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

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 excell...

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Bibliographic Details
Published in:IEEE transactions on semiconductor manufacturing 2007-08, Vol.20 (3), p.323-332
Main Authors: Yota, J., Ly, H., Ramanathan, R., Hsiang-Chih Sun, Barone, D., Nguyen, T., Katoh, K., Ohe, M., Hubbard, R.L., Hicks, K.
Format: Article
Language:English
Subjects:
Buffer layer
Buffer layers
convection curing
Convection furnaces
Curing
Degradation
Devices
Frequency
Furnaces
GaAs
Gallium arsenide
Gallium arsenides
heterojunction bipolar transistor (HBT)
Heterojunction bipolar transistors
Microwave technology
Microwaves
polybenzoxazole (PBO)
polymer
Semiconductors
Stress
Temperature
Thermal degradation
variable frequency microwave (VFM) curing
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Summary: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.
ISSN:0894-6507
1558-2345
DOI:10.1109/TSM.2007.901410