An LDMOS with nearly rectangular-shape safe operation area （SOA） and low specific on-resistance is proposed. By utilizing a split gate, an electron accumulation layer is formed near the surface of the n-drift region to improve current conduction capability during on-state operation. As a result, the specific on-resistance can be low- ered down to 74.7 m^2.cm2 for a 600 V device from simulation. Furthermore, under high-voltage and high-current conditions, electrons and holes flow as majority carriers in the n-drift region and p-type split gate, respectively. Due to charge compensation occurring between holes and electrons, the local electric field is reduced and impact ion- ization is weakened in the proposed device. Therefore, a higher on-state breakdown voltage at large V6s is obtained and snap-back is suppressed as well.
A superjunction（SJ） structure using a high-k（Hk） insulator is studied and optimized by using an analytic model.Results by using the proposed model match well with that of numerical calculations.Numerical calculation results show that,only needing an Hk insulator with a permittivity of ε_I=5ε_S,the optimum specific on-resistance of the MOSFET applying the proposed structure is about 8%-20%lower than that of the conventional SJ-MOSFET with V_B = 200-1000 V.An example with V_B = 400 V shows that,the permissible error range of doping concentration of the p-region to maintain above 80%of V_B is from —37%to ＋32%for the former and is only from-13%to ＋13%for the latter.
The phenomenon that the wide P-emitter region in the conventional reverse conducting insulated gate bipolar transistor （RC-IGBT） results in the non-uniform current distribution in the integrated freewheeling diode （FWD）, and then causes a parasitic thyristor to latch-up during its reverse-recovery process, which induces a hot spot in the local region of the device is revealed for the first time. Furthermore, a novel RC-IGBT based on double trench IGBT is proposed. It not only solves the snapback problem but also has uniform current distribution and high ruggedness during the reverse-recovery process.
Novel reverse-conducting IGBT （RC-IGBT） with anti-parallel MOS controlled thyristor （MCT） is proposed. Its major feature is the introduction of an automatically controlled MCT at the anode, by which the anodeshort effect is eliminated and the voltage snapback problem is solved. Furthermore, the snapback-free characteristics can be realized in novel RC-IGBT by a single cell with a width of 10 μm with more uniform current distribution. As numerical simulations show, compared with the conventional RC-IGBT, the forward conduction voltage is reduced by 35% while the reverse conduction voltage is reduced by 50% at J = 150 A/cm2.
A physically based equation for predicting required p-emitter length of a snapback-free reverse- conducting insulated gate bipolar transistor （RC-IGBT） with field-stop structure is proposed. The n-buffer resis- tances above the p-emitter region with anode geometries of linear strip, circular and annular type are calculated, and based on this, the minimum p-emitter lengths of those three geometries are given and verified by simulation. It is found that good agreement was achieved between the numerical calculation and simulation results. Moreover, the calculation results show that the annular case needs the shortest p-emitter length for RC-IGBT to be snapback-free.
