| 摘要 |
PURPOSE:To form a capacitor with high precision in a semiconductor integrated circuit device by a method wherein a check circuit is provided at the specified part of a wafer, and a mask to decide the capacitance value is selected according to the measured result thereof. CONSTITUTION:Capacitors C1, C2 and resistors R1, R2 form a CR oscillator together with an operational amplifier 5, etc. Oscillating frequency of the CR oscillator thereof is as shown by the expression I , and when there exists realtion C=C1=C2, R=R1=R2, the expression I can be expressed by the expression II. When oscillating frequency obtained by the measurement of a check circuit is expressed by R0(1+DELTAf), and the error of the product CR is expressed by DELTACR, the expression II can be expressed by the expression III. When R is invariable, relation DELTACR=DELTACapprox.=-DELTAf is realized. Then a field oxide film 14 is formed on a silicon substrate 13, and a poly-silicon film 10 is formed thereon moreover to construct a capacitance part. Then an oxide film 15 is formed on the poly-silicon film 10, an aluminum conductive film 11a is formed interposing the oxide film thereof between them, and when an aluminum conductive film 11b is formed moreover on the poly-silicon film 10, and width of the capacitance part is expressed by W, length is by L, and thickness of the oxide film 15 for capacitance is made large, capacitance Cx thereof can be expressed by the expression IV. Accordingly, capacitance can be regulated according to the area of the aluminum conductive film 11a, and a linear IC having the desired oscillating freqeuncy can be formed. |
