A method for enriching noble metal elements on a wafer surface and a method for analyzing the wafer surface

Abstract

The application provides a method for enriching and analyzing noble metal elements on a wafer surface. The method for enriching noble metal elements on a wafer surface comprises the following steps: a, b, c and d, which are sequentially performed, so as to effectively convert the noble metal elements in a metallic state into an ionic state, and convert the hydrophilic surface of the wafer into a hydrogen passivated hydrophobic interface; then, a certain scanning liquid is used to collect metal contamination from the hydrophobic interface layer, and then an alkaline solution is added to dilute and control the pH value. The above-mentioned enrichment method can significantly shorten the scanning time, improve the yield efficiency of noble metal elements, and effectively reduce the corrosion of the equipment.

Description

Technical Field

[0001] This invention relates to the field of detection and analysis, and in particular to a method for enriching and analyzing noble metal elements on a wafer surface. Background Technology

[0002] Silicon wafer processing introduces various metallic impurities, which can lead to the failure of downstream devices. For example, light metals (Na, Mg, Al, K, Ca, etc.) can reduce device breakdown voltage, while heavy metals (Cr, Mn, Fe, Ni, Cu, Zn, etc.) can reduce device lifespan. Therefore, as a raw material for devices, the surface metal content of silicon wafers directly affects the device yield. Thus, elemental analysis of the wafer surface is crucial.

[0003] Specific contamination issues can lead to various defects in semiconductor devices; these metallic impurities are typically present in trace amounts of metal ions. Currently, the most common technique for detecting these trace metal ions on wafer surfaces is VPD (Vapor Phase Decomposition) combined with one of the following elemental analysis devices:

[0004] 1. TXRF (Total Reflectance X-ray Fluorescence Spectrometer)

[0005] Because TXRF uses X-rays as the excitation source for fluorescence, it cannot detect trace amounts of certain light metal elements such as Na, Mg, and Al. It is generally applicable to heavy metals.

[0006] 2. TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry)

[0007] TOF-SIMS can perform full element detection, but the calibration and quantification process is too complicated.

[0008] 3. ICPMS (Inductively Coupled Plasma Mass Spectrometry)

[0009] ICP-MS can analyze almost all elements on Earth (Li-U). This technique, developed in the 1980s, is a novel analytical method. It combines the high-temperature (8000K) ionization characteristics of ICP with the sensitive and rapid scanning capabilities of quadrupole mass spectrometry, forming a powerful new technique for elemental, isotopic, and speciation analysis. This technique offers extremely low detection limits, a very wide dynamic linear range, simple spectral lines, minimal interference, high analytical precision, fast analysis speed, and the ability to provide isotopic information.

[0010] Therefore, among the three methods mentioned above, ICP-MS is the optimal choice.

[0011] The testing process for metallic elements on the surface of silicon wafers (which can be fully automated) mainly includes the following four steps:

[0012] 1. Place the silicon wafer in a VPD chamber and expose it to HF vapor to dissolve the natural oxide or thermally oxidized SiO2 surface layer;

[0013] 2. Place the extraction droplet (usually 250 μL of 2% HF / 2% H2O2) on the wafer and then tilt it in a carefully controlled manner so that the droplet “sweeps” across the wafer surface;

[0014] 3. As the extraction droplets move across the wafer surface, they collect dissolved SiO2 and other contaminant metals;

[0015] 4. Transfer the extracted droplets from the wafer surface to an ICP-MS or ICP-MS / MS system for analysis.

[0016] Driven by Moore's Law, high-performance, low-power chips based on the 7-nanometer technology, primarily FinFETs, are already integrated into today's smartphones. However, few people know that manufacturing such powerful chips requires the introduction of numerous new chemical elements. Each technology generation introduces different chemical elements to meet the demands of improved chip performance; for example, the introduction of hafnium (Hf) ushered in the era of high-k metal gates. The introduction of different chemical elements also increases the difficulty of controlling metal contamination during chip manufacturing. As mentioned earlier, vapor phase decomposition metal contamination collection systems (VPD) combined with inductively coupled plasma mass spectrometry (ICP-MS) are currently common methods for detecting metal contamination, and their sensitivity can improve the detection sensitivity of various elements to E6-7 atoms / cm². 2 .

[0017] Besides the logic devices driven by Moore's Law mentioned above, the "more than Moore" field introduces some noble metal elements (Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, etc.) to manufacture advanced sensors, such as Ag (mirrors), Au (biochips), Ir / Ru (magnetic sensors), and Pd (carbon-based devices). Because noble metal elements are chemically inert, they are generally difficult to collect using conventional vapor phase decomposition metal collection (VPD) systems composed of hydrofluoric acid and hydrogen peroxide, significantly increasing the difficulty of metal contamination control compared to conventional elements. Literature review suggests that the difficulty in collecting metallic noble metals compared to ionic noble metals may be related to their chemical inertness. Although the industry has introduced aqua regia-based scanning liquids, achieving a collection rate of >80% for metallic elements requires an additional scanning time of approximately one hour. First, a collection efficiency of ≥1 hour / piece cannot meet the production capacity requirements of the microelectronics field; second, aqua regia is a highly corrosive and volatile mixture of concentrated nitric acid and concentrated hydrochloric acid, thus placing extremely high demands on the collection equipment. Research indicates that the industry currently lacks VPD equipment and methods that can rapidly collect precious metal contaminants. Summary of the Invention

[0018] In view of this, the purpose of this invention is to provide a method and analysis method for enriching and analyzing noble metal elements on the surface of a wafer. The method provided by this invention can effectively enrich noble metal elements on the wafer surface, improve the yield efficiency of noble metal elements, and reduce equipment corrosion.

[0019] This invention provides a method for enriching noble metal elements on a wafer surface, comprising the following steps:

[0020] a) Place the wafer in the vHF chamber of the VPD equipment, introduce HF vapor into the vHF chamber for etching, and then purge with inert gas to remove any residual HF vapor in the vHF chamber.

[0021] b) Strong acid vapor and oxidizing vapor are introduced into the vHF chamber respectively for corrosion treatment, so that the metallic noble metal elements on the wafer surface are corroded into ionic state. Then, inert gas is introduced to purge and remove the strong acid vapor and oxidizing vapor in the vHF chamber.

[0022] The strongly acidic vapor is selected from at least one of HCl vapor, HNO3 vapor, HBr vapor, HI vapor, and HClO3 vapor;

[0023] The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor;

[0024] c) HF vapor and oxidizing vapor are introduced into the vHF chamber respectively for etching treatment, which removes the 1-50 nm thick surface layer of the wafer.

[0025] The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor;

[0026] d) Continue to introduce HF vapor into the vHF chamber to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer. Then, introduce inert gas to purge and remove the residual HF vapor in the vHF chamber.

[0027] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, and apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, thereby obtaining a collection liquid;

[0028] f) Dilute the collected solution with an alkaline solution to obtain the solution to be analyzed.

[0029] Preferably, in step a), the flow rate of the HF steam is 100-2000 sccm, and the introduction time is 1-3 min.

[0030] Preferably, in step b), the flow rate of the strong acid vapor is 30–5000 sccm, and the introduction time is 2–30 min;

[0031] The flow rate of the oxidizing steam is 30–5000 sccm, and the introduction time is 2–30 min.

[0032] Preferably, in step c), the flow rate of the HF steam is 100-2000 sccm, and the introduction time is 1-5 min;

[0033] The flow rate of the oxidizing steam is 100–1000 sccm, and the introduction time is 1–5 min.

[0034] Preferably, in step d), the flow rate of the HF steam is 500–2000 sccm, and the introduction time is 15–300 s.

[0035] Preferably, in step f), the alkaline solution is at least one of ammonia, tetramethylammonium hydroxide solution, and chlorine solution;

[0036] The amount of alkaline solution used is such that the pH reaches 2-3.

[0037] Preferably, in step e), the scanning solution includes: a mixture of HF acid and other acids;

[0038] The other acid solution is at least one of HNO3 acid solution, HCl acid solution and H2O2 acid solution.

[0039] Preferably, for the precious metal element Ag, the scanning solution used is a mixture of HF acid, HNO3 acid and water;

[0040] The mass percentage concentration of the HF acid solution is 35% to 49%.

[0041] The mass percentage concentration of the HNO3 acid solution is 50% to 69%.

[0042] The volume ratio of HF acid solution: HNO3 acid solution: water is 1:(1-20):(1-100);

[0043] For the precious metal element Au, the scanning solution used is a mixture of HF acid, HCl acid and HNO3 acid.

[0044] The mass percentage concentration of the HF acid solution is 35% to 49%.

[0045] The mass percentage concentration of the HCl acid solution is 20% to 30%.

[0046] The mass percentage concentration of the HNO3 acid solution is 50% to 69%.

[0047] The volume ratio of HF acid solution: HCl acid solution: HNO3 acid solution is 1:(1-15):(1-5);

[0048] For the noble metal element Pt, the scanning solution used is a mixture of HF acid and H2O2 acid.

[0049] The mass percentage concentration of the HF acid solution is 35% to 49%.

[0050] The mass percentage concentration of the H2O2 acid solution is 28% to 35%.

[0051] The volume ratio of HF acid solution to H2O2 acid solution is 1:(1-50).

[0052] Preferably, in step b), the flow rate of the inert gas is 1000-20000 sccm, and the purging time is 2-10 min;

[0053] In step d), the flow rate of the inert gas is 1000-20000 sccm, and the purging time is 1-5 min.

[0054] This invention also provides a method for analyzing noble metal elements on a wafer surface, comprising:

[0055] g) Obtain the solution to be analyzed;

[0056] h) Pass the solution to be analyzed into an inductively coupled plasma mass spectrometer for elemental analysis;

[0057] The solution to be analyzed is obtained by the enrichment method described in the above technical solution.

[0058] The method for enriching noble metal elements on wafer surfaces provided by this invention involves first performing different treatments in steps a), b), c), and d) sequentially to effectively convert metallic noble metal elements into ionic states and transform the hydrophilic surface of the wafer into a hydrogen-passivated hydrophobic interface. Then, a specific scanning solution is used to collect metal contaminants from the hydrophobic interface layer. Afterward, an alkaline solution is added for dilution and pH control. This enrichment method significantly shortens the scanning time and improves the recovery efficiency of noble metal elements. Aqua regia requires a reaction time of over 15 minutes to ensure a recovery rate of over 90%, and the scanning time is generally over 30 minutes. In contrast, the enrichment method of this invention can complete the scanning within 15 minutes, achieving rapid collection of noble metal contaminants. Furthermore, direct scanning with aqua regia leads to the volatilization of strong oxidizing and corrosive gases, causing significant equipment corrosion. The enrichment method of this invention effectively reduces equipment corrosion.

[0059] Experimental results show that the method provided by this invention achieves a precious metal element collection rate of over 90% and a scanning time of less than 15 minutes, significantly shortening the scanning time and improving the scanning collection efficiency while ensuring a high collection rate. Attached Figure Description

[0060] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0061] Figure 1 This is a schematic diagram of the VPD device used in this invention. Detailed Implementation

[0062] This invention provides a method for enriching noble metal elements on a wafer surface, comprising the following steps:

[0063] a) Place the wafer in the vHF chamber of the VPD equipment, introduce HF vapor into the vHF chamber for etching, and then purge with inert gas to remove any residual HF vapor in the vHF chamber.

[0064] b) Strong acid vapor and oxidizing vapor are introduced into the vHF chamber respectively for corrosion treatment, so that the metallic noble metal elements on the wafer surface are corroded into ionic state. Then, inert gas is introduced to purge and remove the strong acid vapor and oxidizing vapor in the vHF chamber.

[0065] The strongly acidic vapor is selected from at least one of HCl vapor, HNO3 vapor, HBr vapor, HI vapor, and HClO3 vapor;

[0066] The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor;

[0067] c) HF vapor and oxidizing vapor are introduced into the vHF chamber respectively for etching treatment, which removes the 1-50 nm thick surface layer of the wafer.

[0068] The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor;

[0069] d) Continue to introduce HF vapor into the vHF chamber to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer. Then, introduce inert gas to purge and remove the residual HF vapor in the vHF chamber.

[0070] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, and apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, thereby obtaining a collection liquid;

[0071] f) Dilute the collected solution with an alkaline solution to obtain the solution to be analyzed.

[0072] [Regarding step a]:

[0073] a) Place the wafer in the vHF chamber of the VPD device, introduce HF vapor into the vHF chamber for etching, and then purge with inert gas to remove any residual HF vapor in the vHF chamber.

[0074] In this invention, there are no special restrictions on the type of wafer; any conventional silicon wafer in the art is acceptable.

[0075] In this invention, the structure of the VPD device (i.e., gas phase decomposition metal collection system) is basically the same as that of a conventional VPD device. This invention makes a slight improvement by increasing the number of nozzles to allow for the simultaneous introduction of different gases. Its structure is as follows: Figure 1 The above, Figure 1This is a schematic diagram of the VPD equipment used in this invention, where 1 is a nozzle, 2 is an exhaust port, 3 is a chiller water inlet, and 4 is a pin lifting mechanism. The VPD equipment generally includes two chambers: a vHF chamber (i.e., a vapor phase etching chamber) and a scanning chamber. In this invention, the vHF chamber is preferably made of corrosion-resistant PVDF (polyvinylidene fluoride) and sealed with a corrosion-resistant sealing ring. An exhaust system is connected to a tail gas collection tank to collect acidic gases, removing and collecting excess acidic gases from the vHF chamber. The tail gas collection tank contains NaOH solution, which cools and absorbs the acidic waste gas. A pH meter is installed on the tail gas collection tank, reminding the user to replace the NaOH solution when the pH value reaches 4-5. The vHF chamber base has water channels for cooling with coolant at temperatures ranging from 5 to 100°C. A special gas leak sensor is installed near the vHF chamber to detect HF, HCl, O3, etc. A pin structure is installed inside the vHF chamber for lifting and lowering the wafer.

[0076] In this invention, after placing the wafer in the vHF chamber of a VPD device, HF vapor is introduced into the vHF chamber for etching. The preferred flow rate of the HF vapor is 100–2000 sccm, specifically 100 sccm, 500 sccm, 1000 sccm, 1500 sccm, or 2000 sccm. The preferred duration of HF vapor introduction is 1–3 minutes, specifically 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, or 3 minutes. The preferred temperature for the etching process is 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, or 25°C. This invention first introduces HF vapor to etch the wafer surface, removing SiO2 and SiN from the wafer surface. x Or a medium such as SiON can be used to hydrophobize the hydrophilic surface of the wafer.

[0077] In this invention, after the above-mentioned corrosion treatment is completed, an inert gas is introduced to purge and remove residual HF vapor from the vHF chamber. This invention does not have any particular limitation on the type of inert gas; any conventional inert gas in the art is acceptable, such as nitrogen, helium, neon, or argon, with nitrogen being more preferred. In this invention, the flow rate of the inert gas is preferably 1000–20000 sccm, and the purging time is preferably 1–3 minutes. The purging with the inert gas allows the residual HF vapor in the vHF chamber to be discharged.

[0078] [Regarding step b]:

[0079] b) Strong acid vapor and oxidizing vapor are introduced into the vHF chamber respectively for etching treatment, so that the metallic noble metal elements on the wafer surface are etched into the ionic state. Then, inert gas is introduced to purge and remove the strong acid vapor and oxidizing vapor from the vHF chamber.

[0080] In this invention, after step a), strong acidic steam and oxidizing steam are introduced into the vHF chamber for corrosion treatment. Specifically, the two types of steam can be introduced into the vHF chamber simultaneously through two nozzles.

[0081] In this invention, the strongly acidic steam is selected from at least one of HCl steam, HNO3 steam, HBr steam, HI steam, and HClO3 steam. The flow rate of the strongly acidic steam is preferably 30–5000 sccm, specifically 30 sccm, 50 sccm, 100 sccm, 500 sccm, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, and 5000 sccm. The duration of the strongly acidic steam introduction is preferably 2–30 min, specifically 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min.

[0082] In this invention, the oxidizing steam is selected from at least one of O3 steam, H2O2 steam, and HClO4 steam. The flow rate of the oxidizing steam is preferably 30–5000 sccm, specifically 30 sccm, 50 sccm, 100 sccm, 500 sccm, 1000 sccm, 1500 sccm, 2000 sccm, 2500 sccm, 3000 sccm, 3500 sccm, 4000 sccm, 4500 sccm, and 5000 sccm. The duration of the oxidizing steam introduction is preferably 2–30 min, specifically 2 min, 5 min, 10 min, 15 min, 20 min, 25 min, and 30 min.

[0083] In this invention, the preferred temperature conditions for the etching treatment are 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, and 25°C. This invention uses two specific types of strong acidic vapor and oxidizing vapor to perform the etching treatment, causing the metallic noble metal elements on the wafer surface to be etched into an ionic state.

[0084] In this invention, after the above-mentioned corrosion treatment is completed, an inert gas is introduced to purge and remove residual strong acid vapors and oxidizing vapors from the vHF chamber. This invention does not have any particular limitation on the type of inert gas; any conventional inert gas in the art is acceptable, such as nitrogen, helium, neon, or argon, with nitrogen being more preferred. In this invention, the flow rate of the inert gas is preferably 1000–20000 sccm, and the purging time is preferably 2–10 min. Through purging with the inert gas, the residual strong acid vapors and oxidizing vapors in the vHF chamber are discharged.

[0085] [Regarding step c]:

[0086] c) HF vapor and oxidizing vapor are introduced into the vHF chamber respectively for etching treatment, which removes the 1-50 nm thick surface layer of the wafer.

[0087] In this invention, after step b), HF steam and oxidizing steam are introduced into the vHF chamber for corrosion treatment. Specifically, the two types of steam can be introduced into the vHF chamber simultaneously through two nozzles.

[0088] In this invention, the flow rate of the HF steam is preferably 100–2000 sccm, specifically 100 sccm, 200 sccm, 300 sccm, 400 sccm, 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, or 1000 sccm. The duration of the HF steam introduction is preferably 1–5 min, specifically 1 min, 2 min, 3 min, 4 min, or 5 min.

[0089] In this invention, the oxidizing steam is selected from at least one of O3 steam, H2O2 steam, and HClO4 steam. The flow rate of the oxidizing steam is preferably 100–1000 sccm, specifically 100 sccm, 150 sccm, 200 sccm, 250 sccm, 300 sccm, 350 sccm, 400 sccm, 450 sccm, 500 sccm, 550 sccm, 600 sccm, 650 sccm, 700 sccm, 750 sccm, 800 sccm, 850 sccm, 900 sccm, 950 sccm, or 1000 sccm. The duration of the oxidizing steam introduction is preferably 1–5 min, specifically 1 min, 2 min, 3 min, 4 min, or 5 min.

[0090] In this invention, the preferred temperature conditions for the etching treatment are 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, and 25°C. This invention uses the two specific HF vapors and oxidizing vapors mentioned above for etching treatment, removing a 1–50 nm thick surface layer from the wafer, and further converting the metallic noble metals into ionic states.

[0091] [Regarding step d]:

[0092] d) Continue to introduce HF vapor into the vHF chamber to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer. Then, introduce inert gas to purge and remove the residual HF vapor in the vHF chamber.

[0093] In this invention, after step c), HF steam continues to be introduced into the vHF chamber. The preferred flow rate of the HF steam is 500–2000 sccm, specifically 500 sccm, 600 sccm, 700 sccm, 800 sccm, 900 sccm, 1000 sccm, 1100 sccm, 1200 sccm, 1300 sccm, 1400 sccm, 1500 sccm, 1600 sccm, 1700 sccm, 1800 sccm, 1900 sccm, or 2000 sccm. The preferred duration of HF steam introduction is 15–300 s, specifically 15 s, 30 s, 45 s, 60 s, 75 s, 90 s, 105 s, 120 s, 135 s, 150 s, 165 s, 180 s, 195 s, or 300 s. In this invention, the preferred temperature conditions for the above treatment are 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, and 25°C. This invention further etches away the natural oxide layer on the wafer through HF vapor treatment, transforming its hydrophilic surface into a hydrogen-passivated hydrophobic interface.

[0094] In this invention, after the above-mentioned corrosion treatment is completed, an inert gas is introduced to purge and remove residual strong acidic and oxidizing vapors from the vHF chamber. This invention does not have any particular limitation on the type of inert gas; any conventional inert gas in the art is acceptable, such as nitrogen, helium, neon, or argon, with nitrogen being more preferred. In this invention, the flow rate of the inert gas is preferably 1000–20000 sccm, and the purging time is preferably 1–5 min. The purging with the inert gas allows the residual HF vapors in the vHF chamber to be discharged.

[0095] [Regarding step e]:

[0096] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, and apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, thereby obtaining a collection liquid.

[0097] After the etching process is completed according to steps a) to d), the resulting wafer is transferred to the scanning cavity of a VPD device, and a scanning solution is applied to the hydrophobic interface layer of the wafer to collect metal contaminants. In this invention, the method of applying the scanning solution is not particularly limited and can be performed according to conventional procedures in the art.

[0098] In this invention, the scanning solution preferably comprises a mixture of HF acid and other acids. The other acids are at least one selected from HNO3, HCl, and H2O2.

[0099] In this invention, different scanning solutions are used for different metal elements, as detailed below:

[0100] For the noble metal element Ag, the scanning solution used is a mixture of HF acid, HNO3 acid, and water. The preferred mass percentage concentration of the HF acid is 35%–49%; the preferred mass percentage concentration of the HNO3 acid is 50%–69%; and the volume ratio of the HF acid to HNO3 acid to water is 1:(1–20):(1–100).

[0101] For the precious metal element Au, the scanning solution used is a mixture of HF acid, HCl acid, and HNO3 acid. The mass percentage concentration of the HF acid is 35%–49%; the mass percentage concentration of the HCl acid is 20%–30%; the mass percentage concentration of the HNO3 acid is 50%–69%; and the volume ratio of the HF acid to the HCl acid to the HNO3 acid is 1:(1–15):(1–5).

[0102] For the noble metal element Pt, the scanning solution used is a mixture of HF acid and H2O2 acid. The HF acid has a mass percentage concentration of 35%–49%, and the H2O2 acid has a mass percentage concentration of 28%–35%. The volume ratio of HF acid to H2O2 acid is 1:(1–50), specifically 1:1, 1:5, 1:10, 1:15, 1:20, 1:25, 1:30, 1:35, 1:40, 1:45, or 1:50.

[0103] In this invention, the scanning solution acts on the wafer scanning surface for ≤15 minutes, specifically 5–15 minutes. The preferred temperature for the scanning solution to act on the wafer surface is 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, or 25°C. After treatment with the scanning solution, metal contaminants on the wafer surface are collected, resulting in a collection solution containing metal contaminants.

[0104] [Regarding step f]:

[0105] f) Dilute the collected solution with an alkaline solution to obtain the solution to be analyzed.

[0106] In this invention, after step e) is completed, an alkaline solution is added to the collected liquid for dilution. The alkaline solution refers to an aqueous solution of an alkaline substance, preferably at least one of ammonia, tetramethylammonium hydroxide solution, and chlorine solution. In this invention, the mass percentage concentration of the alkaline solution is preferably 10% to 25%, specifically 10%, 15%, 20%, or 25%, and more preferably 20%.

[0107] In this invention, the alkaline solution is preferably added dropwise.

[0108] In this invention, the preferred amount of alkaline solution added is to achieve a pH value of 2 to 3, specifically 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, or 3.0. If the pH is too low, it will cause an acid effect on the mass spectrometer, affecting the analytical results. If the pH is too high, some elements will precipitate, which will also affect the analytical structure.

[0109] In this invention, the preferred temperature for step f) is 10–25°C, specifically 10°C, 15°C, 15°C, 20°C, or 25°C. Step f) yields the analytical solution for subsequent elemental analysis.

[0110] The present invention adds an alkaline solution to the collection liquid for dilution, which can prevent the anti-scanning solution from corroding the Pt cone of the mass spectrometer and reducing its service life during ICP-MS analysis. Moreover, the alkaline substance causes the noble metal to form a ligand with ammonia, which helps to maintain the stability of the metal ions and prevents ion precipitation.

[0111] The method for enriching noble metal elements on wafer surfaces provided by this invention involves first performing different treatments in steps a), b), c), and d) sequentially to effectively convert metallic noble metal elements into ionic states and transform the hydrophilic surface of the wafer into a hydrogen-passivated hydrophobic interface. Then, a specific scanning solution is used to collect metal contaminants from the hydrophobic interface layer. Afterward, an alkaline solution is added for dilution and pH control. This enrichment method significantly shortens the scanning time and improves the recovery efficiency of noble metal elements. Aqua regia requires a reaction time of over 15 minutes to ensure a recovery rate of over 90%, and the scanning time is generally over 30 minutes. In contrast, the enrichment method of this invention can complete the scanning within 15 minutes, achieving rapid collection of noble metal contaminants. Furthermore, direct scanning with aqua regia leads to the volatilization of strong oxidizing and corrosive gases, causing significant equipment corrosion. The enrichment method of this invention effectively reduces equipment corrosion.

[0112] This invention also provides a method for analyzing noble metal elements on a wafer surface, comprising:

[0113] g) Obtain the solution to be analyzed;

[0114] h) Pass the solution to be analyzed into an inductively coupled plasma mass spectrometer for elemental analysis;

[0115] The analyte is obtained using the enrichment method described above, i.e., step K1 is the enrichment method described above. In step K2, there are no special restrictions on the method of passing the analyte into an inductively coupled plasma mass spectrometer (ICP-MS) for elemental analysis; it can be performed according to conventional procedures in the field. Through analysis, quantitative analysis results of noble metal contamination on the wafer surface can be obtained.

[0116] Experimental results show that the method provided by this invention achieves a precious metal element collection rate of over 90% and a scanning time of less than 15 minutes. While ensuring a high collection rate, it significantly shortens the scanning time and improves the scanning collection efficiency.

[0117] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0118] Example 1

[0119] a) Place the wafer in the vHF chamber of the VPD equipment, introduce HF vapor (flow rate of 1500 sccm, duration of 2 min) into the vHF chamber and perform etching treatment at 20°C; then, introduce N2 (flow rate of 5000 sccm, duration of 3 min) to purge and remove the residual HF vapor in the vHF chamber.

[0120] b) Strong acid vapor (HCl vapor) and oxidizing vapor (O3 vapor) were introduced into the vHF chamber at 15°C for etching treatment. The flow rate of both vapors was 1000 sccm and the duration of each was 10 min. After etching treatment, the metallic noble metal elements on the wafer surface were etched into the ionic state. Then, N2 (flow rate of 10000 sccm and duration of 5 min) was introduced to purge and remove the residual strong acid vapor and oxidizing vapor in the vHF chamber.

[0121] c) HF vapor and oxidizing vapor (O3 vapor) were introduced into the vHF chamber and etched at 15°C. The flow rate of both vapors was 700 sccm and the introduction time was 5 min. After etching, a 30 nm thick surface layer on the wafer surface was etched away.

[0122] d) Continue to introduce HF vapor (flow rate of 500 sccm, duration of 300 s) into the vHF chamber and perform surface treatment at 20°C to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer; then, introduce N2 (flow rate of 3000 sccm, duration of 3 min) to purge and remove the residual HF vapor in the vHF chamber.

[0123] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, scan at 25°C for 12 minutes, collect the scanning liquid, and obtain the collected liquid.

[0124] The scanning solution used was a mixture of HF acid, HNO3 acid, and water. The concentration of the HF acid was 38%; the concentration of the HNO3 acid was 55%; and the volume ratio of HF acid to HNO3 acid to water was 1:1:1.

[0125] f) Add an alkaline solution (ammonia, 20% by mass) dropwise to the collected solution to bring the pH value to 2, thus obtaining the solution to be analyzed.

[0126] h) The obtained analyte solution is passed into an inductively coupled plasma mass spectrometer for elemental analysis.

[0127] The test results are shown below:

[0128] Sample size: 12-inch wafer.

[0129] Test level: E7 level (i.e., E7 atoms / cm³) 2 )

[0130] See Table 1 for the results data:

[0131] In Table 1, the volume of the spiked recovery scan solution was fixed at 1 mL; the unit of the spiked recovery value was ppt, and the calculation formula was (1-m2 / m1)×100; where m1=C1×V1, m2=C2×V2; C1 refers to the first recovery concentration in ppt, V1 refers to the volume of the first spiked recovery solution in mL, C2 refers to the second recovery concentration in ppt, and V2 refers to the volume of the second spiked recovery solution in mL. The spiked recovery test procedure was as follows: 100 μL of quantitative standard solution (containing ruthenium, silver, hafnium, and platinum) was uniformly dropped onto a new 12-inch wafer by manual operation, and then dried through a drying chamber. The wafer was scanned twice via VPD through the following path: FOUP→aligner→vHF→aligner→scanning→test tube→ICP-MS analysis.

[0132] Table 1: Elemental analysis results of Example 1

[0133]

[0134]

[0135] Example 2

[0136] a) Place the wafer in the vHF chamber of the VPD equipment, and etch it at 20°C by introducing HF vapor (flow rate of 1800 sccm for 3 min); then purge the vHF chamber with N2 (flow rate of 3000 sccm for 2 min) to remove the residual HF vapor.

[0137] b) Strong acid vapor (HNO3 vapor) and oxidizing vapor (H2O2 vapor) were introduced into the vHF chamber at 15°C for etching treatment. The flow rate of both vapors was 1000 sccm and the duration of each was 20 min. After etching treatment, the metallic noble metal elements on the wafer surface were etched into the ionic state. Then, N2 (flow rate of 10000 sccm and duration of 4 min) was introduced to purge and remove the residual strong acid vapor and oxidizing vapor in the vHF chamber.

[0138] c) HF vapor and oxidizing vapor (H2O2 vapor) were introduced into the vHF chamber and etched at 10°C. The flow rate of both vapors was 500 sccm and the introduction time was 3 min. After etching, a 20 nm thick surface layer on the wafer surface was etched away.

[0139] d) Continue to introduce HF vapor (flow rate of 1000 sccm, duration of 200 s) into the vHF chamber for surface treatment at 20°C to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer; then, introduce N2 (flow rate of 5000 sccm, duration of 2 min) to purge and remove the residual HF vapor in the vHF chamber.

[0140] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, scan at 25°C for 15 minutes, collect the scanning liquid, and obtain the collected liquid.

[0141] The scanning solution is a mixture of HF acid, HCl acid, and HNO3 acid. The concentration of the HF acid is 49%; the concentration of the HCl acid is 31%; the concentration of the HNO3 acid is 69%; and the volume ratio of HF acid:HNO3 acid:water is 1:1:5.

[0142] f) Add an alkaline solution (tetramethylammonium hydroxide aqueous solution, 20% by mass) dropwise to the collected solution to bring the pH value to 2.5, thus obtaining the solution to be analyzed.

[0143] h) The obtained analyte solution is passed into an inductively coupled plasma mass spectrometer for elemental analysis.

[0144] The test results are shown below:

[0145] Sample size: 12-inch wafer.

[0146] Test level: E7 level (i.e., E7 atoms / cm³) 2 )

[0147] See Table 2 for the results data:

[0148] Table 2: Elemental analysis results of Example 2

[0149] ruthenium 967.1 65.9 93.2 silver 998.8 46.7 95.3 hafnium 1028.1 45.7 95.5 platinum 1023.4 44.4 95.6 gold 891.3 38.7 95.6

[0150] Example 3

[0151] a) Place the wafer in the vHF chamber of the VPD equipment, and etch it at 25°C by introducing HF vapor (flow rate of 1000 sccm for 3 min); then purge the vHF chamber with N2 (flow rate of 3000 sccm for 1.5 min) to remove the residual HF vapor.

[0152] b) Strong acid vapor (HBr vapor) and oxidizing vapor (HClO4 vapor) were introduced into the vHF chamber at 10°C for etching treatment. The flow rate of both vapors was 3000 sccm and the duration of each was 10 min. After etching treatment, the metallic noble metal elements on the wafer surface were etched into the ionic state. Then, N2 (flow rate of 5000 sccm and duration of 4 min) was introduced to purge and remove the residual strong acid vapor and oxidizing vapor in the vHF chamber.

[0153] c) HF vapor and oxidizing vapor (HClO4 vapor) were introduced into the vHF chamber and etched at 15°C. The flow rate of both vapors was 1000 sccm and the introduction time was 2 min. After etching, a 25 nm thick surface layer on the wafer surface was etched away.

[0154] d) Continue to introduce HF vapor (flow rate of 1500 sccm, duration of 100 s) into the vHF chamber for surface treatment at 25°C to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer; then, introduce N2 (flow rate of 10000 sccm, duration of 1.5 min) to purge and remove the residual HF vapor in the vHF chamber.

[0155] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, scan at 25°C for 10 min, collect the scanning liquid, and obtain the collected liquid.

[0156] The scanning solution is a mixture of HF acid and H2O2 acid. The concentration of the HF acid is 49%; the concentration of the H2O2 acid is 33%; and the volume ratio of HF acid to H2O2 acid to water is 1:10.

[0157] f) Add an alkaline solution (aqueous solution of chlorine, 20% by mass) dropwise to the collected solution to bring the pH value to 3, thus obtaining the solution to be analyzed.

[0158] h) The obtained analyte solution is passed into an inductively coupled plasma mass spectrometer for elemental analysis.

[0159] The test results are shown below:

[0160] Sample size: 12-inch wafer.

[0161] Test level: E7 level (i.e., E7 atoms / cm³) 2 )

[0162] See Table 3 for the results data:

[0163] Table 3: Elemental analysis results of Example 3

[0164] ruthenium 847.1 36.4 95.7 silver 898.1 45.0 94.9 hafnium 935.4 47.3 94.9 platinum 925.9 47.6 94.8 gold 805.4 43.0 94.6

[0165] Example 4

[0166] a) Place the wafer in the vHF chamber of the VPD equipment, and etch it at 25°C by introducing HF vapor (flow rate of 800 sccm for 3 min); then purge the vHF chamber with N2 (flow rate of 4000 sccm for 4 min) to remove the residual HF vapor.

[0167] b) Strong acid vapor (HClO3 vapor) and oxidizing vapor (O3 vapor) were introduced into the vHF chamber at 15°C for etching treatment. The flow rate of both vapors was 5000 sccm and the duration of each was 5 min. After etching treatment, the metallic noble metal elements on the wafer surface were etched into the ionic state. Then, N2 (flow rate of 10000 sccm and duration of 3 min) was introduced to purge and remove the residual strong acid vapor and oxidizing vapor in the vHF chamber.

[0168] c) HF vapor and oxidizing vapor (O3 vapor) were introduced into the vHF chamber and etched at 15°C. The flow rate of both vapors was 1000 sccm and the introduction time was 2 min. After etching, a 25 nm thick surface layer on the wafer surface was etched away.

[0169] d) Continue to introduce HF vapor (flow rate of 2000 sccm, duration of 50 s) into the vHF chamber for surface treatment at 25°C to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer; then, introduce N2 (flow rate of 5000 sccm, duration of 3 min) to purge and remove the residual HF vapor in the vHF chamber.

[0170] e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, scan at 25°C for 8 minutes, collect the scanning liquid, and obtain the collected liquid.

[0171] The scanning solution is a mixture of HF acid and H2O2 acid. The concentration of the HF acid is 35%; the concentration of the H2O2 acid is 28%; and the volume ratio of the HF acid to the H2O2 acid is 1:10.

[0172] f) Add an alkaline solution (aqueous solution of chlorine, 20% by mass) dropwise to the collected solution to bring the pH value to 3, thus obtaining the solution to be analyzed.

[0173] h) The obtained analyte solution is passed into an inductively coupled plasma mass spectrometer for elemental analysis.

[0174] The test results are shown below:

[0175] Sample size: 12-inch wafer.

[0176] Test level: E7 level (i.e., E7 atoms / cm³) 2 )

[0177] See Table 4 for the results data:

[0178] Table 4: Elemental analysis results of Example 4

[0179] ruthenium 868.7 44.8 94.84 silver 879.9 33.2 96.23 hafnium 885.2 39.0 95.59 platinum 858.8 49.0 94.29 gold 832.0 41.6 95.00

[0180] As can be seen from the test results of Examples 1 to 4, the method of the present invention has a noble metal element collection rate of over 90% and a scanning time of less than 15 minutes. While ensuring a high collection rate, it significantly shortens the scanning time and improves the scanning collection efficiency.

[0181] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for enriching noble metal elements on a wafer surface, characterized in that, Includes the following steps: a) Place the wafer in the vHF chamber of the VPD equipment, introduce HF vapor into the vHF chamber for etching, and then purge with inert gas to remove any residual HF vapor in the vHF chamber. The flow rate of the HF steam is 100~2000 sccm, and the introduction time is 1~3 min; b) Strong acid vapor and oxidizing vapor are introduced into the vHF chamber respectively for corrosion treatment, so that the metallic noble metal elements on the wafer surface are corroded into ionic state. Then, inert gas is introduced to purge and remove the strong acid vapor and oxidizing vapor in the vHF chamber. The strongly acidic vapor is selected from at least one of HCl vapor, HNO3 vapor, HBr vapor, HI vapor, and HClO3 vapor; The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor; The flow rate of the strongly acidic vapor is 30~5000 sccm, and the introduction time is 2~30 min; The flow rate of the oxidizing steam is 30~5000 sccm, and the introduction time is 2~30 min; c) Introduce HF vapor and oxidizing vapor into the vHF chamber respectively for etching treatment, etching away the 1~50nm thick surface layer of the wafer. The oxidizing vapor is selected from at least one of O3 vapor, H2O2 vapor, and HClO4 vapor; d) Continue to introduce HF vapor into the vHF chamber to hydrophobize the hydrophilic surface of the wafer and form a hydrophobic interface layer. Then, introduce inert gas to purge and remove the residual HF vapor in the vHF chamber. e) Transfer the wafer obtained in step d) into the scanning cavity of the VPD device, and apply scanning liquid to the hydrophobic interface layer of the wafer to collect metal contaminants, thereby obtaining a collection liquid; f) Dilute the collected solution with an alkaline solution to obtain the solution to be analyzed; The amount of alkaline solution added is such that the pH value reaches 2-3.

2. The enrichment method according to claim 1, characterized in that, In step c), the flow rate of the HF steam is 100~2000 sccm, and the introduction time is 1~5 min; The flow rate of the oxidizing steam is 100~1000 sccm, and the introduction time is 1~5 min.

3. The enrichment method according to claim 1, characterized in that, In step d), the flow rate of the HF steam is 500~2000 sccm, and the introduction time is 15~300s.

4. The enrichment method according to claim 1, characterized in that, In step f), the alkaline solution is at least one of ammonia, tetramethylammonium hydroxide solution, and chlorine solution.

5. The enrichment method according to claim 1, characterized in that, In step e), the scanning solution includes: a mixture of HF acid and other acids; The other acid solution is at least one of HNO3 acid solution, HCl acid solution and H2O2 acid solution.

6. The enrichment method according to claim 1 or 5, characterized in that, For the precious metal element Ag, the scanning solution used is a mixture of HF acid, HNO3 acid and water. The HF acid solution has a mass percentage concentration of 35% to 49%. The mass percentage concentration of the HNO3 acid solution is 50%~69%; The volume ratio of HF acid solution:HNO3 acid solution:water is 1:(1~20):(1~100). For the precious metal element Au, the scanning solution used is a mixture of HF acid, HCl acid and HNO3 acid. The HF acid solution has a mass percentage concentration of 35% to 49%. The mass percentage concentration of the HCl acid solution is 20%~30%; The mass percentage concentration of the HNO3 acid solution is 50%~69%; The volume ratio of HF acid solution: HCl acid solution: HNO3 acid solution is 1:(1~15):(1~5); For the noble metal element Pt, the scanning solution used is a mixture of HF acid and H2O2 acid. The HF acid solution has a mass percentage concentration of 35% to 49%. The mass percentage concentration of the H2O2 acid solution is 28%~35%; The volume ratio of HF acid solution to H2O2 acid solution is 1:(1~50).

7. The enrichment method according to claim 1, characterized in that, In step b), the flow rate of the inert gas is 1000~20000 sccm, and the purging time is 2~10 min; In step d), the flow rate of the inert gas is 1000~20000 sccm, and the purging time is 1~5 min.

8. A method for analyzing noble metal elements on a wafer surface, characterized in that, include: g) Obtain the solution to be analyzed; h) Pass the solution to be analyzed into an inductively coupled plasma mass spectrometer for elemental analysis; The analyte is obtained by the enrichment method according to any one of claims 1 to 7.

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