Scanning picosecond tunable laser system for simulating MeV heavy ion-induced charge collection events as a function of temperature

Abstract

A new methodology for using scanning picosecond laser microscopy to simulate cosmic ray induced radiation effects as a function of temperature is described in detail. The built system is centered on diffraction-limited focusing of the output from a broadband (690-960 nm) ultrafast Ti:sapphire Tsunami laser pumped by a 532 nm Millennia laser. An acousto-optic modulator is used to provide pulse picking down to event rates necessary for the technologies and effects under study. The temperature dependence of the charge generation process for ions and photons is briefly reviewed and the need for wavelength tunability is discussed. An appropriate wavelength selection is critical for proper emulation of ion events over a wide temperature range. The system developed is detailed and illustrated by way of example on a deep-submicron complementary metal-oxide semiconductor test structure.

Temperature Dependence of Spatially Resolved Picosecond Laser Induced Transients in a Deep Submicron CMOS Inverter

“…The most obvious form of error may be associated with the laser LET normalization process. However, similar experiments on a simple structure fabricated on the same CMOS test chip display a similar temperature dependence, even after adjusting the wavelength to correct for the temperature dependent absorption length [12]. Likewise, those particular structures were very simple meaning circuit effects can be discounted as a source of systematic error (although they still might affect the overall pulse shape).…”

“…The phonon density-of-states is important and its decrease at lower temperatures leads to longer absorption lengths which alters the effect laser LET. In theory though, the temperature dependence of the absorption length can be compensated for by scanning wavelength as discussed elsewhere [12]. Unfortunately the method was not applied here and interpreting data is prone to systematic error.…”

“…Devices were mounted on the ceramic carrier with multi-SMK connections shown in Fig. 4 (right) [12]. This carrier mounts into a modified Linkam microscope cryogenic stage for temperature control from K to K. External wide bandwidth bias tees commonly used for these types of experiments [26], [27] were mounted on the air side of the Linkam stage.…”

“…Beside the obvious difference in track widths for MeV ion and laser probing, fundamental differences between the photon-solid and ion-solid interaction is responsible for track differences with temperature [12]. Rapid thermalisation of an ion induced plasma predominantly occurs via Auger scattering and Longitudinal Optical (LO) phonon emission (Raman scattering) [20], [21].…”

“…Schematic of the JPL laser system configured for cryogenic to high temperature analysis of high-speed SEE phenomenon[12].…”