Superjunction has arguably been the most creative and important concept in the power device field since the introduction of the insulated gate bipolar transistor (IGBT) in the 1980s. It is the only concept known today that has challenged and ultimately proved wrong the well-known theoretical study on the limit of silicon in high-voltage devices. This paper deals with the history, device and process development, and the future prospects of Superjunction technologies. It covers fundamental physics, technological challenges as well as aspects of design and modeling of unipolar devices, such as CoolMOS. The superjunction concept is compared to other methods of enhancing the conductivity of power devices (from bipolar to employment of wide-bandgap materials) to derive its set of benefits and limitations. This paper closes with the application of the superjunction concept to other structures or materials, such as terminations, superjunction IGBTs, or silicon carbide Field Effect Transistors (FETs).

Superjunction Power Devices, History, Development, and Future Prospects

A monolithic lateral double diffused MOSFET (LDMOST) based on the super junction (SJ) concept is proposed to significantly improve the device's on-state and off-state characteristics. The device structure features a split drift region made of two parts: 1) an SJ structure that extends over most of the drift region and 2) a terminating reduced surface field (RESURF) region occupying a portion of the drift region adjacent to the n/sup +/ drain. This structure suppresses substrate-assisted depletion effects and ensures complete depletion and near uniform electric field distribution over the entire drift region. In the on-state, the high conductivity of the SJ drift region results in a significant improvement in the specific on-resistance for a given breakdown voltage (BV) and, hence, a reduction in the on-state, switching, and gate-drive losses. In the off-state, the RESURF region, located near the n/sup +/ drain, effectively neutralizes the substrate-assisted depletion effects and results in high BV.

Sj/resurf ldmost

A semiconductor component having a semiconductor body comprises a blocking pn junction, a source zone of a first conductivity type and bordering on a zone forming the blocking pn junction of a second conductivity type complementary to the first conductivity type, and a drain zone of the first conductivity type. The side of the zone of the second conductivity type faces the drain zone forming a first surface, and in the region between the first surface and a second surface areas of the first and second conductivity type are nested in one another. The areas of the first and second conductivity type are variably so doped that near the first surface doping atoms of the second conductivity type predominate, and near the second surface doping atoms of the first conductivity type predominate. Furthermore a plurality of floating zones of the first and second conductivity type is provided.

High-voltage semiconductor component

A power MOSFET is provided that includes a substrate of a first conductivity type. An epitaxial layer also of the first conductivity type is deposited on the substrate. First and second body regions are located in the epitaxial layer and define a drift region between them. The body regions have a second conductivity type. First and second source regions of the first conductivity type are respectively located in the first and second body regions. A plurality of trenches are located below the body regions in the drift region of the epitaxial layer. The trenches, which extend toward the substrate from the first and second body regions, are filled with an epitaxially layered material that includes a dopant of the second conductivity type. The dopant is diffused from the trenches into portions of the epitaxial layer adjacent the trenches.

High voltage power MOSFET having low on-resistance

A super-junction lateral double diffused MOST (SJ-LDMOST) in silicon-on-sapphire technology, targeting power integrated circuits (PICs), is proposed, implemented and characterized. The proposed structure eliminates "substrate-assisted-depletion" effects in lateral SJ devices thus achieving charge compensation between the n and p SJ-pillars as well as a uniform electric field distribution in the drift region in the off-state. Three-dimensional (3-D) simulations of the device, using realistic aspect ratios for the SJ-pillars, indicate that a significant reduction in specific on-resistance for a given breakdown voltage can be achieved as compared to conventional reduced surface field (RESURF) devices. Experimental devices were implemented using a seven mask CMOS compatible process. Fabricated SJ-LDMOSTs with a drift region length of 66 /spl mu/m and a pillar aspect ratio of 1.2 /spl mu/m/0.7 /spl mu/m (width/height) exhibit a specific on-resistance of 0.82 /spl Omega/.cm/sup 2/ and a breakdown voltage (BV) ranging between 500 and 600 V corresponding to less than 8.5% charge imbalance in the pillars.

Super-junction LDMOST on a silicon-on-sapphire substrate

Theory of a novel voltage-sustaining layer for power devices

A novel high-voltage generic power device structure based on an optimum variation in the lateral doping profile is proposed. The structure is implemented with a series of zones having piece-wise constant doping located in the field sustaining region of the device. The structure has been evaluated as an integrated component in a range of high-voltage devices, including MOST, JFET and BJT. The simulation results show the breakdown voltages achieved by the different structures can reach 85% of that, calculated for an equivalent parallel plane abrupt junction. The on-resistance of each device is very low while the switching speed is very high. Among these devices, the MOST shows the best improvement in performance. Since these lateral devices are compatible with modern sub-micrometre IC-technology, and are capable of self-isolation, they are very attractive for applications in HVIC and PIC processes.

C. A. T. Salama

Papers

Theory of a novel voltage-sustaining layer for power devices

Lateral high-voltage devices using an optimized variational lateral doping