Calibration Package

At the heart of TMX Scientific’s thermal imaging devices lies the physics of thermoreflectance: a method of determining surface temperature changes by detecting minute variations of surface reflectivity. In order to transform the measured changes in temperature into absolute temperature results, the user must perform calibration.

In-Situ Calibration   |   Results   |   Calibration Base   |   Dynamic Tracking   |   Benefits   |   Applications

In-Situ Calibration

Thermoreflectance thermal imaging uses a relationship between a change in reflectivity and a change in surface temperature, which is known as the Coefficient of Thermoreflectance (CTR) and is derived from a calibration procedure. Through many years of testing and research, the TMX Scientific team has always stressed the critical dependence of CTR on a test setup. Factors such as the surface material composition, the wavelength of light, the passivation thickness, and the objective lens used during an experiment will affect the local CTR value. Due to the number of variables that can affect CTR, TMX Scientific strongly believes in performing in-situ calibration to obtain consistent, dependable results and to reduce uncertainty between experiments.

In-situ calibration begins with heating and cooling the device under test (DUT) to predefined values. Then, the system captures the DUT’s resulting surface reflectivity variations and derives the surface material’s CTR by relating the reflectivity changes to the known base temperature values. The T°Imager Calibration Package includes all of the necessary hardware and software to achieve these results: a Calibration Base, an external chiller unit, and a Calibration Control Unit. The Calibration Base mounts to an existing probe station (below the T°Imager Measurement Head) and the Calibration Control Unit is packaged as a rackmount enclosure that installs in the T°Imager System Rack Station.

Results

TMX Scientific’s thermal imaging applications combine the calibration results with the device activation results and return the resulting temperature maps in straightforward, comprehensible formats. The T°Imager software pre-analysis feature can calculate average values within a region of interest, but T°Pixel^® takes thermal mapping to extraordinary depths of resolution. The analytical software generates a CTR value at each pixel of the calibration image, combines the calibration results with the device activation results at each pixel, and returns the DUT’s absolute surface temperature at each pixel. Its statisical and analytical features enable the user to generate a highly detailed and accurate thermal map.

Calibration Base

TMX Scientific’s Calibration Base (included with each Calibration Package) is a sample holder with vacuum capability and a copper alloy chuck that can be heated up to 100°C (212°F). The base assembly mounts to the user’s existing probe station (below the Measurement Head) and includes an adapter plate, if necessary. The Calibration Base’s heat sink temperature is regulated by a liquid chiller unit (included) and is monitored by the T°Imager software. If the heat sink temperature exceeds a predetermined safe value, the Calibration Base shuts down automatically to prevent damage to internal system components.

Dynamic Tracking and Alignment

Since TMX Scientific applications compare sets of thermal images at deep submicron resolution, TMX Scientific utilizes both hardware and software corrections to ensure the thermal images align with absolute accuracy. T°Imager and the Calibration Base work together to use dynamic tracking and alignment procedures to correct DUT movement associated with thermal expansion and shifting during data collection.

Each Calibration Base is equipped with dynamic tracking capability to correct any movement in the X-, Y-, and Z-directions caused by thermal expansion during a calibration procedure. The T°Imager program guides the user through a procedure to correct as little as 2 nanometers (7.9E-8 in.) in each direction and then saves the information in the calibration file for easy reference. The dynamic tracking interface also allows the user to visualize the scale of thermal expansion in real time.

To correct DUT shifting during calibration, the T°Imager program features a semi-automatic alignment procedure to easily realign test samples through a selection of DUT reference features. The program also automatically refocuses the DUT (Z-direction alignment) before capturing each calibration image. TMX Scientific’s analysis software, T°Pixel, contains an additional alignment algorithm that synchronizes the images within an activation measurement series and calibration images with activation images in post-processing for pixel-perfect accuracy. Integrating all of these alignment procedures is TMX Scientific’s solution to ensure that your results are consistently delivered with nanometer accuracy.

T°Imager alignment capabilities also enable the user to recall previously saved calibration results and use them in future activation procedures that utilize the same DUT, wavelength of light, and objective lens. Through the T°Imager interface, simply load a saved calibration image, follow the on-screen instructions for aligning the saved image with the live image of the DUT, and perform a new device activation procedure.

The Power of Nanoscale Calibration

Preserving similarities between calibration and activation procedures reduces the uncertainty within subsequent thermal images. By combining physical calibration procedures with software-derived calibration formulas, T°Pixel consistently deliver reliable, dependable results that factor in all of the variables that might affect CTR on a day-to-day basis.