Photosensitive polybenzoxazole (PBO) film has been used in GaAs heterojunction bipolar transistor (HBT) technology for stress buffer and mechanical protection layer applications. However, this film needs to be cured at high temperatures for a long period of time in order to obtain its desired excellent material characteristics. High-temperature curing can result in degradation to the electrical characteristics and performance of the underlying GaAs devices due to limited thermal budget. In this paper, we have characterized the effects of curing the PBO film on GaAs HBT wafers using a conventional convection furnace and using a variable frequency microwave (VFM) furnace. The results show that a VFM cure can achieve similar excellent physical, mechanical, thermal, and chemical material characteristics at a lower curing temperature and in a much shorter time, as compared to convection furnace curing, therefore resulting in minimal GaAs device degradation. Based on these results, an optimum curing condition using the VFM method can be obtained that satisfies both stress buffer layer material and device requirements for GaAs HBT technology.
We have been developing novolak-based chemically amplified positive resists for the next generation photomask fabrication. In this paper, we report two different types of EB resists : RE-5 150P and RE-5 160P. Our resist materials consist offour components : a novolak matrix resin, a polyphenol compound, an acid generator and a dissolution inhibitor.We applied two different types of dissolution inhibitors to our resist materials. RE-5150P and RE-5160P employed respective a high and a low activation energy type of a dissolution inhibitor. RE-5150P has high contrast and RE-5160P has wide process window. As a result, we confirmed RE-5150P could achieve 0.24 ji m line-and-space vertical resist pattern profiles at 8 i C/cm2 using the 50kV EB-wnter HL-800M, and RE-5 160P has wide process window : post exposure delay stability is over 24hrs. and post coating delay stability is over 3Odays.
Because polyimide (PI) / polybenzoxazole (PBO) materials make semiconductor reliability drastically improved, they have been applied to stress buffer layer for over 30 years. Their purpose used to prevent IC chip from mechanical attack by molding compound filler. In recent years, PI / PBO are required to perform stress relief. In addition to this, they have come to be used as dielectric layer for Cu redistribution layer application as semiconductor package type changes. Therefore, various properties and balanced performances are necessary for PI / PBO materials. This paper reviews latest PI / PBO technologies in semiconductor application.
The effect of m/p-cresol novolak molecular-weight-distribution (MWD) and dissolution inhibitor structure on resist performance were investigated. A novolak resin richer in p-cresol ratio gave a large dissolution inhibition capability of polymeric dissolution inhibitor, tetrahydropyranyl (THP) protected-polymeric dissolution inhibitor. In particular, a high molecular-weight novolak resin richer in p-cresol ratio was regarded as an effective matrix of a chemical amplification (CA) positive resist. THP protectedphenolic compounds with extended backbone structures showed a large dissolution inhibition. The resist with MWD controlled resin and a THP-protected phenolic compound can achieve high resolution patterns (100-nm contact holes ) with high sensitivity (6.0 µC/cm2).
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