Copper / Benzocyclobutene Multi Layer Wiring - A flexible base Technology for Wafer Level Integration of passive Components

Abstract

This paper describes the wafer level integration of coils, capacitors and resistors using copper / Benzocyclobutene (Cu / BCB) thin film multi layer wiring. Examples for the application of this technology like integration of passives as above chip structures, realization of integrated passive devices as well as fabrication of thin film substrates with integrated passives prove Cu/BCB multi layer wiring to be a versatile base technology for the application-specific integration of passive components.The basic approach of using BCB as dielectric material is discussed to allow integrating high quality, but only small value capacitors in the range of some Pico Farads, which is due to the low dielectric constant of the material. In order to increase the capacitance density a new process allowing to replace the BCB locally by a thin glass layer in the areas of capacitors was evaluated. Since the BCB is only replaced in the areas of capacitors and still present in the other areas of the multi layer construction, the advantages of using BCB as dielectric material for multi layer wiring still apply. The evaluation of the new capacitor dielectric shows, that a 0.5 µm thick glass dielectric features a 26 times higher capacitance density compared to BCB with a thickness of 8 µm, as it has been used in the standard build-up for RF LC-filter integration so far.In order to show the capability of the new glass dielectric regarding size reduction, an existing layout of an integrated passive device with LC-filters is compared with a redesign based on the new technology. By using a 1 µm thick glass layer as dielectric instead of 8 µm thick BCB the total size of the device could be reduced by 28 %.

A wafer-scale packaging structure with monolithic microwave integrated circuits and passives embedded in a silicon substrate for multichip modules for radio frequency applications

“…Furthermore, because the sidewall of HARVIs cannot be well deposited by the sputtering process, the electrical yields of the vias decrease with the increase in the aspect ratio [11]. In order to achieve large thickness (>20 μm) of ILDs and meet the requirement for HARVI, an approach including electroplating gold bumps first and then coating them with BCB film is proposed [20,21]. This is suitable for the fabrication of gold bumps on the substrate and requires thin die (<30 μm) to match with the height of the metal stud of HARVI.…”

Wafer level 3D system integration based on silicon interposers with through silicon vias

“…Based on the demands of the application, different kinds of metal or solder can be deposited as IO terminal pads (Figure 1 / picture 7). [5,6] After the completion of front side processing of the interposer wafers including TSV formation, high density wiring and contact formation, the TSVs have to be accessed and connected from their backside. That means the silicon between TSV bottom and wafer backside has to be removed and suitable backside connections to the TSVs have to be formed.…”

Inkjet Printing of a Benzocyclobutene-Based Polymer as a Low-k Material for Electronic Applications

“…Benzocyclobutene (BCB)-based polymers are very interesting polymers for the abovementioned applications. The BCB-based polymer is a thermoset polymer adhesive that features a very low k (∼2.65 for the frequency range 10 Hz to 1 MHz), reduced copper diffusion and moisture absorption, an excellent planarization, and high resistance to chemicals. ,− Its excellent adhesion properties toward silicon (Si) made it suitable for wafer bonding and 3D integration. , The BCB-based polymer is usually processed as a solvent-based thermoset polymer. First, the solution is applied to the Si wafer, then the solvent is allowed to evaporate, and finally the BCB-based polymer is cured by heating.…”