Cross-Point Memory Diode Side Wall Film Leakage Control
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Solution Overview
Problem
In cross-point semiconductor memory devices, the use of organic films as interlayer insulating films leads to oxidation of interconnections and deterioration of diodes due to thermal oxidation steps and fixed charges, causing junction leakage and performance degradation, which is exacerbated by the difficulty in burying films between memory cells as capacity increases.
Innovation Solution
The formation of silicon nitride films with specific thicknesses as side wall films on diodes and interconnections to suppress the influence of fixed charges and prevent oxidation, while also moderating electric field concentrations to reduce leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If an applied film (organic film) is used as an interlayer insulating film to correct burying defects, then the burying defect is corrected, but oxidation of interconnection and deterioration of diode occur
Solution Approach 1:
A silicon nitride film is introduced as an intermediary layer between the applied film and the diode/interconnection. This intermediary film acts as a barrier that prevents fixed charges from the applied film from affecting the diode and prevents oxidation of the interconnection during thermal processing, while still allowing the applied film to serve its function of correcting burying defects.
Solution Approach 2:
The interlayer insulating film structure is segmented into multiple layers: the original applied film for correcting burying defects, and an additional silicon nitride film layer positioned closer to the diode and interconnection. This segmentation allows each layer to perform its specific function independently - the applied film handles the burying defect correction while the silicon nitride film handles protection against oxidation and fixed charge effects.
2Quantity of substance
If memory cell size is reduced to achieve large capacity, then storage capacity increases, but aspect ratio increases making film burying difficult
Solution Approach 1:
The invention changes the physical and chemical parameters of the interlayer insulating film system by introducing a silicon nitride film with different properties than the organic applied film. The silicon nitride film has better conformal coverage characteristics and can be deposited at controlled thicknesses, enabling successful film burying even in high-aspect-ratio structures resulting from miniaturized memory cells.
3Reliability
If side wall film thickness is increased to prevent fixed charge influence, then diode performance is protected, but film burying becomes even more difficult
Solution Approach 1:
Instead of uniformly increasing side wall film thickness everywhere, the invention applies the silicon nitride film selectively in specific locations - particularly near the diode and interconnection regions where protection from fixed charges and oxidation is most critical. This localized approach provides necessary protection while minimizing the overall film thickness requirements and maintaining film burying capability.
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 approach effectively prevents diode deterioration, reduces power consumption, and maintains memory cell performance by distancing fixed charges and controlling electric fields, thereby enhancing the reliability and capacity of cross-point memory cell arrays.
Implementation Method 1
impurities of N and C contained in an applied film are present as positive fixed charges, and a band is bent due to an indirect potential effect on the diode caused by the fixed charges
Implementation Method 2
The cause of the oxidation of the interconnection is considered to be a thermal oxidation step performed when N of an organic film serving as an applied film and containing N, C, and Si is replaced with O to form an SiO2 interlayer film
Data Source
AI summary
According to one embodiment, a semiconductor memory device includes a first conductive line, a second conductive line, a rectifying element, a switching element, a first side wall film and a second side wall film. The first conductive line extends in a first direction. The second conductive line extends in a second direction crossing the first direction. The rectifying element is connected between the first and second conductive lines. The switching element is connected in series with the rectifying element between the first and second conductive lines. The first side wall film is formed on a side surface of the rectifying element. The second side wall film is formed on a side surface of at least one of the first and second conductive lines. At least one of a film type and a film thickness of the second side wall film is different from that of the first side wall film.