High Density Plasma Processing Research Articles

Plasma etching dynamics of CaxBa1−xNb2O6 (CBN) material

► We study the plasma etching of the Ca x Ba 1− x Nb 2 O 6 in various gases for varying pressures and substrate temperatures. ► Etching at higher pressure increases the redeposition rate and therefore, surface inhibition decreases the etching yield. ► Etching with chlorine is purely physical between −75 and 375 °C in all the conditions. ► Etching with fluorinated gas is inhibited below 150 °C by adsorption of fluor species. ► Desorption of these fluorinated species occurs at higher temperature, removing the surface inhibition. This work reports an extensive study on the etching of Calcium Barium Niobate (CBN, a novel electro-optical material), using high density plasma processes. Different plasma chemistries (inert, chlorine and fluorine plasmas) are used to etch Ca 0.28 Ba 0.76 Nb 2 O 6 (CBN-28) thin films at pressures going from 1 to 10 mTorr, bias voltages going from 0 to 600 V and substrate temperatures ranging from −75 to 375 °C. For all the conditions investigated, the experimental data are compared with a simple sputtering model and completed with TOF-SIMS measurements of some of the samples processed. This study shows that there is no chemical enhancement or inhibition in the case of chlorinated plasma (Cl 2 ) regardless of the ion energy or the substrate temperature. In the case of an SF 6 -Ar plasma, it is shown that the observed increase of the etch yield above 150 °C results from a reduced inhibition as the temperature increases, this inhibition being caused by F and F 2 species adsorption at the surface of the material.

Reduction in Number of Sparks Generated in High-Density Plasma Process by Fixing the Wall Potential

The effect of the existence of floating potential on spark generation during high-density plasma processes was investigated using an electromagnetic sensor and an on-wafer monitoring sensor. It was observed that the marked change in the potential corresponded to the occurrence of sparks. It was also shown that the connection between the shielding wall and the grounded line significantly reduced the number of generated sparks as compared with that in the case of the existence of a floating shielding wall. Accordingly, it was found that the existence of a floating wall is one of the main reasons for spark generation, and that fixing the wall potential is very effective for preventing spark generation.

Reduction in Number of Sparks Generated in High-Density Plasma Process by Fixing the Wall Potential

Reduction in Number of Sparks Generated in High-Density Plasma Process by Fixing the Wall Potential

GOI Improvement in 65nm Sacrificial Oxide Free Process Integration

GOI (Gate Oxide Integrity) improvement in 65nm SAC OX (Sacrificial Oxide) free process integration was studied in this paper. After studying the effects of various processes in STI (Shallow Trench Isolation) module with SAC OX free scheme on GOI, it was found that the dominant process that could degrade GOI was the STI HDP (High Density Plasma) gap fill process. STI HDP gap fill process could cause Si damage on AA corners, also named as AA clipping, which will result in irregular corners and hence a thinner gate oxide formation at imperfect AA corners. This was observed by a TEM (transmission electron microscopy) study. In SAC OX free scheme, the exposed AA Si corners that were damaged during the HDP process did not get consumed and repaired while they would have gotten in the scheme with SAC OX and hence degraded GOI. By optimizing the STI gap fill processes and hardware configuration, the AA clipping can be greatly reduced and GOI can be improved to the required level.

Low Temperature Growth of Carbon Nanostructures by Radio Frequency‐Plasma Enhanced Chemical Vapor Deposition (Low Temperature Growth of Carbon Nanostructures by RF‐PECVD)

This paper reports the growth of carbon nanostructures on Si (100) substrate in the absence of catalyst using radio‐frequency plasma enhanced chemical vapor deposition (RF‐PECVD). A variety of carbon nanostructures have been grown by low pressure high density plasma process at 400°C using a methane/argon mixture. Various shapes and structures including novel carbon nanoparticles have been found. The surface morphology was studied by Atomic Force Microscope (AFM) and Scanning Electron Microscope (SEM) while the chemical composition was studied using Energy Dispersive Spectroscopy (EDS). The AFM images show that the nanostructures are predominantly either particulate (spherical) in nature or have a sheet‐like morphology. SEM images are in good correspondence to the AFM results and indicate formation of either individual islands or two‐dimensional nanosheet‐like structures. The crux of this work is in the synthesis of the carbon nanostructures at comparatively low fabrication temperature (400°C) as compared to other techniques.

Establishment of very uniform gas-flow pattern in the process chamber for microwave-excited high-density plasma by ceramic shower plate

The authors developed a ceramic upper shower plate used in the microwave-excited high-density plasma process equipment incorporating a dual shower-plate structure to establish a very uniform gas-flow pattern in the process chamber. Thousands of very fine gas-injection holes are implemented on this Al2O3 upper shower plate with optimized allocation to establish a uniform gas-flow pattern of plasma-excitation gases and radical-generation gases for generating intended radicals in the plasma-excitation region. The size of these fine holes must be 50μm or less in diameter and 8mm or more in length because these holes perform an essential role: They completely avoid the plasma excitation in these fine holes and upper gas-supply regions resulting from the plasma penetration into these regions from excited high-density plasma, even if very high-density plasma greater than 1×1012cm−3 is excited just under the ceramic upper shower plate by microwaves supplied from the radial line slot antenna. On the other hand, various process gases, such as material gases for film formations and etching gases, are supplied from the lower shower plate installed in the diffusion plasma region to this very uniform gas-flow pattern region of plasma-excitation gases and radical-generation gases. As a result, the process gases are supplied to the wafer surface in a very effective manner without excess decomposition of those process gas molecules and undesired reaction-product deposition on the inner surface of the process chamber. The process results are improved drastically by introducing the newly developed ceramic upper shower plate. But also, process uniformity on the entire wafer is improved with drastically reducing reaction-product deposition on the inner surface of the process chamber.

Experimental Study of Nanoparticle Generation During High-Density Plasma Chemical Vapor Deposition of Poly-Silicon Films

High-density plasma processes with plasma densities exceeding 10 cm−3 are being employed more in semiconductor fabrication processes because they provide higher deposition rates and highly anisotropic etching. However, relatively few studies on the formation of contaminant particles during these processes have been reported. In this work, particles generated during inductivelycoupled plasma chemical vapor deposition (CVD) of poly-Si films are investigated using transmission electron microscopy (TEM). At 10 and 12 mTorr, TEM measurements were performed to obtain particle diameter and morphology information. The particle sizes were found to be highly uniform with relative standard deviations much less than 0.2. Furthermore, the surface morphologies of the particles changed from smooth to rough as the particles grew. These observations suggest that particle growth occurs by surface deposition of molecules (or ions). Initially, particle growth rates are constant regardless of particle diameter, which is consistent with transport or surface-reactionlimited growth in the free-molecule regime. As particles grow, particle growth rates gradually decrease until they vary in inverse proportion to the square of the particle diameter. We hypothesize that this decrease occurs when the particle’s surface area is sufficient to cause depletion of depositing molecule (or ion) concentrations.

Effect of High-Density Plasma Process Parameters on Carrier Transport Properties in p-to-n Type Converted Hg0.7Cd0.3Te Layer

Exposure of p-type HgCdTe material to Ar/H 2 -based plasma is known to result in p-to-n conductivity-type conversion. While this phenomenon is generally undesirable when aiming to perform physical etching for device delineation and electrical isolation, it can be used in a novel process for formation of n-on-p junctions. The properties of this n-type converted material are dependent on the condition of the plasma to which it is exposed. This paper investigates the effect of varying the plasma process parameters in an inductively coupled plasma reactive ion etching (ICPRIE) tool on the carrier transport properties of the p-to-n type converted material. Quantitative mobility spectrum analysis of variable-field Hall and resistivity data has been used to extract the carrier transport properties. In the parameter space investigated, the n-type converted layer carrier transport properties and depth have been found to be most sensitive to the plasma process pressure and temperature. The levels of both RIE and ICP power have also been found to have a significant influence.

Carrent Status and Future Vision of High Density Plasma Processing

Carrent Status and Future Vision of High Density Plasma Processing

Low temperature plasma carbon nanotubes growth on patterned catalyst

This paper reports on carbon nanotubes (CNT) arrays grown on patterned catalysts by plasma-enhanced chemical vapor deposition (PECVD). CNT growth has been performed by low pressure high-density plasma process at 700 °C in acetylene/ammonia mixture. Prior to CNT growth, a standard lift-off process has been used for catalyst patterning. The chemical impact of the lift-off sequence on the catalyst activity is discussed with respect to the amount of Ni pre-deposited. In particular, it discusses the impact of this wet treatment on CNT growth when the catalyst amount is lower than a threshold value.

Deeply etched waveguide structures for quantum cascade lasers

A high density plasma process was developed for reactive ion etching (RIE) of GaAs/AlGaAs based devices which can be applied for the processing of advanced resonator designs. We present diffractive resonators fabricated using inductively coupled plasma (ICP) RIE with SiCl 4 chemistry. A sidewall protection is formed during the process, which allows for steep vertical and smooth profiles. The technology therefore improves the fabrication of sophisticated QCL cavities and results of the first laterally coupled distributed feedback (DFB) QCLs are presented together with our progress made in etching photonic crystal QCLs.

Quantum cascade lasers with lateral double-sided distributed feedback grating

Midinfrared single mode emission, up to 20°C, for a distributed feedback structure consisting of lateral index variation on both sides of a rib waveguide is achieved on a quantum cascade laser. Fabrication was made possible by a high density plasma process developed for high aspect ratio etching of GaAlAs∕GaAs structures. A lateral grating considerably enhances design freedom by decoupling the vertical waveguide structure from the grating strength. The grating coupling, now being mainly determined by waveguide width, can then be exploited for device applications.

Effects of Fluorine Stability and Stress in SiOF Films on Film Adhesion

Effects of fluorine stability and stress in SiOF films deposited by high-density plasma process on the generation of blisters were investigated by secondary ion mass spectrometry, thermal desorption spectroscopy (TDS), Fourier transform infrared spectroscopy (FTIR) and four point bending method using Top-SiN/TEOS/SiOF/Bottom-SiN multilayer structure. There are two kinds of fluorine in SiOF films, one is stable fluorine detected by FTIR, and the other is unstable one detected by TDS. Unstable fluorine in SiOF films is easy to diffuse and generates blisters at the interface of Top-SiN/TEOS films. Concentration of unstable fluorine is increased as the flow ratio increases and at flow ratios higher than 2.38, blisters are generated. Only the stable fluorine is related with dielectric constant of SiOF film. Hydrogen in gas phase during SiOF-film deposition plays an important role for fluorine stabilization. Compressive stress in SiOF films does not cause blisters. © 2005 The Electrochemical Society. All rights reserved.

Prevention of plasma-induced damage during HDP–CVD deposition

The high-density plasma (HDP)–chemical vapor deposition (CVD) process consists of a simultaneous sputter etch and chemical vapor deposition. As the CMOS process continues to scale down to sub-quarter micron technology, the HDP process has been widely used for the gap-fill of small geometry metal spacing in the inter-metal dielectric (IMD) process. However, the HDP–CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has become an increasingly important issue for integrated circuit process technology. In this paper, the thin gate oxide charge damage caused by the HDP deposition of IMD layer was studied. As an experimental result, the multiple step of HDP deposition process was prevented the plasma-induced damage by introducing an in situ top SiH 4 unbiased liner deposition before conventional deposition.

Low-Temperature Growth of Thermal Quality SiO[sub 2] Thin Films in High-Density He/O[sub 2] Plasma Generated by RF Driven ICP Source

We report on the growth of thermal quality SiO 2 thin films by a high-density plasma process employing an inductively coupled plasma (ICP) source driven by radio-frequency (rf) power. A high SiO 2 growth rate, with a thickness of 100 A after 10 min, was obtained at a substrate temperature of 360°C in a He/O 2 (3%) plasma. The observed low-temperature growth and electrical properties of the metal-oxide-semiconductor capacitors suggest that the high plasma density and energy and low plasma potential are effective in providing a dense microstructure with low defect concentration and good Si/SiO 2 interfacial characteristics.

Impact of NF3-Added Interlayer Dielectric High Density Plasma Process on Hump Effect in Submicron n-type Metal Oxide Silicon Field Effect Transistor

The impact of high-density plasma (HDP) film over a bit line on the hump effect of n-type metal oxide silicon field effect transistor (nMOSFET) has been intensively investigated. In this work, it was found that the hump effect of nMOSFET is mainly due to hydrogen-induced positive charges produced by hydrogen diffusion into Si/SiO2. An interlayer dielectric (ILD)-HDP process with a low concentration of hydrogen suppresses the nMOSFET hump effect effectively compared to that with a high concentration of hydrogen. Additionally, it is noted that a NF3-added HDP process enables removal of hydrogen from the system owing to the strong interaction of fluorine with hydrogen, contributing to the suppression of the nMOSFET hump effect significantly without degradation of the characteristics of the gate oxide.

Surface metallization of alumina ceramics by pulsed high energy density plasma process

Surface metallization of alumina ceramics was carried out by pulsed high energy density plasma (PHEDP). A layer of copper film was deposited on the surface of alumina ceramics. Scanning auger electron microscopy (SAM) analysis revealed that copper diffused deep into the alumina substrate. Bonding of alumina and copper film was good. The reaction between copper and alumina was studied by X-ray diffraction (XRD) analysis. A copper aluminum oxide unstable at high temperature and very difficult to be synthesized, cubic phase CuAl 2O 4, was detected. A kinetics complexity in reaction of PHEDP and ceramics was discussed. An adiabatic model was used to describe heating and quenching of the PHEDP processing and analyze the interaction between PHEDP and alumina ceramics. The experimental results suggest that PHEDP method is a useful technology for various metal–ceramics bonding.

Reduction of Plasma Process Induced Damage during HDP IMD Deposition

The HDP (High Density Plasma) CVD process consists of a simultaneous sputter etch and chemical vapor deposition. As CMOS process continues to scale down to sub- quarter micron technology, HDP process has been widely used fur the gap-fill of small geometry metal spacing in inter-metal dielectric process. However, HBP CVD system has some potential problems including plasma-induced damage. Plasma-induced gate oxide damage has been an increasingly important issue for integrated circuit process technology. In this paper, thin gate oxide charge damage caused by HDP deposition of inter-metal dielectric was studied. Multiple step HDP deposition process was demonstrated in this work to prevent plasma-induced damage by introducing an in-situ top SiH unbiased liner deposition before conventional deposition.

A coupled plasma and sheath model for high density reactors

We present a coupled plasma and collisionless sheath model for the simulation of high-density plasma processing reactors. Due to inefficiencies in numerical schemes and the resulting computational burden, a coupled multidimensional plasma and sheath simulation has not been possible for gas mixtures and high-density reactors of practical interest. In this work, we demonstrate that with a fully implicit algorithm and a refined computational mesh, a self-consistent simulation of a reactor including both the plasma and sheath is feasible. We discuss the details of the model equations, the importance of ion inertia, and the resulting sheath profiles for argon and chlorine plasmas. We find that at low operating pressures (10-30 mtorr), the charge separation occurs only within a 0.5-mm layer near the surface in a 300 mm inductively coupled plasma etch reactor. A unified simulation eliminates the use of offline or loosely coupled and oversimplified sheath models which generally leads to uncertainties in ion flux and sheath electrical properties.

Modelling of inductively coupled plasma processing reactors

A comprehensive model has been developed to study low-pressure,high-density plasma processing reactors. The model couples plasma generation andtransport self-consistently to fluid flow and gas energy equations. The modeland the simulation software have been used to analyse chlorine plasmas used inmetal etching. The effect of the inductive coil frequency on the plasmacharacteristics has been examined and found to influence plasma uniformityonly moderately. Model predictions for a CF4 plasma have been found to agreewell with experimental results.