Method for detecting trace elements of silicon wafer

Abstract

The invention provides a method for detecting trace elements of a silicon wafer. The silicon wafer trace element detection method comprises the following steps: providing a silicon wafer; providing a conductive gasket, and placing the conductive gasket on the surface, away from the ion source, of the silicon wafer; and carrying out glow discharge on the silicon wafer to detect trace elements in the silicon wafer. Glow discharge detection is carried out after the conductive gasket is arranged on the surface, away from the ion source, of the silicon wafer, on one hand, the silicon wafer and the conductive gasket are combined, compared with a pure silicon wafer, the mechanical strength of the silicon wafer is improved, and the probability that the silicon wafer is broken down in the detection process is reduced; on the other hand, the conductive gasket has conductive performance, the silicon wafer and the conductive gasket are combined to serve as a cathode to generate stable plasma, and the conductive gasket is directly contacted with the back surface of the silicon wafer to provide an additional conductive path, so that the surface potential of the whole silicon wafer is uniform, and stable glow discharge is maintained; and the accuracy of a detection result is ensured.

Description

Technical Field

[0001] The present application belongs to the field of photovoltaic technology, and specifically relates to a method for detecting trace elements in silicon wafers. Background Art

[0002] The concentration and spatial distribution of trace impurities in solar cells play an important role in the function of the cell components. Even impurity levels at the ppbw level (parts per billion) can significantly reduce the performance of solar cells. Silicon wafers are the final product. In order to consider the impact of trace chemical elements on the response of crystalline silicon to internal light and the minority carrier capture ability in the actual process, it is necessary to analyze the impurity content of silicon wafers. Glow discharge mass spectrometry (GD-MS) has the characteristics of multi-element detection capability, low detection limit, and high sensitivity. It is a powerful tool for analyzing trace elements in metal and semiconductor silicon. However, the existing technology of GD-MS detection of trace elements in silicon wafers has the problem of inaccurate detection results.

[0003] Therefore, providing a method for accurately detecting trace elements in silicon wafers using GD-MS is a problem that needs to be solved at present. Summary of the Invention

[0004] The purpose of this application is to provide a method for detecting trace elements in silicon wafers, aiming to solve the problem that the detection results of trace elements in silicon wafers in the prior art are inaccurate or even impossible.

[0005] The present invention provides a method for detecting trace elements in a silicon wafer, comprising the following steps:

[0006] Provide silicon wafers;

[0007] Providing a conductive gasket, and placing the conductive gasket on a surface of the silicon wafer away from the ion source;

[0008] Glow discharge of silicon wafers to detect trace elements.

[0009] In some embodiments, the total thickness of the silicon wafer and the conductive spacer is 0.5-1.5 mm.

[0010] In some embodiments, there is at least one conductive gasket, and the thickness of each conductive gasket is 0.2-0.5 mm.

[0011] In some embodiments, the conductive spacer has a resistivity of 50 to 100 μΩ·cm.

[0012] In some embodiments, the conductive spacer is selected from at least one of the following: graphite paper, metal platinum foil, and metal tantalum foil.

[0013] In some embodiments, the conductive gasket is graphite paper, and the purity of the graphite paper is 99.99% to 100%.

[0014] In some embodiments, the glow discharge is in pulsed mode.

[0015] In some embodiments, the pulse mode includes: controlling the silicon signal value intensity of the silicon chip to be 1.0*10 10 ~1.0*10 11 cps.

[0016] In some embodiments, the discharge voltage in the pulse mode is 800-1400V.

[0017] In some embodiments, the discharge current in the pulse mode is 10-15 mA.

[0018] In some embodiments, the discharge gas flow rate in the pulse mode is 350-430 mL / min.

[0019] In some embodiments, the pulse mode includes several pulsed sputterings;

[0020] The duration of each pulse sputtering is 80 to 100 μs, and the time interval between two adjacent pulse sputterings is 400 to 420 μs.

[0021] In some embodiments, before performing glow discharge on the silicon wafer, the method further includes: performing pre-sputtering on the silicon wafer.

[0022] In some embodiments, the pre-sputtering time is 30 to 60 seconds.

[0023] In some embodiments, the trace elements include at least one of B, P, Ga, Sb, Na, Mg, Al, K, Ca, Fe, Cr, Ni, Cu, and Zn.

[0024] The present application provides a method for detecting trace elements in a silicon wafer, comprising: providing a silicon wafer; providing a conductive gasket, and placing the conductive gasket on the surface of the silicon wafer away from the ion source; and performing glow discharge on the silicon wafer to detect trace elements in the silicon wafer. The present application performs glow discharge detection after placing a conductive gasket on the surface of the silicon wafer away from the ion source. On the one hand, the combination of the silicon wafer and the conductive gasket improves the mechanical strength of the silicon wafer compared to a simple silicon wafer and reduces the probability of the silicon wafer being broken down during the detection process. On the other hand, since the conductive gasket has conductive properties, the combination of the silicon wafer and the conductive gasket can generate a stable plasma as a cathode. The conductive gasket is in direct contact with the back of the silicon wafer, which can provide an additional conductive path, thereby making the electric potential of the entire silicon wafer surface uniform, maintaining a stable glow discharge, and thus ensuring the accuracy of the detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] To more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present application. Those skilled in the art can also derive other drawings based on these drawings without inventive effort.

[0026] In order to more completely understand the present application and its beneficial effects, the following description will be given in conjunction with the accompanying drawings, wherein the same drawing numbers represent the same parts in the following description.

[0027] Figure 1 A schematic flow chart of a method for detecting trace elements in silicon wafers provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0029] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "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, an electrical connection, or mutual communication; it can be directly connected, or indirectly connected through an intermediate medium, or indirectly connected through a pipe or pipeline, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. In the description of this application, the meaning of "multiple" is two or more, unless otherwise clearly specified and specifically limited. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more features.

[0030] Methods for detecting trace impurities in silicon wafers include inductively coupled plasma mass spectrometry (ICP-MS) and secondary ion mass spectrometry (SIMS). The pre-treatment process of ICP-MS requires complex sample digestion, acid dissolution, dilution and other steps, which takes several hours or even longer, and has severe matrix effects, making it unsuitable for the rapid detection pace of the photovoltaic industry. Although SIMS can achieve high-sensitivity analysis of surface micro-areas, the technology has problems such as complex quantitative analysis, reliance on standard samples and low detection throughput. Its single application is difficult to meet the needs of rapid silicon wafer detection.

[0031] GD-MS has the advantages of simultaneous multi-element detection, low detection limit (up to ppb level) and high sensitivity. Therefore, it can effectively solve the problems of complex SIMS quantitative analysis, low detection throughput and long detection time. It is a powerful tool for analyzing trace elements in metals and semiconductor silicon.

[0032] However, on the one hand, GD-MS has certain requirements for the thickness of the sample to be tested, and the thickness of silicon wafers is usually less than 0.2mm. Too thin silicon wafer samples will result in low mechanical strength. Since GD-MS applies a high-voltage electric field in a low-pressure gas to ionize the gas to form plasma and bombard the silicon wafer surface with high energy, silicon wafer samples with weak mechanical strength may be broken down, resulting in damage or even rupture, causing detection failure.

[0033] On the other hand, in GD-MS detection, silicon wafers are mostly used as cathodes. When the resistivity of the silicon wafer is too high, the plasma stability during the glow discharge process may decrease. This is because the high-resistance material will hinder the uniform conduction of current, thereby affecting the potential distribution on the cathode surface. This uneven potential distribution may lead to inconsistent sample sputtering rates, thereby affecting the accuracy and repeatability of the detection results.

[0034] The applicant has found through research that the above-mentioned problem can be solved by placing a conductive gasket on the surface of a silicon wafer for detection as a combination.

[0035] The present invention provides a method for detecting trace elements in silicon wafers. Figure 1 As shown, the following steps are included:

[0036] Provide silicon wafers;

[0037] Providing a conductive gasket, and placing the conductive gasket on a surface of the silicon wafer away from the ion source;

[0038] Glow discharge is performed on silicon wafers to detect trace elements in the silicon wafers.

[0039] It is understandable that the silicon wafer can be a single crystal silicon wafer, a polycrystalline silicon wafer, or other silicon-based devices with conductivity. Before performing GD-MS detection, the sample to be tested needs to be placed in the sample pool and lightly pressed and fixed with a clamp. By padding the surface of one side of the silicon wafer with a conductive gasket, on the one hand, compared with a simple silicon wafer, the mechanical strength of the silicon wafer can be increased, thereby greatly reducing the probability of the silicon wafer being broken down during glow discharge detection; on the other hand, after the silicon wafer and the conductive gasket are combined, the conductive gasket is in direct contact with the back of the silicon wafer. The conductive gasket has good conductivity and can provide an additional conductive path. The silicon wafer and the conductive gasket can generate stable plasma as cathodes, thereby making the potential of the entire sample surface uniform, thereby maintaining a stable glow discharge and ensuring that the accuracy of the detection process is not affected.

[0040] Among them, the trace elements include at least one of B, P, Ga, Sb, Na, Mg, Al, K, Ca, Fe, Cr, Ni, Cu, and Zn.

[0041] In some embodiments, the conductive gasket is selected from at least one of the following: graphite paper, platinum foil, and tantalum foil. Further, the conductive gasket is preferably graphite paper, and the purity of the graphite paper is 99.99% to 100%.

[0042] It is understood that platinum foil and tantalum foil refer to foils made of platinum with a purity greater than 99.999% and tantalum with a purity greater than 99.999%, respectively. As metal foils, platinum foil and tantalum foil provide excellent electrical conductivity and, during conventional testing, do not overlap with the elements being measured in silicon wafers, thereby affecting the accuracy of measurement results. The purity of graphite paper can be any of 99.99%, 99.992%, 99.994%, 99.996%, 99.998%, or 100%, or a range between any two values. Graphite paper not only has excellent electrical conductivity, but also possesses high-temperature resistance, excellent thermal stability, high strength and flexibility, lubricity, and thermal shock resistance. It can provide flexible support for silicon wafers, effectively reducing shock and preventing cracking. At the same time, high-purity graphite paper itself has extremely low impurity content and stable chemical properties. It is not easy to decompose or release impurities during high-temperature pulse discharge. Compared with metal substrates that may introduce metal element contamination, high-purity graphite paper can effectively avoid interference with test results and is especially suitable for precise analysis of trace elements at the ppb level.

[0043] In some embodiments, the total thickness of the silicon wafer and the conductive spacer is 0.5-1.5 mm.

[0044] It is understood that the thickness of the silicon wafer and the conductive spacer (unit: mm) can be any value among 0.5, 0.7, 0.9, 1.1, 1.3, 1.5, or a range between any two values. By controlling the total thickness of the silicon wafer and the conductive spacer to meet the above range, the overall structural strength of the sample can be ensured during GD-MS testing, improving the success rate of testing while preventing the accuracy of the test results from being affected by excessive total sample thickness.

[0045] In some embodiments, the thickness of the silicon wafer is 0.15-0.18 mm.

[0046] It can be understood that the thickness of the silicon wafer (unit: mm) can be any value among 0.15, 0.16, 0.17, 0.18, or a value in a range between any two values.

[0047] In some embodiments, the conductive gasket is at least one conductive gasket, and the thickness of each conductive gasket is 0.2-0.5 mm.

[0048] It can be understood that the thickness of each conductive gasket (unit: mm) can be any value among 0.2, 0.3, 0.4, 0.5 or a value in the range between any two values. When multiple conductive gaskets are used in conjunction with silicon wafers for glow discharge detection, the conductive gaskets can be 1, 2 or 3 pieces, etc. Multiple conductive gaskets are stacked and laid on the side of the silicon wafer away from the ion source. Multiple conductive gaskets that meet the above-mentioned thickness range can better provide support for the silicon wafer with both flexibility and structural strength. At the same time, when a very small part of the silicon wafer sample is broken down during detection, the conductive gasket can also serve as a cathode to provide plasma. Especially when graphite paper is used as the conductive gasket, the graphite paper that meets the above-mentioned layer thickness range has both softness and structural strength, and can provide an elastic support buffer layer for single-crystal silicon wafers with a thickness of less than 0.2mm, and achieve a balance in mechanical support, electrical and thermal conductivity, and detection accuracy: it reduces the risk of sample breakage through flexible support, and ensures discharge uniformity and element stability through low resistance and efficient heat dissipation, while controlling equipment pollution and detection costs.

[0049] In some embodiments, the resistivity of the conductive gasket is 50-100 μΩ·cm.

[0050] It is understood that the resistivity of the conductive gasket (unit: μΩ·cm) can be any value among 50, 60, 70, 80, 90, 100, or a value in the range between any two values. The conductive gasket acts as a highly conductive pad, directly contacting the back of the silicon wafer, and can provide an additional conductive path to assist discharge. When the resistivity of the conductive gasket meets the above value range, it can effectively ensure that the entire surface potential of the silicon wafer sample is uniform, maintain stable glow discharge, make the ionization efficiency consistent, improve the repeatability of the impurity signal, and make the detection results more accurate.

[0051] In some embodiments, the detection mode of the glow discharge is a pulse mode.

[0052] It is understandable that when the detection mode of the GD-MS instrument is DC mode, the silicon wafers that have been pre-treated by acid washing are easily broken down due to the local electric field concentration in DC glow discharge mode, resulting in sample damage and inability to achieve effective detection. This application uses pulse mode to detect silicon wafers. The intermittent pulse sputtering has higher instantaneous power, which can improve the excitation and ionization efficiency, while reducing the impact of thermal stress on fragile samples, thereby achieving rapid and accurate quantitative analysis of the impurity content in the silicon wafer.

[0053] In some embodiments, pulse detection further comprises:

[0054] The silicon signal value strength of the control silicon chip is 1.0*10 10 ~1.0*10 11 cps.

[0055] It is understood that the silicon signal value intensity refers to the electrical signal intensity of the silicon element itself in the sample. The value of the silicon signal value intensity (unit: cps) can be controlled within 1.0*10 10 , 2.0*10 10 , 3.0*10 10 , 4.0*10 10 , 5.0*10 10 、6.0*10 10 ,7.0*10 10 ,8.0*10 10 , 9.0*10 10 , 1.0*10 11 When the silicon signal intensity is controlled within the above range, noise interference can be effectively suppressed, the discharge state can be maintained, and statistical errors can be controlled during glow discharge detection, ultimately achieving accurate quantification of trace impurity elements.

[0056] In some embodiments, the discharge voltage of the pulse detection is 800-1400V.

[0057] It is understood that the discharge voltage value (unit: V) for pulse detection can be any value among 800, 900, 1000, 1100, 1200, 1300, 1400, or a value within the range between any two values. By controlling the discharge voltage for pulse detection to meet the above value range, not only can the ion signal intensity generated by the target trace impurity element be maximized, but it can also ensure that the GD-MS instrument has good mass accuracy (the degree of closeness between the measured m / q and the theoretical value) and resolution (the ability to distinguish adjacent m / q peaks) across the entire ion mass-to-charge ratio (m / q) range of the sample to be tested, while also preventing excessive discharge voltage from causing breakdown of the silicon wafer.

[0058] In some embodiments, the discharge current of the pulse detection is 10-15 mA.

[0059] It is understood that the discharge current value (unit: mA) for pulse detection can be any value among 10, 11, 12, 13, 14, and 15, or a value within a range between any two values. When the discharge current for pulse detection meets the above value range, it can be combined with the discharge voltage for pulse detection to further optimize the ion signal intensity generated by the target trace impurity element and ensure that the GD-MS instrument has good mass accuracy and resolution across the entire mass range of the sample to be tested.

[0060] In some embodiments, the discharge gas flow rate for pulse detection is 350-430 mL / min.

[0061] It is understood that the discharge gas flow rate value (unit: mL / min) for pulse detection can be any value among 350, 360, 370, 380, 390, 400, 410, 420, 430, or a value within the range between any two values. When the discharge gas flow rate for pulse detection meets the above value range, it can ensure the formation of a stable and uniform glow discharge plasma in the area to be detected, and ensure that the sputtered target element atoms have an ideal diffusion rate from the cathode surface to the plasma main area, thereby ensuring that the measurement precision and accuracy meet the requirements.

[0062] At the same time, by controlling the discharge voltage, discharge current and discharge gas flow of the pulse detection to meet the above value range, the ionization efficiency of the elements in the silicon wafer can be effectively improved, the signal value can be enhanced, and the silicon signal value intensity in the silicon wafer sample can reach 1.0*10 10 ~1.0*10 11 cps, thereby improving the accuracy of detection.

[0063] In some embodiments, the pulse detection includes several pulse sputterings;

[0064] The duration of each pulse sputtering is 80 to 100 μs, and the time interval between adjacent pulse sputterings is 400 to 420 μs.

[0065] It is understood that the duration of each sputtering pulse (unit: μs) can be any value among 80, 85, 90, 95, 100, or a value within a range between any two values, and the interval between two adjacent sputtering pulses (unit: μs) can be any value among 400, 410, 420, or a value within a range between any two values. Short pulse durations significantly reduce the energy of a single ion beam bombardment, minimizing heat accumulation and mechanical damage to the silicon wafer. By controlling the duration of each sputtering pulse to meet the aforementioned values, effective sputtering can be achieved while avoiding damage to the silicon wafer caused by heat accumulation. Furthermore, controlling the interval between two adjacent sputtering pulses to meet the aforementioned values ​​can form a buffer between the two adjacent sputtering pulses, preventing material deformation or element volatilization due to local overheating.

[0066] Specifically, the parameters for GD-MS pulse detection of silicon wafers can be shown in Table 1.

[0067] Table 1

[0068] Working parameters Value Discharge (working) voltage / V 800～1400 Discharge current / mA 10～15 <![CDATA[Gas flow rate (mL·min －1 )]]> 350～430 Shaping voltage / V 100～140 Extraction voltage / V -1600～2000 Focus voltage / V -800～-1280 Pulse duration / μs 80～100

[0069] In some embodiments, before the step of performing pulse detection on the silicon wafer, the method further includes:

[0070] Pre-sputter the silicon wafer.

[0071] By pre-sputtering the silicon wafer, on the one hand, the contamination that may be brought to the surface during the processing is removed and the sample surface is activated. On the other hand, due to the difference in the surface state of the silicon wafer, the sputtering may be uneven during ion beam bombardment, and some elements (such as B, P and other doping elements) may be segregated on the surface, resulting in a difference between the surface concentration and the bulk concentration. Pre-sputtering can eliminate the detection error caused by the surface morphology and surface concentration difference of the silicon wafer, and improve the accuracy of the detection results.

[0072] In some embodiments, the pre-sputtering time is 30 to 60 seconds.

[0073] It is understood that the pre-sputtering time (unit: s) can be any value among 30, 35, 40, 45, 50, 55, 60, or a range between any two values. The pre-sputtering method is also pulsed sputtering, and the equipment parameters for pulsed sputtering are the same as those used for formal pulse testing. When the pre-sputtering time falls within the above range, it can eliminate surface errors of the silicon wafer while avoiding damage to the sample caused by excessive sputtering.

[0074] In some embodiments, multiple pre-sputtering operations may be performed before pulse testing the silicon wafer. Specifically, the number of pre-sputtering operations may be three. Repeated pre-sputtering operations can gradually remove contaminants or impurities at different depths from the silicon wafer.

[0075] In some embodiments, before the step of placing the silicon wafer on the surface of the conductive spacer, the method further includes:

[0076] Pre-treat the silicon wafer using an acidic solution.

[0077] By using an acidic solution to pre-treat the silicon wafer with pickling, contaminants on the silicon wafer surface can be further removed and the surface state can be regulated, thereby ensuring the accuracy and reliability of the test results.

[0078] In some embodiments, the step of pretreating the silicon wafer with an acidic solution further includes:

[0079] Cleaning the surface of the silicon wafer using a first acid solution;

[0080] Soak the silicon wafer in a second acid solution;

[0081] The first acid solution includes nitric acid solution; the second acid solution includes nitric acid and hydrofluoric acid.

[0082] Furthermore, the first acid solution can be prepared by dissolving nitric acid (HNO3, spectrally pure, SP) in deionized water; the second acid solution can be a mixed solution of hydrofluoric acid (HF, spectrally pure, SP) and nitric acid (HNO3, spectrally pure, SP) (hydrofluoric acid:nitric acid = 4:1, concentration ratio). In some embodiments, the immersion time is 10 to 20 seconds.

[0083] It is understood that the immersion time (unit: s) can be any value among 10, 12, 14, 16, 18, 20, or a value within a range between any two values. When the immersion time falls within the above range, it can ensure that contaminants on the silicon wafer surface are completely removed while avoiding prolonged reaction time with the acid solution, which may result in the silicon wafer being too thin and unfavorable for subsequent testing.

[0084] The following describes the method for detecting trace elements in silicon wafers provided by this application in conjunction with specific examples:

[0085] Example 1

[0086] This embodiment provides a method for detecting silicon wafers, and the specific steps are as follows:

[0087] S1. Sample Pretreatment: Gently pick up a 0.18mm thick silicon wafer sample using a sampling clip. Clean the sample surface with deionized water and nitric acid (HNO3, spectrally pure, SP). Then, soak the wafer in a mixed solution of hydrofluoric acid (HF, spectrally pure, SP) and HNO3 (HF:HNO3 = 4:1, concentration ratio) for 15 seconds. After chemical polishing, rinse the wafer repeatedly with ultrapure water and anhydrous ethanol, then blow dry with high-purity nitrogen.

[0088] S2. Sample fixation: Place the pretreated silicon wafer into the analytical cell of the GD-MS instrument, cover it with two layers of 0.4 mm thick high-purity (99.99%) graphite paper, gently secure it with a sample clamp, and then place it into the GD-MS ion source with the silicon wafer facing the ion source.

[0089] S3. Pulse Detection: An Element GD plus GD-MS instrument was used in pulse detection mode. The instrument measured the silicon signal intensity and analyzed three non-overlapping areas based on sample size. The sample was pre-sputtered for 30 seconds under stable conditions, followed by pulse detection. Each point was analyzed four times. The instrument operating parameters are shown in Table 2.

[0090] Table 2

[0091] Working parameters Value Discharge (working) voltage / V 1000 Discharge current / mA 12 <![CDATA[Gas flow rate (L·min －1 )]]> 400 Shaping (instrument itself) voltage / V 120 Extracted (instrument itself) voltage / V -2000 Focus voltage / V 1030 Pulse duration / μs 100 Pulse interval time / μs 400

[0092] Examples 2 to 6

[0093] The detection steps of Examples 2 to 6 are the same as those of Example 1, and the only difference is the adjustment of the working parameters.

[0094] Comparative Examples 1 to 7

[0095] The detection steps of Comparative Examples 1 to 7 are the same as those of Example 1, with the only difference being the adjustment of the working parameters.

[0096] The operating parameters of Examples 1 to 6 and Comparative Examples 1 to 7 are shown in Table 3.

[0097] Table 3

[0098]

[0099]

[0100] SIMS was used to perform multiple quantitative measurements on the silicon wafer samples from the same batch in Examples 1 to 6 and Comparative Examples 1 to 7, and the average value was taken as the standard content of the sample. The results were compared with the test data in Examples 1 to 6 and Comparative Examples 1 to 7. The comparison of the test results is shown in Table 4.

[0101] Table 4

[0102]

[0103]

[0104] According to Tables 3 and 4, it can be seen that the detection method provided in this application is used to detect trace elements in silicon wafers. Within the process parameter range provided in this application, the signal intensity of the silicon-based sample during the detection process can be effectively optimized, thereby obtaining more accurate trace element concentration detection results, and controlling the error between the GD-MS detection results and the SIMS detection within an ideal range. According to Example 1 and Comparative Example 1, it can be seen that when the discharge voltage is too low, the signal strength of the silicon-based sample will be insufficient, which will lead to a large error between the detection result and the actual concentration; according to Example 2 and Comparative Example 2, it can be seen that when the discharge voltage is too high, the sample will be broken down, resulting in an inability to detect; according to Example 3 and Comparative Example 3, it can be seen that when the discharge current is too low, the signal strength of the silicon-based sample will also be insufficient, which will lead to a large error between the detection result and the actual concentration; according to Example 4 and Comparative Example 4, it can be seen that when the discharge current is too high, the sample will be broken down, resulting in an inability to detect; according to Example 5 and Comparative Example 5, it can be seen that when the discharge gas flow rate is too low, the signal strength of the silicon-based sample will also be insufficient, which will lead to a large error between the detection result and the actual concentration; according to Example 6 and Comparative Example 6, it can be seen that when the discharge gas flow rate is too high, the sample will be broken down, resulting in an inability to detect; according to Example 1 and Comparative Example 7, when the pre-sputtering time is too long, the silicon wafer will be broken down, resulting in the inability to perform subsequent detection.

[0105] Example 7

[0106] Ten silicon wafer samples were randomly selected, and the detection steps in Example 1 were repeated for each silicon wafer sample, and the number of times the sample was broken was recorded.

[0107] Comparative Example 8

[0108] The detection method for silicon wafers in Comparative Example 8 is similar to that in Example 1, except that no conductive gasket is added in step S2.

[0109] Ten silicon wafer samples from the same batch as Example 7 were randomly selected, and the above test steps were repeated for each silicon wafer sample, and the number of times the sample was broken was recorded.

[0110] The number of sample fragmentation in Example 7 and Comparative Example 8 is shown in Table 5.

[0111] Table 5

[0112]

[0113] Table 5 shows that without the protection of a conductive gasket, silicon wafers repeatedly break during GD-MS testing. This is due to uneven heating of the sample surface, resulting in thermal stress, mechanical shock from pulse discharge, or stress concentration caused by electrode pressure. The solution provided in this application using a conductive gasket effectively reduces the risk of silicon wafer breakdown during GD-MS testing, significantly improving the success rate of testing.

[0114] Example 8

[0115] Ten silicon wafer samples were randomly selected, and the detection steps in Example 1 were repeated for each silicon wafer sample, and the number of times the sample was broken was recorded.

[0116] Comparative Example 9

[0117] In the detection steps of the silicon wafer in Comparative Example 9, steps S1 and S2 are the same as those in Example 1, and step S3 is changed to use a DC voltage to detect the silicon sample, with a discharge (working) voltage / V of 1000 V and a discharge current of 60 mA.

[0118] Ten silicon wafer samples from the same batch as Example 8 were randomly selected, and the above test steps were repeated for each silicon wafer sample, and the number of times the sample was broken was recorded.

[0119] The number of sample fragmentation in Example 8 and Comparative Example 9 is shown in Table 6.

[0120] Table 6

[0121] Example 8 Comparative Example 9 Number of sample fragmentations 0 9

[0122] Table 5 shows that when using DC voltage for GD-MS testing of silicon wafers, the wafers often break down. This is because DC voltage is more likely to break down the sample. However, the pulsed glow discharge testing solution provided in this application can effectively reduce the risk of silicon wafer breakdown during GD-MS testing, significantly improving the success rate of testing.

[0123] In addition, by comparing Examples 1 to 8, Comparative Examples 1 to 6, and Comparative Examples 8 and 9, it can be seen that combining the use of conductive gaskets provided in this application with the solution of using pulse mode detection can better improve the overall strength of the sample and improve the success rate and accuracy of detection. This shows that under the premise of using conductive gaskets, the use of pulse mode can better synergize with the conductive gaskets and improve the detection effect.

[0124] The above is a detailed introduction to the method for detecting trace elements in silicon wafers provided in the embodiments of the present application. Specific examples are used in this application to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for detecting trace elements in silicon wafers, characterized in that: include: Provide silicon wafers; Providing a conductive gasket, and placing the conductive gasket on a surface of the silicon wafer away from the ion source; Glow discharge is performed on the silicon wafer to detect trace elements therein.

2. The method for detecting trace elements in silicon wafers according to claim 1, wherein: The total thickness of the silicon wafer and the conductive gasket is 0.5 to 1.5 mm.

3. The method for detecting trace elements in silicon wafers according to claim 1, wherein: There is at least one conductive gasket, and the thickness of each conductive gasket is 0.2-0.5 mm.

4. The method for detecting trace elements in silicon wafers according to claim 1, wherein: The resistivity of the conductive gasket is 50 to 100 μΩ·cm.

5. The method for detecting trace elements in silicon wafers according to claim 1, wherein: The conductive gasket is selected from at least one of the following: graphite paper, metal platinum foil and metal tantalum foil.

6. The method for detecting trace elements in silicon wafers according to claim 5, characterized in that: The conductive gasket is graphite paper, and the purity of the graphite paper is 99.99% to 100%.

7. The method for detecting trace elements in silicon wafers according to any one of claims 1 to 6, characterized in that: The glow discharge is in pulse mode.

8. The method for detecting trace elements in silicon wafers according to claim 7, wherein: The pulse mode includes: controlling the silicon signal value intensity of the silicon chip to be 1.0*10 10 ~1.0*10 11 cps.

9. The method for detecting trace elements in silicon wafers according to claim 8, characterized in that: The discharge voltage of the pulse mode is 800-1400V; and / or, The discharge current of the pulse mode is 10-15 mA; and / or, The discharge gas flow rate in the pulse mode is 350-430 mL / min.

10. The method for detecting trace elements in silicon wafers according to claim 7, wherein: The pulse mode includes several pulse sputterings; The duration of each pulse sputtering is 80 to 100 μs, and the time interval between two adjacent pulse sputterings is 400 to 420 μs.

11. The method for detecting trace elements in silicon wafers according to claim 1, wherein: Before performing the glow discharge on the silicon wafer, the method further includes: performing pre-sputtering on the silicon wafer.

12. The method for detecting trace elements in silicon wafers according to claim 11, characterized in that: The pre-sputtering time is 30 to 60 seconds.

13. The method for detecting trace elements in silicon wafers according to claim 1, wherein: The trace elements include at least one of B, P, Ga, Sb, Na, Mg, Al, K, Ca, Fe, Cr, Ni, Cu and Zn.

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