Tick boxes - at least one has to be ticked

You can make checkboxes required but it won't do you any good since submit check for empty value
and checkboxes are never empty.What you need is make hidden text field and use script in it, when no checkboxes are tick
field will be required and if any checkbox is tick field is not required.
You can try using this script as custom calculation script of hidden text field, and change field names if needed.
var c1 = this.getField("Check Box2").value;
var c2 = this.getField("Check Box3").value;
var c3 = this.getField("Check Box4").value;
if(c1 != "Off" || c2 != "Off" || c3 != "Off"){
event.value = "Required";}
else event.value = "";
if(event.value == ""){
event.target.required = true;}
else event.target.required = false;

Do you want to make checkboxes required if you use submit or you just want that user need to check one of the boxes?

If it's latter then you need to describe us a scenario how you are using boxes?

Just give each field a unique name and they'll work independently of each other.

When you say that "at least one fields needs to be checked", what do you mean by that, exactly? What should happen if no fields are checked?