Abstract
An improved trench lateral double-diffused MOSFET (T-LDMOS) is proposed. It has a quasi vertical super junction (QVSJ) drift region and adopts a resistive field plate (RFP) to help QVSJ satisfy charge-balance. The realization of RFP barely complicates the device fabrication, but it motivates QVSJ to significantly improve the relationship between breakdown voltage (BV) and specific on-state resistance ( ${R} _{\mathrm{ON,SP}}$ ). The simulation results show that compared with the conventional QVSJ T-LDMOS, the proposed one gains the ${R} _{\mathrm{ON,SP}}$ reduced by about 79% under the same BV requirement of about 500 V. It therefore presents an excellent figure of merit (FOM) (FOM = BV2/ ${R} _{\mathrm{ON,SP}}$ , Baliga’s FOM) up to 29.8 MW/cm2, which is superior to the prior art and exhibits a bright prospect of saving energy.
Highlights
As a famous power device, the lateral double-diffused MOSFET (LDMOS) is widely used in power ICs since its coplanar electrodes facilitate the system integration on one chip
The wide gap of Pon stems from the aforementioned distinction of figure of merit (FOM) and, as a result, TLD+quasi vertical super junction (QVSJ)+resistive field plate (RFP) exhibits a much smaller Ptotal than the others, especially at the frequency of 10∼200 kHz which is usually adopted in a switching mode power supply (SMPS) [1]
In the fabrication process of TLD+QVSJ+RFP, the RFP layer coats wafer without distinction and is pruned by Chemical Mechanical Polishing (CMP) without masks, so the realization of it barely complicates the process compared with that for TLD+QVSJ
Summary
As a famous power device, the lateral double-diffused MOSFET (LDMOS) is widely used in power ICs since its coplanar electrodes facilitate the system integration on one chip. The proposed TLD+QVSJ+RFP with the parameters listed in Table 1 obtains RON,SP of only 9.36 m ·cm with BV of 528.5 V This BV is larger than the target, so a better RON,SP can be expected by increasing Ndn-3. A quasi SJ technique is applied to enhance the doping concentration of the drift region, the charge-imbalance due to the effect of trench capacitor seriously damages the potential distribution and limits the benefit from SJ; (c) For TLD+QVSJ+RFP. This is exactly attributed to the impact of Ctrench. It is obvious that due to the combined application of QVSJ and RFP, the proposed device gains more uniform surface e-field distribution on both sides of the trench. The wide gap of Pon stems from the aforementioned distinction of FOM and, as a result, TLD+QVSJ+RFP exhibits a much smaller Ptotal than the others, especially at the frequency of 10∼200 kHz which is usually adopted in a switching mode power supply (SMPS) [1]
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