Maskless lithography method for producing topographic substrates

Abstract

In one embodiment, a method of fabricating a device having at least two features of different heights includes the steps of: depositing a photoresist on a substrate; determining a topographic pattern for at least two features of the device; determining an exposure pattern for at least two features of the device; exposing a first region of the photoresist to a first dose of light, the first region corresponding to a first feature of the at least two features; exposing a second region of the photoresist to a second dose of light different from the first dose of light, the second region corresponding to a second feature of the at least two features; and developing the photoresist.

Description

Technical Field

[0001] The embodiments described herein generally relate to optical and photonic devices. More specifically, the embodiments described herein relate to a method for forming a topographic substrate by maskless photolithography. Background Technology

[0002] Optical and photonic devices manipulate the propagation of light through spatially varying structural patterns of optical or photonic devices formed on a substrate. In some optical and photonic devices, the desired patterned areas will have different heights to achieve ideal optical performance. Such devices include augmented reality (AR) devices or virtual reality (VR) devices.

[0003] To obtain desired patterned regions with different heights, different photolithography processes with corresponding masks are used for each patterned region with different heights. It's easy to imagine that the more patterned regions there are, the more photolithography processes occur, and the more masks are used. With more photolithography processes performed, and therefore more masks used, the processing tends to take longer. For example, two different features with different heights will require two different photolithography processes using two different masks. Adding a third feature will increase the processing time by 50% to produce three different features.

[0004] Therefore, there is a need in the art to create multiple features with different heights on a substrate without having to perform independent photolithography on each feature. Summary of the Invention

[0005] Maskless lithography can produce substrates with multiple morphological features without requiring separate lithography processes for each feature.

[0006] In one embodiment, a method of fabricating a device having at least two features of different heights includes the steps of: depositing a photoresist on a substrate; determining a morphology pattern for at least two features of the device, the two features having different morphologies; determining an exposure pattern for at least two features of the device; exposing a first region of the photoresist with a first dose of light, the first region corresponding to a first feature of the at least two features; exposing a second region of the photoresist with a second dose of light different from the first dose of light, the second region corresponding to a second feature of the at least two features; and developing the photoresist.

[0007] In another embodiment, a method for fabricating a device having at least two features with different heights includes the following steps: depositing a photoresist on a substrate; determining a topographic pattern for at least two features of the device, the two features having different topographic shapes; adjusting a plurality of blades of an exposure apparatus to establish a first exposure region corresponding to a first feature of the at least two features; exposing the first region of the photoresist with a first dose of light, the first region of the substrate corresponding to the first exposure region; adjusting the plurality of blades to establish a second exposure region corresponding to a second feature of the at least two features; exposing the second region of the photoresist with a second dose of light different from the first dose of light, the second region of the substrate corresponding to the second exposure region; and developing the photoresist.

[0008] In another embodiment, a method for fabricating a device having at least two features with different heights includes the following steps: distributing a photoresist on an optical layer deposited on a substrate; determining a topographic pattern for at least two features of the device, the two features having different topographic shapes; determining an exposure pattern for at least two features of the device; exposing a first region of the photoresist with a first dose of light, the first region corresponding to a first feature of the at least two features; exposing a second region of the photoresist with a second dose of light different from the first dose of light, the second region corresponding to a second feature of the at least two features; developing the photoresist; and etching the photoresist and the optical layer. Attached Figure Description

[0009] To gain a more detailed understanding of the features described above in this disclosure, a more specific description of the disclosure, which has been briefly summarized above, can be obtained by referring to the embodiments, some of which are illustrated in the accompanying drawings. However, it should be understood that the drawings illustrate only exemplary embodiments and should not be considered as limiting their scope, and other equally effective embodiments are permissible.

[0010] Figure 1 This is a schematic diagram of a processing device according to one embodiment.

[0011] Figure 2A and Figure 2B According to one implementation method Figure 1 A schematic diagram of the reticle used in the processing equipment.

[0012] Figure 3 This is a schematic diagram of a substrate having a desired exposure pattern according to one embodiment.

[0013] Figure 4 The product is obtained using the exposure method disclosed in this article.

[0014] Figure 5A It is an intermediate product obtained by the exposure method disclosed in this article.

[0015] Figure 5B Is using Figure 5A The product obtained from intermediate products.

[0016] Figures 6A-6C These are schematic diagrams of products manufactured using the methods disclosed herein at various stages.

[0017] Figure 7 This is a flowchart illustrating a method for manufacturing a product according to one embodiment.

[0018] To facilitate understanding, the same reference numerals have been used as much as possible to represent the same elements in the figures. It is contemplated that elements and features of one embodiment may be beneficially incorporated into other embodiments without further description. Detailed Implementation

[0019] The embodiments of this disclosure generally relate to apparatus and methods for fabricating topographic substrates. Using maskless lithography, substrates with multiple topographic features can be produced without requiring separate lithography processes for each feature.

[0020] Figure 1 This is a schematic diagram of a processing apparatus 100 for processing a substrate according to one embodiment. The apparatus 100 includes a light source 102 and a photomask 104. Figure 1 As shown, substrate 106 is arranged in apparatus 100 for processing. Apparatus 100 operates by transmitting light 110 from light source 102 through photomask 104 to a specific area of ​​substrate 106. Once light 110 passes through photomask, it becomes focused light 112 at a specific location on substrate 106, which will be exposed to light 112.

[0021] Figure 2A and Figure 2B According to one implementation method Figure 1A schematic diagram of a photomask 104 used in the processing device 100. The photomask 104 includes a top blade 202, a bottom blade 204, a left blade 206, and a right blade 208. The width of the top blade 202 is at least equal to the width of the photomask body 250, indicated by arrow "A". Similarly, the width of the bottom blade 204 is at least equal to the width of the photomask body 250. The top blade 202 has a height, indicated by arrow "B", which is less than the height of the photomask body 250, indicated by arrow "C". The bottom blade 204 has a height, indicated by arrow "D", which is less than the height of the photomask body 250, indicated by arrow "C". The left blade 206 has a width, indicated by arrow "E", which is less than the width of the photomask body 250, indicated by arrow "A". The left blade 206 also has a height, which is at least equal to the height of the photomask body, indicated by arrow "C". The right blade 208 has a width indicated by arrow "F", which is smaller than the width of the photomask body 250 indicated by arrow "A". The left blade 206 also has a height, which is at least equal to the height of the photomask body indicated by arrow "C". The photomask here may be a virtual object, rather than a physical entity existing on the tool, or may be without a mask.

[0022] Figure 2A This is a top view of the photomask 200. In one embodiment, the photomask 200 is approximately 26 mm wide (indicated by arrow "A") and 33 mm long (indicated by arrow "C"). Blades 202, 204, 206, and 208 establish an exposure window 210. The size of the area of ​​the exposure window 210 is defined by the area to be exposed on the substrate. Blades 202, 204, 206, and 208 define the edge 218 of the exposure window 210. The top blade 202 and the bottom blade 204 define the height 214 of the exposure window 210. The left blade 206 and the right blade 208 define the width 216 of the exposure window 210. Blades 202, 204, 206, and 208 are movable to expand, thereby altering or defining the exposure window 210. For example, the top blade 202 can be moved closer to or further away from the bottom blade 204, or vice versa, to increase or decrease the height 214 of the exposure window 210. Similarly, the left blade 206 can be moved closer to or further away from the right blade 208, or vice versa, to increase or decrease the width 216 of the exposure window.

[0023] Figure 2B Describing having in with Figure 2A The photomasks 200 at different positions of blades 202, 204, 206, and 208 shown in the image result in a larger exposure window 218 (i.e., compared to...). Figure 2A exist Figure 2B The height of 214 is greater than that of the others. Figure 2A exist Figure 2B (The width in the middle is 216, which is larger).

[0024] In operation, the light source 102 has an opening in the form of a slit 212. The slit 212 scans the exposure window 210 from the top blade 202 to the bottom blade 204. Light 110 from the light source 102 passes through the exposure window 210, thereby forming a device pattern on the substrate. Figure 2A and Figure 2B As shown, the slit 212 moves relative to the photomask 104, so that the entire exposure window 210 is exposed.

[0025] Figure 3 This is a schematic diagram of a substrate 302 having desired exposure patterns 306, 308, and 310 according to one embodiment. In this embodiment, each of the patterns 306, 308, and 310 has different dimensions and / or heights. Each exposure pattern 306, 308, and 310 is unique, having different dimensions and positions within the die 304. Pattern positioning accuracy relative to the die size is desirable. In one embodiment, each exposure pattern 306, 308, and 310 can be placed at a specific location within the die 304 with an accuracy of less than 1 nanometer.

[0026] In operation, light from light source 102 is transmitted to photomask 104 in the form of slit 212. Light 110 from light source 102 passes through exposure window 210, thereby forming device patterns, such as patterns 306, 308, and 310, in resist 312. Slit 212 scans exposure window 210, exposing device patterns 306, 308, and 310 in the resist 312 below. In one embodiment, slit 212 is 26 mm wide and approximately 5 mm-7 mm long. Slit 212 scans exposure window 210 from top blade 202 to bottom blade 204.

[0027] The methods disclosed above can be applied to any device size on any substrate size. Exposure window 210 can create an area to be exposed up to 26 mm wide and 33 mm long. Device pattern sizes, such as patterns 306, 308, and 310, can be larger than 26 mm by 33 mm. If the device pattern size is larger than 26 mm by 33 mm, a stitching method is used, in which two exposure windows are used sequentially, each exposure window being 26 mm by 33 mm or smaller. Exposure windows are placed directly adjacent to each other to create larger pattern sizes, such as patterns 306, 308, and 310.

[0028] Different doses of light are used to establish different heights of morphological features. The light dose varies with the exposure time of the photoresist 312. A larger dose of light equals a longer exposure time. Due to the increased crosslinking with increasing exposure time, a longer exposure time will establish a greater height in the photoresist 312. Due to less crosslinking during shorter exposure times, a shorter exposure time will establish a thinner layer.

[0029] Figure 4 Product 400 is obtained by the exposure method disclosed herein. An optical layer 404 is deposited on a substrate 402. In one embodiment, the optical layer 404 comprises a metal oxide material. In one embodiment, the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof. The concentration of the metal oxide content within the resist 406 is designed based on the desired film refractive index. Changing the concentration of the metal oxide material allows manipulation of the refractive index of the characteristics. In one embodiment, the total refractive index under visible light ranges from about 1.3 to 2.5.

[0030] The resulting product 400 includes a substrate 402 having an optical element layer 404 disposed thereon. A photoresist 406 is deposited onto the optical element layer 404 using the method disclosed herein. The photoresist 406 is a negative photoresist. After exposure and development, the photoresist 406 remains on the substrate 402. At least two morphological features 408, 410, and 412 are established in the photoresist 406 according to their respective exposure patterns. The substrate 402 can be used directly after exposure and development.

[0031] Figure 5A It is intermediate product 500 obtained by the exposure method disclosed in this article. Figure 5B Is using Figure 5A The intermediate product 500 is obtained from the intermediate product. The intermediate product 500 contains a substrate 502 having an optical element layer 504 disposed thereon. In one embodiment, the optical element layer 504 comprises a metal oxide material. In one embodiment, the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof. The concentration of the metal oxide content within the resist 406 is designed based on the desired film refractive index. Changing the concentration of the metal oxide material allows manipulation of the characteristic refractive index.

[0032] A photoresist 506 is deposited onto an optical device layer 504 using the methods disclosed herein. The photoresist 506 is a negative photoresist. At least two morphological features 508, 510, and 512 are established in the photoresist 506 according to their respective exposure patterns. In one embodiment, the photoresist 506 is further processed to form an optical device having structures formed in morphological features 508, 510, and 512. The structures formed in at least one of the morphological features 508, 510, and 512 are different. The structures with variable heights formed in morphological features 508, 510, and 512 can be nanostructures with dimensions less than 1 μm. In one embodiment, the optical device is a waveguide combiner, such as an augmented reality waveguide combiner. In another embodiment, the optical device is a planar optical device, such as a metasurface.

[0033] After etching intermediate product 500, product 550 is created. The etch rate of the material will be approximately one to one. Etching product 500 will yield product 550 having morphological features 514, 516, and 518 developed in optical device layer 504. In one embodiment, optical device layer 504 is further processed to form an optical device having structures formed in morphological features 514, 516, and 518. The structures formed in at least one of morphological features 514, 516, and 518 are different. The structures with variable heights formed in morphological features 514, 516, and 518 can be nanostructures with dimensions less than 1 μm. In one embodiment, the optical device is a waveguide combiner, such as an augmented reality waveguide combiner. In another embodiment, the optical device is a planar optical device, such as a metasurface.

[0034] Figures 6A-6C This is a schematic diagram of product 600 at various stages of manufacturing using the methods disclosed herein. Product 600 includes a substrate 602, an optical layer 604, and a resist layer 606. In one embodiment, substrate 602 comprises silicon. In another embodiment, substrate 602 is made of glass. In one embodiment, optical layer 604 comprises a metal oxide material. In one embodiment, the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or a combination thereof. In one embodiment, resist layer 606 comprises a metal oxide material. In one embodiment, the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or a combination thereof. Figure 6A Depicts the product as it is constructed before its exposure. Figure 6BProduct 600 is depicted after exposure and before development. Figure 6B Various features 608, 610 and 612 are depicted after exposure. Figure 6C The resulting product, after development, exhibits the characteristics 614, 616, and 618 of development.

[0035] Figure 7 This is a flowchart illustrating a method 700 for manufacturing an end product with multiple morphological features. In operation 702, a negative resist, such as resist 606, is applied to a substrate, such as substrate 602. In operation 704, a morphological pattern for the resist is determined according to a desired exposure pattern. The morphological pattern determined in operation 704 determines the dimensions of device patterns, such as device patterns 306, 308, and 310. In operation 706, an exposure pattern for the morphological pattern is determined based on the determined morphological pattern. The exposure pattern determined in operation 706 determines the height of the morphological features developed in the resist. In operation 708, the resist, such as resist 606, is exposed to light 110 from a light source 102. In operation 710, the resist is developed. As described in operations 708 and 710, the substrate can be used directly after exposure and development.

[0036] By using different exposure levels on different areas of the photoresist, products with different morphologies can be produced without the need for a mask.

[0037] Although the foregoing describes embodiments of the present disclosure, other and further embodiments of the present disclosure may be devised without departing from the basic scope of the present disclosure, the scope of which is defined by the appended claims.

Claims

1. A method of fabricating a device having at least two features of different heights, comprising the steps of: depositing a resist on a substrate; determining a topography pattern for the at least two features of the device, the two features having different topographies; determining an exposure pattern for the at least two features of the device; exposing a first region of the resist to a first dose of light by scanning a light source having an opening in the form of a slit through the first region of the resist, the first region corresponding to a first feature of the at least two features; exposing a second region of the resist to a second dose of light different from the first dose of light by scanning the light source through the second region of the resist, the second region corresponding to a second feature of the at least two features; and developing the resist, wherein the dose of the first dose of light and the second dose of light varies by exposure time of the resist.

2. The method of claim 1, wherein the first dose of light is greater than the second dose of light.

3. The method of claim 1, wherein the first feature has a greater height than the second feature.

4. The method of claim 1, wherein the resist comprises a metal oxide material.

5. The method of claim 4, wherein the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof.

6. The method of claim 1, wherein the resist is a negative resist.

7. The method of claim 1, wherein the resist has a refractive index between 1.3 and 2.

5.

8. The method of claim 1, wherein both exposing the first region and exposing the second region are performed without a mask.

9. A method of fabricating a device having at least two features of different heights, comprising the steps of: depositing a resist on a substrate; determining a topography pattern for the at least two features of the device, the two features having different topographies; adjusting a plurality of leaves of an exposure apparatus to establish a first exposure region corresponding to a first feature of the at least two features; exposing a first region of the resist to a first dose of light by scanning a light source having an opening in the form of a slit through the first exposure region, the first region of the substrate corresponding to the first exposure region; adjusting the plurality of leaves to establish a second exposure region corresponding to a second feature of the at least two features; exposing a second region of the resist to a second dose of light different from the first dose of light by scanning the light source through the second exposure region, the second region of the substrate corresponding to the second exposure region; and developing the resist, wherein the dose of the first dose of light and the second dose of light varies by exposure time of the resist. ​ 10. The method of claim 9, wherein the first dose of light is greater than the second dose of light.

11. The method of claim 9, wherein the first feature has a greater height than the second feature.

12. The method of claim 9, wherein the resist comprises a metal oxide material.

13. The method of claim 12, wherein the metal oxide material comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof.

14. The method of claim 9, wherein the resist is a negative resist.

15. The method of claim 9, wherein the resist has a refractive index between 1.3 and 2.

5.

16. The method of claim 9, wherein both exposing the first region and exposing the second region are performed without a mask.

17. A method of fabricating a device having at least two features of different heights, comprising the steps of: depositing a resist on an optical device layer, the optical device layer disposed on a substrate; determining a topography pattern for the at least two features of the device, the two features having different topographies; determining an exposure pattern for the at least two features of the device; exposing a first region of the resist to a first dose of light by scanning a light source having an opening in the form of a slit through the first region of the resist, the first region corresponding to a first feature of the at least two features; exposing a second region of the resist to a second dose of light different from the first dose of light by scanning the light source through the second region of the resist, the second region corresponding to a second feature of the at least two features; developing the resist; and etching the resist and the optical device layer, wherein the dose of the first dose of light and the second dose of light varies by exposure time of the resist.

18. The method of claim 17, wherein the optical device layer comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof.

19. The method of claim 17, wherein the resist comprises a material selected from the group consisting of TiOx, NbOx, SbOx, ZrOx, AlOx, HfOx, WOx, ZnOx, or combinations thereof.

20. The method of claim 17, wherein the resist is a negative resist.

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