Yes, according to The Oxford English Dictionary auxiliar verbs are used to form the tenses, moods, voices, etc. of other verbs."
OED Second Edition, 1989. Entry for auxiliary.
In this case (the one that originated the current topic), it falls in the "mood" department.
Notice:In linguistics, grammatical mood (sometimes mode) is a grammatical (and specifically, morphological) feature of verbs, used to signal modality.:p.181; That is, it is the use of verbal inflections that allow speakers to express their attitude toward what they are saying...Some examples of moods are indicative, interrogatory, imperative, emphatic, subjunctive, injunctive, optative, potential. http://en.wikipedia.org/wiki/Grammatical_mood
I do hope it somehow helps!