Chemical-Mechanical Polishing and Material Characterization of Low Dielectric Constant PECVD Fluorinated Oxide Thin Films

• Main Authors: Hsieh, Yuan-Tsu, 謝元智
• Other Authors: Feng Ming-Shiann, Dai Bau-Tong
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/52928629850932934772

碩士 === 國立交通大學 === 材料科學與工程研究所 === 84 === Advanced semiconductor device interconnects are the pivotal component governing the final device yield and reliability. The trend toward shrinking design rules and increased interconnect packing density have driven the development of multilevel interconnect system. As interconnect lines shrink and move closer together, the resistance of conductor lines and plugs and the capacitance of SiO2-based inter-metal dielectrics limit further increase in clock speed. The incorporation of low permittivity (low-k) dielectrics and lower-resistance, electromigration-immune conductors into the interconnect scheme has become imperative to further reduce the RC delay in the deep submicron regime. One of these low-k dielectrics, fluorine-doped silicon dioxide films which have been fabricated by dual frequency plasma enhance chemical vapor deposition (PECVD), are evaluated the feasibility of this technology for ultra-large integrated (ULSI) processes. In this study, the physical and chemical properties of fluorine- doped silicon dioxide (SiOF) films are evaluated. These films were deposited by TEOS-PECVD technique with C2F6 as the fluorine source. The effects of fluorinedoping on dielectric constant, refractive index, chemical bonding, thermal stability and surface morphology of the SiO2 will be assessed. The relative dielectric constant of SiOF films can be lowered to 3.2 with Si-F bonding concentration 8.9 at.% in our experiments. Fourier Transform infrared (FTIR) spectra provide evidence for enhanced moisture absorption of films with higherfluorine content. Moisture absorption and desorption during heat treatments are found to be the critical factor that influences the stability and reliability of SiOF films. One of the basic requirements for the utilization of this multilevel metallization scheme is to achieve the global planarization. Chemical- mechanical polishing(CMP) process has been proven to be the most promising method to accomplish global planarization. In this thesis, results of chemicalmechanical polishing of SiOF thin films were studied. Nanohardness, elastic modulus, and bonding structure of fluorinated silicon dioxides are characterized in order to evaluate their correlations with CMP performance. We find out that under fixed chemistry and mechanical parameters, the CMP removal rate increases significantly with increasing fluorine content in the oxides due to the lower hardness and elastic modulus in the SiOF films. In addition, the greater slope of the removal rate versus pressure line for SiOF films compared with undoped oxides signifies the enhanced chemical erosion during CMP of fluorinated oxides, in agreement with the wet etching results which etched by BOE solutions.