AVS 49th International Symposium
    Manufacturing Science and Technology Monday Sessions
       Session MS-MoA

Paper MS-MoA3
Real-Time Control of Ion Density and Ion Energy in Chlorine Inductively Coupled Plasma Etch Processing

Monday, November 4, 2002, 2:40 pm, Room C-109

Session: Control Issues in Electronics Manufacturing
Presenter: K.C. Leou, National Tsing Hua University, Taiwan, ROC
Authors: C.H. Chang, National Tsing Hua University, Taiwan, ROC
K.C. Leou, National Tsing Hua University, Taiwan, ROC
C. Lin, National Tsing Hua University, Taiwan, ROC
T.L. Lin, National Tsing Hua University, Taiwan, ROC
C.W. Tseng, National Tsing Hua University, Taiwan, ROC
C.H. Tsai, National Tsing Hua University, Taiwan, ROC
Correspondent: Click to Email
The advanced semiconductor fabrication requires more tighten process monitoring and control to improve production yield and reliability. Recently, advanced process control (APC), an in-situ sensor based methodology, has been applied to achieve the desired process goals in operating individual process steps. For instance, in etching of polysilicon using chlorine discharges, in order to obtain a desired etch profiles, the process often is operated at the ion-enhanced regime where the etch rate and etched profile are strongly dependent on the total ion energy flux incident on the wafer surface. Therefore, a better process control can be achieved if one can implement the real-time control of ion energy flux in etch processing. In this study, we have demonstrated experimentally the real-time multiple-input multiple-output (MIMO) control of both ion density and ion energy in etching of polysilicon using chlorine inductively coupled plasma. To measure relative positive ion density, the optical emission at 750.4 nm from trace amounts of Ar is used which is proportional to the total positive ion density. An rf voltage meter is adopted to measure the peak rf voltage on the electrostatic chuck which is linearly dependent on sheath voltage. One actuator is a 13.56 MHz rf generator having a maximum power of 5 kW to drive the inductive coil seated on a ceramic window, along with a L-type matching network to minimize the reflected power. The second actuator is also a 13.56 MHz rf generator to power the electrostatic chuck via a matching network. The two rf generator is locked in phase. The MIMO controller is designed by using Quantitative Feedback Theory (QFT), which compensates process drift, process disturbance, and pilot wafer effect. This system has been used to etch unpatterned polysilicon and silicon oxide. The experiment results showed that the MIMO control system has a better reproducibility in etch rate and uniformity compared with current industrial practice.