| AVS 57th International Symposium & Exhibition | |
| Surface Science | Tuesday Sessions |
| Session SS-TuP |
| Session: | Surface Science Poster Session |
| Presenter: | D. Popovic, University of Belgrade, Serbia |
| Authors: | D. Popovic, University of Belgrade, Serbia A. Zekic, University of Belgrade, Serbia V. Milosavljevic, Dublin City University, Ireland & University of Belgrade, Serbia |
| Correspondent: | Click to Email |
Low dielectric constant materials (low-k) are used as interlevel dielectrics in integrated circuits. As components have scaled and transistors have gotten closer and closer together, the insulating dielectrics have thinned to the point where charge builds up and crosstalk adversely affects the performance of the device. It is this reduction in scale which drives the need for insulating materials with lower dielectric constant. A ‘low-k’ material is one with a small value for dielectric constant relative to silicon dioxide (SiO2) a former dielectric of choice. There are many materials with lower dielectric constants, but few of them can be suitably integrated into a semiconductor manufacturing process.
The SiO2 is frequently used in a plasma chamber as a wafer for etching. The interaction of the plasma and the SiO2 surface leads to incorporations/removing material for structure of SiO2 and also to increasing of the dielectric constant. So the optimization problem in materials development for semiconductors is to lower the permittivity of the dielectric material as far as possible without compromising mechanical integrity.
The dielectric function spectra of low dielectric constant (low-k) materials have been determined using spectroscopic ellipsometry, near-normal incidence spectroscopic reflectometry, and Fourier transform infrared transmission spectrometry over a wide spectral range from 0.03 to 5.4 eV (230nm to 40.5μm wavelength region). The electronic and ionic contributions to the overall static dielectric constant were determined for representative materials used in the semiconductor industry for interlayer dielectrics. The main contributions to the static dielectric constant of the low-k materials studied were found to be the electronic and ionic absorptions.
To perform the study, square shape wafers (15x15mm) are placed in the discharge tube. The angle between wafers plane and a constructed channel is 450. The DC discharge is produced in a Pyrex tube of 5mm inner diameter and an effective plasma length of 72mm. The discharge tube is evacuated using a vacuum pump that gives a base pressure of 2Pa. The working pressures from 50 to 266 Pa are achieved using a gate valve positioned above the rotary pump. Gas flow into the chamber is controlled via mass flow controllers that precisely determine gas content in the discharge tube. The working gas is a sulphur-hexafluoride (SF6) with flow rate up to 40 sccm. The power supply used was a Keithley Model 248 high voltage supply with a maximum voltage of 5kV and discharge current of 5 mA. In this experimental campaign the maximum voltage is 2.2kV. The wafer processing time is 30 min.