Semiconductor structures and methods of forming them

Abstract

A semiconductor structure and its forming method, the forming method comprising: providing a substrate, including a cell memory area and a content addressable memory area; forming a gate structure on the substrate, including a tunnel oxide layer and a floating gate structure located on the tunnel oxide layer A gate layer; a first source-drain doped region is formed in the substrate on both sides of the gate structure of the unit memory region; a second source-drain doped region is formed in the substrate on both sides of the gate structure of the content addressable memory region, and the second The doping concentration of the second source-drain doping region is lower than that of the first source-drain doping region. By reducing the doping concentration of the second source-drain doped region, the initial threshold voltage of the content-addressable memory is increased, and the electrons in the floating gate layer in the intrinsic state are correspondingly increased, so trap-assisted tunneling can be improved. effect, thereby improving the data storage capacity of the content addressable memory; in addition, the doping concentration of the first source-drain doping region is not affected, so that the performance of the unit memory region is not affected.

Description

technical field [0001] The invention relates to the field of semiconductor manufacturing, in particular to a semiconductor structure and a forming method thereof. Background technique [0002] At present, flash memory (Flash), also known as flash memory, has become the mainstream of non-volatile memory. According to different structures, flash memory can be divided into two types: Nor Flash and NAND Flash. The main feature of flash memory is that it can keep stored information for a long time without power on, and has the advantages of high integration, fast access speed, easy erasing and rewriting, etc., so it has been widely used in many fields such as microcomputer and automatic control a wide range of applications. [0003] Among them, NAND Flash includes not only cell (Cell) memory, but also content addressable memory (Content Addressable Memory, CAM). Content-addressable memory is a special type of memory that can search the entire memory in a single operation, so i...

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Problems solved by technology

[0004] However, the performance of the prior art content addressable memory needs to be improved

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