Welcome to the Forum.
Do a search here (search box is in the upper right corner) for family reunification. You'll find many threads that talk about people working here bringing family members over.
As you're presently under 21, you may qualify for a dependent permit. However it will probably depend upon your mother's nationality, the type of permit she holds, the size of her apartment/house, and whether she can prove she has sufficient funds to support you, etc.
Assuming you're EU, there's some info here to get you started: https://www.ch.ch/en/family-reunification-eu-efta/