Structure of mask ROM and method for manufacturing the same

Abstract

A mask read-only memory structure and its manufacturing method, the structure includes a substrate; a plurality of gates arranged above part of the substrate; a gate dielectric layer arranged between the substrate and the gate; An embedded bit line is arranged in the substrate on both sides of the gate; an insulating layer is arranged above the buried bit line and between the gate; a plurality of word lines, each word line is perpendicular to the embedded bit line The direction of the bit lines is arranged on the same row of gates and on the insulating layer; and a coding layer is arranged between the word lines and the gates.

Description

technical field [0001] The present invention relates to a memory structure and its manufacturing method, and in particular to a mask read-only memory (Mask ROM) structure and its manufacturing method. Background technique [0002] A general mask ROM structure includes several bit lines (Bit Line, BL) and several polysilicon word lines (Word Line, WL) across the bit lines. The area below the word line and between two adjacent bit lines is the channel area of ​​the memory cell. For some mask ROMs, the programming method is to store data "0" or "1" by implanting ions in the channel or not. The manufacturing process of implanting ions in specific channel regions is also called code implantation manufacturing process. [0003] Generally, in the manufacturing process of mask ROM code implantation, firstly, a photomask is used to pattern the photoresist layer formed on the substrate, so as to expose the channel region to be coded. Then, an ion implantation manufacturing process ...

AI Technical Summary

Problems solved by technology

However, boron ions implanted in the channel region easily diffuse into the buried bit lines on both sides

In addition, if the code mask used in the code implantation process has misalignment or critical dimension deviation, the code ions originally planned to be implanted in the channel region will also diffuse to the buried bit line. middle

The above two situations will cause the ion concentration in the buried bit line to change, so that the current of the buried bit line will be insufficient.

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