Grant M. Kloster

Mechanistic study of plasma damage of low k dielectric surfaces

Plasma damage to low k dielectric materials was investigated from a mechanistic point of view. Low k dielectric films were treated by Ar, O2, N2, N2∕H2, and H2 plasmas in a standard reactive ion etching chamber and the damage was characterized by angle resolved x-ray photoelectron spectroscopy, x-ray reflectivity, Fourier transform infrared spectroscopy, and contact angle measurements. Both carbon depletion and surface densification were observed on the top surface of damaged low k materials while the bulk remained largely unaffected. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. A downstream hybrid plasma source with separate ions and atomic radicals was employed to study their respective roles in the plasma damage process. Ions were found to play a more important role in the plasma damage process. The dielectric constant of low k materials can increase up to 20% due to p...

Porosity effects on low-k dielectric film strength and interfacial adhesion

The elastic modulus and hardness of low k dielectric films rapidly decrease as porosity increases. By contrast, interfacial adhesion is relatively insensitive to porosity. Adhesion energy values measured by the four-point bend method are similar for porous and non-porous films. Additionally, interfacial adhesion is much stronger for polymer films than for organosiloxane films, regardless of porosity. E-beam treatments significantly improve the modulus and hardness of porous organosiloxane films, sacrificing only a slight increase in dielectric constant. Solid-state NMR and pore size measurements indicate that the improved mechanical properties result from a cross-linking mechanism rather than macroscopic densification. TOFSIMS results show that the increased dielectric constant results from carbon loss and an increase in silanol concentration. E-beam treatments, however, do not improve interfacial adhesion significantly.

Origin of dielectric loss induced by oxygen plasma on organo-silicate glass low-k dielectrics

This study investigated the origin of dielectric loss induced by O2 plasma on organo-silicate glass low-k dielectrics. The contributions from the polarization components to dielectric constant were delineated by analyzing the results from capacitance-voltage measurement, spectroscopic ellipsometry, and Fourier transform infrared spectroscopy together with the Kramers–Kronig dispersion relation. The dielectric loss was found to be dominated by the dipole contribution, compared with the electronic and ionic polarizations. The origin of the dipole contribution was further investigated by performing quantum chemistry calculations. The physisorbed water molecules were found to be primarily responsible for the dipole moment increase and the dielectric loss.

On‐Wafer Crystallization of Ultralow‐κ Pure Silica Zeolite Films

A higher goal: An on-wafer crystallization process to prepare pure silica zeolite (PSZ) MEL-type films that is superior to the previously used hydrothermal process is reported. These striation-free MEL-type films (right, see picture) outperform the traditional spin-on films (left) in terms of the kappa value, mechanical properties, surface roughness, mesopore size, and size distribution.

Hydrofluoric-Acid-Resistant and Hydrophobic Pure-Silica-Zeolite MEL Low-Dielectric-Constant Films

A new technique for the silylation of pure-silica-zeolite MEL low-k films has been developed in which the spin-on films are calcined directly in trimethylchlorosilane or 1,1,1,3,3,3-hexamethyldisilazane (HMDS) in order to protect the films against corrosive wet etch chemicals and ambient moisture adsorption. In an alternative procedure, HMDS is also added to the zeolite suspension before film preparation. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, water-soak tests, and HF etch tests are performed to characterize the films. The dielectric constant is as low as 1.51, and the films resist HF attack up to 5.5 min. These properties are highly desirable by the semiconductor industry for next-generation microprocessors.

Mechanistic Study of Plasma Damage and CH4 Recovery of Low k Dielectric Surface

A mechanistic study was performed to investigate plasma damage and CFL, recovery of porous carbon-doped oxide (CDO) low k surfaces. First the nature of damage was examined for different plasma treatments in a standard RIE chamber then followed by a study using a downstream hybrid plasma source with separate ions and atomic radicals to investigate their respective roles in the plasma process. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. Moisture uptake after plasma damage was found to be a major reason to cause dielectric constant increase. The CFL plasma treatment was found to be promising in repairing oxygen ashing damages by formation of a carbon-rich polymer layer. However, sp2 carbons on the top polymer layer seemed to limit the penetration of plasma CH4 and thus full recovery of low k damage.

Effect of CH4 Plasma Treatment on O2 Plasma Ashed Organosilicate Low-k Dielectrics

During an O 2 plasma ashing process, carbon depletion and subsequent moisture uptake caused increase of keff and the leakage current in an organosilicate (OSG) low-k dielectric. For dielectric restoration, additional CH 4 plasma treatment on the O 2 plasma ashed OSG low-k dielectric was investigated using angle resolved x-ray photoelectron spectroscopy (ARXPS), XPS depth profiling, x-ray reflectivity (XRR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and contact angle goniometer. After CH 4 plasma treatment on the O 2 plasma ashed OSG, the surface carbon concentration and surface hydrophobicity were partially recovered. A dense surface layer containing C=C bonds was found to have formed on the top of the damaged OSG. The C-V hysteresis and the leakage current were reduced as a result of the CH 4 plasma treatment. XPS depth profiling revealed that the recovery effect was limited to the surface region.

Correlation of Surface and Film Chemistry with Mechanical Properties in Interconnects

As the industry moves towards using low k dielectrics in advanced interconnects, interfacial adhesion and film mechanical properties play increasingly important roles in yield and reliability. Improving these mechanical properties requires a better understanding of the surface, interface and film chemistry. Time‐of‐Flight Secondary Ion Mass Spectrometry (TOF‐SIMS) was used to examine the surface molecular structure of organosilicate and organic polymer based low k interlayer dielectrics (ILDs). Strong correlations were established between surface group functionality, reactivity of the TiN precursors with the ILDs during Atomic Layer Deposition (ALD), and adhesion between the copper barrier and the ILDs. Hydrogen plasma treatment significantly changed the surface chemical structure of the polymer ILD through hydrogenation. Correspondingly, degradation of barrier/polymer adhesion and thermal stability was observed. For the organosilicate ILD, the modulation of film chemistry, primarily the siloxane structur...

Printability of extreme ultraviolet lithography mask pattern defects for 22-40 nm half-pitch features

Assessing the printability of EUV (extreme ultraviolet) lithography mask pattern defects is critical for determining EUV mask patterning, defect metrology, and repair technology requirements. Printability of mask defects at the wafer level depends on defect size, defect shape, defect location, and the line width and pitch of the structure being printed. Earlier reports showed the relationship between the defect size on the mask and the printed critical dimension for 40-70 nm dense lines. Improvements in the EUVL process now enable assessment of mask pattern defect printability for 22-40 nm half-pitch features. We report here the smallest mask pattern defects that printed at different locations in 22-40 nm structures using the Intel Micro-Exposure Tool (MET). Various types of defects such as indentations or protrusions were purposely incorporated into features on an EUV mask. The sizes of the patterned defects on the mask were drawn between 10-250 nm (= 2-50 nm on the wafer). The minimum printable defect size varied by over 100 nm, depending on the defect shape and location.

Mechanistic Study of Plasma Damage of Low k Dielectric Surfaces

Plasma damage to low k dielectric materials was investigated from a mechanistic point of view. Low k dielectric films were treated by plasma Ar, O2, N2/H2, N2 and H2 in a standard RIE chamber and the damage was characterized by Angle Resolved X-ray Photoelectron Spectroscopy (ARXPS), X-Ray Reflectivity (XRR), Fourier Transform Infrared Spectroscopy (FTIR) and Contact Angle measurements. Both carbon depletion and surface densification were observed on the top surface of damaged low k materials while the bulk remained largely unaffected. Plasma damage was found to be a complicated phenomenon involving both chemical and physical effects, depending on chemical reactivity and the energy and mass of the plasma species. A downstream hybrid plasma source with separate ions and atomic radicals was employed to study their respective roles in the plasma damage process. Ions were found to play a more important role in the plasma damage process. The dielectric constant of low k materials can increase up to 20% due to plasma damage and we attributed this to the removal of the methyl group making the low k surface hydrophilic. Annealing was generally effective in mitigating moisture uptake to restore the k value but the recovery was less complete for higher energy plasmas. Quantum chemistry calculation confirmed that physisorbed water in low k materials induces the largest increase of dipole moments in comparison with changes of surface bonding configurations, and is primarily responsible for the dielectric constant increase.