Method for making a flash memory device
Flash memory technology is disclosed. In one example, a flash memory cell can include a charge storage structure, a control gate laterally separated from the charge storage structure, and at least four dielectric layers disposed between the control gate and the charge storage structure. Associated systems and methods are also disclosed.
1. A method for making a flash memory device, comprising:
forming at least four dielectric layers between adjacent, vertically spaced apart insulative layers, the at least four dielectric layers including a first layer, a second layer, a third layer and a fourth layer, wherein the first layer is adjacent and directly coupled to a control gate between the insulative layers;
forming a vertically oriented conductive channel extending through the vertically spaced apart insulative layers; and
forming a charge storage structure adjacent and directly coupled to the second layer, such that the charge storage structure is laterally separated from the control gate and between the control gate and the vertically oriented conductive channel, and the at least four dielectric layers are between the control gate and the charge storage structure, wherein:
the second layer includes a nitride material;
portions of the second layer are adjacent to at least portions of three sides of the charge storage structure such that the portions of the second layer are disposed between the charge storage structure and the spaced apart insulative layers; and
the third layer is adjacent the second layer, and the fourth layer is between the third layer and the first layer.
2. The method of claim 1 , wherein the second layer of the at least four dielectric layers has a thickness of from about 1 nm to about 5 nm.
3. The method of claim 1 , wherein a ratio of a thickness of the second layer to a thickness of a third layer of the at least four dielectric layers is from about 1:2 to about 1:5.
4. The method of claim 1 , wherein the at least four dielectric layers are configured to provide a program-erase window that is sufficient for operation of a quad level cell (QLC).
5. The method of claim 1 , wherein the at least four dielectric layers are configured to provide a band gap that is sufficient for operation of a quad level cell (QLC).
6. The method of claim 1 , wherein the charge storage structure is a floating gate or a charge trap.
7. The method of claim 1 , further comprising forming a tunnel dielectric layer on the charge storage structure.
8. The method of claim 1 , wherein portions of at least one of the third layer or the fourth layer are disposed between the charge storage structure and the spaced apart insulative layers.
9. The method of claim 8 , wherein at least one of the third layer or the fourth layer include a nitride material.
10. The method of claim 1 , wherein the at least four dielectric layers include alternating layers of oxide material and nitride material.
11. The method of claim 1 , wherein the portions of the second layer are adjacent to at least portions of more than three sides of the charge storage structure in a same plane.