Metal capacitor structure and preparation method thereof

Abstract

The invention provides a metal capacitor structure and a preparation method thereof, comprising: a substrate; a capacitor structure, including a bottom metal layer, a first interlayer dielectric layer, an intermediate metal layer, and a second interlayer dielectric stacked on the substrate in sequence layer and the top metal layer; a number of first openings are located in the top metal layer and expose the surface of the second interlayer dielectric layer; a number of second openings penetrate the bottom of part of the first openings downwards The second interlayer dielectric layer and the intermediate metal layer are exposed until the surface of the first interlayer dielectric layer is exposed. The invention increases the capacitance value of the metal capacitance structure and reduces the thickness of the metal capacitance structure.

Description

Technical field [0001] The present invention relates to the field of semiconductor technology, in particular to a metal capacitor structure and a method of preparation thereof. Background [0002] Metal capacitors (metal-insulator-metal, MIM), due to their small parasitic resistance, are widely used in analog circuits and RF circuits. Different application requirements require different parasitic resistance requirements for metal capacitors. If used in RF circuits, due to the high frequency (GHz), its capacitive reactance is low, and the total impedance of the parasitic resistance over the entire metal capacitor is high and needs to be minimized. However, for low-frequency analog circuits, such as in the application of panel drive chips, metal capacitors are used as charge pump storage, which requires a higher breakdown voltage, and the corresponding time dependent dielectric Breakdown (TDDB) voltage requirements for metal capacitors are higher. [0003] Figure 1 For a cross-s...

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Problems solved by technology

Wherein the thickness and the width of the relative interlayer dielectric layer 22 between the bottom metal layer 21 and the top metal layer 23 determine the capacitance value of the metal capacitor structure, the thinner the thickness of the dielectric layer, the larger the capacitance value, but the impact of the metal capacitor structure The lower the breakdown voltage, the worse the reliability under the working voltage (characterized by time-dependent dielectric breakdown TDDB). TDDB is one of the reliability indicators for evaluating the quality of the dielectric layer. A constant voltage is applied to both ends of the metal capacitor structure. Make the metal capacitor structure in the accumulation state, after a period of time, the dielectric layer will break down, this period of time is the life of the metal capacitor structure under this condition, if the TDDB performance of the metal capacitor structure declines, then the metal capacitor structure is easy to break down chip failure

[0004] figure 2 For the cross-sectional schematic diagram of the metal capacitor structure, please refer to figure 2 , in order to increase the capacitance value of the metal capacitance structure and maintain the breakdown voltage of the metal capacitance structure, on the basis of the first metal capacitance structure 51, a second metal capacitance structure 52 is formed and connected to form a new metal capacitance structure to increase the metal capacitance The capacitance value of the structure, but the thickness of the metal capacitor structure of this structure is relatively thick, and the process flow is relatively large when it is manufactured, which is not conducive to cost control

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