Micropatterning of Organic Semiconductor Microcrystalline Materials and OFET Fabrication by “Hot Lift Off”

Abstract

Considerable progress toward the development of electronic devices that rely on organic semiconductors as the active material component has been made in recent years. The key step for realization of the advanced organic electronic, or optical, device is the ability to micropattern different kinds of electronic materials, such as organic semiconductor/conducting materials, over large areas with micrometer-sized resolution. Here we demonstrate a simple and direct method for micropatterning small-molecule microcrystalline films using an epoxy stamp. The "hot lift off" method is highly selective, creating patterns with high resolution and relies on straightforwardly tailoring the adhesive properties between the epoxy and the film. This process is well suited for patterning many types of materials.

Direct Patterning of Organic‐Thin‐Film‐Transistor Arrays via a “Dry‐Taping” Approach

“…Patterning organic semiconductors is beneficial because it reduces or eliminates parasitic current paths (crosstalk) between neighboring devices, and results in a significant decrease in the ''off'' current. [9][10][11][12][13][14][15][16] Thin films of polymeric materials are usually prepared from solution, and can be patterned using various techniques such as screen printing, inkjet printing, molding, etc. [17][18][19][20][21][22] Small-molecule semiconducting materials have good thermal and chemical stability and typically exhibit better performance than polymers.…”

“…[17][18][19][20][21][22] Small-molecule semiconducting materials have good thermal and chemical stability and typically exhibit better performance than polymers. [10] However, it is technically challenging to pattern these small-molecule semiconductors because they are often insoluble in many solvents and are commonly vapor-deposited. While photolithography can be used for patterning such films, it is generally avoided because the solvents involved in the subsequent steps can cause degradation and delamination of the organic semiconductors.…”

“…Unfortunately, the resolution of this method is limited, largely due to the existence of an air gap between the mask and the semiconductor thin film. [9,10,23] To overcome this problem, several techniques based on printing or stamping have been recently developed, allowing the patterning of semiconductor thin films in the sub-micrometer range. [9,10,24] However, in these methods, shadow masks are still used to define source/drain contacts after the semiconductor has been independently patterned, which again prohibits the fabrication of devices with small features.…”

On the role of surface tensions and process conditions in detachment nanolithography

“…A number of detachment-based patterning methods have been introduced with different mold ͑polymer, silicon͒ and film materials ͑metal, polymer, or organic layer͒. [2][3][4][5] A key operating condition is a reasonable difference in adhesive forces between the mold/film interface ͑W 12 ͒ and the film/substrate interface ͑W 23 ͒, i.e., W 12 Ͼ W 23 . Despite extensive works in this field, the role of film wettability and process parameters as well as the interplay between them has not been well addressed.…”

“…For relatively lower temperatures ͑Ͻ60°C͒, the pattern fidelity was significantly reduced ͑Ͻ50% ͒, which suggests the importance of the detachment temperature. 4 Second, dewetting was observed at a negative S but the resulting pattern was either guided by physical confinement of mold ͑type III͒ or consisted of an array of droplets with an apparent periodicity ͑type IV͒, a typical pattern for dewetting of a thin liquid film. In type III, the droplets were separated and merged along the line direction.…”