Improved RF Devices for Future Adaptive Wireless Systems Using Two-Sided Contacting and AlN Cooling

Abstract

Abstract-This paper reviews special RF/microwave silicon device implementations in a process that allows two-sided contacting of the devices: the back-wafer contacted Silicon-On-Glass (SOG) Substrate-Transfer Technology (STT) developed at DIMES. In this technology, metal transmission lines can be placed on the low-loss glass substrate, while the resistive/capacitive parasitics of the silicon devices can be minimized by a direct two-sided contacting. Focus is placed here on the improved device performance that can be achieved. In particular, high-quality SOG varactors have been developed and an overview is given of a number of innovative highly-linear circuit configurations that have successfully made use of the special device properties. A high flexibility in device design is achieved by two-sided contacting because it eliminates the need for buried layers. This aspect has enabled the implementation of varactors with special 2 doping profiles and a straightforward integration of complementary bipolar devices. For the latter, the integration of AlN heatspreaders has been essential for achieving effective circuit cooling. Moreover, the use of Schottky collector contacts is highlighted also with respect to the potential benefits for the speed of SiGe heterojunction bipolar transistors (HBTs).

Low temperature pure boron layer deposition for Si diode and micromachining applications

“…Situations where the latter could have been useful were in the past encountered in connection with the fabrication of photodetectors and silicon-on-glass varactors [18,[115][116][117]. Both involved microstructuring of the Si using conventional dielectric masking layers, to either reduce resistance/capacitance parasitics [118][119][120] or to fabricate through wafer apertures [115]. In the course of this past research the robustness of the B-layers used for diode fabrication with respect to etching in TMAH or KOH became apparent and it had to be taken into account when designing process flows.…”

Anti-Series Varactor Network With Improved Linearity Performances in the Presence of Inductive and Capacitive Parasitics

“…Moreover, this network of parallel diodes resulting in the size ⋅ may be augmented with an additional diode of size to represent the anti-series topology, and the inductances in the resulting network may be summed as an equivalent series inductance . The expression of is given by (12). Note that (12) neglects any mutual inductance phenomena for simplification purposes but still adequately captures the negative impact of on linearity.…”

“…It shows a significant degradation of 2 2 − 1 with an increasing between 0 and ~300 . This is because an increasing (and according to (12)) in series with ( ) translates into a decreasing resulting reactance seen by , hence an increasing , which in turn translates into an increasing RF voltage across each nonlinear junction capacitance within the varactor and consequently higher 2 2 − 1 . The peak at ≈ 400 results from ≈ 550 (12) resonating at the frequency 2 0 with 0 ≈ 0.9pF (computed with ( 11)) when = 0 .…”

“…All the solutions in Table I are demonstrated at ∼2.15GHz or lower and are implemented either on SoG MMIC [12], GaAs MMIC or GaN MMIC technologies. The limited frequency of operation and MMIC integration aspects in these works are of particular importance.…”

Low-Complexity Full-Melt Laser-Anneal Process for Fabrication of Low-Leakage Implanted Ultrashallow Junctions

“…The effects of this have been detected up to 0.6 lm away from the implant itself, for example, as a reduced breakdown voltage in devices such as back-wafer-contacted varactors and bipolar transistors. 21 When injected into boron-doped p-type silicon, the interstitials also cause a significant level of dopant deactivation 22 that is readily detected by C-V profiling, an example of which is shown in Fig. 10.…”