Thickness Distribution Of Thin Films Research Articles

Improving Thickness Uniformity of Amorphous Oxide Films Deposited on Large Substrates by Optical Flux Mapping

In this study, three amorphous oxide thin films are prepared by an electron beam evaporation combined with ion-assisted deposition technique. With the aid of optical flux mapping method, thin film thickness distribution with good uniformity can be obtained by appropriate coating masks. Three metal oxide single-layer thin films are SiO2, Ta2O5 and Nb2O5, respectively. These thin films were deposited on a substrate holder with a radius of 275 mm that was divided into five different segments. Based on the optical flux mapping method, we can effectively simulate the geometric dimensions of the coating mask and obtain the width of the coating mask at different segments. If the film thickness uniformity is a function of masking area and center angle, it is necessary to determine the thickness distribution of the different segments and use a surface profiler to accurately measure the film thickness. We analyzed the thickness uniformity of three oxide films deposited at five different segments. The experimental measurement results show that the deviation of thickness uniformity is 0.38% for SiO2, 0.36% for Ta2O5, and 0.15% for Nb2O5 thin films, respectively.

Scattering transmission field of a photonic crystal surface wave to determine the thickness distribution of thin films

In present work, we use an electromagnetic surface mode excited at the interface of a finite one-dimensional photonic crystal utilizing a modified attenuated total reflection setup by capturing the images formed by the scattered surface waves under transmission to determine the thickness distribution of a non-uniform thin film (<100 nm) over an extended millimeter-sized area. The sensitivity of the proposed technique is analyzed by considering a step coating that presents two different regions of different thickness, which shifts the resonant conditions of the surface mode.

Simulation and Optimization of Film Thickness Uniformity in Physical Vapor Deposition

Optimization of thin film uniformity is an important aspect for large-area coatings, particularly for optical coatings where error tolerances can be of the order of nanometers. Physical vapor deposition is a widely used technique for producing thin films. Applications include anti-reflection coatings, photovoltaics etc. This paper reviews the methods and simulations used for improving thin film uniformity in physical vapor deposition (both evaporation and sputtering), covering characteristic aspects of emission from material sources, projection/mask effects on film thickness distribution, as well as geometric and rotational influences from apparatus configurations. Following the review, a new program for modelling and simulating thin film uniformity for physical vapor deposition was developed using MathCAD. Results from the program were then compared with both known theoretical analytical equations of thickness distribution and experimental data, and found to be in good agreement. A mask for optimizing thin film thickness distribution designed using the program was shown to improve thickness uniformity from ±4% to ±0.56%.

Compact surface plasmon holographic microscopy for near-field film mapping.

We develop a compact objective-coupling surface plasmon holographic microscopy with a common-path configuration by introducing a Wollaston prism. Through off-axis hologram recording and numerical reconstruction, amplitude- and phase-contrast surface plasmon resonance (SPR) images can be obtained simultaneously. Based on the four-layer SPR model, the thin film thickness distribution in near field can be mapped unambiguously using a novel demodulation method without a priori knowledge. The technique demonstrates nondestructive and full-field measurement capabilities with sub-nanometer resolution theoretically. Furthermore, owing to the high temporal stability, the recommended system shows great potential for dynamic measurement of near-field tiny refractive index or thickness variation in fields such as chemistry and biomedicine, etc.

Simulation of thin film thickness distribution for thermal evaporation process using a scanning linear source

Thermal evaporation process is the main process involved in the production of OLED displays and with the trends toward larger substrate size and display resolution, film thickness uniformity must be carefully controlled in order to implement exact pixel data. To secure stable film thickness uniformity on the substrate area, thin films are deposited on large-area glass substrates via thermal evaporation process using a linear source. We designed a linear source and mathematical model was developed to describe the system with a focus on the linear source. Then, system parameters were determined to guarantee uniform thickness using computer-based simulation, replacing wasteful actual experiments, followed by carrying out experiments based on the determined parameters. After the deposition process, data from the mathematical model and experiments was compared and the resulting agreement was good, verifying the validity of the proposed method. Consequently, by applying the proposed method, display manufacturing process related to thermal evaporation can be controlled within a tight tolerance in order to maximize the production yield rate.

Silicon thin films thickness estimation: A Monte Carlo simulation study

We propose a theoretical study for Si thin film thickness measurement that is based on incident low energy electron beam on the film and counting the transmitted/incident electron fraction. It estimates the thin film thickness distribution from an exponential relation which obtained from counting the fraction of transmitted/incident electron at different thicknesses. By using this obtained equation, it is possible to estimate unknown thickness of the Si thin film. In order to calculate the Si thin film thickness estimation, the energy of the incident electron beams is varied from 6 to 12keV, while the thickness of the Si film is varied between 100 and 400nm. The most significant feature of this method is that no expensive instruments are required. As anticipated, the proposed method shows that there is a relationship between film thickness and incident beam energy, which by using this relationship, we can find unknown film thickness in 1-D and 2-D conditions. Other advantages include wide measurement range, no calibration need and simple method. Additionally, an investigation by different beam energies helps to avoid artifact from this method.

Theoretical modelling and experimental verification of gradient thickness function for thin film deposition of linear variable filter

This study proposes a theoretical model for a gradient thickness function for thin film deposition of a linear variable filter (LVF), which is used for order sorting for a diffraction grating. To achieve linear variable filtering, the thin film must be fabricated with a gradient of increasing thickness along the direction of wavelength dispersion. The thickness gradient is created using a local mask on top of the substrate during thin film deposition inside the evaporation chamber. A theoretical model and ray tracing simulation are developed to obtain the thin film thickness distribution and the parameters for the fabrication of LVFs. Within the 25%–75% thickness range, the profile distribution exhibits a high degree of linearity (coefficient of determinations are greater than 0.9939). This study shows that the proposed theoretical model and ray tracing predict a thin film profile for an LVF with high precision (root–mean–square deviations are less than 4.52%).

Simulation of the organic thin film thickness distribution for multi-source thermal evaporation process

A model of multi-source thermal evaporation process was proposed to achieve higher deposition rate and uniformity of organic thin film. In this model, several point type sources were uniformly distributed around a circle and evaporated simultaneously to form a surface-like source. Based on the Monte Carlo method, the evaporation process was simulated, and the effect of the number of point type sources, circle radius and source-substrate distance on the uniformity was analyzed. Based on the method proposed in this paper, the uniformity of the thickness in the organic layer was successfully controlled in 5%.

Analysis of Coupled Electro-Thermal-Mechanical of Micro Gas Pressure Sensor Based on Micro-Hotplate Technology

The effect of micro-hotplate (MHP) thermal deformation on the signal output of the MHP-based micro gas pressure sensor is investigated. Combining electro-thermal theoretical analysis and thermal-mechanical finite element modeling, different electro-thermal-mechanical analysis models of the sensors are built and solved at constant current condition and constant temperature condition respectively. The calculated results show that the MHP thermal deformation has little effect on the sensor signal output over the entire pressure range at constant current condition, I=0.7mA. While at constant temperature condition, Ts=400K, thermal deformation has little effect on the sensor signal output at low gas pressure, but at high pressure the effect are great. Moreover, according to the thermal-mechanical analysis, we find that optimizing thickness distribution of thin films in the MHP suspended structure can reduce thermal deformation effectively at higher temperature when the lateral dimension is same, which presents a practicable method to improve the sensor stability.

Simulation of the thin-film thickness distribution for an OLED thermal evaporation process

A design of an OLED (organic light-emitting device) fabrication system strongly depends on a thermal evaporation process. In an OLED evaporation process, the essential requirements include good uniformity of the film thickness over a glass substrate. In this paper, a process simulation model was developed to predict the film thickness distribution by understanding system design parameters that affect the uniformity of film thickness. Based on the method developed in this study, the uniformity of the thickness in an organic layer was successfully controlled. The developed method allowed the manufacture of high quality OLED displays.

Quantitative evaluation of film thickness uniformity: Application to off-axis magnetron source onto a rotating substrate

To predict the thin film thickness distribution in a quantitative way, a theoretical calculation was conducted according to the cosine law approach for off-axis sputtering. The numerical calculation was focused on the optimal geometry instead of the thickness distribution itself, which took into account several variables including the target-to-substrate distance, the off-axis displacement, the emission characteristic, the width of the erosion groove, and the film thickness requirement. The effects of these variables on the optimal geometry were analyzed individually and the subsequent combined equations for optimal geometry were summarized. Thus, the combined equations were multivariable functions. These equations were simple and general and could be applied directly. For many situations, these equations eliminate the need to perform the complex, detailed calculation otherwise needed for each deposition geometry variant.

Dynamic simulation on the preparation process of thin films by pulsed laser

An ablation model of targets irradiated by pulsed laser is established. By using the simple energy balance conditions, the relationship between ablation surface location and time is derived. By an adiabatic approximation, the continuous-temperature condition, energy conservation and all boundary conditions can be established. By applying the analytical method and integral-approximation method, the solid and liquid phase temperature distributions are obtained and found to be a function of time and location. The interface of solid and liquid phase is also derived. The results are compared with the other published data. In addition, the dynamics process of pulsed laser deposition of KTN (Kta0.65Nb0.35O3) thin film is simulated in detail by using fluid dynamics theory. By combining the expression of the target ablation ratio and the dynamic equation and by using the experimental data, the effects of laser action parameters on the thickness distribution of thin film and on the thin film component characteristics are discussed. The results are in good agreement with the experimental data.

Measurements of the thickness distribution of thin films with a slit-beam-profile reflectometer

The thickness distribution of single-layer thin films is measured with a slit-beam-profile reflectometer. A convergent slit beam generated by a cylindrical lens is projected onto a specimen. A CCD chip with a pixel matrix of 512 x 480 is used to detect the intensity distribution of the reflected beam, which is passed through another cylindrical lens. By analyzing the picture taken by the CCD, we can obtain information about the angular reflectance at each reflecting point along the slit line, and the thickness or the refractive index at each point can be evaluated by mathematical fitting to a reflectance formula.

Critical parameters influencing the material distribution produced by pulsed laser deposition

The parameters that control the thickness distribution of thin films produced by pulsed laser deposition are investigated. It is found that highly asymmetric material distribution profiles can be obtained in vacuum when high energy densities are used and the target surface is positioned at the lens focus. The asymmetries are due to asymmetries in the spatial distribution of the beam. Under Ar gas pressure, the profile becomes symmetric and the distribution narrows as a consequence of collisions between the ejected species and the gas. In vacuum, decreasing the energy density, by decreasing the laser energy output or by moving the lens to defocus the beam, leads to symmetric distribution profiles. Nevertheless, in the first case a quite broad distribution and a low deposition rate are obtained, whereas in the second case the distribution is narrow and the deposition rate increases.

Experimental and theoretical studies of coating thickness distributions obtained from high rate electron beam evaporation sources

The study of the thickness distribution of thin films achieved by an electron beam evaporation source is the main purpose of this work. The different parameters which play a rule in the estimation of the coating deposition rate for substrates fixed throughout the deposition chamber are discussed. Three main parameters will be considered: the position of the substrate in relation to the evaporation source, the shape of this source and the space distribution of the evaporated atoms. While the influence of the first two parameters is well known, the effect of the spatial distribution of the vapor beam is considerably less so. Based an previous results showing that, at high evaporation rates, the distribution of vapour atom velocities does not follow a Maxwell form, it was possible to justify the experimental thickness distribution obtained on the entire half space over the vapour source. It is also shown in this paper that the incidence angle of the atoms deposited on the growing film plays an important rule on the film growth mode, leading to an important change in its specific gravity. This variation of specific gravity must be taken into account to correctly predict the deposition rate for any fixed point on the substrate located anywhere in the vacuum chamber. Finally, it was shown that these analytical models can be applied to the deposition of different materials such as copper or titanium and even, for a material like chromium that sublimates below the path of the electron beam. For this last case, a Monte Carlo simulation study of the atom emission from the vapour source was necessary to fit the experimental thickness distribution.

分子線エピタキシ薄膜の膜厚分布シミュレーション

分子線エピタキシ薄膜の膜厚分布シミュレーション

Transport of evaporated material through support gas in conjunction with ion plating: I

This paper deals with theoretical and experimental investigations of the thickness distribution of thin films deposited by evaporation under an inert support gas at various pressures. This approach is considered as a first step to describe the material transport in ion plating. In the first part a quantitative treatment based on numerical solutions of the Laplace equation is presented. The solutions are used to calculate the thickness distribution on plane and cylindrical substrate configurations. A comparison of the results with experimental data obtained for silver deposition in argon at pressures of 1.33–6.6 Pa reveals good agreement between measured and calculated thickness distributions of the films. For lower pressures, however, the diffusion model is no longer realistic, and it should be replaced by Monte Carlo calculations of the particle movement. This will be the topic of the second part.

Analysis of a Ring Cavity Thin-Film Deposition Source

Equations are derived which allow the prediction of the thickness distribution of thin films deposited from sources possessing vertical sides and axial symmetry. These equations are in the form of three double integrals which must be integrated over a variable region of integration. Some correlation with experiment is also reported.

1130. Some problems in thickness distribution of thin films deposited by evaporation: K Lelakowska, Przeglad Electron, 7, 1966, 387–390 (in Polish)

1130. Some problems in thickness distribution of thin films deposited by evaporation: K Lelakowska, Przeglad Electron, 7, 1966, 387–390 (in Polish)

Thin film thickness distribution by alpha absorption

An instrument for the determination of thin film thickness distribution is described. Thickness distribution curves for films of organic compounds, metals, and aluminium oxide which are used primarily for counter windows and in connection with radio-active source preparation are presented. The principle employed, where the “gas-equivalent” of the film or foil of material is measured, provides results to a good degree of accuracy.