Study on the purification technology of 4N electronic-grade diethoxymethylsilane

doi:10.11949/0438-1157.20240994

Abstract

Abstract:

In the thin film deposition process of integrated circuits, electronic-grade diethoxymethylsilane (DEMS) is a key precursor for the fabrication of low dielectric constant silicon-based semiconductor films. Its organic purity is required to reach 99.990% (mass, 4N), total metal ion impurity content ≤5.000 μg/L, and individual impurity content ≤0.500 μg/L. It is difficult for the current process to meet the purity requirements, so the complete purification of electronic-grade DEMS is proposed to be purified by the vacuum azeotropic distillation process technology route, and the main work includes: (1) The purification difficulties of DEMS are analyzed through conventional distillation experiments, and carried out vacuum azeotropic distillation experiments to purify the key component impurity ethanol to less than 0.010%(mass), which reduces the purification difficulty of DEMS, and the organic purity reaches 4N; (2) Through conventional vacuum distillation experiments, the total metal ion impurity content ≤5.000 μg/L and individual impurity content ≤0.500 μg/L; (3) A vacuum azeotropic distillation model is established, and the model is verified using experimental results. The vacuum azeotropic distillation process is further established, and the model is used to optimize the design of the new process. The product indices of DEMS obtained from the results of the study have reached the electronic grade standard, which meets the requirements of the integrated circuit manufacturing process and lays a theoretical foundation for the large-scale and low-cost production of electronic-grade DEMS.

Key words: distillation, azeotropy, purification, separation, simulation

摘要：

在集成电路的薄膜沉积工艺中，电子级二乙氧基甲基硅烷(DEMS)是制造低介电常数硅基半导体薄膜的关键前体，要求其有机纯度达到99.990%(质量分数，4N)，总金属离子杂质含量≤5.000 μg/L，单个金属杂质含量≤0.500 μg/L。目前工艺难以达到纯度要求，因此提出了完整的电子级DEMS纯化的减压共沸精馏工艺技术路线，主要工作包括：(1)通过常规精馏实验分析了DEMS的纯化难点，进行减压共沸精馏实验，将关键组分杂质乙醇提纯至0.010%(质量分数)以下，降低了DEMS的纯化难度，有机纯度达到4N；(2)通过常规减压精馏实验探究，实现总金属离子杂质含量≤5.000 μg/L和单个杂质含量≤0.500 μg/L的目标；(3)建立了减压共沸精馏模型，利用实验结果进行模型验证，进一步建立了减压共沸精馏工艺，利用模型对新工艺进行优化设计。研究结果得到的DEMS产品指标达到了电子级标准，满足集成电路制造工艺要求，为规模化、低成本生产电子级DEMS奠定了理论基础。

关键词: 精馏, 共沸, 纯化, 分离, 模拟

CLC Number:

TQ 028.8

Renze SHI, Qiuyan DING, Zhenjun YUAN, Jian NA, Jianhua LIU, Shuhu GUO, Xiong ZHAO, Hong LI, Xin GAO. Study on the purification technology of 4N electronic-grade diethoxymethylsilane[J]. CIESC Journal, 2025, 76(5): 2186-2197.

时任泽, 丁秋燕, 袁振军, 那健, 刘见华, 郭树虎, 赵雄, 李洪, 高鑫. 4N电子级二乙氧基甲基硅烷的纯化技术研究[J]. 化工学报, 2025, 76(5): 2186-2197.

Figures/Tables 18

Table 1 Control standards for organic purity and impurity content of electronic grade DEMS

名称	组分纯度/%	乙醇含量/%	氯离子含量/（mg/L）	单个杂质含量/（μg/L）	总金属离子杂质含量/（μg/L）
电子级DEMS	≥99.990	≤0.010	≤1.000	≤0.500	≤5.000

Fig.1 Main impurities and their contents in industrial grade DEMS

Fig.2 Test results of segmental sampling for atmospheric batch distillation

Fig.3 Test results of segmental sampling after raising the fill height

Fig.4 Test results of vacuum distillation experiments

Fig.5 Detection results at different reflux ratios in vacuum distillation experiments

Fig.6 Liquid/gas molar fraction of n-hexane

Fig.7 Comparison of experimental results of vacuum distillation with and without addition of C6H14

Fig.8 Experimental results when the molar ratio of C6H14 to EtOH is 5∶1

Table 2 The composition and boiling point statistics of impurities in industrial DEMS

序号	组分	沸点/℃	序号	组分	沸点/℃
1	FeCl₂	1023	8	AlCl₃	182
2	FeCl₃	316	9	TiCl₄	135
3	CaCl₂	1600	10	PCl₃	75
4	NaCl	1465	11	POCl₃	105
5	KCl	1420	12	PCl₅	160
6	MgCl₂	1412	13	BCl₃	12
7	ZnCl₂	732	14	B₂Cl₄	55

Fig.9 Comparison of impurity content among raw material, primary distillation and secondary distillation conditions

Table 3 Boiling points of distillation system substances

化合物	分子式	CAS号	分子量	沸点/℃
二乙氧基甲基硅烷	C₅H₁₄O₂Si	2031-62-1	134.25	98
甲基三乙氧基硅烷	C₇H₁₈O₃Si	2031-67-6	178.30	141
四乙氧基硅烷	C₈H₂₀O₄Si	78-10-4	208.33	168
乙醇	C₂H₆O	64-17-5	46.07	78
正己烷	C₆H₁₄	110-54-3	86.18	69

Fig.10 Comparison of simulated and experimental data for different reflux ratios in atmospheric distillation

Fig.11 Comparison of simulated and experimental data for different reflux ratios in decompression distillation

Fig.12 Plots of the effect of N, NF, NA, D/F, FA/FE and R on DEMS recovery, EtOH removal and DEMS organic purity

Table 4 Comparison of four model parameters

模型名称	1#塔参数		2#塔参数		DEMS回收率/%	DEMS有机纯度/%
模型名称	塔板数	回流比	塔板数	回流比	DEMS回收率/%	DEMS有机纯度/%
AD	33	0.40	20	15.85	95	99.968
VD*	29	0.25	90	8.00	84	99.990
VAD	37	2.34	25	0.25	89	99.568
VAD*	65	10.00	13	1.10	91	99.993

Fig.13 Schematic process diagram of 4N electronic-grade DEMS purification technology

Table 5 Technical specifications for 4N DEMS prepared by the as-proposed process

技术指标	要求	实验结果	模拟结果
有机纯度/%	≥99.990	99.993	99.993
乙醇含量/%	≤0.010	0.007	0.002
氯离子含量/(mg/L)	≤1.000	未检出	—
单个杂质含量/(μg/L)	≤0.500	0.322	—
总金属离子杂质含量/(μg/L)	≤5.000	1.240	—

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