US-12628355-B2 - Capacitor structure and method for fabricating the same

US12628355B2US 12628355 B2US12628355 B2US 12628355B2US-12628355-B2

Abstract

This invention provides a capacitor structure includes a U-shaped bottom electrode having a cap dielectric provided at its open end, a top electrode and a capacitor dielectric layer interposed between the bottom electrode and the top electrode to constitute an outer capacitor around a cylinder type solid inner capacitor, and the outer capacitor and the inner capacitor are divided by the cap dielectric. The cylinder type solid inner capacitor and the outer capacitor are fabricated separately so that the cylinder type solid inner capacitor may support its own weight to prevent its structure from being damaged during the fabrication of the capacitor.

Inventors

Da-Zen Chuang

Assignees

NANYA TECHNOLOGY CORPORATION

Dates

Publication Date: 20260512
Application Date: 20220609

Claims (7)

1 . A capacitor structure having an inner solid cylindrical capacitor and an outer capacitor surrounding the inner solid cylindrical capacitor, comprising: a U-shaped bottom electrode having two spaced vertical legs and a base connected with the two vertical legs, each of the vertical legs having a cap dielectric disposed on its one end away from the base; a capacitor dielectric layer conformally formed on sidewall surfaces of the vertical legs of the bottom electrode and a surface of the base of the bottom electrode facing the cap dielectric as well as sidewall surfaces of the cap dielectric with uncovering a top of the cap dielectric away from the vertical leg; and a top electrode interdigitating with the vertical legs of the U-shaped bottom electrode and covering the capacitor dielectric layer and the top of the cap dielectric so that the capacitor dielectric layer is interposed between the top electrode and the bottom electrode, and the cap dielectric divides the inner solid cylindrical capacitor and the outer capacitor.
2 . The capacitor structure of claim 1 , wherein the cap dielectric comprising silicon nitride (SiN).
3 . The capacitor structure of claim 1 , wherein the bottom electrode comprises titanium nitride (TiN).
4 . The capacitor structure of claim 1 , wherein the top electrode comprises polysilicon material.
5 . A capacitor structure for DRAM with crown capacitors, comprising: an array of capacitor cells, each of the capacitor cells is configured to a capacitor structure as claimed in claim 1 .
6 . The capacitor structure for DRAM with crown capacitors of claim 5 , wherein the capacitor cells share a common top electrode.
7 . The capacitor structure for DRAM with crown capacitors of claim 5 , wherein each of the capacitor cells has its individual bottom electrode.

Description

BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to the field of semiconductor process, and more particularly to a method for fabricating a capacitor structure for DRAM with crown capacitors. Description of the Prior Art With technology continuously migrating to advanced nodes, fabrication of DRAM capacitors is getting tougher. In order to enlarge total surface area of a capacitor to maximize the charge storing for capacitance, crown capacitors have been used for a long time to fully utilize both inner and outer areas of the capacitor. FIG. 1 shows a schematic cross sectional view of partially produced crown capacitors 10, in which an array of bottom electrodes 104 are provided on a substrate 100. Each of the bottom electrodes 104 is aligned over one of conductive landing pads 102 of the substrate 100. A capacitor dielectric layer 106 is conformally deposited on the bottom electrode 104. With technology moving to more advanced node, further shrinking of crown capacitors 10 is facing the issue that the crown capacitors 10 is not rigid nor strong enough to support its own weight and is likely to bend or even to fall during its fabrication process. This may result in short circuit of capacitor-to-capacitor, and causing the function failure of the resulted device. See FIG. 2, for example, the bottom electrodes 104 may become much thinner and bending to abut each other as the ratio of the bottom width to the height of the crown capacitor 100 is increasingly reduced. Therefore, it is difficult to form these fragile free standing capacitor bottom electrodes 104 without resulting in damage during subsequent processing. There is still a need in the semiconductor industry to provide crown capacitors having increased uniform capacitance among individual memory cells while reducing the susceptibility to process damage subsequent to making the capacitor bottom electrodes. SUMMARY OF THE INVENTION The present invention proposes a novel capacitor structure and its fabrication method to resolve the issue described above. The novel capacitor structure includes a U-shaped bottom electrode having a cap dielectric provided at its open end, a top electrode and a capacitor dielectric layer interposed between the bottom electrode and the top electrode to constitute an outer capacitor around a cylinder type solid inner capacitor, and the outer capacitor and the cylinder type solid inner capacitor are divided by the cap dielectric. In its fabrication process, the cylinder type solid inner capacitor and the outer capacitor are fabricated separately so that the cylinder type solid inner capacitor may support its own weight to prevent its structure from bending and/or falling during the fabrication of the capacitors. The present invention also provides a capacitor structure for DRAM with crown capacitors, which includes an array of capacitor cells, each of the capacitor cells is configured to include a U-shaped bottom electrode having a cap dielectric provided at its open end, a top electrode and a capacitor dielectric layer interposed between the bottom electrode and the top electrode to constitute an outer capacitor around a cylinder type solid inner capacitor, and the outer capacitor and the cylinder type solid inner capacitor are divided by the cap dielectric. To obtain the above capacitor structure, in one embodiment, the present invention provides a method for fabricating a capacitor structure with crown capacitors. A substrate having an array of conductive landing pads is provided. A first dielectric layer is formed on the substrate and then forming a plurality of trenches in the first dielectric layer to expose the conductive landing pads, each of the trenches aligned over one of the conductive landing pads. A bottom electrode layer is conformally formed on the first dielectric layer and a first capacitor dielectric layer is conformally formed on the bottom electrode layer. A first top electrode layer is formed on the first capacitor dielectric layer so that the first capacitor dielectric layer is interposed between the first top electrode layer and the bottom electrode layer. A first chemical mechanical polish process is performed until the first dielectric layer, the bottom electrode layer, the first capacitor dielectric layer and the first top electrode layer are coplanar, whereby an array of cylinder type solid inner capacitor predecessors are provided and each of the inner capacitor predecessors is aligned over one of the conductive landing pads, and each of the inner capacitor predecessors comprises the bottom electrode layer, the first top electrode layer and the first capacitor dielectric layer interposed between the bottom electrode layer and the first top electrode layer. Then, removing a portion of the bottom electrode layer to form an array of bottom electrodes and an array of recesses aligned over the bottom electrodes. A cap dielectric layer is then deposited to fill the recesses.