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.     

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.     

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.     

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.     

The worst ill-conditioned silicon wafer slicing machine detected by using grey relational analysis

In the silicon slicing process, machine vibrations and the unstable wire knife motion cause the slicing precision to drift, or other ill-conditions. This process involves several synchronously occurring multiple quality characteristics, such as thickness (THK), bow, warp, total indicator reading (TIR), and total thickness variation (TTV), which must be closely monitored and controlled. In this research, grey relational analysis (GRA) is applied to prevent an ill-conditioned wire saw machine from producing an unconfirmed product that is screened from the synchronously occurring multiple quality characteristics. Five weights of those characteristics are determined by an entropy method. Finally, a case study and the exponential weighted moving average (EWMA) control chart are presented to demonstrate and verify the feasibility and effectiveness of the proposed method.     

Infra-red temperature measurement of bright metal strip using multiple reflection in a roll-strip wedge to enhance emissivity

In a continuous annealing furnace, strip temperature was measured using radiation thermometers aimed, at a shallow angle to the strip, into the wedge-shaped cavity formed between the strip and a roll. The dependence of the observed temperature on thermometer operating wavelength, field-of-view, aiming and polarisation was investigated. Comparison was made against reference temperatures taken with a surface pyrometer and also derived from strip metallurgy. Control of the furnace, using a wedge thermometer, was demonstrated. The technique is potentially applicable in a wide variety of bright metal processing furnaces.     

硅晶片抛光加工工艺的实验研究

双面抛光已成为硅晶片的主要后续加方法,但由于需要严格的加工条件,很难获得理想的超光滑表面.设计了硅片双面抛光加工工艺新路线,并在新研制的双面抛光机上对硅晶片进行抛光加工,实验研究了不同加工参数对桂晶片表面粗糙度和材料去除率的影响.采用扫描探针显微镜和激光数字波面干涉仪分别对加工后的硅晶片进行测量,实验结果表明:在优化实验条件下硅晶片可以获得表面粗糙度0.533nm的超光滑表面.     

Simultaneous measurement of humidity and temperature using a polyvinyl alcohol tapered fiber bragg grating

An optical fiber sensor based on a multimode tapered fiber cascading fiber Bragg grating has been proposed and experimentally demonstrated for the simultaneous measurement of humidity and temperature. The sensor was constructed using a tapered fiber that was coated with polyvinyl alcohol and a fiber Bragg grating with high reflectivity. The measurement of humidity and temperature was achieved by monitoring changes in reflective optical power and spectral shift, respectively. Due to the different measurement methods, the effect of temperature on humidity measurement may be ignored. The theoretical analysis and experimental results show that the highest sensitivities of 0.33 µW/%RH and 10.9?pm/°C were achieved when the diameter of the taper waist was 26?µm and the thickness of coating was 3.3?µm. Due to the advantages of good linearity, low cost of fabrication and convenient operation, the proposed sensor is promising for simultaneously measuring humidity and temperature.     

The upper bound of tool edge radius for nanoscale ductile mode cutting of silicon wafer

For ductile mode cutting of brittle materials, such as silicon wafers, the undeformed chip thickness has to be smaller than the tool edge radius. In practical application, for high production rate, the undeformed chip thickness is expected to be as large as possible. Therefore, the tool edge radius is expected to be as large as possible. In this study, the upper bound of the tool edge radius is investigated through cutting experiments.     

Simultaneous distributed measurement of the strain and temperature for a four-point bending test using polarization-maintaining fiber Bragg grating interrogated by optical frequency domain reflectometry

We demonstrate a simultaneous distributed strain and temperature measurement technique with the spatial resolution of 1 mm using fiber Bragg gratings inscribed in a polarization-maintaining and absorption-reducing fiber (PANDA-FBGs) and optical frequency domain reflectometry (OFDR). We conduct four-point bending tests in an environmental chamber. Using high birefringent PANDA-FBGs that are manufactured specifically for the simultaneous measurements, the uniform temperature distributions and the typical strain distribution profiles of the four-point bending tests were successfully obtained. The measurement errors of strain were from −31 με to 19 με, and of temperature were from −0.9 °C to 1.3 °C. The spatial standard deviation was 7.5 με and 0.9 °C. We also discussed the effect of the residual strain of the sensor-bonding procedures and the data averaging.     

The crystallographic change in sub-surface layer of the silicon single crystal polished by chemical mechanical polishing

The effect of the contact nominal pressure on the surface roughness and sub-surface deformation in chemical mechanical polishing (CMP) process has been investigated. The experimental results show that a better surface quality can be obtained at the lower pressure, and the thickness of sub-surface deformation layer increases with the increase of the pressure. In CMP process, polishing not only introduces amorphous transformation but also brings a silicon oxide layer with a thickness of 2–3 nm on the top surface. The atomic structure of the material inside the damage layer changes with the normal pressure. Under a higher pressure (125 kPa), there are a few crystal grain packets surrounded by the amorphous region in which the lattice is distorted, and a narrow heavy amorphous deformation band appears on the deformation region side of the interface. Under a lower pressure, however, an amorphous layer can only be observed.     

基于叶序仿生抛光垫化学机械抛光温度的研究与分析

为了解决在化学机械抛光过程中抛光温度分布不均匀问题,使用叶序仿生抛光垫进行研究,并建立了抛光温度场模型。利用有限元分析软件ANSYS,对抛光温度场进行了仿真分析,获得了抛光垫的叶序参量对抛光温度分布的影响规律。通过对仿真结果进行分析发现,合理选择仿生抛光垫的叶序参数,能够使抛光温度变得更均匀。