Abstract A method of forming multi-layer interconnections, wherein a porous metal oxide film overlying a metal layer is side-etched by utilizing the larger etching rate of the metal oxide film compared to that of the metal layer, so as to form an electrode interconnection portion of the metal layer which is etched into a gently sloping shape at the ends of its upper surface and its sides corresponding to the side-etched parts of the porous film. Second and higher-order layers of electrode interconnection portions are successively formed in such a manner that an insulating film is interposed between the electrode interconnection portion with the ends of its upper surface and its sides formed into the gently sloping shape and each layer of electrode interconnection portion to be formed over the former electrode interconnection portion.
A method according to claim 1, wherein said first metal layer is aluminum and said etchant is a mixed solution of H3PO4, CH3COOH, HNO3 and H2O.
Claim 2
Dependent Claim
16 words
A method according to claim 2, wherein said solution further includes a prescribed amount of NH4F.
Claim 3
Dependent Claim
14 words
A method according to claim 2, wherein said masking layer is a photoresist film.
Claim 4
Dependent Claim
18 words
A method according to claim 2, wherein the temperature of said etchant is between 20* and 60* C.
Claim 5
Dependent Claim
14 words
A method according to claim 5, wherein said etchant temperature is about 40* C.
Claim 6
Dependent Claim
28 words
A method according to claim 2, wherein said first insulator layer is a layer of silicon oxide and said additional metal layer is a layer of deposited aluminum.
Claim 7
Dependent Claim
27 words
A method according to claim 1, wherein said first metal layer is a metal selected from the group consisting of aluminum, titanium, tantalum, zirconium, hafnium, and molybdenum.
Claim 8
Dependent Claim
23 words
A method according to claim 2, wherein the ratio of the respective components of said etchant is preferably about 76:15: 3:5 by volume.
Claim 9
Dependent Claim
25 words
A method according to claim 9, further including an amount of NH4F in said mixed solution with a volumetric ratio component of less than six.