what's the characters of external rising edge to wakeup the mcu in standby mode?

[Dliu.11]

The minimum requirments of rising edge include but not limited to voltage, lasting time of high level, input current or charge and so on.

[waclawek.jan]

For minimum pulse duration, look at the EXTI specification in Datasheet to your STM32 - you did not tell us which one is it.

Voltage and current is given by the normal GPIO specification, again see datasheet.

JW