Experimental and numerical study of the emitter turn-off thyristor(ETO)

The emitter turn-off thyristor (ETO) is a new family of high power semiconductor devices that is suitable for megawatt power electronics application. ETOs with voltage and current ratings of 4-6 kV and 1-4 kA, have been developed and demonstrated. And those power levels are the highest in silicon power devices and are comparable to those of the gate turn-off thyristor (GTO). Compared to the conventional GTO, the ETO has much shorter storage time, voltage controlled turn-off capability, and much larger reverse biased safe operation area (RBSOA). Furthermore, ETOs have a forward-biased safe operation area (FBSOA) that enables it to control the turn-on di/dt similar to an insulated gate bipolar transistor (IGBT). These combined advantages make the ETO based power system simpler in terms of dv/dt snubber, di/dt snubber, overcurrent protection, resulting in significant savings in the system cost. This paper presents experimental and numerical results that demonstrate the advantages of the ETO     

The di/dt capability of thyristors

This paper describes an experimental investigation of the di/dt failure mechanism of thyristors. The location of the initial turn-on region and the spread of the "on" region were observed on a specially designed thyristor having many monitoring electrodes. The turn-on process was studied for triggering by gate, by breakover, and by dv/dt. In many cases it was found that turn-on occurred at almost the same region, whether it was triggered by breakover or by dv/dt. This area coincided with the final holding position in the turn-off process. The di/dt capability of the thyristor was measured. It was found that the capabilities were almost the same for the three triggering methods. The destruction temperature in the di/dt test was estimated from the area of the burn-out spots and the energy dissipation.     

High-power dual amplifying gate light triggered thyristors

The feasibility of directly light triggering a high power phase control thyristor is investigated. Work is described on an optically triggered gated 53-mm diameter 2600-V 1000-A thyristor which is similar to an electrically gated production version. Test results describing the response of this thyristor to various optical signals are presented. Our work has shown that this cell can be directly triggered by light at an equivalent gate current which is a factor of three below its present dynamic gate requirements and still largely retain all its blocking and dynamic characteristics. This improvement is obtained by the use of a second very sensitive amplifying gate stage which is responsive to light. All wafer processing of the light sensitive thyristor was carried out on standard production lines. Tests made on static dV/dt, di/dt, blocking voltage, and leakage current on light sensitive devices all closely match parameters of the standard electrically fired equivalent cell.     

High-energy pulse-switching characteristics of thyristors

Experiments were conducted to study the high energy, high di/dt pulse-switching characteristics of silicon controlled rectifiers (SCRs) with and without the amplifying gate. High di/dt, high-energy single-shot experiments were first done. Devices without the amplifying gate performed much better than the devices with the amplifying gate. A physical model is presented to describe the role of the amplifying gate in the turn-on process, thereby explaining the differences in the switching characteristics. The turn-on area for the failure of the devices was theoretically estimated and correlated with observations. This allowed calculation of the current density required for failure. Since the failure of these devices under high di/dt conditions was thermal in nature, a simulation using a finite-element method was performed to estimate the temperature rise in the devices. The results from this simulation showed that the temperature rise was significantly higher in the devices with the amplifying gate than in the devices without the amplifying gate. From these results, the safe operating frequencies for all the devices under high di/dt conditions was estimated. These estimates were confirmed by experimentally stressing the devices under high di/dt repetitive operation     

Progress in light activated power thyristors

Light activated power thyristors would have considerable advantages in intermediate- and high-voltage circuits, as power and trigger circuits could be electrically separated by use of glass fiber cables. Besides high-voltage capability, such devices must have turn-on delay times, dv/dt capabilities, and di/dt stabilities which are comparable to conventionally fired thyristors. The necessary trigger power, however, has to be kept low enough to enable firing with GaAs light emitters, which are available now or will be in the near future. The dv/dt sensitivity is an essential limitation for the reduction of the minimum necessary trigger power. Optimizing of the thyristor emitter shunts results in an already acceptable compromise, but much better results can be obtained by a gate structure which actively compensates dv/dt fault triggering. Our test devices show good turn-on behavior. A short survey on different GaAs-light sources and the coupling problem is given.     

Inverter light triggered thyristor with unique arm-structure amplifying gate

A 1200-V 200-A directly light triggered thyristor suitable for inverter application has been developed. A new amplifying gate design with a second amplifying stage was used in achieving a factor of 15 to 50 increase in gate sensitivity without any loss indV/dtcapability and only a small (less than a factor of two) reduction in devicedi/dtrating, despite a ten times smaller initial turn-on line length. In all, three versions were made with gate threshold currents down to 1 mA anddV/dtcapabilities to 1000 V/µs. All three types had 60-Hz di/dt capabilitLes of about 250 A/µs at 125 deg TJand turn-off times of approximately 25 µs. The new light sensitive amplifying gate stage design features a gate thyristor region with extending arms for high gate sensitivity, the inner portion of which is just large enough to accommodate initial on-region spreading duriag the short on-time of the gate stage. The arms increase gate sensitivity while contributing very little to the overalldV/dtcurrent. The turn-on speed can be accounted for by most of the inner region being turned on by the photogate pulse. Like regular electrically fired thyristors, a gate overdrive factor is important. With these devices an overdrive factor of about 3 to 5 is needed for highdi/dtturn-on whereas in an electrically triggered device this factor is closer to 10.     

Low-loss high-speed switching devices, 2300-V 150-A static induction thyristor

Focussing attention to the performance of high-speed high off-state voltage and large current provided in the buried-gate-type static induction (SI) thyristor, a 2300-V 150-A low-voltage-drop high-speed medium-power SI thyristor was developed. Irrespective of the magnitude of switching current, the SI thyristor has the characteristics of fast turn-on time and less on-gate current compared to that of the GTO thyristor. The characteristics of this SI thyristor obtained as the result of manufacturing this prototype were such that the forward blocking voltage was 2300 V at a gate reverse voltage of -5 V, the reverse blocking voltage was 2350 V, and the forward voltage drop was 1.4 V at an anode current of 150 A and 2.2 V at an anode current of 450 A. The switching characteristics were such that the turn-on time was 1.5 µs when an anode current IAof 150 A becomes ON, turnoff time was 2.5 µs at IA= 100 A and 3.6 µs at IA= 200 A. This SI thyristor is able to break the anode current of 1000 A at a gate current of 95 A. Performance exceeding 1100 A/µs was confirmed for the di/dt capability and even for dv/dt, and these normally can be operatable even at 100 times higher current compared with maximum average current.     

Observation of turn-on action in a gate-triggered thyristor using a new microwave technique

The turn-on action by the p-base and n-emitter gates in a thyristor was studied by a new microwave technique. The initial conducting area, the lateral distribution of gate current flowing through the junction, and the time variation of excess carrier density injected into the n-base by the gate current were determined by measuring the reflection of microwave energy, vertically incident upon a small area (0.2 × 0.2 mm²) of the n-emitter layer. The new microwave technique has proved to be useful in designing new gate structures and in studying the operation of new devices.     

Computer-aided experimental investigation of the correct turn-on in thyristors with amplifying gate

A 2-dimensional computer model has been developed for the analysis of the amplifying gate thyristors correct turn-on at the auxiliary emitter prior to the main one. The results of investigation were used in the design of devices having essentially the same di/dt high capability in any possible turn-on conditions.     

提高晶闸管器件对di/dt的耐受能力的途径

介绍了晶闸管器件的通态电流上升率di/dt参数及其损坏晶闸管器件的机理，并进一步介绍了提高晶闸管器件的通态di/dt耐量的设计和工艺方法，及应用过程中限制晶闸管阳极电路的电流上升率，保护晶闸管器件的方法。     

An emitter switched thyristor with base resistance control

An MOS-gated emitter-switched thyristor structure with base resistance control, which combines the best features of both the emitter-switched thyristor (EST) and the base-resistance-controlled thyristor (BRT), is reported. With this structure, it is possible to obtain turn-off (dynamic) current densities above the static latch-up current density of the parasitic thyristor in the EST, while preserving its unique current saturation capability. It has been experimentally demonstrated for 600 V forward blocking devices that the maximum controllable current density under dynamic conditions is a function of both the gate bias and the dimensions of the N⁺ floating emitter. Turn-off measurements have demonstrated that the new structure has a maximum controllable current density of over 2.5 times that for the EST structure without base resistance control     

Theoretical and experimental characteristics of the base resistancecontrolled thyristor (BRT)

Described are the characteristics of a new MOS gated thyristor structure called the base resistance controlled thyristor (BRT), in which the turn-off of a thyristor built with an N drift region is achieved by reducing the resistance of the p-base region under MOS gate control. A p-channel MOSFET used to achieve turn-off is formed in the N drift region. The device is designed so that, when the p-channel MOSFET is switched on, holes are diverted from the p-base region of the thyristor into the adjacent p⁺ region, raising the holding current of the thyristor above the operating current level, and turning off the thyristor. Results of extensive 2-D numerical simulations that have been performed to demonstrate operation of this new device concept are discussed. Experimental results on 600-V devices fabricated with an IGBT process have corroborated theoretical predictions. Current densities above 900 A/cm² have been turned off at room temperature with a gate bias of -10 V     

High dI/dT light-triggered thyristors

Directly light-triggered, 4000- and 6000-V thyristors were designed, fabricated, and tested to obtain high performance in dI/dt, dV/dt, and photosensitivity. Built-in resistors protected both auxiliary stages during high dI/dt turn-on. The novel use of etched moats to define the resistors was compatible with an optical gate structure that gives high dV/dt and good photosensitivity. No additional processing steps were needed to fabricate these devices, as compared to standard light-triggered thyristors. A record value of 1000 A/µs at 60 Hz was measured on a 6000-V thyristor, and 850 A/µs was safely triggered with only 1.8 mW of light. The dV/dt immunity of the photogate structure measured 4000 V/µs, rising exponentially to 80 percent of 4000 V, VDRM. Thyristors triggered by dV/dt were not destroyed. A new model of resistor heating was combined with the first measurements of the current pulses through both built-in resistors to identify the mechanism responsible for occasional burn-out of the second resistor. The failure mechanism was conductivity modulation in the surface of the resistor during its microsecond on-time caused by thermally generated carriers. The test results confirmed the utility of built-in resistors for high dI/dt performance with minimal light power and for nondestructive dV/dt triggering.     

金属氧化物半导体控制晶闸管的di/dt优化

金属氧化物半导体控制晶闸管(MCT)相比于绝缘栅双极型晶体管(IGBT)具有高电流密度、低导通压降和快速开启等优势,在高压脉冲功率领域具有广阔的应用前景.作为脉冲功率开关,MCT开启过程对输出脉冲信号质量有很大影响.采用理论分析并结合仿真优化重点研究了MCT开启瞬态特性.通过对MCT开启过程进行详细地理论分析推导,给出了MCT开启过程中阳极电流和上升时间的表达式.结合Sentaurus TCAD仿真优化,将MCT开启过程中电流上升速率(di/dt)由40 kA/s提升至80 kA/s,极大地改善了器件开启瞬态特性.最后,总结提出了提高器件开启瞬间di/dt的设计途径.     

Optical drive requirements for laser-activated semiconductor switches

Laser-activated semiconductor switch (LASS) devices of the thyristor type exhibit three regimes of operation. At low optical drive, optical triggering is obtained with delay time before conduction and relatively low current rise rates. At intermediate drive levels, fast switching is obtained with no appreciable delay time and fast current rise rates (greater than 10⁹A/s) but with substantial power lost in the switch element. At higher optical drives, saturated switching is observed with the rise rate and power loss relatively independent of the optical drive level. LASS thyristors of 1- and 4-kV operating voltage ratings have been characterized in the lossy fast switching regime. For pulses of 100-ns duration, the devices act as resistive elements. The magnitude of the resistance varies inversely with the optical drive, and can be understood as conductivity modulation of the conduction path by the photogenerated carriers. Such characterization allows switch system design tradeoff between the required optical drive level and the tolerable power loss in the switch elements.     

Vertical channel field-controlled thyristors with high gain and fast switching speeds

A new, planar, surface-grid, field-controlled thyristor (FCT) structure is described. The structure is fabricated by using orientation-dependent (preferential) etching and selective vapor epitaxial growth to obtain vertical grid walls. The resulting high channel-length-to-width aspect ratio produces devices with high blocking gains and fast gate turnoff speeds. Devices have been fabricated with the capability of blocking more than 1000 V with an applied grid bias of 32 V, and simultaneously exhibiting a low forward voltage drop in the on-state. These surface-grid devices exhibit gate turnoff capability with turnoff times of less than 500 ns at a rated cathode-anode current of 1 A.     

New insulated-gate thyristor structure with MOSFET coupled baseregions

A new insulated-gate thyristor (IGTH) structure in which the base of n-p-n transistor is coupled to the base of p-n-p transistor through a MOSFET is described for the first time, In the new structure, called base coupled insulated gate thyristor (BC-IGTH), the parasitic lateral p-n-p carrier injection inherent in previously reported thyristor structures such as the MCT, BRT, and IGTH is absent. The absence of parasitic lateral p-n-p carrier injection results in low on state voltage drop and high controllable current capability for this structure. The turn-on process in the new structure is fundamentally different from other MOS-gated thyristor structures in that in the new structure, the higher gain n-p-n transistor is turned-on first, which then provides the base drive for the lower gain p-n-p transistor. Multicellular 800 V devices of the new thyristor structure were fabricated using a double-diffused DMOS process, and were found to give on-state drop of 1.1 V at 200 A/cm², and controllable currents in excess of 100 A/cm² were obtained by forming MOS-gate controlled emitter-to-base resistive shorts     

Two-dimensional computer design of dual-ring thyristors

The main 2-dimensional equations are presented for the basic computer model of dual-ring amplifying gate thyristors (d.r.t.). These criteria ensure the maintenance of the very high di/dt capability of these devices in any possible triggering conditions.     

一种新的GCT门-阴极图形的设计方法

在分析门极可关断晶闸管(GTO)和门极换流晶闸管(GCT)门-阴极结构的基础上,依据GCT关断时的换流机理,提出了一种新的GCT门-阴极图形的设计方法.与现有的GCT门-阴极图形相比,用该方法设计的门-阴极图形,在保证开关过程中电流均匀分布的前提下,可增加GCT的有效阴极面积,减小热阻,并提高电流容量.     

High-voltage current saturation in emitter switched thyristors

Current saturation at high voltages in MOS-gated emitter switched thyristors (ESTs) is demonstrated. It is shown that by using an improved EST structure containing a dual-channel lateral MOSFET, the thyristor current can be saturated to high voltages through MOS gate control. In experimental devices with 600-V forward blocking capability, it is observed that current densities of 110 A/cm² could be saturated up to 450 V with a gate bias of 3.5 V. Experimental measurements and numerical simulations indicate that, during current saturation, the voltage appears across the junction between the P-base region and the N^- drift region and not across the lateral MOSFET