Technology

Two-Wafer Concept

The thermoelectric elements in Micropelt thermogenerators and Peltier coolers consist of n- and p-type semiconductor materials, which produced separately on two different wafers. The wafers are then sawed and finally the n- and p-parts are bonded together to create Micropelt thermogenerators.

Device concept of Micropelt open


Manufacturing

The manufacturing process uses micro electronic techniques. Standard silicon wafers with silicondioxide are used as a substrate. The thermoelectric Bi2Te3-materials are deposited via sputtering. Finally, n- and p-wafers are structured by dry etching.

Wafers are sawn into single n- and p-type dies. Soldering the n- and p-parts together produces Micropelt thermogenerators and Micropelt Peltier coolers.



Why Use Bi2Te3?

Thermoelectric material crystaldiagram for different thermoelectric materials

Bi2Te3 operates most efficiently around room temperature, c. 300 K.


Process Flow

The following animation shows the process flow for the production of Micropelt devices. This animation requires the Flash player 8 or higher plugin from the » Adobe page. Please observe and be careful with the options.



process-flow static picture without flash



The Thermoelectric Effect

Thermoelectric effects have been known for almost two centuries. In 1821 Thomas Johann Seebeck (1770–1831) discovered the Seebeck effect and in 1834 Jean Charles Athanase Peltier (1785–1845) discovered the Peltier effect. The third thermoelectric effect is the Thomson effect found by Sir William Thomson (1824–1907), better known as Lord Kelvin. In his thermodynamic theory, which was published around 1860, Sir William Thomson explained all three effects – an explanation which is still valid today.

All these effects have been employed in devices using suitable compound semiconductors: thermogenerator devices for converting heat flow into electric energy and Peltier cooler devices for pumping heat using an electric current flow.

Miniaturisation and Micropelt

The trend towards miniaturization in all technical fields demands new concepts for the manufacture of thin film devices. For example, future generation PC processors and lasers for the telecommunications industry will not only require a high cooling power density but also a small form factor. To meet these technical challenges the "thermoelectrical rules of design" require optimized geometries on a micrometer scale. In addition, cost-effective mass-production is a prerequisite for a competitive market position – an option that conventional thermoelectric manufacturing technologies do not offer.



Micropelt stands for a new generation of thermoelectric thin film devices. Micropelt satisfies the design demands on a micrometer scale by applying and employing microelectronic thin film wafer technology and manufacturing methods. This is the fundamental difference to the traditional and largely manual production on a macrometer scale. Micropelt holds the key to a wider and more substantial thermoelectric market with new applications for » thermogenerator and » Peltier cooler devices for use in » energy harvesting and » temperature control.



Micro Thermoelectric Thin Film Devices

  • factor 10 or better size reduction
  • same performance and efficiency
  • array applications possible
  • hybrid integration viable
  • suitable for new design solutions
  • Peltier cooler devices with cooling power densities > 100 W/cm2


Micropelt Peltier coolers on coins