1. An imaging device comprising:
at least one pixel cell comprising:
a photosensitive region for accumulating charges;
a charge storage region;
a transfer transistor for transferring accumulated charges from the photosensitive region to the charge storage region; and
a reset transistor for resetting the charge storage region;
a column sample and hold circuit connected to the at least one pixel cell by a column line;
column line biasing circuitry for selectively biasing the column line with a current of one of a first lower level and a second higher level; and
a control circuit for controlling the biasing circuitry such that a resistance on the column line is reduced before a readout of charges from the charge storage region,
wherein a pulse used to set the bias current at the second level during a reset operation is applied during and continues after the reset pulse, and
wherein a pulse used to set the bias current at the second level during a charge transfer operation is applied during and continues after the transfer pulse.
2. The imaging device of claim 1, wherein the control circuit reduces the resistance on the column line by setting the bias current at the second level when the reset transistor and transfer transistor are operational and setting the bias current at the first level when the reset transistor and transfer transistor are no longer operational and before the readout of charges.
3. The imaging device of claim 1, wherein the storage charge region comprises a floating diffusion region.
4. The imaging device of claim 1, wherein the first level is about 100 nA to about 15 \u03bcA.
5. The imaging device of claim 4, wherein the second level is about 25 \u03bcA to about 1 mA.
6. A method of operating an imaging device comprising the acts of:
resetting a floating diffusion region;
pulsing a column line bias current from a first level to a second higher level during and after the resetting of the floating diffusion region; and
sampling a pixel reset signal from the floating diffusion region when the bias current returns to the first level.
7. The method of claim 6, further comprising repeating the pulsing and sampling steps.
8. The method of claim 6, wherein pulsing the bias current is performed by pulsing a bias control voltage signal.
9. The method of claim 6, wherein the first level is about 100 nA to about 15 \u03bcA.
10. The method of claim 9, wherein the second level is about 25 \u03bcA to about 1 mA.
11. The method of claim 6, wherein sampling the pixel signal is performed by pulsing a sample and hold reset control signal.
12. The method of claim 6, wherein resetting the floating diffusion region is performed by pulsing a reset signal.
13. A method of operating an imaging device comprising the acts of:
resetting a floating diffusion region;
reducing a resistance of a column line by pulsing a column line bias current from a first level to a second higher level during and after the resetting of the floating diffusion region;
sampling a pixel reset signal from the floating diffusion region;
transferring a charge from a photosensitive device to the floating diffusion region;
reducing the resistance of the column line by pulsing a column line bias current from a first level to a second higher level during and after the transferring; and
sampling a pixel signal associated with the transferred charge.
14. The method of claim 13, wherein sampling the pixel reset signal occurs when the column line bias current returns to the first level.
15. The method of claim 13, wherein sampling the pixel signal associated with the transferred charge occurs when the column line bias current returns to the first level.
16. The method of claim 13, wherein pulsing the bias current is performed by pulsing a bias control voltage signal.
17. The method of claim 13, wherein the first level is about 100 nA to about 15 \u03bcA.
18. The method of claim 17, wherein the second level is about 25 \u03bcA to about 1 mA.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method comprising:
forming a first sacrificial cavity material over a plurality of electrodes;
planarizing the first sacrificial cavity material;
forming a second sacrificial cavity material on the planarized first sacrificial cavity material;
patterning the first and second sacrificial cavity materials to form an opening aligned with an underlying electrode of the plurality of electrodes;
forming a transparent or substantially transparent material over the first and second sacrificial cavity materials including within the opening and over the underlying electrode;
patterning the transparent or substantially transparent material to form a transparent or substantially transparent window within the first and second sacrificial cavity materials;
polishing an upper surface of the second sacrificial cavity material and remaining portions of the transparent or substantially transparent material formed in additional patterned areas of the first and second sacrificial cavity materials;
prior to form a Micro-Electro-Mechanical System (MEMS) beam, measuring a thickness of the first and second sacrificial cavity materials from a top surface to the underlying electrode through the opening in the first and second sacrificial cavity materials and which is obtained through the transparent or substantially transparent window; and
tuning the thickness of the first and second sacrificial cavity materials after the measuring, the tuning includes depositing additional sacrificial cavity material on the second sacrificial cavity material.
2. The method of claim 1, wherein the forming the transparent or substantially transparent material comprises depositing an oxide material within the opening.
3. The method of claim 1, wherein the opening is sized to avoid dishing of the transparent or substantially transparent material.
4. The method of claim 3, wherein the opening is about 20 to 50 microns in diameter.
5. The method of claim 1, wherein forming the first sacrificial cavity material comprises depositing silicon.
6. The method of claim 1, wherein the opening is aligned with one of the electrodes, and the measurement is a thickness of the first and second sacrificial cavity materials from a top surface to the one of the electrodes.
7. A method comprising:
forming a first sacrificial cavity material over a plurality of electrodes;
planarizing the first sacrificial cavity material;
forming a second sacrificial cavity material on the planarized first sacrificial cavity material;
patterning the first and second sacrificial cavity materials to form an opening aligned with an underlying electrode of the plurality of electrodes;
forming a transparent or substantially transparent material over the first and second sacrificial cavity materials including within the opening and over the underlying electrode;
patterning the transparent or substantially transparent material to form a transparent or substantially transparent window within the first and second sacrificial cavity materials;
polishing an upper surface of the second sacrificial cavity material and remaining portions of the transparent or substantially transparent material formed in additional patterned areas of the first and second sacrificial cavity materials;
prior to form a Micro-Electro-Mechanical System (MEMS) beam, measuring a thickness of the first and second sacrificial cavity materials from a top surface to the underlying electrode through the opening in the first and second sacrificial cavity materials and which is obtained through the transparent or substantially transparent window; and
tuning the thickness of the first and second sacrificial cavity materials after the measuring, the tuning includes planarizing the second sacrificial cavity material.
8. The method of claim 1, further comprising tuning the thickness of the second sacrificial cavity material after the measuring which occurs in the MEMS structure and a test structure on a same wafer.
9. The method of claim 8, wherein tuning the thickness in the MEMS structure and the test structure occurs at a same time through one of a polishing process and deposition of additional sacrificial cavity material.
10. The method of claim 8, further comprising forming a MEMS beam on the tuned sacrificial cavity material of the MEMS structure, wherein:
the MEMS beam is tuned by measuring a transparent or substantially transparent insulator material between an upper and lower electrode; and
planarizing the transparent or substantially transparent insulator material or depositing additional transparent or substantially transparent insulator material based on the measurement.
11. A method of forming a test structure and a Micro-Electro-Mechanical System (MEMS) structure, comprising the following steps in sequence:
forming a plurality of electrodes on a substrate;
forming a sacrificial material on the substrate and over the plurality of electrodes;
planarizing the sacrificial material;
adding additional sacrificial material over the sacrificial material;
patterning the additional sacrificial material and the sacrificial material to form a MEMS cavity structure and an opening aligned with a single electrode of the plurality of electrodes;
forming a transparent or substantially transparent material over and adjacent the MEMS cavity structure and within the opening, contacting the single electrode of the plurality of electrodes;
patterning the transparent or substantially transparent material over the MEMS cavity structure, leaving the transparent or substantially transparent material within the opening;
planarizing the MEMS cavity structure and remaining portions of the transparent or substantially transparent material on the MEMS cavity structure and adjacent thereto;
measuring a thickness of the sacrificial material and the additional sacrificial material through the transparent or substantially transparent material within the opening, from a top of the additional sacrificial material to the single electrode of the plurality of electrodes;
tuning a thickness of the MEMS cavity structure based on a measurement taken of the transparent or substantially transparent material through the opening; and
forming a MEMS beam on the tuned MEMS cavity structure and tuning the MEMS beam by first measuring an insulator material of the MEMS beam and then adjusting its thickness.
12. The method of claim 11, wherein forming the transparent or substantially transparent material comprises depositing an oxide material within the opening.
13. The method of claim 12, wherein the opening is sized to avoid dishing of the oxide material.
14. The method of claim 11, wherein tuning the thickness comprises planarizing the MEMS cavity structure.
15. The method of claim 11, wherein tuning the thickness includes depositing additional sacrificial cavity material on the MEMS cavity structure.
16. The method of claim 11, wherein tuning the thickness occurs in the MEMS structure and the test structure on a same wafer.
17. The method of claim 11, wherein the opening is aligned with one of the electrodes, and the measurement is a thickness of the MEMS cavity structure from a top surface to the one of the electrodes.