Structure and manufacturing method of photomask read-only memory with low n-type buried source-drain resistance

Abstract

The invention discloses a method for manufacturing a mask type read-only memory with low N-type buried source drain resistance. The steps include: 1) forming a shallow isolation trench and performing P-well injection; 2) coating the first N-type buried source drain The photoresist, the distance between the photoresists is smaller than the target size, expose, and implant arsenic ions or phosphorus ions to form the first N-type buried source drain; 3) Remove part of the photoresist so that the distance between the photoresists is equal to the target size ; 4) Perform arsenic ion implantation to form a second N-type buried source and drain connected to the first N-type buried source and drain; 5) Form gate oxide, polysilicon gate and gate isolation sidewalls. The invention also discloses the structure of the mask type read-only memory produced by the above method. The present invention adopts two injection methods to form an N-type buried source and drain with a special T-shaped structure. While keeping the width of the source and drain unchanged and the effective channel length unaffected, the depth of the source and drain is increased, thereby reducing the cost. Source-drain resistance of mask read-only memory.

Description

technical field [0001] The invention relates to the field of integrated circuit manufacturing, in particular to the structure of a mask type read-only memory and its manufacturing method. Background technique [0002] Read-Only Memory (Read-Only Memory) is a memory that can only read data. The data of this memory is written at the time of production. In the manufacturing process, the data is burned into the circuit with a special mask (mask), so it is sometimes called "mask ROM" (mask ROM). In fact, it is very similar to the principle of a CD disc, in which the data state is written in the photolithography process of the semiconductor. [0003] The data of this mask-type read-only memory cannot be changed after writing, so the data cannot be lost, and its manufacturing cost is very low. Therefore, in devices that do not require data update, Mask ROM is very widely used use. [0004] However, the technical disadvantages of this mask-type ROM are also very obvious. Such a...

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Problems solved by technology

At the same time, the gate, source and drain are long strips, and the current path is narrow and long, which greatly limits the read current of the mask type read-only memory, and the circuit is also limited in the speed of reading signals (the RC delay is large )

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