A three-phase gate driver integrated circuit requires three bootstrap diodes to drive a metal oxide semiconductor field effect transistor (MOSFET). Typically, an external bootstrap diode is used during a high voltage process using bulk silicon except for during a silicon on chip (SOC) process.
Recently, a technique embedding an external 700 V bootstrap diode in a chip has been suggested for competitive prices, but when a built-in bootstrap diode is formed, various problems may occur.
FIG. 1 is a cross-sectional view of a related art built-in bootstrap diode. FIG. 2 is a circuit diagram of FIG. 1.
Referring to FIGS. 1 and 2, a related art bootstrap diode includes a P-type semiconductor substrate 1, an N-type epi layer 2, and a first P-TOP 3 stacked with a PNP structure. When forward voltage is applied to the related art bootstrap diode, this PNP structure operates as a first parasitic bipolar junction transistor (BJT) 5. Additionally, the first P-TOP 3, the N-type epi layer 2, and a second P-TOP 4 are formed with a PNP structure in a horizontal direction, so that this operates as a second parasitic BJT 6.
That is, when a built-in bootstrap is implemented in a related art structure, a parasitic transistor operates in a vertical and a horizontal direction, so that a semiconductor device becomes deteriorated and then useless.