Method of fabricating a stringerless flash memory
AssigneeMacronix International Co., Ltd.
InventorChing-Yu Chang
Life of this patent
Estimating the term…
Abstract
A stringer block is formed on the interface between a HDP silicon oxide layer and a silicon substrate. During an etching process for defining the profile of a floating gate, the stringer block functions to expose a bottom corner stringer. Following that, a polysilicon etching process effectively removes the bottom corner stringer. As a result, a stringerless flash memory cell is formed to prevent leakage currents, resulting from the bottom corner stringer, and improve both the reliability and data retention ability of the device.
Claims13
A method of fabricating a stringerless structure on a semiconductor substrate, the method comprising:
- forming a first layer on the semiconductor substrate;
- forming a spacer on each side wall of the first layer;
- forming a second layer to cover the first layer and the spacer, the second layer being thicker than the first layer;
- forming a patterned photoresist layer on the second layer;
- using the patterned photoresist layer as a mask to perform an anisotropic dry etching process to remove portions of the second layer and the first layer and form a bottom corner stringer beside the spacer;
- removing the spacer to expose the bottom corner stringer;
- and removing the bottom corner stringer.
A method of fabricating a stringerless flash memory, the method comprising:
- providing a semiconductor substrate, the semiconductor substrate comprising a silicon oxide layer;
- forming a plurality of rows of layer stacks on the silicon oxide layer, a shallow trench being formed between two adjacent layer stacks, each layer stack comprising a first polysilicon layer, a sacrificial layer and two side walls;
- forming a spacer on each side wall of the layer stacks, the spacer having a predetermined thickness;
- depositing a high density plasma (HDP) silicon oxide layer to cover the layer stacks and the shallow trenches;
- planarizing the HDP silicon oxide layer to expose the sacrificial layer;
- removing the sacrificial layer and a portion of the spacer, such that a remainder of the spacer forms a stringer block;
- forming a second polysilicon layer on the first polysilicon layer, the first polysilicon layer combining with the second polysilicon layer to form a floating gate layer;
- sequentially forming an insulating layer and a controlling gate layer on the floating gate layer;
- performing an anisotropic dry etching process to remove portions of the controlling gate layer, the insulating layer and the floating gate layer, a bottom corner stringer being formed beside the stringer block during the etching process of the floating gate layer;
- removing the stringer block to expose the bottom corner stringer;
- and removing the bottom corner stringer.
Dependencies are inferred from the claim text.