DOPANT ETCH SELECTIVITY CONTROL

摘要

Methods of etching two doped silicon portions at two different etch rates are described. An n-type silicon portion may be etched faster than a p-type silicon portion when both are exposed and present on the same substrate. The n-type silicon portion may be doped with phosphorus and the p-type silicon portion may be doped with boron. In one example, the n-type silicon portion is single crystal silicon and the p-type silicon portion is polycrystalline silicon (a.k.a. polysilicon). The p-type silicon portion may be a polysilicon floating gate in a flash memory cell and may be located above a gate silicon oxide which, in turn, is above an n-type active area single crystal silicon portion. The additional trimming of the n-type active area silicon portion may reduce the accumulation of trapped charges during use and increase the lifespan of flash memory devices.

主权项

1. A method of etching a substrate, the method comprising:
transferring the substrate into a substrate processing region of a substrate processing chamber; flowing a fluorine-containing precursor into a remote plasma region fluidly coupled to the substrate processing region while forming a plasma in the remote plasma region to produce plasma effluents; flowing the plasma effluents into the substrate processing region housing the substrate, wherein the plasma effluents flow into the substrate processing region through perforations in an ion suppression element disposed between the remote plasma region and the substrate processing region; and etching an n-type silicon portion faster than a p-type silicon portion by flowing the plasma effluents into the substrate processing region, wherein the substrate comprises the n-type silicon portion and the p-type silicon portion.