WO2022117130A1

WO2022117130A1 - Device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions

Info

Publication number: WO2022117130A1
Application number: PCT/CZ2020/000053
Authority: WO
Inventors: Zdeněk Hubička; Vítězslav Straňák; Martin Čada; Jiří Olejníček; Miroslav Hrabovský; Petr Schovánek
Original assignee: Univerzita Palackého v Olomouci
Priority date: 2020-12-03
Filing date: 2020-12-03
Publication date: 2022-06-09
Also published as: EP4081671A1; EP4081671A4

Abstract

Device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions which is formed with a vacuum chamber (1) whose inner volume (101) is through a regulation valve (2) connected with a vacuum pump (3), where the vacuum chamber (1) is in its upper part equipped with an entrance flange (102) for possibility of supply of working gas which is Into the inner volume (101) blown through a mas flowmeter (4) whereas in the Inner volume (101) are opposed a controlled ion source (5) and a pivoted and heated substrate holder (6) and between them are placed a system of sputtering plasma sources (?) which together with the ion source (S) generate flow of neutral and ionized particles. The essence of the invention is that above the pivoted substrate holder (8) is placed a system of at least two stationary high frequency probes (8) for possibility of measurement in real time ion flow and ion energy distribution function of landing ions at given place of placement of the samples of the substrate (9) on the substrate holder (8) whereas not only the ion source (5) is connected with the first power supply unit (10) and the sputtering plasma sources (?) with the second power supply unit (11) when both power supply units (10) and (11) are placed outside of the vacuum chamber (1) but also the substrate holder (6) is connected with a control unit (12) which is also placed outside of the vacuum chamber (1) and also there is, as an integrated part of the device, a processing and control unit (13) which is also placed outside of the vacuum chamber (1) and which is in parallel connected with the first power supply unit (10), the second power supply unit (11) and Individually with each stationary high frequency probe (8) when the connection with particular stationary high frequency probes (8) is realized through digitizers (14) which are placed outside of the vacuum chamber (1).

Description

Device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions

Art Domain

The invention foils within the area of deposition of dielectric optical films by the help of sputtering plasma sources and ion energy beams and solves new design of device for deposition and control of parameters of low pressure plasma and these ion beams directly during the deposition process when are measuring probes covered With dielectric film. Present Prior Art

Dielectric optical thin films have been prepared for a long time by the help of vacuum evaporation with assistance of ion beams. This method is described for example in the file US 2002/0127438A1 (Christopher C. Cook, Controlled stress optical coatings for membranes). Another already existing method of deposition of optical films uses ion beams together with reactive plasmatic sputtering, With this method is obtained better adhesion of dielectric optical films and is possible to prepare more types of materials than in case of evaporation. At present is the use of combination of this method widely spreading. It is described for example in the file US 6.238,537 B1 (James R Kahn; Viacheslav V Zhurin, Ionassited deposition surce) and also in the file US 2008/0050910 A1 (Gary Aden Hart, Robert LeRoy Maier, Jue Wang. Method for producing smooth dense optical films). Problem of this repeatable deposition of these types of optical films is reliable plasma diagnostic applicable directly during the deposition process namely mainly measuring of ion flux on the substrate and measuring of ion distribution function. Measuring of ion distribution function in the plasma is possible to realize with a suitable method which is based on a grid analyzer with retarding field. This type of ion analyzer which is suitable for deposition system is described in the article S. G. Ingramt and N St J Braithwaite, ion and electron energy analysis at a surface in an RF discharge 1988 J.Phys. D. Appl Phys. 21 1496 and further, a superior version of this analyzer with more grids, which is described in the article; G. Bohm and J. Perrin Retarding-fidd analyzer for measurements of ion energy distribution and secondary electron emfosfon coefocfente fo fow-pressure radio frequency discharges, Rev. Sci. Insrum . 64 (I), January 1993. Disadvantage of these grid analyzers is presence of the grids on which is brought DC electric potential which is insulated from the plasma in case of covering of the grid with dielectric film and the sensor is then dysfunctional Modification of the ion analyzer for this type of plasma is the way which instead of the grid for repulsion of electrons from the detecting electrode of ions uses a stationary magnetic field. This system is described in the file CZ 304493 (P Adarnak, M. Cada, Z. Hubicka, L. Jastrabik, J. Adamek, J. Stockel, Zpusob mereni iontove distribucni funkce v nizkoteplotnim plazmatum menci system pro provadeni tohoto zpusobu a sonda pro menci system).- Method of measuring of ion distribution function in low temperature plasma, metasuring system for pursuit of this method and probe for the metasuring system . This system does not have a grid but poles of magnets must be on the same DC potential as surface of the detection probe, and yet it is not possible to sustain, because in the reactive deposition plasma is surface of the magnets also quickly covered with the dielectric film and the system stops to be functional. in the file CZ 29907 U1 (Z. Hubicka. M. Cada, J. Olegnicek, S. Kment , V. Stranak, P. Adamek, Zarizeni k vytvarent tenkych depozicnich vrstev pomocinizkottakeho plazmatu) - Device for generation of thin films by the help of low pressure plasma is described a plasmatic deposition device for preparation of thin films which enables only to measure the thickness of the film during the plasmatic deposition process. However this device does not enable to measure the ion distribution function. In the patent file CZ 307505 ( Z. Hubicka, M. Cada, J. Olegnicek, S. Kment V. Stranak, P. Adamek, Zpusob mereni impedance deponovane vrstvy ve vybojovemplazmatu a zarizeni k provadeni tohoto zpusobu) - Method of measuring of Impedance of deposited layer in discharge plasma and device for pursuit of this method is described a high frequency probe which enables measurement of etectric impedance of a semiconducting deposited film and impedance of wail space charge sheath during the process of deposition of the film. From these measured information on this device is not possible to anyhow detect the energy distribution function of ions in the plasma, in the file CZ 306980 ( J. Olegnicek, J. Smid Z. Hubicka, P Adamek, M. Cada, S. Kment, Zpusob rizeni rychlosti depozice tenkych vrstev ve vakuovem vicetryskovem plazmovem systemu a zarizeni k provadeni tohoto zpusobu)- The method of contolling of speed of deposition of thin layers in vacuum multi nozzle plasmatic system and device for pursuit of this method and in the file CZ 30018 U1 J. Olegnicek J. Smid, Z. Hubicka, P. Adamek, M. Cada, S. Kment, Zarizeni k rizeni depozice tenkych vrstev ve vakuovem vicetryskovem plazmovem systemu) - Device for control of deposition of thin films in vacuum multi nozzle plasma system is described a controlled plasmatic deposition of films where the process of plasmatic sputering is controlled by the help of temperature measurement of sputered plasma nozzle by the help of set of pyrometers. However this device is not able to anyhow offer information concerning character of ion distribution function in the plasma. In the patent file CZ 306799 ( Z. Hubicka, M. Cada, S . Kment, J. Olejnicek P. Adamek V. Stranak, Zpusob mereni depozicniho nizkotlakeho plazmatu s vyuzitim vinove rezonance elektronove cyklotronove viny a zarizeni k provadeni tohoto zpusobu)- Method of measurement of deposition tow pressure plasma with use of wave resonance of an electron cyclotron wave and device for pursuit of this method is described a diagnostic method of plasma parameters which is able to determine temperature and concentration of electrons in the plasma from the character of wave resonance of electron cyclotron wave activated in the plasma yet this method is not able to anyhow determine the character of ion distribution function In the plasma and also to measure ion flow on the substrate.

The aim of presented invention is to introduce device in which is able, by the help of new structure of high frequency ion probes, to measure directly on depositions of dielectric optic films energy distribution function of ion flux on the substrate and total size of their flux at the same time in several points in front of the support with deposition substrate. New invention which measures high frequency probes is designed in the way for this probe to work even in the case that its surface and inner components are covered with a dielectric film which is unique characteristic of this new probe. Essence ofthe invention

The determined goal is reached with a new invention which is a device for measurement and control of homogenity of ion energy distribution function and value of ion flux on the substrate during deposition of dielectric optical thin films which is formed by a vacuum chamber whose inner volume is through a regulating valve connected with a vacuum pump, where the vacuum chamber is in its upper part equipped with an entrance flange for possible entry of working gas, which is into the .inner volume blown through a mas flowmeter, whereas in the inner volume are opposite way placed a controlled ion source and a pivoted and heated substrate holder, between them is placed a system of sputtering plasma sources and an ion source for possibility of generation of flow of neutral and ionized particles. The essence of the invention is that above the substrate pivot holder Is placed a system of at least two stationary high frequency probes for possibility to in real time measure ion flux and ion energy distribution function of landing ions in given place of deposition of substrate samples on the substrate holder, whereas the ion source is connected with the first power supply unit and the sputtering plasma sources are connected with foe second power supply unit when both power supply units are placed outside of the vacuum chamber and not only the substrate holder is connected with the control block which is likewise placed outside of the vacuum chamber and also an integral part of the device is a processing and control unit, which is placed outside of the vacuum chamber and which is in parallel connected with the first power supply unit, the second supply unit and independently with each stationary high frequency probe when the connection with individual stationary high frequency probes is done through digitizers which are placed outside of the vacuum chamber.

In preferred design each high frequency probe consists of a north pole(N) of permanent magnet and south pole(S) of permanent magnet for possibility of generation of a stationary (B) magnetic field which is perpendicular to the cylindrical axis of the probe and direction of the entering ions from the plasma flowing from the controlled ion source, whereas under the horizontal level of position of the permanent magnets are inside of the shell of the high frequency probe placed one after another a grid and a detecting electrode when the grid is electrically connected with poles of the permanent magnets and these are connected to a high frequency source through a blocking capacitor and the detecting electrode is not only connected with an AC generator through a coupling capacitor and a discharging resistor but also is .through a voltage probe, a current probe, a digitizer and a control unit connected with a power supply unit

With presented invention is obtained new and higher efficiency as the device is abb to measure ion distribution function in the plasma and ion flux on the substrate also in case of coating of ail its components which are in contact with the plasma with an electrically nonconductive film.

The particular example of design of the invention is schematically illustrated in enclosed drawings where:

Fig.1) illustrates a general scheme of new device with trinity of high frequency probes which are placed in front of the substrate holder, Fig.2a) is a detail projection view of pivot substrate holder from the fig.1 with illustrated lay out of five deposited samples of the substrate when are used three measuring high frequency probes placed in line,

Fig.2b) is a detail projection view of alternative design of pivot substrate holder with illustrated lay out of five deposited samples of the substrate when are used two measuring high frequency probes placed in the center and close to the edge of the holder,

Fig.2c) is a detail projection view of another alternative design of pivot substrate holder with illustrated lay out of five deposited samples of the substrate when are used three measunng high frequency probes placed in the triangle when one is in the center and two close to the edge of the holder;

Fig.2d) is a detail projection view of another alternative design of pivot substrate holder with illustrated by out of two deposited samples of the substrate when are used three measuring high frequency probes placed in line,

Fig.2e) is a detail projection view of alternative design of pivot substrate holder with illustrated lay out of three deposited samples of the substrate placed in the triangle when are used two measuring high frequency probes placed in the triangle,

Fig.3) is an example of detailed design of high frequency ion probe with illustration of electric connection of its supply and detecting circuits,

Fig.4) is an example of graphic illustration of detail, of measure time course of voltage and currents on the detecting electrode,

Fig.5) is an example of determined volt-ampere characteristic, from measured signals on the detecting electrode after deduction of capacity currents by the probe when is illustrated also derivation of probe current according to probe voltage , which

is proportional to energy distribution function of ions in the deposition plasma, and Fig.6) illustrates example of determined energy distribution functions of ions from measured signals on the detecting electrode for two different values of plasma potential in deposition device.

The drawings which illustrate presented invention and consequently described examples of particular designs do not in any case anyhow limit the extent of the protection yet merely clarify the essence of the invention.

The device for realization of the invention is, in its basic design which is illustrated in fig.1 , formed by a vacuum chamber 1 whose inner volume 1Q1 is through a regulating valve 2 connected with a vacuum pump 2. The vacuum chamber 1 is in its upper part equipped with an entrance flange 102 for possibility of supply of working gas which is into the inner volume 101 blown through a mass flowmeter 4. In the inner volume 101 are opposed a controlled ion source 5 and pivoted and a heated substrate holder 6 between them are placed a system of sputtering plasma sources 7 which together with the ion source 5 generate flow of neutral and ionized particles, and a system of stationary high frequency probes 8 which are able to measure in real time ion flux and ion energy distribution function of landing ions at given place of placement of the samples of the substrate 9. The ion source 5 is connected with the first power supply unit 10 and the sputtering plasma sources 7 with the second power supply unit 11 when both power supply units 10 and 11 are placed outside of the vacuum chamber 1. The substrate holder 6 is then connected with a control unit 12 which is also placed outside of the vacuum chamber 1 and which controls its rotation movement and heating. An integrated part of the device is a processing and control unit 13 which is also placed outside of the vacuum chamber 1 and which is in parallel connected with the first power supply unit 10, the second power supply unit 11 and individually with each stationary high frequency probe 8 when the connection with particular stationary high frequency probes 8 is realized through digitizers 14 which are placed outside of the vacuum chamber 1.

As it is illustrated in all alternative designs fig. 2) it is not necessary to place on the substrate holder 6 five samples of the substrate 9 and above it three ion high frequency probes 8 in one line as in fig. 2a) but for different division of plasma spatial characteristic or ion beam there must be at least two high frequency probes 8. If there are more probes if is better as the measurement of spatial division is more accurate. The samples of the substrate 9 can be also more, but the measurement makes sense for two and more whereas the high frequency probe 8 should not during measurement shadow the substrate thus the high frequency probes 8 and the substrate samples 9 should not meet during the rotation of the substrata holder 6. If there are used three ion high frequency probes 8 as it is illustrated in figs. 2c), 2d) and 2e) they do not have to be at the same level even though is can simplify evaluation of results of measurement.

The high frequency (RF) probe 8 which is illustrated in fig. 3) consists of a north pole (N) of the permanent magnet 81 and a south pole (S) of the permanent magnet 82 which generate a stationary (8) magnetic field 83 which is perpendicular to the cylindrical axis of the probe 8 and the direction of entering ions for plasma flowing from the controlled ion source 5. Under horizontal level of position of the permanent magnets 81 and 82 are inside of the cover 84 of the high frequency probe 8 placed one behind another a grid 85 and a detecting electrode 86 where the grid 85 is electrically connected with the poles of the permanent magnets 81 and 82 and. these are connected to a high frequency source 23 through a blocking capacitor 22. The detecting electrode 86 is then not only connected with an AC generator 24 through a coupling capacitor 25 and a discharging resistor 26 but also through a voltage probe 27 a current probe 28 a digitizer 14 and a control unit 13 with the second power supply unit 11.

During operation cf the device the stationary (B) magnetic field S3 works as an electron filter which nearly eliminates flow of electrons toward the detecting probe 86 whereby the higher efficiency of elimination of electrons flow on the detecting electrode 86 is achieved by placement the grid 85 which is connected to a high frequency source 23 in front of this detecting electrode 86. The high frequency source 23 has to operate on frequency f which is higher than is plasmatic frequency of ions in the plasma . The high frequency voltage from the high frequency -source

23 causes generation of DC negative bias voltage

on layer of space charge which exists around the grid 85 and the poles 81 and 82 of the magnet and also in case that the poles 81 and 82 of the magnet and the grid 85 will be covered with dielectricfilm. The high frequency (HF) voltage will get into the plasma through capacity coupling through this dielectric film. The value

will be approximately the same as the value of the amplitude

on the output of the high frequency source 23 and will be oriented in the way that the surface of the grid 85 will be negative towards the plasma. In this case will be eliminated electric field between the grid 85 and the poles 81, 82 of the magnet and there will not exist any flow of electrons in direction toward the grid 85 and the detecting electrode 38 thanks to ExB drift. This function remains even in the case of coating of the poles 81 and 82 of the magnet and the grid 85 with the dielectric film. Furthermore, the potential of the grid 85 is always negative towards the plasma and will still repulse the elecfrons. The detecting electrode 86 is at the same time connected with an AC generator 24 through a coupling capacitor 25 and a discharging resistor 26. The current probe 28 and the voltage probe 27 detect AC voltage U and current I through the detecting electrode 86. These signals are processed with the digitizer 14 and then the control unit 13 which sends this information to control to the first power supply unit 10 of the sputtering plasma source 7 and the second power supply unit 11 of control of the ion source 5. Because the electron flow on the detecting electrode 86 is completely eliminated the current on the detecting: electrode 86 is formed only by ions. From the signals I and U obtained on the voltage probe 27 and the current probe 28 is possible to obtain the volt- ampere characteristic of ion gas in front of toe detecting electrode 86 from which is possible to determine, with known process, total ion flow and ion distribution function from derivation of detected current based on voltage from the volt-ampere characteristic. The frequency of the AC generator 24 must be lower than the

plasmatic frequency of ions in the plasma

This new invention describes the device which is able to measure ion distribution function in the plasma and ion flux on the substrate even in case of coating of all its components which interact with the plasms with nonconductive thin film. This function is reached with placement of the metal grid 85 in front of the detecting electrode 86. This grid 85 is then electrically connected with the poles 81 and 82 of the stationary magnets S and N and these are then connected with the high frequency source 23 through the blocking capacitor 22. After bringing of this RF voltage on the grid 85 and the poles 81 and 82 of the magnets S and N is thanks to rectifying of this RF voltage on the surface layer a space charge induced on this layer of the space charge DC bias voltage which is oriented in the way that the surface of the grid 85 and the poles 81 and 82 of the magnets S and N is negative with regard to potential of the plasma. This induced negative bias voltage on the grid 85 and the poles 81, 82 of the magnets S and N initiate repulsion of electrons from the surface of the detecting electrode 86 and this way oriented DC electric field which is generated between the poles 81 and 82 of the magnet directs ExB drift of electrons in direction away from the surface of the detecting electrode 86. The detecting electrode 86 thus collects only ions and can measure their energy distribution function. The significant advantage of this new technical layout is the fact that this induced DC bias voltage is generated around the surface of the grid 85 and the poles 81 and 82 of the magnet S and N even in case of existence of dielectric film on their surfaces because RF voltage from the high frequency source 23 can get on the wall layer of the space charge through capacity coupling through this film and proper function of the device stay unchanged. The function of the detecting electrode 86 will remain for measurement of distribution function of ions also in case of coating with dielectric film because it is powered with AC style brake voltage from the AC generator 24. This can get into the plasma through an alternating coupling through capacity of this dielectric film. Possible induced direct bias voltage on this detecting electrode 86 is not desired for measurement of ion distribution function and. it will not occur as it will be shorted out through the discharging resistor 26

Industrial utility

The device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions according to the invention is designed and intended above all for use for optical and optoelectronic applications when are measuring probes covered with the dielectric film.

Claims

PATENT CLAIMS

1. Device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions which is formed with a vacuum chamber (1) whose inner volume (101) Is through a regulation valve (2) connected with a vacuum pump (3), where the vacuum chamber (1) is in its upper part equipped with an entrance flange (102) for possibility of supply of working gas which is into the Inner volume (101) blown through a mas flowmeter (4) whereas in the inner volume (101) are opposed a controlled ion source (5) and a pivoted and heated substrate holder (6) and between them are placed a system of sputtering plasma sources (7) which together with the ion source (5) generate flow of neutral and ionized particles, wherein above the pivoted substrate holder (6) is placed a system of at least two stationary high frequency probes (8) for possibility of measurement in real time ion flow and ion energy distribution function of landing ions at given place of placement of the samples of the substrate (9) on the substrate holder (6) whereas not only the ion source (5) is connected with the first power supply unit (10) and the sputtering plasma sources (7) with the second power supply unit (11) when both power supply units (10) and (11) are placed outside of the vacuum chamber (1) but also the substrate holder (6) is connected with a control unit (12) which is also placed outside of the vacuum chamber (1) and also there is, as an integrated part of the device, a processing and control unit (13) which is also placed outside of the vacuum chamber (1) and which is in parallel connected with the first power supply unit (10), the second power supply unit (11) and individually with each stationary high frequency probe (8) when the connection with particular stationary high frequency probes (8) is realized through digitizers (14) which are placed outside of the vacuum chamber (1).

2. Device for deposition of dielectric optical thin films by the help of sputtering plasma sources and sources of energy ions according to the daim 1, wherein each high frequency probe (8) consists of a north pole (N) of permanent magnet (81) and a south pole (S) of permanent magnet (82) for possibility of generation of stationary (8) magnetic field (83) which is perpendicular to the cylindrical axis of the probe (8) and the direction of entering ions for plasma flowing from the controlled ion source (5) whereas under horizontal level of position of permanent magnets (81) and (82) are inside of the cover (84) of the high frequency probe (8) placed one behind another a grid (85) and a detecting electrode (86) where the grid (85) is electrically connected with the poles of the permanent magnets (81) and (82) and these are connected to a high frequency source (23) through a blocking capacitor (22) and the detecting electrode (86) is then not only connected with an AC generator (24) through a coupling capacitor (25) and a discharging resistor (26) but also through a voltage probe (27), a current probe (28), a digitizer (14) and a control unit (13) with the second power supply unit (11).