CZ34937U1 - Equipment for measuring and controlling the homogeneity of the ionic energy distribution function and the size of ion fluxes on the substrate during the deposition of dielectric optical thin films - Google Patents

Description

Equipment for measuring and controlling the homogeneity of the ionic energy distribution function and the size of ion fluxes on the substrate during the deposition of dielectric optical thin films

Field of technology

The technical solution falls into the field of deposition of dielectric optical layers using sputtering plasma sources and ion energy beams and solves a new design of equipment for measuring and controlling the parameters of low pressure plasma and these ion beams directly during the deposition process, where measuring probes are covered with dielectric layer.

Prior art

Dielectric optical layers have been prepared by ion beam assisted vacuum evaporation for a long time. This method is described, for example, in US 2002/0127438 A1 (Christopher C. Cook, Controlled stress optical coatings for membranes). Another already developed method of deposition of optical layers uses ion beams together with reactive plasma sputtering. This method achieves better adhesion of the dielectric optical layer and it is possible to prepare more types of materials than in the case of vapor deposition. Currently, the use of a combination of this method is widespread. It is described, for example, in U.S. Pat. No. 6,238,537 B1 (James R. Kahn; Viacheslav VZhurin, lonassisted deposition surce) and in U.S. Pat. No. 2008/0050910 A1 (Gary Allen Hart, Robert LeRoy Maier, Jue Wang, Method for producing smooth dense optical films). . The problem of repeatable deposition of these types of dielectric optical layers is reliable plasma diagnostics applicable directly to the deposition process, especially the measurement of ion flux on the substrate and the measurement of the ion distribution function. The measurement of the ion distribution function in plasma can be realized by a suitable method based on a grid analyzer with a braking field. Such an ion analyzer suitable for a deposition system is described in 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. 211496, and a more advanced version of this multi-grid analyzer, which is described in C. Bohm and J. Perrin Retarding-fidd analyzer for measurements of ion energy distributions and secondary electron emission coefficients in low-pressure radio frequency discharges, Rev. Sci. Instrum. 64 (I), January 1993. The disadvantage of these grating analyzers is the presence of gratings to which a direct current electric current is applied, which is isolated from the plasma when the grating is covered by a dielectric layer and the sensor is then inoperative. A modification of the ion analyzer for this type of plasma is a method that uses a stationary magnetic field instead of a grid to repel electrons from the ion detection electrode. This system is described in CZ 304493 (P. Adámek, M. Čada, Z. Hubička, L. Jastrabík, J. Adámek, J. Stóckel, Method for measuring the ion distribution function in low-temperature plasma, measuring system for performing this method and probe for measuring system). Although this system does not have a grid, the poles of the magnets must be at the same DC potential as the surface of the detection probe, and this cannot be maintained, because in reactive deposition plasma the surface of the magnets is also quickly covered by a dielectric layer and the system ceases to function.

CZ 29907 U1 (Z. Hubička, M. Čada, J. Olejníček, S. Kment, V. Straňák, P. Adámek, Device for the formation of thin deposition layers using low-pressure plasma) describes a plasma deposition device for the preparation of thin layers, which only allows the thickness of the layer to be measured during the plasma deposition process. However, this device does not allow the ion distribution function to be measured. The patent document CZ 307505 (Z. Hubička, M. Čada, J. Olejníček, S. Kment, V. Straňák, P. Adámek, Method of measuring the impedance of a deposited layer in a discharge plasma and a device for performing this method) describes a high-frequency probe enabling to measure the electrical impedance of the semiconducting deposited layer and the impedance of the wall layer of the space charge in the plasma during the layer deposition process. From this measured information on this device, it is not possible in any way to determine the energy distribution function of the ions in the plasma. In the patent document CZ 306980 (J. Olejníček, J. Šmíd, Z. Hubička, P. Adámek, M.

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A method of controlling the deposition rate of thin films in a vacuum multi - jet plasma system and a device for carrying out this method) and in the document CZ 30018 Ul J. Olejníček, J. Šmíd, Z. Hubička, P. Adámek, M. Čada, Controlled thin film deposition is described, where the process of plasma dedusting is controlled by measuring the temperature of the dedusted plasma nozzle using a system of pyrometers. However, this device is in no way able to provide information about the nature of the ion distribution function in the plasma. The patent document CZ 306799 (Z. Hubička, M. Čada, Š. Kment, J. Olejníček, P. Adámek, V. Straňák, A method for measuring deposition low-pressure plasma using wave resonance of an electron cyclotron wave and a device for performing this method) describes a diagnostic method of plasma parameters that is able to determine the temperature and concentration of electrons in the plasma from the wave resonance pattern of the electron cyclotron wave excited in the plasma, but this method is not able to determine the ionic distribution pattern in the plasma or measure the ion flux to the substrate.

The task of the present technical solution is to present a device in which it is possible to measure the energy distribution function of ion flux on a substrate and their total flux at several points in front of a carrier with coated substrates directly during deposition of dielectric optical layers by a new design of high frequency ion probes. The new technical solution of the measuring high-frequency probe is designed so that this probe fulfills its function even if its surface and internal components are covered with a dielectric layer, which is a unique feature of this new probe.

The essence of the technical solution

The stated goal is achieved by a new technical solution, which is a device for measuring and controlling the homogeneity of ion energy distribution function and ion flux size on the substrate during deposition of dielectric optical thin films, which consists of a vacuum reactor whose interior is connected to a vacuum pump via a control valve. , wherein the vacuum reactor is provided in the upper part with an inlet neck to allow the supply of working gas, which is blown into the interior through a flow meter, in the interior a controlled ion source and a rotatably mounted and heated substrate carrier are arranged opposite, between which a set of sputtering plasma sources and an ion source to allow the generation of a flow of neutral and ionized particles. The essence of the technical solution lies in the fact that a system of at least two stationary high-frequency probes is placed above the substrate rotating carrier to allow real-time measurement of ion flux and ion energy distribution function of incident ions at a given location of substrate samples on substrate support. connected to the first power supply unit and the sputtering plasma source to the second power supply unit when both power supply units are located outside the vacuum reactor, the substrate carrier is connected to the control unit, which is also located outside the vacuum reactor, and evaluation and control unit, which is installed outside the vacuum reactor and which is connected in parallel with the first power supply unit, with the second power supply unit and separately with each stationary high-frequency probe, when connected to individual stationary high-frequency probes i is implemented via digitizers located outside the vacuum reactor.

In a preferred embodiment, each high frequency probe consists of a north (S) pole of a permanent magnet and a south pole (J) of a permanent magnet to allow generation of a stationary (B) magnetic field perpendicular to the cylinder axis and direction of incoming ions from plasma flowing from a controlled ion source. below the horizontal level of the permanent magnets, a grid and a detection electrode are arranged one behind the other inside the high-frequency probe housing, the grid being electrically connected to the permanent magnet poles and connected to a high-frequency source via a decoupling capacitor and the detection electrode being connected to an AC generator via a coupling capacitor and discharge resistor, and through

- 2 EN 34937 UI voltage probe, via current probe, via digitizer and control unit with power supply unit.

The present solution achieves a new and higher effect in that the device is able to measure the ion distribution function in plasma and ion current on the substrate even in the case of covering all its components that are in contact with plasma with an electrically non-conductive thin layer.

Explanation of drawings

A specific example of an embodiment of the technical solution is schematically shown in the accompanying drawings where, Fig. 1) shows a general diagram of a new device comprising three high frequency probes placed in front of a substrate carrier, Fig. 2a) is a detailed front view of the rotating substrate carrier of Fig. five coated substrate samples using three high frequency measuring probes arranged in a row, Fig. 2b) is a detailed elevational view of an alternative embodiment of a rotating substrate carrier showing the distribution of five coated substrate samples using two high frequency measuring probes placed in the center and at the edge of the carrier; Fig. 2c) is a detailed elevational view of another alternative embodiment of a rotating substrate carrier showing the distribution of five coated substrate samples using three measuring high frequency probes placed in a triangle, one acting in the center and two at the edge of the carrier, Fig. 2d) is a detailed elevational view of the substrate; next a An alternative embodiment of a rotating substrate carrier showing the distribution of two coated substrate samples using three measuring high frequency probes arranged in series, Fig. 2e) is a detailed front view of another alternative embodiment of a rotating substrate carrier showing the distribution of three coated substrate samples placed in a triangle and using three measuring high-frequency probes placed in a triangle, Fig. 3) is an example of a detailed construction of a high-frequency ion probe showing the electrical connection of its power supply and detection circuits, Fig. 4) is an example of a graphical representation of detail of measured voltage and current time courses on the detection electrode; 5) is an example of the determined volt-ampere characteristic from the measured signals on the detection electrode after subtracting the capacitive currents by the probe, showing the derivation of the probe current according to the probe voltage d1 p / dU _p , which is proportional to the energy distribution function of ions in the deposition plasma; 6) stmp shows an example of determined energy distribution functions of ions from measured signals on a detection electrode for two different magnitudes of the plasma potential in a deposition device.

The drawings, which show the presented technical solutions and the subsequently described examples of specific embodiments, in no way limit the scope of protection stated in the definition, but only clarify the essence of the technical solution.

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Examples of technical solution

The device for implementing the technical solution in the basic embodiment shown in Fig. 1 consists of a vacuum reactor whose inner space 101 is connected via a control valve 2 to a vacuum pump 3. The vacuum reactor 1 is provided in the upper part with an inlet 102 to allow the supply of working gas. is injected into the inner space 101 via a flow meter 4. In the inner space 101 a controlled ion source 5 and a rotatably mounted and heated substrate carrier 6 are arranged opposite, between which a set of sputtering plasma sources 7 are placed, which together with the ion source 5 generate a flow of neutral and ionized particles, and a set of stationary radio frequency (RF) probes 8, which are able to measure in real time the ion flux and the ionic energy distribution function of the incident ions at a given location of the substrate samples 9. The ion source 5 is connected to the first power supply unit 10 and the dusting plasma source 7 to the second power supply unit 11 when both power supply units 10 and 11 are located outside the vacuum reactor 1. The substrate carrier 6 is then connected to the control block 12. also located outside the vacuum reactor 1 and which controls its rotational movement and heating. An integral part of the device is an evaluation and control unit 13, which is installed outside the vacuum reactor 1 and which is connected in parallel to the first power supply unit JO, to the second power supply unit 11 and separately to each stationary high frequency probe 8 when connected to individual stationary high frequency the probes 8 are realized via digitizers 14 located outside the vacuum reactor 1.

As shown in all alternative embodiments of Fig. 2), it is not necessary to place five substrate samples 9 on the substrate carrier 6 and three ionic high-frequency probes 8 in a row as in Fig. 2a), but for different distributions of plasma or ionic spatial properties. the beam must have at least two high-frequency probes 8. If there are more probes, the better, because the measurement of the spatial distribution is more accurate. There may be several samples 9 of substrates, but the measurement makes sense for two or more, and the high-frequency probe 8 should not overshadow the substrate during the measurement, i.e. the high-frequency probes 8 and the substrate samples 9 should not meet when rotating the substrate carrier 6. If the three ionic high-frequency probes 8 shown in Fig. 2c), Fig. 2d) and Fig. 2e) are used, they do not have to be in one plane, although this can then simplify the evaluation of the measurement results.

The radio frequency (RF) probe 8 shown in Fig. 3 consists of the north pole S of the permanent magnet 81 and the south pole J of the permanent magnet 82, which generate a stationary magnetic field 83 perpendicular to the cylindrical axis of the probe 8 and the direction of incoming ions from plasma flowing from the controlled. Below the horizontal level of placement of the permanent magnets 81 and 82, a grid 85 and a detection electrode 86 are arranged one behind the other inside the housing 84 of the high frequency probe 8, where the grid 85 is electrically connected to the poles of the permanent magnets 81 and 82 and these are connected to the high frequency source. 23 via a separating capacitor 22. The detection electrode 86 is connected to the AC generator 24 via a coupling capacitor 25 and a discharge resistor 26, and via a voltage probe 27, a current probe 28, a digitizer 14 and a control unit 13 with a power supply unit 11.

In operation, the stationary magnetic field 83 acts as an electron filter that nearly eliminates the flow of electrons to the detection electrode 86, with a greater effect of eliminating the flow of electrons to the detection electrode 86 by placing a grid 85 connected to a high frequency source in front of the detection electrode 86. 23. The high frequency source 23 must operate at a frequency f higher than the plasma frequency of the ions in the plasma f _pi . The high frequency voltage from the high frequency source 23 causes a DC negative bias voltage Udc to be generated on the space charge layer existing around the grid 85 of the magnet poles 81 and 82, even if the magnet poles 81 and 82 and the grid 85 are covered with a dielectric layer. The high frequency (HF) voltage enters the plasma by capacitive coupling through this dielectric layer. The magnitude of Udc will be approximately the same as the magnitude of the amplitude Vrf at the RF output of the high frequency source 23 and will be oriented so that the surface of the grating 85 will be negative to the plasma. In this case, the electric field between the grating 85 and the poles 81, 82 of the magnet will be eliminated and thus there will be no electron flow towards the grating 85 and the detection electrode 86 due to the ExB drift. This function remains

-4EN 34937 UI maintained even in case the poles 81. 82 of the magnet and the grid 85 are covered with a dielectric layer. In addition, the potential of the surface of the grid 85 is always negative to the plasma and will thus further repel electrons. The detection electrode 86 is connected to the AC generator 24 via a coupling capacitor 25 and a discharge resistor 26. The current probe 28 and the voltage probe 27 detect the AC voltage Ua current I through the detection electrode 86. These signals are processed by the digitizer 14 and passed by the control unit 13. control information of the first power supply unit 10 of the sputtering plasma sources 7 and the second power unit 11 of the control of the ion source 5. Since the electron current on the detection electrode 86 is completely eliminated, the current on the detection electrode 86 is formed only by ions. From the signals I and U obtained on the voltage probe 27 and the current probe 26, the volt-ampere characteristics of the ionic gas before the detection probe 86 can be obtained, from which the total ionic flux and ion distribution function can be determined in a known manner by deriving the detected current according to the volt-ampere characteristic voltage. The frequency f _{pr of the} alternator 24 must be less than the plasma frequency f _{pi of the} ions in the plasma.

The new technical solution describes a device that is able to measure the ion distribution function in plasma and ion current on the substrate even if all its components that interact with plasma are covered with an electrically non-conductive thin layer. This function is achieved by placing a metal grid 85 in front of the detection electrode 86. This grid 85 is further electrically connected to the poles 81, 82 of the stationary magnets and these are then connected to a high frequency source 23 via a decoupling capacitor 22. After applying this RF voltage to the grid 85 and the poles 81, 82 of the magnets, by directing this RF voltage on the surface layer of the space charge, a DC bias is induced on this layer of the space charge, which is oriented such that the surface of the grid 85 and the poles 81 and 82 of the magnets is negative to the plasma potential. This induced negative bias at the grid 85 and the poles 81 and 82 of the magnets J and S causes the electrons to repel the surface of the detection electrode 86, and the thus directed DC electric field generated between the magnet poles 81 and 82 further directs ExB drift of the electrons away from the detection electrode surface 86. Thus, the detection electrode 86 collects only ions and can measure their energy distribution function. A significant advantage of this new technical arrangement is the fact that this induced DC bias is created around the surface of the grid 85 and the poles 81 and 82 of the magnet even in the presence of a dielectric layer on their surfaces, because the RF voltage from the high frequency source 23 reaches the wall charge layer. capacitive coupling through this dielectric layer and the correct function of the device will be maintained. The function of the detection electrode 86 will be retained for measuring the ion distribution function also in the case of dielectric layer coverage, since it is supplied with a braking voltage from an alternating current generator 24. This enters the plasma by alternating coupling through the capacitance of this dielectric layer. A possible induced DC bias on this detection electrode 86 is not desirable for measuring the ion distribution function and will not occur because it will be shorted across the discharge resistor 26.

Industrial applicability

The device for measuring and controlling the homogeneity of the ionic energy distribution function and the size of ion fluxes on the substrate during the deposition of dielectric optical thin films is intended and planned primarily for use in optical and optoelectronic applications where measuring probes are covered with a dielectric layer.

Claims (2)

CLAIMS FOR PROTECTION An apparatus for measuring and controlling the homogeneity of the ionic energy distribution function and the magnitude of ion fluxes on a substrate during the deposition of dielectric optical thin films, comprising a vacuum reactor (1) whose interior (101) is connected to a vacuum reactor via a control valve (2). pump (3), where the vacuum reactor (1) is provided in the upper part with an inlet neck (102) to allow the supply of working gas, which is blown into the inner space (101) through a flow meter (4), while in the inner space (101) a controlled ion source (5) and a rotatably mounted and heated substrate carrier (6) are arranged opposite each other, between which a set of sputtering plasma sources (7) and an ion source (5) are arranged to allow the generation of a flow of neutral and ionized particles, characterized in that a set of at least two stationary high-frequency probes (8) is placed above the substrate rotating carrier (6) to allow real-time measurement of ionic flux and ionic energy distribution function incident h ions at a given location of the substrate samples (9) on the substrate carrier (6), wherein on the one hand the ion source (5) is connected to the first power supply unit (10) and the sputtered plasma source (7) to the second power supply unit (11) when both power supply units (10) and (11) are located outside the vacuum reactor (1), on the one hand the substrate carrier (6) is connected to the control block (12), which is also located outside the vacuum reactor (1), and on the other hand an integral part of the device is an evaluation and control unit (13), which is installed outside the vacuum reactor (1) and which is connected in parallel with the first power supply unit (10), with the second power supply unit (11) and separately with each stationary high frequency probe (8), when the connection to the individual stationary high-frequency probes (8) is realized via digitizers (14) placed outside the vacuum reactor (1). Device for measuring and controlling the homogeneity of the ionic energy distribution function and the magnitude of ion fluxes on a substrate during the deposition of dielectric optical thin films according to claim 1, characterized in that each high-frequency probe (8) consists of a north pole (S) of a permanent magnet ( 81) and the south pole (J) of the permanent magnet (82) to allow the generation of a stationary (B) magnetic field (83) perpendicular to the cylindrical axis of the probe (8) and the direction of incoming ions from the plasma flowing from the controlled ion source (5). the horizontal level of placement of the permanent magnets (81) and (82) j is a grid (85) and a detection electrode (86) arranged inside the housing (84) of the high-frequency probe (8), the grid (85) being electrically connected to the poles of the permanent magnets (81) and (82) and these are connected to the high-frequency source (23) via an isolating capacitor (22) and the detection electrode (86) is connected to the AC generator (24) via a coupling capacitor (25) and a discharge resistor (26), and on the one hand via a voltage probe (27), via a current probe (28), via a digitizer (14) and a control unit (13) with a power supply unit (11).