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" Sparse gallium arsenide to silicon metal waferbonding for heterogeneous monolithic microwave integrated circuits "
Bickford, Justin Robert
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Latin Dissertation
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English
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898412
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TL59v7p40c
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| Main Entry
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Beahrs, Robert Oliver
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Sparse gallium arsenide to silicon metal waferbonding for heterogeneous monolithic microwave integrated circuits\ Bickford, Justin Robert
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| Date
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2008
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2008
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| Abstract
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Waferbonding is a technique that integrates different semiconductors together, in order to obtain hybrid structures that exploit the strengths of each material. Work was done at the University of California at San Diego to investigate the waferbonding of III/V compound semiconductors to silicon using a metal interface. GaAs and other III/V compound semiconductors surpass silicon in their ability to create high performance microwave devices, while silicon offers an inexpensive platform with a proven digital architecture that can interface with microwave devices and support passive components and driver circuitry. Intimate integration of the two will be required, as mixed RF/digital and optical/digital systems for communications devices such as cell phones, wi-fi, and optical communications systems are pushed smaller, faster, and to higher power. The metalbonding implementation of a proposed heterogeneous monolithic microwave integrated circuit (HMMIC) system was investigated, and was shown to extend the capabilities of existing homogeneous monolithic microwave integrated circuit (MMIC) systems. The main goals of this work were two-fold; first to implement a robust heterogeneous integration technique, and second, to show that this approach uniquely improves upon existing microwave integration technology. The metalbonding technique investigated sparsely integrated GaAs structures onto silicon, in pursuit of this HMMIC scheme. Both bottom -up and top-down fabrication methods were implemented. These approaches required the development of a myriad of meticulously designed fabrication procedures capable of avoiding the many incompatibilities between the compound semiconductor, bondmetal, and silicon materials. The bondmetal interface, provided by these techniques, broadens the scope of existing monolithic microwave integrated circuit technology design possibilities. Essential bond interface properties were measured to establish the performance of this heterogeneous integration method. Passive bond test structures were designed, fabricated, and measured to extract the bond interface electrical behavior, electrical contact resistivity, and thermal conductivity. The In-Pd alloy, employed as the bondmetal interface between these GaAs/ silicon test structures, provided a universal ohmic contact between all doping combinations. The bond interface contact resistivity between n-type GaAs and p- type Si was found to be 1.03x10⁻⁵ ohm-cm² and a bondmetal thermal conductivity of 2.51 W/m-K was also determined. In addition, passive un-bonded and bonded microwave waveguides were constructed to test the microwave propagation properties of the bondmetal. The characteristics of these test structures qualified the metalbonding technique for use in heterogeneous microwave systems. The successful fabrication of these structures demonstrated that this metalbonding method could be extended to active devices as well, which would be of similar size, form factor, and utilize the same fabrication methods. An un-bonded active microwave waveguide, similar to one which could become common in heterogeneous microwave systems, was investigated to illustrate its unique microwave properties. This un-bonded traveling wave PIN semiconductor waveguide propagated microwaves in a 'slow-wave' manner, as a consequence of its diode structure
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Bickford, Justin Robert
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UC San Diego
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