Collider just for Tag (2D) (C#)

This is aggain a pretty basic Question I guess, but I can't figure out how to do this:

I want to use a 2D Boxcollider to check for collision with a tag with

   void OnCollisionEnter2D (Collision2D something) {
   if (something.collider.tag == "someTag")
   //do something
   }

But I dont want my Objects to actually collide. So basically what I want is to check if my player is at a certain position (not via transform or something like that), but I want to be able to walk past or through that collider...

Any Tips?

Thanks