Zhengxuan Zhang

Research on metastable electron traps in the modified SOI materials induced by Si ion implantation

Silicon-On-Insulator (SOI) materials were modified by Si ion implantation with different doses, as reported in this letter. The electrical performance was studied and the effect of a modification technique on the SOI materials was investigated. The characteristic, obtained by pseudo-metal-oxide-semiconductor (pseudo-MOS) method, showed that the drain ID current versus gate voltage VG(ID−VG) curves shifted along the axis of VG with the change of Si ion implantation doses. The results of electron paramagnetic resonance (EPR), x-ray photoelectron spectroscopy (XPS), and electronic test suggested that the parameters of implantation affect the electrical performance and that the metastable electron traps are introduced into the buried oxide layers of SOI materials.

Relaxed silicon–germanium-on-insulator fabricated by oxygen implantation and oxidation-enhanced annealing

The application of separation-by-implantation-of-oxygen (SIMOX) for silicon–germanium-on-insulator (SGOI) fabrication is always limited by the Ge loss caused by the high temperature annealing. A unique SIMOX method was introduced to fabricate SGOI and resolve the problem of Ge loss. During the process, a SiO2 layer was formed pre-annealing to block the Ge out-diffusion. As the x-ray rocking curve and Raman spectra studies show, the Ge fraction of the SGOI was improved to 17 at.%. The final sample exhibits a planar and continuous buried oxide layer, sharp interfaces and a defect free top SiGe layer as the cross-sectional transmission-electron- microscopy (XTEM) and secondary-ion-mass-spectrometry studies show. The Rutherford backscattering spectroscopy demonstrated that the superficial SiGe layer was superior in quality (derived channelling yield of 10%). The results indicate that the additional step of thermal oxidation pre-annealing is vital to resolve the problem of Ge loss and the modified SIMOX process is applicable for SGOI fabrication.

Improvement of the radiation hardness of SIMOX buried layers using nitrogen implantation

An investigation of hardening the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers to total-dose irradiation has been made by implanting nitrogen into the BOX layers with a constant dose at different implantation energies. The total-dose radiation hardness of the BOX layers is characterized by the high frequency capacitance–voltage (C–V) technique. The experimental results show that the implantation of nitrogen into the BOX layers can increase the BOX hardness to total-dose irradiation. Particularly, the implantation energy of nitrogen ions plays an important role in improving the radiation hardness of the BOX layers. The optimized implantation energy being used for a nitrogen dose, the hardness of BOX can be considerably improved. In addition, the C–V results show that there are differences between the BOX capacitances due to the different nitrogen implantation energies.

Research on the effect of nitrogen implantation doses on the structure of separation by implantation of oxygen and nitrogen

In our work, separation by implantation of oxygen and nitrogen (SIMON) wafers were fabricated with different nitrogen implantation doses and post-annealing. Secondary ion mass spectrometer (SIMS) analysis showed that for the samples with low nitrogen dose some nitrogen ions were distributed in the buried oxide layers and some others were collected at the Si/SiO2 interface after annealing, and for the samples with large nitrogen dose distinct delamination appeared between the layer containing the nitrogen element and that containing the oxygen element. The results of the spreading resistance probe (SRP) suggested that a buried insulator was formed for wafers with large nitrogen implantation dose. The results of cross section transmission electron microscopy (XTEM) confirmed the analysis above. The results show that the quality of SIMON materials is closely related to nitrogen implantation parameters.

Effect of the implantation of fluorine on the mobility of channel electron for partially depleted SOI nMOSFET

The mobility of channel electron, for partially depleted SOI nMOSFET in this paper, decreases with the increase of implanted fluorine dose in buried oxide layer. But, the experimental results also show that it is larger for the transistor corresponding to the lowest implantation dose than no implanted fluorine in buried layer. It is explained in terms of a lubricant model. When fluorine atoms are implanted in the top silicon layer, the mobility is the largest. In addition, a positive shift of threshold voltage has also been observed for the transistors fabricated on the SOI wafers processed by the implantation of fluorine. The causes of all the above results are discussed.

Effect of implantation dose and annealing time on the formation of si nanocrystals embedded in thermal oxide

Photoluminescence (PL) and X-ray Photoelectron Spectroscopy (XPS) are employed to study the Si nanocrystals formed in the thermal oxide by Si + implantation. PL results estimate the size of nanocrystals and the concentration of Pb centers in the Si-SiO 2 nanocrystal-matrix interfaces. It is shown that the size of Si nanocrystals increase with implantation dose. Increasing the dose from 1×10 16 to 1×10 17 Si + /cm 2 shifts the size of nanocrystals from ~2 nm to ~3.5nm, while prolonging the annealing time from 1h to 2h has no effect on the position of PL peak. P and Ar implantations into the SiO 2 films are also investigated to suggested that the PL peak is due to implant induced chemical changes rather than implant induced damage. XPS analysis shows that the concentration of Si nanocrystals increases with Si implantation dose. Research on the annealing dependence of the forming of Si nanocrystals suggests that 1000°C annealing produces larger amount of Si nanocrystals than 1100°C annealing.