Deposition method

Abstract

To deposit additive-containing aluminum nitride films that have a low defect density and a high electromechanical coupling coefficient (Keff) and are suitable for use in resonator devices.SOLUTION: Provided is a method for sputter depositing an additive-containing aluminum nitride film containing an additive element selected from Sc and Y. Pulsed DC reactive sputtering is used to deposit a first layer of the additive-containing aluminum nitride film onto a substrate disposed within a chamber, and to deposit a second layer having the same composition as the first layer onto the first layer. In the first-layer deposition step (810), a gas or gaseous mixture, 87-100% of the flow rate (in sccm) of which is a flow of nitrogen gas, is introduced into the chamber. In the second-layer deposition step (812), a gaseous mixture, which comprises nitrogen gas and an inert gas, and the percentage of the nitrogen gas in the flow rate (in sccm) of which is lower than that in the first-layer deposition step, is introduced into the chamber.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for sputter depositing additive-containing aluminum nitride films, in particular to a reactive pulsed DC sputtering method for depositing additive-containing aluminum nitride films, such as scandium or yttrium-containing aluminum nitride films, and the invention relates to the additive-containing aluminum nitride films themselves as well as to piezoelectric devices comprising those films. [Background technology]

[0002] Applications of piezoelectric aluminum nitride (AlN) films include RF resonator devices, such as bulk acoustic wave (BAW) filters. The electromechanical coupling efficiency (K eff For example, the incorporation of scandium in the alloy at the expense of aluminum has been shown to improve the Al 100-x Sc x It is an aluminum nitride containing N type additive, and has a relatively high K eff As can be seen, the composition is Al 100-x Sc x When expressed in the N form, the values ​​100-x and x are expressed as percentages, and the percentage x can be equated to 0.01x in stoichiometric chemical terms. In particular, for use in resonant devices, c-axis oriented Al is preferred because this orientation provides a material with excellent piezoelectric properties. 100-x Sc x N membranes are preferred.

[0003] In order to manufacture higher quality RF resonator devices, it is desirable to increase the electromechanical coupling coefficient. For example, the electromechanical coupling coefficient (K eff) may be increased. However, as the amount of additive element present in the additive aluminum nitride increases, the tendency for crystallographic defects to form increases. Crystallographic defects reduce the quality and crystallinity of the additive aluminum nitride film. These crystallographic defects are piezoelectrically inactive and therefore have a detrimental effect on the electromechanical coupling coefficient of the additive aluminum nitride film. That is, the defects may exhibit little piezoelectric response and thus reduce the piezoelectric coupling per unit volume of the film. FIG. 1 shows an SEM image of observed crystallographic defects in an AlScN film made using known deposition methods. FIG. 2 shows a higher magnification SEM image of the crystallographic defects 20. In addition, these defects may be difficult to etch and may have a detrimental effect on the growth of subsequent layers and therefore may be impactful to subsequent processing steps.

[0004] Therefore, it is desirable to develop a method for increasing the amount of additive elements present in additive-containing aluminum nitride while maintaining an acceptable defect density and crystallinity (or texture). 2 A defect specification of less than 50 defects per square is desirable for producing high quality devices. Typically, a texture specification of less than 2.0° FWHM is desirable for producing high quality devices.

[0005] US Patent Publication 2005 / 0133963 discloses a method for depositing doped aluminum nitride films by reactive pulsed DC sputtering. However, further methods need to be developed to suppress defect levels in doped aluminum nitride films, especially when the dopant concentration is greater than about 8 atomic %. It is therefore desirable to further increase the dopant concentration (especially to greater than about 8 atomic %) while suppressing defects and improving film texture to levels suitable for commercial production of high quality RF resonator devices. A further condition for eventual commercialization would be that the method be able to be carried out in an economically viable manner. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] European Patent Application Publication No. 3153603 [Patent Document 2] European Patent Application Publication No. 2871259 [Non-patent literature]

[0007] [Non-Patent Document 1] Journal of Applied Physics, Vol.107, No.12, June 2010, Hoglund et al., "Wurtzite structure Sc1-xAlxN solid solution films grown by reactive magnetron sputter epitaxy: Structural characterization and first-principles calculations", pp.123515-1 - 123515-7. Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention, in at least some of its embodiments, seeks to address at least some of the problems, desires and needs set forth above. The present invention, in at least some of its embodiments, provides a method for manufacturing a semiconductor device having low defect density and low electromechanical coupling coefficient (K eff The present invention provides a method for depositing doped aluminum nitride films having high surface area and suitable for use in resonant devices. [Means for solving the problem]

[0009] A first aspect of the present invention is a method for sputter depositing an additive-containing aluminum nitride film containing an additive element selected from Sc and Y, comprising the steps of: depositing a first layer of the doped aluminum nitride film onto a substrate disposed in a chamber by reactive pulsed DC sputtering; depositing a second layer of the doped aluminum nitride film, the second layer having the same composition as the first layer, onto the first layer by reactive pulsed DC sputtering; having the first layer deposition step includes the step of introducing a gas or gas mixture into the chamber at a flow rate (unit: sccm), wherein 87-100% of the flow rate (unit: sccm) is a nitrogen gas flow; The second layer deposition step includes introducing a gas mixture into the chamber at a flow rate (unit: sccm), the gas mixture including nitrogen gas and an inert gas; The percentage of nitrogen gas in the flow rate (unit: sccm) used in the first layer deposition step is higher than the percentage of nitrogen gas in the flow rate (unit: sccm) used in the second layer deposition step.

[0010] The first layer can act as a seed layer. The first layer can provide nucleation sites for directional crystal growth of the second layer, e.g., in a c-axis orientation. It has been found that depositing the first layer in a highly nitrogen-rich atmosphere (e.g., 87-100%) allows for the incorporation of high concentrations of additive elements into the aluminum nitride material while maintaining acceptable levels of crystal defects, crystallinity, and texture.

[0011] The additive element may be scandium.

[0012] The amount of the additive element present may be in the range of 0.5 atomic % to 40 atomic %, and optionally in the range of 8 atomic % to 40 atomic %, 10 atomic % to 35 atomic %, 15 atomic % to 30 atomic %, or 20 atomic % to 25 atomic %. The amount of the additive element present may be greater than 8 atomic %, greater than 10 atomic %, greater than 15 atomic %, greater than 20 atomic %, or greater than 25 atomic %. The amount of the additive element present may be 40 atomic % or less. The additive element may be present in any combination of the upper and lower limits described above. The method of the present invention may be particularly useful for depositing additive-containing aluminum nitride films having high concentrations of the additive element (e.g., greater than 8 atomic %) while maintaining acceptable levels of defect density, crystallinity, and texture.

[0013] The flow rate (unit: sccm) used in the first layer deposition step can be 88% or more, 89% or more, 90% or more, 91% or more, 92% or more, 93% or more, 94% or more, 95% or more, 96% or more, 97% or more, 98% or more, 99% or more, or 100% can be nitrogen gas flow. The flow rate (unit: sccm) used in the first layer deposition step can be 90-100%, 94-100%, or optionally 98-100% can be nitrogen gas flow. The flow rate (unit: sccm) used in the first layer deposition step can include or be composed of a nitrogen gas flow and an inert gas flow, such as an argon flow.

[0014] The flow rate (unit: sccm) used in the first layer deposition step can be composed essentially of only nitrogen gas flow. Preferably, about 100% of the flow rate (unit: sccm) used in the first layer deposition step is nitrogen gas flow. That is, it is desirable that the flow rate (unit: sccm) used in the first layer deposition step is only nitrogen gas flow. The flow rate (unit: sccm) of the nitrogen gas used in the first layer deposition step can be 50 to 500 sccm, and optionally 60 to 250 sccm, 100 to 200 sccm, or about 150 sccm. The flow rate (unit: sccm) of the nitrogen gas used in the first layer deposition step can be more than 50 sccm, more than 60 sccm, more than 100 sccm, or more than 150 sccm. The flow rate (unit: sccm) of the nitrogen gas used in the first layer deposition step can be less than 500 sccm, less than 250 sccm, less than 200 sccm, or less than 150 sccm.

[0015] By using a nitrogen-rich or nitrogen-only atmosphere during deposition of the first layer, the defect density, crystallinity and texture of the resulting additive-containing aluminum nitride film can be significantly improved over known methods. These effects are particularly observed in nitrogen-only atmospheres. Taking various theories and hypotheses into account, depositing the first layer in a nitrogen-rich or nitrogen-only atmosphere has two beneficial effects. First, the number of argon atoms that are introduced into the first layer is reduced. This reduces the potential source of atomic defects, which may lead to crystallographic defects proliferating in the additive-containing aluminum nitride film. Second, since the target material is sputtered with only nitrogen instead of nitrogen and argon, it is believed that the sputtering efficiency of the target is reduced. Therefore, fewer aluminum (or additive element, e.g., Sc or Y) atoms are sputtered from the target. This is believed to increase the proportion of active nitrogen species in the deposition chamber, which is more likely to be deposited on the substrate. This results in a more nitrogen-rich first layer (e.g., initial seed layer) with fewer atomic point defects on the substrate. Therefore, there are fewer nucleation points for crystallographic defects to grow, thereby suppressing defect formation. In addition, there are more nucleation sites, which can be exploited to grow c-axis nitrogen-terminated AlScN in a well-oriented textured mode. 1-x Sc x N growth can enhance the piezoelectric properties of the doped aluminum nitride films. Overall, it can reduce the number and density of defects in the doped aluminum nitride films and improve the electromechanical coupling efficiency of the films. This allows for a higher concentration of the doped element to be present in the films while maintaining an acceptable level of defect density and texture.

[0016] The gas or gas mixture used in the first layer deposition step may comprise nitrogen gas and an inert gas. An example of the inert gas is a noble gas. A noble gas is understood to be a gas belonging to group 18 of the periodic table of the elements. The inert gas may be xenon, krypton, or preferably argon. If the percentage of the inert gas used in the first layer deposition step is increased to the level used in the known prior art, the beneficial effects of the present invention are not observed.

[0017] The flow rate of the gas mixture used in the second layer deposition step may be about 83% nitrogen gas and about 17% inert gas, for example argon. The flow rate of nitrogen in the gas mixture used in the second layer deposition step (unit: sccm) may be in the range of 50-250 sccm, optionally in the range of 75-150 sccm or about 83 sccm. The flow rate of the inert gas, for example argon, used in the second layer deposition step (unit: sccm) may be in the range of 8-50 sccm, optionally in the range of 10-25 sccm or about 17 sccm. In the reactive pulsed DC sputtering process, the inert gas does not chemically react with the species. The inert gas may be the sputter gas. The inert gas in the gas mixture used in the second layer deposition step may be a noble gas, for example xenon, krypton, and preferably argon. By noble gas, it is understood that a gas belongs to group 18 of the periodic table of elements.

[0018] The proportion of nitrogen gas in the gas or gas mixture used in the first layer deposition step is typically higher than the proportion of nitrogen gas in the gas mixture used in the second layer deposition step. Based on a combination of various theories and hypotheses, the use of a gas mixture containing a lower proportion of nitrogen gas for the second layer deposition can improve sputtering efficiency and increase the deposition rate during the second layer deposition.

[0019] The chamber pressure during the first layer deposition step may be between 2 and 6 mTorr, and optionally may be about 4 mTorr.

[0020] The chamber pressure during the second layer deposition step may be between 1.5 and 7.5 mTorr, and optionally may be about 3 mTorr.

[0021] The first layer may have a thickness of less than 70 nm, and optionally less than 60 nm, less than 50 nm, less than 30 nm, less than 25 nm, less than 20 nm or about 17 nm.

[0022] The second layer may be at least 6 times thicker than the first layer, and optionally at least 20 times, at least 25 times, at least 50 times, or about 60 times thicker.

[0023] The thickness of the doped aluminum nitride film may be at least 0.3 μm, at least 0.6 μm, or about 1 μm.

[0024] The thickness of the additive-containing aluminum nitride film can be 2 μm or less.

[0025] The first layer deposition step can be performed while applying a bias power to the substrate. The bias power applied to the substrate in the first layer deposition step can be an RF bias power. The bias power applied to the substrate in the first layer deposition step can be greater than 200 W or greater than 250 W. The bias power applied to the substrate in the first layer deposition step can be less than 350 W or less than 300 W. By applying a relatively large bias power (e.g., greater than 200 W) to the substrate, the deposited additive-containing aluminum nitride film can have a compressive stress. The inventors of the present invention have found that a first layer (e.g., a seed layer) that exhibits compressive stress usually results in a lower defect density and better texture and crystallinity of the resulting additive-containing aluminum nitride film.

[0026] The second layer deposition step can be performed without applying a bias power to the substrate or while applying a bias power to the substrate that is less than the bias power applied in the first layer deposition step. The bias power applied to the substrate in the second layer deposition step can be an RF bias power. The bias power applied in the second layer deposition step can be selected such that the total film stress (i.e., the stress of the first layer and the second layer) is about 0. The bias power applied in the second layer deposition step can be less than 100 W.

[0027] Reactive pulsed DC sputtering can be carried out using a magnetron.

[0028] Reactive pulsed DC sputtering typically involves the application of DC power pulses to a sputter target during sputter deposition. Reactive pulsed DC sputtering can be performed using a single target. The target can be a composite target formed of aluminum and an additive element. Using multiple targets is also possible, but may be less economically attractive.

[0029] The method may further comprise the step of etching a surface of the substrate prior to the first layer depositing step, such that the first layer is deposited on an etched surface of the substrate.

[0030] The substrate may be a silicon substrate.

[0031] The substrate may include a metal layer, e.g., a molybdenum layer, on which the first layer of the additive-containing aluminum nitride film is deposited. The method may further include depositing the metal layer on a substrate precursor. The first layer is deposited on the metal layer, e.g., a molybdenum layer, when the metal layer is deposited on the substrate precursor. The metal layer deposition step may be performed prior to the substrate etching step.

[0032] A second aspect of the present invention is an additive-containing aluminum nitride film produced by the method according to the first aspect.

[0033] A third aspect of the present invention is an additive-containing aluminum nitride film containing an additive element selected from Sc and Y, the amount of the additive element being within a range of 8 atomic % to 40 atomic %, optionally within a range of 10 atomic % to 35 atomic %, 15 atomic % to 30 atomic %, or 20 atomic % to 25 atomic %, and the defect density is 100 μm 2 The amount of the additional element present may be greater than 8 atomic %, greater than 10 atomic %, greater than 15 atomic %, greater than 20 atomic %, greater than 25 atomic %. The amount of the additional element present may be up to 40 atomic %. The range of the additional element present may be any combination of the upper and lower limits listed above.

[0034] A fourth aspect of the present invention is a piezoelectric device comprising the additive-containing aluminum nitride film according to either the second or third aspect of the present invention.

[0035] The piezoelectric device may be a bulk acoustic wave (BAW) device.

[0036] The piezoelectric device may include first and second electrodes with a doped aluminum nitride film deposited between the first and second electrodes.

[0037] The invention has been described above, but this extends to any combination of the features set out above or below in the description, drawings and claims, for example any feature disclosed in connection with one aspect of the invention may be combined with any feature provided in any of the other aspects of the invention.

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

[0039] [Figure 1]FIG. 13 shows an SEM image of an Al80Sc20N defect cluster. [Diagram 2] FIG. 1 shows an SEM image of one Al80Sc20N defect. [Diagram 3] FIG. 1 shows a TEM cross-sectional image of an Al80Sc20N defect group. [Figure 4] FIG. 1 is an illustration of a first layer in an AlScN film having point defects. [Diagram 5] FIG. 1 is an illustration of a first layer in an AlScN film that is free of point defects. [Figure 6] FIG. 13 shows an SEM image of an Al80Sc20N film with a 17 nm thick first layer exhibiting tensile stress. [Figure 7] FIG. 1 shows an SEM image of an Al80Sc20N film with a 17 nm thick first layer exhibiting compressive stress. [Figure 8] 1 is a flow chart illustrating a method of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] What the inventors have discovered is an advantageous process by which doped aluminum nitride films can be sputter deposited. The method can aid in improving the crystallinity and texture and reducing microcrystalline defects in doped aluminum nitride films. The doped aluminum nitride films contain an added element, such as scandium (Sc) or yttrium (Y). The results presented below show that aluminum scandium nitride (Al 1-x Sc x However, the method generally relates to aluminum yttrium nitride (Al 1-x Y x N) can also be applied.

[0041] The deposition of the film is carried out by reactive sputtering, for example reactive pulsed DC sputtering. General details regarding apparatus that may be used in, or readily adapted for, the present invention are described in the Applicant's European Patent Applications WO 2005 / 023363 and WO 2005 / 023991, which are hereby incorporated by reference in their entirety.

[0042] The apparatus has a chamber in which a substrate is placed. The apparatus further includes a target. The target is a composite target formed of aluminum and an additive element. The composition of the target determines the amount of additive element contained in the sputter deposited film. The use of multiple targets is possible, but may be less economically attractive. In pulsed DC sputtering, DC power pulses are applied to the target during the deposition process.

[0043] In a first step, a first layer of the additive-containing aluminum nitride film is sputter deposited from the target onto a substrate placed in a chamber. The first layer is deposited by reactive pulsed DC sputtering. The first layer can be a seed layer. During the deposition of the first layer, a gas or gas mixture containing nitrogen and optionally also an inert gas, such as argon, is introduced into the chamber. The flow rate of the nitrogen gas in the first step (unit: sccm) is 87-100% of the total gas flow rate in the first step (unit: sccm). Optionally, the flow rate of the nitrogen gas in the first step (unit: sccm) is 90-100%, 95-100%, 98-100% or about 100% of the total gas flow rate in the first step (unit: sccm). Preferably, the gas or gas mixture is composed exclusively of nitrogen gas. A typical thickness of the first layer is less than about 70 nm, less than 60 nm, less than 50 nm, preferably less than 20 nm. In some embodiments, the first layer has a thickness of about 17 nm.

[0044] In a second step, a second layer of the additive-containing aluminum nitride film is subsequently deposited on the first layer, e.g., the initial seed layer. The deposition of the second layer can be a bulk deposition. The deposition of the second layer is performed by reactive pulsed DC sputtering. During the deposition of the second layer, a second gas mixture containing nitrogen and an inert gas, e.g., argon, is introduced into the chamber. Other inert gases, e.g., xenon and krypton, can be envisaged, but are less desirable due to their high cost. The proportion of nitrogen gas in the second gas mixture is typically lower than the proportion of nitrogen gas in the first gas or gas mixture. In one embodiment, the flow rate of nitrogen gas in the deposition of the second layer is 83 sccm, and the flow rate of argon gas is 17 sccm. That is, the flow rate of nitrogen gas in the second step is about 83% of the total flow rate (unit: sccm).

[0045] For experiments on silicon substrates, typical deposition parameters are shown in Table 1. [Table 1]

[0046] 1μm Al 80 Sc 20 N films were sputter deposited on silicon substrates using the method described above and a single target. Table 2 shows the effect of varying the nitrogen gas ratio during the deposition of the first layer (i.e., the initial seed layer) on the resulting 1 μm Al 80 Sc 20 Defect density in N films (100 μm 2 The defect density was determined using scanning electron microscope (SEM) images at 6000x magnification. Table 3 shows how varying the nitrogen gas ratio during the deposition of the first layer (i.e., the initial seed layer) affects the Al deposited accordingly. 80 Sc 20The results show how the texture of the silicon substrate affects the texture of the N film. The texture (or crystallinity) of the specimens at the center, mid-radius and edge of the substrate was determined using X-ray diffraction (XRD) full width at half maximum (FWHM) measurements. A lower FWHM value corresponds to a higher crystallinity of the film. Prior to the deposition process, the silicon substrate was subjected to a 2 min degassing step at 350°C. The example shown in the last row of Tables 2 and 3 incorporates an additional step of subjecting the substrate to a 7.5 nm low bias etch step at 350°C prior to the sputter deposition process. A commercially available SE-LTX module from SPTS Technologies Limited is suitable for carrying out these pre-treatment degassing and etching steps. (As shown in Tables 2 and 3) 80 Sc 20 The N film comprises a 17 nm thick compressive first layer (e.g., initial seed layer) and a 983 nm second layer (e.g., bulk layer). The first layer was deposited using a 300 W RF bias on the platen. The second layer was deposited using a RF bias power selected to achieve zero stress across the entire film, i.e., zero stress across both the first and second layers. Typically, the bias applied to the platen in the second step is lower than the bias applied to the platen in the first step. The nitrogen gas flow rate for the second layer deposition was 83 sccm and the argon gas flow rate was 17 sccm. [Table 2] [Table 3]

[0047] As shown in Table 2, as the nitrogen gas ratio (i.e., percentage flow) increases, the defect density at the edge, mid-radius, and center of the substrate decreases. As shown in Table 3, as the nitrogen gas ratio in the first (seed) step increases, the texture (0002) FWHM values ​​at the edge, mid-radius, and center of the substrate tend to decrease. These effects are most evident when the gas used in the first layer (seed layer) deposition consists of only nitrogen gas.

[0048] Taking into account various theories and hypotheses, crystallographic defects are caused by point defects, such as atom misalignment, atom misplacement, and atomic vacancies. It is believed that most of the crystal defects in AlScN films originate from the surface of the substrate material on which the AlScN film is grown. The resulting defects then grow in the film and become observable at the film surface. Figure 3 shows the crystallographic defects of AlScN films. 80 Sc 20 TEM cross-section of crystal defects 30 in an AlScN film. The defects 30 proliferate in the film. These defects are particularly prominent in additive-containing aluminum nitride films where the atomic concentration of the additive element (e.g., Sc or Y) is greater than about 8 atomic %. It is believed that in an AlScN film, the AlScN grains can be nitrogen or aluminum (scandium) terminated. Based on a combination of various theories and hypotheses, when a nitrogen layer is deposited as the initial atomic layer, crystallographic defects will form when other atoms also penetrate into the initial nitrogen atomic layer. FIG. 4 shows a point defect formed by the penetration of an Al / Sc atom 40 into the initial nitrogen atomic layer. This defect can proliferate in the AlScN film. Based on a combination of various theories and hypotheses again, increasing the nitrogen gas content in the first layer deposition is favorable for depositing a seed layer that is substantially free of point defects. For example, the initial atomic layer 50 (as shown in FIG. 5) will be composed substantially of only nitrogen.

[0049] It is desirable to use a nitrogen-rich or pure nitrogen atmosphere during deposition of the first layer (i.e., initial seed layer) to reduce the number and density of defects in the additive-containing aluminum nitride film and improve the electromechanical coupling efficiency of the film. This allows for a higher concentration of the additive element to be present in the film while maintaining an acceptable level of defect density and texture. Maintaining an acceptable level of defect density and texture in additive-containing aluminum nitride films having a high concentration of the additive element (e.g., >8 atomic %) is not easily achievable using known methods, such as those that use less than about 83-87% nitrogen gas in the first step deposition.

[0050] The Al shown in Tables 2 and 3 80 Sc 20 The AlN film is grown by depositing a compressive initial seed layer. 80 Sc 20 The 1 μm AlN film was prepared by bulk deposition so that the total stress in the film was zero. The stress in the deposited film can be controlled by changing the substrate bias power. Table 4 shows the results of the first layer with tensile or compressive stress. 80 Sc 20 The figure shows how the XRD-FWHM measurement value of the 1 μm AlN film changes. 80 Sc 20 The AlN film was formed by introducing only nitrogen gas into the chamber during the deposition of the first layer. The thickness of the first layer was 17 nm, and the thickness of the second layer (bulk layer) was 983 nm. Figures 6 and 7 show the AlN film deposited with a tensile and compressive first layer, respectively. 80 Sc 20 The SEM image of the N surface shows the Al deposited with a compressive first layer. 80 Sc 20 The N film has a tensile first layer and a deposited Al layer. 80 Sc 20 It exhibits lower defect density and improved texture compared to the N film. [Table 4]

[0051] The effects of the substrate material and surface condition were investigated. 80 Sc 20 A Mo film was deposited on a Mo-coated substrate using a single composite target. Other metal materials can be used as the coating material instead of Mo. The Mo-coated substrate was prepared according to the method shown in FIG. 8. First, the substrate precursor was degassed (step 802). A Mo coating was deposited on the degassed substrate precursor in a Mo deposition module (step 806). The Mo coating was etched using a low bias etch procedure (step 808). The substrate was then transferred to a sputter deposition module where a two-step AlScN deposition process was performed (steps 810 and 812). In the two-step AlScN deposition process, i) a first layer was deposited on the Mo-coated surface of the substrate in a nitrogen-rich or pure nitrogen atmosphere (step 810), followed by ii) a second layer was deposited on the first layer (i.e., bulk deposition) (step 812). The process conditions used in steps 810 and 812 can be similar or different to those described above in connection with other embodiments of the present invention.

[0052] Tables 5 and 6 show the results of 1 μm Al on a molybdenum (Mo)-coated substrate using the method of FIG. 80 Sc 20 We show how the defect density and texture of N films change by changing the nitrogen gas ratio in the first layer deposition. [Table 5] [Table 6]

[0053] As shown in Tables 5 and 6, by using only nitrogen gas in the gas phase atmosphere during deposition of the first layer, the 1 μm Al 80 Sc 20It can reduce defect density and improve texture for AlScN. In addition, conditioning the surface of the substrate by mild etching prior to AlScN deposition can also help suppress the formation of crystallographic defects and improve the texture and crystallinity of the resulting AlScN film.

[0054] The effect of the thickness of the first layer on the defect density, crystallinity and texture was investigated. 80 Sc 20 A N film was prepared on a Mo-coated substrate using only nitrogen gas during the first layer deposition. The Mo substrate was prepared according to the method in FIG. 8. The thickness of the first layer was varied and the texture of the resulting film was measured using XRD-FWHM measurements. The results are shown in Table 7. A thinner first layer resulted in a more textured (i.e., improved texture) AlN film. 80 Sc 20 N film was obtained. This effect is more pronounced at the edge of the substrate. The preferred thickness of the first layer is typically less than 70 nm, less than 60 nm, less than 50 nm, less than 30 nm, less than 25 nm or less than 20 nm. [Table 7]

[0055] In particular, it has been found that in combination with deposition of a thin first layer in a nitrogen-rich or pure nitrogen atmosphere, defect density is significantly reduced and crystallinity and texture are improved. These beneficial effects are observed even at high concentrations of the additive element. Thus, the method of the present invention is particularly suitable for depositing additive-containing aluminum nitride films having high concentrations of the additive element while maintaining acceptable levels of defect density, crystallinity and texture.

[0056] By using the above-mentioned method, it is possible to obtain an aluminum nitride film containing an additive, e.g., Al 1-x Sc x N can be deposited with various additive element concentrations. 1-x Sc xN films were deposited on bare silicon substrates with 0 at%, 9 at%, 15 at%, and 20 at%. The deposition of the additive-containing aluminum nitride films was performed from a single composite target. The composition of the target determined the amount of additive material in the deposited film. RF bias power of 200-350 W was applied to the substrate during the deposition of the first layer. Only nitrogen gas was introduced into the chamber during the deposition of the first layer. That is, the flow rate during the first layer deposition step consisted of only nitrogen gas flow. The thickness of the first layer was about 20 nm. The texture of the deposited film was measured at the edge and center, with the results shown in Table 8. [Table 8]

[0057] According to the inventors of the present invention, when depositing a first layer (e.g., an initial seed layer) of about 20 nm, 100% of the flow rate (unit: sccm) is a nitrogen gas flow (N 2 ), the texture of the deposited film is improved over a range of additive element concentrations. Improvements are observed at all additive element concentrations. This is particularly advantageous at higher additive element concentrations where known conventional methods result in unacceptable levels of defects and poor texture. The method allows for the achievement of acceptable texture and defect density at additive element concentrations of 8 at.%, 9 at.%, 10 at.%, 15 at.%, 20 at.% and above 25 at.%.

Claims

1. A method for producing an additive-containing aluminum nitride film containing an additive element selected from Sc and Y by sputter deposition, comprising the steps of: depositing a first layer of the additive-containing aluminum nitride film on a substrate disposed in a chamber by reactive pulsed DC sputtering, the additive-containing aluminum nitride film being deposited under compressive stress by an applied bias power; depositing a second layer of the doped aluminum nitride film, the second layer having the same composition as the first layer, onto the first layer by reactive pulsed DC sputtering; having the step of depositing the first layer includes the step of introducing a gas or gas mixture into the chamber at a flow rate (unit: sccm), wherein 87-100% of the flow rate (unit: sccm) is a nitrogen gas flow; the second layer depositing step includes introducing a gas mixture into the chamber at a flow rate (in sccm), the gas mixture including nitrogen gas and an inert gas; the percentage of nitrogen gas in the flow rate (unit: sccm) used in the first layer deposition step is higher than the percentage of nitrogen gas in the flow rate (unit: sccm) used in the second layer deposition step; The method, wherein the substrate is a silicon substrate or a metallized substrate which has been degassed and etched.

2. 2. The method of claim 1, wherein the additive element is scandium.

3. 3. The method according to claim 1, wherein the amount of the added element present is within the range of 0.5 atomic % to 40 atomic %.

4. 4. The method according to claim 1, wherein the flow rate (unit: sccm) used in the first layer deposition step is 90 to 100% nitrogen gas flow.

5. 5. The method of claim 4, wherein the flow rate (in sccm) used in the first layer deposition step consists essentially of a nitrogen gas flow.

6. The method according to any one of claims 1 to 5, wherein the nitrogen gas flow used in the first layer deposition step is in the range of 50 to 500 sccm.

7. 10. The method of claim 1, wherein the gas or gas phase mixture used in the first layer deposition step comprises nitrogen gas and an inert gas.

8. The method according to any one of claims 1 to 7, wherein the chamber pressure in the first layer deposition step is in the range of 2 to 6 mTorr.

9. The method according to any one of claims 1 to 8, wherein the chamber pressure in the second layer deposition step is in the range of 1.5 to 7.5 mTorr.

10. The method according to any one of claims 1 to 9, wherein the first layer has a thickness of less than 70 nm.

11. 11. The method according to claim 1, wherein the thickness of the additive-containing aluminum nitride film is 0.3 μm or more, 0.6 μm or more, or 1 μm or more.

12. 12. The method according to claim 1, wherein the thickness of the additive-containing aluminum nitride film is 2 μm or less.

13. The method according to any one of claims 1 to 12, wherein the first layer deposition step is carried out whilst applying a bias power to the substrate.

14. 10. The method of claim 9, wherein the second layer deposition step is performed without applying a bias power to the substrate or while applying a bias power to the substrate that is less than the bias power applied in the first layer deposition step.

15. A method according to any one of claims 1 to 14, further comprising the step of etching a surface of the substrate prior to the first layer deposition step, such that the first layer is deposited on an etched surface of the substrate.

16. The method according to any one of claims 1 to 15, wherein the substrate is a silicon substrate.

17. A method according to any one of the preceding claims, wherein the substrate comprises a metal layer and the first layer of the doped aluminium nitride film is deposited on the metal layer.

18. 20. The method of claim 17, further comprising depositing the metal layer on a substrate precursor.

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