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引言 1990年处于这样一种状况,各DRAM厂家都结束了16M DRAM的开发而开始了正式的试制,并着手开发更大容量的64M DRAM。据报导,这一年中,16M DRAM的最小加工尺寸已达到0.5μm,64M DRAM已达到0.35μm。其中,0.5μm的最小加工尺寸是由采用NA0.5左右透镜的缩小投影曝光实现的。而要实现0.35μm的线宽必须采用i线曝光,不过,如果仅是采用i线源和高NA化透镜,在焦深等方面却又不尽人意。当前,光刻技术在透镜和抗蚀剂方面的改进已接近极限,故剩下来的一个可能性当然就
Introduction In 1990, a situation was underway. All DRAM manufacturers ended the formal development of 16M DRAM and started to develop 64M DRAMs with higher capacity. It is reported that in the year, the minimum processing size of 16M DRAM has reached 0.5μm, 64M DRAM has reached 0.35μm. Among them, the minimum processing size of 0.5μm is achieved by the reduced projection exposure using NA 0.5 lens. To achieve 0.35μm line width must be used i-line exposure, however, if only the use of i-line source and high-NA lens, in terms of depth of focus but not satisfactory. Currently, lithography advances in lenses and resists are nearing the limit, so one of the remaining possibilities is of course