A method for measuring metal content on a wafer surface

Abstract

The application discloses a method for measuring the metal content on the surface of a wafer, comprising: obtaining a wafer to be detected, wherein the surface of the wafer comprises N sub-zones, N is a natural number and N>=2; performing a heating treatment on the wafer, so that the metal ions inside the wafer diffuse to the surface of the wafer; and performing a VPD solution scanning measurement step on each of the N sub-zones respectively, so as to obtain the surface metal content of each of the N sub-zones. According to the method for measuring the metal content on the surface of a wafer provided by the application, the wafer is first heated, so that the metal ions inside the wafer diffuse to the surface of the wafer, and then the surface metal content of each of the multiple sub-zones on the surface of the wafer is measured, so that the metal contamination and the position of the metal contamination can be more accurately identified, and the yield and reliability of the semiconductor device are ensured.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and more specifically to a method for measuring the metal content on the surface of a wafer. Background Technology

[0002] In wafer manufacturing, processes such as dicing, grinding, polishing, and cleaning are required. Metal contamination on the wafer surface is a significant indicator affecting wafer yield. Methods for measuring the metal content on the wafer surface typically employ two instruments: VPD (Vapor Phase Decomposition) and ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). Specifically, in VPD, a VPD solution is dropped onto the wafer surface. A scanning nozzle is used to purge the VPD droplets, dissolving the metal on the wafer surface. Then, an ICP-MS device is used to collect the VPD droplets from the wafer surface. After dilution, the metal concentration in the VPD test solution is measured and converted into the metal content on the wafer surface.

[0003] However, during wafer manufacturing processes, such as the SC1 / SC2 cleaning process, some surface metal ions diffuse into the wafer due to acid and alkali reagents and / or liquid environment, resulting in a lower detection result for the metal content on the wafer surface, making it impossible to accurately identify potential metal contamination risks. In addition, when the metal content is high in a localized area on the wafer surface, obtaining only the overall metal content of the wafer surface may not accurately identify potential metal contamination risks, affecting the yield and reliability of semiconductor devices. Summary of the Invention

[0004] The summary section introduces a series of simplified concepts, which will be further explained in detail in the detailed description section. The summary section of this invention is not intended to limit the key features and essential technical features of the claimed technical solution, nor is it intended to determine the scope of protection of the claimed technical solution.

[0005] This invention provides a method for measuring the metal content on a wafer surface, comprising:

[0006] Obtain a wafer to be inspected, wherein the surface of the wafer comprises N partitions, where N is a natural number and N≥2;

[0007] The wafer is subjected to a heat treatment to allow metal ions inside the wafer to diffuse to the surface of the wafer;

[0008] A VPD solution scanning measurement step is performed on each of the N partitions to obtain the surface metal content of each of the N partitions.

[0009] For example, the temperature range for heating the wafer includes 1000℃ to 1200℃; the time range for heating the wafer includes 3min to 5min.

[0010] Exemplarily, after the wafer is heated, a step of cooling the wafer is further included, comprising:

[0011] Cooling gas is introduced to reduce the temperature of the wafer to below 800°C;

[0012] Cooling gas is continued to be introduced to lower the temperature of the wafer to room temperature.

[0013] Exemplarily, the process further includes a preheating step of the wafer before the heat treatment, comprising:

[0014] The wafer is preheated to 400°C to 500°C.

[0015] For example, the surface of the wafer includes a central partition and edge partitions, wherein the central partition includes one partition and the edge partitions include four partitions.

[0016] For example, performing a VPD solution scanning measurement step on each of the N partitions to obtain the surface metal content of each of the N partitions includes:

[0017] Obtain the first volume of VPD solution;

[0018] The VPD solution is blown onto the surface of the first partition to absorb metal ions from the surface of the first partition;

[0019] Collect the first volume of VPD solution and dilute the first volume of VPD solution to the volume to be tested;

[0020] Metal analysis is performed on the VPD solution of the volume to be tested to obtain the surface metal content of the first partition.

[0021] Exemplarily, it also includes the step of detecting blank VPD solution samples:

[0022] Dilute the first volume of VPD solution to the volume to be tested;

[0023] Metal analysis was performed on the volume of VPD solution to be tested to obtain the metal content of the blank sample.

[0024] For example, the VPD solution includes HF, H2O2 and deionized water, and the volume ratio of HF, H2O2 and deionized water in the VPD solution is 1:2:7.

[0025] For example, the metal includes nickel and / or copper.

[0026] For example, inductively coupled plasma mass spectrometry was used to detect the surface metal content.

[0027] According to the method for measuring the metal content on the surface of a wafer provided by the present invention, the wafer is first heated to allow metal ions inside the wafer to diffuse to the surface of the wafer. Then, the surface metal content of each of the multiple partitions on the wafer surface is measured, thereby more accurately identifying metal contamination and its location, and ensuring the yield and reliability of semiconductor devices. Attached Figure Description

[0028] The following drawings, which are incorporated herein by reference as part of this invention, are provided for understanding the invention. The drawings illustrate embodiments of the invention and their descriptions, serving to explain the principles of the invention.

[0029] In the attached image:

[0030] Figure 1 This is a schematic flowchart of a method for measuring the metal content on a wafer surface according to an embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of wafer surface partitioning according to an embodiment of the present invention. Detailed Implementation

[0032] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid obscuring the invention.

[0033] It should be understood that the invention can be embodied in various forms and should not be construed as being limited to the embodiments set forth herein. Rather, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, for clarity, the dimensions and relative dimensions of layers and regions may be exaggerated. The same reference numerals denote the same elements throughout.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the invention. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising” and / or “including,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0035] To fully understand this invention, detailed steps and structures will be presented in the following description to illustrate the technical solution proposed by this invention. Preferred embodiments of the invention are described in detail below; however, in addition to these detailed descriptions, the invention may have other embodiments.

[0036] During wafer manufacturing, such as in the SC1 / SC2 cleaning process, some surface metal ions diffuse into the wafer due to acid and alkali reagents and / or liquid environment, resulting in a low detection result of the metal content on the wafer surface, making it impossible to accurately identify potential metal contamination risks. In addition, when the metal content is high in a local area on the wafer surface, obtaining only the overall metal content of the wafer surface may not accurately identify potential metal contamination risks, affecting the yield and reliability of semiconductor devices.

[0037] To address the aforementioned problem of inaccurate identification of potential metal contamination risks, this invention provides a method for measuring the metal content on a wafer surface, such as... Figure 1 As shown, it includes the following steps:

[0038] Step S110: Obtain the wafer to be inspected, wherein the surface of the wafer includes N partitions, where N is a natural number and N≥2;

[0039] Step S120: Heat the wafer to allow metal ions inside the wafer to diffuse to the surface of the wafer;

[0040] Step S130: Perform a VPD solution scanning measurement step on each of the N partitions to obtain the surface metal content of each of the N partitions.

[0041] First, see Figure 2 Step S110: Obtain the wafer to be inspected, wherein the surface of the wafer includes N partitions, where N is a natural number and N≥2.

[0042] In the wafer manufacturing process, crystal ingots are typically processed through cutting, grinding, polishing, and cleaning to obtain individual wafers. In one embodiment, one or more wafers are selected from the same batch of wafers obtained after performing the same batch of cutting, grinding, polishing, and cleaning processes on the same crystal ingot as the wafers to be inspected. It should be noted that the wafers to be inspected can be selected as needed, and this invention does not limit this selection.

[0043] In one embodiment, the surface of the wafer includes a central partition and edge partitions, such as Figure 2 As shown, the central partition includes one partition: partition E; the edge partitions include four partitions: partition A, partition B, partition C, and partition D. The radius of the wafer is R, and partition E includes a circular region with the center of the wafer as its center and a radius of R / 2. Partitions A, B, C, and D are each part of a fan-ring region, and the areas of two or more of partitions A, B, C, and D may be equal or unequal. It should be noted that... Figure 2 The partitioning of the wafer surface shown is merely exemplary. The wafer surface can be partitioned as needed, for example, dividing the wafer surface into one or more fan-shaped regions, one or more annular regions, or one or more irregular regions. Furthermore, the areas of the N partitions of the wafer surface can be equal or unequal.

[0044] Next, step S120 is performed: the wafer is heated to allow metal ions inside the wafer to diffuse to the surface of the wafer.

[0045] Exemplarily, the process further includes a preheating step before heating the wafer. In one embodiment, before placing the wafer in the heating chamber for heating, the wafer is first placed in a preheating chamber, which can preheat the wafer to 400°C to 500°C.

[0046] Next, the wafer is placed in a heating chamber, a protective gas is introduced, and the temperature is raised to 1000℃~1200℃ for 3min~5min. This heat treatment causes metal ions inside the wafer to diffuse to the surface of the wafer.

[0047] Next, after heating the wafer, a cooling process is included. In one embodiment, cooling gas is introduced to lower the wafer temperature to below 800°C within 20 seconds; cooling gas is then introduced to further lower the wafer temperature to room temperature within 40 seconds. Through these cooling steps, the wafer can be cooled from 1000°C to 1200°C to room temperature within 1 minute.

[0048] Next, step S130 is performed: a VPD solution scanning measurement step is performed on each of the N partitions to obtain the surface metal content of each of the N partitions.

[0049] VPD solution is a chemical reagent for gas-phase decomposition, mainly composed of HF, H2O2 and deionized water. In one embodiment of the present invention, the volume ratio of HF, H2O2 and deionized water in the prepared VPD droplet reagent is 1:2:7.

[0050] The VPD (Vacuum Diode Probe) equipment uses a VPD solution for scanning and measurement. The VPD equipment includes an inlet and gate for introducing the wafer, a process chamber, a wafer stage inside the process chamber, a vacuum chuck, and a scanning module. The wafer is introduced into the process chamber stage through the wafer inlet and fixed on the stage by the vacuum chuck. The scanning module supplies the VPD solution to the scanning nozzles through a flow path. The scanning nozzles scan the surface of the wafer partitions. After scanning the surface of the wafer partitions, the VPD solution is returned to the storage device through a pipeline for analysis.

[0051] In one embodiment, refer to Figure 2 The following describes the steps for VPD solution scanning measurement of a wafer surface partition, using partition E as an example: First, a certain volume V1 (e.g., 150 μL) of VPD solution is taken from the VPD solution supply device. It should be noted that the volume V1 of VPD solution obtained is the same for each partition. Next, the VPD solution of volume V1 is used to scan the surface of partition E using a scanning nozzle to absorb metal ions (e.g., Ni ions, Cu ions) from the surface of partition E. Then, the VPD solution containing the absorbed metal ions is collected in a storage device and diluted with deionized water to a detection volume V2 (e.g., 600 μL). The concentration of metal ions in the VPD solution diluted to the detection volume V2 is detected using inductively coupled plasma mass spectrometry (ICP-MS), and the surface metal content of partition E is calculated based on the concentration of metal ions in the VPD solution. Using the above method, the surface metal content of partitions A, B, C, and D can be obtained respectively. It should be noted that for the N partitions on the wafer surface, the measurement of surface metal content can be performed simultaneously or sequentially. When measuring sequentially, the measurement order can be set as needed, and this invention does not impose any restrictions on this.

[0052] Because the preparation and transportation of VPD reagents often lead to contamination of the VPD solution, the method according to the present invention further includes a step of detecting a blank VPD solution sample to improve the accuracy of the measurement results: obtaining a certain volume V1 (e.g., 150 μL) of VPD solution, diluting the VPD solution with deionized water to a detection volume V2 (e.g., 600 μL), and detecting the concentration of metal ions in the blank VPD solution sample using ICP-MS.

[0053] In one embodiment, when analyzing the surface metal content of two adjacent wafers whose edges were damaged during handling, the overall metal content of the wafer surface is measured using conventional methods, while the surface metal content of individual zones on the wafer surface is measured using the method of the present invention. Table 1 shows the overall surface metal content of the wafer surface (measured using conventional methods) and the surface metal content of the POR wafer:

[0054] Table 1. Overall surface metal content of the wafer

[0055] element Overall surface POR Ni 0.0060 0.00553 Cu 0.01664 0.01587

[0056] As can be seen from Table 1, the difference between the overall metal content of the wafer surface measured by the traditional method and the metal content in the POR comparison sample is not significant. Therefore, it is impossible to determine whether the wafer is contaminated by measuring the metal content of the wafer surface.

[0057] Table 2 Metal content on wafer partition surfaces

[0058] element Partition A Partition B Partition C Partition D Partition E Ni 0.01446 0.00825 28.97031 0.00723 0.00080 Cu 0.00815 0.01494 3.4382 0.0099 0.00027

[0059] However, as shown in Table 2, using the method of the present invention, with regions A and C as PORs for each other, and regions A and C having the same area, the metal content should be at the same level. However, it is known that the wafer damage area is located in region C. In region C, which corresponds to region A, the content of Ni and Cu ions in region C significantly exceeds the threshold. Compared with the damage area region C, the measurement results of region A are several times different. It can be determined that the wafer is contaminated with metal, and the location of the metal contamination is confirmed as region C.

[0060] According to the method for measuring the metal content on the surface of a wafer provided by the present invention, the wafer is first heated to allow metal ions inside the wafer to diffuse to the surface of the wafer. Then, the surface metal content of each of the multiple partitions on the wafer surface is measured, thereby more accurately identifying metal contamination and its location, and ensuring the yield and reliability of semiconductor devices.

[0061] The present invention has been described through the above embodiments. However, it should be understood that the above embodiments are for illustrative purposes only and are not intended to limit the invention to the scope of the described embodiments. Furthermore, those skilled in the art will understand that the present invention is not limited to the above embodiments, and many more variations and modifications can be made based on the teachings of the present invention, all of which fall within the scope of protection claimed by the present invention. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for measuring the metal content on a wafer surface, characterized in that, include: Obtain a wafer to be inspected, wherein the surface of the wafer comprises N partitions, where N is a natural number and N≥2; The wafer is subjected to a heat treatment to allow metal ions inside the wafer to diffuse to the surface of the wafer; A VPD solution scanning measurement step is performed on each of the N partitions to obtain the surface metal content of each of the N partitions; Based on the surface metal content of each of the N partitions, localized metal contamination on the wafer surface and its location are identified.

2. The method as described in claim 1, characterized in that, The temperature range for heating the wafer includes 1000℃ to 1200℃; the time range for heating the wafer includes 3 min to 5 min.

3. The method as described in claim 2, characterized in that, The process includes a cooling step after the wafer is heated, comprising: Cooling gas is introduced to reduce the temperature of the wafer to below 800°C; Cooling gas is continued to be introduced to lower the temperature of the wafer to room temperature.

4. The method as described in claim 1, characterized in that, The process includes a preheating step before heating the wafer, comprising: The wafer is preheated to 400°C to 500°C.

5. The method as described in claim 1, characterized in that, The surface of the wafer includes a central partition and edge partitions, wherein the central partition includes one partition and the edge partitions include four partitions.

6. The method as described in claim 1, characterized in that, Perform a VPD solution scanning measurement step on each of the N partitions to obtain the surface metal content of each of the N partitions, including: Obtain the first volume of VPD solution; The VPD solution is blown onto the surface of the first partition to absorb metal ions from the surface of the first partition; Collect the first volume of VPD solution and dilute the first volume of VPD solution to the volume to be tested; Metal analysis is performed on the VPD solution of the volume to be tested to obtain the surface metal content of the first partition.

7. The method as described in claim 6, characterized in that, It also includes the step of testing blank VPD solution samples: Dilute the first volume of VPD solution to the volume to be tested; Metal analysis was performed on the volume of VPD solution to be tested to obtain the metal content of the blank sample.

8. The method as described in claim 1, characterized in that, The VPD solution includes HF, H2O2 and deionized water, and the volume ratio of HF, H2O2 and deionized water in the VPD solution is 1:2:

7.

9. The method as described in claim 8, characterized in that, The metals include nickel and / or copper.

10. The method as described in claim 1, characterized in that, The surface metal content was detected using inductively coupled plasma mass spectrometry.

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