ESD robustness of thin-film devices with different layout structures in LTPS technology

The electrostatic discharge (ESD) robustness of different thin-film devices, including three diodes and two thin-film transistors (TFTs) in low-temperature polysilicon (LTPS) technology, is investigated. By using the transmission line pulse generator (TLPG), the high-current characteristics and the secondary breakdown current (It2) of these thin-film devices are observed. The experimental results with different parameters and layout structures of these LTPS thin-film devices have been evaluated for optimizing ESD protection design for liquid crystal display (LCD) panel.     

ESD implantation for subquarter-micron CMOS technology to enhance ESD robustness

A new electrostatic discharge (ESD) implantation method is proposed to significantly improve ESD robustness of CMOS integrated circuits in subquarter-micron CMOS processes, especially the machine-model (MM) ESD robustness. By using this method, the ESD current is discharged far away from the surface channel of nMOS, therefore the nMOS (both single nMOS and stacked nMOS) can sustain a much higher ESD level. The MM ESD robustness of the gate-grounded nMOS with a device dimension width/length (W/L) of 300 /spl mu/m/0.5 /spl mu/m has been successfully improved from the original 450 V to become 675 V in a 0.25-/spl mu/m CMOS process. The MM ESD robustness of the stacked nMOS in the mixed-voltage I/O circuits with a device dimension W/L of 300 /spl mu/m/0.5 /spl mu/m for each nMOS has been successfully improved from the original 350 V to become 500 V in the same CMOS process. Moreover, this new ESD implantation method with the n-type impurity can be fully merged into the general subquarter-micron CMOS processes.     

Technology design for high current and ESD robustness in a deepsubmicron CMOS process

The intrinsic ESD/EOS robustness of a technology is determined by the sensitivity to thermal initiated second breakdown. We show, for the first time, high current and ESD robustness results for a deep submicron CMOS technology with drawn poly gate lengths of 0.35 μm and oxide thicknesses down to 4.5 nm. It is shown that a transistor design window can be determined for optimized drive current and good robustness, while maintaining low off currents. An important observation is that robustness increases for smaller channel lengths and is directly proportional to the transistor drive current. Hence, robust deep submicron technologies can be designed with optimized transistor performance without using additional masks or increasing process complexity     

New layout design for submicron CMOS output transistors to improve driving capability and ESD robustness

New layout design to effectively reduce the layout area of CMOS output transistors but with higher driving capability and better ESD reliability is proposed. The output transistors of large device dimensions are assembled by a plurality of the basic layout cells, which have the square, hexagonal or octagonal shapes. The output transistors realized by these new layout styles have more symmetrical device structures, which can be more uniformly triggered during the ESD-stress events. With theoretical calculation and experimental verification, both higher output driving/sinking current and stronger ESD robustness of CMOS output buffers can be practically achieved by the proposed new layout styles within a smaller layout area in the non-silicided bulk CMOS process. The output transistors assembled by a plurality of the proposed layout cells also have a lower gate resistance and a smaller drain capacitance than that realized by the traditional finger-type layout.     

Design of SCR-based ESD protection device for power clamp using deep-submicron CMOS technology

The proposed device has a high holding voltage and a high triggering current characteristic. These characteristics enable latch-up immune normal operation as well as superior full chip electro-static-discharge (ESD) protection. The device has a small area in requirement robustness in comparison to gate-grounded NMOS (ggNMOS). The proposed ESD protection device is designed in 0.25 μm CMOS technology. In the experimental result, the proposed ESD clamp has a double trigger characteristic, a high holding voltage of 3.8 V and a high trigger current of greater than 120 mA. The robustness has measured to HBM 8 kV (HBM: human body model) and MM 400 V (MM: machine model). The proposed device has a high-level It2 of 52 mA/μm approximately.     

寄生电阻对高压器件ESD性能的影响

本文从理论上分析了衬底寄生电阻以及漏端镇流电阻对高压LDMOS器件ESD特性的影响。文中采用了多种结构对上述参数进行优化,并将其在0.35μm BCD工艺下进行试验,测试结果表明增加寄生电阻可以有效地提高器件的ESD泄放能力,最优结构的二次击穿电流由原始器件的0.75A增大到3.5A,即泄放电流增加了367%。     

栅长L对GGNMOS抗静电能力的影响

本文讨论了ESD保护器件GGNMOS(Gate Grounded NMOS)的栅长对其抗静电能力的影响,并用MEDICI进行仿真验证.基于仿真结果首次讨论了GGNMOS的栅长对其一次击穿电压、二次击穿电压和电流、导通电阻、耗散功率等的作用.     

A strategy for characterization and evaluation of ESD robustness of CMOS semiconductor technologies

This paper proposes an ESD technology strategy for characterization, evaluation and benchmarking the ESD “robustness” of CMOS semiconductor technologies. The ESD methodology uses a set of CMOS “building block” ESD test structures, matrices of critical ESD layout variables, electrical characterization parameters, and testing and extraction procedures, and ESD metrics. This work is the first step in the development of a common ESD language.     

Body ballast resistor enhances ESD robustness of deep sub-micron CMOS circuit

In this paper, the body ballast resistor design is introduced in electrostatic discharges (ESD) protection circuit for deep submicron CMOS integration circuit applications. With having the resistor, the ESD strength, turn-on resistance and trigge-on speed are greatly modulated. Those good characteristics enhance the efficiency of ESD protection circuit and keep the gate-oxide away from ESD damages. The consequence is caused from the fact that body ballast resistor builds up a positive substrate potential during the ESD stressing; consequently, reduces source to substrate barrier height. It should be further addressed that only a few design complexity is added, which is especially useful in deep sub-micron ULSI manufacturing.     

Design of 2.4-GHz T/R switch with embedded ESD protection devices in CMOS process

As CMOS processes advanced, the integration of radio-frequency (RF) integrated circuits was increasing. In order to protect the fully-integrated RF transceiver from electrostatic discharge (ESD) damage, the transmit/receive (T/R) switch of transceiver frond-end should be carefully designed to bypass the ESD current. This work presented a technique of embedded ESD protection device to enhance the ESD capability of T/R switch. The embedded ESD protection devices of diodes and silicon-controlled rectifier (SCR) are generated between the transistors in T/R switch without using additional ESD protection device. The design procedure of RF circuits without ESD protection device can be simplified. The test circuits of 2.4-GHz transceiver frond-end with T/R switch, PA, and LNA have been integrated and implemented in nanoscale CMOS process to test their performances during RF operations and ESD stresses. The test results confirm that the embedded ESD protection devices can provide sufficient ESD protection capability and it is free from degrading circuit performances.     

Neural net analysis of integrated circuit yield dependence on CMOS process control parameters

In this practical case study the method of self-organizing map (SOM) neural net is applied to analyze a CMOS process problem, where the device under study is a heartbeat rate monitor integrated circuit. The wafer yield is analyzed against the process control monitoring (PCM) parameter measurement values. The SOM efficiently reduces the parameter space dimensions and helps in visualizing the different parameter relations. This makes it possible to identify the most probable PCM parameters affecting the yield. Those were found out to be NMOS transistor drain current and aluminium sheet resistance.     

Complementary-SCR ESD protection circuit with interdigitatedfinger-type layout for input pads of submicron CMOS IC's

A new ESD protection circuit with complementary SCR structures and junction diodes is proposed. This complementary-SCR ESD protection circuit with interdigitated finger-type layout has been successfully fabricated and verified in a 0.6 μm CMOS SRAM technology with the LDD process. The proposed ESD protection circuit can be free of VDD-to-VSS latchup under 5 V VDD operation by means of a base-emitter shorting method. To compensate for the degradation on latching capability of lateral SCR devices in the ESD protection circuit caused by the base-emitter shorting method, the p-well to p-well spacing of lateral BJT's in the lateral SCR devices is reduced to lower its ESD-trigger voltage and to enhance turn-on speed of positive-feedback regeneration in the lateral SCR devices. This ESD protection circuit can perform at high ESD failure threshold in small layout areas, so it is very suitable for submicron CMOS VLSI/ULSI's in high-pin-count or high-density applications     

A closed-form back-gate-bias related inverse narrow-channel effectmodel for deep-submicron VLSI CMOS devices using shallow trenchisolation

This paper reports an analytical inverse narrow-channel effect threshold voltage model for shallow-trench-isolated (STI) CMOS devices using a conformal mapping technique to simplify the two-dimensional (2-D) analysis. As verified by the experimentally measured data and the 2-D simulation results, the analytical model predicts well the inverse narrow-channel effect threshold voltage behavior of the STI CMOS devices. Based on the study, the inverse narrow-channel effect also affects the saturation-region output conductance of a small geometry STI CMOS device in addition to the short-channel effect     

ESD implantations for on-chip ESD protection with layout consideration in 0.18-/spl mu/m salicided CMOS technology

One method to enhance electrostatic discharge (ESD) robustness of the on-chip ESD protection devices is through process design by adding an extra "ESD implantation" mask. In this work, ESD robustness of nMOS devices and diodes with different ESD implantation solutions in a 0.18-/spl mu/m salicided CMOS process is investigated by experimental testchips. The second breakdown current (I/sub t2/) of the nMOS devices with these different ESD implantation solutions for on-chip ESD protection are measured by a transmission line pulse generator (TLPG). The human-body-model (HBM) and machine-model (MM) ESD levels of these devices are also investigated and compared. A significant improvement in ESD robustness is observed when an nMOS device is fabricated with both boron and arsenic ESD implantations. The ESD robustness of the N-type diode under the reverse-biased stress condition can also be improved by the boron ESD implantation. The layout consideration in multifinger MOSFETs and diodes for better ESD robustness is also investigated.     

5V CMOS中GGNMOS ESD失效电流和沟道长度正向关系的分析

Contrary to general understanding,a test result shows that devices with a shorter channel length have a degraded ESD performance in the advanced silicided CMOS process.Such a phenomenon in a gate-grounded NMOSFET(GGNMOS) was investigated,and the current spreading effect was verified as the predominant factor. Due to transmission line pulse(TLP) measurements and Sentaurus technology computer aided design(TCAD) 2-D numerical simulations,parameters such as current gain,on-resistance and power density were discussed in detail.     

Circuit and process design considerations for ESD protection in advanced CMOS processes

This paper reviews many of the important issues for building ESD protection with NMOS transistors containing silicided diffusions and lightly doped drain junctions. The impact of device process parameters, such as gate length, side-wall spacer and silicided, graded junctions, on NMOS ESD performance are discussed. More recent process advances, such as LATID and halo implants, are also reviewed. Several varieties of circuits for triggering NMOS protection transistors under ESD conditions are covered.     

Analysis of ESD failure mechanism in 65nm bulk CMOS ESD NMOSFETs with ESD implant

Electrical and SEM analysis of gate-silicided (GS) ESD NMOSFETs in a 65nm bulk CMOS technology show that the failure mechanism changes from source-to-drain filamentation to drain-to-substrate short when a p-type ESD implant (ED) is used. Simulations show that the reason for change in failure mode is the different current and temperature distribution when the device is operated in bipolar mode due to the presence of ED. The size of the drain silicide blocking can be reduced from 3 to 0.75 μm by the use of ED while keeeping the same ESD failure current with the corresponding area saving benefit. When the ED implant extends under the drain contacts, the on-resistance (Ron) of the device can be reduced by 50% with respect to a design where ED is not located under the contacts.     

Temperature dependence of latch-up characteristics in LDD CMOS devices

The incremental rate of the latch-up holding current (Ih) with decreasing temperature is larger in the bulk substrate than in the epitaxial substrate. The substrate dependence is mainly due to the difference in the temperature coefficients of the material resistivity. Although Ihincreases significantly with decreasing temperature, the latch-up triggering voltage (Vtrig) in an inverter remains relatively constant, posing a limit for VLSI device miniaturization at low temperatures.     

Design and integration of novel SCR-based devices for ESD protection in CMOS/BiCMOS technologies

Robust and novel devices called high-holding low-voltage trigger silicon controlled rectifiers (HH-LVTSCRs) for electrostatic discharge (ESD) protection of integrated circuits (ICs) are designed, fabricated and characterized. The S-type current-voltage (I-V) characteristics of the HH-LVTSCRs are adjustable to different operating conditions by changing the device dimensions and terminal interconnections. Comparison between complementary n- and p-type HH-LVTSCR devices shows that n-type devices perform better than p-type devices when a low holding voltage (V/sub H/) is allowed during the on-state of the ESD protection structure, but when a relatively high holding voltage is required, p-type devices perform better. Results further demonstrate that HH-LVTSCRs with a multiple-finger layout render high levels of ESD protection per unit area, applicable in the design of ICs with stringent ESD protection requirements of over 15 kV IEC.