Method of removing bump balls from a sample surface
By cutting the top Al layer of the chip and combining it with a wet process to remove the bump balls, the problem of time-consuming and easily scratched processes in existing technologies is solved, achieving rapid and efficient sample processing.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SHANGHAI HUALI INTEGRATED CIRCUIT CORP
- Filing Date
- 2026-03-11
- Publication Date
- 2026-06-30
AI Technical Summary
Existing technologies are time-consuming and prone to scratching samples when removing bump balls from the surface of semiconductor chips, making it difficult to achieve efficient processing.
The softer top Al layer of the chip is cut with a cutting tool to remove the top Al layer, passivation layer and bump balls. The remaining Al layer is then treated with dilute hydrochloric acid using a wet process, taking advantage of the softness of Al material to bypass the bump balls and process it directly.
It significantly shortens the processing time and improves the preparation efficiency, reducing the processing time from 0.5-1.5 hours to 5 minutes and avoiding sample scratches.
Smart Images
Figure CN122307301A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of semiconductor integrated circuit manufacturing, and in particular to a method for removing bumps from the surface of a sample. Background Technology
[0002] In semiconductor failure analysis, engineers need to manually remove layers from the chip down to the layer to be analyzed, and then perform electrical or physical failure analysis. For wafer samples with bump balls soldered to the surface, the large size of the bump balls makes grinding time lengthy and can easily scratch the sample.
[0003] Existing methods for removing bumps from sample surfaces include: The first method is a physical method, using sandpaper for grinding. The disadvantage of the first method is that removing the bump balls is time-consuming, with a processing time of 0.5 to 1 hour, and it is easy to over-grind and scratch the sample.
[0004] The second method is a physical and chemical approach, such as reactive ion etching (RIE) combined with aqua regia heating reaction. The disadvantage of the existing second method is that removing the bump ball is time-consuming, with a processing time of 1.5 hours. Engineers need to wear PPE properly for the acid boiling operation, which is not breathable. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a method for removing bumps from the surface of a sample, which has the advantages of being simple and quick, and can greatly shorten the processing time and thus greatly improve the preparation efficiency.
[0006] To solve the above-mentioned technical problems, the present invention provides a method for removing bumps from the surface of a sample, comprising the following steps: Provide the sample to be analyzed and confirm the target location of the sample. The sample includes a semiconductor substrate, a metal interconnect layer, a top Al layer and a passivation layer, with a plurality of bump balls formed on the surface of the passivation layer.
[0007] Taking advantage of the relatively soft Al in the top Al layer, a cutting tool is used to cut the top Al layer to remove the passivation layer and the bump ball above the top Al layer.
[0008] The remaining top Al layer after the cutting is removed using a wet process.
[0009] A further improvement is that, prior to the cutting, the following steps are included: The sample was fixed to the stage using adhesive tape.
[0010] A further improvement is that, before fixing the sample, the following steps are also included: The target location of the sample is confirmed by an optical microscope (OM). After the sample is fixed, the target location is exposed and used for cutting.
[0011] A further improvement is that the cutting process also includes: Use an air gun to blow away the residue that has been cut off to prevent scratching the sample.
[0012] A further improvement is that, after the cutting is completed, the process further includes: The optical microscope is used to confirm whether the top surface within the area of the target location is in the top Al layer.
[0013] A further improvement is that the etching solution used in the wet process is dilute hydrochloric acid.
[0014] A further improvement is that the top A1 layer is used as a redistribution layer (RDL).
[0015] A further improvement is that the passivation layer includes a silicon oxide passivation layer and a silicon nitride passivation layer.
[0016] A further improvement is that a top opening is formed in the passivation layer at the bottom of each of the bump balls; a bump under metal layer (UBM) is formed on the inner surface of the top opening, and the bump under metal layer extends to the surface of the passivation layer outside the top opening.
[0017] A further improvement is that the metal layer under the bump includes a first copper layer and a first nickel layer stacked sequentially.
[0018] A further improvement is that the material of the bump ball includes tin.
[0019] A further improvement is that the semiconductor substrate comprises a silicon substrate.
[0020] A further improvement is that the metal interconnect layer comprises multiple copper layers, which are connected by vias and isolated by interlayer films.
[0021] Unlike existing methods that use layer-by-layer removal to process samples, this invention utilizes the characteristic of the chip sample having a softer top Al layer, meaning the Al material is softer than the bump ball material. This allows the top Al layer to be directly cut with a cutting tool. This invention removes the passivation layer and bump balls above the top Al layer by cutting the top Al layer, thus bypassing the more difficult-to-remove bump balls. Compared to the process of directly removing the bump balls, the cutting process of the top Al layer has the advantages of being simple and fast, which can greatly shorten the processing time and thus greatly improve the preparation efficiency. For example, this invention can reduce the processing time to 5 minutes. Attached Figure Description
[0022] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: Figure 1 This is a flowchart of a method for removing bumps from the sample surface according to an embodiment of the present invention; Figure 2 This is a top view of the sample before cutting in the method for removing bump balls from the sample surface in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the sample before cutting in the method for removing bump balls from the sample surface in an embodiment of the present invention; Figure 4 yes Figure 3 Enlarged view of the bump sphere in the middle; Figure 5 This is a schematic diagram of the sample fixation process before cutting in the method for removing bump balls from the sample surface according to an embodiment of the present invention; Figure 6 This is a cross-sectional view of the sample after cutting in the method for removing bump balls from the sample surface in an embodiment of the present invention; Figure 7 This is a top view of the sample after cutting in the method for removing bump balls from the sample surface in an embodiment of the present invention. Detailed Implementation
[0023] like Figure 1 The diagram shown is a flowchart of a method for removing bump balls 103 from the surface of sample 101 according to an embodiment of the present invention; as shown... Figure 2 This is a top view of sample 101 before cutting in the method for removing bump balls 103 from the surface of sample 101 according to an embodiment of the present invention; as shown. Figure 3 The image shown is a cross-sectional view of sample 101 before cutting in the processing method for removing bump balls 103 from the surface of sample 101 according to an embodiment of the present invention. Figure 4 yes Figure 3 Enlarged view of the bump ball 103 in the middle; the method for removing the bump ball 103 from the surface of sample 101 according to an embodiment of the present invention includes the following steps: Step S101, as follows Figure 3 As shown, a sample 101 to be analyzed is provided and the target location of the sample 101 is confirmed. The sample 101 includes a semiconductor substrate 108, a metal interconnect layer 105, a top Al layer 104 and a passivation layer 102. A plurality of bump balls 103 are formed on the surface of the passivation layer 102.
[0024] In this embodiment of the invention, the semiconductor substrate 108 includes a silicon substrate.
[0025] The metal interconnect layer 105 includes multiple copper layers 106, which are connected by vias and isolated by interlayer films 107.
[0026] In embodiments of the present invention, such as Figure 4 As shown, the top Al layer 104 serves as a rewiring layer. Figure 4 The diagram shows the metal interconnect layer 105 and the semiconductor substrate 108 at the bottom of the top Al layer 104, represented by an underlying structure 111.
[0027] In some embodiments, the passivation layer 102 includes a silicon oxide passivation layer 102a and a silicon nitride passivation layer 102b.
[0028] A top opening is formed in the passivation layer 102 at the bottom of each of the bump balls 103; a bump under-metal layer is formed on the inner surface of the top opening, and the bump under-metal layer extends to the surface of the passivation layer 102 outside the top opening.
[0029] In some embodiments, the under-bump metal layer comprises a first copper layer 109 and a first nickel layer 110 stacked sequentially. The material of the bump ball 103 includes tin.
[0030] In this embodiment of the invention, it further includes: Figure 5 As shown, the sample 101 is fixed on the stage 201 using tape 202.
[0031] Before fixing the sample 101, the process also includes: The target position of the sample 101 is confirmed by an optical microscope. After the sample 101 is fixed, the target position is exposed and used for cutting.
[0032] Step S102, as follows Figure 4 As shown, taking advantage of the relatively soft Al in the top Al layer 104, a cutting tool 203 is used to cut the top Al layer 104 to remove the passivation layer 102 and the bump ball 103 above the top Al layer 104.
[0033] In this embodiment of the invention, the cutting process further includes: Use an air gun to blow away the residue that has been cut off to prevent scratching sample 101.
[0034] like Figure 6 As shown, after the cutting is completed, the process also includes: The optical microscope is used to confirm whether the top surface within the area of the target location is in the top Al layer 104.
[0035] Step S103: Remove the remaining top Al layer 104 after cutting using a wet process.
[0036] In some embodiments, the etching solution used in the wet process is dilute hydrochloric acid.
[0037] In order to complete the failure analysis, we can then use existing known processes to locate the failure location and confirm the cause of the failure.
[0038] Unlike existing methods that use layer-by-layer removal to process sample 101, this embodiment of the invention utilizes the characteristic of the relatively soft top Al layer 104 of the chip sample 101. Specifically, the Al material is softer than the material of the bump balls, allowing the top Al layer 104 to be directly cut with a cutting tool. This embodiment removes the passivation layer 102 and bump balls 103 above the top Al layer 104 by cutting the top Al layer 104, thus bypassing the more difficult-to-remove bump balls 103. Compared to directly removing the bump balls 103, the cutting process of the top Al layer 104 is simpler and faster, significantly shortening the processing time and thus greatly improving the preparation efficiency. For example, this embodiment can reduce the processing time to 5 minutes. In existing methods, for example, when using physical methods such as sandpaper polishing, the processing time is 0.5 to 1 hour; when using physical and chemical methods such as reactive ion etching (RIE) combined with aqua regia thermal reaction, the processing time is 1.5 hours. Therefore, this embodiment of the invention can significantly shorten the processing time and thus greatly improve the preparation efficiency.
[0039] The present invention has been described in detail above through specific embodiments, but these are not intended to limit the invention. Many modifications and improvements can be made by those skilled in the art without departing from the principles of the invention, and these should also be considered within the scope of protection of the present invention.
Claims
1. A method for removing bumps from the surface of a sample, characterized in that, Including the following steps: Provide the sample to be analyzed and confirm the target location of the sample. The sample includes a semiconductor substrate, a metal interconnect layer, a top Al layer and a passivation layer, with multiple bump balls formed on the surface of the passivation layer. The top Al layer is cut with a cutting tool to remove the passivation layer and the bump ball above the top Al layer; The remaining top Al layer after the cutting is removed using a wet process.
2. The method for removing bumps from the sample surface as described in claim 1, characterized in that: Prior to the cutting, the following are included: The sample was fixed to the stage using adhesive tape.
3. The method for removing bumps from the sample surface as described in claim 2, characterized in that: Before fixing the sample, the process also includes: The target location of the sample is confirmed by an optical microscope. After the sample is fixed, the target location is exposed and used for cutting.
4. The method for removing bumps from the sample surface as described in claim 3, characterized in that: The cutting process also includes: Use an air gun to blow away the residue that has been cut off to prevent scratching the sample.
5. The method for removing bumps from the sample surface as described in claim 3, characterized in that: After the cutting is completed, the process also includes: The optical microscope is used to confirm whether the top surface within the area of the target location is in the top Al layer.
6. The method for removing bumps from the sample surface as described in claim 1, characterized in that: The etching solution used in the wet process is dilute hydrochloric acid.
7. The method for removing bumps from the sample surface as described in claim 1, characterized in that: The top A1 layer serves as a rerouting layer.
8. The method for removing bumps from the sample surface as described in claim 7, characterized in that: The passivation layer includes a silicon oxide passivation layer and a silicon nitride passivation layer.
9. The method for removing bumps from the sample surface as described in claim 8, characterized in that: A top opening is formed in the passivation layer at the bottom of each of the bump balls; a bump under-metal layer is formed on the inner surface of the top opening, and the bump under-metal layer extends to the surface of the passivation layer outside the top opening.
10. The method for removing bumps from the sample surface as described in claim 9, characterized in that: The metal layer under the bump includes a first copper layer and a first nickel layer stacked sequentially.
11. The method for removing bumps from the sample surface as described in claim 10, characterized in that: The material of the bump ball includes tin.
12. The method for removing bumps from the sample surface as described in claim 1, characterized in that: The semiconductor substrate includes a silicon substrate.
13. The method for removing bumps from the sample surface as described in claim 1, characterized in that: The metal interconnect layer includes multiple copper layers, which are connected by vias and isolated by interlayer films.