BF_2~+离子注入时磷杂质离子污染控制的研究

同一台离子注入机B,P离子交叉注入,残留的磷和BF3分解产生的F生成50PF ,成为难控隐患.研究指出,实际注入晶圆的平均质量数,呈以目标离子质量数为中心的正态分布;49BF2 与50PF 因质量数接近而存在可能的重叠分布区,这是出现磷污染的原因;指出改善质量分析器的控制精度,可在线调控以避免磷污染.通过比较发现,当质量分析器设定为49±0.5且注入高束流达800μA时,离子注入机不能侦测到临近目标质量数的杂质离子.离子注入机经80 h注入31P 后再交叉注入的老化实验准备,当引孤电流达3 100 μA时,电性测试发现,质量分析器设定为49±0.3(质量分辨率m/△m=169.3)的样品无磷污染.进一步研究了多重老化因素叠加效应,经同样的老化实验准备、引弧电流为3 100 μA且注入束流为800 μA时,注入剂量为2.2×1015的49BF2 ,当质量分析器严控为49±0.3,经SIMs(secondarv ion mass spectrosoopy)分析二个样品均未发现磷的高能峰.改进质量分析器控制设定数值的解决方案经生产验证有效,无需Frederic Sahores(2002 IEEE)的如增加清洗频率或分离子源专用注入机等高成本方案,提高了效益与产品良率.

How to Control Phosphorus Contamination in ~(49)BF_2~+ Implants

When Boron and Phosphorous had been alternately implanted with the same implanter,the PF molecules would be generated,due to the P+ residue reacted with F cracked from BF3.It is pointed out that the average mass of dopant into the wafer following normal distribution,with the target dopant mass as center value.The potential overlap area between the distributions of 49BF2+ and 50PF+ was the root cause of phosphorus contamination.In order to prevent PF contamination real time,the precision of mass analyzer had...