Eugene Joseph Karwacki

Ion energy distributions and optical emission spectra in NF3-based process chamber cleaning plasmas

To minimize ion bombardment induced damage in NF3-based chamber cleaning plasmas, we have studied the effects of diluent gases and reactor pressure on ion energy distribution functions in NF3 plasmas. We have utilized plasma ion mass spectrometry, ion energy analysis, and optical emission spectroscopy in 25 mol % NF3 plasmas with argon, helium, and oxygen diluents. We have also compared the NF3-based plasma measurements to those of 50 mol % C2F6/O2 plasmas. We have demonstrated that diluting with helium and operating at higher pressures will reduce ion energies in NF3 plasmas while maintaining superior chamber cleaning performance. In addition, we have correlated the intensity ratio of specific argon emission lines to average ion energies at the grounded electrode. This correlation provides a practical diagnostics tool for further optimization work.

Impact of Pore Size and Morphology of Porous Organosilicate Glasses on Integrated Circuit Manufacturing

Porous organosilicate materials produced by plasma enhanced chemical vapor deposition are the leading candidates for back-end-of-line dielectric insulators for IC manufacturing at 45nm design features and beyond. The properties of porous organosilicate glass films of dielectric constant k=2.50 ± 0.05 formed using diethoxymethylsilane and five different porogen precursors with an ultraviolet post treatment are reported. By varying the porogen precursor type pore sizes of 1-2 nm (equivalent spherical diameter) and porosities in the range of 24-31% were measured. While there were no observable trends in pore size with the molecular volume or plasma reactivity of the porogen precursor, modulus values ranged from 6.6 to 10.8 GPa. Porous films with the highest mechanical properties were found to have the highest matrix dielectric constant, highest network connectivity (lowest methyl content), and highest density. Within this process space, maximizing the network connectivity of the film was found to be more important to mechanical properties than lowering the total porosity. In effect, the choice of porogen precursor dictates the film morphology through its impact on the organosilicate glass matrix and pore size.

Optimization and analysis of NF3 in situ chamber cleaning plasmas

We report on the optimization and analysis of a dilute NF3 in situ plasma-enhanced chemical vapor deposition chamber cleaning plasma for an Applied Materials P-5000 DxL chamber. Using design of experiments methodology, we identified and optimized operating conditions within the following process space: 10–15 mol % NF3 diluted with helium, 200–400 sccm NF3 flow rate, 2.5–3.5 Torr chamber pressure, and 950 W rf power. Optical emission spectroscopy and Fourier transform infrared spectroscopy were used to endpoint the cleaning processes and to quantify plasma effluent emissions, respectively. The results demonstrate that dilute NF3-based in situ chamber cleaning can be a viable alternative to perfluorocarbon-based in situ cleans with added benefits. The relationship between chamber clean time and fluorine atom density in the plasma is also investigated.

Power dependence of NF3 plasma stability for in situ chamber cleaning

We investigated the stability of NF3 plasmas for in situ chamber cleaning in a production plasma-enhanced chemical vapor deposition reactor. An rf power threshold, normalized by NF3 molar number (Pnn) and NF3 flow rate (Pnf), is observed to be PnnPnf=39 (W/μ mol)(W/sccm) for stable plasmas with high NF3 destruction efficiency. This is rationalized by the energy required to maintain sufficient electron–ion pair creation in an electronegative discharge.

Plasma Enhanced Chemical Vapor Deposition of Porous Organosilicate Glass ILD Films With k ≤ 2.4.

We report on our work to develop a process for depositing nanoporous organosilicate (OSG) films via plasma enhanced chemical vapor deposition (PECVD). This approach entails codepositing an OSG material with a plasma polymerizable hydrocarbon, followed by thermal annealing of the material to remove the porogen, leaving an OSG matrix with nano-sized voids. The dielectric constant of the final film is controlled by varying the ratio of porogen precursor to OSG precursor in the delivery gas. Because of the need to maintain the mechanical strength of the final material, diethoxymethylsilane (DEMS) is utilized as the OSG precursor. Utilizing this route we are able to deposit films with a dielectric constant of 2.55 to 2.20 and hardness of 0.7 to 0.3 GPa, respectively.

Submillimeter-wavelength plasma chemical diagnostics for semiconductor manufacturing

Submillimeter-wavelength linear-absorption spectroscopy has been applied to the chemical diagnostics of reactive-ion etching plasmas in a modified capacitively coupled gaseous electronics conference reactor. Approximately 1 mW of narrow-band (<10 kHz) submillimeter radiation between 450 and 750 GHz is produced using a backward-wave oscillator (BWO). The BWO is frequency stabilized to a harmonic of a 78–118 GHz frequency synthesizer. The submillimeter method offers high sensitivity for the ≈1 MHz linewidth, Doppler-broadened absorption lines typical of gas-phase molecules at a total pressure of less than 133 Pa (1 Torr). A large number of molecules can be detected, limited primarily by the need for a permanent electric dipole moment and for accurate line frequency predictions, the latter of which are often available in the literature. The capabilities of the diagnostic method have been demonstrated by the following three applications: (1) the measurement of water-vapor contamination in the reactor and in the precursor gas by monitoring a rotational transition of H2O in the reactor just prior to the initiation of the plasma; (2) the assessment of progress in the cleaning of the reactor by an O2/Ar plasma after a fluorocarbon plasma etch by monitoring the build up of the concentration of O3 and the depletion of the concentration of CF2O in the plasma; and (3) the determination of the endpoint in the etching of a SiO2 thin film on silicon by an octafluorocyclobutane/O2/Ar plasma by monitoring the decrease in the concentration of SiO in the plasma. The last observation is made possible by the large electric dipole moment for SiO of 1×10−29 C m (3.1 D), which gives a low minimum detectable number density for the radical of 2×107 cm−3 for an optical pathlength of 39 cm.Submillimeter-wavelength linear-absorption spectroscopy has been applied to the chemical diagnostics of reactive-ion etching plasmas in a modified capacitively coupled gaseous electronics conference reactor. Approximately 1 mW of narrow-band (<10 kHz) submillimeter radiation between 450 and 750 GHz is produced using a backward-wave oscillator (BWO). The BWO is frequency stabilized to a harmonic of a 78–118 GHz frequency synthesizer. The submillimeter method offers high sensitivity for the ≈1 MHz linewidth, Doppler-broadened absorption lines typical of gas-phase molecules at a total pressure of less than 133 Pa (1 Torr). A large number of molecules can be detected, limited primarily by the need for a permanent electric dipole moment and for accurate line frequency predictions, the latter of which are often available in the literature. The capabilities of the diagnostic method have been demonstrated by the following three applications: (1) the measurement of water-vapor contamination in the reactor and in t...

Electron Attachment: A New Approach to

Wafer bumping, via fluxless solder reflow, can be performed using electron attachment (EA) with nonflammable mixtures of hydrogen (= 4 vol%) in nitrogen. The EA process facilitates dissociation of molecular hydrogen at ambient pressure and a temperature significantly lower than that of thermal dissociation. Our studies suggest that the EA process promotes the formation of atomic hydrogen anions, which reduce solder oxides and facilitate fluxless solder reflows at temperatures close to the solder melting point.

{\rm H} _{2}

In this paper we examine the relationship between precursor structure and material properties for films produced from several leading organosilicon precursors on a common processing platform. Results from our study indicate that for the precursors tested the nature of the precursor has little effect upon film composition but significant impact on film structure and properties. Introduction There are a variety of materials being considered for the next generation interlayer dielectric (ILD) materials. The leading candidates for the 90nm generation are organosilicate glasses produced by Plasma-Enhanced Chemical Vapor Deposition (PECVD). Providing materials with extendibility beyond a single generation solution requires the optimization of both electrical and mechanical properties. These are competing goals since concomitant with reducing the dielectric constant (k) is, in general, a decrease in the mechanical strength of a material. The goal of this work is to build a better understanding of the structure of low k dielectric films deposited from a PECVD process. In attempts to elucidate structureproperty relationships for OSG precursors we assessed a variety of chemicals including those used in various commercial product offerings. Experimental All experiments were performed on an Applied Materials Precision 5000 fitted with a 200mm DxZ chamber. Every attempt was made to optimize process regimes for each precursor to provide the best mechanical properties at a given dielectric constant (k). Films were analyzed for refractive index and thickness with a SCI FilmTek 2000 reflectometer calibrated daily. Electrical tests were performed on low resistivity wafers ( 20 ohm-cm) using a Thermo Nicolet 750 at 4 cm resolution, nitrogen purged cell and background corrected with Si. Selected samples were analyzed using Carbon-13 and Silicon-29 Nuclear Magnetic Resonance (NMR). Density Molecule Si–CH3:Si Si–O:Si Si–H:Si Structure

Fluxless Solder Reflow for Wafer Bumping

As the feature sizes of integrated circuits shrink, highly anisotropic etching process (i.e., ion-assisted plasma etch, or reactive ion etch (RIE)), becomes even more essential for successful pattern transfer in the fabrication of semiconductor devices. The stringent 193 nm lithography process necessitates the use of bottom anti-reflective coating (BARC) for controlling reflections and improving swing ratios. Prior to RIE of a patterned wafer, the BARC layer must first be opened to allow pattern transfer from the resist mask to the underlying films. As we enter the era of sub-90nm imaging, minimum loss of the photoresist during the BARC open step is becoming more critical, since the demand for higher optical resolution dictates the use of ever thinner resist films. This in turn requires higher etch rate of BARC materials. In this paper we report on the impact of etching gas chemistries on the etch rates of BARC materials. The correlation between the etch chemistry and BARC products will be discussed. Reactive ion etch rates for blanket BARC coatings and BARCs under resist patterns were measured. Etch rates of BARC products of various material compositions were measured with a typical ArF resist as reference. It is well known that the chemical composition and structure of organic materials essentially determine the etch rates under certain etch process conditions. The correlations between etch rates and BARC polymer chemistry are reported. Etch chemistries, (i.e. the chemical interaction of plasma reactive ions with BARC materials), may also have profound effects on etch rates. Here we report on results obtained using four etching gas chemistries to study how oxygen contents, polymerizing gases, and inert gas effect the etch rates of different ArF BARC products.

Optimized Materials Properties for Organosilicate Glasses Produced by Plasma-Enhanced Chemical Vapor Deposition

Submillimeter‐wavelength, linear‐absorption spectroscopy has been applied as a chemical diagnostic of a reactive‐ion etching plasma in a modified capacitively coupled Gaseous Electronics Conference (GEC) reactor. Approximately 1 mW of narrow‐band (< 10 kHz) submillimeter radiation between 450 GHz and 750 GHz is produced using a backward‐wave oscillator (BWO). The submillimeter method offers high sensitivity for the ≈ 1 MHz linewidth, Doppler‐broadened absorption lines typical of gas‐phase molecules at a total pressure of less than 133 Pa (1 Torr). A large variety of molecules can be detected, limited primarily by the need for a permanent electric dipole moment and for accurate line frequency predictions, which are often available in the literature. The capabilities of the diagnostic method have been demonstrated by the following three applications: 1) the measurement of water‐vapor contamination in the reactor and in the precursor gas; 2) the assessment of progress in the cleaning of the reactor; and 3) t...