TECHNICAL FIELD

The present disclosure relates generally to low emissivity glass, and more particularly to low emissivity glass including spacer dielectric layers that is resistant to heat treatment.

BACKGROUND

Sunlight control materials, such as treated glass sheets, are commonly used for building glass windows and vehicle windows. Such materials typically offer high visible transmission and low emissivity thereby allowing more sunlight to pass through the glass window while block infrared (IR) radiation to reduce undesirable interior heating. In low emissivity (low-E) materials, IR radiation is mostly reflected with minimum absorption and emission, thus reducing the heat transferring to and from the low emissivity surface. Low-E panels are often formed by depositing a reflective layer (e.g., silver) onto a substrate, such as glass. The overall quality of the reflective layer is important for achieving the desired performance. In order to provide adhesion, as well as protection, several other layers are typically formed both under and over the reflective layer. These layers typically include dielectric layers, such as silicon nitride, tin oxide, and zinc oxide, which protect the stack from both the substrate and the environment. The dielectric layers may also act as optical fillers and function as anti-reflective coating layers to improve the optical characteristics of the panel.

A typical approach to reduce emissivity involves increasing the thickness of the reflective layer (e.g., the silver layer). However, as the thickness of the reflective layer increases, the visible light transmission of this layer is also reduced. Furthermore, the high thickness slows manufacturing throughput and increases costs. It may be desirable to keep the reflective layer as thin as possible, while still providing emissivity suitable for low-e applications.

SUMMARY

Disclosed herein are systems, methods, and apparatus for forming low-emissivity (low-E) panels. In some embodiments, low emissivity panels may include a first reflective layer and a second reflective layer. The low emissivity panels may further include a first spacer dielectric layer formed between the first reflective layer and the second reflective layer and a second spacer dielectric layer formed between the first reflective layer and the second reflective layer. The first spacer dielectric layer may include zinc tin oxide. The second spacer dielectric layer may include tin aluminum oxide. In some embodiments, the low emissivity panels may have a color change as determined by Rg ΔΕ (i.e. as determined on the glass side) that is less than about 2.0 in response to the application of a heat treatment to the low emissivity panels. In some embodiments, a combined thickness of the first spacer dielectric layer and the second spacer dielectric layer is between about 40 nm and 90 nm. Moreover, a thickness of the first spacer dielectric layer may be between about 20 nm and 50 nm, and a thickness of the second spacer dielectric layer may be between about 20 nm and 50 nm.

In some embodiments, each of the first spacer dielectric layer and the second spacer dielectric layer may be substantially amorphous. As used herein, a material may be a substantially amorphous material if the crystalline phase composes less than 5% of the material by volume. Furthermore, an atomic ratio of tin to aluminum in the second spacer dielectric layer may be between about 0.8 and 1.2, and an atomic ratio of zinc to tin in the first spacer dielectric layer may be between about 1.8 and 2.2.

In some embodiments, the low emissivity panels may further include a seed layer formed between and directly interfacing the second reflective layer and the second spacer dielectric layer. The seed layer may include one of zinc oxide, tin oxide, scandium oxide, or yttrium oxide. The low emissivity panels may also include a barrier layer formed between the first reflective layer and the first spacer dielectric layer. The barrier layer may include nickel and chromium. In some embodiments, the low emissivity panels are heat treated panels. Moreover, the low emissivity panels may have a light to solar gain ratio of at least about 1.8.

In some embodiments, methods of fabricating low emissivity panels are disclosed. The methods may include forming a first reflective layer, forming a barrier layer over the first reflective layer, and forming a first spacer dielectric layer over the barrier layer. The methods may further include forming a second spacer dielectric layer over the first spacer dielectric layer, forming a seed layer over the second spacer dielectric layer, and forming a second reflective layer over the seed layer. The first spacer dielectric layer may include zinc tin oxide. The second spacer dielectric layer may include tin aluminum oxide. The seed layer may include one of zinc oxide, tin oxide, scandium oxide, or yttrium oxide. The barrier layer may include nickel, titanium, and niobium. In some embodiments, the methods may include applying a heat treatment to the low emissivity panel. Moreover, the low emissivity panels may have a color change as determined by Rg ΔΕ (i.e. as determined on the glass side) that is less than about 2.0 in response to the application of the heat treatment to the low emissivity panel.

In some embodiments, the first spacer dielectric layer is formed using a reactive sputtering of a first target comprising an alloy of zinc and tin, and the second spacer dielectric layer is formed using a reactive sputtering of a second target comprising an alloy of tin and aluminum. Furthermore, applying the heat treatment to the low emissivity panels may include heating the low emissivity panels at a temperature of 650 degrees Celsius for 8 minutes. In some embodiments, the low emissivity panels may have a color change as determined by Rg ΔΕ (i.e. as determined on the glass side) that is less than about 1.7 in response to the application of the heat treatment to the low emissivity panels.

In some embodiments, the methods also include forming an additional barrier layer over the second reflective layer, forming a top dielectric layer over the additional barrier layer, and forming a top diffusion barrier layer over the top dielectric layer. The top dielectric layer may include zinc tin oxide. Moreover, the low emissivity panels may have a light to solar gain ratio of at least about 1.8.

These and other embodiments are described further below with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

To facilitate understanding, the same reference numerals have been used, where possible, to designate common components presented in the figures. The drawings are not to scale and the relative dimensions of various elements in the drawings are depicted schematically and not necessarily to scale. Various embodiments can readily be understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic illustration of an article including a substrate and a stack of layers including two reflective layers formed over the substrate, in accordance with some embodiments.

FIG. 2 is a schematic illustration of another article including a substrate and a stack of layers including two reflective layers formed over the substrate, in accordance with some embodiments.

FIG. 3 is a schematic illustration of yet another article including a substrate and a stack of layers including three reflective layers formed over the substrate, in accordance with some embodiments.

FIG. 4 is a process flowchart corresponding to a method for forming an article including one or more reflective layers and barrier layers for protecting materials in the one or more reflective layers from oxidation, in accordance with some embodiments.

FIG. 5 is a graph illustrating transmission and reflection properties of articles including one or more spacer dielectric layers prior to and after the application of a heat treatment, implemented in accordance with some embodiments.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, numerous specific details are set forth in order to provide a thorough understanding of the presented concepts. The presented concepts may be practiced without some or all of these specific details. In other instances, well known process operations have not been described in detail so as to not unnecessarily obscure the described concepts. While some concepts will be described in conjunction with the specific embodiments, it will be understood that these embodiments are not intended to be limiting. It must be noted that as used herein and in the claims, the singular forms "a," "and" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a layer" includes two or more layers, and so forth.

Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range, and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention. The term "about" generally refers to ±10% of a stated value.

The term "horizontal" as used herein will be understood to be defined as a plane parallel to the plane or surface of the substrate, regardless of the orientation of the substrate. The term "vertical" will refer to a direction perpendicular to the horizontal as previously defined. Terms such as "above", "below", "bottom", "top", "side" (e.g. sidewall), "higher", "lower", "upper",

"over", and "under", are defined with respect to the horizontal plane. The term "on" means there is direct contact between the elements. The term "above" will allow for intervening elements.

As used herein, the notation "Al-Zn-Sn-O" and "AlZnSnO" and AlZnSnO _x "will be understood to be equivalent and will be used interchangeably and will be understood to include a material containing these elements in any ratio. Where a specific composition is discussed, the atomic concentrations (or ranges) will be provided. The notation is extendable to other materials and other elemental combinations discussed herein.

As used herein, the terms "film" and "layer" will be understood to represent a portion of a stack. They will be understood to cover both a single layer as well as a multilayered structure (i.e. a nanolaminate). As used herein, these terms will be used synonymously and will be considered equivalent.

Introduction

Conventional low emissivity (low-E) panels do not include a single low-E coating that provides a high light to solar gain ratio and is also compatible with both as-coated fabrication processes and heat treatment fabrication processes. Conventional panels may include one or more layers made from a material, such as such as only SnO _x . However, such layers exhibit large electrical resistances that are not suitable for low-E applications. Some conventional panels include several thinner layers with interspersed layers that include nitrides. However, such layers are susceptible to unacceptable color changes in response to the application of a heat treatment, such as a tempering process. Thus, they do not provide a single coating which provides a high light to solar gain ratio and is also compatible with both as-coated fabrication processes and heat treatment fabrication processes.

Provided herein are low emissivity panels and methods of fabricating such panels. Low emissivity panels as disclosed herein may include two reflective layers and two spacer dielectric layers. The two spacer dielectric layers may be formed between the two reflective layers. The first spacer dielectric layer may be formed from zinc tin oxide, while the second spacer dielectric layer may be formed from tin aluminum oxide. Both spacer dielectric layers may have substantially amorphous structures without a need for any intermediate nitride layers between the two reflective layers, which substantially reduces design and manufacturing complexity and costs. In some embodiments, a material may be a substantially amorphous material if the crystalline phase composes less than 5% of the material by volume. A combined thickness of the first spacer dielectric layer and the second spacer dielectric layer may be between about 40 nm and 90 nm. Each spacer dielectric layer may have a thickness of between about 20 nm and 50 nm while maintaining an amorphous structure. In some embodiments, the low emissivity panels may also include a seed layer formed between and directly interfacing the second reflective layer and the second spacer dielectric layer. The seed layer may be formed from one of zinc oxide, tin oxide, scandium oxide, or yttrium oxide. In some embodiments, the low emissivity panels also include a barrier layer formed between the first reflective layer and the first spacer dielectric layer. The barrier layer may include nickel, titanium, and niobium.

Examples of Low-Emissivity Coatings

A brief description of low-E coatings is provided for context and better understanding of various features associated with barrier layers and silver reflective layers. One having ordinary skills in the art would understand that these barrier and silver reflective layers may be also used for other applications, such as light emitting diodes (LED), reflectors, and other like applications. Some characteristics of low-E coatings are applicable to these other applications as well. For purposes of this disclosure, low-E is a quality of a surface that emits low levels of radiant thermal energy. Emissivity is the value given to materials based on the ratio of heat emitted compared to a blackbody, on a scale of 0 (for a perfect reflector) to 1 (for a back body). The emissivity of a polished silver surface is 0.02. Reflectivity is inversely related to emissivity. When values of reflectivity and emissivity are added together, their total is equal to 1.

FIG. 1 is a schematic illustration of an article 100 including a substrate 102 and a stack 120 of layers 104-119, in accordance with some embodiments. Specifically, stack 120 includes one or more reflective layers, such as reflective layer 110 which may be formed over substrate 102 and protected by a barrier layer, such as barrier layer 111. Other layers in stack 120 may include bottom diffusion barrier layer 104, top diffusion barrier layer 116, bottom dielectric layer 106, top dielectric layer 114, and seed layer 108. Stack 120 may further include another reflective layer, such as reflective layer 117, which may be protected by barrier layer 112. Moreover, stack 120 may also include one or more layers between the reflective layers, such as first spacer dielectric layer 113 and second spacer dielectric layer 119. Each one of these components will now be described in more details. One having ordinary skills in the art would understand that the stack may include fewer layers or more layers as, for example, described below with reference to FIG. 2 and FIG. 3.

Substrate 102 can be made of any suitable material. Substrate 102 may be opaque, translucent, or transparent to visible light. For example, for low-E applications, the substrate may be transparent. Specifically, a transparent glass substrate may be used for this and other applications. For purposes of this disclosure, the term "transparency" is defined as a substrate characteristic related to a visible light transmittance through the substrate. The term

"translucent" is defined as a property of passing the visible light through the substrate and diffusing this energy within the substrate, such that an object positioned on one side of the substrate is not visible on the other side of the substrate. The term "opaque" is defined as a visible light transmittance of 0%. Some examples of suitable materials for substrate 102 include, but are not limited to, plastic substrates, such as acrylic polymers (e.g., polyacrylates, polyalkyl methacrylates, including polymethyl methacrylates, polyethyl methacrylates, polypropyl methacrylates, and the like), polyurethanes, polycarbonates, polyalkyl terephthalates (e.g., polyethylene terephthalate (PET), polypropylene terephthalates, polybutylene terephthalates, and the like), polysiloxane containing polymers, copolymers of any monomers for preparing these, or any mixtures thereof. Substrate 102 may be also made from one or more metals, such as galvanized steel, stainless steel, and aluminum. Other examples of substrate materials include ceramics, glass, and various mixtures or combinations of any of the above.

Bottom diffusion barrier layer 104 and top diffusion barrier layer 116 may be two layers of stack 120 that protect the entire stack 120 from the environment and improve chemical and/or mechanical durability of stack 120. Diffusion barrier layers 104 and 116 may be made from the same or different materials and may have the same or different thickness. In some embodiments, one or both diffusion barrier layers 104 and 116 are formed from silicon nitride. In some embodiments, silicon nitride may be doped with aluminum and/or zirconium. The dopant concentration may be between about 0% to 20% by weight. In some embodiments, silicon nitride may be partially oxidized. Silicon nitride diffusion barrier layers may be silicon-rich, such that their compositions may be represented by the following expression, Si _x N _Y , where the X-to-Y ratio is between about 0.8 and 1.0. The refraction index of one or both diffusion barrier layers 104 and 116 may be between about 2.0 and 2.5 or, more specifically, between about 2.15 to 2.25. The thickness of one or both diffusion barrier layers 104 and 116 may be between about 50 Angstroms and 300 Angstroms or, more specifically, between about 100 Angstroms and 200 Angstroms. In addition to protecting stack 120 from the environment, bottom diffusion barrier layer 104 may help with adhering bottom dielectric layer 106 to substrate 102. Without being restricted to any particular theory, it is believed that deposition of dielectric layer 106 and in particular subsequent heat treatment of this layer results in heat-induced mechanical stresses at the interfaces of dielectric layer 106. These stresses may cause delamination of dielectric layer 106 from other layers and coating failure. A particular example is a titanium oxide layer deposited directly onto the glass substrate. However, when silicon nitride diffusion barrier layer 104 is provided between bottom dielectric layer 106 and substrate 102, the adhesion within this three- layer stack remains strong as evidenced by improved durability, especially after heat treatment.

In some embodiments, stack 120 may further include one or more dielectric layers, such as bottom dielectric layer 106 and top dielectric layer 114 as shown in FIG. 1. Dielectric layers 106 and 114 may be used to control reflection characteristics of reflective layer 110 and reflective layer 117 as well as overall transparency and color of stack 120 and, in some embodiments, of article 100. Dielectric layers 106 and 114 may be made from the same or different materials and may have the same or different thickness. In some embodiments, one or both dielectric layers 106 and 114 are formed from at least one of T1O2, ZnO, SnC>2, SiAIN, ZnSn, Zn ₂ SnOx, or SnA10 _x . In general, dielectric layers 106 and 114 may be formed from various oxides, stannates, nitrides, and/or oxynitrides. In some embodiments, one or both dielectric layers 106 and 114 may include dopants, such as one or more of Al, Ga, In, Mg, Ca, Sr, Sb, Bi, Ti, V, Y, Zr, Nb, Hf, or Ta.

Dielectric layers 106 and 114 can each include different dielectric materials with similar refractive indices or different materials with different refractive indices. The relative thicknesses of the dielectric films can be varied to optimize thermal-management performance, aesthetics, and/or durability of article 100.

The materials of dielectric layers 106 and 114 may be in amorphous phases, crystalline phases, or a combination of two or more phases. In some embodiments, a dielectric layer may be, at least in part, amorphous. As stated above, a material may be a substantially amorphous material if the crystalline phase composes less than 5% of the material by volume. Accordingly, dielectric layer 106 and dielectric layer 114 may each be substantially amorphous. For example, when stack 120 includes seed layer 108, bottom dielectric layer 106 may be substantially amorphous. Alternatively, when stack 120 does not include seed layer 108, bottom dielectric layer 106 may be in a crystalline phase (e.g. greater than 30% crystalline as determined by X-ray diffraction) and may function as a nucleation template for overlying layers, e.g., reflective layer 110. The thickness of dielectric layers 106 and 114 may be between about 50 Angstroms and 1000 Angstroms or, more specifically, between 100 Angstroms and 300 Angstroms.

In some embodiments, stack 120 includes one or more seed layers, such as seed layer 108.

A seed layer, such as seed layer 108, may be formed from one of ZnO, Sn0 ₂ , SC2O3, Y2O3, T1O2, Zr0 ₂ , Hf0 ₂ , V ₂ 0 ₅ , Nb ₂ 0 ₅ , Ta ₂ 0 ₅ , Cr0 ₃ , WO3, M0O3, various combinations thereof, or other metal oxides. The material of a seed layer may be in a crystalline phase (e.g. greater than 30% crystalline as determined by X-ray diffraction). Accordingly, seed layer 108 may function as a nucleation template for overlying layers, such as reflective layer 110. In some embodiments, the thickness of seed layer 108 is between about 50 Angstroms and 200 Angstroms, such as about 100 Angstroms.

As similarly stated above, stack 120 may include one or more reflective layers, such as reflective layer 110 and reflective layer 117, which may be formed from silver. The thickness of this layer may be between about 50 Angstroms and 200 Angstroms or, more specifically, between about 100 Angstroms and 150 Angstroms.

As noted above, stack 120 also includes barrier layer 112 to protect reflective layer 110 from oxidation and other damage. In some embodiments, barrier layer 112 may be formed from a partially oxidized alloy of any of nickel, titanium, chromium, and niobium. In some

embodiments, a partially oxidized alloy may be an alloy or metals in which one or more metals included in the alloy have sub-stoichiometric oxidation. Barrier layer 112 may be formed from a quaternary alloy that includes nickel, chromium, titanium, and aluminum. The concentration of each metal in this alloy is selected to provide adequate transparency and oxygen diffusion blocking properties. In some embodiments, a combined concentration of nickel and chromium in the barrier layer is between about 20% by weight and 50%o by weight or, more specifically, between about 30% by weight and 40% by weight. A weight ratio of nickel to chromium in the alloy may be between about 3 and 5 or, more specifically, about 4. A weight ratio of titanium to aluminum is between about 0.5 and 2, or more, specifically about 1. In some embodiments, the concentration of nickel in the barrier layer is between about 5% and 10% by weight, the concentration of chromium - between about 25% and 30% by weight, the concentration of titanium and aluminum - between about 30% and 35% by weight each. This composition of barrier layer 112 may be achieved by using one or more sputtering target containing nickel, chromium, titanium, and aluminum, controlling concentration of these metals in the sputtering targets, and controlling power levels applied to each sputtering target. For example, two sputtering targets may be used. The first target may include nickel and chromium, while the second target may include titanium and aluminum. The weight ratio of nickel to chromium in the first target may be about 4, while the weight ratio of titanium to aluminum in the second target may be about 1. These weight ratios may be achieved by using corresponding alloys for the entire target, target inserts made from different materials, or other features allowing combination of two or more materials in the same target. The two targets may be exposed to different power levels. In the above example, the first target may be exposed to twice smaller power than the second target to achieve the desired composition. The barrier can be deposited substantially free of oxygen (e.g., predominantly as a metal) in the inert environment (e.g., argon environment). Alternatively, some oxidant (e.g., 15% by volume of 0 ₂ in Ar) may be used to oxide the four metals. The concentration of oxygen in the resulting barrier layer may be between about 0% and 5% by weight.

In some embodiments, nickel, chromium, titanium, and aluminum are all uniformly distributed throughout the barrier layer, i.e., its entire thickness and coverage area. Alternatively, the distribution of components may be non-uniform. For example, nickel and chromium may be more concentrated along one interface than along another interface. In some embodiments, a portion of the barrier layer near the interface with the reflective layer includes more nickel for better adhesion to the reflective layer. In some embodiments, substantially no other components other than nickel, chromium, titanium, and aluminum are present in barrier layer 112.

As stated above, barrier layer 112 may include a material that is an alloy of several metals. For example, barrier layer 112 may be a layer of a material, such as NiTiNb which may be configured to have a thickness between about 1.5nm and 5nm. In one example, barrier layer 112 has a thickness of 2.4nm. Barrier layer 112 may be formed using a deposition technique, such as sputtering. During the forming process, a small amount of oxygen may be mixed with Argon to create a layer of NiTiNb oxide having an oxygen content between 10% to 30% by atomic weight. In some embodiments, barrier layer 112 may have a thickness of between about 1 Angstrom and 100 Angstroms or, more specifically, between about 5 Angstroms and 30

Angstroms, and even between about 10 Angstroms and 20 Angstroms.

Without being restricted to any particular theory, it is believed that when the barrier layer is exposed to oxygen (e.g., during deposition of the top dielectric), some metals of the barrier layer (e.g., Cr, Ti, and Al) will be easily oxidized thereby consuming oxygen and preventing oxygen from penetrating through the barrier layer and reaching the reflective layer. As such, the barrier layer may be considered as a scavenging layer.

In some embodiments, reflective layers included in stack 120 may be separated by one or more layers which may include one or more spacer dielectric layers, such as first spacer dielectric layer 113 and second spacer dielectric layer 119, to achieve a high light to solar gain ratio, which may be greater than 1.8, while also maintaining a low change in color of a glass-side reflectance of the low-E panels which may include article 100. In some embodiments, first spacer dielectric layer 113 may directly interface reflective layer 110 or barrier layer 111, if included in article 100, as discussed in greater detail below. Second spacer layer 119 may directly interface first spacer dielectric layer 113 and reflective layer 117 or seed layer 115, if included in article 100, as discussed in greater detail below. As illustrated in FIG. 1, in some embodiments, no intermediate nitride layers are included between reflective layer 110 and reflective layer 117. The exclusion of nitride layers substantially reduces design and manufacturing complexity and costs. Moreover, eliminating nitride layers that may be included with conventional layers may also eliminate color shifting of a glass-side reflectance typically caused by heat treatments. Accordingly, in contrast to conventional spacer layers that may include SnO _x and nitride layers, spacer dielectric layers as disclosed herein do not experience a substantial change in color and transmissivity or an increase in film haze and maintain resistance and emissivity characteristics that are suitable for low-E applications.

More specifically, low emissivity panels that include spacer dielectric layers as disclosed herein may have a very low ΔΕ, which may be a metric that describes a change in color of a low emissivity panel, or one or more layers included in the low emissivity panel. For example, color characteristics may be described using the CIE LAB a*, b* coordinates and scale. In the CIE LAB color system, the "L*" value indicates the lightness of the color, the "a*" value indicates the position between magenta and green (more negative values indicate stronger green and more positive values indicate stronger magenta), and the "b*" value indicates the position between yellow and blue (more negative values indicate stronger blue and more positive values indicate stronger yellow). In various embodiments, a ΔΕ value may be calculated based on a difference in L*, a*, and b* values before and after the application of a heat treatment to a low emissivity panel. For example, a ΔΕ value may be determined based on color properties before heat treatment (L ^* ₀ , a ₀ ^* ,b ₀ ^* ) and color properties after heat treatment (L _x , a _l ,b _l ) . ΔΕ may be calculated based on the following equation:

AE' = <J(AL' J + (Aa' J + (Ab' J

where:

AL = L ₁ - L ₀

Aa = a - a ₀

In some embodiments, low emissivity panels having spacer dielectric layers as disclosed herein may have a color change as determined by Rg ΔΕ (i.e. as determined on the glass side) that is less than about 2.0 as determined based on a comparison of their L*, a*, and b* values before and after the application of a heat treatment, such as an anneal. Further still, the ΔΕ may be less than about 1.7. Accordingly, low emissivity panels that include spacer dielectric layers, such as first spacer dielectric layer 113 and second spacer dielectric layer 119, may experience very little shift in color in response to the application of a heat treatment to the low emissivity panel.

Moreover, low emissivity panels that include spacer dielectric layers as disclosed herein may exhibit a very low amount of haze because they may include so few layers between reflective layers, and do not include layers having nitrides. In some embodiments, haze may be a standard measurement of a transmittance characteristic of a low emissivity panel, such as an amount of light scattered. According to some embodiments, haze may be determined based on the ratio of diffuse or scattered light relative to the total light transmitted through the low emissivity panel. For example, the amount of haze after the application of a heat treatment to a low emissivity panel as disclosed herein may be less than about 5%. For example, the amount of haze may be about 4.7% after the application of a heat treatment to a low emissivity panel that includes spacer dielectric layers, such as first spacer dielectric layer 113 and second spacer dielectric layer 119.

In some embodiments, first spacer dielectric layer 113 and second spacer dielectric layer 119 may be formed from one or more metal oxides. First spacer dielectric layer 113 and second spacer dielectric layer 119 may be made of the same or different materials. For example, first spacer dielectric layer 113 may be made of a first metal oxide, such as zinc tin oxide, while second spacer dielectric layer 119 may be made of a second metal oxide, such as tin aluminum oxide. In some embodiments, an atomic ratio of zinc to tin in first spacer dielectric layer 113 is between about 1.8 and 2.2. In some embodiments, an atomic ratio of tin to aluminum included in second spacer dielectric layer 119 is between about 0.8 and 1.2.

The use of two spacer dielectric layers where the second space dielectric layer includes tin aluminum oxide yields a surprising result in that the color change (i.e. after a heat treatment) in the glass-side reflection may have a ΔΕ of less than or equal to 2, and may be about 1.7. Those skilled in the art will understand that this color change cannot be detected by the human eye. The addition of the aluminum to the tin oxide has a number of benefits. First, the addition of aluminum allows the layer to remain amorphous after a subsequent heat treatment. This allows the color change to be very small after heat treatment. Second, the addition of the aluminum to the tin oxide lowers the absorbance of the layer, especially toward the "blue" end of the spectrum. In contrast, those skilled in the art will understand that space dielectric layers that include only zinc tin oxide, only tin oxide, or multilayers of zinc tin oxide and tin oxide will exhibit a color change (i.e. after a heat treatment) in the glass-side reflection that is easily detected by the human eye. Meanwhile, the tin aluminum oxide layer maintains desirable properties such as high transmissivity, low absorbance, chemical stability, and mechanical stability (e.g. remains amorphous after heat treatment).

In some embodiments, first spacer dielectric layer 113 and second spacer dielectric layer 119 may have a thickness sufficiently large to provide a high light to solar gain ratio while not degrading emissivity performance of the article 100 and low-E panels that may include article 100. Applicants have determined that a spacer layer as disclosed herein may preferably have a thickness of between about 40 nm and 90 nm and achieve sufficient light to solar gain ratio and emissivity performance. Furthermore, each of first spacer dielectric layer 113 and second spacer dielectric layer 119 may have a thickness of between about 20 nm and 50 nm, and the combined thickness of first spacer dielectric layer 113 and second spacer dielectric layer 119 may be between about 40 nm and 90 nm. In some embodiments, first spacer dielectric layer 113 and second spacer dielectric layer 119 may have substantially amorphous structures, even at the previously described thicknesses. Moreover, first spacer dielectric layer 113 and second spacer dielectric layer 119 may remain substantially amorphous even after the application of a heat treatment to article 100. Thus, first spacer dielectric layer 113 and second spacer dielectric layer 119, in combination, may provide a spacer layer having a thickness sufficient to provide a high light to solar gain ratio while also remaining substantially amorphous even if a heat treatment is subsequently applied to article 100.

Stack 120 may further include seed layer 115. As similarly discussed above with reference to seed layer 108, seed layer 115 may be formed from one of ZnO, Sn0 ₂ , Sc ₂ 0 ₃ , Y2O3, T1O2, Zr0 ₂ , Hf0 ₂ , V ₂ 0 ₅ , Nb ₂ 0 ₅ , Ta ₂ 0 ₅ , Cr0 ₃ , WO3, M0O3, various combinations thereof, or other metal oxides. Seed layer 115 may be in a crystalline phase (e.g. greater than 30% crystalline as determined by X-ray diffraction). In some embodiments, the thickness of seed layer 115 is between about 50 Angstroms and 200 Angstroms, such as about 100 Angstroms.

Stack 120 may also include barrier layer 111 which may be formed over reflective layer 110. For example, barrier layer 111 may be formed between reflective layer 110 and first dielectric spacer layer 113, and may directly interface first dielectric spacer layer 113 and reflective layer 110. Barrier layer 111 may protect reflective layer 110 from oxidation and other damage. As similarly discussed above with reference to barrier layer 112, barrier layer 111 may be formed from a partially oxidized alloy of at least nickel, titanium, and niobium. In some embodiments, barrier layer 111 may be made of silicon nitride.

Top diffusion barrier layer 116 may be similar to bottom diffusion barrier layer 104 described above. In some embodiments, top diffusion barrier layer 116 (e.g., formed from silicon nitride) may be more stoichiometric than bottom diffusion barrier layer 104 to give better mechanical durability and give a smoother surface. Bottom diffusion barrier layer 104 (e.g., formed from silicon nitride) can be silicon-rich to make film denser for better diffusion effect.

While FIG. 1 illustrates a stack, such as stack 120, including two reflective layers, in some embodiments, a stack may include additional reflective layers in order to achieve a specific performance. For example, the stack may include three or more reflective layers. The multiple reflective layers may have the same or different composition and/or thicknesses. Each new reflective layer may have a corresponding seed layer and barrier layer. FIG. 1 illustrates a portion 118 of stack 120 that may be repeated. Stack portion 118 includes dielectric layer 106 (or dielectric layer 114), seed layer 108, reflective layer 110, first spacer dielectric layer 113, second spacer dielectric layer 119, seed layer 115, reflective layer 117, and barrier layer 112. In some embodiments, portion 118 might not include seed layer 108.

FIG. 2 is a schematic illustration of another article 200 including reflective layer 210 and reflective layer 217, in accordance with some embodiments. Article 200 may further include substrate 202, bottom diffusion barrier layer 204, seed layer 208, barrier layer 212, and top diffusion barrier layer 216. As similarly discussed above with reference to FIG. 1, a reflective layer, such as reflective layer 210 and reflective layer 217, may include silver. Moreover, seed layer 208 and seed layer 215 may include a metal oxide, as previously discussed with reference to seed layer 108 of FIG. 1, such as zinc oxide, titanium oxide, or tin oxide. Barrier layer 211 and barrier layer 212 may include a partially oxidized alloy of at least nickel, titanium, and niobium. As similarly discussed above with reference to first spacer dielectric layer 113 and second spacer dielectric layer 119 in FIG. 1, first spacer dielectric layer 213 and second spacer dielectric layer 219 may be made of zinc tin oxide and tin aluminum oxide, respectively.

In some embodiments, instead of a top dielectric layer and a bottom dielectric layer, article 200 may include first dielectric layer 205, second dielectric layer 206, third dielectric layer 214, and fourth dielectric layer 221. In some embodiments, first dielectric layer 205, second dielectric layer 206 may provide a bottom dielectric layer for article 200. First dielectric layer 205 may include a metal oxide, such as zinc tin oxide and may directly interface a layer, such as bottom diffusion barrier layer 204. Second dielectric layer 206 may include a metal oxide, such as tin aluminum oxide and may directly interface first dielectric layer 205 and seed layer 208. Moreover, in some embodiments, third dielectric layer 214 and fourth dielectric layer 221 may provide a top dielectric layer for article 200. Third dielectric layer 214 may include a metal oxide, such as zinc tin oxide, and may directly interface a layer in stack 220, such as barrier layer 212. Fourth dielectric layer 221 may include a metal oxide, such as zinc oxide and may directly interface third dielectric layer 214 and top diffusion barrier layer 216. When first dielectric layer 205, second dielectric layer 206, third dielectric layer 214, and fourth dielectric layer 221 are configured in this way, overall article 200 may have a high light to solar gain ratio which may be greater than 1.8 as well as a very small color change in a glass-side reflection, which may be less than 3. For example, the color change in the glass-side reflection may have a ΔΕ of 1.7.

FIG. 3 is a schematic illustration of yet another article 300 including substrate 301 and three reflective layers, each being a part of a separate stack portion. Specifically, article 300 includes first stack portion 310 having reflective layer 312, second stack portion 320 having reflective layer 322, and third stack portion 330 having reflective layer 332. Other layers of article 300 also include bottom diffusion barrier layer 302, top dielectric layer 334, bottom dielectric layer 303, and top diffusion barrier layer 336. As similarly discussed above with reference to FIG. 1 and FIG. 2, a reflective layer, such as reflective layer 312, may include silver. Furthermore a dielectric layer, such as top dielectric layer 334 and bottom dielectric layer 303, may be formed from one of T1O ₂ , ZnO, Sn02, SiAlN, or ZnSn. Article 300 may also include first spacer dielectric layer 311 and third spacer dielectric layer 313 which may be made of a metal oxide, such as zinc tin oxide. Article may further include second spacer dielectric layer 314 and fourth dielectric spacer layer 315 which may be made of a metal oxide, such as tin aluminum oxide. Processing Examples

FIG. 4 is a process flowchart corresponding to a method 400 of forming an article including one or more reflective layers and one or more barrier layers for protecting the reflective layers from oxidation, in accordance with some embodiments. Method 400 may commence with providing a substrate during operation 402. In some embodiments, the provided substrate is a glass substrate that is transparent. The substrate may include one or more previous deposited layers. For example, the substrate may include a bottom diffusion barrier layer, a bottom dielectric layer, and a seed layer. In some embodiments, one of more of these layers may not be present on the substrate. Various examples of these layers and substrates are described above with reference to FIG. 1.

Method 400 may proceed with forming a first reflective layer over the substrate during operation 404 or, more specifically, over one or more layers previously formed on the provided substrate. This operation may involve sputtering silver in a non-reactive environment. The silver layer may be deposited in an argon environment at a pressure of 2 millitorr using 90W power applied over a sputter area of about 12 cm ² resulting in a power density of about 7500 W/m ² . The resulting deposition rate may be about 2.9 Angstroms per second. The target to substrate spacing may be about 240 millimeters. The thickness of the first reflective layer may be between about 50 Angstroms and 200 Angstroms.

Method 400 may proceed with forming a barrier layer over the first reflective layer during operation 406. As noted above, the barrier layer may be formed from an alloy including one or more of nickel, chromium, titanium, niobium, and aluminum that is formed by co-sputtering of these metals in a non-reactive environment. Moreover, the barrier layer may be formed from a partially oxidized alloy which may include nickel, titanium, and niobium. In some embodiments, the barrier layer is deposited in the same processing chamber as the first reflective layer without breaking the vacuum in the chamber. Overall, the first reflective layer needs to be protected from oxygen prior to deposition of the barrier layer. In some embodiments, a partially fabricated article may be maintained in an oxygen-free environment after forming the first reflective layer and prior to forming the barrier layer.

Method 400 may proceed with forming a first spacer dielectric layer over the barrier layer during operation 408. As similarly discussed above with reference to FIG. 1, the first spacer dielectric layer may include zinc tin oxide. In some embodiments, an atomic ratio of zinc to tin in the first spacer dielectric layer may be between about 1.8 and 2.2. In some embodiments, the first spacer dielectric layer may be formed using a reactive sputtering process which may include reactive sputtering of a first target that includes an alloy of zinc and tin.

Method 400 may proceed with forming a second spacer dielectric layer over the barrier layer during operation 410. As similarly discussed above with reference to FIG. 1, the second spacer dielectric layer may include tin aluminum oxide. In some embodiments, an atomic ratio of tin to aluminum in the second spacer dielectric layer may be between about 0.8 and 1.2. In some embodiments, the second spacer dielectric layer may be formed using a reactive sputtering which may include reactive sputtering of a second target that includes an alloy of tin and aluminum.

Method 400 may proceed with forming a seed layer over the second spacer dielectric layer during operation 412. As similarly discussed above with reference to FIG. 1, a seed layer may include one of ZnO, Sn0 ₂ , Sc ₂ 0 ₃ , Y ₂ 0 ₃ , Ti0 ₂ , Zr0 ₂ , Hf0 ₂ , V ₂ 0 ₅ , Nb ₂ O _s , Ta ₂ 0 ₅ , Cr0 ₃ , W0 ₃ , Mo0 ₃ , various combinations thereof, or other metal oxides. Moreover, the seed layer may be formed using any suitable deposition technique, such as reactive sputtering.

Method 400 may proceed with forming a second reflective layer over the seed layer during operation 413. As discussed above with reference to operation 404, this operation may involve sputtering silver in a non-reactive environment. The thickness of the second reflective layer may be between about 50 Angstroms and 200 Angstroms.

During operation 414, it may be determined whether or not an additional reflective layer should be formed in the article, which may be included in a low-E panel. If another reflective layer is to be formed, method 400 may proceed to operation 404. If another reflective layer is not formed, method 400 may proceed to operation 416. Accordingly, in response to determining that another reflective layer should be formed, method 400 may proceed to operation 404 and another reflective layer as well as corresponding barrier layers, seed layers, and spacer dielectric layers may be formed.

In response to determining that another reflective layer should not be formed, method 400 may proceed to form a barrier layer over second reflective layer during operation 416. As similarly discussed above with reference to operation 406, the barrier layer may be formed from an alloy including one or more of nickel, chromium, titanium, niobium, and aluminum that is formed by co-sputtering of these metals in a non-reactive environment. Moreover, the barrier layer may be formed from a partially oxidized alloy which may include nickel, titanium, and niobium.

Method 400 may then proceed with forming a dielectric layer over the barrier layer during operation 418. This operation may involve sputtering titanium or tin in an oxygen containing environment. During this operation, the barrier layer prevents oxygen in the oxygen containing environment from reaching and reacting with metallic silver in the reflective layer. In some embodiments, the dielectric layer may include zinc tin oxide.

Method 400 may then proceed with forming a diffusion barrier layer over the dielectric layer during operation 420. As similarly discussed above, the diffusion barrier layer may include silicon nitride. The thickness of the diffusion barrier layer may be between about 50 Angstroms and 300 Angstroms or, more specifically, between about 100 Angstroms and 200 Angstroms.

Method 400 may then proceed with applying a heat treatment to the article during operation 422. In some embodiments, the heat treatment may be a tempering process which may involve heating the article to a temperature of 650 degrees Celsius for up to about 8 minutes. In response to the heat treatment, the color and transmissivity of the article may remain substantially unchanged. For example, a color change of a glass-side reflectance of low-E panels that include the article may change by less than 3% as compared to the as-coated panel. Moreover, the low emissivity panels may have a light to solar gain ratio of at least about 1.8.

Experimental Results

FIG. 5 is a graph illustrating transmission and reflection properties of articles including one or more spacer dielectric layers prior to and after the application of a heat treatment, implemented in accordance with some embodiments. Graph 500 includes pair of lines 502, pair of lines 504, and pair of lines 506, which may each represent one or more optical characteristics measured as a function of wavelength. Pair of lines 502 represents the fraction of light transmission of low emissivity panels including spacer layers as disclosed herein. Moreover, pair of lines 506 represents a film side reflection of such low emissivity panels. Pair of lines 504 represents a glass-side reflection of such low emissivity panels. Each pair of lines may include a solid line and a dashed line. Solid lines represent the spectra measured for non-heat-treated sample which are as-coated (AC). Dashed lines represent the spectra measured for heat treated samples (HT). As shown in FIG. 5 the spectra for heat treated and as-coated low emissivity panels are very similar indicating little to no change in color or other optical characteristics of the low emissivity panels in response to the application of the heat treatment.

Conclusion

Although the foregoing concepts have been described in some detail for purposes of clarity of understanding, it will be apparent that certain changes and modifications may be practiced within the scope of the appended claims. It should be noted that there are many alternative ways of implementing the processes, systems, and apparatuses. Accordingly, the present embodiments are to be considered as illustrative and not restrictive.