| Summary: | 碩士 === 國立臺灣科技大學 === 電子工程系 === 100 === Frequency synthesizers are used to implement for the frequency up/down converting of signal. Because they have to meet a strict requirement, frequency synthesizers still be the most challenging part of RF system design. In a frequency synthesizer, voltage-controlled oscillator (VCO) and frequency divider are the key building blocks. For VCOs, low phase-noise outputs are required to avoid corrupting the mixer-converted signal by close interfering tones. The frequency of output signal of VCOs is divided down to the level of reference signal, and is compared with reference signal by a phase frequency detector (PFD) to adjust the outputs of VCOs. Therefore the frequency dividers must have the ability of high frequency operation. Because of wireless application, both of them should operate at low power consumption.
This thesis proposes hot-carrier effects on VCOs. The size of MOSFET is small due to Semiconductor Manufacturing Technology improvement. It can meet the requirement of low current consumption and small component dimension. When the MOSFET is small, the electric field effect is higher than channel-length shorting effect. That will get hot-carrier effects serious and impact the components performance. Most hot-carrier effects research is for N-MOSFET due to the mobility of electron is higher that hole. Because the hot-carrier effects of P-MOSFET is more important, this paper focus on hot-carrier effects of P-MOSFET and N-MOSFET VCO.
Firstly, we present the hot-carrier effects of 0.35µm P-core LC-tank VCOs. We provided the voltage that is higher than normal operating voltage. The performance of the component will degrade. According to the experiment result, we will get oscillation frequency decreases and increase in phase noise due to electron tapping in the gate oxide during the over-bias RF stress period.
Secondly, we present the hot-carrier effects of 90nm P-core LC-tank VCOs. We provided the voltage that is higher than normal operating voltage. The performance of the component will degrade. According to the experiment result, we will get the increase in oscillation frequency by the hole trapping in the gate oxide. Besides, we will get decrease in oscillation frequency by the electron trapping in the gate oxide.
Finally, we present the hot-carrier effects of NMOS-Core dual band VCO. We provided the voltage that is higher than normal operating voltage. The performance of the component will degrade. According to the experiment result, the hot-carrier stress changes the parasitic capacitance of active transistors. This leads to the shifts of the oscillation frequencies. Besides, the stressing also increases device current noises and leads to the increase in the phase noise.
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