Po-Tsun Liu

Effective repair to ultra-low-k dielectric material (k∼2.0) by hexamethyldisilazane treatment

O2 plasma ashing is commonly used to remove photoresist. The effect of O2 plasma ashing on the porous organosilicate glass (CH3SiO1.5)n, one of the spin-on materials, is investigated. O2 plasma can oxidize the methyl groups in porous organosilicate glass (POSG), which leads to the formation of Si–OH groups. The hydrophilic Si–OH groups will induce moisture uptake so that electrical degradation will occur in POSG film. Pure hexamethyldisilazane (HMDS) vapor (100% HMDS) can react with the Si–OH groups in POSG film. It converts hydrophilic Si–OH groups into hydrophobic Si–O–Si(CH3)3 groups against moisture uptake. The leakage current density decreases by a factor of 2–3 and the dielectric constant decreases from 3.62 to 2.4 when O2 plasma-damaged POSG undergoes HMDS treatment at 80u200a°C for 15 min. Therefore, HMDS treatment is the effective technique to repair the electrical degradation to POSG film during photoresist stripping processing.

Enhancing the resistance of low-k hydrogen silsesquioxane (HSQ) to wet stripper damage

Abstract The interaction between low-k hydrogen silsesquioxane (HSQ) film and wet stripper was investigated. The wet stripper has been commonly used to remove photoresister in IC integration processing. However, the high content of alkalinity in the stripper solution often leads to the hydrolysis of HSQ film, forming dangling bonds in the HSQ. The dangling bonds in the HSQ film can easily react with hydroxide ion (OH−) in wet stripper solution and form Si–OH bonds. The resultant HSQ film will tend to uptake water and consequently increase both the leakage current and dielectric constant. In this study, H2-plasma pre-treatment was applied to the HSQ film. The hydrogen plasma treatment passivates the HSQ surface and prevent HSQ from water uptake during photoresist stripping. Therefore, dielectric degradation can be avoided with the H2-plasma pre-treatment.

The novel precleaning treatment for selective tungsten chemical vapor deposition

Abstract The new solutions, hydroxylamine sulfate [(NH2OH)2H2SO4] combined with CuSO4, for cleaning Al via were investigated. It is found that the cleaning capability of hydroxylamine sulfate combined with CuSO4 is better than that of hydroxylamine sulfate. Low via resistance of electrical test structure is obtained if the via is cleaned by this new cleaning solution. The hydroxylamine sulfate can efficiently remove Al3O2 and leave the clean Al on the surface 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. The copper is more stable than aluminum in the environment and hard to be oxidized. Therefore, hydroxylamine sulfate combined with CuSO4 can provide excellent 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 tungsten plug are obtained when the Al via is precleaned with this new solution.