Shih-Cheng Hu

Power consumption of semiconductor fabs in Taiwan

This paper reports and analyzes power consumption for nine representative semiconductor fabs in Taiwan. The power consumption data were obtained by surveys and site visits. Analysis results indicate that the average power consumption for the fabs is 2.18 kW/m2 and the average cooling load is 0.434 RT/m2. The average power consumption per unit product (wafer) area is 1.432 kWh/cm2, which is consistent with the data (3.1 kWh/cm2 in 1983 to 1.41 kWh/cm2 in 1995) reported by the US Department of Commerce and Dataquest. The facility system consumes the most of the power consumption (about 56.6%) of the semiconductor fabs. Process tools are the next largest power consuming item, accounting for 40.4% of the power consumed in the fabs. A facility system includes the chiller plant, makeup air, recirculation air, exhaust air, gases, compressed dry air, process cooling water, vacuum and ultra-pure water systems. The power consumption of the different facility components is analyzed and compared.

Design and evaluation of a minienvironment for semiconductor manufacture processes

A new minienvironment for controlling the process area from ambient air contamination was designed and evaluated. The new design has a buffer zone between the ambient and the process zones. A parametric study of this design using a Computational Fluid Dynamics (CFD) method was conducted for various cases. A full-scale experimental model was fabricated. The evaluation was completed by measurements of airflow patterns, zone pressure differentials and particle concentration levels for the fabricated minienvironment. It is concluded that this new minienvironment is capable of maintaining a cleanliness of less than one particle per cubic meter, and the buffer zone is effective in preventing cross contamination between the process and the ambient zones.

INFLUENCE OF PLATFORM SCREEN DOORS ON ENERGY CONSUMPTION OF THE ENVIRONMENT CONTROL SYSTEM OF A MASS RAPID TRANSIT SYSTEM: CASE STUDY OF THE TAIPEI MRT SYSTEM

This investigation studies how platform screen doors (PSD) affect the energy consumption of the environmental control system of a mass rapid transit (MRT) system in Taipei. The environmental parameter simulation was conducted using the subway environmental simulation (SES) program, while the associated air conditioning (A/C) cooling load was predicted with the carrier E20-II program. Results show that PSD can significantly decrease average and peak cooling load, thus reducing the capacity/size of cooling equipment and allowing the chiller cooling load to be abridged. However, electricity consumption by ventilation equipment increases notably when PSD are used, particularly the electricity consumption by the under platform exhaust (UPE) fan, and thus, ultimately, little difference exists in the overall energy consumption with and without UPE.

Deterministic simulation and assessment of air-recirculation performance of unidirectional-flow cleanrooms that incorporate age of air concept

Abstract The airflow characteristics of a unidirectional cleanroom are largely determined by the airflow in the supply air plenum, the return air plenum and the return air shaft. A deterministic computational fluid dynamic model that incorporates fan-performance characteristics was applied to investigate and compare the air-recirculation performance of the two general designs of unidirectional-flow cleanrooms. Typical flow-resistance models of the various components in the air path were used in the simulation. Non-uniformity (NU) of supply air velocity (at the filter face), airflow parallelism (deflection angle, α), and the distribution of the mean age of air were computed for the two types of unidirectional-flow cleanrooms. The results show that the performance of the fan filter unit system is generally superior to that of an axial fan system in terms of NU, deflection angle of airflow in the working zone, and the air-change efficiency derived from the age of air distribution. It was also found that the three performance indices provide a good assessment of the air-recirculation performance of unidirectional-flow cleanrooms.

Airflow characteristics in the outlet region of a vortex room air diffuser

Abstract For turbulent type clean rooms, terminal devices with high diffusion performance are required because the supply flow rate is usually provided only in the margin value. Vortex diffuser is generally assumed with high diffusion performance. However, its detailed technology data are not available. In this study, the airflow characteristics in the outlet region of a generic vortex diffuser were experimentally and numerically investigated. The zonal hybrid meshes were used in grid generation, where the regions around the disk and the guide vanes were meshed with tetrahedral cells, the inlet duct of the diffuser and the room space were meshed with hexahedra cells. The prismatic (or wedge) cells were used as the transitional cells to enable a change in cell type from hexahedra to tetrahedral. Such arrangement of the cell types has been found to be ideal for analysis of room air movement due to an air diffuser. Corresponding airflow measurements were conducted by using a three-dimensional ultrasonic anemometer. In the region very adjacent to the ceiling ( 0.05 m from the ceiling), the velocity magnitude was conducted by using a hot-wire anemometer. The results show that the flow pattern in the vicinity of outlet region for vortex diffuser is three-dimensional and highly turbulent. The experimental results were found to agree well with the results of the numerical analysis. The K value of the vortex diffuser investigated is in the range 2.1–2.3. It is concluded that the zonal hybrid meshes are well suited for analysis of the complicated flow structure issuing from the vortex diffuser. This study also shows that the vortex diffuser has a greater entrainment ratio than that of a multi-cone circular ceiling diffuser, due to the influence of the stationary twists guide vanes. Therefore, the vortex diffuser is a good option as a terminal device for turbulent type clean room.

Numerical study on the dispersion of airborne contaminants from an isolation room in the case of door opening

Abstract A negative pressure isolation room is built to accommodate and cure patients with highly infectious diseases. An absolutely airtight space effectively prevents infectious diseases from leaking out of the isolation room. Opening the door leads to a breakdown in isolation conditions and causes the dispersion of infectious air out of the isolation room. Extensively employed to manage smoke in cases of fires at subway and highway tunnels, a concept of controlling airflow is applied to the study. This study proposes a design of ventilation system to control air flow rate for containing airborne contaminant and preventing its spread to the adjacent rooms when the door to the isolation room is opened and closed. This paper employs computational fluid dynamics (CFD) as a more effective approach to examine the concentration maps of airborne contaminants and the airflow patterns of room air and discuss the influence of temperature differences between two rooms on airborne dispersion. Results show that an air velocity above 0.2 m/s via a doorway effectively prevents the spread of airborne contaminants out of the isolation room in the state of door opening.

Measurements of air flow characteristics in a full-scale clean room

Abstract Detailed air turbulence characteristics in a full-scale and running fan—filter unit type clean room (4.20 m × 2.97 m × 2.70 m) with and without a clean bench loaded are investigated experimentally. The measurements of the three components of air velocity were conducted by means of a three-dimensional ultrasonic anemometer. Velocity vectors, turbulence intensity, turbulence kinetic energy, and probability density functions of velocity direction and velocity contours in the space domain are presented. The results show that the non-uniformity and deflection angle of air velocity are within 13% and 7.9 degrees, respectively. Moreover, the mean flow patterns, turbulence characteristics, and histogram features of the air flow are discussed. The detailed experimental data are not only useful for clean room design and equipment layout but also helpful for use in the evaluation of numerical modeling in clean room flow fields.

Simultaneous control of particle contamination and VOC pollution under different operating conditions of a mini-environment that contains a coating process

Abstract Improvement in contamination control for a LCD color filter coater was studied by using a mini-environment design. Different operating conditions of the door and the exhaust of the mini-environment were studied. Measurements of particle concentration, flow field, and VOC concentration were performed. Both the particle contamination to the coating process and the VOC contamination to the outside cleanroom environment were considered in this study. It was found that a mini-environment could be designed to significantly reduce the particle concentration. Also, the exhaust of the mini-environment was found to affect the flow field in the mini-environment and result in an increase of particle contamination at a level close to the coating process. The design of the mini-environment requires optimal operating conditions.

Particle Dynamics in a Front-Opening Unified Pod/Load Port Unit Minienvironment in the Presence of a 300 mm Wafer in Various Positions

This article reports airflow, particle transport, and pressure differential control of a front-opening unified pod/load port unit (FOUP/LPU) minienvironment system using both experimental and computational fluid dynamics (CFD) approaches. The stochastic tracking approach in the Discrete Phase Model of Fluent software was adopted to predict particle trajectory. The predicted velocity vectors were verified by experimental ones, which were measured by a 3D ultrasonic anemometer. Particles from the upper edge of the FOUP produce a greater contamination risk than those from the lower edge of the FOUP. Particles generated on the moving part of the LPU can be entrained to the back surface of wafer in the bottom position. The parameters that affect the pressure differential between the minienvironment and surrounding environment were analyzed. The minimum pressure differential required to prevent particles from ingression to the minienvironment was determined.

Purging of front-opening unified pod with nitrogen for 300 mm wafer manufacturing

The control of airborne molecular contamination (AMC) plays an increasing role in semiconductor manufacturing processes. We conducted a parametric study of purging a front-opening unified pod (FOUP), a wafer box for handling 300 mm wafers, with nitrogen experimentally, analytically and numerically. Factor considered to affect purging include the coefficient of absorption and desorption of water vapor through the FOUPs polycarbonate material, the configuration of plenum injector, the best composition of plenum injector and the FOUP, and the selection on purge flow rate. This study clarified purge phenomena.