Conductive sputtering target and method of depositing layer using same

Abstract

A target (2) for sputtering in an intermediate frequency alternating current sputtering process or direct current sputtering process, the target (2) comprising a layer (21) of target material predominantly comprising M-doped LixPOy, where x is from 2.5 to 3.5 and where y is from 2.5 to 4.5, where M represents at most 40% by weight of the layer (21) of target material, and where M is at least one chemical element from Groups 13 to 15 of the Periodic Table of Elements, wherein M is selected to provide electrical conductivity to the target material layer (21) such that the resistivity of the target material layer (21) at room temperature is at most 1000 Omega * cm, and wherein the target material layer (21) has a lamellar structure consisting of microsplutters (3) of material.

Description

Technical Field

[0001] The present invention relates to the field of sputtering targets. More specifically, the present invention relates to a conductive sputtering target that can be used to deposit a LiPON layer, a method of forming the conductive sputtering target, and a method of sputtering the conductive sputtering target. Background Art

[0002] The technique of material deposition by sputtering has been known for decades. Typically, a plasma is generated in a low-pressure chamber in the presence of an inert gas (such as argon) and / or a reactive gas (such as oxygen or nitrogen), and a negative voltage is applied to a so-called "sputtering target" (i.e., a target for sputtering, which contains the material to be deposited), with the intention of depositing a layer of the sputtered material onto a "substrate". The gas atoms may be ionized, and the sputtering target is bombarded by the gas ions, causing the atoms to break away from the sputtering target and move to the substrate, where they are deposited.

[0003] In such sputtering processes, three power sources are typically used: a DC power source, an AC or pulsed power source (in the kHz range, such as a frequency of 1 to 100 kHz), and an RF power source (in the MHz range, such as a frequency of 0.3 to 100 MHz). When the deposited material forms a substantially conductive layer, a DC power source is typically used. When the deposited layer has a lower conductivity or is a dielectric, an AC power source is typically used. Although high-frequency power sources (RF power sources) are capable of sputtering materials of low conductivity, uniform deposition over a larger substrate area is challenging due to the standing wave effect. In addition, the sputtering rate for the same power level is typically significantly lower compared to the DC process. In addition, the application of RF power is not simple (due to problems associated with impedance matching, shielding, etc.), and RF sputtering requires a very expensive power supply (price / kW) while providing only a limited maximum power. In addition, it is difficult to uniformly apply such an RF field across a target of large size (e.g., a scale of more than 0.5m, or even 1m or more), which is preferably used for commercial manufacturing to coat substrates with large surface areas. Therefore, it is more difficult to obtain certain types of layers particularly uniformly across larger substrates.

[0004] The dielectric material LiPON has received increasing attention, especially for its use as an electrolyte material. The main reasons for this are: its wide stability window, i.e. from 0 to 5 V, relative to Li + / Li; its reasonable ionic conductivity (about 10 -6 S / cm); and its low electronic conductivity (electronic resistivity is about 10 14 Ω*cm). Currently, LiPON is used in commercial thin film batteries as the most commonly used solid electrolyte in the thin film battery industry. One technique for forming the LiPON layer is to deposit the LiPON material by sputtering.

[0005] LiPON can be deposited by sputtering from a Li3PO4 target. In fact, when Li3PO4 is sputtered in a reactive gas atmosphere containing nitrogen so that a nitrogen plasma is formed during sputtering, the nitrogen is incorporated into the layer, resulting in the formation of LiPON. Since the Li3PO4 target is a dielectric, i.e., non-conductive, it is typically necessary to use a radio frequency (RF) alternating field to maintain long-term stable sputtering. Therefore, sputtering LiPON from a Li3PO4 target may have any of the problems associated with RF sputtering described above.

[0006] Some prior art documents describe possible solutions to these problems. US11081325B2 discloses a conductive target comprising a region formed of Li3PO4 and a different region formed of carbon. In addition, the target comprises a permeated region of Li2CO3, which can improve the conductivity of the target. During sputtering, the carbon in the target can react with the oxygen in the sputtering atmosphere to form CO and CO2, which can be pumped out of the system, so that the carbon is not incorporated into the deposited layer.

[0007] WO2015158607A1 discloses a target comprising LiPON, which is used to form a solid electrolyte layer comprising LiPON. The target is made conductive by the presence of conductive materials such as carbon, polymers and salts, such as lithium salts or ammonium salts. The conductive material can be converted into an inert material during sputtering and may not be present in the deposited solid electrolyte layer, or may be included therein only in a small amount or in a modified form. Therefore, the layer properties of the solid electrolyte layer are not negatively affected. In particular, carbon can react with oxygen in the reaction chamber to form CO and CO2. For example, the decomposition products of a conductive polymer used as a conductive material can be incorporated into the deposited solid electrolyte layer. When the material is a salt, the components of the corresponding ions forming the salt are also deposited on the solid electrolyte layer or maintained in the gas phase.

[0008] WO2007042394A1 describes a target that can be formed from LiPON, which is made conductive by adding a doping element. The doping element or its reaction product (e.g., by reaction with a sputtering gas) can sublime or evaporate during the sputtering process. Due to the sublimation or evaporation of the doping element, the deposited coating, such as LiPON, does not contain the doping element. Some preferred doping elements are tin, bismuth and antimony. In particular, tin can form an oxide with a low evaporation / sublimation temperature. The target can be heated to a temperature higher than the atmosphere temperature in the sputtering chamber to prevent oxidized doping materials from being deposited in the deposited coating.

[0009] However, there remains room in the art for alternative devices and methods that address at least some of the above-mentioned issues. Summary of the invention

[0010] It is an object of the present invention to provide a good target for providing a layer mainly comprising LiPON on a substrate by sputtering. Another object of the present invention is to provide a good method for depositing a layer using said target for sputtering.

[0011] The above objects are achieved by devices and methods according to embodiments of the present invention.

[0012] An advantage of embodiments of the present invention is that material is present in the target material layer to make it conductive and during deposition by sputtering the material reacts to form an insulating layer. As a result, the target can be conductive while the deposited layer can be electrically insulating.

[0013] An advantage of embodiments of the present invention is that the target can be used in a medium frequency AC sputtering process or a DC sputtering process, such as a pulsed DC sputtering process. The frequency of the periodic variation of the electrical signal used in these sputtering processes can be between 0 Hz (DC) and up to 250 kHz, but more typically between 20 kHz and 100 kHz.

[0014] Another advantage of embodiments of the present invention is that the target material has a lamellar structure consisting of microscopic splats. Thus, the target can have a continuous and large single surface area and can have a large thickness and therefore a large material inventory, which can allow large-area coatings to be deposited without having to frequently replace the target, thereby limiting the downtime of the sputtering system using the target of the present invention.

[0015] An advantage of embodiments of the present invention is that the formation of a highly resistive deposited layer (such as an electrolyte layer) containing LiPON can be facilitated. The electrolyte layer acts as a conductor of ions but has a high resistivity for electrical conduction (driven by electrons).

[0016] In a first aspect, the present invention relates to a target that can be used for sputtering in a medium frequency AC sputtering process or a DC sputtering process, wherein the DC sputtering process can be a pulsed or non-pulsed DC sputtering process. The target comprises a target material layer, which mainly comprises M-doped Li x PO y, i.e. at least 50 wt %, such as at least 60 wt %, or even more, such as at least 80 wt %, at least 90 wt %, at least 95 wt %, at least 97 wt % of the target material layer weight. Here, x is 2.5 to 3.5, y is 2.5 to 4.5, and M accounts for up to 40 wt %, such as up to 30 wt %, such as up to 25 wt %, such as up to 20 wt % of the target material layer. In a specific embodiment, M accounts for at least 1 wt %, such as at least 5 wt %, such as at least 10 wt % of the target material layer. M comprises at least one chemical element selected from Groups 13 to 15 of the Periodic Table of Elements (according to the IUPAC group numbering), and is selected to provide electrical conductivity to the target material layer, so that the resistivity of the target material layer at room temperature (i.e. 20° C.) is at most 1000 Ω*cm. The M additive is preferably not oxidized or nitrided, since its main purpose is to provide electrical conductivity at the target level. In addition, Li x PO y It may be substoichiometric, which may help to further improve the conductivity of the target.The target material layer has a lamellar structure consisting of microscopic sputtered flakes of material, such as is typically produced by spraying.

[0017] An advantage of embodiments of the present invention is that the sputtered sheet structure results in reduced stress in the target so that the target can be thick without risk of target cracking during sputtering.

[0018] The target material layer formed by the sputtering of the material may result in pores in the target material layer. The target material layer may have a porosity (defined as the pore volume per unit volume of the target material layer in the target material layer) of at least 0.1%, preferably at least 0.5%, and more preferably at least 1%. The target material layer may have a porosity of less than 20%, preferably less than 10%, and more preferably less than 5%. The pores may be beneficial in reducing internal stress and mechanical damage during target manufacturing or sputtering deposition.

[0019] In an embodiment, the target material layer comprises at least 80 wt %, such as at least 90 wt %, such as at least 95 wt %, such as at least 97 wt % of M-doped Li x PO y .

[0020] In an embodiment, M accounts for 0.01 wt % to 40 wt %, such as 1 wt % to 40 wt %, such as 5 to 25 wt %, such as 10 to 20 wt % of the total weight of the target material layer. In an embodiment, M accounts for M-doped Li of the target material layer. x PO y 0.01 wt% to 40 wt%, for example 1 wt% to 40 wt%, such as 5 to 25 wt% of the total weight of the fraction.

[0021] In an embodiment, selecting M so as to provide conductivity to the target material layer means at least that M is present in the target in a conductive form. For example, preferably, the dopant M is in a non-oxidized or non-nitrided state, in particular when M is a metal or a metalloid. For example, when M is a metal, it is preferably present in the target material layer in a metallic state. In addition, although, for example, elemental nitrogen is typically electrically insulating (therefore, excluding it as at least one chemical element of the M described), M can be a conductive compound containing nitrogen. Furthermore, M can also be an oxygen-containing conductive compound. In an embodiment, M can include any material configured to provide conductivity to the target material layer, and is formed by at least one chemical element of Groups 13 to 15 of the periodic table, which can include, for example: conductive carbon compounds, such as graphene; conductive polymers; or metals and / or metalloids.

[0022] In an embodiment, M comprises or consists of at least one chemical element from the 2nd to 4th periods of the periodic table. In an embodiment, M comprises or consists of at least one chemical element selected from boron, aluminum, gallium, silicon, germanium, nitrogen, phosphorus and arsenic. In a specific embodiment, M comprises or consists of at least one metal and / or metalloid element. The following elements are understood to be metalloid elements: boron, silicon, germanium, arsenic, antimony and tellurium. In an embodiment, M is a metal and / or metalloid. In an embodiment, M comprises or consists of at least one chemical element from the 13th group of the periodic table. In an embodiment, M comprises or consists of at least one chemical element selected from silicon, boron, aluminum and gallium. In a specific embodiment, M is aluminum. The advantage of these embodiments is that metals and metalloids typically have high electrical conductivity. Another advantage of these embodiments is that metals and metalloids can react with reactive gases such as nitrogen or oxygen during sputtering to form nitrides or oxides that are typically electrically insulating. This material can then be combined with LiPON (which is composed of Li x PO y In the embodiment, M is a material having a resistivity of at most 1000 Ω*cm, preferably at most 10 Ω*cm, and more preferably at most 0.1 Ω*cm.

[0023] In an embodiment, the target is a cylindrical target. A cylindrical target can facilitate uniform use of the target material, such as when the cylindrical target is rotated during sputtering. However, the present invention is not limited to any target shape, but rather, the target can be, for example, planar, such as typically rectangular or circular, or prismatic.

[0024] In certain embodiments, the microscopic sputter comprises a first region of M and Li x PO y In other words, there may be substantially no M and Li in the target material layer. x PO y In an embodiment, the microscopic sputtering sheet may include a first microscopic sputtering sheet formed of M and a first microscopic sputtering sheet formed of Li x PO y In an alternative embodiment, a single microscopic sputter may include a first region of M and a second microscopic sputter formed. x PO y The second area.

[0025] In embodiments, selecting M to provide conductivity to the target material layer means that the structure of the target material layer is such that there is a conductive path that permeates through the target material layer. In other words, preferably, an uninterrupted path of M (i.e., not blocked by Li x PO y discontinuities, or, when present, another electrically insulating material) are present in the target material layer. To achieve this, for at least some of the sputtered sheets, the first regions of M of adjacent sputtered sheets may be in electrical contact with each other. An advantage of these embodiments of the invention is that the conductivity of the target material layer may be substantially defined by the conductivity of M. An advantage of these embodiments is that the front surface of the target material layer (from which the target material may be sputtered) may be electrically coupled to the rear surface of the target material layer (which may contact a backing substrate to which an AC or DC sputtering voltage may be applied). However, the invention is not limited to uninterrupted M paths: for example, regions of non-M material (e.g., Li+) between discontinuous regions formed by M may be formed by a layer of non-M material (e.g., Li+). x PO y ) can be sufficiently thin so as not to significantly inhibit the electrical conduction of the entire target material layer. To this end, M can be provided in an amount of at least 1 wt % of the total weight of the target material layer, such as at least 5 wt %, preferably greater than 10 wt %. In addition, by non-M materials (such as Li x PO y The electronic conductivity of the region formed by the MgO2O3 may be due to the presence of defects, and electronic conduction along the grain boundaries is also possible.

[0026] The resistivity may be the resistivity between two different locations through the target material layer (eg, between the front and back surfaces of the target material layer). The resistivity may be measured by any method known to those skilled in the art.

[0027] In some embodiments, the target is composed of a target material layer. However, preferably, the target also includes a backing substrate, such as a backing plate, in electrical contact with the target material layer (however, the backing substrate is not limited to any shape). In an embodiment, the target material layer is bonded to the backing substrate by means of a specific interface morphology and / or a conductive adhesive layer. For example, the adhesive layer may include a metal, a metal compound, a metal-doped epoxy resin, or a metal-doped elastomer, but the present invention is not limited thereto. The interface morphology may include or consist of a specific roughness to facilitate mechanical interlocking of the target material layer to the backing structure.

[0028] In the present invention, the target material layer has a lamellar structure. The lamellar structure includes fine distinguishable layers (at the microscopic level), called lamellae. In the present invention, the lamellae is formed by splashes of raw materials sprayed onto the target backing substrate, for example in a molten, semi-molten or non-molten form. The lamellae is formed when the raw material impacts the backing substrate. In an embodiment of the present invention, the lamellae can be a layer with a thickness of 0.1 μm to 10 μm. Different lamellae can have different degrees of crystallinity, different densities, etc. The lamellae can be formed by microscopic splashes of material, with an average volume of, for example, 0.00001 to 0.001 mm³, for example, 0.0001 mm³, depending on the target manufacturing conditions (e.g., powder of sprayed particles). The composition of the lamellae depends on the raw material that has been sprayed. In an embodiment of the present invention, the lamellar structure is due to a spraying process, such as, but not limited to, a thermal spraying process.

[0029] In a second aspect, the present invention relates to a method for forming a target for sputtering. The target thus formed can be used for sputtering in a medium frequency AC sputtering process or a DC sputtering process. The method includes providing a powder, the powder comprising: particles of lithium phosphate and particles of M; and / or particles of M-doped lithium phosphate. Here, M comprises at least one chemical element from Groups 13 to 15 of the periodic table. The method also includes providing a backing substrate. The method also includes spraying a sputtered sheet formed when the powder impacts onto the backing substrate to form a Li-doped M-doped x PO y A target material layer, wherein x is 2.5 to 3.5, and wherein y is 2.5 to 4.5, wherein M accounts for up to 40 wt % of the total target material, and wherein M is selected to provide conductivity to the target material layer so that the resistivity of the target material layer at room temperature (i.e., 20° C.) is up to 1000 Ω*cm. An advantage of using spraying to form a target for sputtering is that the target material layer can have a structure consisting of sputtered flakes of the target material. Such a sputtered flake-like structure can have the following advantages: stress in the target material layer can be relaxed, so that a large target can be formed.

[0030] Typically, the powder has (i.e., the particles have on average) a particle size suitable for forming the M-doped Li xPO y Typically, the powder and the target material layer formed from the powder typically have substantially the same composition. However, this does not necessarily mean that each particle is composed of M-doped Li x PO y , Li x PO y In fact, the composition of some particles may be different: for example, although at least some of the (eg, M-doped) lithium phosphate particles may be composed of (eg, M-doped) Li x PO y Formed, but at least some other (e.g., M-doped) lithium phosphate particles may be formed of (e.g., M-doped) Li4P2O7 or Li3PO4. In embodiments, the M-doped lithium phosphate particles may include lithium phosphate having M on its surface, for example, coated with M.

[0031] In a specific embodiment in which the powder comprises particles of lithium phosphate and particles of M, the particles of M may account for up to 40% by weight of the powder, such as up to 30% by weight, such as up to 20% by weight. In these specific embodiments, the particles of M may account for at least 1% by weight of the powder, such as at least 5% by weight, such as at least 10% by weight.

[0032] In an embodiment, providing a backing substrate comprises providing a backing substrate comprising a specific interface morphology and / or an adhesive layer. In an alternative embodiment, providing a backing structure and providing a specific interface morphology and / or an adhesive layer on the backing structure can be two independent steps. The specific interface morphology and / or the adhesive layer can be configured to fix the splash sheet to the backing substrate during the spraying of the powder onto the backing substrate.

[0033] In embodiments, the spraying is thermal spraying. In embodiments, the spraying includes melting particles, or at least partially melting particles, which can include heating the particles to a temperature that is at least the melting temperature of the particles, for example, at least the melting temperature of M and / or at least the melting temperature of lithium phosphate. In the thermal spraying process, superheated molten or semi-molten particles are sprayed at high speed onto a much colder carrier material in proportion, and rapidly solidify with a typical spatter-like microstructure, thereby forming a coating of desired thickness. Controlling the production temperature and microstructure of the thermal spray target material layer allows minimizing its internal stress, therefore, minimizing the risk of target failure caused by cracking or fragmentation during sputtering, particularly in the case of ceramic materials. However, other spraying techniques, such as cold spraying, may also be used.

[0034] In some embodiments, the surface of the target layer can be polished to reduce its roughness and possible subsequent problems during sputtering, such as arcing.

[0035] In a third aspect, the invention relates to a method for depositing a layer on a substrate. The method comprises obtaining a target according to an embodiment of the first aspect of the invention. The method further comprises sputtering a target material from a target material layer of the target onto a substrate in a reactive gas atmosphere comprising at least N2. The sputtering is performed so that M reacts with components of the reactive gas atmosphere to form an electrically insulating material to form a deposited layer comprising LiPON and the electrically insulating material. An advantage of embodiments of the invention is that during sputtering, M that provides electrical conductivity to the target can be converted into an insulating material and, together with Li x PO y LiPON formed by reaction with N2 is deposited in the deposition layer. In an embodiment, the relative amounts of Li, P and M in the deposition layer are substantially the same as those in the target material layer, however, the present invention is not limited thereto.

[0036] In an embodiment, the sputtering is DC sputtering or AC sputtering with a frequency of up to 250 kHz. In an embodiment, the DC sputtering process can be non-pulsed or pulsed DC sputtering, wherein the pulse frequency, i.e., the periodic variation frequency of the electrical signal, is from 0 Hz to 250 kHz, more typically from 20 kHz to 100 kHz. An advantage of these embodiments is that the sputtering process can be highly efficient.

[0037] In an embodiment, the sputtering is performed so that during the sputtering, M reacts with nitrogen to form a nitride of M. Nitrides of chemical elements of Groups 13 to 15 of the Periodic Table of Elements are generally electrically insulating. Examples include: AlN, which has a resistivity exceeding 10 11 Ω*cm; BN, whose resistivity exceeds 10 14 Ω*cm; and Si3N4, whose resistivity exceeds 10 13 Ω*cm. However, N2 is preferred for the reaction with M, since N2 is available for the reaction with Li x PO y In the embodiment, the reactive gas atmosphere in the sputtering chamber may further comprise an inert gas, such as Ne, Ar, Kr or Xe, preferably Ar.

[0038] In embodiments, the pressure of the atmosphere in the sputtering chamber is typically 0.1 Pa to 10 Pa. Typically, a controlled flow of reactive gas into the vacuum chamber is used to compensate for any loss of N2 and possibly O2 due to their reaction with the target material layer. Thus, the composition of the reactive gas atmosphere can remain the same during sputtering.

[0039] In an embodiment, the sputtering is performed to form a layer having a resistivity of at least 10 4 Ω*cm, at least 10 7 Ω*cm, preferably at least 10 9 Ω*cm, more preferably at least 10 11 Ω*cm, more preferably at least 10 13 In an embodiment, the thickness of the deposited layer may range from 20 to 2000 nm, preferably from 50 to 1500 nm, more preferably from 100 to 1200 nm.

[0040] In an embodiment, the substrate on which the layer is deposited includes silicon, glass, or an electrode material, but the present invention is not limited thereto.

[0041] In a fourth aspect, the present invention provides use of the target according to any embodiment of the first aspect in a stable plasma sputtering process by a medium frequency sputtering process or a direct current sputtering process.

[0042] Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims as appropriate and with features of other dependent claims and not only as explicitly stated in a claim.

[0043] The above and other features, characteristics and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which illustrate the principles of the present invention by way of example. This description is given as an example only and does not limit the scope of the present invention. The reference numerals cited below relate to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a schematic diagram of a method according to an embodiment of the second aspect of the present invention.

[0045] Figure 2 is a schematic diagram of a cross section of a sputtering target according to an embodiment of the present invention.

[0046] Figure 3 1 is a first exemplary schematic diagram of a part of a cross section of a target material layer of a sputtering target according to an embodiment of the present invention.

[0047] Figure 4 is a second exemplary schematic diagram of a part of a cross section of a target material layer of a sputtering target according to an embodiment of the present invention.

[0048] Figure 5 is an optical microscope image of a portion of a target material layer of a target according to an embodiment of the present invention.

[0049] Figure 6 According to an embodiment of the present invention Figure 5 Scanning electron microscope image of a local portion of the target material layer of the target.

[0050] Figure 7 is an X-ray diffraction (XRD) pattern of a first region formed of Al in a single target material layer of a target according to an embodiment of the present invention, superimposed with a first region formed of Li x PO y XRD pattern of the second region formed.

[0051] Figures 8 to 11 is a schematic diagram of a setup that can be used to measure the electrical conductivity of a target material layer of a target according to an embodiment of the present invention.

[0052] Fig.12 is a schematic diagram of a sputtering setup used in a method for depositing a layer according to an embodiment of the present invention.

[0053] The same reference numbers in different drawings identify the same or similar elements. DETAILED DESCRIPTION

[0054] The present invention will be described with respect to specific embodiments and with reference to certain drawings, but the invention is not limited thereto but only by the claims. The drawings are merely illustrative and non-restrictive. In the drawings, for illustrative purposes, the dimensions of some elements may be exaggerated and not drawn to scale. The dimensions and relative dimensions do not correspond to actual reductions in practicing the invention.

[0055] In the specification and claims, the terms first, second, third, etc. are used to distinguish similar elements and are not necessarily used to describe a sequence in time, space, level or in any other manner. It should be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0056] In addition, the terms top and above, etc. in the specification and claims are used for descriptive purposes and not necessarily for describing relative positions. It should be understood that the terms so used are interchangeable under appropriate circumstances, and that the embodiments of the invention described herein are capable of operating in other orientations than those described or shown herein.

[0057] It should be noted that the term "comprising" used in the claims should not be interpreted as being limited to the means listed thereafter; it does not exclude other elements or steps. Therefore, it should be interpreted as specifying the presence of the features, integers, steps or elements mentioned, but does not exclude the presence or addition of one or more other features, integers, steps or elements or groups thereof. Therefore, the term "comprising" covers the case where only the features are present as well as the case where these features and one or more other features are present. Therefore, according to the present invention, the term "comprising" also includes an embodiment in which no other elements are present. Therefore, the scope of the expression "a device comprising means A and B" should not be interpreted as being limited to a device consisting only of elements A and B. This means that, for the present invention, the only relevant elements of the device are A and B.

[0058] Similarly, it should be noted that the term "couple" should not be interpreted as being limited to direct connections. The terms "couple" and "connect" and their derivatives may be used. It should be understood that these terms are not intended to be synonymous with each other. Therefore, the scope of the expression "device A coupled to device B" should not be limited to devices or systems in which the output of device A is directly connected to the input of device B. This means that there is a path between the output of A and the input of B, which may be a path that includes other devices or means. "Coupled" may mean that two or more elements are in direct physical or electrical contact, or that two or more elements are not in direct contact with each other, but still cooperate or interact with each other.

[0059] References throughout this specification to "one embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in conjunction with that embodiment is included in at least one embodiment of the present invention. Thus, the phrases "in one embodiment" or "in an embodiment" appearing throughout this specification do not necessarily all refer to the same embodiment, but may refer to the same embodiment. Furthermore, it will be apparent to one of ordinary skill in the art from this disclosure that, in one or more embodiments, the particular features, structures, or characteristics may be combined in any suitable manner.

[0060] Similarly, it should be understood that in the description of the exemplary embodiments of the present invention, various features of the present invention are sometimes combined in a single embodiment, figure or description thereof to simplify the present disclosure and help understand one or more of the various inventive aspects. However, the method of the present disclosure should not be interpreted as reflecting the following intention: the claimed invention requires more features than the features explicitly stated in each claim. On the contrary, as reflected in the attached claims, aspects of the present invention do not lie in all the features of a single above-mentioned disclosed embodiment. Therefore, the claims following the detailed description are hereby expressly incorporated into the detailed description, and each claim independently serves as a different embodiment of the present invention.

[0061] In addition, although some embodiments described herein include some features included in other embodiments but not other features, the combination of features of different embodiments is intended to be within the scope of the present invention and form different embodiments, as will be understood by those skilled in the art. For example, in the following claims, any claimed embodiment can be used in any combination.

[0062] In addition, some embodiments are described herein as methods or combinations of method elements that can be implemented by a processor of a computer system or by other means for performing the functions. Thus, a processor having the necessary instructions for performing the method or method elements forms a means for performing the method or method elements. In addition, the elements described herein of the device embodiments are examples of means for performing the functions performed by the elements of the present invention.

[0063] In the description provided herein, many specific details are listed. However, it should be understood that embodiments of the present invention can be implemented without these specific details. In other cases, well-known methods, structures and techniques are not shown in detail to avoid confusing the understanding of this description.

[0064] The following terms are provided solely to aid in the understanding of the present invention.

[0065] As used herein and unless otherwise specified, a sputtering sheet is a microscopic entity obtained by ejecting (e.g., spraying) particles of a target material (e.g., molten or semi-molten particles) onto a surface (e.g., onto the top surface of a carrier or onto a previously formed sputtering sheet. By stacking the sputtering sheets on top of each other, a target material layer (e.g., a target material coating) is obtained. In an embodiment, the sputtering sheet may include (e.g., consist of) an amorphous and / or crystalline target material.

[0066] As used herein and unless otherwise specified, a property denoted as "splatter [property]" corresponds to the property evaluated for the splatter itself. For example, the splatter composition may correspond to the composition within the boundaries of the splatter. In the present invention, such splatter properties need not be constant for all splatters and may vary from splatter to splatter.

[0067] As used herein and unless otherwise specified, the properties represented as "layer [property]" correspond to the properties evaluated outside the splash boundaries, such as within the region of the target material layer (or within the entire target material layer). For example, the layer density may correspond to the density within the region of the target material layer, the region including the collection of splashes and gaps therebetween. In an embodiment, the region of the target material layer may be selected so that it contains at least 100 splashes, preferably at least 500 splashes, most preferably at least 2000 splashes, and at most, for example, 10,000 or 100,000 splashes. In the present invention, such layer properties do not need to be constant across the entire layer, and in fact, one or more layer properties will typically vary across the entire layer (e.g., across the layer width).

[0068] As used herein and unless otherwise specified, the properties of the microstructure of the target material layer include properties related to sputter orientation, sputter size, sputter shape, sputter crystallinity, layer crystallinity, layer density, layer porosity, layer structure, layer sequence, layer stress, etc.

[0069] As used herein and unless otherwise specified, a structure may typically have a first dimension (e.g., width), a second dimension (e.g., length), and a third dimension (e.g., thickness or height). In an embodiment, these three dimensions may typically be perpendicular. In an embodiment, the layer thickness may be the direction in which the sputtering sheets are stacked in layers, and the layer width and layer length may be perpendicular to this direction. In an embodiment, the target thickness, target width, and target length may be parallel to the layer thickness, layer width, and layer length, respectively. In a specific embodiment, the layer width may be equal to or shorter than the layer length. Similarly, the target width may be equal to or shorter than the target length. Of course, the latter does not apply to cylindrical targets.

[0070] As used herein and unless otherwise specified, a backing structure is a carrier for a layer of target material that is suitable for use in a method of making a sputtering target. In embodiments of the present invention, the backing structure may be pre-shaped to compensate for different layer thicknesses of target material applied at different locations across the width of the target material layer.

[0071] In the embodiments of the present invention, when referring to M-doped Li x PO y When referring to a composition comprising Li x PO y (i.e., lithium phosphate) and M, wherein lithium serves as a counter ion of the phosphate group; the Li x PO y comprises P, x Li atoms per P atom, and y O atoms per P atom. In an embodiment, Li x PO y and M are respectively confined to different, continuous regions.

[0072] In the context of the present invention, any reference to conductivity or resistivity is understood to be the conductivity or resistivity defined at room temperature (ie 20°C) and a pressure of 1 atm.

[0073] The present invention will now be described by a detailed description of several embodiments of the present invention. Obviously, other embodiments of the present invention can be configured according to the knowledge of those skilled in the art without departing from the technical teaching of the present invention, and the present invention is limited only by the appended claims.

[0074] In a first aspect, the present invention relates to a target for sputtering in a medium frequency AC sputtering process or a DC sputtering process. These sputtering processes can be non-pulsed or pulsed DC sputtering processes or AC sputtering processes, wherein the pulse frequency (i.e., the frequency of the periodic variation of the electrical signal) is 0 Hz (DC) to 250 kHz, more typically 20 kHz to 100 kHz.

[0075] The target comprises a target material layer, wherein the target material layer mainly comprises M-doped Li x PO y Here, x is 2.5 to 3.5, y is 2.5 to 4.5, and M accounts for up to 40% by weight of the target material layer. M comprises at least one chemical element from Groups 13 to 15 of the periodic table, and M is selected to provide electrical conductivity to the target material layer, so that the resistivity of the target material layer is at most 1000 Ω*cm at room temperature. The target material layer has a lamellar structure consisting of microscopic sputtered flakes of material.

[0076] refer to Figure 1 , which is a schematic diagram of a method for forming a sputtering target in a medium frequency AC sputtering process or a DC sputtering process according to an embodiment of the second aspect of the present invention.

[0077] The method includes providing 10 a powder, the powder comprising: particles of lithium phosphate and particles of M; and / or particles of lithium phosphate doped with M. Here, M comprises at least one chemical element of Groups 13 to 15 of the periodic table. The method also includes providing 11 a backing substrate. The method also includes spraying 12 a spatter formed when the provided powder impacts onto the backing substrate to form a Li phosphate containing M doped therein. x PO y A target material layer, wherein x is 2.5 to 3.5, and wherein y is 2.5 to 4.5, wherein M accounts for up to 40 weight % of the total target material, and wherein M is selected to provide conductivity to the target material layer so that the resistivity of the target material layer is up to 1000 Ω*cm at room temperature.

[0078] The powder particles are typically in the range of 10 to 200 microns in size and are free-flowing, which allows the powders to be continuously fed into the spraying equipment while being carried by a gas (typically argon) and delivered to the equipment through a feed hose and an injector. The thermal spraying process includes accelerating and spraying droplets of a source material (comprising lithium phosphate, M and / or M-doped lithium phosphate) onto a sputtering backing substrate, where they flatten on the substrate to form a coating. In embodiments of the present invention, different types of spraying may be applied, such as thermal spraying (where droplets of at least partially molten source material are sprayed onto a backing substrate where they solidify), such as flame spraying, plasma spraying or HVOF, but cold spraying may also be applied (if the particles are plastically deformable).

[0079] The environment of the spraying process can be controlled during target production, which allows the degree of redox of the powder as the original base material to be controlled.

[0080] Figure 2 is a schematic diagram of a cross section of an exemplary target 2 for sputtering, wherein the target is in accordance with an embodiment of the present invention. In this example, the target 2 is a cylindrical target. Figure 1 The target 2 is manufactured by the method shown. The target 2 includes a backing substrate 22, which in this example has a cylindrical shape. However, the present invention is not limited thereto, and in other embodiments, the backing substrate may be flat. The backing substrate 22 is typically formed of a conductive material, such as (stainless) steel, copper or titanium. The backing substrate 22 includes an interface morphology and / or an adhesive layer 221 to promote adhesion of the target material layer 21 to the backing substrate 22. The interface morphology or adhesive layer 221 may be formed of any material known to those skilled in the art for bonding the target material layer 221 to the backing substrate 22, but is preferably formed of a conductive material, for example, having a resistivity of at most 1000 Ω*cm, for example at most 100 Ω*cm.

[0081] Figure 3 The diagram is shown in greater detail in Figure 2 . The target material layer is formed of a lamellar structure consisting of microscopic spatters 3 of material. The spatters 3 are the result of a spraying method (e.g., a thermal spraying method) for forming the target material layer 21, wherein powder particles sprayed toward a backing substrate are deformed, e.g., at least partially melted, when the powder particles impact the backing substrate to form spatters 3, thereby forming the target material layer. These spatters 3 are in physical contact with each other in the target material layer. Pores 31 may be present in the target material layer, e.g., between adjacent spatters 3. These pores 31 may be introduced during the spraying method for forming the target material layer.

[0082] In this first example, each sputtered sheet 3 includes a first region 32 formed of M and a second region 33 formed of Li xPO y The second region 33 is formed. It can be observed that at least some of the conductive first regions 32 of adjacent sputters are in electrical contact with each other, thereby forming an electrically conductive path through the target material layer. Preferably, the target material layer contains at least some electrically conductive paths that penetrate through the target material layer. For example, this may be the case when the M concentration in the target material layer is high enough, so that the chance of forming such a penetration path by randomly spraying the sputters to form the target material layer by spraying (e.g., thermal spraying) becomes high enough.

[0083] Figure 4 The diagram is shown in greater detail in Figure 2 3. As can be observed, a sputtered piece 34 of M (i.e., a first region 34 of M) exists in the target material layer 21 formed by Li x PO y The splash film 35 (ie Li x PO y Although in the illustrated embodiment, different sputtering sheets 34 of M may be isolated from each other, due to defects in the matrix or along grain boundaries (e.g., the boundary between sputtering sheets 34 and 35), the sputtering sheets 34 of M may be isolated from each other due to defects in the matrix or along grain boundaries (e.g., the boundary between sputtering sheets 34 and 35). x PO y In the matrix formed by the sputtering pieces 35 of M, there may be electrical conduction between different sputtering pieces 34 of M. Alternatively, in an embodiment not shown in the drawings, the concentration of M may be high enough so that the sputtering pieces 34 formed by M are in electrical contact with each other, thereby forming an electrically conductive path through the target material.

[0084] However, the present invention is not limited to these two examples, or a combination of the two is also possible.

[0085] Figure 5 : is an optical microscope image of a portion of a target material layer of a target according to an embodiment of the present invention. From the ICP (inductively coupled plasma) spectrum, it is concluded that the target material layer is composed of Li 2.97 PO 4.3 and 13.5 wt % of a dopant M (which is Al in this example). The target material layer is formed by plasma spraying a molten powder onto a backing substrate. The non-molten powder used in this example contains particles formed of Al and particles formed of lithium phosphate. This figure is a result of a cross section of a target material layer having a lamellar structure consisting of microscopic sputtering flakes. The sputtering flakes contain a first region 32 formed of Al and particles formed of Li x PO y The second region 33 is formed. Figure 6 These different regions can also be observed in Figure 6 yes Figure 5Scanning electron microscope image of a part of the target material layer that hits the target in backscattering mode with atomic number contrast (Z contrast).

[0086] refer to Figure 7 , which is related to Figure 5 and Figure 6 The X-ray diffraction (XRD) pattern of the same target material layer shown, i.e., containing Al as the dopant M. In this pattern, four peaks attributed to Al are marked. The other peaks are attributed to Li x PO y The XRD pattern shows a single orthorhombic lithium phosphate phase, which is also observed in a pure Li3PO4 reference coating (the pure reference coating is not in accordance with the present invention). Therefore, the XRD pattern of the target material layer according to the present invention also clearly shows that Al and Li x PO y In addition, the spectrum shows that aluminum exists in metallic form and is embedded in Li x PO y In the matrix, aluminum may therefore be selected to provide electrical conductivity to the target material layer.

[0087] Figures 8 to 11 is a schematic diagram of exemplary setups that can be used to measure the resistivity of a target material layer 21 of a target according to an embodiment of the present invention. In each setup, the target material layer 21 is placed on a carrier backing 102, and a different probe (depending on the setup) is applied to the surface of the target material layer 21.

[0088] The 4-point method for measuring resistivity is based on the 4-point probe 101. Figure 8 The arrangement thereof is shown, including a voltage source providing a voltage V and a current source providing a current I. The resistivity is obtained by the following equation:

[0089]

[0090] where the parameters t and s are the target thickness and the spacing between the contacts, respectively. The equation can be simplified to:

[0091]

[0092] The 4-point method is the preferred method for determining the resistivity of the target. The resistivity of targets according to embodiments of the present invention has been measured to range from 0.001 Ω*cm to 0.5 Ω*cm, with the resistivity being typically about 0.01 Ω*cm.

[0093] Fig.9A The setup for the 3-point method for measuring resistivity is shown, which is based on sending a current through a predetermined area (a circular area provided by the circular plate 1101 in this example, Fig. 9B), and then the current and voltage of the target material layer 21 are measured while measuring through the center 1102 of the plate 1101. The resistivity is obtained by the following equation:

[0094]

[0095] Where D is the thickness of the target material layer 21 (cm), and S is the contact surface between the circular plate 1101 and the target material layer 21 (cm²).

[0096] Fig.10 , a setup for a 2-point method is shown in FIG. 1 , which simply measures the resistance between two probes 1201 , 1202 (eg, probes with steel points or Ni-plated brass probes) at a predetermined distance d.

[0097] Fig.11 , a setup for a single point method is shown, which is based on measuring the resistance between an electrode 1301 in contact with a first surface of the target material layer 21 and a carrier backing serving as an electrode 1302 .

[0098] For the 2-point method and the single-point method, which are relatively simple to perform experimentally, modeling is typically required in order to determine the resistivity from the measured resistance. Suitable models are known to those skilled in the art.

[0099] Preferably, for each of the above methods, the contact surface area between each probe or electrode used to measure the resistance and the target material layer 21 is equal to at least 1 times, such as at least 10 times, preferably at least 100 times, and more preferably at least 1000 times, the average diameter of the sputtered pieces in the target material layer 21. Thus, multiple regions of the dopant M can be electrically contacted by the probe or electrode, so that the resistivity can be accurately determined. Therefore, any of the above settings can be used to verify that the resistivity of the target material layer 21 at room temperature is at most 1000 Ω*cm.

[0100] In a third aspect, the present invention relates to a method for depositing a layer on a substrate. The method comprises obtaining a target according to an embodiment of the first aspect of the present invention, and sputtering a target material from a target material layer of the target onto a substrate in a reactive gas atmosphere containing at least N. The sputtering is performed so that M reacts with components of the reactive gas atmosphere to form an electrically insulating material, so as to form a deposited layer comprising LiPON and the electrically insulating material.

[0101] refer to Fig.12, which is a schematic diagram of a sputtering arrangement 4, which can be used in a method for depositing a layer, wherein the method is in accordance with an embodiment of the third aspect of the invention. A sputtering chamber 41 of the sputtering arrangement 4 comprises a target 2 for sputtering according to an embodiment of the first aspect of the invention. In this example, the target 2 is a planar target, but it can also be a cylindrical target such as described above. The sputtering chamber 41 also comprises a substrate 5. The substrate 5 can be any suitable type of substrate. For example, the substrate 5 can be a silicon substrate or a glass substrate.

[0102] The target 2 is electrically coupled to a power source 8 so that the target 2 acts as a cathode. The power source 8 is used to generate a negative potential on the target 2. The power source 8 is preferably a DC power source or an AC power source, wherein the DC power source can be used in a pulsed mode or a non-pulsed mode. In the example shown, the power source 8 is configured for DC operation. When a dual target setup (not shown) in a pulsed DC mode or an AC mode is used, the electric field can be generated at a frequency of up to 250 kHz. The target 2 or its backing substrate 22 can optionally be coupled to a cooling system (not shown). The present invention can also provide an unsupported target without a backing substrate 22.

[0103] The gas inlet 71 of the sputtering chamber 41 allows gas to be introduced into the sputtering chamber 41, thereby forming a sputtering atmosphere 9 in the sputtering chamber 41. The gas outlet 72 can be connected to a vacuum pump for removing gas from the sputtering chamber 41. According to an embodiment of the present invention, the gas introduced into the sputtering chamber 41 includes nitrogen (N2) and possible inert gas, typically argon. Optionally, the gas also includes oxygen (O2). The reactive sputtering atmosphere includes nitrogen (N2). The atmosphere pressure in the sputtering chamber can be typically 0.1 Pa to 10Pa.

[0104] In such a low pressure environment, an abnormal glow discharge may be generated whenever electricity is applied by a power supply. The abnormal glow discharge may ionize the gas to form ionized atoms or molecules 91 near the target 21, such as Ar. + 、N2 + or O2 + Due to the applied field, these atoms or molecules can be accelerated toward the target material layer 21 and bombard the target material layer 21. By the bombardment of the ionized atoms or molecules 91, target material particles 210 are sputtered from the target material layer 21 of the target 2 toward the substrate 5, thereby forming a deposition layer 6 above the substrate 5.

[0105] Since Li from the target material layer 21 x PO y LiPON may be formed by reaction with nitrogen of the reactive sputtering atmosphere 9. In addition, due to the reaction between the dopant M from the target material layer 21 and the components of the reactive sputtering atmosphere (which may be nitrogen and / or oxygen when present), an electrically insulating material such as M-nitride and / or M-oxide may be formed. Without being bound by theory, when Lix PO y and M still exist in target 2, or when Li x PO y When Li and M are deposited onto a substrate to form a deposition layer 6, Li x PO y The reaction between the target material particles 210 and the nitrogen gas and the reaction between the conductive dopant M and the reactive sputtering gas (e.g., oxygen and / or nitrogen). Within the pressure range typically used (0.1 Pa to 10 Pa), the reaction can occur on any surface exposed to the target material particles 210. The deposited layer 6 thus formed on the substrate 5 comprises a mixture of LiPON and an electrically insulating material and substantially does not contain a conductive component (i.e., substantially all of the deposited M has reacted to form an insulating material), and is therefore electrically insulating.

[0106] It should be understood that although preferred embodiments, specific configurations and arrangements, and materials have been discussed herein with respect to devices according to the present invention, various changes or modifications may be made in form and detail without departing from the scope of the present invention. For example, any of the schemes given above represent only processes that may be used. Functions may be added or deleted in block diagrams, and operations may be interchanged between functional blocks. Steps may be added or deleted in the methods described within the scope of the present invention.

Claims

1. A target (2) comprising mainly M-doped Li x PO y a target material layer (21) wherein x is 2.5 to 3.5, and wherein y is 2.5 to 4.5, wherein M accounts for up to 40 wt % of the target material layer (21), and wherein M comprises at least one chemical element from Groups 13 to 15 of the Periodic Table of Elements, wherein M is selected to provide conductivity to the target material layer (21) so that the resistivity of the target material layer (21) at room temperature is at most 1000 Ω*cm, and The target material layer (21) has a lamellar structure composed of microscopic sputtered flakes (3) of the material.

2. The target (2) according to claim 1, wherein M accounts for 5 to 25% by weight of the total target material layer (21), preferably 10 to 20% by weight of the total target material layer (21).

3. The target (2) according to any of the preceding claims, wherein M comprises metal and / or metalloid elements.

4. The target (2) according to claim 3, wherein M comprises at least one chemical element selected from silicon, boron, aluminum and gallium.

5. The target (2) according to any one of the preceding claims, wherein M comprises at least one chemical element from group 13 of the periodic table.

6. The target (2) according to any one of the preceding claims, wherein the target material layer (21) comprises at least 80 wt. % of M-doped Li x PO y , such as at least 90 wt %, such as at least 95 wt % or more M-doped Li x PO y .

7. The target (2) according to any one of the preceding claims, wherein the target (2) is a cylindrical target.

8. The target (2) according to any one of the preceding claims, wherein the microscopic sputtering piece (3) comprises a first region (32, 34) of M and Li x PO y The second area (33, 35).

9. The target (2) according to any of the preceding claims, wherein the porosity of the target material layer is lower than 20%, even lower than 10%, preferably lower than 5%.

10. A method for forming a target (2) for sputtering, the method comprising: (10) providing a powder comprising lithium phosphate particles and M particles and / or comprising M-doped lithium phosphate particles, wherein M comprises at least one chemical element from Groups 13 to 15 of the Periodic Table of Elements, providing (11) a backing substrate (22), and The splashed sheets formed when the powder impacts are sprayed onto the backing substrate (22) to form a Li-doped M-containing x PO y A target material layer (21) wherein x is 2.5 to 3.5, and wherein y is 2.5 to 4.5, and wherein M accounts for at most 40 wt % of the total target material layer (21), and M is selected to provide electrical conductivity to the target material layer (21), so that the resistivity of the target material layer (21) at room temperature is at most 1000 Ω*cm.

11. A method for depositing a layer (6) on a substrate (5), the method comprising: obtaining a target (2) according to any one of claims 1 to 8, and In a reactive gas atmosphere (9) containing at least N2, a target material is sputtered from a target material layer (21) of a target (2) onto a substrate (5), wherein the sputtering is performed so that M reacts with components of the reactive gas atmosphere (9) to form an electrically insulating material, so as to form a deposited layer (6) containing LiPON and the electrically insulating material.

12. The method according to claim 11, wherein the sputtering is direct current sputtering or alternating current sputtering with a frequency of at most 250 kHz.

13. The method according to any one of claims 11 or 12, wherein the sputtering is performed such that M reacts with nitrogen and / or oxygen during sputtering to form a nitride, oxide or oxynitride of M.

14. The method according to any one of claims 11 to 13, wherein the sputtering is performed to form a deposited layer (6) having a resistivity of at least 10 7 Ω*cm, preferably at least 10 9 Ω*cm, more preferably at least 10 11 Ω*cm, even more preferably at least 10 13 Ω*cm.

15. Use of a target according to any one of claims 1 to 9 in a stable plasma sputtering process powered by a medium frequency sputtering process or a direct current sputtering process.

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