JP4778958B2 - Manufacturing method of optical film - Google Patents

Description

TECHNICAL FIELD The present invention relates to optical films and related articles, systems, and methods.

BACKGROUND Optical devices and optical systems are commonly used when light manipulation is desired. Examples of optical devices include lenses, polarizers, optical filters, anti-reflective coatings, retarders (eg, quarter wave plates), and beam splitters (eg, polarized and non-polarized beam splitters).

SUMMARY The present invention relates to films for optical applications, articles comprising such films, methods for producing such films, and systems utilizing such films.

  In a first aspect, the invention provides an article comprising a first layer of material, the first layer of material comprising at least one trench, the layer comprising a particular axis. A step of being birefringent with respect to light of wavelength λ propagating in the layer along the λ, wherein λ is between 150 nm and 2,000 nm, and sequentially forming a plurality of single layers of the second material in the trench Filling with at least about 50% of the volume of the trench by forming.

  In another aspect, the invention features a method that includes forming a layer of material on a lattice surface using atomic layer deposition.

  In another aspect, the invention features a method that includes forming an optical retardation film using atomic layer deposition.

  In another aspect, the present invention is an article comprising a continuous layer comprising alternating rows of first materials and rows of nanolaminate materials, wherein the continuous layers are continuous layers along a particular axis. It is characterized by an article that is birefringent with respect to light of wavelength λ propagating through it and λ is between 150 nm and 2,000 nm.

  In another aspect, the invention features an article that includes a birefringent optical retardation film that includes a nanolaminate material.

  Embodiments of the invention can include one or more of the following features.

  This filling can further include forming one or more monolayers of a third material in the trench, wherein the second material and the third material are different materials. Single layers of the second and third materials can form a nanolaminate material. By sequentially forming a plurality of monolayers of the second material in the trench, at least about 80% (eg, at least about 90%, at least about 99%) of the volume of the trench can be filled. The second material may be different from the first material. The layers of the first material and the second material can form one continuous layer. This continuous layer can be birefringent for light of wavelength λ propagating in the continuous layer along a specific axis, where λ is between 150 nm and 2,000 nm. The article can include additional trenches formed in the surface of the first material layer. The method can further include filling at least about 50% of the respective volume of the additional trench by sequentially forming multiple monolayers of the second material in the additional trench. The method includes at least about 80% (eg, at least about 90%, at least about 99%) of the respective volume of the additional trench by sequentially forming a plurality of monolayers of the second material in the additional trench. The method may further include filling. These trenches can be separated by a first row of material. The layer of the first material can form a surface relief grating. The surface relief grating can have a grating period of about 500 nm or less (eg, about 400 nm or less, about 300 nm or less, about 200 nm or less, about 100 nm or less).

  The trench can be formed by etching a continuous layer of a first material (eg, reactive ion etching). The trench can be formed using lithography. For example, the trench can be formed using nanoimprint lithography or holographic lithography. When the trench is formed using nanoimprint lithography, the nanoimprint lithography includes forming a pattern in the thermoplastic material. Alternatively or in addition, the nanoimprint lithography can include forming a pattern in the UV curable material.

  The method can further include forming a layer of the second material over the filled trench by sequentially forming a single layer of the second material over the trench. The layer of the second material has an arithmetic average roughness surface of about 50 nm or less (eg, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 10 nm or less).

The second material may be a dielectric material. In some embodiments, forming a plurality of monolayers of the second material includes laminating a monolayer of a precursor and exposing the monolayer of the precursor to a particular reagent to form a monolayer of the second material. Forming. This reagent can chemically react with the precursor to form a second material. For example, the reagent can oxidize the precursor to form the second material. The deposition of the precursor monolayer can include introducing a first gas containing the precursor into a chamber containing the article. During the deposition of the precursor monolayer, the pressure of the first gas in the chamber can be about 0.01 to about 100 Torr. Exposure of the precursor monolayer to the reagent can include introducing a second gas containing the reagent into the chamber. During the exposure of the precursor monolayer to the reagent, the pressure of the second gas in the chamber can be from about 0.01 to about 100 Torr. A third gas can be introduced into the chamber after introducing the first gas and before introducing the second gas. This third gas may be inert to the precursor. The third gas can include at least one gas selected from the group consisting of helium, argon, nitrogen, neon, krypton, and xenon. The precursor is selected from the group consisting of tris (tert-butoxy) silanol, (CH ₃ ) ₃ Al, TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , AlCl ₃ , Hf-ethoxide, and Ta-ethoxide. can do.

  The trench may have a width of about 1,000 nm or less (eg, about 900 nm or less, about 800 nm or less, about 700 nm or less, about 600 nm or less, about 500 nm or less, about 400 nm or less, about 300 nm or less, about 200 nm or less). it can. The trench is about 10 nm or more (e.g., about 20 nm or more, about 30 nm or more, about 40 nm or more, about 50 nm or more, about 75 nm or more, about 100 nm or more, about 150 nm or more, about 200 nm or more, about 300 nm or more, about 400 nm or more, about 500 nm or more, about 1,000 or more, about 1,500 nm or more, about 2,000 or more).

  The method may further include forming a second birefringent layer on the first material layer after filling the trench. The second birefringent layer can include a plurality of trenches, and forming the second birefringent layer sequentially forms a plurality of single layers of the third material in the trenches of the second birefringent layer. Optionally filling the plurality of trenches. The method can also include forming an additional birefringent layer on the second birefringent layer.

  In certain embodiments, the grating may be a surface relief grating. The grating can have a grating period of about 2,000 nm or less (eg, about 1,500 nm or less, about 1,000 or less, about 750 nm or less, about 500 nm or less, about 300 nm or less, about 200 nm or less).

  The optical retardation film may be birefringent.

  The article can further include at least one antireflective coating, wherein the surface of the article includes the surface of the antireflective coating. In certain embodiments, the article also includes a layer of a third material adjacent to the continuous layer. The article can include a layer of nanolaminate material adjacent to the continuous layer. The layer of nanolaminate material adjacent to the continuous layer can have an arithmetic average roughness surface of about 50 nm or less (eg, about 40 nm or less, about 30 nm or less, about 20 nm or less, about 10 nm or less). The nanolaminate material is about 1.3 or more at λ (eg, about 1.4 or more, about 1.5 or more, about 1.6 or more, about 1.7 or more, about 1.8 or more, about 1.9 or more. , About 2.0 or more, about 2.1 or more). The first material has a λ of about 1.3 or more (eg, about 1.4 or more, about 1.5 or more, about 1.6 or more, about 1.7 or more, about 1.8 or more, about 1.9). The refractive index can be about 2.0 or more and about 2.1 or more. The nanolaminate material can include a second material portion and a third material portion, wherein the second material and the third material are different materials. In some embodiments, the first material and the third material are the same material.

Nanolaminate materials can include dielectric materials, inorganic materials, and / or metals. The nanolaminate material includes a material selected from the group consisting of SiO ₂ , SiN _x , Si, Al ₂ O ₃ , ZrO ₂ , Ta ₂ O ₅ , TiO ₂ , HfO ₂ , Nb ₂ O ₅ , and MgF _2. be able to.

The first material may be a dielectric material, an inorganic material, glass, a polymer, a semiconductor, and / or a metal. In certain embodiments, the first material _consists of _{SiO 2, SiN x, Si,} Al 2 O 3, ZrO 2, Ta 2 O 5, TiO 2, HfO 2, Nb 2 O 5, and MgF ₂ Selected from the group.

  The continuous layer can form a lattice having a lattice period of about 500 nm or less (eg, about 200 nm or less, about 100 nm or less, about 50 nm or less). The first row of materials can have a minimum width of about 500 nm or less (about 200 nm or less, about 100 nm or less, about 50 nm or less, about 20 nm or less, about 10 nm or less). The first row of materials can have a minimum width that is the same as or different from the minimum width of the row of nanolaminate materials. The minimum width of each of the first material rows may be substantially the same. Alternatively, or in addition, the minimum width of each of the nanolaminate material rows is substantially the same.

  The continuous layer is about 15 nm or more (e.g., about 30 nm or more, about 50 nm or more, about 75 nm or more, about 100 nm or more, about 150 or more, about 200 nm or more, about 300 nm or more, about 500 nm or more, about 1,000 nm or more, about And a thickness of 1,500 nm or more, about 2,000 or more). In certain embodiments, when λ is between 150 nm and 2,000 nm, the continuous layer is about 1 nm or more (eg, for light of wavelength λ propagating in the continuous layer along a specific axis (eg, About 2 nm or more, about 5 nm or more, about 10 nm or more, about 20 nm or more, about 50 nm or more). When λ is 200 nm to 2,000 nm, the continuous layer can have a wavelength optical retardation of about 2,000 nm or less for light of wavelength λ propagating in the composite layer along a specific axis. . In some embodiments, λ is between about 400 nm and about 700 nm (eg, between about 510 nm and about 570 nm). In certain embodiments, the continuous layer has an optical retardation of about 4 nm or more for light of wavelength λ propagating in the continuous layer along a particular axis when λ is between about 400 nm and about 700 nm. Have

  The article can include a second continuous layer comprising a third row of alternating materials and a second row of nanolaminate materials, wherein the second continuous layer is along the axis. Birefringent with respect to light of wavelength λ propagating in the second continuous layer. The article can further include an additional birefringent layer, each birefringent layer being birefringent with respect to light of wavelength λ propagating within the respective birefringent layer along the axis. It is.

  Embodiments of the invention can have one or more of the following advantages.

  In certain embodiments, the article can be a relatively robust optical retarder that can have a high transmission for the wavelength of interest and has a precisely controllable retardation. The optical retarder can include one or more birefringent layers. Birefringence is obtained by a subwavelength structure in the medium, which can be achieved by alternating at least two different materials (eg, optically isotropic materials). Birefringence can be obtained by a subwavelength grating structure in which the medium has periodic modulation in its refractive index, the period of which is substantially shorter than the wavelength of interest. Since this period is shorter than the wavelength of interest, substantially zero order diffraction occurs, and all higher order diffraction disappears (eg, the beam of interest wavelength is substantially transmitted, and / Or reflect). The material comprising the birefringent medium may be optically isotropic (ie has an isotropic refractive index), but the medium itself is optically anisotropic to cause birefringence. It is sex.

  In certain embodiments, the optical retarder can include one or more birefringent layers formed of a continuous material, as opposed to having a trench filled with a gas (eg, air). Thus, an optical retarder can be mechanically more robust than an optical retarder that includes a discontinuous layer (eg, a layer that includes one or more trenches filled with air).

  In certain embodiments, a continuous birefringent layer having a relatively high aspect ratio between the width and thickness of a portion of the layer can be formed. As an example, a high aspect ratio trench can be etched into a layer, and then the conformal coating method (eg, atomic layer deposition) is used to fill the trench to provide a continuous with a relatively high aspect ratio. The birefringent layer can be formed.

  The birefringence of the optical retarder can be precisely controlled. To achieve this, for example, the refractive index of one or more portions of a birefringent layer in an optical retarder is adjusted to a desired value by adjusting the composition of that portion, thereby controlling birefringence. can do. As an example, one or more portions of a layer can be formed from a nanolaminate. The refractive index of the nanolaminate can be tuned by selecting the ratio of two or more different materials in the nanolaminate, when the nanolaminate is formed using atomic layer deposition The single layer can be controlled on the basis of the single layer.

  Alternatively, or in addition, the birefringence of the birefringent layer can be precisely controlled by precise control of the layer structure. For example, by using lithographic techniques (eg, electron beam lithography, nanoimprint lithography, holographic lithography) to define the structure of the birefringent layer (eg, grating depth, width, and cross section) It can be controlled precisely.

  In certain embodiments, the retardance of the optical retarder can be precisely controlled. For example, a desired retardance can be obtained by precisely controlling the birefringence and / or depth of the birefringent layer in the optical retarder. As an example, the optical retarder can include one or more layers, such as one or more etch stop layers, to control the thickness of a portion of the birefringent layer in the retarder.

  In some embodiments, the optical retarder has a high transmission at the wavelength of interest. For example, an optical retarder can include one or more anti-reflective coatings on one or more interfaces to reduce reflection of light of a wavelength of interest. Alternatively, or in addition, the optical retarder layer can be formed from a material that has relatively low absorption at the wavelength of interest.

  Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.

  Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION Referring to FIG. 1, an optical retarder 100 according to one embodiment includes a retardation layer 110 and two antireflection films 150 and 160. The optical retarder 100 also includes a substrate 140, an etch stop layer 130, and a cap layer 120. Retardation layer 110 is in the form of a lattice and includes a portion 111 having a first refractive index and a portion 112 having a second refractive index. The retardation layer 110 is birefringent with respect to light having a wavelength λ propagating along an axis 101 parallel to the z-axis of the Cartesian coordinate system shown in FIG. Generally, λ is between about 150 nm and about 5,000 nm. In certain embodiments, λ corresponds to a wavelength within the visible portion of the electromagnetic spectrum (eg, about 400 nm to about 700 nm).

Portions 111 and 112 extend along the y-axis and form a periodic structure consisting of a series of alternating rows having different refractive indices. The column corresponding to portion 111 has a width Λ _{111 in the} x direction, while the column corresponding to portion 112 has a width Λ _{112 in the} x direction. The width of these columns is less than λ, and retardation layer 110 is birefringent with respect to light of wavelength λ without encountering significant higher order diffraction. Light waves in different polarization states propagate in retardation layer 110 with different phase changes, which depends on the thickness of retardation layer 110, the refractive indices of portions 111 and 112, and Λ ₁₁₁ and Λ ₁₁₂ . Accordingly, these parameters can be selected to provide the desired amount of retardation for the polarization at λ.

式（１）において、ｎ_１１１およびｎ_１１２ならびにΛ_１１１およびΛ_１１２は、それぞれ部分１１１および１１２の屈折率および厚さ（ｘ方向に沿った）を意味する。一般に、ｎ_ｅおよびｎ_０の値は、ｎ_１１１、ｎ_１１２、Λ_１１１、およびΛ_１１２に依存し、ｎ_１１１とｎ_１１２との間にある。Λ_１１１およびΛ_１１２は、式（１）によって求められるｎ_ｅおよびｎ_０の値に基づいて所望のΔｎの値が得られるように選択することができる。さらに、部分１１１および１１２のそれぞれの組成に依存する屈折率ｎ_１１１およびｎ_１１２は、所望のΔｎの値が得られるように選択することができる。ある実施形態においては、Δｎは比較的大きい（たとえば、約０．１以上、約０．１５以上、約０．２以上、約０．３以上、約０．５以上、約１．０以上、約１．５以上、約２．０以上）。あるいは、別の実施形態においては、Δｎは比較的小さい（たとえば、約０．０５以下、約０．０４以下、約０．０３以下、約０．０２以下、約０．０１以下、約０．００５以下、約０．００２以下、０．００１以下）。 Retardation layer 110 has birefringence Δn, which corresponds to n _e −n ₀ , where n _e and n ₀ are the effective extraordinary refractive index and the effective ordinary ray refractive index of layer 110, respectively. For retardation layer 110, _{n e} and _{n 0} is given by the following equation. That is,

In equation (1), n ₁₁₁ and n ₁₁₂ and Λ ₁₁₁ and Λ ₁₁₂ mean the refractive index and thickness (along the x direction) of the portions 111 and 112, respectively. In general, the value of _{n e} and _{n 0 is,} n _{111, n 112,} depending on the lambda ₁₁₁ and lambda _112,, it is between _{n 111} and _{n 112.} Lambda ₁₁₁ and lambda ₁₁₂ may be selected as desired value of Δn based on the values of _{n e} and _{n 0} obtained by the equation (1) is obtained. Further, the refractive indices n ₁₁₁ and n ₁₁₂ depending on the respective compositions of the portions 111 and 112 can be selected to obtain a desired value of Δn. In some embodiments, Δn is relatively large (eg, about 0.1 or more, about 0.15 or more, about 0.2 or more, about 0.3 or more, about 0.5 or more, about 1.0 or more, About 1.5 or more, about 2.0 or more). Alternatively, in another embodiment, Δn is relatively small (eg, about 0.05 or less, about 0.04 or less, about 0.03 or less, about 0.02 or less, about 0.01 or less, about 0.0. 005 or less, about 0.002 or less, 0.001 or less).

  Generally, the refractive index of portion 111 is about 1.3 or greater (eg, about 1.4 or greater, about 1.5 or greater, about 1.6 or greater, about 1.7 or greater, about 1.8 or greater, about 1. 9 or more, about 2.0 or more, about 2.1 or more, or about 2.2 or more). Further, in general, the refractive index of portion 112 is about 1.3 or greater (eg, about 1.4 or greater, about 1.5 or greater, about 1.6 or greater, about 1.7 or greater, about 1.8 or greater, about 1.9 or more, about 2.0 or more, about 2.1 or more, or about 2.2 or more).

Generally, Λ ₁₁₁ is about 0.2λ or less (eg, about 0.1λ or less, about 0.05λ or less, about 0.04λ or less, about 0.03λ or less, about 0.02λ or less, 0.01λ or less). can do. For example, in some embodiments, Λ ₁₁₁ is about 200 nm or less (eg, about 150 nm or less, about 100 nm or less, about 80 nm or less, about 70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less). is there. Similarly, Λ ₁₁₂ is about 0.2λ or less (eg, about 0.1λ or less, about 0.05λ or less, about 0.04λ or less, about 0.03λ or less, about 0.02λ or less, 0.01λ or less). It can be. For example, in some embodiments, Λ ₁₁₂ is about 200 nm or less (eg, about 150 nm or less, about 100 nm or less, about 80 nm or less, about 70 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less). It is. Λ ₁₁₁ and Λ ₁₁₂ may be the same or different from each other.

Along the x-axis, the refractive index of retardation layer 110 is periodic and has a period Λ corresponding to Λ ₁₁₁ + Λ ₁₁₂ . Generally, Λ is less than λ, for example about 0.5λ or less (eg, about 0.3λ or less, about 0.2λ or less, about 0.1λ or less, about 0.08λ or less, about 0.05λ or less, about 0 0.04λ or less, about 0.03λ or less, about 0.02λ or less, 0.01λ or less). In some embodiments, Λ is about 500 nm or less (eg, about 300 nm or less, about 200 nm or less, about 100 nm or less, about 80 nm or less, about 60 nm or less, about 50 nm or less, about 40 nm or less).

  Although retardation layer 110 is shown as having 19 portions, in general, the number of portions in the retardation layer can be varied as desired. The number of parts depends on the period Λ and the area required for the end use of the retarder. In some embodiments, the retardation layer 110 has about 50 or more portions (eg, about 100 or more portions, about 500 or more portions, about 1,000 or more portions, about 5,000 or more portions). , More than about 10,000 parts, more than about 50,000 parts, more than about 100,000 parts, more than about 500,000 parts).

  The thickness d of the retardation layer 110 measured along the z-axis can be varied as desired. In general, the thickness of layer 110 is selected based on the refractive indices of portions 111 and 112 and the desired retardation of retardation layer 110 at λ. In some embodiments, d is about 50 nm or more (eg, about 75 nm or more, about 100 nm or more, about 125 nm or more, about 150 nm or more, about 200 nm or more, about 250 nm or more, about 300 nm or more, about 400 nm or more, about 500 nm or more. , About 1,000 or more, for example, about 2,000 nm).

The aspect ratio of the retardation layer thickness d to Λ ₁₁₁ and / or d to Λ ₁₁₂ is relatively large. For example, d: Λ ₁₁₁ and / or d: Λ ₁₁₂ is about 2: 1 or more (eg, about 3: 1 or more, about 4: 1 or more, about 5: 1 or more, about 8: 1 or more, about 10: 1 or more).

  The retardation of the retardation layer 110 corresponds to the product of the thickness d of the retardation layer 110 and Δn. By appropriately selecting the values of Δn and layer thickness, the retardation can be changed as desired. In some embodiments, the retardation of the retardation layer 110 is about 50 nm or more (eg, about 75 nm or more, about 100 nm or more, about 125 nm or more, about 150 nm or more, about 200 nm or more, about 250 nm or more, about 300 nm or more, about 400 nm. As described above, it is about 500 nm or more, about 1,000 or more, for example, about 2,000 nm. Alternatively, in another embodiment, the retardation is about 40 nm or less (eg, about 30 nm or less, about 20 nm or less, about 10 nm or less, about 5 nm or less, about 2 nm or less). In some embodiments, the retardation corresponds to λ / 4 or λ / 2.

たとえば、四分の一波長リターデーションはΓ＝π／２に対応し、半波長リターデーションはΓ＝πに対応する。一般に、位相リターデーションは希望通りに変化させることができる。ある実施形態においては、位相リターデーションは、２π以下（たとえば、約０．８π以下、約０．７π以下、約０．６π以下、約０．５π以下、約０．４π以下、約０．２π以下、０．２π以下、約０．１π以下、約０．０５π以下、０．０１π以下）であってよい。あるいは、別の実施形態においては、リターデーション層１１０の位相リターデーションは、２πを超えることができる（たとえば、約３π以上、約４π以上、約５π以上）。 Retardation can also be expressed as phase retardation Γ, where

For example, a quarter wavelength retardation corresponds to Γ = π / 2, and a half wavelength retardation corresponds to Γ = π. In general, the phase retardation can be varied as desired. In some embodiments, the phase retardation is 2π or less (eg, about 0.8π or less, about 0.7π or less, about 0.6π or less, about 0.5π or less, about 0.4π or less, about 0.2π or less). Hereinafter, it may be 0.2π or less, about 0.1π or less, about 0.05π or less, 0.01π or less). Alternatively, in another embodiment, the retardation retardation of retardation layer 110 can exceed 2π (eg, about 3π or more, about 4π or more, about 5π or more).

  In general, the composition of portions 111 and 112 can be varied as desired. Portions 111 and / or 112 can include inorganic and / or organic materials. Examples of inorganic materials include metal semiconductors and inorganic dielectric materials (eg, glass). Examples of organic materials include polymers.

In some embodiments, portion 111 and / or portion 112 may be a dielectric oxide (eg, metal oxide), fluoride (eg, metal fluoride), sulfide, and / or nitride (eg, metal nitride). ) And the like. Examples of oxides include SiO ₂ , Al ₂ O ₃ , Nb ₂ O ₅ , TiO ₂ , ZrO ₂ , HfO ₂ , SnO ₂ , ZnO, ErO ₂ , Sc ₂ O ₃ , and Ta ₂ O _5. . Examples of fluorides include MgF _2. Other examples include ZnS, SiN _x , SiO _y N _x , AlN, TiN, and HfN.

The composition of the portions 111 and 112 is typically used for their optical properties and their compatibility with the processes used to manufacture the optical retarder 100, and the formation of other layers of the optical retarder 100. Selected based on their compatibility with the material. The composition of portion 111 and / or portion 112 can be selected to have a specific refractive index at λ. In general, the refractive index of the portion 111 at λ is different from the refractive index or portion 112. In some embodiments, portion 111 or portion 112 is a relatively high index of refraction such as TiO ₂ having a refractive index of about 2.35 at 632 nm or Ta ₂ O ₅ having a refractive index of 2.15 at 632 nm. Formed from material. Alternatively, portion 111 or portion 112 can be formed from a relatively low refractive index material. Examples of low refractive index materials include SiO ₂ and Al ₂ O _{3, which} have a refractive index at 632 nm of 1.45 and 1.65, respectively.

  In some embodiments, the composition of portion 111 and / or portion 112 has a relatively low absorbency at λ, so that retardation layer 110 exhibits a relatively low absorbency at λ. For example, retardation layer 110 may have about 5% or less of radiation at λ propagating along axis 101 (eg, about 3% or less, about 2% or less, about 1% or less, about 0.5% or less, about 0 .2% or less, about 0.1% or less).

The portion 111 and / or the portion 112 can be formed from one type of material, or can be formed from a plurality of different materials. In some embodiments, one or both of the portions 111 and 112 are formed from a nanolaminate material, the nanolaminate material being composed of at least two different layers of material, wherein the at least one layer of material is highly By thin (e.g., a monolayer thickness of 1 to about 10) is meant. In some cases, the nanolaminate material has a locally uniform refractive index that depends on the refractive index of its constituent materials. By changing the amount of each constituent material, the refractive index of the nanolaminate can be changed. Examples of the nano-stacked portion include a portion composed of a SiO ₂ single layer and a TiO ₂ single layer, a SiO ₂ single layer and a Ta ₂ O ₅ single layer, or an Al ₂ O ₃ single layer and a TiO ₂ single layer. .

Portions 111 and / or portions 112 can include crystalline, semi-crystalline, and / or amorphous portions. Typically, amorphous materials are optically isotropic and can transmit light better than portions that are partially or mostly crystalline. As an example, in some embodiments, both portions 111 and 112 are formed of an amorphous material, such as an amorphous dielectric material (eg, amorphous TiO ₂ or SiO ₂ ). Alternatively, in certain embodiments, portion 111 is formed of a crystalline or semi-crystalline material (eg, crystalline or semi-crystalline Si) and portion 112 is an amorphous material (eg, TiO ₂ or SiO _{2 2} or other amorphous dielectric material).

  Referring now to other layers in the optical retarder 100, the substrate 140 generally supports the optical retarder 100 mechanically. In certain embodiments, the substrate 140 is transparent to light of wavelength λ, and substantially all light (eg, greater than or equal to about 90%, greater than or equal to about 95% About 97% or more, about 99% or more, or about 99.5% or more).

In general, the substrate 140 can support other layers and can be formed from any material that is compatible with the manufacturing process used to manufacture the retarder 100. In certain embodiments, the substrate 140 may be BK7 (available from Abrisa Corporation), borosilicate glass (eg, pyrex® available from Corning), aluminosilicate, and the like. It is formed from acid glass (eg C1737 available from Corning) or glass such as quartz / fused quartz. In some embodiments, the substrate 140 is a non-linear optical crystal (eg, LiNbO ₃ , or a magneto-optic rotator such as garnet) or a crystalline (or semi-crystalline) semiconductor (eg, Si, InP). , Or GaAs). The substrate 140 can also be formed from an inorganic material such as a polymer (eg, plastic).

The etch stop layer 130 is formed from a material that is resistant to the etching method used to etch the material from which the portion 112 is formed (see discussion below). The material forming the etch stop layer 130 should be compatible with the substrate 140 and the material forming the retardation layer 110. Examples of materials that can form the etch stop layer 130 include HfO ₂ , SiO ₂ , Ta ₂ O ₅ , TiO ₂ , SiN _x , or metal (eg, Cr, Ti, Ni).

  The thickness of the etch stop layer 130 can be varied as desired. Typically, the etch stop layer 130 is thick enough to prevent significant etching of the substrate 140, but should not be thick enough to adversely affect the optical performance of the optical retarder 100. In some embodiments, the etch stop layer is about 500 nm or less (eg, about 250 nm or less, about 100 nm or less, about 75 nm or less, about 50 nm or less, about 40 nm or less, about 30 nm or less, about 20 nm or less).

  The cap layer 120 is typically formed from the same material as the portion 111 of the retardation layer 110, thereby providing a surface 121 and depositing additional layers, such as the layer that forms the anti-reflective coating 150 thereon. be able to. Surface 121 may be substantially planar.

The antireflection films 150 and 160 can collide with the optical retarder 100 and reduce the reflectance of light having a wavelength λ emitted therefrom. Anti-reflective coatings 150 and 160 generally include one or more layers with different refractive indices. As an example, one or both of the antireflective films 150 and 160 can be formed from four alternating high and low refractive index layers. The high refractive index layer can be formed from TiO ₂ or Ta ₂ O ₅ and the low refractive index layer can be formed from SiO ₂ or MgF ₂ . The antireflection film may be a broadband antireflection film or a narrowband antireflection film.

  In some embodiments, the optical retarder 100 is about 5% or less (eg, about 3% or less, about 2% or less, about 1% or less, about 0.5% or less, about. 2% or less). Furthermore, the optical retarder 100 can have a high transmittance with respect to light having a wavelength λ. For example, the optical retarder can transmit about 95% or more (eg, about 98% or more, about 99% or more, about 99.5% or more) of light impinging on the wavelength λ.

  In general, the optical retarder 100 can be made as desired. 2A-2J illustrate the different stages of an example manufacturing method. Initially, a substrate 140 is provided as shown in FIG. 2A. The surface 141 of the substrate 140 can be polished and / or cleaned (eg, by exposing the substrate to one or more solvents, acids, and / or baking the substrate).

Referring to FIG. 2B, an etch stop layer 130 is deposited on the surface 141 of the substrate 140. The material forming the etch stop layer 130 may be chemical vapor deposition (CVD) such as sputtering (eg, radio frequency sputtering), vapor deposition (eg, electron beam evaporation, ion assisted vapor deposition (IAD) electron beam vapor deposition), or plasma enhanced CVD (PECVD). ), ALD, or one of various techniques such as oxidation. As an example, a layer of HfO ₂ can be deposited on the substrate 140 by IAD electron beam evaporation.

Referring to FIG. 2C, an intermediate layer 210 is then deposited on the surface 131 of the etch stop layer 130. Because portion 112 is etched from intermediate layer 210, intermediate layer 210 is formed from the material used for portion 112. The material forming the intermediate layer 210 is deposited using one of various techniques such as sputtering (eg, radio frequency sputtering), vapor deposition (eg, electron beam evaporation), or chemical vapor deposition (CVD) (eg, plasma enhanced CVD). be able to. As an example, a SiO ₂ layer can be deposited over etch stop layer 130 by sputtering (eg, radio frequency sputtering), CVD (eg, plasma enhanced CVD), or electron beam evaporation (eg, IAD electron beam evaporation). The thickness of the intermediate layer 210 is selected based on the desired thickness of the retardation layer 110.

  The portion 112 of the retardation layer 110 is formed by processing the intermediate layer 210 using a lithography technique. For example, the portion 112 can be formed from the intermediate layer 210 using electron beam lithography or photolithography (eg, using a photomask or using holographic techniques). In some embodiments, portion 112 is formed using nanoimprint lithography. Referring to FIG. 2D, nanoimprint lithography includes forming a resist layer 220 on the surface 211 of the intermediate layer 210. This resist may be, for example, polymethyl methacrylate (PMMA) or polystyrene (PS). Referring to FIG. 2E, a specific pattern is embossed on the resist layer 220 using a mold. The patterned resist layer 220 includes a thin portion 221 and a thick portion 222. The patterned resist layer 220 is then etched (eg, by oxygen reactive ion etching (RIE)) to remove the thin portion 221 and a portion 224 of the surface 211 of the intermediate layer 210 as shown in FIG. 2F. Is exposed. The thick portion 222 is also etched but not completely removed. Therefore, the resist portion 223 remains on the surface 211 after etching.

Referring to FIG. 2G, the exposed portion of the intermediate layer 210 is subsequently etched to form a trench 212 in the intermediate layer 210. The unetched portion of the intermediate layer 210 corresponds to the portion 112 of the retardation layer 110. The intermediate layer 210 can be etched using, for example, reactive ion etching, ion beam etching, sputtering etching, chemical enhanced ion etching (CAIBE), or wet etching. The exposed portion of the intermediate layer 210 is etched until it reaches an etch stop layer 130 formed from a material that is resistant to the etching method. Therefore, the depth of the trench 212 formed by etching is the same as the thickness of the portion 112. After the trench 212 is etched, the remaining resist 223 is removed from the portion 112. The resist can be removed by cleaning the article with a solvent (eg, in an organic solvent such as acetone or alcohol), O ₂ plasma ashing, O ₂ RIE, or ozone cleaning.

  Referring to FIG. 2I, after the remaining resist is removed, material is deposited on the article, filling the trench 212 and forming the cap layer 120. The filled trench corresponds to the portion 111 of the retardation layer 110. The material can be deposited on the article by various methods such as sputtering, electron beam evaporation, CVD (eg, high density CVD), or atomic layer deposition (ALD). Note that if cap layer 120 is formed and trench 212 is filled in the same deposition step, portion 111 and cap layer 120 are formed from successive portions of material.

  Finally, antireflection films 150 and 160 are deposited on the surface 121 of the cap layer 120 and the surface 142 of the substrate 140, respectively. The material forming the anti-reflective coating can be deposited on the article, for example, by sputtering, electron beam evaporation, or ALD.

  As described above, in some embodiments, one or both of the portion 111 of the retardation layer 110, the cap layer 120, and / or the anti-reflective coatings 150 and 160 are formed using atomic layer deposition (ALD). Is done. For example, referring to FIG. 3, using ALD system 300, trench 212 of intermediate article 301 (consisting of substrate 140, cap layer 130, and portion 112) is filled with a nanolaminate multilayer film to form portion 111. And the cap layer 120 is formed. The deposition of the nanolaminate multilayer film is performed on a monolayer basis, thereby substantially controlling the composition and thickness of the film. During deposition of the monolayer, precursor vapor is introduced into the chamber, and this vapor is deposited on the exposed surface of portion 112, etch stop layer surface 131, or a previously deposited monolayer adjacent to these surfaces. Adsorbed. Subsequently, a reactant that chemically reacts with the adsorbed precursor is introduced into the chamber, thereby forming a single layer of a desired material. Because the chemical reaction is self-limited on the surface, the thickness of the deposited layer and the uniformity over a large area can be precisely controlled. Further, since the precursor is adsorbed on each exposed surface regardless of the direction, the material is uniformly deposited on the exposed surface regardless of the direction of the surface with respect to the chamber 110. Accordingly, the layer of the nanolaminate film conforms to the shape of the trench of the intermediate article 301.

  The ALD system 300 includes a reaction chamber 310 that is coupled to sources 350, 360, 370, 380, and 390 via a manifold 330. Sources 350, 360, 370, 380, and 390 are coupled to manifold 330 via supply lines 351, 361, 371, 381, and 391, respectively. Valves 352, 362, 372, 382, and 392 regulate gas flow from sources 350, 360, 370, 380, and 390, respectively. Sources 350 and 380 contain first and second precursors, respectively, and sources 360 and 390 contain a first reagent and a second reagent, respectively. The source 370 contains a carrier gas that is constantly flowed into the chamber 310 during the deposition process to supply precursors and reagents to the article 301 and pull reaction byproducts away from the substrate. . Precursors and reagents are introduced into chamber 310 by mixing with carrier gas in manifold 330. Gas is exhausted from chamber 310 through outlet 345. The pump 340 exhausts gas from the chamber 310 via the outlet 345. Pump 340 is connected to outlet 345 via tube 346.

  The ALD system 300 includes a temperature controller 395 that controls the temperature of the chamber 310. During deposition, temperature controller 395 raises the temperature of article 301 above room temperature. In general, this temperature should be high enough to promote a rapid reaction between the precursor and reagent, but should not damage the substrate. In some embodiments, the temperature of the article 301 is about 500 ° C. or less (eg, about 400 ° C. or less, about 300 ° C. or less, about 200 ° C. or less, about 150 ° C. or less, about 125 ° C. or less, about 100 ° C. or less). can do.

  Typically, this temperature should not vary significantly between different parts of the article 301. When the temperature variation is large, the reaction rate between the precursor and the reagent in different parts of the substrate may vary, and this may cause variations in the thickness and / or form of the layer to be laminated. In some embodiments, the temperature variation between different portions of the deposition surface can be about 40 ° C. or less (eg, about 30 ° C., about 20 ° C., about 10 ° C., about 5 ° C. or less). .

  The parameters of the deposition process can be controlled and synchronized by an electronic controller 399. Electronic controller 399 is in communication with temperature controller 395, pump 340, and valves 352, 362, 372, 382, and 392. The electronic controller 399 also includes a user interface that allows an operator to set deposition process parameters, monitor the deposition process, and even interact with the system 300.

  Referring to FIG. 4, the ALD process begins (410) when the system 300 introduces a first precursor from the source 350 into the chamber 310 (420) by being mixed with a carrier gas from the source 370. ). The first precursor monolayer is adsorbed onto the exposed surface of the article 301 and the remaining precursor is purged from the chamber 310 by the continuous flow of carrier gas into the chamber (430). Next, the system introduces a first reagent from the source 360 into the chamber 310 via the manifold 330 (440). The first reagent reacts with the monolayer of the first precursor to form a monolayer of the first material. As with the first precursor, the carrier gas stream purges the remaining reagents from the chamber (450). Steps 420-460 are repeated until the first layer of material reaches the desired thickness (460).

  In embodiments where the film is a layer of one material, the process ends when the first layer of material reaches the desired thickness (470). However, in the case of a nanolaminate film, the system introduces the second precursor into the chamber 310 via the manifold 330 (380). The monolayer of the second precursor is adsorbed onto the exposed surface of the deposited first material layer and the carrier gas purges the remaining precursor from the chamber (490). The system then introduces the second reagent from the source 380 into the chamber 310 via the manifold 330. The second reagent reacts with the second precursor monolayer to form a second monolayer of material (500). Residual reagent is purged (510) by the carrier gas flow flowing through the chamber. Steps 580-510 are repeated until the second layer of material reaches the desired thickness (520).

  Additional layers of first and second materials are deposited by repeating steps 520-530. Once the desired number of layers has been formed (eg, the trench is filled and / or the cap layer has the desired thickness), the process ends (540) and the coated article is removed from chamber 310. It is taken out.

  In each cycle of the above process, the precursor is introduced into the chamber before the reagent, but in another example, the reagent can be introduced before the precursor. The order in which precursors and reagents are introduced can be selected based on their interaction with the exposed surface. For example, if the binding energy between the precursor and the surface is greater than the binding energy between the reagent and the surface, the precursor can be introduced before the reagent. Alternatively, if the binding energy of the reagent is greater, the reagent can be introduced before the precursor.

  The thickness of each monolayer generally depends on a number of factors. For example, the thickness of each monolayer depends on the type of material being deposited. A material composed of larger molecules may result in a thicker monolayer than a material composed of smaller molecules.

  The temperature of the article can also affect the thickness of the monolayer. For example, for some precursors, higher temperatures may reduce the adsorption of the precursor to the surface during the deposition cycle, thereby creating a thinner monolayer than that formed when the substrate temperature is low. can get.

  The type or precursor, and the type of reagent, and the amount of precursor and reagent input can also affect the thickness of the monolayer. In certain embodiments, a monolayer of a particular material can be deposited using a particular precursor, but using different reagents can result in different monolayer thicknesses in each combination. Similarly, monolayers of material formed from different precursors may have different monolayer thicknesses for different precursors.

Examples of other factors that can affect the thickness of the monolayer include purge time, precursor residence time on the surface to be coated, pressure in the reactor, physical shape of the reactor, and material being deposited Possible by-product effects on An example of when the by-product affects the film thickness is when etching the material on which the by-product is deposited. For example, if a TiCl ₄ precursor is used and TiO ₂ is deposited using water as a reagent, HCl is a byproduct. HCl may etch the deposited TiO ₂ before it is exhausted. Etching reduces the thickness of the deposited monolayer, and if a particular portion of the substrate is exposed to HCl longer than other portions, the monolayer thickness can vary across the substrate (eg, exhaust The portion of the substrate close to the tube can be exposed to by-products for a longer time than the portion of the substrate away from the exhaust pipe).

  Typically, the monolayer thickness is between about 0.1 nm to about 5 nm. For example, the thickness of one or more deposited monolayers can be about 0.2 nm or more (eg, about 0.3 nm or more, about 0.5 nm or more). In certain embodiments, the thickness of one or more deposited monolayers can be about 3 nm or less (eg, about 2 nm, about 1 nm or less, about 0.8 nm or less, about 0.5 nm or less).

The average deposited monolayer thickness can be measured by depositing a predetermined number of monolayers on the substrate to form a layer of material. Subsequently, the thickness of the deposited layer is measured (eg, by ellipsometry, electron microscopy, or other methods). The average deposited monolayer thickness can then be determined by dividing the measured layer thickness by the number of deposition cycles. The average deposited monolayer thickness can correspond to the theoretical monolayer thickness. The theoretical monolayer thickness refers to the characteristic dimensions of the molecules making up the monolayer that can be calculated from the bulk density of the material and the molecular weight of the molecules. For example, the estimated single layer thickness for SiO ₂ is about 0.37 nm. This thickness is estimated as the cubic root of the formula weight of amorphous SiO ₂ with a density of 2.0 g / cubic centimeter.

  In certain embodiments, the average deposited monolayer thickness may correspond to a portion of the theoretical monolayer thickness (eg, about 0.2 of the theoretical monolayer thickness, about 0 of the theoretical monolayer thickness). .3, theoretical single layer thickness of about 0.4, theoretical single layer thickness of about 0.5, theoretical single layer thickness of about 0.6, theoretical single layer thickness of about 0.7, theoretical single layer thickness Thickness of about 0.8, theoretical monolayer thickness of about 0.9). Alternatively, the average deposited monolayer thickness may be greater than 1 times the theoretical monolayer thickness and may correspond to up to about 30 times the theoretical monolayer thickness (eg, more than about 2 times the theoretical monolayer thickness). Approx. 3 times the theoretical single layer thickness, Approx. 5 times the theoretical single layer thickness, Approx. 8 times the theoretical single layer thickness, Approx. 10 times the theoretical single layer thickness, The theoretical single layer thickness About 20 times more).

  During the deposition process, the pressure in the chamber 310 can be maintained at a substantially constant pressure or can be varied. In general, the pressure is controlled by controlling the flow rate of the carrier gas into the chamber. In general, this pressure saturates the surface with chemisorbed species by the precursor, reacts the surface species and reagents left behind by the precursor, leaving a reactive site for the next cycle of the precursor. The pressure should be high enough. If the chamber pressure is too low (which can occur if the precursor and / or reagent input is too low and / or if the pump speed is too high), the surface may not be saturated by the precursor and the reaction is self It may not be limited. This can result in a non-uniform thickness of the deposited layer. Furthermore, the chamber pressure should not be so high as to interfere with the removal of reaction products produced by the reaction of the precursor with the reagent. When the next precursor is introduced into the chamber, residual by-products can interfere with surface saturation. In some embodiments, the chamber pressure is maintained between about 0.01 Torr and about 100 Torr (eg, between about 0.1 Torr and about 20 Torr, between about 0.5 Torr and 10 Torr, such as about 1 Torr).

  In general, the amount of precursor and / or reagent introduced during each cycle can be selected according to chamber size, substrate exposed surface area, and / or chamber pressure. The amount of precursor and / or reagent introduced during each cycle can be determined experimentally.

  The amount of precursor and / or reagent introduced during each cycle can be controlled by the opening and closing timing of valves 352, 362, 382, and 392. The amount of precursor and / or reagent introduced corresponds to the length of time that the valve is opened in each cycle. These valves should be open long enough to introduce enough precursor to properly coat the substrate surface with a single layer. Similarly, the amount of reagent introduced during each cycle should be sufficient to react with substantially all of the precursor deposited on the exposed surface. Introducing more precursors and / or reagents than required may extend cycle times and / or waste precursors and / or reagents. In certain embodiments, the precursor dosage is between about 0.1 seconds and about 5 seconds in each cycle (eg, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more). About 0.5 seconds or more, about 0.6 seconds or more, about 0.8 seconds or more, about 1 second or more) corresponding to opening an appropriate valve. Similarly, the reagent input is between about 0.1 seconds and about 5 seconds in each cycle (eg, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more, about 0.5 seconds). Seconds or more, about 0.6 seconds or more, about 0.8 seconds or more, about 1 or more) can correspond to opening an appropriate valve.

  The time between the precursor and reagent inputs corresponds to the purge. The time for each purge should be long enough to remove residual precursors or reagents from the chamber, but if longer, the cycle time can increase without any advantage. The different purge times in each cycle may be the same or may vary. In some embodiments, the purge time is about 0.1 seconds or more (eg, about 0.2 seconds or more, about 0.3 seconds or more, about 0.4 seconds or more, about 0.5 seconds or more, about 0.6 Seconds or more, about 0.8 seconds or more, about 1 second or more, about 1.5 seconds or more, about 2 seconds or more). Generally, the purge time is about 10 seconds or less (eg, about 8 seconds or less, about 5 seconds or less, about 4 seconds or less, about 3 seconds or less).

  The time between successive introductions of the precursor multiple times corresponds to the cycle time. This cycle time may or may not be the same as the cycle of laminating single layers of different materials. Furthermore, the cycle time may be the same as or different from the cycle with a single layer of the same material, but using different precursors and / or different reagents. In some embodiments, the cycle time is about 20 seconds or less (eg, about 15 seconds or less, about 12 seconds or less, about 10 seconds or less, about 8 seconds or less, about 7 seconds or less, about 6 seconds or less, about 5 seconds or less. Second or less, about 4 seconds or less, or about 3 seconds or less). Reducing the cycle time can reduce the time of the lamination process.

Generally, the precursor is selected to be compatible with the ALD process and to obtain the desired deposition material by reaction with the reagent. Furthermore, the precursors and materials should be compatible with the material on which they are deposited (eg, substrate material, or material of previously deposited layers). Examples of precursors include chlorides (eg, metal chlorides), such as TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , HfCl ₄ , InCl ₃ , and AlCl ₃ . In some embodiments, organic compounds can be used as precursors (eg, Ti-ethoxide, Ta-ethoxide, Nb-ethoxide). Another example of an organic compound precursor is (CH ₃ ) ₃ Al.

Reagents are also generally selected to be compatible with the ALD process and are selected based on the chemical nature of the precursors and materials. For example, if the material is an oxide, the reagent may be an oxidizing agent. Examples of suitable oxidants include water, hydrogen peroxide, oxygen, ozone, (CH ₃ ) ₃ Al, and various alcohols (eg, ethyl alcohol, CH ₃ OH). For example, to obtain Ta- ethaoxide to obtain AlCl _{3, Ta} 2 _{O 5} to obtain a TiCl _{4, Al} 2 _{O 3} to obtain a TiO _2, Nb- ethaoxide for obtaining _Nb 2 _{O 5,} the HfO ₂ HfCl _4, ZrCl ₄ to obtain the ZrO _2, and as a reagent for oxidation of precursor such as InCl ₃ for obtaining the _in 2 _{O 3} water is suitable for. In each case, HCl is produced as a by-product. In some embodiments, (CH ₃ ) ₃ Al can be used to oxidize silanol to obtain SiO ₂ .

  While specific embodiments have been described, the invention is generally not limited thereto. For example, while optical retarder 100 (see FIG. 1) shows specific configurations of various layers, other embodiments can include additional layers or fewer layers. For example, in certain embodiments, the optical retarder need not include one and both of the anti-reflective coatings 150 and 160. In certain embodiments, the optical retarder can include an additional antireflective coating (eg, between the substrate layer 140 and the etch stop layer 130). Embodiments can also include a protective layer such as a hard coat layer (eg, hard coat polymer) on one or both of the anti-reflective coatings 150 and 160. In certain embodiments, the optical retarder need not include a cap layer. For example, the cap layer formed when filling the trench between the portions 112 can be removed after the portion 111 is formed. The cap layer can be removed by, for example, chemical mechanical polishing or etching.

  Referring to FIG. 5, in one embodiment, optical retarder 600 is formed by partially etching a trench directly into the substrate layer and subsequently filling the trench to form a continuous retardation layer 610. Is done. The optical retarder 600 also includes a cap layer 620 and a base layer 630 corresponding to the unetched portion of the original substrate layer. An antireflection film 640 is deposited on the surface 621 of the cap layer 602, and a second antireflection film 650 is deposited on the surface 631 of the base layer 630.

  In certain embodiments, the optical retarder can be formed from two or more retardation layers. For example, referring to FIG. 6, the optical retarder 800 includes four retardation layers 810, 820, 830, and 840. The optical retarder 800 also includes a substrate layer 801, an etch stop layer 805, and cap layers 811, 821, 831, and 841.

  Retardation layers 810, 820, 830, and 840 may have the same retardation or different retardations for a beam of light having a wavelength λ.

  The optical retarder 800 can be made using the methods disclosed herein. For example, each retardation layer and its corresponding cap layer may be an etch stop layer 805 (eg, for retardation layer 810) or a previously deposited cap layer (eg, for retardation layers 820, 830, and 840). A cap layer can be formed by depositing and etching as an intermediate layer on any of these, and then depositing a material to fill the etched trenches.

  In some embodiments, an additional etch stop layer can be deposited over the cap layer before forming a later retardation layer. Of course, other layers such as anti-reflective coatings can also be included.

  In general, the thickness of the retardation layers 810, 820, 830, and 840 along the z-axis, the width of those portions (along the x-axis), and the materials used to form them vary as desired. be able to. In some embodiments, the retardation layers 810, 820, 830, and 840 are the same, but in other embodiments, one or more of the retardation layers may be different (eg, other retardations). Composed of one or more materials different from the layer, have different thicknesses and / or have different birefringence).

  Further, although the optical retarder 800 has four retardation layers, in general, embodiments can include more or less than four retardation layers. The optical retarder has two retardation layers, three retardation layers, or five or more retardation layers (eg, about 10 or more retardation layers, about 20 or more retardation layers, about 30 or more retardation layers). , About 100 or more retardation layers, and about 1000 or more retardation layers).

  The overall phase retardation for light of wavelength λ propagating in an optical retarder having two or more retardation layers can be relatively large. For example, the optical retarder at λ is about 2π or more (eg, about 3π or more, about 4π or more, about 5π or more, about 8π or more, about 10π or more, about 12π or more, about 15π, about 20π or more, about 30π or more). It can have a phase retardation.

  The total thickness (along the z-axis) of the optical retarder including two or more retardation layers is about 200 μm or more (eg, about 500 μm or more, about 800 μm or more, about 1,000 μm or more, about 1,500 μm or more) , About 2,000 μm or more, about 5,000 μm or more).

  In certain embodiments, the optical retarder is an optical where non-normally incident light (ie, light that does not propagate along the z-axis) is split into ordinary and extraordinary rays and exits the retarder along different paths. It can be used as an optical walk-off crystal. Such optical walk-off crystals can be re-cut and polished to rust. The walk-off crystals can be used in a number of applications such as telecommunications isolators, circulators, or interleavers, and / or consumer applications such as optical low pass filters.

  While embodiments of optical retarders have been described that include a birefringent layer having a rectangular grating profile, other embodiments are possible. For example, in some embodiments, the grating profile of the birefringent layer may be curved, such as having a sinusoid. In another example, the grid can have a triangular or jagged profile.

  Furthermore, although the description has been given assuming that the grating period of the birefringent layer of the optical retarder is constant, in certain embodiments, this grating period may vary. In some embodiments, portions of the birefringent layer can be non-periodically arranged.

  Optical retarders as described herein can be incorporated into optical devices such as passive optical devices (eg, polarizers) and active optical devices (eg, liquid crystal displays). The optical retarder can be integrated with the device to obtain an integrated device, or it can be placed independently of other parts of the device.

  Referring to FIG. 7, an example of a passive optical device that incorporates an optical retarder is a polarizer 660. The polarizer 660 includes a polarizing film 670 and an optical retarder 680. The polarizing film 670 is a sheet polarizer (for example, polyvinyl alcohol dyed with iodine), or US Patent Application No. 10/10, entitled “Multilayer Structure for Polarization and Beam Control”. 644,643, and PCT Patent Application No. PCT / US03 / 26024, entitled "Method and System for Polarizing a Beam" (METHOD AND SYSTEM FOR PROVIDING) Such nanostructured polarizers, the entire contents of both of which are incorporated herein by reference.

  The polarizing film 670 linearly polarizes light that propagates along the axis 661 and enters the polarizer 660. Next, the optical retarder 680 delays the phase of this linearly polarized light and obtains polarized light that has passed through the polarizer 660 with a desired ellipticity. The ellipticity of the passed light can be varied as desired by selecting parameters associated with the retardation layer of the optical retarder 680 so that the desired amount of retardation is obtained. For example, the passed light may be circularly polarized or elliptically polarized.

  Referring to FIG. 8, an example of an active optical device in which an optical retarder is incorporated is a liquid crystal display 700, which includes a substrate 710 (eg, silicon substrate), a reflective electrode 720, a liquid crystal layer 730 (eg, nematic liquid crystal or ferroelectric). Liquid crystal), a transparent electrode 740 (formed of indium tin oxide, for example), an optical retarder 750, and a polarizing film 760. The optical retarder 750 delays the phase of polarized light transmitted through the polarizing film 760. This light is reflected from the electrode 720 and propagates twice in the liquid crystal layer 730. The reflected light is again delayed in phase by the optical retarder 760 and then reaches the polarizing film 760 again. Depending on the voltage applied across electrodes 720 and 740, the reflected light is either absorbed or transmitted by polarizing film 760, corresponding to dark or bright pixels, respectively. In some cases, LCD 700 includes a color filter that absorbs certain wavelengths in the visible spectrum, thereby obtaining a color image. Although LCD 700 is a reflective display, the optical retarders disclosed herein can also be used in other types of displays, such as transmissive displays or transflective displays.

  The following examples are illustrative and not intended to be limiting.

An optical retarder was produced as follows. A 0.5 mm thick BK7 wafer (4 inches in diameter) obtained from Abrisa Corporation (Santa Paula, Calif.) Was added to a H ₂ O: H ₂ O ₂ : NH ₄ OH solution. Insoluble organic pollutants were removed with and cleaned by removing ionic and heavy metal atom contaminants with H ₂ O: H ₂ O ₂ : HCl solution. The wafer was then washed with isopropyl alcohol and deionized water and spin dried.

The subwavelength grating was etched into the BK7 wafer as follows. This BK7 wafer was spin coated with a thin layer (about 180 nm) of PMMA (molecular weight 15K, purchased from Sigma-Aldrich, St. Louis, Mo.), St. Louis, MO, on a hot plate at about 115 ° C. Baking was performed for about 1 hour. After baking, the resist was embossed with a lattice mold having a period of 200 nm, a depth of about 110 nm, and a lattice line width of about 100 nm. This mold included a SiO ₂ layer (about 200 nm thick) patterned on a 0.5 mm thick silicon substrate. This type is described in J. Wang, Z. Yu and S. Y. Chou J.C. Vac. Sci. Technol. , B17, 2957 (1999). After the embossing, the deformed UV curable resist was completely cured by exposing the BK7 substrate side to UV light. The mold was then removed from the resist, leaving a mask with a negative pattern of the mold profile. The mask was etched with O ₂ RIE until the BK7 wafer was exposed in the recessed portion of the mask. This etch was performed using a plasma-therm 790 (available from Unaxis, Inc., St. Petersburg, FL), St. Petersburg, Florida. The pressure during etching was 4 mtorr. The output was set to 70 W, and the oxygen flow rate during etching was 10 sccm. The total thickness of the resist etched to expose the BK7 wafer was about 120 nm.

After etching the mask, it is approximately on the remaining resist / exposed BK7 wafer by e-beam evaporation at a certain tilt angle from the normal direction of the wafer in high vacuum (ie, less than about 5 × 10 ⁻⁶ torr). 50 nm of Cr was deposited. The tilt angle was about 65 °. Cr was deposited on top of the remaining mask lines and on the sidewalls to form a hard mask for etching BK7. After Cr deposition, O ₂ RIE was again used to etch all exposed resist not covered by Cr. Next, using CHF ₃ RIE, the exposed portion of the BK7 wafer surface was etched to form a subwavelength grating in the wafer. The BK7 was etched using a plasma-term 720. The chamber pressure was about 5 mtorr, the output was about 100 W, and the CHF ₃ and O ₂ flow rates were 10 sccm and 1 sccm, respectively. A 100 nm wide trench having a depth of about 630 nm was etched into the BK7 wafer. After etching BK7, Cr was removed by immersing the wafer in a CR-7Cr etchant (obtained from Cyantek, Fremont, Calif.) For about 30 minutes. Subsequently, the residual resist was removed by O ₂ RIE.

The trench was filled with a nanolaminate material composed of TiO ₂ and SiO ₂ . The nanolaminate material was deposited by ALD performed using a P-400A ALD apparatus obtained from Planar Systems, Inc. (Beaverton, OR). Prior to depositing the nanolaminate, the etched wafer was heated to 300 ° C. for about 3 hours in an ALD chamber. The chamber was flushed with nitrogen gas at about 2 SLM and the chamber pressure was maintained at about 0.75 Torr. The TiO ₂ precursor was Ti-ethoxide, which was heated to about 140 ° C. The SiO ₂ precursor was silanol and was heated to about 110 ° C. For both precursors, the reagent used was water, which was maintained at about 13 ° C. Ti-ethoxide and silanol were 99.999% grade pure and were obtained from Sigma-Aldrich (St. Louis, Mo.). This nanolaminate was formed by repeating a cycle of depositing one monolayer of SiO ₂ after depositing ten monolayers of TiO ₂ . To deposit a single layer of TiO _2, was introduced for 2 seconds water chamber, it was followed by a nitrogen purge of 2 seconds. Next, after introducing Ti-ethoxide into the chamber, a nitrogen purge was further performed for 2 seconds. After introducing water into the ALD chamber for 1 second to deposit a SiO ₂ monolayer, a 2 second nitrogen purge was performed. Next, silanol was introduced for 1 second. The chamber was then purged with nitrogen for 3 seconds before introducing the next reagent. When determined from the measurement of a nanolaminate film similarly formed on a flat glass substrate, the refractive index of the nanolaminate is estimated to be about 1.88 at 632 nm.

  M-2000V® Spectroscopic Ellipsometer (commercially available from JA Woollam Co., Inc., Lincoln, NE), Lincoln, Nebraska. ) To measure the retardation of the optical retarder, it was 23.85 nm at a wavelength of 551 nm.

  An LEO thermo-emission scanning electron microscope was used to examine unfilled and filled grids using scanning electron microscopy. To perform this test, the sample was cleaved and coated with a thin layer of Au. Next, the cross section of the cleaved interface was observed. 9A and 9B show SEM micrographs of the grating before and after filling the trench, respectively.

  Other embodiments are set forth in the following claims.

It is a perspective view of one Embodiment of an optical retarder. FIG. 2 shows steps in the production of the optical retarder shown in FIG. 1 is a schematic diagram of an atomic layer deposition system. 2 is a flow chart illustrating steps for forming a nanolaminate using atomic layer deposition. It is sectional drawing of another embodiment of an optical retarder. It is sectional drawing of one Embodiment of the optical retarder containing a some retardation layer. It is sectional drawing of the polarizer with which the optical retarder was integrated. It is sectional drawing of the liquid crystal display in which the optical retarder was integrated. It is a scanning electron micrograph of a subwavelength grating before filling a trench. 9B is a scanning electron micrograph of the subwavelength grating shown in FIG. 9A after filling the trench.

Claims (40)

Providing an article including a layer of a first material, wherein the layer of the first material includes at least one trench, the layer propagating within the layer along a particular axis. Being birefringent with respect to light of wavelength λ, λ being between 150 nm and 2,000 nm;
By sequentially forming a plurality of monolayers of the second material in the trench, the method comprising the steps of filling a least 50% also of the volume of the trench.   The method of claim 1, wherein the filling step further includes forming one or more monolayers of a third material in the trench, wherein the second material and the third material are different. .   The method of claim 2, wherein the monolayers of the second and third materials form a nanolaminate material. By sequentially forming a plurality of monolayers of the second material in the trench, the method according to claim 1 for filling a least 80% also of the volume of the trench. By sequentially forming a plurality of monolayers of the second material in the trench, the method according to claim 1 for filling a least 90% also of the volume of the trench. By sequentially forming a plurality of monolayers of the second material in the trench, the method according to claim 1 for filling a least 99% also of the volume of the trench.   The method of claim 1, wherein the second material is different from the first material.   The method of claim 1, wherein the layers of the first material and the second material form a continuous layer.   The method of claim 1, wherein the article includes an additional trench formed in a surface of the layer of the first material. By sequentially forming a plurality of monolayers of said second material into said additional trench, according to claim 9, further comprising the step of filling the least 50% also of the respective volume of said additional trench the method of. By sequentially forming a plurality of monolayers of said second material into said additional trench, according to claim 9, further comprising the step of filling the least 80% also of the respective volume of said additional trench the method of. By sequentially forming a plurality of monolayers of said second material into said additional trench, according to claim 9, further comprising the step of filling the least 90% also of the respective volume of said additional trench the method of. By sequentially forming a plurality of monolayers of said second material into said additional trench, according to claim 9, further comprising the step of filling the least 99% also of the respective volume of said additional trench the method of.   The method of claim 9, wherein the trenches are separated by the first row of materials.   The method of claim 7, wherein the layer of the first material forms a surface relief grating. The method of claim 15, wherein the surface relief grating has a grating period of 500 nm or less.   The method of claim 7, wherein the trench is formed by etching a continuous layer of the first material.   The method of claim 17, wherein the etching comprises reactive ion etching.   The method of claim 1, wherein the trench is formed by lithography.   The method of claim 19, wherein the trench is formed using nanoimprint lithography.   21. The method of claim 20, wherein the nanoimprint lithography includes forming a pattern in a thermoplastic material.   21. The method of claim 20, wherein the nanoimprint lithography comprises forming a pattern in a UV curable material.   The method of claim 19, wherein the trench is formed using holographic lithography.   The method of claim 1, further comprising forming a layer of the second material over the filled trench by sequentially forming a single layer of the second material over the trench. Wherein said layer of second material, the method according to claim 24 having a surface of 5 0 nm following arithmetic mean roughness.   The method of claim 1, wherein the second material is a dielectric material.   Forming the plurality of monolayers of the second material comprises: depositing a monolayer of a precursor; exposing the monolayer of the precursor to a reagent to form the monolayer of the second material. The method of claim 1 including the step of forming.   28. The method of claim 27, wherein the reagent is chemically reacted with the precursor to form the second material.   30. The method of claim 28, wherein the reagent oxidizes the precursor to form the second material.   28. The method of claim 27, wherein depositing the monolayer of the precursor comprises introducing a first gas containing the precursor into a chamber containing the article. During the deposition of the monolayer of the precursor, the pressure of the first gas in the chamber is 0 . The method of claim 30, wherein the method is 01 to 100 Torr.   32. The method of claim 30, wherein exposing the monolayer of the precursor to the reagent comprises introducing a second gas containing the reagent into the chamber. During the exposure of the monolayer of the precursor to the reagent, the pressure of the second gas in the chamber is 0 . The method of claim 32 , wherein the method is from 01 to 100 Torr. 33. The method of claim 32 , wherein a third gas is introduced into the chamber after the introduction of the first gas and before the introduction of the second gas. 35. The method of claim 34 , wherein the third gas is inert to the precursor. 35. The method of claim 34 , wherein the third gas comprises at least one gas selected from the group consisting of helium, argon, nitrogen, neon, krypton, and xenon. The precursor is selected from the group consisting of tris (tert-butoxy) silanol, (CH ₃ ) ₃ Al, TiCl ₄ , SiCl ₄ , SiH ₂ Cl ₂ , TaCl ₃ , AlCl ₃ , Hf-ethoxide, and Ta-ethoxide. 28. The method of claim 27, wherein: The method of claim 1 , wherein the trench has a width of 1,000 nm or less. The method of claim 1, wherein the trench has a depth of 10 nm or more.   9. The method of claim 8, wherein the continuous layer is birefringent with respect to light of wavelength [lambda] propagating in the continuous layer along a particular axis, and [lambda] is between 150 nm and 2,000 nm.

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