SGT-MOSFET沟槽底部清洗工艺优化

Trench Bottom Oxide Pre-Clean Process Optimization for SGT-MOSFET

屏蔽栅MOSFET(Shielded Gate Trench MOSFET,缩写SGT-MOSFET)功率器件是一种基于传统沟槽式MOSFET(U-MOSFET)的一种改进型的沟槽式功率MOSFET。相比于传统U-MOSFET功率器件,它的开关速度更快,开关损耗更低,具有更好的器件性能。对于SGTMOSFET功率器件,沟槽底部的形貌对器件性能都有非常重要的影响。当SGT-MOSFET功率器件沟槽底部氧化膜出现空洞时,器件IDSS(漏源短路电流)将增大。SGT-MOSFET功率器件相比传统U-MOSFET功率器件的沟槽深度大大加深了,以往的沟槽清洗干燥工艺,沟槽底部易有水渍残留。水渍会导致底部氧化膜生长异常,产生空洞。调整沟槽清洗干燥工艺,晶圆在清洗干燥过程中,将晶圆脱离去离子水水面的速度降低,即可实现晶圆的充分干燥,摆脱水渍残留。

Shielded Gate Trench MOSFET （SGT-MOSFET） power device is a kind of optimized TCH-MOS based on the traditional trench U-MOSFET, which has much lower switching loss and higher switching speed. For SGT-MOSFET, trench bottom part is important for the product performance. If the trench bottom oxide structure is not stable, the shield effect will be worse and IDSS higher. Since the trench depth of SGT-MOSFET is much deeper than that of traditional U-MOSFET. Therefore the traditional wafer cleaning process is limited on the SGT-MOSFET clean process and water-mark always appear on the bottom of deeper trench. The remained water-mark will cause trench bottom oxide profile abnormal and suffered void issue. By optimized the deeper trench cleaning process, we can get wafer dry and clean enough without water-mark. And the SGT-MOSFET gets stable trench bottom oxide, and stable shield effect.