Comprehensively Investigate Electrical, Physical and Reliability Characteristics of Low-k Dielectrics under Oxygen Plasma Treatment

• Main Authors: Ping Hung Lin, 林秉閎
• Other Authors: Yi-Lung Cheng
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/2y9kgw

碩士 === 國立暨南國際大學 === 電機工程學系 === 102 === This thesis comprehensively investigates the effects of oxygen (O2) plasma treatment on porous low-k dielectric materials. It can be divided into five parts as follows. The degradation induced by O2 plasma irradiation to the various low dielectric constant materials (low-k) which dielectric constant range are k = 3.0 ~ 2.5 has been investigated in the first part of the thesis. The dielectric constant was observed to increase upon O2 plasma treatment due to the formation of the Si-OH bond. Moreover, the low-k materials with porogen form more Si-OH bond after O2 plasma treatment, which make the properties of the low-k materials become worse. The low-k materials result in lower dielectric constant after UV curing but also worsen the electrical properties and reliability. However, the O2 damage can be effectively suppressed by densifying the low-k film's surface induced by He/H2 remote plasma treatment due to the removement of the ion bombardment in O2 plasma. The second part is discussing the film properties, electrical properties and reliability of the low-k dielectric materials exposed to O2 plasma treatments with various RF powers, treatment times, and O2 flow rates. The experimental results show that there will be a top modified layer on the film after the O2 plasma treatment. The top modified layer will be thicker with higher RF power or longer treatment time, while top modified layer will be thinner with higher flow rate. This implies that the damage of O2 plasma treatment on low-k films increase with increasing the RF power and the treatment time, while decrease with increasing the flow rate. Ion bombardment removes the weakly bonds and creates the Si-OH bonds related to moisture, and the Si-CH3 bonds which are low polarization will be decreased. It makes the films become hydrophilic from hydrophobic and the dielectric constant also increase. The mechanical strength, electrical properties and reliability are getting worse, and the amplitude of variation will increase with increasing the RF power and the treatment time, while decrease with increasing the flow rate. In the third part of this thesis, the role of ions, photons, and radicals in the plasma in inducing the low-k material degradation was clarified by using a special designed mask structure. The experimental results showed that all components in the plasma have contributions in degrading the electrical and reliability performance of low-k film. The ions result in the most serious damage. Moreover, the synergy between the radicals, photons and ions enhanced the damage. In the fourth part of the thesis, the impact of the sidewall and bottom of the interconnect damascene trench structure after O2 plasma treatment was compared. We designed a simple trench structure to simulate the real trench structure. From the experimental results, the low-k films in both sidewall and bottom of the trench structure show a worse electrical performance and reliability after performing O2 plasma treatment. Moreover, the low-k films in the sidewall of the trench structure suffer a less damage in comparison to those samples in the bottom. Furthermore, as the width of the trench is scaled-down, the O2 plasma damage on the sidewall and bottom low-k films can be alleviated due to a reduced flux of oxygen plasma components. Therefore, the slight downscaled trench structure would not cause more serious degradation for the low-k films under O2 plasma treatment with an identical treatment condition. In the fifth part of the thesis, the impact of the top modified layer on low-k films was clarified by using HF solution to remove the top modified layer. The experimental results show that the top modified layer formed by O2 plasma treatment will degrade the films’ properties. However, when the top modified layer is etched entirely, its’ film properties, electrical properties and reliabilty will be similar to the films without O2 plasma treatment.