Large Silicon Wafers Research Articles

Role of Nitrogen Additive and Temperature on Growth of Diamond Films from Nanocrystalline to Polycrystalline

In this work, the coupled effect of nitrogen addition into CH4/H2 mixtures and surface temperature on diamond growth ranging from large grained polycrystalline to fine-grained nanocrystalline were investigated. Moreover a new growth parameter window for simultaneous growth of nanocrystalline diamond (NCD) and {100} textured large-grained diamond films was developed by using a high power high pressure 5 kW microwave plasma assisted chemical vapor deposition (MPCVD) reactor. Scanning electron microscope (SEM), Raman spectroscopy, and X-ray diffraction (XRD) are employed to characterize the morphology, crystalline quality and texture of the diamond samples. Our results can be grouped by two catalogs: First, deposition run without and with 0.24% N2 addition, while keeping all the other parameters constant, resulted in a high quality transparent large-grained polycrystalline diamond film and a NCD film, respectively. This result clearly evidences nitrogen induced nanocrystallinity. Then, two different substrate surface temperatures were obtained by overlapping a small silicon slice on the top centre of a large silicon wafer of 5.08 cm in diameter in only one deposition run using 0.24% N2 addition and the same set of parameters as the previous runs. From this growth run, a NCD film of growth rate around 2.3 microm/h was obtained at low temperature, while a {100} textured large-grained diamond film of much higher growth rate about 10.4 microm/h was grown at high temperature. These results not only confirm the reproducibility of NCD by N2 addition, but also indicate that distinct growth modes were involved at different substrate temperatures with 0.24% nitrogen addition, or coupled effect of nitrogen addition and temperature on the growth of CVD diamond films happened. Finite element method (FEM) analysis was employed to simulate the temperature gradient and distribution on these two samples, and based on this simulation and other simulation results in the literature, the growth mechanism is briefly discussed.

Role of oxygen additive on hydrogen impurity incorporation in nanocrystalline diamond films fabricated by microwave plasma chemical vapor deposition

AbstractIn this work, we study the influence of oxygen additive in the gas phase on hydrogen impurity incorporation into thick nanocrystalline diamond (NCD) films. Various diamond samples were grown on large silicon wafers of 5.08 cm diameter by adjusting the amount of oxygen and nitrogen additives into a conventional CH4/H2 plasma while keeping the other parameters constant using a 5‐kW microwave plasma‐assisted chemical vapor deposition (MPCVD) reactor. The morphology, crystalline quality, and hydrogen impurity content of the produced diamond samples were characterized using scanning electron microscopy, micro‐Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, respectively. The Raman and the FTIR spectra of the diamond samples indicate that on increasing the amount of oxygen additive in the gas phase, the crystalline quality of the NCD films is significantly enhanced, while their bonded hydrogen content decreases drastically. We conclude that a small amount of oxygen addition has an enhancement effect on the overall quality of diamond films ranging from polycrystalline to nanocrystalline in two ways: improving the diamond crystalline quality and suppressing hydrogen impurity incorporation.

Fabrication of a high aspect ratio thick silicon wafer mold and electroplating using flipchip bonding for MEMS applications

We have developed a microfabrication process for high aspect ratio thick silicon wafer molds and electroplating using flipchip bonding with THB 151N negative photoresist (JSR micro). This fabrication technique includes large area and high thickness silicon wafer mold electroplating. The process consists of silicon deep reactive ion etching (RIE) of the silicon wafer mold, photoresist bonding between the silicon mold and the substrate, nickel electroplating and a silicon removal process. High thickness silicon wafer molds were made by deep RIE and flipchip bonding. In addition, nickel electroplating was developed. Dry film resist (ORDYL MP112, TOK) and thick negative-tone photoresist (THB 151N, JSR micro) were used as bonding materials. In order to measure the bonding strength, the surface energy was calculated using a blade test. The surface energy of the bonding wafers was found to be 0.36–25.49 J m−2 at 60–180 °C for the dry film resist and 0.4–1.9 J m−2 for THB 151N in the same temperature range. Even though ORDYL MP112 has a better value of surface energy than THB 151N, it has a critical disadvantage when it comes to removing residue after electroplating. The proposed process can be applied to high aspect ratio MEMS structures, such as air gap inductors or vertical MEMS probe tips.

Thin-film resistance thermometers on silicon wafers

We have fabricated Pt thin-film resistors directly sputtered on silicon substrates to evaluate their use as resistance thermal detectors (RTDs). This technique was chosen to achieve more accurate temperature measurements of large silicon wafers during semiconductor processing. High-purity (0.999 968 mass fraction) platinum was sputter deposited on silicon test coupons using titanium and zirconium bond coats. These test coupons were annealed, and four-point resistance specimens were prepared for thermal evaluation. Their response was compared with calibrated platinum–palladium thermocouples in a tube furnace. We evaluated the effects of furnace atmosphere, thin-film thickness, bond coats, annealing temperature and peak thermal excursion of the Pt thin films. Secondary ion mass spectrometry (SIMS) was performed to evaluate the effect of impurities on the thermal resistance coefficient, α. We present typical resistance versus temperature curves, hysteresis plots versus temperature and an analysis of the causes of uncertainties in the measurement of seven test coupons. We conclude that sputtered thin-film platinum resistors on silicon wafers can yield temperature measurements with uncertainties of less than 1 °C, k = 1 up to 600 °C. This is comparable to or better than commercially available techniques.

Synthesis and structural characterization of highly 〈1 0 0〉-oriented {1 0 0}-faceted nanocrystalline diamond films by microwave plasma chemical vapor deposition

We report the synthesis and characterization of high-quality highly 〈1 0 0〉 oriented nanocrystalline diamond (NCD) films consisting of {1 0 0} nano-facets with a high growth rate of 2.6 μm/h. The NCD samples were grown on large (1 0 0) silicon wafers of 5.08 cm in diameter by employing CH 4/H 2/O 2/N 2 chemistries without the aid of bias for orientation, microwave power 3 kW and the substrate temperature about 700 °C using a 5 kW-type high-power microwave plasma chemical vapor deposition (CVD) system. The strong 〈1 0 0〉 preferred orientation is unambiguously demonstrated by a detailed crystallographic texture analysis and the conventional X-ray diffraction. Moreover, a detailed morphological characterization by the high-resolution scanning electron microscopy (SEM) and the atomic force microscopy (AFM), reveal that the growth surface consists of square (1 0 0) facets with an average size of about 60 nm and has a cylindrical microstructure. We demonstrate that the root-mean-square surface roughness as low as ∼15 nm, measured by AFM on 1 μm 2 scan areas, can be obtained even for considerably thick (76 μm) films. The high quality of these films is confirmed by the Raman and Fourier-transformer infrared spectra. The high-quality smooth 〈1 0 0〉-oriented {1 0 0}-faceted NCD films may have high potential in mechanical, tribological and micro-electromechanical system (MEMS) applications.

Vibration-desensitized fiber-diffraction interferometer for industrial surface measurements

We describe an industrial interferometer designed to conduct high-precision surface measurements in the presence of severe vibration. The principle of common-path interferometry is realized by devising a single-mode fiber waveguide that generates the reference wave directly from the measurement wave, enabling removal of the temporal wavefront fluctuation caused by vibration. In addition, a continuous-scanning phase-measuring method is adopted to isolate spurious vibration residuals in interferometric fringes captured using a high-speed digital camera. Experimental tests prove that the proposed interferometer is suited for in-line measurements of large mirrors, silicon wafers, and flat display panels with no excessive ground isolation for anti-vibration.

Electrical properties of n-type multicrystalline silicon for photovoltaic application—Impact of high temperature boron diffusion

The effects of boron diffusion were investigated on electronic grade n-type single- and multicrystalline silicon wafers for solar cells application. Doped p +-layers were formed using specific spin-on dopant (SOD) source annealed in a tube furnace. Homogeneous diffused layers with sheet resistance values of 70 Ω/sq were achieved on large area silicon wafers. Bulk electrical properties were investigated measuring the effective carrier lifetime after the diffusion step. A significant degradation of the bulk electrical properties was observed using the SOD technique. Unlike for the single-crystalline silicon, it was determined that this effect was not due to an interstitial iron contamination originating from the SOD, but rather by the thermal degradation of the material. Boron diffusion was followed by a phosphorous diffusion sequence, necessary in the fabrication process for the formation of the back surface field. This additional step leads to an improvement of effective lifetime values due to an efficient gettering of the impurities. Finally, bulk carrier lifetimes from 100 μs to over 300 μs were deduced on n-type multicrystalline silicon after boron and phosphorus diffusion. This underlines the potential of this material for photovoltaic application and its stability after high temperature treatments provided that a gettering step is included after the boron diffusion step.

Monocrystalline silicon used for integrated circuits: still on the way

With the rapid development of semiconductor technology, highly integrated circuits (ICs) and future nano-scale devices require large diameter and defect-free monocrystalline silicon wafers. The ongoing innovation from silicon materials is one of the driving forces in future micro and nano-technologies. In this work, the recent developments in the controlling of large diameter silicon crystal growth processes, the improvement of material features by co-doping with the intend-introduced impurities, and the progress of defect engineered silicon wafers (epitaxial silicon wafer, strained silicon, silicon on insulator) are reviewed. It is proposed that the silicon manufacturing infrastructure could still meet the increasingly stringent requirements arising from ULSI circuits and will expand Moore’s law into a couple of decades.

Texturing of large area multi-crystalline silicon wafers through different chemical approaches for solar cell fabrication

Surface texturing of silicon can reduce the reflectance of incident light and hence increase the conversion efficiency of solar cells. Comparatively lesser concentrated (10%) standard alkaline (NaOH/KOH) solution does not give good textured multi-crystalline silicon (mc-Si) surface, which could give satisfactory open-circuit voltage. This is due to grain-boundary delineation with steps formed between successive grains of different orientations. In this work an attempt has been made to obtain a well-textured mc-Si surface through three different approaches. The first two are with two different types of acid solutions and the third with concentrated alkaline NaOH. Solutions of HF–HNO 3–CH 3COOH/H 2O system with different concentrations of HF and HNO 3 were used for texturing. The results on the effect of texturing of these three solutions on the surface morphology of very large area (125 mm×125 mm) mc-Si wafer as well as on the performance parameters of solar cell are presented in this paper. Attempts have been made to study extensively the surface morphologies of mc-Si wafers in two effective regions of the isoetch curves of the HF:HNO 3:diluent's system. Also we studied the reflectance, uniformity, spectral response, short-circuit current, open-circuit voltage, fill factor and dark current–voltage of the cells fabricated using wafers textured with the three different methods. Short-circuit current of the solar cells fabricated using acid-textured wafers were measured to be in the range of 4.93 A. This value is 0.37 and 0.14 A higher than the short-circuit current values measured in the cells fabricated with isotextured and alkaline-textured wafers, respectively.

Achievement of High Flatness of Large Diameter Silicon Wafer in Double-Sided Polishing (Optimization of Polishing Conditions Based on Kinematical Analysis)

Silicon (Si) wafers are the most commonly used substrates for the production of semiconductor devices. The design rule is miniaturization, and the chip size is increasing to improve the degree of the device integration. As the substrate, Si wafer is then required to be manufactured with higher flatness and larger diameter in order to meet the above demand. The double-sided polishing process is widely adopted as the finishing stage of the wafer manufacturing, because wafers with good surface quality and flatness can be obtained economically. However, the polishing technology has a serious problem : it is very difficult to set the appropriate conditions for stably polishing the Si wafer and wearing pad to high flatness in manufacturing. In this study, the optimization of double-sided polishing conditions was proposed and developed for overcoming the problem. As a basis, the model of the distribution of material removal on the wafer and the distribution of wear on the pad was developed based on kinematical analysis. The amounts of removal and wear are considered to be proportional to the sliding distance between wafer and pads. The optimization of the polishing conditions was performed utilizing a quasi-Newton method. As a result, the polishing conditions are clarified by minimizing the deviation of material removal distribution on the wafer and wear distribution on the pads, that is, achieving high flat wafer and pads.

A new chemical path for fabrication of nanocrystalline diamond films

In this work, we report a new process for synthesis of nanocrystalline diamond films by using a small amount of simultaneous O 2 and N 2 addition into conventional CH 4/H 2 mixtures. The nanocrystalline diamond samples were grown in a 5 kW microwave plasma assisted chemical vapor deposition system on large silicon wafers of 5.08 cm in diameter. Depending on the amount of O 2 and N 2 addition, the growth rates were in the range from 2.5 to 3.5 μm/h. The samples were characterized by scanning electron microscopy, X-ray diffraction and micro-Raman spectroscopy. Our work demonstrates that the morphology, microstructure, grain size, crystalline quality and growth rate of nanocrystalline diamond films can be tailored by simply adjusting the amount of O 2 and N 2 addition, and with increasing the ratio of O 2/N 2 addition, the crystalline quality of the nanocrystalline diamond films is significantly enhanced, while the average grain size increases only slightly from 31 to 45 nm. This new process offers a simple way to tailor the growth of large-area uniform nanocrystalline diamond films of high growth rates and variable microstructures for different applications of nanocrystalline diamond films.

Load induced stresses and plastic deformation in 450mm silicon wafers

The authors present the physical basis for estimation of gravitational constraints in 450mm silicon wafers subjected to high temperature processes. They have identified and quantified the relevant phenomena to predict the mechanical behavior of very large silicon wafers horizontally stacked and ring- or pointlike supported in a vertical-type furnace. It is shown that load induced stress at the supports increases directly proportional with increasing wafer diameter, although the weight of the wafer increases with the square of diameter. The results allow the optimization for a defect-free high temperature treatment of 450mm wafer used for leading edge device fabrication in future.

The effect of oxygen and nitrogen additives on the growth of nanocrystalline diamondfilms

Nanocrystalline diamond (NCD) films have been synthesized byusing either nitrogen addition or oxygen addition to conventionalCH4/H2 mixtures besides themost commonly used Ar/CH4 with or without H2 chemistry. However, the synthesis of NCD films using both nitrogen and oxygen addition simultaneouslyinto CH4/H2 gases has not been reported thus far. In this work, we investigate the effect of simultaneousO2 andN2 additionto CH4/H2 plasmaon the growth of nanocrystalline diamond (NCD) films, focusing particularly on the ratio between the amountof O2 andN2 additives intoconventional CH4/H2 gas mixtures on the morphology, microstructure, texture, and crystalline quality of theNCD films. The NCD samples were produced by using a high microwave power (3 kW) in amicrowave plasma-assisted chemical vapour deposition reactor with a maximum power of 5 kWon large silicon wafers, 2 inches in diameter, and characterized by high-resolution scanningelectron microscopy, x-ray diffraction and micro-Raman spectroscopy. Our work demonstratesthat, under the conditions investigated here, NCD films can be formed when the ratio ofO2/N2 addition is increasedfrom 0 through 1 up to 7/3 (at higher than 7/3, for example 4, a large-grained polycrystalline diamond film will form), and the crystallinequality is significantly enhanced with the increase of oxygen addition. The mechanism ofO2 and N2 additives on the formation of NCD films is briefly studied.

Deposition Uniformity Control in a Commercial Scale HTO-CVD Reactor

AbstractHigh-temperature silicon dioxide chemical vapor deposition (HTOCVD), using SiH2Cl2 and N2O, can realize dense and conformal oxide film, not only on large size silicon wafers, but even inside of microscopic silicon trenches, at high-temperature around 800°C.In this work, we investigated the kinetics of HTOCVD using a commercial scale low pressure (LP) CVD reactor, focusing on the correlation between deposition rate and surface-to-volume ratio (S/V ratio), which is a specific surface area of substrate wafer divided by the space volume between two adjacent wafers. We also investigated the deposition rate profile on wafers, and along the axial direction of the reactor near the region where one, two or three substrate wafers are extracted from the quartz holder. The deposition rate profiles on wafer characteristically change from skillet-like to pancake-like, according to the increase of wafer spacing. The influence on the deposition rate of wafer spacing spreads to ranges not only downstream, but also upstream in the gas flow. These experimental results strongly suggest that in the HTOCVD gas-phase reactions through intermediate states of active species contribute to deposition reaction as well as direct deposition reaction of source gases on Si surface.

Photoluminescence imaging of silicon wafers

Photoluminescence imaging is demonstrated to be an extremely fast spatially resolved characterization technique for large silicon wafers. The spatial variation of the effective minority carrier lifetime is measured without being affected by minority carrier trapping or by excess carriers in space charge regions, effects that lead to experimental artifacts in other techniques. Photoluminescence imaging is contactless and can therefore be used for process monitoring before and after individual processing stages, for example, in photovoltaics research. Photoluminescence imaging is also demonstrated to be fast enough to be used as an in-line tool for spatially resolved characterization in an industrial environment.

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.

Characterization of multicrystalline silicon wafers by non-invasive measurements

Abstract Non-invasive transient photoconductance measurements of large grain multicrystalline silicon wafers ( ρ =1 Ω cm) are presented. It is shown that the surfaces of untreated wafers can be characterized as infinite sinks for excess charge carriers. The value 24.5 cm 2 s −1 for the minority carrier diffusion constant was determined in all samples. So in untreated wafers, surface recombination yields a known contribution to the decay time measured and the volume lifetime can be determined. Application of these measurements as a standard characterization of multicrystalline silicon wafers is discussed.

GaN on Si substrates for LED and LD applications

GaN epitaxial layer has been grown on 2 inch diameter Si substrates by using highly conductive BP buffer crystal. It has been found that the 2-inch GaN on BP/Si wafers are remarkably flat after epitaxial process. BP layer has grown flat and continuously on a large size silicon wafer. GaN has been found to grow continuously on such a substrate.?BP crystals have been found to be highly conductive and controllable depending on the gas ratio. In addition, UV illumination enables us to study the chamber conditions such as contamination by impurity. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The measurement of square resistance for microarea by square four-probe techniques and using a modified Rymaszewski’s formula

The sheet resistance for a microarea in a large silicon wafers was measured by using a modified Rymaszewski's formulas for a square four-point probe technique. An improved Rymaszewski's formulas was deduced taking into account the shift of probes in square four-point probe measurement. The equation of resistivity for square four-point probe measurement when there were shifts of the probes and there was no shift of the probes was deduced theoretically. A possible error produced by the shift of the probes was analyzed in theory and expressed with graphs. The effect upon measuring results arising from the shift of probes was also discussed. Practical-measurement of a specimen has been tested using a self-established equipment of square four-point probes. An equal-value-line graph was plotted for the measurement-results.

The challenges of very large silicon wafer development

The challenges of very large silicon wafer development