Make sure that what you get is a full tuition waiver + TA/RA/scholarship/fellowship ($1800/month) (全奖);
you don't need 财力证明 because 全奖 from US university (since most of 全奖 are from univ with good reputation or public univ) is more reliable than 财力证明. 财力证明 only indicates that you won't work in US illegally.