ION-IMPLANTATION OF SILICON-WAFERS FOR DEFECT-REDUCED DOPED LAYER FORMATION WITH LOW DOPANT ATOM DIFFUSION

A new process for ion implantation into silicon wafers was proposed. T his process has an additional implantation step to form an amorphous p hase. At first self-ions are implanted into a cooled wafer (<-30 degre es C) to form the amorphous phase, and subsequently dopant atoms are i mplanted to form a doped layer within the amorphous layer. After annea ling above 650 degrees C, the silicon wafer is completely recrystalliz ed, and no defects with sizes detectable by TEM are present near the d oped layer. There is indeed a defect layer in the wafer; however, it l ies along the amorphous/crystal interface that is behind the doped lay er. The concentration profile of the dopant atoms is not changed durin g epitaxial recrystallization, and further dopant atom diffusion durin g annealing is limited to about 0.05 mu m, because defect-enhanced dif fusion does not occur. The double implantation method is considered to be effective for doped layer formation in the VLSI fabrication proces s.