Designing a temperature independent current reference is quite complicated cause, in general, for references you always use voltages as your temperature measuring mechanism (Vth, Vbe, ΔVbe) so then, you would need a resistor you generate the current (making the current's tempco proportional to the resistors tempco). So what is usually done is either use low tempco resistors (which might not be available in your process so it would have to be external) or design a VOLTAGE reference, and then use a Gm (Transconductance) circuit to get the current.
Check out the following paper, it should have what you're looking for...
"A New Low Voltage Precision CMOS Current Reference With No External Components"; Rasoul Dehghani and S. M. Atarodi; IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS—II: ANALOG AND DIGITAL SIGNAL PROCESSING, VOL. 50, NO. 12, DECEMBER 2003
Hope this helps,
diemilio