Abstract:
Methods for forming or etching silicon trench isolation (STI) in a silicon-on-insulator (SOI) region and a bulk silicon region, and a semiconductor device so formed, are disclosed. The STI can be etched simultaneously in the SOI and bulk silicon regions by etching to an uppermost silicon layer using an STI mask, conducting a timed etch that etches to a desired depth in the bulk silicon region and stops on a buried insulator of the SOI region, and etching through the buried insulator of the SOI region. The buried insulator etch for this process can be done with little complexity as part of a hardmask removal step. Further, by choosing the same depth for both the bulk and SOI regions, problems with a subsequent CMP process are avoided. The invention also cleans up the boundary between the SOI and bulk regions where silicon nitride residuals may exist.
Abstract:
Methods for forming or etching silicon trench isolation (STI) in a silicon-on-insulator (SOI) region and a bulk silicon region, and a semiconductor device so formed, are disclosed. The STI can be etched simultaneously in the SOI and bulk silicon regions by etching to an uppermost silicon layer using an STI mask, conducting a timed etch that etches to a desired depth in the bulk silicon region and stops on a buried insulator of the SOI region, and etching through the buried insulator of the SOI region. The buried insulator etch for this process can be done with little complexity as part of a hardmask removal step. Further, by choosing the same depth for both the bulk and SOI regions, problems with a subsequent CMP process are avoided. The invention also cleans up the boundary between the SOI and bulk regions where silicon nitride residuals may exist.
Abstract:
A method is disclosed for improving etch uniformity in deep silicon etching of a monocrystalline silicon wafer. Such method includes forming a pad dielectric layer on a wafer including monocrystalline silicon, forming a silicon layer over the pad dielectric layer, and then applying a clamp to an edge of the wafer. The silicon layer is then removed except in areas protected by the clamp. Thereafter, a hardmask layer is applied and patterned on the wafer; and the wafer is then directionally etched with the patterned hardmask to etch trenches in the monocrystalline silicon.In such manner, a source of silicon (in the silicon layer) is provided at the wafer edge, such that the silicon loading is improved. In addition, the silicon layer at the wafer edge forms a blocking layer which prevents formation of black silicon.