Backside metal grid and metal pad simplification
An image sensor includes a semiconductor material including a plurality of photodiodes disposed in the semiconductor material. The image sensor also includes a first insulating material disposed proximate to a frontside of the semiconductor material, and an interconnect disposed in the first insulating material proximate to the frontside of the semiconductor material. A metal pad extends from a backside of the semiconductor material through the first insulating material and contacts the interconnect. A metal grid is disposed proximate to the backside of the semiconductor material, and the semiconductor material is disposed between the metal grid and the first insulating material disposed proximate to the frontside.
1. A method of image sensor fabrication, comprising:
providing a semiconductor material including a plurality of photodiodes disposed in the semiconductor material and a first insulating material disposed on a frontside of the semiconductor material and a second insulating material disposed on a backside of the semiconductor material, wherein the first insulating material includes an interconnect disposed in the first insulating material proximate to a frontside of the semiconductor material;
etching a first trench in the first insulating material to contact the interconnect;
etching a second trench in the second insulating material to contact the semiconductor material;
depositing a first metal in the first trench and the second trench to form a metal pad;
depositing a second metal proximate to the backside so that the semiconductor material is disposed between the second metal and the first insulating material; and
removing a portion of the second metal to form a metal grid proximate to the backside of the semiconductor material.
2. The method of claim 1 , wherein etching the second trench includes etching through a high-k material disposed between the second insulating material and the semiconductor material and etching through a silicon nitride layer, wherein the second insulating material is disposed between the silicon nitride layer and the high-k material.
3. The method of claim 2 , wherein part of the first metal in the second trench extends to the metal grid.
4. The method of claim 1 , wherein the first metal and the second metal include a same chemical composition, and wherein the first insulating material and the second insulating material include a same chemical composition.
5. The method of claim 4 , wherein the first metal and the second metal include aluminum.
6. The method of claim 1 , further comprising depositing a protective layer disposed on the metal grid, wherein the metal grid is disposed between the protective layer and the second insulating material.
7. The method of claim 6 , wherein the protective layer includes titanium and nitrogen.
8. The method of claim 1 , wherein the metal pad is disposed proximate to a lateral edge of the semiconductor material.
9. The method of claim 1 , wherein the interconnect includes at least one of copper or titanium.
10. The method of claim 1 , further comprising depositing an antireflection coating on the metal grid.