How do I make a custom taxomony appear like tags?

I have a custom taxonomy which I want to behave in the same way that tags do on the post edit screen, instead of how categories appear. I have tried passing in the 'show_tagcloud' => true attribute, but it is still behaving like categories.

Pass this argument in register_taxonomy(),

'hierarchical' => false,
'_builtin'=>true,

or use following links

How to Add Tags to Custom Post Type?

Adding post tags to custom post types