| 摘要 |
An improved method for forming a planar borophosphosilicate glass (BPSG) insulating layer having a reduced thermal budget was achieved. The method involves forming a multilayer BPSG comprised of four layers with different boron and phosphorus concentrations in each layer. The first layer deposited has the conventional doping range, and therefore would require higher reflow temperatures for leveling. By the method of this invention, a second low-doped BPSG buffer layer is deposited and then a heavily doped third BPSG layer is deposited having a lower reflow temperature, and therefore is planarized at a lower temperature. A low-doped fourth cap BPSG layer is used over the third BPSG layer to minimize moisture absorption and unstable crystal formation prior to the reflow anneal.
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