This paper overviews clock design problems related to the circuit reliability in deep submicron design technology. The topics include clock polarity assignment problem for reducing peak power/ground noise, clock mesh network design problem for tolerating clock delay variation, electromagnetic interference (EMI) aware clock optimization problem, adjustable delay buffer (ADB) allocation and assignment problem to support multiple voltage mode designs, and state encoding problem for reducing peak current in sequential elements. The last topic belongs to FSM design and is not directly related to the clock design, but it can be viewed that reducing noise at the sequential elements driven by clock signal is contained in the spectrum of reliable circuit design from clock source down to sequential elements inclusive.