Photoetching method
By using X-ray light sources and masks with different density in lithography technology, and using different reflectance to transfer patterns, the problem of difficult to achieve high resolution in existing lithography technologies is solved, and clearer and more accurate lithography effects are achieved.
Patent Information
- Application Number
- CN202311792361.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-22
- Publication Date
- 2025-06-24
AI Technical Summary
The existing lithography technology is difficult to meet the high resolution requirements of the continuous reduction in semiconductor device size, especially when using X-ray light sources, the light-shielding layer cannot effectively block X-rays, resulting in unclear patterns.
Using X-rays as the light source, a mask plate is designed, and the material density on the surface of the second region is smaller than the first region. Through the difference in reflectivity of X-rays in different regions, the pattern of the mask plate is transferred to the photoresist layer to be lithographed, and a patterned mask layer is formed by removing the second pattern layer.
Significantly improves the resolution of lithography, ensures pattern clarity and accuracy, while reducing the need to use high-cost materials.
Smart Images
Figure CN120195936A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the field of semiconductor manufacturing, and particularly to a photolithography method. Background Art
[0002] Photolithography exposes the exposed and unexposed areas by exposing the surface of a material coated with a photosensitive material in a certain pattern (also known as pattern exposure or imagewise exposure). The technology for generating patterns is mainly used in the manufacture of semiconductor components, printed circuit boards, printed boards, liquid crystal display panels, plasma display panels, etc.
[0003] However, with the continuous development of semiconductor technology, the size of semiconductor devices has been continuously reduced, and the resolution requirements for photolithography have also increased accordingly, and the requirements for photolithography technology have become higher and higher. Summary of the Invention
[0004] The technical problem solved by the present invention is to provide a photolithography method to improve the photolithography resolution.
[0005] To solve the above technical problem, the technical solution of the present invention provides a photolithography method, including: providing a wafer to be etched, the surface of the wafer to be etched having a photoresist layer to be photolithographed; providing an X-ray light source for emitting X-rays; providing a mask, the mask including a first area and a second area, the density of the material on the surface of the second area being less than the density of the material on the surface of the first area, the mask being used to reflect the X-rays incident on the surface of the mask to the surface of the photoresist layer to be photolithographed, the X-rays reflected from the surface of the first area being the first reflected rays, the X-rays reflected from the surface of the second area being the second reflected rays, the reflectivity of the X-rays on the surface of the first area being greater than the reflectivity on the surface of the second area, the first reflected rays causing the photoresist layer to be photolithographed to form a first pattern layer, and the second reflected rays causing the photoresist layer to be photolithographed to form a second pattern layer; removing the second pattern layer and the photoresist layer to be photolithographed, and forming a patterned mask layer on the surface of the wafer to be etched, the patterned mask layer including the first pattern layer.
[0006] Optionally, the ratio range of the reflectivity of the X-rays on the surface of the first area to the reflectivity of the X-rays on the surface of the second area is greater than or equal to 100.
[0007] Optionally, the X-rays have a first critical angle on the surface of the first area and a second critical angle on the surface of the second area, and the first critical angle is greater than the second critical angle.
[0008] Optionally, the X-rays are incident on the surface of the mask at an incident angle, the incident angle being greater than the second critical angle and less than the first critical angle.
[0009] Optionally, the incident angle range of the X-rays incident on the mask surface is 0 to 1.5 degrees.
[0010] Optionally, the wavelength range of the X-rays is 0.01 nanometers to 10 nanometers.
[0011] Optionally, the mask includes a functional surface and a non-functional surface, and the X-rays are incident on the functional surface; the mask includes: a substrate, the substrate includes a first region and a second region; a reflective layer located on the first region; an absorption layer located on the second region, the density of the material of the absorption layer is less than the density of the material of the reflective layer; the surface of the absorption layer and the surface of the reflective layer are the functional surface.
[0012] Optionally, the density of the material of the reflective layer is greater than 15 g / cm³.
[0013] Optionally, the material of the reflective layer includes a metal, and the metal includes one or a combination of more of: tungsten, hafnium, tantalum, platinum, and gold.
[0014] Optionally, the density of the material of the absorption layer is less than 8 g / cm³.
[0015] Optionally, the material of the absorption layer includes: silicon, silicon oxide, silicon carbide, or silicon germanium.
[0016] Optionally, the thermal expansion coefficient range of the material of the substrate is -1e-11 / K to 1e-11 / K.
[0017] Optionally, the material of the substrate includes silicon, silicon oxide, glass, or ceramic.
[0018] Optionally, the transmittance of the first reflected ray in the photoresist layer to be lithographed in the first region is greater than 6%; the transmittance of the second reflected ray in the photoresist layer to be lithographed in the second region is less than 6%.
[0019] Optionally, the process of removing the second pattern layer includes a wet etching process, the etching rate of the wet etching process for the second pattern layer is greater than the etching rate for the first pattern layer, and the etching rate of the wet etching process for the photoresist layer to be lithographed is greater than the etching rate for the first pattern layer.
[0020] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:
[0021] The lithography method of the present invention uses X-rays as the light source. The density of the material on the surface of the second region of the mask is less than the density of the material on the surface of the first region. The X-rays are reflected on the surface of the mask. The reflectivity of the X-rays on the surface of the first region is greater than the reflectivity on the surface of the second region. The first reflected rays reflected from the surface of the first region form a first pattern layer on the photoresist layer to be lithographed, and the second reflected rays reflected from the surface of the second region form a second pattern layer on the photoresist layer to be lithographed. The difference in the reflectivity of the X-rays on the surface of the first region and the second region causes the pattern of the mask to be transferred to the photoresist layer to be lithographed. Then, the second pattern layer and the photoresist layer to be lithographed are removed to form a patterned photoresist layer. The resolution of the lithography method has been greatly improved.
[0022] Furthermore, the X-rays have a first critical angle on the surface of the first region and a second critical angle on the surface of the second region, and the first critical angle is greater than the second critical angle. By setting the incident angle of the X-rays on the surface of the mask such that the incident angle is greater than the second critical angle and less than the first critical angle, the reflectivity of the X-rays on the surface of the first region is greater than the reflectivity on the surface of the second region, so that different reflectivities of the X-rays on the surfaces of the first region and the second region are obtained.
[0023] Furthermore, the transmittance of the first reflected rays in the photoresist layer to be lithographed in the first region is greater than 6%, and the transmittance of the second reflected rays in the photoresist layer to be lithographed in the second region is less than 6%. As a result, the degree of optical reaction of the second pattern layer formed in the second region is small, and the second pattern layer and the photoresist layer to be lithographed can have a large etching selectivity ratio with the first pattern layer and be removed, leaving the first pattern layer on the surface of the wafer to be etched to form the mask layer. Description of the Drawings
[0024] Figure 1 is a schematic diagram of lithography in an embodiment;
[0025] Figure 2 is a schematic flow diagram of the lithography method in an embodiment of the present invention;
[0026] Figures 3 to 6 is a schematic structural diagram during the lithography process in an embodiment of the present invention. Detailed Embodiments
[0027] As described in the background art, the requirements for lithography technology in semiconductor products are also getting higher and higher.
[0028] Specifically, the resolution of lithography where k1 is a process-related factor, k1 is a constant, λ is the light wavelength of the light source, and NA is the numerical aperture. It can be known that the lithography resolution CD can be increased by increasing the numerical aperture NA.
[0029] However, due to the process window k2 is a process-related factor and k2 is a constant. The larger the numerical aperture NA, the smaller the process window D F will also decrease accordingly. The process window D F measures the application range of the lithography technology. When the process window D F decreases, the application of this lithography technology is restricted.
[0030] Therefore, the resolution CD of lithography can be improved by reducing the light wavelength λ. The smaller the light wavelength λ, the smaller the resolution CD of lithography.
[0031] At present, the commonly used light source is extreme ultraviolet light (EUV). The light with a smaller wavelength is X-ray, and the wavelength range of X-ray is from 1 picometer to 10 nanometers. However, the commonly used lithography machine is a projection lithography machine. Please refer to Figure 1 , the projection mask for the projection lithography machine includes a substrate 100. The substrate 100 includes a light-transmitting area and a light-shielding area. A light-shielding layer 101 is provided on the light-shielding area. The light-shielding layer 101 is used to block light, and the light irradiates the photoresist layer from the light-transmitting area.
[0032] However, due to the strong penetrability of X-ray, the light-shielding layer 101 cannot block the penetration of X-ray. The light transmitted through the light-transmitting area by the X-ray is T1, and the light transmitted through the light-shielding area is T2. Both T1 and T2 can cause the photoresist to react to form a pattern, and thus the patterns of the light-transmitting area and the light-shielding area cannot be reflected on the photoresist layer.
[0033] In addition, the substrate 100 of the projection mask usually requires silicon carbide or diamond, which has a high cost.
[0034] To solve the above problems, the technical solution of the present invention provides a lithography method, which uses X-ray as the light source. The density of the material on the surface of the second area of the mask is less than the density of the material on the surface of the first area. The X-ray is reflected on the surface of the mask. The reflectivity of the X-ray on the surface of the first area is greater than the reflectivity on the surface of the second area. The first reflected ray reflected from the surface of the first area forms a first pattern layer on the photoresist layer to be lithographed, and the second reflected ray reflected from the surface of the second area forms a second pattern layer on the photoresist layer to be lithographed. The difference in the reflectivity of the X-ray on the surface of the first area and the second area enables the pattern of the mask to be transferred to the photoresist layer to be lithographed. Then, the second pattern layer and the photoresist layer to be lithographed are removed to form a patterned photoresist layer. The resolution of the lithography method is further improved.
[0035] To make the above objects, features, and beneficial effects of the present invention more obvious and understandable, the following detailed description of the specific embodiments of the present invention will be given with reference to the accompanying drawings.
[0036] Figure 2 is a schematic flow chart of the lithography method in an embodiment of the present invention; Figures 3 to 6 is a schematic structural diagram in the lithography process in an embodiment of the present invention.
[0037] Please refer to Figure 2 , the lithography method includes:
[0038] Step S10: Provide a wafer to be etched, and a photoresist layer to be lithographed is provided on the surface of the wafer to be etched;
[0039] Step S20: Provide an X-ray light source, and the X-ray light source is used to emit X-rays;
[0040] Step S30: Provide a mask, the mask includes a first region and a second region, the density of the material on the surface of the second region is less than the density of the material on the surface of the first region, the mask is used to reflect the X-rays incident on the surface of the mask to the surface of the photoresist layer to be lithographed, the X-rays reflected from the surface of the first region are the first reflected rays, the X-rays reflected from the surface of the second region are the second reflected rays, the reflectivity of the X-rays on the surface of the first region is greater than the reflectivity on the surface of the second region, the first reflected rays form a first pattern layer on the photoresist layer to be lithographed, and the second reflected rays form a second pattern layer on the photoresist layer to be lithographed;
[0041] Step S40: Remove the second pattern layer, and a patterned photoresist layer is formed on the surface of the wafer to be etched, and the patterned photoresist layer includes the first pattern layer.
[0042] The lithography method uses X-rays as a light source, and the wavelength range of X-rays is small, so that a large resolution can be obtained.
[0043] Next, each step will be analyzed and described.
[0044] Please combine with Figure 3 Continue to refer to Figure 2 , and execute Step S10: Provide a wafer 200 to be etched, and a photoresist layer 201 to be lithographed is provided on the surface of the wafer 200 to be etched.
[0045] The photoresist layer 201 to be lithographed is an unexposed and undeveloped photoresist.
[0046] The process of forming the photoresist layer 201 to be lithographed includes a spin coating or spraying process, and a curing process.
[0047] The photoresist layer 201 to be lithographed includes a positive photoresist or a negative photoresist.
[0048] Please continue to refer to Figure 2, perform step S20: Provide an X-ray light source for emitting X-rays.
[0049] The wavelength range of the X-rays is 0.01 nanometers to 10 nanometers.
[0050] In this embodiment, the wavelength of the X-rays is 0.1 nanometers.
[0051] Please refer to Figure 4 and Figure 5 and continue to refer to Figure 2 , Figure 5 which is Figure 4 the top view of Figure 4 which is Figure 5 the schematic structural view in the direction of section line AA1 in , perform step S30: Provide a mask, the mask includes a first region and a second region, the density of the material on the surface of the second region is less than the density of the material on the surface of the first region, and the mask is used to reflect the X-rays incident on the surface of the mask to the surface of the photoresist layer to be lithographed.
[0052] The mask includes a functional surface and a non-functional surface, and the X-rays are incident on the surface of the functional surface.
[0053] In this embodiment, the mask includes: a substrate 300, the substrate 300 includes a first region I and a second region II; a reflective layer 303 located on the first region I; an absorption layer 306 located on the second region II, the density of the material of the absorption layer 306 is less than the density of the material of the reflective layer 303; the surfaces of the absorption layer 306 and the reflective layer 303 are the surfaces of the functional surface.
[0054] In this embodiment, when the X-rays are incident on the surface of the first region, it is incident on the surface of the reflective layer 303; when the X-rays are incident on the surface of the second region, it is incident on the surface of the absorption layer 306.
[0055] In this embodiment, the density of the material of the reflective layer 303 is greater than 15 grams per cubic centimeter.
[0056] The material of the reflective layer 303 includes a metal, and the metal includes: one or a combination of tungsten, hafnium, tantalum, platinum, and gold.
[0057] In this embodiment, the material of the reflective layer 303 includes tantalum.
[0058] In this embodiment, the density of the material of the absorption layer 306 is less than 8 grams per cubic centimeter.
[0059] The material of the absorption layer 306 includes: silicon, silicon oxide, silicon carbide, or silicon germanium.
[0060] In this embodiment, the material of the absorption layer 306 includes silicon oxide.
[0061] In this embodiment, the thermal expansion coefficient range of the material of the substrate 300 is from -1e-11 / K to 1e-11 / K.
[0062] The material of the substrate 300 includes silicon, silicon oxide, glass or ceramic. The material of the substrate 300 is easy to obtain and has a low cost.
[0063] In this embodiment, the material of the substrate 300 includes silicon.
[0064] Please refer to Figure 6 Continue to refer to Figure 2 , the mask is used to reflect the X-rays incident on the surface of the mask to the surface of the photoresist layer 201 to be lithographed. The X-rays reflected from the surface of the first region are the first reflected rays L1, and the X-rays reflected from the surface of the second region are the second reflected rays L2. The reflectivity of the X-rays on the surface of the first region is greater than the reflectivity on the surface of the second region. The first reflected rays L1 form the first pattern layer 205 on the photoresist layer 201 to be lithographed, and the second reflected rays L2 form the second pattern layer (not shown) on the photoresist layer 201 to be lithographed.
[0065] In this embodiment, the ratio range of the reflectivity of the X-rays on the surface of the first region to the reflectivity of the X-rays on the surface of the second region is greater than or equal to 100. The greater the ratio of the reflectivity of the X-rays on the surface of the first region to the reflectivity of the X-rays on the surface of the second region, the greater the difference in the light intensity of the first reflected rays and the second reflected rays incident on the photoresist layer 201 to be lithographed, resulting in a greater difference in the reaction degree of the photoresist layer 201 to be lithographed, thereby realizing the transfer of the pattern on the mask to the photoresist layer 201 to be lithographed.
[0066] In this embodiment, the density of the material of the absorption layer 306 is less than the density of the material of the reflection layer 303. The density of the material of the reflection layer 303 is relatively large. The greater the material density, the higher the electron density. X-rays are scattered by electrons. On the surface of the reflection layer 303 with a high electron density, the X-rays are scattered too much and it is more difficult to penetrate the surface of the reflection layer 303 and enter the interior of the reflection layer 303. Therefore, the X-rays are more likely to form total reflection on the surface of the reflection layer 303, and thus the critical angle of the X-rays on the surface of the reflection layer 303 is large; conversely, the density of the material of the absorption layer 306 is small, and the critical angle of the X-rays on the surface of the absorption layer 306 is small.
[0067] Please continue to refer to Figure 4, in this embodiment, the X-ray has a first critical angle α1 on the surface of the first region. The first critical angle α1 is the angle between the X-ray incident from air onto the surface of the reflective layer 303 and the surface of the reflective layer 303. When the incident angle of the X-ray incident from air onto the surface of the reflective layer 303 is less than the first critical angle α1, total reflection of the X-ray occurs on the surface of the reflective layer 303, and the reflectivity of the X-ray on the surface of the reflective layer 303 is high; the X-ray has a second critical angle α2 on the surface of the second region. The second critical angle α2 is the angle between the X-ray incident from air onto the surface of the absorption layer 306 and the surface of the absorption layer 306. When the incident angle of the X-ray incident from air onto the surface of the absorption layer 306 is less than the second critical angle α2, total reflection of the X-ray occurs on the surface of the absorption layer 306.
[0068] In this embodiment, the first critical angle α1 is greater than the second critical angle α2.
[0069] In this embodiment, the range of the incident angle of the X-ray incident on the surface of the mask is 0 to 1.5 degrees. The incident angle is the angle between the X-ray and the surface of the mask, and the incident angles of the X-ray incident on the surfaces of the reflective layer 303 and the absorption layer 306 are the same.
[0070] By adjusting the incident angle of the X-ray incident on the surface of the mask, such that the incident angle is greater than the second critical angle α2 and less than the first critical angle α1, in this way, total reflection of the X-ray occurs on the surface of the reflective layer 303, and the reflectivity of the X-ray on the surface of the reflective layer 303 is high; total reflection of the X-ray does not occur on the surface of the absorption layer 306, and the reflectivity of the X-ray on the surface of the absorption layer 306 is low, so that the reflectivity of the X-ray on the surface of the first region is greater than the reflectivity on the surface of the second region, in order to obtain different reflectivities of the X-ray on the surfaces of the first region and the second region.
[0071] In this embodiment, the range of the first critical angle α1 is 0 to 1.5 degrees, and the range of the second critical angle α2 is 0 to 1.5 degrees.
[0072] By setting the incident angle of the X-ray, such that the first critical angle α1 is greater than the second critical angle α2, and the incident angle of the X-ray is between the second critical angle α2 and the first critical angle α1, in order to obtain different reflectivities of the X-ray on the surfaces of the first region and the second region.
[0073] In this embodiment, the transmittance of the first reflected ray L1 in the photoresist layer 201 to be lithographed in the first region is greater than 6%; the transmittance of the second reflected ray L2 in the photoresist layer 201 to be lithographed in the second region is less than 6%.
[0074] As a result, the optical reaction degree of the first pattern layer 205 formed in the first region is sufficient, and the optical reaction degree of the second pattern layer formed in the second region is slight. The second pattern layer and the photoresist layer 201 to be lithographed can be removed with a large etching selectivity ratio relative to the first pattern layer 205, leaving the first pattern layer 205 on the surface of the wafer to be etched to form the mask layer.
[0075] In this embodiment, the photoresist layer 201 to be lithographed is a positive photoresist. After development, the first pattern layer that has fully reacted and is formed in the first region is retained, and the unreacted photoresist layer 201 to be lithographed and the second pattern layer that has not fully reacted are removed.
[0076] In other embodiments, if the photoresist layer to be lithographed is a negative photoresist, then after development, the first pattern layer that has fully reacted and is formed in the first region is removed, and the unreacted photoresist layer to be lithographed and the second pattern layer that has not fully reacted are retained.
[0077] Please continue to refer to Figure 2 , and perform step S40: Remove the second pattern layer to form a patterned mask layer on the surface of the wafer to be etched. The patterned mask layer includes the first pattern layer 205.
[0078] In this embodiment, the process of removing the second pattern layer includes a wet etching process. The wet etching process has an etching rate for the second pattern layer that is greater than the etching rate for the first pattern layer and greater than the etching rate for the photoresist layer 201 to be lithographed.
[0079] The formed patterned mask layer has a high resolution. When the wafer to be etched is etched with the patterned mask layer in the subsequent process, a semiconductor structure with a smaller dimensional accuracy can be formed.
[0080] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.
Claims
1. A lithography method, characterized in that, Including: Providing a wafer to be etched, on the surface of which there is a photoresist layer to be lithographed; Providing an X-ray light source for emitting X-rays; Providing a mask, which includes a first region and a second region, the density of the material on the surface of the second region being less than that of the material on the surface of the first region. The mask is used to reflect the X-rays incident on the surface of the mask to the surface of the photoresist layer to be lithographed. The X-rays reflected from the surface of the first region are the first reflected rays, and the X-rays reflected from the surface of the second region are the second reflected rays. The reflectivity of the X-rays on the surface of the first region is greater than that on the surface of the second region. The first reflected rays form a first pattern layer on the photoresist layer to be lithographed, and the second reflected rays form a second pattern layer on the photoresist layer to be lithographed; Removing the second pattern layer and the photoresist layer to be lithographed, and forming a patterned mask layer on the surface of the wafer to be etched, the patterned mask layer including the first pattern layer.
2. The lithography method according to claim 1, characterized in that, The ratio range of the reflectivity of the X-rays on the surface of the first region to the reflectivity of the X-rays on the surface of the second region is greater than or equal to 100.
3. The lithography method according to claim 1, wherein The X-rays have a first critical angle on the surface of the first region and a second critical angle on the surface of the second region, and the first critical angle is greater than the second critical angle.
4. The lithography method according to claim 3, characterized in that, The X-rays are incident on the surface of the mask at an incident angle, the incident angle being greater than the second critical angle and less than the first critical angle.
5. The lithography method according to claim 4, characterized in that, The range of the incident angle of the X-rays incident on the surface of the mask is 0 to 1.5 degrees.
6. The lithography method according to claim 1, wherein, The wavelength range of the X-rays is 0.01 nm to 10 nm.
7. The lithography method according to claim 1, characterized in that The mask includes a functional surface and a non-functional surface, and the X-rays are incident on the surface of the functional surface; the mask includes: a substrate, the substrate including a first region and a second region; a reflection layer located on the first region; an absorption layer located on the second region, the density of the material of the absorption layer being less than that of the material of the reflection layer; the surface of the absorption layer and the surface of the reflection layer are the surface of the functional surface.
8. The lithography method according to claim 7, wherein, The density of the material of the reflection layer is greater than 15 g / cm³.
9. The lithography method according to claim 8, wherein The material of the reflection layer includes a metal, and the metal includes one or a combination of more of: tungsten, hafnium, tantalum, platinum, and gold.
10. The lithography method according to claim 7, characterized in that, The density of the material of the absorption layer is less than 8 g / cm³.
11. The lithography method according to claim 10, wherein, The material of the absorption layer includes: silicon, silicon oxide, silicon carbide, or silicon germanium.
12. The lithography method according to claim 7, wherein The range of the thermal expansion coefficient of the material of the substrate is -1e-11 / K to 1e-11 / K.
13. The lithography method according to claim 12, wherein The material of the substrate includes silicon, silicon oxide, glass, or ceramic.
14. The lithography method according to claim 1, characterized in that, The transmittance of the first reflected rays in the photoresist layer to be lithographed in the first region is greater than 6%; the transmittance of the second reflected rays in the photoresist layer to be lithographed in the second region is less than 6%.
15. The lithography method according to claim 1, characterized in that, The process of removing the second pattern layer includes a wet etching process, and the etching rate of the wet etching process for the second pattern layer is greater than that for the first pattern layer, and the etching rate of the wet etching process for the photoresist layer to be lithographed is greater than that for the first pattern layer.