Semiconductor process tail gas treatment method and system

Abstract

The application discloses a semiconductor process tail gas treatment method and system. The method is as follows: inputting the reaction tail gas to be treated into a plasma device, and then inputting the reaction tail gas into a vacuum pump after purifying the reaction tail gas by the plasma generated by the plasma device; wherein, a tip structure is arranged on an electrode plate in a reaction chamber of the plasma device; during operation, a sheath layer is formed at the bottom area of the tip structure on the electrode plate, the tip has a negative bias voltage, after the medium particles in the reaction tail gas are positively charged by the sheath layer, the medium particles move to the tip under the action of electrostatic force, and the medium particles are polarized to obtain dielectrophoretic force which is directed to the tip in the non-uniform electric field near the tip, so that the medium particles move to the tip under the joint action of the electrostatic force and the dielectrophoretic force and are adsorbed on the tip; and the gas output by the vacuum pump is sprayed and washed and then discharged. The application can not only prolong the service life of the vacuum system, but also simplify the design of the vacuum system, and realize cost reduction and benefit increase.

Description

Technical Field

[0001] This invention belongs to the field of exhaust gas treatment technology in the semiconductor industry, and relates to an exhaust gas treatment method, and more particularly to a semiconductor process exhaust gas treatment method and system, which can be used for exhaust gas treatment in the fields of solar cell manufacturing, panel manufacturing, integrated circuit manufacturing, and III-V semiconductors. Background Technology

[0002] In the manufacturing process of semiconductor integrated circuits, processes such as chemical vapor deposition, dry etching, and atomic layer deposition utilize large quantities of specialty gases. Typical process exhaust gases usually contain unreacted perfluorinated compounds (PFCs, such as CF4 and C2F6), chlorine (Cl2), hydrogen chloride (HCl), borane (B2H6), silane (SiH4), ammonia (NH3), and large amounts of nanoscale solid dust (such as SiO2 and Al2O3). These substances are highly corrosive, extremely toxic, flammable, explosive, or have a strong greenhouse effect; therefore, direct release into the atmosphere without treatment is strictly prohibited.

[0003] Currently, the industry commonly uses combustion scrubbers, plasma scrubbers, or a combination of thermal decomposition and wet scrubbing for exhaust gas treatment. Combustion scrubbers mix and burn fuel gas with exhaust gas to convert combustible and highly toxic components into water-soluble or harmless oxides. Plasma scrubbers use an electric field to generate high-energy electrons, breaking the chemical bonds of stable molecules such as PFCs.

[0004] Patent CN121060258A discloses a semiconductor waste gas treatment system and its inlet pipe anti-clogging control method, which belongs to the high-temperature plasma torch (usually driven by a 15-20KW DC power source) plus spray type. In semiconductor manufacturing processes (such as etching, chemical vapor deposition, etc.), a large amount of waste gas containing volatile organic compounds (VOCs), acidic gases (such as HCl, HF), or particulate impurities is generated. This waste gas needs to be treated (such as oxidation-reduction, cooling, and washing) to meet emission standards; otherwise, it will pollute the environment or corrode equipment. The working process is as follows: after passing through a vacuum pump, the reaction tail gas first enters the treatment device, where it undergoes an oxidation reaction under the combustion and catalytic action of the high-temperature plasma torch. Afterwards, it is sprayed and washed with circulating water, causing the various components generated to dissolve in the water, thereby meeting emission standards. Figure 1 As shown.

[0005] The drawbacks of the aforementioned technologies are as follows: Under different pressures, the average energy of electrons in plasma is directly proportional to the reduced electric field (i.e., the ratio of electric field strength to particle number density, E / n). However, in atmospheric pressure plasma, the particle number density is higher, requiring a higher electric field strength to achieve the same electron energy (i.e., maintain the same E / n), thus necessitating the injection of more energy. Furthermore, the mean free path of particles is inversely proportional to pressure; at atmospheric pressure, the free path is very small, significantly increasing the collision frequency. Most of the energy of high-energy particles is dissipated as heat in the gas through collisions, leading to a decrease in the average particle energy. Therefore, to generate the same particle energy, the required power increases with increasing pressure, resulting in higher energy consumption. Current technologies, under atmospheric pressure and with high-temperature plasma torch combustion and catalysis, require extremely high plasma energy density for oxidation reactions, leading to enormous power consumption. The exhaust gas is then treated by a vacuum pump, requiring a specially designed pump to remove corrosive exhaust gases, resulting in high equipment costs.

[0006] Patent CN121889884A discloses a plasma device for treating waste gas from semiconductor manufacturing equipment, such as... Figure 2 As shown, one type of exhaust pipe plasma reaction chamber is ICP, which mainly uses plasma to decompose exhaust gas. However, it will deposit products on the exhaust pipe wall, causing exhaust pipe blockage and affecting the system's vacuum capability. Under the same power, the particle energy in the plasma generated by ICP is lower than that generated by CCP, resulting in lower particle activity and decomposition efficiency. It needs to be used in conjunction with a plasma torch to decompose the exhaust gas in order to achieve the exhaust gas purification effect. The effect of using remote plasma reactive species to degrade the particles generated by the exhaust gas is poor. At the same time, the particle collection / dust removal efficiency is low, the load on the vacuum pump is large, and the service life and service cycle of the pump are short.

[0007] However, existing technologies generally suffer from the following bottlenecks and shortcomings in actual operation: 1. Severe dust blockage and internal scaling: A large amount of ultrafine silica (SiO2) powder is generated in the exhaust gas of CVD or silane-related processes. The packing layer or spray structure of traditional wet scrubbing towers is easily blocked by this highly adhesive dust, resulting in increased system pressure differential, extremely high downtime maintenance frequency, and severely restricting equipment uptime.

[0008] 2. The contradiction between processing efficiency and energy consumption: To achieve a destruction rate of over 99% for highly unstable PFC gases, extremely high combustion temperatures or plasma energy densities are often required, leading to huge fuel or electricity consumption. While some low-temperature plasma solutions have lower energy consumption, their efficiency drops sharply when processing large flow rates or high concentrations of PFCs, making it difficult to reliably meet increasingly stringent environmental regulations.

[0009] 3. Safety Risks and Side Reactions: The lack of efficient pre-dilution and precise control methods for treating high concentrations of silane or spontaneously combustible gases poses a risk of backfire and explosion. Furthermore, in some wet scrubbers treating chlorine-containing tail gas, improper liquid-to-gas ratio control can easily lead to the formation of highly corrosive acid mist condensation on the tower wall, causing equipment perforation and leakage.

[0010] Therefore, there is an urgent need to develop a new generation of exhaust gas treatment device that can adapt to the varied exhaust gas composition of semiconductor processes, is not prone to clogging, can simultaneously and efficiently decompose PFCs and remove dust with low energy consumption, and is also safer. Summary of the Invention

[0011] In view of the problems existing in the prior art, the purpose of this invention is to provide a method and system for treating exhaust gases in semiconductor manufacturing processes.

[0012] The technical solution of this invention is as follows: A method for treating exhaust gases from semiconductor manufacturing processes, comprising the following steps: The reaction exhaust gas to be treated is input into a plasma device. The plasma generated by the plasma device purifies the reaction exhaust gas before it enters a vacuum pump. The electrode plate in the reaction chamber of the plasma device is provided with a pointed structure. During operation, a sheath is formed at the bottom region of the pointed structure on the electrode plate. The tip of the pointed structure has a negative bias voltage. When the dielectric particles in the reaction exhaust gas pass through the sheath and become positively charged dielectric particles, they move towards the tip under the action of electrostatic force. In the non-uniform electric field near the tip, they will be polarized and receive dielectric electrophoretic force pointing towards the tip. Thus, under the combined action of the electrostatic force and the electrophoretic force pointing towards the tip, they move to the tip and are adsorbed on the tip. The gas output from the vacuum pump is sprayed and washed before being discharged.

[0013] Preferably, the tip structure is higher than the sheath thickness on the surface of the electrode plate.

[0014] Preferably, the negative bias voltage ranges from 10 to 100 volts; the spacing between the tip structures is 1 to 5 cm and the height is 1 to 20 cm.

[0015] Preferably, the electrode plate has a regular or irregular hollow structure, and the tip structure is a conical structure that protrudes outward at an angle on the electrode plate.

[0016] Preferably, the plasma device generates plasma via capacitively coupled plasma (CCP).

[0017] Preferably, the plasma device first generates plasma to decompose the reaction tail gas through inductively coupled plasma (ICP), and then generates plasma to purify the decomposed gas through capacitively coupled plasma (CCP).

[0018] Preferably, the plasma device includes multiple cascaded reaction chambers, each used to generate plasma for multi-stage purification of the gas.

[0019] Preferably, each of the reaction chambers is located in a different section of the same chamber, or in different cascaded chambers.

[0020] A semiconductor manufacturing process exhaust gas treatment system, characterized in that it includes a plasma device, a vacuum pump, and a spray scrubbing device; wherein, The plasma device is used to purify the reaction exhaust gas with generated plasma before it enters the vacuum pump. The plasma device has a pointed structure on the electrode plate inside the reaction chamber. During operation, a sheath is formed at the bottom of the pointed structure on the electrode plate. The tip of the pointed structure has a negative bias voltage. When dielectric particles in the reaction exhaust gas pass through the sheath and become positively charged, they move towards the tip under electrostatic force. In the non-uniform electric field near the tip, they become polarized and receive a dielectric electrophoretic force pointing towards the tip. Thus, under the combined action of the electrostatic force and the electrophoretic force pointing towards the tip, they move to the tip and are adsorbed onto it. The vacuum pump is used to discharge the input gas into the spray washing device; The spray washing device is used to spray and wash the gas output from the vacuum pump before discharging it.

[0021] The advantages of this invention are as follows: 1. Multi-stage plasma device to form plasma. The particles in the plasma have high energy and the active particles can easily decompose harmful substances in the exhaust gas, thereby improving the efficiency of exhaust gas treatment.

[0022] 2. The multi-stage plasma device can decompose harmful substances in the exhaust gas, generating solid compounds (oxides or nitrides), which can be collected and recycled periodically to achieve resource reuse. 3. Multi-stage plasma devices perform multi-stage decomposition and dust removal on waste gases generated from different processes. This ensures the waste gases are purified before entering the vacuum pump, significantly extending the lifespan of the vacuum system (dry pump and vacuum piping) and simplifying its design, thus reducing costs and increasing efficiency. For example, it simplifies the special design of dry pumps for handling harmful waste gases and the heating design required for piping where waste gases easily solidify at low temperatures, reducing the load on the vacuum system. It also eliminates the need for a high-power plasma torch exhaust gas treatment device at the downstream end. Attached Figure Description

[0023] Figure 1 This is a flowchart of an existing exhaust gas treatment process.

[0024] Figure 2This is a structural diagram of a plasma reactor used in the existing technology for treating tail gas.

[0025] Figure 3 This is a flowchart of the exhaust gas treatment method of this invention patent.

[0026] Figure 4 This is a diagram of a mesh electrode structure with a pointed tip. (a) Schematic diagram of the three-dimensional structure of the electrode plate, (b) Cross-sectional view of the electrode plate and its tip.

[0027] Figure 5 This is a schematic diagram of an example of exhaust gas treatment.

[0028] Figure 6 This is a schematic diagram of Example 2 of exhaust gas treatment.

[0029] Figure 7 A schematic diagram of a single-stage CCP plasma device structure; (a) Schematic diagram of plate electrode structure, (b) Schematic diagram of columnar electrode structure.

[0030] Figure 8 This is a schematic diagram of a single-stage ICP plasma device.

[0031] Figure 9 This is a schematic diagram of a multi-stage plasma device. Detailed Implementation

[0032] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0033] In the semiconductor manufacturing field, Chemical Vapor Deposition (CVD) encompasses many types, such as Atmospheric Pressure Chemical Vapor Deposition (APCVD), Low Pressure Chemical Vapor Deposition (LPCVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Atomic Layer Deposition (ALD), and Plasma-Enhanced Atomic Layer Deposition (PEALD). These are core technologies in integrated circuit chip manufacturing, used to deposit thin film layers, such as dielectric layers, metal layers, and semiconductor layers, on wafer surfaces. These processes utilize large amounts of specialized gases and generate waste gases containing reactive gases, intermediate products, and other volatile organic compounds (VOCs), acidic gases (such as HCl and HF), or particulate impurities.

[0034] This invention employs a multi-stage plasma device to directly treat exhaust gas, forming a novel exhaust gas treatment process: the reactive exhaust gas enters the multi-stage plasma treatment device, where an oxidation / reduction reaction occurs under the action of plasma, purifying the exhaust gas. Afterward, it is sprayed and washed with circulating water via a vacuum pump, generating various water-soluble gaseous components, thereby meeting emission standards, such as... Figure 3 As shown.

[0035] In this invention, the multi-stage plasma generator uses capacitively coupled plasma (CCP) to generate plasma for purifying waste gas, thus simultaneously achieving residual gas decomposition and dust removal functions. The multi-stage plasma generator can also be used in combination with inductively coupled plasma (ICP) and CCP. First, plasma is generated by ICP to enhance the decomposition of residual gas, and then plasma is generated by the CCP plasma device placed at the end of the multi-stage plasma device for dust removal.

[0036] Furthermore, the CCP plasma generator designed in this invention has a pointed structure (such as...) on the electrode plate in the reaction chamber. Figure 4As shown in the diagram, for example, adding a pointed structure to the electrode plate will create a negative bias voltage of tens or hundreds of volts at these points (the magnitude of the negative bias voltage is related to the electrode shape and power). A sheath layer of about a few millimeters thick will form near the pointed structure on the electrode plate (the plasma sheath refers to the transition region formed between the plasma and the device wall or electrode when they come into contact. Because the electron velocity is much greater than that of ions, the device wall has a negative potential relative to the plasma). The electric field distribution formed here is non-uniform and highly variable. When dielectric particles (reaction products) enter the sheath layer, they will adsorb more positive ions and become positively charged. The positively charged dielectric particles will move towards the negatively charged tips under the action of electrostatic force. At the same time, the dielectric particles will be polarized in the non-uniform electric field near the tips and will be subjected to dielectric electrophoretic force pointing towards the tips. Under the combined action of the electrostatic force and electrophoretic force pointing towards the tips, the dielectric particles are firmly adsorbed onto the tips, realizing the removal of nanoparticle dust in semiconductor exhaust gas processes. As particles are continuously adsorbed onto the tips, a particle coating layer is formed. When a certain amount has accumulated, the electrode plate with the pointed structure can be removed for cleaning. In addition, the electrode plate can also be designed with regular or irregular hollow structure to increase the edges and corners on the electrode plate. Because the curvature of the edges and corners changes greatly, the electric field changes more, which also leads to particle adsorption.

[0037] The CCP plasma device designed in this invention features an electrode plate with a pointed structure, such as... Figure 4 As shown, the electrode plate has square (not limited to square, hexagonal or other polygonal structures are also acceptable) openings to form a mesh structure with pointed structures. The pointed structures are higher than the surface sheath thickness of the electrode plate. The spacing between the pointed structures is 1~5cm, and the height can be 1~20cm. The spacing and height need to be adjusted according to the chamber structure. The pointed structures mainly affect the electric field distribution and are used to adsorb particles.

[0038] This invention generates plasma by producing radio frequency glow discharge (a self-sustaining discharge phenomenon in rarefied gas) via CCP. It utilizes the strong electric field on the tip surface of the electrode plate to adsorb particles, resulting in low power consumption. The tip structure must be higher than the surface sheath thickness of the electrode plate. The tip structure is distributed on the electrode plate, and the sheath thickness on the electrode plate is less than 1 cm. Therefore, the tip structure generally needs to be higher than 1 cm, with the maximum height depending on the structural design. For example, if the electrode spacing is 10 cm, the tip structure can preferably be 5 cm.

[0039] The electrode spacing in this invention is at least a few centimeters to tens of centimeters, providing sufficient space to collect particles. In one embodiment, the electrode spacing can be 10 centimeters.

[0040] Example 1: In CVD reactions, the exhaust gas contains not only a large amount of dust particles, but also unreacted gases and intermediates of the reactants. These intermediates are also prone to forming unstable intermediate solid products under varying temperatures. For this type of process, multi-stage plasma exhaust gas treatment devices offer significant advantages.

[0041] For example, in advanced chip manufacturing processes, the use of high-dielectric material Al2O3 will increase significantly. Currently, the industry lacks a complete solution for treating the exhaust gases from this process. Multi-stage plasma exhaust gas treatment devices can completely solve this problem, reduce the burden on subsequent vacuum systems, and improve production efficiency.

[0042] like Figure 5 As shown, the process exhaust gas is treated by two or more plasma reaction chambers, then pumped by a vacuum pump to a waste treatment unit for further processing before being discharged. The first-stage plasma is preferably designed as a CCP (Central Plasma Reactor) system, which can handle the residual gas reaction, completely remove intermediate products, and also provide dust removal. Alternatively, it can be designed as an ICP (Integrated Policing Reactor), which will have weaker dust removal capabilities but stronger residual gas reaction performance. In practical applications, additional gas can be added to ensure complete reaction of byproducts. Therefore, the first-stage plasma design includes a reserved backup gas inlet, depending on the process.

[0043] The second-stage plasma primarily performs dust removal, generating plasma using CCP mode to handle dust removal. In practice, before entering the first-stage plasma, residual gas reacts and condenses into solid Al2O3 particles, which are then deposited under the influence of the first-stage plasma. Unreacted residual gas reacts in the first-stage plasma to form Al2O3 particles, which then enter the second-stage plasma. There, they are captured by the plasma and deposited. This ensures that the gas entering the dry pump is relatively clean, reducing the likelihood of subsequent residual gas reacting and forming particles within the dry pump, thus extending its lifespan and improving its efficiency. This also reduces the load on the subsequent dedicated exhaust gas treatment unit.

[0044] Example 2 The first and second stage plasmas can be placed in the same chamber, occupying different areas within the chamber. A gas passage is left between the first and second stages, and the two areas are independent of each other, preventing interaction and overlap of the plasma regions and avoiding any impact on plasma control; for example... Figure 6 As shown.

[0045] In subsequent practical applications, multi-stage plasmas can be designed according to different reaction gases to meet the requirements for targeted treatment of by-products.

[0046] For plasma devices, the structure can be a single-stage plasma device or a multi-stage single-chamber plasma device; among them, the single-stage plasma device adopts a CCP structure, such as... Figure 7 As shown. Single-stage plasma devices can also employ an ICP structure, such as... Figure 8 As shown. The structure of the multi-stage single-chamber plasma device is as follows. Figure 9 As shown.

[0047] like Figure 7 As shown in (b), a pointed structure can also be added to the cylindrical electrode to enhance the adsorption effect.

[0048] There are many types of plasma generators, such as microwave, DBD, and radio frequency plasma generators that have the function of synthesis reaction.

[0049] The plasma generator can be a CCP (Chip-based) system or a combination of ICP and CCP, with the CCP at the end performing dust removal. In the CCP plasma reaction chamber, the electrodes have pointed structures to achieve the deposition or attachment of products for recovery.

[0050] A multi-stage plasma device can consist of multiple chambers or be integrated into a single chamber.

[0051] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for treating exhaust gases from a semiconductor manufacturing process, comprising the following steps: The reaction exhaust gas to be treated is input into a plasma device. The plasma generated by the plasma device purifies the reaction exhaust gas before it enters a vacuum pump. The electrode plate in the reaction chamber of the plasma device is provided with a pointed structure. During operation, a sheath is formed at the bottom region of the pointed structure on the electrode plate. The tip of the pointed structure has a negative bias voltage. When the dielectric particles in the reaction exhaust gas pass through the sheath and become positively charged dielectric particles, they move towards the tip under the action of electrostatic force. In the non-uniform electric field near the tip, they will be polarized and receive dielectric electrophoretic force pointing towards the tip. Thus, under the combined action of the electrostatic force and the electrophoretic force pointing towards the tip, they move to the tip and are adsorbed on the tip. The gas output from the vacuum pump is sprayed and washed before being discharged.

2. The method according to claim 1, characterized in that, The tip structure is thicker than the sheath layer on the surface of the electrode plate.

3. The method according to claim 2, characterized in that, The negative bias voltage ranges from 10 to 100 volts; the spacing between the tip structures is 1 to 5 cm and the height is 1 to 20 cm.

4. The method according to claim 1, 2, or 3, characterized in that, The electrode plate has a regular or irregular hollow structure, and the tip structure is a conical structure that protrudes outward at an angle on the electrode plate.

5. The method according to claim 1, 2, or 3, characterized in that, The plasma device generates plasma via capacitively coupled plasma (CCP).

6. The method according to claim 1, 2, or 3, characterized in that, The plasma device first generates plasma to decompose the reaction tail gas through inductively coupled plasma (ICP), and then generates plasma to purify the decomposed gas through capacitively coupled plasma (CCP).

7. The method according to claim 1, 2, or 3, characterized in that, The plasma device includes multiple cascaded reaction chambers, each used to generate plasma for multi-stage purification of the gas.

8. The method according to claim 7, characterized in that, Each of the aforementioned reaction chambers is located in a different section of the same chamber, or in different chambers in a cascade.

9. A semiconductor process exhaust gas treatment system, characterized in that, Includes plasma device, vacuum pump, and spray washing device; among which, The plasma device is used to purify the reaction exhaust gas with generated plasma before it enters the vacuum pump. The plasma device has a pointed structure on the electrode plate inside the reaction chamber. During operation, a sheath is formed at the bottom of the pointed structure on the electrode plate. The tip of the pointed structure has a negative bias voltage. When dielectric particles in the reaction exhaust gas pass through the sheath and become positively charged, they move towards the tip under electrostatic force. In the non-uniform electric field near the tip, they become polarized and receive a dielectric electrophoretic force pointing towards the tip. Thus, under the combined action of the electrostatic force and the electrophoretic force pointing towards the tip, they move to the tip and are adsorbed onto it. The vacuum pump is used to discharge the input gas into the spray washing device; The spray washing device is used to spray and wash the gas output from the vacuum pump before discharging it.

Images