High Density Plasma Chemical Vapor Research Articles

Silicon nitride cover layer prepared by silane-free plasma chemical vapor deposition for high quality surface passivation of silicon solar cells

Passivated emitter and rear contact (PERC) silicon solar cell is one of the most promising high-efficiency solar cells, which uses aluminum oxide (Al2O3) and hydrogenated silicon nitride (SiNx:H) stack as the rear passivation layer. The SiNx:H not only serves as a protective layer but can provide hydrogen atoms that further passivate the dangling bonds on silicon wafer surface. In this study, the SiNx:H cover layers are deposited using high density plasma chemical vapor deposition with a silane-free gas mixture of tetramethylsilane (TMS) and ammonia (NH3). Effects of the TMS gas flow rate on properties of the SiNx:H cover layers and effective minority carrier lifetime of silicon wafers are investigated. The experimental results show that the film density is positively related to the SiN bond proportion. The secondary ion mass spectrometry measurement shows that the dense SiNx:H can make hydrogen atoms move toward wafer surface instead of out-diffusion to the environment. The best SiNx:H film is deposited at a TMS flow rate of 35 sccm. The minority carrier lifetime can be improved from 70 μs for as-cleaned wafer to 373 μs for wafer/Al2O3 and to 1006 μs for wafer/Al2O3/SiNx:H. The surface recombination rate of 23 cm/s is obtained. Therefore, this study demonstrates the dense, silane-free SiNx:H films with high passivation quality for PERC solar cells.

Dielectric barrier layers by low-temperature plasma-enhanced atomic layer deposition of silicon dioxide

Electrothermal measurement techniques often require thin dielectric barriers to isolate active electrical test structures from samples of interest. The combined need for electrical passivation but thermal proximity necessitates the use of an electrically thick but thermally thin barrier layer. Here, we demonstrate a hybrid approach toward constructing sub-300 nm SiO2 multilayer barriers based upon low-temperature plasma-enhanced atomic layer deposition and high density plasma chemical vapor deposition. Using pairs of buried metal test structures, we quantify changes in device resistance and cross-talk after covering the dielectric barrier with thin evaporated gold films and thick electroplated copper films. We show that a hybrid approach to passivating electrothermal measurement devices outperforms individual homogenous barriers formed by either deposition technique.

Characterization of Ammonium Silicate Residue during Polysilazane (PSZ) Dry Etching in NF3/ H2O Gas Chemistry

For 28nm NAND flash memory, the aspect ratio of shallow trench isolation (STI) becomes large, and it makes difficult to fill STI structure by conventional oxide film without void formation. Several gap-fill methods such as high density plasma (HDP) and thermal chemical vapor deposition (CVD) are widely accepted, but they are difficult to make gap fill without void because of gap-fill margin. Recently, STI fill has been tried with polysilazane (PSZ) based inorganic spin-on dielectric (SOD) film. PSZ oxide has its good gap-fill ability, low moisture content and high etching resistance. However, PSZ oxide would produce amine etch residue during the NF3 dry etching process because of NH3component in PSZ oxide. For preventing this resudue, it is very important to control process parameters affecting the chemical reaction because the etch rate, and the surface quality depend upon the process reaction. During the STI etching back process, other layer also exposed. So, selectivity between other oxide must be considered. In this study, we have employed plasma dry etching of nitrogen trifluoride (NF3) and H2O mixtures. We studied the effect of the gas chemistry on the etching of oxides. The materials used for these experiments were thermally grown SiO2 (1000Å, 10000Å), PSZ oxide (500Å), TEOS (315Å) and ALD oxide (300Å). Samples of size 25 x 25 mm were cleaned first in diluted SC-1 [NH4OH(25%): H2O2(38%): DIW =1:2:50] at 60°C for 10 min. The etching mechanism of PSZ oxide was investigated in plasma activated NF3/H2O gas. This process generates ammonium hexafluorosilicate ((NH4)2SiF6) as a by-product. By-products were formed on the PSZ surface which was confirmed by observing N–H, NH4+ and SiF6 2-peak in ATR-FTIR spectrum. These peaks are representative of (NH4)2SiF6 powder composition. Etch rates of several SiO2 were reported as a function of H2O ratio, substrate temperature, and pressure. NF3/H2O mixtures were excited using pulsed RF plasma. The NF3 flow rate for all experiments was kept at 150 sccm. The temperatures were varied from 8 to18ºC, the chamber pressures from 7 to 9 Torr., the H2O flow rates from 1500 to 2500 sccm and process times from 20 to 100 sec. Helium was used as a carrier gas. After dry etching, an annealing process was performed. The reaction mechanism was proposed by analyzing the oxide layer surface. We used an ellipsometer to measure the oxide thickness for evaluation of the etch rate. Also, various analyzing tools such as SEM, contact angle analyzer, and FT-IR were used to characterize the surface contaminants. The optimized drying process provides the high selectivity without any residue formation.

Argon–germane in situ plasma clean for reduced temperature Ge on Si epitaxy by high density plasma chemical vapor deposition

Demand for integration of near infrared optoelectronic functionality with silicon complementary metal oxide semiconductor (CMOS) technology has for many years motivated the investigation of low temperature germanium on silicon deposition processes. This work describes the development of a high density plasma chemical vapor deposition process that uses a low temperature (<460 °C) in situ germane/argon plasma surface preparation step for epitaxial growth of germanium on silicon. It is shown that the germane/argon plasma treatment sufficiently removes SiOx and carbon at the surface to enable germanium epitaxy. The use of this surface preparation step demonstrates an alternative way to produce germanium epitaxy at reduced temperatures, a key enabler for increased flexibility of integration with CMOS back-end-of-line fabrication.

Patterned growth of carbon nanotubes obtained by high density plasma chemical vapor deposition

Patterned growth of carbon nanotubes by chemical vapor deposition represents an assembly approach to place and orient nanotubes at a stage as early as when they are synthesized. In this work, the carbon nanotubes were obtained at room temperature by High Density Plasmas Chemical Vapor Deposition (HDPCVD) system. This CVD system uses a new concept of plasma generation, where a planar coil coupled to an RF system for plasma generation was used with an electrostatic shield for plasma densification. In this mode, high density plasmas are obtained. We also report the patterned growth of carbon nanotubes on full 4-in Si wafers, using pure methane plasmas and iron as precursor material (seed). Photolithography processes were used to pattern the regions on the silicon wafers. The carbon nanotubes were characterized by micro-Raman spectroscopy, the spectra showed very single-walled carbon nanotubes axial vibration modes around 1590 cm-1 and radial breathing modes (RBM) around 120-400 cm-1, confirming that high quality of the carbon nanotubes obtained in this work. The carbon nanotubes were analyzed by atomic force microscopy and scanning electron microscopy too. The results showed that is possible obtain high-aligned carbon nanotubes with patterned growth on a silicon wafer with high reproducibility and control.

Investigation of Plasma Enhanced Chemical Vapor Deposition Chamber Mismatching by Photoluminescence and Raman Spectroscopy

Slight differences between supposedly identical process chambers are a well known problem in semiconductor manufacturing. In particular, individual plasma-aided process chambers are difficult to characterize and tune to match each other because plasma is a non-equilibrium state and can leave its “footprint” in subtle ways on a wafer. This process chamber mismatching phenomena was investigated in a dual chamber, commercial, high density plasma chemical vapor deposition system by monitoring SiO2/Si interface quality using multiwavelength room temperature photoluminescence and Raman spectroscopy. Effects on the SiO2/Si interface quality, from altering the gas flow pattern in the plasma process chamber, are also studied.

A Si-based bulk FinFET by novel etching process with mask-less and photoresist-free lithography technique

In this study, we used maskless and photoresist–free nano injection lithography (NIL) to develop a sub–10 nm fin width for a Si–based fin field–effect transistor (FinFET) with a 50–nm fin pitch. The active layer was fabricated using double alignment technology (electron–beam lithography and NIL), and the fin trench was filled perfectly by using a high–density plasma chemical vapour deposition process. Advanced plasma and wet etching processes were employed to obtain the fin height. The fabricated FinFET could provide a pathfinding solution for the continuous scaling of complementary metal oxide semiconductor technology.

Energy-Filtered Transmission Electron Microscope Tomography of Silicon Nanoparticles in Silicon Dioxide Deposited with High Density Plasma Chemical Vapor Deposition

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Impact of hydrogen dilution on optical properties of intrinsic hydrogenated amorphous silicon films prepared by high density plasma chemical vapor deposition for solar cell applications

P-i-n single-junction hydrogenated amorphous silicon (a-Si:H) thin film solar cells were successfully fabricated in this study on a glass substrate by high density plasma chemical vapor deposition (HDP-CVD) at low power of 50 W, low temperature of 200°C and various hydrogen dilution ratios (R). The open circuit voltage (Voc ), short circuit current density (Jsc ), fill factor (FF) and conversion efficiency (η) of the solar cell as well as the refractive index (n) and absorption coefficient (α) of the i-layer at 600 nm wavelength rise with increasing R until an abrupt drop at high hydrogen dilution, i.e. R > 0.95. However, the optical energy bandgap (Eg ) of the i-layer decreases with the R increase. Voc and α are inversely correlated with Eg . The hydrogen content affects the i-layer and p/i interface quality of the a-Si:H thin film solar cell with an optimal value of R = 0.95, which corresponds to solar cell conversion efficiency of 3.85%. The proposed a-Si:H thin film solar cell is expected to be improved in performance.

Stability of polymer-dielectric bi-layers for athermal silicon photonics

Temperature sensitivity of Si based rings can be nullified by the use of polymer over-cladding. Integration of athermal passive rings in an electronic-photonic architecture requires the possibility of multi-layer depositions with patterned structures. This requires establishing UV, thermal and plasma stability of the polymer during multi-layer stacking. UV stability is enhanced by UV curing to saturation levels. However, thermal stability is limited by the decomposition temperature of the polymer. Further, robust performance in oxidizing atmosphere and plasma exposure requires a SiO(2)/SiN(x) based dielectric coatings on the polymer. This communication uses a low temperature (130°C) High Density Plasma Chemical Vapor Deposition (HDPCVD) for dielectric encapsulation of polymer cladded Si rings to make them suitable for device layer deposition. UV induced cross-linking and annealing under vacuum make polymer robust and stable for Electron Cyclotron Resonance (ECR)-PECVD deposition of 500nm SiO(2)/SiN(x). The thermo-optic (TO) properties of the polymer cladded athermal rings do not change after dielectric cap deposition opening up possibilities of device deposition on top of the passive athermal rings. Back-end CMOS compatibility requires polymer materials with high decomposition temperature (> 400°C) that have low TO coefficients. This encourages the use of SiN(x) core waveguides in the back-end architecture for athermal applications.

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This paper presents a low temperature fabrication of amorphous IGZO TFTs (a-IGZO TFTs) via high density CVD and superimposed rf/dc magnetron sputtering below 150 °C Low temperature processed SiOx films were been prepared in high density plasma chemical vapor deposition with inductively-coupled plasma (ICP) source and their electrical properties of these films have been investigated as a function of an ICP power and an O2 flow rate. Also, we found that a-IGZO semiconductor could be affected by a dc self-bias of a target surface using a superimposed rf/dc magnetron sputtering. Increasing a dc self-bias, higher post-annealing temperature is needed to achieve their electrical characteristics of a-IGZO TFTs. For a low-temperature and high performance a-IGZO TFTs, therefore, it is necessarily considered that a-IGZO semiconductors could be damaged due to accelerated negative oxygen ions during conventional magnetron sputtering.

Micro‐Raman spectroscopy as a tool to analyze mechanical stress in nano‐structured diamond‐like carbon films

AbstractIn this work, we deposited nano‐structured diamond‐like carbon (DLC) films by high density plasma chemical vapour deposition system (HDPCVD) and the study of mechanical stress of these films has been made using micro‐Raman spectroscopy. Recently developed high‐density plasma chemical vapour deposition techniques have made it possible to produce nano‐structured DLC films with low surface roughness and high sp3/sp2 hybridization ratio. Thus, these parameters have been studied in this work. Nano‐structured DLC films were obtained using four methods for the surface modification of the silicon wafers: diamond powder, surface roughness generated by plasma etching, surface roughness generated by wet chemical etching solution and reference sample (silicon wafer only submitted to a chemical clean). The samples were analysed by AFM and SEM, too. We related the mechanical stress with the position of G and D bands, creating a new method to analyze these films (analyzing the displacement of central position G band). Thus, the results obtained in this work, related the Raman spectroscopy bands with the mechanical stress in DLC films obtained with different surface topographies (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

High-Performance N2O Plasma Treated Multiwall Carbon Nanotubes Grown by Thermal Chemical Vapor Deposition

A N2O plasma post-treatment process was performed to etch the surface of MWCNTs and modify the density of MWCNTs and dope nitrogen atoms into MWCNTs in high density plasma chemical vapor deposition (HDPCVD) system. The experimental results show improved field emission properties under proper plasma conditions. The turn-on electric field decreased from 2.5 to 1.7 V/μm, and the emission current density increased from 200 to 889 μA/cm2 at an applied field of 4.8 V/μm.

Blue Shifting of Hydrogenated Silicon Carbide Multiple Quantum Wells

Five-period hydrogenated silicon carbide (SiC) multiple quantum wells with silicon dioxide (SiO2) or silicon nitride (SiN) dielectric that were synthesized by high density plasma chemical vapor deposition were studied using photoluminescence (PL) spectroscopy to understand its blue shift. Rapid thermal annealing induced significant blue shifting in the PL spectra after fluorine ion implantation due to crystallization. The thinning of the SiC causes blue shift due to the quantum confinement effect. The higher PL intensity of the amorphous SiC:H in SiO2 than in SiC/SiN may be attributed to the high number of non-radiative sites on its surface. Annealing with nitrogen may cause impurities in SiC/SiO2, thereby broadening the PL peak.

Electro-Optical Properties of Carbon Nanotubes Obtained by High Density Plasma Chemical Vapor Deposition

In this work, we studied the electro-optical properties of high-aligned carbon nanotubes deposited at room temperature. For this, we used the High Density Plasma Chemical Vapor Deposition system. This system uses a new concept of plasma generation: a planar coil is coupled to an RF system for plasma generation. This was used together with an electrostatic shield, for plasma densification, thereby obtaining high-density plasmas. The carbon nanotubes were deposited using pure methane plasmas. Three methods were used for the surface modification of the sample: reference substrate (silicon wafer only submitted to a chemical cleaning), silicon wafer with surface roughness generated by plasma etching, silicon wafer with a thin iron film and silicon wafer with diamond nano powder used as precursor materials. For each kind of silicon wafer surface, the carbon nanotubes were deposited with two different deposition times (two and three hours). The carbon nanotubes structural characteristics were analyzed by Atomic Force Microscope and Scanning Electronic Microscope. The carbon nanotubes electrical characteristics were observed by Raman Spectroscopy and the carbon nanotubes electro-optical properties were analyzed by current vs voltage electrical measurements and photo-luminescence spectroscopy measurements. The photoelectric effect in the carbon nanotubes were determined by photo-induced current measurements. In this work, we obtained carbon nanotubes with semiconductor properties and carbon nanotubes with metallic properties. The electro-optical effects depend strongly on the substrate preparation and the deposition parameters of the carbon nanotubes. The carbon nanotubes are high aligned and show singular properties that can be used for many applications.

Advanced HDP STI Gap-Fill Development in 65nm Logic Device

High density plasma chemical vapor deposition (HDP-CVD) has been proven to be a sucessful process for shallow trench isolation (STI) gap fill in advanced CMOS device fabrication. As CMOS technology nodes continue to shrink, STI gap-fill requirement become more and more challenging. To keep pace with the stringent requirements, a novel HDP gap-fill process - Integrated Proess Modulation (IPM) has been developed to fill these aggressive structures. IPM process, which is extending from Deposition - Etch - Deposition (DED) process, is made of a serial of deposition/etch cycles, which is one of techniques to keep trench open by using NF3-based plasma dry etch before the trench nearly closed by film deposition. Based on this process model, HDP gap-fill capability has been greatly extended to 65nm and beyond. This paper summarizes the STI gap-fill development and optimization work of IPM processes

Correlation Between Composition and Stress for High Density Plasma CVD Silicon Nitride Films

Intrinsic film stress is an important issue for the fabrication, performance, and application of a device. In the present study, a correlation between stress in high density plasma chemical vapor deposited silicon nitride films and their composition has been established. This has led to the low temperature deposition of low stressed films. The films exhibit a relatively negligible amount of chemically nonbonded hydrogen atoms. The density of the films calculated from the results of Rutherford backscattering spectroscopy and nuclear reaction analysis techniques is high, around , indicating a dense network. The films exhibit a relatively high coefficient of thermal expansion of around , indicating a fairly short-range order in the film. Furthermore, a reversible thermally induced stress, i.e., a negligible stress hysteresis upon thermal cycling between room temperature and , has been observed in the film. From the stress response to the thermal cycling experiments, contributions from the thermal and athermal components to the net room temperature stress have been deconvoluted.

Mechanism and CHARM2 Evaluation of P-Channel Metal Oxide Semiconductor Threshold Voltage Drop during High Density Plasma Heat-up Process

Plasma damage during the plasma deposition process is one of the most critical device characteristic issues facing complementary metal oxide semiconductor field effect transistor (CMOSFET) technology. In this paper, the CHARM2 monitoring system is used to evaluate UV damage and plasma charging damage during a high density plasma chemical vapor deposition (HDP-CVD) heat-up process. As a result, the amount of UV damage and negative charging damage is increased as the HDP-CVD heat-up process source power is increased. The main cause of P-channel metal oxide semiconductor field effect transistor (PMOSFET) threshold voltage drop is UV photon facilitated gate oxide electron trapping at the gate oxide and substrate P-channel interface during the HDP-CVD heat-up process. In N-channel metal oxide semiconductor field effect transistor (NMOSFET), when negative gate voltage stress is increased, gate oxide energy bend is flattened. Electrons cannot be trapped at the gate oxide and substrate N-channel interface. Therefore, the NMOSFET threshold voltage is constant during the HDP-CVD heat-up plasma process.

Capillary jet injection of SiH4 in the high density plasma chemical vapor deposition of SiO2

In this article, the authors compare the thickness profiles and OH content of SiO2 films deposited using capillary jet injection of silane in a high density plasma chemical vapor deposition (HDP CVD) system with the results of phenomenological modeling using direct simulation Monte Carlo (DSMC) gas flow calculations. A tube with an internal diameter of 1mm is located vertically at 3cm in front of the substrate surface and is used for the injection of the silane. The deposition plasma is characterized using optical emission spectroscopy (OES) and differentially pumped quadrupole mass spectrometry (QMS). Studying the thickness-normalized OH absorption in the deposited film at various points on the substrate, the authors gain insight into the contribution of the water flux to the OH content in the deposited SiO2 film. Gas flow simulations using the DSMC technique are used to study the fluxes of the species onto the substrate plane. From the results the authors conclude that (i) the flux of the H2O onto the substrate holder is uniform, while the SiH4 flux varies considerably along the substrate holder, which leads to a lower level of hydroxyl incorporated into the deposited film in regions of high deposition rate; (ii) HDP CVD systems cannot be considered as well mixed when using SiH4 because its reaction products have high sticking coefficients and the ground-state molecules have the possibility to be consumed on the surface through reactions with oxygen radicals and ions when depositing SiO2; (iii) the primary beamlike flux of undissociated SiH4 onto the substrate surface has an important influence on the film’s deposition rate; and (iv) the SiH4 reactive sticking coefficient is estimated to be between 0.01 and 0.03.

Pore sealing of mesoporous silica low- k dielectrics by oxygen and argon plasma treatments

In this study, we have prepared surfactant templated mesoporous silica thin films as the ultralow- k dielectrics and a TaN X thin film deposited by plasma enhanced atomic layer chemical vapor deposition (PE-ALCVD) using TaCl 5 as the gas precursor was used as the diffusion barrier. Without any surface modification for the dielectric layer, Ta atoms could easily diffuse into the mesoporous layer seriously degrading dielectric properties. O 2 and Ar plasmas have been used to modify the surface of the mesoporous dielectric in a high density plasma chemical vapor deposition (HDP-CVD) system, and both of the treatments produced a densified oxide layer a few nanometer thick. According to transmission electron microscopy and Auger electron spectroscopy, the pore sealing treatment could effectively prevent Ta atoms from diffusing into the mesoporous dielectric during the PE-ALCVD process.