Radio frequency ion source discharge chamber mechanism for optical polishing

Abstract

The utility model discloses a radio frequency ion source discharge chamber mechanism for optical polishing, which belongs to the technical field of ion beam processing equipment, solves the problems that the existing radio frequency ion source equipment discharge chamber is complicated in structural design and incompact in integral structure, and has more use limitations, and comprises a discharge chamber and a grid system, the grid mesh system is installed on the end face of the discharge chamber, a radio frequency excitation coil is installed on the outer surface of the discharge chamber, the discharge chamber comprises a ceramic seat, a ceramic cavity is formed in the ceramic seat, an auxiliary anode is installed at the center of the ceramic seat, and a part of the auxiliary anode extends to the inner wall of the ceramic cavity. According to the radio frequency ion source used for optical polishing processing, structure recombination is carried out based on a wide beam ion source excitation principle, a low-potential electric field is locally arranged so as to obtain a low-energy ion beam, and mechanisms such as the discharge chamber and the accelerating electric field are embedded in the ion source, so that the structure of the ion source is more compact.

Description

Technical Field

[0001] The utility model belongs to the technical field of ion beam processing equipment, and in particular relates to a radio frequency ion source discharge chamber mechanism used for optical polishing. Background Art

[0002] In recent years, with the continuous development of optical polishing technology, polishing methods have become more diversified, and polishing equipment has emerged one after another. Fluid polishing and non-contact polishing technology have become important means of ultra-precision optical polishing, and non-contact polishing uses ion beam polishing as the main surface finishing method.

[0003] The hot filament excitation source (Kaufman type) was the original design standard for the ion source. This ion source is easy to use, but requires frequent maintenance and is greatly limited in use in reactive gases. Therefore, researchers developed a radio frequency source (hereinafter referred to as "RF", Radio Frequency abbreviation) with filamentless plasma excitation, which better extends the service life and has better performance in reactive gases.

[0004] For micro or special-shaped optical parts, we need to remove the surface material of the component efficiently in a shorter time. Therefore, a wide beam RF source is the best. Inductively coupled plasma (ICP) or transformer coupled plasma heating (TCP) in the RF field is a very effective electrode-free excitation principle. RF power is transmitted to the plasma through the primary RF coil, and the plasma acts as the secondary part of the transformer.

[0005] In the field of ion beam processing, wide beam ion sources are usually used, such as ion beam etching (IBE), ion beam sputtering (IBS), ion beam implantation (IBI) and ion beam cleaning (IBC). Ion beam polishing is a processing form of ion sputtering. When processing ultra-precision optical components, the required surface accuracy is λ / 200 (λ=632.8nm) and the required surface roughness is 1nm. Therefore, a wide beam and low-energy RF ion source is required. The ion beam energy is 500eV~1500eV for the best. Too low ion beam energy will not achieve efficient surface removal, and too high ion beam energy will lead to secondary ion implantation.

[0006] Based on the characteristics of ion beam processing, this equipment requires a smaller ion source body as a "tool" to remove materials to achieve non-contact and precise removal. Traditional RF ion sources generate plasma through a discharge chamber and then accelerate it through an accelerating electric field. However, the traditional discharge chamber structure design is relatively complex and the overall structure is not compact, resulting in many usage restrictions. Utility Model Content

[0007] The purpose of the utility model is to:

[0008] In order to solve the problem that the discharge chamber structure design of existing radio frequency ion source equipment is relatively complex and the overall structure is not compact, resulting in many usage restrictions, a radio frequency ion source discharge chamber mechanism for optical polishing is provided.

[0009] The technical solution adopted by the utility model is as follows:

[0010] A radio frequency ion source discharge chamber mechanism for optical polishing comprises a discharge chamber and a grid system, wherein the grid system is mounted on the end surface of the discharge chamber, a radio frequency excitation coil is mounted on the outer surface of the discharge chamber, the discharge chamber comprises a ceramic seat, a ceramic cavity is arranged in the ceramic seat, an auxiliary anode is mounted at the center of the ceramic seat, and a part of the auxiliary anode is extended to the inner wall of the ceramic cavity.

[0011] Furthermore, the grid system includes a shielding grid, an accelerating grid and a grounding grid arranged in sequence from the inside of the ceramic cavity to the outside of the ceramic cavity. The shielding grid, the accelerating grid and the grounding grid are connected to the inner wall of the ceramic cavity by bolts at intervals. The inner wall of the ceramic cavity is provided with an installation groove for installing the grid system.

[0012] Furthermore, annular insulating nets are respectively connected between the shielding grid, the accelerating grid and the grounding grid and the inner wall of the ceramic cavity, and ceramic balls are installed between adjacent insulating nets.

[0013] Furthermore, flange adjustment holes are provided on the shielding grid, the accelerating grid and the grounding grid, the ceramic balls are installed in the flange adjustment holes, and six ceramic balls are arranged between adjacent insulating nets.

[0014] Furthermore, the radio frequency excitation coil is a copper coil spirally wound on the outer surface of the discharge chamber, the copper coil is wound by a hollow copper tube, and the cavity inside the copper coil is set as a cooling water flow cavity.

[0015] In summary, due to the adoption of the above technical solution, the beneficial effects of the utility model are:

[0016] The utility model reorganizes the structure based on the excitation principle of a wide-beam ion source, locally sets a low-potential electric field to obtain a low-energy ion beam, and embeds the discharge chamber and the accelerating electric field inside the ion source. The matching structure of the discharge chamber and the radio frequency excitation coil and the structure inside the discharge chamber cavity are more reasonable, making the structure of the ion source more compact and more convenient for the extension of modern processing technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure and voltage of the discharge chamber mechanism of the utility model.

[0018] Figure 2 It is a structural diagram of the grid system and the ceramic seat of the utility model.

[0019] Markings in the figure: 1-discharge chamber, 2-grid system, 3-RF excitation coil, 4-ceramic seat, 5-ceramic cavity, 6-auxiliary anode, 7-shielding grid, 8-acceleration grid, 9-grounding grid, 10-insulating grid, 11-ceramic ball. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solution and advantages of the utility model more clear, the utility model is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the utility model and are not used to limit the utility model.

[0021] A radio frequency ion source discharge chamber mechanism for optical polishing, comprising a discharge chamber 1 and a grid system 2, such as Figure 1 As shown, the grid system 2 is installed on the end surface of the discharge chamber 1, a radio frequency excitation coil 3 is installed on the outer surface of the discharge chamber 1, and the discharge chamber 1 includes a ceramic base 4, a ceramic cavity 5 is arranged in the ceramic base 4, an auxiliary anode 6 is installed at the center of the ceramic base 4, and a part of the auxiliary anode 6 extends to the inner wall of the ceramic cavity 5. Among them, UBEA is the beam voltage, Urf is the radio frequency voltage, and Uacc is the voltage of the acceleration grid 8.

[0022] The grid system 2 includes a shielding grid 7, an accelerating grid 8 and a grounding grid 9 which are arranged in sequence from the inside of the ceramic cavity 5 to the outside of the ceramic cavity 5. The shielding grid 7, the accelerating grid 8 and the grounding grid 9 are connected to the inner wall of the ceramic cavity 5 by bolts at intervals. The inner wall of the ceramic cavity 5 is provided with an installation groove for installing the grid system 2.

[0023] Annular insulating nets 10 are respectively connected between the shielding grid 7, the accelerating grid 8 and the grounding grid 9 and the inner wall of the ceramic cavity 5, and ceramic balls 11 are installed between adjacent insulating nets 10. Flange adjustment holes are provided on the shielding grid 7, the accelerating grid 8 and the grounding grid 9, and the ceramic balls 11 are installed in the flange adjustment holes. As a preferred embodiment, six ceramic balls 11 are provided between adjacent insulating nets 10.

[0024] The ceramic discharge chamber 1 is the main part of the ion source. In addition to containing the discharge plasma, the discharge chamber 1 is also used to provide gas supply and electrical contact, and to install the grid system 2. The permanent magnets placed around the discharge chamber 1 ensure the electron confinement of the ionization, thereby reducing the ion source operating pressure and achieving a higher plasma density.

[0025] A planar auxiliary anode 6 made of graphite is mounted on the back of the cylindrical discharge chamber 1. The purpose of this anode is to fix the plasma potential, thereby controlling the energy of the generated ions and to evenly distribute the process gas in the discharge chamber 1.

[0026] The self-aligning grid system 2 is mounted directly on the ceramic cavity 5. Different grid series can be applied to achieve the best beam profile and the best grid life for each process. The grid system 2 is connected in a special groove at the front end of the ceramic cavity 5, such as Figure 2 As shown. The shielding grid 7 is directly bolted to the ceramic cavity 5. The accelerating grid 8 is suspended above the shielding grid 7, and a group of ceramic balls 11 are placed between the shielding grid 7 and the accelerating grid 8. The ceramic balls 11 play the role of electrical insulation and mechanical adjustment between the grids. For proper power supply operation, such as low accelerator current, stable beam profile and low grid erosion rate, precise grid adjustment is required. Preferably, the grid system 2 of the RF ion source uses 6 ceramic balls 11 for self-alignment, and the ceramic balls 11 have two standard diameters Dsp=3.175mm (1 / 8") and Dsp=3.969mm (5 / 32"). The ceramic balls 11 are placed in the flange adjustment holes with a grid diameter dad=1.95mm. In addition, when standard balls are used, the distances between the grids are fixed, which are dgr=1.00mm and dgr=1.96mm, respectively.

[0027] Depending on the total grid voltage applied, a spacing of 0.5 mm should be used as a minimum, otherwise charge shocks may form between the grids, with a maximum distance of 2 mm for the grid shocks. The distance between the grids affects the resulting beam performance.

[0028] Three bolts are required between the grids for fixing (two fixing bolts and one contact bolt). Two of the fixing bolts mount the grids on the ceramic cylinder. The last contact bolt is connected to the external cable and passes through the larger hole without contacting the internal grid. The contact bolt is fixed in the radial hole of the ceramic shell by a carbon roller.

[0029] The RF excitation coil 3 is a copper coil wound in a spiral shape on the outer surface of the discharge chamber 1. The copper coil is wound by a hollow copper tube, and the cavity inside the copper coil is set as a cooling water flow cavity. The RF excitation coil 3 is wound around the discharge chamber 1; the RF excitation coil 3 is not allowed to directly contact the discharge plasma. RF power transmission can be achieved by driving the secondary transformer current in the discharge. The spiral coil design is very easy to be heated by resistance. In order to prevent such heating and thermal runaway, the mechanism is cooled by water flowing through the coil itself. Otherwise, if the coil becomes hot, its resistance increases, which will absorb more RF power and affect the fixed RF tuning.

[0030] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A radio frequency ion source discharge chamber mechanism for optical polishing, characterized in that: The invention comprises a discharge chamber (1) and a grid system (2), wherein the grid system (2) is mounted on the end surface of the discharge chamber (1), a radio frequency excitation coil (3) is mounted on the outer surface of the discharge chamber (1), the discharge chamber (1) comprises a ceramic seat (4), a ceramic cavity (5) is arranged in the ceramic seat (4), an auxiliary anode (6) is mounted at the center of the ceramic seat (4), and a part of the auxiliary anode (6) is extended to the inner wall of the ceramic cavity (5).

2. A radio frequency ion source discharge chamber mechanism for optical polishing according to claim 1, characterized in that: The grid system (2) comprises a shielding grid (7), an accelerating grid (8) and a grounding grid (9) which are arranged in sequence from the inside of the ceramic cavity (5) to the outside of the ceramic cavity (5); the shielding grid (7), the accelerating grid (8) and the grounding grid (9) are connected to the inner wall of the ceramic cavity (5) by bolts at intervals; and a mounting groove for mounting the grid system (2) is provided on the inner wall of the ceramic cavity (5).

3. A radio frequency ion source discharge chamber mechanism for optical polishing according to claim 2, characterized in that: The shielding grid (7), the accelerating grid (8) and the grounding grid (9) are respectively connected to the inner wall of the ceramic cavity (5) with an annular insulating net (10), and ceramic balls (11) are installed between adjacent insulating nets (10).

4. A radio frequency ion source discharge chamber mechanism for optical polishing according to claim 3, characterized in that: The shielding grid (7), the accelerating grid (8) and the grounding grid (9) are provided with flange adjustment holes, the ceramic balls (11) are installed in the flange adjustment holes, and six ceramic balls (11) are arranged between adjacent insulating nets (10).

5. The radio frequency ion source discharge chamber mechanism for optical polishing according to claim 1, characterized in that: The radio frequency excitation coil (3) is a copper coil spirally wound on the outer surface of the discharge chamber (1); the copper coil is wound by a hollow copper tube, and the cavity inside the copper coil is configured as a cooling water flow cavity.

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