S. Vanhaelemeersch

A 0.314/spl mu/m/sup 2/ 6T-SRAM cell build with tall triple-gate devices for 45nm applications using 0.75NA 193nm lithography

This paper describes the fabrication process of a fully working 6T-SRAM cell of 0.314/spl mu/m/sup 2/ build with tall triple gate (TTG) devices. A high static noise margin of 172 mV is obtained at 0.6 V operation. Transistors with 40nm physical gate length, 70nm tall & 35nm wide fins, 35nm wide HDD spacer are used. Low-tilt extension/HALO implants, NiSi and Cu/low-k BEOL are some of the key features. This is an experimental demonstration of a fully working tall triple gate SRAM cell with the smallest cell size ever reported.

Controllable Change of Porosity of 3-Methylsilane Low-k Dielectric Film

A method for controllable increase of porosity of low-k silicon oxycarbide films (SiOCH), deposited by oxidation of 3-methylsilane, has been developed using etching of the SiOCH film by diluted HF solution. The modified SiOCH film is characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and ellipsometric porosimetry. It is found that the chemical composition of the modified SiOCH film remains almost the same during etching. No significant thickness loss is observed, while the pore radius and the film porosity increase with HF dip time. It was concluded that the increase of the pore radius is caused by isotropic etching inside the pores as well as at the film surface. The very low etch rate of SiOCH film by diluted HF and the large difference between the pore radius and the film thickness allows an increase in the porosity without significant thickness loss. This method is a way to prepare ultralow-k dielectric films with higher chemical stability as compared to oxide and silesquioxane-based porous materials.

Low temperature oxidation and selective etching of chemical vapor deposition a-SiC : H films

Chemical vapor deposition silicon carbide films are considered as a perspective hard mask and stop layer in advanced dry etch technology because of the high chemical and plasma stability. However the a-SiC:H film should be etched away after technological use. In this case the high chemical stability of the a-SiC:H films troubles the solution of this problem. A new approach for the selective removal of the a-SiC:H films is discussed. The basic idea is low-temperature oxidation of the a-SiC:H film and selective removal of the reaction products by wet and/or dry etching. Fourier transform infrared, x-ray photoelectron spectroscopy, and ellipsometry were used for the characterization of the a-SiC:H oxidation and etching of the reaction product. As an example of the practical application, the a-SiC:H films were tested as a dry contact etch stop layer in a 0.18 μm complimentary metal–oxide–semiconductor technology. Results of the electrical evaluation of test structures prepared by this technology are discussed...

SiF2 as a primary desorption product of Si etching by F atoms: Interpretation of laser‐induced fluorescence spectra; rate constant of the gas phase SiF2+F reaction

Using a laser‐induced fluorescence technique, SiF2 radicals are detected as primary gas‐phase products of the chemical etching of silicon by fluorine atoms. The bending frequencies for the lower (X 1A1) and the excited (A 1B1) state of the SiF2 molecule are determined from the observed excitation and fluorescence spectra and are in close agreement with literature. The v‘2 intensity distribution of the fluorescence spectra corroborates the assignment of the upper‐state vibrational levels. In a second series of experiments, the rate constant for the SiF2+F reaction at room temperature was measured: k = (5 ± 1) × 10−13 cm3 molecule−1u2009s−1 at pressures of 1–5 Torr helium. The absence of pressure dependence is rationalized in terms of radiative deactivation of the SiF*3 product.

Comparative study of PECVD SiOCH low-k films obtained at different deposition conditions

Four CVD SiOCH films deposited at various conditions were used for comparative evaluation. The films were evaluated by RBS, spectroscopic ellipsometry, and ellipsometric porosimetry. Oxygen plasma resistance was studied by spectroscopic ellipsometry and TOF-SIMS analysis after exposure of the films to downstream oxygen plasma. The different deposition conditions result in different carbon content and different porosity. The film with the highest carbon content has the lowest porosity and vice versa. As carbon content of films increases and their porosity decreases, the SiOCH films become more resistant to oxygen plasma.

Integration of Cu and low- k dielectrics: effect of hard mask and dry etch on electrical performance of damascene structures

Abstract In this work we discuss the importance of selecting the hard mask material and choosing the optimum dry etch and post-CMP clean processes on the integration of Cu and organic low-k dielectrics. The hard mask material plays an important role in the interline capacitance and in the effective dielectric constant of the interconnects. One generation of effective k can be gained simply by replacing the hard mask material by one with a lower dielectric constant, instead of moving to a more advanced low-k material. Interline leakage is not affected by the hard mask material and low values (∼10−9 A/cm2) are obtained at electric fields of 1 MV/cm for structures with spacing down to 0.2 μm. A non-optimized dry etch process for trench definition can result in undercutting, which affects the Cu filling of the trenches. From our results it is clear that the process conditions (lithography, etch, CMP) affect the geometry of the structures, which has a big impact on the effective dielectric constant of the interconnects.

Process Optimization and Integration of Trimethylsilane-Deposited α-SiC:H and α-SiCO:H Dielectric Thin Films for Damascene Processing

The semiconductor grade organosilicon gas trimethylsilane (Dow Corning Z3MS) can be used to deposit unique amorphous hydrogenated silicon carbide (α-SiC:H)-based alloy films that exhibit desirable properties such as chemical resistance, low stress. low permittivity, and low leakage. These film characteristics are ideal for applications in Cu-damascene interconnect technology. In this work, the results of a comprehensive study of Z3MS plasma enhanced chemical vapor deposition (PECVD) dielectric films are reported where all depositions were performed in commercial production PECVD equipment. Processing for α-SiC:H films deposited from Z3MS/He mixtures was optimized for deposition rate, uniformity, and permittivity. The processing parameters can be tuned for relative permittivity down to κ ∼ 4.2 making α-SiC:H an attractive substitute for PECVD silicon oxide or silicon nitride. Using mixtures of Z3MS and N 2 O precursors, α-SiCO:H films were deposited with very high deposition rates and film permittivity as low as κ ∼ 2.5. These films have been applied in damascene technology. Physical properties and stability of blanket films were studied. Measurement of relative permittivity, leakage current, and breakdown voltage was performed on metal/dielectric/metal structures. Fourier transform infrared, X-ray photoelectron, and high-energy ion scattering spectrometry were used to determine bonding and film compositions. Integration issues related to deep ultraviolet lithography, dry etch, strip, and metallization are discussed. Optimized film processes were integrated into 0.18 μm Cu damascene interconnect process technology and the electrical results were compared to standard PECVD oxide. The results of these studies indicate that the device performance improvements inferred from the blanket film properties can be realized in fully integrated interconnect structures.

Plasma Modification of Porous Low-k Dielectrics

The effect of CF 4 /O 2 -based plasma treatment on two types of porous low dielectric constant (low-k) materials was investigated. For the microporous film, the surface appears to be sealed, most likely by the formation of a silicon oxide-like layer within 5 s of treatment. For both microporous and mesoporous materials, fluorine incorporation at the surface was low (∼3 to 6 atom %) after 15 s exposure to the plasma. Processing using CF 4 /O 2 -based plasma appears not to induce significant change to the porous low-k materials as evidenced by similar atomic compositions measured using Auger spectroscopy. These results point to a mechanism that involves a competition between surface modification/oxidation and material removal under the action of fluorine-containing species in the plasma.

A Novel Deep Trench Isolation Featuring Airgaps for a High-Speed 0.13μm SiGe:C BiCMOS Technology

A novel scheme for deep trench isolation is presented, which uses an airgap as insulator. When incorporated in our 0.13mum SiGe:C BiCMOS technology, the peripheral substrate parasitics decrease with an order of magnitude to a record value of 0.02fF/mum, which significantly improves the device RF performance

Low dielectric constant materials: challenges of plasma damage

Degradation of porous low dielectric constant materials during their exposure in etch and strip plasmas is analyzed from point of view of surface chemistry and recombination of active radicals. Although the degree of damage during the etching can be significantly reduced, the damage in O2 and H2 based strip/cleaning plasma are more challenging. The plasma damage mechanisms are the main subject of this discussion. It is demonstrated why the degree of damage can be reduced using He and H2 based plasmas at elevated processing temperature