Tsung-Lin Tang

Design and implementation of a torque-enhancement 2-axis magnetostatic SOI optical scanner

This study demonstrates the torque-enhancement design for a 2-axis magnetostatic SOI scanner driven by a double-side electroplating ferromagnetic film. The present design has two merits: (1) the slender ferromagnetic material patterns with higher length-to-width ratio enhance the magnetization, (2) the backside electroplating of the ferromagnetic film increases the volume of the ferromagnetic materials. This study also establishes the fabrication processes to implement the proposed design. The processes also have two merits: (1) the handle-layer of the SOI wafer is exploited as the shadow mask to pattern the seed-layer at the backside of the device layer, (2) the device layer of the SOI wafer acts as the cathode to enable simultaneous double-side electroplating. In applications, a 2-axis SOI scanner was implemented and characterized. Measurements show a 149% torque enhancement from the double-side electroplating design. The vertical slender ferromagnetic material patterns further increase the magnetostatic torque to 211%. This study also successfully demonstrates the Lissajous scanning using the presented 2-axis SOI scanner.

Post-CMOS selective electroplating technique for the improvement of CMOS-MEMS accelerometers

This study presents a simple approach to improve the performance of the CMOS-MEMS capacitive accelerometer by means of the post-CMOS metal electroplating process. The metal layer can be selectively electroplated on the MEMS structures at low temperature and the thickness of the metal layer can be easily adjusted by this process. Thus the performance of the capacitive accelerometer (i.e. sensitivity, noise floor and the minimum detectable signal) can be improved. In application, the proposed accelerometers have been implemented using (1) the standard CMOS 0.35 µm 2P4M process by CMOS foundry, (2) Ti/Au seed layers deposition/patterning by MEMS foundry and (3) in-house post-CMOS electroplating and releasing processes. Measurements indicate that the sensitivity is improved 2.85-fold, noise is decreased near 1.7-fold and the minimum detectable signal is improved from 1 to 0.2 G after nickel electroplating. Moreover, unwanted structure deformation due to the temperature variation is significantly suppressed by electroplated nickel.

Improvement of CMOS-MEMS accelerometer using post-CMOS selective electroplating technique

This study presents a simple approach to improve the performance of CMOS-MEMS capacitive accelerometer by means of the post-CMOS metal electroplating process. The metal layer can be selectively electroplated on the MEMS structures at low temperature; and the thickness of metal layer can be easily adjusted by process. Thus, the performance of capacitive accelerometer (i.e., structure deformation, sensitivity) can be improved significantly. In application, the designed accelerometers have been implemented using (1) standard TSMC CMOS 0.35µm 2P4M process, (2) Ti/Au seed-layer deposition/patterning by Asia Pacific Microsystems Inc. (apm), MEMS foundry, and (3) in-house post-CMOS electroplating and releasing processes. Measurements indicate the sensitivity is improved for 2.5-fold, and noise is decreased near 2.5-fold after Ni electroplating. Moreover, unwanted structure deformation due to the temperature variation is significantly suppressed by electroplated Ni.

Magnetostatic torsional actuator with embedded nickel structures for the improvement of driving force and wobble motion

This study demonstrates the magnetostatic torsional actuator consisting in a Si–Ni compound frame to significantly improve the driving force. The present design has three merits: (1) it employs a Si mold to simultaneously electroplate/pattern thick Ni, and the Ni and Si structures respectively provide magnetostatic force and superior mechanical properties, (2) the embedded Ni structures not only increase the ferromagnetic material volume but also enhance magnetization strength to enlarge magnetostatic torque, (3) the Si–Ni compound structure, which is nearly symmetric about the torsional axis in the out-of-plane direction, can decrease the moment of inertia and also reduce the wobble motion. In applications, one-axis torsional actuator is implemented and characterized. The experiments show that the Si–Ni compound scanner has an optical scan angle θoptical = 90° with the input power 81 mW. The input power is decreased as compared with the existing scanner. Moreover, the out-of-plane wobble motion is only 44 nm at θoptical = 15°. Compared with the existing designs consisted of asymmetric structures in the out-of-plane direction, such as electroplated film and silicon rib, about the torsional axis, the equivalent eccentric force is reduced nearly two-fold. In short, the proposed design not only increases the driving force but also decreases the wobble motion.

Implementation of polymer-dispersed liquid crystal microprism array for LED radiation pattern application

This study implements a novel lighting chip with tunable radiation pattern. The lighting chip consists of polymer-dispersed liquid crystal (PDLC) microprism array, LED, and Si-carrier. By integrating the characteristics of microprism and the scattering/transmitting modes of PDLC, the PDLC-microprism enables the tuning of radiation pattern when applying voltage. The lighting chip with PDLC-microprism has the following advantages, (1) no moving parts are required to tune the radiation pattern, (2) the shape of PDLC-microprism array can be easily changed by molding processes, and (3) the fabrication and packaging are performed at low temperature and the damage to PDLC is prevented.

The torque-enhancement design for magnetostatic scanner

This study presents two designs to enhance the magnetostatic torque to drive the scanner, (1) the lever arm, and (2) the ferromagnetic material pattern with higher length to width ratio.

Lorentz force torsional actuator with embedded nickel structures

This study presents a Lorentz force torsional actuator design consisting of a Si-Ni compound frame. The proposed actuator design employs Si mold to simultaneously electroplate/pattern Ni, and the Ni and Si structures respectively provide electric routing and superior mechanical properties. As compare with the traditional design (Al wire routing on Si substrate), the thick Si-Ni compound structure could accommodate more turns and further increase the efficiency of Lorentz force at the same input current and device feature size. Moreover, the Si-Ni compound frame is nearly symmetric about the torsional axis, the proposed design reduces the wobble motion. The measurement results show that the wobble displacement of proposed design is only 52 nm as the optical scan angle is 20°. Comparing with the existing designs, the wobble displacement is decreased to 55% by the proposed design.

A magnetostatic 2-axis MEMS scanner with I-section rib-reinforcement and slender permanent magnet patterns

This study demonstrates the 2-axis epitaxial silicon scanner driven by the coil-less magnetostatic force using electroplated permanent magnet (CoNiMnP) film. The present approach has four merits: (1) the process employs the cheap silicon wafer with epitaxial layer; and the electrochemical etching stop technique is used to precisely control the thickness of scanner; (2) the I-section rib-reinforced structure is implemented to provide high stiffness of the mirror plate; (3) the magnetostatic driving force on scanner is increased by electroplated permanent magnet film with slender patterns; (4) the size of packaged scanner is reduced since the assembled permanent magnets are not required.

Magnetostatic torsional actuator with embedded nickel structures for pure rotation

This study demonstrates the magnetostatic torsional actuator consisting of a Si-Ni compound frame to significantly improve the driving force. The present design has three merits: (1) employ Si mold to simultaneously electroplate/pattern thick Ni, and the Ni and Si structures respectively provide magnetostatic force and superior mechanical properties, (2) the embedded Ni structures not only increase the ferromagnetic material volume but also enhance magnetization strength to enlarge magnetostatic torque, (3) the Si-Ni compound structure, which is nearly symmetric about the torsional axis, can decrease the moment of inertia and also reduce the wobble motion. Experiments show the Si-Ni compound scanner has optical scan angle θ=90°, and wobble motion and power consumption is significantly reduced.

The double-side electroplating and slender ferromagnetic patterns torque-enhancement design for magnetostatic actuator

This study demonstrates the torque-enhancement design for magnetostaic actuators driven by double-side electroplating ferromagnetic film. The present design has two merits: (1) the backside electroplating of the ferromagnetic film increases the magnetostatic torque, (2) the slender ferromagnetic material patterns with higher length-to-width ratio enhance the magnetostatic torque. The actuator is implemented on SOI wafer, and the process also has two merits, (1) the device-layer act as the cathode to enable simultaneous double-side electroplating, (2) the handle-layer is exploited as the shadow mask to pattern the seedlayer at backside wafer. In applications, a scanner were implemented and characterized. Measurements show a 149% torque enhancement from double-side electroplating design. The vertical slender ferromagnetic material patterns further increase the magnetostatic torque to 211%.