A Micromachined Silicon Crystallographic X-ray Detector

我们建议开发用于大分子晶体学的X射线区域探测器，基于晶体硅片中的光电吸收。 在这样的传感器中，衍射X射线将被直接捕获在厚的、高电阻率的、通过电感耦合等离子体蚀刻微加工的硅中。我们将使用的蚀刻工艺在硅中切割干净，清晰的特征，而不会在相邻材料中产生缺陷。 蚀刻孔的2D光栅将填充有导电多晶硅（“poly”）-一半是n型，另一半是p型。 这些多晶硅柱将用作反向偏置二极管阵列的电极，用于产生漂移场和电子捕获。 每个正方形150 μ m像素将具有一个n型电极和一个p型电极，并且将利用导电凸块接合到位于传感器后面的CMOS读出芯片中的对应输入。还将使用等离子体蚀刻来切割每个硅传感器。这样产生的光滑、无缺陷的边缘将衬有导电的聚电极，使传感器晶片在边缘都是有源的。 因此，这些传感器的重叠阵列将没有死间隙。CMOS电子器件将由标准（0.25妈妈技术）的CMOS工艺制造，但将被设计为具有很大的安全系数，防止辐射损伤。 我们将设计，制造，调试，测试，并在拟议项目的第一阶段，随着片外电子，物理封装，使其工作所需的软件几个模块的特性。沿着。 CMOS芯片也将通过等离子体蚀刻切割，因此当凸点键合到传感器芯片时，它们不会突出到传感器边缘之外。在项目的第二阶段，我们将制造一个4x 4的模块阵列，封装成叠瓦状，传感器将读出电子设备屏蔽在后面。 我们将测试芯片安装方案，使用圆柱形安装表面，但倾斜每个传感器指向晶体，最大限度地减少视差。 在该项目的第二阶段，我们将包装这种模块化阵列，并证明这种模块化设计的可行性。每个硅传感器将覆盖0.96 cm 2。 当完全按比例放大时，我们的工艺可以使传感器/读出模块的前端成本低于100/cm 2美元，整体成本低于200/cm 2美元，因此这项技术本质上比CCD便宜。 探测器将区分单个X射线，但对接近400，000/s/像素的辐射水平作出线性响应。 其点响应将保持在单个像素内。 灵敏度将高度均匀，每个传感器内不会发生失真，并且检测器不会显示任何暗信号或暗噪声。

We propose to develop X-ray area detectors for macromolecular crystallography, based on photoelectric absorption in crystalline silicon wafers. In such a sensor, diffracted X rays will be captured directly in thick, high-resistivity, silicon, micromachined by inductively-coupled plasma etching. The etching process we will use cuts clean, sharply-defined features in silicon without creating defects in neighboring material. A 2D raster of etched holes will be filled with conducting polycrystalline silicon ("poly")-half of which will be n type and the other half p type. These poly columns will serve as electrodes of a reverse-biased diode array for generating drift fields and for electron capture. Each square 150 mum pixel will have one n- and one p-type electrode, and will be bonded with a conducting bump to a corresponding input in a CMOS readout chip, located behind the sensor. Plasma etching will also be used to cut out each silicon sensor. The smooth, defect-free edges thus produced will be lined with a conducting poly electrode, making the sensor wafer active to the very edge. Overlapping arrays of these sensors will therefore have no dead gaps. The CMOS electronics will be fabricated by standard (0.25 mum technology) photolithographic processing but will be designed to have a large safety factor against radiation damage. We will design, fabricate, debug, test, and characterize several modules during the first stage of the proposed project, along with the off-chip electronics, physical packaging, and software needed to make it work. CMOS chips will be cut out by plasma etching too, so that when bump-bonded to sensor chips, they will not project beyond the sensor edges. During the second stage of the project we will fabricate a 4x4 array of modules, packaged so they overlap in a shingle pattern, with the sensors shielding the readout electronics behind. We will test chip-mounting schemes that use a cylindrical mounting surface, but tilt each sensor to point to the crystal, minimizing parallax. During this second stage of the project, we will package this modular array and demonstrate the feasibility of this kind of modular design. Each silicon sensor will cover 0.96 cm2. When fully scaled up, our process can make sensor/readout modules for less than 100/cm2 dollars in the front end and less than 200/cm2 dollars overall, so this technology is inherently less expensive than CCDs. The detector will discriminate individual X rays yet respond linearly to radiation levels approaching 400,000/s/pixel. Its point- response will remain within a single pixel. Sensitivity will be highly uniform, no distortion will occur within each sensor, and the detector will not exhibit any dark signal or dark noise.