Nano-precision photo/electrochemical planarization and polishing methods and apparatus therefor

Abstract

The present invention provides a nano-presion photo/electrochemical planarization and polishing method and an apparatus therefor. The method comprises through electrochemical, photochemical or photoelectrochemical means, an etchant being generated on a surface of a tool electrode which has a nanometer-sized planeness; the generated etchant reacting with a scavenger contained in an working electrolyte solution, or decaying itself in the working electrolyte solution, such that a confined etchant liquid layer is generated on the tool electrode surface and having a confined thickness of nanoscale; and by a chemical reaction between the etchant contained in the confined etchant liquid layer and a surface of a workpiece, the surface of the workpiece being polished or planarized to a nanometer scaled profile precision and surface roughness, thereby, realizing the planarization and polishing in nano-precision for the workpiece.

1 . A photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision, comprising:
 through electrochemical, photochemical or photoelectrochemical means, an etchant being generated on a surface of a tool electrode which has a nanometer-sized planeness;   the generated etchant reacting with a scavenger contained in an working electrolyte solution, or decaying itself in the working electrolyte solution, such that a confined etchant liquid layer is generated on the tool electrode surface and has a confined thickness of nanoscale; and   by a chemical reaction between the etchant contained in the confined etchant liquid layer and a surface of a workpiece, the surface of the workpiece being polished or planarized to a nanometer scaled profile precision and surface roughness, thereby, realizing the planarization and polishing in nano-precision for the workpiece.   
     
     
         2 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , wherein a concentration ratio of precursor which generates the etchant or leveling agent to the scavenger usually is in a range of from 10:1 to 1:100 if the scavenger is existed. 
     
     
         3 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , wherein the chemical reaction between the etchant and the workpiece are at least one selected from the group consisting of
 means of controlling the pH of the confined etchant liquid layer to promote the concentration of strong acidic species in the confined etchant liquid layer such that the workpiece is reacted to produce soluble salt;   means of generating a strong oxidative etchant which reacts directly with the workpiece to produce a soluble compound;   means of forming an oxidative material which oxidizes the workpiece surface to an oxide, and then the oxide is dissolved by acidic or alkali species in the working electrolyte solution;   means of adding an additive or surfactant to the working electrolyte solution, which is complex with metal ions of the workpiece through complex reaction; and   means of generating strong oxidants in the confined etchant liquid layer, together adding complexing agents to the confined etchant liquid layer so as to promote solubility of the resultant product.   
     
     
         4 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 3 , wherein the scavenger is selected from the group of consisting of disulfide bond compounds, ferrocene and its derivatives, persulfate salts, nitrites, sulfites, thiosulfates, ascorbic acid, cystine and sorbitols. 
     
     
         5 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , wherein the working electrolyte solution further contains at least one selected from the group consisting of surfactants, supporting electrolytes, pH buffers and the mixtures thereof. 
     
     
         6 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , wherein the tool electrode with nanometer planeness is manufactured by at least one selected from the group consisting of:
 a method of fabricating a tool electrode with nano-planeness of platinum, gold, iridium, tungsten or other metal though the ultra-precision machining;   a method of depositing a metal or semiconductor on a substrate with an atomic planeness through various processes for forming film, or growing a metal or semiconductor on the substrate through crystal epitaxial growth technology to make the substrate conductive;   a method of fabricating a single-crystal electrode having a surface of nano-planeness formed of platinum, gold, iridium and other metals through accurately cooling or drawing of the corresponding metal melt;   a method of fabricating a electrode having a nanometer-precise surface planeness by polishing and planishing polycrystal or single crystal metal electrode through CMP technology together with an electrolytic process;   a method of using a nanometer planeness surface formed by liquid metal or alloys spontaneously; and   a method for photocatalytical or photoelectrocatalytical tool electrode, which comprising a step of using an insulating quartz optical material or conductive ITO or FTO optical glass as a substrate, and a step of covering the substrate with a layer of TiO 2 , ZnO, WO 3 , Fe 2 O 3 , CdSe or the composite photocatalysts thereof through surface modification, electrochemical deposition in situ or chemical vapor deposition.   
     
     
         7 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , further comprising: controlling the distance between the tool electrode and the workpiece less than the thickness of the confined etchant layer, and/or controlling the relative motion between the tool electrode and the workpiece so as to improve the profile precision the workpiece surface and lower the surface roughness of the workpiece surface. 
     
     
         8 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to in  claim 7 , wherein in the case of the tool electrode being a planar tool electrode, the profile precision the workpiece surface can be improved and the surface roughness the workpiece surface can be lowered by means of making the tool electrode or the workpiece rotate in a plane while being parallel swing. 
     
     
         9 . The photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 1 , wherein the method further includes a step of adjusting the distance and parallelity between the tool electrode and the workpiece. 
     
     
         10 . An apparatus for the photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision, wherein the apparatus comprises a tool electrode, a photo/electrochemical reaction control system, a working electrolyte solution recycling system, a working electrolyte solution temperature control system, and an automated control system; and wherein
 the tool electrode is a tool electrode having a surface of nano-planeness;   the photo/electrochemical reaction control system is provided with a potentiostat, an optic control system, a photo/electrochemical working electrode, an auxiliary electrode, a reference electrode, a working electrolyte solution and a container for the working electrolyte solution, and the tool electrode functions as the photo/electrochemical working electrode and connects with the potentiostat and/or the optic control system, and the photo/electrochemical working electrode, the auxiliary electrode and reference electrode are immersed in the container in which the working electrolyte solution is contained, and the workpiece is further contained;   the working electrolyte solution recycling system is used to recycle the working electrolyte solution in the electrochemical reaction system and its instrumental control system;   the working electrolyte solution temperature control system is used to keep the temperature of the working electrolyte solution in the electrochemical reaction system and its instrumental control system at a constant temperature;   the automated computer-controlled system is provided with a fixed mount, a multi-dimension micro manipulator, a video monitor, a force sensor, a parallel laser ranging device, an electrolytic current feedback device and an information processing computer, wherein a lower part of the fixed mount is used to fix the tool electrode, and an upper part of the fixed mount is connected to the Z-axial micro motor of the multi-dimension micro manipulator in the automated computer-controlled system which connects with the information processing computer; the X-Y-axial micro motors of the multi-dimension micro-manipulator are employed as a workbench to support the container; the video monitor is used to monitor an approaching process of the tool electrode to the workpiece; the current feedback device is used to monitor or measure the electrical current flowing through the tool electrode surface; the force sensor is used to detect whether the tool electrode touches the workpiece or not; the parallel laser ranging device is used to detect the distance between the tool electrode surface and the workpiece surface; according to the collected parameters such as the feedback current provided by the electrical current feedback device, the contact force provided by the force sensor, and the distance between the two surfaces provide by the parallel laser ranging device, the information processing computer sends commands to the Z-axial micro motor and the X-Y-axial micro motors of the multi-dimension micro-manipulator to adjust the distance and parallelity between the tool electrode surface and the workpiece surface;   the working electrolyte solution contains precursors of the etchant and/or leveling agent, and the precursors of the etchant and/or leveling agent can produce the etchant and leveling agents on the surface of the tool electrode through photo/electrochemical reaction, wherein if the produced etchant and leveling agents cannot decay spontaneously, the working electrolyte solution needs to further contain scavenger which reacts with the etchant and/or leveling agent contained in the etchant liquid layer and compacts the etchant liquid layer to a nanometer-scaled thickness.   
     
     
         11 . The apparatus for the photo/electrochemically-induced confined chemical etching method for a surface planarization and polishing in nano-precision according to  claim 10 , wherein the apparatus adjusts the thickness of the confined etchant and/or leveling agent liquid layer by tuning the potential of the photo/electrochemical reaction system, wavelength and intensity of incident light, photocatalytical layer parameter, and the formulation, temperature and circulation of the working electrolyte solution.