Method for manufacturing waveguide coupler by direct-etching

Abstract

To provide a method for manufacturing a waveguide structure using a substrate.SOLUTION: A waveguide structure is formed so as to have an input coupling area, a waveguide area, and ab output coupling area formed from a substrate. The areas are formed by stamping a stamp on a resist arranged on a hard mask formed on the surface of the substrate in order to form a convex waveguide pattern. The hard mask formed in a part of the convex waveguide pattern and under the part is removed. The substrate is masked and etched in order to form a diffraction grating in the input coupling area and the output coupling area. Residual parts of the convex shape waveguide pattern and hard mask arranged under the residual parts are removed in order to form the waveguide structure having the input coupling, waveguide, and output coupling areas formed from the substrate.SELECTED DRAWING: Figure 6E

Description

[Technical field]

[0001]

[0001] Embodiments of the present disclosure generally relate to a waveguide for augmented reality, virtual reality, and mixed reality. More specifically, embodiments described herein provide a method for fabricating a waveguide from a substrate. [Background technology]

[0002] 2. Description of Related Art

[0002] Virtual reality is generally considered to be a computer-generated simulated environment in which a user has an apparent physical presence. Virtual reality experiences are generated in 3D and viewed with a head-mounted display (HMD) such as glasses or other wearable display devices that have eyepiece display panels as lenses to display the virtual reality environment that replaces the real environment.

[0003]

[0003] However, augmented reality allows an experience where a user can see the surrounding environment through the display lens of glasses or other HMD device, but can also see images of virtual objects that are generated for display and appear as part of the environment. Augmented reality can include any type of input, such as voice input and haptic input, as well as virtual images, graphics and videos that enhance or extend the environment experienced by the user. As an emerging technology, augmented reality has many challenges and design constraints.

[0004]

[0004] One such challenge is displaying a virtual image superimposed on the surrounding environment. A waveguide is used to assist in the superimposition of the image. Generated light is propagated through the waveguide until the light exits the waveguide and is superimposed on the surrounding environment. Waveguides tend to have non-uniform properties, making them difficult to manufacture. Thus, what is needed in the art are improved enhanced waveguides and methods of manufacture. Summary of the Invention

[0005] In one embodiment, a method for forming a waveguiding structure is presented. The method includes imprinting a stamp into a resist to form a convex waveguiding pattern. The resist is disposed on a hard mask formed on a surface of a portion of a substrate. The convex waveguiding pattern includes a pattern including at least one of a first plurality of grating patterns, a waveguiding pattern, and a second plurality of grating patterns. Each of the first plurality of grating patterns and the second plurality of grating patterns has a residual layer and an upper pattern surface. A hardening process is performed to harden the convex waveguiding pattern. The stamp is removed. A first etching process is performed to remove the residual layer and the hard mask disposed below the residual layer and expose a surface of the substrate. The substrate is masked to expose a first unprotected area of ​​the surface of the substrate. A second etching process is performed for a first predetermined time to form a first plurality of gratings having a first depth. The substrate is masked to expose a second unprotected area of ​​the surface of the substrate. The second etching process is performed for a second predetermined time to form a second plurality of diffraction gratings having a second depth. The top pattern surface, the waveguide pattern, and the hard mask disposed below the top pattern surface and the waveguide pattern are removed to form a waveguide structure including at least one of an input coupling region, a waveguiding region, and an output coupling region.

[0006]

[0006] In another embodiment, a method for forming a waveguiding structure is presented. The method includes imprinting a stamp into a resist to form a convex waveguiding pattern. The resist is disposed on a hard mask formed on a surface of a portion of a substrate. The convex waveguiding pattern includes a pattern including at least one of a first plurality of grating patterns, a waveguiding pattern, and a second plurality of grating patterns. Each of the first plurality of grating patterns and the second plurality of grating patterns has a residual layer, a top pattern surface, and a sidewall pattern surface that are inclined with respect to the surface of the substrate. A hardening process is performed to harden the convex waveguiding pattern. The stamp is removed. A first etching process is performed to remove the residual layer and the hard mask disposed below the residual layer and expose the surface of the substrate. The substrate is masked to expose a first unprotected area of ​​the surface of the substrate. A first plurality of angled gratings having a first depth is formed by etching at a predetermined angle for a first predetermined time. The substrate is masked to expose a second unprotected area of ​​the surface of the substrate. Etching at a predetermined angle for a second predetermined time forms a second plurality of angled gratings having a second depth. The top pattern surface, the waveguiding pattern, and a hard mask disposed below the top pattern surface and the waveguiding pattern are removed to form a waveguiding structure including at least one of an input coupling region, a waveguiding region, and an output coupling region.

[0007]

[0007] In yet another embodiment, a method for forming a waveguiding structure is presented. The method includes imprinting a stamp into a resist to form a convex waveguiding pattern, the resist being disposed on a hard mask formed on a surface of a substrate, the convex waveguiding pattern including at least one of a first plurality of grating patterns, a waveguiding pattern, and a second plurality of grating patterns. Each of the first plurality of grating patterns and the second plurality of grating patterns has a residual layer, a top pattern surface, and a sidewall pattern surface that are inclined with respect to the surface of the substrate. The convex waveguiding pattern is hardened by electromagnetic radiation hardening. The stamp is removed. The residual layer is removed by plasma ashing. The hard mask disposed under the residual layer is reactive ion etched to expose the surface of the substrate. The substrate is masked to expose a first unprotected region of the surface of the substrate. A directional reactive ion etch (RIE) at a predetermined angle for a first predetermined time forms a first plurality of angled gratings having a first depth. The substrate is masked to expose a second unprotected region of the surface of the substrate. Performing directional RIE at a predetermined angle for a second predetermined time forms a second plurality of angled gratings. The substrate is masked to expose a third unprotected area of ​​the surface of the substrate. Performing directional RIE at a predetermined angle for a third predetermined time forms a third plurality of angled gratings having a third depth. The top pattern surface and the waveguide pattern are removed by plasma ashing. Reactive ion etching the top pattern surface and a hard mask disposed beneath the waveguide pattern forms a waveguide structure including at least one of an input coupling region, a waveguide region, and an output coupling region.

[0008]

[0008] In order that the features of the present disclosure described above may be understood in detail, a more particular description of the present disclosure briefly summarized above may be obtained by referring to embodiments, some of which are illustrated in the accompanying drawings. However, it should be noted that the attached drawings show only exemplary embodiments, and therefore should not be considered as limiting the scope of the present disclosure, and other equally effective embodiments may be acceptable. [Brief description of the drawings]

[0009] [Figure 1] FIG. 2 is a perspective front view of a waveguide coupler according to one embodiment. [Diagram 2] FIG. 2 is a flow diagram illustrating method steps for forming a waveguiding structure according to one embodiment. [Figure 3A] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 3B] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 3C] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 3D] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 3E] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 4A] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 4B] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 4C] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 4D] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 4E] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Diagram 5] 2 is a flow diagram that generally illustrates method steps for forming a waveguiding structure, according to one embodiment. [Figure 6A] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 6B] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 6C] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 6D] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. [Figure 6E] 2 is a schematic cross-sectional view of a director during fabrication according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010]

[0015] To facilitate understanding, wherever possible, the same reference numerals have been used to designate identical elements common to the figures. It is envisioned that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.

[0011]

[0016] The embodiments described herein relate to a method for fabricating a waveguiding structure from a substrate. The waveguiding structure is formed having an input coupling region, a waveguiding region, and an output coupling region formed from the substrate. The regions are formed by stamping a resist disposed on a hard mask formed on a surface of the substrate to form a convex waveguiding pattern. A portion of the convex waveguiding pattern and the hard mask disposed below the portion are removed. The substrate is masked and etched to form a diffraction grating in the input coupling region and the output coupling region. A remaining portion of the convex waveguiding pattern and the hard mask disposed below the remaining portion are removed to form a waveguiding structure having an input coupling region, a waveguiding region, and an output coupling region formed from the substrate. In one embodiment, the substrate includes at least one of a glass material and a plastic material. In another embodiment, the substrate has a refractive index between about 1.5 and about 2.5.

[0012]

[0017] 1 is a perspective front view of a waveguide coupler 100. It should be understood that the waveguide coupler 100 described below is an exemplary waveguide coupler. The waveguide coupler 100 includes an input coupling region 102 defined by a number of diffraction gratings 108, a waveguiding region 104, and an output coupling region 106 defined by a number of diffraction gratings 110.

[0013]

[0018] The input coupling region 102 receives an incident beam of intense light (virtual image) from a microdisplay. Each grating of the plurality of diffraction gratings 108 splits the incident beam into a plurality of modes, each beam having a mode. The zeroth order mode (T0) beam is refracted back or lost in the waveguide coupler 100, the positive first order mode (T1) beam undergoes total internal reflection (TIR) ​​through the waveguide coupler 100 from the waveguide region 104 to the output coupling region 106, and the negative first order mode (T - 1) The T0 beam propagates in the waveguide coupler 100 in the opposite direction to the T1 beam. The T1 beam undergoes total internal reflection (TIR) ​​through the waveguide coupler 100 until the T1 beam contacts a grating of the plurality of diffraction gratings 110 in the output coupling region 106. The T1 beam contacts a grating of the plurality of diffraction gratings 110 where the T1 beam is divided into two groups: the T0 beam, which is refracted back or lost within the waveguide coupler 100; the T1 beam, which undergoes TIR in the output coupling region 106 until the T1 beam contacts another grating of the plurality of diffraction gratings 110; and the T1 beam, which is coupled out of the waveguide coupler 100. - 1 beam and

[0014]

[0019] FIG. 2 is a flow diagram illustrating steps of a method 200 for forming a waveguide structure. In one embodiment, the waveguide structure 300 corresponds to at least one of the input coupling region 102, the waveguiding region 104, and the output coupling region 106 of the waveguide coupler 100. In step 201, a stamp having a concave waveguide pattern is imprinted into a resist disposed on a hard mask formed on a surface of a portion of a substrate to form a convex waveguide pattern. The convex waveguide pattern includes a pattern. The pattern includes at least one of an input coupling portion, a waveguide portion, and an output coupling portion, thereby forming at least one of the input coupling region 102, the waveguiding region 104, and the output coupling region 106 of the waveguide coupler 100. The pattern includes a plurality of grating patterns including a residual layer and an upper pattern surface. In one embodiment, the pattern includes a plurality of grating patterns and a waveguiding pattern.

[0015]

[0020] In step 202, a hardening process is performed to harden the convex waveguide pattern. In step 203, the stamp is removed from the resist. In step 204, the residual layer and the hard mask disposed under the residual layer are removed by performing a first etching process to expose a portion of the surface of the substrate. In step 205, the substrate is masked to expose a first unprotected area of ​​the surface of the substrate. In step 206, a first plurality of gratings having a first depth is formed by performing a second etching process for a first predetermined time. In one embodiment, the first plurality of gratings is a first portion of at least one of the plurality of gratings 108 of the input coupling region 102 and the plurality of gratings 110 of the output coupling region 106. In another embodiment, the first plurality of gratings is at least one of the plurality of gratings 108 of the input coupling region 102 and the plurality of gratings 110 of the output coupling region 106.

[0016]

[0021] In step 207, the substrate is masked to expose a second unprotected area of ​​the surface of the substrate. In step 208, a second plurality of gratings having a second depth is formed by performing a second etching process for a second predetermined time. In one embodiment, the second plurality of gratings is a second portion of at least one of the plurality of gratings 108 of the input coupling region 102 and the plurality of gratings 110 of the output coupling region 106. In another embodiment, the second plurality of gratings is at least one of the plurality of gratings 108 of the input coupling region 102 and the plurality of gratings 110 of the output coupling region 106. In step 209, the top pattern surface, the waveguiding pattern, and the hard mask disposed below the top pattern surface and the waveguiding pattern are removed to form a waveguiding structure. The waveguiding structure includes at least one of the input coupling region 102, the waveguiding region 104, and the output coupling region 106 of the waveguiding coupler 100.

[0017]

[0022] 3A-3E, the fabrication of the waveguide structure 300, including imprinting the stamp, performing a curing process, removing the stamp, performing a first etching process, performing a second etching process, and removing the top pattern surface, the waveguide pattern, and the hard mask, will be described in further detail.

[0018]

[0023] As shown in FIG. 3A, to form a convex waveguide pattern 313, a stamp 326 is imprinted on a resist 325 disposed on a hard mask 303 formed on a surface 302 of a portion 330 of a substrate 301. The stamp 326 has a concave waveguide pattern 312 including an inverse pattern 331. The inverse pattern 331 includes at least one of an input coupling portion 314, an inverse waveguide portion 316, and an inverse output coupling portion 318. The stamp 326 is fabricated from a waveguide master having a master pattern. In one embodiment, the master pattern includes at least one of a master input coupling portion, a master waveguide portion, and a master output coupling portion. The stamp 326 is molded from a waveguide master.

[0019]

[0024] The stamp 326 comprises a semi-transparent material such as fused silica or polydimethylsiloxane (PDMS), and in step 202, the convex waveguide pattern 313 can be cured by exposure to radiation such as infrared (IR) radiation or ultraviolet (UV) radiation. In one embodiment, the resist 325 is a UV curable material (such as mr 300 available from Micro Resist Technology, Inc.) that can be nano-imprinted by the stamp 326 that comprises PDMS. - The convex waveguide pattern 313 may alternatively be thermally cured in step 202. In one embodiment, the surface 302 of the substrate 301 is treated with UV ozone, oxygen (O2) plasma, or with a primer (e.g., mr -The resist 325 is prepared for spin-coating of a UV curable material by application of a UV curable material such as APS1. In another embodiment, the resist 325 comprises a thermosetting material that can be cured by a solvent evaporation curing process. The solvent evaporation curing process can include thermal heating or infrared radiation heating. The resist 325 can be disposed on the surface 302 using a liquid material injection casting process, a spin-on coating process, a liquid spray coating process, a dry powder coating process, a screen printing process, a doctor blading process, a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, a flowable CVD (FCVD) process, or an atomic layer deposition (ALD) process.

[0020]

[0025] The convex waveguide pattern 313 includes a pattern 322. The pattern 322 includes at least one of an input coupling section 315, a waveguide section 317, and an output coupling section 319. The pattern 322 includes at least one of a first plurality of diffraction grating patterns 305, a waveguide pattern 333, and a second plurality of diffraction grating patterns 327. Each of the first plurality of diffraction grating patterns 305 and the second plurality of diffraction grating patterns 327 has a residual layer 311, often referred to as a bottom pattern surface, a top pattern surface 307 parallel to the surface 302 of the substrate 301, and a sidewall pattern surface 309 oriented perpendicular to the surface 302 of the substrate 301.

[0021]

[0026] 3B shows a schematic cross-sectional view after stamp 323 has been removed in step 203. In one embodiment, stamp 326 can be coated with a single layer of an anti-stick surface treatment coating, such as a fluorine coating, so that stamp 326 can be mechanically removed by machine tooling or by peeling it off by hand. In another embodiment, stamp 326 can be composed of a water-soluble polyvinyl alcohol (PVA) material such that stamp 326 can be dissolved and removed in water. In yet another embodiment, stamp 326 includes a rigid backing sheet, such as a glass sheet, to enhance mechanical strength.

[0022]

[0027] 3C is a schematic cross-sectional view after a first etching process to remove the residual layer 311 and hard mask 303 disposed under the residual layer 311 and expose the surface 302 of the substrate 301 in step 204. The residual layer 311 can be removed by plasma ashing (often referred to as plasma descum processing) using oxygen gas (O2)-containing plasma, fluorine gas (F2)-containing plasma, chlorine gas (Cl2)-containing plasma, and / or methane (CH4)-containing plasma. In one embodiment, a first radio frequency (RF) power is applied to O2 and an inert gas such as argon (Ar) or nitrogen (N) until the residual layer 311 is removed. The hard mask 303 disposed under the residual layer 311 can be removed by ion etching, reactive ion etching (RIE), or highly selective wet chemical etching. For example, the hard mask 303 may have a first layer including a first material and a second layer including a second material, the second layer formed on the first layer disposed on the surface 302 of the substrate 301. The second layer may be removed by taking advantage of the high etch selectivity of the second material relative to the first material and the material of the substrate 301. The first layer may be removed by taking advantage of the high etch selectivity of the first material relative to the material of the substrate 301. In one embodiment, the hard mask 303 may include a silicon-containing layer (such as OptiStack® HM825 available from Brewer Science) disposed on a carbon-containing layer (such as OptiStack® SOC110D available from Brewer Science). - In another embodiment, the hard mask 303 includes a chromium-containing layer disposed on a silicon dioxide (SiO2)-containing layer. The chromium-containing layer disposed on the residual layer 311 is removed by RIE using a Cl2-containing plasma, such as BCl3, and the silicon dioxide-containing layer is removed by RIE using an F2-containing plasma or a CH4-containing plasma. The silicon-containing layer disposed on the residual layer 311 is removed by RIE using a Cl2-containing plasma, such as BCl3, and the silicon dioxide-containing layer is removed by RIE using an F2-containing plasma or a CH4-containing plasma.

[0023]

[0028] FIG. 3D is a schematic cross-sectional view after steps 205-208. In steps 205-208, the substrate 301 is masked to expose a first unprotected area of ​​the surface 302 of the substrate 301, and a second etching process is performed for a first predetermined time, and the substrate 301 is masked to expose a second unprotected area of ​​the surface 302 of the substrate 301, and a second etching process is performed for a second predetermined time. In one embodiment, an etch endpoint detection system mounted on the chamber is used. Masking the substrate 301 may include placing a shadow mask in physical contact with the surface 302 of the substrate 301, or aligning a photomask on the substrate 301 to expose the first unprotected area. In one embodiment, the shadow mask is metal and can be used repeatedly.

[0024]

[0029] In one embodiment, the first unprotected region corresponds to the first region and the second unprotected region corresponds to the second region of the resulting waveguiding structure 300. In another embodiment, the first unprotected region corresponds to the first region and the second region and the second unprotected region corresponds to the second region. In one embodiment, as shown, the first region is the input coupling region 102 and the second region is the output coupling region 106. In another embodiment not shown, the first region and the second region are regions of the input coupling region 102 or the output coupling region 106. The second etching process may include an etching process such as ion implantation, ion etching, RIE, directional RIE such as directed ribbon-beam ion etching, microblasting, water jet cutting, and laser etching for a first predetermined time to form the first plurality of diffraction gratings 304 having a first depth 321. An example of an ion implanter is the Varian VIISTA® Trident, available from Applied Materials, Inc., Santa Clara, Calif. The ion etch may be in the presence of an etching gas to improve the ion etch rate.

[0025]

[0030] The first plurality of diffraction gratings 304 further includes a top surface 306 and a bottom surface 328 corresponding to the surface 302 of the substrate 301, and a sidewall surface 308 oriented perpendicular to the surface 302 of the substrate 301. The shadow mask may be repositioned or the photomask may be realigned to expose a second unprotected region. A second etching process is performed for a second predetermined time to form a second plurality of diffraction gratings 310 having a second depth 323. The second plurality of diffraction gratings 310 further includes a top surface 306, a bottom surface 328, and a sidewall surface 308.

[0026]

[0031] 3E is a schematic cross-sectional view of the waveguide structure 300 formed after step 209. To form the waveguide structure 300 including at least one of the input coupling region 102, the waveguide region 104, and the output coupling region 106 of the waveguide coupler 100, the upper pattern surface 307 and the waveguide pattern 333 are removed in step 209, and the hard mask 303 disposed under the upper pattern surface 307 and the waveguide pattern 333 in step 207 are removed. The upper pattern surface 307 and the waveguide pattern 333 can be removed by plasma ashing using an O2-containing plasma, an F2-containing plasma, a Cl2-containing plasma, and / or a CH4-containing plasma. In one embodiment, a second radio frequency (RF) power is applied to O2 and an inert gas such as argon (Ar) or nitrogen (N) until the upper pattern surface 307 and the waveguide pattern 333 are removed. The hard mask 303 disposed under the top pattern surface 307 and the waveguide pattern 333 may be removed by ion etching, RIE, or highly selective wet chemical etching. In one embodiment, the hard mask 303 includes a silicon-containing layer disposed on a carbon-containing layer. The silicon-containing layer is removed by RIE with an F2-containing plasma, and the carbon-containing layer is removed by RIE with an O2-containing plasma. In another embodiment, the hard mask 303 includes a chromium-containing layer disposed on a SiO2-containing layer. The chromium-containing layer is removed by RIE with a Cl2-containing plasma, and the silicon dioxide-containing layer is removed by RIE using an F2-containing plasma or a CH4-containing plasma. In another embodiment, the hard mask 303 is not removed, and the hard mask 303 includes a material such as SiO2 and titanium dioxide (TiO2) having a controlled refractive index between about 1.5 and about 2.5.

[0027]

[0032] The waveguide structure 300 resulting from the method 200 has a substantially uniform refractive index. By utilizing a material for the substrate 301 having a refractive index of about 1.5 to about 2.5, compared to the refractive index of air (1.0), total internal reflection, or at least higher orders thereof, is achieved to facilitate the propagation of light through the waveguide structure 300.

[0028]

[0033] 4A-4E, the fabrication of the waveguide structure 400 is described in further detail below, including imprinting the stamp, performing a curing process, removing the stamp, performing a first etching process, performing a second etching process, and removing the top pattern surface, the waveguide pattern, and the hard mask.

[0029]

[0034] In step 201, a stamp 426 is imprinted into a resist 425 disposed on a hard mask 403 formed on a surface 402 of a portion 430 of a substrate 401 to form a convex waveguide pattern 413. As shown in FIG. 4A, the stamp 426 has a concave waveguide pattern 412 including an inverse pattern 431. The inverse pattern 431 includes at least one of a reverse input coupling portion 414, a reverse waveguide portion 416, and a reverse output coupling portion 418. In step 202, the convex waveguide pattern 413 is cured.

[0030]

[0035] The convex waveguide pattern 413 includes a pattern 422. The pattern 422 includes at least one of an input coupling section 415, a waveguide section 417, and an output coupling section 419. The pattern 422 includes at least one of a first plurality of diffraction grating patterns 405, a waveguide pattern 433, and a second plurality of diffraction grating patterns 427. Each of the first plurality of diffraction grating patterns 405 and the second plurality of diffraction grating patterns 427 has a residual layer 411, often referred to as a bottom pattern surface, a top pattern surface 407 that is parallel to the surface 402 of the substrate 401, and a sidewall pattern surface 409 that is inclined by an amount relative to the surface 402 of the substrate 401.

[0031]

[0036] In step 203, the stamp 426 is removed from the resist 425. In step 204, the residual layer 411 and the hard mask 403 located below the residual layer 411 are removed by performing a first etching process to expose the surface 402 of the substrate 401.

[0032]

[0037] In step 205, the substrate 401 is masked to expose a first unprotected region of the surface 402 of the substrate 401. Masking the substrate 401 may include placing a shadow mask in physical contact with the surface 402 of the substrate 401 or aligning a photomask over the substrate 401 to expose the first unprotected region. In one embodiment, the first unprotected region corresponds to the first region and the second unprotected region corresponds to the second region of the resulting waveguiding structure 400. In another embodiment, the first unprotected region corresponds to the first region and the second region and the second unprotected region corresponds to the second region. In one embodiment, as shown, the first region is the input coupling region 102 and the second region is the output coupling region 106. In another embodiment not shown, the first region and the second region are regions of the input coupling region 102 or the output coupling region 106. In step 206, a first plurality of diffraction gratings 404 are formed with a first depth 421 and sidewall surfaces 408 inclined by an amount relative to the surface 402 of the substrate 401 by performing a second etching process for a first predetermined time at a first predetermined angle. The predetermined angle may be determined by computer simulation to maximize the optical coupling efficiency of the waveguiding structure 400, and the predetermined angle may be within a range of about 15 degrees to about 75 degrees. The first plurality of diffraction gratings 404 further includes a top surface 406 parallel to the surface and a bottom surface 328 corresponding to the surface 302.

[0033]

[0038] Etching at an angle may include etching processes such as angled ion implantation, angled ion etching, and directional RIE, such as directional ribbon beam ion etching. Angled ion implantation includes accelerating ions toward the surface 402 of the substrate 401 at a predetermined angle relative to the surface 402 of the substrate 401 and bombarding the substrate 401 with the ions at a predetermined angle to selectively remove material to form the first plurality of gratings 404. In one embodiment, introducing an etching gas near the ion source enhances the ion etching rate. One example of an angled ion implanter is the Varian VIISTA® Trident, available from Applied Materials, Inc., Santa Clara, Calif.

[0034]

[0039] In step 207, the substrate 401 is masked to expose a second unprotected area of ​​the surface 402 of the substrate 401. The shadow mask may be repositioned or the photomask may be realigned to expose the second unprotected area. In step 208, a second plurality of angled gratings 410 having a second depth 423 is formed by etching at a predetermined angle for a second predetermined time. The second plurality of angled gratings 410 further includes a top surface 406, a bottom surface 428, and a sidewall surface 408 that are inclined an amount relative to the surface 402 of the substrate 401.

[0035]

[0040] In step 209, the top pattern surface 407, the waveguide pattern 433, and the hard mask 403 disposed under the top pattern surface 407 and the waveguide pattern 433 are removed to form a waveguide structure 400 having an input coupling region 102, a waveguide region 104, and an output coupling region 106. The top pattern surface 407 and the waveguide pattern 433 may be removed to form a waveguide structure 400 including at least one of the input coupling region 102, the waveguide region 104, and the output coupling region 106 of the waveguide coupler 100. In another embodiment, the hard mask 403 is not removed, and the hard mask 403 comprises a material having a controlled refractive index between about 1.5 and about 2.5. The waveguide structure 400 resulting from the method 200 has a substantially uniform refractive index.

[0036]

[0041] FIG. 5 is a flow diagram showing steps of a method 500 for forming a waveguide structure 600 as shown in FIGS. 6A-6E. In one embodiment, the waveguide structure 600 corresponds to at least one of the input coupling region 102, the waveguide region 104, and the output coupling region 106 of the waveguide coupler 100. In step 501, a stamp 626 is stamped into a resist 625 disposed on a hard mask 603 formed on a surface 602 of a portion 630 of a substrate 601 to form a convex waveguide pattern 613. As shown in FIG. 6A, the stamp 626 has a concave waveguide pattern 612, which is an inverse pattern 631. The inverse pattern 631 includes at least one of a reverse input coupling portion 614, a reverse waveguide portion 616, and a reverse output coupling portion 618.

[0037]

[0042] The convex waveguide pattern 613 includes a pattern 622. The pattern 622 includes at least one of an input coupling portion 615, a waveguide portion 617, and an output coupling portion 619. The pattern 622 includes at least one of a first plurality of diffraction grating patterns 605, a waveguide pattern 633, and a second plurality of diffraction grating patterns 627. Each of the first plurality of diffraction grating patterns 605 and the second plurality of diffraction grating patterns 627 has a residual layer 611, often referred to as a bottom pattern surface, a top pattern surface 607 that is parallel to the surface 602 of the substrate 601, and a sidewall pattern surface 609 that is inclined by an amount relative to the surface 602 of the substrate 601.

[0038]

[0043] In step 502, the convex waveguide pattern 613 is hardened by exposure to electromagnetic radiation, such as infrared (IR) radiation and ultraviolet (UV) radiation. In step 503, the stamp 626 is removed from the resist 625. In step 504, the residual layer 611 is removed by plasma ashing until the residual layer 611 is removed. In step 505, the hard mask 603 disposed under the residual layer 611 is removed by ion etching, reactive ion etching (RIE), and highly selective wet chemical etching.

[0039]

[0044] In step 506, the substrate 601 is masked to expose a first unprotected region of the surface 602 of the substrate 601. Masking the substrate 601 may include placing a shadow mask in physical contact with the surface 602 of the substrate 601 or aligning a photomask over the substrate 601 to expose the first unprotected region. In one embodiment, the first unprotected region corresponds to the first region, the second unprotected region corresponds to the second region, and the third unprotected region corresponds to the third region of the resulting waveguiding structure 600. In another embodiment, the first unprotected region corresponds to the first region, the second region, and the third region, the second unprotected region corresponds to the second region and the third region, and the third unprotected region corresponds to the third region. In one embodiment, the first region is the input coupling region 102 and the second region and the third region are the output coupling region 106 as shown. In another embodiment, not shown, the first region, the second region, and the third region are regions of the input coupling region 102 or the output coupling region 106 .

[0040]

[0045] In step 507, in one embodiment, a first plurality of gratings 604 having a first depth 621 is formed by directional reactive ion etching (RIE) for a first predetermined time at a predetermined angle to the first etch depth. The first plurality of gratings 604 further includes a top surface 606 parallel to the surface 602 of the substrate 601, a bottom surface 628 corresponding to the surface 602 of the substrate 601, and a sidewall surface 608 that is inclined an amount relative to the surface 602 of the substrate 601.

[0041]

[0046] In step 508, the substrate 601 is masked to expose a second unprotected area of ​​the surface 602 of the substrate 601. The shadow mask may be repositioned or the photomask may be realigned to expose the second unprotected area. In one embodiment, the second unprotected area corresponds to the first portion 634 of the output coupling region 106. In another embodiment, the second unprotected portion corresponds to the first portion 634 and the second portion 635 of the output coupling region 106. In one embodiment, in step 509, a second plurality of angled gratings 610 having a second depth 623 within the first portion 634 is formed at a second predetermined time and at a predetermined angle by directional RIE. The second plurality of angled gratings 610 further includes a top surface 606, a bottom surface 628, and a sidewall surface 608 that are inclined an amount relative to the surface 602 of the substrate 601.

[0042]

[0047] In step 510, the substrate 601 is masked to expose a third unprotected area of ​​the surface 602 of the substrate 601. The shadow mask may be repositioned or the photomask may be realigned to expose the third unprotected area. In one embodiment, the third unprotected area corresponds to the second portion 635 of the output coupling region 106. In step 511, at a third predetermined time, a third plurality of angled gratings 632 having a third depth 629 are formed at a predetermined angle by directional RIE. The third plurality of angled gratings 632 further includes a top surface 606 and a bottom surface 628 parallel to the surface 602 of the substrate 601, and a sidewall surface 608 that is inclined an amount relative to the surface 602 of the substrate 601.

[0043]

[0048] In step 512, the top pattern surface 607, the waveguide pattern 633, and the hard mask 603 disposed under the top pattern surface 607 and the waveguide pattern 633 are removed by plasma ashing. In step 513, the hard mask 603 disposed under the top pattern surface 607 and the waveguide pattern 633 is removed by ion etching, RIE, or highly selective wet chemical etching to form the waveguide structure 600 having the input coupling region 102, the waveguide region 104, and the output coupling region 106. In another embodiment, the hard mask 603 is not removed, and the hard mask 603 comprises a material having a controlled refractive index between about 1.5 and about 2.5. The waveguide structure 600 resulting from the method 500 has a substantially uniform refractive index.

[0044]

[0049] In summary, methods are described herein for fabricating a waveguiding structure utilizing a substrate. The utilization of a substrate results in a waveguiding structure having an input coupling region, a waveguiding region, and an output coupling region with substantially uniform refractive indices. By utilizing a material for the substrate that has a refractive index between about 1.5 and about 2.5, compared to the refractive index of air (1.0), total internal reflection, or at least higher orders thereof, is achieved, facilitating light propagation through the extended structure.

[0045]

[0050] While the forgoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, the scope of the present disclosure being determined by the claims that follow.

Claims

1. 1. A method of forming a waveguiding structure, comprising the steps of: forming a convex waveguide pattern having a first plurality of diffraction gratings and a second plurality of diffraction gratings by stamping a resist disposed on a hard mask disposed on a surface of a waveguide material; masking the waveguiding material to expose a first unprotected area of ​​the surface of the waveguiding material corresponding to an input coupling portion of the waveguiding structure; performing a first etching process for a first time to form the first plurality of diffraction gratings in the input coupling portion of the waveguiding structure having a first depth; masking the waveguiding material to expose a second unprotected area of ​​the surface of the waveguiding material corresponding to an output coupling portion of the waveguiding structure; performing a second etching process for a second time period different from the first time period to form the second plurality of gratings having a second depth different from the first depth; The method includes:

2. The method of claim 1, wherein each of the first plurality of diffraction gratings and the second plurality of diffraction gratings has a residual layer, a top pattern surface that is parallel to the surface of the waveguide material, and a sidewall pattern surface oriented perpendicular to the surface of the waveguide material.

3. The method of claim 2, further comprising performing a plasma ashing process to remove the residual layer and expose a portion of the hard mask underlying the residual layer.

4. The method of claim 3, further comprising performing an ion etching process or a wet chemical etching process to remove the portion of the hard mask underlying the residual layer.

5. The method of claim 3, wherein the hard mask comprises a silicon-containing layer disposed on a carbon-containing layer, the silicon-containing layer in contact with the residual layer, and the carbon-containing layer in contact with the waveguide material.

6. Performing a reactive ion etching process using a fluorine-containing plasma to remove the silicon-containing layer; and The method of claim 5 , further comprising performing a reactive ion etching process with an oxygen-containing plasma to remove the carbon-containing layer.

7. The method of claim 3, wherein the hard mask comprises a chromium-containing layer disposed on a silicon-containing layer, the chromium-containing layer in contact with the residual layer, and the silicon-containing layer in contact with the waveguide material.

8. The method of claim 7, further comprising: performing a reactive ion etching process using a chlorine-containing plasma to remove the chromium-containing layer; and 8. The method of claim 7, further comprising performing a reactive ion etching process using a fluorine-containing plasma or a methane-containing plasma to remove the silicon-containing layer.

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