UV-programmed P-type Mask ROM and fabrication thereof
AssigneeMacronix International Co., Ltd.
InventorsTung-Cheng Kuo, Chien-Hung Liu, Shyi-Shuh Pan, Shou-Wei Huang
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Abstract
A method for fabricating an UV-programmed P-type Mask ROM is described. The threshold voltages of all memory cells are raised at first to make each memory cell be in a first logic state, in which the channel is hard to switch on, in order to prevent a leakage current. After the bit lines and the word lines are formed, the Mask ROM is programmed by irradiating the substrate with UV light to inject electrons into the ONO layer under the openings to make the memory cells under the openings be in a second logic state.
Claims13
A method for fabricating an ultraviolet-programmed P-type Mask ROM, comprising the steps of:
- forming a heavily doped N-well in a substrate;
- forming a charge trapping layer on the substrate;
- forming a plurality of bit lines in the heavily doped N-well;
- forming an insulating layer on the bit lines;
- forming a conductive layer on the substrate;
- patterning the conductive layer to form a plurality of word lines crossing over the bit lines, wherein the substrate under a word line and between two bit lines serves as a memory cell;
- forming an ultraviolet-blocking layer over the substrate, the ultraviolet-blocking layer having a plurality of openings therein over selected memory cells;
- and
- writing the selected memory cells by using ultraviolet light.
Dependencies are inferred from the claim text.