Method for electronically pinning a back surface of a back-illuminated imager fabricated on a UTSOI wafer
A method for fabricating a back-illuminated imager which has a pinned back surface is disclosed. A first insulator layer is formed overlying a mechanical substrate. A conductive layer is deposited overlying the first insulator layer. A second insulator layer is formed overlying the conductive layer to form a first structure, an interface being formed between the conductive layer and the second insulator layer, the conductive layer causing band bending proximal to the interface such that the interface is electrically pinned. Hydrogen is implanted in a separate device wafer to form a bubble layer. A final insulator layer is formed overlying the device wafer to form a second structure. The first structure and the second structure are bonded to form a combined wafer. A portion of the combined wafer is removed underlying the bubble layer to expose a seed layer comprising the semiconductor material substantially overlying the second insulator layer.
1. A semiconductor device, comprising:
a first insulator layer formed of a material, overlying a substrate, the first insulator layer having a thickness which minimizes reflection in a predetermined wavelength range based upon the wavelength range and an index of refraction of the material;
a conductive layer substantially overlying the first insulator layer, wherein the conductive layer is optically transparent;
a second insulator overlying the conductive layer, wherein an interface is formed between the conductive layer and the second insulator layer, and wherein the conductive layer causes band bending proximal to the interface such that the interface is electrically pinned; and
a seed layer overlying the second insulator layer;
an epitaxial layer grown substantially overlying the seed layer;
a metal contact on the epitaxial layer extending to the conductive layer; and
one or more anti-reflective coating layers deposited on the first insulator layer to function as an antireflective coating stack, wherein the semiconductor device is configured such that electromagnetic radiation received through the one or more anti-reflective coating layers is absorbed in at least one of the seed layer and the epitaxial layer.
2. The device of claim 1 , wherein the conductive layer comprises metal.
3. The device of claim 2 , wherein the metal is indium-tin oxide.
4. The device of claim 1 , wherein the conductive layer comprises doped polysilicon.
5. The device of claim 1 , wherein the conductive layer has a thickness in the range of about 25 Angstroms to 30 Angstroms.
6. The device of claim 1 , wherein the second insulator layer has a thickness of about 15 Angstroms.
7. The device of claim 1 , wherein the first insulator layer has a thickness of about 1000 Angstroms.
8. The device of claim 1 , further comprising: at least one imaging component fabricated on the epitaxial layer.
9. The device of claim 8 , wherein the at least one imaging component is at least one of a CMOS imaging component, a charge-coupled device component, a photodiode, an avalanche photodiode, and a phototransistor.
10. The device of claim 8 , wherein the epitaxial layer and seed layer comprise silicon and the first and second insulator layers comprise an oxide of silicon.