By using a trench isolated thick SOI process as base topology various optical and high voltage devices can be designed which are not or hardly possible in pnjunction isolated BCD processes. The trench isolation allows the construction of isolated photodiodes with excellent response even for red and infrared wavelengths. The thick SOI material enables the integration of vertical high voltage devices like NPN bipolar transistors. Together with a special collector design the buried layer and the sinker allow the integration of an IGBT device which is tune able between on-state and switching performance. Keywords-HV transistor, photo diode, Trench, thick SOI I.MOTIVATION A trench isolated thick Silicon-On-Insulator (SOI) technology [1] allows not only the easy high side and/or below ground operation of logic blocks and high voltage transistors, a further benefit is the possibility to integrate various optical and high voltage devices. Target of this work was to integrate new functionalities into the existing 650 V technology with a minimum of additional processing effort and a minimum of extra mask layers respectively. The dielectric isolation allows the integration of minority carrier injecting IGBT devices [2], [3], without any risk to inject carriers deeply into a common substrate. Also carriers generated by longer wavelengths in photodiodes deep in the silicon are confined and cross talk problems are reduced. Stacking of photodiodes is a further possibility that is made possible by the dielectric isolation. For integrated vertical devices the thick SOI layer allows breakdown voltages above 700 V. An example is a new vertical NPN transistor which was designed using existing design and process elements. II.STARTING POINT A trench isolated Bipolar-CMOS-DMOS (BCD) process on 55 µm SOI wafers containing 5, 7 and 20 V logic CMOS transistors, medium and high voltage n-channel DMOS and PMOS transistors as well as bipolar and other analogue devices like resistors and capacitors was the base for the development of new devices. Isolation, SOI thickness as well as doping concentrations are sufficient to achieve typical breakdown voltages above 700 V. Figure 1 schematically shows the dielectric isolation topology, consisting of the trench, the trench adjacent doping layer (sinker), the Buried OXide (BOX) and the highly doped buried layer above the BOX, together with the standard high voltage device, a 650 V n-channel quasi-vertical DMOS transistor. A pwell to n-device wafer (the upper wafer of the SOI wafer stack) junction diode in an isolated tub together with the sinker and buried layer dopings were used to build isolated photodiodes. A similar vertical construction as shown in Figure 1 was used to design a vertical NPN bipolar transistor. The pwell to n-device wafer junction allows blocking voltages above 700 V. To achieve such blocking voltages the drift region construction, slightly modified field plate structures and geometrical radii were reused in a slightly modified layout from the original high voltage DMOS.The high...

Silicon photodiode integrated with CMOS has been in extensive study for the past ten years due to its wide use in applications such as short-distance communication, VCD players, ambient light sensors and many other intelligent systems. In recent years, high speed blue-ray DVD is replacing conventional DVD due to its larger storage capacity and higher speed. In this work, the photodiode optimized for blue ray is fully integrated with standard 0.35um CMOS process and the bandwidth dependency upon thermal process and epitaxial material is investigated. It was found that the additional substrate thermal process can improve bandwidth for blue and red light but reduce bandwidth for infra-red. It is also found that higher level p-type epi doping does not impact bandwidth for blue light but reduces bandwidth for red and infra-red. The various mechanisms of bandwidth were discussed based on the experimental results. It indicated that the bandwidth of photodiodes depends on photo carriers travel time which can be explained by simple model of drift transport and diffusion transport. The design of photodiode should optimize the depletion region and reduce the carrier travel time. INTRODUCTIONSilicon photodiodes convert photons into electrical energy and normally operate in the visible and near-infrared range of the electromagnetic radiation spectrum. This kind of photodiodes has already been used for a broad range of signal detection devices because of its very low cost and compatibility with the mature CMOS technology. One of such device is used in display-application market such as VCD, DVD. Typically, with requirement of higher volume optical data storage and higher resolution display image, high speed blue-ray DVD is expected to replace conventional VCD and DVD [1] . A DVD system requires optical pickup units (OPU) to convert light signal reflected from a storage disc to a proportional electrical output signal. This function is realized by photodiodes integrated with CMOS circuits. The advanced DVD system is required to support three kinds of light wavelength: 780nm wavelength for CD, 650nm wavelength for VCD and 405nm wavelength for blue-ray disk [2].As a result, when integrating photodiodes on the same semiconductor chip as other circuit elements such as transistor, resistor, capacitor to perform complex functions in response to incident radiation signals, the constraints of the process for making those elements must be considered in the design of the process flow. It is well-known that the bandwidth and sensitivity of the photodiode are the key challenges for silicon photodiodes [3] . It is desirable to minimize the complexity of the semiconductor fabrication process while maximizing the performance of the integrated photodiode.In X-FAB, the low sensitivity of photodiodes was improved by the utilization of tunable anti-reflective layers to reduce the light reflectivity at near physical limit for blue light (wavelength 405nm); red (wavelength 650nm) and infra-red (wavelength 850nm). In order to optimize the performance...

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