Polyimides as interlayer dielectrics

Polyimides as Interlayer Dielectrics for High-Performance Interconnections of Integrated Circuits... 

Aromatic polyimides have gained wide popularity as dielectric materials in a variety of applications in the manufacturing of electronic circuits due to their thermal, mechanical and electrical properties. Most notable among these applications are as interlayer dielectrics in multilevel VLSI circuits and in multilevel interconnects, as well as in the packaging of integrated circuits. 

All of the newly developed fluorinated diamines and dianhydrides were targeted to prepare processable aromatic polyimides possessing many useful properties, such as high Tg, excellent dimensional stability, low dielectric constants, and outstanding thermal and thermo-oxidative stabilities. The combination of these properties leads the polyimides to be widely used as interlayer dielectrics, flexible circuitry substrates. 

High performance polymer films and coating materials are increasing being required by the electronics industry for use as interlayer dielectrics and as passivation layers. Aromatic polyimides are general the polymers of choice for these applications because of their unique combination of chemical, physical, and mechanical properties (i). Another class of polymers which have been investigated for these applications are the po arylene ether)s that can be prepared by the nucleophilic displacement of activated aromatic dihalides alkali metal bisphenoxides. Heterocycles such as benzoxazoles (2), imidazoles (5), phenylquinoxalines (.4), and 1,2,4-triazoles (5) have been incorporated within poly(arylene ethers) utilizing this thetic procedure. 

Since the invention of integrated circuits (ICs), polyimides as heat-resistant organic polymers have been applied to insulation materials in electronics devices such as flexible printed circuit boards (FPCs), interlayer dielectrics, buffer coatings, and tape automated bonding (TAB). A polyimide thin layer is easily... 

Because of the high functional values that polyimides can provide, a small-scale custom synthesis by users or toll producers is often economically viable despite high cost, especially for aerospace and microelectronic applications. For the majority of industrial applications, the yellow color generally associated with polyimides is quite acceptable. However, transparency or low absorbance is an essential requirement in some applications such as multilayer thermal insulation blankets for satellites and protective coatings for solar cells and other space components (93). For interlayer dielectric applications in semiconductor devices, polyimides having low and controlled thermal expansion coefficients are required to match those of substrate materials such as metals, ceramics, and semiconductors used in those devices (94). 

Aromatic polyimides have found extensive use in electronic packaging due to their high thermal stability, low dielectric constant, and high electrical resistivity. Polyimides have been used as passivation coatings, (1) interlayer dielectrics, (2) die attach adhesives, (3) flexible circuitry substrates, (4) and more recently as the interlevel dielectric in high speed IC interconnections. (5) High speed applications require materials with a combination of low dielectric constant, flat dielectric response versus frequency and low water absorption. 

Polyimides have been widely used in the advanced microelectronics industry such as passivation or stress-relief layers for high-density electronic packaging, interlayer dielectric layers for wafer-level semiconductor fabrication, or alignment layers for liquid crystals in advanced liquid crystal display devices (LCDs) owing to their outstanding thermal, mechanical and good insulation properties with low dielectric constant, good adhesion to common substrates and superior chemical... 

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