Assessment Of Cl 2 /CHF 3 Mixture For Plasma Etching Process On Barc And Tin Layer For 0.21 µm Metal Line: Silterra Case Study

In wafer fabrication manufacturing, aluminum etching process is a dry plasma etching process used as main process for construction of aluminum (Al) interconnects structures. As customer requirement changed for faster, more reliable and lower cost chips, chip manufacturers have learned to reduce the size of component on a chip in order to achieve those requirements(Ibrahim, Chik, & Hashim, 2016). As the geometry of the chip getting smaller, the width of Al line wiring specification also shrinking. To print the smaller geometry pattern requirement, the thickness in masking process also has to be reduced for better resolution. Such a thinner resist will create a challenge during plasma etching to ensure a minimal resist loss process which required new type of equipment but this research insist to sustain similar equipment. The use of oxide film as a hard mask has been evaluated by other researchers but alternative approach still needed to suit specific requirement of semiconductor factory installation base. This approach does require a process integration change and require a full technology qualification and easily take a lengthy qualification procedures especially when to qualify the existing products. It is worth trying at the situation of no other solution available. The challenge of insufficient margin for the metal line etching process for 0.2 µm width has caused the deformed metal pattern formation. This chemistry study of Cl2/CHF3 as a replacement gas to existing Cl2/O2 to address Organic backside anti refractive coating (OBARC) was evaluated and proven novelty where detail discussed in the following content.

STUDY ON SURFACE CHARGING EFFECT ON MASK DURING PLASMA ETCHING PROCESS THROUGH PARTICLE SIMULATION

Damage on the mask surface caused by charging effect during plasma etching process continues to attract much attention currently. For example, the round shape of holes can be changed into hexagonal shape. In our previous paper, the reason for this phenomenon has been explained through a particle simulation approach [P. Zhang et al., Plasma Sci. Technol. 15 (2013) 570]. However, it has been observed that the round shape of holes in a mask can also be etched into an asymmetric shape due to factors such as nonuniform plasma source, inclination or vibration of sample platform, etc. This work further aims to explore the charging effect when the round-shaped holes in a mask have been changed into asymmetric-shaped ones by particle simulation method. The distribution of electric field produced by electrons was calculated for different shaped isolated holes (round, hexagonal and asymmetric shapes) in a mask as well as various heights from the mask surface. It is found that the field strength reaches its maximum around a hole edge and presents uniform distribution for the round hole and nonuniform distribution for the hexagonal- and asymmetric-shaped holes. The nonuniform electric field distribution can affect the trajectories of ions falling on the mask surface, further enhancing the asymmetry of the mask hole shape. Additionally, the charging effect on a mask of asymmetric holes aligned in a hexagonal array is also studied. It is found that due to the alignment of holes, the charging effect is quite different from the case in an isolated hole.