Development of a Microwave-Laser Measurement Technique and Contactless Measurement of Conductivity of Silicon Wafer in an Infinitesimal Area

1.研制了用于探测激光在电光晶体中的位相变化的微波-激光测量系统。这种位相变化是由微波入射到电光晶体时折射率的变化引起的。成功地探测到了由于电光效应而产生的飞秒脉冲激光的偏振光的变化，从而使高频微波(毫米波)的采样成为可能。硅片电导率的非接触式测量与厚度无关一种利用毫米波以非接触式方式定量测量半导体晶片电导率的方法，使用高频毫米波，以确保传输的毫米波在晶片内部迅速衰减，从而可以忽略来自晶片底部表面的反射。因此，可以仅考虑晶片顶表面上的反射，从而毫米波响应信号不受晶片厚度的影响。此外，在实验中还测量了反射系数的幅度和相位，通过这两个参数可以确定与半导体晶片的介电常数无关的电导率。高空间分辨率和高灵敏度的硅片电导率分布测量采用微波成像法测量硅片电导率分布。采用开放式同轴线传感器，提高了测量的空间分辨率和灵敏度。发现反射系数的幅值与晶片的电导率呈线性关系。该方法可用于确定硅片制造过程中或器件制造过程中的电导率分布。

1.Development of a microwave-laser measurement systemA measurement system for detecting the phase variation of a laser light occurring in an electro-optic crystal was developed. The phase variation is induced by the changed index of refraction when a microwave beam is applied to the electro-optic crystal. The variation of the polarized light of a femtosecond pulse laser generated due to the electro-optic effect was successfully detected; thereby the sampling of a high frequency microwave (millimeter-wave) becomes possible.2. Contactless measurement of conductivity of silicon wafer independent of the thicknessA method for quantitative measurement of electrical conductively of semiconductor wafers in a contactless fashion by using millimeter waves was developed, A high-frequency millimeter wave was used in order to ensure the transmitted millimeter wave attenuated rapidly inside the wafer so that the reflection from the bottom surface of the wafer can be neglected. Thereby it becomes possible only to consider the reflection on the top surface of the wafer and thus the millimeter wave response signal is not affected by the thickness of the wafer. In addition, in the experiment, both the amplitude and phase of the reflection coefficient are measured, and by using these two parameters it is possible to determine the conductivity independent of the permittivity of the semiconductor wafers.3. Measurement of conductivity distribution of silicon wafer with high spatial resolution and sensitivityDistribution of the conductivity of silicon wafer was measured by microwave imaging. An open-ended coaxial line sensor was used to increase the spatial resolution and the sensitivity of the measurement. The relationship of the amplitude of the reflection coefficient and the conductivity of a wafer was found to be linear. The demonstrated method could be used to determine conductivity distribution in the process of wafer manufacturing or during device fabrication.