CO_2,O_2,CF_4液体微滴喷射靶激光等离子体光源光谱

The Spectra of a Laser-Produced Plasma Source with CO_2,O_2 and CF_4 Liquid Aerosol Spray Target

基于软X射线辐射计量和极紫外投影光刻(EUVL)应用,研制了一台使用纳秒激光器的液体微滴喷射靶激光等离子体(LPP)极紫外光源。该光源由一个可连续控温的不锈钢电磁喷气阀门、YAG激光器和能同步控制喷气阀门和激光器的脉冲发生器组成。使用液氮作致冷剂,控温范围77～473 K。对于足够高的背景气压和低的阀门温度,当气体经过阀门脉冲式地喷入真空靶室内时,气体经过气-液相变碎裂成大量的液体微滴形成液体微滴喷射靶。首先,依据非相对论量子力学理论,使用原子光谱分析常用的Cowan程序,计算了O2,CO2和CF4等几种液体在1011～1012W.cm-2激光功率密度下可能相应产生的O4+,O5+,O6+,O7+,F5+,F6+和F7+离子的电偶极辐射跃迁波长和跃迁概率。其次,在激光焦点功率密度为8×1011W.cm-2时,测量了CO2,O2,CF4液体微滴喷射靶在6～20 nm波段的光谱。理论计算结果与实验结果相比较,得出了所测量谱线的电偶极辐射跃迁波长和跃迁概率以及跃迁能级所应归属的组态和光谱项。

A laser-produced plasma（LPP） source with liquid aerosol spray target and nanosecond laser was developed,based on both soft X-ray radiation metrology and extreme ultraviolet projection lithography（EUVL）.The LPP source is composed of a stainless steel solenoid valve whose temperature can be continuously controlled, a Nd∶YAG laser with pulse width,working wavelength and pulse energy being 7 ns,1.064 μm and 1J respectively,and a pulse generator which can synchronously control the valve and the laser.A standard General Valve Corporation series 99 stainless steel solenoid valve with copper gasket seals and a Kel-F poppet are used in order to minimize leakage and poppet deformation during high-pressure cryogenic operation.A close fitting copper cooling jacket surrounds the valve body.The jacket clamps a copper coolant carrying tube 3 mm in diameter,which is fed by an automatically pressurized liquid nitrogen-filled dewar.The valve temperature can be controlled between 77 and 473 K.For sufficiently high backing pressure and low temperature,the valve reservoir gas can undergo a gas-to-liquid phase transition.Upon valve pulsing,the liquid is ejected into a vacuum and breaks up into droplets,which is called liquid aerosol spray target.For the above-mentioned LPP source,firstly,by the use of Cowan program on the basis of non-relativistic quantum mechanics,the authors computed the radiative transition wavelengths and probabilities in soft X-ray region for O4＋,O5＋,O6＋,O7＋,F5＋,F6＋ and F7＋ ions which were correspondingly produced from the interaction of the 1011-1012 W·cm-2 power laser with liquid O2,CO2 and CF4 aerosol spray targets.Secondly,the authors measured the spectra of liquid O2,CO2 and CF4 aerosol spray target LPP sources in the 6-20 nm band for the 8×1011 W·cm-2 laser irradiance.The measured results were compared with the Cowan calculated results ones,and the radiative transition wavelength and probability for the measured spectral lines were obtained.