Temperature distribution in semiconductor wafers heated in avertical diffusion furnace

The transient temperature distribution in a row of wafers in a vertical diffusion furnace was calculated as the heating power of the furnace was PID (proportional-integral-derivative)-controlled. Radiative heat transfer was combined with axisymmetric unsteady conduction in wafers and the furnace. With feedforward control of the heating power (which means that when wafers are inserted into the furnace, heater temperature is set higher than the desired heating temperature), the temperature of the wafers reached the heating temperature rapidly. The radiative properties of silicon wafers changed from semitransparent to opaque at 500°C, and the effect of this change on the temperature distribution in the wafers was calculated. It was found that thermoplastic deformation of the wafers is more likely to occur during withdrawal than during insertion     

Radiation thermometry of silicon wafers in a diffusion furnace forfabrication of LSI

A radiation thermometry technique suitable for measuring the temperature of silicon wafers in a diffusion furnace has been developed. A principal feature of this technique is that it measures the temperature of wafers that are not in the line of sight of a conventional pyrometer. An optical guide, consisting of two quartz prisms, gives optical access to interior wafers in the load. A measuring wavelength of 0.9 μm is selected since a silicon wafer is opaque and its emissivity does not depend on temperature at this wavelength. The accuracy of the thermometry is examined by comparing the measured value of the pyrometer with that of a thermocouple. The two measured values agree within ±2°C in a steady state. When wafers are being inserted into or drawn out from the furnace, however, an error is caused by the veiling glare at the optical guide and the wafer     

New anatomies for semiconductor wafers

The mixing and matching of semiconductor materials to produce specific performance characteristics is discussed. Instances are GaAs-on-Si and Si-on-insulator wafers, and wafers that layer various III-V and II-VI materials. The techniques, collectively named wafer engineering make it possible to grow ultrathin freestanding wafers. The discussion focuses on GaAs-on-Si and Si-on-insulator, which have the most immediate commercial potential. Cleft layers, obtained by a technique called lateral overgrowth, and other advanced approaches to engineering materials with specified properties, are examined     

Features of the electric-field distribution in anisotropic semiconductor wafers in a transverse magnetic field

A macroscopic model of the Hall effects and magnetoresistance in anisotropic semiconductor wafers is developed. The results obtained by solving the electrodynamic boundary problem allow the potential and eddy currents in anisotropic semiconductors to be calculated at different current-contact locations, depending on the parameters of the sample material’s anisotropy. The results of this study are of great practical importance for investigating the physical properties of anisotropic semiconductors and simulating the electron-transport phenomena in devices based on anisotropic semiconductors.     

Island size distribution under conditions of dislocation-surface diffusion in semiconductor heterostructures

A mechanism of Ostwald ripening of islands under conditions of dislocation-surface diffusion is suggested for semiconductor heterostructures with quantum dots. The island size distribution is calculated for the suggested growth mechanism. Experimental histograms are compared with calculated curves.     

Features of thermal radiation of plane-parallel semiconductor wafers

The spectra and angular distribution of thermal radiation from semitransparent plane-parallel semiconductor wafers are theoretically and experimentally investigated. It is shown that the spectrum of thermal radiation from these objects is oscillatory due to multiple-beam interference, and the radiation pattern has the lobes. The measurements are performed in the region of free-carrier absorption of n-GaAs and n-Si. It is concluded that the results of this study can be used for calculating new controlled IR-radiation sources.     

浅析半导体硅片的超声和兆声清洗技术

本文主要介绍的是有关半导体硅片生产过程中的超声和兆声清洗技术应用,并对两种清洗技术当中的运行原理与特征等进行了详细阐述。并在此基础上综合研究存在问题与解决对策,分析两者技术之间的差异性。希望能够对进一步提升清洗技术发展起到促进作用。     

用于量子密钥分发的半导体激光器温控系统

由于量子密钥分发(quantum key distribution,QKD)系统对光源的稳定性要求极高,尤其是激光器发出光的波长和光强的稳定性,直接影响了系统的成码率。由此,针对分布反馈式(distributed feedback,DFB)激光器的温度特性,设计一种有效的温度控制系统。系统以 FPGA 为控制核心,采用增量式PID算法,对DFB激光器的工作温度进行实时监控。采用热电制冷控制芯片MAX8520作为半导体制冷器(thermoelectric cooler,TEC)的驱动芯片。利用集成于DFB激光器内部的负温度系数(negative temperature coefficient,NTC)热敏电阻构成温度采集模块,组成闭环负反馈结构。通过实验测试,温度控制精度可达±0.03 ℃,波长漂移可控制在0.01 nm以内。该温控系统具有电路体积小、效率高和可靠性高等特点,可为激光器提供稳定的温度控制,以保证QKD系统的光源波长的稳定性。     

Thermal and stress analysis of semiconductor wafers in a rapidthermal processing oven

Results are presented from studies of heat transfer in a rapid thermal processing (RTP)-type oven used for several semiconductor wafer processes. These processes include: (1) rapid thermal annealing; (2) thermal gradient zone melting; and (3) lateral epitaxial growth over oxide. The heat transfer studies include the measurement of convective heat transfer in a similar apparatus, and the development of a numerical model that incorporates radiative and convective heat transfer. Thermal stresses that are induced in silicon wafers are calculated and compared to the yield stress of silicon at the appropriate temperature and strain rate. Some methods for improving the temperature uniformity and reducing thermal stresses in the wafers are discussed     

由周期型强激光脉冲引起的光学元件的温度分布

在本文中,我们根据强激光脉冲的重复频率较低,脉宽窄的特点,把介质在一个周期中受辐照的温升分为辐照阶段和辐照后热扩散阶段处理。在充分考虑辐照脉冲的周期性特征后,得出了稳定周期运行的系统中光学元件上的温度分布。     

Fast annealing of 4 in. arsenic-implanted silicon wafers using an imaging furnace

An imaging furnace equipped with a 6.5 kW Xe arc lamp has been used to anneal 4 in. arsenic-implanted silicon wafers in a single exposure. Electrical and structural investigations have shown complete activation without appreciable diffusion of the impurities, and the regrown layers are defect free for low implant dose (5×1014/cm2, 100 keV); for high implant dose (1015/cm2, 200 keV), however, dislocation loops are observed.     

A technique for directly plotting the inverse doping profile of semiconductor wafers

A new technique for plotting doping profiles of semiconductor wafers is described. This technique involves driving a Schottky diode deposited on the surface with a small constant RF current (a few hundred microamperes at 5 MHz). The depth of the depletion layer is varied by changing the dc bias, but this is the only role of the dc voltage. The inverse doping profile n^-1(x) is obtained by monitoring the voltage across the diode at the fundamental frequency, which is proportional to the depth x, and the second harmonic voltage, which is proportional to n^-1. This type of plotter has the advantages of simplicity, high resolution (limited only by the Debye length in most cases), immediate results, and economy.     

Temperature stabilization in semiconductor laser diodes

Active layer temperature stabilization in semiconductor lasers is treated theoretically. Laser diodes are assumed to be mounted on a submount which is in contact with a heat sink block. The active layer temperature fluctuation signal is fed back to a Peltier device, an injection current, or a resistor layer in the chip. Active layer temperature stability and conditions required for the control circuit are analyzed theoretically and numerically.     

Hot electron diffusion in fine line semiconductor devices

We present a simple formalism to include hot electron diffusion into device modeling programs. The effectiveness of this method is illustrated for a DMOS-structure and the permeable base transistor. However, the formalism is general and can be applied to any semiconductor device.     

Temperature measurement of metal-coated silicon wafers bydouble-pass infrared transmission

We report the measurement of the temperature of metal-coated silicon wafers by a double-pass infrared transmission technique. Infrared light incident on the backside of the wafer passes through the wafer, and is re-emitted out the backside after reflecting off the metal surface on the front side of the wafer. The temperature is inferred by the change in the re-emitted signal due to absorption in the wafer. The work has been demonstrated on double-polished wafers from 100°C to 550°C using wavelengths from 1.1 to 1.55 μm. A method for overcoming limitations of the present arrangement for wafers with a rough backside is proposed     

Sensitivity analysis of ion implanted silicon wafers after rapid thermal annealing

In this study, we have investigated sensitivities of the ion implanted silicon wafers processed by rapid thermal annealing (RTA), which can reveal the variation of sheet resistance as a function of annealing temperature as well as implantation parameters. All the wafers were sequentially implanted by the arsenic or phosphorous implantations at 40, 80, and 100 keV with the dose level of 10¹⁴ to 2 × 10¹⁶ ions/cm². Rapid thermal annealing was carried out for 10 s by the infrared irradiation at a temperature between 850 and 1150°C in the nitrogen ambient. The activated wafer was characterized by the measurements of the sheet resistance and its uniformity mapping. The values of sensitivities are determined from the curve fitting of the experimental data to the fitting equation of correlation between the sheet resistance and process variables. From the sensitivity values and the deviation of sheet resistance, the optimum process conditions minimizing the effects of straggle in process parameters are obtained. As a result, a strong dependence of the sensitivity on the process variables, especially annealing temperatures and dose levels is also found. From the sensitivity analysis of the 10 s RTA process, the optimum values for the implant dose and annealing temperature are found to be in the range of 10¹⁶ ions/cm² and 1050-1100°C, respectively. The sensitivity analysis of sheet resistance will provide valuable data for accurate activation process, offering a guideline for dose monitoring and calibration of ion implantation process.     

Method for checking ohmic back contact on semiconductor wafers using 4-point-probe measurements

A method is devised to check the ohmic back contact to semiconductor wafers. It is applied to determine the effectiveness of aluminium and nickel plating as a back contact on silicon ptype and ntype wafers, respectively, during the process of alloyed-junction fabrication.