Semiconductor isolation structures and methods of forming the same
Doping a liner of a trench isolation structure with fluorine reduces dark current from a photodiode. For example, the fluorine may be added to a passivation layer surrounding a backside deep trench isolation structure. As a result, sensitivity of the photodiode is increased. Additionally, breakdown voltage of the photodiode is increased, and a quantity of white pixels in a pixel array including the photodiode are reduced.
1 . A method, comprising:
forming, in a substrate, a photodiode for a pixel sensor of a pixel array;
forming, in the substrate, a trench adjacent to the photodiode;
forming an oxide liner layer to be in direct contact with sidewalls of the trench and to be in direct contact with a bottom surface of the trench;
forming a doping layer to be in direct contact with the oxide liner layer;
driving fluorine from the doping layer into the oxide liner layer by bombarding the doping layer with a plasma;
removing the doping layer;
forming, after removing the doping layer, an oxide layer to be in direct contact with the oxide liner layer; and
filling the trench with a dielectric material over the oxide layer to form a deep trench isolation (DTI) structure.
2 . The method of claim 1 , wherein driving the fluorine into the oxide liner layer results in fluorine-silicon bonds at an interface between the oxide liner layer and the substrate.
3 . The method of claim 1 , wherein the doping layer comprises a titanium nitride, tungsten, or a combination thereof.
4 . The method of claim 1 , wherein the doping layer comprises a fluorosilicate glass (FSG).
5 . The method of claim 1 , wherein removing the doping layer comprises:
performing a wet etch process to remove the doping layer.
6 . The method of claim 1 , wherein the oxide layer is a high-κ layer, wherein the dielectric material is formed over the high-κ layer in the DTI structure.
7 . The method of claim 1 , wherein the doping layer is bombarded with the plasma at a temperature that is in a range from 350° C. to 450° C.
8 . The method of claim 1 , wherein the plasma is a hydrogen plasma.
9 . The method of claim 1 , wherein the oxide layer is formed at a temperature that is in a range from 350° C. to 450° C.
10 . A device, comprising:
one or more memories; and
one or more processors, coupled to the one or more memories, configured to:
form, in a substrate, a photodiode for a pixel sensor of a pixel array;
form, in the substrate, a trench adjacent to the photodiode;
form an oxide liner layer to be in direct contact with sidewalls of the trench and to be in direct contact with a bottom surface of the trench;
form a doping layer to be in direct contact with the oxide liner layer;
bombard the doping layer with a plasma to drive fluorine from the doping layer into the oxide liner layer;
remove the doping layer;
form, after the doping layer is removed, an oxide layer to be in direct contact with the oxide liner layer; and
fill the trench with a dielectric material over the oxide liner layer to form a deep trench isolation (DTI) structure.
11 . The device of claim 10 , wherein the one or more processors are further configured to:
form fluorine-silicon bonds at an interface between the oxide liner layer and the substrate based on the fluorine being driven into the oxide liner layer.
12 . The device of claim 10 , wherein the doping layer comprises a titanium nitride, tungsten, or a combination thereof.
13 . The device of claim 10 , wherein the doping layer comprises a fluorosilicate glass (FSG).
14 . The device of claim 10 , wherein the one or more processors, to remove the doping layer, are configured to:
perform a wet etch process.
15 . The device of claim 10 , wherein the oxide layer is a high-κ layer.
16 . A non-transitory computer-readable medium storing a set of instructions, the set of instructions comprising:
one or more instructions that, when executed by one or more processors of a device, cause the device to:
form, in a substrate, a photodiode for a pixel sensor of a pixel array;
form, in the substrate, a trench adjacent to the photodiode;
form an oxide liner layer to be in direct contact with sidewalls of the trench and to be in direct contact with a bottom surface of the trench;
form a doping layer to be in direct contact with the oxide liner layer;
bombard the doping layer with a plasma to drive fluorine from the doping layer into the oxide liner layer;
remove the doping layer;
form, after the doping layer is removed, an oxide layer to be in direct contact with the oxide liner layer; and
fill the trench with a dielectric material over the oxide liner layer to form a deep trench isolation (DTI) structure.
17 . The non-transitory computer-readable medium of claim 16 , wherein the one or more instructions further configured cause the device to:
form fluorine-silicon bonds at an interface between the oxide liner layer and the substrate based on the fluorine being driven into the oxide liner layer.
18 . The non-transitory computer-readable medium of claim 16 , wherein the doping layer comprises a titanium nitride, tungsten, or a combination thereof.
19 . The non-transitory computer-readable medium of claim 16 , wherein the doping layer comprises a fluorosilicate glass (FSG).
20 . The non-transitory computer-readable medium of claim 16 , wherein the one or more instructions, that cause the device to remove the doping layer, cause the device to:
perform a wet etch process.