New Thin-film Thermal Constants Analyser
To measure anisotropic thermal transport properties of thin-film materials with thickness smaller than 50 µm, Hot Disk AB has developed a new and uniquely specialized instrument – the TPS 4500. Intended applications involve materials and structures employed in the fields of microelectronics and optoelectronics, e.g. transistors, Schottky diodes, varactors, light emitting diodes (LEDs), semiconductor lasers and photodetectors. The TPS 4500 is a powerful instrument for studying these materials. It satisfies an important characterization need in the industry and the scientific community alike, helping to improve heat management and power efficiency. Furthermore, the TPS 4500 will facilitate thermal transport measurements of liquid samples with a volume corresponding to a single drop.
The working principle of the TPS 4500 technology is based on the Pulse Transient Hot Strip (PTHS) technique, established and thoroughly described by Dr. Silas E. Gustafsson et al. in early 1980s. The sensing and heating element is a thin micrometer-wide metal strip, called a Hot Strip Sensor, deposited on the surface of the sample. During a measurement an electrical current, consisting of a train of square pulses of low duty cycle, is run through the sensor and the average temperature increase in the sensor is closely monitored. The temperature increase as a function of pulse length is then fitted to a heat dissipation model, from which in-plane and through-plane thermal conductivity as well as thermal diffusivity are extracted. A merit with this technique compared to others is that a defined thermal probing depth is determined to avoid influence from the substrate material (ISO Standard 22007-2).
Furthermore, the heat dissipation model has been extended to analyze a thin film or coating placed on a wafer substrate. This approach is referred to as the Slab PTHS technique, having been verified by measurements on 500-µm-thick single crystal quartz. Anisotropic thermal transport properties were obtained with a precision better than 2.7%, using a thermal probing depth of only 30 µm. Further details on these measurements can be freely downloaded in the open access Review of Scientific Instrument paper “Pulse transient hot strip technique adapted for slab sample geometry to study anisotropic thermal transport properties of μm-thin crystalline films.” The Slab PTHS technique can also be used to study thermal transport properties of isotropic materials. A demonstration on fused Silica was presented at the ITCC conference of 2014. In the continued effort to expand the measurement range of the TPS 4500, tests on low conducting polymer films such as Benzocyclobutene (BCB) and high conducting crystalline materials such as GaAs, Sapphire, and Si are currently being performed.
Contract testing with the TPS 4500 is available.