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).
Photosensitive Benzocyclobutene (Photo-BCB) has been widely reported on for use as a dielectric material in multilayer packaging applications, including: MCMs, IO redistribution, and flat panel display. Photo-BCB has many properties which are highly attractive for these applications, including: a simple processing scheme which is compatible with existing IC manufacturing techniques, low level of ionics, low moisture uptake, low cure temperatures, rapid thermal curing, high optical transparency, high planarization level, high thermal stability, high solvent resistance, very low outgassing, and a low dielectric constant.Photo-BCB is also being actively evaluated for wafer-level applications such as stress-buffer and passivation. In this paper, we will discuss the Photo-BCB properties and processing steps as they relate to these two applications. We will also compare the manufacturing scheme based on a one mask process for memory die, to the steps in a two mask process for stress-buffer and passivation.
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