PNAF Etchant for aluminum and silicon
AssigneeRockwell International Corporation
InventorsJohn E. Martin, Wing P. Ng
Life of this patent
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Abstract
A chemical etchant and a process for chemically etching thin films of aluminum, silicon, and aluminum-silicon alloy on composite structures which may be, for example, integrated circuit devices. The etching process utilizes a mixture of phosphoric acid, nitric acid, acetic acid, a fluoroborate anion containing compound such as fluoroboric acid for providing fluoride ions, a surfactant, and water. This PNAF etchant may be used in fabricating a wafer of integrated circuit devices without lifting photoresist maskant thereon. The formulation provides relatively rapid dissolution of silicon as compared to its etch rates for silicon oxide and silicon nitride. In addition, the etchant has been found suitable for relatively long term use in a production environment.
Claims13
A method of forming a pattern of interconnections on an integrated circuit substrate, comprising:
- forming a thin film layer of metallization on said substrate;
- forming a layer of maskant on said layer of metallization;
- patterning said layer of maskant according to said interconnections;
- and
- etching said layer of metallization with an etchant including:
- between about 20 and about 28 parts by volume of 85% concentrated orthophosphoric acid (H.sub.3 PO.sub.4);
- between about 0.8 and about 1.2 parts by volume of 70% concentrated nitric acid (HNO.sub.3);
- between about 4 and about 6 parts by volume of glacial acetic acid (HOAc);
- and
- between about 0.8 and about 1.2 parts by volume of a 48% concentrated tetrafluoroborate anion containing (BF.sub.4.sup.-) material.
An etchant for aluminum, aluminum-silicon alloy and silicon, comprising:
- between about 20 and about 28 parts by volume of 85% concentrated orthophosphoric acid (H.sub.3 PO.sub.4);
- between about 0.8 and about 1.2 parts by volume of 70% concentrated nitric acid (HNO.sub.3);
- between about 4 and about 6 parts by volume of glacial acetic acid (HOAc);
- and
- between about 0.8 and about 1.2 parts by volume of a 48% concentrated tetrafluoroborate anion (BF.sub.4.sup.-) containing material.
An etchant for aluminum, aluminum-silicon alloy and silicon, comprising:
- about 24 parts by volume of 85% concentrated orthophosphoric acid (H.sub.3 PO.sub.4);
- about 1 part by volume of 70% concentrated nitric acid (HNO.sub.3);
- about 5 parts by volume of glacial acetic acid (HOAc);
- and
- about 1 part by volume of a 48% concentrated tetrafluoroborate anion (BF.sub.4.sup.-) containing material.
Dependencies are inferred from the claim text.