Question

is will make a prepositional phrase

Answer 1

Big no no

Answer 2

preposition + noun, pronoun, gerund, or clause

preposition + modifier(s) + noun, pronoun, gerund, or clause

Answer 3

If you are asking if the word "is" is a preposition or is part of a prepositional phrase, then the answer is simply no.

Here's a quick list of prepositions:
After
Under
Before
Around