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It is well recognized that excellent power performance and linearity can be achieved at low cost using Laterally Diffused Metal-Oxide-Semiconductor (LDMOS) field effect transistor. In fact, it is the preferred technology for base station applications as well as many other RF and microwave applications (Wood et al., 2006). But system’s availability and reliability are important parameters in terms of ownership cost for the customer. That’s the reason why a precise knowledge of the device’s degradation mechanisms and lifetime is of paramount importance. Thus modelling and reliability study of the LDMOS technologies are being increasingly used by the power amplifier design community. Numerous applications for power integrated circuits are emerging, which needs to operate at high temperatures. In the radar field, a crucial issue to tackle with is the reliability of RF LDMOS subjected to RF pulses with high drain-source DC bias for maximum output power under wide temperature range (Maanane et al., 2006). Those requirements raise the stress (thermal, electrical and RF power) applied to the transistors and have a direct impact on their lifetime. A deep understanding of this impact is necessary for better device and radar module reliability assessment. Moreover, a study has been engaged to elaborate new methods for RF power device reliability investigations under pulsed RADAR conditions (Maanane et al., 2004). In this chapter, we present an innovative reliability bench designed and implemented in our laboratory by (Maanane et al., 2004). It is specifically dedicated to high RF power device lifetime tests under pulse conditions for radar application and able to keep track of RF powers, voltages and temperatures whose values correspond to stress operating conditions. It clearly appears the need to track electrical parameters that lead to modifications of both the device RF performances and the critical electrical parameters with time (Poole & Walshak, 1974, Sirenza Microdevices, 2002). In this work, we will go step by step through the individual characterization issues and develop the model parameters extraction strategies which will provide the base for accurate device modelling. A commercial RF LDMOS transistor has been chosen for RF life-tests and a complete device electric characterization, I-V, C-V and S parameters, before and after test ageing has been |
