Chemical vapor deposition of Si in a lamp-heated single-wafer reactor is studied by monitoring the growth rate of films deposited on bare Si, silicon-on-insulator ͑SOI͒, and oxidized Si wafers. The growth rate is consistently higher for deposition of polycrystalline Si than for epitaxy of Si, due to different kinetics dictating the two depositions. Epitaxy of Si on SOI shows a higher overall growth rate than on bare Si. Likewise, deposition of polycrystalline Si on oxidized Si wafer with a 4000 Å thick oxide has a higher growth rate than on that with 15 Å oxide. These are attributed to surface emissivity variation during Si deposition. The difference in kinetics plays a more dominant role than the surface emissivity variation in affecting the growth rate for the depositions studied.Chemical vapor deposition ͑CVD͒ of epitaxial Si ͑epi-Si͒ and that of polycrystalline Si ͑poly-Si͒ are characterized with different apparent activation energies in the surface reaction limited regime. 1-5 In our recent study of CVD Si at 600-750°C and 20-80 Torr in a lamp-heated single-wafer reactor, 5 the apparent activation energy for epi-Si is 2.1 eV and that for poly-Si 1.6 eV, in agreement with earlier published results. 1,3,6 Under these deposition conditions, first-order reaction kinetics was found for the ͑average͒ growth rate of epi-Si as well as for poly-Si with respect to the partial pressures of SiH 4 . However, the ͑average͒ growth rate depended more strongly on the partial pressure of H 2 for epi-Si compared to poly-Si. These differences in growth kinetics were attributed to a higher H surface coverage for epi-Si than for poly-Si. Hence the growth rate of epi-Si is limited by H 2 desorption whereas the growth rate of poly-Si is limited by the balance between the SiH 4 adsorption and the H 2 desorption. 5 As a result, an appreciable difference in thickness of the two types of Si layers is observed under identical deposition conditions. 5 Since the susceptor for bedding the Si wafer is heated by lamp radiation, variation of wafer surface emissivity during Si deposition leading to wafer temperature alternation could also result in different growth rates for epi-Si on bare Si substrates and poly-Si on oxidized Si wafers. [7][8][9] The purpose of the present study is to identify the dominant effect on growth rate, i.e., deposition kinetics vs. wafer surface emissivity.The single-wafer reactor used in this study was a commercial ASM Epsilon-2000 system whose cross section is shown schematically in Fig. 1. The whole graphite susceptor of 240 ϫ 280 mm size is coated with SiC to prevent contamination. It is heated by two tungsten-halogen lamp-banks above and below together with four lamps ͑not shown͒ located under the susceptor and centered around the rotating axis. A part of the susceptor is set to rotation to improve thickness uniformity over a wafer. The susceptor temperature is measured with three thermocouples placed in the surrounding fixed part ͑front, rear, and side͒ and one encapsulated in the middle of the rotating part. ...

In this paper we present the design, fabrication and characterization of arrays of boron doped polycrystalline silicon bolometers. The bolometer arrays have been fabricated using CMOS compatible wafer-level transfer bonding. The transfer bonding technique allows the bolometer materials to be deposited and optimized on a separate substrate and then, in a subsequent integration step to be transferred to the read-out integrated circuit (ROIC) wafer. Transfer bonding allows thermal infrared detectors with crystalline and/or high temperature deposited, high performance temperature sensing materials to be integrated on CMOS based ROICs. Uncooled infrared bolometer arrays with 18x18 pixels and with 320x240 pixels have been fabricated on silicon substrates. Individual pixels of the arrays can be addressed for characterization purposes. The resistance of the bolometers has been measured to be in the 50 kW range and the temperature coefficient of resistance (TCR) of the bolometer has been measured to be -0.52 %/K. The pixel structure is designed as a resonant absorbing cavity, with expected absorbance above 90%, in the wavelength interval of 8 to 12 mm. The measured results are in good agreement with the predicted absorbance values.

Articles you may be interested inPhysics and chemistry of hot-wire chemical vapor deposition from silane: Measuring and modeling the silicon epitaxy deposition rate

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Low-pressure chemical vapor deposition of in situ phosphorus-doped silicon films using disilane (Si,H,) and phosphine (PH 3 ) has been investigated in the growth temperature range of 415 to 560'C and for doping levels between 10 9 and 1021 cm 3. Regarding the film deposition, no significant difference in apparent activation energy was observed between the undoped and heavily doped deposition process. The electrical and structural properties of the films grown at 480°C have been studied as a function of doping level and post-heat-treatment including furnace and rapid thermal annealings. The observed changes in film resistivity after isochronal annealings for doping levels above 102° cm-3 are interpreted in terms of dopant segregation and supersaturation of carriers. The impact on resulting film properties when replacing disilane with silane (SiH 4 ) in the deposition process has been investigated. The films were grown under identical conditions except for the deposition temperature which was 80°C higher for the silane than for the disilane case. There is no indication of different phosphorus incorporation when comparing electrical properties of crystallized silane-and disilane-based films. However, the disilane layers exhibit larger crystallite grains and lower specific resistivities than the silane layers. In addition, the disilane films demonstrate a strongly preferred <111> texture after crystallization which is absent for the silane films. The observations are attributed to the higher degree of disorder of the as-deposited disilane films compared to the silane films resulting from the difference in deposition temperature.

The implementation of a chirped fiber-Bragg grating (FBG) for dispersion compensation in high-speed (up to 120 Gbit/s) transmission systems with differential and coherent detection is, for the first time, experimentally investigated. For systems with differential detection, we examine the influence of group-delay ripple (GDR) in 40 GBd 2-, 4-, and 8-ary differential phase shift keying (DPSK) systems. Furthermore, we conduct a nonlinear-tolerance comparison between the systems implementing dispersion-compensating fibers and FBG modules, using a 5 × 80 Gbit/s 100-GHz-spaced wavelength division multiplexing 4-ary DPSK signal. The results show that the FBG-based system provides a 2 dB higher optimal launch power, which leads to more than 3 dB optical signal-to-noise ratio (OSNR) improvement at the receiver. For systems with coherent detection, we evaluate the influence of GDR in a 112 Gbit/s dual-polarization quadrature phase shift keying system with respect to signal wavelength. In addition, we demonstrate that, at the optimal launch power, the 112 Gbit/s systems implementing FBG modules and that using electronic dispersion compensation provide similar performance after 840 km transmission despite the fact that the FBG-based system delivers lower OSNR at the receiver. Lastly, we quantify the GDR mitigation capability of a digital linear equalizer in the 112 Gbit/s coherent systems with respect to the equalizer tap number (N tap). The results indicate that at least N tap = 9 is required to confine Q-factor variation within 1 dB.