EM and substrate coupling in silicon RFICs

An investigation of coupling between inductors and resonators fabricated in silicon substrates is presented and the effects on RF systems and components are discussed. A novel experimental technique to measure inductor and resonator coupling is presented. The experiment is extremely sensitive, fast, accurate, and unique in that no matching, probe de-embedding, or calibration is necessary as the ratio of two on-chip signals is measured to yield the results.     

Solder-assembled high coupling efficiency single-mode laser modules using micro-heaters and precompensation technique

In this paper, we are proposing a hybrid integration platform, on which a single-mode lensed fiber can be actively aligned to a semiconductor laser, and then solder-attached to the platform with the help of on-board thin-film heaters. We have demonstrated 50% coupling efficiency with conically lensed single-mode fibers, bonded with gold-tin (AuSn) eutectic solder. The loss of alignment due to solder solidification has been carefully measured and compensated during the subsequent correctional alignment step taking advantage of the reworkability feature of the solder-joint. Two types of fiber sub-assemblies have been tested: uncoated bare fiber housed within a metallized ceramic ferrule, and nickel/gold coated bare fiber directly solder-bonded to the platform. Statistical data confirms that in both the cases, 95% of the loss of original coupling was restored by the precompensation technique.     

ULSI硅衬底的化学机械抛光技术

介绍了特大规模集成电路(ULSI)硅衬底的化学机械抛光工艺.对抛光机理、影响抛光速率和抛光质量的因素、抛光液中的成份特别是精抛液中的有机碱和活性剂的选择作了讨论分析,另外对抛光中出现的一些问题及解决方法进行了分析研究.     

Irregular-waveguide elements coupling high-Q resonators with single-mode waveguides

A new type of element coupling a high-Q resonator with single-mode rectangular waveguides is proposed. The element is an irregular tapered section. A technique of electrodynamic calculation of such a coupling element is described. The element is experimentally investigated in the case of two-mirror open resonators. The high efficiency exhibited by the coupling element over a wide frequency band is confirmed by theoretical calculations and demonstrated experimentally.     

Electrochemical etching of macropores in silicon with grooved etch seeds

Specific features of macropore formation in n-Si with grooved etch seeds on the surface have been studied. In contrast to point nucleation centers, linear centers form a half-ordered lattice of pores: in the course of the self-organization process, pores randomly originate along the grooves and follow a prescribed period a across the grooves. The average distance between the pores along the groove line depends on a and decreases as a grows. By choosing the optimal a and etching photocurrent density, separate pores can be merged into grooves to give rise to a periodic structure of trenches with vertical walls. Some aspects of the pore-pore interaction for different surface profiles and the formation of zones free from pore nucleation are considered.     

用腐蚀熔融法制造单模激光二极管与单模光纤相耦合的半球微透镜

近年来由于单模光纤研究的极大成功，促进了单模光纤通信系统和单模光纤应用技术的迅速发展。单模光纤的实际损耗已降到接近理论值，因此为进一步改善单模光纤传输系统的信噪比，提高激     

Reactive sputter etching of silicon with very low mask-material etch rates

Directional etching of deep structures in silicon is often made difficult by a high mask erosion rate. Recent results have given a Si/SiO2etch rate ratio of up to 8 without the undercut problems associated with other selective etches. In this paper a new selectivity mechanism is described which can reproducibly give Si/SiO2etch rate ratios of more than 100 with a nonloading target, and more than about 50 with a loading target. Similar etch ratios are also obtained with masks of MgF2, Al2O3, Al, and Cr. The inherently high Si/SiO2etch rate ratio obtained in Ar/Cl2discharges is here enhanced by causing selective deposition of SiO2onto slowly etched materials. The silicon may be obtained from the target, or, for easier control, from input gases such as SiCl4. The deposition rate is controlled by the oxygen concentration. The results of etching deep grooves in Si are presented. Etch-mask faceting and Si surface decoration appear to limit the attainable etch rate ratios with fine structures; however, 18-µm-deep gratings of 4.5-µm period have been etched in Si.     

Performance comparison of substrate coupling effect between silicon and SOI substrates in RF-CMOS technology

Substrate coupling may severely degrade the electrical performances of high-speed and RF integrated circuits. An isolation technique study of parasitic effects due to substrate coupling between two blocks of integrated circuits in an RF CMOS 90 nm technology is presented. Isolation performances are compared for both bulk silicon (Si) and silicon-on-insulator (SOI) substrate. For every substrate, a compact electrical model matching well with measurement results is proposed for test structures composed of 50times50 mum cells surrounded with an appropriate guard ring. An isolation improvement of 10 dB is reached by an additional P-type guard ring placed around one cell and an isolation level of 45 dB is achieved at 1 GHz for bulk Si substrate     

Prism coupling technique: a method for measurement of propagation constant and beat length in single-mode fibres

We report preliminary investigations on the application of the prism coupling technique to the measurement of the mode spectra of conventional and birefringent single-mode fibres (SMFs). Experimental results on the measurement of the propagation constant in normal SMF, and the application of this technique to the measurement of beat length on an elliptic-core SMF, are presented.     

Optical coupling between single-mode semiconductor lasers and strip waveguides

This analysis describes the optimum conditions for coupling a single-mode semiconductor laser to a single-mode strip waveguide, when both the laser and the waveguide have asymmetric optical beam profiles. The outputs are approximated by two Gaussian fields. Two waveguide cases are treated: 1) the case where the two orthogonal waveguide waists are independent and 2) where the ratio of these waists is fixed. The effect on the coupling efficiency of a spherical surface on the waveguide input face is discussed. The results demonstrate the importance of coupling in the laser far-field and indicate the advantage of having relatively large waveguide modes. An intrinsic minimum in the optimum coupling efficiency was found to exist in the near-field for asymmetric laser/waveguide systems. Expressions describing the optimum waveguide waists and the focal length of the lensed waveguide are given for the waveguide parameters that yield the best coupling conditions.     

Mode excitation theory and experiment of single-mode fiber directional coupler with strong coupling

The mode excitation theory is presented to analyze single-mode optical fiber directional couplers with transverse strong coupling, which either the weakly coupling theory or the ray theory fails to expound. By using the equivalence between the waveguides with square and circular cross sections, regarding the coupling zone of the coupler as a single waveguide, the excitation coefficients of the propagation modes in the coupling zone excited by the modes in the input waveguide have been evaluated. The theoretical coupling amount and insertion loss have been studied. Using a special monitoring technique to control the coupling length, several couplers with various coupling amounts have been made by the polishing method. The spectral characteristic of the coupling amount has been measured and compared with the theoretically inferred result. The two are found to agree with each other. The offset effect on the coupling amount has also been measured and it is different from that of the weak coupling device-the Stanford coupler.     

Multiquantum-well lasers with tapered active stripe for direct coupling to single-mode fiber

We demonstrate narrow beam divergence in 1.3-/spl mu/m wavelength multiquantum-well (MQW) lasers with an active stripe horizontally tapered over the whole cavity, for direct coupling to single mode-fibers. The lasers have reduced output beam divergence in a simple structure which does not contain an additional spot-size transformer. The fabricated laser shows narrow beam divergence of /spl sim/12/spl deg/, while a low-threshold current of 6.9 mA and a high efficiency of 0.62 mW/mA are realized. Furthermore, a direct-coupling efficiency to a single-mode fiber is -4.0-dB and -3-dB alignment tolerance is /spl plusmn/2.5 /spl mu/m.     

DC and RF performance of GaAs MESFET fabricated on silicon substrate using epitaxial lift-off technique

GaAs MESFETs have been fabricated on a silicon substrate using a molecular beam epitaxy grown film detached from its growth substrate and attached on a silicon substrate covered with a dielectric. The device processing is done on the silicon substrate. The MESFETs exhibit I/sub DSS/=130 mA/mm, g/sub m/=135 mS/mm and for 1.3 mu m gate length unity current gain cut-off frequency f/sub T/ of 12 GHz. Excellent device isolation with subpicoampere leakage currents is obtained.<>     

Optimization of deep-etched, single-mode GaAs-AlGaAs opticalwaveguides using controlled leakage into the substrate

This paper presents a detailed experimental and theoretical study of the properties of deep-etched GaAs-AlGaAs optical waveguides designed using a version of the spectral index method which predicts mode losses due to leakage through the lower cladding into the high index GaAs substrate. By predicting and measuring the mode losses due to this mechanism as a function of guide width, we show that waveguides formed by reactive ion etching through the core to the lower cladding layer can be both low-loss (0.2 dB/cm) and single-mode even with core thicknesses and guide widths as large as 4.8 and 5.6 μm, respectively. We demonstrate the advantages of this type of guide for making compact integrated optic devices     

Modeling of silicon oxynitride etch microtrenching using genetic algorithm and neural network

A prediction model of etch microtrenching was constructed by using a neural network. The etching of silicon oxynitride films was conducted in C₂F₆ inductively coupled plasma. The process parameters that were varied in a statistical experimental design include radio frequency source power, bias power, pressure, and C₂F₆ flow rate. The etch microtrenching was quantified from scanning electron microscope images. The prediction accuracy of optimized neural network model with genetic algorithm had a root mean-squared error of 0.03 nm/min. Compared to conventional model, this demonstrates an improvement of about 32%. The constructed model was used to infer etch mechanisms particularly as a function of pressure. Roles of profile sidewall variations were investigated by relating them to the microtrenchings. The pressure effect was conspicuous at lower source power, lower bias power, or higher C₂F₆ flow rate. Microtrenching variations could be reasonably explained by the expected ion reflection from the profile sidewall. The pressure effect seemed to be strongly affected by the relative dominance of fluorine-driven etching over polymer deposition initially maintained in the chamber.     

Low-loss GaAs/GaAlAs strip-loaded waveguides with high coupling efficiency to single-mode fibres

We report measurements of low-loss MOVPE-grown GaAlAs/GaAs strip-loaded waveguides with high coupling efficiency to single-mode fibres. A propagation loss of 2 dB/cm and a coupling efficiency of 70% has been achieved for a p+-i-n+-structure waveguide. A propagation loss of 0.7 dB/cm and a coupling efficiency of 61% has also been achieved for an n?-i-n?-structure waveguide.     

Power coupling from laser diodes into single-mode fibres with quadrangular pyramid-shaped hemiellipsoidal ends

A novel fabrication method for hemiellipsoidal microlenses formed on fibre ends is proposed, for efficient coupling from laser diodes into single-mode fibres. The method permits the realisation of microlenses with the required ellipticities to match the fields of lasers and fibres. A very low coupling loss of 2.65 dB has been achieved.     

Dependence of wet etch rate on deposition, annealing conditions and etchants for PECVD silicon nitride film

tchants for SiO2 and SiNx:H. A high etching selectivity of SiO2 over SiNx:H was obtained using highly concentrated buffered HE     

沉积、退火条件以及刻蚀液对PECVD氮化硅薄膜湿法刻蚀速率的影响

The influence of deposition, annealing conditions, and etchants on the wet etch rate of plasma enhanced chemical vapor deposition （PECVD） silicon nitride thin film is studied. The deposition source gas flow rate and annealing temperature were varied to decrease the etch rate of SiNx：H by HF solution. A low etch rate was achieved by increasing the SiH4 gas flow rate or annealing temperature, or decreasing the NH3 and N2 gas flow rate. Concentrated, buffered, and dilute hydrofluoric acid were utilized as etchants for Sit2 and SiNx：H. A high etching selectivity of Sit2 over SiNx：H was obtained using highly concentrated buffered HE     

Nonlinear coupling with silicon tunnel junctions in integrated logic

Most of the logic schemes that are amenable to integrated semiconductor construction utilize resistances to couple transistor stages to a power supply and to other stages. It is shown that the coupling functions ideally require nonlinear rather than linear current-voltage characteristics. Tunnel junctions can provide very attractive nonlinear characteristics for coupling purposes, and this is the main theme of the present paper. Performance advantages are investigated, particularly the improvement in delay-power product, or energy required to process a binary digit. Techniques for fabricating low-capacitance tunnel junctions in integrated fashion with silicon bipolar transistor regions are discussed.