Printable 3D electronic components and structures
11387178 · 2022-07-12
Assignee
Inventors
Cpc classification
H05K3/325
ELECTRICITY
H01L25/0652
ELECTRICITY
H05K3/3436
ELECTRICITY
H01L24/20
ELECTRICITY
H01L2224/24227
ELECTRICITY
H01L2221/68318
ELECTRICITY
H01L24/82
ELECTRICITY
H01L27/124
ELECTRICITY
H01L2224/82001
ELECTRICITY
H01L2221/68368
ELECTRICITY
H01G4/38
ELECTRICITY
H01L2224/24226
ELECTRICITY
H01L2225/1058
ELECTRICITY
H01G4/232
ELECTRICITY
H01G4/33
ELECTRICITY
H05K2201/1053
ELECTRICITY
H01L2221/6835
ELECTRICITY
H01L2224/24225
ELECTRICITY
International classification
H01L23/498
ELECTRICITY
H01G4/38
ELECTRICITY
H01G4/232
ELECTRICITY
H01G4/33
ELECTRICITY
H01L25/065
ELECTRICITY
Abstract
An example of a printable electronic component includes a component substrate having a connection post side and an opposing contact pad side. The component can include one or more non-planar, electrically conductive connection posts protruding from the connection post side of the component substrate. Each of the one or more connection posts can have a peak area smaller than a base area. The component can include one or more non-planar, electrically conductive exposed component contact pads disposed on (e.g., directly on, indirectly on, or in) the contact pad side of the component substrate. Multiple components can be stacked such that connection post(s) of one are in contact with non-planar contact(s) of one or more others.
Claims
1. A printed electronic component structure, comprising a first printable electronic component and a second printable electronic component, the first printable electronic component and the second printable electronic component each comprising a component substrate having a connection post side and an opposing contact pad side; one or more non-planar, electrically conductive connection posts protruding from the connection post side of the component substrate, wherein each of the one or more connection posts has a peak area smaller than a base area; and one or more non-planar, electrically conductive exposed component contact pads disposed on the contact pad side of the component substrate, wherein at least one component contact pad of the one or more component contact pads extends into the component substrate through the component contact pad side to form an indented component contact pad having a recess, and wherein a connection post of the one or more connection posts of the second printable electronic component is inserted into the recess and electrically connected to a component contact pad of the one or more component contact pads of the first printable electronic component.
2. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, at least one component contact pad of the one or more component contact pads has a peak area smaller than a base area.
3. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, (i) at least one component contact pad of the one or more component contact pads has a recessed sharp point, (ii) at least one connection post of the one or more connection posts has a sharp point, or (iii) both (i) and (ii).
4. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, at least one of the one or more component contact pads is disposed at least partially directly over at least one of the one or more connection posts.
5. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, a distal end of at least one of the one or more component contact pads furthest from the component contact pad side is disposed substantially directly over a distal end of at least one of the one or more connection posts furthest from the connection post side in a direction orthogonal to the connection post side or the contact pad side.
6. The printed electronic component structure of claim 1, comprising an active circuit formed in a semiconductor circuit substrate separate from the component substrate of the first printable electronic component and the component substrate of the second printable electronic component, wherein the semiconductor circuit substrate is disposed in or on the component substrate of the first printable electronic component or the second printable electronic component.
7. The printed electronic component structure of claim 6, wherein in least one of the first printable electronic component and the second printable electronic component, (i) at least one component contact pad of the one or more component contact pads is electrically connected to the active circuit, (ii) at least one of the connection posts of the one or more connection posts is electrically connected to the active circuit, or (iii) both (i) and (ii).
8. The printed electronic component structure of claim 6, wherein at least one component contact pad of the one or more component contact pads is disposed adjacent to the semiconductor circuit substrate on the component substrate of the first printable electronic component or the second printable electronic component on or in which the semiconductor circuit substrate is disposed.
9. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, at least one component contact pad of the one or more component contact pads is directly electrically connected to at least one connection post of the one or more connection posts.
10. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, at least one component contact pad of the one or more component contact pads has a shape substantially similar to a shape of at least one connection post of the one or more connection posts.
11. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, at least one component contact pad of the one or more component contact pads has a surface with a profile substantially similar to a profile of a surface of at least one connection post of the one or more connection posts.
12. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, the component substrate has at least one of a width, a length, and a height from 1 to 50 μm.
13. The printed electronic component structure of claim 1, wherein in least one of the first printable electronic component and the second printable electronic component, the component substrate comprises a fractured or separated tether.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The foregoing and other objects, aspects, features, and advantages of the present disclosure will become more apparent and better understood by referring to the following description taken in conjunction with the accompanying drawings, in which:
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(30) Features and advantages of the present disclosure will become more apparent from the detailed description set forth below when taken in conjunction with the drawings, in which like reference characters identify corresponding elements throughout. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The figures are not drawn to scale since the variation in size of various elements in the Figures is too great to permit depiction to scale.
DETAILED DESCRIPTION OF CERTAIN EMBODIMENTS
(31) The present disclosure provides, inter alia, structures and methods for electrically connecting relatively small electrical components such as integrated circuit chiplets in a simple, efficient, extensible, flexible, and cost-effective way. The integrated circuit chiplets (chiplets) can be electrically connected to a destination substrate or one chiplet can be electrically connected directly to another chiplet, for example in a three-dimensional stack of chiplets, or to three or more chiplets, forming a three-dimensional electronic structure.
(32) Referring to the cross section of
(33) In certain embodiments, components 10 of the present disclosure can be micro-transfer printed. Micro-transfer printing can transfer very small integrated circuit chiplets from a source wafer to a destination substrate. Other methods, such as pick-and-place or surface-mount techniques cannot transfer such small components 10. In some embodiments of the present disclosure, the component substrate 12 has at least one of a width, length, and height from 1 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm.
(34) The circuit 14 can, optionally, include circuit contact pads 13 designating electrical connections to the circuit 14. The electrodes 18 can be electrical conductors electrically connected to the component contact pads 19 or the connection posts 16, or both (as shown in
(35) The connection posts 16 can be electrically connected to the circuit 14 separately from the component contact pads 19 or directly electrically connected in common to the circuit 14 and component contact pads 19 (as shown in
(36) Referring to
(37) A component substrate 12 can be any substrate on which circuits 14, electrodes 18, insulating layers or patterned dielectric structures 15, and electrical conductors (e.g., electrodes 18) can be formed, for example a semiconductor substrate or a glass or plastic substrate as found in the display or integrated circuit industries. The component substrate 12 can be rigid or flexible as well as transparent or opaque. Electrodes 18 can be any patterned electrical conductor, for example electrically conductive metal wires or traces, can be metal oxide conductors, or can be organic conductors and can be transparent or opaque, and can be provided in various widths, materials, and thicknesses.
(38) A circuit 14 can be formed in or on a component substrate 12, and can include, for example, transistors formed in or on a semiconductor component substrate 12 or electrodes 18 formed in or on a semiconductor, glass, or plastic component substrate 12. In some embodiments, a circuit 14 can be formed in a circuit substrate separate from a component substrate 12 and disposed on the component substrate 12, for example, by micro-transfer printing the circuit substrate from a circuit substrate source wafer to the component substrate 12. Circuit connection pads 13 can be metallized or otherwise electrically conductive portions of the component substrate 12 or the circuit substrate (if present), or can simply be designated portions of the component substrate 12 or the circuit substrate (if present) or a designated portion of the circuit 14 to which the electrodes 18 are electrically connected.
(39) In various embodiments of the present disclosure, a circuit 14 is a passive circuit. For example, the circuit 14 can include only wires and only provide electrical connections. For example, in some embodiments, a circuit 14 forms an electrical jumper or electrical pass-through from a connection post 16 to a component contact pad 19. In some embodiments, a circuit 14 is an active circuit including one or more transistors or diodes, for example, light-emitting diodes. A circuit 14 can include resistors or capacitors or be a resistor or capacitor or include multiple capacitors ore resistors electrically connected in series or in parallel. In some embodiments, a circuit 14 comprises both passive and active elements.
(40) Connection posts 16 are electrically conductive and can include a non-conductive structure coated with an electrically conductive layer, such as a metal layer. Connection posts 16 can protrude from a component substrate 12 in a direction orthogonal to the component surface 17 of the component substrate 12. The connection posts 16 can be a spike and have a point with a smaller area than a base adjacent to the component substrate 12.
(41) In some embodiments, and as shown in
(42) Referring to
(43) Multiple directly electrically connected connection posts 16 can be electrically connected to a common destination substrate contact pad 22. Electrically separate connection posts 16 can be electrically connected to electrically separate destination substrate contact pads 22 (as shown in
(44) An adhesive layer 24 can be coated in a pattern over the destination substrate contact pads 22 or, as shown in
(45) Referring to
(46) The first and second components 10A, 10B can have the same structure and circuit 14 or can have different structures and circuits 14. For example, in some embodiments, the circuit 14 in both of first and second components 10A, 10B are capacitors and the capacitors are electrically connected in parallel (as shown in
(47) Referring to
(48) Electronic structures 50 in accordance with certain embodiments of the present disclosure can be extended to a wide variety of components 10 and stacking configurations. Referring to
(49) The electronic structure 50 illustrated in
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(52) In the illustrative embodiments of
(53) Different components 10 can have different sizes (in contrast to their same-sized representation in the figures), include different numbers of connection posts 16, or include different numbers of component contact pads 19. The number of electrically separate connection posts 16 can be different from the number of electrically separate component contact pads 19 in a component 10. Components 10 can comprise different materials, be made in different processes, and have different structures.
(54) Components 10 in accordance with certain embodiments of the present disclosure can be micro-transfer printed from a micro-transfer printable component source wafer 60. An exemplary micro-transfer printable component source wafer is shown in
(55) The substrate of the component source wafer substrate 61 can be silicon, glass, ceramic, plastic or another wafer material suitable for photolithographic processing. In some embodiments, a circuit 14 is an active circuit and a substrate 61 of the component source wafer is a semiconductor. In some embodiments, a circuit 14 is a light-emitting circuit (for example including a light-emitting diode) and a substrate of the component source wafer substrate 61 is sapphire or a compound semiconductor. In some embodiments, a circuit 14 is a passive circuit and a substrate of the component source wafer substrate 61 is glass, ceramic, or plastic.
(56) In various embodiments of the present disclosure, a component source wafer substrate 61 and sacrificial portion 62 include various materials. In some embodiments, a substrate 61 of the component source wafer 60 is anisotropically etchable (for example silicon {1 1 1}) and each sacrificial portion 62 is a designated portion of the component source wafer substrate 61. In some embodiments, each sacrificial portion 62 comprises sacrificial material (e.g., silicon dioxide) that is differentially etchable from the component source wafer substrate 61. In some embodiments, sacrificial portion 62 is an empty space forming a gap (as shown in
(57) Illustrative methods of making certain embodiments of the present disclosure are illustrated in
(58) Referring to
(59) This generic process can be used to make a variety of components 10 having different circuits 14 and having differently patterned conductive layers 66. Referring to
(60) Component contact pads 19 can be specially constructed (for example as a metallized area) or simply be designated portions of the electrodes 18. Referring to
(61) Referring to
(62) The capacitor components 10, 70 of the micro-transfer printable component source wafer 60 can be micro-transfer printed to a destination substrate 20, as shown in
(63) Referring next to the flow charts of
(64) Referring to the illustrative embodiment shown in
(65) Referring to the illustrative embodiment shown in
(66) In some embodiments of the present disclosure, a capacitive micro-transfer printable electronic component 10 does not necessarily include a component contact pad 19. An illustrative embodiment without a separate contact pad component 19 is shown in
(67) According to some embodiments of the present disclosure, a printable electronic component 10 comprises: a component substrate 12 having a connection post side and an opposing contact pad side; one or more non-planar, electrically conductive connection posts 16 protruding from the connection post side of the component substrate 12, wherein each of the one or more connection posts 16 has a peak area smaller than a base area; and one or more non-planar, electrically conductive exposed component contact pads 19 on (e.g., directly on, over (e.g., separated by one or more layers), or in) the contact pad side of the component substrate 12.
(68) According to some embodiments, at least one contact pad 19 of the one or more contact pads 19 extends into the component substrate 12 through the contact pad side. According to some embodiments, at least one contact pad 19 of the one or more contact pads 19 extends through the component substrate 12 and through the connection post side.
(69) According to some embodiments, at least one contact pad 19 of the one or more contact pads 19 has a peak area smaller than a base area. In some embodiments (i) at least one contact pad 19 of the one or more contact pads 19 has a recessed sharp point, (ii) at least one connection post 16 of the one or more connection posts 16 has a sharp point, or (iii) both (i) and (ii), for example as shown in
(70) According to some embodiments, a printable electronic component 10 comprises an active circuit 14 formed in a semiconductor circuit substrate separate from the component substrate 12 disposed in or on the component substrate 12. In some embodiments, (i) at least one contact pad 19 of the one or more contact pads 19 is electrically connected to the active circuit 14, (ii) at least one of the connection posts 16 of the one or more connection posts 16 is electrically connected to the active circuit 14, or (iii) both (i) and (ii).
(71) According to some embodiments, the semiconductor circuit substrate 14 comprises a fractured or separated tether 67B. In some embodiments, the component substrate 12 comprises a fractured or separated tether 67B.
(72) At least one contact pad 19 of the one or more contact pads 19 can be directly electrically connected to at least one connection post 16 of the one or more connection posts 16. At least one contact pad 19 of the one or more contact pads 19 can be disposed adjacent to the semiconductor substrate 14 on the component substrate 12.
(73) At least one contact pad 19 of the one or more contact pads 19 can have a shape substantially similar to a shape of at least one connection post 16 of the one or more connection posts 16. At least one contact pad 19 of the one or more contact pads 19 can have a surface with a profile substantially similar to a profile of a surface of at least one connection post 16 of the one or more connection posts 16. At least one contact pad 19 of the one or more contact pads 19 can be inserted into a back side of at least one connection post 16 of the one or more connection posts 16. A back side of at least one connection post 16 can be the side that is closest to the contact pad side of the component substrate 12.
(74) The component substrate 12 can have at least one of a width, a length, and a height from 1 to 2 μm, 2 to 5 μm, 5 to 10 μm, 10 to 20 μm, or 20 to 50 μm and can be a micro-transfer printable component substrate 12 or electronic component 10.
(75) According to some embodiments, a printable electronic component wafer, e.g., a source wafer, comprises: a wafer and a plurality of component substrates 12, each component substrate 12 of the plurality of component substrates 12 having a connection post side and an opposing contact pad side and one or more non-planar, electrically conductive connection posts 16 protruding from the connection post side of the component substrate 12, wherein each of the one or more connection posts 16 has a peak area smaller than a base area and one or more non-planar, electrically conductive exposed component contact pads 19 on (e.g., directly on, over (e.g., separated by one or more layers), or in) the contact pad side of the component substrate 12. Each component substrate 12 of the plurality of component substrates 12 can be disposed over a sacrificial portion 62 of the wafer and connected to anchor portions of the wafer by a tether. Connection posts 16 can protrude into a sacrificial portion 62 (e.g., as shown in
(76) Referring to
(77) Referring to
(78) As shown in
(79) In some embodiments, a connection post 16 is a multi-layer connection post that includes a conductive layer (e.g., metal layer) on a dielectric layer (e.g., part of a component substrate 12).
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(81) According to some embodiments of the present disclosure and as shown in
(82) According to some embodiments of the present disclosure, a printed electronic component structure 50 comprises a destination (target) substrate 20 and one or more destination substrate contact pads 22 each disposed on or in destination substrate 20. Connection post 16A of the one or more connection posts 16A of first printed electronic component 10A, third printed electronic component 10C, fourth printed electronic component, or fifth printed electronic component can be in contact with and electrically connected to a destination substrate contact pad 22 of the one or more destination substrate contact pads 22.
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(84) Embodiments of the present disclosure have been constructed, operated, and tested, as shown in
(85) Receiving destination substrate 20 was fabricated using 150 mm Si wafers (e.g., in accordance with step 100 of
(86) Once components 10 are released from component source wafer 60 and destination substrate 20 is fabricated, micro-transfer printing can proceed as described with respect to steps 120 and 130 of
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(88) An additional layer of Dow Chemical Intervia 8023 was then spin coated on base-layer 11A populated target substrate 20 at a thickness of 5 μm followed by a hotplate bake of 140° C. for 4 minutes. Second-layer 11B components 10B were transfer printed to target substrate 20 in the same manner as base-layer 11A components 10A, using the same single-post PDMS stamp. Components 10 were aligned so that connection posts 16B of second-layer components 10B spatially overlap component contact pads 19A of two first level 11A printed components 10A to insert the metallized spikes (connection posts 16B) from second-layer 11B component 10B into each of base layer 11A components 10A as illustrated in
(89) As shown in
(90) Post micro-transfer printing, target substrate 20 and printed components 10 were soft baked on a hotplate at 140° C. to improve electrical connection. This bake allows the adhesive to reflow and wick under components 10. A subsequent dry field etch removes excess adhesive, leaving only a layer beneath each printed component 10. Next, an additional thermal reflow step further wets the remaining adhesive under printed components 10 through capillary action. The resulting capillary action paired with the final oven cure, causes contraction of the adhesive which pulls connection posts 16 into contact with destination substrate contact pads 22 or, in the case of second level 11B components 10B, into the metallized recessed pyramids (component contact pads 19A) of base layer 11A components 10A, as shown in
(91) Following base-layer printing, a laser electrically isolated printed components 10 on target substrate 20 by cutting the traces near printed components 10 and electrical power applied with probes to the metallized lines onto which components 10 were printed. By applying electrical power to contact pads 22 on the target substrate 20, printed components 10A and 10B, each incorporating an LED circuit 14, were successfully operated to demonstrate electrical connectivity through component contact pads 19A and connection posts 19B and to emit light, as shown in
(92) A component 10 can be an active component, for example including one or more active elements such as electronic transistors or diodes or light-emitting diodes and photodiodes that produce an electrical current in response to ambient light. In some embodiments, a component 10 is a passive component, for example including one or more passive elements such as resistors, capacitors, or conductors. In some embodiments, a component 10 is a compound component 10 that includes both active and passive elements. A component 10 can be a semiconductor device having one or more semiconductor layers 11, such as an integrated circuit. A component 10 can be an unpackaged die. In some embodiments, a component 10 is a compound element having a plurality of active or passive elements, such as multiple semiconductor devices with separate substrates, each with one or more active elements or passive elements, or both. In certain embodiments, a plurality of elements is disposed and interconnected on a compound element substrate separate from the substrates of any semiconductor or other device or structure. The compound element can be micro transfer printed itself after the elements have been arranged thereon. Components 10 can be electronic processors, controllers, drivers, light-emitting diodes, photodiodes, light-control devices, or light-management devices.
(93) Components 10 can include active elements such as electronic circuits 14 formed using lithographic processes and can include passive elements such as electrical connections (e.g., wires) to component contact pads 19 and connection posts 16. In certain embodiments, component contact pads 19 are planar electrical connections formed on a process side of the component 10 (e.g., a process side of a micro-transfer printable component source wafer 60). Such component contact pads 19 are typically formed from metals such as aluminum or polysilicon using masking and deposition processes used in the art. In certain embodiments, component contact pads 19 are electrically connected to a circuit 14 with wires or electrodes 18. In some embodiments, component contact pads 19 are directly electrically connected to a circuit 14 without intervening wires. In some embodiments, component contact pads 19 and a circuit 14, together with other functional structures formed in the active layer on the component source wafer 60, make up a component 10 or small integrated circuit chiplet of the component 10.
(94) In some embodiments of the present disclosure, components 10 are small integrated circuits, for example chiplets, having a thin substrate with a thickness of only a few microns, for example less than or equal to 25 microns, less than or equal to 15 microns, or less than or equal to 10 microns, and a width or length of 5-10 microns, 10-50 microns, 50-100 microns, or 100-1000 microns. Such chiplet components 10 can be made in a semiconductor component source wafer 60 (e.g., a silicon or GaN wafer) having a process side and a back side used to handle and transport the wafer. In certain embodiments, components 10 are formed using lithographic processes in an active layer on or in the process side of the component source wafer 60. In certain embodiments, an empty release layer space (gap 69) is formed beneath the components 10 with tethers 67 connecting the components 10 to anchors 68 in the component source wafer 60 in such a way that pressure applied against the components 10 breaks the tethers 67 to make broken (e.g., fractured) tether 67B and release the components 10 from the component source wafer 60. Methods of forming such structures are described, for example, in the paper AMOLED Displays using Transfer-Printed Integrated Circuits and U.S. Pat. No. 8,889,485 referenced above. Lithographic processes for forming components 10 in a component source wafer 60, for example transistors, wires, and capacitors, can be found in the integrated circuit art.
(95) According to various embodiments of the present disclosure, a native source wafer can be provided with the components 10, release layer, tethers 67, and connection posts 16 already formed, or they can be constructed as part of a process in accordance with some embodiments of the present disclosure.
(96) In certain embodiments, connection posts 16 are structures that provide electrical connections that extend generally perpendicular to the surface of a component substrate 12. Such connection posts 16 can be formed from metals such as aluminum, titanium, tungsten, copper, silver, gold, or other conductive metals. Connection posts 16 can be formed by repeated masking and deposition processes that build up three-dimensional structures. In some embodiments, the connection posts 16 are made of one or more high elastic modulus metals, such as tungsten. As used herein, a high elastic modulus is an elastic modulus sufficient to maintain the function and structure of the connection post 16 when pressed into a destination substrate contact pad 22.
(97) In certain embodiments, electrodes 18 include patterned metal layers forming component contact pads 19. Component contact pads 19 can be made using integrated circuit photolithographic methods. Likewise, connection posts 16 can be made by etching one or more layers of metal evaporated or sputtered on a component 10. In some embodiments, as illustrated in
(98) Connection posts 16 can have a variety of aspect ratios and typically have a peak area smaller than a base area. Connection posts 16 can have a sharp point for embedding in or piercing destination substrate contact pads 22. Components 10 with protruding connection posts 16 generally are discussed in U.S. Pat. No. 8,889,485, the disclosure of which is hereby incorporated by reference herein in its entirety.
(99) Destination substrate contact pads 22 can be made of a relatively soft metal, such as tin, solder, or tin-based solder, to assist in forming good electrical contact with connection posts 16 and adhesion with components 10. As used herein, a soft metal may refer to a metal into which a connection post 16 can be pressed to form an electrical connection between the connection post 16 and a destination substrate contact pad 22 or the component contact pads 19. In this arrangement, destination substrate contact pad 22 or component contact pad 19 can plastically deform and flow under mechanical pressure to provide a good electrical connection between the connection post 16 and the destination substrate contact pad 22 or the component contact pad 19.
(100) In some embodiments of the present disclosure, connection posts 16 can include a soft metal and destination substrate contact pads 22 or component contact pads 19 can include a high elastic modulus metal. In this arrangement, connection posts 16 can plastically deform and flow under mechanical pressure to provide a good electrical connection between the connection post 16 and the destination substrate contact pads 22 or the component contact pads 19.
(101) If an optional adhesive layer 24 is formed on a destination substrate 20, connection posts 16 can be driven through the adhesive layer 24 to form an electrical connection with destination substrate contact pads 22 beneath the adhesive layer 24. In certain embodiments, an adhesive layer 24 can be cured to more firmly adhere components 10 to a destination substrate 20 and maintain a robust electrical connection between the connection posts 16 and destination substrate contact pads 22 in the presence of mechanical stress. In certain embodiments, an adhesive layer 24 can undergo some shrinkage during the curing process that can further strengthen the electrical connectivity and adhesion between a connection post 16 and a destination substrate contact pad 22 or a component contact pad 19. In some embodiments of the present disclosure, an adhesive layer 24, for example a curable adhesive layer 24, is coated over a first level 11A of first components 10A so that a second level 11B of second components 10B disposed over the first level 11A of first components 10A can be adhered to the first level 11A of first components 10A. In some embodiments, an adhesive layer 24 can be patterned or otherwise coated over component contact pads 19 and connection posts 16 of components 10 in the second level 11B of components 10 make electrical contact with component contact pads 19 in the first level 11A of components 10 through the adhesive layer 24.
(102) As shown in
(103) In some embodiments of the present disclosure, connection posts 16 of components 10 are in contact with, are embedded in, or pierce destination substrate contact pads 22 or component contact pads 19. In some embodiments, either or both of one or more of connection posts 16 and destination substrate contact pads 22 or component contact pads 19 are deformed or crumpled into a non-planar shape or are deformed so that the surfaces of the connection posts 16 and the destination substrate contact pads 22 or component contact pads 19 change shape on contact with each other. Without wishing to be bound by any particular theory, deformation or crumpling can improve the electrical connection between connection posts 16 and destination substrate contact pads 22 or component contact pads 19 by increasing the surface area that is in contact between the connection posts 16 and the destination substrate contact pads 22 or component contact pads 19. To facilitate deformation, in some embodiments, two or more connection posts 16 have a composition softer than that of the destination substrate contact pads 22 or component contact pads 19 or the destination substrate contact pads 22 or component contact pads 19 have a composition softer the two or more connection posts 16.
(104) A connection post 16 can include conductive material such as a solder that is melted to promote the electrical connection between the connection post 16 and a destination contact pad 22 or component contact pad 19. In some embodiments, the destination substrate contact pads 22 or component contact pads 19 include or are coated with a conductive material or solder. Connection posts 16 can contact, be embedded in, or pierce the conductive material. In some embodiments, a destination substrate contact pad 22 or component contact pads 19 has a first conductive layer and a second conductive layer over the first conductive layer, and the second conductive layer has a lower melting temperature than the first conductive layer. With a subsequent heat treatment, the solder can reflow and promote the electrical connection between the connection post 16 and the destination substrate contact pad 22 or component contact pad 19. In some embodiments, both the connection posts 16 and the destination substrate contact pads 22 or component contact pads 19 include a layer of conductive material such as solder or have a layer of conductive material other than the material making up the connection posts 16 or destination substrate contact pads 22 or component contact pads 19 that electrically connects the destination substrate contact pad 22 or component contact pad 19 to the connection post 16. As noted above, a heat treatment can also serve to weld a destination substrate contact pad 22 or component contact pad 19 to a connection post 16. Welding can be facilitated by providing a common material on the surfaces of the connection posts 16 and the destination substrate contact pads 22 or component contact pads 19.
(105) The spatial distribution of components 10 is a matter of design choice for the end product desired. In some embodiments of the present disclosure, all of the components 10 in a component source wafer 60 array are transferred to the stamp 30 (i.e., in a single step). In some embodiments, a subset of the components 10 in a component source wafer 60 array is transferred in a single step. By varying the number and arrangement of pillars 32 on a transfer stamps 30, the distribution of components 10 on the pillars 32 of the transfer stamp 30 can be likewise varied, as can the distribution of components 10 on a destination substrate 20 or onto a layer of components 10.
(106) In certain embodiments, components 10 are pressed onto or into a destination substrate contact pads 22 or component contact pads 19 by micro-transfer printing with sufficient mechanical pressure against the destination substrate contact pads 22 or component contact pads 19 to drive connection posts 16 into or through a surface of the destination substrate contact pads 22 or component contact pads 19 to form a robust electrical contact between the connection posts 16 of the component 10 and the destination substrate contact pads 22 or component contact pads 19. In some embodiments, a sufficient mechanical pressure is an amount of force needed to cause a destination substrate contact pad 22, component contact pad 19, or connection post 16 to plastically deform as the connection post 16 is pressed into the destination substrate contact pad 22 or component contact pads 19. Thus, in some embodiments, connection posts 16 on an active components 10 may have sharp points and/or a high elastic modulus, for example, by incorporating tungsten. A connection post 16 can have a sharp point, for example, if the top of the post has an area less than 10 microns square, less than 5 microns square, or less than one-micron square. Destination substrate contact pads 22 can also provide adhesion to help adhere components 10 to a destination substrate 20 or to another component 10.
(107) Adhesion between components 10 and the receiving side of a destination substrate 20 or component contact pad 19 should be greater than the adhesion between the components 10 and the pillars 32 of a transfer stamp 30. As such, when the transfer stamp 30 is removed from the receiving side of the destination substrate 20 or component 10, the components 10 adhere more strongly to the destination substrate 20 or component 10 than to the transfer stamp 30, thereby transferring the components 10 from the transfer stamp 30 to the receiving side of the destination substrate 20 or another component 10.
(108) The transfer stamp 30 is then removed leaving the components 10 adhered to the destination substrate 20 or component 10. An optional heat treatment can solder or weld the connection posts 16 of the components 10 to the destination substrate contact pads 22 of the destination substrate 20 or component contact pads 19 of a component 10. Thus, in some embodiments of the present disclosure, destination substrate contact pads 22, component contact pads 19, or connection posts 16 are heated, causing the destination substrate contact pad 22 metal to reflow and improve adhesion between the components 10 and the destination substrate 20 or component contact pads 19 and improve the electrical connection to the connection posts 16.
(109) In some embodiments of the present disclosure, a component 10 is a light-emitting component that emits light. In one arrangement, the light is emitted in a direction opposite to the connection posts 16. In some embodiments, a component 10 is covered with a second dielectric layer 15. The second dielectric layer 15 can be transparent to visible light or to the frequencies of light emitted by the light emitter and the light can be emitted through the second dielectric layer 15.
(110) According to some embodiments of the present disclosure, a component source wafer 60 can be provided with components 10 and component contact pads 19 and connection posts 16 already formed on the component source wafer 60. In some embodiments, an unprocessed component source wafer 60 can be provided with components 10 formed on or in the component source wafer 60. As used herein, an unprocessed component source wafer 60 is a substrate that does not yet include components 10. An unprocessed component source wafer 60 can have other processing steps completed, for example, cleaning, deposition of material layers, or heat or chemical treatments, as are used in the photo-lithographic arts. Components 10 are formed, for example using photo-lithographic processes including forming or providing masks over the component source wafer 60, etching materials, removing masks, and depositing materials. Such processes are used in the photo-lithographic arts. Using such processes, components 10 are formed on or in a component source wafer 60.
(111) Components 10 can be small electronic integrated circuits, for example, having a size of about 5 microns to about 5000 microns in a dimension. Electronic circuits can include semiconductor materials (for example inorganic materials such as silicon or gallium arsenide, or inorganic materials) having various structures, including crystalline, microcrystalline, polycrystalline, or amorphous structures. In some embodiments, components 10 are passive, for example including a conductor that, when used in a printed electronic structure 50 serves to electrically connect one conductor (e.g., a destination substrate contact pad 22 or component contact pad 19) to another, thereby forming an electrical jumper. Components 10 can also include insulating layers and structures such as silicon dioxide, nitride, and passivation layers and conductive layers or structures including wires or electrodes 18 made of aluminum, titanium, silver, or gold that form an electronic circuit. Connection posts 16 or component contact pads 19 can be formed of metals such as aluminum or polysilicon semiconductors deposited and patterned on a component substrate 12. Useable methods and materials for making component 10 electronic circuits are known in the integrated circuit arts. In certain embodiments, large numbers of such small integrated circuits are formed on a single component source wafer 60. Components 10 are typically packed as closely as possible to use the surface area of the component source wafer 60 as efficiently as possible.
(112) In some embodiments, components 10 are small integrated circuits formed in a semiconductor wafer, for example gallium arsenide or silicon, which can have a crystalline structure. Processing technologies for these materials typically employ high heat and reactive chemicals. However, by employing transfer technologies that do not or minimally stress a component 10 or substrate materials, more benign environmental conditions can be used as compared to thin-film manufacturing processes. Thus, certain embodiments of the present disclosure have an advantage in that flexible substrates, such as polymeric substrates, that are intolerant of extreme processing conditions (e.g., heat, chemical, or mechanical processes) can be employed for destination substrates 20. Furthermore, without wishing to be bound by any particular theory, it has been demonstrated that crystalline silicon substrates have strong mechanical properties and, in small sizes, can be relatively flexible and tolerant of mechanical stress. This is particularly true for substrates having 5-micron, 10-micron, 20-micron, 50-micron, or even 100-micron thicknesses. In some embodiments, components 10 can be formed in a microcrystalline, polycrystalline, or amorphous semiconductor layer.
(113) In some embodiments, components 10 can be constructed using foundry fabrication processes used in the art. Layers of materials can be used, including materials such as metals, oxides, nitrides and other materials used in the integrated-circuit art. Each component 10 can be a complete semiconductor integrated circuit and can include, for example, transistors. Components 10 can have different sizes, for example, 1000 square microns or 10,000 square microns, 100,000 square microns, or 1 square mm, or larger, and can have variable aspect ratios, for example, 1:1, 2:1, 5:1, or 10:1. Components 10 can be rectangular or can have other shapes.
(114) Certain embodiments of the present disclosure provide advantages over other printing methods described in the prior art. By employing connection posts 16 on components 10 and a printing method that provides components 10 on a destination substrate 20 or in a component stack, a low-cost method for printing chiplets in large quantities at high density over a destination substrate 20 is provided. Furthermore, additional process steps for electrically connecting the components 10 to the destination substrate 20 are obviated in certain embodiments.
(115) A component source wafer 60 and components 10, stamp 30, and destination substrate 20 can be made separately and at different times or in different temporal orders or locations and provided in various process states.
(116) Methods according to certain embodiments of the present disclosure can be iteratively applied to a single or multiple destination substrates 20. By repeatedly transferring sub-arrays of components 10 from a transfer stamp 30 to a destination substrate 20 or to layers of components 10 and relatively moving the transfer stamp 30 and destination substrates 20 between stamping operations by a distance equal to the size of a sub-array of the selected components 10 in the transferred sub-array between each transfer of components 10, an array of components 10 formed at a high density on a component source wafer 60 can be transferred to a destination substrate 20 at a much lower density. In practice, a component source wafer 60 is likely to be expensive, and forming components 10 with a high density on the component source wafer 60 will reduce the cost of the components 10, especially as compared to forming components on the destination substrate 20. Transferring components 10 to a lower-density destination substrate 20 can be used, for example, if the components 10 manage elements distributed over the destination substrate 20, for example in a display, digital radiographic plate, or photovoltaic system.
(117) In particular, in some embodiments wherein an active component 10 is an integrated circuit formed in a crystalline semiconductor material, an integrated circuit substrate provides sufficient cohesion, strength, and flexibility that it can adhere to a destination substrate 20 without breaking as the transfer stamp 30 is removed.
(118) In comparison to thin-film manufacturing methods, using densely populated component source wafers 60 and transferring components 10 to a destination substrate 20 that requires only a sparse array of components 10 located thereon does not waste or require active layer material on a destination substrate 20. Methods in accordance with certain embodiments of the present disclosure can also be used to transfer components 10 made with crystalline semiconductor materials that have higher performance than thin-film active components. Furthermore, flatness, smoothness, chemical stability, and heat stability requirements for a destination substrate 20 used in certain embodiments of the present disclosure may be reduced because the adhesion and transfer process is not substantially limited by the material properties of the destination substrate 20. Manufacturing and material costs may be reduced because of high utilization rates of more expensive materials (e.g., the source substrate) and reduced material and processing requirements for the destination substrate 20.
(119) For a discussion of micro-transfer printing techniques see U.S. Pat. Nos. 8,722,458, 7,622,367 and 8,506,867. Additional details useful in understanding and performing aspects of the present disclosure are described in U.S. Patent Application Ser. No. 62/148,603 filed Apr. 16, 2015, entitled Micro Assembled Micro LED Displays and Lighting Elements and in U.S. Patent Application Ser. No. 62/055,472 filed Sep. 25, 2014, entitled Compound Micro-Assembly Strategies and Devices, the disclosure of each of which is hereby incorporated herein in its entirety by reference.
(120) As is understood by those skilled in the art, the terms “over” and “under” are relative terms and can be interchanged in reference to different orientations of the layers, elements, and substrates included in the present disclosure. For example, a first layer on a second layer, in some implementations means a first layer directly on and in contact with a second layer. In other implementations a first layer on a second layer includes a first layer and a second layer with another layer therebetween.
(121) Having described certain implementations of embodiments, it will now become apparent to one of skill in the art that other implementations incorporating the concepts of the disclosure may be used. Therefore, the disclosure should not be limited to certain implementations, but rather should be limited only by the spirit and scope of the following claims.
(122) Throughout the description, where apparatus and systems are described as having, including, or comprising specific components, or where processes and methods are described as having, including, or comprising specific steps, it is contemplated that, additionally, there are apparatus, and systems of the disclosed technology that consist essentially of, or consist of, the recited components, and that there are processes and methods according to the disclosed technology that consist essentially of, or consist of, the recited processing steps.
(123) It should be understood that the order of steps or order for performing certain action is immaterial so long as the disclosed technology remains operable. Moreover, two or more steps or actions in some circumstances can be conducted simultaneously. The disclosure has been described in detail with particular reference to certain exemplary embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the following claims.
PARTS LIST
(124) A cross section line B cross section line C cross section line x direction y direction 10 printed/printable electronic component/component 10A first component 10B second component 10C third component 11A first level/first layer/base layer 11B second level/second layer 11C third level/third layer 12 component substrate 13 circuit contact pads 14 circuit/semiconductor component substrate 15 dielectric structure/layer 16, 16A, 16B connection post 17 component surface 18 electrode 19, 19A, 19B component contact pad 20 destination substrate/target substrate 22 destination substrate contact pad 24 adhesive layer 30 stamp 32 pillars 50 printed electronic component structure 60 printable component source wafer 61 component source wafer substrate 62 sacrificial portion 64 form/cavity 66 patterned electrically conductive layer/metal layer 67 tether 67B broken tether 68 anchor 69 gap/empty space 70 printed/printable capacitor 100 provide destination substrate step 110 provide source wafer step 120 provide stamps step 130 micro-transfer print first component onto destination substrate step 140 micro transfer print second component onto first component step 150 micro transfer print second component onto first and third components step