| 摘要 |
PURPOSE:To selectively oxidize a semiconductor substrate without pattern conversion difference by laminating SiO2, Si3N4 on the substrate, selectively oxidizing the superposed polysilicon with the SiO2 and Si3N4 as masks of two layers to form an SiO2 mask and etching and opening the lower layer. CONSTITUTION:SiO2 12, Si3N4 13, polysilicon 14, SiO2 15, Si3N4 are superposed on an Si substrate 1, a resist mask 17 of width W is coated, they are then plasme etched to form a film 16'. Then, a side etching alpha1 is produced. When the polysilicon 14 is converted to SiO2 18 via the mask 16', a bird beak beta1 is produced, and when the films 16, 15, 14' are etched by plasma and NH4F, a hole 19 is formed in size difference gamma1. When it is plasma etched via a mask 18 to form a film 13', a side etching alpha2 is produced, the film 18 is removed with NH4F, a hole is opened at the film 12, thereby forming an SiO2 20. When the films 13', 12 are then etched, the bird beak is retarded from beta2 by gamma2. When the thickness of the film and the wet oxidizing conditions are selected at alpha1=alpha2, beta1=beta2, then because gamma1, gamma2 are minute respectively, and the conversion difference can be entirely set to zero. |
