SPUTTERING TARGETS AND DEVICES INCLUDING Mo, Nb, and Ta, AND METHODS

Abstract

Sputtering targets including molybdenum, niobium and tantalum are found to be useful for sputtering films for electronic devices. Sputtering targets with about 88 to 97 weight percent molybdenum show improved performance, particularly with respect to etching, such as when simultaneously etching an alloy layer including the Mo, Nb, and Ta, and a metal layer (e.g., an aluminum layer). The targets are particularly useful in manufacturing touch screen devices.

What is claimed is: 
     
         1 . A sputtering target comprising:
 i. about 88 atomic percent to about 97 atomic percent molybdenum;   ii. about 2 to about 8 atomic percent niobium; and   iii. about 0.5 to 5 atomic percent tantalum (preferably about 0.7 to about 4 atomic percent tantalum);   wherein the sputtering target is adapted to be employed for forming a thin film layer.   
     
     
         2 . The sputtering target of  claim 1 , wherein
 the molybdenum is present at a concentration of about 89 atomic percent or more (more preferably about 90 atomic percent or more, even more preferably about 91 atomic percent or more, and most preferably about 92 atomic percent or more); and/or   the molybdenum is present at a concentration of about 96 atomic percent or less (more preferably about 95.5 atomic percent or less, even more preferably about 95.0 atomic percent or less, and most preferably about 94.5 atomic percent or less),   based on the total number of atoms in the sputtering target.   
     
     
         3 . The sputtering target of  claim 2 , wherein
 the niobium is present at a concentration of about 2.8 atomic percent or more (more preferably about 3.0 atomic percent or more, even more preferably about 3.2 atomic percent or more, and most preferably about 3.4 atomic percent or more); and/or   the niobium is present at a concentration of about 7.6 atomic percent or less (more preferably about 7.2 atomic percent or less, even more preferably about 6.8 atomic percent or less, and most preferably about 6.4 atomic percent or less),   based on the total number of atoms in the sputtering target.   
     
     
         4 . The sputtering target of  claim 3 , wherein the tantalum is present at a concentration of about 0.7 atomic percent or more (more preferably about 0.9 atomic percent or more, even more preferably about 1.1 atomic percent or more, and most preferably about 1.2 atomic percent or more); and/or
 the tantalum is present at a concentration of about 3.7 atomic percent or less (more preferably about 3.3 atomic percent or less, even more preferably about 2.9 atomic percent or less, and most preferably about 2.6 atomic percent or less)   based on the total number of atoms in the sputtering target.   
     
     
         5 . The sputtering target of  claim 1 , wherein the total amount of the molybdenum, the niobium, and tantalum is about 98 atomic percent or more (preferably about 99 atomic percent or more, even more preferably about 99.5 atomic percent or more, even more preferably about 99.8 atomic percent or more, and most preferably about 100 atomic percent). 
     
     
         6 . A device prepared using the sputtering target of  claim 1  comprising:
 i. a substrate; 
 ii. a first layer including a first metal deposited above the substrate; and 
 iii. a second layer deposited above the substrate, wherein the second layer is an alloy prepared from the sputtering of the target of  claim 1 . 
 
     
     
         7 . A device comprising:
 i. a substrate;   ii. a first layer including a first metal deposited above the substrate; and   iii. a second layer deposited above the substrate, wherein the second layer is an alloy including about 88 atomic percent to about 97 atomic percent molybdenum, about 2 to about 8 atomic percent niobium, and about 0.5 to 5 atomic percent tantalum.   
     
     
         8 . The device of  claim 7 , wherein the first layer is deposited above the second layer. 
     
     
         9 . The device of  claim 7 , wherein the second layer is deposited above the first layer. 
     
     
         10 . The device of  claim 7 , wherein the first metal is aluminum, wherein the first layer directly contacts the second layer. 
     
     
         11 . The device of  claim 7 , wherein the first layer is formed of an alloy having an etch rate ratio of about 0.67 or more (preferably about 0.75 or more, more preferably about 0.80 or more, and most preferably about 0.85 or more) wherein the etch rate ratio is the ratio of the etch rate of the Mo, Nb, Ta alloy of the first layer to the etch rate of aluminum, wherein the etch rate is in a PAN etchant at 42° C., wherein the etchant consists of 70 weight percent phosphoric acid, 10 weight percent acetic acid, 2.5 weight percent nitric acid, and 17.5 weight percent deionized water. (Preferably, the etch rate ratio is about 2.0 or less, more preferably about 1.5 or less, even more preferably, about 1.3 or less, even more preferably about 1.2 or less, and most preferably about 1.0 or less). 
     
     
         12 . The device of  claim 7 , wherein
 the second layer has a thickness of about 10 nm or more (preferably about 20 nm or more, more preferably about 30 nm or more, even more preferably about 40 nm or more, and most preferably about 60 nm or more); and/or   the second layer has a thickness of about 1400 nm or less (preferably about 700 nm or less, preferably about 400 nm or less, even more preferably about 300 nm or less, and most preferably about 240 nm or less).   
     
     
         13 . The device of  claim 12  wherein
 the first layer has a thickness from about 10 nm to about 2000 nm (e.g., from about 150 nm to about 350 nm). 
 
     
     
         14 . The device of  claim 7 , wherein the first layer is substantially devoid of any undercut relative to the second layer and the second layer is substantially devoid of any undercut relative to the first layer. 
     
     
         15 . The device of  claim 7 , wherein
 the device is a touch sensitive screen for an electronic device;   the alloy of the second layer has less corrosion than a metal layer consisting of the alloying metal, wherein the corrosion is measured at 60° C., 80% humidity, 4 weeks;   the device includes a capping layer, wherein the first layer is interposed between the capping layer and the second layer, and the capping layer is directly adjacent to the first layer;   wherein alloy of the second layer is a Mo—Nb—Ta alloy, and the capping layer includes an oxide of the Mo—Nb—Ta alloy, wherein i) the ratio of Mo to Nb in the second layer and in the capping layer are substantially the same; and ii) the ratio of Mo to Ta in the second layer and the capping layer are substantially the same; and   the substrate layer is glass, the second layer includes a Mo—Nb—Ta alloy, and the device includes an interface between the Mo—Nb—Ta alloy and the glass having adhesion of 4B or more.   
     
     
         16 . The device of  claim 7 , wherein the device includes a third layer deposited over the substrate, wherein the third layer is an oxide of molybdenum, niobium, and tantalum. 
     
     
         17 . A process comprising the steps of:
 i. depositing a first layer on a substrate;   ii. sputtering an alloy layer over the first layer, wherein the alloy layer includes an alloy having about 88 to 97 atomic percent molybdenum, about 2 to 8 atomic percent niobium, and about 0.5 to 5 atomic percent tantalum over the first layer; wherein the first layer and the alloy layer have different conductivities; and   iii. at least partially etching the first layer and the alloy layer to form an etched component, wherein the etched component is substantially free of an undercut of the first layer relative to the alloy layer.   
     
     
         18 . A process for manufacturing a device using the sputtering target of  claim 1 , comprising the steps of:
 i. depositing a first layer on a substrate;   ii. depositing a second layer over the first layer by sputtering the sputtering target of  claim 1 , wherein the second layer is an alloy layer comprising molybdenum, niobium, and tantalum, wherein the first layer and the alloy layer have different conductivities; and   iii. at least partially etching the first layer and the alloy layer to form an etched component.   
     
     
         19 . The process of  claim 18 , wherein the step of etching includes etching with an etchant, wherein the etchant and the sputtering target are selected so that the etched component is substantially free of an undercut of the first layer relative to the alloy layer. 
     
     
         20 . The device of  claim 7  wherein:
 the substrate is a glass substrate; 
 the first layer is an aluminum layer; and 
 wherein the first layer has a first etch rate, r1 (expressed in nm/min), in a PAN etchant at 25° C. and the second metal layer has a second etch rate, r2 (expressed in nm/min), in a PAN etchant at 25° C., wherein the etch rate ratio (r2/r1) is about 0.67 or more (preferably about 0.75 or more, more preferably about 0.80 or more, and most preferably about 0.85 or more), wherein the etch rate is in a PAN etchant at 42° C., wherein the PAN etchant consists of 70 weight percent phosphoric acid, 10 weight percent acetic acid, 2.5 weight percent nitric acid, and 17.5 weight percent deionized water. (Preferably, the etch rate ratio is about 2.0 or less, more preferably about 1.5 or less, even more preferably, about 1.3 or less, even more preferably about 1.2 or less, and most preferably about 1.0 or less.