Method for forming through silicon via in N+ epitaxy wafers with reduced parasitic capacitance
A semiconductor device includes an epitaxy layer formed on semiconductor substrate, a device layer formed on the epitaxy layer, a trench formed within the semiconductor substrate and including a dielectric layer forming a liner within the trench and a conductive core forming a through-silicon via conductor, and a deep trench isolation structure formed within the substrate and surrounding the through-silicon via conductor. A region of the epitaxy layer formed between the through-silicon via conductor and the deep trench isolation structure is electrically isolated from any signals applied to the semiconductor device, thereby decreasing parasitic capacitance.
1. A method comprising:
forming an n+ epitaxy layer on top of a p-doped semiconductor substrate;
forming a device layer on the epitaxy layer;
forming a trench having a dielectric liner and conductive core within the trench to form a through-silicon via conductor, such that the trench extends through the epitaxy layer and the p-doped semiconductor substrate; and
implanting a p-doped region within the p-doped semiconductor substrate in contact with the p-doped semiconductor substrate and n+ epitaxy layer, beneath the epitaxy layer and adjacent to the through-silicon via conductor, wherein the p-doped region is formed of a higher dopant concentration that of the p-doped semiconductor substrate.
2. The method of claim 1 , wherein, the p-doped region is formed by performing angled implantation p-dopants.
3. The method of claim 2 , wherein the p dopants comprise boron (B) or Iridium (In).
4. The method of claim 2 , wherein the angled implantation is performed after the trench is formed and prior to forming the dielectric liner within the trench.
5. The method of claim 2 , wherein the angled implantation is performed after the trench and the dielectric liner are formed, such that the implantation is performed through the dielectric liner.
6. The method of claim 2 , wherein the angled implantation is performed from at least four different angles.
7. The method of claim 2 , further comprising:
forming a photoresist layer on the device layer; and
performing the angled implantation after forming the photoresist layer on the device layer.
8. The method of claim 2 , further comprising annealing the p-doped region in order to activate the p-doped region after performing the angled implantation.
9. The method of claim 8 , wherein the annealing comprises low temperature annealing at a temperature selected such that n dopants in the epitaxy layer are not diffused into the p-doped region.
10. The method of claim 8 , wherein the annealing comprises laser annealing.