A method for measuring and evaluating the slow release of metal contamination in equipment

Abstract

The present invention provides a method for slow-release and evaluation of metal contamination of an instrument. The measurement method comprises the following steps: (1) a certain amount of slow-release solution is added to the instrument, and the metal content of the solution is analyzed by an inductively coupled plasma mass spectrometer to obtain data ①; (2) after being placed for 30 minutes, the metal content of the instrument under test is analyzed again by an inductively coupled plasma mass spectrometer to obtain data ②; (3) after being placed for 90 minutes, the metal content of the instrument under test is analyzed by an inductively coupled plasma mass spectrometer to obtain data ③; (4) by comparing and calculating the results of ①②③, the metal contamination degree of the instrument is determined. Thus, whether the instrument meets the use standard is evaluated. The evaluation method comprises the following steps: (1) each metal data of the analysis data ① cannot exceed the control limit Ⅰ; (2) each metal data of the analysis data ②③ cannot exceed the control limit Ⅱ; (3) the increment of the analysis data ② is less than 100% of the data ①, and the increment of the data ③ is less than 100% of the data ②.

Description

Technical Field

[0001] The invention relates to the technical field of metal impurity detection of integrated circuit silicon wafers, and in particular to a method for measuring and evaluating the slow-release of metal contamination of an instrument. Background Art

[0002] With the improvement of semiconductor component performance requirements and the gradual improvement of manufacturing processes, the requirements for the impurity content of silicon wafers are getting higher and higher, especially metal trace impurities; different metal contaminations can lead to defects for different reasons. Alkali metal contamination such as Na, Mg, K, and Ca can lead to deterioration of GOI performance. Heavy metal impurities such as Cu, Au, and Ag affect the minority carrier lifetime, conductivity, and stability of the device. Therefore, the silicon wafer manufacturing industry must strictly analyze and control the metal impurity content of silicon wafers.

[0003] At present, the most advanced metal impurity analysis instrument in the silicon wafer manufacturing industry is the inductively coupled plasma mass spectrometer (ICP-MS), which uses the silicon wafer sample preparation system WPS as an auxiliary tool and uses the vapor phase decomposition method (VPD) to recover the metal impurities on the surface of the silicon wafer into the recovery device, and then uses ICP-MS for analysis.

[0004] During this measurement process, the acidic recovery liquid is in direct contact with the recovery equipment. With long-term contact, the metal impurities attached to the recovery equipment will be slowly released and dissolved into the acidic solution. The longer the time, the more impurities will be released. At present, silicon wafer manufacturing technology has become quite mature, and the analysis of metal impurity content in silicon wafers has reached the ultra-trace level. Therefore, any spare parts and equipment used in the metal impurity analysis process will most likely affect the accuracy of the analysis results if there is a certain degree of contamination; therefore, how to avoid using equipment with insufficient cleanliness and further improve the accuracy of metal detection results is a problem that we urgently need to solve. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a method for measuring and evaluating the slow-release of metal contamination on utensils, which can quickly determine the degree of contamination on utensils by simple measurement and calculation, and provide an evaluation benchmark for the utensil cleaning industry.

[0006] To achieve the above object, the present invention provides a method for measuring and evaluating the slow release of metal contamination on a tool, the specific steps of which include:

[0007] 1. Add a certain amount of solution into the apparatus and use an inductively coupled plasma mass spectrometer to analyze the metal content of the solution to obtain data ①;

[0008] 2. Place in a clean room for 30 minutes and analyze the metal content again using an inductively coupled plasma mass spectrometer to obtain data ②;

[0009] 3. Place in the clean room for 90 minutes and use inductively coupled plasma mass spectrometry to analyze the metal content and obtain data ③;

[0010] 4. Determine the metal contamination degree of the equipment by comparing and calculating the results of ①②③; thus evaluate whether the equipment meets the use standards;

[0011] The specific standards of the evaluation method are as follows:

[0012] 1. Analytical data ① The data of each metal cannot exceed the control limit Ⅰ (such as Figure 2 );

[0013] 2. The metal data of analytical data ②③ cannot exceed the control limit Ⅱ (such as Figure 3 );

[0014] 3. The increment of analyzed data ② is less than 100% of that of data ①, and the increment of analyzed data ③ is less than 100% of that of data ②;

[0015] The purpose of the present invention is to provide a method for detecting and evaluating the degree of metal contamination of instruments in the semiconductor industry, in order to address the unstable factors that affect the accuracy of metal detection results due to metal contamination of instruments; thereby effectively avoiding the use of contaminated instruments and improving the accuracy of metal impurity detection.

[0016] The method of the present invention utilizes that metal ions are relatively active in acid solution and have high solubility, and the amount of contaminated ions released has a certain relationship with time. As time goes by, more metal impurities are released and dissolved. The retention time of the recovery device used in this embodiment will not exceed 90 minutes, so it is only necessary to control the amount of metal impurities released within 90 minutes, which can eliminate the influence of the device and achieve the effect of effective monitoring of the device. The method of the present invention uses three-point time recording to analyze the impurity content of the sample at 0 minutes, 30 minutes, and 90 minutes respectively, and obtains the sum of the impurity content released by the acid solution itself and the device within 30 minutes and 90 minutes, as well as the impurity content of the acid solution itself at 0 minutes. The total amount of impurities released by the device during this time can be obtained by simple calculation.

[0017] The positive progressive effect of the present invention is that this embodiment realizes a simple and quick method for measuring and evaluating the slow release of metal contamination in instruments, using an inductively coupled plasma mass spectrometer (ICP-MS), without the need for other equipment, the entire measurement process is short and does not require other operations in the middle, the data analysis and calculation are simple, and the analysis results can be obtained quickly to quickly evaluate the cleanliness of the instrument.

[0018] Optionally, the solution in step 1 of the scheme is a mixture of hydrofluoric acid and hydrogen peroxide in this embodiment, and the specific preparation method is as follows:

[0019] (1-1) Prepare a clean FPA volumetric flask, and mix hydrofluoric acid: hydrogen peroxide: ultrapure water in a ratio of 1:1.95:12.25. Use a clean measuring cup to measure a certain amount of ultrapure water and pour it into the volumetric flask for later use.

[0020] (1-2) Use a measuring cup to measure a certain amount of 38wt% hydrofluoric acid and 35wt% hydrogen peroxide respectively, and pour them into a volumetric flask;

[0021] (1-3) Cover the flask with a cap and gently shake the volumetric flask to mix evenly to obtain a mixed solution of 2.5 wt% hydrofluoric acid and 4.5 wt% hydrogen peroxide.

[0022] Optionally, the material and capacity of the device are different. In this embodiment, the device is made of polypropylene and has a volumetric flask, also known as a vial, with a volume of 6 ml.

[0023] Optionally, the placement time in steps 2 and 3 of the scheme, in this embodiment, a three-point time recording method is adopted, and the impurity content of the sample is analyzed at 0 min (point O), 30 min (point a), and 90 min (point b), respectively; in this embodiment, the analysis equipment adopts an inductively coupled plasma mass spectrometer (ICP-MS 7900), and its measurement accuracy is above 1 ppt.

[0024] In the evaluation method of the present invention, the control limit I in the standard 1 is the upper limit of the blank value ① of the mixed acid solution, and the upper limit is set to ensure the cleanliness of the acid solution while ensuring the prerequisite for subsequent measurements.

[0025] Control limit II mentioned in Standard 2 is the upper limit of the metal impurity content after the contamination of the equipment is released.

[0026] In the standard 3, the analysis result increment △t1=(②-①) / ①,△t2=(③-②) / ②. If the results △t1 and △t2 are both less than 100%, it can be ensured that the speed of contamination release is within a controllable range, thereby determining that the cleanliness of the equipment is within an acceptable range. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a flow chart of a method for measuring and evaluating slow release of metal contamination in an apparatus according to an embodiment of the present invention; Figure 1 , the measurement and evaluation method may include steps S1 to S6.

[0028] Figure 2 It is the upper limit standard of each metal value of the blank value of mixed acid solution. The upper limit is set to ensure the cleanliness of the acid solution while ensuring the prerequisite for subsequent measurements.

[0029] Figure 3 It is the upper limit standard for the content of metal impurities after the equipment is contaminated and released.

[0030] Figure 4① is the result diagram of data in the embodiment.

[0031] Figure 5 It is the result diagram of data② in the embodiment.

[0032] Figure 6 It is the result diagram of data ③ in the embodiment.

[0033] Figure 7 It is the calculation diagram for evaluating the data results of ①②③. DETAILED DESCRIPTION

[0034] It should be understood that the embodiments described herein are only used to explain the present invention and are not used to limit the present invention; the embodiments described are only a part of the embodiments of the present invention; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative work are within the scope of protection of the present invention.

[0035] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below.

[0036] The patented contamination detection of the present invention utilizes an inductively coupled plasma mass spectrometer (ICP-MS) with a low detection limit, which can be an existing product, from Agilent's 7xxx or 8xxx series in the United States, and is configured with Agilent's ASX-500X series automatic sampling device to connect a nebulizer, atomization chamber and other modules. An inert gas such as Ar is used as a carrier to introduce a liquid sample, and the sample is evaporated, dissociated, atomized, and further ionized at high temperature to become a metal ion with a positive charge, which is separated by quadrupole acceleration, thereby performing accurate and rapid quantitative analysis.

[0037] Steps of this embodiment Figure 1 , the specific description is as follows:

[0038] S1 Prepare the solution described in step 1 of the scheme: prepare a clean FPA volumetric flask, according to the preparation ratio of hydrofluoric acid: hydrogen peroxide: ultrapure water of 1:1.95:12.25, use a clean measuring cup to measure 242ml of ultrapure water, pour it into the volumetric flask for later use; use a measuring cup to measure a certain amount of 20ml of 38wt% hydrofluoric acid and 48ml of 35wt% hydrogen peroxide respectively, and pour them into the volumetric flask; cover the bottle cap and gently shake the volumetric flask to mix it evenly to obtain 300ml of a mixed acid solution of 2.5wt% hydrofluoric acid and 4.5wt% hydrogen peroxide.

[0039] S2 uses the acid solution prepared in S1 to prepare standard solutions of metal ions with concentrations of 50 ppt, 100 ppt, and 200 ppt; prepare the ICP-MS standard curve and quality control standard (QC).

[0040] S3 then follows Figure 1 In the steps shown, take 3 vials to be tested, pour 3 ml of the solution prepared in S1 into the vials to be tested, put them into the ICP-MS injection tray, immediately use the ICP-MS injection needle to insert the instrument to be tested, suck in the acid sample, and analyze the impurity concentration, which is recorded as data ①, see Figure 4 .

[0041] After S4 was placed in the sample tray for 30 minutes, the concentration of impurities in the sustained-release solution was analyzed by ICP-MS, recorded as data ②, see Figure 5 .

[0042] After S5 was placed in the sample tray for 90 minutes, the concentration of impurities in the sustained-release solution was analyzed again by ICP-MS, which is recorded as data ③. Figure 6 .

[0043] S6 ①②③Result evaluation criteria 1.Analysis data ①Each metal data cannot exceed the control limit Ⅰ (such as Figure 2 Standard 2. The metal data of analytical data ②③ cannot exceed the control limit Ⅱ (such as Figure 3 Standard 3. The increment of data ② is less than 100% of that of data ①, and the increment of data ③ is less than 100% of that of data ②. The result is as follows Figure 7 As shown;

[0044] The above evaluation standards 1 and 2 control the three groups of values ​​①, ②, and ③, which can effectively evaluate the cleanliness of the equipment after 90 minutes of use.

[0045] Evaluation Criteria 3 is to not only effectively evaluate the impurity release rate of the instrument within 90 minutes, but also to estimate the impurity release rate of the instrument after 90 minutes, thereby evaluating the cleanliness of the instrument.

[0046] It should be noted that the higher the contamination of the instrument, the faster the contaminating ions are released in the acid solution. In the absence of external interference, the release and adsorption of impurities by the instrument will eventually reach a balance at a certain time, and the impurity concentration of the solution will remain relatively stable.

[0047] The invention can be used to detect instruments made of various materials such as PP, PTFE, PFA and other acid-resistant plastics with high cleanliness requirements, has a wide application field, and has low cost and time consumption, and is quick to operate and calculate.

[0048] The above description is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for measuring and evaluating the slow release of metal contamination on an instrument, the measuring method comprising the following steps: (1) A certain amount of sustained-release liquid is placed in the apparatus, and the metal content of the solution is analyzed using an inductively coupled plasma mass spectrometer to obtain data ①; (2) Place the tested device in a clean room for 30 minutes and analyze the metal content of the device again using an inductively coupled plasma mass spectrometer to obtain data ②; (3) Place the tested equipment in the clean room for 90 minutes and use inductively coupled plasma mass spectrometry to analyze the metal content of the tested equipment to obtain data ③; (4) By comparing and calculating the results of ①, ② and ③, determine the degree of metal contamination of the equipment, and thus evaluate whether the equipment meets the use standards; It is characterized in that The specific steps of the evaluation method are as follows: (1) Analytical data ① The data of each metal cannot exceed the control limit I; (2) The metal data of analytical data ②③ cannot exceed control limit Ⅱ; (3) The increment of data ② compared with data ① is △t1 = (②-①) / ①, and the increment of data ③ compared with data ② is △t2 = (③-②) / ②. If the results △t1 and △t2 are both less than 100%, it can be ensured that the speed of contamination release is within the controllable range, thereby determining that the cleanliness of the equipment is within the acceptable range.

2. The method for measuring and evaluating the slow release of metal contamination of an instrument according to claim 1, characterized in that: The concentration of the sustained-release liquid is a mixed acid solution of 2.5wt% hydrofluoric acid, 4.5wt% hydrogen peroxide and ultrapure water (UPW), wherein the ultrapure water (UPW) is characterized by a resistivity of >18 MΩ.cm and a TOC of <5ppb.

3. A method for measuring and evaluating the slow release of metal contamination of an instrument according to claim 1, characterized in that: Metal impurity analysis was performed by inductively coupled plasma mass spectrometry (ICP-MS). The metal ions included: lithium (Li), sodium (Na), magnesium (Mg), aluminum (Al), potassium (K), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), copper (Cu), molybdenum (Mo), and tungsten (W).

4. The method for measuring and evaluating the slow release of metal contamination of an instrument according to claim 1, characterized in that: The apparatus is a container made of polypropylene (PP), polytetrafluoroethylene (PTFE), or a copolymer of perfluoropropyl perfluorovinyl ether and polytetrafluoroethylene (PFA).

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