Active photosensitive structure with buried depletion layer
AssigneeMicron Technology, Inc.
InventorsDmitri Jerdev, Nail Khaliullin
Life of this patent
Estimating the term…
Abstract
An imager pixel has a photosensitive JFET structure having a channel region located above a buried charge accumulation region. The channel region has a resistance characteristic that changes depending on the level of accumulated charge in the accumulation region. During an integration period, incident light causes electrons to be accumulated inside the buried accumulation region. The resistance characteristic of the channel region changes in response to a field created by the charges accumulated in the accumulation region. Thus, when a voltage is applied to one side of the channel, the current read out from the other side is characteristic of the amount of stored charges.
Claims22
A method of forming a pixel sensor comprising steps of:
- forming a photosensitive JFET having a gate region buried beneath a top surface of a substrate;
- forming a channel region located above the gate region;
- and
- forming circuitry electrically coupled to the channel region for reading out a signal representing the amount of charges generated by the photosensitive JFET.
A method of forming a photosensor, comprising:
- forming a light striking region;
- forming a JFET gate region comprising an accumulation region for changing a resistance of a JFET channel region by accumulating charges generated in response to light received by the light striking region;
- and
- forming the JFET channel region above the JFET gate region.
A method of forming a pixel sensor cell, comprising:
- forming a photosensitive element for generating charges in response to applied light;
- forming a JFET gate region comprising an accumulation region for accumulating an amount of charges generated by the photosensitive element;
- and
- forming a JFET channel region above the JFET gate region, the JFET channel region having a changeable resistance dependent upon the amount of charges in the accumulation region.
A method of forming a pixel sensor cell, comprising:
- forming a photosensitive element at least partially in a substrate, the photosensitive element for generating an amount of charges in response to applied light;
- forming a JFET channel region located beneath the top surface of the substrate;
- forming a JFET gate region beneath a top surface of the substrate and under the JFET channel region, the JFET gate region including a charge accumulation region adapted to vary a resistance characteristic of the JFET channel region by accumulating the amount of charges generated by the photosensitive element;
- forming a first contact electrically connected to the JFET channel region and for reading out a signal representing a current flowing through the channel region;
- and
- forming a transistor for draining the accumulated charges from the charge accumulation region to a drain region.
A method of forming an array of pixel sensor cells, comprising:
- forming a plurality of pixel sensor cells in a substrate;
- forming a JFET gate region comprising an accumulation region in at least one pixel cell, the accumulation region for accumulating an amount of charges generated by a photosensor of the at least one pixel cell and located beneath a top surface of the substrate;
- and
- forming a JFET channel region in the at least one pixel cell, the JFET channel region located above the JFET gate region and having a resistance adapted to change in response to the amount of charges accumulated in the accumulation region.
Dependencies are inferred from the claim text.