| 摘要 |
The present invention relates to a process for selectively etching polysilicon utilizing an ammonia solution etchant that is selective to silicon dioxide and photoresist. In one embodiment of the inventive material, a polysilicon layer is formed over a semiconductor substrate. A photoresist layer is then formed over the polysilicon layer. A portion of the photoresist layer is selectively removed by an edge bead removal process along the edge of the semiconductor wafer so as to expose a portion of the polysilicon layer. The exposed polysilicon layer is selectively removed by an etch conducted at a temperature range from about 20 DEG C. to about 30 DEG C. with an ammonium hydroxide etchant having an ammonia concentration in the range of about 1% to about 5% by volume. The etch is selective to the photoresist layer. A second application of the inventive process is conducted upon a semiconductor substrate having thereon a silicon base layer, a pair of gate stacks each having a spacer thereon, a silicon dioxide layer formed upon the silicon base layer over the of gate stacks and defining therein a contact hole between the pair of gate stacks that terminates at the silicon base layer. A HSG polysilicon layer is formed over the silicon dioxide layer, within the contact hole and on the backside of the semiconductor substrate. A photoresist layer is then over the semiconductor substrate. A portion of the photoresist layer that is generally aligned with a pair of gate stacks proximate to the edge of the semiconductor substrate is removed using an edge bead removal process. The HSG polysilicon layer within the contact hole and on the back surface of the semiconductor substrate is then removed by etching using the ammonium hydroxide etch solution. The ammonium hydroxide etch solution will not substantially remove either of the silicon dioxide layer or the photoresist layer. Megasonics can be used with the ammonium hydroxide etch to selectively remove the HSG polysilicon layer at a faster rate.
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