Self-Aligned Hard Mask Patterning for Higher-Density MIM Capacitors
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Solution Overview
Problem
The limitations in achieving a smaller critical dimension in integrated circuit (IC) technology restrict the number of columns in metal-insulator-metal (MIM) capacitors, thereby reducing the maximum capacitance that can be realized.
Innovation Solution
A method of fabricating IC devices with reduced critical dimensions using a self-aligned mask, involving the deposition and etching of hard mask layers to expose dielectric material with a smaller lateral dimension, allowing for the formation of narrower trenches and columns in MIM capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional photolithographic masks are used, then the critical dimension is limited by mask accuracy and precision, but the number of columns in MIM capacitors is restricted, reducing maximum capacitance
Solution Approach 1:
The mask pattern is segmented into multiple exposure steps, allowing the critical dimension to be defined by etch processes rather than direct photolithography. This enables smaller effective critical dimensions by dividing the patterning process into sequential steps with self-alignment
Solution Approach 2:
The patent transitions from two-dimensional planar patterning to three-dimensional self-aligned structures. By forming mandrels and using conformal deposition, the critical dimension is controlled in the vertical dimension through etch depth rather than horizontal mask features, enabling reduced effective critical dimensions
2Quantity of substance
If the critical dimension is reduced to increase the number of columns, then capacitance increases, but the mask accuracy and precision requirements become more stringent
Solution Approach 1:
The process uses self-aligned deposition and etching where previously formed structures serve as their own masks. The conformal deposition on mandrels and the subsequent anisotropic etching automatically align features without requiring additional photolithographic alignment, eliminating mask accuracy limitations
Solution Approach 2:
The patent replaces the photolithographic mechanical system (masks, aligners, exposure) with a self-aligned chemical-vapor deposition and plasma etching system. This substitution eliminates the fundamental resolution limits of optical photolithography
3Quantity of substance
If more columns are added to MIM capacitors to increase capacitance, then the capacitance increases, but the device footprint must increase without the self-aligned method
Solution Approach 1:
The patent utilizes vertical dimension through three-dimensional capacitor structures with extended etch depths. By controlling critical dimension through vertical etch processes rather than horizontal mask features, more columns can be packed into the same planar footprint, increasing capacitance without increasing device area
Data Source
AI summary
Some embodiments relate to a method that includes depositing a first layer of hard mask material over a layer of dielectric material; etching the first layer of the hard mask material, the etched first layer of hard mask material including an etched portion having a first lateral dimension; depositing a second layer of the hard mask material over the first layer of the hard mask material; etching at least a portion of the second layer of the hard mask material, while allowing a remaining portion of the hard mask material, to expose a portion of the layer of the dielectric material that has a second lateral dimension less than the first lateral dimension; and etching a trench into the layer of the dielectric material at the exposed portion of the layer of the dielectric material.