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CN-122028432-A - Preparation method of ONO structure of nonvolatile memory with low chlorine content

CN122028432ACN 122028432 ACN122028432 ACN 122028432ACN-122028432-A

Abstract

The invention provides a preparation method of an ONO structure of a nonvolatile memory with low chlorine content. The method comprises the steps of growing an oxide layer on the surface of a substrate by utilizing an in-situ steam generation process, nitriding the oxide layer by utilizing a plasma nitriding process to form a composite structure of a tunneling oxide layer and a step layer, nitriding the composite structure, annealing, and sequentially forming a charge trapping layer and a blocking insulating layer on the composite structure by utilizing a deposition process. According to the invention, the bottom medium is grown by combining a new process instead of the traditional low-voltage furnace tube process, so that the chlorine content in the ONO structure, especially in the tunneling layer and the step layer, is obviously reduced, and the defect energy level is reduced, thereby effectively improving the charge holding capacity, durability and reliability of the nonvolatile memory.

Inventors

  • BAO FENG
  • ZHANG GUANGBING
  • DU MINGFENG

Assignees

  • 华虹半导体制造(无锡)有限公司
  • 华虹半导体(无锡)有限公司

Dates

Publication Date
20260512
Application Date
20260123

Claims (14)

  1. 1. The preparation method of the ONO structure of the nonvolatile memory with low chlorine content is characterized by at least comprising the following steps: Step one, growing an oxide layer on the surface of a substrate; Nitriding the oxide layer by utilizing a plasma nitriding process to form a composite structure of the tunneling oxide layer and the step layer; Step three, annealing the composite structure; Forming a charge trapping layer on the composite structure by using a deposition process; And fifthly, forming a blocking insulating layer on the charge trapping layer by using a deposition process.
  2. 2. The method of claim 1, wherein in step one, the oxide layer is grown by an in situ steam generation process.
  3. 3. The method of claim 2, wherein in the first step, the reaction environment of the in-situ steam generating process is an oxygen and hydrogen atmosphere, the process temperature is 850 ℃ to 1050 ℃, and the process time is 10 seconds to 40 seconds.
  4. 4. The method of claim 1, wherein in the second step, the plasma nitridation process is a decoupled plasma nitridation process, and the step layer is made of silicon oxynitride.
  5. 5. The method of claim 4, wherein in the second step, the power of the decoupled plasma nitridation process is 1200W to 2200W, and the process time is 60 seconds to 120 seconds.
  6. 6. The method of claim 1, wherein in the third step, the annealing treatment is performed by a post-nitridation annealing process to activate nitrogen atoms in the composite structure and repair defects.
  7. 7. The method of claim 6, wherein in the third step, the temperature of the post-nitridation annealing process is 1050 ℃ to 1150 ℃ for 10 seconds to 60 seconds, and the gas flow ratio of nitrogen to oxygen is 20:0.2 to 20:9.
  8. 8. The method of claim 7, wherein in the third step, the temperature of the post-nitridation annealing process is 1100 ℃.
  9. 9. The method of claim 1, wherein in step four, silicon nitride is deposited on the composite structure as the charge trapping layer by using a low-voltage furnace tube.
  10. 10. The method of claim 9, wherein in the fourth step, the process temperature of the low pressure furnace tube is 700 ℃ to 800 ℃, and the reaction gas comprises dichlorosilane and ammonia.
  11. 11. The method of claim 1, wherein in step five, a low voltage furnace is used to deposit silicon oxide as the blocking insulating layer on the charge trapping layer.
  12. 12. The method of claim 11, wherein in the fifth step, the process temperature of the low-pressure furnace tube is 700 ℃ to 800 ℃, and the reaction gas comprises dichlorosilane and nitrous oxide.
  13. 13. The method of claim 1, wherein the tunneling oxide layer and the step layer have a total thickness of 30 to 40 angstroms.
  14. 14. The method of claim 13, wherein the total thickness of the tunneling oxide layer and the step layer is 35 angstroms.

Description

Preparation method of ONO structure of nonvolatile memory with low chlorine content Technical Field The invention relates to the technical field of semiconductors, in particular to a preparation method of an ONO structure of a nonvolatile memory with low chlorine content. Background Flash Memory (Flash Memory) is used as a nonvolatile Memory, has the characteristics of low price, relatively simple process and capability of rapidly performing multiple erasing operations, and is widely applied to various electronic devices. Among them, SONOS (Silicon-Oxide-Nitride-Oxide-Silicon) technology is an important technical route because it can be well compatible with CMOS process, low operating voltage, low manufacturing cost, and the like. The core of the existing SONOS device is its ONO (Oxide-Nitride-Oxide) dielectric stack structure. Conventional ONO structures are typically divided into four layers, from bottom to top, a tunnel Oxide layer (tunnel Oxide), a stair-step layer (STEP LAYER, typically SiON), a charge trapping layer (TRAP LAYER, typically silicon-rich SiON), and a Block Oxide layer (Block Oxide). In the conventional manufacturing process, the four layers of structures are grown by low-pressure furnace tubes to form a composite ONO structure. However, the inventors have found that such conventional low pressure furnace tube processes have significant drawbacks. First, the low pressure furnace process has a relatively high thermal budget and poor film thickness and composition uniformity between and within different wafers, resulting in limited batch throughput and narrow product process window. Second, more critical is that dichlorosilane (SiH 2Cl2, DCS) must generally be used as a reaction gas in the growth of High Temperature Oxide (HTO), silicon oxynitride (SiON) and silicon nitride (SiN) using a low pressure furnace. The chlorine (Cl) element in DCS gas will remain partially in the ONO dielectric layer. These residual Cl elements are easily combined with nitrogen (N) atoms and silicon (Si) atoms to form defects, which results in poor stability of trapped electrons, thereby reducing charge retention capability of SONOS devices, affecting device durability, and possibly even interfering with signal stability during device reading and writing. Therefore, developing a preparation method that can reduce the thermal budget and effectively reduce the Cl element content in the dielectric layer (especially the tunneling layer and the step layer of the bottom layer) so as to improve the reliability of the device is a technical problem to be solved in the field. Disclosure of Invention The invention provides a preparation method of an ONO structure of a nonvolatile memory with low chlorine content, which aims to solve the problems of poor charge holding capacity, low durability and unstable read-write signals of a device caused by high chlorine content in a dielectric layer due to chlorine-containing reaction gas when the ONO structure is prepared by adopting a low-pressure furnace tube process in the prior art. The invention provides a preparation method of an ONO structure of a nonvolatile memory with low chlorine content, which comprises the following steps of growing an oxide layer on the surface of a substrate; Nitriding the oxide layer by utilizing a plasma nitriding process to form a composite structure of the tunneling oxide layer and the step layer; Step three, annealing the composite structure; Forming a charge trapping layer on the composite structure by using a deposition process; And fifthly, forming a blocking insulating layer on the charge trapping layer by using a deposition process. Preferably, in step one, the oxide layer is grown using an in situ water vapor generation process. Preferably, in the first step, the reaction environment of the in-situ steam generation process is an oxygen and hydrogen atmosphere, the process temperature is 850 ℃ to 1050 ℃, and the process time is 10 seconds to 40 seconds. Preferably, in the second step, the plasma nitridation process is a decoupled plasma nitridation process, and the material of the step layer includes silicon oxynitride. Preferably, in the second step, the power of the decoupled plasma nitridation process is 1200W to 2200W, and the process time is 60 seconds to 120 seconds. Preferably, in the third step, the annealing treatment adopts a post-nitridation annealing process, so as to activate nitrogen atoms in the composite structure and repair defects. Preferably, in the third step, the temperature of the post-nitridation annealing process is 1050 ℃ to 1150 ℃, the time is 10 seconds to 60 seconds, and the gas flow ratio of nitrogen to oxygen is 20:0.2 to 20:9. Preferably, in the third step, the temperature of the post-nitridation annealing process is 1100 ℃. Preferably, in step four, silicon nitride is deposited as the charge trapping layer on the composite structure using a low pressure furnace tube. Preferably, in the fourth step, the process