Liquid phase plasma processing device and method based on floating discharge tool

Abstract

The present invention discloses a liquid-phase plasma processing device and method based on a floating discharge tool. The floating tool is made of a flexible conductive material and electrically connected to an adjustable voltage source via a conductive bearing. The workpiece to be processed is fixed on a workpiece base and then grounded via an adjustable voltage source, so that a circuit is formed between the floating discharge tool and the workpiece. The fluid dynamic pressure generated by the rotation of the main shaft causes the floating discharge tool to elastically deform and retreat, and the position of the air-floating guide rail is dynamically adjusted to maintain the thickness of the liquid film unchanged, thereby achieving stable material removal with sub-nanometer precision. The adjustable voltage source is then used to cause the floating discharge tool to confine plasma discharge within the gap of the liquid film. The photoelectric field generated by the discharge stimulates the synergistic effect of catalytic nanoparticles in the polishing liquid, generating strong oxidizing free radicals, which confine the oxidation of atoms on the surface of the workpiece and reduce the hardness of the material, thereby increasing the material removal rate, thereby achieving both efficient processing and sub-nanometer surface precision control capabilities.

Description

Technical Field

[0001] The present invention belongs to the technical field of polishing devices, relates to ultra-precision liquid phase plasma processing, and in particular to a liquid phase plasma processing device and method based on a floating discharge tool. Background Art

[0002] The widespread application of third-generation semiconductor materials such as silicon carbide and gallium nitride in high-power devices has placed higher demands on processing equipment and process precision. However, these materials have ultra-high hardness second only to diamond, so achieving efficient and deterministic material removal while ensuring ultra-smooth surface quality is a huge challenge.

[0003] Non-contact machining methods have the advantage of avoiding defects and sub-surface damage caused by contact, and thus are expected to achieve atomic-level machining accuracy. Among them, the floating polishing technology, by suspending the workpiece above the liquid film of the rotating grinding disk, uses the rotation of the tool to drive the fluid through the surface of the workpiece to generate fluid dynamic pressure. This fluid dynamic pressure will be balanced with the load applied in the opposite direction. Therefore, the size of the floating machining fluid dynamic pressure can be controlled by adjusting the load to achieve precise, extremely small constant force stable machining, so that the surface flatness of the workpiece can be as low as 30 nanometers. However, due to its full-aperture polishing characteristics, it does not have deterministic removal capabilities, and the machining accuracy is difficult to further converge. Elastic emission machining, which is commonly used in silicon machining, is a deterministic process that can provide higher shape control accuracy, but its material removal rate is low and it is difficult to meet the machining efficiency requirements of hard materials. In recent years, a jet-based elastic emission machining method has been proposed to improve the removal efficiency by increasing the impact velocity of the abrasive on the workpiece, but high impact force may lead to a decrease in surface quality.

[0004] Some methods propose to modify the surface of the workpiece first, forming a softened layer before mechanical removal, such as using helium plasma to oxidize the material surface, and then removing the oxide layer through chemical mechanical polishing. Although this method can have a certain effect on improving the material removal rate, it requires a two-step process and cannot achieve simultaneous modification and removal. Another method uses atmospheric plasma of a specific reactive gas to directly etch the material to achieve atomic-level smoothness. However, it has problems with thermal effects and insufficient surface control accuracy caused by large-area processing.

[0005] Therefore, how to improve material removal efficiency while ensuring ultra-high surface finish remains a difficult problem that non-contact processing technology urgently needs to break through. Summary of the Invention

[0006] In response to the shortcomings of the existing technology, the present invention proposes a liquid-phase plasma processing device and method based on a floating discharge tool. By realizing liquid-phase plasma discharge in a stable liquid film between the floating discharge grinding tool and the workpiece, accompanied by the action of the photoelectric field, the synergistic effect of catalytic nanoparticles is stimulated, the atoms on the surface of the workpiece are confinedly oxidized and the material hardness is reduced, thereby improving the material removal rate. Combined with the dynamic adjustment of the air floating guide rail, the thickness of the liquid film is maintained unchanged, achieving stable material removal with sub-nanometer precision, and realizing efficient processing and sub-nanometer surface accuracy control.

[0007] A liquid phase plasma processing device based on a floating discharge tool comprises a floating discharge tool, a conductive bearing, a workpiece base, a working platform, a grounding electrode, a working electrode, an adjustable power supply, a Z-axis manual adjustment table, an air-floating guide rail, a Z-axis bracket, a main spindle, a Y-axis translation table and an X-axis translation table.

[0008] The floating discharge tool is made of flexible conductive material and is fixed to one end of the spindle. The other end of the spindle is secured to an air-bearing guide via a Z-axis bracket. The air-bearing guide is fixed to the surface of the Z-axis manual adjustment table. The conductive bearing sleeve is mounted on the outside of the floating discharge tool and is electrically connected to an adjustable power supply via a working electrode.

[0009] The workpiece base is located on the side of the floating discharge tool and is fixed to the Y-axis translation stage, which is fixed to the X-axis translation stage. The workpiece base is controlled to move in the X-axis and Y-axis directions by the Y-axis translation stage and the X-axis translation stage. The workpiece base is grounded through a grounding electrode.

[0010] The working platform is located below the workpiece base.

[0011] Preferably, the adjustable power supply is a high-voltage pulse power supply, an AC power supply or a DC power supply with adjustable voltage.

[0012] Preferably, the working platform is a liftable platform.

[0013] A liquid phase plasma processing method based on a floating discharge tool, using the above device to polish a workpiece, specifically comprising the following steps:

[0014] Step 1: Fix the workpiece to be processed on the surface of the workpiece base using conductive glue.

[0015] Step 2: Use the Y-axis and X-axis translation stages to control the position of the workpiece base so that the workpiece and the surface of the floating discharge tool are in contact with each other. Place a water tank filled with polishing fluid on the work platform so that the polishing fluid submerges the floating discharge tool and the workpiece surface to generate sufficient dynamic pressure to achieve floating processing.

[0016] Step 3: Control the spindle to drive the floating discharge tool to rotate, so that the air-floating guide rail drives the floating discharge tool away from the workpiece surface, and the floating discharge tool is deformed, thereby forming a dynamically adjusted micron-level stable liquid film gap between the floating discharge tool and the workpiece surface.

[0017] Step 4: After the liquid film is stable, turn on the adjustable power supply to start discharging. Liquid phase plasma discharge will produce various active substances in the discharge area, and release ultraviolet light and shock waves, converting the workpiece surface into an oxide layer.

[0018] Step 5: The abrasive particles in the polishing liquid pass through the liquid film gap at a high linear velocity under the drive of the fluid, come into contact with the atoms on the surface of the workpiece and form chemical bonds. Then, the surface atoms are peeled off as the fluid moves, achieving deterministic removal of the material.

[0019] Preferably, the workpiece is a semiconductor material or a metal material.

[0020] Preferably, the workpiece is doped conductive silicon carbide, silicon, zinc sulfide, gallium nitride, gallium arsenide, aluminum, iron or copper.

[0021] Preferably, the abrasive particles in the polishing liquid are a combination of one or more of silica sol, aluminum oxide, cerium oxide, diamond, and silicon carbide.

[0022] Preferably, the polishing liquid further comprises catalytic particles, and the catalytic particles are a combination of one or more of titanium dioxide, graphite carbon nitride, zinc oxide, and zirconium dioxide.

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

[0024] 1. Compared with the traditional floating processing method, by introducing a floating discharge tool, liquid-phase plasma discharge is realized in the stable liquid film between the floating discharge tool and the workpiece. At the same time, the photoelectric field generated by the discharge stimulates the synergistic effect of catalytic nanoparticles, generating strong oxidizing free radicals, which confine the oxidation of atoms on the workpiece surface and reduce the hardness of the material. The material is removed under the action of the floating polishing flow field, so that modification and removal are carried out simultaneously, effectively improving the processing efficiency.

[0025] 2. The flexible conductive rubber tool is pressed against the workpiece under the action of an external load. The fluid dynamic pressure generated by the rotation of the spindle causes the tool to elastically deform and retreat. The fluid dynamic pressure and the external load are balanced by movement on the air-floating guide rail. The position of the air-floating guide rail is dynamically adjusted to maintain the thickness of the liquid film unchanged, achieving stable material removal with sub-nanometer precision; thus achieving both efficient processing and sub-nanometer surface accuracy control capabilities.

[0026] 3. Introducing nano-catalytic particles into the polishing liquid can further improve the material removal rate. The photoelectric field generated by liquid-phase plasma discharge can act on titanium dioxide to achieve energy level transitions. The generated electron-hole pairs can further generate more strong oxidizing active groups, synergistically improving the silicon carbide oxidation efficiency and increasing the material removal rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of a liquid phase plasma processing device based on a floating discharge tool;

[0028] Figure 2 It is a schematic diagram of the liquid phase plasma discharge region;

[0029] Figure 3 It is a schematic diagram of the liquid phase plasma processing method based on a floating discharge tool;

[0030] Figure 4 This is a diagram of the liquid phase plasma discharge action mechanism and removal mechanism based on the floating discharge tool. DETAILED DESCRIPTION

[0031] The present invention will be further explained below with reference to the accompanying drawings;

[0032] A liquid phase plasma processing device based on a floating discharge tool 101, such as Figure 1 As shown, it includes a floating discharge tool 101, a conductive bearing 103, a workpiece base 104, a water cylinder 105, a manually adjustable lifting platform 106, a ground electrode 107, a working electrode 108, a high-voltage pulse power supply 109, a voltage regulator 110, a Z-axis manually adjustable platform 111, an air-floating guide rail 112, a Z-axis bracket 113, a spindle adapter 114, a spindle 115, a worktable adapter 116, a Y-axis translation platform 117 and an X-axis translation platform 118.

[0033] The floating discharge tool 101 is made of flexible conductive rubber and is fixed to one end of the spindle 115. The other end of the spindle 115 is fixed to the Z-axis bracket 113 via the spindle adapter 114, and the Z-axis bracket 113 is fixed to the surface of the air-floating guide rail 112. The air-floating guide rail 112 is fixed to the surface of the Z-axis manual adjustment table 111. The conductive bearing 103 is mounted on the outside of the floating discharge tool 101 and connected to the high-voltage pulse power supply 109 via the working electrode 108. It is used to transmit the high-voltage pulse signal from the working electrode 108 to the end face of the floating discharge tool 101. Compared with traditional floating machining methods, by introducing the floating discharge tool 101, plasma discharge is confined within the liquid film gap. The photoelectric field generated by the discharge activates the activity of the nanocatalyst, generating highly oxidizing hydroxyl radicals, achieving confined oxidation of the SiC surface, and removing material under the action of the floating polishing flow field, effectively improving machining efficiency.

[0034] like Figure 2 As shown, the workpiece base 104 is located to the side of the floating discharge tool 101 and is secured to a Y-axis translation stage 117 via a worktable adapter 116. The Y-axis translation stage 117 is secured to an X-axis translation stage 118, thereby controlling the movement of the workpiece base 104 in the X- and Y-axis directions via the Y-axis translation stage 117 and the X-axis translation stage 118. The workpiece base 104 is grounded via a grounding electrode 107. The manually adjustable lift 106 is located below the floating discharge tool 101 and the workpiece base 104. A water cylinder 105 is placed on the surface of the manually adjustable lift 106.

[0035] When the power supply voltage is within the appropriate range, a relatively gentle corona discharge is achieved, generating free radicals and the accompanying photoelectric field facilitating the activation of the nanocatalytic particles. When the voltage is too high, an arc discharge may form between the floating discharge tool 101 and the workpiece 102. In this case, the discharge is intense and the discharge area is randomly dispersed, easily leading to numerous tiny pits on the surface of the workpiece 102. Therefore, a voltage regulator 110 is used to adjust the output voltage of the high-voltage pulse power supply 109. The working electrode 108 is connected to the output terminal of the high-voltage pulse power supply 109, and the ground electrode 107 is connected to the ground terminal of the high-voltage pulse power supply 109. During polishing, the workpiece 102 to be processed is fixed to the surface of the work base 104 using conductive glue, thereby forming an electrical circuit between the floating discharge tool 101 and the workpiece 102, achieving confined liquid-phase plasma discharge within the liquid film.

[0036] In one embodiment, the ground electrode 107 and the working electrode 108 are connected to an AC power source or a DC power source respectively to realize an electrochemical catalytic process between the gap between the floating discharge tool 101 and the workpiece 102 .

[0037] Polishing the workpiece using the above device specifically includes the following steps:

[0038] Step 1: Fix the workpiece 102 to be processed on the surface of the workpiece base 104 using conductive glue. In this embodiment, the workpiece is doped conductive silicon carbide.

[0039] Step 2: Control the position of the workpiece base 104 using the Y-axis translation stage 117 and the X-axis translation stage 118 to bring the workpiece 102 into contact with the surface of the floating discharge tool 101. Place a water tank 105 filled with polishing fluid on a manually adjustable lift 106. In this embodiment, the polishing fluid comprises silica sol and titanium dioxide catalytic particles. Adjust the height of the manually adjustable lift 106 so that the polishing fluid in the water tank 105 submerges the floating discharge tool 101 and the workpiece 102 surfaces, generating sufficient dynamic pressure for floating machining and providing a discharge medium for liquid-phase plasma discharge.

[0040] Step 3: Figure 3As shown, the control spindle 115 drives the floating discharge tool 101 to rotate. Due to the action of the fluid, dynamic pressure is generated, which is balanced with the load applied to the air-floating guide rail 112. The dynamic pressure acts on the floating discharge tool 101, causing the air-floating guide rail 112 to drive the floating discharge tool 101 away from the surface of the workpiece 102, and the floating discharge tool 101 is elastically deformed, thereby forming a dynamically adjusted micron-level stable liquid film gap between the floating discharge tool 101 and the surface of the workpiece 102.

[0041] Step 4: After the liquid film is stable, turn on the adjustable power supply and start discharging through the floating discharge tool 101. Figure 4 As shown, liquid-phase plasma discharge releases ultraviolet light and shock waves, providing energy to stimulate the activity of nanocatalytic particles in the polishing liquid, enabling them to achieve energy level transitions and generate electron-hole pairs. The AC electric field generated by the discharge also prolongs the life of the electron-hole pairs, thereby generating various active substances in the discharge area.

[0042] The electrons in the electron-hole pairs react with dissolved oxygen in the water to form superoxide anions, which then react with hydrogen peroxide produced by the discharge to form hydroxyl radicals. The holes, in turn, react with water to form hydroxyl radicals, increasing the concentration of free radicals within the liquid film. The highly oxidizing free radicals within the liquid film transform the surface of the workpiece 102 into a softer, easier-to-remove oxide layer.

[0043] Step 5: The abrasive particles and catalytic particles in the polishing liquid pass through the liquid film gap at a high linear velocity under the drive of the fluid, come into contact with the surface atoms of the workpiece 102 under the action of shear stress and form chemical bonds. Then, the surface atoms are peeled off as the fluid moves, achieving deterministic removal of the material.

[0044] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

Claims

1. A liquid phase plasma processing device based on a floating discharge tool, comprising a workpiece base (104) for fixing a workpiece to be processed (102), a working platform (106) for placing a polishing liquid, a spindle (115) for driving the floating discharge tool (101) to rotate, an air-floating guide rail (112) equipped with a load and used to fix the spindle (115), a Z-axis manual adjustment table (111) for fixing the air-floating guide rail (112), a Y-axis displacement table (117) and an X-axis displacement table (118) for adjusting the position of the workpiece base (104), characterized in that: The floating discharge tool (101) is made of a flexible conductive material; the device further comprises a conductive bearing (103), a grounding electrode (107), a working electrode (108) and an adjustable power supply (109); the conductive bearing (103) is sleeved outside the floating discharge tool (101) and electrically connected to the adjustable power supply (109) via the working electrode (108); the workpiece base (104) is arranged on the side of the floating discharge tool (101) and is grounded via the grounding electrode (107); The working platform (106) is a liftable platform, which allows the polishing liquid to immerse the floating discharge tool (101) and the surface of the workpiece (102).

2. The liquid phase plasma processing device based on a floating discharge tool according to claim 1, characterized in that: The floating discharge tool (101) is fixed to one end of the main shaft (115); the other end of the main shaft (115) is fixed to the air-floating guide rail (112) via a Z-axis bracket (113).

3. The liquid phase plasma processing device based on a floating discharge tool according to claim 1, characterized in that: The adjustable power supply (109) is a high-voltage pulse power supply, an AC power supply or a DC power supply with adjustable voltage.

4. A liquid phase plasma processing method based on a floating discharge tool, characterized in that: Polishing a workpiece using the device according to any one of claims 1 to 3 specifically comprises the following steps: Step 1: Fixing the workpiece (102) to be processed on the surface of the workpiece base (104) by using conductive glue; Step 2: Control the position of the workpiece base (104) by using the Y-axis displacement stage (117) and the X-axis displacement stage (118) so that the workpiece (102) and the surface of the floating discharge tool (101) are in contact with each other; place a water tank (105) filled with polishing liquid on the work platform so that the polishing liquid immerses the floating discharge tool (101) and the surface of the workpiece (102); the polishing liquid includes nanocatalytic particles; Step 3: Control the main shaft (115) to drive the floating discharge tool (101) to rotate, thereby forming a dynamically adjusted micron-level liquid film gap between the floating discharge tool (101) and the surface of the workpiece (102); Step 4: After the liquid film is stabilized, the adjustable power supply (109) is turned on to form an electrical circuit between the floating discharge tool (101) and the workpiece (102), thereby achieving confined liquid phase plasma discharge within the liquid film; corona discharge is achieved by adjusting the voltage of the adjustable power supply (109), generating free radicals and activating nanocatalytic particles in the polishing liquid; Step 5: Abrasive particles in the polishing liquid pass through the liquid film gap at a high linear speed under the drive of the fluid, come into contact with the surface atoms of the workpiece (102) and form chemical bonds, and then peel off the surface atoms as the fluid moves, thereby achieving deterministic removal of the material.

5. The liquid phase plasma processing method based on a floating discharge tool according to claim 4, characterized in that: The workpiece (102) is a semiconductor material or a metal material.

6. The liquid phase plasma processing method based on a floating discharge tool according to claim 4, characterized in that: The workpiece (102) is doped conductive silicon carbide, silicon, zinc sulfide, gallium nitride, gallium arsenide, aluminum, iron or copper.

7. The liquid phase plasma processing method based on a floating discharge tool according to claim 4, characterized in that: The abrasive particles in the polishing liquid are a combination of one or more of silica sol, aluminum oxide, cerium oxide, diamond and silicon carbide.

8. The liquid phase plasma processing method based on a floating discharge tool according to claim 4, characterized in that: The nano-catalytic particles are a combination of one or more of titanium dioxide, graphite carbon nitride, zinc oxide, and zirconium dioxide.

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