Preparation of tungsten-based thin films using a F-free W precursor and tert-butyl hydrazine via 2- and 3-step atomic layer deposition process

Lee, Jin-Hyeok; Hidayat, Romel; Ramesh, R.; Roh, Hyeonsu; Nandi, Dip K.; Lee, Wonjun; Kim, Soo‐Hyun

doi:10.1016/j.apsusc.2021.152062

Cited by 2 publications

(1 citation statement)

References 56 publications

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“…向: 1)通过改变钨栅沉积前驱体来减少钨栅中的氟含量, 例如Bakke等 [6] 提出的无氟前驱体(WCl x ) 与Lee等 [7] 提出的金属有机物前驱体, 然而此类前驱体会引入新的杂质, 且增加了工艺成本, 因而没有得到广泛应用; 2)增大F阻挡层厚度, 例如Subr-amaniyan等 [8] 进行了增加TiN厚度的实验, 但在下的Perdew-Burke-Ernzerh (PBE)泛函 [9,10] 来描述核与电子之间的交换关联作用. 使用投影扩充波(PAW)方法 [11] 描述H, B, N, O, F和TiN元素的核与价电子.…”

Section: 目前改善氟攻击问题的方法主要有3个方unclassified

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

Fang,

Yang,

Xia

et al. 2024

Acta Phys. Sin.

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3D NAND flash memory stands as a pivotal technology in the domain of mainstream memory solutions, primarily due to its exceptionally low bit cost. The architecture of 3D NAND, characterized by its vertically stacked design, substantially enhances the capacity of individual chips. This advancement aligns perfectly with the demands for high-capacity data storage in contemporary settings, securing its widespread adoption across diverse application scenarios. As storage densities increase, so does the complexity of process integration, introducing new challenges. The word lines in 3D NAND are typically filled using gate replacement techniques, with Atomic Layer Deposition (ALD) favored for its superior step-coverage, especially for depositing tungsten (W) at the gate, compared to Chemical Vapor Deposition (CVD). However, due to the complexity of the replacement gate deposition structure, fluorine (F) residues are found in the voids of the tungsten metal gate filling structure and diffuse into the surrounding structure under subsequent process conditions, corroding other films such as silicon oxide and degrading device performance and reliability. To ameliorate the fluorine attack problem, a thin layer of titanium nitride is usually deposited as a barrier layer before tungsten gate deposition, which blocks the fluorine in the tungsten gate and prevents it from diffusing into the oxide layer. Previously, there are studies to increase the ability to stop F diffusion by varying the thickness of the F blocking layer (TiN). However, increasing the thickness of TiN will further exacerbate the complexity of high aspect ratio etching in the 3D NAND process, thereby adversely affecting subsequent processes. To further minimize the effect of fluorine attack, residual fluorine elements can also be expelled by introducing annealing in the subsequent process stream. In the actual 3D NAND process, elemental fluorine (F) is adsorbed and accumulates on the TiN surface, and is further activated by subsequent high-temperature processes, leading to severe fluorine attack. The delay between TiN deposition and subsequent processing steps is hypothesized to facilitate fluorine adsorption due to the oxidation of TiN. This paper corroborates the hypothesis through first-principles calculations, demonstrating the role of TiN oxidation in fluorine adsorption. This paper evaluates the impact of this oxidation on the fluorine-blocking effectiveness of the TiN barrier layer. We simulate the adsorption of fluorine-containing by-products on TiN and its oxides, providing theoretical insights into mitigating fluorine attack. The higher degree of TiN oxidation is more likely to cause F adsorption, and Ti exposed surface TiN is more prone to oxidation, which is more likely to cause F adsorption in both unoxidized and oxidized conditions. Based on these insights, we implemented an ammonia purge treatment in 3D NAND manufacturing, which effectively minimized fluorine attack, reducing word line leakage probability by 25 % and wafer warpage by 43 %.

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Section: 目前改善氟攻击问题的方法主要有3个方unclassified

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

Fang,

Yang,

Xia

et al. 2024

Acta Phys. Sin.

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Improvement of fluorine attack induced word-line leakage in 3D NAND flash memory

Fang,

Xia,

Yang

et al. 2024

Acta Phys. Sin.

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This study explores the impact of fluorine (F) erosion on the tungsten (W) gate process and proposes measures to mitigate the word line (WL) leakage resulting from F erosion in 3D NAND flash memory. As the number of layers in 3D NAND increases, the tungsten (W) gate word line (WL) layer fill process becomes more challenging during the post-gate process. As the fill path length increases, the tungsten gates become more susceptible to voiding during deposition, resulting in the accumulation of fluorine (F) by-products, and causing fluorine attack issues. In particular, under the influence of subsequent high-temperature processes, the by-products containing fluorine can diffuse into the surrounding structure and corrode the surrounding oxide layer. This leads to WL leakage, thereby affecting device yield and reliability. This paper begins by analyzing the microscopic principles of fluorine erosion in 3D NAND. We also propose a low-pressure annealing method to address the issue of fluorine erosion. Then, we conducted annealing experiments on planar thin film stacks and 3D filled structures under both atmospheric and low-pressure conditions. We used various methods to characterize the concentration and distribution of residual fluorine elements. The experimental results demonstrate that residual fluorine elements in the tungsten gate can be effectively discharged by low-pressure annealing under appropriate conditions, thus reducing the leakage index of the word line. Additionally, as the outer CH is closer to the fluorine discharge channel, the impact of low-pressure annealing on the outer CH is more pronounced than on the inner CH. Low-pressure annealing can significantly reduce the fluorine content in the tungsten gate. This method can also mitigate the issue of fluorine attack oxides and decrease WL leakage. Using low-pressure annealing treatment can also enhance the quality of 3D NAND flash technology.

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Preparation of tungsten-based thin films using a F-free W precursor and tert-butyl hydrazine via 2- and 3-step atomic layer deposition process

Cited by 2 publications

References 56 publications

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

First-principles study of F adsorption by TiN with its oxide surface in three-dimensional NAND flash memory

Improvement of fluorine attack induced word-line leakage in 3D NAND flash memory

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