微米熱電薄膜元件之製備及應用

Abstract

奈米結構化已成為提升大部分類型熱電材料其熱電優值(Thermoelectric figure of merit; ZT)的有效策略之一。至今雖已有許多具應用潛力之奈米熱電塊材及薄膜被相繼發現與報導，然而，在實際應用上，此些奈米結構熱電材料仍須利用繁複的元件化製程，進一步形成多重並聯或串聯之陣列組合，方能提供具應用價值之電能。本研究第一階段主要利用脈衝雷射沉積技術，在絕緣的SiO2/Si基板(六吋晶圓)上，大面積沉積一系列N型之Bi2Te3-xSex與P型之Bi2-ySbyTe3奈米結構熱電薄膜，並選擇具最高功率因子(Power factor)之Bi2Te2.7Se0.3(5 μWcm-1K-2)與Bi0.5Sb1.5Te3(25 μWcm-1K-2)作為下階段微米熱電薄膜元件之主要薄膜材料。本研究第二階段主要整合半導體製程技術，針對本材料系統開發一系列之光罩材料與蝕刻參數，成功將前述之N型與P型熱電薄膜配對，形成各式微米級陣列，並以電極導通串聯，藉以探討陣列幾何因子對熱電特性之影響。結果發現，10對串聯微型熱電薄膜元件(每單條N或P之線寬150 μm，線長1.8 cm)，其量測電壓於高溫端39 oC，低溫端27 oC，溫差12 oC之下，可達0.5 V。

Nanostructuring has been theoretically and experimentally proven as one of the effective strategies for significantly enhancing the thermoelectric (TE) figure of merit (ZT) for most classes of thermoelectric materials. Although numerous promising nanostructured TE bulk and films have been discovered and reported, movement from these raw materials to practical applications definitely requires the fabrication of complicated device architectures comprising serially connected n-p arrays, allowing sufficiently high electrical potential difference to be generated. Firstly, we respectively deposited a series of N-type Bi2Te3-xSex and P-type Bi2-ySbyTe3 nanostructured TE films on large-area insulated SiO2/Si substrates (6 inches in diameter) for tuning the composition, nanostructures, as well as the corresponding TE properties. The optimized Bi2Te2.7Se0.3 and Bi0.5Sb1.5Te3 TE films respectively exhibiting a relatively high power factor of 5 μWcm-1K-2 and 25 μWcm-1K-2 were selected as the regular component for the subsequent device processing. By utilizing the semi-conductor fabrication techniques, a series of photomask materials and etching recipes was specially developed for the present TE materials, leading to the successful fabrication of the serially-connected N-P micro-arrays. It was found that the electrical potential difference obtained from 10 n-p pairs (150 μm in width and 1.8 cm in length for each single N or P band) approximated to 0.5 V with the temperature difference of 12 oC where the high and low temperature end is 39 oC and 27 oC, respectively.