Hydrogen Implanted Silicon Wafers Research Articles

Efficiency of a solar cell with intermediate energy levels: An example study on hydrogen implanted Si solar cells

For any pn junction solar cell, there is a theoretical limit to its conversion efficiency, which is determined by its band gap. This efficiency may exceed the limit by introducing an intermediate level (IL) that can facilitate the sub-band-gap optical absorption, but the IL can simultaneously enhance the carrier recombination rate. To understand the net effects of the IL, it is necessary to estimate the rates of both the optical absorption and carrier capture via the IL. In this study, trap parameters and the optical absorption coefficient are evaluated for defect levels in hydrogen implanted silicon wafers using deep level transient spectroscopy, the optical-capacitance transient spectroscopy, and carrier lifetime measurements. Using the obtained trap parameters, the characteristics of hydrogen implanted silicon solar cells are simulated. The simulation results indicate that it is not possible to realize improvements in efficiency by performing hydrogen implantation.

Hydrogen plasma surface activation of silicon for biomedical applications

Silicon has gradually been recognized to be an essential trace element in the normal metabolism of higher animals, and the role of silicon in the human body has aroused interests in the biomedical community. In fact, the interactions between silicon-based devices and the human body such as biosensors and microelectromechanical systems (MEMS) often suffer from poor biocompatibility. In this work, hydrogen plasma immersion ion implantation (H-PIII) is conducted to improve the bioactivity or bone conductivity of silicon. In order to investigate the formation mechanism of bone-like apatite on the surface of the hydrogen implanted silicon wafer, two comparative experiments, hydrogenation and argon bombardment, are performed. The H-PIII sample exhibits an amorphous surface consisting of Si–H bonds. After immersion in simulated body fluids, a negatively charged surface containing the functional group ( Si–O −) is produced and bone-like apatite is observed to nucleate and grow on the surface. The surface of the H-PIII silicon wafer favors the adhesion and growth of osteoblast cells and good cytocompatibility may be inferred.

Layer Transfer of Hydrogen-Implanted Silicon Wafers by Thermal-Microwave Co-Activation

AbstractSilicon on insulator (SOI) substrate is a key materials for nano-scaling IC device and the requirement for its crystal structure and quality is really high. Nanothick silicon thin film can be transferred onto a handle wafer from a donation wafer to form a SOI wafer after this process including hydrogen implantation of donation wafer, wafer bonding, and thermal treatment at moderately high temperatures of 400 to 600 degree centigrade. The expansion of the hydrogen molecular evolving from the implanted hydrogen ions interacting with silicon dangling bonds and trapped inside the microcavities located near the ion projected range resulted in exfoliation of the silicon thin film in the final heating step. The hydrogen molecules inside the microcavities tend to expand along the bonded interface rather than radially to form individual blisters. Finally, the fracture failure of ion implanted area parallel to the bonded interface near the projected ion range is formed by the sideway expansion of the cavities due to the diffusion supply of implanted hydrogen excited by thermal energy. Microwave processing can lower the activity energy to speed the chemical reaction so that it leads the format of microcavities occurring at low temperature by directly exciting the implanted hydrogen ions by microwave energy and also results in decreasing the critical dosage for layer splitting. However, microwave irradiation alone at room temperature causes the formation of lots of nucleus sites of micro-voids filled by hydrogen molecule which is immobility in silicon resulting in the issue of uniformity of transferred layer. In this study, the hydrogen implanted silicon substrate was irradiated by microwave at low temperature (200 degree centigrade) rather than microwave alone to co-activate the implanted hydrogen ions in silicon to increase not only kinetic energy but also mobility to successfully achieve a completely transferred layer in a short time.

Direct determination of the initial thermal evolution behaviour of the platelet defects in hydrogen implanted silicon wafers

Direct information about initial thermal evolution behaviour of the platelet defects in hydrogen implanted silicon wafers is retained in annealed samples as thin as transmission electron microscopic (TEM) foil and can then be observed using high resolution transmission electron microscopy (HRTEM). It has been found that platelet-like amorphous inclusion appears in the initial stage of the thermal evolution and, additionally, thermal evolution preferentially occurs around the defects of the comparatively larger sized platelets, the reasons for which are discussed. By using the channelling implantation method, the characteristic platelet size distribution was acquired and the crack position was further modified.

Biomimetic growth of apatite on hydrogen-implanted silicon

Hydrogen in silicon has been widely applied in semiconductor fields. In this paper, the application of hydrogen-implanted silicon wafer in biomedical fields was explored by investigating its bioactivity. Hydrogen implanted silicon wafers were prepared using plasma immersion ion implantation. The surface structures of the 1.4×10 17 cm −2 hydrogen-implanted silicon wafers were investigated using atomic force microscopy and transmission electron microscopy (TEM). The hydrogen depth profiles were acquired by SIMS and the crystal quality of the as-implanted silicon was studied by channeling Rutherford backscattering spectrometry (RBS). The bioactivity of the implanted silicon was evaluated using the biomimetic growth of apatite on its surface after it was soaked in simulated body fluid for a period of time. The TEM, SIMS and RBS results indicate the formation of an amorphous hydrogenated silicon (a-Si:H x ) layer has been formed on the surface of the hydrogen-implanted silicon wafer. After immersion in SBF for 14 days, bone-like apatite is observed to nucleate and grow on the surface. With longer soaking time, more apatite appeared on the surface of the hydrogen implanted silicon but our control experiments did not reveal any apatite formation on the surface of the un-implanted silicon wafer, hydrogenated crystalline silicon wafer (with hydrogen, but no amorphous surface), or argon-implanted silicon wafer (amorphous surface but without hydrogen). Our results indicated that the bioactivity of silicon wafer can be improved after hydrogen implantation and the formation of the amorphous hydrogenated silicon (a-Si:H x ) surface also plays a synergistic role to improve the bioactivity.

Biomimetic growth of apatite on hydrogen-implanted silicon

Hydrogen in silicon has been widely applied in semiconductor fields. In this paper, the application of hydrogen-implanted silicon wafer in biomedical fields was explored by investigating its bioactivity. Hydrogen implanted silicon wafers were prepared using plasma immersion ion implantation. The surface structures of the 1.4×10 17 cm −2 hydrogen-implanted silicon wafers were investigated using atomic force microscopy and transmission electron microscopy (TEM). The hydrogen depth profiles were acquired by SIMS and the crystal quality of the as-implanted silicon was studied by channeling Rutherford backscattering spectrometry (RBS). The bioactivity of the implanted silicon was evaluated using the biomimetic growth of apatite on its surface after it was soaked in simulated body fluid for a period of time. The TEM, SIMS and RBS results indicate the formation of an amorphous hydrogenated silicon (a-Si:H x ) layer has been formed on the surface of the hydrogen-implanted silicon wafer. After immersion in SBF for 14 days, bone-like apatite is observed to nucleate and grow on the surface. With longer soaking time, more apatite appeared on the surface of the hydrogen implanted silicon but our control experiments did not reveal any apatite formation on the surface of the un-implanted silicon wafer, hydrogenated crystalline silicon wafer (with hydrogen, but no amorphous surface), or argon-implanted silicon wafer (amorphous surface but without hydrogen). Our results indicated that the bioactivity of silicon wafer can be improved after hydrogen implantation and the formation of the amorphous hydrogenated silicon (a-Si:H x ) surface also plays a synergistic role to improve the bioactivity.

Gettering of Oxygen onto Buried Defect Layer in Hydrogen Implanted Silicon Wafers after Low Temperature Surface Saturation by Oxygen and Vacuum Annealing

Gettering of Oxygen onto Buried Defect Layer in Hydrogen Implanted Silicon Wafers after Low Temperature Surface Saturation by Oxygen and Vacuum Annealing

Silicon layer transfer using wafer bonding and debonding

Two experiments were performed that demonstrate an extension of the ion-cut layer transfer technique where a polymer is used for planarization and bonding. In the first experiment hydrogen-implanted silicon wafers were deposited with two to four microns low-temperature plasma-enhanced tetraethoxysilane (TEOS). The wafers were then bonded to a second wafer, which had been coated with a spin-on polymer. The bonded pairs were heated to the ion-cut temperature resulting in the transfer of a 400 nm layer silicon. The polymer enabled the bonding of an unprocessed silicon wafer to the as-deposited TEOS with a microsurface roughness larger than 10 nm, while the TEOS provided sufficient stiffness for ion cut. In the second experiment, an intermediate transfer wafer was patterned and vias were etched through the wafer using a 25% tetramethylammonium hydroxide (TMAH) solution and nitride as masking material. The nitride was then stripped using dilute hydrofluoric acid (HF). The transfer wafer was then bonded to an oxidized (100 nm) hydrogen-implanted silicon wafer. After ion-cut annealing a silicon-on-insulator (SOI) wafer was produced on the transfer wafer. The thin silicon layer of the SOI structure was then bonded to a third wafer using a spin-on polymer as the bonding material. The sacrificial oxide layer was then etched away in HF, freeing the thin silicon from the transfer wafer. The result produced a thin silicon-on-polymer structure bonded to the third wafer. These results demonstrate the feasibility of transferring a silicon layer from a wafer to a second intermediate “transfer” or “universal” reusable substrate. The second transfer step allows the thin silicon layer to be subsequently bonded to a potential third device wafer followed by debonding of the transfer wafer creating stacked three-dimensional structures.