Preparation method of metal electrode in etching groove
By adopting a step-by-step protection method in the etching groove, the metal electrode is first etched dryly, and then wet etched to remove the metal remaining on the side wall, the optical loss and device damage caused by the side wall residue of the metal electrode in the prior art are solved, and the integrity and electrical performance of the metal electrode structure are maintained.
Patent Information
- Application Number
- CN202510124214.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-26
- Publication Date
- 2025-05-13
AI Technical Summary
Prior art When growing metal electrodes in etching grooves, it is difficult to avoid metal residue on the side walls, resulting in increased optical loss or device damage.
The method of protecting metal electrodes in step by step is adopted. The metal electrode is first formed by dry etching, and then the metal residue on the side wall is removed by wet etching to ensure the integrity of the metal electrode structure.
It effectively protects the metal electrode structure in the etching groove, avoids optical loss and device damage, and does not affect the electrical performance of the metal electrode.
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Figure CN119987129A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of light modulation devices, and in particular to a method for preparing a metal electrode in an etching groove. Background Art
[0002] With the explosive growth of data traffic, silicon photonics, which can manipulate electrons and photons on the same platform, can significantly reduce the energy consumption and cost of optical communication systems, and has received more and more attention. However, how to achieve high-speed, large bandwidth and low-power modulation effects places strict requirements on modulation devices. Lithium niobate material has become one of the effective choices due to its excellent optical properties. At the same time, metal deposition grooves can be prepared by etching silicon oxide, and then metal electrodes can be deposited. After that, lithium niobate materials are bonded. It is compatible with CMOS processes and can prepare high-quality waveguide structures to reduce optical losses. However, it is difficult to grow metal electrodes in the grooves and pattern them.
[0003] The existing technical solution is to first deposit metal electrodes in the etched grooves, and then use dry etching to prepare metal leads, or use dry etching + wet etching to pattern the metal electrodes. In the existing solution, if only dry etching is used, residual metal will be formed on the side walls of the grooves. Since the distance between the etched grooves and the waveguide is small, the residual metal on the side walls will absorb the light transmitted in the waveguide, increase the loss, and reduce the optical performance; if dry etching + wet etching is used, the gas molecules remaining in the grooves during dry etching will encounter the wet solution, which will seriously corrode the metal in the grooves. In mild cases, the metal size will be reduced and the electrical performance will be reduced, and in severe cases, the metal will break and cause device damage. Summary of the invention
[0004] In view of this, an embodiment of the present application provides a method for preparing a metal electrode in an etching groove, so as to achieve the purpose of protecting the metal electrode structure in the etching groove (metal deposition groove) from being damaged during the etching process and not affecting the electrical properties of the metal electrode.
[0005] The embodiment of the present application provides the following technical solution: a method for preparing a metal electrode in an etching groove, comprising:
[0006] etching a metal deposition groove on a waveguide substrate;
[0007] forming a metal electrode layer to cover the surface of the metal deposition tank and the surface of the waveguide substrate through the metal electrode layer, and forming a patterned first photoresist layer on the metal electrode layer in the metal deposition tank;
[0008] Using the first photoresist layer as a mask, patterning the metal electrode layer by dry etching, and then removing the first photoresist layer to form a metal electrode in the metal deposition tank;
[0009] A patterned second photoresist layer is formed on the metal electrode to cover the metal electrode with the second photoresist layer. The metal electrode layer remaining on the inner wall of the metal deposition groove is removed by wet etching using the second photoresist layer as a mask, and the second photoresist layer is then removed to obtain a modulation device structure including the metal electrode.
[0010] According to one embodiment of the present application, the method further includes: preparing a first silicon oxide layer on a silicon substrate, preparing a waveguide layer on the first silicon oxide layer, and patterning the waveguide layer to form a waveguide structure, and forming a second silicon oxide layer on the waveguide structure so that the second silicon oxide layer completely covers the waveguide structure and the first silicon oxide layer to form the waveguide substrate.
[0011] According to an embodiment of the present application, the first silicon oxide layer is prepared by thermal oxidation, and the second silicon oxide layer is prepared by chemical vapor deposition.
[0012] According to an embodiment of the present application, the metal deposition grooves are located on both sides of the waveguide structure, and the bottoms of the metal deposition grooves extend into the first silicon oxide layer.
[0013] According to an embodiment of the present application, the thickness of the metal electrode does not exceed the groove depth of the metal deposition groove, and the top of the metal electrode is not higher than the top of the waveguide structure.
[0014] According to an embodiment of the present application, the thickness of the metal electrode is 0.8-1 μm, and the groove depth of the metal deposition groove is 1.5-2 μm.
[0015] According to an embodiment of the present application, the gap between the top of the metal electrode and the top of the waveguide structure is 0-100 nm.
[0016] According to an embodiment of the present application, the thickness of the second photoresist layer is greater than the height of the metal electrode, and the outer width of the second photoresist layer is greater than the width of the metal electrode, so that the metal electrode is completely wrapped by the second photoresist layer.
[0017] According to an embodiment of the present application, the method further includes: before etching to form the metal deposition groove, performing chemical mechanical polishing on the surface of the second silicon oxide layer.
[0018] Compared with the prior art, the beneficial effects that can be achieved by at least one of the above-mentioned technical solutions adopted in the embodiments of this specification include at least: the method for preparing a metal electrode in an etching groove of the embodiment of the present invention, first, etching a metal deposition groove on a waveguide substrate; forming a metal electrode layer to cover the surface of the metal deposition groove and the surface of the waveguide substrate with the metal electrode layer, and forming a patterned first photoresist layer on the metal electrode layer in the metal deposition groove; using the first photoresist layer as a mask, patterning the metal electrode layer by dry etching, and then removing the first photoresist layer to form a metal electrode in the metal deposition groove; forming a patterned second photoresist layer on the metal electrode, covering the metal electrode with the second photoresist layer, using the second photoresist layer as a mask, removing the metal electrode layer remaining on the inner side wall of the metal deposition groove by wet etching, and then removing the second photoresist layer to obtain a modulation device structure including a metal electrode. The metal electrode layer is etched twice by dry and wet methods in a step-by-step manner to remove the residual metal on the inner wall of the metal deposition tank while protecting the metal electrode leads in the tank from damage, thereby obtaining the desired metal electrode structure without affecting the electrical properties of the metal electrode. BRIEF DESCRIPTION OF THE DRAWINGS
[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0020] Figure 1 It is a schematic flow chart of a method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0021] Figure 2 is a first structural schematic diagram of a method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0022] Figure 3 is a second structural schematic diagram of a method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0023] Figure 4 is a third structural schematic diagram of the method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0024] Figure 5 is a fourth structural schematic diagram of a method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0025] Figure 6 is a fifth structural schematic diagram of a method for preparing a metal electrode in an etching groove according to an embodiment of the present invention;
[0026] Among them, 10 is a silicon substrate, 11 is a thermal oxide silicon layer, 12 is a silicon nitride waveguide layer, 13 is a chemical vapor deposition silicon oxide layer, 14 is a metal deposition tank, 15 is a metal electrode layer, 16 is a first photoresist layer, and 17 is a second photoresist layer. DETAILED DESCRIPTION
[0027] The embodiments of the present application are described in detail below with reference to the accompanying drawings.
[0028] The following describes the implementation methods of the present application through specific specific examples, and those skilled in the art can easily understand other advantages and effects of the present application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The present application can also be implemented or applied through other different specific implementation methods, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present application. It should be noted that, in the absence of conflict, the features in the following embodiments and embodiments can be combined with each other. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without making creative work belong to the scope of protection of the present application.
[0029] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing a metal electrode in an etching groove, comprising:
[0030] 101. Etching a metal deposition groove on a waveguide substrate;
[0031] 102. Forming a metal electrode layer to cover the surface of the metal deposition tank and the surface of the waveguide substrate through the metal electrode layer, and forming a patterned first photoresist layer on the metal electrode layer in the metal deposition tank;
[0032] 103. Using the first photoresist layer as a mask, patterning the metal electrode layer by dry etching, and then removing the first photoresist layer to form a metal electrode in the metal deposition tank;
[0033] 104. A patterned second photoresist layer is formed on the metal electrode to cover the metal electrode with the second photoresist layer, and the metal electrode layer remaining on the inner wall of the metal deposition groove is removed by wet etching using the second photoresist layer as a mask, and then the second photoresist layer is removed to obtain a modulation device structure including the metal electrode.
[0034] The key point of the method for preparing a metal electrode in an etching groove (i.e., the metal deposition groove) of an embodiment of the present invention is that a step-by-step method of protecting the metal electrode in the metal deposition groove is adopted. After the first spin coating of photoresist for protection, dry etching is adopted to form the desired structure. At this time, there are residual metal electrode layers on the inner wall of the metal deposition groove; after the second spin coating of photoresist for protection, wet etching is adopted to remove the residual metal on the inner wall of the metal deposition groove, while protecting the metal electrode structure from damage during the wet etching process and not affecting the electrical properties of the metal electrode.
[0035] In some embodiments of the present invention, the method further includes: preparing a first silicon oxide layer on a silicon substrate, preparing a waveguide layer on the first silicon oxide layer, and forming a waveguide structure after patterning the waveguide layer, and forming a second silicon oxide layer on the waveguide structure, so that the second silicon oxide layer completely covers the waveguide structure and the first silicon oxide layer to form the waveguide substrate. Wherein, the first silicon oxide layer is a silicon oxide layer prepared by thermal oxidation, and the second silicon oxide layer is a silicon oxide layer prepared by chemical vapor deposition. Two layers of silicon oxide are non-same-layer thin film structures, and there is a silicon nitride waveguide structure in the middle: the first silicon oxide layer is prepared by thermal oxidation, with the best density and film quality, and can be used as a lower silicon oxide layer to grow a silicon nitride film layer with good crystal quality to optimize optical performance; after the silicon nitride film layer is grown, it is impossible to continue to prepare silicon oxide by thermal oxidation, so the upper cladding silicon oxide is prepared by chemical vapor deposition to form a second silicon oxide layer, the film quality is slightly worse than the first silicon oxide layer, but it can be used as a cladding to protect the silicon nitride waveguide structure.
[0036] In some embodiments of the present invention, the metal deposition groove is located on both sides of the waveguide structure, and the bottom of the metal deposition groove extends into the first silicon oxide layer. In specific implementation, the metal electrode layer can be made of materials such as Al and Cu, the thickness of the metal electrode layer does not exceed the groove depth of the metal deposition groove, and the top of the metal electrode needs to be no higher than the top of the waveguide structure, and the gap is controlled to be 0-100nm. The reason is that after the metal electrode structure is prepared, the cladding silicon oxide needs to be covered and the second silicon oxide layer needs to be subjected to a CMP process (chemical mechanical polishing) to control the second silicon oxide layer to be 100nm higher than the silicon nitride waveguide layer, optimize the optical performance and prepare for the subsequent bonding process; if the metal electrode is higher than the waveguide layer, there is not enough process window to control the requirement of 100nm silicon oxide thickness on the silicon nitride waveguide layer, thereby affecting the optical performance, and may also cause damage to the metal electrode during the CMP process, thereby affecting the electrical performance.
[0037] In some embodiments of the present invention, the thickness of the second photoresist layer is greater than the height of the metal electrode, and the outer width of the second photoresist layer is greater than the width of the metal electrode, so that the metal electrode is completely wrapped by the second photoresist layer. In specific implementation, the length and width of the pattern on the mask of the first photoresist layer are consistent with the length and width of the metal electrode; and the second photoresist layer needs to cover the entire metal electrode, so the mask pattern size of the second photoresist layer needs to be slightly larger than the length and width of the metal electrode; in order to meet the photolithography alignment deviation, the mask pattern size of the second photoresist layer needs to be larger than the length and width of the metal electrode by 1μm.
[0038] In specific implementation, the thickness of the first silicon oxide layer is 3-8 μm, the thickness of the silicon nitride waveguide layer is 50-450 nm, and the thickness of the second silicon oxide layer is 500 nm-1 um. The specific dimensions of the three are determined according to current design conditions and process windows.
[0039] In specific implementation, the groove depth of the metal deposition groove is 1.5-2μm, which is determined by the final thickness of the second silicon oxide layer; the thickness of the metal electrode is 0.8-1μm, so that the top of the metal electrode is lower than the top of the silicon nitride waveguide structure to prevent subsequent CMP process and bonding process from causing electrode damage.
[0040] In some embodiments of the present invention, the method further includes: before etching to form the metal deposition groove, performing chemical mechanical polishing on the surface of the second silicon oxide layer to make the surface of the second silicon oxide layer smooth and flat, thereby accurately controlling the uniformity of the etching depth of the metal deposition groove.
[0041] like Figure 2-Figure 6 As shown, the following is a specific description of the process steps using Si3N4 waveguide substrate as an example (unless otherwise specified, all schematic diagrams are cross-sectional diagrams):
[0042] First, prepare a silicon nitride waveguide substrate such as Figure 2 As shown, the silicon nitride waveguide substrate includes: a silicon substrate 10, a thermal oxide silicon layer 11, a silicon nitride waveguide layer 12, and a chemical vapor deposited silicon oxide layer 13, and an etched metal deposition groove 14 is formed by etching on the chemical vapor deposited silicon oxide layer 13.
[0043] Next, a metal electrode layer 15 is prepared, such as Figure 3 As shown, the metal electrode layer 15 covers the surface of the chemical vapor deposited silicon oxide layer 13 and the inner surface of the metal deposition groove 14 .
[0044] Next, a first photoresist layer 16 is spin-coated on the metal electrode layer 15 in the metal deposition tank 14 to protect the metal electrode; the first photoresist layer 16 is used as a mask, and then a part of the metal electrode layer 15 is removed by dry etching to form a metal electrode in the metal deposition tank 14. At this time, there is metal residue on the inner side wall of the metal deposition tank 14, such as Figure 4 shown.
[0045] Next, the first photoresist layer 16 used to protect the metal electrode for the first time is removed, and the second photoresist layer 17 is spin-coated on the metal electrode again and then exposed to protect the metal electrode for the second time. Then, the residual metal on the inner wall of the metal deposition groove 14 is removed by wet etching. At this time, due to the secondary protection of the second photoresist layer 17, the metal electrode lead will not be damaged by secondary etching. Figure 5 Finally, the second photoresist layer 17 is removed to form the desired modulation structure, as shown in FIG. Figure 6 shown.
[0046] The embodiment of the present invention adopts a step-by-step method of protecting the metal electrode, and etches the metal electrode layer twice by dry and wet methods. While removing the residual metal on the inner wall of the metal deposition groove, the metal electrode structure is protected from being damaged during the wet etching process, and the desired metal electrode structure is obtained without affecting the electrical properties of the metal electrode.
[0047] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.
Claims
1. A method for preparing a metal electrode in an etching groove, characterized in that: include: etching a metal deposition groove on a waveguide substrate; forming a metal electrode layer to cover the surface of the metal deposition tank and the surface of the waveguide substrate through the metal electrode layer, and forming a patterned first photoresist layer on the metal electrode layer in the metal deposition tank; Using the first photoresist layer as a mask, patterning the metal electrode layer by dry etching, and then removing the first photoresist layer to form a metal electrode in the metal deposition tank; A patterned second photoresist layer is formed on the metal electrode to cover the metal electrode with the second photoresist layer. The metal electrode layer remaining on the inner wall of the metal deposition groove is removed by wet etching using the second photoresist layer as a mask, and the second photoresist layer is then removed to obtain a modulation device structure including the metal electrode.
2. The method for preparing a metal electrode in an etching groove according to claim 1, characterized in that: The method further comprises: A first silicon oxide layer is formed on a silicon substrate, a waveguide layer is formed on the first silicon oxide layer, and the waveguide layer is patterned to form a waveguide structure, and a second silicon oxide layer is formed on the waveguide structure so that the second silicon oxide layer completely covers the waveguide structure and the first silicon oxide layer to form the waveguide substrate.
3. The method for preparing a metal electrode in an etching groove according to claim 2, characterized in that: The first silicon oxide layer is prepared by thermal oxidation, and the second silicon oxide layer is prepared by chemical vapor deposition.
4. The method for preparing a metal electrode in an etching groove according to claim 2, characterized in that: The metal deposition grooves are located at two sides of the waveguide structure, and the bottoms of the metal deposition grooves extend into the first silicon oxide layer.
5. The method for preparing a metal electrode in an etching groove according to claim 2, characterized in that: The thickness of the metal electrode does not exceed the depth of the metal deposition groove, and the top of the metal electrode is not higher than the top of the waveguide structure.
6. The method for preparing a metal electrode in an etching groove according to claim 1, characterized in that: The thickness of the metal electrode is 0.8-1 μm, and the groove depth of the metal deposition groove is 1.5-2 μm.
7. The method for preparing a metal electrode in an etching groove according to claim 2, characterized in that: The gap between the top of the metal electrode and the top of the waveguide structure is 0-100 nm.
8. The method for preparing a metal electrode in an etching groove according to claim 1, characterized in that: The thickness of the second photoresist layer is greater than the height of the metal electrode, and the outer width of the second photoresist layer is greater than the width of the metal electrode, so that the metal electrode is completely wrapped by the second photoresist layer.
9. The method for preparing a metal electrode in an etching groove according to claim 2, characterized in that: The method further includes: before etching to form the metal deposition groove, planarizing the surface of the second silicon oxide layer.