HotSens - temperature diodes for the high temperature range with one-point calibration

02.03.2020

A steadily growing market is forecast for high-temperature components. According to a study by IndustryARC, the market for temperature sensors will grow by 6.2% from USD 4.87 billion in 2017 to USD 7.9 billion in 2023. One growth driver here is the field of high-temperature electronics, which is constantly introducing new technologies as an alternative to conventional metal film resistors. The Asian region in particular is considered a growth driver.

Therefore, the aim of the HotSens research project was to produce temperature diodes that can be used in the high temperature range up to a maximum of 300°C with a one-point calibration. By applying appropriate algorithms, the temperature should be determined as calibration-free as possible. For the product this means a considerable cost reduction due to reduced calibration costs as well as an increase in customer friendliness.

The measurements were carried out with a climatic chamber with a temperature range of -40°C to +140°C and a high temperature chamber with a working range of 50°C to 600°C. The high temperature cabinet was used for cyclic measurements in the range of 50°C to 260°C as well as for load measurements at a temperature over very long periods of time.

These measurements were supplemented by work at the Institute for Process Measurement and Sensor Technology, Department of Process Measurement Technology at the TU Ilmenau. There the experimental investigations of the temperature dependence of the current-voltage characteristic of semiconductor temperature sensors in the range from 5 °C to 250 °C, in a water or oil bath, were carried out. Due to the apparatus, the series of measurements were divided into two overlapping sections (-40°C to 140°C and 50°C to 260°C). In addition to temperature dependence, non-linearity and hysteresis were also investigated.

A one-point calibration is an interesting alternative due to the lower metrological effort required for the application compared to calibration-free measurement. However, it should have a relatively high accuracy (± 0.5K). This goal is achieved and even considerably undercut by taking into account the physically induced parabolic rise in the characteristic curve. This characteristic curve is always identical for a constant stable processing of all temperature diodes of a wafer batch. With this variant, for example, deviations of a maximum of ± 0.2K are achieved in a temperature range of -40°C to +125°C. With a modification of this variant (extension of the data base for higher temperatures) even maximum deviations of ±0.02K can be realized.