Contactless Test Access Mechanism for 3D IC

3D IC integration presents many advantages over the current 2D IC integration. It has the potential to reduce the power consumption and the physical size while supporting higher bandwidth and processing speed. Through Silicon Via’s (TSVs) are vertical interconnects between different layers of 3D ICs with a typical 5μm diameter and 50μm length. To test a 3D IC, an access mechanism is needed to apply test vectors to TSVs and observe their responses. However, TSVs are too small for access by current wafer probes and direct TSV probing may affect their physical integrity. In addition, the probe needles for direct TSV probing must be cleaned or replaced frequently. Contactless probing method resolves most of the TSV probing problems and can be employed for small-pitch TSVs. In this dissertation, contactless test access mechanisms for 3D IC have been explored using capacitive and inductive coupling techniques. Circuit models for capacitive and inductive communication links are extracted using 3D full-wave simulations and then circuit level simulations are carried out using Advanced Design System (ADS) design environment to verify the results. The effects of cross-talk and misalignment on the communication link have been investigated. A contactless TSV probing method using capacitive coupling is proposed and simulated. A prototype was fabricated using TSMC 65nm CMOS technology to verify the proposed method. The measurement results on the fabricated prototype show that this TSV probing scheme presents -55dB insertion loss at 1GHz frequency and maintains higher than 35dB signal-to-noise ratio within 5µm distance. A microscale contactless probe based on the principle of resonant inductive coupling has also been designed and simulated. Experimental measurements on a prototype fabricated in TSMC 65nm CMOS technology indicate that the data signal on the TSV can be reconstructed when the distance between the TSV and the probe remains less than 15µm

An Implantable Microsystem for Autonomous Intraocular Pressure Monitoring .

Glaucoma, a leading cause of blindness worldwide, is a disease in which the pressure within the eye is too high for the eye to tolerate and must be reduced in order to slow or prevent damage to the optic nerve. Conventional methods for monitoring eye pressure are normally only used in the physician’s office and rely on indirect measurement methods, leading to inaccuracies. Furthermore, intraocular pressure can vary throughout the day and also depends on activity. An autonomous implantable microsystem capable of monitoring intraocular pressure with minimal patient intervention would provide useful information to the clinician in the management of glaucoma. This dissertation studies the feasibility of an integrated microsystem for autonomously measuring intraocular pressure. Small size ensures minimal impact on the patient, preventing the device from entering the field of view and simplifying implantation. Integrated haptics aid surgical implantation and minimize trauma while allowing the implant to be removed if needed. A touch-mode capacitive pressure sensor, fabricated using the dissolved wafer process, transduces intraocular pressure into capacitance with a linear response and a sensitivity of 26 fF/mmHg. A new fabrication technique has been developed to embed vertical interconnects within a glass package containing the pressure sensor, a microbattery, readout circuitry, and an antenna. This enables the vertical stacking of these components and very efficient use of limited volume. The 1.5 mm x 2 mm x 0.5 mm transparent parylene-coated glass package enables solar cells to be placed on the circuit chip for power generation, trickle charging an on-board microbattery formed using standard cleanroom materials and a non-toxic electrolyte. Flooded-cell tests verified the electrochemistry and achieved a current capacity of 8 µAh/mm2. A simple integrated readout circuit consuming 35 pW in the idle mode implemented a finite-state machine and used an optical wakeup trigger to further reduce power. The microsystem has also been demonstrated with a microprocessor to autonomously gather and store data, reading it out on demand. Finally, a pulse-based ultrawideband wireless transmission technique is proposed using non-resonant antennas. The all-digital transmitter is expected to consume much less power than conventional encoded wireless transmitters and eliminates complex circuitry.Ph.D.Electrical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/89809/1/rhaque_1.pd