A tungsten hexafluoride synthesis apparatus

Abstract

The application relates to the field of tungsten hexafluoride synthesis, in particular to a tungsten hexafluoride synthesis device. The synthesis device comprises a reaction kettle and a heating mechanism for heating the reaction kettle, the top of the reaction kettle is provided with a tungsten feeding port, and a coarse-diameter screen and a fine-diameter screen are arranged in the reaction kettle, the coarse-diameter screen is arranged above the fine-diameter screen; the bottom of the reaction kettle is provided with a first gas inlet, and the top of the reaction kettle is provided with a first discharge port; a second gas inlet is arranged on the side wall of the reaction kettle, and a second discharge port is arranged on the side wall opposite to the second gas inlet; the tungsten hexafluoride synthesis device can realize tungsten hexafluoride synthesis reactions of two different mechanisms by using the same device, and the utilization rate of raw materials is greatly improved, and in particular, the technical problem of insufficient utilization of tungsten blocks in the synthesis of tungsten hexafluoride by using fluorine gas and tungsten blocks in the prior art is solved.

Description

Technical Field

[0001] This application relates to the field of tungsten hexafluoride synthesis, and more specifically, to an apparatus for tungsten hexafluoride synthesis. Background Technology

[0002] Tungsten hexafluoride is a volatile, colorless gas with a pungent odor. It is an important inorganic compound used in the semiconductor field. Tungsten hexafluoride is mainly used as an etchant in the semiconductor field. It can react with materials such as silicon to precisely etch the surface of semiconductor materials to create tiny circuit components.

[0003] Currently, the main industrial methods for synthesizing tungsten hexafluoride include the following two methods: 1. Reacting NF3 with tungsten, relying on the cracking of NF3 to generate fluorine and nitrogen, and then reacting the fluorine with tungsten to generate tungsten hexafluoride; 2. Directly combining fluorine with tungsten to generate tungsten hexafluoride.

[0004] Regarding the first synthesis method: This method uses relatively easy-to-process and purified NF3 as a raw material, utilizing its cracking reaction to generate fluorine gas. The resulting fluorine gas does not contain difficult-to-treat impurities, and since the fluorine gas originates from the cracking reaction of NF3, it does not require cumbersome raw material purification. This is currently a rapidly developing and widely used method for synthesizing tungsten hexafluoride. However, this method has the disadvantage that nitrogen gas is released during the cracking of NF3. Existing tungsten hexafluoride synthesis equipment has difficulty separating nitrogen and fluorine gas while fluorine gas reacts with tungsten. Therefore, the fluorination reaction of tungsten with fluorine gas is basically carried out in a nitrogen atmosphere. This may be more stable for the reaction itself, but considering the effects of gas convection in the reaction device, it is actually not conducive to the contact between fluorine gas and tungsten, thus hindering the industrial synthesis of tungsten hexafluoride and resulting in relatively low reaction efficiency. Meanwhile, due to the above-mentioned drawbacks, when using this method to prepare tungsten hexafluoride, in order to increase the contact area between fluorine gas and tungsten and thus increase the reaction efficiency, only tungsten powder with a large surface area can be used as the reaction raw material. However, since tungsten itself is very hard, grinding tungsten blocks into powder requires a lot of cost. Therefore, tungsten powder on the market is more expensive than tungsten blocks, making this method less economical.

[0005] Regarding the second synthesis method: Its advantages include sufficient contact between reactants, minimal presence of residual gas in the reactor, and relatively high synthesis rate and efficiency. It can use inexpensive tungsten blocks as the reactant. However, its disadvantages include the need for complex pretreatment processes such as dehydrofluorination and denitrification when using fluorine as a reactant; the gradual consumption of tungsten blocks as the reaction proceeds reduces the likelihood of fluorine reacting with them. In this situation, if the fluorine feed rate is not reduced, the resulting tungsten hexafluoride will contain a large amount of fluorine; reducing the fluorine feed rate will also decrease the tungsten hexafluoride production rate. In actual production, to ensure efficiency, the reaction is often stopped near completion (approximately when about 30 wt% of tungsten remains), and the unreacted tungsten blocks are replaced with new ones, resulting in material waste.

[0006] In summary, the two synthesis methods described above each have their own advantages and disadvantages. Regarding the selection and use of tungsten as a raw material, the first synthesis method is limited by its own reaction mechanism and cannot use tungsten blocks as a reaction raw material. Although the second synthesis method can use inexpensive tungsten blocks, the unreacted tungsten blocks near the end of the reaction will cause waste of raw materials and a decrease in synthesis efficiency.

[0007] In view of this, this application provides a tungsten hexafluoride synthesis apparatus, which aims to solve the above-mentioned technical problems. Summary of the Invention

[0008] In order to improve the technical problems in related technologies, this application provides a tungsten hexafluoride synthesis apparatus.

[0009] The tungsten hexafluoride synthesis apparatus provided in this application adopts the following technical solution:

[0010] A tungsten hexafluoride synthesis apparatus includes a reactor and a heating mechanism for heating the reactor. The reactor has a tungsten feed inlet at the top and includes a coarse-diameter screen and a fine-diameter screen built into the reactor, with the coarse-diameter screen positioned above the fine-diameter screen. The reactor has a first air inlet at the bottom and a first discharge outlet at the top. A second air inlet is provided on the side wall of the reactor, and a second discharge outlet is provided on the side wall opposite to the second air inlet.

[0011] In one specific implementation, both the second air inlet and the second discharge outlet are located on the side wall of the reactor between the coarse-diameter screen and the fine-diameter screen.

[0012] In one specific implementation, the second air inlet and the second discharge outlet are positioned close to the fine-diameter screen.

[0013] In one specific feasible implementation, the aperture of the coarse-diameter screen is 5mm to 8mm.

[0014] In one specific feasible implementation, the aperture of the fine-diameter screen is 300μm to 800μm.

[0015] In one specific implementation, the heating mechanism includes heating tiles that cover the outer surface of the reactor body and provide a start-up temperature to the reactor by voltage-controlled temperature.

[0016] In one specific implementation, the heating temperature range of the heating tile is 250–350°C.

[0017] This application has the following beneficial effects:

[0018] This application, by setting up coarse and fine screens, along with first and second air inlets, first and second discharge outlets at different locations, can satisfy both the synthesis reaction of tungsten hexafluoride using fluorine gas and tungsten blocks as raw materials, and the synthesis reaction using NF3 and tungsten powder as raw materials. Furthermore, when the raw materials are fluorine gas and tungsten blocks, the fluorine gas first enters from the first air inlet at the bottom of the reactor, and after being blocked and dispersed by the fine screen, it can fully fill the space between the coarse and fine screens, thus ensuring sufficient contact with the tungsten blocks on the coarse screen. When the tungsten blocks are consumed to the point where their particle size is smaller than that of the coarse screen, they fall onto the fine screen, allowing for further reuse of the unreacted tungsten blocks, greatly improving the utilization rate of the raw materials. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a tungsten hexafluoride synthesis apparatus provided in this application.

[0020] Explanation of reference numerals in the attached diagram: 1. Reactor; 101. Tungsten feed inlet; 102. Coarse diameter screen; 103. Fine diameter screen; 104. Second air inlet; 105. First discharge outlet; 106. First air inlet; 107. Second discharge outlet; 2. Heating tile. Detailed Implementation

[0021] The present application will be further described in detail below with reference to the accompanying drawings and embodiments.

[0022] Example 1

[0023] This embodiment provides a tungsten hexafluoride synthesis apparatus, which includes a circular cross-section reaction vessel 1 and a heating mechanism. In this embodiment, the heating mechanism is a heating tile 2, which covers the outer wall of the reaction vessel 1 and is used to heat the reaction vessel 1 to promote the smooth reaction of tungsten synthesis of tungsten hexafluoride from fluorine gas. The heating tile 2 is connected to an external power source, and the temperature in the reaction vessel 1 can be controlled by voltage. The temperature range of the heating tile 2 is between 250°C and 350°C to ensure the smooth progress of the reaction.

[0024] The reactor 1 has a tungsten inlet 101 at its top, which is eccentrically positioned for easy feeding. The reactor 1 contains a coarse-diameter screen 102 and a fine-diameter screen 103. The coarse-diameter screen 102 is positioned above the fine-diameter screen 103, and both are horizontally arranged. The coarse-diameter screen 102 is used to hold tungsten blocks, and its aperture can be between 5mm and 8mm; in this embodiment, the aperture of the coarse-diameter screen 102 is 6mm. The fine-diameter screen 103 is used to catch fine-particle tungsten raw materials falling from the coarse-diameter screen 102, or to directly hold tungsten powder; its aperture is between 5mm and 8mm. Between 300μm and 800μm, the aperture of the fine-diameter screen 103 in this embodiment is 500μm; the bottom of the reactor 1 is provided with a first air inlet 106 for feeding the reaction gas, which can be connected to the raw material gas tank through a flange and a gas opening and closing device; correspondingly, the top of the reactor 1 is provided with a first discharge port 105 for discharging the product gas, unreacted raw material gas or other impurity gas. The first discharge port 105 can be connected to the subsequent tungsten hexafluoride purification device through a flange and a gas opening and closing device. The prior art here is relatively mature and will not be described in detail.

[0025] A second air inlet 104 is provided on the side wall of the reactor 1 for feeding the reaction gas. It can be connected to the raw material gas tank through a flange and a gas opening and closing device. A second discharge port 107 is provided on the side wall of the reactor 1 at a horizontal position opposite to the second air inlet 104 for discharging the product gas, unreacted raw material gas, or other impurity gas. The second discharge port 107 can be connected to the subsequent tungsten hexafluoride purification device through a flange and a gas opening and closing device. The existing technology here is relatively mature and will not be described in detail. The second air inlet 104 and the second discharge port 107 are both located on the side wall of the reactor 1 between the coarse diameter screen 102 and the fine diameter screen 103, which facilitates the full contact and reaction of fluorine gas with the tungsten blocks or tungsten powder on the fine diameter screen 103.

[0026] Implementation principle of Example 1:

[0027] The tungsten hexafluoride synthesis apparatus provided in this embodiment can realize two tungsten hexafluoride synthesis reactions with different mechanisms using the same apparatus, and greatly improves the utilization rate of raw materials.

[0028] When the raw material gas is fluorine gas and the raw material tungsten is tungsten blocks, the tungsten blocks are placed into the reactor 1 through the tungsten feed port 101 at the top of the reactor 1. At this time, since the particle size of the tungsten blocks is much larger than the aperture of the coarse-diameter screen 102, the tungsten blocks accumulate on the coarse-diameter screen 102. At this time, the first gas inlet 106 and the second gas inlet 104 are connected to fluorine gas, the second gas inlet 104 is closed for later use, the first gas inlet 106 is opened, and the fluorine gas is forced into the first gas inlet 1 at the bottom of the reactor 1 using a membrane press. The inlet 106 has an outlet pressure of 0.1 MPa. After fluorine gas is fed through the first inlet 106, it is dispersed to a certain extent by the fine-diameter screen 103, and relatively evenly gathers at the bottom of the coarse-diameter screen 102. During its ascent, it comes into contact with the tungsten block and reacts with it at a certain temperature to form tungsten hexafluoride. The tungsten hexafluoride and fluorine gas are discharged from the first outlet 105, and may be further processed by subsequent purification devices, fluorine recovery devices, etc. The raw material fluorine gas is recovered, and the product tungsten hexafluoride is purified. As the reaction proceeds, the tungsten blocks are gradually consumed, and the particle size gradually decreases. Although the surface area increases, the macroscopic contact area between the fluorine gas and the tungsten blocks decreases. When the particle size of the tungsten blocks is smaller than the aperture of the coarse-diameter screen 102, the fine-diameter tungsten blocks fall through the sieve holes of the coarse-diameter screen 102 onto the fine-diameter screen 103. At this time, the first air inlet 106 and the second outlet 107 are closed. The second air inlet 104 and the second storage port are opened, and the fluorine gas is forced into the second air inlet 104 on the side of the reactor 1 using a membrane press. The outlet pressure of the membrane press is set to 0.1 MPa. Since the second air inlet 104 and the second storage port are located below the coarse-diameter screen 102 and above the fine-diameter screen 103, the fluorine gas entering from the second air inlet 104 will fully contact and react with the tungsten powder or tungsten blocks on the fine-diameter screen 103. The generated tungsten hexafluoride is discharged from the second outlet 107.

[0029] When the raw material gas is NF3 and the tungsten raw material is tungsten powder, the tungsten powder is still put into the reactor 1 through the tungsten feed port 101 at the top. Since the particle size of tungsten powder is generally about 1 mm, which is 5-8 mm smaller than the aperture of the coarse screen 102 and larger than the aperture of the fine screen 103, the tungsten powder will pass through the coarse screen 102 and accumulate on the fine screen 103. At this time, the first air inlet 106 and the first discharge port 105 are kept closed, and the second air inlet 104 and the second discharge port 107 are opened. The membrane press is used to press NF3 into the second air inlet 104 on the side of the reactor 1. The outlet pressure of the membrane press is set to 0.1 MPa. This allows NF3 to come into contact with the tungsten powder. The generated nitrogen, fluorine, tungsten hexafluoride, and unreacted NF3 are discharged from the second discharge port 107. After purification by the subsequent purification device, tungsten hexafluoride product is obtained.

[0030] Example 2

[0031] This embodiment is based on the scheme of embodiment 1, and further includes: the second air inlet 104 and the second discharge outlet 107 are arranged close to the fine diameter screen 103. When the raw material gas enters from the second air inlet 104, it can ensure that the raw material gas and tungsten powder or tungsten blocks with smaller particle size can be in more sufficient contact and reaction.

[0032] After testing using the scheme of this embodiment, it was found that when 18 kg of tungsten blocks with an average particle size of about 3 cm were placed in reactor 1 and the fluorine gas flow rate was controlled at 0.2 kg / h, after 48 hours, about 70 wt% of the tungsten blocks were consumed, and the particle size decreased to less than the aperture of the coarse-diameter sieve 102. The remaining about 30 wt% fell onto the fine-diameter sieve 103 and continued to be consumed by the fluorine gas entering through the second inlet 104. If the existing equipment is used to synthesize tungsten hexafluoride, the aforementioned 30 wt% of tungsten blocks with a particle size of less than 5-8 mm would be discarded in actual production due to insufficient reaction, or the number of times tungsten blocks were added would be increased, which is time-consuming, labor-intensive, and causes economic losses. Using the scheme of embodiment 2 of this application, the aforementioned 30 wt% of tungsten blocks with a particle size of less than 5-8 mm can be fully utilized, which greatly increases the raw material utilization rate and reduces the number of times they are added, saving time and labor, and playing a substantial role in promoting actual production.

[0033] Example 3

[0034] This embodiment is based on the scheme of embodiment 2, and further includes: the bottom of the reactor 1 is a conical part, and the first air inlet 106 is set on the side wall of the conical part to facilitate the gas convection inside the reactor 1, thereby making the reaction more complete; the bottom of the conical part is provided with a waste collection port equipped with an opening and closing device to facilitate the collection of tungsten powder falling from the fine-diameter screen 103.

[0035] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A tungsten hexafluoride synthesis apparatus, comprising a reactor (1) and a heating mechanism for heating the reactor (1), wherein the top of the reactor (1) is provided with a tungsten inlet (101), characterized in that: It also includes a coarse-diameter screen (102) and a fine-diameter screen (103) built into the reactor (1), with the coarse-diameter screen (102) positioned above the fine-diameter screen (103); the reactor (1) has a first air inlet (106) at the bottom and a first discharge outlet (105) at the top; the reactor (1) has a second air inlet (104) on its side wall and a second discharge outlet (107) on the side wall opposite to the second air inlet (104); The aperture of the coarse-diameter screen (102) is 5mm to 8mm; The aperture of the fine-diameter sieve (103) is 300μm to 800μm; The second air inlet (104) and the second discharge outlet (107) are both located on the side wall of the reactor (1) between the coarse diameter screen (102) and the fine diameter screen (103); The second air inlet (104) and the second discharge outlet (107) are located near the fine-diameter screen (103).

2. The tungsten hexafluoride synthesis apparatus according to claim 1, characterized in that: The heating mechanism includes a heating tile (2), which covers the outer surface of the main body of the reactor (1) and provides the start-up temperature of the reactor (1) by controlling the temperature with voltage.

3. The tungsten hexafluoride synthesis apparatus according to claim 2, characterized in that: The heating temperature range of the heating tile (2) is 250 to 350°C.

Images