Newly Developed Low-Density Methylsiloxane Spin-On-Glass Films
- PDF / 689,947 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 22 Downloads / 196 Views
conventional gap-filling material because of its excellent gap filling capability, good adhesion, thermal stability above 400 cC and high crack resistance [2-4]. In accordance with the requirement of the low dielectric constant, many of major SOG suppliers are developing new types of methylsiloxane SOGs. Increasing the content of methyl groups tends to lower the dielectric constant of the cured film [5]. When the molar ratio of methyl groups to silicon (Me / Si) reaches 2, however, the formation of a rigid three-dimensional network becomes difficult owing to the increase in chain components, polydimethylsiloxane. Because of the loose threedimensional network, the mechanical properties of the film with a high Me / Si ratio are deteriorated. Methylsilsesquioxanes with the Me / Si ratio of 1 exhibit the dielectric constant of 2.7 which may be the lowest among methylsiloxane SOGs [6]. It would be attractive to reduce the dielectric constant of methylsiloxane SOG film below 2.5 but sill maintain the other desirable properties that conventional methyl siloxane possesses. In the present study, a newly developed SOG solution has been proposed for a low-density methyl siloxane SOG film with k = 2.3. The SOG solution contains hydrolyzed organoalkoxysilane with a bulky organic group that can decompose below the curing temperature. It is intended that the bulky organic groups attached to silicon should leave vacant spaces whose sizes are comparable to those of the bulky organic groups during the cure to give a low-density methylsiloxane film. The structure and general properties of these new SOG films will be described. 279 Mat. Res. Soc. Symp. Proc. Vol. 565 01999 Materials Research Society
EXPERIMENTAL Methyltriethoxysilane and dimethoxymethyl-3,3,3-trifluoropropylsilane were hydrolyzed in organic solvent to prepare the SOG solution. The molar ratio of methyltriethoxysilane and dimethoxymethyl-3,3,3-trifluoropropylsilane was I : 4. A trifluoropropyl group was used as a bulky and thermally decomposable group. The solution was spun onto silicon wafers at a speed of 3000 rpm for 20 sec. The coated wafers were baked on hot plates at 80, 150 and 200 0C in air for 1 min, successively. Then, the wafers were cured at 360 or 4501C in nitrogen for 30 min. The structure of the film was studied with a transmission FTIR system. Film thickness was measured using a profilometer. Film density was calculated from the weight and thickness of the film. The BET surface area of the film coated on a Si wafer was estimated from nitrogen sorption data. Annealing was performed at 450 - 7000C
in nitrogen for 0.5 to 4 h in order to
study the thermal stability of the film. For an electric measurements, the film was formed on a highly doped Si wafer, followed by the deposition of gold conducting electrodes of 1mm in diameter. The measurements were carried out using an impedance analyzer in a chamber which can be evacuated with a rotary pump. The dielectric constant of the sample was calculated from the capacitance at 1 MHz and the film thickness. Th
Data Loading...
