CN106252191A - Exchangeable nozzle ICP generating means in plasma chemistry etching apparatus - Google Patents

Abstract

The invention discloses the exchangeable nozzle ICP generating means in a kind of plasma chemistry etching apparatus, belong to optical surface mirror processing precise processing unit (plant) technical field.This ICP generating means includes nozzle, plasma torch pipe, the induction coil being sheathed on outside plasma torch pipe, high pressure tesla ignition coil, radio-frequency power supply and adapter, radio-frequency power supply and adapter are that induction coil is powered, and high pressure tesla ignition coil is powered by external power source；Nozzle and the front end of ICP generating means plasma quarter bend are dismountable fixing be connected, and the size realized removing function by changing the nozzle of different inner diameters is adjusted.The ICP generating means using the present invention can obtain the removal function of ideal dimensions to optical element processing, it is achieved full frequency band face shape error is restrained.

Description

Replaceable Nozzle ICP Generator in Plasma Chemical Etching Equipment

technical field

The invention relates to a plasma chemical etching device for processing large-diameter complex curved surfaces, in particular to an ICP generating device in the plasma chemical etching device, and belongs to the technical field of optical element processing precision processing devices.

Background technique

Aspherical optical components can improve the performance of the optical system and simplify the system structure. More and more optical systems choose to use aspheric optical mirrors. Large-scale telescope construction, automotive and aerospace mass production, microelectronics manufacturing, electronic communications, medical imaging, and various other large-scale scientific projects have an increasing demand for ultra-precision optical components and increasing complexity, resulting in the need for optical processing technology. requirements are also getting higher.

The commonly used aspheric mirror processing method is CCOS (Computer Controlled Surface Shaping) technology. In the traditional process, a computer-controlled small grinding head of asphalt material is used for deterministic processing. Due to the application of positive pressure on the surface of the workpiece, it will cause subsurface damage to the workpiece. For mirrors with complex surface shapes, the change of curvature will cause the grinding head and the mirror surface to be inconsistent, thus affecting the surface shape convergence. Magneto-rheological processing is also a commonly used processing method, but due to its small single-point processing area, the processing efficiency is low, and it is easy to introduce medium and high frequency errors.

In addition, there are some non-contact processing methods. Compared with contact processing methods, non-contact methods do not cause subsurface damage and have no surface contamination. Among them, the ion beam processing technology is mature and has been widely used in large-diameter aspheric processing. Its application stage is similar to that of magnetorheological technology, and it is applied when the surface shape accuracy is high. The biggest advantage of the ion beam process is its stable removal function. But the biggest limitation is that it must be used in vacuum, which has high requirements for the design, maintenance and operation of the electromechanical system; in addition, the removal rate of ion beam processing is too low, which limits its application range. In addition to pure ion beam physical sputtering material removal, drawing on the RIE (Reactive Ion Etching) technology widely used in the semiconductor industry, some methods of material removal through chemical reactions have been produced. PACE (Plasma Assisted Polishing Technology) is a non-contact chemical processing method based on the improvement of the RIE method. The active radicals generated by ionization react with the workpiece to complete material removal, and the removal efficiency is very high. However, this method requires that the thickness of the workpiece to be processed is less than 10mm, and it still works under vacuum.

In view of the shortcomings of the above-mentioned non-contact processing methods, Osaka University in Japan and Lawrence Livermore National Laboratory in the United States have proposed different atmospheric pressure plasma polishing methods. The removal principle is the same as that of PACE technology, but the equipment works under normal pressure, and the density of active groups increases significantly, so the removal rate is very high. However, the PCVM process of Osaka University has poor stability and low processing repeatability, so it is not suitable for the requirements of deterministic processing. The RAP technology of Lawrence Livermore National Laboratory is limited by the specification of the rectangular tube, and the size of the removal function is single; in addition, it also has high requirements for the motion mechanism.

For the surface shape error of different frequency bands in the traditional small grinding head processing technology, it is necessary to replace the grinding head with different diameters to eliminate it. For this reason, traditional processing machine tools are specially designed with fast grinding head switching devices. A similar capability is required to increase the applicability of plasma processing methods. One possible way is to replace the ICP torch, but it is very inconvenient to replace the ICP torch because of the induction coil that maintains the plasma. Before replacement, you must wait until the ICP tube and coil are cooled, and then disconnect all power, air pipes and water cooling devices and reconnect them after switching to the new ICP tube. For ICP tubes of different sizes, it is also necessary to consider whether the size of the induction coil matches. After all the assembly is completed, it is necessary to test whether stable plasma can be generated and whether the removal function is suitable. Therefore, the replacement of grinding heads with different diameters in the form of replacing the ICP rectangular tube has considerable limitations in the actual processing process.

Contents of the invention

In view of this, the present invention provides a replaceable nozzle ICP generating device of plasma chemical etching equipment, which realizes the replacement of grinding heads with different diameters by replacing nozzles with different diameters, obtains a removal function of ideal size, and realizes full-frequency surface The shape error converges.

A replaceable nozzle ICP generating device in plasma chemical etching equipment, the ICP generating device includes a nozzle, a plasma torch, an induction coil sleeved outside the plasma torch, a high-voltage Tesla ignition coil, and a radio frequency power supply And matching device, RF power supply and matching device supply power to the induction coil, and the high-voltage Tesla ignition coil is powered by an external power supply; Nozzles are used to adjust the size of the removal function.

Further, the nozzle on the ICP generating device adopts a water cooling structure.

Further, the nozzle includes a nozzle inner core, a water-cooling shell top cover, a water-cooling shell and a flow diversion groove. After the nozzle inner core, the water-cooling casing top cover and the water-cooling casing are assembled, a closed cavity is formed, and the flow diversion groove is fixedly connected to the nozzle The inner core corresponds to the outer surface of the cavity, the upper and lower ends of the water-cooled shell correspond to the cavity and are processed with a water-cooled liquid inlet and a water-cooled liquid outlet, and the nozzle is fixedly connected to the mounting plate at the lower end of the plasma torch through the top cover of the water-cooled shell.

Further, a shielding cover is also included, and the plasma torch and the induction coil are set inside the shielding cover.

Further, the outer diameter of the plasma torch is 20 mm, the outer diameter of the nozzle inner core is consistent with the outer diameter of the plasma torch, and the inside of the nozzle inner core is composed of a cylindrical section, a contraction section and an expansion section, and the inside of the nozzle is The total length of the core is 35mm, the length of the cylindrical section is 10mm, the length of the contraction section is 8mm, and the length of the expansion section is 17mm. The diameter is the minimum diameter required for processing, and the expanded diameter of the expansion section is 15 mm.

Further, the plasma chemical etching equipment includes an ICP generating device, a moving mechanism, a gas supply device, and an exhaust gas treatment device; The gas supply device provides the gas required for the reaction to the plasma torch, and the ICP generator adjusts the set ignition power through the RF power supply and the matching device and loads it on the induction coil, and at the same time turns on the high-voltage Tesla ignition The coil makes it discharge to generate a high-voltage electric spark, and the high-voltage electric spark induces electrons inside the quartz torch and breaks down the high-purity argon in the middle tube and the outer tube, and further breaks down the high-purity argon gas under the excitation of the electromagnetic field generated by the radio frequency coil. Argon gas finally ignites the plasma to form a stable plasma torch; the motion mechanism drives the ICP generator to move at a certain distance on the surface of the workpiece according to a certain trajectory, and the airflow sprays active groups onto the surface of the workpiece, and a chemical reaction occurs to generate volatile Gaseous substances, to achieve the purpose of quantitatively removing materials at a specific location; the tail gas treatment device processes the tail gas after the reaction in the processing chamber.

Further, the motion mechanism adopts a five-axis linkage numerical control center, which includes an x-axis, a y-axis, a z-axis, a u-axis, and a v-axis, wherein the x-axis and the y-axis are driven by linear motors, and the drive of linear motors is faster than that of servo motors. The acceleration is greater, the running speed is faster, and it can reach the designated processing position in time, which is suitable for processing large-diameter workpieces.

Further, the material of the nozzle inner core is copper, silver, platinum or ceramics, the nozzle inner core communicates with the shield cover and is grounded, and the plasma torch contacts with it without secondary discharge phenomenon.

Beneficial effect:

1. The etching equipment of the present invention is simple in structure and low in cost, adopts atmospheric pressure plasma processing technology, and realizes removal of optical materials based on chemical reactions, does not produce subsurface damage, and has no residual stress layer.

2. The present invention realizes the replacement of grinding heads with different diameters by replacing the nozzles of different sizes, and can adjust the size of the removal function to obtain a removal function of ideal size, and realize the convergence of surface shape errors in all frequency bands.

3. The present invention adopts CFD (computational fluid dynamics) numerical simulation to optimize the parameters of the nozzle inner core. The shrinkage section of the nozzle inner core can limit the plasma and adjust the removal function; the beam is compressed to The tightest, but if the constraint is lost at this time, it will expand again, and the beam diameter will become larger again, resulting in unpredictable size of the removal function. However, if the rear of the nozzle keeps the diameter at the minimum diameter, due to the continuous compression of the space, the cooling gas stream close to the outer wall will interfere with the high-temperature plasma in the center, resulting in flameout. The expansion section after the contraction section prevents the rapid expansion of the beam diameter and prevents the flameout due to the interference of the cooling gas.

4. The x-axis and y-axis of the motion mechanism in the equipment of the present invention adopt linear motors, with fast motion speed, suitable for processing large-diameter workpieces, and can realize trace removal when the surface shape has high precision, and can reduce heat deposition at the same time.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is the conventional plasma torch structure schematic diagram of PCET among the present invention;

Fig. 3 is the schematic diagram of the plasma rectangular tube structure of PCET after increasing the nozzle and the shielding cover in the present invention;

Fig. 4 is a structural schematic diagram of the nozzle in the present invention.

Among them, 1-RF power supply, 2-Matching device, 3-RF coil, 4-Plasma torch, 5-Cooling circulation pump, 6-Gas supply device, 61-Cooling and auxiliary gas source, 62-Working gas source, 63-oxygen source, 7-cooling gas inlet, 8-auxiliary gas inlet, 9-working gas inlet, 10-processing chamber, 11-nozzle, 11-1-nozzle inner core, 11-2-water-cooling shell top cover, 11 -3-Water-cooled shell, 11-4-Guard, 11-5-Water cooling liquid inlet, 11-6-Water cooling liquid outlet, 12-High voltage Tesla ignition coil, 13-Shield cover, 14-Motion mechanism, 15 - Exhaust gas treatment device.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

As shown in Figure 1, the present invention provides a replaceable nozzle ICP generating device in plasma chemical etching equipment, the ICP generating device includes a nozzle 11, a plasma torch 4, and is sleeved outside the plasma torch. The induction coil 3, the high-voltage Tesla ignition coil 12, the shielding cover 13, the radio frequency power supply 1 and the matcher 2, the radio frequency power supply 1 and the matcher 2 cooperate to supply power for the induction coil 3, and the high-voltage Tesla ignition coil 12 is powered by an external power supply. Power supply, the shielding cover 13 sets the plasma torch 4 and the induction coil 3 inside; the nozzle 11 is detachably fixedly connected to the front end of the plasma torch 4 in the ICP generating device, and by replacing the nozzle 11 with a different inner diameter To achieve the adjustment of the size of the removal function.

As shown in Figure 2, the conventional plasma torch is provided with a cooling gas inlet 7, an auxiliary gas inlet 8 and a working gas inlet 9 connected to the gas supply device, but this structure cannot control the shape and size of the plasma torch.

As shown in Figure 3, the diameter of the nozzle of the ICP generating device can be changed by replacing the water-cooled nozzle 11, without considering the matching problem between the rectangular tube and the coil.

As shown in Figure 4, the nozzle 11 includes a nozzle inner core 11-1, a water-cooled housing top cover 11-2, a water-cooled housing 11-3 and a diversion groove 11-4, a nozzle inner core 11-1, a water-cooled housing top cover 11 -2 and the water-cooling shell 11-3 are assembled to form a closed cavity, the diversion groove 11-4 is fixedly connected to the outer surface of the corresponding cavity part on the nozzle inner core 11-1, and the water-cooling shell 11-3 corresponds to the cavity The upper and lower ends are correspondingly processed with a water-cooling liquid inlet 11-5 and a water-cooling liquid outlet 11-6, and the nozzle 11 is fixedly connected to the mounting plate at the lower end of the plasma torch 4 through the top cover 11-2 of the water-cooling shell;

The material of the nozzle inner core 11 is copper, silver, platinum or ceramics, the nozzle inner core 11 communicates with the shield cover 13 and is grounded, and the contact of the plasma torch has no secondary discharge phenomenon.

The outer diameter of the plasma torch 4 is 20mm, and the outer diameter of the nozzle inner core 11-1 is consistent with the outer diameter of the plasma torch 4. The inside of the nozzle inner core 11-1 is composed of a cylindrical section, a contraction section and an expansion section. The total length of the inner core 11-1 is 35mm, the length of the cylindrical section is 10mm, the length of the contraction section is 8mm, and the length of the expansion section is 17mm. The diameter between the expansion sections is the minimum diameter required for processing, and the diameter of the expansion section after expansion is 15mm.

As shown in Figure 1, the plasma chemical etching equipment includes an ICP generator, a motion mechanism 14, a gas supply device 6 and an exhaust gas treatment device 15. The flow controller is connected to the plasma torch 4, the gas supply device 6 provides the gas required for the reaction of the plasma torch 4, and the ICP generator adjusts the ignition power of 800-1200W through the RF power supply 1 and the matching device 2 and loads it on On the induction coil 3, connect the high-voltage Tesla ignition coil 12 at the same time so that it discharges to generate a high-voltage electric spark, and the high-voltage electric spark induces electrons inside the quartz torch tube 4 and breaks down the high-purity argon in the middle tube and the outer tube At the same time, under the excitation of the electromagnetic field generated by the radio frequency coil 3, the high-purity argon gas is further broken down, and finally the plasma is ignited to form a stable plasma torch; Moving at a distance, the airflow sprays active groups onto the surface of the workpiece, a chemical reaction occurs to generate volatile gaseous substances, and the purpose of quantitatively removing materials at a specific position is achieved; the tail gas treatment device 15 processes the tail gas after the reaction in the processing chamber 10; the gas supply The device 6 includes a cooling and auxiliary gas source 61 , a working gas source 62 and an oxygen source 63 , and the above three gas sources are respectively connected to the cooling gas inlet 7 , the auxiliary gas inlet 8 and the working gas inlet 9 on the plasma torch 4 .

The motion mechanism 14 adopts a five-axis linkage CNC center, which includes an x-axis, a y-axis, a z-axis, a u-axis and a v-axis, wherein the x-axis and y-axis are driven by linear motors, which run with greater acceleration than servo motors The speed is faster, and it can reach the designated processing position in time, which is suitable for processing large-diameter workpieces.

In the embodiment, the working gas is Ar, the reaction gas is CF ₄ , and the workpiece made of SiC material is processed. _In the plasma generator, CF4 is excited to generate excited state F atoms, and react with Si in SiC as follows:

Si+4F ^* →SiF ₄ ↑

The reaction product is gas, which is separated from the adsorption and enters the tail gas treatment device to realize material removal.

In this embodiment, the plasma torch 4 and the shielding cover 13 are installed on a motion mechanism 14 with a five-axis linkage numerical control center, and the motion mechanism 14 communicates with the host computer to precisely control the movement of the motor.

In this embodiment, the motion mechanism 14 is driven by a linear motor. The linear motor has a large acceleration and a maximum operating speed, and with the efficient PCET processing device, it can achieve micro-removal when the surface shape has high precision, and can reduce heat deposition at the same time.

In this embodiment, a water-cooled nozzle 11 is installed at the front end of the plasma torch 4, which can limit the beam diameter of the plasma, obtain removal functions of different sizes, and take away part of the heat at the same time, reducing heat deposition on the workpiece.

Concrete operation steps of the present invention are:

Step 1. According to the surface equation, a processing algorithm is used to generate a processing control file, that is, a motion trajectory and a processing dwell time of a five-axis linkage CNC center are generated.

Step 2: Turn on the cooling circulation pump 5 to feed cooling water into the radio frequency coil 3 and the water-cooling nozzle 11, then open the valve of the cooling and auxiliary gas source 6, and a high-purity argon will be established in the plasma torch 4 after a few minutes Atmospheric environment facilitates the generation of plasma.

Step 3. After the above preparatory work is completed, adjust the power of the radio frequency power supply 1 to the power required for ignition, that is, 800-1200W, and load it on the radio frequency coil 3 at the same time to prepare for plasma ignition.

Step 4, connect the high-voltage Tesla ignition coil 12 to discharge it to generate a high-voltage electric spark, and the high-voltage electric spark induces electrons inside the plasma rectangular tube 4 and breaks down the high-purity argon in the middle tube and the outer tube, At the same time, under the excitation of the electromagnetic field generated by the radio frequency coil 3, the high-purity argon gas is further broken down, and finally the plasma is ignited to form a stable plasma torch flame.

Step 5. After forming a high-temperature and stable plasma torch flame, open the valve of the working gas source 62, and feed working gases such as carbon tetrafluoride (CF4), sulfur hexafluoride (SF6), trifluoride Nitrogen (NF3), etc., form active groups, which are stable after 5 to 10 minutes.

Step 6. Use the processing control file generated in step 1 to control the motion mechanism to move according to the determined trajectory, and drive the ICP generator to move at a certain distance on the workpiece surface. Gaseous substances, to achieve the purpose of quantitative removal of materials at specific positions, and complete processing.

Step 7. If it is necessary to replace nozzles 11 with different calibers, first stop the moving mechanism 14, turn off the radio frequency power supply 2, and then turn off the air source 6 and the water cooling device 5. The nozzle 11 and the shielding cover 13 are fastened by threads, and can be quickly disassembled. After unscrewing, replace the suitable nozzle inner core 11-1, and then repeat the above steps.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (8)

1. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus, this ICP generating means include nozzle, etc. Gas ions torch pipe, the induction coil being sheathed on outside plasma torch pipe, high pressure tesla ignition coil, radio-frequency power supply and coupling Device, radio-frequency power supply and adapter are that induction coil is powered, and high pressure tesla ignition coil is powered by external power source；Its feature Being, described nozzle and the front end of ICP generating means plasma quarter bend are dismountable fixing be connected, by changing difference The size that the nozzle of internal diameter realizes removing function is adjusted.

2. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 1, its feature exists In, the nozzle on described ICP generating means uses water-cooling structure.

3. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 1 or 2, it is special Levying and be, described nozzle includes nozzle inner core, water cooled housing top cover, water cooled housing and guiding gutter, nozzle inner core, water cooled housing top Lid and water cooled housing form a cavity closed after assembling, guiding gutter is fixedly connected on nozzle inner core corresponding chamber portion Outer surface, the correspondence of two ends up and down of water cooled housing correspondence cavity is machined with water-cooled liquid entrance and the outlet of water-cooled liquid, and nozzle passes through water Cold closure head is fixing with the installing plate of plasma torch pipe lower end to be connected.

4. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 3, its feature exists In, also including a radome, plasma torch pipe and induction coil are set with therein by described radome.

5. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 3, its feature exists In, the external diameter of described plasma torch pipe is 20mm, and the external diameter of described nozzle inner core is consistent with the external diameter of plasma torch pipe, spray In mouth, core inner is made up of cylindrical section, contraction section and expansion segment, and the total length of nozzle inner core is 35mm, and cylindrical section is a length of 10mm, a length of 8mm of contraction section, expansion segment length 17mm, cylindrical section realizes for the installing plate with plasma quarter bend lower end Coordinate and install, the minimum diameter needed for a diameter of processing between contraction section and expansion segment, expansion segment expansion after a diameter of 15mm。

6. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 1, its feature exists In, described plasma chemistry etching apparatus includes ICP generating means, motion, gas supply device and vent gas treatment dress Put；Described ICP generating means integral erection above motion, gas supply device via gas mass flow controller with Plasma torch pipe is connected, and gas supply device provides the gas needed for reaction for plasma torch pipe, and ICP generating means passes through Radio-frequency power supply and adapter regulate the firing power set and are carried on induction coil, are also turned on high pressure tesla ignition lead Circle makes its generation high-voltage spark that discharges, and high-voltage spark generates electronics and punctures intervalve and outer tube inside quartz torch pipe In high-purity argon gas, radio-frequency coil produce electromagnetic field excitation under puncture high-purity argon gas further, finally light plasma Form stable plasma torch flame；Motion drives ICP generating means according to determining at a certain distance from surface of the work Movement locus moves, and active group is ejected into surface of the work by air-flow, occurs chemical reaction to generate volatile gaseous material, it is achieved Ad-hoc location quantitatively removes the purpose of material；Tail gas reacted in Processing Room is processed by exhaust gas processing device.

7. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 6, its feature exists In, described motion uses 5-shaft linkage numerical control center, and this numer centre includes x-axis, y-axis, z-axis, u axle and v axle, wherein x Axle and y-axis use linear electric motors to drive, and linear electric motors drive the speed of service bigger than servomotor acceleration faster, can arrive in time Reach appointment Working position, be suitable for processing large aperture workpiece.

8. the exchangeable nozzle ICP generating means in plasma chemistry etching apparatus as claimed in claim 3, its feature exists In, the material of described nozzle inner core is copper, silver, platinum or pottery, nozzle inner core and radome UNICOM and ground connection.