Thermoelectric micro-module with high leg density for energy harvesting and cooling applications

Abstract

Micro-scale thermoelectric devices having high thermal resistance and efficiency for use in cooling and energy harvesting applications and relating fabricating methods are disclosed. The thermoelectric devices include first substrates substantially parallel with second substrates. Scaffold members are deposited between the first and second substrate. The scaffold members include a plurality of cavities having sidewalls. The scaffold members may be formed from the second substrate. The sidewalls are substantially vertical with respect to the second substrate. The sidewalls may be substantially parallel. Thermoelectric materials are deposited on the sidewalls.

1 . A high-aspect thermoelectric device, comprising:
 a first substrate comprised of thermally conductive material;   a second substrate comprised of thermally conductive material and substantially parallel with the first substrate;   a scaffold member having a first surface and a second surface sandwiched between the first substrate and the second substrate, wherein
 the first surface of the scaffold member faces the first substrate and the second surface of the scaffold member faces the second substrate, 
 the first surface of the scaffold member includes a plurality of cavities, and 
 each cavity defining a plurality of sidewalls formed at an angle less than fifteen degrees from vertical and extending between the first substrate and the second substrate; and 
   a thermoelectric film comprised of thermoelectric materials and deposited on the sidewalls of the cavities using a vapor deposition technique.   
     
     
         2 . The high-aspect thermoelectric device of  claim 1 , wherein the thermoelectric film is deposited on the sidewalls of the cavities using a physical vapor deposition process, wherein physical vapor deposition processes include evaporation, sputtering, and pulsed laser techniques. 
     
     
         3 . The high-aspect thermoelectric device of  claim 1 , wherein the second substrate is comprised of silicon (Si) and the scaffold member is formed from the second substrate. 
     
     
         4 . The high-aspect thermoelectric device of  claim 1 , further comprising:
 a plurality of first contacts interposed between the first substrate and the thermoelectric film and selectively interconnecting individual thermoelectric materials to each other; and   a plurality of second contacts interposed between the second substrate and the thermoelectric film and selectively interconnecting individual thermoelectric materials to each other.   
     
     
         5 . The high-aspect thermoelectric device of  claim 1 , further comprising:
 contacts formed by overlapping adjacent thermoelectric materials.   
     
     
         6 . The high-aspect thermoelectric device of  claim 1 , wherein the deposited thermoelectric materials have a square frustum shape. 
     
     
         7 . The high-aspect thermoelectric device of  claim 1 , wherein thermoelectric materials have a height ranging from 10 μm to 500 μm. 
     
     
         8 . The high-aspect thermoelectric device of  claim 1 , wherein the thermoelectric materials are arranged in pairs to form thermoelectric legs, each thermoelectric leg pair including a first leg member comprised of n-type thermoelectric material and a second leg member comprised of p-type thermoelectric material. 
     
     
         9 . The high-aspect thermoelectric device of  claim 8 , wherein the thermoelectric film has a density of thermoelectric legs ranging from 10 to 1000 thermoelectric legs per mm 2 . 
     
     
         10 . The high-aspect thermoelectric device of  claim 8 , wherein the thermoelectric legs of have a length ranging from 10 μm to 500 μm. 
     
     
         11 . The high-aspect thermoelectric device of  claim 8 , wherein the n-type thermoelectric material is selected from the group consisting of: bismuth telluride (Bi 2 Te 3 ); bismuth selenide (Bi 2 Se 3 ); gallium nitride (GaN); lead telluride (PbTe); cobalt antimonide (CoSb 3 ); lanthanum telluride (LaTe); bismuth telluride selenide (Bi 2 Te (3-x) Se x , wherein x ranges from 0.1 to 1); and combinations thereof. 
     
     
         12 . The high-aspect thermoelectric device of  claim 8 , wherein the p-type thermoelectric material is selected from the group consisting of: antimony telluride (Sb 2 Te 3 ); bismuth antimony telluride (Sb 3 BiTe 6 ); lead telluride (PbTe); lead tellurium selenide (Pb 2 SeTe); silicon germanium (SiGe); (GeTe) x (AgSbTe 2 ) y , wherein x ranges from 70 to 75 and y equals 100−x; and combinations thereof. 
     
     
         13 . A high-aspect thermoelectric device, comprising:
 a first substrate comprised of thermally conductive material;   a second substrate comprised of thermally conductive material and substantially parallel with the first substrate, wherein the second substrate includes a plurality of pillars extending from a first surface of the second substrate towards the first substrate, each pillar defines a first sidewall and a second sidewall, the first sidewalls of the pillars face a first direction, the second sidewalls of the pillars face a second direction opposing the first direction, the first sidewall and the second sidewall of each pillar are substantially parallel, and pillars in the plurality of pillars are substantially parallel with each other; and   a thermoelectric film comprised of thermoelectric materials and deposited on the sidewalls of the pillars using a vapor deposition technique.   
     
     
         14 . The high-aspect thermoelectric device of  claim 13 , wherein the second substrate is comprised of silicon (Si). 
     
     
         15 . The high-aspect thermoelectric device of  claim 13 , wherein a first thermoelectric material is deposited on the first sidewalls of the pillars, and a second thermoelectric material is deposited on the second sidewalls of the pillars. 
     
     
         16 . The high-aspect thermoelectric device of  claim 15 , wherein
 the first thermoelectric material is a n-type thermoelectric material selected from the group consisting of: bismuth telluride (Bi 2 Te 3 ), bismuth selenide (Bi 2 Se 3 ), gallium nitride (GaN), lead telluride (PbTe), cobalt antimonide (CoSb 3 ), lanthanum telluride (LaTe), bismuth telluride selenide (Bi 2 Te (3-x) Se x , wherein x ranges from 0.1 to 1), and combinations thereof; and   the second thermoelectric material is a p-type thermoelectric material selected from the group consisting of: antimony telluride (Sb 2 Te 3 ), bismuth antimony telluride (Sb 3 BiTe 6 ), lead telluride (PbTe), lead tellurium selenide (Pb 2 SeTe), silicon germanium (SiGe), (GeTe) x (AgSbTe 2 ) y , wherein x ranges from 70 to 75 and y equals 100−x, and combinations thereof.   
     
     
         17 . The high-aspect thermoelectric device of  claim 15 , wherein
 the first thermoelectric material is deposited on first areas of the second substrate, wherein the first areas are immediately adjacent to the first sidewalls of the pillars; and   the second thermoelectric material is deposited on second areas of the second substrate, wherein the second areas are immediately adjacent to the second sidewalls of the pillars.   
     
     
         18 . The high-aspect thermoelectric device of  claim 17 , wherein the first areas and the second areas overlap to form third areas of the second substrate whereon a thermoelectric composite of the first and second thermoelectric materials is deposited. 
     
     
         19 . A method of fabricating a high-aspect thermoelectric device, the method comprising:
 etching a first silicon substrate to form a plurality of pillars extending upwardly from a first surface of the first substrate, each pillar defining a first sidewall and a second sidewall, wherein the first sidewalls of the pillars face a first direction, the second sidewalls of the pillars face a second direction opposing the first direction, the first sidewall and the second sidewall of each pillar are substantially parallel, and pillars in the plurality of pillars are substantially parallel with each other;   oxidizing the pillars;   depositing a first thermoelectric material onto the first sidewall of each oxidized pillar from a first source;   depositing a second thermoelectric material onto the second sidewall of each oxidized pillar from a second source; and   bonding a second substrate onto the first substrate and thereby sandwiching the thermoelectric material between the first substrate and the second substrate, wherein a first surface of the second substrate faces the first surface of the first substrate.   
     
     
         20 . The method of  claim 19 , further comprising:
 depositing the first thermoelectric material on first areas of the first substrate, wherein the first areas are immediately adjacent to the first sidewalls of the oxidized pillars; and   depositing the second thermoelectric material on second areas of the second substrate, wherein the second areas are immediately adjacent to the second sidewalls of the oxidized pillars.   
     
     
         21 . The method of  claim 20 , wherein the first areas and the second areas overlap to form third areas of the first substrate whereon a thermoelectric composite of the first and second thermoelectric materials is deposited. 
     
     
         22 . The method of  claim 21 , wherein the thermoelectric composite forms electrical contacts. 
     
     
         23 . The method of  claim 21 , wherein the first, second, and third areas of the first substrate are defined by shadow masks deposited on exposed ends of each pillar prior to deposition of the first and second thermoelectric materials. 
     
     
         24 .- 29 . (canceled)