S-Space College of Engineering/Engineering Practice School (공과대학/대학원) Dept. of Chemical and Biological Engineering (화학생물공학부) Theses (Master's Degree_화학생물공학부)
전해 도금 공정을 이용한 DRAM 축전기용 Ru 하부 전극 형성 방법 연구
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- 서울대학교 대학원
- DRAM 하부 전극 ; DRAM bottom electrode ; Ru ; Ru ; 전해 도금 ; Electroplating ; Pd 활성화 ; Pd activation ; 교반 ; Stirring
- 학위논문(석사)--서울대학교 대학원 :응용화학부,2003.
- As DRAM (dynamic random access memory) integration is going
on to Gigabit scale, the formation of 25 fF capacitor becomes
main problem in DRAM fabrication. New dielectric materials such
as Ta2O5, (Ba,Sr)TiO3 and new bottom electrode materials such
as Ru, Pt, and Ir were introduced to solve this problem. Among
them, Ru is considered the most appropriate material as bottom
electrode due to its good etching property.
Up to date, we have been used MOCVD (metal organic chemical
vapor deposition) process to deposit Ru thin film. But MOCVD
process needs strict deposition condition. Thus we studied
electroplating process as Ru film deposition method, because
electroplating is easy and cheap method to deposit thin film.
Main problems in Ru electroplating are low density of nucleation
center because of the high resistivity of TiN substrate and
hydrogen evolution during electroplating due to negative
deposition potential. But these problems were solved
successfully with introduction of Pd activation and stirring. This
Ru film had 45 nm thickness, 4.4 nm surface roughness, and 280
μΩ∙cm resistivity. Though the film resistivity is high, this film has
reasonable film quality in consideration of the reduction of film
resistivity to 38 μΩ∙cm after annealing.
Besides above experiment, the effects of Ru concentration,
electrical reduction and deposition temperature were examined.
As results, we could know that the reduction of Ru concentration
can improve film uniformity and electrical reduction can reduce
film resistivity. But the elevation of temperature deteriorated film quality such as surface roughness.
From these results, we can know that Ru electroplating with Pd
activation and stirring is a new bottom electrode fabrication
method with great potentialities. And it is considered that
continuous study is needed to optimize Ru concentration and
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