BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is related to 3-dimensional memory structures. In particular, the present invention is related to 3-dimensional memory structures organized in arrays of vertical NOR-type memory strings.

2. Discussion of the Related Art

Methods for forming multi-layer Vertical NOR-type memory string arrays have been described previously; for example, various variations of forming such memory arrays are disclosed in Non-Provisional Application and Provisional Applications II and III incorporated by reference above.

SUMMARY

According to one embodiment of the present invention, a method for forming 3-dimensional vertical NOR-type memory string arrays uses damascene local vertical bit lines is provided. The method of the present invention also avoids ribboning by etching local word lines in two steps. By etching the local word lines in two steps, the aspect ratio in the patterning and etching of stacks of local word lines (“word line stacks”) is reduced, which improves the structural stability of the word line stacks. The present invention also addresses alignment issues incidental to etching the word line strips in two steps.

The present invention is better understood upon consideration of the detailed description below in conjunction with the accompanying drawings.

