Method for verifying test precision of a machine by reverse contamination

Abstract

The present application relates to a kind of methods for verifying test precision of machine with reverse pollution, the machine precision detection technical field, including the following operating steps: first step: using VPD machine to generate HF steam to carry out weather corrosion to the surface of silicon wafer.Second step: then VPD machine scanning head scans and collects silicon wafer surface metal contamination, then VPD machine is operated to the silicon wafer drying operation.Third step: the silicon wafer that has passed surface cleaning is placed on ceramic heating plate.Fourth step: uniform drop is in the surface of silicon wafer with standard solution.Fifth step: solution low-temperature drying.Sixth step: using ICP-MS to test the reverse pollution solution collected by VPD.The mixed etching solution configured using VPD machine removes the metal impurities and oxide film indicated by sample, guarantees the cleanliness of experimental silicon wafer, removes the influence of exogenous metal pollution, and the recovery and test of etching solution are also completed automatically by machine, guarantee the precision and accuracy of test data.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of machine precision detection, and particularly relates to a method for verifying machine test precision by adopting reverse pollution. BACKGROUND

[0002] At present, the device size of integrated circuits is continuously reduced, and the integration degree is becoming higher and higher, and any slight process defect can cause the integrated circuit to fail, so the development and management of production processing technology and the requirements for various process parameters of raw materials are also higher and higher. Silicon wafer is one of the important raw materials in the integrated circuit manufacturing process, and metal impurities in the silicon wafer can affect the performance and reliability of the device, and have a significant impact on the yield of the device and the performance of the integrated circuit, so the control of various metal impurities in the silicon wafer is extremely strict, and each institution has always attached great importance to the detection of metal elements in the production and processing of silicon wafers.

[0003] Metal elements are commonly present in the silicon wafer processing process, and the study of the chemical behavior of various metal elements in the silicon wafer has always been the focus of attention of relevant scholars and experts. Excessive metal and heavy metal (Fe, Cr, Ni, Cu, ) pollution such as alkali metals and alkali earth metals (Li, Na, K, Ca, Mg) can shorten the service life of the device or increase the working current, resulting in device failure.

[0004] Therefore, the importance of detection is increasingly prominent, and semiconductor material detection is a technology for analyzing and testing the characteristic parameters of semiconductor materials. Due to the variety of materials in the production process, the complexity of the processing technology, and the different forms, the technical difficulty is high, so we need to accurately determine the characteristic parameters of the semiconductor material, truly reflect the quality situation, and master the key parameter generation process, so as to guide the update iteration of research and development technology. 50% of the yield loss in the semiconductor industry is caused by cleaning reagents and internal trace element pollution of materials. Therefore, it is extremely important to accurately detect the content of each element, and high requirements are put forward for the pollution control of the operating environment and the operating personnel. SUMMARY

[0005] The present application mainly solves the problems existing in the prior art, and provides a method for verifying machine test precision by adopting reverse pollution, which uses a mixed etching liquid configured by a VPD machine to remove metal impurities and an oxide film on the surface of a sample, ensures the cleanliness of the experimental silicon wafer, removes the influence of exogenous metal pollution, and automatically completes the recovery and testing of the etching liquid by the machine, thereby ensuring the precision and accuracy of the test data.

[0006] The above technical problems of the present application are mainly solved by the following technical scheme:

[0007] A method for verifying the precision of a testing machine by reverse contamination, the equipment and tools used including an element detection machine, a vacuum suction pen, a ceramic heating plate, a VPD machine, an etching solution and a 20 ppt reverse contamination standard solution.

[0008] The verification method includes the following operation steps:

[0009] First step: clean the surface of the silicon wafer, generate HF vapor on the surface of the silicon wafer by the VPD machine for gas phase etching, and change the surface of the silicon wafer from hydrophilic to hydrophobic.

[0010] Second step: then scan the VPD machine head to collect the metal contamination on the surface of the silicon wafer, the scanning head needs to scan the entire surface of the silicon wafer to collect metal impurities, after the collection of metal impurities is completed, the etching solution is properly discarded, and then the silicon wafer is dried on the VPD machine.

[0011] Third step: place the cleaned silicon wafer on the ceramic heating plate, and use the vacuum suction pen to transfer the wafer. During the transfer process, pay attention not to touch the cleaned surface of the silicon wafer with foreign matter.

[0012] Fourth step: use a pipette to suck 20 ppt reverse contamination standard solution, the total volume is 1 ml, then evenly drop the standard solution on the surface of the silicon wafer, the droplets should be as small as possible, the number of droplets should be as many as possible, and the droplets should be evenly dropped on the entire surface of the silicon wafer.

[0013] Fifth step: when drying the solution at low temperature, set the heating plate temperature to 25 degrees Celsius, and the heating plate temperature should be uniform to avoid large local temperature difference of the silicon wafer.

[0014] Sixth step: use ICP-MS to test the reverse contamination solution collected by the VPD machine.

[0015] As a preferred embodiment, the element detection machine ICP-MS machine model is ICP-MS-8900, its detection precision is in ppt level, the instrument state should be confirmed before use, the linear of standard curve should be above 0.995, and the blank sample should be tested in advance to confirm that the machine is not contaminated.

[0016] As a preferred embodiment, the VPD machine uses IAS Expert, and the etching solution is mainly made of high-purity HF and H2O2 according to a certain ratio, and the configuration is automatically completed by the VPD machine to reduce unnecessary pollution caused by human factors.

[0017] As a preferred embodiment, the used HF requires metal elements ≤10 ppt, and the used H2O2 requires metal element impurities ≤10 ppt; the H2O2 used for configuring the etching solution is 35% concentration hydrogen peroxide from Tomo Chemical.

[0018] As a preferred option, in order to reduce the impact of external metal impurities on the detection precision and accuracy, the water used in the detection process is ultrapure water with a resistivity ≥18MΩ.cm.

[0019] As a preferred method, after the solution is dried at low temperature, when the liquid droplets on the surface of the silicon wafer are no longer visible, the silicon wafer is transferred to the wafer cassette using a vacuum suction pen, and the surface metal is collected using a VPD. The entire VPD operation process is performed automatically by the machine without any human intervention, ensuring the cleanliness of the metal collection process.

[0020] As a preferred method, inductively coupled plasma mass spectrometry (ICP-MS) is used. The testing principle of ICP-MS is to ionize the elements in the sample through a high-temperature plasma heat source. After sorting, the elements to be tested are analyzed and detected by a mass spectrometer. The sample to be tested is pretreated into a liquid, and the sample solution is formed into an aerosol by an argon gas flow. The aerosol is then sent into a plasma source generated by a high-frequency radio frequency signal and an induction coil, thereby realizing the ionization of elements.

[0021] As a preferred method, after the elements in the sample are ionized into monovalent positive ions, they undergo multiple screening and comparative analyses using a mass spectrometer. The content and isotopic ratio of the analyte can then be obtained through counting calculations. Detection is performed using a mixed standard solution, enabling simultaneous testing of multiple elements by ICP-MS. This allows for simultaneous analysis of multiple element detection results within a single test of the same sample. Furthermore, the element sorting and screening analysis processes of ICP-MS are all completed in a closed environment, resulting in high data repeatability and accuracy.

[0022] The present invention can achieve the following effects:

[0023] This invention provides a method for verifying the accuracy of a testing machine using reverse contamination. Compared with existing technologies, the mixed etching solution configured in the VPD machine removes metal impurities and oxide films from the sample surface, ensuring the cleanliness of the experimental silicon wafer and eliminating the influence of external metal contamination. The recovery and testing of the etching solution are also automatically completed by the machine, ensuring the accuracy and precision of the test data. Attached Figure Description

[0024] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0025] The technical solution of the invention will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0026] Example: Figure 1 As shown, a method for verifying the accuracy of an instrument using reverse contamination is described. The equipment and tools used include an elemental analyzer, a vacuum pen, a ceramic heating plate, a VPD instrument, an etching solution, and a 20ppt reverse contamination standard solution.

[0027] The element detection machine is ICP-MS machine model ICP-MS-8900, and the detection accuracy is in ppt level. Before using the machine, the instrument state should be confirmed, the calibration curve linearity should be above 0.995, and the blank sample should be tested in advance to confirm that the machine is not contaminated.

[0028] The VPD machine adopts IAS Expert, and the etching solution is mainly prepared by high-purity HF and H2O2 according to a certain ratio. The configuration is automatically completed by the VPD machine, which reduces unnecessary pollution caused by corresponding human factors. The used HF requires metal elements ≤10 ppt, and the used H2O2 requires metal element impurities ≤10 ppt. The H2O2 used for preparing the etching solution is 35% concentration hydrogen peroxide from Tomo Chemical. In order to reduce the influence of external metal impurities on detection accuracy and accuracy, the water used in the detection process is ultrapure water with a resistivity of ≥18 MΩ·cm.

[0029] The verification method includes the following operation steps:

[0030] First step: clean the surface of the silicon wafer, generate HF vapor on the surface of the silicon wafer by the VPD machine, and change the surface of the silicon wafer from hydrophilic to hydrophobic.

[0031] Second step: then the VPD machine scanning head scans and collects the metal contamination on the surface of the silicon wafer. The scanning head needs to scan and collect the metal impurities on the whole surface of the silicon wafer. After completing the collection of metal impurities, the etching solution is properly discarded, and then the silicon wafer is dried on the VPD machine.

[0032] Third step: place the silicon wafer cleaned on the ceramic heating plate, and use the vacuum suction pen during the transfer process. Pay attention to not let foreign matter touch the cleaned surface of the silicon wafer during the transfer process.

[0033] Fourth step: use a pipette to suck 20 ppt reverse pollution standard solution, the total volume is 1 ml, and then evenly drop the standard solution on the surface of the silicon wafer. The droplet should be as small as possible, and the number of droplets should be as many as possible, and evenly drop on the whole surface of the silicon wafer.

[0034] Fifth step: when the solution is low-temperature dried, the temperature of the heating plate is set to 25 degrees Celsius. The temperature of the heating plate should be uniform to avoid large local temperature difference of the silicon wafer.

[0035] After low-temperature drying of the solution, when the droplets on the surface of the silicon wafer are not visible, use the vacuum suction pen to transfer the silicon wafer to the wafer box, and use the VPD to collect the surface metal. The VPD operation process is automatically completed by the machine, and there is no human operation in the whole process, which ensures the cleanliness during the metal collection process.

[0036] Sixth step: use ICP-MS to test the reverse pollution solution collected by VPD.

[0037] ICP-MS is the full name of Inductively Coupled Plasma Mass Spectrometry.

[0038] ICP-MS is the full name of Inductively Coupled Plasma Mass Spectrometry.

[0039] After the elements in the sample are ionized into monovalent positive ions, they are screened and analyzed by the mass spectrometer multiple times, and the content of the measured element and the isotope ratio can be obtained after counting and calculation; by detecting the mixed standard solution, ICP-MS can realize the synchronous testing of multiple elements, and realize the synchronous analysis of multiple element detection results in a single detection of the same sample; at the same time, the ICP-MS testing element selection and screening analysis process is completed in a closed environment, and the data has high repeatability and accuracy.

[0040] As described above, the method of using reverse pollution to verify the precision of the test bench uses the mixed etching solution of the VPD machine to remove the metal impurities and oxide film on the surface of the sample, ensuring the cleanliness of the experimental silicon wafer and removing the influence of exogenous metal pollution. The recovery and testing of the etching solution are automatically completed by the machine, ensuring the precision and accuracy of the test data.

[0041] The above is only a specific embodiment of the present application, but the structural features of the present application are not limited to this. Any changes or modifications made by those skilled in the art within the scope of the present application are covered by the patent scope of the present application.

Claims

1. A method for verifying the accuracy of a test machine using reverse contamination, the method comprising: The equipment and tools used include element detection machine, vacuum suction pen, ceramic heating plate, VPD machine, etching liquid and 20 ppt anti-pollution standard solution. ​ The verification method includes the following operation steps: First step: clean the surface of the silicon wafer, generate HF vapor on the surface of the silicon wafer by VPD machine for gas phase etching, and change the surface of the silicon wafer from hydrophilic to hydrophobic. Second step: then scan the head of the VPD machine to collect the metal contamination on the surface of the silicon wafer, the scanning head needs to scan the entire surface of the silicon wafer to collect metal impurities, after the collection of metal impurities is completed, the etching liquid is properly discarded, and then the silicon wafer is dried in the VPD machine. Third step: place the silicon wafer on the ceramic heating plate, and use the vacuum suction pen during the transfer process. Avoid touching the cleaned surface of the silicon wafer with foreign matter during the transfer process. Fourth step: use a pipette to suck 20 ppt anti-pollution standard solution, the total volume is 1 ml, then evenly drop the standard solution on the surface of the silicon wafer, the droplets should be as small as possible, and the number of droplets should be as many as possible, and drop evenly on the entire surface of the silicon wafer. Fifth step: when the solution is dried at low temperature, the temperature of the heating plate is set to 25 degrees Celsius, and the temperature of the heating plate should be uniform to avoid large local temperature difference of the silicon wafer. After low-temperature drying of the solution, when the droplets on the surface of the silicon wafer are not visible, use the vacuum suction pen to transfer the silicon wafer to the wafer box, and use the VPD to collect the metal on the surface. The VPD operation process is automatically performed by the machine, and there is no human operation throughout the process to ensure the cleanliness during the metal collection process. Sixth step: test the anti-pollution solution collected by VPD by ICP-MS.

2. The method for verifying the precision of a test machine using reverse contamination according to claim 1, wherein: The ICP-MS machine model is ICP-MS-8900, which has a detection accuracy of ppt level. Before using the machine, confirm the instrument state, the linear of the standard curve should be above 0.995, and test the blank sample in advance to confirm that the machine is not contaminated.

3. The method of claim 1, wherein the method further comprises: determining a difference between the first and second measurements; and determining a difference between the third and fourth measurements. The VPD machine uses IAS Expert, and the etching liquid is mainly made of high-purity HF and H2O2 according to a certain ratio. The configuration is automatically completed by the VPD machine to reduce unnecessary pollution caused by human factors.

4. The method of claim 3, wherein the method further comprises: determining a difference between the first and second measurements; and determining a difference between the third and fourth measurements. The used HF requires metal elements ≤10 ppt, and the used H2O2 requires metal element impurities ≤10 ppt. The H2O2 used for configuring the etching liquid is 35% concentration hydrogen peroxide from Tomo Chemical.

5. The method of claim 3, wherein the method further comprises: determining a difference between the first and second measurements; and determining a difference between the third and fourth measurements. In order to reduce the influence of external metal impurities on the detection accuracy and accuracy, the water used in the detection process is ultrapure water with a resistivity of ≥18 MΩ·cm.

6. The method of claim 1, wherein the method further comprises: determining a difference between the first and second measurements; and determining a difference between the third and fourth measurements. Inductively coupled plasma mass spectrometry (ICP-MS) is a test principle that ionizes elements in the sample by high-temperature plasma heat source, and analyzes and detects the measured elements by mass spectrometer after sorting. The sample to be tested is pretreated as a liquid, and the sample solution is formed into aerosol by argon gas flow, which is sent into the plasma source generated by high-frequency radio frequency signal and induction coil, so as to realize the ionization of elements.

7. The method of claim 6, wherein the method further comprises: determining a difference between the first and second measurements; and determining a difference between the third and fourth measurements. After the elements in the sample are ionized into monovalent positive ions, multiple screening and analysis of the mass spectrometer are carried out, and the content of the element to be detected and the isotope ratio can be obtained by counting calculation; through the detection of mixed standard solution, ICP-MS realizes the synchronous test of multiple elements, and realizes the synchronous analysis of multiple element detection results in single detection of the same sample; meanwhile, the ICP-MS test element sorting and screening analysis process is completed in a closed environment, and the data has high repeatability and accuracy.

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