This invention concerns semiconductor processing methods for filling structural gaps and integrated circuitry having filled structural gaps.
In semiconductor wafer processing, device structures are formed on a semiconductor substrate. FIG. 6 illustrates a wafer fragment 600 comprising a bulk substrate 45 having a pair of wordline constructions 60 formed thereon. A gate oxide 15, gate conductor 20, cap 25, and spacers 30 comprise the individual structural components of wordline constructions 60. Often, it is desirable to form a layer of insulation material over the device structures formed on a semiconductor wafer, such as substrate 45. An insulation layer 640 on wafer portion 600 may be formed by depositing borophosphosilicate glass (BPSG) and reflowing the deposited insulation material to densify and planarize insulation layer 640.
Before forming insulation layer 640, a gap exists in areas where substrate 45 is not covered by device structures, like wordline constructions 60. Such a gap may expose substrate 45 to boron and/or phosphorous diffusion from the BPSG in insulation layer 640. A barrier layer 635 is often formed over device structures prior to formation of insulation layer 640 to counteract such boron and/or phosphorous diffusion. Unfortunately, barrier layer 635 forms a reduced gap within the original gap that has a higher aspect ratio than the original gap. When the aspect ratio of a gap between device structures is sufficiently high, it may cause formation of voids, such as a void 650, in insulation layer 640 during deposition. It is highly desirable to form insulation layer 640 such that it fills the reduced gap between wordline constructions 60 without formation of void 650.
Accordingly, barrier layer 635 addresses the problem of boron and/or phosphorous diffusion, but exacerbates the problem of void formation. Thus, a need exists to provide a method for protecting against boron and/or phosphorous diffusion while reducing the likelihood of forming voids in structural gaps. Otherwise, semiconductive substrates may either suffer defects resulting from boron and/or phosphorous diffusion or defects resulting from formation of voids.
While motivated from this perspective, the artisan will appreciate other applicabilities, with the invention only being limited by the accompanying claims appropriately interpreted in accordance with The Doctrine of Equivalents.
According to one aspect of the invention, a semiconductor processing method for filling structural gaps includes depositing a substantially boron free silicon oxide comprising material at a first average deposition rate over an exposed semiconductive material in a gap between wordline constructions and at a second average deposition rate less than the first average deposition rate over the wordline constructions. A reduced gap having a second aspect ratio less than or equal to a first aspect ratio of the original gap may be provided. A layer of a boron containing silicon oxide material may be deposited on the substantially boron free silicon oxide material and over the wordline constructions. The boron containing silicon oxide material may be deposited in situ in the same chamber.
According to another aspect of the invention, an integrated circuit includes a pair of wordline constructions separated by a gap therebetween in areas where the wordline constructions do not cover an underlying semiconductive substrate. A layer of substantially boron free silicon oxide material has a first thickness over the substrate within the gap and has a second thickness less than the first thickness over the wordline constructions. A layer of boron containing silicon oxide material is over the substantially boron free silicon oxide comprising material.
Other aspects are, of course, contemplated.