Question: I've set my 2450 to sink 100mA. When I enable the load it sinks 100mA, but when I disable the load with blue button in the corner, it still sinks 10mA when the output if off. I want it to go to zero mA load.
Answer: The 2450 SMU is a four-quadrant instrument, meaning it can both source and sink. By default, the SMU with output OFF will be in the "Normal Output Off State" which sets the SMU to these conditions when the output is OFF:
This would explain why it is sinking ~10mA. I imagine you are using the 100mA range when output is on, and 10% of 100 is 10.
What I believe you want to use is the High Impedance output off state, or one of the other Output Off modes found starting on page 4-16 in the reference manual below.
The High Impedance output off state will disconnect the output relays at the front terminals, which will physically disconnect the SMU circuitry from your DUT, which prevent the SMU from sinking or sourcing while the output is off.
The warning with using this mode is fast use of the output ON/OFF will cause excess wear and tear on the relays which could run the risk of expediting any sort of SMU issues and damage.
Model 2450 Interactive SourceMeter Instrument Reference Manual | Tektronix