Plasma Doping Samples Research Articles

Ultra-shallow Junction Formation Using Plasma Doping and ExcimerLaser Annealing for Nano-technology CMOS Applications

A plasma-doping (PLAD) process utilizing a PH3 plasma is presented to fabricate a n /p ultrashallow junction at room temperature. When PLAD is completed, an excimer laser annealing (ELA) process is performed using an ArF (193 nm) excimer laser with pre-annealing. In our case, the preannealing is conducted for 5 min at 500 ◦C in a thermal furnace. The energy density of the excimer laser used for the ELA process ranged from 400 to 500 mJ/cm. Transmission electron microscope (TEM) and double-crystal X-ray diffraction (DXRD) measurements were employed to investigate defects on the plasma-doped samples. Some point defects were found in the DXRD analysis while TEM images reveal no crystalline defects. The result of a secondary ion mass spectrometry (SIMS) analysis on the formed shallow n/p junction revealed that the junction depth was thinner than 40 nm. We found that the drive-in process of phosphorous occurred only when the energy density of the laser was larger than 460 mJ/cm, and an increased laser energy density resulted in a decreased sheet resistance. With an energy density of 460 mJ/cm, a junction depth of 30 nm and a sheet resistance of 151.6 Ω/ were obtained. The leakage current for the fabricated n/p junction was indirectly investigated by measuring the I-V characteristics of the diode fabricated using PLAD, followed by the ELA processes.

Sub-15 nm n[sup +]∕p-Germanium Shallow Junction Formed by PH[sub 3] Plasma Doping and Excimer Laser Annealing

An n + /p germanium (Ge) ultrashallow junction formed by PH 3 plasma doping (PLAD) and KrF excimer laser annealing is demonstrated. In order to improve the n-type dopant activation without significant diffusion in the n + /p-Ge junction, we applied laser annealing on the PLAD samples. Compared with rapid thermal annealing (RTA), the laser annealing yielded shallower junction depth (∼15 nm) with low sheet resistance and comparable leakage current characteristics in the Ge n + /p junction. Therefore, PLAD with laser annealing can be considered as an alternative method for fabricating future Ge metal-oxide-semiconductor field-effect-transistors.

Profile control in BF3 plasma doping

Plasma doping (PD) is an alternative technique to form shallow junctions in deep-submicrometer microelectronic devices. Previous studies have demonstrated that PD produces shallow junctions with better efficiency than those by conventional low energy beam-line doping (BD). In addition, even though cross-sectional transmission electron microscopy reveals that the surface layer is amorphized after high dose BF3 PD or BD implantation, PD samples show less residual defects after rapid thermal annealing. For ultrashallow junctions, doping profiles with a high dopant concentration near the surface are required for the formation of low resistant contacts. In this article, we demonstrate the use of nonideal voltage pulse shape in achieving advantageous doping profiles that are difficult to obtain via BD. By performing particle-in-cell (PIC) simulation, we derive the ion energy distributions for different sample voltage pulse shapes for BF3 PD. Comparison of the PD boron depth profiles simulated by PIC and an assumed Gaussian implant profile to the BD boron depth profiles simulated by TRIM shows a low energy component that does not exist in BD samples. The rise and fall time of the sample voltage pulse contributes to the overall energy distribution since a long rise or fall time increases the low energy component. We postulate that these low energy ions may also change the nature of the amorphized layer and are one of the reasons for the reduction of residual defects after rapid thermal annealing. The preferred sample voltage pulse for plasma doping is suggested to be a short one with a relatively long rise and fall time. This is something that is very difficult to achieve by beam-line ion implantation.

Ultra - Shallow p+/n Junction Formed by Plasma Ion Implantation

AbstractWe have investigated the electrical characteristics, junction depth and defect of ultrashallow junctions formed by using a plasma doping procedure. Compared with ultralow energy boron ion implantation at 500eV, the plasma doping process exhibits both a shallow junction depth and a low sheet resistance. The junction depths of the plasma doped samples were 15 nm and 33 nm after annealing for 10s at 900 °C and 950 °C, respectively. For the same junction depth, the sheet resistance of the B2H6 plasma doped sample is an order of magnitude less than that of the 500eV B ion implanted sample. Based on cross-sectional transmission electron microscope (TEM) and deep level transient spectroscopy (DLTS) analysis, the defects formed by the B2H6 plasma doping process can be completely removed by annealing at 950 °C for 10s.