A method for preparing electronic-grade hydrofluoric acid for semiconductors

Abstract

This invention discloses a method for preparing electronic-grade hydrofluoric acid for semiconductors, comprising the following steps: a. Liquid anhydrous hydrogen fluoride raw material is preheated and vaporized. After vaporization, the hydrogen fluoride passes sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column, causing some sodium fluoride to be converted into sodium hydrogen fluoride. The unadsorbed tail gas is absorbed by sodium hydroxide alkaline solution; b. The sodium fluoride adsorption column undergoes a first-stage heating process to desorb free water and silicon tetrafluoride gas, and is held at this temperature for 1 hour. The desorbed gas enters the tail gas absorption; c. The sodium fluoride adsorption column is further heated for a second-stage desorption of hydrogen fluoride, and held at this temperature for 1 hour, causing sodium hydrogen fluoride to decompose into high-temperature hydrogen fluoride gas; d. The high-temperature hydrogen fluoride gas from step c is absorbed and prepared with ultrapure water to form crude hydrofluoric acid, which is then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. This invention features a short production process, low energy consumption, and recyclable adsorption materials. Compared with traditional processes, it has lower production costs, better quality, and significant economic benefits.

Description

Technical Field

[0001] This invention relates to a method for preparing electronic-grade hydrofluoric acid for semiconductors. Background Technology

[0002] Electronic-grade hydrofluoric acid is a strong acidic cleaning and etching agent, mainly used in three major fields: solar photovoltaic, liquid crystal displays, and semiconductors. Different application fields have different product quality requirements. Electronic-grade hydrofluoric acid products suitable for the semiconductor industry must meet or exceed UPSS grade, with all cation contents below 0.1 ppb. Currently, only two companies in China possess the technology to prepare electronic-grade hydrofluoric acid for semiconductors.

[0003] Electronic-grade hydrofluoric acid is prepared using anhydrous hydrogen fluoride as raw material, followed by oxidation to remove impurities, multi-stage light and heavy component removal by distillation, and finally blending with ultrapure water. The higher the product grade, the more distillation stages are required. Typically, semiconductor-grade electronic-grade hydrofluoric acid requires three-stage distillation, i.e., three sets of light and heavy component removal distillation columns.

[0004] Chinese invention patent application number 200610096593.1 discloses a method for preparing ultrapure high-purity hydrofluoric acid, specifically disclosing that "anhydrous hydrogen fluoride liquid is used for distillation purification, and KMnO4 solution is added as a purification agent, with the amount added being 1-5% of the raw material anhydrous hydrogen fluoride liquid. The distillation temperature is 19-35℃, and the hydrogen fluoride gas purified by distillation is absorbed with ultrapure water and then filtered through ultrapure water to produce ultrapure high-purity hydrofluoric acid."

[0005] For example, Chinese invention patent application number 201310637338.3 discloses a method for preparing ultrapure electronic-grade hydrofluoric acid, specifically disclosing "the following steps: raw material pretreatment: converting As elements in the raw material HF into HAsF6 and AsF5; gasification distillation treatment: removing impurities; filtration absorption: removing particles with a particle size greater than 0.2μm, thereby obtaining high-purity electronic-grade hydrofluoric acid with a mass percentage concentration of 49±0.2%".

[0006] However, the above methods all involve pretreating hydrogen fluoride with oxidants and then separating it through multi-stage distillation to improve product purity. These methods have long processes, large equipment investments, are difficult to control in terms of quality, and have high production costs. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for preparing electronic-grade hydrofluoric acid for semiconductors that features a streamlined process, low equipment investment, minimal quality control difficulty, and low production cost.

[0008] The technical solution adopted by this invention to solve its technical problem is:

[0009] A method for preparing electronic-grade hydrofluoric acid for semiconductors includes the following steps:

[0010] Liquid anhydrous hydrogen fluoride raw material is preheated and vaporized, and then passed through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column in sequence.

[0011] The primary sodium fluoride adsorption column is heated and desorbed in one stage to remove free water and silicon tetrafluoride gas, and then kept at the temperature. The desorbed gas enters the tail gas absorption.

[0012] The secondary sodium fluoride adsorption column is heated further and subjected to two-stage desorption of hydrogen fluoride, and then kept at the temperature to decompose sodium hydrogen fluoride into high-temperature hydrogen fluoride gas.

[0013] The obtained high-temperature hydrogen fluoride gas was absorbed and mixed with ultrapure water to form crude hydrofluoric acid, which was then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors.

[0014] High-purity sodium fluoride is added to the primary and secondary sodium fluoride adsorption columns. This high-purity sodium fluoride is in the form of spherical particles or flakes, with a purity greater than 99.6%, a silica content of less than 0.1%, and a moisture content of less than 0.01%.

[0015] The vaporization temperature for preheating and vaporizing liquid anhydrous hydrogen fluoride feedstock is 40–80°C.

[0016] The vaporization temperature for preheating and vaporizing liquid anhydrous hydrogen fluoride feedstock is 50–60°C.

[0017] The heating temperature for the first-stage sodium fluoride adsorption column during the desorption process is 100–120 °C.

[0018] The secondary sodium fluoride adsorption column is heated to a temperature of 160–250 °C for two-stage desorption.

[0019] The temperature for heating and two-stage desorption of the secondary sodium fluoride adsorption column is 200–220 °C.

[0020] The concentration of the crude hydrofluoric acid was 49%.

[0021] The crude hydrofluoric acid was filtered using a 3μm pore size membrane.

[0022] The beneficial effects of this invention are:

[0023] By utilizing the selective adsorption and desorption of hydrogen fluoride by sodium fluoride, efficient separation of hydrogen fluoride from other impurities is achieved. The product quality is superior to existing oxidation-removal + distillation separation processes, meeting the quality requirements of electronic-grade hydrofluoric acid for semiconductors and showing better market application prospects. The production process eliminates the traditional oxidation-removal process. Compared to the traditional three-stage distillation and six-stage separation process, this process only requires two stages of adsorption, significantly shortening the process flow and effectively reducing equipment investment. The high-purity sodium fluoride used is recyclable, generating no hazardous waste, making it more environmentally friendly, while traditional distillation processes produce a large amount of PFA packing waste. The production process is short, energy-efficient, and the adsorption material is recyclable, resulting in lower production costs and significant economic benefits compared to traditional processes. Attached Figure Description

[0024] Figure 1 This is a flowchart of a method for preparing electronic-grade hydrofluoric acid for semiconductors according to the present invention. Detailed Implementation

[0025] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] Example 1

[0028] See Figure 1 As shown, a method for preparing electronic-grade hydrofluoric acid for semiconductors includes the following steps:

[0029] Step a: Adsorption: 1 kg of liquid anhydrous hydrogen fluoride feedstock is preheated and vaporized to 40°C. After vaporization, the hydrogen fluoride is passed sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column, causing some sodium fluoride to be converted into sodium hydrogen fluoride. 2 kg of high-purity sodium fluoride spherical particles are added to both the primary and secondary adsorption columns. The unadsorbed tail gas is absorbed by sodium hydroxide alkaline solution, and the absorbent is evaporated and concentrated to recover sodium fluoride.

[0030] Step b: First-stage desorption: The sodium fluoride adsorption column is heated to 100°C for a first stage to desorb free moisture and silicon tetrafluoride gas, and held at this temperature for 1 hour. The desorbed gas enters the tail gas absorption.

[0031] Step c: Two-stage desorption: The sodium fluoride adsorption column is heated to 160°C for two-stage desorption of hydrogen fluoride, and kept at this temperature for 1 hour to decompose the sodium fluoride into high-temperature hydrogen fluoride gas.

[0032] Step d: Preparation and filtration: The high-temperature hydrogen fluoride gas from step c is absorbed and prepared into a crude 49% hydrofluoric acid product using ultrapure water, and then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. The pore size of the filter membrane is 3μm.

[0033] The properties of the electronic-grade sodium fluoride for semiconductors prepared in this embodiment are shown in Table 1.

[0034] Example 2

[0035] See Figure 1 As shown, a method for preparing electronic-grade hydrofluoric acid for semiconductors includes the following steps:

[0036] Step a: Adsorption: 1 kg of liquid anhydrous hydrogen fluoride feedstock is preheated and vaporized to 50°C. After vaporization, the hydrogen fluoride is passed sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column, causing some of the sodium fluoride to be converted into sodium hydrogen fluoride. 2 kg of high-purity sodium fluoride spherical particles are added to both the primary and secondary adsorption columns. The unadsorbed tail gas is absorbed by sodium hydroxide alkaline solution, and the absorbent is evaporated and concentrated to recover sodium fluoride.

[0037] Step b: First-stage desorption: The sodium fluoride adsorption column is heated to 110°C to desorb free moisture and silicon tetrafluoride gas, and held at this temperature for 1 hour. The desorbed gas enters the tail gas absorption.

[0038] Step c: Two-stage desorption: The sodium fluoride adsorption column is heated to 200℃ for two-stage desorption of hydrogen fluoride, and kept at this temperature for 1 hour to decompose the sodium fluoride into high-temperature hydrogen fluoride gas.

[0039] Step d: Preparation and filtration: The high-temperature hydrogen fluoride gas from step c is absorbed and prepared into a crude 49% hydrofluoric acid product using ultrapure water, and then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. The pore size of the filter membrane is 3μm.

[0040] The properties of the electronic-grade sodium fluoride for semiconductors prepared in this embodiment are shown in Table 1.

[0041] Example 3

[0042] See Figure 1 As shown, a method for preparing electronic-grade hydrofluoric acid for semiconductors includes the following steps:

[0043] Step a: Adsorption: 1 kg of liquid anhydrous hydrogen fluoride feedstock is preheated and vaporized to 60°C. After vaporization, the hydrogen fluoride is passed sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column, converting some of the sodium fluoride into sodium hydrogen fluoride. 2 kg of high-purity flake sodium fluoride is added to each of the primary and secondary adsorption columns. The unadsorbed tail gas is absorbed by sodium hydroxide alkaline solution, and the absorbent is evaporated and concentrated to recover sodium fluoride.

[0044] Step b: First-stage desorption: The sodium fluoride adsorption column is heated to 110°C to desorb free moisture and silicon tetrafluoride gas, and held at this temperature for 1 hour. The desorbed gas enters the tail gas absorption.

[0045] Step c: Two-stage desorption: The sodium fluoride adsorption column is heated to 220℃ for two-stage desorption of hydrogen fluoride, and kept at this temperature for 1 hour to decompose the sodium fluoride into high-temperature hydrogen fluoride gas.

[0046] Step d: Preparation and filtration: The high-temperature hydrogen fluoride gas from step c is absorbed and prepared into a crude 49% hydrofluoric acid product using ultrapure water, and then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. The pore size of the filter membrane is 3μm.

[0047] The properties of the electronic-grade sodium fluoride for semiconductors prepared in this embodiment are shown in Table 1.

[0048] Example 4

[0049] See Figure 1 As shown, a method for preparing electronic-grade hydrofluoric acid for semiconductors includes the following steps:

[0050] Step a: Adsorption: 1 kg of liquid anhydrous hydrogen fluoride feedstock is preheated and vaporized to 80°C. After vaporization, the hydrogen fluoride is passed sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column, causing some sodium fluoride to be converted into sodium hydrogen fluoride. 2 kg of high-purity flake sodium fluoride is added to each of the primary and secondary adsorption columns. The unadsorbed tail gas is absorbed by sodium hydroxide alkaline solution, and the absorbent is evaporated and concentrated to recover sodium fluoride.

[0051] Step b: First-stage desorption: The sodium fluoride adsorption column is heated to 120°C to desorb free moisture and silicon tetrafluoride gas, and held at this temperature for 1 hour. The desorbed gas enters the tail gas absorption.

[0052] Step c: Two-stage desorption: The sodium fluoride adsorption column is heated to 250°C for two-stage desorption of hydrogen fluoride, and kept at this temperature for 1 hour to decompose the sodium fluoride into high-temperature hydrogen fluoride gas.

[0053] Step d: Preparation and filtration: The high-temperature hydrogen fluoride gas from step c is absorbed and prepared into a crude 49% hydrofluoric acid product using ultrapure water, and then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. The pore size of the filter membrane is 3μm.

[0054] The properties of the semiconductor-grade hydrofluoric acid prepared in this embodiment are shown in Table 1.

[0055] Table 1. Analysis results of the electronic-grade hydrofluoric acid for semiconductors produced according to this invention.

[0056]

[0057] As shown in Table 1, the electronic-grade hydrofluoric acid for semiconductors prepared in this application all meet industry standards.

[0058] The beneficial effects of this invention are:

[0059] By utilizing the selective adsorption and desorption of hydrogen fluoride by sodium fluoride, efficient separation of hydrogen fluoride from other impurities is achieved. The product quality is superior to existing oxidation-removal + distillation separation processes, meeting the quality requirements of electronic-grade hydrofluoric acid for semiconductors and showing better market application prospects. The production process eliminates the traditional oxidation-removal process. Compared to the traditional three-stage distillation and six-stage separation process, this process only requires two stages of adsorption, significantly shortening the process flow and effectively reducing equipment investment. The high-purity sodium fluoride used is recyclable, generating no hazardous waste, making it more environmentally friendly, while traditional distillation processes produce a large amount of PFA packing waste. The production process is short, energy-efficient, and the adsorption material is recyclable, resulting in lower production costs and significant economic benefits compared to traditional processes.

[0060] The above embodiments of the present invention are not intended to limit the scope of protection of the present invention. The implementation of the present invention is not limited thereto. All other modifications, substitutions or alterations made to the above structure of the present invention based on the above content of the present invention, in accordance with ordinary technical knowledge and common practice in the field, without departing from the basic technical idea of ​​the present invention, shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing electronic-grade hydrofluoric acid for semiconductors, characterized in that, Includes the following steps: Liquid anhydrous hydrogen fluoride raw material is preheated and vaporized, and then passed sequentially through a primary sodium fluoride adsorption column and a secondary sodium fluoride adsorption column. The sodium fluoride adsorption column is heated and undergoes a first-stage desorption of free water and silicon tetrafluoride gas, and the temperature is maintained. The desorbed gas enters the tail gas absorption. The sodium fluoride adsorption column is further heated and undergoes a second-stage desorption of hydrogen fluoride, and the temperature is maintained, causing the sodium fluoride to decompose into high-temperature hydrogen fluoride gas. The obtained high-temperature hydrogen fluoride gas is absorbed and prepared with ultrapure water to form crude hydrofluoric acid, which is then filtered through a membrane to obtain electronic-grade hydrofluoric acid for semiconductors. High-purity sodium fluoride is added to the primary and secondary sodium fluoride adsorption columns. The high-purity sodium fluoride is in the form of spherical particles or flakes, with a purity greater than 99.6%, a silicon dioxide content less than 0.1%, and a moisture content less than 0.01%. The heating temperature for the first-stage desorption is 100–120°C, and the heating temperature for the second-stage desorption is 160–250°C.

2. The method for preparing electronic-grade hydrofluoric acid for semiconductors according to claim 1, characterized in that: The vaporization temperature for preheating and vaporizing liquid anhydrous hydrogen fluoride feedstock is 40–80°C.

3. The method for preparing electronic-grade hydrofluoric acid for semiconductors according to claim 1 or 2, characterized in that: The vaporization temperature for preheating and vaporizing liquid anhydrous hydrogen fluoride feedstock is 50–60°C.

4. The method for preparing electronic-grade hydrofluoric acid for semiconductors according to claim 1, characterized in that: The desorption temperature for the second stage is 200–220℃.

5. The method for preparing electronic-grade hydrofluoric acid for semiconductors according to claim 1, characterized in that: The concentration of the crude hydrofluoric acid was 49%.

6. The method for preparing electronic-grade hydrofluoric acid for semiconductors according to claim 1, characterized in that: The crude hydrofluoric acid was filtered using a 3μm pore size membrane.

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