Multilayer High density

Many polymers are used in the fabrication of multilayer, high-density electronic circuitry consisting of silicon chips containing large numbers of integrated circuits. However, most of the polymers function in a temporary role in photoresist systems that are removed before the devices are completed. 

A number of other applications has been proposed, including SHG (see Structure of the multilayers ), electrochromism (see Chemical modifications of the multilayers ), high density rechargeable lithium-ion batteries [267,268], tunable color filters [227], or pH indicators [232]. A pH-sensitive optrode has also been proposed [209], but first attempts were unsuccessful due to the absence of response of the pH-sensitive dye used (phenol red) to the pH of the surrounding solution, when trapped in the multilayer. 

C. C. Shiflett, D. B. BuchhoF, and C. C. Faudskar, "High-Density Multilayer Hybrid Circuits Made with Polymer Insulating Layers (Polyhic s)," Society of Hybrid Microelectronics Proceedings, 1980, pp. 481—486. 

Molecular calculations provide approaches to supramolecular structure and to the dynamics of self-assembly by extending atomic-molecular physics. Alternatively, the tools of finite element analysis can be used to approach the simulation of self-assembled film properties. The voxel4 size in finite element analysis needs be small compared to significant variation in structure-property relationships for self-assembled structures, this implies use of voxels of nanometer dimensions. However, the continuum constitutive relationships utilized for macroscopic-system calculations will be difficult to extend at this scale because nanostructure properties are expected to differ from microstructural properties. In addition, in structures with a high density of boundaries (such as thin multilayer films), poorly understood boundary conditions may contribute to inaccuracies. 

To restrict water entry into certain parts of the delivery system and to separate the drug layer from the osmotic layer, different materials are used as barrier layers. In a multilayered reservoir, the water-permeable coat consists of hydrophilic polymers. In contrast, water-impermeable layers are formed from latex materials such polymethacrylates (Table 7.1). Further, a barrier layer can be provided between the osmotic composition and the drug layer that consists of substantially fluid-impermeable materials such as high-density polyethylene, a wax, a rubber, and the like.20... 

The final steps involve deposition of fhe interconnect metal (Figure4.25, step s). Copper is now the metal-of-choice due to its more desirable electrical resistivity, relative to A1 (1.7 dQ cm v. 2.7 xO cm, respectively) that was exclusively used in earlier ICs. Due to its low resistivity and high density, titanium nitride is an efficient barrier level that prevents surface oxidation of Cu, as well as the interdiffiision of Cu into adjacent layers. To yield the final multilayer IC shown in step t of Figure 4.25, steps p-s are repeated. Indeed, a long complex process that took weeks in the making. 

Ordered polymer films made from poly benzthiazole (PBZT) and poly benzoxazole (PBO) can be used as substrates for multilayer printed circuit boards and advanced interconnects to fill the current need for high speed, high density packaging. Foster-Miller, Inc. has made thin substrates (0.002 in.) using biaxially oriented liquid crystal polymer films processed from nematic solutions. PBZT films were processed and laminated to make a substrate with dielectric constant of 2.8 at 1 MHz, and a controllable CTE of 3 to 7 ppm/°C. The films were evaluated for use in multilayer boards (MLBs) which require thin interconnect substrates with uniform controllable coefficient of thermal expansion (CTE), excellent dielectric properties, low moisture absorption, high temperature capability, and simple reliable processing methods. We found that ordered polymer films surpass the limitations of fiber reinforced resins and meet the requirements of future chip-to-chip interconnection. 

---