A bulk dielectric polymer film with an intrinsic ultralow k value of 1.52 at 10 kHz has been successfully synthesized based on a novel polyimide FPTTPI. More importantly, such outstanding dielectric properties remain stable up to 280°C. The excellent ultralow dielectric properties are mainly because of the larger free volume (subnanoscale), which intrinsically exists in the amorphous region of polymeric materials. Meanwhile, FPTTPI also shows excellent thermal stability and mechanical properties, with a glass-transition temperature (T g ) of 280°C, 5 wt % loss temperature of 530°C, and a residual of 63% at 800°C under N 2 . It was soluble in common solvents, which made it possible to undergo simple spin-on or efficient, low-cost, and continuous roll-to-roll processes.
■ INTRODUCTIONWith the development of ultralarge-scale integration (ULSI) to high speed and high integration in the semiconductor industry, and with the continuing miniaturization in the dimensions of electronic devices utilized in ULSI circuits, an urgent need exists for high-performance low-k and ultralow-k dielectric materials (low-k: k ≤ 2.5; ultralow-k: k ≤ 2.0) has arisen. 1−4 Such dielectrics materials would reduce the capacitance between the metal interconnects, the resistance-capacitance delay, the line-to-line crosstalk noise, and the power dissipation; 5−7 these materials also have important application prospects in the fields of interlayer dielectric, semiconductor packaging (chips modules, etc.), and high-frequency, low-loss boards etc. So far, research of low-dielectric materials as an alternative to the workhorse dielectrics silicon dioxide (k = 3.9−4.3) are continually being pursued today, which mainly including organosilicates and organic polymers. 8−13 Compared with inorganic dielectric materials, organic polymer materials often have a lower dielectric constant, because of the lower materials density and lower individual bond polarizability. Moreover, they show distinct advantages, in terms of easy chemical and geometric structural design. 14−18 Thus, they have attracted much interest. Generally, by decreasing the dipole strength or the number of dipoles or a combination of both, the dielectric constant of full dense polymer materials can be lowered to 2.2−2.6. 5,19−22 The most common way is fluorination of dielectric materials or increasing the free volume by rearranging the material structure. 23−27 However, it seems that no true dielectric generational extendibility to the ultralow-k region can be achieved without embracing the concept of porosity, either for organosilicates or organic polymers. 28−32 The k-value of these porous materials can be less than 1.5, 33−39 but the method itself is complicated, difficult to control, and expensive. Moreover, the pore structure, the size, and the distribution would greatly affect the homogeneity of the materials, which makes this technique difficult for large-area applications. In addition, the porosity tends to dramatically reduce the mechanical strength and increase the permeability o...
