The effect of the addition of a PBr3 - free, post-soak period, to the megabit BPSG flow/getter operation.

The extent of P over doping of BPSG during the PBr3 - induced flow/getter operation can be characterized by the "penetration depth" of the excess phosphorous. This penetration depth represents the thickness of the liquid-like P-rich BPSG layer. We present here a scheme where a part of the PBr3-soak period is replaced by a post-soak period during which no PBr3 is flowing. It is shown that such a scheme results in a reduction of the "penetration depth" without significantly affecting the planarization obtained from the flow/getter operation. Such a scheme may be useful in the prevention of the crystalline formation in BPSG during the flow/getter operation.