Semiconductor devices and methods for backside photo alignment
Various embodiments of microelectronic devices and methods of manufacturing are described herein. In one embodiment, a method for aligning an electronic feature to a through-substrate via includes forming a self-aligned alignment feature having a wall around at least a portion of the TSV and aligning a photolithography tool to the self-aligned alignment feature. In some embodiments, the self-aligned alignment feature is defined by the topography of a seed material at a backside of the device.
1. A microelectronic device, comprising:
a semiconductor substrate having a frontside and a backside opposite the frontside;
a first passivation material on the substrate, wherein the first passivation material has a first passivation material backside surface;
a second passivation material on the first passivation material, wherein the second passivation material has a second passivation material backside surface;
a through-substrate via (“TSV”) extending through the substrate and including a protruding portion that extends beyond the backside of the substrate, wherein the TSV has a TSV backside surface that is generally coplanar with the second passivation material backside surface;
wherein the fist passivation material backside surface includes
a first portion covered by the second passivation material;
a second portion that surrounds the TSV and is recessed relative to the second passivation material backside surface such that the TSV, the second portion, and the second passivation material together define an indentation around the TSV;
a seed material on the second passivation material and electrically coupled to the TSV,
wherein:
the seed material has a first seed portion in contact with the second passivation material, a second seed portion adjacent the TSV, and a third seed portion in contact with the second portion of the first passivation material; and
the first, second and third seed portions define a gap in the seed material that surrounds the TSV and corresponds with the indentation; and
a self-aligned alignment feature defined by a topography of the seed material that at least partially surrounds the TSV, wherein the self-aligned alignment feature is configured to provide a reference point to a photolithography tool for alignment with respect to the microelectronic device.
2. The microelectronic device of claim 1 wherein:
the first passivation material has a first etching rate; and
the second passivation material has a second etching rate less than the first etching rate.
3. The microelectronic device of claim 1 wherein the seed material is in direct contact with the second passivation material backside surface, the TSV backside surface, and the second portion of the first passivation material backside surface.
4. The microelectronic device of claim 1 wherein the gap in the seed material is identifiable by a photolithography tool and informs the photolithography tool of the position of the TSV on the microelectronic device relative to the photolithography tool.
5. The microelectronic device of claim 1 , further comprising a redistribution structure at the frontside of the substrate.
6. The microelectronic device of claim 1 wherein the self-aligned alignment feature is the gap in the seed material, and wherein the gap generally aligns with a periphery of the TSV.
7. The microelectronic device of claim 1 wherein the indentation is ring-shaped.
8. The microelectronic device of claim 1 wherein the gap is ring-shaped.
9. The microelectronic device of claim 1 , further comprising a resist material on the seed material.
10. The microelectronic device of claim 1 , further comprising a resist material on the seed material, wherein the resist material includes an opening corresponding to the indentation around the TSV.
11. The microelectronic device of claim 1 , further comprising a resist material on the seed material, wherein the resist material includes an opening that exposes a portion of the seed material on the TSV.
12. The microelectronic device of claim 1 , further comprising an under-bump metallization (“UBM”) structure on the seed material.
13. The microelectronic device of claim 1 , further comprising a UBM structure on the seed material and in the gap.
14. The microelectronic device of claim 1 , further comprising a UBM structure on the seed material, wherein the UBM structure is generally aligned with the TSV.
15. A microelectronic device, comprising:
a semiconductor substrate having a frontside and a backside opposite the frontside;
a first passivation material on the substrate, wherein the first passivation material has a first passivation material backside surface;
a second passivation material on the first passivation material, wherein the second passivation material has a second passivation material backside surface;
a TSV extending through the substrate and including a protruding portion that extends beyond the backside of the substrate;
a seed material on the second passivation material and electrically coupled to the TSV; and
a self-aligned alignment feature defined by a topography of the seed material that at least partially surrounds the TSV, wherein the self-aligned alignment feature is configured to provide a reference point to a photolithography tool for alignment with respect to the microelectronic device,
wherein the protruding portion of the TSV extends beyond the first passivation material backside surface and the second passivation material backside surface, and wherein the protruding portion of the TSV defines the self-aligned alignment feature.
16. The microelectronic device of claim 15 , further comprising a backside protrusion projecting beyond the backside of the device, wherein the backside protrusion includes the protruding portion of the TSV and a portion of the seed material on the protruding portion, and wherein the backside protrusion further defines the self-aligned alignment feature.
17. The microelectronic device of claim 15 , further comprising a redistribution structure at the frontside of the substrate.