Structure of double-bit mask type only-read memory and its making method

Abstract

A double-bit mask mode read-only memory structure and its manufacturing method, the structure includes a substrate; a gate structure, arranged on a part of the substrate; a double-bit coding area, arranged under the two sides of the gate structure In the substrate; at least one spacer is arranged on both sides of the gate structure; a buried drain is arranged in the substrate on both sides of the spacer; a doped region is arranged on the buried drain and the double In the substrate between the bit-coded regions, the ion type of the doped region is opposite to that of the double-bit coded region, and the ion concentration of the doped region is higher than that of the double-bit coded region; an insulating layer, It is arranged above the buried drain; and a word line is arranged on the gate structures in the same row.

Description

technical field [0001] The present invention relates to a structure of a mask-mode read-only memory and a manufacturing method thereof, and in particular to a structure of a double-bit mask-mode read-only memory and a manufacturing method thereof. Background technique [0002] Mask ROM is the most basic type of ROM. It mainly adjusts its threshold voltage (Threshold Voltage) through an ion implantation process to achieve the purpose of controlling the memory cell to be turned on (On) or turned off (Off). When the product of the mask mode ROM is changed, the process does not need to be greatly modified, but only a set of photomasks used is changed, so it is very suitable for mass production, and even semi-finished products with part of the process can be made first. , When the order arrives at the factory, these semi-finished products can be quickly programmed (Programming), which can effectively shorten the delivery time. [0003] A dual bit mask mode ROM is currently unde...

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Problems solved by technology

[0009] However, since the buried drain junction of the known dual-bit mask mode ROM is connected to the dual-bit encoding region, junction leakage is very likely to occur, and the second bit is likely to occur. Effect (Second Bit Effect)

In addition, there is still a problem in the known double-bit mask mode ROM, that is, the memory cells in the memory element are easily interfered by other memory cells around.

And because the storage unit of the known double-bit mask mode read-only memory is easily disturbed by other storage units around and is prone to cause the second bit effect, the operating margin (OperationWindow) of the known memory element is relatively small

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