Patent · US9640715B2 · B2 · US

Printable inorganic semiconductor structures

(11) Publication number

US9640715B2

(21) Application number

14/713,877

(22) Filing date

2015-05-15

(30) Priority date

2015-05-15

(43) Publication date

2017-05-02

(45) Date of grant

2017-05-02

(51) IPC

H01L 33/00; H01L 33/32; H01L 33/62; H01L 21/00; H01L 21/30; H01L 21/46; H01L 21/683; H01L 29/78; H01L 33/20; H01L 33/26; H01L 33/38; H01L 33/40

(52) CPC

H01L Semiconductor devices; electric solid state devices not otherwise provided for: 33/007, 21/6835, 2221/68318, 2221/6835, 2221/68381, 29/7848, 2933/0016, 2933/0025, 2933/0033, 33/0079, 33/0095, 33/20, 33/26, 33/32, 33/38, 33/40, 33/62
H10D Inorganic electric semiconductor devices: 30/797
H10H Inorganic light-emitting semiconductor devices having potential barriers: 20/01, 20/01335, 20/018, 20/032, 20/034, 20/036, 20/819, 20/822, 20/825, 20/83, 20/831, 20/832, 20/84, 20/857
H10P Generic processes or apparatus for the manufacture or treatment of devices covered by class H10: 72/74, 72/7412, 72/7414, 72/7426, 72/744
H10W Generic packages, interconnections, connectors or other constructional details of devices covered by class H10: 90/00

(73) Assignee

X Celeprint Ltd

(72) Inventors

Christopher Bower; Matthew Meitl; David Gomez; Carl Prevatte; Salvatore Bonafede

(54) Title

Printable inorganic semiconductor structures

(57) Abstract

The present invention provides structures and methods that enable the construction of micro-LED chiplets formed on a sapphire substrate that can be micro-transfer printed. Such printed structures enable low-cost, high-performance arrays of electrically connected micro-LEDs useful, for example, in display systems. Furthermore, in an embodiment, the electrical contacts for printed LEDs are electrically interconnected in a single set of process steps. In certain embodiments, formation of the printable micro devices begins while the semiconductor structure remains on a substrate. After partially forming the printable micro devices, a handle substrate is attached to the system opposite the substrate such that the system is secured to the handle substrate. The substrate may then be removed and formation of the semiconductor structures is completed. Upon completion, the printable micro devices may be micro transfer printed to a destination substrate.

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Claims (18)

A method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; forming a first electrical contact on the first side of the semiconductor layer opposite the source substrate; removing a portion of the semiconductor layer surrounding the first electrical contact to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering the first electrical contact and covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; forming a second electrical contact on the exposed substrate side of the semiconductor element; forming a tether bridging the exposed substrate side of the semiconductor element to the anchor; and removing the sacrificial layer, thereby forming a printable semiconductor structure partially released from the handle substrate and physically secured to the anchor by the tether.
The method of claim 1, wherein the handle substrate is a glass, metal, or plastic.
The method of claim 1, wherein the source substrate is a sapphire substrate.
The method of claim 1, wherein the semiconductor layer comprises GaN and/or doped GaN.
The method of claim 1, wherein adhering the interlayer to a handle substrate comprises providing an adhesive layer on the interlayer and adhering the handle substrate to the adhesion layer.
The method of claim 1, wherein the trench extends through the semiconductor layer to the source substrate.
The method of claim 1, wherein the trench extends partially into the semiconductor layer such that a portion of the semiconductor layer forms an ablation layer between the semiconductor element and the source substrate.
The method of claim 1, wherein the semiconductor element, the first electrical contact, and the second electrical contact form a diode, a laser, or a light-emitting diode.
A method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; removing a portion of the semiconductor layer to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; removing a portion of the semiconductor element to form a cantilever extension of the semiconductor element; forming a first electrical contact on the cantilever extension; forming a second electrical contact on the exposed substrate side of the semiconductor element; and removing the sacrificial layer, thereby forming a printable semiconductor structure partially released from the handle substrate.
The method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; forming a first electrical contact on the first side of the semiconductor layer opposite the source substrate; removing a portion of the semiconductor layer surrounding the first electrical contact to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering the first electrical contact and covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; and forming a second electrical contact on the exposed substrate side of the semiconductor element, wherein the interlayer has a thermal conductivity greater than or equal to 1 W/mK.
An inorganic semiconductor structure comprising: a source substrate; a semiconductor element surrounded by a trench, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; a first metal contact in electrical contact with the semiconductor element on the handle side; a second metal contact in electrical contact with the semiconductor element on the substrate side; a sacrificial layer covering at least a portion of the semiconductor element and covering the first metal contact and filling a portion of the trench; an interlayer formed over the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at a base of the trench to form an anchor; a handle substrate adhered to the interlayer, wherein at least a portion of the interlayer is between the handle substrate and the sacrificial layer; and a tether bridging the substrate side of the semiconductor element to the anchor.
The structure of claim 11, wherein the handle substrate is a glass, metal, or plastic.
The structure of claim 11, wherein the source substrate is a sapphire substrate.
The structure of claim 11, wherein the trench extends partially into the semiconductor layer such that a portion of the semiconductor layer forms an ablation layer between the semiconductor element and the source substrate.
The structure of claim 11, wherein a portion of the interlayer is in contact with a portion of the semiconductor element and forms the tether.
The structure of claim 11, wherein the interlayer is adhesive and the handle substrate is adhered directly to the interlayer.
The structure of claim 11, wherein the interlayer has a thermal conductivity greater than or equal to 1 W/mK.
The structure of claim 11, wherein the semiconductor element, the first electrical contact, and the second electrical contact form a diode, a laser, or a light-emitting diode.

Description

The present invention relates to structures and methods for providing micro-light-emitting diodes on sapphire substrates that can be printed using massively parallel micro-transfer printing methods.

Light-emitting diodes (LEDs) are widely used in the display industry as indicators and in small textual or graphic displays. More recently, LEDs are used in large, tiled outdoor displays and have been demonstrated for indoor applications. However, such displays are expensive to make, in part because of the need for small LEDs and the cost of locating small LEDs on a display substrate.

LEDs are formed in a semiconductor material, often using gallium nitride (GaN). These materials are deposited, with suitable doping, on a wafer substrate to form a crystalline structure that is the LED. Electrical contacts are then formed using photolithographic methods and the LED device is singulated from the wafer and packaged. Most LEDs are formed on a sapphire wafer rather than a gallium nitride wafer to reduce costs. However, the lattice structure of the sapphire wafer does not match that of the GaN LED crystal and therefore the crystal structure tends to have defects, reducing the performance and acceptability of the resulting LED.

Inorganic light-emitting diode displays using micro-LEDs (for example having an area less than 100 microns square or having an area small enough that it is not visible to an unaided observer of the display at a designed viewing distance) are known. For example, U.S. Pat. No.

Citations (76)

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Record as JSON

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  "publication_number": "US9640715B2",
  "country": "US",
  "kind": "B2",
  "title": "Printable inorganic semiconductor structures",
  "abstract": "The present invention provides structures and methods that enable the construction of micro-LED chiplets formed on a sapphire substrate that can be micro-transfer printed. Such printed structures enable low-cost, high-performance arrays of electrically connected micro-LEDs useful, for example, in display systems. Furthermore, in an embodiment, the electrical contacts for printed LEDs are electrically interconnected in a single set of process steps. In certain embodiments, formation of the printable micro devices begins while the semiconductor structure remains on a substrate. After partially forming the printable micro devices, a handle substrate is attached to the system opposite the substrate such that the system is secured to the handle substrate. The substrate may then be removed and formation of the semiconductor structures is completed. Upon completion, the printable micro devices may be micro transfer printed to a destination substrate.",
  "claims": [
    "1. A method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; forming a first electrical contact on the first side of the semiconductor layer opposite the source substrate; removing a portion of the semiconductor layer surrounding the first electrical contact to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering the first electrical contact and covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; forming a second electrical contact on the exposed substrate side of the semiconductor element; forming a tether bridging the exposed substrate side of the semiconductor element to the anchor; and removing the sacrificial layer, thereby forming a printable semiconductor structure partially released from the handle substrate and physically secured to the anchor by the tether.",
    "2. The method of claim 1, wherein the handle substrate is a glass, metal, or plastic.",
    "3. The method of claim 1, wherein the source substrate is a sapphire substrate.",
    "4. The method of claim 1, wherein the semiconductor layer comprises GaN and/or doped GaN.",
    "5. The method of claim 1, wherein adhering the interlayer to a handle substrate comprises providing an adhesive layer on the interlayer and adhering the handle substrate to the adhesion layer.",
    "6. The method of claim 1, wherein the trench extends through the semiconductor layer to the source substrate.",
    "7. The method of claim 1, wherein the trench extends partially into the semiconductor layer such that a portion of the semiconductor layer forms an ablation layer between the semiconductor element and the source substrate.",
    "8. The method of claim 1, wherein the semiconductor element, the first electrical contact, and the second electrical contact form a diode, a laser, or a light-emitting diode.",
    "9. A method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; removing a portion of the semiconductor layer to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; removing a portion of the semiconductor element to form a cantilever extension of the semiconductor element; forming a first electrical contact on the cantilever extension; forming a second electrical contact on the exposed substrate side of the semiconductor element; and removing the sacrificial layer, thereby forming a printable semiconductor structure partially released from the handle substrate.",
    "10. The method of making an inorganic semiconductor structure suitable for micro-transfer printing, comprising: providing a source substrate; forming a semiconductor layer on the source substrate, wherein the semiconductor layer has a first side and a second side opposite the first side and adjacent to the substrate; forming a first electrical contact on the first side of the semiconductor layer opposite the source substrate; removing a portion of the semiconductor layer surrounding the first electrical contact to form a trench surrounding a semiconductor element made from the semiconductor layer, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; providing a sacrificial layer covering the first electrical contact and covering at least a portion of the handle side of the semiconductor element and filling a portion of the trench; providing an interlayer over the sacrificial layer, the interlayer having different chemical selectivity than the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at the base of the trench to form an anchor; adhering the interlayer to a handle substrate; removing the source substrate to expose the substrate side of the semiconductor element; and forming a second electrical contact on the exposed substrate side of the semiconductor element, wherein the interlayer has a thermal conductivity greater than or equal to 1 W/mK.",
    "11. An inorganic semiconductor structure comprising: a source substrate; a semiconductor element surrounded by a trench, the semiconductor element having a substrate side in contact with the source substrate and a handle side opposite the substrate side; a first metal contact in electrical contact with the semiconductor element on the handle side; a second metal contact in electrical contact with the semiconductor element on the substrate side; a sacrificial layer covering at least a portion of the semiconductor element and covering the first metal contact and filling a portion of the trench; an interlayer formed over the sacrificial layer, wherein a portion of the interlayer contacts the source substrate at a base of the trench to form an anchor; a handle substrate adhered to the interlayer, wherein at least a portion of the interlayer is between the handle substrate and the sacrificial layer; and a tether bridging the substrate side of the semiconductor element to the anchor.",
    "12. The structure of claim 11, wherein the handle substrate is a glass, metal, or plastic.",
    "13. The structure of claim 11, wherein the source substrate is a sapphire substrate.",
    "14. The structure of claim 11, wherein the trench extends partially into the semiconductor layer such that a portion of the semiconductor layer forms an ablation layer between the semiconductor element and the source substrate.",
    "15. The structure of claim 11, wherein a portion of the interlayer is in contact with a portion of the semiconductor element and forms the tether.",
    "16. The structure of claim 11, wherein the interlayer is adhesive and the handle substrate is adhered directly to the interlayer.",
    "17. The structure of claim 11, wherein the interlayer has a thermal conductivity greater than or equal to 1 W/mK.",
    "18. The structure of claim 11, wherein the semiconductor element, the first electrical contact, and the second electrical contact form a diode, a laser, or a light-emitting diode."
  ],
  "description_excerpt": "The present invention relates to structures and methods for providing micro-light-emitting diodes on sapphire substrates that can be printed using massively parallel micro-transfer printing methods.\n\nLight-emitting diodes (LEDs) are widely used in the display industry as indicators and in small textual or graphic displays. More recently, LEDs are used in large, tiled outdoor displays and have been demonstrated for indoor applications. However, such displays are expensive to make, in part because of the need for small LEDs and the cost of locating small LEDs on a display substrate.\n\nLEDs are formed in a semiconductor material, often using gallium nitride (GaN). These materials are deposited, with suitable doping, on a wafer substrate to form a crystalline structure that is the LED. Electrical contacts are then formed using photolithographic methods and the LED device is singulated from the wafer and packaged. Most LEDs are formed on a sapphire wafer rather than a gallium nitride wafer to reduce costs. However, the lattice structure of the sapphire wafer does not match that of the GaN LED crystal and therefore the crystal structure tends to have defects, reducing the performance and acceptability of the resulting LED.\n\nInorganic light-emitting diode displays using micro-LEDs (for example having an area less than 100 microns square or having an area small enough that it is not visible to an unaided observer of the display at a designed viewing distance) are known. For example, U.S. Pat. No.",
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