Source wafer and method of preparation thereof
A source wafer for use in a micro-transfer printing process. The source wafer comprises: a substrate; a device coupon ( 110 ), including an optoelectronic device; and a breakable tether securing the device coupon to the substrate. The breakable tether includes one or more breaking regions which connect the breakable tether to the substrate.
1. A source wafer for use in a micro-transfer printing process, the source wafer comprising:
a substrate;
a device coupon, including an optoelectronic device;
an air cavity extending around a periphery of the device coupon and extending from a bottom surface of the device coupon to the substrate; and
a breakable tether securing the device coupon to the substrate and comprising a different material than the substrate, the breakable tether including one or more breaking regions which connect the breakable tether to the substrate,
wherein a neck of a first breaking region of the one or more breaking regions extends away from the device coupon and across the air cavity along a first direction parallel to a plane of the substrate to a first adjacent portion of the breakable tether,
wherein the air cavity is between the neck and the substrate, and
wherein the neck is thinner, along a second direction perpendicular to the plane of the substrate, than the first adjacent portion, and the neck is narrower, along a third direction parallel to the plane of the substrate, than the first adjacent portion.
2. The source wafer of claim 1 , wherein each of the one or more breaking regions includes a neck of breakable tether material which extends across the air cavity between the device coupon and a tether street which at least partially surrounds the device coupon.
3. The source wafer of claim 1 , wherein each of the one or more breaking regions is thinner than adjacent portions of the breakable tether.
4. The source wafer of claim 1 , wherein each of the one or more breaking regions is narrower than adjacent portions of the breakable tether.
5. The source wafer of claim 1 , wherein the breakable tether includes a plurality of breaking regions which are disposed around the periphery of the device coupon.
6. The source wafer of claim 1 , wherein the device coupon is secured to the substrate only by the one or more breaking regions of the breakable tether.
7. The source wafer of claim 2 , further comprising a sacrificial layer between the tether street and the substrate.
8. The source wafer of claim 1 , wherein the optoelectronic device is formed of one or more III-V semiconductor materials.
9. The source wafer of claim 1 , wherein the optoelectronic device comprises a plurality of layers.
10. The source wafer of claim 1 , wherein the device coupon includes one or more protective outer layers.
11. The source wafer of claim 10 , wherein the protective outer layers include: an outer silicon dioxide layer, an intermediate silicon nitride layer, and an inner silicon dioxide layer.
12. The source wafer of claim 1 , wherein the one or more breaking regions are weaker than adjacent regions of the breakable tether.
13. The source wafer of claim 1 , wherein the optoelectronic device is an optoelectronic device selected from the group consisting of lasers, photodetectors, and electro-absorption modulators.
14. The source wafer of claim 1 , wherein the device coupon is spaced apart from the substrate by the air cavity, which extends entirely around the device coupon, wherein the one or more breaking regions bridge the air cavity to secure the device coupon to the substrate.
15. A method of preparing the source wafer of claim 1 for a micro-transfer printing process, the method comprising:
etching a precursor tether, disposed over at least a portion of the device coupon and substrate, to define the breakable tether.
16. The method of claim 15 , further comprising etching the substrate and/or device coupon so that the device coupon is secured to the substrate by the breaking regions of the breakable tether.
17. The method of claim 16 , wherein further etching the substrate and/or device coupon includes etching away a sacrificial layer located between the device coupon and the substrate.
18. The method of claim 15 , wherein etching the precursor tether includes an initial step of patterning the precursor tether to define the one or more breaking regions.
19. The method of claim 15 , further comprising a step of performing a plasma ashing process, to remove a portion of the breakable tether.
20. The method of claim 15 , further comprising a step of at least partially encapsulating the device coupon in a protective layer.
21. A method of fabricating an optoelectronic component via a micro-transfer printing process using the source wafer of claim 1 , comprising the steps of:
adhering the device coupon to a stamp;
lifting the device coupon away from the substrate, thereby breaking the breakable tether at the or each breaking region; and
printing the device coupon onto a platform wafer.
22. The source wafer of claim 1 , further comprising a tether street above the substrate and extending around the air cavity,
wherein the breakable tether includes a plurality of breaking regions, each of the breaking regions extending across the air cavity to connect the breakable tether to the substrate,
wherein the first breaking region extends across the air cavity along the first direction to the tether street,
wherein the neck of the first breaking region is between the first adjacent portion and a second adjacent portion of the first breaking region along the first direction, and the neck and the first and second adjacent portions of the first breaking region are each positioned between two openings along the third direction,
wherein the third direction is perpendicular to the first direction, and the neck is narrower, along the third direction than each of the first and second adjacent portions.