차세대 반도체 소자에서 Ruthenium의 적용을 위한 CMP (chemical mechanical planarization) slurry 개발
- Title
- 차세대 반도체 소자에서 Ruthenium의 적용을 위한 CMP (chemical mechanical planarization) slurry 개발
- Other Titles
- Development of CMP Slurry for the Application of Ruthenium to Next Generation Semiconductor Device
- Author
- 김인권
- Alternative Author(s)
- Kim, In Kwon
- Advisor(s)
- 박진구
- Issue Date
- 2011-02
- Publisher
- 한양대학교
- Degree
- Doctor
- Abstract
- In MIM capacitor, poly-Si bottom electrode is replaced with metal bottom electrode. Ruthenium (Ru) has been suggested as bottom electrodes of MIM (metal-insulator-metal) capacitors due to its high work function, low leakage of current and compatibility to the high dielectric constant materials. Also, Ru film has been investigated as a Cu diffusion barrier metal and a Cu seed layer in Cu interconnection due to its good electrical conductivity, the immiscibility with Cu, and the good adhesion property to Cu layer. Chemical mechanical planarization (CMP) is one of fabrication processes for the electrode formation and the barrier layer removal. Though there is a great need for the development of a Ru CMP slurry, few studies have been carried out due to its noble properties against chemicals.
In this dissertation, Ru CMP slurry was developed and characterized to fabricate Ru bottom electrodes in capacitor structures. Sodium periodate (NaIO4) was chosen as both the oxidant and etchant due to its strong oxidizing power. The effect of NaIO4 on Ru etching and polishing behaviors was investigated as functions of its concentration and polishing condition. The largest removal rate of 70 nm/min was obtained in a slurry of 0.1 M NaIO4 and 2 wt% alumina particles at pH 9 and a polishing pressure of 4 psi. Planarization and isolation of each capacitor was successfully performed with the developed Ru slurry. However, the properties of the abrasive particle and Ru substance are changed as the pH of slurry. To formulate slurry and understand Ru CMP mechanism, it is greatly important to study chemical and mechanical reactions as the pH of slurry. In this dissertation, the effect of NaIO4 on etching and polishing behavior was investigated as a function of slurry pH. Below pH 8, the high static etch rate was measured due to the dissolution of soluble RuO4. Above pH 8, the static etch rate decreased due to the formation of insoluble RuO2?2H2O and the depletion of periodate ions. The highest etch rate of 20 nm/min was obtained at pH 6. In a slurry of 0.1 M NaIO4 and 2 wt% alumina particles at pH 6, the removal rate of Ru was about 130 nm/min. Even though the highest removal rate was obtained at pH 6, Ru over-etching occurred on Ru patterned wafers due to the high static etch rate of Ru. In slurry of pH 9, the planarity and isolation of each capacitor was reached successfully because Ru over etching was prevented due to low etch rate of Ru.
In Ru CMP, it is necessary to minimize the surface defect formation while good planarity and desirable material removal rate are maintained. The slurry stability occupy important portion to fulfill these requirements. The slurry stability can be improved by the addition of additives such as dispersants. In this study, the zeta potential and mean particle size of alumina particles were measured in slurry with and without dispersant. Effect of the sequence for manufacture of slurry was investigated on the slurry stability. The change of a dispersion volume in slurry with dispersant was observed as functions of a storage time and an adsorption time. The etch rate and removal rate of Ru were evaluated using optimized slurry with dispersant as a function of pH. The mean particle size of Ru CMP slurry decreased and the dispersion stability of Ru CMP slurry was improved by the addition of a dispersant.
During polishing, abrasive particles can be contaminated on the wafer surface. In this dissertation, it was also investigated based on the post Ru CMP cleaning solutions. The cleaning efficiency was measured as a function of pH in citric acid based cleaning solution with and without etchant. In DI water, the alumina particle contamination on Ru surface was hardly removed. Effective removal of the contaminants on Ru surface was achieved in citric acid of 1000 ppm with NaIO4 at pH 10. The effective cleaning of contaminants was possible by optimizing electrostatic force, etching rate and passivation capability.
- URI
- https://repository.hanyang.ac.kr/handle/20.500.11754/140428http://hanyang.dcollection.net/common/orgView/200000416871
- Appears in Collections:
- GRADUATE SCHOOL[S](대학원) > DEPARTMENT OF METALLURGY & MATERIALS ENGINEERING(금속재료공학과) > Theses (Ph.D.)
- Files in This Item:
There are no files associated with this item.
- Export
- RIS (EndNote)
- XLS (Excel)
- XML