Patent ID: 6747334
Filing Date: 2004-06-08
Classification: H01L

Abstract:
An electronic circuit comprising a thin-film capacitor device and a varactor diode connected in parallel to the thin-film capacitor device, wherein the thin-film capacitor device has electrodes connected to respective input-output terminals and has a thin-film capacitor which is placed between the electrodes, and is manufactured by a method for manufacturing a thin-film capacitor having a desired sheet capacitance and a desired temperature coefficient of capacitance by depositing a first dielectric thin-film having a temperature coefficient of capacitance with an absolute value of 50 ppm/Â° C. or less and a second dielectric thin-film having a negative temperature coefficient of capacitance, wherein the second dielectric thin-film has a structure composed of an aggregation of principal grain units each having a principal crystal grain and grain boundary layers surrounding the principal crystal grain, includes a plurality of principal grain units, and has a thickness tN, wherein tN={&egr;0&tgr;t0t/(C/S)}Â·{1/(&tgr;/&kgr;)}, (C/S represents the sheet capacitance, &egr;0&tgr;t0t represents the desired temperature coefficient of capacitance), wherein &tgr; represents the temperature coefficient of capacitance of the second dielectric thin-film, and &kgr; represents the relative dielectric constant of the second dielectric thin-film, the method comprising:depositing the second dielectric thin-film so that the ratio (&tgr;(x)/&kgr;(x))/(&tgr;g/&kgr;g) is 1.10 or more, wherein &kgr;(x)/&kgr;g=&ggr;[(xâˆ’1)2/(&ggr;xâˆ’1+&kgr;g/&kgr;gb)+{(2âˆ’1/x)/&ggr;}/(&kgr;g/&kgr;gb)]/x, that is, &kgr;(x) indicates that the &kgr; is the function of x, &tgr;(x)/&tgr;g=1âˆ’[(&kgr;g/&kgr;gb)Â·(1âˆ’&tgr;gb/&tgr;g)Â·{(&kgr;g/&kgr;gb)2(xâˆ’1)2+(&ggr;xâˆ’1+&kgr;g/&kgr;gb)2(2âˆ’1/x)&ggr;}/(&kgr;g/&kgr;gb)Â·(&ggr;xâˆ’1+&kgr;g/&kgr;gb)Â·{(xâˆ’1)2Â·(&ggr;xâˆ’1+&kgr;g/&kgr;gb)Â·(2âˆ’1/x)/&ggr;}], &tgr;g represents the temperature coefficient of capacitance of the principal crystal grain, &kgr;grepresents the relative dielectric constant of the principal crystal grain, x, which is a dimensionless parameter, represents the ratio a/2&Dgr;a, &ggr;, which is a dimensionless parameter, represents the ratio b/a, &kgr;gb represents the relative dielectric constant of the grain boundary, a represents the width of each principal grain unit, which includes the principal crystal grain and the grain boundary layers, in the lateral direction, &Dgr;a represents the thickness of each grain boundary layer, 2&Dgr;a represents the thickness of a grain boundary, and b represents the height of the principal grain unit.