Self-standing Polysilicon-metal Thermopile
for Accessory Micro Power Generator

Masakazu Yajima1, Toshiyuki Toriyama* and Susumu Sugiyama

Ritsumeikan University
*New Energy and Industrial Technology Development Organization

Key words: self-standing, micro power generator, Seebeck effect, MICS

In order to realize ideal higher thermal isolation, a thermopile without a membrane and having self-standing structure is proposed. Figure 1 shows the final goal of our study. The proposed structure has two advantages, (a) the absorbed heat transfers from hot contacts to cold contacts only through the thermopile and no heat transfer will occur between the hot and cold contacts except for this, (b) the heat absorber area can be increased more than the chip area. As a consequence, temperature difference between the hot and cold contacts approaches the ideal value. In this paper, design, fabrication and characteristics of the self-standing polysilicon-metal junction thermopile for an accessory micro power generator are reported, especially focusing on the advantage of (a).

The thermocouple is composed of an n - type polysilicon and an Au junction (figure 2). The thermopile was fabricated by MICS (Micromachine Integrated Chip Service: three polysilicon layer structure) organized by the Cooperative Research Committee for Standardization of Micromachines in IEE of Japan. Figure 3 shows the SEM image of the prototype thermopile.

Figure 4 shows the experimental results of the Seebeck voltage of the thermopile (N =10 thermocouples). A black body plate having uniform typical human skin temperature (307K) was used as the radiation source. Seebeck voltage of more than 6.2mV was obtained. The experimental results are in reasonable agreement with the theoretical calculation. The prospect for application of the thermopile to an accessory micro power generator was shown. In future work, a thermopile with an upper heat absorber will be fabricated and characterized.


Figure 1. Schematic of self-standing thermopile.



Figure 2. Dimension of thermocouple.


Figure 3. SEM image of thermopile after releasing.


Figure 4. Seebeck voltage of thermopile.