An ion source in which a coil structure can change according to a discharge chamber structure

Abstract

The present invention discloses an ion source in which the coil structure can change along with the discharge chamber structure, comprising an ion source chamber, a coil support, a coil and a discharge chamber body which are coaxially arranged from outside to inside in sequence; the discharge chamber body includes a discharge chamber top, a discharge chamber middle part and a discharge chamber bottom; the discharge chamber top is a hollow ring; the discharge chamber bottom is a disc provided with an air inlet hole at the center; the discharge chamber middle part includes an upper straight cylinder and a lower Dome-shaped cylinder; the outer ring of the coil support is installed on the inner wall surface of the ion source chamber, and the shape of the inner wall surface of the coil support is the same as the shape of the discharge chamber body; the coil is installed in the coil support and includes a cylindrical spiral coil and a Dome-shaped coil; the position of the cylindrical spiral coil corresponds to the position of the upper straight cylinder, and the Dome-shaped coil corresponds to the position of the lower Dome-shaped cylinder; the distance from each layer of the coil to the outer wall surface of the discharge chamber body is equal. The present invention combines a spiral ICP source with a cylindrical ICP source, and can adjust the plasma density in the discharge chamber body in sections, improving the etching uniformity.

Description

Technical Field

[0001] The present invention relates to the field of ion beam etching, and particularly to an ion source whose coil structure can change with the structure of a discharge cavity. Background Art

[0002] An ion source is a device that ionizes neutral atoms or molecules and extracts an ion beam current therefrom. It is an indispensable component of various types of ion accelerators, mass spectrometers, electromagnetic isotope separators, ion implanters, ion beam etching devices, ion thrusters, and neutral beam injectors in controlled fusion devices, etc.

[0003] A radio frequency inductively coupled plasma (RFICP) source can resonate in the megahertz range, can effectively generate plasma at low pressure, and can transfer energy to the plasma efficiently. Due to its simple structure, ability to generate high-density pure plasma, long service life, and good performance-price ratio, etc., it has developed rapidly in recent years. The currently used RFICP sources are mainly cylindrical, such as Figure 1 shown. The RF coil of the RFICP source is wound outside the electrically insulating quartz discharge chamber. When RF power is applied to the coil through a matching network, there is an RF current passing through the coil, thus generating an RF magnetic flux, and an RF electric field is induced axially inside the discharge chamber. The electrons therein are accelerated by the electric field, thereby generating plasma, and at the same time, the energy of the coil is coupled to the plasma.

[0004] Since the RFICP source is cylindrical, when an RF power supply is loaded on the RF coil, due to the skin effect of the current, the current mainly flows inside the cavity wall of the discharge cavity and gradually decays within the skin layer. Therefore, the plasma density in the discharge cavity generally shows a trend of being high at both sides and low in the middle, as Figure 2 shown by the solid line in. Affected by the RF power and working pressure, the plasma density distribution in the reaction cavity also shows a saddle-shaped trend ( Figure 2 dashed line indicates). Due to the uneven plasma density distribution, the etching rate is uneven, affecting the etching uniformity. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide, in view of the deficiencies of the above-mentioned prior art, an ion source whose coil structure can change with the structure of a discharge cavity. This ion source whose coil structure can change with the structure of a discharge cavity combines a spiral-shaped ICP source and a cylindrical ICP source, and can adjust the plasma density in the discharge cavity body in segments, improving the etching uniformity.

[0006] To solve the above technical problem, the technical solution adopted by the present invention is:

[0007] An ion source in which the coil structure can change with the discharge cavity structure, comprising an ion source cavity, a coil support, a coil, and a discharge cavity body coaxially arranged from outside to inside in sequence.

[0008] The discharge cavity body includes a discharge cavity top, a discharge cavity middle part, and a discharge cavity bottom connected in sequence.

[0009] The discharge cavity top is a hollow ring and is located on the plasma outlet side.

[0010] The discharge cavity bottom is a disc with an air inlet hole in the center. Among them, the air inlet hole is used to introduce the gas to be ionized. The centers of the hollow ring and the disc are both located on the central axis of the discharge cavity body.

[0011] The discharge cavity middle part includes an upper straight cylinder and a lower Dome-shaped cylinder connected in sequence. The top of the upper straight cylinder is connected to the discharge cavity top in sequence, and the bottom of the lower Dome-shaped cylinder is connected to the outer edge of the discharge cavity bottom in sequence.

[0012] The outer ring of the coil support is installed on the inner wall surface of the ion source cavity, and the shape of the inner wall surface of the coil support is the same as the shape of the discharge cavity body.

[0013] The coil is installed in the coil support, and both ends of the coil are respectively connected to a radio frequency source. The coil includes a cylindrical spiral coil and a Dome-shaped coil. Among them, the position of the cylindrical spiral coil corresponds to the position of the upper straight cylinder, and the Dome-shaped coil corresponds to the position of the lower Dome-shaped cylinder. The distance from each layer of the coil to the outer wall surface of the discharge cavity body is equal.

[0014] The wall thickness of the discharge cavity body is 2 - 20 mm.

[0015] The material of the discharge cavity body is quartz or ceramic.

[0016] When the material of the discharge cavity body is quartz, the distance from each layer of the coil to the outer wall surface of the discharge cavity body is 2 - 30 mm. When the material of the discharge cavity body is ceramic, the distance from each layer of the coil to the outer wall surface of the discharge cavity body is 0 - 30 mm.

[0017] Assume that the wall thickness of the discharge cavity body is H, and the distance from each layer of the coil to the outer wall surface of the discharge cavity body is L. Then H and L are selected according to the required plasma density in the discharge cavity body.

[0018] When the required plasma density in the discharge cavity body is relatively high, then relatively small H and L are selected. When the required plasma density in the discharge cavity body is relatively low, then relatively large H and L are selected.

[0019] When the wall thickness H of the discharge chamber body is determined, by adjusting the distance L from each layer of coil to the outer wall surface of the discharge chamber body, the plasma density in the discharge chamber body can be adjusted accordingly. When the wall thickness H of the discharge chamber body is relatively large, by reducing L, the plasma density in the discharge chamber body can be made uniform. When the wall thickness H of the discharge chamber body is relatively small, by increasing L, the plasma density in the discharge chamber body can be made uniform.

[0020] A gas distribution plate is coaxially installed on the inner wall surface of the bottom of the discharge chamber. The gas distribution plate has a gas distribution cavity communicating with the air inlet holes.

[0021] Notches for installing coils are provided on the inner wall surface of the coil support.

[0022] The coils are formed by 3D printing.

[0023] The present invention has the following beneficial effects:

[0024] 1. The present invention combines a spiral-shaped ICP source with a cylindrical ICP source, which can adjust the plasma density in segments and improve the etching uniformity.

[0025] 2. Inside the lower Dome-shaped cylinder of the discharge chamber body, plasma ionization is carried out by the Dome-shaped coil. The Dome-shaped coil can be decomposed into an axial helical coil and a radial spiral-shaped planar coil. Among them, the helical coil can induce a radio frequency electric field along the axis in the discharge chamber, while the spiral-shaped planar coil can induce a radio frequency electric field along the radial direction in the discharge chamber. Thus, the plasma density distribution in the entire discharge chamber is made uniform, ensuring the etching uniformity. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Shows a schematic diagram of the coil and discharge chamber structure of an ion source in the prior art.

[0027] Figure 2 Shows a schematic diagram of the plasma density distribution in the discharge chamber of an ion source in the prior art.

[0028] Figure 3 Shows a schematic diagram of an ion source in which a coil structure of the present invention can change with the discharge chamber structure.

[0029] Figure 4 Shows a schematic diagram of the structure of the discharge chamber in the present invention.

[0030] Figure 5 Shows a schematic diagram of the structure of the coil support in the present invention.

[0031] Figure 6 Shows a schematic diagram of the coil in the present invention.

[0032] Figure 7Shows a schematic diagram of making a coil using a coil tooling in the present invention.

[0033] Among them are:

[0034] 1. Discharge chamber body; 11. Discharge chamber top; 12. Discharge chamber middle part; 121. Upper straight cylinder; 122. Lower Dome-shaped cylinder; 13. Discharge chamber bottom; 131. Air inlet hole; 132. Uniform gas plate mounting hole;

[0035] 2. Coil;

[0036] 3. Coil support; 31. Notch;

[0037] 4. Coil tooling;

[0038] 51 - 52. RF columns; 61 - 62. Wires; 7. Uniform gas plate; 10. Grid assembly. Specific embodiments

[0039] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific preferred embodiments.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "left side", "right side", "upper part", "lower part", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. "First", "second", etc. do not represent the importance of components, so they cannot be understood as limitations to the present invention. The specific dimensions used in this embodiment are only for illustrative purposes of the technical solution and do not limit the protection scope of the present invention.

[0041] As Figure 3 shown, an ion source in which a coil structure can change with the discharge chamber structure includes an ion source chamber, a coil support 3, a coil 2, and a discharge chamber body 1 that are coaxially arranged in sequence from outside to inside.

[0042] As Figure 4 shown, the discharge chamber body includes a discharge chamber top 11, a discharge chamber middle part 12, and a discharge chamber bottom 13 that are connected in sequence. The discharge chamber top 11, the discharge chamber middle part 12, and the discharge chamber bottom 13 can be formed by fusion welding or integrally formed.

[0043] The discharge chamber top is a hollow ring and is located on the plasma outlet side, that is, close to the Grid assembly 10 of the ion source. The Grid assembly 10 includes a screen grid and an acceleration grid, etc.

[0044] The discharge chamber bottom is a disc with an air inlet hole 131 at the center. Among them, the centers of the hollow ring and the disc are both located at

[0045] On the central axis of the discharge cavity body.

[0046] The above intake holes are used to introduce the gas to be ionized, such as Ar, etc. A gas distribution plate mounting hole is preferably provided on the outer periphery of the intake holes.

[0047] 132 is used to coaxially mount the gas distribution plate 7 on the inner wall surface of the bottom of the discharge cavity. The gas distribution plate has a gas distribution cavity communicating with the intake holes. The setting of the gas distribution plate 7 can make the intake uniform. The diameter of the bottom 13 of the discharge cavity should be more than 5 mm larger than the outer diameter of the gas distribution plate 7, and the maximum should not exceed the maximum inner diameter of the discharge cavity body 1.

[0048] The middle part of the discharge cavity includes an upper straight cylinder 121 and a lower Dome-shaped cylinder 122 connected in sequence. The top of the upper straight cylinder is connected to the top of the discharge cavity in sequence, and the bottom of the lower Dome-shaped cylinder is connected to the outer edge of the bottom of the discharge cavity in sequence.

[0049] To ensure that the discharge cavity body 1 has sufficient strength, the wall thickness of the discharge cavity body 1 cannot be too thin. At the same time, to ensure the plasma density of the discharge cavity and the influence of material processing, the wall thickness of the discharge cavity body 1 cannot be too thick. Therefore, the wall thickness of the discharge cavity body 1 is preferably between 2 and 20 mm.

[0050] The material of the discharge cavity body 1 is preferably ceramic or quartz material.

[0051] The outer ring of the coil support is installed on the inner wall surface of the ion source cavity, and the shape of the inner wall surface of the coil support is the same as the shape of the discharge cavity body. As Figure 5 shown, the inner wall surface of the coil support is provided with a notch 31 for installing the coil, which is used to install the coil. The material of the coil support 8 is preferably an insulating material such as ceramic or polytetrafluoroethylene.

[0052] Both ends of the coil are respectively connected to the radio frequency source through the radio frequency columns 51 or 52 and the wires 61 or 62.

[0053] As Figure 6 shown, the coil includes a cylindrical spiral coil and a Dome-shaped coil. Among them, the position of the cylindrical spiral coil corresponds to the position of the upper straight cylinder, and the Dome-shaped coil corresponds to the position of the lower Dome-shaped cylinder.

[0054] The distance from each layer of the coil to the outer wall surface of the discharge chamber body is equal. Ensuring the distance between the coil 2 and the discharge chamber body 1 is of great significance for the plasma density distribution within the discharge chamber body 1. The shaping of the coil 2 should be consistent with the structure of the discharge chamber body 1. If the material of the discharge chamber body 1 is quartz, the distance from each layer of the coil to the outer wall surface of the discharge chamber body is 2 - 30 mm. If the material of the discharge chamber body 1 is ceramic, the distance L from each layer of the coil to the outer wall surface of the discharge chamber body is 0 - 30 mm. Due to the high hardness and high temperature resistance of ceramic, when L = 0, that is, the coil is fixed on the ceramic discharge chamber body 1.

[0055] To ensure that the distance from each part of the coil 2 to the middle part 12 of the discharge chamber is consistent, a coil tooling 4 is required when winding the coil 2. The structure of the coil tooling is as Figure 7 shown, which can be integrated or composed of multiple parts. During processing, 3D printing forming etc. can be used.

[0056] In addition, the distance from the coil 2 to the bottom 1 of the discharge chamber is adjustable. The bottom position of the coil 2 can be below or above the bottom 13 of the discharge chamber.

[0057] When the flow rate of the Ar plasma gas entering the discharge chamber body 1 is determined, the wall thickness of the discharge chamber body is H, and the distance from each layer of the coil to the outer wall surface of the discharge chamber body is L, then H and L are selected according to the required plasma density within the discharge chamber body. The specific selection method is preferably:

[0058] A. If a higher plasma density is required within the discharge chamber body 1, the discharge chamber body 1 can be selected with a small wall thickness, and at the same time, the distance between the discharge chamber body 1 and the coil 2 is reduced; that is, both smaller H and L are selected.

[0059] B. If a lower plasma density is required within the discharge chamber body 1, the discharge chamber body 1 can be selected with a large wall thickness, and at the same time, the distance between the discharge chamber body 1 and the coil 2 is increased; that is, both larger H and L are selected.

[0060] In addition, if it is desired that the plasma density within the discharge chamber body 1 tends to be uniform, the wall thickness of the discharge chamber body 1 and the distance from the coil 2 to the outer wall of the middle part 12 of the discharge chamber should be inversely proportional. The specific adjustment method is:

[0061] A. When the wall thickness H of the discharge chamber body 1 is small, the distance between the coil 2 and the discharge chamber body 1 can be selected to be large; that is, by increasing L, the plasma density within the discharge chamber body is made uniform.

[0062] B. When the wall thickness H of the discharge chamber body is large, the distance between the coil 2 and the middle part 1 of the discharge chamber should be reduced; that is, by reducing L, the plasma density within the discharge chamber body is made uniform.

[0063] When etching is required, argon plasma gas enters the main body 1 of the discharge chamber. After applying a radio frequency power supply to the coil 2, the ionized gas in the main body 1 of the discharge chamber is ionized. Since the distance between the coil 2 and the middle part 12 of the discharge chamber remains unchanged, then:

[0064] A. Inside the lower Dome-shaped cylinder of the main body of the discharge chamber, plasma ionization is carried out by the Dome-shaped coil; the Dome-shaped coil can be decomposed into an axial helical coil and a radial spiral-shaped planar coil; among them, the helical coil can induce a radio frequency electric field along the axis in the discharge chamber, and the spiral-shaped planar coil can induce a radio frequency electric field along the radial direction in the discharge chamber, so that the plasma density distribution in the entire discharge chamber is uniform, ensuring etching uniformity.

[0065] B. Inside the upper straight cylinder of the main body of the discharge chamber, plasma ionization is carried out by the cylindrical helical coil; the cylindrical helical coil can induce a radio frequency electric field along the axis in the discharge chamber. No coil is added inside the upper straight cylinder of the main body of the discharge chamber, and it diffuses evenly downward. The length of the coil is related to the inductance. As long as the inductance is sufficient, the plasma density distribution can be evenly distributed.

[0066] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various equivalent transformations can be made to the technical solutions of the present invention, and these equivalent transformations all belong to the protection scope of the present invention.

Claims

1. An ion source in which the coil structure can change with the discharge cavity structure, characterized in that: It includes an ion source cavity, a coil support, a coil, and a discharge cavity body that are coaxially arranged from outside to inside in sequence; The discharge cavity body includes a discharge cavity top, a discharge cavity middle part, and a discharge cavity bottom that are connected in sequence; The discharge cavity top is a hollow ring and is located on the plasma outlet side; The discharge cavity bottom is a disc with an air inlet hole in the center; wherein, the air inlet hole is used to introduce the gas to be ionized; the centers of the hollow ring and the disc are both located on the central axis of the discharge cavity body; The discharge cavity middle part includes an upper straight cylinder and a lower Dome-shaped cylinder that are connected in sequence; the top of the upper straight cylinder is connected to the discharge cavity top in sequence, and the bottom of the lower Dome-shaped cylinder is connected to the outer edge of the discharge cavity bottom in sequence; The outer ring of the coil support is installed on the inner wall surface of the ion source cavity, and the shape of the inner wall surface of the coil support is the same as that of the discharge cavity body; The coil is installed inside the coil support, and both ends of the coil are respectively connected to a radio frequency source; the coil includes a cylindrical spiral coil and a Dome-shaped coil; wherein, the position of the cylindrical spiral coil corresponds to the position of the upper straight cylinder, and the Dome-shaped coil corresponds to the position of the lower Dome-shaped cylinder; the distance from each layer of the coil to the outer wall surface of the discharge cavity body is equal; The distance from the coil to the discharge cavity bottom is adjustable; Assume that the wall thickness of the discharge cavity body is H, and the distance from each layer of the coil to the outer wall surface of the discharge cavity body is L, then H and L are selected according to the required plasma density inside the discharge cavity body.

2. The ion source with a coil structure capable of changing along with the discharge chamber structure according to claim 1, characterized in that: The wall thickness of the discharge cavity body is 2 - 20 mm.

3. The ion source in which the coil structure can change with the discharge chamber structure according to claim 1, characterized in that: The material of the discharge cavity body is quartz or ceramic.

4. The ion source according to claim 1, wherein the coil structure can vary with the discharge chamber structure, characterized in that: When the material of the discharge cavity body is quartz, the distance from each layer of the coil to the outer wall surface of the discharge cavity body is 2 - 30 mm; when the material of the discharge cavity body is ceramic, the distance from each layer of the coil to the outer wall surface of the discharge cavity body is 0 - 30 mm.

5. The ion source according to claim 1, wherein the coil structure can change with the discharge chamber structure, characterized in that: When the required plasma density inside the discharge cavity body is relatively high, then relatively small H and L are selected; when the required plasma density inside the discharge cavity body is relatively low, then relatively large H and L are selected.

6. The ion source with a coil structure capable of changing along with the discharge chamber structure according to claim 1, wherein: When the wall thickness H of the discharge cavity body has been determined, by adjusting the distance L from each layer of the coil to the outer wall surface of the discharge cavity body, and then the plasma density inside the discharge cavity body; when the wall thickness H of the discharge cavity body is relatively large, by reducing L, the plasma density inside the discharge cavity body can be made uniform; when the wall thickness H of the discharge cavity body is relatively small, by increasing L, the plasma density inside the discharge cavity body can be made uniform.

7. The ion source according to claim 1, wherein the coil structure can change with the discharge cavity structure, characterized in that: An air distribution disc is coaxially installed on the inner wall surface of the discharge cavity bottom, and the air distribution disc has an air distribution cavity communicated with the air inlet hole.

8. The ion source in which the coil structure can change with the discharge chamber structure according to claim 1, characterized in that: The inner wall surface of the coil support is provided with a notch for installing the coil.

9. The ion source in which the coil structure can change along with the discharge cavity structure according to claim 1, wherein: The coil is formed by 3D printing.

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