Step and Flash Imprint Lithography What really happens and how is it simulated? A simple version

Overall Logic Randomly populate lattice based on input parameters Generate radicals Polymerize : runs over a user defined number of cycles  Randomly select location in the lattice If a radical  Randomly select neighbor  Check if rxn successful based on RNG and a probability  Update lattice or cycle If non-radical and non-bonded  Randomly select neighbor  Check to see if a move is possible  Update lattice or cycle

Dispense  Monomer mixture called the etch barrier is dispensed onto a substrate (wafer) The composition is known and consists of  Monomers (at least two)  Initiator  Cross-linker (to join polymer chains together- for mechanical strength) Simulation  The lattice is randomly populated with the different molecules in the composition

Imprint TruthSimulation A patterned substrate is brought in contact with the substrate- capturing the etch barrier in its relief patterns (the substrate is optically clear) The substrate is held in place by a vacuum chuck and the template is mechanically lowered with great accuracy into contact with the wafer Template molecules are added around the edge of the chosen feature Substrate molecules at the bottom of the feature are fixed

Initiation TruthSimulation Light of a specific wave length is shined through the template The light causes the initiator to become “excited” and break up into two radical species (one more reactive than the other) (See AICHE paper ignore the Oxygen part) I+hv  2R Since only one radical takes part in the chemistry the weaker one is ignored Initiator molecules are either depending on the version of the model:  randomly turned into radical species until the desired fraction is formed  processed through a initiation routine which occurs during the polymerization step with a probability based on the rate of initiation-k i –this rate is used in determining the energy barrier for the rxn to occur (see Brook’s presentation) to determine if a radical is formed

Polymerization Truth The formed free radical species can them react with monomer molecules or cross-linkers with a known probability which is linked to k p (This is referred to as propagation) The radicals can also recombine and become polymer this probabilty is linked to k t (This is referred to as termination) Propagation  M+R  MR  M n +M  M n+1 R Termination  Combination M n R+M m R  M n+m  Disproportionation M n R+M m R  M n +M m

Polymerization Simulation A location is chosen at random within the feature  If it is a not a radical or polymer it is given the chance to move by choosing a random neighbor and seeing if it is a void and then checking based on a probability if the move is successful  If it is a radical A random neighbor is chosen  A rxn is attempted again another probabilty (kp or kt depending on the identity of the neighbor)  If that neighbor was a radical and the rxn succeeded then both radicals are destroyed and the sites are designated polymer (termination)  If that was a monomer or crosslinker and the rxn succeeded then the radical is now turned into polymer and the neighbor is now given the status of being a radical (Propagation)

The Rest Its basically book keeping..  Counting the number of polymer molecules formed  Labeling the polymer chains and measuring their lengths  Assigning the bond data