Advanced plasma etching processes and the effects of plasma on novel metal oxides for emerging memory applications

There is a constantly growing demand for faster and more reliable devices in memory technology. This demand drives the ongoing exploration and study of new materials to achieve better device performance. Novel metal oxide materials have been widely studied due to their unique properties across various applications. Below are two typical examples:

1. Metal oxide semiconductor

Compared to traditional amorphous silicon channels, oxide semiconductor offers improved carrier mobility, higher current density, and optical transparency. Additionally, the ultra-low off-current of oxide semiconductor transistors, combined with their compatibility with large-scale, low-temperature processing, makes it a promising material for planar DRAM, 3D DRAM, and other applications.

2. Ferroelectric material

Ferroelectric materials have gained significant attention for applications such as ferroelectric field-effect transistors (FeFETs) and ferroelectric random-access memory (FeRAM), thanks to their low switching current, CMOS-compatible processes, and scalability potential.

A key challenge in integrating novel metal oxide materials into practical device manufacturing is achieving precise atom-scale patterning without damaging their intrinsic properties. Advanced plasma etching processes and the study of new plasma chemistries are critical for the patterning of these materials in different device fabrication processes. Some examples of specific processes include:

1. Anisotropic atomic layer etch (ALE)

An anisotropic ALE process for metal oxide semiconductors is required for atom-scale control of the etch recess depth in transistor channels during planar DRAM device fabrication. This precision is enabled by the self-limiting nature of the ALE process.

2. Isotropic thermal ALE

For 3D DRAM device fabrication, an isotropic thermal ALE process is needed for lateral etching of metal oxide semiconductors. In this case, new plasma chemistries are essential for etching metal oxides in high aspect ratio structures.

3. Selective reactive ion etch (RIE)

A selective RIE process for ferroelectric materials is necessary to protect the contact material while etching the ferroelectric layers during FeFET device fabrication. This may also require the development of new plasma chemistries.

In addition to investigating advanced plasma etching processes and new plasma chemistries, it is crucial to study the effects of plasma on novel metal oxides to preserve their intrinsic properties. This can be achieved through plasma characterization and material analysis, correlating plasma characteristics with the material’s properties.