System and methods of mold/substrate separation for imprint lithography

Abstract

A nanoimprint system and methods for separating imprinted substrates with nano-scale patterns from mold for manufacturing. Generally, the system includes means to create, monitor, and control relative movement between the mold and substrate for separation. It is capable of controlling where and when the separation happens and finishes. The relative movement may be generated by motion stages, springs, stage driven flexures, inflatable O-rings, gas flow, and other mechanical means. It may be monitored by separation force, overhead camera, and vacuum/pressures in different area of the system. The relative movement may be any combination of stages movements and movement sequences. The separation speed, direction, and force can be well controlled in the system to achieve fast and reliable separation between mold and substrate, and at the same time maintain the pattern shape and details on the consolidated imprint resist.

What is claimed is: 
     
         1 . A method of separating a mold and an imprinted substrate in imprint lithography comprising the steps of:
 providing an assembly of a mold having a molding surface imprinted into a substrate having a moldable surface at the mold/substrate interface; and   generating a controlled relative movement between the substrate and mold.   
     
     
         2 . The method of  claim 1  wherein the relative movement is generated by multi axis motion stages having at least one of a Z, a pitch, and a roll basic motions. 
     
     
         3 . The method of  claim 2  wherein the motion to generate relative movement can be a single motion throughout the separation process, or it can be a combination of different motions at different phase of the separation, where the speed and acceleration of motions in any time can be controlled to assist the separation. 
     
     
         4 . The method of  claim 3  wherein the single motion can be a one axis movement, or a two axis movement at the same time, or a three axis movement at the same time, where the three moving axis is a Z, a pitch and a roll. 
     
     
         5 . The method of  claim 1  wherein the speed of relative motion can be set to zero at certain period of the separation process to assist separation. 
     
     
         6 . The method of  claim 1  wherein the relative movement is generated by springs, cylinders, inflatable O-rings, or mechanical means which can generate motion. 
     
     
         7 . The method of  claim 1  wherein the relative movement is generated by fluid flow, the fluid pressure, flow rate and flow direction being controllable to assist the separation and a flow direction being controlled to be vertical to the separation front to assist the separation. 
     
     
         8 . The method of  claim 1  wherein the separation speed and direction are controlled by a monitoring of the separation force. 
     
     
         9 . The method of  claim 1  wherein the separation completion may be decided by a factor selected from the group consisting of a sudden change of separation force, a vacuum reading of substrate and mold holding chucks, and an image of separation boundary. 
     
     
         10 . The method of  claim 1  wherein the separation force for different moldable material is measured, the suitable moldable materials selected to minimize the separation force during the separation. 
     
     
         11 . A system for separating a mold and an imprinted substrate in imprint lithography comprising:
 a mold holding fixture for holding a mold having a mold surface with nanostructures;   a substrate holding fixture for holding a substrate having a molding surface;   a stage assembly having three axis movement;   a contact force sensors positioned for sensing the separation force between the moldable surface and the molding surface during separation;   an overhead camera for observation of separation boundary; and   at least one vacuum pump;   
     
     
         12 . A system for separating a mold and an imprinted substrate in imprint lithography comprising:
 a mold holding fixture for holding a mold having a mold surface with nanostructures;   a substrate holding fixture for holding a substrate having a molding surface;   a stage assembly having three axis movement;   a contact force sensors positioned for sensing the separation force between the moldable surface and the molding surface during separation;   a chamber housing defining a chamber having at least a mold held by the mold holding fixture and the substrate held by the substrate holding fixture positionable therein, the chamber housing configured enabling the applying of a pressure inside the chamber that is higher and/or lower than atmospheric pressure;   a pressure regulator and a manifold each being fluidly coupled to the chamber for changing the pressure inside the chamber;   a gas reservoir of high pressure, a regulator and piping to allow the high pressure gas;   at least one vacuum pump;   an overhead camera for observation of separation boundary; and   means to divide the chamber into two fluidly separate sub-chambers, each sub-chamber being configured for a separate controlled sub-chamber environment including a separate pressure and/or vacuum, a separate gas content, and a separate gas flow rate into and out thereof.   
     
     
         13 . The method of  claim 12  wherein both bending of the mold and peeling substrate away from the mold, or a mixture of them can be carried out for separation. 
     
     
         14 . The method of  claim 12  wherein the separation location, speed, and time can be controlled and monitored. 
     
     
         15 . A method of patterning a substrate with microstructure and nanostructure patterns in roller imprint lithography comprising the steps of:
 applying moldable material on the substrate surface;   providing a mold having a molding surface with the patterns;   at least one of the moldable or the molding surfaces is part of a roller, or at least one backside of the mold and the substrate is contacting a roller;   contacting the moldable surface with the molding surface and press; and   curing the contacted area and separate;   
     
     
         16 . The method of  claim 15  wherein the press is provided by fluid pressure. 
     
     
         17 . The method of  claim 15  wherein there is at least one chamber is used for fluid pressure. 
     
     
         18 . The method of  claim 15  wherein the substrate is driving by rollers. 
     
     
         19 . The method of  claim 15  wherein the moldable material is deposited on the surface of the substrate by material dispensing head, or by moving the substrate through the liquid material, or by contacting the substrate with a roller already coated with the material. 
     
     
         20 . The method of  claim 15  wherein the surface of the substrate may be coated with thin layer of material by vapor. The vapor is generated by heating a chemical. 
     
     
         21 . The method of  claim 15  wherein the moldable material thickness on the surface of the substrate may be controlled by a thickness controller placed close to the substrate and take away extra material. 
     
     
         22 . The method of  claim 15  wherein the press pressure can be controlled by the input pressure in the ACP head, the distance from the head to the moldable surface, and the base pressure controllers set up on the roller belt. 
     
     
         23 . A system for patterning substrate surfaces with microstructure and nanostructure patterns in roller imprint lithography compromising:
 a mold having a mold surface with the patterns;   a substrate having a molding surface;   contact force sensors positioned for sensing the force at different locations of the roller system;   at least a chamber housing configured enabling the applying of a pressure inside the chamber that is higher and/or lower than atmospheric pressure; or a ACP head enabling the applying of a pressure on the output of the head;   a pressure regulator and a manifold each being fluidly coupled to the chamber for changing the pressure inside the chamber or coupled to the ACP head to change the output pressure of the head;   a gas reservoir of high pressure, a regulator and piping to allow the high pressure gas;   at least one vacuum pump;   moldable material dispensing head, or moldable material bath in contact with at least a section of the substrate, or a roller in contact with the substrate and moldable material;   a vapor treatment chamber to coat vapor of chemicals on a section of the mold or the substrate;   rollers to move at least one of substrate and mold; and   means to control the thickness of the moldable materials by contacting and taking away extra materials;   
     
     
         24 . The system of  claim 23  wherein ACP head consists of
 a housing with one end open; 
 a light reflector; 
 lens for focusing and expanding light; 
 a UV light source, a thermal light source, or an combination of both; and 
 at least an opening hole for fluid coupling to the high pressure supply. 
 
     
     
         25 . A method of patterning a roller mold with microstructure and nanostructure patterns comprising the steps of:
 having a substrate with the patterns on the surface;   coating roller mold with surfactant coating;   roll the mold on the substrate patterned surface with a controlled pressure, so the pattern on the substrate is transferred to the mold surface;   removing the surfactant coating exposed in the air;   plating the roller mold with metal;   rotating the roller mold to polish its surface so that the patterns are exposed in the air and the metal surface is smooth; and   removing the remaining surfactant and patterns transferred initially from the substrate.   
     
     
         26 . The system of  claim 25  wherein removing the surfactant coating can be completed by a special designed cylindrical RIE chamber where roller is one electrode and chamber is grounded. The RIE chamber can selectively remove the surfactant on the roller surface that is not covered by the pattern transferred from the substrate. The RIE chamber can then etch the patterns into the roller. 
     
     
         27 . A method of patterning a roller mold with microstructure and nanostructure patterns comprising the steps of:
 coating the roller surface with photoresist;   using projection optics with UV light and photomask to exposure a line of the resist on the surface of the roller;   rotating the roller to next field and run exposure again; keeping rotating and exposure each time until all required areas on the roller surface are exposed;   placing roller into a developer to remove unwanted resists; and   etching the pattern into the roller using a wet etching or a dry etching.   
     
     
         28 . A method of patterning a roller mold with microstructure and nanostructure patterns comprising the steps of:
 having a substrate with the molding pattern on the surface;   coating a roller surface with moldable material; and   contacting and rotating the roller with the substrate under a controlled pressure and curing the resists while rotating.   
     
     
         29 . A method of patterning a roller mold with microstructure and nanostructure patterns comprising the steps of:
 having a flexible substrate with the molding pattern on the front surface;   coating the roller surface, the back surface of the substrate, or both with either glue or a magnetic material; and   rotating the roller on the back surface of the substrate to wrap the substrate around the roller;   
     
     
         30 . A system for patterning substrate surfaces with microstructure and nanostructure patterns in step and repeat imprint lithography, compromising:
 a mold having a molding surface with the patterns;   a substrate having a molding surface not smaller than the patterning area of the mold;   a gantry for holding mold holder;   a multi-axis stages;   contact force sensors positioned for sensing the forces during imprint and separation;   a pressure regulator and a manifold each being fluidly coupled to the system;   a gas reservoir of high pressure, a regulator and piping to allow the high pressure gas;   at least one vacuum pump;   a material dispensing system for placing moldable material on the substrate;   a vibration control table;   a robot system with cassettes for automatically loading and unloading of substrates and molds;   a microscopic system for measuring the spatial relation between the mold and the substrates at multiple locations;   a UV exposure light and reflective optics;   a mold holder which has center opening and can change the mold size in the XY plane; and   means to press one area of the substrate using the mold at a time, then separate and continue with other areas.   
     
     
         31 . The system of  claim 30  wherein dispensing system further includes a gantry, a resist dropping head, resist observation microscopes, a camera, a light source, a resist cleaning station, a resist reservoir, driving electronics and software, a multiple axis stages to control vertical dropping gap and resist droplet spacing on substrate. 
     
     
         32 . The system of  claim 30  wherein the moldable material may be placed on the substrate as droplets uniformly, or according to the pattern density on the mold, or arranged in a way so the adjacent droplets can merge together to drive out air quickly. 
     
     
         33 . The system of  claim 30  wherein the mold holder can change the mold size using piezo drives, or air cylinder with accurate pressure control. 
     
     
         34 . The system of  claim 30  wherein the substrate can be a standard wafer of 4″, 6″, 8″, 12″, or 16″ with material ranging from Silicon, semiconductor, and other optical material, and the mold can be a standard quartz plate of 6″ by 6″ by 0.25″ thickness with a smaller die size in the center, raised as a pedestal with height 1-50 um. 
     
     
         35 . A method of patterning a substrate with microstructure and nanostructure patterns in step and repeat imprint lithography comprising the steps of:
 providing a mold having a molding surface with the patterns;   applying moldable material on an area of the substrate surface;   adjusting the gaps between the mold and the substrate so the moldable surface and molding surface is in parallel;   approaching the substrate to the mold while aligning them according to the alignment marks on the mold and the substrate;   contacting the moldable surface with the molding surface;   applying pressure and hold a certain time;   curing the contacted area;   separating the moldable surface from molding surface with patterns left on the moldable surface; and   moving to next area and repeating the pressing again until all areas of the moldable surface is patterned.   
     
     
         36 . The method of  claim 35  wherein the mold may have a much thinner center area. 
     
     
         37 . The method of  claim 36  wherein a quartz plate may be bonded with the back surface of the mold to form a mini-chamber inside the mold. 
     
     
         38 . The method of  claim 37  wherein the mini-chamber can be used to apply a fluid pressure on the mold front pattern surface during imprint. 
     
     
         39 . The method of  claim 37  wherein the mini-chamber can be used to apply a fluid pressure on the mold front pattern surface to bend it and drive the air out before imprint. 
     
     
         40 . The method of  claim 37  wherein the mini-chamber can be used to apply a fluid pressure on the mold front pattern surface to bend it after imprint to separate the surface from the moldable surface on the substrate. 
     
     
         41 . The method of  claim 35  wherein the mold may have an inflatable area on the front surface. The inflatable area may be inflated to either seal off the moldable surface and molding surface before imprint, or to separate the mold from substrate after imprint. 
     
     
         42 . The method of  claim 41  wherein the sealed off area between the moldable and molding surfaces can be vacuumed to remove the air between the surfaces. 
     
     
         43 . The method of  claim 35  wherein a localized pressure can start from the center of the molding surface and propagate to the edge of the molding surface to squeeze the air between the moldable surface and molding surface out. 
     
     
         44 . The method of  claim 43  wherein the localized pressure can be generated by sending fluid pressure to the vacuum grooves either on the mold holder, or on the substrate holder, or both. 
     
     
         45 . The method of  claim 43  wherein the localized pressure can be generated by electrical field established between the moldable surface and molding surface. 
     
     
         46 . The method of  claim 35  wherein a fast diffusion gas such as helium may be used to drive out the air. 
     
     
         47 . The method of  claim 35  wherein holes on the mold, closing to the patterns edge are made to allow helium, vacuum pumping, or other gas flowing. The purpose is to help driving out the air before imprint and separating after imprint. 
     
     
         48 . The method of  claim 35  wherein the separation completion is detected by at least one of a sudden change of vacuum reading of substrate or mold holders, a sudden change of recorded separation force, and an imaging observation of contacting area disappearing; or by a combination of these methods. 
     
     
         49 . The method of  claim 35  wherein the separation may be carried out by a relative motion between the substrate and the mold wherein the relative motion is generated by the multi-axis stages, or bending from localized pressure, or inflatable area on the mold surface, or local gas flow, or a combination of these methods. 
     
     
         50 . The method of  claim 35  wherein the separation force, speed and direction can be controlled using sensors, stages, and cameras, wherein a minimized separation force profile is used for separation. 
     
     
         51 . The method of  claim 35  wherein a low evaporation rate moldable material is dispensed on the substrate and the low evaporation rate enables the coating of all the area of the surface with moldable material at a time before imprint.