Deep reactive ion etching of in situ boron doped LPCVD Ge_0.7Si_0.3 using SF₆ and O₂ plasma

This paper reports on deep reactive ion etching (DRIE) of in situ highly boron doped low pressure chemical vapor deposited Ge0.7Si0.3 alloy in SF6 and O2 plasma. The effect of RF power, SF6 flow, O2 flow and temperature on the etch rate of Ge0.7Si0.3 films with a boron concentration of 2.1 × 1021 atoms/cm3 is investigated. Optimized conditions for a combination of a vertical etch profile and a high selectivity towards PECVD oxide are reported. The effect of boron doping concentration on the etch rate is also investigated. The etch rate is found to decrease with an increase in the dopant concentration. The developed SF6 and O2 based DRIE recipes are applied to fabricate GeSi microresonators

Low Stressed In-situ Boron doped Poly SiGe Layers for High-Q Resonators

Polycrystalline silicon-germanium (Poly SixGe1-x) can be used as one of the microstructural materials for MEMS due to its superior mechanical properties [1,2], high quality factor [3] and low thermal budget requirements based on the Ge contents [4] (<450 oC) for post processing on top of CMOS chip. This work deals with the characterization of in-situ boron doped poly SiGe layers LPCVD deposited at 430 oC with a mixture of 0.2% diborane (B2H6) in Argon on 110 nm SiO2. The concerned properties like sheet resistance and residual stress in the deposited layers are investigated at diborane mixture flow of 50 sccm and 100 sccm. It is observed that the deposition rate is decreased with the increase of B2H6 mixture flow. Whereas, the resistivity of these deposited layers decrease linearly with the increase of B2H6 mixture flow. The stress in the deposited layers shows a trend from low tensile to low compressive with the increase of diborane mixture flow. The properties of the layers deposited at 50 sccm of diborane mixture flow shows good results in terms of resistivity, deposition rate, cross load thickness uniformity and residual stress and therefore qualify them to use as structural layers for the realization of disk resonator

Low-Stress Highly-Conductive In-Situ Boron Doped Ge_0.7Si_0.3 Films by LPCVD

This paper reports on low pressure chemical vapor deposited in-situ boron doped polycrystalline germanium-silicon layers with 70% germanium content. The effect of diborane partial pressure on the properties of the GeSi alloy is investigated. The obtained high boron concentration results in resistivity values less than 1 m_-cm. The layers deposited at low partial pressures of B2H6 exhibit very low stress down to –3MPa.With increasing B2H6 partial pressure first the stress changes from tensile to compressive, followed by a phase transition from polycrystalline to amorphous. The highly doped, low stress poly-Ge0.7Si0.3 layers deposited at 430◦C are further applied in high-Q microelectromechanical resonators envisaged for above-IC integration with CMOS

Capacitively transduced polycrystalline GeSi MEM resonators

Wireless communication technology has revolutionized our daily life through rapid development in the areas of broadcasting, wireless local area networks (WLAN), wireless sensor networks, mobile communication, and satellite communication etc. [1.01]. Wireless communication systems rely on their ability to select or generate signals with a very precise frequency. Filters are used for the reception of a desired signal in an overly crowded frequency spectrum, in the presence of a substantial amount of interference. In the same systems, oscillators are required for a stable reference frequency. The common feature of filters and oscillators is their use of resonators, of which performance is extremely important, especially in the case of low-noise or low-power designs [1.02]

Comparison of gate capacitance extraction methodologies

In recent years, many new capacitance-voltage measurement approaches have been presented in literature. New approaches became necessary with the rapidly increasing gate current density in newer CMOS generations. Here we present a simulation platform using Silvaco software, to describe the full chain from fabrication process until signal interpretation of an NMOS C-V test structure. The platform allows a verification of the validity of an assumed extraction procedure from high-frequency or RF C-V measurements

Deep reactive ion etching of in situ boron doped LPCVD Ge0.7Si0.3 using SF6 and O2 plasma

This paper reports on deep reactive ion etching (DRIE) of in situ highly boron doped low pressure chemical vapor deposited Ge0.7Si0.3 alloy in SF6 and O2 plasma. The effect of RF power, SF6 flow, O2 flow and temperature on the etch rate of Ge0.7Si0.3 films with a boron concentration of 2.1 × 1021 atoms/cm3 is investigated. Optimized conditions for a combination of a vertical etch profile and a high selectivity towards PECVD oxide are reported. The effect of boron doping concentration on the etch rate is also investigated. The etch rate is found to decrease with an increase in the dopant concentration. The developed SF6 and O2 based DRIE recipes are applied to fabricate GeSi microresonators

Materials selection for low temperature processed high Q resonators using ashby approach

MicroElectroMechanical Systems (MEMS) is an emerging class of microfabrication technology that can truly be anticipated as an enabling technology for future radio frequency (RF) communications. This work focuses on the material selection using the Ashby approach for the high-Q resonators that need to be monolithically post processed on top of CMOS chip conforming to the requirement of thermal budget, stress and plasma induced damages for post processing

CMOS-MEMS Post Processing Compatible Capacitively Transduced GeSi Resonators

This paper reports on the fabrication, simulation and characterization of post processing compatible poly GeSi MEM resonators. The resonators are fabricated, following a two masks process flow, using 1.5 μm thick low stress, highly conductive insitu boron doped LPCVD poly Ge0.7Si0.3 structural layers. All the process steps are kept below 450 °C to potentially avoid CMOS degradation, a prime concern for post processing compatible MEMS. A narrow gap of ~40 nm is achieved using a sacrificial gap oxide layer between the vibrating structure and the electrodes. The GeSi resonators, square plate and circular disk, are excited in their respective Lamé and Wine glass modes exhibiting the resonance peaks at 47.9 MHz and 72.77 MHz, respectively, with the quality factor around 200,000 in air, the highest reported till date for post processing compatible capacitively transduced resonator