When I open a modal view, the parent view also can get focus?

I got an issue with the ionic Modal :

I has a view with some input area and a button ,
when I tap the button ,open a modal view , the modal view also has some input area;

on the modal view, I input something into the input area,
then I use keyboard [shift + tab] , i found the focus moved to the parent view’s input area!
(mobile: use the keyboard’s back button also)

I think the ionic modal is not the true modal ,it just a view like modal style,
I’m running out of ideas, can anyone help me?

can anyone give me some ideas??