Plasma-enhanced Chemical Vapor Deposition Chamber Research Articles

In Situ Plasma Impedance Monitoring of the Oxide Layer PECVD Process

The use of plasma in semiconductor fabrication processes has been continuously increasing because of the miniaturization of semiconductor device structure, and plasma enhanced chemical vapor deposition (PECVD) has become a major process in thin film deposition. As a consequence, plasma diagnosis has become crucial during the deposition process, but the lack of in situ plasma monitoring sensors requires further development of existing in situ sensors, such as the Langmuir probe and optical emission spectroscopy (OES), for in situ plasma process monitoring. In this study, electrically equivalent circuit models of the PECVD chamber functioned as a plasma impedance model with respect to the deposited thin film thickness while plasma impedance was measured using a radio frequency voltage–current (VI) probe. We observed a significant correlation between the deposited film thickness of the chamber wall and the measured impedance of the PECVD chamber cleaning application in the semiconductor industry.

Kinetic Mechanism of Reactive Oxygen/Nitrogen Species in Plasma-Assisted Greenhouse Gas Replacement

In semiconductor manufacturing, greenhouse gases, such as perfluorocarbons (PFCs) and nitrogen trifluoride (NF3), which are sources of global warming, are frequently used to remove substances during cleaning and etching. Particularly, NF3, which has a high global warming potential (GWP) is widely used for chamber cleaning in the chemical vapor deposition (CVD) process. There is an urgent need to replace high GWP gases with eco-friendly gases. In this study, we investigated the possibility of replacing NF3 with N2 gas from the existing NF3/O2 gas mixture during the cleaning process in a plasma-enhanced CVD (PECVD) chamber for the formation of an amorphous carbon layer. The kinetic reaction mechanism of nitrogen-augmented plasma was investigated using ANSYS Chemkin-Pro, and the verification was conducted using an environmentally friendly gas-based direct plasma cleaning process in the PECVD chamber with capacitively coupled plasma (CCP). The verification experiment was conducted with a 150-mm laboratory scale and a 300-mm production equipment. Chemical reaction analysis was then performed to analyze the chemical reaction mechanism in the plasma and identify the trends in the cleaning efficiency. The results derived from the analytical and empirical experiments showed that the addition of N2 positively affected the reaction of O2 in the plasma with surface materials; this improved the cleaning, and the effectiveness of eco-friendly cleaning processes using alternative gases could be confirmed.

Effect of Chamber Conditions and Substrate Type on PECVD of SiGeSn Films

In the past studies have shown that the addition of Ge and Sn into Si lattice to form SiGeSn enhances its carrier mobility and band-gap properties. Conventionally SiGeSn epitaxial films are grown using Ultra-High Vacuum (UHV) conditions with pressures ranging from 10-8 torr to 10-10 torr which makes high volume manufacturing very expensive. On the contrary, the use of low-pressure CVD processes (vacuum levels of 10-2 torr to 10-4 torr) is economically more viable and yields faster deposition of SiGeSn films. This study outlines the use of a cost-effective Plasma Enhanced Chemical Vapor Deposition (PECVD) reactor to study the impact of substrate temperature and substrate type on the growth and properties of polycrystalline SiGeSn films. The onset of polycrystallinity in the films is attributed to the oxygen-rich PECVD chamber conditions explained using the Volmer-Weber (3D island) mechanism. The properties of the films were characterized using varied techniques to understand the impact of the substrate on film composition, thickness, crystallinity, and strain.

Plasma Etching of SiO2 with CF3I Gas in Plasma-Enhanced Chemical Vapor Deposition Chamber for In-Situ Cleaning

Non-global-warming CF3I gas has been investigated as a removal etchant for SiO2 film. Thermally fabricated SiO2 films were etched by the plasma generated with a gas mixture of CF3I and O2 (CF3I/O2) in the plasma-enhanced chemical vapor deposition chamber. The etch rate of SiO2 films was studied along with the process parameters of plasma etching such as chamber pressure, etching gas flow ratio of CF3I to CF3I/O2, plasma power, and chamber temperature. Increasing the chamber pressure from 400 to 1,000 mTorr decreased the etch rate of SiO2 film. The etch rate of this film showed a minimum value at a gas flow ratio of 0.71 in CF3I to CF3I/O2 and then increased at a higher CF3I gas flow ratio. In addition, the elevated plasma power increased the etch rate. However, the chamber temperature has little effect on the etch rate of SiO2 films. When only CF3I gas without O2 was supplied for etching, polymerized fluorocarbon was formed on the surface, indicating the role of oxygen in ashing the polymerized fluorocarbon during the etching process.

Adhesion enhancement and amine reduction using film redeposited at the interface of a stack of plasma-enhanced CVD dielectrics for Cu/low-k interconnects

The dielectric interface for a stack of SiOC and SiCN films in Cu/low-k interconnects is engineered using Ar plasma pretreatment of the top surface of SiCN, which prevents oxidization during SiOC film deposition. Oxidized SiCN causes delamination of the SiOC film and resist poisoning through amines generated during resist baking, which can lead to undeveloped photoresist. The Ar plasma pretreatment in the plasma-enhanced chemical vapor deposition chamber modifies the interface by redepositing a thin pre-coated SiOC film from the upper electrode surface. This redeposited SiOC film acts as a buffer for oxygen plasma during SiOC film deposition.

A comprehensive study on different silicon-containing interlayers for a-C:H adhesion on ferrous alloys

Silicon-containing interlayers can be used to promote adhesion of a-C:H thin films on ferrous alloys substrates. In contrast to chromium and titanium intermediate layers, which are often deposited by well-established technologies such as physical vapor deposition (PVD), the deposition of silicon interlayers is more compatible with plasma enhanced chemical vapor deposition (PECVD) techniques since most of the precursors are usually presented as liquids in stantard conditions. In this work, different silicon-containing interlayers were deposited on AISI 4140 steel using three different precursors in a PECVD chamber equipped with electrostatic confinement. The tribological behavior was correlated with the chemical structure of the interlayer. The critical load for delamination depends more strongly on Si/O and C/O ratios than on deposition temperature. In a general way, low oxygen content in the silicon-containing interlayer is leading to high adhesion. The best adhesion was achieved by using hexamethyldisiloxane as precursor when a critical load for delamination of 3.6N was observed.

10-Gb/s Direct Modulation of Widely Tunable 1550-nm MEMS VCSEL

We demonstrate direct modulation of a widely tunable microelectromechanical system (MEMS) vertical-cavity surface-emitting laser (VCSEL). The wavelength tuning is realized with electrothermal actuation of a SiO $_x$ /SiN $_y$ -based MEMS distributed Bragg reflector (DBR). The DBR is deposited in a low-temperature plasma-enhanced chemical vapor deposition chamber on a InP-based half-VCSEL by means of surface micromachining. More than 60 nm of mode-hop free continuous tuning with a center wavelength of 1554 nm is achieved. A maximum 3-dB small-signal modulation response ( $S_{21}$ ) bandwidth of 7.05 GHz is reported. Quasi-error-free operation of a back-to-back link is demonstrated at 10 Gb/s for a record 47-nm tuning range, showing the compatibility of the MEMS tunable VCSEL as a cost-effective optical source in access networks and interconnects.

Influence of deposition pressure on p-type a-Si:H window layer doped by trimethylboron for a-Si:H superstrate solar cell in plasma enhanced chemical vapor deposition

Wide bandgap (Eg) p-type window layer is very important for silicon based thin film solar cell to obtain high performance, especially high open-circuit voltage (VOC). In this work, the influence of the deposition pressure on the properties of p-type a-Si:H window layer doped by trimethylboron (TMB) in plasma enhanced chemical vapor deposition (PECVD) was investigated systematically by transmission, Raman, and Fourier transform infrared (FTIR) spectroscopies. As a result, high performance hydrogenated amorphous silicon (a-Si:H) p–i–n superstrate solar cell with VOC up to 927mV was successfully achieved on Asahi Type-U SnO2:F coated glass. In this case, excellent wide bandgap p-type a-Si:H window layer was fabricated under a mild deposition condition, including a low hydrogen dilution ratio (H2/SiH4) of 20, a relatively high deposition temperature of 220°C, which was also adopted for the i-layer and n-layer deposition, and a moderate deposition pressure of about 160Pa. We think it is the compromise between wide Eg and good microstructure quality of the p-layer that brings about the good solar cell performance. Such p-type window layer will be very helpful for the fabrication of a-Si:H solar cell, especially of the cell finished in a single PECVD chamber, due to its mild deposition condition.

Improvement of multicrystalline silicon wafer solar cells by post-fabrication wet-chemical etching in phosphoric acid

In this study, we have improved electrical characteristics such as the efficiency (η) and the fill factor (FF) of finished multicrystalline silicon (mc-Si) solar cells by using a new chemical treatment with a hot phosphoric (H3PO4) acidic solution. These mc-Si solar cells were made by a standard industrial process with screen-printed contacts and a silicon nitride (SiN) antireflection coating. We have deposited SiN thin layer (80 nm) on p-type mc-Si substrate by the mean of plasma enhanced chemical vapour deposition (PECVD) technique. The reactive gases used as precursors inside PECVD chamber are a mixture of silane (SiH4) and ammonia (NH3) at a temperature of 380°C. The developed H3PO4 chemical surface treatment has improved η from 5·4 to 7·7% and FF from 50·4 to 70·8%, this means a relative increase of up to 40% from the initial values of η and FF. In order to explain these improvements, physical (AFM, EDX), chemical (FTIR) and optical (spectrophotometer) analyses were done.

Novel Particle-Reduction System in Plasma-Enhanced Chemical Vapor Deposition Process of Interlayer Dielectrics

The new particle-reduction system for tetraethoxysilane (TEOS) plasma-enhanced chemical vapor deposition (CVD), TEOS plasma-enhanced CVD was developed. It was found that the successive sparks in the plasma-enhanced CVD chamber caused the abnormal discharge (arc). Based on these findings, the new system for avoiding the transfer to the abnormal discharge by cutting the RF power was proposed. In this system, the RF power-cut was triggered by the successive sparks, which were detected by the electromagnetic sensors. When the RF power was cut at the successive sparks within 20 µs, the generation of abnormal discharge was eliminated, resulting in the drastic decrease of number of particles. Consequently, it is considered that this particle reduction system is very effective tools for stable production of TEOS plasma-enhanced CVD SiO2 dielectrics.

Preparation of Native Oxide and Carbon-Minimized Ge Surface by NH4OH -Based Cleaning for High-k ∕ Ge MOS Gate Stacks

The native oxide and carbon-contaminant-minimized Ge surface with ammonium hydroxide -based cleaning for high- metal-oxide-semiconductor (MOS) gate stack application is reported. Furthermore, the carbon-free interfacial Ge-oxide layer preparation on the cleaned Ge surfaces was also studied. The thickness of on Ge surface before, during, and after different cleaning processes was evaluated by the spectroscopic ellipsometry measurements. The HF rinsing step in the cyclic HF∕deionized water cleaning was not effective for a removal of native because it cannot form the soluble species by a chemical reaction in the low pH HF solution. A cyclic -based cleaning results in a minimum residual at 3 and on Ge(111) and (100), respectively. The fast regrowth of on cleaned Ge surfaces under air exposure was observed, regardless of the cleaning methods. However, Auger electron spectroscopy spectra showed less amount of carbon on Ge surfaces with -based cleaning than HF-based cleaning. The small amount of residual carbon after -based wet cleaning was completely removed by plasma for a very thin surface oxidation in the remote plasma-enhanced chemical vapor deposition chamber.

Plasma Kinetic Study of Silicon-Dioxide Removal with Fluorocompounds in a Plasma-Enhanced Chemical Vapor Deposition Chamber

Plasma kinetics of silicon dioxide plasma cleaning is investigated with C2F6 and CF3CF2OCF=CF2 (perfluoroethyl vinyl ether, PEVE) in this work. Perfluorocompounds (PFCs) are widely used in the semiconductor industry, and they are known to have long atmospheric lifetimes and high global warming potentials (GWP) due to their chemical stability and large cross sections for infrared radiation absorption. The silicon dioxide (SiO2) cleaning process in a plasmaenhanced chemical vapor deposition (PECVD) chamber is known to be the largest PFC emission source for the semiconductor industry. Silicon-dioxide removal rates by surface reactions in plasmas were measured in the temperature range from room temperature to 400 C by using laser interferometry, and the fluorine density was determined by using an optical emission spectroscopy (OES) actinometry technique. The ion density and the ion energy were determined by using an impedance analysis and an equivalent circuit model. The activation energy was determined from Arrehenius plot to be 0.163 eV and 0.169 eV for C2F6 and PEVE plasmas, respectively, in the PECVD chamber cleaning condition. It is shown here that silicon-dioxide removal rate is linearly proportional to the fluorine concentration for the PECVD chamber cleaning condition of 300 400 C and that the removal rate depends on the ion flux and the ion energy below 100 C. The combined etch rate model is suggested to explain this temperature dependence in this work. From this plasma kinetic study, we can conclude that the atomic fluorine concentration is the dominant factor in silicon-dioxide removal for the PECVD chamber cleaning condition.

Substrate Effect on Plasma Clean Efficiency in Plasma Enhanced Chemical Vapor Deposition System

The plasma clean in a plasma-enhanced chemical vapor deposition (PECVD) system plays an important role to ensure the same chamber condition after numerous film depositions. The periodic and applicable plasma clean in deposition chamber also increases wafer yield due to less defect produced during the deposition process. In this study, the plasma clean rate (PCR) of silicon oxide is investigated after the silicon nitride deposited on Cu and silicon oxide substrates by remote plasma system (RPS), respectively. The experimental results show that the PCR drastically decreases with Cu substrate compared to that with silicon oxide substrate after numerous silicon nitride depositions. To understand the substrate effect on PCR, the surface element analysis and bonding configuration are executed by X-ray photoelectron spectroscopy (XPS). The high resolution inductively coupled plasma mass spectrometer (HR-ICP-MS) is used to analyze microelement of metal ions on the surface of shower head in the PECVD chamber. According to Cu substrate, the results show that micro Cu ion and theCuOxbonding can be detected on the surface of shower head. The Cu ion contamination might grab the fluorine radicals produced byNF3ddissociation in the RPS and that induces the drastic decrease on PCR.

Hydrogenation-assisted nanocrystallization of amorphous silicon by radio-frequency plasma-enhanced chemical vapor deposition

The effects of plasma-enhanced hydrogenation on the crystallization of pure, electron-beam evaporated amorphous silicon (a-Si) at temperatures as low as 300°C were investigated. Successive steps of hydrogenation in the plasma-enhanced chemical vapor deposition chamber, and in situ annealing in a N2 ambient environment were applied to the a-Si samples over a range of low temperatures and plasma powers. At specific plasma-power densities, nanocrystalline silicon layers with an average grain size of less than 10nm were formed where their size, distribution, and porosity could be varied by altering the plasma power and hydrogenation temperature. The surface morphology and the nanocrystalline quality of the samples were characterized using scanning electron microscopy, dark-field transmission electron microscopy, and electron diffraction. In addition, by plasma-enhanced oxidation at a temperature of 250°C, a thin layer of oxide was grown and its physical, structural, and electrical characteristics were investigated.

Pulsed-Spray Radiofrequency Plasma Enhanced Chemical Vapor Deposition of CuInS2 Thin Films

Thin films of CuInS2 were grown on various substrates at a temperature of 523 K from two metal-organic precursors using radiofrequency plasma enhanced chemical vapor deposition (PECVD). Two precursor molecules, with different solubility properties, were dissolved in appropriate solvents and sprayed into the plasma region in the PECVD chamber. The resulting films were examined for atomic composition, growth rate, crystalline orientation, and uniformity. Films made from each precursor differed in thickness, atomic composition, and crystallinity. The uniformity of the film was fairly good from near the edge to the center of the substrate, and evidence for a chalcopyrite-like structure was found in several samples deposited from one of the precursor molecules.

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.

Low-temperature PECVD of silicon dioxide on polymeric hydrogels

In this work, a complex investigation of the film surface composition and nanoscale mechanical properties, i.e. hardness and elastic modulus, of plasma-modified and silica-coated hydrogel thin films was carried out. Plasma treatment was performed in a reactive ion etching chamber (SF6, CHF3) at radio frequency (rf, 13.56 MHz) and in a plasma-enhanced chemical vapor deposition chamber (SiH4/N2, NH3, N2O) at radio frequency and dual frequency (13.56 MHz/100 kHz), respectively. The use of the dual-frequency configuration comprising two power supplies and operated in a switched mode enabled the investigation of the ion-bombardment influence on the polymer properties. For the application in silicon micromachined sensors best results were obtained by using a NH3 or SiH4/N2 low-pressure plasma modification and a silica coating of the sensitive hydrogel film.

Segregation of aluminum in Si and SiO2 films deposited by plasma-enhanced chemical vapor deposition in fabrication of low-temperature poly Si thin-film transitor

Metal contamination in Si and SiO2 films deposited by plasma-enhanced chemical vapor deposition (PECVD) in the fabrication of low-temperature poly Si thin-film transitor was investigated. Aluminum was the major metal impurity to have the highest concentration. Segregation of Al was always observed in the films deposited at temperatures above 400 °C. The impurity level in the segregated region was 1018 ∼ 1020 atoms/cm3 for Al, while the concentration in matrix was about 1016 atoms/cm3. From the transmission electron microscopy image, the Al segregated region contains small-size Al precipitates. Although the Al impurity level of 1016 atoms/cm3 did not cause any serious degradation of device performance, the level of 1018 atom/cm3 and higher can induce a fatal degradation of the threshold voltage. This study revealed that the Al originated from the PECVD chamber, carbon precipitates provided the preferred sites for Al precipitates, and the solubility and diffusivity of Al in Si accelerated the segregation of Al.

SiON 박막 증착에 사용된 플라즈마에 대한 진단

In this study we attempted to diagnose the states and properties of plasma generated while depositing SiON thin films using PECVD (Plasma enhanced chemical vapor deposition). The temperature and density of electron gases formed in a PECVD chamber were measured by Langmuir probe method. Their values were also estimated under some assumptions we made in this work. Comparison between experimental and theoretical values of the temperature and density of electron gases was made. The experimental and estimated results revealed that, as RF Power gets higher, the electron density linearly increases, but that the electron temperature does not vary.

Optimizing Chamber Cleans for Better Film Deposition Performance

An layer grows on the showerhead in our plasma-enhanced chemical vapor deposition chamber during fluorinated between-wafer cleans. The additional impedance caused by the layer reduces the power transferred to the plasma, changing film characteristics during subsequent depositions. Moreover, nonuniform growth on the showerhead causes nonuniform plasma densities that result in across-wafer variation in film properties. Proper selection of pressure during the clean affords greater control over the growth and uniformity of Better management of growth yields better control of film characteristics and renders increased tool availability. © 2001 The Electrochemical Society. All rights reserved.