Masato Ikegawa

Decreasing Airflow Velocity in Hard Disk Drives With a Spoiler and Bypass

High-speed disk rotation of hard disk drives (HDDs) produces high-speed airflow, which causes disk vibration called disk flutter, and vibration of the head carriage arm. These vibrations have a significant effect on the positioning precision of the head and should be reduced by considering aerodynamic factors. The airflow changes in HDD with a bypass and a spoiler were clarified by LES and PIV . These analyses show that a spoiler reduces the arm vibration by decreasing the flow velocity near the arm, in particular, decreasing the average flow velocity between the disks, diversing the flow into the bypass channel, and moving the high-speed-flow area toward the inner radius area of the disks.

Particle growth and transport in silane plasma chemical vapour deposition

The model equations for particle formation, growth and transport were proposed for silane plasma chemical vapour deposition and were solved numerically. We included the plasma chemistry of silane, particle nucleation by cluster formation, aerosol dynamics and transport of chemical species and particles. The evolutions of gaseous species and particles along the reactor were presented for several conditions of process variables such as reactor pressure, total gas flow rate and electric field strength. To reduce the CPU time in numerical simulation, we used lower values of electric field strength in the sheath region then the actual values and analysed the effects of electric field strength qualitatively. It was found that the concentration profiles of positive ions show peaks at the centre of the plasma reactor, whereas most of the negative ions are located in the bulk plasma region owing to the electrostatic repulsion from the sheath region. Most of the particles in the plasma reactor are located around the sheath boundaries, owing to the balance of the electrostatic force and the ion drag force. As the reactor pressure increases, the contaminant concentration and diameter increase in the plasma reactor. The lower the total gas flow rate the higher the particle concentration and the larger the particle diameter. The particle concentration and diameter in the plasma reactor increase abruptly as the electric field strength in the sheath region increases.

Airflow-Simulation by Voxel Mesh Method for Complete Hard Disk Drive Structure

Numerical fluid simulation based on the voxel-mesh method was applied to the whole structure of 3.5-inch hard-disk drives. The voxel mesh of a hard-disk drive (HDD) including all components can be generated automatically from a computer-aided design (CAD) software in a short time. The simulation results were compared with the experimental measurements by particle image velocimetry (PIV). The airflow simulation with a whole-HDD-structure model exhibits a better agreement with the PIV results than that of a partial model (namely, a calculation region sliced between two disks) does, and it indicates the existence of an entire flow (from between the disks, up between the shroud gap and filter area, and onto the top disk) in the vertical direction throughout the HDD. This method is useful for airflow simulation of a model with complicated geometry such as that of hard disk drives.

One-Dimensional Modeling for Magneto-Microwave Plasma Using the Monte Carlo Method

This study discusses modeling of a magneto-microwave plasma used in semiconductor manufacturing equipment such as etching reactors and chemical vapor deposition (CVD) reactors. A one-dimensional simulation program for magneto-microwave plasma was developed. This combines a Monte Carlo particle plasma model and an electromagnetic wave damping model. With the use of this simulation, a plasma production mechanism with electron cyclotron resonance and electromagnetic wave damping in a partially ionized gas can be analyzed. Typical results of the effect of gas pressure on the plasma distribution in plasma processing equipment are presented.

Study on the Deposition Profile Characteristics in the Micron-Scale Trench Using Direct Simulation Monte Carlo Method

As integrated circuits are advancing toward smaller device features, step-coverage in submicron trenches and holes in thin film deposition are becoming of concern. Deposition consists of gas flow in the vapor phase and film growth in the solid phase. A deposition profile simulator using the direct simulation Monte Carlo method has been developed to investigate deposition profile characteristics on small trenches which have nearly the same dimension as the mean free path of molecules. This simulator can be applied to several deposition processes such as sputter deposition, and atmospheric- or low-pressure chemical vapor deposition. In the case of low-pressure processes such as sputter deposition, upstream boundary conditions of the trenches can be calculated by means of rarefied gas flow analysis in the reactor. The effects of upstream boundary conditions, molecular collisions, sticking coefficients, and surface migration on deposition profiles in the trenches were clarified.

Scale-up of a Parallel Plate RF Plasma Etching Reactor by Using Reactive Gas Flow Simulations

A parallel plate/narrow gap radio frequency (RF) (400 kHz)-plasma SiO 2 etching reactor for a 200 mm diam wafer was scaled up to that for a 300 mm diam wafer according to numerical simulations of gas flow and mass transfer for the etching gas CF 4 /Ar. Experimental measurements of this reactor (for a 300 mm diam wafer) agree well with the simulated etching rate and etching uniformity on the 300 mm diam wafer. It was shown that the reactor for a 300 mm diam wafer could be scaled up only in the radial direction. It was also clarified that gas inlet showerhead radius and plasma radius correlatively affect the etching rate at the edge of the wafer; they are therefore key parameters that must be controlled to get better uniformity of etching rate.

Effects of gas-flow structures on radical and etch-product density distributions on wafers in magnetomicrowave plasma etching reactors

To achieve high etch rate, uniformity, good selectivity, and etch profile control across large diameter wafers, the distributions of ions, radicals, and etch products in magnetomicrowave high-etch-rate plasma etching reactors must be accurately controlled. In this work the effects of chamber heights, a focus ring around the wafer, and gas supply structures (or gas flow structures) on the radicals and etch products flux distribution onto the wafer were examined using the direct simulation Monte Carlo method and used to determine the optimal reactor geometry. The pressure uniformity on the wafer was less than ±1% when the chamber height was taller than 60 mm. The focus ring around the wafer produced uniform radical and etch-product fluxes but increased the etch-product flux on the wafer. A downward-flow gas-supply structure (type II) produced a more uniform radical distribution than that produced by a radial gas-supply structure (type I). The impact flow of the type II structure removed etch products from t...

Molecular beam sampling to analyze the reaction mechanism of chemical vapor deposition

In order to understand the chemical vapor deposition (CVD) reaction mechanism, forming a thin film from the gas phase, it is important to identify the intermediate chemical active species (radicals) for each reaction. Radicals generally have very short lifetimes; therefore, it is very difficult to detect them. Molecular beam sampling (MBS) is a method that can extract radicals in the gas phase using free jet expansion. A vacuum system using a MBS method was designed to analyze the CVD reaction mechanism in the gas phase near the surface of the wafer. The system consists of a thermal flow‐through type CVD reactor and three differential pumping vacuum chambers with a quadrupole mass analyzer. The performance of the MBS system was tested with various gases. The system was applied to detect radicals produced in the region near the wafer in a thermal TEOS/O3 (tetraethylorthosilicate) CVD reaction to deposit SiO2 thin films. It is proved that the radicals, from which ethoxy bases of TEOS are extracted, are form...

Prevention of oil vapor backstreaming in vacuum systems by gas purge method

Mechanical pumps have been used as roughing pumps in many vacuum systems because of the ease of their operation. However, it is a well known fact that heavy oil vapor backstreaming occurs when mechanical pumps are operated at pressures close to their ultimate pressure. This backstreaming oil vapor contaminates the vacuum system. Recently, oil contamination has become a serious problem in the semiconductor manufacturing process. In this paper, the results from experiments to prevent oil vapor backstreaming in a pipe that is 9 cm in diam. and 220 cm in length in the transition flow region, using gas purge is examined. Backstreaming oil is measured quantitatively with and without gas purge using a quadrupole mass analyzer and a differential pumping system. The results show that even in the transition flow region, oil vapor backstreaming is prevented by a small flow rate of purge gas.

Simulation of Gas-Liquid Free Surface Flows in a Refrigerant Distributor and a Nozzle of Continuous-Inkjet

A gas-liquid flow in the mm-μm scale is often used in industrial equipment, and it is necessary to develop prediction technology to determine the complicated behavior of a free surface transform. Open source CFD software, such as OpenFOAM, has recently attracted attention for use in industrial applications. We investigated the possibility of using OpenFOAM in the development process of fluid machinery products. We started out by conducting a continuous-inkjet simulation. We compared the simulation results for the breakup length of a liquid column with theoretical results, and then, we evaluated the effect of nozzle length on the breakup length of the liquid column. Next, we evaluated a refrigerant distributor by conducting another simulation. The simulated distribution ratio of the refrigerants was compared with the experimental results, and we checked the efficiency of a parallel simulation. The simulation results for each model qualitatively agreed well with the theoretical or experimental results. Therefore, we found that the simulation using OpenFOAM was effective for large scale simulation of gas-liquid free surface flows.Copyright