EP4103760A1

EP4103760A1 - Device and method for producing layers with improved uniformity in coating systems with horizontally rotating substrate and additional plasma sources

Info

Publication number: EP4103760A1
Application number: EP21706497.1A
Authority: EP
Inventors: Michael Vergöhl; Andreas Pflug; Tobias Zickenrott; Stefan Bruns
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2020-02-13
Filing date: 2021-02-12
Publication date: 2022-12-21
Also published as: CN115103928A; DE102020201829A1; US20230067917A1; WO2021160786A1

Abstract

The invention relates to a device and a method for producing layers whose layer thickness distribution can be adjusted in coating systems with horizontally rotating substrate. A very homogeneous or a specific non-homogeneous distribution can be adjusted. The particle loading is also significantly reduced. The service life is significantly higher compared to other methods. Forming of parasitic coatings is reduced.

Description

Device and method for producing layers with improved uniformity in coating systems with horizontally rotating substrate guide with additional plasma sources. The invention relates to a device and a method for producing

Layers with adjustable uniformity in coating systems with horizontally rotating substrate guides. Alternatively, certain layer thickness gradients can be set. In addition, the particle load is significantly reduced. The service life is significantly longer compared to other processes. Para- situs coatings are reduced. The coating rate is also increased.

Optical layers nowadays often consist of a sequence of low and high refractive index layers, in which certain materials are stacked on top of one another. The layer thicknesses can be between a few nm and several pm, depending on the function and wavelength range. Materials are, for example, S1O2, Ta20s, Nb2Ü5, Hf02, ZrC> 2, T1O2. Amorphous, hydrogen-containing Si materials (a-Si: H) are also used.

A desired layer function is achieved by suitable stacking of the layer sequence on top of one another. This can be a bandpass filter or an edge filter, for example. Coatings to control the phase position of the reflected or transmitted light are also possible.

The spectral position of the edge or the bandpass is decisive for the function of the coating. There is therefore great interest in achieving uniform layers on the material to be coated. In other applications, layers are also required in which a certain layer profile is desired. This is the case for bandpass filters where the central wavelength depends on the position (gradient filter). Gradient filters of this kind are used, for example, on photosensitive sensors in image processing. These often have a coating width of a few 10mm and continuously map a central wavelength range from approx. 190 nm to 1100 nm. With a central wavelength of 190 nm for a 30 mm long sensor, only about 1/6 of the layer thickness is required as with 10000 nm. As the sensor area becomes smaller, the layer thickness gradient would increase further, so that steeper gradients would have to be implemented.

A certain layer thickness distribution is often required on 3D components such as lenses. This may require a lateral gradient with a certain shape.

As a rule, a large number of layers are stacked on top of one another. Filter coatings are then produced with a number of layers less than 4 and more than 100, often with a thickness of less than 1 miti and more than 10 miti, or even several tens of miti.

Another requirement is to introduce as few defects as possible into the layer. These can be caused, for example, by the flaking of parasitic coatings from chamber walls or from system components that are located in the area of the coating. Particles can also accumulate in the plasma for a longer period of time and possibly continue to grow there due to the coating flow.

These "parasitic" coatings form because the coating source has a relatively broad distribution of the dusted coating material into the room. A large part of the coating therefore goes onto the chamber walls instead of the substrates, or components that are used for rate correction directly in front of the substrates If the coating is too thick in these areas, or if there are thermal loads, particles can be detached from these coatings or the entire parasitic coating, but particles can also be generated directly on the sputtering sources.

Many attempts have been made to reduce the particle load. At the same time, attempts were made to develop production processes that can produce very uniform layers. Alternatively, layers with a defined gradient in the layer thickness can also be produced.

The production of low-particle optical layers can take place with a magnetron sputtering device, as is known, for example, from US Pat. No. 9,803,276 B2. In this document, the production of low-particle coatings is shown, the cleanliness of the coating is achieved through the use of cylindrical swelling material (rotatable magnetrons), optionally together with a reactive gas component, applied to the substrate by magnetron sputtering. The layer is applied against gravity in a so-called "sputter-up" process. Since there is no provision for substrate subrotation (satellite movement), a layer thickness profile results on the substrate which inversely proportional to the radius to the center of rotation increases. In an arrangement, for example, in which the substrate center point 600mm away from the center of rotation and the substrate has a diameter of 200mm, only about 70% of the layer rate would arrive on the outside compared to the rate on the inside. The layer uniformity is therefore set using masks that restrict the coating flow locally. The mask lies between the source and the substrate; usually close to the substrate in order to be able to adjust the layer distribution as precisely as possible. The mask is thus directly in the coating area. Since, in contrast to the moving substrates, the mask is usually attached statically, it receives a large amount of material. In the geometry described above with a substrate center point of 600 mm from the center, a correction diaphragm receives a rate about 5-10 times as large as the substrates themselves. If 10 .mu.m of layer material is deposited on the substrate, the diaphragm already receives 100 .mu.m. Particularly with cylindrical sputter sources, the material supply is very large, so that in principle a service life of several months would be possible. For example, if these targets have a service life of 8000 kilowatt hours, a service life of 67 days would be possible with an output of 5 kW. At a coating rate of 0.3 nm / s, a layer thickness of 480 μm could thus be deposited on the substrate without the target having to be replaced. If you add the second material, the layer thickness on the uniformity diaphragms would accumulate to over 5mm. However, it is beneficial not to exceed a certain thickness of approx. 1 mm on the uniformity diaphragms.

If the thickness of the panel is too great, flaking and particle formation can occur, so systems are usually cleaned beforehand, with the panels also being cleaned or even replaced. This also limits the service life of the system after cleaning. This is particularly disadvantageous in current systems that work with cylindrical sputter sources, because the sputter sources themselves have a service life that is several times that of conventional linear magnetrons. The production time could be significantly lengthened without cleaning in the meantime if the parasitic coating on the uniformity diaphragms can be reduced. Another method for depositing high-quality optical coatings is described in US Pat. No. 8,956,511 B2. A turntable arrangement is provided there, in which the substrates rotate on a plate and a very thin partial layer of a few ohms is deposited for each passage. Oxygen is added at the location of the magnetron, so that a substoichiometric layer is deposited first. This layer is oxidized through with a subsequent plasma source. The layer thickness distribution is adjusted by means of so-called "correction masks", which remove a greater proportion of the coating in the inner area than in the outer area is highly variable towards the ends.

Another method that is often used is the use of satellite rotation of the substrates. The substrates are on a rotating plate and rotate around themselves. Ring-shaped sputter sources are used here.

A method is known from US Pat. No. 8,574,409 in which a set of magnets rotates in an annular magnetron and the power is periodically modulated at a certain frequency in order to improve the uniformity of the layer distribution.

In US Pat. No. 5,609,772 A, a device for a ring-shaped closed target is described in which the magnetic field lines can be shifted on the target with a magnetic field additionally generated by an excitation current. This means that the profile of the target erosion can be shifted and, for example, the distribution of the rate can be influenced.

A sputtering arrangement without masks is described in US 2011/253529. A high degree of uniformity is achieved there by proposing a special dimensioning of an annular magnetron source with a special diameter. The center of the magnetron cathode is centered on the rotating substrate centers. There, however, a planetary drive is provided so that two rotations are superimposed.

Various types of magnetron sources are used in sputtering systems Mission. A so-called drum geometry is described in US Pat. No. 4,851,095. Here, the sources are usually located as a linear source on the side walls of a chamber. The substrates are located inside on a rotating drum. In a variant, layer distributions on the substrate can be influenced along the target axis by changing the distance between individual magnets and the target surface. Individual magnets are reset here. This method is called "UniTune" and enables the distribution to be set to +/-!% Without a shaper. The setting is therefore possible within very narrow limits (a few%).

This method would not be suitable for the proposed arrangement with a turntable because it would result in a very strong weakening of the magnetic field, so that the impedance and thus the voltage of the process would increase sharply. In addition, a much larger rate change of about 30% is required for the present process.

A similar method is proposed in US 2003/0042130. There, "electron traps" are introduced on the target with the aid of an additional magnetic field, with which the plasma density and thus the sputtering yield along the target can be influenced.

The change in the geometry of magnets to control the layer distribution is also described in US 2013/0032475 for cylindrical magnetron sources. Either the distance between the target and the substrate can be changed, or the angle of rotation of the entire set of magnets ("swing cathodes").

A special magnet system for cylindrical magnetrons is described in US Pat. No. 9,349,576. The magnets have a special shape and the magnetron can be used as a retrofit for planar magnetrons.

In R.D. Arnell et al., “Recent advances in magnetron sputtering”, Surf. Coat. Technol. 112 (1999), p. 170 describes the method of “closed-field unbalanced magnetron sputtering”. This reports on the magnet configuration of double magnetron arrangements.

Magnetron arrangements can be unbalanced as well as balanced. One speaks of an unbalanced arrangement if, for example, the outer magnet net ring has a higher field strength than the inner ring. As a result, some electrons are no longer held on the target, but instead follow the magnetic field lines in the direction of the substrate. The plasma expands further to the substrate, and it can, for example, a better compression of the layer he follow. However, it can also be disadvantageous that more particles are introduced into the layer. In the case of a balanced arrangement, on the other hand, the plasma is held more on the target. Arnell et al. also propose a closed-field arrangement with double magnetrons, in which magnetrons lying next to one another have opposite polarity (dual-co-planar closed field arrangement). A better plasma density and the possibility of producing better materials are seen as advantages of this arrangement. It is proposed there to work in a "closed field" arrangement. Several magnetron sources are required on the chamber. The polarity of the magnets is not the same for all sources, but is opposite to the adjacent cathode. While a cathode has a polarity NSN , the adjacent cathode has a polarity SNS. This means that the plasma leads more from one cathode to the next and is more closed ("closed field"). However, the lateral distribution of the layer along the target axis is not considered there. The purpose of the closed field arrangement is to produce denser layers with better properties.

The magnetrons can be linear sources, round sources or else cylindrical sources. These can be operated with direct current (DC) or alternating current (AC) in the medium frequency range (10-20 kHz). Radio frequencies (RF, mostly 13.56 MHz) are also used in insulating sputtering materials. The sources can be unipolar (sputter source as cathode, the positive pole in each case designed as a separate anode) or bipolar.

US2016 / 0254127 A1 describes an approach in which the layer thickness distribution is influenced by two magnetrons. The approach is based on a twisting of the magnets, which causes a (decoupling) of the magnetic fields. In the case of a turntable arrangement, tilting of the distribution can thus be made possible. However, this approach is only suitable for small changes in the distribution and still relies on the use of masks. US Pat. No. 8,574,409 describes a system in which a power modulation as a function of the rotation of a magnet set is used in an annular magnet. From US2005 / 0061666 A1 magnets are known which are moved during operation by planar magnets ("sweeping"), so that a higher target utilization results. Often so-called. Shunts are used to influence the magnetic field in magnetrons (US 5,415,754). The shunts are ferromagnetic plates that are placed below the target between the rows of magnets. This means that the field lines between the racetracks run flatter on the target. The disadvantage, however, is that a magnetic barrier for the electrons is built up between the targets in bipolar processes Usually the impedance and thus also the discharge voltage of the generator. This is unfavorable because a high voltage can lead to increased particle formation. 3D effects often occur with magnetron discharges. The "cross-corner" effect is known, for example (Siemers, M. et al., Proc. 51 ^st SVC Tech. Conf., 2008, 43-48) with diagonally symmetrical inhomogeneities. There is also such an effect with cylindrical magnetrons. In US 2011/0127157 an asymmetri cal magnet system is described which can be used for cylindrical single or double magnetrons. Due to the asymmetrical design, the plasma is drawn more between the cathodes, whereby the electrons can reach the respective anode better and a lower impedance is created.

The use of plasma sources in the sputtering area is also known. It is often desired to increase the distance between source and substrate in order to achieve a low defect density in the layer. Such a device is described in US Pat. No. 5,851,365. In order for the layers to be of good quality, high density and low roughness, sufficient energetic particles must be present in the plasma. This is achieved by a sufficiently high free path of the sputtered particles. If the distance is increased (in US Pat. No. 5,851,365 to> 30 cm, corresponding to a factor of approx. 3-5), the sputtering process must accordingly be operated at a lower pressure. This is achieved in US 5,851,365 by very powerful pumps under half of the magnetron sources. An ion cannon directed at the substrate can additionally densify the layer. In this arrangement, a shield and a gas inlet were provided around the target. That has the purpose of locally increasing the pressure on the magnetron so that the target can run stably. Without the shield, the pressure on the magnetron would be too low to ignite the plasma.

In M. Misina, J. Musil, Surf. Coat. Technol. 74 (1995, p. 459) describes that an ECR microwave (electron cyclotron resonance) can be used in a magnetron compartment in order to operate a discharge at low pressure.

Based on this, it was the object of the present invention to provide a device which ensures a high and more stable uniformity of the layers and at the same time avoids parasitic deposits in order to increase the production time of the device. However, it is also an object of the present invention to set layers with a targeted inhomogeneity more precisely and also with a steeper layer thickness gradient.

This object is achieved by the device with the features of claim 1 and the method with the features of claim 15. The further dependent claims show advantageous developments.

According to the invention, a device for the deposition of uniform layers on rotationally moving substrates by means of magnetron sputtering is provided, which contains the following components: a) a vacuum chamber with a sputtering compartment, b) at least one inlet for a sputtering gas, c) a turntable with at least one substrate holder and d) at least one magnetron sputter source arranged in the sputtering compartment with at least one electrode, at least one further microwave plasma source being arranged in the sputtering compartment.

The essence of the present invention is based on the fact that an inhomogeneous, ie locally different, plasma density is generated, which makes it possible that the removal rate can be set inhomogeneously in a targeted manner. The inhomogeneity can also be set in such a way that a certain distribution is generated on the substrate in the direction of travel. At the same time, the plasma density at the magnetron sputtering source is increased so that the sputtering process can also be operated at lower pressure.

The locally different plasma density is brought about by the use of at least one microwave plasma source, which generates the plasma in a spatially limited area. This means that the plasma has an expansion that is significantly smaller than the length or the diameter of the magnetron cathode. The at least one microwave plasma source is preferably an ECR microwave plasma source or a plasma source which has the option of magnetic constriction. One or more microwave plasma sources are arranged in the sputtering area and their power can be set and regulated individually. The distribution of the coating rate is changed in the longitudinal direction, i.e. along the target axis of the magnetrons. Influencing the distribution in the running direction of the substrates is also conceivable. This makes it possible to produce layers of high and stable uniformity on the substrate during the coating process. The distribution can also be regulated by measuring the layer thicknesses on the substrate.

The present invention relates to a new configuration of microwave plasma sources for linear magnetron electrodes arranged in relation to one another, with which a coating with very high and stable uniformity can be achieved with substrates to be coated rotie rend (turntable arrangement). The asymmetry is achieved in that the microwave plasma source (s) can be individually adjusted in terms of their power and can also be arranged asymmetrically. At the same time, the sputtering pressure can also be reduced, so that the distance between the substrate and the sources can be increased.

The device according to the invention and the method according to the invention show the advantage that the distribution of the layer thicknesses can be adjusted very quickly and during the coating process. After all, the Discharge can also be operated at low pressure below 3x10-3 mbar, so that with the same energy input into the substrate, a coating with a greater distance is also possible.

The types of microwave plasma sources that can be used according to the invention are in principle not limited. Semiconductor-based sources can be built very compactly, so that a relatively spatially limited plasma is generated. The one or more plasma sources can be arranged below the magnet rons or laterally on the chamber walls. The advantage of this arrangement is that the power of the sources can be changed quickly or switched off completely. This would not be possible with an arrangement based solely on controlling the magnetic field strength.

In contrast to the methods known from the prior art, the layer thickness distribution on the substrate can also be changed.

In DE 102013 207771 A1, a linear tilting of the distribution is proposed, with which a change in the layer thickness distribution is possible. In contrast, the method proposed here is more flexible and faster.

The proposed configuration is also advantageous because it makes it possible to further reduce the impedance of the discharge. This is beneficial for materials that provide a high impedance, such as silicon, or materials with poor conductivity. But also with other materials such as tantalum, niobium, either of metallic targets or of targets that contain metallic components, a low discharge voltage is favorable because this reduces the tendency to arc discharges. These generally lead to particles. This is also particularly advantageous in processes such as the Metamode process, where work is carried out without reactive gas in the area of the sputtering sources. Reactive gas often reduces the discharge voltage. This is also favorable for a process as proposed, for example, in DE 102013 221 029 A1, in which sputtering targets with ceramic components are proposed, but otherwise work is carried out without oxygen in the sputtering area. It is preferred that the inhomogeneous removal rate increases from the turntable center point to the turntable edge, preferably increases linearly, particularly preferably is proportional to the distance from the turntable center point. This results in a largely homogeneous coating on the substrate without the use of additional correction masks.

The device preferably has at least one additional plasma source via the microwave plasma source arranged in the magnetron compartment, which is spatially separate at its own station. This additional plasma source is then preferably used for post-oxidation of the growing layer. A pretreatment of the substrate surface and / or modification of the structure and / or the stoichiometry is also possible. The additional plasma source should be spatially separated from the magnetron compartment in order to avoid interactions.

In the process, the turntable of the device can rotate at a speed of 1-500 U-min-1, preferably 80-300 U-min-1. For a high throughput and high precision, a fast rotation of the turntable in the range of 100-250 rpm can be advantageous.

The at least one magnetron sputter source is preferably a double magnetron source with electrodes made of a cylindrical or planar source material and a holder for this material and an associated target. The at least two electrodes can be operated electrically by means of bipolar pulses. Here, sine or square pulses can be used, whereby the frequency can also be changed. The sputtering frequency can be changed in a range from a few kHz to several 100 kHz. Frequencies between 10 kHz and 100 kHz, particularly preferably 20-60 kHz, are used.

The magnetron sputter sources can be used in a sputter-down or also in a sputter-up arrangement.

The at least one electrode preferably has a target which contains or consists of at least one of the following components: a) ceramic material or material mixtures; b) thermally sprayed material or material mixtures; c) sintered material or material mixtures d) crystalline material; e) metallic material or material mixtures; and / or f) an oxide-containing material or g) mixtures thereof.

The electrode preferably consists of a target containing metal / semiconductors or consisting of ceramic material.

In the case of high-quality optical coatings, there are often compressive stresses. These are of great importance because they can lead to bending of the optics or to the delamination of the layer or even to the breakage of the substrate. According to the invention, the discharge voltage of the plasma can be reduced, which can lead to a reduction in the layer voltage.

The at least one electrode can contain a target. This can consist of a metal or silicon or also contain or consist of an oxide-containing material. Oxide-containing materials have the advantage that they provide a source of oxygen. Sometimes extra oxygen is required in the sputtering area, for example because the oxygen in the plasma source is insufficient for oxidation or because higher coating rates are to be achieved. In this case, it is beneficial to take the oxygen directly from the target, i.e. the magnetron electrode, because this results in greater stability compared to a target made of metal and oxygen as the reactive gas. Because normally the reactive coating of a metallic (or silicon) target using reactive gas leads to a rate instability if the oxygen partial pressure is not kept exactly constant, since the rate of a metallic target can be significantly different compared to the rate of the corresponding oxide. If the target contains the reactive gas (oxygen, nitrogen), the rate is independent of whether it is covered with an oxide layer.

Preferred oxide-containing materials are TiOx, TaOx, NbOx, ZrOx, ZrOx: Y, CeOx, ScOx, HfOx, AlOx, SiOx, ZnOx, InSnOx and / or SnOx, with x being particularly preferably selected so that the target just has conductivity, but at the same time x is close to stoichiometry.

The invention can also be used advantageously for the production of Si-based layers, some of which contain hydrogen. Bandpass filters for the near infrared range can be produced with this. Very thin substrates that bend severely are often used there. According to the invention, the layer tension can also be reduced there.

The distance between the at least one substrate and the at least one magnetron electrode is preferably 5 to 40 cm, more preferably 5 to 30 cm, particularly preferably 10 to 20 cm. A small spacing is beneficial because it enables layers to be made with high density. However, a very short distance is unfavorable because it can enable the increased formation of particles. These can be kept electrically trapped in the plasma and the substrate running through can thus function as a dust collector.

Depending on the support of the microwave plasma source and the process pressure that can be set from it, the distance can also be flexibly designed for the respective application. At a pressure of 3c10 ^L -3 mbar, the distance should be about 6-10 cm, while at a pressure of 1c10 ^L -3 mbar the distance can also be about 18-30 cm in order to achieve the same layer properties.

According to the invention, the device also has the option of significantly increasing the stand between the electrodes and the magnetrons without any loss in the layer properties. The intended applications require very dense, smooth and absorption-free layers, for which, as a rule, high particle energies are necessary. In addition, the process pressure must be as low as possible so that the sputtered particles do not collide with one another on the way from the target to the substrate. This can be achieved by lowering the process pressure in the sputtering chamber to a value below 1c10 ^L -3 mbar. This is possible, please include in the method according to the invention, because the plasma density in the area of the electrodes is significantly higher. Typi cally, magnetrons are at a pressure of a few 10 ^L -3 mbar (3c10 ^L -3 mbar to 6c10 ^L -3 mbar). A pressure variation has the effect of a surface roughness in a high-quality optical coating. This can be measured with an AFM (atomic force microscope). The roughness of the microwave plasma source can also be adjusted via the pressure.

For example, an SiO 2 layer with a thickness of 2 μm has a roughness that is 0.9 nm higher than that of the substrate if it is produced at a pressure of 6 × 10 −6 mbar on the magnetrons. If the pressure is reduced to less than 3 × 10 -3 mbar, the additional roughness compared to the substrate drops to less than 0.1 nm if the distance between the source and the substrate is approximately 7 cm. However, there is the problem with the methods according to the prior art that the target voltage increases with decreasing pressure and thus the tendency to arcing increases.

Something similar can also be observed with a tantalum pentoxide layer. Here, the additional roughness of a 2 μm thick Ta205 layer drops to 0.1 nm compared to 0.2 nm or more when the pressure is reduced.

At a pressure of 1c10 ^L -3 mbar, as is possible according to the invention, the distance can be tripled without any additional roughness of the layer in relation to the substrate.

Due to the lower process pressure of 1c10 ^L -3 mbar or less, the distance can be increased significantly to 15cm, or 20cm or more. Alternatively, with a smaller distance and a pressure of 3c10 ^L -3 mbar, the target voltage and thus the tendency to arcing is reduced.

The advantage of the invention is that a high degree of freedom from particles can be achieved even with a relatively small distance, because the plasma can be drawn very close to the target. By lowering the pressure, the distance can even be increased further without any loss in the density of the layers.

A setting can be made via the power of the at least one microwave plasma source. Since the decrease in the sputtering rate is proportional to the In the case of a given gradient of the sputtering rate over the double magnetron, the gradient on the substrate can be set using a suitable geometry. If the radius for the substrate movement is increased, the relative decrease in the rate towards the outside is smaller and vice versa.

The advantage of this distance is that small components can be coated homogeneously with high density and high precision. If the distance from the magnetron electrode to the substrate is greater, the precision of the coating process decreases. The distance between the turntable and the walls of the magnetron sputtering device is preferably 0.1 to 5 mm. This distance has proven to be particularly advantageous in order to make the magnetron sputtering device gas-tight, i.e. to ensure effective gas space separation within the device.

The double magnetron arrangement according to the invention has the advantage that more source material can be deposited per time that the substrate spends in the magnetron sputtering device compared with a single magnetron arrangement. The result is a much higher efficiency of the sputtering process. Furthermore, better long-term stabilities due to the "non-disappearing anode" and higher plasma densities in combination with denser (but also more strongly stressed) layers can be guaranteed through the use of double magnet arrangements with bipolar excitation.

According to the invention, polymer substrates can be coated more cheaply because the temperature of the discharge can be reduced as a result of the lower discharge voltage and / or the greater distance.

According to the invention, the polymer coating can also be designed more favorably, since as the discharge voltage decreases, the temperature input into the layer is also reduced.

Consequently, the device can advantageously have a device for generating medium-frequency discharges. In a further preferred embodiment, the device preferably contains two, optionally also three, magnetron sputtering devices. The advantage of such designs arises above all in the case of multilayer coatings, ie when a substrate is coated with several different layers. In this case, with two magnetron sputtering devices, stacks of two types of layers can be generated which have different material (source material). Consequently, in the case of three magnetron sputtering devices, there is the possibility of sputtering stacks of three types of layers onto the substrate, each of which has a different material. In addition, material mixtures can also be produced from the respective source materials, ie mixed layers can be deposited. The use of two magnetron sputtering devices for optimizing the layer properties is particularly advantageous in the area of very complex optical multilayer filters with more than 100 individual layers. Depending on the requirements (eg special design), three or more magnetron sputtering devices can also prove to be advantageous.

The generator for the microwave plasma source can ideally be quickly modulated or switched in terms of output. This means that the layer thickness gradient can be changed quickly. For the generator of the magnetron, square or sine pulses can be used as the pulse shape, particularly preferably with a frequency of 40 kHz. Influencing the layer thickness distribution has the consequence that the correction diaphragm (shaper diaphragm) is no longer required. Alternatively, there is also the possibility that the correction diaphragm receives significantly less coating material. In a standard version, with a distance of the substrate center point of 60 cm from the center of the turntable and a substrate diameter of 200 mm, the layer thickness gradient is about 30%. On the inner edge of the substrate, the screen must hold off 30% more layer than on the outside. The layer thickness correction is then more than 30%. At the same time, the aperture receives approximately eight times the rate that arrives on the substrate. The advantage of the invention is that the diaphragm only needs to correct a few% because an almost homogeneous coating is achieved on the substrate. As a result, the panel has a much less layer than in the standard configuration and can be used for much longer. At the same time, the distribution can also be set much more precisely, since only a few% of the layer distribution are corrected Need to become. Since the diaphragm also receives a much less layer, the drift of the distribution in the course of the coating is also smaller.

This offers the option of setting the distribution much more precisely. While in a normal geometry without additional plasma sources the layer rate increases from the outside to the inside according to the dependency 1 / r, according to the invention the increase can be significantly reduced or set as desired. This also makes it possible to significantly increase the service life of the system (cleaning), since the masks can be made smaller. To this extent, in the most favorable case, the plasma impedance can also be reduced. This is generally advantageous for the cleanliness of the coating because the tendency to arc discharges and thus the formation of particles is reduced.

The invention can also be used to create a stronger gradient. Here, the already existing layer thickness gradient can be increased again by means of a diaphragm, without the need for very sharp structures and edges on the mask.

Depending on the magnet design of the magnetron sources, the plasma can reach different distances into the room. Thus, the substrate can be either in the plasma or outside, the transition being fluid. With regard to a low particle load, it is favorable that the substrate is located outside the plasma, since particles are often kept in the vicinity of electrical fields. The method according to the invention makes it possible to decouple the plasma from the substrate. This has advantages for a good distribution of the layer thickness on the running substrate in the running direction. If there are fluctuations in the plasma density when the substrate passes through the plasma, there will be deviations from the uniformity along the direction of travel. This can happen when electrons see either a metallic surface (off the turntable) or an insulating surface (the substrate). Electrons would be withdrawn from the conductive surface, so that less plasma can be generated there and the plasma density is reduced there. This will also have an impact on the sputtering rate, because fewer electrons are present in the plasma at certain times. A sputtering back effect can also occur here. The effect is similar to that of the so-called. "Picture Frame" effects (described in US 2007/0227882 A1). In inline systems, pressure surges in the reactive gas at the beginning and end of the glass panes lead to rate changes, so that a different layer thickness prevails at the ends of the glass panes Effects differ depending on their cause.

The magnetron sputtering device can have an effective gas space separation for gases of 1:25, better 1: 100, within the vacuum. An effective gas space separation of 1: 100 between the coating stations enables the production of clearly defined co-sputtered materials. The reason for this is that noble gas and / or reactive gas of a magnetron sputtering device is prevented from reaching a further magnetron sputtering device of the same device. In addition, through the effective gas space separation, the amount of noble gas and / or reactive gas can be set more precisely to a certain predefined value and / or kept constant.

Plasmas, based on magnetron discharges, usually consist of more than 99% non-ionized particles. These can have high energies and therefore contribute significantly to layer stresses. They can be influenced indirectly, for example by changing the magnetic field design or by using alternative sputtering gases. According to the invention, the sputtering gas can contain or consist of a noble gas. Preferred noble gases are argon, neon, xeon and krypton. Mixtures of noble gases are also possible. According to the invention, the reactive gas can contain or consist of an oxidizing gas. Preferred reactive gases are oxygen, nitrogen, tetrafluoromethane, octafluorocyclobutane, carbon dioxide and hydrogen fluoride. Mixtures of these gases can also be used.

Hydrogen can also be used.

One of the variants of the device preferably contains a photometer.

This makes it possible to photometrically control the thickness of the layer on the substrate during the sputtering process. For this purpose, a fast broadband measurement (eg from 200-2000nm) of the transmission or reflection can be carried out. The measurements can be carried out with a vertical incidence or with an inclined incidence. By comparison The layer thickness can be determined and controlled with the theoretically expected spectrum. In some cases, a quartz oscillator can also be used, for example in cavity filters where only a slight change in the transmission signal is expected for certain layers.

With the help of several measuring heads, the layer thickness can be measured across the running direction at several points. An array spectrometer is also conceivable for this, with which both a spectral and spatial measurement of the transmission can take place transversely to the direction of travel. In this way, the layer thickness can be determined transversely to the running direction and the distribution can be regulated.

The distribution of the layer thickness on the substrate can also be determined with a single photometer by rotating the substrates by 90 ° by measuring in the direction of travel. This is then done by turning the turntable and measuring at several points. With this method, a complete mapping of the layer thickness on the substrate can be carried out with a single spectrometer and a control of the layer thickness can also be built on. If very fast regulation is necessary, this can also be implemented with the help of a mapping spectrometer in a "push-broom" approach. A 2D sensor is used here, which measures across the substrate in one sensor axis and across the substrate in the The substrate can be measured over its entire surface by continuously rotating the axis of rotation of the system.

In a further preferred embodiment of the device, the substrate holder has or consists of polyetheretherketone. The use of polyetheretherketone has the advantage that particle formation is reduced.

It is further preferred that the device has a control system for regulating and / or stabilizing the reactive gas in the magnetron sputtering device. The reactive gas pressure is used as the control variable; either the power of the magnetron sources or, alternatively, the power of the microwave plasma sources can serve as the manipulated variable. The advantage of this regulation is that in the method according to the invention no dielectric layer is removed from the target, but rather the target is never covered with a dielectric layer. This can be implemented, for example, by operating metallic targets in what is known as the "transition mode". Here, the cylindrical source material (target) is permanently in a metallic, oxide-free state by suitable control of the generator, while there is enough oxygen in the process space for the oxidation of the growing layer. The above-mentioned manipulated variables are usually implemented on the basis of the oxygen partial pressure or the voltage of the generator or the target. In this way, the deposition of stoichiometric layers can be achieved in the process at a high deposition rate, while the disruptive influence of particles is minimized, that is to say, a low level of particles is achieved.

According to the invention, a method for depositing uniform layers on rotationally moving substrates by means of magnetron sputtering is provided, in which a) at least one substrate is arranged on a turntable in a vacuum chamber with a sputtering compartment in order to apply a coating while the substrate is rotating enable b) with at least one magnetron sputter source with at least one electrode arranged in the sputtering compartment, at least one layer is deposited on the at least one substrate, the layers being formed from source material of the electrodes with sputtering gas.

It is preferred that in the method according to the invention a homogeneous or inhomogeneous plasma density is generated in the sputtering compartment by means of the at least one microwave plasma source, which causes a homogeneous or inhomogeneous rate of removal of the source material on the substrate. According to the invention, the microwave heads are placed asymmetrically in the sputtering compartment. This can be, for example, at the end of a magnet ron. If the plasma is ignited, the plasma increases locally and the rate increases at the relevant end of the magnetron. The plasma always has a certain range due to the movement of the electrons on the racetrack. Overall, the layer thickness can thus be increased at one end of the magnetron. The overall distribution can be changed by placing several microwave plasma sources.

A temporal modulation of the change in the plasma is also possible. This requires a suitable generator for the microwave plasma source, which is very fast. This is particularly advantageously possible through modern, semiconductor-operated microwave sources, as described in WO2010 / 049456.

In another arrangement, several microwave plasma sources are used along a line along the longitudinal axis of the magnetron sources. A distance of approx. 10-15 cm is favorable, so that with a cathode length of 60 cm, approx. 4 sources are installed. The microwave plasma sources can also deviate to the right or left of the line in order to have further influences on the distribution. In order to avoid coating the plasma heads, they are preferably arranged outside the coating area. This can be between and below the magnetron sources. An arrangement laterally along one or both of the magnetic longitudinal axes is also conceivable. A combination is also possible.

A noble gas, in particular argon, is preferably used as the sputtering gas.

In addition to the sputtering gas, at least one reactive gas can preferably be used, in particular selected from the group consisting of oxygen, nitrogen, hydrogen, carbon dioxide, hydrogen fluoride, tetrafluoromethane, octafluorocyclobutane and mixtures thereof.

A preferred variant provides that, for process control, the thickness of the layer on the substrate is controlled by at least one of the measures a) to e): a) optical transmission monitoring; b) optical reflection monitoring; c) optical absorption monitoring; d) single wavelength ellipsometry or spectral ellipsometry; and / or e) quartz oscillator measurement.

Microwave plasmas are shielded by metallic layers. Therefore, coating the microwave plasma source - in particular with conductive material - should be avoided. The microwave source can therefore advantageously be equipped with a coating protection. Here at an envelope is provided that is flooded with neutral gas so that the outflowing gas prevents particles from reaching the microwave plasma source. The gas supply to the sputtering compartment can then be done from this gas source alone. The device according to the invention is preferably used to carry out the method.

The subject according to the invention is intended to be explained in more detail with reference to the following figures, without restricting it to the specific embodiments shown here.

Fig. 1 shows a device according to the invention without a turntable in plan view. Fig. 2 shows a device according to the invention with a turntable in plan view

3 shows a device according to the invention in a sectional illustration. FIG. 4 shows a device according to the invention in a sectional illustration

FIG. 5 shows the device according to the invention from FIG. 4 in the plane transverse thereto 6 shows a device according to the invention in a second variant in a sectional illustration

FIG. 7 shows the device according to the invention from FIG. 6 in the plane transverse thereto

Fig. 1 shows a schematic plan view of a preferred device according to the invention without a turntable. The device has three magnetron sputtering devices 2, 3, 4, one of which is designed in the single magnetron arrangement 2 and two in the double magnetron arrangement 3, 4. The magnetron sputtering device 2 contains a magnetron electrode 5, sputtering gas 11, optionally reactive gas 8 and is located in a vacuum 1. The magnetron sputtering devices 3, 4 each contain two magnetron electrodes 6, 7, sputtering gas 11, optionally reactive gas 8 and are located in a vacuum 1. In the vicinity of the magnetron sputtering devices 2, 3, 4 there is a microwave plasma source 12 and a photometer 16 and / or an ellipsometric flange 17.

Figure 2 shows schematically in plan view a preferred embodiment of the turntable. The turntable 10 is located in the device and has ten identical substrate holders 9 in this example.

FIG. 3 shows a schematic side view of a preferred embodiment of the device with rotary plate 10. The cross section of a magnetron sputtering device is visible, which contains two cylinders made of swelling material 6, 7 (double magnetron arrangement). The magnetron sputtering device is delimited from the rest of the device in a gas-tight manner on the sides of boundary walls 14, 15 and above by the turntable 10, contains sputtering gas 11, optionally reactive gas 8, and is under vacuum 1. Two substrate holders 9 of the turntable 10 are in the Cross-section shown or visible. Above the turntable 10 is a cover 13, which closes the device gas-tight with boundary walls which are located on the side of the turntable 10.

Figure 4 shows schematically the device according to the invention. 100 shows the variance vacuum chamber in which a sputtering compartment 101 is installed. The sub strate 102 is located on the turntable 103, which rotates continuously around the center during the coating. In this example, the coating is operated from bottom to top against gravity. The Magnetro electrodes 6 are accordingly located below the substrate. A coating mask 104 can be used to set the distribution of the coating in such a way that a homogeneous layer is deposited on the substrate. The arrangement contains two microwave plasma sources 106, which are arranged between tween the two magnetron sources at the ends of the cathodes. The magnetron sources also contain a shutter 107 which can be rotated between the substrate and the magnetron source so that the coating can be stopped. A power feedthrough 108 and a generator 109 are connected to the microwave plasma source. 111 is the pump flange and 110 is a shield against falling particles to protect the pump.

FIG. 5 shows the same arrangement in a view perpendicular thereto.

Figures 6 and 7 show an alternative arrangement according to the invention. Here, the distance between the magnetron source 105 and the substrate 102 has been increased. Two microwave plasma sources 106 were placed at the outer end of the magnetrons. Thus, by increasing the microwave plasma source power, the rate can be increased towards the outer edge, so that less coating of mask 104 has to be shielded. Even with the larger distance, the same layer properties are achieved by operating the process at a pressure of about 7c10 ^L -4 mbar.

Claims

1. Device for the deposition of uniform layers on rotating substrates by means of magnetron sputtering containing a) a vacuum chamber with a sputtering compartment, b) at least one inlet for a sputtering gas, c) a turntable with at least one substrate holder and d) at least one arranged in the sputtering compartment Magnetron sputter source with at least one electrode, at least one further microwave plasma source being arranged in the sputtering compartment.

2. Device according to one of the preceding claims, characterized in that the at least one microwave plasma source has a magnetic field configuration for generating a spatially localized plasma.

3. Device according to one of the preceding claims, characterized in that the device has at least one generator for supplying power to the at least one microwave plasma source, the power of the at least one generator preferably being modulatable over time.

4. The device according to claim 1, characterized in that the at least one microwave plasma source for local plasma compression is arranged asymmetrically to one of the axes of the at least one electrode.

5. Device according to one of the preceding claims, characterized in that the at least one microwave plasma source has a coating protection, in particular a metallic or ceramic or glass-like structure that partially envelops the plasma source and has a gas inlet for a neutral gas and / or reactive gas.

6. Device according to one of the preceding claims, characterized in that the inhomogeneous removal rate increases from the turntable center to the turntable edge, preferably increases linearly, is particularly preferably proportional to the distance from the turntable center.

7. Device according to one of the preceding claims, characterized in that the device has at least one additional plasma source for pretreating the substrate surface and / or for modifying the structure and / or the stoichiometry of the layer.

8. Device according to one of the preceding claims, characterized in that the at least one magnetron sputter source consists of electrodes made of a cylindrical or planar source material and a holder for this material and an associated target.

9. Device according to one of the preceding claims, characterized in that the distance from the substrate to the at least one electrode for each electrode independently of one another from 5 to 40 cm, preferably 5 to 30 cm, particularly preferably 6 to 20 cm and very particularly preferred 6 to 12 cm, preferably as a function of the process pressure in the sputtering compartment

10. Device according to one of the preceding claims, characterized in that the device has a pulsed in the medium frequency range or a pulsed direct current supply (DC ge pulsed).

11. Device according to one of the preceding claims, characterized in that the device contains a photometer for determining the thickness of the layer on the substrate and / or ellipsometric flanges and / or a component which exerts a polarization effect.

12. Device according to one of the preceding claims, characterized in that the device has an optical measuring device for determining the layer thickness distribution.

13. Device according to one of the preceding claims, characterized in that the device has a control system for Re gelation and / or stabilization of the partial pressure in the magnetron sputtering device.

14. Device according to one of the preceding claims, characterized in that the device has at least one Korrek turblende.

15. A method for the deposition of uniform layers on substrates moving in rotation by means of magnetron sputtering, in which a) at least one substrate is arranged on a turntable in a vacuum chamber with a sputtering compartment in order to enable a coating with a rotating movement of the substrate, b) with at least one magnetron sputter source with at least one electrode arranged in the sputtering compartment, at least one layer is deposited on the at least one substrate, the layers being formed from source material of the electrodes with sputtering gas, characterized in that in the sputtering compartment with at least one further microwaves -Plasmaquelle a homogeneous or inhomogeneous plasma density is generated, which causes a homogeneous or inhomogeneous removal rate of the source material on the substrate.

16. The method according to claim 15, characterized in that the at least one further microwave plasma source is used for the magnetron sputter source, whereby the sputtering process in the pressure range below 5x10-3 mbar, preferably below 3 x 10-3 mbar, particularly preferably between 1x10 -4 mbar and 1 x 10-3 mbar, very particularly preferably between 3x10-4 mbar and 8 x 10-4 can be operated.

17. The method according to any one of claims 15 or 16, characterized in that the inhomogeneous removal rate increases from the turntable center to the turntable edge, preferably increases linearly, is particularly preferably proportional to the distance from the turntable center.

18. The method according to any one of claims 15 to 17, characterized in that at least one additional plasma source is used in the method, the at least one additional plasma source pretreating the surface of the substrate via plasma action and / or the at least one plasma source preferably the structure and / or the stoichiometry of the layer modified via the action of plasma.

19. The method according to any one of claims 15 to 18, characterized in that a noble gas, in particular argon, is used as the sputtering gas.

20. The method according to any one of claims 15 to 19, characterized in that the plasma density of the magnetron sputter source is increased locally with the at least one further microwave plasma source via its plasma power, so that in particular an inhomogeneous removal rate results.

21. The method according to any one of claims 15 to 20, characterized in that in addition to the sputtering gas, at least one reactive gas is used, in particular selected from the group consisting of oxygen, nitrogen, hydrogen, carbon dioxide, forming gas, hydrogen fluoride, acetylene, tetrafluoromethane, octafluorocyclobutane and Mixtures thereof.

22. The method according to any one of claims 15 to 21, characterized in that for process control the thickness of the layer on the substrate is controlled by at least one of the measures a) to e): a) time control b) optical transmission monitoring; c) optical reflection monitoring; d) optical absorption monitoring; e) single wavelength ellipsometry or spectral ellipsometry; and / or f) quartz oscillator measurement.

23. The method according to any one of claims 15 to 22, characterized in that a device according to one of claims 1 to 15 is used.