Low frequency imprint for gray scale optical device fabrication

Abstract

Embodiments described herein relate to methods of forming a waveguide with a grating having a depth distributed structure. The method includes disposing a resist material over a region of a device material or substrate corresponding to a grating of a structure to be formed having a depth profile; impressing an imprint into the resist material over regions, the imprint having a positive pattern of the depth profile, imprint the imprint and cure the resist material forming a patterned resist over the regions; releasing the impression; etching the patterned resist, and one of the device material or the substrate to form the depth profiles in the device material or the substrate; and forming the structures in the regions having the depth profile to form the gratings.

Description

Background Art

[0001] field

[0002] Embodiments of the present disclosure generally relate to waveguides. More specifically, embodiments described herein provide methods of forming a waveguide with a grating having a depth profile.

[0003] Related technical description

[0004] Virtual reality is generally considered a computer-generated simulated environment in which the user has the apparent physical presence. The virtual reality experience can be generated in 3D and viewed with a head-mounted display (HMD), such as glasses or other wearable display devices, which have a near-eye display panel as the eyepiece of the optical device to display the virtual reality environment in place of the real environment.

[0005] However, augmented reality allows users to experience the surrounding environment while still seeing through the eyepieces of glasses or other HMDs, and also to see images of virtual objects generated for display that appear to be part of the environment. Augmented reality can include any type of input, such as audio and tactile input, and virtual images, graphics, and video that enhance or augment the environment experienced by the user. As an emerging technology, augmented reality has many challenges and design limitations.

[0006] Therefore, what is needed in the art is a method of forming a waveguide with a grating having a depth profile. Summary of the Invention

[0007] In one embodiment, a method is provided. The method includes placing a resist material over a region of a device material or substrate corresponding to a grating having a depth profile where a structure is to be formed, stamping a stamp having a positive pattern of the depth profile into the resist material over the region, stamping the stamp and curing the resist material to form a patterned resist over the region, releasing the stamp, etching the patterned resist and one of the device material or substrate to form the depth profile in the device material or substrate, and forming a structure in the region having the depth profile to form the grating.

[0008] In another embodiment, a method is provided. The method includes placing a resist material on a positive pattern of a stamp, the positive pattern corresponding to a depth profile of a grating of a structure to be formed, flipping and placing the stamp so that the resist material is placed on an area of a device material or substrate corresponding to the grating of the structure to be formed having the depth profile, curing to form a patterned resist over the area, releasing the stamp, etching the patterned resist and one of the device material or substrate to form the depth profile in the device material or substrate, and forming the structure in the area having the depth profile to form the grating.

[0009] In yet another embodiment, a method is provided that includes disposing a resist material on a patterned hardmask, the patterned hardmask being disposed over a device material or substrate, the resist material being disposed over a region of the device material or substrate corresponding to a grating having a depth-distributed structure to be formed, and imprinting a stamp into the resist material over the region, the stamp having a positive pattern of the depth distribution, imprinting the stamp with the cured resist material to form a patterned resist over the region, releasing the stamp, and etching one of the patterned resist and the device material or substrate to form a grating having a depth-distributed structure in the device material or substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In order that the manner in which the features described above of the present disclosure may be understood in detail, a more particular description of the disclosure, briefly summarized above, may be made with reference to embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only exemplary embodiments and are therefore not to be considered limiting of the scope of the present disclosure, and that other equally effective embodiments may be admitted.

[0011] Figure 1 is a perspective front view of a waveguide according to an embodiment.

[0012] Figure 2A is a cross-sectional view of a portion of a waveguide according to a first configuration of an embodiment.

[0013] Figure 2B is a cross-sectional view of a portion of a waveguide according to a second configuration of an embodiment.

[0014] Figures 3A to 3C is a schematic cross-sectional view of a substrate during a first method according to an embodiment.

[0015] Figure 4A is a schematic cross-sectional view of a stamp during a second method according to an embodiment.

[0016] Figures 4B to 4D is a schematic cross-sectional view of a substrate during a second method according to an embodiment.

[0017] 5A to 5D is a schematic cross-sectional view of a substrate during a third method according to an embodiment.

[0018] 6A to 6D is a schematic cross-sectional view of a stamp according to an embodiment.

[0019] 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

[0020] Embodiments described herein relate to methods of forming a waveguide with a grating having a depth-profiled structure.

[0021] Figure 1 1 is a perspective front view of the waveguide 100. It will be understood that the waveguide 100 described herein is an example waveguide and that other waveguides may be used or modified to accomplish aspects of the present disclosure. The waveguide 100 includes a plurality of structures 102. The structures 102 may be disposed above, below, or on top of the surface 103 of the substrate 101 ( Figure 2B ), or placed in the substrate 101 ( Figure 2A ). The substrate 102 is a nanostructure with a submicron critical dimension (e.g., a width of less than 1 micron). An area of the structure 102 corresponds to one or more gratings 104. In one embodiment that may be combined with other embodiments described herein, the waveguide 100 includes at least a first grating 104a corresponding to an input coupling grating and a third grating 104c corresponding to an output coupling grating. In another embodiment that may be combined with other embodiments described herein, the waveguide 100 further includes a second grating 104b. The second grating 104b corresponds to a pupil expansion grating or a fold grating. The structure 102 of the grating 104 must be tuned to control the intensity of the light beam to adjust the field of view of the virtual image generated by the microdisplay from the user's point of view and to increase the viewing angle at which the user can view the virtual image. The grating 104 is tuned and the structure 102 has a depth profile.

[0022] Figure 2A is a cross-sectional view of a portion of the waveguide 100 according to a first configuration 200a of an embodiment. Figure 2B is a cross-sectional view of a portion of the waveguide 100 according to a second configuration 200b of an embodiment.

[0023] The waveguide 100 of the first configuration 200a includes a grating 104 having a structure 102 disposed in a substrate 101. The waveguide 100 of the second configuration 200b includes a grating 104 having a structure 102 disposed on or above the substrate 101. The structure 102 of the second configuration 200b includes a device material 211. The substrate 101 includes any suitable material, including but not limited to an amorphous dielectric, a non-amorphous dielectric, a crystalline dielectric, a silicon-containing material, a polymer, or a combination thereof. In one embodiment, which may be combined with other embodiments described herein, the substrate 101 is composed of one or more of silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, or quartz. In another embodiment, which may be combined with other embodiments described herein, the substrate 101 is composed of one or more of a material containing nitrogen, titanium, niobium, lanthanum, zirconium, or yttrium. Device materials 211 include, but are not limited to, silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium (IV) oxide (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb2O5), cadmium stannate (Cd2SnO4), silicon nitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiO3), diamond-like carbon (DLC), hafnium (IV) oxide (HfO2), lithium niobate (LiNbO3), silicon carbonitride (SiCN), or a combination of the foregoing.

[0024] The grating 104 has a depth profile 201 from a first end 202 to a second end 204. The depth profile 201 corresponds to a variation in the depth 206 of the channels 208 between adjacent structures 102. 6A to 6D is a schematic cross-sectional view of a stamp according to an embodiment. In one embodiment, which may be combined with other embodiments described herein, the depth profile 201 is linear, such as the depth 206 of the channel 208 changes linearly from the first end 202 to the second end 204. The methods 300-500 utilize a first stamp 601 to form two gratings 104, such as the first grating 104a and the third grating 104c, with a depth profile 201 having a linear shape. Figure 6A As shown, the stamp structure 605 of the first stamp 601 includes an embossed portion 606 that is positive of the linear depth profile 201 (i.e., corresponds to the depth profile 201). The methods 300-500 utilize the second stamp 602 to form: a grating 104 (such as the first grating 104a) having a linear depth profile 201, and another grating 104 (such as the third grating 104c) having a uniform depth profile 201. Figure 6BAs shown, the stamp structure 605 of the second stamp 602 includes an embossed portion 606 (which is the positive of the linear depth distribution 201) and another embossed portion 606 (which corresponds to the uniform depth distribution 201). Figure 2B As shown, the third grating 104c has a uniform depth profile 201, i.e., the depth 206 of the depth profile 201 of the channel 208 is the same from the first end 202 to the second end 204. The methods 300-500 utilize a fourth stamp 604 including an embossed portion 606 that is uniform for both gratings 104 having the uniform depth profile 201. The methods 300-500 utilize a third stamp 603 including an embossed portion 606 that is positive for the nonlinear depth profile 201, such that the grating 104 has a nonlinear depth profile 201 from the first end 202 to the second end 204.

[0025] Such as 6A to 6D As shown, a stamp structure 605 is coupled to a stamp substrate 607. The stamp structure 605 includes, but is not limited to, polydimethylsiloxane (PDMS), UV-curable acrylate, epoxy, polyurethane, or a combination thereof. The stamp substrate 607 includes, but is not limited to, polyethylene terephthalate (PET), glass, silica, or a combination thereof. The stamp structure 605 and the stamp substrate 607 are translucent so that the resist material can be cured by exposure to ultraviolet (UV) light. The stamp substrate 607 can have a thickness of about 10 μm to about 5 mm. The portion width 608 of the stamp portion 606 is about 100 μm to about 100 cm, resulting in a grating 104 having a grating width 210 of about 100 μm to about 100 cm. The distance from the stamp structure 605 to the stamp substrate 607 is less than 1 mm. The grating 104 may include any combination of linear, nonlinear, or uniform depth profiles 201 to control the intensity of the light beam to adjust the field of view of the virtual image produced by the microdisplay from the user's point of view and increase the viewing angle at which the user can view the virtual image.

[0026] Figures 3A to 3C 1 is a schematic cross-sectional view of a substrate 100 during a first method 300 of forming a waveguide 100 having a grating 104 depth profile 201. In a first operation of the first method 300, a patterned resist 306 having a negative pattern 308 is formed. The negative pattern 308 is the inverse of the stamp structure 605. In some embodiments, the negative pattern 308 is formed above the surface 103 of the substrate 101. In other embodiments, the negative pattern 308 is formed above the surface 103 of the substrate 101. The negative pattern 108 is the negative of the depth profile 201. The depth profile 201 can be any linear, nonlinear, or uniform profile corresponding to the stamp structure 605. In one embodiment of the first operation, as Figure 3AAs shown, a stamp such as a first stamp 601 is stamped onto a resist material 304 disposed on or above the surface 103 of the substrate 100. In other embodiments, a second stamp 602, a third stamp 603, or a fourth stamp 605 is used. The resist material 304 is deposited via inkjet printing or spin coating. The resist material 304 is cured to form a patterned resist 306 having a negative pattern 308. After the patterned resist 306 is cured, the stamp is released, as shown. Figure 3B In a second operation, the patterned resist 306 and the device material 211 or substrate 101 are etched to form the waveguide 100. The waveguide 100 has a depth profile 201 in the region 210 corresponding to the grating 104, as shown in FIG. Figure 3C As shown. The grating 104 is formed by placing a hard mask over the substrate 101 and a photoresist over the substrate 101. The photoresist is patterned according to the desired grating pattern to expose the hard mask. The hard mask is then etched to expose the device material 211 or the substrate 101. The device material 211 or the substrate 101 is then etched to form the grating 104. The photoresist and hard mask are then removed.

[0027] Figure 4A 6 is a schematic cross-sectional view of a stamp. The stamp may be a first stamp 601. In other embodiments, a second stamp 602, a third stamp 603, or a fourth stamp 605 is used. Figures 4B to 4D is a schematic cross-sectional view of a substrate 101 during a second method 400 for forming a waveguide 100 having a depth profile 201. In a first operation of the second method 400, a resist material 304 is deposited over the positive pattern of the embossed portion 606 of the stamp. In a second operation, the stamp is flipped and placed on or above the surface 103 of the substrate 100. In a third operation, the resist material 304 is cured to form a patterned resist 306 having a negative pattern that is the inverse of the stamp structure 605. In one embodiment of the third operation, the resist material 304 is cured before the stamp is flipped. In another embodiment of the third operation, the resist material 104 is cured after the stamp is flipped and placed on or above the surface 103 of the substrate 100. In a fourth operation, the substrate 101 or device material 211 having the patterned resist 306 is etched to form the depth profile 201 in the region 210 corresponding to the grating 104. The grating 104 is formed by placing a hard mask over the substrate 101 and a photoresist over the substrate 101. The photoresist is patterned according to the desired grating pattern to expose the hard mask. The hard mask is then etched to expose the device material 211 or the substrate 101. The device material 211 or the substrate 101 is then etched to form the grating 104. The photoresist and hard mask are then removed.

[0028] 5A to 5D1 is a schematic cross-sectional view of a substrate 101 during a third method for forming a waveguide 100 having a grating with a depth profile 201. In a first operation of the third method, a resist material 304 is disposed on a patterned hardmask 502. The patterned hardmask 502 is disposed on or above the surface 103 of the substrate 101. The patterned hardmask 502 exposes the device material 211 or the substrate 101 to be etched to form the structure 102 of each of the gratings 104. In a second operation of the third method 500, a patterned resist 306 having a negative pattern 308 is formed. The negative pattern 308 is the inverse of the stamp structure 605. In some embodiments, the negative pattern 308 is formed above the surface 103 of the substrate 101. In other embodiments, the negative pattern 308 is formed above the surface 103 of the substrate 101. The negative pattern 108 is the negative of the depth profile 201. The depth profile 201 can be any linear, nonlinear, or uniform profile corresponding to the stamp structure 605. The resist material 104 is cured to form a patterned resist 306 having a negative pattern 308. After the patterned resist 306 is formed, the stamp 400 is released, as shown in FIG. Figure 5C In a second operation, the device material 211 or substrate 101 with the patterned resist 306 is etched down to the grating 104 with the structure 102 having the depth profile 210. The patterned hard mask 502 is removed.

[0029] Embodiments described herein relate to methods for forming a waveguide with a grating having a depth profile. Each method utilizes a stamp having a stamp structure that includes an imprinted portion that is positive for the depth profile (i.e., corresponding to the depth profile). The positive pattern of the imprinted portion is designed to correspond to the depth profile. An imprinted resist having a negative pattern controls the etch rate, resulting in a device material or substrate having the depth profile.

[0030] While the foregoing 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 which is to be determined by the claims which follow.

Claims

1. A method comprising: disposing a resist material over an area of the device material or substrate corresponding to the grating having the structure to be formed with a depth profile; pressing a stamp into the resist material over the area, the stamp having a positive pattern of the depth profile, pressing the stamp and curing the resist material to form a patterned resist over the area; releasing the stamp; etching the patterned resist and one of the device material or the substrate to form the depth profile in the device material or the substrate; as well as The structure is formed in the region having the depth profile to form the grating.

2. The method of claim 1 , wherein the grating comprises a first grating or a second grating, wherein: The first depth profile of the first grating is linear, nonlinear or uniform; and The second depth profile of the second grating is linear, nonlinear or uniform. The method of claim 2 , wherein the first depth profile and the second depth profile are different from each other.

4. The method of claim 1, wherein the stamped portion has a partial width of about 100 μm to about 100 cm, such that the grating has a grating width of about 100 μm to about 100 cm.

5. The method of claim 1, wherein the substrate comprises silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, quartz nitride, titanium, niobium, lanthanum, zirconium, yttrium, or a combination of the foregoing.

6. The method of claim 1 , wherein the device material comprises silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiO 2 ), silicon dioxide (SiO 2 ), vanadium (IV) oxide (VO x ), aluminum oxide (Al 2 O 3 ), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO 2 ), zinc oxide (ZnO), tantalum pentoxide (Ta 2 O 5 ), silicon nitride (Si 3 N 4 ), zirconium dioxide (ZrO 2 ), niobium oxide (Nb 2 O 5 ), cadmium stannate (Cd 2 SnO 4 ), silicon nitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiO 3 ), diamond-like carbon (DLC), hafnium (IV) oxide (HfO 2 ), lithium niobate (LiNbO 3 ), silicon carbonitride (SiCN), or a combination thereof.

7. A method comprising: disposing a resist material on the positive pattern of the stamp, the positive pattern corresponding to the depth profile of the grating of the structure to be formed; flipping and positioning the stamp so that the resist material is positioned on a region of the device material or substrate corresponding to the grating having a structure to be formed with a depth profile; curing to form a patterned resist over the area; releasing the stamp; etching the patterned resist and one of the device material or the substrate to form the depth profile in the device material or the substrate; as well as The structure is formed in the region having the depth profile to form the grating.

8. The method of claim 7, wherein the grating comprises a first grating or a second grating, wherein: The first depth profile of the first grating is linear, nonlinear or uniform; and The second depth profile of the second grating is linear, nonlinear or uniform. 9 . The method of claim 8 , wherein the first depth profile and the second depth profile are different from each other.

10. The method of claim 7, wherein the stamped portion has a partial width of about 100 μm to about 100 cm, such that the grating has a grating width of about 100 μm to about 100 cm.

11. The method of claim 7, wherein the substrate comprises silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, quartz nitride, titanium, niobium, lanthanum, zirconium, yttrium, or a combination of the foregoing.

12. The method of claim 7, wherein the device material comprises silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium (IV) oxide (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb2O5), cadmium stannate (Cd2SnO4), silicon nitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiO3), diamond-like carbon (DLC), hafnium (IV) oxide (HfO2), lithium niobate (LiNbO3), silicon carbonitride (SiCN), or a combination of the foregoing.

13. The method of claim 7, wherein the resist material is deposited via inkjet printing or spin coating.

14. A method comprising: disposing a resist material on a patterned hardmask disposed over a device material or a substrate, the resist material disposed over regions of the device material or the substrate corresponding to the grating having the depth profile of the structure to be formed; as well as pressing a stamp into the resist material over the area, the stamp having a positive pattern of the depth profile, pressing the stamp and curing the resist material to form a patterned resist over the area; releasing the stamp; as well as The patterned resist and one of the device material or the substrate are etched to form a grating having the depth profile in the device material or the substrate.

15. The method of claim 14, wherein the grating comprises a first grating or a second grating, wherein: The first depth profile of the first grating is linear, nonlinear or uniform; and The second depth profile of the second grating is linear, nonlinear or uniform. The method of claim 15 , wherein the first depth profile and the second depth profile are different from each other.

17. The method of claim 14, wherein the stamped portion has a partial width of about 100 μm to about 100 cm, such that the grating has a grating width of about 100 μm to about 100 cm.

18. The method of claim 14, wherein the substrate comprises silicon (Si), silicon dioxide (SiO2), silicon carbide (SiC), fused silica, diamond, quartz nitride, titanium, niobium, lanthanum, zirconium, yttrium, or a combination of the foregoing.

19. The method of claim 14, wherein the device material comprises silicon carbide (SiC), silicon oxycarbide (SiOC), titanium dioxide (TiO2), silicon dioxide (SiO2), vanadium (IV) oxide (VOx), aluminum oxide (Al2O3), aluminum-doped zinc oxide (AZO), indium tin oxide (ITO), tin dioxide (SnO2), zinc oxide (ZnO), tantalum pentoxide (Ta2O5), silicon nitride (Si3N4), zirconium dioxide (ZrO2), niobium oxide (Nb2O5), cadmium stannate (Cd2SnO4), silicon nitride (SiN), silicon oxynitride (SiON), barium titanate (BaTiO3), diamond-like carbon (DLC), hafnium (IV) oxide (HfO2), lithium niobate (LiNbO3), silicon carbonitride (SiCN), or a combination of the foregoing.

20. The method of claim 14, wherein the patterned hardmask exposes the device material or the substrate.

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