3D Memory Cell Capping Layer With Air Gaps for Lower Parasitic Capacitance
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Solution Overview
Problem
The challenge is to increase memory cell density while reducing parasitic capacitance in semiconductor devices, as shrinking memory cells leads to structural limitations that hinder further die area increase.
Innovation Solution
A semiconductor device design featuring vertically stacked memory cells with a capping layer containing low-k materials and air gaps between the bit line and word lines, which reduces parasitic capacitance and prevents lateral migration of seams, thereby allowing for increased memory cell density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If memory cells are shrunk to increase net die, then memory cell density is improved, but parasitic capacitance increases and structural limitations arise
Solution Approach 1:
The patent changes the dielectric parameter of the capping layer by using low-k materials (with k < 3.9) and air gaps instead of conventional high-k materials. This parameter change reduces the parasitic capacitance between the bit line and word line, allowing memory cells to be shrunk without the harmful increase in parasitic capacitance that would normally limit further density improvements.
Solution Approach 2:
The patent introduces air gaps (porous structures) within the capping layer as a low-k dielectric material. These air gaps reduce the effective dielectric constant of the capping layer, thereby reducing parasitic capacitance between conductive elements. This enables continued scaling of memory cells to increase density without being constrained by parasitic capacitance effects.
2Productivity
If memory cells are shrunk to increase net die, then memory cell density is improved, but structural limitations prevent further die area increase
Solution Approach 1:
The patent introduces a vertical dimension by stacking multiple memory cells vertically on the base substrate. This three-dimensional arrangement allows increased memory cell density without proportionally increasing the horizontal die area. The low-k capping layer with air gaps enables this vertical stacking by reducing parasitic capacitance between vertically adjacent bit lines and word lines, overcoming structural limitations of planar scaling.
3Reliability
If capping layer is formed between bit line and word lines, then physical distance is secured, but parasitic capacitance must be reduced
Solution Approach 1:
The patent changes the dielectric parameter of the capping layer material from conventional high-k materials to low-k materials with dielectric constants less than 3.9. This parameter change reduces the parasitic capacitance between the bit line and word lines while maintaining the necessary physical distance for reliable operation, thus resolving the contradiction between physical separation and capacitance reduction.
Solution Approach 2:
The patent uses composite structures for the capping layer, combining low-k dielectric materials with air gaps. This composite approach achieves both sufficient physical distance between conductive elements for reliability and reduced parasitic capacitance, as the air gaps (k≈1) significantly lower the effective dielectric constant of the capping layer structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design effectively reduces parasitic capacitance and prevents seam punching, enabling higher memory cell density without compromising performance.
Implementation Method 1
parasitic capacitance between the bit line and the word lines may be reduced
Data Source
AI summary
According to the disclosure, highly integrated memory cells and a semiconductor device having the same are provided. According to an embodiment, a semiconductor device comprises a plurality of memory cells vertically stacked on a base substrate, each of the plurality of memory cells includes, a bit line vertically oriented from the base substrate, a capacitor horizontally spaced apart from the bit line, an active layer horizontally oriented between the bit line and the capacitor, a word line positioned on at least one of a top surface and bottom surface of the active layer and horizontally extending in a direction crossing the active layer, and a capping layer positioned between the word line and the bit line and including, at least, a low-k material and an air gap.