离子注入杂质与缺陷间的相互作用

【作者】 安娜；

【导师】 夏建新；

【作者基本信息】 电子科技大学 ， 微电子与固体电子学， 2004， 硕士

【摘要】 随着集成电路集成度的提高,其横向和纵向尺寸不断减小。对于采用深亚微米工艺的下一代集成电路,其纵向结深应小于0.1微米,这要求进行超浅结形成及其工艺模拟方面的研究。在集成电路制造过程中,p-n结一般是通过热退火激活离子注入杂质来形成的。由于有所谓增速扩散的存在,即在热退火的最初阶段,离子注入杂质的扩散速度是正常值的数千倍,要形成结深小于0.1微米的p-n结是很困难的,因为最初的快速扩散即可使结深超过0.1微米。要得到下一代集成电路用的超浅结,还需获得高浓度的活性杂质。而在集成电路制造过程中,为了得到浅结,常使用低温热退火,但这容易降低离子注入杂质的激活率。本文主要研究了杂质原子与离子注入缺陷的互相作用,解释了在热退火激活后,有效杂质浓度大大低于注入杂质浓度的现象。杂质原子与离子注入缺陷的互相作用是一个复杂的过程,多种作用机制并存,实验数据分析较为困难。为避开这种困难,我们研究了最简单的情况,即在均匀掺杂的P型衬底上用硅离子自注入来产生缺陷,这样可克服由于注入杂质分布不均匀造成的数据分析困难。通过对试验结果的比较和分析,我们发现杂质原子析出到离子注入所引起的缺陷,从而导致离子注入杂质激活率降低。为降低集成电路的研发成本,减少试投片次数,需要对集成电路工艺进行模拟。而现有的工艺模拟程序不适用于超浅结工艺模拟,必需进行改进。因此,本文在研究结果的基础上建立了一个硼析出到Rp缺陷上的模型,利用计算机模拟分析了杂质硼与退火过程中产生的Rp缺陷之间的相互作用,研究了硼原子的析出机理,解释了退火过程中出现的低于固溶度的非活性硼峰,得到了一组能够使模拟与实验结果较好吻合的拟和参数。尽管模型简单,它却能够再现不同退火时间硼的扩散分布,为超浅结工艺模拟提供了新思路。更多还原

【Abstract】 As technology generations advance and devices become smaller, it is necessary to create sharp, ultrashallow profiles with high concentrations of electrically active dopants. Ion implantation is the most widely used technique for forming shallow junctions. The recent trends in integrated circuit processing point towards the use of low temperature anneals to limit the redistribution of dopants. This method decreases the percentage of impurities activation.Boron is the commonly used dopant in Si processing for the formation of p-type doped regions. Anomalous diffusion of ion-implanted boron during thermal anneal is the main problem in shallow junction formation. Besides TED (transient enhanced diffusion), a striking feature of anomalous diffusion is that the peak portion of boron profile is not electrically activated and has remained immobile during annealing. For this study, (100) Czochralski Si wafers with a boron concentration of 3×1017cm-3 were implanted with Si ions at 50 keV using a Veeco-2100MP ion implanter. Implants were carried out at room temperature with doses ranging from 5×1013cm-2 to 2×1015cm-2. Uniformly boron-doped wafers were used to investigate the impact of ion implant damages on the redistribution of boron atoms. Si ions instead of dopants such as B, P and As atoms were implanted into the Si wafers to avoid data analysis difficulties. The boron segregation to three types of dislocation loops, EOR dislocation loops, clamshell defects and Rp defects, was investigated with SIMS and XTEM. The evolution of boron segregation peaks is closely related to the evolution of dislocation loops.At present, simulation tools designed to predict dopant diffusion during device processing are not capable of dealing with this phenomenon in a satisfactory manner. From this perspective, it is crucial to improve our understanding of the physical mechanisms of B diffusion. In this article, a simple model for boron segregation to Rp defects has been developed to explain the boron anomalous diffusion which is not adequately considered by the most <WP=6>widely used process simulation codes. The inactive boron peak below the equilibrium solubility during annealing is explained with this model. Rp defect decay time constant and the boron segregation energy have been found to fit the data to a reasonable extent. The experimental boron profiles for different annealing times can be well reproduced with this model. Implementation of this model into process simulators allows one accurately forecast of the boron and carrier distributions after annealing.更多还原