Study On The Key Technologies Of The Novel Power Semiconductor Devices

As of 2012,electric energy accounts for 40% of global energy consumption.It is expected that this proportion will reach 80% by the middle of this century.How to use energy efficiently has become the key to energy conservation and emission reduction.With the gradual expansion of power applications,especially in areas such as high-speed rail,electric vehicles,and big data,which have extremely high requirements for electrical energy,they gradually enter people's lives.Semiconductor power devices also gradually move toward higher voltages,higher currents,and higher frequency,wider operating temperature range,etc.The composite buffer(CB junction),invented by Prof.Xingbi Chen of the University of Electronic Science and Technology of China,is also known as the super junction structure,which breaks the silicon limit of the traditional voltage-sustain layers and greatly reduces the on-resistance of power MOSFET.However,it has been found that the breakdown voltage of the super-junction device is easily subject to the charge imbalance.That is to say,the device performance imposes a very high requirement on the accuracy of the process.This aspect greatly increases the manufacturing cost of the device and adversely affects the uniformity of the device.In order to solve this problem,Prof.Xingbi Chen has recently proposed a new type of voltage-resistant layer using a high-dielectric constant isolator.The voltage-sustain layer achieves the same on-resistance as the super-junction voltage-sustain layer under the same breakdown voltage by introducing a High-k dielectric material,and solves the problem that the aforementioned device performance is easily affected by the charge imbalance.As an extremely promising device in semiconductor devices,IGBT has received a great deal of attention these years and has become a hot product in the power semiconductor market.Research on IGBTs is also very hot.The IGBTs are also called insulated-gate bipolar transistors.The bipolar device has the advantages of large power density,high breakdown voltage,and the advantages of simple driving circuit and low driving loss.It is widely used in high voltage and high power fields such as locomotive traction.However,because it does not have the reverse current capability itself,an important direction for its research is to study integrating it with the reverse freewheeling diode to form an RC-IGBT.In the early days,independent IGBT devices were generally integrated with independent freewheeling diodes through a package.With the development of process technology,more and more RC-IGBTs have integrated freewheeling diodes on the chip through advanced processes to achieve reverse freewheeling capability.Under the guidance of Prof.Xingbi Chen,the author conducted research work on High-k VDMOS cell and termination structures and RC-IGBTs.The main innovative work is:1.A novel high-k VDMOS cell structure was proposed based on the deep research of the principle of High-k voltage-sustain layer.The improved structure is provided with an split gate in the High-k dielectric layer in the cell,and the proposed structure modulates the surface electric field and improve the breakdown voltage.When the device is turned-on,the split gate in the High-k dielectric layer induces an electron-accumulating layer near the interface of High-k dielectric/N-type drift region,thereby reducing spefic on-resistance.In order to avoid the degradation of the device switching speed caused by the appearance of the split gate,the author proposed a novel High-k VDMOS device with self-driven split gates.The split gate is driven by a low-voltage power supply,so that a higher withstands voltage and a lower on-resistance can be obtained with no degration of the switch performance.2.A new junction-termination structure suitable for High-k VDMOS devices consists of a deep P region and field plate is proposed.The voltage is sustained by the deep P region.And the field plate modulats the surface electric field.Simulation results show that the proposed structure achieves the breakdown voltage of the high-k VDMOS cell,while reducing the capacitance of the device and improving the switching speed of the device.3.A novel type of RC-IGBT structure is proposed which solves the phenomenon of snapback of the traditional RC-IGBTs in the case of a shorter backside size.It also greatly improves the turned-on speed of the integrated freewheeling diode and reduces the overcharge voltage during the freewheeling diode turned-on process.Numerical simulations show that the back dimension of the proposed RC-IGBT is one-ninth that of the traditional RC-IGBT.