Method for testing content of precious metal on surface of wafer

Abstract

The invention discloses a method for testing the content of precious metal on the surface of a wafer, and belongs to the technical field of semiconductors. The method at least comprises the following steps: providing a wafer bearing table, and arranging a wafer to be collected on the wafer bearing table; adding an extracting solution on the wafer, wherein the extracting solution at least comprises hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water; moving the extracting solution until the extracting solution covers a to-be-detected area of the wafer; collecting the extracting solution, and diluting the extracting solution by 5-10 times with ultrapure water; and feeding the diluted extracting solution into an inductively coupled plasma mass spectrometer, and analyzing the content of the noble metal in the extracting solution. By means of the method for testing the content of the precious metal on the surface of the wafer, the precious metal at all positions of the to-be-detected area of the wafer can be collected, and the content of the precious metal on the to-be-detected area of the wafer can be accurately obtained.

Description

Technical Field

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

[0002] During the processing of the wafer, various metal impurities will contaminate its surface, causing failure of the subsequent devices. Therefore, the metal on the wafer surface must be collected and analyzed to determine the metal content on the wafer surface, and then judge the qualified rate of the device. At present, in the process of collecting metals on the wafer surface, on the one hand, the extracting solution cannot extract precious metals such as platinum, and it cannot be guaranteed that the extracting solution has accurately collected all positions on the wafer surface. On the other hand, the surface of the wafer may be hydrophilic. When the extracting solution is collected manually, it is easy to cause the loss of the extracting solution, thereby affecting the accuracy of the analysis of the extracting solution, and it is impossible to accurately obtain the content of precious metals on the wafer surface. Summary of the invention

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

[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 a wafer surface, which at least comprises the following steps: Providing a wafer carrier, placing the wafer to be collected on the wafer carrier; adding an extracting solution onto the wafer, wherein the extracting solution contains at least hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water; Move the extraction liquid to the area to be inspected on the wafer covered by the extraction liquid; collecting the extract and diluting it 5-10 times with ultrapure water; and The diluted extract is sent to an inductively coupled plasma mass spectrometer to analyze the precious metal content in the extract.

[0006] In one embodiment of the present invention, in the extract, 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%.

[0007] In one embodiment of the present invention, oxides on the surface of the wafer are removed before adding the extraction solution.

[0008] In one embodiment of the present invention, the extraction liquid is repeatedly released and sucked by a pipette gun so that the extraction liquid gradually covers the wafer area to be inspected.

[0009] In one embodiment of the present invention, the extraction liquid gradually covers the wafer to-be-tested area, which at least includes 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 extracting liquid is sucked up by a pipette, and the sucked extracting liquid is transferred to another position in the wafer to be inspected area and kept there for a preset time.

[0010] In one embodiment of the present invention, an air gun is used to assist the pipette to absorb the extraction liquid, and the air gun is a stable gas.

[0011] 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.

[0012] In an embodiment of the present invention, the preset time is 20s-120s.

[0013] In one embodiment of the present invention, the extraction liquid volume of the pipette gun is 2.0 μL / mm according to the area of ​​the wafer. 2 -3.1μL / mm 2 Take the liquid.

[0014] In summary, the present invention provides a method for testing the content of precious metals on the surface of a wafer, which can collect precious metals on the area to be tested on the wafer, thereby obtaining the content of precious metals on the surface of the wafer. The added extracting solution can effectively obtain the precious metals on the surface of the wafer, and the extracting solution can accurately cover the points to be tested on the surface of the wafer by repeatedly releasing and absorbing the extracting solution, thereby avoiding residual extracting solution on the surface of the wafer and avoiding the loss of extracting solution, thereby accurately obtaining the content of precious metals on the surface of the wafer.

[0015] Of course, any method of implementing the present invention does not necessarily need to achieve all of the advantages mentioned above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0017] Figure 1 Flow chart of a method for testing the precious metal content on a wafer surface in one embodiment of the present invention.

[0018] Figure 2 FIG. 4 is a flow chart of a manual method in one embodiment of the present invention.

[0019] Figure 3 FIG. 1 is a flow chart of a mechanical method in another embodiment of the present invention. DETAILED DESCRIPTION

[0020] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict.

[0021] It should be understood that the present invention can be implemented in different forms and should not be interpreted as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0022] The technical solution of the present invention is further described in detail below in conjunction with the embodiments and drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0023] See also Figure 1 As shown, the present invention provides a method for testing the precious metal content on the surface of a wafer, for example, including steps S11-S15.

[0024] Step S11, providing a wafer carrying platform, and placing the wafer to be collected on the wafer carrying platform.

[0025] Step S12: adding an extracting solution onto the wafer, wherein the extracting solution at least contains hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water.

[0026] Step S13, moving the extraction liquid until the extraction liquid covers the wafer to-be-tested area.

[0027] Step S14, collecting the extract and diluting it 5-10 times with ultrapure water.

[0028] Step S15, sending the diluted extract to an inductively coupled plasma mass spectrometer to analyze the precious metal content in the extract.

[0029] See also Figure 1As shown, in one embodiment of the present invention, in step S11, the wafer is placed horizontally on a wafer carrier, and the wafer includes a wafer area to be detected. It is necessary to test and analyze the precious metal content in the wafer area to be detected to determine the qualified 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 life of the wafer carrier. In this embodiment, after the wafer is placed, the oxide layer formed on the surface of the wafer due to natural oxidation or thermal oxidation is also removed to avoid the oxide layer blocking the extracting solution from directly contacting the wafer surface, so as to facilitate the extracting solution to collect the precious metals on the wafer surface. Among them, the method of removing the oxide layer is, for example, etching, and the etching is, for example, dry etching or wet etching. Specifically, in this embodiment, for example, HF aerosol is used to etch the surface of the wafer.

[0030] See also Figure 1 As shown, after etching the surface of the wafer, in steps S12-S13, an extracting solution is added to the wafer area to be detected, and the extracting solution is moved to all positions in the wafer area to be detected covered by the extracting solution. Specifically, in the extracting 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 extracting solution can dissolve and effectively extract the precious metals on the wafer area to be detected, and the precious metals include at least platinum.

[0031] See also Figure 1 As shown, in one embodiment of the present invention, in steps S12-S13, when the extraction liquid covers the wafer area to be inspected, the extraction liquid is first added to a position in the area to be inspected, and after the extraction liquid covers the position for a preset time, the extraction liquid at the position is moved to another position in the area to be inspected, and the extraction liquid continues to cover another position for a preset time until the extraction liquid gradually covers all positions in the wafer area to be inspected. The preset time is, for example, 20s-120s, specifically, 30s, 40s or 60s, etc. The method for the extraction liquid to cover the wafer area to be inspected in steps S12-S13 includes, for example, a manual method or a mechanical method.

[0032] See also Figure 1 to Figure 2 As shown, in one embodiment of the present invention, in steps S12-S13, an artificial method such as repeatedly releasing and absorbing the extracting liquid through a pipette gun allows the extracting liquid to gradually cover the wafer area to be inspected, specifically, for example, including steps S121-S122.

[0033] Step S121 , adding extraction liquid using a pipette gun, so that the extraction liquid stays at a position in the wafer to be inspected area for a preset time.

[0034] Step S122: use a pipette to absorb the extract, transfer the absorbed extract to another position in the wafer to be inspected area, and keep it for a preset time.

[0035] See also Figure 1 to Figure 2 As shown, in one embodiment of the present invention, in step S121, a pipette gun is used to drip an extracting liquid at a position in the wafer to be detected, so that the extracting liquid covers the position for a preset time, and the extracting liquid reacts with the precious metal at the position, dissolving the precious metal at the position into the extracting liquid, thereby achieving the purpose of collecting the precious metal at the position. According to the area of ​​the wafer, the amount of extracting liquid of the pipette gun is 2.0 μL / mm 2 -3.1μL / mm 2 Liquid is taken, that is, 2.0μL-3.1μL of extraction liquid is covered on each square millimeter of the wafer surface.

[0036] See also Figure 1 to Figure 2 As shown, in one embodiment of the present invention, after the collection of precious metals at one position is completed, in step S122, the extraction liquid is sucked up by a pipette, and the sucked extraction liquid is transferred to another position in the wafer to be detected area and stays for a preset time, so that the extraction liquid continues to cover the next position for a preset time. After the extraction liquid dissolves the precious metal at the next position, the extraction step is repeated on the extraction liquid at the next position until the extraction liquid covers all positions in the wafer to be detected area, that is, after the extraction liquid collects the precious metals at all positions in the wafer to be detected area, the steps of adding and sucking the extraction liquid are stopped to complete the collection.

[0037] See also Figure 1 to Figure 2 As shown, in one embodiment of the present invention, since the surface of the wafer is hydrophilic, when the liquid pipette draws the extract at a position, there must be residual extract at the position. If the residual extract is not extracted, it will cause the loss of the extract, thereby affecting the judgment of the precious metal content on the surface of the wafer. Therefore, in step S122, when the liquid pipette draws the extract at a position in the wafer to be detected area, the liquid pipette is also assisted by an air gun to draw the extract. Specifically, the liquid extract at a position in the wafer to be detected area is purged and gathered under the gun head of the liquid pipette using an air gun, so that the liquid pipette can draw the extract. Among them, the air gun is a stable gas, and the stable gas includes at least one of nitrogen and inert gas, etc., which can avoid the gas from introducing other impurities to the surface of the wafer, and the gas flow rate of the air gun is controlled at 0.4m / s-0.6m / s. By using the air gun to assist the liquid pipette to draw the extract, all the extracts at a position in the wafer to be detected area can be collected, and the loss of the extract can be avoided, so that the precious metal content on the surface of the wafer can be accurately obtained according to the collected extract later.

[0038] See also Figure 1As shown, in one embodiment of the present invention, after the precious metals on the wafer to be detected are collected, in step S14, the extract on the wafer to be detected is collected and diluted 5-10 times with ultrapure water. Specifically, in this embodiment, for example, a pipette is used to absorb the extract on the surface of the wafer, and at the same time, a stable gas is used to purge and gather the residual extract on the surface of the wafer to avoid the loss of the extract.

[0039] See also Figure 1 As shown, in one 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 extract. 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 wafer surface can be accurately and quickly obtained.

[0040] See also 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 liquid on the wafer to be inspected area. The mechanical method is performed, for example, with the aid of an automatic vapor phase decomposition (VPD), and includes steps S131-S134.

[0041] Step S131 , placing the wafer horizontally on a detection table of an automatic gas phase decomposition instrument.

[0042] Step S132: applying an extraction liquid to the wafer area to be inspected.

[0043] Step S133, moving the extraction liquid so that the extraction liquid covers the wafer area to be inspected.

[0044] Step S134 , collecting the extraction liquid on the wafer area to be inspected.

[0045] See also Figure 1 and Figure 3 As shown, in one embodiment of the present invention, in steps S131-S132, after the wafer is placed on the inspection table of the VPD, the extraction liquid pipeline is controlled to apply a preset dose of extraction liquid to the wafer area to be inspected. The present application does not limit the method of applying the extraction liquid, and the extraction liquid can be applied to the wafer area to be inspected at one time, or applied to different positions of the wafer area to be inspected in multiple times.

[0046] See also Figure 1 and Figure 3As shown, in one embodiment of the present invention, after applying the extracting liquid, in step S133, the extracting liquid is moved so that the extracting liquid covers the wafer area to be detected, and the extracting liquid collects the precious metals on the wafer area to be detected. Among them, the present application does not limit the movement and covering method of the extracting liquid, and can be selected according to actual needs. In this embodiment, when moving the extracting liquid, the detection table can be driven to rotate so that the wafer on the detection table and the extracting liquid on the wafer rotate together, so that the extracting liquid evenly covers the wafer area to be detected. In another embodiment, the extracting liquid can also be gradually covered by repeatedly applying and absorbing the extracting liquid. Specifically, after the extracting liquid stays at a position in the wafer area to be detected for a preset time, the extracting liquid at the position is absorbed, and the absorbed extracting liquid is moved to another position in the wafer area to be detected, so that the extracting liquid continues to stay at another position for a preset time until the extracting liquid gradually covers all positions in the wafer area to be detected.

[0047] See also Figure 1 and Figure 3 As shown, in one embodiment of the present invention, after the extracting liquid covers the wafer area to be inspected, in step S134, the extracting liquid on the wafer area to be inspected is collected. Among them, the present application does not limit the method of collecting the extracting liquid, and specifically, different methods of collecting the extracting liquid can be set according to the methods of applying and moving the extracting liquid introduced in the above steps. Specifically, when the method of repeatedly applying and absorbing the extracting liquid is adopted, in step S134, the extracting liquid is collected by the last method of absorbing the extracting liquid. When the method of applying the extracting liquid once is adopted, the extracting liquid on the wafer area to be inspected can be collected by suction, diversion or rotation.

[0048] See also Figure 1 and Figure 3 As shown, in one embodiment of the present invention, after completing step S134, the steps S14-S15 are continued to dilute and analyze the extract on the wafer surface. Among them, steps S14-S15 are the same as the previous embodiment and will not be elaborated here.

[0049] In summary, the present invention provides a method for testing the content of precious metals on the surface of a wafer. By preparing an extracting solution, the precious metals on the surface of the wafer can be collected and analyzed to obtain the content of precious metals on the surface of the wafer, thereby determining the qualified rate of the device. By repeatedly releasing and absorbing the extracting solution, the extracting solution can collect precious metals at all positions on the wafer to be tested, thereby improving the accuracy of the analysis results of the precious metal content on the surface of the wafer. By purging and gathering the extracting solution on the wafer to be tested area, the loss of the extracting solution can be avoided, thereby accurately obtaining the precious metal content on the surface of the wafer.

[0050] The embodiments of the present invention disclosed above are only used to help illustrate the present invention. The embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only 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 onto the wafer, wherein the extracting solution contains at least hydrofluoric acid, nitric acid, hydrochloric acid and ultrapure water; Move the extraction liquid until the extraction liquid covers the wafer to-be-tested area; Collecting the extract and diluting it 5-10 times with ultrapure water; and The diluted extract is sent to an inductively coupled plasma mass spectrometer to analyze the precious metal content in the extract.

2. The testing method according to claim 1, characterized in that: In the extract, 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%.

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

4. The testing method according to claim 1, characterized in that: The extraction liquid is repeatedly released and sucked by a pipette so that the extraction liquid gradually covers the wafer area to be inspected.

5. The testing method according to claim 4, characterized in that: The extracting liquid gradually covers the wafer area to be inspected, and at least comprises 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 extracting liquid is sucked up by a pipette, and the sucked extracting liquid is transferred to another position in the wafer to be inspected area and kept there for a preset time.

6. The testing method according to claim 5, characterized in that: An air gun is used to assist the pipette to absorb the extraction liquid, and the air gun is a stable gas.

7. The testing method according to claim 6, characterized in that: The gas flow rate of the air gun is controlled at 0.4m / s-0.6m / s.

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

9. The testing method according to claim 5, characterized in that: 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.

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