The novel precleaning treatment for selective tungsten chemical vapor deposition

The new solutions, hydroxylamine sulfate [(NH2OH)(2)H2SO4] combined with Cu SO4, for cleaning Al via were investigated. Tt is found that the cleaning c apability of hydroxylamine sulfate combined with CuSO4 is better than that of hydroxylamine sulfate. Low via resistance of electrical test structure i s obtained if the via is cleaned by this new cleaning solution. The hydroxy lamine sulfate can efficiently remove Al3O2 and leave the clean Al on the s urface of via. Then, the Cu ion in this new solution will immediately react with clean Al and form a copper passivating layer on the surface of via. T he copper is more stable than aluminum in the environment and hard to be ox idized. Therefore, hydroxylamine sulfate combined with CuSO4 can provide ex cellent cleaning capability for aluminum via holes. Also, the clean surface on the bottom of via is helpful for tungsten nucleation in via during CVD- W deposition. Therefore, a low via resistance and good selectivity of tungs ten plug are obtained when the Al via is precleaned with this new solution. (C) 1999 Elsevier Science S.A. All rights reserved.