EBCCD的成像特性及其制作工艺

The Imaging Characteristics and Key Technology of Electron Bombarded CCD

背照式CCD的入射光是从其背面入射,避免了正面入射时电极对光的损耗,因而量子效率高。以背照式CCD为核心器件的EBCCD,具有增益高,噪声小等特点。在简要分析了EBCCD的结构和成像特点基础上,着重介绍了EBCCD的关键制作工艺:减薄和背面处理。减薄的目的是要均匀地去除硅衬底的无源部分,使光信号从CCD背面直接注入到芯片的有源区,减少信号载流子的复合几率。背面处理的主要目的是在CCD基片内建立较强的电场,以减少表面载流子复合所引起的信号电子损失,使增益在容许的最大电压下到达最大值。减薄工艺中采用仅减薄CCD的光敏区,其它面积不减薄法,可以将基片厚度可减薄到8 um,且整个光敏面的均匀性好;硼离子注入退火的背面处理法,使增益控制范围可达到2000。

The incident light of back-illuminated CCD is incident from its back, and avoids loss of light by electrode as positive incident, thus the quantum efficiency is high. The back-illuminated CCD is the key component of EBCCD, with high gain, low noise, etc. The structure and imaging features of EBCCD (Electron Bombarded CCD) is analyzed, and then the key manufacturing process of EBCCD is highlighted: Thinning technology and the back treatment. The purpose of thinning is to remove the silicon substrate passive part evenly, so that low-light or electronic signals back from the CCD chip directly into the active region, and can lower the recombination of signal carrier. The main purpose of the back treatment is to establish a strong electric field, in order to reduce the signal electron loss by surface composite carrier, so gain can get the maximum gain in the allowed maximum voltage. Thinning process is used only in CCD photosensitive area, and the other area needn’t thinning process. The thickness of the substrate can be thinned to 8 um, and the entire photosensitive surface has good uniformity;With boron ion implantation annealing treatment of the back, gain control can be achieved in 2000.