A method to distinguish different charge collection mechanisms in single-particle transient state of nano-MOSFET devices

Abstract

The present invention relates to a method for distinguishing different charge collection mechanisms of single-particle transient in nano MOSFET devices. The method overcomes the problems of low calculation accuracy of traditional charge collection mechanism research methods, inability to distinguish between source-drain conduction and bipolar amplification mechanisms, and inability to provide the physical processes of different charge collection mechanisms. The method includes the steps of device single-particle transient simulation, analysis of the charge collection mechanism of single-particle transient drain contact, and obtaining the charge amount of different charge collection mechanisms and the contribution of each charge collection mechanism to the total charge collection amount of single-particle transient drain contact. By analyzing the changes in the internal electrical parameters of the device, different charge collection mechanisms are distinguished from the microscopic principle, so that not only the contribution of various charge collection mechanisms to the total charge collection amount can be accurately calculated, but also the microscopic physical process of charge collection can be provided, which can provide targeted theoretical guidance for the device's anti-single-particle transient reinforcement.

Description

Technical Field

[0001] The present invention belongs to the field of single particle effect simulation of semiconductor devices, and in particular relates to a method for distinguishing different transient charge collection mechanisms of single particles of nano MOSFET devices. Background Art

[0002] As integrated circuits advance into nanometer process nodes (transistor feature sizes less than 100nm), single-particle effects (SEPs) have become the primary radiation reliability issue facing aerospace integrated circuits. Single-particle transients (SPTEMs), the most important single-particle effect, manifests itself when charged particles strike a sensitive location in a combinational logic circuit. This node collects charge, and when the collected charge exceeds a critical value, a transient pulse is generated. As device size decreases, the proportion of SEPs in the SEP population increases. For MOSFET devices, SEPs are generated by charge collection at the drain contact. Current research indicates that the primary mechanisms for SEP charge collection at the drain contact include drift diffusion, bipolar amplification, and source-drain conduction. Distinguishing the impacts of different charge collection mechanisms can provide targeted theoretical guidance for device radiation hardening.

[0003] Previous studies on the simulation of the single-particle transient drain contact charge collection mechanism of MOSFET devices could only determine the charge collection caused by drift diffusion, and could not distinguish whether the remaining charge collection was bipolar amplification or source-drain conduction. The method used was to float the gate and source of the MOSFET device, so that the device could be approximated as a simple diode device. The single-particle transient drain contact charge collection amount obtained by heavy ion irradiation simulation of this device was considered to be the charge collection amount caused by the drift diffusion mechanism of the MOSFET device. This was then subtracted from the drain contact charge collection amount of the complete MOSFET device to obtain the charge collection amount caused by bipolar amplification or source-drain conduction. Although this method can roughly calculate the collected charge amount of the drift diffusion mechanism and the collected charge amount of bipolar amplification or source-drain conduction, it has many disadvantages. First, the floating of the source not only affects bipolar amplification and source-drain conduction, but also affects the drift diffusion of charges, resulting in a large gap between the calculated drift diffusion mechanism for collecting charges and the actual mechanism. Second, this method cannot distinguish between source-drain conduction and bipolar amplification mechanisms. Finally, this method distinguishes charge collection mechanisms by the amount of charge collected under two bias voltages, and cannot give the physical process of different charge collection mechanisms. Summary of the Invention

[0004] In order to overcome the problems of low calculation accuracy of traditional charge collection mechanism research methods, inability to distinguish between source-drain conduction and bipolar amplification mechanisms, and inability to provide the physical processes of different charge collection mechanisms, the present invention proposes a method that can distinguish different single-particle transient charge collection mechanisms of nano MOSFET devices. This method distinguishes different charge collection mechanisms from a microscopic principle, so that not only can the contribution of various charge collection mechanisms to the total charge collection amount of the drain contact be calculated more accurately, but also the microscopic physical process of charge collection at the drain contact can be given, which can provide targeted theoretical guidance for the device's anti-single-particle transient reinforcement.

[0005] The technical solution of the present invention is:

[0006] A method for distinguishing different transient charge collection mechanisms of single-particle nano-MOSFET devices is characterized in that it includes the following steps:

[0007] Step 1: Device modeling, obtaining a device model;

[0008] Step 2: Single-particle transient simulation of the device to obtain relevant electrical parameters inside the device;

[0009] Use semiconductor device simulation software to perform single-particle transient simulation on the device model to obtain the electron current and hole current transients of the source contact, drain contact, and substrate contact of the device, as well as the curve of the drain contact current changing with time; and call the corresponding command during the simulation process to continuously record the average electron concentration and average hole concentration in the channel region of the device, and obtain the curve of the average electron concentration and average hole concentration changing with time in the channel region of the device; at the same time, record the electron concentration distribution and hole concentration distribution inside the device during the single-particle transient generation process;

[0010] Step 3: Based on the relevant electrical parameters obtained in step 2, analyze the single-particle transient drain contact charge collection mechanism;

[0011] Step 3.1, determine the drift diffusion collection charge portion;

[0012] Obtain the transient electron and hole currents of the device source contact, drain contact, and substrate contact from step 2, and determine the charge portion collected by drift diffusion, where the substrate contact electron current and substrate contact hole current are caused by drift diffusion collection, and the source contact hole current and positive source contact electron current are caused by drift diffusion collection;

[0013] Step 3.2: Distinguish between source-drain conduction and bipolar amplification;

[0014] Based on the time-varying curves of the average electron concentration and the average hole concentration in the device channel region obtained in step 2, as well as the time-varying curve of the drain terminal contact current, and the electron concentration distribution and hole concentration distribution inside the device during the single-particle transient generation process, compare the electron concentration in the device channel during the single-particle transient generation process with the electron concentration in the channel when the device is in the on state. If the electron concentration in the channel during the single-particle transient generation process is greater than or equal to the electron concentration in the channel when the device is in the on state, the negative source terminal contact electron current is source-drain conduction collection;

[0015] If the electron concentration in the channel during the generation of a single-particle transient is much smaller than that in the on-state, the electron current at the negative source contact is bipolar amplified and collected;

[0016] Step 4: Based on the charge collection mechanism determined in step 3, obtain the charge amount of different charge collection mechanisms and the contribution of each charge collection mechanism to the total charge collection amount of the single-particle transient drain contact.

[0017] Furthermore, step 4 is specifically as follows:

[0018] The substrate contact electron current transient, substrate contact hole current transient, source terminal contact hole current transient and positive source terminal contact electron current transient are added together, and then the single particle transient drift diffusion collection charge is obtained by integrating the time.

[0019] The electron current at the negative source terminal is integrated with time to obtain the amount of charge collected by source-drain conduction or bipolar amplification;

[0020] The total charge collected by the single-particle transient drift diffusion is obtained by adding the charge collected by the source-drain conduction or bipolar amplification;

[0021] Based on the ratios of the single-particle transient drift diffusion collected charge, the source-drain conduction collected charge, and the bipolar amplification collected charge to the total charge collected by the single-particle transient drain contact, the contributions of different charge collection mechanisms to the total charge collected by the single-particle transient drain contact are obtained.

[0022] Furthermore, step 1 specifically includes the following steps:

[0023] Step 1.1: Use semiconductor simulation software to perform process modeling and obtain an initial device model;

[0024] Step 1.2: Use the corresponding tools in the semiconductor simulation software to perform conventional electrical performance simulation on the initial device model, compare the electrical performance simulation data with the actual electrical performance of the device, calibrate the initial device model, and obtain the device model.

[0025] Furthermore, the semiconductor simulation software described in step 1.1 is TCAD software. Currently, TCAD software mainly includes some open source TCAD software and commercial TCAD software. Commercial TCAD software includes Silvaco TCAD from Silvaco, Sentaurus TCAD from Synopsys, and ISE-TCAD from ISE (Integrated Systems Engineering). The present invention is mainly based on Sentaurus TCAD, but can be applied to other TCAD software.

[0026] Furthermore, in step 2, the sdevice tool in the Sentaurus TCAD software is used to perform single-particle transient simulation on the device model, and the heavy ions are incident at different positions as needed.

[0027] The beneficial effects of the present invention are:

[0028] The present invention obtains the charge collection mechanism of the nano MOSFET device by analyzing the current conditions of each contact of the device, the average electron concentration and the average hole concentration in the device channel, and the charge concentration distribution inside the device during the single-particle transient generation process, and calculates the contribution of different charge collection mechanisms to the total charge collection. Compared with the traditional method of calculating the contribution of different charge collection mechanisms to the total charge collection of the drain contact by comparing the charge collection conditions of the drain contact under different bias conditions, the present invention distinguishes different charge collection mechanisms from the microscopic principle by analyzing the changes in the electrical parameters inside the device, so that not only can the contribution of various charge collection mechanisms to the total charge collection amount be accurately calculated, but also the microscopic physical process of charge collection can be given. Knowing the microscopic process of charge collection can suppress charge collection by changing the device structure or material, etc., thus providing targeted theoretical guidance for the device's resistance to single-particle transient reinforcement. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is the 16nm FinFET device structure model obtained by modeling in step a of step 1) in the embodiment.

[0030] Figure 2 1 is a curve showing the transient change of electron current and hole current of the source contact and drain contact over time obtained by simulation in step 2) of the embodiment.

[0031] Figure 3 This is the charge concentration distribution in the active region of the device at 1 ns as shown in step 2) of the embodiment.

[0032] Figure 4 This is the charge concentration distribution in the active region when the device is in the on state as shown in step 3) of the embodiment.

[0033] Figure 5 3 is a curve showing the change of the average electron concentration, average hole concentration and drain contact current in the channel region obtained in step 2) of the embodiment over time. DETAILED DESCRIPTION

[0034] To make the above-mentioned objects, features, and advantages of the present invention more clearly understood, the following detailed description of the specific embodiments of the present invention is given in conjunction with the accompanying drawings. It is obvious that the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in this field without creative work should fall within the scope of protection of the present invention.

[0035] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0036] The present invention first uses TCAD software to perform single-particle transient simulation on nano MOSFET devices, and obtains the electron current and hole current transients of the device source contact, drain contact and substrate contact in the simulation; and calls corresponding commands during the simulation process to continuously record the changes in the average electron concentration and average hole concentration of the device channel region over time; and simultaneously records the charge concentration distribution (including electron concentration distribution and hole concentration distribution) of the device during the charge collection process (single-particle transient generation process). Then, visualization software is used to analyze and compare the above data to obtain the type of device single-particle transient drain contact charge collection mechanism, and calculate the contribution of different charge collection mechanisms to the total charge collection of the drain contact. Compared with the traditional method, by comparing the drain contact charge collection situation under different bias conditions, the contribution of different charge collection mechanisms to the total charge collection of the drain contact is calculated. The present invention distinguishes different charge collection mechanisms from a microscopic principle, so that not only can the contribution of each charge collection mechanism to the total charge collection amount of the drain contact be accurately calculated, but also the microscopic physical process of charge collection can be given, so that theoretical guidance can be provided for the device's anti-single-particle transient reinforcement in a targeted manner.

[0037] The specific process may include the following:

[0038] 1) Device modeling and routine characterization;

[0039] a. First, use the sprocess tool in TCAD software to perform process modeling to obtain a device model and perform meshing to meet the simulation requirements of the sdevice module. The process flow is provided by TCAD software, and the device parameters are the same as the actual device.

[0040] b. Then use the sdevice tool in TCAD software to simulate the device's conventional electrical performance and compare it with the actual device electrical performance or the electrical performance of the same process size device obtained by SPICE simulation to perform device calibration.

[0041] 2) Single-particle transient simulation of the device to obtain relevant electrical parameters inside the device;

[0042] The sdevice tool is used to perform single-particle transient simulation of the device. The heavy ion incidence position and incidence direction are optional, and the transient electron current and hole current of each contact of the device (source contact, drain contact and substrate contact) as well as the change of drain contact current over time are obtained.

[0043] Add the CurrentPlot{device parameters at specified position} command in the simulation command file to record the changes of the average electron concentration and average hole concentration in the device channel area over time.

[0044] The Plot command is used to record the electron concentration distribution and hole concentration distribution inside the device during the charge collection process, and then the charge concentration distribution inside the device during the charge collection process is obtained.

[0045] After the transient simulation is completed, the above data are analyzed and compared using the visualization software Sentaurus Visual.

[0046] 3) Analysis of single-particle transient charge collection mechanism;

[0047] According to the internal charge conservation of the device, the drain contact current = -(source contact current + substrate contact current). Therefore, we can determine the drain contact charge collection process by analyzing the charge collection of the source contact and substrate contact, and then determine the single-particle transient drain contact charge collection mechanism and the contribution of various charge collection mechanisms to the total charge collection.

[0048] a. First determine the drift diffusion collection charge portion;

[0049] From 2), the electron current transient and hole current transient of the device source contact, drain contact and substrate contact are obtained, and the drift diffusion collection charge part is determined, among which the substrate contact electron current and substrate contact hole current are mainly caused by drift diffusion collection, and the source contact hole current and positive source contact electron current are due to drift diffusion collection.

[0050] b. Distinguish between source-drain conduction and bipolar amplification;

[0051] Compare the electron concentration in the device channel during the single-particle transient generation process and the electron concentration in the channel when the device is in the on state. If the electron concentration in the channel during the single-particle transient generation process is greater than or equal to the electron concentration in the channel when the device is in the on state, the electron current contacting the negative source terminal is source-drain conduction collection; if the electron concentration in the channel during the single-particle transient generation process is much smaller than the electron concentration in the channel when the device is in the on state, the electron current contacting the negative source terminal is bipolar amplification collection.

[0052] 4) according to the charge collection mechanism obtained in 3), obtaining the charge amount of different charge collection mechanisms and the contribution of each charge collection mechanism to the total charge collection amount of the single particle transient drain contact;

[0053] The substrate contact electron current transient, substrate contact hole current transient, source terminal contact hole current transient and positive source terminal contact electron current transient are added together, and then the single particle transient drift diffusion collection charge is obtained by time integration.

[0054] The electron current at the negative source terminal is integrated with time to obtain the amount of charge collected when the source and drain are turned on or when the bipolar amplification is performed.

[0055] The sum of these two parts is the total transient charge collection of a single particle.

[0056] Based on the ratios of the single-particle transient drift diffusion collected charge, the source-drain conduction collected charge, and the bipolar amplification collected charge to the total charge collected by the single-particle transient drain contact, the contributions of different charge collection mechanisms to the total charge collected by the single-particle transient drain contact are obtained.

[0057] The following uses a single-particle transient simulation example of a 16nm FinFET process MOSFET device (16nm FinFET device) to illustrate the technical solution of the present invention.

[0058] Here are the steps:

[0059] Step 1) 16nm FinFET device modeling and general characterization calibration;

[0060] a. First, use the sprocess tool in Synopsys's sentaurus TCAD software to perform process modeling to obtain a 16nm FinFET device model and perform meshing to meet the simulation requirements of the sdevice module. The process flow is provided by TCAD software, and the device parameters are given by TSMC's 16nm FinFET process library; the device structure model obtained by modeling is Figure 1 given.

[0061] b. Then, the device is simulated using the sdevice tool in Synopsys's sentaurus TCAD software to obtain the Id-Vg characteristic curve. This curve is then compared with the Id-Vg characteristic curve of a FinFET device with the same process size obtained by Hspice simulation for device calibration.

[0062] Step 2) Single-event transient simulation of 16nm FinFET device;

[0063] The sdevice tool was used to perform heavy ion single particle transient simulation of the device. The heavy ion incident position was the center of the device active area, the heavy ion characteristic radius was 15 nm, and the LET value was 5 MeV·cm 2 / mg.

[0064] Single particle transient simulation can obtain the transient electron and hole currents of the source, drain and substrate contacts of FinFET devices, as well as the curves of the drain contact current changing with time. The results are shown in Figure 2 and Figure 5 , where the substrate contact electron current and hole current are 0, so there is no Figure 2 Draw it in.

[0065] Add to the simulation command file

[0066] CurrentPlot{

[0067] eDensity(Average(Region=ChFin))

[0068] hDensity(Average(Region=ChFin))}

[0069] The command is used to obtain the average electron concentration and average hole concentration in the channel region of the FinFET device during the single-particle transient simulation. The results are displayed in Figure 5 middle.

[0070] Use the Plot command to record the electron concentration distribution and hole concentration distribution in the active area of the FinFET device during the single-particle transient simulation of 1ns. The results are given by Figure 3 At 1 ns, the current of each contact of the FinFET device is basically at its peak value, and the charge concentration distribution in the active area is representative at this time.

[0071] After the transient simulation is completed, we use the visualization software Sentaurus Visual to analyze and compare the above data.

[0072] Step 3) Analysis of single-particle transient charge collection mechanism;

[0073] According to the internal charge conservation of the device, the drain contact current = -(source contact current + substrate contact current). Therefore, we can determine the drain contact charge collection process by analyzing the charge collection of the source contact and substrate contact, and then determine the single-particle transient drain contact charge collection mechanism and the contribution of various charge collection mechanisms to the total charge collection.

[0074] a. First determine the drift diffusion collection charge portion;

[0075] From step 2) Figure 2 The device's source and drain contacts show transient electron and hole currents. The substrate contact electron and hole currents are both zero and therefore not shown. Only the source contact hole current is collected by drift diffusion, while the negative source contact electron current is collected by source-drain conduction or bipolar amplification.

[0076] b. Distinguish between source-drain conduction and bipolar amplification;

[0077] From step 2), we get the electron concentration distribution and hole concentration distribution of the active region of the device during the single-particle transient simulation of 1ns. Figure 3 The electron concentration in the channel and the electron concentration in the channel when it is on (see Figure 4 ) by comparing the electron concentration in the channel at 1 ns to 2e19 cm -3 It is about 1.5777m, slightly larger than the electron concentration when the device is turned on. Therefore, it is determined that the electron current contacting the negative source terminal at this time is source-drain conduction collection. Figure 5 The curves of the drain contact current and the average charge concentration in the channel changing with time during the generation of single-particle transients show that the electron concentration in the channel remains basically at 1e19 cm during the generation of leakage current. -3 The above is equivalent to the electron concentration in the channel in the on state. Therefore, the electron current at the negative source terminal is collected by source-drain conduction during the entire single-particle transient generation process.

[0078] Step 4) obtaining the charge amounts of different charge collection mechanisms and the contribution of each charge collection mechanism to the total charge collection amount of the single-particle transient drain contact based on the charge collection mechanism obtained in step 3);

[0079] The hole current at the source contact is collected by drift diffusion. Figure 2 The transient time integration of the hole current at the source contact can yield a drift diffusion collection charge of approximately 0.83 pC.

[0080] The negative source terminal contacts the electron current and collects the source-drain conduction. Figure 2 The time integration of the transient electron current at the negative source terminal can obtain the source-drain collection charge of about 1.75pC.

[0081] The total collected charge is 2.61 pC.

[0082] Therefore, it can be concluded that, in our example, the charge generated in the channel is collected by the combined effects of source-drain conduction and drift-diffusion, with source-drain conduction being the main factor.

Claims

1. A method for distinguishing different transient charge collection mechanisms of single-particle nano-MOSFET devices, characterized in that: The following steps are involved: Step 1: Device modeling, obtaining a device model; Step 2: Single-particle transient simulation of the device to obtain relevant electrical parameters inside the device; The device model was simulated using the sdevice tool in Sentaurus TCAD software. Heavy ions were injected at different locations as needed to obtain transient electron and hole currents in the source, drain, and substrate contacts of the device, as well as a curve of the drain contact current over time. During the simulation, the corresponding commands are called to continuously record the average electron concentration and average hole concentration in the device channel region, and obtain the time-varying curves of the average electron concentration and average hole concentration in the device channel region. At the same time, the electron concentration distribution and hole concentration distribution inside the device during the single-particle transient generation process are recorded. Step 3: Based on the relevant electrical parameters obtained in step 2, analyze the single-particle transient drain contact charge collection mechanism; Step 3.1, determine the drift diffusion collection charge portion; Obtain the transient electron and hole currents of the source, drain, and substrate contacts of the device from step 2, and determine the charge portion collected by drift diffusion, wherein the substrate contact electron current and substrate contact hole current are caused by drift diffusion collection, and the source contact hole current and positive source contact electron current are caused by drift diffusion collection; Step 3.2: Distinguish between source-drain conduction and bipolar amplification; Based on the time-varying curves of the average electron concentration and the average hole concentration in the device channel region obtained in step 2, as well as the time-varying curve of the drain terminal contact current, and the electron concentration distribution and hole concentration distribution inside the device during the single-particle transient generation process, compare the electron concentration in the device channel during the single-particle transient generation process with the electron concentration in the channel when the device is in the on state. If the electron concentration in the channel during the single-particle transient generation process is greater than or equal to the electron concentration in the channel when the device is in the on state, the negative source terminal contact electron current is source-drain conduction collection; If the electron concentration in the channel during the generation of a single-particle transient is less than that in the on-state, the electron current at the negative source contact is bipolar amplified and collected; Step 4: Based on the charge collection mechanism determined in step 3, the charge amount of different charge collection mechanisms and the contribution of each charge collection mechanism to the total charge collection amount of the single-particle transient drain contact are obtained; Specifically: The substrate contact electron current transient, substrate contact hole current transient, source terminal contact hole current transient and positive source terminal contact electron current transient are added together, and then the single particle transient drift diffusion collection charge is obtained by integrating the time. The electron current at the negative source terminal is integrated with time to obtain the amount of charge collected by source-drain conduction or bipolar amplification; The total charge collected by the single-particle transient drift diffusion is obtained by adding the charge collected by the source-drain conduction or bipolar amplification; Based on the ratios of the single-particle transient drift diffusion collected charge, the source-drain conduction collected charge, and the bipolar amplification collected charge to the total charge collected by the single-particle transient drain contact, the contributions of different charge collection mechanisms to the total charge collected by the single-particle transient drain contact are obtained.

2. The method for distinguishing different transient charge collection mechanisms of single-particle nano-MOSFET devices according to claim 1, characterized in that: Step 1 specifically includes the following steps: Step 1.1: Use semiconductor simulation software to perform process modeling and obtain an initial device model; Step 1.2: Use the corresponding tools in the semiconductor simulation software to perform conventional electrical performance simulation on the initial device model, compare the electrical performance simulation data with the actual electrical performance of the device, calibrate the initial device model, and obtain the device model.

3. The method for distinguishing different transient charge collection mechanisms of single-particle nano-MOSFET devices according to claim 2, characterized in that: The semiconductor simulation software described in step 1.1 is TCAD software.

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