Compliant micro device transfer head with integrated electrode leads
A compliant micro device transfer head and head array are disclosed. In an embodiment a micro device transfer head includes a spring arm having integrated electrode leads that is deflectable into a space between a base substrate and the spring arm.
1. A micro device transfer head comprising:
a base substrate;
a spring anchor coupled to the base substrate;
a spring arm coupled to the spring anchor, the spring arm including:
a mesa structure suspended over the base substrate;
a top electrode extending laterally from the spring anchor and over the mesa structure; and
a bottom electrode extending laterally from the spring anchor underneath the mesa structure and wrapping around and over the mesa structure, wherein the top electrode and the bottom electrode are electrically isolated from each other; and
a dielectric layer covering the top electrode and the bottom electrode over the mesa structure.
2. The micro device transfer head of claim 1 , wherein the spring arm further comprises a template defined by the top electrode and the bottom electrode, wherein the template comprises the mesa structure.
3. The micro device transfer head of claim 2 , wherein the template is filled with a dielectric material.
4. The micro device transfer head of claim 2 , wherein the template is filled with air.
5. The micro device transfer head of claim 1 , wherein the top electrode and the bottom electrode are metal.
6. The micro device transfer head of claim 1 , wherein the spring arm is deflectable into an underlying space.
7. The micro device transfer head of claim 6 , wherein the spring arm is coupled to the base substrate via a layer of dielectric material, and wherein the underlying space is a cavity in the dielectric layer.
8. The micro device transfer head of claim 6 , further comprising a sensor electrode on a bottom surface of the underlying space, wherein the sensor electrode is vertically aligned with the mesa structure.
9. The micro device transfer head of claim 6 , wherein the dielectric layer conforms to the spring arm and the underlying space.
10. The micro device transfer head of claim 9 , further comprising a strain sensor formed over a portion of the dielectric layer covering an interface of the spring anchor and the spring arm.
11. The micro device transfer head of claim 1 , wherein the top surface of the transfer head has a length from 1 to 100 μm and a width from 1 to 100 μm.
12. The micro device transfer head of claim 1 , further comprising routing in the base substrate, wherein the routing is electrically connected to the top electrode and the bottom electrode.
13. The micro device transfer head of claim 12 , wherein the routing comprises through vias in the base substrate.
14. The micro device transfer head of claim 1 , wherein the top electrode and bottom electrode are form a bipolar electrode on a top surface of the mesa structure.
15. A micro device transfer head array comprising:
a base substrate; and
an array of transfer heads, each transfer head including:
a spring anchor coupled to the base substrate;
a spring arm coupled to the spring anchor, the spring arm including:
a mesa structure suspended over the base substrate;
a top electrode extending laterally from the spring anchor and over the mesa structure; and
a bottom electrode extending laterally from the spring anchor underneath the mesa structure and wrapping around and over the mesa structure, wherein the top electrode and the bottom electrode are electrically isolated from each other; and
a dielectric layer covering the top electrode and the bottom electrode over the mesa structure.
16. The micro device transfer head array of claim 15 , wherein each spring arm is deflectable into an underlying space.
17. The micro device transfer head array of claim 16 , wherein the underlying space is a trench extending underneath a plurality of transfer heads.
18. The micro device transfer head array of claim 15 , further comprising routing in the base substrate, wherein the routing is electrically connected to the top electrode and bottom electrode of each transfer head.
19. The micro device transfer head of claim 18 , wherein the routing comprises through vias in the base substrate.
20. The micro device transfer head array of claim 15 , further comprising a conductive ground plane formed over the dielectric layer and surrounding each of the transfer heads.
21. The micro device transfer head of claim 15 , wherein the top electrode and bottom electrode of each transfer head form a bipolar electrode on a top surface of the mesa structure.