Wafer surface platinum metal ion recovery method

Abstract

The invention relates to the technical field of semiconductor integrated circuit metal detection, in particular to a wafer surface platinum metal ion recovery method. The wafer surface platinum metal ion recovery method comprises the following steps: titrating a first volume of hydrofluoric acid solution to the center of a wafer to be detected; titrating a second volume of a mixed acid solution to the center of the wafer to be detected, so that the mixed acid solution and the hydrofluoric acid solution are mixed to form a platinum metal recovery solution; the mixed acid solution comprises concentrated hydrochloric acid and concentrated nitric acid; enabling the platinum metal recovery liquid to scan the surface of the to-be-detected wafer, and dissolving platinum metal ions in the surface of the to-be-detected wafer; and diluting and recovering the platinum metal recovery liquid. According to the wafer surface platinum metal ion recovery method, the problems that the concentration of aqua regia in recovered platinum metal ions is gradually increased and aqua regia with relatively high concentration and volume is easy to cause alarm of a detection device due to multiple aqua regia recovery operations in related technologies can be solved.

Description

Technical Field

[0001] The present application relates to the technical field of metal detection of semiconductor integrated circuits, and in particular to a pre-treatment method for detecting platinum metal contamination. Background Art

[0002] In the semiconductor industry, as the size of chip unit patterns becomes increasingly smaller, specific contamination problems on the surface of silicon wafers can lead to different defects in semiconductor devices. Excessive metal content can affect the yield of the chip.

[0003] In order to increase the life of power products, meet the market demand for high-performance super-junction devices or shielded gate trench devices, and improve product competitiveness, the platinum diffusion process is usually used to reduce the reverse recovery time of the switching device and reduce the minority carrier lifetime in the base region. The platinum diffusion process is to use platinum metal technology in the device manufacturing process, which will bring about the problem of platinum metal contamination.

[0004] In order to determine the platinum metal contamination status of semiconductor devices, platinum metal ion analysis technology is usually required. The related technology usually uses an aqua regia system to dissolve and recover platinum metal ions. However, the aqua regia system in the related technology is difficult to obtain a high recovery rate of platinum metal ions through a single recovery scan, so multiple aqua regia recovery operations are usually required. With the multiple aqua regia recovery operations, the aqua regia concentration in the recovered platinum metal ions gradually increases. A higher concentration of aqua regia is likely to cause the detection device to alarm and easily lead to inaccurate test data. Summary of the invention

[0005] The present application provides a method for recovering platinum metal ions on the surface of a chip, which can solve the problem in the related art that multiple aqua regia recovery operations are carried out, the concentration of aqua regia in the recovered platinum metal ions gradually increases, and aqua regia with a higher concentration and volume is likely to cause an alarm in the detection device.

[0006] In order to solve the technical problems in the background technology, the present application provides a method for recovering platinum metal ions on a wafer surface, and the method for recovering platinum metal ions on a wafer surface comprises the following steps:

[0007] titrating a first volume of hydrofluoric acid solution to the center of the wafer to be tested;

[0008] Titrate a second volume of mixed acid solution to the center of the wafer to be tested, so that the mixed acid solution is mixed with the hydrofluoric acid solution to form a platinum metal recovery solution; the mixed acid solution includes concentrated hydrochloric acid and concentrated nitric acid;

[0009] The platinum metal recovery liquid is used to scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested;

[0010] The platinum metal recovery liquid is diluted and recovered.

[0011] Optionally, the first volume of the hydrofluoric acid solution accounts for 1% to 5% of the second volume of the mixed acid solution.

[0012] Optionally, the ratio of concentrated hydrochloric acid to concentrated nitric acid in the mixed acid solution is 3:1 to 5:1.

[0013] Optionally, the step of diluting and recovering the platinum metal recovery solution comprises:

[0014] The platinum metal recovery liquid is recovered and diluted 8 to 12 times.

[0015] Optionally, the step of causing the platinum metal recovery liquid to scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested comprises:

[0016] The platinum metal recovery liquid is scanned in a circular manner from the center to the outer edge of the wafer to be tested, so that the platinum metal recovery liquid is fully and evenly coated on the surface of the wafer to be tested, and the platinum metal ions in the surface of the wafer to be tested are extracted.

[0017] Optionally, the concentration of the hydrofluoric acid solution is 45% to 50%.

[0018] Optionally, the step of diluting and recovering the platinum metal recovery solution comprises:

[0019] The platinum metal recovery solution was diluted and recovered using 800 ul to 900 ul of deionized water.

[0020] The technical solution of the present application includes at least the following advantages: the present application titrates a second volume of mixed acid solution at the center of the wafer to be tested immediately after titrating a first volume of hydrofluoric acid solution at the center of the wafer to be tested, wherein the mixed acid solution can dissolve the platinum metal ions on the surface of the wafer to be tested. The method of first dropping a hydrofluoric acid solution and then dropping a mixed acid solution to form a platinum metal recovery solution can take into account the effect of hydrofluoric acid etching the natural oxide layer of the wafer to be tested and the effect of the mixed acid solution dissolving the platinum metal ions, thereby avoiding the problem in the related art that the platinum metal ions are difficult to be dissolved and recovered due to entering the natural oxide layer. At the same time, the platinum metal recovery solution formed by mixing the hydrofluoric acid solution and the mixed acid solution can optimize the concentration ratio of the mixed acid solution, thereby avoiding the problem of machine alarm caused by excessive concentration of the mixed acid solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0022] Figure 1 A flow chart of a method for recovering platinum metal ions from a wafer surface provided in one embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings to clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0024] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0025] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can also be the internal connection of two components, it can be a wireless connection, or it can be a wired connection. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0026] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0027] Figure 1 The flow chart of the method for recovering platinum metal ions from the wafer surface provided by an embodiment of the present application is shown. Figure 1 As can be seen from the figure, the method for recovering platinum metal ions on the wafer surface comprises the following steps:

[0028] Step S1: titrate a first volume of hydrofluoric acid solution to the center of the wafer to be tested.

[0029] Step S2: titrating a second volume of mixed acid solution to the center of the wafer to be tested, so that the mixed acid solution is mixed with the hydrofluoric acid solution to form a platinum metal recovery solution; the mixed acid solution includes concentrated hydrochloric acid and concentrated nitric acid.

[0030] Exemplarily, the second volume of the mixed acid solution may be dripped to the center of the wafer to be tested by manual titration.

[0031] Step S3: The platinum metal recovery liquid is made to scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested.

[0032] Exemplarily, the platinum metal recovery liquid can be scanned on the surface of the wafer to be tested by a scanning head, wherein the material of the scanning head can be fusible polytetrafluoroethylene (PFA) to reduce the hydrophilicity of the scanning head so that subsequent test data presents convergence.

[0033] Step S4: diluting and recovering the platinum metal recovery liquid.

[0034] In this embodiment, the platinum metal recovery liquid is scanned

[0035] The present application titrates a second volume of mixed acid solution at the center of the wafer to be tested immediately after titrating a first volume of hydrofluoric acid solution at the center of the wafer to be tested, wherein the mixed acid solution can dissolve the platinum metal ions on the surface of the wafer to be tested. The method of first dropping a hydrofluoric acid solution and then dropping a mixed acid solution to form a platinum metal recovery solution can take into account the effect of hydrofluoric acid etching the natural oxide layer of the wafer to be tested and the effect of the mixed acid solution dissolving the platinum metal ions, thereby avoiding the problem in the related art that the platinum metal ions are difficult to be dissolved and recovered due to entering the natural oxide layer. At the same time, the platinum metal recovery solution formed by mixing the hydrofluoric acid solution and the mixed acid solution can optimize the concentration ratio of the mixed acid solution, thereby avoiding the problem of machine alarm due to a high volume of high-concentration mixed acid solution.

[0036] Exemplarily, the first volume of the hydrofluoric acid solution accounts for 1% to 5% of the second volume of the mixed acid solution, and the content of concentrated hydrochloric acid in the mixed acid solution is 35% to 40%, the content of concentrated nitric acid is 65% to 70%, and the concentration of the hydrofluoric acid solution is 45% to 50%. In this embodiment, by making the first volume of the hydrofluoric acid solution account for 1% to 5% of the second volume of the mixed acid solution, the effect of hydrofluoric acid etching the natural oxide layer of the wafer to be tested and the effect of the mixed acid solution dissolving platinum metal ions can be taken into account, avoiding the problem of platinum metal ions entering the natural oxide layer and being difficult to be dissolved and recovered in the related art, and the platinum metal recovery liquid formed by mixing the hydrofluoric acid solution and the mixed acid solution can optimize the concentration ratio of the mixed acid solution, avoiding the problem of machine alarm caused by a high volume of high-concentration mixed acid solution.

[0037] Optionally, the first volume of the hydrofluoric acid solution is 2ul, and the second volume of the mixed acid solution is 110ul, wherein the first volume of the hydrofluoric acid solution is 2ul and the second volume of the mixed acid solution is 110ul, which can avoid the problem of liquid residue after the platinum metal recovery liquid scans the entire surface of the wafer to be tested.

[0038] Exemplarily, the ratio of concentrated hydrochloric acid to concentrated nitric acid in the mixed acid solution is 3: 1 to 5: 1. The platinum metal ions on the surface of the wafer can be fully extracted by using a mixed acid solution in which the ratio of concentrated hydrochloric acid to concentrated nitric acid is 3: 1 to 5: 1.

[0039] Exemplarily, after the platinum metal recovery liquid is recovered, the platinum metal recovery liquid is diluted 8 to 12 times. The diluted platinum metal recovery liquid can then be subjected to ICP-MS (inductively coupled plasma mass spectrometry) for quantitative determination of platinum metal ions.

[0040] Exemplarily, after the step of allowing the platinum metal recovery liquid to scan the surface of the wafer to be tested and dissolving the platinum metal ions on the surface of the wafer to be tested is completed, before the step of diluting and recovering the platinum metal recovery liquid is performed, the following step is further performed: allowing the platinum metal recovery liquid to stand for 8s to 10s. The platinum metal recovery liquid is allowed to stand on the surface of the wafer to be tested so that the platinum metal recovery liquid dissolves the natural oxide layer of the wafer to be tested, and the platinum metal ions are fully dissolved in the platinum metal recovery liquid.

[0041] In addition, when the platinum metal recovery liquid is made to scan the surface of the wafer to be tested, the scanning speed of the platinum metal recovery liquid scanning the surface of the wafer to be tested can also be reduced, so that the platinum metal recovery liquid can fully extract the platinum metal ions. Exemplarily, the scanning speed of the platinum metal recovery liquid scanning the surface of the wafer to be tested is reduced to 10 mm / s, and the scanning direction of the platinum metal recovery liquid scanning is to gradually draw a circular scan from the center of the wafer to be tested to the outer edge of the wafer to be tested, so that the platinum metal recovery liquid is fully and evenly coated on the surface of the wafer to be tested.

[0042] Illustratively, in step S3, the platinum metal recovery liquid is used to scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested. The platinum metal recovery liquid can be scanned in a circular manner from the center to the outer edge of the wafer to be tested, so that the platinum metal recovery liquid is fully and evenly coated on the surface of the wafer to be tested to extract the platinum metal ions on the surface of the wafer to be tested.

[0043] The step of diluting and recovering the platinum metal recovery liquid comprises:

[0044] The platinum metal recovery solution was diluted and recovered using 800ul to 1000ul of deionized water.

[0045] When verifying the method for recovering platinum metal ions on the chip surface described in the present application, by dropping 300 μL of the 5 ppb standard solution in the present application onto a clean chip and letting it stand to dry, the recovery rates of the platinum metal ions after two scans all met the test requirements, that is, the recovery rates were all greater than 80%. Therefore, the recovery rates of the method for recovering platinum metal ions on the chip surface described in the present application all met the test requirements, and the test data was accurate.

[0046] The present application titrates a second volume of mixed acid solution at the center of the wafer to be tested immediately after titrating a first volume of hydrofluoric acid solution at the center of the wafer to be tested, wherein the mixed acid solution can dissolve the platinum metal ions on the surface of the wafer to be tested. The method of first dropping a hydrofluoric acid solution and then dropping a mixed acid solution to form a platinum metal recovery solution can take into account the effect of hydrofluoric acid etching the natural oxide layer of the wafer to be tested and the effect of the mixed acid solution dissolving the platinum metal ions, thereby avoiding the problem in the related art that the platinum metal ions are difficult to be dissolved and recovered due to entering the natural oxide layer. At the same time, the platinum metal recovery solution formed by mixing the hydrofluoric acid solution and the mixed acid solution can optimize the concentration ratio of the mixed acid solution, thereby avoiding the problem of machine alarm due to a high volume of high-concentration mixed acid solution.

[0047] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection created by this application.

Claims

1. A method for recovering platinum metal ions from a wafer surface, characterized in that: The method for recovering platinum metal ions from the wafer surface comprises the following steps: titrating a first volume of hydrofluoric acid solution to the center of the wafer to be tested; Titrate a second volume of mixed acid solution to the center of the wafer to be tested, so that the mixed acid solution is mixed with the hydrofluoric acid solution to form a platinum metal recovery solution; the mixed acid solution includes concentrated hydrochloric acid and concentrated nitric acid; The platinum metal recovery liquid is used to scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested; The platinum metal recovery liquid is diluted and recovered.

2. The method for recovering platinum metal ions from wafer surface as claimed in claim 1, wherein: The first volume of the hydrofluoric acid solution accounts for 1% to 5% of the second volume of the mixed acid solution.

3. The method for recovering platinum metal ions from wafer surface as claimed in claim 1, characterized in that: The ratio of concentrated hydrochloric acid to concentrated nitric acid in the mixed acid solution is 3:1 to 5:

1.

4. The method for recovering platinum metal ions from wafer surface as claimed in claim 1, characterized in that: The step of diluting and recovering the platinum metal recovery liquid comprises: The platinum metal recovery liquid is recovered and diluted 8 to 12 times.

5. The method for recovering platinum metal ions from the wafer surface as claimed in claim 1, characterized in that: The step of making the platinum metal recovery liquid scan the surface of the wafer to be tested to dissolve the platinum metal ions on the surface of the wafer to be tested comprises: The platinum metal recovery liquid is scanned in a circular manner from the center to the outer edge of the wafer to be tested, so that the platinum metal recovery liquid is fully and evenly coated on the surface of the wafer to be tested, and the platinum metal ions in the surface of the wafer to be tested are extracted.

6. The method for recovering platinum metal ions from the wafer surface as claimed in claim 1, characterized in that: The concentration of the hydrofluoric acid solution is 45% to 50%.

7. The method for recovering platinum metal ions from the wafer surface as claimed in claim 1, characterized in that: The step of diluting and recovering the platinum metal recovery liquid comprises: The platinum metal recovery solution was diluted and recovered using 800 ul to 900 ul of deionized water.

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