MKS Instruments, Inc. is a global leader in the supply of process measurement and control instrumentation and advanced vacuum components. We serve markets that depend on advancements in material science and material processing to improve their products, ranging from sophisticated semiconductors to industrial tool coatings. These processes often involve building up thin layers of materials through the interaction of gases and solids in tightly controlled environments.
We control these environments with products that manage the flow rates of entering and exiting process gases, thus controlling the mixture and pressure within a process chamber. We also offer products that analyze and monitor the composition of these gases and isolate them from the environment outside of the chamber.
Realizing that an understanding of vacuum and related process monitoring and control instrumentation is a key area for individuals who are preparing to become technical workers in the semiconductor industry, MKS has developed an integrated set of instructional hardware and literature for the teaching of vacuum and instrumentation practice. The centerpiece is the MKS Vacuum Training System (model VTS-1B), a tabletop vacuum system which replicates the key features and functions of a full-scale process tool. The following material provides an overview of the VTS-1B, an outline of the documented exercises that may be performed with the system, downloadable student worksheets that were developed in cooperation with Austin Community College, and pointers to further information and resources.
What are some of the vacuum and instrumentation concepts that are important in the semiconductor industry and how can they be taught?
Descriptions of Exercises
The instructor's guide for the VTS-1B system currently contains about thirty exercises. The following provides an outline of these exercises and how these relate to semiconductor process tools.
Vacuum system set up (starting with individual components):
The students are presented with a collection of individual components. They must assemble the components into a functional system. They learn:
These exercises delve into the basics of vacuum practice.
A bewildering variety of gauges are used to monitor and control the system pressure. By comparing gauges, students will understand the differences between indirect (as exemplified by Pirani and ionization gauges) and the precision direct vacuum gauges (as exemplified by the capacitance manometer) that are used to control processes. Students learn about critical issues such as transient response, gas sensitivity, accuracy and repeatability, etc.
Closed-Loop Pressure Control
All semiconductor processes live or die by the repeatability and stability of their closed loop control systems. All tools have a variety of pressure and flow control systems. These exercises familiarize the students with pressure control systems in a variety of modes. The effects of various tuning parameters (proportional, integral, derivative) are seen in the way that the system responds while acquiring and maintaining specific set point pressures.
Mass Flow Controllers
Mass flow controllers (MFCs) are the devices by which process and purge gases are delivered to the tool. Mass flow is usually measured in units of standard cubic centimeters per minute (sccm). The mass flow is actually an indication of how many molecules per minute of gas are being delivered to the chamber. MFCs represent another closed-loop control system where an input signal is translated into a specific mass flow of gas. A widely misunderstood component, a typical tool may use up to 100 MFCs. In this set of exercises, the students understand the operation and proper use of flow controllers, calibration and verification techniques, and basic troubleshooting.
High Vacuum System Structure and Operation
Students add a high vacuum (turbo-drag) pump to the system and learn the proper use of a high vacuum pumping system.
Use of the Residual Gas Analyzer (RGA)
Partial pressure measurement using the RGA serves as an important troubleshooting and diagnostic tool. RGAs may be used as part of maintenance routines, during process development and for process monitoring and control.
The RGA exercises introduce the student to the use of the instrument through a series of structured exercises that cover set up, various vacuum system configurations, and operational modes.
Austin Community College has developed a number of student lab worksheets for the VTS-1B. These may be downloaded as an Adobe AcrobatTM file.
More Information from MKS:
Link to the MKS Instruments Education page (http://www.mksinst.com/train.html). Information on educational materials and hardware and article reprints that may be of interest to the educator. The data sheet for the VTS-1B Vacuum Training System is also available here.
Link to the MKS Instruments home page (link to http://www.mksinst.com/)
Contact MKS Instruments' Training Dept. (mailto:firstname.lastname@example.org)
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