Resonator device and method for manufacturing the same, and method for depositing a metal layer on a substrate

Abstract

This application relates to a deposition method. According to the present invention, there is provided a method for sputter-depositing a metal layer on a substrate in the manufacture of a resonator device, wherein the metal layer is composed of a metal selected from molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), platinum (Pt) or ruthenium (Ru), and the method comprises the following steps: providing a magnetron sputtering apparatus including a chamber, a substrate support disposed in the chamber, a target made of a metal material, and a plasma generating device, wherein the substrate support is separated from the target by a distance of 10 cm or less; supporting the substrate on the substrate support; performing a DC magnetron sputtering step, which includes sputtering the metal material from the target onto the substrate to form a metal layer on the substrate, wherein during the DC magnetron sputtering step, the inert gas in the chamber has a pressure of at least 6 mTorr, the target is supplied with power having a power density of at least 6 W / cm<supgt;2< / supgt;, and the substrate has a temperature in the range of 200 to 600 °C.

Description

Technical Field

[0001] The present invention relates to a method for sputter depositing a metal layer on a substrate. More specifically, the present invention relates to a method for sputter depositing a metal layer on a substrate in the manufacture of a resonator device, such as a bulk acoustic wave (BAW) device or a surface acoustic wave (SAW) device. The present invention also relates to a method for manufacturing a resonator device. The present invention also relates to an associated substrate comprising a metal layer and an associated resonator device. Background Art

[0002] Resonator devices such as bulk acoustic wave (BAW) devices and surface acoustic wave (SAW) devices have various applications. For example, BAW devices are used in cell phones and other wireless applications to allow reception and / or transmission of specific radio frequencies. These resonator devices use the piezoelectric effect to generate mechanical resonance from an electrical input and can also convert the mechanical resonance into an electrical output.

[0003] Resonator devices typically include multiple layers sequentially deposited on a substrate such as a patterned silicon substrate. The layers typically include a piezoelectric layer such as AlN or AlScN disposed between two metal electrodes. Physical vapor deposition (PVD) techniques such as sputtering can be used to deposit these layers.

[0004] It is desirable to reduce the thickness of the layers in the resonator devices in order to develop devices suitable for 5G and future RF filter generations. However, as the piezoelectric layers become thinner, the contribution of intra-wafer stress variations across the electrode layers to the coupling properties of the device stack becomes more prominent. That is, intra-wafer stress variations of the electrodes become a more important factor in controlling coupling uniformity across the wafer. It is desirable to develop methods for depositing electrode layers with a stress range of less than about 200 MPa while also maintaining good thickness uniformity (preferably <1% 1σ) across the entire surface of a substrate (e.g., a 200 mm silicon wafer) with minimal (e.g., <5 mm) edge removal areas. It is also desirable that the stress of the electrode layers can be tuned depending on the desired application.

[0005] The electrode layers of a resonator device, such as an AlN or AlScN resonator device, must also conduct electricity with low thermoelastic losses. The electrode layers should also provide a suitable surface for growing piezoelectric material with a preferred crystal orientation.

[0006] Molybdenum (Mo) is known to exhibit 56 times less thermoelastic losses than Al and has been used as a material for electrode layers. The bulk resistivity of Mo is 5.34 μΩ.cm. However, known methods of sputtering deposited Mo electrode layers typically provide Mo layers having a resistivity of not less than about 11 μΩ.cm. Therefore, it is desirable to develop a method of depositing an electrode layer, such as a Mo layer, that exhibits reduced resistivity. This would enable thinning of the electrode layer, thereby reducing device losses and providing a higher quality factor for the resulting resonator device. Summary of the invention

[0007] In at least some embodiments of the present invention, the present invention seeks to address the above-mentioned problems, desires and needs. In particular, embodiments of the present invention seek to provide a method that causes a metal layer to exhibit a resistivity of less than about 10 μΩ.cm while achieving excellent stress control and excellent thickness uniformity of the deposited metal layer. In general, this can lead to higher quality resonator devices, such as BAW and SAW devices, with reduced losses. These desirable properties are critical in developing the next generation of high quality resonator devices.

[0008] According to a first aspect of the present invention, there is provided a method for sputter depositing a metal layer on a substrate in the manufacture of a resonator device, wherein the metal layer consists of a metal selected from molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), platinum (Pt) or ruthenium (Ru), the method comprising the following steps:

[0009] Provide a magnetron sputtering apparatus comprising a chamber, a substrate support disposed in the chamber, a target made of a metal material, and a plasma generating device, wherein the substrate support is separated from the target by a distance of 10 cm or less;

[0010] supporting the substrate on the substrate support;

[0011] performing a DC magnetron sputtering step, which includes sputtering the metal material from the target onto the substrate to form a metal layer on the substrate, wherein during the DC magnetron sputtering step, the inert gas of the chamber has a pressure of at least 6 mTorr (at least about 0.8 Pa), the target is supplied with a power of at least 6 W / cm 2 The power density is 200 to 600° C., and the substrate has a temperature in the range of 200 to 600° C.

[0012] Known methods of sputter depositing metals in the manufacture of resonator devices operate at low chamber pressures, typically less than 4 mTorr. The current general belief in the art is that operating at higher pressures causes the sputtered material to be scattered more by the plasma. As a result, the energy of the species deposited on the substrate is reduced, which results in a less dense film, where more gas becomes bound within the deposited layer. The current general belief in the art is that higher gas pressures result in films exhibiting higher resistivity, which is undesirable. Therefore, the process conditions of the present invention are completely contrary to the current general belief in the art.

[0013] The inventors have discovered that at a chamber pressure of at least 6 mTorr and at least 6 W / cm 2Performing a DC magnetron sputtering step at a combination of a target power density of 200 Å and a target power density of 100 Å provides a metal layer exhibiting a resistivity of less than about 10 μΩ.cm. In addition, by using these process conditions, the stress in the metal layer can be controlled to be compressive, tensile, or about zero as desired, with a stress range of less than about 250 MPa, optionally less than 200 MPa, optionally less than 150 MPa, and optionally less than 120 MPa. In addition, the method achieves excellent thickness control and thickness uniformity.

[0014] Without wishing to be bound by any theory or conjecture, it is believed that by performing the DC magnetron sputtering step at a high chamber pressure and a high power density supplied to the target (cathode), there is still a sufficient flux of energetic ions and neutral species bombarding the substrate to produce a dense metal layer with minimal levels of gas incorporation. More specifically, it is believed that the high power density applied to the target (i.e., at least 6 W / cm 2 ) compensates for the increased gas scattering, and in turn compensates for the energy attenuation of the sputtered species caused by the increased chamber pressure. In general, high chamber pressure (i.e., at least 6 mTorr) and high power density supplied to the target (i.e., at least 6 W / cm 2 ) provide suitable conditions for depositing a metal layer with reduced resistivity.

[0015] The substrate may be a silicon substrate. The substrate may be a silicon wafer.

[0016] The power supplied to the target may have a value of at least 8 W / cm 2 A power density of at least 10 W / cm 2 , optionally at least 12 W / cm 2 , optionally at least 14 W / cm 2 or optionally at least 16 W / cm 2 The power supplied to the target may have a value of less than about 24 W / cm 2 A power density of less than about 22 W / cm 2 , optionally less than about 20 W / cm 2 , optionally less than about 18 W / cm 2 or optionally less than about 16 W / cm 2 The power density can be any combination of these upper and lower limits. In addition to the benefits described above, high power density can increase deposition rates.

[0017] During the DC magnetron sputtering step, the chamber may have a pressure of at least 7 mTorr, optionally at least 8 mTorr, optionally at least 9 mTorr, optionally at least 10 mTorr. During the DC magnetron sputtering step, the chamber may have a pressure of about 20 mTorr or less, optionally about 15 mTorr or less, optionally about 12 mTorr or less, optionally about 10 mTorr or less, or optionally about 8 mTorr or less. The pressure may be any combination of these upper and lower limits.

[0018] The DC magnetron sputtering step is performed at a temperature of at least 200° C., optionally at least 300° C., or optionally about 400° C. The DC magnetron sputtering step is performed at a temperature of about 600° C. or less, optionally about 500° C. or less, or optionally about 400° C. or less. The DC magnetron sputtering step may be performed at any combination of these upper and lower limits.

[0019] During the DC magnetron sputtering step, bias power may be supplied to the substrate support. Supplying bias power to the substrate support may control the stress of the deposited metal layer. Applying a high bias power may result in greater compression (less tension) of the deposited metal layer. The bias power applied to the substrate support may be selected so as to minimize the stress in the metal layer. For example, the bias power applied to the substrate support may be selected so as to provide a metal layer having an average stress of about zero (0 MPa). The bias power may be an RF bias power. The RF bias power has a frequency of 13.56 Hz. The bias power may have a power of at least 10 W, optionally at least 50 W, optionally at least 100 W, optionally at least 200 W, optionally at least 250 W, or optionally at least 300 W. The bias power may have a power of about 600 W or less, optionally about 500 W or less, optionally about 400 W or less, optionally about 300 W or less, or optionally about 200 W or less. The bias power can have a power between any combination of these upper and lower limits.

[0020] The metal material is a metal selected from molybdenum (Mo), tungsten (W), titanium (Ti), tantalum (Ta), platinum (Pt), ruthenium (Ru). These metals have low thermoelastic losses. For example, Mo can exhibit about 56 times less thermoelastic losses than aluminum. Therefore, using these low thermoelastic loss metals as electrode layers in the resonator device can significantly improve (reduce) the thermoelastic losses, thereby improving the quality of the resonator device.

[0021] The DC magnetron sputtering step may include sputtering the metal material from the target using a plasma formed from an inert gas. The inert gas may be argon (Ar), krypton (Kr), xenon (Xe), or a mixture thereof. An inert gas is understood to be a Group 18 gas of the periodic table.

[0022] The metal layer may have a thickness of about 500 nm or less, optionally about 350 nm or less, optionally about 300 nm or less, optionally about 250 nm or less, optionally about 200 nm or less, or optionally about 150 nm or less.

[0023] The substrate support and the target may be separated by a distance of about 75 mm or less.

[0024] The substrate support may be stationary during the DC magnetron sputtering step. For example, the substrate support may be rotationally stationary (ie, not rotating) during the DC magnetron sputtering step.

[0025] The resonator may be an acoustic wave device. The resonator device may be a bulk acoustic wave (BAW) device. The resonator device may be a surface acoustic wave (SAW) device.

[0026] According to a second aspect of the present invention, there is provided a method of manufacturing a resonator device, comprising the following steps:

[0027] (a) providing a substrate;

[0028] (b) depositing a first metal layer onto the substrate;

[0029] (c) depositing a piezoelectric layer onto the first metal layer; and

[0030] (d) depositing a second metal layer onto the piezoelectric layer, wherein at least one of steps (b) and (d) is performed using a method according to the first aspect.

[0031] The substrate may be a silicon substrate. The piezoelectric layer may include AlN, AlScN, or another suitable piezoelectric material. The resonator device may be a BAW device or a SAW device.

[0032] According to a third aspect of the present invention, there is provided a substrate comprising a metal layer, such as a molybdenum layer, deposited using the method according to the first aspect, wherein the metal layer has a resistivity of less than about 10 μΩ·cm.

[0033] The resistivity may be less than about 9 μΩ.cm. The resistivity may be in the range of 8 to 10 μΩ.cm, optionally 8 to 9 μΩ.cm. The low resistivity metal layer may be made thinner while still achieving the same contact resistance. This may result in a smaller, higher quality device. The substrate may be a silicon substrate, such as a silicon wafer. The metal layer may have a stress range of less than about 250 MPa, optionally less than about 200 MPa, optionally less than about 150 MPa, or optionally less than about 120 MPa. The metal layer may be an electrode layer. The metal layer may be a tungsten (W), titanium (Ti), tantalum (Ta), platinum (Pt), or ruthenium (Ru) layer.

[0034] According to a fourth aspect of the present invention, there is provided a resonator device comprising a metal layer, such as a molybdenum layer, deposited using the method according to the first aspect, wherein the metal layer has a resistivity of less than about 10 μΩ·cm.

[0035] The metal layer may have a stress variation of less than 250 MPa, optionally less than about 200 MPa, optionally less than about 150 MPa, optionally less than about 120 MPa. The intra-wafer stress of the resonator device may have a stress range of less than about 250 MPa, optionally less than about 200 MPa, optionally less than about 150 MPa, or optionally less than about 120 MPa. The metal layer may be an electrode layer. The metal layer may be a tungsten (W), titanium (Ti), tantalum (Ta), platinum (Pt), or ruthenium (Ru) layer.

[0036] The resonator device may be an acoustic wave device. The resonator device may be a bulk acoustic wave (BAW) device. The resonator device may be a surface acoustic wave (SAW) device.

[0037] Although the present invention has been described above, it extends to any inventive combination of features set out in the above or following description, drawings or claims. For example, any feature disclosed with respect to one aspect of the present invention may be combined with any feature disclosed with respect to any of the other aspects of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0039] Figure 1 is a schematic diagram of a sputtering apparatus suitable for performing a method according to an embodiment of the present invention;

[0040] Figure 2 Demonstrating the thickness variation of a metal layer deposited using an exemplary method of the present invention;

[0041] Figure 3 Demonstrating radial sheet resistivity of metal layers deposited using exemplary aspects of the present invention;

[0042] Figure 4 A plot showing the variation of resistivity (in μΩ.cm) with pressure (in mTorr);

[0043] Figure 5 Display the average stress and stress range in the metal layer as a function of panel power; and

[0044] Figure 6 Shows the average stress in the metal layer as a function of the plate power. DETAILED DESCRIPTION

[0045] Embodiments of the present invention relate to methods for sputter depositing a metal layer onto a substrate in the manufacture of a resonator device, such as a bulk acoustic wave (BAW) or surface acoustic wave (SAW) device. Exemplary methods of the present invention may be performed using a suitable DC magnetron sputtering apparatus 10, such as Figure 1 Schematically shown in FIG. A SPTS Sigma (RTM) deposition system with a DC magnetron sputtering module commercially available from SPTS Technologies Limited, headquartered in Newport, South Wales, UK, is suitable for performing a DC magnetron sputtering method according to an embodiment of the present invention. For simplicity, some well-known features of the DC magnetron sputtering apparatus 10 have been omitted from the figure. The general operation of this DC magnetron sputtering apparatus (e.g., generating a plasma) is well known in the art and will not be described here except as needed to understand the present invention.

[0046] refer to Figure 1 , magnetron sputtering apparatus 10 includes a substrate support (e.g., a plate) 12 disposed within a chamber 14. The grounded metal chamber 14 is suitable for containing a plasma. The substrate support 12 is adapted to hold a substrate 16 in a substantially horizontal orientation, with the front surface of the substrate facing upward. The substrate 16 may be a wafer, such as a silicon wafer. The substrate 16 may be a patterned silicon wafer. The substrate 16 may be loaded and unloaded via a suitable loading / unloading slot 17.

[0047] The apparatus 10 further includes a target 18 disposed within the chamber 14. The target 18 and the substrate support 12 are arranged so that material sputtered from the target 18 can be deposited onto a substrate 16 supported on the substrate support 12. Typically, the target 18 is held directly opposite and above the substrate support 12. The distance between the target 18 and the substrate 16 is about 10 cm or less or optionally 75 mm or less. The target 18 is made of a sputtered material. The target 18 is made of a metallic material. The target may be made of molybdenum (Mo), tungsten (W), ruthenium (Ru), titanium (Ti), tantalum (Ta), or platinum (Pt). In an exemplary method of the present invention, the metallic material is typically a metal suitable for use as an electrode metal in a resonator device, such as a low thermoelastic loss electrode metal.

[0048] Gas may enter the chamber 14 via a gas inlet 20 and may be pumped from the chamber via an exhaust port 22. The apparatus 10 further includes a plasma generating component for generating a plasma within the chamber 14. The apparatus 10 further includes a magnetron 24 for generating a magnetic field proximate to the target 18 that confines the plasma to the vicinity of the target 18. The magnetron 24 is disposed outside the chamber 14. A power supply 26 is configured to provide DC power to the magnetron 24 during operation.

[0049] The power supply 26 is configured to supply power to the target 18. During the sputter deposition process, the target 18 acts as a cathode.

[0050] The bias radio frequency 28 may supply RF bias power to the substrate support 12. A controller having a graphical user interface (not shown) may be used to control the power supply.

[0051] In operation, a plasma is maintained by a plasma generating means and power is applied to the target 18, causing species in the plasma (e.g., ions and neutral atoms) to sputter material from the target 18. The material sputtered from the target 18 is deposited onto a substrate 16 supported on a substrate support 12 to form a metal layer thereon. In a non-reactive sputtering process, the metal layer is typically composed of the same material as the target 18.

[0052] In a first exemplary method, a metal layer is sputter deposited onto a 200 mm diameter silicon wafer using a DC magnetron sputtering method. This deposition process is part of a process for manufacturing a resonator device such as an acoustic wave device (e.g., a BAW or SAW device). The apparatus 10 for depositing the metal layer is a SPTS Sigma (RTM) deposition system with a DC magnetron sputtering module. In this example, the target 18 is made of molybdenum and the metal layer consists of molybdenum.

[0053] A silicon substrate 16 is positioned onto a substrate support 12 within the deposition apparatus 10. The distance between the target 18 and the substrate 16 is set to about 10 cm.

[0054] Next, a DC magnetron sputtering process is performed to sputter Mo from the target 18 onto the substrate 16. An inert gas is introduced into the chamber 14 via the gas inlet 20 and a plasma is generated. The inert gas may be argon, krypton, xenon, or any combination thereof. In a first exemplary method, the inert gas used to generate the plasma is argon. Power is applied to the target (cathode) 18 so as to promote the species in the plasma to sputter material from the target 18.

[0055] During the DC magnetron sputtering process, the chamber 14 has a pressure of at least 6 mTorr and the power applied to the target 18 has a power of at least 6 W / cm 2 Typically, the chamber pressure is in the range of 6 to 20 mTorr. Typically, the target power density is in the range of 8 to 24 W / cm 2 within the range.

[0056] The thickness, resistivity and stress of the deposited metal layers were measured. The thickness of the metal layers was measured using non-destructive metrology measurements using a MetaPULSE(TM) instrument. Figure 2A contour plot showing the thickness of the as-deposited Mo metal layer. The average film thickness was 189.36 nm, and the film showed excellent thickness uniformity with a 1σ value of 0.458% (see Table 1).

[0057] Table 1

[0058]

[0059] The sheet resistivity of the metal layer (R s ) were measured using a four-point probe technique and the resistivity was determined using the following equation.

[0060]

[0061] Figure 3 A contour plot of sheet resistivity of the as-deposited film is shown. The average bulk resistivity is 8.4 μΩ.cm, as represented by the (thickest) line 32. Values ​​under one standard deviation are represented by the (mid-thickness) line 34. The resistivity values ​​achieved using the present method are far superior (i.e., lower) than known resistivity values ​​that have been previously reported. In addition, the present invention enables excellent thickness uniformity to be achieved.

[0062] The stress of the as-deposited film can be controlled by applying a bias power, such as an RF bias power, to the substrate support 12 during the DC magnetron sputtering process. Typically, the RF bias power has a frequency of 13.56 Hz. However, other RF frequencies may be used. Table 2 shows how the bias power supplied to the substrate support is controlled at the same high power (i.e., at least 6 W / cm 2 ) and high pressure (i.e., at least 6 mTorr) conditions affect the resistivity and stress of the as-deposited Mo film.

[0063] Table 2

[0064]

[0065] The average stress in the deposited metal layer can be tuned by applying an appropriate bias power to the substrate support (e.g., a flat plate) 12. In general, a higher bias power applied to the substrate support 12 during the DC magnetron sputtering step results in a more compressive (less tensile) stress in the initially deposited metal layer. The bias power supplied to the substrate support 12 can be tuned so that the deposited metal layer can have an average stress of about 0 MPa. In addition, the high power and high pressure deposition conditions according to the present invention provide a resulting metal layer that exhibits a cross-film stress variation of <200 MPa. In addition, all films exhibit a low resistivity of ≤9 μΩ.cm. Such metal layers with uniform thickness, uniform stress, and low resistivity exhibit desirable properties that can be used to manufacture higher quality, smaller resonator devices, such as BAW and SAW devices with less loss.

[0066] These methods and results go against current common belief in the art. Current common belief holds that increasing chamber pressure during a DC magnetron sputtering step causes the sputtered material to scatter to a greater extent and the energy of the sputtered material landing on the substrate 16 is reduced. It is believed that this results in increased gas incorporation in the as-deposited film, resulting in a less dense and less conductive metal layer. However, the inventors have discovered that, contrary to this current common belief, high pressure (i.e., at least 6 mTorr) and high target power density (i.e., at least 6 W / cm 2 ) can result in deposited metal layers with improved (lower) resistivity while also providing excellent thickness uniformity and stress uniformity. The excellent (low) resistivity values ​​of the metal layers deposited using the present method indicate that the films are dense and have minimal gas incorporation in the as-deposited films. These metal layers have improved properties and allow for the fabrication of resonator devices with improved quality factors.

[0067] Figure 4 Plots showing how the resistivity of a 300 nm thick Mo metal layer deposited using DC magnetron sputtering varies with chamber pressure (without any bias applied to the substrate support 12). Plot A uses 6.77 W / cm2 applied to the target 18. 2 Plot B uses a power density of 16.92 W / cm applied to target 18. 2 The power density is 200℃.

[0068] Use 6.77W / cm 2 The power density ( Figure 4 , Plot A) provides excellent resistivity (<9 μΩ.cm) at both high pressure (about 7.8 mTorr) and low pressure (about 1.4 mTorr). However, it was found that increasing the pressure further improved the resistivity (to <8.8 μΩ.cm). Operating at higher pressures also provides more stretched films, whose stress can be tuned using the RF bias power applied to the substrate support 12. The RF bias power applied to the substrate support 12 generally causes the average stress in the metal layer to become more compressive (less tensile). Therefore, in order to better control the average stress of the deposited layer, it is advisable to slightly stretch the deposited layer when no bias power is applied. That is, the average stress of the more stretched film (e.g., deposited at higher pressure) can be tuned so that the average stress is about 0 MPa. The excellent (low) resistivity values ​​indicate that these films are very dense.

[0069] 16.92 W / cm2 at low pressure (about 1.4 mTorr) 2 The power density ( Figure 4, Plot B) results in a metal layer with suboptimal resistivity (>10 μΩ.cm). However, as the pressure increases (to about 7.8 mTorr), the sensitivity to high power density operation decreases, thereby achieving higher deposition rates while reducing the resistivity value of the deposited metal layer (<9 μΩ.cm).

[0070] Figure 5 5 shows how the average stress (line 50 represented by circles) and the stress range (line 52 represented by triangles) in an as-deposited 200 nm thick Mo metal layer vary with the bias power applied to the substrate support 12. The Mo metal layer is subjected to a pressure of about 8 mTorr at a temperature of 200°C and at 6.77 W / cm 2 The substrate support bias power of about 240 W results in the Mo metal layer having an average stress of about 0 MPa and a stress range of about 160 MPa.

[0071] Figure 6 60 shows how the average stress in an as-deposited 200 nm thick Mo metal layer varies with the bias power applied to the substrate support 12. The Mo metal layer is heated at a temperature of 200°C, at a pressure of about 8 mTorr and at 16.92 W / cm 2 The substrate support bias power of about 95 W resulted in the Mo metal layer having an average stress of about 0 MPa.

[0072] Using a combination of high target power density and high pressure (according to the present invention), metal layers can be deposited that exhibit excellent stress uniformity of <120 MPa, and thickness uniformity of <0.7 1σ% for metal layers with an average stress of 0 MPa. In addition, a low intra-wafer stress range of <200 MPa can be achieved at various average stresses while maintaining a thickness non-uniformity of <1.5% 1σ.

[0073] Table 3 illustrates exemplary processing parameters that may be used to deposit a metal layer that exhibits an average stress of about zero according to an exemplary method of the present invention. A comparative process is also shown.

[0074] Table 3

[0075]

[0076] Without being bound by any theory or conjecture, it is believed that operating at high pressure and target power density (according to the present invention), there is a sufficient flux of high-energy ions and neutral species bombarding the substrate 16 to produce a dense film with a minimum level of gas binding. The high target (cathode) power density compensates for any additional gas scattering that would otherwise be due to the higher chamber pressure. Accordingly, the high target power density compensates for any attenuation of the energy of the ions and neutral species in the plasma due to the increase in chamber pressure, and thus provides suitable conditions for achieving a dense film. Therefore, the use of a combination of high power density and high chamber pressure applied to the target 18 results in the species in the plasma having optimal energy to form a dense metal layer that exhibits improved resistivity, excellent thickness uniformity, and stress control with excellent stress uniformity. Such films are suitable for application as electrode layers in resonator devices such as BAW and SAW devices.

[0077] Using high chamber pressure and high target (cathode) power density coupled with controlled bias power applied to substrate support 12, the inventors have developed a method for depositing metal layers that exhibit excellent thickness uniformity, improved resistivity (<10 μΩ.cm), and reduced stress range. Although the above examples primarily involve the deposition of Mo metal layers, the same process conditions can be used for sputtering deposition of other metals such as tungsten, titanium, tantalum, platinum, and ruthenium. The metal layers deposited using the present method meet the needs of highly uniform, low stress Mo films and are suitable for use as thin electrode layers in resonator devices such as BAW and SAW devices.

[0078] In another exemplary method, a resonator device, such as a BAW or SAW device, is fabricated. A first metal layer is sputter deposited onto a substrate using the same DC magnetron sputtering method described with respect to the first exemplary method. The substrate is a patterned silicon wafer.

[0079] Subsequently, a piezoelectric material is deposited onto the first metal layer. The piezoelectric material layer may be made of AlN, AlScN or other suitable piezoelectric materials.

[0080] Next, a second metal layer is sputter deposited onto the piezoelectric material layer using the same DC magnetron sputtering method described with respect to the first exemplary method.The resulting resonator device exhibits an improved quality factor.

Claims

1. A method for sputter depositing a metal layer on a substrate in the manufacture of a resonator device, wherein the metal layer is composed of a metal selected from molybdenum Mo, tungsten W, titanium Ti, tantalum Ta, platinum Pt or ruthenium Ru, the method comprising the following steps: Provide a magnetron sputtering apparatus comprising a chamber, a substrate support disposed in the chamber, a target made of a metal material, and a plasma generating device, wherein the substrate support is separated from the target by a distance of 10 cm or less; supporting the substrate on the substrate support; performing a DC magnetron sputtering step, which includes sputtering the metal material from the target onto the substrate to form a metal layer on the substrate, wherein during the DC magnetron sputtering step, the inert gas of the chamber has a pressure of at least 6 mTorr, the target is supplied with a power of at least 6 W / cm 2 The power density is 200 to 600° C., and the substrate has a temperature in the range of 200 to 600° C. The method according to claim 1 , wherein the substrate is a silicon substrate.

3. The method of claim 1 or 2, wherein the power supplied to the target has a power of at least 8 W / cm 2 power density.

4. The method of claim 1 or 2, wherein the power supplied to the target has a power of at least 10 W / cm 2 power density.

5. The method of claim 1 or 2, wherein the power supplied to the target has a power of at least 12 W / cm 2 power density.

6. The method of claim 1 or 2, wherein the power supplied to the target has a power of at least 14 W / cm 2 power density.

7. The method of claim 1 or 2, wherein the power supplied to the target has a power of at least 16 W / cm 2 power density.

8. The method of claim 1 or 2, wherein the power supplied to the target has a power of less than 24 W / cm 2 power density.

9. The method of claim 1 or 2, wherein the power supplied to the target has a power of less than 22 W / cm 2 power density.

10. The method of claim 1 or 2, wherein the power supplied to the target has a power of less than 20 W / cm 2 power density.

11. The method of claim 1 or 2, wherein the power supplied to the target has a power of less than 18 W / cm 2 power density.

12. The method of claim 1 or 2, wherein the power supplied to the target has a power of less than 16 W / cm 2 power density.

13. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of at least 7 mTorr.

14. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of at least 8 mTorr.

15. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of at least 9 mTorr.

16. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of at least 10 mTorr.

17. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of 20 mTorr or less.

18. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of 15 mTorr or less.

19. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of 12 mTorr or less.

20. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of 10 mTorr or less.

21. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, the chamber has a pressure of 8 mTorr or less.

22. The method of claim 1 or 2, wherein the DC magnetron sputtering step is performed at a temperature in the range of 300 to 500°C.

23. The method of claim 1 or 2, wherein the DC magnetron sputtering step is performed at a temperature of about 400°C.

24. The method of claim 1 or 2, wherein during the DC magnetron sputtering step, bias power is supplied to the substrate support. The method of claim 24 , wherein the bias power is an RF bias power.

26. The method of claim 24, wherein the bias power has a power in the range of 10 to 600 W.

27. The method of claim 24, wherein the bias power has a power of 50 to 500 W.

28. The method of claim 24, wherein the bias power has a power of 100 to 400 W.

29. The method of claim 24, wherein the bias power has a power of 200 to 300 W.

30. The method of claim 1 or 2, wherein the DC magnetron sputtering step comprises sputtering the metal material from the target using a plasma formed from the inert gas, the inert gas being argon (Ar), krypton (Kr), xenon (Xe) or a mixture thereof.

31. The method of claim 1 or 2, wherein the metal layer has a thickness of 300 nm or less.

32. The method of claim 1 or 2, wherein the metal layer has a thickness of 250 nm or less.

33. The method of claim 1 or 2, wherein the metal layer has a thickness of 200 nm or less.

34. The method of claim 1 or 2, wherein the metal layer has a thickness of 150 nm or less.

35. The method of claim 1 or 2, wherein the substrate support is separated from the target by a distance of 75 mm or less.

36. The method of claim 1 or 2, wherein the resonator device is an acoustic wave device.

37. The method of claim 36, wherein the acoustic wave device is a bulk acoustic wave (BAW) device.

38. A method of manufacturing a resonator device, comprising the steps of: (a) providing a substrate; (b) depositing a first metal layer onto the substrate; (c) depositing a piezoelectric layer onto the first metal layer; and (d) depositing a second metal layer onto the piezoelectric layer, wherein at least one of steps (b) and (d) is performed using the method of any one of claims 1 to 37.

39. A substrate comprising a molybdenum layer deposited using the method according to any one of claims 1 to 37, wherein the molybdenum layer has a resistivity less than 10 μΩ.cm, wherein the molybdenum layer has a stress range less than 250 MPa and has a thickness non-uniformity less than 1.5% 1σ.

40. A resonator device comprising a molybdenum layer deposited using the method of any one of claims 1 to 37, wherein the molybdenum layer has a resistivity less than 10 μΩ.cm, wherein the molybdenum layer has a stress range less than 250 MPa and has a thickness non-uniformity less than 1.5% 1σ.

41. The resonator device of claim 40, wherein the resonator device is an acoustic wave device.

42. The resonator device of claim 41, wherein the acoustic wave device is a bulk acoustic wave (BAW) device or a surface acoustic wave (SAW) device.

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