I would say go back to the basics. This is a simple problem that doesn't really need FEA. Derive the equations for a beam with fixed ends and two point loads. This is a very common problem. You than can very easy solve the equation based on your fixed parameters to determine if it is possible with the current load/material/area moment/etc.

fair enough. my question is how can it be designed so that the deflection is 0.1 mm while keeping the thickness at 60 mm ?

no, your are faced with dimensional limits. As CPPMable says, go back to basics - at 60mm deep that is the limiting factor that defines the second moment of area - its resistance to bending. the only way to then reduce bending is too increased the youngs modulus of the material but to get close to 0.1mm you need to have E > 1000GPa ! you need to deepened the beam section or reduce the load tony

great I agree. how about making the shape a bit less simple. how about curving the beam upwards !? how is that done ?