Custom electrodes for molecular memory and logic devices

Abstract

A method is provided for fabricating molecular electronic devices comprising at least a bottom electrode and a molecular switch film on the bottom electrode. The method includes forming the bottom electrode by a process including: cleaning portions of the substrate where the bottom electrode is to be deposited; pre-sputtering the portions; depositing a conductive layer on at least the portions; and cleaning the top surface of the conductive layer. Advantageously, the conductive electrode properties include: low or controlled oxide formation (or possibly passivated), high melting point, high bulk modulus, and low diffusion. Smooth deposited film surfaces are compatible with Langmuir-Blodgett molecular film deposition. Tailored surfaces are further useful for SAM deposition. The metallic nature gives high conductivity connection to molecules. Barrier layers may be added to the device stack, i.e., Al 2 O 3 over the conductive layer.

1 - 11 . (canceled)  
   
   
       12 . A method of reliably fabricating a molecular electronic device comprising at least a bottom electrode and a molecular switch film thereon, said method comprising: 
 providing a substrate;    forming said bottom electrode on said substrate, said bottom electrode comprising a layer of tailored conductive material; and    forming said molecular film on at least said bottom electrode,    wherein said bottom electrode is formed by a process including:    cleaning portions of said substrate where said bottom electrode is to be deposited;    pre-sputtering said portions; and    depositing said conductive layer on at least said portions.    
   
   
       13 . The method of  claim 12  wherein said conductive layer is deposited on at least said portions without formation of any sticking layer prior to depositing said conductive layer.  
   
   
       14 . The method of  claim 12  wherein said substrate is provided with a coating on which said bottom electrode is deposited.  
   
   
       15 . The method of  claim 14  wherein said coating is subjected to said cleaning step and said pre-sputtering step before depositing said conductive layer.  
   
   
       16 . The method of  claim 14  wherein said substrate comprises <100> semiconductor-grade prime silicon wafer and wherein said coating comprises tight knit thermal oxide grown on said silicon wafer.  
   
   
       17 . The method of  claim 16  wherein said thermal oxide is grown to a thickness of at least 1,000 Å, but less than a thickness which would cause marked stress of said substrate or film to develop.  
   
   
       18 . The method of  claim 12  wherein cleaning is performed with an oxygen plasma to remove organic contaminants  
   
   
       19 . The method of  claim 12  wherein said pre-sputtering is performed under conditions to further clean said surface and remove environmental contaminants.  
   
   
       20 . The method of  claim 12  wherein said depositing of said conductive layer is performed to a thickness of 50 to 5,000 Å.  
   
   
       21 . The method of  claim 12  further including tailoring properties of the top surface of said conductive layer following its deposition.  
   
   
       22 . The method of  claim 21  wherein said tailoring is performed in a plasma to accomplish at least one of the following: (a) rearrange said conductive layer, (b) smooth said top surface of said conductive layer, (c) alter the hydrophilicity of said top layer, and (d) provide a barrier layer due to the presence of an oxide film on said top surface.  
   
   
       23 . The method of  claim 22  wherein said plasma is selected from the group consisting of oxygen alone to provide a hydrophilic surface, oxygen and subsequent argon to provide a less hydrophilic, more hydrophobic surface, argon alone to provide a hydrophobic surface, or a sequence of oxygen and hydrogen to provide a smooth surface with reduced oxygen, which is passivated.  
   
   
       24 . The method of  claim 23  wherein said plasma contains oxygen, leaving an oxide film on said conductive layer, and wherein said oxide film is subsequently removed, leaving said smooth top surface of said conductive layer.  
   
   
       25 . The method of  claim 21  wherein said tailoring includes at least one of the following steps: cleaning and oxidizing to a predetermined level.  
   
   
       26 . The method of  claim 21  wherein said tailoring includes at least one of the following steps: actively smoothing, actively oxidizing, actively removing said oxide without re-roughening, and actively passivating.  
   
   
       27 . The method of  claim 12  wherein a resist is formed on a coating on said substrate and patterned, said pattern comprising an array of said bottom electrodes, wherein said patterning is done by removing resist from those areas where said conductive layer is to be deposited to form said bottom electrodes.  
   
   
       28 . The method of  claim 27  wherein: 
 said exposed areas are cleaned with an oxygen plasma to remove organic contaminants;    said exposed areas are pre-sputtered to further clean said surface and remove environmental contaminants;    said conductive layer is blanket-deposited everywhere, to deposit a layer about 50 to 5,000 Å thick; and    said conductive layer is patterned to form said bottom electrodes.    
   
   
       29 . The method of  claim 12  wherein said molecular device comprises an electrical element formed with two or more electrodes.  
   
   
       30 . The method of  claim 29  wherein said molecular device is selected from the group consisting of switches, diodes, resistors, transducers, and transistors.  
   
   
       31 . The method of  claim 30  further including forming a top contact on said molecule film and over said bottom layer to form a switch.  
   
   
       32 . The method of  claim 31  wherein said top contact is selected from the group consisting of top electrodes, circular electrodes, tip addressing, and a nanopore over said molecular film covered with an electrode.  
   
   
       33 . The method of  claim 12  wherein said conductive material comprises a material selected from Rows 1B-7B and 8 of the Periodic Table.  
   
   
       34 . The method of  claim 33  wherein said conductive material is selected from the group consisting of platinum, tungsten, silver, aluminum, palladium, copper, nickel, chromium, molybdenum, titanium, and tantalum.  
   
   
       35 . The method of  claim 34  wherein said conductive material consists essentially of platinum.  
   
   
       36 - 53 . (canceled)