Session 24: Displays, Sensors, and MEMS - Imagers and Integrated Sensors
Wednesday, December 12, 9:00 a.m.
Co-Chairs: Edoardo Charbon, Technical University Delft
Monolithic optical structures for light gathering in image sensors are focused. First, microlens progresses, such as gapless microlens, inner microlens and light pipe are explained. Then, back side illumination (BSI) is compared with front side illumination (FSI). Lastly, recent FSI technology, SmartFSITM, is reported along with its pixel shrinkage results.
1.12um backside illuminated CMOS image sensor with backside deep trench isolation (DTI) has been demonstrated for the first time. DTI is fabricated on backside surface after wafer bonding and grinding process. Backside DTI makes its layout simple because no transistor isolation exists on backside. We have confirmed 50% reduction of crosstalk.
This work presents a complete and quantitative analysis of the ultra-high extrinsic quantum efficiency in amorphous oxide hetero-TFT image sensors, taking into account the high sub-gap optical absorption due to oxygen vacancies, extended electron lifetime due to retarded recombination, and the reduced transit time associated with short channel lengths.
We designed and fabricated an In0.53Ga0.47As/InP Single-Photon Avalanche Diode with improved layer structure and diffusion geometry in order to achieve good detection efficiency (30% at 1550 nm), low afterpulsing (gate repetition frequency > 1 MHz) and good timing performance (timing response has 57 ps FWHM and 30 ps tail).
A graphene stack (GS) structure assembled by layer-by-layer (LBL) transfer of single-layer graphene (SLG) is applied in field effect transistors (FETs) for photodetection. Excellent optoelectronic performance of ~3.6 times increased photocurrent (PC) together with increased internal/external quantum efficiency (IQE/EQE) is obtained in the LBL-GS-FET compared to the conventional SLG-FET, owing to (i) the improved electrical transport, e.g., carrier mobility (4.1 times higher), sheet resistance (61% reduced) and contact resistance (81% reduced) etc., and (ii) the increased optical absorption (over fivefold higher in the visible spectrum). A photovoltaic (PV) model of the LBL-GS-FET was established, indicating a peak of PC generation due to the optimized gate modulation. Both the experimental and theoretical results suggest the LBL-GS as an excellent material for high efficiency optoelectronics.
We have developed a CMOS-MEMS-based label-free protein sensor, which utilizes nonlinear optical transmittance change by the Fabry-Perot interference to enhance the sensitivity of surface-stress. A read-out tiny photocurrent from the multidimensional arrayed MEMS sensor is signal-processed by integrated source follower circuit, selector, and decoder. The integrated MEMS sensor array can be used for screening analysis for any cancers.
A highly sensitive and accurate field-effect sensor was obtained in a standard differential pair CMOS structure without Ag/AgCl reference electrode. The device is composed of two sensors each with a ?oating gate (FG) field effect transistor (FET), a control gate (CG) and an extended sensing gate (SG). By extending the sensing gate and engineering the capacitance value of the CG, we achieved a remarkable sensitivity of 130mV/pH for our pH sensor exceeding the fundamental Nernst limit, 59mV/pH. In addition, we removed the bulky Ag/AgCl reference electrode by a novel technique employing differential measurement to cancel the effect of the common abnormal potential change occurs in the solution.