Method of forming high aspect ratio apertures

Details Method of forming high aspect ratio apertures Method of forming high aspect ratio apertures

1998-06-17

2000-09-26

Sergent, Rabon

Etching a substrate: processes

Forming or treating electrical conductor article

Forming or treating of groove or through hole

216 41, 216 67, 216 79, 438710, 438715, 438723, H01L 213065, H01L 21308, B44C 122, C03C 1500, C03C 2568

Patent

active

061238627

ABSTRACT:
A plasma etch process for etching BPSG employing two primary etchants at low flows and pressures, and a relatively low temperature environment within the etch chamber, which includes a fluorine scavenger in the form of silicon. The two primary etchant gases are CHF.sub.3 and CH.sub.2 F.sub.2, delivered at flow rates on the order of between about 10 and 40 sccm for CHF.sub.3 and between about 10 and 40 sccm for CH.sub.2 F.sub.2. Small quantities, on the order of 10 sccm or less, of other gases such as C.sub.2 HF.sub.5 and CF.sub.4 may be added. A variant of the inventive etch process employing only CHF.sub.3 during a second phase thereof may be useful in providing a "punch" or dimple at the contact bottom extending into the pristine substrate silicon under the BPSG and, optionally, other layers, and can be used to etch through both BPSG layers and nitride films to contact a word line (or the like) thereunder wherein the contact so formed has a reduced taper as it passes through the nitride film above the word line, resulting in a desirable, larger contact dimension. The system chamber temperature is defined and controlled at the roof over the wafer and the ring surrounding the wafer, the roof being held at a temperature of about 115.degree. C. to 150.degree. C. and preferably about 140.degree. C., and the ring at about 200.degree. C. to 250.degree. C., and preferably at about 200.degree. C. The temperature of the chuck supporting the wafer is maintained at between about -10.degree. C. and +30.degree. C. Chamber pressure is maintained at least at about >5 mTorr, preferably .gtoreq.20 mTorr, and most preferably between about 20 and 65 mTorr.

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