Synthesis, Fabrication, and Heterostructure of Charged, Substituted Polystyrene Multilayer Dielectrics and Their Effects in Pentacene Transistors

Abstract

Charge trapping and storage in polymer dielectrics can be harnessed to control semiconductor devices. Organic transistor (OFET) gate insulators affect bias stress and threshold voltage (V th), and charging them can preset the operating voltages and control bias stress. We describe a chemical design and film fabrication procedure for construction of stacks of polystyrene (PS) layers, each with arbitrary concentrations of potentially chargeable functional groups. Thermal cross-linking of benzocyclobutene subunits ensures layer integrity while keeping the layers free of polar functionality and small molecule byproducts. Neutron reflectivity (NR), scanning electron microscopy, and atomic force microscopy (AFM) showed that individual layer thicknesses varied systematically with polymer concentration in deposition solutions, and interfacial thicknesses ranged from 1.5 to 4 nm, independent of layer thickness, demonstrating formation of distinct layers with minimal roughness or intermixing. The PS-based materials were used as the sole gate dielectrics for pentacene OFETs. We compared V th before and after charging. Increased bias stress stability as evidenced by reduced V th shift was seen in devices with trilayer dielectrics with substituted PS as the middle layer compared to a dielectric made from unsubstituted PS. On the other hand, increased V th shift was seen in many devices with bilayer dielectrics made with substituted PS as the top layer. We attribute the decreased V th shift seen in trilayer devices to an increased dielectric polarization of the substituted PS in the middle layer that countered the charge trapping effect in the top layer. This demonstration establishes a method for utilizing vertical charge patterns for various electronics applications.

Maximized Hole Trapping in a Polystyrene Transistor Dielectric from a Highly Branched Iminobis(aminoarene) Side Chain

“…In our previous work, neutron reflectivity and scanning electron microscope (SEM) measurements showed the existence of distinct boundaries of multilayer devices created by cross-linked PS (XLPS). , There was also no structural change within the device during the charging process, according to the neutron reflectivity experiment. Therefore, Δ V th should not relate to any structural change-induced effects.…”

“…All of the cross-linkable or chargeable polymers used in this work are listed in Figure . XLPS 6 , PS-2% Cl 7 , and XLPS-2% Cl 8 were synthesized using the protocols described in our previously published work . An NMR of polymer 6 is shown in Figure S4.…”

Preparation and Properties of Low Dielectric Constant Siloxane/Carbosilane Hybrid Benzocyclobutene Resin Composites

“…Polymers containing BCB groups can be heated to prepare thermosetting resin via Diels–Alder reaction without adding a catalyst or additives, and no by-products were produced during curing. Therefore, BCB resins have been widely used in the microelectronics industry due to their excellent comprehensive properties [ 5 , 6 , 7 , 8 , 9 , 10 ]. In order to meet the performance requirements of the next generation of industrial semiconductors, BCB groups have been introduced into linear polymers as thermal cross-linking groups, which can significantly reduce the k of the cured resin and enhance the mechanical and thermal properties [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 ].…”

Synthesis and properties of benzocyclobutene-terminated imide-containing cyano group

“…[1][2][3] BCB has served as a thermally cross-linkable group in the design and fabrication of various thermosetting polymers. [4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] The curing process of BCB resins is carried out by heating without any catalyst or additive, and no by-product is released, leading to the advantages of low shrinkage, good film-forming property, and perfect planarity of BCB cured resins. Unfortunately the temperature required to induce cross-linking in typical BCB resins is as high as 250-350 C, which exceeds the use temperature of many chemical components and thus restricts the application of BCB resins on temperaturesensitive occasions.…”