Uphill screen printing in the manufacturing of microelectronic components

Abstract

Method for screen printing a continuous structure on a substrate wherein the screen printed structure extends from at least a first level to at least a second level. The disclosed method is particularly suitable for the fabrication of microelectronic devices and components thereof including the fabrication of field emission display devices. Preferably, a print screen of a preferred thickness having a preconfigured print pattern formed therethrough, in combination with a squeegee having a hardness within a preferred range, are used to force a screen printable substance onto a substrate while maintaining a portion of the print screen within a preferred reference angle. The resulting screen printed structure extends from at least one lower level to at least one upper level in a continuous “uphill” manner.

1 . A microelectronic device comprising: 
 a substrate having a first surface and at least one second surface located a preselected distance above the first surface;    a continuous screen printed structure extending from at least a portion of the first surface to at least a portion of the second surface formed by sweeping a squeegee across the top surface of a screen forcing at least a portion of a screen printable material through the at least one preconfigured pattern and onto at least a portion of the first surface and at least a portion of the at least one second surface while maintaining an angle formed between the bottom of the screen and the second surface within a preselected range.    
     
     
         2 . The microelectronic device of  claim 1 , further comprising generally maintaining a pre-determined snap-off distance between at portion of the bottom of the screen and a portion of the first surface of the substrate when forming at least a portion of the continuous screen printed structure, the snap-off distance generally comprising a distance of less than approximately 0.2 mils (0.0002 inches/0.0005 cm)  
     
     
         3 . The microelectronic device of  claim 1 , wherein the substrate comprises at least one of the group comprising glass material and ceramic material.  
     
     
         4 . The microelectronic device of  claim 5 , wherein the substrate is comprised of borosilicate glass.  
     
     
         5 . The microelectronic device of  claim 1 , wherein the substrate comprises a fired substrate.  
     
     
         6 . The microelectronic device of  claim 1 , wherein the at least one second surface comprises being located on a spacer structure previously disposed on the substrate and the preselected height above the first surface of the substrate does not exceed approximately 10 mils (0.10 inches/0.025 cm).  
     
     
         7 . The microelectronic device of  claim 6 , wherein the spacer structure is comprised of at least one of the group comprising an insulative material and a dielectric material.  
     
     
         8 . The microelectronic device of  claim 7 , further comprising the spacer structure including a plurality of stacked insulative layers.  
     
     
         9 . The microelectronic device of  claim 1 , wherein the screen printable material comprises electrically conductive paste and the range of the viscosity value of the screen printable substance comprises approximately 50,000 to 600,000 centipoise.  
     
     
         10 . The microelectronic device of  claim 1 , wherein the screen printable material comprises an electrically conductive paste and the range of the viscosity value of the screen printable substance comprises approximately 250,000 to 400,000 centipoise.  
     
     
         11 . The microelectronic device of  claim 1 , wherein the continuous screen printed structure has a nominal depth when wet not exceeding approximately 0.5 mils (0.0005 inches/0.0013 cm).  
     
     
         12 . The microelectronic device of  claim 11 , wherein the continuous screen printed structure has a nominal depth when fired not exceeding approximately 0.2 mils (0.0002 inches/0.0005 cm).  
     
     
         13 . The microelectronic device of  claim 1 , wherein the substrate comprises a plurality of second surfaces each being positioned at a preselected height above the first surface of the substrate and wherein the continuous screen printed structure comprises being formed to extend from at least a portion of the first surface to at least a portion of each of the plurality of second surfaces.  
     
     
         14 . The microelectronic device of  claim 1 , wherein the continuous screen printed structure comprises at least one first portion being generally disposed at a first level, at least one uphill portion having an increased depth in comparison to the at least one first portion of the screen printed structure, and at least one third portion being generally disposed on a second level vertically offset from the first level.  
     
     
         15 . The microelectronic device of  claim 14 , wherein the at least one third portion of the screen printed structure having a depth approximately equal to the depth of the first portion of the continuous screen printed structure.  
     
     
         16 . The microelectronic device of  claim 1 , wherein the at least one preconfigured pattern in the screen comprises a reduced geometry in a region of the pattern corresponding to an uphill region of a continuous structure to be screen printed.  
     
     
         17 . The microelectronic device of  claim 16 , wherein the reduced geometry of the preconfigured pattern is generally perpendicular to the preselected direction.  
     
     
         18 . A method of using multi-level electrically conductive structure in a microelectronic device formed by the method using a print screen screen having a preselected thickness, a top surface, a bottom surface, and at least one preconfigured print pattern therethrough and a squeegee having a preselected hardness and having a generally tapering cross-section terminating in a working edge comprising: 
 arranging a substrate having at least one lower-level surface and at least one upper-level surface so as to be opposite the bottom surface of the print screen;    introducing an electrically conductive, screen printable substance onto at least a portion of the top surface of the print screen;    biasing the squeegee against the top surface of the print screen toward the substrate, resulting in a reference angle being formed between the bottom surface of the print screen ahead of the working edge of the squeegee and the at least one upper-level surface;    sweeping the squeegee in a predetermined forward direction so as to urge at least a portion of the electrically conductive, screen printable substance through the at least one preconfigured print pattern and onto at least a portion of the at least one lower-level surface to form a first portion of at least one continuous electrically conductive structure while maintaining the reference angle within a preselected range;    continuing the biasing and the sweeping of the squeegee so as to urge additional screen printable substance through the at least one preconfigured print pattern to form a second portion of the at least one continuous electrically conductive structure vertically spanning a region intermediate the at least one lower-level surface and the at least one upper-level surface;    continuing the biasing and the sweeping of the squeegee so as to urge additional screen printable substance through the at least one preconfigured print pattern to form a third portion of the at least one continuous electrically conductive structure upon at least a portion of the at least one upper-level surface; and    exposing the substrate having the at least one continuous electrically conductive structure to an elevated temperature.    
     
     
         19 . The method of  claim 18 , wherein exposing the substrate having the at least one continuous electrically conductive structure to an elevated temperature includes firing the at least one continuous electrically conductive structure.  
     
     
         20 . The method of  claim 18 , further comprising: 
 maintaining a preselected snap-off distance not exceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between at least a portion of the bottom surface of the print screen and the at least a portion of the at least one lower-level surface when forming the first portion of the at least one continuous electrically conductive structure.    
     
     
         21 . The method of  claim 18 , further comprising: 
 maintaining a preselected snap-off distance not exceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between at least a portion of the bottom surface of the print screen and the at least a portion of the at least one upper-level surface when forming the third portion of the at least one continuous electrically conductive structure.    
     
     
         22 . The method of  claim 18 , further comprising: 
 maintaining the reference angle within a range of approximately 2° to approximately 12° when forming the second portion of the at least one continuous electrically conductive structure.    
     
     
         23 . The method of  claim 18 , further comprising: 
 maintaining the reference angle within a range of approximately 5° to approximately 10° when forming the second portion of the at least one continuous electrically conductive structure.    
     
     
         24 . The method of  claim 18 , wherein the at least one upper-level surface is within a vertical distance of the at least one lower-level surface not exceeding approximately 10 mils (0.010 inches/0.025 cm).  
     
     
         25 . The method of  claim 18 , wherein the at least one upper-level surface is disposed on an insulative structure comprised of a dielectric material.  
     
     
         26 . The method of  claim 25 , wherein the insulative structure comprises at least two layers of dielectric material.  
     
     
         27 . The method of  claim 18 , wherein the screen printable substance comprises gold and has a viscosity in a range of approximately 50,000 to approximately 600,000 centipoise.  
     
     
         28 . The method of  claim 18 , wherein the screen printable substance comprises gold and has a viscosity in a range of approximately 250,000 to approximately 400,000 centipoise.  
     
     
         29 . The method of  claim 18 , wherein the print screen comprises a mesh ranging from approximately 80 to approximately 500 and wherein the preselected thickness of the print screen does not exceed approximately 0.8 mils (0.0008 inches/0.0020 cm).  
     
     
         30 . The method of  claim 18 , wherein the print screen comprises a mesh ranging from approximately 80 to approximately 500 and wherein the preselected thickness of the print screen does not exceed approximately 0.5 mils (0.0005 inches/0.0013 cm).  
     
     
         31 . The method of  claim 18 , wherein the substrate comprises at least one of a group comprising glass, borosilicate glass, and ceramic material.  
     
     
         32 . The method of  claim 18 , wherein the at least one continuous electrically conductive structure comprises a plurality of continuous electrically conductive structures.  
     
     
         33 . The method of  claim 19 , wherein the at least one continuous electrically conductive structure comprises a plurality of continuous electrically conductive structures being formed in a preselected pattern.  
     
     
         34 . The method of  claim 19 , wherein the at least one upper-level surface comprises a plurality of upper-level surfaces being positioned on the substrate to form an array on the substrate and wherein the at least one continuous electrically conductive structure comprises a plurality of continuous electrically conductive structures.  
     
     
         35 . The method of  claim 34 , wherein each upper-level surface of the plurality of upper-level surfaces comprises at least a portion of the at least one continuous electrically conductive structure being formed thereon.  
     
     
         36 . The method of  claim 35 , wherein each upper-level surface of the plurality of upper-level surfaces respectively comprises a plurality of continuous electrically conductive structures being formed, at least in part, thereon.  
     
     
         37 . The method of  claim 35 , further comprising segmenting the substrate into a plurality of individual substrate segments, each comprising at least one upper-level surface of the plurality of upper-level surfaces therein.  
     
     
         38 . The method of  claim 18 , wherein the at least one preconfigured print pattern of the print screen comprises having a dimensionally reduced portion with respect to the predetermined forward direction of the squeegee, which corresponds to the electrically conductive, screen printable substance being urged through the at least one preconfigured print pattern.  
     
     
         39 . A method of forming electrically conductive traces that extending from one level to at least one other elevated level, the electrically conductive traces having controlled dimensional tolerances and geometries, the method comprising: 
 introducing an electrically conductive, screen printable substance onto at least a portion of a top surface of the print screen;    biasing a squeegee against the top surface of the print screen toward a substrate, resulting in a reference angle being formed between the bottom surface of the print screen ahead of the working edge of the squeegee and the upper-level surface;    sweeping the squeegee in a forward direction so as to urge at least a portion of the electrically conductive, screen printable substance through the pattern and onto at least a portion of the lower-level surface to form a first portion of at least one continuous electrically conductive structure while maintaining the reference angle within a range;    continuing the biasing and the sweeping of the squeegee so as to urge additional screen printable substance through the pattern to form a second portion of the at least one continuous electrically conductive structure vertically spanning a region intermediate the lower-level surface and the upper-level surface;    continuing the biasing and the sweeping of the squeegee urging additional screen printable substance through the pattern to form a third portion of the at least one continuous electrically conductive structure upon at least a portion of the upper-level surface; and    heating a substrate having the at least one continuous electrically conductive structure.    
     
     
         40 . The method of  claim 39 , wherein heating the substrate having the at least one continuous electrically conductive structure to an elevated temperature includes firing the at least one continuous electrically conductive structure.  
     
     
         41 . The method of  claim 39 , further comprising: 
 maintaining a preselected snap-off distance not exceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between at least a portion of the bottom surface of the print screen and the at least a portion of the lower-level surface when forming the first portion of the at least one continuous electrically conductive structure; and    maintaining a preselected snap-off distance not exceeding approximately 0.2 mil (0.0002 inches/0.0005 cm) between at least a portion of the bottom surface of the print screen and the at least a portion of the upper-level surface when forming the third portion of the at least one continuous electrically conductive structure.    
     
     
         42 . The method of  claim 39 , further comprising: 
 maintaining the reference angle within a range of approximately 2° to approximately 12° when forming the second portion of the at least one continuous electrically conductive structure.    
     
     
         43 . The method of  claim 39 , further comprising: 
 maintaining the reference angle within a range of approximately 5° to approximately 10° when forming the second portion of the at least one continuous electrically conductive structure.    
     
     
         44 . The method of  claim 39 , wherein the upper-level surface is within a vertical distance of the lower-level surface not exceeding approximately 10 mils ( 0 0.10 inches/0.025 cm).  
     
     
         45 . The method of  claim 39 , wherein the upper-level surface is disposed on an insulative structure comprised of a dielectric material including at least two layers.  
     
     
         46 . The method of  claim 39 , wherein the electrically conductive, screen printable substance comprises a material having a viscosity in a range of approximately 50,000 to 600,000 centipoise.  
     
     
         47 . The method of  claim 39 , wherein the electrically conductive, screen printable substance comprises a material having a viscosity in a range of approximately 250,000 to approximately 400,000 centipoise.  
     
     
         48 . The method of  claim 39 , wherein the print screen comprises a mesh ranging from approximately 80 to approximately 500 and wherein the thickness of the print screen does not exceed approximately 0.8 mils (0.0008 inches/0.0020 cm).  
     
     
         49 . The method of  claim 40 , wherein the upper-level surface comprises a plurality of upper-level surfaces being positioned on the substrate to form an array on the substrate and wherein the at least one continuous electrically conductive structure comprises a plurality of continuous electrically conductive structures.  
     
     
         50 . The method of  claim 49 , wherein each upper-level surface of the plurality of upper-level surfaces comprises at least a portion of the at least one continuous electrically conductive structure being formed thereon.  
     
     
         51 . The method of  claim 50 , wherein each upper-level surface of the plurality of upper-level surfaces respectively comprises a plurality of continuous electrically conductive structures being formed, at least in part, thereon.  
     
     
         52 . The method of  claim 49 , further comprising segmenting the substrate into a plurality of individual substrate segments, each comprising at least one upper-level surface of the plurality of upper-level surfaces therein.  
     
     
         53 . The method of  claim 39 , wherein the pattern of the print screen comprises having a dimensionally reduced portion with respect to the predetermined forward direction of the squeegee, which corresponds to the electrically conductive, screen printable substance being urged through the pattern.  
     
     
         54 . The method of  claim 39 , wherein the at least one continuous electrically conductive structure is a circuit trace terminating in a contact pad configured to make electrical contact with a complementary second continuous electrically conductive structure.