Well to substrate photodiode for use in a CMOS sensor on a salicide process

A photocell electrically responsive to incident light, comprising:

• a photodiode having a p-n junction between a substrate of a first conductivity type and a well region of a second conductivity type, the well and substrate defining a photosensitive region of said photodiode, the well region being formed in the substrate and having a top substantially covered by a field oxide region being substantially transparent so that incident light can be detected by the photosensitive region, and a tap region of semiconductor material of the second conductivity type in contact with the well, the tap region having a greater dopant concentration than the well to promote electrical contact with the well;
• and
• reset circuitry coupled to the photodiode for initializing the photodiode in preparation for detecting incident light;
• and
• readout circuitry coupled to the photodiode for reading an electrical signal representative of detected light.

An image sensor IC comprising:

• a plurality of photocells arranged in rows and columns, each photocell having a well-to-substrate photodiode and associated reset and readout circuitry, a well of said photodiode having a top being substantially covered by a field oxide region, and a tap region of semiconductor material of the second conductivity type in contact with the well, the tap region having a greater dopant concentration than the well to promote electrical contact with the well;
• a plurality of row decoder/drivers coupled to the photocells for generating a row select signal for a row of photocells;
• and
• a column decoder coupled to the photocells for decoding a column of photocells.

An image capturing system, comprising:

• optical interface exposed to incident light;
• sensor array of photocells electrically responsive to the incident light, each photocell having a well-to-substrate photodiode and associated reset and readout circuitry, a well of said photodiode having a top being substantially covered by a field oxide region, and a tap region of semiconductor material of the second conductivity type in contact with the well, the tap region having a greater dopant concentration than the well to promote electrical contact with the well;
• A/D conversion unit coupled to the sensor array;
• digital signal processing unit coupled to the A/D conversion unit for processing and compressing digital data received from the A/D conversion unit to yield a detected image;
• and
• storage unit coupled to the digital signal processing unit for storing the detected image.

A photodiode for converting incident light into electrical signals, comprising:

• a first region of semiconductor material of a first conductivity type;
• a second region of semiconductor material of a second conductivity type in contact with the first region;
• a p-n junction of the photodiode of defined between the first and second regions, the first and second regions defining a photosensitive region of said photodiode;
• a third region of semiconductor material of the second conductivity type in contact with the second region, the third region having a greater dopant concentration than the second region to facilitate electrical contact with the second region;
• and a field oxide region covering a substantial portion of a top of the second region and receiving the incident light, the oxide region permitting passage of at least some of the incident light into the photosensitive region.