Ag / Ni corrosive liquid as well as preparation and use methods thereof

Abstract

The invention relates to an Ag / Ni corrosive liquid and a preparation and use method thereof, and belongs to the technical field of semiconductor manufacturing. The technical problems that in the prior art, due to the fact that an Ag / Ni corrosive liquid is often corroded uncleanly, and the side tracking of an Ni layer is too large relative to the Ag layer, metal peeling and other abnormalities happen to the Ag layer are solved. The Ag / Ni corrosive liquid disclosed by the invention consists of 40 to 60 weight percent of glacial acetic acid, 15 to 25 weight percent of nitric acid, 0.001 to 1 weight percent of hydrofluoric acid and the balance of water. The Ag / Ni corrosive liquid can simultaneously corrode Ag, Ni and oxides of Ni at one time, the relative corrosion rate of Ag and Ni cannot be greatly increased, and after Ti is corroded by using an HF aqueous solution in the next step, good relative sidetracking can be formed by three metals of Ag, Ni and Ti.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor manufacturing technology, specifically relating to an Ag / Ni etching solution and its preparation and application methods. Background Technology

[0002] During chip manufacturing, one or two layers of metal are often deposited on the chip surface for subsequent soldering. After the deposition is completed, some areas need to be covered with photoresist through photolithography, and the remaining areas are cleaned by wet etching or dry etching to remove excess metal, so as to ensure that there is no metal conduction between the individual chips.

[0003] Compared with dry etching, wet etching has the advantages of lower cost and higher yield. However, due to the fluidity of the etching solution and the differences in various locations during the etching process, there will be significant differences between wafers and between different points on each wafer. Therefore, the amount of etching and the morphology of the side-drilled surface are often difficult to control.

[0004] Currently, when Ag / Ni etchant is used to etch metallic Ni, occasional fluctuations in the previous process and the state of the etchant often lead to incomplete etching, which in turn causes current breakdown. Furthermore, the etchant that can etch Ni and its oxides also increases the side-drilling capacity of Ni relative to Ag, resulting in abnormalities such as metal peeling during subsequent processing. Summary of the Invention

[0005] To address the technical problems frequently encountered in existing Ag / Ni etchants, such as incomplete corrosion and excessive Ni layer relative to Ag layer during side drilling, leading to abnormalities like metal peeling in the Ag layer, this invention provides an Ag / Ni etchant and its preparation and application methods.

[0006] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows.

[0007] In a first aspect, the present invention provides an Ag / Ni etching solution (120-F etching solution) composed of 40wt%~60wt% glacial acetic acid (CH3COOH), 15wt%~25wt% nitric acid (HNO3), 0.001wt%~1wt% hydrofluoric acid (HF) and the balance being water.

[0008] Preferably, it consists of 45wt%~60wt% glacial acetic acid, 17wt%~25wt% nitric acid, 0.001wt%~0.2wt% hydrofluoric acid, and the balance being water.

[0009] More preferably, it consists of 50wt%~60wt% glacial acetic acid, 19wt%~25wt% nitric acid, 0.001wt%~0.1wt% hydrofluoric acid, and the balance being water.

[0010] Particularly preferred is a composition of 55wt%~60wt% glacial acetic acid, 21wt%~25wt% nitric acid, 0.001wt%~0.05wt% hydrofluoric acid, and the balance being water.

[0011] The most preferred composition is 58wt%~60wt% glacial acetic acid, 23wt%-25wt% nitric acid, 0.005wt%~0.02wt% hydrofluoric acid, and the balance being water.

[0012] It should be noted that the glacial acetic acid, nitric acid, and hydrofluoric acid mentioned are measured in pure molar amounts.

[0013] Secondly, the present invention also provides a method for preparing the above-mentioned Ag / Ni etching solution, the steps of which are as follows:

[0014] Weigh each raw material according to its composition, mix them evenly, and obtain Ag / Ni etching solution.

[0015] It should be noted that in the preparation method of the Ag / Ni etching solution of the present invention, the raw material ratio of glacial acetic acid, nitric acid and hydrofluoric acid can be a pure substance ratio or an aqueous solution, as long as the final ratio of each component in the Ag / Ni etching solution can be guaranteed.

[0016] Thirdly, the present invention also provides a method for using the above-mentioned Ag / Ni etching solution, wherein a silicon wafer with an Ag / Ni metal layer is immersed in the Ag / Ni etching solution at room temperature for 300s to 600s, and then rinsed and dried to obtain a silicon wafer (chip) after Ag / Ni etching.

[0017] It should be noted that the Ag / Ni metal layer needs to have an exposed surface. For example, the topmost and second-topmost layers of the silicon wafer with the Ag / Ni metal layer are Ag and Ni layers, respectively. Preferably, the silicon wafer with the Ag / Ni metal layer includes an Ag layer, a Ni layer, and a Ti layer arranged sequentially from top to bottom. More preferably, it comprises an Ag layer, a Ni layer, a Ti layer, an Al layer, a barrier Ti layer, and a silicon wafer arranged sequentially from top to bottom.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] The Ag / Ni etchant of this invention can simultaneously etch Ag, Ni, and Ni oxides in one step without significantly increasing the relative corrosion rate of Ag and Ni. Furthermore, after etching Ti with an HF aqueous solution in the next step, it enables the three metals Ag, Ni, and Ti to form a good relative side-drilling effect.

[0020] The method of using the Ag / Ni etching solution of the present invention is safe and easy to operate.

[0021] The Ag / Ni etching solution of the present invention is applicable to the etching of Ag, Ni and Ni oxides on various silicon wafers with Ag / Ni metal layers, and there are no special limitations on the structure of the silicon wafer. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the silicon wafer with an Ag / Ni metal layer used in Comparative Examples 1-2 and Examples 1-3 of the present invention.

[0023] Figure 2 The corrosion rate of the Ag layer by the mixed acid 120 in Comparative Example 1 of this invention is shown.

[0024] Figure 3 The corrosion rate of the Ag / Ni etchant on the Ag layer in Example 1 of this invention is shown.

[0025] Figure 4 This is a cross-sectional electron microscope image of the silicon wafer with an Ag / Ni metal layer obtained after etching with mixed acid 120 in Comparative Example 1 of the present invention.

[0026] Figure 5 This is a cross-sectional electron microscope image of the silicon wafer after it has been cut open, obtained by etching the silicon wafer with the Ag / Ni metal layer using Ag / Ni etchant in Example 1 of the present invention.

[0027] Figure 6 This is an electron microscope image of the cross-section of a silicon wafer with an Ag / Ni metal layer obtained by etching it with Ag / Ni etchant in Example 1 of the present invention after the core particle is subjected to tensile stress.

[0028] Figure 7 This is a cross-sectional electron microscope image of the silicon wafer after it has been cut open, obtained by etching the silicon wafer with the Ag / Ni metal layer using Ag / Ni etchant in Example 2 of the present invention.

[0029] Figure 8 This is a cross-sectional electron microscope image of the silicon wafer after it has been cut open, obtained by etching the silicon wafer with the Ag / Ni metal layer using Ag / Ni etchant in Example 3 of the present invention. Detailed Implementation

[0030] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to embodiments.

[0031] In the following embodiments, various processes and methods not described in detail are conventional methods known in the art. Unless otherwise specified, the materials, reagents, apparatus, instruments, equipment, etc., used in the following embodiments are commercially available.

[0032] Comparative Example 1

[0033] The structure of the silicon wafer with an Ag / Ni metal layer used is as follows: Figure 1 As shown, from bottom to top, the layers are: a 725μm silicon wafer (i.e., a non-metallic layer), a 0.1μm Ti layer (which forms a potential barrier with the non-metallic layer under nitrogen atmosphere at 800℃), a 4μm Al layer, a 1μm Ti layer, a 2μm Ni layer, and a 15μm Ag layer.

[0034] The fabrication of the silicon wafer with the Ag / Ni metal layer is a prior art technique, which includes: firstly, sputtering metal Ti onto a non-metallic layer to obtain a Ti layer; treating the Ti layer in a nitrogen atmosphere at 800°C to form a barrier; then sputtering metal Al onto the Ti layer to form an Al layer; removing excess metal (part of the Ti layer and Al layer) using photolithography etching to open the dicing path; then sequentially depositing a Ti layer, a Ni layer, and an Ag layer on the Al layer from bottom to top; and finally revealing the area to be etched using photolithography to obtain the silicon wafer with the Ag / Ni metal layer.

[0035] A silicon wafer with an Ag / Ni metal layer is placed on a wet etching machine (tank type). The silicon wafer with the Ag / Ni metal layer is immersed in a tank filled with existing mixed acid 120 (Jiangsu Jingjiu Microelectronics Materials Co., Ltd.) for etching at room temperature for 500 seconds. After that, it is rinsed with water and dried to obtain a silicon wafer with Ag / Ni etched.

[0036] The silicon wafer after etching Ag / Ni was placed in a 0.5wt% HF aqueous solution to etch away the Ti layer. After rinsing and drying, the etching of the three metals was completed, and the chip preparation was finished.

[0037] Cross-sectional electron micrographs of the core particles prepared in Comparative Example 1 were taken by cutting them open. The results are as follows: Figure 4 As shown. From Figure 4 It can be seen that Ni is prominent but Ti is large in the side-drilling section.

[0038] Comparative Example 2

[0039] The mixed acid 120 in Comparative Example 1 was replaced with Ag / Ni etching solution, and the etching time was replaced with 400s. Everything else was the same as in Comparative Example 1. The Ag / Ni etching solution consisted of 20wt% glacial acetic acid, 25wt% nitric acid, 0.3wt% hydrofluoric acid, and the balance being water.

[0040] Observations showed that the Ag / Ni etching solution in Comparative Example 2 had a fast etching rate for both Ag and Ni. The Ag etching rate was about 5 times that of the mixed acid 120 in Comparative Example 1. The Ag etching rate was too fast, making the reaction difficult to control and preventing the formation of electron micrographs.

[0041] Example 1

[0042] The mixed acid 120 in Comparative Example 1 was replaced with Ag / Ni etching solution, and the etching time was replaced with 400s. Everything else was the same as in Comparative Example 1. The Ag / Ni etching solution consisted of 60wt% glacial acetic acid, 25wt% nitric acid, 0.3wt% hydrofluoric acid, and the balance being water.

[0043] Observations showed that the corrosion rate of the Ag / Ni etching solution in Example 1 on the Ag layer was approximately similar to that of mixed acid 120 on the Ag layer. The corrosion rate results for Comparative Example 1 and Example 1 are as follows: Figure 2 and Figure 3 As shown, each solution was measured 15 times, with 9 points measured each time. The final conclusion was that the corrosion rates of the two solutions on the Ag layer were basically the same.

[0044] Cross-sectional electron micrographs of the core particles prepared in Example 1, taken by cutting them open, are shown in the following results. Figure 5 As shown. From Figure 5 It can be seen that the excessively high HF content in the solution leads to a relatively large Ni layer metal size compared to the side-drilled layer. Voids are created between the Ag layer and the underlying layer. During subsequent processing, when the core is subjected to tensile stress, the Ag layer warps, causing metal peeling, such as... Figure 6 As shown.

[0045] Example 2

[0046] The mixed acid 120 in Comparative Example 1 was replaced with Ag / Ni etching solution, and the etching time was replaced with 400s. Everything else was the same as in Comparative Example 1. The Ag / Ni etching solution consisted of 60wt% glacial acetic acid, 25wt% nitric acid, 0.2wt% hydrofluoric acid, and the balance being water.

[0047] Observations showed that the Ag / Ni etchant in Example 2 had a corrosion rate for Ag that was approximately similar to that of Mixed Acid 120.

[0048] Cross-sectional electron micrographs of the core particles prepared in Example 2, taken by cutting them open, show the following results: Figure 7 As shown, reducing the HF content in the solution improved the Ni layer side-drilling to some extent.

[0049] Example 3

[0050] The mixed acid 120 in Comparative Example 1 was replaced with Ag / Ni etching solution, and the etching time was 500s. Everything else was the same as in Comparative Example 1. The Ag / Ni etching solution consisted of 60wt% glacial acetic acid, 25wt% nitric acid, 0.01wt% hydrofluoric acid, and the balance being water.

[0051] Observations showed that the corrosion rate of Ag by the Ag / Ni etchant in Example 3 was approximately similar to that of Mixed Acid 120.

[0052] Cross-sectional electron micrographs of the core particles prepared in Example 3 were taken by cutting them open. The results are as follows: Figure 8 As shown, the three metals are almost level, with the bottom two layers protruding slightly from Ag. The three metals are tightly bonded together, preventing any peeling.

[0053] In summary, the etching solution first etches away the Ag layer, creating side-drilling patterns on both sides of the exposed area in the Ag layer. The etching solution then continues to etch downwards into the Ni layer, where side-drilling patterns also begin to appear. Since the Ag layer remains immersed in the etching solution, these side-drilling patterns continue to grow. Once the Ni layer is completely etched, the Ag layer side-drilling pattern is still larger than the Ni layer side-drilling pattern, and the Ti layer has not been extensively etched, the silicon wafer is removed, rinsed, and dried. The glacial acetic acid content determines the Ag etching rate, while the hydrofluoric acid content controls the relative etching rates between Ag and Ni. The etching time and temperature ensure complete metal etching under the given conditions.

[0054] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the embodiments. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all embodiments here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An Ag / Ni etching solution, characterized in that, It consists of 40wt%~60wt% glacial acetic acid, 15wt%~25wt% nitric acid, 0.001wt%~1wt% hydrofluoric acid, and the balance being water.

2. The Ag / Ni etching solution according to claim 1, characterized in that, It consists of 45wt%~60wt% glacial acetic acid, 17wt%~25wt% nitric acid, 0.001wt%~0.2wt% hydrofluoric acid, and the balance being water.

3. The Ag / Ni etching solution according to claim 2, characterized in that, It consists of 50wt%~60wt% glacial acetic acid, 19wt%~25wt% nitric acid, 0.001wt%~0.1wt% hydrofluoric acid, and the balance being water.

4. The Ag / Ni etching solution according to claim 3, characterized in that, It consists of 55wt%~60wt% glacial acetic acid, 21wt%~25wt% nitric acid, 0.001wt%~0.05wt% hydrofluoric acid, and the balance being water.

5. The Ag / Ni etching solution according to claim 4, characterized in that, It consists of 58wt%~60wt% glacial acetic acid, 23wt%-25wt% nitric acid, 0.005wt%~0.02wt% hydrofluoric acid, and the balance being water.

6. The method for preparing the Ag / Ni etching solution according to any one of claims 1-5, characterized in that, The steps are as follows: Weigh each raw material according to its composition, mix them evenly, and obtain Ag / Ni etching solution.

7. The method of using the Ag / Ni etching solution according to any one of claims 1-5, characterized in that, The silicon wafer with the Ag / Ni metal layer is immersed in the Ag / Ni etching solution at room temperature for 300s~600s, and then rinsed and dried to obtain the silicon wafer after Ag / Ni etching.

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