Fluorosilicate Glass Films Research Articles

Characterization and thermal stability of fluorosilicate glass films deposited by high density plasma chemical vapor deposition with different bias power

High-density plasma chemical vapor deposition (HDP-CVD) fluorosilicate glass (FSG) films were evaluated for the application of inter-metal dielectric (IMD) materials in current devices. Film characteristics were examined as a function of deposition/sputter etch (D/S) ratio, which was controlled by the bias power in HDP-CVD. FTIR spectra show that the positions of Si–O and Si–F peaks are independent of the bias power, but the Si–O shifted to a higher wave number and Si–F 2 appeared upon annealing for the films deposited at lower bias power. Stress hysteresis of the FSG films after the first thermal cycle shows a nonequilibrium nature of the microstructure related to impurity content, especially for the film deposited with lower bias power. Thermal desorption of H 2O, F, O 2 and Ar were examined, while most of the desorption behaviour can be related to the physical pore structure and pore quantity.

Characterization of sputter-induced temperature effect in fluorine doped SiO 2 film deposition by high-density plasma chemical vapor deposition

High-density plasma chemical vapor deposited fluorosilicate glass (FSG) has been successfully used for the inter-metal dielectric material in ultra-large semiconductor integration manufacturing due to its low-dielectric constant and stable gap-filling capability. However, temperatures rise and related effects due to sputter etch from the deposition process have become major concerns for film properties. In this paper, an independent helium-cooling system was employed to control a suitable temperature range from 410 °C to 460 °C during FSG deposition. Subsequently, film properties including fluorine concentration, distribution, refractive index, dielectric constant and gap-filling capability were thus examined as a function of He pressure used in the cooling system. The results show that both deposition rate and fluorine concentration increase with increasing helium pressure; however, more fluorine becomes inactive, which might be present as defects. We have shown that an FSG film with a dielectric constant down to 3.43 as well as good gap-filling capability can be achieved when employing this new cooling system with 9 mTorr helium pressure.

Integration of a stack of two fluorine doped silicon oxide film with ULSI interconnect metallization

Recently, fluorosilicate glass (FSG) has received much attention for application in microelectronics manufacturing due to its low dielectric constant and stable gap-filling ability. Although FSG films have been demonstrated as potential inter metal dielectrics (IMD) for sub-micron devices, integrating a stack of two fluorine doped silicon oxide film deposited on a high-density plasma chemical vapor deposition (HDP-CVD) system for gap filling and a plasma-enhanced chemical vapor deposition (PECVD) system for throughput has not been fully investigated. In this research, an excellent and exceptionally stable process was demonstrated for a stack of HDP-CVD FSG and PECVD FSG layers. Cracks that result from multi-level metal technology were eliminated when higher compressive stress PECVD FSG film was implemented as a capping layer. An 11% capacitance reduction was achieved when comparing a stack of FSG films to undoped silicon oxide. No problem occurred for photo, via etching and chemical mechanical polishing of FSG film. The FSG layer stack’s via resistance (Rc_Via) as well as a full HDP-FSG scheme is comparable. These results are very promising for the integration of FSG films as inter metal dielectric for devices.

Characterization and reliability of low dielectric constant fluorosilicate glass and silicon rich oxide process for deep sub-micron device application

Fluorosilicate Glass (FSG) with low dielectric constant currently has been replaced as an alternative to SiO 2 for device speed improvement. However, several integration aspects, such as Fluorine (F) distribution, F thermal stability, gap fill capability, capacitance reduction and via resistance of FSG prepared by the high density plasma (HDP) chemical vapor deposition (CVD) method are of concern for sub-0.18-μm devices. In this study, HDP–FSG films show different F concentrations at different locations on an 8-inch wafer. In addition, the FSG film shows poor thermal stability and F diffuses out of the film after high temperature annealing and the pressure cook test (PCT). However, the thermal stability of FSG film can be improved by capping with an oxide layer. The results indicate that silicon rich oxide (SRO) has a better effect at blocking the F diffusion out of FSG films at high temperature than plasma enhanced oxide (PE-OX). For the gap fill capability, HDP-FSG can fill all 0.23-μm gaps and some of the 0.21-μm gaps with an aspect ratio <3.8 but not the 0.19-μm gaps. A 8000 Å HDP–FSG film with 600 Å USG liner and 2000 Å cap layer shows approximately 7.5 to 7.7% capacitance reduction on 0.23/0.23-μm gaps when compared with USG (undoped silicate glass). In addition, FSG has a larger capacitance reduction on the wider metal lines than the thinner metal lines at the same gap size due to a capacitance fringe effect. The via resistance for 0.26 μm unlanded via (which allow minor photo mis-alignment) of HDP-FSG film is also similar to that of USG.

Surface-Processing-Enhanced Copper Diffusion into Fluorosilicate Glass

This study investigated copper diffusion into processed fluorosilicate glass (FSG). It is observed that the surface process enhances the flatband voltage shift of the Cu/FSG/Si capacitor structure under bias-temperature stress. Secondary-ion mass spectroscopy analysis confirmed that the flatband voltage shift was due to Cu diffusion into the FSG film. Thermal desorption spectrometer analysis indicated that the surface damage layer took up more moisture. A surface-damage-layer-enhanced Cu ionization model was then proposed to explain the observation. The investigation concludes that the diffusion of Cu into FSG is strongly dependent on the surface condition of the FSG film. The proposed model also provides explanation for the inconsistent results reported in previous literature. © 2001 The Electrochemical Society. All rights reserved.

Sidewall Quality and Step Coverage of Thin Fluorosilicate Glass Films

AbstractThe quality of TEOS fluorosilicate glass (FSG) films deposited on deep silicon trenches was investigated by etching the films with 100:1 HF. The etch rate of the top and sidewall surfaces was measured by SEM as a function of FSG fluorine content. The FSG wet etch rate was correlated to the refractive index, stress and fluorine content. The sidewalls were found to etch slower than the top surfaces, suggesting a lower fluorine content on the sidewalls. Additionally, the step coverage of TEOS oxide improved significantly as fluorine content was increased.

Study of fluorine stability in fluoro-silicate glass and effects on dielectric properties

The stability of PECVD fluorosilicate glass (FSG) layers deposited with a TEOS/O 2/C 2F 6 chemistry was investigated. The FSG water absorption was found to increase with the fluorine concentration. At a fluorine content above 4 at.%, the fluorine seems to react with the water present in the film and then outgasses. In this case the film properties are altered: the stress increases drastically (compressive to tensile) and the dielectric constant rises. But stable layers, with low absorptivity of water and no fluorine outgassing can be obtained at 3.5 at.% fluorine. These stable layers enable a dielectric constant of 3.6 to be reached, no corrosion is detected on metal lines (Ti/TiN/AlCu/TiN) capped with 1 μm of such FSG, after a moisture absorption test (168 H, 85°C, 85%HR) and annealing at 450°C. Good adhesion of the metal lines directly deposited on the FSG, using a TiN barrier, was observed. Furthermore, the gap filling capability of these FSG films is significantly improved compared with standard PECVD TEOS oxide films.

Characterization of PECVD Deposited Fluorosilicate Glass (FSG) After CMP and Cleaning

AbstractA characterization of Plasma-Enhanced CVD Fluorinated Silicate Glass (FSG) is presented. This study investigates the behavior of FSG film in the Chemical Mechanical Polishing (CMP) environment and compares those characteristics to undoped TEOS (UTEOS), Thermal Oxide and Si-Rich oxide capped FSG films. The removal rate, refractive index (RI), surface roughness, contact angle, water content by FTIR and thermal desorption spectroscopy (TDS) were studied.The FSG films are polished ˜ 10% faster than the undoped PECVD oxide films. Their composition was slightly changed after CMP as can be seen by the minor increase in the RI. A layer of Si-Rich oxide (SRO) was found to have a stabilizing effect on the FSG film during CMP and post CMP cleaning operations, and thus can be used in the intermetal dielectric schemes that require low dielectric constant FSG layers.