We characterize relative timing jitter between optical pulses and photocurrent pulses with sub-femtosecond resolution by electro-optic sampling. We found that excess timing jitter at the both edges of photocurrent pulses can show femtosecond-level jitter for both p-i-n and modified uni-traveling carrier (MUTC) photodiode. The rising-edge jitter is much lower than the falling-edge jitter, reaching attosecond-level. To exploit the ultra-low timing jitter of photocurrent pulses, we present femtosecond-precision generation and distribution of electronic clocks using photonic clock distribution network (CDN). Since photocurrent pulses from optical frequency comb directly drives capacitive load of CDN, gigahertz-rate clocking without number of clock buffers can be demonstrated. Femtosecond-level on-chip jitter and skew as well as large reduction of heat dissipation have been achieved with photonic CDN using a test chip fabricated in a 65 nm CMOS technology.