Method and system for obtaining threshold voltage stability, equipment and storage medium

Abstract

A method and system for obtaining threshold voltage stability, a device and a storage medium, the method comprising: performing a negative bias temperature instability test to obtain a relationship of a threshold voltage drift amount with time change under different first test voltages; on the basis of the time-varying relationship of the threshold voltage drift under different first test voltages and the difference value between the second test voltage and the first test voltage, obtaining the time-varying relationship of the threshold voltage drift under the second test voltage; obtaining a threshold voltage drift distance corresponding to the target test time based on a time-varying relationship of the threshold voltage drift distance under the second test voltage, and taking the threshold voltage drift distance as a speculative drift distance; obtaining the correlation between the target drift distance and the speculated drift distance; and based on the correlation between the target drift amount and the speculated drift amount, obtaining the corresponding speculated drift amount when the target drift amount is the target value. According to the embodiment of the invention, the process of obtaining the threshold voltage stability is simplified, and the test period is shortened.

Description

Technical Field

[0001] Embodiments of the present invention relate to the semiconductor field, and in particular, to a method and system, device and storage medium for obtaining threshold voltage stability. Background Art

[0002] Metal oxide semiconductor (MOS) devices are widely used in various fields. The stability of the threshold voltage (Vt) of MOS devices is an important indicator for evaluating their performance. The smaller the drift of the threshold voltage Vt with changes in physical conditions, the more reliable the performance of the MOS device.

[0003] Since there are some free dangling bonds (or hanging bonds, dangling bonds) on the surface of the manufactured MOS device, in the actual application environment, as the physical conditions change, these dangling bonds will cause the stability of the threshold voltage Vt to decrease. Therefore, it is usually necessary to perform high temperature treatment on the manufactured MOS device to simulate the actual application environment in order to test the stability of the threshold voltage Vt in the actual working environment.

[0004] However, the current test cycle for threshold voltage stability is relatively long. Summary of the invention

[0005] The problem solved by the embodiments of the present invention is to provide a method and system, device and storage medium for obtaining threshold voltage stability, thereby simplifying the process of obtaining threshold voltage stability and shortening the test cycle.

[0006] To solve the above problems, an embodiment of the present invention provides a method for obtaining threshold voltage stability, including: performing a negative bias temperature instability test to obtain the relationship between the threshold voltage drift amount and time at different first test voltages; the test voltage for the threshold voltage stability test is a second test voltage, the test time is a target test time, and the obtained threshold voltage drift amount is used as a target drift amount; based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, the relationship between the threshold voltage drift amount and time at the second test voltage is obtained; based on the relationship between the threshold voltage drift amount and time at the second test voltage, the threshold voltage drift amount corresponding to the target test time is obtained as an inferred drift amount; the correlation between the target drift amount and the inferred drift amount is obtained; based on the correlation between the target drift amount and the inferred drift amount, the inferred drift amount corresponding to the target drift amount when the target drift amount is the target value is obtained.

[0007] Correspondingly, an embodiment of the present invention also provides a system for obtaining threshold voltage stability, including: a test module, used to perform a negative bias temperature instability test, and obtain the relationship between the threshold voltage drift amount under different first test voltages and time; the test voltage for the threshold voltage stability test is a second test voltage, the test time is a target test time, and the obtained threshold voltage drift amount is used as a target drift amount; a relationship acquisition module, used to obtain the relationship between the threshold voltage drift amount under the second test voltage and time based on the relationship between the threshold voltage drift amount under different first test voltages and time and the difference between the second test voltage and the first test voltage; an inference module, used to obtain the threshold voltage drift amount corresponding to the target test time as the inferred drift amount based on the relationship between the threshold voltage drift amount under the second test voltage and time; a correlation acquisition module, used to obtain the correlation between the target drift amount and the inferred drift amount; a calculation module, used to obtain the inferred drift amount corresponding to the target drift amount when the target drift amount is the target value based on the correlation between the target drift amount and the inferred drift amount.

[0008] Accordingly, an embodiment of the present invention also provides a device, comprising at least one memory and at least one processor, wherein the memory stores one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the method for obtaining threshold voltage stability provided in an embodiment of the present invention.

[0009] Correspondingly, an embodiment of the present invention further provides a storage medium, wherein the storage medium stores one or more computer instructions, and the one or more computer instructions are used to implement the method for obtaining threshold voltage stability provided by an embodiment of the present invention.

[0010] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0011] The method for obtaining threshold voltage stability provided by an embodiment of the present invention performs a negative bias temperature instability test to obtain a relationship between a threshold voltage drift amount and time at different first test voltages; based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, obtain the relationship between the threshold voltage drift amount and time at the second test voltage, and then obtain the threshold voltage drift amount at the target test time as the estimated drift amount, and obtain the correlation between the target drift amount and the estimated drift amount, so as to obtain the estimated drift amount corresponding to the target value when the target drift amount is the target value based on the correlation. Drift amount, so that the embodiment of the present invention can use the negative bias temperature instability test to obtain the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value, and then obtain the threshold voltage stability by estimating the translation amount. The negative bias temperature instability test is usually performed during the wafer manufacturing process. The embodiment of the present invention does not need to perform packaging-level testing to obtain the threshold voltage stability, and the time of the negative bias temperature instability test is greatly shortened compared to the time of the threshold voltage stability test, which is conducive to shortening the period of obtaining the threshold voltage stability, and then the test data of the threshold voltage stability can be obtained earlier, so as to provide a basis for the improvement of research and development design. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart of an embodiment of a method for obtaining threshold voltage stability according to the present invention;

[0013] Figure 2 A schematic diagram showing a plurality of first relationship straight lines obtained by performing a negative bias temperature instability test;

[0014] Figure 3 A schematic diagram showing an embodiment of a second relationship straight line obtained based on a plurality of first relationship straight lines and a difference between a second test voltage and a first test voltage is shown;

[0015] Figure 4 The gate voltage applied to the structure to be tested and the corresponding failure time when the threshold voltage drift is at a preset value are shown;

[0016] Figure 5 Shows Figure 1 A schematic diagram of a flow chart of an embodiment of step S4 in FIG.

[0017] Figure 6 A box plot made based on Table 1 is shown;

[0018] Figure 7 A scatter plot based on Table 1 is shown;

[0019] Figure 8 Shows Figure 1 A schematic diagram of a flow chart of an embodiment of step S5;

[0020] Fig. 9 is a functional block diagram of an embodiment of a system for achieving threshold voltage stability according to the present invention;

[0021] Fig.10 It is a hardware structure diagram of an embodiment of the device provided by the present invention. DETAILED DESCRIPTION

[0022] As known from the background technology, the current test cycle of threshold voltage stability is relatively long.

[0023] Specifically, the package-level test Vts (Threshold Voltage Stability) is one of the necessary test items for evaluating the reliability of the gate oxide layer. The test steps are as follows: first test the initial Vt value, recorded as Vt (initial); then, put the MOS device to be tested into a high-temperature furnace and bake it for a preset time under a preset high-temperature environment; then, test the final Vt value, recorded as Vt (final), and the Vt drift Vt shift It can be calculated using formula (I):

[0024] Vt shift =[Vt(final)-Vt(initial)] / Vt(initial)(I)

[0025] Among them, Vt drift Vt shift The smaller it is, the better the working stability of the MOS device is and the higher the reliability is. shift When it is greater than a certain predetermined value, the MOS device fails and its performance does not meet the requirements.

[0026] At present, it is usually necessary to conduct packaging-level testing to obtain threshold voltage stability after wafer manufacturing is completed. Specifically, after wafer manufacturing is completed, the wafer is cut to obtain multiple separate dies, and the dies are subjected to bonding and packaging processes to obtain packaged chips. After packaging, the chips are tested for threshold voltage stability. This can easily lead to a long test cycle and a late time to obtain threshold voltage stability, which results in a failure to provide a basis for the improvement of product R&D design in a timely manner, and thus leads to a long product cycle.

[0027] In addition, the current threshold voltage stability test is baked for a long time in a preset high temperature environment, for example: 168 hours, which further increases the test cycle.

[0028] In order to solve the technical problem, an embodiment of the present invention provides a method for obtaining threshold voltage stability. Figure 1 It is a flow chart of an embodiment of a method for obtaining threshold voltage stability according to the present invention.

[0029] refer to Figure 1 In this embodiment, the method for obtaining threshold voltage stability includes the following basic steps:

[0030] Step S1: performing a negative bias temperature instability test at different first test voltages to obtain a relationship between a threshold voltage drift and time at different first test voltages; the test voltage for the threshold voltage stability test is a second test voltage, the test time is a target test time, and the obtained threshold voltage drift is used as a target drift;

[0031] Step S2: based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, obtaining the relationship between the threshold voltage drift amount and time at the second test voltage;

[0032] Step S3: based on the relationship between the threshold voltage drift amount under the second test voltage and time, obtaining the threshold voltage drift amount corresponding to the target test time as the estimated drift amount;

[0033] Step S4: obtaining the correlation between the target drift amount and the estimated drift amount;

[0034] Step S5: Based on the correlation between the target drift amount and the estimated drift amount, the estimated drift amount corresponding to when the target drift amount is the target value is obtained.

[0035] The method for obtaining threshold voltage stability provided by the embodiment of the present invention performs a negative bias temperature instability test to obtain the relationship between the threshold voltage drift amount and time at different first test voltages; based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, the relationship between the threshold voltage drift amount and time at the second test voltage is obtained, and then the threshold voltage drift amount at the target test time is obtained as the estimated drift amount, and the correlation between the target drift amount and the estimated drift amount is obtained, so as to obtain the target drift amount corresponding to the target value based on the correlation. The drift amount is estimated, so that the embodiment of the present invention can use the negative bias temperature instability test to obtain the estimated drift amount corresponding to the target drift amount being the target value, and then obtain the threshold voltage stability by estimating the translation amount. The negative bias temperature instability test is usually performed during the wafer manufacturing process. The embodiment of the present invention does not need to perform packaging-level testing to obtain the threshold voltage stability, and the time for the negative bias temperature instability test is greatly shortened compared to the time for the threshold voltage stability test, which is conducive to shortening the period for obtaining the threshold voltage stability, and then obtaining the test data of the threshold voltage stability earlier, providing a basis for the improvement of research and development design.

[0036] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] refer to Figure 1 , executing step S1: performing a negative bias temperature instability (NBTI) test to obtain a relationship between a threshold voltage drift amount and time at different first test voltages.

[0038] A negative bias temperature instability test is performed to obtain the relationship between the threshold voltage drift and time at different first test voltages, so that based on the relationship between the threshold voltage drift and time at different first test voltages and the difference between the second test voltage and the first test voltage, the relationship between the threshold voltage drift and time at the second test voltage can be obtained, thereby facilitating subsequent inference of the threshold voltage stability.

[0039] The negative bias temperature instability test is usually performed during the wafer manufacturing process, and the time of the negative bias temperature instability test is greatly shortened compared to the threshold voltage stability test, which is conducive to shortening the period for obtaining threshold voltage stability.

[0040] Moreover, in this embodiment, by obtaining information for inferring threshold voltage stability during the negative bias temperature instability test, it can be combined with the existing test process flow, thereby improving compatibility and simplifying the test process, which is correspondingly beneficial to improving test efficiency and shortening the test cycle.

[0041] In this embodiment, the negative bias temperature instability test is performed for 3 hours to 6 hours.

[0042] In the semiconductor field, the first test voltage for negative bias temperature instability testing is usually greater than 1.1 times the device operating voltage, so as to accelerate device degradation at a higher test voltage.

[0043] In this embodiment, the step of performing a negative bias temperature instability test under different first test voltages includes: providing a structure to be tested; and performing a negative bias temperature instability test on the structure to be tested under different first test voltages.

[0044] As an example, the step of providing a structure to be tested includes: providing a substrate; forming a gate oxide layer on the substrate; and thermally treating the gate oxide layer in a nitrogen-containing atmosphere.

[0045] The substrate is used to provide a process platform for forming the structure to be tested.

[0046] In a specific implementation, the substrate may be a three-dimensional substrate or a planar substrate. In this embodiment, for the sake of illustration and description, the substrate is a planar substrate as an example for description. In other embodiments, the substrate may also be a three-dimensional substrate, for example, the substrate may also include a substrate and a fin separated from the substrate.

[0047] In this embodiment, the base includes a substrate. In this embodiment, the substrate is a silicon substrate. In other embodiments, the material of the substrate may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate may also be other types of substrates such as a silicon substrate on an insulator or a germanium substrate on an insulator. The material of the substrate may be a material suitable for process requirements or easy to integrate.

[0048] In a specific implementation, the step of providing a structure to be tested generally further includes: after heat treating the gate oxide layer in a nitrogen-containing atmosphere, a gate layer located on the gate oxide layer and source-drain doping layers located in the substrate on both sides of the gate layer are formed.

[0049] The gate oxide layer is used to isolate the gate layer from the substrate. The quality of the gate oxide layer has a crucial impact on the electrical performance of the device. For example, defects in the gate oxide layer have a significant impact on the threshold voltage drift.

[0050] As an example, the material of the gate oxide layer is silicon oxide. In other embodiments, the material of the gate oxide layer may also be silicon oxynitride.

[0051] As the device size gradually decreases, the gate oxide layer gradually becomes thinner, and accordingly, the breakdown voltage of the device gradually decreases. By heat treating the gate oxide layer in a nitrogen-containing atmosphere, the boron punch-through problem of the PMOS device can be prevented, thereby improving the breakdown voltage.

[0052] In this embodiment, the nitrogen-containing atmosphere includes nitric oxide and nitrogen, wherein the nitric oxide is used to provide a nitrogen source and the nitrogen is used to protect the gate oxide layer.

[0053] However, when the gate oxide layer is heat treated in a nitrogen-containing atmosphere, it is easy to form a Si-N bond at the interface between the substrate and the gate oxide layer (the Si-O interface in this embodiment), and it is difficult to break the Si-N bond at the Si-O interface. The nitrogen atoms in the gate oxide layer can serve as trap centers, thereby enhancing the generation of fixed oxide charge in the negative bias temperature instability (NBTI) effect. In other words, the nitrogen atoms in the gate oxide layer can aggravate the negative bias temperature instability effect.

[0054] Therefore, in this embodiment, the ratio of nitric oxide to nitrogen in the nitrogen-containing atmosphere is adjusted to ensure that the NBTI effect is not significantly aggravated while the breakdown voltage is improved as much as possible.

[0055] As an example, during the heat treatment of the gate oxide layer in a nitrogen-containing atmosphere, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:X, where X should not be too small or too large. If X is too small, the proportion of nitrogen in the nitrogen-containing atmosphere is too small, which easily leads to an insignificant protective effect on the gate oxide layer; if X is too large, the proportion of nitrogen in the nitrogen-containing atmosphere is too large, which easily leads to an insignificant nitrogen doping effect. For this reason, in this embodiment, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:X, where X is at least 5.

[0056] In a specific implementation, based on actual process requirements, X can be 10 to 30, for example, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:10, 0.5:15, or 0.5:20, etc.

[0057] In this embodiment, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:10 as an example for description.

[0058] In this embodiment, the step of performing the negative bias temperature instability test includes: applying stress (e.g., temperature, gate voltage) to the structure to be tested for a certain period of time, and then measuring the change of specific parameters of the device to obtain the change law of parameter degradation with stress time, thereby evaluating the device life. The parameter degradation includes the threshold voltage drift.

[0059] In a specific implementation, the negative bias temperature instability test is performed at room temperature or high temperature. In this embodiment, the negative bias temperature instability test is performed at 125° C. as an example for explanation. In other embodiments, based on actual test requirements, the negative bias instability test can also be performed at other temperatures.

[0060] More specifically, in this embodiment, during the negative bias temperature instability test, the initial Vt value is first tested, which is recorded as Vt(initial); then, the structure to be tested is placed in a high-temperature furnace, a certain stress is applied to the structure to be tested under a preset high-temperature environment, and the Vt value at each moment is tested, which is recorded as V tlin shift , then the threshold voltage drift Vt shift It can be calculated using formula (II):

[0061] Vt shift =[V tlin shift-Vt(initial)] / Vt(initial)(II)

[0062] Therefore, by obtaining the threshold voltage drift at each moment, the relationship between the threshold voltage drift and time under the current first test voltage can be obtained.

[0063] Specifically, in this embodiment, a negative bias temperature instability test is performed under different first test voltages to obtain a relationship between the threshold voltage drift amount and time at different first test voltages, including: a negative bias temperature instability test is performed under different first test voltages to obtain a straight line of the relationship between the threshold voltage drift amount and time at different first test voltages as the first straight line.

[0064] Specifically, a negative bias temperature instability test is performed under different first test voltages, and the step of obtaining the relationship between the threshold voltage drift amount and time under different first test voltages includes: performing a negative bias temperature instability test on multiple structures to be tested under each first test voltage to obtain the average value of the threshold voltage drift amounts corresponding to the multiple structures to be tested at each test time; based on the average value of the threshold voltage drift amounts corresponding to the multiple structures to be tested at each test time, obtaining the relationship between the threshold voltage drift amount and time under the current first test voltage.

[0065] By performing negative bias temperature instability tests on multiple structures to be tested, the average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time is obtained, thereby reducing the measurement error, improving the reliability of the measurement, and correspondingly improving the accuracy of obtaining the relationship between the threshold voltage drift and time under the current first test voltage.

[0066] In a specific implementation, under each first test voltage, a negative bias temperature instability test is performed on multiple structures to be tested to obtain an average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time; based on the average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time, a straight line showing the relationship between the threshold voltage drift and time under the current first test voltage is obtained.

[0067] Combined with reference Figure 2 , shows a schematic diagram of multiple first relationship straight lines obtained by performing a negative bias temperature instability test.

[0068] like Figure 2As shown, the horizontal axis is time Time (unit: hour / Hr), and the vertical axis is the threshold voltage drift VtlinShift. Among them, straight line A1 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 4.4V and time; straight line A2 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 4V and time; straight line A3 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 3.6V and time.

[0069] It should be noted that, in this embodiment, Figure 2 The negative bias temperature instability test performed at three different first test voltages is only an example for illustration. In other embodiments, the negative bias temperature instability test may be performed at first test voltages of other values, and the number of different first test voltages for the negative bias temperature instability test may be greater than three.

[0070] Depend on Figure 2 It can be seen that as the test time increases, the threshold voltage drift generated is also gradually increasing, and the relationship between the threshold voltage drift and time is a linear relationship. Moreover, the slopes of the straight lines between the threshold voltage drift corresponding to the multiple first test voltages and time are the same, which means that for the same structure to be tested, its failure mechanism is the same.

[0071] As an example, in this embodiment, after performing a negative bias temperature instability test and obtaining the relationship between the threshold voltage drift and time under different first test voltages, it also includes: based on the relationship between the threshold voltage drift and time under the first test voltage, obtaining the time corresponding to the threshold voltage drift being a preset value as the first failure time.

[0072] By also obtaining the time corresponding to when the threshold voltage drift is a preset value as the first failure time, the first failure time of the structure to be tested under different first test voltages can be evaluated, thereby evaluating the life of the structure to be tested under different first test voltages.

[0073] Combined with reference Figure 2 As an example, the first failure time TTF1 corresponding to the first test voltage of 4.4V, the first failure time TTF2 corresponding to the first test voltage of 4.0V, and the first failure time TTF3 corresponding to the first test voltage of 3.6V are shown.

[0074] In this embodiment, the preset value is 15% as an example for description. In other embodiments, based on actual test requirements, the preset value may also be other values.

[0075] It should be noted that, at each first test voltage, the number of structures to be tested should not be too small, otherwise it is easy to cause the effect of reducing the measurement error and improving the reliability of the measurement to be not obvious. For this reason, in this embodiment, at each first test voltage, the number of structures to be tested is at least 5.

[0076] In this embodiment, the test voltage for the threshold voltage stability test is the second test voltage, the test time is the target test time, and the obtained threshold voltage drift is the target drift. The threshold voltage stability test refers to the threshold voltage stability test performed in a traditional manner.

[0077] As an example, in the semiconductor field, the second test voltage for threshold voltage stability test is usually the device operating voltage (operation voltage, V op ) times; the test time is usually about 168 hours.

[0078] As an example, the operating voltage of the device is 2.5V. Accordingly, the second test voltage is 2.75V. In other embodiments, based on the device operating voltage of the structure to be tested in the actual test, the second test voltage can also be other values.

[0079] Continue to refer Figure 1 , execute step S2: based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, obtain the relationship between the threshold voltage drift amount and time at the second test voltage.

[0080] In this embodiment, the test voltage for the threshold voltage stability test is the second test voltage, and the relationship between the threshold voltage drift amount and time at the second test voltage is obtained so as to obtain the threshold voltage drift amount corresponding to the target test time as the estimated drift amount.

[0081] Specifically, the relationship between the threshold voltage drift amount and time at different first test voltages can be used to obtain the device failure mechanism, and then the relationship between the threshold voltage drift amount and time at the second test voltage can be obtained through the device failure mechanism and the difference between the second test voltage and the first test voltage.

[0082] In this embodiment, based on the relationship between the threshold voltage drift amount under different first test voltages and the difference between the second test voltage and the first test voltage, the step of obtaining the relationship between the threshold voltage drift amount under the second test voltage and the time includes: based on the relationship between the first relationship straight lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship straight line, obtaining the relationship straight line between the threshold voltage drift amount under the second test voltage and the time as the second relationship straight line.

[0083] More specifically, in this embodiment, based on the relationship between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line, the step of obtaining a relationship line showing how the threshold voltage drift changes over time at the second test voltage includes: obtaining a second relationship line based on the intervals between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line.

[0084] Combined with reference Figure 3 , shows a schematic diagram of an embodiment of a second relationship line obtained based on a plurality of first relationship lines and the difference between the second test voltage and the first test voltage. Specifically, in this embodiment, based on the first relationship line A1, the first relationship line A2 and the first relationship line A3, and the difference between the second test voltage and the first test voltage, the second relationship line A4 is obtained.

[0085] Specifically, in this embodiment, the slopes of the first relationship straight lines A1, A2 and A3 are the same, that is, the first relationship straight lines A1, A2 and A3 are parallel to each other. Therefore, based on the intervals between the first relationship straight lines A1, A2 and A3 along the Y direction, the difference between the first test voltages corresponding to the first relationship straight lines A1, A2 and A3, and the difference between the second test voltage and the first test voltage, the second relationship straight line A4 is obtained.

[0086] It should be noted that, in this embodiment, the method for obtaining the threshold voltage stability further includes: after obtaining the relationship between the threshold voltage drift amount and time at the second test voltage, based on the relationship between the threshold voltage drift amount and time at the second test voltage, obtaining the test time corresponding to when the threshold voltage drift amount is a preset value as the failure time. Specifically, obtaining the test time corresponding to when the threshold voltage drift amount is a preset value as the second failure time TTF4.

[0087] Based on the relationship between the threshold voltage drift under the second test voltage and time, the test time corresponding to the threshold voltage drift being a preset value is obtained as the second failure time TTF4, so that the life of the device under the second test voltage can be evaluated, so as to evaluate the electrical performance of the device from multiple angles.

[0088] Specifically, in this embodiment, the preset value is 15% as an example for description. In other embodiments, based on actual test requirements, the preset value can also be set to other values.

[0089] Combined with reference Figure 4 , shows the gate voltage applied to the structure under test and the corresponding failure time when the threshold voltage drift is at a preset value. Figure 4 As shown, a schematic diagram showing the relationship between the first failure time and the first test voltage obtained by performing negative bias temperature instability tests on multiple structures under test at different first test voltages (Vg) is shown. Figure 4 The horizontal axis is the gate voltage applied to the structure to be tested, and the vertical axis is the failure time corresponding to the current first test voltage.

[0090] Among them, the dotted box C1 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 4.4V, the dotted box C2 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 4V, and the dotted box C3 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 3.6V. Multiple points in the dotted boxes C1, C2, and C3 are fitted to obtain a straight line D showing the relationship between the failure time and the test voltage.

[0091] Furthermore, in this embodiment, based on the relationship straight line D between the failure time and the test voltage, the failure time corresponding to the second test voltage is obtained, and point E is obtained accordingly. The failure time corresponding to point E is the same as the test time corresponding to the second relationship straight line A4 when the threshold voltage drift amount is a preset value.

[0092] Continue to refer Figure 1 , executing step S3: based on the relationship between the threshold voltage drift amount under the second test voltage and time, obtaining the threshold voltage drift amount corresponding to the target test time as the estimated drift amount.

[0093] The test time for the threshold voltage stability test is the target test time. The threshold voltage drift corresponding to the target test time is obtained based on the relationship between the threshold voltage drift under the second test voltage and time, so as to be able to simulate the threshold voltage drift obtained by the test time of the threshold voltage stability test, thereby facilitating the subsequent acquisition of the relationship between the target drift and the inferred drift.

[0094] Based on the relationship between the threshold voltage drift at the second test voltage and time, the step of obtaining the threshold voltage drift corresponding to the target test time includes: based on the second relationship line, obtaining the threshold voltage drift corresponding to the target test time as the estimated drift.

[0095] Combined with reference Figure 3 , obtain the threshold voltage drift amount corresponding to the second relationship straight line at point B as the estimated drift amount.

[0096] Continue to refer Figure 1 , execute step S4: obtain the correlation between the target drift amount and the estimated drift amount.

[0097] The correlation between the target drift amount and the estimated drift amount is obtained so that the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value can be obtained based on the correlation.

[0098] Specifically, in conjunction with reference Figure 5 , showing Figure 1 Schematic diagram of a flow chart of an embodiment of step S4 in FIG. In this embodiment, step S4 of obtaining the correlation between the target drift amount and the inferred drift amount includes: step S41, performing a threshold voltage stability test at a second test voltage and a test time of the target test time to obtain the threshold voltage drift amount as the measured drift amount; step S42, obtaining the correlation between the measured drift amount and the inferred drift amount as the correlation between the target drift amount and the inferred drift amount.

[0099] In this embodiment, a threshold voltage stability test is performed at the second test voltage and the target test time is reached, so that the measured drift amount can be obtained, which facilitates the subsequent acquisition of the correlation between the measured drift amount and the inferred drift amount.

[0100] In a specific implementation, the steps of conducting a threshold voltage stability test may include: packaging the structure to be tested to obtain a packaged structure to be tested; placing the structure to be tested in a high-temperature furnace and allowing the temperature to rise to a first temperature, and maintaining it for one day to measure the initial threshold voltage; raising the temperature in the high-temperature furnace to a second temperature, and maintaining it stable for one day at the second test voltage, and then testing it under the current test environment for seven days; lowering the temperature of the high-temperature furnace to the first temperature, and maintaining it stable for one day under the current test environment to test the final threshold voltage, and based on the final threshold voltage and the initial threshold voltage, calculating the threshold voltage drift as the measured drift.

[0101] As an example, the first temperature is 50° C. and the second temperature is 150° C. In other embodiments, based on actual test requirements, the first temperature and the second temperature may also be other values.

[0102] With reference to Table 1, some embodiments of the obtained measured drift amount and the estimated drift amount are shown respectively.

[0103] Table 1

[0104]

[0105] Among them, variable refers to a test parameter. In this embodiment, the test parameters are all threshold voltage drift Vtshift; test item refers to a test item, including a negative bias temperature instability test (NBTI) and a threshold voltage stability test (Vt); N refers to the number of structures under test; lowerCL mean refers to the average value of the lower limit of the confidence level (Confidence level) of the threshold voltage drift; mean refers to the average value of the threshold voltage drift; upper CL mean refers to the average value of the upper limit of the confidence level of the threshold voltage drift; lower CL Std Dev refers to the standard deviation of the lower limit of the confidence level; stdDev refers to the standard deviation (Standard Deviation); upper CL StdDev refers to the standard deviation of the upper limit of the confidence interval; Std Err refers to the standard error (Standard error).

[0106] It can be seen from Table 1 that the difference between the measured drift amount and the estimated drift amount is small, which indicates that the reliability of obtaining the target drift amount by estimating the drift amount in this embodiment is high.

[0107] With reference to Table 2 and Table 3, the results of the F-test and the results of the T-test are shown respectively.

[0108] Table 2

[0109] Variable Method F value P value Vt shift Folded F 1.42 0.1364

[0110] Here, Equality of Variances refers to homogeneity of variances; method refers to a test method, which in this embodiment refers to a method using a folded F test; F value refers to an F value; and Pvalue refers to a P value.

[0111] It can be seen from Table 2 that the P value is greater than 0.05, which indicates that the assumption is established and the reliability of obtaining the target drift amount by estimating the drift amount in this embodiment is relatively high.

[0112] Table 3

[0113]

[0114] Among them, pooled refers to the homoscedastic method, and Scatterthwaite refers to the Scatterthwaite approximation method. As can be seen from Table 1, Pr>|t| is greater than 0.05, indicating that the original hypothesis is established, and the reliability of obtaining the target drift amount by inferring the drift amount in this embodiment is relatively high.

[0115] Combined with reference Figure 6 , shows a box plot based on Table 1, Figure 6 It can be seen that the difference between the measured drift amount and the estimated drift amount obtained by testing respectively using the two methods is small, and the test results are consistent. The reliability of obtaining the target drift amount by estimating the drift amount in this embodiment is high.

[0116] Combined with reference Figure 7 , shows a scatter plot based on Table 1. The horizontal axis is the measured drift amount obtained by the threshold voltage stability test, and the vertical axis is the estimated drift amount obtained by the negative bias temperature instability test.

[0117] In this embodiment, Figure 7 The scattered points in are fitted to obtain the correlation fitting curve between the measured drift amount and the estimated drift amount, that is, the linear correlation curve G between the target drift amount and the estimated drift amount.

[0118] Continue to refer Figure 1 , executing step S5: based on the correlation between the target drift amount and the estimated drift amount, obtaining the estimated drift amount corresponding to when the target drift amount is the target value.

[0119] In this embodiment, based on the correlation, the estimated drift amount corresponding to the target drift amount being the target value is obtained, so that this embodiment can use the negative bias temperature instability test to obtain the estimated drift amount corresponding to the target drift amount being the target value, and then obtain the threshold voltage stability by inferring the translation amount. The negative bias temperature instability test is usually performed during the wafer manufacturing process. The embodiment of the present invention does not need to perform packaging-level testing to obtain the threshold voltage stability, and the time for the negative bias temperature instability test is greatly shortened compared to the time for the threshold voltage stability test, which is conducive to shortening the period for obtaining the threshold voltage stability, and then obtaining the test data of the threshold voltage stability earlier, providing a basis for the improvement of research and development design.

[0120] As an example, Figure 8 Shows Figure 1 FIG. 1 is a flow chart of an embodiment of step S5 in FIG. 1 .

[0121] In this embodiment, based on the correlation between the target drift and the inferred drift, step S5 of obtaining the inferred drift corresponding to the target value when the target drift is the target value includes: step S51, obtaining a linear correlation curve between the target drift and the inferred drift; step S52, setting a confidence interval based on the linear correlation curve; step S53, taking a lower limit within the confidence interval to obtain a corresponding lower limit correlation curve; step S54, based on the lower limit correlation curve, obtaining the inferred drift corresponding to the target value when the target drift is the target value.

[0122] Combined with reference Figure 7 , a schematic diagram of an embodiment of a linear correlation curve between the obtained target drift amount and the estimated drift amount is shown.

[0123] Continue to refer Figure 7 , the confidence interval is set based on the linear correlation curve. Specifically, in this embodiment, a 95% confidence interval is set based on the linear correlation curve.

[0124] like Figure 7 As shown, the lower limit is taken within the confidence interval to obtain the corresponding lower limit correlation curve G1.

[0125] Accordingly, in this embodiment, based on the lower limit correlation curve G1, the estimated drift amount corresponding to the target drift amount being the target value is obtained.

[0126] By taking the lower limit within the confidence interval to obtain the lower limit correlation curve G1, and then obtaining the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value based on the lower limit correlation curve G1, it is possible to take the most stringent value as the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value within the confidence interval based on the linear correlation curve, which is beneficial to improve the rigor and reliability of the obtained estimated drift amount, and further improve the rigor and reliability of the evaluation of threshold voltage stability.

[0127] In this embodiment, the target value is 15% as an example for description. In other embodiments, based on actual test requirements, the target value can also be set to other values.

[0128] Accordingly, the present invention also provides a system for achieving threshold voltage stability. Fig. 9 4 is a functional block diagram of an embodiment of a system for achieving threshold voltage stability according to the present invention.

[0129] refer to Fig. 9 In this embodiment, the system for obtaining threshold voltage stability includes: a test module 101, which is used to perform a negative bias temperature instability test to obtain a relationship between a threshold voltage drift amount and time at different first test voltages; the test voltage for the threshold voltage stability test is a second test voltage, the test time is a target test time, and the obtained threshold voltage drift amount is used as a target drift amount; a relationship acquisition module 102, which is used to obtain a relationship between a threshold voltage drift amount and time at a second test voltage based on a relationship between a threshold voltage drift amount and time at different first test voltages and a difference between the second test voltage and the first test voltage; an inference module 103, which is used to obtain a threshold voltage drift amount corresponding to a target test time as an inferred drift amount based on a relationship between a threshold voltage drift amount and time at the second test voltage; a correlation acquisition module 104, which is used to obtain a correlation between a target drift amount and an inferred drift amount; and a calculation module 105, which is used to obtain an inferred drift amount corresponding to a target value when the target drift amount is a target value based on the correlation between the target drift amount and the inferred drift amount.

[0130] In this embodiment, the negative bias temperature instability test can be used to obtain the estimated drift amount corresponding to the target drift amount when the target value is the target value, and then the threshold voltage stability is obtained by estimating the shift amount. The negative bias temperature instability test is usually performed during the wafer manufacturing process. The embodiment of the present invention does not need to perform packaging-level testing to obtain the threshold voltage stability, and the time of the negative bias temperature instability test is greatly shortened compared to the time of the threshold voltage stability test, which is conducive to shortening the period for obtaining the threshold voltage stability, and then obtaining the test data of the threshold voltage stability earlier, providing a basis for the improvement of research and development design.

[0131] The test module 101 is used to perform a negative bias temperature instability test to obtain the relationship between the threshold voltage drift amount and time at different first test voltages, so that the relationship acquisition module 102 can obtain the relationship between the threshold voltage drift amount and time at the second test voltage based on the relationship between the threshold voltage drift amount and time at different first test voltages and the difference between the second test voltage and the first test voltage, thereby facilitating the inference of the threshold voltage stability.

[0132] The negative bias temperature instability test is usually performed during the wafer manufacturing process, and the time of the negative bias temperature instability test is greatly shortened compared to the threshold voltage stability test, which is conducive to shortening the period for obtaining threshold voltage stability.

[0133] Moreover, in this embodiment, by obtaining information for inferring threshold voltage stability during the negative bias temperature instability test, it can be combined with the existing test process flow, thereby improving compatibility and simplifying the test process, which is correspondingly beneficial to improving test efficiency and shortening the test cycle.

[0134] In this embodiment, the negative bias temperature instability test is performed for 3 hours to 6 hours.

[0135] In the semiconductor field, the first test voltage for negative bias temperature instability testing is usually greater than 1.1 times the device operating voltage, so as to accelerate device degradation at a higher test voltage.

[0136] In this embodiment, the testing module 101 performs a negative bias temperature instability test under different first test voltages, including: providing a structure to be tested; and performing a negative bias temperature instability test on the structure to be tested under different first test voltages.

[0137] As an example, providing a structure to be tested includes: providing a substrate; forming a gate oxide layer on the substrate; and performing a heat treatment on the gate oxide layer in a nitrogen-containing atmosphere.

[0138] The substrate is used to provide a process platform for forming the structure to be tested. In a specific implementation, the substrate can be a three-dimensional substrate or a planar substrate. In this embodiment, for the convenience of illustration and description, the substrate is a planar substrate as an example for description. In other embodiments, the substrate can also be a three-dimensional substrate, for example: the substrate can also include a substrate and a fin separated from the substrate.

[0139] In this embodiment, the base includes a substrate. In this embodiment, the substrate is a silicon substrate. In other embodiments, the material of the substrate may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate may also be other types of substrates such as a silicon substrate on an insulator or a germanium substrate on an insulator. The material of the substrate may be a material suitable for process requirements or easy to integrate.

[0140] In a specific implementation, providing the structure to be tested generally further includes: after heat treating the gate oxide layer in a nitrogen-containing atmosphere, forming a gate layer on the gate oxide layer and source-drain doping layers in the substrate on both sides of the gate layer.

[0141] The gate oxide layer is used to isolate the gate layer from the substrate. The quality of the gate oxide layer has a crucial impact on the electrical performance of the device. For example, defects in the gate oxide layer have a significant impact on the threshold voltage drift.

[0142] As an example, the material of the gate oxide layer is silicon oxide. In other embodiments, the material of the gate oxide layer may also be silicon oxynitride.

[0143] As the device size gradually decreases, the gate oxide layer gradually becomes thinner, and accordingly, the breakdown voltage of the device gradually decreases. By heat treating the gate oxide layer in a nitrogen-containing atmosphere, the boron punch-through problem of the PMOS device can be prevented, thereby improving the breakdown voltage.

[0144] In this embodiment, the nitrogen-containing atmosphere includes nitric oxide and nitrogen, wherein the nitric oxide is used to provide a nitrogen source and the nitrogen is used to protect the gate oxide layer.

[0145] However, when the gate oxide layer is heat treated in a nitrogen-containing atmosphere, it is easy to form a Si-N bond at the interface between the substrate and the gate oxide layer (the Si-O interface in this embodiment), and it is difficult to break the Si-N bond at the Si-O interface. However, the nitrogen atoms in the gate oxide layer can serve as trap centers, thereby enhancing the generation of fixed oxide charge in the negative bias temperature instability (NBTI) effect. In other words, the nitrogen atoms in the gate oxide layer can enhance the negative bias temperature instability effect.

[0146] Therefore, in this embodiment, the ratio of nitric oxide to nitrogen in the nitrogen-containing atmosphere is adjusted to ensure that the NBTI effect is not significantly aggravated while the breakdown voltage is improved as much as possible.

[0147] As an example, during the heat treatment of the gate oxide layer, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:X, where X should not be too small or too large. If X is too small, the proportion of nitrogen in the nitrogen-containing atmosphere is too small, which easily leads to an insignificant protective effect on the gate oxide layer; if X is too large, the proportion of nitrogen in the nitrogen-containing atmosphere is too large, which easily leads to an insignificant nitrogen doping effect. For this reason, in this embodiment, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:X, where X is at least 5.

[0148] In a specific implementation, based on actual process requirements, X can be 10 to 30, for example, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:10, 0.5:15, or 0.5:20, etc.

[0149] In this embodiment, the gas molar volume ratio of nitric oxide to nitrogen is 0.5:10 as an example for description.

[0150] In this embodiment, the step of performing the negative bias temperature instability test includes: applying stress (e.g., temperature, gate voltage) to the structure to be tested for a certain period of time, and then measuring the change of specific parameters of the device to obtain the change law of parameter degradation with stress time, thereby evaluating the device life. The parameter degradation includes the threshold voltage drift.

[0151] In a specific implementation, the negative bias temperature instability test is performed at room temperature or high temperature. In this embodiment, the negative bias temperature instability test is performed at 125° C. as an example for explanation. In other embodiments, based on actual test requirements, the negative bias instability test can also be performed at other temperatures.

[0152] More specifically, in this embodiment, during the negative bias temperature instability test, the initial Vt value is first tested, recorded as Vt(initial); then, the structure to be tested is placed in a high-temperature furnace, a certain stress is applied to the structure to be tested under a preset high-temperature environment, and the Vt value at each moment is tested, recorded as Vtlinshift, and the threshold voltage drift Vtshift can be calculated using formula (II):

[0153] Vtshift=[Vtlin shift-Vt(initial)] / Vt(initial)(II)

[0154] Therefore, by obtaining the threshold voltage drift at each moment, the relationship between the threshold voltage drift and time under the current first test voltage can be obtained.

[0155] Specifically, in this embodiment, a negative bias temperature instability test is performed under different first test voltages to obtain a relationship between the threshold voltage drift amount and time at different first test voltages, including: a negative bias temperature instability test is performed under different first test voltages to obtain a straight line of the relationship between the threshold voltage drift amount and time at different first test voltages as the first straight line.

[0156] Specifically, a negative bias temperature instability test is performed under different first test voltages, and the step of obtaining the relationship between the threshold voltage drift amount and time under different first test voltages includes: performing a negative bias temperature instability test on multiple structures to be tested under each first test voltage to obtain the average value of the threshold voltage drift amounts corresponding to the multiple structures to be tested at each test time; based on the average value of the threshold voltage drift amounts corresponding to the multiple structures to be tested at each test time, obtaining the relationship between the threshold voltage drift amount and time under the current first test voltage.

[0157] By performing negative bias temperature instability tests on multiple structures to be tested, the average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time is obtained, thereby reducing the measurement error, improving the reliability of the measurement, and correspondingly improving the accuracy of obtaining the relationship between the threshold voltage drift and time under the current first test voltage.

[0158] In a specific implementation, under each first test voltage, a negative bias temperature instability test is performed on multiple structures to be tested to obtain an average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time; based on the average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time, a straight line showing the relationship between the threshold voltage drift and time under the current first test voltage is obtained.

[0159] Combined with reference Figure 2 , shows a schematic diagram of multiple first relationship straight lines obtained by performing a negative bias temperature instability test.

[0160] like Figure 2 As shown, the horizontal axis is time Time (unit: hour / Hr), and the vertical axis is the threshold voltage drift VtlinShift. Among them, straight line A1 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 4.4V and time; straight line A2 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 4V and time; straight line A3 illustrates the relationship between the threshold voltage drift obtained when the first test voltage is 3.6V and time.

[0161] It should be noted that, in this embodiment, Figure 2The negative bias temperature instability test performed at three different first test voltages is only an example for illustration. In other embodiments, the negative bias temperature instability test may be performed at first test voltages of other values, and the number of different first test voltages for performing the negative bias temperature instability test may be greater than three.

[0162] Depend on Figure 2 It can be seen that as the test time increases, the threshold voltage drift generated is also gradually increasing, and the relationship between the threshold voltage drift and time is a linear relationship. Moreover, the slopes of the straight lines between the threshold voltage drift corresponding to the multiple first test voltages and time are the same, which means that for the same structure to be tested, its failure mechanism is the same.

[0163] As an example, in this embodiment, after performing a negative bias temperature instability test and obtaining the relationship between the threshold voltage drift and time under different first test voltages, it also includes: based on the relationship between the threshold voltage drift and time under the first test voltage, obtaining the time corresponding to the threshold voltage drift being a preset value as the first failure time.

[0164] By also obtaining the time corresponding to when the threshold voltage drift is a preset value as the first failure time, the first failure time of the structure to be tested under different first test voltages can be evaluated, thereby evaluating the life of the structure to be tested under different first test voltages.

[0165] Combined with reference Figure 2 As an example, the first failure time TTF1 corresponding to the first test voltage of 4.4V, the first failure time TTF2 corresponding to the first test voltage of 4.0V, and the first failure time TTF3 corresponding to the first test voltage of 3.6V are shown.

[0166] In this embodiment, the preset value is 15% as an example for description. In other embodiments, based on actual test requirements, the preset value may also be other values.

[0167] It should be noted that, at each first test voltage, the number of structures to be tested should not be too small, otherwise the effect of reducing measurement error and improving measurement reliability is not obvious. To this end, in this embodiment, at each first test voltage, the number of structures to be tested is at least 5.

[0168] In this embodiment, the test voltage for the threshold voltage stability test is the second test voltage, the test time is the target test time, and the obtained threshold voltage drift is the target drift. The threshold voltage stability test refers to the threshold voltage stability test performed in a traditional manner.

[0169] As an example, in the semiconductor field, the second test voltage for threshold voltage stability test is usually 1.1 times of the device operation voltage (Vop); the test time is usually about 168 hours.

[0170] As an example, the operating voltage of the device is 2.5V. Accordingly, the second test voltage is 2.75V. In other embodiments, based on the device operating voltage of the structure to be tested in the actual test, the second test voltage can also be other values.

[0171] In this embodiment, the test voltage for the threshold voltage stability test is the second test voltage. The relationship acquisition module 102 obtains the relationship between the threshold voltage drift amount and time under the second test voltage so that the inference module 103 obtains the threshold voltage drift amount corresponding to the target test time as the inferred drift amount.

[0172] Specifically, the relationship between the threshold voltage drift amount and time at different first test voltages can be used to obtain the device failure mechanism, and then the relationship between the threshold voltage drift amount and time at the second test voltage can be obtained through the device failure mechanism and the difference between the second test voltage and the first test voltage.

[0173] In this embodiment, the relationship acquisition module 102 is used to obtain a relationship straight line showing the change of the threshold voltage drift amount over time at the second test voltage based on the relationship between the first relationship straight lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship straight line, as the second relationship straight line.

[0174] More specifically, in this embodiment, based on the relationship between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line, obtaining a relationship line showing how the threshold voltage drift changes over time at the second test voltage includes: obtaining a second relationship line based on the intervals between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line.

[0175] Combined with reference Figure 3, shows a schematic diagram of an embodiment of a second relationship line obtained based on a plurality of first relationship lines and the difference between the second test voltage and the first test voltage. Specifically, in this embodiment, based on the first relationship line A1, the first relationship line A2 and the first relationship line A3, and the difference between the second test voltage and the first test voltage, the second relationship line A4 is obtained.

[0176] Specifically, in this embodiment, the slopes of the first relationship straight lines A1, A2 and A3 are the same, that is, the first relationship straight lines A1, A2 and A3 are parallel to each other. Therefore, based on the intervals between the first relationship straight lines A1, A2 and A3 along the Y direction, the difference between the first test voltages corresponding to the first relationship straight lines A1, A2 and A3, and the difference between the second test voltage and the first test voltage, the second relationship straight line A4 is obtained.

[0177] It should be noted that, in this embodiment, the system 100 for obtaining the stability of the threshold voltage further includes: a failure time acquisition module (not shown), which is used to obtain the test time corresponding to the preset value when the threshold voltage drift amount is based on the relationship between the threshold voltage drift amount under the second test voltage and time, as the failure time. Specifically, the test time corresponding to the preset value when the threshold voltage drift amount is obtained is used as the second failure time TTF4.

[0178] The failure time acquisition module is used to obtain the test time corresponding to the preset value of the threshold voltage drift amount based on the relationship between the threshold voltage drift amount and time under the second test voltage, as the second failure time TTF4, so as to evaluate the life of the device under the second test voltage, so as to evaluate the electrical performance of the device from multiple angles.

[0179] Specifically, in this embodiment, the preset value is 15% as an example for description. In other embodiments, based on actual test requirements, the preset value can also be set to other values.

[0180] Combined with reference Figure 4 , shows the gate voltage applied to the structure under test and the corresponding failure time when the threshold voltage drift is at a preset value. Figure 4 As shown, a schematic diagram showing the relationship between the first failure time and the first test voltage obtained by performing negative bias temperature instability tests on multiple structures under test at different first test voltages (Vg) is shown. Figure 4 The horizontal axis is the gate voltage applied to the structure to be tested, and the vertical axis is the failure time corresponding to the current first test voltage.

[0181] Among them, the dotted box C1 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 4.4V, the dotted box C2 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 4V, and the dotted box C3 shows the failure time obtained by performing a negative bias temperature instability test on multiple structures to be tested when the first test voltage is 3.6V. Multiple points in the dotted boxes C1, C2, and C3 are fitted to obtain a straight line D showing the relationship between the failure time and the test voltage.

[0182] Furthermore, in this embodiment, based on the relationship straight line D between the failure time and the test voltage, the failure time corresponding to the second test voltage is obtained, and point E is obtained accordingly. The failure time corresponding to point E is the same as the test time corresponding to the second relationship straight line A4 when the threshold voltage drift amount is a preset value.

[0183] The test time for the threshold voltage stability test is the target test time. The threshold voltage drift corresponding to the target test time is obtained based on the relationship between the threshold voltage drift at the second test voltage and time, so as to be able to simulate the threshold voltage drift obtained by the test time of the threshold voltage stability test, thereby facilitating the correlation acquisition module 104 to obtain the relationship between the target drift and the inferred drift.

[0184] Specifically, in this embodiment, the estimation module 103 obtains the threshold voltage drift amount corresponding to the target test time based on the second relationship straight line as the estimated drift amount.

[0185] Combined with reference Figure 3 The estimation module 103 obtains the threshold voltage drift amount corresponding to the second relationship straight line at point B as the estimated drift amount.

[0186] The correlation obtaining module 104 is used to obtain the correlation between the target drift amount and the estimated drift amount, so that the calculation module 105 can obtain the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value based on the correlation.

[0187] In this embodiment, the correlation acquisition module 104 is used to perform a threshold voltage stability test under a second test voltage and a test time that is a target test time, and obtain a threshold voltage drift as an actual measured drift; and is also used to obtain a correlation between an actual measured drift and an inferred drift as a correlation between a target drift and an inferred drift.

[0188] The threshold voltage stability test is performed at the second test voltage and the target test time is reached, so that the measured drift amount can be obtained, which makes it easier to obtain the correlation between the measured drift amount and the inferred drift amount based on the subsequent measurement.

[0189] In a specific implementation, performing a threshold voltage stability test may include: packaging the structure to be tested to obtain a packaged structure to be tested; placing the structure to be tested in a high-temperature furnace and allowing the temperature to rise to a first temperature, and maintaining it for one day to measure the initial threshold voltage; raising the temperature in the high-temperature furnace to a second temperature, and maintaining it stable for one day at the second test voltage, and then testing it under the current test environment for seven days; lowering the temperature of the high-temperature furnace to the first temperature, and maintaining it stable for one day under the current test environment to test the final threshold voltage, and based on the final threshold voltage and the initial threshold voltage, calculating the threshold voltage drift as the measured drift.

[0190] Some embodiments of the measured drift and the estimated drift are shown in conjunction with reference to Table 1. As can be seen from Table 1, the difference between the measured drift and the estimated drift is small, which indicates that the reliability of obtaining the target drift by estimating the drift in this embodiment is high.

[0191] Reference Table 2 and Table 3 show the results of the F-test and the T-test, respectively. As shown in Table 2, the P value is greater than 0.05, indicating that the hypothesis is established and the reliability of obtaining the target drift amount by inferring the drift amount in this embodiment is high.

[0192] It can be seen from Table 3 that Pr>|t| is greater than 0.05, indicating that the original hypothesis is established. The reliability of obtaining the target drift amount by inferring the drift amount in this embodiment is relatively high.

[0193] Combined with reference Figure 6 , shows a box plot based on Table 1, Figure 6 It can be seen that the difference between the measured drift and the estimated drift obtained by testing the two methods is small.

[0194] Combined with reference Figure 7 , shows a scatter plot based on Table 1. The horizontal axis is the measured drift amount obtained by the threshold voltage stability test, and the vertical axis is the estimated drift amount obtained by the negative bias temperature instability test.

[0195] In this embodiment, Figure 7 The scattered points in are fitted to obtain the correlation fitting curve between the measured drift amount and the estimated drift amount, that is, the linear correlation curve G between the target drift amount and the estimated drift amount.

[0196] The calculation module 105 is used to obtain the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value based on the correlation between the target drift amount and the estimated drift amount.

[0197] In this embodiment, based on the correlation, the estimated drift amount corresponding to the target drift amount being the target value is obtained, so that this embodiment can use the negative bias temperature instability test to obtain the estimated drift amount corresponding to the target drift amount being the target value, and then obtain the threshold voltage stability by inferring the translation amount. The negative bias temperature instability test is usually performed during the wafer manufacturing process. The embodiment of the present invention does not need to perform packaging-level testing to obtain the threshold voltage stability, and the time for the negative bias temperature instability test is greatly shortened compared to the time for the threshold voltage stability test, which is conducive to shortening the period for obtaining the threshold voltage stability, and then obtaining the test data of the threshold voltage stability earlier, providing a basis for the improvement of research and development design.

[0198] In this embodiment, the calculation module 105 is used to obtain a linear correlation curve between the target drift amount and the inferred drift amount; it is also used to set a confidence interval based on the linear correlation curve; it is also used to take a lower limit within the confidence interval to obtain a corresponding lower limit correlation curve; it is also used to obtain an inferred drift amount corresponding to the target drift amount when the target drift amount is the target value based on the lower limit correlation curve.

[0199] Combined with reference Figure 7 , a schematic diagram of an embodiment of a linear correlation curve between the obtained target drift amount and the estimated drift amount is shown.

[0200] Continue to refer Figure 7 , the confidence interval is set based on the linear correlation curve. Specifically, in this embodiment, a 95% confidence interval is set based on the linear correlation curve.

[0201] like Figure 7 As shown, the lower limit is taken within the confidence interval to obtain the corresponding lower limit correlation curve G1.

[0202] Accordingly, in this embodiment, based on the lower limit correlation curve G1, the estimated drift amount corresponding to the target drift amount being the target value is obtained.

[0203] By taking the lower limit within the confidence interval to obtain the lower limit correlation curve G1, and then obtaining the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value based on the lower limit correlation curve G1, it is possible to take the most stringent value as the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value within the confidence interval based on the linear correlation curve, which is beneficial to improve the rigor and reliability of the obtained estimated drift amount, and further improve the rigor and reliability of the evaluation of threshold voltage stability.

[0204] In this embodiment, the target value is 15% as an example for description. In other embodiments, based on actual test requirements, the target value can also be set to other values.

[0205] The embodiment of the present invention further provides a device, which can implement the method for obtaining threshold voltage stability provided by the embodiment of the present invention by loading the above method for obtaining threshold voltage stability in the form of a program.

[0206] An optional hardware structure of the terminal device provided by the embodiment of the present invention can be as follows Fig.10 As shown, it includes: at least one processor 01, at least one communication interface 02, at least one memory 03 and at least one communication bus 04.

[0207] In the embodiment of the present invention, the number of the processor 01, the communication interface 02, the memory 03, and the communication bus 04 is at least one, and the processor 01, the communication interface 02, and the memory 03 communicate with each other through the communication bus 04;

[0208] Optionally, the communication interface 02 may be an interface of a communication module for network communication, such as an interface of a GSM module;

[0209] The processor 01 may be a central processing unit CPU, or an application specific integrated circuit ASIC (Application Specific Integrated Circuit), or one or more integrated circuits configured to implement the embodiments of the present invention.

[0210] The memory 03 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0211] The memory 03 stores one or more computer instructions, and the one or more computer instructions are executed by the processor 01 to implement the method for obtaining threshold voltage stability provided in the embodiment of the present invention.

[0212] It should be noted that the above-mentioned terminal device may also include other devices (not shown) that may not be necessary for understanding the contents disclosed in the embodiments of the present invention; given that these other devices may not be necessary for understanding the contents disclosed in the embodiments of the present invention, the embodiments of the present invention will not introduce them one by one.

[0213] Correspondingly, an embodiment of the present invention further provides a storage medium, the storage medium stores one or more computer instructions, and the one or more computer instructions are used to implement the method for obtaining threshold voltage stability provided by an embodiment of the present invention.

[0214] The above-mentioned embodiments of the present invention are combinations of elements and features of the present invention. Unless otherwise mentioned, elements or features may be considered as optional. Each element or feature may be put into practice without being combined with other elements or features. In addition, embodiments of the present invention may be constructed by combining some elements and / or features. The order of operations described in the embodiments of the present invention may be rearranged. Some configurations of any one embodiment may be included in another embodiment, and may be replaced by the corresponding configuration of another embodiment. It is obvious to those skilled in the art that claims that do not have a clear reference relationship to each other in the attached claims may be combined into embodiments of the present invention, or may be included as new claims in the amendment after submitting this application.

[0215] The embodiments of the present invention can be implemented by various means such as hardware, firmware, software or a combination thereof. In a hardware configuration, the method according to the exemplary embodiment of the present invention can be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0216] In a firmware or software configuration, the embodiments of the present invention may be implemented in the form of modules, procedures, functions, etc. The software code may be stored in a memory unit and executed by a processor. The memory unit is located inside or outside the processor and may send data to and receive data from the processor via various known means.

[0217] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

[0218] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. A method for obtaining threshold voltage stability, characterized in that: include: Performing a negative bias temperature instability test to obtain a relationship between a threshold voltage drift amount and time at different first test voltages; The test voltage for the threshold voltage stability test is the second test voltage, the test time is the target test time, and the obtained threshold voltage drift amount is used as the target drift amount; Based on the relationship between the threshold voltage drift amount under different first test voltages and the time variation and the difference between the second test voltage and the first test voltage, obtaining the relationship between the threshold voltage drift amount under the second test voltage and the time variation; Based on the relationship between the threshold voltage drift amount under the second test voltage and time, obtaining the threshold voltage drift amount corresponding to the target test time as the estimated drift amount; Obtaining a correlation between the target drift amount and the estimated drift amount; Based on the correlation between the target drift amount and the estimated drift amount, the estimated drift amount corresponding to when the target drift amount is a target value is obtained.

2. The method for obtaining threshold voltage stability according to claim 1, characterized in that: Under different first test voltages, a negative bias temperature instability test is performed to obtain a relationship between the threshold voltage drift amount under different first test voltages and time, including: under different first test voltages, a negative bias temperature instability test is performed to obtain a relationship straight line between the threshold voltage drift amount under different first test voltages and time, as a first relationship straight line; The step of obtaining the relationship between the threshold voltage drift amount and the time variation at the second test voltage based on the relationship between the threshold voltage drift amount and the time variation at different first test voltages and the difference between the second test voltage and the first test voltage includes: obtaining the relationship straight line between the threshold voltage drift amount and the time variation at the second test voltage as the second relationship straight line based on the relationship between the first relationship straight lines corresponding to the different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship straight line; Based on the relationship between the threshold voltage drift at the second test voltage and time, the step of obtaining the threshold voltage drift corresponding to the target test time includes: based on the second relationship straight line, obtaining the threshold voltage drift corresponding to the target test time as the estimated drift.

3. The method for obtaining threshold voltage stability according to claim 2, characterized in that: Based on the relationship between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line, the step of obtaining a relationship line in which the threshold voltage drift amount changes with time under the second test voltage includes: obtaining the second relationship line based on the intervals between the first relationship lines corresponding to different first test voltages, the difference between the second test voltage and the first test voltage, and the slope of the first relationship line.

4. The method for obtaining threshold voltage stability according to claim 1, characterized in that: The steps of performing a negative bias temperature instability test under different first test voltages to obtain a relationship between a threshold voltage drift amount and a time change under different first test voltages include: Under each of the first test voltages, a negative bias temperature instability test is performed on multiple structures to be tested to obtain an average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time; based on the average value of the threshold voltage drift corresponding to the multiple structures to be tested at each test time, a relationship between the threshold voltage drift and time under the current first test voltage is obtained.

5. The method for obtaining threshold voltage stability according to claim 4, characterized in that: Under each of the first test voltages, the number of the structures to be tested is at least 5.

6. The method for obtaining threshold voltage stability according to claim 1, characterized in that: The method for obtaining threshold voltage stability also includes: after obtaining the relationship between the threshold voltage drift amount under the second test voltage and time, based on the relationship between the threshold voltage drift amount under the second test voltage and time, obtaining the test time corresponding to the threshold voltage drift amount being a preset value as the failure time.

7. The method for obtaining threshold voltage stability according to claim 1, characterized in that: The step of obtaining the correlation between the target drift amount and the inferred drift amount includes: under the second test voltage, the test time is the target test time, and a threshold voltage stability test is performed to obtain the threshold voltage drift amount as the measured drift amount; and the correlation between the measured drift amount and the inferred drift amount is obtained as the correlation between the target drift amount and the inferred drift amount.

8. The method for obtaining threshold voltage stability according to claim 1, characterized in that: Based on the correlation between the target drift and the inferred drift, the step of obtaining the inferred drift corresponding to the target value includes: obtaining a linear correlation curve between the target drift and the inferred drift; setting a confidence interval based on the linear correlation curve; taking a lower limit within the confidence interval to obtain a corresponding lower limit correlation curve; based on the lower limit correlation curve, obtaining the inferred drift corresponding to the target value.

9. The method for obtaining threshold voltage stability according to claim 1, wherein: The steps of performing a negative bias temperature instability test under different first test voltages include: providing a structure to be tested; performing a negative bias temperature instability test on the structure to be tested under different first test voltages; The step of providing a structure to be tested includes: providing a substrate; forming a gate oxide layer on the substrate; and performing heat treatment on the gate oxide layer in a nitrogen-containing atmosphere.

10. The method for obtaining threshold voltage stability according to claim 9, characterized in that: The nitrogen-containing atmosphere includes nitric oxide and nitrogen, and the gas molar volume ratio of nitric oxide to nitrogen is 0.5:X, wherein X is at least 5.

11. The method for obtaining threshold voltage stability according to claim 1, characterized in that: The negative bias temperature instability test is performed for a period of 3 hours to 6 hours.

12. A system for achieving threshold voltage stability, characterized in that: include: A test module, used for performing a negative bias temperature instability test to obtain a relationship between a threshold voltage drift amount and a time change under different first test voltages; The test voltage for the threshold voltage stability test is the second test voltage, the test time is the target test time, and the obtained threshold voltage drift amount is used as the target drift amount; A relationship obtaining module, configured to obtain a relationship between a threshold voltage drift amount and a time change at the second test voltage based on a relationship between a threshold voltage drift amount and a time change at different first test voltages and a difference between the second test voltage and the first test voltage; An inference module, configured to obtain, based on a relationship between a threshold voltage drift amount under the second test voltage and a change in time, a threshold voltage drift amount corresponding to the target test time as an inferred drift amount; A correlation obtaining module, used for obtaining the correlation between the target drift amount and the estimated drift amount; The calculation module is used to obtain the estimated drift amount corresponding to the target drift amount when the target drift amount is the target value based on the correlation between the target drift amount and the estimated drift amount.

13. A device, characterized in that The method comprises at least one memory and at least one processor, wherein the memory stores one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the method for obtaining threshold voltage stability according to any one of claims 1 to 11.

14. A storage medium, characterized in that: The storage medium stores one or more computer instructions, and the one or more computer instructions are used to implement the method for obtaining threshold voltage stability as described in any one of claims 1-11.

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