| 摘要 |
PURPOSE:To perform the etching process evenly within a short time by a method wherein a groove is filled with polysilicon in film thickness exceeding 1/2 of the opening width; a PVA layer is formed on overall surface of the polysilicon layer to flatten the surface; and then overall surface is plasma-etched. CONSTITUTION:The etching rate of polysilicon layer 10 normally constant is increased at the central part of a groove 11 in thinner film thickness. On the other hand, the central part of PVA layer 12 at constant etching rate is thicker due to the dent 11 of the polysilicon layer 10 formed at the central part of the groove 11 while the other parts are constant in thickness. When such a structure is evenly plasma-etched, firstly, the PVA layer 12 is removed leaving the central part of the groove 11, later, the etching rate is decreased in the central part of the groove 11 due to the still remaining PVA layer 12. When the etching process is further advanced, the PVA layer 12 at the central part of groove 11 is removed exposing the polysilicon in weak film quality reversely to increase the etching rate. Through these procedures, the increase and decrease in the etching rate are offset to equalize the etching rate with that in other regions at the end of the etching process. |
