Cantilever probe and applications of the same

Abstract

A method of fabricating a nanoscale cantilever probe. In one embodiment, the method includes the steps of forming a cantilever having a tip vertically extending from an end portion of the cantilever, where the tip has an apex portion having a size in a range of about 1-1000 nm, and selectively doping the cantilever with a dopant to define a first doping region in the tip and a second doping region in the rest of the cantilever, where the dopant concentration of the first doping region is substantially lower than that of the second doping region.

1 . A cantilever probe, comprising:
 (a) handle portion having a first end and an opposite, second end and a handle portion body formed therebetween;   (b) a cantilever transversally projecting away from the first end of the handle portion such that an angle, α, is formed between the cantilever and the handle portion body, wherein the cantilever has a first end portion, an opposite, second end portion, and a cantilever body formed therebetween, and wherein the second end portion is anchored at the first end of the handle portion;   (c) a tip vertically extending from the first end portion of the cantilever; and   (d) an electrode member formed on the second end portion of the cantilever,   wherein the cantilever is formed to have a first region and a second region in connection with the first region, each region having an electrical resistivity;   wherein the tip is in the first region; and   wherein the electrical resistivity of the first region is substantially higher than that of the second region such that when an electrical current flows through the cantilever from the electrode member, resistive heating occurs substantially in the tip, wherein the tip has a taper shape having an apex portion and at least one slope portion extending from the apex portion, and wherein the apex portion of the tip has a diameter in a range from about 100 nm to about 1000 nm, and defines an apex angle, β, in the range of 0<β<90°, and wherein the apex portion of the tip has a triangular cross-section defined between a first point, second point, and third point such that the first point and the second point define a base therebetween having a length l 1 , and the third point and the base define a length l 2  therebetween, such that l 1  or each of l 1  and l 2  is in the range of 100 nm to 1000 nm.   
     
     
         2 . (canceled) 
     
     
         3 . (canceled) 
     
     
         4 . The cantilever probe of  claim 1 , wherein the cantilever is formed of silicon, and wherein the silicon comprises an n-type silicon or a p-type silicon. 
     
     
         5 . The cantilever probe of  claim 4 , wherein the first and second regions and of the cantilever are defined by a selective doping of the cantilever with a dopant, each doping region having a dopant concentration. 
     
     
         6 . The cantilever probe of  claim 5 , wherein the dopant comprises an n-type dopant or a p-type dopant. 
     
     
         7 . The cantilever probe of  claim 5 , wherein the dopant concentration of the first region is substantially lower than that of the second region of the cantilever. 
     
     
         8 . The cantilever probe of  claim 7 , wherein the first region of the cantilever is doped through a native doping of the silicon forming the cantilever such that the first region in the tip has a native dopant concentration. 
     
     
         9 . The cantilever probe of  claim 8 , wherein the native doping forms a highly resistive heating region in the tip. 
     
     
         10 . (canceled) 
     
     
         11 . (canceled) 
     
     
         12 . The cantilever probe of  claim 1 , wherein the handle portion has a silicon wafer and a silicon dioxide layer formed on the silicon wafer. 
     
     
         13 . The cantilever probe of  claim 1 , wherein the angle α is in the range of 0<α<180°. 
     
     
         14 . A cantilever probe, comprising:
 (a) a cantilever having a shoulder that has a first end portion and an opposite, second end portion and a pair of arms respectively extending from the first and second end portions of the shoulder; and   (b) a tip vertically extending from the shoulder of the cantilever,   wherein the cantilever and the tip are doped to have a first doping region in the tip and a second doping region in the pair of arms of the cantilever, respectively, each doping region having a dopant concentration, wherein the dopant concentration of the first doping region is substantially lower than that of the second doping concentration such that when an electrical current flows through the cantilever, resistive heating occurs substantially in the tip, and wherein the tip has a taper shape having an apex portion and at least one slope portion extending from the apex portion, and wherein the apex portion of the tip has a triangular cross-section defined between a first point, second point, and third point such that the first point and the second point define a base therebetween having a length l 1  and the third point and the base define a length l 2  therebetween, such that l 1  or each of l 1  and l 2  is in the range of 100 nm to 1000 nm.   
     
     
         15 . (canceled) 
     
     
         16 . (canceled) 
     
     
         17 . The cantilever probe of  claim 14 , wherein each of the cantilever and the tip is formed of silicon, and wherein the silicon comprises an n-type silicon or a p-type silicon. 
     
     
         18 . The cantilever probe of  claim 17 , wherein the first doping region of the cantilever is doped through a native doping of the silicon such that the first doping region in the tip has a native dopant concentration. 
     
     
         19 . The cantilever probe of  claim 18 , wherein the native doping forms a highly resistive heating region in the tip. 
     
     
         20 . (canceled) 
     
     
         21 . (canceled) 
     
     
         22 . The cantilever probe of  claim 14 , wherein the first doping region is in connection with the second doping region. 
     
     
         23 . A cantilever probe, comprising:
 a. a cantilever having a first end portion, an opposite, second end portion, and a cantilever body formed therebetween; and   b. a tip having an apex portion, a bottom portion and a tip body formed therebetween, vertically extending from the first end portion of the cantilever such that the bottom portion of the tip is in the first end portion of the cantilever,   wherein the cantilever and the tip are doped to have a dopant concentration that varies spatially from the apex portion to the bottom portion of the tip and from the first end portion to the second end portion of the cantilever such that the dopant concentration in the apex portion of the tip is substantially lower than that in the bottom portion of the tip, which is substantially identical to that in the first end portion of the cantilever, which in turn, is substantially lower than that in the second end portion of the cantilever.   
     
     
         24 . The cantilever probe of  claim 23 , wherein in operation, when an electrical current flows through the cantilever, resistive heating occurs substantially in the apex portion of the tip. 
     
     
         25 . A method of fabricating a nanoscale cantilever probe, comprising the steps of
 a. providing a silicon-on-insulator (SOI) wafer having a silicon handle portion wafer, a buried silicon dioxide layer formed on the silicon handle portion wafer, and a silicon device layer formed on the buried silicon dioxide layer;   b. patterning the silicon device layer to define a cantilever structure having a first end portion and an opposite, second end portion and a tip vertically extending from the first end portion of the cantilever structure;   c. selectively doping the defined cantilever structure with a dopant to form a first doping region and a second doping region therein, wherein the first doping region contains the tip and is in connection with the first doping region;   d. metallizing the second doping region of the cantilever structure to form an electrode member thereon; and   e. sequentially etching off portions of the silicon handle portion wafer and the buried silicon dioxide layer on the backside of the cantilever structure to form a cantilever.   
     
     
         26 . The method of  claim 25 , wherein the patterning step is performed with photolithography and etching processes. 
     
     
         27 . The method of  claim 25 , wherein the metallizing step is performed with a metal deposition process. 
     
     
         28 . The method of  claim 25 , wherein the sequentially etching step comprises the steps of:
 a. etching off a portion of the silicon handle portion wafer on the backside of the cantilever structure to expose a corresponding region of the buried silicon dioxide layer; and   b. etching off the uncovered region of the buried silicon dioxide layer on the backside of the cantilever structure to form the cantilever.   
     
     
         29 . The method of  claim 25 , wherein the selectively doping step comprises the steps of:
 a. doping the defined cantilever structure with the dopant; and   b. repeating step (a) in a selected region till the first doping region and the second doping region are formed in the defined cantilever structure such that the dopant concentration of the first doping region is substantially different from that of the second doping region.   
     
     
         30 . The method of  claim 29 , wherein the second doping region is substantially coincident with the selected region so that the dopant concentration of the first doping region is substantially lower than that of the second doping region. 
     
     
         31 . The method of  claim 30 , wherein each of the first and second doping regions and has an electrical resistivity, and wherein the electrical resistivity of the first doping regions is substantially higher than that of the second doping regions. 
     
     
         32 . The method of  claim 30 , wherein The tip has an apex portion having, a size in a range of about 1-1000 nm. 
     
     
         33 . A method of fabricating a nanoscale cantilever probe, comprising the steps of:
 a. forming a cantilever having a tip vertically extending from an end portion of the cantilever, wherein the tip has an apex portion having a size in a range of about 1-1000 nm; and   b. selectively doping the cantilever with a dopant to form a first doping region in the tip and a second doping region in the rest of the cantilever, wherein the dopant concentration of the first doping region is substantially lower than that of second doping region.   
     
     
         34 . The method of  claim 33 , wherein the first doping region corresponds to a native doping region. 
     
     
         35 . The method of  claim 34 , further comprising the step of tailoring the impurity doping in the apex portion of the tip. 
     
     
         36 . The method of  claim 35 , wherein the tailoring step comprises the steps of
 a. patterning the apex portion of the tip; and   b. doping the patterned apex portion with a second dopant to form a third doping region having a doping concentration that is higher than that of the first doping region and substantially lower than that of the second doping region.   
     
     
         37 . The method of  claim 36 , wherein the patterning step is performed with a lithography process. 
     
     
         38 . The method of  claim 36 , wherein the third doping region in the apex of the tip is in connection with the second doping region. 
     
     
         39 . The method of  claim 36 , wherein the third doping region has an electrical resistivity that is lower than that of the first doping region and substantially higher than that of the second doping region.