Stress-buffer and passivation processes for Si and GaAs IC's and passive components using photosensitive BCB: process technology and reliability data

Abstract

Polymer coatings are applied to chips and passive components to provide stress relief between the device/component and the plastic package and/or to provide mechanical and environmental protection. The semiconductor industry is actively pursuing a one mask, photosensitive dielectric process for stressbuffer and secondary passivation of memory die. A one mask photo-benzocyclobutene (BCB) process is compared to traditional two mask wet etch processes. This new one mask process reveals 1/3 the total wafer processing time and equivalent reliability (traditional MIL 883C testing) for passivated 100 lead static random access memory components (SRAM's).

Aqueous-Base-Developable Benzocyclobutene (BCB)-Based Material Curable in Air

“…Water was depleted in about 2 min when the relative humidity (RH) was changed from 85% RH to 5% RH. Like DVS-bisBCB based polymer [4], aqueous-base-developable BCB thin film dries off very quickly, as demonstrated in Fig. 10.…”

“…Photosensitive benzocyclobutene (BCB)-based polymer has been widely used in packaging and bumping applications [1]- [4]. 1 It is negative-tone and requires an organic solvent as developer.…”

Variable Frequency Microwave and Convection Furnace Curing of Polybenzoxazole Buffer Layer for GaAs HBT Technology

“…They are utilized in both front-end and back-end semiconductor processing, including as interlevel dielectric, redistribution layer, final passivation, stress buffer layer, and as encapsulants in chip-scale and wafer-level packaging [1]- [9]. Some of these polymers include parylene, polyimide, benzocyclobutene, and polybenzoxazole (PBO).…”

“…In semiconductor processing, the buffer layer should have good physical, mechanical, chemical, electrical, and thermal characteristics, and should be compatible with subsequent processing, including back-side wafer process steps, such as wafer thinning and scribe and break, and assembly process steps, such as die-pick and attach, wirebonding, and mold compound application [1], [4], [13], [26], [28], [38]. In all of these cases, the material used for the buffer layer also has to be stable and be compatible with the materials used in the above processes, including wafer crystal bond material, mold compound, epoxy, and the chemicals used in these processing steps, such as acetone.…”

Overview of Photo-definable Benzocyclobutene Polymer.

“…Derived from these properties, applications have been developed in: bumping/wafer level packaging [5][6], Ga/As chip ILD [7], optical wave guide [8], flat panel display [9], and lately in BCB-coated Cu foil for build-up board [10]. This article summaries the chemistry, the relevant properties and the typical process of photo definable divinylsiloxane bisbenzocyclobutene (DVS-BCB) commercialized by Dow Chemical as CYCLOTENETM resin system.…”