基于二极管单元的高密度掩模ROM设计

Design of High-density Mask ROM Based on Diode Cells

针对传统ROM(Read-Only Memory)存储密度低、功耗高的问题,该文提出一种采用二极管单元并通过接触孔编程来存储数据的掩模ROM。二极管阵列采用双沟槽隔离工艺和无间隙接触孔连接方式实现了极高的存储密度。基于此设计了一款容量为2 Mb的掩模ROM,包含8个256 kb的子阵列。二极管阵列采用40 nm设计规则,外围逻辑电路采用2.5 V CMOS工艺完成设计。二极管单元的有效面积仅为0.017μm^2,存储密度高达0.0268mm^2/Mb。测试结果显示二极管单元具备良好的单元特性,在2.5 V电压下2 Mb ROM的比特良率达到了99.8%。

Since the traditional Read-Only Memory （ROM） has the problems of low density and high power consumption, a mask ROM based on diode cells and contact-programming process is proposed. With dual-trench isolation process and borderless contact scheme, the diode array can realize ultrahigh density. Based on the proposed novel diode array, a mask ROM macro with 2 Mb capacity is designed, which contains 8 256 kb sub-arrays The diode arrays are fabricated with 40 nm design rule and the peripheral logic circuits are achieved in 2.5 V CMOS process. The effective area of the diode cell is only 0.017μm2 and the density of the diode array is 0.0268 mm2/Mb. Test results show that the cell feature of diodes is good and the bit yield of the 2 Mb ROM achieves 99.8% under 2.5 V supply voltage.