Synthesis of Model Alumina Slurries for Damascene Patterning of Copper
- PDF / 527,834 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 7 Downloads / 194 Views
Synthesis of Model Alumina Slurries for Damascene Patterning of Copper Byung-Chan Lee1 , David J. Duquette, and Ronald J. Gutmann Center for Integrated Electronics and Electronics Manufacturing, Rensselaer Polytechnic Institute Troy, NY 12180, U.S.A. 1 Present address: Intel Corporation, 5200 N.E. Elam Young Parkway, Hillsboro, OR 97124 ABSTRACT Model alumina slurries for chemical-mechanical planarization (CMP) of copper have been studied using fundamental electrochemical concepts together with modification of surface tension and zeta-potential. A model slurry was established containing 3 wt% alumina (50 nm nominal size), 2 wt% potassium dichromate (K2Cr2O7) and 1 vol % DOWFAX, as abrasive, oxidizer and anionic surfactant, respectively, which resulted in blanket copper removal rates of 130 nm/min with smooth, low-particulate defect density surfaces without aggressive post-CMP cleaning. When used with a model silica-abrasive slurry to remove the Ta liner, well-defined damascene-patterned structures were achieved with low-particulate defect densities. Open circuit potential measurement, potentiodynamic polarization, surface tension measurement, and zeta-potential measurement were used in developing the model slurries. The variations obtained with alternative abrasives, alternative oxidizers and alternative surfactants illustrate the principles of synthesizing slurries for Cu and Ta. INTRODUCTION Chemical-mechanical planarization (CMP) is a process to remove material from a surface and to achieve a smooth surface by the combined action of chemical reaction and mechanical abrasion. CMP has been used to realize multilevel copper interconnects on patterned surfaces for high performance and high circuit density. A main drawback of the CMP process is the possible introduction of defects, since the process inherently involves contact of fine particles and impurities with the wafer surface. Post-CMP wafers may have different kinds of contaminants, including residual slurry abrasive particles and chemicals, abraded metallic contaminants from the wafer, and hydrocarbons from the pad [1]. Particles and impurities may cause processing and yield problems for ULSI circuits, now and in the future with decreasing feature sizes. In the case of the copper damascene process, metallic contaminants are mainly present on the surface of the wafer in the form of adsorbed ions, oxides, hydroxides and salts, depending on the slurries used for CMP. These metallic species can be readily removed using wet chemical cleans in acidic media, preferably after removing particulate contaminations [2]. The removal of particulate contaminations may be difficult depending upon the composition of the slurry, wafer surface, and method used for post-CMP cleaning due to the small size of the contaminants. Therefore, a reduction of particulate contamination during CMP is desirable to alleviate the postCMP cleaning requirement. The characteristics of the particle/solution interface in the slurry are directly related to the agglomeration of abrasives and particul
Data Loading...
