Patent ID: 12216008

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG.1shows the cross-section of an exemplary embodiment of a calibration arrangement1comprising a sealable and thermally isolated chamber10. Components inside the chamber10are arranged in a stacked manner. In this example, the stack comprises from bottom to top: a thermal mass11, a Peltier element12, a thermal chuck13and circuit board14. In other examples the stack might comprise additional components. The sample mount15with the sample sockets16is arranged above the circuit board14. Also shown is a device-under-test, DUT,17placed inside the sample socket16as well as a reference sample18. The reference samples are for example of the same type as the DUTs17and are calibrated with NIST-traceability. In this embodiment the reference samples are fixated and covered by a cover plate20. A pushdown mechanism22provides thermal contact for the DUTs17as well as electrical contact between pogo pins19of the DUTs17and the circuit board14. Additionally, a pushdown housing21thermally couples the pushdown mechanism22to the cover plate20and the sample mount15. In this example, the chamber10further comprises a gas23surrounding the stack of components, in particular the DUTs17and reference samples18. The gas is introduced for example by means of a temperature controlled gas inlet24. The chamber further comprises a gas outlet25.

The components of the arrangement1, in particular the sample mount15, the circuit board14and the surrounding gas23, are thermalized to a temperature set point. The thermalization can for example be achieved by means of temperature control of heated walls of the chamber10, the Peltier element12and a temperature controlled gas inlet24. To ensure thermalization to the same temperature, the aforementioned components may be thermalized by a single temperature control. For example, the walls of the chamber10and the temperature controlled gas inlet24may be temperature controlled by means of a coolant liquid supplying both components.

For a reliable calibration process a large degree of temperature stability of the sample sockets16and the reference samples18is required. This is achieved by means of the thermal chuck13, which is in thermal contact with the socket mount15and the circuit board14. The thermal chuck is preferably made of a material with high thermal conductivity, for example a metal such as stainless steel or aluminum, and provides a large thermal mass in comparison to the DUTs17. Due to the high thermal conductivity, DUTs17that are placed into the sample sockets16and pushed down by means of the pushdown mechanism22quickly thermalize to the temperature set point of the arrangement1, for example within seconds. Due to their close proximity of a few millimeters causing a short thermal path and small thermal resistance, it is guaranteed that each of the DUTs17thermalizes to the same temperature as the associated reference sample18. This condition holds true also in case of a temperature gradient across the individual components of the arrangement1, which can for example be caused by a long thermal path and high thermal resistance between the sample sockets16and the Peltier element12.

After the DUTs17and the reference samples18are thermalized, the actual calibration process can be performed. For example, an evaluation circuit which is electrically connected to the circuit board14generates, based on a temperature-dependent quantity, respective sets of measurement signals for each of the DUTs17. In particular, each set of measurement signals comprises a test measurement signal from a distinct one of the DUTs17and a reference measurement signal from the associated at least one of the reference samples18.

The evaluation circuit may comprise a memory, containing for example a look-up table for converting the test measurement signal and the reference measurement signals of each measurement set into units of temperature.

The evaluation circuit may further generate a calibration signal for each set of measurement signals, wherein each calibration signal corresponds to a result of a comparison of the test measurement signal and the reference measurement signals of the respective set of measurement signals. Each calibration signal can hence be used for calibrating the corresponding DUT17for accurate absolute temperature measurements. The achievable accuracies are below 100 mK, in particular below 50 mK at the temperature set point, and within 200 mK in a temperature range of ±50 K around the temperature set point.

In particular, the evaluation circuit is configured to generate each set of measurement signals simultaneously or within a given timeframe, for example within seconds. Preferably, also the calibration signals are generated within short time periods, i.e. within seconds.

In some applications, the DUTs17contain additional sensors in addition to a temperature sensor. Hence, a calibration of the additional sensors of the DUTs17in the calibration arrangement1may be desired without the need for modifying the arrangement or disturbing its temperature equilibrium.

Therefore, the arrangement1may be further configured to calibrate the additional sensors of the DUTs17by means of gas, relative humidity and/or pressure analogous to the temperature calibration. To this end, the temperature controlled gas inlet24is further configured to provide an active gas flow for introducing a specific gas23into the chamber and stabilize the gas23by means of relative humidity and/or pressure.

FIG.2shows an exemplary embodiment of the arrangement1featuring the pairwise arrangement of the DUTs17and the reference samples18on the sample mounts15. In particular, the chamber10may comprise more than one sample mount15. In such an embodiment, the arrangement1may host a large number of DUTs17, and a likewise large number reference samples18, at the same time. For example the number of DUTs17that can be placed in the chamber may be in the order of 100.

FIG.3shows a schematic top view of an exemplary sample mount15. The sample mount15in this example features a 1:1 arrangement of each of a number of reference samples18and a sample socket16in its proximity, in which a DUT17can be placed. The distance between each of the reference samples18and the associated sample socket16is the same across the entire sample mount15. For example, this distance is less than 10 mm, in particular less than 5 mm. Assuming that the sample mount15is made from a material with high thermal conductivity, this setup allows for the fast thermalization of each reference sample18and a DUT17to the same temperature.

FIG.4shows a cross section of the exemplary sample mount15shown inFIG.3. In this cross-section, the cover plate20becomes apparent, covering the reference samples18. This cover plate20has the effect of protecting the reference samples18and ensuring that the latter remain thermalized to the temperature set point while the chamber is exposed to the environment, for example during insertion of new DUTs17into the sample sockets16.

FIG.5shows a schematic top view of a further exemplary sample mount15. In this case the ratio between reference samples18and sample mounts16is 1:2, leading to a situation in which two DUTs17placed into the respective sample sockets16can be calibrated by means of one single reference sample18.

Other sample arrangements not shown may feature more than two sample sockets being associated to a reference sample, described by a ratio of 1:N. Typically, ratios of up to 1:4 are realized.

In further sample arrangements not shown more than one reference sample18may be associated to each of the DUTs17in the sample sockets16, leading to a ratio of M:1, whereas typical ratios are as large as 4:1.

FIG.6shows a schematic top view of a further exemplary sample mount15. In this sample arrangement, the ratio between reference samples18and DUTs17in the respective sample sockets16is 2:2. This leads to the fact that each of the DUTs17is arranged at an equal distance from the associated two reference samples18. In such an arrangement, each of the DUTs17can be calibrated by means of two reference samples18, leading to a more accurate calibration while maintaining a small footprint of each group of two DUTs17and two reference samples18.

FIG.7shows a further exemplary sample mount15. This linear sample arrangement likewise allows for calibrating each of the DUTs17by means of multiple reference samples18. Due to the constant distance between each of the sample sockets16and their adjacent reference samples18, DUT17afor example is associated to reference samples18aand18b, while DUT17bis associated to reference samples18band18c. This pattern continues accordingly across the entire sample mount15.

FIG.8shows the result of an exemplary calibration of 252 DUTs17calibrated at a temperature set point of 25° C. of the calibration arrangement1. The graph shows the accuracy of the newly calibrated devices versus the temperature in a verification chamber. The temperature inside the chamber is determined via an independent NIST-traceable reference probe. For this, the deviation between the DUTs17and the temperature reference is evaluated for a temperature range between −40° C. and 100° C. The lowest standard deviation is expectedly observed at the calibration set point of 25° C., resulting in an accuracy of the calibrated temperature sensors of less than wo mK.