Photoelectric image sensor single event effect analogue simulation method

Abstract

The invention relates to a semiconductor device single event effect analogue simulation method, in particular to a photoelectric image sensor single event effect analogue simulation method, and solves the problems that the existing photoelectric image sensor single event radiation damage analogue simulation research is relatively few; and space ion irradiation damage simulation research under different irradiation conditions is difficult to carry out. The photoelectric image sensor single event effect simulation method comprises the following steps: 1) establishing a pixel unit structure model of a photoelectric image sensor in TCAD simulation software; 2) obtaining the incidence depth of ions; 3) establishing a single event effect irradiation model of the photoelectric image sensor; 4) constructing a pixel unit physical model; and 5) introducing the single event effect irradiation model obtained in the step 3) into the pixel unit physical model obtained in the step 4), and performing transient simulation to complete photoelectric image sensor single event effect analogue simulation.

Description

Technical Field

[0001] The present invention relates to a simulation method for single event effects of semiconductor devices, and more particularly to a simulation method for single event effects of optoelectronic image sensors. Background Art

[0002] Optoelectronic image sensors include CMOS image sensors and CCD image sensors. When they work in a space environment, they will be affected by radiation damage, resulting in performance degradation or even functional failure of the optoelectronic image sensors.

[0003] With the increasing demand for optoelectronic image sensors in the aerospace field, the influence of single event effects of space radiation-induced optoelectronic image sensors has become increasingly prominent. Existing technologies have conducted a large number of studies on the single event effects of space radiation-induced optoelectronic image sensors and carried out corresponding ground simulation experiments. However, for optoelectronic image sensors with different structures, there are significant differences in the degree of influence of space radiation on physical parameters and damage mechanisms, making the cost of experimental research relatively high. The simulation of optoelectronic image sensors has the advantages of short time consumption, large amount of data, high accuracy and low cost, and can be used as an important method for studying the analysis of device performance degradation induced by space radiation damage. However, at present, the simulation research on single particle radiation damage of optoelectronic image sensors is relatively less. Summary of the Invention

[0004] The purpose of the present invention is to solve the technical problem that the simulation research on single particle radiation damage of existing optoelectronic image sensors is relatively less, and it is difficult to carry out simulation research on space ion irradiation damage under different irradiation conditions, and to provide a simulation method for single event effects of optoelectronic image sensors.

[0005] In order to achieve the above purpose, the present invention adopts the following technical solutions:

[0006] A simulation method for single event effects of optoelectronic image sensors is characterized by including the following steps:

[0007] 1) Establish a pixel unit structure model of the optoelectronic image sensor in the TCAD simulation software; the pixel unit structure model includes region definition, material definition, electrode definition, doping definition and grid definition;

[0008] 2) Obtain the incident depth of ions according to the relationship between the incident depth and radiation energy of ions incident on the optoelectronic image sensor;

[0009] 3) Based on the incident depth of ions, establish a single event effect irradiation model of the optoelectronic image sensor in the TCAD simulation software;

[0010] 4) Introduce carrier mobility models, carrier recombination models, bandgap models, and light illumination models into the pixel unit structure model obtained in step 1) in the TCAD simulation software to construct a pixel unit physical model;

[0011] 5) Introduce the single-event effect irradiation model obtained in step 3) into the pixel unit physical model obtained in step 4) for transient simulation to complete the single-event effect simulation of the optoelectronic image sensor.

[0012] Further, step 2) is specifically as follows:

[0013] 2.1. Select the P-type substrate of the optoelectronic image sensor;

[0014] 2.2. Use ions to irradiate the P-type substrate;

[0015] 2.3. Through simulation, the relationship between the incident depth l of the ions and the radiation energy E is obtained as follows:

[0016] f(E) = l

[0017] 2.4. Calculate the incident depth of the ions according to the relationship between the incident depth l of the ions and the radiation energy E.

[0018] Further, step 3) is specifically as follows:

[0019] 3.1. Input ion parameters in the Device module of the TCAD simulation software; the ion parameters include the incident angle, incident position, incident time, incident energy diffusion width, radiation energy, and ion energy diffusion function type;

[0020] 3.2. Calculate the spatial distribution and time distribution of ion irradiation energy diffusion according to the ion parameters;

[0021] 3.3. Substitute the spatial distribution and time distribution into the electron-hole pair generation rate function to calculate the electron-hole pair generation rate;

[0022] 3.4. Substitute the electron-hole pair generation rate into the Poisson equation and the continuity equation for solution to obtain the single-event effect irradiation model of the optoelectronic image sensor.

[0023] Further, step 5) is specifically as follows:

[0024] 5.1. Establish a driving timing according to the working stage of the optoelectronic image sensor;

[0025] 5.2. Substitute the single-event effect irradiation model obtained in step 3) into the pixel unit physical model with the driving timing added for transient simulation to complete the single-event effect simulation of the optoelectronic image sensor.

[0026] Further, in step 3.2, the spatial distribution is expressed by a spatial exponential distribution as follows:

[0027]

[0028] Or, it is expressed by a spatial Gaussian distribution as follows:

[0029]

[0030] Wherein, R(w, l) is the spatial distribution of the ion irradiation energy diffusion, w is the diffusion width of the ion, l is the incident depth of the ion, and t is the incident time of the ion;

[0031] The time distribution is expressed by a Gaussian distribution function as follows:

[0032]

[0033] Wherein, T(t) is the time distribution of the ion energy diffusion, t 0 is the starting time of the ion incidence, s hi is the Gaussian eigenvalue, representing the pulse width of the incident ions.

[0034] Further, in step 3.3, the calculation formula for the electron-hole pair generation rate is:

[0035] G(l, w, t) = G LET (l)R(w, l)T(t)

[0036] Wherein, G(l, w, t) is the electron-hole pair generation rate, and G LET (l) is the generation density of the electron-hole pairs.

[0037] Further, step 3) further includes:

[0038] Adding Tcl statements in the Visual module of the TCAD simulation software.

[0039] Advantages of the present invention:

[0040] 1. The single-event effect simulation method of the optoelectronic image sensor of the present invention can simulate the depletion region distribution in the sensitive area inside the optoelectronic image sensor, and can more clearly observe the internal changes of the optoelectronic image sensor, providing a theoretical basis for the analysis of the single-event effect degradation mechanism of the optoelectronic image sensor.

[0041] 2. The single-event effect simulation method of the optoelectronic image sensor of the present invention uses the TCAD simulation software, overcomes the limitations of long experimental time, high professional requirements for experimental operations, and high consumption of manpower, material resources and financial resources, effectively reduces the research cost, and reduces the damage of the radiation source to the experimental personnel and experimental devices. Description of the Drawings

[0042] Figure 1 Flow chart of an embodiment of a simulation method for single - event effect of an optoelectronic image sensor according to the present invention;

[0043] Figure 2a Schematic structural diagram of a CMOS image sensor in an embodiment of the present invention;

[0044] Figure 2b Schematic structural diagram of a CCD image sensor in an embodiment of the present invention;

[0045] Figure 3a Schematic distribution diagram of adding material definition and doping definition to pixel units of a CMOS image sensor in an embodiment of the present invention;

[0046] Figure 3b Schematic distribution diagram of adding material definition and doping definition to pixel units of a CCD image sensor in an embodiment of the present invention;

[0047] Figure 4a Schematic diagram of adding electrode definition to a CMOS image sensor in an embodiment of the present invention;

[0048] Figure 4b Schematic diagram of adding electrode definition to a CCD image sensor in an embodiment of the present invention;

[0049] Figure 5a Schematic diagram of adding driving timing to a CMOS image sensor in an embodiment of the present invention;

[0050] Figure 5b Schematic diagram of adding driving timing to a CCD image sensor in an embodiment of the present invention;

[0051] Figure 6a Timing diagram of a CMOS image sensor obtained by simulation in an embodiment of the present invention, where the horizontal axis is time and the vertical axis is voltage;

[0052] Figure 6b Timing diagram of a CCD image sensor obtained by simulation in an embodiment of the present invention, where the horizontal axis is time and the vertical axis is voltage;

[0053] Figure 7 Schematic diagram of the influence of ions on the depletion region of a CMOS image sensor changing with time in an embodiment of the present invention. Detailed implementation manners

[0054] As Figure 1 shown, a simulation method for single - event effect of an optoelectronic image sensor includes the following steps:

[0055] 1) Establish a pixel unit structure model of the optoelectronic image sensor in TCAD simulation software;

[0056] According to the spatial composition of the optoelectronic image sensor, a pixel unit structure model of the optoelectronic image sensor is constructed using TCAD software. Among them, the pixel unit structure model includes region definition, material definition, electrode definition, doping definition, and mesh definition.

[0057] As Figure 2a shown, the region definition of the CMOS image sensor pixel unit structure model includes the PMD region (Pre-Metal Dielectric, PMD), the gate oxide layer (Gate Oxide), the STI region (Shallow Trench Isolation, STI), the PPD region (Pinned PhotoDiode, PPD), the TG region (Transfer Gate, TG), the FD region (Floating Diffusion, FD), the RST region, the power supply voltage Vdd, and the P-type substrate (P-Sub). As Figure 2b shown, the region definition of the CCD image sensor pixel unit structure model includes the gate oxide layer, the N-channel region (N-channel), multiple TG regions, and the P-type substrate (P-Sub). A voltage is applied to each TG region, and potential wells C are formed on the corresponding P-type substrate (P-Sub). Every four potential wells C1, C2, C3, and C4 form a transfer unit.

[0058] As Figure 3a shown, according to the spatial distribution of the material definition, the CMOS image sensor is divided into the PMD region, the gate oxide layer, the STI region, the PPD region, the TG region, the FD region, the RST region, the power supply voltage V dd and the P-type substrate (P-Sub). As Figure 3b shown, according to the spatial distribution of the material definition, the CCD image sensor is divided into the gate oxide layer, the N-channel region, multiple TG regions, and the P-type substrate (P-Sub).

[0059] From Figure 3a , 3b it can be seen that the material distribution, electrode distribution, and doping distribution of the pixel unit of the optoelectronic image sensor are obtained by simulation. The doping definition includes constant doping, Gaussian doping, and error function doping. The doping atoms are selected as boron (B) atoms and arsenic (As) atoms. Doping with boron (B) results in a P-type semiconductor, and doping with arsenic (As) atoms results in an N-type semiconductor.

[0060] As Figure 4a shown, the electrode definition of the CMOS image sensor is to add electrodes to the P-type substrate, the TG region, the RST region, the power supply voltage V dd and the floating node FD. As Figure 4bAs shown, the electrode definition of the CCD image sensor is to add electrodes to the transfer unit and the P-type substrate.

[0061] In this embodiment, the rectangular area can be determined by the coordinates of two vertices to define the size and position of the rectangular area, and the polygonal area can be defined by the coordinates of multiple vertices to define the shape and position of the polygon. After dividing the spatially distributed area defined by the material, the corresponding material is filled in each area according to the material composition of the pixel unit. The current-dense area of the optoelectronic image sensor is divided into smaller grids, and the current-sparse area is divided into larger grids to ensure the accuracy of the simulation of the optoelectronic image sensor, thereby reducing the time required for the simulation of the optoelectronic image sensor.

[0062] 2) According to the relationship between the incident depth and the radiation energy of ions incident on the optoelectronic image sensor, the incident depth of ions is obtained through SRIM software simulation, specifically:

[0063] step1: Select the P-type substrate of the optoelectronic image sensor (CMOS image sensor or CCD image sensor);

[0064] step2: Select arsenic (As) atoms as the incident ions and incident on the P-type substrate;

[0065] step3: The simulation obtains that the incident depth l of the ions and the radiation energy E satisfy the following relationship:

[0066] f(E) = l

[0067] Step4: Calculate the incident depth of the ions according to the relationship formula between the incident depth l of the ions and the radiation energy E;

[0068] In this embodiment, after simulating the P-type substrate of the optoelectronic image sensor with arsenic (As) atoms with a radiation energy of 400 keV, the corresponding incident depth is 0.25 μm.

[0069] 3) In the Device module of the TCAD simulation software, establish a single-event effect irradiation model for the optoelectronic image sensor, specifically:

[0070] The physical model called by the incident ions is activated by specifying the keyword HeavyIon(). Given the ion parameters, the ion parameters include the incident angle, incident position, incident time, incident energy diffusion width, radiation energy, and ion energy diffusion function type. The ion parameters are input into the Device module of the TCAD simulation software, and its input statement is as follows:

[0071] Physics{

[0072] HeavyIon(

[0073] Direction=(sinα,cosα)

[0074] Location=(X,Y)

[0075] Time = <default>

[0076] Length= <default>

[0077] Wt_hi = <default>

[0078] LET_f = <default>

[0079] Gaussian / Exponential

[0080] PicoCoulomb)

[0081] }

[0082] Among them, HeavyIon is the incident ion; Direction is the incident angle α of the ion; Location is the incident position of the ion, where X and Y represent the X-axis and Y-axis coordinates respectively; Time is the incident time of the ion; Length is the incident depth of the ion; Wt_hi is the incident energy diffusion width of the ion; LET_f is the radiation energy of the incident ion; Gaussian / Exponential is the type of ion energy diffusion function; PicoCoulomb is the unit identifier; Physics is the called physical model.

[0083] A large number of electron-hole pairs are generated along the incident trajectory of the incident ion, thus forming a funnel region and an electric field region. The existence of the funnel region expands the charge collection range, and the electric field extends towards the P-type substrate. In the photoelectric image sensor, under the combined action of the built-in electric field and the external electric field, electrons and holes drift rapidly. As the incident ion irradiation energy decreases, more electron-hole pairs are continuously generated by ionization in the photoelectric image sensor, and the drift motion of electrons and holes further promotes the expansion of the electric field to other regions, which will have different effects on the photoelectric image sensor at different working stages.

[0084] Calculate the spatial and temporal distributions of ion irradiation energy diffusion according to ion parameters. The spatial distribution R(w, l) of ion irradiation energy diffusion is expressed by the spatial exponential distribution as Equation (1):

[0085]

[0086] The spatial distribution R(w, l) of ion irradiation energy diffusion is expressed by the spatial Gaussian distribution as Equation (2)

[0087]

[0088] In the formula, R(w, l) is the spatial distribution of ion irradiation energy diffusion, w is the diffusion width of the ion, l is the incident depth of the ion, and t is the incident time of the ion;

[0089] The temporal distribution T(t) of the incident ion energy diffusion is usually expressed by the Gaussian distribution function as Equation (3)

[0090]

[0091] In the formula, t 0 is the starting time of ion incidence, s hi is the Gaussian eigenvalue, representing the pulse width of the incident ions. exp represents the natural function symbol, and erf represents the error function symbol.

[0092] Substituting the spatial distribution and time distribution into the electron-hole pair generation rate function, the calculated electron-hole pair generation rate G(l, w, t) is expressed as:

[0093] G(l, w, t) = G LET (l)R(w, l)T(t) (4)

[0094] where G LET (l) is the generation density of electron-hole pairs, R(w, l) represents the spatial distribution of ion irradiation energy diffusion, and T(t) represents the time distribution of ion energy diffusion;

[0095] Substitute the electron-hole pair generation rate G(l, w, t) calculated by Equation (4) into the Poisson equation and continuity equation for solution to obtain the single-event effect irradiation model of the optoelectronic image sensor.

[0096] 4) Using the Device module of the TCAD simulation software, introduce the carrier mobility model, carrier recombination model, bandgap model, and light illumination model into the pixel unit structure model obtained in step 1) to construct the pixel unit physical model;

[0097] 5) Introduce the single-event effect irradiation model obtained in step 3) into the pixel unit physical model with the driving timing added for transient simulation to complete the single-event effect simulation of the optoelectronic image sensor, specifically:

[0098] Establish the driving timing according to the working stages of the optoelectronic image sensor, specifically:

[0099] Select different working stages within one cycle for single-event effect simulation. As Figure 5a shown, select the reset stage T 1 , integration stage T 2 , FD region reset stage T 3 and charge transfer stage T 4 of the CMOS image sensor; It can be seen from Figure 5a that in the T 1 stage, at the moment of t 1 , the RST region, TG region, and power supply voltage Vdd are all connected to the high level, and the intrinsic electrons and residual charges in the PPD region are transferred to the RST with a higher potential, making the PPD region in a fully depleted state. At the moment of t 2 , the RST region, TG region, and power supply voltage Vdd are switched to the low level. In the T 2 stage, the PPD region collects the photo-generated charges, from t 2 From 0 to t 6 At this moment, the TG region is at a low level. T 3 During this stage, at t 3 and t 4 moments, the power supply voltage Vdd and the RST region are respectively connected to a high level, the charge in the FD region is transferred to the reset transistor with a higher potential, and the FD region is reset to a high voltage. T 4 During this stage, at t 6 moment, the TG region is connected to a high level, and at t 7 moment, the TG region is turned off.

[0100] As Figure 5b shown, before the potential well of the CCD image sensor is formed, select T 1 , the integration stage T 2 and the charge packet transfer stage T 3 . From Figure 5b it can be seen that during the T 1 stage, the potential wells C3 and C4 are connected to a high level; during the T 2 stage, the potential well C1 is connected to a high level, and the potential well collects photo-generated charges; during the T 3 stage, the potential wells C1 and C2 are connected to a high level, and the charge packet is transferred between the potential wells.

[0101] Add the driving timing to the physical model of the pixel unit obtained in step 4); after adding the driving timing to the physical model of the pixel unit of the CMOS image sensor, obtain the true timing diagram of the output of the CMOS image sensor, as Figure 6a shown; after adding the driving timing to the physical model of the pixel unit of the CCD image sensor, obtain the true timing diagram of the output of the CCD image sensor, as Figure 6b shown.

[0102] Substitute the single-event effect irradiation model obtained in step 3) into the physical model of the pixel unit after adding the driving timing, and perform transient simulation. Specifically:

[0103] As Figure 7 shown, observe the transient changes of the CMOS image sensor at the time nodes of 10 ps, 20 ps, 30 ps, 40 ps, 100 ps and 5 ns after ion incidence, and compare the changes of the depletion region (red area) with time in the physical model of the pixel unit in different working stages. From Figure 7 it can be seen that after the TG region of the CMOS image sensor is irradiated by ions, it changes from the open state to the closed state, affecting its normal operation. Among them, the PPD region is occupied by electron-hole pairs, and the influence on other regions such as FD, RST and STI is relatively small.

[0104] Simulate in the Device module of the TCAD simulation software. Only the simulation diagrams at the specified time nodes are required. Since there are a large number of simulation times, each diagram needs to be manually operated, which is prone to errors. Therefore, the present invention adds the following statements in the Visual module of the TCAD simulation software to convert manual operation into automatic software operation, saving time and effort.

[0105] Step 1: Download the file _n@node@_des.tdr and name it "dataset_ <time>”;

[0106] Step 2: Load all tdr diagrams under the specified file path;

[0107] Step 3: Batch extract the data of the depletion region in the physical model of pixel units;

[0108] Step 4: Use Tcl statements to display the depletion region boundary;

[0109] Step 5: Finally, obtain the change of the depletion region over time and the set of modified tdr diagrams.

[0110] The method of the present invention makes full use of the Visual module in the TCAD software, adds Tcl statements to it, so as to automatically output the desired data on the swb interface of the TCAD simulation software, simplifies the operation, reduces the calculation amount, and saves the time cost. In this embodiment, the Tcl statement is specifically: set_material_prop{DepletionRegion}-border_width(X)-color#(Color code).< / time> < / default> < / default> < / default> < / default>

Claims

1. A method for simulating single particle effects of a photoelectric image sensor, characterized in that: The following steps are involved: 1) Establishing a pixel unit structure model of a photoelectric image sensor in TCAD simulation software; the pixel unit structure model includes region definition, material definition, electrode definition, doping definition and grid definition; 2) obtaining the incident depth of the ions according to the relationship between the incident depth and the radiation energy of the ions incident on the photoelectric image sensor; 3) Based on the ion incidence depth, a single-particle effect irradiation model of the photoelectric image sensor was established in the TCAD simulation software; 4) Introducing a carrier mobility model, a carrier recombination model, a bandgap model, and an illumination model into the pixel unit structure model obtained in step 1) in TCAD simulation software to construct a pixel unit physical model; 5) The single particle effect irradiation model obtained in step 3) is introduced into the pixel unit physical model obtained in step 4) to perform transient simulation to complete the single particle effect simulation of the photoelectric image sensor.

2. According to the method for simulating single particle effect of photoelectric image sensor of claim 1, it is characterized in that step 2] specifically comprises: 2.

1. Select the P-type substrate of the photoelectric image sensor; 2.

2. Using ions to impinge on a P-type substrate; 2.

3. The incident depth l and radiation energy E of the ions obtained by simulation satisfy the following relationship: f(E)=l 2.

4. Calculate the ion incidence depth based on the relationship between the ion incidence depth l and the radiation energy E.

3. The method for simulating single particle effects of a photoelectric image sensor according to claim 2, characterized in that: Step 3] Specifically: 3.

1. Input ion parameters in the Device module of TCAD simulation software; the ion parameters include incident angle, incident position, incident time, incident energy diffusion width, radiation energy and ion energy diffusion function type; 3.

2. Calculate the spatial and temporal distribution of ion irradiation energy diffusion based on ion parameters; 3.

3. Substitute the spatial distribution and time distribution into the electron-hole pair generation rate function and calculate the electron-hole pair generation rate; 3.

4. Substitute the electron-hole pair generation rate into the Poisson equation and the continuity equation to obtain the single particle effect irradiation model of the photoelectric image sensor.

4. The method for simulating single particle effects of a photoelectric image sensor according to claim 3, characterized in that: Step 5] Specifically: 5.

1. Establish the driving timing according to the working stage of the photoelectric image sensor; 5.

2. Substitute the single particle effect irradiation model obtained in step 3) into the physical model of the pixel unit with the driving timing added, perform transient simulation, and complete the single particle effect simulation of the photoelectric image sensor.

5. The method for simulating single particle effects of a photoelectric image sensor according to claim 4, characterized in that: Step 3.2, the spatial distribution is expressed as follows using spatial exponential distribution: Or, it can be expressed as: Where R(w,l) is the spatial distribution of ion irradiation energy diffusion, w is the ion diffusion width, l is the ion incidence depth, and t is the ion incidence time; The time distribution is expressed using a Gaussian distribution function: Where T(t) is the time distribution of ion energy diffusion, t0 is the time when the ion starts to enter, and s hi is the Gaussian eigenvalue, representing the pulse width of the incident ion.

6. The method for simulating single particle effects of a photoelectric image sensor according to claim 5, characterized in that: In step 3.3, the calculation formula for the electron-hole pair generation rate is: G(l,w,t)=G LET (l)R(w,l)T(t) Where G(l,w,t) is the electron-hole pair generation rate, G LET (l) is the generation density of electron-hole pairs.

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