Method and Apparatus for Producing Uniform, Isotropic Stresses in a Sputtered Film

Abstract

The invention provides a method and apparatus for producing uniform, isotropic stresses in a sputtered film. In the presently preferred embodiment, a new sputtering geometry and a new domain of transport speed are presented, which together allow the achievement of the maximum stress that the film material can hold while avoiding X-Y stress anisotropy and avoiding stress non-uniformity across the substrate.

1 . A method for depositing a film on a substrate, comprising the steps of: 
 depositing successive layers of film on said substrate at any of successive different discrete deposition angles of rotation of said substrate and/or of said deposition source about a normal axis of said substrate;    providing a substantially identical amount of deposition from each different deposition angle as for each other deposition angle;    wherein said overall deposited film behaves substantially isotropically in properties in all directions parallel to said substrate and at different angles of rotation about said normal axis.    
     
     
         2 . The method of  claim 1 , further comprising the step of: 
 reducing the thickness of successive layers of said film on the order of a property projection distance within a depositing material;    wherein said property projection distance comprises a distance at which a fluctuation in a relevant film property from point to point through said film's thickness becomes too small to affect overall properties of said film when averaged through said film's thickness; and    wherein said fluctuation is caused by layering.    
     
     
         3 . The method of  claim 2 , wherein said property projection distance is within a minimum of one atomic diameter of said depositing material to a maximum of ten atomic diameters for stress and strain, and a maximum of one magnetic domain diameter for magnetic properties.  
     
     
         4 . The method of  claim 1 , further comprising the step of: 
 moving each substrate past a same one or more sources of depositing material in a planetary manner;    wherein each time said substrate passes by one of said sources of depositing material as said substrate executes a planet orbit, said substrate is rotated about said substrate's normal axis with respect to the planet carrier such that it maintains a constant rotational orientation with respect to a stationary point and said depositing material source by which it is passing.    
     
     
         5 . The method of  claim 4 , wherein said substrate is rotated 360/n degrees with respect to the planet carrier plate each time it passes by one of said depositing material sources, wherein n is an integer larger than 2 and equal to the number of deposition sources.  
     
     
         6 . The method of  claim 4 , further comprising the steps of: 
 providing four depositing material sources arranged about a circle; and    positioning a relevant anisotropic property of each said depositing material source 90 degrees with respect to that of a previous depositing material source;    wherein each substrate maintains a fixed rotational orientation about its normal axis as said substrate orbits, as measured from a stationary point;    wherein said film is deposited in layers having an anisotropy rotated 90 degrees for each successive layer.    
     
     
         7 . The method of  claim 4 , wherein said source of depositing material exhibits two-fold symmetry in a relevant anisotropic property of said depositing material source.  
     
     
         8 . The method of  claim 7 , wherein a 270 degree rotation of said substrate is equivalent to a 90 degree rotation of said substrate with respect to said anisotropy in said relevant property of said film layer.  
     
     
         9 . The method of  claim 7 , further comprising the step of: 
 providing two depositing material sources;    wherein each depositing material source has two-fold symmetry;    wherein said depositing material sources are disposed relative to one another such that a relevant anisotropic property of said depositing material source is rotated 90 degrees with respect to a previous depositing material source;    wherein each substrate maintains a fixed rotational orientation about its normal axis as it orbits, as measured from a stationary point; and    wherein said film is deposited in layers having an anisotropy rotated 90 degrees for each successive layer.    
     
     
         10 . The method of  claim 7 , wherein said sources of depositing material comprise linear magnetron sputtering targets from which said depositing material emanates in a pattern which approximates a rectangle having rounded corners.  
     
     
         11 . The method of  claim 10 , wherein a distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates is sufficiently smaller than a distance between material as it emanates from an end of said rectangular emanation pattern and a nearest edge of said substrate such that a relevant property of said film is sufficiently uniform along said substrate from a center of said substrate to said substrate's edge.  
     
     
         12 . The method of  claim 11 , further comprising the step of: 
 making film stress along directions parallel to said substrate sufficiently uniform across said substrate by making a distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates sufficiently small, as compared to a distance between material as it emanates from an end of said rectangular emanation pattern and the nearest edge of the substrate.    
     
     
         13 . The method of  claim 11 , wherein a ratio of distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates to a distance between material as it emanates from an end of said rectangular emanation pattern and a nearest edge of said substrate is ¼ or less.  
     
     
         14 . A method for depositing a film on a substrate, comprising the steps of: 
 symmetrically disposing at least one deposition source at any of successive different deposition angles of rotation of said substrate and of said deposition source about a normal axis of said substrate; and    depositing successive layers of film on said substrate to achieve high levels of stress in said films, wherein said stress is both isotropic in a film plane and uniform over large areas of a substrate surface.    
     
     
         15 . The method of  claim 14 , wherein said depositing step comprises: 
 providing a monatomic-layer-scale deposition thickness per pass over a deposition source using close-spaced magnetron sputtering from long, substantially rectangular targets or sources of deposition material;    wherein effects on film stress caused by periodic fluctuations in any of deposition incident angle, ion bombardment flux, and substrate azimuthal orientation are minimized.    
     
     
         16 . The method of  claim 14 , further comprising the step of: 
 rotating said substrate by substantially 90 degrees between successive passes to laminate said film;    wherein X-Y anisotropy in a film plane is eliminated.    
     
     
         17 . The method of  claim 14 , further comprising the step of: 
 using magnetron targets that are longer, when compared to a substrate diameter, than is needed for uniform film thickness;    wherein uniform film stress along a long axis of said target is achieved.    
     
     
         18 . The method of  claim 14 , further comprising the step of: 
 providing a drive mechanism comprising a peripheral chain arranged around a ring of substrates, and a chain extending from one substrate to a fixed central sprocket, to impart high speed, planetary motion to said substrate.    
     
     
         19 . An apparatus for depositing a film on a substrate, comprising: 
 a target for depositing successive layers of film on said substrate at any of successive different discrete deposition angles of rotation of said substrate and/or of said deposition source about a normal axis of said substrate;    means for symmetrically disposing a collection of said successive different discrete deposition angles used for an overall deposited film about said normal axis; and    means for providing a substantially identical amount of deposition from each different deposition angle as for each other deposition angle;    wherein said overall deposited film behaves substantially isotropically in properties in all directions parallel to said substrate and at different angles of rotation about said normal axis.    
     
     
         20 . The apparatus of  claim 19 , further comprising: 
 means for reducing the thickness of successive layers of said film on the order of a property projection distance within a depositing material;    wherein said property projection distance comprises a distance at which a fluctuation in a relevant film property from point to point through said film's thickness becomes too small to affect overall properties of said film when averaged through said film's thickness; and    wherein said fluctuation is caused by layering.    
     
     
         21 . The apparatus of  claim 20 , wherein said property projection distance is within a minimum of one atomic diameter of said depositing material to a maximum of ten atomic diameters for stress and strain, and a maximum of one magnetic domain diameter for magnetic properties.  
     
     
         22 . The apparatus of  claim 19 , further comprising: 
 a drive for moving each substrate past a same one or more sources of depositing material in a planetary manner;    wherein each time said substrate passes by one of said sources of depositing material as said substrate executes a planet orbit, said substrate has been rotated about said substrate's normal axis with respect to the planet carrier such that it maintains a constant rotational orientation with respect to a stationary point and to said depositing material source by which it is passing.    
     
     
         23 . The apparatus of  claim 22 , wherein said substrate is rotated 360/n degrees with respect to the planet carrier plate each time it passes by one of said depositing material sources, wherein n is an integer larger than 2 and equal to the number of deposition sources.  
     
     
         24 . The apparatus of  claim 22 , further comprising: 
 four depositing material sources arranged about a circle; and    means for positioning a relevant anisotropic property of each said depositing material source 90 degrees with respect to that of a previous depositing material source;    wherein each substrate maintains a fixed rotational orientation about its normal axis as said substrate orbits, as measured from a stationary point;    wherein said film is deposited in layers having an anisotropy rotated 90 degrees for each successive layer.    
     
     
         25 . The apparatus of  claim 22 , wherein said source of depositing material exhibits two-fold symmetry in a relevant anisotropic property of said depositing material.  
     
     
         26 . The apparatus of  claim 25 , wherein a 270 degree rotation of said substrate is equivalent to a 90 degree rotation of said substrate with respect to said anisotropy in said relevant property of said film layer.  
     
     
         27 . The apparatus of  claim 25 , further comprising: 
 two depositing material sources;    wherein each depositing material source has two-fold symmetry;    wherein said depositing material sources are disposed relative to one another such that a relevant anisotropic property of said depositing material source is rotated 90 degrees with respect to a previous depositing material source;    wherein each substrate maintains a fixed rotational orientation about its normal axis as it orbits, as measured from a stationary point; and    wherein said film is deposited in layers having an anisotropy rotated 90 degrees for each successive layer.    
     
     
         28 . The apparatus of  claim 25 , wherein said sources of depositing material comprise linear magnetron sputtering targets from said depositing material emanates in a pattern which approximates a rectangle having rounded corners.  
     
     
         29 . The apparatus of  claim 28 , wherein a distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates is sufficiently smaller than a distance between material as it emanates from an end of said rectangular emanation pattern and a nearest edge of said substrate such that a relevant property of said film is sufficiently uniform along said substrate from a center of said substrate to said substrate's edge.  
     
     
         30 . The apparatus of  claim 29 , further comprising: 
 means for making film stress along directions parallel to said substrate sufficiently uniform across said substrate by making a distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates sufficiently small, as compared to a distance between material as it emanates from an end of said rectangular emanation pattern and the nearest edge of the substrate.    
     
     
         31 . The apparatus of  claim 29 , wherein a ratio of distance along a substrate normal axis and between a substrate surface and a target surface from which depositing material emanates to a distance between material as it emanates from an end of said rectangular emanation pattern and a nearest edge of said substrate is ¼ or less.  
     
     
         32 . An apparatus for depositing a film on a substrate, comprising: 
 means for symmetrically disposing at least one deposition source at any of successive different deposition angles of rotation of said substrate and of said deposition source about a normal axis of said substrate; and    a target for depositing successive layers of film on said substrate to achieve high levels of stress in said films, wherein said stress is both isotropic in a film plane and uniform over large areas of a substrate surface.    
     
     
         33 . The apparatus of  claim 32 , wherein said target comprises: 
 means for providing a monatomic-layer-scale deposition thickness per pass over a target using close-spaced magnetron sputtering from long, substantially rectangular targets;    wherein effects on film stress caused by periodic fluctuations in any of deposition incident angle, ion bombardment flux, and substrate azimuthal orientation are minimized.    
     
     
         34 . The apparatus of  claim 32 , further comprising: 
 a drive for rotating said substrate by substantially 90 degrees between successive passes to laminate said film;    wherein X-Y anisotropy in a film plane is eliminated.    
     
     
         35 . The apparatus of  claim 32 , further comprising: 
 one or more magnetron targets that are longer, when compared to a substrate diameter, than is needed for uniform film thickness;    wherein uniform film stress along a long axis of said target is achieved.    
     
     
         36 . The method of  claim 32 , further comprising: 
 a drive mechanism comprising a peripheral chain arranged around a ring of substrates, and a chain extending from one substrate to a fixed central sprocket, to impart high speed, planetary motion to said substrate.    
     
     
         37 . A drive mechanism, comprising: 
 a fixed central, driven sprocket;    a peripheral chain arranged around a ring of substrates; and a chain extending from one substrate to said fixed central sprocket, to impart high speed, planetary motion to said substrate.    
     
     
         38 . A substrate having a film deposited thereon in accordance with the process of  claim 1.