Piezoelectric Coating and Deposition Processes

Abstract

1. A substrate having a surface coated with a piezoelectric coating I, the coating comprising A-xMexN, where A is at least one of B, Al, Ga, In, Tl, and Me is at least one metallic element Me of the transition metal groups 3b, 4b, 5b, 6b, the lanthanides, and Mg, the coating I having a thickness d, the substrate further comprising a transition layer (3) in which the ratio of the atomic percentage of Me to the atomic percentage of Al increases steadily along a thickness range δ3 of the coating, where δ3≦d is valid.

Description

[Technical Field]

[0001] The invention relates to a substrate having a surface coated with a piezoelectric coating according to claim 1, a method for producing such a coating according to claim 16, and a process system for depositing such a coating on a substrate. [Background technology]

[0002] The quest for higher electromechanical coupling coefficients in piezoelectric thin films is driven by the commercial need for advances in microelectromechanical devices (MEMS) for a variety of applications, such as broadband filters operating at high frequencies (above 2 GHz) for wireless applications, miniature speakers and microphones, to name a few. Among the various strategies proposed, the partial substitution of Al by Sc in the wurtzite AlN lattice stands out due to the high achievable figure of merit, its incorporation into CMOS structures, and its compatibility with front-end semiconductor devices.

[0003] AlN has been the dominant material for piezoelectric thin film applications for many years. The main drawback of this material, i.e., its low electromechanical coupling coefficient with respect to other classes of materials, can be overcome by the substitution of Sc in the wurtzite lattice, as the longitudinal piezoelectric activity increases by up to 40% with the Sc / (Sc+Al) ratio [Akyama et al., Adv. Mat. 21, 2009]. Furthermore, the structural instability at the heart of the piezoelectric anomaly in this class of materials is due to the substitution of metallic elements "Me" (Y or (Mg)) in the wurtzite structure of nitrides of group III elements "A" (such as AlN, GaN, and InN). 0.5 , Zr 0.5 It has been demonstrated both theoretically [Tholander et al., PRB 87, 2013] and experimentally [Yokohama et al., IEEE TUFFC 61, 2014] that A can be successfully introduced by various permutations of 1-x Me x Wurtzite films of N (Al (1-x) Sc x N, Al (1-x) (Mg, Zr)x N, or In 1-x Y x High-volume production solutions for the deposition of silicon (e.g., N) pose new challenges. The increasing dependence of the coupling coefficient on film stress requires excellent uniformity of film stress, crystallinity, and surface roughness across large-surface substrates. However, with increasing Sc content, the growth of the desired wurtzite structure with c-axis orientation is hindered by the appearance of protruding conical crystallites. Several authors [Fichtner et al.] [Deng et al., JVSTA, 30, 2012] have shown that this case of abnormal grain growth is determined by surface anisotropy within the capture cross-section for different planes of the wurtzite structure for off-normal deposition fluxes. These undesired grains are still in the wurtzite phase but have a non-c-axis orientation. Due to competitive growth mechanisms, the low adatom mobility on these surfaces enhances the growth of these grains, resulting in abnormally sized grains that do not contribute relevantly to the piezoelectric activity of the film. This surface instability increases with the amount of Sc in the film. As a result, the volume fraction of undesired grains increases substantially with Sc substitution. The likelihood of these undesired crystallites appearing is further increased by the substrate / Al 1-x Sc x The nucleation of the wurtzite phase occurs at a very high rate indeed, i.e., a higher surface roughness, and therefore a consequential increase in the probability of nucleation of grains whose c-axes point in directions other than perpendicular to the substrate and significantly misaligned with the direction of the incoming adatom flux. 1-x Sc x While in N, numerous crystallites are typically observable when the Sc concentration is higher than 15 at%. Platinum is less susceptible to this problem due to its increased surface smoothness for a given film thickness. In any case, the choice of substrate surface and microstructure is strongly constrained by device specifications. Therefore, the use of Al, which reduces the possibility of off-axis grain formation, is recommended. 1-x Sc xA robust process solution for the deposition of the AlN layer is highly advantageous. Because the surface instability of pure AlN is limited, the use of a thin, scandium-free seed layer allows for the desired AlN deposition on a variety of substrate types and materials. 1-x Sc x It has been found to be efficient in ensuring high-quality AlN growth. For example, the initial growth of 25 nm of AlN on a molybdenum electrode is achieved with a pure c-axis-oriented wurtzite structure. 75 Sc 25 The positive effect of AlN seed layers on other substrate surfaces, including pure silicon and SiO2, has also been demonstrated. However, as Sc concentrations increase to, for example, 30 at%, the structure of the seed layer and the Al 1-x Sc x The mismatch between the AlN layer and the AlN layer tends to promote renucleation, and the pure AlN seed layer strategy reaches its limit, i.e., the growth of undesired crystals cannot be suppressed efficiently enough. Therefore, the gist of the present invention is to 1-x Me x The object of the present invention is to provide an improved seeding process that ensures the growth of N layers, such as the aforementioned AlScN layers, which should exhibit no or a negligible number of crystallites compared to other known layers with comparable high "B" content. It is a further object of the present invention to provide a method for producing such layers and to provide a processing system for carrying out the method.

[0004] Definition: A 1-x Me x The N layer is constituted by any of the group III elements "A" (such as boron, aluminum, gallium, indium, thallium), including one or more metal elements "Me" from the transition metal group 2 to 6b, such as Y, Zr, and Mg, from group 2a or in particular the cubic species of that group, such as Sc, Nb, Mo, or from the lanthanide series, such as La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Lu, or again in particular the cubic species of that group, such as Ce and Yb. 1-x Me xN refers to a non-centrosymmetric layer. The atomic percentage of element A and element or mixtures of element Me may vary unless an explicit number is referenced, which means that AMeN or AlScN refers to any Me / (A+Me) or Sc / (Al+Sc) ratio, also called the Me or Sc (scandium) ratio, where N may be in a stoichiometric, near-stoichiometric, or superstoichiometric relationship with respect to the metal component of the compound.

[0005] The substrate may be any base material, including substrates pre-coated with different functional layer structures, called pre-coatings, which may be applied in different or the same coating system. Such pre-coatings may include, for example, acoustic mirrors, for example, silicon substrates may be coated with, for example, SiO x and W layer, or SiO x , SiN x , SiN x O y , AlN x The layer stack includes an etch stop layer such as [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Akyama et al., Adv. Mat. 21, 2009 [Non-patent document 2] Tholander et al., PRB 87, 2013 [Non-patent document 3] Yokohama et al., IEEE TUFFC 61, 2014 [Non-patent document 4] Deng et al., JVSTA, 30, 2012 Summary of the Invention [Problem to be solved by the invention]

[0007] Surprisingly, it has been found that AMeN coatings containing a concentration gradient of Me, starting from a low or zero Me concentration and rising towards a high Me / (A+Me) ratio when starting from the substrate side, can efficiently help suppress the appearance of undesirable raised cone-shaped crystallites, also referred to as spikes below. [Means for solving the problem]

[0008] In one embodiment of the present invention, the substrate has a surface coated with a piezoelectric coating. 1-x Me x N, A is at least one of B, Al, Ga, In, Tl, and Me is at least one metallic element of transition metal group 3b, 4b, 5b, 6b, a lanthanide, and Mg, the coating further comprising a transition layer having a thickness d and in which the ratio of the atomic percentage of Me to the atomic percentage of A increases steadily along a thickness range δ3 of the coating, where δ3≦d is valid.

[0009] In a further embodiment of the present invention, Me may be at least one of Sc, Mg, Hf, Nb, Mo, Ce, Y and Yb, whereby Sc is preferred.

[0010] The coating may further comprise a seed layer terminating at the steadily rising beginning of a transition layer, wherein the ratio is constant along a further thickness range δ2 of the coating.

[0011] In a further embodiment, the coating may comprise a top layer beginning at the steadily rising end of the transition layer, wherein the ratio is constant along a further thickness range δ4 of the coating.

[0012] The transition layer may start or end at one of the limiting surfaces of the coating, for example, directly on the surface of the substrate, directly on the surface of the adhesion layer, and / or may end without a top layer with a constant Me / Al ratio. The transition layer may therefore also be the only layer of the system, δ3=d.

[0013] In a further embodiment, the steady rise of the transition layer can begin with the ratio being zero.

[0014] The steadily increasing Me concentration may be at least approximately linear, eg, slope-like.

[0015] Additionally, the coating may further include an adhesion layer deposited directly on the substrate surface, which may be made of at least one of the following materials: Si, Mo, W, Pt, Ru, Ti.

[0016] The seed layer, or transition layer if no seed layer is provided, may be deposited directly on the surface of the substrate S, or on the surface of the adhesion layer if provided.

[0017] At least one surface of the substrate is made of Si, SiO x The surface may be a wafer or a diced and embedded wafer.

[0018] The proportion of the transition layer at the end of said steady rise may be higher than 26% Me, preferably equal to or greater than 30%, for example in the range of 26 to 50%, or even 30 to 60%.

[0019] The surface of one of the transition layer and the top layer, provided that it is provided, can have a uniform surface quality of less than 50, particularly less than 40, or even less than 30 spikes within any 5 μm x 5 μm surface area.

[0020] In particular, the following layer combinations on the substrate S may be realized, the order of the list indicating potential improvements: 1. S / Seed / Transition / Top: High piezoelectric response due to the Me-rich top layer compared to standard surfaces and materials. The surface quality of 3 can be largely maintained. 2. S / Adhesion / Seed / Transition / Top: For difficult surface conditions and materials, same as 1. Surface quality of 4. can be almost maintained. 3. S / Seed / Transition: Superior surface quality associated with reduced roughness / spikes, see e.g. the figures and experiments below. 4. S / Adhesion / Seed / Transition: Same as 3. for difficult surface conditions or materials. 5. S / Adhesion / Transition / Mogami. 6. S / Transition / Mogami. 7. S / transition.

[0021] Best practice examples and applicable thickness ranges are also provided in the figure legends and in Table 2.

[0022] The present invention relates to the above-described A method of the present invention, which includes simultaneous sputtering from an A target (first target) that is a target made of material A, and an Me or AMe target (second target) that is a target made of material Me or a target made of material A plus Me. 1-x Me x The present invention is also directed to a method for depositing a N coating, wherein sputtering is carried out in a nitrogen-containing gas atmosphere while controlling the sputtering time and sputtering rate of said targets, and during a time span t3, the sputtering power P of the first target is A The sputtering power P of the second target relative to Me Power ratio R P =P Me / P A Therefore, for example, the sputtering power P Me can be increased, but the sputtering power P Acan remain constant or decrease. P Me It should be mentioned that refers both to the sputtering power of a pure Me target and to the sputtering power of an AMe target consisting of at least one element A and at least one element Me.

[0023] In one embodiment of the present invention, simultaneous sputtering can be performed within a deposition region where the sputter cones of a first target (the A target) and a second target (the Me target or the AMe target) overlap. The overlapping deposition region can include at least 50% to 100%, or 80% to 100%, of the substrate surface to be coated. Sputtering can also be performed with two first targets and two second targets whose cones overlap in the substrate plane. Thus, the first and second targets can be arranged alternately on circles concentric with the axis Z.

[0024] In any method using overlapping sputter cones, e.g., of a first target and a second target as mentioned, it is beneficial to facilitate alloying or mixing of different materials sputtered from different targets that are mixed within the overlapping cones, just as the respective substrate surface areas to be coated. To provide a large overlapping surface area within the target plane, the target is typically tilted at an angle α from a plane parallel to the substrate plane toward the medial axis Z of the central substrate support. The angle α can be selected from 10° to 30°, e.g., about 15°±5°, see also the examples below.

[0025] In a further embodiment of the present invention, the simultaneous sputtering is carried out by rotating at least one substrate around the central axis Z' at a distance D from the central axis Z' alternately through the sputter cones (C1, C2) of at least one first target and at least one second target, whereby the higher sputter rate of the first or second target and the rotation of the substrate are controlled interdependently to deposit only one or a few atomic material layers per pass of the sputter cone of the target having the higher sputter rate, while the contribution per pass of the target having the lower sputter rate is even lower, for example on the order of a few atoms, one or a few atomic layers.

[0026] Further examples and process parameters showing how to practically implement the invention are provided in the figure legends and Table 1.

[0027] The present invention is also directed to an AMeN multi-chamber process system (MCS) comprising: - a multisource sputter or MSS chamber comprising at least one first target made of at least one element of A and at least one second target (11) made of at least one element of Me or at least one element of Me and at least one element of A, and a gas supply line (19), at least one sputtering chamber 25 containing an AMe target made from at least one element of A and at least one element of Me, and further gas supply lines; a substrate support comprising means for fixing at least one planar substrate to be coated, such means may comprise substrate recesses, lateral nipples, peripheries, mechanical fixtures such as clamps or the like, an electrostatic chuck (ESC), or a combination of such means; - a time and sputter rate control unit operably connected to said process chamber and configured to time and rate control said target to deposit said inventive AMeN coating as described above with an increasing deposition ratio of Me to A over a predetermined deposition time.

[0028] In one embodiment of the inventive process system, the second target is made from one of Sc or Sc and Al, and the AMe target from the sputter chamber is made from an AlSc alloy or AlSc mixture with a scandium ratio between 26 and 50 at% or between 30 and 60%. Further embodiments of the inventive process system are described in the respective figures and descriptions.

[0029] In one embodiment of the process system, the first and second targets are angled at an angle α from a plane parallel to the substrate plane towards the medial axis Z of the central substrate support so that the deposition areas of the targets overlap on the substrate surface to be coated. By way of example, the angle α may be between 10° and 30°, e.g., 15°±5°. The substrate support may comprise means for rotating the stationary disk-shaped substrate about the axis Z.

[0030] In a further embodiment of the inventive process system, the first target and the second target are at laterally opposite distances D from axis Z' in a plane parallel to the substrate plane, and the substrate support is of the carousel type and operatively connected to a drive M' to rotate the substrate in a circle around axis Z. The control unit can be designed to control the speed of the drive depending on the higher sputter power of the first target or the second target.

[0031] The invention will now be further illustrated with the aid of the figures, the description of which follows: [Brief explanation of the drawings]

[0032] [Figure 1]FIG. 1 shows a first concentration profile of an AMe layer. [Figure 2] FIG. 10 shows a second concentration profile of the AMe layer. [Figure 3] FIG. 10 shows a third concentration profile of an AMe layer. [Figure 4] FIG. 10 shows a fourth concentration profile of the AMe layer. [Figure 5] FIG. 10 shows the fifth and sixth concentration profiles of the AMe layer. [Figure 6] FIG. 10 shows a sixth concentration profile of an AMe layer. [Figure 7] FIG. 10 shows a seventh concentration profile of the AMe layer. [Figure 8] FIG. 1 shows an AMeN coating. [Figure 9A] FIG. 1 shows an AFM surface scan of a state-of-the-art coating. [Figure 9B] FIG. 1 shows an AFM surface scan of a coating of the present invention. [Figure 10] FIG. 1 illustrates an exemplary parameter set. [Figure 11] FIG. 11 shows an AFM surface scan with reference to FIG. [Figure 12] FIG. 1 shows a multi-source sputtering (MSS) chamber II for applying the coating of the present invention. [Figure 13] FIG. 1 shows a multi-source sputtering (MSS) chamber II′. [Figure 14] FIG. 1 illustrates a process system for applying the coating of the present invention. [Figure 15] FIG. 1 is a schematic diagram showing process parameters. [Figure 16] FIG. 10 is a diagram of the predicted depth profile of an AlScN coating. [Figure 17] FIG. 1 is a diagram of the measured depth profile of an AlScN coating. DETAILED DESCRIPTION OF THE INVENTION

[0033] 1 to 7 show schematic diagrams of concentration profiles that can be applied by the coating system of the present invention. 1-x Me x 1 shows the basic scheme that applies to all coatings of the present invention that contain an N layer, where thickness d is the overall thickness of coating I, and along the thickness range δ3 of said coating, a transition layer 3 is applied, where the ratio of the atomic percentage of Me to the atomic percentage of A, e.g., x multiplied by 100 to express the percentage, is Me / (x A +x Me ) increases, and δ≦d. The Me content can increase steadily or in small steps, for example, from binarization steps from a processing unit. The curve can include any curve type, from a straight line (dashed line) to a curved line (solid line).

[0034] A can be at least one of B, Al, Ga, In, and Tl.

[0035] Me can be one or a combination of two, three or more of the following metals: Mg, Sc, Y, Zr, Nb, Mo, La, Ce, Pr, Nd, Sm Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb. Most common is Sc or a combination of Sc with one of the metals.

[0036] FIG. 2 shows a variation of FIG. 1, in which the Me ratio is constant along the further thickness range δ2 of the coating and ends at the beginning of the steadily increasing range, i.e., between the substrate and / or just an optional adhesion layer (see below) and transition layer 3, or just below the transition layer. The Me ratio can be zero along the further thickness range δ2 of the coating, meaning that there is no Me in the AlN of thickness δ2, also called seed layer 2. The layers (1, ... 4) in brackets are conditional. A special variation of coating I, which includes a pure AlN seed layer, is shown in FIG. 3, which includes a concentration step of the Me content from the seed layer to the transition layer of the coating. However, preferably, at least a higher concentration step from the seed layer to the transition layer and the final top layer 4 should be avoided.

[0037] Such a top layer, having a further thickness range δ4 of the coating, is shown in Figure 4. Top layer 4 begins at the end of the steadily rising transition layer 3. This top layer 4 typically has the highest Me concentration of coating I.

[0038] FIG. 5 shows two transition layers 4 starting from the limiting surface of the coating. The curve on the left shows a transition layer starting directly from the surface of the substrate, while the curve on the right shows a transition layer ending at the outer surface toward the atmosphere. FIG. 6 shows a transition layer combining both layers from FIG. 5, where the transition layer 4 starts from the inner surface of the coating, e.g., the surface of the substrate, directly as a seed layer or adhesion layer, and ends at the interface with the top layer 4 or outer surface of the coating. Finally, FIG. 7 shows a special embodiment of FIG. 6, where the transition layer starts with a zero Me ratio and ends with the highest concentration. Despite the fact that a coating may consist of only the transition layer 4, a final top layer with a certain high Me concentration is usually applied when the piezoelectric response is to be enhanced, and in many cases, a pure AlN seed layer helps provide a more stable base for proper initiation of crystallization.

[0039] Between the substrate and the seed layer and / or transition layer, some A1-x Me x An adhesion layer 1 may be applied which may be beneficial for the N coating, for example Mo, W, Pt, Si or mixtures of these elements may be useful. The substrate is typically silicon, including the partially or fully oxidized surface of a wafer, and alternatively other semiconductors such as GaAs.

[0040] Further details are given using the following example.

[0041] 7 shows the coating I of the present invention starting from the surface of the substrate (S), where an optional adhesion layer I may be applied directly on the substrate surface, typically followed by a seed layer 2 of thickness δ2 on top of the adhesion layer, or directly on the substrate surface if no adhesion layer is used. The adhesion layer may also serve as the lower electrode layer for the piezoelectric coating, as long as it is electrically conductive. The seed layer may be made of pure AN, e.g., AlN or AlN. 1-x Me x N, e.g., low Me, e.g., Sc concentration, e.g., 1 to 15 at% or 0.5 to 10 at% Al 1-x Me x Alternatively, this layer may consist of a pure AN layer and a respective AMeN layer with a low Me concentration, indicated by the dashed line in the seed layer 2. Following directly on the seed layer 2 is the transition layer 3, which typically starts with the same or up to 5 atomic % higher Me concentration than the seed layer, e.g., from a pure AN seed layer to no Me (x Me = 0), and the final A 1-x Me xThe maximum Sc concentration in the N layer increases to a maximum MeN concentration, resulting in an AMeN top layer with a thickness of δ4 at a constant Me concentration in this example. As an example, with conventional PVD sputtering, such as DC, DC-pulse, or RF techniques, the maximum Sc concentration in the top layer can be selected from approximately 26 at% up to 43 at%. Going to higher concentrations then inevitably leads to harmful cubic precipitates due to the cubic crystal structure of ScN. However, experiments have been carried out using HIPIMS technology (HIPIMS stands for High Power Pulsed Magnetron), which has shown that Sc concentrations up to 50% and even 60% can be deposited in a pure, or at least highly predominant, hexagonal phase.

[0042] It should be mentioned that the top layer does not necessarily have to end with its outer surface in contact with the atmosphere, for example, further layers known in the art may additionally be provided, such as a metal upper electrode layer for a piezoelectric coating and / or a scratch-resistant or moisture-resistant layer.

[0043] 15 shows an exemplary process scheme for applying a coating of the present invention consisting of a seed layer, a transition layer, and a top layer, for example, in sputter chamber II as detailed in FIG. 12. The seed layer is formed by a time span t2 for depositing a pure AMe layer, followed by a sputter power P of a source of a pure Me target (e.g., Sc) or an AMe target with a high Me concentration, e.g., greater than 30 at.%. Me (P Sc ) at a constant sputtering power P of the A target (e.g., Al target) during a time span t3 of depositing the AMeN transition layer by increasing the A (P Al ) is deposited. In this case, a linear ramp is shown. Alternative ramps can be applied to generate concentration curves such as those shown in Figures 1 to 6. In a further alternative process, the power P A '(P Al') can be reduced by ramping it down during at least part of time span 2 (dash-dotted line), which can be particularly useful when an AMe target is used rather than a pure Me target. Finally, during time span t3, a constant power P Me A top layer with a high Me concentration is deposited at 1000 s. Generally, the coating composition of the top layer should be the same as that at the end of the transition layer. Therefore, as long as at least the top layer is deposited in the same process module, for example, in an MMS chamber by co-sputtering as shown in FIG. 14, the deposition parameters can be the same. When the substrate is transferred to an additional sputtering chamber, for example, to deposit the top layer at a higher deposition rate, the parameters must be adapted to achieve approximately the same coating characteristics as the last sublayer of the transition layer. In this example, the flow of reactive gases, as well as the inert gas flow, is kept constant throughout the process. The excess reactive gas allows the deposition of a coating containing at least a nearly or completely stoichiometrically reacted AN-, respectively, A-xMexN layer. Alternatively, one, for example, reactive gas or inert gas, or more, for example, both or more types of gases, each gas lamp, can be expected to achieve a desired degree of reaction. An optional adhesion layer 1, for example from Mo, Pt, W and / or Si, may be applied in time span t1 instead of applying seed layer 2 directly to the substrate surface, and a further concentration ramp can be used between layers 1 and 2 by providing at least one respective target power ramp over time (not shown).

[0044] Table 1 refers to process parameters and useful ranges that can be applied to the coating of the present invention. All experiments were carried out in the multi-source sputtering (MSS) chamber II of each process module 24 of the Evatec Clusterline CLN200 MSQ vacuum system, as shown in FIG. 14. See FIG. 12. As shown in FIG. 12, an Al target and an Sc target were arranged in a paired, opposing configuration, with the Al target being used to generate the seed layer, and both targets being used for the subsequent transition and top layers. The second column of Table 1 shows an example of deposition parameters for depositing the top layer of the coating of the present invention according to FIG. 8. In this example, the top layer is a 500 nm thick Al 0.7 Sc 0.3 The seed layer comprises 15 nm of pure AlN and a transition layer, e.g., 35 nm thick, starting with zero scandium and ending with a 30 at.% Sc concentration in the top layer. In columns 4 and 5, process range 1 and process range 2 are given. Range 1, as above, also includes process ranges for all other Me elements, such as lanthanides and other 3b to 6b metallic or non-metallic X elements, while range 2 includes the parameter range to achieve optimal results in terms of piezoelectric characteristics of a coating where, e.g., the reference coating comprises AlScN.

[0045] A low parameter value in range 1 or 2 may refer to the start of an Me ramp, for example, of pulsed DC power, scandium, nitrogen gas flow.

[0046] In Table 2, column 2 lists the layer thicknesses for the above example 550 nm thick coating, and columns 4 and 5 list thickness ranges 1 and 2, respectively.

[0047] Both Figures 9A and 9B show AFM surface scans as taken with a Park NX20 device (model year 2016) with the following parameters and AFM tip applied:

[0048] Scan grid: Bidirectional line scan Scan Speed: Dynamic Scan area: 5 μm x 5 μm (This also refers to the area used in the numerical analysis of the spike) AFM tip: n-doped Si type NSC15 AL BS Typical radius of uncoated tip of 8nm ○ Resulting tip radius for coatings <8nm ○ Perfect tip cone angle*40° ○ Total tip height 12~18μm Probe material: n-type silicon ○ Probe bulk resistivity 0.01~0.025Ohm*cm Tip coating ○ Detector coating aluminum

[0049] The AFM surface scan in Figure 9A shows a 5 μm × 5 μm surface area from a 25 nm thick AlN seed layer 2, which was grown at a constant pulsed DC power (P Al = 1000W) and constant parameters, the power P ScExcept for the , the seed layer 2 was deposited within a deposition time of t2 = 122 seconds. This seed layer 2 was applied directly to the silicon wafer S, without any prior seed layer. The Z axis is in nanometers, and the color transition from light gray (originally brown) to white is approximately 9 nm. A so-called "spike analysis" of the surface revealed approximately 70 white spike tips, corresponding to crystallites in a height range higher than 9 nm, which is approximately three to four times higher than the average spike-free base roughness, here about 2 nm. Such a relationship between spike height and average spike-free surface roughness is typically observed for thin layers, down to the lower micrometer thickness range. Such a result is neither good nor bad, but is the normal surface quality of seed layers as used today. This number of primarily undesirable high spikes, which obviously affect the surface roughness but also the piezoelectric response of the coating, is usually reproduced by the next layer deposited, which is usually the piezoelectric top layer. As a result, defects in the seed layer are directly transferred, or in many cases even amplified, by the growth mechanism of the next top layer.

[0050] Figure 9B shows the very surprising result of an AFM surface scan of a 25 nm transition layer 3 deposited on the seed layer of Figure 9A. The deposition parameters were the same, but in addition, the power P Sc The final Al is very thin 0.7 SC 0.3 The parameters were ramped from zero to 460 W during the deposition time of layer 3 (t = 122 s), ending at sublayer N. Completely unexpectedly, the surface quality improved dramatically, almost three times, in terms of surface spikes, down to 24 spikes within a corresponding 5 μm × 5 μm surface area.

[0051] Such findings, which are further validated as can be seen from the exemplary time-varying parameter sets, result in dual layer configurations with different layer thicknesses and overall coating thicknesses, both of which are shown in Figure 10. Overall layer thickness D IThe thickness of the transition layer increases from 30 to 50 to 70 nm along the x-axis from left to right, while the thickness of the seed layer decreases from 35 to 15 nm along the z-axis. AFM scans of each surface area are shown in FIG. 11 along with the respective so-called "spike counts" of the spike analysis. This indicates that the best results are obtained with a relatively thin seed layer 2, which should be equal to or even smaller than 30 nm, e.g., 5 to 30 nm or 10 to 25 nm. The thickness of the transition layer 3, on the other hand, should preferably be equal to or greater than the thickness of the seed layer 2, e.g., 10 to 50 nm, e.g., 20 to 40 nm.

[0052] FIG. 12 shows a schematic diagram of a multi-source sputtering (MSS) chamber II of a process system III of the present invention. This MSS chamber includes a first target 10 made from A and a second target 11 made from Me or AMe, for the purposes of the above example. Alternatively, the second target can be made from any of the metals mentioned above, or from a respective AMe alloy, for example, produced metallurgically, or an AMe mixture, for example, from a powder metallurgically produced target. The targets 10 and 11 are powered by respective first and second power sources 15 and 16 via lines 18 and 19. The first and / or second power sources can be DC, pulsed DC, DC superimposed with pulsed DC, DC superimposed with RF, or HIPIMS sources. The target-substrate distance, defined in FIG. 12 here at an angle α of approximately 15° from a plane parallel to the substrate plane 14, is measured from the middle of the angled target toward the middle of the substrate S and the chamber axis Z and can be selected according to Table 1. This allows the deposition areas of up to four targets, e.g., two A targets and two Me targets, to overlap with most or the entire area of ​​the substrate surface, i.e., 50% to 100%, preferably 80% to 100%, of the substrate area. Overlap hereby refers to the sputter cone arising from the outer boundary of the active target surface, i.e., the sputtered surface, with an opening angle of about 35° from the target axis. Rotatable mounting of the sputter source about a central axis Z within the upper region of the MSS chamber and / or rotation of, e.g., the opposing substrate, and / or target axis T 10 , T 11Rotation around the axis Z (both symbolized by respective circular double arrows) can further promote uniform material distribution and layer quality. The substrate is supported by a substrate holder 13, e.g., a chuck, which typically includes heating and / or cooling means. The chuck 13 may be an ESC chuck for securely fixing a flat substrate. A disk-shaped substrate, e.g., a wafer, can be fixedly rotated around axis Z by a drive M. It should be noted that the angle α can vary from 0° to 90° until the actual distance TS, the substrate rotation speed, and / or the target rotation, as well as other geometric parameters, are reached. The chamber is pumped by a high-vacuum pumping system P, which includes a respective pump line, a high-vacuum pump, and at least one forepump or roughing pump. The current parameters are optimized for a chamber for a 200 mm flat circular substrate, such as a wafer, and a circular 100 mm target. Upscaling and downscaling procedures are known to those skilled in the art. In such an MSS chamber, which can be equipped with two or four targets arranged in a circular configuration at opposing positions in each pair as shown in Figure 12, all process steps for depositing the coatings of the present invention as mentioned can be performed, and even adhesion coatings can be performed, provided that at least one of the sputtering stations is equipped with the respective target material. However, such multipurpose use of MSS Chamber II results in a significantly longer process cycle compared to an MCS system, as will be explained next.

[0053] FIG. 13 shows a schematic diagram of an alternative multi-source sputtering (MSS) chamber II' that can be used in place of chamber II in the process system III of the present invention. In chamber II', multiple substrates 5 can be simultaneously coated with a seed layer 2, a transition layer 3, or a top layer 4, respectively, according to selected coating parameters. Again, chamber II' includes at least one first target 10 made of A and at least one second target 11 made of Me or AMe. Similar to chamber II, when two, four, six, or more targets are mounted, the targets of different materials, A or Me, respectively, AMe, are arranged in alternating order. However, in this embodiment, the targets are arranged along a circular path on a substrate support 13', respectively, above and parallel to the surface of the substrate 5. The substrate support 13' is of the carousel type and is driven by a drive M' to rotate the substrates circularly around axis Z, typically with an additional drive M for rotating the substrates around planetary axis Z. Similar rotations (only "planetary" and / or cyclical) can be envisaged for the targets 10, 11, respectively, and the corresponding magnetic system or sputter source (not shown) as a whole. Regarding the target material, sputtering power, target-to-substrate distance, and use for the deposition of the different layers, reference can be made to the respective remarks above. Regarding the deposition of the graded layer 3 and the top layer 4 only, due to the lack of overlap of the target cones or at least less distinct deposition areas compared to angled targets configured in a confocal arrangement within chamber II, it should be noted that the rotation of the carousel 13' and, if applicable, the counter-rotation of the targets 10, 11 around axis Z must be sufficiently fast so that only very thin sublayers of one or only a few atomic layers are deposited as the substrate passes the targets. Therefore, the minimum rotation speed depends primarily on the sputtering power of the target with the highest sputtering rate, which may be the first or second target depending on the respective Me / (A+Me) ratio to be deposited.By depositing such thin layers in rapid succession, atomic mixing or alloying of the AN and MeN or AMeN sublayers can be achieved, resulting in material properties similar to those of overlapping sputter cones as described above.

[0054] The target according to all embodiments of the invention may be a magnetron target. For a better layer distribution, the planetary rotation of the target or of at least a part of the magnetic system of the target may be, for example, about the axis T 10 , T 11 Or it can be foreseen around an axis encompassing the supply lines 17', 18'.

[0055] A vacuum processing system for industrial-scale production of the piezoelectric coatings of the present invention is shown in FIG. 14. Substrates S are transported into and out of the system vacuum via load lock chambers 28 and 29, and placed in six pre- and post-processing modules 30, 30', 31, and 31', located in pairs above and below the wafer handling level. The system also includes six process modules 21 through 26. All modules 21 through 29 are arranged in a circular or polygonal configuration around a central handler compartment 20, which includes a programmable handler 27 for transporting wafers S from pre-processing module 30 to processing modules 21 through 26, transferring wafers between modules, and finally returning wafers to post-processing tool 30. Loading and unloading into the multi-chamber vacuum processing system (MCS) are accomplished via load lock 28 for incoming wafers and load lock 29 for outgoing wafers. At least one additional handler (not shown) transports wafers from load lock chambers 28 and 29, realized here as a single load lock section, to pre-processing module 30 and back to post-processing module 31. Pre-processing modules 30, 30' and post-processing modules 31, 31' may include at least one of a buffer for wafers awaiting processing or transport, a heating station, a cooling station, an etching station, and an aligner station. Module 22 may include an etching station for etching substrates before or during sputter deposition in additional processing modules to adjust the overall process in the MCS. Modules 21 and 26 each include at least one metal sputtering station, each with a Mo target and a Pt target, to apply an adhesion layer to the substrate surface, allowing operators to select the most appropriate adhesion coating for different substrate types or surface conditions, if necessary. Module 23 may include a metal sputtering station with an A target, for example, for quickly applying an Au seed layer.Module 25 may comprise a metal sputtering station with an AMe target, e.g., an AlSc target, for applying a final relatively thick AMeN, e.g., AlScN, layer. In another MCS configuration, even two process modules, e.g., modules 25 and 26, may be equipped with respective targets to split the deposition process of the final layer and thereby speed up the production cycle.

[0056] The MCS's system control unit 32, which may contain the respective system units of the modules or at least control the timing of such units, controls the wafer transport as well as the process details in all modules by means of control and / or adjustment means 33, measurement means, and sensors (not shown), which may again be at least partly contained within the system control unit 32 or separate from each module to be controlled. An input / output unit 34 allows an operator to modify single process parameters and automatically load new processes. In the vacuum processing system as shown, all processing modules are pumped by a high-vacuum pumping system P, which may thus be the central handler compartment 20, the pre-processing module 30, the post-processing module 31, and / or the load lock chambers 28, 29.

[0057] Finally, it should be mentioned that a combination of features described in connection with one embodiment, example or type of the present invention may be combined with other embodiments, examples or types of the present invention, unless inconsistent.

[0058] [Table 1]

[0059] [Table 2] [Explanation of symbols]

[0060] I Piezoelectric Coating 1 Adhesive layer 2. Seed layer 3 Transition layer 4. Top Floor 5 Top surface 6. Cone-shaped crystallites in the seed layer 7. Cone-shaped crystallites in the transition layer S board II MSS Chamber 10 First Target Al 11 Second Target Me 12 Anode (may be at ground potential) 13 Substrate support 14 Board plane 15, 16 Primary and secondary target sources 17 Line from the first supply source 18 Line from second source 19 Supply Line C Spatter Cone M, M' drive unit P High Vacuum Pump System T 10 / 11 Target Axis TS Target / Substrate Distance α is the angle of the target relative to the chamber axis Z chamber axis III Process Systems 20 Central Handler Compartment 21 First Processing Module / Mo 22 Second Processing Module / Etching 23 Third processing module / AlN 24 Fourth Processing Module / MS II 25 5th processing module / AlMeN, AlScN 26 6th Processing Module / Pt 27 Handler 28, 29 Load lock chamber entry / exit 30 Pre-processing module 31 Post-processing module 32 System Controller Unit 33 Control and / or adjustment means 34 Input / Output Unit ↑↓ Loading into / loading out of vacuum ↑↓<-> Transfer between the handler compartment and the module

Claims

1. A substrate having a surface coated with a piezoelectric coating (I), said coating comprising: １－ｘ Me ｘ N, A is at least one of B, Al, Ga, In, Tl, and Me is at least one metal element of the transition metal group 3b, 4b, 5b, 6b, the lanthanides, and Mg, said coating (I) having a thickness d and comprising a transition layer (3) in which, starting from the substrate side, the ratio of the atomic percentage of Me to the sum of the atomic percentages of A and Me increases continuously along a thickness range δ3 of said coating, δ3<d, the coating further comprises a seed layer (2) that terminates at the beginning of the continuous rise of the transition layer (3), the ratio being constant along a thickness range δ2 of the seed layer; the thickness of the transition layer (3) is equal to or greater than the thickness of the seed layer (2); The coating further comprises a top layer (4) starting at the end of the continuous rise of the transition layer (3), and the ratio is constant along a thickness range δ4 of the top layer.

2. The substrate of claim 1 , wherein Me is at least one of Sc, Mg, Hf, and Y.

3. 3. The substrate of claim 1, wherein Me is Sc.

4. 3. The substrate of claim 1, wherein the transition layer (3) has a thickness of 10 to 50 nm, the seed layer (2) has a thickness of 5 to 30 nm, and the surface of the transition layer (3) has a uniform surface quality of less than 50 spikes in any 5 μm x 5 μm surface area.

5. 3. The substrate according to claim 1 or 2, wherein the continuous rise of the transition layer (3) starts with the ratio being zero.

6. 3. The substrate of claim 1, wherein the continuous rise is at least approximately linear, such as a slope.

7. 3. The substrate according to claim 1 or 2, wherein the coating further comprises an adhesion layer (1) deposited directly on the substrate surface.

8. 8. The substrate according to claim 7, wherein the adhesion layer (1) is made of at least one of the following materials: Si, Mo, W, Pt, Ru, Ti.

9. 3. The substrate according to claim 1 or 2, wherein the seed layer (2) is deposited directly on one of the surfaces of the substrate (S).

10. 3. The substrate of claim 1, comprising a seed layer and an adhesion layer, the adhesion layer being deposited directly on one surface of the substrate and the seed layer being deposited directly on the adhesion layer.

11. At least the substrate surface to be coated is made of Si, SiO ｘ 3. The substrate according to claim 1, wherein the substrate is made of GaAs or GaAs.

12. 3. The substrate according to claim 1, wherein the substrate comprises a pre-coating and the piezoelectric coating (I) is deposited directly on the pre-coating.

13. 3. The substrate according to claim 1, wherein the proportion at the end of the continuous rise of the transition layer (3) is higher than 26% Me.

14. 5. The substrate of claim 4, wherein the surface of one of the transition layer (3) and the top layer (4) has a uniform surface quality of less than 30 spikes in any 5 μm×5 μm surface area.

15. A having a thickness d on the substrate １－ｘ Me ｘ 2. A method for depositing a N coating or an A coating according to claim 1 １－ｘ Me ｘ 1. A method for producing a substrate having an AMeN coating, comprising co-sputtering from at least one first target (10) made of at least one element of A and at least one second target (11) made of at least one element of Me or at least one element of Me and at least one element of A, wherein the sputtering is carried out in a nitrogen-containing gas atmosphere while controlling the sputtering time and sputtering rate of the targets, and during a time span t3 for depositing an AMeN transition layer, the sputtering power P of the first target is controlled. Ａ The sputtering power P of the second target relative to Ｍｅ Power ratio R Ｐ =P Ｍｅ / P Ａ increases, Starting from the substrate side, the ratio of the atomic percentage of Me to the sum of the atomic percentages of A and Me is deposited in a continuously increasing manner along a thickness range δ3 of the coating, δ3<d, a seed layer (2) is deposited for a time span t2 before the time span t3 so as to end at the beginning of the continuous rise of the transition layer (3), the ratio being maintained constant along a thickness range δ2 of the seed layer; The thickness of the transition layer (3) is deposited to be equal to or greater than the thickness of the seed layer (2); The method includes providing a top layer (4) starting at an end point of the continuous rise of the transition layer (3), wherein the ratio is constant along a thickness range δ4 of the top layer.

16. The sputtering power P of the second target Ｍｅ is increased or kept constant, while the sputtering power of the first target is kept constant (P Ａ ) or decrease (P Ａ '), the method according to claim 15.

17. 17. The method of claim 15 or 16, wherein co-sputtering is performed in a deposition region in the substrate plane 14, and the sputter cone of the first target and the sputter cone of the second target overlap.

18. 20. The method of claim 17, wherein the deposition area comprises at least 50% to 100% of the substrate surface to be coated.

19. 17. The method according to claim 15 or 16, wherein simultaneous sputtering is performed by rotating at least one substrate around a central axis Z′ at a distance D from the central axis Z′ alternately through the sputter cones (C1, C2) of at least one first target (10) and at least one second target (11), whereby a higher sputter rate of the first target or the second target and the rotation of the substrate are controlled to deposit only one or a few atomic material layers per pass of the sputter cone of the target having the higher sputter rate.

20. 20. The method of any one of claims 15 to 19, wherein co-sputtering is performed using two first targets and two second targets.

21. An AMeN multi-chamber process system (III), comprising: a multi-source sputtering (MSS) chamber (24) comprising at least one first target (10) made of at least one element of A, at least one second target (11) made of at least one element of Me or at least one element of Me and at least one element of A, gas supply lines (19) and a substrate support (13, 13') comprising means for fixing at least one planar substrate to be coated; at least one sputtering chamber (25) equipped with an AMe target made from at least one element of A and at least one element of Me, and additional gas supply lines; and a time and sputter rate control unit (32) operably connected to the MSS chamber (24) and fabricated to time and rate control the target to deposit an AMeN coating with an increasing deposition ratio of Me to A during a predetermined deposition time in accordance with any one of claims 15 to 20.

22. 22. The process system of claim 21, wherein the second target (11) is made from one of Sc or Sc and Al, and the AMe target from the sputtering chamber (25) is made from an AlSc alloy or AlSc mixture having a scandium ratio between 26 and 60 at.%.

23. 23. The process system of claim 21 or 22, wherein the first target (10) and the second target (11) are angled at an angle α from a plane parallel to the substrate plane (14) towards the medial axis Z of the central substrate support (13), so that the deposition areas of the targets overlap on the substrate surface to be coated.

24. 24. The process system of claim 23, wherein 10°≦α≦30°.

25. 25. The process system of any one of claims 21 to 24, wherein the substrate support 13 comprises means for rotating a stationary disk-shaped substrate about axis Z.

26. 23. The process system of claim 21 or 22, wherein the first target (10) and the second target (11) are in a plane parallel to the substrate plane 14, and the substrate support 13' is of the carousel type and is operatively connected to a drive M' for circularly rotating the substrate about an axis Z'.

27. 27. The process system of claim 26, wherein the control unit (32) is designed to control the speed of the drive depending on the higher sputtering power of the first target or the second target.

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