A Laboratory Approach to Semiconductor Process Technology

Transcription

1 A Laboratory Approach to Semiconductor Process Technology Mary Jane Willis Manufacturing Technology Program Albuquerque TVI, A Community College Albuquerque, New Mexico March, 1998 ABSTRACT The recent growth of the semiconductor industry has spurred several partnerships between colleges and industry throughout the United States. In Albuquerque, New Mexico, the partnership between Albuquerque TVI, A Community College and Intel Corporation has lead to the development of a 1200 square foot cleanroom that is used by the college as a laboratory to train students and instructors for the semiconductor industry. This paper will address the philosophy of the laboratory and discuss the various lab activities that are used to prepare students for the semiconductor industry. INTRODUCTION The mission of the Technologies Department at Albuquerque TVI is to provide students with entry-level occupational skills in technicial fields. In order to accomplish this mission, the Technologies Department strives to create and maintain up-to-date laboratories, with modern equipment and relevent exercises that address the skills required of today s industries. In 1994 TVI partnered with local manufacturing industries to develop an Associate of Applied Science (AAS) degree that would prepare students for the entry-level position of manufacturing technician. This degree is currently referred to as Manufacturing Technology with concentrations in Semiconductor Manufacturing, General Manufacturing and Facilities Maintenance. This AAS degree was developed to complement the existing Electronics Technology (ET) AAS degree. TVI s ET degree prepares students for the position of a equipment technician for computers to automated equipment. Once the AAS degree for Manufacturing Technology was developed, TVI began seeking methods for providing hands-on training for the semiconductor concentration, specifically for semiconductor processes. This search led to the development of a partnership between TVI and Intel for the design and construction of a semiconductor manufacturing training laboratory. Intel Corporation funded the construction of the laboratory and donated all of the equipment. Several other local companies donated supplies, materials, and labor. TVI s Regional Semiconductor Manufacturing Training (SMT) Laboratory was completed in May of Since that time over 600 college students, 70 high school students and 90 instructors from all over the country have completed a variety of lab exercises addressing the skills required for the semiconductor industry. As a regional lab, TVI supports colleges throughout the state of New Mexico. The 600 college students have come from six difference colleges, including TVI. The 90 instructors have been trained through instructor workshops, which are funded by a National Science Foundation grant and have represented schools from ten different states. The philosophy of the SMT Lab is to provide students and instructors with an environment in which they can experience working in a cleanroom while practicing

2 cleanroom protocol and running processes similar to those that one might find in the semiconductor industry. Students learn and apply rules related to lab and chemical safety. As part of their AAS degree, students complete 90 hours of training (two terms) in TVI s Regional SMT Lab. Students also complete 60 hours of complementary theory. LABORATORY DESCRIPTION TVI s Regional SMT Lab is located across from the main campus of Albuquerque TVI in the University of New Mexico s Advanced Materials Laboratory. The SMT lab is 1200 sq. ft. It has three production bays, three service chases, donated semiconductor process equipment and supporting facilities. Below is a list of the support facilities and laboratory equipment. Support Facilities Oil-free compressed air DI water filtration system Process Vacuum House Vacuum HEPA Filters Process Chilled water Scrubbed Exhaust Chemical waste disposal Waste water neutralization House nitrogen Required electrical Laboratory Equipment SSI Coater / Developer Tracks Single Wafer spinner Three Spin-Rinse-Dryers Vertical Diffusion Furnace Aluminum Evaporator Solvent Wet Bench with Quick/Dump/Rinse Acid Wet Bench Parts Cleaning Station Nanospec Photospectrometer Surfscan Contact Printer TECHNOLOGY I (SMT I) SMT I consist of 30 hours of process theory and 45 hours of laboratory exercises. The prerequisites to SMT I are basic dc/ac electronics and digital electronics. The purpose of the SMT I lab exercises is to train students in lab and chemical safety, microcontamination, equipment operation daily preventative maintenance, and the basic processes used in semiconductor manufacturing. Each process lab experiment requires the application of lab and chemical safety rules, and microcontamination protocol. Students are not allowed to work in the SMT Lab until they can pass a Hazardous Communications exam with an 80% or better. Students demonstrate the operation of the SMT Lab process equipment through programming and operating the equipment to run the required process recipes. Before and after each process run, students perform a required preventative maintenance procedure. Knowledge of the process is demonstrated through visual and analytical inspection techniques as well as group assignments and successful completion of lab execises. Below are the SMT I Lab Experiments with a brief description of each. TECHNOLOGY I LAB EXPERIMENTS CLEANROOM SAFETY Cleanrooms are constructed to minimize contamination and to help maintain a safe workplace. The purpose of this lab is for students to learn their part in keeping cleanrooms safe as well as identifying potential hazards and all safety equipment in the SMT

3 Lab. Students also study the safety procedures for the SMT lab. HAZARDOUS COMMUNICATIONS Cleanroom processes require a variety of chemicals and can create dangerous byproducts. The purpose of this lab is to inform students of the hazards involved when working with and around chemicals. Students will learn and practice proper chemical hygiene and hazardous material handling techniques. CLEANROOM CONTAMINATION - PREVENTION AND PROTOCOL The SMT Lab is constructed to minimize contamination and to help maintain a safe workplace. The purpose of this lab is for students to learn their part in minimizing contamination and to identify features of the lab that minimize contamination. Students will learn gowning and wafer handling techniques, and cleanroom protocol. OXIDATION / DIFFUSION students to the operation of a diffusion furnace, the methods and parameters for oxidation, and measurement techniques for oxide thickness. Students will learn the operation of a Nanospec photospectrometer through the process of measuring oxide and photoresist thickness. PHOTOLITHOGRAPHY Photolithography is used to transfer patterns to wafers. The purpose of this lab is to introduce students to the process steps in photolithography: wafer preparation, coat, soft bake, expose, develop, and hardbake. Etch and resist strip will be covered in the next lab. Students will learn the operation of a SSI spin track and study the parameters affecting a proper expose and develop. OXIDE ETCH students to the chemical etch process through the etching of oxide with Buffered Oxide Etch (BOE). Students will experiment with the effects of time on etch rate. Students will also study the relationship between oxide thickness and color. Proper gowning in personal protective equipment (PPE) will be required. METALIZATION: ALUMINUM EVAP students to the operation of a metal evaporator by depositing aluminum on the surface of a wafer. The parameters effecting the metal thickness will also be studied. METAL ETCH students to the metal etch process through the chemical etching of aluminum with a solution of phosphoric acid, nitric and acetic acids. TECHNOLOGY II (SMT II) The lab experiments in SMT II apply the processes learned in SMT I to the construction of integrated devices - resistors, capacitors and an NMOS transistor. A process flow procedure using four masks is used. Completed devices are tested for proper operation; however, proper operation is not required for successful completion of these lab experiments. In addition to the process flow, students also perform several experiments to discover the effects of various parameters on semiconductor processes. Some of these experiments include The effects of motor spin speed on photoresist thickness. The effects of HMDS on chemical etch processes. Identification of high particulate materials. The effects of time and temperature on oxide thickness. Process Capability of the SSI coater tract. Process Capability of the vertical diffusion furnace.

4 Identifying the source(s) of wafer contamination from various processes or lab activities. For all SMT II procedures, students are required to continue to demonstrate proper cleanroom protocol, lab safety rules, and chemical safety rules. OTHER ACTIVITIES In order to get the most out of the SMT Lab, TVI s instructors have developed several activities outside of SMT I and II. Students taking TVI s Statistical Process Control course have used the lab to conduct equipment capability studies on the resist coating equipment and the diffusion furnace. In the spring of 1997, the SPC students discovered a problem with the oxidation process of a local semiconductor company. They tested 25 oxidized wafers that had been processed by the company. These measurements and resulting charts showed a severe uniformity problem in their oxidation process. The students reported their findings to the company who had been unaware of the problem. Students in the Electromechanical System classes, to get more experience on operations and maintenance of automated systems, use the equipment in the SMT Lab. The Systems students learn higher level operations and maintenance procedures than the process students. They write recipes, program the equipment, study the equipment manuals and schematics, and perform corrective maintenance on problems inserted into the equipment. TVI provides tours for local high schools, middle schools and elementary schools. Once a term, a local enrichment high school brings its students to the SMT Lab to conduct three, 2-hour lab exercises. This has proven to be a very positive experience for the high students because it gives them an opportunity to work in a bunnysuit, handle wafers, and operate industrial equipment. In 1996 TVI was awarded an Advanced Technology Education National Science Foundation grant. The purpose of this grant was to develop and implement a series of semiconductor training workshops for instructors at colleges and high schools nationwide. This grant funds 12 workshops between October of 1996 and October of 1998 with each workshop training twelve instructors. The workshops are 5 day in length and consist of 16 hours of instruction, 12 hours of lab, 4 hours of brainstorming activities and 8 hours of visitation to industry or with industry representatives. In addition to the workshops, TVI has hosted benchmarking activities with schools from around the country. These activities focus on the program and the SMT Lab. Several schools have used TVI s experiences with the lab to determine if such efforts would be worth their investment and time. Those schools that have decided to pursue a similar lab, have used TVI as a resource for their architects and engineers. MANUFACTURING TECHNOLOGY SYSTEMS LAB As stated earlier, TVI s electromechanical systems students use the SMT Lab to gain more experience with automated equipment. This activity along with all of the other activities has placed a large demand on the SMT Lab. In order to open the SMT Lab for more process classes, TVI funded the construction of a Manfacturing Technology Systems Lab. This lab was completed in the summer of The new systems lab was designed to support several classes found in the Manufacturing Technology Program and the Electronics Technlogy Program. These classes include Electromechanical Systems, Vacuum Systems, and RF Power.

5 Once again Intel Corporation donated the equipment for the systems lab. This equipment includes single wafer plasma etchers, a batch plasma etcher, an evaporator, a Scanning Electron Microscope, two Vacuum- RF trainers, and a variety of system components. Several of the components that were donated are used to show the construction of the device rather than the operation. We have found that students like to take things apart. These spare components give them the opportunity to disassemble, cut, break, and test without having to worry about an operational device once they finish. CONCLUSION TVI s Regional SMT Lab and the new Manufacturing Technology Systems Lab have been very exciting endeavors and well worth the efforts. The feedback from our students and our students employers has been very positive. Our graduates have stated the time spent in the SMT Lab as some of the most valuable education they received in preparation for their current jobs in the semiconductor industry. The employers are pleased with the vocabulary and techniques that these entry-level employees have demonstrated. Unfortunately, a formal study comparing graduates that have been through the SMT Lab with those that have not has not been conducted. Such a study would require the cooperation of industry in collecting and providing the necessary data. Because of the time and the number of people required to conduct such a study, we do not see it happening in the near future. Even with all of the successes that TVI has had with the SMT Lab, TVI would not recommend others to pursue such a project. For a community college, TVI has a very large student population 18,000 FTE. In the Fall of 1997, TVI had 1000 students in the Manufacturing Technology program and another 350 in Electronics. It is this student population that made this project a good investment for Intel and TVI. The cost of SMT lab construction exceeded one million dollars. The yearly maintenance costs and necessary support personnel is more than most schools can budget. To maintain the labs and the equipment, TVI has hired two full-time techncians. Its lab instructors have spent many hours learning the equipment both in operations and maintenance. A partnership for just-in-time technical support has been established between TVI and Intel for the purpose of maintaining the lab equipment in the case of a hard shutdown. Intel technicians are assisting TVI on the installation of the equipment in the systems lab. All equipment should be installed and operational by September of TVI s recommendation is to develop simulated laboratories where students can practice cleanroom protocol and experience wearing a bunnysuit for a few hours at a time. This experience alone is very valuable to the students education. For schools within close proximity to one another, a regional lab such as TVI s could be beneficial. However, one should never attempt such an endeavor without a large student population and industry support. Through the on-going support of Intel and the dedication of TVI s instructors, TVI s Regional SMT Lab has proven to be a very valuable education and training facility. It gives students a unique opportunity to work in a cleanroom environment, wear the bunnysuit, and operate automated equipment. The new Manufacturing Technology Systems Lab is already proving to be just as valuable even though on two systems are completely operational to date. For comments or questions about this paper, please contact Mary Jane (505) or mjwillis@tvi.cc.nm.us.