A method for testing the noble metal content on the surface of a wafer

Abstract

The present invention discloses a method for testing the noble metal content on the surface of a wafer, belonging to the field of semiconductor technology. It at least includes the following steps: providing a wafer carrier, and setting the wafer to be collected on the wafer carrier; adding an extraction solution to the wafer, where the extraction solution at least contains hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water; moving the extraction solution to cover the area to be detected on the wafer; collecting the extraction solution and diluting it 5-10 times with ultrapure water; and feeding the diluted extraction solution into an inductively coupled plasma mass spectrometer to analyze the noble metal content in the extraction solution. Through the method for testing the noble metal content on the surface of a wafer provided by the present invention, it is possible to collect the noble metals at all positions on the area to be detected of the wafer and accurately obtain the noble metal content on the area to be detected of the wafer.

Description

Technical Field

[0001] The present invention relates to the field of semiconductors, and particularly to a method for testing the content of precious metals on the surface of a wafer. Background Art

[0002] During the processing of wafers, various metal impurities will contaminate their surfaces, resulting in the failure of subsequent devices. Therefore, it is necessary to collect and analyze the metals on the wafer surface to determine the metal content on the wafer surface, and then judge the qualification rate of the devices. Currently, in the process of collecting metals on the wafer surface, on the one hand, the extraction liquid cannot extract precious metals such as platinum, and it cannot ensure that the extraction liquid accurately collects all positions on the wafer surface. On the other hand, the surface of the wafer may be hydrophilic, and when manually collecting the extraction liquid, it is easy to cause loss of the extraction liquid, thus affecting the accuracy of the analysis of the extraction liquid and making it impossible to accurately obtain the content of precious metals on the wafer surface. Summary of the Invention

[0003] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a method for testing the content of precious metals on the surface of a wafer, which can effectively collect the precious metals at all positions on the area to be detected of the wafer and accurately obtain the content of precious metals on the area to be detected of the wafer.

[0004] To solve the above technical problems, the present invention is implemented through the following technical solutions.

[0005] The present invention provides a method for testing the content of precious metals on the surface of a wafer, which at least includes the following steps:

[0006] Provide a wafer carrier, and place the wafer to be collected on the wafer carrier;

[0007] Add an extraction liquid to the wafer, and the extraction liquid at least contains hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water;

[0008] Move the extraction liquid to cover the area to be detected of the wafer;

[0009] Collect the extraction liquid, and dilute it 5 - 10 times with ultrapure water; and

[0010] Send the diluted extraction liquid into an inductively coupled plasma mass spectrometer to analyze the content of precious metals in the extraction liquid.

[0011] In an embodiment of the present invention, in the extraction liquid, the content of ultrapure water is 56wt% - 69wt%, the content of hydrofluoric acid is 5wt% - 10wt%, the content of nitric acid is 13wt% - 17wt%, and the content of hydrochloric acid is 13wt% - 17wt%.

[0012] In one embodiment of the present invention, the oxide on the surface of the wafer is removed before adding the extraction solution.

[0013] In one embodiment of the present invention, the extraction solution is gradually covered on the area to be detected of the wafer by repeatedly releasing and sucking the extraction solution with a pipette.

[0014] In one embodiment of the present invention, the extraction solution gradually covering the area to be detected of the wafer includes at least the following steps:

[0015] Adding the extraction solution with a pipette and making the extraction solution stay at a position in the area to be detected of the wafer for a preset time; and

[0016] Sucking the extraction solution with a pipette, transferring the sucked extraction solution to another position in the area to be detected of the wafer and staying for a preset time.

[0017] In one embodiment of the present invention, an air gun is used to assist the pipette in sucking the extraction solution, and the air gun is a stability gas.

[0018] In one embodiment of the present invention, the gas flow rate of the air gun is controlled at 0.4 m / s - 0.6 m / s.

[0019] In one embodiment of the present invention, the preset time is 20 s - 120 s.

[0020] In one embodiment of the present invention, according to the area of the wafer, the extraction solution amount of the pipette is taken at 2.0 μL / mm 2 -3.1 μL / mm 2 for liquid extraction.

[0021] In summary, the present invention provides a method for testing the content of precious metals on the surface of a wafer, which can collect the precious metals on the area to be detected of the wafer, so as to obtain the content of precious metals on the surface of the wafer. The added extraction solution can effectively obtain the precious metals on the surface of the wafer. By repeatedly releasing and sucking the extraction solution, the extraction solution can accurately cover the points to be detected on the surface of the wafer, which can avoid the residual extraction solution on the surface of the wafer and the loss of the extraction solution, so as to accurately obtain the content of precious metals on the surface of the wafer.

[0022] Of course, it is not necessary to achieve all the above advantages simultaneously when implementing any aspect of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] To more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0024] Figure 1 It is a flowchart of a method for testing the noble metal content on the surface of a wafer in an embodiment of the present invention.

[0025] Figure 2 It is a flowchart of an artificial method in an embodiment of the present invention.

[0026] Figure 3 It is a flowchart of a mechanical method in another embodiment of the present invention. Detailed implementation manners

[0027] The following illustrates the implementation manners of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other.

[0028] It should be understood that the present invention can be implemented in different forms and should not be construed as limited to the embodiments presented here. On the contrary, providing these embodiments will make the disclosure thorough and complete, and will fully convey the scope of the present invention to those skilled in the art.

[0029] The following further elaborates on the technical solutions of the present invention in combination with the embodiments and the drawings. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0030] Please refer to Figure 1 As shown, the present invention provides a method for testing the noble metal content on the surface of a wafer, for example, including steps S11 - S15.

[0031] Step S11: Provide a wafer carrier and place the wafer to be collected on the wafer carrier.

[0032] Step S12: Add an extraction solution to the wafer. The extraction solution contains at least hydrofluoric acid, nitric acid, hydrochloric acid, and ultrapure water.

[0033] Step S13: Move the extraction solution to cover the area of the wafer to be detected with the extraction solution.

[0034] Step S14: Collect the extraction solution and dilute it 5 - 10 times with ultrapure water.

[0035] Step S15: Feed the diluted extraction solution into an inductively coupled plasma mass spectrometer to analyze the precious metal content in the extraction solution.

[0036] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S11, the wafer is horizontally placed on the wafer carrier. The wafer includes the area of the wafer to be detected, and it is necessary to test and analyze the precious metal content in the area of the wafer to be detected to determine the qualification rate of the wafer. Among them, the material of the wafer carrier includes, for example, soluble polytetrafluoroethylene to improve the chemical resistance, high-temperature stability and service life of the wafer carrier. In this embodiment, after placing the wafer, it is also necessary to remove the oxide layer formed on the surface of the wafer due to natural oxidation or thermal oxidation, etc., to avoid the oxide layer blocking the direct contact between the extraction solution and the wafer surface and facilitating the extraction solution to collect the precious metals on the wafer surface. Among them, the method for removing the oxide layer is, for example, etching, and the etching is, for example, dry etching or wet etching, etc. Specifically, in this embodiment, for example, the surface of the wafer is etched with HF aerosol.

[0037] Please refer to Figure 1 As shown, after etching the surface of the wafer, in steps S12 - S13, an extraction solution is added to the area of the wafer to be detected, and the extraction solution is moved to cover all positions in the area of the wafer to be detected. Specifically, in the extraction solution, the content of ultrapure water is, for example, 56wt% - 69wt%, the content of hydrofluoric acid is, for example, 5wt% - 10wt%, the content of nitric acid is, for example, 13wt% - 17wt%, and the content of hydrochloric acid is, for example, 13wt% - 17wt%. In this embodiment, the extraction solution can dissolve and effectively extract the precious metals on the area of the wafer to be detected, and the precious metals at least include platinum, etc.

[0038] Please refer to Figure 1 As shown, in an embodiment of the present invention, when the extraction solution covers the area of the wafer to be detected in steps S12 - S13, first add the extraction solution at a position in the area to be detected. After the extraction solution covers this position for a preset time, move the extraction solution at this position to another position in the area to be detected, so that the extraction solution continues to cover another position for a preset time until the extraction solution gradually covers all positions in the area of the wafer to be detected. Among them, the preset time is, for example, 20s - 120s, specifically, for example, 30s, 40s or 60s, etc. The method for the extraction solution to cover the area of the wafer to be detected in steps S12 - S13 includes, for example, manual method or mechanical method, etc.

[0039] Please refer to Figures 1 to 2As shown, in an embodiment of the present invention, in steps S12 - S13, an artificial method, for example, repeatedly releases and aspirates the extraction solution by a pipette, so that the extraction solution gradually covers the area to be detected on the wafer. Specifically, for example, it includes steps S121 - S122.

[0040] Step S121: Add the extraction solution with a pipette to make the extraction solution stay at a position in the area to be detected on the wafer for a preset time.

[0041] Step S122: Aspirate the extraction solution with a pipette, transfer the aspirated extraction solution to another position in the area to be detected on the wafer and stay for a preset time.

[0042] Please refer to Figures 1 to 2 As shown, in an embodiment of the present invention, in step S121, a pipette is used to drop the extraction solution at a position in the area to be detected on the wafer, so that the extraction solution covers this position for a preset time. The extraction solution reacts with the precious metal at this position, dissolves the precious metal at this position into the extraction solution, and achieves the purpose of collecting the precious metal at this position. Among them, according to the area of the wafer, the extraction solution volume of the pipette is taken as 2.0 μL / mm 2 - 3.1 μL / mm 2 for liquid extraction, that is, on the surface of each square millimeter of the wafer, 2.0 μL - 3.1 μL of the extraction solution is covered.

[0043] Please refer to Figures 1 to 2 As shown, in an embodiment of the present invention, after the collection of the precious metal at one position is completed, in step S122, a pipette is used to aspirate the extraction solution, transfer the aspirated extraction solution to another position in the area to be detected on the wafer and stay for a preset time, so that the extraction solution continues to cover the next position for a preset time. After the extraction solution dissolves the precious metal at the next position, the step of aspirating the extraction solution is repeated for the extraction solution at the next position until the extraction solution covers all positions in the area to be detected on the wafer, that is, after the extraction solution collects the precious metals at all positions in the area to be detected on the wafer, the steps of adding and aspirating the extraction solution are stopped, and the collection is completed.

[0044] Please refer to Figures 1 to 2As shown, in an embodiment of the present invention, since the surface of the wafer is hydrophilic, when the pipette aspirates the extraction solution at a position, there will inevitably be residual extraction solution at that position. If the residual extraction solution is not extracted, it will cause loss of the extraction solution, thereby affecting the judgment of the precious metal content on the surface of the wafer. Therefore, when the pipette aspirates the extraction solution at a position in the area to be detected on the wafer in step S122, an air gun is also used to assist the pipette in aspirating the extraction solution. Specifically, the air gun is used to blow and gather the extraction solution at a position in the area to be detected on the wafer under the tip of the pipette, facilitating the pipette to aspirate the extraction solution. Among them, the air gun is a stable gas, and the stable gas includes at least one of nitrogen and inert gases, etc., which can avoid introducing other impurities to the surface of the wafer by the gas, and the gas flow rate of the air gun is controlled at 0.4 m / s - 0.6 m / s. By using the air gun to assist the pipette in aspirating the extraction solution, all the extraction solution at a position in the area to be detected on the wafer can be collected, avoiding loss of the extraction solution, so that the precious metal content on the surface of the wafer can be accurately obtained based on the collected extraction solution later.

[0045] Please refer to Figure 1 As shown, in an embodiment of the present invention, after completing the collection of precious metals on the area to be detected on the wafer, in step S14, the extraction solution on the area to be detected on the wafer is collected and diluted 5 - 10 times with ultrapure water. Specifically, in this embodiment, for example, a pipette is used to aspirate the extraction solution on the surface of the wafer. At the same time, a stable gas is used to blow and gather the residual extraction solution on the surface of the wafer to avoid loss of the extraction solution.

[0046] Please refer to Figure 1 As shown, in an embodiment of the present invention, in step S15, an inductively coupled plasma mass spectrometer is used to test the content of precious metals in the diluted extraction solution. By using an inductively coupled plasma mass spectrometer, interference can be reduced, the precision and speed of the test can be improved, and the precious metal content on the surface of the wafer can be accurately and quickly obtained.

[0047] Please refer to Figures 1 to 3 As shown, in another embodiment of the present invention, in steps S12 - S13, a mechanical method can also be used to add and move the extraction solution on the area to be detected on the wafer. The mechanical method is carried out by means of an automatic vapor phase decomposition instrument (Vapor Phase decomposition, VPD) for example, and includes steps S131 - S134.

[0048] Step S131: Place the wafer horizontally on the detection table of the automatic vapor phase decomposition instrument.

[0049] Step S132: Apply the extraction solution to the area to be detected on the wafer.

[0050] Step S133: Move the extraction solution so that the extraction solution covers the area to be detected on the wafer.

[0051] Step S134: Collect the extraction liquid on the area to be detected of the wafer.

[0052] Please refer to Figure 1 and Figure 3 As shown, in an embodiment of the present invention, in steps S131 - S132, after the wafer is placed on the detection table of VPD, the extraction liquid pipeline is controlled to apply a preset dose of extraction liquid to the area to be detected of the wafer. Among them, the application method of the extraction liquid in this application is not limited. The extraction liquid can be applied to the area to be detected of the wafer at one time, or can be applied to different positions of the area to be detected of the wafer in multiple times.

[0053] Please refer to Figure 1 and Figure 3 As shown, in an embodiment of the present invention, after the extraction liquid is applied, in step S133, the extraction liquid is moved to cover the area to be detected of the wafer, and the extraction liquid collects the precious metals on the area to be detected of the wafer. Among them, the movement and covering methods of the extraction liquid in this application are not limited and can be selected according to actual needs. In this embodiment, when moving the extraction liquid, the detection table can be driven to rotate, so that the wafer on the detection table and the extraction liquid on the wafer rotate together, so that the extraction liquid evenly covers the area to be detected of the wafer. In another embodiment, the extraction liquid can also be gradually covered on the area to be detected of the wafer by repeatedly applying and sucking the extraction liquid. Specifically, after the extraction liquid stays at a position on the area to be detected of the wafer for a preset time, the extraction liquid at this position is sucked, and the sucked extraction liquid is moved to another position on the area to be detected of the wafer, so that the extraction liquid continues to stay at another position for a preset time until the extraction liquid gradually covers all positions in the area to be detected of the wafer.

[0054] Please refer to Figure 1 and Figure 3 As shown, in an embodiment of the present invention, after the extraction liquid covers the area to be detected of the wafer, in step S134, the extraction liquid on the area to be detected of the wafer is collected. Among them, the method of collecting the extraction liquid in this application is not limited, and specifically, different collection methods of the extraction liquid can be set corresponding to the application and movement methods of the extraction liquid introduced in the above steps. Specifically, when the method of repeatedly applying and sucking the extraction liquid is adopted, in step S134, the extraction liquid is collected by the way of sucking the extraction liquid for the last time. When the method of applying the extraction liquid at one time is adopted, the extraction liquid on the area to be detected of the wafer can be collected by sucking, diversion or rotation, etc.

[0055] Please refer to Figure 1 and Figure 3As shown, in an embodiment of the present invention, after step S134 is completed, steps S14 - S15 are continued to dilute and analyze the extraction liquid on the wafer surface. Among them, steps S14 - S15 are the same as those in the previous embodiment and will not be elaborated here.

[0056] In summary, the present invention provides a method for testing the precious metal content on the wafer surface. By preparing the extraction liquid, the precious metals on the wafer surface can be collected and analyzed to obtain the precious metal content on the wafer surface, and then the qualification rate of the device can be judged. By repeatedly releasing and sucking the extraction liquid, the extraction liquid can collect the precious metals at all positions on the area to be detected on the wafer, thereby improving the accuracy of the analysis result of the precious metal content on the wafer surface. By purging and gathering the extraction liquid on the area to be detected on the wafer, the loss of the extraction liquid can be avoided, so as to accurately obtain the precious metal content on the wafer surface.

[0057] The disclosed embodiments of the present invention above are only used to help explain the present invention. The embodiments do not describe all the details in detail, nor limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A method for testing the content of precious metals on a wafer surface, characterized in that: At least the following steps are included: Providing a wafer carrier, placing the wafer to be collected on the wafer carrier; Adding an extracting solution on the wafer, wherein the extracting solution at least comprises hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water, wherein the content of the ultrapure water is 56wt%-69wt%, the content of the hydrofluoric acid is 5wt%-10wt%, the content of the nitric acid is 13wt%-17wt%, and the content of the hydrochloric acid is 13wt%-17wt%; Moving the extracting liquid until the extracting liquid covers the wafer to-be-tested area, wherein the extracting liquid is gradually covered by the extracting liquid by repeatedly releasing and absorbing the extracting liquid with a pipette gun; Collecting the extract and diluting it 5-10 times with ultrapure water; and sending the diluted extract into an inductively coupled plasma mass spectrometer to analyze the precious metal content in the extract; The step of gradually covering the wafer area to be inspected with the extracting solution comprises at least the following steps: Add the extracting solution with a pipette, and allow the extracting solution to stay at a position in the wafer to be inspected area for a preset time; and The extraction liquid is sucked by a pipette, and an air gun is used to assist the pipette in sucking the extraction liquid, and the sucked extraction liquid is transferred to another position in the wafer to be inspected area and stays there for a preset time; According to the area of ​​the wafer, the extraction liquid volume of the pipette gun is 2.0 μL / mm 2 -3.1μL / mm 2 Take the liquid.

2. The testing method according to claim 1, characterized in that: Oxides on the surface of the wafer are removed before adding the extraction solution.

3. The testing method according to claim 1, characterized in that: The air gun is a stable gas.

4. The testing method according to claim 1, characterized in that: The gas flow rate of the air gun is controlled at 0.4m / s-0.6m / s.

5. The testing method according to claim 1, characterized in that: The preset time is 20s-120s.

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