Method and device for removing ammonium chloride crystals in silicon nitride production equipment

Abstract

The invention relates to the technical field of semiconductor manufacturing processes, and discloses a method and a device for removing ammonium chloride crystals in silicon nitride production equipment, and the method comprises the following steps: i) oxygen free radicals are generated by oxygen free radical source gas through thermal ionization to obtain gas containing the oxygen free radicals; and ii) introducing the gas containing the oxygen free radicals into the pipeline containing the ammonium chloride crystal substance, and reacting with ammonium chloride in the pipeline containing the ammonium chloride crystal substance to generate a gaseous product. The oxygen free radicals react with ammonium chloride on the inner wall of the pipeline containing the ammonium chloride crystals, ammonium chloride crystals are converted into gaseous products easy to collect, the ammonium chloride crystals on the inner wall of the pipeline containing the ammonium chloride crystals can be rapidly removed, the pipeline does not need to be disassembled and assembled, the equipment utilization rate and the operation efficiency are improved, and the operation cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of semiconductor manufacturing process, and in particular to a method and a device for removing ammonium chloride crystals in silicon nitride production equipment. Background Art

[0002] Silicon nitride (Si3N4) has been widely used in the field of integrated circuit manufacturing due to its unique physical properties. It is used as an electrical insulating material for substrate isolation, surface passivation, etching mask, suspended beams, bridges and related structures. Silicon nitride production equipment mainly uses chemical vapor deposition technology to prepare silicon nitride films. The gases used are NH3 and SiH2Cl2. These two gases react to form silicon nitride under high temperature conditions of 650-850℃. The chemical reaction formula is: NH3+SiH2Cl2→SI3NH4+HCl. Silicon nitride is deposited on the surface of the wafer to form a silicon nitride film. Since the above reaction also generates HCl as a byproduct, in order to adjust the refractive index, structure and optical properties of the silicon nitride film, excess NH3 will be added to remove HCl. The chemical reaction formula is: HCL+NH3→NH4Cl. Since the temperature of some pipelines in the silicon nitride production equipment is relatively low, such as pump pipes, ammonium chloride (NH4Cl) will produce crystals that adhere to the inner walls of these pipelines. As the number of processes increases, the inner diameter of the pipeline will gradually decrease, affecting the operation of the silicon nitride production equipment. At present, in order to remove ammonium chloride crystals in the pipeline, the pipeline containing ammonium chloride crystals is dismantled, then wet-cleaned, and finally the cleaned pipeline is reinstalled. Each cleaning operation requires the silicon nitride production equipment to be shut down, which seriously affects the utilization rate of the silicon nitride production equipment, reduces production efficiency and benefits, and increases operating costs. Summary of the invention

[0003] In order to solve the technical problem that the above-mentioned method of removing ammonium chloride crystals will seriously affect the utilization rate of silicon nitride production equipment and increase operating costs, the present invention provides a method for removing ammonium chloride crystals in silicon nitride production equipment. The method is easy to operate, does not require disassembly and assembly of pipelines, will not cause the silicon nitride production equipment to stop, thereby improving the equipment utilization rate and reducing operating costs.

[0004] The specific technical scheme of the present invention is: A method for removing ammonium chloride crystals in a silicon nitride production device comprises the following steps: i) generating oxygen free radicals by thermal ionization of an oxygen free radical source gas to obtain a gas containing oxygen free radicals; ii) introducing a gas containing oxygen free radicals into a pipeline containing ammonium chloride crystals, and reacting the gas containing oxygen free radicals with the ammonium chloride crystals to generate a gaseous product.

[0005] The chemical reaction formula involved in the present invention is: 5O -+2NH4Cl→2NO+3H2O+2HCl, oxygen free radicals are generated by thermal ionization of oxygen free radical source gas, and the gas containing oxygen free radicals reacts with ammonium chloride on the inner wall of the pipeline to convert ammonium chloride crystals into easily collectible gaseous products, which can quickly remove the ammonium chloride crystals on the inner wall of the pipeline, without disassembling the pipeline of the silicon nitride production equipment, and will not cause the silicon nitride production equipment to stop, thereby improving the equipment utilization rate and operation efficiency and reducing the operating cost; at the same time, in the process of removing the ammonium chloride crystals, there is no need to significantly cool down or heat up the pipeline containing the ammonium chloride crystals, the operation is simple, and the pipeline containing the ammonium chloride crystals can be cleaned at any time; in addition, compared with wet cleaning, this method does not involve the use of chemical reagents, and will not generate waste liquid due to the participation of chemical reagents in the cleaning process, thereby avoiding the waste liquid treatment link and being highly environmentally friendly.

[0006] Preferably, the oxygen radical source gas comprises at least 95% ozone.

[0007] Ozone is used as the source of oxygen free radicals. The ozone molecule has a V-shaped structure. The covalent bonds between the central oxygen atom and the two end oxygen atoms are easily broken under the action of heat and energy. The efficiency of generating oxygen free radicals is high, and ozone thermal ionization can be achieved within the temperature range that the equipment can withstand.

[0008] Preferably, the oxygen free radical source gas also includes argon.

[0009] When the oxygen free radical source gas is thermally ionized, the gas molecules are ionized into ions and electrons to form a plasma environment. Argon gas is added to the oxygen free radical source gas to stabilize the plasma state and thereby stabilize the rate of oxygen free radical generation.

[0010] Preferably, the thermal ionization temperature of the oxygen free radical source gas is 1100-1300°C.

[0011] Preferably, the reaction temperature of the reaction between the gas containing oxygen free radicals and the ammonium chloride crystals is 370-400°C.

[0012] The present invention also provides a device for removing ammonium chloride crystals in silicon nitride production equipment, comprising a generating chamber connected to a pipeline containing ammonium chloride crystals, an injection pipe connected to an external oxygen free radical source gas source, and a heating device for heating the injection pipe so that the oxygen free radical source gas undergoes a thermal ionization reaction in the injection pipe, wherein the injection pipe at least partially extends into the generating chamber so that the gas containing oxygen free radicals flows into the generating chamber.

[0013] The heating device heats the injection pipe, so that the oxygen free radical source gas therein is thermally ionized to generate oxygen free radicals. The gas containing oxygen free radicals flows from the injection pipe into the generating chamber, and then enters the pipeline containing ammonium chloride crystals through the generating chamber to react with the ammonium chloride crystals. The pipeline containing ammonium chloride crystals is externally connected to the generating chamber. When the pipeline needs to be cleaned, it is only necessary to thermally ionize the oxygen free radical source gas to obtain the gas containing oxygen free radicals, and then pass it into the pipeline. There is no need to disassemble the pipeline. The operation is simple. The pipeline containing ammonium chloride crystals can be cleaned at any time. Ammonium chloride crystals will not accumulate and cause pipeline blockage, thereby improving the equipment utilization rate and equipment operation efficiency and reducing operating costs.

[0014] Preferably, the generating chamber is made of a light-transmitting material, and the heating device comprises a first halogen lamp and a second halogen lamp, and the first halogen lamp and the second halogen lamp are respectively connected to the outer walls on opposite sides of the generating chamber.

[0015] The first halogen lamp and the second halogen lamp are arranged outside the generating chamber to prevent debris, dust or other impurities from falling into the generating chamber, thereby preventing the gas containing oxygen free radicals from being polluted. When they fail to meet the use requirements, they are easy to replace without stopping for maintenance. The first halogen lamp and the second halogen lamp are arranged relative to each other, so that the injection tube is heated evenly and the thermal ionization effect is good.

[0016] Preferably, there is a pressure difference between the pipeline containing ammonium chloride crystals and the generating chamber, and the gas containing oxygen free radicals enters the pipeline containing ammonium chloride crystals due to the pressure difference.

[0017] The pressure difference is used to drive the gas containing oxygen free radicals into the pipeline containing ammonium chloride crystals, without installing an additional driving structure, thus simplifying the device structure.

[0018] Preferably, it further comprises a first electrode plate and a second electrode plate, wherein the first electrode plate and the second electrode plate are respectively connected to the outer walls on opposite sides of the generating chamber, and the first electrode plate and the second electrode plate can form a magnetic field.

[0019] The first electrode plate and the second electrode plate form a magnetic field, and utilize the change of the movement trajectory of the charged particles in the magnetic field to increase the collision between ions and atoms / molecules, thereby increasing the density of oxygen free radicals.

[0020] Preferably, the injection tube is made of an opaque material; or, the injection tube is provided with a plurality of through holes for allowing the gas containing oxygen free radicals to flow into the generating chamber; or, a first control valve is provided between the pipeline containing ammonium chloride crystals and the generating chamber, and the first control valve controls the opening and closing of the gas path between the pipeline containing ammonium chloride crystals and the generating chamber.

[0021] The injection tube is made of opaque material, and its purpose is to utilize its opaque principle to convert the light energy generated by the halogen lamp into heat energy, so as to quickly increase the temperature of the injection tube; a plurality of through holes are arranged on the injection tube to enrich the outflow channel of the gas containing oxygen free radicals, so as to facilitate the gas containing oxygen free radicals to flow into the generating chamber; a first control valve is arranged to control the on-off of the gas path between the pipeline containing ammonium chloride crystals and the generating chamber, so that when the pipeline containing ammonium chloride crystals is not cleaned, the pipeline containing ammonium chloride crystals is isolated from the generating chamber to prevent impurities from entering the generating chamber; in addition, when the pipeline containing ammonium chloride crystals is cleaned, the pipeline containing ammonium chloride crystals is isolated from the generating chamber to prevent the gas with a low oxygen free radical concentration from entering the pipeline containing ammonium chloride crystals and affecting the removal effect of ammonium chloride.

[0022] Compared with the prior art, the present invention has the following advantages: (1) Oxygen free radicals are generated by thermal ionization of an oxygen free radical source gas, and the gas containing the oxygen free radicals reacts with the ammonium chloride on the inner wall of the pipeline containing ammonium chloride crystals, thereby converting the ammonium chloride crystals into easily collectible gaseous products, thereby being able to quickly remove the ammonium chloride crystals on the inner wall of the pipeline containing the ammonium chloride crystals; (2) The oxygen free radicals generated by ozone thermal ionization react with the ammonium chloride on the inner wall of the pipe containing ammonium chloride crystals. Compared with wet cleaning, this method does not involve the use of chemical reagents, and does not generate waste liquid due to the participation of chemical reagents in the cleaning process, thus avoiding the waste liquid treatment link and being highly environmentally friendly. (3) The pipeline containing ammonium chloride crystals is connected to an external generating chamber. When the pipeline needs to be cleaned, it is only necessary to thermally ionize the oxygen free radical source gas to obtain a gas containing oxygen free radicals and pass it into the pipeline. There is no need to disassemble the pipeline. The operation is simple and the pipeline containing ammonium chloride crystals can be cleaned at any time. Ammonium chloride crystals will not accumulate and cause pipeline blockage, thereby improving the equipment utilization rate and equipment operation efficiency and reducing operating costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic structural diagram of a device for removing ammonium chloride crystals in a silicon nitride production device of the present invention; Figure 2 It is a structural schematic diagram of the injection pipe of the present invention.

[0024] Figure numerals: 1. second control valve; 2. pressure sensor; 3. pipeline containing ammonium chloride crystals; 4. first electrode plate; 5. first control valve; 6. docking flange; 7. first halogen lamp; 8. second electrode plate; 9. generating chamber; 10. injection tube; 11. second halogen lamp; 12. through hole. DETAILED DESCRIPTION

[0025] The present invention is described below by specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and the attached claims and any equivalents thereof are the protection scope of the present invention.

[0026] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meanings as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. Unless otherwise specified, the raw materials and equipment used in the present invention are conventional raw materials and equipment in the field and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in the present invention are conventional methods in the field.

[0027] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by “up”, “down”, “left”, “right”, “inside”, etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0028] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. In the description of the present invention, the meaning of "several" is two or more.

[0029] In the present invention, unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0030] Embodiment 1: The present invention provides a method for removing ammonium chloride crystals in silicon nitride production equipment, comprising the following steps: Step 1: The oxygen free radical source gas is thermally ionized at 1100°C to generate oxygen free radicals, thereby obtaining a gas containing oxygen free radicals; Step 2: The gas containing oxygen free radicals is introduced into a pipeline containing ammonium chloride crystals, and the gas containing oxygen free radicals reacts with the ammonium chloride crystals at 370°C to generate a gaseous product, and the reaction formula is: 5O - +2NH4Cl→2NO+3H2O+2HCl.

[0031] The oxygen free radical source gas used in this embodiment contains 5% Ar and 95% O3, and the reaction is carried out by utilizing the temperature of the gas after thermal ionization. At this temperature, NO, H2O and HCl generated by the reaction are all gaseous. The gaseous products thus formed can be treated by tail gas treatment or recycling and reuse according to actual needs.

[0032] The method uses oxygen free radicals generated by ozone thermal ionization to react with ammonium chloride on the inner wall of a pipe containing ammonium chloride crystals, converting the ammonium chloride crystals into easily collectible gaseous products, and can quickly remove the ammonium chloride crystals on the inner wall of the pipe, without the need to disassemble the pipe of the silicon nitride production equipment, and will not cause the silicon nitride production equipment to stop, thereby improving the equipment utilization rate and operation efficiency, and reducing the operating cost; at the same time, in the process of removing the ammonium chloride crystals, the temperature of the gas after thermal ionization is used for reaction, and there is no need to significantly cool or heat the pipe containing the ammonium chloride crystals, the operation is simple, and the pipe containing the ammonium chloride crystals can be cleaned at any time; in addition, compared with wet cleaning, this method does not involve the use of chemical reagents, and will not generate waste liquid due to the participation of chemical reagents in the cleaning process, thereby avoiding the waste liquid treatment link, and is highly environmentally friendly. Ozone is used as the source of oxygen free radicals. The ozone molecule has a V-shaped structure. The covalent bond between the central oxygen atom and the two terminal oxygen atoms is easily broken under the action of heat and energy, and the efficiency of generating oxygen free radicals is high. Ozone thermal ionization can be achieved within the temperature range that the equipment can withstand. Argon is added to the ozone to stabilize the plasma state during thermal ionization, thereby stabilizing the rate of oxygen free radical generation.

[0033] Embodiment 2: The present invention provides a method for removing ammonium chloride crystals in silicon nitride production equipment, comprising the following steps: Step 1: The oxygen free radical source gas is thermally ionized at 1200°C to generate oxygen free radicals, thereby obtaining a gas containing oxygen free radicals; Step 2: The gas containing oxygen free radicals is introduced into a pipeline containing ammonium chloride crystals, and the gas containing oxygen free radicals reacts with the ammonium chloride crystals at 380°C to generate a gaseous product, and the reaction formula is: 5O - +2NH4Cl→2NO+3H2O+2CHl.

[0034] The oxygen free radical source gas used in this embodiment contains 3% Ar and 97% O3. The reaction is carried out by utilizing the temperature of the gas after thermal ionization. At this temperature, NO, H2O and HCl generated by the reaction are all gaseous. The gaseous products thus formed can be treated by tail gas treatment or recycling according to actual needs.

[0035] Embodiment 3: The present invention provides a method for removing ammonium chloride crystals in silicon nitride production equipment, comprising the following steps: Step 1: The oxygen free radical source gas is thermally ionized at 1300°C to generate oxygen free radicals, thereby obtaining a gas containing oxygen free radicals; Step 2: The gas containing oxygen free radicals is introduced into a pipeline containing ammonium chloride crystals, and the gas containing oxygen free radicals reacts with the ammonium chloride crystals at 400°C to generate a gaseous product. The reaction formula is: 5O - +2NH4Cl→2NO+3H2O+2HCl.

[0036] The oxygen free radical source gas used in this embodiment contains 2% Ar and 98% O3, and the reaction is carried out by utilizing the temperature of the gas after thermal ionization. At this temperature, NO, H2O and HCl generated by the reaction are all gaseous. The gaseous products thus formed can be treated by tail gas treatment or recycling and reuse according to actual needs.

[0037] Embodiment 4: Reference Figure 1 and Figure 2 The present invention provides a device for removing ammonium chloride crystals in silicon nitride production equipment, comprising a generating chamber 9, an injection pipe 10 and a heating device. The generating chamber 9 is a closed structure and is connected to the pipeline 3 containing ammonium chloride crystals. The injection pipe 10 partially extends into the generating chamber 9. The generating chamber 9 is connected to a heating device, and the heating device is used to heat the injection pipe 10 so that the oxygen free radical source gas undergoes a thermal ionization reaction in the injection pipe 10. The pipeline 3 containing ammonium chloride crystals is connected to the process chamber, and a second control valve 1 is provided between the two to control the connection and disconnection between the pipeline 3 containing ammonium chloride crystals and the process chamber. The second control valve 1 used in this embodiment is an electric regulating valve. The pipeline 3 containing ammonium chloride crystals is also connected to a pump for extracting the gas in the pipeline 3 containing ammonium chloride crystals. It should be noted that during the production process, the temperature of the pump tube is usually low, and there may be multiple bends, which makes it easy for ammonium chloride to crystallize and aggregate inside the pump tube, thereby causing blockage of the pump tube, which is universal and representative. In view of this, the pipeline 3 containing ammonium chloride crystals in this embodiment uses a pump tube, but it must be clearly pointed out that the pump tube is not the only pipeline where ammonium chloride crystals will adhere. The device described in this embodiment can also be connected to other pipelines containing ammonium chloride crystals.

[0038] In this embodiment, the oxygen free radical source gas source is arranged outside the generating chamber 9, the injection tube 10 partially extends into the generating chamber 9, and its air inlet end extends out of the generating chamber 9 and is connected to the oxygen free radical source gas source, and the oxygen free radical source gas flows into the generating chamber 9 from the air outlet end of the injection tube 10. It can be understood that in another embodiment, the injection tube 10 is fully extended into the generating chamber 9 and is connected to the generating chamber 9 through a connecting bracket, the oxygen free radical source gas source is arranged outside the generating chamber 9, and the air inlet end of the injection tube 10 is connected to the oxygen free radical source gas source through an air guide tube.

[0039] The ammonium chloride removal process of the device is as follows: the second control valve 1 is closed to prevent oxygen free radicals from entering the process chamber, the heating device heats the injection pipe 10 to the thermal ionization temperature, the oxygen free radical source gas is introduced into the injection pipe 10, the oxygen free radical source gas undergoes thermal ionization to generate oxygen free radicals, the gas containing oxygen free radicals flows from the injection pipe 10 into the generating chamber 9, and then enters the pipeline 3 containing ammonium chloride crystals through the generating chamber 9 to react with the ammonium chloride crystals, the reaction generates gaseous products to remove the ammonium chloride crystals, and the gaseous products are pumped away by a pump.

[0040] In the present device, since the pipeline 3 containing ammonium chloride crystals is externally connected to the generating chamber 9, when it is necessary to clean the pipeline 3 containing ammonium chloride crystals, it is only necessary to thermally ionize the oxygen free radical source gas to obtain a gas containing oxygen free radicals, and pass the gas into the pipeline 3 containing ammonium chloride crystals, without disassembling the pipeline, and the pipeline 3 containing ammonium chloride crystals can be cleaned at any time, thereby improving the equipment utilization rate, facilitating operation, and preventing ammonium chloride crystals from accumulating and causing pipeline blockage.

[0041] Embodiment 5: Based on Example 4, Figure 1 and Figure 2 As shown, the present invention provides a device for removing ammonium chloride crystals in silicon nitride production equipment, the generating chamber 9 is made of quartz, the heating device includes a first halogen lamp 7 and a second halogen lamp 11, the first halogen lamp 7 is connected to the upper outer wall of the generating chamber 9, the second halogen lamp 11 is connected to the lower outer wall of the generating chamber 9, and the first halogen lamp 7 and the second halogen lamp 11 are in corresponding positions. The injection pipe 10 is made of silicon carbide, and the injection pipe 10 is provided with a plurality of through holes 12 for gas containing oxygen free radicals to flow into the generating chamber 9. The left outer wall of the generating chamber 9 is connected to the first electrode plate 4, and the right outer wall is connected to the second electrode plate 8. The first electrode plate 4 and the second electrode plate 8 are in corresponding positions, and a magnetic field can be formed between the two. A butt flange 6 is provided between the pipeline 3 containing ammonium chloride crystals and the generating chamber 9, and the pipeline 3 containing ammonium chloride crystals is connected to the generating chamber 9 through the butt flange 6. A first control valve 5 is provided on the butt flange 6 to control the on-off of the gas path between the pipeline 3 containing ammonium chloride crystals and the generating chamber 9. The first control valve 5 used in this embodiment is a pneumatic valve. There is a pressure difference between the pipeline 3 containing ammonium chloride crystals and the generating chamber 9. The gas containing oxygen free radicals enters the pipeline 3 containing ammonium chloride crystals due to the pressure difference. A pressure sensor 2 is provided on the pipeline 3 containing ammonium chloride crystals to detect the pressure in the pipeline 3 containing ammonium chloride crystals. It can be understood that the generating chamber 9 can also be made of other commonly used high-temperature resistant and light-transmitting materials, the injection pipe 10 can also be made of other commonly used high-temperature resistant and opaque materials, the first control valve 5 can also be made of other commonly used valve types, and the heating device can also be a quartz infrared heating tube, a resistance wire heater, and other commonly used heating devices that can reach the thermal ionization temperature.

[0042] The ammonium chloride removal process of the device is as follows: the second control valve 1 is closed to prevent oxygen free radicals from entering the process chamber, the first halogen lamp 7 and the second halogen lamp 11 heat the injection tube 10 to the thermal ionization temperature, the oxygen free radical source gas is introduced into the injection tube 10, the oxygen free radical source gas is thermally ionized to generate oxygen free radicals, and a gas containing oxygen free radicals is obtained. The gas containing oxygen free radicals flows from the injection tube 10 into the generating chamber 9, and the magnetic field formed by the first electrode plate 4 and the second electrode plate 8 increases the density of oxygen free radicals in the gas containing oxygen free radicals. Due to the pressure difference, the oxygen free radicals enter the pipeline 3 containing ammonium chloride crystals and react with the ammonium chloride crystals in the pipeline 3 containing ammonium chloride crystals to generate gaseous products, so as to remove the ammonium chloride crystals, and the gaseous products are pumped away by a pump.

[0043] In the present device, the first halogen lamp 7 and the second halogen lamp 11 are arranged outside the generating chamber 9 to prevent debris, dust or other impurities from falling into the generating chamber 9, thereby preventing the gas containing oxygen free radicals from being contaminated. When a failure occurs and the lamp cannot meet the use requirements, the lamp is easily replaced without stopping for maintenance. The first halogen lamp 7 and the second halogen lamp 11 are arranged relative to each other, so that the injection tube 10 is heated evenly and has a good thermal ionization effect. The first electrode plate 4 and the second electrode plate 8 form a magnetic field, and utilize the changes in the motion trajectory of charged particles in the magnetic field to increase the collision between ions and atoms / molecules, thereby increasing the density of oxygen free radicals. The injection tube 10 is made of an opaque material, and the purpose is to utilize its opaque principle to convert the light energy generated by the halogen lamp into heat energy, thereby quickly increasing the temperature of the injection tube 10. A plurality of through holes 12 are arranged on the injection tube 10 to enrich the outflow of the gas containing oxygen free radicals. A channel is provided to facilitate the gas containing oxygen free radicals to flow into the generating chamber 9; a first control valve 5 is provided to control the on-off of the gas path between the pipeline 3 containing ammonium chloride crystals and the generating chamber 9, so that when the pipeline 3 containing ammonium chloride crystals is not cleaned, the pipeline 3 containing ammonium chloride crystals is isolated from the generating chamber 9 to prevent impurities from entering the generating chamber 9; in addition, when the pipeline 3 containing ammonium chloride crystals is cleaned, the pipeline 3 containing ammonium chloride crystals is isolated from the generating chamber 9, which is convenient for creating a pressure difference between the pipeline 3 containing ammonium chloride crystals and the generating chamber 9, and preventing gas with a low oxygen free radical concentration from entering the pipeline 3 containing ammonium chloride crystals and affecting the removal effect of ammonium chloride; the pressure difference is used to drive the gas containing oxygen free radicals into the pipeline 3 containing ammonium chloride crystals, without installing an additional driving structure, thereby simplifying the device structure.

[0044] Embodiment 6: In combination with the silicon nitride production equipment and the device described in Example 5, the method for removing ammonium chloride crystals is described. The pipeline 3 containing ammonium chloride crystals used in this embodiment is a pump pipe, which includes the following steps: Step 1: close the second control valve 1 to cut off the connection channel between the process chamber and the pipeline 3 containing the ammonium chloride crystals to prevent the subsequent process of removing the ammonium chloride from affecting the process chamber; Step 2: Evacuate the pipeline 3 containing the ammonium chloride crystals until the pressure sensor 2 displays a pressure of 200 mTorr; Step 3: Turn on the first halogen lamp 7 and the second halogen lamp 1111 to heat the injection tube 1010. Heat for 1 minute until the temperature of the injection tube 1010 reaches 1200°C. Step 4: Turn on the first electrode plate 4 and the second electrode plate 8 to form a magnetic field therebetween; Step 5: introducing oxygen free radical source gas into the injection tube 1010, the oxygen free radical source gas comprising 3% Ar and 97% O3, the oxygen free radical source gas is thermally ionized at a temperature of 1200°C and generates oxygen free radicals to obtain a gas containing oxygen free radicals, and the gas containing oxygen free radicals flows out of the injection tube 1010 into the generating chamber 99; Step 6: Open the first control valve 5 to connect the pipeline 3 containing ammonium chloride crystals, the docking flange 6 and the generating chamber 99. The gas containing oxygen free radicals increases the density of oxygen free radicals through the electromagnetic field of the first electrode plate 4 and the second electrode plate 8. The gas enters the pipeline 3 containing ammonium chloride crystals from the docking flange 6 due to the pressure difference between the pipeline 3 containing ammonium chloride crystals and the generating chamber 99. Step 7: The gas containing oxygen free radicals reacts with the ammonium chloride on the inner wall of the pipe 3 containing ammonium chloride crystals. The reaction temperature is 380°C. The reaction formula is: 5O - +2NH4Cl→2NO+3H2O+2HCl, the generated gaseous product is pumped away by a pump connected to pipeline 3 containing ammonium chloride crystals.

[0045] It should be noted that the method described in this embodiment can also be used for ammonium chloride crystallization in pipelines other than pump pipes containing ammonium chloride crystals.

[0046] The raw materials and equipment used in the present invention, unless otherwise specified, are all commonly used raw materials and equipment in the art; the methods used in the present invention, unless otherwise specified, are all conventional methods in the art.

[0047] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for removing ammonium chloride crystals in a silicon nitride production device, characterized in that: The following steps are involved: i) generating oxygen free radicals by thermal ionization of an oxygen free radical source gas to obtain a gas containing oxygen free radicals; ii) introducing a gas containing oxygen free radicals into a pipeline containing ammonium chloride crystals, and reacting the gas containing oxygen free radicals with the ammonium chloride crystals to generate a gaseous product.

2. The method for removing ammonium chloride crystals in a silicon nitride production equipment according to claim 1, characterized in that: The oxygen radical source gas comprises at least 95% ozone.

3. A method for removing ammonium chloride crystals in a silicon nitride production equipment according to claim 2, characterized in that: The oxygen free radical source gas also includes argon gas.

4. The method for removing ammonium chloride crystals in a silicon nitride production equipment according to claim 1, characterized in that: The thermal ionization temperature of the oxygen free radical source gas is 1100-1300°C.

5. A method for removing ammonium chloride crystals in a silicon nitride production device according to any one of claims 1 to 4, characterized in that: The reaction temperature of the reaction between the gas containing oxygen free radicals and the ammonium chloride crystals is 370-400°C.

6. A device for removing ammonium chloride crystals in silicon nitride production equipment, characterized in that: The invention comprises a generating chamber connected to a pipeline gas path containing ammonium chloride crystals, an injection pipe connected to a gas source of an oxygen free radical source gas, and a heating device for heating the injection pipe so that the oxygen free radical source gas undergoes a thermal ionization reaction in the injection pipe. The injection pipe at least partially extends into the generating chamber so that the gas containing oxygen free radicals flows into the generating chamber.

7. The device for removing ammonium chloride crystals in a silicon nitride production device according to claim 6, characterized in that: The generating chamber is made of a light-transmitting material, and the heating device comprises a first halogen lamp and a second halogen lamp, wherein the first halogen lamp and the second halogen lamp are respectively connected to the outer walls of the generating chamber on two opposite sides.

8. The device for removing ammonium chloride crystals in a silicon nitride production equipment according to claim 6 or 7, characterized in that: There is a pressure difference between the pipeline containing the ammonium chloride crystals and the generating chamber, and the gas containing oxygen free radicals enters the pipeline containing the ammonium chloride crystals due to the pressure difference.

9. The device for removing ammonium chloride crystals in a silicon nitride production equipment according to claim 6 or 7, characterized in that: It also includes a first electrode plate and a second electrode plate, which are respectively connected to the outer walls of the generating chamber on opposite sides, and the first electrode plate and the second electrode plate can form a magnetic field.

10. The device for removing ammonium chloride crystals in a silicon nitride production device according to claim 6, characterized in that: The injection tube is made of opaque material; or, the injection tube is provided with a plurality of through holes for the gas containing oxygen free radicals to flow into the generating chamber; or, a first control valve is provided between the pipeline containing ammonium chloride crystals and the generating chamber, and the first control valve controls the opening and closing of the gas path between the pipeline containing ammonium chloride crystals and the generating chamber.

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