Method of making active pixel sensor cell that minimizes leakage current
AssigneeFoveon, Inc.
InventorRichard Billings Merrill
Life of this patent
Estimating the term…
Abstract
Isolation between the heavily-doped active regions of an active pixel sensor cell is provided by utilizing a series of isolation regions which have a doping concentration that is approximately equal to the doping concentration of a low-density drain (LDD) region. A first isolation region of the series, which has the same conductivity type as the active regions, is formed to adjoin a first active region. A second isolation region of the series, which has the opposite conductivity type as the active regions, is formed to adjoin the first isolation region. A third isolation region, which has the same conductivity type as the active regions, is formed to adjoin the second isolation region and a second active region.
Claims9
A method for forming an active pixel sensor cell in a semiconductor substrate of a first conductivity type, the method comprising the steps of:
- forming a plurality of spaced-apart active regions of a second conductivity type in the substrate, the active regions including a photodiode region and a row-select region, the photodiode and row-select regions each having a doping concentration;
- forming a first isolation region of the second conductivity type in the substrate to adjoin the photodiode region, the first isolation region having a doping concentration substantially less than the doping concentration of the photodiode region;
- forming a second isolation region of the first conductivity type in the substrate to adjoin the first isolation region, the second isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region;
- and
- forming a third isolation region of the second conductivity type in the substrate to adjoin the second isolation region and the row-select region, the third isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region.
A method for forming an active pixel sensor cell on a semiconductor substrate of a first conductivity type, the method comprising the steps of:
- forming a plurality of spaced-apart active regions of a second conductivity type in the substrate, the active regions including a photodiode region and a row-select region, the photodiode and row-select regions each having a doping concentration;
- forming a first isolation region of the second conductivity type in the substrate to adjoin the photodiode region, the first isolation region having a doping concentration substantially less than the doping concentration of the photodiode region;
- forming a second isolation region of the first conductivity type in the substrate to adjoin the first isolation region, the second isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region;
- forming a third isolation region of oxide in the substrate to adjoin the second isolation region;
- forming a fourth isolation region of oxide the first conductivity type in the substrate to adjoin the third isolation region, the fourth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region;
- and
- forming a fifth isolation region of the second conductivity type in the substrate to adjoin the fourth isolation region and the row-select region, the fifth isolation region having a doping concentration which is approximately the same as the doping concentration of the first isolation region.
Dependencies are inferred from the claim text.