Highly selective doped oxide etchant

Abstract

Etch solutions for selectively etching doped oxide materials in the presence of silicon nitride, titanium nitride, and silicon materials, and methods utilizing the etch solutions, for example, in the construction of container capacitor constructions are provided. The etch solutions are formulated as a mixture of hydrofluoric acid and an organic acid having a dielectric constant less than water, optionally with an inorganic acid, and a pH of 1 or less.

Description

FIELD OF THE INVENTION [0001] The invention relates generally to semiconductor and MEMS processing methods and constructions, and more particularly to methods of forming capacitor structures in memory devices. BACKGROUND OF THE INVENTION [0002] A dynamic random access memory (DRAM) device is commonly used in electronic systems to store data. A typical DRAM device will have one region corresponding to a memory array and another region peripheral to the memory array in which logic or other circuitry is to be formed. Each memory cell generally consisting of a capacitor coupled through a transistor gate electrode or wordline stack to a bit or digit line. [0003] Continuing advances in miniaturization and densification of integrated circuits have led to smaller areas available for devices such as transistors and capacitors. With shrinkage of the cell size, maintaining a sufficient amount of cell charge storage capacitance is a challenge in a DRAM construction. [0004] Several techniques ha...

AI Technical Summary

Benefits of technology

[0027] Without being bound by any particular theory, it is believed that the effectiveness of the current etchants in providing a highly selective etch of doped oxides is based, at least in part, on the lack of dissociation of HF within the solution, and driven by pH and the dielectric constant of the solution. Advantageously, the present etch solutions and methods provide a significant improvement in doped oxides selectivity relative to silicon nitride, titanium nitride, and silicon materials, compared to existing etching processes. The increased etch selectivity allows for higher density components in microelectronic devices, and increased precision in the fabrication of such devices. In addition, the improved etch selectivity and etch rates provided by the present etch composition significantly increase throughput during the manufacture of micro-devices. The present etch solutions enable the implementation of a low temperature flow, and the use of HCD nitride as a processing layer, for which there is no viable etch chemistries available for the present application. BRIEF DESCRIPTION OF THE DRAWINGS

Problems solved by technology

With shrinkage of the cell size, maintaining a sufficient amount of cell charge storage capacitance is a challenge in a DRAM construction.

A draw-back of the foregoing process is that exposure of both the interior and exterior surfaces of a “free-standing” container, particular a container having a high aspect ratio, can render the container structurally weak and subject to collapse during exposure to a wet-etch process to remove the doped oxide material from adjacent the bottom electrode.

Conventionally, the SiN layer 24 is formed using a high temperature deposition process at about 700-780° C. However, high process temperatures can be detrimental, and the trend for future generation devices is the use of low temperature depositions of about 600° C. or less due to thermal budget limitations and to avoid damaging existing features.

However, the etch rate is relatively slow at about 2,000 Å / minute, which impacts processing throughput.

Thus, current H2O:HF etch chemistries for high temperature silicon nitrides do not provide the selectivity of doped oxide relative to low temperature silicon nitrides that is needed in the fabrication of container constructions.

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