MXPA99001137A - Magnetron - Google Patents

Abstract

Methods and devices for producing plasmas of more uniform density and greater height thanplasmas generated by previously known magnetron-type plasma-generating devices. The present invention utilizes electrodes containing multiple magnets positioned such that like magnetic poles of the magnets are all facing in substantially the same direction.

Description

MAGNETRON This invention relates to plasma generation devices. More specifically, this invention relates to magnetron-type plasma generating devices (ie, magnetrons) capable of holding plasmas of more uniform density than the plasmas generated by the previously known magnetron-type plasma generating devices. Magnetrons have been known in the art for a long time and have been used, for example, in etching, surface modification and plasma-enhanced chemical vapor deposition ("DVQAP"). DVQAP devices are also known in the art. Examples of DVQAP devices can be found in the Patents of E.U.A. Nos. 5,298,587; 5,320,875; 5,433,786 and 5,494,712 (collectively "Hu and others") the teachings of which are incorporated herein by reference. Other magnetron-type devices are taught in EP-A-0 297 235 ("Leybold") and DE-A-30 04 546 ("Kertesz and others"). As explained in Chapter 6 of Handbook of Plasma Technology, Noyes Publications 1990, magnetrons are a class of cathode discharge devices generally used in a diode mode. A plasma is initiated between the cathode and the anode at pressures on the mTorr scale by the application of a high voltage, which may be of or rf. The plasma is supported by the ionization caused by secondary electrons emitted from the cathode due to the bombardment of ions which are accelerated in the plasma through the cathode cover. That differentiates a magnetron cathode from a conventional diode cathode in the presence of a magnetic field. The magnetic field in the magnetron is oriented so that one component of the magnetic field is parallel to the surface of the cathode. The local polarity of the magnetic field is orientalized in such a way that the flow paths ExB of the secondary electrons emitted form a closed cycle. Due to the increased confinement of the secondary electrons and in this flow cycle of ExB compared to a diode or rf device, the density of the plasma is much higher, often by an order of magnitude or more, than a diode plasma. rf or conventional. The result of high plasma density and its proximity to the cathode is a relatively low voltage discharge of high current. Leybold teaches a magnetron that has two or more rows of magnets of the same polarity with the single-row magnets being deflected from the magnets of the adjacent row. The configuration in Leybold produces a serpentine "track" plasma for every two rows of adjacent magnets. Kertesz and others, teach a Penning deposit source.

The deposit source of Kertesz and others uses an auxiliary magnet to compensate for the decrease of the magnetic field of a magnet in excitation. In this way, a more homogeneously distributed magnetic field is obtained only with slight loss of intensity.

Hu et al. Teach a method for forming a protective abrasion resistant coating on a substrate surface. In the method taught in Hu et al., A DVQAP method that uses a magnetic confined electrode and is used to initiate the polymerization reaction of an organosilicon compound and an excess oxygen using a power density ranging from 106 to 108 Joules (J) / Kiiogram (Kg), in the presence of a substrate having a suitable surface to cause the polymerization product of the plasma process to adhere to the surface of the substrate. In Hu et al., The magnetic confined electrode uses magnets that have sufficient strength to provide at least 100 gauss. It is also known in the art that when a magnetron is used in a process for coating a substrate such as a DVQAP process, it is difficult to obtain a coating of uniform thickness and quality. One aspect of quality is the uniform chemical composition of the coating in both thickness and width directions. To obtain a coating of uniform thickness and quality the substrate must be moved in relation to the electrodes. This is especially true for large substrates. Moving the substrates in relation to the electrodes causes a decrease in the pitch. The present invention allows more uniform coatings (thickness and quality) to be obtained more easily than prior art devices do, especially on large substrates. In one aspect, the present invention is an electrode containing multiple magnets positioned so that the magnetic poles in the magnets are all facing substantially in the same direction. Each magnet produces a magnetic field between the opposite magnetic poles on the same magnet. Each magnetic field has a component parallel to the surface of the electrode. The electrodes of the present invention have a higher number of closed cycle ExB flow paths per number of magnets than the prior art electrodes. The electrodes of the present invention are capable of producing a more uniform plasma across the surface of an electrode. In addition, the electrodes of the present invention produce plasmas at a greater height than the electrodes of the prior art. In accordance with the present invention, large numbers of magnets (ie, two or more) can be aligned in various configurations so as to create several electrodes capable of producing large, more uniform plasmas. In another aspect, the present invention is an improved plasma generation device using electrodes of the present invention. In yet another aspect, the present invention is an improved method for forming a plasma and an improved method for coating various substrates. In one embodiment of the present invention, the electrode is a flat electrode comprising two or more magnets positioned so that the similar poles of the magnets are in a single geometric plane parallel to the geometrical plane of the flat electrode and the polarity of the magnets is perpendicular to the geometric plane of the flat electrode. Each magnet producing a magnetic field that has a component parallel to the geometrical plane of the electrode. Figure 1 is a schematic view of a plasma apparatus of the present invention. Figure 2 is a developed view of an electrode of the present invention. Figure 3 is another view of the electrode of Figure 2. Figure 4 is a view of another electrode of the present invention. Figure 5 is a view of an alignment of magnets useful in an electrode of the present invention. Figure 6 is a view of another alignment of useful gems in an electrode of the present invention. Figure 1 illustrates an apparatus of the present invention in which an electrode of the present invention can be used effectively. The apparatus comprises a reactor vessel 10 in which gaseous reactants can be introduced from sources 11, 12, 13 and 14 through the flow of mass flow controllers 15, 16, 17 and 18. If desired, the different gases and vapors of the indicated sources can be mixed in a mixer 19 before being introduced into the reactor vessel. A pair of opposing electrodes 20 and 21 is arranged in the reactor vessel 10. The substrate to be treated is placed between the electrodes 20 and 21. The electrode 21, the cathode, is connected to a variable frequency power source 22. The electrode 20 can advantageously be connected through the walls of the reactor vessel. The gaseous reactants are dispersed inside the gas supply line vessel 23. The reactor vessel 10 can advantageously be connected to a vacuum system 24 to evacuate the vessel 10. Optionally, the reactor vessel could be equipped with monitoring devices such as the optical monitor 25 to determine the thickness of the coating. Preferably, both electrodes 20 and 21 are embodiments of the present invention. However, it is not necessary that both electrodes be embodiments of the present invention. If only one electrode is an embodiment of the present invention, then preferably the electrode 21, the cathode, is an embodiment of the present invention. In operation, the reactor vessel 10 is evacuated first by means of the vacuum pump 24 before introducing gaseous reagents (e.g., organosilicon and oxygen) and inert gases, if any, the container at a predetermined flow rate through the supply line 23. When the flow regime of the gases becomes constant the variable frequency power 22 is turned on a predetermined value for generating a plasma which causes the reagents to form a film on the substrate. Figure 2 describes a developed view of an electrode 21 of the present invention. In Figure 2, the bar magnets 30 are placed on a lower plate 32. The magnets 30 can advantageously adhere to the lower plate 32. An upper plate 31 is placed on the magnets 30. The upper plate 31 can optionally have holes or slots therein to allow gaseous reactants and inert gases, if present, to pass through it as taught in the US Patent No. 5,433,786. It is a key aspect of the present invention that each magnetic pole of each magnet in an electrode of the present invention produces a magnetic field with the opposite magnetic pole of the same magnet. This is described in Figure 3, where the north pole of each magnet 30 forms a magnetic field 33 with the south pole of the same magnet. Each magnet 30 has a magnetic field 33 that is parallel to the surface of the electrode. Each magnet that forms a magnetic field with the opposite magnetic pole of the same magnet creates at least one closed cycle ExB bypass path. Therefore, the magnets in the electrodes of the present invention are configured so that each magnet creates its own closed loop ExB derivation routes. Preferably, this is done by aligning the magnets in the electrodes of the present invention so that the similar magnetic poles all look substantially in the same direction, as shown in Figure 3. By substantially the same direction, it is understood that the magnetic poles Similar of all the magnets look at the same direction in relation to the surface of the electrode. Therefore, although the electrode described in Figure 3 is a flat electrode, it is envisioned that the electrode could be curved. For example, the electrode can be formed into a cylindrical shape with all the north poles facing outward from the center of the cylinder. When the magnets in the electrodes of the present invention are aligned so that similar magnetic poles look substantially in the same direction, the magnets can be placed in close proximity to each other without any of the magnets forming magnetic fields with each other. the magnets placed near it. Therefore, even when the magnets are placed in close proximity to one another, each magnet still creates its own closed loop ExB derivation path. Because the magnets are placed in close proximity to each other while each magnet maintains its own closed loop ExB bypass path, the electrodes of the present invention enjoy the benefit of having ExB bypass paths of the most closed cycle by electrode surface area. Therefore, this increased number of closed loop bypass paths per electrode surface area results in a more uniform plasma than the plasmas produced using confined magnetic type electrodes of the prior art. It has been observed visually that the plasmas generated using the electrodes of the present invention diffuse farther from the electrode surface in the space between the electrodes than the plasmas generated using electrodes of the prior art. Although it is not definitively known exactly why this behavior is observed, it is thought that a portion of each magnetic field is repelled away from the electrode surface by similar magnetic poles on the surface of the electrode. It is also thought that these magnetic field portions result in a portion of plasma that will be produced from the electrode surface additional to what could be possible if the magnets were placed with alternating polarity. The large electrodes of the present invention can be created by configuring large numbers of magnets, all having similar magnetic poles looking substantially in the same direction. For example, Figure 4 shows a flat electrode of the present invention containing two rows of magnets 30. Even larger electrodes can be produced by increasing the number of magnets in each row or by adding more rows of magnets. When the bar magnets are used in accordance with the teachings of the present invention as shown in Figure 4, each magnet 30 creates a single closed cycle ExB bypass path 35. However, if circular magnets are used as shown in FIG. shown in Figure 5 or Figure 6, each magnet creates two closed cycle ExB derivation routes. For example, Figure 5 shows concentric rings of magnets 50 in which the visible surface of each magnet (ie, the flat surface facing the reader) has the same polarity. Each magnet in Figure 5 generates two separate closed cycle ExB derivation routes. Figure 6 shows circular magnets 60 all having the same radius aligned in a cylindrical shape. If the curved surface of each magnet 60 that faces outwardly from the center of the cylinder has the same polarity, then each magnet 60 will generate two branch paths ExB of closed cycle. The magnets used in the electrodes of the present invention can not be placed so close to each other in such a way as to prevent a magnetic pole of the magnet from producing a magnetic field with the opposite magnetic pole of the same magnet. If the magnets are placed very close to each other, they can behave like a single magnet. There is no critical limitation as to how far the magnets can be placed. However, since the magnets are set apart, their corresponding closed loop ExB derivation paths are further separated and the resulting plasma produced will be less uniform than a plasma produced when the magnets are placed closer together. A distance between the magnets suitable for a given application can be determined without undue experimentation. The wider bar magnets will produce a larger space in the center of the corresponding closed loop ExB bypass path. The larger spaces in the closed cycle ExB derivation routes also result in the production of a less uniform plasma. Therefore, it is generally more convenient to use relatively narrow bar magnets. However, if the magnets used in the electrodes of the present invention are very narrow, then the closed-cycle derivation route ExB will also be narrower, making it increasingly difficult to start the plasma. The width of the magnet suitable for a given application can be determined without undue experimentation. The electrodes of the present invention can be used advantageously with the teachings of the U.S. Patent Nos. Nos. 5,298,587; 5,320,875; 5,433,786; and 5,494,712 to produce improved DVQAP devices and methods for forming plasmas and coatings on various substrates. For example, another embodiment of the present invention is a plasma generating device comprising: a) two electrodes, at least one of the electrodes defining an electrode surface and containing two or more magnets, each magnet having two opposite magnetic poles , the magnets placed so that the similar magnetic poles of the magnets all look substantially in the same direction, each magnetic pole of each magnet producing a magnetic field with the opposite magnetic pole on the same magnet, each magnetic field having a component parallel to the magnet. the surface of the electrode, the magnets having enough resistance to generate at least 100 gauss; and b) a means for injecting gaseous reactants through at least one electrode, the medium driving substantially all the reactants through the magnetic fields. Yet another embodiment of the present invention is a method for providing an abrasion-resistant coating on the surface of a substrate that employs increased chemical vapor deposition of plasma from an organosilicon monomer gas in a plasma and gas reaction zone. oxygen, comprising the steps of: a) plasma by poiimerizing the organosilicon monomer in the presence of excess oxygen using a powder density within the range of about 106 to about 108 J / Kg in the presence of the substrate; and b) conducting the oxygen and the organosilicon monomer gases in a direction that is essentially perpendicular to the surface of the substrate and through a magnetic field of at least 100 gauss which is contained essentially in an area adjacent to the plasma zone and in the reaction zone of the plasma, where the magnetic field of at least 100 gauss is produced by an electrode, the electrode defining an electrode surface and containing two or more magnets, each magnet having two opposite magnetic poles, the magnets placed so that the similar magnetic poles of the magnets all look substantially in the same direction, each magnetic pole of each magnet producing a magnetic field with the opposite magnetic pole on the same magnet, each magnetic field having a component parallel to the surface of the magnet. electrode. EXAMPLES The deposit of SiOxCyHz was carried out in accordance with the teachings of the U.S. Patent. No. 5,433,786 except that the deposit was carried out in a DVQAP stainless steel case equipped with a pair of electrodes of the present invention. Each electrode was a flat electrode that has dimensions of 76.2 cm by 304.8 cm. Each electrode was constructed of 5 segments, each segment having dimensions of 76.2 cm by 60.96 cm. Each segment was constructed by arranging two rows of 12 bar magnets on a reinforcement plate made of 0.15 cm soft iron sheet. The magnets were arranged in the manner described in Figure 4. Each of the magnets was 21.69 cm long, 1.9 cm wide and 1.27 cm wide. The magnets in each row were placed 3.81 cm apart. Each magnet had a surface area of 1 kilogram. The magnets were obtained from Midwest Industries. In an electrode each magnet was placed so that the north pole of each magnet looked out of the reinforcement plate and on the other electrode, each magnet was placed so that the south pole of each magnet looked out of the plate. reinforcement. The magnets were covered with an aluminum foil of 0.47 cm (top plate) that was converted to the surface of the electrode. The electrodes were placed in the DVQAP chamber in parallel 22.86 cm apart so that the surface of one electrode (all north poles) facing the electrode surface (all south poles). Using these two electrodes, the DVQAP device generated uniform plasma conditions over an area of approximately 76.2 cm by 304.8 cm.

Claims (2)

1. CLAIMS 1. A plasma generation device that has two electrodes, at least one of the electrodes defining an electrode surface and containing two or more magnets, where each magnet has two opposite magnetic poles, the magnets are placed so that the magnetic similar poles of the magnets all look substantially in the same direction, each magnetic pole of each magnet produces a magnetic field with the opposite magnetic pole on the same magnet and each magnetic field has a component parallel to the surface of the electrode characterized by the magnets are positioned so that the magnetic field produced between the opposite poles of each magnet creates at least one closed circuit ExB path that produces plasma, parallel to the electrode surface.
2. 2. A plasma generating device according to claim 1, wherein the magnets are positioned such that each magnet creates two closed cycle ExB derivation paths, parallel to the electrode surface.