A method for monitoring the quality of a chemical plating layer of a wafer

Abstract

The present application relates to a kind of methods for monitoring wafer chemical plating quality, comprising: providing the wafer of surface has formed chemical plating, and chemical plating includes first metal layer and the second metal layer on the surface of first metal layer, and second metal layer is formed using different metal elements with first metal layer;In the surface of second metal layer of wafer paste film, the wafer after pasting film is continuously heated within a predetermined time, after heating a period of time, film is stripped, then using microscope observes the surface of second metal layer, if observing there is local chromatic aberration, then indicate that the plating quality of first metal layer is abnormal.If the surface of first metal layer produces sharp spike defect, then second metal layer plating solution can penetrate into it along the gap of sharp spike defect, the gas volatilized in the gap of wafer after heating plating solution cannot escape and continuously corrodes the adhesive layer of film surface and the surface of second metal layer under the microscope can be observed to form local chromatic aberration on the surface of second metal layer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically to a method for monitoring the quality of chemical plating on wafers. Background Technology

[0002] In the manufacturing process of semiconductor devices, the metallization layer on the chip surface is often formed using chemical plating. For example, the nickel layer on the chip surface is mostly formed by chemical nickel plating. When using chemical plating, the temperature and reaction rate of the plating solution have a significant impact on the quality of the plating layer. When the wafer is placed in the chemical plating solution, if there is a significant difference in the chemical plating rate on the wafer surface, uneven plating deposition will occur at the lattice junctions of the wafer, forming sharp-shaped plating defects (such as…). Figure 1 As shown in the image, this spike-like defect affects the quality of the coating and poses a potential threat to the reliability of semiconductor devices. This spike-like defect is difficult to detect both macroscopically and microscopically, making it challenging to monitor the quality of chemical plating in actual production. Summary of the Invention

[0003] This invention discloses a method for monitoring the quality of chemical plating on wafers, which can be used in actual production to inspect whether there are spike-like defects in the chemical plating. Controlling the quality of the chemical plating through this method can help improve the reliability of semiconductor devices.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for monitoring the quality of chemical coatings on wafers includes:

[0006] A wafer with a pre-formed electroless plating layer, the electroless plating layer comprising a first metal layer formed by electroless plating and a second metal layer formed by electroless plating on the surface of the first metal layer, wherein the second metal layer and the first metal layer are formed using different metal elements, characterized in that:

[0007] A film is attached to the surface of the second metal layer of the wafer;

[0008] The wafer after the film is applied is continuously heated for a preset time.

[0009] The film on the heated wafer surface is peeled off;

[0010] The wafer after the film is peeled is placed under a microscope to observe whether there is any color abnormality on the surface of the second metal layer. If local color difference is observed, it indicates that the coating quality of the first metal layer is abnormal.

[0011] Furthermore, the metal element used in the first metal layer is more reactive than the metal element used in the second metal layer.

[0012] Furthermore, the first metal layer is a nickel layer, and the second metal layer is a gold layer.

[0013] Furthermore, the heating temperature is 50℃~90℃.

[0014] Furthermore, the preset time is 30 min to 60 min.

[0015] When using the monitoring methods described above to inspect the quality of the chemical coating on wafers in the same batch during actual production, the following technical solutions can be adopted:

[0016] A method for monitoring the quality of chemical coatings on wafers includes:

[0017] Provides multiple wafers that are simultaneously immersed in the same electroless plating solution to form an electroless plating layer, the electroless plating layer including a first metal layer formed by electroless plating and a second metal layer formed on the surface of the first metal layer by electroless plating, wherein the second metal layer and the first metal layer are formed using different metal elements;

[0018] At least one wafer is selected from multiple wafers that have formed chemical plating layers as an inspection wafer, and a film is applied to the surface of the second metal layer of the inspection wafer.

[0019] The test wafer, after being coated with the film, is continuously heated for a preset time.

[0020] The film on the surface of the heated test wafer is peeled off;

[0021] After the film is peeled off, the test wafer is placed under a microscope to observe whether there is any color abnormality on the surface of the second metal layer. If local color difference is observed, it indicates that the coating quality of the first metal layer of each wafer that was chemically plated together with the test wafer is abnormal.

[0022] Furthermore, the metal element used in the first metal layer is more reactive than the metal element used in the second metal layer.

[0023] Furthermore, the first metal layer is a nickel layer, and the second metal layer is a gold layer.

[0024] Furthermore, the heating temperature is 50℃~90℃.

[0025] Furthermore, the preset time is 30 min to 60 min.

[0026] This invention involves attaching a film to the surface of the second metal layer formed by the second chemical plating process on a wafer, and then heating the wafer. If spike-like defects are present on the surface of the first metal layer formed after the first chemical plating, the second plating solution will seep into the gaps of these defects during the second chemical plating. When the wafer with the film attached is heated, the second plating solution that has seeped into the spike-like defects evaporates due to the heat. The evaporated gas is blocked by the film and cannot escape. The evaporated gas continuously corrodes the adhesive layer on the film surface and the surface of the second metal layer, causing the surface of the second metal layer to form dots with color differences at the locations corresponding to the spike-like defects. After the film is peeled off, the wafer can be observed under a microscope, and the dots with local color differences can be clearly seen. This invention can monitor the quality of the chemical plating layer on the wafer for any abnormalities, enabling timely detection and handling to avoid affecting the reliability of semiconductor devices. Attached Figure Description

[0027] Figure 1 This is a cross-sectional view of the spike-like defects on the wafer surface after electroless nickel plating, which were monitored using the method of the present invention during the production process, observed under a microscope.

[0028] Figure 2 This is a flowchart of the monitoring method in the embodiment. Detailed Implementation

[0029] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0030] This embodiment discloses a method for monitoring the quality of chemical plating on wafers. This method is particularly effective in detecting whether spike-like defects have formed in the chemical plating layer, such as... Figure 2 As shown, the monitoring methods include the following:

[0031] S1: Provides a wafer with a pre-formed chemical plating layer on its surface;

[0032] The aforementioned chemical plating layer includes a first metal layer formed by chemical plating and a second metal layer formed on the surface of the first metal layer by chemical plating, wherein the second metal layer and the first metal layer are formed using different metal elements.

[0033] S2: Apply a film to the surface of the wafer to cover the surface of the second metal layer;

[0034] S3: Continuously heats the wafer after film application for a preset time;

[0035] S4: Peel off the film from the heated wafer surface;

[0036] S5: Place the wafer after stripping under a microscope to observe whether there is any color abnormality on the surface of the second metal layer. If local color difference is observed, it indicates that the coating quality of the first metal layer is abnormal.

[0037] As a further optimization of the above technical solution, the metal element used in the first metal layer mentioned above has a higher reactivity than the metal element used in the second metal layer. For example, the first metal layer is a nickel layer formed by chemical nickel plating, and the second metal layer is a gold layer formed by chemical gold plating.

[0038] To further clarify, the temperature used for heating the wafer mentioned above is 50℃~90℃, and the preset heating time is 30min~60min.

[0039] The method described above can detect whether spike-like defects are generated on the surface of the first metal layer. Taking the first electroless nickel plating and the second electroless gold plating as examples, the principle is explained as follows: When the wafer is placed in the nickel plating solution, if there is a difference in the nickel plating rate on the wafer surface, uneven nickel deposition will cause spike-like defects to form at the lattice junctions. Figure 1 The spike-like defects shown are caused by the fact that when a wafer with spike-like defects is placed in a gold plating solution for gold plating, the gold plating solution seeps into the spike-like defects. When the wafer is heated, the gold plating solution evaporates gas, and the large amount of gas emitted continuously corrodes the adhesive layer on the film surface and the surface of the gold layer. Because a large amount of gold plating solution seeps into the spike-like defects, the gold plating solution in these areas is blocked by the film and accumulates between the gold layer and the film. The gas emitted from the areas corresponding to the spike-like defects is more than that from other areas and the corrosion of the gold layer lasts longer. The color of the gold layer after corrosion forms a significant dotted color difference with other areas. The above phenomenon can be clearly seen under a microscope after the film is peeled off, which can be used to determine whether the plating quality of the first metal layer is abnormal.

[0040] When applying the monitoring methods described above to inspect coating quality in actual production, considering the operability and speed of the inspection methods, the following technical solution can be adopted:

[0041] Step 1: Provide multiple wafers that are simultaneously placed in the same chemical plating solution to form a chemical plating layer. The chemical plating layer includes a first metal layer formed by chemical plating and a second metal layer formed on the surface of the first metal layer by chemical plating. The second metal layer and the first metal layer are formed using different metal elements.

[0042] The metal element used in the first metal layer is more reactive than the metal element used in the second metal layer. For example, the first metal layer is a nickel layer formed by electroless nickel plating, and the second metal layer is a gold layer formed by electroless gold plating.

[0043] Step 2: Select at least one wafer from the multiple wafers that have completed Step 1 as the test wafer, and apply a film to the second metal layer surface of the test wafer;

[0044] When the number of wafers that have completed electroless plating in the same batch is large (i.e., the number of wafers that have formed an electroless plating layer is large), such as dozens of wafers, a few wafers can be randomly selected from the large number of wafers as test wafers to improve the accuracy of the monitoring method; when the number of wafers that have formed an electroless plating layer is small, such as a few to a dozen wafers, one wafer can be randomly selected as a test wafer.

[0045] Step 3: Apply a film only to the surface of the test wafer, so that the film covers the surface of the second metal layer of the test wafer;

[0046] Step 4: Continuously heat the test wafer after film application for a preset time;

[0047] For example, the temperature used for heating is 50℃~90℃, and the preset heating time is 30min~60min.

[0048] Step 5: Peel off the film on the surface of the heated test wafer;

[0049] Step 6: Place the stripped test wafer under a microscope to observe whether there is any color abnormality on the surface of its second metal layer. If local color difference is observed, it indicates that the plating quality of the first metal layer of each wafer that was chemically plated together with the test wafer is abnormal.

[0050] In the above-described scheme, for wafers in the same batch that are simultaneously placed in the electroless plating solution, the process conditions are the same each time. Randomly selecting wafers as test wafers to monitor the coating quality after the first electroless plating is representative. In actual production, there are a large number of wafers undergoing electroless plating in the same batch. Inspecting only the selected test wafers can save time on film application and peeling. After the test wafers are used up, they can be directly scrapped, or the residual adhesive and coating on the surface after peeling can be removed and they can be reused.

[0051] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for monitoring the quality of chemical coatings on wafers, comprising: A wafer with a pre-formed electroless plating layer, the electroless plating layer comprising a first metal layer formed by electroless plating and a second metal layer formed by electroless plating on the surface of the first metal layer, wherein the second metal layer and the first metal layer are formed using different metal elements, characterized in that: A film is attached to the surface of the second metal layer of the wafer; The wafer after the film is applied is continuously heated for a preset time; The film on the heated wafer surface is peeled off; The wafer after the film is peeled is placed under a microscope to observe whether there is any color abnormality on the surface of the second metal layer. If local color difference is observed, it indicates that the coating quality of the first metal layer is abnormal.

2. The method for monitoring the quality of chemical coatings on wafers according to claim 1, characterized in that: The metal element used in the first metal layer is more reactive than the metal element used in the second metal layer.

3. The method for monitoring the quality of chemical coatings on wafers according to claim 2, characterized in that: The first metal layer is a nickel layer, and the second metal layer is a gold layer.

4. The method for monitoring the quality of chemical coatings on wafers according to claim 1, characterized in that: The heating temperature is 50℃~90℃.

5. A method for monitoring the quality of a wafer chemical plating layer according to claim 1 or 4, characterized in that: The preset time is 30 min to 60 min.

6. A method for monitoring the quality of chemical coatings on wafers, characterized in that, include: Provides multiple wafers that are simultaneously immersed in the same electroless plating solution to form an electroless plating layer, the electroless plating layer including a first metal layer formed by electroless plating and a second metal layer formed on the surface of the first metal layer by electroless plating, wherein the second metal layer and the first metal layer are formed using different metal elements; At least one wafer is selected from multiple wafers that have formed chemical plating layers as an inspection wafer, and a film is applied to the surface of the second metal layer of the inspection wafer. The test wafer, after being coated with the film, is continuously heated for a preset time. The film on the surface of the heated test wafer is peeled off; After the film is peeled off, the test wafer is placed under a microscope to observe whether there is any color abnormality on the surface of the second metal layer. If local color difference is observed, it indicates that the coating quality of the first metal layer of each wafer that was chemically plated together with the test wafer is abnormal.

7. The method for monitoring the quality of a wafer chemical plating layer according to claim 6, characterized in that: The metal element used in the first metal layer is more reactive than the metal element used in the second metal layer.

8. The method for monitoring the quality of chemical coatings on wafers according to claim 7, characterized in that: The first metal layer is a nickel layer, and the second metal layer is a gold layer.

9. The method for monitoring the quality of a wafer chemical plating layer according to claim 6, characterized in that: The heating temperature is 50℃~90℃.

10. A method for monitoring the quality of a wafer chemical coating according to claim 6 or 9, characterized in that: The preset time is 30 min to 60 min.

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