并五苯有机薄膜晶体管中厚度检测方案(椭偏仪)

Application NoteMM-16Spectroscopic EllipsometrySE02 Semiconductor LCM Characterization of Pentacene-Based Thin Film Transistorsusing the MM-16 Spectroscopic Ellipsometer Celine Eypert- Application Scientist - Thin Film Division The performance of organic thin-film transistors (OTFTs) using small molecules has considerably im-proved during recent years. Organic materials have the key advantage of potentially simple and low-temperature thin film processing， using techniques as spin coating， inkjet printing or stamping. Thisfact suggests that OTFTs could be usetul tor applications requiring large-area coverage， low temper-ature processing and low cost. Thin film transistors (TFTs) using organic semiconductors as theactive material are of interest for a number of applications. Usedas pixel-access devices in active-matrix displays， organic TFTscould complement liquid-crystal valves or organic light emittingdiodes to allow inexpensive display fabrication on flexible， light-weight polymeric substrates. Moreover， among the OTFTs with organic semiconductor as theactive chanel， those fabricated with pentacene allowed the high-est performance. Its high hole mobility approaches or even sur-passes the mobility values found in amorphous Si. The mostUSUallggate dielectric in these pentacene devices is thermallygrown silicon dioxide on crystalline silicon. The effects of penta-cene channel tthickness influence the field-effect mobility of thematerial， and spectroscopic ellipsometry is an ideal， non-de-structive tool for its characterization. entacene (C22H14) is a polycyclic aromaticnydrocarbon that contains five benzene rings. There are two types of geometry of organic field effect transistor，below you can see two representations ot these structures： Top-contact structure Bottom-contact structure Organic semiconductor Dielectric Metal source-drainConductor substrate The ellipsometric data were measured using the HORIBA JobinYvon MM-16 spectroscopic ellipsometer which is based on liq-uid crystals modulators. The experimental data were acquired at an angle of 70°acrossthe spectral range 450-850nm. The analysis is made in two steps， firstly the characterization ofsilicon oxide followed by characterization of the pentacene lay-er. characterization of Silicon Dioxide A single layer model has been used. The optical properties ofthe SiO， are taken from the standard DeltaPsi2 optical library. Pentacene characterization The oxide thickness has been fixed in the sample structure ofOTFT. First the model was fitted using the spectral range 600-850nmThe optical constants of the pentacene were determined using afour oscillator dispersion formula. The optical properties werethen extended near the lower energies using an advanced func-tion of DeltaPsi2 software： the NK fit. This NK fit function makes a direct inversion of ellipsometric datato n and k， and allows us to extend a dispersion formula and tocharacterise teatures ot the retractive index curve that are notpossible using a dispersion formula. This function is not basedon the Kramers-Kroning relation and must be used with care.For this characterization we believe that this approach providesa valid description of the material’s optical properties. The model fits the sample perfectly. There is an excellent agree-.ment between the experimental data and the model.Furthermore， the ellipsometry results show a sharp and strongpeak in the extinction coefficient k at 654nm， with additional ab-sorption peaks at 630nm，580nm and 540nm. Conclusion Spectroscopic Ellipsometry based on the liquid crystal devices isan excellent technique for the highly accurate characterizationof organic semiconductor in OTFTs device in the visible range. HORIBA (All HORIBA Jobin Yvon companies were formerly known as Jobin Yvon)HORIBAExplore the future Spectroscopic Ellipsometry based on the liquid crystal devices is an excellent technique for the highly accurate characterization of organic semiconductor in OTFTs device in the visible range.