In approximately half of our study population, the use of the RIA technique for autologous bone graft harvesting in cases of segmental bone loss resulted in a successful outcome with bone healing. Defect size seems to be a critical issue regarding the outcome. Although our results are less promising than previously published, the RIA technique has its place in the treatment algorithm of segmental bone defects.
This paper investigates the influence of the electrode spacing, chamber pressure, total gas flow, and H 2 dilution on the crystallinity, resistivity, uniformity, and stress of polycrystalline silicon-germanium ͑poly-SiGe͒ films grown by plasma-enhanced chemical vapor deposition ͑PECVD͒. Boron-doped PECVD SiGe films of 1.6 m thick are deposited on 400 nm chemical vapor deposition layers from SiH 4 , GeH 4 , and B 2 H 6 precursors. The microstructure is verified by transmission electron microscopy and by X-ray diffraction. It was discovered that for constant temperature and deposition rate, the PECVD SiGe microstructure changes from completely amorphous to polycrystalline by increasing the electrode spacing and pressure due to reduced ion bombardment. A process window of an electrode spacing and pressure for the PECVD poly-SiGe deposition is thus identified based on a sheet resistance mapping method. Increasing the total gas flow dramatically improves the within-wafer crystallinity variation and further reduces the resistivity. Increasing the H 2 flow during PECVD shifts the stress from −51 to 17 MPa and further reduces the crystallinity variation over the wafer. In addition, the effect of changing the SiH 4 to GeH 4 ratio and the in situ boron doping by adding B 2 H 6 is also investigated. The findings in this paper are expected to facilitate the use of poly-SiGe in the above complementary metal oxide semiconductor ͑CMOS͒ microelectromechanical system ͑MEMS͒ applications.Polycrystalline silicon-germanium ͑poly-SiGe͒ has been demonstrated to be an excellent material for the fabrication of integrated microsystems in an above complementary metal oxide semiconductor ͑CMOS͒ microelectromechanical system ͑MEMS͒ approach. 1-3 Poly-SiGe has the mechanical and electrical properties similar to polysilicon but can be deposited and crystallized at low temperatures ͑e.g., 450°C for CMOS compatible applications͒. At the same time, poly-SiGe has a relatively high stiffness value ͑around 140 GPa for 60-70 atom % Ge 4 ͒.The deposition rate ͑DR͒ of poly-SiGe can be significantly enhanced by utilizing plasma-enhanced chemical vapor deposition ͑PECVD͒. 5 A typical DR of poly-SiGe deposited using chemical vapor deposition ͑CVD͒ is around 0.6 nm/s after the incubation period, whereas the DR of PECVD deposited poly-SiGe is around 2.3 nm/s and there is no or minimal incubation time. 6 PECVD is therefore the most promising technology in commercializing polySiGe for MEMS applications, where many thick structural/capping layers ͑4-10 m͒ are commonly used. To ensure a good crystalline growth, the bulk PECVD layer is deposited on top of a thin CVD SiGe layer. With this technique, the crystalline grains that form in the slowly grown CVD layer continue up to the PECVD layer. 6 In the meantime, this CVD layer, typically 400 nm, can also be used for the anchor filling of the surface micromachined MEMS structures, where a highly conformal deposition is preferred. The polySiGe films in this paper thus always start with a CVD grown layer.However, di...
Poly-crystalline Silicon-Germanium is a promising structural material for post-processing Micro Electro-Mechanical Systems (MEMS) above CMOS due to its excellent mechanical and electrical properties when deposited at CMOS compatible temperatures. In this work an optimized process to deposit high quality crystalline poly-SiGe layers with low stress, low strain gradient and good within-wafer uniformity at a manufacturable throughput is developed. The process used to deposit the layers is based on a combination of CVD and PECVD SiGe depositions. Firstly, the CVD SiGe process has been extensively characterized to the extent that the influence of thickness, Ge concentration and B concentration on film stress and strain gradient is now well understood. Then the interaction between the PECVD SiGe and the underlying CVD layer has been investigated. This combined knowledge enables specific tailoring of the CVD-PECVD SiGe stack to give the desired strain gradient for a certain layer thickness.
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