Image sensor pixel and metal shielding of charge storage device of image sensor pixel formed by one step process
View Patent ↗A method is provided for light shielding a charge storage device of an image sensor pixel that includes a photosensitive device and the charge storage device and a dielectric layer covering the photosensitive device and the charge storage device. The method includes performing etching of the dielectric layer to define an undercut volume beneath the dielectric layer and an access opening through the dielectric layer to the undercut volume, and performing physical vapor deposition (PVD) of a light blocking material to both: fill the undercut volume with the light blocking material to form a light blocking layer covering the charge storage device, and fill the access opening with the light blocking material to form a light blocking plug. An image sensor pixel formed by such a process, and an image sensor comprising an array of image sensor pixels, are also disclosed.
1. An image sensor pixel comprising:
a photosensitive device;
a charge storage device;
a charge transfer path that transfers electrical charge from the photosensitive device to the charge storage device;
a light blocking layer disposed over the charge storage device;
a light blocking plug disposed over the charge storage device; and
a dielectric layer disposed over the light blocking layer;
wherein the light blocking plug passes through the dielectric layer and contacts the light blocking layer, and also electrically contacts the charge storage device.
2. The image sensor pixel of claim 1 wherein there is no gap between the light blocking layer and the light blocking plug.
3. The image sensor pixel of claim 1 wherein the light blocking layer and the light blocking plug comprise a contiguous structure.
4. The image sensor pixel of claim 3 wherein the contiguous structure is made of a metal or of a multilayer.
5. The image sensor pixel of claim 1 further comprising:
a shutter gate transistor connected to reset the photosensitive device;
readout circuitry configured to read out electrical charge stored in the charge storage device; and
wherein the charge transfer path includes a transfer gate transistor via.
6. An image sensor comprising an array of image sensor pixels as set forth in claim 5 .
7. The image sensor pixel of claim 1 wherein the dielectric layer includes:
a first dielectric layer of a first material proximate to the charge storage device, and
a second dielectric layer of a second material distal from the charge storage device, the second dielectric material being different from the first dielectric material.
8. The image sensor pixel of claim 7 wherein:
the light blocking layer is disposed in the first dielectric layer,
the second dielectric layer is disposed over the light blocking layer and the first dielectric layer, and
the light blocking plug passes through the second dielectric layer and contacts the light blocking layer.
9. The image sensor pixel of claim 1 wherein the dielectric layer includes:
a borophosphosilicate glass (BPSG) layer proximate to the charge storage device, and
a plasma enhanced tetraethoxysilane (PE-TEOS) layer distal from the charge storage device.
10. The image sensor pixel of claim 9 wherein:
the light blocking layer is disposed in the BPSG layer,
the PE-TEOS layer is disposed over the light blocking layer and the BPSG layer, and
the light blocking plug passes through the PE-TEOS layer and contacts the light blocking layer.
11. An image sensor pixel comprising:
a charge storage device;
a charge transfer path that transfers electrical charge from a photosensitive device to the charge storage device;
a light blocking layer disposed over the charge storage device;
a dielectric layer disposed over the light blocking layer; and
a light blocking plug disposed over the charge storage device and passing through the dielectric layer to provide electrical access to the charge storage device;
wherein the light blocking layer and the light blocking plug comprise a contiguous structure.
12. The image sensor pixel of claim 11 wherein there is no gap between the light blocking layer and the light blocking plug.
13. The image sensor pixel of claim 11 wherein the contiguous structure is made of a metal or of a multilayer.
14. The image sensor pixel of claim 11 wherein the dielectric layer includes:
a first dielectric layer of a first material proximate to the charge storage device, and
a second dielectric layer of a second material distal from the charge storage device, the second dielectric material being different from the first dielectric material.
15. The image sensor pixel of claim 14 wherein:
the light blocking layer is disposed in the first dielectric layer,
the second dielectric layer is disposed over the light blocking layer and the first dielectric layer, and
the light blocking plug passes through the second dielectric layer.
16. The image sensor pixel of claim 14 wherein the dielectric layer includes:
a borophosphosilicate glass (BPSG) layer proximate to the charge storage device, and
a plasma enhanced tetraethoxysilane (PE-TEOS) layer distal from the charge storage device.
17. The image sensor pixel of claim 16 wherein:
the light blocking layer is disposed in the BPSG layer,
the PE-TEOS layer is disposed over the light blocking layer and the BPSG layer, and
the light blocking plug passes through the PE-TEOS layer.
18. An image sensor comprising:
a charge storage device;
a charge transfer path that transfers electrical charge from a photosensitive device to the charge storage device;
a first dielectric layer disposed over the charge storage device;
a second dielectric layer disposed over the first dielectric layer, the second dielectric layer comprising a different material than the first dielectric layer; and
a structure comprising an electrically conductive material, the structure electrically contacting the charge storage device, the structure including a light blocking shield disposed in the first dielectric layer and disposed over the charge storage device.
19. The image sensor of claim 18 , wherein the second dielectric layer is disposed over the light blocking shield.
20. The image sensor of claim 19 , wherein the first dielectric layer is a borophosphosilicate glass (BPSG) layer and the second dielectric layer is a plasma enhanced tetraethoxysilane (PE-TEOS) layer.