4H-SiC Device Al-based Wire Bonding Package

As the third-generation semiconductor material,SiC material has higher performance than other semiconductor materials,and can produce stable high-temperature and radiation-resistant detectors.As an important part of the detector's external output,packaging shows the importance of packaging for the detector.Compared with flip chip and carrier tape automatic packaging,the wire bonding method has the simplest,most convenient and most efficient features,and is the preferred method of detector packaging.Wire Bonding is also the packaging method currently adopted most.This article is mainly based on Au/Ni/4H-SiC Schottky junction detector packaging,comparing the electrical performance of the detector before and after packaging.When the ohmic contact electrode of the detector chip is connected to the outside of the PCB board,the reflow soldering method is used,and the solder is PbSn,so that the PCB and the chip are firmly connected;The chip Schottky contact electrode is connected to the outside by wire bonding(Al wire)to form a complete chip scale package.Before the detector was packaged,the quality of Al wire bonding was analyzed.The key parameters were analyzed for the shape,quality and surface morphology of the bonding point,and the appropriate key parameters were selected.Improper selection of key bonding factors can cause damage to the bonding interface and electrode contact interface.The relationship between key parameters and effective area is analyzed.Due to the double bonding points during wire bonding,the standard for the bonding strength of the Al wire package is 2.5gf.The bonding strength test failed to meet the standard only once,and the fracture position appeared at the neck of the first and second solder joints and the wire in the middle,all meet the fracture standards.After the detector packaging was completed,the electrical performance of the detector was tested and analyzed.The ideal factor for the Al package of the C13 and C23 detectors is slightly higher than that of the In package and unpackaged detectors,and the Schottky barrier height is lower than that of the unpackaged With In packaged detectors,different barrier heights appear in the positive IV curve,and negative capacitance appears in the CV curve.This is mainly due to the contamination of the surface by the gas generated by reflow soldering during the packaging process.The current saturation phenomenon appears in the reverse I-V curve,which is mainly related to the area leakage.The solder has fluidity at high temperature,and the outward diffusion causes the leakage.The C33 detector has taken protective measures during the packaging process,and its ideal factor and barrier height are 1.40 and 1.32 eV.The reverse current of the I-V curve of the C33 detector is too small,and the current is oscillating under the influence of the test instrument.The anomalous peak phenomenon appears in the C-V curve,which is related to the polarization properties,composite effect and diffusion effect of the material.When the forward bias voltage is at a certain value,the composite effect is greater than the diffusion effect and the capacitance decreases rapidly.After encapsulation,the detector's performance has reached the normal use standard.