WO2007103972A2 - dispositif thermoélectrique vertical à facteur de remplissage élevé - Google Patents

dispositif thermoélectrique vertical à facteur de remplissage élevé Download PDF

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Publication number
WO2007103972A2
WO2007103972A2 PCT/US2007/063481 US2007063481W WO2007103972A2 WO 2007103972 A2 WO2007103972 A2 WO 2007103972A2 US 2007063481 W US2007063481 W US 2007063481W WO 2007103972 A2 WO2007103972 A2 WO 2007103972A2
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WO
WIPO (PCT)
Prior art keywords
thermoelectric
thermoelectric elements
adjacent
recited
conductivity type
Prior art date
Application number
PCT/US2007/063481
Other languages
English (en)
Other versions
WO2007103972A3 (fr
Inventor
Uttam Ghoshal
Original Assignee
Nanocoolers, Inc.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Nanocoolers, Inc. filed Critical Nanocoolers, Inc.
Publication of WO2007103972A2 publication Critical patent/WO2007103972A2/fr
Publication of WO2007103972A3 publication Critical patent/WO2007103972A3/fr

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Classifications

    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N19/00—Integrated devices, or assemblies of multiple devices, comprising at least one thermoelectric or thermomagnetic element covered by groups H10N10/00 - H10N15/00
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/10—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects
    • H10N10/17—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects operating with only the Peltier or Seebeck effects characterised by the structure or configuration of the cell or thermocouple forming the device

Definitions

  • thermoelectric devices and, in particular, to vertical thermoelectric devices having a relatively large ratio of the area of active devices to the area of thermoelectrically inactive surface.
  • thermoelectric devices and materials are well-known in the art and a wide variety of configurations, systems and exploitations thereof will be appreciated by those skilled in the art.
  • exploitations include those in which a thermal potential is developed as a consequence of an electromotive force (typically voltage) across an appropriate material, material interface or quantum structure, as well as those in which an electromotive force (typically voltage) results from a thermal potential across an appropriate material, material interface or quantum structure.
  • Peltier, or thermoelectric, coolers and refrigerators operate on the former principal, while thermoelectric power generators employ the second.
  • Typical cooling systems for small devices are based on passive cooling methods and active cooling methods.
  • the passive cooling methods include heat sinks and heat pipes. Such passive cooling methods may provide limited cooling capacity due to spatial limitations.
  • Active cooling methods may include use of devices such as mechanical vapor compression refrigerators and thermoelectric coolers.
  • Vapor compression based cooling systems generally require significant hardware such as a compressor, a condenser and an evaporator. Because of the large required volume, moving mechanical parts, poor reliability and associated cost of the hardware, use of such vapor compression based systems might not be suitable for cooling small electronic devices.
  • Thermoelectric cooling for example using a Peltier device, provides a suitable cooling approach for cooling small electronic devices.
  • a typical Peltier thermoelectric cooling device includes a semiconductor with two metal electrodes. When a voltage is applied across these electrodes, heat is absorbed at one electrode producing a cooling effect, while heat is generated at the other electrode producing a heating effect. The cooling effect of these thermoelectric Peltier devices can be utilized for providing solid-state cooling of small electronic devices.
  • thermoelectric devices Unlike conventional vapor compression-based cooling systems, thermoelectric devices have no moving parts. The lack of moving parts increases reliability and reduces maintenance of thermoelectric cooling devices as compared to conventional cooling systems. Thermoelectric devices may be manufactured in small sizes making them attractive for small-scale applications. In addition, the absence of refrigerants in thermoelectric devices has environmental and safety benefits. Thermoelectric coolers may be operated in a vacuum and/or in weightless environments and may be oriented in different directions without affecting performance. DISCLOSURE OF INVENTION
  • thermoelectric elements of complementary conductivity types are disposed on the lower electrodes, such that each lower electrode couples together a respective complementary pair of adjacent thermoelectric elements disposed thereon.
  • a conformal dielectric layer is formed over the thermoelectric elements of one conductivity type, the thickness of the conformal layer on the sidewalls of these elements determining the spacing between adjacent pairs of complementary thermoelectric elements.
  • a plurality of upper electrodes, each straddling a pair of adjacent lower electrodes and coupling together a complementary pair of adjacent thermoelectric elements may complete the high fill-factor complementary thermoelectric device.
  • FIG. 1 is a top view of an arrangement of monolithic vertical thermoelectric devices exhibiting a high fill-factor.
  • FIGS. 2 A through 2F depict top views of alternative arrangements of monolithic vertical thermoelectric devices exhibiting a high fill-factor.
  • FIG. 3 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 4 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 5 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 6 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 7 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 8 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 9 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication.
  • FIG. 10 depicts a cross-sectional view of a portion of the monolithic high- fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 11 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 12 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 13 depicts a cross-sectional view of a portion of the monolithic high- fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 14 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 15 depicts a cross-sectional view of a portion of the monolithic high- fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 16 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 17 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 18 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 19 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 20 depicts a cross-sectional view of a portion of the monolithic high- fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 21 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 22 depicts a cross-sectional view of a portion of the monolithic high-fill vertical thermoelectric device array at an incomplete stage of fabrication
  • FIG. 23 depicts a solder-free complementary vertical thermoelectric device as viewed from the top after formation of the n-type thermoelements
  • FIG. 24 depicts a solder-free complementary vertical thermoelectric device as viewed from the top after formation of the passivated metal links - A -
  • FIG. 1 is a top view of an arrangement of monolithic vertical thermoelectric devices exhibiting a high fill-factor
  • the thermoelectric elements 110, 120 are square, but other space-filling shapes such as triangles, rectangles, rhombi, etc , could be employed
  • thermoelectric elements 110, 120 are arranged m an alternating pattern by conductivity type, i e , p-type 110 and n-type 120, such that adjacent thermoelectric elements separated by their opposing sides are opposite in conductivity type
  • thermoelectric elements of like type do not adjoin along their sides or edges, but rather at their corners or apexes
  • a minimum lateral separation between adjacent thermoelectric elements is provided by a conformal layer 130, for example, of parylene, deposited over thermoelectric elements of one type or the other
  • a conformal layer 130 for example, of parylene
  • thermoelectric element 110 is serially coupled to the rest of the array (not shown) by a lower electrode 150 and to the adjacent n-type thermoelectric element 120 by an upper electrode 140
  • This n-type thermoelectric element 120 is coupled to the adjacent p-type thermoelectric element 110 by a lower electrode 150, and so on across the row of elements
  • the last element is coupled to the adjacent element (of complementary type) in the next row by the appropriate upper or lower electrode, and so on until all desired array elements have been electrically coupled in series
  • Current flow withm each thermoelectric element is vertical, i e , through the thickness of the thermoelectric material layer from the lower electrode to the upper electrode or vice versa
  • a temperature differential develops between the upper and lower electrodes
  • FIGS. 2 A through 2F demonstrate top views of alternative arrangements of complementary thermoelectric elements forming monolithic vertical thermoelectric devices exhibiting a high fill-factor
  • FIGS. 2A through 2D depict arrays having similarly- or identically-shaped thermoelectric elements squares (or, more generally, rectangles) in FIG. 2A, triangles in FIG. 2B, parallelograms (or rhombn) in FIG. 2C, and trapezoids in FIG. 2D
  • FIGS. 2E and 2F depict dissimilarly shaped thermoelectric elements arranged to fill the available area densely, triangles and parallelograms in FIG. 2E, and triangles and trapezoids in FIG. 2F
  • FIG. 3 depicts a cross-sectional view of a portion of the monolithic high- fill vertical thermoelectric device array at an incomplete stage of fabrication
  • the fabrication substrate 160 is a silicon wafer polished on one side with a coating of about 300 nm of silicon nitride 170 deposited by low-pressure chemical vapor deposition (LPCVD), which together provide the support structure 200 for the thermoelectric device Blanket layers of TiW (about 10 nm) 180 and Al (about 1.5 ⁇ m) 190 are deposited, partially protected with photoresist 210, and patterned by wet etching to form conducting ribs.
  • LPCVD low-pressure chemical vapor deposition
  • the remaining photoresist 210 is removed and spin-on glass 220 is applied to at least partially fill the openings between the conducting ribs.
  • the glass 220 is baked at about 400 0 C.
  • FIG. 5 shows the structure that may result after planarization.
  • the glass layer 220 may be dry-etched using CF 4 for BCl 3 , leaving glass wells 230 to provide electrical insulation between the conducting ribs and thermal insulation between the fabrication substrate 160 and the surface of the well.
  • a blanket composite layer of about 10 run of TiW, 300 nm of Pt, and 10 nm of TiW 240 is deposited and patterned to form the lower electrodes of the thermoelectric device. Gaps 250 between individual electrodes are approximately centered over the glass wells 230, as depicted in FIG. 6. These half-micron (0.5- ⁇ m) gaps 250 are easily defined by contact printing followed by dry etching of the top TiW layer, dry etching of the Pt layer, and wet etching of the bottom TiW layer.
  • a blanket layer 260 of SiO 2 about 300 nm thick may then be deposited by plasma-enhanced CVD (PECVD). This layer 260 protects, among other areas, the previously defined gaps 250, either by bridging over them or by filling them completely, as depicted in FIG. 7.
  • FIG. 7 shows the structure after patterning of the SiO 2 layer 260 by wet etching. Photolithographic alignment during this step is not critical, as long as each gap 250 is sufficiently protected that subsequently deposited thermoelectric material does not simultaneously contact both sides of the gap.
  • Thermoelectric material 270 of a first conductivity type, here n-type, is deposited over the SiO 2 layer 260. This layer is topped with a cap of about 50 nm of Pt 280 deposited in situ under vacuum. The resulting structure is depicted in FIG. 8. These layers are photolithographically patterned and selectively removed by dry etching unprotected areas of the Pt cap 280 and then wet etching unprotected areas of the thermoelectric material 270.
  • FIG. 9 depicts a cross-sectional view of a portion of the structure at this stage of fabrication, with n-type thermoelectric elements and lower electrodes defined. Wet etching with buffered oxide etch (BOE) removes the remaining oxide 260 and other residues, resulting in the structure of FIG. 10.
  • BOE buffered oxide etch
  • a conformal layer of dielectric 290 such as about 1 ⁇ m of parylene, can be deposited atop the structure. (See FIG. 11.)
  • This conformal layer 290 is deposited at least on the sidewalls of the n-type thermoelectric elements, and may close the gaps 250 by bridging over them or partially or completely filling them.
  • the protected thermoelectric elements may be annealed if desired.
  • the conformal layer 290 is patterned and selectively removed, by dry etching in the case of a parylene layer, with a resulting structure depicted in FIG. 12.
  • thermoelectric material of complementary conductivity type has been deposited over the protected n-type thermoelectric elements and exposed portions of the lower electrodes, making electrical contact with the electrodes while maintaining electrical isolation from the n-type material.
  • This layer 310 of p-type thermoelectric material is topped with a cap of about 50 nm of Pt 320 deposited in situ under vacuum After patterning and selectively removing exposed material by dry etching the Pt 320 and wet etching the p-type thermoelectric material 310, the structure of FIG. 14 may result At this stage of fabrication, each individual lower electrode couples a complementary pair of adjacent thermoelectric elements disposed atop it
  • the conformal layer of dielectric 290 determines, by at least its sidewall thickness, the minimum lateral spacing between adjacent thermoelectric elements of complementary type This layer 290 electrically insulates the two complementary thermoelectric materials 270, 310 and/or elements 110, 120, from each other laterally and vertically, in addition to defining the areas in which the second layer of thermoelectric material 310 makes contact with the lower electrodes 150
  • the layer may be dry etched using an O 2 plasma This step is followed by an anneal at 300°C and redeposition of about 300 nm of parylene to form a continuous conformal layer 295, as depicted in FIG. 15 This layer 295 is then patterned and dry etched to form openings 330, 340 through which the thermoelectric elements may electrically contact the upper electrodes, as shown m FIG. 16
  • blanket layers of TiW and Al are sputter deposited, making contact with the Pt-capped thermoelectric elements through the contact holes 330, 340
  • This metal layer 350 is patterned and wet etched, forming upper electrodes 140, each of which straddles a pair of adjacent lower electrodes and couples together a complementary pair of adjacent thermoelectric elements, as seen in FIG. 18
  • the upper electrodes 140 may be formed by electroplating After the contact holes 330, 340 (see FIG.
  • an isolation layer of SiN 370 may be deposited over the entire structure by PECVD, after which it may be patterned and dry etched to result in the structure of FIG. 21
  • a 100-nm layer 380 of TiW/Pt may be deposited over the nitride 370 and it, too, may be patterned and etched as shown in FIG. 22, forming part of the upper electrodes 140
  • FIGS. 23 and 24 depict a solder-free complementary vertical thermoelectric device from the top after formation of the n-type thermoelements 120 and passivated metal links 145, respectively
  • a probe hole or via (unfilled) 390 may be formed in the thermoelectric device structure for allowing electrical contact directly to the substrate 160 or other underlayer which would otherwise be inaccessible due to intervening material layers
  • additional mask steps and etching processes which may in some cases be deleterious to the material, electrical, or other characteristics of the device may be avoided
  • solder-free in this context means that the complete vertical thermoelectric device comprising thermoelectric elements of complementary type, is formed without resort to soldering individual or pairs of thermoelectric elements together to form a functional device
  • the solder-free vertical thermoelectric device itself may be connected to external circuitry after its completion by any appropriate means, including solder, wire bonding, and other electrical and/or mechanical attachment means, without exception.

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  • Cooling Or The Like Of Semiconductors Or Solid State Devices (AREA)
  • Hall/Mr Elements (AREA)
  • Measuring Temperature Or Quantity Of Heat (AREA)

Abstract

L'invention concerne un dispositif thermoélectrique vertical complémentaire à facteur de remplissage élevé. Dans certains modes de réalisation, une pluralité d'électrodes inférieures sont disposées sur une structure support. Des paires d'éléments thermoélectriques de type de conductivité complémentaire sont disposées sur les électrodes inférieures, de telle sorte que chaque électrode inférieure couple une paire complémentaire respective d'éléments thermoélectriques adjacents disposés sur celle-ci. Une couche diélectrique conformée est formée au-dessus des éléments thermoélectriques d'un type de conductivité, l'épaisseur de la couche conformée sur les parois latérales de ces éléments déterminant l'espacement entre des paires adjacentes d'éléments thermoélectriques complémentaires. Une pluralité d'électrodes supérieures, chacune chevauchant une paire d'électrodes inférieures adjacentes et couplant une paire complémentaire d'éléments thermoélectriques adjacents peut compléter le dispositif thermoélectrique complémentaire à facteur de remplissage élevé.
PCT/US2007/063481 2006-03-08 2007-03-07 dispositif thermoélectrique vertical à facteur de remplissage élevé WO2007103972A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US78029906P 2006-03-08 2006-03-08
US60/780,299 2006-03-08

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WO2007103972A2 true WO2007103972A2 (fr) 2007-09-13
WO2007103972A3 WO2007103972A3 (fr) 2007-10-25

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5168339A (en) * 1990-04-20 1992-12-01 Matsushita Electrical Industrial Co., Ltd. Thermoelectric semiconductor having a porous structure deaerated in a vacuum and thermoelectric panel using p-type and n-type thermoelectric semiconductors
US5837929A (en) * 1994-07-05 1998-11-17 Mantron, Inc. Microelectronic thermoelectric device and systems incorporating such device
US6232542B1 (en) * 1996-11-15 2001-05-15 Citizen Watch Co., Ltd. Method of fabricating thermoelectric device
US6492585B1 (en) * 2000-03-27 2002-12-10 Marlow Industries, Inc. Thermoelectric device assembly and method for fabrication of same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5168339A (en) * 1990-04-20 1992-12-01 Matsushita Electrical Industrial Co., Ltd. Thermoelectric semiconductor having a porous structure deaerated in a vacuum and thermoelectric panel using p-type and n-type thermoelectric semiconductors
US5837929A (en) * 1994-07-05 1998-11-17 Mantron, Inc. Microelectronic thermoelectric device and systems incorporating such device
US6232542B1 (en) * 1996-11-15 2001-05-15 Citizen Watch Co., Ltd. Method of fabricating thermoelectric device
US6492585B1 (en) * 2000-03-27 2002-12-10 Marlow Industries, Inc. Thermoelectric device assembly and method for fabrication of same

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WO2007103972A3 (fr) 2007-10-25

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