Thermal stability of fluorine doped silicon oxide films

Seoghyeong Lee,Jae-Yoon Yoo,Jong-Wan Park 한국진공학회(ASCT) 1998 Journal of Korean Vacuum Science & Technology Vol.2 No.1

The reliability of fluorine doped silicon oxide (SiOF) films for intermetal dielectrics in multilevel interconnections of ultra-large scale integrated circuits (ULSIs) is investigated. SiOF films were deposited by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECRPECVD) using H-free source gases, i.e., SiF₄ and O₂. The effect of post plasma treatment on the moisture absorption and dielectric properties of SiOF films was carried out in terms of air exposure time. The reliability test of Cu/TiN/SiOF/Si specimen was carried out in terms of temperature by rapid thermal annealing (RTA) in N₂ ambient. After O₂ plasma treatment, no appreciable peak directly related to moisture absorption was detected. The capacitance-voltage (C-V) characteristics of the O₂ plasma treated SiOF film showed that the film remained to hold the sound dielectric properties even after boiling treatment. The Cu/TiN/SiOF/Si system was found to be reliable up to 600℃.

플라즈마 후처리 시간에 따른 저유전율 SiOF 박막의 특성

이석형(Seoghyeong Lee),박종완(Jong-Wan Park) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.3

ECR plasma CVD를 이용한 SiOF 박막은 낮은 유전상수를 가지고 있으며, 기존의 공정과의 정합성이 우수해 다층배선 공정에 채용이 유망한 재료이지만 수분의 흡수로 인한 유전율의 상승과 후속공정의 안정성이 문제점으로 부각되고 있다. 따라서 본 연구에서는 SiOF 박막의 내흡습성과 후속공정에서의 안정성을 향상시키기 위하여 SiOF 박막을 증착한 후 후속 산소 플라즈마 처리를 행하였다. SiOF 박막은 산소 플라즈마 처리를 수행함으로써 SiOF 박막 표면에 SiO₂막이 형성되어 내흡습성이 개선되었다. 이와 같은 산소 플라즈마에 의한 내흡습성의 향상은 SiOF 박막의 밀도가 증가하고, 수분과의 친화력이 강한 Si-F 결합이 감소하는 것이 주요한 원인으로 사료된다. 하지만 플라즈마 처리 시간이 5분 이상으로 증가하면 유전율의 증가가 일어난다. 따라서 본 실험에서는 산소 플라즈마 처리조건이 마이크로파 전력이 700 W, 공정압력이 3 mTorr, 기판온도가 300℃일 경우 플라즈마 처리시간은 3분이 적당한 것으로 생각된다. The fluorine doped silicon oxide (SiOF) intermetal dielectric (IMD) films have been of interest due to their lower dielectric constant and compatibility with existing process tools. However, instability issues related to bond and increasing dielectric constant due to water absorption when the SiOF film was exposured to atmospheric ambient. Therefore, the purpose of this research is to study the effect of post oxygen plasma treatment on the resistance of moisture absorption and reliability of SiOF film. Improvement of moisture absorption resistance of SiOF film is due to the forming of thin SiO₂ layer at the SiOF film surface. It is thought that the main effect of the improvement of moisture absorption resistance was densification of the top layer and reduction in the number of Si-F bonds that tend to associate with OH bonds. However, the dielectric constant was increased when plasma treatment time is above 5 min. In this study, therefore, it is thought that the proper plasma treatment time is 3 min when plasma treatment condition is 700 W of microwave power, 3 mTorr of process pressure and 300℃ of substrate temperature.

Deposition and Surface Modification of SiOF Films with low Dielectric Constant

Park, Jong Wan,Lee, Seoghyeong,YOO, Jae Yoon 대한금속재료학회(대한금속학회) 1997 METALS AND MATERIALS International Vol.3 No.3

Low dielectric constant fluorine-doped silicon dioxide (SiOF) films were deposited using electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECRPECVD) with SiF₄ and O₂ as source gases. The effect of fluorine addition on the dielectric properties of the film as a function of the SiF₄/O₂ gas flow ratio is described in this paper. Also, the effect of post-plasma treatment on the moisture absorption of SiOF films for IMD materials in multilevel interconnections of ultra-large scale integrated circuits (ULSIs) was investigated. The SiOF film deposited at an SiF₄/O₂ gas flow ratio of 1.0 exhibited a fluorine content of 11.8 at.% and a dielectric constant of 3.14. When the duration time of post-plasma treatment increased, the following results were obtained: The etch rate of SiOF films decreased from 80 Å/sec to 10 Å/sec, and surface roughness of the plasma-treated SiOF films increased in relation to the ion bombardment effect of the plasma. The refractive index and relative dielectric constant increased from 1.391 to 1.461 and from 3.14 to 3. 90, respectively, due to the changes of surface chemistry in post-plasma treatment. The leakage current density of SiOF films prepared by ECRPECVD using SiF₄O₂ and O₂ was less than 1 × 10^(-9) A/㎠ and the breakdown field strength increased from 3.5 MV/㎝ to 8 MV/㎝.

펄스전착법과 첨가제를 사용하여 전착된 ULSI배선용 구리박막의 특성

이경우,양성훈,이석형,신창희,박종완,Lee Kyoung-Woo,Yang Sung-Hoon,Lee Seoghyeong,Shin Chang-Hee,Park Jong-Wan 한국전기화학회 1999 한국전기화학회지 Vol.2 No.4

펄스전착법에 의한 구리박막의 특성과 via hole 충진 특성을 연구하였다. 특히 구리박막의 특성에 미치는 첨가제의 영향을 중점적으로 다루었다. 펄스 전류와 첨가제를 사용하여 전착한 구리박막은 83.4 MPa이하의 낮은 인장응력을 가졌으며 높은 Cu (111) 우선 배향성을 나타냈다. Superfilling에 의해 최고 $0.25{\mu}m, 6: 1$ 정도의 고 종횡비를 가지는 via hole에 결함 없이 성공적으로 충진할 수 있었으며 미세 구조를 관찰한 결과 쌍정에 의한 변형이 일어났음을 알 수 있었다. $500^{\circ}C$에서 1시간 동안 진공열처리를 했을 경우 두께의 $1\~2$배에 달하는 결정립을 가지는 bamboo구조를 나타냈으며 이때 전기비저항은 $1.8\~2.0{\mu}{\Omega}{\cdot}cm$을 나타냈다. The characteristics of copper thin films and via hole filling capability were investigated by pulsed electrodeposition method. Especially, the effects of additives on the properties of copper thin films were studied. Copper films, which were deposited by pulsed electrodeposition using commercial additives, had low tensile stress value under 83.4 MPa and high preferred Cu (111) texture. Via holes with $0.25{\mu}m$ in diameter and 6 : 1 aspect ratio were successfully filled without any defects by superfilling. It was observed that copper microstructure deformed by twining. After heat treatment at $500^{\circ}C$ for 1 k in vacuum furnace, grain size was 1 or 2 times as large as film thickness and the bamboo structure was formed. Heat treated copper films showed good resistivities of $1.8\~2.0{\mu}{\Omega}{\cdot}cm$.

가스 조성이 저유전상수 a-C:F 층간절연막의 특성에 미치는 영향

박정원(Jeongwon Park),양성훈(Sung-Hoon Yang),이석형(Seoghyeong Lee),손세일(Seil Sohn),오경희(Kyunghui Oh),박종완(Jong-Wan Park) 한국진공학회(ASCT) 1998 Applied Science and Convergence Technology Vol.7 No.4

초고접적 회로의 미세화에 따라 다층배선에서 기생저항(parasitic resistance)과 정전용량의 증가는 RC 시정수(time constant)의 증가로 인하여 소자의 동작속도를 제한하고 있다. 이로 인하여 발생되는 배선지연의 문제를 해결하기 위하여 매우 낮은 유전상수를 갖는 층간 절연물질이 필요하다. 이러한 저유전상수 층간결연물질로서 현재 유기계 물질중의 하나인 a-C:F이 주목받고 있는 물질이다. 본 연구에서는 ECRCVD를 이용하여 a-C:F 박막과 Si기판사이의 밀착력을 향상시키기 위하여 a-C:H 박막을 500Å 증착한 후 a-C:F을 증착전력 500 W에서 원료가스의 유량비(C₂F_6/(C₂F_6+CH₄))를 0~1.0까지 변화시키면서 상온에서 증착하였다. a-C:F 박막의 특성은 SEM, FT-IR, XPS, C-V meter와 AFM등을 이용하여 두께, 결합상태, 유전상수, 표면형상 및 표면 거칠기를 관찰하였다. a-C:F 박막에서 불소함량은 가스 유량비가 1.0일 경우에는 최대 약 31 at.%정도 검출되었으며, 가스 유량비가 증가됨에 따라 증가하였다. 또한 유전상수는 a-C:H의 유전상수 ε=3.8에서 ε=2.35까지 감소하였다. 이는 영구 쌍극자 모멘트가 1.5인 C-H 결합은 감소하고 영구 쌍극자 모멘트가 0.6, 0.5인 CF, CF₂결합이 증가하였기 때문이다. 하지만 400℃에서 질소분위기로 1시간 동안 furnace 열처리 후에 가스유량비가 1.0인 a-C:F 박막에서 불소의 함량이 감소하여 C-F 결합이 줄어들었다. 이로 인하여 유전상수가 열처리전의 2.7에서 열처리후 3.2까지 상승하였다. As device dimensions approach submicrometer size in ULSI, the demand for interlayer dielectric materials with very low dielectric constant is increased to solve problems of RC delay caused by increase in parasitic resistance and capacitance in multilevel interconnections. Fluorinated amorphous carbon is one of the promising materials in ULSI for the interlayer dielectric films with low dielectric constant. However, poor thermal stability and adhesion with Si substrates have inhibited its use. Recently, amorphous hydrogenated carbon (a-C:H) film as a buffer layer between the Si substrate and a-C:F has been introduced because it improves the adhesion with Si substrate. In this study, therfore, a-C:F/a-C:H films were deposited on p-type Si(100) by ECRCVD from C₂F_6, CH₄ and H₂ gas source and investigated the effect of forward power and composition on the thickness, chemical bonding state, dielectric constant, surface morphology and roughness of a-C:F films as an interlayer dielectric for ULSI. SEM, FT-IR, XPS, C-V meter and AFM were used for determination of each properties. The dielectric constant in the a-C:F/a-C:H films were found to decrease with increasing fluorine content. However, the dielectric constant increased after furnace annealing in N₂ atmosphere at 400℃ for 1hour due to decreasing of fluorine concentration.