LabVIEW controller for storage results and control

DOI: 10.15199/13.2016.2.6

LabVIEW controller for storage results and control parameters of low thickness antireflection coatings deposition processes (System kontroli i rejestracji parametrów procesu depozycji cienkowarstwowych powłok antyrefleksyjnych pracujący w środowisku LabVIEW) dr inż. Konstanty Marszałek1, dr inż. Anna Małek1, mgr inż. Paweł Winkowski2, mgr inż. Krzysztof Woźny3,4 AGH University of Science and Technology, Department of Electronics, Kraków 2  Pevin, Kraków 3  AGH University of Science and Technology, Faculty of Electrical Engineering, Automatics, Computer Science and Biomedical Engineering, Department of Power Electronics and Energy Control Systems, Kraków 4  CBRTP SA Research and Development Center of Technology for Industry, Warsaw 1 

Streszczenie W artykule przedstawiono system do kontroli, wizualizacji i zapisu danych procesów PVD. System został zaprojektowany w  oparciu o środowisko LabVIEW i został z powodzeniem zastosowany w  przemyśle optycznym. Wizualizacja jest bardzo intuicyjna dla operatora daje łatwą możliwość kontroli wszystkich parametrów procesu. Zapisane dane pomagają w polepszeniu jakości powłok i  dają możliwość analizy procesów. Niski koszt wprowadzenie systemu czyni go również bardzo użytecznym narzędziem do modyfikacji starszego typu napylarek próżniowych oraz daje szansę stopniowej jego rozbudowy. Słowa kluczowe: sterownik procesu, programowanie graficzne LabVIEW, Regulator przepływu masy, powłoki antyrefleksyjne

Abstract System for control, visualization and storage of PVD processes data is presented in this paper. The system has been designed in LabVIEW environment and has been implemented successfully in optical industry. Visualization is very intuitive for the operator and gives easy control of all important process data. Stored process data help improve the quality of the coatings and provide the ability to analyze processes. Low cost of implementation of the system also makes it a very useful tool for modifying older types of vacuum coaters and gives a possibility of gradual further expansion of systems. Keywords: process control system, LabVIEW graphical programming, mass flow controller, antireflective coatings

Dynamic development of PVD (Physical Vapour Deposition) technology noticeable in the recent years causes increasing technological restrictions concerning repeatability of coatings processes. In case of production of multilayers AR (Antireflective Coatings) on optical parts the restrictions are especially high. The most important parameters in PVD technology for AR coatings are: rate of deposition, final thickness of layers of coatings, level of vacuum during deposition processes and stability of temperature of substrates. In many cases a stable dosing of technological gases is a critical point for deposition. The design of the dedicated system for AR coatings deposition processes working in graphical LabVIEW programming environments for control, intuitive visualization and storage of results is presented in this paper. The system allows to create a kind of library that helps to recreate the process, analysis and changes of the process data. Use of high flexibility of the LabVIEW environment additionally, the system was designed to allow dosing of process gases during deposition material from e-gun. In the Department of Electronics at AGH University of Science and Technology for several years, work is underway on the use of LabVIEW to control the PVD processes. An example is the control device for magnetron sputtering processes. The presented project is an example of practical application in specific industrial application. The system was implemented in vacuum coater Leybol-Heraeus A700Q working in thin films laboratory PEVIN. The main production of the laboratory are multilayers AR coatings for optical parts made of glass [1, 2]. Although there are known similar solutions based

on PLC controllers, e.g. Simatic, it was decided to use this solution because it provides a high ease of implementation in existing process equipment without costly modifications, flexibility in visualization of processes and easy control of process parameters. An important advantage is also the possibility of gradual further expansion of the system.

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Description of the system Vacuum coater Leybold-Heraeus A700Q presented in Fig. 1, in which was implemented the described system, consists of the vacuum chamber connected to the pumping system. Pumping system consists of turbomolecular pump and two stages backing pump by the valves system. In the vacuum chamber there are two kinds of evaporation sources: three thermal and one electron gun with four crucibles. The vacuum coater is connected to four basic sources of process signal data: the system vacuum control based on the vacuum head Inficon BPG400 (5) connected to the controller Pfeiffer TPG261 (1), dosing process gases valve MKS Mass Flow Controller 1179 (6), the heater of substrates controlled by the regulator Apar AR650 (3) and the thin film controller Inficon XTC/2 (2) used to measure rate and thickness of deposited coatings. Outlined above elements are connected with a PC via the USB bus. The various transmission media in addition to the data-transfer features, also provides a function of separation actuators. A system block diagram is shown in Fig. 2. Process Control system is prepared in a graphical programming language using the National Instruments LabVIEW

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a)  sensing head BPG 

= 10

− 7.75 + 0.75

 = 0.75 • (

Fig. 1. Vacuum coater A700Q, 1 – TPG261, 2 – XTC/2, 3 – AR650, 4 – PC, 5 – BPG400, 6 – Flow Rys. 1. Napylarka próżniowa A700Q, 1 – TPG261, 2 – XTC/2, 3 – AR650, 4 – PC, 5 – BPG400, 6 – Flow Controller 1179

2013. The process used 3 media communication with sensors and actuators. The driver XTC / 2 uses an RS232 serial interface. Consecutively temperature AR650 uses a differential RS485 interface. To control the gas flow MKS uses a  multifunction data acquisition (DAQ) module optimized for superior accuracy at fast sampling rates, National Instruments USB6211. However, in the case of the head to measure pressure in order to ensure the accuracy of the process and security, read data is redundantly using the transmitted digital RS232 interface and analog signal measured using a measurement module, the NI USB-6211. The analog signal is sampled and then subjected to a transforming function (1)(2).

b)  sensing head HPG − 1

(1)

= 1 + log

(2)

= 10 − ) + 7.75

where: p – pressure depending on the parameter “c” given in [mbr] [Pa], U – voltage of the sensor [V],c – constant 0 [mbar], 2 for [Pa], c1 constant 7.5 for [mbar] to 5.5 [Pa]. Analysis of processes occurring during the test available in vacuum technology developed state diagram is presented in Fig. 3. Various states and materials used in technical processes defined the optimal program modules and allowed us to create a library of parameters for optimization of technical processes. The program allows the control, monitoring and visualization of the process parameters such as time to read the sensors, the temperature, pressure (technical vacuum), measuring the thickness of applied layers, the speed of the application and monitoring, and controls the flow metering valve. Furthermore, the program carries out gas injection in an automated fashion using a feedback loop and PID control so as to maintain a predetermined pressure level by the operator [3, 4, 5]. In addition, the operator can at any time switch to manually control the level of flow from the operation panel, as well as the complete closure or opening of the valve. The program has a modular structure which allows its scalability for more complex installations and application in older type chambers, which did not provide read and write most of the parameters [6].The configuration data of individual processes can be entered by the user or read from a previously created the library values for different materials. The whole process is stored in the form of a csv file. The operator panel was prepared in a transparent manner in accordance with accepted conventions of industrial interfaces to track and process control Fig. 4 [7, 8].

Research Analysis of the system was carried out during the processes of deposition of wide band antireflective coatings for UV region.

Fig. 2. Block diagram of the system. Rys. 2. Schemat blokowy systemu

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Fig. 3. Implementation of application diagram. Rys. 3. Realizacja diagramu aplikacji

Fig. 4. User Control Panel. Rys. 4. Panel użytkownika

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mal evaporation method and started at vacuum higher than 8×10-5 mbar without any processes gases. Temperature of substrates during evaporation was T = 270oC. Deposition rates and the final thicknesses of the films Al2O3 / HfO2 / / MgF2 were 0,5 nm/s, 1,0 nm/s, 7,0 nm/s and 45,6 nm/88,9 nm/ / 54,0 nm respectively. The example of the process data recorded by the system was shown on Fig. 4.

Conclusion The paper presents the implementation of an automatic continuous dosing control gas, and reading and writing the relevant process parameters thin film deposition systems using graphical development environment of LabVIEW 2013. Developed control system has a modular structure which allows its scalability and expansion to other process chambers. Prepared in the laboratory program has been implemented in the industry and ultimately can be used in lines pipelined. Environment options integration with huge amounts of industrial equipment and the fact that while extensive use of the environment is an argument may be inclined to such a solution. The advantage of the software is clarity and readability for the user and the opportunity to observe the process and condition of the equipment during the process. In addition, the acquisition and archiving of process parameters makes it possible to analyse at a later date. The paper was financially supported by AGH University Science and Technology project no 11.11.230.16.

References

Rys. 5. Parametry procesu otrzymywania powłoki antyrefleksyjnej Al2O3 / HfO2 / MgF2 Fig. 5. Data of Al2O3 / HfO2 / MgF2 antireflection coatings. deposition processes

The thin films consisted of three layers made of different materials: Al2O3, HfO2, MgF2. [9, 10] The deposition processes started at the pressure lower than 5×10-5 mbar. Thin films of the Al2O3 and HfO2 [11] were deposited from e-gun evaporator in 02 atmosphere with pressure 2×10-4mbar. MgF2 was deposited by ther-

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[1] Ishikawa H., Honjo Y., Watanabe K., Three-layer broad-band antireflective coating on web, Thin Solid Films, Volume 351, Issues 1–2, 1999, 212–215. [2] Rey-Stolle, C. Algora Optimum antireflection coatings for heteroface AlGaAs/GaAs solar cells—Part II: The influence of uncertainties in the parameters of window and antireflection coatings, Journal of Electronic Materials , Volume 29, Issue 7, 2000, 992–999. [3] Bitter A.,. Mohiuddin R. T., Nawrocki M., LabVIEW Adwanced Programming Techniques SECOND EDITION, CRC Press, (2007). [4] Driankov D., Hellendorn H., Reinfrank M., An Introduction to Fuzzy Control, NewYork (1995). [5] Bress T., Effective LabVIEW Programming, 2013. [6] Marszałek K. W., Sobków Z., Pisarkiewicz T., LCD displays test system working in LabVIEW environment , Elektronika, nr 9, (2009), 85–86. [7] http://www.ni.com/white-paper/2995/pl/ „Zaawansowane funkcje regulacji za pomocą algorytmu PID” (2013) [15.12.2015] [8] http://www.ni.com/pdf/manuals/372192d.pdf „PID and Fuzzy Logic Toolkit User Manual”, (2009) [15.12.2015] [9] Selhofer H., Mueller R., Comparison of pure and mixed coating on materials for AR coatings for use by reactive evaporation on glass and plastic lenses, Thin Solid Films, 351, (1999), 180–183. [10] Winkowski P., Marszałek K. W., Wide band antireflective coatings Al2O3 / HfO2 / MgF2 for UV region, Proc. of SPIE Vol. 8902 890228-1 890228-5 (2014) [11] J. Yuan, L.Yuan, H. He, K. Yi, Z.Fan, et al.,”Influence of ZrO2 in HfO2 on reflectance of HfO2  /SiO2 multilayer at 248 nm prepared by electron-beam evaporation”, Applied Surface Science, 254, 15, 4864–4867, ( 2008).

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