Method for improving spherical defects

Abstract

The invention discloses a method for improving spherical defects, which comprises the following steps that: the etching process of a target layer on a wafer is completed, the etching process is chemical etching and can generate polymer by-products, and the polymer by-products can be agglomerated, backsplashed and adhered to the surface of the wafer. The surface of the wafer is cleaned with hot DIW at a temperature higher than normal temperature to remove polymer by-products so as to reduce spherical defects. Spherical defects can be reduced, and the product yield can be improved.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a semiconductor integrated circuit, and in particular to a method for improving a ball defect. Background Art

[0002] Spherical defects may occur in products of some existing process platforms, such as Figure 1A As shown, it is a distribution map of inline defects on a conventional wafer. There are a large number of defects 102 on the map 101 , and each defect 102 is distributed in a cluster.

[0003] like Figure 1B As shown, Figure 1A Magnified photo of the defect in FIG; it can be seen that the morphology of the defect 102 is spherical, so it is a spherical defect.

[0004] like Figure 1C 1 is a map of offline defects after wet etching of a conventional wafer. Wet etching is usually chemical etching. It can be seen that in the map 103 , there are multiple defects 104 .

[0005] like Figure 1D As shown, Figure 1C Magnified photo of the defect in FIG; it can be seen that the defect 104 is spherical in shape, so it is also a spherical defect.

[0006] like Figure 1E , which is an enlarged photograph of a spherical defect formed after dummy polysilicon gate removal (DPR) of a conventional wafer; it can be seen that a spherical defect 105 is formed after the DPR process.

[0007] In the metal gate process, the area where the pseudo polysilicon gate is removed will form a gate trench. In subsequent processes, the metal gate needs to fill the gate trench. If there is a spherical defect 105, it will have an adverse effect on the filling of the metal gate.

[0008] like Figure 1F As shown, Figure 1E A magnified photo of the Al missing defect generated after the chemical mechanical polishing (CMP) of the metal gate (MG) is completed when the spherical defect exists; Figure 1F It can be seen that the mark 106 indicates the Almissing defect, which is a hole.

[0009] Among existing methods, DPR is a process that etches a large amount of A-Si, or amorphous silicon, and DGO is an all-wet strip process. Both processes produce a large amount of byproducts during the cleaning process, which can easily form spherical defects due to agglomeration and splashback. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for improving spherical defects, which can reduce spherical defects and improve product yield.

[0011] In order to solve the above technical problems, the method for improving spherical defects provided by the present invention comprises the following steps:

[0012] An etching process for a target layer on a wafer is completed. The etching process is chemical etching and will produce polymer by-products. The polymer by-products will agglomerate, splash back, and stick back to the wafer surface.

[0013] Hot DIW with a temperature higher than room temperature is used to clean the wafer surface to remove the polymer byproducts and reduce spherical defects.

[0014] A further improvement is that the target layer includes a dummy gate material layer.

[0015] A further improvement is that the material of the dummy gate material layer includes polysilicon or amorphous silicon.

[0016] A further improvement is that the etching process is dry etching or wet etching.

[0017] A further improvement is that the target layer includes a TiN layer.

[0018] A further improvement is that the etching process is dry etching or wet etching.

[0019] A further improvement is that, during the cleaning, the hot DIW is sprayed onto the wafer surface through a nozzle and the wafer is rotated by a rotating device to remove the polymer by-products.

[0020] A further improvement is that the temperature of the hot DIW is 70°C to 80°C.

[0021] A further improvement is that, there are multiple target layers on the wafer that need to be subjected to the etching process, and after the etching process of each target layer is completed, the hot DIW is used to clean the surface of the wafer.

[0022] In existing methods, after chemical etching is completed on the wafer, the surface of the wafer is usually directly cleaned with room temperature DIW without controlling the temperature of the DIW. However, in the present invention, after chemical etching is completed on the wafer, the surface of the wafer is cleaned with hot DIW. Hot DIW can effectively remove polymer byproducts, thereby reducing spherical defects.

[0023] In addition, when there are multiple target layers on the wafer that need to be chemically etched, the present invention can perform hot DIW cleaning after chemical etching of each target layer is completed, which can minimize spherical defects on the wafer and improve product yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0025] Figure 1A It is a map of inline defects of existing wafers;

[0026] Figure 1B yes Figure 1A Magnified photographs of defects in the

[0027] Figure 1C This is a map of offline defects after wet etching of existing wafers;

[0028] Figure 1D yes Figure 1C Magnified photographs of defects in the

[0029] Figure 1E This is a magnified photo of defects formed after DPR of an existing wafer;

[0030] Figure 1F yes Figure 1E A magnified photo of an Al missing defect generated after the subsequent chemical mechanical polishing (CMP) of the metal gate MG is completed when a spherical defect exists;

[0031] Figure 2 is a flow chart of a method for improving spherical defects according to an embodiment of the present invention;

[0032] Figure 3 2. It is a schematic structural diagram of a cleaning chamber during hot DIW cleaning in a method for improving spherical defects according to an embodiment of the present invention;

[0033] Figure 4 This is a defect map of a wafer processed by the method for improving spherical defects according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] like Figure 2FIG. 1 is a flow chart of a method for improving spherical defects according to an embodiment of the present invention. The method for improving spherical defects according to an embodiment of the present invention comprises the following steps:

[0035] Step S101 : completing an etching process for a target layer on a wafer. The etching process is chemical etching and will produce polymer by-products. The polymer by-products will aggregate, splash back, and stick back to the wafer surface.

[0036] Step S102 : Cleaning the wafer surface with hot DIW at a temperature higher than room temperature to remove the polymer byproducts and reduce spherical defects.

[0037] In the embodiment of the present invention, there are multiple target layers on the wafer that need to be subjected to the etching process. After the etching process of each target layer is completed, the hot DIW is used to clean the surface of the wafer.

[0038] In some embodiments, the target layer is a dummy gate material layer. The material of the dummy gate material layer includes polysilicon or amorphous silicon. The etching process is dry etching or wet etching. The process of removing the dummy gate material layer, such as the dummy polysilicon gate, is also called a DPR process.

[0039] A gate trench is formed in the area where the dummy gate material layer is removed. The gate trench is filled with a gate dielectric layer, a corresponding metal work function layer, and a metal conductive material layer. For PMOS, the metal work function layer is a P-type metal work function layer, and the corresponding material includes TiN; for NMOS, the metal work function layer is an N-type metal work function layer, and the corresponding material includes TiAl.

[0040] In some embodiments, the target layer includes a TiN layer.

[0041] The etching process is dry etching or wet etching.

[0042] like Figure 3 Figure 2 shows a schematic diagram of the cleaning chamber structure for hot DIW cleaning in accordance with a method for improving spherical defects according to an embodiment of the present invention. During cleaning, hot DIW is sprayed onto the wafer surface through nozzle 203, and the wafer is rotated by a rotating device to remove polymer byproducts. The rotating device is mounted on the surface of the wafer carrier 202. As the wafer rotates, the hot DIW is evenly distributed across the wafer surface due to centrifugal force and ejected from the wafer. Figure 3 In the figure, the hot DIW is indicated by reference numeral 204. After being thrown out of the wafer, the hot DIW is discharged from the cleaning chamber 201 through a pipeline.

[0043] In the embodiment of the present invention, the temperature of the hot DIW is 70° C. to 80° C. The hot DIW is preheated before the nozzle 203 , and a heater does not need to be provided in the cleaning chamber 201 .

[0044] In the existing method, after chemical etching is completed on the wafer, the surface of the wafer is usually directly cleaned with DIW at room temperature without controlling the temperature of the DIW. However, in the embodiment of the present invention, after chemical etching is completed on the wafer, the surface of the wafer is cleaned with hot DIW. Hot DIW can effectively remove polymer byproducts, thereby reducing spherical defects. Figure 4 Figure 301 shows a defect map of a wafer after treatment using the method for improving spherical defects according to an embodiment of the present invention. Map 301 shows a relatively small number of defects 302, meeting the requirement. Due to the small number of defects 302, the number of spherical defects included in all defects 302 is even smaller, or even zero. Therefore, the embodiment of the present invention can ultimately reduce wafer surface defects, particularly spherical defects.

[0045] The embodiment of the present invention comprehensively optimizes the process by adding thermal DIW after chemical etching to enhance the ability to remove byproducts, thereby ultimately improving product yield. Therefore, the present invention can improve product yield and reduce round defects.

[0046] The present invention has been described in detail above by means of specific embodiments, but these do not constitute limitations of the present invention. Without departing from the principles of the present invention, those skilled in the art may make many variations and improvements, which should also be considered as the scope of protection of the present invention.

Claims

1. A method for improving spherical defects, characterized in that: The steps include: completing an etching process for a target layer on a wafer, wherein the etching process is chemical etching and produces polymer byproducts, which aggregate and splash back onto the wafer surface; Hot DIW with a temperature higher than room temperature is used to clean the wafer surface to remove the polymer byproducts and reduce spherical defects.

2. The method for improving spherical defects according to claim 1, wherein: The target layer includes a dummy gate material layer.

3. The method for improving spherical defects according to claim 2, wherein: The material of the dummy gate material layer includes polysilicon or amorphous silicon.

4. The method for improving spherical defects according to claim 3, wherein: The etching process is dry etching or wet etching.

5. The method for improving spherical defects according to claim 1, wherein: The target layer includes a TiN layer.

6. The method for improving spherical defects according to claim 5, wherein: The etching process is dry etching or wet etching.

7. The method for improving spherical defects according to claim 1, wherein: During the cleaning, the hot DIW is sprayed onto the wafer surface through a nozzle and the wafer is rotated by a rotating device to remove the polymer byproducts.

8. The method for improving spherical defects according to claim 1, wherein: The temperature of the hot DIW is 70°C to 80°C.

9. The method for improving spherical defects according to claim 1, wherein: There are multiple target layers on the wafer that need to be subjected to the etching process. After the etching process of each target layer is completed, the hot DIW is used to clean the surface of the wafer.

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