Method to fabricate a blazed grating using spacer and trim

Abstract

Aspects of the present disclosure includes methods of forming a waveguide. The method of forming a waveguide includes depositing a photo resist over a mandrel disposed over a substrate. Portions of the mandrel exposed by the photo resist are etched. A spacer material is deposited over the mandrel and the substrate. A mask layer is deposited over the mandrel. A first exposed portion of the spacer material exposed by the photo resist is removed. The mask layer and a second exposed portion of the spacer material are removed to form a spacer. A first step etch is performed on a first portion of the substrate exposed by the mandrel to form a first step. The mandrel is trimmed to expose a second portion of the substrate. The mandrel and the spacer are removed.

Description

METHOD TO FABRICATE A BLAZED GRATING USING SPACER AND TRIMBACKGROUNDField

[0001] Embodiments of the present disclosure generally relate to optical waveguides. More specifically, embodiments described herein provide techniques for forming a waveguide having blazed gratings.Description of the Related Art

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

[0003] Augmented reality, however, enables an experience in which a user can still see through the display lenses of the glasses or other HMD device to view the surrounding environment, yet 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 audio and haptic inputs, as well as virtual images, graphics, and video that enhances or augments the environment that the user experiences. As an emerging technology, there are many challenges and design constraints with augmented reality.

[0004] Blazed gratings are desired in AR waveguides for high diffraction efficiency into the targeted order. However, blazed gratings are difficult to manufacture using traditional patterning.

[0005] Accordingly, there is a need for improved systems and methods of forming blazed grating structures.SUMMARY

[0006] Embodiments of the present disclosure generally relate to optical waveguides. More specifically, embodiments described herein provide techniques for forming a waveguide having blazed gratings.

[0007] In another embodiment, a method of making a waveguide is disclosed. The method of forming a waveguide includes depositing a photo resist over a mandrel disposed over a substrate. Portions of the mandrel exposed by the photo resist are etched. A spacer material is deposited over the mandrel and the substrate. A mask layer is deposited over the mandrel. A first exposed portion of the spacer material exposed by the photo resist is removed. The mask layer and a second exposed portion of the spacer material are removed to form a spacer. A first step etch is performed on a first portion of the substrate exposed by the mandrel to form a first step. The mandrel is trimmed to expose a second portion of the substrate. The mandrel and the spacer are removed.

[0008] In yet another embodiment, a method of making a waveguide is disclosed. The method includes depositing a first mandrel over a substrate and etching the first mandrel. A spacer material is deposited over the substrate and the first mandrel and the spacer material is etched to form a spacer. The first mandrel is trimmed to expose a first portion of the substrate. A second mandrel is deposited over the spacer and etched. A first etch is performed on the first portion of the substrate to form a first step. The second mandrel is trimmed to expose a second portion of the substrate. The second mandrel and the spacer are removed.

[0009] In yet another embodiment, a method of making a waveguide is disclosed. The method includes depositing a mandrel over a substrate and etching the mandrel. A spacer material is deposited over the substrate and the mandrel. A photo resist is deposited over a portion of the spacer material. A first exposed portion of the spacer material is etched to expose a first portion of the substrate. The photo resist is removed to expose a second exposed portion and a third exposed portion of the spacer material. The second exposed portion of the spacer material is etched to form a spacer. A first step etch is performed on the first portion of the substrate to form a second step. The mandrel is trimmed to expose a second portion of the substrate. The mandrel and the spacer are removed.

[0010] In yet another embodiment, a method of making a waveguide is disclosed. The method includes depositing a mandrel over a substrate. The mandrel is etched and a spacer material is deposited over the substrate and the mandrel. A photo resist is deposited over a portion of the spacer material. A first exposed portion of the spacermaterial is etched to expose a first portion of the substrate. The photo resist is removed to expose a second exposed portion and a third exposed portion of the spacer material. The second exposed portion of the spacer material is etched to form a spacer. A first step etch is performed on the first portion of the substrate to form a second step. The mandrel is trimmed to expose a second portion of the substrate. The mandrel and the spacer are removed.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of scope, and may admit to other equally effective embodiments.

[0012] Figure 1A is a perspective, frontal view of a waveguide, according to embodiments.

[0013] Figure 1 B is a schematic, cross-section view of a plurality of device structures, according to embodiments.

[0014] Figure 2 is a flow diagram of a first method of forming a waveguide structure, according to embodiments.

[0015] Figures 3A-3H are schematic, cross-sectional views of a waveguide structure during the method of Figure 2, according to embodiments.

[0016] Figure 4 is a flow diagram of a second method of forming a waveguide structure, according to embodiments.

[0017] Figures 5A-5K are schematic, cross-sectional views of a waveguide structure during the method of Figure 4, according to embodiments.

[0018] Figure 6 is a flow diagram of a third method of forming a waveguide structure, according to embodiments.

[0019] Figures 7A-7O are schematic, cross-sectional views of a waveguide structure during the method of Figure 6, according to embodiments.

[0020] Figure 8 is a flow diagram of a fourth method of forming a waveguide structure, according to embodiments.

[0021] Figures 9A-9N are schematic, cross-sectional views of a waveguide structure during the method of Figure 8, according to embodiments.

[0022] Figure 10 is a flow diagram of a fifth method of forming a waveguide structure, according to embodiments.

[0023] Figures 11A-11 L are schematic, cross-sectional views of a waveguide structure during the method of Figure 10, according to embodiments.

[0024] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated in other embodiments without further recitation.DETAILED DESCRIPTION

[0025] Embodiments of the present disclosure generally relate to optical waveguides. More specifically, embodiments described herein provide techniques for forming a waveguide having blazed gratings.

[0026] Figure 1A is a front view of a waveguide combiner 100. It is to be understood that the waveguide combiner 100 described below is an exemplary waveguide combiner. The waveguide combiner 100 includes a substrate 101 and a plurality of optical devices 104. The plurality of optical devices 104 include an input coupling region 104A defined by a plurality of gratings 106, a waveguide region 104B, and an output coupling region 104C.

[0027] The input coupling region 104A received incident beams of light (a light image) having an intensity from a micro-display. Each grating of the plurality of gratings 106 splits the incident beams into a plurality of modes. Zero-order mode (To) beams are refracted back or lost in the waveguide combiner 100. Positive first order mode (T1 ) beams undergo total-internal-reflection (TIR) through the waveguidecombiner 100 across the waveguide region 104B to the output coupling region 104C and output for display. Negative first-order mode (T-1 ) beams propagate in the waveguide combiner 100 a direction opposite the T1 beams. Among the diffracted orders, only the T1 beams output to display through output coupling region 104C, while other modes are lost due to different directionally. Therefore, it is beneficial to increase T1 beam intensity and decrease other orders beam intensity for higher device optical efficiency. One approach to increase the intensity of T1 beams and to reduce the intensity of the other order beams is to control the shape of each grating of the plurality of gratings 106. The plurality of grating 106 may include blazed gratings. The blazed shape for each grating of the plurality of gratings 106 provides for increased optical efficiency.

[0028] Figure 1 B is a schematic, cross-sectional view of a plurality of input coupling region 104A. In one embodiment, which can be combined with other embodiments described herein, the input coupling region 104A includes a plurality of blazed gratings 106 of an optical device. The methods 200, 400, 600, 800, and 1000 described herein form the plurality of blazed gratings 106. The waveguide combiner 100 includes blazed gratings 106. Each of the blazed grating 106 includes a blazed surface 108, sidewall 112, a depth h, and a linewidth d. The blazed surface 108 has a plurality of steps 110. In one embodiment, the blazed surface 108 includes at least 3 steps 110, such as greater than 16 steps 110, such as 32 steps 110. Increasing the number of steps results in an increase in the efficiency of the input coupling region 104A. The blazed surface has a blaze angle y. The blaze angle y is the angle between the blazed surface 108 and the surface parallel to the substrate 101 and the angle between the surface normal of the substrate 101 and facet normal f of the blazed surface 108. The depth h corresponds to the height of the sidewall 112 and the linewidth d corresponds to the distances between sidewalls 112 of adjacent blazed gratings 106.

[0029] In one embodiment, which may be combined with other embodiments, blaze angle y of two or more blazed gratings 106 are different. In another embodiment, which may be combined with other embodiments, the blaze angle y of two or more blazed gratings 106 are the same. In another embodiment, the depth h of two or more blazed gratings are different. In another embodiment, which may be combined with other embodiments, the depth h of two or more blazed gratings are the same. In one embodiment, which may be combined with other embodiments, thelinewidths d of two or more blazed gratings 106 are different. In one embodiment, which may be combined with other embodiments, the linewidths of two or more blazed gratings 106 are the same.

[0030] Figure 2 is a flow diagram of a method 200 of forming a waveguide structure. Figures 3A-3H are schematic, cross-sectional views of a waveguide structure during the method 200. The waveguide structure corresponds to the input coupling region 104A of the waveguide combiner 100.

[0031] At operation 202, as shown in Figure 3A, a mandrel 303 is deposited and etched to form a plurality of trenches 305. Generally, the mandrel 303 is a material layer that defines where a spacer (e.g., a spacer 309) are subsequently situated. The mandrel 303 is disposed over a substrate 301 . The substrate 301 corresponds to the substrate 101 of the waveguide combiner 100. The mandrel 303 includes an organic film (e.g., an advanced patterning film (APF) or an optical planarization layer (OPL) or an amorphous silicon (a-Si). The mandrel 303 is etched using a wet etch or a dry etch process. The plurality of trenches 305 include wide trenches 305A and narrow trenches 305B.

[0032] At operation 204, as shown in Figure 3B, a spacer material 307 is deposited over the substrate 301 and the mandrel 303. The spacer material 307 that is deposited in the narrow trenches 305B merges during deposition, such that the narrow trenches 305B are filled with the spacer material 307. The spacer material 307 that is deposited in the wide trenches 305A remains unmerged. The spacer material 307 includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), a combination thereof, or other suitable semiconductor material. In some embodiments, the spacer material is deposited using an atomic layer deposition (ALD) process.

[0033] At operation 206, as shown in Figure 3C, the spacer material 307 is etched to form a spacer 309 in the narrow trenches 305B and expose a first portion 311 of the substrate 301 . The spacer material 307 is etched using an isotropic etch process, a wet etch process, or a dry etch process. In some embodiments, in which the spacer material 307 is an oxide, a DHF material is used to perform the etch process. In other embodiments, in which the spacer material 307 is a nitride, a hot phosphor wet etch or an isotropic dry etch is used to perform the etch process. During the isotropicetching of the spacer material 307, the unmerged spacer material 307 in the wide trenches 305A is removed entirely, or nearly entirely, while only a small portion of the merged spacer material 307 in the narrow trenches 305B is removed, as the unmerged spacer material 307 has an increased amount of exposure to the isotropic etch.

[0034] At operation 208, as shown in Figure 3D, a first portion 303A of the mandrel 303 is trimmed to further expose the first portion 311 of the substrate 301. During the trimming, the first portion 303A and the second portion 303B of the mandrel 303 are etched at the same rate. A second portion 303B portion of the mandrel 303 is partially protected from trimming by the spacer 309. The mandrel 303 is etched using a wet etch or a dry etch process.

[0035] At operation 210, as shown in Figure 3E, a first step etch is performed on the first portion 311 of the substrate 301 exposed by the mandrel 303 to form a first step 312. The etch process can be a dry etch of a wet etch process. The chemistry of the etching process is selected such that the mandrel 303 and the spacer 309 are etched at a slower rate than the substrate 301 , e.g., the mandrel 303 and the spacer 309 are etched at a rate of about 5 time slower than the substrate 301 , due to the high degree of etch selectivity between the materials of the mandrel 303, the spacer 309, and the substrate 301.

[0036] At operation 212, as shown in Figure 3F, the mandrel 303 is trimmed to expose a second portion 313 of the substrate 301 . During operation 212, a timed etch is performed in order to partially trim the mandrel 303. Similar to operation 210, the etch selectivity between the mandrel 303, the substrate 301 , and the spacer 309 is high, allowing selective etching based on the etch chemistry.

[0037] At operation 214, as shown in Figure 3G, a second step etch is performed on the second portion 313 the substrate 301 exposed by the mandrel 303 to form a second step 314. At operation 216, as shown in Figure 3H, the mandrel 303 is trimmed to expose a third portion 315 of the substrate 301 .

[0038] The operations 214 and 216 may be repeated any number of times to achieve the desired number of steps 110 on the blazed grating of the waveguide structure. At operation 218, the mandrel 303 is removed. In some embodiments,which can be combined with other embodiments, the mandrel 303 is removed in a final trimming operation subsequent to the formation of the final step. At operation 218, the spacer 309 is removed. The spacer 309 is removed using a wet etch or a dry etch process.

[0039] Figure 4 is a flow diagram of a method 400 of form ing a waveguide structure500. Figures 5A-5K are schematic, cross-sectional views of a waveguide structure during the method 400. The waveguide structure 500 corresponds to the input coupling region 104A of the waveguide combiner 100.

[0040] At operation 402, as shown in Figure 5A, a photo resist 520 is deposited over a mandrel 503 and patterned. The mandrel 503 is disposed over the substrate501. The substrate 501 corresponds to the substrate 101 of the waveguide combiner 100. The mandrel 503 includes an organic film (e.g., an advanced patterning film (APF) or an optical planarization layer (OPL) or an amorphous silicon (a-Si). The photo resist 520 can be a positive photo resist or a negative photo resist. The photo resist 520 includes a plurality of openings 521. Portions of the mandrel 503 are exposed by the plurality of openings 521 in the photo resist 520.

[0041] At operation 404, as shown in Figure 5B, the portions of the mandrel 503 exposed by the plurality of openings 521 in the photo resist 520 are etched to form a plurality of trenches 505. The mandrel 503 is etched using a wet etch or a dry etch process.

[0042] At operation 406, as shown in Figure 5C, a spacer material 507 is deposited over the substrate 501 and the mandrel 503. The spacer material 507 includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), a combination thereof, or other suitable semiconductor material. In some embodiments, the spacer material is deposited using an atomic layer deposition (ALD) process or a chemical vapor deposition (CVD) process. The thickness of the spacer material 507 may be tailored to control the top critical dimension of the waveguide structure 500.

[0043] At operation 408, as shown in Figure 5D, a mask layer 530 is deposited over the mandrel 503 and patterned. The mask layer 530 is patterned using a lithography process. The mask layer 530 exposes a portion of the spacer material507. The mask layer includes a patterned resist or other organic material such as optical planarization layer (OPL) material, spin on carbon, bottom antireflection material (e.g., a bottom antireflection coating or BARC), or a combination thereof.

[0044] At operation 410, as shown in Figure 5E, a first portion of the spacer material 507 exposed by the mask layer 530 is etched. The spacer material 507 is etched using an isotropic etch process, a wet etch process, or a dry etch process. In some embodiments, in which the spacer material 507 is an oxide (e.g., silicon oxide, aluminum oxide, etc.), a DHF material is used to perform the etch process. In other embodiments, in which the spacer material 507 is a nitride (e.g., silicon nitride, aluminum nitride, etc.), a hot phosphor material or an isotropic dry etch is used as the dry etch material.

[0045] At operation 412, as shown in Figure 5F, the mask layer 530 and a second portion of the spacer material 507 are removed to form a spacer 509. The removal of the mask layer 530 and the second portion of the spacer material 507 exposes a first portion 511 of the substrate 501 .

[0046] At operation 414, as shown in Figure 5G, a first step etch is performed on the first portion 511 of the substrate 501 exposed by the mandrel 503 to form a first step 512. The etch process can be a dry etch of a wet etch process. At operation 416, as shown in Figure 5H, the mandrel 503 is trimmed to expose a second portion 513 of the substrate 301 .

[0047] At operation 418, as shown in Figure 5I, a second step etch is performed on the second portion 513 the substrate 501 exposed by the mandrel 503 to form a second step 514. At operation 420, as shown in Figure 5J, the mandrel 503 is trimmed to expose a third portion 515 of the substrate 501 .

[0048] The operation 418 and 420 may be repeated any number of times to achieve the desired number of steps 110 on the blazed grating of the waveguide structure 500. In one embodiment, at operation 420, the mandrel 503 is removed during the trimming. In some embodiments, the mandrel 503 is removed in a final trimming operation subsequent to the formation of the final step. At operation 422, as shown in Figure 5K, the spacer 509 is removed. The spacer 509 is removed using a wet etch or a dry etch process.

[0049] Figure 6 is a flow diagram of a method 600 of form ing a waveguide structure 700. Figures 7A-7N are schematic, cross-sectional views of a waveguide structure 700 during the method 600. The waveguide structure 700 corresponds to the input coupling region 104A of the waveguide combiner 100.

[0050] At operation 602, as shown in Figure 7A, a first mandrel 703A is deposited and patterned to form a plurality of trenches 705. The first mandrel 703A is disposed over a substrate 701. The substrate 701 corresponds to the substrate 101 of the waveguide combiner 100. The first mandrel 703A includes an organic film (e.g., an advanced patterning film (APF) or an optical planarization layer (OPL) or an amorphous silicon (a-Si). The first mandrel 703A is patterned using a wet etch or a dry etch process.

[0051] At operation 604, as shown in Figure 7B and Figure 7C, a spacer material 707 is deposited over the substrate 701 and the first mandrel 703A and patterned to form a spacer 709. The spacer material 707 includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), a combination thereof, or other suitable semiconductor material. In some embodiments, the spacer material 707 is deposited using an ALD process or a CVD process. The spacer material 707 is patterned using an isotropic etch process, a wet etch process, or a dry etch process. In some embodiments, in which the spacer material 707 is an oxide, a DHF material is used to perform the etch process. In other embodiments, in which the spacer material 707 is a nitride, a hot phosphor material or an isotropic dry etch is used as the dry etch material.

[0052] At operation 606, as shown in Figure 7D, the first mandrel 703A is trimmed to expose the substrate 701. The first mandrel 703A is removed using a wet etch or a dry etch process. The etch selectivity between the first mandrel 703A and the spacer material 707 enables the removal of the first mandrel 703A without removing the spacer material 707. At operation 608, as shown in Figure 7E, a second mandrel 703B is deposited over a portion of the spacer 709 and patterned. The second mandrel is blanket deposited over the portion of the spacer 709. The second mandrel 703B is patterned such that the second mandrel 703B exposes a first portion 711 of the substrate 701 . The second mandrel 703B may include an OPL, a BARC, a resist, or a combination thereof.

[0053] At operation 610, as shown in Figure 7F, a first step etch is performed on the first portion 711 of the substrate 701 exposed by the second mandrel 703B to form a first step 712. The etch process can be a dry etch of a wet etch process. At operation 612, as shown in Figure 7G, the second mandrel 703B is trimmed to expose a second portion 713 of the substrate 701.

[0054] At operation 614, as shown in Figure 7H, a second step etch is performed on the second portion 713 the substrate 701 exposed by the second mandrel 703B to form a second step 714. At operation 616, as shown in Figure 7I, the second mandrel 703B is trimmed to expose a third portion 715 of the substrate 701.

[0055] At operation 618, as shown in Figure 7J, a third step etch is performed on the third portion 715 the substrate 701 exposed by the second mandrel 703B to form a third step 716. At operation 620, as shown in Figure 7K, the second mandrel 703B is trimmed to expose a fourth portion 717 of the substrate 701.

[0056] The operations 618 and 620 may be repeated any number of times to achieve the desired number of steps 110 on the blazed grating of the waveguide structure 700. For example, operations 618 and 620, as shown in Figure 7L, may be repeated to form steps 740, 742, and 744.

[0057] At operation 622, as shown in Figure 7M, the second mandrel 703B is removed to expose a fifth portion 745 of the substrate 701. At operation 624, as shown in Figure 7N, a fourth step etch is performed on the fifth portion 745 of the substrate 701 exposed by the second mandrel 703B to form a final step 746. The etch process can be a dry etch of a wet etch process.

[0058] At operation 626, as shown in Figure 70, the spacer 709 is removed. The spacer 709 is removed using a wet etch or a dry etch process.

[0059] Figure 8 is a flow diagram of a method 800 of forming a waveguide structure. Figures 9A-9N are schematic, cross-sectional views of a waveguide structure during the method 800. The waveguide structure 900 corresponds to the input coupling region 104A of the waveguide combiner 100.

[0060] At operation 802, as shown in Figure 9A, a mandrel 903 is deposited and patterned to form a plurality of trenches 905. The mandrel 903 is disposed over asubstrate 901 . The substrate 901 corresponds to the substrate 101 of the waveguide combiner 100. The mandrel 903 includes an organic film (e.g., an advanced patterning film (APF) or an optical planarization layer (OPL) or an amorphous silicon (a-Si). The mandrel 903 is patterned using a wet etch or a dry etch process.

[0061] At operation 804, as shown in Figure 9B, a spacer material 907 is deposited over the substrate 901 and the mandrel 903. The spacer material 907 includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), a combination thereof, or other suitable semiconductor material. In some embodiments, the spacer material is deposited using an atomic layer deposition (ALD) process.

[0062] At operation 806, as shown in Figure 9C, a photo resist 920 is deposited over a portion of the spacer material 907. A first exposed portion 907A of the spacer material 907 is exposed by the second mandrel 903B.

[0063] At operation 808, as shown in Figure 9D, the first exposed portion 907A of the spacer material 907 exposed by the photo resist 920 is etched to expose a first portion 911 of the substrate 901 . The first exposed portion 907A is etched by an isotropic etch process.

[0064] At operation 810, as shown in Figure 9E and Figure 9F, the photo resist 920 is sequentially removed to expose a second exposed portion 907B of the spacer material 907 and a third exposed portion 907C of the spacer material 907. The photo resist 920 is anisotropically etched to expose the second exposed portion 907B of the spacer material 907. The photo resist 920 is isotropically etched to expose the third exposed portion 907C of the spacer material 907.

[0065] At operation 812, as shown in Figure 9G, the second exposed portion 907B of the spacer material 907 is etched to form a spacer 909. The second exposed portion 907B of the spacer material 907 is anisotropically etched. The spacer material 907 is etched using an isotropic etch process, a wet etch process, or a dry etch process. In some embodiments, in which the spacer material 907 is an oxide, a DHF material is used to perform the etch process. In other embodiments, in which the spacer material 907 is a nitride, a hot phosphor material or an isotropic dry etch is used as the dry etch material.

[0066] At operation 814, as shown in Figure 9H, a first step etch is performed on the first portion 911 of the substrate 901 to form a first step 912. The etch process can be a dry etch of a wet etch process. At operation 816, as shown in Figure 9I, the mandrel 903 is trimmed to expose a second portion 913 of the substrate 901 .

[0067] At operation 818, as shown in Figure 9J, a second step etch is performed on the second portion 913 the substrate 901 exposed by the mandrel 903 to form a second step 914. The etch selectivity between the mandrel 903 and the substrate 901 enables the removal of the substrate 901 at a different rate than the mandrel 903. At operation 820, as shown in Figure 9K, the mandrel 903 is trimmed to expose a third portion 915 of the substrate 901 .

[0068] At operation 822, as shown in Figure 9L, a third step etch is performed on the third portion 915 the substrate 901 exposed by the mandrel 903 to form a third step 916.

[0069] The operations 820 and 822 may be repeated any number of times to achieve the desired number of steps 110 on the blazed grating of the waveguide structure 900. For example, operations 820 and 822 may be repeated to form steps 918, 940, and 942. At operation 824, as shown in Figure 9M, the mandrel 903 is removed to expose a fourth portion 943 of the substrate 901 .

[0070] At operation 826, as shown in Figure 9N, the spacer 909 is removed. The spacer 909 is removed using a wet etch or a dry etch process.

[0071] Figure 10 is a flow diagram of a method 1000 of forming a waveguide structure. Figures 11A-11 L are schematic, cross-sectional views of a waveguide structure 1100 during the method 1000. The waveguide structure 1100 corresponds to the input coupling region 104A of the waveguide combiner 100.

[0072] At operation 1002, as shown in Figure 11 A, a mandrel 1103 is deposited and patterned to form a plurality of trenches 1105. The mandrel 1103 is disposed over a substrate 1101. The substrate 1101 corresponds to the substrate 101 of the waveguide combiner 100. The mandrel 1103 includes an organic film (e.g., an advanced patterning film (APF) or an optical planarization layer (OPL) or anamorphous silicon (a-Si). The mandrel 1103 is patterned using a wet etch or a dry etch process.

[0073] At operation 1004, as shown in Figure 11 B, a spacer material 1107 is deposited over the substrate 1101 and the mandrel 1103. The spacer material 1107 includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), a combination thereof, or other suitable semiconductor material. In some embodiments, the spacer material 1107 is deposited using an ALD process or a CVD process.

[0074] At operation 1006, as shown in Figure 11 C, the spacer material 1107 is etched to expose the mandrel 1103. The spacer material 1107 is etched using an isotropic etch process, a wet etch process, or a dry etch process. In some embodiments, in which the spacer material 1107 is an oxide, a DHF material is used to perform the etch process. In other embodiments, in which the spacer material 1107 is a nitride, a hot phosphor material or an isotropic dry etch is used as the dry etch material.

[0075] At operation 1008, as shown in Figure 11 D, a mask layer 1130 is disposed over the spacer material 1107 and patterned. An exposed portion 1107A of the spacer material 1107 is exposed by the mask layer 1130.

[0076] At operation 1010, as shown in Figure 11 E, the exposed portion 1107A of the spacer material 1107 exposed by the mask layer 1130 is etched to expose a first portion 1111 of the substrate 101 and form a spacer 1109. The exposed portion 1107A is etched by an isotropic etch process.

[0077] At operation 1012, as shown in Figure 11 F, a first step etch is performed on the first portion 1111 of the substrate 1101 to form a first step 1112. The etch process can be a dry etch of a wet etch process. At operation 101 , as shown in Figure 11 G, the mandrel 1103 and mask layer 1130 are trimmed to expose a second portion 1113 of the substrate 1101. In some embodiments, the mandrel 1103 and the mask layer 1130 are the same material. In other embodiments, the mandrel 1103 and the mask layer 1130 are different materials.

[0078] At operation 1016, as shown in Figure 11 H, a second step etch is performed on the second portion 1113 the substrate 1101 exposed by the mandrel 1103 to form a second step 1114.

[0079] The operations 1014 and 1016 may be repeated any number of times to achieve the desired number of steps 110 on the blazed grating of the waveguide structure 1100. For example, operations 1014 and 1016, as shown in Figure 111, may be repeated to form steps 1116, 1118, and 1140. At operation 1018, as shown in Figure 11 J, the mandrel 1103 is removed to expose a third portion 1115 of the substrate 1101.

[0080] At operation 1020, as shown in Figure 11 K, a third step etch is performed on the third portion 1115 the substrate 1101 exposed by the mandrel 1103 to form a third step 1142.

[0081] At operation 1022, as shown in Figure 11 L, the spacer 1109 is removed. The spacer 1109 is removed using a wet etch or a dry etch process.

[0082] The methods 200, 400, 600, 800, and 1000 enable the formation of the blazed gratings 106 on the waveguide structure 500, 700, 900, 1100, respectively, without the use of a hardmask. Eliminating the hardmask enables a reduction in the size of the top critical dimension 570, 770, 970, 1170. In addition, the methods 200, 400, 600, 800, and 1000 do not require the use of ion beam etching (IBE). The methods 200, 400, 600, 800, and 1000 further enable increased process control.

[0083] The term “comprises” and grammatical equivalents thereof are used herein to mean that other components, ingredients, operations, etc. are optionally present. For example, an article “comprising” (or “which comprises”) components A, B, and C can consist of (i.e., contain only) components A, B, and C, or can contain not only components A, B, and C but also one or more other components. In addition, whenever a composition, an element or a group of elements is preceded with the transitional phrase “comprising” or grammatical equivalents thereof, it is understood that it is contemplated that the same composition or group of elements may be preceded with transitional phrases “consisting essentially of,” “consisting of,” “selected from the group of consisting of,” or “is” preceding the recitation of the composition, element, or elements and vice versa.

[0084] Where reference is made herein to a method comprising two or more defined operations, the defined operations can be carried out in any order or simultaneously (except where the context excludes that possibility), and the method can include one or more other operations which are carried out before any of the defined operations, between two of the defined operations, or after all of the defined operations (except where the context excludes that possibility).

[0085] When introducing elements of the present disclosure or exemplary aspects or implementation(s) thereof, the articles “a,” “an,” “the” and “said” are intended to mean that there are one or more of the elements.

[0086] The terms “comprising,” “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.

[0087] While the foregoing is directed to implementations of the present disclosure, other and further implementations of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

What is claimed is:1 . A method of forming a waveguide, comprising: depositing a photo resist over a mandrel disposed over a substrate; etching portions of the mandrel exposed by the photo resist; depositing a spacer material over the mandrel and the substrate; depositing a mask layer over the mandrel; removing a first exposed portion of the spacer material exposed by the photo resist; removing the mask layer and a second exposed portion of the spacer material to form a spacer; performing a first step etch on a first portion of the substrate exposed by the mandrel to form a first step; trimming the mandrel to expose a second portion of the substrate; removing the mandrel; and removing the spacer.

2. The method of claim 1 , wherein the mandrel includes an organic film or an amorphous silicon (a-Si).

3. The method of claim 1 , the spacer material includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), or a combination thereof.

4. The method of claim 1 , wherein the spacer material is deposited using an atomic layer deposition (ALD) process.

5. The method of claim 1 , the spacer material is etched using an isotropic etch process, a wet etch process, or a dry etch process.

6. A method of forming a waveguide, comprising: depositing a first mandrel over a substrate and etching the first mandrel;depositing a spacer material over the substrate and the first mandrel and etching the spacer material to form a spacer; trimming the first mandrel to expose a first portion of the substrate; depositing and etching a second mandrel over the spacer; performing a first etch on the first portion of the substrate to form a first step; trimming the second mandrel to expose a second portion of the substrate; removing the second mandrel; and removing the spacer.

7. The method of claim 6, wherein the first mandrel and the second mandrel include an organic film or an amorphous silicon (a-Si).

8. The method of claim 6, the spacer material includes silicon nitride (S i N ) , silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), or a combination thereof.

9. The method of claim 6, wherein the spacer material is deposited using an atomic layer deposition (ALD) process or a chemical vapor deposition (CVD) process.

10. The method of claim 6, the spacer material is etched using an isotropic etch process, a wet etch process, or a dry etch process.

11. A method of forming a waveguide, comprising: depositing a mandrel over a substrate and etching the mandrel; depositing a spacer material over the substrate and the mandrel; depositing a photo resist over a portion of the spacer material; etching a first exposed portion of the spacer material to expose a first portion of the substrate; removing the photo resist to expose a second exposed portion and a third exposed portion of the spacer material; etching the second exposed portion of the spacer material to form a spacer; performing a first step etch on the first portion of the substrate to form a second step; trimming the mandrel to expose a second portion of the substrate;removing the mandrel; and removing the spacer.

12. The method of claim 11 , wherein the mandrel includes an organic film or an amorphous silicon (a-Si).

13. The method of claim 11 , the spacer material includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), or a combination thereof.

14. The method of claim 11 , wherein the spacer material is deposited using an atomic layer deposition (ALD) process.

15. The method of claim 11 , the spacer material is etched using an isotropic etch process, a wet etch process, or a dry etch process.

16. A method of forming a waveguide, comprising: depositing a mandrel over a substrate; etching the mandrel; depositing a spacer material over the substrate and the mandrel; depositing a photo resist over a portion of the spacer material; etching a first exposed portion of the spacer material to expose a first portion of the substrate; removing the photo resist to expose a second exposed portion and a third exposed portion of the spacer material; etching the second exposed portion of the spacer material to form a spacer; performing a first step etch on the first portion of the substrate to form a second step; trimming the mandrel to expose a second portion of the substrate; removing the mandrel; and removing the spacer.

17. The method of claim 16, wherein the mandrel includes an organic film or an amorphous silicon (a-Si).

18. The method of claim 16, the spacer material includes silicon nitride (SiN), silicon oxide (SiOx), aluminum nitride (AIN), aluminum oxide (AIO), hafnium oxide (HfO), or a combination thereof.

19. The method of claim 16, wherein the spacer material is deposited using an atomic layer deposition (ALD) process or a chemical vapor deposition (CVD) process.

20. The method of claim 16, the spacer material is etched using an isotropic etch process, a wet etch process, or a dry etch process.

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