SIMOX SOI埋氧注氮工艺对埋氧中固定正电荷密度的影响

Effect of implantation of nitrogen into SIMOX buried oxide on its fixed positive charge density

在SIMOX SOI材料的埋氧中注氮是为了增强该类材料的抗辐射能力.通过C-V研究表明,对于埋氧层为150nm的SIMOX SOI材料来说,当在其埋氧中注入4×1015cm-2剂量的氮后,与未注氮埋氧相比,注氮埋氧中的固定正电荷密度显著增加了;而对于埋氧层为375nm的SIMOX SOI材料来说,当注氮剂量分别为2×1015cm-2和3×1015cm-2时,并未发现埋氧中固定正电荷密度的增加.所有SIMOX注氮后的退火条件是完全相同的.通过SIMS分析,将薄埋氧中固定正电荷密度的增加归结为注氮后的退火所引起的氮在埋氧与Si界面附近的积累.同时还发现,未注氮埋氧中的固定正电荷密度是非常小的.这意味着通常情况下在热生长SiO2膜中大量存在的氧化物电荷,其数量在SIMOX埋氧中则要相对少得多.

In order to obtain greater radiation hardness for SIMOX （separation by implanted oxygen） materials, nitrogen was implanted into SIMOX BOX （buried oxide）. However, it has been found by the C-V technique employed in this work that there is an obvious increase of the fixed positive charge density in the nitrogen-implanted BOX with a 150 nm thickness and 4×10^ 15 cm ^-2 nitrogen implantation dose, compared with that unimplanted with nitrogen. On the other hand, for the BOX layers with a 375 nm thickness and implanted with 2×10^ 15 and 3×10 ^15 cm ^-2 nitrogen doses respectively, the increase of the fixed positive charge density induced by implanted nitrogen has not been observed. The post-implantation annealing conditions are identical for all the nitrogen-implanted samples. The increase in fixed positive charge density in the nitrogen-implanted 150 nm BOX is ascribed to the accumulation of implanted nitrogen near the BOX/Si interface due to the post-implantation annealing process according to SIMS results. In addition, it has also been found that the fixed positive charge density in initial BOX is very small. This means SIMOX BOX has a much lower oxide charge density than thermal SiO2 which contains a lot of oxide charges in most cases.