3D NAND flash scaling require technology that can reduce the stress on thin films, a Lam Research executive said on Thursday.
Production of high performance was leading to more bow on wafers, Lam Research marketing manager Alice Hollister said at Semicon Korea. Technology that can control stress to avoid wafer bow was needed, she said.
Wafer bow leads to lower yield rate from low performances of DoF and overlay as well as structural defects during exposure processes, which compromises patterning registration.
As more layer are added to wafers, this has also increased the chance of wafer bow. NAND flash today are made in 3D structure __ cells are stacked vertically at a 90 degree angle. HAR and etching are core technologies to 3D NAND scaling but structure changes in wafer causes low yields.
Lam Research has developed several products to manage wafers, such as Vector Datum backside deposition tool and EOS GS wet etching equipment to control the stress on thin films.
Vector Datum is a PECVD that attaches a variable counter stress thin film on the backside of wafers. Lam Research said use of the solution could improve photo-registration results and decrease bow, as well as the application of high-performance, high-stress thin films on wafers.
EOS GS controls wafer pressure during 3D NAND flash production. It can be paired with Vector Datum at remove the thin film on the back and bevel of wafers.
3D NAND flash will have more layers going forward and require new ways to prevent wafer bow, Hollister said. Lam Research will focus on the development of related technology, she added.
