Photo diode with dual backside deep trench isolation depth
AssigneeTaiwan Semiconductor Manufacturing Company, Ltd.
InventorYimin Huang
Life of this patent
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Abstract
In some embodiments, the present disclosure relates to an image sensor, including a first photodiode and a second photodiode disposed in a semiconductor substrate. A floating diffusion node is disposed along a frontside of the semiconductor substrate and between the first and second photodiodes. A partial backside deep trench isolation (BDTI) structure is disposed within the semiconductor substrate and between the first and second photodiodes. The partial BDTI extends from a backside of the semiconductor substrate and is spaced from the floating diffusion node. A full BDTI structure extends from the backside of the semiconductor substrate to the frontside of the semiconductor substrate.
Claims20
An image sensor, comprising:
- a first photodiode disposed in a semiconductor substrate;
- a second photodiode disposed in the semiconductor substrate;
- a floating diffusion node disposed along a frontside of the semiconductor substrate between the first photodiode and the second photodiode;
- a partial backside deep trench isolation (BDTI) structure disposed within the semiconductor substrate between the first photodiode and the second photodiode, and extending from a backside of the semiconductor substrate, wherein the partial BDTI structure is spaced from the floating diffusion node;
- a full BDTI structure extending from the backside of the semiconductor substrate to the frontside of the semiconductor substrate;
- a first transfer transistor above the first photodiode and between the full BDTI structure and the partial BDTI structure;
- and
- a second transfer transistor above the second photodiode and between the full BDTI structure and the partial BDTI structure.
An image sensor, comprising:
- a plurality of pixel regions disposed in a semiconductor substrate;
- a floating diffusion (FD) node extending into the semiconductor substrate from a frontside of the semiconductor substrate, wherein the FD node is shared amongst the plurality of pixel regions;
- a partial backside deep trench isolation (BDTI) structure extending from a backside of the semiconductor substrate, underlying the FD node, and spaced from the FD node;
- and
- a full BDTI structure extending from the backside of the semiconductor substrate to the frontside of the semiconductor substrate, wherein the plurality of pixel regions are laterally separated from one another by the full BDTI structure and partial BDTI structure.
A method for forming an image sensor, the method comprising:
- forming a photodiode within a substrate;
- forming a floating diffusion node along a frontside of the substrate and spaced apart from a backside of the substrate;
- forming a first patterned photoresist layer over a hard mask layer on the backside of the substrate;
- performing a first etch of the hard mask layer according to the first patterned photoresist layer to form a first opening in the hard mask layer over the photodiode, wherein the first opening in the hard mask layer has a first width after the first etch;
- performing a second etch according to a second patterned photoresist layer to remove portions of the substrate under the first opening and to thin the hard mask layer over the floating diffusion node, wherein the second patterned photoresist has a second opening over the first opening after the second etch, and wherein the second opening has a second width that is less than the first width;
- performing a third etch to form a full cavity beneath the first opening and a partial cavity over the floating diffusion node, wherein the partial cavity is spaced from the floating diffusion node, and wherein the full cavity extends from the backside of the substrate to the frontside of the substrate;
- and
- filling the partial and full cavities with a fill material.
Dependencies are inferred from the claim text.