A method for detecting a total dose effect induced defect distribution of a SiGe HBT

Abstract

The application provides a detection method for total dose effect induced defect distribution of SiGe HBT, which comprises the following steps: detecting the SiGe HBT to be detected by using 1 / f noise at a first preset temperature to obtain a first 1 / f noise parameter; detecting the SiGe HBT to be detected by using 1 / f noise at a second preset temperature to obtain a second 1 / f noise parameter, wherein the second preset temperature is lower than the first preset temperature and lower than normal temperature; detecting the SiGe HBT to be detected by using 1 / f noise under a preset irradiation condition and the first preset temperature to obtain a third 1 / f noise parameter; detecting the SiGe HBT to be detected by using 1 / f noise under the preset irradiation condition and the second preset temperature to obtain a fourth 1 / f noise parameter; and determining the change of the total dose effect induced defect distribution of the SiGe HBT to be detected under a low-temperature condition according to the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter and the fourth 1 / f noise parameter.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of transistors, in particular to a method for detecting total dose effect induced defect distribution of SiGe HBT. BACKGROUND

[0002] Germanium-silicon heterojunction bipolar transistor (SiGe HBT) is the earliest silicon-based device to realize band engineering, and has excellent low-temperature characteristics. By controlling the composition gradient of the base region Ge, it can realize the working temperature range from low temperature to high temperature. At the same time, SiGe HBT utilizes band engineering and shows excellent performance in gain, frequency response noise and linearity; it also has good compatibility with Si CMOS process and strong applicability to different circuit applications, and is one of the powerful competitors in space environment applications. However, space electronic systems working in space radiation environment will be affected by ionizing radiation, resulting in degradation or even failure of device performance, which seriously threatens the stability and reliability of device operation. In addition, when the device is applied to the outside of the spacecraft, the extreme temperature environment in space will also have a great impact on it. For example, in the typical extreme wide temperature range of-180℃ to +120℃ on the moon, the application of SiGe HBT devices can make it possible for related space exploration equipment to not need a large heat preservation device, thereby reducing launch costs.

[0003] Therefore, how to accurately detect the total dose effect induced defect distribution of SiGe HBT devices under low temperature conditions has become a problem for technical personnel to concern. SUMMARY

[0004] The purpose of the present application is to provide a method for detecting total dose effect induced defect distribution of SiGe HBT, which solves the problem of how to accurately detect the total dose effect induced defect distribution of SiGe HBT devices under low temperature conditions.

[0005] To solve the above technical problems, according to some embodiments, the present application provides a method for detecting total dose effect induced defect distribution of SiGe HBT, comprising:

[0006] At a first preset temperature, the SiGe HBT to be detected is detected by using 1 / f noise, and a first 1 / f noise parameter is obtained;

[0007] At a second preset temperature, the SiGe HBT to be detected is detected by using 1 / f noise, and a first 1 / f noise parameter is obtained, and the second preset temperature is lower than and lower than normal temperature;

[0008] Under preset irradiation conditions and a first preset temperature, the SiGe HBT to be measured is detected by using 1 / f noise to obtain a third 1 / f noise parameter;

[0009] Under preset irradiation conditions and a second preset temperature, the SiGe HBT to be measured is detected by using 1 / f noise to obtain a fourth 1 / f noise parameter;

[0010] According to the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter and the fourth 1 / f noise parameter, the total dose effect induced defect distribution change of the SiGe HBT to be measured under a low temperature condition is determined.

[0011] Further, the total dose effect induced defect distribution change of the SiGe HBT to be measured under a low temperature condition is determined, comprising:

[0012] According to the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter and the fourth 1 / f noise parameter, the concentration of oxide trap charge and the position of interface state in the SiGe HBT to be measured are respectively determined;

[0013] Based on the concentration of oxide trap charge and the position of interface state, the total dose effect induced defect distribution change of the SiGe HBT to be measured under a low temperature condition is determined.

[0014] Further, the test method further comprises: annealing the SiGe HB to be measured under preset irradiation conditions and a first preset temperature at a normal temperature, and detecting the SiGe HB to be measured by using 1 / f noise to obtain a fifth 1 / f noise parameter;

[0015] Annealing the SiGe HB to be measured under preset irradiation conditions and a second preset temperature at a normal temperature, and detecting the SiGe HB to be measured by using 1 / f noise to obtain a sixth 1 / f noise parameter; the normal temperature annealing time is greater than 160 minutes.

[0016] Further, the first preset temperature is 300K; and the second preset temperature is 93K.

[0017] Further, it further comprises setting a bias voltage when irradiation is performed:

[0018] Under the second preset temperature, the cutoff bias is V BE =-0.2V, V BC =-2V;

[0019] Under the second preset temperature, the full zero bias is V BE =0V, V BC =0V;

[0020] Under the first preset temperature, the cutoff bias is V BE =-0.2V, V BC= -2V

[0021] Full zero bias, V BE = 0V, V BC = 0V.

[0022] Further, the SiGe HBT to be detected is detected by using 1 / f noise, including:

[0023] The emitter of the SiGe HBT is grounded, the base-emitter is connected with a scanning voltage of 0-0.5V, and the collector-emitter is connected with a scanning voltage of 0-1.2V, both with a step of 10mA.

[0024] Further, the third 1 / f noise parameter and the fourth 1 / f noise parameter are obtained, both within 30 minutes after the irradiation ends.

[0025] Further, before the detection, the Gummel characteristics and the 1 / f noise parameters of SiGe HBTs of the same model are tested, and SiGe HBTs with consistent electrical performance are selected as the SiGe HBT to be detected.

[0026] Further, before the detection, the SiGe HBT to be detected is connected to a PCT board and connected with a series protection resistor.

[0027] The above technical solutions of the present application have at least the following beneficial technical effects:

[0028] (1) The 1 / f noise measurement is used to measure the defect density in the sensitive region of the SiGe HBT device; the 1 / f noise is very sensitive to the oxide trap charge and the interface state, and has a great relationship with the radiation environment and the trap trapping / detraping, therefore, the 1 / f noise measurement can be used as a diagnostic tool to help locate and identify the defects caused by the radiation effect in the SiGe HBT device.

[0029] (2) The 1 / f noise in the SiGe HBT is closely related to the defects, by analyzing the changes of the 1 / f noise data before irradiation, after irradiation and after annealing, a large amount of information about the device reliability related to the concentration, spatial position and energy distribution of the defects in the sensitive region of the SiGe HBT can be obtained, which is used to evaluate the device reliability. BRIEF DESCRIPTION OF DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0031] Figure 1 This is a flowchart of a method for detecting the total dose effect induced defect distribution of SiGe HBT in one embodiment of the present invention.

[0032] Figure 2 This is a schematic diagram of the SiGe HBT device structure in one embodiment of the present invention.

[0033] Figure 3 This is a schematic diagram of the 1 / f noise test circuit in one embodiment of the present invention.

[0034] Figure 4 In one embodiment of the present invention, the 1 / f noise parameters of a SiGe HBT device before irradiation at 93K and 300K are shown.

[0035] Figure 5 In one embodiment of the present invention, the 1 / f noise parameters of a SiGe HBT device after irradiation under cutoff bias (a) and zero bias (b) conditions at 93K and 300K are shown.

[0036] Figure 6 The 1 / f noise parameters of a SiGe HBT device after 168 hours of irradiation and annealing under 300K conditions with cutoff bias (a) and all-zero bias (b) are shown in one embodiment of the present invention.

[0037] Figure 7 This is the 1 / f noise parameter of a SiGe HBT device after 168 hours of annealing under irradiation in cutoff bias (a) and all-zero bias (b) conditions at 93K in one embodiment of the present invention. Detailed Implementation

[0038] Currently, there is a technical problem in existing technologies regarding how to accurately detect the total dose effect induced defect distribution of SiGe HBT devices under low-temperature conditions.

[0039] To solve the above problems, such as Figure 1 As shown, an embodiment of the present invention provides a method for detecting the total dose effect induced defect distribution in SiGe HBT, comprising:

[0040] S1. At the first preset temperature, the SiGe HBT under test is detected using 1 / f noise to obtain the first 1 / f noise parameter;

[0041] S2. At the second preset temperature, the SiGe HBT under test is detected using 1 / f noise to obtain the second 1 / f noise parameter. The second preset temperature is lower than the first preset temperature and lower than the room temperature.

[0042] S3. Under preset irradiation conditions and a first preset temperature, the SiGe HBT under test is detected using 1 / f noise to obtain the third 1 / f noise parameter.

[0043] S4. Under preset irradiation conditions and second preset temperature, the SiGe HBT under test is detected using 1 / f noise to obtain the fourth 1 / f noise parameter.

[0044] S5. Based on the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter, and the fourth 1 / f noise parameter, determine the change in the total dose effect induced defect distribution in the SiGe HBT under low temperature conditions.

[0045] In the above steps, in step S1 at the first preset temperature and in step S2 at the second preset temperature, 1 / f noise is detected in the SiGe HBT under radiation-free conditions. The obtained first and second 1 / f noise parameters are used as comparative examples for subsequent experiments. Then, in steps S3 and S4, 1 / f noise is detected under preset irradiation conditions at the first and second preset temperatures, respectively, yielding the corresponding third and fourth 1 / f noise parameters. Each detection uses only one or a group of SiGe HBTs to avoid mutual interference of the measured parameters. The first, second, third, and fourth 1 / f noise parameters are then compared and analyzed to accurately obtain the changes in the total dose effect induced defect distribution in the SiGe HBT under low-temperature conditions.

[0046] In one embodiment of this application, determining the change in the total dose-induced defect distribution in the SiGe HBT under low-temperature conditions includes:

[0047] Based on the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter, and the fourth 1 / f noise parameter, the concentration of oxide trap charge and the position of interface state in the SiGe HBT under test are determined respectively.

[0048] Based on the concentration of oxide trap charges and the location of interface states, the total dose effect induced defect distribution changes of the SiGe HBT under test were determined under low temperature conditions.

[0049] The low-frequency noise of SiGe HBTs is mainly base current noise, while 1 / f noise is the main source of low-frequency noise. The physical mechanism of 1 / f noise and gain degradation after irradiation is the same: accumulation of oxide trapped charges and interface states, leading to increased recombination current. Figure 1 As shown, the sensitive region of SiGe HBT is the oxide layer and LOCOS region between the base and emitter.

[0050] In SiGe HBT devices, the power spectral density of 1 / f noise is proportional to the base current, such as... Figure 3 As shown, it is inversely proportional to the frequency, as shown in equation (1):

[0051]

[0052] K = 1.6 x 10-19 f - constant determined by electrical parameters of the device; for SiGe HBT device K = 1.6 x 10-19 f Typical value of K is 10-16

[0053] α, γ - dimensionless constants; for calculation of 1 / f noise in silicon material, α = 2, γ = 1

[0054] Δf - frequency band width, Δf = 1 Hz

[0055] Experiments show that 1 / f noise of SiGe HBT device is mainly originated from base-emitter region, and the size of 1 / f noise is closely related to current density of base current, 1 / f noise power spectrum density is directly proportional to base current density The smaller the current density, the smaller the 1 / f noise. Base current density of SiGe HBT device is as formula (2)

[0056]

[0057] In the formula, V T - turn-on voltage of SiGe HBT device. With the decrease of temperature, intrinsic carriers in semiconductor are frozen out, resistance increases, and turn-on voltage also increases. Base current density at low temperature will also decrease; analysis shows that 1 / f noise performance at low temperature is also significantly enhanced with the decrease of temperature.

[0058] Temperature plays an important role in the formation of defects. In the process of total dose effect induced defect formation, when γ-ray is incident into SiGe HBT device, energy is deposited in the oxide layer, and the energy is transferred to lattice atoms. When the energy given to atoms is greater than the minimum ionization energy of the material (in SiO2, the energy is 17 eV), electron-hole pairs are formed. The generated electron-hole pairs are proportional to the radiation energy of SiGe HBT device. When the minimum radiation ionization energy is introduced, as formula (3):

[0059] Q = W / ε, (3)

[0060] In the formula, Q - electron-hole pair yield; W - incident material radiation energy; ε - minimum radiation ionization energy.

[0061] Experiments show that the value of ε will change at different temperatures, as formula (4)

[0062]

[0063] In the formula, K - constant: The total energy of LO phonons required to maintain the momentum of the crystal: r - the average number of optical phonons emitted between impact ionizations; E g The band gap energy.

[0064] From the above analysis, it can be found that the change of ε is mainly caused by the change of E g , which can be estimated as E g The change affected by temperature is shown in equation (5):

[0065]

[0066] Where: E g (0) - the band gap of the material at 0 K; a and b - fitting parameters.

[0067] Analysis shows that the increase of E g at low temperature will significantly reduce the net yield of electron-hole pairs after irradiation of the semiconductor material. Since the distance between the electron and the hole is very close, a part of them will initially recombine, while the other part will separate under the action of the electric field to form free electrons and holes. Generally, the proportion of holes that escape initial recombination to the total ionization number is called the initial production rate of holes, which is closely related to the type of incident particles and the electric field of the oxide layer. At low temperature irradiation, the temperature first affects the initial production rate of free electron-hole pairs, which is shown in equation (6):

[0068]

[0069] Further, under low electric field conditions, the probability of escaping initial recombination of electron-hole pairs can be approximately solved as shown in equation (7):

[0070] P(r, E) = exp(-r c / r)(1 + (e 2 / 2εk 2 T 2 )E), (7)

[0071] In equations (6) and (7): r - the distance of the initially formed electron-hole pair; E - the electric field; θ - the angle between the electric field and the electron-hole pair connection line; μ = e / 2kT, r c = e 2 / εkT, e - charge; k - Boltzmann constant; T - temperature; Jo - zero-order Bessel function.

[0072] From equation (7), the relationship between the escape probability of electron-hole pairs and temperature and electric field can be known. Under low temperature irradiation, the number of generated electron-hole pairs is much lower than that at room temperature, resulting in much lower radiation damage at low temperature than at room temperature.

[0073] In addition, in the oxide layer, the mobility of free electrons is much greater than the mobility of holes, and the transport process of holes in the oxide layer is actually a random hopping process, i.e., a process of being trapped by a shallow level trap, thermal excitation, transport, re-trapping, and re-excitation; the hopping time (t s ) of holes in the oxide layer is related to the electric field and temperature, as shown in formula (8):

[0074]

[0075] In the formula, a is the average hopping distance, which is a disorder parameter determining the hopping time (t s ); and b is a constant.

[0076] Δ Act (E ox ) is related to the electric field and can be expressed as Δ Act (E ox ) = Δ0-bE ox , where Δ0 is the activation energy, and b is a constant.

[0077] It can be obtained from formula 8 that, under a low electric field, the lower the temperature, the slower the transport time of holes in the oxide layer, thereby slowing down the generation of oxide trap charges and interface traps. By comparing and analyzing the 1 / f noise parameters measured under different temperatures and irradiation conditions, the distribution of oxide trap charges and interface traps under different irradiation conditions and temperature conditions is determined, and then the distribution change of total dose effect induced defects of the SiGe HBT to be measured under a low temperature condition is determined.

[0078] In an embodiment of the present application, the test method further comprises: performing normal temperature annealing on the SiGe HB to be measured under the preset irradiation condition and a first preset temperature, and detecting the normal temperature annealing by using 1 / f noise to obtain a fifth 1 / f noise parameter.

[0079] Performing normal temperature annealing on the SiGe HB to be measured under the preset irradiation condition and a second preset temperature, and detecting the normal temperature annealing by using 1 / f noise to obtain a sixth 1 / f noise parameter; the normal temperature annealing time is greater than 160 minutes.

[0080] In an embodiment of the present application, before the detection, the Gummel characteristics and the 1 / f noise parameters of SiGe HBTs of the same type are tested, and SiGe HBTs with consistent electrical properties are selected as the SiGe HBT to be measured.

[0081] In an embodiment of the present application, the first preset temperature is 93K, and the second preset temperature is 300K.

[0082] In an embodiment of the present application, the bias voltage during irradiation is further set.

[0083] Second preset temperature, cutoff bias, V BE =-0.2V, V BC =-2V;

[0084] Second preset temperature, full zero bias, V BE =0V, V BC =0V;

[0085] First preset temperature, cutoff bias, V BE =-0.2V, V BC =-2V;

[0086] First preset temperature, full zero bias, V BE =0V, V BC =0V.

[0087] The application uses a FS-380 semiconductor parameter analyzer to test SiGe HBT devices, selects KT9041 type SiGe HBT devices with consistent parameters, and performs tests at a first preset temperature of 93K and a second preset temperature of 300K, Figure 4 indicates a 1 / f noise parameter curve measured at 93K and 300K under no irradiation conditions; when the total dose accumulates to 1Mrad(Si), the 1 / f noise changes in Figure 3 compared with 300K, the 1 / f noise degradation at 93K is obviously reduced, and the 1 / f noise degradation degrees in the cutoff bias and full zero bias states are similar; the oxide trap charges and interface states in the Si / SiO2 interface and the vicinity thereof within a few nanometers are obviously reduced at low temperatures.

[0088] The emitter of the SiGe HBT device to be tested is grounded, the base-emitter (V BE ) is connected to a 0-0.5V scanning voltage, and the collector-emitter is connected to a 0-1.2V scanning voltage, both with a step of 10mA.

[0089] In an embodiment of the application, the third 1 / f noise parameter and the fourth 1 / f noise parameter are obtained, both of which are completed within 30 minutes after the irradiation ends, so as to reduce the influence of damage annealing on subsequent tests

[0090] In an embodiment of the application, the SiGe HBT to be tested is detected by using 1 / f noise, which includes:

[0091] The emitter of the SiGe HBT is grounded, the base-emitter is connected to a 0-0.5V scanning voltage, and the collector-emitter is connected to a 0-1.2V scanning voltage, both with a step of 10mA.

[0092] In an embodiment of the present application, before detection, the method further comprises: connecting the SiGe HBT to be detected to a PCT board and connecting a series protection resistor to the SiGe HBT.

[0093] The device structure selected in the experiment of the present application is shown in Figure 2 ; Figure 3 is a schematic diagram of a 1 / f noise test circuit; Figure 4 are 1 / f noise parameters of SiGe HBT devices 93K and 300K before irradiation, and the 1 / f noise decreases with the decrease of temperature and power spectrum density. Figure 5 are 1 / f noise parameters of SiGe HBT devices 93K and 300K under the conditions of off-bias and full zero-bias after irradiation, and it can be seen from the figure that when the irradiation accumulates to 1 Mrad (Si), the degradation degrees of the two biases are close, and the degradation under the condition of 93K is less than that under the condition of 300K. Figure 6 and Figure 7 are test results of the devices after 168 hours of room temperature annealing after irradiation.

[0094] It can be seen from Figure 6 and Figure 7 that after 168 hours of room temperature annealing, the off-bias and full zero-bias under the conditions of 300K and 93K both show different experimental phenomena; under the condition of 300K, the 1 / f noise under the condition of off-bias shows a small amplitude recovery, and the 1 / f noise under the condition of full zero-bias shows no change. The oxide trap charge can be annealed at room temperature, while the interface state cannot be annealed. Therefore, the interface state yield under the condition of full zero-bias is more than that under the condition of off-bias. Under the condition of 93K, the "annealing damage enhancement effect" appears after annealing, and the 1 / f noise after annealing is larger than that when the total dose accumulates to 1 Mrad (Si) under the condition of 93K; it can be known that the defects induced by the total dose effect at low temperature are consistent with the logical relationship in the above formula, and most of them are oxide trap charges near the Si / SiO2 interface. After annealing, a small part of holes continue to transport to the interface, thereby generating interface states, so that the 1 / f noise degrades after annealing.

[0095] It should be understood that the above specific embodiments of the present application are only used for illustrative or explanatory purposes of the principles of the present application, and do not constitute a limitation on the present application. Therefore, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present application shall be included in the protection scope of the present application. In addition, the appended claims of the present application are intended to cover all changes and modifications falling within the scope and boundary of the appended claims, or the equivalent forms of such scope and boundary.

Claims

1. A method of detecting SiGe HBT total dose effect induced defect profiles, characterized by, The method comprises the following steps: detecting the SiGe HBT to be measured by using 1 / f noise at a first preset temperature to obtain a first 1 / f noise parameter; detecting the SiGe HBT to be measured by using 1 / f noise at a second preset temperature to obtain a second 1 / f noise parameter, wherein the second preset temperature is lower than the first preset temperature and lower than normal temperature; the first preset temperature is 300K; and the second preset temperature is 93K; detecting the SiGe HBT to be measured by using 1 / f noise under a preset irradiation condition and the first preset temperature to obtain a third 1 / f noise parameter; detecting the SiGe HBT to be measured by using 1 / f noise under the preset irradiation condition and the second preset temperature to obtain a fourth 1 / f noise parameter; determining the distribution change of total dose effect induced defects in the SiGe HBT to be measured under a low-temperature condition according to the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter and the fourth 1 / f noise parameter, wherein the low-temperature condition is 93K-300K; The determination of the distribution change of total dose effect induced defects in the SiGe HBT to be measured under the low-temperature condition comprises: determining the concentration of oxide trap charges and the position of interface states in the SiGe HBT to be measured according to the first 1 / f noise parameter, the second 1 / f noise parameter, the third 1 / f noise parameter and the fourth 1 / f noise parameter respectively; determining the distribution change of total dose effect induced defects in the SiGe HBT to be measured under the low-temperature condition based on the concentration of oxide trap charges and the position of interface states.

2. The detection method according to claim 1, characterized in that, The method further comprises the following steps: detecting the SiGe HBT to be measured under the preset irradiation condition and the first preset temperature by using 1 / f noise after normal-temperature annealing to obtain a fifth 1 / f noise parameter; detecting the SiGe HBT to be measured under the preset irradiation condition and the second preset temperature by using 1 / f noise after normal-temperature annealing to obtain a sixth 1 / f noise parameter; the normal-temperature annealing time is greater than 160 minutes.

3. The method of claim 1, wherein, The method further comprises setting a bias voltage during irradiation. at a second preset temperature, cutoff bias, V BE = -0.2 V, V BC = -2 V; at the second preset temperature, full zero bias, V BE = 0V, V BC = 0V; at a first preset temperature, cut-off bias, V BE = -0.2 V, V BC = -2 V; full zero bias at the first preset temperature, V BE = 0V, V BC = 0V.

4. The method of claim 1, wherein The detection of the SiGe HBT to be measured by using 1 / f noise comprises the following steps: grounding the emitter of the SiGe HBT, connecting the base-emitter with a scanning voltage of 0-0.5V, and connecting the collector-emitter with a scanning voltage of 0-1.2V, wherein the step length is 10mA.

5. The method of claim 1, wherein The third 1 / f noise parameter and the fourth 1 / f noise parameter are obtained within 30 minutes after the irradiation is completed.

6. The method of claim 1, wherein Before the detection, the method further comprises the following steps of testing the Gummel characteristics and 1 / f noise parameters of SiGe HBTs of the same type, and screening SiGe HBTs with consistent electrical properties as the SiGe HBT to be measured.

7. The detection method according to claim 6, characterized in that, Before the detection, the method further comprises the following step of connecting the SiGe HBT to be measured to a PCT plate and connecting a series protection resistor to the SiGe HBT to be measured.

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