A surge voltage is generated by high di/dt, and wiring inductance outside the module, at the time of switching (L*di/dt). Some of the ways to suppress this problem are as follows:
(1) Add a protective circuit
(2) Reduce di/dt by adjusting RG or –VGE
(3) Reduce inductance by making the main circuit wiring thicker and shorter, and using a copper bar and parallel flat wiring
For details, refer to Application Manual Chapter 5.