How to create atlas index for object's property

Hi All expert,
I have a document which has one attribute is an object contains two fields. Hierarchy as following. I need provide wildcard search for inco1 and inco2. How should be the atlas index definition for them?
Thanks in advance.
Document
->deliveryNumber(string)
->incoterm(object)
inco1(string)
inco2(string)

It seems like embeddedDocument’s might be a good path forward for you.