A Study on Chamber Contamination Control of Rapid Thermal Nitridation Process By Applying Quartz Liner

To improve the characteristics of barrier wall in DRAM plug contact via, the rapid thermal nitridation(RTN)  process has been widely used via rapid thermal  process chamber. With combination of high temperature heat, process gas such as NH3 and wafer being processed, the Ammonium Chloride(NH4Cl) is generated as a byproduct of this process and chamber is contaminated by NH4Cl depositing on the reflector. This contaminant diffracts the thermal energy which comes into pyrometers and degrades process quality. To prevent this chamber contamination from the byproduct such as NH4Cl, the transparent quartz liner on reflector plate is adopted.

In this study, the influence of quartz liner on reflector plate, the improvement of chamber contamination and pyrometer sensitivity were investigated.

In RTN process, TiSix or CoSix is formed in Si contract area as an ohmic contact and improves the adhesion with tungsten by transducing Ti to TiN.[1]

Eq.1 shows how Ammonium Chloride (NH4Cl(s)) is generated during RTN process as a byproduct.

NH4Cl sublimes at 337.6°C and the reflector plate increases no more than 225.3°C at 1000°C, 90sec process condition. Therefore NH4Cl is deposited on the chamber wall as well as reflector plate. Fig.1 shows the diagram of NH4Cl deposition on reflector plate as a contaminant. This contaminant diffracts the thermal energy which comes into pyrometers and degrades the silicide uniformity.

In Fig.2, device “A” at target temperature has more uniform shape than device “B” which has been processed in lower temperature than target of “A”.

Fig.3 shows transparent quartz in RTP chamber to prevent reflector plate from the contaminant.

Fig.4 shows presence of quartz liner has very stable halogen lamps power dissipation than without quartz.

Fig.5 shows temperature error against target value with quartz liner is much lower than without quartz.

In this paper, the influence of quartz liner on reflector plate, the improvement of chamber contamination and pyrometer sensitivity were investigated. From experimental result, presence of quartz liner protects reflector plate from contamination and keeps power dissipation of halogen lamps in stable. As a result, it means that more accurate heat control is possible in RTN process which could affect the quality of plug contacts of semiconductor device.

Reference

[1] ] Zhao Wenbin, Chen Haifeng, XiaoZhiqiang, Li leilei, Yu Zongguang, Journal of Semiconductors (2009) 056001