Method for removing particles in ion beam etching system

Abstract

This invention relates to a method and apparatus for removing particles from an ion beam etching system. The method involves adding a metal grid to the bottom of the reaction chamber of the ion beam etching system. This grid is connected to a DC power supply to generate a positive voltage, the value of which is adjustable within 100 kV depending on the size of the particles to be removed. The metal grid c is made of a hard metal such as molybdenum or nickel, with mesh sizes smaller than 5 mm. After the etching process is complete, the ion source of the ion beam etching system is disconnected, and the lower electrode is rotated to a position perpendicular to the metal grid c. A neutralizer is activated, generating a large number of electrons that attach to the particles to be removed, making them negatively charged. A positive voltage is applied to the metal grid c through the DC power supply c. The negatively charged particles move towards the metal grid c under the influence of the electric field. The particles pass through the mesh of the metal grid c, are pumped away by a molecular pump, and discharged from the chamber, thus quickly and effectively removing particles, preventing particle deposition inside the reaction chamber, and improving the production efficiency of the ion processing equipment.

Description

Technical Field

[0001] This invention relates to a method and apparatus for removing particles from an ion beam etching system. It involves a structural modification of the ion beam etching equipment to efficiently remove particles generated by the ion beam etching system without opening cavities. Prior Technology

[0002] Ion beam etching (IBE) involves filling an ion source discharge chamber with inert gases such as argon, krypton, or xenon, ionizing them to form plasma, and then using a grid to extract and accelerate the ions into a beam. This high-energy ion beam enters the working chamber and strikes the solid surface, bombarding the surface atoms and causing sputtering, thus achieving the etching effect. It is a purely physical bombardment process. When etching complex systems such as various metals and oxides, various sizes of debris and particles are sputtered into the reaction chamber. Due to the low pressure within the chamber, larger and more distant non-volatile particles are difficult to remove by the molecular pump, leading to byproduct deposition on the chamber walls. This not only causes particle contamination but also leads to process drift over time, reducing process repeatability. Therefore, cleaning the plasma processing chamber is necessary. However, in actual use, cleaning will cause process interruptions, reducing the production efficiency of the plasma processing equipment.

[0003] Currently, research on polymer deposition on the etching chamber walls during etching processes has yielded various industrial solutions with significant improvement effects. Among these, the most widely used method, fabless automated dry etching cleaning, typically uses fluorine-rich gases such as NF3 to remove inorganic polymers and oxygen-rich gases such as O2 to remove organic polymers, depositing a silicon dioxide-like polymer layer on the inner wall of the etching chamber after cleaning. These fabless self-cleaning steps effectively improve chamber deposition. However, there is still no effective industrial solution for handling debris such as metal particles generated during ion beam etching (IBE) processes. The only solution is to open the chamber periodically, severely impacting equipment throughput.

[0004] Chinese patent application CN105097445B discloses a method for removing particles from an etching chamber, comprising: forming a coating in a dry etching chamber; placing a wafer in the dry etching chamber; etching the metal-containing layer of the wafer; and removing the wafer from the dry etching chamber. After removing the wafer from the dry etching chamber, the coating is removed. This patent is equivalent to applying a protective film to the inner wall of the chamber. The protective film is removed after the process, and the chamber still needs to be cleaned, but this method can maintain the cleanliness of the inner wall of the chamber and prevent particle adhesion.

[0005] Patent application CN101727025A discloses a method for removing photoresist residue and etching reactant particles, comprising: sequentially forming a layer to be etched and a patterned photoresist layer on a semiconductor substrate; etching the layer to be etched using the photoresist layer as a mask; removing the photoresist layer by ashing; placing the semiconductor substrate with each film layer into a solution jet circulation tank, removing photoresist residue by jetting with a first solution, while the first solution containing photoresist residue flows out of the solution jet circulation tank; introducing a second solution by jetting to remove etching reactant particles remaining during the etching process, while the second solution containing etching reactant particles flows out of the solution jet circulation tank. This invention ensures that photoresist residue and etching reactant particles can be effectively removed, improving the performance of semiconductor devices. However, this invention addresses how to remove particles already present on the etched wafer while protecting the desired wafer layer from damage, and is unrelated to my invention.

[0006] Chinese patent application CN109216241B discloses a smart self-cleaning method for etching byproducts, applicable to semiconductor dry etching processes. It provides a process control system and a dry etching device, and includes the following steps: Step S1, before the start of the corresponding dry etching process, the process control system collects first process parameters from the dry etching process previously executed by the dry etching device; Step S2, based on the first process parameters, the process control system obtains second process parameters for self-cleaning the dry etching device; Step S3, the process control system performs a self-cleaning process on the dry etching device based on the second process parameters; Step S4, the dry etching device executes the corresponding dry etching process, and returns to step S1 after the dry etching process is completed. This invention reduces the source of etching defects caused by polymer accumulation during etching, improving the first-egg effect problem in wafer batch operations. This invention provides a process control system that reads process parameters from different batches, compares them with standard values, and then performs self-cleaning to ensure consistency of process conditions. However, the method of self-cleaning is not explained and is not directly related to this invention. Summary of the Invention

[0007] To overcome the limitations of existing semiconductor ion beam etching equipment, which uses inert gas for physical bombardment and is therefore unsuitable for inductively coupled plasma (ICP) waferless cleaning processes, requiring open-cavity cleaning to remove particles and severely impacting equipment capacity, this invention aims to provide a method and apparatus for removing particles from an ion beam etching system. By adding a metal grid with a positive voltage applied, electrons are emitted from the neutralizer component in the ion beam etching system, causing the particles inside the cavity to become negatively charged. The charged particles are then attracted away, eliminating the need for an open cavity and achieving efficient particle removal, thus improving the production efficiency of the plasma processing equipment.

[0008] To solve the above-mentioned technical problems, the present invention is implemented as follows:

[0009] An apparatus for removing particles from an ion beam etching system comprises adding a metal grid to the reaction chamber of the ion beam etching system. Specifically, the grid is fixed to the inner wall of the reaction chamber by threaded holes at both ends and insulating components. The grid is connected to a DC power supply to generate a positive voltage, the value of which is adjustable within 100 kV according to the size of the particles to be removed.

[0010] Preferably, the metal grid c is located at the bottom of the cavity to improve efficiency.

[0011] The metal grid is made of a hard metal, such as molybdenum or nickel, with mesh sizes of less than 5 mm to allow particles of different sizes to pass through. The shape of the metal grid can be circular, square, or irregular.

[0012] The operation method of the above-mentioned device for removing particles from the ion beam etching system involves disconnecting the ion source of the ion beam etching system after the etching process is completed, rotating the lower electrode 90° to a position perpendicular to the metal grid c, and turning on the neutralizer for a period of time. A large number of electrons generated by the neutralizer will adhere to the particles, causing the various particles originally sputtered in the reaction chamber to become negatively charged. Then, a positive voltage is applied to the metal grid c through the DC power supply c. At this time, the negatively charged particles will move towards the metal grid c under the action of the electric field. The bottom of the metal grid c is the suction port of the molecular pump. At this time, the particles will pass through the mesh of the metal grid c and be pumped away by the molecular pump and discharged from the chamber, which facilitates rapid and effective removal of particles and prevents the deposition of particles inside the reaction chamber.

[0013] The ion source is a radio frequency excited ion source used to generate ion beams during the etching process. It consists of a radio frequency power supply, a matching unit, a radio frequency coil, a grounding capacitor C, a discharge cavity, a DC power supply a, a filter a, a grid a, a DC power supply b, a filter b, and a grid b.

[0014] Alternatively, the ion source can be a Kaufman type ion source or an electron cyclotron resonance (ECR) ion source.

[0015] The radio frequency power supply is connected to the radio frequency coil via a matching device to ionize the gas introduced into the discharge cavity. The ion beam is then extracted through two layers of grids, which is the principle of ion beam generation in the ion beam etching system.

[0016] The lower electrode serves as the wafer stage for the ion beam etching system. It can rotate and revolve to change the ion beam incident angle, achieving etching at different angles on both sides. When removing particles, rotating it 90° to a position perpendicular to the metal grid c serves two purposes: firstly, to reduce particle deposition on the lower electrode surface, and secondly, to fully expose the metal grid c within the reaction chamber, thereby allowing for more thorough particle adsorption.

[0017] The neutralizer is used to generate electrons that attach to the particles in the reaction chamber, making them negatively charged. It can be a radio frequency neutralizer, a thermionic neutralizer, a hollow cathode neutralizer, or an electron cyclotron resonance neutralizer.

[0018] The present invention has the following positive effects: (1) The present invention addresses the specific conditions provided by the ion beam etching system containing a neutralizer, which provides a large number of electrons. The addition of a grid makes the particles negatively charged. Other etching systems, without this environment, cannot achieve efficient particle removal even if a grid is added. (2) This invention is easy to implement. It only requires fixing the grid in the cavity with screws and fasteners and connecting the grid to a DC power supply. Placing it at the bottom is to improve efficiency. (3) The efficiency of particle removal in this invention can be improved by increasing the number of electrons generated by the neutralizer and increasing the voltage of the DC power supply c. The more electrons there are, the easier they are to be collided and adsorbed by particles; the higher the voltage on the metal grid c, the stronger the electric field generated. Even larger particles far away from the grid can move towards the grid under the action of the electric field, and thus be pumped away by the molecular pump and discharged from the cavity. (4) The working principle of this invention differs from that of an electrostatic precipitator, which uses high-voltage direct current to maintain an electrostatic field sufficient to ionize the gas on two metal anodes and cathodes with significantly different radii of curvature. The electrons, anions, and cations generated after gas ionization are adsorbed onto the dust passing through the electric field, thus giving the dust an electrical charge. Under the action of the electric field force, the charged dust moves to the electrodes with opposite polarities and is deposited on the electrodes, achieving the purpose of separating dust and gas. Simple Explanation of the Diagram

[0019] Figure 1 is a schematic diagram of the structure of a device for removing particles from an ion beam etching system according to the present invention. Figure 2 shows a comparison experiment of particle removal effects before and after installing the metal grid c in Example 1. Implementation

[0020] The present invention will now be described in further detail with reference to specific embodiments.

[0021] Example 1

[0022] This invention provides a schematic diagram of a device for removing particles from an ion beam etching system. The device involves adding a metal grid to the bottom of the reaction chamber of the ion beam etching system. This grid is connected to a DC power supply to generate a positive voltage, the value of which is adjustable within 100 kV according to the size of the particles to be removed.

[0023] When wafer etching is required, the RF power supply 6 is connected to the RF coil 8 via a matching converter. The other end of the RF coil 8 is connected to a grounding capacitor, which is used to balance the voltage across the RF coil. Inductive coupling is used to ionize the gas introduced into the discharge chamber 7 to generate plasma. The DC power supply a applies a positive voltage to the grid a through filter a to accelerate and attract electrons in the plasma, energizing it. Positive ions in the plasma pass through the grid a under the influence of the sheath voltage. The DC power supply b applies a negative voltage to the grid b through filter b. Positive ions passing through the grid a are accelerated through the grid b under the influence of this negative electric field, forming an ion beam. The ion beam is then neutralized by electrons in the neutralizer 15, and finally bombards the wafer on the lower electrode surface with a certain energy and angle, causing material atoms to sputter, achieving the etching purpose.

[0024] When the etching process is complete and the particles sputtered by the ion beam etching system need to be removed, the ion source of the ion beam etching system is first disconnected. Then, the lower electrode 13 is rotated 90° to a position perpendicular to the metal grid c (this is to reduce particle deposition on the lower electrode surface and to fully expose the metal grid c to the reaction chamber, allowing for more thorough particle adsorption). The neutralizer 15 is then turned on, and a large number of electrons generated by the neutralizer attach to the particles, causing the various non-volatile particles originally sputtered in the reaction chamber to become negatively charged. A positive voltage is then applied to the metal grid c via a DC power supply c. At this point, the negatively charged particles move towards the metal grid c under the influence of the electric field. Below the metal grid c is the suction port of the molecular pump 14. The particles pass through the mesh of the metal grid c and are drawn away by the molecular pump below, exiting the chamber through the pipe, thus achieving the purpose of particle removal.

[0025] Example 2: Experimental Confirmation of Particle Removal Effect

[0026] To investigate the particle removal effect of this invention, firstly, without the grid installed, after ion beam etching, the number of 0.12µm particles was measured using an SP1 detector, and 10 sets of data were recorded. The number of 0.12µm particles was generally around 900. Then, using the device and method provided by this invention, a circular molybdenum grid with a diameter of 38cm and a mesh diameter of 2mm was selected and fixed to the bottom of the reaction chamber (the two ends of the metal grid were connected to the reaction chamber through insulating parts). After the process was completed, the neutralizer was turned on for 10 minutes, and then an 8KV positive voltage was applied through the DC power supply connected to the metal grid c. After 5 minutes, the number of 0.12µm particles was measured again using an SP1 detector. This experiment was repeated 10 times and the data was recorded. At this time, the number of 0.12µm particles was generally around 20, which met the process requirements, as shown in Figure 2.

[0027] In this embodiment 2, only the number of particles with a size of 0.12 μm was detected for comparison. In reality, the particle size in the reaction chamber varies. A larger grid, a larger grid voltage and application time, and a longer neutralizer energizing time can all greatly improve the particle removal efficiency.

[0028] The above specific embodiments do not limit the technical solutions of the present invention in any way. All technical solutions obtained by means of equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

[0029] 1: DC power supply a 10: Fence a 11: Fence b 12: Metal grid c 13: Lower electrode 14: Molecular pump 15: Neutralizer 16: DC power supply c 17: Reaction Chamber 2: DC power supply b 3: Filter a 4: Filter b 5: Capacitor C 6: Radio Frequency Power Supply 7: Discharge cavity 8: Radio Frequency Coil 9: Plasma FT: Vacuum Electrode (Feed Through) Gas in: Gas enters S1, S2, S3, S4: Steps

Claims

1. A method for removing particles from an ion beam etching system, applied in an apparatus for removing particles from an ion beam etching system, wherein the apparatus comprises: Neutralizer, used to generate electrons that attach to the particles to be removed, so that the various particles originally sputtered in the reaction chamber are negatively charged; A metal grid c is added to the reaction chamber of the ion beam etching system, and the metal grid c is connected to a DC power supply to generate a positive voltage, and the metal grid c is set at the bottom of the reaction chamber; Lower electrode, the lower electrode is the stage of the wafer of the ion beam etching system, and it can be rotated to a position perpendicular to the metal grid c; The method includes: (1) When the etching process is completed and the particles of the etching system need to be processed, the ion source of the ion beam etching system is first disconnected, and then the lower electrode is rotated to a position perpendicular to the metal grid c; (2) The neutralizer is turned on, and a large number of electrons generated by the neutralizer will attach to the particles to be removed, so that the various particles originally sputtered in the reaction chamber are negatively charged; (3) A positive voltage is applied to the metal grid c through the DC power supply c, and the negatively charged particles will move towards the metal grid c under the action of the electric field; (4) The bottom of the metal grid c is the pump hole of the molecular pump. At this time, the particles will pass through the mesh of the metal grid c and be pumped away by the molecular pump and discharged out of the chamber, which quickly and effectively removes the particles and prevents the deposition of particles inside the reaction chamber.

2. The method for removing particles from an ion beam etching system as described in claim 1, wherein: In step (3), the applied positive voltage is adjusted within 100 kV according to the size of the particles to be removed.

3. The method for removing particles from an ion beam etching system as described in claim 1, wherein: The lower electrode in step (1) is the stage of the wafer in the ion beam etching system. It can rotate and revolve to change the incident angle of the ion beam, so as to achieve etching at different angles on both sides. When removing particles, it is rotated 90° to a position perpendicular to the metal grid c.

4. The method for removing particles from an ion beam etching system as described in claim 1, wherein: The neutralizer in step (2) is any one of the following: radio frequency neutralizer, hot cathode neutralizer, hollow cathode neutralizer, or electron cyclotron resonance neutralizer.

5. The method for removing particles from an ion beam etching system as described in claim 1, wherein: The efficiency of particle removal can be improved by adjusting the number of electrons generated by the neutralizer and adjusting the voltage of the DC power supply c.

6. The method for removing particles from an ion beam etching system as described in claim 1, wherein: The etching process in step (1) involves ionizing the gas introduced into the discharge cavity to generate plasma through inductive coupling.

7. The method for removing particles from an ion beam etching system as described in claim 6, wherein the apparatus further includes a grid a disposed on the side of the reaction chamber, the grid a being perpendicular to the metal grid c, the method further comprising: DC power supply a applies a positive voltage to the grid a through filter a to accelerate and attract electrons in the plasma, thus energizing the plasma.

8. The method for removing particles from an ion beam etching system as described in claim 7, wherein: Positive ions in the plasma pass through the grid a under the influence of the sheath voltage.

9. A method for removing particles from an ion beam etching system as claimed in claim 8, wherein the apparatus further includes a grid b disposed between the grid a and the metal grid c, the grid b being parallel to the metal grid c, the method further comprising: A DC power supply b applies a negative voltage to the grid b through a filter b. Positive ions passing through the grid a are accelerated through the grid b under the influence of the negative electric field to form an ion beam.

10. The method for removing particles from an ion beam etching system as described in claim 9, wherein: The ion beam is then neutralized by electrons in the neutralizer, and finally bombards the wafer on the lower electrode surface with a certain energy and angle, causing material atoms to sputter and achieving the etching purpose.

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