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

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+hv2R

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-ki –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 kp (This is referred to as propagation)

The radicals can also recombine and become polymer this probabilty is linked to kt (This is referred to as termination)

Propagation M+RMR Mn+MMn+1R

Termination Combination

MnR+MmRMn+m

Disproportionation MnR+MmRMn+Mm

PolymerizationSimulation 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