Development of new fluoride single crystals as VUV window materials for next-generation optical lighography

开发新型氟化物单晶作为下一代光学光刻的 VUV 窗口材料

基本信息

批准号：
12555001
负责人：
FUKUDA Tsuguo
金额：
$ 8.64万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2001
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-12555001/
关键词：
LiCaAlF_6 KMeF_3 BaLiF_3 F_2laser Optical lithography Window material VUV Single crystal

项目摘要

In order to develop new fluoride single crystal materials as window materials for next-generation optical lithography, especially for F_2 laser with 157 nm, crystal growth and VUV optical characterization have been done for different fluorides. Among them, LiCaAlF_6, KMgF_3, BaLiF_3, and Sr:BaF_2 were focused in this work. The advantage of LiCaAlF_6 was its high transparency until 112 nm. Detailed refractive index measurement down to 5 decimal points also showed that the birefringence diminish at 152 nm which is very close to the wavelength of F_2 laser. The advantages of other three crystals were their cubic structure, which enables 0 birefringence, and high transparency as well. Successful growth of LiCaAlF_6, KMgF_3, and BaLiF_3 single crystals with 2 inches in diameter showed that these crystals have possibility to be grown with larger diameter. Especially, 4-inch diameter LiCaAlF_6 single crystal was successfully grown by the Czochralski technique to show the real possibility of diameter extension. For further investigation to extend the diameter, the Bridgman technique was used. KMgF_3 crystal with 10 cm in diameter was grown, although it contained white milky material. Transparent LiCaAlF_6 crystals with 6-inch diameter were grown by the insertion of several plates inside a crucible. The insertion of plates was effective to separate transparent crystal and white material which contained impurity phases. Damage resistance of grown crystals were investigated. Total damage obtained after high power X-ray radiation showed that LiCaAlF_6 and Sr:BaF_2 have very high resistance. These two crystals also showed almost no damage formation after F_2 laser irradiation with 10 times high power than that is used in a practical optical lithography.

为了开发新型氟化物单晶材料作为下一代光学光刻尤其是157 nm F_2激光器的窗口材料，对不同氟化物进行了晶体生长和VUV光学表征。其中，LiCaAlF_6、KMgF_3、BaLiF_3和Sr:BaF_2是本次工作的重点。 LiCaAlF_6的优点是在112 nm之前具有高透明度。精确到小数点后 5 位的详细折射率测量还表明，双折射在 152 nm 处减弱，该波长非常接近 F_2 激光的波长。其他三种晶体的优点是它们的立方结构，可以实现0双折射，并且透明度也很高。 2英寸直径LiCaAlF_6、KMgF_3和BaLiF_3单晶的成功生长表明这些晶体具有生长更大直径的可能性。特别是，利用直拉技术成功生长了4英寸直径的LiCaAlF_6单晶，展示了直径延伸的真正可能性。为了进一步研究扩大直径，使用了布里奇曼技术。尽管含有白色乳状物质，但仍生长出直径为10cm的KMgF_3晶体。通过在坩埚内插入几块板来生长直径为 6 英寸的透明 LiCaAlF_6 晶体。插入板可有效分离透明晶体和含有杂质相的白色材料。研究了生长晶体的抗损伤性。高能X射线辐射后得到的总损伤表明LiCaAlF_6和Sr:BaF_2具有很高的电阻。这两种晶体在以实际光学光刻所用功率10倍高的F_2激光照射后也几乎没有形成损伤。