As people's demand for modern life is increasingly higher, more and more attention is paid to the performance of power semiconductor devices, wherein, the integratability, high withstand voltage and high current, and outstanding isolation capability from the low-voltage circuit part are top technical requirements for power semiconductor devices. Besides the type of power semiconductor device, the structure and manufacturing technique of power semiconductor device are also important influencing factors for high voltage and high current processing capability of a power integratable circuit.
Through the years, commonly used power semiconductor devices were high-voltage triodes and high-voltage insulated-gate field-effect transistors (IGFETs). These two types of devices brought many adverse effects to power integratable circuits, though they essentially met people's demand for high withstand voltage and integratability. The drawbacks of high voltage triodes mainly include low input impedance and low switching speed. Though high-voltage IGFETs have high input impedance, their current driving capability is very limited; in addition, there is an inevitable contradiction between the high withstand voltage and the turn-on impedance in high-voltage IGFETs.
As science and technology develop, insulated-gate bipolar type devices emerged and met most of people's demand for power semiconductor devices. Insulated-gate bipolar devices integrate the advantages of high-voltage triodes and IGFETs, and have performances such as high input impedance, high switching speed, high withstand voltage, high current driving capability, and low turn-on impedance, etc. However, the insulated-gate bipolar devices developed in the early stage were longitudinal devices, which had poor integratability. Lateral insulated-gate bipolar devices that emerged later overcame the problem.
After the requirements for integratability, high withstand voltage and high current of power semiconductor devices are met, the isolation capability of power semiconductor devices became the main contradiction. In the bulk silicon process, since the high voltage circuit and the low voltage circuit are integratable in the same chip, the drain current of the high voltage circuit is high and leaks into the low voltage circuit through the substrate, causing the low voltage circuit latched up and the chip burnt finally. To solve that problem, a SOI technique was put forward.
With the emergence of SOI technique, the isolation problem of power semiconductor devices was solved effectively. Up to now, SOI lateral insulated-gate bipolar devices have become the main devices of power semiconductor devices, and are widely applied in the domain of 600V Dc voltage or above conversion systems, such as AC motors, frequency converters, switching power supplies, lighting circuits, and traction driving devices, etc.
A major problem related with SOI lateral insulated-gate bipolar devices is: compared to longitudinal devices, the current density is not high enough; therefore, high current driving capability is obtained often by increasing the area of the device; as a result, the chip area is severely consumed and the cost is increased. The present invention introduces a novel SOI integratable high-current N-type combined semiconductor device, which can improve current density significantly without increasing the layout area, when compared to conventional SOI N-type lateral insulated-gate bipolar type devices of the same size, current density increased significantly .
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