World Engineering Congress 2007, Penang, Malaysia, 5 – 9 August 2007 ISBN 978-983-41705-6-1 2007 FEIIC 1 EEE_04 THE FIRST INVERTER FABRICATION IN UTHM CLEANROOM USING COST EFFECTIVE MASK Mohd Zainizan Sahdan, Hashim Saim, Siti Hawa Ruslan, Rahmat Sanudin and Mohd Helmy Abd. Wahab Faculty of Electrical & Electronic Engineering, Universiti Tun Hussein Onn Malaysia, Batu Pahat, Johor, Malaysia. Email: zainizan@uthm.edu.my ABSTRACT In MOSFET fabrication process, the process recipe is very important. A good process recipe will produce good MOSFET device. Universiti Tun Hussein Onn Malaysia (UTHM) has setup a cleanroom for ISO Class 100 and Class 1000. However, our cleanroom do not have its own recipe to develop MOSFET device. Therefore, it is a challenge for UTHM research group to develop this recipe. In this work, the first attempt to develop a process recipe for nMOS inverter has been done, which involved three stages. The first stage was designing and fabrication of cost effective mask using transparency films with channel length range from 500um to 30um. Then, the second stage was optimizing the process parameters. Finally, the third stage was fabrication of nMOS inverter using Modu-lab fabrication toolset. The nMOS inverter was successfully fabricated and this work becomes a starting point for the UTHM research group to do further research in nanoscale transistor and Microelectromechanical System (MEMS) device. Keywords: Cleanroom, process recipe, nMOS inverter and MEMS. INTRODUCTION Semiconductor wafer fabrication is one of the most complex manufacturing processes found today [1]. A lot of research has been done by industries and universities to reduce the manufacturing cost. In MOSFET fabrication process, several modules are involved such as photolithography, oxidation, diffusion and metallization [2]. Each modules involved several processing equipments and chemical which is very expensive to handle. Photolithography process module is very critical since it needs to produce an accurate dimension of the pattern, which is called pattern transfer. In the photolithography process, mask design is very important because it will determine whether the circuit designed is able to be fabricated. However, advanced mask especially for smaller scale microchip is very expensive [3]. This advanced mask can be replaced with a low cost simple mask technology using transparency film. This simple technology can reduced the manufacturing cost. The process recipe is a set of optimized process parameters which is obtained from experimentation. The parameters of each module will be optimized by controlling the gas flow, time and temperature. There are two methods of finding the process parameters; using software and using experimentation. Software such as TCAD Synopsis will provide good result of determining the process recipe. However, experimentation will provide more accurate result. In this paper, the first nMOS inverter has been fabricated using Modu-lab toolset. The nMOS inverters are the building blocks of nMOS digital circuits. They use only n-channel MOSFETS, which have low channel resistance because of greater mobility of electrons in an n-channel. There are several types of nMOS inverter but for this project enhancement load nMOS inverter type was used which fabrication procedure becomes simpler with this type. The nMOS inverter is a combination of two enhancement-type transistors and used as the driver because it will be off when the input voltage V in is low and because its drain and gate voltages have the same polarity as shown in Figure 1. This feature allows direct coupling between stages (that is, one stage can be connected to the next one without any coupling capacitor) [4]. brought to you by CORE View metadata, citation and similar papers at core.ac.uk provided by UTHM Institutional Repository