A magnetic core cluster enhanced radio frequency ion source for reactive etching

Abstract

The application discloses a magnetic core gathering enhanced radio frequency ion source for reactive etching, which comprises a mounting flange, an ion source module is mounted on one side of the mounting flange, and a water cooling plate is mounted on the other side of the mounting flange, a lower shielding shell is mounted outside the water cooling plate, the ion source module comprises a discharge chamber, a radio frequency coil, a static magnet and an iron core which are arranged outside the discharge chamber in sequence, a gas distributor is arranged on the side of the discharge chamber close to the mounting flange, and an acceleration grid ion optical system is mounted on the other side of the discharge chamber, an upper shielding cover is arranged outside the iron core and the acceleration grid ion optical system, and an opening is arranged on the upper shielding cover and located at the ion source outlet of the discharge chamber and the acceleration grid ion optical system. The application aims at overcoming the shortcomings of the prior art, such as poor adaptability of electronegative gas, difficulty in igniting and maintaining plasma, and requirement of high radio frequency power for ionization, improving process gas adaptability, improving gas ionization rate, and realizing long-time stable etching application of the ion source.

Description

Technical Field

[0001] This invention belongs to the field of reactive ion etching technology for optical components and micro / nano structures, and specifically relates to a magnetic core aggregation enhanced radio frequency ion source for reactive etching. Background Technology

[0002] In recent years, reactive ion beam etching (RIBE) technology has been widely used in the fabrication of ultra-smooth optical surfaces, large-scale integrated circuits, metasurfaces, and micro / nano structures to obtain nanoscale precision structures, low surface damage, and high verticality sidewalls. RIBE technology originates from reactive ion etching (RIE) technology. During processing, a targeted corrosive reactive gas is introduced into the ion source according to the material to be processed. Ionization occurs within the ion source, forming a plasma containing a certain concentration of reactive ions. These reactive ions are then accelerated and extracted by an accelerating gate ion optical system, reaching the material to be processed. Therefore, the atoms on the material surface combine with the reactive ions and are simultaneously subjected to physical impacts, achieving material removal under the combined conditions of physical and chemical effects. Furthermore, since the etching process is carried out in a chamber separate from the ion source, the main parameters affecting the etching process are ion energy, ion current, and the residual gas environment within the etching chamber. These can all be independently and flexibly controlled by adjusting the parameters of the ion source.

[0003] In existing reactive ion beam etching, considering the limited lifespan and metal ion contamination of Kaufman cathode ion sources (cathode materials are LaB6 and barium tungsten), radio frequency (RF) ion sources with simple structures and ceramic plasma edges are often used (represented by the RIT series developed by the University of Giessen and the RF ion sources from Veeco in the United States) to achieve reactive ion etching. However, the power feed and ignition start-up of RF ion sources have always been unavoidable drawbacks. This is because gas ionization is achieved by electrons colliding with gas molecules through a half-cycle of RF circumferential electric field E. Therefore, when electronegative gases such as SF6 and O2 are introduced, the electron density in the discharge chamber decreases significantly, making the ion source unstable or even extinguishing. Currently, high RF power is commonly used to achieve ionization, but excessively high RF power will lead to excessive current and temperature in the RF coil, and the ceramic discharge chamber is prone to deformation or even cracking under prolonged heating. Currently, many domestic institutions have developed radio frequency ion sources for reactive etching according to their own needs, such as the Institute of Plasma Physics of the Chinese Academy of Sciences, the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences, the University of Science and Technology of China, and Boton Optoelectronic Co., Ltd. However, the products developed by many institutions currently adopt radio frequency ion source structures similar to those of the University of Giessen, and have failed to solve the shortcomings such as difficulty in ionization when facing electronegative gases and difficulty in maintaining stable plasma, making it difficult to achieve long-term stable application. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a magnetic core aggregation enhanced radio frequency ion source for reactive etching, which addresses the above-mentioned problems of the prior art. The present invention aims to overcome the shortcomings of existing radio frequency ion sources, such as poor adaptability to electronegative gases, difficulty in ignition and maintaining plasma, and the need for high radio frequency power to achieve ionization, thereby improving the adaptability to process gases, increasing the gas ionization rate, and realizing the long-term stable etching application of the ion source.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A magnetic core focusing enhanced radio frequency ion source for reactive etching includes a mounting flange. An ion source module is mounted on one side of the mounting flange and a water-cooled plate is mounted on the other side. A lower shielding shell is mounted on the outside of the water-cooled plate. The ion source module includes a discharge chamber and a radio frequency coil, a static magnet, and an iron core arranged sequentially outside the discharge chamber. A gas distributor is provided on one side of the discharge chamber near the mounting flange, and an accelerating gate ion optical system is mounted on the other side. An upper shielding cover is provided outside the iron core and the accelerating gate ion optical system, and an opening is provided on the upper shielding cover at the ion source outlet of the discharge chamber and the accelerating gate ion optical system.

[0007] Optionally, the accelerating gate ion optical system includes a screen grid, an accelerating grid, and a decelerating grid arranged sequentially at intervals. The pinholes on the screen grid are arranged in a hexagonal pattern. There is a voltage difference between the screen grid and the accelerating grid to draw out ions in the discharge chamber. The decelerating grid is grounded to prevent electron backflow.

[0008] Optionally, the discharge chamber is a hollow cylindrical structure made of ceramic.

[0009] Optionally, the radio frequency coil is a cylindrical spiral tube wound around the outer wall of the discharge chamber, with one end of the cylindrical spiral tube serving as a water inlet and the other end as a water outlet for introducing deionized water through the cylindrical spiral tube to cool the radio frequency coil and the discharge chamber.

[0010] Optionally, the static magnet is a tubular structure and is sleeved on the outside of the radio frequency coil.

[0011] Optionally, the iron core is a tubular structure with tubular edges at both ends that are perpendicular to the tube wall and extend inward, so that the end faces of the radio frequency coil and the static magnet are embedded and installed between the two tubular edges.

[0012] Optionally, the mounting flange, water-cooled plate, and lower shielding shell are all provided with openings in the middle, and the gas inlet pipe of the gas distributor passes through the mounting flange, water-cooled plate, and lower shielding shell in sequence and extends out to the outside of the lower shielding shell.

[0013] Optionally, the water-cooled plate is a disc-shaped plate with a through hole in the middle and an annular water-cooling cavity inside, and the water-cooled plate is provided with an inlet and an outlet that are both connected to the annular water-cooling cavity.

[0014] Optionally, the process gas supplied through the gas inlet pipe of the gas distributor is an electronegative process gas.

[0015] Furthermore, the present invention also provides a method for applying the aforementioned magnetic core aggregation-enhanced radio frequency ion source for reactive etching, comprising the following steps:

[0016] S101, the magnetic core gathering enhanced radio frequency ion source for reactive etching is placed in a sealed environment and the sealed environment is evacuated to a first preset pressure, so that the radio frequency coil is supplied with radio frequency power so that the ion source module can be started directly without arcing through ignition voltage.

[0017] S102, an electronegative process gas is introduced into the sealed environment to raise the sealed environment to the second preset pressure. The electronegative process gas is delivered to the discharge chamber through the gas inlet pipe of the gas distributor. The voltage difference between the screen grid and the accelerating grid of the accelerating grid ion optical system is used to extract ions in the discharge chamber. The deceleration grid is grounded to prevent electron backflow and generate a stable ion flow. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the magnetic core aggregation-enhanced radio frequency ion source used for reactive etching in an embodiment of the present invention.

[0019] Legend: 1. Gas inlet pipe; 2. Lower shielding shell; 3. Water-cooled plate; 4. Mounting flange; 5. Gas distributor; 6. Iron core; 7. Static magnet; 8. Radio frequency coil; 9. Discharge chamber; 10. Accelerating gate ion optical system; 11. Upper shielding cover. Detailed Implementation

[0020] like Figure 1 As shown, this embodiment provides a magnetic core focusing enhanced radio frequency ion source for reactive etching, including a mounting flange 4. An ion source module is mounted on one side of the mounting flange 4, and a water-cooled plate 3 is mounted on the other side. A lower shielding shell 2 is mounted on the outside of the water-cooled plate 3. The ion source module includes a discharge chamber 9 and a radio frequency coil (RF coil) 8, a static magnet 7, and an iron core 6 arranged sequentially on the outside of the discharge chamber 9. A gas distributor 5 is provided on one side of the discharge chamber 9 near the mounting flange 4, and an accelerating gate ion optical system 10 is mounted on the other side. An upper shielding cover 11 is provided on the outside of the iron core 6 and the accelerating gate ion optical system 10, and an opening is provided on the upper shielding cover 11 at the ion source outlet of the discharge chamber 9 and the accelerating gate ion optical system 10. Other confinement magnetic fields, gas distribution systems, etc. are omitted here and not labeled.

[0021] like Figure 1 As shown, the accelerating grid ion optical system 10 of this embodiment includes a screen grid, an accelerating grid and a decelerating grid arranged sequentially at intervals. The small holes on the screen grid are arranged in a hexagonal pattern. There is a voltage difference between the screen grid and the accelerating grid to draw out ions in the discharge chamber 9. The decelerating grid is grounded to prevent electron backflow and improve the stability of discharge and beam attraction.

[0022] like Figure 1 As shown, the discharge chamber 9 in this embodiment adopts a hollow cylindrical structure made of ceramic. The inner diameter and length of the discharge chamber 9 meet the dimensional calibration rules of the radio frequency ion source discharge chamber. In this embodiment, the inner diameter is 52 mm and the wall thickness is 2 mm. In the plasma, molecular dissociation and ion recombination occur constantly, maintaining the overall electroneutrality of the plasma. Therefore, the plasma density depends on the ionization velocity of atoms and the recombination velocity of ions. Existing theories indicate that ions recombine during the movement of the plasma and also recombine on the discharge chamber wall. In the low-pressure plasma commonly used in reactive etching, recombination mainly occurs on the discharge chamber wall. Therefore, in order to maintain a high plasma density, the discharge chamber 9 in this embodiment uses a ceramic discharge chamber made of Al2O3 ceramic with a low recombination velocity. The radio frequency coil 8 is tightly wound around the discharge chamber 9, which on the one hand increases the plasma absorption power, and on the other hand, provides better cooling to the discharge chamber through water cooling in the coil.

[0023] like Figure 1 As shown, in this embodiment, the RF coil 8 is a cylindrical spiral tube wound around the outer wall of the discharge chamber 9. One end of the cylindrical spiral tube serves as a water inlet, and the other end serves as a water outlet, allowing deionized water to be introduced through the spiral tube to cool the RF coil 8 and the discharge chamber 9. In this embodiment, the cylindrical spiral tube is specifically made of soft hollow copper tubing, connected to an independent RF power supply, with an RF antenna frequency of 13.56MHz. It is tightly wound around the outer perimeter of the discharge chamber, with a total of 5 turns, a diameter of 4mm, and a turn spacing of 3mm. The surface is silver-plated to increase conductivity, and deionized water is circulated inside for cooling, so that the RF coil 8, the circuit, and the wall of the discharge chamber 9 are cooled simultaneously.

[0024] Static magnets 7 are uniformly distributed around the coil to form a static magnetic field. These magnets 7 are fixed by the iron core 6, forming a magnetic field shielding structure that enhances the magnetic core and increases the coil's magnetic coupling efficiency. Furthermore, by utilizing this core-enhanced structure, the magnetic field is concentrated only on the load (i.e., plasma), reducing the antenna loss in the loop of the RF coil 8. Therefore, higher ionization efficiency and plasma density can be achieved at the same RF power. Figure 1 As shown, the static magnet 7 in this embodiment has a tubular structure and is sleeved on the outside of the radio frequency coil 8. The static magnets 7 are evenly distributed around the radio frequency coil 8 and are fixedly surrounded by the iron core 6, so that the magnetic field is concentrated only on the load (i.e., plasma), reducing the antenna loss in the circuit and obtaining higher ionization efficiency and plasma density.

[0025] like Figure 1 As shown, the iron core 6 in this embodiment has a tubular structure with inwardly extending tube edges perpendicular to the tube wall at both ends, allowing the end faces of the RF coil 8 and the static magnet 7 to be embedded between the two tube edges. The iron core 6 is externally shielded by a ferromagnetic material to prevent leakage of the magnetic field induced by high-frequency voltage. The outer metal shield shell formed by the upper shield shell 11 is cylindrical, shielding the high-frequency energy leaked by the antenna from the electron-rich vacuum environment outside, thus preventing Penning discharge from the source surface. It can be specifically designed according to the plasma aperture D.

[0026] like Figure 1 As shown, in this embodiment, the mounting flange 4, the water-cooled plate 3, and the lower shield shell 2 are all provided with openings in the middle. The gas inlet pipe 1 of the gas distributor 5 passes through the mounting flange 4, the water-cooled plate 3, and the lower shield shell 2 in sequence and extends out to the outside of the lower shield shell 2.

[0027] like Figure 1As shown, in this embodiment, the mounting flange 4 is located in the middle of the magnetic core focusing enhanced radio frequency ion source used for reactive etching. The lower shield shell 2, the water-cooled plate 3, and the mounting flange 4 are tightly fitted together, allowing the water-cooled temperature of the water-cooled plate 3 to be transferred to the entire ion source shell. The mounting flange 4 can be customized with mounting screw holes according to different equipment to adapt to different equipment installation and use.

[0028] like Figure 1 As shown, the water-cooled plate 3 in this embodiment is a disc-shaped plate with a through hole in the middle and an annular water-cooling cavity inside. The water-cooled plate 3 is provided with an inlet and an outlet that are both connected to the annular water-cooling cavity.

[0029] The process gas supplied through the gas inlet pipe 1 of the gas distributor 5 can be oxygen, chlorine, nitrogen, Ar, etc., and it also has a good ionization effect, especially for highly electronegative gases such as SF6. Through the gas distributor, the working gas passes through the distributor and diffuses evenly and rapidly into the discharge chamber. Therefore, in this embodiment, the process gas supplied through the gas inlet pipe 1 of the gas distributor 5 is an electronegative process gas, such as SF6. The gas supply is controlled in real time by a computer-controlled mass flow meter, and the gas enters the discharge chamber through the ceramic gas inlet pipe 1 and the gas distributor 5, ensuring uniform lateral ejection of the gas. When the ion source operating environment is 10... -2 At Pa, the ion source can be started directly without requiring an ignition voltage to initiate the arc. The vacuum pumping system, combined with an adjustable throttle valve, can stabilize the working environment vacuum at 10 Pa. -2 Pa, when the process gas is introduced, the vacuum level in the vacuum chamber rises to 10. -1 Pa.

[0030] In summary, the magnetic core-enhanced radio frequency ion source for reactive etching in this embodiment includes a gas inlet pipe 1, a lower shielding shell 2, a water-cooled plate 3, a mounting flange 4, a gas distributor 5, an iron core 6, a static magnet 7, a radio frequency coil 8, a discharge chamber 9, an accelerating gate ion optical system 10, and an upper shielding cover 11. Utilizing the magnetic core-enhanced structure, the magnetic field is concentrated only on the load (i.e., plasma), reducing antenna losses in the loop. Therefore, higher ionization efficiency and plasma density can be obtained at the same radio frequency power. This embodiment can operate normally at a low pressure of 0.001 Pa and can be applied to reactive etching processes on various substrate materials. The ion source exhibits high stability. Under different gas ratios, for commonly used electronegative gases in reactive etching processes (such as SF6, CHF3, O2, etc.), increasing the ion density in the plasma accelerates process efficiency and avoids instability or even extinction of the ion source due to excessively low electron density.

[0031] The working process of the magnetic core aggregation-enhanced radio frequency ion source used in this embodiment for reactive etching is as follows: When the radio frequency current passes through the radio frequency coil 8, an axial radio frequency magnetic field is generated, such as... Figure 1 As shown in E, the magnetic field changes over time, generating a vortex-induced electric field. This induced electric field accelerates electrons within the discharge chamber 9, causing them to collide with and ionize gas particles, thereby generating and maintaining plasma. The accelerating gate ion optical system 10 employs a three-gate accelerating gate ion optical system, including a screen grid, an accelerating grid, and a decelerating grid. The screen grid has multiple small holes, forming a plasma sheath near the plasma boundary to accelerate ions. These ions are then focused and accelerated by the accelerating gate ion optical system to form an ion beam. This embodiment of the magnetic core-enhanced radio frequency ion source for reactive etching can be applied to reactive ion etching manufacturing. This embodiment utilizes a magnetic core-enhanced structure to increase the ion density in the electronegative gas plasma commonly used in reactive etching processes, avoiding instability or even extinction of the ion source due to excessively low electron density. It can be applied to processes such as large-scale integrated circuit manufacturing, grating manufacturing, and micro / nanostructure and metasurface manufacturing, exhibiting strong manufacturing feasibility and high ion source reliability.

[0032] Furthermore, this embodiment also provides a method for applying the aforementioned magnetic core aggregation-enhanced radio frequency ion source for reactive etching, comprising the following steps:

[0033] S101, the magnetic core gathering enhanced radio frequency ion source for reactive etching is placed in a sealed environment and the sealed environment is evacuated to a first preset pressure, so that radio frequency power is supplied to the radio frequency coil 8 so that the ion source module can be started directly without arcing through ignition voltage.

[0034] S102, an electronegative process gas is introduced into the sealed environment to raise the sealed environment to the second preset pressure. The electronegative process gas is delivered to the discharge chamber 9 through the gas inlet pipe 1 of the gas distributor 5. The voltage difference between the screen grid and the acceleration grid of the accelerating grid ion optical system 10 is used to extract ions from the discharge chamber 9. The deceleration grid is grounded to prevent electron backflow and generate a stable ion flow.

[0035] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A magnetic core focusing enhanced radio frequency ion source for reactive etching, characterized in that, The system includes a mounting flange (4), on one side of which an ion source module is mounted and on the other side a water-cooled plate (3). A lower shielding shell (2) is mounted on the outside of the water-cooled plate (3). The ion source module includes a discharge chamber (9) and a radio frequency coil (8), a static magnet (7), and an iron core (6) arranged sequentially on the outside of the discharge chamber (9). A gas distributor (5) is provided on one side of the discharge chamber (9) near the mounting flange (4), and an accelerating gate ion optical system (10) is mounted on the other side. The iron core (6) and the accelerating gate ion optical system... (10) is provided with an upper shield (11) on the outside, and the upper shield (11) has an opening at the ion source outlet of the discharge chamber (9) and the accelerating gate ion optical system (10); the radio frequency coil (8) is a columnar spiral tube wound on the outer wall of the discharge chamber (9); the static magnet (7) is a tubular structure and is sleeved on the outside of the radio frequency coil (8); the iron core (6) is a tubular structure and has tube edges that are perpendicular to the tube wall and extend inward at both ends, so that the end faces of the radio frequency coil (8) and the static magnet (7) are embedded and installed between the two tube edges.

2. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 1, characterized in that, The accelerating gate ion optical system (10) includes a screen grid, an accelerating grid and a decelerating grid arranged in sequence at intervals. The small holes on the screen grid are arranged in a hexagonal pattern. There is a voltage difference between the screen grid and the accelerating grid to draw out ions in the discharge chamber (9). The decelerating grid is grounded to prevent electron backflow.

3. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 2, characterized in that, The discharge chamber (9) is a hollow cylindrical structure made of ceramic.

4. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 3, characterized in that, One end of the columnar spiral tube serves as the water inlet, and the other end serves as the water outlet, so that deionized water can be introduced through the columnar spiral tube to cool down the radio frequency coil (8) and the discharge chamber (9).

5. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 1, characterized in that, The mounting flange (4), water-cooled plate (3) and lower shield shell (2) are all provided with openings in the middle. The gas inlet pipe (1) of the gas distributor (5) passes through the mounting flange (4), water-cooled plate (3) and lower shield shell (2) in sequence and extends out to the outside of the lower shield shell (2).

6. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 5, characterized in that, The water-cooled plate (3) is a disc-shaped plate with a through hole in the middle and an annular water-cooled cavity inside. The water-cooled plate (3) is provided with an inlet and an outlet that are connected to the annular water-cooled cavity.

7. The magnetic core focusing enhanced radio frequency ion source for reactive etching according to claim 6, characterized in that, The process gas supplied by the gas inlet pipe (1) of the gas distributor (5) is an electronegative process gas.

8. A method for applying the magnetic core focusing enhanced radio frequency ion source for reactive etching as described in any one of claims 1 to 7, characterized in that, Includes the following steps: S101, the magnetic core gathering enhancement radio frequency ion source for reactive etching is placed in a sealed environment and the sealed environment is evacuated to the first preset pressure, so that the radio frequency coil (8) is supplied with radio frequency power so that the ion source module can be started directly without arcing through the ignition voltage. S102, an electronegative process gas is introduced into the sealed environment to raise the sealed environment to the second preset pressure. The electronegative process gas is sent into the discharge chamber (9) through the gas inlet pipe (1) of the gas distributor (5). The voltage difference between the screen grid and the acceleration grid of the accelerating gate ion optical system (10) is used to extract ions in the discharge chamber (9). The deceleration grid is grounded to prevent electron backflow and generate a stable ion flow.

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