so many thanks for your reply, infact i am designing "bootstrapped switch in 0.18um CMOS" and i can not change circuit diagram, would you help me to transistor sizing for this circuit? i have attached the circuit as a picture(M4 and M5 are inverter) in the following link https://obrazki.elektroda.pl/85_1322502487.jpg
The problem you describe above seems to be a typical case for a circuit optimization software. My company (MunEDA) works in this field, you could check our website for case studies.