Patent Description:
An ordinary surface-relief diffraction grating, a so-called binary grating, comprises a plurality of ridges and grooves, wherein the tops of the ridges and the bottoms of the grooves extend parallel to each other. Well-known manufacturing processes exist for fabricating such binary gratings. In case of such binary gratings, normally incident light is diffracted such that equal diffraction efficiencies are produced in both negative and positive diffraction orders. This effect arises from the mirror symmetry of the cross-sectional profiles of binary gratings.

In many applications, for example, in many waveguide-based display structures, diffraction preferentially toward one or more specific diffraction orders may be desirable and diffraction into other diffraction orders may be considered optical loss. To direct light preferentially toward specific diffraction orders, gratings with non-mirror symmetric cross-sectional profiles must be used. One example of such non-symmetric gratings is the so-called blazed grating with a triangular or sawtooth-shaped cross-sectional profile.

Typically, blazed gratings are manufactured using processes based on grayscale lithography. Although such processes have been refined to yield gratings with acceptable characteristics, the features, especially, the apexes, of blazed gratings produced using grayscale lithography are generally relatively rounded due to the low contrast of typical greyscale lithography resists. Such deviation from ideal blazed profiles may reduce the diffraction efficiency of blazed gratings produced using grayscale lithography and/or increase the optical scattering caused by such gratings.

In light of the above, it may be desirable to develop new solutions related to blazed gratings.

Pertinent prior art is disclosed in <CIT> and <CIT>.

In this specification, a method for fabricating a blazed grating comprising a ridge having a blaze facet facing a blaze facet direction and an anti-blaze facet facing an anti-blaze facet direction, the blaze facet direction and the anti-blaze facet direction extending along a grating cross-sectional plane, is provided. The method comprises providing a substrate and a patterned mask layer on the substrate, performing primary dry etching of the substrate such that primary ions are accelerated towards a primary etch direction to impinge on the substrate, and performing secondary dry etching of the substrate such that secondary ions are accelerated towards a secondary etch direction to impinge on the substrate.

A primary projection of the primary etch direction onto the grating cross-sectional plane and a secondary projection of the secondary etch direction onto the grating cross-sectional plane extend perpendicular to one and the other of the blaze facet direction and the anti-blaze facet direction, respectively, and ions (of the primary ions and the secondary ions) accelerated towards a direction with a projection onto the grating cross-sectional plane perpendicular to the blaze facet direction are collimated to form a collimated ion beam for etching the substrate.

The present disclosure will be better understood from the following detailed description read in light of the accompanying drawings, wherein:.

Unless specifically stated to the contrary, any drawing of the aforementioned drawings may be not drawn to scale such that any element in said drawing may be drawn with inaccurate proportions with respect to other elements in said drawing in order to emphasize certain structural aspects of the embodiment of said drawing.

Corresponding, e.g., identical or similar, elements of the embodiments presented in the drawings have been referred to using the same reference numbers. Corresponding elements in the aforementioned drawings may be disproportionate to each other in said drawings in order to emphasize certain structural aspects of the embodiments of said drawings.

<FIG> illustrates method <NUM> for fabricating a blazed grating comprising a ridge having a blaze facet facing a blaze facet direction and an anti-blaze facet facing an anti-blaze facet direction, the blaze facet direction and the anti-blaze facet direction extending along a grating cross-sectional plane. In other embodiments, a method for fabricating a blazed grating may be identical, similar, or different to the method <NUM> of the embodiment of <FIG>.

In the embodiment of <FIG>, the method <NUM> comprises providing a substrate and a patterned mask layer <NUM> on the substrate, performing primary dry etching <NUM> of the substrate such that primary ions are accelerated towards a primary etch direction to impinge on the substrate, and performing secondary dry etching <NUM> of the substrate such that secondary ions are accelerated towards a secondary etch direction to impinge on the substrate.

Throughout this specification, "dry etching" may refer to removal of material by exposure to ion bombardment. Typical dry etching techniques include Reactive Ion Etching (RIE), Deep Reactive Ion Etching (DRIE), Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE), ion milling, Ion beam Etching (IBE), Reactive Ion Beam Etching (RIBE), and variants thereof.

In this specification, performing dry etching of a substrate such that specific ions are "accelerated towards" a specific direction to impinge on the substrate may refer to the ions being provided with an average velocity, e.g., a drift velocity, towards the specific direction. Typically, such ions may be accelerated towards a specific direction by an electric field.

In the embodiment of <FIG>, a primary projection of the primary etch direction onto the grating cross-sectional plane and a secondary projection of the secondary etch direction onto the grating cross-sectional plane extend perpendicular to one and the other of the blaze facet direction and the anti-blaze facet direction, respectively, and ions (of the primary ions and the secondary ions) accelerated towards a direction with a projection onto the grating cross-sectional plane perpendicular to the blaze facet direction are collimated to form a collimated ion beam for etching the substrate. Generally, such primary etch direction and secondary etch direction and utilization of a collimated ion beam for etching a substrate perpendicular to a blaze facet direction may facilitate fabricating blazed gratings with sharper or less-rounded features, e.g., apexes and/or facets.

Herein, a "collimated ion beam" may refer to a beam of ions propagating from a collimator towards a specific etch direction, e.g., a primary etch direction or a secondary etch direction. Additionally or alternatively, an ion beam propagating from a collimator towards a specific etch direction may be referred to as a collimated ion beam, for example, if the ion beam has a maximum angular deviation from the primary etch direction of <NUM>°, <NUM>°, or <NUM>°. In case a collimated ion beam is formed for etching a substrate, such maximum angular deviation may be determined at the location of the substrate.

As indicated in <FIG> using dashed lines, the process of performing primary dry etching <NUM> may optionally comprise forming a groove extending in the substrate <NUM> along the primary etch direction, the method <NUM> may optionally comprise depositing first material into the groove <NUM> to form an interstitial feature, and the process of performing secondary dry etching <NUM> may optionally comprise utilizing the interstitial feature as an etch stop <NUM>. In general, utilization of an interstitial feature as an etch stop while performing secondary dry etching may facilitate fabrication of blazed gratings with sharper, less rounded features and/or smoother and/or more even facets. In other embodiments, a method for fabricating a blazed grating may or may not comprise one or more of such features.

In this specification, a "process" may refer to a series of one or more steps, leading to an end result. As such, a process may be a single-step or a multi-step process. Additionally, a process may be divisible to a plurality of sub-processes, wherein individual sub-processes of such plurality of sub-processes may or may not share common steps.

Herein, a "step" may refer to a measure taken in order to achieve a pre-defined result. For example, an "atomic layer deposition step" may refer to a step of a process, whereby a layer is formed by atomic layer deposition. As again indicated in <FIG> using dashed lines, the method <NUM> may optionally comprise revealing a ridge portion <NUM> of the substrate prior to the process of performing secondary dry etching <NUM>. Generally, revealing a ridge portion of a substrate prior to a process of performing secondary dry etching may facilitate forming blazed gratings without post-processing step(s), whereby portions of a substrate released during the process of performing secondary dry etching are removed. In embodiments according to the claimed subject-matter, a method for fabricating a blazed grating does not comprise revealing a ridge portion of a substrate prior to a process of performing secondary dry etching.

Further, the process of depositing first material into the groove <NUM> may optionally comprise an atomic layer deposition <NUM> step. Generally, a process of depositing first material into the groove comprising an atomic layer deposition step may facilitate forming interstitial features in narrower grooves and/or with increased uniformity. In other embodiments, a process of depositing first material into the groove may or may not comprise an atomic layer deposition step.

As also indicated in <FIG> using dashed lines, the process of providing a substrate and a patterned mask layer <NUM> may optionally comprise providing a plurality of elongated through-holes in a coating <NUM> arranged on the substrate to form the mask layer, the plurality of elongated through-holes extending perpendicular to the grating cross-sectional plane. In other embodiments, a process of providing a substrate and a patterned mask layer may or may not comprise providing a plurality of elongated through-holes in a coating arranged on the substrate to form the mask layer.

In an embodiment, a method for fabricating a blazed grating comprises steps implementing processes corresponding to the processes of the method <NUM> of the embodiment of <FIG>. In other embodiments, a method for fabricating a blazed grating may comprise steps implementing processes corresponding to the non-optional processes of the method <NUM> of the embodiment of <FIG>. In general, a method for fabricating a blazed grating may comprise any number of additional processes or steps that are not disclosed herein in connection to the method <NUM> of the embodiment of <FIG>.

Steps of a method for fabricating a blazed grating implementing processes corresponding to any of the processes of the method <NUM> of the embodiment of <FIG> need not be executed in a fixed order. However, any steps implementing a process corresponding to the process of providing a substrate and a patterned mask layer <NUM> of the method <NUM> may be generally executed prior to steps implementing any process corresponding to any of the processes of performing primary dry etching <NUM> and performing secondary dry etching <NUM>; any steps implementing a process corresponding to the process of forming a groove extending in the substrate <NUM> of the method <NUM> may be generally executed prior to steps implementing any process corresponding to the process of depositing first material into the groove <NUM>; and any steps implementing a process corresponding to the process of depositing first material into the groove <NUM> of the method <NUM> may be generally executed prior to steps implementing any process corresponding to the process of utilizing the interstitial feature as an etch stop <NUM>.

<FIG>, collectively referred to throughout this specification as <FIG>, schematically depict a series of subsequent stages of a method for fabricating a blazed grating <NUM>, which comprises a ridge <NUM> having a blaze facet <NUM> facing a blaze facet direction <NUM> and an anti-blaze facet <NUM> facing an anti-blaze facet direction <NUM>, the blaze facet direction <NUM> and the anti-blaze facet <NUM> extending along a grating cross-sectional plane <NUM>, according to an embodiment. In <FIG>, the grating cross-sectional plane <NUM> extends perpendicular to the plane of the drawings of <FIG>. In other embodiments, a method for fabricating a blazed grating may comprise a series of stages similar or different to the stages of the method of the embodiment of <FIG>.

The embodiment of <FIG> may be in accordance with any of the embodiments disclosed with reference to and/or in conjunction with <FIG>. Additionally or alternatively, although not explicitly stated in the following, the embodiment of <FIG> may generally comprise any features of any of the embodiments disclosed with reference to and/or in conjunction with <FIG>.

With reference to <FIG>, the blazed grating <NUM> comprises a plurality of ridges <NUM>, each ridge of the plurality of ridges <NUM> having a blaze facet <NUM> facing the blaze facet direction <NUM> and an anti-blaze facet <NUM> facing the anti-blaze facet direction <NUM>. In other embodiments, a blazed grating may comprise at least one such ridge or a plurality of, i.e., at least two, such ridges.

With reference to <FIG>, the method comprises providing a substrate <NUM> and a patterned mask layer <NUM> on the substrate <NUM>. The process of providing the substrate <NUM> and the patterned mask layer <NUM> comprises providing a coating <NUM> on the substrate <NUM> and providing a plurality of elongated through-holes <NUM> in the coating <NUM> to form the mask layer <NUM>. The plurality of elongated through-holes <NUM> extends perpendicular to the grating cross-sectional plane <NUM>.

The substrate <NUM> of the embodiment of <FIG> may be formed of high-refractive-index polymer material(s), using any suitable application method(s), for example, spin coating, spray coating, and/or inkjet printing. In other embodiments, a substrate may comprise any suitable material (s), which may be formed using any suitable process (es).

The mask layer <NUM> of the embodiment of <FIG> may be formed of aluminum oxide (AlO<NUM>) deposited by electron beam evaporation. In the claimed subject-matter, a mask layer comprises inorganic material(s), including oxide and/or nitride material(s), such as aluminum oxide (AlO<NUM>/AlOx), titanium oxide (TiO<NUM>/TiO<NUM>), silicon oxide (SiO<NUM>/SiOx) and/or silicon nitride (Si<NUM>N<NUM>/SiNx), which may be formed using any suitable process(es), for example, sputtering, evaporation, Chemical Vapor Deposition (CVD), Plasma Enhanced Chemical Vapor Deposition (PECVD), Inductively Coupled Plasma Chemical Vapor Deposition (ICP-CVD), Atomic Layer Deposition (ALD), and/or variants thereof.

The method of the embodiment of <FIG> may constitute an example of a method for fabricating a blazed grating, whereby a blazed grating is formed onto a face of a waveguide for coupling light into the waveguide and/or out of the waveguide. As such, the substrate <NUM> may be arranged onto a face <NUM> of a waveguide <NUM>. In other embodiments, a blazed grating may be formed for any suitable use(s) in any suitable application(s), for example, onto a face of a waveguide for coupling light into the waveguide and/or out of the waveguide.

In case the substrate <NUM> is arranged onto a face <NUM> of a waveguide <NUM>, the blazed grating <NUM> of the embodiment of <FIG> is formed into an additional material layer arranged onto the waveguide <NUM>. In other embodiments, wherein a blazed grating is formed onto a face of a waveguide for coupling light into the waveguide and/or out of the waveguide, said blazed grating may or may not be arranged onto such additional material layer. In some such embodiments, a blazed grating may be formed directly into a waveguide.

In this disclosure, a "waveguide" may refer to an optical waveguide. Additionally or alternatively, a waveguide may refer to a two-dimensional waveguide, wherein light may be confined along a thickness direction of said waveguide.

Further, a "face" of a waveguide may refer to a part of a surface of said waveguide viewable from or facing a certain viewing direction. Additionally or alternatively, faces of a waveguide may refer to surfaces suitable for or configured to confine light in said waveguide by total internal reflection.

With reference to <FIG>, the method comprises performing primary dry etching of the substrate <NUM> such that primary ions <NUM>, indicated schematically by white dots, are accelerated towards a primary etch direction <NUM> to impinge on the substrate <NUM>.

In the embodiment of <FIG>, a primary projection <NUM> of the primary etch direction <NUM> onto the grating cross-sectional plane <NUM> extends perpendicular to anti-blaze facet direction <NUM>.

The process of performing primary dry etching of the embodiment of <FIG> comprises forming a groove <NUM> extending in the substrate <NUM> along the primary etch direction <NUM>. In other embodiments, a process of performing primary dry etching may or may not comprise forming such groove.

As indicated in <FIG>, an interface <NUM> between the substrate and the mask layer extends along a base plane <NUM>, and the primary projection <NUM> extends perpendicular to the base plane <NUM>. The base plane <NUM> extends perpendicular to the grating cross-sectional plane <NUM>. Generally, a primary projection or a secondary projection extending perpendicular to a base plane may enable forming blazed gratings with upright anti-blaze facets, which may impart increased diffraction efficiency. In other embodiments, a primary projection or a secondary projection may or may not extend perpendicular to a base plane.

Herein, a "base plane" may refer to a fictitious surface along which an interface between a substrate and a mask layer extends. A base plane may be planar, for example, in case of a flat interface, or curved, for example, in case of a curved interface.

In the embodiment of <FIG>, the primary etch direction <NUM> may extend parallel to the grating cross-sectional plane <NUM>. Consequently, the primary etch direction <NUM> may extend perpendicular to the base plane <NUM>. Generally, a primary etch direction or a secondary etch direction extending perpendicular to a base plane may enable utilization of a wider range of dry etching techniques, including reactive ion etching (RIE) and ion milling. In other embodiments, a primary etch direction or a secondary etch direction may or may not extend perpendicular to a base plane. For example, in some embodiments, each of a primary projection and a secondary projection may extend obliquely with respect to a base plane. Generally, a primary projection and a secondary projection extending obliquely with respect to a base plane may enable forming blazed gratings with slanted anti-blaze facets, which may, for example, facilitate spatially modulating diffraction efficiencies of the blazed gratings.

Since the primary etch direction <NUM> may extend perpendicular to the base plane <NUM>, the process of performing primary dry etching of the embodiment of <FIG> may comprise a RIE step. During the RIE step, the substrate <NUM> may be etched, for example, using oxygen plasma. In other embodiments, wherein a primary etch direction or a secondary etch direction extends perpendicular to a base plane, a process of performing primary dry etching may comprise any suitable step(s), for example, a RIE step and/or an ion milling step.

With reference to <FIG>, the method comprises performing secondary dry etching of the substrate <NUM> such that secondary ions <NUM>, indicated schematically by black dots, are accelerated towards a secondary etch direction <NUM> to impinge on the substrate <NUM>.

In the embodiment of <FIG>, a secondary projection <NUM> of the secondary etch direction <NUM> onto the grating cross-sectional plane <NUM> extends perpendicular to blaze facet direction <NUM>. In other embodiments, a secondary projection of a secondary etch direction onto a grating cross-sectional plane may extend perpendicular to a blaze facet direction or an anti-blaze facet direction.

In the embodiment of <FIG>, the secondary ions <NUM> are collimated to form a collimated secondary ion beam for etching the substrate <NUM>. In other embodiments, primary ions and/or secondary ions may be collimated to form a collimated primary ion beam and/or a collimated secondary ion beam for etching a substrate.

The process of performing secondary dry etching of the embodiment of <FIG> may comprise a RIBE step. During such RIBE step, the substrate <NUM> may be etched, for example, using oxygen ions. In other embodiments, a process of performing dry etching, wherein ions are accelerated towards a direction with a projection onto a grating cross-sectional plane perpendicular to a blaze facet direction and said ions are collimated to form a collimated ion beam for etching a substrate, may comprise any suitable step(s), for example, an IBE and/or a RIBE step.

With reference to <FIG>, the method further comprises a post-processing step, whereby portions of the substrate <NUM> released during the process of performing secondary dry etching are removed to form the plurality of ridges <NUM>. In other embodiments, a method for fabricating a blazed grating may or may not comprise such post-processing step.

The post-processing step of the embodiment of <FIG> may be implemented as a wet cleaning step, such as, a water immersion step. In other embodiments, wherein a method for fabricating a blazed grating comprises a post-processing step, whereby portions of a substrate released during a process of performing secondary dry etching are removed to form one or more ridges, the post-processing step may be implemented in any suitable manner, for example, as a wet cleaning step, such as, a water immersion step.

In the embodiment of <FIG>, under primary etching conditions (i.e., in the process of performing primary dry etching), the primary ions <NUM> may exhibit a first primary chemical reactivity with the mask layer <NUM> and a second primary chemical reactivity higher than the first primary chemical reactivity with the substrate <NUM>. Additionally, under secondary etching conditions (i.e., in the process of performing secondary dry etching), the secondary ions <NUM> may exhibit a first secondary chemical reactivity with the mask layer <NUM> and a second secondary chemical reactivity higher than the first secondary chemical reactivity with the substrate <NUM>. Generally, utilization of such reactive ions for etching a substrate may increase selectivity of dry etching processes, which may, in turn, facilitate fabricating blazed gratings with sharper, less rounded features. Examples of dry etching techniques, wherein such reactive ions are utilized, include RIE, DRIE, ICP-RIE, RIBE and variants thereof. In other embodiments, primary ions may or may not exhibit, under primary etching conditions, a first primary chemical reactivity with a mask layer and a second primary chemical reactivity higher than the first primary chemical reactivity with a substrate, and/or secondary ions may or may not exhibit, under secondary etching conditions, a first secondary chemical reactivity with the mask layer and a second secondary chemical reactivity higher than the first secondary chemical reactivity with the substrate.

<FIG>, collectively referred to throughout this specification as <FIG>, schematically depict a series of subsequent stages of a method for fabricating a blazed grating <NUM> comprising a ridge <NUM> having a blaze facet <NUM> facing a blaze facet direction <NUM> and an anti-blaze facet <NUM> facing an anti-blaze facet direction <NUM>, the blaze facet direction <NUM> and the anti-blaze facet <NUM> extending along a grating cross-sectional plane <NUM>, according to an embodiment. In <FIG>, the grating cross-sectional plane <NUM> extends perpendicular to the plane of the drawings of <FIG>. In other embodiments, a method for fabricating a blazed grating may comprise a series of stages similar or different to the stages of the method of the embodiment of <FIG>.

The embodiment of <FIG> may be in accordance with any of the embodiments disclosed with reference to and/or in conjunction with any of <FIG> and <FIG>. Additionally or alternatively, although not explicitly stated in the following, the embodiment of <FIG> may generally comprise any suitable features of any of the embodiments disclosed with reference to and/or in conjunction with any of <FIG> and <FIG>.

With reference to <FIG>, the method comprises providing a substrate <NUM> and a patterned mask layer <NUM> on the substrate <NUM>, comprising providing a coating <NUM> on the substrate <NUM> and providing a plurality of elongated through-holes <NUM> in the coating <NUM> to form the mask layer <NUM>, as well as performing primary dry etching of the substrate <NUM> such that primary ions <NUM>, indicated schematically by white dots, are accelerated towards a primary etch direction <NUM> to impinge on the substrate <NUM>.

In the embodiment of <FIG>, a primary projection <NUM> of the primary etch direction <NUM> onto the grating cross-sectional plane <NUM> extends perpendicular to anti-blaze facet direction <NUM>. Additionally, the process of performing primary dry etching of the embodiment of <FIG> comprises forming a groove <NUM> extending in the substrate <NUM> along the primary etch direction <NUM>.

As the processes of providing a substrate and a patterned mask layer and performing primary dry etching of the embodiment of <FIG> may be implemented in accordance with what is disclosed above with reference to <FIG>, further details of these processes are omitted herein for brevity and conciseness.

With reference to <FIG> and <FIG>, the method comprises depositing first material <NUM> into the groove <NUM> to form an interstitial feature <NUM> and, prior to the process of depositing first material <NUM> into the groove <NUM>, removing the patterned mask layer <NUM>. In other embodiments, a method for fabricating a blazed grating may or may not comprise depositing first material into a groove to form an interstitial feature. In embodiments, wherein a method for fabricating a blazed grating comprises depositing first material into a groove to form an interstitial feature, the method may or may not comprise removing a patterned mask layer prior to a process of depositing first material into the groove.

The first material <NUM> of the embodiment of <FIG> may be aluminum oxide (AlO<NUM> or AlOx) deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD). In other embodiments, a mask layer may comprise any suitable material(s), which may be formed using any suitable process(es), for example, an oxide or a nitride material, such as aluminum oxide (AlO<NUM>/AlOx), titanium oxide (TiO<NUM>/TiO<NUM>), silicon oxide (SiO<NUM>/SiOx) or silicon nitride (Si<NUM>N<NUM>/SiNx), or a mixture thereof. A first material may generally be deposited using any suitable deposition method(s), for example, sputtering, evaporation, Chemical Vapor Deposition (CVD), PECVD, Inductively Coupled Plasma Chemical Vapor Deposition (ICP-CVD), Atomic Layer Deposition (ALD), and/or variants thereof.

With reference to <FIG>, the method comprises revealing a ridge portion <NUM> of the substrate <NUM> prior to a process of performing secondary dry etching, which is not according to the claimed subject-matter. In embodiments according to the claimed subject-matter a method for fabricating a blazed grating does not comprise revealing a ridge portion of a substrate prior to a process of performing secondary dry etching.

In the embodiment of <FIG>, the process of revealing the ridge portion <NUM> of the substrate <NUM> may comprise an additional dry etching step. In other words, at least part of the first material <NUM> covering the ridge portion <NUM> may be etched using dry etching methods. In other embodiments, wherein a method for fabricating a blazed grating comprises revealing a ridge portion of a substrate, said process of revealing a ridge portion may be implemented in any suitable manner.

With reference to <FIG>, the method comprises performing secondary dry etching of the substrate <NUM> such that secondary ions <NUM>, indicated schematically by black dots, are accelerated towards a secondary etch direction <NUM> to impinge on the substrate <NUM>. The secondary ions <NUM> are collimated to form a collimated secondary ion beam for etching the substrate <NUM>.

In the embodiment of <FIG>, the process of performing secondary dry etching comprises utilizing the interstitial feature <NUM> as an etch stop. In other embodiments, a process of performing secondary dry etching may or may not comprise utilizing the interstitial feature as an etch stop.

In the embodiment of <FIG>, the interstitial feature <NUM> is arranged towards the anti-blaze facet direction <NUM> from the ridge portion <NUM>. In other embodiments, an interstitial feature may be arranged towards a blaze facet direction or towards an anti-blaze facet direction from a ridge portion. In other embodiments, wherein a secondary projection of the secondary etch direction onto the grating cross-sectional plane extends perpendicular to one of the blaze facet direction and the anti-blaze facet direction, an interstitial feature may be arranged towards the other of the blaze facet direction and the anti-blaze facet direction from a ridge portion.

With reference to <FIG>, the method further comprises a post-processing step, whereby the interstitial feature <NUM> is removed. Such step may be implemented, for example, as a wet etching step. In other embodiments, a method for fabricating a blazed grating may or may not comprise such post-processing step.

<FIG>, collectively referred to throughout this specification as <FIG>, schematically depict a series of subsequent stages of a method not according to the claimed subject-matter for fabricating a blazed grating <NUM> comprising a ridge <NUM> having a blaze facet <NUM> facing a blaze facet direction <NUM> and an anti-blaze facet <NUM> facing an anti-blaze facet direction <NUM>, the blaze facet direction <NUM> and the anti-blaze facet <NUM> extending along a grating cross-sectional plane <NUM>, according to an embodiment. In <FIG>, the grating cross-sectional plane <NUM> extends perpendicular to the plane of the drawings of <FIG>. In other embodiments, a method for fabricating a blazed grating may comprise a series of stages similar or different to the stages of the method of the embodiment of <FIG>.

The embodiment of <FIG> may be in accordance with any of the embodiments disclosed with reference to and/or in conjunction with any of <FIG>. Additionally or alternatively, although not explicitly stated in the following, the embodiment of <FIG> may generally comprise any features of any of the embodiments disclosed with reference to and/or in conjunction with any of <FIG>.

With reference to <FIG>, the method comprises providing a substrate <NUM> and a patterned mask layer <NUM> on the substrate <NUM>. The method of the embodiment of <FIG> may constitute an example of a method for fabricating a blazed grating, whereby the blazed grating is formed onto a contact face of a nanoimprint stamp. As such, the substrate <NUM> of the embodiment of <FIG> may be a nanoimprint stamp <NUM> having a contact face <NUM>.

In the embodiment of <FIG>, the nanoimprint stamp <NUM> may be formed of single-crystalline silicon. In other embodiments, a nanoimprint stamp may be formed of or comprise any suitable material(s). For example, in some embodiments, a nanoimprint stamp may comprise a plurality of stacked layers formed of different materials.

As indicated in <FIG>, an interface <NUM> between the substrate <NUM> and the mask layer <NUM> extends along a base plane <NUM> extending perpendicular to the grating cross-sectional plane <NUM>.

With reference to <FIG>, the method performing primary dry etching of the substrate <NUM> such that primary ions <NUM>, indicated schematically by white dots, are accelerated towards a primary etch direction <NUM> to impinge on the substrate <NUM>. In the embodiment of <FIG>, the primary ions <NUM> are collimated to form a collimated primary ion beam for etching the substrate <NUM>. In other embodiments, primary ions may or may not be collimated to form a collimated primary ion beam for etching a substrate.

In the embodiment of <FIG>, a primary projection <NUM> of the primary etch direction <NUM> onto the grating cross-sectional plane <NUM> extends perpendicular to blaze facet direction <NUM>. Additionally, the process of performing primary dry etching of the embodiment of <FIG> comprises forming a groove <NUM> extending in the substrate <NUM> along the primary etch direction <NUM>.

With reference to <FIG>, the method comprises depositing first material <NUM> into the groove <NUM> to form an interstitial feature <NUM>. In other embodiments, a method for fabricating a blazed grating may or may not comprise depositing first material into a groove to form an interstitial feature.

In the embodiment of <FIG>, the process of depositing first material <NUM> into the groove <NUM> comprises an atomic layer deposition step. In other words, at least part of the first material <NUM> deposited into the groove <NUM> is deposited using atomic layer deposition. The first material <NUM> of the embodiment of <FIG> may be aluminum oxide (AlO<NUM> or AlOx). In other embodiments, wherein a process of depositing first material into a groove comprises an atomic layer deposition step, any suitable type of first material may be used.

With reference to <FIG>, the method comprises revealing a ridge portion <NUM> of the substrate <NUM> prior to a process of performing secondary dry etching. In the embodiment of <FIG>, the process of revealing the ridge portion <NUM> of the substrate <NUM> may comprise, for example, a lift-off step for removing the mask layer <NUM> and first material <NUM> covering the ridge portion <NUM>.

With reference to <FIG>, the method comprises performing secondary dry etching of the substrate <NUM> such that secondary ions <NUM>, indicated schematically by black dots, are accelerated towards a secondary etch direction <NUM> to impinge on the substrate <NUM>. The process of performing secondary dry etching comprises utilizing the interstitial feature <NUM> as an etch stop. The interstitial feature <NUM> is arranged towards the blaze facet direction <NUM> from the ridge portion <NUM>.

In the embodiment of <FIG>, the secondary etch direction <NUM> may extend parallel to the grating cross-sectional plane <NUM>. Consequently, the secondary etch direction <NUM> may extend perpendicular to the base plane <NUM>. Since the secondary etch direction <NUM> may extend perpendicular to the base plane <NUM>, the process of performing primary dry etching of the embodiment of <FIG> may comprise a RIE step.

Finally, with reference to <FIG>, the method further comprises a post-processing step, whereby the interstitial feature <NUM> is removed, for example, by wet etching.

It is to be understood that the embodiments described above may be used in combination with each other. Several of the embodiments may be combined together to form a further embodiment.

It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above, instead they may vary within the scope of the claims.

It will be understood that any benefits and advantages described above may relate to one embodiment or may relate to several embodiments.

Claim 1:
A method (<NUM>) for fabricating a blazed grating comprising a ridge having a blaze facet facing a blaze facet direction and an anti-blaze facet facing an anti-blaze facet direction, the blaze facet direction and the anti-blaze facet direction extending along a grating cross-sectional plane, the method comprising:
- providing a substrate and a patterned mask layer (<NUM>) on the substrate,
- performing primary dry etching (<NUM>) of the substrate such that primary ions are accelerated towards a primary etch direction to impinge on the substrate, and
- performing secondary dry etching (<NUM>) of the substrate such that secondary ions are accelerated towards a secondary etch direction to impinge on the substrate;
wherein a primary projection of the primary etch direction onto the grating cross-sectional plane extends perpendicular to the anti-blaze facet direction and a secondary projection of the secondary etch direction onto the grating cross-sectional plane extends perpendicular to the blaze facet direction and ions accelerated towards a direction with a projection onto the grating cross-sectional plane perpendicular to the blaze facet direction are collimated to form a collimated ion beam for etching the substrate;
wherein the method (<NUM>) comprises not revealing a ridge portion of the substrate prior to the process of performing secondary dry etching (<NUM>) and the mask layer comprises an inorganic material.