In this paper, we present design, fabrication, and test results of a novel wavelength-selective MEMS switch for integrated optics. The device is based on switching of a ring resonator add-drop filter by use of an electrostatically-actuated MEMS bridge. We have demonstrated the wavelength-dependant switching capabilities of a prototype device; however, the residual stress in the bridge caused sagging of the bridge and high insertion loss to the optical output. Therefore, we are investigating the use of titanium nitride (TiN) for the MEMS bridge material. TiN has ideal characteristics both mechanically and electrically. It can also be annealed to lower the residual stress to almost zero. We have fabricated the MEMS bridge with TiN and done some preliminary experiments on the structure. The results show promise for the use of this material in our device, and more generally as a structural material. We have also designed closed-loop feedback control for precision positioning of the bridge. This enables this device to tune the selected wavelength over one full channel (30nm) for use as a tunable optical filter. The feedback scheme is based on using the bridge as one electrode of a capacitive sensor, and simulations indicate that the bridge position can be controlled to 2.5pm accuracy. Modifications of the device could also be used as a variable optical attenuator.
This paper reports on the use of titanium nitride (TiN) in a MEMS-based wavelength specific waveguide optical switch. By interfering a conductive MEMS bridge with the evanescent field of a ring resonator add/drop filter, the device can switch between enabling or disabling the ring resonator Problems with residual stresses in the MEMS bridges, leading to bridge deflection and thereby causing incomplete switching between the states, was addressed by the use of TiN as the MEMS bridge material. TiN has the virtue of being able to almost completely. We demonstrate the ability to virtually eliminate the residual stresses in TiN and thereby improve the bridge profile, promising much improved switching characteristics
Mach-Zehnder electro-optic waveguide modulators were fabricated based on BaTiO3 (BTO)-SrTiO3 (STO) multilayer thin film stacks grown on single crystal MgO substrates by pulsed laser deposition. X-ray diffraction measurements confirmed the formation of a BTO-STO superlattice with periodicity of 11unit cells. Strip-loaded waveguides were formed by patterning a SixNy film deposited onto the BTO-STO stack while Al electrodes of 3mm length and 13μm separation were fabricated in the vicinity of the active waveguide arm of the Mach-Zehnder modulator. An effective electro-optic coefficient of 73pm∕V at 1550nm wavelength was determined for the deposited BTO-STO superlattice by measuring the output intensity as a function of applied electric field.
An integrated optical microelectromechanical system (MEMS) switch that provides wavelength selectivity is described. The switching mechanism is based on moving a MEMS actuated optically absorbing membrane into the evanescent field of a high-index-contrast optical ring resonator. By controlling the loss, and thus, the cavity quality factor, the resonant wavelength is switched between the drop and through ports.
The integration of large die complex on panel scale requires significant manufacturing technology development with thickness variation control as a key enabler for pitch scaling and redistribution layers (RDLs) with ultra high-density routing. This paper will focus on CMP process development for very large form factor panel-scale (510x515 mm) The magnitude and panel-level uniformity of removal rate are optimized across various materials, slurries, pads, and process parameters. Capabilities for reducing total thickness variation (TTV) are also demonstrated on substrate dielectric layers and on a bridge die interconnect substrate.
The demand for higher performance is driving package transmission lines to operate at higher frequencies with lower package insertion loss budgets. A typical solution to create adhesion between the copper and dielectric is by roughening the copper surface to provide anchors on which the laminated dielectric adheres. However, the requirements for next generation of high-speed input/output (HSIO) drives the need for lower roughness copper surface. A non-roughened solution, therefore, using chemical adhesive layer to enable a smoother copper-dielectric interface without compromising this metal-organic interfacial adhesion is required. In this work, we develop a series of characterization methods to understand the structure-property relationship of an organic adhesive film as example, which give significant insights to guide the materials/chemical screening processes to facilitate the development cycle. It is also demonstrated that the corrosion protection offered by the adhesive films plays a key role on improving interfacial integrity and reliability of next generation interconnects.
Organic substrates used in flip-chip packaging consist of multiple layers of alternating dielectric and copper layers built around a glass-fiber Core material. These materials have widely different mechanical properties which makes the interfaces between these layers susceptible to delamination. As a result, adhesion between them is a critical mechanical property governing the reliability performance of substrate packages. Developing metrologies which can quantify the adhesive properties of an interface is an essential component of substrate process development. Peel-test is a popular metrology used to characterize adhesion of a film deposited over an underlying material. When inelastic materials are involved (like copper in this case) the peel-force measured is a convoluted function of thickness of the film, mechanical properties of the materials involved, test speed, and the true interfacial properties. Due to this, a clear understanding of the true adhesion strength based solely on experimentation is not possible. Focus of this publication is to utilize mechanical modeling (Finite element analysis) coupled with experimentation to extract the key adhesion metric - the interface fracture energy (Gc). We present our analysis in the case of copper films electroplated on a desmeared dielectric layer. We discuss in detail our findings on the effect of various parameters - peel film thickness, peel velocity, film width on the peel force, from experiments, sample fractography and modeling.
