Atomic-Scale Precision

Shaping and removing materials is becoming increasingly critical. It takes precision to remove targeted atoms without removing or damaging the remainder of the target film along with adjacent films and structures.

Conductor etch removes conducting and semiconductor materials, such as metals and silicon, deposited during the device fabrication process. Dielectric etch removes insulating films, which tend to have stronger atomic bonds and require higher energies. Both typically employ reactive ion etch in which reactive chemistries and high-energy ions bombard the wafer surface to create holes, lines, and shapes. Atomic layer etching with its low ion energy is emerging as device dimensions shrink and precise shaping of small, densely packed structures becomes more difficult. In contrast, etching contacts in increasingly high aspect ratio NAND structures is requiring higher ion energies.

Selective removal uses radical-based chemistries to remove a target material without damaging surrounding materials and can work even when there is no line of sight. Selective removal technology provides new degrees of freedom in shaping complex vertical structures like finFETs, 3D NAND memory arrays and emerging gate-all-around transistors.

Chemical mechanical planarization (CMP) is a physical polishing technology that leverages chemistry and abrasives to quickly and precisely remove targeted metal and dielectric films, leaving a strong, uniform, and planar foundation for subsequent process steps. CMP is critical in the creation of vertical structures as these structures require an excellent base to build upon.

CMP

At various stages in making a microchip, the surface of the wafer has to be made perfectly flat (planarized). This is done either to remove excess material, or to create a perfectly flat foundation for adding the next layer of circuit features. To do this, chipmakers use a process called chemical-mechanical planarization (CMP).

CMP removes and planarizes excess material on the wafer’s front surface by applying precise downforce across the backside of the wafer and pressing the front surface against a rotating pad of special material that also contains a mixture of chemicals and abrasives. To ensure that the right amount of material remains evenly across an entire 300mm wafer, the process must apply varying amounts of downforce during material removal, while stopping at the right point to avoid polishing away critical underlying features.