing the inductance of the discharge circuit can be good approaches.