LDMOS


LDMOS is a planar double-diffused MOSFET used in amplifiers, including microwave power amplifiers, RF power amplifiers and audio power amplifiers. These transistors are often fabricated on p/p+ silicon epitaxial layers. The fabrication of LDMOS devices mostly involves various ion-implantation and subsequent annealing cycles. As an example, The drift region of this power MOSFET is fabricated using up to three ion implantation sequences in order to achieve the appropriate doping profile needed to withstand high electric fields.
The silicon-based RF LDMOS is the most widely used RF power amplifier in mobile networks, enabling the majority of the world's cellular voice and data traffic. LDMOS devices are widely used in RF power amplifiers for base-stations as the requirement is for high output power with a corresponding drain to source breakdown voltage usually above 60 volts. Compared to other devices such as GaAs FETs they show a lower maximum power gain frequency.
Manufacturers of LDMOS devices and foundries offering LDMOS technologies include TSMC, , Tower Semiconductor, GLOBALFOUNDRIES, Vanguard International Semiconductor Corporation, STMicroelectronics, Infineon Technologies, RFMD, NXP Semiconductors, SMIC, MK Semiconductors, Polyfet and Ampleon.

History

The invention of the metal–oxide–semiconductor field-effect transistor by Mohamed M. Atalla and Dawon Kahng at Bell Labs in 1959 was a breakthrough in power electronics. Generations of power MOSFETs enabled power designers to achieve performance and density levels not possible with bipolar transistors. In 1969, the DMOS with self-aligned gate was first reported by Y. Tarui, Y. Hayashi and Toshihiro Sekigawa of the Electrotechnical Laboratory.
In 1977, Hitachi introduced the LDMOS, a planar type of DMOS. Hitachi was the only LDMOS manufacturer between 1977 and 1983, during which time LDMOS was used in audio power amplifiers from manufacturers such as HH Electronics and Ashly Audio, and were used for music, high-fidelity equipment and public address systems.

RF LDMOS

In the early 1990s, RF LDMOS was introduced, as RF power amplifiers for cellular network infrastructure. They eventually displaced RF bipolar transistors, because RF LDMOS provided superior linearity, efficiency and gain along with lower costs. With the introduction of the 2G digital mobile network, LDMOS became the most widely used RF power amplifier technology in 2G and then 3G mobile networks. By the late 1990s, the RF LDMOS had become the dominant RF power amplifier in markets such as cellular base stations, broadcasting, radar, and Industrial, Scientific and Medical band applications. LDMOS has since enabled the majority of the world's cellular voice and data traffic.
In the mid-2000s, RF power amplifiers based on single LDMOS devices suffered from relatively low efficiency when used in 3G and 4G networks, due to the higher peak-to-average power of the modulation schemes and CDMA and OFDMA access techniques used in these communication systems. In 2006, the efficiency of LDMOS power amplifiers was boosted using typical efficiency enhancement techniques, such as Doherty topologies or envelope tracking.
, RF LDMOS is the dominant device technology used in high-power RF power amplifier applications for frequencies ranging from 1MHz to over 3.5GHz, and is the dominant RF power device technology for cellular infrastructure., RF LDMOS is the leading technology for a wide range of RF power applications., LDMOS is the de facto standard for power amplifiers in mobile networks such as 4G and 5G.

Applications

Common applications of LDMOS technology include the following.
Common applications of RF LDMOS technology include the following.