Abstract-The high index contrast silicon-on-insulator platform is the dominant CMOS 1 compatible platform for photonic integration. The successful use of silicon photonic chips in optical communication applications has now paved the way for new areas where photonic chips can be applied. It is already emerging as a competing technology for sensing and spectroscopic applications. This increasing range of applications for silicon photonics instigates an interest in exploring new materials, as silicon-oninsulator has some drawbacks for these emerging applications, e.g. silicon is not transparent in the visible wavelength range. Silicon nitride is an alternate material platform. It has moderately high index contrast, and like silicon-on-insulator, it uses CMOS processes to manufacture photonic integrated circuits. In this paper, the advantages and challenges associated with these two material platforms are discussed. The case of dispersive spectrometers, which are widely used in various silicon photonic applications, is presented for these two material platforms.

No abstract

No abstract

No abstract

No abstract

This paper reports on wafer-level packaged RF-MEMS switches fabricated in a commercial CMOS fab. Switch fabrication is based on a metal surface micromachining process. A novel wafer-level packaging scheme is developed, whereby the switches are housed in on-chip sealed cavities using benzocyclobutene (BCB) as the bonding and sealing material. Measurements show that the influence of the waferlevel package on the RF performance can be made very small.

The RF-power handling capability is an important characteristic for RF-MEMS switching devices. Apart from excessive heat dissipation, the power handling capability is mainly limited by the so-called self-biasing and/or RF-latching. These two phenomena result from the fact that the available RF-power from the source induces a non-zero electrostatic pulling force on the suspended structure. So far, self-biasing of RF-MEMS switches has always been studied assuming a perfect match of the device to the network in the ON-state (i.e. no reflection) and thus a fixed dc-equivalent rms voltage on the capacitor. If the RF-power exceeds a critical value, pull-in or self-biasing occurs. In practice, however, the assumption of the perfect match is not correct as the switch capacitance increases with increasing RF-power. This will cause a change in the reflected signal and thus a decrease in the dc-equivalent voltage source. This paper gives a new insight into the RF-power handling of RF-MEMS shunt switches and, per extension, of RF-MEMS shunt tunable capacitors. We analytically show how the negative feedback on the electrostatic force introduced by the capacitive mismatch changes the pull-in characteristics of the structure and can even stabilize it, totally avoiding the pull-in phenomenon.

Surface micromachined metal armatures are commonly used for MEMS applications of which RF-MEMS is the most well known. In most cases metals with a high conductivity, such as aluminum or gold, are used. These metals often have a low melting point and therefore have a low thermal stability and show plastic deformation of the structures at relatively low temperatures (<200 • C). High melting point metals, such as platinum, are expected to show plastic deformation only at higher temperatures which makes them interesting for use as a structural layer in RF-MEMS devices. In this paper, we present a technology to realize suspended platinum structures by means of surface micromachining. An improved lift-off process allows patterning 1 μm Pt films on a polyimide sacrificial layer. A comparison of the characteristics and armature resonance frequencies between RF-MEMS switches with Pt armatures and AlCu 0.5% alloy armatures reveals an increased thermal stability for the former up to at least 250 • C. This enables zero-level packaging of switches at relative high temperatures without affecting their performances. The lower conductivity of Pt compared to AlCu 0.5% does not lead to a significant increase in RF losses. Implementing AlN as a dielectric material, the Pt-based capacitive shunt switches reported in this paper showed lifetimes in excess of 5×10 7 cycles under standard testing conditions.