Multi-layer tethers for micro-transfer printing
A micro-device structure comprises a source substrate comprising sacrificial portions laterally spaced apart by anchors. Each sacrificial portion is exposed through an opening. A micro-device is disposed on each sacrificial portion and laterally attached to an anchor by a multi-layer tether. In certain embodiments, a micro-device structure is constructed by providing the source substrate, disposing micro-devices on each sacrificial portion, depositing a first tether layer over at least a portion of the source substrate and the micro-device, depositing a second tether layer over the first tether layer, and patterning the first tether layer and the second tether layer to form (i) a multi-layer tether for each of the micro-devices such that the multi-layer tether laterally attaches the micro-device to one of the anchors, and (ii) an opening exposing each of the sacrificial portions.
1. A method of making a micro-device structure, comprising:
providing a source substrate comprising sacrificial portions spaced apart by anchors;
disposing micro-devices in association with the source substrate such that each of the micro-devices is disposed exclusively on, in, or over one of the sacrificial portions;
depositing a first tether layer over at least a portion of the source substrate and the micro-devices;
depositing a second tether layer over the first tether layer, the first tether layer thicker than the second tether layer; and
patterning the first tether layer and the second tether layer to form (i) a corresponding multi-layer tether for each of the micro-devices such that the corresponding multi-layer tether laterally attaches the micro-device to one of the anchors, and (ii) an opening exposing each of the sacrificial portions,
wherein after the patterning (i) the first tether layer extends over at least a portion of each of the micro-devices, (ii) the second tether layer extends over at least a portion of each of the micro-devices, or (iii) the first tether layer extends over at least a first portion of each of the micro-devices and the second tether layer extends over at least a second portion of each of the micro-devices.
2. The method of claim 1 , comprising etching the sacrificial portions to release the micro-devices from the source substrate.
3. The method of claim 1 , wherein each of the micro-devices comprises one or more contact pads, deposition of the first tether layer is an unpatterned blanket deposition, and the method comprises removing the first tether layer at least from the one or more contact pads of each of the micro-devices before depositing the second tether layer over the first layer.
4. The method of claim 1 , wherein the second tether layer deposition is an unpatterned blanket deposition.
5. The method of claim 1 , comprising removing the second tether layer after patterning the first tether layer and the second tether layer.
6. The method of claim 5 , comprising contacting the micro-devices with a stamp to adhere the micro-devices to the stamp, removing the stamp and the micro-devices from the source substrate, adhering the micro-devices to a destination substrate, and removing the stamp from the destination substrate.
7. The method of claim 1 , wherein the first tether layer, the second tether layer, or both the first tether layer and the second tether layer encapsulate the micro-devices.
8. The method of claim 1 , wherein the first tether layer is 1.5 to 3 times as thick as the second tether layer.
9. The method of claim 1 , wherein the micro-devices each have a thickness greater than or equal to 5 μm.
10. The method of claim 1 , wherein the micro-devices each have one or more of a length greater than or equal to 250 μm and a width greater than or equal to 250 μm.
11. The method of claim 1 , wherein each of the micro-devices has at least one of a length and a width that is two to four times a length of the corresponding multi-layer tether.
12. The method of claim 1 , wherein each of the micro-devices is laterally attached to the one of the anchors only by the corresponding multi-layer tether.
13. The method of claim 1 , wherein each of the micro-devices is laterally attached to a second one of the anchors by a second multi-layer tether.
14. The method of claim 1 , wherein the sacrificial portions comprise a sacrificial material that is the same material as a material of the source substrate, and wherein the sacrificial material is an anisotropically etchable material.
15. The method of claim 1 , wherein the sacrificial portions comprise a sacrificial material that is a different material from a material of the source substrate, and wherein the sacrificial material is differentially etchable from the material of the source substrate.
16. The method of claim 1 , wherein the multi-layer tether is a bilayer tether consisting essentially of the first tether layer and the second tether layer.
17. The method of claim 1 , wherein the multi-layer tether comprises an oxide, a nitride, or both an oxide and a nitride.
18. The method of claim 1 , wherein the first tether layer comprises silicon dioxide and the second tether layer comprises silicon nitride.
19. The method of claim 18 , wherein the first tether layer of silicon dioxide is disposed between the second tether layer of silicon nitride and the sacrificial portions.
20. The method of claim 1 , wherein the micro-devices each comprise one or more contact pads and the first tether layer encapsulates the micro-devices except for the one or more contact pads and the second tether layer encapsulates each of the micro-devices including the one or more contact pads.