Leakage current analysis of silicon diode with anode activated by furnace annealing or laser annealing using deep level transient spectroscopy

Silicon P-i-N diodes with a p+ region in the anode—where boron atoms are implanted and activated with relatively low-temperature furnace annealing (FA) or high-temperature laser annealing (LA)—show a large difference between the leakage currents of the diode samples activated using FA and LA. In this paper, in order to clarify the cause of the difference in leakage current, the generation current and diffusion current are verified. For estimating the generation current, the trap level was analyzed by deep level transient spectroscopy (DLTS) in a wide bias range of +0.3 V to −160 V, which corresponds to a depletion region width of 0 µm–37 µm, and trap density depth profiles are analyzed using DLTS. The DLTS analysis shows that the trap density is relatively uniform in the FA sample; however, the LA sample has a lower trap density near the p+ region of the anode. The leakage current of the diodes is calculated using the trap density profiles based on the leakage current model that includes generation and diffusion currents. The calculated and measured leakage currents are compared, and the relationship between the trap density and the leakage current is investigated. The reverse bias dependence of the calculated leakage current corresponds with the measured value for the LA sample, which implies that the trap density in the n-substrate obtained by DLTS can explain the measured leakage current well. For the FA sample, the measured leakage current is larger than the calculated value in the high reverse bias region. This suggests that there are large amounts of inactivated boron in the p+ region of the anode of the FA sample because of the low activation temperature. Only a few parts of the inactivated boron are believed to form a deep energy level trap that increases the generation leakage current. In order to reduce the leakage current of the P-i-N diode, it is effective to increase the activation rate of boron in the anode p+ region. By applying the LA method to a reverse-blocking insulated gate bipolar transistor with a built-in P-i-N diode on the collector side, the reverse leakage current can be reduced, and the operating temperature can be improved.