Charge Quantizing CCDs Optimized for Astronomy

光谱学是在科学和工业的许多分支中使用的关键工具。以特定颜色发出的光可以识别存在的元素，它们的相对浓度，温度甚至是源的速度。然而，信号很弱，传感器本身增加的电噪声会限制测量范围。 这种电噪声无法消除，但在称为“电荷耦合器件”（CCD）的传感器中，信号产生的电荷可以多次测量并取平均值，直到确定像素中电子的确切数量。不幸的是，这种技术大大增加了读取完整图像的时间。该团队将展示在几分钟内而不是几小时内读出图像的能力。图像传感器将由供应商Semiconductor Technology Associates（STA）设计，具有4096x4096像素，具有数百个并行优化输出。加州理工学院将开发位于传感器附近的紧凑型电子设备，以消除许多输出信号。这些传感器将在亚利桑那州的Microchip Technology硅铸造厂生产，随后将投入商业使用。这些CCD通常会将天文学中使用的光谱仪的灵敏度提高2到4倍。在化学、生物学和医学的低光应用中也有可能获得类似的收益。加州理工学院将让本科生参与电子和探测器的测试。该团队将生产一个n沟道量化CCD（qCCD），采用常用的4K x 4K格式（分帧传输），每个扩展串行寄存器有128个浮栅放大器。一个新的差分版本的标准浮栅放大器（FGA）将减半读出时间为任何给定的通道数和像素采样率。差分FGA输出将首先使用SILVACO的商业软件包在数值模拟中进行优化，然后通过测试一系列晶体管几何形状和掺杂分布进行验证。支持高引脚数的新安装封装将通过柔性电路连接到设计用于支持128个差分通道的紧凑型电子模块。这将在检测器附近执行数字差分平均，以大大减少通过真空壁所需的信号连接数量。4K x 4K qCCD将使用传统的外延n沟道技术在陆上铸造厂制造。从传统的6”晶圆到8”晶圆的转变将使每个晶圆的器件数量从1个增加到4个。背面处理和减薄将进行优化，以最大限度地提高紫外线和蓝光响应。该计划将包括在帕洛玛天文台部署的新光谱仪的演示。创建一个4Kx 4K蓝色优化的CCD，在2分钟内实现电荷量化，这将为天文望远镜的灵敏度增益开辟一条道路。 该项目将使大幅面图像传感器的制造再次在美国实现，并将提高从事半导体设计和制造的美国小型企业的全球竞争力。该奖项反映了NSF的法定使命，通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Spectroscopy is a key tool used in many branches of science and industry. Light emitted in specific colors can identify the elements present, their relative concentration, temperature or even the velocity of the source. However, the signals are weak, and the electrical noise added by the sensor itself can limit what can be measured. This electrical noise cannot be eliminated, but in sensors called “Charge Couple Devices” (CCD) the electrical charge generated by the signal can be measured many times and averaged until the exact number of electrons in the pixel is determined. Unfortunately, this technique greatly increases the time to readout a complete image. This team will demonstrate the ability to readout an image in a few minutes instead of hours. The image sensor will be designed by the vendor Semiconductor Technology Associates (STA) to have 4096x4096 pixels, with several hundred optimized outputs operating in parallel. Caltech will develop compact electronics located near the sensor to digitize the many output signals. These sensors will be manufactured at Microchip Technology silicon foundry in Arizona and will subsequently become commercially available. These CCDs will typically improve the sensitivity of spectrographs used in astronomy by a factor of two to four. Similar gains will be possible in low light applications in chemistry, biology, and medicine. Caltech will involve undergraduate students in the testing of electronics and detectors.This team will produce an n-channel Quantizing CCD (qCCD) in a commonly used 4K x 4K format (split frame transfer) with 128 floating gate amplifiers per extended serial register. A new differential version of the standard Floating Gate Amplifier (FGA) will halve the readout time for any given channel count and pixel sampling rate. The Differential FGA output will first be optimized in numerical simulations using a commercial software package from SILVACO and then validated by testing a range of transistor geometries and doping profiles. A new mounting package to support the high pin count will connect by flex circuit to a compact electronics module designed to support 128 differential channels. This will perform digital differential averaging close to the detector to greatly reduce the number of signal connections needed through the vacuum wall. The 4K x 4K qCCD will be manufactured using conventional epitaxial n-channel technology at an onshore foundry. The move from traditional 6” wafers to 8” wafers will increase the number of devices per wafer from one to four. Backside processing and thinning will be optimized to maximize UV and blue response. This program will include a demonstration on a new spectrograph being deployed at Palomar Observatory. The creation of a 4Kx 4K blue optimized CCD that achieves charge quantization in under 2 minutes should open a pathway to very significant sensitivity gains at astronomical telescopes. This project will result in large-format image sensor manufacturing in the USA again, and it will promote global competitiveness of USA-based small businesses engaged in semiconductor design and fabrication.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.