Arc evaporator with a poweful magnetic guide for targets having a large surface area

Abstract

Incorporating an anode ( 1 ) and a cathode or target ( 2 ), from which is obtained the evaporated material which will be applied to piece ( 10 ) to be coated within a vacuum chamber, and where with a magnetic guide it is endeavoured that the action of the electric arc on the target be displaced over the whole surface thereof, in a homogeneous way, the aforementioned magnetic guide is constituted by means of two independent magnetic systems, a first magnetic system constituted by a group of permanent magnets ( 3 ) located on the periphery of the cathode or target ( 2 ), in a disposition noticeably coplanar with the same, so that magnetization thereof is perpendicular to the surface of said target ( 2 ), and a second magnetic system constituted by an electromagnet ( 4 - 5 ), located in the rear part of target ( 2 ), housed in electrically insulating body ( 6 ) of the evaporator and at a certain distance from said target ( 2 ), with at least one of its magnetic poles parallel to the surface of said target ( 2 ), so that the combined action of the two magnetic systems determines uniform use or consumption of target ( 2 ), at the same time as an increased reliability of the evaporator.

1 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, which being of the type of those which incorporate an anode ( 1 ) and a cathode or target ( 2 ), housed within a vacuum bell jar, in which is also housed a piece ( 10 ) to be coated with material evaporated from target ( 2 ) by means of an electric arc produced between anode ( 1 ) and cathode ( 2 ), in which also participates a magnetic guide to control and direct the movement of the electric arc, is characterised in that said magnetic guide is constituted by two independent magnetic systems, that is, four magnetic poles which allow the resultant magnetic intensity to be varied at will so that the electric arc follows the track desired on the target, one of the magnetic systems being constituted by a group of permanent magnets ( 3 ), located on the periphery of the evaporator, in a disposition coplanar with target ( 2 ), with its magnetization perpendicular to the surface of said target ( 2 ), and the second magnetic system constituted by an electromagnet ( 4 - 5 ), located in the rear part of the target ( 2 ), at a distance from the latter, the upper magnetic pole or that nearer target ( 2 ) being arranged parallel to the surface of the aforementioned target ( 2 ).  
     
     
         2 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to  claim 1 , characterised in that electromagnet ( 4 - 5 ) corresponding to the second magnetic system is housed within body ( 6 ) of the evaporator, which constitutes a species of trough to the mouth of which is secured target ( 2 ), which is sufficiently distanced from electromagnet ( 4 - 5 ) to permit the installation between these elements of the cooling systems of target ( 2 ), the target being secured to body ( 6 ) with the collaboration of the relevant screws and on these, constituting kind of perimeter frame, a barrier of slats ( 7 ) of a high temperature insulating material, body ( 6 ) being finished with a plurality of hangers ( 8 ) and a rear base ( 9 ), all of which pieces being of materials electrically insulating at high temperature such as alumina, vitroceramic, boron nitride or PTFE.  
     
     
         3 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to  claim 1 , characterised in that electromagnet ( 4 - 5 ) constituting the second magnetic system, is structured on the basis of a core ( 4 ) of high magnetic permeability and scant coercive force, such as wrought iron, located in correspondence with the central area of the evaporation surface, an electric coil ( 5 ) being arranged around it which serves for generating the necessary magnetic flux to magnetize core ( 4 ).  
     
     
         4 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to previous claims, characterised in that the aforementioned magnetic core ( 4 ) has a rectangular cross-section with the two magnetic poles arranged parallel to the surface of target ( 2 ).  
     
     
         5 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to claims  1 ,  2  and  3 , characterised in that core ( 4 ) of the electromagnet has a T-shaped cross-section, in such a manner that one of its poles is parallel to target ( 2 ), the other pole being perpendicular to the aforementioned target ( 2 ).  
     
     
         6 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to  claim 1 , characterised in that permanent magnets ( 3 ) are of reduced height and are located so that the centre line of the magnets coincides with the middle plane defined between the initial surface of target ( 2 ) and the surface which it will have at the end of its useful life, presenting the greatest possible width to achieve maximum power and they will be obtained from materials of high coercive force, like for example SmCo, NdFeB or hard ferrites.  
     
     
         7 . Arc evaporator with a powerful magnetic guide for targets having a large surface area, according to  claim 1 , characterised in that the two magnetic systems are constituted by electromagnets.