Fabrication methods of stepped metal structures and silicon photonic device structures
By combining dry metal etching and isotropic etching processes and adjusting the etching thickness ratio, the problem of long etching time for high-step surface metal layers in silicon photonics technology was solved, achieving efficient metal layer removal and reducing process time and cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- SHANGHAI IND U TECH RES INST
- Filing Date
- 2021-11-24
- Publication Date
- 2026-05-26
AI Technical Summary
In existing technologies, the dry etching of the metal layer on the high-step surface in thick silicon photonics processes takes too long, leading to increased process time and cost.
A stepped metal structure fabrication method is adopted, which combines metal dry etching and isotropic etching processes. By adjusting the etching thickness ratio, the top surface metal is first vertically etched, and then the sidewall metal is removed using isotropic etching, thus achieving rapid and effective metal layer removal.
The method cleanly etches the metal layer on the sidewall of a high step in a short time, solving the problem of metal etching on the surface of a high step, improving process efficiency and reducing costs.
Smart Images
Figure CN116169023B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of semiconductor device design and manufacturing, and in particular relates to a method for fabricating a stepped metal structure and a silicon photonic device structure. Background Technology
[0002] The development trend of integrated circuits is shallow junctions, shallow steps, and high integration density. Typically, the height of silicon steps will not exceed 1 micrometer. When the height of silicon steps is greater than 1 micrometer, after the silicon surface steps are filled using a planarization process, subsequent processes can still be carried out on the flat surface after the steps are filled.
[0003] However, the waveguide size of thick silicon processes in typical silicon photonics technology exceeds 3 micrometers, and the step height formed in metal-level processes can even exceed 10 micrometers. When performing metal wiring on such substrates, the traditional dry metal etching process etches from top to bottom. Theoretically, it takes several hours to completely etch the metal at the sidewalls of the step, which will seriously increase the process time and process cost.
[0004] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention
[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a method for fabricating stepped metal structures and silicon photonic device structures, in order to solve the problem of long dry etching time for high-step surface metal layers in thick silicon processes of silicon photonics technology.
[0006] To achieve the above and other related objectives, the present invention provides a method for fabricating a stepped metal structure, the method comprising: 1) providing a substrate and forming a raised stepped structure on the substrate, the stepped structure including a top surface and a sidewall located between the top surface and the substrate; 2) depositing an isolation medium layer on the top surface and the sidewall of the stepped structure; 3) depositing a metal layer on the isolation medium layer, the metal layer including a top surface metal located on the top surface of the stepped structure and a sidewall metal located on the sidewall of the stepped structure, the thickness of the top surface metal being greater than the thickness of the sidewall metal; 4) forming a patterned barrier on the metal layer. 5) Dry etching the exposed second portion of the top surface metal, wherein the etching direction of the dry etching is perpendicular to the top surface metal, to remove part of the thickness of the second portion of the top surface metal, so that the thickness of the second portion of the top surface metal is approximately equal to that of the second portion of the sidewall metal; 6) Removing the exposed second portion of the top surface metal and the second portion of the sidewall metal using an isotropic etching process; 7) Removing the pattern barrier layer.
[0007] Optionally, the height of the stepped structure is greater than or equal to 3 micrometers.
[0008] Optionally, the top surface of the stepped structure is parallel to the base surface, and the sidewalls of the stepped structure are perpendicular to the base surface.
[0009] Optionally, the isotropic etching process in step 6) has a higher etching rate on the metal layer than the dry etching process in step 5).
[0010] Optionally, the etching rate of the metal layer by the isotropic etching process in step 6) is more than twice the etching rate of the metal layer by the dry etching process in step 5).
[0011] Optionally, the isotropic etching process has the same etching rate for the second portion of the top surface metal and the same etching rate for the second portion of the sidewall metal.
[0012] Optionally, the isotropic etching process includes one of wet etching and isotropic dry etching.
[0013] Optionally, after the second portion of the top surface metal is exposed by dry etching in step 5), the thickness difference between the second portion of the top surface metal and the second portion of the sidewall metal is less than or equal to 0.1 micrometers.
[0014] Optionally, a process connection time limit is set between the dry etching process in step 5) and the isotropic etching process in step 6), wherein the connection time shall not exceed 4 hours.
[0015] Optionally, the metal layer comprises an alloy of one or both of Al and Cu.
[0016] The present invention also provides a method for fabricating a silicon photonic device structure, the method comprising the method for fabricating a stepped metal structure as described in any one of the above claims, wherein the stepped structure is a waveguide structure of a silicon photonic device structure.
[0017] As described above, the method for fabricating the stepped metal structure and silicon photonic device structure of the present invention has the following beneficial effects:
[0018] The method for fabricating stepped metal structures of the present invention can effectively etch the metal layer of the high-step sidewalls cleanly in a short time, solving the problem of metal etching on high-step surfaces. This invention can be widely applied to silicon photonics technology, and also to the processing of similar high-step products, such as the production of integrated circuit special process products and MEMS products, demonstrating broad application prospects.
[0019] This invention combines dry metal etching and isotropic etching processes (such as wet etching). By further adjusting the etching thickness ratio of dry metal etching and isotropic etching, the transverse corrosion of the metal layer at the cross-section of the top surface of the stepped structure can be reduced, and the transverse corrosion size of the metal layer can be more controllable. Attached Figure Description
[0020] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the embodiments of this application and to illustrate the implementation of this application, together with the textual description, to explain the principles of this application. Obviously, the drawings described below are merely some embodiments of this application.
[0021] Figures 1 to 7 The diagram shows the structural schematics of each step in the preparation method of the stepped metal structure according to an embodiment of the present invention.
[0022] Component designation explanation
[0023] 101 base
[0024] 102 Step Structure
[0025] 1021 Stepped structure sidewall
[0026] 1022 Top surface of the stepped structure
[0027] 103 Isolation Medium Layer
[0028] 104 Metal Layer
[0029] 1041 Sidewall Metal
[0030] 1042 Top surface metal
[0031] 1043 First part of the sidewall metal
[0032] 1044 The first part of the top metal
[0033] 1045 Second part of the sidewall metal
[0034] 1046 The second part of the top metal
[0035] 105 Graphics Blocking Layer Detailed Implementation
[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
[0037] It should be emphasized that the term "including / comprises" as used herein refers to the presence of a feature, whole, step, or component, but does not exclude the presence or addition of one or more other features, wholes, steps, or components.
[0038] Features described and / or illustrated for one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.
[0039] In the detailed description of embodiments of the present invention, for ease of explanation, the cross-sectional views illustrating the device structure may be partially enlarged and not to scale. Furthermore, the schematic diagrams are merely examples and should not limit the scope of protection of the present invention. In actual fabrication, the three-dimensional spatial dimensions of length, width, and depth should be included.
[0040] For ease of description, spatial relation terms such as “below,” “under,” “lower than,” “below,” “above,” and “upper” may be used herein to describe the relationship between one element or feature shown in the accompanying drawings and other elements or features. It will be understood that these spatial relation terms are intended to include directions other than those depicted in the drawings for devices in use or operation. Furthermore, when a layer is referred to as being “between” two layers, it may be the only layer between the two layers, or there may be one or more layers in between.
[0041] In the context of this application, the structure described above the first feature may include embodiments in which the first and second features are formed in direct contact, or embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.
[0042] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the illustrations only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.
[0043] like Figures 1 to 7 As shown, this embodiment provides a method for preparing a stepped metal structure, the method comprising the following steps:
[0044] like Figure 1 As shown, step 1) is performed first, a base 101 is provided, and a raised step structure 102 is formed on the base 101. The step structure 102 includes a top surface 1022 and a side wall 1021 located between the top surface and the base 101.
[0045] In one embodiment, the substrate 101 may be silicon, germanium, silicon-germanium, silicon-on-insulator, germanium-on-insulator, silicon-germanium-on-insulator, silicon carbide, group III-V semiconductor compounds, sapphire, etc. In this embodiment, the material of the substrate 101 is silicon.
[0046] The stepped structure 102 is formed as a boss on the substrate 101. The stepped structure 102 can be formed on the substrate 101 by an etching process. The height of the stepped structure 102 is greater than or equal to 3 micrometers. For example, the height of the stepped structure 102 can be 3 micrometers, 5 micrometers, 6 micrometers, etc. The width of the stepped structure 102 can be adjusted according to actual needs, for example, it can be set according to the parameters required by the optical waveguide. In one embodiment, the top surface 1022 of the stepped structure 102 is parallel to the surface of the substrate 101, and the sidewall 1021 of the stepped structure is perpendicular to the surface of the substrate 101.
[0047] like Figure 2 As shown, then step 2) is performed, depositing an isolation medium layer 103 on the surface of the substrate 101, the top surface of the stepped structure 102, and the sidewalls.
[0048] In one embodiment, the insulating dielectric layer 103 can be an insulating material such as silicon dioxide, silicon nitride, or silicon oxynitride, which can be prepared by processes such as plasma-enhanced chemical vapor deposition (PECVD).
[0049] like Figure 3 As shown, step 3) is then performed, depositing a metal layer 104 on the isolation medium layer 103. The metal layer 104 includes a top surface metal 1042 located on the top surface of the stepped structure 102 and a side wall metal 1041 located on the side wall of the stepped structure 102. The thickness of the top surface metal 1042 is greater than the thickness of the side wall metal 1041.
[0050] In one embodiment, a metal layer 104 is deposited on the isolation medium layer 103 by a metal sputtering process. Due to the characteristics of metal deposition, the deposition rate of metal on the horizontal plane is greater than that on the vertical plane, and the final thickness of the top surface metal 1042 is greater than the thickness of the side wall metal 1041.
[0051] In one embodiment, the metal layer 104 comprises an alloy of one or both of Al and Cu.
[0052] like Figure 4 As shown, step 4) is then performed, in which a pattern barrier layer 105 is formed on the metal layer 104. The pattern barrier layer 105 covers the first portion 1044 of the top surface metal 1042, exposes the second portion 1046 of the top surface metal 1042, and covers the first portion 1043 of the sidewall metal 1041, exposes the second portion 1045 of the sidewall metal 1041.
[0053] In one embodiment, the patterned barrier layer 105 may be a patterned photoresist layer, which may be formed by spin coating, exposure and development processes.
[0054] like Figure 5As shown, step 5) is then performed, where the second portion 1046 of the exposed top surface metal 1042 is dry-etched. The etching direction of the dry etching is perpendicular to the top surface metal 1042 to remove a portion of the thickness of the second portion 1046 of the top surface metal 1042, making the thickness of the second portion 1046 of the top surface metal 1042 approximately equal to the thickness of the second portion 1045 of the exposed sidewall metal 1041. "Approximately equal" means that the thickness of the second portion 1046 of the top surface metal 1042 is set to be equal to the thickness of the second portion 1045 of the exposed sidewall metal 1041. However, due to limitations of existing process conditions, there may be a certain reasonable error. Within this reasonable error range, it can be considered that the thickness of the second portion 1046 of the top surface metal 1042 is approximately equal to the thickness of the second portion 1045 of the exposed sidewall metal 1041. In one embodiment, after dry etching exposes the second portion 1046 of the top surface metal 1042, the thickness difference between the second portion 1046 of the top surface metal 1042 and the second portion 1045 of the sidewall metal 1041 is less than or equal to 0.1 micrometers.
[0055] like Figure 6 As shown, step 6) is then performed, in which the second portion 1046 of the exposed top surface metal 1042 and the second portion 1045 of the sidewall metal 1041 are removed using an isotropic etching process.
[0056] Since the thickness of the top surface metal 1042 deposited in step 3) is greater than the thickness of the sidewall metal 1041, firstly, if a single vertical dry etching process is used, the height of the sidewall metal 1041 is very large. Therefore, completely removing the sidewall metal 1041 requires a very long process time, which greatly increases the process time cost and etching cost. Secondly, if a single isotropic etching process is used, since the thickness of the top surface metal 1042 is greater than the thickness of the sidewall metal 1041, after the sidewall metal 1041 is completely removed, there will be a large thickness residue of the top surface metal 1042, which needs to be further removed by isotropic etching. Therefore, this will cause large lateral etching at the cross-section of the top surface metal 1042, resulting in significant morphological defects in the top surface metal 1042 and greatly reducing the performance of the device. This invention employs a combination of dry metal etching and isotropic etching processes (such as wet etching). By further adjusting the etching thickness ratio of dry metal etching and isotropic etching, the transverse corrosion of the metal layer 104 at the cross-sectional position of the top surface of the stepped structure 102 can be reduced, and the transverse corrosion size of the metal layer 104 can be more controllable.
[0057] In this embodiment, the isotropic etching process has the same etching rate for the second portion 1046 of the top surface metal 1042 and the second portion 1045 of the sidewall metal 1041, so that the second portion 1046 of the top surface metal 1042 and the second portion 1045 of the sidewall metal 1041, which are of approximately equal thickness, can be removed substantially simultaneously, thereby greatly reducing the transverse corrosion of the metal layer 104 at the cross-sectional position of the top surface of the stepped structure 102.
[0058] In one embodiment, the isotropic etching process includes one of wet etching and isotropic dry etching.
[0059] In one embodiment, the isotropic etching process in step 6) has an etching rate for the metal layer 104 that is greater than the dry etching process in step 5) that has an etching rate for the metal layer 104. For example, the isotropic etching process in step 6) has an etching rate for the metal layer 104 that is more than twice the etching rate of the dry etching process in step 5) that has an etching rate for the metal layer 104, thereby improving the removal efficiency of the metal layer 104.
[0060] In one embodiment, a process transition time limit is set between the dry etching process in step 5) and the isotropic etching process in step 6), wherein the transition time is no more than 4 hours.
[0061] like Figure 7 As shown, step 7) is performed last to remove the graphic blocking layer 105.
[0062] This embodiment also provides a method for fabricating a silicon photonic device structure, the method including the method for fabricating a stepped metal structure as described in the above embodiment, wherein the stepped structure 102 is a waveguide structure of the silicon photonic device structure.
[0063] As described above, the method for fabricating the stepped metal structure and silicon photonic device structure of the present invention has the following beneficial effects:
[0064] The method for fabricating stepped metal structures of the present invention can effectively etch the metal layer 104 of the high-step sidewalls cleanly in a short time, solving the problem of metal etching on high-step surfaces. This invention can be widely applied to silicon photonics technology, and also to the processing of similar high-step products, such as the production of special process products for integrated circuits and MEMS products, and has broad application prospects.
[0065] This invention employs a combination of dry metal etching and isotropic etching processes (such as wet etching). By further adjusting the etching thickness ratio of dry metal etching and isotropic etching, the transverse corrosion of the metal layer 104 at the cross-sectional position of the top surface of the stepped structure 102 can be reduced, and the transverse corrosion size of the metal layer 104 can be more controllable.
[0066] Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.
[0067] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.
Claims
1. A method for preparing a stepped metal structure, characterized in that, The preparation method includes: 1) A base is provided, on which a raised step structure is formed, the step structure including a top surface and a sidewall located between the top surface and the base; 2) Deposit an isolation medium layer on the top surface and sidewalls of the stepped structure; 3) Deposit a metal layer on the isolation medium layer, the metal layer comprising a top surface metal located on the top surface of the stepped structure and a side wall metal located on the side wall of the stepped structure, the thickness of the top surface metal being greater than the thickness of the side wall metal; 4) A pattern barrier layer is formed on the metal layer, the pattern barrier layer covering a first portion of the top surface metal, exposing a second portion of the top surface metal, and covering a first portion of the sidewall metal, exposing a second portion of the sidewall metal; 5) The second portion of the top surface metal exposed by dry etching, wherein the etching direction of the dry etching is perpendicular to the top surface metal, so as to remove part of the thickness of the second portion of the top surface metal, so that the thickness of the second portion of the top surface metal is approximately equal to that of the second portion of the sidewall metal. 6) The exposed second portion of the top surface metal and the second portion of the sidewall metal are removed using an isotropic etching process; 7) Remove the graphic blocking layer.
2. The method for preparing the stepped metal structure according to claim 1, characterized in that: The height of the stepped structure is greater than or equal to 3 micrometers.
3. The method for preparing a stepped metal structure according to claim 1, characterized in that: The top surface of the stepped structure is parallel to the base surface, and the sidewalls of the stepped structure are perpendicular to the base surface.
4. The method for preparing a stepped metal structure according to claim 1, characterized in that: Step 6) The isotropic etching process has a higher etching rate on the metal layer than the dry etching process in step 5).
5. The method for preparing a stepped metal structure according to claim 4, characterized in that: Step 6) The etching rate of the metal layer by the isotropic etching process is more than twice the etching rate of the metal layer by the dry etching process in step 5).
6. The method for preparing a stepped metal structure according to claim 1, characterized in that: The isotropic etching process has the same etching rate for the second part of the top surface metal and the same etching rate for the second part of the sidewall metal.
7. The method for preparing a stepped metal structure according to claim 1, characterized in that: The isotropic etching process includes one of wet etching process and isotropic dry etching process.
8. The method for preparing a stepped metal structure according to claim 1, characterized in that: Step 5) After the second part of the top surface metal is exposed by dry etching, the thickness difference between the second part of the top surface metal and the second part of the sidewall metal is less than or equal to 0.1 micrometers.
9. The method for preparing a stepped metal structure according to claim 1, characterized in that: There is a process connection time limit between the dry etching process in step 5) and the isotropic etching process in step 6), and the connection time shall not exceed 4 hours.
10. The method for preparing a stepped metal structure according to claim 1, characterized in that: The metal layer comprises an alloy of one or both of Al and Cu.
11. A method for fabricating a silicon photonic device structure, characterized in that: The preparation method includes the preparation method of the stepped metal structure as described in any one of claims 1 to 10, wherein the stepped structure is a waveguide structure of a silicon photonic device structure.