Planarization Materials for Active Matrix Thin Film Transistor Arrays
- PDF / 2,293,584 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 81 Downloads / 217 Views
1030-G01-07
Planarization Materials for Active Matrix Thin Film Transistor Arrays Ahila Krishnamoorthy1, Richard Spear1, Amanuel Gebrebrhan1, Mehari Stifanos1, Hai Bien1, Marie Lowe2, Deborah yellowaga2, and Peter Smith3 1 Honeywell, Sunnyvale, CA, 94089 2 Honeywell, Chandler, AZ, 85226 3 Honeywell, Morristown, NJ, 07962 ABSTRACT Traditional plasma based dielectric films are conformal and cost-prohibitive for large displays. Solution based dielectrics are planarizing in nature and provide a flat surface for indium tin oxide (ITO) layer with the resultant uniform liquid crystal response throughout the pixel. In this paper, we present the display-related material properties and integration results obtained by using a solution-based organosilsesquioxane material. The material exhibits extremely high transmittance and planarization, low outgassing, high resistance to moisture absorption and diffusion, good adhesion to other layers integrated with it and ease of integration. INTRODUCTION Traditionally the dielectric in flat panel displays is SiNx or SiO2 and is deposited by plasma enhanced chemical vapor deposition (PECVD). It is known that the CVD methods give rise to a conformal coating with almost the same dielectric thickness all over the surface topology. The electrical performance of SiNx is excellent and it is the most commonly used interlayer dielectric [1] in thin film transistor (TFT) that functions as the on/off switch in flat panel screens. However, when the topology of the surface and the substrate size (with generations) are large, CVD cannot meet the requirements of cost and planarization of surface [2]. Solution-based coating of dielectric materials is able to planarize the surface on the TFT array glass and provide a flat surface upon which LCD or OLED can be integrated easily. Patterning precision is also improved by using solution-based coating methods. Flat panel display industry is open to solution based coatings because of the planarizing ability and cost advantages in coating huge panels. EXPERIMENT Dielectric formulation (Planarizing and Thermally Stable-PTS) comprising organosilsesquioxane was prepared in organic solvents and spin-coated on to silicon or glass wafers. The film was formed under two different bake and cure conditions: (1) baked on a hot plate at 160/200/230°C for 1min each and cured at 230°C for 1 hour and (2) baked at 160/200/300°C and cured at 400°C for 1 hour in a furnace under flowing N2. However, various combinations of bake/cure conditions are possible to form the dielectric films for different applications. The film was characterized for the property sets required for planarization and passivation layer applications.
The dielectric properties were measured using a mercury probe at 100 kHz frequency. Film thickness was measured after bake and after cure using Thermawave® to calculate the film thickness shrinkage (in z direction) upon curing. Refractive index (RI) of the film was also measured after bake and cure. Thermal stability of cured films was measured using a Therma
Data Loading...
