Non-contact temperature measurement of silicon wafers based on the combined use of transmittance and radiance

We propose a non-contact temperature measurement method that combines the temperature dependence of transmittance below 600 °C and radiation thermometry above 600 °C. The combined method uses a polarization technique and the Brewster angle between air and a dielectric film such as SiO₂ or Si₃N₄ grown on silicon wafers. A prominent feature of this method is that both measurements of transmittance and radiance are performed with the same geometrical arrangement.For a semitransparent wafer, the measurement of p-polarized transmittance at the wavelengths of 1.1, 1.2 and 1.3 μm enables temperature measurement in the range from room temperature to 600 °C. For an opaque wafer above 600 °C, the p-polarized radiation thermometry at the wavelength of 4.5 μm allows the temperature measurement without the emissivity problem. The combined method with the use of transmittance and radiance is valid in the entire temperature range irrespective of variations of film thickness and resistivity.     

Warping of silicon wafers subjected to back-grinding process

This study investigates warping of silicon wafers in ultra-precision grinding-based back-thinning process. By analyzing the interactions between the wafer and the vacuum chuck, together with the machining stress distributions in damage layer of ground wafer, the study establishes a mathematical model to describe wafer warping during the thinning process using the elasticity theory. The model correlates wafer warping with machining stresses, wafer final thickness, damage layer thickness, and the mechanical properties of the monocrystalline silicon. The maximum warp and the warp profile are measured on the wafers thinned to various thicknesses under different grinding conditions, and are used to verify the modeling results.     

Error analysis on measurement temperature by means dual-color thermography technique

Dual color thermography is a non-contact measurement temperature technique used mainly when the emissivity of surface is unknown; it is based on ratio of monochromatic emissive power calculated by means Planck’s radiation equation and allows measuring the temperature of gray body surface objects without being assigned their emissivity and without approximations.For real surfaces, the emissivity varies with the temperature of surface as well as the wavelength and the direction of radiation. In this case, the dual color thermometry is executed by equipping the IR camera of two narrow band pass filters, so as to consider the surface emissivity of a quite constant value. This allows calculating the ratio between the radiative fluxes of the two different emission wavelengths that is almost independent to the surface emissivity.One of the crucial factor in this technique is the choice of the two narrow filter wavelengths. In fact the measurement errors depends directly on the two wavelengths and the variation of spectral emissivity related to the wavelength chosen and it also depends inversely on distance between central value of filters.In this paper, the authors have developed and validated a mathematical model of experimental setup to measure object surface temperature by means IR thermo-camera. This mathematical model was used to quantify the temperature measurement error in the dual-color technique. A novel correlation to estimate temperature measurement error was provided.     

Dual-band pyrometry for emissivity and temperature measurements of gray surfaces at ambient temperature: The effect of pyrometer and background temperature uncertainties

A dual-band pyrometry model for target temperature (240–360 K) and emissivity measurement was developed, in which two pyrometers with different spectral bands are surrounded by an enclosure at a given background temperature. Nine equal-power spectral bands were selected for the pyrometers from wavelengths between 8 and 14 μm. The Monte Carlo method was used to compute the dual-band measurement uncertainties of temperature and emissivity caused by the propagation of the uncertainties associated with the temperatures of the two pyrometers and the temperature of the background. It was found that the rate of decrease of dual-band measurement uncertainties with increasing difference between target and background temperatures decreases with increasing target temperature. Considering the uncertainty of the background temperature, it was found that dual-band measurement uncertainties are virtually not affected by the background temperature uncertainty when the background temperature is lower than the target temperature, and dual-band measurement uncertainties increase significantly with increasing background temperature uncertainty when the background temperature is higher than the target temperature.     

Surface integrity of silicon wafers in ultra precision machining

Silicon wafers are the most extensively used material for integrated circuit (IC) substrates. Before taking the form of a wafer, a single crystal silicon ingot must go through a series of machining processes, including slicing, lapping, surface grinding, edge profiling, and polishing. A key requirement of the processes is to produce extremely flat surfaces on work pieces up to 350 mm in diameter. A total thickness variation (TTV) of less than 15 μm is strictly demanded by the industry for an 0.18 μm IC process. Furthermore, the surfaces should be smooth (R_a<10 nm) and have minimum subsurface damage (<10 μm) before the final etching and polishing. The end product should have crack-free mirror surfaces with a micro-roughness less than 1.8 Å. In this paper, experiments are conducted to investigate the effects of various parameters on the subsurface damage of ground silicon wafers.     

Methodology for spectral emissivity measurement by means of single color pyrometer

The application of non-intrusive optical devices, such as infrared pyrometers able to measure the temperature of surfaces, makes possible the evaluation of emissivity curve of the tested materials at different temperature values. In this paper the authors propose a methodology for the spectral emissivity measurement by means of a single color pyrometer providing a semi-empirical formula, obtained experimentally at CIRA’s laboratory. The semi-empirical formula allows to know the actual emissivity value of the sample’s surface for whatever emissivity value set up on the pyrometer. The agreement between the experimental emissivity and the emissivity predicted by semi-empirical formula was verified.     

A compact and sensitive two-dimensional angle probe for flatness measurement of large silicon wafers

A two-dimensional (2D) angle probe was developed to realize a new scanning multi-probe instrument employing 2D angle probes for flatness measurement of large silicon wafers. Each probe, which utilizes the principle of autocollimation, detects the 2D local slope components of a point on the wafer surface. The 2D local slopes (angles) are obtained through detecting the corresponding 2D positions of the reflected light spot on the focal plane of the object lens using position-sensing devices (PSDs). To make the probe compact in size, it is more effective to improve the sensitivity of angle detection by selecting proper PSDs than using an objective lens with a larger focal distance. Two kinds of photo devices, linear lateral effect PSDs and quadrant photodiodes (QPD), for sensing 2D positions were discussed theoretically and experimentally. It was shown that a QPD is the best for highly sensitive 2D angle detection. In the experiments, a compact prototype angle probe with dimensions 90(L)mm×60(W)mm×30(H) mm employing a QPD as the PSD was confirmed to have a resolution of approximately 0.01 arc-second.     

A study of the effect of tool cutting edge radius on ductile cutting of silicon wafers

Ductile mode cutting of silicon wafers can be achieved under certain cutting conditions and tool geometry. An experimental investigation of the critical undeformed chip thickness in relation to the tool cutting edge radius for the brittle-ductile transition of chip formation in cutting of silicon wafers is presented in this paper. Experimental tests for cutting of silicon wafers using diamond tools of different cutting edge radii for a range of undeformed chip thickness are conducted on an ultra-precision lathe. Both ductile and brittle mode of chip formation processes are observed in the cutting tests. The results indicate that ductile cutting of silicon can be achieved at certain values of the undeformed chip thickness, which depends on the tool cutting edge radius. It is found that in cutting of silicon wafers with a certain tool cutting edge radius there is a critical value of undeformed chip thickness beyond which the chip formation changes from ductile mode to brittle mode. The ductile-brittle transition of chip formation varies with the tool cutting edge radius. Within the range of cutting conditions in the present study, it has also been found that the larger the cutting edge radius, the larger the critical undeformed chip thickness for the ductile-brittle transition in the chip formation.     

Experimental mathematical model as a generalization of sensitivity analysis of high temperature spectral emissivity measurement method

The development of an experimental mathematical model describing temperature state of the sample during high temperature spectral emissivity measurement is introduced. Dimensional analysis of the measurement process gives the physical dimensionless quantities and sensitivity analysis of the measurement process provides the large set of performed model experiments. Evaluated experimental mathematical models are presented including their accordance with model experiments. Established equations are generalization of sensitivity analysis of high temperature spectral emissivity measurement method and can be used for computation of spectral emissivity total uncertainty.     

Simultaneous measurement of temperature and emissivity of lunar regolith simulant using dual-channel millimeter-wave radiometry

Millimeter wave (MMW) radiometry can be used for simultaneous measurement of emissivity and temperature of materials under extreme environments (high temperature, pressure, and corrosive environments). The state-of-the-art dual channel MMW passive radiometer with active interferometric capabilities at 137 GHz described here allows for radiometric measurements of sample temperature and emissivity up to at least 1600?°C with simultaneous measurement of sample surface dynamics. These capabilities have been used to demonstrate dynamic measurement of melting of powders of simulated lunar regolith and static measurement of emissivity of solid samples. The paper presents the theoretical background and basis for the dual-receiver system, describes the hardware in detail, and demonstrates the data analysis. Post-experiment analysis of emissivity versus temperature allows further extraction from the radiometric data of millimeter wave viewing beam coupling factors, which provide corroboratory evidence to the interferometric data of the process dynamics observed. These results show the promise of the MMW system for extracting quantitative and qualitative process parameters for industrial processes and access to real-time dynamics of materials behavior in extreme environments.     

大尺寸硅片的高效超精密加工技术

本文根据下一代IC对大尺寸硅片（≥300mm)面型精度和表面完整性的要求，分析了大尺寸硅片超精密加工的关键问题，介绍了工业发达国家在硅片超精密加工技术和设备方面的研究现状和最新进展，指出了大尺寸硅片高效超精密加工技术的发展趋势,通过对国内技术现状的分析，强调了针对大尺寸硅片超精密加工理论和关键技术开展基础研究的必要性。     

Effects of support method and mechanical property of 300 mm silicon wafer on sori measurement

This paper describes the effects of support methods and mechanical properties of 300 mm silicon wafer on sori measurement. A new supporting method, named three-point-support method, used in the sori measurement of a large diameter silicon wafer was proposed in this study to obtain a more stable measuring process. The wafer was supported horizontally by three steel balls on the vertexes of a regular triangle at the wafer edge. The measuring repeatability and anti-disturbance ability were compared between the proposed method and the conventional one-point-support method, in which the wafer is supported with a small-area chuck at the wafer center. The effects of friction between the supports and wafer surface for the three-point-support were also estimated. Finally, the influences of different mechanical characteristics at the front and back surfaces and the crystal orientation on sori measurement were investigated.     

硅晶片的液流悬浮超光滑加工机理与实验

建立了基于机器人的液流悬浮超光滑加工系统。配置出了适用的悬浮加工液,通过对硅晶片的大量加工实验研究,得到了加工时间、工具转速和粒子浓度对工件表面质量的影响规律。实验结果表明:当加工时间在60 min、工具转速为6 000 r/min上下、粒子浓度为30 g/L左右时,加工效果最佳。加工后的硅晶片表面粗糙度Ra能达到1.55 nm。深入分析了液流悬浮超光滑加工的去除机理,硅晶片的液流悬浮超光滑加工是机械冲击作用和化学作用的综合结果,加工液中的磨料颗粒有对工件表面的机械冲击作用和对化学反应的催化作用。理论分析和实验结果表明,通过采用液流悬浮加工新技术,可以实现对半导体材料硅晶片的纳米水平的超光滑加工,获得表面无塑性变形和晶格缺陷的纳米精度表面。     

Simultaneous measurement of strain and temperature using a hybrid local and distributed optical fiber sensing system

Structure multi-parameters measurement, such as strain, displacement, corrosion and temperature, is of the utmost importance for structural health monitoring. Meanwhile uncoupling method of temperature and strain has still a technical problem in structure sensing measurement. In this paper, we proposed a method for simultaneous measurement of strain and temperature using a hybrid local and distributed optical fiber sensing system. The principle of the method is investigated and then validated by the theoretical simulation experiments and tensile tests in laboratory. Furthermore, one experiment for internal force measurement of a smart stranded wire, under the interaction of temperature and strain, is also conducted in lab. The experimental results show that the strain and temperature can be well measured simultaneously by using one multi-signal optical fiber sensor.     

Effects of taping on grinding quality of silicon wafers in backgrinding

Frontiers of Mechanical Engineering - Taping is often used to protect patterned wafers and reduce fragmentation during backgrinding of silicon wafers. Grinding experiments using coarse and fine...     

Application of multispectral radiation thermometry in temperature measurement of thermal barrier coated surfaces

Ceramics coatings are materials widely used in gas turbines to provide thermal shielding of superalloy materials against excessive turbine temperatures. However, measurement of their surface temperatures using conventional radiation thermometers, more so in the presence of high ambient radiation and low emissivity is quite challenging. A multispectral method employing curve fitting technique to measure the temperature of such targets in the range of 800–1200 K and ambient temperature of 1273 K is implemented in this paper through simulation. Several simulated experiments were carried out to identify emissivity models best suited for multispectral radiation thermometry applicable to ceramic coatings. The best emissivity model applicable to yttria-stabilized zirconia of coating thickness of 330 μm in the wavelength range of 3.5–3.9 μm was found to predict temperature with an error of less than 1.5% in the presence and absence of background noise.     

Machining characteristics on the ultra-precision dicing of silicon wafer

Recently, the slightest damage to a circuit can cause great damage due to the sizes of semiconductor chips becoming smaller. To prevent damage to the circuit, the dicing process for silicon wafer must be controlled. In this study, the relationship between the chipping effect and the force of dicing was analyzed. The rate of chipping decreased with a decrease in the force of dicing. The force of dicing also decreased according to a lower feed rate and higher blade speed. The lower feed rate and the higher blade speed must be controlled to achieve a chip-free process.     

Nano‐scratch study of molecular deposition films on silicon wafers using nano‐indentation

Experiments on molecular deposition (MD) films with and without alkyl terminal groups deposited on silicon wafers were conducted using nano‐indentation. It was found that MD films and alkyl‐terminated MD films exhibit a higher critical load and a lower coefficient of friction than the silicon substrate. The critical load increases with the number of layers, and the coefficients of friction of MD films with alkyl terminal groups are lower than those of the corresponding MD films with the same number of layers but without alkyl terminal groups.     

Temperature propagation through a mercury vapour calibration source and assessment of possible analytical biases caused by measurement of temperature variations

A combination of experimental data, and validated modelling studies, has shown that external temperature variations propagate very quickly within mercury vapour calibration apparatus, and thus any internal temperature inhomogeneities may be largely neglected. However the study has shown that the response time of the temperature measuring device used to make readings within the mercury vapour calibration apparatus can impose a bias as a result of the device’s inability to respond quickly to changes in temperature within the mercury vapour calibration apparatus. The size of this possible bias has been quantified and strategies for its elimination proffered.     

Dependence of pad performance on its texture in polishing mono-crystalline silicon wafers

Mono-crystalline silicon wafers are important materials in the semiconductor industry for fabricating integrated circuits and micro-electro-mechanical systems. To ensure high surface integrity of polished wafers, the effect of pad texture and its variation on the pad performance needs to be understood. This paper studies experimentally the dependence of pad performance on its texture deterioration by investigating its correlation with polishing time, polishing pressure, and material removal rate. The study concludes that material removal rate decreases as the cylindrical cell structure of a pad is gradually deteriorated, that there is a pad life limit beyond which polishing quality can no longer be maintained, and that the workable pad life can be extended to a certain degree by applying higher polishing pressure.