DOI: 10.1007/s00339-007-3866-3 Appl. Phys. A 87, 705–708 (2007) Materials Science & Processing Applied Physics A s. halder 1 t. schneller 1, ✉ r. waser 1,2 Enhanced stability of platinized silicon substrates using an unconventional adhesion layer deposited by CSD for high temperature dielectric thin film deposition 1 Institut fuer Werkstoffe der Elektrotechnik, RWTH Aachen, 52056 Aachen, Germany 2 IFF, Forschungszentrum Juelich, 52425 Juelich, Germany Received: 12 September 2006/Accepted: 4 January 2007 Published online: 23 February 2007 • © Springer-Verlag 2007 ABSTRACT Almost all platinized substrates manufactured presently use an TiO 2 adhesion layer to improve the adhesion between the SiO 2 and the Pt. These substrates however are sta- ble till only 800 ◦ C. We show that simply by replacing the TiO 2 with Al 2 O 3 , the stability of the electrodes can be increased to 1000 ◦ C and more. These substrates can be used for high temperature depositions which standard platinized substrates cannot withstand. Further we show that dielectric thin films of BaTiO 3 and (Ba,Sr)TiO 3 crystallized at higher temperatures show almost a threefold increase in permittivity on these high temperature stable platinized silicon substrates.The large in- crease in permittivity is attributed to an increase in grain size at high temperatures. PACS 61.82.Fk; 68.35.Np; 68.60.Dv; 77.55.+f; 81.20.Fw 1 Introduction Platinized silicon substrates are ubiquitous. Plat- inum has also been deposited on various substrates by sput- tering, evaporation and pulsed laser deposition. In most cases a stable and smooth electrode layer is essential for the realiza- tion of thin film devices. With research on physical and elec- trical properties of dielectric thin films in the metal-insulator- metal (MIM) configuration increasing the use of commercial platinized silicon wafers have been further augmented. How- ever the dielectric thin films have to be processed at tempera- tures below 800 ◦ C because most of commercially available substrates develop hillocks or disintegrate at temperatures higher than this. There have been some reports on the epitaxial growth of Pt on various single crystal substrates but there has been no report on high temperature stable Pt on silicon [1, 2]. Thin films of dielectric materials often have lower dielec- tric constant as compared to their ceramic counterpart. The reasons cited are often (a) size effects (b) interfacial strain or (c) limits of processing temperature due to the substrate. Ceramics are usually crystallized at higher temperatures and therefore have larger grain sizes but thin films which are de- posited on platinized silicon substrates have a maximum tem- ✉ Fax: +49 241 8022300, E-mail: schneller@iwe.rwth-aachen.de perature limit. In order to study the effect of temperature on the crystallization and electrical properties of pure and sub- stituted BaTiO 3 a high temperature stable platinized substrate stable upto 1000 ◦ C would certainly be beneficial. In this com- munication we show that simply by replacing the TiO 2 ad- hesion layer with Al 2 O 3 the stability of the bottom electrode can be increased considerably. Further we show that the per- mittivity values of perovskites (as an example) are improved tremendously when processed at 1000 ◦ C. 2 Experimental The Si(100) wafers were first oxidized at 1050 ◦ C for 50 min under humid conditions till the surface had a 450 nm thick SiO 2 layer. On this wafer an aluminium sec- butoxide-based precursor solution (0.05 M) was spin coated at 500 rpm for 5s and then at 4000 rpm for 30 s. This layer was directly crystallized in the diffusion oven at 1000 ◦ C for 30 min. The alumina films were approximately 20–22 nm thick. Platinum films (100 nm) were then deposited on this Al 2 O 3 layer at 150 ◦ C by radio-frequency magnetron sputter- ing with a base pressure of approximately 2.5 × 10 −6 . These wafers were then diced into 2.54 cm 2 pieces and annealed at various temperatures between 700 ◦ C and 1000 ◦ C for 30 min. BaTiO 3 and (Ba,Sr)TiO 3 thin films were deposited on these electrodes by chemical solution deposition from a 0.3M precursor solution [3]. The details of the precursor solution preparation can be found elsewhere [4]. The films after de- position were directly crystallized in the diffusion furnace at three different temperatures. This process was repeated five times till the desired thickness was achieved. Platinum top electrodes of area 0.07 mm 2 and thickness 100 nm were deposited at room temperature by sputtering and were struc- tured using a photolithographic lift-off process. The film thicknesses were measured using a DEKTAK surface pro- filometer, after etching a corner of the dielectric film. The thicknesses for the different films were BT1000 (245 nm) BT700 (260 nm), BST1000 (255 nm) BST700 (315 nm). 3 Results and discussion X-ray diffraction patterns obtained by θ − 2θ scan mode of the Pt films as-deposited and annealed at higher