Method for making ROM

Abstract

The invention is a read-only memory making method, forming an electron capture layer structure on a substrate, then patternizing the structure to form plural mouths, successively making a first ion implantation process to form a first doped region on the substrate surface in the mouth, making a second ion implantation process to form a second doped region in the substrate in the mouth, where the doping depth of the first doped region is less than that of the second one, and then forming a buried drain insulating layer on the substrate surface in the mouth.

Description

technical field [0001] The present invention relates to a manufacturing method of a memory, and in particular to a manufacturing method of a read-only memory (Read Only Memory, ROM). Background technique [0002] In read-only memory, flash memory has the advantages of being programmable, erasable, and retaining data after power-off, and compared with erasable and programmable read-only memory, it has the advantages of in-circuit Due to the advantages of electrical programming and electrical removal, it has become a read-only memory device widely used in personal computers and electronic equipment. [0003] In the manufacturing process of the known Silicon Nitride Read Only Memory (Silicon Nitride Read Only Memory), the top oxide layer in the electron capture layer structure (silicon oxide / silicon nitride / silicon oxide stack layer) is usually used with wet hydrogen / oxygen ( h 2 / O 2 gas) to oxidize part of the silicon nitride layer to form a wet oxidation method. However,...

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Problems solved by technology

[0003] In the manufacturing process of the known Silicon Nitride Read Only Memory (Silicon Nitride Read Only Memory), the top oxide layer in the electron capture layer structure (silicon oxide / silicon nitride / silicon oxide stack layer) is usually used with wet hydrogen / oxygen ( h 2 / O 2 gas) to oxidize part of the silicon nitride layer to form a wet oxidation method. However, during the long-term wet oxidation method, part of the nitrogen will diffuse to the interface between the bottom oxide layer and the substrate, resulting in kooi effect

This kooi effect will cause the subsequently formed buried drain insulating layer to have a smaller thickness around the edge, so that leakage current may occur at the edge of the buried drain insulating layer, and the buried drain insulating layer Insufficient thickness at the edge may lead to rupture of the buried drain insulating layer, so that the subsequently formed word line (Word line) may contact with the substrate and short circuit, resulting in reliability problems of the device

[0004] Moreover, if the thickness of the buried drain insulating layer at the edge is insufficient, the electron trapping layer may be in contact with the subsequently formed control gate. Although the electrons in the electron trapping layer are concentrated in a local area, over time The operation will gradually diffuse. At this time, because the electron capture layer is in contact with the control gate, electrons may flow into the control gate along the connected path, resulting in the loss of stored data.

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