表面通道P型金氧半場效電晶體中以新閘極製程抑制硼穿透效應之研究

Abstract

在CMOS 元件進入深次微米後，以P+型多晶矽製造表面通道P型金氧半場效電晶體是無法避免的。然而，在製作P+型多晶矽和源極汲極離子佈植時所用的硼原子，在佈植之後會穿透閘極氧化層，甚而進入矽底層，造成臨界電壓的不穩定和降低氧化層的可靠性；再者，為了要製作超淺接面，一般都以BF2做離子佈植，而當中的氟原子卻會使硼穿透的效應更加的嚴重。 在本論文中，提出一個新的製作場效電晶體的閘極結構，方法是在製作P+型多晶矽閘極時，以硼離子源代替一般製程的氟化硼 (BF2) 離子源，但是在源極和汲極extension 的離子佈植源還是用BF2，所以還是保有淺接面，主要的目的是讓閘極中沒有氟離子的存在，可以防止因氟離子而增加的硼穿透效應。 結果顯示，在提出的新結構中，氧化介電層的品質獲得明顯的改善、短通道效應減少。另外，也對此結構的元件與一般的元件做熱載子效應的比較，也顯示出此一新的結構，也有較佳的熱載子可靠性。

For deep sub-micro CMOS devices, the p+-polysilicon gate used to achieve surface-channel p-MOSFET becomes indispensable. However, boron atoms implanted into polysilicon gate will penetrate through the gate oxide into Si substrate and alter the channel doping. This, in turn, causes instability of threshold voltage and reduces the oxide reliability. For ultra shallow junctions, BF2 has been employed as an implantation species, but this will enhance boron diffusion through the thin gate oxide. In this dissertation, we use the method of a new method for boron implantation without fluorine atoms. It is to use boron implantation instead of BF2 to form the p+-polysilicon gate. The results show that the oxide quality is improved. The new processing devices exhibit superior characteristics. Furthermore, the short-channel effect, especially the hot-carrier reliability, has also been improved.