Microwave Effects and Chaos in 21st Century Analog & Digital Electronics V. Granatstein, S. Anlage, T. Antonsen, Y. Carmel, N. Goldsman, A. Iliadis, J. Melngalis, P. O’Shea, E. Ott, O. Ramahi & J. Rogers, University of Maryland and R.J. Baker, Boise State University

PART A Study Vulnerability of Low-Voltage, Submicron-Scale Semiconductor Devices Circuits and Systems Diagnostics of Failure Modality Using Focused Ion Beams

MW Effects on Nanoscale Circuits and Devices: Background Modern IC’s can contain 10s of millions of deep submicron transistors. Transistors are connected by complex network of metal interconnects containing millions of nodes. Network forms extremely complex active RLC, transmission line circuit structure. Future IC’s are likely to contain billions of very fragile nanoscale transistors and billions of metal interconnects in a complex 3-D network. Future IC supply voltages are likely to be as low as 25mV.

MW Effects on Nanoscale Circuits and Devices: Problems Such complex circuits and small devices are likely to be extremely vulnerable to temporary upsets and permanent damage resulting from MW radiation. Unwanted MW radiation may enter circuits, especially at I/O ports. Radiation can then induce high voltage and current levels on interconnect network. High voltage levels can cause bit errors in digital circuits leading to circuit failure and undetected errors. Very high levels can cause permanent damage to nanoscale devices resulting from oxide breakdown and electrostatic discharge (ESD).

MW Effects on Nanoscale Circuits and Devices: Goals Determine IC subcircuits and physical layouts most vulnerable to MW coupling. Understand and predict characteristics of transmission line and RLC network formed by interconnect structure. Understand and predict behavior of nanoscale devices (CMOS, BJT, HBT) with terminal voltages rapidly varying due to MW coupling. Understand and predict interaction of device and interconnect network for typical circuit topologies. Find most vulnerable locations for soft and hard errors. Offer improved designs and models.

MW Effects on Nanoscale Circuits and Devices: Experimental Approach Design and fabricate IC’s with test structures containing typical circuit blocks (LNA, PLL, DAC, ADC, Clock, Processors, ALU, Register, Control Logic). The block diagram CPU shown represents one of our test IC’s. Design and incorporate test equipment directly into IC’s being investigated. Expose circuits to MW radiation. Have internal IC test equipment measure levels of induced voltages and currents, and determine locations of failure.

MW Effects on Nanoscale Circuits and Devices: Theoretical and Modeling Approach Extract RLC network resulting from interconnects using both new and existing methods. Calculate MW induced currents and voltages in RLC interconnect network. Use SPICE to model complex circuit. Incorporate MW induced voltages as sources to determine effects of MW on entire circuit. Use existing and develop new methods to model nanoscale devices based on the Boltzmann and Schrodinger equations. Use device simulation methods to predict internal behavior of transistors coupled to rapid MW transitions.

Example of Detailed Internal Analysis of Submicron MOSFET Using Boltzmann and Schrodinger Equations Y=  mY=0.4  m Distribution Function Electron Concentration MOS Cross Section

Use of focused ion beams to diagnose effects of microwaves on integrated circuits determine how the threshold for soft failure depends on neighboring circuits or structures by cutting (or reconnecting) conductors analyze the nature of hard failures by cross sectioning the burned out component (e.g. transistor) isolate a damaged transistor and connect probe pads to measure its characteristics

Cross section of two conductors in an IC showing FIB steps to make a connection

Focused ion beam cut of conductor and deposited connection

Focused ion beam milled cross section of a part of an IC illustrating defect analysis

PART B, CHAOS STUDIES Chaos offers at least 2 uniquely useful perspectives for study of the influence of microwaves on electronic circuits. Wave Chaos uses new ideas on the properties of solutions of wave equations in complex topologies to develop statistical descriptions of fields and resonances in enclosures containing circuits. Chaos in Circuits considers the possibility that RF radiation might cause upset or damage by inducing chaotic behavior in circuits. This is expanded upon in the following slides.

The Resistor-Inductor-Diode Circuit Varactor diode (capacitance depends on voltage) Approximate equation for charge flowing in the circuit: As the amplitude of the drive (V 0 ) increases, the system will show period doubling and chaos

Setup for the Experiment

Examples of Period 1,2,3 and Chaotic Voltage Waveforms

Results of the Test, so far L = 39  H, C = 510 pF, Narda GC3207 varactor diode, National LM741CN op-amp Period doubling seen, e.g., at 50 MHz, +16 dBm in RLD No failure of op-amp observed (10->60 MHz, 0->20 dBm) L = 390 nH, C = 510 pF, NTE 610 varactor diode, Motorola MC1741SCP1 and MC1741CU op-amps Period doubling seen, e.g., at 20 MHz, +20 dBm in RLD No failure of op-amps observed (10->60 MHz, -20->20 dBm)

Conclusions We have just begun work, so our results are preliminary… Period doubling and chaos are common in RLD and RLD/Op-Amp circuits driven with rf signals No evidence of op-amp failure under circumstances similar to those employed by Wallace

PART C MICROWAVE TESTING Frequency Range 100 MHz to 100 GHz Single and Repetitive Pulses Clock Frequency Effects Coupling Through Apertures

Direct Injection Purpose:to evaluate and understand the test circuit response under well-controlled conditions; to identify components that are particularly susceptible to RF upset. RF Frequency and power level Microprocessors and associated circuitry may be sensitive to upset from relatively low power RF at the clock frequency or harmonics thereof. Initial Experiment To test the susceptibility of generic dynamic random access memory (DRAM) RF was injected directly into its 33MHz clock input. The DRAM module was modified to include a capacitance coupler and was installed in a personal computer running a memory-checking program. CW and pulsed signals from an RF synthesizer were applied to the coupler and the power was increased until the program detected data faults. The procedure was repeated for frequencies of MHz in 5 MHz steps.

Results Integrated circuits may be an order of magnitude more susceptible to upset at specific frequencies. In the above case the frequencies correspond loosely to harmonics of the DRAM’s 33 MHz clock frequency. Device sensitivity may be highly frequency-dependent and suggests that it is important to know the upset characteristics of constituent electronic devices before complete systems can be analyzed for upset thresholds. For pulsed RF waveforms upset occurred at about the same power as in the CW case, however, pulsed RF caused the computer system to halt (operating system failure) while CW injection corrupted only the digital data, and the error detecting program continued to function.

Electronic Circuitry source Understanding Energy Penetration Mechanism Externally coupled devices Conducted and radiated coupling through attached power cables “imperfect” source (antenna) Apertures (screens) diffusion through shield

Numerical Simulation of EM Coupling through Slots

Understanding Behavior of Currents Near Slots