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纵然人们使光学系统的各光组最优化,散射光亦被减少,成象用的光敏列阵所能获得的空间分辨率还会受到光生载流子在均匀掺杂半导体中扩散的限制。一种旨在改善极限空间分辨率的技术已经研究成熟;此项技术在于加入一个准表面电场,这个电场使光生载流子要么加速趋向表面,要么加速离开表面,从而防止了载流子向远处的光敏元件扩散。在光敏列阵结构中掺入浓度梯度适当的杂质便获得了准表面电场。在已经制成的一种结构中,准表面场是由加在一片轻掺杂衬底上的一个重掺杂埋入层和一个轻掺杂外延层来产生的,而且它们的导电类型都相同。这种结构与在同一单片衬底上加入一些别的半导体器件的结构类似。该项技术已在一种硅集成电路里的光二极管列阵中应用。但其原理可以直接应用于其他类型的光敏列阵和半导体材料,例如电荷耦合器件(CCD)。
Even though the optics of the optical system are optimized and the scattered light is reduced, the spatial resolution available for imaging photosensitive arrays is limited by the diffusion of photo-generated carriers in uniformly doped semiconductors. A technology that aims to improve the ultimate spatial resolution has been developed; the technique consists of adding a quasi-surface electric field that either accelerates the photo-generated carriers toward the surface or accelerates away from the surface, preventing the carriers from moving farther The photosensitive element at the diffusion. A quasi-surface electric field is obtained by incorporating an impurity of appropriate concentration gradient into the photosensitive array structure. In a structure that has been made, a quasi-surface field is created by a heavily doped buried layer and a lightly doped epitaxial layer applied to a lightly doped substrate, all of which have the same conductivity type . This structure is similar to the structure of adding some other semiconductor devices on the same monolithic substrate. This technique has been used in a photodiode array in silicon integrated circuits. However, its principle can be applied directly to other types of photosensitive arrays and semiconductor materials such as charge coupled devices (CCDs).