Test device and method for key parameters of electrostatic protection mechanism with flyback characteristic

Abstract

The application discloses a kind of test device and method with the key parameter of electrostatic protection mechanism with back sweep characteristic.The Pwell region, Nc gradually varying capacitance region, Nr resistance region, heavily doped N++, heavily doped N++, Psw region, upper electrode of inversion oxide layer and metal connection constitute the main body of the test device with the key parameter of electrostatic protection mechanism with back sweep characteristic.The application overcomes the defect that minimum back-through voltage and minimum holding current are not easy to measure directly, and can directly measure the minimum back-through voltage and minimum holding current of the electrostatic protection mechanism with back sweep characteristic;It is free from dependence on high-end power semiconductor scanner and TLP test system, and the test equipment used is common basic equipment rather than expensive and complex test equipment;During the test process, voltage and current change are relatively smooth, avoiding the influence of dv / dt, inductance impact, etc., and the measurement result is stable, and the measurement consistency is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of integrated circuit reliability and manufacturability, and in particular to a testing device and method for key parameters of an electrostatic discharge protection mechanism with a back-scan feature in the field of semiconductor. BACKGROUND

[0002] Electrostatic discharge (ESD) is the main cause of over- electrical stress (EOS) damage to all electronic components or integrated circuit systems. Electrostatic discharge usually has a voltage of several thousand volts, which can cause permanent damage to the circuit. Protecting integrated circuit components from electrostatic damage is a difficult problem for all IC design and manufacturing.

[0003] Common electrostatic discharge protection mechanisms are usually divided into diode type, transistor type, and silicon controlled type. Diode type electrostatic discharge protection mechanisms do not have a back-scan feature, while transistor type and silicon controlled type electrostatic discharge protection mechanisms have a back-scan feature.

[0004] Electrostatic discharge protection mechanisms with a back-scan feature are the first choice for low-capacitance high-performance electrostatic discharge components. However, the back-scan feature also brings new problems and challenges to low-capacitance high-performance electrostatic discharge components. Key parameters such as minimum back-through voltage and minimum holding current in the back-scan process must be carefully designed and accurately tested.

[0005] For electrostatic discharge protection mechanisms without a back-scan feature such as diode type, only the working voltage greater than the turn-on voltage of the electrostatic discharge protection mechanism is required, and no additional parameters need to be measured. However, for electrostatic discharge protection mechanisms with a back-scan feature such as transistor type and silicon controlled type, in addition to ensuring that the turn-on voltage of the electrostatic discharge protection mechanism is greater than the normal working voltage, it is also necessary to ensure that the minimum back-through voltage is also greater than the normal working voltage. The current corresponding to the minimum back-through voltage is the minimum holding current.

[0006] Currently, there are two urgent problems in testing the minimum back-through voltage and minimum holding current of electrostatic discharge protection mechanisms with a back-scan feature.

[0007] The first problem is the lack of testing means. Electrostatic discharge is a high-energy short-time impact within a 2ns to 100ns cycle. It is difficult to excite and detect such a signal with a short time period and high energy using ordinary voltage and current tests. Currently, only high-end power semiconductor scanners and TLP test systems can be used to preliminarily test the minimum back-through voltage and minimum holding current of electrostatic discharge protection mechanisms with a back-scan feature.

[0008] Secondly, the existing test equipment system is expensive. Compared with the ordinary voltage and current meter, the configuration cost of the high-end power semiconductor scanner and TLP test system is high, which forms a serious bottleneck in the use cost and efficiency of the electrostatic protection mechanism with the back-scan feature. In addition, considering the parallel operation demand of multiple test systems in large-scale testing, the existing minimum back-through voltage and minimum holding current cannot be used for large-scale testing, which is one of the reasons why no manufacturer tests the minimum back-through voltage and minimum holding current one by one.

[0009] Thirdly, the accuracy problem is the most important. As mentioned above, the electrostatic impact is a high-energy short-time impact in nanoseconds, and the influence of signal dv / dt change, inductance impact and cable parasitic effect will seriously affect the test accuracy. The minimum back-through voltage and minimum holding current obtained by different manufacturers and different models of power semiconductor scanners often have great differences, which greatly troubles the staff in the production, acceptance and sales links. The number of TLP manufacturers is much smaller than that of power semiconductor scanners, and the principle can strictly regulate the emitted square wave. However, on the one hand, the TLP system is expensive and cannot be configured in the production, acceptance and sales links; on the other hand, once different manufacturers' TLP systems are used, the quality of the emitted square wave will also affect the consistency of the minimum back-through voltage and the minimum holding current. The minimum back-through voltage and the minimum holding current of the electrostatic protection mechanism with the back-scan feature need to be improved in terms of test consistency

[0010] The present application discloses a novel test device and method for key parameters of an electrostatic protection mechanism with a back-scan feature, which can be applied to transistors and silicon-controlled static protection mechanisms with a back-scan feature, and can test the minimum back-through voltage and the minimum holding current with good consistency at a very low implementation cost. SUMMARY

[0011] The main content of the present application is to disclose a novel test device and method for key parameters of an electrostatic protection mechanism with a back-scan feature.

[0012] The present application discloses a novel test device and method for key parameters of an electrostatic protection mechanism with a back-scan feature.

[0013] In terms of structure, the first Pwell region, the Nc gradual change capacitor region, the Nr resistance region, the first heavily doped N++, the second heavily doped N++, the Psw region, the upper electrode of the reverse type oxide layer and the metal connection together constitute the main body of the test device for key parameters of the electrostatic protection mechanism with the back-scan feature.

[0014] Thus, an equivalent circuit is formed, including the additional test device part electrode corresponding to the first heavily doped N++ region and the first hole and metal thereon, and the main function is to lead out the connectable electrode.

[0015] The first Pwell region and the Nc gradual capacitance region constitute an energy storage capacitor, and the main structure is a gradual junction between the first Pwell region and the Nc gradual capacitance region.

[0016] The Nc gradual capacitance region, the first Pwell region, and the Nr resistance region constitute a switching transistor, and the first Pwell region and the Nc gradual capacitance region of the switching transistor are on one side of the gradual junction.

[0017] The back type oxide layer upper electrode and the Psw region constitute a back type channel switch.

[0018] The RC and the voltage dividing resistance constitute a parasitic resistance formed in the Nr resistance region.

[0019] In combination with a series of test methods disclosed by the present application, including the peripheral equipment and connection mode used for testing the key parameters of the electrostatic protection mechanism with the back sweep feature, the test process and steps, the intermediate data in the test and the reading method thereof, the minimum back-through voltage and the minimum holding current of the electrostatic protection mechanism with the back sweep feature are tested.

[0020] Compared with the prior art, the present application has the following beneficial effects:

[0021] Firstly, the test device and method for the key parameters of the electrostatic protection mechanism with the back sweep feature disclosed by the present application can directly measure the minimum back-through voltage and the minimum holding current of the electrostatic protection mechanism with the back sweep feature, overcoming the defect that the minimum back-through voltage and the minimum holding current are not easy to directly measure.

[0022] Secondly, the test device and method for the key parameters of the electrostatic protection mechanism with the back sweep feature disclosed by the present application are free from the dependence on the middle and high-end power semiconductor scanner and TLP test system, and the test equipment used is a common basic equipment rather than an expensive and complex test equipment such as TLP or power semiconductor scanner.

[0023] Thirdly, in the test process of the test device and method for the key parameters of the electrostatic protection mechanism with the back sweep feature disclosed by the present application, the voltage and current change are relatively gentle, avoiding the influence of dv / dt and inductive impact, and the measurement result is stable, and the consistency and repeatability of the measurement are good. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 The schematic diagram of the test device for the key parameters of the MOSFET type electrostatic protection mechanism with the back sweep feature provided by the embodiment of the present application is suitable for testing the lateral electrostatic protection mechanism.

[0025] Figure 2 The schematic diagram of the key parameter testing device of the static protection mechanism of the silicon controlled rectifier type with the flyback characteristic provided by the embodiment of the present application is suitable for testing the transverse static protection mechanism;

[0026] Figure 3 The equivalent circuit schematic diagram of the key parameter testing device of the MOSFET type static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0027] Figure 4 The equivalent circuit schematic diagram of the key parameter testing device of the silicon controlled rectifier type static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0028] Figure 5 The schematic diagram of the peripheral equipment and the connection mode used for the key parameter testing of the static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0029] Figure 6 The flowchart of the key parameter testing of the static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0030] Figure 7 The intermediate data and the reading method thereof in the voltage-time testing of the static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0031] Figure 8 The intermediate data and the reading method thereof in the current-time testing of the static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0032] Figure 9 The intermediate data and the reading method thereof in the current-voltage testing of the static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0033] Figure 10 The three-dimensional structure schematic diagram of the key parameter testing device of the MOSFET type static protection mechanism with the flyback characteristic provided by the embodiment of the present application;

[0034] Figure 11 The three-dimensional structure schematic diagram of the key parameter testing device of the silicon controlled rectifier type static protection mechanism with the flyback characteristic provided by the embodiment of the present application. DETAILED DESCRIPTION

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative effort belong to the protection scope of the present application.

[0036] Please refer to Figures 1-11 The present application provides several technical solution embodiments based on the present application:

[0037] Embodiment one:

[0038] The disclosed novel key parameter testing device for an electrostatic protection mechanism with a back-scan feature can be well applied in an electrostatic protection mechanism with a back-scan feature of a MOSFET. The structure of the device is shown in Figure 1 .

[0039] As shown in Figure 1 , silicon is taken as an example in the embodiment, but the protection scope of the patent is not excluded when the present principles and key technologies are used in germanium-based, germanium-silicon-based, and SiC-based semiconductors. The substrate 101 is an N-type semiconductor doped with phosphorus, and the doping concentration is 1E15 to 1E17. The Pwell region 102 / 103 doped with boron is formed in the substrate 101, and the doping concentration is 5E16 to 5E18.

[0040] The Nc gradual capacitance region 104 doped with phosphorus or arsenic is formed in the Pwell region 102, and the doping concentration is 5E16 to 5E18. The number of the Nc gradual capacitance region 104 in practice is not limited and is often more than 1. Only one Nc gradual capacitance region 104 is shown in the figure for simplicity, which does not affect the right interests of the protection scope of the present application. The Nc gradual capacitance region 104 and the Pwell region 102 form a capacitor with a gradual junction. The capacitor is not easy to break down and burn out, has a good function of storing electric charges and storing electric energy.

[0041] The Nr resistance region 105 doped with phosphorus or arsenic is formed in the Pwell region 102, and the doping concentration is 5E16 to 5E18. In actual design, without affecting the protection scope of the present application, the Nr resistance region 105 and the Nc gradual capacitance region 104 can be set to the same doping concentration to achieve the purpose of simplifying the process and reducing the cost. When the Nr resistance region 105 and the Nc gradual capacitance region 104 have the same doping concentration, the Nr resistance region 105 is used as a diffusion resistor to meet the design requirements of the resistance value as the primary target, and the capacitor formed by the Nc gradual capacitance region 104 and the Pwell 102 guarantees not to break down as the secondary target. The capacitance value of the capacitor formed by the Nc gradual capacitance region 104 and the Pwell 102 is adjusted in size and position under the condition of guaranteeing the above conditions.

[0042] Psw region 106 is formed in substrate 101 with a boron doping concentration of 2.5E17 to 2.5E18. Psw region 106 is in contact with Nr resistance region 105 and Pwell region 103. Polysilicon over-oxide electrode 107 is capable of forming an inversion layer in Psw region 106 at a certain voltage. Polysilicon over-oxide electrode 107 is not electrically connected to Psw region 106, but is electrically connected to heavily doped N++ 108 through a via, metal. In actual design, without affecting the scope of protection of the present application, polysilicon over-oxide electrode 107 can be prepared at the same time as MOSFET gate 109, achieving the purpose of simplifying the process and reducing costs, but it is necessary to ensure that the gate oxide thickness is sufficient to ensure that it is not broken down when prepared at the same time as gate 109. It should be noted that, in general, Psw region 106 cannot be prepared at the same time as Pwell region 102 / 103 because Psw region 106 is a relatively shallow region prepared using ion implantation, while Pwell region 102 / 103 is prepared using deep diffusion.

[0043] Heavily doped N++ regions 108 / 110 / 111 / 112 are N-type semiconductor heavily doped, and heavily doped P++ region 113 is P-type semiconductor heavily doped, with a doping concentration of 1E19 to 1E20. Optionally, a silicide process can be additionally added to achieve better doping.

[0044] Figure 1 The Pwell region 102 on the left, Nc gradual capacitance region 104, Nr resistance region 105, heavily doped N++ 110, heavily doped N++ 108, Psw region 106, polysilicon over-oxide electrode 107, and metal connections as shown together form the main body of the test device for the key parameters of the static protection mechanism with the back-scan feature, referred to herein and hereinafter as the additional test device part.

[0045] Figure 1 The Pwell region 103 on the right, heavily doped N++ 111 / 112, heavily doped P++ 113, and MOSFET gate 109 form the silicon-based MOSFET-type static protection mechanism being tested by embodiment one of the present application, which is included in the concept of the tested static protection mechanism part defined herein and hereinafter.

[0046] The hole and metal 114 are the anode of the tested static protection mechanism part, the hole and metal 115 are the cathode of the tested static protection mechanism part, and the hole and metal 116 are the test terminals of the additional test device part. In a lateral MOSFET-type semiconductor device, the back surface metal is not necessarily connected, and is generally in a grounded state, which can be considered to be short-circuited with the cathode when the silicon-based MOSFET-type static protection mechanism is working.

[0047] The above embodiments use silicon as an example, but the scope of patent protection is not excluded when the principles and key technologies of this invention are implemented in germanium-based, germanium-silicon-based, and SiC-based semiconductors. When the principles and key technologies of this invention are applied to germanium-based, germanium-silicon-based, and SiC-based semiconductors, the corresponding doping elements are transformed into corresponding doping elements such as nitrogen and silver, and the doping concentration and method are changed accordingly based on the corresponding process.

[0048] Example 2:

[0049] This invention discloses a novel testing device for key parameters of electrostatic discharge (ESD) protection mechanisms with flyback characteristics. This device can be effectively applied to silicon-based thyristor-based ESD protection mechanisms with flyback characteristics. The structure of the device is as follows: Figure 2 As shown.

[0050] like Figure 2 As shown, in this embodiment, the substrate 201 is a phosphorus-doped N-type semiconductor with a doping concentration of 1E15 to 1E17. Boron-doped Pwell regions 202 / 203 are formed in the substrate 201 with a doping concentration of 5E16 to 5E18, and phosphorus- or arsenic-doped Nwell regions 221 are formed in the substrate 201 with a doping concentration of 5E16 to 5E18.

[0051] In the Pwell region 202, a phosphorus- or arsenic-doped Nc gradually changing capacitor region 204 is formed, with a doping concentration of 5E16 to 5E18. In practice, the number of Nc gradually changing capacitor regions 204 is not limited and is often more than one. For simplicity, only one Nc gradually changing capacitor region 204 is shown in the illustration, which does not affect the scope of protection of this invention. The Nc gradually changing capacitor region 204 and the Pwell region 202 form a capacitor with a gradually changing junction. This capacitor is not easily broken down and burns out, and has good charge storage and energy storage functions.

[0052] In Pwell region 202, a phosphorus or arsenic-doped Nr resistive region 205 is formed with a doping concentration of 5E16 to 5E18. In practical design, without affecting the scope of protection of this invention, the Nr resistive region 205 and the Nc gradually changing capacitor region 204 can be set to have the same doping concentration, thereby simplifying the process and reducing costs. When the Nr resistive region 205 and the Nc gradually changing capacitor region 204 have the same doping concentration, the primary goal is to ensure that the Nr resistive region 205, as a diffusion resistor, meets the resistance value design requirements. The secondary goal is to ensure that the capacitor formed by the Nc gradually changing capacitor region 204 and Pwell 202 does not break down. The capacitance value of the capacitor formed by the Nc gradually changing capacitor region 204 and Pwell 102 is adjusted in size while ensuring the above conditions are met.

[0053] A boron doped Psw region 206 is formed in the substrate 201 with a doping concentration of 2.5E17 to 2.5E18. The Psw region 206 is in contact with the Nr resistive region 205 and the Pwell region 203. The gate oxide over region 207 is capable of forming an inversion layer in the Psw region 206 at a certain voltage. The gate oxide over region 207 is not electrically connected to the Psw region 206, but is electrically connected to the heavily doped N++ 208 through a via and a metal. In actual designs, the thickness of the oxide layer under the gate oxide over region 207 is sufficient to ensure that it is not broken down. It should be noted that, in general, the Psw region 206 is formed by ion implantation, while the Pwell region 202, 221 is formed by deep diffusion, so the Psw region 206 cannot be formed at the same time as the Pwell region 202, 203.

[0054] The heavily doped N++ 208, 210, 211, 212 is N-type semiconductor heavy doping, and the heavily doped P++ 213, 222 is P-type semiconductor heavy doping, with a doping concentration of 1E19 to 1E20. Optionally, a silicide process can be added to improve the doping.

[0055] Figure 2 The Pwell region 202 on the left, the Nc gradual capacitance region 204, the Nr resistive region 205, the heavily doped N++ 210, the heavily doped N++ 208, the Psw region 206, the gate oxide over region 207, and the metal as shown together form the main body of the test device for the key parameters of the static protection mechanism with the flyback characteristic of the second embodiment of the present application, which is referred to as the additional test device part here and in the following.

[0056] Figure 2 The Pwell region 203 on the right, the Nwell region 221, the heavily doped N++ 211, 212, and the heavily doped P++ 213, 222 form the silicon-based silicon-controlled static protection mechanism to be tested by the second embodiment of the present application, which is included in the concept of the tested static protection mechanism part defined here and in the following.

[0057] Note that, unlike the first scheme, the hole and the metal 215 are the anode of the tested static protection mechanism part, the hole and the metal 214 are the cathode of the tested static protection mechanism part, and the hole and the metal 216 are the test terminal of the additional test device part. In a lateral silicon-controlled semiconductor device, the back surface metal is not necessarily connected to the ground, and can be considered to be shorted to the cathode when the silicon-based silicon-controlled static protection mechanism is working.

[0058] The above embodiments take silicon as an example, but the protection scope of the patent is not excluded when the principles and key technologies of the application are implemented in germanium-based, germanium-silicon-based, and SiC-based semiconductors. When the principles and key technologies of the application are applied to germanium-based, germanium-silicon-based, and SiC-based semiconductors, the corresponding doping elements are converted into corresponding doping elements such as nitrogen elements and silver elements, and the doping concentration and method are changed according to the corresponding process.

[0059] All the doping concentrations and doping methods in the above embodiments can be selected within the recommended range of the actual process according to the actual semiconductor process without affecting the protection scope of the application. Alternatively, the semiconductor doping type can also be reversed without affecting the protection scope of the application, and the semiconductor type and the corresponding equivalent element type of the other part can also be reversed.

[0060] Corresponding to the above embodiments, Figures 3-4 The equivalent circuit schematic diagram of the test device for testing the key parameters of the electrostatic protection mechanism with the flyback characteristic provided by the embodiments of the application is shown.

[0061] Figure 3 Corresponding Figure 1 The test device for testing the key parameters of the MOSFET-type electrostatic protection mechanism with the flyback characteristic provided by the embodiments of the application is shown. All the components in the dashed box 301 are part of the additional test device, and all the components in the dashed box 302 are part of the electrostatic protection mechanism to be tested.

[0062] Corresponding to Figure 1The structure in the figure, the additional test device part electrode 316 corresponds to the heavily doped N++ region 110 and the hole and metal 116 thereon, the main function is to lead out the connectable electrode. The Pwell region 102 and the Nc gradual change capacitor region 104 constitute the energy storage capacitor 303, the main structure is the gradual change junction between the Pwell region 102 and the Nc gradual change capacitor region 104, and the main function is to store a certain amount of charge. The Nc gradual change capacitor region 104, the Pwell region 102, and the Nr resistance region 105 constitute the switching transistor 304, the Pwell region 102 and the Nc gradual change capacitor region 104 side of the switching transistor 304 are gradual change junctions, and because the doping concentration of the Nr resistance region 105 is one to two orders of magnitude higher than that of the Nc gradual change capacitor region 104, the Pwell region 102 and the Nr resistance region 105 are abrupt junctions in comparison. When the heavily doped N++ region 110 applies a sufficient voltage to cause breakdown to open, the abrupt junction on the side of the Nr resistance region 105 and the Pwell region 102 breaks down first, and the gradual change junction on the side of the Nc gradual change capacitor region 104 and the Pwell region 102 expands but does not break down, so that the gradual change structure of the energy storage capacitor 303 can ensure that the energy storage capacitor 303 does not break down even in the open state of the switching transistor 304, thereby ensuring that the charge stored in the energy storage capacitor 303 is still stored in the capacitor and does not dissipate when the switching transistor 304 is open. The reverse type oxide layer upper electrode 107 and the Psw region 106 constitute the reverse channel switch 307, and when a certain voltage is applied to the reverse type oxide layer upper electrode 107, a reverse channel is formed in the Psw region 106, causing the reverse channel switch 307 to open; when the applied voltage drops to a certain value, the reverse channel formed in the Psw region 106 cannot be maintained, so that the reverse channel switch 307 is turned off.

[0063] The RC and voltage dividing resistor 305 / 306 is a parasitic resistance formed inside the Nr resistance region 105.

[0064] The main function is to form an RC discharge circuit together with the energy storage capacitor 303, and the time constant is

[0065] τ=Cc×Rtot

[0066] Cc is the capacitance value of the energy storage capacitor 303, which can be adjusted and designed by the area of the Nc gradual change capacitor region 104 and the Pwell region 102; Rtot is the sum of the resistance values of the RC and voltage dividing resistor 305 / 306, which can be adjusted by the doping concentration of the Nr resistance region 105 and the position of the heavily doped N++ region 108.

[0067] The second main function is voltage division. The voltage is applied to the upper electrode 107 of the inversion oxide layer by the heavily doped N++ region 108, so that the inversion channel switch 307 composed of the upper electrode 107 of the inversion oxide layer and the Psw region 106 is turned off before the energy storage capacitor 303 is completely discharged. In the present application, it is a key point to ensure that the inversion channel switch 307 is turned off before the energy storage capacitor 303 is completely discharged, because only in this way can it be ensured that the tested ESD protection mechanism part 302 is turned off by the spontaneous turn-off current of the tested ESD protection mechanism part 302, rather than the disappearance of the excited current of the additional test device part 301.

[0068] The heavily doped N++ region 111, the Pwell region 103, and the heavily doped N++ region 112 constitute the main body of the tested ESD protection mechanism, which is an NPN transistor 308 in this embodiment. The base-emitter resistance 310 is the base-emitter resistance of the NPN transistor 308, which is connected with the base region, the cathode electrode 318, and the inversion channel switch 307 of the NPN transistor 308. The anode electrode 317 is the lead-out of the hole and the metal 114, which is the anode electrode of the tested ESD protection mechanism in this embodiment. The cathode electrode 318 is the lead-out of the hole and the metal 115, which is the cathode of the tested ESD protection mechanism.

[0069] The working states of the key components in the test process of the present embodiment are as follows:

[0070] ① The anode electrode 317 and the cathode electrode 318 are biased at a certain voltage Uak, and when Uak is less than the turn-on voltage of the tested ESD protection mechanism, no current flows through the anode electrode 317 and the cathode electrode 318, and there is also no current in the additional test device part 301 and the tested ESD protection mechanism part 302.

[0071] ② A sufficient voltage is applied to the hole and the metal 116, i.e. a voltage is applied to the heavily doped N++ region 110. When a certain threshold is reached, the switching transistor 304 is broken down, and the Nc gradual change capacitor region 104 and the Pwell region 102 of the energy storage capacitor 303 are only expanded as a barrier without breakdown, so that the structure of the energy storage capacitor 303 is not damaged.

[0072] ③ After the switching transistor 304 breaks down and conducts, the voltage is directly applied to the electrode 107 on the inversion oxide layer, forming an inversion channel, which causes the inversion channel switch 307 to conduct. Once the inversion channel switch 307 is turned on, an excitation current is generated and enters the tested electrostatic discharge protection mechanism 302 through the inversion channel switch 307. Inside the tested electrostatic discharge protection mechanism 302, the current flows through the base region emitter resistor 310 via the inversion channel switch 307 and then out through the cathode electrode 318. At this time, the base region potential rises, the NPN transistor 308 turns on, and a significant current appears between the anode electrode 317 and the cathode electrode 318.

[0073] ④ When a significant current is detected between the anode electrode 317 and the cathode electrode 318, the voltage applied to the electrode 316 of the additional testing device is disconnected. Due to the presence of the energy storage capacitor 303, the voltage will not disappear immediately. As mentioned above, due to the effective design of this invention, the potential barrier expanded by the Nc slow-changing capacitance region 104 and the Pwell region 102 of the energy storage capacitor 303 will shrink back as the voltage gradually decreases, and the stored charge will not be completely dissipated. At this time, a discharge RC network is formed on the RC and voltage divider resistors 305 / 306 paths. Even if the voltage source of the electrode 316 of the additional testing device is removed, there will still be an excitation current flowing into the electrostatic protection mechanism 302 under test, so that current continues to exist between the anode electrode 317 and the cathode electrode 318.

[0074] ⑤ As time progresses, the excitation current injected by the discharge RC network gradually decreases, and the voltage at the upper electrode 107 of the inversion oxide layer of the inversion channel switch 307 also gradually decreases. Through the voltage divider design of this invention, before the voltage of the energy storage capacitor 303 drops to zero, the voltage at the upper electrode 107 of the inversion oxide layer of the inversion channel switch 307 is already less than the opening threshold, and the inversion channel switch 307 actively closes, at which point the excitation current disappears.

[0075] ⑥ The sudden disappearance of the excitation current leads to two possible results. First, if the applied Uak is less than the sustaining voltage, the disappearance of the excitation current causes 308 to be unable to continue to maintain the on state. At this time, the current between the anode electrode 317 and the cathode electrode 318 disappears, and the entire electrostatic discharge protection mechanism 302 under test is turned off. Second, if the applied Uak is greater than the sustaining voltage, even if the excitation current disappears, the NPN transistor 308 continues to be turned on. At this time, the current between the anode electrode 317 and the cathode electrode 318 can still be detected. Since the inversion channel switch 307 can be completely turned off without the influence of external force, the additional test device 301 and the electrostatic discharge protection mechanism 302 under test do not affect each other at all. Therefore, this current is the accurate minimum sustaining current.

[0076] The additional testing device part 301 involved in the above flow is part of the core protection range of the present application. The tested electrostatic protection mechanism part 302 can be changed according to the actual situation, for example Figure 2 The tested electrostatic protection mechanism of the embodiment shown is different from Figure 1 , but the same effect can also be achieved by the method of the present application.

[0077] Next, the technical solution of the present application is illustrated by Figure 4 the embodiment of the present application is also effective for the silicon-based silicon-controlled static protection mechanism with the flyback feature.

[0078] Figure 4 Corresponding to Figure 2 The key parameter testing device of the silicon-controlled static protection mechanism with the flyback feature provided by the embodiment of the present application is shown. All components in the additional testing device part 401 in the dashed box are additional testing device parts, and all components in the tested electrostatic protection mechanism part 402 in the dashed box are tested electrostatic protection mechanism parts.

[0079] Similarly, corresponding to Figure 2The structure in the figure, the additional test device part electrode 416 corresponds to the heavily doped N++ region 210 and the hole and metal 216 thereon, and the main function is to lead out the connectable electrode. The Pwell region 202 and the Nc gradual change capacitor region 204 constitute the energy storage capacitor 403, and the main structure is the gradual change junction between the Pwell region 202 and the Nc gradual change capacitor region 204, and the main function is to store a certain amount of charge. The Nc gradual change capacitor region 204, the Pwell region 202, and the Nr resistance region 205 constitute the switching transistor 404, and the Pwell region 202 and the Nc gradual change capacitor region 204 on one side of the switching transistor 404 are gradual change junctions, and the Nr resistance region 205 has a doping concentration one to two orders of magnitude higher than the Nc gradual change capacitor region 204, and the Pwell region 202 and the Nr resistance region 205 are abrupt junctions in relative terms. When the heavily doped N++ region 210 applies a sufficient voltage to cause breakdown to open, the abrupt junction on one side of the Nr resistance region 205 and the Pwell region 202 breaks down first, and the gradual change junction on one side of the Nc gradual change capacitor region 204 and the Pwell region 202 expands but does not break down, so that the gradual change structure of the energy storage capacitor 403 can ensure that the energy storage capacitor 403 does not break down even in the open state of the switching transistor 404, thereby ensuring that the charge stored in the energy storage capacitor 403 is still stored in the capacitor and does not dissipate when the switching transistor 404 is open. The reverse type oxide layer upper electrode 207 and the Psw region 206 constitute the reverse channel switch 407, and when a certain voltage is applied to 407, a reverse channel is formed in the Psw region 206, causing the reverse channel switch 407 to open; when the applied voltage drops to a certain value, the reverse channel formed in the Psw region 206 cannot be maintained, so that the reverse channel switch 407 is turned off.

[0080] The RC and voltage dividing resistor 405 / 406 is a parasitic resistance formed inside the Nr resistance region 205.

[0081] The main function is to form an RC discharge circuit together with the energy storage capacitor 403, and the time constant is

[0082] τ=Cc×Rtot

[0083] Cc is the capacitance value of the energy storage capacitor 403, which can be adjusted by the area of the Nc gradual change capacitor region 204 to design the capacitance value; Rtot is the sum of the resistance values of the RC and voltage dividing resistor 405 / 406, which can be adjusted by the doping concentration and size of the Nr resistance region 205 to adjust the resistance value.

[0084] The second main function is voltage division. The voltage is applied to the upper electrode 207 of the inversion oxide layer from the position of the heavily doped N++ region 208, so that the inversion channel switch 407 composed of the upper electrode 207 of the inversion oxide layer and the Psw region 206 is turned off before the energy storage capacitor 403 is completely discharged. In the present application, it is a key point to ensure that the inversion channel switch 407 is turned off before the energy storage capacitor 403 is completely discharged, because only in this way can it be ensured that the thyristor type electrostatic protection mechanism part 402 is turned off spontaneously due to the disappearance of the test current, rather than the disappearance of the excitation current of the additional test device part 401.

[0085] As shown in Figure 2 , the heavily doped P++ region 222, the heavily doped N++ region 211, the Nwell region 221, the Pwell region 203, the heavily doped P++ region 213, and the heavily doped N++ region 212 constitute the main body of the tested electrostatic protection mechanism, i.e. the thyristor type electrostatic protection mechanism. As shown in Figure 4 In the embodiment, the PNPN thyristor composed of the nested NPN transistor 408 and PNP transistor 409 is the tested electrostatic protection mechanism 402. The 410 is the base-emitter resistance of the NPN transistor 408, which is connected with the base region of the NPN transistor 408, the cathode 417, and the inversion channel switch 407. The cathode 417 is the lead-out of the hole and metal 214, which is different from the previous example. In the present embodiment, it is the cathode of the tested electrostatic protection mechanism; the anode 418 is the lead-out of 215, which is the anode of the tested electrostatic protection mechanism in the present embodiment.

[0086] In the test process, the working states of the various key components in the present embodiment are as follows:

[0087] (1) The anode 418 and the cathode 417 are biased at a certain voltage Uak, and when Uak is less than the turn-on voltage of the tested electrostatic protection mechanism, no current flows through the anode 418 and the cathode 417, and there is also no current in the additional test device part 401 and the tested electrostatic protection mechanism part 402.

[0088] (2) A sufficient voltage is applied to the electrode 416 of the additional test device part, i.e. a voltage is applied to the heavily doped N++ region 210. When a certain threshold is reached, the switching transistor 404 breaks down, and the Nc gradual change capacitor region 204 and the Pwell region 202 of the energy storage capacitor 403 only expand as a barrier without breakdown, so the structure of the Pwell region 202 of the energy storage capacitor is not damaged.

[0089] (3) When the switch transistor 404 is turned on, the voltage is directly applied to the 207 to form a reverse channel, causing the reverse channel switch 407 to turn on. Once the reverse channel switch 407 is turned on, an excitation current is generated through the reverse channel switch 407 into the tested ESD protection mechanism part 402, specifically, through the base-emitter resistance 410 of the reverse channel switch 407 and then out of the cathode 417. At this time, the base potential of the NPN transistor 408 is raised, the NPN transistor 408 is turned on, and the PNP transistor 409 nested therein is also turned on, and then the entire PNPN thyristor is turned on, and a significant current appears between the cathode 417 and the anode 418.

[0090] (4) When a significant current is detected between the cathode 417 and the anode 418, the voltage applied by the electrode 416 of the additional test device part is turned off. Due to the presence of the energy storage capacitor 403, the voltage will not disappear immediately. As described above, due to the effective design of the present application, the Nc gradual capacitance region 204 and the Pwell region 202 of the energy storage capacitor 403 expand the barrier at this time, which shrinks with the gradual decrease of the voltage, and the stored charge will not be completely lost. At this time, a discharge RC network is formed on the RC and voltage dividing resistance 405 / 406 path, so that even if the voltage source of the additional test device part electrode 416 is removed, the excitation current still flows into the tested ESD protection mechanism part 402, so that the current between the cathode 417 and the anode 418 continues to exist.

[0091] (5) With the passage of time, the excitation current injected by the discharge RC network gradually decreases, and the voltage at the electrode 207 end of the reverse channel switch 407 on the reverse channel switch 407 gradually decreases. Through the voltage dividing design of the present application, before the voltage of the energy storage capacitor 403 drops to zero, the voltage at the electrode 207 end of the reverse channel switch 407 of the reverse channel switch 407 is already less than the opening threshold, and the reverse channel switch 407 is actively closed, at which time the excitation current suddenly disappears.

[0092] (6) The sudden disappearance of the excitation current leads to two possible results. First, if the applied Uak is less than the holding voltage, the disappearance of the excitation current causes the PNPN thyristor nested by the NPN transistor 408 and the PNP transistor 409 to no longer be able to continue to maintain the open state, at which time the current between the cathode 417 and the anode 418 disappears, and the entire tested ESD protection mechanism part 402 is closed; second, if the applied Uak is greater than the holding voltage, even if the excitation current disappears, the PNPN thyristor nested by the NPN transistor 408 and the PNP transistor 409 still continues to be turned on, at which time the current between the cathode 417 and the anode 418 can still be detected, and since the reverse channel switch 407 is completely closed at this time, the additional test device part 401 and the tested ESD protection mechanism part 402 do not affect each other.

[0093] Figure 5 The schematic diagram of the peripheral equipment and connection mode for testing the key parameters of the electrostatic protection mechanism with the flyback characteristic according to the embodiment of the present application is provided.

[0094] The detailed contents are explained in combination with Figure 3 、 Figure 4 According to Figure 5 、 Figure 3 、 Figure 4 , the additional testing device part 501 in Figure 5 is the additional testing device part 301 / 401 shown in Figure 3 、 Figure 4 , and the tested electrostatic protection mechanism part 502 is the tested electrostatic protection mechanism part 302 / 402 shown in Figure 3 、 Figure 4 .

[0095] The voltage excitation source 503 is connected to the control end of the additional testing device part 501, i.e. the metal 116, 216, through the double-end switch 508. The voltmeter 504 is also connected to the control end of the additional testing device part 501 through the other path of the double-end switch 508. The ammeter 505 is connected between the tested electrostatic protection mechanism part 502 and the anode terminal 507, which is the anode electrode 317, 418. Optionally, the ammeter 505 can also be connected between 502 and the cathode terminal 506, which is the cathode electrode 318, 417.

[0096] The selection and use of each peripheral equipment are related to the actual situation, and generally satisfy the following principles: the double-end switch 508 can be automatically controlled by a computer or manually controlled; the voltage excitation source 503 should be greater than the breakdown voltage of the switching transistor 304, 404, and the range of the voltmeter 504 should match the voltage excitation source 503; the range of the ammeter 505 is recommended to be between 100 microamperes and 100 milliamperes, but is not limited thereto.

[0097] Figure 6 The flowchart of the key parameter test of the electrostatic protection mechanism with the flyback characteristic according to the embodiment of the present application is provided.

[0098] S1: The test instruments including the voltage excitation source 503, the voltmeter 504 and the ammeter 505 are reset to zero, and the cathode terminal 506 and the anode terminal 507 are grounded to clear the charge of the parasitic capacitance.

[0099] S2: The voltage difference Uak is applied between the anode and the cathode of the tested electrostatic protection mechanism part 502.

[0100] S3: The voltage Usource of the voltage excitation source 503 is increased in a step or linear manner by the additional testing module voltage source.

[0101] S4: Until the current meter 505 of the main protection module shows a significant current, operate the double pole switch 508 manually or automatically to disconnect the additional test module voltage excitation source 503.

[0102] S5: Optionally use the voltage meter 504 to measure the additional test module port voltage value and draw a voltage time curve.

[0103] S6: Record the current meter 505 current value of the main protection module and draw a current time curve.

[0104] S7: If the current value shown in the current time curve falls back to zero and the tested electrostatic protection mechanism part 502 does not burn out, go to S8; if the current cannot spontaneously fall back to zero or the tested electrostatic protection mechanism part 502 burns out, go to S9 to end

[0105] S8: Record the current Uak value and continue to increase the voltage difference Uak between the anode terminal 507 and the cathode terminal 506 of the tested electrostatic protection mechanism part 502 according to a certain step. After multiple cycles, the voltage current curve is drawn.

[0106] Figures 7-9 The intermediate data of the key parameters of the electrostatic protection mechanism with a flyback feature provided by the embodiment of the present application and the reading method thereof are shown in the schematic diagram, which includes Figure 7 a voltage time schematic diagram, Figure 8 a current meter time schematic diagram, Figure 9 a schematic diagram of extracted minimum holding current voltage key parameters.

[0107] In combination with the foregoing Figure 3 , Figure 4 equivalent circuit schematic diagram, Figure 5 peripheral circuit schematic diagram, and Figure 6 flowchart schematic diagram, the following embodiment intermediate data and reading method are described, and all data points in the diagram are not specifically named, and are marked as numerical designations.

[0108] During the initial S0-S2 steps, the readings of the excitation source, voltage meter, and current meter are all zero.

[0109] During the S3 step, the excitation voltage source applies a voltage, and in the Figure 7 voltage time schematic diagram, the energy storage capacitor 304 / 404 is charged, and the time period from zero to the time point of the horizontal axis 701, the voltage shown in the excitation source changes from zero to the vertical axis voltage value of 701. Due to the existence of the energy storage capacitor 304 / 404, the slope is not high, and the influence of dv / dt is avoided. During this process, the current meter does not change and maintains zero value.

[0110] When S4 step, inFigure 8 The current meter shows a clear current at 801. The source 503 is switched to the voltage meter 504 at 701 to 702, i.e. 801 to 802, in computer automatic control mode or manual mode.

[0111] As shown in the voltage time diagram, after the initial sharp drop from 702, the voltage value slowly approaches 703.

[0112] As shown in the current diagram, although the source 503 is removed, the measured unit is able to maintain its opening due to the injection of current from the charge released from the energy storage capacitor 304 / 404 through the RC path. The current changes slightly from 802, but does not disappear.

[0113] The change curves of the voltage meter and the current meter are continuously recorded during the process, and a voltage time curve and a current time curve can be drawn at each cycle.

[0114] The recorded voltage and current continue to decrease, and two situations can occur:

[0115] The first situation is that the voltage slowly decreases to a certain non-zero value, such as Figure 7 703, and the current decreases to a certain value and suddenly disappears, such as Figure 8 803. At this time, it means that the current injected by the RC discharge circuit decreases to below the minimum holding current required by the tested ESD protection mechanism part 502 to maintain opening, and the tested ESD protection mechanism part 502 can no longer maintain opening. The current at the 803 point obtained at this time is the minimum holding current.

[0116] The second situation is that Figure 8 the current does not fall to zero or the device is burned out. This indicates that the tested ESD protection mechanism part 502 does not normally turn off, and the Uak at this time exceeds the back-through voltage.

[0117] In addition, it should be noted that if Figure 7 the voltage value falls to zero before the current disappears, it indicates that the tested ESD protection mechanism part 502 has prematurely turned off before completing the test of the tested ESD protection mechanism part 502, which is an undesirable situation. The simplest way to handle it is to increase the capacitance value of the energy storage capacitor 304 / 404 or to increase the RC and the voltage dividing resistor 306 / 406 to reduce 305 / 405 and thus increase the voltage divided by 306 / 406.

[0118] When a complete cycle of S2-S7 is finished, a complete voltage-time curve and a complete current-time curve can be drawn. The minimum holding current is read from the current-time curve, and the Uak voltage value applied at this time and the back-through voltage data are recorded. The minimum holding current and Uak voltage value data form a data point in the Uak-Umin curve, as shown by example 901. Figure 9

[0119] If the current falls to zero and the tested protection unit is not burned out, the Uak is increased according to the actual situation with a step precision, and the cycle is repeated, as shown by examples 902 and 903.

[0120] When the current does not fall to zero, as shown by examples 904, 905 and 906 in Figure 9 , it means that Uak is greater than the minimum back-through voltage, and the 902 after excitation can still maintain conduction when 901 is completely closed. The true minimum back-through voltage is between the voltage values shown by the horizontal axes of 903 and 904, and the true minimum holding current is the current value shown by the vertical axes of 904, 905 and 906 (the current values of 904, 905 and 906 are basically the same).

[0121] Thus, the method disclosed in the present application finally obtains the key parameters of the electrostatic protection mechanism with the back-scan characteristic: the minimum back-through voltage and the minimum holding current.

[0122] As can be seen from the above examples, the method disclosed in the present application not only overcomes the method that the minimum back-through voltage and the minimum holding current are not easy to directly measure, but also does not use expensive and complex test equipment such as TLP or power semiconductor scanners. At the same time, the voltage and current change during the test are relatively gentle, avoiding the influence of dv / dt and inductive impact, and the measurement has good repeatability, solving the problem that the measurement results are greatly different between different devices and different methods in the current test back-through type electrostatic protection mechanism field, and the problem that it is inconvenient to evaluate.

[0123] On the basis of the structural schematic diagram, Figures 1-2 in order to more directly show the composition of the device, Figures 10-11 an embodiment of a three-dimensional structure of a test device for the key parameters of the MOSFET type and thyristor type electrostatic protection mechanism with the back-scan characteristic in specific application cases is provided.

[0124] The three-dimensional structure of the test device for the key parameters of the MOSFET type electrostatic protection mechanism with the back-scan characteristic is shown in example 901. Figure 10

[0125] ​​The substrate 1001 is a N-type semiconductor doped with phosphorus. The Nc gradual capacitance region 1004 is formed in the Pwell region 1002 and doped with phosphorus or arsenic with a doping concentration of 1.75E17. In this embodiment, the actual number of Nc gradual capacitance regions is 4 to ensure that the capacitance is large enough.

[0126] The Nr resistance region 1005 is formed in the Pwell region 1002 and doped with phosphorus or arsenic with a doping concentration of 2.05E18.

[0127] The Psw region 1006 is formed in the substrate 1001 and doped with boron. The Nr resistance region 1005 and the Pwell region 1003 are connected to the Psw region 1006. The upper electrode of the reverse type oxide layer 1007 can form a reverse layer in the Psw region 1006 under a certain voltage. The upper electrode of the reverse type oxide layer 1007 is not electrically connected to the Psw region 1006, but is electrically connected to the heavily doped N++ region 1008 through a via and a metal. In this embodiment, the upper electrode of the reverse type oxide layer 1007 is prepared at the same time as the MOSFET gate 1009 to simplify the process and reduce the cost.

[0128] The heavily doped N++ regions 1008 / 1010 / 1011 / 1012 are N-type semiconductor heavily doped regions, and the heavily doped P++ region 1013 is a P-type semiconductor heavily doped region. The surface of the heavily doped P++ region 1013 has a silicide process.

[0129] The Pwell region 1002, the Nc gradual capacitance region 1004, the Nr resistance region 1005, the heavily doped N++ regions 1008 / 1010, the heavily doped N++ region 1008, the Psw region 1006, the upper electrode of the reverse type oxide layer 1007, and the metal connection as shown constitute the main body of the test device for the key parameters of the static protection mechanism with the back-scan feature, which is referred to as the additional test device part.

[0130] The Pwell region 1003, the heavily doped N++ regions 1011 / 1012, the heavily doped P++ region 1013, and the MOSFET gate 1009 constitute the silicon-based MOSFET type static protection mechanism to be tested by the first embodiment of the present application, which is included in the concept of the tested static protection mechanism part.

[0131] The hole and the metal 1014 are the anode of the tested static protection mechanism part, the hole and the metal 1015 are the cathode of the tested static protection mechanism part, and the hole and the metal 1016 are the test terminal of the additional test device part.

[0132] The three-dimensional structure of the test device for the key parameters of the static protection mechanism with the back-scan feature of the silicon-controlled rectifier typeFigure 11 as shown.

[0133] The substrate 1101 is N type semiconductor doped with phosphor, in which a Pwell region 1102 / 1103 doped with boron is formed, and an Nwell region 1121 doped with phosphor or arsenic is formed.

[0134] An Nc gradual capacitance region 1104 doped with phosphor or arsenic is formed in the Pwell region 1102, with a doping concentration of 1.75E17. In this embodiment, in order to ensure that the capacitance value is large enough, the actual number of Nc gradual capacitance regions is 4. The Nc gradual capacitance region 1104 and the Pwell region 1102 form a capacitance with a gradual junction, which is not prone to breakdown and burnout, and has good functions of storing charge and storing energy.

[0135] An Nr resistance region 1105 doped with phosphor or arsenic is formed in the Pwell region 1102, with a doping concentration of 2.05E18.

[0136] A Psw region 1106 doped with boron is formed in the substrate 1101 and is connected to the Nr resistance region 1105 and the Pwell region 1103. The upper electrode of the inversion layer 1107 can form an inversion layer in the Psw region 1106 under a certain voltage. The upper electrode of the inversion layer 1107 is not electrically connected to the Psw region 1106, but is electrically connected to the heavily doped N++ 1108 through a via and a metal.

[0137] The heavily doped N++ 1108 / 1110 / 1111 / 1112 is N type semiconductor heavily doped, and the heavily doped P++ 1113 / 1122 is P type semiconductor heavily doped, with a doping concentration of 1E19 to 1E20, and a silicide process on the surface thereof.

[0138] The Pwell region 1102, the Nc gradual capacitance region 1104, the Nr resistance region 1105, the heavily doped N++ 1108 / 1110, the heavily doped N++ 1108, the Psw region 1106, the upper electrode of the inversion layer 1107, and the metal as shown together constitute a main body of a test device for key parameters of an electrostatic protection mechanism with a flyback characteristic according to the second embodiment of the present application, referred to as an additional test device part.

[0139] The Pwell region 1103, the Nwell region 1121, the heavily doped N++ 1111 / 1112, and the heavily doped P++ 1113 / 1122 constitute a silicon-based thyristor type electrostatic protection mechanism to be tested according to the second embodiment of the present application, which is included in the concept of a tested electrostatic protection mechanism part.

[0140] The hole and metal 1114 are cathodes of the tested electrostatic protection mechanism part, the hole and metal 1115 are anodes of the tested electrostatic protection mechanism part, and the hole and metal 116 are test terminals of the additional testing device part.

[0141] In summary, the application discloses a novel testing device and method for key parameters of an electrostatic protection mechanism with a back-scan feature. In terms of structure, the Pwell region, the Nc gradual capacitance region, the Nr resistance region, the heavily doped N++, the heavily doped N++, the Psw region, the upper electrode of the inversion oxide layer, and the metal connection together constitute the main body of the testing device for key parameters of the electrostatic protection mechanism with the back-scan feature. An equivalent circuit is formed, including the electrode pair of the additional testing device part corresponding to the heavily doped N++ region and the hole and metal thereon, which mainly functions to lead out connectable electrodes. The Pwell region and the Nc gradual capacitance region constitute an energy storage capacitor, and the main structure thereof is the gradual junction between the Pwell region and the Nc gradual capacitance region. The Nc gradual capacitance region, the Pwell region, and the Nr resistance region constitute a switching transistor, and the Pwell region and the Nc gradual capacitance region of the switching transistor are on one side of the gradual junction. The upper electrode of the inversion oxide layer and the Psw region 106 constitute an inversion channel switch. The RC and the voltage dividing resistor constitute a parasitic resistance formed in the Nr resistance region. In combination with a series of testing methods disclosed by the application, including peripheral equipment and connection modes for testing key parameters of the electrostatic protection mechanism with the back-scan feature, a testing process and steps, intermediate data in the testing, and a reading method thereof, the minimum back-through voltage and the minimum holding current of the electrostatic protection mechanism with the back-scan feature are tested.

[0142] Compared with the prior art, first, the application overcomes the defect that the minimum back-through voltage and the minimum holding current are not easy to be directly measured, and can directly measure the minimum back-through voltage and the minimum holding current of the electrostatic protection mechanism with the back-scan feature. Second, the application breaks away from the dependence on high-end power semiconductor scanners and TLP testing systems, and uses common basic equipment instead of expensive and complex testing equipment such as TLP or power semiconductor scanners. Third, the voltage and current change during the testing process are relatively gentle, avoiding the influence of dv / dt and inductive impact, and the measurement result is stable, and the consistency and repeatability of the measurement are good.

[0143] With the disclosed technology, first, the minimum back-through voltage and minimum maintaining current of the back-scan characteristic electrostatic protection mechanism can be tested only by using common voltage source, ammeter and voltmeter, which greatly reduces the testing difficulty of the minimum back-through voltage and minimum maintaining current of the back-scan characteristic electrostatic protection mechanism. Second, when implemented in large-scale chip testing, the minimum back-through voltage and minimum maintaining current of the back-scan characteristic electrostatic protection mechanism can be tested by using existing common basic equipment without increasing the manufacturing cost of additional testing devices, which greatly reduces the testing cost of the minimum back-through voltage and minimum maintaining current of the back-scan characteristic electrostatic protection mechanism, and makes it possible to test the minimum back-through voltage and minimum maintaining current of the back-scan characteristic electrostatic protection mechanism on a large scale. Third, the disclosed technology does not affect the testing results due to the use of different testing devices, solves the problem of large differences between the measurement results of different devices and different methods in the current testing of back-through electrostatic protection mechanisms, and is convenient for evaluation, which can produce great beneficial effects in the production, acceptance and sales links.

Claims

1. A testing device for key parameters of an electrostatic protection mechanism with retrace characteristics, characterized in that: The main body of the test device, namely the additional test module, consists of the first Pwell region, the Nc slowly changing capacitor region, the Nr resistor region, the first heavily doped N++, the second heavily doped N++, the Psw region, the electrode on the inversion oxide layer, and the metal connection, which together form the key parameters of the electrostatic discharge (ESD) protection mechanism with retracement characteristics. The second Pwell region is formed by heavy doping to constitute the ESD protection mechanism under test. Specifically, the second Pwell region, the heavily doped N++, the heavily doped P++, and the MOSFET gate constitute the silicon-based MOSFET-type ESD protection mechanism under test, or the second Pwell region, the Nwell region, the heavily doped N++, and the heavily doped P++ constitute the silicon-based thyristor-type ESD protection mechanism under test. The Nc gradually changing capacitor region and the Nr resistive region are disposed in the first Pwell region. The first heavily doped N++ is disposed in the Nc gradually changing capacitor region, and the second heavily doped N++ is disposed in the Nr resistive region. The Psw region is connected to the Nr resistive region and the second Pwell region. The electrode on the inversion oxide layer can form an inversion oxide layer in the Psw region under a predetermined voltage. The electrode on the inversion oxide layer is not electrically connected to the Psw region, but is connected to the second heavily doped N++ through a metal connection.

2. The testing device for key parameters of an electrostatic protection mechanism with retrace characteristics according to claim 1, characterized in that: The substrate is a phosphorus-doped N-type semiconductor with a doping concentration of 1E15 to 1E17; a boron-doped Pwell region is formed in the substrate with a doping concentration of 5E16 to 5E18. A phosphorus- or arsenic-doped Nc slow-changing capacitor region is formed in the first Pwell region, with a doping concentration of 5E16 to 5E18; a phosphorus- or arsenic-doped Nr resistor region is formed in the first Pwell region, with a doping concentration of 5E16 to 5E18. A boron-doped Psw region is formed in the substrate with a doping concentration of 2.5E17 to 2.5E18.

3. The testing device for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 1, characterized in that: The number of Nc gradually changing capacitor regions is not limited, and the Nc gradually changing capacitor regions and the first Pwell region form a capacitor with a gradually changing junction. The primary goal is to ensure that the Nr resistance region meets the resistance design requirements as a diffusion resistor. The secondary goal is to ensure that the capacitance formed by the Nc gradually changing capacitor region and the first Pwell does not break down. The capacitance value of the capacitor formed by the Nc gradually changing capacitor region and the first Pwell is adjusted in size and position while ensuring the above conditions are met.

4. The testing device for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 1, characterized in that: The first hole and metal lead-out are the cathode of the electrostatic discharge protection mechanism under test, the second hole and metal lead-out are the anode of the electrostatic discharge protection mechanism under test, and the third hole and metal lead-out are the test terminals of the additional test device.

5. The testing device for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 1, characterized in that: The resulting equivalent circuit includes: The electrodes of the additional test device correspond to the first heavily doped N++ region and the third hole and metal thereon. Their main function is to lead out connectable electrodes. The first Pwell region and the Nc gradually changing capacitor region constitute the energy storage capacitor, whose main structure is the gradually changing junction between the Pwell region and the Nc gradually changing capacitor region. The Nc gradually changing capacitor region, the first Pwell region, and the Nr resistor region constitute the switching transistor. The first Pwell region and the Nc gradually changing capacitor region of the switching transistor form a gradually changing junction on one side. The electrode on the inversion oxide layer and the Psw region constitute an inversion channel switch; RC and voltage divider resistors are parasitic resistances formed within the Nr resistance region.

6. The testing device for key parameters of an electrostatic protection mechanism with retrace characteristics according to claim 5, characterized in that: In the equivalent circuit: The doping concentration in the Nr resistive region is one to two orders of magnitude higher than that in the Nc slowly changing capacitor region. When a predetermined voltage is applied to the electrode on the inversion oxide layer, an inversion channel is formed in the Psw region, causing the inversion channel switch to open; when the applied voltage drops to a certain value, the formation of the inversion channel in the Psw region cannot be maintained, thus turning off the inversion channel switch. The RC and voltage divider resistors, together with the energy storage capacitor, form an RC discharge circuit. On the other hand, the voltage is divided in the RC discharge circuit, and part of the voltage is applied to the upper electrode of the inversion oxide layer.

7. A test method for key parameters of the electrostatic protection mechanism with retrace characteristics based on the device described in any one of claims 1-6, characterized in that: The voltage excitation source is connected to the control terminal, i.e., the test terminal, of the additional test device via a double-ended switch; the voltmeter is also connected to the control terminal of the additional test device via the other path of the double-ended switch; the ammeter is connected between the electrostatic protection mechanism under test and the anode terminal; alternatively, the ammeter can be connected between the anode and cathode terminals.

8. The test method for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 7, characterized in that: The steps include: S0: Start; S1: The test instruments include a voltage excitation source, a voltmeter, and an ammeter. The cathode and anode terminals are grounded to clear the parasitic capacitance charge. S2: Apply a voltage difference Uak between the anode and cathode of the electrostatic protection mechanism being tested; S3: The additional test module voltage source increases the voltage Usource of the voltage excitation source in a step-by-step or linear manner; S4: Until the ammeter of the main protection module shows a significant current, manually or automatically operate the double-ended switch to disconnect the voltage excitation source of the additional test module. S5: Selectively use a voltmeter to measure the port voltage of the additional test module and plot the voltage-time curve; S6: Record the current value of the ammeter of the main protection module and plot the current-time curve; S7: If the current value displayed in the current-time curve drops back to zero and the tested electrostatic discharge protection mechanism is not burned out, proceed to S8; if the current cannot drop back to zero spontaneously or the tested electrostatic discharge protection mechanism is burned out, proceed to S9. S8: Record the current Uak value, and continue to increase the voltage difference Uak between the anode terminal and the cathode terminal of the electrostatic protection mechanism (502) under test in a certain step; after multiple cycles, complete the plotting of the voltage and current curve; S9: End.

9. The test method for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 8, characterized in that: Key parameters including minimum sustaining current voltage and minimum sustaining current are extracted from the voltage-time, ammeter-time, and voltage-current curve results.

10. The test method for key parameters of the electrostatic protection mechanism with retrace characteristics according to claim 9, characterized in that: During the initial S0-S2 steps, the readings of the excitation source, voltmeter, and ammeter are all zero; In step S3, the excitation voltage source applies voltage, and the voltage displayed in the excitation source changes from the vertical axis voltage value that changes from zero. When S4, a significant current appears in the ammeter in the current-time diagram. The excitation source is switched to the voltmeter by computer automatic control or manual method. The voltage-time diagram shows that after an initial sharp drop, the voltage value gradually decreases. Although the excitation source is removed in the current diagram, the current change decreases slightly but does not disappear; During this process, the change curves of the voltmeter and ammeter are continuously recorded, and a voltage-time curve and a current-time curve can be plotted in each cycle. The voltage decreases slowly to a certain non-zero value and then stops decreasing, while the current decreases to a certain value and then suddenly disappears; the non-zero current obtained at this point is the minimum holding current. Alternatively, the current may not have returned to zero or a device may have burned out. When a complete cycle of S2-S7 is completed, a complete voltage-time curve and a complete current-time curve can be plotted. The minimum sustaining current is read from the current-time curve, and the applied Uak and the back-through voltage data are recorded. The minimum sustaining current and Uak voltage values ​​form a data point of the voltage-current curve. If the current drops back to zero and the tested protection unit is not burned out, increase the step accuracy of Uak according to the actual situation and repeat the cycle. Until the current fails to drop back to zero, the actual minimum breakdown voltage is between the zero and non-zero values ​​shown on the horizontal axis, and the actual minimum sustaining current is between the zero and non-zero values ​​shown on the vertical axis. Thus, the key parameters of the electrostatic protection mechanism with backflip characteristics were finally obtained: minimum backflip voltage and minimum holding current.

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