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Design and Characterization of RF-LDMOS Transistors and Si-on-SiC Hybrid Substrates

Lotfi, Sara (author)
Uppsala universitet,Fasta tillståndets elektronik
Olsson, Jörgen, Prof. (thesis advisor)
Uppsala universitet,Fasta tillståndets elektronik
Vallin, Örjan, Dr. (thesis advisor)
Uppsala universitet,Fasta tillståndets elektronik
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Raskin, Jean-Pierre, Prof. (opponent)
Université catholique de Louvain, Institute of Information and Communication Technologies, Electronics and Applied Mathematics
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 (creator_code:org_t)
ISBN 9789155488529
Uppsala : Acta Universitatis Upsaliensis, 2014
English 58 s.
Series: Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, 1651-6214 ; 1113
  • Doctoral thesis (other academic/artistic)
Abstract Subject headings
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  • With increasing amount of user data and applications in wireless communication technology, demands are growing on performance and fabrication costs. One way to decrease cost is to integrate the building blocks in an RF system where digital blocks and high power amplifiers then are combined on one chip. This thesis presents LDMOS transistors integrated in a 65 nm CMOS process without adding extra process steps or masks. High power performance of the LDMOS is demonstrated for an integrated WLAN-PA design at 2.45 GHz with 32.8 dBm output power and measurements also showed that high output power is achievable at 5.8 GHz. For the first time, this kind of device is moreover demonstrated at X-band with over 300 mW/mm output power, targeting communication and radar systems at 8 GHz. As SOI is increasing in popularity due to better device performance and RF benefits, the buried oxide can cause thermal problems, especially for high power devices. To deal with self-heating effects and decrease the RF substrate losses further, this thesis presents a hybrid substrate consisting of silicon on top of polycrystalline silicon carbide (Si-on-poly-SiC). This hybrid substrate utilizes the high thermal conductivity of poly-SiC to reduce device self-heating and the semi-insulating properties to reduce RF losses. Hybrid substrates were successfully fabricated for the first time in 150 mm wafer size by wafer bonding and evaluation was performed in terms of both electrical and thermal measurements and compared to a SOI reference. Successful LDMOS transistors were fabricated for the first time on this type of hybrid substrate where no degradation in electrical performance was seen comparing the LDMOS to identical transistors on the SOI reference. Measurements on calibrated resistors showed that the thermal conductivity was 2.5 times better for the hybrid substrate compared to the SOI substrate. Moreover, RF performance of the hybrid substrate was investigated and the semi-insulating property of poly-SiC showed to be beneficial in achieving a high equivalent substrate parallel resistance and thereby low substrate losses. In a transistor this would be equal to better efficiency and output power. In terms of integration, the hybrid substrate also opens up the possibility of heterogeneous integration where silicon devices and GaN devices can be fabricated on the same chip.

Subject headings

TEKNIK OCH TEKNOLOGIER  -- Elektroteknik och elektronik -- Annan elektroteknik och elektronik (hsv//swe)
ENGINEERING AND TECHNOLOGY  -- Electrical Engineering, Electronic Engineering, Information Engineering -- Other Electrical Engineering, Electronic Engineering, Information Engineering (hsv//eng)

Keyword

LDMOS
RF
losses
crosstalk
silicon carbide
Si-on-SiC hybrid substrate
wafer bonding
CMOS
Teknisk fysik med inriktning mot elektronik
Engineering Science with specialization in Electronics

Publication and Content Type

vet (subject category)
dok (subject category)

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