Try Boric acid powder. Pretty harmless to humans (unless you ingested a humungous amount) but they get it on their feet and take it back their nest and everyone goes feet up. (not instantly - but just picture that - an entire ant hill of ants laying on their backs with their three pairs of tennies in the air) We used this in Guam for both ants and roaches. Threw it in the dead spaces behind the kitchen cabinets and ran a line of it down the edges of the carpets by the baseboards.
It's pretty cheap - can get it in the drug store - likely is what Borax is made from but I didn't look up the ingredients of Borax so don't really know.