CN116169002A - Magnetic field enhanced coupling plasma processing device and method - Google Patents
Magnetic field enhanced coupling plasma processing device and method Download PDFInfo
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- H—ELECTRICITY
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- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32009—Arrangements for generation of plasma specially adapted for examination or treatment of objects, e.g. plasma sources
- H01J37/32082—Radio frequency generated discharge
- H01J37/32091—Radio frequency generated discharge the radio frequency energy being capacitively coupled to the plasma
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J37/00—Discharge tubes with provision for introducing objects or material to be exposed to the discharge, e.g. for the purpose of examination or processing thereof
- H01J37/32—Gas-filled discharge tubes
- H01J37/32431—Constructional details of the reactor
- H01J37/3266—Magnetic control means
- H01J37/32669—Particular magnets or magnet arrangements for controlling the discharge
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2237/00—Discharge tubes exposing object to beam, e.g. for analysis treatment, etching, imaging
- H01J2237/32—Processing objects by plasma generation
- H01J2237/33—Processing objects by plasma generation characterised by the type of processing
- H01J2237/334—Etching
- H01J2237/3343—Problems associated with etching
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention provides a magnetic field enhanced coupling plasma processing device and a method, comprising the following steps: a capacitively coupled plasma device and a racetrack pole device; the capacitive coupling plasma device comprises an upper anode plate and a lower cathode plate, wherein a plasma working area is arranged between the upper anode plate and the lower cathode plate, and an electric field is formed between the upper anode plate and the lower cathode plate; the runway magnetic pole device comprises a moving device and runway magnetic poles arranged on the moving device, and the moving device drives the runway magnetic poles to move along a plane parallel to the lower cathode plate; the racetrack poles comprise adjacently placed permanent magnets of opposite magnetic polarity, forming an additional coupling magnetic field that constrains bipolar diffusion movement of electrons in the electric field. The density, distribution and directional drift of the multi-field coupling modulation plasma greatly improve the actual processing efficiency of difficult-to-process materials, also enable the plasma of the medium-large caliber optical element to be processed rapidly, and improve the laser damage resistance of the element.
Description
Technical Field
The invention belongs to the technical field of plasma processing, and relates to a magnetic field enhanced coupling plasma processing device and method.
Background
Plasma devices are widely used in Integrated Circuits (ICs), MEMS devices, and in medium and large aperture optical element manufacturing processes. Among the commonly used plasma devices are Capacitively Coupled Plasma (CCP) devices and Inductively Coupled Plasma (ICP) devices. The capacitive coupling plasma device has a simple structure, is relatively easy to discharge, is the earliest commercialized plasma processing technology, but has the biggest problem that the energy and density of the plasma cannot be controlled. The Inductively Coupled Plasma (ICP) device utilizes a multi-turn radio frequency antenna coil outside a chamber, the radio frequency coil is loaded with radio frequency power in the plasma etching process, and the chamber radio frequency power is coupled into the chamber through a dielectric window to excite the process gas introduced into the chamber to form plasma.
Although the radio frequency capacitive coupling plasma makes up the defects of the capacitive coupling plasma method, the ICP vacuum plasma source is adopted, the ICP processing efficiency is still low due to the limitation of the electrode size and the plasma uniformity, and the batch production of semiconductor elements and the processing of medium-and large-caliber optical elements cannot be realized.
In the prior art, the high-efficiency processing of materials is realized by wires and surfaces based on a magnetron sputtering abnormal glow discharge mode. Although the method overcomes the defects of the existing plasma processing, the magnetron sputtering discharge method has two defects, namely, the vacuum working conditions of the capacitive coupling discharge and the magnetron sputtering abnormal glow discharge are not uniform, and the optimal state of discharge is not easy to realize; secondly, most of processed materials are semiconductors or non-conductive optical elements (silicon carbide, fused quartz and sapphire), if a magnetron sputtering abnormal glow discharge mode is adopted, larger power supply is required to meet the requirements of mass and medium-large caliber element processing, so that the cost is higher.
Therefore, it is a need for those skilled in the art to provide a magnetic field enhanced coupled plasma processing apparatus and method that can achieve plasma density adjustment and efficient etching of a workpiece surface.
Disclosure of Invention
In view of the above, the present invention provides a magnetic field enhanced coupled plasma processing apparatus and method, which solve the technical problems in the prior art.
In order to achieve the above purpose, the present invention adopts the following technical scheme:
the invention discloses a magnetic field enhanced coupling plasma processing device, which comprises: a capacitively coupled plasma device and a racetrack pole device; wherein,,
the capacitive coupling plasma device comprises a vacuum chamber, an upper anode plate and a lower cathode plate which are positioned in the vacuum chamber, wherein a plasma working area is arranged between the upper anode plate and the lower cathode plate, a radio frequency power supply is loaded on the lower cathode plate, and an electric field is formed between the upper anode plate and the lower cathode plate; the upper surface of the lower cathode plate is provided with a component to be processed;
the runway magnetic pole device is positioned in the bottom space of the lower cathode plate and comprises a moving device and runway magnetic poles arranged on the moving device, and the moving device drives the runway magnetic poles to move along a plane parallel to the lower cathode plate; the runway magnetic poles comprise permanent magnets which are adjacently arranged and have opposite magnetic poles, arch-shaped magnetic induction lines are formed above the lower cathode plate, and an additional coupling magnetic field for restraining bipolar diffusion movement of electrons in an electric field is formed.
Preferably, the movement device comprises a guide rail, a stepping motor and a sliding block; the guide rail is arranged in parallel in the bottom space of the lower cathode plate, one end of the guide rail is connected with the output end of the stepping motor, and the runway magnetic poles are connected to the guide rail through the sliding blocks in a transmission manner and do linear motion along the guide rail.
Preferably, the runway magnetic pole comprises an outer ring rectangular magnet and a strip rectangular magnet horizontally arranged in the middle of the symmetry axis of the outer ring rectangular magnet; the top of the outer ring rectangular magnet is an N pole, and the bottom of the outer ring rectangular magnet is an S pole; the top of the rectangular magnet is an S pole, and the bottom of the rectangular magnet is an N pole.
Preferably, the outer ring rectangular magnets and the long rectangular magnets are all linear and densely arranged magnetic pole arrays.
Preferably, the top of the runway magnetic pole is covered with an insulating gasket, and the bottom of the runway magnetic pole is provided with a magnetic conduction sheet for conducting magnetic induction lines between permanent magnets with opposite magnetic polarities of the adjacently placed magnetic poles.
Preferably, the distance between the runway magnetic pole and the surface of the element to be processed is 40-60 mm.
Preferably, the upper anode plate is of a hollow structure, the hollow space is a gas mixing chamber, a plurality of holes which are distributed and arranged are formed in the bottom of the upper anode plate, and the holes are communicated with the gas mixing chamber; the top of the gas mixing chamber is communicated with an air inlet pipeline for conveying process gas.
Preferably, a metal shielding cover is arranged on the periphery of the lower cathode plate, the top of the metal shielding cover is opened, and the to-be-processed element placing area of the lower cathode plate is exposed.
The invention also discloses a plasma processing method of the magnetic field enhanced coupling plasma processing device, which comprises the following steps:
placing an element to be processed in the capacitive coupling plasma device, and forming a plasma working area between an upper anode plate and a lower cathode plate by utilizing capacitive coupling discharge;
the runway magnetic pole device applies an additional coupling magnetic field to the plasma working area to form a linear plasma area with the density higher than a set threshold value;
and controlling the runway magnetic pole to move along a plane parallel to the lower cathode plate, and enabling the linear plasma region to move directionally along with the runway magnetic pole to modulate the density and the distribution of the plasma so as to finish etching the surface of the element to be processed.
Preferably, the method further comprises the step of adjusting the working air pressure in the vacuum chamber according to the selection of the element to be processed.
Compared with the prior art, the technical scheme has the beneficial effects that:
on the basis of capacitive coupling discharge, an additional magnetic field is applied to the bottom of a capacitive coupling discharge electrode (a lower cathode plate), the magnetic field can move in one dimension along the horizontal direction of the electrode, secondary electrons generated by plasma discharge can be modulated by the magnetic field, the density and distribution of plasma are modulated, a linear high-density plasma region is formed, efficient etching of the surface of a workpiece is realized, and then the high-density plasma region moves in a directional manner along with the horizontal movement of the magnetic field, and uniform etching of the surface of the workpiece is completed by lines and surfaces.
The invention effectively solves the key technical bottleneck of ultra-precise optical elements, creatively provides a linear magnetic field coupling enhanced plasma polishing technology, and greatly improves the actual processing efficiency of difficult-to-process materials such as sapphire and the like, expands the range of processing materials and also enables the rapid processing of the medium-large caliber optical element plasma by designing the moving magnetic field driving and multi-field coupling modulation plasma density, distribution and directional drift.
The invention is also beneficial to solving the problem of temperature effect in the plasma processing process, fundamentally ensures the certainty and reliability of a plasma removal function, avoids the factor that an optical element with high thickness-to-diameter ratio possibly generates deformation in the processing process, effectively realizes the rapid removal of the damage on the surface and subsurface of a processed workpiece, reduces the loss on the surface of the element, and improves the laser damage resistance of the element.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, it will be apparent that the drawings in the following description are only embodiments of the present invention, and other drawings can be obtained according to the provided drawings without inventive effort to a person skilled in the art;
FIG. 1 is a schematic diagram of a magnetic field enhanced coupled plasma processing apparatus according to an embodiment of the present invention;
FIG. 2 is an enlarged schematic view of a portion of a connection relationship between a lower cathode plate according to an embodiment of the present invention;
FIG. 3 is a diagram of an RF capacitively coupled plasma profile according to an embodiment of the present invention;
FIG. 4 is a graph of an enhanced magnetic field coupled plasma profile provided by one embodiment of the present invention;
FIG. 5 is a schematic diagram of a track pole structure and arrangement according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of an array structure of racetrack poles according to an embodiment of the present invention;
FIG. 7 is a schematic view of an array structure of racetrack poles according to an embodiment of the present invention;
FIG. 8 is a schematic diagram of a B-B direction of an array structure of racetrack poles according to an embodiment of the present invention;
FIG. 9 is a cross-sectional view in the C-C direction of an array structure of racetrack poles provided by one embodiment of the invention;
fig. 10 is a cross-sectional view of an array structure B-B of racetrack poles according to an embodiment of the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
As shown in fig. 1, a first aspect of the embodiment of the present invention provides a magnetic field enhanced coupled plasma processing apparatus, which can be used for processing semiconductor materials, optical elements, etc.; comprising the following steps: a capacitively coupled plasma device and a racetrack pole device; the capacitive coupling plasma device comprises a vacuum chamber 4, an upper anode plate 3 and a lower cathode plate 11 which are positioned in the vacuum chamber 4, a plasma working area 7 is arranged between the upper anode plate 3 and the lower cathode plate 11, a radio frequency power supply is loaded on the lower cathode plate 11, and an electric field is formed between the upper anode plate 3 and the lower cathode plate 11; the upper surface of the lower cathode plate 11 is provided with a component 9 to be processed; the runway magnetic pole device is positioned in the bottom space of the lower cathode plate 11 and comprises a moving device and runway magnetic poles 13 arranged on the moving device, and the moving device drives the runway magnetic poles 13 to move along a plane parallel to the lower cathode plate 11; the racetrack pole 13 comprises adjacently placed permanent magnets of opposite magnetic polarity forming arch-shaped magnetically induced lines above the lower cathode plate 11 forming an additional coupling magnetic field that constrains bipolar diffusion movement of electrons in the electric field.
When the enhanced magnetic field is not introduced, the distribution of the capacitively coupled plasma is shown in fig. 3 only under the excitation of the radio frequency power supply, and the distribution of the enhanced magnetic field coupled plasma is shown in fig. 4. The magnetic aggregation phenomenon after the additional coupling magnetic field is introduced is obvious. When only an electric field exists, particles in the plasma move to the surface of the cathode only under the action of the electric field, the collision path between the particles and gas molecules is small in the process, the probability of collision ionization among the particles is small, and the plasma density is low. The plasma generated by radio frequency excitation is symmetrically distributed in the geometric center of the discharge area and has a certain distance from the surface of the cathode; the electron density of the plasma, the electron temperature and the distribution of the plasma after coupling the plasma by the magnetic field are greatly affected. The external magnetic field can restrict bipolar diffusion movement of electrons perpendicular to the magnetic field direction, limit electron to pass through the constraint of break-away magnetic field, the whole plasma region is subjected to combined action of an electric field and a magnetic field, active particles generate rotary movement and drift diffusion on the surface of a cathode, the total length of a path is increased in the drift diffusion process, collision ionization of the particles is greatly increased, the plasma density above an etching region is increased, the distribution is contracted towards the central position, and the voltage of a plasma sheath layer is reduced.
Moreover, the magnetic field also binds electrons on the surface of the cathode, so that electron loss of a discharge area is reduced, the electrons also attract reactive ions to move towards the surface of the cathode, the chemical reaction rate is increased, the electrons attracted by the surface can strengthen an electric field in plasma, the enhanced electric field can increase an ohmic heating process in the plasma, cascade collision enhancement of the magnetic field on the electrons can also cause subsequent heating enhancement, subsequent heating can cause more high-energy electrons on the surface of the cathode, the collision rate of the electrons and gas molecules is increased, gas ionization enhancement is carried out, and the distribution of the plasma on the surface of the cathode is more uniform. Meanwhile, the contact area between the plasma and the processed surface is contracted, the energy is concentrated, the bombardment sputtering of the plasma and the surface is reduced, the chemical reaction is enhanced, the processing efficiency is increased, and the processing quality is improved. Compared with the existing magnetron sputtering discharge mode, the power required by the plasmas with the same ion flux is much smaller, and the processing cost is saved.
In the embodiment, the capacitive coupling plasma device generates plasma by capacitive coupling discharge, the capacitive coupling discharge is easy to realize in a vacuum environment, a 13.56MHZ radio frequency power supply is adopted, the power supply power is 1-2 KW, and the capacitive coupling plasma device has good cost advantages. The runway magnetic pole device realizes magnetic field coupling modulation, and can realize plasma density adjustment by adjusting working air pressure according to different processing elements, so that the working range is wide, and the working vacuum degree can be adjusted within the range of 1-1000 Pa.
It should be noted that, in this embodiment, the rf capacitive coupling plasma generation technology is applied, the rf capacitive coupling is a way of coupling the input power into discharge, and two electrodes and the sheath layer thereof are used to form a capacitor, so that the discharge is easier to generate large-area high-density active plasma.
In one embodiment, the capacitive coupling plasma device adopts a single-frequency driving mode, the discharging frequency of the radio frequency power supply is 13.56MHz, the radio frequency driving voltage is 100-1000V, the radio frequency power is adjustable between 100-2000 w, and the air pressure is 2 Pa-1000 Pa, so that plasma can be generated by discharging.
The radio frequency power supply consists of a radio frequency signal generator and a matching network. The ion source is mainly generated by applying radio frequency voltage (or current) to two electrodes (an upper anode plate 3 and a lower cathode plate 11) through an external matching network, and the matching network ensures that the impedance of a radio frequency generator and a vacuum chamber 4 automatically realizes accurate conjugate matching. The signal output by the rf power supply is connected to the bottom of the lower cathode plate 11 of the vacuum chamber 4 via an rf signal connector 16. The workpiece is placed on the lower cathode electrode, and meanwhile, direct current negative bias voltage can be applied on the lower cathode plate to adjust the energy of ions bombarding the surface of the workpiece, so that when elements with hard brittleness and difficult processing such as sapphire, silicon carbide, glass ceramics and the like are processed, the plasma energy can be improved, and the ions are accelerated to bombard the surface.
In one embodiment, the bottom of the vacuum chamber 4 is supported by a bracket, the vacuum chamber 4 comprises a top plate and a side plate, the bottom of the side plate is provided with a fixed plate, and one end of the fixed plate, which faces the center direction of the bottom of the vacuum chamber 4, is fixedly connected with the lower cathode plate 11. One of the fixing plates is provided with a vacuum pumping pipeline interface 8 for communicating the vacuum pumping pipeline to the inside of the vacuum chamber 4.
In this embodiment, the vacuum pumping duct interface 8 is located at the bottom edge of the circular vacuum chamber 4, and its outer portion is connected to a vacuum unit. In order to improve the uniformity of the air flow, a partition 18 is arranged vertically on the circumference of the lower cathode plate 11, and a vacuum air suction pipeline interface 8 is positioned between the partition 18 and the side plate.
In one embodiment, the movement means comprises a guide rail 1, a stepper motor 2 and a slider; the guide rail 1 is arranged in parallel in the bottom space of the lower cathode plate 11, one end of the guide rail 1 is connected with the output end of the stepping motor 2, and the runway magnetic pole 13 is connected to the guide rail 1 through a sliding block in a transmission manner and moves linearly along the guide rail 1.
In the concrete implementation, the upper electrode plate and the lower cathode plate 11 are horizontally arranged, the guide rail 1 is a horizontal guide rail 1, and the moving magnetic poles can move linearly along the guide rail 1 at a uniform speed in the horizontal direction. The stepping motor 2 can drive the magnetic poles to move in a directional and uniform speed; the other end is connected with a programmable controller PLC, and executes instruction operation corresponding to the PLC signal.
In one embodiment, the grounded anode (usually the wall of the whole vacuum chamber 4 is also grounded) of the upper anode plate 3 is a hollow stainless steel disc, the hollow space is a gas mixing chamber, and a plurality of holes which are distributed and arranged like a shower are arranged below the disc and are communicated with the gas mixing chamber. An air inlet pipeline 6 for conveying process gas is connected above the disc and communicated to the top of the gas mixing chamber.
When the equipment works, process gas (such as mixed gas of fluorine-containing gas, argon, oxygen and the like) can enter the gas mixing chamber at the upper part of the disc through the gas inlet pipeline 6, and then is uniformly guided into the reaction chamber (the vacuum chamber 4) through the holes. In order to ensure etching uniformity, the area of the electrode plate of the upper electrode is larger than that of the electrode plate of the lower electrode. In this embodiment, the diameter of the upper anode plate 3 is set to 450mm, and the diameter of the lower cathode plate 11 is set to 350mm.
In one embodiment, the lower cathode plate 11 is a copper cathode plate that is connected to a radio frequency power source through an annular copper radio frequency signal connector 16. The lower cathode plate 11 is a hollow cake-shaped body, a circular groove is formed in the top of the lower cathode plate 11, and the element 9 to be processed is arranged above the lower cathode plate 11. A water cooling device 10 is arranged in the hollow space of the lower cathode plate 11, and a water inlet pipe of the water cooling device is connected into the hollow space through a through hole on one side of the lower cathode plate 11 and flows out from a through hole on the other side of the lower cathode plate 11.
In this embodiment, the plasma density of the magnetic field surface area is increased by means of magnetic field coupling to form a linear W-shaped etching area, and although the temperature of the etching area is increased by the ion sputtering action in the etching process, the etching area moves along with the movement of the magnetic field, so that the etching area is sufficiently cooled by the water cooling device 10 with the electrode plate in a line-to-surface manner, the temperature rise of the workpiece to be processed is greatly suppressed, and meanwhile, the applied rf energy mainly acts on the plasma area, so that the energy consumed in the electrode (including the workpiece placed on the electrode) is very small, and the workpiece temperature is not obviously affected.
In one embodiment, the spacing between the upper anode plate 3 and the lower cathode plate 11 is adjustable. The upper anode plate 3 is connected to the ceiling of the vacuum chamber 4 by a linear drive 5. The air inlet pipe 6, the ground wire and the linear driver 5 are installed together, and the longitudinal position of the upper anode plate 3 can be adjusted by the linear driver 5 so as to change the distance between the upper electrode and the lower electrode.
The plasma working region 7 applies a high-frequency electric field between the electrode plates filled with low-pressure gas, and the gas ionizes to generate plasma. In the case of reactive ion etching, in order to ensure that the oscillating electrons driven by radio frequency have a long enough distance in the discharge to collide with neutral particles for excitation, a sufficient distance between the upper and lower electrodes is required. For example, the mean free path for the ionizing collisions of electrons with neutral particles at a gas pressure of 4Pa is around 1cm, so that the minimum distance between the electrodes is related to the gas pressure and is generally at least greater than 10mm. In this embodiment, in order to increase the flexibility of the process, the distance between the upper and lower electrode plates is adjusted by using the linear driver 5, and the distance between the upper and lower electrode plates is set to 40 mm-150 mm.
The generation mode of the plasma refers to the radio frequency abnormal glow discharge in the radio frequency magnetron sputtering coating technology. The gas is broken down when the electric field strength is enhanced to a certain value, and a discharge phenomenon is generated. The device can meet the requirements of two processes of magnetron sputtering and plasma etching.
The gas breakdown voltage required for high frequency discharge is lower than that required for direct current, radio frequency discharge is performed at low gas pressure (2-150 Pa), in this gas pressure range, lower gas pressure is used for etching, and higher gas pressure is used for deposition. Typically, the plasma density is 1015-1017 m -3 The electron temperature is between 1 and 4 eV.
For etching processes, the operating gas pressure is typically low, typically in the range of 1.33Pa to 13.3Pa. For example, in the etching process of sapphire, the reaction chamber is filled with the reaction gas, such as BCl, according to a certain working pressure and matching proportion 2 、Cl 2 The flow ratio was 2:1 (set Cl) 2 20 sccm) is filled into the reaction chamber, the RF power is set to be 500w, when the pressure of the vacuum chamber 4 is set to be 2Pa, plasma etching is enhanced through one-dimensional motion magnetic field coupling, and the etching rate and the etching uniformity of different parameters (RF power, pressure, gas flow, proportion, polar plate distance and the like) on the sapphire are explored.
For the magnetron sputtering coating process, a target is placed on a copper cathode plate with DC (RF) bias, an inert working gas with partial pressure of about 0.1 to 1Pa (the radio frequency magnetron sputtering can be filled with about 0.1 to 0.05 Pa) is filled into a vacuum chamber to be used as a carrier of gas discharge, electrons collide with argon atoms under the action of an electromagnetic coupling field, ar+ and new electrons are generated by ionization, and Ar+ ions fly to a cathode target in an accelerating way under the action of an electric field to bombard the surface of the target with high energy, so that the target is sputtered. In sputtered particles, neutral target atoms or molecules deposit on the substrate to form a thin film. And controlling the one-dimensional motion magnetic pole, and exploring the processing such as film forming uniformity.
The plasma polishing belongs to the field of pure chemical polishing, can obtain high-quality optical surfaces, but has low processing efficiency, adopts an external magnetic field to regulate and control in order to improve the processing efficiency of the plasma polishing, and aims to bind charged particles in a certain area, increase the collision probability among the particles, further increase the plasma density, increase the number of active atoms participating in chemical reaction and improve the processing efficiency.
In one embodiment, the magnets of the runway magnetic pole 13 are neodymium iron boron (NdFeB), and the arrangement and the size structure of the enhanced magnetic poles are shown in fig. 5, and the runway magnetic pole 13 comprises an outer ring rectangular magnet and a long rectangular magnet horizontally arranged in the middle of the symmetry axis of the outer ring rectangular magnet; the top of the outer ring rectangular magnet is an N pole, and the bottom is an S pole; the top of the rectangular magnet is an S pole, and the bottom is an N pole.
In this embodiment, the outer ring rectangular magnets and the elongated rectangular magnets are all linear and densely arranged magnetic pole arrays, that is, are formed by combining small magnetic poles which are linearly and densely arranged, so as to construct a large-size linear magneto-electric coupling plasma region. The small magnetic poles have two specifications, 23 cuboid magnets with length, width and height of 20mm, 10mm and 10mm are horizontally arranged on the long edges of the two ends of the outer ring rectangular magnet, 4 cuboid magnets with length, width and height of 20mm, 15mm and 10mm are horizontally arranged on the wide edges of the two ends of the outer ring rectangular magnet, the middle of the outer ring rectangular magnet is horizontally arranged, and 20 cuboid magnets with length, width and height of 20mm, 15mm and 10mm are respectively arranged on the long edges of the two ends of the outer ring rectangular magnet. Sequentially and horizontally arranging and combining the rectangular magnet arrays into an outer ring rectangular magnet array with the length of 490mm, the width of 80mm and the upward N pole, and horizontally arranging the rectangular magnet array with the length of 400mm in the middle of a symmetrical axis. The outer ring rectangular magnets and the strip rectangular magnets also comprise soft irons positioned at the bottom of the magnetic pole array. The racetrack poles 13 are distributed and sized as shown in fig. 6-10.
The linear length of the magnetic field enhanced ion source is 300mm, so that the plasma for processing the large-caliber optical element can be ensured to be in a uniform and stable magnetic field with enough strength.
The permanent magnet is used for regulating and controlling the plasma instead of electromagnetic excitation, so that a circuit in the device can be effectively simplified, interaction between the plasma and external electric excitation is reduced, and the device has stability for regulating and controlling the plasma distribution.
Permanent magnets with opposite magnetic polarities are arranged in a staggered manner and fixed by a magnetic permeability iron framework, and are arranged below the lower cathode plate 11 in parallel, and the horizontal tangential direction of the magnetic induction lines is parallel to the cathode plate. The runway magnetic pole 13 is fixed on a horizontal guide rail 1 parallel to the cathode plate, and can reciprocate and orient to perform one-dimensional motion along the guide rail 1 under the drive of a motor. The magnetic pole structure can generate Gaussian magnetic force line distribution between adjacent magnetic poles, the maximum intensity of a magnetic field is generated at the magnetic pole surface, and the magnetic field is reduced along with the direction away from the magnetic pole surface, so that the confinement regulation and control of the magnetic field on plasma is generally considered to be mainly performed on the magnetic pole surface, and the influence of the magnetic field on a plasma device can be reduced while the plasma density is enhanced.
The PLC controls the stepping motor 2 to drive the runway magnetic pole 13 to move along the guide rail 1 in the direction orthogonal to the arrangement direction, so that the linear and uniformly distributed high-density plasma is guided to drift along the magnetic pole moving direction, and the rapid and uniform etching processing of the large-area optical elements with lines and surfaces can be realized. The multi-dimensional regulation and control of the plasmas by taking the magnetic field, the electric field and the one-dimensional motion field as parameters breaks through the limit of the existing plasma polishing technology, increases the control dimension and the control margin of the plasmas, introduces more and more reliable control means for plasma processing, improves the precision of plasma density and distribution regulation and control, solves the defect that the existing vacuum plasma technology cannot perform etching processing on a medium-large-caliber element due to the fact that the existing vacuum plasma technology is limited by the electrode size or the plasma density requirement, and expands the application range of the vacuum plasma etching technology in the field of manufacturing optical elements.
In one embodiment, the top of the racetrack pole 13 is covered with an insulating spacer 12 to prevent the pole from interfering with the rf field; the bottom is provided with a magnetic conductive sheet 14 for conducting magnetic induction lines between permanent magnets with magnetic poles placed adjacently and opposite in magnetism.
In one embodiment, the runway pole 13 surface is 40-60 mm from the surface of the element 9 to be machined. The magnetic field strength and uniformity can be regulated and controlled by parameters such as magnetic pole materials, magnetic pole spacing, magnetic pole height, magnetic yoke, pole shoe shape and the like, and the horizontal component of the magnetic field on the surface of the processing element is measured on 200GS according to Gaussian measurement, so that the magnetic field can be ensured to effectively bind electrons. The magnetic field and the electric field form orthogonal coupling fields to form high-density plasma for improving the magnetron sputtering efficiency and the etching efficiency.
In one embodiment, as shown in fig. 2, a metal shield 17 is mounted on the periphery of the lower cathode plate 11, and the top of the metal shield 17 is opened and the area where the component 9 to be processed of the lower cathode plate 11 is placed is exposed. The radio frequency signal connector 16 is located at the bottom of the outer edge of the lower cathode plate 11, and the metal shielding cover 17 covers the outer side face and the top face of the radio frequency signal connector 16, so that when the sample stage (the lower cathode plate 11) works, gas glow discharge is concentrated in a region where the element 9 to be processed is placed, and the cathode is prevented from being sputtered, so that pollution is reduced, and etching efficiency is greatly improved.
An insulating sealing gasket 15 is placed between the end of the vacuum chamber 4 fixing plate and the lower cathode plate 11 to prevent the cathode from contacting the vacuum chamber 4 to influence the electric potential.
A second aspect of the embodiment of the present invention provides a plasma processing method using the magnetic field enhanced coupled plasma processing apparatus provided in the first aspect, including the steps of:
placing the element 9 to be processed in a capacitive coupling plasma device, and forming a plasma working area 7 between the upper anode plate 3 and the lower cathode plate 11 by using capacitive coupling discharge;
the runway magnetic pole device applies an additional coupling magnetic field to the plasma working area 7 to form a linear plasma area with the density higher than a set threshold value;
the runway magnetic pole 13 is controlled to move along a plane parallel to the lower cathode plate 11, the linear plasma region moves along with the plane, the plasma density and distribution are modulated, and the etching of the surface of the element 9 to be processed is completed.
In this embodiment, the externally applied magnetic field can restrict the bipolar diffusion motion of electrons perpendicular to the magnetic field direction, limit the electron from crossing the break-away magnetic field, and under the combined action of the electric field and the magnetic field, the active particles generate the cyclotron motion and the drift diffusion on the surface of the cathode in the whole plasma region, and in the process of the drift diffusion, the total path length is increased, so that the impact ionization of the particles is greatly increased, the plasma density above the etching region is increased, and the magnetron sputtering efficiency and the etching efficiency are improved.
In one embodiment, the method further comprises the step of adjusting the working air pressure in the vacuum chamber 4 according to the selection of the element 9 to be processed, so as to realize the adjustment of the plasma density, and the working vacuum degree of the method can be adjusted within the range of 1Pa to 1000 Pa.
The magnetic field enhanced coupled plasma processing device and method provided by the invention are described in detail above, and specific examples are applied in this embodiment to illustrate the principle and implementation of the invention, and the description of the above embodiments is only used to help understand the method and core idea of the invention; meanwhile, as those skilled in the art will vary in the specific embodiments and application scope according to the idea of the present invention, the present disclosure should not be construed as limiting the present invention in summary.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined in this embodiment may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A magnetic field enhanced coupled plasma processing apparatus, comprising: a capacitively coupled plasma device and a racetrack pole device; wherein,,
the capacitive coupling plasma device comprises a vacuum chamber, an upper anode plate and a lower cathode plate which are positioned in the vacuum chamber, wherein a plasma working area is arranged between the upper anode plate and the lower cathode plate, a radio frequency power supply is loaded on the lower cathode plate, and an electric field is formed between the upper anode plate and the lower cathode plate; the upper surface of the lower cathode plate is provided with a component to be processed;
the runway magnetic pole device is positioned in the bottom space of the lower cathode plate and comprises a moving device and runway magnetic poles arranged on the moving device, and the moving device drives the runway magnetic poles to move along a plane parallel to the lower cathode plate; the runway magnetic poles comprise permanent magnets which are adjacently arranged and have opposite magnetic poles, arch-shaped magnetic induction lines are formed above the lower cathode plate, and an additional coupling magnetic field for restraining bipolar diffusion movement of electrons in an electric field is formed.
2. The magnetic field enhanced coupled plasma processing apparatus according to claim 1, wherein the moving means comprises a guide rail, a stepping motor, and a slider; the guide rail is arranged in parallel in the bottom space of the lower cathode plate, one end of the guide rail is connected with the output end of the stepping motor, and the runway magnetic poles are connected to the guide rail through the sliding blocks in a transmission manner and do linear motion along the guide rail.
3. The magnetic field enhanced coupled plasma processing apparatus according to claim 1, wherein the racetrack magnetic pole comprises an outer ring rectangular magnet and a long rectangular magnet horizontally placed in the middle of the symmetry axis of the outer ring rectangular magnet; the top of the outer ring rectangular magnet is an N pole, and the bottom of the outer ring rectangular magnet is an S pole; the top of the rectangular magnet is an S pole, and the bottom of the rectangular magnet is an N pole.
4. A magnetic field enhanced coupled plasma processing apparatus according to claim 3, wherein said outer ring rectangular magnets and said elongated rectangular magnets are each a linear densely arranged magnetic pole array.
5. The magnetic field enhanced coupled plasma processing apparatus according to claim 1, wherein the runway magnetic pole is covered with an insulating spacer at the top and a magnetic conductive sheet for conducting magnetic induction lines between the adjacently placed permanent magnets with opposite magnetic polarities is provided at the bottom.
6. The magnetic field enhanced coupled plasma processing apparatus according to claim 1, wherein the runway magnetic pole is spaced from the surface of the element to be processed by a distance of 40 to 60mm.
7. The magnetic field enhanced coupling plasma processing device according to claim 1, wherein the upper anode plate is of a hollow structure, the hollow space is a gas mixing chamber, a plurality of holes distributed and arranged are formed in the bottom of the upper anode plate, and the holes are communicated with the gas mixing chamber; the top of the gas mixing chamber is communicated with an air inlet pipeline for conveying process gas.
8. The magnetic field enhanced coupled plasma processing apparatus according to claim 1, wherein a metal shield is mounted on the periphery of the lower cathode plate, the metal shield being open at the top and exposing a component placement area of the lower cathode plate to be processed.
9. A plasma processing method of the magnetic field enhanced coupled plasma processing apparatus according to any one of claims 1 to 8, comprising the steps of:
placing an element to be processed in the capacitive coupling plasma device, and forming a plasma working area between an upper anode plate and a lower cathode plate by utilizing capacitive coupling discharge;
the runway magnetic pole device applies an additional coupling magnetic field to the plasma working area to form a linear plasma area with the density higher than a set threshold value;
and controlling the runway magnetic pole to move along a plane parallel to the lower cathode plate, and enabling the linear plasma region to move directionally along with the runway magnetic pole to modulate the density and the distribution of the plasma so as to finish etching the surface of the element to be processed.
10. The plasma processing method according to claim 9, further comprising the step of adjusting the operating gas pressure in the vacuum chamber in accordance with the selection of the element to be processed.
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| CN116453925A (en) * | 2023-06-16 | 2023-07-18 | 通威微电子有限公司 | Magnetic control enhanced plasma polishing device |
| CN116453925B (en) * | 2023-06-16 | 2023-08-25 | 通威微电子有限公司 | Magnetic control enhanced plasma polishing device |
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