Effect Of Bias Power Research Articles

Smooth, low rate, selective GaN/AlGaN etch

The aluminum content is widely used in III-N semiconductors as a determiner of material etch characters. Applications consisting of thin GaN/AlGaN heterostructures can afford a maximum of 6 nm of a thin AlGaN layer over etch demand complex processes with precise low etch rates and low etched GaN surface roughness. In this paper, the effects of bias power and SF6 flow ratios on the chlorine chemistry etch rate, selectivity, and GaN surface roughness are investigated in a high-frequency bias generator and low power inductively coupled plasma configuration. Bias power and SF6 flow control the etch responses and are used to find the optimal spots for low etch rate, low GaN roughness, and high GaN:AlGaN selectivity for the fabrication of devices consisting of thin GaN/AlGaN heterostructures. The results are compared with the other selective gas chemistries and the more common 13.56 MHz frequency bias generator.

Effect of radio frequency bias on plasma characteristics of inductively coupled argon discharge based on fluid simulations**Project supported by the National Natural Science Foundation of China (Grant Nos. 11875101 and 11905307).

A fluid model is employed to investigate the effect of radio frequency bias on the behavior of an argon inductively coupled plasma (ICP). In particular, the effects of ICP source power, single-frequency bias power, and dual-frequency bias power on the characteristics of ICP are simulated at a fixed pressure of 30 mTorr (1 Torr = 1.33322 × 102 Pa). When the bias frequency is fixed at 27.12 MHz, the two-dimensional (2D) plasma density profile is significantly affected by the bias power at low ICP source power (e.g., 50 W), whereas it is weakly affected by the bias power at higher ICP source power (e.g., 100 W). When dual-frequency (27.12 MHz/2.26 MHz) bias is applied and the sum of bias powers is fixed at 500 W, a pronounced increase in the maximum argon ion density is observed with the increase of the bias power ratio in the absence of ICP source power. As the ratio of 27.12-MHz/2.26-MHz bias power decreases from 500 W/0 W to 0 W/500 W with the ICP source power fixed at 50 W, the plasma density profiles smoothly shifts from edge-high to center-high, and the effect of bias power on the plasma distribution becomes weaker with the bias power ratio decreasing. Besides, the axial ion flux at the substrate surface is characterized by a maximum at the edge of the substrate. When the ICP source power is higher, the 2D plasma density profiles, as well as the spatiotemporal and radial distributions of ion flux at the substrate surface are characterized by a peak in the reactor center, and the distributions of plasma parameters are negligibly affected by the dual-frequency bias power ratio.

Inductively coupled BCl3/Cl2/Ar plasma etching of Al-rich AlGaN

Varying atomic ratios in compound semiconductors is well known to have large effects on the etching properties of the material. The use of thin device barrier layers, down to 25 nm, adds to the fabrication complexity by requiring precise control over etch rates and surface morphology. The effects of bias power and gas ratio of BCl3 to Cl2 for inductively coupled plasma etching of high Al content AlGaN were contrasted with AlN in this study for etch rate, selectivity, and surface morphology. Etch rates were greatly affected by both bias power and gas chemistry. The authors detail the effects of small variations in Al composition for AlGaN and show substantial changes in the etch rate with regard to bias power as compared to AlN.

Chlorine-based dry etching of β-Ga2O3

Reactive ion etching (RIE) and inductively coupled plasma (ICP) etching techniques were used to determine the optimal dry etch conditions for β-Ga2O3. RF power and chamber pressure were examined to study their effects on etch rate and surface roughness for three crystallographic planes, i.e., (100); (010); and ( by RIE. BCl3 etch rate calibrations were performed on all β-Ga2O3 planes studied, in comparison to Cl2. RIE yielded moderate etch rates (<20 nm min−1), and surface roughness showed no clear trend with RF power. Moreover, the effect of bias power, plasma power, and the choice of etchant were studied using ICP. The etches performed by ICP were shown to be superior to RIE in both etch rate and surface roughness, due to the much higher plasma densities and uniformities possible with plasma powers beyond those realized in RIE. The maximum etch rate of 43.0 nm min−1 was achieved using BCl3 in ICP. SF6/BCl3 mixtures, which yield high GaN etch rates, were also studied. However, in contrast to GaN etching, SF6/BCl3 was found to be far less effective than pure BCl3 in etching β-Ga2O3.

Plasma sensor for monitoring laser-interacting particles in contact with an electrode

A particle imaging system adopting digital in-line holography (DIH) was applied to monitor plasma with variations in radio frequency bias power. This work is the first attempt to examine the effect of bias power on DIH-captured particle distributions in contact with an electrode. The bias power was varied from 0 to 100 W by intervals of 10 W. Particle count specific to a grayscale range of 61 to 80 showed an increasing tendency with the bias power. Particle counts in the bulk plasma fluctuated randomly irrespective of the grayscale range. The peak intensity variations measured with optical emission spectroscopy (OES) showed a little variation in the range of 0–40 W and an increase in the range of 50–100 W. Over the entire range of bias power, the particle count strongly correlated with the two intensities peaked at 539.013 and 583.949 nm. The DIH imaging system demonstrated improved detection performance tan OES at low bias powers. The identified position of a sheath was close to the reported one.

The Effect of Bias Power on the Etching Rate and Uniformity of Silicon Dioxide for N-Slot Inductively Coupled Plasma in TFT Application

The etching in SiO2 is a crucial step in fabricating thin film transistor. For large area etching, high density plasma which independently controls ion energy and ion flux is preferable than conventional RIE etcher for its high etching capability. In an attempt to understand how the bias power of N-slot ICP affects the etching rate and uniformity, we study the correlation among bias power, inductive power, etching rate and uniformity. The results show that the etching rate is proportional to the bias power up to 800 W which has the best uniformity. Beyond that power, the etching rate enters the different slope and the uniformity become worse. This phenomenon might be attributed to the combined effects of resist etching and polymer film growth. For N-slot ICP system, high etching rate and good uniformity can be obtained only when the bias power is in the moderate range.

Prediction of surface microtrenching by using neural network

Abstract Silicon oxynitride films were etched in a C 2 F 6 inductively coupled plasma. A prediction model of microtrenching depth (MD) was constructed by using a neural network and a genetic algorithm. For a systematic modeling, etching data were collected by using a statistical experimental design. The process parameters and ranges were 400–1000 W, 30–90 W, 6–12 mTorr, and 30–60 sccm for source power, bias power, pressure, and C 2 F 6 flow rate, respectively. The root mean-squared prediction error of the constructed model was about 0.019. The model was utilized to generate 3-D plots, which were used to examine etch mechanisms under various plasma conditions. Depending on the plasma conditions, parameter effects on MD were quite different. For most of the parameter variations, MD variations were strongly related to profile angle variations. The effect of bias power on MD seems to be dominated by polymer deposition due to the variations in C 2 F 6 flow rates maintained in the chamber.

Photoresist ashing in nitrogen gas using ferrite core inductively coupled plasmas

The characteristics of photoresist (PR) ashing using N 2 plasmas in a ferrite core inductively coupled plasma etcher have been studied and the effect of bias power and gas flow rate on PR ash rate and low- k material etch rate has been investigated. Fourier transform infrared spectroscopy revealed that the ashing process with N 2 gas produced less damage to the low- k material compared to the process with O 2 gas. The HF etch test was used to evaluate the ash damage to the low- k material.

Analysis of Pore and Pore-Related Properties in Plasma-Enhanced Chemical Vapor Deposition Low Dielectric Constant Films

The effects of bias power on the pore size, pore distribution, relative dielectric constant density, composition, and leakage current of plasma enhanced chemical vapor deposited (PE-CVD) low-k film were studied. The pore diameter of the PE-CVD film changes from 1.23 to 0.73 nm with the application of bias power from 0 to 100 W. Pores with an average diameter larger than 0.63 nm were found to decrease the k value of the PE-CVD low-k film. The pore volume ratio of the PE-CVD low-k film with different compositions was calculated from the measured pore size, k value, and density. The relationships between the k value and the density, and the calculated pore volume ratio, were estimated with a simple model. The k value and the density were found to increase with increasing silicon and oxygen contents and decreasing hydrogen content in the film at the same pore volume ratio. The pore volume ratio of the PE-CVD low-k film with the lowest k value, 2.66, was estimated as 31% from the relationship between the k value and the calculated pore volume ratio. © 2002 The Electrochemical Society. All rights reserved.

The effect of bias power on some properties of titanium and titanium oxide films prepared by r.f. magnetron sputtering

Titanium and titanium oxide thin films have been deposited on (100) silicon wafers and glass substrates by r.f. reactive sputtering magnetron. Substrates have been r.f. biased during the growth of the film and the influence of the bias power on some properties of the coatings has been investigated. The results of the deposition rate measurements show that this is weakly affected when bias power is low. As the r.f. bias power increases, the deposition rate decreases strongly due to an increase of the layer density and resputtering phenomena. Atomic force microscopy showed that the surface morphology of metallic and oxide films can be modified using bias treatment. Roughness analyses exhibited a similar evolution as the deposition rate and surface topography when bias power changes. Optical properties like refractive index followed the same variations as previous results. So, when r.f. bias power increases, various phenomena take place and different zones can be defined from these investigations. Argon ion to atom arrival rate ratio and average energy per deposited atom have been calculated from experimental values of current density applied to the substrate and energy of argon ions impinging on the growing film. Their evaluations have been discussed for metallic and oxide materials.

Damage formed by electron cyclotron resonance plasma etching on a gallium arsenide surface

Radiation damage induced on a gallium arsenide surface by electron cyclotron resonance (ECR) plasma etching is studied. The number of displaced atoms (displaced atom density) formed by exposure to ECR plasma is determined quantitatively by Rutherford backscattering spectrometry aligned spectra. The density increases with increasing microwave power. The amount of increase of displaced atom density from the undamaged virgin surface ΔDda is 2.9×1015 and 4.4×1015 atoms/cm2 at microwave power of 500 W (ion current density, Ii: 0.80 mA/cm2) and 800 W (Ii: 2.00 mA/cm2), respectively. The reflection high-energy electron diffraction study shows that an amorphous layer is formed on the surface at 800 W (Ii: 2.00 mA/cm2). The effect of bias power and chamber pressure on the damage is also studied. The increase of damage (ΔDda: 3.2×1015 atom/cm2) from ECR plasma etching with an rf bias of 15 W is less by a factor of 2 than damage of reactive ion etching (ΔDda: 6.9×1015 atom/cm2) when compared at an ion current density of 1.17 mA/cm2. Low-damage anisotropic etching can be achieved by ECR plasma etching.