How to design 3rd order RC filter

[xiexi]

I just want 4kHz LPF, I design R=780K, C=10pF, and 3 same RC in series, the -3dB is about 4KHz, is the design right?
if right but the size is too big to integrate in IC, can anyone give me some instruction, thanks!

 

[neter]

because -3dB=4KHz request, so fc1=fc2=fc3=4kHz,
fc=1/2pi*R*C (if you use passive RC filter)