Method for fabricating an optical device

Patent metadata

Field	Value
Publication number	US-11316066-B2
Application number	US-201916708014-A
Country	US
Kind code	B2
Filing date	Dec 9, 2019
Priority date	Dec 10, 2018
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

An optical device and a method for fabricating an optical device are described. The optical device may be a light emitting diode (LED) device, e.g. a micro-LED (μLED) device, or a photodiode (PD) device, e.g. an imager. The method comprises processing, on a first semiconductor wafer, an array including a plurality of compound semiconductor LEDs or compound semiconductor PDs and a plurality of first contacts, each first contact being electrically connected to one of the LEDs or PDs. The method further comprises processing, on a second semiconductor wafer, a CMOS IC and a plurality of second contacts electrically connected to the CMOS IC. The method further comprises hybrid bonding the first semiconductor wafer to the second semiconductor wafer such that the plurality of LEDs or PDs are individually connected to the CMOS IC via the first and second contacts.

First claim

What is claimed is:

1. A method for fabricating an optical device, the method comprising:
processing an array including a plurality of compound semiconductor light emitting diodes (LEDs) or compound semiconductor photodiodes (PDs) on a first semiconductor wafer;
processing a plurality of first contacts on the first semiconductor wafer, each first contact being electrically connected to one of the LEDs or PDs from below;
processing a Complementary Metal-Oxide-Semiconductor (CMOS) integrated circuit (IC) on a second semiconductor wafer;
processing a plurality of second contacts electrically connected to the CMOS IC on the second semiconductor wafer; and
hybrid bonding the first semiconductor wafer to the second semiconductor wafer such that the plurality of LEDs or PDs are individually connected to the CMOS IC via the first and second contacts,
wherein the array includes a plurality of LEDs and processing the array on the first semiconductor wafer comprises:
growing or transferring LED layers on the first semiconductor wafer, wherein the LED layers include quantum well layers and a highly-doped contact layer on the quantum well layers; and
structuring the plurality of LEDs by etching the LED layers, wherein the highly-doped contact layer is etched but the quantum well layers are not etched.

2. The method according to claim 1 , wherein the array is processed without any vertical interconnect access (VIA) through the array between the plurality of LEDs or PDs.

3. The method according to claim 1 , wherein processing, before the hybrid bonding, the plurality of first contacts on the first semiconductor wafer comprises:
processing a plurality of contact layers, each contact layer being applied to a bottom surface of a different one of the LEDs or PDs; and
processing a plurality of vertical interconnect access (VIAs), each VIA being electrically connected to one of the contact layers from below and extending from the contact layer to a bonding surface of the first semiconductor wafer.

4. The method according to claim 3 , wherein a size of each contact layer is equal to or smaller than a size of an active area of the LED or PD, to which it is applied.

5. The method according to claim 1 , further comprising, after the hybrid bonding:
processing at least one third contact on the first semiconductor wafer, the at least one third contact being electrically connected to the plurality of LEDs or PDs from above.

6. The method according to claim 5 , wherein the at least one third contact is transparent for LED light or light to be captured by the PDs and is connected to several or to each of the plurality of LEDs or PDs.

7. The method according to claim 5 , further comprising, after the hybrid bonding:
processing at least one electrical connection element, particularly a vertical interconnect access (VIA), connecting the at least one third contact to the CMOS IC,
wherein the electrical connection element is passed by or around the array.

8. The method according to claim 7 , wherein a plurality of electrical connection elements is processed, the plurality of electrical connection elements being arranged with a lower density than the plurality of first contacts and second contacts.

9. The method according to claim 5 , further comprising, after the hybrid bonding:
processing a conductive grid, particularly using a damascene process, electrically connected to the at least one third contact from above.

10. The method according to claim 1 , wherein the array has a pixel pitch of the plurality of LEDs or PDs between 1-10 μm.

11. The method according to claim 1 , wherein the array has a pixel pitch of the plurality of LEDs or PDs equal to or below 3 μm.

12. An optical device, comprising:
a first semiconductor part comprising:
an array including a plurality of compound semiconductor light emitting diodes (LEDs) or compound semiconductor photodiodes (PDs); and
a plurality of first contacts, each first contact being electrically connected to one of the LEDs or PDs from below; and

a second semiconductor part arranged below the first semiconductor part and comprising:
a Complementary Metal-Oxide-Semiconductor (CMOS) integrated circuit (IC); and
a plurality of second contacts electrically connected to the CMOS IC;

wherein the first semiconductor part is hybrid bonded to the second semiconductor part, and the plurality of first contacts are directly connected one-by-one to the plurality of second contacts, and
wherein at least one third contact is electrically connected to the CMOS IC by at least one electrical connection element arranged outside of the array.

13. The optical device according to claim 12 , wherein the array comprises no vertical interconnect access (VIA) between the plurality of LEDs or PDs.

14. The optical device according to claim 13 , wherein
the at least one third contact is electrically connected to the plurality of LEDs or PDs from above, and
the at least one third contact is transparent for LED light or light to be captured by the PDs and is connected to several or to each of the plurality of LEDs or PDs.

15. The optical device according to claim 12 , wherein:
the at least one third contact is electrically connected to the plurality of LEDs or PDs from above, and
the at least one third contact is transparent for LED light or light to be captured by the PDs and is connected to several or to each of the plurality of LEDs or PDs.

Assignees

• Imec Vzw

Inventors

• Steudel Soeren
• Mityashin Alexander
• Beyne Eric
• Rosmeulen Maarten

Classifications

• H10W90/00 Primary

  Package configurations · CPC title

• H10H20/0364

  of interconnections · CPC title

• H10H20/857

  Interconnections, e.g. lead-frames, bond wires or solder balls · CPC title

• H10H20/812

  within the light-emitting regions, e.g. having quantum confinement structures · CPC title

• H10F39/811

  Interconnections · CPC title