Aluminum word line and bit line fabrication technology for COB DRAM using a polysilicon-aluminum substitute

It is possible to employ the low resistance (but low melting point) material aluminum in word lines and bit lines for COB (capacitor-over-bit line) type DRAM or DRAM/logic, even though high temperature processes are adapted after word line and bit line fabrications. Aluminum successfully diffuses into 0.1-0.5 /spl mu/m width primary polysilicon lines through polysilicon vertical plugs using the polysilicon-aluminum substitute (PAS) technique (Horie et al, IEDM Tech. Dig., p. 946, 1996) after completion of all high temperature processes. This aluminum line provides enough length to create even 512 bit/line, with high purity (99% Al), large grains and low resistance.