Etching processing method of wafer structure
By using two yellow photoetching methods in the etching and processing of wafer structures, the side walls of multi-layer metal electrodes are protected, and the problems of metal layer fall off and exposure are solved, and the stability and production efficiency of wafer structure are improved.
Patent Information
- Application Number
- CN202411922440.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-03-28
AI Technical Summary
The prior art is difficult to avoid the problem of metal layer falling off and exposure when etching multi-layer metal electrodes, resulting in poor appearance and performance stability of the wafer structure.
Two yellow photoetching methods are used to form a metal electrode for the first etching, and the side walls of the intermediate metal layer are protected by a larger mask plate of the second etching to prevent the metal layer from falling off.
It effectively avoids the problems of metal layer falling off and exposure, improves the appearance and performance stability of the wafer structure, reduces production costs, and improves production efficiency.
Smart Images
Figure CN119706737A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of etching technology, in particular to an etching processing method for a wafer structure. Background Art
[0002] MEMS (Micro-Electro-Mechanical System) can achieve ultra-precision processing to obtain corresponding hardware products, such as MEMS accelerometers. In the wafer structure formed based on MEMS technology, one type of wafer structure needs to have a metal electrode. In the case where the metal electrode includes multiple metal layers, it is necessary to ensure that the metal layers are prevented from falling off and being exposed to the outside and oxidized during the processing of each metal layer. The existing processing of metal electrodes composed of multiple metal layers is often completed by one-time etching. It is difficult to avoid the problem of metal layer falling off and exposure by one-time etching. Therefore, it is necessary to improve the corresponding etching processing method for the wafer structure with metal electrodes composed of multiple metal layers. Summary of the invention
[0003] In view of the deficiencies in the prior art, an object of the present invention is to provide an etching processing method for a wafer structure, which can solve the problems described in the background technology.
[0004] The technical solution to achieve the purpose of the present invention is: an etching processing method for a wafer structure, wherein the wafer structure includes a wafer, the wafer includes a back cavity, the back cavity includes a TSV structure, the end face where the back cavity is located is recorded as a first end face, and a metal electrode connected to the first end face of the wafer, the metal electrode includes a first metal layer, a second metal layer, a third metal layer and a fourth metal layer, the first metal layer, the second metal layer, the third metal layer and the fourth metal layer are arranged in sequence along a direction away from the first end face,
[0005] The etching method comprises the following steps:
[0006] Step 1: Processing to form the metal electrode;
[0007] Step 2: After the metal electrode is deposited on the wafer, the first end surface is subjected to the first yellow light etching. During the first yellow light etching process, the first mask is sequentially exposed, developed and hardened;
[0008] Step 3: After the exposure is completed, each metal layer is wet-etched using Au etching solution, Ti etching solution and Cu etching solution respectively;
[0009] Step 4: After the wet etching is completed, the photoresist is removed by wet method;
[0010] Step 5: Perform a second yellow light etching on the first end surface to expose the second mask, the size of the second mask is larger than the first mask, so that the edges of the second mask are larger than the corresponding positions of the edges of the first mask by a preset threshold;
[0011] Step 6: After the exposure is completed, Ti etching solution is used to continue etching;
[0012] Step 7: Use wet stripping to remove the photoresist, thereby removing the barrier layer, obtaining the final first metal layer, and completing the processing.
[0013] Furthermore, in step 1, the processing to form the metal electrode comprises the following steps:
[0014] Sputtering is performed on the first end surface to form a first metal layer, then sputtering and electroplating are performed in sequence to form a second metal layer, then sputtering is performed to form a third metal layer, and finally sputtering or evaporation is performed to form a fourth metal layer,
[0015] The first metal layer is a Ti metal layer, the second metal layer is a Cu metal layer, the third metal layer is a Ti metal layer, and the fourth metal layer is an Au metal layer.
[0016] Furthermore, the thickness of the first metal layer is 1000A-2000A, the thickness of the second metal layer is 1.5 μm-2 μm, the thickness of the third metal layer is 1000A-2000A, and the thickness of the fourth metal layer is 3000A-8000A.
[0017] Furthermore, in step 2, during the first yellow light etching process, the thickness of the photoresist is 2 μm-6 μm, the exposure time lasts for 18S-42S, the development adopts a positive photoresist developer, the hardening temperature during hardening is 100°C-115°C, and the hardening duration is 1 minute.
[0018] Furthermore, in step 3, the Au etching solution, the Ti etching solution and the Cu etching solution are respectively used to wet-etch each metal layer, and the specific implementation process includes the following steps:
[0019] First, use Au etching solution to etch for 3-6 minutes, then rinse and spin dry to achieve drying; then, use Ti etching solution to etch for 7-30 seconds, then rinse and spin dry to achieve drying; then, use Cu etching solution to etch for 7-10 minutes, then rinse and spin dry to achieve drying.
[0020] Furthermore, the Ti etching solution includes HF and H2O, and the mass ratio of HF to H2O is 1:50. The Cu etching solution includes phosphoric acid, glacial acetic acid, nitric acid and water, and the mass ratio of phosphoric acid, glacial acetic acid, nitric acid and water is 30:2:1:8. The Au etching solution includes potassium iodide and iodine, and the mass ratio of potassium iodide to iodine is 1:2.
[0021] Further, in step 6, etching is continued with Ti etching solution for 25 seconds, and then flushing and drying are performed to achieve drying.
[0022] The beneficial effects of the present invention are as follows: the present invention performs two yellow light etchings, and the second mask plate of the second yellow light etching is larger in size, thereby effectively avoiding the problem of metal layer shedding and exposure of the intermediate metal layer caused by traditional one-time etching, improving the appearance of the wafer structure and the performance stability of the wafer structure, reducing production costs, and improving production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0023] Figure 1 It is a schematic diagram of the process of the present invention;
[0024] Figure 2 A schematic diagram of the structure of a wafer obtained by an existing etching processing method;
[0025] Figure 3 It is a schematic diagram of the state of the wafer structure during the second yellow light etching process of the present invention;
[0026] Figure 4 A schematic structural diagram of a wafer structure obtained by the etching processing method of the present invention;
[0027] In the figure, 1 is wafer, 2 is first metal layer, 3 is second metal layer, 4 is third metal layer, 5 is fourth metal layer, and 6 is photoresist. DETAILED DESCRIPTION
[0028] The present invention will be further described below in conjunction with the accompanying drawings and specific implementation plans:
[0029] like Figure 1-Figure 4 As shown, a method for etching a wafer structure is provided, wherein the wafer structure includes a wafer 1, the wafer 1 includes a back cavity, the back cavity includes a TSV structure, the end face where the back cavity is located is recorded as a first end face, and a metal electrode connected to the first end face of the wafer 1, the metal electrode includes a first metal layer 2, a second metal layer 3, a third metal layer 4 and a fourth metal layer 5, and the first metal layer 2, the second metal layer 3, the third metal layer 4 and the fourth metal layer 5 are arranged in sequence along a direction away from the first end face.
[0030] The etching method comprises the following steps:
[0031] Step 1: Sputtering is performed on the first end face to form a first metal layer 2, and then sputtering and electroplating are performed in sequence to form a second metal layer 3, followed by sputtering to form a third metal layer 4, and finally, sputtering or evaporation is performed to form a fourth metal layer 5.
[0032] Wherein, the first metal layer 2 is a Ti (titanium) metal layer, and the thickness of the first metal layer 2 is 1000A-2000A (angstroms). The second metal layer 3 is a Cu (copper) metal layer, and the thickness of the second metal layer 3 is 1.5μm-2μm (micrometers). The third metal layer 4 is a Ti metal layer, and the thickness of the third metal layer 4 is 1000A-2000A (angstroms). The fourth metal layer 5 is an Au (gold) metal layer, and the thickness of the fourth metal layer 5 is 3000A-8000A.
[0033] Step 2: After the metal electrode deposition is completed on the wafer 1, the first yellow light etching (i.e., photolithography) is performed on the first end face. During the first yellow light etching process, the thickness of the photoresist 6 is 2μm-6μm, and the first mask is sequentially exposed, developed, and hardened, and the exposure time lasts for 18S (seconds)-42S. During the exposure process, the pattern on the first mask is formed on the wafer 1 after exposure, and the development adopts a positive photoresist developer. The hardening temperature during hardening is 100℃-115℃ (degrees Celsius), preferably 107℃, and the hardening duration is 1 minute.
[0034] Step 3: After the exposure is completed, wet etching is continued. First, Au etching solution is used for etching and the etching lasts for 3-6 minutes, preferably 5 minutes, and then water is rinsed and dried to achieve drying; then, Ti etching solution is used for etching and the etching lasts for 7-30 seconds, preferably 25 seconds, and then water is rinsed and dried to achieve drying; then, Cu etching solution is used for etching and the etching lasts for 7-10 minutes, preferably 9 minutes, and then water is rinsed and dried to achieve drying.
[0035] Exemplarily, the Ti etching solution includes HF (hydrogen fluoride) and H2O (water), and the mass ratio of HF to H2O is preferably 1:50. The Cu etching solution includes phosphoric acid, glacial acetic acid, nitric acid and water, and the mass ratio of phosphoric acid, glacial acetic acid, nitric acid and water is preferably 30:2:1:8. The Au etching solution includes KI (potassium iodide) and I (iodine), and the mass ratio of potassium iodide to iodine is preferably 1:2.
[0036] The three etching solutions only etch the corresponding metal layers. For example, the Ti etching solution only etches the first metal layer 2 and the third metal layer 4 , the Cu etching solution etches the second metal layer 3 , and the Au etching solution etches the fourth metal layer 5 .
[0037] Step 4: After the wet etching is completed, the photoresist 6 is removed by wet etching to achieve the purpose of photoresist removal.
[0038] Step 5: Perform a second yellow light etching on the first end face, and expose the second mask. The size of the second mask is larger than that of the first mask, so that the four edges of the second mask are larger than the corresponding positions of the four edges of the first mask by a preset threshold. The preset threshold can be set to 1μm, that is, the four edges of the second mask are located outside the four edges of the first mask, and the four edges of the second mask are located within 1μm of the four edges of the first mask. The purpose of this setting is to protect the side walls of the second metal layer 3, the third metal layer 4 and the fourth metal layer 5 formed by the first yellow light etching through the second mask, and to serve as a barrier layer for the first metal layer 2.
[0039] refer to Figure 3 , Figure 3 The yellow color in the figure shows the schematic diagram of the photoresist 6 used in the second yellow light etching process. The photoresist 6 covers the top surface of the fourth metal layer 5 and also covers the side walls of the second metal layer 3-fourth metal layer 5, so that the side walls of the second metal layer 3-fourth metal layer 5 can be protected by the photoresist 6. In this way, the second mask covering the photoresist 6 can protect the side walls of the second metal layer 3-fourth metal layer 5, and also serves as a barrier layer for the first metal layer 2 to prevent the photoresist 6 from affecting the first metal layer 2.
[0040] Step 6: After the exposure is completed, wet etching is continued, and Ti etching solution is used to continue etching for 25 seconds, and then rinsed and dried to achieve drying.
[0041] Step 7: Use a wet stripping method to remove the photoresist 6, thereby removing the barrier layer to obtain the final first metal layer 2 and complete the processing.
[0042] The present invention performs two yellow light etchings, and the second yellow light etching uses a larger second mask, thereby effectively avoiding the problem of metal layer shedding and exposure caused by traditional one-time etching on the intermediate metal layer, improving the appearance of the wafer structure and the performance stability of the wafer structure, reducing production costs, and improving production efficiency.
[0043] The embodiment disclosed in this specification is only an example of a unilateral feature of the present invention, and the protection scope of the present invention is not limited to this embodiment, and any other functionally equivalent embodiments fall within the protection scope of the present invention. For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.
Claims
1. A method for etching a wafer structure, characterized in that: The wafer structure includes a wafer, the wafer includes a back cavity, the back cavity includes a TSV structure, the end face where the back cavity is located is recorded as a first end face, and a metal electrode connected to the first end face of the wafer, the metal electrode includes a first metal layer, a second metal layer, a third metal layer and a fourth metal layer, the first metal layer, the second metal layer, the third metal layer and the fourth metal layer are arranged in sequence along a direction away from the first end face, The etching method comprises the following steps: Step 1: Processing to form the metal electrode; Step 2: After the metal electrode is deposited on the wafer, the first end surface is subjected to the first yellow light etching. During the first yellow light etching process, the first mask is sequentially exposed, developed and hardened; Step 3: After the exposure is completed, each metal layer is wet-etched using Au etching solution, Ti etching solution and Cu etching solution respectively; Step 4: After the wet etching is completed, the photoresist is removed by wet method; Step 5: Perform a second yellow light etching on the first end surface to expose the second mask, the size of the second mask is larger than the first mask, so that the edges of the second mask are larger than the corresponding positions of the edges of the first mask by a preset threshold; Step 6: After the exposure is completed, Ti etching solution is used to continue etching; Step 7: Use wet stripping to remove the photoresist, thereby removing the barrier layer, obtaining the final first metal layer, and completing the processing.
2. The etching method of the wafer structure according to claim 1, characterized in that: In step 1, the metal electrode is formed by processing, and its specific implementation process includes the following steps: Sputtering is performed on the first end surface to form a first metal layer, then sputtering and electroplating are performed in sequence to form a second metal layer, then sputtering is performed to form a third metal layer, and finally sputtering or evaporation is performed to form a fourth metal layer, The first metal layer is a Ti metal layer, the second metal layer is a Cu metal layer, the third metal layer is a Ti metal layer, and the fourth metal layer is an Au metal layer.
3. The etching method of the wafer structure according to claim 2, characterized in that: The thickness of the first metal layer is 1000A-2000A, the thickness of the second metal layer is 1.5μm-2μm, the thickness of the third metal layer is 1000A-2000A, and the thickness of the fourth metal layer is 3000A-8000A.
4. The etching method of the wafer structure according to claim 3, characterized in that: In step 2, during the first yellow light etching process, the thickness of the photoresist is 2 μm-6 μm, the exposure time lasts for 18S-42S, the development adopts a positive photoresist developer, the hardening temperature during hardening is 100° C.-115° C., and the hardening duration is 1 minute.
5. The etching method of the wafer structure according to claim 4, characterized in that: In step 3, the Au etching solution, the Ti etching solution and the Cu etching solution are respectively used to wet-etch each metal layer, and the specific implementation process includes the following steps: First, use Au etching solution to etch for 3-6 minutes, then rinse with water and spin dry to achieve drying; then, use Ti etching solution to etch for 7-30 seconds, then rinse with water and spin dry to achieve drying; then, use Cu etching solution to etch for 7-10 minutes, then rinse with water and spin dry to achieve drying.
6. The etching method of the wafer structure according to claim 5, characterized in that: The Ti etching solution includes HF and H2O, and the mass ratio of HF to H2O is 1:
50. The Cu etching solution includes phosphoric acid, glacial acetic acid, nitric acid and water, and the mass ratio of phosphoric acid, glacial acetic acid, nitric acid and water is 30:2:1:
8. The Au etching solution includes potassium iodide and iodine, and the mass ratio of potassium iodide to iodine is 1:
2.
7. The etching method of the wafer structure according to claim 6, characterized in that: In step 6, etching is continued with Ti etching solution for 25 seconds, and then flushing and drying are performed to achieve drying.