Method for avoiding metal contamination caused by wafer thinning and polishing

Abstract

The present invention provides a method for avoiding metal contamination caused by wafer thinning and polishing, wherein the CMP equipment is stopped from being rinsed and wiped clean; a UV heat insulation film is arranged on the outer surface of the head of the CMP equipment; except for the pad, the grinding liquid nozzle and the deionized water nozzle, the outer surfaces of other directly exposed parts in the CMP equipment are all provided with a UV protective film; during thinning and polishing, the exhaust fan is adjusted to the maximum wind speed; when thinning and polishing a wafer containing heterogeneous metals, the UV heat insulation film and the UV protective film are irradiated with a UV lamp to make them lose their stickiness and be torn off, and the thinning and polishing pad is replaced and re-filmed. The present invention adopts a UV heat insulation film and a UV protective film for protection, so that when performing thinning and polishing of wafers containing different metals, only the UV heat insulation film and the UV protective film need to be replaced, and the heterogeneous wafer to be thinned and polished will not be contaminated by other metal ions due to the residual adsorbed metal particles of the CMP equipment itself, thereby avoiding the situation that the wafer has defects or even functional losses.

Description

Technical Field

[0001] The invention relates to the field of semiconductor processing and manufacturing, and specifically provides a method for avoiding metal contamination caused by wafer thinning and polishing. Background Art

[0002] With the rapid development of integrated circuit technology, the integration of devices is getting higher and higher, semiconductor processing technology is becoming more and more complex, more semiconductor materials are being discovered and applied in some high-end designs, and some problems are also emerging. Among them, metal contamination has become the most important problem in semiconductor processing technology. Products contaminated by metal will have performance defects, which greatly affects the yield of product devices. One of the main sources of metal contamination of product devices is process equipment. Therefore, ensuring that process equipment is not contaminated by metal is an important measure to improve the yield of product devices.

[0003] Wafer thinning and surface flattening technology is an indispensable step in semiconductor processing. Chemical mechanical polishing (CMP) is currently recognized as the semiconductor process technology with the best wafer surface polishing effect and the highest flatness. When processing semiconductor wafers, they must be finely thinned and polished by CMP equipment to improve their surface flatness and provide good conditions for subsequent bonding, lithography and other processes. Therefore, it is crucial to ensure that the CMP equipment is not contaminated by metal.

[0004] When the CMP equipment is thinning and polishing the metal film layer on the surface of the wafer, the grinding liquid and deionized water sprayed on the pad will rotate with the pad, head and wafer, and the ground metal particles will be irregularly splashed around with the grinding liquid and stay in every corner of the equipment. This will cause the self-cleaning program to flush the metal particles temporarily attached to the inside of the equipment to the surface of the wafer to be thinned when the equipment is thinning and polishing other wafers. Due to the different properties of hardness, thermal expansion coefficient and other properties of different metals, the metal-contaminated wafer to be thinned may have defects on the wafer surface after the CMP process, such as surface scratches, device short circuits and metal residues, and have an inestimable impact on subsequent processes such as bonding and lithography. For CMP equipment in semiconductor factories, special metal contamination cleaning of the equipment also requires a lot of capital investment. If you choose to directly deposit a passivation layer such as a protective film inside the CMP equipment, there are many disadvantages, such as:

[0005] 1. The process of preparing the passivation layer is complicated. The passivation layer can only be deposited on some small parts that are detachable, high temperature resistant and corrosion resistant. It is impossible to deposit the passivation layer inside the entire CMP equipment.

[0006] 2. The maintenance cost of the passivation layer is high in the later stage, and the raw materials of the passivation layer need to be stored separately under specific conditions.

[0007] 3. The deposited passivation layer can only protect the equipment itself, but cannot avoid metal contamination during the thinning and polishing process of wafers of different materials.

[0008] 4. It is also difficult to remove the passivation layer, and the passivation layer with different materials attached to the surface needs to be cleaned multiple times.

[0009] Therefore, a method that can effectively avoid metal contamination during wafer thinning and polishing is urgently needed. Summary of the invention

[0010] In order to solve the above problems, the present invention provides a method for avoiding metal contamination caused by wafer thinning and polishing, which mainly aims at the problem of metal contamination of CMP equipment during operation, and uses UV protective film and UV heat insulation film to protect the polishing unit, transmission unit, connection points of each unit, switch door and exhaust vent of the equipment. When the equipment converts other metal materials for thinning and polishing, it is only necessary to use UV lamp to irradiate the protected area, so that the UV protective film and UV heat insulation film lose their stickiness and tear them off, and then replace them with new UV protective film, UV heat insulation film and thinning polishing pad, which is simple and convenient, and effectively protects the CMP equipment from metal contamination.

[0011] The method for avoiding metal contamination caused by wafer thinning and polishing provided by the present invention comprises the following steps:

[0012] S1. Stop flushing the CMP equipment and wipe it clean with a dust-free cloth;

[0013] S2. UV heat insulation film is set on the outer surface of the head of the CMP equipment; except for the pad, polishing liquid nozzle and deionized water nozzle, UV protective film is set on the outer surface of other directly exposed parts in the CMP equipment;

[0014] S3. When the CMP equipment is thinning and polishing the wafer, adjust the exhaust fan to the maximum wind speed;

[0015] S4. When thinning and polishing a wafer containing heterogeneous metals, use a UV lamp to irradiate the UV thermal insulation film and the UV protective film to make them lose their stickiness and tear them off, replace the thinning polishing pad and repeat S2.

[0016] Preferably, after the S2 treatment, the CMP equipment is also rinsed to prevent the UV thermal insulation film and the UV protective film from being deformed and water accumulated due to the impact of water flow. If deformation and water accumulation problems exist, the UV thermal insulation film and the UV protective film are removed and S2 is repeated.

[0017] Preferably, the CMP equipment also includes metal content detection before wafer thinning and polishing, and the specific process is as follows:

[0018] The pure test wafer is thinned and polished in the CMP equipment, and the surface of the test wafer is corroded by HF gas. Deionized water is then dropped on the center of the test wafer. The test wafer is rotated to move the ionized water from the center of the test wafer to the edge of the test wafer. The ionized water is collected and the metal content is tested.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0020] The present invention designs a method for avoiding metal contamination caused by wafer thinning and polishing for CMP equipment. The method is not limited by conditions such as the size of the CMP equipment and whether the parts are detachable, thereby avoiding metal contamination of the CMP equipment and metal contamination of the processed wafers.

[0021] The present invention adopts UV heat insulation film and UV protective film for protection, so that when thinning and polishing wafers containing different metals, only the UV heat insulation film and UV protective film need to be replaced, and the heterogeneous wafers to be thinned and polished will not be contaminated by other metal ions due to residual adsorbed metal particles in the CMP equipment itself, thereby avoiding defects or even functional losses of the wafers, greatly improving the process yield of wafer thinning and polishing, and reducing the production cost of the entire process production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a flow chart of a method for avoiding metal contamination caused by wafer thinning and polishing provided in an embodiment of the present invention;

[0023] Figure 2 This is a diagram showing the effect of protecting the head with a UV heat insulation film provided by an embodiment of the present invention;

[0024] Figure 3 This is a diagram showing the effect of a UV protective film protecting a disk according to an embodiment of the present invention;

[0025] Figure 4 This is a rendering of a delivery device for UV protective film protection grinding liquid and deionized water provided according to an embodiment of the present invention;

[0026] Figure 5 It is a curve chart of metal content detection results of a CMP device provided according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same modules are represented by the same reference numerals. In the case of the same reference numerals, their names and functions are also the same. Therefore, the detailed description thereof will not be repeated.

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation of the present invention.

[0029] Figure 1 The flow of a method for avoiding metal contamination caused by wafer thinning and polishing provided according to an embodiment of the present invention is shown.

[0030] like Figure 1 As shown, in order to solve the problem that the CMP equipment is contaminated by metal during operation, the method for avoiding metal contamination caused by wafer thinning and polishing provided by the embodiment of the present invention includes the following steps:

[0031] S1. Turn off the flushing unit and self-cleaning program of the CMP equipment, stop flushing the equipment, and use a dust-free cloth to wipe the parts of the CMP equipment that need to be protected, especially the polishing unit, transfer unit, connections between units, switch doors and exhaust vents, etc. to ensure that there is no liquid residue.

[0032] Figure 2 The UV heat insulation film protection head provided according to an embodiment of the present invention is shown.

[0033] Figure 3 It shows that a UV protective film is provided according to an embodiment of the present invention to protect a disk.

[0034] Figure 4 A delivery device for UV protective film protection grinding liquid and deionized water provided according to an embodiment of the present invention is shown.

[0035] like Figure 2 As shown in the figure, the head of the CMP equipment is removed. Since the temperature at the head is high during the wafer thinning and polishing process, the outer surface of the head is wrapped with UV thermal insulation film to prevent film peeling due to high temperature. The pad, grinding liquid nozzle and deionized water nozzle are not coated, while the outer surfaces of other directly exposed parts in the CMP equipment need to be wrapped with a layer of UV protective film. The specific wrapping conditions are as follows: Figure 3 As shown in the figure, the Disk is mainly responsible for polishing the pad to prevent burrs or residual debris on the pad surface. Therefore, a layer of UV protective film needs to be wrapped on the outer surface of the Disk, such as Figure 4As shown, the outer surface of the conveying device for the grinding liquid and deionized water is also wrapped with a layer of UV protective film.

[0036] After the UV thermal insulation film and UV protective film are wrapped, turn on the flushing unit and self-cleaning program of the CMP equipment. During the flushing process, observe whether the UV thermal insulation film and UV protective film are deformed, have water accumulation or openings during the water flow impact. If the above problems occur, repeat the process of wrapping the CMP equipment with the UV thermal insulation film and UV protective film in S2.

[0037] S3. After the processing in S2, the CMP equipment is started to perform thinning and polishing on the wafer with the metal layer. During the thinning and polishing process, the exhaust of the polishing unit of the CMP equipment needs to be adjusted to the maximum to make the internal air circulation more sufficient and reduce the accumulation of metal elements inside the equipment as much as possible.

[0038] S4: When thinning and polishing wafers containing the same metal, there is no need to process the CMP equipment. When thinning and polishing wafers containing different metals, use a UV lamp to irradiate the UV insulation film and UV protective film on the CMP equipment to make them lose their stickiness and tear them off. At the same time, the thinning polishing pad needs to be replaced, and then S2 is repeated to rewrap the UV insulation film and UV protective film. Before the CMP equipment thins and polishes the wafer, it is also necessary to detect the metal content to avoid metal contamination of the CMP equipment causing damage to the wafer. The specific process of metal content detection is as follows:

[0039] The pure test wafer is thinned and polished in the CMP equipment, and the surface of the test wafer is corroded by HF gas. Then, deionized water is dropped on the center of the test wafer, and a suction pen with a certain suction force is brought into contact with the deionized water droplet to ensure that the position of the deionized water droplet can be adjusted by controlling the suction pen. The test wafer is rotated, and the suction pen is controlled to move the deionized water droplet from the center of the test wafer to the edge of the test wafer, so that the ionized water contains the surface material of the test wafer. The ionized water is collected and placed in a gold content tester to analyze the content of various metals in the ionized water to check whether the metal content exceeds the standard.

[0040] Figure 5 The figure shows the result curve of metal content detection of the CMP equipment provided by the embodiment of the present invention.

[0041] like Figure 5 As shown, in this embodiment, in order to verify the effectiveness of the present invention, a silicon wafer with a layer of aluminum oxide (Al2O3) on the surface is used for experimental analysis. Figure 5In the figure, curve c is the metal content curve on the CMP equipment before thinning and polishing, and the content of aluminum particles and other metal particles on the CMP equipment is low. Curve a is the metal content curve on the surface of the CMP equipment when the CMP equipment wrapped with UV insulation film and UV protective film thins and polishes the wafer containing the same metal, and curve b is the aluminum particle and other metal particle content curve on the CMP equipment after removing the UV insulation film and UV protective film. Curve a is the thinning and polishing of wafers containing the same metal. It is normal for the content of aluminum ions and other related particles to increase slightly. Thinning and polishing of wafers containing the same metal will not cause metal pollution. After removing the UV thermal insulation film and the UV protective film, the content of aluminum particles and other metal particles on the CMP equipment, curve b, shows that the content of aluminum particles and other metal particles on the surface of the CMP equipment decreases rapidly, close to the state before the CMP equipment is used, that is, curve c. Therefore, it is shown that after attaching the UV thermal insulation film and the UV protective film to the CMP equipment, when thinning and polishing of wafers containing the same metal is performed, the CMP equipment does not need to be processed, and this process will not cause metal pollution. When thinning and polishing of wafers containing different metals, the UV thermal insulation film and the UV protective film are torn off, and the surface of the CMP equipment is not contaminated by metal.

[0042] To ensure that the CMP equipment is continuously free from metal contamination, after removing the UV thermal insulation film and UV protective film, it is necessary to reapply the UV thermal insulation film and UV protective film on the CMP surface before processing the wafer.

[0043] The economic cost of UV heat insulation film and UV protective film is low, and it is easy to completely remove them by UV lamp irradiation. The economic cost of protecting CMP equipment by the present invention is low, the effect of avoiding metal pollution is good, and no damage is caused to the equipment. The maintenance cost of existing methods such as depositing passivation layer is high, the surface of CMP equipment is not easy to clean, and when wafers containing heterogeneous metals are thinned and polished, the passivation layer cannot be eliminated and then deposited. Although metal pollution of the CMP equipment itself is avoided, it will still cause pollution to the wafer.

[0044] Although the embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and cannot be understood as limiting the present invention. Those skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0045] The above specific implementations of the present invention do not constitute a limitation on the protection scope of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A method for avoiding metal contamination caused by wafer thinning and polishing, characterized in that: The following steps are involved: S1. Stop flushing the CMP equipment and wipe it clean with a dust-free cloth; S2, setting a UV heat insulation film on the outer surface of the head of the CMP equipment; except for the pad, the polishing liquid nozzle and the deionized water nozzle, the outer surfaces of other directly exposed parts in the CMP equipment are all set with UV protective films; S3, when the CMP equipment is thinning and polishing the wafer, the exhaust fan is adjusted to the maximum wind speed; S4, when thinning and polishing a wafer containing heterogeneous metals, irradiate the UV heat insulation film and the UV protective film with a UV lamp to make them lose their stickiness and tear them off, replace the thinning polishing pad and repeat S2; The CMP equipment also includes metal content detection before wafer thinning and polishing. The specific process is as follows: A pure test wafer is thinned and polished in the CMP equipment, and the surface of the test wafer is corroded by HF gas. Deionized water is then dropped on the center of the test wafer. The test wafer is rotated to move the ionized water from the center of the test wafer to the edge of the test wafer. The ionized water is collected and the metal content is detected.

2. The method for avoiding metal contamination caused by wafer thinning and polishing as claimed in claim 1, characterized in that: After the S2 treatment, the CMP equipment is also rinsed to prevent the UV thermal insulation film and the UV protective film from deformation and water accumulation due to the impact of water flow. If deformation and water accumulation exist, the UV thermal insulation film and the UV protective film are removed and S2 is repeated.

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