Manufacturing method of flash memory embedded into logic circuit

Abstract

The invention provides a manufacturing method of a flash memory embedded into a logic circuit. When a gate oxide layer of a logic transistor and tunneling insulating layers of the flash memory and a high-voltage floating gate transistor are formed, a buffer oxide layer with relatively low density is removed, so that insulating materials, corroded by an HF acid, in shallow trench isolation structures are relatively few; gaps between the insulating materials and the semiconductor substrate are relatively small; the residual conductive polycrystalline silicon is also relatively little; the adjacent flash memory, high-voltage floating gate transistor and logic transistor extending along the shallow trench isolation structures are not easy to short-circuit; and a process window is relatively large. Furthermore, removal of silicon nitride on the buffer oxide layer is divided into the following two steps of firstly carrying out dry etching on one part of thickness and then removing the remaining thickness through a wet process. The damage to a channel of the logic transistor and the channel of the flash memory or the high-voltage floating gate transistor at the lower part of the buffer oxide layer is avoided.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a manufacturing method of a flash memory embedded in a logic circuit. Background technique [0002] Random access memory, such as DRAM and SRAM, has the problem of data loss after power failure during use. To overcome this problem, various nonvolatile memories have been designed and developed. Recently, flash memory based on floating gate concept has become the most general non-volatile memory due to its small cell size and good performance. [0003] A structure commonly used in flash memory is a stack gate structure. The stacked gate structure memory includes a tunnel insulating layer, a floating gate polysilicon layer (ploy 1) for storing electrons, and an oxide / nitride-oxide (ONO) layer formed sequentially on the substrate. Stack and control gate polysilicon layer (ploy 2) for electron storage and release. [0004] To complete the writing, erasing and reading of the...

AI Technical Summary

Problems solved by technology

[0005] In recent years, with the development of flash memory, in order to improve storage reliability and extend storage life, flash memory is required to have a thicker tunnel insulating layer and a floating gate. To match this, the gate oxide layer of the high-voltage transistor It also needs to be thicker, and the logic transistor of the logic circuit needs a thinner gate oxide layer and gate to achieve a fast response speed, which leads to some problems when making flash memory, high-voltage transistors and logic transistors at the same time

For example, the channel of logic transistors will have pinhole effect, and adjacent logic transistors are prone to short circuits. These problems will lead to low yield of flash memory embedded in logic circuits.

Images