US 9,312,293 B2 · Range modulated implants for image sensors

Abstract

Image sensors may include a plurality of photodiodes. The photodiodes may be isolated from each other using isolations regions formed from p-well or n-well implants. Deep and narrow isolation regions may be formed using a multi-step process that selectively places implants at desired depths in a substrate. If desired, the multi-step process may include only one photolithographic patterning step, which in turn can help reduce costs, fabrication time, and alignment errors. The process may include passing ions through a stack of alternating layers of material such as alternating layers of oxide and nitride. After each implant, a layer in the stack may be removed and ions may be passed through the layers remaining in the stack to form an implant at a different depth in the substrate.

Claims17

Dependent claims

A method of forming an image sensor with isolation regions in an image sensor substrate, comprising:

depositing a plurality of layers onto an upper surface of the image sensor substrate, wherein the plurality of layers comprises at least a first layer formed from a first material, a second layer formed from a second material, a third layer formed from a third material, and a fourth layer formed from a fourth material, and wherein the first layer is interposed between the upper surface of the image sensor substrate and the second layer;
implanting a first set of ions into the image sensor substrate through the first and second layers;
after implanting the first set of ions into the image sensor substrate, removing the second layer;
after removing the second layer, implanting a second set of ions into the image sensor substrate through the first layer;
implanting a third set of ions into the image sensor substrate through the first, second, and third layers;
and
implanting a fourth set of ions into the image sensor substrate through the first, second, third, and fourth layers.

4 more elements

A method of forming implants in a substrate having an upper surface, comprising:

implanting a first set of ions in the substrate by passing the first set of ions through a plurality of layers that are formed on and over the upper surface of the substrate, wherein the first set of ions are implanted at a first depth in the substrate;
after implanting the first set of ions in the substrate, removing an uppermost layer in the plurality of layers from the substrate;
implanting a second set of ions in the substrate by passing the second set of ions through a first group of layers that remain on the substrate after removing the uppermost layer, wherein the second set of ions are implanted at a second depth in the substrate and wherein the second depth is greater than the first depth;
after implanting the second set of ions, removing an additional layer from the first group of layers that remain on the substrate;
and
implanting a third set of ions in the substrate by passing the third set of ions through a second group of layers that remain on the substrate after removing the additional layer, wherein the third set of ions are implanted at a third depth in the substrate and wherein the third depth is greater than the second depth.

3 more elements

Dependencies are inferred from the claim text.

Range modulated implants for image sensors

Life of this patent

Range modulated implants for image sensors

Life of this patent

Abstract

Claims17