high-tech business established with a goal of becoming the world’s premier solution for reliability and noise assessment/analysis.
Korea Sensor Lab.


    

    Evaluation/Analysis of Reliability

    What is reliability?

    • Reliability is generally defined as the lifetime that how long the product or component can be used safely without failure.
    • Semiconductor devices and semiconductor chips should satisfy the various reliability specifications.
    • Exact evaluation and analysis of reliability characteristics are high necessary for exact estimation of device lifetime.

    Necessitates of reliability evaluation

    • General semiconductor chip is consisted of tens of millions or several billions of devices.
    • If one device among the billions of devices goes wrong, the semiconductor chip would not operate properly.
    • Moreover, the system which includes the semiconductor chip will not operate properly.
    • Reliability spec. of semiconductor device is much more severe than general electronic products and components.
    • Therefore, accurate evaluation of diverse reliability items is a key for exact estimation of reliability lifetime.

    Test and Analysis Items

    • Hot Carrier, BTI(Bias Temperature Instability), TDDB (Time Dependent Dielectric Breakdown) and others
    • Voltage stress and/or current stress is applied for the passive devices such as capacitor, resistor and inductor.
    • Electro-migration(EM) and stress migration(EM) for back-end-of-line process.

    Extraction of Hot Carrier Lifetime

    • High energy carriers named hot carrier are generated by high electric field near the drain edge of MSOFETs.
    • Hot carrier transfers its energy to silicon lattice through phonon emission and breaks bond at the interface between Si and SiO2
    • A portion of hot carriers become trapped inside the gate dielectric (SiO2)
    • Trapping of hot carriers and breakdown of bond generate oxide trapped charge and interface charge and results in the decrease of carrier mobility.
    • Degradation of device performance due to the increase of Threshold voltage (VT), decrease of Transconductance(gm) and Drain current (ID)
    • Measurements of the variation ratio of above three device parameters as a function of stress time and extraction of lifetime at the operation voltage

    Extraction of NBTI(Negative Bias Temperature Instability) Lifetime

    • Two BTI stresses : PBTI of NMOS and NBTI of PMOS
    • NBTI reliability is normally evaluated in SiO2 based CMOS technology because PMOS degradation by NBTI is much more severe than NMOS degradation by PBTI.
    • Although Negative Bias Temperature Instability (NBTI) phenomenon is one of the key reliability issue, its physical mechanism is not fully understood.
    • It is believed that NBTI is controlled by the electro-chemical reaction.
    • Holes in PMOSFET channel react with silicon bond(Si-H, Si-D, etc) at the interface and donor type interface state and positive fixed charge.
    • NBTI stress is performed at high temperature because the electro-chemical reaction is dependent on the electric field and stress temperature.
    • Generation of Interface state and positive fixed charge induce the increase of threshold voltage (VT)
    • Variation of threshold voltage is commonly used to evaluate the degradation of MOSFET by NBTI stress.

    Evaluation of TDDB (Time Dependent Dielectric Breakdown) Lifetime

    • Reliability of gate dielectric which determines the performance of MOSFET or Capacitor is one of key items in developing MOSFET devices.
    • Fabrication of MOSFET or Capacitor is meaningless if the reliability of dielectric does not meet the spec.
    • Analysis of Time Dependent Dielectric Breakdown(TDDB) of gate dielectric is one of the key reliability factor.
    • Dielectric breakdown greatly affects the dielectric reliability as the thickness of MOS gate dielectric becomes thinner due to the scale down of MOSFET
    • TDDB reliability is getting more and more important as the high-k dielectric is adopted for the gate dielectric or capacitor dielectric.

    Gate leakage current versus stress time under constant voltage stress(CVS). At first, gate leakage increases due to the hole trapping and then decreases due to the electron trapping. [Ref : Journal of Applied Physics, Vol. 85, No. 11, 1 June 1999]

    Applicable devices and products

    • Semiconductor devices (Si MOSFET, III-V MOSFET, Power MOSFET, etc..)
    • Capacitors (Discrete capacitor, 3-D capacitor, etc..)
    • Resistors
    • Inductors
    • Bio device/sensor
    • MEMS device/sensor
    

    Evaluation/Analysis of Low frequency noise

    What is Low frequency noise?

    • MOSFET is widely used in RF and analog circuits as well as digital circuits.
    • Relative ratio of analog and RF semiconductor becomes greater due to development of portable appliances like smart phone.
    • Therefore, the analog performances of passive devices such as resistor, capacitor along with the active devices such as MOSFET and BJT are getting more and more important.
    • Among the analog performances, the low frequency noise property of MOSFETs and resistors has become crucial as the bit resolution of analog circuits becomes higher.
    • Low frequency noise is commonly referred as the noise below 100 kHz.
    • There are two typical low frequency noise, 1/f noise (Flicker noise) and RTS (Random Telegraph Signal) noise.
    • Power spectral density of Flicker noise shows the inversely proportional to the frequency (1/f) as shown in left figure below, and RTS noise shows 1/f2 dependence as exhibited in right figure.

    Necessity of the evaluation of low frequency noise

    • Low frequency noise can determines the performance of analog circuits.
    • Noise current due to the 1/f noise can be expressed as functions of Power Spectral density of noise current(SID) and bandwidth(BW) as in equation (1).
    • For instance, if SID of analog resistor is about 10-18 A2/Hz as shown below and bandwidth is 10 kHz, noise current, IN is calculated as 100nA using equation (1).
    • Accurate analysis of the analog circuits would be difficult if the magnitude of signal current is below 100nA
    • Therefore, Flicker noise of semiconductor devices and sensor devices should be evaluated accurately.
    • The low frequency noise level should be accurately evaluated so that various methods to reduce the low frequency noise can be tried precisely.
    • It is not easy to evaluate the low frequency noise level of semiconductor devices and circuits or sensor devices because there are a lot of noise sources around the general noise measurement environment and the noise itself of DUT can be small.
    • Shielding room which can perfectly shield the noises from out of DUT is a must for measurement o flow frequency noise.
    • SMAT Solutions utilize the shielding room for accurate evaluation of low frequency noise of various devices and chips.

    Test and Analysis Items

    Measurement and Analysis of 1/f noise (Flicker noise)

    • The low frequency noise performance of MOSFETs and resistors is one of key parameters for application of them to RF and analog circuits.
    • Physical mechanism of 1/f noise is not fully understood yet.
    • It is known that 1/f is generated by either of mobility fluctuation or channel charge fluctuation.
    • Charge fluctuation is due to the trapping and detrapping of electrons and holes at the interface traps between silicon and SiO2 (Si/SiO2) and mobility fluctuation is due to the lattice vibration in the channel region.
    • Degradation of transconductance of MOSFET due to the 1/f noise can result in the malfunction of RF and analog circuits.
    • Resistors and bio and MEMS sensors which have small signal are very susceptible to the low frequency noise.
    • Accurate evaluation of low frequency noise is crucial in analog applications.

    Measurement and Analysis of RTS (Random Telegraph Signal) noise

    • RTS noise is originated from the trapping and detrapping of single electron or hole in the gate oxide trap.
    • PSD of RTS noise decreases as the frequency increases like the 1/f noise. However, its dependence on frequency is 1/f2 rather than 1/f of flicker noise.
    • Significant feature of RTS noise is two level fluctuation of current or voltage at the time scale as shown below.
    • Discrete fluctuation of noise can be amplified in the amplifier such as Audio CODEC, which results in the great fluctuation of output sound; that’s why the RTS noise is also called as Burst noise or Pop-corn noise.
    • RTS noise is a key parameter of amplifier such as Audio CODEC and OP Amp and CIS image sensor in smart phone camera.
    • Exact evaluation of RTS noise and decrease of RTS noise level is one of keys in analog applications.

    Applicable devices and products

    • Semiconductor devices (Si MOSFET, III-V MOSFET, Power MOSFET, etc..)
    • Resistors
    • Inductors
    • Bio device/sensor
    • MEMS device/sensor
    

    Evaluation/Analysis of radio frequency (RF) characteristics

    Necessity of measurement in RF range

    • There have been great efforts to apply MOSFET devices in mixed signal circuits and SOC (System On a Chip) due to the continuous scale down of device size and increase of device performance.
    • MOSFET performance is enough to be applied in analog circuits or RF circuits in GHz range due to the great improvement of device performance.
    • Analog and RF circuits necessitate the resistors, capacitors, inductors and varactors as well as MOSFETs, which implies that accurate evaluation of RF characteristics of passive devices is important.
    • RF performance of devices and circuits necessitate the two-port system because they cannot be evaluated accurately using normal measurement and analysis.
    • Two port systems is consisted of two ports where each port has two parameters. (For example, gate-source, and drain-source form each port)
    • There are four signals of which two forms input signals and the other two forms outputs.
    • Two-port system is expressed by Z-Parameter if the input analog signals are I1 and I2 and output signals are V1 and V2
    • Two-port system is expressed by Y-Parameter if the input analog signals are Y1 and Y2 and output signals are I1 and I2
    • Either of Z-Parameter and Y-Parameter implies that exterior signals from the outside of the two-port system are transferred to the two-port system 100 percent.
    • In real world more than 100 MHz range, the exterior signals could not be transferred completely to the input stage, which means that there happens high frequency characteristics i.e., reflection of input signal at the input stage or at the either of port.
    • Z-Parameter and Y-Parameter cannot be measured directly from the two-port system doe to the reflection of signals.
    • S-parameters are measured in high frequency range using Network analyzer.
    • Test pattern techniques and network analyzer for RF measurement are necessary for accurate evaluation of RF performance.

    Test and Analysis Items

    High frequency measurement and analysis of semiconductor devices

    • GSG type test pattern is necessary for measurement of S-parameters of MOSFET devices, Resistors, Capacitors, Varactors and Inductors in high frequency range.
    • Key parameters such as Cutoff frequency (fT) are extracted after conversion of S-Parameters into H-Parameters or Y-/Z- parameters.
    • Device modeling of devices in RF range should be performed.

    Applicable devices and products

    • Semiconductor devices (Si MOSFET, III-V MOSFET, Power MOSFET, etc..)
    • Capacitors (Discrete capacitor, 3-D capacitor, etc..)
    • Resistors
    • Inductors
    • Bio device/sensor
    • MEMS device/sensor
    

    Evaluation/Analysis of Memory device characteristics

    • Memory semiconductor performs data storage and date readout contrary to the non-memory devices which has diverse functions.
    • Memory device should have superior retention property that stored data can be conserved for longtime and endurance property that memory function can be sustained for a long time in spite of frequent writing and reading operation of each memory cell.
    • Accurate evaluation of retention and endurance properties and precise failure analysis of reasons when the spec is not fulfilled are highly necessary.

    Measurement and Analysis of Retention characteristics

    • Retention is a key parameter of Non-volatile memory, which represents how long the stored data can be preserved without loss.
    • Analysis of device parameters as a function of Retention time.

    Measurement and Analysis of Endurance property

    • Program and erasing of data in a cell happens periodically in the memory device.
    • Endurance is the number of program and erase that can be applied to the flash memory cell without malfunction.
    • Accurate analysis of Endurance characteristics of Flash Memory is highly important because the hot carriers which can degrade the device performance are used for data programming.

    Applicable devices and products

    • Memory device
    • Embedded Memory device
    

    Self-Heating effect of Devices

    What is self-heating?

    • Self-heating : Increase of device temperature due to the power consumption inside the device during operation.
    • Self-heating pronounces as the operating voltage or current increases.
    • The Self-heating effect results in the decrease of electron and hole mobility that is decrease of device current and chip speed.

    Need to analyze the Self-heating effect

    • There is a strong need for the Energy efficient power device due to the energy issue in the world.
    • Power device and chip inevitably show the reduction of operating current due to high voltage and high current operation which incurs the self-heating effect.
    • SOI (Silicon On Insulator) and SOS (Silicon On Sapphire) devices are susceptible to the self-heating due to the insulating layer between thin film and bulk substrate.

    Problems due to the Self-heating effect

    • Decrease of Carrier mobility
    • Decrease of Operating current
    • Reduction of drain transconductance and speed
    • Device reliability issue
    • Inaccurate modeling of device property

    Applicable devices and products

    • MOSFET Device
    • Power Device
    • High Current Device
    • High Voltage Device
    • SOI/SOS Device
    • Thermistors
    • Sensors
    • Heterojunction Device
    • Wire and Interconnection
    

    Test Services

    Electrical test and Analysis at high temperature

    • Characterization of Electrical parameters at high temperature ( ~ 200 ℃)
    • Analysis of device and sensor performance as a function of temperature

    Electrical test and Analysis at Low temperature

    • Characterization of Electrical parameters at low temperature (~ 100 K)
    • Analysis of device and sensor performance as a function of temperature
    • Low frequency noise at low temperature

    Reliability of Display devices

    • Amorphous TFT, LTPS TFT, OLED, ZnO devices
    • Hot Carrier reliability of Display device
    • BTI reliability of Display device
    • Mobile ion effect of Display device
    • Parameter variation of Display device as a function of temperature

    Reliability of interconnection (BEOL)

    • EM (Electro-migration) property
    • SM (Stress migration) property

    Environment Test

    Temperature-Humidity Environment Test

    • The purpose of this test is to evaluate the changes of characterization of a sensor or semiconductor device in high temperature and humidity environment.
    • Temperature and humidity chamber is used to accelerate metal corrosion particularly that of the metallizations on the die surface of the device under test.

    Thermal Shock Environment Test

    • The purpose of this test is to determine the resistance of a sensor or semiconductor device to sudden exposure to extreme changes in temperature and to the effect of alternate exposures to these extremes.