Michael C. Lorek
University: Undergrad: Ohio University, Athens; Grad: University of California, Berkeley
Major: Electrical Engineering
Graduation Date: Undergrad: 6/2009
Hometown: Northfield, OH
Project: Charge-Based Capacitance Measurement methods (CBMCM) are growing in popularity as an accurate technique to characterize small capacitances on-chip. As MOSFET transistors continue shrinking in the deep sub-micron regime, their respective intrinsic device capacitances are reaching levels not accurately measurable by traditional LCR meters. These capacitances are vital for circuit designers to carry out accurate circuit simulations. Small capacitance measurement techniques are going to play an important role in the accurate modeling of emerging devices such as nanowire, nanotube, and FinFET transistors.
A design approach for a Charge-Based Capacitance Measurement circuit is presented. Fundamental electrical and mathematical equations are used to derive a linear equation for extracting capacitance from measurable average currents in a CBCM circuit. A traditional CMOS-based four transistor pseudo-inverter CBCM design is compared to a similar topology using transmission gate devices. MATLAB code is described that simulates the operation of an Ammeter and averages SPICE simulation-generated transient current signals to yield Device Under Test (DUT) capacitance values. SPICE and MATLAB results are presented that show the circuit’s theoretical ability to accurately measure capacitances to the atto-farad (10-18) level. Extracted parasitics from a single transmission gate-based CBCM cell layout for an ON 0.5µ process are used to yield more realizable simulation results. The extracted circuit was simulated to examine measurable current levels across various DUT capacitances, frequencies, and transistor widths. These results will be used to determine test points for fabricated chip lab characterization for a wide range and large quantity of semiconductor capacitors in the future.
About me: I spent a lot of time on the computer growing up and became very interested hardware and software. Frequent computer hardware upgrades and subsequent benchmarking inspired me to read reviews that talked about CPU/GPU architecture and operation. I found all of this very interesting and, along with my interests in math and the hard sciences, drove me to major in Computer Engineering at Ohio University.
I began my co-op work experience at Advanced Micro Devices (AMD) in Austin, TX during the Spring Quarter of my sophomore year. I stayed through the proceeding summer, and returned to the same group during the summer after my junior year. I had an influential mentor who spent years as an analog and mixed-signal circuit designer. His broad knowledge and passion for his work made me seek in-depth learning in this area that I also enjoyed. This is what encouraged me to change my undergraduate major to Electrical Engineering, and apply to graduate schools to study analog and mixed-signal circuit design.