Dry etch of phosphosilicate glass with selectivity to undoped oxide
AssigneeTexas Instruments Incorporated
InventorMonte A. Douglas
Life of this patent
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Abstract
An etchant of PSG (14) or BPSG with high selectivity to substantially undoped oxide (12) includes a fluorine-liberating compound and a fluorine-scavenging compound. The fluorine-liberating compound is preferably a perfluorinated inorganic compound, and the fluorine-scavenging compound is preferably a hydrogen-liberating compound such as hydrogen. A particularly preferred inorganic fluorine-liberating compound is nitrogen trifluoride. In an exemplary embodiment, etch rate ratios of PSG to undoped oxide as high as 11 to 1 were obtained.
Claims26
An etchant for etching a glass selected from the group consisting of phosphosilicate glass and borophosphosilicate glass with high selectivity to substantially undoped silicon dioxide, and capable of attaining a phosphosilicate glass/silicon dioxide etch rate ratio of at least six to one.
An etchant for etching a glass having a substantial phosphorus impurity with high selectivity to substantially undoped silicon dioxide, comprising:
- a plasma in a gas including a perfluorinated inorganic compound and a hydrogen-liberating compound, the molar ratio of fluorine to hydrogen in said gas selected from the range between about 3:1 and about 25:1.
A method for creating an orifice through a glass to a silicon layer, the glass selected from the group consisting of phosphosilicate glass and borophosphosilicate glass, comprising the steps of:
- forming a silicon dioxide layer suitable as a phosphorus diffusion barrier on a surface of the silicon layer;
- forming a layer of the glass on the oxide layer;
- masking the glass layer to leave an exposed area thereon;
- etching the glass in the exposed area down to the oxide layer using a gas etchant having high selectivity to the oxide layer;
- and
- etching the exposed silicon dioxide layer to form an orifice through the glass layer and the silicon dioxide layer to the silicon layer.
A conductor contact for an integrated circuit device, comprising:
- a semiconductor layer;
- a phosphorus-resistant silicon dioxide layer formed on said semiconductor layer;
- a glass layer selected from the group consisting of phosphosilicate glass and borophosphosilicate glass and formed on said silicon dioxide layer;
- an orifice formed at least through said glass layer, sloped sidewalls of said orifice formed by etching the glass layer to the oxide layer with selectivity to the oxide and then reflowing said glass layer;
- and
- a conductor formed in said orifice having good conformity to said sloped sidewalls.
A process for etching a glass comprising a major portion of silica and a minor proportion of phosphorus oxide, and having with high selectivity to substantially undoped silicon dioxide, comprising the step of exposing a structure comprising the glass and the silicon dioxide to a plasma in a gas comprising:
- a minor portion of a compound selected from the group consisting of hydrogen-liberating compounds, (CN).sub.2, CO and NO;
- and
- a major portion of a perfluorinated inorganic gas compound.
Dependencies are inferred from the claim text.