JP2020047591A - Hollow cathode plasma source - Google Patents

Abstract

To provide a simple plasma source capable of providing a uniform plasma of significant length that can treat and/or coat large substrates with high efficiency and low amounts of contamination and defects in the field of a large area surface treatment and large area coating.SOLUTION: A hollow cathode plasma source includes a first electrode and a second electrode (1, 2) each having an elongated hole (4), and in order to ensure high electron density and/or low sputtering at the plasma source hole surface, there is provided a hollow cathode plasma source in which the value of at least one of the following parameters such as a hole cross-section shape, a hole cross-sectional area, a hole distance (11), and an exit nozzle width (12) is selected, and there is also provided a method for surface treatment or coating using such a plasma source.SELECTED DRAWING: Figure 1

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is filed on the same day as the present application and is hereby incorporated by reference herein, under the name of "Plasma Source Utilizing a Macro-Particle Reduction Coating and Method of Medicine in the United States of America." -PCT International Application _____________________________________________________________________ entitled, "Particle Reduction Coating for Deposition of Thin Film Coatings and Modification of Surfaces" (Attorney Docket No. 0124-374.PCT).

  The present invention relates to a plasma source for surface treatment and / or coating of large substrates. In particular, the present invention relates to linear plasma sources for plasma enhanced chemical vapor deposition and plasma surface treatment, and more particularly to a plasma source utilizing a hollow cathode type discharge.

  Various plasma sources for thin film deposition and surface chemical modification have been disclosed in the prior art.

  When processing large substrates, these plasma sources are generally linear ion sources as disclosed in U.S. Pat. No. 7,411,352 to Madocks. The plasma source utilizes a magnetron discharge to generate a linear ion beam or a combination of a plurality of plasma sources to generate a plurality of parallel ion beams directed at the surface of the substrate. Madocks discloses that coating materials can be provided outside the plasma source for coating purposes. The plasma extends essentially only in one dimension, ie, along the length of the plasma source. The width of the ion beam is constrained by the pressure in the process chamber which limits the mean free path length. For this reason, when transporting a substrate under this plasma source, the contact time is relatively short. Thus, for example, if it is necessary to increase the time for treating a substrate with plasma, the number of plasma sources must be increased. Further, the coating material injected adjacent to the plasma source has a limited opportunity to interact with the plasma beam. As a result, the adhesion rate becomes relatively low, and the danger of contaminating the coater with a raw material that has failed to react with the substrate surface increases.

  Madocks also discloses that sputtering of the electrode material occurs and the sputtered material re-adheres and remains in the plasma source. However, when the electrode material is sputtered, the life of the electrode is shortened. Redeposition of the sputtered material can also block the nozzle of the plasma source, making uniform substrate processing or coating impossible. In addition, the sputtered electrode material may further condense and / or react to form debris that may block the nozzle of the plasma source or fall onto the substrate and cause defects. These nozzles are constituted by one of the electrodes of the plasma source. For this reason, the electrodes are exposed to the coating process environment in the vacuum chamber and are therefore prone to contamination with the injected coating material.

  Furthermore, the magnet source disclosed in Madocks using a magnetron discharge requires a magnet. Because magnets are sensitive to high temperatures, such plasma sources cannot be operated at high temperatures and must be cooled by active or passive means. Not only are these magnets present, but also the need for shunts, resulting in a complex and expensive assembly.

  Further, this plasma source generates free electrons at a relatively low density as compared with a plasma source using a hollow cathode discharge. For the purpose of coating, the plasma electrons serve to ionize the coating material. Thus, using a plasma source that utilizes magnetron plasma, such as that disclosed by Madocks, reduces coating efficiency.

  Jung, in EP-A-0 727 508 (A1), discloses a hollow cathode linear plasma source utilizing two parallel electrodes. The plasma extends essentially only in one dimension, ie, along the length of the plasma source, forming a narrow plasma beam. Jung discloses that a stream of inert gas must be injected parallel to the electrodes to avoid sputtering of the electrode material. However, the injection of an inert gas parallel to the electrodes leads to a decrease in the rate of generation of reactive ions, thereby reducing the processing efficiency or the coating rate.

U.S. Pat. No. 7,411,352 European Patent Application Publication No. 0727508

  One of the main problems with this type of high deposition rate plasma source is the fact that the walls of the plasma source quickly become fouled by reacting early with the raw material flowing through the plasma. Due to this problem, the industrial application of the process is very limited and requires frequent cleaning cycles which limit throughput on the production line.

  Another disadvantage of these high deposition rate plasma sources is that it is difficult for the source to remain on the surface of the substrate only after leaving the plasma source. As a result, a significant portion of the raw material cannot be used to form a coating on the substrate. This leads to a decrease in coating rate and a fouling of the coater due to changes in the raw material on the surface surrounding the plasma source.

  Thus, in the field of large area surface treatments and large area coatings, it is possible to provide a fairly long, uniform plasma capable of treating and / or coating large substrates with high efficiency and low amounts of contamination and defects. A simple plasma source is still needed.

  In one aspect of the present invention, a linear plasma source is provided that is useful for depositing a thin film on a large substrate and for plasma treating the surface of the large substrate. Plasma treatment is meant to include, for example, surface activation, surface cleaning and surface etching.

In one aspect of the present invention, a plasma source utilizing a hollow cathode, wherein the linear plasma is very wide, is provided.
In one embodiment of the present invention, a plasma source capable of forming a uniform and wide linear plasma is provided.

In one embodiment of the present invention, a plasma source having a low sputtering rate on a surface of an electrode hole is provided.
In one aspect of the invention, a plasma source with a high density of free electrons is provided.
In one aspect of the present invention, a method is provided for forming a large area coating using a uniform and broad linear plasma.

  These and other aspects of the invention will become apparent in the detailed description of particular embodiments of the invention with reference to the drawings.

FIG. 1 shows a cross-sectional view of a plasma source according to the present invention. FIG. 2 shows a cross-sectional view of another plasma source according to the present invention. FIG. 3 shows a cross-sectional view of another plasma source according to the present invention. FIG. 4 shows a cross-sectional view of a plasma source according to the present invention used for surface treatment or coating of a substrate. FIG. 5 shows a sectional view of a possible variant of the plasma source according to the invention.

  FIG. 1 shows a first electrode 1 having a first electron emission surface, which is a wall of a hole, and a second electrode having a second electron emission surface, which is a wall 3 of a hole, arranged close to each other. 2 shows a cross-sectional view of a hollow cathode plasma source according to the invention comprising The first electrode and the second electrode each substantially surround an elongated space 4 containing gas, ie, a hollow cathode hole.

  The distance 11 between the hollow cathode holes is measured as the distance from the center 14a of one hole to the center 14b of the other hole. The electrodes extend substantially parallel to one another. The cathode may be arranged in a direction perpendicular to the moving direction of the substrate to be treated, or may be arranged obliquely to this moving direction.

  The first electrode and the second electrode are essentially surrounded by an insulating material 5. The first electrode and the second electrode are provided with a gas inlet 6 for a gas forming plasma and a gas outlet 7 for an ionized plasma gas.

  At the outlet, gas is sent via an outlet nozzle 13 towards a vacuum chamber in which the plasma source is located and a substrate in the vacuum chamber. The gas outlet nozzle has a certain width 12.

  The first electrode and the second electrode are electrically connected to an AC power supply (not shown) that applies a voltage that alternates between positive and negative. Between the electrodes and the vacuum chamber structure 8 supporting the plasma source is a dark or solid electrical insulator 9. Also, the plasma source may be combined with the coating material injection nozzle 10 to perform the plasma enhanced chemical vapor deposition. The nozzle 10 sends the coating material containing the gas to the plasma generated by the plasma source in the vacuum chamber. Structural elements and cooling elements and electrical connections are not shown.

  Hollow cathode plasma source is taken to mean a device for forming a plasma, commonly described as two holes in which a positive potential (anode) and a negative potential (cathode) alternate with a 180 ° phase shift. In a cathode hole, electrons oscillate between the negative electric fields of the hole, thereby being confined within the hole.

  Plasma is taken to mean a conductive gaseous medium containing both free electrons and positive ions.

  Reaction gas is taken to mean oxygen and / or nitrogen.

  It is often desirable to attach a compound to the surface that may not be chemically obtainable from the source gas alone. In many cases, a reactive gas such as oxygen or nitrogen may be added to a chemical vapor deposition (CVD) process to form an oxide or nitride.

Other reaction gases may include fluorine, chlorine, other halogens or hydrogen. The reaction gas can be distinguished from the source gas by the fact that no condensable molecular species are formed when excited or chemically decomposed. Normally, the reactant gas or a portion of the reactant gas cannot itself grow a solid deposit, but the reaction causes the reactant gas or solid deposit from the source of the other solid deposit to react with the solid deposit. It is possible to chemically incorporate a part of the gas or the reaction gas. Preferred reaction gas _{is O 2, N 2, NH 3} , CH 4, N 2 O, H 2.

  Raw material is meant to mean a gas or liquid in molecular form containing chemical elements that are condensed into a solid coating, selected based on vapor pressure. Elements condensed from the raw materials include metals, transition metals, boron, carbon, silicon, germanium and / or selenium.

  Typically, the source molecules are non-reactive or difficult to adhere to the surface until excited, partially decomposed, or completely decomposed by the energy source, and when excited, partially decomposed, or completely decomposed, the coating becomes A chemical portion of the raw material containing the desired chemical element can be chemically bonded or condensed in solid form to the surface. The condensed part of the starting compound can be mainly a pure element, a mixture of elements, a compound or a mixture of compounds derived from the components of the starting compound.

Preferred raw material _{gas, SiH 4, N (SiH 3} ) 3, TMDSO, HMDSO, inorganic compounds such as TTIP · · · _{or, SiO 2, Si x N y} , ZrO 2, TiO 2, Al 2 O 3, AlN, Any other compound containing a metal suitable for depositing an oxide, nitride, or oxynitride film, such as SnO2, ZnO, etc., and a mixture of one or more of these materials, for example, SiO _x , etc. _{N y, Si x Al y N} z.

  Substrate is taken to mean either a small or large area item whose surface is chemically modified or coated according to the present invention. As used herein, a substrate can be comprised of glass, plastic, metal, inorganic, organic, or any other material having a surface to be coated or modified.

  AC power or AC power is taken to mean power from an alternating power supply, which varies in frequency with a sine wave, square wave, pulse or some other waveform. Voltage fluctuations often occur from negative to positive. For the bipolar type, the output power provided by the two leads is typically about 180 ° out of phase.

  Secondary electron or secondary electron current is taken to mean the emission of electrons from a solid surface and the resulting current, respectively, due to the impact of particles on the surface.

  A dark area is taken to mean a narrow zone or area around the electrode where the plasma current is very low. Normally, substantially no current flows between the plasma electrode and the ground potential conductor which are separated by a dark portion distance or between two oppositely charged plasma electrodes.

  The material of the electrode must be sufficiently conductive so that electrons can be emitted from the electrode surface and carry the current necessary to sustain the discharge. Electrode materials include metals, metal alloys, metal compounds, carbon, carbon compounds, ceramics or semiconductors. The most commonly used materials are metals, metal alloys or graphite carbon.

  The electrode material may be selected according to specific electron emission characteristics. These materials may include those with a low work function or a high secondary electron emission coefficient that can lower the operating voltage and increase the electron current.

  The electron emission surface can include a metal coating, a metal-based coating, a metalloid coating, a metalloid-based coating, or a carbon-based coating deposited on the electrode. These coatings may include materials having a low work function or a high secondary electron emission coefficient that can lower the operating voltage and increase the electron current.

Almost any gas can be used as a gas for forming plasma. Most commonly, the gas forming the plasma contains the He, Ne, Ar, _{Kr, Xe,} and _{O 2, N 2, H 2} , NH 3 or any mixture of these gases. Gas flow rates are generally between 0.5 sccm and 10 sccm per linear millimeter of hole length.

  The outlet and the nozzle can have different arrangements and shapes. Generally, they are an array of holes. It may also be a slot or an elongated orifice. There is a gas pressure drop between the hollow cathode hole and the outside or vacuum chamber. This maintains a sufficiently high pressure level in the cathode hole to keep the plasma stable and allows the ionized gas to flow out of the hole. In this manner, the nozzle separates the electrode from the coating process environment in the vacuum chamber, reducing the potential for contamination by the injected coating material.

  The first hollow cathode electrode and the second hollow cathode electrode alternately function as a cathode and an anode. When one electrode is electrically positive with respect to the plasma potential, the other electrode is electrically negative with respect to the plasma potential, and this electric polarity is reversed at a certain period.

  This may be achieved by using an AC power supply or a pulsed DC power supply. In general, a power supply applies a bipolar voltage whose phase is switched alternately by about 180 degrees out of phase so that the electron current between the electrodes is inverted at a certain period. The preferred voltage range is 300 V to 1200 V, and the preferred frequency range is 10 kHz to 1 MHz, preferably 10 kHz to 100 kHz, most preferably about 40 kHz.

  The plasma formed by the hollow cathode plasma source of the present invention is a non-equilibrium non-thermal plasma, which is highly conductive and carries a charge, typically tens of volts positive ground potential. The electrodes are positioned close enough to allow an electron current to flow between electrodes of opposite polarity at the operating pressure of the vacuum chamber.

  The operating pressure in the vacuum chamber can be maintained between 0.001 mbar and 1 mbar, typically between 0.002 mbar and 0.1 mbar, more usually between 0.007 mbar and 0.05 mbar.

  Plasma is formed in a space surrounded by the first electron emission surface and the second electron emission surface, and spreads over the entire space between the electron emission surfaces where gas exists. The plasma is substantially free of closed-circuit electron drift and is made substantially uniform throughout its length.

  Thereby, the plasma source according to the invention forms a linear plasma beam with a high free electron density, extending between the two hollow cathode holes without being limited to a narrow width below the plasma source. Therefore, the use of the plasma source according to the present invention can increase the contact time between the substrate and the plasma. It also provides a better opportunity for coating material injected near the plasma beam to interact with the beam. This achieves high deposition rates and high processing efficiencies while reducing the risk of fouling the plasma source and the entire coater.

  Further, the plasma source according to the present invention does not require additional electrodes, acceleration grids, magnetic fields, shunts or neutralizers. For this reason, it is less complex than other plasma sources and therefore less costly. However, if desired for specific reasons, magnets and / or additional electrodes can be used in combination with the hollow cathode arrangement according to the invention.

In one aspect of the invention, values of certain key parameters of a hollow cathode plasma source are provided. Important parameters identified by the inventors are:
-Cross-sectional shape of hole-Cross-sectional area of hole-Width of outlet nozzle-Distance of hole.

  We have recognized the surprising effect of these important parameters. In addition, the present inventors have found that, among all the parameters that govern these plasma sources, the above parameters are particularly, alone or in combination, not only the free electron density of the plasma generated in the hollow cathode plasma source, but also the plasma source. It has been found that it has a significant effect on the amount of sputtering at the surface of the hole. To achieve these effects, the present inventors have discovered that the above important parameters need to be specific values. The values of these important parameters may be different for each hole of the hollow cathode plasma source, but are preferably the same for both holes of the hollow cathode plasma source.

  According to an advantageous embodiment, specific values of these important parameters, separately or in any combination, reduce the amount of sputtering at the surface of the holes. Thus, the plasma source according to the invention does not require the injection of an inert gas parallel to the electrodes. Therefore, reactive species are obtained in high yield, leading to high processing efficiency or coating rate.

  Therefore, the plasma source according to the present invention suppresses the sputtered material from re-adhering to the inside of the plasma source and its nozzle, and reduces the formation of debris. This improves the uniformity of the treatment or coating and reduces the amount of defects in the treatment or coating.

  According to an advantageous embodiment, in plasma sources utilizing hollow cathode discharges, the use of these important parameters separately at certain values or in any combination leads to an increase in free electron density. Therefore, processing efficiency or coating efficiency is improved. Furthermore, using the coating material more efficiently leads to a reduction in contamination of the vacuum chamber and the vacuum pump due to the unreacted coating material.

  In long-term tests of over 100 hours, a plasma source having a rectangular cross-sectional shape with rounded corners (FIG. 2) was more effective at the surface of the hole than a plasma source with a circular cross-sectional shape (FIG. 3). Quite a lot of sputtering was observed.

  By comparing the experimental results with the data of computer simulation, the present inventors found that the amount of sputtering on the surface of the hollow cathode hole was more affected by the absorption of reactive ions on the surface of the hollow cathode hole when determined by numerical simulation. I found something related.

  The simulation software used to simulate gas flow and gas discharge is a program called PIC-MC developed by the Fraunhofer-Institute for Surface Engineering and Thin Films IST in Braunschweig, Germany. The software combines gas flow, magnetic field, and plasma simulations.

  The gas flow simulation uses the direct simulation Monte Carlo (DSMC) method, the magnetic field simulation uses the boundary element method (BEM), and the plasma simulation uses the in-cell particle Monte Carlo method (PIC-MC).

  The simulation was performed using a pseudo 2D model, which is a slice obtained by cutting the hollow cathode plasma source in a width direction at a thickness of 1.016 mm. Pseudo 2D means that the slices are thin and periodic conditions are applied laterally in each plane.

For the simulation, many different gases that form the plasma can be used, and the following examples used argon. In order to limit the calculation time, Si ₂ H ₆ was selected as a coating material, and the following two of the possible reactions were selected.

Si ₂ H ₆ + e ⁻ → Si ₂ H ₄ ⁺ + 2H + 2e ⁻ (1)
Si ₂ H ₆ + e ⁻ → SiH ₃ + SiH ₂ + H + e ⁻ (2)

  Hydrogen species were not included in the simulation.

  For each set of input parameters, the simulation provides data on the number and velocity of different gaseous species (atoms, ions, molecules, electrons) over the space occupied by them. From this data, certain values such as density and flux can be calculated.

Here, the flux is the movement amount of the gas phase species per unit area (unit: mol · m ⁻² · s ⁻¹ ).

  Another useful calculation is the flux absorbed on a surface. Given a certain sticking coefficient of the cathode pore material, the ion absorption at the surface can be calculated from the ion flux directed at that surface. By correlating the experimental results with the simulation data, the present inventors have determined that, according to the simulation model, the formation of debris observed in the actual plasma source, and hence the sputtering at the surface of the hole, will result in the ionized plasma species at the surface of the electrode hole. Was found to be related to the level of absorption.

  The lower the level of ionized plasma absorption at the surface of the electrode hole, the lower the level at which sputtering occurs in the hole and the less debris is formed.

  Another important quantity is the electron density generated. The electron density has a great influence on the surface treatment or coating efficiency, and the higher the electron density, the higher the surface treatment or coating efficiency.

  In this simulation, the electron density was measured in a vacuum chamber on a line set at a distance of 2.54 mm from the chamber structure supporting the plasma source, and the average was measured.

  In one aspect of the present invention, a cross-sectional shape of a hollow cathode hole is provided.

  We have surprisingly found that the cross-sectional shape of a rectangular hole can be reduced to a rectangular shape with at least one rounded corner or preferably a rounded rectangular shape with four rounded corners (a rectangular rounded corner). Shape) or preferably a cross-section surrounding the same surface area having a rectangular shape with rounded corners, with a radius of four corners equal to half its width, or most preferably a circular shape. Alternately, it has been found that the level of absorption of ionized plasma species at the surface of the cathode hole is reduced.

  FIG. 2 shows a cross-sectional view of a plasma source according to the invention, wherein the cross-sectional shape of the hole is a rectangle with rounded corners.

  FIG. 3 shows a cross-sectional view of a plasma source according to the present invention, wherein the cross-sectional shape of the hole is circular.

  Variations on these shapes, especially those leading to intermediate shapes, can be made without departing from the invention. In particular, it is an elliptical shape, an oval shape, or a modified example of a shape as shown in FIG.

  Further, the present inventors have also found that the electron density is improved when the cross-sectional shape of the hole is circular, as compared with the case where the hole has a rectangular shape.

In one aspect of the invention, a cross-sectional area of a hollow cathode hole is provided.
According to an embodiment of the present invention, the cross-sectional area of the ^holes, 100mm ^{2 ~10000mm 2,} preferably 500mm ² ~4000mm ^2.

According to another embodiment of the present invention, the cross-sectional area of the ^holes, 100mm ^{2 ~1000mm 2,} it is preferably 500mm ² ~1000mm ^2, most preferably 500mm ² ~750mm ^2. The present inventors have surprisingly found that the smaller the hole cross-sectional area, the higher the electron density.

According to another embodiment of the present invention, the cross-sectional area of the ^hole, 1000mm ^{2 ~4000mm 2,} it is preferably 1500mm ² ~4000mm ^2, most preferably 2000mm ² ~4000mm ^2. The present inventors have surprisingly found that the larger the cross-sectional area, the lower the level of absorption of ionized plasma species by the surface of the cathode hole.

According to another embodiment of the present invention, the cross-sectional area of the ^holes, 750mm ^{2 ~1500mm 2,} preferably 750mm ² ~1250mm ^2, and most preferably 1000 mm ² before and after. The present inventors have found that at some intermediate cross-sectional area, the level of absorption of the ionized plasma species by the surface of the cathode hole and the electron density can be balanced.

  In one aspect of the invention, a measured distance of the hollow cathode hole from the center of one hole to the center of the other hole is provided. The center of the hole is the geometric center of the cross section of the hole if the hole has a regular geometry, or the center of gravity of the hole if the hole is irregular.

  The present inventors have surprisingly found that increasing the distance of the hollow cathode hole to a certain threshold reduces the level of absorption of ionized plasma species by the surface of the cathode hole as the electron density decreases. According to the invention, the distance of the holes is between 85 mm and 160 mm, preferably between 100 mm and 145 mm, most preferably around 125 mm.

  It will be apparent to those skilled in the art that the hole distance also depends on the hole size, insulation requirements, structural requirements, and cooling requirements.

  In one aspect of the invention, an outlet nozzle width is provided.

  In this design, the outlet nozzle is centered on a vertical line passing through the center of the cross-sectional shape of the hole. The center of the cross section of each hole and the center of its outlet nozzle are aligned with a vertical line passing through the center of the cross section of the hole. However, the arrangement and orientation of the outlet nozzle may be changed and modified without departing from the invention.

  In a basic design, the width of the outlet nozzle ranges from 3.5 mm to 5 mm. The inventors have found that increasing this width reduces the level of absorption of the ionized plasma species by the surface of the cathode hole and increases the electron density. However, when the width of the outlet nozzle is larger than the threshold, the electron density is significantly reduced. This is probably because the pressure in the holes cannot be maintained at a high enough level to produce a significant plasma discharge.

  According to the invention, the width of the outlet nozzle is between 1 mm and 25 mm, preferably between 3 mm and 25 mm, more preferably between 8 mm and 22 mm, more preferably between 8 mm and 12 mm, most preferably around 10 mm.

  According to another embodiment of the invention, a single power supply is commonly used, or multiple separate power supplies are used to combine two or more plasma sources to increase the duration of a surface treatment or coating. Can be.

  According to another embodiment of the present invention, the plasma source is used for surface treatment of a substrate, for example, surface cleaning, surface renewal, surface activation, and the like. The substrate is transported beneath the plasma source and is exposed to plasma ions and electrons that span the vacuum space between the plasma source outlet nozzles.

  According to another embodiment of the present invention, a plasma source is used to coat a substrate. FIG. 4 shows the substrate 15 exposed to the ions and electrons of the plasma 16 carried beneath the plasma source and extending throughout the vacuum space between the two nozzles of the plasma source. To form a coating on a substrate, a coating source gas is injected through a nozzle 17 and activated by a plasma.

<Example>
Examples 1 and 2
A plasma source having two 10 cm (plasma length) stainless steel hollow electrodes according to the present invention was constructed and operated for more than 100 hours under the following conditions.

・ Voltage amplitude ± 1200V
・ Frequency 40kHz
・ Voltage function: bipolar, sine wave with voltage control ・ Power set point 20 kW, operating plasma source in power control mode ・ Gas O2 forming plasma; flow rate is 2 sccm per linear millimeter of hole length
・ Cross-sectional area of cathode hole 2000mm ²
-Vacuum chamber pressure: 8 to 12 mTorr
・ Width of outlet nozzle: 3.5mm

The cross-sectional shapes of two different holes having a rounded corner and a rectangular shape were compared.
Sputtering at the surface of the holes leads to the formation of debris particles. At 24 hour intervals, debris on the glass substrate was collected and the number of debris particles was counted. As is evident from the table below, the number of debris particles increased in a much shorter time in the cross-sectional shape of the rectangular holes with rounded corners than in the circular shape.

Example of Simulation In Examples 3 to 17, hollow cathode plasma sources were simulated.

  For each of the important parameters, up to five variant sets were compared. In each set, one variation was selected as a criterion. After calculating the absorption level and the electron density of the ionized plasma species on the surface of the cathode hole for each modification, the ratio between this value and the reference value was determined.

  The following parameters are not changed in all simulation examples.

・ Voltage amplitude ± 1200V
・ Frequency 100kHz
-Voltage function: Bipolar, sine wave with voltage control-Power set point 25 kW / m
・ Wall temperature 300K
-Flow rate of raw material gas type Si2H6 is 0.13sccm per linear meter with hole length
The flow rate of Ar gas for forming plasma is 2.65 sccm per linear meter of hole length.
-An electrode material with a secondary electron emission coefficient of 0.1 (comparable to Ag, Cu, Al, Ti, Zn, Fe)
By tuning the vacuum pump, the pressure of the vacuum chamber is about 10 mTorr

Examples 3 to 5 Important parameters: cross-sectional shape of hole The cross-sectional shapes of three types of holes, that is, a rectangle, a rectangle with rounded corners, and a circle were simulated. The rectangular section had a width of 10 mm and a height of 50 mm. The rectangular shape with rounded corners had four rounded corners (corner radius: 7 mm), a width of about 14 mm, and a height of 45 mm. The circular cross section had a radius of 13 mm.

  The following parameters were the same in Examples 3 to 5.

The cross-sectional area of the hole: about 500 mm ²
The width of the outlet nozzle: 5 mm
-Hole distance 122 mm

As the cross-sectional shape changes from a rectangle to a rectangle with rounded corners and a circle, the absorption of ionized plasma species in the cathode hole, and hence the sputtering of the hole and the formation of debris, decrease.
When the cross-sectional shape of the hole changes from a rectangle to a circle, the electron density and thus the process efficiency increase.

Examples 6-8 important parameters: the cross-sectional area of the cross-sectional area 500mm ^2, 1000mm ^2, 2000mm ² three cathode holes of the hole was simulated.

  The following parameters were the same in Examples 6 to 8.

-Cross-sectional shape of hole: circular-Width of outlet nozzle: 5 mm
-Hole distance 122 mm

  As the cross-sectional area of the holes increases, the absorption of ionized plasma species at the cathode holes, and thus the sputtering of holes and the formation of debris, decreases.

As the hole cross-section decreases, the electron density and thus the process efficiency increases.
At a hole cross-sectional area of about 1000 mm ² , the level of absorption of ionized species and the level of electron density are balanced.

Examples 9 to 13 Important Parameters: Hole Distance The distances of five types of holes 168 mm, 142 mm, 114 mm, 104 mm and 84 mm were simulated.

  The following parameters were the same in Examples 9 to 13.

- hole cross-sectional shape: circular - sectional area of the holes: 500 mm ²
The width of the outlet nozzle: 5 mm

  As the hole distance increases, the absorption of ionized plasma species at the cathode hole, and thus the sputtering of holes and the formation of debris, decreases.

  The electron density, and thus the process efficiency, remains good at the distance of all holes tested except the highest. An interesting balance of both ratios is obtained when the hole distance is between 100 mm and 145 mm.

Examples 14 to 17 Important parameters: width of outlet nozzles The widths of four types of nozzles of 5 mm, 10 mm, 20 mm and 40 mm were simulated.

  The following parameters were the same in Examples 9 to 13.

-Cross section of hole: circular-Cross section of hole: 500 mm ²
-Hole distance: 122mm

  The wider the outlet nozzle, the less the ionized plasma species will be absorbed by the cathode hole, and hence the less the hole will sputter and the formation of debris.

  The wider the outlet nozzle, the higher the electron density and thus the process efficiency. If the width of the outlet nozzle is very wide, for example, 40 mm, the pressure difference between the vacuum chamber and the inside of the hole cannot be maintained at a level sufficient to maintain a stable plasma, and the electron density level is very low. Lower.

Claims (11)

A hollow cathode plasma source,
It has an elongated hole (4), a gas inlet (6) for the gas forming the plasma, and a gas outlet (7) leading to an outlet nozzle (13) directed at the substrate, alternating positive and negative. A first electrode (1) and a second electrode (2) electrically connected to a power supply for applying a switching voltage;
A plurality of said cathodes, wherein said plurality of said cathodes are substantially parallel to each other;
As the values of the following parameters:
i. The cross section of the hole is a rectangle, a rectangle with rounded corners or a circle, or an intermediate shape between these shapes; ii. Iii It sectional area of the holes ^is 500mm ² ~4000mm 2. The distance (11) of the hole is 85 mm to 160 mm iv. A hollow cathode plasma source, wherein at least one of the outlet nozzles has a width (12) of 1 mm to 25 mm.   The value of the parameter i. To iv. 2. The hollow cathode plasma source according to claim 1, wherein at least two are selected.   The value of the parameter i. To iv. The hollow cathode plasma source according to claim 1, wherein all of the following are selected:   The hollow cathode plasma source according to claim 1, wherein a cross-sectional shape of the hole is circular. Cross-sectional area of the holes ^is 500mm ² ~1000mm 2, hollow cathode plasma source as claimed in claim 1. Cross-sectional area of the holes ^is 1000mm ² ~4000mm 2, hollow cathode plasma source as claimed in claim 1. Cross-sectional area of the holes ^is 750mm ² ~1500mm 2, hollow cathode plasma source as claimed in claim 1.   The hollow cathode plasma source according to claim 1, wherein the distance (11) of the holes is between 500 mm and 1000 mm.   The hollow cathode plasma source according to claim 1, wherein the width (12) of the outlet nozzle is between 3.5 mm and 25 mm. Providing a vacuum chamber having a hollow cathode plasma source according to claim 1;
Injecting a gas forming plasma through a gas inlet (6) forming plasma of said electrode;
Applying a voltage to the hollow cathode plasma source,
A method for treating a surface of a substrate, comprising introducing a substrate (15) into the plasma (16) generated by the plasma source in the vacuum chamber. Providing a vacuum chamber having a hollow cathode plasma source according to claim 1;
Injecting a gas forming plasma through a gas inlet (6) forming plasma of said electrode;
Applying a voltage to the hollow cathode plasma source,
Injecting a coating material gas toward the plasma generated by the plasma source,
Introducing a substrate (15) into said plasma (16) generated by said plasma source in said vacuum chamber;
A method for coating a substrate, comprising applying a coating from the source gas activated by the plasma.

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